JP2007003964A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve the noise problem of an environment where an image forming apparatus is used, by making noises (high-frequency noises) of a high-frequency region, which sound unpleasant to users, less likely to be heard by users, without increasing the size and cost of the apparatus. <P>SOLUTION: In the image forming apparatus, an image forming means for forming images on a recording medium based on image information includes low-frequency components (e.g., drum drive motor gears and corresponding gears) that emit low-frequency noises, and high-frequency components (e.g., paper feed stepping motor, drum drive motors, and a polygon mirror motor) that emit high-frequency noises. This apparatus has a low-frequency amplifying means for amplifying low-frequency noises (e.g., engaging noises of the drum drive motor gears and corresponding gears) emitted by the low-frequency components. By using masking effect produced by the low-frequency noises, high-frequency noises (e.g., motor drive noises) emitted by the high-frequency components are made less likely to be heard by users. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an image forming apparatus such as a copying machine, a printer, and a facsimile.

  In recent years, noise in image forming apparatuses has become a problem in environments where image forming apparatuses such as offices are used. In the image forming apparatus, many components are mechanically connected, and various noises are generated from these components when the image forming apparatus is driven. This noise may cause discomfort to the user. . In particular, it is known that noise in a high frequency region and noise of a pure tone component having a high sound pressure level at a single frequency are likely to be uncomfortable for humans. In particular, the noise of the pure tone component in the high frequency region is heard with a metallic sound like a kinkin, and therefore, the degree of discomfort is high.

  Patent Document 1 discloses an image forming apparatus that suppresses vibration resonance of a rotating body drive system that may cause noise. In this image forming apparatus, a tie toner that adjusts the tension of the timing belt constituting the rotating body drive system is used to suppress occurrence of string vibration resonance of the timing belt in accordance with the rotational speed of the motor and the meshing frequency of the gear. .

  Patent Document 2 discloses an image forming apparatus that generates a secondary sound having a waveform opposite to the waveform of the noise generated by a drive mechanism that is a source of noise to reduce the noise. Yes. The image forming apparatus detects a waveform of noise generated from the drive mechanism, generates a secondary sound having a waveform opposite to the waveform from the detection result, and outputs the secondary sound from the speaker. According to this image forming apparatus, the secondary sound output from the speaker and the noise generated from the drive mechanism interfere with each other and cancel each other, and the sound pressure level of the noise can be reduced. Further, this image forming apparatus is configured to output a tertiary sound for masking the noise reduced by the secondary sound from the speaker. The tertiary sound has a frequency distribution such that the sound pressure increases as the frequency decreases. By outputting such a tertiary sound, the noise in the high frequency region among the noises reduced by the secondary sound is not emphasized, and the user's discomfort can be effectively reduced.

JP 2002-39296 A JP-A-9-193504

However, in the image forming apparatus described in Patent Document 1, since noise due to string vibration resonance of the timing belt is in a relatively low frequency region, it is difficult to suppress noise in a high frequency region that is likely to be uncomfortable for humans. Can not. Therefore, the suppression effect about the noise which a user feels unpleasant cannot be obtained.
In the image forming apparatus described in Patent Document 2, a mechanism for detecting a waveform of noise generated from a drive mechanism, a mechanism for generating and outputting a secondary sound, a mechanism for generating and outputting a tertiary sound, and the like Therefore, there is a problem in that it is difficult to make a space and the cost increases.

  The present invention has been made in view of the above background, and an object of the present invention is to provide noise (high frequency noise) having a high frequency region in which a user easily feels uncomfortable without increasing the size and cost of the device. It is an object of the present invention to provide an image forming apparatus that makes it difficult for the user to hear and can improve noise problems in the usage environment.

In order to achieve the above object, the invention of claim 1 is provided with an image forming means for forming an image on a recording material based on image information, and the image forming means generates a low frequency noise. An image forming apparatus comprising a constituent article and a high-frequency constituent article that generates high-frequency noise has low-frequency amplification means for amplifying low-frequency noise generated by the low-frequency constituent article. .
According to a second aspect of the present invention, in the image forming apparatus according to the first aspect, the low-frequency component article generates low-frequency noise in a frequency range of 300 [Hz] to 800 [Hz]. The high frequency component is one that generates high frequency noise in a frequency region of 1000 [Hz] or higher.
According to a third aspect of the present invention, in the image forming apparatus according to the first or second aspect, the low frequency amplifying means amplifies the low frequency noise so that the level is higher than the high frequency noise generated by the high frequency component. It is characterized by making it.
According to a fourth aspect of the present invention, in the image forming apparatus according to the first, second, or third aspect, the low frequency amplification means has a natural frequency that matches or approximates the frequency of the low frequency noise generated by the low frequency component. It is a resonance member which has this.
According to a fifth aspect of the present invention, in the image forming apparatus of the fourth aspect, the resonance member is obtained by fixing a member for adjusting the mass of the constituent article to the constituent article constituting the image forming means. It is a feature.
According to a sixth aspect of the present invention, in the image forming apparatus according to the fifth aspect, the mass adjusting member is a vibration damping member that suppresses the vibration that causes the high-frequency noise among the vibrations generated in the constituent articles. It is characterized by being.
According to a seventh aspect of the present invention, in the image forming apparatus according to the fourth, fifth, or sixth aspect, the low-frequency component is a component of a driving device, and the resonance member is a support member that supports the component. It is characterized by being.
The invention according to claim 8 is the image forming apparatus according to claim 1, 2, 3, 4, 5, 6 or 7, further comprising a sound absorbing means for absorbing at least the high frequency noise.

