JP4110376B2 - Image forming apparatus - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an image forming apparatus configured to be able to control a fixing device in an optimum state in any of operation modes during standby, monochrome printing control, and color printing control.
[0002]
[Prior art]
2. Description of the Related Art In an electrophotographic image forming apparatus such as a printer or a copying machine, a fixing device is provided for thermally fixing a toner image onto a transfer paper or the like. This fixing device has a heating roller, and a fixing heater such as a halogen lamp is used as a heat source of the heating roller.
[0003]
The fixing heater is connected in series to a commercial AC power supply having a power supply frequency of 50 Hz or 60 Hz, and is on / off controlled by a switch element. As described above, the fixing heater is controlled to be on / off, so that the temperature of the fixing heater is maintained at the set temperature.
[0004]
The fixing heater has a characteristic that the resistance value increases as the temperature rises, and the resistance value decreases as the temperature falls. For this reason, if the halogen lamp is controlled to be turned on / off by the switch element, an inrush current flows when the switch element is turned on.
[0005]
Incidentally, the power consumption of the fixing heater generally reaches about 80% of the entire image forming apparatus, and the rated current is large and a large amount of power is consumed. For this reason, when the switch element is turned on while the temperature of the fixing heater is low, a current that is 2 to 10 times larger than the rated current flows through the circuit, and a voltage drop ΔV due to this current and the power source impedance occurs.
[0006]
Depending on the magnitude of the rate of change (ΔV / dt) per unit time of the voltage drop ΔV, flickering occurs, causing problems such as flickering of a lighting fixture sharing a commercial power source. Regarding flicker, the International Electric Commission IEC 555-3 flicker standard and the European flicker standard (EN61000-3-3) are defined.
[0007]
In these standards, Pst (the integrated value of the change rate ΔV / dt of the voltage drop during the printing operation is measured for 10 minutes) is defined. In addition, Plt (Pst is measured 12 times for 10 minutes during standby, that is, measured for 2 hours, and the cube average of 12 Pst values is obtained) is defined.
[0008]
As described above, in the image forming apparatus, strict regulations are imposed on the flicker associated with the on / off control of the fixing heater. Various countermeasures have been taken against these regulations.
[0009]
FIG. 9 is a circuit diagram showing a conventional basic configuration for performing on / off control of the fixing heater (conventional example 1). In FIG. 9, 51 is a commercial AC power supply (AC), 52 is a fixing heater connected in series to the AC power supply 51, and 54 is a switch element that controls on / off of the fixing heater 52. As the switch element 54, a triac having generally good control efficiency is used.
[0010]
FIG. 18 is a characteristic diagram showing an example of control by the control circuit of FIG. 9 and shows the on / off state of the switch element 54 with respect to time t. FIG. 18A shows the standby control state. When the temperature of the fixing heater 52 is greatly increased during standby and the switch element 54 is turned off for a long time, the temperature of the fixing heater 52 decreases, and a large current flows when the fixing heater 52 is energized. Will occur.
[0011]
For this reason, since the regulation value of Plt may not be satisfied as described above, the fixing heater is turned on at regular intervals to prevent a decrease in temperature, that is, a decrease in resistance value. In this example, the ON / OFF cycle of the switch element 54 is selected so that the Plt satisfies Plt <0.65.
[0012]
FIG. 18B shows the characteristics of the monochrome printing control state. In this example, the ON / OFF cycle of the switch element 54 is selected so that the Pst satisfies Pst <1.0. Also in the color printing control state of FIG. 18C, the on / off cycle of the switch element 54 is selected so that Pst <1.0.
[0013]
FIG. 10 is a circuit diagram of an example in which a fixing heater and a resistor are used in combination (conventional example 2). In FIG. 10, a resistor 53 is connected in series with the fixing heater 52. The switch element 55 is connected in parallel with the switch element 54.
[0014]
In the example of FIG. 10, when it is necessary to limit the inrush current when the power is turned on, the switch element 54 is turned off and the switch element 55 is turned on, and the resistor 53 is connected in series with the fixing heater 52. In this way, the inrush current is suppressed by increasing the resistance value of the circuit. In a steady state, the switch element 54 is turned on and the switch element 55 is turned off, and only the fixing heater 52 is connected to the AC power source 51.
[0015]
FIG. 11 is a circuit diagram showing another example in which a fixing heater and a resistor are used in combination (conventional example 3). In FIG. 11, a first resistor 53 is connected in series with the fixing heater 52, and a second resistor 56 is connected in parallel with the first resistor 53. In addition, switch elements 55 and 57 are connected in series with the resistors 53 and 56.
[0016]
In the example of FIG. 11, when the temperature of the fixing heater 52 is lowered as when the image forming apparatus is started up, one resistor, for example, the first resistor 53 is connected in series with the fixing heater 52 ( Stage a). In this case, the switch elements 54 and 57 are turned off and the switch element 55 is turned on to suppress the inrush current.
[0017]
When the fixing heater 52 is heated to a predetermined temperature, the switch element 57 is turned on to connect a parallel circuit of resistors 53 and 56 in series with the fixing heater 52 (step b). In this case, the resistance value of the entire circuit is reduced as compared with the above (step a) in which only the first resistor 53 is connected to the fixing heater 52, and the circuit current increases.
[0018]
Further, when the temperature of the fixing heater 52 rises with time, the switch elements 55 and 57 are turned off to disconnect the resistors 53 and 56 from the circuit. Further, the switch element 54 is turned on, and only the fixing heater 52 is energized to operate the fixing device at the rated current (step c). Thus, in the example of FIG. 11, the resistance value of the entire circuit is switched to three stages.
[0019]
FIG. 12 is a circuit diagram showing another example in which a fixing heater and a resistor are used in combination (conventional example 4). In FIG. 12, a resistor 58 and a switch element 59 are added to the circuit of FIG. The second resistor 58 is connected in series with the first resistor 53.
[0020]
In the example of FIG. 12, when starting up the image forming apparatus, the switch elements 54 and 55 are turned off and the switch element 59 is turned on (step a). Therefore, the first resistor 53 and the second resistor 58 are connected in series to the fixing heater 52 to suppress the inrush current.
[0021]
Next, the switch element 54 and the switch element 59 are turned off, the switch element 55 is turned on (step b), and the resistor 53 is connected in series with the fixing heater 52 to suppress the circuit current. When the fixing heater 52 is heated to a predetermined temperature, the switch elements 55 and 59 are turned off, the switch element 54 is turned on (step c), and only the fixing heater 52 is energized. Also in the example of FIG. 12, the magnitude of the circuit resistance is switched in three stages as in FIG.
[0022]
FIG. 13 is a circuit diagram illustrating an example in which the fixing heater is controlled by being divided into a main heater and a sub heater (conventional example 5). In the example of FIG. 13, the switch elements 66, 67, and 68 are arranged so that the main heater 62 and the sub heater 63 are connected in series and parallel. In the example of FIG. 13, when the resistance value of the main heater 62 is Rm and the resistance value of the sub heater 63 is Rs, Rm <Rs is selected.
[0023]
When the image forming apparatus is started up (standby) and when color printing is performed, the switch element 66 and the switch element 68 are turned off, the switch element 67 is turned on, and the main heater 62 and the sub heater 63 are connected in series. The resistance value is increased to suppress the inrush current.
