JP4679915B2 - Image forming apparatus - Google Patents

Description

The present invention relates to an image forming apparatus such as an electrophotographic copying machine, a printer, and a facsimile using a fixing device having a capacitor such as a capacitor, and more particularly, to an apparatus for improving the efficiency of using the capacitor by these devices.

In an image forming apparatus such as a copying machine, an image is formed on a recording medium such as plain paper or OHP, and an electrophotographic method is often employed because of high-speed image formation, image quality, cost, and the like. The electrophotographic method is a method in which a toner image is formed on a recording medium, and the formed toner image is fixed on the recording medium with heat and pressure. As the fixing method, the heat roller method is currently most frequently used from the viewpoint of safety and the like. In the heat roller method, a heat roller heated by a heat generating member such as a halogen heater and a pressure roller disposed opposite to the heat roller are pressed to form a mutual pressure contact portion called a nip portion, and a toner image is formed in the nip portion. Is heated and pressurized through the recording medium to which the toner has been transferred, thereby fixing the toner to the recording medium.

In recent years, environmental problems have become important, and energy saving is also progressing in image forming apparatuses such as copying machines and printers. In considering the energy saving of this image forming apparatus, what cannot be ignored is the power saving of the fixing device for fixing the toner to the recording medium. Therefore, to reduce the power consumption of the fixing device during standby of the image forming apparatus, the temperature of the heating roller is kept at a constant temperature slightly lower than the fixing temperature during standby, and immediately rises to a usable temperature during use. Many methods are employed so that the user does not wait for the temperature of the fixing roller to rise. In the case of this method, a certain amount of power must be supplied even when the fixing device is not used, thereby consuming extra energy. This standby energy consumption is said to correspond to approximately 70% to 80% of the energy consumption of the devices constituting the image forming apparatus.

Accordingly, it has been desired to reduce energy consumption during standby and to further save power, and there is a demand for zero power supply when not in use. However, if energy consumption is reduced to zero during standby, the heating roller of the fixing device mainly uses a metal roller such as iron or aluminum and has a large heat capacity, so that the temperature rises to a usable temperature of about 180 ° C. Requires a long heating time of several minutes to several tens of minutes. Such a waiting time deteriorates the usability of the user, so that a heating method that consumes as little power as possible while rapidly rising from the standby state is desired.

In order to shorten the heating time of the heating roller, it is clear that it is better to increase the input energy per unit time, that is, the rated power. In fact, in an image forming apparatus called a high-speed machine with a high printing speed, In many cases, the power supply voltage is 200V. However, in general offices in Japan, the commercial power supply is 100V, 15A, and it is necessary to carry out special work on the power-related equipment at the installation site in order to make it compatible with 200V. It's not an ideal solution.

That is, as long as a commercial power supply of 100 V and 15 A is used, the maximum input energy is determined by the power supply even when the temperature of the heating roller is to be raised in a short time. When the temperature of the fixing device becomes low, a voltage lower by a certain level is supplied to the heating roller to delay the temperature of the fixing device from dropping (for example, refer to Patent Document 1), or the secondary battery as an auxiliary power source is charged during standby of the fixing device, When the fixing device is started up, power is supplied from the main power supply device and the secondary battery or the primary battery to shorten the rising time (see, for example, Patent Document 2).

However, the technique disclosed in Japanese Patent Laid-Open No. 2004-228561 is not sufficient power saving because it supplies a low voltage to the fixing device by a certain level even during standby. Moreover, the maximum supply power at the time of start-up is not mainly intended to be higher than the power supplied from the main power supply device. On the other hand, the fixing device disclosed in Patent Document 2 supplies power from a main power supply device and a secondary battery or a primary battery at the time of start-up. As a secondary power supply, a lead storage battery, a nickel cadmium battery, or a nickel metal hydride battery is generally used. I use it. Such a secondary battery has a property that the capacity deteriorates and decreases when charging and discharging are repeated, and the life is shortened as discharging is performed with a large current.

There is also a phenomenon of capacity reduction due to the memory effect. Even if it is generally considered to have a long life with a large current, the number of charge / discharge cycles is about 500 to 1000 times. If 20 cycles of charge / discharge are repeated per day, the battery life will be reached in about one month. It will end up. Therefore, the replacement frequency of the battery is increased, and it takes much time and the running cost such as the cost of the battery to be replaced increases. Furthermore, in lead storage batteries, liquid sulfuric acid is used as the electrolyte, which is undesirable for office equipment.

In addition, the load on the heating circuit built in the heating roller increases due to a sudden current change or inrush power when starting or stopping the supply of large power, and input current is also applied to the peripheral circuits. There is also a problem that noise flows and flows. For this reason, it is not preferable to frequently turn on and off the power supply from the large-capacity auxiliary power supply. In addition, if a large amount of power is supplied at once, there is a possibility that the supply will be excessive and the temperature of the heating circuit will rise too much.

