Abstract:
An image forming apparatus including a toner bottle, accommodation unit, door unit, drive unit and developing unit. The toner bottle stores toner. The accommodation unit accommodates the toner bottle such that the toner bottle lies in the accommodation unit. The door unit covers the toner bottle. The drive unit rotates the toner bottle to supply the toner stored in the toner bottle and renders the toner bottle not to be rotated during a time the door is opened. The developing unit is set in a printable state during a time the toner bottle is detached from the accommodation unit after the door unit is opened. A corresponding method is also described.

Description:
The present application is a Continuation of U.S. application Ser. No. 12/235,186, filed Sep. 22, 2008, which is a Continuation of U.S. application Ser. No. 11/727,443, filed Mar. 27, 2007, which is a Continuation of U.S. application Ser. No. 10/985,897, filed Nov. 12, 2004, the entire contents of which are incorporated herein by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to an image forming apparatus, such as a facsimile, a laser printer or a copying machine, to which electrophotography is applied, and more particularly to an image forming apparatus and an image forming method, which can execute a control to enable toner replenishment (toner bottle replacement) while continuing a printing operation without a halt when printing is being effected. 
     2. Description of the Related Art 
     In general, an image forming apparatus, such as a facsimile, a laser printer or a copying machine, to which electrophotography is applied, includes an image forming section that applies toner to an electrostatic latent image, which is formed on the surface of a photoconductor drum, and forms a visible toner image. The toner image, which is formed on the surface of the photoconductor drum by a developing unit that is a part of the image forming section, is transferred to paper by a transfer unit. The paper with the transferred toner image is conveyed to a fixing unit, and the toner image is fixed on the paper by a fixing device of the fixing unit. 
     In the prior-art image forming apparatus, the developing unit is provided with a sensor for detecting the amount of toner. If the sensor detects that the toner amount is a preset value or less, the image forming apparatus executes a control not to perform a further printing operation in order to prevent a decrease in density of a print image, to display a message prompting the user to replenish toner, and to stop a printing operation until the toner replenishment is completed. 
     In recent years, many users execute large-volume printing with an increase in operation speed of the image forming apparatuses. Hence, there is a demand for increasing productivity by decreasing an idle time of the image forming apparatus due to a shortage of toner. 
     In order to meet this demand, a modern image forming apparatus comprises a developing unit that forms an image on a photoconductor drum using toner; a storage unit that stores toner that is to be supplied to the developing unit; a first supply unit that supplies toner from the storage unit to the developing unit; a first drive unit for driving the first supply unit; a toner bottle that contains toner and is detachably attached to the image forming apparatus; a second supply unit that supplies the toner in the toner bottle to storage unit; a second drive unit for driving the second supply unit; a first door that is openably/closably provided to remove the toner bottle; and a first sensor unit that senses the opening/closing of the first door. While the first sensor unit detects that the first door is open, the first drive unit and developing unit are controlled to be operable and the second drive unit is controlled to be inoperable. 
     When the toner bottle is to be taken out, the second drive unit is controlled to be inoperable on the basis of the detection result that the first door is opened. Thus, the operation of the second supply unit is stopped, and the toner bottle is not rotated and can easily be taken out. In addition, at this time, the first drive unit and developing unit are controlled to be operable. Therefore, the printing operation can be continued. 
     However, in this type of image forming apparatus, when the first door is opened, the printing operation is continued in the state in which the supply of toner from the toner bottle to the storage unit is stopped. Consequently, the toner in the storage unit may decrease to a predetermined amount, and the image density may lower. 
     Furthermore, when the first door remains opened, the temperature in the image forming apparatus lowers and the turn-on time of the heater of the fixing unit increases, leading to an increase in power consumption. 
     To solve these problems, a technique has been disclosed, wherein the operation of the image forming section is stopped if closing of the first door is not detected by the first sensing unit within a predetermined time period after the detection of the opening of the first door by the first sensing unit. 
