JP2009236962A - Image forming apparatus and method of measuring capacitance of capacitor thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To accurately measure the capacitance of an electric double-layer capacitor functioning as an auxiliary power source of a fixing heater in an image forming apparatus, with a simple constitution, and to judge the service life of the capacitor. <P>SOLUTION: In the case the charging circuit of the electric double-layer capacitor is in a constant-current charging mode of a charging current I, the capacitance measurement of the electric double-layer capacitor is started as the electric double-layer capacitor finished charging and the voltage of the electric double-layer capacitor is reduced equal to or less than a fixed voltage. When the charged voltage reaches E1 after starting to charge the electric double-layer capacitor through the charging circuit, a timer is operated so as to count a time (t) until the voltage of the electric double-layer capacitor reaches E2. The capacitance C of the electric double-layer capacitor in this case can be obtained by an expression of C=I×t/(E2-E1)(F). The service life of the electric double-layer capacitor is judged based on the value C. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an image forming apparatus using an electric double layer capacitor as an auxiliary power source of a fixing device and a method for measuring the capacitance of the image forming apparatus.

  A fixing heater of a fixing device used in an electrophotographic image forming apparatus requires a large amount of power in a short time. Therefore, a technique for heating the fixing heater more rapidly by using power from an auxiliary power source such as a chargeable electric double layer capacitor as well as power supply from a commercial power source has been proposed.

  When determining the life of an electric double layer capacitor, it is necessary to know its capacity, but it is necessary to measure current in order to accurately determine the capacity of the electric double layer capacitor. There are two methods for measuring the current: (1) using a shunt resistor and (2) using a Hall element. However, in the method (1), the power loss due to resistance is large. In the method (2), the structure is complicated and expensive. Both methods are unnecessary as an image forming apparatus, and the cost is increased. There was a problem. Further, the internal resistance of the electric double layer capacitor can be used for the electric double layer capacitor in order to determine the life.

For example, Patent Document 1 discloses a fixing device that includes a main heater and a sub-heater in a fixing device, supplies power from a commercial power source to one of the heaters during warm-up, and supplies power from the power storage device to the other heater. In addition, a method for determining the life by measuring the internal resistance of the electric double layer capacitor is disclosed.
Japanese Patent No. 3784681

  However, in the method using the internal resistance, a plurality of electric double layer capacitors are connected in series and the internal resistance is measured as a unit. Therefore, the resistance value including the wiring resistance for connecting the electric double layer capacitor is measured. Therefore, there is a problem that the internal resistance of the electric double layer capacitor cannot be measured accurately. In addition, measuring the internal resistance of each electric double layer capacitor requires voltage detection for all electric double layer capacitors, resulting in a problem that the structure is complicated and the cost is increased.

  An object of the present invention is to easily and accurately measure the capacity of an electric double layer capacitor without adding parts and to determine the life of the electric double layer capacitor.

  An image forming apparatus according to the present invention stores a fixing device having a fixing heater, power storage means for supplying power to the fixing device, charging means for charging the power storage means at a constant current value, and a constant current value by the charging means. Storage means, a voltage measuring means for measuring the voltage of the power storage means, a charging time measuring means for measuring the voltage change time of the power storage means, a voltage change amount measured by the voltage measuring means and an electric time measuring means. And calculating means for calculating the capacity of the power storage means from the voltage change time and the current value stored in the storage means.

  The charging means charges the power storage means at a constant power value, the storage means stores the constant power value by the charging means, and the calculating means is based on the voltage change amount measured by the voltage measuring means and the charging time measuring means. The capacity of the power storage means is calculated from the measured voltage change time and the power value stored in the storage means.

  A fixing device having a fixing heater; a power storage means for supplying power to the fixing device; a discharging means for discharging the power storage means at a constant current value; a storage means for storing a constant current value by the discharging means; Voltage measuring means for measuring voltage, charging time measuring means for measuring voltage change time of power storage means, voltage change amount measured by voltage measuring means, voltage change time measured by charging time measuring means, and storage means And calculating means for calculating the capacity of the power storage means from the stored current value.

  The discharging means discharges the power storage means at a constant power value, the storage means stores the constant power value by the discharging means, and the calculating means uses the voltage change amount measured by the voltage measuring means and the charging time measuring means. The capacity of the power storage means is calculated from the measured voltage change time and the power value stored in the storage means.

  The fixing heater is a halogen heater, the storage means stores the resistance value of the halogen heater, and the calculation means stores the voltage change amount measured by the voltage measurement means and the voltage change time measured by the charging time measurement means. The capacity of the power storage means is calculated from the current value stored in the means.

  Further, the present invention is characterized by comprising warning means for judging the life of the power storage means from the capacity calculated by the calculation means and giving a warning.

  A method for measuring a capacitor capacity of an image forming apparatus according to the present invention includes a power storage step for supplying power to a fixing device, a charging step for charging the power storage step with a constant current value, and a storage step for storing a constant current value for the charging step. A voltage measurement step for measuring the voltage of the storage step, a charge time measurement step for measuring the voltage change time of the storage step, a voltage change amount measured by the voltage measurement step, and a voltage change measured by the charge time measurement step And a calculation step for calculating a capacity stored in the storage step from the time and the current value stored in the storage step.

