JP2005345906A - Rotary drive apparatus and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve the problem that an image becomes light and dark at a fixed interval to cause density unevenness and image deterioration, when variations in the speed occurs on a surface of a photoreceptor drum due to cause oscillation or the like, due to the rotational drive of a driving motor for rotating a photoreceptor drum or an oscillation caused by the engagement of gears or belts of a driving transmission system. <P>SOLUTION: The rotary driving apparatus is provided with an inertial ring 11 with inertia moment which is loosely fitted to an outer periphery of a driving shaft 2; and a magnetic viscous fluid 10, sealed between the outer periphery of the driving shaft 2 and an inner periphery of the inertial ring 11 and with viscosity varying by the application of a magnetic field. A dynamic damper 9 is formed by the inertial ring 11 and the magnetic viscous fluid 10. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a rotary drive device and an image forming apparatus, and more particularly, to a rotary drive device in all technical fields, and a rotary drive device in an electrophotographic laser printer, copying machine, facsimile machine, plotter, printing machine, and the like. The present invention relates to an image forming apparatus.

In an electrophotographic image forming apparatus including a photosensitive drum and a transfer drum, a dynamic vibration absorber (dynamic damper) is formed by providing an inertial body, an elastic element, and a damping element inside the transfer drum, and the natural vibration of the drive system There is known a technique for reducing vibration by actively absorbing water (see Patent Document 1).
On the other hand, in the technical field of bearing devices that can maintain a constant bearing gap or set an arbitrary bearing gap in response to a load change, the shaft and the bearing are provided via a voltage controller that can change the voltage. By applying an electric field to the electrode and controlling the viscosity of the electrorheological fluid that lubricates between the shaft and the bearing, the viscous resistance of the flow in the bearing gap can be controlled freely, and the load capacity, flying height, rigidity, etc. can be controlled. A technique capable of controlling an arbitrary value in real time is known (see Patent Documents 2 and 3).

  In the technical field of viscous damper devices that attenuate vibrations in the rotational direction of the rotating shaft, the damper case is filled with an inertial body and a magnetorheological fluid, and the magnetic force applied to the magnetorheological fluid by the magnetizing means is changed. A technique is also known in which the damping constant with respect to the rotating shaft can be made variable to thereby attenuate the vibration in the rotating direction of the rotating shaft (see Patent Document 4).

JP-A-11-52764 Japanese Patent Laid-Open No. 3-24316 Japanese Patent No. 2635171 JP 2003-35337 A

  One of the factors that hinders the high image quality of electrophotography is a phenomenon called jitter or banding. “Jitter” or “banding” refers to a defect phenomenon in which a striped pattern is generated in an image due to a change in the rotational speed of the photosensitive drum, taking an example of the photosensitive drum in the image forming apparatus. In particular, image quality has been improved by the introduction of digital technology. In recent years, position accuracy for each line of laser writing is strictly required, and one of the factors governing this is a photoconductor due to torsional vibration of a rotary drive system. Drum speed fluctuation can be mentioned. Therefore, the reduction of torsional vibration in this rotational drive system is an important technology for the development of products capable of obtaining high quality images.

  The relationship between the visual sensitivity of images and the spatial frequency is said to be easily noticeable when the spatial frequency of visualization is in the range of about 0.3 to 2 line / mm (line / millimeter) due to the characteristics of the human visual system. . Considering this and the rotational speed of the photosensitive drum, it is required to avoid vibration in a frequency range of several Hz (hertz) to several hundred Hz.

  The configuration of the rotational drive system of the image forming apparatus to which the present invention is applied includes a photosensitive drum as an example of a rotating body, its driving shaft, a driving motor (driving means) for rotating the photosensitive drum via the driving shaft, and It has a drive transmission system (drive transmission means) that transmits the drive force of the drive motor to the drive shaft, and vibrations due to the rotation of the drive motor and vibrations due to the engagement of gears and belts that are the drive transmission system occur. This causes speed fluctuations on the surface of the photosensitive drum. When the surface speed fluctuation of the photosensitive drum occurs in this way, the image becomes light and shade at regular intervals, resulting in density unevenness.

  As means for solving the density unevenness due to the surface speed fluctuation of the photosensitive drum, the technique described in Patent Document 1 (Japanese Patent Application Laid-Open No. 11-52764) is focused on the point that a flexible dynamic damper is formed with a simple configuration. As a result, it is impossible to form a flexible dynamic damper with a simple configuration because changing the spring constant of the elastic element and the damping factor of the damping element involves changing and attaching the elastic element and damping element. There is a problem. In addition, by providing an inertial body, an elastic element, and a damping element inside the transfer drum, there are problems that the number of components increases and that the mounting method is complicated and troublesome.

  Although the techniques described in Patent Documents 2 and 3 (Japanese Patent Laid-Open No. 3-24316 and Japanese Patent No. 2635171) can control the viscosity of an electrorheological fluid with a simple configuration, in the end, a flexible dynamic damper is formed. Therefore, density unevenness due to fluctuations in the surface speed of the photosensitive drum cannot be solved.

  In the technique described in Patent Document 4 (Japanese Patent Laid-Open No. 2003-35337), the vibration in the rotational direction of the rotating shaft can be attenuated by making the damping constant variable, but in the end, a flexible dynamic damper is formed. Therefore, density unevenness due to fluctuations in the surface speed of the photosensitive drum cannot be solved. Further, since the damper case is filled with the inertial body and the magnetorheological fluid, there is a problem that the configuration is complicated and the inertial moment of the inertial body is not efficiently exhibited.

  Therefore, the present invention pays attention to the above points, and the inner periphery and the outer periphery of a drive system such as a roller bearing of a drive shaft with respect to a drive system such as a photosensitive drum or an intermediate transfer member that is a rotating body and an image carrier. Is a part that can rotate independently, and proposes a simple structure that can obtain the effect of a dynamic vibration absorber (sealing damper) in which a magnetorheological fluid is sealed (sealed) and an inertial body is placed on the outer periphery. In particular, it is a first object of the present invention to obtain a vibration reduction effect and a speed fluctuation reduction effect of a photoconductor including a photoconductor drum which is a main inertial body and an intermediate transfer body by a vibration absorption effect by a flexible dynamic damper, thereby reducing image deterioration. It is aimed.

  Furthermore, in a rotational drive device of any technical field, a dynamic vibration absorber (dynamic damper) in which a magnetorheological fluid is sealed (sealed) inside a portion corresponding to a bearing (bearing) of a drive shaft and an inertial body is disposed on the outer periphery. The second object of the present invention is to obtain a vibration reduction effect and a speed fluctuation reduction effect of a rotating body that is a main inertial body by a vibration absorption effect by a flexible dynamic damper.

In order to solve the above-described problems and achieve the above-described object, the invention for each claim employs the following characteristic means and invention-specific matters (hereinafter referred to as “configuration”).
The invention according to claim 1 includes a rotating body, a driving shaft of the rotating body, a driving means for rotating the rotating body via the driving shaft, and a drive transmission means for transmitting the driving force of the driving means to the driving shaft. In the rotary drive device provided, an inertial body loosely fitted on the outer periphery of the drive shaft and having an inertial moment is sealed between the outer periphery of the drive shaft and the inner periphery of the inertial body, and the viscosity is increased by applying a magnetic field. A dynamic vibration absorber is formed by the inertial body and the magnetorheological fluid.
In the rotary drive device according to the first aspect of the present invention, the “rotary body” may be any shape as long as it solves the above-described problems and achieves the following effects and advantages in order to achieve the above-described object. Any rotating body is included.

The “rotary driving device including a driving shaft of the rotating body, a driving unit that rotates the rotating body via the driving shaft, and a driving transmission unit that transmits the driving force of the driving unit to the driving shaft” includes a driving unit (for example, a driving motor). ), But also includes a structure that is directly connected to the drive shaft via a drive transmission means (for example, coupling, bolt / nut coupling, etc.) with a simple structure, or a structure that is directly connected without a coupling or the like. Is also included.
In a configuration in which the rotating body is rotatably supported around a support shaft as a driving shaft via a bearing or the like, for example, a driving means (for example, a driving motor) is connected to a gear or pulley attached to an end plate or the like of the rotating body. Drive means (via a gear that is attached to the side and meshes with the gear, or a drive means such as a pulley attached to a drive means (for example, an output shaft of a drive motor) and an endless belt stretched between the pulleys. For example, the structure which transmits the driving force of a drive motor to a rotary body is also included.

According to a second aspect of the present invention, in the rotary drive device according to the first aspect, the inertial body has a substantially ring shape.
Here, “substantially ring-shaped” means that it includes a ring-shaped shape, and includes a ring-shaped shape having a certain degree of unevenness within a tolerance range in design, for example.
According to a third aspect of the present invention, in the rotary drive device according to the first or second aspect, a magnetic field applying means for applying the magnetic field is disposed in the vicinity of the magnetorheological fluid.

According to a fourth aspect of the present invention, in the rotary drive device according to the third aspect, the magnetic field applying means is a coil that generates the magnetic field, and includes a circuit including a power source that supplies current to the coil. .
According to a fifth aspect of the present invention, in the rotary drive device according to the third aspect, the magnetic field applying means is a permanent magnet that generates the magnetic field.
According to a sixth aspect of the present invention, in the rotary drive device according to the third, fourth, or fifth aspect of the present invention, the rotary drive device further includes a magnetic field varying unit that changes the strength of the magnetic field.

A seventh aspect of the present invention is the rotary driving apparatus according to the sixth aspect, wherein the magnetic field varying means is a current adjusting means for adjusting a current flowing through the coil.
Instead of changing the strength of the magnetic field by adjusting the current by the current adjusting means, it may be a voltage adjusting means that changes (adjusts) the current flowing through the coil through changing the voltage applied to the coil. The voltage adjusting means is equivalent to the current adjusting means in terms of function.

The invention according to claim 8 is the rotary drive apparatus according to claim 6, wherein the magnetic field varying means is a distance adjusting means for changing a distance of the permanent magnet with respect to the magnetorheological fluid.
According to a ninth aspect of the present invention, in the rotary drive device according to any one of the third to eighth aspects, the magnetic field applied by the magnetic field applying unit or the magnetic field changed by the magnetic field varying unit is the magnetic viscous fluid. It is characterized by being uniform in the circumferential direction.

According to a tenth aspect of the present invention, in the rotary drive device according to the sixth, seventh, or eighth aspect, the driving unit is a driving motor, and the magnetic field varying unit, the current adjusting unit, or the distance adjusting unit is adjusted. The frequency of the dynamic vibration absorber can match the rotational frequency (fs) of the drive motor.
According to an eleventh aspect of the present invention, in the rotary drive device according to the sixth, seventh or eighth aspect, the drive means is a drive motor comprising a stepping motor, and the magnetic field varying means, the current adjusting means, or the distance adjusting means. By adjusting the frequency, the frequency of the dynamic vibration absorber can coincide with the frequency (fs × sm) determined by the rotation frequency (fs) of the stepping motor and the number of steps (sm) per rotation of the stepping motor. It is characterized by that.

