JP7206908B2 - Droplet ejection device and control method for droplet ejection device - Google Patents

Description

The present invention relates to a droplet ejection device that ejects droplets from a plurality of nozzles and a control method for the droplet ejection device.

2. Description of the Related Art In a droplet ejection device such as an inkjet printer, there are cases where nozzles that cannot eject droplets (non-ejection nozzles) occur due to thickening or solidification of ink, clogging of nozzles, malfunction of actuators, and the like. Therefore, it is necessary to check the ejection state of the nozzles at a predetermined timing, and if there is a non-ejection nozzle, restore it through maintenance such as purging or flushing.

Therefore, as a printer for detecting non-ejection of droplets, a metal electrode (detection plate) or the like is erected along the flight area (droplet passage space) of the droplets ejected from the nozzles. A droplet ejecting device (droplet ejecting device) configured to read a change in the capacitance of a sensing plate when passing along and near the sensing plate has been proposed (for example, Patent Document 1). .

Here, if droplets are ejected at different timings for each channel (ch), changes in capacitance can be detected for each channel, and non-ejection channels can be individually confirmed. However, such a detection method requires too long a detection time. Therefore, in Japanese Patent Laid-Open No. 2002-100000, the droplet flight region (droplet passage space) is configured such that the portion overlapping the detection plate when viewed from the side is different for each channel with respect to the ejection direction.

JP 2015-066819 A

However, in the configuration of Patent Document 1, when the density of the channel arrangement progresses, in order to accurately identify adjacent channels, for example, it is necessary to increase the number of detection plates, so the structure becomes complicated. . Along with this, there is a problem that the circuit configuration of the detection mechanism becomes complicated.

SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to provide a droplet ejecting apparatus that can detect whether or not droplets are not ejected from a plurality of nozzles with a simple configuration while suppressing the space required for arranging a detection plate.

A droplet ejection device according to one aspect of the present invention comprises a droplet ejection head having a plurality of nozzles arranged at regular intervals in one direction, and part of each of the flight regions formed by the droplets ejected from the plurality of nozzles. When the droplet passes through a detection plate having a detection surface arranged to face in a direction perpendicular to the ejection direction of the droplet and a range in which the detection surface faces in the flying region, the detection plate and a controller for detecting an electrical signal induced in the detection surface. an end position on the upstream side and an end position on the downstream side of the detection surface in the ejection direction are defined so that timings at which the droplets pass are different for each of the nozzles; Based on the waveform of the electrical signal detected by the signal detection unit when droplets are simultaneously ejected from all the nozzles, the positions of the nozzles in the non-ejection state are estimated, and the nozzles estimated to be in the non-ejection state are estimated. A non-ejection state is determined based on the waveform of the electrical signal detected by the signal detection unit when droplets are ejected from a predetermined number of the nozzles, including the nozzles, which are arranged continuously in the one direction. Locate the nozzle.

Therefore, the liquid droplet ejection device according to an aspect of the present invention can reduce the space required for arranging the detection plate, and can detect the presence or absence of non-ejection of liquid droplets and its position for a plurality of nozzles with a simple configuration. Effective.

A control method for a droplet ejection device according to an aspect of the present invention comprises a droplet ejection head having a plurality of nozzles arranged at equal intervals in one direction, and a flying area formed by the droplets ejected from the plurality of nozzles. When the droplet passes through a detection plate having a detection surface arranged to face a part in a direction perpendicular to the ejection direction of the droplet, and a range in which the detection surface in the flight region faces, A signal detection unit for detecting an electrical signal induced in the detection plate, and a control unit, wherein the detection surface faces the detection surface when droplets are simultaneously discharged from all the nozzles. A droplet ejecting device in which an upstream end position and a downstream end position of the detection surface in the ejection direction are defined so that the timing at which the droplets pass through the range is different for each nozzle. 1), wherein the position of the nozzle in the non-ejection state is estimated based on the waveform of the electrical signal detected by the signal detection unit when droplets are simultaneously ejected from all the nozzles. a second step of extracting a predetermined number of the nozzles arranged continuously in the one direction, including the nozzle estimated to be in a non-ejecting state; and a third step of specifying the position of the nozzle in the non-ejection state based on the waveform of the electrical signal detected by the signal detection unit when the droplet is ejected.

Therefore, a method for controlling a liquid droplet ejection device according to an aspect of the present invention can reduce the space required for arranging the detection plate, and can detect the presence or absence of non-ejection of liquid droplets and the position thereof for a plurality of nozzles with a simple configuration. It has the effect of being able to

According to the present invention, it is possible to reduce the space required for arranging the detection plate and to detect the presence or absence of non-ejection of liquid droplets and the position thereof for a plurality of nozzles with a simple configuration.

FIG. 1 is a schematic diagram showing a schematic configuration of a droplet ejection device according to an embodiment of the present invention. FIG. 2 is a block diagram showing the functional configuration of the droplet ejection device. FIG. 3 is a diagram showing the configuration of the head of the droplet discharge device when viewed from above. FIG. 4 is a diagram showing the configuration of the head of the droplet discharge device when viewed from the side. FIG. 5 is a diagram schematically showing the configuration of the non-ejection nozzle detector. FIG. 6 is a diagram showing an example of waveform information of an electrical signal detected by the signal detection section. FIG. 7 is a graph showing variations between channels of nozzles that are actually in the non-ejection state and channels that are determined to be in the non-ejection state. FIGS. 8A to 8C are graphs showing magnitudes of synthesized values of electrical signal waveforms when a predetermined number of nozzles are divided into odd-numbered channel groups and even-numbered channel groups and compared. FIG. 9 is a flow chart showing the procedure of a non-ejection nozzle determination process in the droplet ejection device. FIG. 10 is a flowchart showing a procedure for estimating the non-ejection nozzle position in the droplet ejection device. FIG. 11 is a diagram showing waveform information of an electrical signal when the end nozzle is a non-ejection nozzle. FIG. 12 is a diagram showing waveform information of an electrical signal when non-ejection nozzles are included in the near-end nozzles. FIG. 13 is a diagram showing waveform information of an electrical signal when a non-ejection nozzle is included in the central nozzle. FIG. 14 is a flow chart showing a process procedure for identifying non-ejecting nozzles in the droplet ejection device. FIG. 15 is a diagram showing the configuration of the head of the droplet ejection device according to Modification 1 when viewed from above. FIG. 16 is a diagram showing the configuration of the head of the droplet discharge device 1 according to Modification 1 when viewed from the side.

(embodiment)
A droplet ejection device 1 according to an embodiment of the present invention will be described with reference to the drawings. In the following description, as the droplet ejection device 1, an ink ejection device that ejects ink droplets (liquid droplets) onto a sheet will be described as an example.

[Configuration of Droplet Ejecting Device]
FIG. 1 is a schematic diagram showing a schematic configuration of a droplet ejection device 1 according to an embodiment of the present invention. The droplet ejection device 1 forms an image on the conveyed paper P with an inkjet head (hereinafter simply referred to as a head) 10 . The droplet ejection device 1 accommodates various mechanical units such as a paper feed/conveyance system, a printing system, an ink supply system, a maintenance system, etc., and a control unit 100 inside a housing 1a. The upper portion of the housing 1a is a paper ejection section 35, from which the printed paper P is ejected.

