A method for washing and drying workpieces using a one-bath sealed vacuum washer / dryer

Abstract

To make it possible to virtually null solvent vapor loss in a one-bath type hermetic type vacuum cleaning drier that uses fluorine-based solvent as a washing agent to wash and dry a work-piece in a state that it is tightly sealed from an atmosphere side.SOLUTION: During vacuum drying of a work-piece in a vacuum drying washing machine 1, exhaust air from a vacuum dry pump 5 that vacuums a vacuum cleaning drying tank 4 is collected in a pressure absorption tank 8 via a solvent steam collection tank 7, the collected exhaust air is returned to the vacuum cleaning drying tank 4 that is vacuumed and decompressed after the work-piece is charged in the following operation cycle, and the tank internal pressure is put into a decompressed state at the same level as the vacuum cleaning drying tank 4. Internal volume and the like of the pressure absorption tank 8 are set so that the tank internal pressure after exhaust air is collected does not reach an atmospheric pressure or more. The solvent vapor loss can be reduced as much as possible.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a workpiece washing and drying method using a one-bath sealed vacuum washer-dryer that washes and dries workpieces using a fluorine-based solvent as a cleaning agent in a state sealed from the atmosphere, and more specifically to a completely sealed workpiece washing and drying method that reduces solvent evaporation loss to substantially zero. [Background technology]

[0002] Cleaning equipment that uses fluorine-based solvents as cleaning agents to clean various electronic components and the like is known; for example, the applicant manufactures and sells a single-bath vacuum cleaning machine (product name: FLOVA) (Non-Patent Document 1). This single-bath vacuum cleaning machine fully automatically performs rough ultrasonic cleaning, finish ultrasonic cleaning, steam cleaning, and vacuum drying of workpieces, all of which are performed in a conventional three-bath cleaning machine, while adding and removing the solvent in a single bath. All processes from cleaning to drying are performed in the same sealed cleaning tank, and even when the cleaning tank is opened to load or unload workpieces, the fluorine-based solvent is not exposed to the atmosphere, significantly reducing solvent vapor loss. [Prior art documents] [Non-patent literature]

[0003] [Non-Patent Document 1] "Fluorine-based one-bath vacuum cleaner FLOVA", [online], Clinbee Co., Ltd., [Retrieved October 12, 1992], Internet,<URL:https: / / www.cleanvy.co.jp / businesses / businesses-363 / > Summary of the Invention [Problem to be solved by the invention]

[0004] In such a closed-type, single-bath vacuum washer / dryer, it is necessary to further reduce the loss of solvent vapor that escapes to the outside of the machine. To achieve this, it is important to maintain the internal pressure of the machine's piping system, including the vacuum washer / dryer tank that is isolated from the atmosphere, at a level below atmospheric pressure to prevent solvent vapor from escaping to the atmosphere.

[0005] In view of this, an object of the present invention is to provide a method for washing and drying workpieces using a one-bath sealed vacuum washer-dryer that uses a fluorine-based solvent to wash and dry workpieces in a state sealed from the atmosphere, in which loss of solvent flowing into the atmosphere can be reduced to substantially zero. [Means for solving the problem]

[0006] In order to solve the above problems, the present invention provides a workpiece washing and drying method using a one-bath type sealed vacuum washer-dryer that uses a fluorine-based solvent as a cleaning agent to wash and dry workpieces, comprising the steps of: The sealed vacuum cleaning and drying machine is a storage tank that stores the cleaning agent; a steam generator that generates steam of the cleaning agent; a vacuum cleaning and drying tank for immersion cleaning of the workpiece using the cleaning agent supplied from the storage tank, steam cleaning of the workpiece using vapor of the cleaning agent supplied from the steam generator, and vacuum drying of the cleaned workpiece; a vacuum dry pump that draws a vacuum from the vacuum cleaning and drying tank; a cleaning agent circulation means for returning the cleaning agent from the vacuum cleaning and drying tank to the storage tank; a distillation / regeneration unit for distilling and regenerating the cleaning agent; a pressure absorption tank; It is equipped with Before supplying the cleaning agent to the vacuum cleaning and drying tank, The vacuum dry pump is used to evacuate the vacuum cleaning and drying tank into which the workpieces have been placed and sealed until the internal pressure of the tank reaches a predetermined vacuum level from atmospheric pressure, and the exhaust gas from the vacuum dry pump is released into the atmosphere. the pressure absorption tank is connected to the vacuum cleaning and drying tank after evacuation, and the vacuum cleaning and drying tank and the pressure absorption tank are brought into a reduced pressure state with a vacuum level lower than the vacuum level; In this reduced pressure state Close the pressure absorption tank; during the vacuum drying, which is performed by evacuating the vacuum cleaning and drying tank with the vacuum dry pump, the pressure absorption tank is opened, and the exhaust gas discharged from the vacuum cleaning and drying tank is collected in the pressure absorption tank without being released into the atmosphere; After the vacuum drying, the vacuum cleaning and drying tank is opened to the atmosphere to return to atmospheric pressure. The internal volume of the pressure absorption tank and the degree of vacuum are set so that the internal pressure of the pressure absorption tank after the exhaust gas recovery is maintained in a reduced pressure state below atmospheric pressure.

