JP4705612B2 - Electrostatic coating system - Google Patents

Description

  The present invention relates to an electrostatic coating system capable of discharging and coating a conductive paint on an object such as a vehicle body.

  2. Description of the Related Art Conventionally, a method is known in which a high voltage is applied to a conductive paint and electrostatic coating is applied to an object to be coated such as an automobile body. In this method, after the conductive coating material is once introduced into the intermediate storage tank that is insulated from the ground potential, the supply passage that communicates the intermediate storage tank and the coating material supply source is cleaned and dried, and the voltage block Is formed. In this state, by supplying the conductive paint to which a high voltage is applied from the intermediate storage tank to the painting gun, the electrostatic painting work is performed on the object to be painted.

  By the way, in a conventional electrostatic coating system (electrostatic coating apparatus), for example, paint control for changing the paint discharge amount of a coating gun according to changes in conditions of a surface to be painted such as a corner curved surface portion or a flat surface portion of an automobile body. Since the control is performed by the delivery amount control of the delivery pump separated from the coating gun by a predetermined distance, the paint control cannot be controlled with high accuracy, and there is a problem that overspray or spray shortage occurs.

Therefore, in order to solve the above-mentioned problem, the applicant of the present invention has a paint pool portion of the paint capacity for one shot of intermittent paint and a monochromatic material that is sent by rotating the pool paint of the paint pool portion to the paint gun. There has been proposed an electrostatic coating apparatus that includes a spray unit having a monopump part in the form of a delivery bar and that can adjust the amount of paint delivered by controlling the number of revolutions of the monopump part (see Patent Document 1).
JP 2001-246295 A (paragraph 0014, FIG. 2)

  The present invention has been made in connection with the above-mentioned proposal, and is capable of controlling the amount of paint discharged from a coating gun with higher accuracy and capable of stably supplying a constant amount of paint. The object is to provide an electropainting system.

In order to achieve the above object, the present invention provides an electrostatic coating system for applying a high voltage to a coating material supplied from a coating tank to a coating gun, and coating an object to be coated . Is divided into one paint supply chamber and the other paint supply chamber and reciprocates linearly, and one end is connected to the discharge piston and the other end extends to the rod cleaning part. It consists of a single rod type metering discharge pump having a rod that displaces integrally with the discharge piston, and the discharge piston is linearly moved in the cylinder tube by the driving action of the drive means connected to the rod via an insulating part. The paint piston is pushed out from the one paint supply chamber to the paint gun and the paint is sucked into the other paint supply chamber at the same time. Comprising a feed Kyusuru paint dispenser means continuously a certain amount of paint to the spray gun by reciprocating, and a displacement speed control unit for controlling the displacement speed of the dispensing piston, the paint dispensing The means is configured such that the other components excluding the coil spring provided in the rod cleaning unit are made of an electrically insulating material, and the displacement speed control unit is configured to discharge discharge per unit time discharged by the forward stroke of the discharge piston. amount and, to match the discharge quantity per unit time discharged by the backward stroke of the dispensing piston, Rukoto predetermined amount to increase or decrease the displacement speed of the dispensing piston in one of the forward stroke or backward stroke It is characterized by.

According to the present invention, the paint is continuously applied to the paint gun by providing the fixed quantity discharge pump that linearly reciprocates the discharge piston that simultaneously performs the push-out action of the paint and the suction action of the paint during one stroke. It is possible to discharge and supply alternately. As a result, in the present invention, the flow of the paint flowing through the flow passage becomes smooth, and the paint can be continuously and stably supplied to the paint gun.

In addition, according to the present invention, the other components of the paint quantitative supply means excluding the coil spring provided in the rod cleaning unit are formed of an electrically insulating material, so that the current supply is interrupted. Generation of leakage current can be prevented. In this way the present invention, the elements of all the parts of the paint dispenser means excluding the coil spring consists of electrically insulating material, for example, because it does not use an electric supply medium such as an electric motor, high insulating properties It is possible to ensure a suitable environment in which a water-soluble paint can be used.

Further, the paint constant supply means has a single discharge piston that reciprocates linearly by dividing the inside of the cylinder tube into one paint supply chamber and the other paint supply chamber, and one end connected to the discharge piston. The other end portion extends to the rod cleaning portion and is constituted by a single rod type metering discharge pump having a rod that is displaced integrally with the discharge piston. In this case, the displacement speed control unit controls the displacement speed of the discharge piston so that the discharge amount per unit time discharged by the forward stroke of the discharge piston and the unit time discharged by the return stroke of the discharge piston. The discharge amount can be matched.

That is, according to the present invention, when the paint piston is continuously supplied by reciprocating the delivery piston of the constant delivery pump, the displacement speed of the delivery piston in one-side stroke is determined by, for example, an electropneumatic positioner. By controlling the amount of paint supplied per unit time by the displacement speed control unit to be constant (substantially constant) between the reciprocating strokes, in the single rod type metering discharge pump, between the forward stroke and the return stroke of the discharge piston It is possible to eliminate the volume difference of the generated paint to be supplied, and to supply paint more stably and with high accuracy to the paint gun.