The main components of the paper feed/transport system are the paper feed mechanism 1c, the transport mechanism 30, and the guide mechanism 25. FIG. Among these, the paper feed mechanism 1 c has a paper feed tray 23 and a paper feed roller 24 . When the paper feed roller 24 rotates under the control of the controller 100 , the paper P is fed out from the paper feed tray 23 . The transport mechanism 30 includes transport nip rollers 31 and 32 and a platen 40 . The transport nip rollers 31 and 32 are arranged to sandwich the platen 40 in the sub-scanning direction, and transport the paper P. As shown in FIG. The platen 40 supports the paper P from below. The guide mechanism 25 includes an upstream guide section and a downstream guide section. The upstream guide section connects the paper feed mechanism 1 c and the transport mechanism 30 . The downstream guide section connects the conveying mechanism 30 and the paper discharge section 35 .

Among them, the platen 40 includes a pair of door members 41 and 42, a pair of rotating shafts 40a, and a platen motor 43 (see FIG. 2). The door members 41 and 42 are rotatably supported by a rotary shaft 40a. When the platen motor 43 (see FIG. 2) rotates under the control of the controller 100, the door members 41 and 42 rotate around the rotation shaft 40a.

As a result, the door members 41 and 42 are in a closed state (shown by solid lines in FIG. 1) along the sub-scanning direction and an open state (indicated by dashed lines in FIG. 1) hanging down in the vertical direction (direction perpendicular to the sub-scanning direction). state shown) can be selectively taken. The closed state is used during print processing, and the open state is used during flushing or non-ejection nozzle determination processing.

A main component of the printing system is the head 10 . The head 10 is a line head and elongated in the main scanning direction. A lower surface of the head 10 is a nozzle surface 10a, and a large number of nozzles 15 are opened. As shown in FIG. 3, the plurality of nozzles 15 are arranged at regular intervals in the main scanning direction to form nozzle rows, and four nozzle rows are arranged in the sub-scanning direction. Ink droplets are ejected from the nozzles 15 during printing, flushing, and determination. Ink is supplied from an ink cartridge through a tube.

Main components of the maintenance system include the liquid droplet receiver 9 and the non-ejection nozzle detector 50 . Among them, the droplet receiver 9 includes a substrate 9a, a flushing foam 9b, an elevating mechanism, and a horizontal movement mechanism. Further, a detection plate 51 is erected in the vertical direction at the end (the front end in FIG. 1) of the base material 9a. The flushing foam 9b is a porous member such as sponge and supported by the base material 9a. The flushing foam 9b receives ejected ink droplets during flushing and judgment processing. During flushing, the elevating mechanism is driven under the control of the control unit 100 to reciprocate the base member 9a in the vertical direction. Further, the horizontal movement mechanism is driven to reciprocate the substrate 9a in the sub-scanning direction.

On the other hand, the ejection failure detection unit 50 includes a detection plate 51 and a signal detection unit 52 and shares the elevating mechanism and horizontal movement mechanism of the droplet receiving unit 9 . The detection plate 51 is an electrode and a plate-like metal member. The signal detection section 52 is a detection circuit and detects an electrical signal induced in the detection plate 51 . During the determination process, the elevating mechanism is driven under the control of the control unit 100, and the detection plate 51 reciprocates in the vertical direction. Further, the horizontal movement mechanism is driven to reciprocate the detection plate 51 in the sub-scanning direction. A detailed configuration of the non-ejection nozzle detection unit 50 will be described later.

Here, when the droplet discharge device 1 is installed horizontally, the main scanning direction is the direction perpendicular to the paper surface in FIG. 1 and the longitudinal direction of the head 10 . The sub-scanning direction is parallel to the horizontal direction and is the direction in which the paper P is conveyed on the platen 40 . The vertical direction is a direction orthogonal to the main scanning direction and the sub-scanning direction, and is the direction in which ink droplets are ejected.

The control unit 100 controls each part included in the droplet ejection device 1 and governs the operation of the droplet ejection device 1 as a whole. The control unit 100 includes a CPU (Central Processing Unit), a ROM (Read Only Memory) that unrewritably stores programs executed by the CPU and data used in these programs, and temporarily stores data during program execution. and a random access memory (RAM). Each functional unit that constitutes the control unit 100 is constructed by cooperation of these hardware and software in the ROM.

As shown in FIG. 2 , the control unit 100 has a receiving unit 141 , a print processing unit 142 , a maintenance control unit 143 , a non-ejection nozzle determination control unit 144 and a storage unit 145 . FIG. 2 is a block diagram showing the functional configuration of the droplet discharge device 1. As shown in FIG.

The receiving unit 141 receives a print command from an external device via the interface 60 . Image data to be recorded on the paper P is included in the print command. The print processing unit 142 performs print processing (records an image on the paper P) based on the print command. The print processing unit 142 controls the operation of the head 10 (actuator) in addition to the operations of the paper feed/conveyance system based on the image data.

At this time, the paper P is fed out from the paper feed tray 23 and guided to the upstream guide portion to reach the platen 40 . An image is formed on the paper P on the platen 40 by ejecting ink droplets from the head 10 . Thereafter, the paper P is guided to the downstream side guide section and discharged to the upper paper discharge section 35 .

The maintenance control unit 143 performs maintenance for maintaining and recovering the ink ejection characteristics of the head 10 . Maintenance includes discharge processing, wiping processing, capping processing, and the like.

Among these, the discharge processing is flushing and purging. The maintenance control unit 143 controls the head 10, the platen motor 43, the lifting mechanism, the horizontal movement mechanism, and the like during flushing. The head 10 is driven to eject ink droplets onto the flushing foam 9b. Here, flushing is performed for each nozzle row. In addition, the maintenance control unit 143 controls the pump 54, the platen motor 43, etc. during purging. The pump 54 is driven and ink is forcibly discharged from the head 10 .

The ejection failure nozzle determination control section 144 works in cooperation with the maintenance control section 143 . In the determination process, the ejection failure nozzle determination control unit 144 causes each nozzle row 16 to eject ink droplets all at once. All the nozzles 15 belonging to the nozzle row 16 are targeted for simultaneous ejection.

At this time, the non-ejection nozzle determination control section 144 determines whether or not there is a non-ejection nozzle based on the detection result of the non-ejection nozzle detection section 50 . This determination is made for each nozzle row 16 . When it is determined that there are ejection failure nozzles, the ejection failure nozzle determination control unit 144 estimates the number and positions of the ejection failure nozzles for the nozzle row of interest. Then, the ejection failure nozzle determination control unit 144 selects a predetermined number of nozzles including the estimated nozzles, and specifies ejection failure nozzles among them.

(Composition around the head)
3 and 4 are diagrams showing the configuration around the head 10 of the droplet discharge device 1. FIG. FIG. 3 is a configuration diagram of the head 10 viewed from above. FIG. 4 is a configuration diagram of the head 10 viewed from the side (the left side of the platen 40). A droplet catcher 9 is located below the platen 40 . Although the nozzle 15 on the lower surface of the head 10 is not originally visible, it is indicated by a solid black circle in order to make it easier to understand the positional relationship with other parts.

