JP2017017813A - Electronic circuit and image formation device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the problems when an electromotive force is generated in a motor while power is not supplied thereto, without requiring a complex configuration, while suppressing cost increase as much as possible.SOLUTION: An electronic circuit includes a power supply line R1 for supplying power to a motor 501 from a power supply 56, an interlock switch 57 interlocked with opening/closing of a cover provided in the apparatus body, a cover open/close detector 53, a control unit 10 performing control according to the detection results from the cover open/close detector 53, and a comparator 55 for comparing the voltage values at both ends of a body diode 522 in which a voltage drop occurs when an electromotive force is generated in the motor 501 while power is not supplied thereto (cover open state). When a determination is made that a voltage drop is occurring by the comparator 55, the comparator 55 outputs a signal indicating cover open to a control section 100. The control section 100 maintains a switch mechanism 52 in a state not supplying power to the motor 501, regardless of the detection results from the cover open/close detector 53.SELECTED DRAWING: Figure 3

Description

  The present invention relates to an electronic circuit and an image forming apparatus, and more particularly to a technique for preventing a malfunction when an electromotive force is generated in a motor in a state where power is not supplied.

  In the image forming apparatus, the conveyance roller conveys the recording paper by the driving force supplied from the motor, and the image forming unit forms an image on the conveyed recording paper. In this image forming apparatus, when the recording paper is jammed in the conveyance path, that is, when a jam occurs, the operator opens the main body cover to expose the internal mechanism, and removes the recording paper jammed in the conveyance path. At this time, the interlock switch is turned off with the opening of the main body cover, the power supply to the motor is cut off, and the power cut-off detection circuit (cover open / close detection unit) detects the power cut-off to detect the CPU (Central Processing). (Unit), the operation of each mechanism of the image forming apparatus is stopped.

  In addition, today, a mechanism for transmitting a driving force from the motor to the conveying roller in the image forming apparatus uses a one-way clutch without providing a bidirectional clutch from the viewpoint of cost reduction, or a mechanism without a clutch. Sometimes used. In this case, during the jam processing, the operator pulls out the recording paper jammed in the conveyance path from the conveyance path, the conveyance roller that has sandwiched the recording sheet rotates, and the motor rotates by following this, the motor is A counter electromotive force may be generated by operating as a generator.

  As described above, when the back electromotive force is generated in the motor during the jam processing, and the current flows through the power supply line due to the back electromotive force, the cover open / close detection unit that detects the opening / closing of the main body cover is closed. An erroneous detection is performed, and based on the detection result, the CPU causes a malfunction such as causing each mechanism of the image forming apparatus to resume a normal operation. As a result, for example, although the main body cover is open, the CPU causes the display unit to display an erroneous display that the main body cover is closed, which makes the operator feel uncomfortable. Examples of methods for solving such a problem include the following (1) to (7).

  (1) A time lag (for example, about several seconds) is provided before the closing of the cover is detected so that the closing of the cover is not detected during the time when the electromotive force of the motor is generated.

  (2) The electromotive force generated by the motor is consumed by a predetermined device, for example, a light source that neutralizes the photosensitive drum.

  (3) A diode is provided in parallel with the interlock switch, and the electromotive force generated by the motor is regenerated to the power source (see Patent Documents 1 and 2 below).

  (4) A diode for preventing backflow is provided on a power supply line that supplies power from a power source to the motor.

  (5) A current detector for detecting the current flowing through the motor is provided, and an abnormality of the motor is detected from the magnitude of the detected current (see Patent Document 3 below).

  (6) When an electromotive force is generated in the motor, an electromotive current generated by the generated electromotive force is passed to a common potential (ground) (see Patent Document 4 below).

  (7) The interlock switch that interlocks with the opening and closing of the cover is set to 3 poles, and when the cover is opened, both ends of the motor are short-circuited using this 3 pole interlock switch (see Patent Document 5 below).

JP 2008-164999 A JP 2010-028952 A JP 7-123583 A JP 2008-199707 A JP 2010-2331036

  However, the above (1) to (7) have the following problems.

