JP4656125B2 - Inkjet recording device - Google Patents

Description

  The present invention relates to an ink jet recording apparatus that includes a recording head that ejects ink droplets from nozzle openings and performs recording by moving the recording head in the main scanning direction.

  As an ink jet recording apparatus, an ink jet printer, an ink jet plotter, and the like are well known. In such an ink jet recording apparatus, the recording head is moved from the standby position in the main scanning direction, and ink droplets are ejected in synchronization with the movement, and further, the sub scanning direction is orthogonal to the main scanning direction. Characters and images are recorded on the recording paper by feeding the recording paper.

  As a recording head used in this recording apparatus, there is a recording head using a pressure generating element such as a heat generating element or a piezoelectric vibrator. In this recording head, the ink is held by the surface tension at the nozzle opening, and the meniscus, which is the free surface of the ink, is exposed to the air. The viscosity of the ink increases, and there is a problem that the image quality is lowered due to the increased viscosity of the ink.

  Therefore, in the recording apparatus, a maintenance operation is performed to prevent thickening of ink near the nozzle opening. As the maintenance operation, for example, a flushing operation for forcibly discharging ink at the start of main scanning, or a fine vibration operation for finely vibrating the meniscus of the nozzle opening at the start is performed. In addition, a fine vibration pulse for finely vibrating the meniscus is included in the drive signal for operating the pressure generating element, and the fine vibration pulse is supplied to the pressure generating element for the nozzle openings that do not eject ink droplets. Thus, there is also a device that allows a fine vibration operation to be performed even during main scanning.

  By the way, in a large-sized recording apparatus capable of recording on a large-sized recording sheet, a maintenance operation at the time of start-up is performed by unit scanning (one main scanning) in order to guarantee image quality in an end region far from the standby position. ) Every time. However, when an extremely large recording paper such as B0 size is used, the moving distance of the recording head in the main scanning direction becomes long. When the first ink discharge in the unit scan is performed in the end region far from the standby position, the period from the end of the maintenance operation until the ink droplet is discharged becomes longer, and the ink solvent evaporates during this period. As a result, the ink in the vicinity of the nozzle opening may be thickened. If a small amount of ink droplets are ejected while the ink in the vicinity of the nozzle opening is thickened, the size and trajectory of the ink droplets are disturbed, and the shape and position of the dots that have landed on the recording paper vary and the image quality deteriorates. The problem arises.

  On the other hand, in the case where the fine vibration pulse is included in the drive signal so that the fine vibration operation is performed even during the main scanning, the deterioration of the image quality in the end region can be prevented even in a large recording apparatus. . However, the printing cycle (that is, the repetition cycle for recording one dot) in the drive signal becomes longer by the amount of the minute vibration pulse included. For this reason, it is difficult to increase the scanning speed of the recording head, and it becomes difficult to shorten the printing time.

  The present invention has been made in view of such circumstances, and provides an ink jet recording apparatus capable of reducing the printing time while improving the image quality in the end region far from the standby position. With the goal.

  The present invention has been proposed in order to achieve the above object. According to the first aspect of the present invention, there is provided a recording head for ejecting ink droplets from a nozzle opening by the operation of a pressure generating element, and a standby for the recording head. A head scanning mechanism that moves in the main scanning direction from the position; a drive signal generating means that generates a drive signal for operating the pressure generating element; and a drive signal supply to the recording head based on print data for each dot. In the ink jet recording apparatus including the discharge control unit that discharges ink droplets, the discharge control unit acquires a non-discharge period of ink droplets for each nozzle opening prior to main scanning of the recording head. And the amount of ink discharged in at least the first discharge operation after the non-discharge period has passed on condition that the non-discharge period is equal to or longer than the predetermined period. An ink jet recording apparatus characterized by having a discharge amount changing means for setting more than a predetermined amount defined by over data.

  According to a second aspect of the present invention, the non-ejection period acquisition unit acquires an elapsed time from the start time of main scanning to the first ink droplet ejection time as an ink droplet non-ejection period. An ink jet recording apparatus according to claim 1.

  According to a third aspect of the present invention, the non-ejection period acquisition means calculates the elapsed time from the ejection point of the previous ink droplet to the ejection point of the subsequent ink droplet in one main scan as the non-ejection period of the ink droplet The inkjet recording apparatus according to claim 1, wherein the inkjet recording apparatus is acquired as follows.

  According to a fourth aspect of the present invention, a recording head that ejects ink droplets from a nozzle opening by an operation of a pressure generating element, a head scanning mechanism that moves the recording head from a standby position in the main scanning direction, and an operation of the pressure generating element In an ink jet recording apparatus, comprising: a drive signal generating means for generating a drive signal for causing the ink to be discharged; and an ejection control means for ejecting ink droplets by controlling the supply of the drive signal to the recording head based on the print data for each dot The discharge amount change region is set in the end region far from the standby position, and the discharge control means sets a predetermined amount of ink discharge amount defined by the print data for the ink droplets discharged in the discharge amount change region. The ink jet recording apparatus is characterized by having a discharge amount changing means for increasing the ink discharge amount on condition that the ink discharge amount is less than the upper limit.