During the printing process, the droplet receiver 9 is positioned at the standby position shown in FIG. If the droplet receiver 9 is at the standby position, the opening and closing of the door members 41 and 42 are not hindered.

During flushing, the platen motor 43 is driven to open the door members 41 and 42 . After that, the elevating mechanism is driven, and the droplet receiver 9 is lifted from the standby position to a predetermined position near the nozzle surface 10a. Further, the horizontal movement mechanism is driven, and the droplet receiver 9 is moved in the sub-scanning direction to a position facing the front row of nozzles 16 (position (A) in FIG. 4). After that, the droplet receiver 9 starts moving toward the last nozzle row 16 . During this time, the droplet receiver 9 sequentially receives ink droplets from each nozzle row.

Here, during the determination process, the liquid droplet receiver 9 is operated in the same manner as during flushing. That is, every time the droplet receiver 9 faces the nozzle row, an ink droplet receiving operation is performed for each group. An electrical signal is induced in the detection plate 51 each time. The signal detection unit 52 detects this and outputs it as a detection signal to the ejection failure nozzle determination control unit 144 . The non-ejection nozzle determination control unit 144 determines whether or not there is a nozzle in the non-ejection state based on this detection signal.

(non-ejection nozzle detector)
FIG. 5 shows the arrangement relationship among the nozzle row 16, the flight area R, and the detection plate 51. As shown in FIG. For convenience, the head 10 has 16 channels.

The non-ejection nozzle detection unit 50 includes one detection plate 51 having a detection surface 51a facing the flying region R of ink droplets in a direction orthogonal to the ink ejection direction, and the detection surface of the detection plate 51. A signal detection unit 52 is provided for detecting an electrical signal induced in the detection plate 51 by the passage of ink droplets through the range where the detection plate 51a faces.

The detection plate 51 of the non-ejection nozzle detection unit 50 has a side surface as a detection surface 51a. The detection surface 51a faces the flying region R of the ink droplets from the side thereof (direction orthogonal to the ink ejection direction) with a small gap therebetween. The detection plate 51 is long along the main scanning direction (nozzle rows 16). Therefore, an electrical signal is induced in the detection plate 51 when an ink droplet passes through the front area of the detection surface 51a. As described above, the signal detector 52 detects this electrical signal.

It should be noted that "passing" also means that the ink droplet enters and leaves the range of the flying region R facing the detection surface 51a. An electrical signal having two peaks is induced in the detection plate 51 in accordance with the entry and retreat of one ink droplet.

In this embodiment, the shape of the detection surface 51a is a parallelogram. The long sides of the parallelogram obliquely intersect the ink droplet ejection direction (for example, the vertical direction). Therefore, in the ejection direction, the timing at which ink droplets reach the end (upstream end) 51b of the detection surface 51a on the upstream side (ink droplet entry timing) is different between adjacent nozzles 15 . The same applies to the withdrawal timing of ink droplets at the downstream end 51c. Also, one detection surface 51a overlaps all the flight regions R when viewed from the sub-scanning direction. That is, the range in which one detection surface 51a faces includes the range of all flight regions R.

Further, since the detection surface 51a has the above-described shape, when the ink droplets cross the range facing the detection surface 51a, the timing at which the ink droplets pass through the adjacent nozzles 15 differs from each other. At this time, the change in the current induced in the detection plate 51 is detected by the signal detection section 52 and transmitted to the non-ejection nozzle determination control section 144 as an electrical signal.

However, when the nozzles 15 come closer to each other, the timing at which the ink droplets pass becomes closer, and it becomes difficult to specify the nozzle 15 with high accuracy.

Therefore, in the present embodiment, one nozzle row 16 is targeted for simultaneous ejection. The ejection failure nozzle determination control unit 144 compares the waveform information of the detected electrical signal with the waveform information of the reference signal. If the waveform information does not match, the ejection failure nozzle determination control unit 144 determines that there is a nozzle 15 in the ejection failure state in the ejection target nozzle row 16 . Furthermore, the non-ejection nozzle determination control unit 144 estimates the position of the nozzle 15 in the ejection failure state from the waveform information of the detection result for the nozzle row 16 to be the ejection target.

Note that the reference signal is an electrical signal when there is no ejection failure nozzle. The target of simultaneous ejection is the representative nozzle row 16 . The storage unit 145 stores in advance as waveform information of the electrical signal.

The electrical signal waveform information is information relating to a composite waveform of electrical signals induced by each ink droplet. At this time, the reference signal becomes a substantially trapezoidal synthetic electrical signal. FIG. 6 is a diagram showing an example of the composite electrical signal, and the dashed line corresponds to the waveform information of the reference signal. The dashed-dotted line corresponds to waveform information of the detected electrical signal. In FIG. 6, the horizontal axis represents time and the vertical axis represents current intensity.

Specifically, even if the ink droplets are ejected all at once, the detection surface 51a detects the passage of the ink droplets at different timings for each ink droplet. Therefore, assuming that there is no ejection failure nozzle, the waveform information of the reference signal draws a substantially trapezoidal profile as indicated by the dashed line in FIG. On the other hand, when there is a non-ejecting nozzle, the waveform information draws a trapezoidal shape with a depressed upper base, as indicated by the dashed line in FIG.

Therefore, by comparing the waveform information of the detected electrical signal and the waveform information of the reference signal, it is possible to determine the presence or absence of the nozzle 15 in the non-ejection state. Further, the position of the nozzle 15 in the non-ejection state can be estimated from the position of the depression described above.

Next, the non-ejection nozzle determination control unit 144 identifies the position of the nozzle 15 in the non-ejection state. For the nozzle row 16 including the nozzles 15 in the non-ejection state, a predetermined number of nozzles 15 that include the nozzles 15 that are assumed to be in the non-ejection state and are arranged continuously with the nozzles 15 are selected. This predetermined number is determined as follows.

First, as a device for verification, a device having the same configuration as the droplet discharge device 1 is prepared. For one nozzle row 16, one nozzle 15 is set as a virtual non-discharging nozzle, and all nozzles 15 other than this nozzle 15 perform simultaneous discharge. From the electrical signal obtained at this time, a virtual non-ejecting nozzle is specified, and the difference between the specified nozzle position and the true nozzle position is obtained. This series of processes is repeated many times.

Here, when the detected electrical signals are compared for the adjacent nozzles 15, there is a large overlap between the signals, and in addition there is an overlap of noise. As such, the identified nozzle location may correspond to the true nozzle location, but may also be a neighboring nozzle location. That is, the identified nozzle positions have some variation with respect to the true nozzle positions.

In this way, the specified nozzle positions are distributed with a certain spread. For example, as shown in FIG. 7, the identified nozzle positions have a normal distribution centered on the true nozzle position. In FIG. 7, the horizontal axis represents the specified nozzle position, and the vertical axis represents the frequency of occurrence (the number of occurrences). Note that the notation of the horizontal axis is based on the true nozzle position (0), and the specified position of the nozzle 15 is determined from the positional difference. If the nozzle 15 identified from the positional difference is adjacent to the true nozzle 15, the position of the identified nozzle 15 is set to "1" or "-1".

