JP2019088083A - Motor unit and image formation device - Google Patents

Abstract

To provide a motor unit capable of efficiently silencing a sound generated from a motor.SOLUTION: A motor unit comprises a motor 70 and a Helmholtz resonator having a communication section 211 and a cavity section 212. By providing a contact face 216 where a surface of the motor 70 comes into contact with a wall on which the communication section 211 is provided, a closed space including the surface of the motor 70 and the wall is configured.SELECTED DRAWING: Figure 6

Description

  The present invention relates to a motor unit provided with a Helmholtz resonator, and an image forming apparatus provided with the motor unit.

  In an image forming apparatus such as a copying machine or a printer, a motor, a fan or the like is operated at the time of image formation to generate an operating noise. On the other hand, noise reduction in image forming apparatuses has been strongly demanded from recent customer needs.

  As a configuration for reducing the operation noise of an image forming apparatus, an image forming apparatus incorporating a Helmholtz resonator has been proposed.

  The Helmholtz resonator is configured of a cavity whose volume is determined by a frequency band to be muffled, and a communication unit that communicates the cavity with the outside.

  In Patent Document 1, by providing a Helmholtz resonator so as to be close to a sound source such as a motor, noise is absorbed by absorbing the sound into the Helmholtz resonator before the operation sound of the motor is diffused from the inside of the machine to the outside of the machine. ing.

JP, 2016-143714, A

  A stepping motor, which is a type of motor, is driven by inputting a clock pulse signal of hundreds to thousands of pulses per second. At this time, motor noise of a frequency corresponding to the applied signal is generated from the stepping motor.

  If the frequency of the motor sound is several thousand Hz, the sound may be offensive by the person who hears the sound because it is a relatively high sound (high frequency sound). Particularly in recent years, noise reduction during operation of the copying machine has progressed, so the volume of the motor sound has become relatively large, and the motor noise also needs to be suppressed.

  However, as in the configuration of Patent Document 1, when there is a space between the stepping motor and the Helmholtz resonator, the motor sound emitted from the motor is absorbed by the hollow part of the Helmholtz resonator without excess. It is difficult to mute. The motor noise that can not be absorbed is radiated to the outside of the copying machine through the discharge port and the suction and discharge port of the copying machine.

  Then, this invention is made in view of said subject, and it aims at using the Helmholtz resonator to muffle a motor sound generated from a stepping motor efficiently.

  One aspect of a motor for achieving the above object includes a motor, and a Helmholtz resonator including a communication portion and a hollow portion, and a surface of the motor and a wall provided with the communication portion include A closed space including the surface and the wall is configured by providing a contact surface in contact.

  According to the present invention, motor noise can be muffled efficiently by the Helmholtz resonator.

FIG. 1 shows a schematic configuration of an image forming apparatus of the present invention. The schematic diagram of a Helmholtz resonator. FIG. 2 is a schematic view of a motor and a pair of discharge rollers that constitute a discharge unit. FIG. 2 is a perspective view of a stepping motor. FIG. 2 is a perspective view of a motor unit provided with a Helmholtz resonator in the first embodiment. 1 is a schematic cross-sectional view of a motor unit provided with a Helmholtz resonator according to a first embodiment. The measurement result of the motor sound which provided the Helmholtz resonator in 1st Embodiment. The perspective view of the motor unit which provided Helmholtz resonator in a 2nd embodiment. The schematic sectional drawing of the motor unit which provided Helmholtz resonator in 2nd Embodiment. The measurement result of the motor sound which provided the Helmholtz resonator in 2nd Embodiment. The measurement result of the motor temperature which provided the Helmholtz resonator in 2nd Embodiment.

