JP2001296754A - Image forming device - Google Patents

Abstract

(57) [Problem] To provide an image forming apparatus which has a control margin for a sudden increase in load and does not cause an error stop. A photosensitive drum (11) and a belt member (16) are driven by vibration wave motors (50, 51).
The belt member 16 is not in contact with the photosensitive drum 11 when the drive is stopped, when the drive is started, and when the drive is stopped, the vibration wave motor
When the belt members 16 are in contact with or separated from the photosensitive drum 11 when the motors 50 and 51 are driven at a constant speed, the vibration wave motors 50 and 51 are driven by closed loop control, and the value of the control gain is such that the motor is driven. The acceleration gain at the time of startup and the belt member 16 and the photosensitive drum after the motor shifts to the constant speed drive
The contact gain until after the contact of 11 and the image forming gain at the time of constant speed drive from the contact between the belt member 16 and the photosensitive drum 11 to the time when the drive of the motor is lowered are configured to take different values. It is characterized by the following.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field 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 copying machine, a facsimile machine, etc., which drives an image carrier or a moving body by a vibration wave motor which is a driving means having good rotational accuracy. About.

[0002]

2. Description of the Related Art Conventionally, a driving means having good rotational accuracy, for example, a vibration wave motor, has a piezoelectric element adhered to one side of an elastic body made of metal, for example, in an annular shape with an adhesive and formed on the piezoelectric element. By applying alternating voltages having different phases to the driving piezoelectric element groups thus driven, two standing waves are excited on the elastic body, and the combination of these standing waves leads to a progressive vibration which is a bending vibration. Form a wave. On the other hand, on the other surface side of the elastic body, for example, a ring-shaped 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 has been moved or the elastic body has been moved. Further, the drive circuit has a drive pulse generator for generating an AC wave, and a control system for feeding back the rotation speed of the motor from an encoder attached to the motor.

[0003] This vibration wave motor has good rotation accuracy and is resistant to transient load fluctuations, and is advantageous for color shift, pitch unevenness, and paper feed shock. Therefore, at present, the photosensitive drum of an image forming apparatus such as a copying machine is used. And transfer belts.

[0004]

However, an image forming apparatus using a vibration wave motor as a driving means for the transfer belt and the photosensitive drum, wherein the transfer belt and the photosensitive drum respectively drive the transfer belt and the photosensitive drum It is non-contact at the time of stopping of multiple vibration wave motors and at the time of start-up / falling of the drive, and the multiple vibration wave motors come into contact after shifting to constant speed rotation and separate while performing constant speed rotation. In an image forming apparatus, the control gain of the control system of the vibration wave motor is set to a constant value during the start-up / fall-down of the vibration wave motor and during the constant-speed rotation, or at the time of start-up / fall-off of the drive. And the constant speed rotation, and the two values are taken. Therefore, control is performed against a sudden increase in load generated at the moment when the transfer belt contacts the photosensitive drum. There is no Yutaka, had to be error stop at the load weight.

An object of the present invention is to solve the above-mentioned conventional problems, and an object of the present invention is to provide a control margin against a sudden increase in load generated at the moment when an image carrier and a moving body come into contact with each other.
An image forming apparatus that does not cause an error stop is provided.

[0006]

A typical configuration according to the present invention for achieving the above object is an image forming apparatus for transferring an image on an image carrier to a moving body or a transfer material carried on the moving body. In driving the image carrier and the moving body provided between the image carrier and the transfer unit, the image carrier and the moving unit provided between the image carrier and the transfer unit may be driven. The body is driven by a vibration wave motor, and when the vibration wave motor stops driving, when the drive starts up and when the drive falls, the moving body is not in contact with the image carrier, and the vibration wave motor is driven at a constant speed. When the moving body is in contact with or separated from the image carrier, and the vibration wave motor is driven by closed loop control, the control gain value is an acceleration gain at the time of starting the drive of the motor; After shifting to constant speed drive The contact gain between the movable body and the image carrier after contact is different from the contact gain between the movable body and the image carrier after the contact between the movable body and the image carrier and the image forming gain at the time of constant speed drive from the time when the drive of the motor is shut down. It is characterized by taking a value.

In the above configuration, when the moving body is brought into contact with the image carrier after the vibration wave motor has shifted to the constant speed driving, the moving gain is driven by a control gain for that purpose, so that a sudden load due to the contact is obtained. The control has a margin for the increase. Therefore, without stopping with an error,
Stable image formation can be performed.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, an image forming apparatus according to an embodiment of the present invention will be described with reference to the drawings.