From the distribution of positions shown in FIG. 7, the standard deviation σ of the identified positions is obtained. If the distribution is partitioned by a distance of 3σ from the central position (average value) of the distribution, the specified nozzle position will appear within the partitioned range with a probability of 99.7%. Note that the occurrence probability is 95% if the distance is 2σ, and the occurrence probability is 99.994% if the distance is 4σ. In the example shown in FIG. 7, five nozzles 15 are included in this range when divided by a distance of 3σ from the central position (average value).

Here, since the number of nozzles in this section is 5, which is an odd number, one continuous nozzle 15 may be added to either side of the row, and the number of nozzles to be selected may be 6, which is an even number. At this time, it becomes easy to specify the nozzle position by comparing the waveform information.

The predetermined number of nozzles 15 to be selected in the nozzle row 16 of interest is appropriately set according to the distance between adjacent nozzles 15, the velocity of ejected ink droplets, the shape of the detection plate 51, and the like.

In the above description, when determining the predetermined number, the variation in the specific accuracy of the non-ejecting nozzles is determined in advance using the actual machine, but it may be determined using a simulation.

A specific method of specifying the nozzle position will be described with reference to FIG. Here, it is assumed that there are three or four nozzles 15 to be selected within the 3σ section. If there are three nozzles 15 among them, one new nozzle 15 is added based on the above criteria.

The ejection failure nozzle determination control unit 144 divides the four nozzles 15 into odd-numbered groups and even-numbered groups. In FIG. 8, it is assumed that the non-ejecting nozzle 15 is positioned at the ninth position in the nozzle row 16 .

In FIG. 8(a), the sixth to ninth nozzles 15 are selected. The non-ejection nozzle determination control unit 144 configures the even-numbered group with the sixth and eighth nozzles 15 and configures the odd-numbered group with the seventh and ninth nozzles 15 . The figure shows the waveforms of the combined electrical signals for both groups.

In this case, between the two groups, the peak height of the waveform is higher in the even-numbered group. The peak positions of the waveforms are the same. From this, it can be said that the ninth nozzle 15 is in a non-ejecting state.

In FIG. 8B, the eighth to eleventh nozzles 15 are selected. The non-ejection nozzle determination control unit 144 forms an even-numbered group with the eighth and tenth nozzles 15 and an odd-numbered group with the ninth to eleventh nozzles 15 .

In this case, between the two groups, the peak height of the waveform is higher in the even-numbered group. The peak positions of the waveforms are different, and the peak of the odd-numbered group is located on the right side of the peak of the even-numbered group (the side where the nozzle number increases). From this, it can be said that the ninth nozzle 15 is in a non-ejecting state.

In FIG. 8(c), the seventh to tenth nozzles 15 are selected. The non-ejection nozzle determination control unit 144 forms an even-numbered group with the eighth and tenth nozzles 15 and forms an odd-numbered group with the seventh to ninth nozzles 15 .

In this case, between the two groups, the peak height of the waveform is higher in the even-numbered group. The peak positions of the waveforms are different, and the peak of the odd-numbered group is located to the left of the peak of the even-numbered group (the side where the nozzle numbers are smaller). From this, it can be said that the ninth nozzle 15 is in a non-ejecting state.

Next, the procedure of the non-ejection nozzle determination process will be described with reference to the flowchart of FIG.

It should be noted that the ejection failure nozzle determination process may be performed each time the number of printed sheets reaches a predetermined number, or each time the print processing time elapses. Also, if the droplet discharge device 1 has not been used for a long time, the cleaning may be performed at the start of use. Alternatively, after ejecting ink droplets by purging, it may be checked whether or not the nozzles 15, which have been in a non-ejecting state due to purging, are now capable of ejecting ink droplets.

(Determination process for non-ejection nozzles)
The non-ejection nozzle determination control unit 144 causes all the nozzles 15 forming the nozzle row 16 to eject ink droplets all at once. Further, the ejection failure nozzle determination control section 144 generates waveform information from the electrical signal detected by the signal detection section 52 . (Step S10). Then, the non-ejection nozzle determination control unit 144 compares the waveform information of the detected electrical signal with the waveform information of the reference signal (step S11). Waveform information of the reference signal is pre-stored in the storage unit 145 . At this time, the non-ejection nozzle determination control unit 144 determines whether there is a non-ejection nozzle depending on whether or not the waveform information matches.

In this determination, the non-ejection nozzle determination control unit 144 uses the waveforms of the signals indicated by both waveform information to determine the presence or absence of the difference or the magnitude relationship. For example, when a difference equal to or greater than a predetermined value is calculated, the ejection failure nozzle determination control unit 144 determines that the corresponding nozzle row 16 includes nozzles 15 in the ejection failure state.

If it is determined in step S11 that there is no ejection failure nozzle ("NO" in step S11), the ejection failure nozzle determination control unit 144 determines whether or not there is a nozzle row 16 for which determination processing has not been completed (step S15). . If determination processing has been completed for all nozzle rows 16 ("YES" in step S15), the ejection failure nozzle determination processing ends (END). On the other hand, if there is an unprocessed nozzle row 16 ("NO" in step S15), the ejection failure nozzle determination control unit 144 sets the target of the determination process to the adjacent nozzle row 16, and the process proceeds to step S11. back to As a result, when there is no non-ejecting nozzle 15, it is not necessary to spend time on the determination process, and the process can be simplified.

On the other hand, if it is determined in step S11 that there is a non-ejection nozzle ("YES" in step S11), the non-ejection nozzle determination control unit 144 performs the non-ejection nozzle position estimation process (step S12, according to the present invention). (corresponds to the first step of ). At this time, the ejection failure nozzle determination control unit 144 divides the nozzle array 16 into three regions (end, near-end, and central portion) and sets them as target regions for estimation processing. The content of estimation processing differs for each target region.

Further, the non-ejection nozzle determination control unit 144 performs the process of specifying the position of the non-ejection nozzle (step S13, corresponding to the third step of the present invention). In this specifying process, the ejection failure nozzle determination control unit 144 selects a predetermined number of nozzles 15 including the nozzles 15 at positions specified in the estimation process (second step of the present invention). These nozzles 15 are targeted for specific processing.

The non-ejection nozzle position estimation process and the non-ejection nozzle position identification process are performed as a series of processes by switching target regions in order. In this embodiment, two processes are performed in the order of the edge, the vicinity of the edge, and the central part. Details of the two processes (estimation process and specific process) will be described later.

Further, the non-ejection nozzle determination control unit 144 determines whether or not the specific process has been performed for all the ranges (three regions described above) of the nozzle row 16 (step S14). Then, if the target area for the specific process remains ("NO" in step S14), the ejection failure nozzle determination control section 144 returns the process to step S12. On the other hand, if there is no target area for the specific process ("YES" in step S14), the ejection failure nozzle determination control unit 144 shifts the process to step S15.

Subsequently, the ejection failure nozzle determination control unit 144 determines whether or not the above-described estimation processing and specific processing have been performed for all the nozzle rows 16 (step S15). If there is a nozzle row 16 for which two processes have not been performed ("NO" in step S15), the ejection failure nozzle determination control section 144 returns the process to step S11. If the two processes have been performed for all the nozzle rows 16 ("YES" in step S15), the ejection failure nozzle determination control unit 144 ends the ejection failure nozzle determination process.