These points are improved to improve the power saving effect, reduce noise due to inrush current and sudden current change when supplying large power, shorten the rise time, and prevent the temperature from rising excessively. As the fixing device that can be used, a chargeable / dischargeable capacitor is used for the auxiliary power supply, the charger charges the capacitor of the auxiliary power supply with power supplied from the main power supply, and the switching device charges the auxiliary power supply. There has been proposed a device that switches power supply from an auxiliary power supply to an auxiliary heating element and adjusts the amount of power supplied from the auxiliary power supply to the auxiliary heating element (see, for example, Patent Document 3).

That is, for the purpose of turning on the power of the capacitor, first, by turning on the capacitor power when starting up the copying machine or the like, it is possible to supply power exceeding the amount that can be supplied from the commercial power supply to the fixing device. It is possible to raise. In addition, the high-speed machine has a problem that the heat of the fixing roller is taken away from the recording member and the roller temperature drops significantly, so there is a problem that a thin fixing roller with a small heat capacity cannot be used. By doing so, it is possible to prevent a drop in temperature and to use a thin roller in a high speed machine.

Japanese Patent Laid-Open No. 10-10913 Japanese Patent Laid-Open No. 10-282821 JP 2002-184554 A

By the way, the use of capacitors such as capacitors as described above is given the highest priority on preventing fixing failure, so that the capacitance of the electrostatic capacity may drop regardless of the number of continuous sheets and types of paper depending on the specifications of the copying machine. It is set not to occur. At present, the cost of capacitors is very high, and mounting of capacitors more than necessary increases the cost of image forming apparatuses such as copying machines. It is difficult to determine the optimum capacitance, and as a result, the conventional model has more capacitors than necessary. Therefore, in the past, it cannot be said that a capacitor such as a capacitor is efficiently utilized.

An object of the present invention is to provide an image forming apparatus capable of solving the above-described conventional problems by improving the setting and control of a capacitor such as a capacitor.

The image forming apparatus according to the present invention comprises a capacitor which is charged by the commercial power source, and a heating unit powered from the commercial power source and the capacitor, an unfixed image on a recording medium by heating by the heating unit a fixing device for fixing an image forming apparatus and an image reading unit for reading an original image on a document which is the source of the unfixed image, when power storage energy of the capacitor is equal to or higher than the threshold, the from the capacitor at the time of image reading A control unit that permits the start of power supply to the heating unit, and the time during which the temperature of the heating unit can be maintained at a set temperature or higher when the image is read by supplying power from the capacitor to the heating unit is the image. The reading unit is set to be longer than a maximum time during which a plurality of documents can be read continuously.

According to the second aspect of the present invention, in the image forming apparatus according to the first aspect, after the power supply from the power storage unit to the heating unit is started, the control unit stores a stored energy of the power storage unit that is lower than a discharge end threshold value that is lower than the threshold value. and Turkey to stop controlling the electric power supply to the heating unit from said condenser and said if it becomes.

According to the third aspect of the present invention, there is provided a capacitor charged by a commercial power source and a heating unit supplied with power from the commercial power source or the capacitor, and fixing an unfixed image on a recording medium by heating by the heating unit In the image forming apparatus including the fixing device to be operated and the image reading unit that reads the original image on the original document that is the basis of the unfixed image , when the energy stored in the capacitor is equal to or greater than a threshold value, A control unit that permits the start of power supply to the device , and the threshold value is a maximum time during which power can be supplied from the capacitor to the heating unit so that the image reading unit can continuously read a plurality of documents. It is characterized by being set so as to be more than time.

Those according to the fourth aspect is the image forming apparatus according to claim 3, wherein, after starting power supply from the capacitor to the heating unit, the power storage energy of the capacitor is lower discharge end threshold or less than the threshold value to stop the power supply from the capacitor to the heating unit if it becomes characterized Rukoto.

According to the fifth aspect of the present invention, there is provided a capacitor charged by a commercial power source, and a heating unit supplied with power from the commercial power source and the capacitor, and an unfixed image on the recording medium is heated by the heating unit. In an image forming apparatus including a fixing device for fixing and an image reading unit that reads an original image on a document that is a source of the unfixed image, when the energy storage energy of the capacitor is equal to or greater than a threshold value, A control unit that permits start of power supply to the heating unit, and controls to stop power supply from the capacitor to the heating unit when the stored energy of the capacitor is equal to or lower than a discharge end threshold lower than the threshold; The charging target voltage of the capacitor is equal to or higher than the threshold value, and the temperature of the heating unit is set during image reading by supplying power from the capacitor to the heating unit. Time can be maintained above the temperature, characterized in that said image reading portion is set to be equal to or greater than the maximum time capable of reading a plurality of originals continuously.

