JP7788082B2 - Head control device, liquid ejection system, and head manufacturing method - Google Patents

Description

The present invention relates to a head control device, a liquid ejection system, and a head manufacturing method.

Patent Document 1 discloses a droplet ejection head in which an actuator is used to control a pin to move toward and away from a nozzle, so that liquid is ejected as droplets from the nozzle only while the pin is away from the nozzle.

Some actuators used in heads have the property that their overall length shrinks as the temperature of the actuator rises. When incorporating an actuator with such a shrinking property into a head, if it is assembled without taking into consideration the temperature specifications of the liquid used in the head or the environment in which the head is installed, the actuator may shrink during actual liquid ejection operation. If the actuator shrinks, it will no longer be possible to close the nozzle, leading to a state in which liquid continues to leak from the nozzle.

The present invention is a head control device for controlling a head system comprising a head having a valve body that moves between a position that closes and a position that opens a nozzle that ejects liquid, and an actuator that applies power to the valve body to move the valve body, and a temperature measurement means, wherein the valve body moves in a direction that closes the nozzle by a first drive voltage to the actuator, and moves in a direction that opens the nozzle by a second drive voltage to the actuator that is different from the first drive voltage, and is characterized by comprising a control means that increases the second drive voltage together with the first drive voltage the higher the temperature measured by the temperature measurement means.

The present invention provides a head control device and head manufacturing method that can reliably maintain the nozzle closed state regardless of temperature.

FIG. 1 is an overall perspective view of a head according to an embodiment of the present invention. FIG. 1 is an overall cross-sectional view of a head according to an embodiment of the present invention. FIG. 2 is an explanatory diagram of a single drive unit according to the embodiment of the present invention. FIG. 10 is an explanatory diagram showing the relationship between the piezoelectric element temperature and the amount of contraction of the drive unit. FIG. 2 is an explanatory diagram showing an example of the hardware configuration of a head control device according to an embodiment of the present invention. FIG. 4 is an explanatory diagram of an actuator driving voltage according to the embodiment of the present invention. FIG. 4 is an explanatory diagram of an actuator driving voltage according to the embodiment of the present invention. FIG. 4 is an explanatory diagram of an actuator driving voltage according to the embodiment of the present invention. 1 is an overall perspective view of a system according to an embodiment of the present invention. FIG. FIG. 1 is an explanatory diagram showing an example of the hardware configuration of a printing apparatus according to an embodiment of the present invention. 10 is a flowchart showing an example of actuator drive voltage control. 10 is a flowchart showing an example of actuator drive voltage control. FIG. 10 is an explanatory diagram showing another example of the hardware configuration of the head control device according to the embodiment of the present invention. FIG. 1 is a block diagram showing an example of the configuration of a head assembly device according to an embodiment of the present invention. 10 is a flowchart showing an example of a head manufacturing process. FIG. 1 is a schematic diagram showing a first application example of a system according to an embodiment of the present invention. FIG. 10 is a schematic diagram showing a second application example of the system according to the embodiment of the present invention. FIG. 10 is a schematic diagram showing a third application example of the system according to the embodiment of the present invention. FIG. 10 is a schematic diagram showing a fourth application example of the system according to the embodiment of the present invention. FIG. 10 is a schematic diagram showing a fifth application example of the system according to the embodiment of the present invention.

The following describes the embodiments of the invention with reference to the drawings. Note that in the description of the drawings, identical elements are designated by the same reference numerals, and duplicate explanations will be omitted.

<Head configuration>
First, the configuration of the head will be described using Figures 1 and 2. Figure 1 is an overall perspective view of the head according to an embodiment of the present invention. Figure 2 is an overall cross-sectional view of the head according to an embodiment of the present invention (cross-sectional view taken along line A-A in Figure 1).

In FIG. 1, the head 300 mainly comprises a housing 310, a connector 350, a liquid supply port 311, and a liquid recovery port 313. The housing 310 is made of a metal or resin material. The connector 350 is a terminal for transmitting electrical signals such as drive signals for ejecting liquid, and in this embodiment, the connector 350 is provided on the top of the housing 310.

The liquid supply port 311 and liquid recovery port 313 are located on the left and right sides of the housing 310. The liquid supply port 311 supplies liquid into the head. The liquid recovery port 313 discharges liquid from the head. Next, the internal structure of the head 300 will be explained with reference to Figure 2.

In Figure 2, the housing 310 has a connector 350 at its top for transmitting electrical signals, and a nozzle plate 301 at its bottom, which has nozzles 302 for ejecting liquid. The housing 310 also has a flow path 312 that sends liquid from the liquid supply port 311 over the nozzle plate 301 to the liquid recovery port 313.

Furthermore, the housing 310 accommodates a drive unit 330 between the liquid supply port 311 and the liquid recovery port 313 for ejecting the liquid in the flow path 312 from the nozzle 302. The drive unit 330 will be described in more detail below, but in brief, the drive unit 330 includes a needle valve 331, a piezoelectric element 332, and a leaf spring frame 333. The leaf spring frame 333 holds the piezoelectric element 332 and elastically deforms when driven by the piezoelectric element 332, transmitting the driving force of the piezoelectric element 332 to the needle valve 331. The needle valve 331 opens and closes the nozzle 302 in response to the elastic deformation of the leaf spring frame 333. Here, the needle valve 331 that constitutes the drive unit 330 is an example of a "valve," the piezoelectric element 332 is an example of an "actuator," and the leaf spring frame 333 is an example of an "elastic member." The housing 310 is also an example of a "casing."

The number of drive units 330 corresponds to the number of nozzles 302, and in this embodiment, a configuration including eight drive units 330 corresponding to eight nozzles 302 arranged in a row is exemplified. Note that the number and arrangement of nozzles 302 and drive units 330 are not limited to those described above. For example, the number of nozzles 302 and drive units 330 may be nine or more, or there may be one instead of multiple. Furthermore, the nozzles 302 and drive units 330 may be arranged in multiple rows rather than a single row.

In the above configuration, the liquid flow is as follows: the liquid supply port 311 takes in pressurized liquid from the outside, sends the liquid in the direction of arrow a1, and supplies the liquid to the flow path 312. The flow path 312 sends the liquid from the liquid supply port 311 in the direction of arrow a2. The liquid recovery port 313 then discharges any liquid not ejected from the nozzles 302 arranged along the flow path 312 in the direction of arrow a3.

When the piezoelectric element 332 is activated and the needle valve 331 is displaced upward in the figure, the nozzle 302, which was closed by the needle valve 331, opens, and the liquid flowing through the flow path 312 is ejected from the nozzle 302. When the piezoelectric element 332 is activated and the needle valve 331 is displaced downward, the tip of the needle valve 331 abuts against the nozzle 302, closing the nozzle 302 and preventing liquid from being ejected from the nozzle 302. While liquid is being ejected from the nozzle 302, the liquid may be temporarily not discharged from the liquid recovery port 313 to prevent a decrease in the ejection efficiency from the nozzle 302.

In this embodiment, the nozzle plate 301 and the housing 310 are separate components, but they may also be formed integrally as a single component. When both are formed as a single component, the position where the tip of the needle valve 331 abuts against the nozzle plate 301 is used as the boundary, and the area on the side where the needle valve 331 is provided is defined as the housing 310, and the area on the side where the needle valve 331 is not provided is defined as the nozzle plate 301.

