Patent Grant
7215907
The present application claims priority under 35 U.S.C. § 119 to Japanese Patent Applications No. 2003-192821 filed on Jul. 7, 2003, No. 2003-408291 filed on Dec. 5, 2003, and No. 2004-114717 filed on Apr. 8, 2004 in the Japanese Patent Office, the entire contents of which are incorporated herein by reference.
1. Field of the Invention
The present invention relates to an image forming method and apparatus, and more particularly to a method and apparatus for image forming capable of effectively eliminating color displacement by controlling a clock control motor controlled by a command clock signal and a feedback signal, in accordance with a velocity curve.
2. Discussion of the Background
Background image forming apparatuses are commonly known as electrophotographic copying machines, printing machines, facsimile machines, and multi-functional apparatuses having at least two functions of copying, printing and facsimile functions. Some of the background apparatuses use an intermediate transfer method, and some use a direct transfer method.
The background image forming apparatus using the intermediate transfer method is referred to as an “intermediate transfer image forming apparatus”, and transfers an electrostatic latent image formed on a photoconductor onto an intermediate transfer member before transferring the electrostatic latent image onto a recording medium.
The background image forming apparatus using the direct transfer method is referred to as a “direct transfer image forming apparatus”, and directly transfers the electrostatic latent image onto the recording medium which is conveyed by a recording medium bearing member.
In both background image forming apparatuses, the photoconductor is driven by a photoconductor motor to rotate, and the intermediate transfer member and the recording medium bearing member are driven by a drive motor to rotate.
The photoconductor and the intermediate transfer member rotate while they are held in contact to each other, a surface linear velocity of the photoconductor is required to have the same rate as that of the intermediate transfer member. In a case where the photoconductor rotates at a different rate from the intermediate transfer member, a surface of the photoconductor rubs a surface of the intermediate transfer member, hastening their surface wear.
To prevent the wearing of the surfaces, the intermediate transfer image forming apparatus has employed a stepping motor as the photoconductor motor and the drive motor for controlling the number of input pulses of the stepping motor to synchronize the surface linear velocities of the photoconductor and the intermediate transfer member. Also, the direct transfer image forming apparatus has employed the stopping motor for synchronizing the surface linear velocities of the photoconductor and the recording medium bearing member.
The stepping motor, however, generally consumes a large amount of electric power and produces a loud noise. Therefore, a clock control motor such as a direct current (DC) brushless motor is used as an alternative to the stepping motor. The DC brushless motor is controlled by a command clock signal and a feedback signal, and can reduce the power consumption and the loud noise.
The DC brushless motor, however, may vary its rotation speed particularly when it is started and stopped. In a case where the DC brushless motor is used as the photoconductor motor and the drive motor, the surface linear velocity of the photoconductor may be greatly different from that of the intermediate transfer member or that of the recording medium bearing member, which results in significant wear that shortens its life. Consequently, the DC brushless motor has been thought to be unsuitable for the background image forming apparatus.
When a motor stop signal is issued to stop inputting the command clock signal to the photoconductor motor and the drive motor as shown in
As described above, the significant difference between the surface linear velocity of the photoconductor and the surface linear velocity of the intermediate transfer member may cause damages such as scratches on the surfaces thereof and defects such as streaks on an image, resulting in a deterioration of the image. The defects may be observed when the DC brushless motor is used as the drive motor for the recording medium bearing member. Due to the drawbacks as described above, the stepping motor has preferably been used, without solving the problems of high power consumption and loud noise.
The present invention has been made under the above-described circumstances.
An object of the present invention is to provide a novel image forming apparatus which can control a clock control motor controlled by a command clock signal and a feedback signal, in accordance with the velocity curve.
In one exemplary embodiment, a novel image forming apparatus includes at least one image bearing member, a transferring member, at least one first motor, a second motor, and a control mechanism. The at least one image bearing member is configured to bear a toner image on a surface thereof. The transferring member is arranged close to or in contact with the at least one image bearing member and is configured to rotate in substantially synchronism with the at least one image bearing member to transfer the toner image born on the at least one image bearing member onto a recording medium. The at least one first motor rotates the at least one image bearing member. The second motor rotates the transferring member. The control mechanism is configured to control a rotation number of at least one of the at least one first motor and the second motor during at least one of rise and fall time periods with a command clock signal and a feedback signal in accordance with a predetermined velocity curve.
A novel image forming apparatus includes at least one image bearing member, an intermediate transfer member, a third motor, a fourth motor, a transfer mechanism, and a control mechanism. The at least one image bearing member is configured to bear a toner image on a surface thereof. The intermediate transfer member is configured to receive the toner image from the at least one image bearing member. The third motor rotates the at least one image bearing member. The fourth motor rotates the intermediate transfer member. The transfer mechanism is configured to transfer the toner image from the intermediate transfer member to a recording medium. The control mechanism is configured to control rotations of the third and fourth motors. At least one of the third and fourth motors includes a clock control motor controlled by a command clock signal and a feedback signal. The control mechanism controls a rotation number of the clock control motor in accordance with a predetermined velocity curve during at least one of rise and fall time periods of the clock control motor.
The third motor may include the clock control motor, and the fourth motor may include a stepping motor.
Each of the third and fourth motors may include the clock control motor.
The clock control motor may be controlled to be rotated by the command clock signal having the clock number in accordance with the predetermined velocity curve during the at least one of rise and fall time periods of the clock control motor.
The clock control motor may be controlled to be rotated by the command clock signal having a gradually increasing pulse number during the rise time period, having a substantially constant pulse number during a steady rotation time period, and having a gradually decreasing pulse number during the fall time period.
The image forming apparatus may further include a braking mechanism configured to forcedly reduce a rotation number of the clock control motor during the fall time period of the clock control motor.
The rotation number of the clock control motor may be controlled by changing a pulse number of the command clock signal in steps during the at least one of rise and fall time periods of the clock control motor.
The predetermined velocity curve may be stored in a memory and may be changed by controlling an operation panel of the image forming apparatus or a connecting terminal of the image forming apparatus.
The clock control motor may include a direct current brushless motor.
A novel image forming method includes the steps of driving an image bearing member with a primary driving member, driving an overlaying member with a secondary driving member, forming a toner image on the image bearing member, moving the toner image with the image bearing member to a primary transfer position, overlaying at least one toner image formed on the bearing member into a single toner image at the primary transfer position, transporting the single toner image to a secondary transfer position, transferring the single toner image transported to the secondary transfer position by the transporting step onto a recording medium, and controlling a rotation number of at least one of the primary and secondary driving members with a command clock signal and a feedback signal in accordance with a predetermined velocity curve.
