Abstract:
A user-friendly ink jet recording apparatus is capable of preventing a sudden ink exhaustion and a resulting unclear print that may result from canceling a no-ink error signal without an ink tank replacement. In the ink jet recording apparatus, in a case of a no-ink error signal, a no-ink timer is activated and time information of a no-ink state is stored in a non-volatile memory, a period from such time is measured and compared, and after the lapse of predetermined time, a no-ink error signal is generated even before a threshold value for the no-ink error signal is reached, thereby issuing a request for ink tank replacement to the user.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to an ink jet recording method and a control method therefor. 
     2. Related Background Art 
     In the prior art, a no-ink error signal in an ink jet recording apparatus is cancelled by an ink tank replacement, and, in case a same ink tank is used in continuation without the ink tank replacement, such no-ink error signal can be cancelled by an operation of a resume key or the like. 
     In case the no-ink error signal is cancelled by the resume key operation, a no-ink error signal of second time is generated with a threshold value same as that in the first-no-ink error signal. 
     There is also proposed a method of changing the threshold value to ½ and to ¼ in the second time and thereafter. 
     SUMMARY OF THE INVENTION 
     In such prior configuration, a user with a low frequency of use of the printer may forget that the no-ink error signal has been cancelled without replacing the ink tank. In case of use by plural users in a home, a next user does not know such history on the no-ink error signal. Therefore the user may encounter a situation where the ink is exhausted and the print becomes unclear without the no-ink error signal. 
     An object of the present invention is to provide a user-friendly ink jet recording apparatus capable of preventing a sudden ink exhaustion and a resulting unclear print by canceling the no-ink error signal without an ink tank replacement. 
     According to the present invention, when a no-ink state is reached, a no-ink timer is activated and time information when the no-ink state is reached is stored in a non-volatile memory. Then a lapse of a predetermined time is measured from the timing of storage of the time information, and, after the lapse of the predetermined time, an ink tank replacement is requested to the user even before a threshold value for the no-ink error signal is reached. 
     The present invention provides an effect of preventing a situation where the ink is abruptly exhausted to result in an unclear printing by canceling a no-ink error signal without an ink tank replacement. 
     In particular, in case a user who has cancelled a no-ink error signal had not executed an ink tank replacement, a no-ink situation can be immediately informed when another user uses a printer after the lapse of a long period. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a block diagram showing an ink jet recording apparatus PR 1  constituting a first embodiment of the present invention; 
         FIG. 2  is a perspective view, seen from a left side, of the entire ink jet recording apparatus PR 1 ; 
         FIG. 3  is a cross-sectional view showing ink tanks  52 ,  53 ,  54 ,  55 ; 
         FIG. 4  is a flow chart showing an ink remain checking operation of the ink jet recording apparatus PR 1 ; 
         FIG. 5  is a flow chart showing an ink tank checking operation of the ink jet recording apparatus PR 1 ; 
         FIG. 6  is a flow chart showing a printing operation in the ink jet recording apparatus PR 1 ; 
         FIG. 7  is a flow chart showing a power-on operation in the ink jet recording apparatus. PR 1 ; and 
         FIG. 8  is a flow chart showing an ink remain checking operation II in a second embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The present invention can be best realized by the following embodiments. 
     First Embodiment 
       FIG. 1  is a block diagram showing an ink jet recording apparatus PR 1  constituting a first embodiment of the present invention. 
     The ink jet recording apparatus PR 1  is equipped with a CPU  1 , a ROM  2 , a switch  4 , an LED  5 , various sensors  6 , a CPU bus  7 , an ASIC  8 , a recording head driver  10 , a black recording head  11 , a color recording head  12 , a DC motor driver  13 , a line feed motor  14 , a carriage motor  15 , a stepping motor driver  16 , a recovery motor  18 , a non-volatile memory  19 , an interface  20 , a host computer  21 , a RAM  22 , a timer  23 , a power source  24 , a carriage  30  and a conveying roller  33 . 
     The CPU  1  is a central processing unit constituted as an example of a programmable microprocessor. 
     The ROM  2  stores font data, program instruction sequences to be executed by the CPU  1  for controlling the ink jet recording apparatus PR 1 , and various control tables. 
