Patent Application
20110020561
The present invention relates to an electrostatic painting apparatus and an electrostatic painting method for performing electrostatic painting or coating an opening/closing object provided in an object to be painted by a painting means while opening and closing the opening/closing object by an opening/closing means.
As a technique of this type, heretofore, there have been known painting techniques disclosed in for example Patent Literatures 1 to 4 listed below. In particular, Patent Literature 1 discloses a technique of painting or coating the periphery of a door of a vehicle by use of a robot to which a painting gun, an engaging piece engageable with the door, and a sensor for detecting the position of the door are attached. In this technique, the position of the robot is compensated according to the position of the door detected by the sensor and the engaging piece is engaged with the door. Then, the engaging piece is moved by the robot to open the door, and the robot moves the painting gun to coat the periphery of the door. Herein, after the door is opened, the door position is detected again by the sensor to determine whether the door is in an open state or not. Only when the door is in the open state, painting is carried out.
However, in the painting technique disclosed in Patent Literature 1, the sensor is constituted of a proximity switch, but there is no disclosure about an explosion-proof structure. In a painting environment for vehicles or the like, an electric sensor has to be added with the explosion-proof structure. Accordingly, the sensor is housed in an explosion-proof case. In the case where the sensor disclosed in Patent Literature 1 is added with the explosion-proof structure, the peripheral parts of the sensor are increased in size and further the sensor might erroneously detect the door position. In case the door position is erroneously detected, the engaging piece cannot be correctly engaged with the door and the door cannot be opened. Furthermore, the engaging piece and the painting gun or the robot itself could improperly touch the door.
The present invention has been made in view of the above circumstances and has a purpose to provide an electrostatic painting apparatus and an electrostatic painting method capable of realizing prediction of interference with an opening/closing object without providing a special explosion-proof structure.
(1) To achieve the above purpose, a first aspect of the invention provides an electrostatic painting apparatus for electrostatically painting an opening/closing object provided in an object to be pained by a painting means while opening and closing the opening/closing object by an opening/closing means, comprising; a high-voltage applying means for applying high voltage to the opening/closing means; a discharge current detecting means for detecting a current value of discharge current flowing between the opening/closing means and the opening/closing object; and a positional relationship determining means for determining a positional relationship between the opening/closing object and the opening/closing means based on the detected current value, the positional relationship determining means being configured to determine that (1) the positional relationship is abnormal when the detected current value exceeds a first current value while the opening/closing means is moving closer to or away from the opening/closing object and (2) the positional relationship is abnormal when the detected current value exceeds the first current value or is between a second current value smaller than the first current value and a third current value smaller than the second current value while the opening/closing means is engaged with the opening/closing object and operated to open and close the opening/closing object.
According to the above configuration of the invention, the opening/closing means applied with high voltage by the high-voltage applying means is moved closer to the opening/closing object and then the discharge current flowing between the opening/closing means and the opening/closing object is detected by the discharge current detecting means. This detected discharge current varies according to differences in positional relationship between the opening/closing means and the opening/closing object. This enables prediction of interference between the opening/closing means and the opening/closing object without adding a special explosion-proof structure.
According to the above configuration of the invention, based on the variation in the detected discharge current, the positional relationship determining means determines the positional relationship between the opening/closing means and the opening/closing object. Therefore, the opening/closing state of the opening/closing object by the opening/closing means can be monitored.
(2) To achieve the above purpose, in the above configuration (1), preferably, the opening/closing means includes an articulated robot having a plurality of arms connected in series and an engaging tool engageable with the opening/closing object, the tool being placed at a distal end portion of a distal-side arm of the arms, the discharge current detecting means includes an electrode pin placed in the distal-side arm so as to be able to come closer to the opening/closing object, and the high voltage is applied to at least the distal-side arm.
According to the above configuration of the invention, in addition to the operations of the above configuration (1), the engaging tool provided at the distal end of the distal-side arm is engaged with the opening/closing object and the articulated robot is freely operated to open or close the opening/closing object. When the distal-side arm is moved, the discharge current flowing between the distal-side arm and the opening/closing object is detected in a concentrated manner by the electrode pin. Therefore, in addition to the advantages of the above configuration (1), the interference between the distal-side arm and the opening/closing object can be predicted correctly.
(3) To achieve the above purpose, in the above configuration (2), preferably, the engaging tool is provided with a position sensor for detecting the position of the opening/closing object.
