Paint temperature regulating device

Abstract

[Problem] To provide a paint temperature regulating device which is capable of stably regulating paint temperature even in an explosion-proof zone. [Solution] A paint temperature regulating device 50 comprises: a painting head 32 for ejecting paint onto an object being painted; a supply pipe 33 which is provided in an explosion-proof zone and supplies the paint toward the painting head 32; a multilayer pipe 51 which is installed along the supply pipe 33 and has a multilayer structure comprising an inner pipe 51a and an outer pipe 51b, wherein the inner pipe 51a is connected to the supply pipe 33 and air or an inert fluid flows in an outer pipe flow path 51c constituting a gap between the inner pipe 51a and the outer pipe 51b; and a control unit 100 for controlling at least one of a temperature and a flow rate of the air or the inert fluid flowing through the outer pipe flow path 51c.

Description

[Technical Field]

[0001] The present invention relates to a paint temperature regulating device.[Background Art]

[0002] The performance of a painting apparatus having a painting head, in terms of ejecting paint from the painting head, varies according to the temperature of the paint, so there is a need to keep the paint temperature stable. However, the paint temperature is largely equivalent to the ambient temperature inside a painting booth, therefore making it difficult to set the paint temperature at a temperature higher or lower than the ambient temperature inside the painting booth.

[0003] Patent Document 1 discloses a painting apparatus having a painting head, wherein a heater for warming paint is provided in a flow path constituting a paint circulation system for delivering paint to the painting head, and an electric heater could conceivably be used as the heater.[Prior Art Documents][Patent Documents]

[0004] [Patent Document 1] JP 2024-055933 A[Summary of the Invention][Problem to be Solved by the Invention]

[0005] However, the inside of the painting booth is an explosion-proof zone, so an electric heater cannot be used inside this explosion-proof zone and it is difficult to stably regulate the paint temperature.

[0006] The objective of the present invention therefore lies in providing a paint temperature regulating device which is capable of stably regulating paint temperature even in an explosion-proof zone.[Means for Solving the Problem]

[0007] A paint temperature regulating device according to one aspect of the present invention comprises: a painting head for ejecting paint onto an object being painted; a supply pipe which is provided in an explosion-proof zone and supplies the paint toward the painting head; a multilayer pipe which is installed along the supply pipe and has a multilayer structure comprising an inner pipe and an outer pipe, wherein the inner pipe is connected to the supply pipe and air or an inert fluid flows in an outer pipe flow path constituting a gap between the inner pipe and the outer pipe; and a control unit for controlling at least one of a temperature and a flow rate of the air or the inert fluid flowing through the outer pipe flow path.[Advantageous Effects of the Invention]

[0008] The present invention makes it possible to provide a paint temperature regulating device capable of stably regulating paint temperature even in an explosion-proof zone.[Brief Description of the Drawings]

[0009] [Fig. 1] Fig. 1 is a schematic configuration diagram showing a painting robot of a vehicle painting machine comprising the paint temperature regulating device according to the embodiment. [Fig. 2] Fig. 2 is a circuit diagram showing a paint circulation pathway comprising the paint temperature regulating device according to the embodiment. [Fig. 3] Fig. 3 is a circuit diagram showing the paint temperature regulating device according to the embodiment. [Fig. 4] Fig. 4 is a view in cross section showing a double pipe in the circuit diagram of fig. 3, sectioned along the surface of the page. [Fig. 5] Fig. 5 is a flowchart showing a flow of control by a control unit of the paint temperature regulating device according to the embodiment. [Fig. 6] Fig. 6 is a diagram showing a relationship between paint temperature before and after the double pipe and feed air temperature in the supply line. [Embodiments of the Invention]

[0010] A paint temperature regulating device 50 according to the embodiment will be described below with reference to the drawings.

