JPH049967A - Abnormal rotation detecting device for image forming device - Google Patents

Abstract

PURPOSE:To rapidly detect the abnormal rotation of a rotor with high sensitivity and to prevent the damage of the rotor and a large amount of faulty image forming from occurring by comparing the peak position of vibration obtained by reading the vibration of the rotor by a sensor and Fourier-transforming it with that at a normal time. CONSTITUTION:After the detection signal of a gap sensor 2 which is provided to be opposed to the outer peripheral surface of a photosensitive drum 12d is A/D converted by an A/D converter 4, it is inputted in a microcomputer 5 and stored in a RAM 51. This data is Fourier-transformed by an arithmetic means 52 so as to calculate vibrational spectrum, and a discrimination means 54 compares the output level of a band pass filter 53 with a threshold, that means, a level range obtained by adding a little margin to the output level at the time of normal rotation. In the case of judging that the level is changed and exceeds the threshold, a display means 6 performs the display of abnormality and a driving stop means 7 stops the driving of the drum 12d or the driving of an entire copying machine, thereby preventing the damage of the rotor and the large amount of faulty copying from occurring.

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention is intended to prevent abnormal rotation of rotating bodies such as photosensitive drums, developing sleeves, and optical system drive pulleys in image forming apparatuses such as copying machines, facsimiles, and printers. The present invention relates to a rotation abnormality detection device that can easily detect abnormal rotation.

<Prior Art> Conventionally, in image forming apparatuses such as copying machines, abnormal vibrations of rotating bodies such as photoconductor drums, developing sleeves, and optical system drive pulleys have caused blurring and density in images transferred from the photoconductor drums. Image formation defects such as unevenness may occur.

Conventional image forming apparatuses are not equipped with means for detecting such abnormal vibrations of the rotating body. For this reason, abnormal vibrations of the rotating body can be detected by visually evaluating the formed image, by listening to the noise generated due to abnormal vibrations, or by attaching a vibration sensor to the main body of the image forming apparatus to detect the vibrations and outputting the output signal. It was detected by reading and evaluating.

<Problems to be Solved by the Invention> However, when visually judging an image, if the density of the image is low or the difference in density is small, it may be difficult to judge whether the image is good or bad. Furthermore, when distinguishing between the noises generated by abnormal vibrations or when detecting vibrations using an attached vibration sensor, the noises generated by the abnormal vibrations may be canceled out by surrounding noise. Furthermore, the vibration sensor has a complicated structure and is large in size, which poses a problem of installation location.

Furthermore, even in the above case, the abnormality cannot be detected until the abnormality has progressed to a certain extent.

As a result, the rotating body may be damaged due to a delay in detecting an abnormality, affecting the developing section, bearings, cleaning section, etc. around the rotating body, or causing a large number of defective image formations. there were.

In particular, the higher the speed, the more susceptible to the effects of vibration (1), so the above problem was serious.

Therefore, the inventor of the present invention focused on the fact that when abnormal vibration occurs in a rotating body, the natural frequency of the rotating body apparently moves.

The natural frequency apparently shifts when combined with a force unique to the rotating body and an element other than the rotating body, and also shifts depending on temperature and load. In some cases, the sum of these influences causes an apparent change in the natural frequency.

FIG. 4 shows the results of generating an artificial single vibration by loosening the timing belt tension by loosening the drive belt drive tension of a rotating body drive system created in a laboratory.

The figure (A) shows the frequency spectrum when the tension is at a normal value, and the natural vibration, that is, the peak position of the spectrum appears at the position of the frequency ν0, which is 0.

The same figure (B) shows the frequency spectrum immediately after loosening the driving tension roller, and the same figure (C) shows the frequency spectrum 5 minutes after loosening the driving tension roller.

As you can see from each spectrum, when the tension is loosened, the peak position of the spectrum shifts by 1Δ.

The shift in the peak position of the spectrum as described above is also observed when the bearing of the rotating body becomes loose.

From the above results, it can be inferred that when a rotating body exhibits rotational abnormality, some change appears in the frequency spectrum.

