Image forming apparatus

Abstract

To prevent destruction of an electrolytic capacitor and restrict the height of the electrolytic capacitor.SOLUTION: An image forming apparatus comprises: a rectification circuit that rectifies a current supplied from a commercial power supply; a smoothing circuit that smooths a current output from the rectification circuit; and a determination unit that determines whether a voltage supplied from the commercial power supply is an overvoltage exceeding a threshold. The smoothing circuit has two electrolytic capacitors, and a switching unit being a switch that switches the electrolytic capacitor to be used according to output from the determination unit. The determination unit has a voltage detection circuit that detects a voltage value being the value of the voltage supplied from the commercial power supply, and a control circuit for switching that outputs a switching control signal for the switching unit based on the voltage value from the voltage detection circuit.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The present invention relates to an image forming apparatus.

Background Art

[0002] Conventionally, in an image forming apparatus (for example, a copier, a printer, a facsimile apparatus, and a device that combines these functions) equipped with a switching power supply having an electrolytic capacitor, a film capacitor or a ceramic capacitor is connected to a first electrolytic capacitor and an electrolytic capacitor is connected to a second electrolytic capacitor, respectively, in front of DC / DC converters in first and second power supply units. When it is detected by an AC voltage detection method that an overvoltage greatly exceeding the rated input voltage of the electrolytic capacitor is input, a technique is already known in which overvoltage protection of circuit components is achieved by switching the electrolytic capacitor to be used to the electrolytic capacitor mounted in the first power supply unit.

Summary of the Invention

Problems to be Solved by the Invention

[0003] In the prior art, two smoothing capacitors are respectively mounted in front of DC / DC converters in the first and second power supply units, and a film capacitor or a ceramic capacitor is selected for the first electrolytic capacitor and an electrolytic capacitor is selected for the second electrolytic capacitor. The components constituting the first power supply unit have higher withstand voltage characteristics than the components constituting the second power supply unit, and overvoltage protection of circuit components is realized by disconnecting the second power supply unit with a lower withstand voltage at the time of overvoltage detection.

[0004] However, to supply sufficient power to image forming equipment (such as photocopiers, printers, facsimile machines, and devices combining these functions) that generally form images using an electrophotographic process, a smoothing capacitor with a capacitance of 100 μF or more is required. Since the capacitance of film capacitors or ceramic capacitors is only a few μF at most, conventional technology cannot supply sufficient power to image forming equipment as described above. Therefore, it is necessary to implement electrolytic capacitors with a large capacitance instead of film capacitors or ceramic capacitors, but the larger the capacitance, the larger the electrolytic capacitor becomes, and there is a problem in particular that the vertical space required by the electrolytic capacitor becomes large.

[0005] Patent Document 1 discloses a configuration in which, for the purpose of overvoltage protection of circuit components of an image forming apparatus, two smoothing capacitors are mounted in front of the DC / DC converters in the first and second power supply units of the image forming apparatus. In this configuration, a film capacitor or ceramic capacitor with a higher voltage rating than the electrolytic capacitor mounted in the second power supply unit is selected for the capacitor in the first power supply unit, thereby disconnecting the second power supply unit with a lower voltage rating when voltage is detected, and performing overvoltage protection of the circuit components. However, this prior art involves switching the power supply circuit itself, and the selection of capacitors depends on the configuration of the power supply circuit, so the problem of the large vertical space required for the electrolytic capacitors has not been resolved.

[0006] The present invention has been made in view of the above, and aims to prevent the destruction of electrolytic capacitors and to limit the height of electrolytic capacitors. [Means for solving the problem]

[0007] To solve the above-mentioned problems and achieve the objective, the present invention provides an image forming apparatus equipped with a switching power supply having an electrolytic capacitor, comprising: a rectifier circuit for rectifying the current supplied from a commercial power supply; a smoothing circuit for smoothing the output current from the rectifier circuit; and a determination unit for determining whether the voltage supplied from the commercial power supply is an overvoltage exceeding a threshold; wherein the smoothing circuit comprises two electrolytic capacitors and a switching unit which is a switch for switching the electrolytic capacitor to be used according to the output of the determination unit; and the determination unit comprises a voltage detection circuit for detecting a voltage value which is the value of the voltage supplied from the commercial power supply, and a switching control circuit which outputs a switching control signal for the switching unit based on the voltage value from the voltage detection circuit. [Effects of the Invention]