There is a masking effect as a human auditory characteristic. The masking effect refers to a phenomenon in which when a certain mask sound is generated while another sound is generated, the certain sound is completely inaudible or difficult to hear due to the mask sound. In general, the masking effect is characterized in that a masking effect can be obtained over a wide range for noise in a frequency region higher than the mask sound, but a masking effect is difficult to obtain for a sound in a frequency region lower than the mask sound. In addition, as the mask sound level increases, the masking effect increases and the frequency region where the masking effect can be obtained is widened.
In the present invention, in order to make it difficult for the user to hear high-frequency noise generated by the high-frequency component constituting the image forming means, particularly noise of a pure tone component in the high-frequency region, using such a masking effect. The low-frequency noise generated from the low-frequency component that constitutes is amplified. Thereby, the high frequency noise which a high frequency component produces | generates with the amplified low frequency noise can be made hard to hear by a masking effect.
In addition, in the present invention, the low-frequency noise generated by the low-frequency component constituting the image forming means is used as the mask sound for masking the high-frequency noise generated by the high-frequency component, so that the mask sound other than the image forming means is used. There is no need to provide a separate mechanism for generating. Accordingly, it is possible to save space and reduce costs accordingly.
Here, the image forming means is a means related to image formation, and generates a secondary sound and generates a tertiary sound in the apparatus described in Patent Document 2 that does not participate in image formation. Therefore, it does not include a mechanism for outputting the output.

  As described above, according to the present invention, among the noises generated from the image forming apparatus, high-frequency noise that is easily uncomfortable for the user becomes difficult to be heard by the user without increasing the size and cost of the apparatus, and the noise in the usage environment. There is an excellent effect that the problem can be improved.

Hereinafter, an embodiment in which the present invention is applied to an electrophotographic color printer as an image forming apparatus will be described. The printer is an image forming apparatus that employs a tandem image forming system of four drums, but may be an image forming apparatus of another type.
FIG. 1 is an explanatory diagram showing a schematic configuration of the entire printer according to the present embodiment.
The printer mainly includes an optical unit 1 as a latent image forming unit, a photosensitive unit 3 as a latent image carrier, a developing unit 4 as a developing unit, a transfer unit 5 as a transferring unit, and a fixing unit. As a fixing unit 46 and a paper feeding unit 110. At the time of image formation, paper (including printing paper, OHP sheets, etc.) as a recording material accommodated in a paper feeding unit 110 disposed at the bottom of the printer is obliquely left upward from the lower right side in the drawing. It is transported along a paper transport path that extends toward it. On this sheet conveyance path, there are provided four photosensitive units 3 arranged side by side along the path, and a transfer unit 5 disposed so as to oppose them. It is conveyed so as to pass between the body unit 3 and the transfer unit 5. Around each photoconductor unit 3, a charging unit as a uniform charging unit, a developing unit 4, a photoconductor cleaning unit, and the like are arranged. The surface of the photosensitive drum included in each photosensitive unit 3 is uniformly charged to a predetermined potential by the charging unit, and then an electrostatic latent image corresponding to each color is formed by the optical unit 1. The electrostatic latent image on each photoconductor drum is developed with each color developer by the developing unit 4, thereby forming a toner image of each color. In each region (transfer region) where each photosensitive drum and the transfer belt 29 of the transfer unit 5 face each other, the color toner images are transferred so as to overlap each other on the paper passing through the transfer region. When the transferred paper is sent to the fixing unit 46 on the downstream side in the paper transport direction from these transfer regions, the toner images superimposed on each other are fixed on the paper by the fixing unit. Thereafter, the sheet is discharged to a discharge tray 510.

FIG. 2 is an explanatory diagram showing the configuration of the optical unit 1.
The optical unit 1 extends along the direction in which the four photoconductor units 3 are arranged (paper transport direction). Laser diodes (LDs) 17, 18, 19, and 20 for each color are attached to the upper part of the housing 11 constituting the optical unit 1. Also, the housing 11 includes a polygon mirror motor 2 for main scanning line scanning, double-layer fθ lenses 21 and 22 for dot position correction, and long WTL lenses 23 and 24 for correcting surface tilt for each color. 25, 26, and a cylinder lens or the like for correcting a laser beam diameter (not shown). A polygon mirror 27 in which two upper and lower six-side mirrors are integrally formed is attached to the polygon mirror motor 2, and laser light emitted from the LDs 17, 18, 19, and 20 is applied to the polygon mirror 27. Irradiated. Each of the LDs 17, 18, 19, and 20 corresponding to each color emits light in accordance with the conveyance timing of the paper, and the laser beam (shown by a thick line in the figure) is a cylinder lens, a polygon mirror 27, and a two-layer fθ lens 21 and 22. The photosensitive drum 28 of each color is irradiated through the long WTL lenses 23, 24, 25, and 26.

  As shown in FIG. 1, the photosensitive unit 3 and the developing unit 4 are independent units for each color. That is, the photosensitive unit 3 and the developing unit 4 for magenta (M), the photosensitive unit 3 and the developing unit 4 for cyan (C), the photosensitive unit 3 and the developing unit 4 for yellow (Y), black (Bk ) Photosensitive unit 3 and developing unit 4. Since the photoconductor units 3 for M, C, and Y except for Bk have the same configuration, any new unit can be used for any color (M, C, Y). .

FIG. 3 is an explanatory diagram showing a peripheral configuration of the photoconductor unit 3.
The photosensitive unit 3 has a photosensitive drum 28 (for example, φ30). The photosensitive drum 28 has a hollow cylindrical shape and can be rotated clockwise in the drawing by a driving mechanism described later. A charging roller 36 (for example, φ11) is disposed obliquely above and to the right of the photosensitive drum 28. The surface of the charging roller 36 is disposed at a position separated from the surface of the photosensitive drum 28 by about 0.05 [mm]. The charging roller 36 is rotated in a direction opposite to that of the photosensitive drum 28, that is, counterclockwise in the drawing, and applies a uniform charge on the surface of the photosensitive drum 28. A cleaning brush 37 is disposed above the charging roller 36. Further, a cleaning brush 39 and a counter blade 38 are disposed obliquely above and to the left of the photosensitive drum 28, and the photosensitive drum 28 is cleaned by these. A waste toner collecting coil 40 is disposed on the left side of the cleaning brush 39, and the waste toner collected by the waste toner collecting coil 40 is conveyed to the waste toner bolt 16 shown in FIG. ing.
The developing unit 4 employs a dry two-component magnetic brush developing system, and includes a developing roller 30, a developing doctor 31, a conveying screw left 32, a conveying screw right 33, a toner concentration sensor 34, and an agent cartridge 35. With.

