Abstract:
A printing device includes a heater that heats a fuser to fuse toner on a printing medium, a sense circuit that generates a temperature signal indicating a voltage value corresponding to a temperature of the fuser, a comparator that compares the voltage value indicated by the temperature signal with a threshold voltage value corresponding to a target temperature for the fuser and outputs a first signal that maintains the temperature of the fuser at the target temperature, a processor that executes a program after a power supply for the printing device is initiated and outputs a second signal that controls the temperature of the fuser, and an energization control circuit that, before the processor starts execution of the program, controls power distribution to the heater according to the first signal, and, after the processor has started the execution, controls the power distribution to the heater according to the second signal.

Description:
TECHNICAL FIELD 
       [0001]    The present invention relates generally to a printing device. 
       BACKGROUND ART 
       [0002]    Various techniques have been studied to reduce time required to begin printing immediately after power is turned on or for printing immediately after being restored from a deep sleep mode where supply of the main power is turned off. These printings are called a first print, and a majority of time required for the first print is occupied by a warm-up time to heat a fuser by a heater. 
         [0003]    For example, Patent Document 1 discloses a technology with an image forming device comprising a main processor and a sub-processor where the sub-processor carries out a fusing temperature control program stored in a read only memory (ROM) when the power supply of the image forming device is turned on, and the main processor carries out a loader program. Further when a sub-program has been loaded into a random access memory (RAM), load end notification is conveyed to the sub-processor, and when the sub-processor receives the load end notification, the sub-program loaded into the RAM is executed instead of the fusing temperature control program. 
         [0004]    According to Patent Document 1, the warming-up time can be reduced by starting up the fusing temperature control program when the power supply is turned on by the image forming device configured in this manner described above. 
       RELATED ART DOCUMENTS 
     Patent Documents 
       [0005]    [Patent Documents] Japanese Unexamined Patent Application Publication No. 2011-227360 
         [0006]    However, the conventional technique above cannot be applied to a printing device that comprises only one processor. 
       SUMMARY OF THE INVENTION 
       [0007]    In one aspect, embodiments of the invention provide a printing device having a configuration suitable to reduce the time required for first print. 
         [0008]    A printing device according to one aspect of the present invention may include a heater that heats a fuser to fuse toner on a printing medium; a sense circuit that generates a temperature signal indicating a voltage value corresponding to a temperature of the fuser; a comparator that compares the voltage value indicated by the temperature signal with a threshold voltage value corresponding to a target temperature for the fuser and outputs a first energization control signal that maintains the temperature of the fuser at the target temperature; a processor that executes a program after a power supply for the printing device is initiated and outputs a second energization control signal that controls the temperature of the fuser; and an energization control circuit that, before the processor starts execution of the program, controls power distribution to the heater according to the first energization control signal, and, after the processor has started execution of the program, controls the power distribution to the heater according to the second energization control signal. 
         [0009]    According to one or more embodiments of this configuration, the program may carry out temperature control according to a software function in the processor, and in parallel with all processing performed prior to starting the temperature control by the program, temperature control can be carried out by a hardware circuit. Accordingly, the heating of the fuser may be started at the same time when the power supply is turned on so that the time required for the first print can be reduced. 
         [0010]    Further, for example, the processor may, by executing the program, further output a startup notification signal, and the energization control circuit comprises a disabling circuit that disables the first energization control signal according to the startup notification signal. 
         [0011]    According to one or more embodiments of this configuration, more advanced temperature control may be performed using a software function because temperature control by a hardware circuit is disabled after temperature control using a software function is started. 
         [0012]    Furthermore, for example, the printing device may further comprise a threshold voltage generating circuit that comprises a plurality of resistors connected in series and that outputs the threshold voltage value from a connection point of the resistors by applying a predetermined voltage to both ends of the resistors; and the disabling circuit comprises a transistor that connects the connection point and one of the end points of the threshold voltage generating circuit according to the startup notification signal. 
