JP4457249B2 - Inkjet printer - Google Patents

Description

  The present invention relates to detection of ejection failure of nozzles of an ink jet printer.

  Conventional inkjet printers record an image by ejecting ink droplets onto a storage medium from a plurality of nozzles using a thermal method, a piezo method, or the like, based on an image signal. In an ink jet printer, ink may adhere to the vicinity of the nozzle discharge port due to ink drying or increase in viscosity when left unused for a long period of time, or impurities (dust) may adhere to the nozzle discharge port. The nozzle is clogged by the nozzle, and the nozzle ejection failure (hereinafter referred to as nozzle missing) is that ink droplets are not ejected from the nozzle ejection port even though the ink ejection signal is normally output from the drive circuit unit. Occurs. When the nozzles are missing, the printed characters and images are whitened to form white stripes, or the print quality is deteriorated such that the color of the recorded image is different due to insufficient ink coloring material. As such a missing nozzle detection means, an optical detection means is disclosed (for example, see Patent Document 1).

Japanese Patent Application Laid-Open No. 2004-133826 discloses a nozzle missing detection unit for a carriage-type inkjet printer that ejects ink in a direction (main scanning direction) perpendicular to the paper transport direction (sub-scanning direction). An ink discharge state detection method is disclosed in which a missing nozzle is detected by changing a detection timing using a photosensor that combines a light emitting element and a light receiving element at a distance corresponding to the head width.
JP-A-11-188853

However, when Patent Document 1 is applied to a line head type ink jet printer, since the length of one line head is long, it is necessary to adjust the amount of light and the beam diameter of the light emitting element with high accuracy. Must be moved using a highly accurate positioning sensor, which causes an increase in cost. And the distance from a light emitting element to a light receiving element becomes long, and there exists a possibility that it may be misdetected by the ink droplet which became dust or a mist form.
Furthermore, 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.

  SUMMARY OF THE INVENTION An object of the present invention is to provide an ink jet printer capable of accurately detecting a missing nozzle by using an impact force when ink ejected from a nozzle is landed.

According to a first aspect of the present invention, in an ink jet printer that records an image on a recording medium by ejecting ink from a nozzle, the ink cartridge is curved in a semi-cylindrical shape, and the maximum protrusion on the curved outer peripheral surface is the arrival of the ink droplet. A film-like piezoelectric element that is disposed in front of the nozzle and is provided in front of the ink droplet ejection direction of the nozzle to detect ejection failure of the nozzle, and the film-like piezoelectric element in which one end in the bending direction is fixed The other end side of the element can be moved toward and away from the one end side, and the maximum projecting portion on the curved outer peripheral surface is adapted to the landing position of the ejected ink droplet, and supports the film-like piezoelectric element. An ink droplet receiver that receives ink droplets that are interposed between the position adjusting means and the nozzles and the film-like piezoelectric element and are ejected from the nozzles. And a plurality of grooves that are parallel to each other are formed on the ink droplet landing surface of the ink droplet receiving means, and the grooves are open at least at one end in the longitudinal direction, and on one end side in the longitudinal direction. The open portion is inclined so as to be positioned vertically downward with respect to the other end side.
According to a second aspect of the present invention, in an ink jet printer that records an image on a recording medium by ejecting ink from a nozzle, the ink cartridge is curved in a semi-cylindrical shape, and the maximum protrusion on the curved outer peripheral surface is the arrival of the ink droplet. A film-like piezoelectric element that is disposed in front of the nozzle in the ink droplet ejection direction to detect ejection failure of the nozzle, and one end side in the bending direction of the film-like piezoelectric element; It is configured to be able to translate in the same direction while maintaining a constant distance from the other end side, and is configured to adapt the maximum protruding portion on the curved outer peripheral surface to the landing position of the ejected ink droplet, and supports the film-like piezoelectric element An ink droplet receiver that receives ink droplets that are interposed between the position adjusting means and the nozzles and the film-like piezoelectric element and are ejected from the nozzles And a plurality of grooves that are parallel to each other are formed on the ink droplet landing surface of the ink droplet receiving means, and the grooves are open at least at one end in the longitudinal direction, and open at one end in the longitudinal direction. The portion is inclined so as to be positioned vertically downward with respect to the other end side.
According to a third aspect of the present invention, in an ink jet printer that records an image on a recording medium by ejecting ink from a nozzle, the ink cartridge is curved in a semi-cylindrical shape, and the maximum protrusion on the curved outer peripheral surface is the arrival of the ink droplet. A film-like piezoelectric element that is provided in front of the ink droplet ejection direction of the nozzle to detect ejection failure of the nozzle, one end side in the bending direction of the film-like piezoelectric element, and A position adjusting means for supporting the film-like piezoelectric element, wherein the other end side can be moved relatively close to and away from, and the maximum projecting portion on the curved outer peripheral surface is adapted to the landing position of the ejected ink droplet; An ink droplet receiving means interposed between the nozzle and the film-like piezoelectric element for receiving ink droplets ejected from the nozzle. The ink droplet receiving surface of the ink droplet receiving means is formed with a plurality of grooves that are parallel to each other, at least one end in the longitudinal direction is open, and the opening on one end in the longitudinal direction is the other end It is characterized by being inclined so as to be positioned vertically downward with respect to the side.

According to a fourth aspect of the present invention, in the ink jet printer according to any one of the first to third aspects, the arrangement pitch of the grooves is equal to the arrangement pitch of the nozzles.

According to a fifth aspect of the present invention, in the ink jet printer according to any one of the first to third aspects, the bottom of the groove and the landing position of ink droplets flying from the nozzle coincide with each other. A drip receiving means is provided.

According to a sixth aspect of the present invention, in the ink jet printer according to any one of the first to third aspects, the ink droplet receiving means can transmit an impact force upon landing of the ejected ink droplets to the film-like piezoelectric element. It is featured in that.

A seventh aspect of the present invention is the ink jet printer according to any one of the first to sixth aspects, wherein the ink droplet receiving means opposes a maximum protrusion on the curved outer peripheral surface of the film-like piezoelectric element. It has a protruding portion that is provided at a position and transmits an impact force upon landing of an ink droplet to the maximum protruding portion.

According to an eighth aspect of the present invention, in the ink jet printer according to any one of the first to seventh aspects, a sampling signal is generated by delaying an ink ejection signal for ejecting an ink droplet from a nozzle by a predetermined time. A sampling means for extracting a detection signal output from the film-like piezoelectric element upon landing of an ink droplet based on the sampling signal, a voltage value of the sampling detection signal extracted by the sampling means, and a preset reference voltage value And a judging means for judging a discharge failure of the nozzle by comparing with the above.

The invention described in claim 9, in an ink jet printer according to claim 8, wherein the determination means compares the said reference voltage value and the maximum voltage value of the sampling detection signal, the maximum voltage value of the sampled detection signal Is lower than the reference voltage value, it is determined that there is a nozzle ejection failure.

According to a tenth aspect of the present invention, in the ink jet printer according to any one of the first to ninth aspects, the number of ink droplet ejections and the voltage value of the sampling detection signal are equal to or higher than a preset reference voltage value. It is characterized by comprising a judging means for comparing the number of times and, if the two times do not match, judging that there is a nozzle ejection failure.

The invention described in claim 11, in the ink jet printer according to any one of claims 1 to 10, compares the output period of the output frequency as the ink ejection signal of the sampling detection signal, both periods coincide If not, a determination means for determining that there is a nozzle ejection failure is provided .

