Electronic device

Abstract

To reduce radiated noise by a simpler method than the prior art.SOLUTION: An electronic device includes a motor 107, a motor driver 104 for driving the motor 107, a wiring member 106 electrically connecting the motor 107 and the motor driver 104, a non-conductive elastic member 111 for damping vibrations of the motor 107, a conductive housing 114, and a conductive member 108 electrically connecting the motor 104 and housing 114.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present disclosure relates to an electronic device including a motor driver and a motor. [Background technology]

[0002] Electronic devices such as image forming devices, typified by copiers, are equipped with motors for transporting paper and other operations inside the device. These types of electronic devices also include a motor driver that holds the drive signals supplied to the motor, and a cable, which is a wiring member for supplying the drive signals from the motor driver to the motor. Radiation noise from the cable or other components can adversely affect the operation of the motor and other components within the electronic device. Patent Document 1 discloses that a relay board equipped with noise suppression components is attached between the cable and the motor to reduce radiation noise. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2010-154687 Summary of the Invention [Problem to be solved by the invention]

[0004] However, the method disclosed in Patent Document 1 requires the separate manufacture and installation of a relay board equipped with noise suppression components. This increases costs and requires installation space. Therefore, a simpler method that is lower cost and saves space has been desired. [Means for solving the problem]

[0005] An aspect for solving the above problem is an electronic device comprising: a motor; a motor driver that drives the motor; a wiring member that electrically connects the motor and the motor driver; a non-conductive elastic member that damps vibrations of the motor; a conductive housing; and a conductive member that electrically connects the motor and the housing. [Effects of the Invention]

[0006] According to the present disclosure, radiation noise can be reduced using a simpler method than conventional techniques. [Brief explanation of the drawings]

[0007] [Figure 1] 1A is a front view of an image forming apparatus which is an example of an electronic device according to the first embodiment, and FIG. 1B is a rear view of the image forming apparatus according to the first embodiment. [Figure 2] 2 is a schematic diagram showing a part of the motor module according to the first embodiment. FIG. [Figure 3] 3 is a diagram showing a path along which a common mode current propagates in the motor module according to the first embodiment. FIG. [Figure 4] FIG. 2 is a schematic diagram illustrating a part of a motor module when performing an electromagnetic field analysis in the first embodiment. [Figure 5] FIG. 2 is a schematic diagram showing a motor equivalent circuit when performing electromagnetic field analysis in the first embodiment. [Figure 6] 1 is a graph showing the results of electromagnetic field analysis of radiation noise in Example 1 and Comparative Example 1. [Figure 7] 4 is a graph showing the radiation noise reduction effect of Example 1. [Figure 8] 10 is a graph showing the results of electromagnetic field analysis of radiation noise in Example 2 and Comparative Example 2. [Figure 9] 10 is a graph showing the radiation noise reduction effect of Example 2. [Figure 10] FIG. 10 is a schematic diagram showing a part of an image forming apparatus according to a comparative example. DETAILED DESCRIPTION OF THE INVENTION

[0008] [First embodiment] FIG. 1A is a front view of an image forming apparatus 1000, which is an example of an electronic device according to a first embodiment. FIG. 1B is a rear view of the image forming apparatus 1000 according to the first embodiment. The image forming apparatus 1000 is an electrophotographic digital device such as a printer, a copier, a fax machine, or a multifunction peripheral. The image forming apparatus 1000 includes a device main body 160 that forms an image on a sheet, a control module 200 that controls the device main body 160, and a motor module 400 that supplies power to the device main body 160 and the control module 200. The image forming apparatus 100 also includes a conductive chassis 161 that supports the device main body 160, the control module 200, and the motor module 400, and a decorative cover 162 that encloses the chassis 161. The chassis 161 is a metal frame. The decorative cover 162 is made of, for example, resin. The control module 200 and the motor module 400 are installed on the rear surface of the device main body 160.

[0009] The apparatus main body 160 includes an image forming unit 300 that forms an image on a sheet, and a sheet conveying mechanism (not shown). The image forming unit 300 includes a photosensitive drum, a charging unit, a developing unit, a transfer unit, a fixing unit, and the like (not shown).

[0010] The control module 200 receives image data from an external device via an interface such as a LAN (Local Area Network) or a USB (Universal Serial Bus). Then, the control module 200 processes the received image data, transmits the image data to the device main body 160, and controls the device main body 160 to form an image on a sheet.

[0011] FIG. 2 is a cross-sectional view showing a portion including a motor module 400 of an image forming apparatus 1000, which is an example of an electronic device according to the first embodiment.