[0011] Fig. 1 is a schematic configuration diagram showing a painting robot 11 of a vehicle painting machine 10 according to the embodiment. The painting robot 11 is arranged in the vicinity of a painting line in an automobile production plant and paints vehicle bodies FR which are conveyed along the painting line. The vehicle body FR of an automobile is described as an example of an object being painted in the embodiment, but the object being painted may equally be an object other than the vehicle body FR of an automobile.[Painting robot]

[0012] The painting robot 11 paints the vehicle body FR which is conveyed on the painting line from an upstream side. In a painting process, the vehicle body FR may be painted as it moves along the painting line, or the flow of the line may be stopped at a predetermined position to paint the vehicle body FR. The vehicle body FR which has been painted by means of the painting robot 11 is conveyed toward a downstream side of the painting line.

[0013] In the embodiment, the painting robot 11 is described as an example of an apparatus for painting the vehicle body FR, but the apparatus need not be the painting robot 11, provided that it comprises a paint circulation pathway 30 which will be described later. Furthermore, the painting robot 11 is depicted, by way of example, as having a painting head unit 24 capable of pivoting in directions centred on three axes, namely an X axis, a Y axis and a Z axis, but the painting head unit 24 may pivot about any one of the X axis, Y axis and Z axis, or may pivot about two of those axes.

[0014] The painting is carried out for the purpose of forming a paint film on a surface of the object being painted, in order to protect the surface and to impart an attractive appearance. The painting process may involve simply painting using a paint having a specific colour or a paint having a specific function, but also includes successively overcoating paints having multiple colours or paints having specific functions.

[0015] The painting robot 11 is illustrated as a multi-joint robot, but may equally be a SCARA robot, provided that it is capable of painting. As shown in fig. 1, the painting robot 11 comprises: a stand 20, a leg portion 21, a rotational drive unit 22, a robot arm 23, and the painting head unit 24.

[0016] The stand 20 is a fixing member for fixing the painting robot 11 to a floor surface of the painting line and supporting the painting robot 11. The stand 20 may be movable over the floor surface of the painting line.

[0017] The leg portion 21 has a lower portion fixed to the stand 20 and an upper portion connected to the rotational drive unit 22, and extends to a vertical height suitable for painting to be performed by the painting robot 11.

[0018] The rotational drive unit 22 is connected to an upper end of the leg portion 21 and comprises a rotary shaft portion 25 and a rotating arm 26. The rotary shaft portion 25 causes the rotating arm 26 to rotate by means of a motor (not depicted) about a direction parallel to the floor surface (the X axis direction shown in fig. 1). The rotating arm 26 causes the robot arm 23 connected to the rotating arm 26 to rotate with a straight line orthogonal to the centre of rotation of the rotary shaft portion 25 (the Z axis direction shown in fig. 1) serving as a rotational centre.

[0019] The robot arm 23 comprises a first pivoting arm 27 and a second pivoting arm 28. The first pivoting arm 27 is connected to the rotating arm 26 at one end portion and connected to the second pivoting arm 28 at another end portion. The first pivoting arm 27 is pivoted by means of a motor (not depicted) mounted on the rotating arm 26, with the Z axis direction shown in fig. 1 serving as a centre of pivoting. The second pivoting arm 28 is connected to the first pivoting arm 27 at one end portion and has a wrist portion 29 (to be described later) at another end portion. The second pivoting arm 28 is pivoted by means of a motor (not depicted), with the Z axis direction shown in fig. 1 serving as a centre of pivoting.

[0020] The painting head unit 24 is disposed on the far tip end side of the painting robot 11 and sprays the vehicle body FR of the automobile with paint. The wrist portion 29 is held between the painting head unit 24 and the second pivoting arm 28. The wrist portion 29 causes the painting head unit 24 to pivot 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 internally comprises a paint circulation pathway 30 for spraying paint from the painting head, and sprays the vehicle body FR moving over the painting line with paint at a suitable timing.[Paint circulation pathway 30]

[0022] The paint circulation pathway 30 of the vehicle painting machine 10 will be described next with reference to fig. 2. Fig. 2 is a circuit diagram showing the paint circulation pathway 30 of the vehicle painting machine 10 comprising the paint temperature regulating device 50 according to the embodiment.

[0023] The paint circulation pathway 30 comprises: a paint tank 31, a painting head 32, a supply line 33, a return flow path 34, a bypass flow path 44, and the paint temperature regulating device 50. A portion or all of the paint circulation pathway 30 is provided in an explosion-proof zone, which is an area where flammable gases are produced.

