JPH068581A - Noise preventing mechanism of image forming apparatus - Google Patents

Abstract

PURPOSE:To reduce the noise of a rotary body by the interference with the sound of which the phase is reverse to that of the noise of a rotary body such as a fan and having the same sound pressure as the noise emitted from a newly provided speaker. CONSTITUTION:The number of rotations of a cooling fan 2 is measured by a number-of-rotation detection circuit 55 to be inputted to a digital/analogue processor 50 (hereinbelow referred to as DSP) to operate the noise frequency of the fan in the DSP 50. This frequency is set to a reference signal and a signal reverse to fan noise in phase and having the same amplitude as the fan noise is formed by the digital filter and delay circuit in the DSP 50 and a control speaker 3 is sounded through a D/A converter 51 and a power amplifier 52. Next, the reduction effect of noise due to mutual interference is measured by an evaluation microphone 4 to be inputted to the DSP 50 through a microphone amplifier 54 and an A/D converter 53 and, by adapting the digital filter in the DSP 50 so as to reduce the noise from a microphone 4, the noise 2 of the fan 2 can be reduced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to, for example, print paper,
Laser beam printers, electrophotographic copiers, etc. that perform processing such as forming images on sheet materials such as copy paper and printing paper.
The present invention relates to a noise prevention mechanism that is generated by the rotation of a cooling fan, a motor, etc. in an image forming apparatus such as a printing machine.

[0002]

2. Description of the Related Art Generally, a heat source in an image forming apparatus to which an electrophotographic method is applied is mainly a fixing section, a power source section, a drive motor, a scanner motor, an electric board section and the like.

Since toner, waste toner, electric parts such as ICs in the power source section and electric board section, optical lens box, etc. must be used at a temperature lower than a predetermined upper limit,
Cooling is performed by using a cooling fan so that the temperature inside the device becomes equal to or lower than a predetermined temperature.

As a concrete example, FIG. 7 shows a conventional image forming apparatus.

This will be described in detail with reference to FIG. 7. In the conventional image forming apparatus 1, a paper feed cassette 8 is inserted, and a recording sheet 12 is inserted in the cassette, and the sheet is an intermediate plate. 10, the rotating portion 11 and the coil spring 9 cause the recording sheet 12 to be attached to the half-moon-shaped feed roller 13.
Are contacted under pressure.

When the paper feed roller 13 rotates in the direction of the arrow in the figure, paper is fed and the separation pad 14 separates the paper. The separating pad 14 is adhered to a holder 15 and is connected by a coil spring 16 to the paper feed roller 13
Is pressed against.

The separated recording sheet 12 is a paper guide 1
The registration rollers 18 are guided by 7a and 17b.
It abuts against a and 18b, and at this time, a slight loop is set between the separating pad and the registration roller pair.

When a sensor (not shown) detects that the recording sheet 12 has come into contact with the registration roller,
The sheet 12 is moved between the photosensitive drum 22a and the transfer roller 20 while being guided between the paper guide 19 and the photosensitive drum 22a, the primary charger, the developing device, and the process cartridge 22 containing the toner by driving the registration roller. Transfer is performed by being transported to. Furthermore, the heater 25 is arranged in the center, and the heat roller 24 whose temperature is controlled,
The fixing is performed by being conveyed between the heat roller 24 and the pressure roller 23 which is in pressure contact with the heat roller 24 by a pressure spring (not shown).

Then, the stacker 33 is guided by the paper guides 26a and 26b and is discharged by the paper discharge rollers 27 and 28.
Is discharged to. 35 is a rubber foot.

The paper feed roller 13 and the registration roller 18
a, cartridge 22, heat roller 24, paper discharge roller 27
Is driven by a drive motor (not shown) and
N, OFF controlled.

In the actual image forming process, the cartridge 22
To expose an image on the photosensitive drum 22a therein, a laser unit and a collimator lens (not shown) irradiate the polygon mirror 31 attached to the shaft of the scanner motor 32 with the laser light emitted by the laser unit and the collimator lens. The polygon mirror 31 is driven to rotate, and fθ
Laser light is scanned onto the photosensitive drum 22a through the lens 30 and the mirror 29.

