JP2013035137A - Image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming apparatus in which noise generated by the rotary parts such as a cooling fan cooling the inside of the apparatus is reduced.SOLUTION: The image forming apparatus 100 includes the cooling fan 150 and a noise reduction portion 600 besides an image forming portion 1. The noise reduction portion 600 includes a reference microphone 610, an error detection microphone 620, an antiphase speaker 630, and a signal processing section 310. The noise of the cooling fan 150 collected by the reference microphone 610 is input to the signal processing section 310. The signal processing section 310 produces the antiphase waveform of an input sound wave. The antiphase speaker 630 generates the sound wave having the produced antiphase waveform. The error detection microphone 620 collects a composite sound of the noise from the cooling fan 150 and an antiphase sound from the antiphase speaker 630. The signal processing section 310 corrects the antiphase waveform, on the basis of the composite sound.

Description

  The present invention relates to an image forming apparatus. More specifically, the present invention relates to an image forming apparatus that reduces noise generated from a cooling fan or the like that cools the inside of the apparatus.

  In the image forming apparatus, each part inside the apparatus generates heat. For example, an image forming unit that forms an image and a fixing device that fixes a transferred toner image on a sheet are main heat sources. In order to cool these heat sources and the inside of the apparatus, a cooling fan may be provided inside the image forming apparatus.

  However, the cooling fan generates noise due to its rotation. In this way, the rotating parts that are rotationally driven generate noise. The image forming apparatus is used in an office or the like, and it is preferable to suppress such noise as much as possible. Therefore, silencers that suppress such noise have been developed. For example, in Patent Document 1, a receiving unit that detects the frequency of noise of rotating parts such as a motor and a fan, a storage unit that stores detected frequency information, and a sound recording unit that records external sound are detected. There is disclosed a silencer (active noise canceller: ANC) having an audio signal generation unit that generates an audio signal having an antiphase with respect to noise and a sound generation unit that generates the generated audio signal as sound (patent) (See Claims 1 and 2 of Document 1 and FIGS. 2 and 4).

JP 2007-171487 A

  A silencer that silences sound by separately generating a sound wave having a phase opposite to that of the noise source is called an active noise canceller. In the silencer described in Patent Document 1, the sound generator only generates a sound wave having a phase opposite to that of the sound wave stored in advance. Therefore, it is good when the fan rotates at a predetermined rotational speed. However, when the rotational speed of the fan changes with time, it is difficult to generate sound waves according to the change. That is, a sufficient silencing effect cannot be obtained.

  The present invention has been made to solve the above-described problems of the prior art. That is, an object of the present invention is to provide an image forming apparatus in which noise generated by rotating parts such as a cooling fan for cooling the inside of the apparatus is reduced.

The image forming apparatus of the present invention, which has been made for the purpose of solving this problem, includes a driving unit that rotationally drives a rotating component inside the image forming apparatus, and a first sound wave receiving unit that receives a rotating sound of the rotating component or the driving unit A reverse phase waveform generation unit that generates a reverse phase waveform of the sound wave received by the first sound wave reception unit, a sound wave generation unit that generates a sound wave of the reverse phase waveform generated by the reverse phase waveform generation unit, and a rotation To reduce the synthesized sound received by the second sound wave receiving unit and the second sound wave receiving unit that receives the synthesized sound of the rotating sound of the component or the drive unit and the sound wave generated by the sound wave generating unit, And a correction unit that corrects the antiphase waveform to generate a corrected waveform. The sound wave generating unit generates a sound wave having a corrected waveform instead of the antiphase waveform after the correction waveform is generated by the correcting unit. In such an image forming apparatus, it is possible to reduce noise generated from a rotating part such as a cooling fan or a driving unit. By collecting the synthesized sound and feeding it back, the correction unit corrects the antiphase waveform, so the noise reduction effect is high.

  In the image forming apparatus described above, the antiphase waveform generation unit generates an antiphase signal for a frequency band equal to or higher than a predetermined first frequency threshold when the operation mode of the image forming apparatus is in a sleep state. It is good to be. This is because noise can be reduced in a frequency band excluding the low frequency band that is easily affected by pop noise.

  In the image forming apparatus described above, the antiphase waveform generation unit has an antiphase for a frequency band equal to or higher than the first frequency threshold and higher than the second frequency threshold when the operation mode of the image forming apparatus is in the standby state. It is good to generate a signal. This is because noise can be reduced in a frequency band excluding the low frequency band that is easily affected by pop noise.

  In the image forming apparatus described above, the antiphase waveform generation unit is configured to perform a frequency band greater than or equal to the third frequency threshold greater than the second frequency threshold when the operation mode of the image forming apparatus is performing image stabilization processing. In addition to generating an anti-phase signal, an anti-phase signal is generated for a frequency band greater than or equal to the fourth frequency threshold value and greater than the third frequency threshold value when the operation mode of the image forming apparatus is in the state of forming an image on cardboard. In addition, when the operation mode of the image forming apparatus is in the state of forming an image on plain paper, an antiphase signal is generated for a frequency band equal to or higher than the fifth frequency threshold greater than the fourth frequency threshold. Good. This is because even when the rotating part rotates quickly, noise can be reduced in a frequency band that is not easily affected by pop noise.

