CLEANING METHOD AND CLEANING APPARATUS

Abstract

Provided is a cleaning method of reducing the power consumption. The cleaning method including: generating a jet of a cleaning liquid from a nozzle; moving the nozzle so that the jet collides with a target portion of a workpiece; acquiring a current position of the nozzle; determining whether the current position is within a target region corresponding to the target portion; ejecting the jet having an ejection pressure of a first pressure when the current position is within the target region; and ejecting the jet having the ejection pressure lower than the first pressure when the current position is other than the target region.

Claims

1. A cleaning method, comprising: generating a jet of a cleaning liquid from a nozzle using a positive displacement pump; moving the nozzle so that the jet collides with a plurality of target portions of a workpiece; acquiring a current position of the nozzle; acquiring, based on the current position, a remaining moving amount to a target position; determining whether the current position is within a target region corresponding to the target portion; ejecting the jet having an ejection pressure of a first pressure when the current position is within the target region; ejecting the jet having the ejection pressure of a second pressure that is lower than the first pressure when the current position is other than the target region, the second pressure being the ejection pressure configured to reach the first pressure within a predetermined period during which the nozzle moves between the two of the target portions among the plurality of the target portions; increasing the ejection pressure toward the first pressure when the remaining moving amount is within a first range from the target position; and lowering the ejection pressure toward the second pressure when the remaining moving amount is out of the first range.

2. The cleaning method according to claim 1, further comprising: acquiring, based on the current position, a moved amount of the nozzle from a start position; and lowering the ejection pressure toward the second pressure when the remaining moving amount is out of the first range and the remaining moving amount is out of a second range from the start position.

3. The cleaning method according to claim 1, further comprising: ejecting the jet at the first pressure from the nozzle when the nozzle moves along the target position at a constant speed.

4. The cleaning method according to claim 2, further comprising: ejecting the jet at the first pressure from the nozzle when the nozzle moves along the target position at a constant speed.

5. The cleaning method according to claim 2, further comprising: setting a target pressure to the first pressure when the remaining moving amount is within the first range, or when the remaining moving amount is out of the first range and the moved amount is within the second range, otherwise, setting the target pressure to the second pressure; wherein performing a feedback control of the ejection pressure so that a difference between the ejection pressure and the target pressure becomes zero.

6. The cleaning method according to claim 5, further comprising: starting the feedback control in response to an ejection start command; and stopping the feedback control in response to an ejection stop command to stop the rotation of the positive displacement pump or to set an idling rotation speed.

7. The cleaning method according to claim 6, further comprising setting the target pressure to the first pressure while the nozzle moves along the target position at a constant speed.

8. The cleaning method according to claim 1, wherein the second pressure is given by a function of the first pressure.

9. The cleaning method according to claim 1, wherein when the ejection pressure increases toward the first pressure, the ejection pressure is performed by proportional control when the ejection pressure is lower than a first threshold that is in the vicinity of the first pressure and lower than the first pressure, and the ejection pressure is performed by PI control when the ejection pressure exceeds the first threshold.

10. The cleaning method according to claim 1, wherein when the ejection pressure is lowered toward the second pressure, the ejection pressure is performed by proportional control when the ejection pressure is equal to or higher than a second threshold that is in the vicinity of the second pressure and larger than the second pressure, and the ejection pressure is performed by PI control when the ejection pressure is lower than the second threshold.

11. The cleaning method according to claim 4, further comprising: setting a target pressure to the first pressure when the remaining moving amount is within the first range, or when the remaining moving amount is out of the first range and the moved amount is within the second range, otherwise, setting the target pressure to the second pressure; wherein performing a feedback control of the ejection pressure so that a difference between the ejection pressure and the target pressure becomes zero.

12. The cleaning method according to claim 2, wherein the second pressure is given by a function of the first pressure.

13. The cleaning method according to claim 3, wherein the second pressure is given by a function of the first pressure.

14. The cleaning method according to claim 4, wherein the second pressure is given by a function of the first pressure.

15. The cleaning method according to claim 5, wherein the second pressure is given by a function of the first pressure.

16. The cleaning method according to claim 6, wherein the second pressure is given by a function of the first pressure.

17. The cleaning method according to claim 7, wherein the second pressure is given by a function of the first pressure.

18. A cleaning apparatus, comprising: a nozzle configured to eject a jet of a cleaning liquid; a moving device configured to relatively move the nozzle to a plurality of target portions of a workpiece; a positive displacement pump connected to the nozzle, the positive displacement pump configured to change a rotation speed; a pressure gauge configured to measure an ejection pressure of the positive displacement pump; a control device including a storage device configured to store a numerical control program, a first pressure, a second pressure lower than the first pressure, the second pressure being the ejection pressure configured to increase to the first pressure within a predetermined period during which the nozzle moves between the two of the target portions among the plurality of the target portions, and a first range, a numerical control unit configured to control the moving device based on the numerical control program, a pressurizing unit configured to set a target pressure to the first pressure when a remaining moving amount to a target position that is acquired based on a current position is within the first range, and configured to set the target pressure to the second pressure otherwise, and a feedback control unit configured to perform a feedback control of the rotation speed so that the difference between an ejection pressure of the nozzle and the target pressure becomes zero.

