JPH04221965A - Image forming device provided with noise eliminating device - Google Patents

Abstract

PURPOSE:To reduce a noise radiated from the part of a fan. CONSTITUTION:A noise source signal emitted from the part of the fan 28 is outputted by a noise source signal output means 30 consisting of a microphone as an electrical signal and processed by a signal processing circuit 31 to drive a speaker 32 for a control sound, so that a sound which negates the noise source signal each other is generated.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention reduces noise radiation from the fan section by generating secondary sound that cancels out the noise emitted from the fan section that radiates or exhausts heat to the outside. The present invention relates to an image forming apparatus equipped with a noise removing device such as a copying machine, a printer, a facsimile, etc., which has a noise removing means.

0002

2. Description of the Related Art Conventionally, no image forming apparatus such as a copying machine, a printer, or a facsimile machine has a noise removing means for removing noise emitted from a fan portion that radiates or exhausts heat to the outside. Generally, an image forming apparatus uses a motor as a driving source, feeds paper using a roller or the like, and radiates heat to the outside using a heat radiating fan. Also, JP-A-61-262
Publication No. 166 describes a silencer for erasing the printing sound of an impact printer.

0003

[Problems to be Solved by the Invention] Image forming apparatuses 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. Put it away. Therefore, conventionally, soundproofing measures have been taken in image forming apparatuses using sound absorbing materials, soundproofing materials, sound insulation materials, vibration damping materials, etc. However, due to the structure of image forming apparatuses,
Openings for heat dissipation were always required, and complete sound insulation was difficult. Furthermore, since a heat dissipation fan is used, the noise generated by the fan is added to the noise emitted from the inside through the heat dissipation opening, so reducing the noise radiation from the opening is an issue. It had become. Further, in electrophotographic image forming apparatuses, harmful ozone is generated from the developing device, so it is necessary to exhaust air with high ozone concentration through the ozone filter using an exhaust fan so that the ozone is absorbed by the ozone filter. For this reason, high noise is also emitted from the heat dissipation opening where the exhaust air is exhausted by the exhaust fan, which has been an obstacle to reducing noise. SUMMARY OF THE INVENTION An object of the present invention is to provide an image forming apparatus with a noise removing device that can improve the above-mentioned drawbacks and reduce the noise emitted from the fan section.

0004

[Means for Solving the Problem] In order to achieve the above object, the invention of claim 1 provides a fan that radiates or exhausts heat to the outside, an air flow path extending from the outside toward the fan,
a noise source signal output means for outputting a noise source signal emitted from the fan section as an electric signal; a control sound speaker installed near the outlet or in the middle of the air flow path to generate sound; The invention of claim 2 is provided with a signal processing circuit that processes the output signal of the output means and drives the control sound speaker to generate a sound that cancels each other out with the noise source signal. Item 1
In the image forming apparatus with a noise removal device described above, there is provided an error observation microphone installed near the exit of the air flow path or in the middle part of the air flow path to observe sound, and a signal of the signal processing circuit so as to reduce the output signal from the microphone. Adaptive signal processing means for changing processing, and the invention according to claim 3 is an electrophotographic image forming apparatus having a developing section that generates ozone, in which ozone is exhausted through a filter by an ozone exhaust fan. A mechanism for absorbing ozone generated from the developing section by the filter, an air flow path extending from the outside toward the ozone exhaust fan, and a noise source signal emitted from the ozone exhaust fan as an electrical signal. A noise source signal output means for outputting a noise source signal, a control sound speaker installed near the outlet of the air flow path or at an intermediate portion to generate sound, and a control sound speaker for processing the output signal of the noise source signal output means. The apparatus is equipped with a signal processing circuit that, when driven, generates sounds that cancel each other out with the noise source signal.

[0005]