Therefore, the present invention scans the original placed on the original table with illumination, guides the reflected light from the original to a rotating photoreceptor, and transfers the image formed on the photoreceptor onto transfer paper, thereby creating an image. In an image forming device, it is possible to accurately detect abnormal rotation of a rotating body by capturing changes in the frequency spectrum, thereby preventing damage to the rotating body and the occurrence of a large number of defective image formations. An object of the present invention is to provide a rotation abnormality detection device that can detect rotation abnormalities.

Means for Solving the Problems> A rotational abnormality detection device of the present invention to achieve the above object includes a sensor that detects vibrations of a rotating body as the rotating body rotates, and a Fourier method that converts an output signal from the sensor. a calculation means for converting and calculating a frequency spectrum; a storage means for storing in advance the peak position of the spectrum during normal rotation of the rotating body; and a storage means for storing the peak position of the frequency spectrum calculated by the calculation means. a determining means for determining whether the peak position of the frequency spectrum stored by the means is more than a certain frequency apart from the peak position of the spectrum; The device also includes a display means for displaying that there is an abnormal vibration in the body.

According to the rotational abnormality detection device with the above configuration, the vibration of the rotating body is read by the sensor, and the read signal is Fourier-transformed to detect whether the peak position of the frequency spectrum or the distance from the peak position of the spectrum is more than a certain frequency. Determine whether the

When a rotating body causes abnormal vibrations, it is usually possible to determine whether there is a deviation in the frequency of the rotating body, so the abnormal vibrations of the rotating body can be easily determined.

The rotating body may be selected from a photosensitive drum, a developing sleeve, and a pulley for driving an optical system.

In addition to the display means described above, the apparatus may further include a drive stop means for stopping the drive of the rotating body. According to this, when an abnormality in the rotating body is detected, the rotation can be immediately stopped.

<Embodiments> Hereinafter, embodiments of the present invention will be described with reference to the drawings.

FIG. 2 shows the internal configuration of a copying machine. In the figure, this copying machine has an electrostatic latent image corresponding to an original image in the copying machine main body 1 on a photoreceptor tram 12d as a rotating body. an optical system 11 for forming a toner image, and an image forming section 1 for developing the electrostatic latent image into a toner image by a developing device 12c and then transferring it onto copy paper.
2, and a transfer paper transport unit that sequentially passes the transfer paper fed from the paper feed cassette 14 or the paper feed cassette 15 through the image forming unit 12, the transport kite] 3a, and the fixing device 17, and then discharges it onto the paper output tray 16. 13.

FIG. 1 is a block diagram showing a device for detecting abnormal rotation of the photosensitive drum 12d.

A gap sensor 2 is attached opposite to the outer peripheral surface of the photoreceptor drum 12d, and this cap sensor 2
A filter 3 cuts unnecessary signals from the signal, and the signal is input to a microcomputer 5 via an A/D converter 4. The cap sensor 2 is of a type that uses the directional angle of the projected light to detect the amount of reflected light that changes depending on the distance, a type that uses magnetic induction to detect changes in impedance due to the approach of a metal object, and a type that uses reflection of ultrasonic waves. You can use well-known tools such as ones that check the time.

The microcomputer 5 includes a RAM 51 that stores signals from the gap sensor 2 over a predetermined period of time (for example, one rotation time of the photoreceptor drum 12d), and an operation that performs Fourier transform on the data stored in the RAM 51 to calculate a frequency spectrum. means 52, a band pass filter 53 for checking whether the peak value of the frequency spectrum is within a certain hunt width (for example, ±5 Hz), and comparing the output level of the band pass filter 53 with a threshold value Vo. and determining means 54 for determining whether the peak position of the photoreceptor tram 12d has changed.

The threshold value Vo is set within a level range that is slightly wider than the output level of the band pass filter 53 when the photoreceptor tram 12d is rotating normally. In addition,
The natural frequency ν0 of the rotating body vibration system including the photosensitive drum 12d is determined experimentally in advance, and the center frequency of the band pass filter 53 is also set to be the same as this natural frequency ν0. .