The invention according to claim 1 2, in the inkjet printer according to any one of claims 1 1 1, the inkjet printer is characterized in that, with a maintenance unit to eliminate the ejection failure of the nozzle .

The invention according to claim 1 3, in the ink jet printer according to claim 1 2, wherein the maintenance unit is characterized in that, to eliminate the ejection failure of the nozzle by the suction operation or the flushing operation.

According to the invention described in any one of claims 1 to 3, a plurality of grooves that are parallel to each other are formed on the ink droplet landing surface of the ink droplet receiving means, and the grooves are open at least at one end in the longitudinal direction. In addition, since the opening portion on one end side in the longitudinal direction is inclined so as to be positioned vertically downward with respect to the other end side, the ink droplet flows down along the groove every time the ink droplet lands, It is possible to remove ink droplets from the landing surface without actively removing ink droplets that have landed on the landing surface, and to accurately detect the impact force due to the landing of ink droplets, thereby determining the ejection failure of the nozzle. Accuracy can be improved.
Moreover, the sensitivity characteristic and directivity of a piezo film can be improved by arranging the piezo film so as to be curved in a semi-cylindrical shape and the maximum protruding portion on the curved outer peripheral surface thereof to be directed in the arrival direction of the ink droplet.
Further, by providing a position adjusting means for adapting the maximum protrusion on the curved outer peripheral surface of the film-like piezoelectric element to the landing position of the ink droplet, the shape of the film-like piezoelectric element can be adjusted, and the response of the film-like piezoelectric element The characteristics can be adjusted. In addition, by adjusting the response characteristics of the film-shaped piezoelectric element before ink droplet ejection, a signal from the film-shaped piezoelectric element is generated due to some kind of impact (such as operation vibration of the machine itself or improper installation position of the ink droplet receiving means). Can be adjusted so as not to be output, and a high response characteristic can be ensured, so that a change in detection signal due to the landing of a minute ink droplet can be detected with high accuracy.
Further, according to the invention described in claim 1, the other end side of the film-like piezoelectric element having one end side in the bending direction fixed can be moved toward and away from the one end side, and the maximum projecting portion on the curved outer peripheral surface is By being configured to be adapted to the landing position of the ejected ink droplets, the position of the maximum protrusion can be adjusted vertically and horizontally, and the response characteristics of the film-like piezoelectric element can be adjusted.
Furthermore, according to the second aspect of the present invention, the maximum protrusion on the curved outer peripheral surface can be translated in the same direction while keeping the distance between the one end side and the other end side of the film-shaped piezoelectric element constant. By being configured to match the landing position of the ejected ink droplets, the position of the maximum protrusion on the curved outer peripheral surface can be adjusted to the left and right without changing the curved shape of the film-like piezoelectric element. The response characteristic of the piezoelectric element can be adjusted.
Furthermore, according to the third aspect of the invention, the one end side and the other end side in the bending direction of the film-like piezoelectric element can be relatively moved toward and away from each other, and the maximum protruding portion on the curved outer peripheral surface is landed on the ejected ink droplet. By being configured to adapt to the position, the curved shape of the film-like piezoelectric element can be changed, and the position of the maximum protrusion on the curved outer peripheral surface can be adjusted up and down, and the response characteristics of the film-like element can be adjusted It becomes.

According to the fourth aspect of the present invention, the same effect as in any one of the first to third aspects can be obtained, and since the groove pitch is equal to the nozzle pitch, the nozzle A groove corresponding to each ejection port can be formed, and ink droplets can be discharged efficiently.

According to the fifth aspect of the present invention, the same effects as in any one of the first to third aspects can be obtained, as well as the bottom of the groove and the landing positions of ink droplets flying from the nozzles. By providing the ink drop receiving means so that they match, the ink drop can be prevented from splashing on the upper end of the groove and scattered, and the ink drop can be discharged efficiently, and the impact force due to the landing of the ink drop Can be received efficiently.

According to the sixth aspect of the present invention, the ink droplet receiving means can not only obtain the same effect as any one of the first to third aspects but also the impact force when the ejected ink droplets land. By being provided so as to be able to transmit to the film-like piezoelectric element, ink droplet landing can be detected using the film-like piezoelectric element, and the lack of nozzles can be detected with an easy configuration. Can be planned.

According to the seventh aspect of the invention, it is possible to obtain the same effect as in any one of the first to sixth aspects, and the ink droplet receiving means is the maximum on the curved outer peripheral surface of the film-like piezoelectric element. When the protrusion on the curved outer peripheral surface comes into contact with the protrusion by providing the protrusion that is provided at a position facing the protrusion and transmits the impact force upon landing of the ink droplet to the maximum protrusion, the nozzle When the ink droplets from the ink droplets land on the ink droplet receiving member, a minute impact force due to the landing of the ink droplets received by the landing surface of the ink droplet receiving member can be concentrated on the protruding portion, and the maximum protruding portion of the piezo film can Therefore, the impact force due to the landing of the ink droplet can be transmitted efficiently, and high sensitivity characteristics and response characteristics can be obtained.

According to the eighth aspect of the invention, the same effect as in any one of the first to seventh aspects can be obtained, and an ink ejection signal for ejecting ink droplets from the nozzles is delayed by a predetermined time. A sampling means for extracting a detection signal output from the film-like piezoelectric element upon landing of the ink droplet, and a voltage value of the sampling detection signal extracted by the sampling means based on the sampling signal. By means of comparing with a set reference voltage value to determine a nozzle ejection failure, ink droplet landing is detected using a film-like piezoelectric element, and nozzle ejection failure is facilitated. Therefore, it is possible to reduce the apparatus cost.

According to the ninth aspect of the invention, it is possible to obtain the same effect as that of the eighth aspect, and the judging means compares the maximum voltage value of the sampling detection signal with a preset reference voltage value. When the maximum voltage value of the sampling detection signal is lower than the reference voltage value, it can be determined that there is a nozzle ejection failure, so that it is possible to improve the detection accuracy of the nozzle ejection failure.

According to the tenth aspect of the present invention, it is possible to obtain the same effect as any one of the first to ninth aspects , and the judging means can determine the number of ink droplet ejections and the voltage of the sampling detection signal. Compare the number of times the value is greater than or equal to a preset reference voltage value, and if the two numbers do not match, it can be determined that there is a nozzle ejection failure, so the accuracy of detecting nozzle ejection failure can be improved. it can.

According to the invention described in claim 11, that of course obtain the same effects as any one of claims 1 to 10, the determination unit includes an output period of the sampling detection signal of the ink ejection signal Compared with the output cycle, if the two cycles do not match, it can be determined that there is a nozzle ejection failure, so the detection accuracy of the nozzle ejection failure can be improved.

According to the invention of claim 1 2, that of course obtain the same effects as any one of claims 1 1 1 is provided with the maintenance unit to eliminate the ejection failure nozzle, It is possible to reliably and efficiently eliminate nozzle discharge defects.

According to the invention described in claims 1 to 3, that of course obtain the same effect as claim 1 2, by eliminating the ejection failure of the nozzle by the suction operation or the flushing operation, reliably and efficiently Nozzle ejection defects can be eliminated.

Hereinafter, embodiments 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 head type ink jet printer 1 according to the present embodiment. As shown in FIG. 1, the inkjet printer 1 includes a paper feeding unit 10, a transport unit 20, a head unit unit 30, a paper discharge unit 40, a maintenance unit 50 as maintenance means, a nozzle missing detection unit 60, and the like. ing.