The controlling step may control the rotation number of the at least one of the primary and secondary driving members during at least one of rise and fall time periods with the command clock signal and the feedback signal in accordance with the predetermined velocity curve.
A novel image forming apparatus includes at least one image bearing member, a recording medium bearing member, a fifth motor, a sixth motor, a transfer mechanism, and a control mechanism. The at least one image bearing member is configured to bear a toner image on a surface thereof. The recording medium bearing member is configured to carry a recording medium to receive the toner image from the at least one image bearing member. The fifth motor rotates the at least one image bearing member. The sixth motor rotates the recording medium bearing member. The transfer mechanism is configured to transfer the toner image from the image bearing member to a recording medium. The control mechanism is configured to control rotations of the fifth and sixth motors. At least one of the fifth and sixth motors includes a clock control motor controlled by a command clock signal and a feedback signal. The control mechanism controls a rotation number of the clock control motor in accordance with a predetermined velocity curve during at least one of rise and fall time periods of the clock control motor.
The fifth motor may include the clock control motor, and the sixth motor includes a stepping motor.
Each of the fifth and sixth motors may include the clock control motor.
The clock control motor may be controlled to be rotated by the command clock signal having the clock number in accordance with the predetermined velocity curve during the at least one of the rise and fall time periods of the clock control motor.
The clock control motor may be controlled to be rotated by the command clock signal having a gradually increasing pulse number during the rise time period, having a substantially constant pulse number during a steady rotation time period, and having a gradually decreasing pulse number during the fall time period.
The novel image forming apparatus may further include a braking mechanism configured to forcedly reduce a rotation number of the clock control motor during the fall time period of the clock control motor.
The rotation number of the clock control motor may be controlled by changing a pulse number of the command clock signal in steps during the at least one of the rise and fall time periods of the clock control motor.
The predetermined velocity curve may be stored in a memory and can be changed by controlling an operation panel of the image forming apparatus or a connecting terminal of the image forming apparatus.
The clock control motor may include a direct current brushless motor.
A novel image forming method includes the steps of energizing an image bearing member with a primary driving member, driving an overlaying member with a secondary driving member, forming a toner image on the image bearing member, moving the toner image with the image bearing member to a transfer position, transferring at least one toner image formed on the bearing member onto the recording sheet driven by the driving step in a single overlaid toner image at the transfer position, and controlling a rotation number of at least one of the primary and secondary driving members with a command clock signal and a feedback signal in accordance with a predetermined velocity curve.
A novel image forming apparatus includes a plurality of color image bearing members, a monochrome image bearing member, an intermediate transfer member, a first gear, a second gear, a seventh motor, an eighth motor, a ninth motor, a transfer mechanism, and a control mechanism. The plurality of color image bearing members have surfaces to bear a plurality of color toner images. The monochrome image bearing member has a surface to bear a monochrome toner image. The intermediate transfer member is configured to receive the plurality of color toner images from the plurality of color image bearing members and the monochrome toner image from the monochrome image bearing member. The first gear is coupled with at least one of the plurality of color image bearing members. The plurality of a second gear coupled with the monochrome image bearing member. The seventh motor includes the clock control motor rotating the at least one of the plurality of color image bearing members via the first gear. The eighth motor includes the clock control motor rotating the monochrome image bearing member via the second gear. The ninth motor rotates the intermediate transfer member. The transfer mechanism is configured to transfer the toner image from the intermediate transfer member to a recording medium. And, the control mechanism is configured to control rotations of the seventh, eighth and ninth motors. The control mechanism controls rotation numbers of the clock control motors during at least one of rise and fall time periods in accordance with a predetermined velocity curve.
A rotation number of at least one of the clock control motors of the seventh and eighth motors may be controlled to be changed to set positions of the first and second gears to have a predetermined phase relationship therebetween, after completion of the rise time periods of the seventh and eighth motors and before start of a subsequent image forming operation.
The control mechanism may have a plurality of operation modes which are selectable and bi-directionally switchable without stopping the eighth and ninth motors. The plurality of operation modes may include a color mode and a monochrome mode. The color mode has a function of producing a full-color image by sequentially overlaying the plurality of color toner images formed on the surfaces of the plurality of color image bearing members and the monochrome toner image formed on the surface of the monochrome image bearing member onto the intermediate transfer member, and onto the recording medium. The monochrome mode has a function of producing a monochrome image by stopping rotations of the plurality of color image bearing members, separating the intermediate transfer member from the plurality of color image bearing members, rotating the monochrome image bearing member, and transferring the monochrome toner image onto the intermediate transfer member, and onto the recording medium.
A rotation number of the at least one of the clock control motors of the seventh and eighth motors may be controlled to be changed to set positions of the first and second gears to have a predetermined phase relationship therebetween, before the subsequent image forming operation starts in the color mode which is previously switched from the monochrome mode.
The control mechanism may have a plurality of switchable surface linear velocities and a plurality of speed modes. The plurality of switchable surface linear velocities may include a first surface linear velocity, and a second surface linear velocity which is slower than the first surface linear velocity, The plurality of speed modes may include a full speed color mode, a low speed color mode, a full speed monochrome mode, and a low speed monochrome mode. The full speed color mode may have a function of rotating the plurality of color image bearing members, the monochrome image bearing member and the intermediate transfer member at the first surface linear velocity in the color mode. The full speed monochrome mode may have a function of rotating the monochrome image bearing member and the intermediate transfer member at the first surface linear velocity in the monochrome mode. The low speed color mode may have a function of rotating the plurality of color image bearing members, the monochrome image bearing member and the intermediate transfer member at the second surface linear velocity in the color mode. The low speed monochrome mode may have a function of rotating the monochrome image bearing member and the intermediate transfer member at the second surface linear velocity in the monochrome mode. The rotation number of the at least one of the clock control motors of the seventh and eighth motors is controlled to be changed to set positions of the first and second gears to have a predetermined phase relationship therebetween, before the subsequent image forming operation starts in one of the full speed color mode and the low speed color mode which is previously changed from different one of the full speed color mode, the low speed color mode, the full speed monochrome mode and the low speed monochrome mode.
The novel image forming apparatus may further include a first sensor and a second sensor. The first sensor is configured to detect a first position of the first gear in a circumferential direction of the first gear. The second sensor is configured to detect a second position of the second gear in a circumferential direction of the second gear. A rotation number of at least one the clock control motors of the seventh and eight motors may be controlled in accordance with a detection time difference between a first time period in which the first sensor detects the first position and a second time period in which the second sensor detects the second position, when the predetermined phase relationship between the first and second gears is adjusted.