[0007] In this invention, a pressure absorption tank with a fixed internal volume is attached to the in-machine cleaning agent distribution system, and exhaust gas discharged from the vacuum cleaning and drying tank during vacuum drying of workpieces is recovered in the pressure absorption tank. In the next workpiece cleaning and drying cycle, the recovered exhaust gas is returned to the vacuum cleaning and drying tank, which has been evacuated to a predetermined vacuum level after the workpieces are loaded, thereby maintaining the tank's internal pressure at a reduced pressure equivalent to that of the vacuum cleaning and drying tank. Furthermore, the internal volume and the vacuum level of the vacuum cleaning and drying tank, evacuated after the workpieces are loaded, are set so that the tank's internal pressure after exhaust gas recovery does not exceed atmospheric pressure. This ensures that exhaust gas is released from the machine to the atmosphere only when the vacuum cleaning and drying tank is opened to the atmosphere to remove the cleaned and dried workpieces and load new workpieces to be cleaned, minimizing solvent vapor loss. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a schematic diagram showing the configuration of the main parts of a single-bath sealed vacuum washer / dryer to which the present invention is applied. [Figure 2] 2 is an explanatory diagram showing the operation procedure of the closed-type vacuum washer / dryer of FIG. 1 and pressure changes at various parts inside the machine. FIG. DETAILED DESCRIPTION OF THE INVENTION

[0009] Below, with reference to the drawings, we will explain a one-bath type sealed vacuum washer-dryer that cleans and dries workpieces using a fluorine-based solvent to which the method of the present invention is applied, and the workpiece cleaning and drying operation of this sealed vacuum washer-dryer.

[0010] The configuration of a single-bath, closed-type vacuum washer-dryer will be described with reference to Figure 1. The closed-type vacuum washer-dryer 1 includes a vacuum buffer tank 2, which is a storage tank for a fluorinated solvent (hereinafter simply referred to as "solvent") used as a cleaning agent; a distillation / regeneration / steam generator 3, which generates solvent vapor and distills the solvent back into the tank; a vacuum washer-drying tank 4, which performs immersion cleaning using the solvent and vapor cleaning using the solvent vapor on workpieces and then vacuum-dries the cleaned workpieces; a vacuum dry pump 5, which draws a vacuum inside the vacuum washer-drying tank 4; a solvent reflux means 6, which returns the solvent from the vacuum washer-drying tank 4 to the vacuum buffer tank 2; a solvent vapor recovery tank 7, which recovers the solvent vapor; and a pressure absorption tank 8, which is attached to maintain the internal pressure of each component of the machine at a level below atmospheric pressure. Also included is a controller (not shown) that controls the operation of each of these components and executes the cleaning / drying operation of the workpieces according to a preset procedure (see Figure 2).

[0011] The vacuum buffer tank 2, which serves as a solvent storage tank, contains a finishing solvent tank 21 for storing the solvent for finishing cleaning and a crude solvent tank 22 for storing the solvent for rough cleaning. The solvent from the finishing solvent tank 21 overflows into the adjacent crude solvent tank 22. The distillation regeneration / steam generator 3 is housed inside a vertically-mounted cylindrical vessel 31. The bottom side of the vessel is a solvent storage section 33 equipped with a heater 32, the upper side of the storage section is a solvent vapor generation section 34, and the upper end is a solvent condensation section 36 equipped with a cooling coil 35 for condensing the solvent vapor. The generated solvent vapor is supplied to the vacuum cleaning / drying tank 4, and the solvent condensate obtained in the solvent condensation section 36 is collected in the finishing solvent tank 21 of the vacuum buffer tank 2 via a heat exchanger 9 and a water separator 10.

