Patent Grant
9223265
1. Field
Aspects of the present invention generally relate to an image forming apparatus such as a copying machine or a printer which includes a fixing unit.
2. Description of the Related Art
In recent years, there are image forming apparatuses such as the copying machine and the printer which operate at higher speed. Further, there is an increase in color image forming apparatuses, so that power consumption is increasing in portions other than the fixing unit of such image forming apparatuses. On the other hand, the maximum current which can be supplied from a commercial power supply to the image forming apparatus is restricted by a standard. As a result, the power which can be allocated to the fixing unit is decreasing. To solve such a problem, Japanese Patent Application Laid-Open No. 2007-108297 discusses setting timing at which a recording material starts to be conveyed based on warm-up state of the fixing unit, a voltage state of power supply, and an environmental temperature when forming an image. A fixing failure can thus be prevented, and a first print output time (FPOT) can be shortened.
However, if the image forming apparatus operates with an option external device such as an option sheet discharge device or an image scanner connected thereto, the power suppliable to the fixing unit is further reduced. To solve such a problem, when the option external device is connected to the image forming apparatus, the power to be allocated to the fixing unit is previously reduced by an amount of the power required by such an option device to operate. However, if the power to be supplied to the fixing unit is reduced, it becomes necessary to increase a warm-up time of the fixing unit to maintain fixing performance. In such a case, the FPOT becomes long.
According to an aspect of the present invention, an image forming apparatus, to which an option device is connectable, for forming a toner image on a recording material includes an image forming unit configured to form an unfixed toner image on a recording material, a fixing unit, having a heater, configured to fix the unfixed toner image on a recording material, a temperature detection unit configured to detect a temperature of the fixing unit, a power control unit configured to control power to be supplied to the heater so that the detected temperature becomes a target temperature for enabling fixing the unfixed toner image, and to set a maximum power suppliable to the heater according to a total power to be supplied to the image forming apparatus, and a conveyance control unit configured to control conveyance of a recording material, wherein the conveyance control unit executes, in a case where the maximum power is greater than a threshold power when the heating unit has started to warm up, a first mode where conveyance of a recording material is performed according to a time that has elapsed from when power supply to the heater has started, and executes, in a case where the maximum power is less than the threshold power, a second mode where conveyance of a recording material is performed according to the detected temperature, and wherein the power control unit sets a larger value to the threshold value when the option device is connected to the image forming apparatus as compared to when the option device is not connected to the image forming apparatus.
Further features of the present disclosure will become apparent from the following description of exemplary embodiments with reference to the attached drawings.
Various exemplary embodiments will be described in detail below with reference to the drawings.
It should be noted that dimensions, materials, shapes, and relative positioning of constituent components described in the following exemplary embodiments are appropriately changeable depending on an actual configuration of an apparatus to which these exemplary embodiments are applied. Therefore, these exemplary embodiments are not seen to limit the scope of the present disclosure.
<Configuration Outline of Image Forming Apparatus>
An intermediate transfer belt 19 contacts the photosensitive drums 13Y, 13M, 13C, and 13K. Primary transfer rollers 18Y, 18M, 18C, and 18K are disposed on opposite sides of the photosensitive drums 13Y, 13M, 13C, and 13K sandwiching the intermediate transfer belt 19.
A cassette 22 storing a recording material 21 in a sheet feed unit includes a recording material detection sensor 24 which detects whether there is a recording material therein. Further, a sheet feed roller 25, separation rollers 26a and 26b, and a registration roller 27 are disposed in a recording material conveyance path. Furthermore, a registration sensor 28 is arranged downstream of the registration roller 27 with respect to a recording member conveyance direction. Moreover, a secondary transfer roller 29 is disposed downstream with respect to the recording member conveyance direction and contacting the intermediate transfer belt 19. Further, a fixing unit 30 is disposed downstream of the secondary transfer roller 29 with respect to the recording member conveyance direction.
A controller 31, i.e., a control unit of the image forming apparatus, includes a CPU 32 having a read-only memory (ROM) 32a, a random access memory (RAM) 32b, and a timer 32c, and various input-output control circuits (not illustrated).