FIG. 4 is an explanatory diagram of the driving mechanism of the photosensitive unit 3.
The three photoconductor units 3 for M, C, and Y (for color) and the photoconductor unit 3 for Bk are driven by separate drive mechanisms. That is, the driving of the color photosensitive unit 3 is transmitted to each photosensitive drum by the gears 43 and 44 and the joint 45 that transmit the driving force using the color drum driving motor 41 as a driving source. On the other hand, the driving of the photosensitive unit 3 for black is transmitted to the photosensitive drum by the gear 44 and the joint 45 that transmit the driving force using the black drum driving motor 42 as a driving source. Accordingly, during color mode printing, only the color drum drive motor 41 operates and the black drum drive motor 42 stops. On the other hand, during monochrome mode printing, only the black drum drive motor 42 operates and the color drum drive motor 41 stops. The color drum drive motor 41 and the black drum drive motor 42 are stepping motors.

  Returning to FIG. 1, the transfer unit 5 includes a plurality of rollers and an endless transfer belt 29 wound around the rollers. When the roller is rotated by a motor (not shown), the transfer belt 29 rotates counterclockwise in the drawing, and the sheet fed from the sheet feeding unit 110 is transported along the sheet transport path in a state of being placed on the surface of the transfer belt 29. . A pattern sensor (hereinafter referred to as “P sensor”) 6 is disposed on the downstream side of the transfer unit 5 in the sheet conveyance direction. The P sensor 6 detects the density of a test toner image (test pattern) formed on the transfer belt 29, and the detection result is used for feedback control of various units.

FIG. 5 is a perspective view showing the internal structure of the fixing unit 46.
FIG. 6 is an enlarged view of the oil application unit 47 provided in the fixing unit 46.
The fixing unit 46 employs a belt fixing method. Since the belt used in the belt fixing method has a smaller heat capacity than the roller used in the roller fixing method, the belt fixing method can generally reduce the warm-up time and the set temperature during standby compared to the roller fixing method. There are merits such as being able to decrease. The fixing unit 46 fixes the toner image on the paper by heating and pressurizing the paper after the transfer. The fixing unit 46 includes an oil application unit 47 that applies silicone oil to the fixing belt 13. In the oil application unit 47, silicone oil is supplied from the application felt 48 to the application roller 49. A small amount of silicone oil is applied to the fixing belt 13 while the application roller 49 rotates. By thus applying the silicone oil to the fixing belt 13, the peelability between the fixing belt 13 and the paper is improved. The application operation by the oil application unit 47 is performed every time a sheet is conveyed, and the oil application unit is conveyed every time a sheet is conveyed by a mechanism having a solenoid or a spring (not shown). 47 is driven, and the application roller 49 comes into contact with the fixing belt 13. On the other hand, when one sheet of paper passes, the oil application unit 47 is separated from the fixing belt 13 by the above mechanism. Further, as shown in FIG. 5, a cleaning roller 50 is provided on the upstream side of the fixing belt 13 in the sheet conveying direction. The cleaning roller 50 adsorbs dirt on the fixing belt 13, thereby performing belt cleaning. Made.

FIG. 7 is an explanatory diagram illustrating a configuration of the paper feeding unit 110.
The paper feed unit 110 has three trays, a first tray 9, a second tray 10, and a manual paper feed tray 8. As a system for feeding out the paper stored in each of the trays 8, 9, and 10, an FRR paper feeding system is adopted. The feed mechanism using the FRR paper feed system is reversely rotated with respect to the paper feed roller that is driven to rotate in the paper feed direction in order to separate the paper fed from the paper bundle stacked in the paper feed tray one by one. It has a configuration in which a roller is in contact. Under this configuration, the reverse roller is given a weak torque in the opposite direction to the paper feed roller via the torque limiter, so that it is in contact with the paper feed roller or a sheet of paper is between the two rollers. In the state where the sheet enters the roller, the sheet rotates with the sheet feeding roller. On the other hand, when the sheet is separated from the sheet feeding roller or two or more sheets enter between the rollers, the sheet rotates in the reverse direction. For this reason, when the multi-feed paper enters, the paper in contact with the reversing roller is returned to the downstream side in the paper feeding direction, and multi-feed is prevented.

When the sheets stored in the first tray 9 are separated by the first sheet feeding unit 51 and sent out from the first tray 9, the sheets are conveyed by the relay roller 53 and reach the conveying roller 55. The sheet is conveyed toward the registration roller 7 on the upper left side in the drawing while being turned by the conveyance roller 55, and abuts against the stopped registration roller 7. Due to this contact, the skew of the sheet is corrected. Then, timing adjustment with the image forming process by the photoconductor unit 3 or the like is performed, a registration clutch (not shown) is connected at a predetermined timing, the registration roller 7 is driven, and the sheet is conveyed toward the transfer unit. Thereafter, the sheet is conveyed by the transfer belt 29 as described above, and is discharged to the main body tray 510 through the transfer process and the fixing process.
The paper stored in the second tray 10 is transported toward the transport roller 55 by the second paper feed unit 52 and the relay roller 54, and thereafter the same as the paper stored in the first tray 9. It is.
Further, the paper set on the manual feed tray 8 is transported toward the registration roller 7 by the paper feed unit 56, and the subsequent processing is the same as the paper transport from the first tray 9.

FIG. 8 is an explanatory diagram showing a drive system of the first paper feed unit 51 and the second paper feed unit 52 that send out paper from the first tray 9 and the second tray 10.
Both of these units 51 and 52 are driven by a single paper feed stepping motor 83, and the driving force is transmitted to each of the units 51 and 52 via the first paper feed clutch 57 and the second paper feed clutch 58. Done. That is, when the paper is sent out from the first tray 9, only the first paper feed clutch 57 is engaged, and when the paper is sent out from the second tray 10, only the second paper feed clutch 58 is engaged.