According to the sixth aspect of the present invention, there is provided a storage battery that is charged by a commercial power source, and a heating unit that is supplied with power from the commercial power source and the storage battery, and an unfixed image on the recording medium is heated by the heating unit. In an image forming apparatus including a fixing device for fixing and an image reading unit that reads an original image on a document that is a source of the unfixed image, when the energy stored in the capacitor is equal to or greater than a threshold value, A control unit that permits start of power supply to the heating unit, and controls to stop power supply from the capacitor to the heating unit when the stored energy of the capacitor is equal to or lower than a discharge end threshold lower than the threshold; When the charge target voltage of the battery is equal to or higher than the threshold and power can be supplied from the battery to the heating unit, the image reading unit has a plurality of original values. The is characterized by being set to be equal to or greater than the maximum hours that can be read continuously.
According to the seventh aspect of the present invention, there is provided a main power supply device and a fixing device having a heating unit to which power is supplied from the main power supply device, and fixing an unfixed image on a recording medium by heating by the heating unit; An auxiliary power supply device having a rechargeable battery that increases power supplied from the main power supply device to the heating unit, an image reading unit that reads an original image on a document that is a source of the unfixed image, and the document In an image forming apparatus comprising an automatic document feeder that conveys to the image reading unit, when the charging voltage of the capacitor is equal to or higher than a predetermined threshold, discharging from the capacitor during image reading is permitted, and A control unit that stops discharging when the charging voltage drops to a discharge end threshold lower than the threshold, and a discharge time required when discharging from the predetermined threshold to the discharge end threshold, Serial wherein the original image reading unit of the maximum number of stackable sheets of the automatic document feeder is characterized by being obtained by setting the predetermined threshold value so as to continuously read time or more.
According to the eighth aspect of the present invention, there is provided a main power supply device and a fixing device having a heating unit to which power is supplied from the main power supply device, and fixing an unfixed image on a recording medium by heating by the heating unit; An auxiliary power supply device having a rechargeable battery that increases power supplied from the main power supply device to the heating unit, an image reading unit that reads an original image on a document that is a source of the unfixed image, and the document An image forming apparatus including an automatic document conveying device that conveys to the image reading unit, and a control unit that permits discharge from the capacitor during image reading when a charge voltage of the capacitor is equal to or higher than a predetermined threshold, When the predetermined threshold value is set, the time for which the temperature of the heating unit can be maintained at a set temperature or higher when an image is read by discharging from the capacitor is set to the maximum number of documents in the automatic document feeder. Wherein the image reading portion is set so as to be continuously read time or more.
According to the ninth aspect of the present invention, in the image forming apparatus according to the seventh or eighth aspect , the capacitor is charged from the main power supply device to a charging target voltage during standby, and the charging target voltage is equal to the predetermined threshold value. It is characterized by being higher.
According to a tenth aspect of the present invention, in the image forming apparatus according to any one of the seventh to ninth aspects, a sheet passing operation continued from the end of the image reading operation of the image reading unit after the end of the image reading operation. Until the operation is completed, the power supplied from the main power supply device to the heating unit is made higher than that during the image reading.
Which according to the claim 1 1, an image forming apparatus wherein the capacitor according to any one of claims 1 to 1 0, characterized in that a capacitor.

The present invention, it is possible to prevent the power supplied to the fixing device at the time of images read operation is insufficient, to improve the utilization efficiency of 蓄 Appliances, cost reduction, downsizing achieved.

The best mode for carrying out the present invention will be described below with reference to the embodiments shown in the drawings.

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a cross-sectional view conceptually showing an image forming apparatus such as an electrophotographic copying machine or printer according to the present invention. The image forming apparatus according to the present embodiment is capable of, for example, 100 continuous sheets (75 CPM (CPM: copy speed)), and mainly includes a reading unit 11 for reading a document, and image formation for forming an image. Unit 12, automatic document feeder (ADF) 13, document discharge tray 14 for stacking documents sent from ADF 13, sheet feed unit 19 having sheet cassettes 15 to 18, and sheet discharge unit (sheet discharge) for stacking recording sheets It is constituted by a tray 20). For example, the ADF 13 has a maximum stacking number of 100 sheets, and the reading unit 11 sets the reading time of 100 originals to 60 seconds.

Then, when the document D is set on the document table 21 of the ADF 13 and an operation on an operation unit (not shown), for example, a press operation of a print key is performed, the uppermost document D is sent out in the direction of the arrow B1 by the rotation of the pickup roller 22. Then, by the rotation of the document conveying belt 23, the paper is fed onto the contact glass 24 fixed to the image reading unit 11, and stops there. The image of the document D placed on the contact glass 24 is read by a reading device 25 located between the image forming unit 12 and the contact glass 24. The reading device 25 includes a light source 26 that illuminates the document D on the contact glass 24, an optical system 27 that forms an image of the document, a photoelectric conversion element 28 that includes a CCD that forms an image of the document, and the like. After the image reading is completed, the document D is transported in the direction of arrow B2 by the rotation of the transport belt 23 and discharged onto the paper discharge tray 14. In this way, the document D is fed one by one onto the contact glass 14 and the document image is read by the image reading unit 1.