The electrophotographic process will be described below. The processes performed up until the developing process will be described below using the Y cartridge 12Y. The charging roller 15Y uniformly charges a surface of the photosensitive drum 13Y in a dark area inside the cartridge 12Y. The laser scanner 11Y then irradiates the surface of the photosensitive drum 13Y with a laser beam modulated according to image data. A charging potential of the portion irradiated with the laser beam is removed, so that an electrostatic latent image is formed on the surface of the photosensitive drum 13Y. A developing bias is applied in the developing unit, so that the toner on the developing roller 16Y adheres to the electrostatic latent image on the photosensitive drum 13Y to perform development. Such a developing process is performed in each of the cartridges 13M, 13C, and 13K.
A primary transfer bias is applied at a primary transfer portion at which the photosensitive drums 13Y, 13M, 13C, and 13K contact the intermediate transfer belt 19. The toner images formed on the photosensitive drums 13Y, 13M, 13C, and 13K are thus transferred to the intermediate transfer belt 19. Further, the CPU 32 controls image forming timing in each of the cartridges 12Y, 12M, 12C, and 12K according to a conveyance speed of the intermediate transfer belt 19. The CPU 32 thus sequentially transfers each of the toner images to be superimposed on the intermediate transfer belt 19. As a result, the full-color image is formed on the intermediate transfer belt 19.
On the other hand, the sheet feed roller 25 conveys the recording material 21 in the cassette 22, and the separation rollers 26a and 26b convey the recording material 21 sheet-by-sheet to the secondary transfer roller 29 via the registration roller 27. The toner image on the intermediate transfer belt 19 is transferred to the recording material 21 at a secondary transfer portion at which the secondary transfer roller 29 disposed downstream of the registration roller 27 contacts the intermediate transfer belt 19. According to the present exemplary embodiment, the image forming unit performs the above-described process until transfer of the toner image to the recording material 21. Further, according to the present exemplary embodiment, the registration roller 27 in the image forming apparatus controls conveyance of the recording material 21 so that the recording material 21 reaches the secondary transfer portion at the timing the toner image transferred to the intermediate transfer belt 19 reaches the secondary transfer portion.
The fixing unit 30 then fixes the toner image on the recording material 21, and the recording material 21 is thus discharged to outside the image forming apparatus.
<Configuration of the Fixing Unit>
The pressing roller 103 is rotationally driven by a drive source (not illustrated) at a predetermined circumferential speed in a counterclockwise direction indicated by an arrow illustrated in
An amount of power to be supplied to the heater 100 is controlled so that the temperature detected by the temperature detection member 104 becomes the target temperature.
<A Power Supplying Circuit>
A predetermined amount of power is supplied to the heating resistor 111 from a phase control circuit 60. One end of a temperature detection member 104 arranged on the back surface of the heater 100 is connected to a ground, and the other end to a resistor 55 and an analog input port AN0 in the CPU 32 via a resistor 59. Resistivity of the resistor 59 becomes low as the temperature becomes high. The CPU 32 thus detects the temperature of the heater 100 by dividing the voltage between the temperature detection member 54 and the fixed resistance 55, and converting the voltage to the temperature using a preset temperature table (not illustrated).
On the other hand, the power from the commercial power supply 50 is input to a zero-cross (zerox) generation circuit 56. The zerox generation circuit 56 outputs a high-level signal when a commercial power supply voltage is less than or equal to a threshold voltage near 0 V, and outputs a low-level signal in other cases. A pulse signal of approximately the same period as the period of the commercial power supply voltage is then input to a port PA1 in the CPU 32 via a resistor 57. The CPU 32 detects an edge at which the zerox signal changes from high-level to low-level, and uses the detected edge in controlling the timing in performing phase control and switching control.
The CPU 32 determines lighting timing for driving the phase control circuit 60 based on the detected temperature, and outputs a drive signal from a port PA3. The phase control circuit 60 will be described below. When the signal output from the output port PA3 becomes high-level at predetermined lighting timing, a transistor 65 is switched on via a base resistor 58. As a result, a phototriac coupler 62 is switched on. The phototriac coupler 62 is a device for maintaining a creeping distance between the primary side and the secondary side. Further, a resistor 66 limits the current flowing in a light-emitting diode in the phototriac coupler 62.