[Noise analysis]
As described above, in the printer, many components are mechanically connected and the like, and various noises are generated from the image forming means involved in image formation of the printer. Therefore, first, the present inventors conducted noise analysis during operation of a conventional printer having the same configuration as the above-described printer.
In this noise analysis, the horizontal distance from the front of the printer (the surface on which the operation panel is provided) is 1 [m], the height from the floor is 1.5 [m], and from the front of the printer A dummy head was installed at the center in the width direction of the printer, and the noise emitted from the printer was measured. This dummy head is obtained by simulating the sound transmission characteristics of a human head and installing a microphone at the position of the eardrum. By using this dummy head, the sound recorded in binaural (both ears) is played back with dedicated headphones, so that the sound is heard in the same state as actually heard at the location of the dummy head by the person wearing the headphones. Can be heard.
In this noise analysis, psychoacoustic parameter values were calculated from sound data recorded with a dummy head using predetermined software. Typical psychoacoustic parameters are as follows (units in parentheses). (For example, the Japan Society of Mechanical Engineers "7th Design Engineering and System Division Lecture" Designing for the 21st Century, Aiming for an Innovative Leap of Systems! "" November 10 and 11, 1997, Design, color and design (1) ”see section 089B)
Loudness (sone): loudness of hearing, sharpness (acum): relative distribution of high-frequency components, tonality (tu): relative distribution of articulation and pure tone components, roughness: coarseness of sound There is also a psychoacoustic parameter such as feeling of feeling, fractation, strength (vacil): fluctuation intensity, groaning, and impulsiveness (iu): impact, relative approach: feeling of fluctuation.

  Any parameter described above tends to increase discomfort that humans feel uncomfortable. Among these parameters, only loudness is standardized by ISO532B, but the basic concept and definition of other parameters are the same, but the programs and calculation methods differ depending on the original research by the instrument manufacturer. Usually, the value is slightly different depending on the instrument. In this noise analysis, noise measurement is performed using a head acoustic system dummy head HMS (Head Measurement System) III, and analysis is performed using head acoustics sound quality analysis software ArtemiS. It was. ArtemiS can calculate impulsiveness. In addition, you may measure a noise using a common microphone, without using a dummy head.

ArtemiS can select various settings when calculating the psychoacoustic parameters, but this time, the analysis was performed using the default settings.
Specifically, for loudness, “FFT / ISO0532”, “Filter / ISO0532”, and “FFT / HEAD” can be selected as “Calculation method”, but the default “FFT / ISO0532” was adopted. Also, “SpectrumSize” is set to the default “4096”.
As for the sharpness, the default “FFT / ISO532” is adopted for “Calculation method”, and the default “Aures” among “Aures” and “vonBismark” is adopted for “Sharpness method”. Also, “SpectrumSize” is set to the default “4096”.
Other psychoacoustic parameters are correlated with loudness and change automatically depending on the loudness setting.
Using the sound quality analysis software ArtemiS set as described above, the sound pressure level and psychoacoustic parameter value of noise emitted from a conventional printer were obtained. Frequency analysis was also performed from the measured sound pressure level.

FIG. 9 is a graph showing the result of FFT analysis of the sound pressure level measured in the noise analysis. In this graph, the horizontal axis represents frequency (logarithmic scale display), and the vertical axis represents sound pressure level.
When the noise source at the main peak portion of the sound pressure level was examined in order from the lowest wave number, the peak at 401 [Hz] is the engagement sound between the drum drive motor gears 61 and 62 and the gear 44, and 1132 [ The peak of [Hz] is the drive sound of the paper feed stepping motor 83, the peak of 2292 [Hz] is the drive sound of the drum drive motors 41 and 42, and 2953 [Hz] is the drive sound of the polygon mirror motor.

  Describing the meshing sound between the drum drive motor gears 61 and 62 and the gear 44, the drum drive motor is 687.75 [rpm] as described above, and the number of teeth of the drum drive motor gears 61 and 62 is 35. The frequency of the meshing sound is (687.75 / 60) × 35 = 401 [Hz]. This meshing sound is also a pure tone component having a steep peak as shown in FIG. 9, but it is not a high frequency and is not particularly unpleasant for humans.

  The driving sound of the paper feed stepping motor 83 will be described. The paper feed stepping motor 83 only needs to satisfy the function of normally carrying the paper, and thus is composed of a two-phase excitation stepping motor. Since the input pulse is 1132 [pps], a sound having the frequency of the input pulse itself is generated as a driving sound. The driving sound of the paper feed stepping motor 83 has a high frequency of 1132 [Hz], and is a sound called a pure sound component having the highest sound pressure level as shown in FIG. Such a pure tone component has a high tonality value and can be heard by humans as an irritating sound.

  Explaining the drive sound of the drum drive motor, the drum drive motor is a two-phase stepping motor and rotates at 687.75 [rpm]. This drum drive motor is controlled to be driven by 2W1-2 phase excitation (1/8 division of two phase excitation) in order to rotate the photosensitive drum 28 with high definition. The input pulse is 18339.965 [pps], and the step angle of the 2W1-2 phase is 0.225 [°]. The number of revolutions of the drum drive motor is calculated from (input pulse × step angle × 60) / 360 [rpm]. Therefore, as described above, the driving sound of the drum driving motor is generated in the frequency region of 2292 [Hz], which is 1/8 the frequency of 18339.965 [pps]. As described above, the driving sound of the drum driving motor composed of the stepping motor is also a high-frequency sound of 2292 [Hz] and is a pure sound component sound having a steep peak as shown in FIG. Therefore, the driving sound of the drum driving motor is also heard by humans as an irritating sound.

  Explaining the drive sound of the polygon mirror motor 2, the wind noise of the polygon mirror is dominant in the drive sound. Since the polygon mirror motor 2 has six mirror surfaces and the motor rotation speed is 29530 [rpm], the polygon mirror motor 2 generates driving sound having a frequency of (29530/60) × 6 = 2953 [Hz]. This driving sound is also a high-frequency sound of 2953 [Hz] and is a pure sound component sound having a steep peak as shown in FIG. Therefore, the driving sound of the drum driving motor is also heard by humans as an irritating sound.

