JPH04221967A - Image forming device - Google Patents

Abstract

PURPOSE:To reduce a noise radiating toward the outside. CONSTITUTION:A signal with frequency in accordance with the revolving speed of a motor 12 in a device is outputted by an output means consisting of a revolving speed sensor 28 and processed by a signal processing means 29, then it is outputted as a sound wave which negates the noise caused by the revolution of the motor 12 each other.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention is applicable to copying machines, printers, facsimile machines, etc., which have a noise removal means for reducing noise emission by generating secondary sound that cancels out noise emitted to the outside. The present invention relates to a forming device.

0002

[Prior Art] Image forming devices such as copying machines, printers, and facsimile machines generate noise in the surrounding area due to resonance caused by the rotation of the motor that is the drive source, and noise generated from the paper and rollers during paper feeding. will occur. Therefore, in the past, image forming apparatuses have taken soundproofing measures using sound absorbing materials, sound insulating materials, vibration damping materials, etc., but none of them have a noise removal means for removing noise radiated to the outside. Furthermore, Japanese Patent Application Laid-Open No. 61-262166 describes a noise reduction device for erasing the printing sound of an impact printer.

0003

[Problems to be Solved by the Invention] Soundproofing measures have been taken in the above-mentioned image forming apparatus by using sound absorbing materials, sound insulating materials, vibration damping materials, etc., but due to space constraints inside the machine, paper entrances and exits, and heat radiation. Complete sound insulation was difficult due to the openings in the building. In particular, in electrophotographic image forming apparatuses, periodic noise generated by the motor for driving the photoreceptor drum and the accompanying rotating body is large, and due to its structure,
Since a paper entrance/exit is required, noise leaking outside from the paper entrance/exit has become a major problem. SUMMARY OF THE INVENTION An object of the present invention is to provide an image forming apparatus that can improve the above-mentioned drawbacks and reduce noise radiated to the outside.

0004

[Means for Solving the Problems] In order to achieve the above object, the invention of claim 1 provides an electrophotographic image forming apparatus having a motor as a driving source and an aperture. output means for outputting a signal with a frequency corresponding to the rotation speed; a speaker for outputting sound waves that cancel out noise caused by the rotation of the motor inside the device; and a speaker for processing the output signal of the output means. and a signal processing means for outputting sound waves that cancel each other out with the noise by driving the image forming apparatus. The image forming apparatus according to claim 3 has an error observation microphone for observing an error, and performs signal processing in the signal processing circuit so that an output signal from the microphone becomes small. In the apparatus, the output means outputs to the signal processing means an output signal including a signal with a frequency corresponding to the rotational speed of a motor inside the device and a signal with a frequency multiple times that frequency.

[0005]

[Operation] In the invention of claim 1, the output means outputs a signal with a frequency corresponding to the rotational speed of the motor inside the device, and the output signal of the output means is processed by the signal processing means, and the speaker outputs the signal with a frequency corresponding to the rotation speed of the motor inside the device. It is output as a sound wave that cancels out the noise caused by the rotation of the Claim 2
In the invention, the error observation microphone observes sound near the opening, and the signal processing circuit performs signal processing so that the output signal from the error observation microphone becomes small. In the third aspect of the invention, the output means outputs to the signal processing means an output signal including a signal with a frequency corresponding to the rotational speed of a motor inside the device and a signal with a frequency multiple times that frequency.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows an embodiment of the present invention. This embodiment is an example in which the present invention is applied to an electrophotographic copying machine. During a copying operation, the photosensitive drum 11 is rotationally driven by a main motor 12 and uniformly charged by a charger (not shown), and then the original image is exposed by an exposure device to form an electrostatic latent image. In this exposure device, the original on the original table is illuminated by a light source, and the reflected light image is reflected from the mirrors 13 to 13.
15, a lens 16, and mirrors 17 to 19 onto the photoreceptor drum 11, as well as a light source and a mirror 13.
A movable optical system consisting of 15 to 15 moves to scan the original. The electrostatic latent image on the photosensitive drum 11 is developed into a developed image by the developing device 20, and a transfer sheet is fed from the paper feeding device 21 to the registration rollers 22. This transfer paper is sent out by the registration roller 22 with its leading edge aligned with the developed image on the photoreceptor drum 11, and then transferred to the photoreceptor drum 1 by the transfer device 23.
The developed image on the sheet 1 is transferred, conveyed by a paper conveying section 24, fixed by a fixing section 25, and then discharged as a copy from a paper discharging port 26 to a paper discharging table 27. Main motor 1
Reference numeral 2 drives the photosensitive drum 11, the paper transport section 24, and the like. A rotation speed sensor 28 attached to the main motor 12 constantly measures the rotation speed of the main motor 12, and sends the rotation speed of the main motor 12 to a signal processing circuit 29 as an electrical signal converted into an electrical frequency. In addition, the main motor 12
is controlled by a control circuit using a signal of a predetermined frequency from the pulse generator so that the rotation speed becomes a predetermined value according to the frequency, but the signal from the pulse generator is used instead of the output signal of the rotation speed sensor 28. Alternatively, the signal may be sent to the signal processing circuit 29. The output signal of the rotation speed sensor 28 is subjected to appropriate signal processing by a signal processing circuit 29.
The sound waves are converted into sound waves and output by a speaker 30 installed at the paper discharge port 26. In this case, the signal processing circuit 29 needs to perform signal processing so that the noise that has propagated inside the copying machine to the paper ejection port 26 and the sound waves from the speaker 30 cancel each other out, and this point will be described in detail later. . For example, the speaker 30 is connected to the paper output port 26 as shown in FIG.
It is installed near the copying machine and emits sound waves to the outside through an opening 31 provided in the side plate of the copying machine. Incidentally, the speaker 30 may be arranged near the paper ejection port 26 toward the inside of the copying machine, as shown in FIG. When the speaker 30 emits sound waves to the outside through the opening 31,
The paper discharge port 26 and the speaker 30 form a dipole, and the noise emitted from the paper discharge port 26 is reduced. In the case of FIG. 3, the noise and the sound waves from the speaker 30 cancel each other out, creating a zone with no sound pressure inside the paper ejection port 26, and the noise flowing from the paper ejection port 26 to the outside is pre-empted. becomes smaller.