[0008] According to the present invention, it is possible to prevent the destruction of electrolytic capacitors and to limit the height of electrolytic capacitors. [Brief explanation of the drawing]

[0009] [Figure 1] Figure 1 shows the configuration of an image forming apparatus according to an embodiment. [Figure 2] Figure 2 is a block diagram showing the configuration of the image forming apparatus according to the embodiment. [Figure 3] Figure 3 is a circuit diagram of the image forming apparatus according to the embodiment. [Figure 4] Figure 4 is a flowchart showing an example of a process performed by the image forming apparatus of the embodiment. [Figure 5] Figure 5 is a flowchart showing an example of a process performed by the image forming apparatus of the embodiment. [Modes for carrying out the invention]

[0010] An embodiment of the image forming apparatus 100 will be described in detail below with reference to the attached drawings.

[0011] Figure 1 shows the configuration of an image forming apparatus 100 according to an embodiment. The image forming apparatus 100 basically consists of a paper feeding unit 103, the main body of the image forming apparatus 100 104, a scanner (image reading device) 101, and an automatic document feeder (ADF) 102.

[0012] The main body 104 of the image forming apparatus 100 includes a tandem-type image forming unit 105, a registration roller 108 that supplies recording paper to the image forming unit 105 from the paper feeding unit 103 via a transport path 107, an optical writing device 109, a fixing and transport unit 110, and a double-sided tray 111.

[0013] The image-forming unit 105 has four photoreceptor drums arranged side by side, corresponding to the four YMCK colors, and around each photoreceptor drum 112 are image-forming elements including a charger, developer 106, transfer unit, cleaner, and static eliminator.

[0014] Furthermore, an intermediate transfer belt 113 is positioned between the transfer unit and the photoreceptor drum 112, stretched between the drive roller and the driven roller while being held between the nip of both.

[0015] In the tandem-type image forming apparatus 100 configured in this way, light is written to the photosensitive drum 112 corresponding to each color (Y, M, C, K), and each toner is developed in the developer unit 106. These are then primary-transferred onto the intermediate transfer belt 113 in the order of, for example, Y, M, C, K. After the four superimposed full-color image from the primary transfer is secondary-transferred onto recording paper, the paper is fixed and ejected to form a full-color image on the recording paper.

[0016] The image forming apparatus 100 described above has two operating states: standby operation state and print operation state. In the print operation state, the paper feeding unit 103, scanner (image reading device) 101 and automatic document transport device 102, tandem image forming unit 105, registration roller 108 that supplies recording paper via transport path 107, optical writing device 109, fuser and transport unit 110, and duplex tray 111 are all in operation. In the standby operation state, the operation of the image forming apparatus 100 is stopped.

[0017] FIG. 2 is a block diagram showing the configuration of the image forming apparatus 100 according to the embodiment. The power supply circuit of the power supply unit (switching power supply) of the image forming apparatus 100 includes a rectifier circuit 201, a smoothing circuit 202, a determination unit 203, and a switching unit 204. The switching unit 204 is included in the smoothing circuit 202.

[0018] The rectifier circuit 201 rectifies the supply current from the commercial power supply. The smoothing circuit 202 smooths the output current from the rectifier circuit 201. The determination unit 203 determines whether the supply voltage from the commercial power supply is an overvoltage exceeding a threshold value. When the determination unit 203 determines that it is an overvoltage, the switching unit 204 switches the electrolytic capacitor C (FIG. 3) to be used.

[0019] FIG. 3 is a circuit diagram of the image forming apparatus 100 according to the embodiment. The rectifier circuit 201 is constituted by a diode bridge.

[0020] The smoothing circuit 202 has two electrolytic capacitors C having different capacitances and rated input voltages for smoothing the output current from the rectifier circuit 201. The two electrolytic capacitors C are a first electrolytic capacitor C1 and a second electrolytic capacitor C2.

