IMAGE FORMING APPARATUS

Abstract

The image forming apparatus in this disclosure includes a main body, a plate-shaped frame member, a perforated portion, a sound generating source, an external cover member, and a space forming portion. The plate-shaped frame member configures a part or the whole of the side surface of the main body. The perforated portion has a plurality of holes and is formed in the frame member. The sound generating source is an inner portion of the main body and is disposed at a position corresponding to the perforated portion. The external cover member is disposed at and separated by a predetermined distance from the frame member on an outer side of the frame member. The space forming portion forms a space between the perforated portion and the external cover member that is tightly enclosed except for the perforated portion.

Description

This application is based on and claims the benefit of priority from Japanese Patent Application No. 2010-287071, filed on 24 Dec. 2010, the content of which is incorporated herein by reference.

BACKGROUND OF THE DISCLOSURE

1. Field of the Disclosure

The present disclosure relates to an image forming apparatus.

2. Related Art

Recently, problems caused by an increase in sound with operating of machines due to an enhanced operating speed of the machines have occurred in relation to a so-called electrographic type of image forming apparatus used in offices and the like. As a result, for example, various proposals have been made to suppress emission to the outside of sound generated in an internal portion of an apparatus, such as fan rotational sound, gear driving sound, or the like.

For example, a configuration has been disclosed as a related technique in which emission of fan rotational sound to the outside is suppressed by increasing a suppressible frequency by disposing a silencing apparatus on an outer side of the fan. The silencing apparatus includes two plate members that have a plurality of holes adapted for silencing.

SUMMARY OF THE DISCLOSURE

However, the silencing apparatus in the related technique is a separate component to the frame or the external cover of the apparatus. As a result, increase in the product size or the manufacturing cost may result.

The present disclosure has the object of providing an image forming apparatus having a configuration in which emission of sound produced in the apparatus internal portion is suppressed.

The image forming apparatus in this disclosure includes a main body, a plate-shaped frame member, a perforated portion, a sound generating source, an external cover member, and a space forming portion. The plate-shaped frame member configures a part or the whole of the side surface of the main body. The perforated portion has a plurality of holes and is formed in the frame member. The sound generating source is an inner portion of the main body and is disposed at a position corresponding to the perforated portion. The external cover member is disposed at and separated by a predetermined distance from the frame member on an outer side of the frame member. The space forming portion forms a space between the perforated portion and the external cover member that is tightly enclosed except for the perforated portion.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an external perspective view of an image forming apparatus according to an embodiment of the present disclosure.

FIG. 2 is a perspective view seen from the inner side of the main body frame in the image forming apparatus according to an embodiment of the present disclosure.

FIG. 3 is a perspective view seen from the outer side of the main body frame in the image forming apparatus according to an embodiment of the present disclosure.

FIG. 4 is a perspective view of the main body frame mounting a drive unit and a right cover in the image forming apparatus according to an embodiment of the present disclosure.

FIG. 5 is a perspective view seen from the inner side of the drive unit in the image forming apparatus according to an embodiment of the present disclosure.

FIG. 6 is a perspective view seen from the outer side of the drive unit in the image forming apparatus according to an embodiment of the present invention.

FIG. 7 is a perspective view of the right cover in the image forming apparatus according to an embodiment of the present disclosure.

FIG. 8 is a perspective view of the shape of a space formed between a main body frame and a right cover in the image forming apparatus according to an embodiment of the present disclosure.

FIG. 9 is a perspective view illustrating the positional relationship of the drive unit and the right cover in the image forming apparatus according to an embodiment of the present disclosure.

FIG. 10 is a perspective view describing the shape of a space formed between an attachment plate and a right cover in the image forming apparatus according to an embodiment of the present disclosure.

FIG. 11 is a table describing the interval between the main body frame and the right cover, and the aperture diameter and hole interval in each embodiment in relation to the image forming apparatus according to an embodiment of the present disclosure.

FIG. 12 is a table describing the relationship between the sound pressure level and the sound frequency in the embodiments and comparative examples in the image forming apparatus according to an embodiment of the present disclosure.

FIG. 13 is a graph describing the relationship between the sound pressure level and the sound frequency in the embodiments and comparative examples in the image forming apparatus according to an embodiment of the present disclosure.