  In the image forming apparatus described above, at least one of the rotating parts may be a cooling fan that cools the inside of the image forming apparatus. This is because the noise generated from the cooling fan can be suitably reduced.

  In the image forming apparatus described above, the first sound wave receiving unit may be arranged at a position on the suction side of the cooling fan. This is because noise from the cooling fan can be collected in a situation where pop noise is unlikely to occur.

  In the image forming apparatus described above, the first sound wave receiving unit may be arranged at a position on the ejection side of the cooling fan. This is because noise close to noise leaking outside the image forming apparatus can be collected to reduce noise.

  In the image forming apparatus described above, it is preferable that a buffer member that relaxes the wind generated by the cooling fan is disposed between the cooling fan and the first sound wave receiving unit. This is because noise from the cooling fan can be collected in a situation where pop noise is unlikely to occur.

  According to the present invention, there is provided an image forming apparatus in which noise generated by rotating parts such as a cooling fan for cooling the inside of the apparatus is reduced.

1 is a schematic configuration diagram for explaining an image forming apparatus according to an embodiment. 3 is a conceptual diagram for explaining a configuration of a noise reduction unit of the image forming apparatus according to the embodiment. FIG. 2 is a block diagram illustrating a control system of the image forming apparatus according to the embodiment. FIG. 6 is a graph showing frequency characteristics when a reference microphone is arranged on the ejection side or suction side of a cooling fan in the noise reduction unit of the image forming apparatus according to the embodiment. 6 is a graph showing frequency characteristics when a reference microphone is arranged on the ejection side of a cooling fan in the noise reduction unit of the image forming apparatus according to the embodiment. 6 is a graph illustrating frequency characteristics when a reference microphone is arranged on the suction side of a cooling fan in the noise reduction unit of the image forming apparatus according to the embodiment. 5 is a graph showing sound waves generated by a cooling fan, sound waves generated by an antiphase speaker, and synthesized sound thereof in the image forming apparatus according to the embodiment. 5 is a flowchart for explaining noise reduction processing by a noise reduction unit of the image forming apparatus according to the first embodiment. 6 is a conceptual diagram for explaining a case where a reference microphone is arranged on the suction side of a cooling fan in the noise reduction unit of the image forming apparatus according to the embodiment. FIG. FIG. 5 is a conceptual diagram (No. 1) for explaining another noise reduction unit of the image forming apparatus according to the embodiment. FIG. 6 is a conceptual diagram (No. 2) for explaining another noise reduction unit of the image forming apparatus according to the embodiment. 6 is a graph showing the number of rotations of a cooling fan in an image forming apparatus according to a second embodiment. 12 is a flowchart (No. 1) for explaining a noise reduction process by a noise reduction unit of the image forming apparatus according to the second embodiment. 12 is a flowchart (No. 2) for explaining the noise reduction processing by the noise reduction unit of the image forming apparatus according to the second embodiment.

  DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments embodying the present invention will be described below in detail with reference to the accompanying drawings. In the present embodiment, the present invention is embodied in an image forming apparatus.

(First embodiment)
1. Image Forming Apparatus The image forming apparatus 100 according to the present embodiment is a tandem color copier having image forming units 1Y, 1M, 1C, and 1K for each color, as shown in FIG. The image forming apparatus 100 includes a primary transfer roller 111, an intermediate transfer belt 101, a secondary transfer roller 115, a paper feed cassette 112, a conveyance path 114, a fixing device 130, an image reading unit 210, and a touch panel 230. And have. The image forming apparatus 100 includes a cooling fan 150, a motor M, a noise reduction unit 600, and a control unit 300.

  Each of the image forming units 1Y, 1M, 1C, and 1K includes a photoreceptor unit 20 and a developing unit 10. In FIG. 1, it is represented by 1Y as a representative. The photoconductor unit 20 has a photoconductor drum 21. The photosensitive drum 21 is an image carrier for carrying a toner image. The exposure device 30 is for writing an electrostatic latent image on the surface of the photosensitive drum 21. The developing unit 10 applies toner to the electrostatic latent image on the photosensitive drum 21 and develops it.

  The primary transfer roller 111, the intermediate transfer belt 101, and the secondary transfer roller 115 are transfer units for transferring the toner image developed on the photosensitive drum 21 to the sheet P. The sheet P is fed from the sheet feeding cassette 112, passes through the conveyance path 114, and the toner image is transferred at the location of the secondary transfer roller 115. The sheet P to which the toner image has been transferred is then conveyed to the fixing device 130. The fixing device 130 is for heating and pressing the sheet P to fix the toner image on the sheet P.

  The image reading unit 210 is for reading a document placed on the image reading unit 210 as an image image. The touch panel 230 is an operation display unit for receiving an image formation instruction from the user.

  The cooling fan 150 is for cooling the inside of the main body of the image forming apparatus 100. The rotating part is rotated by receiving the rotational drive of the motor M. The motor M is a drive unit for driving the cooling fan 150 to rotate. Further, the transfer unit such as the photosensitive drum 21 and the primary transfer roller 111 is also rotationally driven. The noise reduction unit 600 is for reducing the noise generated by the cooling fan 150. The control unit 300 is also for controlling the noise reduction unit 600. In addition, the control unit 300 controls each part of the image forming apparatus 100 including the image forming unit 1. The positional relationship between the cooling fan 150 and the noise reduction unit 600 will be described in detail later.