[0024]
  When performing monochrome printing, the switch element 67OFF, switch element 66, switch element 68The main heater 62 and the sub heater 63 are connected in parallel. It is also possible to energize only the main heater 62 by turning off the switch element 66 and the switch element 67 and turning on the switch element 68. Furthermore, it is possible to energize only the sub-heater 63 by turning off the switch element 67 and turning on the switch elements 66 and 68.
[0025]
14 to 16 are characteristic diagrams showing states of current change in the circuits of FIGS. 9 to 13. FIG. 14 corresponds to the circuit diagram of FIG. In the example of FIG. 14, when the image forming apparatus is started up, the inrush current Ix₁Flows. When the temperature of the heating roller rises with time, the current decreases and the rated current Ia flows.
[0026]
FIG. 15 corresponds to the circuit diagrams of FIGS. 10 and 13. In the example of FIG. 15, the current is limited at the initial stage where the resistance value is large, and the inrush current Iy₁Flows. When the resistance value is switched to a smaller value, the inrush current Ix₂When the temperature of the heating roller rises with time, the resistance value increases. For this reason, the current decreases and the rated current Ia flows. Thus, in the example of FIG. 15, the inrush current is suppressed in two stages by switching the resistance value.
[0027]
FIG. 16 corresponds to the circuit diagrams of FIGS. 11 and 12. In FIG. 16, inrush current Iz flows when the resistance value is the maximum value. When the resistance value is switched to an intermediate magnitude, the inrush current Iy is larger than Iz₂Flows. Furthermore, when the resistance value is switched to minimize the resistance value, the inrush current Ix_ThreeAnd gradually converges to the rated current Ia as time elapses. In the example of FIG. 16, the inrush current is suppressed in three stages by switching the resistance value.
[0028]
[Problems to be solved by the invention]
The conventional method 1 using the circuit diagram shown in FIG. 9 cannot cope with the shortening of the standby time (warm-up time) accompanying the recent increase in the printing speed and the increase in the capacity of the fixing heater power. was there.
[0029]
That is, since the power value of the fixing heater is increased, the inrush current is increased. This shows that the number of inrush current flows increases even if the ON / OFF cycle of the switch element is shortened in FIG. 18A, and as a result, there is a problem that there is no room for the standard Plt. Yes.
[0030]
When color printing is performed using a 4-cycle color laser printer, the on / off cycle Tx of the switch element shown in FIG. 18C is four times larger. This is because it takes time for four-color image formation, and during that time, it is not possible to supply a transfer material such as recording paper and perform fixing control.
[0031]
That is, the value of the drive duty (Ty / Tx) of the switch element that energizes the fixing heater is reduced. Therefore, since the non-sheet passing period during which the transfer material is not supplied to the fixing heater is increased, the time for turning off the switch element is also increased. In this way, since the cooling time becomes longer than the energization time, the resistance value of the fixing heater is lowered. For this reason, there is a problem that when the switch element is turned on, the inrush current is not suppressed and flicker generation cannot be prevented.
[0032]
As shown in FIGS. 10 to 12, in the method of limiting the inrush current by connecting an external resistor to the fixing heater, there is a problem that the power consumption by the external resistor is large and the power efficiency is deteriorated. That is, the power supplied from the AC power source is not consumed for the original operation of the image forming apparatus, but is consumed for other purposes at the time of start-up.
[0033]
In addition, since a resistor having a large heat capacity such as a cement resistor is used as the external resistor, there is a problem that it takes time to dissipate heat and the ambient temperature rises. Furthermore, there is a problem that the temperature of the fixing heater cannot be accurately controlled if the fixing heater is affected by the residual heat of the external resistance.
[0034]
As shown in FIG. 13, in the method of switching the connection between the main heater and the sub-heater in series-parallel, if the operation timing of the series-parallel switching switch element is not accurately controlled, all the switch elements become conductive and the power line is disconnected. There is a risk of short circuit. For this reason, there is a problem that it is necessary to take a measure such as connecting a resistor for short-circuit protection, and the circuit configuration is complicated.
[0035]
In addition, even when the method shown in FIG. 13 is used, there is a problem that it cannot cope with the special characteristics when performing color printing control using the 4-cycle color laser printer. That is, the cooling time is longer than the energization time for the fixing heater, so that there is a problem that the resistance value decreases and the inrush current cannot be suppressed.
[0036]
The present invention has been made in view of the above-described problems of the prior art, and the object thereof is to fix the fixing device in any of the operation modes of the fixing device in the standby control state, the monochrome printing control state, and the color printing control state. It is an object of the present invention to provide an image forming apparatus configured to be capable of controlling the image in an optimum state.
[0037]
[Means for Solving the Problems]
  The image forming apparatus of the present invention that achieves the above object includes a fixing heater that is divided into a first heater and a second heater and arranged in a fixing device,
The first heaterWhenThe second heaterExchangeFirst switching element connected to the flow power supplyandA second switch element;
  Temperature detecting means for detecting the temperature of the fixing device;In an image forming apparatus comprising:
  The first switch element connects the first heater to the AC power source in series via the second heater,
  The second switch element short-circuits the second heater and directly connects the first heater to the AC power source,
  In order to change the amount of electric power supplied to the fixing device according to the detection result of the temperature detection means, the ratio of the energization time (first duty) to the first switch element and the energization to the second switch element Control means for controlling the rate of time (second duty);Possess,
  The control means turns off the second switch element.For the first switch elementIncreasing the first duty and fixing it at a predetermined value;Increase the temperature of the fixing heater,
  At the stage where the first duty is fixedIf the amount of power is insufficient according to the detection result of the temperature detection means,The second switch elementAgainstThe amount of power supplied to the fixing device is controlled by increasing the second duty.
[0038]
  The present invention also provides a first heater.WhenA fixing heater divided into a second heater and disposed in the fixing device;
  The first heaterAnd the second heaterFirst switch element for connecting a power source to an AC power sourceandA second switch element;
  Temperature detecting means for detecting the temperature of the fixing device;In an image forming apparatus comprising:
  The first heater is connected to the AC power supply via the first switch element, and the second heater is connected to the AC in parallel with the first heater via the second switch element. Connected to the power supply,
  The second heater has the same rated power as the first heater or a higher rated power than the first heater,
  In order to change the amount of electric power supplied to the fixing device according to the detection result of the temperature detection means, the ratio of the energization time (first duty) to the first switch element and the energization to the second switch element Control means for controlling the rate of time (second duty);Possess,
  The control means is,in frontTurn off the second switch elementFor the first switch elementIncreasing the first duty and fixing it at a predetermined value;Increase the temperature of the fixing heater,
  At the stage where the first duty is fixedAccording to the detection result of the temperature detection means, if the amount of power is insufficient,The second switch elementAgainstThe amount of power supplied to the fixing device is controlled by increasing the second duty.
[0039]
  The present invention also provides the first heater andSaidThe second heater,SaidIt is arranged on either the heating roller or the pressure roller of the fixing device.
[0040]
  Further, according to the present invention, the amount of electric power when the first switch element is turned on is smaller than the amount of electric power necessary for performing a color image forming operation.SaidThe first heater and the first heater so that the amount of electric power when the first switch element is turned on is larger than the amount of electric power required to make the fixing device stand by at a predetermined temperature.SaidA resistance value of the second heater is set.
[0041]
  Further, according to the present invention, the amount of power required when the first switch element is turned on is larger than the amount of power required when performing the color image forming operation, and the amount of power required when performing the monochrome image forming operation. On the other hand, the first heater and the first heater so that the amount of power when the first switch element is turned on becomes small.SaidA resistance value of the second heater is set.
