JP2002257621A - Image forming apparatus and method of evaluating sound quality of image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming apparatus capable of alleviating a mentally uncomfortable sound by improving a charging sound in the image forming apparatus that is operated at a relatively low speed. SOLUTION: The sound being generated when an image holding body is charged is reduced so that a discomfort index S being obtained from a sound quality evaluating equation, i.e., S=0.3135×(loudness value)+3.4824×(tonality value)-31460, which employs a loudness value and a tonality value of the mental acoustic parameter extracted from the sound of the image forming apparatus at the position 1±0.03 m apart from the edge of the image forming apparatus, satisfies the following: S<-0.5.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for evaluating sound quality of an image forming apparatus and an image forming apparatus.
The present invention relates to a method for improving discomfort noise in an image forming apparatus such as an electronic copying machine or a laser beam printer that generates noise such as motor driving noise, clutch and solenoid operation noise, charging noise, and paper conveyance noise during operation. It relates to generally applicable technologies.

[0002]

2. Description of the Related Art In recent years, there has been an increasing interest in noise problems from the viewpoint of environmental friendliness, and there are many demands for office office equipment to solve noise problems. For this reason, the OA equipment has been reduced in noise, and has been more silent than before.

As a technique for solving the above-mentioned noise problem, for example, there is a technique disclosed in Japanese Patent Application Laid-Open No. 9-193506. In the same publication, in a noise masking device such as a laser beam printer or a copying machine, a sounding body that generates a masking sound for masking this noise with respect to a driving mechanism that is a source of noise during operation, and a sounding body that is controlled. And a masking sound control unit for generating a masking sound having a frequency in a range including the main component frequency of the noise to reduce discomfort of the noise.

[0004] However, Japanese Patent Application Laid-Open No.
According to the technology disclosed in Japanese Patent Application Laid-Open No. 6-260, a masking sound is further added to the generated sound without reducing the sound generated from the main body, and the noise level increases. The disadvantage is that you may feel it. Further, since a sounding body for generating a masking sound and a control device for generating a masking sound only during a generation time of a sound to be masked are required, an extra space is required on a machine layout, and However, there is a disadvantage that the cost is greatly increased.

At present, OA equipment generally uses a sound power level (ISO777) as a method for evaluating noise.
9) is used. However, since the sound power level is a value of sound energy generated from office equipment such as a copying machine or a printer, there is a case where a correlation between the sound power level and a subjective discomfort of a human to noise is not so good.
For example, when listening to sounds with the same sound power level, there may be differences in discomfort, and even if the sound power level is low, it can be heard by a person as a very unpleasant sound There is also.

Therefore, in order to improve the office environment in the future, it is necessary not only to reduce the sound power level of the OA equipment but also to improve the sound quality. To improve sound quality, quantitative measurement of sound quality to understand the current situation,
It is necessary to measure how much improvement has been made before and after the improvement. However, since sound quality is not a physical quantity, it cannot be measured quantitatively. That is, even when compared by listening to the ear, the evaluation may differ from person to person. In addition, "the sound quality is a little improvement" and can not be only a qualitative representation such as "has been considerably improved." If the sound quality cannot be quantitatively represented by physical characteristics, it is impossible to objectively evaluate the effect even if measures are taken to improve the sound quality.

By the way, as a physical quantity for evaluating the sound quality,
There is a psychoacoustic parameter. Representative examples are as follows (for example, "The 7th Design Engineering and System Division Lecture" Aiming for innovative leap in design and systems for the 21st century! ", November 10, 1997, Japan Society of Mechanical Engineers)
See “Sound / Vibration and Design, Color and Design (1)”, Section 089B Units in parentheses are units. ). -Loudness (sone): size of hearing-Sharpness (acum): relative distribution of high-frequency components-Tonality (tu): content of tonality and pure tone components-Roughness (asper): sound roughness Fracture strength (vacil): Fluctuation strength, beat

The psychoacoustic parameters tend to increase discomfort as the value of any of the psychoacoustic parameters increases. Among them, only the loudness is standardized by ISO532B. The basic concept of other psychoacoustic parameters is the same, but since the programs and calculation methods differ depending on the original research of each measuring instrument manufacturer, the measured values usually differ slightly depending on the manufacturer. Efforts to reduce all of these psychoacoustic parameters can improve sound quality.

[0009]

However, a great deal of labor is required to take measures for all psychoacoustic parameters. Noise generated from OA equipment such as copiers and printers is composed of noises of many timbres due to the complexity of the mechanism. For example, low-frequency heavy noise, high-frequency high-pitched sound, and shock are generated. Sound or the like is generated from a plurality of sound sources such as a motor, paper, and a solenoid while changing over time.

Humans judge these sounds comprehensively and judge whether or not they are unpleasant. However, it is considered that the judgment is made by weighting which parts are particularly related to unpleasantness. . That is, there are psychoacoustic parameters that have a large effect on discomfort and psychoacoustic parameters that have a small effect on discomfort. And this depends on the tone of the machine. For example, a high-speed printer that generates a large number of impact sounds feels the most unpleasant impact noise, and a desktop printer that is relatively slow and relatively quiet generates less impact noise, so the charging noise generated during AC charging is most unpleasant. May be felt. Thus, the part that is unpleasant is different. Therefore, the part for improving the sound quality may be different between the low-speed machine and the high-speed machine. Accordingly, if a psychoacoustic parameter having a large improvement effect on discomfort is searched for and the psychoacoustic parameter is improved to improve sound quality efficiently, the labor is reduced.

Therefore, a psycho-acoustic parameter having a great improvement effect on discomfort is combined, a psycho-acoustic parameter is weighted to calculate a sound quality evaluation formula, and a subjective evaluation value for discomfort is calculated using the sound quality evaluation formula. This makes it possible to objectively evaluate the sound quality and improve the sound quality. Further, by determining the subjective evaluation value for discomfort to determine how much the discomfort will be eliminated, and providing an image forming apparatus with improved sound quality that is equal to or less than the value, the problem regarding noise in the office can be solved. Can be solved.