     The switch  4  includes switches to be operated by the user, such as a power switch  4   a  and a resume switch  4   b.    
     The sensors  6  include a PE sensor (paper end sensor)  6   a , an ASF sensor (sheet feeding sensor)  6   b , a PG sensor (purge sensor)  6   c , an ink remain sensor  6   d , an encoder  6   e  and an encoder  6   f.    
     The non-volatile memory  19  stores printer information such as an ink status  19   a  in an ink cartridge, an ink consumption history  19   b , a used ink counter  19   c ′ etc. 
     The RAM  22  stores, during an execution of a program stored in the ROM  2  by the CPU  1 , various recording data transferred from the host computer  21  through an interface  20  in a print buffer in the RAM  22 , in order to achieve a print output by the black recording head  11  and the color recording head  12 . 
     The ASIC  8  is a control logic circuit which controls the recording head driver  10  in order to output control signals for nozzles in the recording heads  11 ,  12 , also controls data transfer among the interface  20 , the CPU  1  and the RAM  22 , and is further provided with control logic circuits for the DC motor driver  13  and the stepping motor driver  16 . 
     The CPU  1  is connected to the CPU bus  7 . The interface  20  is provided with a signal path capable of bi-directional signal exchange between the ink jet recording apparatus PR 1  and the host computer  21 , and receives recording data and commands from the host computer  21 . 
     The DC motor driver  13  controls the line feed motor  14  and the carriage motor  15 . The line feed (LF) motor  14  drives the conveying roller  33 , thereby controlling conveying and feed-discharge of a sheet. The carriage motor  15  drives a carriage  30  thereby controlling displacements of the recording heads  11 ,  12  to a recording position on a scanning row. 
     The stepping motor driver  16  controls the sheet feed motor  17  and the recovery motor  18 . The sheet feed motor  17  controls a sheet pickup operation at a sheet feeding operation. The recovery motor  18  controls recovery operations such as cleaning, wiping, capping, etc., for the recording heads  11 ,  12 . 
     The black recording head  11  and the color recording head  12 , controlled by the recording head driver  10 , are removable units displaced by the carriage. Such heads  11 ,  12  include an ink discharge nozzle for forming a recorded image on a recording medium, and a head diode  9  for feeding back information on the presence and characteristics of the removable recording head. 
     Based on an electrical signal transferred from the recording head driver  10 , an electrothermal converting element of the recording head  11  or  12  is driven to generate thermal energy for causing a film boiling in the ink. As an ink discharge amount varies by a temperature of the recording head  11  or  12 , a thermistor  3  for measuring an ambient temperature of the ink jet recording apparatus PR 1  monitors a temperature output from the head diode  9  of the recording head  11 ,  12 . 
     Various sensors  6  are mounted on the ink jet recording apparatus PR 1 . A PE sensor (pager end sensor) detects a passing sheet. An ASF sensor (sheet feed sensor)  6   b  detects a rotational position of a cam in a sheet feeding unit. 
     A PG sensor (purge sensor)  6   c  detects a cam position of a head recovery unit. An ink remain detecting sensor  6   d  is an optical sensor which detects presence/absence of ink in an ink tank, by an optical transmittance when the ink tank, supported on the carriage  30 , passes over the sensor by a displacement of the carriage  30 . In addition, there are also included a cover sensor linked with a cover switch  4   c , an encoder  6   e  for reading positional information of the carriage, and an encoder  6   f  for reading positional information of the line feed (LF) motor. 
     There are also provided switches to be operated by the user, such as a power switch  4   a , a resume switch  4   b , etc. Also there is provided a display LED  5  for informing the user of a status of the ink jet recording apparatus PR 1 . An LED  5   a  is a light-emitting element used for detecting an ink remaining amount. The timer  23  is involved in controlling the motors, and the power source  24  supplies electric power for driving the ink jet recording apparatus PR 1 . 
       FIG. 2  is a perspective view of the entire ink jet recording apparatus PR 1 , seen from left side. 
