JP2005119072A - Inkjet printer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To detect nozzle missing for every head module by an inexpensive configuration in a short time in a line type inkjet printer. <P>SOLUTION: In the line type inkjet printer which has a printing region T1 where an image is recorded to a recording medium P from head units 31, 32, 33 and 34 comprised of a plurality of head modules 31a, 32a, 33a and 34a, and a maintenance region T3 where a maintenance part 70 for solving discharge failures of nozzles is set, and which is configured to move the head units 31, 32, 33 and 34 from the printing region T1 to the maintenance region T3 at the time of solving the discharge failures of nozzles, an ink confirmation region T2 is set in the middle of a movement route of the head units 31, 32, 33 and 34 from the printing region T1 to the maintenance region T3, and ink detecting parts 61, 62, 63 and 64 for detecting the discharge failures of nozzles are installed at the ink confirmation region T2. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to detection of ejection failure of nozzles of a line type ink jet printer.

  Conventional inkjet printers form an image by ejecting ink droplets onto a recording medium from a plurality of nozzles using a thermal method, a piezo method, or the like, based on an image signal. Ink used in ink jet printers adheres to the vicinity of the nozzle outlet due to ink drying or increased viscosity when left unused for a long period of time, or impurities (dust) adhere to the nozzle outlet. The nozzle is clogged, and the ejection failure of the nozzle (hereinafter referred to as “nozzle missing”) is that ink droplets are not ejected from the nozzle ejection port even though the ejection signal is normally output from the control unit. .) Occurs. When nozzles are missing, the printed characters and images may appear white and become white stripes, or the color quality of the recorded image may be different due to lack of ink coloring material, resulting in a decrease in print quality. . Therefore, optical detection means and electrical detection means are disclosed as nozzle missing detection means.

  For example, according to Japanese Patent Application Laid-Open No. 2004-133620, detection of nozzle missing in a carriage-type inkjet printer that forms an image by ejecting ink in a direction (main scanning direction) perpendicular to the paper transport direction (sub-scanning direction). As a means, there is disclosed an ink discharge state detection method in which a missing nozzle is detected by changing a detection timing by a photo sensor in which a light emitting element and a light receiving element are combined at a distance corresponding to the head width.

According to Patent Document 2, an ink receiving unit that collects ink droplets ejected from each nozzle of the head is provided, and the presence or absence of the ink droplets collected in all the ink receiving units is detected by flowing an electric current. An ink jet recording apparatus that determines the presence or absence of a proper nozzle is disclosed.
JP-A-11-188853 JP 2003-182115 A

However, when Patent Document 1 is applied to a line-type ink jet printer, the missing nozzle detection means must be moved using a highly accurate positioning sensor, which causes an increase in cost. In addition, since there are a large number of nozzles of one line head that must be detected, there arises a problem that the detection time increases.
According to Patent Document 2, since a voltage is applied to an ink receiving portion that detects the presence or absence of ink, consideration must be given to the ink material so as not to cause a chemical change or a change in physical properties of the ink of the head.

  An object of the present invention is to detect nozzle shortage for each head module in a short time in a line-type ink jet printer with an inexpensive configuration.

  According to a first aspect of the present invention, there is provided a print area in which an image is recorded on a recording medium by a head unit comprising a plurality of head modules having a plurality of nozzles, and ejection failure of the nozzles provided at a position adjacent to the print area. A line-type ink jet printer configured to move the head unit from the print area to the maintenance area when the nozzle discharge failure is resolved. An ink confirmation area is provided in the movement path of the head unit from the area to the maintenance area, and detection means for detecting ejection failure of the nozzle is provided in the ink confirmation area.

  According to a second aspect of the present invention, in the line type ink jet printer according to the first aspect, the detection means includes a strain gauge that converts a mechanical displacement generated by landing of ink droplets ejected in units of head modules into an electric quantity. It is characterized by using.

  According to a third aspect of the present invention, in the line type ink jet printer according to the second aspect, the detection means includes a detection voltage value based on an electric quantity from the strain gauge, and a preset reference voltage value. In comparison, it is characterized in that a nozzle discharge failure is determined for each head module.

  According to a fourth aspect of the present invention, in the line type ink jet printer according to the second or third aspect, the strain gauge is installed on a landing surface of a one-end fixed member having a landing surface that receives the landing of an ink droplet. It is characterized by that.

  According to a fifth aspect of the present invention, in the line type ink jet printer according to the fourth aspect, a plurality of the strain gauges are provided corresponding to the nozzle arrangement of the head module.

  According to a sixth aspect of the present invention, in the line type ink jet printer according to the second or third aspect, the strain gauge includes a landing surface of a one-end fixed member having a landing surface that receives the landing of an ink droplet, and a landing surface It is characterized by being installed on the back side of

  According to a seventh aspect of the present invention, in the line type ink jet printer according to any one of the third to sixth aspects, an average voltage value of a detected voltage value based on an electric quantity from the strain gauge, and the reference voltage value And when the average voltage value is lower than the reference voltage value, it is determined that there is a nozzle ejection failure.

  According to an eighth aspect of the present invention, in the line type ink jet printer according to any one of the third to sixth aspects, a maximum voltage value of a detected voltage value based on an electric quantity from the strain gauge, and the reference voltage value. And when the maximum voltage value is lower than the reference voltage value, it is determined that there is a nozzle ejection failure.

  According to a ninth aspect of the present invention, in the line-type ink jet printer according to any one of the first to eighth aspects, the maintenance means removes nozzle discharge defects by a suction operation.