     Jpn. Pat. Appln. KOKAI Publication No. 2003-114567, for instance, discloses a technique wherein the printing operation is stopped if a time period in which the first door is opened exceeds a predetermined value. However, in some cases, the printing operation is performed in the state in which the first door is opened, and the printing operation is stopped despite that the amount of toner in the storage unit has not yet been consumed to a predetermined level and no decrease has occurred in the density of print images. In addition, there is such a problem that if a great number of images with a high print ratio are printed after the first door is opened, the amount of toner in the storage unit decreases below a predetermined level before a predetermined time period expires, resulting in a decrease in image density. 
     Besides, the modern image forming apparatus includes a tray paper feed unit having a plurality of stages (e.g. trays 1-3) and a manual paper feed unit. In most of image forming apparatuses of this type, different print speeds per minute are set for the respective paper feed units. For example, tray 1 permits printing of 60 A4-size sheets per minute, tray 3 permits printing of 50 A4-size sheets per minute, and the manual paper feed unit permits printing of only 30 A4-size sheets per minute. 
     In this type of image forming apparatus, when continuous paper-feed printing is performed with the paper feed unit (e.g. tray 1) having a high printing speed per minute, there may be a case where the amount of toner in the storage unit decreases to a predetermined level while the time period in which the first door is opened is within a predetermined time range. This leads to a decrease in image density. On the other hand, when continuous paper-feed printing is performed with the paper feed unit (manual paper feed unit) having a low printing speed per minute, there may arise such a problem that more than a predetermined amount of toner still remains in the storage unit even when the time period in which the first door is opened is within a predetermined time range, and the operation of the image forming apparatus is stopped despite that printing with normal image density can be performed. 
     BRIEF SUMMARY OF THE INVENTION 
     The object of an aspect of the present invention is to provide an image forming apparatus and an image forming method, which can enhance productivity by enabling toner replenishment (replacement of a toner bottle) during a printing operation, and can prevent a decrease in image density during a printing operation. 
     According to an aspect of the present invention, there is provided an image forming apparatus comprising: a developing unit that visualizes an image; image forming material storing means for storing an image forming material; a supply unit that supplies the image forming material, which is stored in the image forming material storing means, to a downstream side; a door that covers the image forming material storing means and is openably provided; cut-off means for rendering, if the door is open, the supply unit inoperable, and rending, if the door is closed, the supply unit operable; and opening/closing sensing means for detecting opening/closing of the door, wherein while the opening/closing sensing means detects the opening of the door, the supply unit is rendered inoperable by the cut-off means and a control unit counts a number of prints during this time period, and if the counted number of prints is less than a predetermined value, the developing unit is rendered operable and the image forming apparatus is set in a printable state, and if the counted number of prints becomes equal to the predetermined value, the image forming apparatus is set in a non-printable state. 
     According to another aspect of the present invention, there is provided an image forming method comprising: a developing step of controlling a developing unit that visualizes an image; a supply step of controlling a supply unit that supplies an image forming material, which is stored in image forming material storing means, to a downstream side; an opening/closing sensing step of detecting opening/closing of a door that covers the image forming material storing means and is openably provided; a cut-off step of rendering, if the door is open, the supply unit inoperable, and rending, if the door is closed, the supply unit operable; a step of counting, while the opening of the door is detected in the opening/closing sensing step, a number of prints during this time period; a step of rendering, if the counted number of prints is less than a predetermined value, the developing unit operable, and setting the image forming apparatus in a printable state; and a step of setting, if the counted number of prints becomes equal to the predetermined value, the image forming apparatus in a non-printable state. 
     Additional objects and advantages of an aspect of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of an aspect of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out hereinafter. 
    
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING 
       The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate presently preferred embodiments of the invention, and together with the general description given above and the detailed description of the embodiments given below, serve to explain the principles of an aspect of the invention. 