  Hereinafter, preferred embodiments of the present invention will be exemplarily described in detail with reference to the drawings. However, the dimensions, materials, shapes, relative positions and the like of the component parts described in the following embodiments should be appropriately changed according to the configuration of the apparatus to which the present invention is applied and various conditions. Accordingly, the scope of the present invention is not intended to be limited only to those unless otherwise specified. In the present embodiment, although an example of an image forming apparatus for forming an image using an electrophotographic method is described, the present invention is also applicable to an apparatus using an image forming method other than the electrophotographic method. Further, the present invention is applicable to various apparatuses such as printers, various printing machines, copying machines, multifunction machines, and the like.

  FIG. 1 is a view showing a schematic configuration of an image forming apparatus according to an embodiment of the present invention.

  In FIG. 1, the image forming apparatus 100 includes an image forming apparatus main body 100 </ b> A (hereinafter, referred to as an apparatus main body) and an image reading unit 41 provided on the top of the apparatus main body 100 </ b> A. The image reading unit 41 includes an image sensor or the like that emits light to a document placed on a platen glass as a document placement table and converts reflected light into a digital signal. A document for reading an image is conveyed onto a platen glass by the automatic document feeder 41a. In the apparatus main assembly 100A, the image forming unit 55, the sheet feeding devices 51 and 52 for feeding the sheet S to the image forming unit 55, and the sheet reversing unit for inverting the sheet S and conveying it to the image forming unit 55 59 are provided.

  The image forming unit 55 includes an image forming unit for forming a four-color toner image of yellow (Y), magenta (M), cyan (C) and black (Bk). Hereinafter, in order to distinguish the components of each image forming unit, y, m, c and k are added after the numbering. In addition, description of y, m, c, k is abbreviate | omitted when not distinguishing.

  The image forming unit 55 includes an exposure unit 42, four photosensitive drum cartridges 43 (43y, 43m, 43c, 43k) and four developing cartridges 44 (44y, 44m, 44c, 44k). The image forming unit 55 also includes a photosensitive drum cartridge 43, and an intermediate transfer unit 45 disposed above the developing cartridge 44, a secondary transfer unit 56, and a fixing unit 57.

  Here, the photosensitive drum cartridge 43 includes the photosensitive drum 21 (21y, 21m, 21c, 21k), the charging roller 22 (22y, 22m, 22c, 22k), and the drum cleaning blade 23 (23y, 23m, 23c, 23k). Is equipped. The photosensitive drum 21 is configured to be rotatable clockwise in FIG. The photosensitive drum cartridge 43 is configured to be removable from the apparatus main assembly 100A. The photosensitive drum cartridge 43 is supported inside the apparatus body 100A by drum cartridge support members 46 (46y, 46m, 46c, 46k) provided in the apparatus body 100A. The photosensitive drum cartridge 43 can be pulled out in the front direction of the paper surface of FIG. 1, and can be mounted in the back direction of the paper surface of FIG.

  In the image forming unit 55 of the present embodiment, the Helmholtz resonator 200 is configured by the photosensitive drum cartridge 43 and the drum cartridge support member 46. Details will be described later.

  The developing cartridge 44 includes developing rollers 24 (24y, 24m, 24c, 24k). The developing cartridge 44 is configured to be insertable into and removable from the apparatus main assembly 100A, and is supported by developing cartridge support members 47 (47y, 47m, 47c, 47k) provided in the apparatus main assembly 100A.

  The intermediate transfer unit 45 includes an intermediate transfer belt 25 stretched around a belt drive roller 26, a secondary transfer inner roller 56 a, and the like, and a primary transfer roller 27 contacting the intermediate transfer belt 25 at a position facing the photosensitive drum 21. (27y, 27m, 27c, 27k) are provided. Then, as described later, by applying a transfer bias of positive polarity to the intermediate transfer belt 25 by the primary transfer roller 27, the toner images having the negative polarity on the photosensitive drum 21 are sequentially multiple-transferred onto the intermediate transfer belt 25. Ru. Thus, a full color image is formed on the intermediate transfer belt 25.