The novel image forming apparatus may further include a third sensor, a fourth sensor and a second sensor. The third sensor is configured to detect a third position of the first gear in a circumferential direction of the first gear. The fourth sensor is configured to detect a fourth position of the second gear in a circumferential direction of the second gear. A rotation number of at least one of the clock control motors of the seventh and eight motors may be controlled in accordance with a value obtained by adding a predetermined correction value to a detection time difference between a third time period in which the third sensor detects the third position and a fourth time period in which the fourth sensor detects the fourth position, when the predetermined phase relationship between the first and second gears is adjusted.
The novel image forming apparatus may further include a third sensor and a fourth sensor. The third sensor may be configured to detect a third position of the first gear in a circumferential direction of the first gear. The fourth sensor may be configured to detect a fourth position of the second gear in a circumferential direction of the second gear. A rotation number of at least one of the clock control motors of the seventh and eight motors may be controlled in accordance with a value obtained by adding a predetermined correction value to a detection time difference between a third time period in which the third sensor detects the third position and a fourth time period in which the fourth sensor detects the fourth position, when the predetermined phase relationship between the first and second gears is adjusted.
A rotation number of at least one of the clock control motors of the tenth and eleventh motors may be controlled to be changed to set positions of the third and fourth gears to have a predetermined phase relationship, after completion of the rise time period of the tenth and eleventh motors and before start of a subsequent image forming operation.
The control mechanism may have a plurality of operation modes which are selectable and bi-directionally switchable without stopping the eleventh and twelfth motors. The plurality of operation modes may include a color mode and a monochrome mode. The color mode may have a function of producing a full-color image by sequentially overlaying the plurality of color toner images formed on the surfaces of the plurality of color image bearing members and the monochrome toner image formed on the surface of the monochrome image bearing member onto the recording medium carried by the recording medium bearing member. The monochrome mode may have a function of producing a monochrome image by stopping rotations of the plurality of color image bearing members, separating the recording medium bearing member from the plurality of color image bearing members, rotating the monochrome image bearing member, and transferring the monochrome toner image onto the recording medium carried by the recording medium bearing member.
A rotation number of the at least one of the clock control motors of the tenth and eleventh motors may be controlled to be changed to set positions of the third and fourth gears to have a predetermined phase relationship, before the subsequent image forming operation starts in the color mode which is previously switched from the monochrome mode.
The control mechanism may have a plurality of switchable surface linear velocities and a plurality of speed modes. The plurality of switchable surface linear velocities may include a third surface linear velocity, and a fourth surface linear velocity which is slower than the third surface linear velocity. The plurality of speed modes may include a full speed color mode, a low speed color mode, a full speed monochrome mode, and a low speed monochrome mode. The full speed color mode may have a function of rotating the plurality of color image bearing members, the monochrome image bearing member and the recording medium bearing member at the third surface linear velocity in the color mode. The full speed monochrome mode may have a function of rotating the monochrome image bearing member and the recording medium bearing member at the third surface linear velocity in the monochrome mode. The low speed color mode may have a function of rotating the plurality of color image bearing members, the monochrome image bearing member and the recording medium bearing member at the fourth surface linear velocity in the color mode. The low speed monochrome mode may have a function of rotating the monochrome image bearing member and the recording medium bearing member at the fourth surface linear velocity in the monochrome mode. A rotation number of the at least one of the clock control motors of the tenth and eleventh motors may be controlled to be changed to set positions of the third and fourth gears to have a predetermined phase relationship, before the subsequent image forming operation starts in one of the full speed color mode and the low speed color mode which is previously changed from different one of the full speed color mode, the low speed color mode, the full speed monochrome mode and the low speed monochrome mode.
The novel image forming apparatus further include a fifth sensor and a sixth sensor. The fifth sensor may be configured to detect a fifth position of the third gear in a circumferential direction of the third gear. The sixth sensor may be configured to detect a sixth position of the fourth gear in a circumferential direction of the fourth gear. A rotation number of at least one of the clock control motors of the tenth and eleventh motors may be controlled in accordance with a detection time difference between a fifth time period in which the fifth sensor detects the fifth position and a sixth time period in which the sixth sensor detects the sixth position, when the predetermined phase relationship between the third and fourth gears is adjusted.
The novel image forming apparatus may further include a seventh sensor and an eighth sensor. The seventh sensor may be configured to detect a seventh position of the third gear in a circumferential direction of the third gear. The eighth sensor may be configured to detect an eighth position of the fourth gear in a circumferential direction of the fourth gear. A rotation number of at least one of the clock control motors of the tenth and eleventh motors may be controlled in accordance with a value obtained by adding a predetermined correction value to a detection time difference between a seventh time period in which the seventh sensor detects the seventh position and an eighth time period in which the eighth sensor detects the eighth position, when the predetermined phase relationship between the third and fourth gears is adjusted.
A more complete appreciation of the disclosure and many of the attendant advantages thereof will be readily obtained as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings, wherein:
In describing preferred embodiments illustrated in the drawings, specific terminology is employed for the sake of clarity. However, the disclosure of this patent specification is not intended to be limited to the specific terminology so selected and it is to be understood that each specific element includes all technical equivalents that operate in a similar manner.
Referring now to the drawings, wherein like reference numerals designate identical or corresponding parts throughout the several views, preferred embodiments of the present invention are described.
As described above, the photoconductors 2y, 2c, 2m and 2bk are held in contact with the intermediate transfer member 3, and are rotated in a same direction that the intermediate transfer member 3 travels in
The photoconductor 2 has image forming components for forming an image around it. A charging unit including a charging roller 7 is applied with a charged voltage. When the photoconductor 2 is driven to rotate clockwise in
The intermediate transfer member 3 is held in contact with a primary transfer roller 10 (namely 10y, 10c, 10m, and 10bk) corresponding to the photoconductor 2. The primary transfer roller 10 is disposed opposite to the photoconductor 2, sandwiching the intermediate transfer member 3. The primary transfer roller 10 receives a transfer voltage to transfer the color toner image onto the surface of the intermediate transfer member 3 which is rotated in the direction A. After the toner image formed on the surface of the photoconductor 2 is transferred onto the surface of the intermediate transfer member 3, a cleaning unit 11 removes residual toner on the surface of the photoconductor 2.
Through the operations similar to those as described above, yellow, cyan, magenta and black images are formed on the surfaces of the respective photoconductors 2y, 2c, 2m and 2bk. Those color toner images are sequentially overlaid on the surface of the intermediate transfer member 3, such that a full-color toner image is formed on the surface of the intermediate transfer member 3.