On the other hand, inside the image forming unit 12, a photoconductor 30 as an image carrier is disposed. The photoconductor 30 is rotated in the clockwise direction in the figure, and the charging device 31 charges the surface to a predetermined potential. Further, the writing unit 32 emits laser light L that is light-modulated in accordance with image information read by the reading device 25, and the surface of the charged photoreceptor 30 is exposed with the laser light L, whereby the photoreceptor is exposed. An electrostatic latent image is formed on the surface 30. When the electrostatic latent image passes through the developing device 33, the electrostatic latent image is transferred to the recording medium P fed between the photosensitive member 30 and the transfer device 34 by the opposing transfer device 34. The surface of the photoconductor 30 after the toner image is transferred is cleaned by a cleaning device 35.

A plurality of paper feed cassettes 15 to 18 arranged below the image forming unit 12 contain recording media P such as paper, and the recording media P is fed from any of the paper feed cassettes 15 to 18 in the direction of arrow B3. The toner image formed on the surface of the photoreceptor 30 as described above is transferred onto the surface of the recording medium P. Next, the recording medium P is passed through the fixing device 36 in the image forming unit 12 as indicated by an arrow B4, and the toner image transferred to the surface of the recording medium P by the action of heat and pressure is fixed. The recording medium P that has passed through the fixing device 36 is conveyed by the discharge roller pair 37, discharged to the discharge tray 20 as indicated by an arrow B5, and stacked.

FIG. 2 is a cross-sectional view showing an example of a fixing device 36 that heats and pressurizes the toner image transferred to the recording medium P and fixes the toner image to the recording medium. FIG. 3 shows one example of the heating device according to the present invention provided in the fixing device 36. It is a circuit diagram which shows the structure of embodiment.

The fixing device 36 shown in the figure has a fixing roller 40 and a pressure roller 41. For example, in a 75 cpm machine used for preventing the temperature of the fixing roller from being lowered during paper passing, the fixing roller 40 has an outer diameter φ40 and a wall thickness t0.7 mm. Aluminum rollers are used. This is because the thickness is such that the temperature can be raised to a state where fixing can be performed within 30 seconds, and even the load necessary to form the nip width N necessary for fixing is not destroyed. The 75 cpm machine used a thick roller of about t5.0 to 10 mm when the auxiliary power supply was not used. However, by combining the thin roller and the auxiliary power supply, the start-up time can be greatly shortened. Yes. Further, it is desirable that a release layer such as PFA or PTFE is formed on the outermost layer of the fixing roller. The fixing roller 40 includes a heating unit 2 including a main heating element 2a made of, for example, a halogen heater and an auxiliary heating element 2b. The fixing roller 40 and the pressure roller 41 pass through the recording medium P on which the toner T is placed. Thus, a nip portion N to be pressurized and heated is formed.

The heating device 1 of this embodiment includes a heating unit 2, a main power supply device 3, an auxiliary power supply device 4, a main switch 5, a charger 6, a switching device 7, and a control unit 8. In FIG. 3, the heating unit 2 composed of the main heating element 2a and the auxiliary heating element 2b is drawn outside the fixing roller 40. However, this is for convenience of illustration, and both the heating elements 2a, 2b Provided in the fixing roller 40.

The heating unit 2 includes a main heating element 2a that generates heat by the electric power supplied from the main power supply device 3, and an auxiliary heating element 2b that generates heat by the electric power supplied from the auxiliary power supply device 4, and is a fixing roller that is a heated object. 40 is heated. Although not shown in detail, the main power supply device 3 is supplied with power from a commercial power supply in the image forming apparatus in which the heating device 1 is installed. The main power supply device 3 has a function of adjusting, for example, power supplied from an outlet or the like to a voltage corresponding to the heating unit 2. However, since the main power supply device 3 is well known, detailed illustration and description are omitted.