DETAILED DESCRIPTION OF THE DISCLOSURE

A monochrome printer 1 will be described below making reference to FIG. 1 to FIG. 10 as an example of the image forming apparatus according to an embodiment of the present disclosure. In the following description, the surface at the front of FIG. 1 is used as the front side of the monochromatic printer 1.

As illustrated in FIG. 1, the monochromatic printer 1 includes a substantially rectangular main body 2 and an external cover 3 that covers the external periphery of the main body 2.

A plate-shaped main body frame 4 that acts as a frame member is configured in an upright orientation on an inner right side of the main body 2 to be substantially parallel to the right surface of the main body 2. The main body frame 4 is configured as a portion of the right side surface in the main body 2. FIG. 2 is a perspective view of the main body frame 4 seen from the inner side of the main body 2, and the right side in FIG. 2 is the front side of the main body 2. In contrast, FIG. 3 is a perspective view of the main body frame 4 seen from the outer side of the main body 2, and the left side in FIG. 3 is the front side of the main body 2.

The main body frame 4 is formed by a sheet metal member. As illustrated in FIG. 2 and FIG. 3, a bulging portion 5 is provided on the main body frame 4 to project from the central longitudinal portion toward the rear end portion in an inward orientation in the main body 2. The bulging portion 5 is configured to include an upper portion 6 provided from a central portion in a longitudinal direction of the main body frame 4 to a predetermined rear position and a lower portion 7 formed below the upper portion 6 and positioned further towards a rear outer edge. The bulging portion 5 is formed in the shape of a letter “L” when viewed from the side.

A motor mounting portion 11 including a circular insertion hole 8, and engaging holes 10, 10 provided above and below the insertion hole 8 is provided on the upper portion 6 of the bulging portion 5. A motor 12 is mounted from the outer side onto the motor mounting portion 11 (refer to FIG. 4).

A perforated portion 14 is formed as a horizontally long rectangle on the lower portion 7 of the bulging portion 5 from a predetermined forward position of the lower portion 7 towards the rear end portion. A gear train 16 configured to include a plurality of intermeshing gears 15 is disposed on an inner side of the perforated portion 14 in a state in which the position in the longitudinal direction is slightly staggered forward with respect to the perforated portion 14. In other words, the front end of the gear train 16 in relation to the longitudinal direction is disposed more in a forward orientation than the front end of the perforated portion 14, and the rear end is disposed more in a forward orientation than the rear end of the perforated portion 14. The gear train 16 is omitted from the figures other than FIG. 4.

The perforated portion 14 includes a plurality of holes 13. The aperture diameter and the hole interval (refer to the arrow a in FIG. 2) of the plurality of holes 13 is set in response to the frequency band of the meshing of the gears 15 provided in the gear train 16.

A unit mounting portion 20 that includes a horizontally elongated upper attachment hole 17 and a lower attachment hole 18 provided below the upper attachment hole 17 is provided on the front portion of the main body frame 4. A drive unit 21 is mounted on the unit attachment portion 20 (refer to FIG. 4).

As illustrated in FIG. 5 and FIG. 6, the drive unit 21 includes a plate-shaped attachment plate 22 as a frame member, a clutch 23 fixed to a lower portion of the inner surface of the attachment plate 22, and a gear train 25 fixed with the clutch 23 to an inner surface of the attachment plate 22. FIG. 5 is a perspective view of the drive unit seen from an inner side of the main body 2, in which the right side of FIG. 5 is the front side of the main body 2. In contrast, FIG. 6 is a perspective view of the drive unit 21 seen from an outer side of the main body 2, in which the left side of FIG. 6 is the front side of the main body 2.

The attachment plate 22 is formed by a sheet metal member, and constitutes a portion of the gear box 26 that encloses the gear train 25.

The perforated portion 28 that includes a plurality of holes 27 is formed along the whole region of the attachment plate 22. The gear train 25 is disposed on an inner side of the perforated portion 28. The hole interval and aperture diameter of the plurality of holes 27 in the perforated portion 28 (refer to the arrow b in FIG. 6) is set in response to the frequency band of meshing of the gear train 25.

The clutch 23 is inserted into the lower attachment hole 18 of the main body frame 4.

The gear train 25 is configured by a plurality of intermeshing gears 30. A portion of the gear train 25 is inserted into the upper attachment hole 17 of the main body frame 4.