         [0013]    According to one or more embodiments of this configuration, the first energization control signal can be disabled by shifting the threshold voltage. 
         [0014]    According to another aspect of the present invention, a method for a printing device is provided, the method including: generating a temperature signal indicating a voltage value corresponding to a temperature of a fuser of toner; comparing the voltage value indicated by the temperature signal with a threshold voltage value corresponding to a target temperature for the fuser; outputting a first energization control signal that maintains the temperature of the fuser at the target temperature; controlling power distribution to a heater according to the first energization control signal; executing a program after a power supply for the printing device is initiated and outputting a second energization control signal that controls the temperature of the fuser; and controlling, before the processor starts execution of the program, power distribution to the heater according to the first energization control signal, and controlling, after the processor has started execution of the program, the power distribution to the heater according to the second energization control signal. 
         [0015]    These overall or specific aspects may be realized by a system, a method, an integrated circuit, a computer program, or a recording medium such as a computer readable CD-ROM or the like, and may also be realized by various combinations of a system, method, integrated circuit, computer program or recording medium. 
         [0016]    With the printing device according to one of the embodiments of the present invention, all processing performed prior to starting temperature control by the software function can be carried out in the processor in parallel to temperature control being carried out by the hardware circuit. 
         [0017]    For example, with a conventional printing device comprising only a single processor, a process requiring considerable time, such as loading a program, must be carried out by the single processor when the power supply is initiated. In such cases, heating of the fuser begins at the same time as when the power supply is initiated by carrying out temperature control by the hardware function using the control circuit in parallel with processing so the time required for the first print can be reduced. 
         [0018]    Furthermore, the configuration of one or more embodiments may be applied to, for example, the processor for carrying out temperature control in the fuser with a printing device comprising two or more processors. Accordingly, at the same time that the power supply is initiated, heating in the fuser is started by carrying out temperature control by the hardware function in the control circuit, and processes that require a considerable time, such as loading a program, are carried out in parallel and distributed in two or more processors so that the time required for fast printing can be reduced. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0019]      FIG. 1  is a perspective view illustrating one example of an external appearance of a printing device according to one or more embodiments of the present invention. 
           [0020]      FIG. 2  is a block diagram illustrating one example of a functional configuration of the printing device according to one or more embodiments of the present invention. 
           [0021]      FIG. 3  is a circuit diagram illustrating one example of a controller of the printing device according to one or more embodiments of the present invention. 
           [0022]      FIG. 4  is a flowchart illustrating one example of an operation of the printing device according to one or more embodiments of the present invention. 
       
    
    
     DETAILED DESCRIPTION OF EMBODIMENTS 
       [0023]    Embodiments of the present invention are described in detail hereinafter with reference to drawings. Each embodiment described below illustrates one specific example of the present invention. Numerical values, shapes, materials, compositional elements, disposed positions and connection modes of the compositional elements, steps and order of steps are illustrated as an example and these are not intended to limit the present invention. Of the elements in the following embodiments, elements not described in the independent claims indicating the most significant concept are described as any given element. 
         [0024]    A printing device according to one or more embodiments is a printing device having a configuration suitable for reducing the time required for a first print, and the device may be, for example, an electrophotographic printing device having a fuser that requires temperature control. 
         [0025]      FIG. 1  is a perspective view illustrating one example of an external appearance of a printing device according to one or more embodiments. The printing device illustrated in  FIG. 1  may comprise a paper feeding section  10 , a printing unit  20 , a paper discharging section  30 , and power supply  70 . 
         [0026]      FIG. 2  is a block diagram illustrating one example of a functional configuration of the printing unit  20 .  FIG. 2  illustrates one example of a configuration of the printing unit  20  provided in an electrophotographic printing device. 
         [0027]    The printing unit  20  may form any image using a toner  92  on a printing medium  91  such as a paper that is fed from the paper feeding section  10  and sent to the paper discharging section  30 . The printing unit  20  may be configured with an image forming unit  40 , a fuser  50 , and a controller  60 . The printing unit  20  may operate by electric power supplied from the power supply  70 . 
