JP2008167596A - Electric device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electric device where destruction of a driving part can easily be prevented when back electromotive force occurs in a motor, in a state where prescribed voltage from a power supply is not supplied to the driving part. <P>SOLUTION: The electric device 101 is provided with the body part 104, a cover member 103 and an interlocking switch 105. The body part 104 has the motor 125, the motor driving part 124 and a power wiring R1. The cover member 103 can assume an open attitude for exposing an inner part of the body part 104 and a close attitude for separating the inner part of the body 104 from the outside. The interlocking switch 105 is installed in the middle of the power wiring R1 and connects the power supply 121 and the motor driving part 124, when the cover member 103 takes the close attitude. The interlocking switch 105 disconnects the power supply 121 and the motor drive part 124 and connects a power wiring R1 of a motor drive part 124-side in the disconnected power wirings R1 to GND, when the cover member 103 takes the open attitude. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an electrical device.

  An image forming apparatus such as a printer or a multifunction peripheral includes various units for forming an image inside a main body, and the main body is covered with a cover member. Examples of the unit include an image forming unit that performs image formation, a paper transport path that transports paper to the image forming unit, and a medium-high voltage power source that supplies power to these units.

  In such an image forming apparatus, in order to ensure the safety of the user even when the cover member is opened during the operation of forming an image, the unit is connected to the power source in conjunction with the operation of opening the cover member. Some of them are provided with an interlock switch for cutting off the power supply wiring for supplying the electric power and stopping the operation of the unit.

  However, for example, when a paper jam occurs in the registration roller on the paper conveyance path, and the cover is opened and the paper is pulled out to eliminate the paper jam, the motor for rotating the registration roller rotates. . Then, a counter electromotive force is generated in the motor, and a current due to the counter electromotive force flows in the drive unit that drives the motor, and the drive unit may be destroyed.

On the other hand, an image forming apparatus as shown in FIG. 1 is known (Patent Document 1). The image forming apparatus 1 of FIG. 1 includes a power source 2, an interlock switch 3, a drive unit 4, and a motor 5 driven by the drive unit 4. The motor 5 rotates a unit of the image forming apparatus 1 such as a registration roller. The drive unit 4 includes a CPU 11, a driver 12, switching elements Q1 to Q4, and diodes D1 to D4. In particular, the CPU 11 controls the switching elements Q1 to Q4 in the driving unit 4 to be turned off when the cover member is opened and the interlock switch 3 is turned off.
JP 2006-208502 A

  However, since CPU11 which concerns on patent document 1 performs control which turns off switching element Q1-Q4 when a cover member is opened, control will become complicated.

  In general, the switching elements Q1 to Q4 in the drive unit 4 include, as shown in FIG. 1, for example, the drive unit 4 due to the counter electromotive force generated in the motor 5 when the motor 5 stops suddenly. Diodes D1 to D4 for preventing destruction are connected in parallel. As a result, when the predetermined voltage output from the power supply 2 is supplied to the power supply wiring V1 ′ on the drive unit 4 side, the diode D1 even if the back electromotive force exceeds the withstand voltage of the drive unit 4. , D3 can clip a voltage corresponding to the back electromotive force from the motor 5 applied to the drive unit 4 with a predetermined voltage. And the electric current by a counter electromotive force flows through the diodes D1 and D3. However, when the interlock switch 3 is turned off and the power supply wiring V1 is disconnected, the predetermined voltage from the power supply 2 is not supplied to the power supply wiring V1 'on the drive unit 4 side. When a back electromotive force is generated in the motor 5 in this state, the diodes D1 to D4 cannot clip the back electromotive force with a predetermined voltage. Therefore, even if the CPU 11 turns off the switching elements Q1 to Q4, if the back electromotive force exceeds the withstand voltage of the drive unit 4, the drive unit 4 may be destroyed.