A first object of the present invention is made in view of the above, and calculates a sound quality evaluation formula using a psychoacoustic parameter having a large improvement effect on discomfort sound of an image forming apparatus, and It is an object of the present invention to provide a sound quality evaluation method for an image forming apparatus, which makes it possible to easily perform a measure for improving the sound quality of the image forming apparatus by enabling an effective evaluation of the sound quality.

A second object of the present invention has been made in view of the above, and in an image forming apparatus operating at a relatively low speed, sound quality evaluation using a psychoacoustic parameter having a large improvement effect on unpleasant sound. An object of the present invention is to provide an image forming apparatus that calculates an equation and uses the sound quality evaluation equation to alleviate discomfort.

A third object of the present invention has been made in view of the above, and in an image forming apparatus which operates at a relatively low speed, an image forming apparatus in which discomfort is reduced by improving charging noise. To provide.

[0015]

In order to achieve the first object, according to the first aspect of the present invention, a step of collecting a sound emitted from an image forming apparatus at a position at a predetermined distance from the image forming apparatus. Measuring a psychoacoustic parameter of the collected sound, performing a subjective evaluation of the collected sound to calculate a subjective evaluation value, and performing a multiple regression analysis of the measured psychoacoustic parameter and the subjective evaluation value Calculating a sound quality evaluation formula for estimating a subjective evaluation value using the psychoacoustic parameter based on the result of the multiple regression analysis; and forming an image of the subjective evaluation value estimated by the sound quality evaluation formula. Calculating an appropriate range for the device;
It is characterized by including.

According to the above invention, a sound emitted from the image forming apparatus is sampled at a position away from the image forming apparatus by a predetermined distance, and psychoacoustic parameters of the collected sound are measured and subjectively evaluated to perform a subjective evaluation value. Is calculated, and the measured psychoacoustic parameter and the subjective evaluation value are subjected to multiple regression analysis, and a sound quality evaluation formula for estimating the subjective evaluation value using the psychoacoustic parameter is calculated based on the result of the multiple regression analysis. Further, by calculating an appropriate range of the subjective evaluation value estimated by the sound quality evaluation formula in the image forming apparatus, a sound quality evaluation formula using a psychoacoustic parameter having a large improvement effect on the unpleasant sound of the image forming apparatus is calculated. The sound quality evaluation formula is used to objectively evaluate the sound quality, and furthermore, presents an appropriate range in the image forming apparatus.

Further, in order to achieve the second object,
According to a second aspect of the present invention, the following sound quality evaluation formula (a) using a loudness value and a tonality value of a psychoacoustic parameter obtained from a sound of the image forming apparatus at a predetermined distance from an end face of the image forming apparatus: S = A × (Loudness value) + B × (Tonality value) + C (a) where the coefficients A, B and C are 0.247 ≦ A ≦ 0.38
0 2.075 ≦ B ≦ 4.890 −3.649 ≦ C ≦ −2.643 The discomfort index S is characterized by satisfying S <−0.5.

According to the invention, the discomfort index S calculated by the sound quality evaluation formula (a) using the loudness value and the tonality value of the psychoacoustic parameter is S <-.
By providing an image forming apparatus satisfying the condition of 0.5, discomfort is reduced in an image forming apparatus that operates at a relatively low speed.

The invention according to claim 3 is based on claim 2.
, The coefficient A = 0.3135, the coefficient B = 3.4824, and the coefficient C = -3.1.
460.

The invention according to claim 4 is based on claim 2.
Alternatively, in the invention according to claim 3, a psychoacoustic parameter obtained from a sound of the image forming apparatus at a position away from an end face of the image forming apparatus by a predetermined distance is a sharpness value ≦ 270 acum, a roughness value ≦ 1.24 asp.
er, and fraction strength value ≤
It satisfies the condition of 1.31 vacil.

The invention according to claim 5 is the same as the claim 2.
In the invention according to any one of the first to fourth aspects, the predetermined distance is 1.00 ± 0.03 m.

Further, in order to achieve the third object, the invention according to claim 6 is directed to any one of claims 2 to 5
According to another aspect of the present invention, at least an image carrier for forming an image and charging means for applying an AC bias to the image carrier to perform charging are provided, and the frequency f of the AC bias is 200 Hz <f. Is satisfied.

According to the present invention, by setting the frequency f of the AC bias of the charging means to be 200 Hz <f, the discomfort of noise caused by the AC bias is reduced.

The invention according to claim 7 is the invention according to claim 6.
In the invention according to the first aspect, there is provided a charging noise reduction unit for reducing a charging noise when the image carrier is charged by the charging unit.

According to the present invention, the charging noise when the charging means charges the image carrier is reduced by the charging noise reducing means.

The invention according to claim 8 is the invention according to claim 7.
In the invention according to the invention, the charging noise reducing unit is configured to set a natural frequency of the image carrier to a frequency different from a frequency obtained by multiplying a frequency f of the AC bias by a natural number.
It is a frequency changing member provided on the image carrier.

According to the invention, the frequency changing member sets the natural frequency of the image carrier to a frequency different from the frequency obtained by multiplying the frequency f of the AC bias by a natural number.

The invention according to claim 9 is the invention according to claim 8
In the invention according to the invention, the frequency changing member may be a member having high rigidity for preventing vibration of the image carrier, a sound absorbing member for sucking sound of the image carrier, or vibration of the image carrier. Characterized in that it is a vibration damping member for preventing

According to the invention, a member having high rigidity for preventing vibration of the image carrier, a sound absorbing member for sucking sound of the image carrier, or a member for preventing vibration of the image carrier is provided. The natural frequency of the image carrier is set to a frequency different from the frequency obtained by multiplying the natural frequency of the frequency f of the AC bias by the vibration damping member.