According to a twelfth aspect of the present invention, in the rotary drive device according to the sixth, seventh, or eighth aspect, the driving unit is a driving motor, and the magnetic field varying unit, the current adjusting unit, or the distance adjusting unit is adjusted. The frequency of the dynamic vibration absorber can match a phase excitation switching frequency (k × n) determined by the number of poles (k) and the number of phases (n) of the drive motor.
According to a thirteenth aspect of the present invention, in the rotary drive device according to the sixth, seventh or eighth aspect, the frequency of the dynamic vibration absorber is adjusted by the adjustment of the magnetic field varying means, the current adjusting means or the distance adjusting means. It is possible to match the rotational frequency (fd) of the shaft.

According to a fourteenth aspect of the present invention, in the rotary drive device according to the sixth, seventh, or eighth aspect, the drive transmission means is a gear train, and adjustment is performed by the magnetic field variable means, the current adjustment means, or the distance adjustment means. The frequency of the dynamic vibration absorber can be matched with the meshing frequency (fg × z) determined by the number of rotations (fg) of the gear train and the number of teeth (z) of the gear train. .
According to a fifteenth aspect of the present invention, in the rotary drive device according to the sixth, seventh, or eighth aspect, the drive unit is a drive motor, and the magnetic field variable unit, the current adjustment unit, or the distance adjustment unit is adjusted. The frequency of the dynamic vibration absorber can coincide with a frequency that is an integral multiple of the rotational frequency (fs) of the drive motor.

According to a sixteenth aspect of the present invention, in the rotary drive device according to the sixth, seventh, or eighth aspect, the frequency of the dynamic vibration absorber is adjusted by the adjustment of the magnetic field varying unit, the current adjusting unit, or the distance adjusting unit. It is possible to coincide with a frequency that is an integral multiple of the rotational frequency (fd) of the shaft.
The invention according to claim 17 is an image forming apparatus comprising the rotation drive device according to claim 6, 7 or 8, wherein the image quality resolution, image forming mode, printing mode, etc. set in the image forming apparatus are set. Control means for controlling the magnetic field varying means, the current adjusting means, or the distance adjusting means so that the magnetic field corresponding to at least one is applied.

According to an eighteenth aspect of the present invention, in the rotary drive device according to the sixth, seventh, or eighth aspect, the speed fluctuation detecting unit that detects a fluctuation in the rotational speed of the drive shaft or the rotating body, and the speed fluctuation detecting unit detect the rotational fluctuation. Frequency data converting means for converting the velocity fluctuation component into frequency data, and the magnetic field varying means, the current adjusting means, or the frequency adjusting means so that the frequency of the dynamic vibration absorber matches the frequency data converted by the frequency data converting means. Control means for controlling the distance adjusting means.
According to a nineteenth aspect of the present invention, in the rotary drive device according to the eighteenth aspect, the speed fluctuation detecting means is an encoder.

  According to a twentieth aspect of the present invention, in the rotary drive device according to the eighteenth or nineteenth aspect, the drive means is a drive motor, and is rotated by applying a random frequency fluctuation to the drive motor at a timing other than actual operation. Motor control means, and the resonance frequency of the dynamic vibration absorber via the drive motor rotated by adding random frequency fluctuations by the motor control means, the speed fluctuation detection means, and the frequency data conversion means Can be identified.

The invention according to claim 21 is the rotary drive device according to claim 6, 7 or 8, wherein the resonance frequency grasping means for grasping the torsional resonance frequency of the rotation drive device, and the frequency of the dynamic vibration absorber is the resonance frequency grasping. Control means for controlling the magnetic field variable means, the current adjusting means, or the distance adjusting means so as to coincide with the torsional resonance frequency grasped by the means.
According to a twenty-second aspect of the present invention, in the rotary drive device according to any one of the tenth to sixteenth aspects, a plurality of the dynamic vibration absorbers are provided.

A twenty-third aspect of the invention is characterized in that the rotary drive device according to any one of the first to sixteenth aspects or the eighteenth to twenty-second aspect is provided.
According to a twenty-fourth aspect of the present invention, in the image forming apparatus according to the seventeenth or twenty-third aspect, the rotating body is a photosensitive body including a photosensitive drum as an image carrier, an intermediate transfer body, or the like.

According to the present invention, the configuration described in each claim can solve the above-described problems and provide a novel rotation drive device and image forming apparatus. The effects of each claim are as follows.
According to the present invention, a dynamic vibration absorber (dynamic damper) is formed by the inertial body and the magnetorheological fluid, so that the inertial body (inertia) is connected to the rotating body that is the main vibration system via the spring and the attenuator. This is the same structure as the dynamics / vibration model that adds, and the vibration of the added inertial body reduces the vibration energy of the main vibration system. Dynamic dampers can reduce vibration for a specific frequency by taking into account the size of the inertial body to be added, the torsion spring constant of the elastic body (magneto-viscous fluid), the damping ratio, and the like. Vibration (hereinafter referred to as “vibration” in the effect column of the invention) can be reduced (claim 1).

According to the present invention, since the inertial body has a substantially ring shape, an equal moment of inertia having no distribution in the rotational direction can be obtained from its shape characteristics, so there is no eccentric component and it is specified in the circumferential and centrifugal directions. The effect of being able to uniformly absorb the vibration of the frequency of (2).
According to the present invention, it is possible to apply a magnetic field to the magnetorheological fluid by arranging the magnetic field applying means for applying a magnetic field in the vicinity of the magnetorheological fluid, and determine the viscosity damping ratio and the torsion spring constant of the magnetorheological fluid. Therefore, the vibration with respect to a specific frequency can be reduced by the dynamic damper configured as described above.

  According to the present invention, the magnetic field applying means is a coil that generates a magnetic field, and the magnetic viscous fluid is applied to the magnetorheological fluid by using the magnetic field generated in the coil with a simple configuration that includes a circuit including a power source that supplies current to the coil. Since the viscous damping ratio and the torsion spring constant of the magnetorheological fluid can be determined, the vibration with respect to a specific frequency can be reduced by the dynamic damper thus configured. ).

According to the invention, the magnetic field applying means can be applied to the magnetorheological fluid by using the magnetic field generated by the permanent magnet by a simple configuration that is a permanent magnet that generates the magnetic field. Since the damping ratio and the torsion spring constant can be determined, the vibration with respect to a specific frequency can be reduced by the dynamic damper thus configured.
According to the present invention, it is possible to change the viscous damping ratio and the torsion spring constant of the magnetorheological fluid by adjusting the magnetic field variable means for changing the strength of the magnetic field, and it is possible to adjust for various vibration frequencies. A dynamic damper can be formed, and the vibration of the rotating body can be further reduced (claim 6).

  According to the present invention, it is possible to change the viscosity damping ratio and the torsion spring constant of the magnetorheological fluid by changing the strength of the magnetic field by adjusting the current by the current adjusting means as the magnetic field varying means, and various vibrations can be obtained. A dynamic damper that can be adjusted with respect to the frequency can be configured, and the vibration of the rotating body can be further reduced.

According to the present invention, it is possible to change the viscosity damping ratio and the torsion spring constant of the magnetorheological fluid by changing the strength of the magnetic field by adjusting the distance by the distance adjusting unit as the magnetic field varying unit, and various vibrations can be obtained. A dynamic damper that can be adjusted with respect to the frequency can be configured, and the vibration of the rotating body can be further reduced.
According to the present invention, the dynamic damper formed by the magnetorheological fluid and the inertial body is obtained when the magnetic field applied by the magnetic field applying unit or the magnetic field changed by the magnetic field varying unit is uniform in the circumferential direction of the magnetorheological fluid. Since it has uniform viscosity damping and elasticity in the circumferential direction, vibration can be absorbed into the rotating body without generating new vibration or speed fluctuation in the rotation direction, and speed fluctuation can be reduced. (Claim 9).

  According to the present invention, by adjusting the magnetic field variable means, the current adjusting means or the distance adjusting means, the frequency of the dynamic vibration absorber can coincide with the rotational frequency (fs) of the drive motor, thereby dissipating energy and rotating By absorbing the vibration to the body, it is possible to reduce the speed fluctuation of the rotating body in which the rotational frequency (fs) of the drive motor causes a problem (claim 10).

  According to the present invention, by adjusting the magnetic field varying means, the current adjusting means, or the distance adjusting means, the frequency of the dynamic vibration absorber becomes the rotation frequency (fs) of the stepping motor and the number of steps (sm) per rotation of the stepping motor. Can be matched with the frequency (fs × sm) determined by, and by absorbing vibrations to the rotating body, the speed fluctuation of the rotating body where the frequency of (fs × sm) is a problem can be reduced. (Claim 11).

  According to the present invention, the phase excitation switching in which the frequency of the dynamic vibration absorber is determined by the number of poles (k) and the number of phases (n) of the drive motor by adjusting the magnetic field varying means, the current adjusting means, or the distance adjusting means. By being able to match the frequency (k × n), the energy is dissipated and the vibration to the rotating body is absorbed, thereby reducing the speed fluctuation of the rotating body where the frequency of (k × n) is a problem. Therefore, high image quality can be achieved (claim 12).

  According to the present invention, by adjusting the magnetic field varying means, the current adjusting means or the distance adjusting means, the frequency of the dynamic vibration absorber can match the rotational frequency (fd) of the drive shaft, thereby dissipating energy, By absorbing the vibration to the rotating body, it is possible to reduce the speed fluctuation of the rotating body in which the rotation frequency (fd) becomes a problem (claim 13).

  According to the present invention, the frequency of the dynamic vibration absorber is determined by the rotation number (fg) of the gear train and the number of teeth (z) of the gear train by adjusting the magnetic field varying device, the current adjusting device, or the distance adjusting device. By being able to match the meshing frequency (fg × z), the energy fluctuation is dissipated and the vibration to the rotating body is absorbed, so the speed variation of the rotating body where the meshing frequency (fg × z) of the gear train becomes a problem Can be reduced (claim 14).

  According to the present invention, by adjusting the magnetic field varying means, the current adjusting means, or the distance adjusting means, the frequency of the dynamic vibration absorber is the rotational frequency of the drive motor that is generated when the drive transmission means such as a gear train has an eccentric component ( By being able to match the frequency of an integral multiple (n) of fs), energy is dissipated and vibration to the rotating body is absorbed, so that the frequency of the harmonics (fs × n) becomes a problem. Speed fluctuation can be reduced (claim 15).

  According to the present invention, the rotational frequency (fd) of the drive shaft generated when the frequency of the dynamic vibration absorber has an eccentric component in the drive shaft or the like by adjusting the magnetic field varying means, the current adjusting means, or the distance adjusting means. Rotating body in which the frequency of (fd × n) becomes a problem by dissipating energy and absorbing vibration to the rotating body by being able to match the frequency (fd × n) of an integer multiple of (n) Can be reduced (claim 16).

  According to the present invention, the magnetic field variable means and the current adjustment are applied by the control means so that a magnetic field according to at least one condition such as image quality resolution, image formation mode, and print mode set in the image forming apparatus is applied. By controlling the means or the distance adjusting means, in other words, it becomes possible to match the vibration reduction frequency of the dynamic damper formed by the magnetorheological fluid and the inertia body in accordance with the at least one condition. The speed fluctuation of the rotating body can be reduced by dissipating the energy and absorbing the vibration to the rotating body.

  According to the present invention, the frequency data converting means for converting the speed fluctuation component detected by the speed fluctuation detecting means for detecting the rotational speed fluctuation of the drive shaft or the rotating body into the frequency data by the control means. The magnetic field variable means, current adjustment means, or distance adjustment means are controlled so as to match the frequency data converted by the above, thereby forming an optimum dynamic damper to reduce the actual speed fluctuation frequency And fluctuations in the speed of the rotating body can be reduced (claim 18).

