JP2008009112A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus with a power supply device that supplies power to a load so that the operation of the load generating a rush current may be normally performed at any time. <P>SOLUTION: A current is supplied from an electric double-layer capacitor to the second load generating the rush current, and a charging current to the electric double-layer capacitor is controlled in accordance with the using current of a first load other than the second load. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an improvement in a power supply device that supplies power to a load such as a motor and a clutch provided in an image forming apparatus.

  In a multifunctional image forming apparatus such as an electrophotographic image forming apparatus, a large number of motors, clutches, and the like are used, and the value of a current supplied from a power source varies depending on the operation stage of the apparatus.

As a power supply apparatus that can cope with such a change in supply current value, Patent Document 1 proposes a power supply apparatus in which a current limiting circuit and an energy storage means are connected between a DC power supply and a load. This power supply device is adapted to cope with a load in which an inrush current is generated by a small power supply device by absorbing an inrush current that becomes a large current periodically by a current limiting circuit and an energy storage means. .
JP 2003-250228 A

  With the power supply device of Patent Document 1, it is not necessary to match the power supply capacity to the maximum inrush current assumed in the load, and the power supply device can be miniaturized.

  However, in Patent Document 1, the limit current value is set uniformly with reference to the maximum current. Therefore, when the power supply device of Patent Document 1 is used for an image forming apparatus, charging of the energy storage unit consumes current. There is a problem that the voltage of the energy storage means gradually decreases without catching up.

  For example, in the stapler, in the case of the process of binding 100 recording materials, the inrush current is large, but the generation period of the inrush current is long. On the other hand, in the case of processing for binding a small number of recording materials such as two sheets, the inrush current is moderate, but the cycle is short.

  Therefore, when a small number of sheets are bound in a short cycle, charging within the short cycle cannot catch up with current consumption, and the voltage of the energy storage means gradually decreases. For this reason, the stapler does not operate normally.

  An object of the present invention is to solve such a problem, that is, a problem in a conventional power supply device using energy storage means.

The object is achieved by the following invention.
1.
A first load unit, a second load unit, a power source, a current limiting circuit and an electric double layer capacitor;
The first load unit and the current limiting circuit are connected to an output of the power source, the electric double layer capacitor and the second load unit are connected to an output of the current limiting circuit, and the power source is connected to the first load unit. An image forming apparatus comprising a power supply device that is supplied with electric power and is supplied with electric power from the current limiting circuit and the electric double layer capacitor to the second load unit,
An image forming apparatus comprising control means for controlling a charging current for charging the electric double layer capacitor.
2.
2. The image forming apparatus according to claim 1, wherein the control unit controls the charging current according to a use current in the first load unit.
3.
The image forming apparatus according to 1 or 2, wherein the second load unit includes a stapler driving unit.
4).
The image forming apparatus according to any one of claims 1 to 3, wherein the control unit controls the charging current to change in accordance with an operation mode.
5.
An image can be formed in a single-sided mode or a double-sided mode, and the first load unit has a conveyance driving unit for conveying a recording material, and the control unit is configured to supply the charging current in the single-sided mode in the double-sided mode 5. The image forming apparatus according to item 4, wherein the current limiting circuit is controlled to be less than in the mode.
6).
6. The image forming apparatus according to claim 1, wherein the current limiting circuit outputs a linearly changing current in response to a command signal from the control unit.
7).
The image forming apparatus according to any one of claims 1 to 6, wherein the current limiting circuit outputs a current that changes in a plurality of stages in response to a command signal from the control unit.
8).
8. The image forming apparatus according to claim 1, further comprising a restriction release unit that bypasses the current limiting circuit and charges the electric double layer capacitor from the power source.
9.
A first load unit, a second load unit, a power source, a current limiting circuit and an electric double layer capacitor;
The first load unit and the current limiting circuit are connected to an output of the power source, the electric double layer capacitor and the second load unit are connected to an output of the current limiting circuit, and the power source is connected to the first load unit. An image forming apparatus comprising a power supply device that is supplied with electric power and is supplied with electric power from the current limiting circuit and the electric double layer capacitor to the second load unit,
An image forming apparatus comprising switching means for switching a charging current for charging the electric double layer capacitor.
10.
10. The image forming apparatus according to 9, wherein the switching unit switches whether the current limiting circuit performs current limitation or not.

  According to the present invention, it is possible to secure a large charging current for the electric double layer capacitor, and a situation where normal operation is hindered due to insufficient charging of the electric double layer capacitor is avoided.