Resistors 63 and 64 are bias resistors for a triac 61, and the triac 61 becomes energized when the phototriac coupler 62 is switched on. When an ON trigger is applied while the AC is supplied to the triac 61, the triac 61 is maintained in the energized state until the AC is not supplied thereto. The power is thus supplied to the heating resistor 111 according to the timing the triac 61 is triggered on.
Further, a sum of the current supplied to the power supply device 53 from the commercial power supply 50 via the AC filter 52 and the current supplied to the heating resistor 111 become the current supplied to the inlet 51, and are input to an inlet current detection circuit 71 via a current transformer 70. The inlet current detection circuit (i.e., a detection unit) 71 performs voltage conversion on the input current. A current detection signal which has been voltage-converted is then input to the PA0 in the CPU 32 via a resistor 72, analog/digital (A/D)-converted, and managed as a digital value.
The current supplied to the heating resistor 111 is similarly input to a heater current detection circuit 81 (i.e., a current detection unit) via a current transformer 80. The heater current detection circuit 81 performs voltage conversion on the input current. The current detection signal which has been voltage-converted is input to the PA2 in the CPU 32 via a resistor 82, A/D-converted, and managed as the digital value.
<The Current Detection Circuit of the Heater>
Referring to
A waveform 505 indicates the waveform which has been inverted and amplified based on the reference voltage 217. The output from the operation amplifier 209 is input to the plus terminal of an operational amplifier 212. The operational amplifier 212 controls a transistor 213 so that the current determined by a voltage difference between the reference voltage 217 and the waveform input to the plus terminal thereof and a resistor 211 flows into a condenser 214. The condenser 214 is thus charged by the current determined by voltage difference between the reference voltage 217 and the waveform input to the plus terminal thereof, and the resistor 211.
When the diode 203 ends performing the half-wave rectification, the charging current stops flowing into the condenser 214, so that a voltage value thereof is peak-held. A digital identification signal (DIS) then switches on the transistor 215 while the diode 201 is performing the half-wave rectification as indicated by a waveform 507. As a result, a charging voltage of the condenser 214 is discharged. The DIS signal output from the CPU 32 switches on and off the transistor 215, and performs on-off control of the transistor 215 based on a ZEROX signal indicated by a waveform 502. The DIS signal switches on the transistor 215 after a predetermined time Tdly has elapsed from a rising edge of the ZEROX signal and switches off the transistor 215 at the same timing as or immediately before a falling edge of the ZEROX signal. As a result, control can be performed without interfering with an energizing period of the fixing heater 100 which is the half-wave rectification period of the diode 201.
In other words, a peak-hold voltage V1f of the condenser 214 becomes an integrated value of a half period of the squared value of the waveform obtained by the current transformer 80 performing voltage-conversion of the current waveform in the secondary side. The voltage value which has been peak-held by the condenser 214 is thus transmitted to the CPU 32 from the heater current detection circuit 81 as an HCRRT1 signal 506. The CPU 32 performs A/D conversion of the HCRRT1 signal until the predetermined time Tdly elapses from the rising edge of the ZEROX signal 502. The heater current I1 which has been A/D-converted becomes the heater current I1 corresponding to one whole wave of the commercial power supply voltage. The CPU 32 then averages the heater current I1 corresponding to four whole waves of the commercial power supply voltage, multiplies the averaged result by a previously provided coefficient, and calculates the power consumed by the heating resistor 111. The current detection method of the heater current I1 is not limited to the above-described method.
<The Inlet Current Detection Circuit>
Referring to
Diodes 301 and 303 illustrated in
The operational amplifier 312 controls a transistor 313 so that the current determined by the voltage difference between the reference voltage 317 and the waveform input to the plus terminal thereof, and a resistor 311 flows into a condenser 314. The condenser 314 is thus charged by the current determined by the voltage difference between the reference voltage 317 and the waveform input to the plus terminal thereof and the resistor 311. When the diode 203 ends performing the half-wave rectification, the charging current stops flowing into the condenser 314, so that the voltage value thereof is peak-held, as indicated by a waveform 706. If a transistor 315 is then switched on while the diode 301 is performing the half-wave rectification, the voltage charged in the condenser 314 is discharged. The transistor 315 is switched on and off by the DIS signal from the CPU 32 and is controlled based on the ZEROX signal indicated by the waveform 502. The DIS signal is switched on after the predetermined time Tdly has elapsed from the rising edge of the ZEROX signal and is switched off at the same timing as or immediately before the falling edge of the ZEROX signal. As a result, control can be performed without interfering with the period the current flows in the heater 100 which is the half-wave rectification period of the diode 303.
