JPH08160687A - Image forming device - Google Patents

Abstract

(57) [Abstract] [Purpose] To reduce the noise effectively by paying attention to the fact that most of the noise generated inside the image forming apparatus is radiated to the external space from the paper discharge port. [Structure] A duct 3 is continuously provided to a sheet discharge port 2 of a copying apparatus 1,
A noise detection microphone 4 is provided near the entrance in the duct 3, and a speaker 5 and a monitor microphone 6 are provided near the exit in the duct 3 to incorporate an active silencer. The noise generated inside the device propagates through the discharge port 2 in the duct 3 and is radiated to the outside. At this time, the noise is detected by the noise detection microphone 4 provided in the duct 3, and the vicinity of the outlet of the duct 3 is detected. The control circuit 7 calculates, generates, and radiates a sound wave having a waveform exactly opposite in phase to the detected sound wave and having the same amplitude as the detected sound wave. As a result, the two sound waves interfere with each other, and the noise level emitted from the outlet of the duct 3 to the outside is greatly reduced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus such as a copying machine or a printer, and more particularly, to a noise reducing function capable of effectively reducing noise radiated from a sheet discharge port of the apparatus. The present invention relates to an image forming apparatus having the same.

[0002]

2. Description of the Related Art Conventionally, noise generated by driving an image forming apparatus has been caused by internal drive mechanism sound, resonance sound, vibration sound, paper passing sound and the like. For example, "improving the sound quality of copiers"
(Yoji Okazaki et al., Proceedings of Acoustical Society of Japan, 1990)
March, pp.525-526) describes reduction of mechanical noise, especially noise generated by driving a copying machine and improvement of sound quality. According to this document, recently, a large number of motors are used to realize a high-performance copying apparatus, and in particular, a brushless DC motor with a high rotation speed is used as a main motor for driving a drum or the like. Because it is used, the meshing frequency of the timing belt and pulley (48
It is revealed that a discrete sound having a frequency of 0 Hz) is generated, and further, a sound is generated from the subframe to which the drive system is attached. Therefore, in order to suppress the vibration of the sub-frame, which is the noise emission surface, the U-shaped reinforcing rib is fixed to the sub-frame to reduce the noise.

As another method, in order to reduce the noise generated when the copying machine is driven, conventionally, the materials of the gears and belts used in the drive mechanism are changed, and the processing precision of these is improved. And filling the inside of the device with sound absorbing material,
This was dealt with by installing a Helmholtz type silencer.

[0004]

As described above, in the noise reduction measures in the conventional copying machine, noise reduction is achieved by mitigating the collision noise of gears and belts or absorbing the noise by the sound absorbing material inside the apparatus. However, due to such a conventional noise reduction measure, the frequency range of noise that can be reduced is noise with a frequency of about 1 kHz or higher, and noise in the low frequency range is still left, and By the reinforcement of the frame described above, the noise generated in the low frequency range due to the meshing of the pulleys has been reduced to some extent, but the actual noise reduction function has not been realized. Further, in such a conventional noise reduction measure, it is necessary to determine a countermeasure by trial and error each time the internal configuration of the copying apparatus is changed, so that the development period is increased and efficient device development is performed. There was a problem that could not be done.

The present invention has been made in view of the above circumstances, and it is said that most of the noise generated inside the image forming apparatus, particularly the noise in the low frequency range, is radiated from the paper exit to the external space. Provided is an image forming apparatus having a noise reducing function, which is capable of performing noise reduction in a relatively low frequency range in a versatile manner without changing the internal configuration of the apparatus based on the knowledge of the present inventors. Is intended.

[0006]

In order to solve the above-mentioned problems, the image forming apparatus of the present invention is, in the invention as set forth in claim 1, a discharge port for discharging a sheet on which an image is formed. A duct having a shape surrounding the paper mouth is provided, and sound detecting means for detecting the sound propagating in the duct and radiated to the external space is provided, and the sound detected by the sound detecting means is caused to interfere with the sound. The sounding means for generating a sound having a waveform that cancels

Further, the invention according to claim 2 is characterized in that the duct has a shape which also serves as a sheet discharge tray.

In the invention according to claim 3,
The duct and the paper discharge tray are integrated, and all or part of them are built in the apparatus.

[0009]

According to the image forming apparatus of the present invention, in the above structure, most of the noise generated inside the image forming apparatus is radiated from the sheet discharge port to the external space. In the invention of claim 1, the duct has a shape surrounding an ejection port for ejecting a sheet on which an image is copied and transferred, and a sound radiated from the ejection port to an external space is detected in the duct provided at the ejection port. However, since it is made to interfere with the detected sound and generate a sound that cancels the sound, the level of noise radiated to the external space from the opening end of the duct provided at the paper ejection port is significantly increased. Is reduced to.