  According to the present invention, the speed fluctuation detecting means is an encoder, and therefore, by using an encoder having a pulse number of one rotation, for example, capable of detecting the speed fluctuation in the frequency band affecting the image, the driving shaft or the rotation It is possible to detect the speed fluctuation of the body at low cost, and it can be easily implemented because it is only necessary to use a coupling, for example.

  According to the present invention, the drive motor rotated by applying random frequency fluctuations by the motor control means for rotating the drive motor by adding random frequency fluctuations at timings other than actual operation, speed fluctuation detecting means, and frequency data The resonance frequency of the dynamic vibration absorber can be identified via the conversion means, so that the resonance frequency of the rotary drive body, which is determined by the shape, physical properties of the components, etc., tends to vary among individuals. On the other hand, since it is possible to form dynamic dampers effective for reducing the respective resonance frequencies by setting the magnetic field of the magnetorheological fluid, it is possible to reduce the speed fluctuation of the rotating body due to resonance.

  According to the present invention, the magnetic field variable means and the current adjustment are performed by the control means so that the frequency of the dynamic vibration absorber matches the torsional resonance frequency grasped by the resonance frequency grasping means grasping the torsional resonance frequency of the rotary drive device. By controlling the means or the distance adjusting means, the resonance frequency can be grasped by using the drive motor as an excitation source. Therefore, the use of another excitation means leads to downsizing of the drive system and cost reduction. Further, since the resonance frequency is identified at a timing other than actual operation, that is, timing other than the time of image formation, it is possible to prevent the influence of vibration on the image.

  According to the present invention, the rotational drive system has various speed fluctuation components such as the rotational frequency of the drive motor, the rotational frequency of the drive shaft, and the meshing frequency of the gear train so as to match these various frequencies. By providing a plurality of controlled dynamic dampers, a plurality of speed fluctuation frequencies can be absorbed, and the speed fluctuation of the rotating body can be reduced.

According to the present invention, the image forming apparatus including the rotation drive device according to any one of claims 1 to 16 or any one of 18 to 22 exhibits the effect of the rotation drive device. Of course, it is possible to selectively reduce the speed fluctuation frequency of the rotating body of the rotary drive device in the image forming apparatus, and to improve the image quality.
According to the present invention, in particular, it is possible to selectively reduce the speed fluctuation frequency of a photosensitive member including a photosensitive drum as an image carrier that is a rotating body and a main inertia member, an intermediate transfer member, and the like. High image quality can be achieved (claim 24).

  DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention (hereinafter referred to as “embodiments”) including the best mode for carrying out the present invention and examples will be described below with reference to the drawings. Constituent elements such as members and components having the same function and shape throughout the embodiment and the modified examples are given the same reference numerals and will not be described after being described once. In order to simplify the drawings and the description, even components that are to be represented in the drawings may be omitted as appropriate without being specifically described in the drawings. When describing with reference to components of such patent publications are given the same parentheses the code shall be distinguished from that of such embodiments.

First, with reference to FIG. 16, the operation will be described together with an outline of the overall configuration of a color duplex copying machine 100 as an example of an image forming apparatus having a rotation drive device to which the present invention is applied.
The color double-sided copying machine 100 performs image formation on one side of a transfer sheet as a sheet-like recording medium (single-sided image formation mode), and then reverses the transfer sheet so that an image is formed on the other side of the transfer sheet. A double-sided image forming apparatus that performs formation (double-sided image forming mode). The color double-sided copying machine 100 can operate using a single-sided image forming mode and a double-sided image forming mode, a later-described thick paper mode, a single-color mode (so-called monochrome mode), and a full-color mode.
This color duplex copying machine 100 has a processing capability of 50 PPM (sheets per minute) or more in a single color copying operation using, for example, transfer paper P (or paper P) as a recording material of size A4 (horizontal). This is a high-speed copying machine having (for example, a maximum speed of 70 PPM).

  The color duplex copying machine 100 includes a color scanner 99, a writing optical unit 40 as an exposure unit, a photosensitive drum 1 as an image carrier, a photosensitive member cleaning unit 54, a static elimination lamp 56, a potential sensor 60, a rotary developing device 62, A development density pattern detector 61, an intermediate transfer belt 67, a fixing device 85, a paper supply bank 75, and the like are included.

  The writing optical unit 40 converts the color image data from the color scanner 99 into an optical signal, performs optical writing corresponding to the original image, and forms an electrostatic latent image on the photosensitive drum 1. The writing optical unit 40 includes a laser diode 41, a polygon mirror 42, a motor 43 for rotation thereof, an f / θ lens 44, a reflection mirror 45, and the like.

The photosensitive drum 1 is rotated counterclockwise as indicated by an arrow, and a developing device selected from the photosensitive member cleaning unit 54, the charge eliminating lamp 56, the potential sensor 60, and the rotary developing device 62 is provided around the photosensitive drum 1. (Developer 64 in FIG. 16), a development density pattern detector 61, an intermediate transfer belt 67, and the like are arranged.
The rotary developing device 62 includes a black developing unit 63, a cyan developing unit 64, a magenta developing unit 65, a yellow developing unit 66, and a rotation driving unit (not shown) that rotates each developing unit. Each developing device rotates to bring the developer ear into contact with the surface of the photosensitive drum 1 and to rotate the developer sleeve to pump up and stir the developer in order to visualize the electrostatic latent image. Has a development paddle and the like.

In the standby state, the rotary developing device 62 is set at the black development position. When the copying operation is started, the color scanner 99 starts reading the black image data at a predetermined timing. Based on the above, optical writing with a laser beam and formation of an electrostatic latent image (black latent image) are started.
In order to develop the black latent image from the leading edge of the black latent image, before the latent image leading edge reaches the developing position of the black developing device 63, the developing sleeve is rotated to develop the black latent image with black toner.
Thereafter, the development operation of the black latent image area is continued, but when the trailing edge of the latent image passes the black development position, the rotary development is quickly performed from the development position for black to the development position for the next color. The device 62 rotates. This operation is completed at least before the leading edge of the latent image by the next image data arrives.

  When the image forming cycle is started, first, the photosensitive drum 1 is rotated counterclockwise as indicated by an arrow, and the intermediate transfer belt 67 is rotated clockwise via a drive transmission means such as a gear train (both shown in FIG. (See FIG. 17 described later). As the intermediate transfer belt 67 rotates, black toner image formation, cyan toner image formation, magenta toner image formation, and yellow toner image formation are performed. Finally, black (Bk), cyan (C), and magenta (M) are formed. And yellow (Y) in this order are superimposed on the intermediate transfer belt 67 to form a toner image.

  Here, when the thick paper mode is set, control is performed by a control device (not shown) so that the rotational speed of each of the drive motors is slower than when other transfer paper is used. On the contrary, when the monochrome mode is set, for example, the rotational speed of each drive motor is controlled by a control device (not shown) so as to be faster than that in the full color mode.

The intermediate transfer belt 67 is stretched around a drive roller 68, transfer counter rollers 69a and 69b, a cleaning counter roller 70, and a driven roller group, and is driven and controlled by a drive motor (not shown).
The black, cyan, magenta, and yellow toner images sequentially formed on the photosensitive drum 1 are accurately and sequentially aligned on the intermediate transfer belt 67, whereby a four-color superimposed belt transfer image is formed. The belt transfer image is collectively transferred onto transfer paper by a transfer corona discharger 73.

Each of the recording paper cassettes 76, 77, 78 in the paper supply bank 75 contains various sizes of transfer paper different from the size of the transfer paper stored in the cassette 79 in the apparatus main body. The designated transfer paper is fed / reversely conveyed in the direction of the registration roller pair 82 by the paper feed roller 80 from the sized paper storage cassette. In FIG. 16, reference numeral 81 denotes a manual paper feed tray for OHP transfer paper, thick paper, and the like.
At the time when image formation is started, the transfer paper is fed from the paper feed port of one of the cassettes and waits at the nip portion of the registration roller pair 82. When the leading edge of the toner image on the intermediate transfer belt 67 approaches the transfer corona discharger 73, the registration roller pair 82 is driven so that the leading edge of the transfer paper exactly coincides with the leading edge of the image. Matching is done.

In this way, the transfer paper is overlapped with the intermediate transfer belt 67 and passes over the transfer corona discharger 73 connected to a positive potential. At this time, the transfer paper is charged with a positive charge by the corona discharge current, and the toner image is transferred to the transfer paper. Subsequently, the transfer paper is neutralized when passing through a portion of a neutralization brush (not shown) arranged on the left side of the transfer corona discharger 73 in the drawing, and is peeled off from the intermediate transfer belt 67 and transferred to the paper conveyance belt 83.
The transfer paper onto which the four-color superimposed toner images are collectively transferred from the intermediate transfer belt 67 is conveyed to the internal heating type fixing device 85 by the paper conveying belt 83, and the toner image is fixed by the fixing device 85 by heat and pressure. . After the fixing, the transfer paper passes over a path switching member 89 indicated by a solid line provided in the transfer paper discharge path between the fixing device 85 and the discharge roller pair 88, and the transfer paper pair 88 is rotated forward so as to be out of the machine. And is stacked on a tray (not shown). Thereby, a full color copy is obtained.

  In the case of the single color mode, only the developing device for that color is in the developing operation state until the predetermined number of sheets is completed, and the intermediate transfer belt 67 is kept in contact with the surface of the photosensitive drum 1 in the forward movement direction. The copy operation is performed while driving at the speed.

In the case of duplex copying, it is performed as follows. First, as described above, any one of single-color or four-color image formation is formed on one surface (front surface) of the transfer paper, and the unfixed images are sequentially heat-fixed by the fixing device 85. When the transfer paper having a fixed image formed on one side thereof passes through the discharge roller pair 88 in the vicinity of the rear end portion thereof, the discharge roller pair 88 is temporarily stopped, and immediately thereafter, the discharge roller pair 88 is reversed. This time, the paper is again introduced into the apparatus main body by a so-called switchback system in which the rear end side of the transfer paper is the leading end.
At this time, the passage switching member 89 is displaced to a position for guiding the transfer paper between the introduction roller pair 90 by a driving means such as a solenoid (not shown). As a result, the transfer paper Pa indicated by a two-dot chain line in the figure in which a fixed image is formed on one surface is sent to a conveyance path 91 in which transfer paper conveyance members such as a plurality of conveyance rollers are arranged. One side faces upward and is loaded and accommodated in the cassette 79.

  When the transfer paper Pa is accommodated in the cassette 79 for a predetermined number of sheets, any one of monochrome or four-color image formation is performed on the other surface (back surface) of the transfer paper Pa. The transfer paper with one side facing upward is fed and reversed and conveyed in the direction of the registration roller pair 82 by the paper feeding roller 80, and the other side where no image is formed faces upward, and the other side is monochrome or Any one of the four-color image formation is performed, and then the toner image is fixed by the fixing device 85 again by heat and pressure. The transfer paper on which images are formed on both sides after fixing passes again on the path switching member 89 displaced to the position indicated by the solid line, and is discharged out of the apparatus by the forward rotation of the discharge roller pair 88, and is placed on a tray (not shown). Stacked. As a result, a double-sided copy in which any one of monochromatic or four-color image formation is formed on both sides is obtained.