[0042]
  Further, according to the present invention, the control means includes the following control algorithm.SaidThe fixing heater is controlled.
  A) The step of obtaining the amount of power Wa supplied to the fixing device according to the detection result of the temperature detecting means.
  B) calculating the first duty (duty1) from the ratio between the supplied power amount Wa and the fixing heater power value Wb when the first switch element is turned on.
  C) If the first duty (duty1) is less than or equal to a predetermined value (dutyA), driving the first switch element with the first duty (duty1)
  D) driving the first switch element with the predetermined duty (duty A) if the first duty (duty 1) exceeds a predetermined duty (duty A);
  E) calculating the second duty (duty2) by the following equation:
  (Wa-WbXdutyA) / (Wc-WbXdutyA)
  Where Wa: the amount of power supplied to the fixing device
          Wb: fixing heater power value when the first switch element is turned on
          Wc: fixing heater power value when the first switch element and the second switch element are turned on
    dutyA: duty of a predetermined value (0 <dutyA ≦ 1)
  F) Driving the second switch element with the calculated second duty (duty2)
[0043]
  Further, according to the present invention, the control means includes the following control algorithm.SaidThe fixing heater is controlled.
  X) When the fixing device is put on standby at a predetermined temperature, the steps A) to F) are executed.
Y) When a color image forming operation is performed by a fixing device or a black and white image forming operation is performed, the steps E) and F) are performed after the step A) is performed.
[0044]
  Further, according to the present invention, the control means includes the following control algorithm.SaidThe fixing heater is controlled.
  A ′) calculating the amount of electric power Wa supplied to the fixing device in accordance with the detection result of the temperature detecting means.
  B ′) calculating the second duty (duty 2) by the following equation:
  (Wa-WbXdutyA) / (Wc-WbXdutyA)
  Where Wa: the amount of power supplied to the fixing device
          Wb: fixing heater power value when the first switch element is turned on
           Wc: fixing heater power value when the first switch element and the second switch element are turned on
   dutyA: duty of a predetermined value (0 <dutyA ≦ 1)
  C ′) If the second duty (duty 2) is equal to or greater than 0 (%), the calculated second duty (duty 2)The second switch elementAnd driving the first switch element with the predetermined duty (duty A).
  D ′) If the second duty (duty 2) is less than 0 (%), the ratio of the supplied power amount Wa to the fixing heater power value Wb when the first switch element is turned on is Step of calculating duty 1 of 1
  E ′) driving the first switch element with the calculated first duty (duty 1)
[0045]
  Further, according to the present invention, the control means includes the following control algorithm.SaidThe fixing heater is controlled.
  Z) When the fixing device is put on standby at a predetermined temperature, and when a color image forming operation is performed by the fixing device, the procedure of A ′) to E ′) is executed.
[0046]
  An image forming apparatus according to the present invention includes a fixing heater that is divided into a first heater and a second heater and arranged in a fixing device;
The first heaterWhenThe second heaterExchangeFirst switching element connected to the flow power supplyandA second switch element;
  Temperature detecting means for detecting the temperature of the fixing device;In an image forming apparatus comprising:
  The first switch element connects the first heater to the AC power source in series via the second heater,
  The second switch element short-circuits the second heater and directly connects the first heater to the AC power source,
  In order to change the amount of electric power supplied to the fixing device according to the detection result of the temperature detection means, the ratio of the energization time (first duty) to the first switch element and the energization to the second switch element Control means for controlling the rate of time (second duty);Possess,
  The control means turns off the second switch element.For the first switch elementIncreasing the first duty and fixing it at a predetermined value;Increase the temperature of the fixing heater,
  At the stage where the first duty is fixedIf the amount of power is insufficient according to the detection result of the temperature detection means,The second switch elementAgainstThe second duty is increased to control the amount of power supplied to the fixing device. For this reason, the amount of electric power supplied to the fixing heater can be controlled to control the fixing device in an optimum state. In addition, when the first heater is driven and controlled, the resistance value increases due to the preheating effect, so that inrush current can be suppressed and flicker can be prevented.
[0047]
In the present invention, the fixing heater is divided into a first heater and a second heater having the same rated power as that of the first heater or a rated power larger than that of the first heater. In this case, the first switch element and the second switch element for individually controlling the first heater and the second heater are provided, and the ratio of the energization time to each switch element is controlled. Yes. For this reason, even when the fixing heater is arranged as described above, the inrush current is restricted by the first heater and the second heater to prevent flickering, and the amount of power supplied to the fixing heater is controlled. The fixing device can be controlled in an optimum state.
[0048]
In the present invention, the first heater and the second heater are arranged on either the heating roller or the pressure roller of the fixing device in consideration of the amount of power supplied to the fixing heater. For this reason, the freedom degree of fixing device design can be raised.
[0049]
The present invention also provides resistance values of the first heater and the second heater in consideration of the electric energy required when the operation mode of the fixing device is each of the standby control state, the monochrome printing control state, and the color printing control state. Is set. For this reason, in any of the operation modes, the inrush current can be limited to prevent flicker, and the fixing heater can be rationally driven to avoid wasteful power consumption. Even when a four-cycle color laser printer is used, the temperature drop of the fixing heater, that is, the decrease in the resistance value can be reduced to suppress the inrush current and prevent the occurrence of flicker.
[0050]
Further, according to the present invention, the fixing device is provided with temperature detecting means, and the fixing means is fixed based on a control algorithm in which the control means distributes the driving control of the first heater and the driving control of the second heater according to the detection result of the temperature detecting means. The amount of power required for the instrument is being sought. Various modes can be applied to this control algorithm according to the operation mode of the fixing device, and rational control of the fixing device can be performed.
[0051]
DETAILED DESCRIPTION OF THE INVENTION
  The present invention will be described below with reference to the drawings. FIG. 1 is a circuit diagram showing a schematic configuration of a circuit for controlling a fixing heater applied to an image forming apparatus according to the present invention. In FIG. 1, 1 is a commercial AC power source, 2 is a main heater (first heater) of a fixing heater, and 3 is a sub-heater (second heater) of the fixing heater. Also,5Is a sub-switch element (first switch element), and 4 is a main switch element (second switch element).
[0052]
As shown in FIG. 1, in the present invention, the fixing heater is divided into a main heater 2 and a sub-heater 3 as in the conventional example 5, but the circuit configuration and details thereof will be described later. The energization control algorithm is different. In the configuration of FIG. 1, the main heater 2 and the sub heater 3 are connected in series with the main switch element 4 turned off and the sub switch element 5 turned on.
[0053]
Further, only the main heater 2 is energized with the sub switch element 5 turned on and the main switch element 4 turned on. As described above, the main heater 2 alone and the main heater 2 and the sub heater 3 are connected in series by the operation of the main switch element 4 and the sub switch element 5 to energize, but only the sub heater 3 is not energized. It is configured. When the resistance value of the main heater 2 is Rm and the resistance value of the sub heater 3 is Rs, the resistance value is basically selected so that Rm <Rs.
[0054]
In FIG. 2, the fixing heater is divided into a main heater 2 (second heater) and a sub-heater 3 (first heater), and the main switch element 4 (second switch element) and sub-switch element 5 (first switch), respectively. It is a circuit diagram which shows the example connected to AC power supply 1 via a switch element). When both the main switch element 4 and the sub switch element 5 are turned on, the main heater 2 and the sub heater 3 are connected to the AC power source 1 in parallel.
