Vehicle painting machine

Abstract

The present invention provides a vehicle painting machine that can improve the cleanability of the tubing inside the inkjet-type paint head even under low pressure. [Solution] The vehicle painting machine includes a supply passage 32 that supplies paint to an inkjet type painting head 31, a bypass passage 33 that bypasses the painting head 31 with the paint from the supply passage 32, a switching unit 35 that switches the paint from the supply passage 32 between the head passages 31a, 31b and the bypass passage 33, a supply unit 36 ​​that selectively supplies cleaning liquid and air to the supply passage 32, and a cleaning control unit 37 that controls the switching unit 35 and the supply unit 36 ​​to clean the painting head 31. The cleaning control unit 37 supplies air when the supply passage 32 is filled with cleaning liquid in the bypass passage 33 supply state, and when the air and cleaning liquid are in two layers along the flow direction, it switches the first three-way valve 35 to the head passages 31a, 31b side to allow the cleaning liquid to flow, thereby cleaning the painting head 31 with the cleaning liquid in a gas-liquid mixed state.

Description

Technical Field

[0001] The present invention relates to a vehicle painting machine.

Background Art

[0002] There is known a painting machine that paints the body of an automobile (hereinafter simply referred to as the body) using inkjet technology. An inkjet-type vehicle painting machine includes a painting head that discharges droplets of a predetermined amount of paint toward the body from each of a plurality of nozzles provided on a nozzle forming surface (discharge surface).

[0003] Patent Document 1 discloses that in an inkjet-type vehicle painting machine, a cleaning operation is performed by flowing a cleaning liquid through the painting head. In order to improve the cleaning performance of the painting head, methods such as using a cleaning liquid mixed with high-pressure compressed air or using a cleaning liquid containing microbubbles generated at high pressure can be considered.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, since the painting head in an inkjet-type vehicle painting machine has a low pressure resistance value in terms of structure, a method of performing cleaning under high pressure cannot be adopted.

[0006] The present invention has been made in view of the above circumstances, and an object thereof is to provide a vehicle painting machine capable of improving the cleaning performance of the pipelines inside an inkjet-type painting head even under low pressure.

Means for Solving the Problems

[0007] One aspect of the present invention is a vehicle painting machine comprising: an inkjet type painting head having a plurality of nozzles for discharging paint and a head channel for supplying paint to the nozzles; a supply channel for supplying paint toward the painting head; a bypass channel for flowing the paint in the supply channel downstream of the painting head, bypassing the painting head; a switching unit for switching the paint supply state from the supply channel between the head channel and the bypass channel; a supply unit for selectively supplying cleaning liquid and air to the supply channel; and a cleaning control unit for cleaning the painting head by controlling the switching unit and the supply unit. The cleaning control unit supplies air when the switching unit is switched to a state for supplying to the bypass channel and the supply channel is filled with cleaning liquid, and when the air and cleaning liquid are in two layers along the flow direction, the switching unit is switched to a state for supplying to the head channel and the cleaning liquid flows into the head channel, thereby cleaning the painting head with the cleaning liquid in a gas-liquid mixed state. [Effects of the Invention]

[0008] According to the present invention, it is possible to provide a vehicle painting machine that can improve the cleanability of the tubing inside the inkjet type painting head even under low pressure. [Brief explanation of the drawing]

[0009] [Figure 1] Figure 1 is a schematic diagram showing the painting robot of a vehicle painting machine according to this embodiment. [Figure 2] Figure 2 is a circuit diagram showing a part of the paint circulation path of a vehicle painting machine according to this embodiment. [Figure 3] Figure 3 is a flowchart showing the cleaning process of the paint circulation path of the vehicle painting machine according to this embodiment. [Figure 4] Figure 4 is an explanatory diagram illustrating the mechanism by which a gas-liquid mixture state occurs in the cleaning solution. [Figure 5] Figure 5 is a circuit diagram showing a part of the paint circulation path of the vehicle painting machine according to this embodiment, and shows the state in which the bypass flow path is open. [Figure 6]Figure 6 is a circuit diagram showing a part of the paint circulation path of the vehicle painting machine according to this embodiment, and shows the state with the head flow path open. [Modes for carrying out the invention]

[0010] The vehicle painting machine 10 according to this embodiment will be described below with reference to the drawings.