The peripheral edge portion 31 of the main body frame 4 is curved outwardly in a substantially orthogonal configuration in the main body 2. A lower end engaging hole 32 is provided respectively in the front portion, the rear portion and longitudinal central portion of the lower end portion of the peripheral edge portion 31. An upper end engaging hole 33 is provided in the rear portion of the upper end portion of the peripheral edge portion 31 (refer to FIG. 3).

A resinous right cover 34 is provided on an outer side of the main body frame 4 as an external cover member that constitutes a portion of the external cover 3.

As illustrated in FIG. 7, the lower edge portion 35, the upper edge portion 36 and the front edge portion 37 of the right cover 34 curves inwardly (towards the main body 2, towards the main body frame 4) in a substantially orthogonal configuration. A lower end hook 38 is respectively provided on the lower end portion 35 at a position corresponding to the lower end engaging hole 32 of the main body frame 4. An upper end hook 40 is provided on the upper end portion 36 at a position corresponding to the upper end engaging hole 33 of the main body frame 4. The right cover 34 is configured to be assembled with the main body frame 4 by engaging the lower end hook 38 with the lower end engaging hole 32 and engaging the upper end hook 40 with the upper end engaging hole 33.

A rear rib 41 is formed on a lower rear portion of an inner surface of the right cover 34 to configure a first space forming portion 100 at a position corresponding to the perforated portion 14 provided on the bulging portion 5 of the main body frame 4. The rear rib 41 projects to form an annular configuration that forms a horizontally long rectangle when viewed from the side. The “annular configuration” referred to above means that the rear rib 41 is provided continuously so that a portion of the inner surface of the right cover 34 is partitioned from the other portion, and there is no necessity for the formation of a circular shape.

As illustrated in FIG. 8, the rear rib 41 adjusts the height of projection from the inner surface of the right cover 34 to abut with the outer surface of the bulging portion 5 on an outer peripheral portion of the perforated portion 14 in a state in which the right cover 34 is assembled with the main body frame 4. In this manner, a substantially rectangular space 42 that is enclosed on an outer side is formed between the right cover 34 and the perforated portion 14 of the main body frame 4 by the rear rib 41, the outer surface of the perforated portion 14, and the inner surface of the right cover 34. The first space forming portion 100 forms a space between the perforated portion 14 and the right cover 34 that is tightly enclosed except for the perforated portion 14. In the present embodiment, the first space forming portion 100 is configured by the rear rib 41, the outer surface of the perforated portion 14 and the inner surface of the right cover 34. The interval between the inner surface of the right cover 34 and the outer surface of the perforated portion 14 in the space 42 (refer to the arrow X in FIG. 8) is set in response to the meshing frequency band of the gear train 16.

A front rib 43 configuring a second space forming portion 200 is formed on the front side of the inner surface of the right cover 34 from a predetermined upper position to a predetermined lower position. The front rib 43 projects to form an annular configuration. The “annular configuration” referred to above means that the front rib 43 is provided continuously so that a portion of the inner surface of the right cover 34 is partitioned from the other portion, and there is no necessity for the formation of a circular shape.

The front rib 43 is configured in a shape corresponding to the outer edge shape of the attachment plate 22, and the height of projection of the front rib 43 from the inner surface of the right cover 34 is adjusted so that the front rib 43 abuts with the attachment plate 22 on an outer peripheral portion of the perforated portion 28 in a state in which the right cover 34 is assembled with the main body frame 4. In this manner, as illustrated in FIG. 10, a flat space 44 that is enclosed on an outer side is formed between the right cover 34 and the perforated portion 28 of the attachment plate 22 by the front rib 43, the outer surface of the perforated portion 28, and the inner surface of the right cover 34. The second space forming portion 200 forms a space between the perforated portion 28 and the right cover 34 that is tightly enclosed except for the perforated portion 28. In the present embodiment, the second space forming portion 200 is configured by the front rib 43, the outer surface of the perforated portion 28 and the inner surface of the right cover 34. The interval between the inner surface of the right cover 34 and the outer surface of the perforated portion 28 in the space 44 (refer to the arrow Y in FIG. 10) is set in response to the meshing frequency band of the gear train 25. In the present embodiment, the interval between the perforated portion 28 and the right cover 34 in the space 44 is narrower than the interval between the right cover 34 and the perforated portion 14 in the space 42.