  The secondary transfer portion 56 is composed of a secondary transfer inner roller 56 a and a secondary transfer outer roller 56 b in contact with the secondary transfer inner roller 56 a via the intermediate transfer belt 25. Then, as described later, a full-color image formed on the intermediate transfer belt 25 is transferred onto the sheet S by applying a secondary transfer bias of positive polarity to the secondary transfer outer roller 56b.

  The fixing unit 57 includes a fixing roller 57a and a fixing backup roller 57b. Then, the sheet S is nipped and conveyed between the fixing roller 57a and the fixing backup roller 57b, whereby the toner image on the sheet S is pressed and heated and fixed to the sheet S.

  The sheet feeding devices 51 and 52 include cassettes 51 a and 52 a that are storage means for storing the sheet S, respectively. The sheet separation and feeding sections 51b and 52b have a function of feeding the sheets S stored in the cassettes 51a and 52a one by one while separating them by friction.

  In FIG. 1, the pre-secondary transfer conveying path 103 is a path for conveying the sheet S fed from the cassettes 51 a and 52 a to the secondary transfer unit 56. The pre-fixing conveyance path 104 is a path for conveying the sheet S conveyed to the secondary transfer unit 56 from the secondary transfer unit 56 to the fixing unit 57. The post-fixing conveyance path 105 is a path for conveying the sheet S conveyed to the fixing unit 57 from the fixing unit 57 to the switching member 61. The sheet discharge path 106 is a path for conveying the sheet S conveyed to the switching member 61 from the switching member 61 to the sheet discharge unit 58. The re-conveying pass 107 is a pass for conveying the sheet S reversed by the sheet reversing unit 59 to the image forming unit 55 again in order to form an image on the back side of the sheet S on which an image is formed on one side by the image forming unit 55. is there.

  Next, an image forming operation of the image forming apparatus 100 having such a configuration will be described. When the image forming operation is started, the exposure unit 42 irradiates the surface of the photosensitive drum 21 with a laser beam based on image information from a personal computer (not shown) or the like. At this time, the surface of the photosensitive drum 21 is uniformly charged to a predetermined polarity and potential by the charging roller 22, and when the laser beam is irradiated, the charge of the portion irradiated with the laser beam is attenuated. An electrostatic latent image is formed on the surface.

  After that, a predetermined potential is applied to the developing roller 24, and toners of yellow (Y), magenta (M), cyan (C) and black (Bk) are supplied from the developing roller 24, respectively, to form an electrostatic latent image. Is developed as a toner image. The color toner images are sequentially transferred to the intermediate transfer belt 25 by the primary transfer bias applied to the primary transfer roller 27, whereby a full color toner image is formed on the intermediate transfer belt 25.

  On the other hand, in parallel with the toner image forming operation, the sheet feeding devices 51 and 52 separate and feed only one sheet S from the cassettes 51a and 52a by the sheet suction and separation feeding units 51b and 52b. After this, the sheet S reaches the drawing roller pair 51c, 51d. Further, the sheet S nipped by the drawing roller pair 51c and 51d is sent to the conveyance path 103 through the sheet thickness detection by the sheet thickness detecting means 53, and abuts on the registration roller pair 62a and 62b stopped. The position of the tip is adjusted.

  Next, in the secondary transfer portion 56, the registration roller pair 62a, 62b is driven at timing when the full-color toner image on the intermediate transfer belt and the position of the sheet S coincide with each other. As a result, the sheet S is conveyed to the secondary transfer portion 56, and a full color toner image is collectively transferred onto the sheet S at the secondary transfer portion 56 by the secondary transfer bias applied to the secondary transfer outer roller 56b. Be done.

  The sheet S on which the full-color toner image has been transferred is conveyed to a fixing unit 57, and heat and pressure are applied to the fixing unit 57 to fuse and mix the toners of the respective colors, and the sheet S is fixed as a full-color image. Thereafter, the sheet S on which the image is fixed is discharged by the paper discharge unit 58 provided downstream of the fixing unit 57. When forming an image on both sides of the sheet, the sheet reversing unit 59 reverses the transport direction of the sheet S and transports the sheet S to the image forming unit 55 again.

