JP6780731B2 - Discharge device - Google Patents

Description

The present invention relates to the discharge equipment.

As a coating device such as a coating device, a device including a liquid discharge means (droplet discharge means) such as a liquid discharge head (droplet discharge head) is known.

For example, it is known that a coating liquid is discharged from a rotating cylindrical object to be coated toward the center of the cylinder, which is the axis of rotation, and the coating liquid is applied so as to overlap the surface of the object to be coated. (Patent Document 1).

JP-A-11-19554

However, in the configuration disclosed in Patent Document 1, when the number of rotations of the object to be coated is increased in order to realize coating at a higher speed, an air flow in the rotation direction is generated on the surface of the rotating body, and the air flow causes the object to be coated. Droplets that do not land on the object to be coated are generated, causing uneven coating at that site. Therefore, there is a problem that the coating speed cannot be increased and the productivity cannot be increased.

The present invention has been made in view of the above problems, and an object of the present invention is to improve the productivity of coating work while suppressing coating unevenness.

In order to solve the above problems, the discharge device according to the present invention
A liquid ejection means having a nozzle for ejecting droplets toward the peripheral surface of the ejected member is provided.
The droplet ejection direction of the droplet linearly ejected from the nozzle is more than the point where the straight line connecting the nozzle and the rotation center of the ejected member intersects the peripheral surface of the ejected member. The direction of rotation is toward the upstream side,
The nozzle is arranged in a position lower than the highest position of the discharged member in the direction of gravity.

According to the present invention, the productivity of coating work can be improved while suppressing coating unevenness.

It is a schematic explanatory drawing seen from the rotation center direction of the member to be coated as the member to be discharged which is used for the description of one Embodiment of this invention. It is explanatory drawing provided to the operation explanation of the same embodiment. It is also the explanatory diagram provided for the operation explanation. It is also the explanatory diagram provided for the operation explanation. It is also the explanatory diagram provided for the operation explanation. Similarly, it is explanatory drawing which provides the explanation of an example of the landing state when the droplet does not land on the coating surface from the normal direction of the member to be coated . Also is an explanatory diagram for the description. Similarly, it is explanatory drawing which provides for the explanation of another example of the landing state when the droplet does not land on the coating surface from the normal direction of the member to be coated . Also is an explanatory diagram for the description. It is a schematic explanatory drawing of the coating device as a discharge device which concerns on this invention. It is an enlarged explanatory view of the movable part of the coating apparatus. It is a schematic explanatory drawing provided for the explanation of the arrangement of the drop measuring means. It is a schematic explanatory drawing of an example of a liquid discharge head. It is a plane explanatory view of the nozzle plate of the head. Similarly, it is a plan explanatory view of a flow path plate. It is a flow figure which provides the explanation of the rotation speed setting process of a member to be painted. It is a flow figure which provides the explanation of the control (processing) which concerns on a coating operation. FIG. 5 is a flow chart to be used for explanation following FIG. It is explanatory drawing explaining the coating state at the time of performing the coating operation of FIG. Similarly, it is explanatory drawing explaining the coating state. Similarly, it is explanatory drawing explaining the coating state. Similarly, it is explanatory drawing explaining the coating state. It is explanatory drawing of the head specification provided to the description of specific Example 1 and Comparative Examples 1 and 2. It is explanatory drawing which provides the arrangement of the head and the member to be coated, and the rotation direction of Example 1 and Comparative Examples 1 and 2. It is explanatory drawing provided to the operation explanation of Example 1. FIG. It is explanatory drawing provided to the operation explanation of the comparative example 2.

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. An embodiment of the present invention will be described with reference to FIG. FIG. 1 is a schematic explanatory view seen from the direction of the center of rotation of the member to be coated as the member to be discharged, which is used for the description of the embodiment.

The coating device of the present embodiment includes a liquid discharging head 1 which is a liquid discharging means for discharging droplets 61 of the coating liquid on the peripheral surface of the member 51 to be coated. The member to be coated 51 is a cylindrical (including cylindrical) member that is rotated in the arrow direction (B direction).