[First Embodiment] FIG. 1 is an explanatory longitudinal sectional view showing the overall structure of a four-color full-color copying machine which is one mode of a color electrophotographic image forming apparatus according to a first embodiment.

{Overall Configuration of Image Forming Apparatus} First, the overall configuration of a 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 formed, and a color apparatus which forms a color image on a transfer material P in a recording apparatus B based on document information read by the reading apparatus A is provided. It is configured as a copying machine.

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 3a, 3b, 3c and the lens 4. The element 5 converts the signal into a digital electric signal. The light source 2 and the mirror 3a are mounted on a first carriage 6, and the mirrors 3b and 3c are mounted on a second carriage 7, and move in the direction of arrow a when reading a document.

A document feeder 8 for feeding documents one by one onto the platen glass 1 is mounted on the upper portion of the platen glass 1. Note that, instead of the document feeder 8, a document pressure plate for pressing a document onto the platen glass 1 may be attached.

The electric signal read by the reading device A is transmitted to a recording device B via an image processing section 9 and an interface section 10, where a color image is recorded on a transfer material. This recording apparatus B has four image forming units Y, M, C, and K arranged in a horizontal direction, and is arranged from the upstream side (the right side in FIG. 1) in the transport direction of the transfer material P to the downstream side (the left side in FIG. 1). ), Toner images of respective colors of yellow Y, magenta M, cyan C, and black K are sequentially formed.

That is, the photosensitive drums 11 (11Y, 11M, 11C, 11K) as image carriers are provided.
The photosensitive drum 11 is driven by driving means (not shown).
It is driven to rotate clockwise in FIG. Photoconductor drum
The charging means 12 (12Y, 12M, 12M) for uniformly charging the surface of the photosensitive drum 11 in order according to the rotation direction around the photosensitive drum 11
C, 12K), a scanner unit 13 for irradiating a laser beam based on image information to form an electrostatic latent image on the photosensitive drum 11
(13Y, 13M, 13C, 13K), developing means 14 (14Y, 14K) for attaching toner to the electrostatic latent image and developing it as a toner image.
M, 14C, 14K) and a transfer member 15 (15) composed of a transfer roller for transferring the toner image on the photosensitive drum 11 to a transfer material.
Y, 15M, 15C, and 15K).

Next, the configuration of each part will be described sequentially.
Since the four image forming units have the same configuration, only one image forming unit will be described here as an example.

The photoreceptor drum 11 is formed, for example, by applying an organic photoconductive layer (OPC photoreceptor) to the outer peripheral surface of an aluminum cylinder. The photosensitive drum 11 has both ends rotatably supported by support members, and has a vibration wave motor 50 (50Y, 50M, 50C, 50K) at one end.
By transmitting the driving force from the motor, the motor is driven to rotate clockwise in the figure.

The charging means 12 charges the surface of the photosensitive drum 11 uniformly, and the surface of the photosensitive drum 11 charged by the charging means 12 is exposed to an electrostatic latent image by exposure from a scanner unit 13. Is formed. The scanner unit 13 is composed of an LED array having a short focus imaging lens (not shown) mounted on the tip thereof, and the lighting of the LEDs is controlled by a drive circuit (not shown) according to an image signal, thereby selecting the charged surface of the photosensitive drum 11. Exposure to form an electrostatic latent image.

The developing means 14 is constituted by a developing device containing a color toner corresponding to an image forming color. At the time of development, the toner in the toner container 14a of the corresponding developing device is sent to the application roller 14b by a feeding mechanism, and the magnet 14c is turned on. A thin layer of toner is applied to the outer periphery of the developing roller 14d which is built and rotated, and a charge is applied to the toner (frictional 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.

Then, the developed toner image is transferred to the transfer member 15.
Is transferred to the transfer material P by applying a transfer bias to the transfer material P. The four photosensitive drums for sequentially transporting the transfer material P to the toner image transfer positions of the respective image forming means;
11Y, 11M, 11C, 11K
A transfer / conveying belt 16 which is an endless belt-like moving member that circulates between the transfer member 11 and a transfer member 15 as a transfer unit is provided. The transfer transport belt 16 constitutes a transport unit that transports the transfer material.

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. Supported by 20. Then, the driving roller 18 is driven and rotated by a vibration wave motor 51 that is drivingly connected to the shaft end. Further, an adsorption charger 21 is provided on the upstream side of the transfer conveyance belt 16 in the conveyance direction (the right side in FIG. 1). When the transfer material P is transported, a bias voltage is applied to the attraction charger 21 to generate an electrostatic attraction force on the transfer transport belt 16 so that the transfer material P is attracted to the belt 16 and transported. ing.

