JP5358953B2 - Power control device and image forming apparatus using power control device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a power control device and an image forming apparatus employing the power control device capable of exactly detecting (determining) a malfunction of a relay and a semiconductor device (discharge transistor) and the content of the malfunction. <P>SOLUTION: The power control device is equipped: with a relay S2 and a discharge transistor S3 connected in series to an electric power load; bias transistors S1 and D10 connected between the relay S2 and the discharge transistor S3 and supplying voltage to the discharge transistor S3; and a CPU 2 determining an occurrence of a malfunction in at least one of the relay S2 and the discharge transistor S3. <P>COPYRIGHT: (C)2009,JPO&amp;INPIT

Description

  The present invention relates to a power control apparatus and an image forming apparatus using the power control apparatus.

  In a power supply device (circuit) that supplies power from a capacitor or a charger to a fixing heater of an image forming apparatus, a semiconductor element (discharge) that controls power on (closed) / off (open) as a power control device (circuit). Transistor) and a relay as a safety device connected in series to the semiconductor element.

  This relay controls the contact of the semiconductor element to be on (closed) / off (open) when the semiconductor element is off (open), so the heater current is directly turned on (closed) / off (open) at the contact of the relay. Never do. For this reason, a small-sized relay for small current can be used as a safety device.

  However, since the semiconductor element controls large current on (closed) / off (open), on (closed) / off (open) at the relay contact due to failure of the semiconductor element or malfunction of the semiconductor element. ) May occur. As a result, there is a possibility that a problem of welding of the relay contact occurs.

  When the relay contact is welded, the safety circuit is not activated and the fixing unit is overheated to a predetermined temperature or more. In this case, since the temperature fuse is cut, no smoke or fire occurs. However, the roller of the fixing device deteriorates and needs to be replaced.

  In order to solve this problem, for example, in Patent Document 1, a series circuit including a relay and a semiconductor element is connected to a fixing heater of an image forming apparatus to control power supply from a capacitor. A method has been proposed in which detection or detection of either a relay malfunction or a short circuit failure of a semiconductor element is performed. This is because, in a series circuit of a relay and a semiconductor element in which power supply from the capacitor to the fixing heater of the image forming apparatus is on (closed) / off (opened), detection of a relay contact welding failure and relay contact opening failure or Means for detecting two modes, that is, detection of a short circuit failure of a semiconductor element, is provided.

JP 2005-221773 A

  However, in the technique described in Patent Document 1, it is impossible to distinguish whether the cause of the failure is a relay contact open failure or a semiconductor element short-circuit failure. Furthermore, the technique described in Patent Document 1 cannot detect an open defect of a semiconductor element.

  The present invention has been made in view of the above, and is an image using a power control device and a power control device that can accurately detect (determine) abnormality of relays and semiconductor elements (discharge transistors) and their contents. An object is to provide a forming apparatus.

In order to solve the above-described problems and achieve the object, the present invention provides a first opening / closing unit disposed in a path of a current output from a current output unit, and the current path than the first opening / closing unit. a second opening and closing means arranged downstream, being connected to a path of said current between said first switching means and the second switching means, and voltage supply means for supplying a voltage to said second switching means, before When the first opening / closing means is instructed to open, the second opening / closing means is instructed to open, and the voltage supply means supplies voltage, the first opening / closing means and And determining means for determining that the second opening / closing means is not open when the voltage between the second opening / closing means is not higher than a predetermined voltage .
Further, the present invention provides a first opening / closing means arranged in a path of a current output from the current output means, and a second opening / closing means arranged downstream in the current path from any one of the first opening / closing means. A voltage supply means connected to the current path between the first opening / closing means and the second opening / closing means to supply a voltage to the second opening / closing means; and an instruction to open the first opening / closing means. The second opening / closing means is instructed to close, and the voltage supply means supplies a voltage, and the voltage between the first opening / closing means and the second opening / closing means is a predetermined value. And a judging means for judging that the second opening / closing means is defective so as not to be closed when the voltage is higher than the voltage.
Further, the present invention provides a first opening / closing means disposed in a path of a current output from the current output means, a second opening / closing means disposed downstream in the current path from the first opening / closing means, Connected to the current path between the first opening / closing means and the second opening / closing means, a voltage supply means for supplying a voltage to the second opening / closing means, and an instruction to open the first opening / closing means. The second opening / closing means is instructed to open and the voltage supply means is not supplied with a voltage, and the voltage between the first opening / closing means and the second opening / closing means is a predetermined voltage. If higher, the first opening / closing means has a judging means for judging that the first opening / closing means is not open.

  According to the present invention, the voltage can be supplied or stopped between the relay that is the two switching circuits connected in series to the fixing heater that is the power load and the semiconductor element (discharge transistor). The voltage change of a specific part in the power control device when each switching circuit opens and closes when the power is supplied or stopped, and the abnormality of the relay and the semiconductor element (discharge transistor) can be confirmed from the voltage change In addition, it is possible to accurately detect (determine) the contents thereof (the welding failure of the relay contact, the opening failure of the relay contact, the shorting failure of the discharge transistor, and the opening failure of the discharge transistor).

  Exemplary embodiments of a power control apparatus and an image forming apparatus using the power control apparatus according to the present invention will be explained below in detail with reference to the accompanying drawings. In this embodiment, a power control apparatus that performs power control on a fixing device of a digital copying machine will be described. In this embodiment, an example in which the image forming apparatus of the present invention is applied to a digital copying machine is shown. However, the present invention is not limited to this and can be applied to a printer, a facsimile, or the like.

(First embodiment)
FIG. 1 is a longitudinal sectional view of a digital copying machine according to a first embodiment of the present invention. The digital copying machine 1 is a so-called multifunction machine. That is, the digital copying machine 1 has a copying function and other functions, for example, a printer function and a facsimile function, and a copying function, a printer function, a facsimile function are operated by operating an application switching key of an operation unit (not shown). It is possible to select the functions by switching them sequentially. Thus, the copy mode is selected when the copy function is selected, the print mode is selected when the printer function is selected, and the facsimile mode is selected when the facsimile mode is selected.