In other words, a peak-hold voltage V2f of the condenser 314 becomes the integrated value of the half period of the squared value of the waveform obtained by the current transformer 70 performing voltage conversion on the current waveform in the secondary side. The voltage value which has been peak-held by the condenser 314 is thus transmitted to the CPU 32 from the inlet current detection circuit 71 as an HCRRT2 signal 706. The CPU 32 performs A/D conversion of the HCRRT2 signal 706 within the predetermined time Tdly from the rising edge of a ZEROX signal 701 input from the port PA0. The inlet current I2 which has been A/D-converted becomes the inlet current I2 corresponding to one whole wave of the commercial power supply voltage. The CPU 32 then averages the inlet current corresponding to four whole waves of the commercial power supply voltage, multiplies the averaged by a previously provided coefficient, and calculates the power consumed by the entire image forming apparatus. The current detection method of the heater current I2 is not limited to the above-described method.
<Connection of the CPU 32 to the Option Devices>
According to the present exemplary embodiment, the external option device is not limited thereto as long as the device is externally connected to the image forming apparatus.
According to the present exemplary embodiment, when the image forming apparatus is turned on, the number and the types of the connected external option devices are detected. A consumed power Po by the operation of the detected external option device is then calculated using the power table of the external option devices which is previously provided as illustrated in
Functions of the image scanner 34, the automatic document feeder 33, the sheet discharge option A 35, and the sheet discharge option B 36 will be described below with reference to
According to the present exemplary embodiment, the maximum consumed power is calculated by assuming that there is a case where the connected external option devices operate at the same time. However, if there are external option devices which do not operate at the same timing, the maximum consumed power is calculated by considering such devices.
<Warm-Up>
The method for calculating power Pf_max suppliable to a heater and limiting the power when performing control according to the present exemplary embodiment will be described below with reference to
The present exemplary embodiment is also applicable to warm-up processing of the fixing unit from the state where the image forming apparatus is performing preheating in a stand-by mode, or an initial warm-up after the power has been turned on.
Referring to
When the image forming apparatus completes activating all loads at the timing B, the CPU 32 monitors the inlet current I2 and confirms whether the inlet current I2 is greater than a preset current limit Ilim. If the inlet current I2 does not exceed the current limit Ilim as illustrated in
Referring to
According to the present exemplary embodiment, when the image forming process is started at the timing B illustrated in
A control specification according to the present exemplary embodiment will be described below. If the power Pf_max suppliable to the heater is greater than the Ready power Pth (i.e. the threshold power) in the above-described warm-up control, the image forming apparatus immediately starts writing the image.
The case where the external option devices, i.e., the automatic document feeder 33, the image scanner 34, the sheet discharge option A 35, and the sheet discharge option B 36, are connected to the image forming apparatus will be described below. It is desirable for the external option devices to be standing by to immediately operate when there is a user operation or an operation instruction. In other words, it is desirable in view of usability that the operations of the external option devices are not synchronous with the image forming process. Therefore, when the CPU 32 monitors the inlet current I2 and confirms whether the inlet current I2 is greater than the preset current limit Ilim as described above, the power consumed by the option devices is not considered. If the external option devices then operate during the warm-up period of the fixing unit, there is a power shortage in the entire image forming apparatus. The CPU 32 thus limits the power to be supplied to the heater 100, so that the temperature of the heater 100 may not reach the temperature at which the fixing process can be performed within a scheduled time.
To solve such a problem, according to the present exemplary embodiment, when the external option devices are connected, a new Ready power Pth is calculated by adding the power necessary for the option devices to operate, to the Ready power Pth. When the external option devices are connected, the image forming apparatus determines the start timing of the image writing based on whether the power Pf_max suppliable to the heater is greater than the new Ready power Pth during the warm-up control.