  According to a fifth aspect of the present invention, the drive signal generating means generates a drive signal in which a plurality of drive pulses for discharging different amounts of ink droplets are connected in series, and the discharge amount changing means is a pressure generating element. 5. The ink discharge amount is increased by changing the drive pulse supplied to the drive pulse to a drive pulse having a larger discharge amount than the drive pulse specified by the print data. Inkjet recording apparatus.

  According to a sixth aspect of the present invention, the drive signal generating means generates a drive signal in which a plurality of drive pulses each ejecting the same amount of ink droplets are connected in series, and the ejection amount changing means is a pressure generating element. 5. The ink jet recording apparatus according to claim 1, wherein an ink discharge amount is increased by increasing a supply number of drive pulses to the ink supply amount more than a supply number specified by print data. is there.

  According to a seventh aspect of the present invention, the drive signal generating means generates a drive signal including a drive pulse for discharging a predetermined amount of ink droplets, and the discharge amount changing means is a drive pulse supplied to the pressure generating element. 5. The ink jet recording apparatus according to claim 1, wherein the ink discharge amount is increased by increasing a peak value.

  According to an eighth aspect of the present invention, a standby time measuring unit that measures the standby time of the recording head is provided, and the ejection amount changing unit further increases the ink ejection amount when the standby time of the recording head is equal to or longer than a predetermined time. An ink jet recording apparatus according to any one of claims 1 to 7, wherein

  The invention according to claim 9 is characterized in that the ejection amount changing means does not increase the amount of ink droplets when the ink ejected from the nozzle opening is a light-colored ink. An ink jet recording apparatus according to claim 8.

  Here, “light color ink” refers to light color inks such as yellow, light cyan, and light magenta.

  Hereinafter, an ink jet recording apparatus according to an embodiment of the present invention will be described with reference to the drawings. Here, FIG. 1 is a perspective view of an ink jet printer 1 which is a typical ink jet recording apparatus. The illustrated ink jet printer 1 (hereinafter referred to as the printer 1) includes a cartridge holder 3 that holds a plurality of ink cartridges 2 (2K, 2C, 2M, and 2Y) and a carriage 5 that has a recording head 4. The carriage 5 is movably attached to a guide member 6 installed on the housing 11, and is reciprocated along the guide member 6 (that is, along the main scanning direction) by a head scanning mechanism.

  The head scanning mechanism includes a pulse motor 7 provided at one of the left and right ends of the housing 11, a drive pulley 8 connected to the rotation shaft of the pulse motor 7, an idle pulley 9 provided at the left and right other ends of the housing 11, A timing belt 10 that is spanned between the drive pulley 8 and the idle pulley 9 and connected to the carriage 5, a printer controller 44 (see FIG. 3) that controls the rotation of the pulse motor 7, and the like are configured. is there. That is, this head scanning mechanism operates the pulse motor 7 to reciprocate the carriage 5, that is, the recording head 4 in the width direction of the recording paper 12 that is a kind of print recording medium. The printer 1 also includes a paper feed mechanism that feeds the recording paper 12 in the sub-scanning direction orthogonal to the main scanning direction. This paper feed mechanism is composed of a paper feed motor 13 and a paper feed roller 14 and the like, and sequentially feeds the recording paper 12 in conjunction with the main scanning of the recording head 4. Note that these head scanning mechanism and paper feeding mechanism are configured to correspond to a large recording paper 12 of about B0 size, for example.

  A standby position and a home position, which are standby positions in the present invention, are set in an end area within the moving range of the carriage 5 (recording head 4) and outside the recording area. Are provided with a cap member 15 or the like for sealing the nozzle plate 28 (see FIG. 2) of the recording head 4. The cap member 15 is an elastic member such as rubber and is formed in a tray shape having a depression at the center of the upper surface of a substantially square shape. A moisturizing material such as felt is attached to the inside of the depression. Therefore, by sealing the nozzle plate 28 with the cap member 15, the inside of the cap is kept at high humidity, and evaporation of the ink solvent from the nozzle opening 25 is prevented. As shown in FIG. 5, the home position is set at the end of the head movement range, and the standby position is set adjacent to the recording area side of the home position.

  The home position is a place where the recording head 4 is positioned when recording is not performed for a long time or when the power is turned off. The recording head 4 positioned at the home position has a position as shown in FIG. The cap member 15 described above is pressed against the nozzle plate 28 to seal the nozzle opening 25.

  The standby position is a position that is a starting point when the recording head 4 is main-scanned. That is, the recording head 4 normally stands by at this standby position, moves from the standby position to the recording area side during the recording operation, and returns to the standby position as the recording operation ends. An ink receiving member is disposed at the standby position. This ink receiving member is a member for collecting the ink ejected from the recording head 4 in the flushing operation, and is constituted by the cap member 15 in this embodiment. That is, the cap member 15 is normally disposed on the standby position side and slightly below the recording head 4 as shown in FIG. Then, as the recording head 4 moves to the home position, as shown in FIG. 6D, the recording head 4 is moved to the home position side and pressed against the nozzle plate 28 at this home position to seal the nozzle opening 25. To do. In this embodiment, an acceleration area is set between the standby position and the recording area. This acceleration area is an area for accelerating the recording head 4 to a predetermined scanning speed.