2. Noise reduction part The schematic structure of the noise reduction part 600 of this form is shown in FIG. As shown in FIG. 2, the noise reduction unit 600 includes a reference microphone 610, an error detection microphone 620, an antiphase speaker 630, and a signal processing unit 310.

  The reference microphone 610 is a sound wave receiving unit that receives a rotating sound emitted from the cooling fan 150. The reference microphone 610 is disposed at the position on the ejection side or the suction side of the cooling fan 150. That is, it is arranged at a downstream position or upstream position of the air blown from the cooling fan 150. However, in order to perform control for adjusting the phase and amplitude of the antiphase sound described later, it is preferable to arrange the reference microphone 610 at a position on the ejection side of the cooling fan 150. The reference microphone 610 is disposed at a position not far from the cooling fan 150. This is because the noise from the cooling fan 150 is preferably collected.

  The error detection microphone 620 is a sound wave receiving unit for receiving a synthesized sound of the rotating sound emitted from the cooling fan 150 and the reversed phase sound emitted from the reversed phase speaker 630. The error detection microphone 620 is disposed at a position slightly away from the cooling fan 150 and the antiphase speaker 630. This is because the synthesized sound of the sound wave from the cooling fan 150 and the sound wave from the antiphase speaker 630 is preferably collected. Therefore, the distance between the cooling fan 150 and the error detection microphone 620 is longer than the distance between the cooling fan 150 and the reference microphone 610. Note that the error detection microphone 620 is disposed at a position other than the line segment connecting the cooling fan 150 and the antiphase speaker 630. This is because the synthesized sound is preferably received.

  The anti-phase speaker 630 is a sound wave generator that emits sound waves having an anti-phase waveform generated by the signal processor 310. Here, the sound wave having an antiphase waveform is a sound wave having an antiphase waveform with respect to the sound wave detected by the reference microphone 610. As will be described later, the anti-phase speaker 630 generates sound waves of the corrected waveform after the correction instead of the anti-phase waveform after the anti-phase waveform is corrected. The anti-phase speaker 630 is disposed at a position not far from the position of the cooling fan 150. The distance between the cooling fan 150 and the antiphase speaker 630 is shorter than the distance between the cooling fan 150 and the error detection microphone 620.

  The signal processing unit 310 is an antiphase waveform generation unit for generating an antiphase waveform of a sound wave received by the reference microphone 610. The signal processing unit 310 also serves as a correction unit for correcting the antiphase waveform to generate a corrected waveform. As will be described later, this correction is executed so that the synthesized sound received by the error detection microphone 620 is reduced. That is, the signal processing unit 310 generates a corrected waveform by feeding back the synthesized sound received by the error detection microphone 620.

3. Control System of Image Forming Apparatus FIG. 3 is a block diagram showing a control system of the image forming apparatus 100 of this embodiment. The image forming apparatus 100 includes an image processing unit 360, a ROM 410, a RAM 420, a data storage unit 430, and a communication unit 440 in addition to those shown in FIGS.

  The image processing unit 360 is for processing the image image read by the image reading unit 210. The ROM 410 and the RAM 420 are storage units attached to the main body of the image forming apparatus 100. The RAM 420 is used as a work area when converting an image image into electronic data. The data storage unit 430 is a storage unit for storing various data converted into electronic data. The communication unit 440 is for communicating with the network 500 outside the image forming apparatus 100.

  In the noise reduction unit 600, the waveform information of the sound wave received by the reference microphone 610 is input to the signal processing unit 310. Then, the signal processing unit 310 generates an antiphase waveform and transmits the waveform information to the antiphase speaker 630. Waveform information is also input to the signal processing unit 310 from the error detection microphone 620. This is to correct the antiphase waveform.

4). Here, how the noise emitted from the cooling fan 150 changes when the position of the reference microphone 610 is changed will be described. As described above, the position where the reference microphone 610 is disposed is one of the ejection side and the suction side of the cooling fan 150.

  The flow of the air blown from the cooling fan 150 is different when the reference microphone 610 is at the position on the ejection side of the cooling fan 150 and when it is at the position on the suction side of the cooling fan 150. This is because when the reference microphone 610 is disposed on the ejection side of the cooling fan 150, the reference microphone 610 becomes an obstacle to the flow of wind. Therefore, the frequency characteristic of the sound wave detected by the reference microphone 610 differs depending on where the reference microphone 610 is arranged.

  The difference in frequency characteristics depending on the arrangement of the reference microphone 610 is shown in FIG. The horizontal axis in FIG. 4 represents the frequency (Hz) of the sound wave detected by the reference microphone 610. The vertical axis in FIG. 4 represents the sound pressure level (dB) at that frequency. As shown in FIG. 4, when the reference microphone 610 is arranged on the ejection side of the cooling fan 150 and the case where it is arranged on the suction side, in the high frequency band of several hundred Hz or higher, both There is no difference. On the other hand, in the frequency band on the low sound side where the frequency is several hundred Hz or less, the sound pressure level when arranged on the ejection side is higher than the sound pressure level when arranged on the suction side.