In order to form an image by the above-described image forming apparatus, the transfer materials P stored in the cassettes 22a and 22b are separated and fed one by one by feeding rollers 23a and 23b according to the size. Transfer belt by
It is adsorbed by 16 and transported from upstream to downstream. At this time, the leading end sensor 31 detects the leading end of the transfer material P,
The number of transferred transfer materials P is detected. The tip sensor
The detection signal of 31 is used to monitor the image forming timing required when the control of the respective vibration wave motors 50 and 51 for driving the photosensitive drum 11 and the driving roller 18 is switched. Then, each image forming unit forms a yellow, magenta, cyan, and black toner image in synchronization with the transfer of the transfer material P, and transfers the toner image to the transfer material P that is transferred by the transfer transfer belt 16. A color image is formed on the transfer material by successively superimposing and transferring.

The image forming apparatus according to the present embodiment employs a transfer material P
Although cleaning means for the photosensitive drum 11 and the transfer / conveying belt is not provided because the toner transfer efficiency to the toner is high, it goes without saying that such a cleaning means may be provided.

The transfer material P on which the color image has been transferred as described above is conveyed by the transfer / conveyance belt 16, and is discharged from the transfer / conveyance belt 16 after the charge is removed by the charge removal charger 25.
In addition, a peeling charger 26 is provided adjacent to the charge removing 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.

The transfer material P separated from the transfer / conveying belt 16 is charged by a pre-fixing charger 27 so as to supplement the toner attraction force to prevent image disturbance, and to pass through the fixing means 28 for heat fixing. Then, the sheet is discharged to a discharge section 30 at the upper portion of the apparatus by a discharge roller pair 29.

In the image forming apparatus of this embodiment, when the driving of the vibration wave motors 50 and 51 is stopped, when the driving is started and when the driving is stopped, the transfer conveyance belt 16 is in non-contact with the photosensitive drum 11. The transfer conveyance belt 16 is configured to come into contact with or separate from the photosensitive drum 11 when the vibration wave motors 50 and 51 are driven at a constant speed. here,
The term "contact" means not only the case where the photosensitive drum 11 and the transfer / conveying belt 16 are in direct contact, but also the case where the transfer material P is interposed between the two.

{Driving Control of Vibration Wave Motor} Next, the drive control of the vibration wave motors 50 and 51 for driving the photosensitive drum 11 and the transfer / transport belt 16 will be described. Here, the vibration wave motor 51 for driving the transfer conveyance belt will be described as an example.

The driving of the vibration wave motor 51 is for performing a closed loop control as shown in FIG. 2, and a rotary means attached to the vibration wave motor 51 as monitoring means for monitoring the rotation speed of the vibration wave motor 51. From the encoder 60, a speed difference detection unit 61 detects a speed difference from a target speed which is a target value of the rotation speed of the vibration wave motor 51. The speed difference is input into the drive frequency generation section 62 and given to the frequency control section 63. The drive frequency generated by the frequency controller 63 is input to the drive pulse generator 64 to generate a drive pulse. Vibration wave motor
Target speed value, which is the target value of 51 rotation speed, vibration wave motor
The initial frequency, which is the driving frequency at the start of driving of 51, the control gain of the frequency control unit 63, and the pulse width of the driving pulse generated by the driving pulse generation unit 64 are obtained by loading the value stored in the RAM 65 into the register 66 and reading each block Sent to The drive pulse output from the drive pulse generator 64 is input to an AC voltage generator 67 mainly composed of a transformer, and the AC voltage generator
67 generates AC voltages having different phases which are input to the piezoelectric element group in the vibration wave motor 51. 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 by combining these standing waves, a progressive vibration wave that is a bending vibration is generated. Form. On the other hand, on the other surface side of the elastic body, for example, a ring-shaped 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. By moving or moving the elastic body, the vibration wave motor 51 rotates.

A vibration wave motor for driving the photosensitive drum
50 is also controlled by a similar configuration.

As shown in FIG. 3, a trapezoidal drive is used to drive the vibration wave motor 51 for driving the transfer / transport belt.
As described above, the conventional vibration wave motor control method is to loosen the vibration wave motor when driving one drive gain or when accelerating or decelerating (starting / falling) the vibration wave motor. In the case of constant speed (constant speed rotation), there is a case where a tight control gain that guarantees position accuracy and speed accuracy is set.