     The ink jet recording apparatus PR 1  is equipped with a recording head  30 , a carriage  31 , a chassis  32 , a guide shaft  33 , a guide rail  34 , a timing belt  35 , a carriage encoder  36 , a base chassis  37 , a left side plate  38 , a right side plate  39 , a recovery unit  40 , a conveying roller  41 , a pinch roller  42 , a pinch roller holder  43 , an automatic sheet feeder  44 , a line feed encoder  46 , a first sheet guide member  48 , a position detector  51 , sheet discharge rollers  49 , a black ink tank  52 , a cyan ink tank  53 , a magenta ink tank  54 , and a yellow ink tank  55 . 
     The recording head  30  constitutes image recording means. The carriage  31  constitutes head mounting means for mounting the recording head  30 . The guide shaft  33  serves as a guide member for guiding the carriage  31  in a direction A in  FIG. 2 , and also as a support means for supporting the carriage  31 . A right hand side of the guide shaft  33  is positioned and fixed on the right side plate  39 , and a left hand side of the guide shaft  33  is positioned and fixed on the left side plate  38 . 
     The guide rail  34  is another guide/support member for guiding the carriage  31 , thereby guiding the displacement thereof. A right hand side of the guide rail  34  is positioned on the right side plate  39 , and a left hand side of the guide rail  34  is positioned on the left side plate  38 . 
     A part of the timing belt  35  is fixed to the carriage  31 . The carriage motor is positioned and fixed on the chassis  32 . A drive of the carriage motor causes a scanning motion of the carriage  31 , supporting the recording head  30 , in a direction A in  FIG. 2 . 
     The carriage encoder  36  is a scale indicating an absolute position of the carriage  31  in the scanning direction, and constitutes position detecting means. A right hand side of the carriage encoder  36  is positioned and fixed on the right side plate  39 , and a position of the carriage encoder  36  in height is restricted by the left side plate  38 . 
     The recovery unit  40  executes a discharge recovery operation of the recording head  30 . It includes an unillustrated cleaning means for cleaning a head face of the recording head  30 , and an unillustrated cap means for forming a closed system on a discharge port portion of the recording head  30 , and is positioned and fixed on the base chassis  37 . 
     The conveying roller  41  is a sheet conveying rotary member (conveying means) for conveying a recording sheet as a recording medium. The pinch roller  42  maintains, by an unillustrated spring, the recording sheet in contact with the conveying roller  41 . The pinch roller holder  43  rotatably supports the pinch roller  42 . 
     The line feed encoder  46  is a scale for detecting a rotational position of the conveying roller  41 , and is mounted on an end portion of the conveying roller  41 . The position detector  51  is fixed on the left side plate  38 , and detects a rotation amount of the conveying roller  41 . The sheet discharge rollers  49  discharge the recording sheet to the exterior of the ink jet recording apparatus PR 1 . 
     The automatic sheet feeder  44  supports a stack of plural recording sheets, and separates and feeds a sheet at a time. The recording sheet fed by the automatic sheet feeder  44  is guided by the pinch roller holder  43  and the first sheet guide member  48 , and is conveyed to a nip portion of the conveying roller  41  and the pinch roller  42 . The first sheet guide member  48  is positioned and fixed, like the second sheet guide member, on the positioning portion of the base chassis  37 . 
     The black ink tank  52 , the cyan ink tank  53 , the magenta ink tank  54  and the yellow ink tank  55  are mounted on the recording head  30 , detachably from the recording head  30 , and constitute ink reservoirs for discharging inks, designated by the host, onto the recording sheet. 
       FIG. 3  is a cross-sectional view showing the inks tank  52 ,  53 ,  54  or  55 . 
     The ink tank  52 ,  53 ,  54  or  55  for each color is provided, on an outside thereof, with an elastically deformable, integral lever member  66 . Each color ink tank  52 ,  53 ,  54  or  55  communicates with the air in an upper part through a communicating aperture  64 , and with an ink supply aperture  65  in a lower part, and includes therein a chamber  61  containing an absorbent member constituting a negative pressure generating member, and a substantially enclosed liquid chamber  60  for containing a liquid ink. The chambers  60  and  61  are separated by a partition. 