A control process according to the present exemplary embodiment will be described below with reference to the flowchart illustrated in
In step S109, the CPU 32 sets the predetermined Ready power Pth. The Ready power Pth is supplied to the heater 100 from when the image forming process is started to when the recording material 32 reaches the fixing nip portion N. The Ready power Pth thus allows the temperature of the fixing heater 100 to reach the target temperature T_print (° C.) at which the fixing process can be performed. In step S110, the CPU 32 confirms whether the image forming apparatus is connected to the external option devices as illustrated in
As described above, according to the present exemplary embodiment, the first mode or the second mode is selected and executed according to the connection status of the external option devices to the image forming apparatus and the maximum power suppliable to the heater. As a result, an image forming apparatus can be provided which satisfies the fixing performance and is capable of shortening the FPOT even when the external option devices operate during the warm-up.
According to the first exemplary embodiment, the threshold power is changed according to the connection status of the external option devices to the image forming apparatus and the maximum power suppliable to the fixing heater. According to the second exemplary embodiment, a plurality of the threshold temperatures at which the image writing is started in the second mode according to the first exemplary embodiment is set based on the power Pf_max suppliable to the heater. Further, the Ready power Pdth for setting the threshold temperature is set according to the connection status of the external option devices to the image forming apparatus. According to the present exemplary embodiment, the differences from the first exemplary embodiment will be mainly described, and description on the common configurations will be omitted. The items which are not described below are thus similar to the first exemplary embodiment.
Warm-up control performed according to the second exemplary embodiment will be described below with reference to
The control process according to the present exemplary embodiment will be described below with reference to the flowchart illustrated in
Step S202 corresponds to the control process performed in step S112 illustrated in
The processes of step S203 to step S207 are unique to the present exemplary embodiment. In step S113, the CPU 32 compares the power Pf_max suppliable to the heater with the Ready power Pth. If the power Pf_max suppliable to the heater is less than the Ready power Pth (NO in step S113), the CPU 32 shifts to the second mode in which the image writing is started according to the detected temperature of the fixing heater 100. The threshold temperature at which the image writing is started according to the power Pf_max suppliable to the heater is set in the processes performed in step S203 to step S207. In step S203, the CPU 32 compares the power Pf_max suppliable to the heater with the Ready power Pth1. If the power Pf_max suppliable to the heater is greater than the Ready power Pth1 (YES in step S203), the process proceeds to step S205. In step S205, the CPU 32 compares the temperature of the fixing heater 100 with T_print−30 (° C.). If the temperature of the fixing heater 100 reaches T_print−30 (° C.) (YES in step S205), the process proceeds to step S115, and the CPU 32 starts the image writing. If the power Pf_max suppliable to the heater is less than the Ready power Pth1 (NO in step S203), the process proceeds to step S204. In step S204, the CPU 32 compares the power Pf_max suppliable to the heater with the Ready power Pth2. If the power Pf_max suppliable to the heater is greater than the Ready power Pth2 (YES in step S204), the process proceeds to step S206. In step S206, the CPU 32 compares the temperature of the fixing heater 100 with T_print−25 (° C.). If the temperature of the fixing heater 100 reaches T_print−25 (° C.) (YES in step S206), the process proceeds to step S115, and the CPU 32 starts the image writing. On the other hand, if the power Pf_max suppliable to the heater is less than the Ready power Pth2 (NO in step S204), the process proceeds to step S207. In step S207, the CPU compares the temperature of the fixing heater with T_print−15 (° C.). If the temperature of the fixing heater reaches T_print−15 (° C.) (YES in step S207), the process proceeds to step S115, and the CPU 32 starts the image writing.
According to the present exemplary embodiment, the timing of starting the image forming process can be more finely set according to the heater suppliable power in the second mode as compared to the first exemplary embodiment. The FPOT can thus be further shortened.
The control sequence, the table, and the circuit configurations according to the above-described exemplary embodiments are not limited thereto.
While the present disclosure has been described with reference to exemplary embodiments, it is to be understood that these exemplary embodiments are not seen to be limiting. The scope of the following claims is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures and functions.
This application claims the benefit of Japanese Patent Application No. 2013-163896 filed Aug. 7, 2013, and No. 2014-145069 filed Jul. 15, 2014, which are hereby incorporated by reference herein in their entirety.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2013-163896 | Aug 2013 | JP | national |
| 2014-145069 | Jul 2014 | JP | national |
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| Number | Date | Country | |
|---|---|---|---|
| 20150043934 A1 | Feb 2015 | US |
