JP4447729B2 - Image forming apparatus - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an image forming apparatus, and more particularly, to an image forming apparatus such as a printer, a copier, or a facsimile machine that drives an image carrier or a moving body with a vibration wave motor that is a driving means with good rotational accuracy.
[0002]
[Prior art]
Conventionally, a driving means with good rotational accuracy, such as a vibration wave motor, has a piezoelectric element bonded to one side of an elastic body made of metal, for example, in an annular shape, and a driving element formed on the piezoelectric element. By applying alternating voltages having different phases to the piezoelectric element group, two standing waves are excited on the elastic body, and a progressive vibration wave that is a bending vibration is formed by combining these standing waves. Meanwhile, on the other surface side of the elastic body, for example, an annular member is pressed through a pressing means such as a spring, and the member is moved by frictional driving by a progressive vibration wave formed on the elastic body. It was moved or the elastic body was moved. The drive circuit has a drive pulse generator for generating an AC wave and a control system for feeding back the rotational speed of the motor from an encoder attached to the motor.
[0003]
This vibration wave motor has good rotation accuracy and is strong against transient load fluctuations, and is advantageous for color misalignment, pitch unevenness, and paper feed shock. Therefore, at present, the photosensitive drum and transfer belt of image forming apparatuses such as copiers are used. It is being used for driving.
[0004]
[Problems to be solved by the invention]
However, it is an image forming apparatus that uses a vibration wave motor as a driving means for the transfer belt and the photosensitive drum, and the transfer belt and the photosensitive drum are stopped when a plurality of vibration wave motors that respectively drive the stop and In an image forming apparatus that is non-contact at the time of start-up / falling of the drive, contacts a plurality of vibration wave motors after shifting to constant speed rotation, and leaves while performing constant speed rotation, vibration waves The control gain of the motor control system was set to a constant value during drive start-up / down and constant-speed rotation of the vibration wave motor, or switched between drive start-up / fall-down and constant speed rotation Since there are two values, there is no control margin for sudden load increase that occurs at the moment when the transfer belt and the photosensitive drum come into contact with each other. It had to be stopped.
[0005]
SUMMARY OF THE INVENTION The present invention solves the above-mentioned conventional problems, and its object is to provide a control margin against sudden load increase that occurs at the moment when the image carrier and the moving body come into contact with each other, without causing an error stop. An image forming apparatus is provided.
[0006]
[Means for Solving the Problems]
In order to achieve the above object, a representative configuration according to the present invention includes a rotatable image carrier, a transfer belt that is rotatable while carrying a toner image or a recording material, and an image carrier that faces the transfer belt. A transfer means for transferring the toner image formed thereon; a vibration wave motor for driving the image carrier and the transfer belt; and a control means for controlling the vibration wave motor in a closed loop. When the drive is stopped, when the drive is started up, and when the drive is turned off, the transfer belt and the image carrier are separated from each other, and the transfer belt rotates at a constant speed after the vibration wave motor starts up. in the transfer belt and the image image forming apparatus and carrying member abuts when driving, the acceleration gain provided in the section of the drive start-up operation of the vibration wave motor, the next section of the acceleration gain And a contact gain provided in a section including a timing at which the image carrier and the transfer belt contact each other when the transfer belt rotates at a constant speed, and a section next to the contact gain. And an image forming gain provided in a section until the vibration wave motor starts decelerating, so that the control means controls the vibration wave motor, and the image carrier, the transfer belt, Is separated during the image forming gain section, and the response of the image forming gain is set to be tighter than the response of the acceleration gain, so that the transfer belt and the image carrier are separated from each other. The vibration wave motor is set to be drivable, and the contact gain responsiveness is set to be the loosest among the acceleration gain, the contact gain, and the image forming gain.
[0007]
In the above configuration, when the moving body is brought into contact with the image carrier after the vibration wave motor shifts to the constant speed driving, driving by the control gain for the moving body prevents the sudden load increase due to the contact. However, it has a control margin. Therefore, stable image formation can be performed without stopping the error.
[0008]
DETAILED DESCRIPTION OF THE INVENTION
Next, an image forming apparatus according to an embodiment of the present invention will be described with reference to the drawings.
[0009]
[First Embodiment]
FIG. 1 is an explanatory longitudinal sectional view showing the overall configuration of a four-color full-color copying machine which is an aspect of a color electrophotographic image forming apparatus according to the first embodiment.