According to the above configuration of the invention, in the operations of the above configuration (2), the engaging tool is moved toward the opening/closing object and thus the position of the opening/closing object is detected by the position sensor. In addition to the advantages of the above configuration (2), accordingly, the engaging tool can be aligned with the position of the opening/closing object based on detection of the opening/closing object by the position sensor.
(4) To achieve the above purpose, a second aspect of the invention provides an electrostatic painting method for electrostatically painting an opening/closing object provided in an object to be pained by a painting means while opening and closing the opening/closing object by the opening/closing means, comprising; applying high voltage to the opening/closing means by a high-voltage applying means; detecting a current value of discharge current discharged between the opening/closing means and the opening/closing object by a discharge current detecting means; performing electrostatic painting while determining a positional relationship between the opening/closing object and the opening/closing means based on the current value detected by the discharge current detecting means, the positional relationship being determined (1) to be abnormal when the detected current value exceeds a first current value while the opening/closing means is moving closer to or away from the opening/closing object and (2) to be abnormal when the detected current value exceeds the first current value or is between a second current value smaller than the first current value and a third current value smaller than the second current value while the opening/closing means is engaged with the opening/closing object and operated to open and close the opening/closing object.
A detailed description of a preferred embodiment of an electrostatic painting apparatus and an electrostatic painting method embodying the present invention will now be given referring to the accompanying drawings.
The door painting robot 4 includes a base member 7, a pivot member 8 pivotally connected to the base member 7, a first arm 9 and a second arm 10 both being pivotally connected in series to the pivot member 8, and a painting nozzle 11 provided at a free end of the second arm 10. The nozzle 11 is configured to eject or spray paint in the form of atomized particles. The above members 7 to 10 are mutually pivoted to allow the nozzle 11 to freely move in all directions; up and down, back and forth, and right and left in a predetermined range.
In this electrostatic painting apparatus 1, the painting nozzle 11 is made negative in polarity and the vehicle body 2 is made positive in polarity, and a high voltage of 30000 to 100000 volts is applied between the nozzle 11 and the vehicle body 2 to perform painting. The atomized particle paint to be ejected through the nozzle 11 is attracted by the vehicle body 2 which is a ground, so that the paint thus elastically adheres to the surface of the vehicle body 2. At that time, the atomized particle paint also flies to the back side of the vehicle body 2 that does not face the nozzle 11 and adheres to the surface of the back side.
The door opening/closing apparatus 5 includes an articulated robot 12 and an opening/closing tool 13 provided at a distal end of the articulated robot 12. The articulated robot 12 includes a base member 14, a first arm 15, a second arm 16, and a third arm 17 which are connected in series to the base member 14. The first arm 15 is supported horizontally to the base member 14 and rotatably in a horizontal direction. The second arm 16 is supported horizontally to the distal end of the first arm 15 and rotatably in a horizontal direction. The third arm 17 on a most distal side is supported vertically to a distal end portion of the second arm 16 so that the arm 17 is rotatable in a horizontal direction and movable in a vertical direction. In this embodiment, the first arm 15 and the third arm 17 are made of metal and the second arm 16 is made of resin.
The opening/closing tool 13 is provided at a distal end of the third arm 17 vertically supported. The opening/closing tool 13 includes a frame 13a bent at right angles and an opening/closing hook 18 provided at a distal end of the frame 13a. The hook 18 corresponds to an example of an engaging tool of the invention and is provided facing downward to be engageable with the door 3. The hook 18 is made of a conductive material with a resistor, a semi-conducting material, or an insulating material. In this embodiment, the hook 18 is formed of resin which is an insulating material.
In this embodiment, as shown in
In this embodiment, an electrode pin 22 is placed to protrude outward from the middle of the third arm 17 located on the most distal side. This electrode pin 22 is connected to the high-voltage generator 19 through a wiring 23. The electrode pin 22 and the wiring 23 constitute an example of a discharge current detecting means of the invention for detecting discharge current between the door opening/closing apparatus 5 and the door 3. The above electrode pin 22 is connected to the high-voltage controller 20 through the wiring 23 and the high-voltage generator 19.
The high-voltage controller 20 is configured to receive the discharge current detected through the electrode pin 22 and others and determine the positional relationship between the door 3 and the third arm 17 based on the discharge current. The high-voltage controller 20 corresponds to an example of a positional relationship determining means of the invention.