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. Further, the transport belt 21 is provided with an opening 21a so that a later-described nozzle missing detection unit 60 can operate and the capping module covers the nozzle discharge port. An encoder film and an encoder sensor are provided at the end of the conveyor belt so that the opening 21a is positioned below the nozzle discharge port at the time of nozzle missing determination and maintenance, and the opening is based on a detection signal from the encoder sensor. The position of 21a is detected (not shown).

  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 head type head units 31, 32, 33, 34 for each ink color provided with a plurality of nozzle discharge ports (not shown) for discharging are provided over the entire width of the transport 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.

  Each head unit 31, 32, 33, 34 extends in a direction substantially orthogonal to the recording medium P conveyance direction X. In addition, each head unit 31, 32, 33, 34 has a plurality of head modules arranged in parallel in the longitudinal direction. The head modules extend in the longitudinal direction of the head units 31, 32, 33, and 34 and are arranged in parallel so as to be staggered (staggered arrangement) at a predetermined interval in the conveyance direction X of the recording medium P.

  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.

  The maintenance unit 50 is provided so as to face the lower part of the head unit part 30 with the vicinity of the lower part of the upper surface of the transport belt 21 interposed therebetween. The maintenance unit 50 includes a plurality of cap units 51, 52, 53, and 54 that cover the nozzle discharge ports, a suction pump (not shown), a waste ink tank, and the like.

  Each cap unit 51, 52, 53, 54 is provided with a plurality of capping modules (not shown) corresponding to each head module of each head unit 31, 32, 33, 34. Each capping module is movable to a cap position that covers the nozzle ejection port of the corresponding head module and a separation position that is separated from the nozzle ejection port. Each capping module is connected to a suction pump that sucks fluid in the space formed after moving to the cap position, covering the entire nozzle discharge port with a rubber member, etc., and blocking and sealing the outside air, etc. Yes. 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. Note that 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 present embodiment, an example in which a typical suction operation is employed as a maintenance method as means for eliminating nozzle shortage will be described. However, an electrical signal is given to the head, ink droplets are ejected, and nozzle ejection is performed. You may employ | adopt the flushing operation | movement which blows away the foreign material adhering to an exit and a nozzle discharge surface.
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.

  The nozzle missing detection unit 60 is provided so as to face the lower part of the head unit part 30 with the vicinity of the lower part of the upper surface of the transport belt 21 interposed therebetween, and at a predetermined position corresponding to each head unit 31, 32, 33, 34. It is movable. A plurality of the head modules are arranged in parallel at predetermined intervals in the transport direction X of the recording medium P so as to correspond to the head modules.

FIG. 2 shows an end view of the nozzle missing detector 60.
FIG. 2A shows a state where no ink droplets are received from the head module 31a (initial state), and FIG. 2B shows a state where ink droplets are received from the head module 31a (operation state).
As shown in FIG. 2, the nozzle missing detection unit 60 includes an ink droplet receiving unit 61 as an ink droplet receiving unit, a piezo film 62 as a film-like piezoelectric element, a support unit 63 and an adjusting unit 64 as position adjusting units. It is configured.

  The ink droplet receiver 61 is formed of a cover 61a and an elastic support member 61b, and transmits an impact force upon landing of the ink droplets to the piezo film 62.

  The cover 61a has a landing surface S1 that receives ink droplets, and a contact surface S2 that transmits impact force by contacting the piezo film 62 when the ink droplets land on the landing surface S1. The contact surface S2 is provided at a position facing the maximum protrusion on the curved outer peripheral surface of the piezo film 62, and has a protrusion that transmits the impact force upon ink droplet landing to the maximum protrusion.

FIG. 3 shows the landing surface S1 of the cover 61a.
3A shows a schematic end view of the landing surface S1 of the cover 61a, and FIG. 3B shows a perspective view of an example of the plurality of grooves formed on the landing surface S1.
As shown in FIG. 3A, the landing surface S1 is inclined in one direction at a predetermined inclination angle θ with respect to a direction D perpendicular to the ink droplet ejection direction B, which is the same direction as the vertical direction. ing.

As shown in FIG. 3B, a plurality of grooves that are parallel to each other are formed on the landing surface S1. The groove is slanted so that one end side in the longitudinal direction is open and the open part on one end side in the longitudinal direction is positioned below the other end side in the vertical direction (that is, the discharge direction B). The groove pitch (hereinafter referred to as the groove pitch) d2 is formed to be equal to the nozzle pitch (hereinafter referred to as the nozzle pitch) d1.
The cover 61a in which such a groove is formed is provided so that the bottom of each groove matches the landing position of the ink droplets flying from the discharge port h of each nozzle.

By providing such a groove, the ink droplet ejected from the nozzle ejection port h flows down along the sloping direction C of the groove every time the ink droplet is landed, so that it is positively applied to the landing surface S1. The ink droplets can be discharged without removing the landed ink droplets, and the impact force due to the landing of the ink droplets can be detected with high accuracy, thereby improving the accuracy of determining the ejection failure of the nozzles.
Further, since the groove pitch d2 and the nozzle pitch d1 are equal, a groove corresponding to each nozzle outlet h can be formed, ink droplets can be discharged efficiently, and the bottom of the groove and the ink can be discharged. By being provided so that the landing positions of the droplets coincide with each other, it is possible to prevent ink droplets from colliding with the upper end of the groove and to scatter the ink droplets. The force can be efficiently received by the cover 61a.
The groove according to the present invention is effective in an ink jet printer using an ink having a relatively low viscosity at room temperature, such as oil-based ink or water-based ink. As a method for further improving the effect, for example, in an ink jet printer using water-based ink, ink droplets can be effectively eliminated by performing a water-repellent treatment on the surface of the cover 61a on which the ink droplets land.

  The cross-sectional shape of the groove shown in the present embodiment may be a curved shape other than a substantially semicircular shape as shown in FIG. 3, is a shape that efficiently discharges ink droplets, and This is not necessarily limited as long as it is easy to mold.

  Further, the cover 61a corresponds to the longitudinal direction of the head module so as to be interposed between the nozzle and the piezo film 62 in order to protect the piezo film 62 from various ink droplets in order to protect the response characteristics of the piezo film 62. It is extended and provided. More specifically, depending on the ink used, an ink jet printer that discharges ink by changing the physical property (viscosity) of the ink may detect ink droplets at a higher temperature by heating the ink than normal temperature. In such an ink, the temperature of the piezo film rises while receiving several tens of drops of ink, and the response characteristics of the piezo film may change. For this reason, the cover 61a has the purpose of preventing such a change in response characteristics. Further, when the ink to be used is a conductive ink, it also has an object of touching the output signal terminal of the piezo film to prevent the piezo film from being damaged.

  The cover 61a is kept in a fixed state by an elastic support member 61b provided at the bottom, and transmits a small impact force upon landing of an ink droplet to the piezo film 62. Therefore, the cover 61a is a lightweight member such as plastic. It is preferable to use a molded member that can produce a free shape.

  The elastic support portion 61b maintains the non-contact state between the contact surface S2 of the cover 61a and the piezo film 62 when the ink droplets are not landed on the landing surface S1, and the contact of the cover 61a when the ink droplets land. The cover 61a is supported so that the surface S2 and the piezo film 62 are in contact with each other.

