JPH0863041A - Rotating body driving device for image forming device - Google Patents

Abstract

PURPOSE: To provide a rotating body driving device for an image forming device capable of completely restraining the fluctuation of the rotation of a rotating body by surely avoiding the trouble of resonance with excitation frequency caused by the shifting phenomenon of the characteristic frequency of a rotating driving system by the addition of an inertial body even though image forming speed or the characteristic frequency is changed. CONSTITUTION: Plural inertial bodies 4 and 5 attached to the rotary shaft 2 of the rotating body 1 are used, and switching operation to make the integral rotation of the inertial body with the rotary shaft possible or impossible is performed by an inertial mass adjusting means 7 based on detected information from a detection means 6 concerning the change of the image forming speed. Then, a division type inertial body attached to the rotary shaft 2 of the rotating body 1 is used, and the divided body of the division type inertial bodies 4 and 5 is properly displaced in a radial direction by an inertial body diameter adjusting means based on the detected information from the detection means 6 concerning the change of the image forming speed or the change of the characteristic frequency of the driving system.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rotating body driving apparatus for an image forming apparatus for rotating a rotating body such as a photosensitive drum used in an image forming apparatus such as an electrophotographic copying machine or a printer, and more particularly to an inertial unit. The present invention relates to a rotating body drive device that can reliably suppress rotation fluctuations of a rotating body by using a body.

[0002]

2. Description of the Related Art Conventionally, in an image forming apparatus such as a color copying machine, there has been a problem that image quality deterioration such as color misregistration and image distortion is caused by rotational fluctuation of a rotating body such as a photosensitive drum. Therefore, in order to suppress such a rotational fluctuation of the rotating body, for example, a drive device has been proposed in which an inertial body (flywheel) is integrally rotated with a rotating shaft of a photosensitive drum (for example, Japanese Patent Application Laid-Open No. 2000-242242). 63-177190
No. Hei 1-52170).

This type of driving device is composed of a driving source such as a motor, a gear for transmitting a rotational driving force from the driving source to the photosensitive drum, a timing belt and the like by an inertial body which rotates integrally with the photosensitive drum. The vibration in the high frequency range generated in the transmission mechanism can be reduced, and thus the rotational fluctuation of the photosensitive drum can be suppressed.

[0004]

However, in the drive device using the inertial body as described above, the addition of the inertial body causes the natural frequency of the rotary drive system including the drive source and the rotation transmission mechanism to fall within the low frequency range. Have the problem of moving to. As a result, the natural frequency of the moved rotary drive system coincides with the cycle (hereinafter, these are referred to as excitation frequency) of the microvibration of the motor or the vibration of the drive gear of the rotation transmission mechanism in which the teeth are pressed against each other. When they are close to each other, resonance is caused, which causes a fluctuation in rotation, which in turn hinders high image quality in image formation.

Therefore, in order to avoid the above-mentioned problems, the inertial characteristic of the inertial body is set to an optimum condition so that the natural frequency of the rotary drive system that moves by the addition of the inertial body does not match or come close to the vibration frequency. It is possible to take measures to set.

However, the above-mentioned vibration frequency is OHP.
In the case of an image forming apparatus having a function of changing the image forming speed (in other words, the rotation speed) in the image forming mode for the (overhead projector) and the setting changing mode of the resolution, it changes by changing the image forming speed. There is a property. Also, the natural frequency of the rotary drive system is
It has a property of changing due to aging and the like, including tolerances of materials, dimensions and the like of constituent parts such as a driving gear and a frame constituting the driving system.

Therefore, it is usually impossible to set the optimum inertial characteristics corresponding to these plural kinds of vibration frequencies and natural frequencies with one inertial body. Further, in order to cope with the change in the image forming speed, for example, it is conceivable to make the inertial mass of the inertial body very large and move the natural frequency of the rotary drive system to an extremely low frequency range.
In this case, the size of the device becomes large, and when the natural frequency itself changes, it cannot be dealt with at all.

The present invention has been made in view of the above-mentioned problems, and it is assumed that the resonance problem with the vibration frequency caused by the movement phenomenon of the natural frequency of the rotary drive system due to the addition of the inertial body will be temporarily reduced. It is an object of the present invention to provide a rotating body driving device for an image forming apparatus, which can surely avoid even if the natural frequency of the rotating body changes and thereby sufficiently suppress the rotational fluctuation of the rotating body.