         FIG. 1  shows the external appearance of an image forming apparatus according to an embodiment of the present invention; 
         FIG. 2  schematically shows the structure of an image forming section of the image forming apparatus according to the embodiment of the present invention; and 
         FIG. 3  is a flow chart that illustrates the operation of the image forming apparatus according to the embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     An embodiment of the present invention will now be described with reference to the accompanying drawings. 
       FIG. 1  shows the external appearance of an image forming apparatus according to an embodiment of the invention.  FIG. 1  is a perspective view showing the front side of the image forming apparatus in the state in which a first door  90  that is openably provided for removing a toner bottle  100 , which is image forming material storing means, is opened. The toner bottle  100  and an accommodation section for accommodating the toner bottle  100  are disposed on the inside of the first door  90 . The toner bottle  100  can be taken out. The toner bottle  100  is a container having a helical portion on the inner peripheral surface thereof. The toner bottle  100  is rotated by an external drive force, and toner in the toner bottle is supplied through an opening portion thereof. A control panel  91  for executing various operational inputs is provided on the upper front part of the image forming apparatus. 
       FIG. 2  schematically shows the structure of the region of the image forming section of the image forming apparatus. 
     The region of the image forming section of the image forming apparatus includes a control unit  10 , a developing unit  11 , a developing unit toner amount sensor  12 , a storage unit  13 , a storage unit toner amount sensor  14 , a first supply unit  15 , a first drive unit  16 , a second supply unit  17 , a second drive unit  18 , first door  90 , a cut-off switch  94  that is cut-off means, an opening/closing detection switch  95  that is opening/closing sensing means, accommodation section  96 , and toner bottle  100 . 
     The control unit  10  includes a counter  10   a  that is composed of, for example, a program for counting the number of prints, as will be described later in detail. The developing unit toner amount sensor  12 , storage unit toner amount sensor  14 , cut-off switch  94  and opening/closing sensing switch  95  are connected to the control unit  10 . The control unit  10  controls at least the first drive unit  16 , second drive unit  18  and developing unit  11 . 
     The cut-off switch  94 , or the cut-off means, is turned on when the first door  90  is opened and is turned off when the first door  90  is closed. In the turn-on state, the cut-off switch  94  renders a power supply circuit  18   a  of the second drive unit  18  conductive. In the turn-off state, the cut-off switch  94  cuts off the power supply circuit  18   a  and renders it non-conductive. 
     The developing unit  11  forms an image on a photoconductor drum (not shown) using toner. 
     The developing unit toner amount sensor  12  detects the amount of toner in the developing unit  11 . 
     The storage unit  13  stores toner that is to be supplied to the developing unit  11 . 
     The storage unit toner amount sensor  14  detects the amount of toner in the storage unit  13 . 
     The first supply unit  15  supplies toner from the storage unit  13  to the developing unit  11 . The first drive unit  16  drives the first supply unit  15 . 
     The second supply unit  17  supplies toner, which is contained in the toner bottle  100 , to the storage unit  13 . 
     The second drive unit  18  drives the second supply unit  17 . When the first door  90  is closed, the cut-off switch  94  is turned on to render the power supply circuit  18   a , which supplies power to the second drive unit  18 , conductive. In this state, if a drive signal is output from the control unit  10 , the second drive unit  18  is enabled to drive the second supply unit  17 . 
     On the other hand, when the first door  90  is opened, the cut-off switch  94  is turned off to render the power supply circuit  18   a , which supplies power to the second drive unit  18 , non-conductive. In this state, even if a drive signal is output from the control unit  10 , the second drive unit  18  is inoperable and the second supply unit  17  remains in the off-state. 
     When the storage unit toner amount sensor  14  detects that the amount of toner in the storage section  13  has decreased to a predetermined value or less, the control unit  10  executes a control to activate the second drive unit  18  and to supply toner from the toner bottle  100  to the storage unit  13 . 