In
The recording medium P that has the full-color toner image thereon is conveyed further upward and passes between a pair of fixing rollers of a fixing unit 17. The fixing unit 17 includes a heat roller 18 having a heater therein and a pressure roller 19 for pressing the recording medium P for fixing the full-color toner image. The fixing unit 17 fixes the full-color toner image to the recording medium P by applying heat and pressure. After the recording medium P passes the fixing unit 17, the recording medium P is discharged by a sheet discharging roller pair 20 to a sheet discharging tray 21 provided at the upper portion of the image forming apparatus 1. After the full-color toner image is transferred onto the recording medium P, a transfer member cleaning unit 22 removes residual toner adhering on the surface of the intermediate transfer member 3. As described above, the image forming apparatus 1 of this embodiment of the present invention performs its image forming operation such that the full-color toner image formed on the photoconductor 2 is transferred onto the intermediate transfer member 3 and then onto the recording medium P to obtain a recorded image.
The above-described image forming operations are performed in a color mode for producing a full-color image on the recording medium P. The image forming apparatus 1 also performs image forming operations in a black-and-white mode for producing a single black-and-white toner image on the recording medium P.
Referring to
In the black-and-white mode, the intermediate transfer member 3 is detached from the surfaces of the photoconductors 2y, 2c and 2m used for producing a full-color toner image and is held in contact with the photoconductor 2bk used for producing a black-and-white toner image. In the black-and-white mode, the photoconductors 2y, 2c, and 2m are not rotated while the photoconductor 2bk is rotated.
The black-and-white toner image is formed on the photoconductor 2bk through the same operations as those for the full-color toner image. The black-and-white toner image formed on the photoconductor 2bk is transferred onto the surface of the intermediate transfer member 3 that is rotated in the direction A in
The recording medium P is also fed from the sheet feeding unit 14, is fed and stopped in synchronization with the registration roller pair 15, and is conveyed to the portion between the supporting roller 4 held in contact with the intermediate transfer member 3 and the secondary transfer roller 16. Consequently, the black-and-white toner image is transferred onto the recording medium P at the portion. The recording medium P also passes through the fixing unit 17. At this time, the black-and-white toner image on the recording medium P is fixed, and is then discharged to the sheet discharging tray 21. In the black-and-white mode, the photoconductors 2y, 2c, and 2m do not operate and are not held in contact with the intermediate transfer member 3. As a result, the photoconductors 2y, 2c, and 2m may be used longer, compared to a case where the photoconductors 2y, 2c, and 2m are held in contact with the intermediate transfer member 3 during an image forming operation of a black-and-white toner image.
The image forming apparatus 1 using the intermediate transfer method as shown in
As described above, the image forming apparatus using the intermediate transfer method according to this embodiment of the present invention includes at least one photoconductor for bearing a toner image and an intermediate transfer member for receiving the toner image formed on the photoconductor, so that the toner image transferred onto the intermediate transfer member onto a recording medium to obtain a recorded image.
Referring to
In
Through the operations similar to those as described in the discussion of
As described above, the image forming apparatus 101 with the direct transfer method of
The image forming apparatus 101 of
As described above, the image forming apparatus 101 using the direct transfer method according to this embodiment of the present invention includes at least one photoconductor for bearing a toner image and a recording medium bearing member for carrying a recording medium for receive the toner image formed on the photoconductor, so that the toner image is directly transferred onto the recording medium bearing member to obtain a recorded image.
Hereinafter, the discussion will be made mainly for structures and functions with respect to the image forming apparatus with the intermediate transfer method. However, structures and functions with respect to the image forming apparatus with the direct transfer method may also be applied to the present invention.
Referring to
As shown in
The image forming apparatus 101 of
The photoconductors 2y, 2c, 2m and 2bk include gears 23y, 23c, 23m and 23bk, respectively. The gears 23y, 23c, 23m and 23bk, which are concentrically coupled with the respective photoconductors 2y, 2c, 2m and 2bk have a common radius and a common number of teeth.
Referring to
The photoconductor 2 is supported by a photoconductor shaft 40 which is concentrically fixed thereto. The photoconductor shaft 40 is connected with a drive shaft 42 via a joint set 41. The joint set 41 includes a first joint set 41a and a second joint set 41b. The first joint set 41a is attached onto a portion of the photoconductor shaft 40 on the side close to the photoconductor 2, and the second joint set 41b is attached onto a portion of the photoconductor shaft 40 on the side close to the gear 23. The drive shaft 42 is concentrically mounted to the photoconductor shaft 40, and is rotatably supported by a frame of the image forming apparatus 1 via first and second shaft bearings 43a and 43b. The drive shaft 42 is also provided with the gear 23 that is also shown in
The photoconductor shaft 40 is rotatably mounted to a housing 45 via a third shaft bearing 44. A process cartridge 46 is formed by a component at least one of the photoconductor 2, the photoconductor shaft 40 corresponding to the photoconductor 2, and the housing 45. In
As shown in
When the photoconductor motor M1 starts, the first output gear 25 rotates counterclockwise in
When the photoconductors 2c and 2m are rotated, the gear 23y, which is meshed with the gear 23c via the intermediate gear 24, is also rotated. Accordingly, the photoconductor 2y is rotated in a same direction as that of the gear 23y and at a same number of rotations as that of the gear 23y. The photoconductor 2y has the same number of rotations as those of the photoconductors 2c and 2m.
Further, when the photoconductor motor M2 starts, the second output gear 26 rotates counterclockwise in
In a case where needed, each of the gears 23y, 23c and 23m coupled with the photoconductors 2y, 2c and 2m, respectively, is hereinafter referred to as a “color gear”, and the gear 23bk coupled with the photoconductor 2bk is hereinafter referred to as a “black-and-white gear.”
Further, as shown in
In
In the image forming system of
In addition to the photoconductor motors M1 and M2, the drive motor DM may also include the clock control motor employing the DC brushless motor. By doing so, the above-described power consumption and noise may further be reduced. Nevertheless, the image forming apparatus 1 of the present invention uses a stepping motor for the drive motor OM because of reasons described below.
Generally, the intermediate transfer member 3 and the recording medium bearing member 103 can be rotated with a small amount of driving force. Accordingly, a small motor is required for the drive motor DM. However, a DC brushless motor which is compact in size and less expensive in cost is not in the market at the present time, so a small-sized stepping motor is reasonable for the driving motor DM to reduce manufacturing costs of the image forming apparatus 1. That is why the stepping motor is employed as the drive motor DM for the image forming apparatus 1.
By controlling the number of input pulses, the stepping motor can correctly control the rotation numbers during a rise time period, a fall time period, and a steady rotation time of the stepping motor.
On the contrary, it is difficult to correctly control the number of rotations of the DC brushless motor during the rise and fall time periods to obtain a desired number of rotations. When a background image forming apparatus uses the DC brushless motor for driving a photoconductor and an intermediate transfer member, a surface linear velocity of the photoconductor and that of the intermediate transfer member contacting the photoconductor may be substantially different during the rise and fall time periods. That is, a surface of the photoconductor rubs that of the intermediate transfer member extremely hard, and thereby the surfaces thereof may be worn away.