  Next, the structure of the recording head 4 will be described. As shown in FIG. 2, the exemplified recording head 4 has a flow path unit 22 bonded to the front end surface of a box-shaped case 21. The vibrator unit 23 housed in the housing chamber 26 inside the case causes a pressure fluctuation in the pressure chamber 24 in the flow path unit 22 and ejects ink droplets from the nozzle openings 25. The case 21 is a block-shaped member in which the storage chamber 26 is formed, and is produced by molding a resin material, for example. The accommodation chamber 26 is continuous from the opening on the joint surface side with the flow path unit 22 to the opposite surface. The flow path unit 22 has a configuration in which the nozzle plate 28 is bonded to one surface of the flow path substrate 27 and the vibration plate 29 is bonded to the other surface of the flow path substrate 27.

  The flow path substrate 27 is a plate-like member partitioned into a predetermined pattern by, for example, etching a silicon wafer, and includes a plurality of pressure chambers 24 communicating with the nozzle openings 25, a common ink chamber 31, and the like. In addition, a plurality of ink supply paths 32 that communicate the common ink chamber 31 and the pressure chambers 24 are appropriately formed. The common ink chamber 31 is provided with a connection port connected to the ink supply pipe 33, and the ink stored in the ink cartridge 2 is supplied to the common ink chamber 31 through the ink supply pipe 33.

  In the nozzle plate 28, a plurality of nozzle openings 25 are formed in a row at a pitch corresponding to the dot formation density. The recording head 4 is attached so that the rows of nozzle openings 25 (nozzle rows) are arranged substantially parallel to the sub-scanning direction.

  The vibration plate 29 has a double structure in which an elastic film 36 such as a PPS film is laminated on a stainless steel plate 35, and the portion corresponding to each pressure chamber 24 is etched in an annular shape on the stainless steel plate 35 side, and an island is formed in the ring. A portion 37 is formed.

  The vibrator unit 23 includes a piezoelectric vibrator 40 which is a kind of pressure generating element of the present invention, and a fixed substrate 41 to which a base end portion of the piezoelectric vibrator 40 is bonded. The piezoelectric vibrator 40 is a comb in which slit portions are formed at a predetermined pitch corresponding to each pressure chamber 24 of the flow path unit 22 on one piezoelectric vibrator plate in which piezoelectric bodies and electrode layers are alternately laminated. It is formed in a tooth shape. The vibrator unit 23 is inserted into the housing chamber 26 of the case 21 with the tip of the piezoelectric vibrator 40 facing the opening, and is housed by fixing the fixed substrate 41 to the inner wall of the housing chamber 26. In this accommodated state, each tip of the piezoelectric vibrator 40 is fixed to the corresponding island portion 37 of the diaphragm 29.

  Each piezoelectric vibrator 40 expands and contracts in the element longitudinal direction perpendicular to the stacking direction by applying a potential difference between the opposing electrodes, and displaces the elastic film 36 that partitions the pressure chamber 24. That is, in the recording head 4, by extending the piezoelectric vibrator 40 in the element longitudinal direction, the island portion 37 is pushed toward the nozzle plate 28, and the elastic film 36 around the island portion 37 is deformed to cause the pressure chamber 24. Contracts. When the piezoelectric vibrator 40 is contracted in the longitudinal direction of the element, the pressure chamber 24 expands due to the displacement of the elastic film 36. As the pressure chamber 24 expands and contracts, pressure changes in the filled ink in the pressure chamber 24, and ink droplets are ejected from the nozzle openings 25.

  In this embodiment, the recording head 4 is configured for color recording that discharges a plurality of different colors. That is, the nozzle plate 28 is provided with a plurality of rows of nozzle openings 25 (nozzle rows), and a plurality of sets of components such as the pressure chambers 24 and the vibrator unit 23 are provided corresponding to each nozzle row. Yes. Further, as shown in FIG. 1, the cartridge holder 3 includes a black ink cartridge 2K storing black ink, a cyan ink cartridge 2C storing cyan ink, a magenta ink cartridge 2M storing magenta ink, and a yellow ink. A plurality of ink cartridges composed of yellow ink cartridges 2Y are stored.

  Next, the electrical configuration of the printer 1 will be described. As shown in FIG. 3, the printer 1 includes a printer controller 44, a print engine 45, and the like.

  First, the printer controller 44 will be described. The printer controller 44 includes an interface 46 (hereinafter referred to as an external I / F 46) that receives various data from a host computer (not shown), a RAM 47 that temporarily stores various data, and a ROM 48 that stores a control program and the like. , A control unit 49 including a CPU, an oscillation circuit 50 that generates a clock signal, a drive signal generation circuit 51 that generates a drive signal COM to be supplied to the piezoelectric vibrator 40 of the recording head 4, and dots An interface 52 (hereinafter referred to as an internal I / F 52) for transmitting the print data, the drive signal COM and the like developed for each time to the print engine 45 is provided.

The external I / F 46 receives print data composed of, for example, a character code, a graphic function, image data, and the like from a host computer or the like.
In addition, a busy signal (BUSY) and an acknowledge signal (ACK) are output to the host computer or the like through the external I / F 46.

  The RAM 47 functions as a reception buffer, an intermediate buffer, an output buffer, and a work memory (not shown). The reception buffer temporarily stores print data received via the external I / F 46, the intermediate buffer stores intermediate code data converted by the control unit 49, and the output buffer prints data for each dot (pixel). (Dot pattern data) is stored.