[0011] Figure 1 is a schematic diagram showing the painting robot 11 of the vehicle painting machine 10 according to this embodiment. The painting robot 11 is positioned near the painting line in an automobile manufacturing plant and paints the vehicle body FR as it is transported along the painting line. In this embodiment, the object to be painted is an automobile vehicle body FR, but it may be something other than an automobile vehicle body FR.

[0012] [Painting robot] The painting robot 11 paints the vehicle body FR as it is transported from the upstream side of the painting line. The painting process may be carried out by painting the vehicle body FR while it is moving along the painting line, or by stopping the flow of the line at a predetermined position to perform the painting. The vehicle body FR that has been painted by the painting robot 11 is transported downstream of the painting line.

[0013] In this embodiment, a painting robot 11 is exemplified as a device for painting the vehicle body FR, but any device having a paint circulation path 30, as described later, may be used instead of a painting robot 11. Furthermore, while the painting robot 11 is exemplified as having a painting head unit 24 that can rotate around three axes, the X axis, the Y axis, and the Z axis, the painting head unit 24 may rotate around one of the X, Y, or Z axes, or around two axes.

[0014] Painting is performed with the purpose of forming a paint film on the surface of an object to be painted, thereby protecting the surface and providing an aesthetically pleasing appearance. The painting process may involve simply applying paint of a specific color or paint with a specific function, or it may involve applying multiple colors of paint or paints with specific functions in sequence.

[0015] The painting robot 11 exemplifies an articulated robot, but a scalar robot may also be used as long as it can perform painting. As shown in FIG. 1, the painting robot 11 includes a base 20, legs 21, a rotational drive unit 22, a robot arm 23, and a painting head unit 24.

[0016] The base 20 is a fixing member that fixes the painting robot 11 to the floor surface of the painting line and supports the painting robot 11. The base 20 may be movable on the floor surface of the painting line.

[0017] The legs 21 have a lower part fixed to the base 20, an upper part connected to the rotational drive unit 22, and extend to a vertical height suitable for performing painting by the painting robot 11.

[0018] The rotational drive unit 22 is connected to the upper end of the legs 21 and has a rotary shaft portion 25 and a rotary arm 26. The rotary shaft portion 25 rotates the rotary arm 26 about an axis parallel to the floor surface (the X-axis direction shown in FIG. 1) by a motor (not shown). The rotary arm 26 rotates the robot arm 23 connected to the rotary arm 26 about a straight line orthogonal to the rotation center of the rotary shaft portion 25 (the Z-axis direction shown in FIG. 1).

[0019] The robot arm 23 has a first rotating arm 27 and a second rotating arm 28. One end of the first rotating arm 27 is connected to the rotary arm 26, and the other end is connected to the second rotating arm 28. The first rotating arm 27 rotates about the Z-axis direction shown in FIG. 1 by a motor (not shown) mounted on the rotary arm 26. One end of the second rotating arm 28 is connected to the first rotating arm 27, and the other end has a wrist portion 29 described later. The second rotating arm 28 rotates about the Z-axis direction shown in FIG. 1 by a motor (not shown).

[0020] The painting head unit 24 is arranged at the most distal end side of the painting robot 11 and sprays paint onto the vehicle body FR of the automobile. A list part 29 is held between the painting head unit 24 and the second rotating arm 28. The list part 29 rotates the painting head unit 24 about at least one of the three axes (X-axis, Y-axis, and Z-axis) shown in FIG. 1.

[0021] The painting head unit 24 has a paint circulation path 30 inside for spraying paint from the painting head, and sprays paint at an appropriate timing onto the vehicle body FR flowing on the painting line.

[0022] [Paint circulation path] Next, the paint circulation path 30 of the vehicle painting machine 10 will be described while referring to FIG. 2. FIG. 2 is a circuit diagram showing a part of the paint circulation path 30 of the vehicle painting machine 10 according to the present embodiment.

[0023] The paint circulation path 30 includes a painting head 31, a supply path 32, a bypass flow path 33, a return flow path 34, a first three-way valve 35, a supply valve 36, and a cleaning control unit 37.