  In the present embodiment, when no ink droplet is received on the landing surface S1, the contact surface S2 and the piezo film 62 are set in a non-contact state, but both may be in contact with each other. It is only necessary that the film 62 and the contact surface S2 remain stationary while maintaining a certain equilibrium state.

  The piezo film 62 is curved in a substantially semi-cylindrical shape by a support portion 63 in front of the ink droplet ejection direction from the nozzle, and is supported so that the maximum protruding portion on the curved outer peripheral surface is directed in the ink droplet arrival direction. The head module is provided so as to extend in the longitudinal direction of the head module.

  The present invention detects the landing of ink droplets using the piezoelectric effect of the piezo film 62. Therefore, in order to further improve the sensitivity characteristics and directivity of the piezo film 62, the piezo film 62 is curved into a substantially semi-cylindrical shape, and the ink droplets from the ink droplet arrival direction land on the maximum projecting portion of the curved outer peripheral surface ( That is, the maximum projecting portion of the piezo film 62 curved in a substantially semi-cylindrical shape is in contact with the projecting portion of the contact surface S of the cover 61a.

  The piezo film 62 used in the present invention is a film-like piezoelectric element that has a piezoelectric effect, good workability, a large area and can be easily thinned, and has excellent flexibility compared to conventional piezoelectric ceramics. The piezoelectric element may be any piezoelectric element that has high performance, impact resistance, chemical stability, etc., good output responsiveness to impact and shape change, and wide frequency characteristics.

  FIG. 4 shows an example of a cross-sectional view of the contact state between the contact surface S2 of the cover 61a and the piezo film 62. As shown in FIG. 4A shows a state where the maximum protrusion of the contact surface S2 of the cover 61a is in contact with the maximum protrusion of the piezo film 62, and FIG. 4B shows the contact surface S2 of the cover 61a and the piezo film 62. Shows a state of contact with.

  As shown in FIG. 4A, when the maximum protrusion of the cover 61a comes into contact with the maximum protrusion of the curved outer peripheral surface of the piezo film 62, when the ink droplet from the nozzle discharge port lands on the landing surface S1, the landing surface Since the minute impact force due to the landing of the ink droplet received in S1 can be concentrated on the maximum projecting portion of the contact surface S2, and can be received by the maximum projecting portion of the piezo film 62, the impact force due to the landing of the ink droplet is obtained. It can be transmitted efficiently, and high sensitivity characteristics and response characteristics can be obtained.

  As shown in FIG. 4B, when the contact is made at a position other than the maximum protrusion, the impact force due to the landing of the ink droplet received on the landing surface S1 is dispersed, and the dispersed impact force is further curved by the bending of the piezo film 62. Since it is received by the surface, the transmission efficiency of force is lowered, and sensitivity characteristics and response characteristics are lowered.

  In view of this, the position of the maximum projecting portion on the curved outer peripheral surface of the piezo film 62 is movable, and a support portion 63 and an adjustment portion 64 that match the ink droplet landing position are provided. By adapting the maximum protrusion on the curved outer peripheral surface of the piezo film 62 to the landing position of the ink droplet, the shape of the piezo film can be adjusted, and the response characteristics of the piezo film 62 can be adjusted.

The support part 63 supports the piezo film 62 by bending it into a substantially semicylindrical shape. The support part 63 is formed of a fixed support part 63a and a movable support part 63b. Opposing surfaces of the fixing instruction portion 63a and the movable support portion 63b are orthogonal to a rotation axis A of a screw 64a described later, and are provided in parallel to each other.
The fixed support portion 63a is fixed at one end in the bending direction of the piezo film 62, and is installed so as not to move regardless of the rotation of a screw 64a described later.
The movable support portion 63b supports the other end side facing the one end side in the bending direction fixed to the fixed support portion 63a, and has a female screw hole to be screwed with a male screw portion of a screw 64a described later. According to the rotation direction of the screw 64a, the fixed support portion 63a is provided so as to be able to approach or separate.

The adjustment part 64 is formed of a screw 64a and a support base 64b.
The screw 64 a is arranged so that the ink droplet ejection direction B and the rotation axis A of the screw 64 b are orthogonal to each other, and is rotatably supported by the support base 64 b and the casing 69. The screw 64a has a male screw portion formed in a movable range of the movable support portion 63b, and is screwed into a female screw hole of the movable support portion 63a.
For example, in FIG. 2A, when the screw 64a is rotated in the direction of the right screw, the movable support portion 63b is moved to the right side, and when rotated in the direction of the left screw, it is moved to the left side.

  Therefore, the opposite other end side where one end side of the piezo film 62 in the bending direction is fixed is supported so as to be movable toward or away from the fixed one end side, and the position of the maximum protrusion on the curved outer peripheral surface is landed on the ink droplet. By adapting to the position, the position of the maximum protrusion on the curved outer peripheral surface can be adjusted vertically and horizontally, and the response characteristics of the piezo film 62 can be adjusted.

5 and 6 show other end view examples 1 and 2 of the nozzle missing detector 60 shown in FIG.
5 and 6 has the same configuration except that the support portion 63 and the adjustment portion 64 of the nozzle loss detection portion 60 shown in FIG. 2 are different from the support portions 65 and 67 and the adjustment portions 66 and 68. Therefore, the description thereof is omitted.

The support portion 65 shown in FIG. 5 supports the piezo film 62 by bending it into a substantially semicylindrical shape. The support part 65 is formed of a first movable support part 65b1 and a second movable support part 65b2. Opposing surfaces of the first movable support portion 65b1 and the second movable support portion 65b2 are orthogonal to a rotation axis A of a screw 66a, which will be described later, and are provided in parallel with each other at a constant interval.
The first movable support portion 65b1 is fixed at one end in the bending direction of the piezo film 62, has a female screw hole that is screwed with a male screw portion of a screw 66a described later, and corresponds to the rotation direction of the screw 64a. It is provided so as to be able to reciprocate in the direction of the rotation axis A.
The second movable support portion 65b2 is fixed at the other end facing the one end side in the bending direction fixed to the first movable support portion 65b1, and has a female screw hole that is screwed with a male screw portion of a screw 66a described later. It is provided so as to be able to reciprocate in the direction of the rotation axis A according to the direction of rotation of the screw 64a.

The adjustment part 66 is formed of a screw 66a and a support base 64b.
The screw 66a is disposed so that the ink droplet ejection direction B and the rotation axis A of the screw 64b are orthogonal to each other, and is rotatably supported by the support base 64b and the casing 69. The screw 66a is formed with a male screw portion in the movable range of the first movable support portion 65b1 and the second movable support portion 65b2, and the female screw hole of the first movable support portion 65b1 and the second movable support portion 65b2. Screw together.
The first movable support portion 65b1 and the second movable support portion 65b2 are moved in parallel in the same direction according to the direction of the rotation axis A of the screw 66a while keeping the distance between them constant.
For example, in FIG. 5, when the screw 66a is rotated in the direction of the right screw, the first movable support portion 65b1 and the second movable support portion 65b2 are moved in parallel to the right side while maintaining a constant distance from each other. When it is rotated in the direction of, it is translated to the left side.

  Therefore, one end side of the piezo film 62 in the curving direction and the other end facing the other end side are supported so that they can be moved in parallel in the same direction, and the position of the maximum protrusion on the curved outer peripheral surface is adapted to the ink droplet landing position. By doing so, the position of the maximum protrusion on the curved outer peripheral surface can be adjusted to the left and right without changing the curved shape of the piezo film, and the response characteristics of the piezo film 62 can be adjusted.