The auxiliary power supply 4 has a chargeable / dischargeable capacitor C. As the capacitor C, for example, a module having a module configuration in which 15 to 40 cells having a rated voltage of 2.5 V and a capacitance of about 400 to 1000 F are connected in series to obtain a predetermined rated voltage and capacity is desirable. Further, for use in preventing a decrease in the fixing temperature during continuous paper feeding, for example, a heater having a rating of about 300 to 600 w, in which 18 to 22 cells of 500 to 700 F are connected in series, is suitable. This has sufficient capacity for power supply for about 1 to 2 minutes, and when all the stored power is supplied from a high temperature state due to a runaway control system, the power decreases as the voltage decreases, reducing the risk of ignition. This is because the capacity can be reduced. Another reason is that the voltage is about 50V and there is no danger of electric shock. In addition, for the purpose of supplying power at the time of start-up, for example, a heater having a rating of 800 to 1000 w is connected in parallel to the auxiliary power supply device to supply a total power of about 1600 to 2000 w. 44 connected in series is suitable. This is equipped with a capacity and voltage for supplying sufficient power for power supply for about 10 seconds, and a capacity capable of preventing a decrease in fixing temperature by using only one heater even when shifting during continuous paper feeding. It is for having. In actual operation, a voltage lower than the rated voltage is set as the charge target voltage because the reliability can be improved in consideration of variations in the voltage circuit and the durability of the capacitor cell. Also, a module configuration in which cells with lower capacitances of about 100 F are connected in parallel may be used. However, the number of electronic circuits required per cell can be reduced, and it is easy to detect when a failure occurs in the cell. It is desirable to connect the cells in series. The reason why the above configuration is adopted is that, unlike a secondary battery, a capacitor such as an electric double layer capacitor has excellent characteristics because it does not involve a chemical reaction.

As described above, in the auxiliary power supply using a general nickel-cadmium battery as a secondary battery, it takes a long time of several tens of minutes to several hours even if rapid charging is performed. The device 4 can be charged quickly for several minutes, and when the standby state and the heating state are repeated within the same time, the auxiliary power supply device 4 using a capacitor is used to reliably assist when starting up the heating. Electric power can be supplied from the power supply device 4, and the heating unit 2 can be raised to a predetermined temperature in a short time. In addition, since the nickel-cadmium battery has an allowable number of repetitions of charge / discharge of about 500 to 1000 times, it has a short life as an auxiliary power source for heating, and the trouble and cost of replacement are problematic. Auxiliary power supply device 4 using a battery has an allowable number of repetitions of charge and discharge of several million times or more, and is less susceptible to deterioration due to repeated charge and discharge, and does not require liquid replacement or replenishment unlike lead-acid batteries. It requires little maintenance and can be used stably for a long time.

An electric double layer capacitor does not have a dielectric, and uses the absorption and desorption reactions (charging and discharging) of the ion adsorbing layer of the electric double layer in which the charge of ions or solvent molecules formed at the solid electrode and solution interface is concentrated. Resistant to repeated charging / discharging, long life, no maintenance required, environmentally friendly, shorter charging time compared to other types of batteries, high charging / discharging efficiency, and easy detection of remaining power through voltage detection Recently, a large-capacity capacitor having an electrostatic capacity of tens of thousands of F and an energy density of several tens of wh / kg has been developed, and the capacity is being further increased.

The main switch 5 turns on / off the power supplied from the main power supply 3 to the main heating element 2a, and the charger 6 turns on the capacitor C of the auxiliary power supply 4 with the power supplied from the main power supply 3. Charge. The switching device 7 switches charging of the auxiliary power supply 4 and power supply from the auxiliary power supply 4 to the auxiliary heating element 2b.

The control means 8 has a switch 9 and a CPU 10 and performs control to turn on / off the power supplied from the auxiliary power supply device 4 to the auxiliary heating element 2b under preset conditions described later. However, the configuration of the control means 8 shown in the drawing is merely an example showing only a portion that controls the heating unit 2, and various configurations such as a device that controls the entire image forming apparatus can be employed. Further, the connection form for controlling the auxiliary power supply 4 is not limited to the illustrated example. For example, various forms such as a configuration in which the switching device 7 is switched to perform on / off control or the like can be employed.

The basic operation of the heating device 1 will be described. First, at the time of standby, the switching device 7 is switched and the charger 6 is connected to the auxiliary power supply device 4 to charge the capacitor C of the auxiliary power supply device 4. When the heating unit 2 is heated by the heating device 1 in this state, the main switch 5 is turned on to supply power from the main power supply device 3 to the main heating element 2a, and at the same time, the switching device 7 is switched and the auxiliary power supply device 4 is switched. Electric power is supplied to the auxiliary heating element 2b, and a large amount of electric power is supplied to the heating unit 2. Thus, when heating of the heating unit 2 is started, a large amount of power is supplied from both the main power supply device 3 and the auxiliary power supply device 4 to the heating unit 2, so that the heating unit 2 is brought to a predetermined temperature in a short time. Can be launched.

