JP2012022202A - Image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To achieve both the safety of a load when a main power switch is turned off and the protection of a fixing device, with an inexpensive configuration.SOLUTION: A first power source voltage VCC_A and a second power source voltage VCC_B are output from a DC power source 101. The VCC_A is supplied to a control circuit 112, and the VCC_B is supplied to a second load driving circuit 114 for separating a pair of fixing rollers and a first load driving circuit 113 for driving other loads. The VCC_B supplied to the first load driving circuit 113 synchronizes with the turning off of a main power source switch 102, and is thereby immediately shut off by a relay 109. Upon reception of a signal 105 indicating the off-state of the main power source switch 102, the control circuit 112 separates the pair of fixing rollers 41 by the second load driving circuit 114, subsequently outputs a signal for turning off the relay 103 to stop the DC power source 101.

Description

  The present invention relates to control when a main power switch of an image forming apparatus is shut off.

  In the fixing device of the image forming apparatus, if the fixing roller and the pressure roller are left pressed for a long time without forming an image, the same position of the fixing roller is continuously pressed. The part that continues to be pressurized is deformed. Then, when image formation is performed again, there is a risk that a fixing failure will occur until the deformation of the fixing roller returns.

  Therefore, in Patent Document 1, a mechanism for separating the fixing roller and the pressure roller is provided, and after the power source of the image forming apparatus is turned off, the heat of the fixing device is converted into electric energy to operate the separation mechanism. It has become. According to this configuration, the separation mechanism can be operated even after the power of the image forming apparatus is shut off.

  However, in patent document 1, the mechanism for converting a thermal energy into an electrical energy is needed, and the cost of an apparatus will become high.

  Therefore, even if the main power switch of the image forming apparatus is turned off, it is conceivable that the power is maintained for a certain time and the power is turned off after the fixing roller is separated. However, from the viewpoint of safety, when the user turns off the main power switch, it is desirable to immediately cut off the power supply to the heater or the like.

JP-A-2005-122168

  Therefore, a circuit as shown in FIG. 5 can be considered. The first DC power supply 501 outputs a power supply VCC_A (5 V) for the control circuit 512. The second DC power source 504 outputs a power supply VCC_B (24 V) for driving a load such as a separation drive circuit 514 that operates the contact / separation motor 515 and other motors. When the main power switch 502 is turned on, the output from the first DC power supply 501 is input to the control circuit 512 via the state detection switch of the main power switch 502, and the control circuit 512 turns on the relay 503. Note that the three switches of the main power switch 502 are interlocked. Therefore, even if the main power switch 502 is turned off, AC power continues to be supplied to the first DC power source 501 via the relay 503. On the other hand, the AC power of the second DC power source 504 is cut off as soon as the main power switch is turned off. A direct current supply circuit 505 is provided so that the separated drive circuit 514 can operate when power is supplied from either the first direct current power source 501 or the second direct current power source 504.

  According to this configuration, when the main power switch 502 is turned on, the fixing roller is driven to be separated by the power from the second DC power supply 504. When the main power switch is turned off, the first DC power switch 502 is turned on. The fixing roller is driven to be separated by the power from the power source 501. After the separation operation of the fixing roller is completed, the control circuit 512 outputs a shutdown signal and turns off the relay 503 so that the AC power to the first DC power supply 501 is also cut off and the entire power supply of the image forming apparatus is turned off. To do.

  However, the separation / contact motor 515 and the separation drive circuit 514 for separating the fixing roller must operate with the power supply voltages of both the first DC power supply 501 and the second DC power supply 504. Therefore, the cost of the apparatus is increased as compared with a drive circuit that can be operated with an inexpensive single power source.

  In addition, it is necessary to separately supply AC power to each of the first DC power supply 501 and the second DC power supply 504. Therefore, cables 530 and 531 for performing AC power supply are necessary. However, since a cable used for AC power supply is generally more expensive than a DC power supply cable, this power supply cable also increases costs. There is a problem.

  In order to solve the above problems, an image forming apparatus of the present invention includes an image forming unit that forms a toner image on a sheet, and a pair of separable fixing rollers that fix the toner image formed on the sheet by the image forming unit. An image forming apparatus including: a DC power source that is supplied with power from an AC power source and outputs a first DC power source voltage and a second power source voltage; and is provided between the AC power source and the DC power source. The first power supply voltage is supplied from the DC power supply, and the image forming unit is supplied with a power switch that is turned on and off, a switch detection signal output unit that outputs a signal indicating an on and off state of the power switch A control circuit that controls the operation of the apparatus and controlled by a signal from the control circuit, and maintains the power supply from the AC power source to the DC power source even after the power switch is turned off. Holding means, connected to be supplied with the second power supply voltage from the DC power supply, and supplied with the second power supply voltage from the DC power supply, the first drive means for driving the load of the image forming apparatus And a second driving means for separating and abutting the pair of fixing rollers, and the second power supply voltage supplied to the first driving means in synchronization with the power switch being turned off. And the control circuit is configured to turn off the power switch from the switch detection signal output means, while maintaining the supply of the second power supply voltage to the second drive means. The fixing roller pair is separated by the second driving means in response to receiving a signal indicating the above.