[0021] The voltage rectified by the diode bridge is smoothed using one of the electrolytic capacitors C switched according to a control signal from the determination unit 203 described later to generate a DC voltage from the AC voltage. The generated DC voltage is transformed by a DC / DC converter 205 and a switch and output to a drive load (drive system load) 206 and a control load (control system load) 207.

[0022] The two electrolytic capacitors C are such that the first electrolytic capacitor C1 is used during standby operation and printing, and the second electrolytic capacitor C2 is used during standby operation under overvoltage. Considering that generally the size of the electrolytic capacitor C increases in proportion to the rated input voltage and capacitance, for the first electrolytic capacitor C1, one that cannot withstand overvoltage but has a rated input voltage that satisfies the commercial power supply voltage and a large capacitance is selected, and for the second electrolytic capacitor C2, one that can withstand overvoltage and has a high rated input voltage and a capacitance lower than that of the first electrolytic capacitor C1 is selected. That is, the first electrolytic capacitor C1 has a first rated input voltage that satisfies the commercial power supply and a first capacitance, and the second electrolytic capacitor C2 has a second rated input voltage higher than the first rated input voltage and a second capacitance smaller than the first capacitance.

[0023] The determination unit 203 is composed of an AC voltage detection circuit (voltage detection circuit) 208 and an AC path switching control circuit (switching control circuit) 209. The AC voltage detection circuit 208 is composed of a transformer, a diode bridge, a low-pass filter, and a voltage follower circuit. First, the AC voltage is reduced by the transformer and then rectified by the diode bridge. The rectified DC voltage is stabilized by the low-pass filter and the voltage follower circuit, and then a voltage corresponding to the input voltage is output.

[0024] When a voltage is applied from a commercial power AC power supply, the voltage value applied is detected by the AC voltage detection circuit 208, and a voltage corresponding to the voltage value of the commercial power supply is output to the AC path switching control circuit 209 having a microcontroller or the like to perform overvoltage determination. If the voltage value input to the AC path switching control circuit 209 exceeds the overvoltage threshold value, overvoltage of the commercial AC power supply is detected, and a signal for switching the switch SW of the switching unit 204 described later is output.

[0025] The switching unit 204 has two switches SW that switch the electrolytic capacitor C to be used according to the output of the determination unit 203. The two switches SW are the first switch SW1 and the second switch SW2. The first switch SW1 and the second switch SW2 are switching elements that can be switched between open and closed by a signal from the determination unit 203. The first switch SW1 is mounted before the first electrolytic capacitor C1, and the second switch SW2 is mounted before the second electrolytic capacitor C2.

[0026] To account for the case where an overvoltage is input when power is turned on to the image forming apparatus 100, the state of the first switch SW1 and the second switch SW2 of the switching unit 204 when the power is not turned on is such that the first switch SW1 is OFF and the second switch SW2 is ON, thereby providing overvoltage protection for the electrolytic capacitor C when power is turned on.

[0027] Furthermore, the image forming apparatus 100 has a control unit 300 (Figure 3) that controls each part. The control unit 300 has a CPU 300a.

[0028] In this embodiment, the electrolytic capacitor C mounted on the power supply unit of the image forming apparatus 100 is protected from overvoltage by performing the following process (method).

[0029] Figure 4 is a flowchart showing an example of the process performed by the image forming apparatus 100 of the embodiment. As shown in Figure 4, the image forming apparatus 100 performs S1 to S17. That is, the image forming apparatus 100 performs the following processes.

[0030] <When the power cord is inserted into the image forming apparatus 100> To account for overvoltage due to errors, such as connecting a 200V power supply to a 100V image forming apparatus 100, a second electrolytic capacitor C2 is connected to protect against overvoltage when the power cord is inserted into the image forming apparatus 100.

[0031] <When the power button is pressed and power is supplied to the image forming apparatus 100> When the power button is pressed to start supplying power to the image forming apparatus 100, if the voltage detected by the AC voltage detection circuit 208 of the determination unit 203 is below the overvoltage threshold, the first electrolytic capacitor C1 is connected and standby and printing operations are performed. If the voltage detected by the AC voltage detection circuit 208 of the determination unit 203 is above the overvoltage threshold, the second electrolytic capacitor C2 is connected for overvoltage protection, and after transitioning to standby operation, an error is displayed on the operation unit 210 to notify the user and service personnel of the overvoltage abnormality. After transitioning to standby operation, printing operations cannot be performed. Voltage detection by the AC voltage detection circuit 208 continues even after transitioning to standby operation, and when the detected voltage drops below the overvoltage threshold, the capacitor used is switched to the first electrolytic capacitor and printing operations are resumed.

