JP4789905B2 - Image forming apparatus - Google Patents

Description

  The present invention relates to, for example, a heating device for heating various materials and apparatuses, a fixing device using the same, and an image forming apparatus such as an electrophotographic copying machine, a printer, and a facsimile using the fixing device. The present invention relates to an improvement in efficiency of a heating device in a fixing device.

  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 the input energy per unit time, that is, the rated power, should be increased. 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 this happens, a voltage lower by a certain level is supplied to the heating roller to delay the temperature of the fixing device from falling (see, for example, Patent Document 1), or the secondary battery as an auxiliary power supply device 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 primary battery to shorten the rise 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, so that much labor is required and the running cost such as the cost of the battery to be replaced is increased. 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 sudden current changes and inrush power when starting and stopping the supply of large power, and the 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 device. 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). As a basic function of the capacitor, the auxiliary heater is heated by the electric power supplied from the capacitor, and using this heat, the time for the heating roller to rise to a predetermined temperature is shortened, and the fixing temperature is prevented from lowering when passing paper. It is.

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

  By the way, in the apparatus as described above, the auxiliary heating body generates heat until the heating portion of the capacitor reaches a predetermined temperature every time, and whenever the main heating body is not heated by the main power supply device, The auxiliary heating body is controlled to be heated by the auxiliary power supply device, and the burden on the auxiliary power supply device becomes large, such as ON / OFF control of the large DC power.

  Further, in order to prevent the temperature decrease as described above, it is necessary to use the capacitor after it has been charged to a predetermined minimum voltage and can be discharged. Although the time required for charging is about several tens of seconds to about 2 minutes, the capacitor cannot be used during that time, so it is necessary to shorten the charging time.

SUMMARY OF THE INVENTION An object of the present invention is to provide an image forming apparatus that can solve the above-mentioned conventional problems by increasing the efficiency of use of an auxiliary power supply device that uses a capacitor as a power storage means .

The invention according to claim 1 for solving the above-mentioned problems is an image forming apparatus comprising a main power supply device, an auxiliary power supply device, and a fixing device for thermally fixing an image to a heated body , wherein the auxiliary power supply device is the main power supply device. A device having a capacitor as a power storage means that is charged by power from the device and that can be discharged to increase the maximum supply power from the power supplied from the main power supply device. A discharge voltage varying means for varying a discharge startable voltage at which discharge is possible in the middle;
It is characterized by that.

The invention according to claim 2, in the image forming apparatus according to claim 1, comprising a voltage measuring means of said main power supply, the discharge voltage varying means, when the voltage of the main power supply is higher than a predetermined voltage, the and performing control to lower the discharge electric start available-voltage.

The invention of claim 3 is the image forming apparatus according to claim 1 or 2, comprising a voltage measuring means of said main power supply, the discharge voltage varying means, when the voltage of the main power supply is lower than a predetermined voltage , and performs control for increasing the discharge electric start available-voltage.

According to a fourth aspect of the present invention, in the image forming apparatus according to any one of the first to third aspects, an environmental temperature measuring unit is provided, and the discharge voltage varying unit has a predetermined environmental temperature measured by the environmental temperature measuring unit. when higher than the value, and performs control to lower the discharge starting voltage capable.

According to a fifth aspect of the present invention, in the image forming apparatus according to any one of the first to third aspects, an environmental temperature measuring unit is provided, and the discharge voltage varying unit has a predetermined environmental temperature measured by the environmental temperature measuring unit. Control is performed to increase the discharge startable voltage when the value is lower than the value.

The invention of claim 6 is the image forming apparatus according to claim 4 or 5, a fixing paper feed quantity detecting means for detecting a fixing sheet passing number of the previous job in the fixing device, the the discharge voltage varying means in accordance with the detection information obtained by fixing paper feed quantity detecting means, characterized in that to perform control for varying the discharge start voltage capable of the auxiliary power unit.

The invention of claim 7 is the image forming apparatus according to claim 6, wherein the discharge voltage variable means when the sheet passing number in the previous job is larger than a predetermined value lowers the discharge start voltage capable of the auxiliary power unit Control is performed .

According to an eighth aspect of the present invention, there is provided the image forming apparatus according to any one of the fourth to seventh aspects, further comprising job time interval detecting means for detecting a time interval between the previous job and the current job in the fixing device. The discharge voltage varying means performs control to vary the discharge startable voltage of the auxiliary power supply device in accordance with detection information obtained by the job time interval detecting means.