  According to a tenth aspect of the present invention, in the line-type ink jet printer according to any one of the first to eighth aspects, the maintenance means removes nozzle discharge defects by a flushing operation.

  According to the first aspect of the present invention, the ink confirmation area is provided on the transport path that is moved from the print area to the maintenance area, and the detection means is provided in the ink confirmation area, so that the nozzles of each head module can be ejected in a short time. Since a defect can be detected and at least a head module having a nozzle ejection defect is reliably maintained, the reliability can be improved.

  According to the second aspect of the present invention, the same effect as in the first aspect can be obtained, and the detection means is a detection means using a strain gauge. Detection can be performed with an easy configuration, and the cost of the apparatus can be reduced.

  According to the third aspect of the invention, the same effect as in the second aspect can be obtained, and the nozzle discharge failure can be reliably detected by comparing the detected voltage value with the reference voltage value. can do.

  According to the fourth aspect of the present invention, the same effect as in the second or third aspect can be obtained, and the strain gauge is installed on the landing surface of the one-end fixed type member, so that the ink droplet It is possible to reliably detect that has landed on the landing surface of the one-end fixed mold member.

  According to the fifth aspect of the present invention, the effect similar to that of the fourth aspect can be obtained, and a plurality of strain gauges are installed corresponding to the nozzle arrangement of each head module, so that the nozzle array A nozzle discharge failure can be detected every time, and the detection accuracy of the nozzle discharge failure can be improved.

  According to the invention described in claim 6, the strain gauge is installed on the landing surface of the one-end fixed mold member and the back surface of the landing surface as well as the same effect as in claim 2 or 3. As a result, the sensitivity of the detection means can be improved.

  According to the seventh aspect of the invention, the same effect as in the third to sixth aspects can be obtained, but the average voltage value is compared with the reference voltage value, and the average voltage value is lower than the reference voltage value. In this case, in order to determine that there is a nozzle ejection failure, even if the ink droplets were ejected in the first half even though the ink droplets were ejected in the first half to detect nozzle ejection failure, It can be reliably determined that a nozzle ejection failure has occurred, and the detection accuracy of the nozzle ejection failure can be improved.

  According to the eighth aspect of the invention, the maximum voltage value is lower than the reference voltage value by comparing the maximum voltage value with the reference voltage value as well as obtaining the same effect as the third to sixth aspects. In this case, in order to determine that there is a nozzle ejection failure, the maximum value is detected when ink droplets are ejected in the second half, even if ink droplets are not ejected in the first half of the ink droplet ejection operation to detect nozzle shortage. The maintenance can be performed only when the maintenance is surely required.

  According to the ninth aspect of the present invention, the same effects as those of the first to eighth aspects can be obtained, and nozzle discharge defects can be removed reliably and efficiently by suction operation. Defects can be eliminated.

  According to the tenth aspect of the present invention, the same effects as those of the first to eighth aspects can be obtained, and nozzle ejection defects can be reliably and efficiently ejected by eliminating nozzle ejection defects by a flushing operation. Defects can be eliminated.

[Embodiment 1]
Hereinafter, Embodiment 1 of the present invention will be described in detail with reference to the drawings.
First, the configuration will be described.
FIG. 1 is a schematic configuration diagram of the inside of a line-type inkjet printer 1 according to the first embodiment. As shown in FIG. 1, the ink jet printer 1 includes a paper feed unit 10, a transport unit 20, a head unit unit 30, a paper discharge unit 40, and the like.

The paper feed unit 10 is provided with a paper feed tray 11 in which a plurality of recording media P are stacked and stored below the interior of the inkjet printer 1. A take-out device 12 is provided above one end of the paper feed tray 11 to take out the recording medium P on which an image is to be recorded from the paper feed tray 11 one by one.
The recording medium P may be in the form of a cut sheet made of various papers such as plain paper, recycled paper, and glossy paper, and various fabrics, various non-woven fabrics, resin, metal, glass, and the like.

The transport unit 20 is disposed above the paper feed unit 10 and transports the recording medium P.
The transport unit 20 includes a transport belt 21, a tension roller 22, a pressing roller 23, a transport roller 24, and a transport path 25.
The conveyance belt 21 is an annular belt that supports the recording medium P in a planar shape and conveys the recording medium P in the horizontal direction, and is stretched by a plurality of tension rollers 22 so as to be movable. The pressing roller 23 is rotatably provided as a roller that presses the conveyance belt 21 at a position where the conveyance belt 21 and the recording medium P start to contact each other in order to convey the recording medium P in a planar shape.
The conveyance path 25 conveys the recording medium P supplied from the paper feed tray 11 to the conveyance belt 21, and after the recording medium P is conveyed along the peripheral surface of the conveyance belt 21, the conveyance belt 25 discharges the discharge medium 40. It is a route to discharge. The transport rollers 24 are provided as a plurality of pairs of rollers for transporting the recording medium P in the transport direction X at predetermined positions on the transport path 25.

The head unit 30 is arranged in the vicinity of the upper portion of the transport belt 21 along the transport direction X in order of black (Bk), cyan (C), magenta (M), and yellow (Y) ink on the recording medium P. Line-type head units 31, 32, 33, 34 provided with a plurality of nozzle discharge ports (not shown) for discharging are provided over the entire width of the conveyor belt 21. Each head unit 31, 32, 33, 34 is arranged so that the ejection surface and the peripheral surface of the conveyor belt 21 face each other.
The recording medium P on which an image is formed by discharging ink droplets from the head units 31, 32, 33, 34 is sequentially discharged to the paper discharge unit 40.