However, as in the present embodiment, the transfer / transport belt and the photosensitive drum are not in contact with each other when the vibration wave motor for driving each of the belts is stopped and when the vibration motor is started / falled.
When the vibration wave motor moves to constant speed rotation and then comes into contact and then separates while performing constant speed rotation, the maximum load torque is generated when the transfer conveyance belt and the photosensitive drum contact. In some cases, the machine stopped responding to excessive load fluctuations and stopped with an error.

Therefore, in the present embodiment, the control gain of the vibration wave motor 51 for driving the transfer conveyance belt is described with respect to the transfer conveyance belt 16 and the photosensitive drum 11 when the vibration wave motor 51 rises / falls (acceleration / deceleration gain). Vibration wave motor including contact
After the transfer of the transfer belt 51 and the photosensitive drum 11 (contact gain) until the transfer conveyor belt 16 and the photosensitive drum 11 come into contact with each other, the vibration wave motor It is configured to have different values during the period when 51 rotates at a constant speed (gain during image formation).

Even when the vibration wave motor is at a constant speed, the transfer conveyance belt 16 and the photosensitive belt can be connected to each other by switching from the loosest contact gain to the image forming gain that guarantees appropriate position accuracy and speed accuracy for image formation. A control margin is also provided for a sudden increase in load when the body drum 11 abuts. For this reason, the error stop does not occur due to the heavy load, and the image can be formed with an appropriate control gain even during the image formation after the contact.

In this embodiment, an example has been shown in which the acceleration / deceleration gain, the abutment gain, and the image forming gain have different values. However, the acceleration gain and the deceleration gain do not necessarily have to match. At least the acceleration gain at the time of starting the vibration wave motor 51, the contact gain, and the imaging gain may be set to have different values.

[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 in the first embodiment described above are denoted by the same reference numerals, and description thereof is omitted.

This electrophotographic image forming apparatus employs the first
Similarly to the image forming apparatus of the embodiment, the photosensitive drums 11 (11Y, 11M, 11C, 11K) as four drum-shaped image carriers are provided.
Are juxtaposed. The process of forming images on the four photosensitive drums is the same as the description of the image forming apparatus of the first embodiment, and thus the description thereof will be omitted, and the description will be made from the part of the intermediate transfer belt 41 as a moving body.

An endless intermediate transfer belt 41 is arranged opposite to each photosensitive drum 11 by being stretched by a driving roller 42 and driven rollers 43 and 44.

The photosensitive drum 11 and the driving roller 42 are connected to the vibration wave motor 50, as in the first embodiment.
When the driving of the vibration wave motors 50 and 51 is stopped, when the driving is started and when the driving is stopped, the transfer conveyance belt 16 is driven.
Is not in contact with the photosensitive drum 11, and the vibration wave motor 5
The transfer / conveying belt 16 is configured to come into contact with or separate from the photosensitive drum 11 when the reference numerals 0 and 51 are driven at a constant speed.

The toner image formed on the photosensitive drum 11Y comes into contact with the intermediate transfer belt 41 by its rotation, and a predetermined bias is applied to the transfer member 15Y disposed on the back surface of the intermediate transfer belt 41. Is primarily transferred onto the intermediate transfer belt 41. Hereinafter, three photosensitive drums 11M, 11C, 11K and transfer members 15M, 15C,
The process is repeated at 15K, and a toner image of four colors is formed on the intermediate transfer belt 41 by a series of operations.

Then, the toner image formed on the intermediate transfer belt 41 is moved to a secondary transfer section 45, and is collectively moved by a secondary transfer roller 46 onto a transfer material conveyed at a predetermined timing by a pair of registration rollers 47. Is secondarily transcribed.

The process of transporting the transfer material P to the secondary transfer portion 45 and the process of fixing the toner image transferred to the transfer material are the same as in the case of the image forming apparatus of the first embodiment, and will not be described. I do.

In the image forming apparatus using the intermediate transfer belt 41, the same effects as in the above-described embodiment can be obtained by controlling the driving of the vibration wave motors 50 and 51 in the same manner as in the above-described embodiment. Can be.

[0042]

The present invention is constructed as described above.
When the moving object comes into contact with the image carrier after the vibration wave motor shifts to constant speed driving, it is driven by the control gain for that purpose, so that there is control margin even for sudden load increase due to contact. become. For this reason, stable image formation can be performed without error stop.