  Next, the schematic configuration of the digital copying machine 1 and the operation in the copy mode will be described. In FIG. 1, in an automatic document feeder (hereinafter referred to as ADF) 101, a document placed on a document table 102 with an image surface facing upward is pressed when a start key on an operation unit (not shown) is pressed. Then, the sheet is fed to a predetermined position on the document table 102 made of contact glass by the feeding belt 104. The ADF 101 has a count function that counts up the number of documents every time a document is fed. After the image information is read by the image reading device 106, the document on the contact glass 105 is discharged onto the paper discharge tray 108 by the feeding belt 104 and the discharge roller 107.

  When the document set detector 109 detects that the next document is present on the document table 102, the lowermost document on the document table 102 is similarly contacted by the feed roller 103 and the feed belt 104. It is fed to a predetermined position on the glass 105. After the image information is read by the image reading device 106, the original on the contact glass 105 is discharged onto the paper discharge tray 108 by the feeding belt 104 and the discharge roller 107. Here, the feeding roller 3, the feeding belt 4, and the discharging roller 7 are driven by a conveyance motor.

  When selected, the first paper feeding device 110, the second paper feeding device 111, and the third paper feeding device 112 feed the stacked transfer paper, and the transfer paper is photosensitized by the vertical conveyance unit 116. It is transported to a position where it contacts the body 117. For example, a photosensitive drum is used as the photosensitive member 117, and is rotated by a main motor (not shown).

  Image data read from the document by the image reading device 106 is subjected to predetermined image processing by an image processing device (not shown), and then converted into optical information by the writing unit 118. The photosensitive drum 117 is charged by a charger (not shown). After being uniformly charged, it is exposed with optical information from the writing unit 118 to form an electrostatic latent image. The electrostatic latent image on the photosensitive drum 117 is developed by the developing device 119 to become a toner image. A printer engine that forms an image on a medium such as paper by an electrophotographic system is configured by the writing unit 118, the photosensitive drum 117, the developing device 119, and other well-known devices around the photosensitive drum 117 (not shown). .

  The conveyance belt 120 serves as a sheet conveyance unit and a transfer unit, and a transfer bias is applied from the power source. The conveyance belt 120 is transferred onto the photosensitive drum 117 while conveying the transfer sheet from the vertical conveyance unit 116 at a constant speed with the photosensitive drum 117. The toner image is transferred onto the transfer paper. The transfer paper is fixed with a toner image by a fixing device 121 and is discharged to a paper discharge tray 123 by a paper discharge unit 122. The photosensitive drum 117 is cleaned of residual toner by a cleaning device (not shown) after the toner image is transferred.

  The above operation is an operation for copying an image on one side of a sheet in a normal mode. When an image is copied on both sides of a transfer sheet in a duplex mode, one of the paper feed trays 113 to 115 is copied. The transfer paper that is further fed and has an image formed on the surface as described above is switched by the paper discharge unit 122 to the double-sided paper feed path 124 side instead of the paper discharge tray 123 side, and is switched back by the reversing unit 125. Then, the front and back sides are reversed and conveyed to the duplex conveying unit 126.

  The transfer paper transported to the double-sided transport unit 126 is transported to the vertical transport unit 116 by the double-sided transport unit 126, transported to the position where it abuts on the photoconductive drum 117 by the vertical transport unit 116, and is transferred onto the photoconductive drum 117. The toner image formed in the same manner as above is transferred to the back surface, and the toner image is fixed by the fixing device 121, whereby double-sided copying is performed. This double-sided copy is discharged to the paper discharge tray 123 by the paper discharge unit 122.

  Further, when the transfer paper is reversed and discharged, the transfer paper that is switched back by the reversing unit 125 and turned upside down is not conveyed to the duplex conveying unit 126 but is discharged via the reverse discharge conveyance path 127. The paper is discharged to the paper discharge tray 123 by the unit 122.

  In the print mode, image data from the outside is input to the writing unit 118 instead of the image data from the above-described image processing apparatus, and an image is formed on the transfer paper as described above.

  Further, in the facsimile mode, the image data from the image reading device 106 is transmitted to the other party by a facsimile transmission / reception unit (not shown), and the image data from the other party is received by the facsimile transmission / reception unit, instead of the image data from the image processing device described above. As described above, an image is formed on the transfer paper.

  The digital copying machine 1 includes a large quantity paper supply device (not shown), a finisher that performs sorting, punching, stapling, and the like, a mode for reading a document, a setting of a copying magnification, a setting of a paper feed stage, and a finisher. And an operation unit for performing post-processing settings and display to the operator.

(Fixing device)
Next, the configuration of the fixing device 121 will be described. FIG. 2 is a configuration diagram of the fixing device 121 used in the digital copying machine 1. As shown in FIG. 2, the fixing device 121 implements the heat generating device and the fixing device of the present invention. A pressure roller 302 made of an elastic member such as silicon rubber is attached to a fixing roller 301 that is an object to be heated. It is pressed with a constant pressure by a pressing means (not shown). As described above, the fixing member and the pressure member are generally in the form of a roller, but for example, either one or both may be configured in an endless belt shape. In the fixing device 121, fixing heaters HT1 and HT2 are provided at arbitrary positions. For example, the fixing heaters HT1 and HT2 are disposed inside the fixing roller 301, and heat the fixing roller 301 that is an object to be heated from the inside.

  The fixing roller 301 and the pressure roller 302 are rotationally driven by a driving mechanism (not shown). A temperature sensor TH1 such as a thermistor is in contact with the surface of the fixing roller 301 and detects the surface temperature (fixing temperature) of the fixing roller 301. The sheet 307, which is a medium such as transfer paper carrying the toner 306, is heated and pressed by the fixing roller 301 and the pressure roller 302 when passing through the nipping portion between the fixing roller 301 and the pressure roller 302. As a result, the toner 306 is fixed as an image.

  The fixing heater HT1, which is the first heat generating element, is turned on (closed) when the predetermined target temperature Tt serving as a reference for the fixing roller 301 serving as a fixing member has not been reached, and is a main heater that heats the fixing roller 301 (Main heater). The fixing heater HT2, which is the second heat generating element, is used when the main power supply of the copying machine 1 is turned on, when starting up until returning from the energy saving mode described later and when copying is possible, that is, when the fixing device 121 is warm. This is an auxiliary heater (auxiliary heater) that is turned on (closed) when heated to heat the fixing roller 301.