It should be noted that, in the above configuration, ink droplets are simultaneously ejected from all the nozzles 15 to confirm the presence or absence of a non-ejection nozzle before performing the process of estimating the position of the non-ejection nozzle. However, if it is known in advance that the nozzle row 16 always includes a non-ejection nozzle, the process of estimating the position of the non-ejection nozzle in step S13 may be performed immediately.

Further, in the above-described embodiment, the estimation process and the identification process are a series of processes, and the non-ejection nozzle determination process is sequentially repeated for the three regions. However, the estimation process is completed in advance for the three regions. After that, the estimated positions of the ejection failure nozzles extracted at this time may be sequentially subjected to the identification process.

(Processing for estimating non-ejection nozzle position)
Next, a process for estimating the non-ejection nozzle position will be described with reference to the flowchart of FIG. 10 . The non-ejection nozzle determination control unit 144 divides one nozzle array 16 into three areas (end, near-end, and central area) and sequentially performs estimation processing. The identification of non-ejection nozzles is completed for each region.

First, the non-ejection nozzle determination control unit 144 determines whether or not two end nozzles in the end region of the nozzle row 16 are non-ejection nozzles (step S20). In the example shown in FIG. 5, the 1st and 16th nozzles 15 from the right in the figure are subject to initial estimation processing.

Here, when the end nozzle is a non-ejecting nozzle, the detected electrical signal has a smaller signal width than the reference signal. FIG. 11 exemplifies the form of the signal together with the reference signal when one end nozzle is in the non-ejecting state. As shown, there is a relationship of signal width a1>signal width a2. The non-ejection nozzle determination control unit 144 makes a determination based on the magnitude relationship of the signal width in this way when executing the estimation process in the end region.

If it is determined that there is a non-ejection nozzle in the end region ("YES" in step S20), the non-ejection nozzle determination control unit 144 performs the non-ejection nozzle position specifying process for the end nozzle (step S20 in FIG. 9). S13). After completion of the specific processing, the non-ejection nozzle determination control unit 144 raises a specific processing completion flag for the end region. When this flag is set, in the next estimation process, the edge area will be ignored and another area (for example, the area near the edge) will be identified as the target area. Furthermore, the ejection failure nozzle determination control unit 144 returns the process to step S20 again. On the other hand, if it is determined that there are no ejection failure nozzles in the end region ("NO" in step S20), the ejection failure nozzle determination control unit 144 shifts the estimation processing target area to the edge vicinity area.

The non-ejection nozzle determination control unit 144 determines whether or not the end vicinity nozzle is a non-ejection nozzle in the end vicinity region (step S21). In the example shown in FIG. 5, the 2nd to 4th and 13th to 15th nozzles 15 are near-end nozzles (subjects of estimation processing). The near-end nozzles are appropriately set according to the arrangement density of the nozzles 15 in the head 10 .

Here, when the near-end nozzle is a non-ejecting nozzle, the detected electrical signal has a longer rise time than the reference signal. FIG. 12 exemplifies the form of the signal, together with the reference signal, in the case where the end-near-end nozzle at the left end of the paper surface (nozzle adjacent to the left end nozzle) is in the non-ejection state. As shown, there is a relationship of rise time b2 of the detected signal>rise time b1 of the reference signal. The non-ejection nozzle determination control unit 144 makes a determination based on the magnitude relationship of the rise time in this manner when executing the estimation process in the end vicinity region.

When it is determined that there is a non-ejection nozzle in the end vicinity region (“YES” in step S21), the non-ejection nozzle determination control unit 144 performs the non-ejection nozzle position specifying process for the end vicinity nozzle (FIG. 9). step S13). After completing the specific processing, the non-ejection nozzle determination control unit 144 raises a specific processing completion flag for the end vicinity region. When this flag is set, in the next estimation process, the area near the edge will be ignored and another area (for example, the central part) will be recognized as the target area. Furthermore, the ejection failure nozzle determination control unit 144 returns the process to step S20 again. On the other hand, when it is determined that there are no ejection failure nozzles in the end vicinity area ("NO" in step S21), the ejection failure nozzle determination control unit 144 shifts the target area of the estimation process to the central part.

Subsequently, the ejection failure nozzle determination control unit 144 determines whether the central nozzle is an ejection failure nozzle in the central portion (step S22). In the example shown in FIG. 5, the 5th to 12th nozzles 15 are the center nozzles (targets of the estimation process).

Here, when the central nozzle is a non-ejecting nozzle, the detected electrical signal has a shape with a depression at the upper base with respect to the substantially trapezoidal reference signal. FIG. 13 exemplifies the form of the signal together with the reference signal when the central nozzle is in the non-ejection state. In this case, the position of the nozzle in the non-ejection state can be estimated from the distance to the depression, with the peak position of the electrical signal corresponding to the endmost nozzle being used as a reference.

If it is determined that there is a non-ejection nozzle in the central portion ("YES" in step S22), the non-ejection nozzle determination control unit 144 performs the non-ejection nozzle position specifying process for the central nozzle (step S22 in FIG. 9). S13). On the other hand, if it is determined that there is no ejection failure nozzle in the central portion ("NO" in step S22), the ejection failure nozzle estimation process ends, and the process proceeds to step S15.

Here, the order of step S21 and step S22 may be reversed. However, step S20 is preferably always performed first. This is because the position of the endmost nozzle 15 is used as a reference when estimating the position of the central nozzle in the non-ejecting state. If the identity of the endmost nozzle 15 (end nozzle or near-end nozzle) is unknown, the estimated position is also unknown. Further, in determining whether or not the near-end nozzle is in the non-ejection state, the rise time of the combined signal differs between when the end nozzle is in the non-ejection state and when the end nozzle is not in the non-ejection state. Therefore, it is because estimation with good accuracy cannot be performed.

(Specifying processing of non-ejection nozzle position)
Next, the process of specifying the non-ejection nozzle position will be described with reference to the flowchart of FIG. 14 .

Here, the method of specifying the position, the selection of nozzles to be specified, and the grouping described with reference to FIG. 8 are common. However, in the present embodiment, the object of peak height comparison is different. At this time, the specified group includes nozzles in the non-ejection state.

First, the ejection failure nozzle determination control unit 144 extracts a predetermined number of nozzles 15 including the nozzle 15 at the estimated position (step SS30). The predetermined number is determined by the standard deviation σ of the positions. Then, the extracted nozzles 15 are divided into two groups, an even-numbered group and an odd-numbered group (step S31). Here, the non-ejection nozzle determination control unit 144 performs simultaneous ejection for each group and generates waveform information of each combined electrical signal.

The storage unit 145 stores waveform information of two electrical signals corresponding to the two groups described above. Each waveform information is obtained when there is no ejection failure nozzle. At this time, the number of nozzles involved in each waveform information is the same as the number of nozzles forming each group described above.

Then, the non-ejection nozzle determination control unit 144 compares the waveform of the electrical signal of the even-numbered group with the waveform of the corresponding stored electrical signal (ideal waveform 1). Similarly, the non-ejection nozzle determination control unit 144 compares the waveform of the electrical signal of the odd-numbered group with the waveform of the corresponding stored electrical signal (ideal waveform 2). (Step S32).