  The metering discharge pump includes a paint supply unit having a discharge piston that linearly reciprocates in a cylinder tube, a rod connected to the discharge piston and displaced integrally with the discharge piston, and a paint attached to the rod And a rod supply chamber formed in the paint supply unit, and a rod cleaning chamber formed in the rod cleaning unit, respectively, by nitrogen gas supplied from the gas supply means It should be enclosed.

  According to the present invention, it is possible to reliably prevent leakage of paint to the outside even when a part of the rod is exposed to the outside by pressurizing and sealing the inside of the rod cleaning chamber of the metering discharge pump with nitrogen gas. Can do. For example, when a water-soluble paint is used as the conductive paint, prevention of leakage of the water-soluble paint to the outside is particularly important in order to prevent the occurrence of leak current, and versatility can be increased.

  A means for scraping the paint adhering to the outer peripheral surface of the rod may be provided in the rod cleaning section.

  According to the present invention, as a means for scraping the paint adhering to the outer peripheral surface of the rod by sliding in contact with the outer peripheral surface of the rod in the rod cleaning portion, for example, by providing a ring brush or the like, a part of the rod is externally provided. Even when it is exposed, it is possible to prevent leakage of the paint to the outside, and it is possible to prevent the leakage of electric current due to the decrease in electrical insulation due to the dirt of the paint adhering to the rod.

  Provided is an electrostatic coating system capable of controlling the amount of paint discharged from a coating gun with higher accuracy and supplying a constant amount of paint stably.

  Next, embodiments of the present invention will be described in detail with reference to the drawings as appropriate. FIG. 1 is a schematic configuration diagram of an electrostatic coating system according to an embodiment of the present invention applied to electrostatic coating of an automobile body, and FIG. 2 is a block configuration diagram of the electrostatic coating system.

As shown in FIGS. 1 and / or 2, the electrostatic coating system 10 includes a color changer valve and supplies paint supplied from each color paint tank (not shown), and supplies paint to a desired specific color (paint). And a color switching unit 12, a plunger pump 14 for intermittently supplying a predetermined amount of paint supplied from the paint supply and color switching unit 12 by a predetermined amount, and adjusting the paint supplied from the plunger pump 14 to a predetermined amount. In addition, in order to ensure electrical insulation, a paint dropping supply unit 20 that drops from the resin dropping nozzle 16 toward the resin float 18 is included. Under side of the float 18, flow meter 21 is provided for detecting the flow rate of the paint stored in the float 18. As the paint, a conductive paint including an organic solvent-type paint is used, but a water-soluble paint is preferably used.

Further, the electrostatic coating system 10 includes a first paint inlet / outlet port 24a and a second paint inlet / outlet port connected to the paint dripping supply unit 20 via a first three-way selector valve 22a and a second three-way selector valve 22b, respectively. 24b (see FIG. 3) is provided, the dispensing pump (paint dispenser means) 28 for sucking and discharging the coating material by the reciprocating operation of the discharge piston 2 6 to be described later, via said insulating portion 30 dispensing pump 28 A drive cylinder (drive means) 32 that is coaxially connected to drive the discharge piston 26, and a displacement that controls the displacement (stroke) of the piston (not shown) and the piston rod 34 of the drive cylinder 32 to a desired speed. It consists of a speed control unit 36, a controller 38 for deriving control signals to the displacement speed control unit 36, a keyboard (not shown), etc. Having an input unit 40 for inputting and setting a desired control signal to the controller 38, and a painting gun 42 which discharges towards the motor vehicle body (not shown) supplied paint (coating object) from the dispensing pump 28.

  The paint supply and color switching unit 12 selects a predetermined color paint based on the color selection signal introduced from the controller 38 and supplies the selected paint to the plunger pump 14. The paint supply and color switching unit 12 is connected to a cleaning liquid supply means and a drying means (not shown), and a cleaning liquid (for example, water) is supplied to a paint supply passage (not shown) based on a paint / cleaning liquid switching signal from the controller 38. The paint supply passage is provided so that it can be cleaned.

  The plunger pump 14 is provided so that the discharge amount per stroke can be adjusted via an adjustment mechanism (not shown), and the number of strokes can be arbitrarily set, and the vehicle body can be set by a discharge amount supply signal introduced from the controller 38. A predetermined amount of paint set in advance is intermittently supplied.

  The paint dripping supply unit 20 has the same configuration as that of a medical drip, and is provided on the lower side of the dripping nozzle 16 by naturally dropping the paint (foam) from the resin dripping nozzle 16 provided on the upper side. The resin float 18 is received at the opening and is stored for a predetermined amount for a while. At that time, the paint supplied intermittently from the plunger pump 14 is dropped non-continuously from the dropping nozzle 16, whereby the current conduction is cut off and the current path is cut off reliably.