  Next, the structure of the Helmholtz resonator 200 provided in the image forming apparatus 100 of the present invention will be described with reference to FIG. FIG. 2 is a schematic view of the Helmholtz resonator 200.

  The Helmholtz resonator 200 roughly includes a cavity 202 having a space of volume V, and a communicating portion 201 extending from the cavity 202 by a length L and having an opening of a cross-sectional area S. The mass of air in the communicating portion 201 vibrates and resonates by the air spring formed by the space of the hollow portion 202, thereby silencing the specific frequency f of the sound entering the communicating portion 201. The specific frequency f to be muffled is expressed by equation (1).

  Here, c: sound velocity, ΔL: opening end correction, and ΔL is 1.6a (a is a radius when the cross section of the communicating portion 201 is circular).

  In the present embodiment, the high frequency sound generated from the motor 70 is targeted for muffling, and the parameters of the Helmholtz resonator 200 are determined so that the frequency of the generated high frequency sound and the specific frequency f in equation (1) coincide. ing.

First Embodiment
FIG. 1 is a schematic view of an image forming apparatus. A sheet discharge unit 58 that discharges the sheet to the outside of the image forming apparatus is one of the portions that generate a large radiation noise. When there is a sound source such as a motor in the vicinity of the paper discharge unit 58, the sound generated from the motor has a large member because it does not shield the outside of the main body. On the other hand, the sound generated from the motor disposed inside the apparatus main body 100A rather than the vicinity of the paper discharge unit 58 rather than the vicinity of the paper discharge unit 58 is shielded by the exterior cover, the frame, etc. In recent years, the internal noise of the main body has been made quieter, and the sound emitted from the paper discharge unit 58 exposed to the outside is relatively larger than the overall sound of the apparatus main body 100A. Therefore, in the present embodiment, an example applied to the discharge unit 58 will be described.

  FIG. 3 is an explanatory view of the configuration of the paper discharge unit 58. As shown in FIG.

  The transport roller pair 71 is driven by a motor 70. The transport roller pair 71 is the transport roller pair closest to the discharge port. The type of motor used is a hybrid type (HB type) stepping motor. The stepping motor operates by alternately exciting two phases of A-phase and B-phase by a clock pulse signal.

  A schematic view of the appearance of the HB stepping motor is shown in FIG.

  A housing 72, which is an exterior surface of the motor 70, comprises a rear bracket 73, a front bracket 74 on the shaft side, and a stator 75. The motor sound is radiated from the surface layer surface to the outside by the surface layer surface of the housing 72 vibrating due to the clock pulse signal.

  FIG. 5 is a block diagram of a motor unit 230 provided with a first covering member 210 provided with a Helmholtz resonator on the motor 70.

  The motor 70 is provided with a first covering member 210 so as to cover the housing 72. The first covering member 210 is an example of the Helmholtz resonator in the present embodiment. The first covering member 210 is divided into two parts of a first member and a second member (210a, 210b) and covers the motor 70 so as to sandwich it.

  FIG. 6 is a cross-sectional view of a motor unit 230 in which the first covering member 210 is provided on the motor 70. As shown in FIG.

  The first covering member 210a has a Helmholtz resonator. The Helmholtz resonator is disposed to face the rear bracket 73. The material of the first covering member 210 is a resin.