  Therefore, the present invention provides an electrical device such as an image forming apparatus that can easily prevent the destruction of the drive unit when a back electromotive force is generated in the motor in a state where a predetermined voltage from the power source is not supplied to the drive unit. The purpose is to provide equipment.

  The electric device according to the first aspect includes an electric device main body, a cover member, and an interlock switch. The electric device main body includes a motor, a drive unit that drives the motor, and power supply wiring that supplies a predetermined voltage output from the power source to the drive unit. The cover member can take an open posture that exposes the inside of the electric device body and a closed posture that separates the inside of the electric device body from the outside. The interlock switch is provided in the middle of the power supply wiring, and connects the power supply and the drive unit so that a predetermined voltage is supplied to the drive unit when the cover member takes the closed posture. The interlock switch disconnects the connection between the power source and the drive unit so that a predetermined voltage is not supplied to the drive unit when the cover member is in the open posture, and the drive unit side of the disconnected power supply wiring Connect the power supply wiring to GND.

  According to this electrical device, when the cover member is open, the power supply wiring on the drive unit side is connected to GND. At this time, if the user unexpectedly rotates the motor or drives the motor, a counter electromotive force is generated in the motor, and the drive unit is in a direction opposite to the current that flows normally (on the power supply wiring side). Although current flows, this current flows into GND through the power supply wiring. Therefore, even when a counter electromotive force is generated in the motor with the cover member open, a current due to the counter electromotive force exceeding the withstand voltage of the drive unit flows into the drive unit to prevent the drive unit from being destroyed. be able to.

  An electric device according to a second aspect is the electric device according to the first aspect, wherein the drive unit includes a switching element and a diode. The switching element is turned on or off to generate a drive signal for driving the motor. The diode is connected in parallel to the switching element.

  As a result, for example, when a back electromotive force is generated in the motor with the interlock switch turned off, the current due to the back electromotive force flows through the diode without flowing through the switching element in the drive unit, and passes through the diode to the power supply wiring side. Flowing. Therefore, even when a counter electromotive force is generated in the motor, it is possible to prevent the switching element in the drive unit from being destroyed.

  According to the electric device of the present invention, even if a counter electromotive force is generated in the motor in a state where a predetermined voltage from the power source is not supplied to the drive unit, it is possible to easily prevent the drive unit from being destroyed.

(1) Configuration FIG. 2 is an external view of an image forming apparatus 101 in which the electrical apparatus according to the present embodiment is employed. The image forming apparatus 101 is a multifunction machine model having functions as a copying machine, a printer, a facsimile machine, and a scanner. The image forming apparatus 101 in FIG. 2 includes a document cover 102, a cover member 103, a main body 104, an interlock switch 105, and a paper feed cassette 106.

[Original cover]
The document cover 102 is for pressing a document placed on a document placement table (not shown) provided in a portion of the main body 104 facing the document cover 102 and can be opened and closed with respect to the document placement table. Is attached to the main body 104.

[Cover member]
The cover member 103 is attached to the front portion of the main body portion 104 so as to be rotatable about the end portion 103 a of the cover member 103 with respect to the main body portion 104, and has an open posture that exposes the inside of the main body portion 104. A closed posture in which the inside of the main body 104 is separated from the outside can be adopted.

  Further, the cover member 103 is provided with a protruding member 105a. More specifically, as shown in FIG. 3, the protruding member 105 a protrudes toward the inside of the main body 104 with respect to the cover member 103, and when the cover member 103 takes a closed posture, The cover member 103 is provided so as to correspond to the position.

[Main body]
As shown in FIG. 2, the main body unit 104 includes a photosensitive drum 111, a paper conveyance path 112, a registration roller 113, a transfer belt 114, a fixing device 115, and the like. An electrostatic latent image is formed on the surface of the photosensitive drum 111 based on the image data. The paper transport path 112 transports the paper in the paper feed cassette 106 to the registration rollers 113. The registration roller 113 controls the timing at which the sheet sent from the sheet conveyance path 112 is sent to the transfer belt 114. The transfer belt 114 transfers the image onto the sheet sent from the sheet conveyance path 112. The fixing device 115 fixes the image transferred on the paper.