According to a tenth aspect of the present invention, in the invention according to any one of the second to fifth aspects, at least an image carrier for forming an image and a voltage applied to the image carrier. Charging means for applying and charging,
The charging unit charges the image carrier with a DC bias.

According to the present invention, the charging means charges the image carrier with a DC bias, thereby reducing charging noise when the charging means charges the image carrier.

[0032]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of an image forming apparatus and a sound quality evaluation method for the image forming apparatus according to the present invention will be described below with reference to the accompanying drawings.
(Derivation of the sound quality evaluation formula of the image forming apparatus) and (measures for reducing the unpleasant sound of the image forming apparatus) will be described in detail in this order.

(Structure of Image Forming Apparatus) FIG. 1 is a structural view of a main part for explaining an example of an image forming apparatus according to the present invention. In the image forming apparatus shown in FIG. 1, 1 is a photosensitive drum as an image carrier, 2 is a transfer roller for transferring a toner image formed on the photosensitive drum 1 to paper, and 3 is a photosensitive roller on the photosensitive drum 1. Process cartridge for forming a toner image on the main body, 4 is a main body tray, 5 is a bank paper feed tray,
Reference numeral 6 denotes a manual feed tray, 7 denotes a fixing unit, 8 denotes a writing unit for writing an image on the photosensitive drum 1, 9 denotes a paper discharge tray, 10 denotes a paper feed roller, and 11 denotes a registration roller.

In the image forming apparatus shown in FIG. 1, a paper feed system such as a main body tray 4, a bank paper feed tray 5, a manual feed tray 6, a paper feed roller 10, and a registration roller 11 is provided. Is transported from the paper feed and transport system to the paper discharge tray 9 via the process cartridge 3, the fixing unit 7 and the paper discharge rollers 12.

Above the process cartridge 3, an image writing unit 8 including an LD unit, a polygon mirror, an fθ mirror (not shown) and the like is provided. In addition, a drive transmission system including the photosensitive drum 1, a drive motor for rotating the rollers, a solenoid, and a clutch (not shown) is provided. In the image forming apparatus having such a configuration, at the time of image formation, the drive sound of the drive motor and the drive transmission system, the operation sound of the solenoid / clutch, the paper conveyance sound, the charging sound and the like are emitted.

FIG. 2 is a sectional view of an essential part for explaining an example of the process cartridge 3 shown in FIG. In the process cartridge 3 shown in FIG. 1, 21 is a charging roller as charging means, 22 is a developing roller as developing means, 23 is a cleaning blade as cleaning means, 24 is toner, 25 is an agitator, and 26 is a stirring shaft. , 27 indicate developing blades.

Around the photosensitive drum 1 as an image carrier, a charging roller 21 as charging means, a developing roller 22 as developing means, and a cleaning blade 23 as cleaning means are arranged. Then, the toner 24 in the process cartridge 3 is stirred by the agitator 25 and the stirring shaft 26 and transported to the developing roller 22. Toner 24 attached to developing roller 22 by magnetic force
When passing through the developing blade 27, it is negatively charged by frictional charging. The negatively charged toner moves to the photosensitive drum 1 by the bias voltage and adheres to the electrostatic latent image.

When the transfer paper passing through the registration roller 11 passes between the photosensitive drum 1 and the transfer roller 2, the toner on the photosensitive drum 1 is transferred to the transfer paper by the positive charge from the transfer roller 2. The toner remaining on the photosensitive drum 1 is scraped off by the cleaning blade 23, and is collected as waste toner in a tank above the cleaning blade 23. The components other than the transfer roller 2 are integrated as a process cartridge 3 so that the user can easily replace it.

FIG. 3 shows the charging roller 21 shown in FIG.
It is a principal part perspective view for demonstrating an example. As shown in FIGS. 2 and 3, the charging roller 21 is
Is a charging member that uniformly rotates the outer surface of the photosensitive drum 1 by primary rotation while being driven by frictional force while constantly contacting the surface of the photosensitive drum 1. As shown in FIG. 2, the charging roller 21 includes a core part 21a of a rotating shaft and a charging part 21b formed concentrically around the core part 21a.

In charging operation, the charging roller 21 is supplied with a DC voltage to an AC voltage from a high-voltage power supply to a core 21 a of the charging roller 21 via an electrode terminal 31, a charging roller pressing spring 32, and a conductive bearing 33. Is applied, and the charging roller 21 uniformly charges the photosensitive drum 1 to the same voltage as the DC component of the bias voltage. The AC component of the bias voltage causes the photosensitive drum 1 to
The charging roller 21 functions to uniformly and uniformly charge.

Here, the appropriate value of the frequency of the AC component that does not cause unevenness in the image will be described. Generally, as the number of prints per minute (hereinafter referred to as ppm) increases, the frequency of the AC component also needs to increase. Specifically, when the number of copies per minute is 16 ppm or more, the appropriate value of the frequency of the AC component is 1000 Hz.
The above is desirable. However, it is not necessary to set such a high frequency for a machine having a smaller ppm.

When the photosensitive drum 1 is contact-charged by the charging roller 21, in general, an attractive force and a repulsive force alternate between the surface of the charging roller 21 and the surface of the photosensitive drum 1 due to the AC component of the bias voltage. This causes the charging roller 21 to vibrate. This vibration of the charging roller 21 causes the charging roller 21 itself to generate an unpleasant vibration sound (charging sound) having a high frequency, and is also transmitted to the photosensitive drum 1 side to vibrate the photosensitive drum 1 to generate noise. Let it.

Generally, the charging noise is composed of the frequency of an AC component and a harmonic that is an integral multiple of the frequency. When the fundamental frequency of the AC component is 1000 Hz, charging noise often occurs as a second harmonic 2000 Hz, a third harmonic 3000 Hz..., But the higher the order, the lower the sound pressure level may be. Many. By the way, when a vibration is generated from the image forming apparatus, a frequency of less than 200 Hz appears as banding in an image, and a frequency of 200 Hz or more is often heard as sound. Perceptually, a sound having a frequency of less than 200 Hz does not cause much problem because the sensitivity of the ear is deteriorated. Therefore, regarding the charging noise, a case where the AC component at the time of charging is 200 Hz or more may be considered.