         [0028]    The power supply  70  may be, for example, a switching power supply device that converts alternating current voltage supplied from a commercial power supply to direct current voltage used in the operation of the printing unit  20 . 
         [0029]    The image forming unit  40  may comprise a photosensitive drum  41  and a transfer roller  42 . The toner  92  may be adhered to a latent image formed on the photosensitive drum  41  using a light source (not illustrated) and then the adhered toner  92  may be transferred onto the printing medium  91  by the transfer roller  42 . 
         [0030]    The fuser  50  may comprise a heating roller  51  and a pressure roller  52 . The toner  92  transferred onto the printing medium  91  may be fused to the printing medium  92  by applying heat and pressure. The heating roller  51  may comprise a heater  53  and a temperature sensor  54 , and the temperature is controlled by the controller  60 . For example, the heater  53  may be composed of a halogen heater, and the temperature sensor  54  may be composed of a thermistor. 
         [0031]    The controller  60  may perform a complete set of processing in the printing device  1  including image processing and communication processing in addition to the control of the printing unit  20  including temperature control for the fuser  50  and is configured with a hardware circuit including a processor. 
         [0032]      FIG. 3  is a circuit diagram illustrating one example of the controller  60 . The power supply  70 , heater  53 , and temperature sensor  54  are illustrated with the controller  60  in  FIG. 3 . 
         [0033]    As illustrated in  FIG. 3 , the controller  60  may comprise, for example, a processor (e.g., CPU), comparator CP 1 , CP 2 , digital to analog (DA) converters DAC, resistors R 1 , R 2 , and R 3 , transistor Q 1 , an OR gate G 1 , and a relay RL. 
         [0034]    The temperature sensor  54  and the resistor R 1  may be connected in series to configure a sense circuit. The sense circuit, with both ends connected to the power supply voltage and the ground voltage, may output, from the connection point between the temperature sensor  54  and the resistance R 1 , a temperature signal SENSE having a voltage value indicating the temperature (particularly the temperature of the heating roller  51 ) of the fuser  50 . 
         [0035]    The resistors R 2  and R 3  may be connected in series to configure a threshold voltage generating circuit. The threshold voltage generating circuit, with both ends connected to the power supply voltage and the ground voltage, may output, from the connection point of the resistors R 2  and R 3 , a threshold voltage VTH 1  that corresponds to a target temperature for the warm up of the fuser  50 . 
         [0036]    The comparator CP 1  may compare the temperature signal SENSE and the threshold voltage VTH 1  in an analog value and output a first energization control signal to maintain the temperature of the fuser  50  at the target temperature. The comparator CP 1  is a circuit that can compare two input voltages without intervention by the processor, and it may be configured of, for example, an analog circuit such as an operational amplifier or the like. As an example, the first energization control signal may instruct power distribution (HW_ON) at an H level and instruct power disconnection (HW_OFF) at an L level. 
         [0037]    The processor may output a startup notification signal READY and also output a reference signal TMEP and a second energization control signal to control a temperature of the fuser  50  by executing a predetermined program. As an example, the second energization control signal may instruct power distribution (SW_ON) at an H level and instruct power disconnection (SW_OFF) at an L level. 
         [0038]    Here, a situation that requires considerable time to start the program in the processor is assumed. Such situation is not limited to any particular situation; however, the following situation is given as an assumed example. That is, the program may carry out a complete set of processing in the printing device  1  including the temperature control of the fuser  50 , and as described in the background section, the processor launches the program in RAM (not illustrated) and then executes the program launched in RAM by executing a loader program stored in ROM (not illustrated). 
         [0039]    The processor does not output the startup notification signal READY until the temperature control is started by the program, and outputs the second energization signal in the L level that instructs the power disconnection (SW_OFF). 