     When the developing unit toner amount sensor  12  detects that the amount of toner in the developing unit  11  has decreased to a predetermined value or less, the control unit  10  executes a control to activate the first drive unit  16  and to supply toner from the storage unit  13  to the developing unit  11 . 
     The image forming apparatus includes the first door  90  that is openably provided to take out the toner bottle  100 , and the opening/closing sensing switch  95  that detects opening/closing of the first door  90 . The image forming apparatus includes a second door (not shown), in addition to the first door  90 . Since the second door is not related to the present invention, a description thereof is omitted. 
     If the first door  90  is opened and the cut-off switch is turned off, the power supply circuit  18   a  of the second drive unit  18  is cut off and the second drive unit  18  is rendered inoperable. Accordingly, the second supply unit  17  is set in the off-state. In other words, the image forming apparatus is set in the state in which no toner can be supplied from the toner bottle  100  to the storage unit  13 . 
     Thus, at this time, the toner bottle  100  is not rotated, and the operator can safely take out the toner bottle  100 . 
     Furthermore, during the time in which the opening/closing sensing switch  95  detects the opening of the first door  90 , the counter  10   a  of the control unit  10  counts the number of prints. If the count value reaches a predetermined value, the control unit  10  stops the operations of the first drive unit  16  and developing unit  11 , thereby preventing a decrease in image density due to shortage in toner amount. In this case, the predetermined value of the number of prints is set at, e.g. 100. This predetermined value may be varied by an input operation through the control panel  91 , which is a setting unit, by choosing a number from a range of 100 to 2000 in units of 100. The setting unit may be configured such that the setting unit is connected to an external controller (not shown) such as a personal computer, and the predetermined value is varied by inputting a desired number through the external controller. 
     Regardless of whether the toner bottle  100  is replaced or not, if the opening/closing sensing switch  95  detects the closing of the first door  90 , the control unit  10  resets the count value of the counter  10   a , which is indicative of the number of prints. Further, if the developing unit toner amount sensor  12  detects that the amount of toner in the developing unit  11  decreases to a predetermined value or less, the control unit  10  executes a control to operate the first drive unit  16  and to supply toner from the storage unit  13  to the developing unit  11 . In addition, if the storage unit toner amount sensor  14  detects that the amount of toner in the storage unit  13  decreases to a predetermined value or less, the control unit  10  executes a control to operate the second drive unit  18  and to supply toner from the toner bottle  100  to the storage unit  13 . Hence, the control unit  10  resumes the printing operation. 
     Next, the control operation of the image forming apparatus according to the embodiment is described referring to a flow chart of  FIG. 3 . 
     When a print start button (not shown) on the control panel  91  is pressed, the control unit  10  starts a printing operation (S 01 ). 
     When the printing operation is started, the control unit  10  instructs the developing unit toner amount sensor  12  to detect the whether the amount of toner in the developing unit  11  is a predetermined value or less (S 02 ). 
     If the amount of toner in the developing unit  11  is the predetermined value or less, the control unit  10  activates the first drive unit  16  for supplying toner from the storage unit  13  to the developing unit  11 , and the second drive unit  18  for supplying toner from the toner bottle  100  to the storage unit  13  (S 03 ). In step S 02 , if the amount of toner in the developing unit  11  is greater than the predetermined value, the control unit  10  goes to step S 04 . 
     Then, the control unit  10  detects, with use of the storage unit toner amount sensor  14 , whether the amount of toner in the storage unit  13  is a predetermined amount or less (S 04 ). 
     If the amount of toner in the storage unit  13  is the predetermined amount or less, the control unit  10  determines shortage of toner in the toner bottle  100  and causes the display section (not shown) of the control panel  91  to display an alarm message indicating the toner empty state (S 05 ). Alternatively, alarm sound may be produced, or both the alarm message and alarm sound may be used. 