  The paper discharge unit 40 includes a paper discharge tray 41 provided on the side of the ink jet printer 1, and the recording media P on which images are formed are sequentially discharged.

FIG. 2 shows a transport mechanism of the head mount. FIG. 2 is a view of a head unit section 30 as viewed from above the ink jet printer 1 of FIG. 1.
As shown in FIG. 2, each head unit 31, 32, 33, 34 is mounted on a head mount 50. The head mount 50 is movably supported by a transport mechanism 51 for transporting the head mount to the print area T1, the ink confirmation area T2, and the maintenance area T3. The transport mechanism 51 is driven by a drive motor M.

The print area T1 is an area where the recording medium P is conveyed and an image is recorded.
The ink confirmation area T2 is an area on a path along which the head mount 50 is transported from the print area T1 to the maintenance area T3, and ink droplet detection units 61, 62, 63, and 64 are provided as detection means.
In the maintenance area T3, a maintenance unit 70 is provided as a maintenance unit for removing nozzle clogging (nozzle shortage) for each head module.

  Each head unit 31, 32, 33, 34 extends in a direction substantially orthogonal to the recording medium P conveyance direction X. Moreover, it has the some head module 31a, 32a, 33a, 34a juxtaposed in the longitudinal direction of each head unit 31,32,33,34. The head modules 31a, 32a, 33a, and 34a extend in the longitudinal direction of the head units 31, 32, 33, and 34, and are staggered (staggered) at a predetermined interval in the conveyance direction X of the recording medium P. Are installed side by side.

  The maintenance unit 70 is provided with a plurality of capping modules 71a, 72a, 73a, and 74a corresponding to the head modules 31a, 32a, 33a, and 34a. Each of the capping modules 71a, 72a, 73a, and 74a is movable to a cap position that covers the nozzle discharge port of the corresponding head module 31a, 32a, 33a, and 34a and a separation position that is detached from the nozzle discharge port. Each capping module 71a, 72a, 73a, 74a includes a suction pump that moves to a cap position, covers the entire nozzle discharge port with a rubber member, etc., and shuts off and seals the outside air. Connected flights are connected. That is, air and ink inside the space are sucked by the suction pump. Ink sucked by the suction pump is discharged to a waste ink tank. The configurations of the suction pump, the air communication valve, the waste ink tank, and the like are the same as those conventionally known and will not be described in detail here.

In the first embodiment, a description will be given of an example in which the most effective suction operation is employed as a representative mechanism of the maintenance method as means for removing the nozzle gap. A flushing operation may be employed in which ink droplets are ejected and foreign matter or the like adhering to the nozzle ejection port and the nozzle ejection surface is blown off.
Furthermore, after the suction operation or the flushing operation, a mechanism for performing a wiping operation for removing useless ink droplets attached on the nozzle ejection surface may be provided.

  FIG. 3 is a partially enlarged view of the black (Bk) head unit 31. As shown in FIG. 3, four rows of nozzle ejection openings h of a to d are arranged on the nozzle ejection surface facing the recording medium P of the head module 31a. In each of the rows a to d, the nozzle discharge ports h are arranged at a predetermined interval in a direction orthogonal to the transport direction X while being shifted in the transport direction X by a predetermined pitch in a cycle of three. The start points of the nozzle rows a to d are arranged so as to be shifted in the direction orthogonal to the transport direction X by one pixel in the order of a, c, b, and d.

FIG. 4 shows a schematic configuration diagram of the ink droplet detection unit 61 according to the first embodiment.
4A is a schematic view of the ink droplet detection unit 61 as viewed from above, and FIG. 4B is a schematic cross-sectional view of the ink droplet detection unit 61 from the viewpoint A shown in FIG.
The ink droplet detection unit 61 includes an ink receiving member 61a, a cleaning unit 61b, a support member 61c, and the like.
The ink receiving member 61a has a landing surface S that receives ink droplets from the head module 31a, and one end of the ink receiving member 61a is fixed to the support member 61c. The ink receiving member is formed by landing ink droplets on the landing surface S. A first strain gauge Ga and a second strain gauge Gb that convert the mechanical displacement (strain) of 61a into an electric quantity are provided.
The first strain gauge Ga and the second strain gauge Gb are arranged on the landing surface S corresponding to the arrangement of the nozzle outlets h of the head module 31a. In the present embodiment, the first strain gauge Ga is , A, b rows and the second strain gauge Gb are arranged corresponding to the c, d rows.

FIG. 5 is a control block diagram for controlling the ink jet printer 1 according to the first embodiment.
As shown in FIG. 5, a CPU (Central Processing Unit) 110, a ROM (Read Only Memory) 120a, a RAM (Random Access Memory) 130, an operation unit 140, various control units 150, an I / F 160, and a nozzle missing as detection means. The determination unit 170 and the like are connected to the local bus 180 and are connected to the system bus 230 via the I / F 160. The system bus 230 is connected to a RIP (Raster Image Processor) unit 210, a host I / F 220, head units 31, 32, 33, and 34, a drive circuit unit DV, and the like.

  The CPU 110 reads the system program and each processing program and data stored in the ROM 120a, expands them in the RAM 130, and centrally controls the operation of the entire inkjet printer 1 according to the expanded programs. Performs overall system timing control, data storage and storage control using the RAM 130, output of data to the head unit 30, input / output control of the operation unit 140, interface (I / F) and operation control with other applications Is.