(Power control device)
Next, the power control apparatus will be described. FIG. 3 is a circuit diagram of the power control apparatus according to the first embodiment of the present invention. The power control device 2 controls the power supply to the fixing heater HT2 in order to shorten the start-up time of the fixing heater HT2 and prevent the temperature drop when the fixing heater HT2 continuously passes. The power control device 2 uses an electric double layer capacitor CP1 as a capacitor.

  The anode of the electric double layer capacitor CP1 whose cathode is connected to GND is connected to the charger via the diode D1, and charging is controlled by a signal from the output port P1 of the CPU2. The output of the electric double layer capacitor CP1 is connected to one end (right side in the figure) of the fixing heater HT2 via the thermal fuse F1. The other end (left side in the figure) of the fixing heater HT2 is connected to the drain of the discharge transistor S3, which is a field effect transistor (FET), via a contact a of the relay S2. The source of the discharge transistor S3 is connected to the cathode of the electric double layer capacitor CP1.

  The thermal fuse F1 is installed in the vicinity of the fixing roller 301, is cut at a predetermined temperature in the event of any abnormality, and stops energization to the fixing heater HT2.

  In the vicinity of the fixing roller 301, a thermistor TH1 whose one end (upper side in the figure) is pulled up with a voltage Vc is installed. The other end (upper side in the figure) of the resistor R1 whose one end (lower side in the figure) is connected to GND is connected to the other end (lower side in the figure) of the thermistor TH1. A connection point between the thermistor TH1 and the resistor R1 is connected to the AD conversion terminal AD of the CPU 1 through an integration circuit, and the temperature is input to the AD conversion terminal AD as a voltage change. If the temperature detected by the thermistor TH1 is higher than a predetermined value, there is some abnormality, and the CPU 2 is instructed by the communication port UART to disconnect the contact of the relay S2.

  The coil of the relay S2 whose one end (upper side in the figure) is pulled up to the voltage Va is connected to the output port P4 of the CPU 2 via the driver IC5, and is driven by the instruction from the communication port UART. Is turned off and the contacts are opened. Thereby, the energization to the fixing heater HT2 is stopped. The diode D2 is for preventing the driver IC 5 from being destroyed by circulating the induced electromotive force generated when the driver IC 5 changes from the H logic level to the L logic level.

  Normally, whether or not the CPU 2 lights the fixing heater HT2 based on the detected value of the fixing temperature (value input to the AD conversion terminal AD) and the target temperature value with the contact of the relay S2 being on (closed). The discharge transistor S3 is turned on (closed) / off (opened) by applying a signal from the output port P5 of the CPU 2 to the gate of the discharge transistor S3 via the driver IC4. The fixing roller 301 is controlled to a predetermined temperature by the on (close) / off (open) operation of the discharge transistor S3.

  Here, in the present embodiment, an FET is used as the discharge transistor S3, but an IGBT may be used instead of the FET. However, when the IGBT is used, the drain of the FET becomes the collector of the IGBT and the source of the FET becomes the emitter of the IGBT. The thermistor TH1 may use another temperature detection element, such as a thermopile.

  Now, it is assumed that the fixing heater is a halogen heater rated at 200 W, and the charging voltage (output voltage) V2 of the electric double layer capacitor CP1 is 45V. The resistance value of the halogen heater is about 10Ω when rated, and about 1Ω when cold. For this reason, when the halogen heater is turned on in the cold state, a large current of 45 V / 1Ω = 45 A flows according to Ohm's law, and a current of about 4 A flows at the rated time. In order to directly open and close a large current circuit of 45 A at the contact of the relay S2, it is necessary to use a large and high cost circuit corresponding to the large current.

  However, the current of 45A is instantaneous, and there is no problem at all even if a large current of 45A is passed instantaneously with the contact of the relay S2 closed.

  For this reason, it is possible to use a small and low-cost relay by controlling the contact of the relay S2 to be on (closed) / off (open) without fail. For this purpose, before the relay S2 is turned on (closed) / off (opened), it is necessary to confirm that the discharge transistor S3 for controlling energization to the fixing heater HT2 does not cause a short circuit failure. Therefore, the contact of the relay S2 is turned off, the discharge transistor S3 is turned off, that is, the output port P5 of the CPU 2 is set to the L logic level, and in that state, a bias voltage is applied to the drain of the discharge transistor S3, If the drain voltage Vd can be detected, it is possible to determine whether a short circuit failure or an open failure has occurred in the discharge transistor S3.

  In the power control device 2, the bias voltage is taken out from the power supply of the power control device 2, and is a circuit composed of a resistor R 20, a bias transistor S 1 that is a PNP bipolar transistor with a built-in resistor, and a diode D 10. A bias voltage is applied to the drain.

  The bias transistor S1 is connected to the output port P2 of the CPU 2 via the driver IC 3 and is turned on (closed) / off (opened) as necessary. The drain of the discharge transistor S3 is connected to the base of a transistor Q20 which is an NPN bipolar transistor whose emitter is connected to GND through a resistor R21. The base of the transistor Q20 is connected to GND through a resistor R22. Yes. When the voltage is converted by the resistor R21 and the resistor R22 and the drain voltage Vd becomes a predetermined value, the transistor Q20 is turned on (closed). The collector of the transistor Q20 is pulled up to the voltage Vc by the resistor R10, is connected to the input port P3 of the CPU2, and is recognized as a binary of H logic level / L logic level by a logic circuit in the CPU2.

(How to judge the quality of relays and discharge transistors)
Next, the quality determination method for the relay S2 and the discharge transistor S3 by the power control device 2 will be described. FIG. 4 is a flowchart of a method for determining the quality of the relay S2 and the discharge transistor S3.

  First, the contact of the relay S2 and the discharge transistor S3 for discharge are turned off (step S101). Next, a bias voltage is applied to the drain of the discharge transistor S3, and the bias transistor S1 is turned on (closed) (step S102).

  In this state, when the discharge transistor S3 is normally off (open), the current from the bias transistor S1 does not flow to the discharge transistor S3 side but flows to the base side of the transistor Q20. For this reason, a current flows between the emitter and collector of the transistor Q20, and the voltage at the input port P3 decreases (actually changes from the H logic level to the L logic level).