The cooling fan 2 is arranged near the upper surface of the main body of the image forming apparatus 1, and an exhaust louver 6a is provided on the cooling fan 2.

The cooling fan 2 is attached to a duct 5, and below the duct, the air passages are divided into two directions by ports 7a and 7b.

The port 7a sucks the outside air as indicated by the arrow from the intake louver 6a by the negative pressure of the cooling fan 2, and uses the outside air to scan the scanner motor 32, a laser unit (not shown), the fθ lens 30, and the like. It is connected to an optical box (not shown) that houses the optical system and a duct (not shown) that forms an air passage for cooling the toner and the waste toner portion in the process cartridge 22.

The port 7b communicates with the power source section 34, and an intake port (not shown) for outside air therefor is provided on the lower surface of the main body, and is configured to introduce outside air as indicated by an arrow.

Therefore, by the cooling fan 2, from the intake louver 6b and the intake port (not shown) on the lower surface of the main body 1,
A structure in which outside air is introduced, while cooling the above-mentioned units, flows into the duct 5 from the ports 7a and 7b, finally cools the electric board portion 36, and exhausts from the exhaust louver 6a as shown by an arrow. Has become.

[0017]

However, in the above-mentioned conventional example, although sufficient performance was obtained as the function of the image forming apparatus and the cooling capacity of the cooling fan, on the other hand,
Fan noise tends to be particularly loud. On the other hand, recent O
The demand for noise reduction of the A-type equipment and the information equipment is intensifying, and satisfying this requirement has become an important issue.

In the above-mentioned conventional example, the cause of noise will be described. As the noise source, the cooling fan 2, the scanner motor 32, and the primary charger (cartridge 22) are used.
Inner) and a drive motor (not shown).

The highest noise level from these noise sources is the cooling fan, and the size of the other noise sources is 5 dB (A) higher than this cooling fan in terms of noise level.
It is as small as -10 dB (A).

Therefore, it is known that the cooling fan is the most problematic noise source in the overall noise of the apparatus.

As a general characteristic of the cooling fan,
Since the number of revolutions and the noise level are in a proportional relationship, it is possible to reduce the noise level by reducing the number of revolutions, but at the same time, the cooling capacity also declines. However, the upper limit temperature of the required component cannot be satisfied.

Therefore, in the above-mentioned conventional example, the noise of the cooling fan is the largest in the apparatus, and the noise of the apparatus as a whole cannot be reduced due to this noise, so that the recent demand for noise reduction cannot be satisfied. It was

An object of the present invention is to solve the above problems and reduce the noise generated from a rotating body rotating at high speed in an image forming apparatus and the noise caused by an applied bias.

[0024]

DISCLOSURE OF THE INVENTION The present invention emits a sound having the same sound pressure and a phase opposite to that of the noise of a rotating body such as a fan of the present invention, and interference with the sound causes the rotating body to rotate. It is designed to reduce the noise.

In the embodiment, the speaker is a DS
The DSP may be controlled by a P (digital signal processor), and the DSP may have a structure in which a rotation speed detection circuit of the rotating body and a noise evaluation microphone provided in the duct as a feedback system are connected. .

(Function) The relationship between the rotation frequency N of the rotating body such as a fan and the noise frequency f can be expressed by the equation (1).

[0027]

[Outer 1]

The method of controlling the speaker by the DSP is to turn on the main power source of the device, measure the rotation speed after the fan reaches the steady rotation, and use the relation of the equation (1) to determine the signal input to the speaker. The frequency is decided. Next, measure the noise of the actual rotating body such as a fan with the evaluation microphone, and let the speaker emit a signal with the same sound pressure as the opposite phase, but the output of the evaluation microphone is always small. Therefore, the phase of the speaker is controlled.

Further, the positional relationship between the rotating body such as a fan and the speaker is arranged at such a position that effectively acts on the influence of the wavelength at the noise frequency of the rotating body and the standing wave in the duct.

[0030]

An embodiment of the present invention will be described below with reference to the drawings. (Embodiment 1) FIG. 1 is a main sectional view of an image forming apparatus of the present invention.

In the figure, parts having the same functions and functions as those of the conventional example of FIG.
Since the description of the sheet feeding, conveyance, transfer, fixing and exposure of the photosensitive drum 22a of No. 2 is exactly the same as the conventional example, the description thereof is omitted here.