  In (1), even when the cover is actually closed, the cover is treated as being open for a while. For example, “cover open” is displayed on the display unit even though the cover is actually closed. Control may be performed, which may cause the operator to feel uncomfortable.

  (2) is effective when the power consumed is larger than the power generated by the motor, but there is not always a power consumption circuit exceeding the generated power. For example, depending on how the paper is pulled out, a large amount of power may be generated.

  In the case of (3), a diode capable of flowing a relatively large current is required. A diode capable of flowing a large current is not cheap, leading to an increase in cost.

  In the case of (4), the cost is increased for the same reason as in (3) above. Further, since power is consumed even in a normal use state where the cover is closed, there is a waste and a new problem of heat generation due to power consumption arises.

  In the case of (5), the resistor used as the current detector is not cheap and leads to an increase in cost.

  In the case of (6), a switching circuit is required to cause an electromotive current generated by the generated electromotive force to flow to the common potential. The switching circuit must be able to handle a relatively large current, which is expensive and increases costs.

  In the case of (7), there is a problem that the three-pole interlock switch is expensive, leading to an increase in cost.

  The present invention has been made in view of the above circumstances, and prevents a problem in the case where an electromotive force is generated in a motor in a state where power is not supplied by suppressing cost increase as much as possible without requiring a complicated configuration. With the goal.

An electronic circuit according to one aspect of the present invention includes a power supply line that supplies power from a power source to a motor,
A power cut-off switch that cuts off the power supply line when a cover provided on a device body on which the electronic circuit is mounted is opened, and connects the power supply line to the motor when the cover is closed;
A cover opening / closing detection unit for detecting opening / closing of the cover from the magnitude of the current flowing through the power supply line;
A power supply control circuit having a body diode and a switch mechanism that is provided between the power supply and the motor in the power supply line and switches power supply and non-supply from the power supply to the motor;
A control unit that controls switching between the power supply and non-supply by the power supply control circuit according to a detection result by the cover opening / closing detection unit;
A comparison unit for comparing voltage values at both ends of the power supply control circuit,
When the comparison result by the comparison unit indicates a voltage drop at both ends of the power supply control circuit, the control unit causes the power supply control circuit to be connected to the motor regardless of the detection result by the cover open / close detection unit. The power is not supplied.

An image forming apparatus according to one aspect of the present invention includes the electronic circuit described above.
A transport roller for transporting paper for forming an image,
The motor is a drive source for rotating the transport roller.

  According to the present invention, when an electromotive force is generated in the motor when power from the power source is not supplied to the motor by the power supply control circuit (in a state where the cover is opened), the power is supplied by the comparison unit. If the voltage value at both ends of the control circuit is compared and a voltage drop occurs, the control unit maintains the power supply control circuit in a state in which power is not supplied to the motor regardless of the detection result by the cover open / close detection unit. .

  As a result, according to the present invention, even when the main body cover of the device main body is opened and jam processing is performed, even if the drive motor of the motor unit generates back electromotive force, for example, erroneous control or malfunction due to back electromotive force generation And a normal interlock function can be secured. Further, since a general-purpose comparator can be applied to the comparison unit, an increase in cost can be suppressed.

1 is a schematic partial cross-sectional front view showing the structure of an image forming apparatus equipped with an electronic circuit according to an embodiment of the present invention. 2 is a functional block diagram schematically illustrating a main internal configuration of the image forming apparatus. FIG. FIG. 2 is a diagram illustrating an electronic circuit mounted on the image forming apparatus.

  Hereinafter, an electronic circuit and an image forming apparatus according to an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a schematic partial cross-sectional front view showing the structure of an image forming apparatus equipped with an electronic circuit according to an embodiment of the present invention.

  An image forming apparatus 1 according to an embodiment of the present invention is a multifunction machine having a plurality of functions such as a copy function, a printer function, a scanner function, and a facsimile function. The image forming apparatus 1 includes an apparatus body 11 including an operation unit 47, an image forming unit 12, a fixing unit 13, a paper feeding unit 14, a document feeding unit 6, and a document reading unit 5.

  The operation unit 47 receives instructions such as an image forming operation execution instruction and a document reading operation execution instruction from the operator for various operations and processes that can be executed by the image forming apparatus 1, and displays operation guidance and the like to the operator. The display unit 473 is provided.