19. The cleaning apparatus according to claim 18, wherein the storage device stores a second range, and the pressurizing unit sets the target pressure to the first pressure when a moved amount of a nozzle from a starting position is within the second range.

20. The cleaning apparatus according to claim 18, wherein the numerical control program includes an ejection start command and an ejection stop command, the control device includes a depressurizing unit configured to stop a feedback control by the feedback control unit upon receipt of the ejection stop command, and the feedback control unit performs the feedback control upon receipt of the ejection start command.

Description

BRIEF DESCRIPTION OF DRAWINGS

[0059] FIG. 1 is a perspective view of a cleaning apparatus according to an embodiment with a part of the cleaning apparatus cutout.

[0060] FIG. 2 is a block diagram showing the cleaning apparatus of the embodiment.

[0061] FIG. 3 is a block diagram showing the feedback control of the embodiment.

[0062] FIG. 4 is a perspective view showing a cleaning state of the embodiment.

[0063] FIG. 5 is a graph showing an ejection pressure for a moving distance along a trajectory and a cleaning target portion during the cleaning in FIG. 4.

[0064] FIG. 6 is a flowchart showing the cleaning method of the embodiment.

DETAILED DESCRIPTION

[0065] As shown in FIG. 1, a cleaning apparatus 10 includes a pump 11, a moving device 14, a turret 15, a nozzle 16, and a control device 20. The cleaning apparatus 10 cleans a workpiece 19.

[0066] The pump 11 is, for example, a piston pump. The pump 11 is driven by a PM synchronous motor. The pump 11 draws up a cleaning liquid from the tank (not shown) to supply it to the nozzle 16.

[0067] The moving device 14 is, for example, a column traverse moving device. The moving device 14 includes the turret 15 at its distal end. The plurality of nozzles 16 may be installed on the turret 15. The turret 15 selects one nozzle 16 to be ejected among the plurality of nozzles 16, and rotate it to direct downward. Preferably, the downwardly directed nozzle 16 is rotatable about a rotation axis 17 extending in a vertical direction. The downwardly directed nozzle 16 is connected to the pump 11 to eject the cleaning liquid. For example, the moving device 14 freely moves the nozzle 16 in a lateral direction, a vertical direction, and a longitudinal direction.

[0068] As shown in FIG. 2, the control device 20 is, for example, a numerical control device programmed with G code. The control device 20 includes a storage device 35, and an arithmetic device 21.

[0069] The storage device 35 is, for example, a non-volatile memory. The storage device 35 stores a cleaning program 36, a first range 37, a second range 38, a first pressure p1, a second pressure p2, and PID control parameters 42. The storage device 35 may store a first threshold value (not shown), a second threshold (not shown), and an idling rotation speed r3. The first pressure p1 is higher than the second pressure p2. The second pressure p2 may be a pressure corresponding to the idling rotation speed of the pump 11.

[0070] The first threshold value is in the vicinity of the first pressure p1, and is less than the first pressure pl. The second threshold value is in the vicinity of the second pressure p2, and is higher than the second pressure p2.

[0071] The idling rotation speed r3 may be 0 min.sup.−1.

[0072] The cleaning program 36, which is a G-code program, includes a designation of the first pressure p1 as a macro variable. For example, M code includes the following code.

[0073] M21: Ejection start command

[0074] M22: Ejection stop command

[0075] M30: End of Block (End of Program)

[0076] The arithmetic device 21 includes a numerical control unit 23, and a pressure adjustment unit 25.

[0077] The arithmetic device 21 has a main memory. The numerical control unit 23 controls the moving device 14 based on the cleaning program 36 to move the nozzle 16. The numerical control unit 23 reads the current position from the moving device 14, and calculates a remaining moving amount from the current position to the target position, and the moved amount from the movement start position to the current position. The remaining moving amount and the moved amount are stored in the main memory.