  FIG. 17 shows an outline of the rotational drive system of the rotational drive device in the image forming apparatus such as the color duplex copying machine 100. The rotational drive system includes a drum-shaped photosensitive drum 1 as a rotating body, a driving shaft 2 of the photosensitive drum 1, and a driving motor 3 as a driving unit that rotates the photosensitive drum 1 via the driving shaft 2. The gear train 4 as drive transmission means for transmitting torque, which is the driving force of the drive motor 3, to the drive shaft 2, and an inertial body 8 that is mounted coaxially with the drive shaft 2. The inertial body 8 is a general flywheel.

  The gear train 4 is rotatably supported by a drive gear 5 attached and fixed to the output shaft end portion of the drive motor 3 and a main body side plate (not shown) provided immovably on the apparatus main body (not shown). A first intermediate gear 6a that meshes with the second intermediate gear 6b that is rotatably supported by the main body side plate and meshes with the first intermediate gear 6a, and a second intermediate gear that is attached and fixed to the end of the drive shaft 2 of the photosensitive drum 1. The drum driven gear 7 meshes with the gear 6b. The drive shaft 2 is attached and fixed to a drum flange 1 a that is an end plate of the photosensitive drum 1.

  The operation of the main part of the image forming apparatus shown in FIG. 17 is as follows. That is, the torque of the drive motor 3 rotated by a drive control device (not shown) rotates the drive shaft 2 via the gear train 4. The rotational drive system having such a configuration has a rotational vibration mode, and is likely to affect the image, and is generated through the drive shaft 2 of the photosensitive drum 1 and the drum flange 1a. And a torsional vibration mode of the photosensitive drum 1 to be used. In this vibration mode, the resonance frequency of the torsional vibration mode can be calculated by replacing the rotational drive system with a vibration model using inertia and a spring.

  In Formula 1, f is a natural frequency of torsional vibration, k is a torsion spring constant of the drive shaft 2 and the drum flange 1a, and J is a moment of inertia of the photosensitive drum system. When this resonance frequency and the rotational vibration of the drive motor 3 serving as the excitation source and the meshing frequency of the gear train 4 serving as the drive transmission system are coincident or close to each other, the rotational drive system resonates greatly and causes image degradation. Formula 1 represents a calculation formula when the inertia of the inertial body 8 is sufficiently larger than that of the photosensitive drum 1 and is regarded as a fixed end as a vibration model.

  FIG. 18 shows the vibration transmissibility of the excitation frequency / resonance frequency when the damping ratio is 0.01. As shown in the figure, when the excitation frequency / resonance frequency is 1, that is, when both coincide, the vibration transmissibility becomes maximum, and in this case, it becomes 100 times. Further, the vibration may be amplified 1000 times or more depending on the damping ratio. Therefore, in order to prevent such resonance, there are methods in which the resonance frequency and the excitation frequency do not exist in the vicinity, and the influence of resonance is reduced by attenuating and absorbing the vibration component to be excited.

(First embodiment)
With reference to FIG. 1, the first embodiment will be described by taking as an example a case where the first embodiment is applied to the rotation driving device in the image forming apparatus shown in FIG. 17 for the sake of simplicity. Of course, the embodiment of the present invention is not limited to the embodiment shown in FIG.
As shown in FIG. 1, the main part of the rotary drive device of the first embodiment includes an inertia ring 11 as an inertia body loosely fitted on the outer periphery of the drive shaft 2, and an outer periphery and inertia of the drive shaft 2. The magnet 11 is enclosed between the inner periphery of the ring 11 and has a magnetorheological fluid 10 whose viscosity changes by applying a magnetic field. The inertial ring 11 and the magnetorheological fluid 10 cause a dynamic vibration absorber 9 (hereinafter referred to as “dynamic damper”). 9 ”) is formed.

  The magnetorheological fluid 10 is modeled and shown in a number of granular patterns in FIG. 1, and is a cylindrical bearing case (not shown) provided between the inertia ring 11 loosely fitted on the outer periphery of the drive shaft 2. ) Sealed inside. The drive shaft 2 is fixed to the inner peripheral portion of the bearing case, and the inertia ring 11 is supported on the outer peripheral portion of the bearing case, and is allowed to deviate and rotate from the center of the drive shaft 2. In other words, the rotary drive device shown in FIG. 1 can also be expressed as the drive shaft 2 having an inertia ring 11 having an inertia moment via the magnetorheological fluid 10. The drive shaft 2 is rotatably supported by a known bearing such as a rolling bearing at a portion other than the portion where the dynamic damper 9 is formed by the inertia ring 11 and the magnetorheological fluid 10.

  Since the present invention does not relate to the technology itself for enclosing the magnetorheological fluid 10 between the outer periphery of the drive shaft 2 and the inner periphery of the inertia ring 11, various known technologies for sealing the magnetorheological fluid are used. You may select and employ | adopt suitably. As a specific example, for example, a sealing example using a damper case structure in which the inertia body (8) is removed from the damper case (5) shown in FIG. 2 of the above-mentioned Japanese Patent Application Laid-Open No. 2003-35337 can be given.

  The magnetorheological fluid 10 is a kind of functional fluid whose rheological characteristics can be changed by an external magnetic field (external magnetic field), and is an MR fluid (Magnetic Rheological Fluid) or simply a magnetic fluid (Magnetic Fluid) or a magnetorheological fluid. Also called. The magnetorheological fluid 10 used here is a slurry in which, for example, ferromagnetic metal fine particles are dispersed at a high concentration in a liquid as a medium, and the particles magnetized by an external magnetic field strongly attract each other and become highly viscous. It has. The liquid used as the medium is fluorinated oil or the like, and the magnetic material is made of magnetic ultrafine particles such as extremely fine magnetite or Mn-Zn composite ferrite with a particle diameter of several nanometers to several micrometers. A stable dispersion state is maintained without agglomeration by the adsorbed surfactant. When a magnetic field is applied to the magnetorheological fluid 10 (hereinafter sometimes referred to as “applying a magnetic field”), the viscosity of the magnetorheological fluid 10 increases, and when the magnetic field strength increases, the viscosity also increases. .

  Accordingly, when an inertia ring 11 having an inertia moment is attached to the drive shaft 2 via the magnetorheological fluid 10 as shown in FIG. In such a dynamic damper, an inertial body (inertia) is added to the main vibration system via a spring and an attenuator, so that the vibration of the added inertial body reduces the vibration energy of the main vibration system. is there.

  The inertial ring 11 as the inertial body used here can obtain a uniform moment of inertia having no distribution in the rotational direction due to its shape characteristics, so that it has no eccentric component and can uniformly absorb vibrations of a specific frequency. Therefore, it is formed in a ring shape. The inertia ring 11 preferably has a large inertia such as metal, but may be a resin material or the like if there is no problem even with a small inertia when the dynamic damper 9 is considered. In addition, the dynamic damper 9 takes into account the size of the inertial body to be added, the spring constant of the elastic body (magneto-viscous fluid 10), the viscous damping ratio (viscosity damping rate), and the like, thereby reducing vibrations at a specific frequency. Is obtained. Therefore, the vibration reducing effect of the main inertial body such as the photosensitive drum 1 can be obtained by using the dynamic damper 9 configured to use the viscosity of the magnetorheological fluid 10 as an elastic body.

(Second Embodiment)
FIG. 2 shows a second embodiment.
Compared with the first embodiment shown in FIG. 1, the second embodiment generates a magnetic field as a magnetic field applying unit that applies a magnetic field to the outer periphery of the magnetorheological fluid 10 in the vicinity of the magnetorheological fluid 10. The main difference is that the coil 12 is wound around and an electric circuit 14 including a power source 13 for supplying current to the coil 12 is provided. The magnetorheological fluid 10 and the coil 12 shown in FIG. 2 and FIG. 3 to be described later are exaggerated in the axial direction of the drive shaft 2 in order to clarify their characteristics.

  The power source 13 means a wide concept including, for example, a DC power source that can change the magnitude of a current, a constant current power source, or a battery. In the case of using a constant current power supply or a battery, a configuration is also possible in which the magnitude of the current is changed by adding a resistor or the like, or on / off of the current can be switched by adding various switching elements. (Since the same applies to the embodiments and modifications described later, the following is omitted).

  A parameter that determines the spring constant of the dynamic damper 9 includes the magnitude of a magnetic field (magnetic field) applied to the magnetorheological fluid 10. Therefore, in the second embodiment, in order to actively determine the spring constant of the dynamic damper 9, it is preferable that the magnetic field be controlled. Therefore, a magnetic field can be generated by forming an electric circuit 14 that causes a current to flow through the coil 12 by the power supply 13 in order to control the magnetic field.

(Modification 1)
FIG. 3 shows a first modification of the second embodiment.
The modification 1 is different from the second embodiment shown in FIG. 2 only in that a magnetic field varying means capable of changing the strength of the magnetic field applied to the magnetorheological fluid 10 is added, and the other is the same. It is. That is, the modified example 1 includes a controller 15 as a current adjusting unit that adjusts a current flowing through the coil 12 instead of the electric circuit 14 as compared with the second embodiment shown in FIG. The main difference is that the electric circuit 14 </ b> A is provided, and the strength of the magnetic field generated in the coil 12 is changed by adjusting the current by the controller 15.

The controller 15 as the current adjusting unit is an example of a magnetic field varying unit. As the power source 13, for example, a DC constant current power source or a battery is used.
Since the viscosity of the magnetorheological fluid 10 can be controlled by a magnetic field, it is possible to change the strength of the generated magnetic field by providing a controller 15 that can adjust the magnitude of the current. As the viscosity / viscosity of the magnetorheological fluid 10 changes, the spring constant and the viscous damping ratio of the dynamic damper 9 change. Therefore, the frequency of vibration that can be reduced by the dynamic damper 9 can be determined by the strength of the generated magnetic field. Therefore, by providing the controller 15 in the electric circuit 14A, the strength of the magnetic field can be controlled, and the vibration reduction frequency of the dynamic damper 9 can be controlled as the magnetic field changes.

(Modification 2)
FIG. 4 shows a second modification of the second embodiment.
As compared with the second embodiment shown in FIG. 2, the modified example 2 replaces the arrangement of the coil 12 wound around the outer periphery of the magnetorheological fluid 10 with the magnetorheological fluid near the outer end of the inertia ring 11. The main difference is that a coil 12 </ b> B that generates a magnetic field as a magnetic field applying means for applying a magnetic field is disposed in the vicinity of 10.

  Also in the second modification, paying attention to the magnitude of the magnetic field (magnetic field) applied to the magnetorheological fluid 10 as a parameter for determining the spring constant of the dynamic damper 9 as in the second embodiment, the dynamic damper is actively activated. In order to determine the spring constant of 9, it is preferable that the magnetic field be controlled. Therefore, a magnetic field can be generated by forming an electric circuit 14B that causes a current to flow through the coil 12B by the power source 13 in order to control the magnetic field.

(Modification 3)
FIG. 5 shows a third modification of the second modification.
The modification 3 is different from the modification 2 shown in FIG. 4 only in that a magnetic field variable means capable of changing the strength of the magnetic field applied to the magnetorheological fluid 10 is added, and the others are the same. . That is, the modified example 3 is configured to include an electric current controller 16 as a current adjusting unit that adjusts the current flowing through the coil 12B, instead of the electric circuit 14B, as compared with the modified example 2 shown in FIG. The main difference is that the circuit 14C is provided, and the strength of the magnetic field generated in the coil 12B is changed by adjusting the current by the current controller 16. The current controller 16 is an example of a magnetic field varying unit.