Here, in the liquid discharge head 1, the droplet discharge direction A is such that the straight line a connecting the nozzle 40 for discharging the droplet 61 and the rotation center O of the member 51 to be coated is the peripheral surface (coating surface) of the member 51 to be coated. The member 51 to be coated is arranged in a direction toward the upstream side in the rotation direction of the member 51 to be coated.

Further, the liquid discharge head 1 is arranged in a state in which the drop discharge direction is in the direction of gravity (vertical direction) and directly downward.

Further, in the liquid discharge head 1, the nozzle 40 is arranged in the second quadrant when the rotation direction of the member to be coated 51 is a clockwise direction. At this time, the liquid discharge head 1 has the nozzle 40 at a position lower than the highest position c or the position c of the member 51 to be coated in the direction of gravity.

Further, the liquid discharge head 1 is arranged at a position where the droplet 61 lands on the normal line d with respect to the rotation center O of the member 51 to be coated. Here, the droplet ejection speed of the droplet 61, the rotation speed of the member 51 to be coated, and the position of the liquid ejection head 1 are set so that the droplet 61 lands on the normal line d.

Next, the operation of the embodiment configured in this way will be described.

First, the behavior of the droplet 61 until the droplet 61 discharged from the liquid discharge head 1 has landed on the peripheral surface (applied surface) of the member 51 to be coated will be described.

The liquid droplet 61 discharged from the nozzle 40 of the liquid discharge head 1 flies in a direction perpendicular to the surface on which the nozzle 40 is formed (vertically downward in FIG. 1).

At this time, due to the rotation of the member 51 to be coated, an air flow in the rotation direction is generated in the vicinity of the coated surface of the member 51 to be coated.

As a result, as the droplet 61 approaches the coated surface of the member 51 to be coated, the airflow generated by the rotation of the member 51 to be coated gradually causes the droplet 61 to flow in the direction of the airflow indicated by the thick arrow in FIG.

At this time, assuming that the discharge direction from the nozzle 40 is directed to the rotation center O of the member 51 to be coated, the droplets flowed in the air flow are flowed in the direction away from the member 51 to be coated. Then, when the velocity of the airflow exceeds a certain velocity, the airflow does not land on the member 51 to be coated.

Since the actual droplets have variations in the droplet velocity and the droplet amount, the impact loss gradually increases as the air flow increases, which causes coating unevenness.

On the other hand, in the coating apparatus of the present embodiment shown in FIG. 1, the droplet ejection direction A is the straight line a connecting the nozzle 40 for ejecting the droplet 61 and the rotation center O of the member 51 to be coated. By making the member 51 to be coated toward the upstream side in the rotation direction rather than the point where it intersects the peripheral surface (coating surface) of 51, the droplet 61 is rather coated even if the droplet 61 is flowed into the airflow. By approaching the member 51, the impact rate of the droplet 61 on the member to be coated 51 is significantly increased. This enables high-speed coating without uneven coating.

Further, since the liquid discharge head 1 is arranged so that the drop discharge direction is in the direction of gravity (vertical direction) and directly downward, the action direction of the air flow is in the direction opposite to the gravity, so that the air flow is faster. Even if it is (rotational speed of the member to be coated 51), the impact rate can be maintained.

Further, the liquid discharge head 1 causes the droplet 61 to be above the discharge position (nozzle 40) by setting the nozzle 40 at a position lower than the highest position c or the position c of the member 51 to be coated in the direction of gravity. As long as the airflow is not strong enough to fly, it can surely land on the member to be coated 51.

Further, as shown in FIG. 1, when the droplet 61 is discharged from the liquid discharge head 1, a minute mist 62 may be generated, but this lightweight mist 62 rotates the member 51 to be coated. It is swept away by the airflow generated by the member 51 and is blown off without landing on the coated surface of the member 51 to be coated. As a result, the droplet 61 is surely landed and the mist 62 is not landed, so that uniform coating is possible.

Further, here, the liquid discharge head 1 is arranged so that the droplet 61 flowed by the air flow lands on the painted surface of the member 51 to be coated from the normal direction.

As a result, as shown in FIG. 2, the droplet 61 starts to come into contact with the coated surface substantially perpendicularly to the painted surface, and at the same time, the member 51 to be coated is rotating. Therefore, as shown in FIG. It is thinly stretched in the direction of rotation of the member 51 to be coated. Then, as shown in FIGS. 4 and 5, when the landing of the droplet 61 is completed, the coating droplet 67 can be thinly stretched to a substantially uniform thickness on the coating surface.