According to FIG. 1, in the duct 5, a cooling fan 2, a speaker 3 controlled to prevent noise according to the present invention, and a microphone 4 for evaluating generated noise are arranged.
The cooling fan 2 is arranged below the duct, and ports 7a and 7b are provided directly below the fan, and the ports divide the air passage into two directions.

External air is sucked into the port 7a from the intake louver 6a by the negative pressure of the cooling fan 2 as shown by the arrow, and the scanner motor 32, a laser unit (not shown), and optical elements such as the fθ lens 30 are used by the external air. The system is connected to an optical box (not shown) accommodating the system and a duct (not shown) forming an air passage for cooling the toner and the waste toner portion in the process cartridge 22.

The port 7b communicates with the power supply unit 34, and an intake port (not shown) for outside air therefor is provided on the lower surface of the main body, and is configured to introduce outside air as indicated by an arrow.

Therefore, by the cooling fan 2, from the intake louver 6b and the intake port (not shown) on the lower surface of the main body 1,
A structure in which outside air is introduced, and while cooling each unit described above, flows into the duct 5 from the ports 7a and 7b, finally cools the electric board portion 36, and exhausts from the exhaust louver 6a as shown by an arrow. Has become.

Further, at the rear of the control speaker 3,
The wall 38a constitutes a hermetically sealed enclosure 38 between the outer wall of the duct and the exterior, and is further filled with a suitable amount of glass wool 37 so that the sound from the rear surface of the control speaker 3 is also transmitted to the exterior. Not configured.

FIG. 2 shows a block diagram of the adaptive control system of this embodiment.

In this configuration, the DPS 50, the rotation speed detection circuit 55, the power amplifier 52, the microphone amplifier 54, the A / D converter 53, the D / A converter 51, the cooling fan 2, the evaluation microphone 4, and the control speaker 3 are the main components. It is configured.

Further, in the DPS 50, a digital filter and a delay circuit (not shown) are formed.

According to FIG. 2, the rotation speed of the cooling fan 2 is measured by the rotation speed detection circuit and is input to the DSP 50 to
The noise frequency of the fan is calculated inside, and this frequency is used as the reference signal, and the digital filter inside the DSP,
The delay circuit is used to create a signal with the same phase and the opposite phase as the fan noise, and the D / A converter 51 and power amplifier 5
Sound the control speaker 3 via 2.

Next, the evaluation microphone 4 measures the noise reduction result due to the mutual interference between the noise of the cooling fan itself and the sound from the control speaker, and inputs it to the DSP 50 via the microphone amplifier 54 and the A / D converter 53. The noise of the cooling fan 2 can be reduced by adapting a digital filter (not shown) in the DSP 50 so as to always reduce the noise from the microphone.

The measurement results of the fan noise of the above embodiment are shown in FIG.
Shown in.

FIG. 3 is a diagram in which the data before and after the use of the embodiment is overwritten, and the blackened portion represents the effect area according to the present embodiment.

The effect is clear from the figure, and the noise of about 10 dB can be reduced at the fan noise primary frequency of 350 Hz. Furthermore, noise reduction is performed at the secondary and tertiary frequencies, and the size is about several dB.
Although the reduction effect is inferior to the case of the primary 350 Hz, it can be said that the final effect is sufficient since the noise level in the state before the implementation is originally small.

As described above, the noise level of 35 is the highest.
Since the noise peak at 0 Hz is almost eliminated, the noise level of the entire fan noise can be reduced to the same level as other noise sources (scanner motor, drive motor, primary charger), and the entire device can be reduced. It has become possible to reduce noise.

Also, from the viewpoint of hearing, there is almost no fan-specific "humming" sound.

(Embodiment 2) FIG. 4 shows a second embodiment.

The outline is the same as that of the embodiment of FIG. 1, but in this embodiment, a soundproof wall 39 is provided inside the duct 5 to prevent direct sound from the control speaker 3 from leaking from the exhaust louver 6a. .

That is, according to the present embodiment, by further providing this soundproof wall 39, the directional characteristic of the sound from the speaker 3 is directed toward the fan 2 which is the noise source,
The muffling effect could be further enhanced.