[0078] Upon reading the ejection start command M21, the arithmetic device 21 stores in the main memory that the ejection is in progress. For example, the arithmetic device 21 substitutes “1” for an ejection parameter which is a binary variable. Upon reading the ejection stop command M22, the arithmetic device 21 deletes the memory that the ejection is in progress. For example, the arithmetic device 21 substitutes “0” for the ejection parameter. Upon reading the end of block M30, the arithmetic device 21 stops the program operation.

[0079] The pressure adjustment unit 25 includes a pressurizing unit 26, a depressurizing unit 27, and a feedback control unit 28.

[0080] Upon reading the ejection start command M21, the pressurizing unit 26 rotates the pump 11. The pressurizing unit 26 reads the remaining moving amount and the first range 37 for comparing. The pressurizing unit 26 reads the moved amount and the second range 38 for comparing. The target pressure p0 is set as a result of the comparison.

[0081] Upon reading the ejection stop command M22, the depressurizing unit 27 rotates the pump 11 at the idling rotation speed r3. At this time, the depressurizing unit 27 may stop the pump 11. Preferably, the depressurizing unit 27 stops the feedback control.

[0082] As shown in FIG. 3, the feedback control unit 28 includes a first rotation speed converting unit 28a, a PI control unit 28b, and a second rotation speed converting unit 28d. A control target 28c include the pump 11, the nozzle 16, the pipe 13, and a pressure gauge 12. The first rotation speed converting unit 28a and the second rotation speed converting unit 28d have the same structure. The transfer functions of the first and second rotation speed converting units 28a, 28d are given by a constant K, for example. The constant K is given, for example, as a function of the rotation speed and pressure of the pump 11. The transfer functions of the PI control unit 28b and the control target 28c are G1 and G2, respectively.

[0083] The first rotation speed converting unit 28a receives the target pressure p0, and output the target rotation speed r0. The PI control unit 28b receives a difference “e” between the target rotation speed r0 and the rotation speed r, and outputs an operation amount Kp. The sum of the operation amount Kp and the rotation speed r is input to the pump 11 as a rotation speed command value r1. The pump 11 is rotated according to the rotation speed command value r1. The nozzle 16 ejects the cleaning liquid. The pressure gauge 12 measures and outputs an ejection pressure p in the pipe 13. The second rotation speed converting unit 28d receives the ejection pressure p, and outputs the rotation speed r for feeds back.

[0084] When the ejection pressure p rises toward the first pressure p1, the feedback control unit 28 performs a proportional control of the ejection pressure p when the ejection pressure p is equal to or lower than the first threshold value. When the ejection pressure p exceeds the first threshold value, the feedback control unit 28 performs PI control of the ejection pressure p.

[0085] When the ejection pressure p decreases toward the second pressure p2, the feedback control unit 28 performs a proportional control of the pressure p when the ejection pressure p is equal to or higher than the second threshold value. When the ejection pressure p is lower than the second threshold value, the feedback control unit 28 performs PI control of the ejection pressure p.

[0086] The cleaning method will now be described with reference to FIGS. 4 to 6.

[0087] As shown in FIG. 4, the workpiece 19 has the target portions 19a, 19b, and 19c. The target portions 19a, 19b, and 19c are, for example, female screws. Note that the workpiece 19 may have any number of the target portions.

[0088] The numerical control unit 23 numerically controls the moving device 14 to move the nozzle 16 so that a jet 55 collides with the target portions 19a, 19b, and 19c. The nozzle 16, which is located at a position apart a nozzle offset distance 53 from an opening of the target portions 19a, 19b, and 19c one after another, moves along a trajectory 51 defined by the cleaning program 36. The jet 55 collides perpendicularly with the openings of the target portions 19a, 19b, and 19c to clean the target portions 19a, 19b, and 19c.

[0089] The positions of the nozzle 16 when the target portions 19a, 19b, and 19c are cleaned are set as target positions 51a, 51b, and 51c, respectively. Regions in the vicinity of the target positions 51a, 51b, and 51c are referred to as target regions 54a, 54b, and 54c, respectively. The target regions 54a, 54b, and 54c are defined by the size of the target portions 19a, 19b, and 19c. For example, when the target portions 19a, 19b, and 19c are M6 female threads, the target regions 54a, 54b, and 54c are closed regions that are spheres having a diameter of 6 mm having a center at the target positions 51a, 51b, and 51c. When the nozzle 16 is located in the target region 54a, 54b, and 54c by moving the nozzle 16, the ejection pressure p of the jet 55 is increased. The ejection pressure p is lowered at the middle position thereof.