Although omitted from the figures, the inner portion of the monochrome printer 1 is provided with a drum unit that houses photosensitive drums, a charging unit that applies a charge up to a predetermined voltage to the surface of the photosensitive drums, an exposure unit that exposes light onto the surface of the photosensitive drums that have been charged by the charging device, a development unit that uses toner to develop an electrostatic latent image formed by the exposure device into a toner image, a transfer unit that operates cooperatively with the photosensitive drums to execute transfer of the toner image onto the surface of a transfer sheet, and a fixing unit that fixes the toner image that has been transferred onto the transfer sheet.

When the monochrome printer 1 that has the above configuration is operated, the gear train 16, 25 is driven by the motor 12. At the same time, each unit is driven and an image forming process is performed in the monochrome printer 1.

On the other hand, when the gear train 16, 25 (sound generating source) is driven, each gear 15 in the gear train 16 and each gear 30 in the gear train 25 rotate. In this manner, a driving sound is generated. However, in the present embodiment, as described above, the gear train 16, 25 is disposed at a position corresponding respectively to the perforated portion 14, 28 in an inner portion of the main body 2. Spaces 42, 44 (the space enclosed with the exception of the perforated portions 14, 28) that are enclosed on an outer side between the perforated portion 14, 28 and the right cover 34 are respectively formed.

The sound that is generated by the gear train 16, 25 is screened and absorbed when passing through the spaces 42, 44. In this manner, sound is reduced.

As a result, the monochrome printer 1 (image forming apparatus) enables a reduction in sound emitted to the outside after passing through the main body frame 4, the attachment plate 22 and the right cover 34.

The space 42 is configured only by the main body frame 4 and the right cover 34, and the space 44 is only configured by the attachment plate 22 and the right cover 34. That is to say, the provision of the perforated portion 14 directly to the existing main body frame 4 or the attachment plate 22 means that the spaces 42, 44 can be formed without addition of a new member provided with holes. Consequently, the monochrome printer 1 (image forming apparatus) according to the present embodiment enables sound reduction as described above based on cost reduction and space-efficient design.

Furthermore, the gear train 16 driven by a motor 12 mounted on a main body frame 4 is a sound generating source, and the monochrome printer 1 (image forming apparatus) according to the present embodiment enables an integrated configuration of the gear train 16 that is the sound generating source, the main body frame 4, and the motor 12. As a result, sound reduction and downsizing of the monochrome printer 1 are realized simultaneously.

An annular front rib 43 and rear rib 41 project on an inner surface of the right cover 34 in the monochrome printer 1 (image forming apparatus) according to the present embodiment. Furthermore the monochrome printer 1 (image forming apparatus) forms spaces 42, 44 by the front rib 43 and the rear rib 41, the outer surface of the perforated portion 14 and the inner surface of the right cover 34. In this manner, the monochrome printer 1 (image forming apparatus) enables formation of the spaces 42, 44 with a simple configuration.

The aperture diameter and the hole interval of the holes 13 provided in the perforated portion 14 are set in response to the frequency band of the sound of the gear train 16 (the meshing frequency band of the gear train 16), and the aperture diameter and the hole interval of the holes 27 provided in the perforated portion 28 are set in response to the frequency band of the sound of the gear train 25 (the meshing frequency band of the gear train 25). As a result, the monochrome printer 1 (image forming apparatus) ensures suppression of driving sound of a specific frequency produced by the gear trains 16, 25.

Furthermore, the interval between the perforated portion 14 and the right cover 34 is set in response to the frequency band of the sound of the gear train 16 (the meshing frequency band of the gear train 16), and the interval between the perforated portion 28 and the right cover 34 is set in response to the frequency band of the sound of the gear train 25 (the meshing frequency band of the gear train 25). Consequently, the monochrome printer 1 (image forming apparatus) enables a further reduction in sound of a specific frequency generated by the sound generating source.

As described above in the present embodiment, the monochrome printer 1 (image forming apparatus) is configured to enable setting of a frequency band enabling sound reduction by a component design in which the interval between the perforated portion 14, 28 and the right cover 34, and the aperture diameter and hole interval of the holes 13, 27 are set in response to the frequency band of the sound of the gear train 15, 25 that is the sound generating source. The monochrome printer 1 (image forming apparatus) combines a plurality of spaces 42, 44 respectively configured to set an interval between the perforated portion 14, 28 and the right cover 34, and the aperture diameter and hole interval of the holes 13, 27 to thereby enable suppression of sound emission to the outside by ensuring reduction in driving sound even when a driving sound is produced in a frequency band that is different from the plurality of gear trains 16, 25.