  However, if the discharge transistor S3 is not normally off (open), that is, is short-circuited (on), the current from the bias transistor S1 flows to the discharge transistor S3 side, and to the base side of the transistor Q20. Does not flow. Therefore, no current flows between the emitter and collector of the transistor Q20, and the voltage at the input port P3 does not change (actually remains at the H logic level).

  In addition, although the case where the contact of relay S2 is short-circuited is also considered, since the bias voltage is applied to the drain of discharge transistor S3, it is not necessary to consider the short-circuit of contact of relay S2 at this time.

  Then, the CPU 2 determines whether or not the input port P3 is at the L logic level (step S103). When the CPU 2 determines that the input port P3 is not at the L logic level, that is, the H logic level (step S103: No), the CPU 2 determines that the discharge transistor S3 has a short circuit failure and sets a service command SC to that effect. (Step S111), the pass / fail judgment is terminated.

  When the CPU 2 determines that the input port P3 is at the L logic level (step S103: Yes), the CPU 2 determines that the discharge transistor S3 is not a short circuit failure.

  Next, the discharge transistor S3 is turned on (closed) (step S104).

  In this state, when the discharge transistor S3 is normally on (closed), the current from the bias transistor S1 flows to the discharge transistor S3 side and does not flow to the base side of the transistor Q20. For this reason, no current flows between the emitter and collector of the transistor Q20, and the voltage at the input port P3 rises (actually changes from the L logic level to the H logic level).

  However, when the discharge transistor S3 is not normally on (closed), that is, is opened (off), the current from the bias transistor S1 does not flow to the discharge transistor S3 side, but to the base side of the transistor Q20. It will continue to flow. For this reason, a current flows between the emitter and collector of the transistor Q20, and the voltage at the input port P3 remains reduced (actually remains at the L logic level).

  In addition, although the case where the contact of relay S2 is short-circuited is also considered, since the bias voltage is applied to the drain of discharge transistor S3, it is not necessary to consider the short-circuit of contact of relay S2 at this time.

  Then, the CPU 2 determines whether or not the input port P3 is at the L logic level (step S105). When the CPU 2 determines that the input port P3 is L logic (step S105: Yes), the CPU 2 determines that the discharge transistor S3 is defective in opening, sets a service command SC to that effect (step S112), and determines whether it is acceptable. finish.

  If the CPU 2 determines that the input port P3 is not at the L logic level, that is, is at the H logic level (step S105: No), the CPU 2 determines that the discharge transistor S3 is not an open failure.

  Note that whether or not the discharge transistor S3 is defective in opening can be determined later by separately detecting an abnormality in the fixing temperature control flow. Therefore, there is no problem with safety, so steps S104 and S105. , And step S112 may be omitted.

  Since it has been confirmed that there is no short circuit failure of the discharge transistor S3 in the flow so far, next, the bias transistor S1 is turned off (step S106), and further, the contact of the relay S2 and the discharge transistor S3 are connected. It is set to off (open) (step S107).

  In this state, when the contact of the relay S2 is normally off (open), the current from the electric double layer capacitor CP1 does not flow to the base side of the transistor Q20. Therefore, no current flows between the emitter and collector of the transistor Q20, and the voltage at the input port P3 does not change (actually remains at the H logic level).

  However, when the contact of the relay S2 is not normally off (opened), that is, welded (on), the current from the electric double layer capacitor CP1 flows to the base side of the transistor Q20. For this reason, a current flows between the emitter and collector of the transistor Q20, and the voltage at the input port P3 decreases (actually changes from the H logic level to the L logic level).

  Then, the CPU 2 determines whether or not the input port P3 is at the L logic level (step S108). When the CPU 2 determines that the input port P3 is at the L logic level (step S108: Yes), the CPU 2 determines that the contact of the relay S2 is poorly welded and sets a service command SC to that effect (step S113). End the decision.

  If the CPU 2 determines that the input port P3 is not at the L logic level, that is, the H logic level (No at Step S108), the CPU 2 determines that the contact of the relay S2 is not defective in welding.

  Next, the contact of the relay S2 is turned on (step S109).

  In this state, when the contact of the relay S2 is normally on (closed), the current from the electric double layer capacitor CP1 flows to the base side of the transistor Q20. For this reason, a current flows between the emitter and collector of the transistor Q20, and the voltage at the input port P3 decreases (actually changes from the H logic level to the L logic level).

  However, when the contact of the relay S2 is not normally on (closed), that is, is opened (off), the current from the electric double layer capacitor CP1 does not flow to the base side of the transistor Q20. Therefore, no current flows between the emitter and collector of the transistor Q20, and the voltage at the input port P3 does not change (actually remains at the H logic level).

  Then, the CPU 2 determines whether or not the input port P3 is at the L logic level (step S110). When the CPU 2 determines that the input port P3 is not at the L logic level, that is, the H logic level (step S110: No), the CPU 2 determines that the contact of the relay S2 is defective in opening, and sets a service command SC to that effect. (Step S114), the pass / fail judgment is terminated.

  When the CPU 2 determines that the input port P3 is at the L logic level (step S110: Yes), the CPU 2 determines that the contact of the relay S2 is not an open failure. In this case, finally, it is determined that the relay S2 and the discharge transistor S3 are good products.

  Whether or not the contact of the relay S2 is defective in opening can be determined later by separately detecting an abnormality in the fixing temperature control flow. S110 and step S114 may be omitted.

  When the service command SC is issued, processing corresponding to each service command is executed. For example, if the service command SC indicates that the discharge transistor S3 is short-circuited, the contact on (closed) of the relay S2 is prohibited and a display indicating that the discharge transistor S3 is defective is displayed on a display unit (not shown). Alternatively, a process of notifying the service that the discharge transistor S3 is defective is performed. The same processing is performed for other service commands SC as well, but this processing is normally performed in a digital copying machine, and a description thereof will be omitted.

  Table 1 shows a combination of the bias transistor S1, the contact of the relay S2, and the on (closed) / off (open) state of the discharge transistor S3, the logic level of the input port P3 of the CPU 2, and The correlation of the judgment result of relay S2 and discharge transistor S3 is put together. Note that this determination method is based on the assumption that no failure occurs in the bias transistor S1 and the transistor Q20, which are signal transistors.