As described above, in the conventional printer used in this noise analysis, many noises of pure tone components were generated on the high frequency side of 1000 [Hz] or more, and even when actually heard, it felt uncomfortable. Using the sound quality analysis software ArtemiS described above, the sound pressure level and psychoacoustic parameters were calculated for the noise emitted from this conventional printer, and the results shown in Table 1 below were obtained. As psychoacoustic parameters, loudness, sharpness, tonality, and impulsiveness, which are highly correlated with actual discomfort, were used.

Next, a configuration for making it difficult for the user to hear high-frequency noise (high-frequency noise), which is a characteristic part of the present invention, is likely to be uncomfortable for the user.
Before describing the specific configuration, the principle of making it difficult for the user to hear high-frequency noise will be described. In the present embodiment, a so-called auditory masking effect is used to make it difficult for the user to hear high-frequency noise. As described above, the masking effect refers to a phenomenon in which if a certain mask sound is generated while a certain sound is generated, the certain sound becomes completely inaudible or difficult to hear due to the mask sound. In a broad sense, this includes a phenomenon that the volume of a certain sound is reduced. The masking effect also appears in a phenomenon in which, for example, when a train arrives at a subway platform, it becomes difficult to hear the voice of the other party who is talking at the platform. The train sound used as the mask sound in this case is a wide-band noise, but a masking effect can be obtained even when a pure tone component is used as the mask sound.

  Specifically, when two pure tone components with different frequencies are generated, the masking effect is high when low frequency sounds mask high frequency sounds, and high frequency sounds are low frequency sounds. The masking effect when masking is low. Further, as the sound pressure level of the sound on the masking side increases, the masking effect is enhanced and the frequency region to be masked is expanded. It is known that the excitability pattern of the nerve layer of the ear becomes such a state.

From the above, considering the FFT distribution shown in FIG. 9, in the conventional printer used in this noise analysis, the engagement sound (low frequency noise) between the drum drive motor gears 61 and 62 and the gear 44 is amplified. Is used as a masking sound to drive the sheet feeding stepping motor 83 (1132 [Hz]), the drum driving motors 41 and 42 (2292 [Hz]), and the polygon mirror motor driving sound (2953 [Hz]). ) And other high-frequency noise can be masked.
Furthermore, not only the masking effect but also actively reducing high frequency noise is effective in removing the user's discomfort.
Even if the engagement sound between the drum drive motor gears 61 and 62 and the gear 44 is amplified, the high-frequency noise is reduced as compared with that before the amplification. As a result, the sound pressure level and the sound power level after amplification in the entire printer are It is possible to suppress to approximately the same level or lower.

Next, a specific configuration for making it difficult for the user to hear high-frequency noise will be described.
FIG. 10 is a perspective view showing a drum drive mechanism including a color drum drive motor 41 and a black drum drive motor 42.
The color drum drive motor 41, the black drum drive motor 42, and the gears 43 and 44 are supported by a motor bracket 59, respectively. The motor bracket 59 is a member made of sheet metal with strength by drawing or the like. The motor bracket 59 is formed with a screw hole or the like to be attached to the printer casing by bending, and is fixed to the printer casing by the screw hole or the like. The motor bracket 59 rotatably supports four gears 44 corresponding to the respective photosensitive drums 28. Of these gears 44, the rightmost gear 44 in the drawing and the gear 61 attached to the motor shaft of the black drum drive motor 42 mesh with each other. As a result, the gear 44 is rotated by the black drum driving motor 42, and accordingly, the photosensitive drum 28 for black (Bk) is rotated. On the other hand, among the remaining three gears 44, the left and center two gears 44 in the figure are rotated by the motor shaft 62 of the color drum drive motor 41. On the other hand, among the remaining three gears 44, the right and center two gears 44 in the drawing mesh with the relay gear 43. As a result, the right gear 44 in the drawing rotates as the central gear 44 rotates. That is, with the rotation of the color drum drive motor 41, the remaining three gears 44 are rotated, whereby the C, M, and Y photoconductive drums 28 are simultaneously rotated.

The four gears 44 do not employ a special anti-vibration structure or the like for mounting the motor so that the distance between the shafts of the gears can be accurately adjusted to the design value by the module 0.5. That is, the black drum drive motor 42 and the color drum drive motor 41 are directly attached to the motor bracket 59 and fixed. By directly attaching the motors 41 and 42 to the motor bracket 59 in this way, the vibration of the motor when the motor is driven propagates to the motor bracket 59 in a solid state. The vibrations that are solid-propagated to the motor bracket 59 in this way are vibrations that include a lot of drive frequency components of the drum drive motor and meshing vibrations between the drum drive motor gears 61 and 62 and the drum gear 44. Here, the natural frequency of the motor bracket 59 is set to 401 Hz which is the same as the meshing sound between the drum drive motor gears 61 and 62 and the drum gear 44 or in the vicinity thereof. Therefore, it resonates with the meshing vibration between the drum drive motor gears 61 and 62 and the gear 44 that has propagated solidly to the motor bracket 59, and this is amplified and the meshing sound between the drum drive motor gears 61 and 62 and the gear 44 is generated from the motor bracket 59. Radiated. That is, in the present embodiment, the motor bracket 59 is a resonance member and functions as a low frequency amplification means.
When such resonance is generated, density unevenness or the like corresponding to the resonance frequency may appear in the image. However, human eyes can perceive as density unevenness up to a frequency of 200 to 300 [Hz] or lower, and density unevenness cannot be perceived at frequencies higher than that. Therefore, even if resonance of 401 [Hz] is generated as in the present embodiment, there is no problem because the density unevenness caused by this cannot be perceived by humans.