[0012] The motor module 400 supplies power to the apparatus main body 160 and the control module 200. The motor module 400 also includes motors that drive the photosensitive drum, charging unit, developing unit, transfer unit, and fixing unit, which are part of the apparatus main body 160 and are not shown.

[0013] The motor module 400 includes a motor 107, a motor driver 104, a wiring member 106, a non-conductive elastic member 111, a conductive second housing 114, and a conductive member 108.

[0014] The motor 107 has a conductive motor housing 107A. The motor 107 drives a photosensitive drum, a charging unit, a developing unit, a transfer unit, a fixing unit, and the like (not shown), which are part of the apparatus main body 160. The type of the motor is not particularly limited, but may be, for example, a stepping motor.

[0015] The motor driver 104 is an IC that has a function of generating a drive signal for driving the motor 107, and is mounted on the printed circuit board 103. The motor driver 104 has a RAM (not shown) that stores the waveform of the drive signal for driving the motor.

[0016] The printed circuit board 103 is a rigid board, such as a multilayer board in which glass epoxy resin or ceramic is used for the insulating layer and copper is used for the wiring layer and conductor pattern. A power supply circuit for driving the motor driver, a connector 105 to which a wiring member 106 (described later) is connected, and the like are mounted on the printed circuit board 103. In Fig. 2, the printed circuit board 103 is attached via a spacer 102 provided on a first housing 101 having electrical conductivity.

[0017] The wiring member 106 is a member that electrically connects the motor 107 and the motor driver 104, and in FIG. 2, one end is connected to the motor 107 and the other end is connected to the connector 105. A drive signal sent from the motor driver 104 is transmitted to the motor 107 via the wiring member 106. The wiring member 106 is not particularly limited, but may be, for example, a rigid cable, a flexible flat cable, or a flexible printed wiring board. In FIG. 2, the wiring member 106 is a conductive cable, and one phase of a multi-phase cable is shown here.

[0018] The non-conductive elastic member 111 has a function of damping vibrations of the motor 107. The elastic member 111 not only damps vibrations of the motor 107 but also damps transmission of vibrations of the motor 107 to the second housing 114, which may also become an exterior part. The material constituting the elastic member 111 is not particularly limited, but rubber is preferable from the viewpoint of high vibration damping properties. In FIG. 2, the elastic member 111 is provided between the non-conductive plate-like member 113 and the non-conductive plate-like member 110 via an adhesive (not shown).

[0019] The conductive second housing 114 is provided on the first housing 101. In Fig. 2, the second housing 114 is provided perpendicular to the first housing 101, but the present invention is not limited to this.

[0020] The conductive member 108 electrically connects the second housing 114 and the motor 107 and serves to suppress common mode noise, which will be described later. In FIG. 2, the conductive member 108 includes a conductive screw 108B and a conductor 108A that is different from the screw 108B. The second housing 114, the screw 108B, the conductor 108A, and the motor housing 107A are directly and electrically connected to each other. There is no particular limitation on the means of electrical connection between the motor 107 and the conductive member 108, but it is preferable that the motor housing 107A and the conductive member 108 are connected. There is no particular limitation on the material of the conductor 108A, but it is preferable that the conductor 108A be made of rubber or sponge.

[0021] Here, a motor module 400X of a comparative example will be described. Fig. 10 is a cross-sectional view showing a portion including a motor module 400X of an image forming apparatus, which is an example of an electronic device of a comparative example.

[0022] The motor module 400X of the comparative example differs from the motor module 400 of the first embodiment in the configuration of the conductive member 108. Specifically, the conductive member 108 does not have a conductor 108A, and therefore the motor housing 107A and the screw 108B are not electrically connected. As a result, the motor 107 and the second housing 114 are connected only via the non-conductive member, and are not electrically connected. The other configurations are the same as those of the motor module 400 of the first embodiment.

[0023] A drive signal for operating the motor 107 is transmitted from the motor driver 104 (an IC) to the motor 107 via the wiring member 106 (a cable). While most of the current flows through the wiring member 106 and returns to the motor driver 104, a portion of the current returns via the second housing 114 and the first housing 101, as shown by the arrows in Figure 3. This current is generally called a common-mode current, and it is known to be a major cause of radiated noise due to the constructive magnetic fields. The common-mode current, which is a problem here, varies depending on the impedance value of the current path. The common-mode current increases at the resonant frequency where the impedance is at its minimum, and the radiated noise also increases. In this case, if the motor 107 is connected to the second housing 114 only via a non-conductive member, the motor 107 and the second housing 114 are electrically connected via a capacitive component, resulting in a large Q value for the impedance resonance. This causes a sharp peak in the radiated noise.