The support portion 67 shown in FIG. 6 supports the piezo film 62 by bending it into a substantially semicylindrical shape. The support part 67 is formed of a first movable support part 67b1 and a second movable support part 67b2. Opposing surfaces of the first movable support portion 67b1 and the second movable support portion 67b2 are orthogonal to a rotation axis A of a screw 68a described later, and are provided in parallel to each other.
The first movable support portion 67b1 is fixed at one end in the bending direction of the piezo film 62, and has a female screw hole that is screwed with a male screw portion of a screw 68a described later, depending on the rotation direction of the screw 68a. It is provided so as to be relatively close to or away from the second movable support portion 67b2 in the direction of the rotation axis A.
The second movable support portion 67b2 is fixed to the other end side facing the one end side in the bending direction fixed to the first movable support portion 67b1, and has a female screw hole that is screwed with a male screw portion of a screw 68a described later. The first movable support portion 67b1 can be moved relatively close to or away from the first movable support portion 67b1 in the direction of the rotation axis A in accordance with the rotation direction of the screw 68a.

The adjustment unit 68 is formed of a screw 68a and a support base 64b.
The screw 68a is disposed such that the ink droplet ejection direction B and the rotation axis A of the screw 68b are orthogonal to each other, and is rotatably supported by the support base 64b and the casing 69. The screw 68a is formed in a direction in which the male screw portion faces the movable range of the first movable support portion 67b1 and the movable range of the second movable support portion 67b2, and the female portion of the first movable support portion 67b1. The screw holes are screwed into the female screw holes of the second movable support portion 67b2. The first movable support portion 67b1 and the second movable support portion 67b2 are relatively moved toward or away from each other according to the direction of the rotation axis A of the screw 68a.
For example, in FIG. 6, when the screw 68a is rotated in the direction of the right screw, the distance between the first movable support portion 67b1 and the second movable support portion 67b2 is moved away from it and rotated in the direction of the left screw. If it is, it is moved in the approaching direction.

  Accordingly, by supporting the one end side of the piezo film 62 in the bending direction and the other end side facing each other so as to be relatively close to or away from each other, and adjusting the position of the maximum protrusion on the curved outer peripheral surface to the landing position of the ink droplet, By changing the curved shape of the piezo film, the position of the maximum protrusion on the curved outer peripheral surface can be adjusted up and down, and the response characteristics of the piezo film 62 can be adjusted.

  Thus, by providing the support portion 63 and the adjustment portion 64, the curvature of the piezo film can be changed, the position of the maximum protrusion on the curved outer peripheral surface can be adjusted, and the distance between the cover 61a and the piezo film 62, And the initial shape of the piezo film 62 can be adjusted. Therefore, in the initial state, appropriate position adjustment can be performed so that a signal is not output from the piezo film 62 due to some impact (such as operation vibration of the apparatus itself or poor adjustment of the installation position of the ink droplet receiving member 60). . In addition, when an appropriate position adjustment is performed so as to match the landing of the ink droplet, a high response characteristic can be ensured in the operating state, so that a change in the landing of a minute ink droplet can be accurately detected. it can.

  The turning operation of the screws 64a, 66a, and 68a by the adjusting unit 64 may be performed manually or automatically. When the turning operation is performed automatically, for example, a feed screw mechanism using a ball screw or the like as the screws 64a, 66a, 68a may be applied to the adjustment unit 64. That is, for example, in the case of adjusting the initial shape of the piezo film 62, a rotation amount value corresponding to the shape of the piezo film 62 is stored in advance in a non-volatile memory under the control of the CPU, and a predetermined control device is used. The drive power from the drive source configured to be controllable can be transmitted to the screws 64a, 66a, 68a, so that the drive power of the drive source can be controlled based on the stored data in the nonvolatile memory. Thus, the amount of rotation can be automatically adjusted to adjust the position of the maximum protrusion on the curved outer peripheral surface, and the initial shape of the piezo film 62 can be adjusted.

  FIG. 7 shows a control block diagram for controlling the ink jet printer 1 in the present embodiment. As shown in FIG. 7, the control unit 100 and the nozzle missing detection circuit unit 200 are configured.

The control unit 100 includes a central processing unit (CPU) 110, a read only memory (ROM) 120, a random access memory (RAM) 130, an input / output (I / O) 140, and various machine control units 150. The I / F 160, the drive circuit unit 170, and the like are connected to the system bus 180, and are connected to the nozzle missing detection circuit unit 200 via the I / F 160.
The nozzle missing detection circuit unit 200 includes a shape correction circuit unit 210, an amplification circuit unit 220, a filter circuit unit 230, a peak hold unit 240 as sampling means, an A / D conversion circuit unit 250, and the like. ing.

  The CPU 110 reads the system program and each processing program and data stored in the ROM 120, expands them in the RAM 130, and centrally controls the operation of the entire inkjet printer 1 according to the expanded programs. Timing control of the entire system, data storage and accumulation control using the RAM 130, output of print data to each head module, input / output control of an operation unit (not shown), interface (I / F) and operation control with other applications Is what you do.

  In order to realize the present embodiment, the nozzle shortage is determined by appropriately setting the maximum voltage value, the number of counts, and the output cycle as the determination criteria for the nozzle shortage determination operation. If it is determined that there is a missing nozzle, control is performed to drive the maintenance unit 50 to eliminate the missing nozzle.

When the maximum voltage value is used as a determination criterion, a maximum voltage value V _max for each discharge of a sampling detection signal Sd ′ described later stored in the RAM 130 is calculated, and the maximum voltage value V _max and the reference voltage value V ₀ are calculated. Are compared to determine whether the nozzle is missing.

When the number of counts is used as a determination criterion, the number of times that the sampling detection signal Sd ′ is equal to or higher than a preset reference voltage value V ₀ is counted, and the counted number N is compared with the number of ejections n. Judge nozzle missing.

In the case where the output cycle is used as a determination criterion, the reference cycle T0 as the output cycle in which the ink discharge signal S _m1 is output is compared with the detection cycle T1 as the output cycle in which the sampling detection signal Sd ′ is output. Judge missing.

The ROM 120 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.
In order to realize the present embodiment, the reference voltage value V ₀ that is the maximum voltage value of the sampling detection signal Sd ′ when the ink droplets are appropriately ejected onto the landing surface S1, and the preset ink droplets The number of discharges n and a delay time t _d described later 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 order to realize the present embodiment, the sampling detection signal Sd ′ input from the A / D conversion circuit unit 250 via the I / F, the maximum voltage value V _max calculated by the CPU 110, and the sampling detection signal Sd by the counter. The number N of the number of times' is greater than or equal to the reference voltage value V ₀ , the reference period T 0 for outputting the ink ejection signal S _m1 timed by a timer, and the detection period T 1 for outputting the sampling detection signal Sd ′ Are temporarily stored in time series.

  The I / O 140 performs data input and output between the control unit 100 and the control unit of each unit. In order to realize the present embodiment, the shape correction control unit that controls the shape of the piezo film 62 and the maintenance control unit that controls the operation of the maintenance unit 50 are connected, and the ink supply / waste liquid control unit, waste It is connected to a control unit such as an ink control unit.

  Various machine control units 150 are configured to control various rollers of the sheet feeding unit 10 and the take-out device 12 based on an instruction from the CPU 110, a conveyance control unit that controls various rollers of the conveyance unit 20, and an inkjet printer. 1 is connected to a sensor control unit or the like that drives various sensors installed in the apparatus 1.