  A case where a document reading operation is performed in the image forming apparatus 1 will be described. An original image fed by the original document feeding unit 6 or an image of the original document placed on the original document placing glass 161 is optically read by the original reading unit 5 including the reading mechanism 163, and image data is generated. To do. Image data generated by the document reading unit 5 is stored in a built-in HDD (Hard Disk Drive), a network-connected computer, or the like.

  A case where an image forming operation is performed in the image forming apparatus 1 will be described. The image forming unit 12 is fed from the paper feeding unit 14 based on image data generated by the document reading operation, image data stored in the built-in HDD, image data received from a computer connected to the network, and the like. A toner image is formed on a sheet P as a recording sheet.

  The transfer unit 120 includes an intermediate transfer belt 125, a driving roller 125a, a driven roller 125b, and a primary transfer roller 126 on which a toner image is transferred to the outer peripheral surface thereof.

  The intermediate transfer belt 125 is stretched between the driving roller 125 a and the driven roller 125 b, is driven by the driving roller 125 a in contact with the peripheral surface of the photosensitive member 121, and runs endlessly in synchronization with the photosensitive member 121. To do.

  Next, a case where color printing is performed will be described. The magenta image forming unit 12M, the cyan image forming unit 12C, the yellow image forming unit 12Y, and the black image forming unit 12Bk of the image forming unit 12 are respectively configured as the image data. Based on the image composed of color components, a toner image is formed on the photosensitive drum 121 by charging, exposing, and developing processes, and the toner image is transferred onto the intermediate transfer belt 125 by the primary transfer roller 126.

  The toner images of the respective colors (black, yellow, cyan, and magenta) transferred onto the intermediate transfer belt 125 are superimposed on the intermediate transfer belt 125 with the transfer timing adjusted to form a color toner image.

  The secondary transfer roller 210 passes a color toner image formed on the surface of the intermediate transfer belt 125 from the paper supply unit 14 through the conveyance path 190 at a nip N between the intermediate transfer belt 125 and the driving roller 125a. This is transferred onto the conveyed paper P. The above description is for color printing. In the case of monochrome printing, the yellow, cyan, and magenta photoconductors 121 are not used, and only the black photoconductor 121 is used. The

  The fixing unit 13 fixes the toner image on the paper P by thermocompression bonding, and the paper P on which the color image has been formed is discharged to the discharge tray 151.

  The paper feeding unit 14 includes a plurality of paper feeding cassettes and a pickup roller 145 for picking up recording paper stored in each paper feeding cassette, and is a recording paper having a size specified by an instruction from an operator or the like. The corresponding pickup roller 145 is rotationally driven so as to pick up the sheet, and the designated recording paper is conveyed toward the nip portion N.

  Next, the main internal configuration of the image forming apparatus 1 will be described. FIG. 2 is a functional block diagram showing the main internal configuration of the image forming apparatus 1.

  The image forming apparatus 1 includes a control unit 10, a document feeding unit 6, a document reading unit 5, an image forming unit 12, an image memory 32, an HDD 92, a fixing unit 13, an electronic circuit 500 (FIG. 3), an operation unit 47, and facsimile communication. Unit 71, network interface unit 91, and motor unit 50. Components similar to those of the image forming apparatus 1 shown in FIG. 1 are denoted by the same reference numerals, and detailed description thereof is omitted here.

  The motor unit 50 includes a motor 501 and a drive circuit (driver) that drives the motor 501. The motor 501 is a driving source that applies a rotational driving force to each rotating member such as the transport roller pair 19 (FIG. 1) and other image forming units 12, for example. The rotational driving force of the motor 501 is transmitted to each rotating member via a gear (not shown). In the present embodiment, a mechanism that uses a one-way clutch or does not provide a clutch is employed as a mechanism that transmits driving force from the motor 501 to each of the rotating members.

  The switch mechanism (power supply control circuit) 52 includes an FET (field effect transistor) 521 and a body diode 522 shown in FIG. 3 to be described later, and is provided between the control unit 10 and the motor unit 50. The switch mechanism 52 switches between power supply and non-supply from the power source to the motor 501 in accordance with a voltage signal output from the control unit 100 of the control unit 10.