(Third Embodiment) A third embodiment will be described with reference to FIGS. 5 and 6.

The outline of FIG. 5 is the same as the embodiment of FIGS. 1 and 2, but in this embodiment, instead of the control speaker,
A sounding body 40 made of an electromagnetic actuator is attached. This sounding body 40 can be used in exactly the same way as the control speaker 3 in FIG. 1, and its effect can be obtained in exactly the same way.

The structure of the sounding body 40 will be described in detail with reference to FIG.

The sounding body 40 is configured to drive the diaphragm 41 by an electromagnetic actuator to emit sound, and the diaphragm 41 is attached to a part of the wall of the duct 5 by the damper 45. A voice coil 42 is adhered to the diaphragm 41. Further, on the outside thereof, there is a yoke 44 to which the magnet 43 is bonded.

With the above structure, the electric force is converted into a force for moving the diaphragm, and the diaphragm 41 is driven according to the current flowing in the voice coil 42.

(Embodiment 4) A fourth embodiment will be described.

The method described in the first embodiment can be applied to the noise source other than the rotating body with the same effect.

In the process cartridge 22 shown in FIG.
There is a charging roller (not shown), and this roller is the photosensitive drum 2.
2a under pressure contact with a predetermined force, and the drum 22
It is supported so as to be able to follow a, and the material is conductive urethane foam rubber, and the shaft is inserted into the roller rubber part, and the shaft slides against its rotation. Contacting electrodes are provided.

By applying a potential to the electrodes, charges can be injected into the photosensitive layer on the surface of the photosensitive drum 22a.

However, it has been known that the above-mentioned potential applies a voltage in which AC is superimposed on the DC offset, and as a result, noise with a frequency twice the frequency of the applied AC is emitted.

From the above, this noise spectrum is
In order to generate a sound close to a single sound, the control speaker 3 and the evaluation microphone 4 used in the first embodiment are connected to the intake louver 6b, the scanner motor 32, an optical box (not shown), and a duct (not shown) for cooling the process cartridge 22. The same effect as that of the first embodiment can be obtained by arranging the same in the drawing.

Further, with respect to the noise of the scanner motor in the same duct as described above, similar noise control can be performed by arranging the control speaker 3 and the evaluation microphone 4 at optimum positions, and the same effect can be obtained. It goes without saying that you can get

[0062]

As described above, a sound having a phase opposite to the noise phase of a rotating body such as a cooling fan, which is the most noisy, is emitted from a speaker or a sounding body and interferes with the sound.
By reducing the noise of the rotating body, it is possible to reduce the noise from the inside of the image forming apparatus.

The present invention is effective not only for a cooling fan but also for a rotating body such as a motor for driving a rotating mirror for scanning.

[Brief description of drawings]

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

FIG. 2 is a block diagram of a control system according to the first embodiment of the present invention.

FIG. 3 is a graph showing experimental results of the first embodiment of the present invention.

FIG. 4 is a main sectional view of a second embodiment of the present invention.

FIG. 5 is a main sectional view of a third embodiment of the present invention.

FIG. 6 is a sectional view of a sounding body according to a third embodiment of the present invention.

FIG. 7 is a main cross-sectional view of a conventional device.

[Explanation of symbols]

 1 image forming apparatus 2 cooling fan 3 control speaker 4 evaluation microphone 5 duct 39 soundproof wall 40 sounder

Claims (4)

[Claims] 1. An image forming apparatus equipped with at least a rotating body such as a fan; means for measuring noise of the noise source, a speaker or a sounding body, and the speaker or the sounding body based on the noise. And a control means for performing the adaptive control described above, wherein a noise having a phase opposite to that of the rotating body noise is emitted from the speaker. 2. The mechanism according to claim 1, wherein the control means is D
A noise prevention mechanism for an image forming apparatus characterized by using an SP (digital signal processor). 3. The noise of an image forming apparatus according to claim 1, wherein an exhaust duct is provided in the apparatus, and the rotating body, the speaker or sounding body, and the microphone are simultaneously arranged in the duct. Prevention mechanism. 4. The image forming apparatus according to claim 1, wherein the control system turns on a main power source of the image forming apparatus and starts the operation in synchronization with the rotating body reaching a steady rotation speed. Noise prevention mechanism.