  The image forming apparatus of the present invention is an image forming apparatus having an image forming unit for forming a toner image on a sheet and a pair of separable fixing rollers for fixing the toner image formed on the sheet by the image forming unit. A DC power source that is supplied with power from an AC power source and outputs a first power source voltage and a second power source voltage; and is provided between the AC power source and the DC power source, and is turned on and off. A power switch, a switch detection signal output means for outputting a signal indicating an on / off state of the power switch, and a control for controlling the operation of the image forming apparatus by being supplied with the first power voltage from the DC power source. A first relay connected in parallel with the power switch between the AC power source and the DC power source, and turned on and off by a signal from the control circuit; A first drive unit connected to be supplied with the second power supply voltage and driving a load of the image forming apparatus; and the second power supply voltage supplied from the DC power source to the first drive unit. And a second driving means for separating and contacting the pair of fixing rollers, and a power supply path for supplying the first power supply voltage to the first driving means, A second relay for supplying or cutting off the first power supply voltage to the first driving means in synchronization with ON and OFF of the power switch, and the control circuit includes the switch detection signal output means The fixing roller pair is separated by the second driving means in response to receiving a signal indicating that the power switch is turned off.

  According to the present invention, when the main power switch is turned off, it is possible to maintain a power source for performing the separating operation of the pair of fixing rollers while immediately shutting off the power supply to the load with an inexpensive configuration. Can be prevented, deformation of the fixing roller, and cost increase of the apparatus can be prevented.

Sectional view showing configuration of image forming apparatus The figure which shows the power supply structure of an image forming apparatus The figure which shows the contact / separation mechanism of a fixing roller pair Flow chart showing operation of control circuit The figure which shows an example of the power supply structure of an image forming apparatus

(First embodiment)
FIG. 1 is a schematic sectional view showing the overall configuration of an image forming apparatus to which the present invention is applied. The image forming apparatus includes an image reading unit 1R and an image output unit 1P. The image reading unit 1R optically reads a document image, converts it into an electrical signal, and transmits it to the image output unit 1P. The image output unit 1P includes four image forming units 10 (10a, 10b, 10c, and 10d) arranged in parallel, a paper feeding unit 20, an intermediate transfer unit 30, a fixing unit 40, a cleaning unit 50, and a control unit. Unit 80. The image forming units 10a, 10b, 10c, and 10d form black, cyan, magenta, and yellow toner images, respectively. Since the configuration of each image forming unit is the same, the yellow image forming unit 10d disposed on the most upstream side will be described.

  A drum-shaped electrophotographic photosensitive member as the first image bearing member, that is, a photosensitive drum 11d, is rotatably supported and rotated in the direction of the arrow in the figure. A primary charger 12d, an optical system 13d, a folding mirror 16d, a developing device 14d, and a cleaning device 15d are arranged in the rotational direction so as to face the outer peripheral surface of the photosensitive drum 11d. A charging high voltage (1 to 2 KV) is applied to the photosensitive drum 11d by the primary charger 12d, and the surface thereof is uniformly charged. Next, the optical system 13d irradiates the photosensitive drum 11d with a laser beam modulated in accordance with the recording image signal from the recording image signal output unit 1R via the folding mirror 16d, thereby forming an electrostatic latent image. . The electrostatic latent image is visualized by the developing device 14d containing black toner. The visualized toner image is applied with a transfer high pressure (1 to 2 KV) in the image transfer region Td, and is a belt-like intermediate transfer member as a second image carrier constituting the intermediate transfer unit 30, that is, an intermediate The image is transferred to the transfer belt 31. The toner remaining on the photosensitive drum 11d without being transferred to the intermediate transfer belt 31 is scraped off by the cleaning device 15d, and the drum surface is cleaned. The above-described process is performed by the image forming units 10c, 10b, and 10a, and yellow, magenta, cyan, and black toner images are transferred onto the intermediate transfer belt 31 in an overlapping manner.