  Thus, the measured sound pressure level varies depending on the position where the reference microphone 610 is disposed. However, actually, the noise generated from the cooling fan 150 is not so different. However, when the reference microphone 610 is disposed at the position on the ejection side of the cooling fan 150, the reference microphone 610 picks up the wind pressure in addition to the sound pressure. This noise caused by wind pressure is generally called pop noise or blowing. This pop noise appears on the bass side of the measured sound wave.

  On the other hand, when the reference microphone 610 is disposed on the suction side of the cooling fan 150, the reference microphone 610 does not pick up such pop noise. Therefore, in order to cancel the sound on the low frequency side, it is better to place the reference microphone 610 at a position on the suction side of the cooling fan 150.

  However, the sound waveform leaked to the outside of the image forming apparatus 100 heard by the user is closer to the sound waveform measured on the ejection side of the cooling fan 150. Therefore, in order to cancel the high-frequency sound that is not affected by pop noise, it is better to place the reference microphone 610 at the position on the ejection side of the cooling fan 150. As described above, whether the reference microphone 610 is arranged in the position on the ejection side or the position on the suction side of the cooling fan 150 has advantages and disadvantages.

4-1. FIG. 5 is a graph showing the sound pressure level when the reference microphone 610 is arranged on the ejection side of the cooling fan 150. The horizontal and vertical axes in FIG. 5 are the same as those in FIG. FIG. 5 shows the difference in frequency characteristics when the voltage applied to the motor M that rotationally drives the cooling fan 150 is changed.

  As shown in FIG. 5, when the applied voltage applied to the motor M is 12V, there are peaks P1 and P2. The peak P1 is in the vicinity of 400 Hz, and the peak P2 is in the vicinity of 800 Hz. The peak P1 is considered to be the fundamental frequency of the cooling fan 150. The peak P2 is considered to be the first harmonic of the cooling fan 150. When the applied voltage applied to the motor M is 10 V, the peaks P3 and P4 are considered to be the fundamental frequency and the first harmonic, respectively. Whether or not to use such fundamental frequencies and harmonics for noise reduction control is free.

  As shown in FIG. 5, as the applied voltage applied to the motor M increases, the sound pressure level of the noise generated from the cooling fan 150 increases. This is because, as described above, the higher the applied voltage of the motor M, the greater the rotational speed of the cooling fan 150. In FIG. 5, the sound pressure level is high in the low frequency side frequency band where the frequency is low, similar to the ejection side shown in FIG.

  A region R1 in FIG. 5 is a region where pop noise is picked up when the applied voltage applied to the motor M is 12V. That is, this is a region where the waveform collected by the reference microphone 610 is not reliable. A region R2 in FIG. 5 is a region where pop noise is picked up when the applied voltage applied to the motor M is 10V. That is, this is a region where the waveform collected by the reference microphone 610 is not reliable. Here, the region R1 is wider than the region R2. It is located up to the high frequency side frequency band from the region R2. In other words, the faster the cooling fan 150 rotates, the more pop noise extends to the high frequency band.

4-2. Suction Side FIG. 6 is a graph showing the sound pressure level when the reference microphone 610 is arranged on the suction side of the cooling fan 150. The horizontal and vertical axes in FIG. 6 are the same as those in FIG. FIG. 6 shows the difference in frequency characteristics when the output voltage of the motor M that rotationally drives the cooling fan 150 is changed.

  As shown in FIG. 6, when the reference microphone 610 is disposed on the suction side of the cooling fan 150, the frequency band on the high sound side is almost the same as that on the ejection side (see FIG. 5). On the other hand, in the low frequency band, when the applied voltage of the motor M is small, the sound pressure level is slightly higher than that on the high sound side. However, when the applied voltage of the motor M is large, such an increase in the sound pressure level is hardly observed.

4-3. Comparison between the ejection side and the suction side A comparison between the case where the cooling fan 150 is arranged on the ejection side (FIG. 5) and the case where the cooling fan 150 is arranged on the suction side (FIG. 6) will be described. In the lines of 6V and 8V applied voltages applied to the motor M that rotationally drives the cooling fan 150, there is almost no difference between FIG. 5 and FIG. On the other hand, there is a significant difference between FIG. 5 and FIG. 6 in the lines where the applied voltage applied to the motor M is 10V and 12V.

  As described above, when the cooling fan 150 is arranged on the ejection side (FIG. 5), the sound pressure level rises in the low frequency band. The increase of the sound pressure level, that is, the deviation of the measured value is larger as the applied voltage to the motor M is larger. This is because the wind pressure applied to the reference microphone 610 increases as the rotational speed of the motor M increases. As described above, the intensity distribution of the sound pressure level varies depending on the arrangement of the reference microphone 610, and it is necessary to generate an antiphase waveform according to each intensity.

5. Basic Principle of Noise Reduction Method Here, the basic principle of the noise reduction method of this embodiment will be described. FIG. 7 is a graph showing the waveform of a sound wave at a certain time. Further, although it is actually a superposition of waveforms of various frequencies, for the sake of easy understanding, a waveform of a single frequency is shown in FIG. The upper graph (FIG. 7A) of FIG. 7 is a graph showing the waveform of the sound wave generated by the cooling fan 150. The middle graph (FIG. 7B) in FIG. 7 is a graph showing the waveform of the sound wave emitted by the antiphase speaker 630. The lower graph in FIG. 7 (FIG. 7C) is a graph showing the waveform of the synthesized sound of the sound wave emitted from the cooling fan 150 and the sound wave emitted from the antiphase speaker 630.