On the other hand, the landing state when the droplet 61 does not land on the coated surface from the normal direction of the member 51 to be coated will be described with reference to FIGS. 6 to 9.

Even when the liquid discharge head 1 is arranged as in the above embodiment, for example, when the rotation speed of the member 51 to be coated is high (or the drop speed is low), the flight path of the droplet 61 is shown in FIG. Will be. That is, the droplet 61 enters the coated surface at an acute angle from the upstream side to the downstream side in the rotational direction and lands.

At this time, since the speed difference between the coated surface and the droplet 61 becomes smaller with respect to the moving direction of the coated surface, the degree of stretching of the landed droplet 61 becomes smaller and the film thickness becomes thicker as shown in FIG. Therefore, it becomes difficult to form a uniform thin film.

On the other hand, for example, when the rotation speed of the member 51 to be coated is slow (or the drop speed is high), the flight path of the droplet 61 is as shown in FIG. That is, the droplet 61 enters the coated surface at an acute angle from the downstream side in the rotation direction toward the upstream side and lands.

At this time, the flight direction of the droplet 61 and the rotation direction of the member 51 to be coated are substantially opposite to each other, and the relative velocities of the two become extremely large. As shown in FIG. 9, the droplet 61 that has landed on the member 51 to be coated in such a state has a distorted landing shape, and the uniformity of the film thickness is slightly lowered.

Further, when the rotation speed of the member to be coated 51 is slowed down, the airflow around the member to be coated 51 is also reduced, so that the mist 62 generated when the droplet 61 is discharged may land on the coated surface. .. In this case, the uniformity of the film thickness is further lowered.

As described above, by making the droplet 61 land on the coated surface of the member 51 to be coated from the normal direction, a uniform thin film can be applied to the member 51 to be coated.

Next, the coating device as the discharge device according to the present invention will be described with reference to FIGS. 10 to 12. 10 is a schematic explanatory view of the coating device, FIG. 11 is an enlarged explanatory view of a movable portion of the coating device, and FIG. 12 is a schematic explanatory view for explaining the arrangement of the drop measuring means.

A coating liquid is supplied to the liquid discharge head 1 from a liquid tank (not shown) that stores the coating liquid. A trigger sensor 58 is arranged corresponding to the liquid discharge head 1.

The work stage 54 is arranged so as to be reciprocally movable in the direction of the arrow with respect to the liquid discharge head 1.

The work stage 54 includes, on the stage 57, rotatable holders 56 and 56 that support the member to be coated 51 at both ends in the axial direction, and a drive motor 57 that rotates the member to be coated 51 via the holder 56. ing.

Further, on the bottom surface side of the stage 57, sensor dogs 52 and 53 detected by the trigger sensor 58 are provided. The trigger sensor 58 detects the edges 52R, 52L, 53R, 53L of the sensor dogs 52 and 53 to control the start and end of coating.

Further, as shown in FIG. 12, a camera 70 for measuring the flight speed and direction of the droplet 61 ejected from the liquid ejection head 1 and a droplet measuring means including illumination (not shown) are provided.

Next, an example of the liquid discharge head will be described with reference to FIGS. 13 to 15. FIG. 13 is a schematic explanatory view of the liquid discharge head, FIG. 14 is a plan explanatory view of the nozzle plate of the head, and FIG. 15 is a plan explanatory view of the flow path plate.

The liquid discharge head 1 includes a drive unit 3 and a liquid chamber unit 2 joined to the drive unit 3.

The drive unit 3 is formed by alternately arranging a plurality of piezoelectric element drive units (hereinafter, drive units) 14a and support columns 14b on the substrate 15, and these drive units 14a and support columns 14b are spaced apart from each other on the substrate. It is joined to 15.

The liquid chamber unit 2 corresponds to a nozzle plate 11 having a plurality of nozzles 40 for ejecting droplets 61, a flow path plate 12 in which an individual liquid chamber 30 through which the nozzles 40 communicate is formed, and an individual liquid chamber 30. Moreover, it is composed of a diaphragm member 13 that transmits the vibration of the drive unit 14a of the drive unit 3 to the individual liquid chamber 30.