  Hereinafter, the present invention will be described based on an embodiment of the present invention, but the present invention is not limited to the embodiment.

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

  The main control unit 100 of the image forming apparatus A is connected to the post-processing control unit 103 of the sheet post-processing apparatus FS via the communication unit 101.

  Above the image forming apparatus A, an image reading apparatus EX and an automatic document feeder DF are arranged.

  The image forming apparatus A includes an image forming unit 1, a fixing unit 9, and a paper transport system. The image forming unit 1 includes a charging unit 3, an image exposure unit (image writing unit) 4, a developing unit 5, a transfer unit 6, a charge removing unit 7 A, a separation claw 7 B, and a cleaning unit 8 disposed around the image carrier 2. Etc.

  The paper transport system circulates the paper S and the first transport path composed of the paper feed cassette 10, the first paper feed means 11, the second paper feed means 12, the transport means 13, the paper discharge means 14, and the manual paper feed means 15. It is composed of a second transport unit 17 (circulation refeed unit) that feeds paper again.

  The second transport unit 17 branches the paper S on which the image is formed by the image forming unit 1 before the paper discharge unit 14 by the transport path switching plate 16, transports the paper S along the circulation refeeding path, and circulates it. In the middle of the paper re-feeding path, the paper S is reversed by the reversing conveyance means and then re-fed to the image forming unit 1.

  The paper S sent out from the large-capacity paper feeding unit 18 of the large-capacity paper feeding device LT is fed to the second paper feeding unit 12.

  The document placed on the document table of the automatic document feeder DF is conveyed, an image on one or both sides of the document is read by the optical system of the image reading device EX, and is read by the image sensor CCD. The analog signal photoelectrically converted by the image sensor CCD is subjected to analog processing, A / D conversion, shading correction, image compression processing, etc. in an image processing unit (not shown), and then the image signal is sent to the image exposure means 4. send.

  In the image exposure unit 4, the output light from the semiconductor laser is irradiated onto the image carrier 2 of the image forming unit 1 to form a latent image. In the image forming unit 1, processes such as charging, exposure, development, transfer, separation, and cleaning are performed. An image is transferred by the transfer means 6 to the paper S fed from the paper feed cassette 10 and the large capacity paper feeder LT. The sheet S carrying the image is fixed by the fixing unit 9 and discharged from the sheet discharge unit 14 and sent to the sheet post-processing device FS.

  In double-sided image formation, the single-sided image-treated paper S sent to the second transport unit by the transport path switching plate 16 is reversed by the reverse transport unit 17 and then again after the double-sided image processing in the image forming unit 1. It is discharged from the paper means 14.

  The post-processing device FS includes a fixed paper discharge tray 30 from which the paper S is discharged when a small number of images are formed, a lift paper discharge tray 40 from which the paper S is discharged when a large number of images are formed, and a staple mode.

  FIG. 2 is a circuit diagram of an example of a power supply device in the image forming apparatus according to the embodiment of the present invention.

  In the figure, reference numeral 20 denotes a power source, which receives an AC current from the outside and outputs a constant DC voltage.

21 is a 1st load part, and has load 21A, 21B ..., such as a motor and a clutch.
22 is a 2nd load part, and has load 22A, 22B ..., such as a motor and a clutch.

  Reference numeral 23 denotes a current limiting circuit, which is composed of an FET and a capacitor as described in Patent Document 1, and outputs a current corresponding to a control signal to limit the upper limit of the current.

  Reference numeral 24 denotes an electric double layer capacitor, and 25 denotes a control means that controls the output current of the current limiting circuit 23.

  The first load unit 21 is a load that does not need to supply power from the electric double layer capacitor 24, and the second load unit 22 is a load that generates an inrush current, that is, a consumption current having a peak, and the electric double layer This is a load that needs to be supplied with power from the capacitor 24.

  The basic operation of the circuit of FIG. 2 will be described with reference to FIG.

  3A shows a change with time of the charging current of the electric double layer capacitor 24, and FIG. 3B shows a change with time of the discharge current of the electric double layer capacitor 24. FIG.

  The discharge current peaks Q <b> 1 and Q <b> 2 occur during the operation of the second load unit 22. This discharge current covers the inrush current generated in the second load. As a result of the discharge indicated by Q1 and Q2, the voltage between the terminals of the electric double capacitor 24 is lowered, so that the peak of the charging current in FIG.

  In charging, the upper limit is limited by the current limiting circuit 23. When the upper limit value due to the limitation is high, charging is performed with the current indicated by the peaks P1A and P2A, and when the upper limit value due to the limitation is low, the peak P1B. , P2B is charged with current.