[0024] The paint circulation pathway 30 constitutes a circulation circuit for supplying paint stored in the paint tank 31 to the painting head 32 via the supply line 33 when the vehicle body FR is being painted, and for returning the paint which was not used by the painting head 32 to the paint tank 31 via the return flow path 34. Furthermore, the paint circulation pathway 30 also functions as a circulation circuit for returning the paint stored in the paint tank 31 from the supply line 33 by way of the bypass flow path 44 to the paint tank 31 via the return flow path 34, when the vehicle body FR is not being painted.

[0025] Here, a direction of supply of the paint in the supply line 33 is described in terms of a paint tank 31 side, which is the upstream side, and a painting head 32 side, which is the downstream side. Furthermore, the direction of supply of the paint in the return flow path 34 is described in terms of the painting head 32 side, which is the upstream side, and the paint tank 31 side, which is the downstream side.

[0026] The paint tank 31 stores the paint which is used when the vehicle body FR is being painted using the painting head 32. The paint tank 31 is disposed outside the painting robot 11 (e.g., on a floor surface of a painting chamber, etc.), or on the robot arm 23, etc. The paint tank 31 is refilled with paint from the outside, as required, in the course of painting the vehicle body FR using the painting head 32.

[0027] The painting head 32 is an inkjet-type head having a nozzle-forming face 32b with an array of multiple nozzles 32a, and forms a paint film on a surface of the vehicle body FR by ejecting the paint supplied via the supply line 33 from each of the multiple nozzles 32a. Nozzle rows (not depicted) are formed by a predetermined number of nozzles 32a, and the nozzle rows are provided diagonally in relation to a scanning direction, which is a direction of movement of the painting head 32, but the nozzle rows may equally be provided so as to follow the scanning direction or lie orthogonal thereto. Note that the detailed configuration of the painting head 32 is omitted.

[0028] The supply line 33 is a flow path for supplying the paint stored in the paint tank 31 toward the painting head 32. The supply line 33 comprises, in succession from the upstream side: a flowmeter 35, a first gear pump 36, a first pressure sensor (PS1) 37, the paint temperature regulating device 50, a first three-way valve 38, and a second pressure sensor (PS2) 39. The flowmeter 35 measures the flow rate of the paint flowing through the supply line 33. The first gear pump 36 pumps the paint from the paint tank 31 toward the painting head 32 along the supply line 33. The first pressure sensor (PS1) 37 measures the pressure of the paint on the downstream side of the first gear pump 36 in the supply line 33. The paint temperature regulating device 50 regulates the temperature of the paint flowing through the supply line 33. The paint temperature regulating device 50 will be described later.

[0029] When the vehicle body FR is being painted by the painting head 32, the first three-way valve 38 maintains a state of communication between the supply line 33 and a first head flow path 33a in which the painting head 32 is provided. When a vehicle body FR is not being painted by the painting head 32, the first three-way valve 38 switches to a state of communication between the supply line 33 and the bypass flow path 44. The second pressure sensor (PS2) 39 measures the pressure of the paint in the first head flow path 33a on the downstream side of the first three-way valve 38.

[0030] The bypass flow path 44 connects the first three-way valve 38 and a second three-way valve 41 (to be described later), and causes the paint supplied from the supply line 33 to flow back to the return flow path 34 while bypassing the painting head 32 when painting is not being performed by the painting head 32.

[0031] The return flow path 34 is a flow path for causing the paint which was not used by the painting head 32 to flow toward the downstream side of the return flow path 34, which is the upstream side of the supply line 33, in order to return this paint to the paint tank 31. The return flow path 34 comprises, in succession from the upstream side: a third pressure sensor (PS3) 40, a second three-way valve 41, a fourth pressure sensor (PS4) 42, and a second gear pump 43.