  The cover opening / closing detection unit 53 detects opening / closing of a body cover (not shown) that is disposed on the front surface, side surface, or the like of the image forming apparatus 1. The cover open / close detection unit 53 opens and closes the main body cover according to an on state and an off state of an interlock switch 57 (FIG. 3) that switches between supply and non-supply of power to a motor unit 50 from a power source 56 (FIG. 3) described later. Is detected.

  The comparison unit 55 includes a comparator (FIG. 3) to be described later, and compares the voltages at both ends of the FET 521 and the body diode 522 constituting the switch mechanism 52 to determine whether or not a voltage drop has occurred in the switch mechanism 52. to decide. Hereinafter, it is referred to as a comparator 55.

  The control unit 10 includes a CPU, a RAM (Random Access Memory), a ROM (Read Only Memory), and a dedicated hardware circuit, and includes a control unit 100 that controls the overall operation of the image forming apparatus 1. ing. When power is supplied from the power source 56 to the motor unit 50 by the interlock switch 57 that is turned on when the main body cover is closed, the control unit 100 normally operates each mechanism of the image forming apparatus 1.

  Further, when processing a jam occurring inside the image forming apparatus 1 or replacing toner, the operator opens the main body cover to expose the recording paper jam portion. At this time, the main body cover is opened. Then, the interlock switch 57 is turned off, and power is not supplied from the power source 56 to the motor unit 50. At this time, the control unit 100 stops the operation of each mechanism of the image forming apparatus 1. That is, in the image forming apparatus 1, the interlock function works when the main body cover is open. The control unit 100 performs control to display the open / close state of the main body cover on the display unit 473.

  FIG. 3 is a diagram illustrating an electronic circuit mounted on the image forming apparatus 1. The same components as those of the image forming apparatus 1 shown in FIG. 2 are denoted by the same reference numerals, and detailed description thereof is omitted here.

  The electronic circuit 500 includes a power supply line R1, an interlock switch 57, a cover open / close detection unit 53, a switch mechanism 52, a control unit 100, and a comparator 55.

  A motor 501 constituting the motor unit 50 supplies a driving force to a conveyance roller pair 19 (FIG. 1) that conveys a recording sheet on which an image is formed. The motor unit 50 is connected to the power source 56 via the power supply line R1. The interlock switch 57 is provided in the middle of the power supply line R <b> 1 that connects the motor unit 50 and the power source 56. The interlock switch 57 is interlocked with the opening / closing of the main body cover. When the main body cover is opened, the interlock switch 57 is turned off to shut off the power supply line R1. When the main body cover is closed, the interlock switch 57 is turned on. The power supply line R1 between the units 50 is connected. The interlock switch 57 is an example of a power cut-off switch in the claims.

  The FET 521 constituting the switch mechanism 52 (FIG. 2) is a switch that controls driving of the motor 501. That is, the FET 521 is provided between the power supply 56 and the motor unit 50 in the power supply line R1 and switches between supply and non-supply of power from the power supply 56 to the motor 501. The control unit 100 (FIG. 2) of the control unit 10 controls ON (power supply state) / OFF (power non-supply state) of the FET 521. When the control unit 100 applies a voltage to the gate G of the FET 521, a current flows from the drain D to the source S, the FET 521 is turned on, and power is supplied to the motor 501 from the power supply 56. The switch mechanism 52 is further provided with a body diode 522 as shown in FIG.

  The cover open / close detection unit 53 is connected to the power supply line R1 and detects opening / closing of the cover based on the magnitude of the current flowing through the power supply line R1. The control unit 10 and the cover open / close detection unit 53 are connected by a signal line L1. When the main body cover is opened, the interlock switch 57 is opened, and the power supply line R1 is cut off, the input voltage from the power supply line R1 to the cover open / close detection unit 53 decreases. On the other hand, when the main body cover is closed, the interlock switch 57 is closed, and the power supply line R1 is established, the input voltage from the power supply line R1 to the cover open / close detection unit 53 increases. The cover open / close detection unit 53 detects the opening of the main body cover when the input voltage (current flowing through the power supply line R1) decreases below a threshold value, and detects the closing of the main body cover otherwise.