[0010]
{Overall configuration of image forming apparatus}
First, the overall configuration of the color image forming apparatus will be described with reference to FIG. In the color image forming apparatus shown in FIG. 1, a reading apparatus A and a recording apparatus B are integrally configured, and a color that forms a color image on a transfer material P by a recording apparatus B based on document information read by the reading apparatus A. It is configured as a copier.
[0011]
The reading device A irradiates the original placed on the platen glass 1 with light from the light source 2 and causes the reflected light to reach the photoelectric conversion element 5 via the mirrors 3 a, 3 b, 3 c and the lens 4. To convert it into a digital electrical signal. The light source 2 and the mirror 3a are mounted on the first carriage 6, and the mirrors 3b and 3c are mounted on the second carriage 7 and move in the direction of arrow a when reading the document.
[0012]
A document supply device 8 for supplying documents one by one onto the platen glass 1 is attached to the top of the platen glass 1. Instead of the document feeder 8, a document pressure plate that presses the document onto the platen glass 1 may be attached.
[0013]
The electric signal read by the reading device A is transmitted to the recording device B via the image processing unit 9 and the interface unit 10, and a color image is recorded on the transfer material there. In this recording apparatus B, four image forming units Y, M, C, and K are arranged in parallel in the horizontal direction, and the upstream side (right side in FIG. 1) of the transfer material P in the conveyance direction to the downstream side (left side in FIG. 1). ), Toner images of respective colors of yellow Y, magenta M, cyan C, and black K are formed in order.
[0014]
That is, the photosensitive drum 11 (11Y, 11M, 11C, 11K) is provided as an image carrier. The photosensitive drum 11 is rotationally driven in a clockwise direction in FIG. 1 by a driving means (not shown). A charging means 12 (12Y, 12M, 12C, 12K) for uniformly charging the surface of the photosensitive drum 11 in order according to the rotation direction, and a laser beam is irradiated around the photosensitive drum 11 based on image information. A scanner unit 13 (13Y, 13M, 13C, 13K) that forms an electrostatic latent image on the drum 11, and developing means 14 (14Y, 14M, 14C, 14K) that attaches toner to the electrostatic latent image and develops it as a toner image. ), A transfer member 15 (15Y, 15M, 15C, 15K) constituted by a transfer roller for transferring the toner image on the photosensitive drum 11 to a transfer material is disposed.
[0015]
Next, the configuration of each unit will be described sequentially. Since the four image forming units have the same configuration, here, one image forming unit will be described as an example.
[0016]
The photoconductor drum 11 is configured by applying an organic photoconductive layer (OPC photoconductor) to the outer peripheral surface of an aluminum cylinder, for example. Both ends of the photosensitive drum 11 are rotatably supported by a support member, and the driving force from the vibration wave motor 50 (50Y, 50M, 50C, 50K) is transmitted to one end thereof. It is rotated clockwise in the figure.
[0017]
The charging unit 12 uniformly charges the surface of the photosensitive drum 11, and forms an electrostatic latent image on the surface of the photosensitive drum 11 charged by the charging unit 12 by exposure from the scanner unit 13. Is. The scanner unit 13 is composed of an LED array with a short focus imaging lens (not shown) attached to the tip, and the LED is controlled to be turned on according to an image signal by a driving circuit (not shown), which selects the surface of the charged photosensitive drum 11 Exposure is performed to form an electrostatic latent image.
[0018]
The developing means 14 is composed of a developing unit containing color toner corresponding to the image forming color. During development, the toner in the toner container 14a of the corresponding developing unit is fed to the application roller 14b by a feeding mechanism, and a magnet 14c is built in. A thin layer of toner is applied to the outer periphery of the rotating developing roller 14d, and a charge is applied to the toner (friction charging). By applying a developing bias between the developing roller 14d and the photosensitive drum 11 on which the electrostatic latent image is formed, toner is attached to the electrostatic latent image and developed as a toner image.
[0019]
The developed toner image is transferred onto the transfer material P by applying a transfer bias to the transfer member 15. In order to sequentially transfer the transfer material P to the toner image transfer position by the respective image forming means, the photosensitive drum 11 and the transfer means are in contact with the four photosensitive drums 11Y, 11M, 11C, and 11K. A transfer conveyance belt 16, which is an endless belt-like moving body that circulates between the transfer members 15, is provided. This transfer / conveying belt 16 constitutes a conveying means for conveying the transfer material.