  On the first inner wall 215 side of the first covering member 210, a first communicating portion 211 and a first hollow portion 212 which constitute a Helmholtz resonator are formed. The first communication portion 211 and the first hollow portion 212 are Helmholtz resonance portions of the first covering member 210. Further, a first contact surface 216 and a second contact surface 217 are provided between the surface of the housing 72 and the first inner wall 215 such that a portion of the first inner wall 215 is in contact with a portion of the surface of the housing 72. A first closed space 213 is formed. The closed space referred to here is a gap between the surface of the motor 70 and the first covering member 210 within 50 mm to prevent sound from leaking. Even if there is a gap of 50 mm or more, it is a closed space if an elastic member such as rubber is interposed in the gap to prevent sound leakage. That is, even if a gap is created due to a manufacturing dimensional error that occurs when the motor 70 and the first covering member are assembled, it is considered to constitute a closed space. Preferably, the gap generated in the manufacturing process is filled with a buffer member.

  The first contact surface 216 is an example of a first exposed portion that exposes the motor 70 from the first covering member 210 a. The first contact surface 216 is configured by providing a cutout shape in a part of the first covering member 210.

  The second contact surface 217 is an example of a second exposed portion that exposes the motor 70 from the first covering member 210 b. The second contact surface 217 is configured by providing a notch on a part of the first covering member 210. The first contact surface 216 and the second contact surface 217 position the motor 70 and the first covering member 210. By positioning each of the first covering member 210a and the first covering member 210b, the positioning between the first covering member 210 and the motor 70 can be accurately performed.

  A shock absorbing material of an elastic member is provided (not shown) so that no gap is generated between the first contact surface 216 and the housing 72. Similarly, a buffer is provided between the first contact surface 217 and the housing 72, and a buffer is provided between the first covering member 210a, the first covering member 210b, and the contact surface.

  Further, a first clearance A is provided between the first inner wall 215 having the first communicating portion 211 and the surface of the housing 72. In the present embodiment, the distance of the first clearance A is 5 mm. By providing such a first closed space 213, the motor sound emitted from the surface of the housing 72 hardly leaks to the outside of the first covering member 210, and the sound is efficiently absorbed to the first communication portion 211. . If the clearance A is too small, it is difficult for the sound generated from the entire motor to be absorbed by the Helmholtz resonator, and if it is too large, the sound to be muffled diverges and the muffling effect of the Helmholtz sound absorber is reduced. Therefore, the clearance A is preferably about 1 mm to 100 mm. The clearance A is defined as the shortest distance between the first inner wall 215 and the motor 70 when an imaginary line is drawn perpendicularly from the surface of the first inner wall 215 having the first communication portion 211.

  In order to keep the first clearance A between the first inner wall 215 and the surface layer of the housing 72 at a predetermined value, the first inner wall 215 is provided with a convex shape 214. The convex shape 214 maintains the first clearance A by bringing its tip into contact with the housing 72. The shape of the convex shape 214 is a cylindrical shape having a small diameter so as not to block the motor sound propagating to the first communication portion 211 in the first closed space 213.

  The first covering member 210 covers almost the entire area of the housing 72 so that the motor noise is absorbed as much as possible to the first communication portion 211.

  The clock pulse signal applied to the motor in the present embodiment is 2620 pps, and the frequency of the motor sound is 2620 Hz.

Therefore, the diameter of the first communication portion 211 is φ10 mm, and the volume of the first hollow portion 212 is 2400 mm ² so that the specific frequency f of the Helmholtz resonator to be muffled becomes 2620 Hz.

  FIG. 7 shows the measurement results of the radiation noise in the case where the first covering member 210 is provided with the Helmholtz resonator and in the case where the Helmholtz resonator is not provided in the configuration of the motor 70 and the first covering member 210 shown in FIG. In addition, the structure which does not provide a Helmholtz resonator in the 1st coating member 210 obstruct | occluded the 1st communication part 211 of the 1st coating member 210 shown in FIG. As understood from FIG. 7, by providing the Helmholtz resonator, the motor sound in the 2620 Hz band is reduced by about 13 dB as compared with the case where the Helmholtz resonator is not provided.