<Configuration of drive unit>
Next, the configuration of the drive unit 330 will be described in detail with reference to Fig. 3. Fig. 3 is an explanatory diagram of the drive unit alone according to the embodiment of the present invention.

In Figure 3, the drive unit 330 includes a needle valve 331, a piezoelectric element 332, and a leaf spring frame 333. The nozzle plate 301 is joined to the housing 310. The flow path 312 is a common flow path for multiple drive units 330 provided in the housing 310.

The tip of the needle valve 331 faces the nozzle 302 provided in the nozzle plate 301, and the nozzle 302 is closed when the tip of the needle valve 331 abuts against the nozzle plate 301. In this embodiment, the needle valve 331 is provided with an elastic body 331a at its tip, which increases adhesion to the nozzle 302 and more reliably closes the nozzle 302. The housing 310 supports the needle valve 331 via a bearing 321, and a sealing member 315 such as an O-ring is installed between the bearing 321 and the needle valve 331 to prevent liquid from flowing from the flow path 312 toward the piezoelectric element 332.

A leaf spring frame 333 is disposed in space 322 formed inside housing 310. Leaf spring frame 333 includes a needle valve holding portion 333a, frame portion 333b, expandable portion 333c, space 333d, and piezoelectric element holding portions 333e and 333f. Needle valve holding portion 333a holds the rear end of needle valve 331. Frame portion 333b is made of, for example, a metal plate, and includes space 333d in the center. Expandable portion 333c is a leaf spring formed integrally with part of frame portion 333b, and this portion is expandable and contractible.

Space 333d forms the installation space for piezoelectric element 332. Piezoelectric element holder 333e protrudes toward space 333d from the rear side of needle valve holder 333a of frame 333b, and piezoelectric element holder 333f protrudes toward space 333d at a position facing piezoelectric element holder 333e of frame 333b.

When attaching a piezoelectric element 332 to the leaf spring frame 333 configured as described above, the elastic deformation of the expansion/contraction portion 333c is used to slightly expand the leaf spring frame 333, widening the space 333d. Once the piezoelectric element 332 is inserted into the expanded space 333d, the leaf spring frame 333 is released from its expanded state. As a result, the leaf spring frame 333 holds both longitudinal ends of the piezoelectric element 332 between the piezoelectric element holding portions 333e and 333f due to the restoring force of the expansion/contraction portion 333c as it tries to return to its original shape. Therefore, in the default state where the piezoelectric element 332 is inserted into the space 333d, the expansion/contraction portion 333c is slightly expanded from its natural length.

In this embodiment, the leaf spring frame 333 serving as the elastic member is configured such that the needle valve holding portion 333a, frame portion 333b, expandable portion 333c, and piezoelectric element holding portions 333e and 333f are integrated into a single member, but some of these portions may be configured as separate members. For example, the expandable portion 333c may be configured from a spring or the like, and the spring may be attached to the frame portion 333b.

The drive unit 330 is attached to the housing 310 by fastening a screw 310b through a screw hole 310a in the housing 310 and a screw hole 314a in the restricting member 314. In other words, the restricting member 314 holds the end of the leaf spring frame 333 on the piezoelectric element holding portion 333f side, and the housing 310 holds the drive unit 330 via the restricting member 314. The restricting member 314 thereby restricts the position of the leaf spring frame 333 and acts as a fixed point to prevent the leaf spring frame 333 from moving upward due to expansion of the piezoelectric element 332. Note that fastening with the screw 310b is not limited to one location. For example, a similar screw hole may be provided on the right side of the figure, allowing the restricting member 314 to be fastened from both the left and right. Here, the screw holes 310a, 314a, and the fastening points using the screw 310b are examples of "holding positions."

With the above configuration, the needle valve 331 and piezoelectric element 332 are arranged coaxially, i.e., in series in the liquid ejection direction, via the leaf spring frame 333. When a drive voltage is applied to the piezoelectric element 332, the piezoelectric element 332 expands. As the piezoelectric element 332 expands, the expandable portion 333c of the leaf spring frame 333 elastically deforms to absorb the expansion and push the needle valve holder 333a installed at the tip of the piezoelectric element 332 toward the nozzle 302 (downward in the figure). In this way, the leaf spring frame 333 elastically deforms due to the drive of the piezoelectric element 332, transmitting the driving force of the piezoelectric element 332 to the needle valve 331. As a result, the tip of the needle valve 331 (elastic body 331a in this embodiment) abuts against the nozzle 302, closing the nozzle 302 and stopping the ejection of liquid supplied under pressure to the flow path 312 from the nozzle 302.

Furthermore, when the application of the drive voltage to the piezoelectric element 332 is stopped, the piezoelectric element 332 contracts. When the piezoelectric element 332 contracts, the expandable portion 333c elastically deforms to absorb the contraction and pulls the needle valve holder 333a installed at the tip of the piezoelectric element 332 toward the rear end (upward in the figure). As a result, the tip of the needle valve 331 (elastic body 331a in this embodiment) separates from the nozzle 302, opening the nozzle 302 and causing the liquid supplied under pressure to the flow path 312 to be ejected from the nozzle 302.

In addition, in the configuration shown in Figure 3, a thermistor 334 is provided as a temperature measurement means in part of the leaf spring frame 333, and the temperature of the leaf spring frame 333 is measured by the thermistor 334. Note that the location of the thermistor 334 is not limited to the leaf spring frame 333. The thermistor 334 may also be provided in other head components, such as the housing 310 or the piezoelectric element 332.

<About drive unit contraction>
Next, the relationship between the temperature of the piezoelectric element 332 and the amount of contraction of the drive unit 330 will be described with reference to Fig. 4. Fig. 4 is an explanatory diagram showing the relationship between the temperature of the piezoelectric element and the amount of contraction of the drive unit.

The piezoelectric element 332 used in the head 300 is a so-called high-displacement type piezoelectric element capable of generating a large amount of displacement. Some piezoelectric elements of this type have the characteristic that their overall length shrinks as the temperature of the piezoelectric element rises. When using a piezoelectric element with this characteristic, care must be taken to prevent self-destruction due to overshoot (a phenomenon in which the voltage temporarily exceeds 100% when a signal changes from low level to high level) or ringing (signal vibration). For this reason, in this embodiment, the piezoelectric element 332 is held in place by a leaf spring frame 333 to prevent self-destruction of the piezoelectric element 332.

When the plate spring frame 333 holds the piezoelectric element 332, it is slightly extended from its natural length as described above. However, when the temperature of the piezoelectric element 332 rises due to self-heating caused by driving the piezoelectric element 332, the overall length of the piezoelectric element 332 shrinks. As the overall length of the piezoelectric element 332 shrinks, the plate spring frame 333 also shrinks in a direction returning to its natural length. As the plate spring frame 333 shrinks, the needle valve 331 attached to the plate spring frame 333 also moves in a direction away from the nozzle 302. As a result, the overall length of the drive unit 330 becomes shorter.

For example, in Figure 4, for head A (solid line), the drive unit barely shrinks at a piezoelectric element temperature of 25°C, but the overall length of the drive unit shrinks by approximately 5 μm at a piezoelectric element temperature of 50°C.