  This print data is obtained, for example, by decoding gradation data included in the print data, and serves as a selection signal for selecting the drive pulses DP1, DP2, DP3 from the drive signal COM shown in FIG. In this embodiment, the print data for one dot is composed of 3-bit data (D1, D2, D3), the most significant bit D1 is the selection bit of the medium dot drive pulse DP1, and the second bit D2 is a small dot. The selection bit and the least significant bit D3 of the drive pulse DP2 are set as the selection bits of the large dot drive pulse DP3.

  The ROM 48 stores a control program (control routine) for performing various data processing, font data, graphic functions, and the like. The ROM 48 also stores various setting data for performing the maintenance operation of the recording head 4.

  The control unit 49 controls the operation of the printer 1 and also functions as a discharge control means in the present invention. That is, the control unit 49 controls the supply of the drive signal COM to the recording head 4 based on the print data for each dot.

  The control unit 49 reads the print data in the reception buffer, and stores the intermediate code data obtained by converting the read print data in the intermediate buffer. Further, the intermediate code data read from the intermediate buffer is analyzed, and is developed into print data for each dot by referring to the font data and graphic function stored in the ROM 48. Then, the decoration processing necessary for the expanded print data is performed, and the print data after the decoration processing is stored in the output buffer.

  When the print data necessary for unit scanning, which is one main scanning, is obtained, the control unit 49 functions as a non-ejection period acquisition unit of the present invention, and prior to the main scanning of the recording head 4, A non-ejection period, which is a period during which ink droplets are not ejected, is acquired from the print data. If the non-ejection period is acquired, the control unit 49 functions as the ejection amount changing means of the present invention, and at least the first ejection operation after the non-ejection period has elapsed for the nozzle opening whose non-ejection period is a predetermined period or more. The ink discharge amount is set to be larger than a predetermined amount defined by the print data. The acquisition of the non-ejection period and the change of the ink ejection amount will be described in detail later.

  When the necessary setting is completed, print data for unit scanning is sequentially output from the output buffer to the electric drive system 39 of the recording head 4 through the internal I / F 52, and the carriage 5 is moved in synchronization with this output. Print for the unit scan. When print data for unit scan is output from the output buffer, the developed intermediate code data is erased from the intermediate buffer, and the development process of the intermediate code data related to the next unit scan is performed.

  The drive signal generation circuit 51 functions as drive signal generation means of the present invention. In this embodiment, the drive signal generation circuit 51 generates a drive signal COM in which a plurality of drive pulses for ejecting different amounts of ink droplets are arranged in series. To do. That is, as shown in FIG. 4, within a predetermined printing cycle T, a signal in which a medium dot drive pulse DP1, a small dot drive pulse DP2, and a large dot drive pulse DP3 are arranged in this order is generated. This printing cycle T is a set time for recording one dot, and serves as a basic timing for synchronization in the recording operation (main scanning). The small dot drive pulse DP2 has a waveform for ejecting ink droplets capable of forming small dots from the nozzle openings 25. The medium dot drive pulse DP1 has a waveform for ejecting ink droplets that can form a medium dot from the nozzle opening 25. The large dot drive pulse DP3 has a waveform for ejecting ink droplets capable of forming large dots from the nozzle openings 25.

  Next, the print engine 45 will be described. The print engine 45 includes a pulse motor 7 constituting a part of the head scanning mechanism, a paper feed motor 13 constituting a part of the paper feed mechanism, an electric drive system 39 of the recording head 4 and the like. The electric drive system 39 of the recording head 4 includes a shift register circuit 54, a latch circuit 55, a level shifter circuit 56, a switch circuit 57, and a piezoelectric vibrator 40, and has a circuit configuration in which these are connected in order. A plurality of shift register circuits 54, latch circuits 55, level shifter circuits 56, and switch circuits 57 are provided corresponding to the piezoelectric vibrators 40.

  The recording head 4 appropriately ejects ink droplets having different ink amounts based on print data sent from the printer controller 44 to the electric drive system 39. That is, in the ink droplet ejection control, the control unit 49 first serially transmits the most significant bit data D1 in the print data of the first dot from the output buffer in synchronization with the clock signal CLK from the oscillation circuit 50. The shift register circuits 54 are sequentially set.

When the most significant bit data D1 for all the nozzle openings 25 is set in the shift register circuits 54, the control unit 49 outputs the latch signal LAT to the latch circuits 55 at a predetermined timing. In response to the latch signal LAT, the latch circuits 55... Latch the data D1 set in the shift register circuits 54.
The latched data D1 is supplied to level shifter circuits 56, which are voltage amplifiers.

  When the set data D1 is “1”, for example, the level shifter circuits 56... Boost the data to a voltage value that can be driven by the switch circuits 57. The boosted data D1 is applied to the switch circuits 57... And the switch circuits 57. On the other hand, when the set data D1 is “0”, for example, the corresponding level shifter circuit 56. Further, the drive signal COM from the drive signal generation circuit 51 is also applied to the switch circuit 57... When the switch circuit 57 becomes conductive, the dot drive pulse DP 1 in the drive signal COM is selected, and the piezoelectric vibrator. 40...