  The ROM 120a stores a program and a system program for driving the inkjet printer 1, various processing programs corresponding to the system, data necessary for processing by the various processing programs, and the like. Further, the reference voltage value Vn1 when ink droplets are ejected from all the nozzle ejection ports of each nozzle row included in each head module and the number of head modules of the head units 31, 32, 33, and 34 are stored.

  The RAM 130 is a temporary storage area for programs, input, or output data and parameters read from the ROM 120 in various processes controlled and executed by the CPU 110. In addition, a sampling counter that counts the number of ink ejections and a counter that counts the number of head modules are provided.

  The operation unit 140 includes various settings for image recording, operation buttons for performing maintenance instructions to be described later, and the like.

  The various control units 150 are a recording medium conveyance control unit that controls various rollers such as the paper supply unit 10 and the conveyance unit 20 in FIG. 1, a maintenance control unit that controls the operation of the maintenance unit, and a head that controls the operation of the head mount 50. Control units such as a gantry control unit, an ink supply control unit, and a waste ink control unit are provided.

  The nozzle shortage determination unit 170 generates, for each ink droplet detection unit 61, 62, 63, 64, a value generated from the detection voltage value Eout based on the change in the electric quantity from the first strain gauge Ga and the second strain gauge Gb. The reference voltage value Vn is compared, and a nozzle missing judgment circuit unit 171a that judges nozzle missing for each head module is provided.

  The RIP unit 210 converts data input from the host PC or the like via the host I / F 220 into a set of pixels (bitmap data) according to the resolution.

  The drive circuit unit DV drives the head modules 31 a, 32 a, 33 a, 34 a of the head units 31, 32, 33, 34 to discharge ink droplets from the nozzle discharge ports to the recording medium P.

FIG. 6 shows a schematic circuit configuration diagram of the nozzle missing determination circuit unit 171a of the first embodiment.
As shown in FIG. 6, the nozzle shortage determination circuit unit 171a uses a two-sheet one-gauge Wheatstone bridge circuit (hereinafter abbreviated as a bridge circuit) for the amount of change from the first strain gauge Ga and the second strain gauge Gb. The amount of electricity is converted into an electric quantity (voltage), and the lack of nozzle is determined based on the output voltage value from the bridge circuit.

The constants of the bridge circuit of FIG. 6 are defined as follows.
Bridge circuit input voltage value: E [V]
Output voltage value from the bridge circuit: Eout [V]
Fixed resistance value of bridge circuit: R [Ω]
Gauge rate of first and second strain gauges: K
Resistance value of first strain gauge Ga: Ra = R + ΔRa [Ω]
Initial resistance value of the first strain gauge Ga: R [Ω]
Fluctuating resistance value of the first strain gauge Ga: ΔRa [Ω]
First strain gauge strain: εa
Resistance value of second strain gauge Gb: Rb = R + ΔRb [Ω]
Initial resistance value of the second strain gauge Gb: R [Ω]
Fluctuating resistance value of the second strain gauge Gb: ΔRb [Ω]
Second strain gauge strain: εb
The distortion ε obtained from the defined bridge circuit is shown in Equation 1, and the output voltage value Eout is shown in Equation 2.

[Formula 1]
ε = (εa + εb) / 2

[Formula 2]
Eout = (E × K × ε) / 4

  The variation value of the resistance value Ra of the first strain gauge Ga and the resistance value Rb of the second strain gauge Gb connected to one side of the bridge to which the constant input voltage value E is applied is proportional to the output voltage value Eout. It becomes a relationship. Therefore, the lack of ink can be determined by comparing with a preset reference voltage value Vn1.

  The output voltage value Eout from the bridge circuit is amplified and adjusted by the gain AMP 301 and is output to the peak hold unit 302 as a detected voltage value. The peak hold unit 302 receives a delay signal (that is, a waiting time until ink droplets land on the landing surface S based on the ink discharge signal) from the delay circuit unit 303 that has received an ink discharge signal (described later). Based on this, the detected voltage value input from the gain AMP 301 is peak-held. The detected voltage value that has been peak-held is input to the A / D converter 304 and converted into a digital signal. The digitally converted detection voltage value is stored in the RAM 305.

  The access control unit 306a reads the reference voltage value Vn1 stored in the ROM 120a via the I / O 307. Further, an average voltage value Vnr of the detected voltage values stored in the RAM 305 is calculated. The reference voltage value Vn1 is compared with the calculated average voltage value Vnr. When the average voltage value Vnr is lower than the reference voltage value Vn1, it is determined that the nozzle is missing. If there is a nozzle shortage, a flag (determination information) indicating whether maintenance is necessary for the head module detected in the RAM 305 is written.

  The flag indicating the necessity of maintenance may be written in the RAM 305 or the I / O register, and is not limited to this as long as the determination of the necessity of maintenance for each head module can be stored.

FIG. 7 shows a time chart example of the ink ejection operation.
As shown in FIG. 7, as a signal output from the CPU 110 to the nozzle missing determination unit 170, a test signal St for confirming nozzle missing, an ink droplet on the ink receiving member 61a is cleaned and stopped, and the first strain gauge Ga, stop signal Sp for stabilizing the shape (vertical deformation) of the second strain gauge Gb, a row ejection signal Sa instructing the ink ejection operation of the nozzle row a, b row instructing the ink ejection operation of the nozzle row b In order to count the number of ink ejections based on the ejection signal Sb, the c row ejection signal Sc instructing the ink ejection operation of the nozzle row c, the d row ejection signal Sd instructing the ink ejection operation of the nozzle row d, and the ejection signal of each row. The sampling signal Ss and the data fetch signal Sh for instructing the reading operation of the data of the detected voltage value based on the ejection signal of each column.