The effect of the present invention was confirmed by an experiment performed under actual conditions using a monochrome printer LS-4020DN (45 PPM) that is modified (60 PPM) and manufactured by Kyocera Mita Corporation.

In the experiment, a space 42 is formed between the right cover 34 and the perforated portion 14 of the main body frame 4. In example 1 to example 3, a sound frequency and sound pressure level for sound emitted to the outside from the monochrome printer was measured. The interval between the main body frame 4 and the right cover 34, and the aperture diameter and hole interval of the holes 13 in the perforated portion 14 in each example are respectively illustrated in FIG. 11. In a comparative example, a monochrome printer not provided with the main body frame 4 and the right cover 34 (comparative example 1) and a monochrome printer provided with the main body frame 4 and the right cover 34 but without the perforated portion 14 in FIG. 4 (comparative example 2) were measured in the same manner as the examples.

In the experiment, the sound frequency that is the object for reduction was 750 Hz. This frequency corresponds to the frequency of a meshing sound of large-bore gears and the motor pinion fixed to an output shaft of the motor 12. The raw data for sound on the right of the monochrome printer is recorded, and the frequency and sound pressure level were analyzed using FFT analysis software (DS-0250 manufactured by Ono Sokki Co., Ltd.) and an FFT analyzer (DS-2000 manufactured by Ono Sokki Co., Ltd.).

As clearly shown by the experimental results in FIG. 12 and FIG. 13, in all of example 1 to example 3, the sound pressure level is suppressed more than comparative example 1 and comparative example 2 in the 630-800 Hz frequency band that includes the 750 Hz that is the target frequency to suppress(refer to the portion enclosed by the dotted line in FIG. 12 and FIG. 13). Use of the configuration disclosed in the embodiments has been verified to enable a reduction in sound of a specific frequency in an image forming apparatus.

As illustrated in FIG. 12 and FIG. 13, the sound pressure level in each sound frequency is modified by varying the hole interval and aperture diameter of the holes 13 in the perforated portion 14. The present embodiment has proved that component design enables determination of a frequency band that can be reduced (suppressed).

In the present embodiment, although the motor 12 was provided on an outer portion of the spaces 42, 44, in a different embodiment, the motor 12 may be disposed in an inner portion of the spaces 42, 44. The image forming apparatus enables reduction (suppression) of emission of the rotational sound of the motor 12 to the outside, and further improves reduction of sound emitted to the outside of the monochrome printer 1.

In the present embodiment, although a monochrome printer was described as an image forming apparatus, there is no particular limitation in this regard, and for example, the image forming apparatus may be a color printer, a monochrome or color copying machine, a facsimile, or a multifunction peripheral combining such devices.

Claims

1. An image forming apparatus comprising:

a main body;

a plate-shaped frame member configuring a part or the whole of the side surface of the main body;

a perforated portion having a plurality of holes and formed in the frame member;

a sound generating source in an inner portion of the main body and disposed at a position corresponding to the perforated portion;

an external cover member disposed at and separated by a predetermined distance from the frame member on an outer side of the frame member; and

a space forming portion forming a space between the perforated portion and the external cover member, the space forming portion being tightly enclosed except for the perforated portion.

2. The image forming apparatus according to claim 1, wherein the sound generating source is a gear train mounted on the frame member.

3. The image forming apparatus according to claim 1, further comprising an annular rib projecting on an inner surface of the outer covering member, and

the space forming portion configured by the rib, the outer surface of the perforated portion, and the inner surface of the outer covering member.

4. The image forming apparatus according to claim 3, wherein the frame member comprises a bulging portion that projects on a main body inner portion, and

the perforated portion is formed on the bulging portion.

5. The image forming apparatus according to claim 1, wherein the plurality of holes that configure the perforated portion is formed with an aperture diameter and a hole interval that are set in response to the frequency band of the sound of the sound generating source.

6. The image forming apparatus according to claim 1, wherein the space forming portion sets the interval between the inner surface of the outer covering member and the outer surface of the perforated portion in response to the frequency band of the sound generated by the sound generating source.

7. The image forming apparatus according to claim 1, wherein the sound generating source includes a motor that drives the gear train, and

the motor is disposed in a space formed by the space forming portion.