JPH08115041A - Automatic inertia adjusting device - Google Patents

Abstract

PURPOSE: To prevent speed fluctuation in drive system by providing a means calculating the characteristic frequency of a drive transmission system and automatically adjusting the inertia of the drive transmission system so that the calculated characteristic frequency is not superposed with a frequency of an exciting source. CONSTITUTION: Four mass bodies 21 for adjusting the inertia are arranged on a drive roll 61 so as to surround the drive roll 61. Mass body position movement shafts 22 penetrating respective mass bodies 21 are provided, and contact surfaces between both are thread. The mass body position movement shaft 22 is rotated by a mass body movement adjusting jig 23 arranged on its periphery, and the mass body 21 is moved in the direction of the arrow P. The frequency response characteristic of the drive transmission system is measured, and the characteristic frequency of the drive transmission system is obtained. Then, the mass body 21 is moved so that no resonance occurs by that the characteristic frequency of the drive transmission system superposes on the frequency of the exciting source such as the number of revolution of respective shafts and an engaging frequency of a gear and the inertia value is adjusted automatically.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an automatic inertia adjusting device capable of preventing speed fluctuation of a drive system in an image forming apparatus such as an electrophotographic copying machine.

[0002]

2. Description of the Related Art In an image forming apparatus such as an electrophotographic copying machine, in order to obtain a highly accurate image, the rotational speed and position of a drive shaft such as an intermediate transfer member such as a photoconductor or a belt or a paper conveying device is controlled. There is a need.

Conventionally, when the above control is performed, the speed of the photosensitive member, the intermediate transfer member, the sheet conveying device, etc. (that is, the final operation target) is not directly detected, but the motor itself or the motor for driving these final operation targets. Since the speed detected by the encoder mounted on the shaft is fed back to control the rotation speed of the motor, the characteristics (drive system transfer function) of the drive transmission system such as gears from the motor shaft to the final operation target are Not included in the control loop. For this reason, the speed of the final operation target is not necessarily controlled with high accuracy, and speed fluctuations in a high frequency band occur due to the frequency of vibration generated by gear meshing (hereinafter referred to as gear meshing frequency).

Therefore, in order to suppress velocity fluctuations and vibrations in the high frequency band that occur in the photoconductor, the intermediate transfer member or the sheet conveying device, conventionally, a mass body of an appropriate size is attached to these shafts so that the inertia (inertia) can be obtained. Is being adjusted. For example, in Japanese Patent Laid-Open No. 4-56885, inertia is adjusted by moving a mass body attached to a photosensitive drum in the radial direction of the drum,
A method of changing the natural frequency of a drive train is disclosed.

[0005]

However, in the inertia adjusting method disclosed in the above publication, the inertia is mechanically adjusted manually, so that the wear of the gear and the change in rigidity over time, the environment, and the like. If the characteristics of the drive transmission system change due to changes in temperature or the like, it may not be possible to cope with the change, resulting in an oscillating system.

Further, in the conventional inertia adjusting method, the speed fluctuation due to the meshing frequency of the gear in the high frequency band of the vibration source of the drive transmission system is suppressed, but the inertia value is increased as the inertia value is increased. , The natural frequency of the drive transmission system moves to the low frequency side, and in some cases, the natural frequency of the drive transmission system may be equal to or close to the rotation speed of each shaft or gear that is another vibration source of the drive transmission system. Resonance may occur at the rotational speed, and the speed fluctuation may increase even before the inertia adjustment.

The present invention has been made under such a background, and in an image forming apparatus such as an electrophotographic copying machine,
The inertia value is automatically set so as not to resonate with the vibration source such as rotation of each axis of the drive transmission system from the motor shaft to the final operation target such as the photoconductor, the intermediate transfer member, and the paper transport device, gear rotation, and meshing between gears. It is an object of the present invention to provide an inertia automatic adjustment device that can be adjusted mechanically.