The microcomputer 5 also includes a determining means 54.
a display means 6 that displays an abnormality when it is determined that the output level of the bandpass filter 53 has changed compared to a threshold value Vo; and a drive stop means that stops driving the photosensitive drum 12d or the entire copying machine. 7 is connected.

With the above configuration, the detection signal of the cap sensor 2 is
After A/D conversion by the A/D converters 4a and 4b, the data is input to the microcomputer 5 and stored in the RAM 51.
The stored data is Fourier-transformed by the calculating means 52 to calculate a frequency spectrum, and the determining means 54 determines whether or not the output level of the band pass filter 53 has changed compared to the threshold value ■0. If it is determined that the VO has changed, the display means 6 displays an abnormality, and the drive stop means 7 stops the photosensitive tram 1.
2d or the entire copying machine can be stopped.

In this way, the above-mentioned rotational abnormality detection device can detect problems by Fourier transforming the vibration data from the cap sensor 2, even if the level of the frequency component of the photoreceptor drum contained in the vibration data is small. Changes in the frequency can be detected with sensitivity.

Furthermore, since abnormal rotation of the photoreceptor tram 12d can be detected at an early stage and countermeasures can be taken, damage to the photoreceptor drum 12d and a large number of defective copies can be prevented. I can do it.

In addition, since the apparent movement of the natural frequency may be based on the influence of other vibration sources, the quality of rotation of the photoreceptor drum 12d is determined comprehensively, including the influence of other vibration sources. I can do something.

Note that it is preferable that the vibration measurement of the photosensitive drum 12d be repeatedly carried out for a certain period of time while the photosensitive tram 12d is being rotated, since this allows the rotational state of the photosensitive tram 12d to be constantly monitored.

It should be noted that the present invention is not limited to the above embodiments, and in the above embodiments, abnormal vibrations of the photoreceptor drum 12d are detected, or the developing sleeve of the developing device 12c, the optical system drive burr, etc. Of course, it is also possible to detect vibrations of other rotating bodies.

Furthermore, instead of the gap sensor 2, as shown in FIG. 3, an acceleration sensor 2a may be attached to the inner peripheral surface of the photoreceptor drum 12d to detect vibrations of the photoreceptor tram 12d.

Various design changes can be made without changing the gist of the invention.

<Effects of the Invention> As described above, according to the rotation abnormality detection device in the image forming apparatus of the present invention, the vibration of the rotating body is read by the sensor, the read signal is Fourier-transformed, and the position of the vibration peak is determined from normal vibration. By comparing it with the actual rotation, abnormal rotation of the rotating body can be detected with high sensitivity and quickly, which can prevent damage to the rotating body or large number of image formation defects. .

[Brief explanation of the drawing]

Figure 1 is a block diagram showing the rotational abnormality detection device. Figure 2 is a schematic diagram showing the internal configuration of the copying machine. Figure 3 is a block diagram showing the rotational abnormality detection device using an acceleration sensor installed inside the rotating body. 4 are graphs showing spectral data after Fourier transformation of vibration data of a rotating body. 2 gap sensor, 2a acceleration sensor, 6 display means, 7 drive stop means, 12d photosensitive drum, 52 calculation means, 53 second bus filter, 54 discrimination means, Figure 4

Claims (1)

[Claims] 1. By illuminating and scanning a document placed on a document table, guiding light reflected from the document to a rotating photoconductor, and transferring the image formed on the photoconductor to a transfer paper. An image forming apparatus that forms an image includes a sensor that detects vibrations of the rotating body as it rotates, a calculation means that performs Fourier transform on the output signal from the sensor to calculate a frequency spectrum, and a sensor that detects the vibration of the rotating body as it rotates. Whether the peak position of the frequency spectrum calculated by the storage means that stores in advance the peak position of the spectrum during rotation and the calculation means is more than a certain frequency apart from the peak position of the spectrum stored by the storage means. and a display means for displaying that there is a vibration abnormality in the rotating body if the peak position of the frequency spectrum is more than a certain frequency away from the peak position of the spectrum as a result of the determination. A rotation abnormality detection device in an image forming apparatus.