  Further, as shown in FIG. 4, the main body 104 according to the present embodiment includes a 24 V power supply 121, a 5 V power supply 122, power supply wirings R 1 and R 2, GND wirings G 1 and G 2, a CPU 123, a motor driving unit 124, and a motor 125. .

  The 24V power supply 121 and the 5V power supply 122 generate a DC voltage of 24V and 5V, for example, using an AC voltage supplied from a commercial power supply outside the image forming apparatus 101, for example.

  The power supply wiring R <b> 1 connects the 24V power supply 121 and the motor drive unit 124, and supplies the 24V DC voltage output from the 24V power supply 121 to the motor drive unit 124. Further, the power supply wiring R1 is branched in the middle, and supplies a DC voltage of 24V to other loads. Here, examples of other loads include a drive unit (not shown) for driving a motor (not shown) as a drive source of the photosensitive drum 111. The power supply wiring R <b> 2 connects the 5V power supply 122 and the CPU 123, and supplies the CPU123 with a DC voltage of 5V output from the 5V power supply 122.

  The GND wiring G1 is a GND wiring for a DC voltage of 24V, and extends from the 24V power supply 121 toward the motor drive unit 124 and other loads. The GND wiring G2 is a GND wiring for a DC voltage of 5V and extends from the 5V power supply 122 toward the CPU 123.

  The CPU 123 controls each unit of the image forming apparatus 101 such as the transfer belt 114 and the fixing device 115 when a DC voltage of 5 V is supplied via the power supply line R2.

  The motor driving unit 124 drives the motor 125 when a DC voltage of 24 V is supplied via the power supply wiring R1. As shown in FIG. 5, the motor drive unit 124 includes a CPU 124a, a driver 124b, and an output circuit 124c.

  The CPU 124a controls the driver 124b. More specifically, the CPU 124a determines drive signals SU and SV for driving the motor 125, and outputs instructions for generating the drive signals SU and SV to the driver 124b.

  The driver 124b receives gate signals Gu, Gx, and G for turning on and off bipolar transistors Q101 to Q104 (described later) in the output circuit 124c so that the drive signals SU and SV determined by the CPU 124a are output from the output circuit 124c. Gv and Gy are generated and output to the output circuit 124c.

  The output circuit 124c includes bipolar transistors Q101 to Q104 (corresponding to switching elements, hereinafter simply referred to as transistors) and diodes D101 to D104 connected in parallel to the transistors Q101 to Q104. The transistors Q101 and Q102, Q103 and Q104 are connected in series between the power supply line R1 and the GND line G1, respectively. The diodes D101 and D103 are connected so as to short-circuit the transistors Q101 and Q103, respectively, and the diodes D102 and D104 are connected so as to short-circuit the transistors Q102 and Q104, respectively. More specifically, the diodes D101 and D103 are connected so that the power supply wiring R1 'side becomes a cathode, and the diodes D102 and D104 are connected so that the GND wiring G1 side becomes an anode. In the output circuit 124c having such a configuration, the gate signals Gu, Gx, Gv, and Gy output from the driver 124b are applied to the gate terminals of the transistors Q101 to Q104, so that the transistors Q101 to Q104 are turned on and off. The drive signals SU and SV are generated. The generated drive signals SU and SV are output to the motor 125 via the output terminals NU and NV of the motor drive unit 124.

  The motor 125 is a rotational drive source of the registration roller 113 and rotates based on drive signals SU and SV output from the motor drive unit 124. Here, in the present embodiment, as shown in FIG. 5, the motor 125 is a two-phase motor having a drive coil (not shown). Examples of the motor 125 include a brushless motor, a sensorless motor, and a direct current motor.