[0020]
The upstream side of the transfer conveyance belt 16 is supported by a driven roller 17 as a first support member, and the downstream side is supported by a drive roller 18 as a second support member, and is supported by tension rollers 19 and 20 that apply appropriate tension. Has been. Then, it is driven to rotate by a vibration wave motor 51 drivingly connected to the shaft end of the driving roller 18. Further, an adsorption charger 21 is provided on the upstream side (right side in FIG. 1) of the transfer conveyance belt 16 in the conveyance direction. When the transfer material P is conveyed, a bias voltage is applied to the adsorption charger 21 to generate an electrostatic adsorption force on the transfer conveyance belt 16, and the transfer material P is adsorbed to the belt 16 and conveyed. ing.
[0021]
In order to form an image with the image forming apparatus, the transfer material P stored in the cassettes 22a and 22b is separated and fed one by one by the feeding rollers 23a and 23b according to the size, and transferred and conveyed by the conveying roller pair 24. Adsorbed to the belt 16 and conveyed from the upstream side to the downstream side. At this time, the leading edge sensor 31 detects the leading edge of the transfer material P and also detects the number of transfer materials P to be conveyed. The detection signal of the tip sensor 31 is used to monitor the image forming timing required when switching the control of the respective vibration wave motors 50 and 51 for driving the photosensitive drum 11 and the driving roller 18. Then, each image forming unit forms a toner image of each color of yellow, magenta, cyan, and black in synchronization with the conveyance of the transfer material P, and the toner image is transferred to the transfer material P conveyed by the transfer conveyance belt 16. By sequentially superimposing and transferring, a color image is formed on the transfer material.
[0022]
Note that the image forming apparatus according to the present embodiment does not include a cleaning unit for the photosensitive drum 11 and the transfer conveyance belt because the toner transfer efficiency to the transfer material P is good. However, such a cleaning unit may be provided. Needless to say.
[0023]
The transfer material P on which the color image has been transferred as described above is transported by the transfer transport belt 16, neutralized by the charge eliminating charger 25, and then separated from the transfer transport belt 16. In addition, a peeling charger 26 is provided adjacent to the charge eliminating charger 25 so as to prevent image disturbance due to peeling discharge when the transfer material P is separated from the transfer conveyance belt 16.
[0024]
Then, the transfer material P separated from the transfer conveyance belt 16 is charged by the pre-fixing charger 27 to supplement the toner adsorption force to prevent image disturbance, and is passed through the fixing means 28 to be thermally fixed, and the discharge roller It discharges to the discharge part 30 of the apparatus upper part by 29.
[0025]
In the image forming apparatus according to the present embodiment, the transfer conveyance belt 16 is not in contact with the photosensitive drum 11 when the driving of the vibration wave motors 50 and 51 is stopped, when the driving is started, and when the driving is started. When the vibration wave motors 50 and 51 are driven at a constant speed, the transfer / conveying belt 16 contacts or is separated from the photosensitive drum 11. Here, the “contact” means not only the case where the photosensitive drum 11 and the transfer conveyance belt 16 are in direct contact but also the case where the transfer material P is interposed therebetween.
[0026]
{Drive control of vibration wave motor}
Next, drive control of the vibration wave motors 50 and 51 for driving the photosensitive drum 11 and the transfer conveyance belt 16 will be described. Here, the vibration wave motor 51 that drives the transfer conveyance belt will be described as an example.
[0027]
The driving of the vibration wave motor 51 is to perform closed loop control as shown in FIG. 2, and from a rotary encoder 60 attached to the vibration wave motor 51 as a monitoring means for monitoring the rotational speed of the vibration wave motor 51. Then, the speed difference detection unit 61 detects the speed difference from the target speed, which is the target value of the rotational speed of the vibration wave motor 51. The speed difference is input into the drive frequency generation unit 62 and given to the frequency control unit 63. The drive frequency generated by the frequency controller 63 is input to the drive pulse generator 64 to generate a drive pulse. The target speed value that is the target value of the rotational speed of the vibration wave motor 51, the initial frequency that is the drive frequency at the start of driving of the vibration wave motor 51, the control gain of the frequency control unit 63, and the drive generated by the drive pulse generation unit 64 As for the pulse width of the pulse, the value stored in the RAM 65 is taken into the register 66 and sent to each block. The drive pulse output from the drive pulse generator 64 is input to an AC voltage generator 67 mainly composed of a transformer. The AC voltage generator 67 is input to the piezoelectric element group in the vibration wave motor 51 and has different phases. Generate voltage. By applying this AC voltage to the piezoelectric element group in the vibration wave motor 51, two standing waves are excited on the elastic body, and a progressive vibration wave, which is a flexural vibration, is generated by combining these standing waves. Form. Meanwhile, on the other surface side of the elastic body, for example, an annular member is pressed through a pressing means such as a spring, and the member is moved by frictional driving by a progressive vibration wave formed on the elastic body. The vibration wave motor 51 rotates by moving or moving the elastic body.