  The charging time T2 when charging is performed at the peaks P1B and P2B is longer than the charging time T1 when charging is performed at the peaks P1A and P2A. In any case, the electric double layer capacitor 23 has a predetermined amount of charge. Accumulated.

  FIG. 4 shows the relationship between the operation of the load and the discharge current.

  FIG. 4A shows a case where the load unit 22 consumes a large current but the operation cycle D1 is long, and FIG. 4B shows a case where the load unit 22 consumes a moderate current but the operation cycle D2 is short. Show the case.

  In the case of FIG. 4 (a), the discharge amount at the discharge peak Q1, Q2 of the electric double layer capacitor 24 in one operation is large, but since the period D1 is long, the charging is completed before the second operation. The electric double layer capacitor 24 stores a predetermined amount of charge. As a result, discharge peaks Q1, Q2,... Having a constant height occur, and the second load portion 22 operates normally.

  On the other hand, in the case of FIG. 4B, the discharge amount of the electric double layer capacitor 24 in one operation is small, but since the operation cycle D2 is short, the electric double layer capacitor 24 is charged in the next operation. Does not complete.

  For this reason, in the operation of FIG. 4B, the peaks Q1, Q2... Gradually decrease in height and discharge amount, and as a result, the second load portion 22 does not operate normally or operates. Disappear.

  For example, when the second load portion 22 is a stapler, the inrush current value is large in the processing mode in which the number of sheets to be bound is large, such as 100 sheets, but the operation cycle is long, which hinders the operation. There is no. However, in the processing mode in which a small number of sheets, such as several sheets, are bound, since the operation cycle D2 is short, charging may not catch up, and the drive current value may gradually decrease and may not operate.

  In the present embodiment, in order to prevent such malfunction, the charging current of the electric double layer capacitor 24 is made variable so that the electric double layer capacitor 24 is always charged with a predetermined amount.

  The control means 25 controls the output current of the current limiting circuit 23 according to the current used in the first load unit 21. That is, when the use current value in the first load unit 21 is high, the output current of the current limit circuit 23 is decreased, and when the use current value in the first load unit 21 is low, the output current of the current limit circuit 23 is increased. To do. With this control, each unit of the image forming apparatus can be operated normally with limited power consumption.

  For example, the control unit 25 performs control to change the output current of the current limiting circuit 23 according to a mode in which the large capacity sheet feeding unit is used and a mode in which the large capacity sheet feeding unit is not used, or in a single-sided image forming mode and a double-sided image forming mode.

  Conventionally, the charging current value of the electric double layer capacitor 24 is set uniformly. And the value was set based on the maximum electric current which flows into load. For this reason, as described above, the charging current is insufficient and the discharge amount of the electric double layer capacitor 24 gradually decreases.

  By controlling the charging current by the control means 25, it becomes possible to increase the charging current value, and the above-described operation failure is eliminated.

  FIG. 5 is a flowchart of an example of such current control.

  When the image forming using the large-capacity paper feeding unit 18 (see FIG. 1) is performed (YES in STEP 1) and in the double-sided image forming mode (YES in STEP 2), the control unit 25 is the current limiting circuit 23. Is set to the lowest level (STEP 3).

  When the large-capacity paper feeding unit 18 is not used (NO in STEP 1), the output current of the current limiting circuit 23 is set to the maximum (STEP 4). In the case of single-sided image formation (YES in STEP 1 and no in STEP 2), the output current of the current limiting circuit 23 is set to an intermediate level (STEP 5).

  In such a control, the charging current value of the electric double layer capacitor 24 is not set by assuming the maximum current consumption of the image forming apparatus. If the current consumption is small, the charging current value of the electric double layer capacitor 24 is set. Is increased and charging is performed, so that the second load portion 22 operates normally.

  In addition to the control shown in FIG. 5, the output of the current limiting circuit 23 may continuously change linearly with respect to the command signal of the control means 25.

  FIG. 6 shows the discharge current of the load operation when the current control shown in FIG. 5 is performed. As shown in the figure, even in the load operation in the short cycle D2, the discharge current peaks Q1, Q2,... Are constant, and the load operation of the stapler and the like is normally performed.

  FIG. 7 is a circuit diagram of another example of the power supply device in the image forming apparatus according to the embodiment of the present invention.

  In this example, a bypass circuit 26 for bypassing the current limiting circuit 23 is provided, and the supply current to the electric double layer capacitor 24 and the load unit 22 is controlled by the control means 25 conducting / blocking the bypass circuit 26. . Thereby, the charging current to the electric double layer capacitor 24 is controlled at two levels.

