Patent Publication Number: US-7587148-B2

Title: Image formation apparatus, an image formation method, an image formation program, and a recording medium

Description:
BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates to an image formation apparatus, an image formation method, an image formation program, and a recording medium, wherein driving sources are started in different sequences. 
   2. Description of the Related Art 
   Conventionally, an image formation apparatus includes a current detecting unit arranged in a power-source line to which two or more functional units are connected, where the current detecting unit measures a starting current when each of the functional units is started so that a peak of current consumption by an overlap of the starting currents may be controlled by adjusting starting timing of the functional units based on a measurement result (for example, Patent Reference 1). 
   [Patent Reference 1] JPA 2004-138840 
   DISCLOSURE OF INVENTION 
   Objective of the Invention 
   However, according to a technique disclosed by Patent Reference 1, only the starting timing is controlled according to the magnitude of the current measured by the current detecting unit, while the functional units are started in a predetermined sequence. For example, a fixing unit is started earlier in the predetermined sequence despite the fixing unit having not reached a predetermined temperature. This delays printing operations, and causes wasteful power consumption. 
   SUMMARY OF THE INVENTION 
   The present invention provides an image formation apparatus, an image formation method, an image formation program, and a recording medium that substantially obviate one or more of the problems caused by the limitations and disadvantages of the related art. 
   According to the image formation apparatus, the image formation method, the image formation program, and the recording medium of the present invention, the sequence of starting driving sources is adjusted depending on situations. 
   Features of embodiments of the present invention are set forth in the description that follows, and in part will become apparent from the description and the accompanying drawings, or may be learned by practice of the invention according to the teachings provided in the description. Problem solutions provided by an embodiment of the present invention may be realized and attained by an image formation apparatus, an image formation method, an image formation program, and a recording medium particularly pointed out in the specification in such full, clear, concise, and exact terms as to enable a person having ordinary skill in the art to practice the invention. 
   To achieve these solutions and in accordance with an aspect of the invention, as embodied and broadly described herein, an embodiment of the invention provides an image formation apparatus, an image formation method, an image formation program, and a recording medium as follows. 
   Means for Solving the Problem 
   The image formation apparatus according to the embodiment comprises: 
   a first driving source for driving a feed roller and a fixing unit; 
   a second driving source for driving at least one photo conductor out of two or more photo conductors and a middle transfer belt; 
   a third driving source for driving photo conductors other than the photo conductor driven by the second driving source; 
   a temperature detecting unit for detecting temperature of the fixing unit, and for determining whether the temperature is greater than a predetermined threshold value; and 
   a control unit for starting the first driving source, the second driving source, and the third driving source in this sequence if the temperature detecting unit determines that the temperature of the fixing unit is greater than the predetermined threshold value. 
   According to an aspect of the embodiment, the image formation apparatus further comprises: 
   a current detecting unit for detecting a current flowing through the first driving source, the second driving source, and the third driving source, and for determining whether the current is stabilized; wherein 
   the control unit starts driving the first driving source, the second driving source, and the third driving source in this sequence every time the current flowing through the corresponding preceding driving source is determined to have been stabilized if the temperature detecting unit determines that the temperature of the fixing unit is greater than the predetermined threshold value. 
   According to another aspect of the embodiment, the control unit of the image formation apparatus starts driving the second driving source, the third driving source, and the first driving source in this sequence if the temperature detecting unit determines that the temperature of the fixing unit is less than the predetermined threshold value. 
   According to another aspect of the embodiment, the control unit of the image formation apparatus starts driving the second driving source and the first driving source in this sequence if a monochrome printing request is received. 
   According to another aspect of the embodiment, the control unit of the image formation apparatus starts driving the second driving source, the third driving source, and the first driving source in this sequence if a color printing request is received. 
   According to another aspect of the embodiment, each of the first driving source, the second driving source, and the third driving source includes a DC brushless motor. 
   The embodiment further provides an image formation method for the image formation apparatus described above. 
   The embodiment further provides a computer-executable program for carrying out the image formation method. 
   The embodiment further provides a computer-readable recording medium that stores the computer-executable program. 