  Subsequently, the control unit 49 serially transmits the second bit D2 in the print data and sets it in the shift register circuit 54. If the data D2 is set in the shift register circuit 54, the latch signal LAT is output to cause the second data D2 to be latched by the latch circuit, and the small dot drive pulse DP2 of the drive signal COM is selected. Are supplied to the piezoelectric vibrators 40.

  Subsequently, the control unit 49 serially transmits the least significant bit D3 in the print data and sets it in the shift register circuit 54. When the data D3 is set in the shift register circuit 54, the latch signal LAT is output, so that the least significant bit data D3 is latched in the latch circuit, and the large dot drive pulse DP3 of the drive signal COM is output. The piezoelectric vibrators 40 are selectively supplied.

  When the first dot is recorded as described above, the same operation is repeated for the second and subsequent dots.

  Thus, in the illustrated recording head 4, whether or not to apply the drive signal COM to the piezoelectric vibrator 40 can be controlled by the print data from the control unit 49. That is, when the print data (D1, D2, D3) is set to D1 = 1, D2 = 0, D3 = 0, only the medium dot drive pulse DP1 is applied to the piezoelectric vibrator 40, and the nozzle opening 25 Ink droplets are ejected. When the print data is set to D1 = 0, D2 = 1, and D3 = 0, only the small dot drive pulse DP2 is applied to the piezoelectric vibrator 40, and a small ink droplet is ejected from the nozzle opening 25. When the print data is set to D1 = 0, D2 = 0, and D3 = 1, only the large dot drive pulse DP3 is applied to the piezoelectric vibrator 40, and a large ink droplet is ejected from the nozzle opening 25.

  As described above, by selecting the drive pulse to be applied to the piezoelectric vibrator 40, a plurality of types of ink droplets having different amounts can be ejected from the same nozzle opening 25, and recording with variable dots can be performed.

  Next, the operation of the printer 1 will be described. When the power is turned on, the necessary initialization operation is performed, and then the recording head 4 stands by at the standby position (FIG. 6A). The printer controller 44 waits for print data from a host computer such as a personal computer. When the print data is received, the control unit 49 (ejection control means) develops the print data into print data for each dot and stores it in the output buffer of the RAM 47. If print data necessary for unit scanning is obtained, the control unit 49 (non-ejection period acquisition unit) acquires a non-ejection period, which is a period during which ink droplets are not ejected, for each nozzle opening 25.

  In the present embodiment, the non-ejection period for each nozzle opening 25 is acquired based on the print data for each dot stored in the output buffer of the RAM 47 as described above. That is, the print data for each dot corresponds to a recording area on the recording paper 12, and the ink droplet ejection operation for forming each dot is performed in synchronization with the movement of the recording head 4 in unit scanning. . Further, since the moving speed of the recording head 4 in the recording area is a constant speed, the interval between print data (that is, the interval between dots) can be regarded as a time in unit scanning.

  Therefore, the control unit 49 acquires print data (initial discharge data) for performing the first discharge from the print data array for each nozzle opening 25..., In other words, the main scan scanning interval. The elapsed time from the start time to the first ink droplet ejection time is acquired as the ink droplet non-ejection period. Further, the control unit 49 acquires the interval between the adjacent ejection data from the print data array for each nozzle opening 25..., And the interval from the previous ejection data to the subsequent ejection data, in other words, one main time. The elapsed time from the previous ink droplet ejection time point to the subsequent ink droplet ejection time point in the scan is acquired as the ink droplet non-ejection period.

  If the non-ejection period of the ink droplet is acquired, the control unit 49 (non-ejection period determination unit) determines whether or not there is a non-ejection period equal to or longer than a predetermined period. Here, when it is determined that there is a non-ejection period equal to or longer than the predetermined period, the control unit 49 (ejection amount changing means) determines the first ink droplet ejected after the non-ejection period equal to or longer than the predetermined period. The amount is set to be larger than the ink amount specified by the print data.

  The increase in the ink discharge amount is performed by rewriting print data, for example. That is, the driving pulse supplied to the piezoelectric vibrator 40 is changed to a driving pulse having a larger ejection amount than the driving pulse defined by the print data. For example, when the print data to be rewritten indicates the small dot drive pulse DP2, that is, when D1 = 0, D2 = 1, and D3 = 0, this print data is printed with the medium dot drive pulse DP1. Data (D1 = 1, D2 = 0, D3 = 0) or print data (D1 = 0, D2 = 0, D3 = 1) of the large dot drive pulse DP3.

  In this embodiment, the print data rewrite conditions are set in two stages. For example, as shown in FIG. 7, when the non-ejection period is equal to or longer than the first predetermined time T1 and shorter than the second predetermined time T2, the original print data to be rewritten is printed with the small dot drive pulse DP2. Only when it is data, this print data is rewritten to the print data of the medium dot drive pulse DP1. Further, when the non-ejection period is equal to or longer than the second predetermined time T2, if the original print data is the print data of the small dot drive pulse DP2 or the print data of the medium dot drive pulse DP1, this print data Is rewritten as a large dot drive pulse DP3. When the original print data is the print data of the large dot drive pulse DP3, this print data is used without rewriting. This is because a large dot ink droplet has little variation in ink amount and flight trajectory due to this thickening even if the ink near the nozzle opening is somewhat thickened. When the necessary print data is rewritten in this way, the control unit 49 outputs the rewritten print data from the output buffer to the electric drive system 39 of the recording head 4.