     The first chamber  60  and the second chamber  61  mutually communicate only through a communicating aperture  69  formed in the partition in the vicinity of the bottom of the ink tank. On an upper wall defining the first chamber  60 , plural ribs  63  protruding inwardly are formed integrally. The absorbent member in the first chamber  61  is formed by a thermally compressed urethane foam, and is contained in a compressed state in order to generate a predetermined capillary force. 
     The ink remain detecting sensor unit  56  is provided with a light-emitting element  67  emitting an infrared light, and a photosensor element  68  capable of receiving the light from the light-emitting element  67 . In each color ink tank, a light-reflecting prism  62  is provided integrally with the ink tank and is formed by an almost transparent material such as polypropylene. In the absence of ink on inclined top faces of the prism, the light from the light-emitting element  67  can be reflected and can reach the photosensor element  68 . In a state where the ink is filled around the inclined top faces of the prism, the light from the light-emitting element  67  is less reflected to reduce the light amount reaching the photosensor element  68 , whereby presence/absence of the ink can be detected. 
     An ink amount remaining in each of the color ink tanks  52 ,  53 ,  54 ,  55  can be detected by passing the carriage  31  over the ink remain detecting sensor unit  56 . 
       FIG. 4  is a flow chart showing an ink remain checking operation in the ink jet recording apparatus PR 1 , showing details of S 22  in  FIG. 5 . 
     A step S 1  initiates an ink remain checking operation. In a step S 2 , when the carriage  31  passes over the ink remain detecting sensor unit  56 , an optical remaining amount detection in the ink tank is executed by emitting an infrared light from the light-emitting element  67 , receiving the light from the light-emitting element  67  by the photosensor element  68 , thereby detecting an ink amount remaining in each color ink tank. 
     A step S 3  checks whether the ink is present in the liquid chamber  60 , and compares the result with the result of optical detection of the ink tank in S 2 . In case the ink is present in the liquid chamber  60 , the sequence proceeds to S 11 . In case the ink is absent in the liquid chamber  60 , a step S 4  checks an ink status. The sequence proceeds to S 7  unless the ink status indicates “ink present”. In case the ink status is “ink present”, a step S 5  changes the ink status to “ink low”. Then a step S 6  starts a dot counting for ink error detection, and the sequence proceeds to S 15 . 
     A step S 4  checks the ink status, and, in case the ink status is not “ink present”, a step S 7  checks whether the dot count for ink error started in S 6  has reached an ink error level. Then a step S 8  checks whether a no-ink timer has passed a predetermined time from a timing of a previous ink error. In case the predetermined time has not elapsed, the sequence returns to the main routine in S 15  and continues the process. In case the no-ink timer has passed the predetermined time, the sequence proceeds to S 9 . 
     In case the dot count in S 7  has reached the ink error level, the sequence proceeds to S 9  to shift the ink status to “ink error”. Then a step S 10  stores the current time information, namely an ink error generation time information, in a non-volatile memory and executes an error notice and an error display, whereupon the sequence proceeds to S 15 . 
     The ink error generation time information, stored in the non-volatile memory, is maintained even when the power supply is turned off. The current time information is informed from the host to the no-ink timer, then renewed to latest information when the power supply is turned on, and is renewed thereafter in the printer. 
     In case S 3  identifies that the ink is present in the liquid chamber  60 , a step S 11  checks whether the ink status is “ink low” or an ink error. In case neither state is found, the sequence proceeds to S 15  to continue the process. On the other hand, in case the ink status is “ink low” or an ink error, it is identified that a tank replacement has been executed and a step S 14  changes the ink status to “ink present”. Also a step S 13  stops the no-ink timer, then the step S 14  stops the dot count for ink error and the sequence proceeds to S 15 . 
       FIG. 5  is a flow chart showing an ink tank checking operation of the ink jet recording apparatus PR 1 . 
     A step S 21  initiates an ink tank check. A step S 21  returns to S 1  in  FIG. 4  to execute an ink remain checking operation. Then a step S 23  checks whether the ink status is “ink error”. If not an “ink error”, the sequence proceeds to S 30  to clear a reset counter, and then proceeds to S 31 . In case the ink status is an “ink error”, a step S 24  checks whether a tank replacement has been made. In case the tank replacement is identified, the sequence proceeds to S 30 . If not, a step S 25  checks whether a resume switch  4   b  has been depressed. 