[0012] The vacuum cleaning and drying tank 4 is located below the vacuum buffer tank 2 and has an openable lid 41 attached to its top end. The openable lid 41 can be opened to load and unload a basket 42 containing the workpieces to be cleaned (not shown). An ultrasonic generator 43 is located at the bottom of the interior of the vacuum cleaning and drying tank 4. Solvent is supplied to the vacuum cleaning and drying tank 4 from the finishing solvent tank 21 and crude solvent tank 22 of the vacuum buffer tank 2. After the workpieces have been cleaned in the vacuum cleaning and drying tank 4, the solvent is returned to the vacuum buffer tank 2 by the solvent circulation means 6. The solvent circulation means 6 returns the crude solvent supplied to the vacuum cleaning and drying tank 4 to the crude solvent tank 22 via the crude solvent buffer tank 61, crude solvent pump 62, and crude solvent filter 63, and returns the finishing solvent supplied to the vacuum cleaning and drying tank 4 to the finishing solvent tank 21 via the finishing solvent buffer tank 64, finish solvent pump 65, and finish solvent filter 66.

[0013] The vacuum dry pump 5 has an intake port 51 that can communicate with the vacuum cleaning and drying tank 4 via a valve. The vacuum dry pump 5 has an outlet port 52 that can communicate with the atmosphere and the distillation regeneration / steam generator 3 via valves, respectively.

[0014] A cooling coil 71 is disposed inside the solvent vapor recovery tank 7. An exhaust inlet 72 of the solvent vapor recovery tank 7 communicates with the solvent vapor generating section 34 of the distillation regeneration / steam generator 3, and an exhaust outlet 73 thereof can communicate with the pressure absorption tank 8 via a valve. The pressure absorption tank 8 can communicate with the vacuum cleaning / drying tank 4 via a valve.

[0015] Figure 2 is an explanatory diagram showing the workpiece washing and drying operation of the sealed vacuum washer / dryer 1 and the pressure changes in various parts of the machine. The workpiece washing and drying operation will be explained using this diagram. The operating cycle in the vacuum washer / dryer tank 4 includes the following steps: loading the workpiece, vacuuming, supplying crude solvent, crude vacuum ultrasonic immersion cleaning (rough cleaning), draining the crude solvent, supplying finishing solvent, finish vacuum ultrasonic immersion cleaning (finish cleaning), draining the finishing solvent, reduced pressure steam cleaning, draining the liquid, vacuum drying, and releasing the vacuum and removing the workpiece.

[0016] In the workpiece loading process, a basket 42 containing the workpieces to be cleaned is loaded into the vacuum cleaning and drying tank 4, which is open to the atmosphere. In the subsequent evacuation process, the vacuum cleaning and drying tank 4, which has been sealed after the workpieces have been loaded, is evacuated by the vacuum dry pump 5, creating a reduced pressure state of a first vacuum level, for example, 5 kPa (times T1 to T2). After this (time T2), the vacuum cleaning and drying tank 4 is connected to the pressure absorption tank 8, and negative pressure is supplied from the vacuum cleaning and drying tank 4 to the pressure absorption tank 8, creating a reduced pressure state of a second vacuum level lower than the first vacuum level, for example, 50 kPa, and the two are isolated from each other. In other words, the exhaust gas collected in the pressure absorption tank 8 during the previous operation cycle is returned to the vacuum cleaning and drying tank 4. After this, the pressure absorption tank 8 remains sealed until the start of the vacuum drying process (time T10).

[0017] In the crude solvent supply process following the evacuation process, the crude solvent stored in the crude solvent tank 22 is supplied to the vacuum cleaning and drying tank 4 by utilizing the pressure and elevation difference between the vacuum cleaning and drying tank 4, which is at a second vacuum level, and the vacuum buffer tank 2, which is at an internal pressure slightly lower than atmospheric pressure, e.g., 100 kPa (times T2 to T3). With the exception of the closed pressure absorption tank 8, all components, including the vacuum cleaning and drying tank 4 and the vacuum buffer tank 2, are at the same reduced pressure, e.g., 80 kPa. In this state, the ultrasonic generator 43 is driven to perform the crude vacuum ultrasonic immersion cleaning process (times T3 to T4). In the subsequent crude solvent drainage process, the crude solvent pump 62 of the solvent reflux means 6 is driven to return the crude solvent from the vacuum cleaning and drying tank 4 to the crude solvent tank 22 in the vacuum buffer tank 2 (times T4 to T5).