[0055]
In the example of FIG. 2, when the resistance value of the main heater 2 is Rm and the resistance value of the sub heater 3 is Rs, Rm ≦ Rs is selected. That is, the rated power of the main heater 2 is equal to or larger than the rated power of the sub heater 3.
[0056]
In the present invention, in common with the examples of FIGS. 1 and 2, the switch element that energizes the sub-heater 3 is the first switch element, and the switch element that connects only the main heater 2 to the AC power source is the second switch element. indicate. Therefore, in the example of FIG. 2, the sub switch element 5 (first switch element) connects the sub heater 3 (first heater) to the AC power source 1. The main switch element 4 (second switch element) connects the main heater 3 (second heater) to the AC power source 1.
[0057]
FIG. 5 is an explanatory diagram comparing the operating characteristics of the circuit of FIG. 1 with a conventional example. In FIG. 5, the vertical direction (X) column describes the prior art, the (Y) column describes Example 1 according to the present invention, and the (Z) column describes Example 2 according to the present invention. .
[0058]
In the (a) column in the horizontal direction of FIG. 5, the main power, that is, the fixing heater power value (W) when the main switch element 4 of FIG. 1 is turned on is described. The column (b) describes the sub power, that is, the fixing heater power value (W) when the sub switch element 5 in FIG. 1 is turned on.
[0059]
In the column (c), the operation mode of the fixing device is described. This operation mode defines the characteristics of the standby control state, the color print control state, and the monochrome print control state for each of the prior art (X), the first embodiment (Y), and the second embodiment (Z). .
[0060]
Here, the standby control state in the operation mode is a state in which the temperature control of the fixing device is performed without printing, and is controlled, for example, at a cycle of 3 seconds. The color printing control state is a state in which four colors of Y (yellow), M (magenta), C (cyan), and K (black) are sequentially formed and printed and fixed, for example, controlled at a cycle of 6 seconds. Further, in the monochrome printing control state, one color of K (black) is formed and printed and fixed. For example, control is performed at a cycle of 3 seconds.
[0061]
  In the (d) column, the main duty (No.2) (%). The main duty (%) indicates a ratio of time for energizing only the main heater 2 with the main switch element 4 turned on and the sub switch element 5 turned on.
[0062]
  In (e) column, sub-duty (No.1) (%). The sub-duty (%) indicates a ratio of time for energization when the main heater 2 and the sub heater 3 are connected in series with the sub switch element 5 turned on and the main switch element 4 turned off.
[0063]
In the (f) column, the heater power amount (Wh), that is, the power amount (Wh) supplied to the fixing device is described. The heater power amount (Wh) is represented by the product of the main power or sub power heater power and the main duty or sub duty heater driving duty, and indicates the required power amount of the fixing device.
[0064]
FIG. 17 shows characteristics corresponding to the operation mode (c) in the standby mode (Sa), color printing control (Ta), and monochrome printing control (Ua) in the prior art (X) of FIG. . The characteristics of FIG. 17 correspond to the circuit diagram of FIG.
[0065]
The characteristics of the prior art shown in FIG. 5 are created for comparison with the embodiment of the present invention. Actually, such characteristics are not described in the official gazette as a prior art.
[0066]
  In the prior art (X), the main heater52The power value (main power) is 1000 (W).
[0067]
At the time of standby in the operation mode (Sa), the main duty for turning on only the switch element 54 and energizing only the main heater 52 is 10 (%).
[0068]
The heater power amount (Wh) at this time is 1000 × 0.1 = 100 (Wh) because the main power is 1000 (W) and the main duty is 10 (%).
[0069]
  In FIG.MAIN"Shows the waveform of the drive signal of the switch element (switch element 54 in FIG. 9) energized to the main heater. A triac used as a switch element is basically subjected to zero cross control.
[0070]
ΔV is a voltage drop when a predetermined resistance is connected to the AC power source. That is, ΔV = (fixing heater current value X predetermined resistance value). At the time of standby (Sa), only the main heater 52 is connected and the resistance value is low, so that the current value of the fixing heater is large and the peak value of ΔV is also large.
[0071]
At the time of color printing control (Ta), referring to FIG. 5, the main duty is 30 (%). The heater power amount (Wh) at this time is 1000 × 0.3 = 300 (Wh).
[0072]
  In the (Ta) column of FIG. 17, the drive signal waveform of the switch element 54 during color printing control (MAIN) And ΔV. Also in this case, since only the main heater 52 is connected to the circuit and the resistance value is low, the current value of the fixing heater is large and the peak value of ΔV is also large.
[0073]
Referring to FIG. 5, when the operation mode is monochrome printing control (Ua), the main duty is 80 (%). The heater power amount (Wh) at this time is 1000 × 0.8 = 800 (Wh).
[0074]
  The waveform at the time of monochrome printing control (Ua) in FIG. 17 is that the main duty is changed from 30 (%) to 80 (%) and the energization time is longer than that at the time of color printing control (Ta). Corresponding to the aboveMAIN, ΔV have the same peak value and the pulse width increases.
[0075]
The characteristic corresponding to Example 1 according to the present invention in FIG. 5 (Y) is shown in FIG. Example 1 will be described with reference to FIG. Also in this example, the main power is set to 1000 (W) for comparison with the conventional example. The following control is performed by a control means not shown. For example, a CPU or the like can be used as the control means.
[0076]
The sub power is assumed to be 200 (W). As for the operation mode at this time, the main duty is set to 0 (%) and the sub-duty is set to 50 (%) during standby (Sb). The heater power amount (Wh) is 200 × 0.5 = 100 (Wh) because only the sub-duty is executed.
[0077]
  The waveform at the time of standby (Sb) in FIG. 7 is the drive signal of the main switch element 4 (FIG. 1).
0(%),subThe drive signal of the switch element 5 is 50 (%) duty (triac is basically 0 cross drive). Further, since a series circuit of the main heater 2 and the sub-heater 3 is connected to the AC power source 1 to increase the resistance value and reduce the current, the peak value of ΔV is smaller than that of the conventional example shown in FIG.
[0078]
Next, when the operation mode of FIG. 5Y is the color printing control (Tb), the main duty is 12.5 (%) and the sub-duty is 87.5 (%). The heater power (Wh) at this time is as follows.
[0079]
Heater electric energy = (1000 × 0.125) + (200 × 0.875) = 300 (Wh)
[0080]
In FIG. 7, with respect to the characteristics during color printing control (Tb), the drive signal of the main switch element 4 is energized and controlled with a duty of 12.5 (%), that is, a (1/8) cycle. The drive signal of the sub switch element 5 has a continuous energization waveform.
[0081]
Therefore, in the circuit diagram of FIG. 1, the sub switch element 5 is continuously energized, but the main switch element 4 is ON / OFF controlled with a duty of 12.5 (%). For this reason, when the main switch element 4 is on, the sub heater 3 is short-circuited and a heater current flows only through the main heater 2.
[0082]
  That is, the sub heater 3 is driven by continuous energization (100% duty), but the main switch element.4At a duty of 12.5 (%) when is turned on, no heater current flows through the sub heater 3. Therefore, the substantial sub-duty is 87.5 (%).
[0083]
In the characteristic diagram of FIG. 7 (Tb), at time ta, the sub-switch element 5 is energized, the main heater 2 and the sub-heater 3 are connected in series, and a heater current is supplied for preheating. As described above, after the resistance value of the main heater 2 is increased by preheating, the main heater 2 is energized only.