The nozzle plate 11, the flow path plate 12, and the diaphragm 13 constituting these liquid chamber units 2 are coated with an adhesive 16 on the upper surface of the flow path plate and are joined with high accuracy via the adhesive 16.

Further, the liquid chamber unit 2 is adhesively bonded to the upper surfaces of the piezoelectric element drive portions 14a and the support columns 14b of the drive unit 3 with high accuracy via an adhesive 16.

The liquid discharge head 1 supplies a coating liquid from a storage tank (not shown), fills the individual liquid chamber 30, and selectively drives the drive unit 14a, whereby the droplet 61 is discharged from the nozzle 40.

Here, the liquid discharge head 1 has a second quadrant in a cross section orthogonal to the rotation center axis of the member 51 to be coated, as shown in FIG. 1 described above, with respect to the member 51 to be coated held on the work stage 54. It is located in the quadrant. As a result, the nozzle row in which the plurality of nozzles 40 of the liquid discharge head 1 are arranged is located diagonally above the rotation center axis of the member to be coated 51, and is the center of rotation in the direction along the rotation center axis of the member to be coated. The droplet 61 is arranged so as to be parallel to the axis and the ejection direction of the droplet 61 is vertically downward.

Next, the coating operation in the coating apparatus configured as described above will be described.

First, a drive waveform is set to be applied to the piezoelectric element drive unit 14a necessary for controlling the droplet 61 discharged from the liquid discharge head 1 to land vertically on the coating region 65 of the member to be coated 51.

The viscosity of the coating liquid discharged as the droplet 61 changes depending on the elapsed time after formation. Therefore, in order to eject the droplet 61 at a constant drop velocity and drop size, the drive waveform applied to the piezoelectric element drive unit 14a is adjusted according to the elapsed time after the coating liquid is generated (for example, the drive voltage is increased). To do) is required.

Therefore, by an experiment in advance, the elapsed time after the coating liquid is generated and the data of the driving waveform are tabulated and stored in a storage means of a control unit (not shown).

Next, the rotation speed setting process of the member to be coated will be described with reference to the flow chart of FIG.

First, a dummy coated member 51 used for setting the rotation speed is set on the work stage 54, and is rotationally driven by the motor 55 at the maximum speed of the coating device.

Then, the liquid discharge head 1 is driven with a drive waveform and a constant drive frequency corresponding to the elapsed time after the coating liquid is generated, which correlates with the viscosity of the coating liquid. As a result, the liquid droplet 61 is continuously ejected from the liquid ejection head 1 at a constant frequency at a constant droplet ejection speed and droplet size.

At this time, the landing direction of the ejected droplet 61 is measured by the camera 70. If the landing direction of the droplet 61 is not perpendicular to the coating surface (normal direction), the rotation speed of the dummy coated member 51 is reduced by a constant speed previously obtained in an experiment or the like.

Similarly, the measurement of the landing direction of the droplet 61 and the reduction of the rotation speed are repeated until the landing direction of the droplet 61 with respect to the coated surface is perpendicular to the coated surface (becomes normal).

Then, the rotation speed when the landing direction of the droplet 61 is perpendicular to the coating surface is stored and stored in a storage means of a control unit (controller) (not shown).

Next, the control (processing) related to the coating operation will be described with reference to the flow charts of FIGS. 17 and 18 and the explanatory diagrams of FIGS. 19 to 22.

The member to be coated 51 is set on the work stage 54 of the coating device, and the motor 55 is driven to set the member 51 to be coated as described above and rotate it at a rotational speed.

Then, a scanning motor (not shown) starts the work stage 54 to move to a position where the liquid droplets are discharged by the liquid discharge head 1 at a set speed set by obtaining the work stage 54 in advance by an experiment or the like.

After that, when the edge 52L (see FIG. 11) of the sensor dog 52 is detected by the trigger sensor 58, the coating liquid is applied from the first nozzle 40 (40-1) of the liquid discharge head 1 as shown in FIG. The droplet 61 is started to be ejected with a drive waveform corresponding to the elapsed time after generation and a constant ejection cycle (see FIG. 19).