[0018] Similarly, in the next finishing solvent supply step, the vacuum dry pump 5 is driven to evacuate the vacuum cleaning and drying tank 4, returning it to a reduced pressure state of the second vacuum level. The exhaust gas from the vacuum dry pump 5 is sent to the distillation regeneration / steam generator 3 and, via this, to the vacuum buffer tank 2, creating a pressure difference between the vacuum cleaning and drying tank 4 and the vacuum buffer tank 2, supplying the finishing solvent from the finishing solvent tank 21 to the vacuum cleaning and drying tank 4 (times T5-T6). In this state, the ultrasonic generator 43 is driven to perform the finishing vacuum ultrasonic immersion cleaning step (times T6-T7). In the subsequent finishing solvent drainage step, the finishing solvent pump 65 of the solvent reflux means 6 is driven to return the finishing solvent from the vacuum cleaning and drying tank 4 to the finishing solvent tank 21 in the vacuum buffer tank 2 (times T7-T8).

[0019] In the next reduced-pressure vapor cleaning process, the vacuum dry pump 5 is driven intermittently to reduce the pressure in the vacuum cleaning and drying tank 4, and the solvent vapor generated in the distillation regeneration / steam generator 3 is supplied to the vacuum cleaning and drying tank 4 to clean the workpieces with reduced-pressure vapor (times T8 to T9). The exhaust gas from the vacuum dry pump 5 is discharged into the distillation regeneration / steam generator 3. The internal pressure of the vacuum cleaning and drying tank 4, vacuum buffer tank 2, etc. rises to, for example, 80 kPa to 90 kPa. In the vacuum cleaning and drying tank 4, the solvent vapor condenses on the workpieces and accumulates at the bottom. In the next liquid removal process, the finishing solvent pump 65 is driven to recover the condensed solvent vapor accumulated in the vacuum cleaning and drying tank 4 into the finishing solvent tank 21 of the vacuum buffer tank 2 (times T9 to T10).

[0020] In the next vacuum drying process, the vacuum cleaning and drying tank 4 is connected to the pressure absorption tank 8 via the vacuum dry pump 5, distillation regeneration / steam generator 3, and solvent vapor recovery tank 7. The vacuum dry pump 5 is driven to evacuate the vacuum cleaning and drying tank 4, and the workpieces are vacuum-dried (times T10 to T11). The exhaust gas from the vacuum dry pump 5 is recovered in the pressure absorption tank 8 via the distillation regeneration / steam generator 3 and solvent vapor recovery tank 7. The solvent vapor contained in the exhaust gas is condensed by the cooling coil 35 in the solvent condenser 36 of the distillation regeneration / steam generator 3 and recovered in the finishing solvent tank 21 of the vacuum buffer tank 2. In addition, the remaining solvent vapor contained in the exhaust gas that passed through the distillation regeneration / steam generator 3 and flowed into the solvent vapor recovery tank 7 is recovered in the solvent vapor recovery tank 7, and the exhaust gas from which the solvent vapor has been removed is recovered in the pressure absorption tank 8. By collecting exhaust gas, the pressure absorption tank 8 changes from a reduced pressure state of the second vacuum degree to a reduced pressure state close to atmospheric pressure, but the internal volume, first vacuum degree, etc. are set so that the pressure does not exceed atmospheric pressure.

[0021] In the vacuum release and workpiece removal process after vacuum drying, the vacuum cleaning and drying tank 4 is isolated from other parts and opened to the atmosphere to return to atmospheric pressure (time T11). After this, the vacuum cleaning and drying tank 4 is opened and the workpieces are removed. The internal pressure of parts other than the vacuum cleaning and drying tank 4 is maintained at a reduced pressure slightly lower than atmospheric pressure.

[0022] (Other embodiments) In the above-described vacuum washer / dryer 1, the solvent vapor recovery tank 7 and the pressure absorption tank 8 are arranged separately and connected by piping. It is also possible to combine these into one and arrange a pressure absorption tank with a solvent vapor recovery function and a size that can ensure the required internal volume. [Explanation of symbols]