  As described in the first modification, since the viscosity of the magnetorheological fluid 10 can be controlled by a magnetic field, a magnetic field generated by providing a current controller 16 for adjusting the magnitude of the current in the electric circuit 14C. It is possible to control the change of the strength of the magnetic damper 9, thereby changing the viscosity and viscosity of the magnetorheological fluid 10, thereby changing the spring constant and the viscosity damping ratio of the dynamic damper 9. Therefore, the frequency of vibration that can be reduced by the dynamic damper 9 can be determined by the strength of the generated magnetic field. Therefore, by providing the current controller 16 in the electric circuit 14C, the strength of the magnetic field can be controlled, and the vibration reduction frequency of the dynamic damper 9 can be controlled as the magnetic field changes.

  Specific examples of the controller 15 of the first modification and the current controller 16 of the third modification include a variable resistor that can adjust a current manually or automatically by changing a resistance value. As an example of automatically changing the resistance value, the output shaft of a stepping motor is connected to the rotating shaft of a variable resistor having a rotating shaft via a reduction device such as a gear or a coupling. There is one that controls the amount of rotation of the stepping motor using a microcomputer equipped with a CPU, ROM, RAM, and the like.

  In place of the current adjustment means (controller 15, current controller 16), voltage adjustment means for changing (adjusting) the current flowing through each coil 12, 12B through changing the voltage applied to each coil 12, 12B. Also good.

(Third embodiment)
FIG. 6 shows a third embodiment.
Compared with the second embodiment shown in FIG. 2, the third embodiment removes the coil 12 and replaces it with the outer end of the magnetorheological fluid 10 in the vicinity of the outer end of the inertia ring 11. The main difference is that the permanent magnet 20 for generating a magnetic field as a magnetic field applying means for applying a magnetic field is disposed and the electric circuit 14 including the power source 13 is removed.

  The permanent magnet 20 changes the spring constant and the viscous damping ratio of the magnetorheological fluid 10 forming the dynamic damper 9 by the viscosity and viscosity change of the magnetorheological fluid 10. Therefore, a specific vibration frequency that can be reduced by the dynamic damper 9 can be determined by the magnetic field generated by the permanent magnet.

(Modification 4)
FIG. 7 shows a fourth modification of the third embodiment.
The modification 4 is different from the third embodiment shown in FIG. 6 only in that a magnetic field variable means capable of changing the strength of the magnetic field applied to the magnetorheological fluid 10 is added, and the other is the same. It is. That is, the modification 4 is a distance adjustment that changes the distance of the permanent magnet 20 in the arrow Y direction (the axial direction of the drive shaft 2) of the permanent magnet 20 with respect to the magnetorheological fluid 10 as compared with the third embodiment shown in FIG. The only difference is that a means (not shown) is added, and the strength of the magnetic field by the permanent magnet 20 with respect to the magnetorheological fluid 10 is changed by adjusting the distance by the distance adjusting means. The distance adjusting unit is an example of a magnetic field varying unit.

  By making the permanent magnet 20 movable in the direction of arrow Y in the figure by the distance adjusting means, the strength of the magnetic field from the permanent magnet 20 to the magnetorheological fluid 10 can be adjusted. The vibration reduction frequency of 9 can be controlled. The distance adjusting means of the permanent magnet 20 may be anything, and a person skilled in the art can easily implement a configuration that moves horizontally using, for example, a motor.

  As an example of the distance adjusting means, guide means for guiding and supporting the permanent magnet 20 so as to be movable in the direction of arrow Y in the figure (extending along the direction of arrow Y in the figure of the permanent magnet 20 is attached and fixed to the upper part of the permanent magnet 20. And a moving means (permanent magnet) having a driving means for reciprocating the permanent magnet 20 in the direction of arrow Y in the figure. A movable member that extends along the direction of arrow Y in FIG. 20 and is fixedly attached to the lower portion of the permanent magnet 20 and has a pinion formed downward, and a drive means that fixes a rack that meshes with the pinion of the movable member to the output shaft. As a stepping motor). In addition to this, it is possible to easily control the rotation amount and forward / reverse rotation of the stepping motor using a microcomputer including a CPU, a ROM, a RAM, and the like.

  Although the description will be mixed, the configuration in which the coils 12 and 12B are installed in the vicinity of the magnetorheological fluid 10 arrangement part as shown in FIGS. 2 to 5 and the magnetorheological fluid 10 arrangement part as shown in FIGS. The configuration in which the permanent magnet 20 is installed in the vicinity is a configuration in which the magnetic field applied to the magnetorheological fluid 10 is uniform in the circumferential direction of the magnetorheological fluid 10. With the configuration as shown in the figure, the spring constant in the circumferential direction of the dynamic damper 9 does not vary, and the target vibration frequency can be effectively reduced. When the magnetic field is not uniformly applied in the circumferential direction, a dynamic damper having different spring constants in the circumferential direction is formed due to variations in the magnetic field strength. In such a case, the drive shaft 2 may vibrate due to the dynamic damper.

(Modification 5)
In the rotational driving device or the like in the image forming apparatus shown in FIG. 17, the vibration component of the rotational frequency (fs) of the drive motor 3 becomes a factor of speed fluctuation of the photosensitive drum 1 as one of the problematic factors. Banding may occur or color misregistration may occur.

  Therefore, the rotation drive device in the image forming apparatus of the first modification shown in FIG. 3, the third modification shown in FIG. 5 or the fourth modification shown in FIG. By adjusting the controller 16 or the distance adjusting means, the vibration reduction frequency of the dynamic damper 9 formed by the magnetorheological fluid 10 and the inertia ring 11 is matched with the vibration component generated at the rotational frequency (fs) of the drive motor 3. By setting as described above, the energy is dissipated, and the vibration to the photosensitive drum 1, which is the main inertial body, is absorbed, so that the speed fluctuation of the photosensitive drum 1 can be reduced.

(Modification 6)
When the rotation drive device in the image forming apparatus shown in FIG. 17 is employed and a stepping motor is used as the drive motor 3, the rotation frequency (fs) of the stepping motor and the number of steps (sm) per rotation of the stepping motor There is a problem that speed fluctuation occurs in the photosensitive drum 1 at a frequency (fs × sm) determined by the above, and image deterioration occurs.

  Therefore, the rotation drive device in the image forming apparatus of the first modification shown in FIG. 3, the third modification shown in FIG. 5 or the fourth modification shown in FIG. By adjusting the controller 16 or the distance adjusting means, the vibration reduction frequency of the dynamic damper 9 formed from the magnetorheological fluid 10 and the inertia ring 11 is set to coincide with the frequency (fs × sm), and the energy is set. It is possible to reduce the speed fluctuation of the photosensitive drum 1 by dissipating and absorbing the vibration to the photosensitive drum 1 which is the main inertial body.

(Modification 7)
In the case where the rotational driving device in the image forming apparatus shown in FIG. 17 is employed and the configuration of the driving motor 3 of the photosensitive member driving system is k pole n phase, there is a vibration component at the time of each excitation and switching. Sometimes. Such a vibration component may affect the surface speed fluctuation of the photosensitive drum 1 and cause image deterioration. The phase excitation switching frequency generated here is determined by (k × n).

  Therefore, the rotation drive device in the image forming apparatus of the first modification shown in FIG. 3, the third modification shown in FIG. 5 or the fourth modification shown in FIG. By adjusting the controller 16 or the distance adjusting means, the vibration reduction frequency of the dynamic damper 9 formed from the magnetorheological fluid 10 and the inertia ring 11 is set to coincide with the phase excitation switching frequency (k × n), By dissipating energy and absorbing the vibration to the photosensitive drum 1 which is the main inertial body, it is possible to reduce the speed fluctuation of the photosensitive drum 1.

(Modification 8)
The rotational drive device in the image forming apparatus shown in FIG. 17 is employed, and as one of the problematic factors, the vibration component of the rotational frequency fd of the drive shaft 2 in the photosensitive drum 1 becomes a speed variation factor and the image color shift. It may cause.

  Therefore, the rotation drive device in the image forming apparatus of the first modification shown in FIG. 3, the third modification shown in FIG. 5 or the fourth modification shown in FIG. By adjusting the controller 16 or the distance adjusting means, the vibration reduction frequency of the dynamic damper 9 formed by the magnetorheological fluid 10 and the inertia ring 11 is matched with the vibration component generated at the rotational frequency (fd) of the drive shaft 2. By setting as described above, the energy is dissipated, and the vibration to the photosensitive drum 1, which is the main inertial body, is absorbed, so that the speed fluctuation of the photosensitive drum 1 can be reduced.

(Modification 9)
In the gear train 4 of the rotation drive device in the image forming apparatus shown in FIG. 17, when the rotational speed of the gear train 4 is fg (rps) and the number of teeth of the gear train 4 is z, the meshing frequency of the gear train 4 is ( fg × z). The vibration due to the meshing of the gear train 4 causes the speed fluctuation of the photosensitive member drive system, and often causes banding that causes a stripe pattern in the image.

  Therefore, in order to reduce the vibration of the meshing frequency in the gear train 4 as the drive transmission system, the first modification shown in FIG. 3, the third modification shown in FIG. 5, or the fourth modification shown in FIG. The vibration of the dynamic damper 9 formed from the magnetorheological fluid 10 and the inertia ring 11 is adjusted by adjusting the controller 15 as the current adjusting means, the current controller 16 or the distance adjusting means by adopting the rotation driving device in the image forming apparatus. The reduction frequency is set so as to coincide with the meshing frequency (fg × z) of the gear train 4, the energy is dissipated, and the vibration to the photosensitive drum 1, which is the main inertial body, is absorbed, thereby the photosensitive drum 1. It is possible to reduce the speed fluctuation.

  As an example of the modified example 9, the magneto-rheological fluid 10 and inertia are applied to a photosensitive member drive system having a configuration in which the number of teeth z of the gear train 4 is 20 and the rotational speed (fg) of the gear train 4 is 4 (rps). The effect of the dynamic damper 9 of the first modification shown in FIG. The vibration generated in this photosensitive member drive system was 80 Hz. The current value flowing through the coil 12 was adjusted by the controller 15 in order to match the frequency that causes the speed fluctuation of the photoreceptor driving system. FIG. 8 shows a comparison of speed fluctuations with respect to the target speed of the photosensitive member drive system when the dynamic damper 9 is present and absent. From this result, it can be seen that the peak speed fluctuation value at 80 Hz is reduced by the effect of the dynamic damper 9.

(Modification 10)
In a rotary drive device, a fluctuation component that is an integral multiple of the rotation basic fluctuation component n (an integer of n ≧ 2) is often generated due to eccentricity of a rotating body. In particular, when there is an eccentric component in the drive transmission system such as the gear train 4 in the rotary drive device in the image forming apparatus shown in FIG. 17, an integral multiple of the rotational frequency (fs) of the drive motor 3 that is the basic fluctuation component ( In n), speed fluctuations may be amplified, causing image degradation.