[0032] <When an overvoltage is input during standby or printing operation> If an overvoltage is input while the first electrolytic capacitor C1 is connected and standby or printing operation is in progress, the printing operation will be stopped, the second electrolytic capacitor C2 will be connected for overvoltage protection, and the system will transition to standby operation. After that, an error will be displayed on the operation unit 210 to notify the user and service personnel of the overvoltage abnormality. After transitioning to standby operation, printing operation will not be possible. Voltage detection by the AC voltage detection circuit 208 will continue even after transitioning to standby operation, and if the detected voltage drops below the overvoltage threshold, the capacitor used will be switched back to the first electrolytic capacitor, and printing operation will be resumed.

[0033] In the above process, the electrolytic capacitor C for normal operation is disconnected when an overvoltage occurs, and the electrolytic capacitor C for overvoltage protection is connected to achieve overvoltage protection of the circuit components. Alternatively, one could keep the electrolytic capacitor C for overvoltage protection connected at all times, and disconnect only the electrolytic capacitor C for normal operation when an overvoltage occurs. This method is shown in Figure 5. Figure 5 is a flowchart of an example of the process performed by the image forming apparatus 100 of the embodiment. That is, Figure 5 shows a flowchart when the electrolytic capacitor C for overvoltage protection is always connected. The image forming apparatus 100 performs steps S21 to S38.

[0034] In this case, during normal operation, two electrolytic capacitors C—one for normal operation and one for overvoltage protection—are used to supply power to the downstream load. Therefore, it is possible to select an electrolytic capacitor C with a smaller capacitance than those used in typical image forming machines.

[0035] Table 1 shows the specifications of the first electrolytic capacitor C1 and the second electrolytic capacitor C2 in the embodiment and the capacitor in the comparative example. The comparative example is an image forming apparatus equipped with one electrolytic capacitor. Note A in Table 1 states that "the rated input voltage should be selected to satisfy the power supply rating × 2 × √2 (approximately 283V in Japan) from the standard value." [Table 1]

[0036] Here, the operating states of the image forming apparatus 100 include a print operation state in which the drive system load is also operated in order to perform a printing operation, and a standby state in which it is waiting for a printing operation. In the standby operation state, unlike the print operation state, the power supplied to the load is reduced.

[0037] In the comparative example, when performing a printing operation with the image forming apparatus, a large-capacity electrolytic capacitor (560μF is listed as an example in Table 1) is required in the power supply unit to supply sufficient power to each load. In contrast, in this embodiment, since the system switches to a standby operation state in the event of sudden overvoltage (such as incorrect insertion of commercial power or lightning surge), it is possible to select an electrolytic capacitor C with a high rated input voltage and small capacity (315V, 120μF is listed as an example in Table 1) for use during overvoltage.

[0038] Table 1 shows that, compared to mounting one electrolytic capacitor capable of withstanding overvoltage and operating in standby and print mode, mounting two electrolytic capacitors C—one for standby and print mode and one for overvoltage protection—reduces the vertical length of the electrolytic capacitors C by approximately 20 mm.

[0039] In this embodiment, two smoothing electrolytic capacitors C with different capacitances and rated input voltages are mounted in the power supply unit. When an overvoltage significantly exceeding the rated input voltage of electrolytic capacitor C is detected by the AC voltage detection method, the electrolytic capacitor C being used is switched to the one with the higher rated input voltage, thereby providing overvoltage protection, preventing damage to the electrolytic capacitor C, and allowing for a reduction in the size of the electrolytic capacitor C, thus reducing vertical space requirements.