[0024] Therefore, in the first embodiment, a configuration is adopted in which a conductor 108A different from the screw is sandwiched between the screw 108B and the motor 107.

[0025] Even in this configuration, a common mode current is generated along the path indicated by the arrow in Fig. 3. However, in the first embodiment, motor 107 and second housing 114 are electrically connected via conductor 108A and screw 108B. This causes the common mode current to flow to second housing 114 via conductor 108A and screw 108B. Here, because conductor 108 has a resistance component, the Q value of the impedance resonance in the path of the common mode current becomes small, and the level at the peak frequency of the radiation noise is reduced.

[0026] In the first embodiment, the case where motor 107 is fixed to second housing 114 by screw 108B, non-conductive plate-like member 110, non-conductive elastic member 111, conductive screw 112, and non-conductive plate-like member 113 has been described, but the present invention is not limited to this. For example, screw 112 and non-conductive plate-like member 113 may not be present, and non-conductive elastic member 111 and motor 107 may be directly bonded together.

[0027] However, if the non-conductive elastic member 111 and the motor 107 are directly bonded, there is a risk that the bonded portion between the elastic member 111 and the motor 107 may separate due to vibrations during operation of the motor 107. If this occurs, stable vibration isolation, which is the main purpose of using an elastic member made of rubber, may not be achieved. For this reason, it is preferable to place a non-conductive plate-like member 113 between the elastic member 111 and the motor 107. One method of increasing the adhesive strength by using rubber made of a highly adhesive material as the elastic member 111 is conceivable, but it is recommended to use a thickness of 2000 mm to achieve vibration isolation. 3 Therefore, there are significant disadvantages in terms of cost and manufacturing difficulty.

[0028] 2, when the main surface of second housing 114 is viewed in a plane from the Y direction, it is preferable that conductive member 108 is positioned so that the entirety of conductive member 108 overlaps with motor 107. In other words, when the main surface of second housing 114 is viewed in a plane from the Y direction, it is preferable that conductive member 108 does not protrude from motor 107. This is to reduce the installation space for motor module 400 within the electronic device and increase the degree of freedom in arranging motor module 400 within the electronic device.

[0029] The conductive member 108 is 100 mm 3 ] may be a small amount.

[0030] Furthermore, the non-conductive elastic member 111 may be conductive. Furthermore, the non-conductive plate-like member 110 and the non-conductive plate-like member 113 may be conductive. [Example]

[0031] (Example 1 and Comparative Example 1) To confirm the above-mentioned effects, the results of radiated noise simulation are shown below. The radiated noise was calculated using MW-STUDIO, an electromagnetic field analysis software from CST.

[0032] FIG. 4 is a schematic diagram showing a portion of the motor module used in electromagnetic field analysis. The first housing 301 was a conductive flat plate measuring 1000 mm in width (X direction), 1200 mm in length (Y direction), and 1 mm in height (Z direction). A substrate 303 measuring 100 mm in width, 70 mm in length, and 1.6 mm in height was placed on top of the first housing 301, and a second housing 314 measuring 90 mm in width, 1 mm in length, and 170 mm in height was placed on top of the first housing 301. The second housing 314 had a bent portion, which was located 12 mm above the first housing 301 and measured 30 mm in length and 1 mm in height. The height of the spacer 302 was 10 mm. The GND pattern of the substrate 303 and the second housing 314 were connected by a cable 306, which was a wiring member and consisted of four two-phase drive signal lines each 40 cm long. Cable 306 runs parallel to first housing 301 at a height of 9.8 mm from first housing 301, and is bent vertically at a position 6.5 cm from second housing 314, where it is connected to the second housing. Cable 306 has a cross-sectional structure in which a rectangular copper piece with sides of 0.48 mm is covered with polyvinyl chloride having a thickness of 0.2 mm.

[0033] A GND pattern measuring 97 mm wide and 67 mm long is arranged on substrate 303, and is electrically connected to first housing 301 via spacer 302. A Gaussian pulse of 1 V is output as a drive signal at the connection between the GND pattern on substrate 303 and cable 306. The circuit shown in Fig. 5 is connected as an equivalent circuit of the motor at the connection between cable 306 and second housing 314.