[0084]
When the main switch element 4 is energized at time tb and the main switch element 4 is turned off at time tc, only the main heater 2 is energized during the period from time tb to time tc, and the peak value Va of ΔV at this time Is formed based on the heater current flowing through the main heater 2.
[0085]
During a period from time tc to time td, a heater current flows in a state where the main heater 2 and the sub heater 3 are connected in series, and a peak value Vb of ΔV is formed based on the heater current at this time.
[0086]
When the operation mode of FIG. 5 (Y) is black and white printing control (Ub), the main duty is 75 (%) and the sub-duty is 25 (%). The heater power (Wh) at this time is obtained as follows.
[0087]
Heater electric energy = (1000 × 0.75) + (200 × 0.25) = 800 (Wh)
[0088]
As shown in FIG. 7 (Ub), during monochrome printing control, the main switch element 4 is energized and controlled with a duty of 75 (%). The sub switch element 5 is continuously energized. Therefore, as in the color printing control (Tb), when the main switch element 4 is turned on, the sub heater 3 is short-circuited and the heater current flows only to the main heater 2.
[0089]
Also in the case of FIG. 7 (Ub), the main heater 2 and the sub-heater 3 are connected in series at the beginning of the startup, a heater current is supplied, and the temperature of the main heater 2 is increased by preheating, and then only the main heater is used. Energization control is performed.
[0090]
  In the first embodiment, the sub power is set to (1/5) of the main power. Further, the relationship between the resistance value Rm of the main heater 2 and the resistance value Rs of the sub heater 3 is selected as Rm <Rs. For this reason, the heat generated when the sub switch element 5 is turned on is generated by the sub heater 3.Is betterMain heater 2thangrowing.
[0091]
Further, the heater power amount at the time of color printing control is 300 (Wh), which is a value larger than the sub power 200 (W), but is a value obtained by bringing them closer together. As shown in the characteristic of (Tb) in FIG. 7, the main power is added to the sub power, in other words, the shortage of the sub power is compensated by the main power to control the fixing device.
[0092]
Thus, in the first embodiment, during color printing control, the main heater 2 is continuously energized to prevent the temperature of the main heater 2 from decreasing. For this reason, flicker prevention can be performed more effectively than the conventional configuration.
[0093]
FIG. 6 is a characteristic diagram showing the relationship between the amount of heater power, that is, the amount of power supplied to the fixing heater, and the duty. In FIG. 6, electric power is supplied to the fixing heater at the first duty (duty 1). When the first duty (duty 1) exceeds a predetermined value (duty A), for example, 100 (%), the first switch element is driven with the predetermined duty (duty A). However, (0 <dutyA ≦ 1).
[0094]
In addition, the second switch element is driven with the second duty (duty 2). In the example of FIG. 6, the first duty (duty 1) is increased to 100 (%) and then fixed at 100 (%) to supply power to the fixing heater.
[0095]
In addition, when the first duty (duty 1) is fixed at 100 (%), the second duty (duty 2) is increased to supply power to the fixing heater. As described above, when the main heater is driven and controlled with the second duty, the resistance value is increased in advance due to the preliminary heating effect by the first duty, so that the inrush current is suppressed and the occurrence of flicker is prevented. be able to.
[0096]
In the above description, the first duty (duty1) is fixed when the predetermined value duty (dutyA) is 100 (%), but the predetermined value duty (dutyA) That is, an arbitrary value can be set within the range of 0 <dutyA ≦ 1.
[0097]
FIG. 6 also shows an example in which the first duty (duty 1) is fixed at a predetermined value duty (duty A) of 80 (%), for example. At the stage where the first duty (duty 1) is fixed at 80 (%), the second duty (duty 2) is increased to supply power to the fixing heater.
[0098]
Next, Example 2 according to the present invention described in the column (Z) of FIG. 5 will be described. In this example, the main power is set to 1000 (W) and the sub power is set to 500 (W). In the standby mode (Sc) of the operation mode, the main duty is 0 (%) and the sub-duty is 20 (%). In addition, the heater power amount is set to 500 × 0.2 = 100 (Wh).
[0099]
The characteristics when the operation mode is color printing control (Tc) are as follows: the main duty is 0 (%), the sub-duty is 60 (%), and the heater power is 500 × 0.6 = 300 (Wh).
[0100]
  In this example, the heater power amount is 300 (Wh), which is close to the sub power of 500 W. This is the figure8As shown in (Tc), the ratio of the energization time when the main heater and the sub-heater are connected in series is large, that is, the ratio of the energization time to the main heater is large, so the decrease in resistance value is reduced. . Therefore, inrush current can be effectively suppressed.
[0101]
Further, when the operation mode is black and white printing control (Uc), the main duty is 60 (%), the sub duty is 40 (%), and the heater power is (1000 × 0.6) + (500 × 0.4) = 800. (Wh).
[0102]
FIG. 8 is a characteristic diagram of the second embodiment. Compared with the characteristic of Example 1 in FIG. 7, the peak value of ΔV is larger in the characteristic during standby (Sc). Assuming that the resistance value Rm of the main heater 2 is fixed, the relationship with the resistance value of the sub-heater Rs is selected as Rm <Rs in the first embodiment as described above. Rm = Rs is selected.
[0103]
For this reason, the value of the circuit resistance R = Rm + Rs is smaller in the second embodiment than in the first embodiment, and the heater current is increased. Therefore, the voltage drop ΔV of the AC power supply increases.
[0104]
In the characteristic at the time of color printing control (Tc), since the main duty is 0 (%) and the sub duty is 60 (%) in the second embodiment, ΔV corresponding to only the sub duty is shown. Also in this case, the value of the circuit resistance R = Rm + Rs is smaller in the second embodiment than in the first embodiment, and the heater current is increased. Therefore, the peak value of the voltage drop ΔV of the AC power supply when controlled by the sub-duty is larger than that in the first embodiment.
[0105]
The characteristic at the time of monochrome printing control (Uc) indicates a voltage drop ΔV of the AC power source when the main duty is 40 (%) and the sub duty is 60 (%). Also in this example, the peak value of ΔV when controlled by the sub-duty is larger than that of the first embodiment.
[0106]
In the second embodiment, the sub power is 500 (W) and is set to (1/2) of the main power. In this example, the heater average power at the time of color printing control is 300 (W), which is a value smaller than the sub power 500 (W).
[0107]
Further, as described above, the relationship between the resistance value Rm of the main heater and the resistance value Rs of the sub heater is selected as Rm = Rs. For this reason, when the sub-switch element 5 is turned on and the main heater 2 and the sub-heater 3 are connected in series, the heat generation amounts of the main heater 2 and the sub-heater 3 are substantially equal. The relationship between the amount of power supplied to the fixing heater and the duty described with reference to FIG. 6 is naturally applied to the second embodiment.
[0108]
In the first embodiment, the sub power amount when the first switch element is turned on is 200 (Wh) with respect to the power amount (300 Wh) necessary for the color image forming operation. Get smaller. Further, since the sub power amount when the first switch element is turned on is 200 (Wh) with respect to the power amount 100 (Wh) required for making the fixing device stand by at a predetermined temperature, the power amount is growing. The resistance values of the main heater (first heater) and the sub heater (second heater) are set so as to obtain such characteristics.
[0109]
In the second embodiment, the sub power amount when the first switch element is turned on is 500 (Wh) with respect to the power amount 300 (Wh) necessary for the color image forming operation. Becomes larger. Further, since the sub power amount when the first switch element is turned on is 500 (Wh) with respect to the power amount 800 (Wh) required for the monochrome image forming operation, the power amount is small. The resistance values of the first heater and the second heater are set so as to obtain such characteristics.