(Derivation of Expression for Evaluating Sound Quality of Image Forming Apparatus) The inventor of the present invention performs sound weighting by combining psychoacoustic parameters having a large improvement effect on the unpleasant sound of the relatively low-speed image forming apparatus. The sound quality evaluation formula for estimating the subjective evaluation value of, that is, the objective sound quality evaluation formula was successfully derived. Furthermore, the inventor of the present application has succeeded in proposing a condition that does not cause discomfort in the derived sound quality evaluation formula. Hereinafter, the derivation of the sound quality evaluation formula of the image forming apparatus and the conditions under which the user does not feel uncomfortable will be described.

FIG. 4 is a graph for explaining an example of a frequency analysis result of noise of the image forming apparatus. In the figure, the horizontal axis indicates frequency (Hz), and the vertical axis indicates sound pressure level dB. Since the main purpose of the graph shown in this figure is to examine the frequency distribution, the relative comparison of the sound pressure level at each frequency is meaningful, but the absolute value of the sound pressure level is accurately calibrated. There is not much meaning because there is no. In the figure, the steep peaks at 1 kHz and 2 kHz are called charging noise as described above.

Further, as shown in the figure, the charged sound has a sound pressure level higher by 10 dB or more than other surrounding frequencies.
Although seen as a whole from a small energy standpoint, such high-level pure tone components are clearly masked as unpleasant sounds without being masked by other sounds.

Incidentally, when objectively evaluating the degree of discomfort of mechanical sound, a criterion for measuring discomfort is required.
When evaluating the energy of sound, as in the case of measuring with a sound level meter, when evaluating discomfort, measure the physical quantity of the sound and substitute the value into the sound quality evaluation formula to evaluate the value. Need to do.

The inventor of the present application conducted a subjective evaluation experiment by a human, and made a sound quality evaluation formula for predicting discomfort of sound by performing a statistical analysis of these using a plurality of psychoacoustic parameters. This sound quality evaluation formula needs to be statistically significant at least 95%. As the psychoacoustic parameters, the above-mentioned loudness, tonality, sharpness, roughness, fracturing strength, and the like were used.

An example of the sound quality evaluation test of the unpleasant sound by the present inventors will be described. The sound quality evaluation test of the unpleasant sound was performed in the following procedure. (1) Sampling of the operation sound of the image forming apparatus (2) Processing of the operation sound (creating a plurality of processing sounds (test sounds)) (3) Measurement of psychoacoustic parameters of the created test sounds (4) Test sounds Paired comparison experiment by → → calculation of subjective evaluation value for discomfort (5) Multiple regression analysis using subjective evaluation value and psychoacoustic parameter measurement value for discomfort パ ラ メ ー タ Derivation of sound quality evaluation formula

Hereinafter, each step will be described specifically. (1) Collection of operation sound of image forming apparatus In order to collect operation sound, image forming apparatus A (20 pp)
m), machine B (16 ppm), and machine C (16 ppm). The operating sounds on the front of these three different models were measured under the following measurement conditions under the head acoustics dummy head HMS (Head Measurement).
ent System) and recorded on digital audio tape (DAT) in binaural (binaural) sense. When recording is performed in this manner, the sound can be reproduced as if the human had actually heard the sound of the machine by reproducing the sound through dedicated headphones.

[Measurement conditions] Recording environment: semi-anechoic room (using standard stand) Ear position of dummy head: height 1.2 m, horizontal distance 1 m from device end face Recording mode: FF (free field) → Anechoic room) ・ HP filter: 22Hz

(2) Processing of operation sound (preparation of a plurality of processing sounds (test sounds)) The operation sound of Aircraft A is converted to an acoustic analysis device BAS (Binaural Analysis Sy) manufactured by Head Acoustic.
(stem). As a method of processing the operating sound, remove the part related to each sound source of the image forming apparatus on the frequency axis or time axis from the recorded operating sound, or use a method that emphasizes the sound pressure level. Sounds 1-9 were created. Note that the test sound 1 is the original sound of the aircraft A.

(3) Measurement of psychoacoustic parameters of created test sound The sound (9 sounds) obtained by processing the operation sound of Aircraft A and the operation sound of Aircraft B and C were used as the test sound, manufactured by Head Acoustic Co., Ltd. The values of the psychoacoustic parameters were measured by the acoustic analyzer BAS. Table 1 shows the measurement results of the test sounds and the psychoacoustic parameters.

(4) Pair of Scheffe's paired comparison method (Ura's modified method) using test sounds → Subjective evaluation value calculation for discomfort Subjects who are evaluated for the test sounds are collected, and the test sounds are compared in a pair to find which one. They were asked if they were uncomfortable. Ura's variant is a pairwise comparison as follows. Considering the comparison order, one subject compares all combinations one by one. Specifically, two combinations are made from each of the t materials, and N subjects make the combinations (i, j) and (j,
i) are all compared. As a result, the subjective evaluation value of each test sound is obtained and ranked. For example, when the test sound 1 and the test sound 2 are compared (with reference to the test sound 1), the subjective evaluation value of the test sound 1 is 1 point when the test sound 1 is unpleasant. If sound 2 was unpleasant, it was calculated as -1 point.
The results were tabulated and subjected to statistical processing to obtain a subjective evaluation value α (−1 ≦ α ≦ 1) of each test sound. The greater the subjective evaluation value α, the more unpleasant. Table 1 below shows the subjective evaluation value α of each test sound.
Shown in Table 1 below shows the measurement results of the subjective evaluation value α and the psychoacoustic parameters of each test sound.