[0024] The paint circulation path 30 is a circulation circuit that supplies the paint stored in a paint tank (not shown) to the painting head 31 via the supply path 32 when painting the vehicle body FR, and returns the paint not used by the painting head 31 to the paint tank via the return flow path 34. Also, the paint circulation path 30 functions as a circulation circuit that returns the paint stored in the paint tank from the supply path 32, via the bypass flow path 33, and via the return flow path 34 to the paint tank when not painting the vehicle body FR.

[0025] Here, in the supply path 32, the paint supply direction refers to the paint tank side as the upstream side and the painting head 31 side as the downstream side. Also, in the return flow path 34, the painting head 31 side is referred to as the upstream side and the paint tank side is referred to as the downstream side.

[0026] The paints are water-based paints or solvent-based paints that use pigments. Therefore, by circulating the paint within the paint circulation path 30, it is possible to prevent the pigments contained in the paint from separating or agglomerating within the paint circulation path 30, and to reduce the viscosity of the paint.

[0027] The paint head 31 is an inkjet type head that has a nozzle forming surface 52 on which a plurality of nozzles 51 are arranged, and ejects paint supplied via a supply passage 32 from each of the plurality of nozzles 51 to form a paint film on the surface of the vehicle body FR. A predetermined number of nozzles 51 constitute a nozzle row (not shown), and this nozzle row is arranged diagonally with respect to the scanning direction, which is the direction in which the paint head 31 moves, but the nozzle row may also be arranged along or perpendicular to the scanning direction. The detailed configuration of the paint head 31 is omitted.

[0028] The supply passage 32 is a flow path that supplies paint stored in the paint tank to the paint head 31. The supply passage 32 is divided into three different flow paths 32a, 32b, and 32c by a plurality of components interposed in the supply passage 32. The paint in the supply passage 32 is pumped by a first gear pump 38 interposed in the middle of the supply passage 32. The supply passage 32 has, in order from the upstream side, a switching valve 40, a first gear pump 38, and a first three-way valve 35 as a switching part.

[0029] The first three-way valve 35 is connected to the downstream end of the first gear pump 38 in the supply passage 32. When the vehicle body FR is being painted by the painting head 31, the first three-way valve 35 maintains a state in which the flow path 32c and the head flow path 31a provided by the painting head 31 are in communication. When the vehicle body FR is not being painted by the painting head 31, the first three-way valve 35 switches to a state in which the flow path 32c and the bypass flow path 33 are in communication. The flow path 32c is connected to the first gear pump 38 on its upstream side and to the first three-way valve 35 on its downstream side.

[0030] The bypass channel 33 connects the first three-way valve 35 and the second three-way valve 41 (described later), and when painting is not performed by the painting head 31, the paint supplied from the supply channel 32 is recirculated to the return channel 34, bypassing the painting head 31.

[0031] The return passage 34 is a passage that directs paint not used by the paint head 31, or paint circulating in the paint circulation path 30, toward the downstream side of the return passage 34, which is upstream of the supply path 32, and returns it to the paint tank. The return passage 34 is divided into two different passages 34a and 34b by several components interposed in the return passage 34. The paint in the return passage 34 is pumped by a second gear pump 42 interposed in the middle of the return passage 34. The return passage 34 has, in order from the upstream side, a second three-way valve 41 and a second gear pump 42. The upstream side of passage 34a is connected to the second three-way valve 41 and the downstream side is connected to the second gear pump 42. The upstream side of passage 34b is connected to the second gear pump 42 and the downstream side is connected to a paint tank (not shown).

[0032] The second three-way valve 41 is connected to the downstream end of the head passage 31b. The second three-way valve 41 maintains a state in which the head passage 31b and the passage 34a are in communication when the vehicle body FR is being painted by the painting head 31. When the vehicle body FR is not being painted by the painting head 31, the second three-way valve 41 switches to a state in which the bypass passage 33 and the passage 34a are in communication. The second gear pump 42 draws in the paint flowing through the passage 34a and pumps it into the passage 34b, which is connected to the downstream side of the second gear pump 42.

[0033] The supply passage 32 has a switching valve 40 on the upstream side of the first gear pump 38. The switching valve 40 is connected to the downstream end of the flow path 32a. The switching valve 40 has four valve sections 40a, 40b, 40c, and 40d. Valve section 40a is connected to the upstream flow path 32a, and valve section 40b is connected to the downstream flow path 32b. Therefore, when supplying paint from the paint tank to the paint head 31, or when circulating paint, valve sections 40a and 40b are opened, and paint from flow path 32a flows towards flow path 32b.