  In this case, the float 18 may be fixed to a wall surface (not shown), and the paint may be supplied to the metering discharge pump 28 via a flexible resin tube 44 connected to the float 18, or The float 18 may be directly attached to the metering discharge pump 28 using the attachment means 45. When the float 18 is directly attached to the metering discharge pump 28, the upper opening has a small diameter and a temporary paint storage amount in consideration of overflow due to movement of a robot arm 46 (not shown). A small float shape consisting of a small amount is preferable.

  As shown in FIGS. 3 and 4, the fixed discharge pump 28 is configured so that the coating material is introduced from the coating material dropping supply unit 20 through the first three-way switching valve 22 a and the second three-way switching valve 22 b, and at the same time, It is basically composed of a paint supply unit 48 for supplying paint to the coating gun 42 and a rod cleaning unit 52 for cleaning the rod 50 connected to the discharge piston 26 described later.

  Each of the first three-way switching valve 22a and the second three-way switching valve 22b is a three-port two-position switching valve, and is turned on when a solenoid unit (not shown) is energized based on an urging signal from the controller 38 described later. By entering the state, the coating gun 42 and the first paint entrance / exit port 24a or the second paint entrance / exit port 24b are provided so as to communicate with each other via a passage 54 (electrically insulating conduit).

  The first three-way switching valve 22a and the second three-way switching valve 22b have the same configuration including a solenoid part and a valve mechanism part, respectively. In this case, the paint dripping supply unit 20 and the metering discharge pump 28 are communicated with each other by displacing a valve body (not shown) of the valve mechanism unit in accordance with a valve switching control signal introduced from the controller 38 to the solenoid unit. Then, the first valve position (on state) at which the paint can be introduced (filled) into the metering discharge pump 28, the metering pump 28 and the coating gun 42 are communicated with each other from the metering pump 28. The second valve position (off state) for supplying (discharging) a predetermined amount of the extruded paint to the coating gun 42 is controlled to be switched.

  As shown in FIG. 4, the coating material supply unit 48 constituting the fixed discharge pump 28 is connected to a cylindrical first cylinder tube 56a formed thick and one end of the first cylinder tube 56a. A first end cap 58a that closes the one end, and a cylindrical ceramic body (including a ceramic sintered body) that is fitted into a through hole of the first cylinder tube 56a and is thinly formed of a ceramic material. ) 60, a discharge piston 26 slidably displaced along the internal space of the ceramic body 60, and formed with a pair of partial spherical surfaces 62 a and 62 b facing each other, and the discharge piston 26 One end portion is connected, and the other end portion has a long rod 50 extending to the rod cleaning unit 52. A piston packing 63 slidably contacting the inner wall of the ceramic body 60 is mounted on the outer peripheral surface of the discharge piston 26 via an annular groove.

  In this case, by inserting the ceramic body 60 inside the first cylinder tube 56a, the first cylinder tube 56a formed of an electrically insulating resin material expands due to a temperature difference ( (Expansion of diameter) or contraction (reduction of diameter) can be suitably prevented. Further, by forming the discharge piston 26 with a pair of partial spherical surfaces 62a, 62b in a circular arc shape in the longitudinal section, it has a function of easing the discharge characteristic of the paint when sucked and buffering an abrupt suction action.

  The internal space formed in the ceramic body 60 is divided into one paint supply chamber 64a and the other paint supply chamber 64b by the discharge piston 26, as shown in FIG. The one paint supply chamber 64a is connected to a first paint inlet / outlet port 24a and a first communication port 70a formed in the first end cap 58a via a communication passage 66, and the other paint supply chamber 64b is connected to the first end cap 58a. The second paint inlet / outlet port 24b formed at a position separated from the first paint inlet / outlet port 24a by a predetermined distance along the axial direction is connected in communication. A second communication port 70b is provided on the opposite side of the second paint entrance / exit port 24b along the circumferential direction.

  In this case, as shown in FIG. 3, a first on / off valve 72a is connected to the first communication port 70a, and a second on / off valve 72b is connected to the second communication port 70b. The first on / off valve 72a and the second on / off valve 72b are connected to each other by a passage 74 (electrically insulating conduit). Therefore, as will be described later, the nitrogen gas or the cleaning liquid fed from the rod cleaning unit 52 passes through the first communication port under the valve opening action of the first on / off valve 72a and / or the second on / off valve 72b. While being supplied to one paint supply chamber 64a via 70a, it is provided to be supplied to the other paint supply chamber 64b via the second communication port 70b.