(Interlock switch)
As shown in FIG. 4, the interlock switch 105 is provided in the middle of the power supply wiring R <b> 1, and switches the voltage applied to the power supply wiring R <b> 1 ′ on the motor drive unit 124 side in accordance with the attitude that the cover member 103 can take. .

  More specifically, when the cover member 103 is in the closed position, the 24V power supply 121 and the motor drive unit 124 are connected so that a 24V DC voltage is supplied to the power supply wiring R1 ′ on the motor drive unit 124 side. To do. When the cover member 103 is in the open position, the interlock switch 105 cuts off the connection between the 24V power source 121 and the motor drive unit 124 so that a 24V DC voltage is not supplied to the motor drive unit 124. The power supply wiring R1 ′ on the motor driving unit 124 side is connected to the GND wiring G1. As a result, when the cover member 103 is in the open posture, the GND voltage, that is, about 0 V is applied to the power supply wiring R1 'on the motor driving unit 124 side.

  Here, as the type of the interlock switch 105, for example, an electromagnetic lock type constituted by an actuator and a solenoid, a magnet type which is turned on when a magnetic field of the magnet is detected by a sensor, a push type which is turned on when pressed directly, and the like are given. However, in this embodiment, a case where a push-down interlock switch is used is taken as an example. That is, in this embodiment, as shown in FIG. 3, when the cover member 103 changes from a closed state to an open state, for example, the protruding member 105 a of the cover member 103 is separated from the interlock switch 105. Thereby, the interlock switch 105 switches the connection path of the power supply wiring R1 'from the output side of the 24V power supply 121 to the GND wiring G1 side.

[Paper cassette]
The paper feed cassette 106 can store paper, and is provided in two stages below the main body 104 as shown in FIG.

(2) Operation Next, the operation of the image forming apparatus 101 according to the present embodiment will be described with reference to FIGS. 6 and 7 are diagrams for explaining the state of the interlock switch 105 and the direction in which the current flows when the cover member 103 takes each posture. 6 and 7, the main body 104, the cover member 103, the interlock switch 105, the 24V power supply 121, the output circuit 124c of the motor driving unit 124, the motor 125, and various wirings R1 and G1 are extracted from the image forming apparatus 101. It expresses.

  First, as shown in FIG. 6, it is assumed that the cover member 103 is in a closed state, that is, a closed posture. In this case, the interlock switch 105 is pushed down by the protruding member 105a of the cover member 103, and the power supply wiring R1 ′ on the motor drive unit 124 side is connected to the output side of the 24V power supply 121 (that is, the power supply wiring R1 on the 24V power supply 121 side). '') Is connected. As a result, the 24 V DC voltage output from the 24 V power supply unit 121 is supplied to the motor drive unit 124. When the motor 125 rotates in this state, the current is output from the 24V power supply 121 through the power supply wiring R1 ″ on the 24V power supply 121 side, the interlock switch 105, and the power supply wiring R1 ′ on the motor drive section 124 side. It flows to the circuit 124c. Next, this current flows to GND through the upper transistor Q101 in the output circuit 124c, the motor 125, the lower transistor Q104 in the output circuit 124c, and the GND wiring G1 (arrow A in FIG. 6). Here, FIG. 6 shows a case where the transistors Q101 and Q104 are on and the transistors Q102 and Q103 are off.

  In addition, when the cover member 103 is closed and a DC voltage of 24 V is supplied to the power supply wiring R1 ′ of the motor drive unit 124, for example, a load is applied to the motor 125 and a drive coil (not shown) in the motor 125 is provided. Suppose that a back electromotive force is generated. In this case, the generated back electromotive force is applied to the output terminals NU and NV of the motor drive unit 124. However, since a DC voltage of 24V is supplied to the power supply wiring R1 ′ on the motor drive unit 124 side, the motor drive The voltage applied to the output terminals NU and NV of the unit 124 is clipped to a value close to the voltage output from the 24V power source 121 by the upper diodes D101 and D103 in the output circuit 124c. More specifically, the voltage applied to the output terminals NU and NV is obtained by adding a DC voltage of 24 V to a value according to the diode characteristics of the diodes D101 and D103 (approx. 24.7 V when the diode is approximated by 0.7 V). ). Then, the current flowing into the output circuit 124c of the motor drive unit 124 via the output terminals NU and NV of the motor drive unit 124 due to the counter electromotive force flows through the diodes D101 and D103 without flowing through the transistors Q101 to Q104. It flows into the 24V power supply 121 via the interlock switch 105.