The drive circuit unit 170 drives the nozzles of the head modules of the head units 31, 32, 33, and 34 and discharges ink droplets from the nozzle discharge ports based on the print data and the discharge drive signal S _m0 from the CPU 110. The ejection signal S _m1 and the sampling signal Ss obtained by delaying the ink ejection signal S _m1 by the time until the ink droplets land on the landing surface S1 from the nozzle ejection port (hereinafter referred to as a delay time t _d ) are calculated. .
The calculated ink ejection signal S _m1 is output to the nozzles of each head module, and the sampling signal Ss is output to the peak hold unit 240.

Delay time t _d is determined based on the drive waveform condition of the ink ejection signal S _m1.
The drive waveform conditions are the type of ink to be ejected (for example, water-based ink, oil-based ink, UV curable ink, solid ink, etc.), ejection method (piezo method using a piezoelectric element, thermal method using a heater, etc.) It is determined by the head configuration and the like.

  Based on an instruction from the shape correction control unit, the shape correction circuit unit 210 makes the output piezoelectric vibration signal Sd constant within a preset initial value range when the piezo film 62 is in the initial state. The output signal from the piezo film 62 is adjusted.

  The piezo vibration signal Sd as a detection signal output from the piezo film 62 is amplified and adjusted by the amplifier circuit 220, and noise is removed by the filter circuit unit 230. The noise-removed piezo vibration signal Sd is input to the peak hold unit 240.

  The peak hold unit 240 extracts the piezo vibration signal Sd input from the filter circuit unit 230 based on the sampling signal Ss input from the drive circuit unit 170. The extracted piezo vibration signal Sd is A / D converted by the A / D conversion circuit unit 250 as a sampling detection signal Sd ′ and stored in the RAM 130 via the I / F 160.

FIG. 8 shows an example of a time chart of the operation of ejecting ink droplets from the nozzle ejection port.
As shown in FIG. 8, the ejection drive signal S _m0 as a signal for instructing the ink ejection operation output from the CPU 110 to the drive circuit unit 170, and the head of the head module 31a from the drive circuit unit 170 based on the ejection drive signal S _m0. There are an ink discharge signal S _m1 output to the piezo film 62 based on the sampling signal Ss output to the peak hold unit 240 and the ink discharge signal S _m1 .

When the ejection drive signal S _m0 is output, the ink ejection signal S _m1 is output. When the ink ejection signal S _m1 is output and the delay time t _d elapses, the sampling signal Ss is output. Further, when the delay time t _d has elapsed, since the ink droplets land on the landing surface S1, the piezoelectric vibration signal Sd is outputted. A piezo vibration signal Sd is extracted based on the sampling signal Ss, and a nozzle missing determination operation is performed.
When there is no missing nozzle, the reference period T0 at which the ink ejection signal S _m1 is output is equal to the detection period T1 at which the piezo vibration signal Sd is output.

Next, the nozzle missing operation performed in the control unit 100 will be described.
9 to 10 are flowcharts of the nozzle missing determination operation in the present embodiment.
The nozzle missing determination operation shown in FIG. 9 shows a case where determination is made based on the maximum voltage value V _max of the sampling detection signal Sd ′ as a determination criterion.

  A head unit for determining whether a nozzle is missing is set. After the head unit for determining whether or not the nozzle is missing is set, the nozzle missing detection unit 60 is moved to a predetermined position below the set head unit (step S1).

  After the nozzle missing detector 60 is moved to a predetermined position, the mechanical vibration of the nozzle missing detector 60 is stopped (step S2).

  After the nozzle missing detector 60 is stopped, the shape of the piezo film 62 is adjusted. Further, the output signal from the piezo film 62 is adjusted so that the piezo vibration signal Sd output from the piezo film 62 becomes constant within a preset initial value range. (Step S3).

  After the initial setting of the output signal from the piezo film 62 is completed, a nozzle for determining nozzle shortage is set (step S4).

An ink discharge signal S _m1 is output to the set nozzle, and ink droplets are discharged. When the ejected ink droplets land on the landing surface S1, a piezo vibration signal Sd is output from the piezo film 62, and a sampling detection signal Sd 'is stored in the RAM 130 based on the sampling signal Ss. The maximum voltage value V _max of the sampling detection signal Sd ′ is calculated and stored in the RAM 130 every time the ink droplet is ejected (step S5).

When the ink ejection operation from the set nozzle is performed n times, the maximum voltage value V _{max for} each ejection time stored in the RAM 130 in time series and the reference voltage value set in the ROM 120 V ₀ is read to the CPU 110 (step S6).

Then, in decision as decision means (S7), all the maximum voltage value V _max for each read discharge times is whether or not the reference voltage value greater than or equal _to V ₀ is determined.

When all the maximum voltage values V _max are equal to or higher than the reference voltage value V ₀ (step S7; Yes), it is determined that the ink droplet ejection operation is normal, and it is determined that there is no missing nozzle (step S8).

If all the maximum voltage values V _max are not equal to or higher than the reference voltage value V ₀ (step S7; No), it is determined whether or not the maximum voltage value V _{max in} the second half of the ink droplet ejection operation is equal to or higher than the reference voltage value V _0. Determination is made (step S9).

If the maximum voltage value V _max of the second half operation is greater than or equal to the reference voltage value V ₀ (step S9; Yes), it is determined that the ink droplet ejection operation is normal, and it is determined that there is no missing nozzle (step S8). .

If the maximum voltage value V _{max for} the second half of the operation is not equal to or higher than the reference voltage value V ₀ (step S9; No), it is determined that the ink droplet ejection operation has not been performed normally, and it is determined that there is a nozzle shortage (step S10). ).

  If it is determined that there is a nozzle shortage, a maintenance operation (for example, a suction operation) for eliminating the nozzle shortage is performed on the head module having a nozzle discharge port that requires maintenance (step S11).

Ink droplets are ejected from the nozzle ejection port a predetermined number of times, and the maximum voltage value V _max of the sampling detection signal Sd ′ based on the landing of the ink droplet is calculated for each ejection time, and the maximum voltage value V for all ejection times _{When max} and the reference voltage value V ₀ are compared, and the maximum voltage value V _max is lower than the reference voltage value V ₀ , it is determined that no ink droplets are ejected from the set nozzle ejection port (ie, there is a nozzle missing). can do. Furthermore, due to the structural characteristics of the ink jet head, ink discharge is not performed at the initial stage of the ink discharge operation, and the ink discharge is recovered by repeated operations (ink discharge operation) several times. Ink may be ejected during the operation, and the maximum voltage value V _max may be detected. Even in such a case, it is determined that there is no nozzle missing, and maintenance is performed only when maintenance is necessary. be able to.

  The nozzle missing determination operation shown in FIG. 10 shows a case where determination is made based on the count number N of the sampling detection signal Sd ′ as a determination criterion. Steps S21 to S24 shown in FIG. 10 are the same as steps S1 to S4 shown in FIG.

An ink discharge signal S _m1 is output to the set nozzle, and ink droplets are discharged. When the ejected ink droplets land on the landing surface S1, a piezo vibration signal Sd is output from the piezo film 62, and a sampling detection signal Sd 'is stored in the RAM 130 based on the sampling signal Ss. If the sampling detection signal Sd ′ is greater than or equal to the reference voltage value V _{0 for} each ink droplet ejection, counting is performed (step S25).