  As the sheet feeding unit 20, cassettes 21 a and 21 b for storing sheets P and a manual feed tray 27 are provided. Further, pickup rollers 22a, 22b, and 26 for feeding the sheets P one by one from the cassettes 21a and 21b and the manual feed tray 27 are provided. The sheet P sent out from each pickup roller 22a, 22b, 26 is conveyed to the registration roller 25 (25a, 25b) by the pair of paper feed rollers 23. The registration roller 25 sends the sheet P to the secondary transfer region Te at a timing that matches the position of the toner image transferred to the intermediate transfer belt 31.

  The sheet P fed from the registration roller 25 is transferred with the toner image in the secondary transfer region Te and is conveyed to the fixing unit 40 by the conveying belt 43. The fixing unit 40 heats and presses the sheet P by a pair of fixing rollers 41 (41a and 41b) that can be separated to fix the toner image on the sheet P.

  The fixing rollers 41a and 41b are heated to a temperature required for fixing by a built-in heater (not shown). In addition, the structure which incorporated the heater only in the fixing roller 41a may be sufficient. Further, in order to widen the nip width of the fixing rollers 41a and 41b, a rubber layer is formed on the surface of each roller. The sheet P on which the toner image is fixed by the fixing unit 40 is discharged to the outside by the discharge rollers 44 and 45, and the image forming process is completed.

  FIG. 2 is a block diagram showing a power supply configuration of the image forming apparatus. A main power switch 102 of the image forming apparatus is provided between the commercial AC power supply 99 and the DC power supply 101. When the main power switch is turned on, AC power is supplied from the commercial AC power supply 99 to the DC power supply 101 via the power supply paths 110 and 130. When receiving power supply, the DC power supply 101 generates a first power supply voltage VCC_A (5 V) and supplies it to the control circuit 112. The main power switch 102 is provided with a detection switch 104 which is turned on / off in synchronization with the main power switch 102 and operates as a switch detection signal output means for detecting the on / off state of the main power switch 102. One terminal of the detection switch 104 is connected to VCC_A from the DC power supply 101, and the other terminal is connected to the control circuit 112 and input to the control circuit 112 as the switch detection signal 105. That is, when the main power switch 102 is turned on, the detection switch 104 is also turned on in synchronization, and the detection signal 105 has substantially the same potential as VCC_A. When the main power switch 102 is turned off, the detection switch 104 is also turned off in synchronization, and the detection signal 105 has a substantially zero potential. The control circuit 112 detects the on / off state of the main power switch 102 based on the detection signal 105 that changes in this way.

  A power supply path 111 is provided between the commercial AC power supply 99 and the DC power supply 101 in parallel with the path 110 via the main power switch 102. A relay 103 that is on / off controlled by the control circuit 112 is provided in the path 111. The control circuit 112 outputs a shutdown signal 106 (high level) to the transistor 121 when the operation is started by supplying the power supply voltage VCC_A. The transistor 121 functions as a relay driving element that turns on the relay 103, and turns on the relay 103 when a high-level shutdown signal is input. When the relay 103 is turned on, AC power is supplied from the commercial AC power source 99 to the DC power source 101 via the paths 111 and 130. Accordingly, the AC power is supplied to the DC power source 101 from two paths, and even if the main power switch 102 is turned off, the supply of AC power on the paths 111 and 130 is maintained until the relay 103 is turned off. The control circuit 112 includes a ROM and a CPU that store a control program and various data, and controls the image forming apparatus in accordance with information stored in the ROM.

  When the control circuit 112 receives a switch detection signal indicating that the main power switch 102 is turned off, the control circuit 112 executes an operation end process of the image forming apparatus, and switches the shutdown signal 106 to a low level as soon as the process is completed. As a result, the drive element 121 of the first relay and the first relay 103 are turned off, and the image forming apparatus is turned off. Note that as one of the operation end processing of the image forming apparatus, a separation operation of the fixing roller pair 41 described later is included.

  When AC power is supplied to the DC power supply 101 by turning on the main power switch 102, the DC power supply 101 generates a second power supply voltage VCC_B (24V) that is higher than the first power supply voltage. . That is, the DC power supply 101 generates two power supply outputs from one system of AC input and supplies them to the first load drive circuit 113 as the first drive means. The first load driving circuit 113 drives each load of the image forming apparatus. For example, the first load driving circuit 113 supplies high-voltage power to the motors 116 that rotate the respective driving units such as the photosensitive drum 11 and the primary charger 12. High-voltage power supplies 117, heaters 118 in the fixing unit 40, and the like. A second relay 109 is provided in the power supply path to the first load drive circuit 113. The second relay 109 is turned on / off by a drive signal 122 via the detection switch 104. That is, when the main power switch 102 is turned off, the power supply VCC_B from the DC power supply 101 to the first load driving circuit 113 is immediately cut off regardless of the operating state of the image forming apparatus. As a result, the loads of the image forming apparatus including the motors 116, the high voltage power supplies 117, and the heaters 118 are immediately turned off, so that the safety of the image forming apparatus is ensured.