Second Embodiment
Next, a second embodiment of the image forming apparatus 100 to which the present invention is applied will be described. In the second embodiment, the shape of the first covering member 210 in the first embodiment is different.

  In the stepping motor, the temperature of the motor rises due to internal heat generation caused by the applied current at the time of driving. When image formation is continuously performed for a long time using the image forming apparatus 100, the motor is driven in synchronization with image formation, so the temperature of the motor tends to rise.

  When the first covering member 210 covers most of the housing 72 of the motor 70 as in the first embodiment, the cooling efficiency of the motor 70 is reduced compared to the case where the first covering member 210 is not provided. As a result, when image formation is performed for a long time, the temperature of the motor may exceed the upper limit temperature of the use range of the motor.

  In the present embodiment, a configuration in which cooling of the motor temperature is also possible while muffling the motor noise will be described.

  FIG. 8 is a block diagram of a motor unit 230 provided with a second covering member 220 provided with a Helmholtz resonator on the motor 70. The second covering member 220 is an example of the Helmholtz resonator in the present embodiment.

  The second covering member 220 covers the stator 75 and does not cover the rear bracket 73 and the front bracket 74. The material of the second covering member 220 is a resin.

  FIG. 9 is a cross-sectional view of a motor unit 230 in which the second covering member 220 is provided on the motor 70. As shown in FIG.

  On the second inner wall 225 side of the second covering member 220, a second communicating portion 221 and a second hollow portion 222 which constitute a Helmholtz resonator are formed. The second communication portion 221 and the second hollow portion 222 are Helmholtz resonance portions of the second covering member 220. The second communication portion 221 is provided to face the surface of the stator 75.

  A second closed space 223 is provided between the surface of the stator 75 and the second inner wall 225 having the second communication portion 221. The second closed space 223 is provided by bringing a portion of the inner wall 225 into contact with a portion of the surface of the housing 72 at the second contact surface 226. By keeping the second clearance B between the second inner wall 225 and the surface layer of the housing 72 at 5 mm, the motor noise can be easily transmitted to the second communication portion 221.

  A shock absorbing material of an elastic member is provided (not shown) so that a gap does not occur between the second contact surface 226 and the housing 72. The position at which the second communication portion 221 and the second hollow portion 225 are provided is not particularly limited as long as it is a surface continuous with the second inner wall 225 side in the second closed space 223.

  The clock pulse signal applied to the motor in the present embodiment is 2580 pps, and the frequency of the motor sound is 2580 Hz.

Therefore, the diameter of the second communication portion 221 is 9 mm, and the volume of the second hollow portion 222 is 2000 mm ² so that the specific frequency f of the Helmholtz resonator to be muffled is 2580 Hz.

  FIG. 10 shows the measurement results of the radiation noise in the case where the second covering member 220 is provided with the Helmholtz resonator and in the case where the Helmholtz resonator is not provided in the configuration of the motor 70 and the second covering member 220 shown in FIG. In addition, the structure which does not provide a Helmholtz resonator in the 2nd coating member 220 blocked the 2nd communication part 221 of the 2nd coating member 220 shown in FIG. As understood from FIG. 10, by providing the Helmholtz resonator, the motor sound in the 2620 Hz band is reduced by about 13 dB as compared with the case where the Helmholtz resonator is not provided.

  In the configurations of the first embodiment and the second embodiment, transition of the temperature of the motor when the motor 70 is continuously driven is shown in FIG.

  In the first embodiment, the temperature of the motor continues to rise even after 50 minutes of continuous driving time. On the other hand, in the second embodiment, the temperature rise of the motor is gradual compared to the first embodiment.

  That is, compared with the first embodiment, the configuration of the second embodiment has a high motor cooling efficiency, and can perform continuous driving for a long time.

  The muffling effect of the second embodiment is smaller than that of the first embodiment. This difference is due to the fact that the amount of exposure of the housing 72, which is a motor sound radiation source, is larger than that of the first embodiment in the configuration of the second embodiment.