[0055]

[Table 1]

Incidentally, among the psychoacoustic parameters, only the loudness is standardized by ISO532B. The basic concept of other psychoacoustic parameters is the same, but since the programs and calculation methods differ depending on the original research of each measuring instrument manufacturer, the measured values usually differ slightly depending on the manufacturer. In this experiment, in particular, a dummy head HMSIII manufactured by HEAD acoustics and an acoustic analyzer BAS manufactured by HEAD acoustics were used.
The experiment was performed using.

(5) Multiple Regression Analysis Based on Subjective Evaluation Values for Discomfort and Measured Values of Psychoacoustic Parameters By the way, in order to accurately measure the subjective evaluation values (objective variables), a plurality of psychoacoustic parameters (a group of explanatory variables) must be measured. It is effective to use multiple regression analysis. In simple regression analysis, the objective variable is predicted by a single explanatory variable, so the accuracy may be poor with a single explanatory variable.Multiple regression analysis that predicts the objective variable by combining multiple explanatory variables It is valid.

That is, the multiple regression analysis is a method of calculating a prediction formula with as few explanatory variables as possible and with high accuracy by using the addition relation (linear combination) of the explanatory variables. The reason for using as few explanatory variables as possible is to minimize the measurement of psychoacoustic parameter values, and to calculate meaningless psychoacoustic parameters that are not related to subjective evaluation values (discomfort). Is unreasonable.

The actual multiple regression analysis can be performed using commercially available spreadsheet software or statistical analysis software. For example, regression analysis using an analysis tool of spreadsheet software "Excel (registered trademark of Microsoft Corporation)" or statistical analysis software "JMP (registered trademark of SAS Institute Inc.)" or "SPSS (registered trademark of SPSS Inc.)" can do. The data of Table 1 above (measurement results of the subjective evaluation value α and the psychoacoustic parameter)
By inputting to "Excel" or "JMP" and performing analysis while selecting an explanatory variable, statistical results such as regression coefficients, P values of the selected explanatory coefficients, and contribution rates of equations are output. . Here, the P value is the probability of a significant difference test, and it is determined that it is significant at 5% or less and not significant at 5% or more (irrelevant).

First, a simple regression analysis is performed beforehand on the subjective evaluation value (discomfort) α and the group of psychoacoustic parameters to find out which psychoacoustic parameter has a large relationship with the subjective evaluation value α. Variables for regression analysis are easier to select. As a result of the variable selection, it was found that the subjective evaluation α can be accurately predicted when the loudness (hearing level) and the tonality (the content of the pure tone component) are selected. Other psychoacoustic parameters were found to be meaningless (not significant) psychoacoustic parameters even when included in the prediction formula (speech evaluation formula).

Table 2 shows estimated values of regression coefficients in the case of subjecting the subjective evaluation value α and loudness and tonality of Table 1 to multiple regression analysis. Table 2 shows a part of the output when analyzed by “Excel”. Here, the regression coefficient has a 95% confidence interval. Also, sections,
For both loudness and tonality, the P value is 0.
Highly significant below 05. In addition, the contribution ratio R ² to the subjective evaluation value α when the loudness and the tonality were combined was 97%. This means that the discomfort of sound contributes 97% to loudness and tonality. The remaining 3% are uncomfortable due to other factors.

[0062]

[Table 2]

Using the results in Table 2 above, the subjective evaluation value α
The following sound quality evaluation formula (a) for predicting the sound quality using psychoacoustic parameters (loudness and tonality) was derived. The predicted value of the subjective evaluation value α according to the sound quality evaluation formula (a) is referred to as “discomfort index S”. The discomfort index S has no unit. Since the sounds of not only the machine A but also the machines B and C of different models could be predicted, it can be said that the sound quality evaluation formula generally holds for a plurality of image forming apparatuses (machines) of about 16 to 20 ppm.

S = A × (Loudness value) + B × (Tonality value) + C (a) where 0.247 ≦ A ≦ 0.380 2.075 ≦ B ≦ 4.890-3.649 ≦ C ≦ −2.643 Here, A, B, and C indicate multiple regression coefficients, and are 95%
The range when the confidence interval is set to is shown.

When the above-mentioned multiple regression coefficients A, B, and C are the average values in the above range (regression coefficients shown in Table 2), the discomfort index S can be expressed as a sound quality evaluation formula (b) shown below. it can.

[0066]

Here, it was found that the unpleasantness of the noise of the image forming apparatus of the 16 to 20 ppm class was expressed by loudness (loudness of sound) and tonality (content of pure tone component). Further, in the image forming apparatus having the frequency components as shown in FIG. 6, the charging sound is unpleasant.

Incidentally, the above sound quality evaluation formulas (a) and (b)
States that other psychoacoustic parameters are not related to discomfort, or that the influence of other psychoacoustic parameters is exerted through loudness and tonality. Even if the psychoacoustic parameter is not related to discomfort at present, if it takes a larger value than the present condition, there is a possibility that the discomfort will be affected. Also, if the psychoacoustic parameter that is currently related to discomfort through loudness and tonality takes a larger value than the current situation, the effect on discomfort may reverse the loudness and tonality and replace the most uncomfortable psychoacoustic parameter. is there. Therefore, from Table 1 above, it can be said that the sound quality evaluation expressions (a) and (b) are satisfied within a range satisfying the following conditions.

-Sharpness is 2.70 (acum) or less-Roughness is 1.24 (asper) or less-Fractionation strength is 1.31 (v)
acil)

FIG. 5 is a scatter diagram plotting the relationship between the subjective evaluation value α and the discomfort index S (predicted value by the above sound quality evaluation formula (b)). As shown in the figure, the subjective evaluation value α, which is the result of a human subjective evaluation experiment, and the discomfort index S have a good correlation, and by using the above-mentioned sound quality evaluation formula (b), the discomfort of the sound quality can be objectively reduced. It becomes possible to evaluate.