  When the print data array for unit scanning is output from the output buffer of the RAM 47, the recording head 4 starts to move from the standby position to the recording area [FIG. 6B]. Here, the control unit 49 instructs a maintenance operation prior to the recording operation in order to maintain the ink droplet ejection capability of the recording head 4. This maintenance operation includes, for example, a flushing operation and a fine vibration operation, which are appropriately selected.

  After the maintenance operation is performed in this way, a recording operation (unit scan) based on the print data is performed in the recording area. In this unit scan, with respect to the nozzle openings 25 that do not eject ink droplets over a predetermined period, the ink ejection amount in the first ejection operation after the non-ejection period has elapsed is increased from the ejection amount defined by the print data. Yes. As described above, when the non-ejection period during the unit scan is equal to or longer than the predetermined period, that is, when there is a concern about ink thickening at the meniscus portion of the nozzle opening 25, the first after the non-ejection period has elapsed. When the ink droplets are discharged, the ink droplets are increased.

  As a result, even if ink thickening occurs in the vicinity of the nozzle opening, the amount of ink ejected is increased, so that variations in ink droplet size and trajectory disturbance caused by this thickened ink are minimized. Can do. As a result, it is possible to improve the image quality in the end region far from the standby position. Further, since it is not necessary to perform the fine vibration operation during the main scanning, it is not necessary to include a drive pulse for the fine vibration operation in the drive signal COM. For this reason, the printing cycle T in the drive signal COM can be shortened, and the recording head 4 can be scanned at high speed. As a result, the printing time can be shortened.

  Note that the increase in ink droplets in the present embodiment is targeted for the first ink droplet ejected after the non-ejection period determined to be equal to or longer than the predetermined period, but is not limited thereto. . For example, the ink droplets ejected for the first time to the ink droplets ejected several times may be targeted for increase.

  By the way, in the first embodiment described above, the drive signal generating circuit 51 is caused to generate the drive signal COM in which a plurality of drive pulses DP1, DP2, and DP3 for ejecting different amounts of ink droplets are connected in series, and the control unit 49, the drive pulse supplied to the piezoelectric vibrator 40 is changed to a drive pulse having a larger discharge amount than the drive pulse specified by the print data, and the discharge amount is increased. It is not limited. For example, the drive signal generating circuit 51 generates a drive signal in which a plurality of drive pulses for ejecting a predetermined amount of ink droplets are connected in series, and the number of drive pulses supplied to the piezoelectric vibrator 40 is supplied as specified by the print data. The discharge amount may be increased by setting more than the number. Hereinafter, the second embodiment configured as above will be described.

Here, FIG. 8 is a diagram illustrating the drive signal COM in the second embodiment.
In the second embodiment, the drive signal generation circuit 51 generates a drive signal COM in which three drive pulses DP0... Having the same waveform shape are arranged in series within one printing cycle T. Then, by increasing or decreasing the supply number of the drive pulse DP0 to the piezoelectric vibrator 40, the number of ejection operations by the drive pulse DP0 is varied to form dots of different sizes.

This drive pulse DP0 has a waveform for ejecting ink droplets of an amount capable of forming small dots from the nozzle openings 25. Therefore, when recording small dots, the print data is set to D1 = 0, D2 = 1, D3 = 0, and the number of supply of the drive pulse DP0 in the print cycle T is set to “1”. The ejection operation by DP0 is performed once. Further, when recording a medium dot, the print data is set to D1 = 1, D2 = 0, D3 = 1, and the number of supply of the drive pulse DP0 in the print cycle T is set to “2”. The discharge operation by DP0 is performed twice. As a result, two ink droplets are superimposed on the recording paper 12 to record a medium dot.
Further, when recording a large dot, the print data is set to D1 = 1, D2 = 1, D3 = 1, and the number of supply of the drive pulse DP0 in the print cycle T is set to “3”. The discharge operation by DP0 is performed three times. As a result, three ink droplets are superimposed on the recording paper 12 to record a large dot.

  Also in this embodiment, the control unit 49 serving as the ejection amount changing means sets the amount of ink droplets ejected first after the non-ejection period equal to or longer than the predetermined period to be greater than the ink amount defined by the print data. Set a lot. In this case, the control unit 49 increases the ink discharge amount by increasing the supply number of the drive pulse DP0 to the piezoelectric vibrator 40 more than the supply number specified by the print data.

  For example, if the original print data to be rewritten (target for increase) is small dot print data (D1 = 0, D2 = 1, D3 = 0), this print data is used as medium dot print data ( D1 = 1, D2 = 0, D3 = 1) or large dot print data (D1 = 1, D2 = 1, D3 = 1). The rewriting conditions are the same as in the first embodiment described above.

  As described above, also in this embodiment, when the non-ejection period during the unit scan is equal to or longer than the predetermined period, the ink droplets are increased when the first ink droplet is ejected after the non-ejection period has elapsed. As a result, even if ink thickening occurs in the vicinity of the nozzle opening 25, variations in ink droplet size and orbital disturbance due to the thickening ink can be suppressed to a minimum. Therefore, it is not necessary to include a waveform for fine vibration in the drive signal COM, and the printing cycle T can be shortened. As a result, in this embodiment as well, the image quality in the end region far from the standby position can be improved, and the printing time can be shortened.