[0009]

A rotary body driving device of the present invention is a rotary body driving device for rotating a rotary body used in an image forming apparatus, wherein at least one of the rotary bodies is rotatable about a rotary shaft. A plurality of inertial bodies mounted on the vehicle, a detection means for detecting at least one of a change in image forming speed and a change in natural frequency of the rotary drive system, and a rotation axis of the inertial body based on a detection signal from the detection means. And an inertial mass adjusting means for performing a switching operation for enabling or disabling the integral rotation with.

In this technical means, all of the plurality of inertial bodies may be rotatably mounted on the rotary shaft of the rotary body, but some of them may be mounted so as to be rotatable integrally with the rotary shaft. Further, the plurality of inertial bodies may be of the same type or different from each other, and their types are appropriately set.

Further, the rotating body driving device of the present invention is a rotating body driving device for rotating a rotating body used in an image forming apparatus, which is mounted on a rotating shaft of the rotating body and has a radius about the axis. Direction-displaceable inertial body composed of a plurality of divided bodies, detection means for detecting at least one of a change in image forming speed and a change in natural frequency of the drive system, and detection from the detection means And an inertial body diameter adjusting means for displacing the divided body of the divided inertial body based on a signal.

In this technical means, the number of divided bodies forming the divided inertial body is arbitrary, and especially if the radius of the entire divided inertial body can be changed by displacement movement of the divided body. Not limited.

[0013]

According to the present invention, when there is a change in the image forming speed or a change in the natural frequency of the rotary drive system, the inertial mass can be changed by appropriately switching the type and number of inertial bodies that rotate integrally with the rotating body. The diameter of the inertial body is adjusted by adjusting or by appropriately displacing the divisional body of the divisional inertial body in the radial direction. As a result, the moment of inertia (characteristic) of the inertial body is appropriately changed according to the change in the image forming speed or the natural frequency, so that the natural frequency of the rotary drive system is set to a frequency band that does not resonate with the excitation frequency. It can be arranged appropriately. Therefore, it is not necessary to make the inertial body very large, and the rotational drive of the rotating body can be stabilized.

[0014]

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

FIG. 1 shows a rotary body driving apparatus according to an embodiment (Embodiment 1) of the present invention. In FIG.
Reference numeral 1 denotes a photosensitive drum as a rotating body, 2 denotes a rotating shaft of the photosensitive drum 1 rotatably supported by a bearing 2a, and the like, 3
Is a rotary drive system for rotating the photosensitive drum 1 via the rotary shaft 2, 4 is a disk-shaped inertial body mounted so as to rotate integrally with the rotary shaft 2, and 5 is rotatable about the rotary shaft 2. A disk-shaped inertial body mounted, 6 is a detection control unit as a detection unit, 7 is an actuator as an inertial mass adjustment unit, and 8 is an image formation speed control unit.

The rotary drive system 3 includes a motor 9 as a drive source.
A rotation transmission mechanism 10 for transmitting the rotation driving force of the motor 9 to the rotation shaft 2 and a device frame (not shown) and the like constitute a main part thereof. This rotation transmission mechanism 10
Is a plurality of drive gears 11a designed with a predetermined gear ratio,
It is a combination of 11b and 11c.

In the actuator 7, the advancing / retreating connecting rod 7a installed at a predetermined position of the inertial body 4 corresponds to the inertial body 5 by a control signal from the detection control section 6 at the time of connection, as shown in FIG. The connecting groove 5a provided at the position is advanced and connected. In addition, when not connected, the connecting rod 7a retracts and is housed on the inertial body 4 side.

The image forming speed control unit 8 has, for example, a speed S ₁ for performing normal image formation and a speed S ₂ for OHP.
It has various kinds of speed modes, and is connected so that control signals relating to each speed are sent to the motor 9 and the detection control unit 6.

The inertial mass M of the inertial body 4 is such that when the image forming speed is the speed S ₁ , the natural frequency of the rotary drive system 3 is the motor 9
And the inertial mass M ₁ that is not close to the cycle of vibration (excitation frequency) of the rotation transmission mechanism 10 is set in advance. Further, the inertial mass M of the inertial body 5 is such that when the image forming speed is the speed S ₂ ,
When summed with the inertial mass M ₁ of the inertial body 4, the natural frequency of the rotary drive system 3 is preset to the inertial mass M ₂ which is not close to the vibration frequency.

The drive device of this embodiment having such a structure operates as follows.