[0028]
The vibration wave motor 50 for driving the photosensitive drum is also controlled by the same configuration.
[0029]
As shown in FIG. 3, trapezoidal driving is used to drive the vibration wave motor 51 that drives the transfer conveyance belt. However, as described above, the conventional vibration wave motor control method is consistent when the vibration wave motor is driven. When taking one control gain, or when accelerating / decelerating (starting / falling) the vibration wave motor, a loose control gain is set, and at constant speed (constant speed rotation), position accuracy and speed accuracy are guaranteed. A tight control gain may have been set.
[0030]
However, as in this embodiment, the transfer / conveyor belt and the photosensitive drum are not contacted when the vibration wave motor that drives them is stopped, and when the vibration wave motor is started up / down, and the vibration wave motor shifts to constant speed rotation. That are separated from each other while moving at a constant speed, responds excessively to load fluctuations that generate the maximum load torque when the transfer conveyance belt and the photosensitive drum come into contact, and stops error There was a case.
[0031]
Therefore, in the present embodiment, with respect to the control gain of the vibration wave motor 51 for driving the transfer conveyance belt 51, when the vibration wave motor 51 is started up / down (acceleration / deceleration gain), the transfer conveyance belt 16 and the photosensitive drum 11 are in contact with each other. After the vibration wave motor 51 including the time shifts to constant speed rotation until after the contact between the transfer conveyance belt 16 and the photosensitive drum 11 (contact gain), the subsequent transfer conveyance belt 16 and the photosensitive drum 11 contact each other. The vibration wave motor 51 is set to have a different value during the constant rotation (gain during image formation).
[0032]
Even when the same vibration wave motor is in a constant speed state, the transfer conveyance belt 16 and the photosensitive drum 11 can be switched from the contact gain that is set most loosely to the image formation gain that guarantees appropriate position accuracy and speed accuracy for image formation. A control margin is also created for a sudden load increase at the time of contact. For this reason, the error stop does not occur due to the load, and image formation with an appropriate control gain can be performed even during image formation after contact.
[0033]
In this embodiment, the acceleration / deceleration gain, the contact gain, and the image forming gain have different values. However, the acceleration gain and the deceleration gain do not necessarily coincide with each other, and at least the vibration wave What is necessary is just to set so that the acceleration gain at the time of starting of the motor 51, the contact gain, and the image forming gain have different values.
[0034]
[Second Embodiment]
Next, an image forming apparatus using a moving body as an intermediate transfer body will be described as a second embodiment. FIG. 4 is an explanatory longitudinal sectional view showing the overall configuration of the four-color full-color laser beam printer according to the second embodiment. Note that members having the same functions as those of the first embodiment described above are denoted by the same reference numerals and description thereof is omitted.
[0035]
The electrophotographic image forming apparatus is provided with four photosensitive drums 11 (11Y, 11M, 11C, and 11K) that are four drum-shaped image carriers, as in the image forming apparatus of the first embodiment described above. . Since the process of forming images on the four photosensitive drums is the same as that described in the image forming apparatus of the first embodiment, the description thereof will be omitted, and the description will be given starting from the intermediate transfer belt 41 as a moving body.
[0036]
Opposing each photoconductor drum 11, an endless intermediate transfer belt 41 is stretched and disposed by a driving roller 42 and driven rollers 43 and 44.
[0037]
Then, the photosensitive drum 11 and the driving roller 42 are driven by the vibration wave motors 50 and 51 in the same manner as in the first embodiment, and the driving of the vibration wave motors 50 and 51 is stopped, the driving is started, and the falling is stopped. In some cases, the transfer conveyance belt 16 is not in contact with the photosensitive drum 11, and the transfer conveyance belt 16 is in contact with or separated from the photosensitive drum 11 when the vibration wave motors 50 and 51 are driven at a constant speed. It is configured.
[0038]
The toner image formed on the photoreceptor drum 11Y comes into contact with the intermediate transfer belt 41 due to its rotation, and a predetermined bias is applied to the transfer member 15Y disposed on the back surface of the intermediate transfer belt 41, thereby intermediate transfer. Primary transfer is performed on the belt 41. Thereafter, the same process is repeated with the remaining three photosensitive drums 11M, 11C, and 11K and the transfer members 15M, 15C, and 15K, and a four-color toner image is formed on the intermediate transfer belt 41 by a series of operations.