  As shown in FIG. 4, the rod cleaning unit 52 includes a cylindrical second cylinder tube 56 b whose one end is coaxially connected to the first cylinder tube 56 a of the paint supply unit 48, and the first A second end cap 58b is connected to the other end portion of the two-cylinder tube 56b along the axial direction so as to close the other end portion and support the rod 50 slidably.

  A connecting portion between the first cylinder tube 56a and the second cylinder tube 56b is provided with a first seal member 76a such as an O-ring through an annular groove in order to maintain liquid tightness and air tightness. A ring plate 78 is attached to an annular step formed on the inner wall of the first cylinder tube 56a, and a second seal member 76b such as an O-ring surrounding the outer peripheral surface of the rod 50 is attached to the ring plate 78. Retained. Further, a third seal member 76c such as an O-ring is provided at a connection portion between the other end of the second cylinder tube 56b and the second end cap 58b in order to maintain liquid tightness and air tightness. .

As shown in FIG. 3 or 4, the second cylinder tube 56 b has a third three-way switching valve 22 c that controls switching between supply of cleaning liquid (cleaning water) and nitrogen gas (also referred to as N ₂ gas). A third port 24c communicating with the second port 24d, a fourth port 24d communicating with an N ₂ gas supply source (gas supply means) 80 for supplying nitrogen gas, and the fourth port 24d introduced into the second cylinder tube 56b. A fifth port 24e that feeds nitrogen gas toward the third three-way selector valve 22c and a third port 24c that is disposed on the opposite side along the circumferential direction of the third port 24c and is supplied from the third port 24c via a passage 74. And a third communication port 70c for feeding the cleaning liquid or nitrogen gas toward the one and the other paint supply chambers 64a and 64b.

The third three-way switching valve 22c is composed of, for example, a three-port three-position switching valve having a spool valve (not shown) that is displaced by a pilot pressure. A cleaning liquid supply source 68 is connected to the inlet port, and a rod is connected to the outlet port. The third port 24c of the cleaning unit 52 is connected (see FIG. 3). In the third three-way valve 22c, an intermediate position the center valve position, communicates with the right valve position that communicates with the third port 24c and the fifth port 24 e, a cleaning liquid supply source 68 and a third port 24c The left valve position is switched and controlled.

  The third to fifth ports 24c to 24e and the third communication port 70c provided in the second cylinder tube 56b communicate with a rod cleaning chamber 82 which is an internal space formed in the second cylinder tube 56b. It is provided as follows.

  A portion of the second cylinder tube 56b adjacent to the third port 24c and the third communication port 70c is fixed in the rod cleaning chamber 82 and surrounds and seals the outer peripheral surface of the rod 50. A retainer 84 that holds the ring 50, a resin-made ring brush 86 that cleans the rod 50 by sliding contact with the outer peripheral surface of the rod 50, a cylindrical holding member 88 that holds the ring brush 86, and the retainer 84. And a coil spring 90 which is mounted between the ring brush 86 and presses the ring brush 86 toward the second end cap 58b. The ring brush 86 functions as a means for scraping off the paint adhering to the outer peripheral surface of the rod 50.

  In the rod cleaning chamber 82 adjacent to the fourth port 24d and the fifth port 24e, a cylindrical collar member 92 is formed of a porous body in which numerous holes are formed and surrounds the outer peripheral surface of the rod 50. Provided. Between the collar member 92 and the second end cap 58b, there is provided a fifth seal member 76e made of an O-ring that slides on the outer peripheral surface of the rod 50 and exhibits a sealing function.

  As shown in FIG. 3, in the metering discharge pump 28, all components except for the coil spring 90 formed of a metal material such as SUS are made of the following materials having electrical insulation, that is, resin. Material (for example, first cylinder tube 56a, second cylinder tube 56b, discharge piston 26, first end cap 58a, second end cap 58b, etc.), ceramic material (ceramic body 60), and rubber material (for example, The first to fifth seal members 76a to 76e) made of nitrile rubber (NBR) and the like are cut off to prevent the occurrence of leak current.

  An insulating portion 30 is provided at the free end of the rod 50 that protrudes from the other end of the fixed discharge pump 28 by a predetermined length and is exposed to the outside. The insulating portion 30 causes the current from the drive cylinder 32 and the displacement speed control portion 36 to be present. Is de-energized. The insulating portion 30 is made of a coupling member formed of a resin material having electrical insulation, and the rod 50 of the metering discharge pump 28 and the piston rod 34 of the drive cylinder 32 are connected coaxially.

  The drive cylinder 32 includes a well-known air cylinder having a piston (not shown) housed in a cylinder chamber formed in a metal cylinder tube and a piston rod 34 having a free end connected to the piston exposed to the outside. Is done. In this case, pressure air supplied from an air supply source (not shown) is supplied into the cylinder chamber and presses the piston, whereby the piston is displaced from one displacement end to the other displacement end, and the piston rod 34 is connected to the piston. It is provided so as to move integrally and move forward and backward (reciprocating).