The invention of claim 9 is the image forming apparatus according to claim 8, wherein the discharge voltage varying means is the auxiliary when the job time interval detected by the previous article job time interval detecting means have shorter than a predetermined value It is characterized in that control is performed to lower the discharge startable voltage of the power supply device.

The invention of claim 10 is the image forming apparatus according to any one of claims 4 to 9, has a job running time Maken known means for detecting during time the previous job running in the fixing device, the job runs the discharge voltage variable means and performing control to vary the firing voltage capable of the auxiliary power unit in accordance with the detection information obtained when Maken known means.

The invention of claim 11 is the image forming apparatus according to claim 10, the discharge start voltage permitted previous job uptime is the discharge voltage variable means when not longer than a predetermined value at the fixing device the auxiliary power unit It is characterized in that control for lowering is performed .

The invention of claim 12 is the image forming apparatus according to any one of claims 1 to 11, the capacitor is a storage means before Kiho auxiliary power supply and said electric double layer capacitor der Rukoto .

The present invention makes the temperature setting of the auxiliary heating element variable and reduces the voltage when the required power from the auxiliary power device may be small, thereby reducing the use ratio of the capacitor as the power storage means , Efficiency and optimization of charging of the auxiliary power supply can be achieved.

  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 mainly includes a reading unit 11 that reads a document, an image forming unit 12 that forms an image, an automatic document feeder (ADF) 13, a document discharge tray 14 that stacks documents sent from the ADF 13, The sheet feeding unit 19 includes sheet feeding cassettes 15 to 18 and a sheet discharge unit (sheet discharge tray 20) for stacking recording sheets.

  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 24 and the document image is read by the image reading unit 11.

  On the other hand, inside the image forming unit 12, a photoconductor 30 as an image carrier is disposed. The photosensitive member 30 is driven to rotate clockwise in the drawing, and the surface is charged to a predetermined potential by the charging device 31. Further, the writing unit 32 emits a laser beam 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 beam 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 in the lower part of the image forming unit 2 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 2 as indicated by an arrow B4, and the toner image transferred onto 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 mm 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, and auxiliary power supply control means 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 and 2b are fixed. Provided in the 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 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 with 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 the actual operation state, a voltage lower than the rated voltage is set as the charging 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. Further, since the nickel-cadmium battery has an allowable number of charge / discharge repetitions of about 500 to 1000 times, it has a short life as an auxiliary power supply for heating, and there is a problem in replacement labor and cost. The auxiliary power supply device 4 using a capacitor has an allowable number of repetitions of charge / discharge of several million times or more, is less deteriorated by repeated charge / discharge, and does not require liquid replacement or replenishment unlike a lead storage battery. Therefore, 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. It has excellent features such as strong resistance to repeated charge and discharge, long life, no maintenance, environmental friendliness, and high charge and discharge efficiency. Recently, capacitance is tens of thousands of F, energy density is several. A large capacity of 10 wh / kg has been developed, and the capacity is being increased further.

  The main switch 5 turns on / off the power supplied from the main power supply device 3 to the main heating element 2a, and the charger 6 sets the voltage according to the auxiliary power supply device 4 with the power supplied from the main power supply device 3. The capacitor C is charged by adjusting and rectifying from AC to DC.

  The auxiliary power control means includes a switching device 7, a switch 9, and a CPU 10, and serves as a discharge control means 8a and a power supply control means 8b. The discharge control means 8a switches between charging of the auxiliary power supply 4 and power supply from the auxiliary power supply 4 to the auxiliary heating element 2b under conditions described later.

  The power supply control means 8b performs power supply control for turning on / off the power supplied from the auxiliary power supply device 4 to the auxiliary heating element 2b under the conditions set later which are set in advance. 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.

  The basic operation of such a 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 heating the heating unit 2 with 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.

  In addition, the auxiliary power supply control means receives auxiliary power from the auxiliary power supply device 4 when a predetermined time elapses after the auxiliary power supply device 4 supplies power to the auxiliary heating element 2b of the heating unit 2 and starts heating. The electric power supplied to the heating element 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 in accordance with the reduction amount of the supplied power. 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 having such a configuration is transferred is conveyed between the fixing roller 40 and the pressure roller 41, and the toner T is heated by the fixing roller 40 heated to a constant temperature. Is heated and melted and fixed on the recording medium P as a toner image. 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.