[0008]

In order to solve the above-mentioned problems, the invention according to claim 1 is to provide a photosensitive member in an image forming apparatus such as an electrophotographic copying machine, an intermediate transfer member such as a belt, a sheet conveying section and the like. A device for automatically adjusting the inertia of a drive transmission system for transmitting the driving force of a motor, wherein a frequency response characteristic of the drive transmission system is obtained, and a natural frequency of the drive transmission system is calculated from the characteristic. A means for automatically adjusting the inertia of the drive transmission system so that the calculated natural frequency does not overlap with the frequency of the vibration source such as the rotational speeds of the shaft and gears forming the drive transmission system and the meshing frequency between the gears. It is characterized by having.

According to a second aspect of the present invention, in the first aspect of the invention, the means for automatically adjusting the inertia has a predetermined mass body on a shaft constituting the drive transmission system in a radial direction of the shaft. It is characterized in that it is movably attached and the inertia is adjusted by changing the displacement from the axis of the mass body.

[0010]

According to the first aspect of the present invention, the natural frequency of the drive transmission system and the frequencies of the vibration source such as the rotational speeds of the shaft and gears forming the drive transmission system and the meshing frequency between the gears are determined. The inertia of the drive transmission system is automatically adjusted so as not to overlap. As a result, resonance does not occur with the vibration source such as rotation of the shaft or gear in the drive transmission system or meshing between the gears. Further, even if the characteristics of the drive transmission system change due to changes in wear of the gears, changes in rigidity over time, changes in temperature due to changes in the environment, the inertia is automatically adjusted according to the state at that time, and resonance can be avoided.

According to the second aspect of the invention, the inertia value is automatically adjusted by the displacement of the mass body from the axis.

[0012]

Embodiments of the present invention will be described below with reference to the drawings. The present invention is not limited to the embodiments described below.

A: Configuration of the Embodiment (1) Overall Configuration FIG. 1 is a sectional view showing the overall configuration of a multicolor image forming apparatus to which the present invention is applied. In FIG. 1, the image forming apparatus includes an image forming unit 1 that forms a color image based on image data, an image reading unit 2 that reads a document and converts it into image data, and a laser that drives a laser according to the read image data. It is composed of an image writing unit 3 which irradiates the body 4 with a light beam. In addition to the photoconductor 4 and the developing device 5, the image forming unit 1 mainly includes an intermediate transfer belt 60, a drive roll 61, and a mark detection sensor 6 that form a drive system.
2, a transfer cleaner 63, a transfer corotron 64, a drive assisting roll 65, a transfer assisting roll 66, a transfer roll 67, a photoconductor cleaner 7, a sheet conveying device 8 and a fixing device 9.

(2) Structure of the drive transmission system to which the present invention is applied FIG. 2 is an enlarged view showing the vicinity of the drive transmission system (belt drive system) to which the present invention is applied in the above apparatus. In FIG. 2, the intermediate transfer belt 60 is made of polyimide having a thickness of 0.1 mm, and is driven at a belt speed v = 100 mm / s by a driving roll 61 having a diameter of 30 mm. The peripheral length of the intermediate transfer belt 60 is 567 mm, and is rotated once every six rotations of the drive roll 61.

Further, on the surface of the intermediate transfer belt 60, a mark having a reflectance different from that of the background portion of the belt is formed. By detecting this mark by the sensor 62 (see FIG. 1), an image of each color is formed. The timing is determined and the toner image is accurately superimposed on the belt 60. The mark may be formed by making a hole in the intermediate transfer belt 60 and detecting the hole, or may be formed by other means as long as it can detect one place of the belt 60.

The driving force for conveying the belt 60 is from the motor shaft 12 of the drive motor (not shown) to the gear 1
0, 11 is transmitted, and an external encoder 13 (or incorporated in the motor) for detecting the rotation speed of the drive motor is provided on the motor shaft 12. Further, an encoder 68 that detects the rotation speed and the position of the drive roll 61 is provided on the shaft of the drive roll 61.

From the encoder 68, it is possible to obtain a signal corresponding to one rotation of the drive roll 61 by using the Z phase. The Z-phase signal is used to perform positioning when adjusting the inertia value described later.