  Therefore, the rotation drive device in the image forming apparatus of the first modification shown in FIG. 3, the third modification shown in FIG. 5 or the fourth modification shown in FIG. By adjusting the controller 16 or the distance adjusting means, the vibration reduction frequency of the dynamic damper 9 formed by the magnetorheological fluid 10 and the inertia ring 11 is a frequency that is an integral multiple (n) of the rotational frequency (fs) of the drive motor 3. It is possible to reduce the speed fluctuation of the photosensitive drum 1 by setting it to coincide with (fs × n), dissipating energy, and absorbing the vibration to the photosensitive drum 1 which is the main inertial body. Become.

(Modification 11)
In a rotary drive device, a fluctuation component that is an integral multiple of the rotation basic fluctuation component (an integer of n ≧ 2) is often generated due to the eccentricity of the drive shaft and the rotating body. In particular, when there is an eccentric component in the drive shaft 2 of the photosensitive drum 1 or the like in the rotational drive device in the image forming apparatus shown in FIG. 17, the rotational frequency of the drive shaft 2 of the photosensitive drum 1 which is a basic fluctuation component. Speed fluctuation may be amplified at an integer multiple (n) of the frequency of (fd), causing image degradation.

  Therefore, the rotation drive device in the image forming apparatus of the first modification shown in FIG. 3, the third modification shown in FIG. 5 or the fourth modification shown in FIG. By adjusting the controller 16 or the distance adjusting means, the vibration reduction frequency of the dynamic damper 9 formed by the magnetorheological fluid 10 and the inertia ring 11 is set to a frequency that is an integral multiple (n) of the rotational frequency (fd) of the drive shaft 2. It is possible to reduce the speed fluctuation of the photosensitive drum 1 by setting it to coincide with (fd × n), dissipating energy, and absorbing the vibration to the photosensitive drum 1 which is the main inertial body. Become.

(Modification 12)
FIG. 9 shows a twelfth modification.
In the image forming apparatus using the rotation driving device shown in FIG. 17, the image forming mode, the printing mode, and the resolution of the image (hereinafter referred to as “image quality resolution”) are more specifically shown in FIG. There are cases where the rotational speed of the drive motor 3 is different as in the “thick paper mode” and “normal plain paper copy mode”, “monochrome mode” and “full color mode” as described in the color duplex copying machine 100. is there. Due to the difference in these modes, the speed fluctuation frequency generated in the rotary drive device may be different. Therefore, if the vibration reduction frequency of the dynamic damper 9 formed from the magnetorheological fluid 10 and the inertia ring 11 is not matched with these conditions, the vibration component may be amplified conversely. The modified example 12 solves such a problem. It can be said that the image quality resolution, the image forming mode, the printing mode, and the like are image forming speed parameters that affect the image forming speed of the image forming apparatus.

  Compared to Modification 1 shown in FIG. 3, Modification 12 shown in FIG. 9 includes at least one of the image quality resolution, image formation mode, and print mode set in the image forming apparatus (in FIG. As a control means for controlling the controller 15 so that a magnetic field corresponding to the image forming mode information is applied to the magnetorheological fluid 10 based on a signal of “the image forming mode information”. The main difference is that the current control calculation unit 22 is provided.

  The current control calculation unit 22 can be configured by a control circuit, for example, but a more versatile microcomputer including a CPU, a ROM, a RAM, and the like may be used. That is, in the ROM, data on the relationship between at least one of image quality resolution, image formation mode, print mode, etc. (image formation mode information, etc.) and the magnitude of the current to be passed through the coil 12 under the control of the controller 15 is tested in advance. And stored as a data table or the like. The CPU is configured to control the controller 15 by comparing the image forming mode information and the like with the ROM data table to extract the magnitude of the current to be passed through the coil 12 (the deformation shown in FIG. 10). The same applies to the current control calculation unit 22B of Example 13).

  When a speed fluctuation component such as a drive motor changes for each image forming mode, it is necessary to apply a magnetic field corresponding to the information to the magnetorheological fluid 10 by flowing a current corresponding to the information to the coil 12. This process is determined by the current control calculation unit 22 and the controller 15 is controlled so that the vibration reduction frequency of the dynamic damper 9 formed from the magnetorheological fluid 10 and the inertia ring 11 corresponds to the image forming mode information and the like. The frequency can be set, energy is dissipated, and the vibration to the photosensitive drum 1 which is the main inertial body is absorbed, whereby the speed fluctuation of the photosensitive drum 1 can be reduced.

  Instead of the combination of the current adjustment means (controller 15) and the control means (current control calculation section 22), a voltage adjustment means for adjusting the voltage applied to the coil 12, and a control means (voltage control calculation section) for controlling the voltage, A combination of these may be used. The same applies hereinafter.

(Modification 13)
FIG. 10 shows a thirteenth modification.
In the modified example 13, as compared with the modified example 3 shown in FIG. 5, the current controller 16 is configured so that a magnetic field corresponding to the image forming mode information is applied to the magnetorheological fluid 10 based on a signal such as image forming mode information. The main difference is that it has a current control calculation unit 22B as a control means for controlling.

  Similar to the modified example 12, when the speed fluctuation component of the drive motor or the like changes for each image forming mode, the current corresponding to these pieces of information is passed through the coil 12B so that the magnetorheological fluid 10 corresponds to the above information. It is necessary to apply a magnetic field, and this process is determined by the current control calculation unit 22B, and the current controller 16 is controlled to thereby reduce the vibration reduction frequency of the dynamic damper 9 formed from the magnetorheological fluid 10 and the inertia ring 11. It is possible to set a frequency corresponding to the image forming mode information, etc., to dissipate energy and to absorb the vibration to the photosensitive drum 1 as the main inertial body, thereby reducing the speed fluctuation of the photosensitive drum 1. It becomes possible.

  Further, in the rotational driving device in the image forming apparatus of the modification 4 shown in FIG. 7, as in the modifications 12 and 13, when the speed fluctuation component such as the drive motor changes for each image forming mode, the magnetic viscosity The magnetic viscous fluid 10 and the inertia ring 11 are formed by providing a control means for controlling the distance adjusting means so that the distance of the permanent magnet 20 with respect to the fluid 10 becomes a distance corresponding to image forming mode information or the like. The vibration reduction frequency of the dynamic damper 9 can be set to a frequency corresponding to the image forming mode information and the like, and the vibration to the photosensitive drum 1 that is the main inertial body is absorbed by energy dissipation, so that the photosensitive drum 1 speed fluctuation can be reduced.

(Modification 14)
FIG. 11 shows a modified example 14.
In the rotation drive system of the image forming apparatus using the rotation drive device shown in FIG. 17, there are many frequency components that cause speed fluctuations, and this causes a problem that image quality deteriorates due to speed fluctuations. Occur. The modification 14 solves such a problem.

  Compared to Modification 1 shown in FIG. 3, Modification 14 has speed fluctuation detection means 24 that detects the rotational speed fluctuation of the drive shaft 2, and the speed fluctuation component detected by the speed fluctuation detection means 24 is different. The point having the frequency data conversion means 26 for converting to frequency data, and the frequency of the dynamic damper 9 formed from the magnetorheological fluid 10 and the inertia ring 11 are matched with the frequency data converted by the frequency data conversion means 26. The main difference is that it has a current control calculation unit 22C as a control means for controlling the controller 15.

  The speed fluctuation detecting means 24 can detect and grasp the speed fluctuation of the photosensitive drum 1 as the driving shaft 2 or the rotating body by attaching an encoder (not shown) to the driving shaft 2. Therefore, the speed fluctuation detecting means 24 using the encoder has an advantage that the encoder itself is low in cost and can be easily implemented with a simple configuration since the installation is only performed using the coupling. As a specific example of the encoder, a transmissive photosensor fixed to the main body side plate in such a manner that a plurality of slits are provided on the outer peripheral portion and fixed to the drive shaft 2 and the outer peripheral slit portion of the photo encoder is sandwiched between the photo encoder. Is a combination of Moreover, the thing using a magnetism is also used.

In addition, as the speed fluctuation detecting means 24, the photosensitive drum 1 itself is provided with a linear scale and sensed by the optical pickup, thereby controlling the speed fluctuation component of the photosensitive drum 1 itself as the driven body. It is also possible. Further, the encoder may be provided on the drum flange 1a of the photosensitive drum 1 coaxial with the drive shaft 2 so as to detect and grasp the speed fluctuation of the photosensitive drum 1 itself as a rotating body.
As the frequency data conversion means 26, known frequency conversion means such as FFT (First Fourier Transform) is used.

  The current control calculation unit 22C can be configured by, for example, a control circuit, but a more versatile microcomputer including a CPU, a ROM, a RAM, and the like may be used. That is, in the ROM, the relational data between the frequency data corresponding to the speed fluctuation component converted by the frequency data conversion means 26 and the magnitude of the current to be passed through the coil 12 under the control of the controller 15 is obtained in advance through experiments or the like. Store it as a table. Then, the control configuration is such that the CPU collates the frequency data and the ROM data table to extract the magnitude of the current to be passed through the coil 12 and controls the controller 15 (the modification shown later in FIG. 12). The same applies to the 15 current control calculation units 22D).

  Next, the operation of the main part will be briefly described. As shown in FIG. 11, the rotational speed fluctuation of the drive shaft 2 of the rotational drive system is detected by the speed fluctuation detecting means 24 including the encoder, and then detected by the speed fluctuation detecting means 24 by the frequency data converting means 26 such as FFT. The obtained speed fluctuation component is converted into frequency data. Based on the frequency data obtained here, the frequency at which the dynamic damper 9 formed by the magnetorheological fluid 10 and the inertia ring 11 can absorb vibration is determined by the current control calculation unit 22C, and the frequency of the dynamic damper 9 is the frequency data. The controller 15 is controlled so as to match the frequency data converted by the conversion means 26. As a result, the optimum dynamic damper 9 can be formed, and the speed fluctuation of the photosensitive drum 1 can be reduced.

(Modification 15)
FIG. 12 shows a modification 15.
Compared to Modification 3 shown in FIG. 5, Modification 15 includes speed fluctuation detection means 24 that detects the rotational speed fluctuation of the drive shaft 2, and the speed fluctuation component detected by the speed fluctuation detection means 24 is different. The point having the frequency data conversion means 26 for converting to frequency data, and the frequency of the dynamic damper 9 formed from the magnetorheological fluid 10 and the inertia ring 11 are matched with the frequency data converted by the frequency data conversion means 26. The main difference is that it has a current control calculation unit 22D as a control means for controlling the current controller 16.

  The speed fluctuation detecting means 24 and the frequency data converting means 26 are the same as in the modified example 14. When the current control calculation unit 22D is compared with the current control calculation unit 22C, for example, when a microcomputer is used, the ROM stores frequency data corresponding to the speed fluctuation component converted by the frequency data conversion unit 26 and a current controller. The relational data with the magnitude of the current to be passed through the coil 12B by the control of 16 is obtained in advance by experiments or the like and stored as a data table or the like, and the CPU collates the frequency data with the data table of the ROM, and the coil The only difference is that the magnitude of the current to be supplied to 12B is extracted and the current controller 16 is controlled.