  In particular, in the present embodiment, by increasing the number of drive pulses supplied, that is, the number of ink droplet ejections, the ink ejection amount is increased from a predetermined amount defined by the print data. Even if the ink amount or landing position of the droplets varies, the ink droplets ejected later overlap with the previously ejected ink droplets, and the variation in the ink amount or landing position of the previous ink droplets can be made inconspicuous.

  By the way, in each of the above embodiments, when a non-ejection period is acquired for each nozzle opening 25 based on the print data developed for each dot, and the non-ejection period equal to or greater than a predetermined period exists in the acquired non-ejection period. Increases the amount of ink droplets ejected first after the non-ejection period. However, in these embodiments, the burden on the CPU is large. Therefore, a third embodiment will be described in which the burden on the control unit 49 can be reduced while improving the image quality in the end region far from the standby position.

  In the third embodiment, an increase range (discharge amount change region) is set in the end region far from the standby position of the recording head 4, and the control unit 49 prints ink droplets discharged in this increase range. When the ink amount specified by the data is less than the predetermined amount, the ink amount is increased.

  Here, as shown in FIG. 9, in this embodiment, two standby positions of the recording head 4 are provided. That is, the first standby position P1 set next to the home position and the second standby position P2 set at the end of the scanning area far from the home position are provided as the standby positions of the present invention. Then, the printing operation is performed in both directions during forward scanning when moving from the first standby position P1 to the second standby position P2 and during backward scanning when moving from the second standby position P2 to the first standby position P1. It is comprised so that it can perform. Further, the first increase range W0 at the time of forward scanning is set in the end region far from the first standby position P1, and the end region at the side far from the second standby position P2 is set at the end scanning at the time of backward scanning. A second increase range W0 ′ is set.

  The control unit 49 (ejection amount changing means) then ejects ink droplets that are ejected in the first increase range W0 during forward scanning, and ink that is ejected within the second increase range W0 ′ during backward scanning. When the ink discharge amount specified by the print data is less than a predetermined amount, the discharge amount is set to be larger than the discharge amount specified by the print data. The increase in the number of ink droplets is made in the same manner as in the first and second embodiments described above. For example, when the print data to be rewritten is small dot print data, the control unit 49 rewrites the small dot print data to medium dot or large dot print data. Similarly, when the print data to be rewritten is a small dot and a medium dot, the control unit 49 rewrites the print data for the small dot and the medium dot to the print data for the large dot.

  As described above, in the present embodiment, the increase ranges W0 and W0 ′ are set in the end regions on the side far from the standby positions P1 and P2 of the recording head 4, and the ink ejected within these increase ranges W0 and W0 ′. The droplet is set to a predetermined amount or more (for example, a medium ink droplet or more). As a result, even if the ink is thickened in the vicinity of the nozzle opening, it is possible to reduce the variation in the size of the ink droplets and the disturbance of the trajectory caused by the thickened ink. In addition, since it is not necessary to include a waveform for fine vibration in the drive signal COM, the printing cycle T can be shortened.

As a result, in the present embodiment as well, it is possible to improve the image quality in the end area far from the standby positions P1, P2, and to shorten the printing time.
In particular, in this embodiment, since it is determined whether or not to increase the amount of ink based on a simple correspondence between whether or not it is within the increase ranges W0 and W0 ′, the processing in the control unit 49 is easy and the burden is light. . For this reason, even when a relatively low-speed CPU is used as the control unit 49, the printing speed can be shortened.

  By the way, the present invention is not limited to the above-described embodiments, and various modifications can be made within the scope described in the claims.

  For example, the ink discharge amount may be increased by increasing the peak value Vh (see FIG. 8) of the drive pulse supplied to the piezoelectric vibrator 40. That is, when increasing the amount of ink droplets, the control unit 49 serving as the ejection amount changing unit controls the drive signal generating circuit 51 serving as the drive signal generating unit to drive the peak value higher than the standard peak value Vh. Generate a pulse. When a drive pulse with an increased peak value is supplied to the piezoelectric vibrator 40, the piezoelectric vibrator 40 greatly changes the volume of the pressure chamber 24 by an amount corresponding to the increased peak value. Thereby, the pressure fluctuation in the pressure chamber 24 increases, and the amount of ejected ink droplets increases.

  As described above, when the configuration in which the ink drop is increased by increasing the crest value, the ink drop is increased even for the drive signal COM having only one drive pulse within one printing cycle. Can do. Also, with this configuration, the amount of ink droplets can be finely controlled, so that an optimal ink amount can be easily set according to the degree of ink thickening.

  Further, as shown in FIG. 1, a standby time timer 38 (standby time measuring means) for measuring the standby time of the recording head 4 is provided, and the control is performed on the condition that the standby time of the recording head 4 is a predetermined time or more. The unit 49 (discharge amount changing means) may be controlled to further increase the amount of ink droplets to be increased. In this case, for example, the elapsed time from the end of the maintenance operation to the start of the unit scan is acquired as the standby time of the recording head 4, or the recording head 4 [ 6 (C) to 6 (A)] can acquire the period of waiting at the standby position as the standby time. As described above, when the ink amount is determined in consideration of the waiting time of the recording head 4, the degree of increase in ink viscosity in the vicinity of the nozzle opening 25 can be grasped more accurately, so that an appropriate ink amount can be set. .