Here, if any of the groups includes non-ejection nozzles, the waveform of the electrical signal will be lower than the ideal waveform. Therefore, a group in which the value of the waveform information is lower than that of the ideal waveform is specified as a group including non-ejection nozzles (step S33). Further, the non-ejection nozzle determination control unit 144 identifies the position of the non-ejection nozzle from within the group including the non-ejection nozzle (step S34). At this time, this nozzle position is determined based on the peak position of the waveform of the electrical signal.

Referring again to FIG. 8, a method of determining nozzle positions will be described. In FIG. 8, the waveform with a large peak value is the detected synthetic waveform, but the description will be made by replacing it with a stored ideal waveform. Here, one group is composed of two nozzles 15, and one nozzle 15 is in a non-ejecting state. Note that if there is no nozzle 15 in the non-ejection state, the ideal waveform and the actually measured combined waveform will match.

For example, in the example of (b), the waveform of the odd-numbered group (the pair of the 9th and 11th nozzles 15) is smaller than the ideal waveform, so it is specified as a group including non-ejection nozzles. Furthermore, the odd-numbered group waveform overlaps the right half of the ideal waveform with respect to the peak position of the ideal waveform. Also, the odd-numbered group of waveforms corresponds to the 11th nozzle 15 . Therefore, the ninth nozzle 15 is identified as the ejection failure nozzle.

Before dividing into the odd-numbered channel group and the even-numbered channel group in step S31, the predetermined number of extracted channels may be divided into several groups, and steps S31 to S34 may be performed for each group.

(Modification 1)
Modification 1 according to the present embodiment will be described with reference to FIGS. 15 and 16. FIG. FIG. 15 is a top view showing the configuration of the head 10 and its surroundings. FIG. 16 is a side view showing the configuration of the head 10 and its surroundings.

The droplet ejection device 1 according to the present embodiment has a configuration in which a line head is provided as the head 10 . On the other hand, the droplet ejection device 1 according to Modification 2 has a configuration in which a serial head is provided as the head 10 .

First, as shown in FIG. 15, in the head 10, a plurality of nozzles 15 are arranged at equal intervals in the sub-scanning direction to form nozzle rows 16, and four nozzle rows 16 are arranged along the main scanning direction. The head 10 then reciprocates in the main scanning direction. Two transport nip rollers 31 and 32 sandwich the reciprocating region of the head 10 in the sub-scanning direction (transport direction). In the main scanning direction, a droplet receiver 9 is arranged facing the head 10 at the left end of the reciprocating region. A detection plate 51 is erected on the right end of the base of the droplet receiver 9 . The detection plate 51 is arranged over the entire length of the base in the sub-scanning direction. A flushing foam is also arranged on the base, avoiding the detection plate 51 .

The flushing foam has the same shape and size as the nozzle surface 10 a of the head 10 . Therefore, during flushing, the nozzle surface 10a faces the entire flushing foam ((A) in FIG. 16). However, during the ejection failure nozzle determination process, each time one nozzle row 16 passes over the detection plate 51 toward the flushing foam side, this nozzle row 16 is subjected to the determination process.

That is, when executing the ejection failure nozzle determination process, the head 10 is moved from the image forming area (for example, FIG. 16B) toward the droplet receiver 9 by a carriage (not shown). Of the four nozzle rows 16, when the rightmost nozzle row 16 in the main scanning direction passes over the detection plate 51 toward the flushing foam side, the carriage temporarily stops, and ink droplets are ejected from the rightmost nozzle row 16. be. Each time a series of ink droplets is discharged, the carriage moves rightward by one nozzle row. At the same time, an electrical signal induced in the detection plate 51 is detected in accordance with ejection of ink droplets. In this manner, the head 10 ejects ink droplets sequentially from each nozzle row 16 while moving by one row of the nozzle rows 16 .

This determination process can also be applied to check the recovery state of the ejection characteristics of the nozzles after the maintenance process. For example, during flushing, the nozzle surface 10a faces the flushing foam. When checking the recovery state, the head 10 moves from the flushing area (see FIG. 16A) toward the image forming area.

When the rightmost nozzle row 16 in the main scanning direction of the four nozzle rows 16 approaches the detection plate 51 at a predetermined distance, the carriage stops temporarily and ink is discharged from the rightmost nozzle row 16 . Dispense. At the same time, an electrical signal induced in the detection plate 51 is detected in accordance with ejection of ink droplets. Each time ink droplet ejection is completed, the carriage moves rightward by one nozzle row. In this manner, the head 10 ejects ink droplets sequentially from each nozzle row 16 while moving by one row of the nozzle rows 16 . Determination of the ejection characteristic recovery state is performed based on the result of determination processing. If it has recovered, for example, the process proceeds to image forming processing. If recovery is insufficient, purging or flushing is performed again.

As described above, the droplet ejection device 1 according to an aspect of the present invention includes the head 10 having the plurality of nozzles 15 arranged in one direction at regular intervals, and the flight area formed by the ink droplets ejected from the plurality of nozzles 15 . Ink droplets pass through a range in which the detection plate 51 having a detection surface 51a arranged to face a part of each R in the direction perpendicular to the ejection direction of the ink droplets and the detection surface 51a in the flight region R face each other. Thus, the detection surface 51a is provided with a signal detection section 52 for detecting an electrical signal induced in the detection plate 51 and a control section 100. The upstream end position and the downstream end position of the detection surface 51a in the ejection direction are defined so that the timing at which ink droplets pass through each nozzle 15 differs for the range where the surface 51a faces. , the control unit 100 estimates the position of the nozzle 15 in the non-ejection state based on the waveform of the electrical signal detected by the signal detection unit 52 when ink droplets are simultaneously ejected from all the nozzles 15, and detects the non-ejection state. Including the nozzles 15 estimated to The position of the nozzle 15 in the ejection state is specified.

According to the above configuration, the control unit 100 causes ink droplets to be ejected all at once from one nozzle row 16, and estimates the positions of non-ejecting nozzles. Furthermore, the controller 100 selects a predetermined number of nozzles 15 . The predetermined number of nozzles 15 includes nozzles 15 at estimated positions. Thereafter, for a predetermined number of nozzles 15, ejection of ink droplets and comparison of waveforms are performed, and the positions of non-ejection nozzles are specified.

Therefore, the droplet ejection device 1 according to an aspect of the present invention combines rough detection processing and detailed detection processing when specifying the position of a non-ejection nozzle. The former is a process of estimating the positions of non-ejection nozzles, and ejects ink droplets from all the nozzles 15 all at once. The latter is a process of specifying the non-ejection nozzle position, and ejects an ink droplet from the selected nozzle 15 . Therefore, even with a simple configuration that does not include a plurality of detection plates 51, the positions of non-ejection nozzles can be specified efficiently in a short period of time.

Therefore, the detection plate 51 occupies a small space. Therefore, the droplet discharge device 1 can detect the presence or absence of non-discharge nozzles and their positions with a simple configuration.

Further, in the configuration described above, when the signal detection section 52 detects an electrical signal, the control section 100 causes each nozzle 15 to eject one ink droplet with the maximum droplet volume.