  Next, a first case to which the present invention is applied among the image forming apparatuses according to the present example will be described. In this case, the auxiliary power supply control means 8 controls the operation of the auxiliary power supply device 4 as follows. That is, the auxiliary power supply control means 8 stops the power supply from the capacitor C to the auxiliary heating body when it is determined from various conditions that the temperature of the heating element 2 does not decrease even if the auxiliary heating body 2b is not heated. State.

That is, in this example, when the temperature sensor S1 that measures the temperature of the fixing roller 40 as the temperature of the heating element 2 is used as an index and is smaller than the rate of temperature decrease detected by the temperature sensor S1, the auxiliary power supply control is performed. The on / off control reference of the switch 9 of the means 8 is changed.

  FIG. 4 is a view showing the temperature of the fixing roller of the image forming apparatus having such a configuration. In the figure, the set temperature 1 of the auxiliary heating element represents a normal time, that is, when the temperature of the fixing roller 40 is drastically decreased (inclination is large) in this example.

Whereas the set temperature second auxiliary heating element when the primary power supply apparatus can afford, i.e. represents the time is gentle than the temperature lower under the fixing roller 40 is fixed threshold in this example in the present embodiment (the slope is small) Yes. In this example, when the temperature drop of the temperature T of the fixing roller 40 is small, it is assumed that there is no influence of the temperature drop of the heating element 2 even when the auxiliary heating element 2b is not heated, and power is supplied to the auxiliary heating element 2b. It stops.

  In this example, the control timing is τ, and at t0, the heating device 2 is supplied with power only from the main power supply device 3, and the temperature is equal to or higher than the threshold value of the minimum fixing temperature T0. Further, the rate of temperature decrease of the fixing roller 40 is small. In this case, the auxiliary power control means 8 sets the set temperature from T1 to T2. Then, the power supply from the auxiliary power supply is started at time t2, and the fixing roller 40 is temperature-controlled as shown by the solid line A in FIG. The temperature can be controlled to be less than the temperature setting T0 and with less ripple. Note that the values of T1 and T2 vary depending on the apparatus, and are appropriately determined by experiments or the like.

In contrast, it shows the state in FIG. 4 in dashed lines B, and when the temperature decreases similarly fixing roller and the above example is large. Also to fix the threshold of the power-up from the auxiliary power supply to the set temperature T _1. At this time, the power supply from the auxiliary power unit is started at the time of t _1. Therefore, the fixing roller 40 is temperature-controlled as shown in FIG. 4 in dashed lines B, the temperature of the fixing roller 40 becomes higher than necessary, the proportion of the capacitor becomes large.

Further, the state shown in FIG. 4 in broken line C is a case where the temperature drop of the fixing roller 40 unlike the example described above is small, in the fixed and the threshold of the power-up from the auxiliary power unit to the setting temperature T ₂ Is the case. At this time, the power supply from the auxiliary power unit is started at the time of t _1. Therefore, the fixing roller 40 is temperature-controlled as shown C line broken in FIG. 4, the power supply time from the auxiliary power supply becomes longer, the proportion of the capacitor becomes large.

Then, from the state shown in FIG. 4 in dashed lines D is when the temperature drop of the fixing roller is small. Further, the case that a fixed threshold of power application from the auxiliary power supply to the set temperature T _0. At this time, the power supply from the auxiliary power unit is started at time t _2, the fixing roller 40 is temperature-controlled as shown D line broken in FIG. 4, the ripple becomes large in this case, the set temperature T ₀ the falls below Rukotogaa Ri fixing becomes defective.

  Therefore, in the image forming apparatus according to the present example, the power supply setting of the auxiliary power supply device is controlled by the temperature change of the fixing roller 40, so that the proportion of use of the capacitor C can be reduced, and the auxiliary power supply is reduced. There exists an effect that the lifetime of an apparatus can be improved.

  In the image recording apparatus according to the present invention, in addition to the degree of temperature decrease of the heating unit 2 described above, the following may be used as an index for the auxiliary power supply control means to determine the timing of power feeding from the auxiliary power supply apparatus. it can. That is, the auxiliary power supply control means can perform control to change the lighting setting temperature based on the temperature state of the heating unit.

  In addition, a lighting state detection unit that measures the lighting state of the main power supply device is provided, and the auxiliary power supply control means changes the set temperature of the auxiliary power source, assuming that there is room when the lighting rate of the main power supply device is higher than a predetermined threshold. Can be controlled.

  Furthermore, a voltage measuring means for measuring the lighting state of the main power supply device is provided, and when the voltage of the main power supply device is higher than a predetermined threshold, the auxiliary power supply control means can perform control to change the set temperature of the auxiliary power supply. it can.