In the first aspect of the invention, the fan radiates or exhausts heat to the outside through the air flow path, and the noise source signal output means outputs the noise source signal emitted from the fan portion as an electrical signal. The control sound speaker generates sound near the exit of the airflow path or in the middle part, and the signal processing circuit processes the output signal of the noise source signal output means to drive the control sound speaker, thereby making the noise source signal and the sound mutually Generates sounds that cancel each other out. In the invention as claimed in claim 2, the error observation microphone observes the sound near the exit of the air flow path or at the intermediate portion, and the adaptive signal processing means adjusts the signal of the signal processing circuit so that the output signal from the error observation microphone becomes small. Change processing. In the invention according to claim 3, the ozone exhaust fan exhausts ozone through the filter and causes the filter to absorb ozone generated from the developing section, and the noise source signal output means operates the ozone exhaust fan in the vicinity of the ozone exhaust fan. The noise source signal emitted from the part is output as an electrical signal. The control sound speaker generates sound near the exit of the airflow path or in the middle part, and the signal processing circuit processes the output signal of the noise source signal output means to drive the control sound speaker, thereby making the noise source signal and the sound mutually Generates sounds that cancel each other out.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows a first embodiment of the present invention. This first 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, an original on an original platen 13 is illuminated by a light source, and a reflected light image thereof is projected onto the photoreceptor drum 11 via mirrors 14 to 16, lenses 17, and mirrors 18 to 20, and the light source A movable optical system including mirrors 14 to 16 moves to scan the original. The electrostatic latent image on the photosensitive drum 11 is developed by the developing device 21 to become a developed image, and the electrostatic latent image is transferred to the paper feeding device 2.
The transfer paper is fed from the register roller 23 to the registration roller 23. This transfer paper is sent out by the registration roller 23 with its leading edge aligned with the developed image on the photoreceptor drum 11, the developed image on the photoreceptor drum 11 is transferred by the transfer device 24, and the paper is transported by the paper transport section 25 to the fixing section. After the developed image is fixed by 26, it is discharged onto a paper discharge tray 27 as a copy. Main motor 1
A heat dissipation fan 28 is installed near the copying machine 2 for the purpose of cooling the optical system, and a duct-shaped air flow path 29 is provided from the outer wall of the copying machine toward the heat dissipation fan 28. The heat dissipation fan 28 rotates and exhausts air to the outside through the air flow path 29, thereby cooling the heat generated inside the copying machine. In this case, the sound generated by the heat dissipation fan 28 itself and the sound generated inside the copying machine are radiated to the outside through the air flow path 29 as noise. Therefore, a noise source signal observation microphone 30 is installed in the part of the airflow path 29 closest to the fan 28.
0 observes the sound generated by the heat dissipation fan 28 itself or the sound generated inside the copying machine as a noise source signal and converts it into an electrical signal. The output signal of this noise source signal observation microphone 30 is subjected to appropriate signal processing in a signal processing circuit 31.
The sound is added to a speaker 32 installed near the exit of the air flow path 29 and output as a sound wave. In this case, the signal processing circuit 31 processes the output signal of the noise source signal observation microphone 30 so that the noise propagating through the air flow path 29 and the sound wave from the speaker 32 cancel each other out. This process will be described in detail later. explain.

In the first embodiment, the noise source signal observation microphone 30 detects that the generated noise is caused by the fan 2.
In the case where the number of rotations of the fan 28 is determined by the number of rotations of the fan 28, the number of rotations of the fan 28 may be converted into an electrical frequency and output as a noise source signal. Further, the speaker 32 may be installed somewhere near the outlet of the air flow path 29 or in the middle of the air flow path 29, and in the second embodiment of the present invention, as shown in FIG. emits sound waves towards the outside of the As a result, when the outlet of the airflow path 29 is viewed as a noise source, the exit of the airflow path 29 and the speaker 32 form a dipole, and the acoustic power radiated from the dipole can be reduced. In the third embodiment of the present invention, as shown in FIG.
In the first and third embodiments, by creating a sound pressure-free zone in the area outside the speaker 32 in the airflow path 29, the sound pressure is directed outward from the airflow path 29. The sound will be reduced in advance.

Signal processing in the signal processing circuit 31 can be roughly divided into two types. One type is a fixed signal processing method in which the transfer function of the noise propagating through the air flow path 29 is measured in advance and fixed signal processing is performed assuming that it remains unchanged.The other type is a fixed signal processing method in which a microphone for error observation is prepared. This is an adaptive signal processing method that performs adaptive signal processing. The signal processing circuit 31 in the first to third embodiments uses a fixed signal processing method, and the signal processing circuit 31 using the fixed signal processing method will be described below. The signal processing circuit 31 of this fixed signal processing method is an example using a digital filter, and as shown in FIGS. 4 and 5, the noise source signal from the noise source signal observation microphone 30 passes through a low-pass filter (LPF) 33. The signal is passed through and subjected to A/D conversion 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 copying operation and fan 2
8 is actually carried out to measure the transfer function G from the noise source signal observation section to the noise signal at the outlet of the airflow path 29 using the noise source signal observation microphone 30. In addition, the characteristics of the LPF 33 and A/D converter 34 on the input side are determined by the transfer function A,
The characteristics of the portion 39 from the output-side digital/analog (D/A) converter 36 through the LPF 37, power amplifier 38, and speaker 32 to the outlet of the air flow path 29 are expressed as a transfer function C.
Measure these in advance. For the measurement, L
Well-known techniques such as the MS method and the cross-spectral method may be used. If the frequency characteristic of the digital filter 35 is W, then as can be seen from FIG. 5, G=C・W・A, so it should be designed so that W=G/(A・C). . 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 32. Output.