This trend is also seen in the case of head B (dashed line), which uses a different material from head A. At a piezoelectric element temperature of 25°C, the drive unit barely shrinks, but at a piezoelectric element temperature of 40°C, the overall length of the drive unit shrinks by approximately 5 μm.

Therefore, if head A in Figure 4 is assembled in a room temperature environment and used in a system in which the temperature of the piezoelectric element reaches 50°C or higher, there is a risk that the needle valve 331 will no longer close the nozzle 302 as the temperature of the piezoelectric element 332 rises.

<Hardware configuration of head control device>
Next, the hardware configuration of the head control device will be described with reference to Fig. 5. Fig. 5 is an explanatory diagram showing an example of the hardware configuration of a head control device according to an embodiment of the present invention. Note that components may be added or deleted from the hardware configuration shown in Fig. 5 as necessary.

In FIG. 5, the head control device 902 includes a control unit 9020, a drive waveform amplifier 9022, and an AD converter 9023. Of these, the control unit 9020 includes a drive waveform generator 9021, a temperature data storage unit 9024, and a correction value calculator 9025. The head control device 902 can also be electrically connected to the head system 30, which includes the head 300 and thermistor 334. Here, the thermistor 334 is an example of a "temperature measurement means."

The drive waveform generation unit 9021 generates a drive waveform and transmits the generated drive waveform signal to the drive waveform amplification unit 9022. Furthermore, when the drive waveform generation unit 9021 receives correction value information related to the drive voltage correction value of the piezoelectric element 332 from the correction value calculation unit 9025, it corrects the drive waveform based on the correction value information. The drive waveform amplification unit 9022 amplifies the voltage and current of the drive waveform signal received from the drive waveform generation unit 9021 and applies a drive voltage to the piezoelectric element 332 of the head 300. The AD conversion unit 9023 performs AD conversion on the signal received from the thermistor 334 and outputs the converted signal to the temperature data storage unit 9024.

The temperature data storage unit 9024 stores a table that links, for example, temperature, the amount of contraction of the drive unit 330 at that temperature, and the drive voltage value required to compensate for that amount of contraction. The temperature data storage unit 9024 also stores information about the drive waveform signal received from the drive waveform generation unit 9021 and information about the signal received from the thermistor 334 via the AD conversion unit 9023. The correction value calculation unit 9025 calculates a correction value based on the information received from the temperature data storage unit 9024 and transmits the calculated correction value information to the drive waveform generation unit 9021.

By providing a head control device 902 with the above configuration for each piezoelectric element 332 of the head 300 shown in Figure 2, it becomes possible to correct the ejection state for each nozzle, and to adjust the liquid ejection amount, droplet size, etc. for each nozzle. Here, the control unit 9020 is an example of a "control means."

The location of the thermistor 334 in the head system 30 is not limited to a specific location. The thermistor 334 may be provided in a head component such as the housing 310, piezoelectric element 332, or leaf spring frame 333, or it may be provided in a location separate from the head 300 on the system (printing device main body) side, which will be described later. Alternatively, the thermistor 334 may be provided in both the head 300 and the system. In this case, for example, the head temperature is measured using a thermistor provided in the head 300, and the environmental temperature around the system is measured using a thermistor provided in the system, and a drive waveform is generated based on the temperature data from the multiple thermistors.

<Explanation of actuator drive voltage>
Next, the drive voltage of the actuator (piezoelectric element) will be described with reference to Figures 6 to 8. Figures 6 to 8 are explanatory diagrams of the actuator drive voltage, Figures 6 and 7 are explanatory diagrams of the drive voltage during execution of a liquid ejection operation, and Figure 8 is an explanatory diagram of the drive voltage before the liquid ejection operation starts.

In Figure 6, when a first drive voltage V1 is applied to the piezoelectric element 332, the piezoelectric element 332 expands. When the piezoelectric element 332 expands, the needle valve 331 moves toward the nozzle plate 301 via the leaf spring frame 333, and the needle valve 331 closes the nozzle 302. When a second drive voltage V2 (0 V in this embodiment) is applied, the piezoelectric element 332 contracts, and the leaf spring frame 333 moves the needle valve 331 away from the nozzle plate 301, opening the nozzle 302.

If the thermistor 334 measures a high temperature, the first drive voltage V1 is corrected to a higher voltage V1H. In other words, the higher the temperature measured by the thermistor 334, the higher the first drive voltage V1 is. The correction from drive voltage V1 to drive voltage V1H is primarily performed by the control unit 9020 shown in Figure 5. By correcting the first drive voltage V1 as described above in accordance with the temperature measured by the thermistor 334, it becomes possible to compensate for the amount of contraction of the drive unit 330 that accompanies the contraction of the piezoelectric element 332, and the nozzle can be reliably maintained in a closed state regardless of the temperature.

As described above, this embodiment provides a head control device 902 for controlling a head system 30 including a head 300 having a needle valve 331 that moves between a position that closes and a position that opens a nozzle 302 that ejects liquid, a piezoelectric element 332 that applies power to the needle valve 331 to move the needle valve 331, and a thermistor 334. The needle valve 331 moves in a direction that closes the nozzle 302 in response to a first drive voltage V1 applied to the piezoelectric element 332, and moves in a direction that opens the nozzle 302 in response to a second drive voltage V2 that is different from the first drive voltage V1 applied to the piezoelectric element 332. The head control device 9020 increases the first drive voltage V1 (to drive voltage V1H) as the temperature measured by the thermistor 334 increases.

As described above, the thermistor 334 is provided in one of the components, the housing 310 of the head 300, the piezoelectric element 332, or the leaf spring frame 333 that holds the piezoelectric element 332, and the thermistor 334 measures the temperature of that component.

This makes it possible to compensate for the amount of contraction of the drive unit 330 caused by the contraction of the piezoelectric element 332 due to temperature rise, ensuring that the nozzle 302 remains closed regardless of temperature.

Figure 7 is a modified example of Figure 6. If only the first drive voltage V1 is corrected, the potential difference with the second drive voltage V2 will change before and after correction (|V1-V2| < |V1H-V2|), which may affect the ejection characteristics (ejection volume, ejection speed, etc.) of the liquid from the nozzle 302. In this modified example, the second drive voltage V2 is increased along with the first drive voltage V1 according to the temperature measured by the thermistor 334. Preferably, the potential difference between the first drive voltage V1 and the second drive voltage V2 is varied so that it remains constant before and after correction (|V1-V2| = |V1H-V2H|).

As described above, in this embodiment, the control unit 9020 increases both the first drive voltage V1 and the second drive voltage V2 as the temperature measured by the thermistor 334 increases.

Furthermore, as described above, the control unit 9020 varies the first drive voltage V1 and the second drive voltage V2 so that the potential difference between the first drive voltage V1 and the second drive voltage V2 is constant.

This ensures that the nozzle 302 remains closed regardless of temperature, while also reducing fluctuations in the liquid ejection characteristics.