  According to the present invention, the capacity of the electric double layer capacitor used in the fixing device of the image forming apparatus can be measured with high accuracy and easily, and deterioration of the electric double layer capacitor can be appropriately determined.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is a block diagram showing a configuration of a fixing device using an electric double layer capacitor as an auxiliary power supply in an image forming apparatus according to an embodiment of the present invention, and shows a configuration for supplying power to a fixing heater as a heating unit. Show.

  In FIG. 1, the fixing unit 1 includes fixing heaters (1) and (2). An electric double layer capacitor 2 serving as an auxiliary power source is connected to a charging circuit 3 and a discharging circuit 4, and the discharging circuit 4 is connected to a fixing heater (1). The main fixing heater (2) is connected to a commercial power source 6 through an AC control circuit 5. The charging circuit 3, the discharging circuit 4, and the AC control circuit 5 are controlled by a control signal from the control unit 7 to perform power control necessary for fixing.

  The charging circuit 3 includes an AC / DC converter and has a constant current charging mode or a constant power charging mode or both charging modes. The current value and the power value are measured in advance, and the storage device of the control unit 7 8 is stored. The control unit 7 includes an AD converter that measures the charging voltage of the electric double layer capacitor 2 and a timer 9 that measures the charging time of the electric double layer capacitor 2. The DC power source 10 converts the AC power of the commercial power source 6 into DC power and supplies it to the control unit 7. When the charging circuit 3 is configured by a DC / DC converter, the charging circuit 3 is connected to the DC power source 10. Further, the warning display unit 11 displays a warning when the capacitance C of the electric double layer capacitor 2 falls below a predetermined capacity.

  First, a first embodiment of the present invention will be described. FIG. 2 is a diagram showing the relationship between the voltage change of the electric double layer capacitor 2 during charging and time.

  When the discharge of the electric double layer capacitor 2 is completed and the voltage of the electric double layer capacitor 2 falls below a certain voltage, the capacity measurement is started. The charging circuit 3 starts charging the electric double layer capacitor 2 in response to a control signal from the control unit 7, and when the charging voltage reaches E1 in FIG. 2, the timer 9 is operated to set the voltage of the electric double layer capacitor 2 to E2. The time t until it reaches is measured. Using the measured charging start voltage E1, charging end voltage E2, and charging time t, the capacitance C of the electric double layer capacitor 2 is calculated as follows.

  When the charging circuit 3 is in the constant current charging mode, the capacity C is calculated by the following equation using the charging current I measured in advance and stored in the control unit 7.

  When the charging circuit 3 is in the constant power charging mode, the capacity C is obtained by the following equation using the charging power value W measured in advance and stored in the control unit 7.

  As described above, the capacitance of the electric double layer capacitor 2 can be easily calculated. In addition, since the measurement is performed in the constant current and constant power regions, the calculation can be performed with high accuracy.

  At the time of the measurement, immediately after the start of charging, the voltage changes abruptly due to the resistance of the electric double layer capacitor 2 and the wiring.

  Next, a second embodiment of the present invention will be described. The fixing heater (1) in FIG. 1 is composed of a halogen heater. The resistance value of the halogen heater is measured in advance and stored in the storage device 8 of the control unit 7.

  FIG. 3 shows the voltage change of the electric double layer capacitor 2 when discharging to the halogen heater. When the voltage of the electric double layer capacitor 2 is equal to or higher than E0, the discharge circuit 4 is operated by the control signal from the control unit 7, and the electric double layer capacitor 2 starts discharging. The discharge circuit 4 operates as a switch, and uses a relay, an FET, or the like. The voltage of the electric double layer capacitor 2 decreases with an exponential function. When the voltage reaches E1, the timer 9 is operated, and the time t when the voltage decreases from E1 to E2 is measured. The capacitance C of the electric double layer capacitor 2 is obtained from the following equation from the halogen heater resistance R, the measurement start voltage E1, the measurement end voltage E2, and the time t when the voltage of the electric double layer capacitor 2 decreases from E1 to E2. It is done.

  As described above, the resistance value R of the halogen heater is measured in advance and stored in the control unit 7 to measure the voltage change and the time required for the voltage change in the same manner as in the first embodiment. The capacitance C of the double layer capacitor 2 can be easily obtained.

  In the case of a halogen heater immediately after the discharge, the resistance value fluctuates due to a temperature change. Therefore, it is preferable to start measurement after the resistance value of the halogen heater has stabilized after a while.

  Next, a third embodiment will be described. The discharge circuit 4 in FIG. 1 has a constant current discharge mode, a constant power discharge mode, or both discharge modes. The current value I and the power value W are measured in advance and stored in the storage device 8 of the control unit 7. .

  FIG. 4 shows the voltage of the electric double layer capacitor 2 during constant current discharge. When the charging voltage of the electric double layer capacitor 2 is E0 or more, the discharge circuit 4 is operated by the control signal from the control unit 7 and the electric double layer capacitor 2 starts discharging. At the same time as the discharge is started, the voltage of the electric double layer capacitor 2 decreases. When the voltage of the electric double layer capacitor 2 reaches E1, the timer 9 is operated, and the time t when the voltage decreases from E1 to E2 is measured.