  Further, the power output VCC_B is branched from the power supply path to the first load driving circuit 113 and is also supplied to the second load driving circuit 114 as the second driving means. Since the power supply path to the second load drive circuit 114 does not go through the second relay, even if the main power switch 102 is turned off, the power supply of VCC_B to the second load drive circuit 114 is maintained. That is, the second load driving circuit 114 drives the motor 119 for switching the fixing roller 41a and the pressure roller 41b in the fixing unit 40 to a contact state or a separation state in accordance with a control signal from the control circuit 112. . When the main power switch 102 is turned on, the fixing roller 41a and the fixing roller 41b are controlled to be in contact with each other. Therefore, when the sheet P passes through the fixing unit 40 during printing, the toner image placed on the sheet P is heated and pressed to be fixed.

  If the state in which the fixing roller 41a and the fixing roller 41b are in contact with each other with rotation stopped is continued for a long time, the rubber layer at the contact portion is deformed, and unevenness occurs when the sheet P is heated and pressed. May occur and image defects may occur. Therefore, when a predetermined time (for example, 8 hours) has passed while the fixing roller pair 41 is in contact with the rotation stopped, the fixing roller pair 41 is rotated by a predetermined phase to fix the fixing roller 41a to the fixing roller 41a. The position of contact with the roller 41b is shifted. The fixing roller pair 41 is rotationally driven by a motor connected to the first load driving circuit 113.

  On the other hand, when the power is not supplied to the control circuit 112 and the first load driving circuit 113, the contact position between the fixing roller 41a and the fixing roller 41b cannot be shifted. Therefore, when the main power switch 102 is turned off, the fixing roller pair 41 is brought into a separated state as an operation end process. Accordingly, it is possible to prevent the deformation of the fixing roller pair 41 due to the fixing roller pair 41 continuing to press the same position and the occurrence of image defects due to the deformation.

  The separation operation of the fixing roller pair 41 will be described with reference to FIG. 3A shows a state where the fixing roller pair 41 is not separated, and FIG. 3B shows a state where the fixing roller pair 41 is separated. When the eccentric cam 52 is at the position shown in FIG. 3A, the fixing rollers 41 a and 41 b are in contact with each other by the action of the pressure spring 51. When the motor 119 is driven and the eccentric cam 52 moves to the position shown in FIG. 3B, the pressure spring 51 is pulled downward in the figure, and the fixing roller 41b is separated from the fixing roller 41a. At this time, the sensor 53 is detecting the eccentric cam 52, and the control circuit 112 inputs the signal of the sensor 53 to recognize that the fixing roller pair 41 is separated. The fixing roller 41a may be moved instead of moving the fixing roller 41b.

  Next, the control of the control circuit 112 will be described using the flowchart of FIG. When the main power switch 102 is turned on and the control circuit 112 starts operating, the control circuit 112 sets the shutdown signal 106 to a high level (S1), and turns on the first relay driving element 121 and the first relay 103. As a result, AC power is supplied to the DC power supply 101 also from the AC power supply path 111. Therefore, even if the main power switch 102 is turned off by the user, the AC power supply to the DC power supply 101 is not cut off, and the supply of the power supply output VCC_A to the control circuit 112 and the power supply output to the second load driving circuit 114 are performed. The supply of VCC_B is continued.

  Thereafter, the control circuit 112 performs an initialization operation of the image forming apparatus (S2), and periodically monitors the switch detection signal 105 to determine whether or not the switch detection signal 105 becomes low level, that is, the main power switch 102. It is determined whether or not is turned off (S3). When the control circuit 112 detects that the detection signal 105 is at a low level, the control circuit 112 executes an operation end process of the image forming apparatus including the separation operation of the fixing roller pair 41 (S4). The operation end process includes a process for ending the writing if the storage device is writing. The control circuit 112 controls the second load driving circuit 114 to operate the motor 119 and separate the fixing roller pair 41. When the control circuit 112 determines that the operation end process including the separation process has ended (S5), the control circuit 112 sets the shutdown signal to a low level (S6). As a result, the first relay 103 is turned off, the supply of AC power to the DC power supply 101 is interrupted, and the power supply to the image forming apparatus is all turned off. At the same time as the main power switch 102 is turned off, the drive signal 122 of the first relay becomes low level, and the first relay 109 is turned off. As a result, the first load driving circuit 113 is turned off, and the high-output load connected to the first load driving circuit is immediately and safely cut off.