  2 and 7 can be combined, and in the control of FIG. 5, the maximum current setting in STEP 4 can be conducted through the bypass circuit 26 of FIG. 6 to release the current limitation.

  In the embodiment described above, the supply current value to the current limiting circuit is controlled according to the operation mode of the image forming apparatus. However, the supply current value to the current limiting circuit is set according to the configuration of the image forming apparatus. It can also be configured to change.

  FIG. 8 is a circuit diagram of the power supply apparatus in the example of such an embodiment. The same parts as those in FIG. Reference numeral 27 denotes a changeover switch for selecting the current limiting circuit 23 and the bypass 26. The changeover switch 27 is operated according to the configuration of the image forming apparatus, and the output of the power source 20 is supplied to the electric double layer capacitor 24 and the second load unit 22 via the current limiting circuit 23 or bypassed. Supplied.

  For example, in an image forming apparatus equipped with a large-capacity paper feeding device, the power supply device is set with a current limit by the current limiting circuit 23, but the power supply device of an image forming apparatus without a large-capacity paper feeding device is a current limiting circuit. In the image forming apparatus equipped with a post-processing device having a stapler function, the power supply device is limited by the current limiting circuit 23, but is not equipped with a post-processing device. In the image forming apparatus, a configuration such as releasing the current limitation by the current limiting circuit 23 is possible.

  Furthermore, it is possible to variously change the degree of restriction depending on the configuration of the image forming apparatus as well as whether or not the restriction is released by the current limiting circuit.

1 is a diagram illustrating an overall configuration of an image forming apparatus according to an embodiment of the present invention. 1 is a circuit diagram of an example of a power supply device in an image forming apparatus according to an embodiment of the present invention. FIG. 3 is a diagram for explaining the operation of the circuit of FIG. 2. It is a figure which shows the relationship between the action | operation of load, and discharge current. It is a flowchart of an example of current control. FIG. 6 shows a discharge current for load operation when the current control shown in FIG. 5 is performed. FIG. FIG. 6 is a circuit diagram of another example of the power supply device in the image forming apparatus according to the embodiment of the present invention. It is a circuit diagram of the power supply device in the other example of embodiment.

Explanation of symbols

20 power supply 21 first load 22 second load 23 current limiting circuit 24 electric double layer capacitor 25 control means

Claims (10)

A first load unit, a second load unit, a power source, a current limiting circuit and an electric double layer capacitor;
The first load unit and the current limiting circuit are connected to an output of the power source, the electric double layer capacitor and the second load unit are connected to an output of the current limiting circuit, and the power source is connected to the first load unit. An image forming apparatus comprising a power supply device that is supplied with electric power and is supplied with electric power from the current limiting circuit and the electric double layer capacitor to the second load unit,
An image forming apparatus comprising control means for controlling a charging current for charging the electric double layer capacitor. The image forming apparatus according to claim 1, wherein the control unit controls the charging current in accordance with a current used in the first load unit. The image forming apparatus according to claim 1, wherein the second load unit includes a stapler driving unit. The image forming apparatus according to claim 1, wherein the control unit controls the charging current to change according to an operation mode. An image can be formed in a single-sided mode or a double-sided mode, and the first load unit has a conveyance driving unit for conveying a recording material, and the control unit is configured to transfer the charging current to the single-sided mode in the double-sided mode. The image forming apparatus according to claim 4, wherein the current limiting circuit is controlled to be less than in the mode. The image forming apparatus according to claim 1, wherein the current limiting circuit outputs a linearly changing current in response to a command signal from the control unit. The image forming apparatus according to claim 1, wherein the current limiting circuit outputs a current that changes in a plurality of stages in response to a command signal from the control unit. The image forming apparatus according to claim 1, further comprising a restriction releasing unit that bypasses the current limiting circuit and charges the electric double layer capacitor from the power source. A first load unit, a second load unit, a power source, a current limiting circuit and an electric double layer capacitor;
The first load unit and the current limiting circuit are connected to an output of the power source, the electric double layer capacitor and the second load unit are connected to an output of the current limiting circuit, and the power source is connected to the first load unit. An image forming apparatus comprising a power supply device that is supplied with electric power and is supplied with electric power from the current limiting circuit and the electric double layer capacitor to the second load unit,
An image forming apparatus comprising switching means for switching a charging current for charging the electric double layer capacitor. The image forming apparatus according to claim 9, wherein the switching unit performs switching between current limiting and non-current limiting by the current limiting circuit.

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