  Next, a case where a paper jam occurs when the image forming apparatus 101 is performing a printing operation with the registration roller 113 sandwiching a sheet fed from the sheet feeding cassette 106 will be described. It is assumed that the user using the image forming apparatus 101 first opens the cover member 103 in order to eliminate the paper jam.

  As shown in FIG. 7, when the cover member 103 is in an open state, that is, in an open posture, the protruding member 105 a of the cover member 103 is separated from the interlock switch 105. Then, the interlock switch 105 cuts off the connection between the power supply wiring R1 ″ on the 24V power supply 121 side and the power supply wiring R1 ′ on the motor drive section 124 side, and connects the power supply wiring R1 ′ on the motor drive section 124 side to the GND wiring. Connect to G1. As a result, the voltage of GND, that is, about 0 V is applied to the motor driving unit 124 through the power supply wiring R1 '. In this embodiment, when the cover member 103 is opened, the driver 124b in the motor driving unit 124 stops the output of the gate signals Gu, Gx, Gv, Gy. That is, when the cover member 103 is opened, the gate signals Gu, Gx, Gv, and Gy are not applied to the transistors Q101 to Q104 in the output circuit 124c in the motor driving unit 124.

  Next, it is assumed that the user pulls out the jammed paper in order to remove the jammed paper at the position of the registration roller 113.

  When the sheet jammed at the registration roller 113 is pulled out by the user, a load is applied to the registration roller 113 and the registration roller 113 rotates. Then, the motor 125 that is a rotational drive source of the registration roller 113 also rotates, and a back electromotive force is generated in a drive coil (not shown) in the motor 125. The counter electromotive force is applied to the output terminals NU and NV of the motor driving unit 124. Since the power supply wiring R1 ′ on the motor driving unit 124 side is connected to the GND wiring G1, the current due to the counter electromotive force is Without flowing through Q101 to Q104, the current flows to GND through the output terminals NU and NV of the motor driving unit 124, the upper diodes D101 and D103 in the output circuit 124c, and the power supply wiring R1 ′ (arrow B in FIG. 7). As a result, the phenomenon in which the transistors Q101 to Q104 are destroyed due to the occurrence of a back electromotive force exceeding the breakdown voltage of the transistors Q101 to Q104 is suppressed.

  In addition, since the power supply line R1 ′ on the motor drive unit 124 side is connected to GND through the GND line G1, the voltage supplied to the motor drive unit 124 through the power supply line R1 ′ rises due to the influence of the back electromotive force. The phenomenon is less likely to occur.

(3) Effects According to the image forming apparatus 101 according to the present embodiment, when the cover member 103 is open, the interlock switch 105 includes the power supply wiring R1 ″ on the 24V power supply 121 side and the power supply wiring on the motor drive unit 124 side. The connection to R1 ′ is cut off, and the power supply wiring R1 ′ on the motor driving unit 124 side is connected to the GND wiring G1. In this case, if the user unexpectedly rotates and drives the motor 125 by removing paper jammed in the registration rollers 113, a back electromotive force is generated in the motor 125, and a current that flows through the motor driving unit 124 during normal time is generated. Current flows in the opposite direction (that is, the power supply wiring R1 ′ side). However, this current does not flow through the transistors Q101 to Q104 in the output circuit 124c in the motor driving unit 124, but GND through the output terminals NU and NV, the upper diodes D101 and D103 in the output circuit 124c, and the power supply wiring R1 ′. Flow into. As described above, even if a current due to the counter electromotive force flows through the motor drive unit 124, the power supply line R1 ′ on the motor drive unit 124 side is connected to the GND, and therefore the motor 124 is in a state where the cover member 103 is open. Even if a back electromotive force is generated, a current caused by a back electromotive force exceeding the withstand voltage of the motor drive unit 124 flows into the motor drive unit 124, and the transistors Q101 to Q104 in the motor drive unit 124 are destroyed. Can be prevented.