In the first to third embodiments described above, a fixed signal processing type signal processing circuit 31 was used, but in the fourth and fifth embodiments of the present invention, a fixed signal processing circuit 31 was used in the second embodiment. In place of the signal processing circuit 31 of the adaptive signal processing method, a signal processing circuit of the adaptive signal processing method is used. A signal processing circuit using this adaptive signal processing method will be described in detail below. In the fourth embodiment, as shown in FIG. 7, an error observation microphone 40 is installed near the outlet of the airflow path 29,
In the fifth embodiment, as shown in FIG. 8, an error observation microphone 40 is installed near the speaker 32 in the middle of the airflow path 29. Microphone 30 for noise source signal observation
The output signal is subjected to signal processing in the signal processing means 41 and outputted as a sound wave by the speaker 32, and the adaptive signal processing means 42 processes the signal of the signal processing means 41 so that the output signal from the error observation microphone 40 becomes small. change. As shown in FIG. 6, the signal processing means 41 is an LPF
43, A/D converter 44, digital filter 45, D/
Consisting of an A converter 46, an LPF 47, and a power amplifier 48, the noise source signal from the noise source signal observation microphone 30 is passed through the LPF 43, A/D converted by the A/D converter 44, and then converted by the digital filter 45. filtered. The signal filtered by the digital filter 45 is converted into a D/A converter 46.
The signal is A-converted, passes through the LPF 47, is amplified by the power amplifier 48, and is then converted into a sound wave by the speaker 32 and output. At this time, the coefficients of the digital filter 45 are constantly updated by the adaptive signal processing means 42 so that the output signal from the error observation microphone 40 becomes smaller. In this way, by constantly updating the coefficients of the digital filter 45 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 the transfer functions in advance, unlike when using a signal processing circuit using a fixed signal processing method, which improves practicality.

Next, the coefficient updating rule of the digital filter 45 by the adaptive signal processing means 42 will be explained using the Filtered-X LMS algorithm, which is commonly used at present, as an example. The error observation microphone 40 receives the noise y(n) (n represents a discrete time) transmitted from the noise source inside the copying machine, and the speaker 3.
The adaptive signal processing means 42 processes the digital filter 45 so that the output signal e(n) of the error observation microphone 40 is minimized. Update coefficients. Output signal e of the error observation microphone 40 at time n
As shown in FIG. 6, x(n) is the output signal of the A/D converter 44, c is the transfer function from the output of the digital filter 45 to the error observation microphone 40, and s(n)=Σ
If wi(n)・x(n-i), then e(n)=y(n
)+Σcj・s(n-j)...(1). In order to set the coefficient w of the digital filter 45 to an appropriate coefficient,
w is updated for each sample so that the squared error E(n)={e(n)}2 becomes smaller at each time n. 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 45 at time (n+1) is w
i(n+1)=wi(n)+Δwi(n)...(3)
However, Δwi(n)=α・e(n)・Σcj・x(n
−i−j) α: Given by a 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 45 and the error observation microphone 40 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 45. With the above, noise emitted to the outside from the heat radiation opening can be removed.

FIG. 9 shows a portion of a sixth embodiment of the present invention. This embodiment is a modification of the above embodiment in which the noise emitted from the ozone exhaust fan is removed. The developing device 21 generates ozone, and an ozone exhaust fan 49 installed inside the copying machine exhausts the ozone to the outside through an ozone filter 50. A duct-shaped air flow path 5 extends from the outer wall of the copying machine toward the ozone exhaust fan 49.
1 is provided, and exhaust by an ozone exhaust fan 49 is performed through an air flow path 51. When the air inside the copying machine is exhausted to the outside through the ozone filter 50 by the ozone exhaust fan 49, ozone is absorbed by the ozone filter 50, and only harmless air is radiated to the outside. In this case, the noise generated by the ozone exhaust fan 49 itself and the noise generated inside the copying machine are radiated to the outside through the air flow path 51 as noise. Therefore, a noise source signal observation microphone 52 is installed in the part of the airflow path 51 closest to the fan 49.
2 observes the sound generated by the ozone exhaust fan 49 itself or the sound generated inside the copying machine as a noise source signal and converts it into an electrical signal. The output signal of this noise source signal observation microphone 52 is subjected to appropriate signal processing in a signal processing circuit 53, and is added to a speaker 54 installed near the exit (or in the middle) of the airflow path 51 and output as a sound wave. . The signal processing circuit 53 is configured in the same manner as the signal processing circuit 31 described above, and processes the output signal of the noise source signal observation microphone 52 so that the noise propagating through the air flow path 51 and the sound wave from the speaker 54 cancel each other out. . therefore,
A sound pressure-free zone is created in the portion of the airflow path 51 outside the speaker 54, and the sound traveling outward from the airflow path 51 is reduced in advance. Note that although the noise source signal observation microphone 52 is provided inside the ozone filter 50, the ozone filter 50 is placed close to the ozone exhaust fan 49, and the noise source signal observation microphone 52 is installed just outside the ozone filter 50. You can do it like this. Further, although the above embodiment is an example of a copying machine, the present invention can be similarly applied to other image forming apparatuses such as printers and facsimiles.