When the test signal St is output, the a-row ejection signal Sa is output. When the a-row ejection signal Sa is output, the sampling signal Ss is output and the data capture signal is output. When the sampling signal Ss is counted a predetermined number of times (three times in FIG. 7), the stop signal Sp is output, and when the ink receiving member 61a is cleaned and the vibration in the vertical direction is stopped, the ink ejection operation in the a row is performed. Is terminated.
Next, when the test signal St is output, the ink ejection operation in the b column is performed in the same manner as the a column, and the same ink ejection operation is performed in the c column and the d column.

Next, the operation of the first embodiment will be described.
8 and 9 are flowcharts of the nozzle missing determination operation in the first embodiment.
When the operation unit 140 instructs to determine the lack of nozzles, the position of the head mount 50 is confirmed, and the count number of the head module counter is set to 0 (set to the initial value) (step S1). .

  After the head module count reaches 0, two sets of new head modules for each color enter the ink drop confirmation area T2, and each head module corresponds to each ink drop detection unit from the print area T1 to the ink confirmation area T2. The head mount 50 is moved to (step S2).

  After the new head module is moved, the ink drop detection unit cleans the ink receiving member by the cleaning member and stops the vibration of each ink receiving member, so that the shapes of the first strain gauge Ga and the second strain gauge Gb are changed. It is stabilized. Further, the output voltage value Eout of the bridge circuit of the nozzle missing detection circuit unit is set to an initial value. After the above initial setting is completed, the nozzle row is selected (one of the rows a, b, c, and d is selected) (step S3).

  The count number of the sampling counter that counts the number of ink ejections is set to 0 (set to the initial value) (step S4).

  An ink ejection signal (any one of the a-row ejection signal Sa, the b-row ejection signal Sb, the c-row ejection signal Sc, and the d-row ejection signal Sd) is output to the selected nozzle row to perform ink ejection. (Step S5)

  The output voltage value Eout from the bridge circuit is held based on the delay signal calculated by receiving the ink ejection signal, and the held detection voltage value is A / D converted and stored in the RAM 305 (step S6).

  The sampling signal Ss is output, and the count number of the sampling counter is incremented by 1 (1 is added to the count number) (step S7).

  It is determined whether the count number of the sampling counter is a preset count number (for example, 3) (step S8). When the count number is not the preset count number, the process returns to the operation of discharging ink from the selected nozzle (step S5) (step S8; No).

When the count number is a preset count number (step S8; Yes), the average voltage value Vnr of the detected voltage values stored in the RAM 305 is calculated (step S9).
Further, the reference voltage value Vn1 stored in the ROM 120 is read out and stored in the RAM 305 (step S10).

The calculated average voltage value Vnr is compared with the reference voltage value Vn1 (step S11).
When the average voltage value Vnr is lower than the reference voltage value Vn1 (step S11; No), it is determined that a nozzle shortage has occurred in the nozzle discharge port of the selected nozzle row, and maintenance of the selected nozzle row is necessary. Is written in the RAM 305 (step S12).

  When the average voltage value Vnr is equal to or higher than the reference voltage value Vn1 (step S11; Yes), it is determined that no nozzle is missing at the nozzle discharge port of the selected nozzle row, and maintenance of the selected nozzle row is unnecessary. Is written in the RAM 305 (step S13).

  After the flag indicating the necessity of maintenance is written, the determination of the undetermined nozzle row is performed (step S14). If there is an undetermined nozzle row (step S14; No), the operation returns to the operation for selecting the nozzle row (returns to step S3).

  When there is no undetermined nozzle row (step S14; Yes), the count number of the counter of the head module is incremented by 2 (2 is added to the count number) (step S15).

  It is determined whether the count number of the head modules is equal to the number of head modules of each color (step S16). If the count number of the head modules is not equal to the number of head modules for each color (step S16; No), the operation returns to the operation for determining the nozzle shortage for the new head module (returns to step S2).

  When the count number of the head modules is equal to the number of head modules of each color (step S16; Yes), the nozzle missing determination operation is ended (step S17).

  After the determination of missing nozzles for all the head modules, maintenance such as removal of missing nozzles by suction operation is performed in the maintenance area for the head modules having nozzle rows that require maintenance that are stored in the RAM 305. Is called.

By providing the ink confirmation region T2 on the transport path for moving the head mount 50 from the print region T1 to the maintenance region T3, and providing the ink droplet detection units 61, 62, 63, 64 in the ink confirmation region T2, The nozzle missing of the head modules 31a, 32a, 33a and 34a can be detected, and at least the head module having the nozzle missing is reliably maintained, so that the reliability of the ink jet printer can be improved.
In addition, a plurality of strain gauges that detect the landing of ink droplets from the nozzle ejection port are installed corresponding to the nozzle arrangement of each head module 31a, 32a, 33a, 34a, and ink droplets are ejected for each nozzle array in a time-sharing manner. By doing so, it is possible to determine the missing nozzle for each nozzle row, and it is possible to improve the accuracy of the missing nozzle detection.
An ink droplet is ejected from the nozzle ejection port a plurality of times, and the average value (average voltage value Vnr) of the detected voltage value based on the landing of the ink droplet is compared with the reference voltage value Vn1, and the average voltage value Vnr is lower than the reference voltage value Vn1. In this case, it can be reliably determined that no ink droplet is ejected from a predetermined nozzle ejection port (that is, a nozzle shortage has occurred). Further, even when ink droplets are ejected in the first half of the ink droplet ejection operation for detecting nozzle missing, it is determined that a nozzle missing has surely occurred even if ink droplets are not ejected in the second half. And maintenance can be performed to remove the missing nozzle.