[Brief description of the drawings]

FIG. 1 is an explanatory longitudinal sectional view showing an overall configuration of a four-color full-color copying machine, which is one mode 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 sectional view showing an 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 source 3a, 3b, 3c: Mirror 4: Lens 5: Photoelectric conversion element 6: First carriage 7: Second carriage 8: Document supply device 9 ... Image processing section 10 ... Interface section 11 ... Photoreceptor drum 12 ... Charging means 13 ... Scanner section 14 ... Developing means 14a ... Toner container 14b ... Coating roller 14c ... Magnet 14d ... Developing roller 15 ... Transfer member 16 ... Transfer and transport belt 17 … Follower roller 18… Driving rollers 19, 20… Tension roller 21… Adsorption charger 22a, 22b… Cassette 23a, 23b… Feeding roller 24… Carrier roller pair 25… Static eliminator 26… Peeling charger 27… Charging before fixing Unit 28 fixing means 29 discharge roller pair 30 discharge unit 31 tip sensor 41 intermediate transfer belt 42 drive rollers 43 and 44 driven rollers 45 secondary transfer unit 46 secondary rotation Copying roller 47… Registration roller pair 50, 51… Vibration wave motor 60… Rotary encoder 61… Speed difference detector 62… Drive frequency generator 63… Frequency controller 64… Drive pulse generator 65… RAM 66… Register 67… AC Voltage generator

Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat II (reference) H02N 2/00 H02N 2/00 C 5H680 F term (reference) 2H027 DA17 EE04 EE07 EF06 EF07 EF09 EF13 2H030 AA01 AB02 AD05 AD17 BB02 BB23 BB42 BB44 2H032 AA02 AA05 BA01 BA09 BA18 BA23 CA02 CA13 2H035 CA07 CB01 CG01 2H071 CA02 CA05 CA07 EA18 5H680 BB02 BC04 BC05 CC04 EE21 EE23 FF23 GG32

Claims (9)

[Claims] 1. An image forming apparatus for transferring an image on an image carrier to a moving body or a transfer material carried on the moving body, wherein the image forming apparatus is provided between the image carrier and the transfer means. In driving the moving body, the image carrier and the moving body provided between the image carrier and the transfer unit are driven by a vibration wave motor, and when the driving of the vibration wave motor is stopped, the driving is started. The moving body is in non-contact with the image carrier at the time of falling and when the moving body is in contact with or separated from the image carrier when the vibration wave motor is driven at a constant speed; The wave motor is driven by the closed loop control, and the value of the control gain is the acceleration gain at the time of starting the drive of the motor, and from the time when the motor shifts to the constant speed drive until after the contact between the moving body and the image carrier. Contact gain of the moving object and image An image forming apparatus, wherein the image forming apparatus is configured to take different values depending on an image forming gain at the time of constant speed driving from the time of contact with a carrier to the time of a drive fall of the motor. 2. The vibration wave motor is driven by closed-loop control, and the control gain value is the acceleration / deceleration gain at the time of startup and shutdown of the drive of the motor, and after the motor is shifted to the constant speed drive. The contact gain between the moving body and the image carrier after contact is different from the contact gain between the contact between the moving body and the image carrier and the imaging gain at the time of constant-speed driving from the time when the drive of the motor is shut down. The image forming apparatus according to claim 1, wherein the image forming apparatus is configured to take a value. 3. The image forming apparatus according to claim 1, further comprising monitor means for monitoring a rotation speed of the vibration wave motor, and having a rotary encoder as the monitor means. 4. The image forming apparatus according to claim 1, further comprising monitor means for monitoring a rotation speed of said vibration wave motor, and a closed loop control system for feeding back an output signal from said monitor means. 5. A frequency control unit that frequency-controls a speed difference between a target speed which is a target value of a rotation speed of the vibration wave motor and a rotation speed of the vibration wave motor, and generates a drive frequency having a target speed. The image forming apparatus according to claim 1, further comprising: 6. The image forming apparatus according to claim 5, further comprising a drive pulse generator that generates a drive pulse having a drive frequency generated by said frequency controller. 7. The image forming apparatus according to claim 6, further comprising a drive frequency generation unit including the frequency control unit and the drive pulse generation unit. 8. A target speed which is a target value of a rotation speed of the vibration wave motor, a pulse width of the drive pulse, an initial frequency which is a drive frequency at the start of driving of the vibration wave motor, and a control gain of a frequency control unit. The image forming apparatus according to claim 7, wherein is set in a RAM. 9. The image forming apparatus according to claim 1, wherein a plurality of the image carriers are arranged to record a color image.