Table 3 summarizes the results of experiments on how much the discomfort index S becomes uncomfortable. The test subjects heard the test sounds 1 to 17 obtained by processing the operation sound of the aircraft A and the operation sounds of the aircraft B and C, and evaluated the discomfort in three levels. In Table 3, “○” indicates a good sound, “×” indicates a bad sound,
“△” is in the middle.

[0072]

[Table 3]

According to the results in Table 3 above, S <−0.5 ·
If the condition (c) is satisfied, the discomfort is alleviated. That is, if the loudness value and the tonality value of the sound quality evaluation formula (b) are set so as to satisfy the condition (c), it is possible to provide an image forming apparatus in which discomfort is reduced.

Further, if S <−0.7... Condition (d) is satisfied, it is possible to provide an image forming apparatus with a sound that hardly causes discomfort.

(Method of Reducing Unpleasant Sound of Image Forming Apparatus) In the image forming apparatus shown in FIG. 1, the charging caused by the charging roller 21 for satisfying the condition (c) in the sound quality evaluation formula (b). The sound reduction method will be described in the order of [reduction method 1], [reduction method 2], [reduction method 3], and [reduction method 4].

[Reduction Method 1] In reduction method 1, a natural number is multiplied by the natural frequency of the image bearing member and the frequency f of the AC bias of the charging roller 21 by press-fitting a rigid cylindrical member into the image bearing member. The charging noise is reduced by setting the frequency to a value different from the frequency.

The charging roller 21 and the photosensitive drum 1
If the frequency of the vibration generated between and is equal to or close to the frequency obtained by multiplying the natural frequency fd of the photosensitive drum 1 itself by a natural number, the photosensitive drum 1 causes resonance,
The sound pressure level of the charging noise sharply increases. As a result, the discomfort index S sharply increases. Therefore, the natural frequency fd of the photosensitive drum 1 is previously set to the frequency f of the AC bias at the time of charging.
Is set to a frequency different from the frequency obtained by multiplying by a natural number, thereby preventing resonance of the photosensitive drum 1 and reducing the charging noise. For example, in the example shown in FIG.
And the natural frequency fd of the photosensitive drum 1 do not coincide with each other.

FIG. 6 is a sectional view of an essential part for explaining an embodiment for changing the natural frequency of the photosensitive drum. In the figure, a cylindrical member 41 having high rigidity is provided in the photosensitive drum 1.
Is press-fitted. By press-fitting the cylindrical member 41, the weight and rigidity of the photosensitive drum 1 are increased, so that the natural frequency of the photosensitive drum 1 changes. Accordingly, the natural frequency of the photosensitive drum 1 can be changed when the frequency obtained by multiplying the natural frequency by the natural frequency to the frequency f of the AC bias matches or is close to the natural frequency of the photosensitive drum 1. In addition, generation of unpleasant charging noise due to resonance can be prevented.

[Reduction Method 2] In reduction method 2, by providing a sound absorbing member inside the image carrier, the natural frequency of the image carrier is multiplied by a frequency obtained by multiplying the frequency f of the AC bias of the charging roller 21 by a natural number. As a value different from the above, the charging noise is reduced.

FIG. 7 is a view for explaining another embodiment in which the natural frequency of the photosensitive drum is changed. FIG. 7A is a sectional view of the photosensitive drum 1 into which the sound absorbing member 42 is press-fitted. FIG. 2B is a cross-sectional view of the sound-absorbing member 42 and the measurement surface of the photosensitive drum 1.

As shown in FIG. 7B, the photosensitive drum 1
A cylindrical sound-absorbing member 42 having a diameter 2R, which is slightly larger than the inner diameter 2r, is prepared. The sound absorbing member 42 is made of foamed polyurethane and is easy to handle. For example, a sound absorbing material Hama Damper HU-4 manufactured by Yokohama Rubber Co., Ltd. can be used. This is elastically deformed and inserted into the photosensitive drum 1.
FIG. 7A shows a state where the sound absorbing member 42 is pressed into the photosensitive drum 1. The inserted sound absorbing member 42 expands in order to return to the shape before deformation, and is fixed in the photosensitive drum 1. Since the sound absorbing member 42 is not fixed by bonding or the like, the sound absorbing member 42 can be easily removed from the photosensitive drum 1. Thereby, the charging noise generated from the photosensitive drum 1 can be absorbed.

[Reduction Method 3] In reduction method 3, the natural frequency of the image carrier is set to a natural number for the AC bias frequency f of the charging roller 21 by attaching the vibration damping member 43 inside the image carrier. The charging noise is reduced as a value different from the multiplied frequency.

FIG. 8 is a sectional view of an essential part for explaining another embodiment for changing the natural frequency of the photosensitive drum, and shows a state in which a vibration damping member 43 is attached to the photosensitive drum 1. It is. The vibration damping member 43 has an effect of absorbing energy that the photoconductor drum 1 vibrates and converting it into thermal energy, attenuating a vibration speed or a vibration amplitude to reduce acoustic radiation. For example, there is Nitto Denko Corporation's lightweight vibration damping material Rejetrex. This is obtained by attaching a highly viscous adhesive to a thin-walled aluminum as a substrate, and absorbs vibration energy by the adhesive. This absorbs the vibration energy between the charging roller 2 and the photosensitive drum 1 caused by the frequency f of the AC bias at the time of charging, and prevents the generation of charging noise.

[Reducing Method 4] In the reducing method 4, the charging noise is reduced by charging the image carrier with a DC bias by a charging roller.

FIG. 9 is a sectional view of an essential part for explaining an embodiment of the process cartridge 3 in which the charging system is a DC charging system. Around the photosensitive drum 1 as an image carrier, a charging roller 21 as a charging unit for applying a DC bias to the photosensitive drum 1, a developing roller 22 as a developing unit, a cleaning blade 23 as a cleaning unit, A static elimination lamp 28 is provided. The toner 24 in the process cartridge 3
5. The toner is agitated by the agitating shaft 26 and transported to the developing roller 22. The toner 24 attached to the developing roller 22 by the magnetic force is negatively charged by frictional charging when passing through the developing blade 27. The negatively charged toner moves to the photosensitive drum 1 by the bias voltage,
Attaches to electrostatic latent image.