  The horizontal axis of the graph in FIG. 7A indicates the distance from the cooling fan 150. The origin is the position of the cooling fan 150. The origins of FIGS. 7B and 7C are also drawn as in FIG. 7A. This is because the anti-phase speaker 630 is disposed at a position near the cooling fan 150, and the error detection microphone 620 is disposed at a position away from the cooling fan 150. Therefore, any position of the cooling fan 150 and the antiphase speaker 630 may be set as the origin. The vertical axis of each graph in FIG. 7 indicates the amplitude of the sound wave. The amplitude in the upper graph and the middle graph in FIG. 7 is 2A.

A comparison between the upper graph of FIG. 7 and the middle graph of FIG. 7 is as follows. Here, if the origin of these graphs is the start point of the cycle, the point 4B away from the origin is the end point of the cycle.
Distance from cooling fan B 2B 3B 4B
Amplitude value of cooling fan sound-A 0 A 0
Amplitude value of sound wave from anti-phase speaker A 0 -A 0
As described above, the phase of the sound wave of the antiphase speaker 630 (the middle graph in FIG. 7) is opposite to the phase of the sound wave of the cooling fan 150 (the upper graph in FIG. 7).

  Then, by superimposing the sound wave emitted from the cooling fan 150 and the sound wave emitted from the anti-phase speaker 630, a waveform of the synthesized sound is obtained as shown in the lower graph of FIG. In the lower graph of FIG. 7, the waveform of the synthesized sound is constantly zero.

  However, in reality, noise is added to the waveform of the synthesized sound. There are various causes for this noise. One of them is that it is difficult to obtain a waveform that completely cancels the sound waves of the cooling fan 150. For this purpose, feedback is applied to the antiphase waveform generated by the signal processing unit 310.

  An error detection microphone 620 is used to feed back the antiphase waveform. Here, the amplitude of the sound wave measured by the error detection microphone 620 may be zero. As a result, the waveform of the synthesized sound becomes a waveform that is close to zero more constantly.

6). Noise Reduction Flow FIG. 8 is a flowchart for explaining the noise reduction flow according to this embodiment. First, the noise generated by the cooling fan 150 is measured by the reference microphone 610 (S101). Here, when the cooling fan 150 rotates at a constant speed, the waveform of the sound generated by the cooling fan 150 is substantially the same waveform. Next, the signal processing unit 310 generates an antiphase sound of the measured sound wave, that is, an antiphase waveform (S102). Next, the antiphase speaker 630 emits the generated antiphase sound (S103). Next, the synthesized sound obtained by synthesizing the sound wave from the cooling fan 150 and the sound wave from the antiphase speaker 630 is measured by the error detection microphone 620 (S104).

  Next, the signal processing unit 310 adjusts the amplitude and phase so that the measured waveform of the synthesized sound becomes zero (S105). For example, when the amplitude of the combined wave is in the same direction as the amplitude of the cooling fan 150, the amplitude of the antiphase waveform is increased. Conversely, when the amplitude of the combined wave is opposite to that of the cooling fan 150, the amplitude of the antiphase waveform is reduced.

  Next, it is confirmed whether or not there is an instruction to end the noise reduction control (S106). If there is an instruction to end the noise reduction control (S015: Yes), the noise reduction control is ended. If there is no instruction to end the noise reduction control (S105: No), the process proceeds to S105. In other words, we continue to apply feedback.

  As described above, the image forming apparatus 100 according to the present embodiment measures noise generated from the cooling fan 150 with the reference microphone 610, and generates sound waves having an antiphase waveform of the sound waves from the antiphase speaker 630. Is reduced. In addition, since the error detection microphone 620 that measures the synthesized sound of noise and antiphase sound is provided, feedback can be applied to the sound wave generated by the signal processing unit 310.

7). Modified example 7-1. Microphone Screen In this embodiment, the reference microphone 610 is arranged at the position on the ejection side of the cooling fan 150. At that time, the reference microphone 610 is arranged in a bare state. However, a screen member that reduces the influence of wind from the cooling fan 150 may be disposed in the reference microphone 610. As a result, the occurrence of the above-mentioned phenomenon called pop noise or blowing can be suppressed.

  For example, as shown in FIG. 10, the reference microphone 610 may be covered with a sponge 710. Further, as shown in FIG. 11, a pop guard 720 may be disposed between the cooling fan 150 and the reference microphone 610. The sponge 710 and the pop guard 720 are buffer members that mitigate the wind generated by the cooling fan 150.

7-2. Other Rotating Parts In this embodiment, the cooling fan 150 has been described as an example of the noise source. However, in addition to the cooling fan 150, the image forming apparatus 100 includes the photosensitive drum 21, the fixing device 130, the primary transfer roller 111, the secondary transfer roller 115, and the intermediate transfer belt 101. In addition, there are rotating parts that rotate by receiving rotational driving. Noise is generated by the rotation of these rotating parts or the rotation of the motor M. In this embodiment, the noise generated from these rotating parts or the drive unit can be reduced by performing feedback.