According to the above configuration, since the size of the ink droplet is the largest, the electrical signal detected by the signal detection section 52 has the strongest detection strength.

Therefore, the droplet ejection device 1 can improve the detection accuracy of the presence or absence of non-ejection nozzles and their positions with respect to the plurality of nozzles 15 .

Further, in the above configuration, the head 10 has a pressure chamber communicating with the nozzle 15 and a piezoelectric element that changes the volume of the pressure chamber. When an electrical signal is detected, no ink droplets are ejected from the nozzles 15 other than the predetermined number of nozzles 15 that eject ink droplets, and the piezoelectric element is driven so that the meniscus formed in the nozzles 15 vibrates. .

According to the above configuration, when detecting the position of a non-ejecting nozzle, the meniscus is vibrated without ejecting ink droplets for the nozzles 15 that are not the target of the detection process. Therefore, drying of these nozzles 15 is suppressed.

Further, in the above configuration, the plurality of nozzles 15 constitute a nozzle row 16 extending along one direction, and the range in which one detection surface 51a faces with respect to one direction covers all the nozzles constituting the nozzle row 16. It extends over 15 flight areas R.

A single detection surface 51 a covers the flying region R of all the nozzles 15 that make up the nozzle row 16 . Therefore, the configuration of the droplet discharge device 1 is simplified.

In the above configuration, the nozzle row 16 includes, in one direction, an end nozzle arranged at an end, a plurality of near-end nozzles continuously arranged adjacent to the end nozzle, and the end nozzle and the near-end nozzle. and the rest of the central nozzles excluding It is determined whether or not the end nozzle is in the non-ejection state, and if the end nozzle is not in the non-ejection state, the positions of the non-ejection nozzles are estimated for the nozzles near the end and the central nozzle.

According to the above configuration, the control unit 100 determines whether or not the end nozzle is in the non-ejection state. After that, if the end nozzle is not in the non-ejection state, the control unit 100 estimates the position of the nozzle in the non-ejection state for the nozzles near the end and the central nozzle. Therefore, it is possible to estimate the position of the non-ejecting nozzle without including a large error.

In the above-described configuration, the control unit 100 forms a plurality of groups of the same number of nozzles 15 adjacent in one direction without other nozzles 15 interposed therebetween for a predetermined number of nozzles 15, and for each group Based on the waveform of the electrical signal detected when the ink droplets are ejected all at once, the position of the nozzle 15 in the non-ejection state is identified.

According to the above configuration, the control unit 100 divides the predetermined number of nozzles into a plurality of groups. At this time, the number of nozzles 15 included in each group is the same. Therefore, when specifying the position of the ejection failure nozzle, the control unit 100 can specify the position with high accuracy.

Also, the number of nozzles 15 constituting each group is the same. Therefore, if the reference waveform is stored in advance, the control unit 100 can easily identify groups that include non-ejection nozzles. Therefore, the control unit 100 can easily identify the position of the ejection failure nozzle with a simple device configuration.

In the above description, each group was composed of the same number of nozzles. However, if the inclusion of non-ejection nozzles can be individually determined for each nozzle, each group does not necessarily have to have the same number.

Further, when the predetermined number of nozzles 15 is an odd number, the control unit 100 newly adds one nozzle 15 that is continuous on either side of the predetermined number of nozzles 15 in one direction, and Configure multiple non-overlapping groups. By setting the predetermined number to an even number in the non-ejection nozzle position specifying process, the control unit 100 can specify the position in a short time with high accuracy.

In the above-described configuration, the droplet ejection device 1 stores in advance the waveform information of the electrical signals detected by the signal detection unit 52 when ink droplets are simultaneously ejected from all the nozzles 15 when there is no ejection failure nozzle. The control unit 100 is further provided with a storage unit 145 for storing, and prior to estimating the position of the ejection failure nozzle, the control unit 100 simultaneously ejects ink droplets from all the nozzles 15, and detects the electric signal detected by the signal detection unit 52. The waveform information is compared with the waveform information stored in the storage unit 145 to determine the presence or absence of non-ejecting nozzles 15, and when it is determined that there are non-ejecting nozzles 15, end nozzles are non-ejecting. Determine whether the state is

According to the above configuration, first, it is determined whether or not there is a nozzle 15 that is in a non-ejection state. Therefore, when there is no non-ejecting nozzle 15, there is no need to perform simultaneous ejection to specify the position of the non-ejecting nozzle. Therefore, it is possible to suppress ink consumption and simplify the process of specifying the non-ejection nozzle position.

In the configuration described above, the predetermined number of nozzles 15 selected when identifying the positions of non-ejecting nozzles is given by the standard deviation of the positions of the nozzles 15 determined by the control unit 100 based on the electrical signal as σ. , the total number of nozzles 15 within a range of 2σ on both sides in one direction from the position of one nozzle 15 as the center, and less than or equal to the total number of nozzles 15 within a range of 4σ on both sides in one direction. is.

Here, the range defined by 2σ includes non-ejection nozzles with a probability of 95%. A non-ejection nozzle is included in the range defined by 3σ with a probability of 99.7%. Furthermore, the range defined by 4σ includes non-ejection nozzles with a probability of 99.994%. In other words, the predetermined number of nozzles 15 includes non-ejection nozzles with a probability of almost 100%.

Therefore, the accuracy of specifying the nozzles 15 is improved. Further, since the upper limit is set to be equal to or less than the total number of nozzles 15 within the range of 4σ, it is possible to shorten the time required for the non-ejection nozzle determination process without excessively increasing the number of groups to be set.

Therefore, the position of the nozzle 15 in the non-ejection state can be efficiently specified without omission.

A control method of the droplet ejection device 1 according to an aspect of the present invention is the control method of the droplet ejection device 1 described above. The control method of the droplet ejection device 1 estimates the position of the non-ejection nozzle 15 based on the waveform of the electrical signal detected by the signal detection unit 52 when ink droplets are simultaneously ejected from all the nozzles 15 . A first step, a second step of extracting a predetermined number of nozzles 15 arranged continuously in one direction, including the nozzles 15 estimated to be in a non-ejecting state, and a second step of extracting the nozzles 15 included in the predetermined number of nozzles. and a third step of identifying the position of the nozzle 15 in the non-ejection state based on the waveform of the electrical signal detected by the signal detection unit 52 when the ink droplet is ejected.

According to the above method, when specifying the position of the ejection failure nozzle, rough detection processing and detailed detection processing are combined. The former is a process of estimating the positions of non-ejection nozzles, and ejects ink droplets from all the nozzles 15 all at once. The latter is a process of specifying the non-ejection nozzle position, and ejects an ink droplet from the selected nozzle 15 . Therefore, even with a simple configuration that does not include a plurality of detection plates 51, the positions of non-ejection nozzles can be specified efficiently in a short period of time.

Therefore, in the control method of the droplet ejection device 1, the sensing plate 51 occupies a small space. Therefore, the droplet discharge device 1 can detect the presence or absence of non-discharge nozzles and their positions with a simple configuration.

Further, in the above method, the plurality of nozzles 15 constitute a nozzle row 16 extending along one direction, and the range in which one detection surface 51a faces with respect to the one direction corresponds to all the nozzles constituting the nozzle row 16. It extends over the flight area R.