Figure 8 is an explanatory diagram of the drive voltage before the start of liquid ejection operation. The head system 30 and head control device 902 of this embodiment are used in a wide variety of environments depending on the application, and in some environments the head temperature may be lower than the temperature range in which the head operates normally. In this case, if a high voltage is applied to the piezoelectric element 332 from the beginning, the piezoelectric element 332 will stretch too much, causing the needle valve 331 to come into excessive contact with the nozzle plate 301, which may result in deformation or damage to the needle valve 331 or nozzle plate 301.

Therefore, when the head temperature is lower than the temperature range in which the head operates normally, the head control device 902 applies a voltage V1L, which is lower than the first drive voltage V1, to the piezoelectric element 332. Driving of the piezoelectric element 332 with voltage V1L continues until the temperature measured by the thermistor 334 falls within the temperature range in which the head can operate normally (for example, 30°C or higher).

Note that while the head 300 is being driven at voltage V1L, the supply of liquid to the flow path 312 is stopped and liquid is not ejected from the nozzle 302. The inside of the head is then heated, and when the temperature measured by the thermistor 334 reaches, for example, 30°C or higher, the head control device 902 applies the first drive voltage V1 to the piezoelectric element 332 to close the nozzle 302.

As described above, in this embodiment, if the temperature measured by the thermistor 334 is lower than a predetermined temperature, the head 300 is driven at a voltage V1L lower than the first drive voltage V1 until the temperature reaches the predetermined temperature.

This prevents deformation or damage caused by excessive contact of the needle valve 331 with the nozzle plate 301 due to the low temperature of the head 300.

<System Overview>
Next, a system equipped with the above-described head will be described. Fig. 9 is an overall perspective view of the system according to an embodiment of the present invention. The system illustrated here is a printing device that forms an image on the side of a truck body or the like.

In Figure 9, the printing device 1000 is installed facing an object 100, such as the side of a truck body. The printing device 1000 has an X-axis rail 101, a Y-axis rail 102 that intersects with the X-axis rail 101, and a Z-axis rail 103 that intersects with the X-axis rail 101 and Y-axis rail 102. The Y-axis rail 102 holds the X-axis rail 101 so that it can move in the Y direction (positive and negative). The X-axis rail 101 holds the Z-axis rail 103 so that it can move in the X direction (positive and negative). The Z-axis rail 103 holds the carriage 1 so that it can move in the Z direction (positive and negative).

The printing device 1000 includes a first Z-direction drive unit 92 that moves the carriage 1 in the Z direction along the Z-axis rail 103, and an X-direction drive unit 72 that moves the Z-axis rail 103 in the X direction along the X-axis rail 101. The printing device 1000 also includes a Y-direction drive unit 82 that moves the X-axis rail 101 in the Y direction along the Y-axis rail 102, and a second Z-direction drive unit 93 that moves the head holder 70 in the Z direction relative to the carriage 1.

In the printing device 1000 configured as described above, the carriage 1 moves back and forth on the X-axis rail 101 from side to side (negative and positive sides in the X direction) each time the X-axis rail 101 moves down toward the negative side in the Y direction at regular intervals. As the carriage 1 moves back and forth, the head provided on the head holder 70 ejects ink, an example of a liquid, while scanning the object 100, forming an image on the object 100, an example of a liquid ejection process.

Here, the movement of the carriage 1 and head holder 70 in the Z direction does not necessarily mean that it is parallel to the Z direction; it may be diagonal movement as long as it includes at least a component in the Z direction. Note that while the surface shape of the object 100 is shown as flat in the figure, the surface shape of the object 100 may also be a nearly vertical surface, a surface with a large radius of curvature, or a surface with some unevenness. Furthermore, the system configuration is not limited to one in which the head moves relative to the object 100. It is sufficient that the head and object 100 are capable of moving relative to each other, and the system may also be configured to move the object 100 relative to the head.

<Carriage configuration>
Next, the configuration of the carriage will be described with reference to Fig. 10. Fig. 10 is an overall perspective view of the carriage 1 of the printing device 1000 shown in Fig. 9, as seen from the target object 100 side.

In FIG. 10, the carriage 1 is equipped with a head holder 70. The carriage 1 is movable in the Z direction (positive and negative) along the Z-axis rail 103 using power from the first Z-direction drive unit 92 shown in FIG. 9. The head holder 70 is movable in the Z direction (positive and negative) relative to the carriage 1 using power from the second Z-direction drive unit 93 shown in FIG. 9. The head holder 70 is equipped with a head fixing plate 70a for mounting the heads 300. In this embodiment, a configuration is illustrated in which six heads, each with eight nozzles 302, are mounted on the head fixing plate 70a, and the six heads 300a-300f are arranged in a stacked configuration. In the following description, the heads 300a-300f will be collectively referred to as "heads 300."

The type and number of ink colors used by heads 300a-300f may be different for each head, or they may all be the same color. For example, if the printing device 1000 is a coating device that uses a single color, the inks used by heads 300a-300f may be the same color. Also, the number of heads making up head 300 is not limited to six. It may be more or less than six.

As shown in the figure, the heads 300 are fixed to the head fixing plate 70a with the nozzle rows of each head intersecting the horizontal plane (X-Z plane) and the arrangement direction of the multiple nozzles 302 tilted relative to the X axis. In this state, the nozzles 302 eject ink in a direction intersecting the vertical direction (positive Z direction).

<Hardware configuration of printing device>
Next, the hardware configuration of the printing device 1000 will be described using Fig. 11. Fig. 11 is an explanatory diagram showing an example of the hardware configuration of a printing device according to an embodiment. Note that components may be added or deleted from the hardware configuration shown in Fig. 11 as needed.

In FIG. 11, the printing device 1000 includes a controller 901, a head control device 902, and a head system 30. A computer 903 is connected to the controller 901. The computer 903 includes a RIP (Routing Information Protocol) unit 9031 that performs image processing according to the color profile and user settings, and a rendering unit 9032 that breaks down the image data of the image to be formed on the object 100 into image data for each scan (movement of the carriage 1 in the X-axis direction). An input device 9033 is also connected to the computer 903, which sets the image data and coordinate data of the image to be formed on the object 100, selects the image formation mode, sets the image formation (printing) range, and issues printing instructions. The input device 9033 includes a keyboard, mouse, touch panel, etc., and accepts input from the user.

The controller 901 includes a system control unit 9011, a data storage unit 9012, a memory control unit 9013, an ejection period signal generation unit 9014, a carriage control unit 9015, and a maintenance control unit 9016. The system control unit 9011 receives image data and commands from the computer 903 and controls the overall operation of the printing device 1000. The data storage unit 9012 includes memory such as ROM (Read Only Memory), RAM (Random Access Memory), and HDD (Hard Disk Drive), and stores image data, print range data, etc. received from the computer 903. The memory control unit 9013 controls the data storage unit 9012.

The printing device 1000 is equipped with a linear encoder installed, for example, along the X-axis rail 101. An encoder sensor 109 that optically detects each slit of the linear encoder is installed on a member that can move on the X-axis rail 101, such as the carriage 1 or the maintenance and recovery device 105, so that position information of that member on the X-axis can be obtained. The ejection period signal generation unit 9014 generates an ink ejection period signal from the output signal of the encoder sensor 109 on the carriage 1 and information indicating the resolution of the image data received from the computer 903.