  As described above, according to the power control apparatus of the first embodiment, a circuit including the bias transistor and the diode is provided between the relay and the discharge transistor connected in series to the fixing heater, and this circuit is provided. Since the bias voltage can be applied to or stopped from the drain of the discharge transistor, the application / non-application of the bias voltage, the relay contact on (closed) / off (open), and the discharge transistor on (closed) / off (Open) can be used to check the voltage change of a specific part in the power control device, and the abnormality of the relay and discharge transistor and its contents (relay contact failure, relay contact) Open circuit failure, discharge transistor short circuit failure, and discharge transistor open failure) Possible it is.

  Furthermore, according to the power control device according to the first embodiment, it is possible to determine the abnormality of the relay and the discharge transistor and the contents thereof by converting the level of the voltage with the transistor and detecting it with the input port. The pass / fail judgment circuit of the power control apparatus can be simplified, and the size and cost can be reduced.

(Second Embodiment)
In the power control device according to the first embodiment, the bias voltage is extracted from the power supply of the power control device. However, in the power control device according to the second embodiment, the bias voltage is configured as an electric double layer capacitor. Take out from between a plurality of cells connected in series.

  A second embodiment will be described with reference to the accompanying drawings. Since the configuration of the digital copying machine according to the present embodiment is the same as that of the digital copying machine of the first embodiment except for the power control device, the description is omitted with reference to the above description. To do. In addition, regarding the configuration example of the power control apparatus, a different part from the first embodiment will be described. The other parts are the same as those in the first embodiment, so the description is omitted with reference to the above description.

  FIG. 5 is a circuit diagram of a power control apparatus according to the second embodiment of the present invention. The power control device 3 uses an electric double layer capacitor CP1 as a capacitor, and the electric double layer capacitor CP1 is configured in a form in which a plurality of cells C1 and C2 are connected in series. Then, the emitter of the bias transistor S1 is connected to the connection point between the cell C1 and the cell C2 via the resistor R13, the collector of the bias transistor S1 is connected to the anode of the diode D10, and the cathode of the diode D10 is connected to the discharge transistor S3. Connected to the drain.

  Therefore, in the power control device 3, the bias voltage is taken out from between the cell C1 and the cell C2 of the electric double layer capacitor CP1, and the drain of the discharge transistor S3 is a circuit constituted by the resistor R13, the bias transistor S1, and the diode D10. A bias voltage is applied to. In this way, by taking out the voltage from the middle of the electric double layer capacitor row CP1 whose cathode is connected to the GND, a low voltage circuit can be obtained, so that the circuit can be configured simply and inexpensively.

  Similarly to the power control device according to the first embodiment, the bias transistor S1 is turned on (off) by the output signal of the driver IC3 to which the signal from the output port P2 of the CPU2 is input as the base. (Open) controlled. The drain of the discharge transistor S3 is connected through a resistor R11 to the base of a transistor Q20, which is an NPN bipolar transistor whose emitter is connected to GND, and the base of the transistor Q20 is connected to GND through a resistor R12. Yes. When the voltage is converted between the resistor R11 and the resistor R12 and the drain voltage Vd becomes a predetermined value, the transistor Q20 is turned on (closed). The collector of the transistor Q20 is pulled up to the voltage Vc by the resistor R10, connected to the input port P3 of the CPU 2, and recognized as a binary value of H logic level / L logic level.

  Note that the method for determining the quality of the relay S2 and the discharge transistor S3 by the power control device 3 is the same as that in the flowchart of FIG. 4 described in the first embodiment, and thus the description thereof is omitted here.

  As described above, according to the power control apparatus according to the second embodiment, the bias voltage applied to the drain of the discharge transistor can be taken out from among a plurality of cells constituting the electric double layer capacitor. The device pass / fail judgment circuit can be simplified as a low voltage circuit, and the size and cost can be reduced.

(Third embodiment)
In the power control device according to the second embodiment, the drain voltage Vd of the discharge transistor S3 is seen at the port of the CPU 2, but in the power control device according to the third embodiment, the drain voltage Vd of the discharge transistor S3. Is seen by AD conversion. Furthermore, in the power control apparatus according to the third embodiment, the determination voltage for determining whether the relay S2 and the discharge transistor S3 are abnormal is corrected based on the charging voltage of the electric double layer capacitor.

  A third embodiment will be described with reference to the accompanying drawings. Since the configuration of the digital copying machine according to the present embodiment is the same as that of the digital copying machine of the second embodiment except for the power control device, the description is omitted with reference to the above description. To do. In addition, regarding the configuration example of the power control device, a different part from the second embodiment will be described. The other parts are the same as those in the second embodiment, so the description is omitted with reference to the above description.

  FIG. 6 is a circuit diagram of a power control apparatus according to the third embodiment of the present invention. Similar to the power control device 3 according to the second embodiment, the power control device 4 is configured to extract the bias voltage of the discharge transistor S3 from between the cells C1 and C2 of the electric double layer capacitor CP1.

  However, the power control device 4 does not have the resistors R10, R11, R12, and the transistor Q20 that existed in the power control device 3 according to the second embodiment. Instead, the drain voltage Vd of the discharge transistor S3 is voltage-converted by the resistors R31 and R32 connected in series, and is connected to the AD conversion input AD1 of the CPU 2 through a filter composed of the resistor R30 and the capacitor C30. The AD conversion input AD1 is connected to the power supply of the AD conversion circuit by a diode D30 and is protected from overvoltage.

  Further, in a circuit for reading a charging voltage composed of resistors R34, R35 and a resistor R36 and a capacitor C31 connected via the switch S4, a charging voltage (output voltage) V2 of the electric double layer capacitor CP1 Is voltage-converted by resistors R34 and R35, and is connected to an AD conversion input AD2 of the CPU 2 through a filter including a resistor R36 and a capacitor C31. The switch S4 is for eliminating unnecessary discharge in the circuit for reading the charging voltage. The AD conversion input AD2 is connected to the power supply of the AD conversion circuit by a diode D31 and is protected from overvoltage.

  When the drain voltage Vd of the discharge transistor S3 is viewed at the input port P3 of the CPU 2 as in the power control device 3 according to the second embodiment, the charging voltage (output voltage) V2 of the electric double layer capacitor CP1 is a predetermined value. There is a limitation that it is necessary to be above.