In this embodiment, the above electrostatic painting apparatus 1 is used to perform electrostatic painting by the door painting robot 4 while opening and closing the door 3 provided in the vehicle body 2 by the door opening/closing apparatus 5. For this electrostatic painting, the opening/closing hook 18 which comes into contact with the door 3 of the door opening/closing apparatus 5 is made of resin. The electrostatic painting is conducted by causing the high-voltage generator 19 to apply a high voltage having the same negative polarity as the atomized particle paint for electrostatic painting to the surfaces of the second arm 16 and the third arm 17 and the opening/closing tool 13 of the door opening/closing apparatus 5. For this electrostatic painting, furthermore, the high voltage is applied to the second and third arms 16 and 17 of the door opening/closing apparatus 5 by the high-voltage generator 19 and the discharge current to be discharged between the third arm 17 and the door 3 is detected by the electrode pin 22 and others. Thus, the electrostatic painting is performed while the positional relationship between the third arm 17 and the door 3 is determined based on the detected discharge current.
According to the electrostatic painting apparatus 1 in this embodiment explained above, in the door opening/closing apparatus 5, the opening/closing hook 18 which directly contacts with the door 3 is made of resin. Accordingly, the hook 18, while retaining engaged with the door 3, is applied with the high voltage having the same polarity as the atomized particle paint for electrostatic painting. Thus, all the electric current does not flow to the door 3 and a high voltage is applied to the hook 18, so that the electric charge is retained on the surface of the hook 18. Consequently, floating atomized paint particles not having been deposited repel the electric charge of the surface of the hook 18 and are unlikely to adhere to the surface. As a result, it is possible to reduce stains on the hook 18 to be used for opening and closing the door 3 caused by the undeposited paint.
In this embodiment, the opening/closing tool 13 including the opening/closing hook 18 and also the second arm 16 and the third arm 17 constituting the articulated robot 12 are applied with high voltage having the same polarity as the atomized particle paint. The electric charge thereof is also retained on the surfaces of the tool 13 and the second and third arms 16 and 17. Therefore, the floating atomized particle paint not having been deposited repels the electric charge of the surfaces of those members 13, 16, and 17 and is unlikely to adhere to their surfaces. As a result, it is similarly possible to reduce stains on the tool 13 and the second and third arms 16 and 17 caused by the undeposited paint.
In this embodiment, the high-voltage generator 19 is placed in the second arm 16 of the articulated robot 12. Accordingly, a special installation space for the high-voltage generator 19 is not required. The door opening/closing apparatus 5 can therefore be made compact while maintaining a high-voltage application function.
In this embodiment, as explained above, it is possible to reduce stains caused by the undeposited paint on the opening/closing tool 13 and the second and third arms 16 and 17 which are parts comes into contact or closer to the door 3 in the door opening/closing apparatus 5. Thus, cleaning frequency to remove stains from the door opening/closing apparatus 5 can be reduced. For example, the cleaning to remove stains is heretofore conducted once after the electrostatic painting operation for about one hour. On the other hand, according to this embodiment, the cleaning to remove stains has only to be conducted once after the electrostatic painting operation for about four to five hours. Furthermore, the stain paint is prevented from adhering in the form of spits to the vehicle body 2 and the door 3. This makes it possible to prevent deterioration in painting quality of the vehicle body 2 and others.
In this embodiment, while the high-voltage generator 19 applies a high voltage to the door opening/closing apparatus 5, the third arm 17 of the door opening/closing apparatus 5 is moved with respect to the door 3. At that time, the discharge current flowing between the third arm 17 and the door 3 is detected in a concentrated manner by the electrode pin 22. In this embodiment, therefore, the high-voltage controller 20 can correctly predict interference between the third arm 17 and the door 3 based on changes in discharge current detected in a concentrated manner through the electrode pin 22. The opening/closing state of the door 3 by the third arm 17 can be monitored by the high-voltage controller 20. In this embodiment, for monitoring the opening/closing state of the door 3, it is only necessary to detect the discharge current between the third arm 17 and the door 3. Thus, no special explosion-proof structure needs to be added.