         [0040]    After the temperature control is started by the program, the processor may output the startup notification signal READY in the L level that indicates the temperature control is started, and also output a reference temperature signal TEMP where a reference temperature is expressed with pulse width modulation (PWM). The DA converter DAC may convert the reference temperature signal TEMP to a threshold voltage VTH 2  that corresponds to the reference temperature. The DA convertor DAC may be configured with, for example, a simple low-pass filter. The comparator CP 2  may compare the temperature signal SENSE and the threshold voltage VTH 2  in an analog value and then supply the comparison result signal indicating the result of the comparison to the processor. 
         [0041]    The processor may read the temperature of the fuser  50  from the comparison result signal by sweeping the reference temperature expressed by the reference temperature signal TEMP within a predetermined range. Thereby, the processor may output the second energization control signal that instructs for power distribution (SW_ON) and power disconnection (SW_OFF) based on not only a simple temperature control logic by the threshold comparison, but also based on a more advanced temperature control logic such as hysteresis control or predictive control. 
         [0042]    When the processor has a built-in analog to digital converter (ADC) that can convert a voltage acquired from the outside, the temperature signal SENSE may be converted to a digital value by the ADC. In this case, the DA converter DAC and the comparator CP 2  may be omitted. 
         [0043]    The OR gate G 1 , relay RL, and transistor Q 1  may constitute the energization control circuit. 
         [0044]    The OR gate G 1  supplies to the relay RL an OR signal that indicates whether or not the power distribution (HW —  ON, SW_ON) is instructed by at least one of the first energization control signal and the second energization control signal. 
         [0045]    The relay RL may carry out power distribution and power disconnection to the heater  53  according to the OR signal supplied from the OR gate G 1 . The relay RL may be, for example, an electronic relay configured with a triac, photo-coupler, or the like. 
         [0046]    The transistor Q 1  may conduct, or turn on, according to the startup notification signal READY, and connect an endpoint connected to the power supply voltage of the threshold voltage generating circuit that is configured with the resistors R 2  and R 3 , and the connection points with the resistors R 2  and R 3 . When the transistor Q 1  is conducted, the first energization control signal becomes the L level to instruct the power disconnection (HW_OFF) at all times due to shifting of the threshold value voltage VTH 1 . The transistor Q 1  is an example of a disabling circuit that disables the first energization control signal according to the start notification signal READY. 
         [0047]    The energization control circuit with such configuration may carry out the power distribution and power disconnection to the heater  53  according to the first energization control signal until the temperature control is started by the program, and carry out the power distribution and power disconnection to the heater  53  according to the second energization control signal after the temperature control is started by the program. 
         [0048]    An operation of the printing device  1  configured as described above will be described here below. 
         [0049]      FIG. 4  is a flow chart as one example of the operation of the printing device  1 , illustrating the operation carried out in the controller  60  when the power supply is initiated at the time of startup. Such operation may be carried out, for example, when the power activation is operated by user while the power supply of the printing device  1  is turned off, or when a printing instruction is given from an information equipment while the printing device in a deep sleep mode state in which the supply of the main power is stopped. 
         [0050]    The flowchart illustrated in  FIG. 4  divides the operation of the controller  60 : an operation where the processor carries out by software function and an operation carried out where the control circuit configured with hardware other than the processor is carried out by the hardware function. 
         [0051]    The processor loads a program (S 101 ). The program loading may include, for example, a program deployment process from ROM to RAM by the loader grogram. The processor may first carry out an initialization process (S 102 ) when the operation is started according to the loaded program, and the temperature control may be started (S 103 ) by the program thereafter. 
         [0052]    In parallel with the operations in steps S 101  to S 103  that are carried out in the processor, the controller may carry out the temperature control (S 201 ) by the hardware function. For example, the first energization control signal that instructs the power distribution (HW_ON) or the power disconnection (HW_OFF) may be generated according to whether the temperature of the fuser  50  reaches the target temperature by comparing the temperature signal SENSE and the threshold voltage VTH 1  with the comparator CP 1 . The first energization control signal may be transferred to the relay RL via the OR gate G 1 , and the power distribution and the power disconnection to the heater  53  may be carried out according to the first energization control signal by the relay RL. 