[0034] The switching valve 40 is connected to the supply valve 36, which serves as the supply unit. The supply valve 36 is connected to the valve section 40c of the switching valve 40 and can selectively switch between a valve section 36a that allows cleaning fluid supplied from the cleaning tank 43 to pass through, and a valve section 36b that allows air supplied from the air compressor 44 to pass through. Therefore, during cleaning, when either valve section 36a or valve section 36b is opened, cleaning fluid or air selectively flows to the downstream side of the supply passage 32.

[0035] Valve section 40d is connected to the drain tank 45. Therefore, separately from the cleaning operation in this embodiment, when the supply passage 32 is cleaned upstream of the switching valve 40, opening valve sections 40a and 40d causes the cleaning fluid and air flowing through the passage 32a connected to the opened valve section 40a to flow into the drain tank 45 via valve section 40d.

[0036] The cleaning control unit 37 cleans the painting head 31 by switching the supply valve 36, the first three-way valve 35, and the second three-way valve 41 while the valve section 40c and valve section 40b of the switching valve 40 are connected.

[0037] [Painted head cleaning process] The cleaning of the paint head 31 by the cleaning control unit 37 will be explained with reference to Figure 3. Figure 3 is a flowchart showing the cleaning process of the paint head 31 of the vehicle painting machine 10 according to this embodiment.

[0038] In step S1, the cleaning control unit 37 determines whether or not the cleaning process for the paint head 31 has started. If it is determined that the cleaning process has started, the process proceeds to step S2; if it is not determined that the cleaning process has started, the process repeats step S1. Whether or not to perform the cleaning process is determined by a control unit (not shown) of the paint circulation path 30.

[0039] In step S2, the cleaning control unit 37 opens the head passages 31a and 31b. The head passages 31a and 31b are opened when the cleaning control unit 37 switches the first three-way valve 35 to connect the passage 32c with the head passage 31a provided by the painting head 31 downstream, and also switches the second three-way valve 41 to connect the head passage 31b provided by the painting head 31 upstream with the passage 34a.

[0040] In step S3, the cleaning control unit 37 supplies cleaning fluid to the supply passage 32. By opening the valve section 36a of the supply valve 36 and the valve sections 40b and 40c of the switching valve 40, the first gear pump 38 and the second gear pump 42 are driven, thereby supplying cleaning fluid from the cleaning tank 43 to the supply passage 32.

[0041] In step S4, the cleaning control unit 37 determines whether or not the cleaning fluid has filled the supply passage 32. If it is determined that the cleaning fluid has filled the supply passage 32, the process proceeds to step S5. If it is not determined that the cleaning fluid has filled the passage, the process returns to step S3, and the filling of the cleaning fluid continues.

[0042] Whether or not the cleaning fluid has filled the supply passage 32 can be determined by first determining the volume of the flow path from the cleaning tank 43 to the first three-way valve 35 located at the upstream end of the painting head 31 through experiments or other means, or by determining it by the elapsed time since the cleaning fluid started flowing.

[0043] In step S5, the cleaning control unit 37 opens the bypass channel 33. The cleaning control unit 37 switches the first three-way valve 35 to connect the channel 32c and the bypass channel 33, and also switches the second three-way valve 41 to connect the bypass channel 33 and the channel 34a. As a result, the bypass channel 33 is opened, and the cleaning fluid flows into the bypass channel 33 without flowing into the paint head 31.

[0044] In step S6, the cleaning control unit 37 supplies air to the supply passage 32. By switching the supply valve 36 and opening the valve section 36b, air supplied from the air compressor 44 is supplied to the supply passage 32. Here, the volume of air supplied is smaller than the volume of cleaning fluid supplied in step S3, for example, set to about 10% of the volume of cleaning fluid.

[0045] Furthermore, since this embodiment uses an inkjet type paint head 31, the pressure resistance performance of the paint head 31 is relatively low. However, in order to later form a two-layer structure with the cleaning solution, the air pressure supplied in step S6 needs to be set to a certain extent higher than the pressure resistance value of the paint head 31. However, as mentioned above, the volume of air is sufficiently smaller than the volume of the cleaning solution, so when air mixes with the cleaning solution and a gas-liquid mixture is formed, the overall pressure will be lower than the pressure resistance value of the paint head 31, and the high air pressure will not adversely affect the paint head 31.