  Accordingly, when the drive cylinder 32 is driven and the piston rod 34 moves back and forth, the linear motion of the piston rod 34 is transmitted to the rod 50 of the metering discharge pump 28 and discharged along the axial direction of the first cylinder tube 56a. The piston 26 is provided so as to reciprocate linearly.

  In this case, the paint in the paint supply chamber 64a (or 64b) existing on the displacement direction side of the discharge piston 26 of the fixed discharge pump 28 is pushed out by the discharge piston 26 and is supplied to the first three-way switching valve 22a (or second three-way). In addition to being fed (discharged) to the coating gun 42 via the switching valve 22b), the second three-way switching valve 22b (or 64a) is provided in the paint supply chamber 64b (or 64a) on the side opposite to the displacement direction of the discharge piston 26. Alternatively, new paint is sucked (sucked) through the first three-way switching valve 22a).

  In this way, the one-stroke (displacement from one displacement end position to the other displacement end position) of the discharge piston 26 of the fixed discharge pump 28 causes the paint piston to be pushed out (discharge action) and the paint is sucked and filled. The action (suction filling action) is performed simultaneously.

  Further, in the forward stroke (see FIG. 3) in which the discharge piston 26 is displaced from the second end cap 58b to the first end cap 58a, the paint push-out action is performed in the paint supply chamber 64a on the left side of the discharge piston 26 in FIG. At the same time, although the paint suction and filling operation is performed in the paint supply chamber 64b on the right side of the discharge piston 26 in FIG. 4, the return stroke in which the discharge piston 26 is displaced from the first end cap 58a to the second end cap 58b. In FIG. 3, the paint pushing-out action and the suction filling action in the left and right paint supply chambers 64 a and 64 b are reversed. The direction of the forward stroke and the backward stroke is not limited to the direction shown in FIG. 3 and may be the opposite direction.

  In other words, in the forward stroke and the backward stroke of the discharge piston 26, the paint pushing-out action and the paint suction and filling action are opposite to each other in the left and right paint supply chambers 64a and 64b, and the first three-way switching valve. The ON state and the OFF state are reversed between 22a and the second three-way switching valve 22b (see FIG. 5A).

  Accordingly, when the discharge piston 26 of the fixed discharge pump 28 reciprocates a plurality of times under the drive action of the drive cylinder 32 and the stroke continues, the push-out action of the previously filled paint and the new paint suction and fill action. Can be continuously supplied to the coating gun 42. The point that a constant amount of paint is supplied in the unit time of each stroke will be described later.

  The displacement speed control unit 36 that controls the displacement speed of the piston of the drive cylinder 32 is constituted by, for example, a known electro-pneumatic positioner having an electro-pneumatic conversion mechanism that converts an electrical signal into a pneumatic signal. In this electro-pneumatic positioner, pressure air proportional to an electric signal (input signal) input (set) in advance can be obtained from the output side, and the pressure air is supplied to the cylinder chamber of the drive cylinder 32 to thereby provide a piston. Can be controlled to a desired speed.

  The electro-pneumatic conversion mechanism may be a nozzle flapper mechanism (not shown) that adjusts the nozzle back pressure with a flapper made of a piezoelectric element or the like, or a diaphragm mechanism (not shown) that adjusts the nozzle back pressure with a plurality of diaphragms.

  A painting robot (not shown) is disposed in the vicinity of a production line (not shown) through which an automobile body, which is an object to be coated, is conveyed. The robot arm 46 (see FIG. 1) has, for example, a painting gun. 42, a fixed discharge pump 28, a drive cylinder 32, a displacement speed control unit 36 (electro-pneumatic positioner), and the like are mounted via a fixing means (not shown) and provided so as to be displaced integrally with the arm 46.

  As a high voltage application method for the paint, an external application method (a method in which a high voltage is applied to the paint sprayed by the coating gun 42) and an internal application method (for a fluid paint in the coating gun 42) are applied. In this embodiment, any method is possible, but it is preferable to use an internal application method for a water-soluble paint having high coating efficiency.

  The painting robot is, for example, an industrial articulated robot whose operation is programmed and controlled by the controller 38, and a painting gun is applied to the tip (wrist) of the arm 46 constituting the turning unit. It is good to use what 42 is attached.

  The electrostatic coating system 10 according to the present embodiment is basically configured as described above, and the operation and effects thereof will be described next.

  First, the paint of a specific color selected by the paint supply and color switching unit 12 is introduced into the plunger pump 14, and a predetermined amount of paint (for example, the amount of paint for one shot) is supplied to the dropping nozzle 16 of the paint dropping supply unit 20. Supplied. The paint mist dripped from the lower end of the dripping nozzle 16 is received and stored in the float 18.