The carriage control unit 9015 calculates position information for the carriage 1 based on the output signal of the encoder sensor 109 and controls the driving of the X-direction drive unit 72, Y-direction drive unit 82, first Z-direction drive unit 92, and second Z-direction drive unit 93. The maintenance control unit 9016 calculates position information for the maintenance and recovery device 105 based on the output signal of the encoder sensor 109 in the maintenance and recovery device 105, and controls the operation of the maintenance and recovery device 105. Here, the maintenance and recovery device 105 is a device that performs maintenance such as idle ejection, wiping, and cleaning at predetermined times on the head 300 mounted on the carriage 1.

As described above, the controller 901 includes a system control unit 9011, a data storage unit 9012, a memory control unit 9013, an ejection period signal generation unit 9014, a carriage control unit 9015, and a maintenance control unit 9016. The controller 901 has an arithmetic processing unit and a storage device, and the arithmetic processing unit executes a program pre-recorded in the storage device to realize each of these functional units.

The head control device 902 receives an ejection period signal from the ejection period signal generation unit 9014 of the controller 901, and controls the ink ejection operation of the head 300 based on the ejection period signal. The head control device 902 also generates a drive waveform for the head 300 based on temperature information received from the thermistor 334, and applies a drive voltage corresponding to the drive waveform to the head 300 (piezoelectric element 332). Note that the configuration of the head control device 902 and head system 30 has been explained in Figure 5, so a detailed explanation will be omitted here.

The RIP unit 9031 and rendering unit 9032 may be provided in the system control unit 9011 of the controller 901, rather than in the computer 903. In addition, while this embodiment uses an encoder sensor as an example of a sensor for detecting the positions of the carriage 1 and the maintenance and recovery device 105, the sensor is not limited to this. Other than the encoder sensor, a mechanical sensor such as a push sensor may also be used, or an optical sensor using laser light, for example.

<Operation of the embodiment>
Next, an example of the printing operation of the printing device 1000 will be described.

When the printing device 1000 receives a print command from the computer 903, it moves the X-axis rail 101 toward the positive Y-axis direction, positioning the carriage 1 so that it faces the print start position. When printing begins, the carriage 1 moves on the X-axis rail 101 from the print start position toward the positive X-axis direction, and the head 300 mounted on the carriage 1 ejects ink to form the desired image on the target object 100. Once the first scan by moving the carriage 1 toward the positive X-axis direction is complete, the X-axis rail 101 is moved a fixed distance toward the negative Y-axis direction (line feed).

Then, the carriage 1 moves on the X-axis rail 101 in the negative X direction, and the desired image is formed on the object 100 using ink ejected by the head 300. Once the second scan by moving the carriage 1 in the negative X direction is complete, the X-axis rail 101 is further moved a fixed distance in the negative Y direction. By repeating the above operation until the printing end position, the printing device 1000 completes image formation on the object 100.

In addition, each time the carriage 1 finishes scanning in the X direction, the maintenance and recovery device 105 may perform maintenance operations on the head 300. The maintenance and recovery device 105 may be mounted on the carriage 1, or may be installed at the end of the X-axis rail 101.

<Flow of actuator drive voltage control>
Next, an example of the control operation of the actuator (piezoelectric element) drive voltage will be described with reference to Figures 12 and 13. Figure 12 is a flow chart showing an example of actuator drive voltage control, and shows the process from temperature measurement to head drive.

In Figure 12, temperature measurement for controlling the drive voltage of the piezoelectric element 332 begins first (step S1). The temperature is measured by a thermistor 334 provided in a head component such as the housing 310, piezoelectric element 332, or leaf spring frame 333, or by a thermistor 334 provided in a location separate from the head 300, such as the main body of the printing device 1000. The thermistor 334 then transmits the temperature data to the head control device 902. The head control device 902 stores the received temperature data in the temperature data storage unit 9024 within the head control device 902 (step S2).

Next, the correction value calculation unit 9025 in the head control device 902 calculates a correction value for the drive voltage based on the temperature data stored in the temperature data storage unit 9024 (step S3). The temperature data storage unit 9024 stores a table that links, for example, temperature, the amount of contraction of the drive unit 330 at that temperature, and the drive voltage value required to compensate for that amount of contraction. The correction value calculation unit 9025 then compares the table in the temperature data storage unit 9024 with the temperature data received from the thermistor 334 to calculate a correction value for the drive voltage, and transmits information about the calculated correction value to the drive waveform generation unit 9021.

When the drive waveform generation unit 9021 receives the correction value information, it generates (corrects) a drive waveform based on the correction value information (step S4). That is, it generates the drive waveform shown by the dashed lines in Figures 6 and 7. The drive waveform generation unit 9021 then transmits the generated drive waveform signal to the head 300 via the drive waveform amplifier unit 9022. As a result, the head 300 operates in accordance with the voltage of the drive waveform (step S5).

Figure 13 is a flowchart showing an example of actuator drive voltage control, illustrating the process up to driving the head in a low-temperature state.

Figure 13 differs from Figure 12 in that a step for determining whether the head 300 is within the operating temperature range has been added between step S1 (temperature measurement) and step S2 (temperature data storage). That is, based on the temperature measured by the thermistor 334 in step S1 (temperature measurement), it is determined whether the head 300 is within the temperature range in which it can operate normally (step S11). If the determination in step S11 is NO (not within the temperature range in which it can operate normally), a drive voltage V1L lower than the first drive voltage V1 is applied to the piezoelectric element 332 (step S12), as described in Figure 8.

While continuing to apply the drive voltage V1L, the thermistor 334 measures the temperature, and when the head 300 reaches a temperature within the operating temperature range, the process proceeds to step S2 (storing temperature data). The processing from step S2 onwards is the same as in Figure 12, so a detailed explanation will be omitted. By controlling the drive voltage as described above when driving a head in a low-temperature state, it is possible to prevent deformation or damage caused by excessive contact of the needle valve 331 with the nozzle plate 301 due to the head being at a low temperature.

<Modification of Head Control Device>
FIG. 14 is an explanatory diagram showing another example of the hardware configuration of a head control device according to an embodiment of the present invention. In this modification, the temperature of the head 300 is calculated from the number of times the head 300 is driven or the drive frequency, without using a temperature measurement device such as a thermistor as shown in FIG. 5. In other words, it is believed that the temperature of the piezoelectric element 332 rises as the cumulative number of times the head 300 is driven continuously increases, and that the temperature of the piezoelectric element 332 rises more quickly as the drive frequency of the head 300 increases. Based on the above considerations, in this modification, the temperature of the head 300 is calculated (estimated) from the number of times the head 300 is driven or the drive frequency. Note that components may be added or deleted from the hardware configuration shown in FIG. 14 as needed.

In FIG. 14, the head control device 902 includes a control unit 9020 and a drive waveform amplifier 9022. The control unit 9020 includes a drive waveform generator 9021, a drive information acquisition unit 9026, and a correction value calculation unit 9025, and the head control device 902 can be electrically connected to the head 300.

The drive waveform generation unit 9021 generates a drive waveform and transmits the generated drive waveform signal to the drive waveform amplification unit 9022 and drive information acquisition unit 9026. Furthermore, when the drive waveform generation unit 9021 receives correction value information related to the drive voltage correction value of the piezoelectric element 332 from the correction value calculation unit 9025, it corrects the drive waveform based on the correction value information. The drive waveform amplification unit 9022 amplifies the voltage and current of the drive waveform signal received from the drive waveform generation unit 9021 and applies a drive voltage to the piezoelectric element 332 of the head 300.