[0032] The third pressure sensor (PS3) 40 measures the pressure of the paint in a second head flow path 34a on the upstream side of the second three-way valve 41. The second three-way valve 41 is connected to a downstream end of the second head flow path 34a. When the vehicle body FR is being painted by the painting head 32, the second three-way valve 41 maintains a state of communication between the second head flow path 34a and the return flow path 34. Furthermore, when a vehicle body FR is not being painted by the painting head 32, the second three-way valve 41 switches to a state of communication between the bypass flow path 44 and the return flow path 34.

[0033] The fourth pressure sensor (PS4) 42 measures the pressure of the paint on the upstream side of the second gear pump 43 in the return flow path 34. The second gear pump 43 draws in paint and pumps it toward the paint tank 31 along the return flow path 34.

[0034] The paint circulation pathway 30 is configured in the manner described above, with paint stored in the paint tank 31 being pumped along the supply line 33 by means of the first gear pump 36, and paint remaining in the painting head 32 after painting, or paint that has passed through the bypass flow path 44, being pumped to the paint tank 31 along the return flow path 34 by means of the second gear pump 43.[Paint temperature regulating device 50]

[0035] The paint temperature regulating device 50 will be described with reference to fig. 3 and 4. Fig. 3 is a circuit diagram showing the paint temperature regulating device 50, and fig. 4 is a view in cross section showing a double pipe 51 in the circuit diagram of fig. 3, sectioned along the surface of the page. As indicated above, the paint circulation pathway 30 is provided in an explosion-proof zone, so the paint temperature regulating device 50 is also similarly disposed in the explosion-proof zone.

[0036] It should be noted that the viscosity of the paint varies according to temperature: the higher the temperature the lower the viscosity, and the lower the temperature the higher the viscosity. This is dependent on the shear stress of the paint varying due to temperature, and it is preferable for the temperature to be kept at or above a predetermined level, without being excessively high, from the perspective of preventing clogging of the nozzles 32a in the painting head 32. Furthermore, the temperature of the paint needs to be stably kept at a constant level in order to maintain the desired painting quality. The paint temperature regulating device 50 which stably maintains the temperature of the paint is therefore provided in this embodiment, as will be described below.

[0037] The paint temperature regulating device 50 comprises: a double pipe 51, an air supply pipe 52, an air return pipe 53, and a control unit 100.

[0038] As shown in fig. 4, the double pipe 51 is a pipe having a double structure comprising an inner pipe 51a with a circular cross section and an outer pipe 51b with a circular cross section accommodating the inner pipe 51a. The double pipe 51 is constructed by combining the inner pipe 51a which is connected to the supply line 33 at both ends, and the outer pipe 51b which extends parallel to the inner pipe 51a while internally accommodating the inner pipe 51a in the centre thereof so as to maintain an outer pipe flow path 51c constituting a cylindrical space between the inner pipe 51a and the outer pipe 51b. The outer pipe 51b is connected to joints 54 at left / right ends on the page, and the outer pipe flow path 51c inside the outer pipe 51b communicates with spaces 54a inside the joints 54. That is to say, in fig. 4, a lower end of the joint 54 at the left end on the page and a lower end of the joint 54 at the right end on the page communicate with each other via the outer pipe 51b.

[0039] The inner pipe 51a is supported by each of the joints 54 on the left / right of the page, and an outer surface of the inner pipe 51a and an inner surface of the outer pipe 51b are not normally in contact. However, the inner pipe 51a is formed by a fluororesin and the outer pipe 51b is formed by nylon, so if the inner pipe 51a and the outer pipe 51b flex between the joints 54, the inner pipe 51a and the outer pipe 51b will bend according to their bendability. It should be noted that there is no problem if the outer surface of the inner pipe 51a and the inner surface of the outer pipe 51b come into contact, provided that there is a sufficient gap for a flow of air between the outer surface of the inner pipe 51a and the inner surface of the outer pipe 51b.

[0040] Returning to fig. 2 and 3, the double pipe 51 is connected between the first pressure sensor (PS1) 37 and the first three-way valve 38 in the supply line 33 so that the inner pipe 51a of the double pipe 51 is installed partway along the supply line 33. That is to say, paint which has passed through the first pressure sensor (PS1) 37 flows into the inner pipe 51a of the double pipe 51, and paint which has flowed out from the inner pipe 51a flows toward the first three-way valve 38.