   EFFECTIVENESS OF INVENTION 
   According to the image formation apparatus, the image formation method, the image formation program, and the recording medium, the driving sources are started in a sequence appropriate in various situations so that a power source having a small output current capacity can be used without a shutdown due to excessive starting current. In this way, power-source cost is decreased without delaying the printing operations. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a cutaway drawing of an image formation apparatus according to the embodiment of the present invention; 
       FIG. 2  is a schematic drawing showing the configuration of driving sources of the image formation apparatus; 
       FIG. 3  is a block diagram showing the hardware configuration of the image formation apparatus; 
       FIG. 4  is a graph showing an example of currents flowing through the driving sources; 
       FIG. 5  is a flowchart of an example of an initialization sequence of an image formation process; 
       FIG. 6  is a flowchart of an example of the image formation process when receiving a color printing request; 
       FIG. 7  is a flowchart of an example of the image formation process when receiving a monochrome printing request; and 
       FIG. 8  is a graph showing an example of the currents flowing through the driving sources when a DC brushless motor is used. 
   

   DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   In the following, embodiments of an image formation apparatus, an image formation method, an image formation program, and a recording medium of the present invention are described with reference to the accompanying drawings. 
   Embodiments 
   (Overall Configuration of the Image Formation Apparatus) 
   First, the configuration of an image formation apparatus  100  according to the embodiment of the present invention is described with reference to  FIG. 1 . The image formation apparatus  100  includes a feed cassette  101 , a feed roller  102 , a conveyance way  103 , a middle transfer belt  104 , development units  105 K,  105 C,  105 M, and  105 Y (they are collectively called  105 , which nomenclature system applies to other functional units), photo conductors  106  (K, C, M, Y), a sensor  107 , a tension roller  108 , a driving roller  109 , a cleaning unit  110 , a secondary transfer roller  111 , and a fixing unit  112 . 
   The feed cassette  101  stores sheets of paper before printing. The feed roller  102  feeds the paper stored in the feed cassette  101  to the conveyance way  103  sheet by sheet from the top. Each of the sheets is conveyed to the secondary transfer roller  111  at timing at which an image on the middle transfer belt  104  is transferred to the sheet. The middle transfer belt  104  is wound around the driving roller  109  and the tension roller  108 . The middle transfer belt  104  is driven by the driving roller  109 , and sag is prevented by the tension roller  108 . 
   The image formation apparatus  100  is a so-called tandem type, wherein the development units ( 105 K,  105 M,  105 C,  105 Y) for different colors are arranged along with the middle transfer belt  104 . The colors have complementary-color relations. “K” stands for black, “M” stands for magenta, “C” stands for cyan, and “Y” stands for yellow. The development units ( 105 K,  105 M,  105 C, and  105 Y) include corresponding photo conductors ( 106 K,  106 M,  106 C, and  106 Y, respectively) for supporting toner images in the corresponding colors. 
   With reference to  FIG. 1 , the middle transfer belt  104  rotates counterclockwise, and the development units  105 K,  105 M,  105 C, and  105 Y are arranged in this sequence from upstream side to downstream side. The development units  105 K,  105 M,  105 C, and  105 Y are structured the same, but form toner images in different colors. In the following, all the development units and all the photo conductors are called the development unit  105  and the photo conductor  106 , respectively, where descriptions are commonly applicable. 
   For forming an image, the photo conductor  106  is uniformly charged on its perimeter. Then, a laser light corresponding to an image of a color is irradiated to the perimeter of the photo conductor  106 , and the uniform charge is exposed according to the image. That is, an electrostatic latent image is formed. Then, toner of each color is applied to the photo conductor  106  such that a toner image in the color is formed, which toner image is visible. 
   The toner image is transferred to the middle transfer belt  104  with a primary transfer roller that is not illustrated at a primary transfer location where the photo conductor  106  meets the middle transfer belt  104 . That is, the toner image is transferred to the middle transfer belt  104 . 