Then, when the work stage 54 moves by the distance between the nozzles, discharge from the second nozzle 40 (40-2) is started in the discharge cycle. Similarly, while moving the work stage 54 at a constant speed, ejection from the nozzle 40 is sequentially started for each movement corresponding to the distance between the nozzles. Examples of the state of the coated surface of the member 51 to be coated at this time are shown in FIGS. 20 and 21.

After that, when the edge 53L of the sensor dog 53 is detected by the trigger sensor 58, the discharge from the first nozzle 40 (40-1) is stopped. Then, when the work stage 54 moves by the distance between the nozzles, the discharge from the second nozzle 40 (40-2) is stopped. Similarly, the ejection of all the nozzles 40 is stopped while the work stage 54 continues to move at a constant speed. FIG. 22 shows an example of the state of the coated surface of the member 51 to be coated at this time.

Then, the work stage 54 is stopped from moving on the outward route. As a result, as shown in FIG. 22B, the coating liquid is applied to the member to be coated 51 on the outward route.

After that, the work stage 54 starts moving in the direction opposite to the outward direction (return direction) described above, and when the edge 53R (see FIG. 11) of the sensor dog 53 is detected by the trigger sensor 58, the final nozzle 40 (see FIG. 11) From 40-N), the droplet 61 is sequentially started to be ejected every time the nozzles move by the distance between the nozzles. Then, in the same manner, when the edge 52R of the sensor dog 52 is detected by the trigger sensor 58, the droplet 61 is sequentially stopped from the last nozzle 40 (40-N) for each movement by the distance between the nozzles. After discharging and stopping the discharge from all the nozzles 40, the movement of the work stage 54 on the return path is stopped.

As a result, the coating film applied on the outward trip is coated in the same manner as on the outward trip, and the coating of the member 51 to be coated on the coating region 65 is completed.

Therefore, the member to be coated 51 is taken out from the coating device.

Next, the effects of the present invention will be described with reference to FIGS. 23 to 26.

The member to be coated was coated under the following coating conditions by the coating devices of Example 1 and Comparative Examples 12 and 3 in which the following liquid discharge head, coating liquid, and member to be coated were incorporated.

<Liquid discharge head>
Those having the head specifications of the shape characteristics / components, ejection characteristics, and ink required characteristics shown in FIG. 23 were used.
<Coating liquid>
Viscosity: 5.06 mPa · s
<Member to be coated>
(1) Outer diameter: φ12.7 mm
(2) Coating range: 345 mm
<Painting conditions>
(1) Rotation speed of the object to be coated: 2000 rpm
(2) Feeding speed of the object to be coated: 29 mm · s
(3) Head discharge frequency: 6000 Hz
(4) Droplet flight distance discharged from the head: 2 mm
(5) Film thickness: 10 μm

<Example 1>
As shown in FIG. 24A, the liquid discharge head 1 is arranged at a position offset by 3 mm from the normal of the rotation center 0 of the member to be coated 51, and the direction of discharging the coating liquid is the head 1 and the member to be coated 51. The coating was performed by arranging the member 51 to be coated in the direction upstream of the rotation direction (direction of arrow B) from the point where the straight line connecting the rotation centers of the members 51 and the coating surface of the member 51 to be coated intersect.

<Comparative example 2>
As shown in FIG. 24B, painting was performed under the condition that the liquid discharge head 1 was arranged at the normal position of the rotation center 0 of the member 51 to be coated. The rotation direction of the member to be coated 51 was opposite to that in the first embodiment (arrow C direction).

<Comparative example 3>
As shown in FIG. 26, the liquid discharge head 1 is arranged at a position offset by 3 mm from the normal of the rotation center 0 of the member 51 to be coated, and the direction in which the coating liquid is discharged is the rotation center of the head 1 and the member 51 to be coated. The coating was performed by arranging the members 51 to be coated in a direction downstream of the rotation direction of the member 51 from the intersection of the straight line connecting the two members and the coating surface of the member 51 to be coated. That is, the coating was performed with the rotation direction of the member to be coated 51 opposite to that of the first embodiment (arrow C direction).

The coating efficiency in Examples 1 and Comparative Examples 1 and 2 was calculated by measuring the weight remaining on the member 51 to be coated from the weight of the coating liquid required to coat one member 51 to be coated.