[Embodiment 2]
Hereinafter, the second embodiment of the present invention will be described in detail with reference to the drawings.
First, the configuration will be described.
Since the schematic configuration inside the inkjet printer 1 and the partially enlarged view of the head unit 31 in the second embodiment are the same configuration and operation as those in the first embodiment, their illustration and description are omitted.
Further, in the transport mechanism of the head gantry, the ink droplet detection unit 61 becomes the ink droplet detection unit 81, and the control block for controlling the ink jet printer 1 includes the ink droplets from all the nozzle discharge ports h of each head module in the ROM 120a. ROM 120b storing nozzle reference voltage value Vn2 and the number of head modules of each head unit 31, 32, 33, 34, nozzle missing judgment circuit unit 171a becomes nozzle missing judgment circuit unit 172a Since the configuration is the same as that of the first embodiment, its illustration and description are omitted.

FIG. 10 shows a schematic configuration diagram of the ink droplet detection unit 81 according to the second embodiment.
FIG. 10A shows a schematic view of the ink droplet detection unit 81 as viewed from above, and FIG. 10B shows a schematic cross-sectional view of the ink droplet detection unit 81 from the viewpoint A shown in FIG.
The ink droplet detection unit 81 includes an ink receiving member 81a, a cleaning unit 81b, a support member 81c, and the like.
The ink receiving member 81a has a landing surface S that receives ink droplets from the head module 31a, and one end of the ink receiving member 81a is fixed to the support member 81c. The ink receiving member is formed by landing ink droplets on the landing surface S. A third strain gauge Gc and a fourth strain gauge Gd that convert the mechanical displacement (strain) of 81a into an electric quantity are provided.
The third strain gauge Gc is disposed on the landing surface S of the ink receiving member 81a, and the fourth strain gauge Gd is disposed on the back surface facing the landing surface S of the ink receiving member 81a. Since the third strain gauge Gc and the fourth strain gauge Gd are distorted in the directions in which the strain gauges oppose each other due to the impact of the ink droplets, the outputs from the third strain gauge Gc and the fourth strain gauge Gd are absolute values. Are equal and the output polarity is symmetric.

FIG. 11 shows a schematic circuit configuration diagram of the nozzle missing determination circuit unit 172a of the second embodiment.
As shown in FIG. 11, the nozzle shortage determination circuit unit 172a uses a 2-gauge 2-active Wheatstone bridge circuit (hereinafter abbreviated as a bridge circuit) for the amount of change from the third strain gauge Gc and the fourth strain gauge Gd. The amount of electricity is converted into an electric quantity (voltage), and the lack of nozzle is determined based on the output voltage value from the bridge circuit.

The constants of the bridge circuit of FIG. 11 are defined as follows.
Bridge circuit input voltage value: E [V]
Output voltage value from the bridge circuit: Eout [V]
Fixed resistance value of bridge circuit: R [Ω]
Gauge rate of third and fourth strain gauges: K
Resistance value of third strain gauge Gc: Rc = R + ΔR [Ω]
Initial resistance value of the third strain gauge Gc: R [Ω]
Fluctuating resistance value of the third strain gauge Gc: ΔR [Ω]
Strain of third strain gauge: ε
Resistance value of the fourth strain gauge Gd: Rd = R−ΔR [Ω]
Initial resistance value of the fourth strain gauge Gd: R [Ω]
Fluctuation resistance value of the fourth strain gauge Gd: -ΔR [Ω]
Strain of the fourth strain gauge: -ε
The output voltage value Eout obtained from the defined bridge circuit is shown in Equation 3.

[Formula 3]
Eout = (E × K × ε) / 2

  The variation value of the resistance value Rc of the third strain gauge Gc connected to one side of the bridge to which the constant input voltage value E is applied and the resistance value Rd of the fourth strain gauge Gd is proportional to the output voltage value Eout. It becomes a relationship. Therefore, the lack of ink can be determined by comparing with a preset reference voltage value Vn2. Furthermore, by installing the third strain gauge Gc and the fourth strain gauge Gd on the front and back surfaces of the ink receiving member 81a, it is possible to obtain a voltage sensitivity that is twice that of the 1 gauge method.

  The output voltage value Eout from the bridge circuit is amplified and adjusted by the gain AMP 301 and is output to the peak hold unit 302 as a detected voltage value. The peak hold unit 302 receives a delay signal (that is, a waiting time until ink droplets land on the landing surface S based on the ink discharge signal) from the delay circuit unit 303 that has received an ink discharge signal (described later). Based on this, the detected voltage value input from the gain AMP 301 is peak-held. The detected voltage value that has been peak-held is input to the A / D converter 304 and converted into a digital signal. The digitally converted detection voltage value is stored in the RAM 305.