[0110]
In the present invention, as in the first embodiment and the second embodiment, by appropriately setting the resistance values of the first heater and the second heater, the first switch with respect to the power supplied to the fixing device. Inrush current can be suppressed even when the amount of sub power when the element is turned on is large or small.
[0111]
Although description of the characteristic diagram is omitted, in the present invention, the following setting can be made as the third embodiment. That is, heater average power at the time of color printing control = sub power, for example, both are set to 300 W.
[0112]
In this case, assuming that the main power is a common value of 1000 (W), sub power ≈ (1/3) main power. In the third embodiment, the sub power is 300 (W), and is set to a value between 200 (W) in the first embodiment and 500 (W) in the second embodiment.
[0113]
Therefore, the fixing heater control at the time of color printing control in the third embodiment is a state in which the state of the first embodiment and the state of the second embodiment are switched. That is, the main heater 2 composed of a halogen lamp is intermittently turned on or completely turned off. Further, the sub heater 3 is fully lit or intermittently lit.
[0114]
Such a state varies depending on the amount of heat removed from the fixing device. In Example 3, the relationship between Rm and Rs is selected as Rm <Rs. For this reason, the heat generated when the sub switch element 5 is turned on is larger in the sub heater 3 than in the main heater 2.
[0115]
In each of the above embodiments, when the main power is 1000 (W), the sub power is 200 (W), 300 (W), and 500 (W), and the ratio of the main power to the sub power (power value ratio). Is changing.
[0116]
Even if the power value ratio is changed in this way, according to the present invention, by appropriately changing the main duty and the sub duty corresponding to the operation mode, the inrush current can be suppressed and flicker can be prevented. it can.
[0117]
In the present invention, as shown in FIG. 1, the basic configuration is that the sub switch element is turned on, the main switch element is turned off, and the main heater and the sub heater are connected in series and energized. When the heater power is insufficient, the main switch element is turned on and energization of only the main heater is used together.
[0118]
In this case, the temperature of the main heater has already increased due to preheating, and the resistance value has increased. For this reason, even if only the main heater is energized, the heater current is close to the rated current, the inrush current is limited, and flicker does not occur.
[0119]
  The present invention can also be applied to the case where the main heater 2 and the sub-heater 3 are connected to the AC power source 1 by the switch elements 4 and 5 alone or in parallel as shown in FIG. In this case, the main power in column (a) in the explanatory diagram of FIG.This is the power value when the main heater 2 and the sub heater 3 are connected in parallel when the switch element 4 (second switch element) and the switch element 5 (first switch element) are turned on.
[0120]
  Also, the sub power in column (b) isThis is the power value of the sub heater 3 (first heater) when the switch element 4 (second switch element) is turned off and the switch element 5 (first switch element) is turned on.The main duty in the column (d) indicates the ratio of energization to the switch element 4, and the sub-duty in the column (e) indicates the ratio of energization to the switch element 5.
[0121]
Also in the case of the circuit configuration of FIG. 2, the characteristic diagram of the relationship between the amount of power supplied to the fixing device and the duty shown in FIG. 6 is applied. That is, the first duty (duty 1) is increased to a predetermined value (duty A), and then fixed at this duty to supply power to the fixing heater. In addition, when the first duty (duty 1) is fixed, the second duty (duty 2) is increased to supply power to the fixing heater.
[0122]
In the present invention, as described above, the fixing heater is divided into the main heater and the sub heater. Next, an example of the arrangement of the divided fixing heaters will be described.
[0123]
FIG. 3 is an explanatory view showing an arrangement example of the fixing heater. In FIG. 3, 6 is a heating roller of the fixing device, 7 is a pressure roller, and 8 is a transfer material such as recording paper. In this example, the main heater 2 and the sub heater 3 are both disposed on the heating roller 6. A temperature detector 9 is arranged in the vicinity of the heating roller 6 and functions as a temperature detecting means for detecting the temperature of the fixing device.
[0124]
FIG. 4 is an explanatory view showing another arrangement example of the fixing heater. In FIG. 4, the main heater 2 is separated from the heating roller 6 and the sub-heater 3 is separated from the pressure roller 7. The temperature detector 9 is disposed in the vicinity of the heating roller 6.
[0125]
  The power value of the main heater 2 and the sub heater 3 is defined by the resistance value of each heater. In the present invention, as described above, no matter what the ratio (power value ratio) between (main power) and (sub power) is, the inrush current is limited to prevent the occurrence of flicker. As described above, the main duty and the sub-duty are controlled.
[0126]
For this reason, the setting of the power value ratio, that is, the resistance value setting of each heater can be secured. Therefore, even if each heater is placed on either the heating roller or the pressure roller of the fixing device, the amount of heat generated when the main heater alone or the main heater and the sub-heater are both connected to an AC power source is considered. By controlling the temperature, the amount of heat necessary for fixing can be obtained.
[0127]
Thus, the degree of freedom in which the heaters of the main heater and the sub-heater are arranged on which roller of the fixing device can be obtained, and according to the present invention, there is an advantage that the degree of freedom in designing the fixing device is increased.
[0128]
Next, an algorithm for temperature control of the fixing heater according to the present invention will be described. Normally, in the fixing device, a temperature detector is installed in the vicinity of the fixing heater, and data of the detected temperature is given to the control means to determine the driving duty of the fixing heater.
[0129]
In the present invention, the control means obtains the amount of power supplied to the fixing device from the data of the temperature detector. And the algorithm of the drive control distribution regarding a main heater and a sub heater is performed as follows from the obtained power supply amount.
[0130]
(Procedure example 1)
A) The step of obtaining the amount of power Wa supplied to the fixing device according to the detection result of the temperature detecting means.
B) calculating the first duty (duty1) from the ratio between the supplied power amount Wa and the fixing heater power value Wb when the first switch element is turned on.
C) If the first duty (duty1) is less than or equal to a predetermined value (dutyA), driving the first switch element with the first duty (duty1)
D) driving the first switch element with the predetermined duty (duty A) if the first duty (duty 1) exceeds a predetermined duty (duty A);
E) calculating the second duty (duty2) by the following equation:
(Wa-WbXdutyA) / (Wc-WbXdutyA)
Where Wa: the amount of power supplied to the fixing device
Wb: fixing heater power value when the first switch element is turned on
Wc: fixing heater power value when the first switch element and the second switch element are turned on
dutyA: duty of a predetermined value (0 <dutyA ≦ 1)
F) Driving the second switch element with the calculated second duty (duty2)
[0131]
  When the procedure example 1 is applied to the embodiment 1 according to the present invention shown in FIG. 4, in standby (Sb),
  A) Supply power is 100 (Wh)
  B) Sub-duty = 100/200 = 50 (%)
  C) With 50% dutyFirst switch elementThe drive
  It becomes. D) The following processing is not performed.
[0132]
  At the time of color printing control (Tb) in the first embodiment, the procedure 1 is
  A) Supply power is 300 (Wh)
  B) Sub-duty = 300/200 = 150 (%)
  D)First switch elementIs continuously driven at a predetermined duty, in this example 100% duty
  E) Main duty = (300−200) / (1000−200) = 12.5 (%)
  F)Second switch elementWith a duty of 12.5 (%)
  It becomes. Next, procedure example 2 will be described.
[0133]
  (Procedure example 2)
  A ′) calculating the amount of electric power Wa supplied to the fixing device in accordance with the detection result of the temperature detecting means.