[0046] In step S7, the cleaning control unit 37 determines whether the elapsed time since the start of air supply has exceeded a predetermined two-layer formation time. If it is determined that the elapsed time since the start of air supply has exceeded the two-layer formation time, the process proceeds to step S8. If it is not determined that the elapsed time has exceeded the two-layer formation time, the process returns to step S6 and the air supply continues.

[0047] The predetermined two-layer formation time is the time required for the air and cleaning solution in the supply channel 32 to form two layers along the flow direction when air is supplied into the supply channel 32 while the cleaning solution is flowing towards the bypass channel 33. This time is determined in advance through experiments or other means.

[0048] In step S8, the cleaning control unit 37 opens the head flow paths 31a and 31b of the painting head 31. The cleaning control unit 37 switches the first three-way valve 35 to connect the flow path 32c and the head flow path 31a, and also switches the second three-way valve 41 to connect the head flow path 31b and the flow path 34a. As a result, the head flow paths 31a and 31b are opened.

[0049] When the head channels 31a and 31b are opened, the cleaning fluid and air in the two-layered supply channel 32 flow into the head channels 31a and 31b. At this time, since the volume of air is sufficiently smaller than the volume of cleaning fluid, the air is pushed into the head channels 31a and 31b by the cleaning fluid, resulting in a gas-liquid mixture in which the air is mixed with the cleaning fluid. As the gas-liquid mixed cleaning fluid flows through the head channels 31a and 31b, the cleaning performance within the channels can be improved compared to when only the cleaning fluid flows.

[0050] Furthermore, although the air pressure is set to be higher than the pressure resistance value of the paint head 31 in step S6, the air pressure in the cleaning solution, which is in a gas-liquid mixture state, is lower than the pressure resistance value of the paint head 31, so cleaning can be performed without damaging the paint head 31.

[0051] Now, referring to Figure 4, we will explain the mechanism by which the cleaning solution becomes a gas-liquid mixture. Figure 4 is an explanatory diagram illustrating the mechanism by which the gas-liquid mixture of the cleaning solution occurs.

[0052] After the supply channel 32 is filled with cleaning fluid, while the cleaning fluid in the supply channel 32 is flowing to the bypass channel 33 (Figure 4A), a volume of air smaller than that of the cleaning fluid is supplied to the supply channel 32. After a predetermined two-layer formation time has elapsed since the air was supplied, the supply channel 32 will consist of two layers: air and cleaning fluid (Figure 4B). In this state, when the flow path is switched from the bypass channel 33 to the head channels 31a and 31b, the air is pushed into the head channels 31a and 31b by the cleaning fluid, generating a gas-liquid mixed cleaning fluid (Figure 4C).

[0053] The volume of the gas-liquid mixed cleaning solution changes according to the volume of air introduced in step S6. However, since the volume of air is sufficiently small compared to the volume of the cleaning solution, the volume of the gas-liquid mixed cleaning solution is also relatively small. Therefore, after flowing through the head passages 31a and 31b, the gas-liquid mixed cleaning solution returns to a state where it does not contain air, and the supply passage 32 is once again filled with cleaning solution (Figure 4A).

[0054] Returning to Figure 3, in step S9, the cleaning control unit 37 determines whether to repeat the cleaning cycle in which the cleaning liquid in a gas-liquid mixed state is introduced into the head channels 31a and 31b of the painting head 31, which was performed from step S2 to step S8. If it is determined that the cleaning cycle should be repeated, the process returns to step S5; if it is not determined that the cleaning cycle should be repeated, the process ends.

[0055] [Washing cycle] Next, the cleaning cycle of the head flow paths 31a and 31b of the painting head 31 will be described with reference to Figures 5 and 6. Figure 5 is a circuit diagram showing a part of the paint circulation path 30 of the vehicle painting machine 10 according to this embodiment, showing the state in which the bypass flow path 33 is open. Figure 6 is a circuit diagram showing a part of the paint circulation path 30 of the vehicle painting machine 10 according to this embodiment, showing the state in which the head flow paths 31a and 31b are open.