  The access control unit 306b reads the reference voltage value Vn2 stored in the ROMb 120 via the I / O 307. Further, the maximum voltage value Vxr of the detected voltage value stored in the RAM 305 is calculated. The reference voltage value Vn2 is compared with the calculated maximum voltage value Vxr. If the maximum voltage value Vxr is lower than the reference voltage value Vn2, it is determined that there is a nozzle shortage. If there is a nozzle shortage, a flag (determination information) indicating whether maintenance is necessary for the head module detected in the RAM 305 is written.

  The flag indicating the necessity of maintenance may be written in the RAM 305 or the I / O register of the CPU 110, and is not limited to this as long as the determination of the necessity of maintenance for each head module can be stored.

Next, the operation of the second embodiment will be described.
12 and 13 are flowcharts of the nozzle missing determination operation in the second embodiment.
When the operation unit 140 is instructed to determine whether the nozzle is missing, the position of the head mount 50 is confirmed, and the count number of the head module counter is set to 0 (set to the initial value) (step S21). .

  After the head module count reaches 0, two sets of new head modules for each color enter the ink drop confirmation area T2, and each head module corresponds to each ink drop detection unit from the print area T1 to the ink confirmation area T2. The head mount 50 is moved to (step S22).

  After the new head module is moved, the ink drop detection unit of the ink drop detection unit is stopped by the cleaning member to clean the ink receiving member and the vibration of the ink receiving member, and the shapes of the third strain gauge Gc and the fourth strain gauge Gd are stabilized. The Further, the output voltage value Eout of the bridge circuit of the nozzle missing detection circuit unit is set to an initial value. (Step S23).

  The count number of the sampling counter that counts the number of ink ejections is set to 0 (set to the initial value) (step S24).

  Ink discharge signals are output to the two sets of head modules for each color that detect nozzle shortage, and ink is discharged (step S25).

  The detection voltage value Eout from the bridge circuit is held based on the delay signal calculated by receiving the ink ejection signal, and the held detection voltage value is A / D converted and stored in the RAM 305 (step S26).

  The count number of the sampling counter is incremented by 1 (1 is added to the count number) (step S27).

  It is determined whether the count number of the sampling counter is a preset count number (for example, 3) (step S28). When the count number is not the preset count number, the process returns to the operation of discharging ink from the selected nozzle (step S25) (step S28; No).

When the count number is a preset count number (step S28; Yes), the maximum voltage value Vxr of the detected voltage value stored in the RAM 305 is calculated (step S29).
Further, the reference voltage value Vn2 stored in the ROM 120 is read out and stored in the RAM 305 (step S30).

The calculated maximum voltage value Vxr is compared with the reference voltage value Vn2 (step S31).
When the maximum voltage value Vxr is lower than the reference voltage value Vn2 (step S31; No), it is determined that a nozzle shortage has occurred in one of the nozzle ejection ports of the selected head module, and maintenance of the selected head module is performed. Is written in the RAM 305 (step S32).

  When the maximum voltage value Vxr is equal to or higher than the reference voltage value Vn2 (step S31; Yes), it is determined that no nozzle is missing at any nozzle discharge port of the selected head module, and the selected head module A flag indicating that maintenance is not required is written in the RAM 305 (step S33).

  After the necessity of maintenance is written, the count number of the counter of the head module is incremented by 2 (2 is added to the count number) (step S34).

  It is determined whether the count number of the head modules is equal to the number of head modules for each color (step S35). If the count number of the head modules is not equal to the number of head modules of each color (step S35; No), the operation returns to the operation of determining the nozzle shortage for the new head module (returns to step S22).

  When the count number of the head modules is equal to the number of head modules of each color (step S35; Yes), the nozzle missing determination operation is ended (step S36).

  After the determination of the missing nozzles for all the head modules, a maintenance operation such as removal of the missing nozzles by a suction operation is performed on the head modules stored in the RAM 305 that require maintenance in the maintenance area.

By providing the ink confirmation region T2 on the transport path for moving the head mount 50 from the print region T1 to the maintenance region T3, and providing the ink droplet detection units 81, 82, 83, 84 in the ink confirmation region T2, The nozzle missing of the head modules 31a, 32a, 33a and 34a can be detected, and at least the head module having the nozzle missing is reliably maintained, so that the reliability of the ink jet printer can be improved.
Ink droplets are ejected from the nozzle ejection port a plurality of times, and the maximum (maximum voltage value Vxr) of the detection voltage value based on the landing of the ink droplet is compared with the reference voltage value Vn2, and the maximum voltage value Vxr is lower than the reference voltage value Vn2. In this case, it can be reliably determined that ink droplets are not ejected from the predetermined number of nozzle ejection ports (that is, nozzle missing occurs). In addition, because the head discharge port is structurally difficult to eject ink droplets for the first time, if the ink droplets are ejected in the latter half even if the ink droplets were not ejected in the first half of the ink droplet ejection operation for detecting nozzle shortage, the maximum By detecting the value, the maintenance can be performed only when the maintenance is surely required.

In addition, Embodiment 1 demonstrated the example which compared the reference voltage value with the average voltage value of the detection voltage value based on the change of the electric quantity from a strain gauge, when a strain gauge is installed corresponding to a nozzle row. However, the missing nozzle may be detected by comparing the maximum voltage value of the detected voltage value with the reference voltage value.
In the second embodiment, when the strain gauge is installed on the landing surface and the back surface of the landing surface, the maximum voltage value of the detection voltage value based on the change in the amount of electricity from the strain gauge is compared with the reference voltage value. As described above, the nozzle missing may be detected by comparing the average value of the detected voltage values with the reference voltage value.