The drive information acquisition unit 9026 receives a drive waveform signal from the drive waveform generation unit 9021 and acquires information on the number of times the head 300 is driven or the drive frequency from the drive waveform signal. The drive information acquisition unit 9026 then calculates the temperature of the head 300 based on the acquired information on the number of times the head is driven or the drive frequency. The correction value calculation unit 9025 calculates a correction value based on the information received from the drive information acquisition unit 9026 and transmits the calculated correction value information to the drive waveform generation unit 9021. The control unit 9020 then controls the drive voltage so that the first drive voltage V1 increases as the temperature calculated by the drive information acquisition unit 9026 increases.

By providing the head control device 902 configured as described above for each of the piezoelectric elements 332 of the head 300 shown in Figure 2, it becomes possible to correct the ejection state for each nozzle, and to adjust the liquid ejection amount, droplet size, etc. for each nozzle. Here, the drive information acquisition unit 9026 is an example of a "drive information acquisition means."

As described above, this embodiment provides a head control device 902 for controlling a head 300 having a needle valve 331 that moves between a position that closes and a position that opens a nozzle 302 that ejects liquid, and a piezoelectric element 332 that applies power to the needle valve 331 to move the needle valve 331. The needle valve 331 moves in a direction that closes the nozzle 302 in response to a first drive voltage V1 applied to the piezoelectric element 332, and moves in a direction that opens the nozzle 302 in response to a second drive voltage V2 that is different from the first drive voltage V1 applied to the piezoelectric element 332. The head control device 902 also includes a drive information acquisition unit 9026 that acquires information on the number of times the head 300 is driven or the drive frequency, and a control unit 9020 that increases the first drive voltage V1 (to drive voltage V1H) the greater the drive count or the higher the drive frequency acquired by the drive information acquisition unit 9026. This ensures that the nozzle 302 remains closed regardless of temperature.

<System Variations>
11, in the system exemplified as a printing apparatus, the thermistor 334, which is an example of a temperature measuring means, is provided inside the head system 30, but the location of the temperature measuring means is not limited to this. For example, in order to reduce the installation location and size of the head 300, the thermistor 334 may be provided in a location near the head inside the printing apparatus 1000, rather than in the head 300.

That is, the thermistor 334 is provided on the printing device 1000 side, which is a system equipped with the head 300 and ejects liquid. By using the thermistor 334 to detect the temperature near the head within the printing device 1000 equipped with the head 300, it is possible to roughly determine the temperature of the head 300.

Furthermore, if the temperature measured by the thermistor 334 is lower than a predetermined temperature, the head 300 is driven at a voltage V1L lower than the first drive voltage V1 until the temperature reaches the predetermined temperature. This makes it possible to prevent deformation or damage to the needle valve 331 due to excessive contact with the nozzle plate 301 caused by the head 300 being at a low temperature, even in this modified example.

<Explanation of head assembly device>
Next, an assembly device used when assembling the head 300 will be described with reference to Fig. 15. Fig. 15 is a block diagram showing an example of the configuration of the head assembly device.

By performing the above-mentioned drive voltage control, the head can reliably maintain a closed nozzle state regardless of temperature. However, the head system 30 and head control device 902 vary widely depending on the application, including the operating environment and temperature specifications of the liquid used in the head 300. Therefore, it is preferable to assemble the head 300 taking into consideration not only drive voltage control by the head control device 902, but also the temperature specifications of the liquid used in the head 300 and the environment in which the head 300 will be used, from the assembly stage onwards. In particular, it is preferable to adjust the holding position of the drive unit 330 relative to the housing 310 of the head 300 (the fastening parts using screw holes 310a, 314a and screws 310b) taking the above into consideration.

The head assembly device 1500 shown in Figure 15 is used to assemble the drive unit 330 relative to the housing 310, taking into consideration the temperature specifications of the liquid used in the head 300, the environment in which the head 300 will be used, etc. Note that the configuration shown in Figure 15 is just one example, and components may be added or removed as needed.

In Figure 15, the head assembly device 1500 comprises an input device 1501, a computer 1502, a head control device 902, and a head 300. The input device 1501 is a device for inputting information such as the temperature specifications of the liquid used in the head 300 and the environmental temperature in which the head 300 is used, and comprises a keyboard, mouse, touch panel, etc., and accepts input from an operator. The computer 1502 receives information and instructions regarding the temperature specifications of the liquid and the environment in which the head 300 is used from the input device 1501. The computer 1502 also transmits the information received from the input device 1501 to the head control device 902 (control unit 9020).

The head control device 902 can be, for example, the head control device described in Figure 5. Because the head 300 is an object to be assembled by the head assembly device 1500, it is replaced with another head 300 each time assembly is completed. The head control device 902 may be provided on the head 300 side, or on the head assembly device 1500 side. In the former case, the head control device 902 will be replaced with the head assembly device 1500 when the head 300 is replaced. In the latter case, a single head control device 902 will be used in common when assembling multiple heads 300. The configurations of the head control device 902 and head 300 have been described in Figure 5, so a description thereof will be omitted here.

<Head manufacturing method>
Next, the flow of processes (work) during head assembly will be described. Figure 16 is a flowchart showing an example of a head manufacturing process, and represents the processes carried out when assembling a head.

In Figure 16, first, the worker inputs information such as the temperature specifications of the liquid used by the head 300 and the environmental temperature in which the head 300 will be used (step S161). The information is input by the worker using the input device 1501 of the head assembly device 1500. The information input by the worker is received by the head control device 902 via the computer 1502. The head control device 902 then stores the received information such as the temperature specifications of the liquid and the environmental temperature in which the head will be used in the temperature data storage unit 9024 of the head control device 902 (see Figure 5).

Next, the correction value calculation unit 9025 in the head control device 902 calculates a correction value for the drive voltage to be used for assembly adjustment based on the data stored in the temperature data storage unit 9024 in step S161 (step S162). The temperature data storage unit 9024 stores a table that links, for example, the liquid temperature specifications, the head usage environment temperature, the amount of contraction of the drive unit 330 at each temperature, and the drive voltage value to compensate for that amount of contraction. The correction value calculation unit 9025 then compares the table in the temperature data storage unit 9024 with the information received from the input device 1501 to calculate a correction value for the drive voltage to be used for assembly adjustment, and transmits the correction value information to the drive waveform generation unit 9021.

When the drive waveform generation unit 9021 receives the correction value information, it generates a drive waveform based on the correction value information (step S163). The drive waveform generation unit 9021 transmits the generated drive waveform signal to the head 300 via the drive waveform amplifier unit 9022, and applies a drive voltage for assembly adjustment to the head 300. The worker then assembles the head 300 in an environment where the drive voltage for assembly adjustment is applied (step S164).

This makes it possible to position the housing 310 and drive unit 330 of the head 300 under conditions and environments that are close to actual usage, thereby reducing the load on the control circuit during correction processing. It also makes it possible to reduce the time required for initial adjustments at the system installation site. Specific examples of assembly adjustments are described below.