   Specifically, first, a toner image in black is transferred to the middle transfer belt  104  by the development unit  105 K, and then is conveyed to the next development unit  105 M if color printing is requested. Then, a toner image in magenta is formed on the photo conductor  106 M of the development unit  105 M through the same image formation process of the development unit  105 K. The toner image in magenta is transferred to the middle transfer belt  104  such that the toner image in magenta is superposed onto the toner image in black. 
   The middle transfer belt  104  is further conveyed to the following development units  105 C and  105 Y, and a toner image in cyan formed on the photo conductor  106 C and the toner image in yellow formed on the photo conductor  106 Y are transferred and superposed onto the middle transfer belt  104  by the same operation as described above. By the process described above, a full color image is formed on the middle transfer belt  104 . The middle transfer belt  104  bearing the full color is conveyed to the secondary transfer roller  111 , and the full color image is transferred from the middle transfer belt  104  to the paper. The sensor  107 , which includes a luminous source and an optical receiver component, reads a pattern image on the middle transfer belt  104 . Further, unnecessary toner that remains on the middle transfer belt  104  without being transferred to the paper after transfer of the color image is removed by the cleaning unit  110 , and the middle transfer belt  104  stands by for the next image formation. 
   Then, the color image is fixed to the paper by thermal fusion by the fixing unit  112 . The fixing unit  112  is heated by a driving source (not illustrated), and operates when the temperature of the fixing unit  112  is greater than a threshold value. The paper, to which the color image is fixed and adhered by the fixing unit  112 , is discharged out of the image formation apparatus  100 . 
   In addition, if monochrome printing (that is, printing only in black) is requested, the photo conductors  106 M,  106 C, and  106 Y are separated from the middle transfer belt  104  so that the image formation process is performed only for the black color. 
   (Configuration of the Driving Sources) 
   Next, driving sources that drive various parts of the image formation apparatus  100  are described with reference to  FIG. 2 . The image formation apparatus  100  includes a first driving source  201  for driving the feed roller  102  and the fixing unit  112 , a second driving source  202  for driving the driving roller  109  (for driving the middle transfer belt  104 ), and at least one of the photo conductors (the photo conductor  106 K in an example shown in  FIG. 2 ), and a third driving source  203  for driving the remaining photo conductors (the photo conductors  106 C,  106 M, and  106 Y in  FIG. 2 ) that are not driven by other driving sources. 
   (Hardware Configuration) 
   The hardware configuration of the image formation apparatus  100  is described with reference to  FIG. 3 . The image formation apparatus  100  includes a control unit  301 , a temperature detecting unit  310 , the fixing unit  112 , the first driving source  201 , the second driving source  202 , and the third driving source  203 . Functional units that have been described with reference to  FIGS. 1 and 2  bear the same reference numbers, and descriptions are not repeated. 
   The control unit  301  includes a CPU  302 , a current detecting unit  303 , and a rotation detecting unit  304 . The CPU  302  is for controlling the image formation apparatus  100 . The CPU  302  controls the first driving source  201 , the second driving source  202 , and the third driving source  203  based on a detection result of the current detecting unit  303 , the rotation detecting unit  304 , and the temperature detecting unit  310  (details are described below). 
   The current detecting unit  303  detects whether a current flowing through each driving source is stabilized. The rotation detecting unit  304  detects whether the rotation of each driving source is stabilized. The temperature detecting unit  310  detects whether the temperature of the fixing unit  112  is greater than a predetermined threshold value. 
   (An Example of the Current Flowing Through the Driving Source) 
   Next, an example of the current flowing through the driving sources detected by the current detecting unit  303  is described with reference to  FIG. 4 , wherein the horizontal axis represents the time, and the vertical axis represents the current. In  FIG. 4 , a dotted line  400  shows the magnitude of the current if the first driving source  201 , the second driving source  202 , and the third driving source  203  are simultaneously started. Here, it is shown that a current IA is required. 
   A solid line  410  shows the magnitude of the current when the first driving source  201 , the second driving source  202 , and the driving source  203  are started in sequence at predetermined intervals T 1  and T 2 . The solid line  410  also shows that the starting current of the first driving source  201  is I 1 , a current I 2  is required at the time of starting the second driving source  202 , and a current value I 3  is required at the time of starting the third driving source  203 . The current I 3  is smaller than the current IA required when all the driving sources  201 ,  202 , and  203  are simultaneously started. 