  The capacitance C of the electric double layer capacitor 2 from the time t when the discharge current I of the discharge circuit 4 measured in advance, the measurement start voltage E1, the measurement end voltage E2, and the voltage of the electric double layer capacitor 2 decrease from E1 to E2 When 4 is a constant current discharge mode, it is obtained by the following equation.

  Further, in the case of the constant power charging mode, it is obtained by the following equation.

  As described above, the capacitance C of the electric double layer capacitor 2 can be easily calculated. In addition, since the measurement is performed in the constant current and constant power regions, the calculation can be performed with high accuracy.

  At the time of the above measurement, immediately after the start of discharge, the voltage changes abruptly due to the resistance of the electric double layer capacitor and the wiring.

  According to the first to third embodiments, when the electric capacity C of the electric double layer capacitor 2 falls below a predetermined capacity, it is determined that the electric power for fixing by the electric double layer capacitor 2 is insufficient. Here, the warning display unit 11 displays a screen display, a warning by sound, etc., and prompts replacement, so that the electric double layer capacitor 2 can be used until the end of its life.

  According to the first embodiment, since the capacity is calculated using the current value or power value of the charging circuit 3 measured in advance, it can be easily obtained. Further, since the capacity is calculated using a constant current or constant power region, it can be obtained with high accuracy.

  According to the second embodiment, since the capacity is calculated using the resistance value of the halogen heater measured in advance, it can be easily obtained. In addition, since the change in the resistance value of the halogen heater is small when the temperature is stable, it can be obtained with high accuracy.

  According to the third embodiment, since the capacity is calculated using the current value or power value of the discharge circuit measured in advance, it can be easily obtained. Further, since the capacity is calculated using a constant current or constant power region, it can be obtained with high accuracy.

1 is a block diagram showing a configuration of a fixing device using an electric double layer capacitor according to an embodiment of the present invention. It is a graph which shows the voltage change and measurement timing of an electric double layer capacitor at the time of charge. It is a graph which shows the voltage change and measurement timing of an electric double layer capacitor when discharging to a halogen heater. It is a graph which shows the voltage and measurement timing of an electric double layer capacitor at the time of constant current discharge.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Fixing unit 2 Electric double layer capacitor 3 Charging circuit 4 Discharging circuit 7 Control unit 8 Storage device 9 Timer 11 Warning display unit

Claims (7)

A fixing device having a fixing heater;
Power storage means for supplying power to the fixing device;
Charging means for charging the power storage means at a constant current value;
Storage means for storing a constant current value by the charging means;
Voltage measuring means for measuring the voltage of the power storage means;
Charging time measuring means for measuring a voltage change time of the power storage means;
A calculation means for calculating a capacity of the power storage means from a voltage change amount measured by the voltage measurement means, a voltage change time measured by the charging time measurement means, and a current value stored in the storage means. An image forming apparatus. The charging means charges the power storage means with a constant power value,
The storage means stores a constant power value by the charging means,
The calculating means calculates the capacity of the power storage means from the voltage change amount measured by the voltage measuring means, the voltage change time measured by the charging time measuring means, and the power value stored in the storage means. The image forming apparatus according to claim 1, wherein: A fixing device having a fixing heater;
Power storage means for supplying power to the fixing device;
Discharging means for discharging the power storage means at a constant current value;
Storage means for storing a constant current value by the discharging means;
Voltage measuring means for measuring the voltage of the power storage means;
Charging time measuring means for measuring a voltage change time of the power storage means;
A calculation means for calculating a capacity of the power storage means from a voltage change amount measured by the voltage measurement means, a voltage change time measured by the charging time measurement means, and a current value stored in the storage means. An image forming apparatus. The discharging means discharges the power storage means at a constant power value,
The storage means stores a constant power value by the discharge means,
The calculating means calculates the capacity of the power storage means from the voltage change amount measured by the voltage measuring means, the voltage change time measured by the charging time measuring means, and the power value stored in the storage means. The image forming apparatus according to claim 3. The fixing heater is a halogen heater,
The storage means stores a resistance value of the halogen heater,
The calculation means calculates the capacity of the power storage means from the voltage change amount measured by the voltage measurement means, the voltage change time measured by the charge time measurement means, and the current value stored in the storage means. The image forming apparatus according to claim 1, wherein the image forming apparatus is an image forming apparatus.   6. The image forming apparatus according to claim 1, further comprising a warning unit that determines a life of the power storage unit from the capacity calculated by the calculation unit and issues a warning. A power storage step for supplying power to the fixing device;
Charging step for charging the power storage step with a constant current value;
A storage step for storing a constant current value by the charging step;
A voltage measuring step for measuring a voltage of the power storage step;
A charging time measuring step for measuring a voltage change time of the storage step;
A calculation step for calculating a capacity stored in the storage step from a voltage change amount measured in the voltage measurement step, a voltage change time measured in the charge time measurement step, and a current value stored in the storage step. A capacitor capacitance measuring method for an image forming apparatus.

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