In the case where the ink ejection operation from the set nozzle is performed n times, the sampling detection signal Sd ′ stored in the RAM 130 in time series is the count number N that is equal to or higher than the reference voltage value V ₀ , and the ROM 120 The set number of discharges n is read out to the CPU 110 (step S26).

  Then, it is determined whether or not the count number N read in the determination step (S27) as determination means is equal to the number of ejections n.

  If the count number N is equal to the ejection number n (step S27; Yes), it is determined that the ink droplet ejection operation is normal, and it is determined that there is no missing nozzle (step S28).

  If the count number N and the ejection number n are not equal (step S27; No), it is determined whether or not the count is counted as the second half of the ink droplet ejection operation (step S29).

  When counted in the second half operation time (step S29; Yes), it is determined that the ink droplet ejection operation is normal, and it is determined that there is no missing nozzle (step S28).

  If it is not counted in the second half of the operation (step S29; No), it is determined that the ink droplet ejection operation has not been performed normally, and it is determined that there is a nozzle shortage (step S30).

  If it is determined that there is a nozzle shortage, a maintenance operation (for example, a suction operation) for eliminating the nozzle shortage is performed on the head module having a nozzle discharge port that requires maintenance (step S31).

Preset is discharged discharge count n times is the ink droplets from the nozzle discharge port, sampling the detection signal based on the landing of the ink droplet Sd 'counts the case where the reference voltage value greater than or equal _to V _0, are counted for each discharge times The count number N and the discharge number n are compared, and if the count number N and the discharge number n are not equal, it is determined that no ink droplet is discharged from the set nozzle discharge port (that is, there is a nozzle shortage). be able to. Furthermore, due to the structural characteristics of the ink jet head, ink discharge is not performed at the initial stage of the ink discharge operation, and the ink discharge is recovered by repeated operations (ink discharge operation) several times. Ink may be ejected and counted during the operation, but even in such a case, it is determined that there is no nozzle shortage, so that maintenance can be performed only when maintenance is necessary.

  The nozzle missing determination operation shown in FIG. 11 shows a case where determination is made based on an output cycle (detection cycle T1) in which the sampling detection signal Sd ′ is output as a determination criterion. Steps S41 to S44 shown in FIG. 11 are the same as steps S1 to S4 shown in FIG.

An ink discharge signal S _m1 is output to the set nozzle, and ink droplets are discharged. When the ejected ink droplets land on the landing surface S1, a piezo vibration signal Sd is output from the piezo film 62, and a sampling detection signal Sd 'is stored in the RAM 130 based on the sampling signal Ss. Each time an ink droplet is ejected, a reference period T0 at which the ink ejection signal S _m1 is output and a detection period T1 at which the sampling detection signal Sd ′ is output are timed and stored in the RAM 130. Ink droplets are ejected up to a preset ejection number n (step S45).

  When the ink ejection operation from the set nozzle is ejected n times in advance, the detection period T1 and the reference period T0 stored in time series in the RAM 130 are read to the CPU 110 (step S46). .

  Then, in a determination step (S47) as a determination unit, it is determined whether or not the detection period T1 and the reference period T0 for every read discharge are equal.

  When all the detection periods T1 are equal to the reference period T0 (step S47; Yes), it is determined that the ink droplet ejection operation is normal, and it is determined that there is no missing nozzle (step S48).

  If all the detection cycles T1 are not equal to the reference cycle T0 (step S47; No), it is determined whether the detection cycle T1 of the second half of the ink droplet ejection operation is equal to the reference cycle T0 (step S49). ).

  When the detection cycle T1 of the latter half operation times is equal to the reference cycle T0 (step S49; Yes), it is determined that the ink droplet ejection operation is normal, and it is determined that there is no missing nozzle (step S48).

  If the detection cycle T1 of the latter half operation times and the reference cycle T0 are not equal (step S49; No), it is determined that the ink droplet ejection operation has not been performed normally, and it is determined that there is a nozzle shortage (step S50).

  If it is determined that there is a nozzle shortage, a maintenance operation (for example, a suction operation) for eliminating the nozzle shortage is performed on the head module having a nozzle discharge port that requires maintenance (step S51).

  Ink droplets are ejected from the nozzle ejection port n times in advance, and the detection cycle T1 and the reference cycle T0 based on the landing of the ink droplet are detected for each ejection cycle, and the detection cycle T1 of all ejection times Comparing with the reference period T0, if all the detection periods T1 are not equal to the reference period T0, it is determined that no ink droplet is ejected from the set nozzle ejection port (that is, there is a nozzle missing). it can. Furthermore, due to the structural characteristics of the ink jet head, ink discharge is not performed at the initial stage of the ink discharge operation, and the ink discharge is recovered by repeated operations (ink discharge operation) several times. Ink may be ejected during the operation, and the detection cycle T1 may be detected. Even in such a case, it is determined that there is no nozzle missing, so that maintenance can be performed only when maintenance is necessary. .

  The set nozzle may be a head module unit, a nozzle row, or each nozzle, or a combination thereof.

  In the present embodiment, the nozzle missing determination operation has been described with reference to the case where the control unit 100 appropriately determines the determination criteria (maximum voltage value, count number, output cycle) shown in FIGS. However, the lack of nozzles may be determined by combining determination criteria.

In this way, the piezoelectric film 62 provided in the ink droplet ejection direction of the nozzles, and the ink force ejected from the nozzles interposed between the nozzles and the piezoelectric film 62 receive the impact force upon landing of the ink droplets. An ink droplet receiving portion that transmits to the film 62 is provided, and a nozzle missing detection portion 60 that outputs a piezo vibration signal Sd based on the amount of electricity from the piezo film 62, and a sampling signal Ss obtained by delaying the ink ejection signal S _m1. A peak hold unit 240 for extracting the ink droplets based on the sampling detection signal Sd ′ extracted from the peak hold unit 240, and a control unit 100 for determining whether the nozzle is missing. Because it is used to detect, nozzle shortage can be detected with an easy configuration, and the device cost can be reduced. It can be.

  In this embodiment, a screw is used as a position adjusting means for adapting the maximum protrusion on the curved outer peripheral surface of the piezo film to the ink droplet landing position, but a motor with high positioning accuracy such as a stepping motor is used. The support part 63 may be moved electrically. When electrically adjusting using a motor, etc., a position where there is no response of the piezo film without ejecting ink drops, and a position where the periodic response of the piezo film is high while ejecting ink drops Control is performed as follows.