[0041] The air supply pipe 52 is a pipe for supplying air to the outer pipe flow path 51c of the double pipe 51 by means of a pump which is not depicted. The air return pipe 53 is a pipe for expelling air from the outer pipe flow path 51c. The outer pipe flow path 51c is connected on its upstream side to the air supply pipe 52 and on its downstream side to the air return pipe 53. This allows air to flow through the outer pipe flow path 51c while paint flows through the inner pipe 51a of the double pipe 51. In this case, the temperature of the paint can be raised by means of heat exchange between the low-temperature paint and air which is warmed to a high temperature.

[0042] The air supply pipe 52 further comprises, in succession from the upstream side: a regulator 55, an air heater 56, an air flowmeter 57, and an air temperature sensor 58. The regulator 55 regulates the pressure and flow rate of compressed air flowing through the air supply pipe 52 in accordance with commands from the control unit 100. The air heater 56 heats the air in accordance with commands from the control unit 100 by using compressed air supplied from the regulator 55. It should be noted that the air heater 56 used here is a device for supplying air which is heated by means of compression, rather than using electricity or a flame, etc., but another type of device is equally possible. There may also be a function to lower the temperature of the paint by supplying the air supply pipe 52 only with cold air which is expelled to the outside, separately from warm air, while the air heater 56 is running, in other words by using the air heater 56 as an air cooler. The air flowmeter 57 measures the flow rate of the air flowing through the air supply pipe 52. The air temperature sensor 58 measures the temperature of the air flowing through the air supply pipe 52.

[0043] A first temperature sensor 59 and a second temperature sensor 60 are further provided in the supply line 33. The first temperature sensor 59 measures the temperature of the paint flowing upstream from the double pipe 51. The second temperature sensor 60 measures the temperature of the paint flowing downstream from the double pipe 51.

[0044] The control unit 100 uses the regulator 55 and the air heater 56 to control the temperature and flow rate of the air fed to the double pipe 51, based on measured values obtained from the first temperature sensor 59, the second temperature sensor 60, the air temperature sensor 58, and the air flowmeter 57. The temperature and amount of air supplied to the outer pipe flow path 51c of the double pipe 51 is controlled by this means.[Control]

[0045] A flow of control by the control unit 100 of the paint temperature regulating device 50 will be described with reference to the flowchart in fig. 5. The following control is performed in a situation where the paint is to be heated.

[0046] In step S1, the control unit 100 determines whether or not the paint temperature is lower than a target temperature. The processing advances to step S2 if the paint temperature is lower than the target temperature, and the processing advances to step S5 if the paint temperature is equal to or greater than the target temperature.

[0047] In step S2, the control unit 100 increases the output of the regulator 55 and the air heater 56. When the output is increased, the regulator 55 generates more highly compressed air and the heater 56 generates higher-temperature air by virtue of the increased pressure of the compressed air.

[0048] In step S3, the control unit 100 determines whether or not the temperature of the air flowing through the air supply pipe 52 is equal to or greater than a set temperature. The processing advances to step S4 if the temperature of the air is equal to or greater than the set temperature, and the processing returns to step S2 if the temperature of the air is less than the set temperature. The set temperature is a set value which is used in order to calculate the output of the air heater 56 required to efficiently heat the paint, based on a temperature difference of the paint between the inlet and the outlet of the double pipe 51, this set value being obtained in advance by means of testing, etc. For example, the set temperature is defined so that when there is a small temperature difference of the paint between the inlet and the outlet of the double pipe 51, the increase in temperature of the paint is prevented from overshooting the target temperature due to excessively large output of the air heater 56.

[0049] In step S4, the control unit 100 determines whether or not the flow rate of the air flowing through the air supply pipe 52 is equal to or greater than a set flow rate. The processing returns to step S1 if the flow rate of the air is equal to or greater than the set flow rate, and the processing returns to step S2 if the flow rate of the air is less than the set flow rate. The set flow rate is a set value which is used in order to calculate the output of the regulator 55 required to efficiently heat the paint, based on the temperature difference of the paint between the inlet and the outlet of the double pipe 51, this set value being obtained in advance by means of testing, etc. For example, the set flow rate is defined so that when there is a small temperature difference of the paint between the inlet and the outlet of the double pipe 51, the increase in temperature of the paint is prevented from overshooting the target temperature due to excessively large output of the regulator 55.