  B ′) calculating the second duty (duty 2) by the following equation:
  (Wa-WbXdutyA) / (Wc-WbXdutyA)
  Where Wa: the amount of power supplied to the fixing device
          Wb: fixing heater power value when the first switch element is turned on
          Wc: fixing heater when the first switch element and the second switch element are turned on
                Power value
   dutyA: duty of a predetermined value (0 <dutyA ≦ 1)
  C ′) If the second duty (duty 2) is equal to or greater than 0 (%), the calculated second duty (duty 2)The second switch elementAnd driving the first switch element with the predetermined duty (duty A).
  D ′) If the second duty (duty 2) is less than 0 (%), the ratio of the supplied power amount Wa to the fixing heater power value Wb when the first switch element is turned on is Step of calculating duty 1 of 1
  E ′) driving the first switch element with the calculated first duty (duty 1)
[0134]
As described above, the algorithm of the procedure example 2 is a procedure opposite to the algorithm of the procedure example 1.
[0135]
  When Procedure Example 2 is applied to the characteristics of the monochrome printing control (Ub) of Example 1,
  A ′) Supply electric energy is 800 (W)
  B ′) Main duty = (800−200) / (1000−200) = 75 (%)
  C ')Second switch elementIs driven at 75 (%),First switch elementIs driven by energizing continuously at a predetermined duty, in this example, 100 (%) duty.
[0136]
As described above, when controlling the main heater, and both the main heater and the sub heater, the control algorithm may be changed depending on whether the operation mode is standby, color printing control, or monochrome printing control.
[0137]
In the first embodiment, the sub switch element is continuously energized (sub duty is 100%) during color printing control and monochrome printing control. In such a case, the procedure example 1 can be changed to the setting of the procedure example 3.
[0138]
(Procedure 3)
X) When the fixing device is put on standby at a predetermined temperature, the steps A) to F) are executed.
Y) When a color image forming operation is performed by a fixing device or a black and white image forming operation is performed, the steps E) and F) are performed after the step A) is performed.
[0139]
In the case of the second embodiment, the algorithm control of the procedure example 4 can be performed.
[0140]
Z) When the fixing device is made to stand by at a predetermined temperature and when the color image forming operation is performed by the fixing device, the steps A ′) to E ′) are executed.
W) When a monochrome image forming operation is performed by the fixing device, the procedure of D ′) and E ′) is executed after the procedure of A ′) is performed.
[0141]
Thus, in the present invention, the fixing heater is provided with a temperature detector, and is required for the fixing device based on the control algorithm that distributes the driving control when the main heater and the sub heater are connected to the AC power source. Looking for the right amount of electricity. Various modes can be applied to this control algorithm according to the operation mode of the fixing device, and rational control of the fixing device can be performed.
[0142]
When the main duty and the sub-duty are used in combination, the sub-duty is always preceded to increase the temperature of the main heater to recover the resistance value and limit the inrush current.
[0143]
The present invention can be applied not only to the two-roller fixing device described with reference to FIGS. 3 and 4, but also to a three-roller fixing device. It can also be applied to a belt fixing device.
[0144]
In the present invention, as shown in FIG. 1, the fixing heater is divided into a main heater (first heater) and a sub heater (second heater) and arranged on any roller of the fixing device. The second heater is connected to an AC power source by a sub switch element (first switch element), and the first heater is connected to an AC power source by a main switch element (second switch element). Yes.
[0145]
Then, a sub-duty (first duty) that is a ratio of energization time to the first switch element and a main duty (second duty) that is a ratio of energization time to the second switch element are set in the fixing device. It is changed according to the operation mode.
[0146]
For this reason, by setting the heater power amount of the fixing device to a predetermined value based on the power value of the first heater and the power value when the first heater and the second heater are connected to the AC power source, In any of the operation modes, the inrush current is limited to prevent flicker, and the fixing device can be controlled in an optimum state according to the operation mode.
[0147]
Although the image forming apparatus of the present invention has been described based on the embodiments, the present invention is not limited to these embodiments and can be variously modified.
[0148]
  As described above, the image forming apparatus of the present invention includes a fixing heater that is divided into a first heater and a second heater and arranged in a fixing device, and
The first heaterWhenThe second heaterExchangeFirst switching element connected to the flow power supplyandA second switch element;
  Temperature detecting means for detecting the temperature of the fixing device;In an image forming apparatus comprising:
  The first switch element connects the first heater to the AC power source in series via the second heater,
  The second switch element short-circuits the second heater and directly connects the first heater to the AC power source,
  In order to change the amount of electric power supplied to the fixing device according to the detection result of the temperature detection means, the ratio of the energization time (first duty) to the first switch element and the energization to the second switch element Control means for controlling the rate of time (second duty);Possess,
  The control means turns off the second switch element.For the first switch elementIncreasing the first duty and fixing it at a predetermined value;Increase the temperature of the fixing heater,
  At the stage where the first duty is fixedIf the amount of power is insufficient according to the detection result of the temperature detection means,The second switch elementAgainstThe second duty is increased to control the amount of power supplied to the fixing device. For this reason, the amount of electric power supplied to the fixing heater can be controlled to control the fixing device in an optimum state. In addition, when the first heater is driven and controlled, the resistance value increases due to the preheating effect, so that inrush current can be suppressed and flicker can be prevented.
[0149]
In the present invention, the fixing heater is divided into a first heater and a second heater having the same rated power as that of the first heater or a rated power larger than that of the first heater. In this case, the first switch element and the second switch element for individually controlling the first heater and the second heater are provided, and the ratio of the energization time to each switch element is controlled. Yes. For this reason, even when the fixing heater is arranged as described above, the inrush current is restricted by the first heater and the second heater to prevent flickering, and the amount of power supplied to the fixing heater is controlled. The fixing device can be controlled in an optimum state.
[0150]
In the present invention, the first heater and the second heater are arranged on either the heating roller or the pressure roller of the fixing device in consideration of the amount of power supplied to the fixing heater. For this reason, the freedom degree of fixing device design can be raised.
[0151]
The present invention also provides resistance values of the first heater and the second heater in consideration of the electric energy required when the operation mode of the fixing device is each of the standby control state, the monochrome printing control state, and the color printing control state. Is set. For this reason, in any of the operation modes, the inrush current can be limited to prevent flicker, and the fixing heater can be rationally driven to avoid wasteful power consumption. Even when a four-cycle color leather printer is used, the temperature drop of the fixing heater, that is, the decrease in the resistance value can be reduced to suppress the inrush current and prevent the occurrence of flicker.
[0152]
Further, according to the present invention, the fixing device is provided with temperature detecting means, and the fixing means is fixed based on a control algorithm in which the control means distributes the driving control of the first heater and the driving control of the second heater according to the detection result of the temperature detecting means. The amount of power required for the instrument is being sought. Various modes can be applied to this control algorithm according to the operation mode of the fixing device, and rational control of the fixing device can be performed.
[Brief description of the drawings]
FIG. 1 is a circuit diagram illustrating an example of an image forming apparatus according to an embodiment of the present invention.
FIG. 2 is a circuit diagram showing an example of an image forming apparatus according to another embodiment of the present invention.
FIG. 3 is an explanatory diagram showing a configuration of a fixing device used in the image forming apparatus of the present invention.
FIG. 4 is an explanatory diagram showing a configuration of a fixing device used in an image forming apparatus according to another embodiment of the present invention.