[0056] As shown in Figure 5, when the cleaning fluid supplied from the supply passage 32 is flowing through the bypass passage 33, air is supplied to the supply passage 32, and the supply passage 32 becomes composed of two layers of air and cleaning fluid, the flow path is switched to the head passages 31a and 31b.

[0057] As shown in Figure 6, air is then pushed in by the cleaning solution, and the cleaning solution, now in a gas-liquid mixture state, flows through the head channels 31a and 31b. At this time, the gas-liquid mixture of cleaning solution cleans the inside of the head channels 31a and 31b with a higher cleaning power than when cleaning with the cleaning solution alone.

[0058] Subsequently, as shown in Figure 5, the flow path is switched again to the bypass flow path 33, and once the supply path 32 is again composed of two layers of air and cleaning liquid, the flow path is switched to the head flow paths 31a and 31b, and as shown in Figure 6, the gas-liquid mixed cleaning liquid is flowed into the head flow paths 31a and 31b. In this way, the state from the state in which the flow path is switched to the bypass flow path 33 and composed of two layers of air and cleaning liquid (Figure 5) to the state in which the flow path is switched to the head flow paths 31a and 31b and the gas-liquid mixed cleaning liquid is flowed into the head flow paths 31a and 31b (Figure 6) is considered one cleaning cycle, and the cleaning cycle is repeated for the number of cycles necessary for cleaning the head flow paths 31a and 31b.

[0059] [Differentiation] In the above embodiment, the first three-way valve 35 and the second three-way valve 41 are used to switch between the bypass flow path and the head flow path, but other valves may be used as long as they can reliably switch between the flow paths.

[0060] Furthermore, in the above embodiment, the discharge of cleaning fluid and air was switched by switching one supply valve 36, but a discharge valve for cleaning fluid and a discharge valve for air may be provided independently, and the two discharge valves may be selectively opened and closed.

[0061] Furthermore, although the cleaning control unit 37 was described as an independent control unit in the above embodiment, it may also be integrated into a control unit that controls the switching valve 40, the first gear pump 38, and the second gear pump 42 for integrated control.

[0062] [Supplementary explanation of the embodiment] The embodiments described above are all preferred examples of the present invention. The numerical values, components, arrangement positions of components, and connection configurations shown in the embodiments above are examples only and are not intended to limit the present invention. Furthermore, the figures are not necessarily strictly illustrative.

[0063] Although embodiments of the present invention have been described above, these embodiments only represent a part of the application examples of the present invention, and are not intended to limit the technical scope of the present invention to the specific configurations of the above embodiments.

[0064] The series of processes described above can be executed by hardware or by software. When the series of processes are executed by software, the programs that make up the software are installed from a program storage medium on a computer that is built into dedicated hardware, or on a general-purpose computer that can perform various functions by installing various programs.

[0065] The programs executed by the computer may be programs that are processed chronologically in the order described herein, or they may be programs that are processed in parallel or at necessary times, such as when a call is made.

[0066] [Note] The contents described in some of the embodiments above can be understood, for example, as follows:

[0067] (1) A gas-liquid mixture of cleaning solution is flowed into the head passage. The vehicle painting machine 10 includes an inkjet-type painting head 31 having multiple nozzles 51 for discharging paint and a head channel 31a for supplying paint to the nozzles 51, a supply channel 32 for supplying paint toward the painting head 31, a bypass channel 33 for directing the paint in the supply channel 32 downstream of the painting head 31 by bypassing the painting head 31, a first three-way valve 35 for switching the paint supply state from the supply channel 32 between the head channels 31a, 31b and the bypass channel 33, and a supply for selectively supplying cleaning liquid and air to the supply channel 32. The system includes a valve 36 and a cleaning control unit 37 that controls the first three-way valve 35 and the supply valve 36 to clean the paint head 31. The cleaning control unit 37 supplies air when the first three-way valve 35 is switched to a supply state to the bypass passage 33 and the supply passage 32 is filled with cleaning fluid. When the air and cleaning fluid are in two layers along the flow direction, the cleaning control unit 37 switches the first three-way valve 35 to a supply state to the head passages 31a and 31b and flows the cleaning fluid into the head passages 31a and 31b, thereby cleaning the paint head 31 with the cleaning fluid in a gas-liquid mixed state.