(3) Structure of Automatic Inertia Adjustment Device Next, the structure of the inertia automatic adjustment device according to this embodiment will be described. 3A and 3B are views showing a mechanical configuration of the inertia automatic adjustment device. FIG. 3A is a sectional view and FIG. 3B is a side view. In the figure, the drive roll 61 is provided with four mass bodies 21, 21, 21, 21 for adjusting the inertia thereof so as to surround the drive roll 61 from four directions. When increasing the inertia value, move the mass body 21 in the direction of arrow P
Move away from. When decreasing the inertia value, the mass body 21 is moved in the opposite direction to the above.

As a mechanism for moving the mass body 21, as shown in the figure, a mass body position moving shaft 22 penetrating each mass body 21 is provided, the contact surfaces of both are threaded, and the mass body is moved. The position moving shaft 22 is rotated by the mass body movement adjusting jig 23 arranged around the position moving shaft 22. Further, the mass body position moving shaft 22 is positioned with respect to the mass body movement adjusting jig 23 by the Z-phase signal of the encoder 68 installed on the shaft of the drive roll 61.

Since the mass body 21 is slidably in contact with the outer wall 20 of the inertia adjusting device as shown in the figure, it does not rotate with the rotation of the mass body position moving shaft 22. . Further, the mass body position moving shaft 22 meshes with the mass body 21 by being threaded, while the tip end portion of the mass body position moving shaft 22 rotates idly with respect to the drive roll 61. As a result, the mass body 21 moves in the direction of the arrow P according to the rotation of the mass body position moving shaft 22.
In this case, the mass body 21 is the inertia movement adjusting jig 23.
Depending on the direction of rotation of the drive roll 61. Further, the rotation of the mass body movement adjusting jig 23 is controlled by a control device (not shown). The control device is composed of a CPU, a memory, and the like, and performs various arithmetic processes such as a natural frequency described later.

In the example shown in FIG. 3, the moving operation as described above is performed for the four mass bodies 21, 21, 21, 21 (that is, four points). If the threads of the body 21 and the mass body position moving shaft 22 are formed in opposite directions, and one pair of mass bodies 21 is moved by one inertia movement adjusting jig 23, the above-mentioned 4 can be performed by rotating two points. It becomes possible to move the points.

B: Operation of Embodiment (1) Overall Operation of Automatic Inertia Adjustment Next, steps ST1 to S of the flowchart shown in FIG.
The overall operation of the inertia automatic adjustment will be described along T3. First, in step ST1, in order to obtain the natural frequency of the drive transmission system shown in FIG. 2, the frequency response characteristic of the drive transmission system is measured. Here, when the configuration of the entire drive system is expressed as in the block diagram shown in FIG. 5, the speed detection signal obtained by the encoder 13 (see FIG. 2) on the motor shaft 12 is fed back for speed control. The transfer function of the control loop corresponds to Gsc (s) in the block diagram representation of the transfer function shown in FIG.
The frequency response of this Gsc (s) is generally shown in FIG.
The characteristics are as shown in.

Further, in FIG. 6, Gmd (s) corresponds to the transfer function of the drive transmission system (see FIG. 5) outside the control loop, specifically from the motor shaft 12 to the final drive target. Gears 10, 1 existing up to belt 60
It corresponds to a transfer characteristic such as 1. This transfer function Gmd
The frequency response of (s) has a characteristic as shown in FIG. 8, for example, gain peaks appear at some frequencies, and these peaks are in an oscillating state.

Usually, one of such gain peaks corresponds to the natural frequency, and in the next step ST2, the natural frequency is predicted from these. That is, although details will be described later, in brief, in order to specify the natural frequency from the gain peak, the transfer function Gmd (s) of the drive transfer system or the transfer function Gg (s) of the entire drive system is specified. Frequency response characteristics (Figs. 8 and 9)
(Refer to FIG. 3) while measuring the inertia value by the inertia automatic adjusting device shown in FIG.

If the gain peak of the frequency response characteristic shown in FIG. 8 or 9 moves in the horizontal axis (frequency) direction by changing the inertia value in this way, the frequency at which the gain peak appears is changed to the natural vibration. Consider as a number.
This makes it possible to specify the natural frequency of the drive transmission system.