FIG. 11 is a schematic diagram showing a model for forcibly applying a cosine wave excitation force P cosωt to an object of mass m. In the model shown in the figure, the vibration is one axis in the vertical direction in the figure, and therefore the vibration is one degree of freedom. In this model, the amount of displacement of the object is x, the spring constant is k, the viscosity damping coefficient is C, the critical viscosity coefficient is C _C , the natural frequency is f ₀ , the natural angular frequency is ω ₀ , The damping ratio is ζ, and the static displacement is Xst.
In the above model, the following relational expression holds.
ω ₀ = (k / m) / 2
ζ = C / C _C
C _C = 2 × (m × k) / 2
Xst = P / k
From the above relational expression, the natural frequency f ₀ is ω ₀ / 2π and can be expressed as follows.
f ₀ = (1 / 2π) × (k / m) / 2
That is, the natural frequency f ₀ can be adjusted by changing the mass m. Therefore, in the present embodiment, the mass of the motor bracket 59 is adjusted so that the natural frequency of the motor bracket 59 is set to 401 [Hz], which is the same as the engagement sound between the drum drive motor gears 61 and 62 and the drum gear 44, or the vicinity thereof. To do.

FIG. 12 is an explanatory diagram showing the configuration of the motor bracket 59 in the present embodiment.
As a method of adjusting the mass of the motor bracket 59, the material of the motor bracket is replaced with a material having a different mass, the thickness t of the motor bracket itself is changed, or another member for adjusting the mass is fixed to the motor bracket. The method of doing is mentioned. In this embodiment, a method of fixing a member for mass adjustment to the motor bracket is adopted, and the natural frequency of the motor bracket 59 is set to 401 Hz or the vicinity thereof. Specifically, the damping member 63 is used as a member for adjusting the mass, and the mass of the motor bracket 59 is adjusted by attaching the damping member 63 to the motor bracket 59 with an adhesive or the like. If the damping member 63 is used as a member for mass adjustment in this way, not only can the natural frequency of the motor bracket 59 be set, but also the effect of suppressing vibrations that deviate from the natural frequency can be obtained. Can be actively reduced. As a result, the sound pressure level of high frequency noise unpleasant for the user can be reduced. Of course, even if the damping member 63 is not used as the mass adjusting member, the vibration in the high frequency region cannot be actively reduced, but the improvement by the masking effect can be achieved. The same applies to the case where the mass of the motor bracket 59 is adjusted by changing the material of the motor bracket 59 with a different mass or changing the thickness t of the motor bracket 59.

FIG. 13 is a graph showing the results of an experiment for confirming the vibration damping effect of the motor bracket 59 by the vibration damping member 63.
In this experiment, the mass is adjusted by the motor bracket of the comparative example whose natural frequency deviates from 401 [Hz] and the damping member 63, and the natural frequency is adjusted to be equal to or close to 401 [Hz]. Using the motor bracket of the experimental example, only the drum drive motors 41 and 42 were driven to compare the 1/3 octave analysis of the sound power level. In the frequency region of 400 [Hz] (portion surrounded by a broken line in the figure), the motor bracket of the experimental example has a higher acoustic power level than the motor bracket of the comparative example due to its resonance effect. On the other hand, in the high frequency region surrounded by the solid line, it was confirmed that the level was reduced particularly in the frequency of the driving sound of the drum drive motors 41 and 42 and in the higher frequency band due to the effect of the damping member 63. In the high frequency region that is not surrounded by the solid line, there is no difference in the sound power level between the comparative example and the experimental example. This is considered to be because the effect of the damping member 63 is effective for the solid propagation sound radiated from the motor bracket, but is not effective for the sound not passing through the motor bracket. .

  Incidentally, as described above, it is more effective to remove not only the masking effect but also the high-frequency noise to remove the user's discomfort. Therefore, hereinafter, the paper feed stepping motor 83 which is a source of high-frequency noise is described below. A configuration for reducing noise generated from the drum drive motors 41 and 42 and the polygon mirror motor will be described.

First, noise reduction of the paper feed stepping motor 83 will be described.
Figure 14 (a) to (e) are explanatory views for explaining movement of the rotor of the paper feed stepping motor 83 driven by the step angle theta _0.
FIG. 15 is a simple electric circuit diagram of the paper feed stepping motor 83.
The step angle of the paper feed stepping motor 83 is determined in terms of the mechanical structure, and normally the rotor moves by one step angle θ _{0 at a} time. Therefore, the larger the step angle θ ₀ , the less smooth the rotor movement, resulting in increased vibration and the like, and high-frequency noise becomes conspicuous. Therefore, in the present embodiment, so-called microstep driving is performed in which control is performed by an electric circuit as shown in FIG. 15 and driving is performed at a step angle smaller than the step angle θ ₀ determined by the mechanical structure. That is, by performing current supply control in which the current value supplied to one phase of the excitation phase is gradually increased while the current value supplied to the other one phase is gradually decreased, the current supply control in FIG. As shown in (e), driving at a step angle smaller than the step angle θ ₀ is possible, and the movement of the rotor is made smooth. Thereby, high-frequency noise generated from the paper feed stepping motor 83 can be reduced.

FIG. 16 is a sequence diagram when performing 1-2 phase excitation, which is one of microstep driving, in the electric circuit shown in FIG.
1-2 phase excitation is an excitation method that alternately repeats one phase excitation for exciting a coil one phase and two phase excitation for exciting a coil two phases. When a stepping motor is driven using this excitation method, The motor step angle is halved, and the movement of the rotor is smoother than normal driving, and vibration can be reduced.

Next, noise reduction of the polygon mirror motor 2 will be described.
FIG. 17 is an explanatory diagram showing a peripheral configuration of the polygon mirror motor 2 in the housing 11 of the optical unit 1.
The polygon mirror motor 2 is attached inside the housing 11 of the optical unit 1. The inside of the housing 11 has a substantially sealed structure in order to prevent foreign matter from entering. For this reason, the level of the sound pressure generated inside the housing 11 by the driving sound of the polygon mirror motor 2 is high, and noise leaks out to the outside. Therefore, in the present embodiment, a sound absorbing material 64 as a sound absorbing means is attached inside the housing 11. Specifically, a sound absorbing material 64 is attached to the upper part of the polygon mirror motor 2 in the housing 11.