  The cover opening / closing detection unit 53 outputs a High signal indicating the opening of the cover to the control unit 100 via the signal line L1 when detecting the opening of the main body cover, and detects the closing of the main body cover via the signal line L1. A low signal indicating closure of the cover is output to the control unit 100. When the control unit 100 receives the High signal from the cover open / close detection unit 53, it applies a voltage to the gate G of the FET 521, causes a current to flow from the drain D to the source S, turns on the FET 521, and turns on the FET 521. Power is supplied to 501. On the other hand, when the control unit 100 receives the Low signal from the cover opening / closing detection unit 53, the control unit 100 does not apply a voltage to the gate G of the FET 521, and does not flow current from the drain D to the source S, thereby turning off the FET 521. The power is not supplied from the power source 56 to the motor 501. Further, when receiving a High signal from the main cover opening / closing detection unit 53, the control unit 100 causes the display unit 473 to display a message indicating that the main body cover is open. When receiving a Low signal from the cover open / close detection unit 53, the control unit 100 causes the display unit 473 to display a message indicating that the main body cover is closed.

  The non-inverting input (+) terminal of the comparator 55 is connected to the anode side (the motor unit 50 side of the power supply line R1) of the body diode 522, and the inverting input (−) terminal is the cathode side (power) of the body diode 522. Connected to the power supply 56 side of the supply line R1. The output terminal of the comparator 55 is connected to the signal line L 1, and the output from the comparator 55 is input to the control unit 100.

  A high signal is output from the output terminal of the comparator 55 when the voltage input to the non-inverting input terminal is higher than the voltage input to the inverting input terminal, and the voltage input to the non-inverting input terminal is When the voltage is not higher than the voltage input to the inverting input terminal, the Low signal is output.

  That is, in the state where the FET 521 supplies power from the power source 56 to the motor 501, no current flows through the body diode 522 connected to both ends of the FET 521. Therefore, the voltage on the cathode side of the body diode 522 is the anode side voltage. The voltage is not lower than the voltage, and a low signal is output from the comparator 55.

  On the other hand, an electromotive force is generated in the motor 501 in a state where the FET 521 is not supplying the electric power from the power source 56 to the motor 501 (the cover is opened and the interlock switch 57 is opened). When the current from the motor 501 flows through the power supply line R1, the current flows through the body diode 522. Therefore, the voltage on the cathode side of the FET 521 becomes lower than the voltage on the anode side, causing a voltage drop. High signal is output.

  Here, when the output from the comparator 55 is a Low signal, that is, when the comparison result by the comparator 55 does not indicate the voltage drop, the control unit 100 follows the detection result by the cover opening / closing detection unit 53. As described above, the on / off (power supply state) / off (power non-supply state) of the FET 521 from the cover open / close detection unit 53 is controlled.

  On the other hand, when the output from the comparator 55 is a high signal, that is, when the comparison result by the comparator 55 indicates the voltage drop, the control unit 100 determines whether the FET 521 The voltage is not applied to the gate G, the FET 521 is turned off, and the power from the power source 56 is not supplied to the motor 501.

  For example, when the motor 501 is not supplied with power from the power source 56 (the body cover is opened and the interlock switch 57 is opened), the back electromotive force is generated in the motor 501 and the cover open / close detection unit 53 is covered. When erroneously detected as closed, the signal input from the cover opening / closing detection unit 53 to the control unit 100 is a low signal and the signal input from the comparator 55 to the control unit 100 is a high signal. However, at this time, as long as the control unit 100 receives the high signal from the comparator 55, the control unit 100 displays a message indicating that the main body cover is open on the display unit 473, and sends a low signal from the cover open / close detection unit 53. Even if it is received, a message indicating that the main body cover is closed is not displayed on the display unit 473.