7-3. Basic frequency As shown in FIGS. 5 and 6, the sound pressure level is high near the basic frequency. Therefore, if the sound pressure level in the vicinity of the fundamental frequency of the cooling fan 150 is reduced, there is an effect of canceling noise even in that case. Therefore, the signal processing unit 310 may generate an antiphase waveform in the vicinity of the fundamental frequency of the cooling fan 150, for example, in a frequency band within the range of the fundamental frequency ± 50 Hz.

8). Summary As described above in detail, the image forming apparatus according to the present embodiment measures the sound wave generated by the cooling fan 150, generates an opposite phase waveform opposite to the measured sound wave, and outputs the opposite phase. Waveform sound waves are emitted from the anti-phase speaker 630. The sound emitted from the cooling fan 150 is reduced by the sound wave emitted from the antiphase speaker 630. Further, since feedback is always applied, even when noise is generated in addition to the cooling fan 150, the noise can be reduced. Thereby, an image forming apparatus capable of reducing noise is realized.

  Note that this embodiment is merely an example, and does not limit the present invention. Therefore, the present invention can naturally be improved and modified in various ways without departing from the gist thereof. For example, the image forming apparatus may be one-sided printing or two-sided printing. Also, it is not limited to color printing. When color printing is not used, the image quality degradation determination value may be calculated for only one color. The image forming apparatus may be a printer. Further, the present invention can be applied to an image reading apparatus and an image forming apparatus that transmit a read image as a print job through a public line. Of course, it may be a multifunction machine. Also, it can be applied regardless of the type of toner.

(Second Embodiment)
A second embodiment will be described. The mechanical configuration of the image forming apparatus of the present embodiment is substantially the same as that of the image forming apparatus 100 of the first embodiment. The image forming apparatus according to the present embodiment is different from the image forming apparatus 100 according to the first embodiment in that the cooling fan 150 is disposed on the ejection side and noise reduction control executed by the noise reduction unit 600. . Therefore, the difference will be mainly described.

1. The number of rotations of the cooling fan The mechanical configuration of the image forming apparatus according to the present embodiment is almost the same as that of the image forming apparatus 100 according to the first embodiment. And However, in this embodiment, the cooling fan 150 is arranged at the position on the ejection side, and is not arranged at the position on the suction side. This is because the reference microphone 610 is preferably disposed at the position on the ejection side of the cooling fan 150 in order to perform control for adjusting the phase and amplitude of the antiphase sound as described above.

  In this embodiment, the rotational speed of the cooling fan 150 is freely controlled. In that case, the rotational speed of the cooling fan 150 may be set according to the amount of heat generated inside the image forming apparatus 100. That is, when the image formation is not performed, a low rotation speed is set as the rotation speed value of the cooling fan 150, and when the image formation is performed, a high rotation speed is set as the rotation speed value of the cooling fan 150. is there.

  FIG. 12 is a graph showing an example when the number of rotations of the cooling fan 150 is set. The horizontal axis in FIG. 12 is time. The vertical axis in FIG. 12 represents the rotation speed of the cooling fan 150. As shown in FIG. 12, in the standby state where image formation is not performed, the number of rotations of the cooling fan 150 is set to 1000 rotations per minute. Here, the number of rotations of the cooling fan 150 during standby is smaller than the number of rotations of the cooling fan 150 when image formation is performed on thick paper. The rotational speed of the cooling fan 150 when forming an image on thick paper is smaller than the rotational speed of the cooling fan 150 when forming an image on plain paper.

  When image formation is performed, the number of rotations set in the cooling fan 150 is changed depending on whether the sheet used for image formation is plain paper or thick paper thicker than that. When image formation is performed on plain paper, the rotation speed set for the cooling fan 150 is set to 3000 rotations per minute. That is, the rotational speed of the cooling fan 150 is increased. When image formation is performed on thick paper, the rotation speed set for the cooling fan 150 is set to 2000 rotations per minute. That is, when an image is formed on thick paper after waiting, the rotation speed of the cooling fan 150 is increased. When the image is formed on the thick paper after the image is formed on the plain paper, the rotational speed of the cooling fan 150 is decreased. Thereby, the inside of the image forming apparatus 100 can be suitably cooled.

  However, as described in the description of FIGS. 4 and 5, it is difficult to measure the frequency band on the low sound side as the number of rotations of the cooling fan 150 increases. In that case, the antiphase waveform generated by the signal processing unit 310 may not necessarily be suitable for canceling the noise from the cooling fan 150. Although it is possible to cancel the high frequency components of noise, it is difficult to cancel the low frequency components of noise. Furthermore, there is a possibility that the amplitude may be increased by overlapping the sound wave waveform of the cooling fan 150 and the waveform of the antiphase speaker 630. That is, noise may increase.

  Therefore, in this embodiment, an antiphase sound is generated by cutting a low frequency region that is difficult to measure. That is, an antiphase sound having a component only in a frequency band equal to or higher than a predetermined frequency threshold is generated. Therefore, the component of the frequency band less than the frequency threshold in the antiphase sound is zero. As this frequency threshold value, a different value may be set depending on the number of rotations of the cooling fan 150. The higher the rotation speed of the cooling fan 150, the higher the frequency threshold value should be set to the higher sound side.