[0050] In step S5, the control unit 100 stabilizes the output of the regulator 55 and the air heater 56 to a steady output. When the output is stabilized, the temperature of the paint in the supply line 33 is stably maintained by the supply of air heated by the regulator 55 and the air heater 56.[Change in paint temperature]

[0051] A relationship between the paint temperature before and after the double pipe 51 and the temperature of feed air in the supply line 33 will be described with reference to fig. 6.

[0052] Note that the horizontal axis shows time and the vertical axis shows temperature in fig. 6. Furthermore, the vertical axis on the left hand side shows the temperature of the paint and the vertical axis on the right hand side shows the temperature of the air. In addition, the paint inlet temperature is a measured value from the first temperature sensor 59, and the paint outlet temperature is a measured value from the second temperature sensor 60.

[0053] As shown in the drawing, when the temperature of the paint at the inlet of the double pipe 51 is approximately 25°C, air at approximately 26.5°C which has not yet been heated is supplied from the air supply pipe 52. From this state, when the air heater 56 and the regulator 55 are actuated to heat the air supplied from the air supply pipe 52, there is an increase in temperature difference between the temperature of the paint at the inlet of the double pipe 51 and the temperature of the paint at the outlet, as the temperature of the heated air rises. In other words, the temperature of the paint at the outlet of the double pipe 51 rises along with the temperature of the air flowing through the outer pipe flow path 51c of the double pipe 51.

[0054] If the target temperature of the paint at the outlet after having passed through the inner pipe 51a of the double pipe 51, and the temperature and flow rate of heated air which should be made to flow through the outer pipe flow path 51c of the double pipe 51 are mapped beforehand, it is thus possible to keep the paint temperature stable at the desired temperature.[Variant Examples]

[0055] The embodiments above described the example of a vehicle painting machine 10 having an inkjet-type painting head 32, but the same advantageous effects can still be achieved if a painting head 32 of a type other than an inkjet-type painting head is used.

[0056] Furthermore, air is made to flow through the air supply pipe 52 in the embodiments above, but an inert fluid which is stable in the explosion-proof zone may equally be used instead of air.

[0057] Furthermore, in the embodiments above, the outer pipe flow path 51c is connected on its upstream side to the air supply pipe 52, and is connected on its downstream side to the air return pipe 53, but the configuration may equally be arranged so that the downstream side of the outer pipe flow path 51c is connected to the air supply pipe 52, and the upstream side is connected to the air return pipe 53.

[0058] Furthermore, the embodiments above described an exemplary case in which the paint temperature regulating device 50 raises the temperature of the paint, but this may also be applied to a case in which the temperature of the paint is lowered. In this case, air at a temperature lower than the paint temperature should be supplied from the air supply pipe 52.

[0059] Furthermore, in the embodiments above, only one inner pipe 51a is provided inside the outer pipe 51b, but multiple inner pipes 51a may be provided in parallel. In this case, the overall surface area of the inner pipe 51a is increased simply by connecting all of the inner pipes 51a to the supply line 33, therefore enabling greater heat exchange efficiency.

[0060] Furthermore, in the embodiments above, the inner pipe 51a was provided substantially parallel along the outer pipe 51b, but the inner pipe 51a may equally have a continuously curved shape, such as a helical shape, inside the outer pipe 51b. In this case, the overall surface area of the inner pipe 51a is increased, therefore enabling greater heat exchange efficiency.

[0061] Furthermore, the embodiments above described an example in which the inner pipe 51a is formed from a fluororesin and the outer pipe 51b is formed from nylon, but the inner pipe 51a and the outer pipe 51b may equally be formed by using other resins. Furthermore, the inner pipe 51a and the outer pipe 51b may also be formed by a metal in order to increase heat exchange efficiency in a painting head structure in which there is no need to take account of bendability of the supply line 33.