Further, when a predetermined time elapses after the auxiliary power supply 4 supplies electric power to the auxiliary heating element 2b of the heating unit 2 and starts heating, the control means 8 receives auxiliary heating from the auxiliary power supply 4. The electric power supplied to the body 2b is cut off to prevent overheating of the heating unit 2 and maintained at a predetermined temperature. The power supplied from the auxiliary power supply 4 to the auxiliary heating element 2b decreases as time elapses after the supply is started. A time for cutting off the power supplied from the auxiliary power supply 4 to the auxiliary heating element 2b is determined according to the reduction amount of the supplied power, and when the supply power is reduced to some extent, the auxiliary power supply 4 changes to the auxiliary heating element 2b. When the supplied power is cut off, it is possible to prevent deterioration of each component of the surrounding circuit and electromagnetic noise that occur when cutting off in the state of supplying a large amount of power.

The recording medium P to which the toner image T sent to the fixing device 36 is transferred is conveyed between the fixing roller 40 and the pressure roller 41, and the toner T is heated and melted by the fixing roller 40 heated to a constant temperature. The toner image is fixed on the recording medium P. Therefore, power is supplied from the main power supply device 3 and the auxiliary power supply device 4 to the main heating element 2a and the auxiliary heating element 2b included in the heating unit 2 of the fixing roller 40, thereby increasing the temperature of the fixing roller 40 and the auxiliary power supply. By controlling on / off of the power supplied from the device 4, the temperature of the fixing roller 40 is prevented from becoming too high, and the fixing temperature is kept at a constant temperature or a desired temperature, or a required temperature change is shown. Thus, the toner T is stably heated and melted, and a good quality toner image T is fixed on the recording medium P. Further, since the power is supplied from the main power supply device 3 and the auxiliary power supply device 4 to the main heating element 2a and the auxiliary heating element 2b of the heating unit 2 built in the fixing roller 40, the temperature of the fixing roller 40 is raised. The surface temperature of the toner can be quickly raised to a predetermined fixing temperature.

FIG. 4 is a diagram showing changes in the temperature of the fixing roller 40, the power supplied to the heating unit 2, the discharged power of the main power supply 3, and the remaining power of the auxiliary power supply 4 during the operation of the image forming apparatus configured as described above. It is. In this example, 100 originals are continuously fed (75 CPM), the maximum number of ADFs is 100, the rated voltage of the capacitor C is 45 V, the charging target value is 44 V (not to be fully charged to prevent deterioration), and the capacitor C The discharge start permission range is 30 to 44 V, and the discharge end value is 20 V (the discharge time from the target voltage 44 V to the end value 20 V is 60 seconds, for example). When the voltage of the capacitor C is less than 20V, the heat generation of the auxiliary heating element 2b of the heating unit 2 becomes small, so the voltage 20V is set as the end threshold value.

The temperature of the fixing roller 40 rises from the state of not consuming much power during standby, with the start of the start-up operation by the continuous copy command (time point a), and heat to the recording medium P by the start of the sheet passing operation (time point b). The temperature decreases as a result of the movement, and then increases slightly until the end of document reading (time point c) and the end of copying (time point d), and the temperature decreases when returning to the standby operation. In addition, between the time points a and b is, for example, 30 seconds, between the time points b and c, for example, 60 seconds, and between the time points b and d, for example, 80 seconds.

The power supplied to the heating unit 2 during this operation is from a power non-supply state (up to time point a) during standby, power supply by the main power supply device 3 (between time points a and b) at startup, and paper feeding operation. Power supply by the main power supply device 3 and the auxiliary power supply device 4 (between time points b and c), power supply by the main power supply device 3 (between time points c and d) after completion of document reading, and a non-supply state during standby Return (after time d) changes. The power supply (between time points b and c) by the main power supply device 3 and the auxiliary power supply device 4 is a capacitor of the auxiliary power supply device 4 in order to prevent the temperature of the fixing roller 40 from being lowered due to insufficient power supply during continuous paper feeding. Power is supplied using C to prevent a decrease in productivity such as a decrease in copy speed (cpm down) or stop until the temperature of the fixing roller 40 recovers during continuous paper feeding.

  Correspondingly, the power supply by the main power supply device 3 is the normal power of the commercial power supply whose power consumption is the upper limit value when image formation is started from the non-supply state in the standby state (for example, if the rated power is 1200 W, the value or (Neighbor value thereof) (between time points a and b), and power is distributed to the image reading and other driving units, so that the power of the fixing device 36 is reduced (for example, decreased to 800 W: between time points b and c), and image reading is completed. The power is restored by power recovery (for example, recovery up to 900 W: between time points c and d), and after the completion of copying, charging power for charging the capacitor C is supplied until time point e, and then returns to the standby state.

Further, the output voltage of the capacitor C of the auxiliary power supply device 4 shows a target value 44V which is the maximum value during standby, and is decreased by supplying power for heating the fixing roller 40 during the sheet passing operation (time points b and c). In the meantime, the voltage rises by receiving the charge after the copying is completed, reaches the target voltage at the time point e, and returns to the standby state.