When the transfer paper that has passed through the registration roller 11 passes between the photosensitive drum 1 and the transfer roller 2, the toner on the photosensitive drum 1 is transferred to the transfer paper by the positive charge from the transfer roller 2. The toner remaining on the photosensitive drum 1 is scraped off by the cleaning blade 23, and is collected as waste toner in a tank above the cleaning blade 23. In order to erase the residual potential on the photosensitive drum 1, the charge is removed by exposing the entire surface of the LED to prepare for the next image formation. The components other than the transfer roller 2 are integrated as a process cartridge 3 so that the user can easily replace it.

In the case of charging by the AC bias, the charging roller 2 is charged due to the AC component of the bias voltage.
Attraction and repulsion may alternately act between the surface of the photosensitive drum 1 and the surface of the photosensitive drum 1, causing the charging roller 21 to vibrate. On the other hand, in the case of charging by DC bias,
Since no vibration of the charging roller 21 occurs, no charging noise is generated. In the case where only a DC bias is applied to the charging roller 21, a static eliminator is required to remove the residual charge that is unnecessary in the AC charging. As described above, by changing the charging system from the AC charging to the DC charging system, it is possible to prevent generation of unpleasant charging noise.

The present invention is not limited to the above-described embodiment, and can be appropriately modified and executed without changing the gist of the invention. For example, the sound quality evaluation formulas (a) and (b) of the present invention and the condition (c) of the discomfort index S
Is not limited to the configuration of the image forming apparatus shown in FIG. 1, but can be widely applied to general image forming apparatuses such as an electronic copying machine and a laser beam printer.

[0089]

As described above, according to the method for evaluating sound quality of an image forming apparatus according to the first aspect, a sound emitted from the image forming apparatus is collected at a position at a predetermined distance from the image forming apparatus, and collected. Subjective evaluation value is calculated by performing psychoacoustic parameter measurement and subjective evaluation of the sound,
Based on the multiple regression analysis of the measured psychoacoustic parameter and the subjective evaluation value, based on the result of this multiple regression analysis, it was decided to calculate a sound quality evaluation formula for estimating the subjective evaluation value using the psychoacoustic parameter. Therefore, a sound quality evaluation formula using a psychoacoustic parameter having a large improvement effect on the unpleasant sound of the image forming apparatus is calculated, and an appropriate range of the subjective evaluation value estimated by the sound quality evaluation formula in the image forming apparatus is calculated. It is possible to provide a sound quality evaluation method for an image forming apparatus that can objectively evaluate sound quality using the sound quality evaluation formula and can easily take measures to improve the sound quality of the image forming apparatus. This has the effect of being possible.

According to the image forming apparatus of the present invention, the loudness value and the tonality value of the psychoacoustic parameter obtained from the sound of the image forming apparatus at a position separated from the end face of the image forming apparatus by a predetermined distance are used. The following sound quality evaluation formula (a): S = A × (loudness value) + B × (tonality value) + C (a) where coefficients A, B, and C are 0.247 ≦ A ≦ 0.38.
0 2.075 ≦ B ≦ 4.890 −3.649 ≦ C ≦ −2.643 Since the discomfort index S is determined to satisfy S <−0.5, the image operates at a relatively low speed. In the formation, it is possible to calculate a sound quality evaluation formula using a psychoacoustic parameter having a large improvement effect on unpleasant sound, and to provide an image forming apparatus in which discomfort is reduced by using the sound quality evaluation formula. It works.

According to the image forming apparatus of the third aspect, in the invention of the second aspect, the coefficient A =
0.3135, the coefficient B = 3.4824, and the coefficient C = -3.1460. Therefore, in addition to the effect of the invention according to claim 2, an optimal sound quality evaluation formula (a) is used. It is possible to do.

According to the image forming apparatus of the fourth aspect, in the invention of the second or third aspect,
Psychoacoustic parameters obtained from the sound of the image forming apparatus at a position separated from the end face of the image forming apparatus by a predetermined distance include a sharpness value ≦ 2.70 acum, a roughness value ≦ 1.24 asper, and a fracture strength value ≦ 1. .31 vacil, the sound quality evaluation formula (a) can be used under optimal conditions.

According to the image forming apparatus of the fifth aspect, in the invention of any one of the second to fourth aspects, the predetermined distance is set to 1 ± 0.03 m.
In addition to the effect of the invention according to any one of claims 2 to 4, it becomes possible to calculate the discomfort index S by a standard measuring method.

According to the image forming apparatus of claim 6, in the invention according to any one of claims 2 to 5, at least an image carrier for forming an image and the image carrier Charging means for applying an AC bias to the body to perform charging, wherein the frequency f of the AC bias is
Since 200 Hz <f is satisfied, in addition to the effect of the invention according to any one of claims 2 to 5, it is possible to reduce the discomfort of noise caused by the AC bias.

According to a seventh aspect of the present invention, in the image forming apparatus according to the sixth aspect, the charging means reduces the charging sound when the image carrier is charged by the charging means. Therefore, in addition to the effect of the invention according to claim 6, the charging noise when the charging unit charges the image carrier can be reduced by the charging noise reduction unit.

According to the image forming apparatus of the eighth aspect, in the invention of the seventh aspect, the frequency changing member includes a frequency obtained by multiplying the natural frequency of the image carrier by a natural number to the frequency f of the AC bias. In addition to the effects of the invention according to claim 7, the charging noise is set by setting the natural frequency of the image carrier to a frequency different from the frequency obtained by multiplying the frequency f of the AC bias by a natural number. Can be reduced.