1 is a schematic configuration diagram of the inside of an ink jet printer 1 according to Embodiment 1. FIG. It is a figure which shows the conveyance mechanism of a head mount. 4 is a partially enlarged view of a black (Bk) head unit 31. FIG. 3 is a schematic configuration diagram of an ink droplet detection unit 61 according to Embodiment 1. FIG. 3 is a control block diagram for controlling the ink jet printer 1 according to Embodiment 1. FIG. FIG. 3 is a schematic circuit configuration diagram of a nozzle missing determination circuit unit 171a according to the first embodiment. 4 is a time chart example of an ink ejection operation according to the first embodiment. The flowchart of the nozzle missing determination operation | movement in this Embodiment 1 is shown. The flowchart of the nozzle missing determination operation | movement in this Embodiment 1 is shown. 6 is a schematic configuration diagram of an ink droplet detection unit 81 according to Embodiment 2. FIG. FIG. 6 is a schematic circuit configuration diagram of a nozzle missing determination circuit unit 172a according to a second embodiment. The flowchart of the nozzle missing determination operation | movement in this Embodiment 2 is shown. The flowchart of the nozzle missing determination operation | movement in this Embodiment 2 is shown.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Inkjet printer 10 Paper feed part 11 Paper feed tray 12 Unloader 110 CPU
120a, 120b ROM
130 RAM
140 Operation unit 150 Various control units 160 I / F
170 Nozzle missing judgment unit 171a, 172a Nozzle missing judgment circuit unit 180 Local bus 20 Conveying unit 21 Conveying belt 22 Tension roller 23 Pressing roller 24 Conveying roller 25 Conveying path 210 RIP unit 220 Host I / F
230 System bus 30 Head unit part 31, 32, 33, 34 Head unit 31a, 32a, 33a, 34a Head module 301 Gain AMP
302 Peak hold unit 303 Delay circuit unit 304 A / D conversion unit 305 RAM
306a, 306b Access control unit 307 I / O
40 Paper discharge unit 41 Paper discharge tray 50 Head mount 51 Transport mechanisms 61, 62, 63, 64, 81, 82, 83, 84 Ink droplet detection units 61a, 81a Ink receiving members 61b, 81b Cleaning units 61c, 81c Support member 70 Maintenance parts 71a, 72a, 73a, 74a Capping modules a, b, c, d Nozzle array DV Drive circuit part Ga First strain gauge Gb Second strain gauge Gc Third strain gauge Gd Fourth strain gauge h Nozzle outlet M Drive Motor P Recording medium S Landing surface Sa row ejection signal Sb row ejection signal Sc row ejection signal Sd row d ejection signal Sh data acquisition signal Sp stop signal Ss sampling signal St test signal T1 printing area T2 ink confirmation area T3 maintenance Region Vn1, Vn2 Reference voltage value Vnr Average voltage value xr maximum voltage value X the recording medium conveyance direction (sub scanning direction)
Y frame transport direction (main scanning direction)

Claims (10)

Maintenance provided with a print area for recording an image on a recording medium by a head unit comprising a plurality of head modules having a plurality of nozzles, and a maintenance means provided at a position adjacent to the print area to eliminate ejection failure of the nozzles A line-type inkjet printer configured to move the head unit from the print area to the maintenance area when the nozzle discharge failure is eliminated,
An ink check area is provided in a movement path of the head unit from the print area to the maintenance area, and a detection unit for detecting a discharge failure of the nozzle is provided in the ink check area;
A line-type inkjet printer characterized by this. The line type ink jet printer according to claim 1,
The detection means uses a strain gauge that converts a mechanical displacement generated by the landing of ink droplets ejected in units of head modules into an electrical quantity,
A line-type inkjet printer characterized by this. The line-type inkjet printer according to claim 2,
The detection means includes
Comparing a detection voltage value based on the amount of electricity from the strain gauge and a preset reference voltage value to determine a nozzle ejection failure for each head module;
A line-type inkjet printer characterized by this. The line-type inkjet printer according to claim 2 or 3,
The strain gauge is installed on a landing surface of a one-end fixed member having a landing surface for receiving ink droplets;
A line-type inkjet printer characterized by this. The line-type inkjet printer according to claim 4,
A plurality of strain gauges are installed corresponding to the nozzle arrangement of the head module;
A line-type inkjet printer characterized by this. The line-type inkjet printer according to claim 2 or 3,
The strain gauge is installed on a landing surface of a one-end fixed member having a landing surface for receiving ink droplet landing, and a back surface of the landing surface;
A line-type inkjet printer characterized by this. The line type ink jet printer according to any one of claims 3 to 6,
Comparing the average voltage value of the detected voltage value based on the amount of electricity from the strain gauge and the reference voltage value, and determining that there is a nozzle ejection failure if the average voltage value is lower than the reference voltage value;
A line-type inkjet printer characterized by this. The line type ink jet printer according to any one of claims 3 to 6,
Comparing the maximum voltage value of the detection voltage value based on the amount of electricity from the strain gauge and the reference voltage value, and determining that there is a nozzle ejection failure when the maximum voltage value is lower than the reference voltage value;
A line-type inkjet printer characterized by this. In the line type ink jet printer according to any one of claims 1 to 8,
The maintenance means is to remove nozzle discharge defects by suction operation;
A line-type inkjet printer characterized by this. In the line type ink jet printer according to any one of claims 1 to 8,
The maintenance means removes nozzle discharge defects by a flushing operation;
A line-type inkjet printer characterized by this.

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