  However, by using AD conversion as in the power control device 4 according to the present embodiment, the charge state of the electric double layer capacitor CP1 is detected, and the detected discharge transistor is determined by the value of the charge voltage (output voltage) V2. Compared to the drain voltage Vd of S3, the determination voltage Vth for determining whether the relay S2 and the discharge transistor S3 are abnormal can be corrected.

(How to judge the quality of relays and discharge transistors)
Next, a quality determination method for the relay S2 and the discharge transistor S3 by the power control device 4 will be described. FIG. 7 is a flowchart of a method for determining whether the relay S2 and the discharge transistor S3 are acceptable.

  First, the voltage AD2 corresponding to the charging voltage (output voltage) V2 is read by the AD conversion input AD2 of the CPU 2 (step S201). The determination voltage Vth corresponding to the drain voltage Vd of the discharge transistor S3 is corrected according to the read voltage value of AD2 (step S202).

  Next, the contact of the relay S2 and the discharge transistor S3 for discharge are turned off (open) (step S203), and a bias voltage is applied to the drain of the discharge transistor S3, and the bias transistor S1 is turned on (closed) (step S203). S204).

  In this state, when the discharge transistor S3 is normally off (opened), since the same voltage as the bias voltage is generated at the contact point a, the value of the AD conversion input AD1 of the CPU 2 is higher than the determination voltage Vth ( growing.

  However, when the discharge transistor S3 is not normally off (opened), that is, is short-circuited (on), the current from the bias transistor S1 flows to the discharge transistor S3 side, and the voltage at the contact a is biased. Since the voltage is lower than the voltage, the value of the AD conversion input AD1 of the CPU 2 becomes lower (smaller) than the determination voltage Vth.

  In addition, although the case where the contact of relay S2 is short-circuited is also considered, since the bias voltage is applied to the drain of discharge transistor S3, it is not necessary to consider the short-circuit of contact of relay S2 at this time.

  Then, the CPU 2 reads the AD conversion input AD1, and determines whether or not the value is larger than the determination voltage Vth (step S205). If the CPU 2 determines that the value of AD1 is not greater than the determination voltage Vth (step S205: No), the CPU 2 determines that the discharge transistor S3 has a short circuit failure, and issues a service command SC to that effect (step S213). End the decision.

  If the CPU 2 determines that the value of AD1 is greater than the determination voltage Vth (step S205: Yes), it determines that the discharge transistor S3 is not a short circuit failure.

  Next, the discharge transistor S3 is turned on (step S206).

  In this state, when the discharge transistor S3 is normally turned on (closed), the current from the bias transistor S1 flows to the discharge transistor S3 side, and the voltage at the contact point a becomes lower than the bias voltage. The value of the conversion input AD1 is lower (smaller) than the determination voltage Vth.

  However, when the discharge transistor S3 is not normally on (closed), that is, is opened (off), the same voltage as the bias voltage is generated at the contact point a. Therefore, the AD conversion input AD1 of the CPU 2 is generated. Is higher (larger) than the determination voltage Vth.

  In addition, although the case where the contact of relay S2 is short-circuited is also considered, since the bias voltage is applied to the drain of discharge transistor S3, it is not necessary to consider the short-circuit of contact of relay S2 at this time.

  Then, the CPU 2 reads the value of the AD conversion input AD1, and determines whether or not the value is larger than the determination voltage Vth (step S207). If the CPU 2 determines that the value of AD1 is greater than the determination voltage Vth (step S207: Yes), the CPU 2 determines that the discharge transistor S3 is defective in opening, sets a service command SC to that effect (step S214), and determines whether it is good or bad. Exit.

  If the CPU 2 determines that the value of AD1 is not greater than the determination voltage Vth (step S207: No), it determines that the discharge transistor S3 is not an open failure.

  Note that whether or not the discharge transistor S3 is defective in opening can be determined later by separately detecting an abnormality in the fixing temperature control flow, so that there is no problem with safety. Steps S206 and S207 , And step S214 may be omitted.

  Since it has been confirmed that there is no short-circuit failure of the discharge transistor S3 in the flow so far, next, the bias transistor S1 is turned off (step S208), and the contact of the relay S2 and the discharge transistor S3 are further connected. It is set to off (open) (step S209).

  In this state, when the contact of the relay S2 is normally off (opened), the voltage of the electric double layer capacitor CP1 is not generated at the contact a. Therefore, the value of the AD conversion input AD1 of the CPU 2 is the determination voltage Vth. It becomes lower (smaller).

  However, when the contact of the relay S2 is not normally off (open), that is, when the relay S2 is short-circuited (on), the voltage of the electric double layer capacitor CP1 is generated at the contact a. The value of the conversion input AD1 is higher (larger) than the determination voltage Vth.

  Then, the CPU 2 reads the value of the AD conversion input AD1, and determines whether or not the value is larger than the determination voltage Vth (step S210). If the CPU 2 determines that the value of AD1 is greater than the determination voltage Vth (step S210: Yes), the CPU 2 determines that the contact of the relay S2 is poorly welded and issues a service command SC to that effect (step S215). End the decision.

  If the CPU 2 determines that the value of AD1 is not greater than the determination voltage Vth (step S207: No), it determines that the contact of the relay S2 is not defective in welding.

  Next, the contact of the relay S2 is turned on (step S211).

  In this state, when the contact of the relay S2 is normally turned on (closed), the voltage of the electric double layer capacitor CP1 is generated at the contact a. Therefore, the value of the AD conversion input AD1 of the CPU 2 is the determination voltage Vth. Become higher (bigger).

  However, if the contact of the relay S2 is not normally on (closed), that is, is open (off), the voltage of the electric double layer capacitor CP1 is not generated at the contact a. The value of the conversion input AD1 is lower (smaller) than the determination voltage Vth.

  Then, the CPU 2 reads the value of the AD conversion input AD1, and determines whether or not the value is larger than the determination voltage Vth (step S212). When the CPU 2 determines that the value of AD1 is not greater than the determination voltage Vth (step S212: No), the CPU 2 determines that the contact of the relay S2 is defective in opening, and issues a service command SC to that effect (step S216). The pass / fail judgment ends.