The above-described control is performed by the control means 8, but since the power supply amount by the main power supply 3 that can be supplied to the fixing device 36 increases at the time point c when the document reading is completed, the discharge time of the capacitor C is set to the maximum number of sheets to be read ( If the number is set to 100 or more in the above example, the temperature drop of the fixing roller 40 can be avoided. Therefore, the setting is made as shown in FIG.

That is, referring to FIG. 5, as described above, the upper limit value 44V of the discharge start permission range is set as the first threshold value, and the lower limit value 30V of the discharge start permission range is set as the second threshold value. The time (A and B in FIG. 5 ) during which the temperature of the fixing roller 40 can be maintained at the set temperature or higher by the discharge from either threshold value to the discharge end voltage of 20 V is 100% for both of the originals. Is set to be longer than the maximum time that can be read continuously. Note Speaking in connection with the example of FIG. 4, the document reading time in FIG. 4 since it is 60 seconds, A, first in so that such a on B together 60 seconds or sets the second threshold value. For example A is 60 seconds or more, B is greater than or equal to 90 seconds. However, the time B may be set to be equal to or longer than the maximum time during which the document can be continuously read.

Of course, the above threshold value may be determined in other forms. For example, the reading unit 11 continuously supplies 100 originals not during the time during which the temperature of the fixing roller 40 can be maintained above the set temperature but during the time during which power can be supplied to the heating unit 2 by the discharge until the end of the discharge. You may set so that it may become more than the maximum time which can be read.

In the embodiment described above, various controls are performed by the control means 8 provided in the heating device 1, but the present invention is not limited to this, and the fixing device 36 or the image forming apparatus provided with the same is provided. Control means may be provided, and control may be performed by this, and in any case, a dedicated control means for controlling the discharge voltage may be provided, or any other control means may be used. However, it is not limited to the illustrated example.

In the embodiment described above, the nip portion N is formed by two rollers, that is, the fixing roller 40 and the pressure roller 41. However, the fixing device of the present invention and the image forming apparatus using the same are as follows. The present invention is not limited to such a configuration, and there are various configurations such as a type in which the recording medium P is slidably in contact with or close to the heated body, such as a roller and belt, a belt and a belt forming a nip portion N, and the like. It can be adopted. The present invention is not limited to the illustrated type of image forming apparatus. For example, the photosensitive member is not a drum but a belt type, and a color image forming apparatus using an intermediate transfer belt. Applicable. Furthermore, not only those using capacitors as auxiliary power supply devices, but also those using other capacitors such as secondary batteries may be used.

1 is a conceptual cross-sectional view showing an embodiment of an image forming apparatus according to the present invention. FIG. 1 is a conceptual cross-sectional view showing a configuration of a fixing device used in the image forming apparatus of FIG. 1 is a circuit diagram showing a configuration of an embodiment of a heating device used in the image forming apparatus of FIG. 1 is a diagram illustrating changes in the temperature of the fixing roller, the power supplied to the heating unit, the discharge power of the main power supply, and the remaining power of the auxiliary power supply during the operation of the image forming apparatus of FIG. FIG. 3 is a diagram illustrating an example of threshold setting in the image forming apparatus of FIG.

Explanation of symbols

1: heating device 2: heating unit 2a: main heating element 2b: auxiliary heating element 3: main power supply device 4: auxiliary power supply device 5: main switch 6: charger 7: switching device 8: control means 9: switch 10: CPU 11 : Reading unit 12: Image forming unit 13: Automatic document feeder (ADF) 14: Document discharge trays 15, 16, 17, 18: Paper feed cassette 19: Paper feed unit 20: Paper discharge tray 21: Document table 25: Reading device 30: photoreceptor 31: charging device 32: writing unit 33: developing device 34: transfer device 35: cleaning device 36: fixing device 37: discharge roller pair 40: fixing roller 41: pressure roller C: capacitor D: document P: Recording medium T: Toner N: Nip part

Claims (11)