Therefore, different frequency thresholds are set according to the operation mode of the image forming apparatus 100. In that case, the following relational expression holds.
A <B <C <D <E
A: Frequency threshold applied when the operation mode is sleeping
B: Frequency threshold applied when the operation mode is standby
C: Frequency threshold applied when the operation mode is image stabilization processing
D: Frequency threshold applied when image is being formed on cardboard
E: Frequency threshold applied when an image is being formed on plain paper

2. Noise Reduction Flow The noise reduction flow of this embodiment will be described with reference to the flowchart of FIG.

S210:
First, the operation mode of the image forming apparatus 100 is confirmed. It is confirmed whether or not the operation mode of the image forming apparatus 100 is sleeping (S210). Here, when the operation mode is sleeping (S210: Yes), the process proceeds to S211 described later. If the operation mode is not sleeping (S210: No), the process proceeds to S220.

S220:
In S220, it is determined whether the operation mode of the image forming apparatus 100 is on standby. When the operation mode is waiting (S220: Yes), the process proceeds to S221 described later. If the operation mode is not standby (S220: No), the process proceeds to S230.

S230:
In S230, it is determined whether or not the operation mode of the image forming apparatus 100 is an image stabilization process. The image stabilization process is a process of processing an image read by the image reading unit 210 to obtain a clearer image. When the operation mode is the image stabilization process (S230: Yes), the process proceeds to S231 described later. When the operation mode is not in the image stabilization process (S230: No), the process proceeds to S240.

S240:
In S240, the operation mode of the image forming apparatus 100 determines the type of sheet that is being printed. When the operation mode is printing thick paper (S240: Yes), the process proceeds to S241 to be described later. If the operation mode is printing plain paper (S240: No), the process proceeds to S251.

After S211:
In S <b> 211, noise due to the rotation of the cooling fan 150 is measured by the reference microphone 610. Next, the signal processing unit 310 analyzes the frequency characteristics of the measured sound wave (S212). Subsequently, the signal processing unit 310 generates an antiphase waveform for a frequency band equal to or higher than a predetermined frequency threshold A (S213). In addition, the anti-phase speaker 630 generates sound waves having the generated anti-phase waveform (S213).

After S221:
In step S <b> 221, noise due to the rotation of the cooling fan 150 is measured by the reference microphone 610. Next, the signal processing unit 310 analyzes the frequency characteristics of the measured sound wave (S222). Subsequently, the signal processing unit 310 generates an antiphase waveform for a frequency band equal to or higher than a predetermined frequency threshold B (S223). In addition, the anti-phase speaker 630 generates a sound wave having the generated anti-phase waveform (S223).

After S231:
In S231, noise due to the rotation of the cooling fan 150 is measured by the reference microphone 610. Next, the signal processing unit 310 analyzes the frequency characteristics of the measured sound wave (S232). Subsequently, the signal processing unit 310 generates an antiphase waveform for a frequency band equal to or higher than a predetermined frequency threshold C (S233). In addition, the anti-phase speaker 630 generates sound waves having the generated anti-phase waveform (S233).

After S241:
In S241, the noise due to the rotation of the cooling fan 150 is measured by the reference microphone 610. Next, the signal processing unit 310 analyzes the frequency characteristics of the measured sound wave (S242). Subsequently, the signal processing unit 310 generates an antiphase waveform for a frequency band equal to or higher than a predetermined frequency threshold D (S243). In addition, the anti-phase speaker 630 generates sound waves having the generated anti-phase waveform (S243).

After S251:
In S251, the noise due to the rotation of the cooling fan 150 is measured by the reference microphone 610. Next, the signal processing unit 310 analyzes the frequency characteristics of the measured sound wave (S252). Subsequently, the signal processing unit 310 generates an antiphase waveform for a frequency band equal to or higher than a predetermined frequency threshold E (S253). In addition, the anti-phase speaker 630 generates sound waves having the generated anti-phase waveform (S253).

  As described above, in this embodiment, different frequency threshold values (A to E) are set according to the operation mode of the image forming apparatus 100, and an antiphase waveform is generated for a frequency band equal to or higher than the frequency threshold values (A to E). At the same time, the antiphase waveform is generated from the antiphase speaker 630. As a result, an image forming apparatus in which noise is reduced is realized.

3. Modification 3-1. Noise Reduction Flow In this embodiment, the operation modes of the image forming apparatus 100 are classified in detail, and the noise reduction flow of the cooling fan 150 is performed according to the operation modes. However, the operation mode classification may be more coarse. For example, as shown in FIG. 14, it may be classified into two cases, that is, a case of sleeping or waiting, and a case of image formation. On the contrary, you may make it finer.

  First, it is confirmed whether or not the operation mode of the image forming apparatus 100 is in sleep (S310). If the operation mode is sleeping (S310: Yes), the process proceeds to S311. Otherwise (S310: No), the process proceeds to S320. In S320, it is determined whether the operation mode is standby. When the operation mode is standby (S320: Yes), the process proceeds to S311. If the operation mode is not standby (S320: No), the process proceeds to S321.

  In S <b> 311, noise due to the rotation of the cooling fan 150 is measured by the reference microphone 610. Next, the signal processing unit 310 analyzes the frequency characteristics of the measured sound wave (S312). Subsequently, the signal processing unit 310 generates an antiphase waveform for a frequency band equal to or higher than a predetermined frequency threshold A (S313). In addition, the anti-phase speaker 630 generates sound waves having the generated anti-phase waveform (S313).