That is, first
(1) Discharge was performed under the same conditions as when one coating member 51 was coated, and the entire amount of the discharged coating liquid was received by the container.
(2) The weight difference between the containers before and after discharge was measured, and the weight G3 of the discharged coating liquid was determined.
(3) Subsequently, a container containing the coating liquid was placed in a firing furnace, and the weight after firing was measured.
(4) The dry weight G5 of the discharged coating liquid was determined from the difference from the initial weight of the container.

next,
(5) The member to be painted 51 was painted under the three conditions of Example 1, Comparative Example 1, and Comparative Example 2.
(6) The weight difference between the member to be coated 51 before and after coating was measured, and the weight G31 of the coating liquid applied to the member 51 to be coated was determined.
(7) Subsequently, the member 51 to be coated to which the coating liquid was applied was placed in a firing furnace, and the weight after firing was measured.
(8) The dry weight G51 of the coating liquid applied to the member to be coated 51 was determined from the difference from the initial weight of the member to be coated 51.

And
(9) G51 / G5 × 100 (%) was calculated to obtain the coating efficiency under each condition of Example 1, Comparative Example 1, and Comparative Example 2.

The weight before firing changes due to the influence of the volatilization state of the solvent, and is therefore a reference value only.

The coating efficiency calculated as described above was 80% in Example 1, 45% in Comparative Example 1, and 15% in Comparative Example 2.

From this, it can be confirmed that the coating liquid is less scattered in Example 1, and the coating efficiency is very good as described above.

By adopting the configuration of the first embodiment, as shown in FIG. 25 (b), the force P1 by the airflow 301 during the rotation of the member 51 to be coated on the droplet 300, the propulsive force of the droplet 300, and the gravity. The combined force P is reduced by the total value P2 of. Therefore, as shown by the arrow 303 in FIG. 25 (a), it is presumed that the effect is that the ejected droplets 300 fly stably and go straight toward the coated surface of the member 51 to be coated. ..

On the other hand, in Comparative Example 1, the coating liquid is scattered more than in Example 1, and the coating efficiency is also lower than that in Example 1 as described above.

Further, in Comparative Example 2, it was confirmed that the coating liquid was scattered a lot, and as described above, the coating efficiency was very poor.

As shown in FIG. 26B, this is because the force P1 due to the airflow 302 during rotation of the member 51 to be coated on the droplet 300 and the combined force P due to the total value P2 of the propulsive force and gravity of the droplet 300 are calculated. The direction is along the peripheral surface of the member 51 to be coated, and when the member 51 to be coated has a small diameter and is coated at a high speed, a strong air flow around the liquid discharge head 1 and the member 51 to be coated is generated. .. Therefore, as shown by the arrow 304 in FIG. 26 (a), it is presumed that the discharged droplet 300 rides on the air flow 302 and flows along the peripheral surface of the member 51 to be coated and does not land on the painted surface. ..

1 ... Liquid discharge head 11 ... Nozzle plate 40 ... Nozzle 51 ... Member to be coated 54 ... Work stage 55 ... Motor 56 ... Holder 57 ... Stage 58 ... Trigger sensor 61 ... Droplet 62 ... Mist 67 ... Paint droplet after landing

Claims (5)

A liquid ejection means having a nozzle for ejecting droplets toward the peripheral surface of the ejected member is provided.
The droplet ejection direction of the droplet linearly ejected from the nozzle is more than the point where the straight line connecting the nozzle and the rotation center of the ejected member intersects the peripheral surface of the ejected member. The direction of rotation is toward the upstream side,
A discharge device characterized in that the nozzle is arranged in a position lower than the highest position of the discharge member in the direction of gravity. It said liquid discharge means, the discharge device according to claim 1, characterized in that the droplet discharge direction is arranged in a state where the downward gravity direction. Said liquid discharge means, the discharge device according to claim 1, characterized in that the droplet discharge direction is arranged in a state in which the direction toward the right under gravity direction. Said liquid ejecting means, when said rotational direction of the supplying members and the clockwise direction, the nozzle ejecting apparatus according to any one of 3 claims 1, characterized in that it is disposed in the second quadrant .. The discharge device according to any one of claims 1 to 4, wherein the discharged member is a columnar member whose peripheral surface rotates .

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