[0062] Furthermore, the embodiments above described the example of a structure in which the outer pipe 51b internally accommodates the inner pipe 51a in the centre thereof, but the inner pipe 51a may equally be provided radially eccentric from the centre inside the outer pipe 51b.

[0063] Furthermore, the embodiments above described the example of using the air heater 56 which supplies air heated by means of compression, rather than using electricity or a flame, etc., but an electric heater or the like for heating the air may equally be provided outside the area of the explosion-proof zone, and the air having been heated may be made to flow to the supply line 33 via the air supply pipe 52.

[0064] Furthermore, in the embodiments above, the paint temperature regulating device 50 is provided between the first pressure sensor (PS1) 37 and the first three-way valve 38 in the supply line 33, but the paint temperature regulating device 50 may equally be provided at another position, provided that the paint can be heated at that position.

[0065] Furthermore, in the embodiments above, heat exchange is performed between the paint and the air by means of the double pipe 51 comprising the inner pipe 51a and the outer pipe 51b, but it is equally possible to use a multilayer pipe having a multilayer structure in which the inner pipe 51a and the outer pipe 51b are radially arranged in three or more layers. In this case, the inner pipes and outer pipes of the multilayer pipe are alternately radially arranged, and a passage contacting the inner surface of the inner pipe is connected to the supply line 33. This makes it possible to increase a contact area between the inner pipe and the outer pipe, therefore enabling even better heat exchange efficiency.

[0066] Furthermore, the embodiments above described the example of the inner pipe 51a and the outer pipe 51b having a circular cross section, but a shape other than circular is equally possible.[Supplementary Description of Embodiments]

[0067] The embodiments described above all merely illustrate preferred specific examples of the present invention. The numerical values, components, and arrangement locations and ordering of connection configurations of the components, etc. which are given in the embodiments above are merely examples and are not intended to limit the present invention. Furthermore, the drawings are not necessarily strict depictions.

[0068] Embodiments of the present invention were described above, but those embodiments merely illustrate some examples of application of the present invention, and are not intended to limit the technical scope of the present invention to the specific configurations of the embodiments.

[0069] The series of processes described above may also be implemented by means of hardware, or may also be implemented by means of software. When the series of processes are implemented by means of software, a program constituting the software is installed from a program recording medium onto a computer incorporated into dedicated hardware, or onto a general-purpose computer, etc. capable of implementing various functions by installing various programs, or similar.

[0070] Note that the program run by the computer may be a program that performs processing in time series in the sequence described in this specification, or may be a program that performs processing in parallel or at the required timing, such as when called up.[Additional Notes]

[0071] Details of the disclosure of the several embodiments described above will be understood as follows, for example.(1) Multilayer pipe

[0072] A multilayer pipe comprises: a painting head 32 for ejecting paint onto an object being painted; a supply line 33 which is provided in an explosion-proof zone and supplies the paint toward the painting head 32; a double pipe 51 which is installed along the supply line 33 and has a double structure comprising an inner pipe 51a and an outer pipe 51b, wherein the inner pipe 51a is connected to the supply line 33 and air flows in an outer pipe flow path 51c constituting a gap between the inner pipe 51a and the outer pipe 51b; and a control unit 100 for controlling at least one of a temperature and a flow rate of the air flowing through the outer pipe flow path 51c.

[0073] By this means, the temperature of paint being directed to the painting head 32 is regulated by means of heat exchange with air along the supply line 33, therefore making it possible to regulate the temperature of the paint even in the explosion-proof zone, and enabling the paint ejection performance to be stably maintained. Furthermore, since air is used for heat exchange, there is no need for costly control equipment compatible with an explosion-proof environment, and costs can be kept down. The viscosity of the paint can also be suitably maintained by regulating the temperature of the paint, and painting quality can be improved during painting of an object being painted such as a vehicle.

[0074] Air or an inert fluid may flow through the outer pipe flow path 51c of the double pipe 51.