For example, when assembling the head 300 for use in an environment with a temperature of less than 30°C, the amount of temperature-induced contraction of the drive unit is small, as shown in Figure 4. Therefore, the head 300 is assembled using the first drive voltage V1 (solid line in Figure 6) as the drive voltage for assembly adjustment. This makes it possible to manufacture (assemble) a head that can accurately open and close nozzles in an environment with a temperature of less than 30°C.

Furthermore, for example, when assembling the head 300 for use in an environment with a temperature between 30°C and 50°C, the amount of shrinkage of the drive unit due to temperature is large. Therefore, if assembly adjustment is performed using the first drive voltage V1, there is a possibility that the needle valve 331 will not completely close the nozzle 302. In this case, the head 300 is assembled using drive voltage V1H (dashed line in Figure 6) as the drive voltage for assembly adjustment. This makes it possible to manufacture (assemble) a head that can accurately open and close the nozzle even when the head 300 is placed in an environment with a temperature between 30°C and 50°C. By incorporating the manufacturing process described above, assembly adjustment that is suited to the actual usage environment becomes possible.

<Application example>
An application example of the system according to the embodiment of the present invention will be described below with reference to FIGS.

<First application example>
17A and 17B are schematic diagrams showing a first application example of a system according to an embodiment of the present invention, in which FIG. 17A is an overall configuration diagram and FIG. 17B is an enlarged view of a main part of FIG. 17A.

The illustrated system is a printing device that forms an image on, for example, the side of an aircraft fuselage. The printing device 2000 includes a linear rail 404 that supports a carriage 1 so that it can move linearly back and forth, and an articulated robot 405 that moves the linear rail 404 to a predetermined position as needed and holds it in that position. The articulated robot 405 includes a robot arm 405a that has multiple joints that allow it to move freely like a human arm, and the tip of the robot arm 405a can be moved freely and positioned accurately.

The articulated robot 405 may be, for example, a six-axis controlled industrial robot with six axes, i.e., six joints. With a six-axis articulated robot, by teaching information about its operation in advance, the linear rail 404 can be positioned at a predetermined position on the machine body 702 with great accuracy and speed. The robot 405 is not limited to six axes, and articulated robots with an appropriate number of axes, such as five or seven, can also be used.

The robot arm 405a of the robot 405 is equipped with a fork-shaped support member 424. A vertical linear rail 423a is attached to the tip of the left branch 424a of this support member 424, and a vertical linear rail 423b is attached to the tip of the right branch 424b so that they are parallel to each other. The two vertical linear rails 423a, 423b support both ends of the linear rail 404, which movably holds the carriage 1.

The carriage 1 is equipped with the above-mentioned head system 30 and head control device 902, and is equipped with a head that ejects liquid toward the machine body 702. The head may be the above-mentioned head 300, or multiple heads 300 that eject liquid of each color, such as yellow, magenta, cyan, black, and white, or a head 300 with multiple nozzle rows. Liquid of each color is supplied from an ink tank 400 to each head 300 or each nozzle row of the head 300 of this carriage 1.

Carriage 1 moves in a first direction by moving on linear rail 404, and can move in a second direction intersecting the first direction by moving linear rail 404 on vertical linear rails 423a and 423b. Carriage 1 also has a first slide mechanism that moves carriage 1 in a third direction intersecting the first and second directions (in this example, the direction of liquid ejection toward machine body 702). Carriage 1 also has a second slide mechanism that moves the head relative to carriage 1 in the third direction.

The printing device 2000 uses the robot 405 to move the linear rail 404 to the image formation area of the machine body 702, and drives the head 300 while moving the carriage 1 along the linear rail 404 according to the image data to form an image. Then, when printing of one line is completed, the vertical linear rails 423a and 423b are driven to move the head 300 of the carriage 1 from one line to the next. By repeating this operation, it is possible to form an image in the required image formation area of the machine body 702.

<Second Application Example>
FIG. 18 is a schematic diagram showing a second application example of the system according to the embodiment of the present invention.

The illustrated system is an unmanned vehicle-type printing device, such as a wall-climbing robot. The printing device 7000 is capable of moving an object 100 (the wall of a building in this example) by driving a roller 710 while sucking it at the bottom of the printing device 7000. The printing device 7000 is equipped with a head 720 that ejects liquid such as ink, and supplies liquid contained in a liquid tank 730 to the head 720 via a cable 740. The printing device 7000 then ejects the liquid from the head 720 toward the object 100, applying the liquid to the painted area P of the object 100.

In this application example, the liquid tank 730 is installed on the ground and liquid is supplied from the liquid tank 730 to the head 720 via the cable 740, but the liquid tank 730 may also be provided in the printing device 7000. By providing the liquid tank 730 in the printing device 7000, the movement range restriction imposed by the cable 740 can be eliminated, allowing the printing device 7000 to move freely.

The effects of the present invention can also be achieved when the head system 30 and head control device 902 described above are applied to the head 720 of such a printing device 7000.

<Third Application Example>
FIG. 19 is a schematic diagram showing a third application example of the system according to the embodiment of the present invention.

The illustrated system is an unmanned vehicle-type printing device, such as a road-traveling robot. The unmanned vehicle 9000 is capable of moving an object 100 (in this embodiment, a road surface such as a roadway or sidewalk) by driving wheels 910. The unmanned vehicle 9000 is equipped with a head 920 that ejects liquid such as ink, and liquid stored in a liquid tank 930 is supplied to the head 920 via a cable 940. The unmanned vehicle 9000 then ejects the liquid from the head 920 toward the object 100, applying the liquid to a painted area P of the object 100 and forming, for example, a crosswalk, a stop line, a center line, etc. on the road surface.

In this application example, the liquid tank 930 is installed on the ground and liquid is supplied from the liquid tank 930 to the head 920 via the cable 940, but the liquid tank 930 may also be provided on the unmanned vehicle 9000. By providing the liquid tank 930 on the unmanned vehicle 9000, the movement range restriction imposed by the cable 940 can be eliminated, allowing the unmanned vehicle 9000 to move freely.

Furthermore, the effects of the present invention can be obtained even when the above-described head system 30 and head control device 902 are applied to the head 920 of such an unmanned vehicle 9000.

<Fourth Application Example>
FIG. 20 is a schematic diagram showing a fourth application example of the system according to the embodiment of the present invention.

The illustrated system is a painting robot 8000 that paints, for example, the body of an automobile. The painting robot 8000 is equipped with a robot arm 810 that has multiple joints that allow it to move freely like a human arm, and a head 820 that ejects liquid at the tip of the robot arm 810. The robot arm 810 also has a 3D sensor 830 near the head 820. The painting robot 8000 can be a multi-joint robot with an appropriate number of axes, such as five, six, or seven. The painting robot 8000 detects the position of the head 820 relative to the object (a car body in this embodiment) 100 using the 3D sensor 830, and moves the robot arm 810 based on the detection results to paint the object 100.

The effects of the present invention can also be obtained when the head system 30 and head control device 902 described above are applied to the head 820 of such a painting robot 8000.

<Fifth Application Example>
FIG. 21 is a schematic diagram showing a fifth application example of the system according to an embodiment of the present invention.