A fixing device that has a capacitor charged by a commercial power source, and a heating unit that is powered by the commercial power source and the capacitor, and fixes an unfixed image on a recording medium by heating by the heating unit; In an image forming apparatus including an image reading unit that reads an original image on a document that is a source of an image,
When the energy storage energy of the capacitor is equal to or greater than a threshold, a control unit that permits the start of power supply from the capacitor to the heating unit at the time of image reading,
The threshold value is a maximum time during which the image reading unit can continuously read a plurality of documents while the temperature of the heating unit can be maintained at a set temperature or higher during image reading by supplying power from the capacitor to the heating unit. An image forming apparatus, wherein the image forming apparatus is set to be longer than the time. 2. The image forming apparatus according to claim 1, wherein after the start of power supply from the capacitor to the heating unit, the control unit removes the capacitor from the capacitor when the stored energy of the capacitor becomes equal to or lower than a discharge end threshold value lower than the threshold value. An image forming apparatus, wherein power supply to a heating unit is stopped. A non-fixed image having a capacitor charged by a commercial power source, a heating unit powered by the commercial power source or the capacitor, and fixing an unfixed image on a recording medium by heating by the heating unit; In an image forming apparatus including an image reading unit that reads an original image on a document that is a source of
When the energy storage energy of the capacitor is equal to or greater than a threshold, a control unit that permits the start of power supply from the capacitor to the heating unit at the time of image reading,
The threshold is set such that the time during which power can be supplied from the capacitor to the heating unit is equal to or longer than the maximum time during which the image reading unit can continuously read a plurality of documents. An image forming apparatus. In the above image forming apparatus according to claim 3, wherein, after starting power supply from the capacitor to the heating unit, from the capacitor when the power storage energy of the capacitor becomes equal to or less than a lower discharge end threshold than the threshold value an image forming apparatus comprising that you stop the power supply to the heating unit. A fixing device that has a capacitor charged by a commercial power source, and a heating unit that is powered by the commercial power source and the capacitor, and fixes an unfixed image on a recording medium by heating by the heating unit; In an image forming apparatus including an image reading unit that reads an original image on a document that is a source of an image ,
When the power storage energy of the battery is equal to or higher than a threshold, the power supply start from the battery to the heating unit is permitted at the time of image reading, and the power storage energy of the battery is lower than the discharge end threshold lower than the threshold. A control unit for stopping and controlling power supply from a capacitor to the heating unit ;
A time during which the temperature of the heating unit can be maintained at a set temperature or higher when an image is read by supplying electric power from the capacitor to the heating unit when the charging target voltage of the battery is equal to or higher than the threshold value . an image forming apparatus comprising Rukoto a set to be equal to or greater than the maximum time which can read the original continuously. A fixing device that has a capacitor charged by a commercial power source, and a heating unit that is powered by the commercial power source and the capacitor, and fixes an unfixed image on a recording medium by heating by the heating unit; In an image forming apparatus including an image reading unit that reads an original image on a document that is a source of an image ,
Before when power storage energy of the Ki蓄 collector is not less than the threshold value, as well as allow the starting power supply from the capacitor when the image reading to the heating section, if the power storage energy of the capacitor becomes equal to or less than a lower discharge end threshold than the threshold value A control unit for stopping and controlling power supply from the capacitor to the heating unit,
The charging target voltage of the battery is equal to or higher than the threshold value, and the time during which power can be supplied from the battery to the heating unit is equal to or longer than the maximum time during which the image reading unit can continuously read a plurality of documents. An image forming apparatus configured to be configured as follows. And the main power supply,
A fixing device having a heating unit to which electric power is supplied from the main power unit, and fixing an unfixed image on a recording medium by heating by the heating unit;
An auxiliary power supply device having a rechargeable battery that increases power supplied from the main power supply device to the heating unit;
An image reading unit that reads an original image on a document that is a source of the unfixed image ;
An image forming apparatus comprising: an automatic document feeder that conveys the document to the image reading unit ;
When the charging voltage of the capacitor is equal to or greater than a predetermined threshold value, the co Allowing discharge from the capacitor at the time of image reading, the charging voltage to lower than the predetermined threshold discharge end threshold to stop discharging when lowered With a control unit,
Wherein said predetermined such discharge time when discharged to the discharge end threshold value from the threshold, such that the said image reading unit the maximum loading number of sheets of original automatic document feeder is equal to or greater than during time that continuously reading An image forming apparatus characterized by setting a predetermined threshold value . And the main power supply,
A fixing device having a heating unit to which electric power is supplied from the main power unit, and fixing an unfixed image on a recording medium by heating by the heating unit;
An auxiliary power supply device having a rechargeable battery that increases power supplied from the main power supply device to the heating unit;
An image reading unit that reads an original image on a document that is a source of the unfixed image ;
An image forming apparatus comprising: an automatic document feeder that conveys the document to the image reading unit ;
If the charge voltage of the capacitor is equal to or greater than a predetermined threshold, with a to that control part permits the discharge from the capacitor at the time of image reading,
The predetermined threshold value, the discharge time to maintain the temperature of the heating portion when the image reading above the set temperature by from the storage battery, the maximum number of stackable sheets document the image reading portion is continuous target of the automatic document feeder an image forming apparatus characterized by being set to be higher during the time in that reading. The image forming apparatus according to claim 7 , wherein the capacitor is charged from the main power supply device to a charging target voltage during standby, and the charging target voltage is higher than the predetermined threshold value. Between before SL when the image reading operation end of the image reading portion to the sheet passing operation is continued after the image reading operation is completed is completed, the electric power supplied to the heating unit from the main power source device, when the image reading the image forming apparatus according to any one of claims 7 to 9, wherein the high to Rukoto than. The image forming apparatus according to any one of claims 1 to 10, wherein the capacitor is a capacitor.