   By staggering the starting of the driving sources  201 ,  202 , and  203  as described above, the total current requirement of the image formation apparatus  100  can be decreased, and a power source with a smaller current capacity may be used without causing a shutdown due to an excessive current draw. 
   (An Example of Initialization Sequence) 
   Below, an example of the image formation process carried out by the image formation apparatus  100  is described.  FIG. 5  is a flowchart of an example of the image formation process in the case of an initialization sequence. In  FIG. 5 , first, it is determined whether an initialization sequence request is received (step S 501 ). When an initialization sequence request is received (step S 501 : Yes), the temperature detecting unit  310  determines whether the temperature of the fixing unit  112  is greater than a predetermined threshold (step S 502 ). Since the fixing unit  112  does not operate until the temperature becomes greater than a predetermined temperature, the fixing unit  112  is not started until its temperature is raised to the predetermined temperature by another driving source (not illustrated). If the temperature of the fixing unit  112  is greater than the threshold value (step S 502 : Yes), the first driving source  201  is turned on (step S 503 ). 
   Then, after turning on the first driving source  201  at step S 503  the process waits for a predetermined time at step S 504  (a waiting loop is formed if No). If the time is up (step S 504 : Yes), the second driving source  202  is turned on (step S 505 ). 
   Then, after turning on the second driving source  202  at step S 505  the process waits for a predetermined time (step S 506 : a waiting loop is formed if No). If the time is up (step S 506 : Yes), the third driving source  203  is turned on (step S 507 ), and the process is finished. 
   Here, the predetermined times may be different from driving source to driving source, and may be determined based on experiments with the different driving sources. For example, by the experiments, starting time until the current is stabilized is measured with the current detecting unit  303  for every driving source. 
   On the other hand, when the temperature of the fixing unit  112  is not greater than the threshold value (step S 502 : No), the second driving source  202  is turned on (step S 508 ). Then, after turning on the second driving source  202  at step S 208  the process waits (step S 509 ) for a predetermined time (a waiting loop is formed if NO). If the time is up (step S 509 : Yes), the third driving source  203  is turned on (step S 510 ). 
   Then, after turning on the third driving source  203  at step S 510  the process waits (step S 511 ) for a predetermined time (a waiting loop is formed if No). If the time is up (step S 511 : Yes), the first driving source  201  is turned on (step S 512 ), and the process is finished. 
   Further, if there is no initialization sequence request at step S 501  (step S 501 : No), the process is finished with no actions. 
   As described, at step S 504 , step S 506 , step S 509 , and step S 511 , whether the corresponding predetermined time has passed is determined; however, timing for turning on the next driving source may be determined in other ways. For example, if the current detecting unit  303  determines that the current is stabilized after starting, the next driving source is turned on. 
   Further, at step S 504 , step S 506 , step S 509 , and step S 511 , whether the corresponding predetermined time has passed is determined; however, timing for turning on the next driving source may be determined in other ways. For example, if the rotation detecting unit  304  detects the rotational speed of a motor driven by each driving source, and determines that the rotational speed is greater than a predetermined speed, the next driving source is turned on. 
   (Example of Process when Receiving a Color Printing Request) 
   Below, another example of the image formation process of the image formation apparatus  100  is described with reference to  FIG. 6 , which process is carried out when a color printing request is received. First, it is determined whether a color printing request is received (step S 601 ). 
   If the determination is affirmative, i.e., a color printing request is received at step S 601  (step S 601 : Yes), the second driving source  202  is turned on first (step S 602 ). After turning on the second driving source  202  the process waits for a predetermined time (step S 603  No: a waiting loop is formed). If the time is up (step S 603 : Yes), the third driving source  203  is turned on (step S 604 ). 