[0039]
Then, the toner image formed on the intermediate transfer belt 41 is moved to the secondary transfer unit 45, and is then collectively transferred onto the transfer material conveyed at a predetermined timing by the registration roller pair 47 by the secondary transfer roller 46. Transcribed.
[0040]
The process of transporting the transfer material P to the secondary transfer unit 45 and the process of fixing the toner image transferred onto the transfer material are the same as in the case of the image forming apparatus of the first embodiment, and a description thereof will be omitted.
[0041]
Also in the image forming apparatus using the intermediate transfer belt 41, the same effect as that of the above-described embodiment can be obtained by controlling the vibration wave motors 50 and 51 in the same manner as in the above-described embodiment.
[0042]
【The invention's effect】
Since the present invention is configured as described above, when the moving body is brought into contact with the image carrier after the vibration wave motor shifts to the constant speed driving, driving by the control gain for the moving body makes sudden movement due to contact. A control margin is also provided for an increase in load. Therefore, stable image formation can be performed without stopping the error.
[Brief description of the drawings]
FIG. 1 is an explanatory longitudinal cross-sectional view showing the overall configuration of a four-color full-color copying machine that is an aspect of a color electrophotographic image forming apparatus according to a first embodiment.
FIG. 2 is a block diagram showing a drive control configuration of a vibration wave motor.
FIG. 3 is an explanatory diagram of a drive control gain of a vibration wave motor.
FIG. 4 is an explanatory longitudinal cross-sectional view showing the overall configuration of a four-color full-color laser beam printer according to a second embodiment.
[Explanation of symbols]
A ... Reading device B ... Recording device P ... Transfer material 1 ... Platen glass 2 ... Light sources 3a, 3b, 3c ... Mirror 4 ... Lens 5 ... Photoelectric conversion element 6 ... First carriage 7 ... Second carriage 8 ... Document feeder 9 ... Image processor
10… Interface section
11… Photoreceptor drum
12 ... Charging means
13… Scanner section
14 ... Developing means
14a ... Toner container
14b ... Application roller
14c… Magnet
14d: Developing roller
15… Transfer member
16 Transfer transfer belt
17… driven roller
18… Drive roller
19, 20… tension roller
21… Adsorption charger
22a, 22b ... cassette
23a, 23b ... Feed roller
24… Conveying roller pair
25 ... Static elimination charger
26… Peeling charger
27… Pre-fixing charger
28… Fixing means
29… discharge roller pair
30… discharge section
31… Advanced sensor
41 ... Intermediate transfer belt
42… Drive roller
43, 44… driven roller
45 ... Secondary transfer section
46… Secondary transfer roller
47… Registration roller pair
50, 51… Vibration wave motor
60… Rotary encoder
61 Speed difference detector
62… Drive frequency generator
63 ... Frequency control unit
64… Drive pulse generator
65… RAM
66… Register
67… AC voltage generator

Claims (1)

A rotatable image carrier, a transfer belt that is rotatable while carrying a toner image or a recording material, a transfer unit that transfers a toner image formed on the image carrier toward the transfer belt, and the image carrier A vibration wave motor for driving the body and the transfer belt, and a control means for controlling the vibration wave motor in a closed loop, and when the vibration wave motor is stopped, when the drive is started up and when the drive is turned off, the transfer is performed. The belt and the image carrier are separated from each other, and the transfer belt and the image carrier are in contact with each other when the transfer belt is driven at a constant speed after the start-up operation of the vibration wave motor. In the image forming apparatus in contact,
Acceleration gain provided in the drive start-up operation section of the vibration wave motor, and provided in the section next to the acceleration gain, and when the transfer belt rotates at a constant speed, the image carrier and the transfer A contact gain provided in a section including a timing of contact with the belt, an image forming gain provided in a section next to the contact gain, and provided in a section until the vibration wave motor starts deceleration; Is set, the control means controls the vibration wave motor,
The separation between the image carrier and the transfer belt is performed during the image gain section,
The responsiveness of the image forming gain is set to be tighter than the responsiveness of the acceleration gain, and the vibration wave motor is set to be drivable even when the transfer belt and the image carrier are separated from each other.
The image forming apparatus according to claim 1, wherein the responsiveness of the contact gain is set most loosely among the acceleration gain, the contact gain, and the image forming gain.

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