0012

[Effect of the invention] As described above, according to the invention of claim 1,
A fan that radiates or exhausts heat to the outside, an air flow path extending from the outside toward the fan, a noise source signal output means that outputs a noise source signal emitted from the fan portion as an electrical signal, and the air flow path. a control sound speaker that is attached near the exit or in the middle of the sound source and generates sound, and processes the output signal of the noise source signal output means to drive the control sound speaker so as to cancel each other out with the noise source signal. Since the image processing apparatus includes a signal processing circuit that generates sound, it is possible to reduce the noise emitted from the fan section, and it is possible to realize a low-noise image processing apparatus. According to a second aspect of the invention, in the image forming apparatus with a noise removing device according to the first aspect, there is provided an error observation microphone installed in the vicinity of the exit of the air flow path or in the middle part of the air flow path for observing sound; Since the present invention includes an adaptive signal processing means for changing the signal processing of the signal processing circuit so that the output signal of the signal becomes small, there is no need to measure the transfer function in advance, and the practicality is improved. Furthermore, according to the invention of claim 3, in an electrophotographic image forming apparatus having a developing section that generates ozone, ozone is exhausted through a filter by an ozone exhaust fan, and the ozone generated from the developing section is absorbed by the filter. an airflow path extending from the outside toward the ozone exhaust fan, a noise source signal output means for outputting a noise source signal emitted from the ozone exhaust fan as an electrical signal, and the airflow path. a control sound speaker that is attached near the exit or in the middle of the sound source and generates sound, and processes the output signal of the noise source signal output means to drive the control sound speaker so as to cancel each other out with the noise source signal. Since the image processing apparatus includes a signal processing circuit that generates sound, it is possible to reduce the noise emitted from the ozone exhaust fan, and it is possible to realize a low-noise image processing apparatus.

[Brief explanation of the drawing]

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

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

FIG. 3 is a schematic diagram showing a part of a third embodiment of the invention.

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

FIG. 5 is a block diagram showing a transfer function of the signal processing circuit using the same fixed signal processing method.

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

FIG. 7 is a schematic diagram showing a part of a fourth embodiment of the present invention.

FIG. 8 is a schematic diagram showing a part of a fifth embodiment of the present invention.

FIG. 9 is a schematic diagram showing a part of a sixth embodiment of the present invention.

[Explanation of symbols]

28 Heat dissipation fan 29, 51 Air flow path 30, 52 Noise source signal observation microphone 31, 4
1, 53 Signal processing circuit 32, 54 Speaker 40 Error observation microphone 42 Adaptive signal processing means 49 Ozone exhaust fan 50 Ozone filter

Claims (3)

[Claims] 1. A fan that radiates or exhausts heat to the outside, an airflow path extending from the outside toward the fan, and a noise source signal output means that outputs a noise source signal emitted from the fan as an electrical signal. a control sound speaker that is attached to the vicinity of the exit of the airflow path or an intermediate portion thereof and generates sound; and a control sound speaker that processes the output signal of the noise source signal output means to drive the control sound speaker. An image forming apparatus with a noise removing device, comprising a signal processing circuit that generates a signal and a sound that cancel each other out. 2. The image forming apparatus with a noise removal device according to claim 1, further comprising: an error observation microphone installed near the exit of the air flow path or at an intermediate portion for observing sound; and an output signal from the microphone is small. An image forming apparatus with a noise removal device, comprising: adaptive signal processing means for changing signal processing of the signal processing circuit. 3. An electrophotographic image forming apparatus having a developing section that generates ozone, comprising: a mechanism for exhausting ozone through a filter by an ozone exhaust fan and absorbing ozone generated from the developing section by the filter; an airflow path extending toward the ozone exhaust fan, a noise source signal output means for outputting a noise source signal emitted from the ozone exhaust fan as an electrical signal, and a portion near or in the middle of the exit of the airflow path. a control sound speaker that is attached to and generates a sound, and signal processing that processes the output signal of the noise source signal output means to drive the control sound speaker to generate a sound that cancels each other out with the noise source signal. An image forming apparatus with a noise removing device, characterized in that it is equipped with a circuit.