Signal processing in the signal processing circuit 29 can be roughly divided into two types. One type is a fixed signal processing method in which the noise transfer function from the motor rotation signal to the paper discharge port 26 is measured in advance, and fixed signal processing is performed assuming that this remains unchanged.The other type is as shown in Fig. As shown in FIG. 1, this is an adaptive signal processing method in which an error observation microphone 39 is prepared and adaptive signal processing is performed. First, a case where a fixed signal processing method is used will be explained. Here, an example using a digital filter will be described. In the signal processing circuit 29, as shown in FIGS. 4 and 5, an electric signal having a frequency corresponding to the rotation speed of the main motor 12 from the rotation speed sensor 28 is passed through a low-pass filter (L
PF) 33, is A/D converted by an analog/digital (A/D) converter 34, and then filtered by a digital filter 35. In this example, the coefficients of the digital filter 35 are determined and fixed in advance. As a method for determining the coefficients of the digital filter 35,
First, the main motor 12 is actually operated, and the transfer function G to the noise signal at the paper discharge port 26 is measured from the motor rotation signal from the rotation speed sensor 28. In addition, the LPF on the input side
33. The characteristics of the A/D converter 34 are the transfer function A, and the output side digital/analog (D/A) converter 36 to LPF 3
7. Measure the characteristics of the power amplifier 38 and speaker 30 in advance, using them as a transfer function B. The coefficients of the digital filter 35 are as shown in FIG.
As can be seen, since G=B・W・A, it is sufficient to design so that W=G/(A・B). The signal that has been filtered by the digital filter 35 designed in this way is D/A converted by the D/A converter 36, passes through the LPF 37, is amplified by the power amplifier 38, and is then converted into a sound wave by the speaker 30. Output.

[0008] Furthermore, the signal sent from the rotation speed sensor 28 to the signal processing circuit 29 during the above-mentioned preliminary transfer function measurement and actual noise reduction is not only a signal with a frequency corresponding to the rotation speed of the main motor 12; Add to this the n (n=1, 2, ・
...) may be added to a signal with twice the frequency. Inside a copying machine, the rotation of the motor causes resonance through various transmission paths, so in many cases, not only sound waves with a frequency that matches the motor's rotation speed, but also sound waves with a frequency n times that number are generated. . Therefore, by sending not only a signal with a frequency corresponding to the rotation speed of the main motor 12 from the rotation speed sensor 28 to the signal processing circuit 29, but also a signal with a frequency n times that frequency, it is possible to eliminate overtones. This further increases the sound deadening effect.