  For example, the mechanism for transmitting the driving force from the motor 501 to the conveying roller 19 in the image forming apparatus 1 uses a one-way clutch without providing a bidirectional clutch from the viewpoint of cost reduction, or a mechanism without a clutch. Sometimes used. In this image forming apparatus 1, when the recording paper P is jammed in the conveyance path, that is, when a paper jam occurs, the operator opens the main body cover to expose the internal mechanism, and the recording jammed in the conveyance path 190. Remove the paper P. At the time of the jam processing, when the operator pulls out the recording paper P jammed in the transport path 190 from the transport path 190, the transport roller 190 sandwiching the recording paper P rotates, and the motor 501 rotates following the rotation. The motor 501 may operate as a generator to generate back electromotive force.

  As described above, when a counter electromotive force is generated in the motor 501 during the jam processing and a current flows through the power supply line R1 due to the counter electromotive force, the cover open / close detection unit 53 may erroneously detect that the cover is closed. However, according to the present embodiment, since a high signal is output from the comparator 55 to the control unit 100, the control unit 100 turns off the FET 521 regardless of the detection result by the cover opening / closing detection unit 53, and the power source 56. The power from is not supplied to the motor 501.

  Thus, according to the present embodiment, even when the motor 501 generates the counter electromotive force when the operator opens the main body cover of the image forming apparatus 1 and performs jam processing, the control by the generation of the counter electromotive force is performed. The erroneous control of the unit 100 and the malfunction of each operation mechanism are reduced, and a normal interlock function can be secured. Further, since a general-purpose comparator can be applied to the comparison unit 55, an increase in cost can be suppressed.

  Thus, problems that have occurred in the past, for example, it is necessary to detect the current flowing in the motor 501, a time lag that gives the operator a sense of incongruity occurs, and it is necessary to newly add a device that wastes power. In the present exemplary embodiment, it is possible to prevent a malfunction when an erroneous detection of the opening / closing of the main body cover of the image forming apparatus 1 occurs. Note that a circuit that compares the voltages at both ends of the body diode 522 may be replaced with a combination of transistors instead of the comparator 55.

  The present invention is not limited to the configuration of the above embodiment, and various modifications can be made. In the above-described embodiment, the multi-function device is described as an embodiment of the electronic circuit and the image forming apparatus according to the present invention. However, this is merely an example, and other electronic devices such as a printer, a copy machine, and the like. Other image forming apparatuses such as a printer or a facsimile machine may be used.

  Moreover, in the said embodiment, the structure and process which were shown by the said embodiment using FIG. 1 thru | or FIG. 3 are only one Embodiment of this invention, and are not the meaning which limits this invention to the said structure and process.

10 Control unit 52 Switch mechanism 521 FET
522 Body Diode 53 Cover Open / Close Detection Unit 55 Comparator 56 Power Supply 57 Interlock Switch 100 Control Unit 501 Motor L1 Signal Line R1 Power Supply Line

Claims (4)

A power supply line for supplying power from the power source to the motor;
A power cut-off switch that cuts off the power supply line when a cover provided on a device body on which the electronic circuit is mounted is opened, and connects the power supply line to the motor when the cover is closed;
A cover opening / closing detection unit for detecting opening / closing of the cover from the magnitude of the current flowing through the power supply line;
A power supply control circuit having a body diode and a switch mechanism that is provided between the power supply and the motor in the power supply line and switches power supply and non-supply from the power supply to the motor;
A control unit that controls switching between the power supply and non-supply by the power supply control circuit according to a detection result by the cover opening / closing detection unit;
A comparison unit for comparing voltage values at both ends of the power supply control circuit,
When the comparison result by the comparison unit indicates a voltage drop at both ends of the power supply control circuit, the control unit causes the power supply control circuit to be connected to the motor regardless of the detection result by the cover open / close detection unit. An electronic circuit that maintains no power.   The electronic circuit according to claim 1, wherein the comparison unit includes a comparator. An electronic circuit according to claim 1 or 2,
A transport roller for transporting paper for forming an image,
An image forming apparatus in which the motor is a drive source for rotating the transport roller. A display unit;
When the comparison result by the comparison unit indicates a voltage drop at both ends of the power supply control circuit, the control unit causes the power supply control circuit to be connected to the motor regardless of the detection result by the cover open / close detection unit. The image forming apparatus according to claim 3, wherein the image forming apparatus maintains a state in which power is not supplied and displays a message indicating that the cover is in an open state on the display unit.