  In step S <b> 321, noise due to the rotation of the cooling fan 150 is measured by the reference microphone 610. Next, the signal processing unit 310 analyzes the frequency characteristics of the measured sound wave (S322). Subsequently, the signal processing unit 310 generates an antiphase waveform for a frequency band equal to or higher than a predetermined frequency threshold B (S323). However, the anti-phase speaker 630 does not generate the generated anti-phase waveform sound wave (S323).

  When the rotational speed of the cooling fan 150 increases, the wind of the cooling fan 150 strongly strikes the reference microphone 610 disposed in the vicinity of the cooling fan 150. For this reason, it is difficult to accurately detect the low frequency region of the sound wave generated by the cooling fan 150. That is, in this case, it is difficult to accurately cancel the sound wave of the cooling fan 150. Therefore, in this case, no sound wave is generated from the antiphase speaker 630. This is because if an inappropriate sound wave is generated from the anti-phase speaker 630, there is a possibility that the noise will be generated rather than canceling the noise.

4). Summary As described above in detail, the image forming apparatus according to the present embodiment measures the sound wave generated by the cooling fan 150, generates an opposite phase waveform opposite to the measured sound wave, and outputs the opposite phase. Waveform sound waves are emitted from the anti-phase speaker 630. The sound emitted from the cooling fan 150 is reduced by the sound wave emitted from the antiphase speaker 630. Further, since feedback is always applied, even when noise is generated in addition to the cooling fan 150, the noise can be reduced. Thereby, an image forming apparatus capable of reducing noise is realized.

  Note that this embodiment is merely an example, and does not limit the present invention. Therefore, the present invention can naturally be improved and modified in various ways without departing from the gist thereof. For example, the image forming apparatus may be one-sided printing or two-sided printing. Also, it is not limited to color printing. When color printing is not used, the image quality degradation determination value may be calculated for only one color. The image forming apparatus may be a printer. Further, the present invention can be applied to an image reading apparatus and an image forming apparatus that transmit a read image as a print job through a public line. Of course, it may be a multifunction machine. Also, it can be applied regardless of the type of toner.

DESCRIPTION OF SYMBOLS 1 ... Image forming part 10 ... Developing unit 20 ... Photoconductor unit 21 ... Photoconductor drum 30 ... Exposure apparatus 100 ... Image forming apparatus 150 ... Cooling fan 210 ... Image reading part 230 ... Touch panel 300 ... Control part 310 ... Signal processing part 600 ... Noise reduction unit 610 ... Reference microphone 620 ... Error detection microphone 630 ... Anti-phase speaker

Claims (8)

An image forming apparatus for forming an image,
A drive unit that rotationally drives a rotating component inside the image forming apparatus;
A first sound wave receiving unit that receives a rotating sound of the rotating component or the driving unit;
An antiphase waveform generating unit for generating an antiphase waveform of the sound wave received by the first sound wave receiving unit;
A sound wave generator for generating a sound wave having an antiphase waveform generated by the antiphase waveform generator;
A second sound wave receiving unit that receives a synthesized sound of a rotating sound of the rotating component or the driving unit and a sound wave generated by the sound wave generating unit;
A correction unit that corrects an antiphase waveform and generates a corrected waveform so as to reduce a synthesized sound received by the second sound wave receiving unit;
The sound wave generator
An image forming apparatus, wherein after the correction waveform is generated by the correction unit, a sound wave having a correction waveform is generated instead of an antiphase waveform. The image forming apparatus according to claim 1,
The anti-phase waveform generator is
When the operation mode of the image forming device is in the sleep state,
An image forming apparatus for generating an antiphase signal for a frequency band equal to or higher than a predetermined first frequency threshold. The image forming apparatus according to claim 2,
The anti-phase waveform generator is
When the operation mode of the image forming device is standby
An image forming apparatus, wherein an antiphase signal is generated for a frequency band equal to or greater than a second frequency threshold that is equal to or greater than the first frequency threshold. The image forming apparatus according to claim 3, wherein
The anti-phase waveform generator is
When the operation mode of the image forming device is image stabilization processing,
Generating an antiphase signal for a frequency band greater than or equal to a third frequency threshold greater than the second frequency threshold;
When the operation mode of the image forming device is an image forming state on cardboard,
Generating an antiphase signal for a frequency band greater than or equal to a fourth frequency threshold greater than the third frequency threshold;
When the operation mode of the image forming device is in the state of forming an image on plain paper,
An image forming apparatus, wherein an antiphase signal is generated for a frequency band equal to or greater than a fifth frequency threshold value greater than the fourth frequency threshold value. An image forming apparatus according to any one of claims 1 to 4, wherein
At least one of the rotating parts is
An image forming apparatus comprising a cooling fan for cooling the inside of the image forming apparatus. The image forming apparatus according to claim 5, wherein
The first sound wave receiving unit includes:
An image forming apparatus, wherein the image forming apparatus is disposed at a position on a suction side of the cooling fan. The image forming apparatus according to claim 5, wherein
The first sound wave receiving unit includes:
An image forming apparatus, wherein the image forming apparatus is disposed at a position on an ejection side of the cooling fan. The image forming apparatus according to claim 7, wherein
An image forming apparatus, wherein a buffer member for relaxing wind generated by the cooling fan is disposed between the cooling fan and the first sound wave receiving unit.

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