The illustrated system is an unmanned aerial vehicle 6000, such as a drone. The unmanned aerial vehicle 6000 controls its position based on the detection results of a detector 610, such as a distance sensor, mounted on the unmanned aerial vehicle 6000. The unmanned aerial vehicle 6000 is equipped with a head 620 that ejects liquid such as ink, and supplies liquid stored in a liquid tank 630 to the head 620 via a cable 640. Then, based on the above position control, the unmanned aerial vehicle 6000 ejects liquid from the head 620 toward an object 100 (the wall surface of a building in this embodiment), applying the liquid to a coating area P of the object 100.

In this application example, the liquid tank 630 is installed on the ground and liquid is supplied from the liquid tank 630 to the head 620 via the cable 640, but the liquid tank 630 may also be provided on the unmanned aerial vehicle 6000. By providing the liquid tank 630 on the unmanned aerial vehicle 6000, the movement range restriction imposed by the cable 640 can be eliminated, allowing the unmanned aerial vehicle 6000 to move freely.

Furthermore, the effects of the present invention can be obtained even when the above-described head system 30 and head control device 902 are applied to the head 620 of such an unmanned aerial vehicle 6000.

<Additional Information>
In the present invention, the liquid may be a solution, suspension, emulsion, or the like containing a solvent such as water or an organic solvent, a colorant such as a dye or a pigment, a polymerizable compound, a resin, a surfactant, or the like, a functional material such as DNA, an amino acid, a protein, or calcium, an edible material such as a natural colorant, etc. These can be used, for example, in inkjet inks, coating materials, surface treatment solutions, liquids for forming components of electronic elements or light-emitting elements, or electronic circuit resist patterns, and material liquids for three-dimensional modeling.

The above is just one example, and the present invention offers unique advantages in each of the following aspects:

The first aspect is a head control device (e.g., head control device 902) for controlling a head system (e.g., head system 30) that includes a head (e.g., head 300) having a valve element (e.g., needle valve 331) that moves between a position that closes and a position that opens a nozzle that ejects liquid, and an actuator (e.g., piezoelectric element 332) that applies power to the valve element to move the valve element, and temperature measurement means (e.g., thermistor 334), wherein the valve element moves in a direction that closes the nozzle in response to a first drive voltage (e.g., drive voltage V1) applied to the actuator, and moves in a direction that opens the nozzle in response to a second drive voltage (e.g., drive voltage V2) that is different from the first drive voltage applied to the actuator, and is characterized by comprising control means (e.g., control unit 9020) that increases the first drive voltage (e.g., to drive voltage V1H) as the temperature measured by the temperature measurement means increases.

The second aspect is the first aspect, characterized in that the temperature measurement means (e.g., thermistor 334) is provided in any of the following members: the casing (e.g., housing 310) of the head (e.g., head 300), the actuator (e.g., piezoelectric element 332), or the elastic member (e.g., leaf spring frame 333) that holds the actuator, and the temperature measurement means measures the temperature of the member.

According to the first and second aspects, the nozzle can be reliably maintained in a closed state regardless of temperature.

The third aspect is the first aspect, characterized in that the control means (e.g., control unit 9020) increases the first drive voltage (e.g., drive voltage V1) and the second drive voltage (e.g., drive voltage V2) (e.g., to drive voltage V2H) as the temperature measured by the temperature measurement means (e.g., thermistor 334) increases.

The fourth aspect is the first aspect, wherein the control means (e.g., control unit 9020) varies the first drive voltage (e.g., drive voltage V1) and the second drive voltage (e.g., drive voltage V2) so that the potential difference between them is constant.

The third and fourth aspects allow the nozzles to be reliably maintained in a closed state regardless of temperature, while also reducing fluctuations in the liquid ejection characteristics.

The fifth aspect is characterized in that, in any of the first to fourth aspects, if the temperature measured by the temperature measurement means (e.g., thermistor 334) is lower than a predetermined temperature, the head (e.g., head 300) is driven at a voltage (e.g., voltage V1L) lower than the first drive voltage (e.g., drive voltage V1) until the temperature reaches the predetermined temperature.

The fifth aspect prevents deformation or damage caused by excessive contact of the valve body with the nozzle plate due to the head being at a low temperature.

30 Head system 300 Head 302 Nozzle 331 Needle valve 332 Piezoelectric element 334 Thermistor 902 Head control device 9020 Control unit 9021 Drive waveform generation unit 9022 Drive waveform amplification unit 9024 Temperature data storage unit 9025 Correction value calculation unit 9026 Drive information acquisition unit 1000 Printing device

Japanese Patent Application Laid-Open No. 2010-241003

Claims (8)

A head control device for controlling a head system including a head having a valve body that moves between a position for closing and a position for opening a nozzle that ejects liquid, and an actuator that applies power to the valve body to move the valve body, and a temperature measuring means,
the valve element is a valve element that moves in a direction to close the nozzle in response to a first drive voltage applied to the actuator, and moves in a direction to open the nozzle in response to a second drive voltage applied to the actuator that is different from the first drive voltage,
a control unit for controlling the second driving voltage together with the first driving voltage so that the higher the temperature measured by the temperature measuring unit is, the higher the head control device is; 2. A head control device according to claim 1, wherein the temperature measuring means is provided in any one of a housing of the head, the actuator, and an elastic member that holds the actuator, and the temperature measuring means measures the temperature of the member . 2. The head control device according to claim 1, wherein the control means varies the first drive voltage and the second drive voltage so that a potential difference between the first drive voltage and the second drive voltage is constant. 4. A head control device according to claim 1, wherein when the temperature measured by the temperature measuring means is lower than a predetermined temperature, the head is driven at a voltage lower than the first driving voltage until the temperature reaches the predetermined temperature. A head control device for controlling a head having a valve body that moves between a position for closing a nozzle and a position for opening a nozzle that ejects liquid, and an actuator that applies power to the valve body to move the valve body,
the valve element is a valve element that moves in a direction to close the nozzle in response to a first drive voltage applied to the actuator, and moves in a direction to open the nozzle in response to a second drive voltage applied to the actuator that is different from the first drive voltage,
a drive information acquisition means for acquiring information on the number of times the head is driven or the drive frequency;
a control unit that increases the first drive voltage as the number of drive times acquired by the drive information acquisition unit increases or as the drive frequency increases. A liquid ejection system comprising the temperature measurement means according to any one of claims 1 to 4, the temperature measurement means being provided on the liquid ejection system side, which is a system equipped with the head and ejects liquid. 7. A liquid ejection system according to claim 6, wherein, when the temperature measured by the temperature measuring means is lower than a predetermined temperature, the head is driven at a voltage lower than the first driving voltage until the temperature reaches the predetermined temperature. A method for manufacturing a head of the head control device according to any one of claims 1 to 5 , comprising the steps of:
The head
a drive unit including the valve body, the actuator, and an elastic member that holds the actuator and is elastically deformed by driving the actuator to transmit the driving force of the actuator to the valve body;
a housing for holding the drive unit,
the first driving voltage and the second driving voltage are set in accordance with at least one of a temperature specification of the liquid used in the head and an environmental temperature in which the head is used;
a holding position of the drive unit relative to the housing being determined based on the first drive voltage and the second drive voltage obtained by the setting;