Further, according to the second aspect of the present invention, since the duct has a shape that also serves as a paper discharge tray, it is possible to have both the noise reduction function of the duct and the function of the paper discharge tray.

According to the third aspect of the present invention, the duct surrounds the sheet discharge port, the duct and the sheet discharge tray are integrated, and all or a part of the duct is built into the inside of the apparatus to reduce noise. The reduction function is easily attached, and the external dimensions and appearance of the device are not adversely affected. If the duct integrated with the paper ejection tray is detachably attached to the device,
It can be installed on other models that want to reduce noise.

[0012]

Embodiments of the image forming apparatus of the present invention will be described below with reference to the drawings. FIG. 1 is a configuration diagram for explaining a case where an embodiment of an image forming apparatus according to the present invention is applied to a copying apparatus, and is a perspective view of a main part centered around a sheet discharge port of the copying apparatus. In the figure, 1 is a copying machine,
Reference numeral 2 denotes a sheet discharge port for discharging a sheet on which an image is formed, 3 is a duct having a shape surrounding the sheet discharge port 2, and 4 is a noise detection microphone for detecting a sound propagating in the duct 3 and radiated to an external space. (Sound detection means) 5 is a speaker (sound generation means) that interferes with the sound detected by the noise detection microphone 4 to generate a sound having a waveform that cancels the sound, and 6 is installed at the outlet of the duct 3. , A monitor microphone that monitors the noise reduced by the speaker 5, and 7 interferes with the sound detected by the noise detection microphone 4,
A control circuit (signal processing circuit) 8 for generating a waveform having the opposite phase and the same amplitude for canceling the sound is a discharge tray which is integrated with the duct 3 and wholly or partly is detachably incorporated in the apparatus. is there.

In the copying machine of the present invention, attention is paid to the fact that most of the noise generated within the copying machine at 1 kHz or less, particularly 700 Hz or less, is radiated to the external space from the paper discharge port connected to the internal drive mechanism. However, the noise radiated from the discharge port is reduced. In the copying apparatus 1 according to this embodiment, as shown in FIG.
After passing through (indicated by a dotted line in the figure), the sheet is discharged into a duct 3 formed so as to surround the sheet discharge port 2. In this case, the overall length of the duct 3 is determined by the howling prevention between the noise detection microphone 4 and the speaker 5 and the calculation speed of the control circuit 7 from the relationship between the noise detection microphone 4 and the speaker 5.
Since the distance between the speaker 5 and the speaker 5 is required to be about 10 cm or more, the dimension is set so that the distance can be provided.

In the above case, if the duct 3 is projected outside and becomes a hindrance, the duct 3 is installed inside the copying apparatus 1 in addition to the duct 3 mounted outside the discharge port 2.
It is also possible to install so as to embed. As a result, the size of the duct 3 protruding to the outside of the copying apparatus 1 is shortened, and problems in appearance and function can be solved. Further, the duct 3 is shaped so as to surround the paper discharge port 2 and serves as both the duct 3 and the paper discharge tray 8. For example, the duct 3 and the discharge tray 8 are integrated,
It is also possible to incorporate all or part of the device inside the device. The drive power supply for the active muffler can be provided separately (independently) from the drive power supply for the copying machine, and can also be detachably mounted on the copying machine in a shape that also serves as the duct 3 and the paper discharge tray 8. In this case, the noise reduction effect can be easily exhibited even in the copying machine which has been conventionally used by exchanging it with the conventionally used discharge tray.

The noise detection microphone 4 is generated inside the copying machine 1 by driving the copying machine 1, and the paper discharge port 2 is generated.
It is for detecting the sound radiated to the outside space (mainly noise of 1 KHz or less), and is installed near the discharge port 2 and near the inlet of the duct 3. The speaker 5 generates a sound that cancels the sound, and is installed near the outlet of the duct 3. In this case, the sound emitted from the speaker 5 is a sound wave having an opposite phase and the same amplitude waveform that interferes with the sound detected by the noise detection microphone 4 and cancels the sound.
Then, this waveform is calculated and generated, for example, by the control circuit 7 installed inside the device.

FIG. 2 is a diagram for explaining a connection state of the control circuit, and portions having the same functions as those in FIG. 1 are designated by the same reference numerals. The control circuit 7 performs a predetermined process on the signal provided from the noise detection microphone 4 to generate a sound source (noise source, 1
A signal is sent to the speaker 5 so as to generate a sound wave having a waveform opposite in phase to the sound wave generated from the drive mechanism sound of KHz or less). At this time, the signal processing performed in the control circuit 7 is the transfer characteristic when the sound wave emitted from the sound source propagates the distance from the position of the noise detection microphone 4 to the position of the speaker 5, and the output from the speaker 5. The sound waves are taken into consideration in consideration of characteristics such as acoustic feedback caused by reaching the noise detection microphone 4 again.