  As described above, by appropriately setting the exposure amount of the housing 72 in accordance with the use condition of the motor, it is possible to adjust the balance between the muffling and the cooling.

  For example, in the case of a copying machine in which the number of continuous paper sheets assumed is small, the temperature of the motor does not increase, so the configuration of the first embodiment can be selected to enhance the silencing effect.

  On the other hand, in the case of a copying machine in which the number of continuous paper sheets assumed is large, the temperature of the motor becomes high, so the configuration of the second embodiment in which the cooling is emphasized is selected.

  In addition, it is also possible to raise the cooling efficiency of motor temperature compared with resin by making the material of the 1st coating member 210 or the 2nd coating member 220 into a metal.

[Modification]
In the above embodiment, although the example applied to the motor 70 for driving the conveyance roller pair 71 has been described, the present invention is not limited to this. The present invention may be applied to a motor for driving a roller, a rotating body, and the like other than the conveyance roller pair 71.

100 image forming apparatus 55 image forming unit 43 photosensitive drum cartridge 44 developing cartridge 46 drum cartridge supporting member 47 developing cartridge supporting member 48 charging high voltage power source 49 developing high voltage power source 21 photosensitive drum 22 charging roller 23 drum cleaning blade 24 developing roller 70 motor 71 discharge Feed roller pair 72 Housing 73 Rear bracket 74 Front bracket 75 Stator 200 Helmholtz resonator 201 Communication portion 202 Hollow portion 210 First covering member 211 First communication portion 212 First hollow portion 213 First closed portion 214 Convex shape 215 First inner wall 216 first contact surface 220 second covering member 221 second communication portion 222 second hollow portion 223 second closed space 225 second inner wall 226 second contact surface 230 motor unit A first clearance B first clearance B 2 clearance

Claims (13)

Motor,
And a Helmholtz resonator comprising a communicating portion and a hollow portion,
A motor unit comprising a closed space including the surface and the wall by providing a contact surface where the surface of the motor and the wall provided with the communication portion are in contact with each other.   The motor unit according to claim 1, wherein the contact surface is provided with a shock absorbing material that fills a gap between the surface and the wall. Provide a convex shape on the wall,
When the convex shape is in contact with the surface,
The motor unit according to claim 1 or 2, wherein a distance between the surface and the wall is kept predetermined. Motor,
A covering member provided in contact with the surface of the motor and covering at least a part of the motor, the covering member including a Helmholtz resonance part including a communication part and a hollow part, ,
The communication unit is provided on a wall of the covering member facing the surface.   The image forming apparatus according to claim 4, wherein a shock absorbing material filling the gap is provided on a contact surface between the surface and the covering member. Provide a convex shape on the wall,
When the convex shape is in contact with the surface,
The motor unit according to claim 4 or 5, wherein the distance between the surface and the wall is maintained at a predetermined distance. The covering member includes a first member and a second member,
The first member has a first exposed portion that exposes the motor from the covering member,
The motor unit according to any one of claims 4 to 6, wherein the second member has a second exposed portion that exposes the motor from the covering member. The first exposed portion positions the first member and the motor,
The motor unit according to claim 7, wherein the second exposed portion positions the second member and the motor.   The motor unit according to any one of claims 4 to 8, wherein a distance between a surface of the covering member including the communication portion and the motor is 1 mm to 100 mm.   The motor unit according to any one of claims 4 to 9, wherein a closed space is formed by the motor and the covering member, and the communication portion is provided in the closed space.   The image forming apparatus according to any one of claims 1 to 10, wherein the motor is a stepping motor. An image forming unit that forms an image on a sheet;
An image forming apparatus comprising: the motor unit according to any one of claims 1 to 11.   The image forming apparatus according to claim 12, wherein the motor unit drives a conveyance roller that conveys a sheet on which an image is formed by the image forming unit.

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