  If the CPU 2 determines that the value of AD1 is greater than the determination voltage Vth (step S212: Yes), it determines that the contact of the relay S2 is not an open failure. In this case, finally, it is determined that the relay S2 and the discharge transistor S3 are good products.

  Whether or not the contact of the relay S2 is defective in opening can be determined later by separately detecting an abnormality in the fixing temperature control flow. S212 and step S216 may be omitted.

  When the service command SC is issued, processing corresponding to each service command is executed. For example, if the service command SC indicates that the discharge transistor S3 is short-circuited, the contact on (closed) of the relay S2 is prohibited and a display indicating that the discharge transistor S3 is defective is displayed on a display unit (not shown). Alternatively, a process of notifying the service that the discharge transistor S3 is defective is performed. The same processing is performed for other service commands SC as well, but this processing is normally performed in a digital copying machine, and a description thereof will be omitted.

  Table 2 shows the combinations of the bias transistor S1, the contact of the relay S2, and the on (closed) / off (open) state of the discharge transistor S3, the relationship between the voltages AD1 and Vth, and the relay in the above-described pass / fail judgment method The correlation between the determination results of S2 and discharge transistor S3 is summarized. This determination method is based on the assumption that no failure occurs in the bias transistor S1, which is a signal transistor.

  As described above, according to the power control device according to the third embodiment, the determination voltage for determining the presence or absence of abnormality of the relay and the discharge transistor can be corrected based on the charging voltage of the electric double layer capacitor. It is possible to determine the abnormality of the relay and the discharge transistor and the contents thereof regardless of the charging voltage of the electric double layer capacitor.

  Furthermore, according to the power control apparatus according to the third embodiment, the abnormality of the relay and the discharge transistor and the contents thereof can be determined by detecting the voltage change after AD conversion. In addition to being able to be widened, it is possible to simplify the pass / fail judgment circuit of the power control device, and it is possible to reduce the size and cost.

(Fourth embodiment)
In the fourth embodiment, whether or not the fixing heater HT2 is good is determined using the power control apparatus according to the third embodiment. A fourth embodiment will be described with reference to the accompanying drawings. Since the configuration of the digital copying machine and the configuration example of the power control apparatus according to this embodiment are the same as the configuration of the digital copying machine and the power control apparatus according to the third embodiment, refer to the above description. The description here is omitted.

(Quality determination method of fixing heater HT2)
A method for determining whether the fixing heater HT2 is good or bad by the power control device 4 will be described. FIG. 8 is a flowchart of a quality determination method for the fixing heater HT2. The pass / fail judgment method of the present embodiment is such that a resistance is applied from the electric double layer capacitor CP1 via the fixing heater HT2 when the charging voltage (output voltage) V2 of the electric double layer capacitor CP1 and the contact of the relay S2 are on (closed). The quality of the fixing heater HT2 is determined from the relationship of the drain voltage Vd generated by the current flowing through R31 and R32.

  First, the bias transistor S1 is turned off (opened) (step S301), the discharge transistor S3 is turned off (opened) (step S302), and the contact of the relay S2 is turned on (closed) (step S303).

  Next, the CPU 2 reads the voltage AD2 corresponding to the charging voltage (output voltage) V2 (step S304), and reads the voltage AD1 corresponding to the drain voltage Vd that has dropped through the fixing heater (step S305).

In the present embodiment, the resistance value of the fixing heater HT2 is expressed by the following mathematical formula (1).
Resistance value of fixing heater HT2 = (V2−Vd) × (R31 + R32) / Vd (1)
Further, the voltage values of the voltage AD1 and the voltage AD2 at the AD conversion input of the CPU 2 are expressed by the following mathematical formulas (2) and (3), respectively.
Voltage AD1 = Vd × R32 / (R31 + R32) (2)
Voltage AD2 = V2 × R35 / (R34 + R35) (3)

  Next, the CPU 2 obtains a voltage difference HA = AD2−AD1 between the voltage AD2 and the voltage AD1 (step S306), and determines whether or not the voltage difference HA is within a predetermined range of predetermined values H1 and H2. (Step S307).

  When the CPU 2 determines that the voltage difference HA is within the range between the predetermined values H1 and H2 (step S307: Yes), the fixing heater HT2 is determined not to have failed and is an appropriate heater. End the decision.

  When the CPU 2 determines that the voltage difference HA is not within the range between the predetermined values H1 and H2 (step S307: No), the fixing heater HT2 is an inappropriate heater, or has failed or deteriorated. Is displayed, a display for prompting replacement is performed (step S308), and the quality determination is terminated.

  As described above, according to the power control apparatus of the fourth embodiment, the voltage value obtained by directly detecting the charging voltage (output voltage) of the battery and the voltage value after passing through the fixing heater from the battery are detected. Thus, it is possible to estimate the characteristics of the fixing heater from these voltage values, and to determine whether the fixing heater is good or not, such as whether the fixing heater has an appropriate specification, or whether the fixing heater has failed or deteriorated. Therefore, it is possible to improve reliability.

  In the first to fourth embodiments, the power control device using an electric double layer capacitor as a capacitor has been described. However, the same effect can be obtained with a power control device using a storage battery, another capacitor, or the like. be able to.

  In the first to fourth embodiments, the power control device that controls the power supply to the fixing heater HT2 has been described. However, the power supply to other power loads that require a large amount of power, such as a lamp, is controlled. Even in the power control device, the same effect can be obtained with the same configuration.

  In the first to fourth embodiments, the power control apparatus using the relay S2 that mechanically opens and closes has been described. However, the power control apparatus that uses a semiconductor element such as a thyristor that does not require mechanical opening and closing. However, the same effect can be obtained with the same configuration.

  The above-described embodiment shows an example of a preferred embodiment of the present invention, and the present invention is not limited thereto, and various modifications can be made without departing from the scope of the invention. is there.

  The present invention includes a self-diagnosis device (including a circuit), a power supply device (including a circuit), an image forming device, a fixing device that heats a fixing member using charging power of a capacitor such as an electric double layer capacitor as an auxiliary power source, and It can be used for an image forming apparatus.