To eliminate the problem, tests were conducted and it was found that if the DC brushless motor is controlled to rotate according to a predetermined velocity curve, a substantially desired rotation rate may be obtained during a steady rotation time, a rise time period and a fall time period of the DC brushless motor. That is, the DC brushless motor that rotates at a rate according to the number of clocks of the command clock signal may be constructed such that the DC brushless motor is controlled to rotate during its rise and fall time periods by the command clock signal having the number of input pulses according to the predetermined velocity curve. The number of input pulses represents the number of input pulses generated in a unit time, that is a frequency.
Specifically, the image forming system of
In the image forming system of the image forming apparatus 1 shown in
The easy wearing of the surfaces of the intermediate transfer member 3 and the photoconductors 2y, 2c, 2m and 2bk may also be reduced even if the above-described controls are performed during one of the rise and fall time periods. That is, at least one motor of the photoconductor motors M1 and M2 and the drive motor DM includes the clock control motor, more specifically the DC brushless motor, and a control unit for controlling the number of the clock control motor according to a predetermined velocity curve during at least one of the rise and fall time periods. By using the control unit, the wearing of the intermediate transfer member 3 and the photoconductors 2y, 2c, 2m and 2bk may be reduced and, at the same time, the power consumption and the operation noise may also be reduced. In the image forming apparatus 1, the control circuit 30 and the memory 33 of
As described above, the rotation of the clock control motor is controlled by the command clock signal having the number of input pulses according to the above-described velocity curve during at least one of the rise and fall time periods. More preferably, the rotation of the clock control motor is controlled by the command clock signal having the gradually increasing number of input pulses during the rise time period, by the command clock signal having the constant number of clocks during the steady rotation time, and by the command clock signal having the gradually decreasing number of input pulses during the fall time period. The above-described structure is also applied to the image forming apparatus 101 with the direct transfer method.
Next, a detailed example of the above-described embodiment of the image forming apparatus 1 shown in
The drive motor DM is a stepping motor having specifications shown in Table 1 as described below.
The photoconductor motors M1 and M2 are DC brushless motors. Rotations of the DC brushless motor are controlled according to a velocity curve corresponding to the specifications of the stepping motor that is shown in Table 1.
Generally, a primary frequency F (Hz) is obtained by a formula of:
F=N*Fd;
where “N” represents a natural number, and “Fd” represents a dividing frequency based on the primary frequency. According to the above-described formula, a relationship between a fundamental frequency F (Hz) and a predetermined dividing frequency Fd (Hz) of the image forming apparatus 1 is defined as the above-described formula, F=N*Fd, that is, Fd=F/N.
On the other hand, the dividing frequencies Fd (Hz) of the photoconductor motors M1 and M2 that include the DC brushless motors are obtained by a formula of:
Fd=R*P/60(s);
where “R” represents the number of rotations of the DC brushless motor (rpm), and “P” represents the number of frequency generation (FG) pulses to rotate the DC brushless motor for one cycle. According to the above-described formulae, the primary frequency F (Hz) can be obtained by a formula of:
F=N*R*P/60(s).
That is, the number of rotations of the DC brushless motor (rpm) can be obtained by a formula of:
R=F*60(s)/(P*N).
According to the relationships as described above, the rotation numbers of the photoconductor motors M1 and M2 can be modified by changing the natural number N. Further, by changing the number of pulses (FG pulses) of the command clock signal supplied to the photoconductor motors M1 and M2, the dividing frequency Fd can be controlled to set the rotation numbers of the respective photoconductor motors M1 and M2 to respective desired numbers. Thus, the rotation numbers of the photoconductor motors M1 and M2 are controlled to adjust the surface linear velocities of the photoconductors 2y, 2c, 2m and 2bk.
As an example of the surface linear velocities of the stepping motor used for the image forming apparatus 1, it was assumed the fundamental frequency F is 9830400 (Hz), and the number of FG pulses P is 45. Table 2 shows exemplary results according to the formulae as described above.
Referring to
The rotation speeds of the first and second photoconductor motors M1 and M2 shown as the velocity curves B and C of
A time required for the rise and fall time periods of the first and second photoconductor motors M1 and M2 is 1000 msec, which is the same as the time required to the drive motor DM. The DC brushless motor generally completes its rise time period of approximately 400 msec when a load to the motor drive shaft is 0.8 kgfcm. However, as shown in
In this example, the number of rotations of the photoconductor motors M1 and M2 during the steady rotation time is approximately 1576.33. Accordingly, as shown in Table 2, the natural number during-the steady rotation time of the photoconductor motors M1 and M2 is 8315, the divided frequency is approximately 1182.2489, and the surface linear velocities of the photoconductors 2y, 2c, 2m and 2bk are 155.12 mm/sec.
By controlling the number of clocks of the command clock signal to be supplied to the photoconductor motors M1 and M2 as described above, the surface linear velocities of the photoconductors 2y, 2c, 2m and 2bk may be substantially equal to that of the intermediate transfer member 3 during the steady rotation time, the rise time period, and the fall time period.
When the number of rotations of the DC brushless motor become below a predetermined number of rotation, its control becomes difficult even during the fall time period. To eliminate the problem, as shown in
Referring to
Referring to
As described above, the image forming apparatus 1 of the present invention includes the braking unit forcedly decreasing the speed of the clock control motor, when the number of rotations of the clock control motor becomes equal to or less than a predetermined value at the stop of the clock control motor including the DC brushless motor.
Referring to
As shown in
Referring to
In
Hence, in a period at least one of the start and stop of the clock control motor including the DC brushless motor, the number of clocks of the command clock signal is changed in stages to control the number of rotations of the clock control motor. By doing so, an excessive amount of memory is not required and the cost of the image forming apparatus may be reduced.
Referring to
As previously described, the image forming apparatus 1 shown in
When the above described gears 23y, 23c, 23m and 23bk include a resin material, it is generally mandatory that they have eccentricity to their respective shafts. With such eccentricity, an overlaid full-color image transferred from the photoconductors 2y, 2c, 2m and 2bk onto the intermediate transfer member 3 may have color shift therein. Hence, in the image forming apparatus 1 of the present invention, to prevent the color shift of the overlaid full-color image, the gears 23y, 23c, 23m and 23bk are disposed to have their predetermined phases in the rotation direction of the gears 23y, 23c, 23m and 23bk. It is commonly known that background image forming apparatuses have such structure as described above.