  Further, it is known that the ease of thickening ink varies depending on the type of ink. For example, when comparing black ink, cyan ink, magenta ink, and yellow ink, the black ink is most easily thickened and the yellow ink is most difficult to thicken. Also, cyan ink and magenta ink are less likely to thicken than black ink, and more likely to thicken than yellow ink. Further, light cyan ink having a lighter color than cyan ink and light magenta ink having a lighter color than magenta ink are unlikely to thicken similarly to yellow ink.

  Therefore, when the ink ejected from the nozzle opening 25 is light color ink such as light cyan ink, magenta ink, and yellow ink, the ink droplets are increased to the control unit 49 (ejection amount changing means). You may comprise so that it may not let. If comprised in this way, it can prevent increasing the amount of ink droplets with respect to the ink with which it is hard to produce the viscosity of an ink.

  In addition to the piezoelectric vibrator 40, a heat generating element, a magnetostrictive element, or the like can be used as a pressure generating element that causes a pressure fluctuation in the pressure chamber 24.

  As described above, according to the present invention, the following effects are exhibited. That is, for nozzle openings with a non-ejection period equal to or longer than a predetermined period, the ink ejection amount in at least the first ejection operation after the non-ejection period has elapsed is set to be larger than the predetermined amount defined by the print data. Even if the ink viscosity in the vicinity of the nozzle opening is increased due to evaporation of the solvent or the like, since the ink droplets are increased, the variation in the shape and position of the dots due to the increase in the ink viscosity can be reduced. As a result, it is possible to improve the image quality in the end region far from the standby position.

  Furthermore, during the main scanning of the recording head, it is not necessary to perform a fine vibration operation, so that it is not necessary to include a waveform for the fine vibration operation in the drive signal. For this reason, the printing cycle in the drive signal can be shortened, and the scanning speed of the recording head can be increased accordingly. As a result, the printing time can be shortened.

1 is a perspective view illustrating a configuration of an ink jet printer. FIG. 3 is a cross-sectional view illustrating a configuration of a recording head. FIG. 2 is a block diagram illustrating an electrical configuration of a printer. It is a timing diagram which shows a drive signal and the drive pulse in each mode. FIG. 6 is a side view illustrating a moving range of a recording head in main scanning. FIG. 6 is an enlarged side view of the main part of FIG. 5 for explaining the movement operation of the recording head, in which (A) shows a standby position state, (B) shows an acceleration state toward the recording area, and (C) shows a recording area. (D) shows a state of being returned to the home position. FIG. 5 is a plan view illustrating a recording area of a recording paper and explaining an operation of increasing an ink discharge amount in main scanning. It is a figure which shows 2nd Embodiment of this invention and demonstrates the drive signal and the drive pulse in each mode. FIG. 10 is a plan view illustrating an operation of increasing an ink discharge amount in reciprocating scanning according to a third embodiment of the present invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Inkjet printer, 2 ... Ink cartridge, 3 ... Cartridge holder part, 4 ... Recording head, 5 ... Carriage, 6 ... Guide member, 7 ... Pulse motor, 8 ... Drive pulley, 9 ... Free-wheel pulley, 10 ... Timing Belt 11, housing 12, recording paper, 13 paper feed motor, 14 paper feed roller, 15 cap member, 21 case, 22 channel unit, 23 vibrator unit, 24 pressure chamber, 25 ... Nozzle opening, 26 ... accommodating chamber, 27 ... channel substrate, 28 ... nozzle plate, 29 ... vibrating plate, 31 ... common ink chamber, 32 ... ink supply path, 33 ... ink supply pipe, 35 ... stainless steel plate, 36 ... Elastic film 37 ... Island part 38 ... Standby time timer 39 ... Electric drive system 40 ... Piezoelectric vibrator 44 ... Printer controller 45 ... Print Engine 46 ... External interface 47 ... RAM 48 ... ROM 50 ... Oscillation circuit 51 ... Drive signal generation circuit 52 ... Internal interface 54 ... Shift register circuit 55 ... Latch circuit 56 ... Level shifter circuit 57 ... Switch circuit.

Claims (1)

A recording head that forms ink dots of a plurality of sizes by ejecting ink droplets from the nozzle openings by the operation of the pressure generating element, a head scanning mechanism that moves the recording head from the standby position in the main scanning direction, and a pressure generating element Inkjet recording apparatus comprising: drive signal generating means for generating a drive signal for operation; and discharge control means for controlling supply of the drive signal to the recording head based on print data for each dot to discharge ink droplets In
The discharge control means includes
A non-ejection period acquisition means for acquiring an elapsed time from the start time of main scanning to the first ink droplet ejection time as an ink droplet non-ejection period for each nozzle opening;
On the condition that the non-ejection period is equal to or longer than a predetermined period, a part of the ink dots ejected in the ejection operation in at least the first ejection operation after the non-ejection period has elapsed except the maximum size of the plurality of sizes. An ink jet recording apparatus comprising: an ejection amount changing unit that sets an ink dot size to be larger than a size defined by print data only when the size is a size.

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