In this embodiment, as explained above, the high-voltage controller 20 monitors the positional relationship between the third arm 17 and the door 3, i.e., the opening/closing state of the door 3 by the door opening/closing apparatus 5 based on the discharge current detected through the electrode pin 22 and determines whether the opening/closing state is normal or abnormal. In the case where the opening/closing state of the door 3 is determined as normal, the door painting robot 4 and the door opening/closing apparatus 5 are operated in accordance with a previously set program to perform electrostatic painting on the door 3 as scheduled. In the case where the opening/closing state of the door 3 is determined as abnormal, the operations of the door painting robot 4 and the door opening/closing apparatus 5 have only to be immediately stopped to interrupt the electrostatic painting. As above, the electrostatic painting can be properly performed with respect to the door 3 while the opening/closing state of the door 3 is monitored.
In this embodiment, the opening/closing hook 18 is provided with the position sensor 31 to detect the position of the door 3. When the hook 18 is moved toward the door 3, accordingly, the position sensor 31 detects the position of the door 3. The hook 18 can be precisely aligned with the position of the door 3 based on detection of the door 3 by the position sensor 31.
As indicated by the chain double-dashed line in
In this embodiment, the position sensor 31 is placed in the opening/closing hook 18 and thus is protected from dust (stains). Since purge air is supplied into the opening/closing hook 18, the position sensor 31 can be further protected from dust (stains). In this embodiment, furthermore, since the position sensor 31 is an optical fiber sensor requiring no explosion-proof measure, no explosion-proof structure needs to be added. Consequently, the position sensor 31 can be placed in a smaller size in the opening/closing hook 18.
The present invention is not limited to the above embodiment and may be embodied in other specific forms without departing from the essential characteristics thereof.
(1) In the above embodiment, the door 3 to be opened/closed horizontally is considered as an opening/closing object. The door opening/closing apparatus 5 for opening and closing the door 3 is configured to detect discharge current through the electrode pin 22 provided in the third arm 17 to determine the opening/closing state of the door 3. Alternatively, the opening/closing object may be a trunk cover or a bonnet (hood) of a vehicle body or a flip-up rear door of a vehicle body, which are opened and closed in a vertical direction. Accordingly, an opening/closing apparatus for opening and closing the trunk cover, bonnet, or flip-up door is configured to detect discharge current through an electrode pin to determine the opening/closing state of the trunk cover or the like. For instance, as shown in
(2) In this embodiment, the door 3 is an opening/closing object. The door opening/closing apparatus 5 for opening and closing the door 3 is configured to detect the discharge current through the electrode pin 22 provided in the third arm 17 to determine the opening/closing state of the door 3. In addition, as shown in
(3) In the above embodiment, the opening/closing tool 13 and both the second arm 16 and the third arm 17 are applied with high voltage. An alternative is to apply high voltage only to the opening/closing tool 13 and the third arm 17.
(4) In the above embodiment, the opening/closing hook 18 is made of resin which is an insulating material. This opening/closing hook may be made of a conductive material with a resistor or a semi-conducting material. The conductive material with a resistor may include “resin containing carbon” and the semi-conducting material may include “polyurethane”. The resin which is an insulating material may be covered with fluorinated coating (e.g., “Teflon” (Registered Trademark)).
(5) In the above embodiment, the third arm 17 is provided with the electrode pin 22 and the wiring 23 as an example of the discharge current detecting means. An alternative is to omit the electrode pin 22 and provide only the wiring 23. In this case, the third arm 17 itself acts as a means for detecting discharge current between the third arm 17 and the door 3.
(6) The above embodiment is explained about the case of electrostatically painting an object to be painted, i.e., the vehicle body 2 provided with the door 3 as the opening/closing object. Any object to be painted other than a vehicle body may be adopted if only it includes an opening/closing object.
The present invention, as clearly from the above explanation, can provide an electrostatic painting apparatus for electrostatically painting an opening/closing object provided in an object to be painted by a painting means while opening and closing the opening/closing object by an opening/closing means, in which prediction of interference with the opening/closing object is enabled without adding a special explosion-proof structure. The present invention can also provides an electrostatic painting method for electrostatically painting an opening/closing object provided in an object to be painted by a painting means while opening and closing the opening/closing object by an opening/closing means, in which prediction of interference with the opening/closing object is enabled without adding a special explosion-proof structure.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2007-198731 | Jul 2007 | JP | national |
This is a 371 national phase application of PCT/JP2008/063085 filed 15 Jul. 2008, claiming priority to Japanese Patent Application No. 2007-198731 filed 31 Jul. 2007, the contents of which are incorporated herein by reference.
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/JP2008/063085 | 7/15/2008 | WO | 00 | 12/28/2009 |