Referring to
As shown in
As described above, the circumferential phases of the gears 23y, 23c, 23m and 23bk and the meshing positions of the intermediate gear 24 and the first and second output gears 25 and 26 that drive the gears 23y, 23c, 23m and 23bk are specified. With this structure, even if the gears 23y, 23c, 23m and 23bk have a slight eccentricity, the overlaid full-color toner image transferred onto the intermediate transfer member 3 may be prevented from color shift. The circumferential phases of the gears 23y, 23c, 23m and 23bk and the meshing positions of the intermediate gear 24 and the first and second output gears 25 and 26 that drive the gears 23y, 23c, 23m and 23bk, as shown in
Here, in the image forming apparatus 1 of the present invention, a color image is produced in the color mode and a black-and-white image is produced in the black-and-white mode, as previously described. In an image forming operation in the color mode, the first photoconductor motor M1 drives the photoconductors 2y, 2c and 2m to-rotate for forming respective single color toner images on the surfaces thereon, and the second photoconductor motor M2 drives the photoconductor 2bk to rotate for forming a black-and-white toner image on the surface thereon. The respective single color toner images and the black-and-white toner image are then transferred onto the intermediate transfer member 3, and onto the recording medium P to obtain a full-color image. Further, in an image forming operation in the black-and-white mode, the first photoconductor motor M1 does not operate the photoconductors 2y, 2c and 2m while the second photoconductor motor M2 drives the photoconductor 2bk to rotate for forming a black-and-white toner image on the surface thereon. The black-and-white toner image is then transferred onto the intermediate transfer member 3, and onto the recording medium P to obtain a black-and-white image. Specifically, while the photoconductors 2y, 2c, 2m and 2bk are held in contact with the intermediate transfer member 3 in the color mode, the photoconductors 2y, 2c, and 2m are separated from the intermediate transfer member 3 and the photoconductor 2bk is held in contact with the intermediate transfer member 3 in the black-and-white mode. The color mode and the black-and-white mode are selectably provided to the image forming apparatus 1 of the present invention.
As previously described, when the image forming operation is performed in-the black-and-white mode, only the photoconductor 2bk is rotated but the photoconductors 2y, 2c and 2m are stopped. Therefore, the gears 23y, 23c, 23m and 23bk shown in
However, the image forming apparatus 1 of the present invention is provided with the feelers Fm and Fbk, and the first and second sensors 34m and 34bk. And, the image forming apparatus 1 also applies the brake on the first and second photoconductor motors M1 and M2 including the DC brushless motor at the stop thereof in the color mode, and it also applies the brake on the second photoconductor motor M2 in the black-and-white mode. Therefore, the gears 23y, 23c, 23m and 23bk and the photoconductors 2y, 2c, 2m and 2bk can be stopped at an approximately same position. By doing so, the previously described relationship of the gears 23y, 23c, 23m and 23bk is prevented from significantly being out of the above-described phase.
However, it is difficult for the above-described braking unit to maintain the relationship of phases of the gears 23y, 23c, 23m and 23bk with a high precision. Therefore, another structure instead of the above-described braking unit is preferably employed for adjusting the relationship of phases-of the gears 23y, 23c, 23m and 23bk.
As previously described with reference to
As described above, the image forming apparatus 1 includes the first sensor 34m for detecting the first position in the circumferential direction of the gear 23m (in
More specifically, when the color gears 23y, 23c and 23m and the black-and-white gear 23bk are correctly arranged to maintain the above-described respective predetermined phases for preventing the color shift and are rotated at the steady rotation, a reference time lag generated between a time when the first sensor 34m detects the feeler Fm and a time when the second sensor 34bk detects the feeler Fbk, which is defined as “ΔT”. The time lag ΔT may include an appropriate number including zero (0). In this example, the reference time lag ΔT is set to zero. And, before adjusting the actual phases, according to a time difference between the time lag Δt and the reference time lag ΔT (zero in this example), the number of clocks of-the command clock signal to be supplied from the control circuit 30 to the first and second photoconductor motors M1 and M2 is increased or decreased. By doing so, the number of the photoconductor motors M1 and M2 can be controlled and the relationship of the phases of the gears 23y, 23c, 23m and 23bk are adjusted as described above. Then, the numbers of rotations of the photoconductor motors M1 and M2 are returned to those for the steady rotations to perform the image forming operations. With this structure, a color shift may be reduced and a high quality image may be obtained. When the time difference between the time lag Δt and the reference time lag ΔT is defined as a sensor detection time lag ΔS, the sensor detection time lag ΔS of the image forming apparatus 1 of the present invention may be equal to the time lag Δt.
As described above, the control unit including the control circuit 30 is configured such that when adjusting the relationship of the phases of the color gears 23y, 23c and 23m and the black-and-white gear 23bk, according to the time lag generated between a time when the first sensor 34m detects the first position and a time when the second sensor 34bk detects the second position, the number of rotations of at least one of the photoconductor motors M1 and M2. The control unit controls by changing the number of rotations of at least one of the first and second photoconductor motors M1 and M2 the color photoconductors 2y, 2c and 2m, so that the predetermined relationship of the phases of the color gears 23y, 23c and 23m and the black-and-white gear 23bk may be obtained in a period after the first and second photoconductor motors M1 and M2 are stopped and before the next image forming operation is started, that is, before the first and second photoconductor motors M1 and M2 steadily rotate.
Referring to
In Step S1 of
In Step S4 of
In Step S5 of
In Step S6 of
In Step S7 of
In Step S8 of
In Step S9 of
In Step S10 of
In Step S11 of
For example, when the sensor detection time lag ΔS is less than 40 ms in Step S4 or when the sensor detection time lag ΔS is equal to or more than 570 ms and less than 610 ms, the gears 23y, 23c, 23m and 23bk are, fox example, approximately ±22.5 degrees and are rarely out of phases. Accordingly, it is determined that the operation states of the gears 23y, 23c, 23m and 23bk are regarded as being within a regular range and the process is completed. Here, a time of 610 ms indicates a time required for one cycle of the photoconductor 2bk. When the sensor detection time lag ΔS makes any value indicated in Steps S5 through 10, one of the following processes C1 through C6 is performed according to the value. Rates (%) indicated below represent a rotation rate of each photoconductor during the steady rotation time:
As described above, when the second sensor 34bk does not detect the feeler Fbk before the first sensor 34m detects the feeler Fm and when the determination result in Step S3 is NO, the procedure goes to Step S12.
In Step S12, it is determined whether the first sensor 34m detects the feeler Fm before the second sensor 34bk detects the feeler Fbk. When the first sensor 34m detects the feeler Fm before the second sensor 34bk detects the feeler Fbk and when the determination result in Step S12 is YES, the procedure goes to Steps S13 through 520 of
In Step S13 of
In Step S14 of
In Step S15 of
In Step S16 of
In Step S17 of
In Step S18 of
In Step S19 of
In Step S20 of
Similar to the processes of Steps S4 through S11, when the sensor detection time lag ΔS makes any value indicated in Steps S14 through 19, one of the following processes B1 through B6 is performed according to the value. When the sensor detection time lag ΔS is less than 40 ms and when the sensor detection time lag ΔS is equal to or more than 570 ms and less than 610 ms, the phase adjusting process is completed.