  Next, the operation of the main part will be briefly described. As shown in FIG. 12, the rotational speed fluctuation of the drive shaft 2 of the rotational drive system is detected by the speed fluctuation detecting means 24 including an encoder, and then detected by the speed fluctuation detecting means 24 by the frequency data converting means 26 such as FFT. The obtained speed fluctuation component is converted into frequency data. Based on the frequency data obtained here, the frequency at which the dynamic damper 9 formed by the magnetorheological fluid 10 and the inertia ring 11 can absorb vibration is determined by the current control calculation unit 22D, and the frequency of the dynamic damper 9 is the frequency data. The current controller 16 is controlled so as to match the frequency data converted by the conversion means 26. As a result, the optimum dynamic damper 9 can be formed in the same manner as in the modified example 14, and the speed fluctuation of the photosensitive drum 1 can be reduced.

  Further, in the rotational driving device in the image forming apparatus according to the fourth modification shown in FIG. 7, as in the fourteenth and fifteenth modifications, the speed component is present due to the presence of frequency components that cause the speed fluctuation of the drive shaft 2 and the photosensitive drum 1. When fluctuations occur, speed fluctuation detecting means 24 for detecting the rotational speed fluctuations of the drive shaft 2 or the photosensitive drum 1 and frequency data converting means for converting the speed fluctuation components detected by the speed fluctuation detecting means 24 into frequency data. 26, and a control means for controlling the separation adjusting means so that the frequency of the dynamic damper 9 formed by the magnetic viscous fluid 10 and the inertia ring 11 matches the frequency data converted by the frequency data converting means 26. Also good. As a result, the optimal dynamic damper 9 can be formed in the same manner as the modified examples 14 and 15, and the speed fluctuation of the photosensitive drum 1 can be reduced.

(Modification 16)
FIG. 13 shows a sixteenth modification.
Regardless of the rotational drive system described above, all structures have a natural frequency, and when the structure is vibrated at the natural frequency, the vibration component is amplified and vibrates greatly. This is conspicuous even in the rotational drive system, and when a vibration component exists at the natural frequency related to torsion of the rotational drive device, speed fluctuation occurs at this resonance frequency. That is, even in the rotational drive system of the image forming apparatus using the rotational drive device shown in FIG. 17, the speed fluctuation occurs at the above-described resonance frequency, thereby causing a problem that the image quality is deteriorated. The modified example 16 solves such a problem.

  Compared to Modification 1 shown in FIG. 3, Modification 16 has resonance frequency grasping means 25 for grasping the torsional resonance frequency of the rotary drive device as shown in FIG. 13, and the frequency of the dynamic damper 9 is The main difference is that it has a current control calculation unit 22E as control means for controlling the controller 15 so as to coincide with the torsional resonance frequency grasped by the resonance frequency grasping means 25.

The resonance frequency grasping means 25 preferably employs the modified example 18 described later with reference to FIG. 15 or the like. However, if it is not necessary to obtain the advantage, it is experimental using another vibration means. Of course, it is also possible to grasp.
The current control calculation unit 22E can be configured by, for example, a control circuit or the like, but a more versatile microcomputer including a CPU, a ROM, a RAM, and the like may be used. That is, in the ROM, relational data between the torsional resonance frequency data grasped by the resonance frequency grasping means 25 and the magnitude of the current to be passed through the coil 12 under the control of the controller 15 is obtained in advance by experiments or the like and stored as a data table or the like. Let me. Then, the control configuration is such that the CPU collates the resonance frequency data with the data table of the ROM, extracts the magnitude of the current to be passed through the coil 12, and controls the controller 15 (modified example 17 shown in FIG. 14). The same applies to the current control calculation unit 22F).
As described above, the resonance frequency is determined by the shape, the physical property value of the component, etc., but in the rotary drive device, since there are variations among individuals, in order to set a more effective dynamic damper Preferably, the resonance frequency is identified for each individual object.

  The operation of the modification 16 will be briefly described. First, after grasping the torsional resonance frequency of the rotary drive device by the resonance frequency grasping means 25, the current control calculation unit 22E makes the frequency of the dynamic damper 9 coincide with the torsional resonance frequency grasped by the resonance frequency grasping means 25. By controlling the controller 15, the optimum dynamic damper 9 can be formed, whereby the fluctuation in the speed of the photosensitive drum 1 due to resonance can be reduced.

(Modification 17)
FIG. 14 shows a seventeenth modification.
The modified example 17 also solves the same problems as the modified example 16.
Compared to Modification 3 shown in FIG. 5, Modification 17 has resonance frequency grasping means 25 for grasping the torsional resonance frequency of the rotary drive device as shown in FIG. 14, and the frequency of the dynamic damper 9 is The main difference is that it has a current control calculation unit 22F as control means for controlling the current controller 16 so as to coincide with the torsional resonance frequency grasped by the resonance frequency grasping means 25.

When the microcomputer is used as compared with the current control calculation unit 22E of the modification 16, the current control calculation unit 22F includes the torsional resonance frequency data obtained by the resonance frequency grasping means 25 in the ROM, and the current controller 16. The relational data with the magnitude of the current to be passed through the coil 12B by the control of the above is obtained in advance by experiments or the like and stored as a data table or the like, and the CPU collates the resonance frequency data with the ROM data table. The only difference is that the magnitude of the current to be passed through the coil 12B is extracted and the current controller 16 is controlled.
The operation of the modification 17 will be briefly described. First, after grasping the torsional resonance frequency of the rotary drive device by the resonance frequency grasping means 25, the current control calculation unit 22F is set so that the frequency of the dynamic damper 9 matches the torsional resonance frequency grasped by the resonance frequency grasping means 25. By controlling the current controller 16, it is possible to form the optimum dynamic damper 9, thereby reducing the speed fluctuation of the photosensitive drum 1 due to resonance.

  Further, in the rotational drive device in the image forming apparatus of the modification 4 shown in FIG. 7, similarly to the modifications 16 and 17, a resonance frequency grasping means (not shown) for grasping the torsional resonance frequency of the rotation drive device; By providing control means (not shown) for controlling the distance adjusting means so that the frequency of the dynamic damper 9 coincides with the torsional resonance frequency grasped by the resonance frequency grasping means, an optimum dynamic damper 9 is provided. This makes it possible to reduce fluctuations in the speed of the photosensitive drum 1 due to resonance.

(Modification 18)
FIG. 15 shows a modified example 18.
The means for grasping the resonance frequency of the rotary drive device, that is, the resonance frequency grasping means 25 shown in FIGS. 13 and 14 can be identified by the fluctuation obtained from the excitation force and the response when vibrating in the rotation direction. Is possible. The modified example 18 shows a preferred example of the resonance frequency grasping means 25 capable of grasping the resonance frequency using the drive motor 3 as an excitation source, and discloses a control example based on this.

  Compared to the modified example 14 shown in FIG. 14, the modified example 18 includes an arbitrary waveform generating device 28 that generates random noise as a random frequency variation, and is different from the drive motor 3 at a timing other than actual operation. Instead of the motor control unit 30 as a motor control unit that rotates by adding random noise from the arbitrary waveform generation unit 28, and in place of the current control calculation unit 22C, the drive motor 3, the speed fluctuation detection unit 24, and the frequency data conversion The main difference is that it has a current control calculation unit 22G as a control means for controlling the controller 15 omitted in FIG. 15 so as to coincide with the resonance frequency of the dynamic damper 9 identified through the means 26.

  The current control calculation unit 22G can be configured by, for example, a control circuit, but a more versatile microcomputer including a CPU, a ROM, a RAM, and the like may be used. That is, in the ROM, relational data between the resonance frequency data converted by the frequency data conversion means 26 and the magnitude of the current to be passed through the coil 12 under the control of the controller 15 is obtained in advance by experiments and stored as a data table or the like. Keep it. The CPU collates the resonance frequency data and the ROM data table, extracts the magnitude of the current to be passed through the coil 12, and controls the controller 15 (such as a modified example 19 described later). The same applies to the current control calculation unit 22H).

  Actually, the timing for grasping the resonance frequency of the rotary drive device is preferably when the image is not formed, for example, at the time of start-up after power-on or before the image is formed. In this configuration, the drive motor 3 is used as an excitation source, but random noise is generated using the arbitrary waveform generator 28, and random vibration components are put on the rotation via the motor controller 30 to which the random noise is input. By doing. How the vibration component of the drive motor 3 driven with a random excitation component affects the surface speed fluctuation of the photosensitive drum 1 as the driven body or the speed fluctuation of the drive shaft 2 is determined by an encoder or laser. The speed fluctuation detecting means 24 such as the above detects and grasps the speed fluctuation data, and converts the speed fluctuation data into frequency data by the FFT described above. Therefore, the frequency at which the dynamic damper 9 formed from the magnetorheological fluid 10 and the inertia ring 11 can absorb vibrations is determined by the current control calculation unit 22G with respect to the frequency determined as the resonance frequency, and is appropriately set via the controller 15. By flowing an appropriate current, the optimum dynamic damper 9 can be formed, and the speed fluctuation of the photosensitive drum 1 can be reduced.

(Modification 19)
FIG. 15 shows a modified example 19 different from the modified example 18.
The modified example 19 has an arbitrary waveform generator 28 similar to the modified example 18, a motor control device 30 similar to the modified example 18, and current control compared to the modified example 15 shown in FIG. 12. In place of the calculation unit 22D, the current controller 16 is omitted in FIG. 15 so as to coincide with the resonance frequency of the dynamic damper 9 identified through the drive motor 3, the speed fluctuation detection unit 24, and the frequency data conversion unit 26. The main difference is that it has a current control calculation unit 22H as a control means for controlling the current.

  When the microcomputer is used as compared with the current control calculation unit 22C, the current control calculation unit 22H includes the resonance frequency data converted by the frequency data conversion unit 26 and the coil 12B under the control of the current controller 16 in the ROM. The data relating to the magnitude of the current to be supplied to the current is obtained in advance through experiments or the like and stored as a data table or the like, and the CPU should check the resonance frequency data against the data table of the ROM and pass it through the coil 12B. The only difference is that the magnitude of the current is extracted and the current controller 16 is controlled.

Also in the modified example 19, the vibration of the dynamic damper 9 formed from the magnetorheological fluid 10 and the inertia ring 11 by the current control calculation unit 22H with respect to the frequency determined to be the resonance frequency obtained in the same manner as in the modified example 18. By determining a possible frequency and supplying an appropriate current through the current controller 16, the optimum dynamic damper 9 can be formed, and the speed fluctuation of the photosensitive drum 1 can be reduced.
Further, in the rotation driving device in the image forming apparatus of the modification 4 shown in FIG. 7, as in the modifications 18 and 19, the speed fluctuation detecting means 24, the frequency data converting means 26, the arbitrary waveform generating device 28, and the motor control device. 30 and a control means (not shown) for controlling the distance adjusting means so as to coincide with the resonance frequency of the dynamic damper 9 identified through the drive motor 3, the speed fluctuation detecting means 24 and the frequency data converting means 26. 2), the optimum dynamic damper 9 can be formed, and the speed fluctuation of the photosensitive drum 1 due to resonance can be reduced.