Further, according to the image forming apparatus of the ninth aspect, in the invention of the eighth aspect, the frequency changing member is a member having high rigidity for preventing the image carrier from vibrating, A sound absorbing member for sucking the sound of the carrier,
Alternatively, since the vibration damping member is provided for preventing the vibration of the image carrier, in addition to the effect of the invention according to claim 8, the natural frequency of the image carrier can be reduced by a simple and low-cost configuration. The charging noise can be reduced by setting the frequency different from the frequency obtained by multiplying the frequency f of the AC bias by a natural number.

[0098] According to the image forming apparatus of the tenth aspect, in the invention of any one of the second to fifth aspects, at least an image carrier for forming an image and the image carrier are provided. Charging means for applying a voltage to the body to perform charging, wherein the charging means charges the image carrier with a DC bias. It is possible to reduce charging noise when the means charges the image carrier.

[Brief description of the drawings]

FIG. 1 is a main part configuration diagram for explaining an example of an image forming apparatus according to the present invention.

FIG. 2 is a sectional view of an essential part for explaining an example of the process cartridge shown in FIG.

FIG. 3 is a perspective view of an essential part for explaining an example of a charging roller shown in FIGS. 1 and 2;

FIG. 4 is a graph illustrating an example of a result of frequency analysis of noise of the image forming apparatus of FIG. 1;

FIG. 5 is a scatter diagram in which a relationship between a subjective evaluation value α and a discomfort index S (predicted value by a sound quality evaluation formula) is plotted.

FIG. 6 is a cross-sectional view of a main part for describing an example in which the natural frequency of the photosensitive drum is changed.

FIG. 7 is a diagram for explaining another embodiment for changing the natural frequency of the photosensitive drum.

FIG. 8 is a sectional view of a main part for explaining another embodiment in which the natural frequency of the photosensitive drum is changed.

FIG. 9 is a sectional view of an essential part for explaining an embodiment of a process cartridge in which a charging system is a DC charging system.

[Explanation of symbols]

 Reference Signs List 1 photosensitive drum 3 process cartridge 4 main body tray 5 bank paper feed tray 6 manual feed tray 7 fixing unit 8 writing unit 9 paper discharge tray 10 paper feed roller 11 registration roller 12 paper discharge roller 21 charging roller 21a core metal part 21b charging part 22 developing Roller 23 Cleaning blade 24 Toner 25 Agitator 26 Stirring shaft 27 Developing blade 28 Static elimination lamp 31 Electrode terminal 32 Charging roller pressing spring 33 Conductive bearing 41 Cylindrical member 42 Sound absorbing member 43 Damping member

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 2G064 AA12 AB15 AB23 BD02 CC41 CC45 2H134 QA01 2H200 HA02 HA28 HB12 HB48 NA03 NA10

Claims (10)

[The claims] A step of collecting a sound emitted from the image forming apparatus at a position away from the image forming apparatus by a predetermined distance; a step of measuring a psychoacoustic parameter of the collected sound; and a subjective evaluation of the collected sound. Performing a subjective evaluation value, performing a multiple regression analysis of the measured psychoacoustic parameter and the subjective evaluation value, based on the result of the multiple regression analysis, using the psychoacoustic parameter to calculate a subjective evaluation value. Calculating a sound quality evaluation formula for estimating; and calculating an appropriate range of the subjective evaluation value estimated by the sound quality evaluation formula in the image forming apparatus. Method. 2. The following sound quality evaluation formula (a) using a loudness value and a tonality value of a psychoacoustic parameter obtained from a sound of the image forming apparatus at a position separated by a predetermined distance from an end face of the image forming apparatus: S = A × ( (Loudness value) + B × (Tonality value) + C (a) where the coefficients A, B, and C are 0.247 ≦ A ≦ 0.38
0 2.075 ≦ B ≦ 4.890 −3.649 ≦ C ≦ -2.643 An image forming apparatus characterized by satisfying an unpleasant index S satisfying S <−0.5. 3. The coefficient A = 0.3135, the coefficient B
3. The image forming apparatus according to claim 2, wherein = 3.4824 and the coefficient C = −3.1460. 4. 4. A psychoacoustic parameter obtained from a sound of the image forming apparatus at a position apart from an end face of the image forming apparatus by a predetermined distance, wherein a sharpness value ≦ 2.70 acu.
4. The image forming apparatus according to claim 2, wherein a condition of m, a roughness value ≦ 1.24 asper, and a fracture strength value ≦ 1.31 vacil are satisfied. 5. 5. The predetermined distance is 1.00 ± 0.03 m.
The image forming apparatus according to any one of claims 2 to 4, wherein 6. An image carrier for forming an image, and charging means for applying an AC bias to the image carrier to charge the image carrier, wherein the frequency f of the AC bias is 200 Hz <f. The image forming apparatus according to claim 2, wherein the image forming apparatus satisfies the following condition. 7. The image forming apparatus according to claim 6, further comprising a charging noise reduction unit configured to reduce charging noise when the charging unit charges the image carrier. 8. The image forming apparatus according to claim 1, wherein the charging noise reducing unit is provided on the image carrier for setting a natural frequency of the image carrier to a frequency different from a frequency obtained by multiplying a frequency f of the AC bias by a natural number. The image forming apparatus according to claim 7, wherein the image forming apparatus is a vibration frequency changing member. 9. The image forming apparatus according to claim 1, wherein the frequency changing member includes a member having high rigidity for preventing vibration of the image carrier, a sound absorbing member for absorbing sound of the image carrier, or vibration of the image carrier. The image forming apparatus according to claim 8, wherein the image forming apparatus is a vibration damping member for preventing image formation. 10. An image forming apparatus comprising: at least an image carrier for forming an image; and charging means for applying a voltage to the image carrier to charge the image carrier, wherein the charging means applies a DC bias to the image carrier. The image forming apparatus according to claim 2, wherein charging is performed.