  The paint stored in the float 18 is fed to the first three-way switching valve 22a and the second three-way switching valve 22b through a resin tube. Here, a valve switching control signal from the controller 38 is introduced into the first three-way switching valve 22a or the second three-way switching valve 22b, and a desired valve switching position is obtained. For example, in FIG. 3, the second three-way switching valve 22b is turned on, the second port 24b of the metering discharge pump 28 and the paint dripping supply unit 20 are in communication with each other, and the first three-way switching valve 22a in the off state is turned on. An example in which the first port 24a of the metering discharge pump 28 and the coating gun 42 are in communication with each other will be described below.

  An air supply source (not shown) is energized to supply driving air to the drive cylinder 32 via the displacement speed control unit 36 (electropneumatic positioner), and a control signal (input signal) is sent from the controller 38 to the electropneumatic positioner. By introducing and controlling the displacement speed of the piston of the drive cylinder 32 to a predetermined speed, a constant amount of paint per unit time is supplied to the coating gun 42 from the fixed discharge pump 28.

  That is, when the discharge piston 26 of the fixed discharge pump 28 is displaced in the forward stroke direction of FIG. 3, the amount of paint pushed out from the one paint supply chamber 64a toward the paint gun 42 and the other paint supply chamber 64b. The amount of paint to be sucked and filled differs by the volume of the rod 50. In other words, the side surface of the discharge piston 26 facing the paint supply chamber 64a on the left side as viewed in FIG. 4 has only the partial spherical surface 62a and the rod 50 is not connected thereto, whereas the paint supply chamber on the right side in FIG. Since the rod 50 is connected to the other side of the discharge piston 26 facing the 64b, a volume difference is generated between the left paint supply chamber 64a and the right paint supply chamber 64b by the volume of the rod 50.

  For example, the stroke amount (displacement amount) of the forward path and the return path of the discharge piston 26 is constant, the amount of paint supplied from the left paint supply chamber 64a to which the rod 50 is not connected is 100 cc / min, and the rod 50 is connected. Assuming that the amount of paint supplied from the right-hand paint supply chamber 64b is 85 cc per minute, assuming that the displacement speeds of the discharge piston 26 in the forward stroke and the backward stroke are the same, between the forward stroke and the backward stroke, A volume difference of 15 cc / min occurs in the paint supplied to the coating gun 42.

  Therefore, in order to make the supply amount of paint per minute (per unit time) constant (substantially constant), the supply amount per unit time of the entire forward stroke (the total supply amount of paint in each forward stroke is added per unit time). Discharge in the forward stroke so that the divided amount) and the supply amount per unit time in the entire return stroke (the amount obtained by adding the paint supply amount in each return stroke and dividing by the unit time) match (substantially match) The displacement speed of the discharge piston 26 in the return stroke is increased by, for example, about 15 percent with respect to the displacement speed of the piston 26.

  In other words, when the discharge piston 26 is displaced so that the paint is pushed out and sucked and filled at the same time, the discharge piston 26 is reciprocated to supply the paint continuously (continuously). The volume difference of the supply paint generated between the forward stroke and the return stroke of the piston 26 is increased, and the displacement speed of the discharge piston 26 in one side stroke is increased so that the paint supply amount per unit time is constant between the reciprocating strokes (substantially). Constant).

  In this case, a control signal (input signal) is introduced from the controller 38 to the electropneumatic positioner so as to achieve a desired displacement speed, and an air pressure proportional to the control signal is supplied to the cylinder chamber of the drive cylinder 32 and the piston. , It is possible to control the displacement speed of the rod 50 of the fixed discharge pump 28 and the discharge piston 26 connected to the piston rod 34 of the drive cylinder 32. It is also possible to use a so-called cylinder positioner in which the drive cylinder 32 and the electropneumatic positioner are integrally assembled.

  Here, an operation example of the electropneumatic positioner will be described. The stroke length (displacement amount) of the drive cylinder 32 composed of an air cylinder is determined in accordance with the discharge capacity of the paint, and the stroke length is divided by each point ( For example, 1 to 60 points), the voltage of each of the divided points is set. The air pressure output to the drive cylinder 32 is controlled by the potential difference (0 to 24 V) generated by supplying this voltage signal, and the displacement speed of the discharge piston 26 of the fixed discharge pump 28 is controlled to a desired speed. Is possible.

  When the discharge piston 26 of the fixed discharge pump 28 reciprocates, the valve switching positions of the first three-way switching valve 22a and the second three-way switching valve 22b are opposite to each other by the valve switching control signal introduced from the controller 38. (See FIG. 5A).

  Thus, the paint supplied from the first three-way switching valve 22a and the second three-way switching valve 22b is fed to the coating gun 42 through the passage 54. Further, after being applied with a high voltage by an internal high voltage method by a high voltage applying means (not shown), a certain amount of paint per unit time is stably and continuously discharged from the coating gun 42 toward the automobile body. Electrostatic coating is performed.