In step ST3, the natural frequency of the drive transmission system does not overlap with the frequency of the vibration source such as the rotational speed of each shaft or the meshing frequency of the gears to cause resonance.
Again, the inertia value is automatically adjusted by the inertia automatic adjustment device.

(2) Measurement of frequency response characteristic (step S
Detailed Operation Regarding T1) Next, details of a method for measuring the frequency response characteristics of the transfer function Gmd (s) of the drive transfer system and the transfer function Gg (s) of the entire drive system will be described. The transfer function Gmd (s) of the drive transmission system shown in FIG. 6 is a mechanical transfer characteristic such as inertia and torsional rigidity of the drive transmission system, and it is generally difficult to make it a function as a drive transfer function equation, In this embodiment, noise of a low frequency to a high frequency (that is, a frequency band in which the characteristics of the transfer function Gmd (s) can be grasped) is intentionally added to the target speed (that is, reference speed) Vref of the control system in the actual machine. While driving the motor.

The frequency band of the noise added here is arbitrary, but it is also possible to set it to a specific frequency or frequency band in order to shorten the calculation processing time, for example. The specific frequency in this case is important for understanding the characteristics of the transfer function Gmd (s) of the drive transmission system, such as the rotation speed of the motor shaft, the rotation speed of each drive shaft, or the meshing frequency between gears. Frequency or band.

Then, the response speed signals of the encoder 13 on the motor shaft 12 and the encoder 68 on the drive roll 61 driving the belt 60 with respect to the speed command value to which the noise is added are subjected to comparison calculation processing, whereby Gmd ( The frequency response characteristics of s) and Gg (s) are obtained.

(3) Calculation of natural frequency (step ST
Detailed Operation of 2) Next, details of the method of calculating the natural frequency will be described. First, from the gain peaks appearing in the frequency response characteristics of Gmd (s) or Gg (s) obtained as described above, some frequencies that are expected to correspond to the natural frequency are selected (for example, in FIG. Fn1 and f in 10
n2). Next, the mass body 21 is moved in the direction of arrow P by the inertia automatic adjustment device shown in FIG.
The inertia value at 1 is changed, and the frequency response characteristic at each inertia value is obtained. At this time, it is determined whether or not the position (frequency) of each of the selected gain peaks has moved according to the change in inertia, and the moved gain peak is regarded as corresponding to the natural frequency (for example, in FIG. 10). Is the natural frequency of fn1).

(4) Detailed operation of automatic adjustment of the inertia to the optimum value (step ST3) Next, details of the method of automatically adjusting the inertia to the optimum value will be described. When the natural frequency obtained as described above is equal to or close to the frequency of the vibration source such as the shaft rotational speed of the gears 10 and 11 or the meshing frequency between the gears, resonance is avoided. Therefore, it is necessary to adjust the inertia to the optimum value. For example, as shown in FIG.
The frequency f2 of the vibration source detected by the T analysis and FIG.
When the natural frequency fn1 shown in (1) matches, resonance occurs in the drive transmission system and the speed fluctuation becomes extremely large. In such a case, the inertia value is adjusted by the inertia automatic adjusting device shown in FIG. 3 to be the optimum value for avoiding resonance. The algorithm for adjusting to this optimum value has the following procedure, for example.

Performing FFT analysis as shown in FIG.
The frequencies f1, f2, f3, ... Of the vibration source are obtained (or previously obtained and stored). The current natural frequency fn is the frequency f1, f of each excitation source.
The adjustable inertia value is calculated so that the interval with the closest frequency (2, f3, ..., This frequency may have a different value in the process of adjusting the inertia value) becomes the maximum. The rotation amount of the inertia movement adjusting jig 23 is calculated so as to obtain the obtained inertia value. The mass body 21 is moved by the rotation amount obtained by the above calculation, and the inertia value is changed.

By adjusting the inertia value by the above-mentioned algorithm, the natural frequency moves from fn to fn 'as shown in FIG. As a result, FIG.
The speed fluctuation at the frequency f2 before the inertia adjustment shown in (4) is reduced as shown in FIG. As a result, it is possible to obtain a highly accurate image in image formation.