Next, a case using the adaptive signal processing method will be explained based on FIG. 6. Error observation microphone 3
9 is installed near the paper discharge port 26 to observe the sound. The output signal of the rotation speed sensor 28 is passed through the LPF 40 and converted into an A/D converter 41 as in the fixed signal processing method.
/D conversion and then filtering by the digital filter 42. At this time, the output signal of the rotation speed sensor 28 is not only a signal of a frequency corresponding to the rotation speed of the main motor 12, but also a signal of a frequency corresponding to the rotation speed of the main motor 12, as well as a signal of a frequency corresponding to the rotation speed of the main motor 12 (n=1, 2, . . .
) The overtones may also be eliminated by adding a signal with twice the frequency. The signal filtered by the digital filter 42 is D/A converted by the D/A converter 43, passes through the LPF 44, is amplified by the power amplifier 45, and is converted into a sound wave by the speaker 30 and output. At this time, the coefficients of the digital filter 42 are constantly updated so that the output signal from the error observation microphone 39 is as small as possible, as will be described later. in this way,
By constantly updating the coefficients of the digital filter 42 to the optimum state, it is possible to follow changes in transfer characteristics and changes over time of the audio equipment, and to obtain a stable silencing effect at all times. Furthermore, there is no need to measure all transfer functions in advance as is the case when a fixed signal processing method is used, which improves practicality.

[0010] Next, regarding the coefficient updating rule of the digital filter 42, as an example, the currently frequently used Filter
The explanation will be based on the red-X LMS algorithm. The error observation microphone 39 receives a combination of the noise y(n) (n represents a discrete time) transmitted from the noise source inside the copying machine and the control sound transmitted from the outside world from the speaker 30. The coefficients of the digital filter 42 are updated by the adaptive signal processing means 46 so that the output signal e(n) of the error observation microphone 39 is minimized. As shown in FIG. 6, the output signal e(n) of the error observation microphone 39 at time n is the noise entering the error observation microphone 39 as y(n), A
The output signal of the /D converter 41 is x(n), the output signal of the digital filter 42 is s(n), the transfer function from the output of the digital filter 42 to the error observation microphone 39 is c, and s(n)= If Σwi(n)・x(n-i), then e(n)=y(n)+Σcj・s(n-j)...
Multiply by (1). In order to set the coefficient w of the digital filter 42 to an appropriate coefficient, the square error E(n)=
The adaptive signal processing means 46 updates w for each sample so that {e(n)}2 becomes smaller. In other words, when E(n) is viewed as a quadratic equation related to wi, wi is updated every time so that the graph (quadratic surface) of y=E(n)...(2) descends. I'm going. In this case, the coefficient wi(n+1) of the digital filter 42 at time (n+1) is
wi(n+1)=wi(n)+Δwi(n)
...(3) However, Δwi(n)=α・
e(n)・Σcj・x(n-i-j)
α: Given by convergence coefficient. As can be seen from equation (3), the update rule for w includes a transfer function c, so a transfer function between the digital filter 42 and the error observation microphone 39 is required in advance. . This can be measured by generating white noise or the like once when the copying machine is powered on, and then used when updating the coefficients of the digital filter 42.

[0011]

As described above, according to the present invention, the output means outputs a signal with a frequency corresponding to the rotation speed of the motor inside the device, and the output means outputs a signal with a frequency corresponding to the rotation speed of the motor inside the device. The present invention includes a speaker that outputs sound waves, and a signal processing means that processes the output signal of the output means and drives the speaker to output sound waves that cancel each other out with the noise. It is possible to reduce the noise emitted from the part, and the level of noise exerted on the surroundings can be reduced. Also,
By causing the output means to output an output signal including a signal with a frequency corresponding to the rotational speed of the motor and a signal with a frequency multiple times the frequency to the signal processing means, overtones can be suppressed.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing an embodiment of the present invention.

FIG. 2 is a schematic diagram showing a part of the same embodiment.

FIG. 3 is a schematic diagram showing a portion of another embodiment of the invention.

FIG. 4 is a block diagram showing a signal processing circuit in the above embodiment.

FIG. 5 is a diagram showing a transfer function of the signal processing circuit.

FIG. 6 is a block diagram showing a signal processing circuit in another embodiment of the present invention.

[Explanation of symbols]

28 Rotation speed sensor 29 Signal processing circuit 30 Speaker 39 Error observation microphone 46 Adaptive signal processing means

Claims (3)

[Claims] 1. An electrophotographic image forming apparatus having a motor as a driving source and an aperture, comprising: an output means for outputting a signal of a frequency corresponding to the number of rotations of a motor inside the apparatus; a speaker that outputs sound waves that cancel out noise caused by the rotation of the motor; and signal processing means that processes the output signal of the output means and drives the speaker to output sound waves that cancel out the noise that is generated by the rotation of the motor. An image forming apparatus comprising: 2. The image forming apparatus according to claim 1, further comprising: an error observation microphone installed near the opening for observing sound; An image forming apparatus characterized by performing processing. 3. The image forming apparatus according to claim 1, wherein the output means processes the output signal including a signal with a frequency corresponding to the rotational speed of a motor inside the apparatus and a signal with a frequency multiple times that frequency. An image forming apparatus characterized by outputting to a means.