FIG. 5 is an explanatory diagram comparing the operation of the circuit of FIG. 1 with a conventional example.
6 is a characteristic diagram showing the relationship between the power supply amount and the duty in FIG.
7 is a characteristic diagram of Example 1. FIG.
8 is a characteristic diagram of Example 2. FIG.
FIG. 9 is a circuit diagram of a conventional example.
FIG. 10 is a circuit diagram of a conventional example.
FIG. 11 is a circuit diagram of a conventional example.
FIG. 12 is a circuit diagram of a conventional example.
FIG. 13 is a circuit diagram of a conventional example.
FIG. 14 is a characteristic diagram of a fixing current.
FIG. 15 is a characteristic diagram of a fixing current.
FIG. 16 is a characteristic diagram of a fixing current.
FIG. 17 is a characteristic diagram of a conventional example.
18 is a characteristic diagram showing an example of control by the control circuit of FIG. 9;
[Explanation of symbols]
1 ... AC power supply
2 ... Main heater
3 ... Sub-heater
4. Main switch element (second switch element)
5. Sub-switch element (first switch element)
6 ... Heating roller
7 ... Pressure roller
8 ... Transfer material
9 ... Temperature detector
51 ... AC power supply
52. Fixing heater
53 ... Resistance
54 ... Switch element
55 ... Switch element
56 ... Resistance
57 ... Switch element
58 ... resistance
59 ... Switch element
61 ... AC power supply
66 ... Switch element
67 ... Switch element
68 ... Switch element
Sa: standby characteristics of the prior art
Ta ... Characteristic of color printing control of the prior art
Ua: Characteristics of conventional monochrome printing control
Sb: standby characteristic of Example 1
Tb: Characteristic during color printing control of Example 1
Ub: Characteristic for black-and-white printing control of Example 1
Sc: standby characteristic of Example 2
Tc: Characteristic during color printing control of Example 2
Uc: Characteristic at the time of black-and-white printing control of Example 2
Main: Main switch element drive signal
Sub: Sub switch element drive signal
△ V ... Voltage drop of AC power supply

Claims (9)

A fixing heater that is divided into a first heater and a second heater and arranged in the fixing device;
A first switching element and the second switching element which connects the second heater and the first heater to ac power source,
In an image forming apparatus comprising a temperature detecting means for detecting the temperature of the fixing device,
The first switch element connects the first heater to the AC power source in series via the second heater,
The second switch element short-circuits the second heater and directly connects the first heater to the AC power source,
In order to change the amount of electric power supplied to the fixing device according to the detection result of the temperature detection means, the ratio of the energization time (first duty) to the first switch element and the energization to the second switch element and control means for controlling the percentage of time (second duty),
The control means turns off the second switch element, increases the first duty for the first switch element and fixes it at a predetermined value, raises the temperature of the fixing heater,
Wherein when the electric energy in accordance with the detection result of the first duty said temperature detecting means in a fixed stage is insufficient further increasing the second duty for the second switching element, the fuser An image forming apparatus that controls an amount of power to be supplied. A fixing heater that is divided into a first heater and a second heater and arranged in the fixing device;
A first switch element and a second switch element for connecting the first heater and the second heater to an AC power source;
In an image forming apparatus comprising a temperature detecting means for detecting the temperature of the fixing device,
The first heater is connected to the AC power supply via the first switch element, and the second heater is connected to the AC in parallel with the first heater via the second switch element. Connected to the power supply,
The second heater has the same rated power as the first heater or a higher rated power than the first heater,
In order to change the amount of electric power supplied to the fixing device according to the detection result of the temperature detection means, the ratio of the energization time (first duty) to the first switch element and the energization to the second switch element and control means for controlling the percentage of time (second duty),
Wherein, prior SL increases the first duty for the turn off the second switching element and the first switching element is fixed at a predetermined value, increasing the temperature of the fixing heater,
According detection result of said temperature detecting means at the stage of fixing the first duty, when the power amount is insufficient further increasing the second duty for the second switching element, said fixing device An image forming apparatus that controls an amount of electric power supplied to the image forming apparatus.   The image forming apparatus according to claim 1, wherein the first heater and the second heater are arranged on either a heating roller or a pressure roller of the fixing device.   Compared to the amount of power required for color image forming operation, the amount of power when the first switch element is turned on is small, and the amount of power required to make the fixing device stand by at a predetermined temperature. The resistance values of the first heater and the second heater are set so that the amount of power when the first switch element is turned on is increased. The image forming apparatus described.   The amount of power when the first switch element is turned on is larger than the amount of power required when performing a color image forming operation, and the amount of power required when performing a monochrome image forming operation is larger than the amount of power required when performing the monochrome image forming operation. 3. The image according to claim 1, wherein the resistance values of the first heater and the second heater are set so that the amount of electric power when one switch element is turned on becomes small. Forming equipment. The image forming apparatus according to claim 1, wherein the control unit controls the fixing heater by a control algorithm as follows.
A) obtaining electric power Wa supplied to the fixing device in accordance with the detection result of the temperature detecting means B) between the supplied electric power Wa and the fixing heater electric power value Wb when the first switch element is turned on A step of calculating the first duty (duty1) from the ratio C) If the first duty (duty1) is equal to or less than a predetermined value (dutyA), the first switch at the first duty (duty1) D) Driving the element D) If the first duty (duty 1) exceeds a predetermined duty (duty A), the first switching element is driven with the predetermined duty (duty A). E) The step of calculating the second duty (duty2) by the following equation (Wa-WbXdutyA) / (Wc-WbXdutyA)
Where Wa: the amount of power supplied to the fixing device
Wb: fixing heater power value when the first switch element is turned on
Wc: fixing heater power value when the first switch element and the second switch element are turned on dutyA: duty of a predetermined value (0 <dutyA ≦ 1)
F) Driving the second switch element with the calculated second duty (duty2) The image forming apparatus according to claim 6, wherein the control unit controls the fixing heater by the following control algorithm.
X) When the fixing device is kept at a predetermined temperature, the procedure of A) to F) is executed. Y) When the color image forming operation is performed with the fixing device or the monochrome image forming operation is performed, the procedure of A) is performed. After executing the procedure, execute steps E) and F) The image forming apparatus according to claim 1, wherein the control unit controls the fixing heater by a control algorithm as follows.
A ′) calculating the amount of electric power Wa supplied to the fixing device according to the detection result of the temperature detecting means B ′) calculating the second duty (duty2) by the following equation (Wa−WbXdutyA) / (Wc) -WbXdutyA)
Where Wa: the amount of power supplied to the fixing device
Wb: fixing heater power value when the first switch element is turned on
Wc: fixing heater power value when the first switch element and the second switch element are turned on dutyA: duty of a predetermined value (0 <dutyA ≦ 1)
C ′) If the second duty (duty 2) is equal to or greater than 0 (%), the second switch element is driven with the calculated second duty (duty 2), and the first switch element is set to the predetermined duty. D ′) Driving with a value duty (duty A) D ′) If the second duty (duty 2) is less than 0 (%), the supplied power amount Wa and fixing when the first switch element is turned on A step of calculating the first duty (duty 1) from the ratio to the heater power value Wb. E ′) A step of driving the first switch element with the calculated first duty (duty 1). The image forming apparatus according to claim 8, wherein the control unit controls the fixing heater by the following control algorithm.
Z) When the fixing device is put on standby at a predetermined temperature, and when a color image forming operation is performed by the fixing device, the procedure of A ′) to E ′) is executed

Images