     Then, the control unit  10  detects, with use of the opening/closing sensing switch  95 , whether the first door  90  is opened (S 06 ). 
     If the first door  90  is opened and the cut-off switch  94  is turned off, the power supply circuit  18   a  of the second drive unit  18  is cut off and the second drive unit  18  is rendered inoperative (i.e. stop of operation of the toner bottle  100 ). In this case, the counter  10   a  of the control unit  10  starts counting the number of prints of the image forming apparatus from the time of detection of the opening of the first door  90  (S 07 ). 
     Assuming that the replacement of the toner bottle  100  is completed, the control unit  10  detects, by means of the opening/closing sensing switch  95 , whether the first door  90  is closed (S 08 ). 
     If the first door  90  is still open in step  308 , the control unit  10  checks whether the number of prints, which is counted by the counter  10   a  from the time of opening of the first door  90 , has reached a predetermined value (S 09 ). If the number of prints does not reach the predetermined value in step S 09 , the control unit  10  returns to step S 08 . 
     If the number of prints reaches the predetermined value in step S 09 , the control unit  10  stops the printing operation (S 10 ). 
     If the closing of the first door  90  is detected in step S 08 , the control unit  10  resets the count value of the number of prints in the counter  10   a , and continues the printing operation (S 11 ). 
     Subsequently, the control unit  10  determines whether the initial value of the number of prints, which was set through the control panel  91  at the time of starting the printing operation, is reached (S 12 ). 
     If the initial value of the number of prints is not reached, the control unit  10  returns to step S 02  and continues the printing operation. If the initial value of the number of prints is reached, the printing operation is completed. 
     In an applied example of the present invention (although not shown, the cut-off switch  94  in  FIG. 2  is omitted, and the power supply circuit  18   a  of the second drive unit  18  is always connected), the cut-off switch  94  that is the cut-off means, which is operated by the opening/closing of the first door  90 , may be omitted. In the applied example in which the cut-off switch  94  for stopping the second drive unit  18  is omitted, if the opening/closing sensing switch  95  detects the opening of the first door  90 , the control unit  10  executes a control to render the first drive unit  16  and developing unit  11  operable and to render the second drive unit  18  inoperable. Thereby, when the first door  90  is opened to take out the toner bottle  100 , the second drive unit  18  is controlled to be inoperable and the supply of toner from the second supply unit is stopped. At this time, no toner flows from the toner bottle  100  to the downstream side, and the operator can take out the toner bottle  100  from the image forming apparatus. 
     According to the above structure, while the opening/closing sensing means detects the opening of the door that covers the image forming material storing means and is openably provided, the control unit counts the number of prints. If the count value of the number of prints is less than a predetermined value, the supply unit that supplies the image forming material from the image forming material storing means to the downstream side is set in the inoperable state, the developing unit is set in the operable state and the image forming apparatus is thus set in the printable state. If the count value of the number of prints reaches the predetermined value, the image forming apparatus is set in the non-printable state. 
     In the present embodiment, the toner bottle that is the image forming material storing means is of the type wherein the toner bottle has a helical inner peripheral wall for conveying toner and does not include the second supply unit. Alternatively, the toner bottle may be of the type wherein the toner bottle includes a convey member as the second supply unit. 
     The toner bottle may be a toner cartridge (or a toner hopper) that includes a convey member as the second supply unit, or may be a toner cartridge (or a toner hopper) that does not include a convey member as the second supply unit. 
     As has been described above, according to the present embodiment of the invention, toner replenishment (replacement of a toner bottle) is enabled during a printing operation, thereby enhancing productivity, and a decrease in image density during the printing operation can be prevented. 
     Additional advantages and modifications will readily occur to those skilled in the art. Therefore, the invention in its broader aspects is not limited to the specific details and representative embodiments shown and described herein. Accordingly, various modifications may be made without departing from the spirit or scope of the general inventive concept as defined by the appended claims and their equivalents.