[0034] Figure 5 shows only two cables per phase; for a two-phase system with four cables, the same circuit is connected to the other phase. In the circuit shown in Figure 5, the inductance 401 is 9 nH, the resistance 402 is 4.65 Ω, the capacitance 403 is 8 pF, the inductance 404 is 50 nH, the resistance 405 is 12 Ω, the resistance 406 is 5 kΩ, the inductance 407 is 0.6 mH, the resistance 408 is 50 Ω, the inductance 409 is 9 nH, the resistance 410 is 4.65 Ω, the capacitance 411 is 8 pF, the inductance 412 is 50 nH, the resistance 413 is 12 Ω, the resistance 414 is 400 Ω, and the resistance 415 is 400 Ω. This simulation model was created to simulate the electrical characteristics of a 56 mm stepping motor manufactured by Nidec Servo. Note that inductance 401, resistance 402, resistance 406, inductance 407, resistance 408, inductance 409, and resistance 410 simulate the electrical characteristics of the motor windings. Capacitance 403, inductance 404, resistance 405, capacitance 411, inductance 412, and resistance 413 simulate the electrical characteristics of the motor and second housing 314 when no conductor other than the screw is sandwiched between the conductive screw and the motor. Resistors 414 and 415 simulate the electrical characteristics of a conductor other than the screw sandwiched between the conductive screw and the motor. Since one element is assigned to each cable to simulate the electrical characteristics of the conductive material, in the case of four two-phase cables, there are four elements connected in parallel, and the combined resistance value is equivalent to 1 / 4 of the resistance value of one element. For example, a resistance element of 400 [Ω] simulates a conductor other than the screw of 100 [Ω].

[0035] Comparative Example 1 had the same configuration as Example 1, except that the motor equivalent circuit did not have resistors 414 and 415. Resistors 414 and 415 simulate the electrical characteristics of a conductor sandwiched between the conductive screw and the motor, and therefore represent a state in which no conductor is present.

[0036] Fig. 6 is a graph showing the results of electromagnetic field analysis of radiation noise at a position 3 [m] away from Example 1 and Comparative Example 1. The horizontal axis of the graph is frequency [MHz], and the vertical axis is field strength [dBμV / m]. The solid line shows the results of Example 1, and the dashed line shows the results of Comparative Example 1. It can be seen from Fig. 6 that the peak of radiation noise that occurred at a frequency of 50 [MHz] in Comparative Example 1 was reduced by 13 [dB] in Example 1.

[0037] Next, we investigated the effect of radiated noise reduction on the resistance of the conductor. The graph in Figure 7 compares the results at a frequency of 50 MHz, where the radiated noise peaked. The horizontal axis represents the conductor's resistance (Ω), and the vertical axis represents the reduction effect (dB). When a 10 Ω conductor was simulated using four 40 Ω resistors in parallel, a reduction effect of 17 dB was achieved. However, as the resistance increased, the reduction effect gradually decreased. When a 500 Ω conductive material was simulated using four 2000 Ω resistors in parallel, the reduction effect was reduced to 6 dB. Furthermore, when a 1000 Ω conductor was simulated using four 4000 Ω resistors in parallel, the reduction was confirmed to be less than 5 dB. Therefore, we concluded that a conductor resistance of 500 Ω or less is preferable.

[0038] (Example 2 and Comparative Example 2) Regarding Example 2, only the differences from Example 1 will be described. Example 2 is assumed to be implemented using a different motor than Example 1. Example 2 has a different motor equivalent circuit than Example 1. The following are the settings: inductance 401 is 12.75 [nH], resistance 402 is 7.65 [Ω], capacitance 403 is 8 [pF], inductance 404 is 30 [nH], resistance 405 is 12 [Ω], resistance 406 is 6 [kΩ], inductance 407 is 0.3 [mH], resistance 408 is 90 [Ω], inductance 409 is 12.75 [nH], resistance 410 is 7.65 [Ω], capacitance 411 is 8 [pF], inductance 412 is 30 [nH], resistance 413 is 12 [Ω], resistance 414 is 400 [Ω], and resistance 415 is 400 [Ω]. This simulation model was created to mimic the electrical characteristics of a 42mm stepping motor manufactured by Nidec Servo.

[0039] Comparative Example 2 had the same configuration as Example 2, except that the motor equivalent circuit did not have resistors 414 and 415. Resistors 414 and 415 simulate the electrical characteristics of a conductor different from the screw sandwiched between the conductive screw and the motor, and therefore represent a state in which there is no conductor.

[0040] Fig. 8 is a graph showing the results of electromagnetic field analysis of radiation noise at a position 3 [m] away from Example 2 and Comparative Example 2. The horizontal axis of the graph is frequency [MHz], and the vertical axis is field strength [dBμV / m]. The solid line shows the results of Example 2, and the dashed line shows the results of Comparative Example 2. It can be seen from Fig. 8 that the peak of radiation noise that occurred at a frequency of 50 [MHz] in Comparative Example 2 was reduced by 13 [dB] in Example 2.