Therefore, the configuration related to the signal detection section is simplified, and the degree of freedom in arranging the detection plate is increased.

Further, in the above method, the predetermined number of nozzles 15 selected when specifying the positions of non-ejecting nozzles is given by the following: More than the total number of nozzles 15 within a range of 2σ on both sides in one direction from the position of one nozzle 15 as the center, and less than the total number of nozzles 15 within a range of 4σ on both sides in one direction. be. Therefore, the position of the nozzle 15 in the non-ejection state can be efficiently specified without omission.

INDUSTRIAL APPLICABILITY The present invention can be applied to, for example, an inkjet printer that ejects droplets onto a medium from a plurality of nozzles.

1 droplet discharge device 10 inkjet head 10a nozzle surface 15 nozzle 16 nozzle row 50 non-discharge nozzle detection section 51 detection plate 51a detection surface 52 signal detection section 100 control section 144 non-discharge nozzle determination control section 145 storage section P paper R flying area

Claims (12)

a droplet discharge head having a plurality of nozzles arranged at regular intervals in one direction;
a detection plate having a detection surface arranged to face part of each of the flight areas formed by the droplets ejected from the plurality of nozzles in a direction orthogonal to the ejection direction of the droplets;
a signal detection unit that detects an electrical signal induced in the detection plate by the droplet passing through the range in the flight region where the detection surface faces;
a control unit;
When the droplets are simultaneously discharged from all the nozzles, the detection surface is arranged in the discharge direction such that the timing at which the droplets pass through the range differs for each nozzle with respect to the range where the detection surface faces. An upstream end position and a downstream end position of the sensing surface are defined,
The control unit
estimating the position of the nozzle in the non-ejection state based on the waveform of the electrical signal detected by the signal detection unit when droplets are simultaneously ejected from all the nozzles;
of the electrical signal detected by the signal detection unit when droplets are further ejected from a predetermined number of the nozzles arranged continuously in the one direction, including the nozzle estimated to be in a non-ejecting state; A liquid droplet ejecting device that identifies positions of the nozzles that are in a non-ejecting state based on waveforms. When detecting the electrical signal induced in the detection plate by the signal detection unit,
The control unit
2. The droplet ejection device according to claim 1, wherein each nozzle ejects one droplet of maximum droplet volume. The droplet discharge head is
having a pressure chamber communicating with the nozzle and a piezoelectric element that changes the volume of the pressure chamber;
The control unit
When the signal detection unit detects the electrical signal induced in the detection plate, droplets are not ejected from the nozzles other than the predetermined number of nozzles that eject droplets, and the nozzles are formed. 3. The droplet discharge device according to claim 1, wherein the piezoelectric element is driven so that the meniscus vibrates. The plurality of nozzles constitute a nozzle row extending along the one direction, and the range in which the one detection surface faces in the one direction is the flying region corresponding to all the nozzles constituting the nozzle row. 4. A droplet ejection device according to any one of claims 1 to 3, extending across. The nozzle row is
an end nozzle arranged at an end in the one direction, a plurality of near-end nozzles continuously arranged adjacent to the end nozzle, and remaining central nozzles excluding the end nozzle and the near-end nozzle; including
The control unit
When estimating the position of the nozzle in the non-ejection state, determining whether or not the end nozzle is in the non-ejection state based on the waveform of the electrical signal when droplets are simultaneously ejected from all of the nozzles; 5. The liquid droplet ejecting apparatus according to claim 4, wherein if an end nozzle is not in a non-ejecting state, the positions of the nozzles in the non-ejecting state are estimated for the near-end nozzles and the central nozzle. The control unit
For the predetermined number of nozzles, a plurality of groups consisting of the same number of the nozzles adjacent to each other in the one direction without intervening other nozzles are formed, and detection is performed when droplets are simultaneously discharged for each of the groups. 6. The liquid droplet ejection device according to claim 1, wherein the position of the nozzle in the non-ejection state is specified based on the waveform of the electrical signal applied. The control unit
When the predetermined number of nozzles is an odd number, one nozzle is newly added that is continuous on either side of the predetermined number of nozzles in the one direction, and the plurality of nozzles that do not overlap each other are added. 7. The droplet ejection device according to claim 6, forming a group. a storage unit for pre-storing waveform information of the electrical signal detected by the signal detection unit when droplets are simultaneously ejected from all the nozzles when there is no nozzle in the non-ejection state ;
The control unit
Prior to estimating the positions of the nozzles in the non-ejection state, liquid droplets are simultaneously ejected from all the nozzles, and waveform information of the electrical signal detected by the signal detection unit is stored in the storage unit. It is determined whether or not there is a non-ejecting nozzle by comparing with the stored waveform information, and if it is determined that there is a non-ejecting nozzle, it is determined whether the end nozzle is in the non-ejecting state. 8. A droplet ejection device according to any one of claims 5 to 7, wherein the droplet ejection device is defined. The predetermined number of the nozzles selected when specifying the positions of the nozzles in the non-ejection state is
Let σ be the standard deviation of the positions of the nozzles determined by the control unit based on the electrical signals. 9. The liquid droplet ejection device according to claim 1, wherein the total number of nozzles is greater than or equal to the total number of nozzles and less than or equal to the total number of nozzles within a range of 4[sigma] on both sides in the one direction. a droplet discharge head having a plurality of nozzles arranged at regular intervals in one direction;
a detection plate having a detection surface arranged to face part of each of the flight areas formed by the droplets ejected from the plurality of nozzles in a direction orthogonal to the ejection direction of the droplets;
a signal detection unit that detects an electrical signal induced in the detection plate by the droplet passing through the range in the flight region where the detection surface faces;
a control unit;
When the droplets are simultaneously discharged from all the nozzles, the detection surface is arranged in the discharge direction such that the timing at which the droplets pass through the range differs for each nozzle with respect to the range where the detection surface faces. A control method for a droplet discharge device in which an upstream end position and a downstream end position of the detection surface are defined,
a first step of estimating the position of the non-ejecting nozzle based on the waveform of the electrical signal detected by the signal detection unit when droplets are simultaneously ejected from all the nozzles;
a second step of extracting a predetermined number of the nozzles arranged continuously in the one direction, including the nozzles estimated to be in a non-ejecting state;
a third step of specifying the position of the nozzle in the non-ejection state based on the waveform of the electrical signal detected by the signal detection unit when droplets are ejected again from the nozzles included in the predetermined number of nozzles; and a control method for a droplet ejection device. The plurality of nozzles constitute a nozzle row extending along the one direction, and the range in which the one detection surface faces in the one direction is the flying region corresponding to all the nozzles constituting the nozzle row. 11. The method of controlling a droplet ejection device according to claim 10, wherein the droplet ejection device extends over a The predetermined number of the nozzles selected when specifying the positions of the nozzles in the non-ejection state is
Let σ be the standard deviation of the positions of the nozzles determined by the control unit based on the electrical signals. 12. The method of controlling a droplet discharge device according to claim 10, wherein the total number of nozzles is greater than or equal to the total number of nozzles and less than or equal to the total number of nozzles within a range of 4[sigma] on both sides in the one direction.

Images