  And it is provided with the environmental temperature detection means which measures the environmental temperature of the environment where the heating device is arranged, and the auxiliary power supply control means, when the detected environmental temperature is higher than a predetermined value, the auxiliary power supply control means, Control to lower the set temperature of the auxiliary heating element can be performed.

  Next, a second case to which the present invention is applied will be described. In this example, in order to shorten the charging time, the discharge startable voltage of the capacitor C is varied by the discharge voltage varying means 8b. However, it is not merely variable, but information relating to the status of the heating device 1, in other words, information such as the temperature relating to the heating device 1 itself, the fixing device 36 using the same, and the image forming apparatus is detected, and the detection information. In response to this, the discharge startable voltage of the capacitor C is varied.

FIG. 5 shows a voltage change of the capacitor C used for heating the fixing roller 40 in the image forming apparatus described above, from a discharge stop state to a charge start, full charge (charge stop), and a voltage drop due to discharge. The capacitor C in the illustrated example has a fully charged voltage of 50 V, and discharge can be started when the voltage becomes 30 V or higher during charging, but the present invention is set to 30 V in this example. the discharge starting voltage capable, in which varying the auxiliary power control means in response to various conditions. Of course, the voltage values described above are merely examples, and there are, for example, configurations such as 45 V when fully charged, a minimum voltage capable of starting discharge of 32 V, a discharge stop voltage of 20 V, and the present invention is not limited to this example. Further, for example, the time from the start of charging t1 to the time when the lowest voltage at which discharge can start is reached is less than 1 minute, and the time until full charge (charge stop) t3 is within 2 minutes (1 to 1.5 minutes). It is.

The information is a condition for varying the discharge start voltage capable of capacitor C, it can be a voltage value of the main power supply 3. Various known means may be employed as voltage detecting means for detecting the voltage value of the main power supply device 3. The auxiliary power supply control means varies the discharge startable voltage of the capacitor C in accordance with the change in the voltage detection value of the main power supply device 3.

  For example, when the voltage value of the main power supply device 3 is higher than a predetermined value, the discharge startable voltage of the capacitor C is lowered. If the voltage of the main power supply 3 is high, it can be determined that the power supply amount of the main power supply 3 is large. In such a case, the amount of power supplied to the auxiliary heating element 2b by discharging the capacitor C may be small. Therefore, the charging time can be shortened by making the minimum charging voltage that enables the start of discharging variable and reducing the voltage when the required power is small. In addition, shortening the charging time is, in other words, realizing the shortening of the charging time by enabling discharge even in a normal charging state. Is the same.

  On the other hand, when the voltage value of the main power supply device 3 is lower than a predetermined value, the discharge startable voltage of the capacitor C is increased. If the voltage of the main power supply device 3 is low, it can be determined that the power supply amount of the main power supply device 3 is small. In such a case, unless the power supply amount to the auxiliary heating element 2b due to the discharge of the capacitor C is increased, the fixing roller 40 This is because the temperature of the fixing device 36 does not rise sufficiently and an image fixing failure in the fixing device 36 may occur. Such control is possible regardless of whether the main power supply 3 is an AC power supply or a DC power supply. It should be noted that the predetermined voltage value may be appropriately determined by experiments or the like. In each of the embodiments described below, the predetermined value is the same as in this example.

The information is a condition for varying the discharge start voltage capable of capacitor C, may be the temperature of the pressure roller 41 is a pressure member against the fixing roller 40. As temperature detecting means for detecting the temperature of the pressure roller 41, means such as various known temperature sensors may be employed. The auxiliary power supply control means varies the discharge startable voltage of the capacitor C according to the change in the temperature of the pressure roller 41.

  For example, when the temperature of the pressure roller 41 is higher than a predetermined value, the discharge startable voltage of the capacitor C is lowered. For example, when continuous image formation is performed by continuously passing paper through the image forming apparatus, the temperature of the pressure roller 41 becomes sufficiently high. In such a case, since the amount of heat from the fixing roller 40 taken away by the pressure roller 41 is small, the amount of power supplied to the auxiliary heating element 2b by the discharge of the capacitor C may be small. Therefore, the charging time can be shortened by making the minimum charging voltage that enables the start of discharging variable and reducing the voltage when the required power is small.

  Conversely, when the temperature of the pressure roller 41 is lower than a predetermined value, the discharge startable voltage of the capacitor C is increased. When the temperature of the pressure roller 41 is low, unless the amount of power supplied to the auxiliary heating element 2b due to the discharge of the capacitor C is increased, the heat of the fixing roller 40 is consumed to increase the temperature of the pressure roller 41, and fixing. This is because the temperature of the roller 40 does not rise sufficiently and an image fixing failure in the fixing device 36 may occur.