As previously described, to increase and decrease the numbers of rotations of the gears 23y, 23c, 23m and 23bk and the respective photoconductors 2y, 2c, 2m and 2bk, the numbers of rotations of the first and second photoconductor motors M1 and M2 during the steady rotation time are controlled to be changed. The photoconductor motors M1 and M2 are then rotated at the changed numbers of rotations to adjust the phases of the gears 23y, 23c, 23m and 23bk. After adjusting the phases of the gears 23y, 23c, 23m and 23bk, the changed numbers of rotations of the photoconductor motors M1 and M2 are changed back to their original numbers of rotations during the steady rotation time to perform the image forming operations.
Table 3 shows the above-described sensor detection time lag ΔS, an angular difference with respect to the sensor detection time lag ΔS, and fluctuation in the numbers of rotations of the respective photoconductor motors for correcting the sensor detection time lag ΔS.
Referring to
As shown in
In the example as described above, the numbers of rotations of the first and second photoconductor motors. M1 and M2 are controlled according to the values of the sensor detection time lag ΔS to adjust the phases of the gears 23y, 23c, 23m, and 23bk to the predetermined states at short times. As an alternative, the number of rotations of one of the photoconductor motors M1 and M2 may be controlled. Table 4 shows the sensor detection time lag ΔS, an angular difference with respect to the sensor detection time lag ΔS, and fluctuation in the number of rotations of the photoconductor motor for correcting the sensor detection time lag ΔS.
Referring to
The number of rotation may be changed every time the sensor detection time lag ΔS is detected, to make the number of rotation set back to the number of rotation of the photoconductor motor M1 for its steady rotation time (a rated number of rotations).
Referring to
The above-described phase adjustment may be performed when the image forming operation in the black-and white mode is completed and that in the color mode is restarted. However, when the phase adjustment is performed when the image forming operation is started in the color mode and in the black-and-white mode, the gears 23y, 23c, 23m and 23bk may be configured to constantly have their desired phases, and thereby the image produced may be of high quality.
When the above-described braking unit is employed, the braking unit may stop the first position of the gear 23m in the vicinity of the first sensor 34m when the photoconductor motor M1 stops, and may stop the second position of the gear 23bk in the vicinity of the second sensor 34bk when the photoconductor motor M2 stops. Accordingly, if the braking unit and the above-described phase adjusting structure may be used together, when the photoconductor motors M1 and M2 start their rotations, the first and second positions of the gears 23m and 23bk are disposed at respective positions close to the first and second sensors 34m and 34bk, respectively. With this structure, the sensors 34m and 34bk detect the first and second positions, respectively, at short times. Thereby, the phases of the photoconductors 2y, 2c, 2m and 2bk may be adjusted at short times.
The image forming apparatus 1 of the present invention is Delectably provided with the color mode and the black-and-white mode, as described above. With a background image forming apparatus, a plurality of image forming operations including some jobs in the color mode and other Jobs in the black-and-white mode cannot sequentially be performed. That is, when a job performed in the color mode is completed, the photoconductor motors M1 and M2 and the drive motor DM are stopped once. Next, the photoconductors 2y, 2c, 2m and 2bk and the intermediate transfer member 3 are stopped. After that, the second photoconductor motor M2 and the drive motor DM are started again to start another job in the black-and-white mode. This structure, however, increases the number of ON and OFF operations to start the photoconductor motors M1 and M2 and the drive motor DM. Every time the ON and OFF operations are performed, the gears 23y, 23c, 23m and 23bk receive impacts caused by the ON and OFF operations, and thereby the gears 23y, 23c, 23m and 23bk may deteriorate in durability.
To eliminate the above-described inconvenience, the image forming apparatus of the present invention includes a structure such that the mode may bi-directionally be switched between the color mode and the black-and-white mode without stopping the second photoconductor motor M2 and the drive motor DM.
For example, assume that ten jobs of the image forming operations are sequentially performed, where the first five jobs are performed in the color mode before the other five jobs are performed in the black-and-white mode. Firstly, the first and second photoconductor motors M1 and M2 and the drive motor DM of
When switching the mode from the black-and-white mode to the color mode, the second photoconductor motor M2 and the drive motor DM are started, and the image forming operations are performed in the black-and-white mode. After the jobs in the black-and-white mode are completed, the first photoconductor motor M1 is started while the second photoconductor motor M2 and the drive motor DM keeps their rotations, and then the jobs are performed in the color mode.
With the structure as described above, the number of the ON and OFF operations and the impacts made to the resin-based gears 23y, 23c, 23m and 23bk may be reduced, and thereby the lives of the gears 23y, 23c, 23m and 23bk may be made long.
Further, the image forming apparatus 1 with the direct transfer method shown in
Assuming that the image forming mode is switched from the black-and-white mode to the color mode without stopping the second photoconductor motor M2 and the drive motor DM, as described above if the drive unit has a structure that the number of rotations of one of the first and second photoconductor motor M1 and M2 may be controlled to obtain the predetermined phases of the color gears 23y, 23c and 23m before starting the image forming operation in the color mode, the image forming operation in the color mode may produce a full-color image without the color shift. The phase adjusting operation may be performed in the same manner as the operations previously described with regard to
The image forming apparatus 1 shown in
Referring to
When the speed mode is changed from the high speed mode HM to the low speed mode LM, the first and second photoconductor motors M1 and M2 and the drive motor DM are still activated without stopping. At this time, in a period IS, which is a predetermined period before the surface linear velocity of the photoconductor is stably controlled to the low speed V2, the surface linear velocities of the photoconductors 2y, 2c and 2m and that of the photoconductor 2bk may become drastically different to each other, according to an over shoot of the photoconductors 2y, 2c, 2m and 2bk. When such difference occurs, the gears 23y, 23c, 23m and 23bk may drastically be out of phase, and the color shift may occur in the subsequent color mode. The above-described inconvenience may occur when the speed mode is changed from the low speed mode to the high speed mode.
Accordingly, when the image forming operation is performed in the color mode, by changing the speed mode without stopping the second photoconductor motor M2 and the drive motor DM, the phase adjustment of the gears 23y, 23c, 23m and 23bk needs to be done. To avoid the above-described necessity, the image forming apparatus 1 of the present invention has the structure as described below.