  As the sound absorbing material 64, for example, Thinsulate (registered trademark) manufactured by Sumitomo 3M Co., Ltd., which has a high sound absorbing effect even if it is thin, can be used. The sound-absorbing material of the sound-absorbing material 64 is a non-woven fabric made of microfibers having a fiber diameter of 1 to 4 [μm] and short fibers having a fiber diameter of 20 to 30 [μm] made by a melt blown method, rather than felt or glass wool. It is a fine fiber. The vibration energy of the sound passing through the sound absorbing material 64 is efficiently absorbed by being converted into thermal energy through the pores partitioned by the microfibers. For this reason, even if the thickness of the sound absorbing material 64 is relatively thin, sufficient sound absorbing performance can be exhibited. Note that the sound absorbing material 64 has relatively low sound absorbing performance in a frequency region of less than 1000 [Hz].

  For the purpose of reducing the overall noise of the printer, it is desirable to provide a sound absorbing material similar to the sound absorbing material 64 in an empty space inside the printer. Specifically, for example, as shown in FIG. 18, a sound absorbing material 65 is attached inside the printer located below the paper discharge tray 510. Although not shown, noise of 1000 [Hz] or more generated from the drive system can be silenced by affixing a sound absorbing material in the vicinity of the drive system provided inside the printer on the back side of the printer. Since such a sound absorbing material is a non-woven fabric as described above, there are advantages that a slit is inserted and the slit portion can be easily hooked and fixed inside the printer, and that it is convenient for recycling.

FIG. 19 is a graph showing the result of FFT analysis of the sound pressure level measured under the same conditions as in the case of the noise analysis for the printer in this embodiment.
That is, this result amplifies (emphasizes) the meshing sound between the drum drive motor gears 61 and 62 and the gear 44 as described above, and the drive sound (1132 [Hz]) of the paper feed stepping motor 83, the drum drive motor. The above-mentioned noise reduction measures are taken for the drive sound of 41 and 42 (2292 [Hz]) and the drive sound of the polygon mirror motor 2 (2953 [Hz]), and a sound-absorbing material is provided in the empty space inside the printer. This is when noise reduction measures are taken. As shown in the figure, the engagement sound (401 [Hz]) between the drum drive motor gears 61 and 62 and the gear 44 has the highest sound pressure level in the frequency distribution of noise generated by the printer, and the noise in the high frequency range. A masking effect can be obtained.

FIG. 20 is a graph showing the results of comparative analysis in which the results shown in FIG. 9 and the results shown in FIG. 19 are changed to 1/3 octave analysis.
As shown in the figure, since the meshing sound (401 [Hz]) between the drum drive motor gears 61 and 62 and the gear 44 is amplified and the sound pressure level is increased, the noise in the high frequency region can be reduced by the masking effect. I understand that. Furthermore, it was also confirmed that the noise reduction effect by the sound absorbing materials 64 and 65 appears greatly for noise in a frequency region exceeding 4000 [Hz].

Table 2 below shows the results of comparison between this printer and the above-described conventional printer regarding the sound pressure level and psychoacoustic parameters.

  According to Table 2 above, in the printer of this embodiment, the sound pressure level is lowered, and the psychoacoustic parameter values for loudness (aural level), sharpness (high frequency component), and tonality (pure sound component) are also lowered. Therefore, user discomfort can be reduced. The value of the psychoacoustic parameter regarding impulsiveness (impact) is increasing. This is because the high-frequency noise becomes difficult to hear in the printer of this embodiment, and the impact sound is conspicuous. It is thought that it was because it came to be heard. Therefore, it can be said that it is more preferable to improve a noise source having high impulsiveness (impactability).

As described above, the printer of this embodiment includes image forming means for forming an image on a sheet of recording material based on image information, and the image forming means is a low-frequency component that generates low-frequency noise. The drum driving motor gears 61 and 62 and the gear 44, and a paper feeding stepping motor 83, drum driving motors 41 and 42, and a polygon mirror motor 2, which are high-frequency components that generate high-frequency noise. The drum driving motor gears 61 and 62 and the gear 44 have a motor bracket 59 as a low frequency amplifying means for amplifying a meshing sound which is a low frequency noise generated by the gear 44. Thereby, the high frequency noise generated by the paper feed stepping motor 83, the drum drive motors 41 and 42, and the polygon mirror motor 2 can be made difficult to hear due to the masking effect due to the amplified meshing sound. Moreover, in this printer, the meshing sound of the drum drive motor gears 61 and 62 and the gear 44 constituting the image forming means is used as the masking sound for obtaining this masking effect, so that the masking sound is generated in addition to the image forming means. Therefore, it is not necessary to provide a separate mechanism, and space saving and cost reduction can be realized.
In the present embodiment, the drum drive motor gears 61 and 62 and the gear 44 (low-frequency component) generate low-frequency noise in a frequency region of 300 [Hz] or more and 800 [Hz] or less. A high frequency component such as the motor 83 generates high frequency noise in a frequency region of 1000 [Hz] or higher. As described above, high-frequency noise having a noise frequency of 1000 [Hz] or higher sounds like a particularly unpleasant sound for humans. Therefore, according to this printer, it is possible to effectively make it difficult to hear sounds unpleasant for humans.
Further, in the present embodiment, the motor bracket 59 amplifies the engagement sound of the drum drive motor gears 61 and 62 and the gear 44 so that the level is higher than the high frequency noise generated by the high frequency component such as the paper feed stepping motor 83. Let Thereby, the masking effect by this meshing sound can be acquired effectively.
In the present embodiment, the motor bracket 59 used as the low-frequency amplification means has a natural frequency that matches or approximates the frequency (401 [Hz]) of the meshing sound of the drum drive motor gears 61 and 62 and the gear 44. It is a member. Thereby, the said engagement sound can be amplified with a simple structure.
In particular, as in this embodiment, the motor bracket 59 used as the resonance member is a component that constitutes the image forming means, and the mass adjustment member 63 of the component is fixed. Even if the motor bracket 59 does not have a natural frequency that matches or approximates the frequency of the meshing sound (401 [Hz]), the motor bracket 59 can be used as the resonance member. In addition, in this embodiment, the damping member 63 that suppresses the vibration that causes generation of high-frequency noise of 1000 [Hz] or more among the vibrations generated in the motor bracket 59 is used as the mass adjusting member. The vibration member 63 can make the natural frequency of the motor bracket 59 match or approximate the frequency of the meshing sound (401 [Hz]), and can also actively reduce high-frequency noise.
In the present embodiment, the drum drive motor gears 61 and 62 and the gear 44 (low-frequency component) that generate low-frequency noise used as the mask sound are components constituting the drive device, and the motor bracket used as the resonance member. A support member 59 supports the drum drive motor gears 61 and 62 and the gear 44. As a result, the engagement sound (low frequency noise) generated by the drum drive motor gears 61 and 62 and the gear 44 has a relatively high sound pressure level among the low frequency noises generated in the printer. By using it as a mask sound, a high masking effect with high frequency noise can be effectively obtained. In addition, the use of the motor bracket 59 that supports the drum drive motor gears 61 and 62 and the gear 44 as a resonance member effectively amplifies the meshing sound (low frequency noise) generated by the drum drive motor gears 61 and 62 and the gear 44. Can be made.
Further, in this embodiment, since the sound absorbing materials 64 and 65 are provided as sound absorbing means for absorbing at least the high frequency noise, the noise of the entire printer, particularly high frequency noise that is particularly uncomfortable for humans, is actively reduced. The noise of the printer can be reduced.