The information is a condition for varying the discharge start voltage capable of capacitor C, the heating device 1, the fixing device 36, environmental temperature of the image forming apparatus may be, for example, the nip temperature of the fixing roller 40 and the pressing roller 41 . Of course, since the temperature of the nip portion N between the fixing roller 40 and the pressure roller 41 is difficult to measure, the environmental temperature in this embodiment is only the internal temperature of the heating device 1, the fixing device 36, or the image forming apparatus. In addition, the external temperature of these devices can also be targeted. In any case, it is possible to set information detection targets for all such temperatures that affect or are thought to affect the fixing of images in the fixing device 36. The dischargeable voltage of the capacitor C is varied according to the change.

  For example, when the environmental temperature is higher than a predetermined value, the discharge startable voltage of the capacitor C is reduced to shorten the charging time, and when it is low, the discharge startable voltage of the capacitor C is increased. If the environmental temperature is as described above, the power supply amount to the fixing roller 40 may be small if it is high, and if it is low, the power supply to the auxiliary heating element 2b by discharging the capacitor C in order to prevent fixing failure. Increase the amount. The reason for this is the same as in the previous example for the temperature of the pressure roller.

The information is a condition for varying the discharge start voltage capable of capacitor C, it may be a fixing sheet passing number of the previous job in the fixing device 36. As a means for detecting the number of sheets that have been fixed, various known means such as a paper passing counter may be employed. The auxiliary power control means varies the voltage at which the capacitor C can start discharging according to the value of the number of sheets passing through the fixing sheet.

  For example, when the number of sheets to be passed in the previous job in the fixing device 36 is larger than a predetermined value, the discharge startable voltage of the capacitor C is lowered. If the number of sheets passed in the previous job is large, the temperature of the pressure roller 41 is sufficiently high, so that the auxiliary heating element 2b due to the discharge of the capacitor C is discharged as in the previous example corresponding to the temperature of the pressure roller. The amount of power supplied can be small, and the charging time can be shortened.

The information is a condition for varying the discharge start voltage capable of capacitor C, it may be the time interval between the previous job and the current job in the fixing device 36. Various known means such as a timer may be employed as means for detecting the time interval between jobs. The auxiliary power supply control means varies the discharge startable voltage of the capacitor C according to the job time interval. For example, when the job time interval is shorter than a predetermined value, the discharge startable voltage of the capacitor C is lowered. If the job time interval is short, the temperature of the pressure roller 41 is high, and the amount of power supplied to the auxiliary heating element 2b due to the discharge of the capacitor C may be small as in the previous example corresponding to the temperature of the pressure roller. , Can shorten the charging time.

The information is a condition for varying the discharge start voltage capable of capacitor C, it may be the operating time of the previous job in the fixing device 36. Various known means such as a timer may be employed as means for detecting the job operating time. The auxiliary power supply control unit varies the discharge startable voltage of the capacitor C according to the operation time of the previous job. For example, when the previous job operating time in the fixing device 36 is longer than a predetermined value, the temperature of the pressure roller 41 is high, and this is also the capacitor C as in the example corresponding to the temperature of the pressure roller 41 above. The amount of power supplied to the auxiliary heating element 2b due to the discharge may be small, and the charging time can be shortened.

The various corresponding embodiments described above can be implemented either alone or in combination with others. In each embodiment, although to carry out by the auxiliary power supply control means for the heating device 1 comprises a control for varying the discharge start voltage capable of capacitor C, the present invention is not limited to this, the fixing device 36 or it a control unit in an image forming apparatus comprising, thereby may be performed to control the discharge start voltage, also be provided with a dedicated control unit for the even discharge voltage control for each case, or other, Any of these may be used, and the present invention 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 described above. Various configurations such as a type in which the recording medium P is slidably in contact with or in close proximity to the heated object, such as a roller and belt, a nip portion N formed by a belt and a belt, can be adopted. It is. 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.