         [0053]    The processor may output the startup notification signal READY when the temperature control is started (S 104 ). The transistor Q 1  is turned on according to the startup notification signal READY to shift the threshold voltage VTH 1 . Accordingly, the first energization control signal may be fused in the L-level to instruct the power disconnection (HW_OFF) and be disabled (S 202 ). 
         [0054]    The processor may output a reference temperature signal TEMP (S 105 ), acquire a comparison result signal from the comparison result signal from the comparator CP 2 , and identify the necessity of power distribution to the heater  53  from the acquired comparison result signal (S 106 ). The details of the process for identifying the necessity of the power distribution are not limited; however, the necessity of the power distribution may be identified by, for example, a simple temperature control logic by comparing threshold values, or it may be identified based on a more advanced temperature control logic such as a hysteresis or predictive control. 
         [0055]    The processor may output a second energization control signal (S 107  to S 109 ) that instructs one of the power distribution (SW_ON) or the power disconnection (SW_OFF) corresponding to the necessity of the identified power distribution. 
         [0056]    The second energization signal may be transferred to the relay RL via the OR gate G 1 , and the power distribution or power disconnection is carried out (S 203 ) to the heater  53  according to the second energization control signal by the relay RL. 
         [0057]    According to the configuration and operation of one or more embodiments of the controller  60  as evident from the descriptions given above, the temperature control by the hardware function can be carried out in the control circuit in parallel with all the processing carried out until the temperature control is started by the software function. 
         [0058]    For example, a situation is assumed where a printing device comprising just one processor and a process requires considerable time such as loading a program must be carried out by the processor when the power supply is initiated. Even in such situation, the controller  60  may start heating in the fuser at the same time when the power supply is initiated by carrying out the temperature control by the hardware function in the control circuit in parallel with the processing so that the time required for the first print can be reduced. 
         [0059]    Further, the configuration of the controller  60  may be applied to, for example, the processor for carrying out the temperature control in the fuser with a printing device comprising two or more processors. Accordingly, at the same time the power supply is initiated, heating in the fuser may be started by carrying out the temperature control by the hardware function in the control circuit and at the same time, the processing that require a considerable time such as loading a program is carried out in parallel and distributed to two or more processors so that the time required for the first print can be reduced. 
         [0060]    Descriptions of the printing device according to one or a plurality of modes of the present invention were given above based on the embodiments; however, the present invention is not limited to the embodiments. Without departing from the spirit of the present invention, various modifications that can be conceived by one skilled in the art, or a mode that is built by combining compositional elements in a different embodiment may be included within the scope of one or more aspects of the present invention. 
         [0061]    One or more embodiments of the present invention can be widely used in printing devices having a fuser that requires temperature control, for example, laser printers, LED printers, or the like. 
         [0062]    Although the disclosure has been described with respect to only a limited number of embodiments, those skilled in the art, having benefit of this disclosure, will appreciate that various other embodiments may be devised without departing from the scope of the present invention. Accordingly, the scope of the invention should be limited only by the attached claims. 
       DESCRIPTION OF THE NUMERICAL REFERENCES 
       [0000]    
       
           1  printing device 
           10  paper feeding section 
           20  printing unit 
           30  paper discharging section 
           40  image forming unit 
           41  photosensitive drum 
           42  transfer roller 
           50  fuser 
           51  heating roller 
           52  pressure roller 
           53  heater 
           54  temperature sensor 
           60  controller 
           70  power supply 
           91  printing medium 
           92  toner 
         CP 1 , CP 2  comparator 
         CPU processor 
         DAC DA convertor 
         G 1  OR gate 
         Q 1  transistor 
         R 1 , R 2 , R 3  resistor 
         RL relay