The above-described automatic inertia adjustment operation may be performed in real time so as to always be in an optimum state with respect to changes over time of the drive transmission system and changes in the environment. When there is no change, the change in torsional rigidity due to wear of gears may be taken into consideration, and the adjustment may be made at the timing when the power is turned on.

[0035]

As described above, according to the present invention, in an image forming apparatus such as an electrophotographic copying machine, driving from a motor shaft to a final operation target such as a photoconductor, an intermediate transfer member and a sheet conveying device is performed. The inertia value is automatically adjusted so as not to resonate with the vibration sources such as the rotation of each axis of the transmission system, the rotation of gears, and the meshing of gears. This not only prevents resonance with the meshing frequency between gears as in the past, but also does not resonate with the frequencies of other vibration sources such as the rotation speed of each shaft of the drive transmission system and gears, and the final operation target It is possible to suppress speed fluctuations and vibrations of objects. In addition, even if the characteristics of the drive transmission system change due to changes in gear wear or rigidity over time, temperature changes due to environmental changes, etc., the inertia is automatically adjusted according to the state at that time to reduce speed fluctuations and vibrations. It can be prevented. As a result, a high quality image is always obtained.

[Brief description of drawings]

FIG. 1 is a sectional view showing a schematic configuration of a multicolor image forming apparatus to which the present invention is applied.

FIG. 2 is an enlarged sectional view showing a drive transmission system of the device.

3A and 3B are diagrams showing a mechanical configuration of an automatic inertia adjusting device of the present embodiment, in which FIG. 3A is a sectional view and FIG. 3B is a side view.

FIG. 4 is a flowchart showing the operation of the embodiment.

FIG. 5 is a block diagram showing the configuration of the entire drive system.

FIG. 6 is a block diagram showing a transfer function of the drive system.

FIG. 7 is a frequency response characteristic diagram of a transfer function Gsc (s) in the drive system.

FIG. 8 is a frequency response characteristic diagram of a transfer function Gmd (s) in the drive system.

FIG. 9 is a frequency response characteristic diagram of a transfer function Gg (s) in the drive system.

FIG. 10 is a transfer function Gg showing a characteristic of natural vibration.
It is a frequency response characteristic figure of (s).

FIG. 11 is a diagram showing an FFT analysis result of a vibration source before inertia adjustment.

FIG. 12 is a frequency response characteristic diagram of a transfer function Gg (s) after inertia adjustment.

FIG. 13 is a diagram showing an FFT analysis result of a vibration source after inertia adjustment.

[Explanation of symbols]

13, 68 Encoder 20 Inertia automatic adjusting device (means for automatically adjusting inertia) 21 Mass body 22 Mass body position moving shaft 23 Mass body position moving adjusting jig 61 Drive roll

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Masakazu Kobayashi 2274 Hongo, Ebina City, Kanagawa Prefecture, Fuji Xerox Co., Ltd. (72) Inventor Susumu Kibayashi 2274, Hongo, Ebina City, Kanagawa Prefecture, Fuji Xerox Co., Ltd. (72) Inventor Junichi Murakami 2274 Hongo, Ebina City, Kanagawa Prefecture Fuji Xerox Co., Ltd.

Claims (2)

[Claims] 1. An apparatus for automatically adjusting the inertia of a drive transmission system for transmitting a driving force of a motor to a photosensitive member, an intermediate transfer member such as a belt, a sheet conveying unit and the like in an image forming apparatus such as an electrophotographic copying machine. A means for obtaining the frequency response characteristic of the drive transmission system and calculating the natural frequency of the drive transmission system from this characteristic; and the calculated natural frequency being the number of rotations of the shaft and the gear constituting the drive transmission system. , A means for automatically adjusting the inertia of the drive transmission system so that it does not overlap with the frequency of the vibration source such as the meshing frequency between gears. 2. The means for automatically adjusting the inertia comprises:
2. The inertia is adjusted by attaching a predetermined mass body to a shaft constituting the drive transmission system so as to be movable in the radial direction of the shaft, and changing the displacement of the mass body from the axial center. Automatic inertia adjustment device described.