First, when the image forming speed is the speed S ₁ , a control signal of the speed is sent from the image forming speed controller 8 to the motor 9 and the motor 9 is driven to rotate,
As a result of the driving force being transmitted to the rotary shaft 2 via the rotation transmission mechanism 10, the photosensitive drum 1 rotates. At this time, since the detection control unit 6 detects the image forming speed as the speed S ₁ , the actuator 7 does not operate in particular, and the connecting rod 7a thereof is not operated.
Is accommodated on the inertial body 4 side. As a result, only the inertial body 4 rotates integrally with the photosensitive drum 1 via the rotary shaft 2. Therefore, at the image forming speed S ₁ , the photosensitive drum 1
The moment of inertia acting on the rotational movement of
Based on the inertial mass M ₁ of.

When the image forming speed is changed from the speed S ₁ to the speed S ₂ , a control signal for the speed is sent from the image forming speed controller 8 to the motor 9, and the same operation as described above is performed. The photoconductor drum 1 rotates. Further, at this time, since the image forming speed is detected as the speed S ₂ in the detection control unit 6, the actuator 7 is operated and the connecting rod 7a is projected and connected to the connecting groove 5A (FIG. 2). As a result, in addition to the inertial body 4, the inertial body 5 simultaneously rotates integrally with the photosensitive drum 1. Therefore, at this image forming speed S ₂ , the moment of inertia acting on the rotational movement of the photosensitive drum 1 is the sum of the inertial mass M ₁ of the inertial body 4 and the inertial mass M ₂ of the inertial body 5. It is based on the mass (M ₁ + M ₂ ).

The frequency response characteristics when the image forming speed is the speed S ₁ and the speed S ₂ are shown in FIGS. 3 and 4.

When the image forming speed is the speed S ₁ , as shown in FIG. 3, the natural frequency (Fn) is lower than that in the case where the inertial body 4 is not present (frequency response curve indicated by a chain double-dashed line in the figure). Although moving to the area, velocity S ₁ due to the addition of inertial body 4
It does not match or approach the excitation frequency at. From this, it is understood that, in the rotational driving at the image forming speed S ₁ , there is no resonance and the rotational fluctuation is suppressed by the action of the inertia moment of the inertial body 4.

When the image forming speed is the speed S ₂ ,
As shown in FIG. 4, the natural frequency (Fn) has moved to a lower frequency range compared to the case of the speed S ₁ (frequency response curve indicated by a two-dot chain line in the figure). At the same time, the vibration frequency also changes as compared with the vibration frequency at the speed S ₁ . However, the natural frequency when the rate S ₂ (Fn) is the excitation frequency when the rate of S ₂ by the addition of the inertial body 4 and the inertial body 5 is not closed or close match. From this, in the rotational drive at the image forming speed S ₂ ,
It can be seen that due to the action of the combined inertia moment of the inertial body 4 and the inertial body 5, there is no resonance and the rotation fluctuation is suppressed.

FIG. 5 shows another embodiment (second embodiment) of the present invention.
2 shows a rotary body drive device according to the present invention. The drive device of this embodiment uses disk-shaped inertial bodies 24 and 25 which are rotatably mounted on the rotary shaft 2 as inertial bodies, and uses electromagnetic clutches 27a and 27b as inertial mass adjusting means. It has the same configuration as that of the first embodiment. This electromagnetic clutch connects or disconnects the inertial body and the rotating shaft.

That is, in this drive device, when the image forming speed is the speed S ₁ , the detection control section 6 causes the electromagnetic clutch 2 to operate.
When the operation signal is sent to 7a and the clutch is operated, the inertial body 24 composed of the inertial mass M ₁ is coupled to the rotating shaft 2 and integrally rotated. Further, when the image forming speed is the speed S ₂ , the detection control unit 6 sends an operation signal to the electromagnetic clutches 27a and 27b to operate both clutches, thereby causing the inertial body 24 and the inertial mass M ₂ to move.
An inertial body 25 made of is coupled to the rotary shaft 2 so as to rotate integrally at the same time. And Example 1
According to the same principle as in the case of the apparatus described above, the natural frequency at each image forming speed does not coincide with or come close to the vibration frequency at any time, so that the rotation fluctuation of the photosensitive drum 1 is suppressed.

FIG. 6 and FIG. 7 show a rotating body drive device according to another embodiment (embodiment 3) of the present invention. In the drive device of this embodiment, the split inertial body 30 is used as the inertial body, the detection control unit 60 that detects changes in the image forming speed and the natural frequency of the rotary drive system is used as the detection means, and the inertial mass is further used. The structure is the same as that of the first embodiment except that the inertial body diameter adjusting means is used instead of the adjusting means.