The sound wave emitted from the sound source and the sound wave emitted from the speaker 5 cause sound wave interference as described above. Therefore, the interfering sound wave passing through the monitor microphone 6 is weaker than the sound wave generated from the sound source. However, in order to further improve the muffling performance of the active muffling device, the sound pressure of the sound wave passing through this portion detected by the monitor microphone 6 is used as the muffling error signal for the control of the control circuit 7. That is, the monitor microphone 6 detects the sound pressure of the sound wave after the interference and gives it to the control circuit 7 as a muffling error signal. The control circuit 7 is controlled so that the silencing error signal becomes smaller. An adaptive digital filter is often used as the control circuit 7.

FIG. 3 is a diagram for explaining a connection state of the active silencer, 11 is a control circuit using an adaptive digital filter, 12 is an adaptive digital filter,
13 is an adaptive algorithm, 14 is an error signal,
The parts having the same functions as those in FIG. 2 are designated by the same reference numerals.

The sound wave generated from the sound source enters the duct 3 from one end and is first detected by the noise detection microphone 4. The noise detection microphone 4 detects the sound pressure level of a sound wave passing therethrough and gives the signal to the adaptive digital filter 12. The adaptive digital filter 12 generates a sound wave having a waveform opposite in phase to the sound wave generated from the sound source while considering the transfer characteristics of the sound wave while the filter coefficient is sequentially updated by the adaptive algorithm 13. As described above, a drive signal is given to the speaker 5.

The sound wave generated from the speaker 5 and the sound wave generated from the sound source cause interference in the duct 3 and pass through the monitor microphone 6. The monitor microphone 6 detects the sound pressure level of the sound wave passing therethrough and gives it as an error signal 14 to the adaptive algorithm 13. The adaptive algorithm 13 sequentially updates the filter coefficient of the adaptive digital filter 12 according to the LMS (Least Mean Square) algorithm so that the root mean square value of the error signal 14 is minimized.

As described above, the speaker 5 and the control circuit 7 interfere with the sound detected by the noise detecting microphone 4 to generate a sound having a waveform that cancels the sound. Is configured. Further, in this embodiment, a monitor microphone 6 is installed at the outlet of the duct 3 to monitor the noise reduced by the sounding means.

In the copying machine 1 constructed as described above, most of the noise (1 KHz or less) generated inside the copying machine by driving the copying machine is provided in the discharge port 2. 3 Propagate inside and radiate to the outside.
At this time, the noise detection microphone 4 detects a sound wave emitted from the paper discharge port 2 inside the apparatus. When the sound wave reaches the position of the speaker 5 near the outlet of the duct 3, the sound wave is emitted from the speaker 5 so as to have a phase opposite to that of the sound wave and have the same sound pressure.

As a result, the two sound waves interfere with each other, and a sound deadening operation is performed in which the sound waves whose sound pressure is greatly reduced are radiated from the outlet of the duct 3 to the outside. At this time, the monitor microphone 6 monitors the reduction amount of the sound pressure after the muffling, and the result is fed back to the control circuit 7 to determine whether the reduction amount of the sound pressure after the muffling is maximum. .
In this case, the control circuit 7 controls the configuration and operation described in detail with reference to FIGS. 2 and 3. In this way, the output signal to the speaker 5 is adjusted so that the silencing effect is maximized.

Here, the noise frequency f having the noise reducing effect by the above configuration is expressed by the following formula (1) with respect to the major axis D of the duct 3 (shown in FIG. 1). f <C / 2D (Hz) (1) C: sound velocity (m / s) D: major axis of duct (m) At a noise frequency f satisfying the above formula (1), sound waves are generated in the duct 3 within the duct. A one-dimensional sound field having a distribution only in the direction from the entrance to the exit of 3 is formed. Therefore, at the noise frequency f satisfying the above formula (1), the sound wave radiated from the outlet of the duct 3 can be interfered by the one speaker 5 installed near the outlet of the duct 3, and the noise can be sufficiently reduced. The effect is obtained. Therefore, it is possible to obtain a great silencing effect even in a low frequency region where the conventional copying apparatus could not sufficiently reduce noise.

FIG. 4 shows the front side of the discharge side showing the noise reduction effect when the major axis D of the duct 3 of the embodiment shown in FIG. 1 is 30 cm (corresponding to the width of the discharge tray 8 of the current copying apparatus). 1m
3 is a spectrum diagram of noise frequencies in FIG. In FIG. 4, the horizontal axis represents the noise frequency (KHz) and the vertical axis represents the sound pressure level (dB). As can be seen from FIG. 4, 60
There is a peak value of the sound pressure level near 0 Hz, which was 30.5 dB before muffling, but 2 after muffling.
The sound pressure level has decreased to 0.5 dB, and the sound pressure level after muffling has considerably decreased for noise frequencies of 600 Hz and below. Thus, as a whole, the noise reduction effect is observed in a wide frequency range of 700 Hz or less, and the effect of the present invention is recognized.