1 is a longitudinal sectional view of a digital copying machine according to a first embodiment of the present invention. 1 is a configuration diagram of a fixing device used in a digital copying machine. 1 is a circuit diagram of a power control apparatus according to a first embodiment of the present invention. It is a flowchart of the quality judgment method of relay S2 and discharge transistor S3. It is a circuit diagram of the electric power control apparatus concerning the 2nd Embodiment of this invention. It is a circuit diagram of the electric power control apparatus concerning the 3rd Embodiment of this invention. It is a flowchart of the quality judgment method of relay S2 and discharge transistor S3. It is a flowchart of the quality determination method of fixing heater HT2.

Explanation of symbols

1 Digital copier 2, 3, 4 Power control device 101 Automatic document feeder (ADF)
DESCRIPTION OF SYMBOLS 102 Document base 103 Paper feed roller 104 Paper feed belt 105 Contact glass 106 Image reading device 107 Transport roller 108 Paper discharge stand 109 Document set detector 110 First paper feed device 111 Second paper feed device 112 Third paper feed device 113- 115 Tray 116 Longitudinal Conveying Unit 117 Photoconductor 118 Writing Unit 119 Developing Device 120 Conveying Belt 121 Fixing Device 122 Paper Discharging Unit 123 Paper Discharging Tray 124 Double-Sided Paper Conveying Path 125 Reversing Unit 126 Double-Sided Conveying Unit 127 Reversing Paper Discharging Conveying Path 301 Fixing Roller 302 Pressure roller 306 Toner 307 Sheet

Claims (17)

A first opening / closing means disposed in a path of a current output from the current output means;
Second opening / closing means disposed downstream of the first opening / closing means in the current path;
Voltage supply means connected to the current path between the first opening and closing means and the second opening and closing means, and for supplying a voltage to the second opening and closing means;
Before SL are open instruction to the first opening and closing means, the second being the open instruction to open and close means, the voltage supply means in a case that supplies voltage, the first switching means Determining means for determining that the second opening / closing means is not open when the voltage between the second opening / closing means and the second opening / closing means is not higher than a predetermined voltage ;
A power control apparatus comprising: A first opening / closing means disposed in a path of a current output from the current output means;
Second opening / closing means disposed downstream of the first opening / closing means in the current path;
Voltage supply means connected to the current path between the first opening and closing means and the second opening and closing means, and for supplying a voltage to the second opening and closing means;
When the first opening / closing means is instructed to open, the second opening / closing means is instructed to close, and the voltage supply means supplies a voltage, and the first opening / closing means A judging means for judging that the second opening / closing means is a defect that does not close when a voltage between the second opening / closing means is higher than a predetermined voltage;
A power control apparatus comprising: A first opening / closing means disposed in a path of a current output from the current output means;
Second opening / closing means disposed downstream of the first opening / closing means in the current path;
Voltage supply means connected to the current path between the first opening and closing means and the second opening and closing means, and for supplying a voltage to the second opening and closing means;
The first opening / closing means is instructed to open, the second opening / closing means is instructed to open, and no voltage is supplied by the voltage supply means, and the first opening / closing means A judging means for judging that the first opening / closing means is not open when the voltage between the second opening / closing means is higher than a predetermined voltage;
A power control apparatus comprising: The determination means includes
When the voltage between the first opening / closing means and the second opening / closing means is not higher than the predetermined voltage,
When the first opening / closing means is instructed to close, the second opening / closing means is instructed to open, and the voltage supply means is not supplying voltage, the first opening / closing means and the second opening / closing means 2. The power control apparatus according to claim 1, wherein when the voltage between the two is not higher than the predetermined voltage, it is determined that the first opening / closing means is not defective. Further comprising a third switching means a voltage between said first switching means and second switching means are closed is higher than a predetermined voltage,
The determination means determines that the voltage between the first opening / closing means and the second opening / closing means is higher than a predetermined voltage based on the third opening / closing means being in a closed state, and the third opening / closing means any one of claims 1 to 4 but the voltage between the second opening and closing means and said first switching means based on an open state is characterized Rukoto, be determined not higher than the predetermined voltage The power control device according to item. The third opening / closing means includes a voltage converting means connected to a connection point between the first opening / closing means and the second opening / closing means, and a transistor pulled up by a resistor, and is connected to a logic circuit .
The judging means judges that the voltage between the first opening / closing means and the second opening / closing means is not higher than a predetermined voltage when the output of the third opening / closing means is at the H logic level, and the third opening / closing means Rukoto be determined voltage between the output of said first switching means when a logic L level and the second switching means is higher than the predetermined voltage,
The power control apparatus according to claim 5. Said voltage supply means, the power control system according to any one of claims 1 to 6, characterized in that, to supply a voltage based on said current output means to said second switching means. It said current output means, a power control device according to any one of claims 1 to 7, characterized in, that the electric storage means. Based on the charging voltage before Symbol storage means, further, the determination voltage determining means for determining the judgment voltage to determine whether higher than a predetermined voltage a voltage between said first opening and closing means and said second switching means The power control apparatus according to claim 8 , further comprising: Voltage converting means for converting a voltage between the first opening and closing means and the second opening and closing means;
First AD conversion means for AD converting the voltage converted by the voltage conversion means;
Charging voltage conversion means for converting the charging voltage of the power storage means;
A second AD converting means for AD converting the voltage converted by the charging voltage converting means;
The determination voltage determination means determines a determination voltage based on a charge voltage of the battery that has been AD converted by the second AD conversion means,
It said determination means that the voltage between the AD converted first switching means and said second switching means by the first AD conversion means determines a high squid whether than the determination voltage,
The power control apparatus according to claim 9 . The power control apparatus according to claim 1, wherein a load to which a current is supplied from the current output unit is disposed in the path. 12. The device according to claim 1, wherein the first opening / closing means is a relay, the second opening / closing means is a discharge transistor, and the voltage supply means is a circuit composed of a bias transistor and a diode. The power control apparatus according to claim 1. The power control apparatus according to claim 11 , wherein the load is a fixing heater.   The power control apparatus according to claim 11, wherein the load is a lamp. The power control apparatus according to any one of claims 1 to 11, wherein the first opening / closing means is a thyristor. The accumulator unit, it is an electric double layer capacitor, the power control apparatus according to any one of claims 8 to 10, characterized in. Further comprising a power control device according to any one of claims 1 to 16, an image forming apparatus according to claim.

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