(Modification 20)
In the rotational drive system of the rotational drive device in the image forming apparatus described in the modified examples 5 to 11 and the like, various speed fluctuation components may cause image deterioration. For example, as described in the sixth modification, when a stepping motor is used as the drive motor 3, it is determined by the rotation frequency (fs) of the stepping motor and the number of steps (sm) per rotation of the stepping motor (fs). The speed fluctuation occurs in the photosensitive drum 1 at a frequency of × sm), resulting in image degradation. Further, as described in the modification example 7, when the configuration of the drive motor 3 is k pole n phase, it may have a vibration component determined by (k × n) at the time of each excitation and switching. Further, as described in the modified example 8, when the gear train 4 is used in the drive transmission system, when the gear train 4 has the number of teeth z and the gear train 4 has the rotation speed fg (rps), the gear train 4 The mesh frequency is generated and is determined by (z × fg). In order to effectively reduce the plurality of vibration components, by providing a plurality of dynamic dampers 9 formed of the magnetorheological fluid 10 and the inertia ring 11 controlled as described in the above-described modifications, A plurality of speed fluctuation frequencies can be absorbed, and the speed fluctuation of the photosensitive drum 1 can be reduced.

  In the above-described embodiments, modifications, examples, and the like, the photosensitive drum 1 has been mainly described as a rotating body and a main inertial body. However, in the color double-sided copying machine 100 shown in FIG. It goes without saying that the present invention can also be applied to a rotational drive device that drives the transfer belt 67. Further, not only the drum-shaped photosensitive drum 1 but also a photosensitive member such as a belt-shaped photosensitive belt is included. Furthermore, in the field of printing presses, the present invention can also be applied to a rotary drive device including a plate cylinder, an impression cylinder, a transfer cylinder, and the like as a rotating body.

  As described above, the present invention has been described with respect to specific embodiments, modifications, and examples. However, the technical scope disclosed by the present invention is exemplified in the above-described embodiments, modifications, and examples. The present invention is not limited to those described above, and may be configured by appropriately combining them, and various embodiments, modifications, or examples may be configured within the scope of the present invention according to the necessity and application. It will be apparent to those skilled in the art.

  As described above, the present invention is not limited to the rotation drive device in the image forming apparatus, but can be used or applied to rotation drive devices in all industrial fields.

1 is a simplified partial cross-sectional perspective view around a dynamic damper and a drive shaft of a rotary drive device in an image forming apparatus showing a first embodiment of the present invention. It is a figure which shows 2nd Embodiment, Comprising: It is a simple perspective view containing the electric circuit provided with the coil wound around the outer periphery of the magnetorheological fluid which comprises a dynamic damper, and a power supply. It is a figure which shows the modification 1 of 2nd Embodiment, Comprising: It is a simple perspective view containing the electric circuit provided with the controller in the structure of FIG. It is a figure which shows the modification 2 of 2nd Embodiment, Comprising: The electric circuit provided with the coil arrange | positioned close to the magnetorheological fluid near the outer end part of the inertial ring which comprises a dynamic damper, and a power supply FIG. It is a figure which shows the modification 3 of the modification 2, Comprising: It is a simple perspective view containing the electric circuit provided with the current controller in the structure of FIG. It is a figure which shows 3rd Embodiment, Comprising: It is a simple perspective view around the permanent magnet arrange | positioned close to the magnetorheological fluid near the outer end part of the inertia ring which comprises a dynamic damper. It is a figure which shows the modification 4 of 3rd Embodiment, Comprising: The distance adjustment means (not shown) which changes the distance with respect to the magnetorheological fluid which comprises a dynamic damper by moving a permanent magnet to the arrow both directions in a figure is shown. It is a simple perspective view to explain. It is the graph which compared and represented the influence which it has on the speed fluctuation of the Example with a dynamic damper of the modification 9 which concerns on the meshing frequency in a gear train etc., and the comparative example without a dynamic damper which concerns on the meshing frequency. It is a block diagram which shows simply the control structure of the modification 12 which concerns on image formation mode information etc. It is a block diagram which shows simply the control structure of the modification 13 which concerns on image formation mode information. It is a block diagram which shows simply the control structure of the modification 14 which concerns on a speed fluctuation. It is a block diagram which shows simply the control structure of the modification 15 which concerns on a speed fluctuation. It is a block diagram which shows simply the control structure of the modification 16 which concerns on a resonance frequency grasping means. It is a block diagram which shows simply the control structure of the modification 17 which concerns on a resonance frequency grasping means. It is a block diagram which shows simply the control structure of the modifications 18 and 19 which concern on the control using the resonance frequency grasped | ascertained by the resonance frequency grasping means. 1 is a front view showing an overall configuration of a color duplex copying machine having a rotary drive device to which the present invention is applied. FIG. 17 is a perspective view around a general rotational drive system in a rotational drive device such as a color duplex copying machine shown in FIG. 16. 18 is a graph showing the vibration transmissibility of the excitation frequency / resonance frequency when the damping ratio is 0.01 in the general rotary drive system shown in FIG.

Explanation of symbols

1 Photosensitive drum (rotary body, image carrier)
2 Drive shaft 3 Drive motor (drive means)
4 Gear train (drive transmission means)
9 Dynamic damper (dynamic vibration absorber)
10 Magnetorheological fluid 11 Inertial ring (inertial body)
12, 12B Coil (magnetic field applying means)
13 power supply 14, 14A, 14B, 14C electric circuit 15 controller (magnetic field varying means, current adjusting means)
16 Current controller (magnetic field varying means, current adjusting means)
20 Permanent magnets 22, 22A to 22H Current control calculation unit (control means)
24 Speed fluctuation detection means 25 Resonance frequency grasping means 26 Frequency data conversion means 30 Motor control device (motor control means)

Claims (24)

In a rotary drive device comprising: a rotary body; a drive shaft for the rotary body; a drive means for rotating the rotary body via the drive shaft; and a drive transmission means for transmitting the drive force of the drive means to the drive shaft.
An inertial body loosely fitted on the outer periphery of the drive shaft and having an inertial moment;
A magnetorheological fluid enclosed between the outer periphery of the drive shaft and the inner periphery of the inertial body, the viscosity of which changes by applying a magnetic field;
A rotary vibration drive device, wherein a dynamic vibration absorber is formed by the inertial body and the magnetorheological fluid. The rotary drive device according to claim 1, wherein
The rotary drive device characterized in that the inertial body has a substantially ring shape. The rotary drive device according to claim 1 or 2,
A rotary drive device characterized in that magnetic field applying means for applying the magnetic field is disposed in the vicinity of the magnetorheological fluid. The rotary drive device according to claim 3, wherein
The magnetic field applying means is a coil that generates the magnetic field,
A rotary drive device comprising a circuit including a power source for passing a current through the coil. The rotary drive device according to claim 3, wherein
The rotary drive device, wherein the magnetic field applying means is a permanent magnet that generates the magnetic field. The rotary drive device according to claim 3, 4 or 5,
A rotary drive device comprising magnetic field varying means for changing the strength of the magnetic field. The rotary drive device according to claim 6, wherein
The rotation driving device according to claim 1, wherein the magnetic field varying means is current adjusting means for adjusting a current flowing through the coil. The rotary drive device according to claim 6, wherein
The rotary drive device according to claim 1, wherein the magnetic field varying means is a distance adjusting means for changing a distance of the permanent magnet with respect to the magnetorheological fluid. In the rotation drive device according to any one of claims 3 to 8,
The rotary drive device characterized in that the magnetic field applied by the magnetic field applying means or the magnetic field changed by the magnetic field varying means is uniform in the circumferential direction of the magnetorheological fluid. The rotary drive device according to claim 6, 7 or 8,
The drive means is a drive motor;
The rotation drive device according to claim 1, wherein the frequency of the dynamic vibration absorber can coincide with the rotation frequency (fs) of the drive motor by adjusting the magnetic field variable means, the current adjustment means, or the distance adjustment means. The rotary drive device according to claim 6, 7 or 8,
The drive means is a drive motor comprising a stepping motor;
By adjusting the magnetic field varying means, the current adjusting means or the distance adjusting means, the frequency of the dynamic vibration absorber is determined by the rotation frequency (fs) of the stepping motor and the number of steps (sm) per rotation of the stepping motor. A rotary drive device characterized by being able to coincide with a determined frequency (fs × sm). The rotary drive device according to claim 6, 7 or 8,
The drive means is a drive motor;
The phase excitation switching frequency in which the frequency of the dynamic vibration absorber is determined by the number of poles (k) and the number of phases (n) of the drive motor by adjusting the magnetic field variable means, the current adjusting means, or the distance adjusting means. A rotary drive device characterized by being able to match (k × n). The rotary drive device according to claim 6, 7 or 8,
The rotation drive device characterized in that the frequency of the dynamic vibration absorber can be matched with the rotation frequency (fd) of the drive shaft by adjusting the magnetic field variable means, the current adjustment means, or the distance adjustment means. The rotary drive device according to claim 6, 7 or 8,
The drive transmission means is a gear train;
The frequency of the dynamic vibration absorber is determined by the number of rotations (fg) of the gear train and the number of teeth (z) of the gear train by adjustment of the magnetic field varying device, the current adjusting device, or the distance adjusting device. A rotary drive device characterized by being able to coincide with a meshing frequency (fg × z). The rotary drive device according to claim 6, 7 or 8,
The drive means is a drive motor;
The frequency of the dynamic vibration absorber can be matched with a frequency that is an integral multiple of the rotational frequency (fs) of the drive motor by adjusting the magnetic field varying means, the current adjusting means, or the distance adjusting means. Rotation drive device. The rotary drive device according to claim 6, 7 or 8,
By adjusting the magnetic field varying means, the current adjusting means, or the distance adjusting means, the frequency of the dynamic vibration absorber can be matched with a frequency that is an integral multiple of the rotational frequency (fd) of the drive shaft. Rotation drive device. An image forming apparatus comprising the rotation drive device according to claim 6, 7 or 8,
Control means for controlling the current adjustment means or the distance adjustment means so that the magnetic field according to at least one of image quality resolution, image formation mode, print mode, and the like set in the image forming apparatus is applied. An image forming apparatus comprising: The rotary drive device according to claim 6, 7 or 8,
Speed fluctuation detection means for detecting a rotational speed fluctuation of the drive shaft or the rotating body;
Frequency data conversion means for converting the speed fluctuation component detected by the speed fluctuation detection means into frequency data;
Control means for controlling the magnetic field variable means, the current adjusting means, or the distance adjusting means so that the frequency of the dynamic vibration absorber coincides with the frequency data converted by the frequency data converting means. Rotation drive device. The rotary drive device according to claim 18,
The rotational drive device characterized in that the speed fluctuation detecting means is an encoder. The rotary drive device according to claim 18 or 19,
The drive means is a drive motor;
Motor control means for rotating the drive motor by adding random frequency fluctuations at a timing other than actual operation;
The resonance frequency of the dynamic vibration absorber can be identified through the drive motor rotated by applying random frequency fluctuations by the motor control means, the speed fluctuation detecting means, and the frequency data converting means. Rotation drive device. The rotary drive device according to claim 6, 7 or 8,
Resonance frequency grasping means for grasping the torsional resonance frequency of the rotary drive device;
Control means for controlling the magnetic field varying means, the current adjusting means, or the distance adjusting means so that the frequency of the dynamic vibration absorber coincides with the torsional resonance frequency grasped by the resonance frequency grasping means. Rotation drive device. The rotary drive device according to any one of claims 10 to 16,
A rotary drive device comprising a plurality of the dynamic vibration absorbers.   An image forming apparatus comprising the rotation drive device according to any one of claims 1 to 16, or 18 to 22. The image forming apparatus according to claim 17 or 23.
The image forming apparatus according to claim 1, wherein the rotating member is a photosensitive member including a photosensitive drum as an image carrier, an intermediate transfer member, or the like.

Images