[0068] As a result, with the supply passage 32 filled with cleaning fluid, the cleaning fluid is supplied to the bypass passage 33, and once the air and cleaning fluid are in two layers, the passage is switched to the head passages 31a and 31b to form a gas-liquid mixed cleaning fluid. Therefore, even in a vehicle painting machine 10 having an inkjet type painting head 31 with a low structural pressure resistance value, the cleaning performance of the painting head 31 can be improved without using high-pressure compressed air or a cleaning fluid containing microbubbles generated at high pressure.

[0069] (2) Timing of flowing into the head channel The cleaning control unit 37 may switch the paint supply state from the supply path 32 to the head flow paths 31a and 31b when the air and cleaning liquid form two layers in the supply path 32.

[0070] As a result, air is forced into the head channels 31a and 31b by the cleaning fluid, creating a gas-liquid mixed state in the cleaning fluid, in which air is incorporated. Therefore, the cleaning fluid can exhibit sufficient cleaning performance within the head channels 31a and 31b.

[0071] (3) Time determination of the gas-liquid mixed state The cleaning control unit 37 may determine that two layers of air and cleaning liquid have formed in the supply passage 32 when a predetermined two-layer formation time has elapsed since the initial supply of air to the supply passage 32.

[0072] This allows us to determine over time when the supply channel 32 has become a two-layer system of cleaning fluid and air. By pre-determining the time through experiments, we can accurately predict when the cleaning fluid can be flowed into the head channels 31a and 31b to create a gas-liquid mixed state.

[0073] Furthermore, even though the supply path 32 has two layers of air and cleaning fluid, the fact that the flow path does not switch to the head flow paths 31a and 31b prevents a delay in the time until cleaning begins.

[0074] (4) Air < Cleaning liquid The amount of air supplied to the supply passage 32 by the supply valve 36, which is controlled by the cleaning control unit, may be less than the amount of cleaning fluid.

[0075] This prevents the air itself from being supplied to the head channels 31a and 31b when switching the flow path of the cleaning fluid from the bypass channel 33 to the head channels 31a and 31b due to insufficient gas-liquid mixing, thus preventing high-pressure air from being supplied to the paint head 31, which has a low pressure resistance value.

[0076] Furthermore, the air itself is supplied to the nozzle 51, preventing paint from ceasing to be discharged from the nozzle 51 after the cleaning is complete. [Explanation of symbols]

[0077] 10 Vehicle painting machines 31 Painting head 31a Head channel 31b Head channel 32 Supply route 33 Bypass channel 35. First three-way valve (switching section) 36. Supply valve (supply unit) 37 Cleaning Control Unit 51 nozzles

Claims

1. An inkjet type paint head having multiple nozzles for dispensing paint and a head channel for supplying the paint to the nozzles, A supply path for supplying the paint toward the painting head, A bypass channel that flows the paint in the supply channel to the downstream side of the painting head, bypassing the painting head, A switching unit that switches the supply state of the paint from the supply path between the head flow path and the bypass flow path, A supply unit that selectively supplies cleaning liquid and air to the supply passage, A cleaning control unit that controls the switching unit and the supply unit to clean the painting head, Equipped with, The cleaning control unit supplies air when the switching unit is switched to the bypass flow path supply state and the supply path is filled with the cleaning liquid, and when the air and the cleaning liquid are in two layers along the flow direction, the switching unit is switched to the head flow path supply state and the cleaning liquid flows into the head flow path, thereby cleaning the paint head with the cleaning liquid which has become a gas-liquid mixture. A vehicle painting machine characterized by the following features.

2. A vehicle painting machine according to claim 1, The cleaning control unit, when the air and cleaning liquid are in two layers in the supply path, switches the supply state of the paint from the supply path to the head flow path. A vehicle painting machine characterized by the following features.

3. A vehicle painting machine according to claim 2, The cleaning control unit determines that the air and cleaning liquid have formed two layers in the supply passage when a predetermined two-layer formation time has elapsed since the air was first supplied to the supply passage. A vehicle painting machine characterized by the following features.

4. A vehicle painting machine according to claim 1, The amount supplied to the supply path by the supply unit, controlled by the cleaning control unit, is less than the amount of cleaning liquid. A vehicle painting machine characterized by the following features.

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