[0041] Next, we investigated the effect of radiated noise reduction on the resistance of the conductor. The graph in Figure 9 compares the results at a frequency of 50 MHz, where the radiated noise peaked. The horizontal axis represents the conductor's resistance (Ω), and the vertical axis represents the reduction effect (dB). When a 10 Ω conductive material was simulated using four 40 Ω resistors in parallel, a reduction effect of 16 dB was achieved. However, as the resistance increased, the reduction effect gradually decreased. When a 500 Ω conductive material was simulated using four 2000 Ω resistors in parallel, the reduction effect was reduced to 6 dB. Furthermore, when a 1000 Ω conductive material was simulated using four 4000 Ω resistors in parallel, the reduction effect was confirmed to be less than 5 dB. Therefore, it was found that a conductor resistance of 500 Ω or less is preferable.

[0042] The above effects are not limited to the conditions and configurations examined here, and are similarly applicable to cases where the length, cross-sectional size, and height from the housing of the cable 306 are different.

[0043] The above-described embodiment can be modified as appropriate within the scope of the technical concept.

[0044] Furthermore, new matters may be added to at least one embodiment. The disclosure of this specification includes not only what is explicitly described in this specification, but also all matters that can be understood from this specification and the drawings attached hereto.

[0045] The present disclosure includes the following:

[0046] (Section 1) A motor; a motor driver that drives the motor; a wiring member that electrically connects the motor and the motor driver; a non-conductive elastic member that damps vibrations of the motor; a conductive housing; and a conductive member electrically connecting the motor and the housing.

[0047] (Section 2) Item 1. The electronic device according to item 1, further comprising a non-conductive first plate-shaped member connecting the housing and the elastic member.

[0048] (Section 3) 3. The electronic device according to item 2, wherein the conductive member includes a conductive screw that fixes the first plate-shaped member to the housing.

[0049] (Section 4) the motor has a conductive motor housing; the conductive member includes the screw and a conductive material different from the screw; Item 4. The electronic device according to item 3, wherein the conductor is provided between the motor housing and the screw.

[0050] (Section 5) Item 5. The electronic device according to item 4, wherein the resistance of the conductor is 500 [Ω] or less.

[0051] (Section 6) Item 6. The electronic device according to item 4 or 5, wherein the conductor is rubber or sponge.

[0052] (Section 7) 7. The electronic device according to any one of items 1 to 6, wherein the conductive member is disposed at a position overlapping the motor when viewed from above the main surface of the housing.

[0053] (Section 8) 8. The electronic device according to any one of items 1 to 7, wherein the electronic device is an image forming device that forms an image on a sheet. [Explanation of symbols]

[0054] 1000 Image forming equipment (electronic equipment) 101 First enclosure 102 Spacer 103 Substrate 104 Motor Driver 105 Connector 106 Wiring materials 107 Motor 108 Conductive materials 108 Conductors 108B screw 110 Plate-shaped member 111 Elastic member 112 screws 113 Plate-like members 114 Second enclosure 301 First enclosure 302 Spacer 303 Substrate 306 Wiring materials 314 Second Enclosure 401 Inductance 402 Resistance 403 capacity 404 Inductance 405 Resistance 406 Resistance 407 Inductance 408 Resistance 409 Inductance 410 Resistance 411 capacity 412 Inductance 413 Resistance 414 Resistance 415 Resistance

Claims

1. A motor; a motor driver that drives the motor; a wiring member that electrically connects the motor and the motor driver; a non-conductive elastic member that damps vibrations of the motor; a conductive housing; and a conductive member electrically connecting the motor and the housing.

2. The electronic device according to claim 1 , further comprising a non-conductive first plate member connecting the housing and the elastic member.

3. The electronic device according to claim 2 , wherein the conductive member includes a conductive screw that fixes the first plate-like member to the housing.

4. the motor has a conductive motor housing; the conductive member includes the screw and a conductive material different from the screw; The electronic device according to claim 3 , wherein the conductor is provided between the motor housing and the screw.

5. 5. The electronic device according to claim 4, wherein the resistance of the conductor is 500 [Ω] or less.

6. The electronic device according to claim 4 , wherein the conductor is rubber or sponge.

7. The electronic device according to claim 1 , wherein the conductive member is disposed in a position where the entire conductive member overlaps the motor when viewed from above the main surface of the housing.

8. 8. The electronic device according to claim 1, wherein the electronic device is an image forming device that forms an image on a sheet.

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