     In case the resume switch  4   b  has not been depressed, the sequence returns to S 24  to continue the process. In case the resume switch  4   b  has been depressed, a step S 26  changes the ink status to “ink low”. Then a step S 27  resets the dot count for ink error, a step S 28  executes an increment +1 of the reset counter, a step S 29  starts the no-ink timer, and a step S 31  terminates the ink tank check. A timer value set in S 29  may be determined from a table in the ROM  2  by referring to the reset count. 
     The table assigns a timer value for each reset count. For example, a smaller timer value is set for a larger reset count. 
       FIG. 6  is a flow chart showing a printing operation in the ink jet recording apparatus PR 1 . 
     A step S 41  initiates a printing operation. A step S 42  executes a sheet feeding, and S 43  executes a printing. In the course of printing, a periodically interrupting handler S 50  measures dots of the ink used for printing (S 51 , S 52 ). Upon completion of the printing in S 43 , a step S 44  executes a sheet discharge, then S 45  returns to S 1  in  FIG. 4  to execute an ink remain checking operation, and a step S 46  terminates the printing process. 
       FIG. 7  is a flow chart showing a power-on operation in the ink jet recording apparatus PR 1 . 
     A step S 61  initiates a power-on procedure. A step S 62  clears the reset counter, and S 63  starts the no-ink timer. The set timer value may be determined from a table in the ROM  2  by referring to the reset count. 
     Since the reset counter is 0 in the power-on procedure, a particular value may be set at the top of the table, or the step S 63  is so constructed as not to start the timer. 
     A step S 64  activates a periodical handler. Then a step S 65  checks whether a print signal has arrived from the interface  20 . In case the print signal is not available, the operation of S 65  is repeated until the print signal arrives. In case the print signal is available, a step S 66  executes the printing, and the sequence returns to S 65  for continuing the process. 
     Second Embodiment 
       FIG. 8  is a flow chart showing an ink remain checking operation II, constituting a second embodiment of the present invention, and providing a checking method in the absence of the mechanism for detecting the ink remain in the ink tank, in S 22  in  FIG. 5 . 
     A step S 71  initiates an ink remain checking operation. A step S 72  checks whether the no-ink timer has passed a predetermined time from the timing of a previous ink error generation. The sequence proceeds to S 78  if the predetermined time has elapsed. In case the predetermined time Y has not elapsed, a step S 73  checks whether the dot count is in an “ink low” level. If not, the sequence proceeds to S 81 . In case the “ink low” level has been reached, a step S 74  checks the ink status. 
     In case the ink status is not “ink present”, the sequence proceeds to S 77 . In case the ink status is “ink present”, a step S 76  sets a predetermined value X in the no-ink timer, and the sequence proceeds to S 84 . 
     A step S 74  checks the ink status, and, in case the ink status is not “ink present”, a step S 77  checks whether the dot count has reached an ink error level. In case the ink error level has not been reached, the sequence proceeds to S 84 . In case the ink error level has been reached, a step S 78  changes the ink status to “ink error”, and a step S 79  sets a predetermined value Y in the no-ink timer. Then a step S 10  stores the current time information, namely an ink error generation time information, in a non-volatile memory and executes an error notice and an error display, whereupon the sequence proceeds to S 84 . The ink error generation time information, stored in the non-volatile memory, is maintained even when the power supply is turned off. 
     In case the step S 73  identifies that the dot count is not in the “ink low” level, S 81  checks whether the ink status is “ink low” or an ink error. In case neither state is found, the sequence proceeds to S 84  to continue the process. On the other hand, in case the ink status is “ink low” or an ink error, a step S 82  changes the ink status to “ink present”, and a step S 83  sets a predetermined value Z in the no-ink timer, whereupon the sequence proceeds to S 84 . 
     This application claims priority from Japanese Patent Application No. 2004-296765 filed on Oct. 8, 2004, which is hereby incorporated by reference herein.