  In addition, since the power supply line R1 ′ on the motor drive unit 124 side is connected to GND through the GND line G1, the voltage supplied to the motor drive unit 124 through the power supply line R1 ′ rises due to the influence of the back electromotive force. The phenomenon is less likely to occur.

<Other embodiments>
(A) In the above embodiment, when the cover member 103 is opened, the driver 124b in the motor driving unit 124 outputs the gate signals Gu, Gx, Gv, and Gy to the transistors Q101 to Q104 in the output circuit 124c. However, the present invention is not limited to this. The driver 124b may output gate signals Gu, Gx, Gv, Gy for turning off the transistors Q101 to Q104.

  (B) Although the case where the switching element included in the motor driving unit 124 is a bipolar transistor has been described as an example in the above embodiment, the switching element may be other than the bipolar transistor. Other types include MOS transistors and insulated gate bipolar transistors.

  (C) In the above embodiment, the cover member 103 in the front portion of the main body 104 of the image forming apparatus 101 has been described as an example. However, the present invention is not limited to this. For example, the present invention can be applied to a cover member at the side portion of the main body portion 104.

  The electrical apparatus of the present invention can be applied to finishers and the like in addition to various types of copiers, printers, and facsimile machines, and multifunctional image forming apparatuses that have a scanner function in addition to these functions. That is, the electrical device of the present invention can be applied to any device provided with a cover member that covers the inside of the main body and provided with an interlock switch in order to ensure the safety of the user. .

1 is a diagram illustrating a configuration of a conventional image forming apparatus. FIG. 2 is a diagram schematically illustrating an appearance and an internal configuration of the image forming apparatus according to the embodiment. FIG. 3 is a top view of the image forming apparatus according to the present embodiment. The motor drive part inside a main-body part which concerns on this embodiment, a power supply, and the connection diagram of a motor. The figure which showed the inside of the motor drive part which concerns on this embodiment in detail. The figure which showed the path | route of the electric current supplied with a motor when the cover member which concerns on this embodiment was closed. The figure which showed the path | route of the electric current which flows through the inside of a motor drive part by the counter electromotive force which a motor produced when the cover member which concerns on this embodiment opened.

Explanation of symbols

101 Image forming apparatus 103 Cover member 104 Main body part 105 Interlock switch 113 Registration roller 124 Motor drive part 124a CPU
124b Driver 124c Output circuit 125 Motor R1 Power supply wiring Q101 to Q104 Bipolar transistors D101 to D104 Diodes

Claims (2)

An electric device main body having a motor, a driving unit that drives the motor, and a power supply wiring that supplies a predetermined voltage output from a power source to the driving unit;
A cover member capable of adopting an open posture for exposing the inside of the electric device main body and a closed posture for separating the inside of the electric device main body from the outside;
An interlock switch that is provided in the middle of the power supply wiring and connects the power supply and the drive unit so that the predetermined voltage is supplied to the drive unit when the cover member takes a closed position; With
The interlock switch disconnects the connection between the power source and the drive unit so that the predetermined voltage is not supplied to the drive unit when the cover member is in the open posture, and the power supply wiring that is disconnected Of these, an electric device that connects the power supply wiring on the drive unit side to GND.   The electric device according to claim 1, wherein the driving unit includes a switching element that generates a driving signal for driving the motor by turning it on or off, and a diode connected in parallel to the switching element.

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