[0040] As described above, in this embodiment, the image forming apparatus 100 includes a rectifier circuit 201 that rectifies the current supplied from the commercial power supply, a smoothing circuit 202 that smooths the output current from the rectifier circuit 201, and a determination unit 203 that determines whether or not the supply voltage from the commercial power supply is an overvoltage exceeding a threshold. The smoothing circuit 202 includes two electrolytic capacitors C and a switching unit 204 which is a switch that switches which electrolytic capacitor C to use according to the output of the determination unit 203. The determination unit 203 includes an AC voltage detection circuit 208 (voltage detection circuit) that detects a voltage value which is the value of the supply voltage from the commercial power supply, and an AC path switching control circuit 209 (switching control circuit) that outputs a switching control signal for the switching unit 204 based on the voltage value from the AC voltage detection circuit 208.

[0041] With this configuration, it is possible to switch the electrolytic capacitor C with a simple setup.

[0042] Furthermore, the two electrolytic capacitors C are the first electrolytic capacitor C1 and the second electrolytic capacitor C2. The first electrolytic capacitor C1 has a first rated input voltage and a first capacitance that satisfies the commercial power supply. The second electrolytic capacitor C2 has a second rated input voltage that is higher than the first rated input voltage and a second capacitance that is smaller than the first capacitance.

[0043] This configuration allows for limiting the height of the electrolytic capacitor C and preventing its failure.

[0044] Furthermore, the electrolytic capacitor C connected when the power is off is the second electrolytic capacitor C2. In other words, when the power is off, the second electrolytic capacitor C2 is selected and connected.

[0045] This configuration makes it possible to prevent the electrolytic capacitor C from being damaged.

[0046] Furthermore, the image forming apparatus 100 uses the second electrolytic capacitor C2 when powered on. If the voltage value detected by the AC voltage detection circuit 208 of the determination unit 203 is below a threshold, the image forming apparatus 100 switches the electrolytic capacitor C to the first electrolytic capacitor C1 and performs standby operation, which is when the image forming apparatus 100 is not operating, and printing operation, which is when the image forming apparatus 100 is operating. If the voltage value detected by the AC voltage detection circuit 208 of the determination unit 203 is above a threshold, the image forming apparatus 100 does not switch to the first electrolytic capacitor C1 and proceeds to standby operation. The above operation is also referred to as the operation of the first example.

[0047] With this configuration, it is possible to prevent the electrolytic capacitor C from being damaged, regardless of the operating state of the image forming apparatus 100.

[0048] Furthermore, when the image forming apparatus 100 is performing standby or printing operations, if the voltage value detected by the AC voltage detection circuit 208 of the determination unit 203 is above a threshold value, it switches the electrolytic capacitor C being used to the second electrolytic capacitor C2, stops the printing operation if printing is in progress, and switches to standby operation.

[0049] With this configuration, it is possible to prevent the electrolytic capacitor C from being damaged, regardless of the operating state of the image forming apparatus 100.

[0050] Furthermore, with the second electrolytic capacitor C2 constantly connected, the image forming apparatus 100 disconnects only the first electrolytic capacitor C1 if the voltage value detected by the AC voltage detection circuit 208 of the determination unit 203 is above a threshold value.

[0051] With this configuration, it is possible to select an electrolytic capacitor C with a smaller capacitance than in the first example, further limit the height of the electrolytic capacitor C, and realize an inexpensive configuration.

[0052] Furthermore, the image forming apparatus 100, after the AC voltage detection circuit 208 of the determination unit 203 detects a voltage value exceeding a threshold and transitions to standby operation, notifies the user that the detected voltage of the AC voltage detection circuit 208 of the determination unit 203 was above the threshold, and prevents the transition to printing operation.

[0053] This configuration prevents the electrolytic capacitor C from being damaged after the system transitions to standby mode, and also allows for notification to the user.

[0054] Furthermore, if the voltage value detected by the AC voltage detection circuit 208 of the determination unit 203 is above a threshold, the electrolytic capacitor C used is switched to the second electrolytic capacitor C2, and if a print operation is in progress, the print operation is stopped and the system transitions to standby mode. This operation is the first operation. After the first operation, the AC voltage detection circuit 208 of the determination unit 203 resumes voltage detection, and if the voltage value detected by the AC voltage detection circuit 208 is below the threshold, the electrolytic capacitor C used is switched back to the first electrolytic capacitor C1, and the first operation is resumed.

[0055] With this configuration, it is possible to prevent the electrolytic capacitor C from being damaged, regardless of the operating state of the image forming apparatus 100.