The split inertial body 30 described above is shown in FIGS.
As shown in FIG. 5, the inertial body as a whole basically has a disk shape, and the small disk-shaped central support portion 31 integrally mounted on the rotary shaft 2 and the central support portion 31 are hollowed out. The main part is constructed by combining four divided construction bodies 32 each having a shape of a donut disc divided into four. In addition, the split inertial body 30 includes four split structures 32.
The inertial body diameter adjusting means 33 having the following configuration for displacing the inertial body is provided. That is, all of the four divided structures 32 are radially implanted from the central support portion 31 in the radial direction and penetrate the inside of the divided structures.
4, and a moving motor 35 provided inside the central support portion 31 and the motor 3
A worm gear 36 that is directly connected to the drive shaft of No. 5 and that passes through a gear receiving hole inside the split structure is displaceable along the guide rod 34 (that is, in the radial direction).

The detection control unit 60 includes an image forming speed control unit 8
Is also connected to the natural frequency detection processing unit 61 which sends out a data signal of the natural frequency of the rotary drive system. The natural frequency detection processing unit 61 includes an encoder 62 attached to the rotary shaft 2, and is further connected to the image forming speed control unit 8.

The drive device of this embodiment having such a structure operates as follows.

First, when the image forming speed is changed to either the speed S ₁ or the speed S ₂ as in the first embodiment, the control signal relating to the speed is sent from the image forming speed control section 8 as in the first embodiment. To the motor 9, and the detection control unit 60
Also sent to. The detection control unit 60 detects either the speed S ₁ or the speed S _{2 as} the image forming speed, and calculates the moving distance of the divided body 32 of the divided inertial body 30 corresponding to each speed. That is, the inertial characteristics of the divided inertial body 30 are
Since it is determined by the position of 2 (that is, the radius of the divided inertial body), the movement distance is set so that the natural frequency of the rotary drive system does not match or approach the vibration frequency when the divided inertial body 30 is added. .

For example, if the moving distance is the speed S _{1 and} the setting is zero, the control signal is sent from the detection control unit 60 to the moving motor 35, and the moving motor 35 is moved.
Is not activated, the divided body 32 is not displaced, and as a result, the divided inertial body 30 is in a disk-shaped state as shown in FIG. 7a. The radius r of the divided inertial body 30 at this time is the distance r ₁ from the center of the rotating shaft 2 to the outer edge of the divided body 32. Therefore, at the image forming speed S _1, the moment of inertia acting on the rotational movement of the photosensitive drum 1 is based on the inertial characteristic of the divided inertial body 30 having the radius r ₁ .

When the moving distance is the speed S ₂ , if the distance d is set, the control signal is sent from the detection control section 60 to the moving motor 35, and the moving motor 3 is moved.
When the worm gear 5 operates for a predetermined time and the worm gear 36 rotates, the divided body 32 is displaced by the distance d along the guide rod 34, and as a result, the divided inertial body 30 has a shape as shown in FIG. 7b. The radius r of the divided inertial body 30 at this time is
The distance r ₂ is obtained by adding the moving distance d to the radius r ₁ of the divided inertial body 30 in the disk shape. Therefore, at the image forming speed S _2, the moment of inertia acting on the rotational movement of the photosensitive drum 1 is based on the inertial characteristic of the divided inertial body 30 having the radius r ₂ adjusted as described above. Become.

By properly adjusting the radius of the split inertial body 30 in accordance with the change in the image forming speed in this manner, the natural frequency of the rotary drive system at each speed is the split inertial body of each radius. It is arranged so that it does not coincide with or come close to the vibration frequency at the time.

On the other hand, when the natural frequency of the rotary drive system changes, the natural frequency detection processing section 61 receives the speed control signal from the image forming speed control section 8 and the output signal from the encoder 62, and In the detection processing unit 61, the natural frequency is obtained by performing a fast Fourier transform (FFT) operation on the angular velocity of the photosensitive drum. Then, the data of the detected natural frequency is detected by the detection control unit 6.
When sent to 0, the detection control unit 60 compares the detected natural frequency with a reference natural frequency stored in a table in the memory in advance, and determines whether the difference exceeds a predetermined threshold value. Determine. At this time, if the difference in the natural frequency exceeds the threshold value, the division body 32 corresponding to the difference is deleted so that the detection control unit 60 cancels the difference.
Is calculated.