1 is a schematic configuration diagram of the inside of an inkjet printer 1 according to an embodiment to which the present invention is applied. 4 is an end view of a nozzle missing detection unit 60. FIG. It is the figure which showed typically an example of the landing surface S1 of the cover 61a. It is an example of a sectional view of the contact state between the contact surface S2 of the cover 61a and the piezo film 62. FIG. 3 is another end view example 1 of the nozzle missing detection unit 60 shown in FIG. 2. It is the other end face example 2 of the nozzle missing detection part 60 shown in FIG. It is a control block diagram for controlling the inkjet printer 1 in the present embodiment. It is an example of a time chart of the operation which an ink drop discharges from a nozzle discharge mouth. It is a flowchart of a nozzle missing judgment operation in case a judgment standard in this embodiment is a maximum voltage value. It is a flowchart of a nozzle shortage determination operation when the determination criterion in the present embodiment is a count number. It is a flowchart of a nozzle shortage determination operation when the determination criterion in the present embodiment is an output cycle.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Inkjet printer 10 Paper feed part 11 Paper feed tray 12 Take-out apparatus 100 Control part 110 CPU
120 ROM
130 RAM
140 I / O
150 Various machine control units 160 I / F
170 Drive circuit unit 180 System bus 20 Conveying unit 21 Conveying belt 21a Opening portion 22 Tension roller 23 Pressing roller 24 Conveying roller 25 Conveying path 200 Nozzle missing detection circuit unit 210 Shape correction circuit unit 220 Amplifying circuit unit 230 Filter circuit unit 240 Peak Hold unit 250 A / D conversion circuit unit 30 Head unit units 31, 32, 33, 34 Head unit 31a Head module 40 Paper discharge unit 41 Paper discharge tray 50 Maintenance units 51, 52, 53, 54 Cap unit 60 Nozzle missing detection unit 61 Ink drop receiving portion 61a Cover 61b Elastic support portion 62 Piezo film 63, 65, 67 Support portion 63a Fixed support portion 63b Movable support portions 64, 66, 68 Adjustment portions 64a, 66a, 68a Screws 64b Support bases 65b1, 67b1 First Movable support 65b2, 67b2 Second movable support 69 Casing A Rotating shaft B Discharge direction C Inclination direction d1 Nozzle pitch d2 Groove pitch n Discharge number N Count number S _m0 Discharge drive signal S _m1 Ink discharge signal Ss Sampling signal Sd Piezo vibration signal Sd ′ Sampling Detection signal S1 Landing surface S2 Contact surface T0 Reference cycle T1 Detection cycle V0 Reference voltage value V _max Maximum voltage value X Transport direction θ Inclination angle

Claims (13)

In an inkjet printer that records an image on a recording medium by discharging ink from a nozzle,
It is curved in a semi-cylindrical shape, and is arranged so that the maximum protrusion on the curved outer peripheral surface is oriented in the direction of ink droplet arrival, and is provided in front of the ink droplet ejection direction of the nozzle to prevent ejection failure of the nozzle. A film-like piezoelectric element for detection;
The other end side of the film-like piezoelectric element, to which one end side in the bending direction is fixed, can be moved toward and away from the one end side, and the maximum protrusion on the curved outer peripheral surface is adapted to the landing position of the ejected ink droplet. A position adjusting means configured to support the film-like piezoelectric element;
An ink droplet receiving means that is interposed between the nozzle and the film-like piezoelectric element and receives ink droplets ejected from the nozzle;
A plurality of grooves that are parallel to each other are formed on the ink droplet landing surface of the ink droplet receiving means, and at least one end in the longitudinal direction of the grooves is open, and the open portion on one end in the longitudinal direction is the other end Being inclined so as to be positioned vertically downward with respect to
Inkjet printer characterized by. In an inkjet printer that records an image on a recording medium by discharging ink from a nozzle,
It is curved in a semi-cylindrical shape, and is arranged so that the maximum protrusion on the curved outer peripheral surface is oriented in the direction of ink droplet arrival, and is provided in front of the ink droplet ejection direction of the nozzle to prevent ejection failure of the nozzle. A film-like piezoelectric element for detection;
The film-like piezoelectric element can be translated in the same direction while maintaining a constant distance between the one end side and the other end side in the bending direction, and the maximum protrusion on the curved outer peripheral surface is adapted to the landing position of the ejected ink droplet. A position adjusting means configured to support the film-like piezoelectric element;
An ink droplet receiving means that is interposed between the nozzle and the film-like piezoelectric element and receives ink droplets ejected from the nozzle;
A plurality of grooves that are parallel to each other are formed on the ink droplet landing surface of the ink droplet receiving means, and at least one end in the longitudinal direction of the grooves is open, and the open portion on one end in the longitudinal direction is the other end Being inclined so as to be positioned vertically downward with respect to
Inkjet printer characterized by. In an inkjet printer that records an image on a recording medium by discharging ink from a nozzle,
It is curved in a semi-cylindrical shape, and is arranged so that the maximum protrusion on the curved outer peripheral surface is oriented in the direction of ink droplet arrival, and is provided in front of the ink droplet ejection direction of the nozzle to prevent ejection failure of the nozzle. A film-like piezoelectric element for detection;
The film-like piezoelectric element is configured such that one end side and the other end side in the bending direction can be relatively moved toward and away from each other, and a maximum protruding portion on the curved outer peripheral surface is adapted to a landing position of the ejected ink droplet, Position adjusting means for supporting the piezoelectric element;
An ink droplet receiving means that is interposed between the nozzle and the film-like piezoelectric element and receives ink droplets ejected from the nozzle;
A plurality of grooves that are parallel to each other are formed on the ink droplet landing surface of the ink droplet receiving means, and at least one end in the longitudinal direction of the grooves is open, and the open portion on one end in the longitudinal direction is the other end Being inclined so as to be positioned vertically downward with respect to
Inkjet printer characterized by. The inkjet printer according to any one of claims 1 to 3,
The arrangement pitch of the grooves is equal to the arrangement pitch of the nozzles,
Inkjet printer characterized by. The inkjet printer according to any one of claims 1 to 3,
The ink droplet receiving means is provided so that the bottom of the groove matches the landing position of the ink droplet flying from the nozzle;
Inkjet printer characterized by. The inkjet printer according to any one of claims 1 to 3,
The ink droplet receiving means is provided so as to be able to transmit an impact force upon landing of the ejected ink droplet to the film-like piezoelectric element;
Inkjet printer characterized by. In the ink jet printer according to any one of claims 1 to 6,
The ink droplet receiving means has a protruding portion that is provided at a position facing the maximum protruding portion on the curved outer peripheral surface of the film-like piezoelectric element and transmits an impact force upon ink droplet landing to the maximum protruding portion. ,
Inkjet printer characterized by. In the inkjet printer according to any one of claims 1 to 7,
Sampling that generates a sampling signal obtained by delaying an ink ejection signal for ejecting an ink droplet from a nozzle by a predetermined time, and extracts a detection signal output from the film-like piezoelectric element upon landing of the ink droplet based on the sampling signal Means,
Judgment means for judging ejection failure of the nozzle by comparing a voltage value of the sampling detection signal extracted by the sampling means with a preset reference voltage value ;
Inkjet printer characterized by. The inkjet printer according to claim 8, wherein
The determination means compares the said reference voltage value and the maximum voltage value of the sampling detection signal, when the maximum voltage value of the sampling detection signal is lower than the reference voltage value can be determined that there is ejection failure of the nozzle,
Inkjet printer characterized by. In the ink jet printer according to any one of claims 1 to 9 ,
Comparing the number of ink droplet ejections with the number of times that the voltage value of the sampling detection signal is equal to or greater than a preset reference voltage value, and a judgment means for judging that there is a nozzle ejection failure if the number of times does not match. ,
Inkjet printer characterized by. In the ink jet printer according to any one of claims 1 to 10,
Comparing the output period of the sampling detection signal and the output period of the ink ejection signal, and comprising a determination means for determining that there is a nozzle ejection failure if both periods do not match,
Inkjet printer characterized by. The inkjet printer according to any one of claims 1 to 11,
The inkjet printer includes a maintenance unit that eliminates nozzle discharge defects;
Inkjet printer characterized by. The inkjet printer according to claim 12, wherein
The maintenance means eliminates nozzle discharge defects by suction operation or flushing operation,
Inkjet printer characterized by.

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