[0090] FIG. 5 shows a graph 59 of the pressure with respect to the moving distance along the trajectory 51, and a plan view 57 of the workpiece 19 corresponding to the graph 59. In the plan view 57, the trajectory 51 is shown in a straight line. As shown in FIG. 5, the ejection pressure p varies momentarily depending on the position of the nozzle 16.

[0091] When the nozzle 16 is located within the target region 54a, the ejection pressure p becomes the first pressure p1. At this time, the jet 55 directly collides with the target portion 19a. When the nozzle 16 leaves the target region 54a, the ejection pressure p becomes lower than the first pressure p1. As the nozzle 16 approaches to the target region 54b, the ejection pressure p rises towards the first pressure p1. When the nozzle 16 is positioned within the target region 54b, the ejection pressure p becomes the first pressure p1. Thereafter, the ejection pressure p similarly fluctuates according to the position of the nozzle 16. As a result, when the jet 55 collides with the target portions 19a, 19b, and 19c, the ejection pressure p becomes the first pressure p1 to properly clean the target portions 19a, 19b, and 19c.

[0092] Specifically, while the numerical control unit 23 moves the nozzle 16, the pressure adjustment unit 25 controls the control target 28c in the background, based on the moved amount and the remaining moving amount calculated by the numerical control unit 23.

[0093] The numerical control unit 23 reads and executes the cleaning program 36 by each block. While the numerical control unit 23 executes the cleaning program 36, the pressurizing unit 26 always processes the operation shown in FIG. 6, in the background processing. During ejection, the feedback control unit 28 performs feedback control of the ejection pressure p at all times with the target pressure p0 as a target.

[0094] As shown in FIG. 6, in step S1, the pressure adjustment unit 25 acquires a value of the ejection parameter to determine whether or not the ejection is in progress. If yes, the process proceeds to step S2. If no, the process proceeds to step S10.

[0095] In step S2, the pressure adjustment unit 25 determines whether the moving block executed by the numerical control unit 23 is an interpolated movement. For example, it is no if rapid traverse, and yes if linear interpolation movement or circular interpolation movement. If yes, the process proceeds to step S7. If no, the process proceeds to step S3.

[0096] In step S3, the pressurizing unit 26 acquires the moved amount.

[0097] In step S4, the pressurizing unit 26 acquires the remaining moving amount. Step S4 may be performed simultaneously with step S3.

[0098] In step S5, the pressurizing unit 26 determines whether or not the remaining moving amount is within the first range 37. If yes, the process proceeds to step S7. If no, the process proceeds to step S6.

[0099] In step S6, the pressurizing unit 26 determines whether or not the moved amount is within the second range 38. If yes, the process proceeds to step S7. If no, the process proceeds to step S8.

[0100] In step S7, the first pressure p1 is substituted into the target pressure p0.

[0101] In step S8, the second pressure p2 is substituted into the target pressure p0.

[0102] In step S10, preferably, the depressurizing unit 27 rotates the pump 11 at the idling rotation speed r3. At this time, the feedback control unit 28 stops.

[0103] In step S9, the pressure adjustment unit 25 determines whether or not the program is completed. If yes, the process ends. If no, the process returns to step S1.

[0104] According to the cleaning method of the present embodiment, the ejection pressure p is increased when the jet 55 collides with the target portions 19a, 19b, and 19c, while the ejection pressure p is lowered when the jet 55 collides with other portion of the workpiece 19. As the pump 11 is a positive displacement pump, the driving power is reduced when the ejection pressure p is lowered. Lowering the ejection pressure p during the jet 55 does not collide with the target portions 19a, 19b, 19c allows to reduce the power consumption of the pump 11.

[0105] The jet of the first pressure collides with the target portion, while the jet of the pressure lower than the first pressure collides with the other portions. Thus, the surface is suppressed from being damaged even when the surface of the workpiece is easily damaged by the jet.

[0106] The present invention is not limited to the embodiments described above, and various modifications can be made without departing from the gist of the present invention, and all technical matters included in the technical idea described in the claims are the subject matter of the present invention. While the foregoing embodiments illustrate preferred examples, those skilled in the art will appreciate that various alternatives, modifications, variations, or improvements may be made in light of the teachings disclosed herein and are within the scope of the appended claims.

REFERENCE SIGNS LIST

[0107] 10 Cleaning apparatus [0108] 11 Pump (Positive displacement pump) [0109] 12 Pressure gauge [0110] 14 Moving device [0111] 16 Nozzle [0112] 19 Workpiece [0113] 19a, 19b, 19c Target portion [0114] p Ejection pressure [0115] p0 Target pressure [0116] p1 First pressure [0117] p2 Second pressure [0118] r Rotation speed