The image forming apparatus 1 of
As previously described, the mode may be changed without stopping the second photoconductor motor M2 and the drive motor DM. When the changed mode is the full speed color mode or the low speed color mode, the control unit may be configured to control the change of the rotation number-of at least one motor of the first and second photoconductor motors M1 and M2 to obtain the predetermined phases of the gears 23y, 23c, 23m and 23bk before starting the image forming operation in the changed mode.
With the above-described structure, the full-color image produced at the last stage of the image forming operation may be prevented from the color shift even when the mode is changed from the black-and-white mode to the color mode.
Referring to
At t0 of
During a period of t3, which is a time after the starting operation of the photoconductor motors M1 and M2 and the drive motor DM are completed, the phase adjusting operations of the gears 23y, 23c, 23m and 23bk are performed, which is same as shown in
At t5, the numbers of rotations of the first and second photoconductor motors M1 and M2 and the drive motor DM are decreased so that the surface linear velocities of the photoconductors 2y, 2c and 2m and the intermediate transfer member 3 the second surface linear velocity V2. In a period of t6, the phase adjusting operations of the gears 23y, 23c, 23m and 23bk are performed. In the example shown in
In a period of t7, the image forming operation is performed in the low speed color mode, which is a combination of the low speed mode and the color mode. At t8, as shown in
Subsequently, in a period of t10, the image forming operation is performed in the low speed black-and-white mode, which is a combination of the low speed mode and the black-and-white mode. During the period of t10, the phase adjusting operation of the gears 2y, 2c and 2m are not performed before this image forming operation.
Next, at t11, the surface linear velocities of the photoconductor 2bk and the intermediate transfer member 3 are started to increase. At t12, the surface linear velocities of the photoconductor 2bk and the intermediate transfer member 3 are returned to the first surface linear velocity V1. At this moment, the phase adjusting operation of the photoconductor 2bk and the intermediate transfer member 3 is not performed. Subsequently, in a period of t13, the image forming operation is performed in the full speed black-and-white mode, which is a combination of the high speed and the black-and-white mode.
At t14, the first photoconductor motor M1 starts the rotation, and at tl5, the starting operation of the photoconductor motor M1 completes. The starting operation at t5 also takes approximately 1000 msec. Subsequently, in a period of t16, the phase adjusting operation of the gears 23y, 23c, 23m and 23bk is performed. At t17, the intermediate transfer member 3 contacts the photoconductors 2y, 2c and 2m. After the intermediate transfer member 3 and the photoconductors 2y, 2c and 2m are held in contact with each other at t17, the image forming operation is performed in the full speed color mode, which is a combination of the high speed mode and the color mode.
The intermediate transfer member 3 may contact with the photoconductors 2y, 2c and 2m while the phase adjusting operation is performed. With the structure, however, a great impact is given onto the surfaces of the gears 23y, 23c, 23m and 23bk to promote the wearing. Accordingly, as shown in
The above-described structure may be applied to the image forming apparatus 1 with the direct transfer method as shown in
Referring to
Here, the curve C1 of
In fact, the curves representing the deflections of the pitch circles of the gears 23bk and 23m rarely approximate to each other as shown in
In such cases, when the phase of the curve C4 is shifted by an amount of a color shift angle Y as shown in
More specifically, the image forming operation may be controlled as shown in Table 5 described below instead of Table 3 which is previously described.
Referring to
As previously described, the photoconductor motors M1 and M2 and the drive motor DM may include the DC brushless motor. In this case, when the photoconductor motors M1 and M2 and the drive motor DM are started, the command clock signal having the number of clocks gradually increasing as shown in
Referring to
When the photoconductor motors M1 and M2 and the drive motor DM including the DC brushless motor are started, the command clock signal having the number of clocks gradually increasing as indicated by reference characters g, h and i as shown in
Referring to
In the above-described examples, the first photoconductor motor M1 controls the rotations of the photoconductors 2y, 2c and 2m, the second photoconductor motor M2 controls the rotation of the photoconductor 2bk. As an alternative, a drive method of each photoconductor may have another drive method. For example, as shown in
In the image forming apparatus 1 as shown in
At least one motor of the above-described photoconductor motors M3, M4, M5 and M6 and the drive motor DM includes the clock control motor including the DC brushless motor, and the DC brushless motor is controlled as described above. With this structure, when the photoconductor motors M3, M4, M5 and M6 and the drive motor DM are started and stopped, a significantly different value between the surface linear velocities of the photoconductors 2y, 2c, 2m and 2bk and that of the intermediate transfer member 3 are prevented. Other basic structures are the same as the structures of the image forming apparatus as shown in
In addition, the present invention may be applied to the image forming apparatus 1 which forms a single toner image on one photoconductor, transfers the single toner image onto a recording medium carried by the recording medium bearing member, and repeats the same image forming operations for four times to complete one full-color toner image.
Referring to
The image forming apparatus described here, which includes a gear 27 concentrically fixed to the photoconductor 2, is engaged with an output gear 25 of the photoconductor motor M. The photoconductor motor M drives the photoconductor 2 clockwise in
A recording medium bearing member 3b which is an endless belt extended by supporting rollers 4a and 5a. The supporting roller 5a includes a gear 27b which is concentrically coupled threrewith. The gear 27b is engaged with an output gear 28b of the drive motor DM. The drive motor DM drives the recording medium bearing member 3b in a direction A as shown in
A recording medium P which is fed from a sheet feeding unit (not shown) is carried by the recording medium bearing member 3b and is conveyed to a transferring unit (not shown). The transferring unit transfers the single color toner image formed on the surface of the photoconductor 2 onto the recording medium P. After the image forming operations for transferring the different single color toner images onto the recording medium P are performed for four times and the full-color toner image is formed on the recording medium P, the recording medium P is separated from the recording medium bearing member 3b and passes through a fixing unit, where the full-color toner image is fixed onto the recording medium P.
At least one motor of the photoconductor motor M and the drive motor DM includes a clock control motor including a DC brushless motor, and the DC brushless motor is controlled the same way as previously described. With this structure, when the photoconductor motor M and the drive motor DM are started, stopped, and stably rotated, a significantly different value between the surface linear velocities of the photoconductor 2 and that of the recording medium bearing member 3b is prevented.
In the image forming apparatus as described above, the number of rotations of the DC brushless motor is controlled according to a predetermined velocity curve. The predetermined velocity curve is recorded in the memory 33, for example, a nonvolatile memory, as shown in
The present invention may be widely used for an image forming apparatus other than a printer, that is, a copying machine, a facsimile machine, and a multifunction machine.
Numerous additional modifications and variations are possible in light of the above teachings. It is therefore to be understood that within the scope of the appended claims, the disclosure of this patent specification may be practiced otherwise than as specifically described herein.
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