1 is a conceptual cross-sectional view showing an embodiment of an image forming apparatus according to the present invention. FIG. 2 is a conceptual cross-sectional view showing a configuration of a fixing device according to an embodiment of the present invention used in the image forming apparatus of FIG. 1. It is a circuit diagram which shows the structure of one Embodiment of the heating apparatus which concerns on this invention. FIG. 2 is a diagram illustrating a temperature control state of a fixing roller of the image forming apparatus in FIG. 1. FIG. 2 is a diagram illustrating a state from the start of charging of a capacitor of the image forming apparatus of FIG. 1 to full charge.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Heating apparatus 2 Heating part 2a Main heating element 2b Auxiliary heating element 3 Main power supply apparatus 4 Auxiliary power supply apparatus 5 Main switch 6 Charger 7 Switching apparatus 8 Auxiliary power supply control means 8a Power supply control part 8b Discharge control part 9 Switch 10 CPU
DESCRIPTION OF SYMBOLS 11 Reading unit 12 Image forming part 13 Automatic document feeder (ADF)
14 Document discharge tray 15, 16, 17, 18 Paper feed cassette 19 Paper feed unit 20 Paper discharge tray 21 Document base 25 Reading device 30 Photoconductor 31 Charging device 32 Writing unit 33 Developing device 34 Transfer device 35 Cleaning device 36 Fixing device 36 Fixing device 36 37 discharge roller pair 40 fixing roller 41 pressure roller C capacitor D document P recording medium T toner N nip S1 temperature sensor

Claims (12)

In an image forming apparatus comprising a main power supply device, an auxiliary power supply device, and a fixing device for thermally fixing an image to a heated object, the auxiliary power supply device comprises:
While being charged with power from the main power supply,
It is a device having a capacitor that can increase the maximum supply power as compared with the power supplied from the main power supply device by discharging, as a power storage means,
The auxiliary power supply device includes a discharge voltage varying means for varying a discharge startable voltage at which discharge is possible during charging.
An image forming apparatus. The image forming apparatus according to claim 1.
Voltage measuring means for the main power supply device,
The discharge voltage varying means includes
An image forming apparatus, wherein when the voltage of the main power supply device is higher than a predetermined voltage, control is performed to reduce the discharge startable voltage. The image forming apparatus according to claim 1 or 2,
Voltage measuring means for the main power supply device,
The discharge voltage varying means includes
An image forming apparatus, wherein when the voltage of the main power supply device is lower than a predetermined voltage, control is performed to increase the discharge startable voltage. The image forming apparatus according to any one of claims 1 to 3,
With environmental temperature measuring means,
The image forming apparatus according to claim 1, wherein the discharge voltage varying unit performs control to decrease the discharge startable voltage when the environmental temperature measured by the environmental temperature measuring unit is higher than a predetermined value. The image forming apparatus according to any one of claims 1 to 3, comprising an environmental temperature measuring means, the discharge voltage varying means, when the temperature of the environment measured by the environmental temperature measuring means is lower than a predetermined value, the discharge An image forming apparatus that performs control to increase a startable voltage. 6. The image forming apparatus according to claim 4 , further comprising a fixing sheet passing number detecting unit that detects the number of sheet passing through the fixing device in a previous job in the fixing device. image forming apparatus has the discharge voltage varying means in accordance with the obtained detection information and performing control to vary the firing voltage capable of the auxiliary power unit. The image forming apparatus according to claim 6, and characterized by performing control sheet passing number of the previous job is the discharge voltage variable means when more than a predetermined value lower the discharge starting voltage capable of the auxiliary power unit Image forming apparatus. The image forming apparatus according to any one of claims 4 to 7, has the job time interval detecting means for detecting a time interval between the previous job and the current job in the fixing device, resulting in the job time interval detecting means The image forming apparatus, wherein the discharge voltage varying means performs control to vary a discharge startable voltage of the auxiliary power supply device according to the detected information. The image forming apparatus according to claim 8, before Article job discharge starting voltage capable of jobs time interval detected by the time interval detecting means is the discharge voltage variable means when had shorter than a predetermined value the auxiliary power unit An image forming apparatus that performs control to lower the image. The image forming apparatus according to any one of claims 4 to 9, has a job running time Maken known means for detecting during time the previous job running in the fixing device, resulting in the job operation at Maken known means The image forming apparatus, wherein the discharge voltage varying means performs control to vary a discharge startable voltage of the auxiliary power supply device according to the detected information. The image forming apparatus according to claim 10, to carry out control in which the previous job operation time of the fixing device is the discharge voltage variable means when not longer than a predetermined value lower the discharge starting voltage capable of the auxiliary power unit An image forming apparatus. The image forming apparatus according to any one of claims 1 to 11, a storage means before Kiho auxiliary power supply capacitor is an image forming apparatus, wherein an electric double layer capacitor der Rukoto.