In this embodiment, the case where the drum drive motor gears 61 and 62 and the gear 44 constituting the drive device are low-frequency components has been described. However, other components that generate the same low-frequency noise may be used. Good.
Further, in the present embodiment, the case where the motor bracket 59 is used as the low frequency amplifying means has been described as an example, but other members may be used as long as the low frequency noise generated by the low frequency component can be amplified. There may be.

FIG. 3 is an explanatory diagram illustrating a schematic configuration of the entire printer according to the embodiment. FIG. 3 is an explanatory diagram illustrating a configuration of an optical unit of the printer. FIG. 3 is an explanatory diagram illustrating a peripheral configuration of a photoconductor unit of the printer. Explanatory drawing of the drive mechanism of the photoconductor unit. FIG. 2 is a perspective view showing an internal structure of a fixing unit of the printer. FIG. 3 is an enlarged view of an oil application unit provided in the fixing unit. FIG. 3 is an explanatory diagram illustrating a configuration of a paper feeding unit of the printer. FIG. 4 is an explanatory diagram illustrating a drive system of a first paper feed unit and a second paper feed unit that send out paper from a first tray and a second tray in the paper feed unit. The graph which shows the result of having carried out the FFT analysis of the sound pressure level of the noise which the conventional printer generate | occur | produced measured in the noise analysis which the present inventors performed. FIG. 3 is a perspective view showing a drum drive mechanism including a color drum drive motor and a black drum drive motor in the photoreceptor unit. The schematic diagram which shows a model when giving the excitation force Pcos (omega) t of a cosine wave compulsorily with respect to the object of mass m. Explanatory drawing which shows the structure of the motor bracket of the photoconductor unit. The graph which shows the experimental result when the natural frequency of the motor bracket is set to 401 [Hz] or the vicinity thereof. (A) thru | or (e) is explanatory drawing for demonstrating the motion of the rotor of the paper feed stepping motor driven by step angle (theta) ₀ . A simple electric circuit diagram of the paper feeding stepping motor. The sequence diagram when performing 1-2 phase excitation which is one of the micro step drive in the electric circuit shown in FIG. Explanatory drawing which shows the periphery structure of the polygon mirror motor in the housing of the optical unit. FIG. 3 is an explanatory diagram illustrating an example in which a sound absorbing material is attached to the inside of a printer located below a paper discharge tray. The graph which shows the result of having carried out FFT analysis of the sound pressure level measured on the same conditions as the case of the said noise analysis about the printer. The graph which shows the result of having changed the result shown in FIG. 9, and the result shown in FIG. 19 into the 1/3 octave analysis, and performing the comparative analysis.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Optical unit 2 Polygon mirror motor 3 Photosensitive unit 41,42 Drum drive motor 44 Drum gear 59 Motor bracket 61,62 Drum drive motor gear 63 Damping member 64,65 Sound absorbing material 83 Paper feed stepping motor 110 Paper feed part 510 Paper discharge tray

Claims (8)

An image forming unit for forming an image on a recording material based on image information is provided, and the image forming unit includes a low-frequency component that generates low-frequency noise and a high-frequency component that generates high-frequency noise. In the image forming apparatus
An image forming apparatus comprising low frequency amplification means for amplifying low frequency noise generated by the low frequency component. The image forming apparatus according to claim 1.
The low-frequency component article generates low-frequency noise in a frequency range of 300 [Hz] to 800 [Hz],
The image forming apparatus according to claim 1, wherein the high-frequency component article generates high-frequency noise in a frequency region of 1000 [Hz] or higher. The image forming apparatus according to claim 1 or 2,
The image forming apparatus characterized in that the low frequency amplification means amplifies the low frequency noise so that the level is higher than the high frequency noise generated by the high frequency component. The image forming apparatus according to claim 1, 2 or 3.
The image forming apparatus according to claim 1, wherein the low frequency amplification means is a resonance member having a natural frequency that matches or approximates a frequency of low frequency noise generated by the low frequency component. The image forming apparatus according to claim 4.
The resonance member is an image forming apparatus in which a member for adjusting the mass of the constituent article is fixed to the constituent article constituting the image forming means. The image forming apparatus according to claim 5.
2. The image forming apparatus according to claim 1, wherein the mass adjusting member is a damping member that suppresses vibration that causes generation of the high-frequency noise among vibrations generated in the component. The image forming apparatus according to claim 4, 5 or 6.
The low-frequency component is a component of a driving device,
The image forming apparatus, wherein the resonance member is a support member that supports the constituent article. The image forming apparatus according to claim 1, 2, 3, 4, 5, 6 or 7.
An image forming apparatus comprising sound absorbing means for absorbing at least the high frequency noise.

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