Then, a control signal based on the calculated moving distance is sent from the detection control unit 60 to the moving motor 35, and the moving motor 35 operates for a predetermined time corresponding to each moving distance, thereby dividing as described above. The body 32 is displaced by a predetermined distance. Therefore, when the natural frequency of the rotary drive system changes by a predetermined amount or more as compared with the reference natural frequency, the inertia moment acting on the rotational movement of the photoconductor drum 1 has the radius adjusted as described above. Inertial body 3 consisting of
It is based on the inertia characteristic of zero.

Therefore, by appropriately adjusting the radius of the divided inertial body 30 in accordance with the change in the natural frequency of the rotary drive system, the natural frequency of the rotary drive system is corrected so that it is always constant. Moreover, the natural frequency is arranged so as not to match or approach the vibration frequency when the divided inertial body having each radius is added.

Although the photosensitive drum is described as an example of the rotating body in the first to third embodiments, the present invention is not limited to this, and any rotating body which requires suppression of rotation fluctuation may be used. The same applies to other rotating bodies. Therefore, the rotating body in the present invention may be, for example, a transfer drum, a belt-shaped photosensitive body or a transfer body, or the like.

In the first and second embodiments, a case has been described in which a plurality of inertial bodies are appropriately switched according to changes in the image forming speed. For example, as in the third embodiment, the natural frequency of the rotary drive system is changed. It is also possible to appropriately switch a plurality of inertial bodies in accordance with changes.

[0041]

As described above, according to the rotation driving device of the present invention, the inertial mass is adjusted or the diameter of the inertial body is adjusted according to the change of the image forming speed and the change of the natural frequency of the rotation driving system. By adjusting, the inertia moment (characteristic) of the inertial body can be appropriately changed, and the natural frequency of the rotary drive system can be accurately arranged in the frequency band that does not resonate with the excitation frequency. Therefore, even if the image forming speed or the natural frequency changes, the inertial body does not need to be made very large, and the vibration frequency and the vibration frequency caused by the movement of the natural frequency of the rotary drive system due to the addition of the inertial body Since the resonance problem can be reliably avoided, the rotational fluctuation of the rotating body can be sufficiently and reliably suppressed. Then, according to the image forming apparatus to which the present driving device is applied, it is possible to form a high-quality image without problems such as color misregistration due to rotation fluctuation.

[Brief description of drawings]

FIG. 1 is a conceptual diagram showing a rotary body drive device according to a first embodiment of the present invention.

FIG. 2 is an explanatory view of a main part showing a state in which the inertial bodies of FIG. 1 are connected to each other.

3 is a characteristic diagram showing the frequency response characteristic of the time the image forming speed S ₁ in the first embodiment.

FIG. 4 is a characteristic diagram showing frequency response characteristics at the image forming speed S ₂ in the first embodiment.

FIG. 5 is a conceptual diagram showing a rotary body driving device according to a second embodiment of the invention.

FIG. 6 is a conceptual diagram showing a rotary body driving device according to a third embodiment of the invention.

FIG. 7 is an explanatory diagram showing the split inertial body of FIG. 6;

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Rotating body (photosensitive drum), 2 ... Rotating shaft, 3 ... Rotating driving body, 4, 5 ... Multiple inertial bodies, 6, 60 ... Detection means,
7, 27 ... Inertial mass adjusting means, 30 ... Divided inertial body, 3
2 ... Divided body, 33 ... Inertial body diameter adjusting means.

Claims (2)

[Claims] 1. A rotating body driving device for rotating a rotating body used in an image forming apparatus, comprising a plurality of inertial bodies at least one of which is rotatably mounted on a rotating shaft of the rotating body, and at least an image forming speed. Or a change in the natural frequency of the rotary drive system, and a switching operation that enables or disables the integral rotation of the rotating shaft of the inertial body based on the detection signal from the detecting means. A rotating body driving apparatus for an image forming apparatus, comprising: an inertial mass adjusting means for performing the operation. 2. A rotary body driving device for rotating a rotary body used in an image forming apparatus, comprising a plurality of divided bodies mounted on a rotary shaft of the rotary body and displaceable in a radial direction around the rotary shaft. And a detection means for detecting at least one of a change in the image forming speed or a change in the natural frequency of the drive system, and a division type inertial body based on a detection signal from the detection means. An inertial body diameter adjusting means for displacing the divided body, and a rotating body drive device for an image forming apparatus.