  If the switch detection signal 105 is at the high level in step S3, the control circuit 112 determines whether or not a predetermined time has elapsed since the rotation of the fixing roller pair 41 was stopped (S7). If the predetermined time has elapsed, the control circuit 112 causes the first load driving circuit 113 to operate a motor that rotates the fixing roller pair 41 by a predetermined amount (S8), and again monitors the state of the switch detection signal 105. . If the predetermined time has not elapsed, the control circuit 112 determines whether or not an image formation instruction has been issued (S9). If there is an instruction, the control circuit 112 executes an image formation operation (S10), and again detects a switch detection signal. 105 is monitored.

  In step S8, instead of rotationally driving the fixing roller pair 41, the fixing roller pair 41 may be separated. The switch detection signal 105 may be monitored not by the main routine but by periodic interrupt processing.

  According to this embodiment, even when the main power switch 102 is turned off at any timing, it is possible to immediately shut off the load such as the heater and ensure safety. Further, the separation process of the fixing roller pair 41 can be executed to prevent deformation of the fixing roller due to the fixing roller continuing to pressurize the same position, and occurrence of image defects due to the deformation.

  In addition, two AC power supply cables as shown in FIG. 5 are not required, and the cost of the cables can be reduced.

  Furthermore, since a drive circuit that can handle two types of DC power supply voltages as shown in FIG. 5 is not required and an inexpensive configuration that operates with only a single power supply can be achieved, the cost of the apparatus can be reduced. Can do.

101 DC power supply 102 Main power switch 103 First relay 104 Detection switch 109 Second relay 113 First load drive circuit 114 Second load drive circuit

Claims (4)

An image forming apparatus comprising: an image forming unit that forms a toner image on a sheet; and a pair of separable fixing rollers that fix the toner image formed on the sheet by the image forming unit.
A DC power source that is supplied with power from an AC power source and outputs a first power source voltage and a second power source voltage;
A power switch provided between the AC power source and the DC power source and turned on and off;
Switch detection signal output means for outputting a signal indicating on and off states of the power switch;
A control circuit that is supplied with the first power supply voltage from the DC power supply and controls the operation of the image forming apparatus;
Maintaining means for maintaining power supply from the AC power source to the DC power source even after the power switch is turned off, controlled by a signal from the control circuit;
A first drive unit connected to be supplied with the second power supply voltage from the DC power supply and driving a load of the image forming apparatus;
A second driving means connected to be supplied with the second power supply voltage from the DC power supply, and separating and abutting the fixing roller pair;
In synchronization with the power switch being turned off, the second power supply voltage supplied to the first drive means is cut off while the second power supply voltage supplied to the second drive means is maintained. Blocking means;
And the control circuit separates the pair of fixing rollers by the second driving unit in response to receiving a signal indicating that the power switch is turned off from the switch detection signal output unit. An image forming apparatus.   The image forming apparatus according to claim 1, wherein the control circuit stops the supply of power from the AC power source to the DC power source by the maintaining unit after the fixing roller pair is separated. An image forming apparatus comprising: an image forming unit that forms a toner image on a sheet; and a pair of separable fixing rollers that fix the toner image formed on the sheet by the image forming unit.
A DC power source that is supplied with power from an AC power source and outputs a first power source voltage and a second power source voltage;
A power switch provided between the AC power source and the DC power source and turned on and off;
Switch detection signal output means for outputting a signal indicating on and off states of the power switch;
A control circuit that is supplied with the first power supply voltage from the DC power supply and controls the operation of the image forming apparatus;
A first relay connected in parallel with the power switch between the AC power source and the DC power source, and turned on and off by a signal from the control circuit;
A first drive unit connected to be supplied with the second power supply voltage from the DC power supply and driving a load of the image forming apparatus;
A second driving means connected to be supplied with the second power supply voltage supplied from the DC power source to the first driving means, and for separating and abutting the fixing roller pair;
Provided in a power supply path through which the first power supply voltage is supplied to the first drive means, and supplies the first power supply voltage to the first drive means in synchronization with turning on and off of the power switch. Or a second relay to shut off,
And the control circuit separates the pair of fixing rollers by the second driving unit in response to receiving a signal indicating that the power switch is turned off from the switch detection signal output unit. An image forming apparatus.   The image forming apparatus according to claim 3, wherein the control circuit turns off the first relay after the fixing roller pair is separated.

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