   Then, after turning on the third driving source  203  at step S 604  the process waits for a predetermined time (step S 605  NO: a waiting loop is formed). If the time is up (step S 605 : Yes), the first driving source  201  is turned on (step S 606 ), and the process is finished. On the other hand, at step S 601 , if no color printing request is received (step S 601 : No), the process is finished with no actions. 
   (Example of Process when Receiving a Monochrome Printing Request) 
   Below, another example of the image formation process of the image formation apparatus  100  is described with reference to  FIG. 7 , which process is carried out when receiving a monochrome printing request. First, it is determined whether a monochrome printing request is received (step S 701 ). Since monochrome printing usually uses only the photo conductor  106 K for the black color, the third driving source  203  is not required to be driven. Further, the monochrome printing may be performed not necessarily by the photo conductor  106 K for the black color, but by another photo conductor for a color other than black so long as the photo conductor is driven by the second driving source  202 . 
   If a monochrome printing request is received at step S 701  (step S 701 : Yes), the second driving source  202  is turned on (step S 702 ). After turning on the second driving source  202  the process waits for a predetermined time (step S 703  NO: a waiting loop is formed). If the time is up (step S 703 : Yes), the first driving source  201  is turned on (step S 704 ), and the process is finished. On the other hand, if no monochrome printing request is received at step S 701  (step S 701 : No), the process is finished with no actions. 
   (Example of Current Flowing Through Driving Sources when DC Brushless Motor is Used) 
   The image formation process when a DC brushless motor is used for each driving source is described with reference to  FIG. 8 . The horizontal axis represents the time, and the vertical axis represents the current. Further, a dashed line  800  shows the magnitude of the current when the first driving source  201 , the second driving source  202 , and the third driving source  203  are simultaneously started. 
   A solid  810  shows the magnitude of the current when the first driving source  201 , the second driving source  202 , and the third driving source  203  are started in sequence.  FIG. 8  is different from  FIG. 4  in that  FIG. 8  shows a rotation state LOCK signal. The DC brushless motor is capable of providing a rotation state LOCK signal that indicates a rotation state detected. When rotation of the motor is stabilized, a value of the rotation state LOCK signal is changed and fixed. Since rotation being stabilized means that the starting current is stabilized, when the value of the rotation state LOCK signal is fixed, it can be determined that the starting current is stabilized. 
   According to the process shown in  FIG. 8 , when the rotation state LOCK signal of the first driving source  201  is stabilized after starting the first driving source  201 , the second driving source  202  is started. When, the rotation state LOCK signal of the second driving source  202  is stabilized, the third driving source  203  is started. That is, only when the starting current of a driving source is stabilized, the next driving source is started. Accordingly, the current value I 1  when starting the first driving source  201 , the current value I 2  when starting the second driving source  202 , and the current value I 3  when starting the third driving source  203  are less than the current value IA that is required when simultaneously starting all the driving sources. 
   In this way, the total current requirement of the image formation apparatus  100  is minimized, and a power source having a small output current capacity can serve the purpose without causing a shutdown due to an excessive current when starting the driving sources. 
   As described above, according to the image formation apparatus, the image formation method, the image formation program, and the recording medium, the output current capacity of the power source can be small; therefore, power-source cost can be minimized, because the driving sources are sequentially started in turn according to the situations. Here, a shutdown due to the excessive current draw when starting the driving sources is prevented without delaying the printing operations. 
   The embodiment of the present invention further provides a computer executable program for realizing the image formation method described above. Further, the embodiment provides a recording medium that is computer readable and executable, such as a hard disk, a flexible disk, a CD-ROM disk, a MO disk, and a DVD disk, which recording medium stores the program. 
   AVAILABILITY TO INDUSTRY 
   As described above, the image formation apparatus, the image formation method, the image formation program, and the recording medium according to the present invention are useful to digital copiers such as a copier, a facsimile apparatus, and a printer, and especially to a color copier. 
   Further, the present invention is not limited to these embodiments, but variations and modifications may be made without departing from the scope of the present invention. 
   The present application is based on Japanese Priority Application No. 2006-199470 filed on Jul. 21, 2006 with the Japanese Patent Office, the entire contents of which are hereby incorporated by reference.