[0056] In the above embodiment, the image processing apparatus of the present invention is described using an example in which it is applied to a multifunction device having at least two functions from among a copy function, a printer function, a scanner function, and a facsimile function. However, it can be applied to any image forming apparatus such as a copier, printer, scanner, or facsimile machine. [Explanation of symbols]

[0057] 100 Image forming apparatus 201 Rectifier circuit 202 Smoothing circuit 203 Judgment section 204 Switching section 208 AC voltage detection circuit (voltage detection circuit) 209 AC path switching control circuit (switching control circuit) C electrolytic capacitor C1 First electrolytic capacitor C2 Second electrolytic capacitor [Prior art documents] [Patent Documents]

[0058] [Patent Document 1] Japanese Patent Publication No. 2018-57104

Claims

1. In an image forming apparatus equipped with a switching power supply having an electrolytic capacitor, A rectifier circuit that rectifies the current supplied from the commercial power supply, A smoothing circuit that smooths the output current from the rectifier circuit, A determination unit that determines whether the voltage supplied from the commercial power supply is an overvoltage exceeding a threshold, Equipped with, The smoothing circuit is Two electrolytic capacitors, A switching unit, which is a switch that switches the electrolytic capacitor to be used according to the output of the determination unit, It has, The determination unit, A voltage detection circuit that detects a voltage value which is the value of the supply voltage from the commercial power supply, A switching control circuit outputs a switching control signal for the switching unit based on the voltage value from the voltage detection circuit, It has, The image forming apparatus is characterized in that the two electrolytic capacitors are a first electrolytic capacitor having a first rated input voltage and a first capacitance that satisfies the commercial power supply, and a second electrolytic capacitor having a second rated input voltage higher than the first rated input voltage and a second capacitance smaller than the first capacitance that can supply sufficient power to the image forming apparatus.

2. In the image forming apparatus according to claim 1, The image forming apparatus is characterized in that the electrolytic capacitor connected when the power is not turned on is the second electrolytic capacitor.

3. In the image forming apparatus according to claim 1 or claim 2, An image forming apparatus characterized in that, when power is turned on, the second electrolytic capacitor is used, and if the voltage value detected by the voltage detection circuit of the determination unit is below a threshold, the electrolytic capacitor used is switched to the first electrolytic capacitor, and the standby operation, which is when the image forming apparatus is not operating, and the printing operation, which is when the image forming apparatus is operating, are performed, and if the voltage value detected by the voltage detection circuit of the determination unit is above a threshold, the switch to the first electrolytic capacitor is not performed, and the system proceeds to the standby operation.

4. In the image forming apparatus according to claim 3, An image forming apparatus characterized in that, when the standby operation and the printing operation are being performed, if the voltage value detected by the voltage detection circuit of the determination unit is equal to or greater than a threshold value, the electrolytic capacitor being used is switched to the second electrolytic capacitor, and if the printing operation is being performed, the printing operation is stopped and the system transitions to the standby operation.

5. In the image forming apparatus according to claim 1 or claim 2, An image forming apparatus characterized in that, with the second electrolytic capacitor constantly connected, if the voltage value detected by the voltage detection circuit of the determination unit is equal to or greater than a threshold value, only the first electrolytic capacitor is disconnected.

6. In the image forming apparatus according to claim 4, An image forming apparatus characterized in that, after the voltage detection circuit of the determination unit detects a voltage value that is equal to or greater than a threshold value and the system transitions to the standby operation, the system notifies the user that the voltage detected by the voltage detection circuit of the determination unit was equal to or greater than a threshold value, and prevents the system from transitioning to the printing operation.

7. In the image forming apparatus according to claim 4, If the voltage detected by the voltage detection circuit of the determination unit is equal to or greater than the threshold value, the electrolytic capacitor used is switched to the second electrolytic capacitor, and if the printing operation is in progress, the printing operation is stopped and the system switches to standby mode. This operation is the first operation. An image forming apparatus characterized in that, after the first operation, the voltage detection by the voltage detection circuit of the determination unit is restarted, and if the voltage value detected by the voltage detection circuit is less than or equal to a threshold, the electrolytic capacitor to be used is switched to the first electrolytic capacitor, and the first operation is restarted.

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