FIG. 5 is a block diagram for explaining another embodiment of the image forming apparatus according to the present invention, in which 9 is a duct.
Reference numeral 10 denotes a paper discharge tray, and other parts having the same operations as those in FIG.

As shown in FIG. 1, the duct 3 provided at the paper discharge port 2 is attached to the side of the exterior cabinet on the paper discharge side of the copying apparatus 1 at a substantially right angle, and along the paper conveyance direction. However, in the case of such a shape, when the size of the paper discharged from the paper discharge port 2 is small, the paper is piled in the duct 3 and it is difficult to take out the paper. In order to solve this problem, as in the embodiment shown in FIG.
It is preferable that the lower wall be inclined downward as it goes to the outlet of the duct 9. With such a shape, the ejected paper slides along the lower wall of the duct 9 toward the exit of the duct 9, and the ejected paper can be easily taken out. Further, as a duct shape having the same effect as that of FIG. 5, a shape in which the entire duct is installed so as to be inclined downward as it goes toward the exit direction of the duct 9 can be considered.

As described above, according to the present invention, by driving an image forming apparatus such as a copying machine, most of the noise generated inside the apparatus is radiated to the external space through the sheet discharge port, and the duct is used. Is provided in a shape surrounding the discharge port, and a propagation path is formed so that the generated noise radiates to the external space through the duct, and the noise generated from the inside of the apparatus is detected and detected. The sound is generated in the duct by causing interference with the sound and canceling the sound. In this way, even if there is a change in the internal configuration of the device, it is possible to achieve a significant reduction in noise without taking measures to reduce noise for each change.

[0029]

Since the image forming apparatus of the present invention has the above-mentioned structure, in the invention described in claim 1, the sound propagating through the duct from the sheet discharge port to the outside is detected. However, since the sound having the waveform of the opposite phase and the same amplitude that cancels the sound is generated, the effect of significantly reducing the noise radiated from the paper discharge port can be exhibited. It can also contribute to making the office environment comfortable. Further, in the invention described in claim 2, in addition to the effect described in claim 1, it is possible to combine the function of noise reduction by the duct and the function of the discharge tray, and it has been conventionally used. By replacing the sheet with the sheet discharge tray, the noise reduction effect can be easily exhibited even in the image forming apparatus which has been used conventionally. Further, in the invention described in claim 3, in addition to the effect described in claim 1, the entire device does not become larger than the conventional device, and the external dimensions and the external appearance are greatly adversely affected. Further, it is possible to realize an image forming apparatus having a noise reducing function without requiring a large space for leaving the apparatus.

[Brief description of drawings]

FIG. 1 is a perspective view of a principal part of a copying machine, illustrating the vicinity of a sheet discharge port, for explaining an embodiment of an image forming apparatus according to the present invention.

FIG. 2 is a diagram for explaining a connection state of a control circuit of the image forming apparatus according to the present invention.

FIG. 3 is a diagram for explaining a connection state of an active silencer of the image forming apparatus according to the present invention.

FIG. 4 is a noise frequency spectrum diagram of the image forming apparatus according to the present invention.

FIG. 5 is a configuration diagram for explaining another embodiment of the image forming apparatus according to the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Copier, 2 ... Paper exit, 3 ... Duct, 4 ... Noise detection microphone (sound detection means), 5 ... Speaker (sound generation means), 6 ... Monitor microphone, 7 ... Control circuit, 8 ...
Paper output tray, 9 ... Duct, 10 paper output tray, 11 ... Control circuit, 12 ... Adaptive digital filter, 13 ... Adaptive algorithm, 14 ... Error signal.

Continuation of front page (51) Int.Cl. ⁶ Identification number Office reference number FI Technical display location G03G 21/00 530 G10K 11/178 H04R 29/00 320

Claims (3)

[Claims] 1. A duct having a shape surrounding the sheet discharge port is provided at a sheet discharge port of a device for discharging a sheet having an image formed thereon, and a sound propagating in the duct and radiated to an external space is detected. An image forming apparatus comprising: a sound detecting unit, and a sound generating unit that generates a sound having a waveform that cancels the sound by interfering with the sound detected by the sound detecting unit. 2. The image forming apparatus according to claim 1, wherein the duct has a shape that also serves as a sheet discharge tray. 3. The duct and the discharge tray are integrated,
The image forming apparatus according to claim 1, wherein all or a part of the image forming apparatus is built in the apparatus.