[0075] In addition to higher explosion-proofing performance, this also reduces the weight of fluid flowing through the outer pipe flow path 51c, therefore making it possible to reduce the weight of the double pipe 51 during painting and to increase the degree of freedom in the position where the double pipe 51 is installed along the supply line 33. It is furthermore possible to use a compact pump since there is a reduced load on the pump when air, which is light, flows through the outer pipe flow path 51c. Furthermore, as long as some air can be introduced into the air supply pipe 52 from a device which supplies air to the paint circulation pathway 30 for cleaning purposes, air can be fed to the air supply pipe 52 even if a pump is not newly provided. It is therefore possible to reduce the overall weight of the paint temperature regulating device 50.(2) Heating or cooling

[0076] The control unit 100 may control the temperature of the air so as to differ from the temperature of the paint inside the supply line 33.

[0077] This makes it possible to raise the temperature of the paint and reduce the viscosity thereof so that ejection performance from the painting head 32 can be improved. Furthermore, since the temperature of the paint is increased by using air, the paint can be stably heated even in the explosion-proof zone.

[0078] Furthermore, the temperature of the paint can also be reduced if the temperature of the air is set to be lower than the temperature of the paint inside the supply line 33. When there is a high temperature inside a painting booth, the paint also reaches a temperature almost the same as the ambient temperature, leading to an increase in the temperature of the paint. In such a case, the paint can be kept at the desired viscosity by cooling the paint.(3) Outer pipe material

[0079] The outer pipe 51b may be formed from a resin.

[0080] This makes it possible to ensure heat insulating properties of the outer pipe 51b and also makes it possible to improve the degree of freedom in the position where the double pipe 51 is provided, because even in places where the supply line 33 is bent or in places where a bending load is exerted during painting, the bendability of the outer pipe 51b allows it to follow changes in shape.(4) Multiple inner pipes

[0081] Multiple inner pipes 51a may be provided inside the outer pipe 51b, and the multiple inner pipes 51a may each be connected to the supply line 33.

[0082] This makes it possible to increase the overall surface area of the inner pipe 51a, therefore enabling better heat exchange efficiency between the paint flowing through each of the inner pipes 51a and the air flowing through the outer pipe flow path 51c, and the paint temperature can be regulated more effectively.(5) Joint

[0083] At least one end of the inner pipe 51a may be connected to the supply line 33 by way of a joint 54 supported by the outer pipe 51b.

[0084] This allows the inner pipe 51a to be supported by means of the outer pipe 51b via the joint 54, so it is possible to inhibit radial displacement of the inner pipe 51a inside the outer pipe 51b, and it is possible to prevent a circumferential portion of the outer pipe flow path 51c from being obstructed by deformation of the inner pipe 51a. Accordingly, it is possible to prevent a reduction in heat exchange efficiency between the paint flowing through the inner pipe 51a and the air flowing through the outer pipe flow path 51c, and the paint temperature can be regulated more effectively.[Key to Symbols]

[0085] 10Vehicle painting machine 32Painting head 33Supply line (supply path) 50Paint temperature regulating device 51Double pipe 51aInner pipe 51cOuter pipe flow path 54Joint 100Control unit

Claims

1. Paint temperature regulating device <b>characterized by comprising: a painting head for ejecting paint onto an object being painted; a supply pipe which is provided in an explosion-proof zone and supplies the paint toward the painting head; a multilayer pipe which is installed along the supply pipe and has a multilayer structure comprising an inner pipe and an outer pipe, wherein the inner pipe is connected to the supply pipe and air or an inert fluid flows in an outer pipe flow path constituting a gap between the inner pipe and the outer pipe; and a control unit for controlling at least one of a temperature and a flow rate of the air or the inert fluid flowing through the outer pipe flow path.

2. Paint temperature regulating device according to Claim 1, characterized in that the control unit controls the temperature of the air or the inert fluid so as to differ from the temperature of the paint inside the supply pipe.

3. Paint temperature regulating device according to Claim 1 or 2, characterized in that the outer pipe is formed from a resin.

4. Paint temperature regulating device according to any of Claims 1-3, characterized in that multiple inner pipes are provided inside the outer pipe, and the multiple inner pipes are each connected to the supply pipe.

5. Paint temperature regulating device according to any of Claims 1-4, characterized in that at least one end of the inner pipe is connected to the supply pipe by way of a joint supported by the outer pipe.

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