  Before starting electrostatic coating and during execution of electrostatic coating, the gas supply source 80 is energized to supply nitrogen gas into the rod cleaning chamber 82 from the fourth port 24d, and the rod cleaning chamber 82 is filled with nitrogen gas. By pressurizing with and enclosing, leakage of the paint to the outside can be surely prevented. For example, when a water-soluble paint is used as the conductive paint, prevention of paint leakage to the outside is particularly important in order to prevent the occurrence of leak current. In this case, the pressure of the nitrogen gas sealed in the rod cleaning chamber 82 is set higher than the supply pressure of the paint, so that the sealing function can be exhibited smoothly.

  The nitrogen gas supplied from the fourth port 24d is surrounded by the inner wall of the second cylinder tube 56b, the outer peripheral surface of the rod 50, and the side wall of the second end cap 58b through a number of small holes formed in the collar member 92. The entire rod cleaning chamber 82 is filled, and the sealing action of the fourth seal member 76d and the fifth seal member 76e surrounding the outer peripheral surface of the rod 50 prevents the leakage of nitrogen gas to the outside. Sex is preserved.

  Further, during the electrostatic coating, the rod cleaning unit 52 can scrape off the paint adhering to the outer peripheral surface of the rod 50 by the ring brush 86 being in sliding contact with the outer peripheral surface of the rod 50. Even if a part of the rod 50 is exposed, leakage of the paint to the outside can be prevented.

  Next, for example, a cleaning operation for cleaning the paint flow path with the cleaning liquid at the time of paint color switching or maintenance will be described.

  The valve position of the third three-way switching valve 22c is switched to the right valve position in FIG. 3 to bring the third port 24c and the fifth port 24e into communication, and the first on / off valve 72a and the second on Each of the / off valves 72b is turned on (see FIG. 5B). The nitrogen gas supplied through the third three-way switching valve 22c and the third port 24c passes through the third communication port 70c, the passage 74, the first on / off valve 72a and the second on / off valve 72b, respectively. Both paint supply chambers 64a and 64b are filled, respectively.

  After being filled with nitrogen gas in this way, the valve position of the third three-way switching valve 22c is switched to the valve position on the left side in FIG. 3 to cut off the communication between the third port 24c and the fifth port 24e, The cleaning liquid supplied from the cleaning liquid supply source 68 is supplied to the third port 24c (see FIG. 5B). At that time, the first on / off valve 72a and the second on / off valve 72b are each kept in the on state. Accordingly, the cleaning liquid introduced from the third port 24c is supplied to both the paint supply chambers 64a and 64b through the third communication port 70c, the first on / off valve 72a and the second on / off valve 72b, respectively. Thus, the insides of both the paint supply chambers 64a and 64b are preferably cleaned. The used cleaning liquid is drained from the coating gun 42 through the first three-way switching valve 22a and the second three-way switching valve 22b.

In this way, after the paint flow passage is cleaned by the cleaning liquid supplied for a predetermined time, the valve position of the third three-way switching valve 22c is switched again to the right valve position in FIG. By leaving the fifth port 24e in communication and supplying nitrogen gas again, the remaining cleaning liquid can be suitably blown off (see FIG. 5B). In this case, nitrogen gas (N ₂ ) is a colorless and odorless inert gas, and its specific gravity (1.2506 g / cm ³ ) is heavier than water and has a low thermal conductivity (0.02598 m · ° C.). It can be suitably used as a blowing gas for discharging the cleaning liquid remaining in the paint flow passage.

  In addition, after the supply of nitrogen gas as a blowing gas has elapsed for a predetermined time, the first on / off valve 72a and the second on / off valve 72b are turned off by a valve switching signal from the controller 38, and both paint supply chambers The nitrogen gas filled in 64a and 64b may be kept in a sealed state and function as a sealing gas.

  In the present embodiment, the coating gun 42 is provided with a quantitative discharge pump 28 that reciprocates linearly the discharge piston 26 that simultaneously performs the push-out action of paint and the suction-filling action of paint during one stroke. The discharge can be continuously and alternately supplied. As a result, in the present embodiment, the flow of the paint flowing through the flow passage becomes smooth, and the paint can be continuously and stably supplied to the paint gun 42.

  In this case, in this embodiment, when the discharge piston 26 of the fixed discharge pump 28 is reciprocated to supply the paint continuously (continuously), the displacement speed of the discharge piston 26 in one-side stroke is determined by the displacement speed control unit 36. The volume of the supplied paint generated between the forward stroke and the backward stroke of the discharge piston 26 is increased by the (electro-pneumatic positioner) to make the paint supply amount per unit time constant (substantially constant) between the reciprocating strokes. The difference can be eliminated, and the coating gun 42 can be supplied with a more stable and highly accurate paint.

  Further, in this embodiment, all the components of the metering discharge pump 28 except for the coil spring 90 formed of a metal material are formed of an electrically insulating material, and the current flow is interrupted to leak current. Is prevented. For example, the first cylinder tube 56a, the second cylinder tube 56b, the discharge piston 26, the first end cap 58a, the second end cap 58b, etc. are each formed of a resin material, the ceramic body 60 is formed of a ceramic material, The first to fifth seal members 76a to 76e are formed of a rubber material such as nitrile rubber (NBR).

  As described above, in this embodiment, almost all the elements of the metering discharge pump 28 are made of an insulating material and, for example, do not use an electric supply medium such as an electric motor. It can be set as the suitable environment which can use a coating material.

  Furthermore, in the present embodiment, the inside of the rod cleaning chamber 82 of the fixed discharge pump 28 is pressurized and sealed with nitrogen gas, so that even if a part of the rod 50 is exposed to the outside, the leakage of paint to the outside is ensured. Can be prevented. For example, when a water-soluble paint is used as the conductive paint, prevention of leakage of the water-soluble paint to the outside is particularly important in order to prevent the occurrence of leak current, and versatility can be increased.

  Furthermore, in the present embodiment, by providing the ring brush 86 in sliding contact with the outer peripheral surface of the rod 50 in the rod cleaning portion 52, the paint adhering to the outer peripheral surface of the rod 50 can be scraped off. Even when a part of the rod 50 is exposed, leakage of the paint to the outside can be prevented, and the electrical insulation is deteriorated due to the dirt of the paint adhering to the rod 50, and a leakage current is generated. Can be prevented.

  Furthermore, in the present embodiment, under the switching action of the third three-way switching valve 22c, supply of cleaning liquid for cleaning the flow path of the paint, and nitrogen that blows away the cleaning liquid remaining in the flow path after cleaning and pushes it outside. Gas supply can be easily switched, paint color switching work and maintenance work can be easily performed, and color switching work time and maintenance work time can be shortened.

It is a schematic block diagram of the electrostatic coating system which concerns on embodiment of this invention applied to the electrostatic coating of a motor vehicle body. It is a block block diagram of the said electrostatic coating system. It is a circuit block diagram of the coating material supplied to the coating gun from the fixed discharge pump which comprises the said electrostatic coating system. It is a longitudinal cross-sectional view along the axial direction of the said fixed delivery pump. (A) is a time chart when performing electrostatic coating using the electrostatic coating system, and (b) is a time chart when cleaning the flow path of the paint with a cleaning liquid.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Electrostatic coating system 22a-22c Three-way switching valve 26 Discharge piston 28 Fixed discharge pump 36 Displacement speed control part 42 Coating gun 48 Paint supply part 52 Rod cleaning part 64a, 64b Paint supply room 82 Rod cleaning room 86 Ring brush

Claims (4)

An electrostatic coating system that applies a high voltage to paint supplied from a paint tank to a paint gun and paints an object to be coated.
A single discharge piston that reciprocates linearly by dividing the inside of the cylinder tube into one paint supply chamber and the other paint supply chamber, one end connected to the discharge piston, and the other end to the rod cleaning section It consists of a single rod type metering discharge pump having a rod that extends and displaces integrally with the discharge piston, and the discharge piston is connected to the rod by means of a drive means connected via an insulating part to the cylinder tube. By displacing the interior linearly, the paint push-out action from the one paint supply chamber to the paint gun and the suction action of the paint to the other paint supply chamber are simultaneously performed, and the discharge piston reciprocates. Paint constant quantity supply means for continuously feeding a constant amount of paint to the paint gun,
A displacement speed controller for controlling the displacement speed of the discharge piston;
With
In the paint constant supply means, the other components excluding the coil spring provided in the rod cleaning unit are made of an electrically insulating material ,
The displacement speed control unit is configured to match the discharge amount per unit time discharged by the forward stroke of the discharge piston with the discharge amount per unit time discharged by the return stroke of the discharge piston. or electrostatic coating system characterized Rukoto only by increasing or decreasing a predetermined amount of displacement speed of the dispensing piston in one of the backward stroke. In claim 1 Symbol placement electrostatic coating system,
Before Symbol dispensing pump, said the one and the other paint supply chamber has been that the paint supply unit provided in the first cylinder tube, the first cylinder tube and the second cylinder tube connected coaxially provided having a rod cleaning chamber has an electrostatic coating system, characterized in that they are composed of said rod cleaning unit for cleaning the coating material adhering to the rod. The electrostatic coating system according to claim 2 ,
The one and the other of the paint supply chamber, and, before km head cleaning chamber, respectively, an electrostatic coating system, characterized in that it is encapsulated by the nitrogen gas supplied from the gas supply means. In the electrostatic coating system according to claim 1 or 2 ,
The rod in the cleaning portion, the electrostatic coating system, characterized in that means for scraping the paint adhering to the outer peripheral surface of the rod is provided.

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