[0023] 1 Vacuum washer / dryer 2 Vacuum buffer tanks 3 Distillation and regeneration steam generator 4. Vacuum cleaning and drying tank 5. Vacuum dry pump 6 Solvent reflux means 7 Solvent Vapor Recovery Tank 8. Pressure absorption tank 9 Heat exchanger 10 Moisture separator 21 Finishing solvent tank 22 Crude solvent tank 31 Cylindrical container 32 Heater 33 Solvent reservoir 34 Solvent vapor generating section 35 Cooling coil 36 Solvent condensation section 41 Opening and closing lid 42 Basket 43 Ultrasonic Generator 51 Intake port 52 Discharge port 61 Crude solvent buffer tank 62 Crude solvent pump 63 Crude Solvent Filter 64 Finishing solvent buffer tank 65 Finishing Solvent Pump 66 Finishing solvent filter 71 Cooling coil 72 Exhaust inlet 73 Exhaust outlet

Claims

1. A workpiece washing and drying method using a one-bath sealed vacuum washer-dryer that uses a fluorine-based solvent as a cleaning agent to wash and dry workpieces in a state sealed from the atmosphere, comprising: The sealed vacuum cleaning and drying machine is a storage tank that stores the cleaning agent; a steam generator that generates steam of the cleaning agent; a vacuum cleaning and drying tank for immersion cleaning of the workpiece using the cleaning agent supplied from the storage tank, steam cleaning of the workpiece using vapor of the cleaning agent supplied from the steam generator, and vacuum drying of the cleaned workpiece; a vacuum dry pump that draws a vacuum from the vacuum cleaning and drying tank; a cleaning agent circulation means for returning the cleaning agent supplied to the vacuum cleaning and drying tank to the storage tank; a distillation / regeneration unit for distilling and regenerating the cleaning agent; a pressure absorption tank; It is equipped with Before supplying the cleaning agent to the vacuum cleaning and drying tank, the vacuum dry pump is used to evacuate the vacuum cleaning and drying tank in which the workpieces have been placed and sealed until the internal pressure reaches a predetermined vacuum level from atmospheric pressure, and the exhaust gas from the vacuum dry pump is released to the atmosphere. the pressure absorption tank is connected to the vacuum cleaning and drying tank after evacuation, the vacuum cleaning and drying tank and the pressure absorption tank are brought into a reduced pressure state with a vacuum level lower than the above-mentioned vacuum level, and the pressure absorption tank is closed in this reduced pressure state; during the vacuum drying, which is performed by evacuating the vacuum cleaning and drying tank with the vacuum dry pump, the pressure absorption tank is opened, and the exhaust gas discharged from the vacuum cleaning and drying tank is collected in the pressure absorption tank without being released into the atmosphere; After the vacuum drying, the vacuum cleaning and drying tank is opened to the atmosphere to return to atmospheric pressure. a pressure absorption tank having a volume and a degree of vacuum set so that the internal pressure of the pressure absorption tank after collecting the exhaust gas is maintained at a reduced pressure below atmospheric pressure;

2. A one-bath sealed vacuum washer / dryer that uses a fluorine-based solvent as a cleaning agent to clean and dry workpieces in a sealed state from the atmosphere side, a storage tank that stores the cleaning agent; a steam generator that generates steam of the cleaning agent; a vacuum cleaning and drying tank for immersion cleaning of the workpiece using the cleaning agent supplied from the storage tank, steam cleaning of the workpiece using vapor of the cleaning agent supplied from the steam generator, and vacuum drying of the cleaned workpiece; a vacuum dry pump that draws a vacuum from the vacuum cleaning and drying tank; a cleaning agent circulation means for returning the cleaning agent supplied to the vacuum cleaning and drying tank to the storage tank; a distillation / regeneration unit for distilling and regenerating the cleaning agent; a pressure absorption tank; a control device for controlling the driving of each of the above-mentioned parts; It is equipped with The control device a control operation function of using the vacuum dry pump to evacuate the vacuum cleaning and drying tank, in which the workpieces have been placed and sealed, until the internal pressure reaches a predetermined vacuum level from atmospheric pressure, and then releasing the exhaust gas from the vacuum dry pump into the atmosphere before supplying the cleaning agent to the vacuum cleaning and drying tank; a control operation function of communicating the pressure absorption tank with the vacuum cleaning and drying tank after evacuation, bringing the vacuum cleaning and drying tank and the pressure absorption tank into a reduced pressure state with a vacuum level lower than the above-mentioned vacuum level, and closing the pressure absorption tank in this reduced pressure state; a control operation function of opening the pressure absorption tank and recovering the exhaust gas discharged from the vacuum cleaning and drying tank into the pressure absorption tank without releasing it into the atmosphere during the vacuum drying, which is performed by evacuating the vacuum cleaning and drying tank with the vacuum dry pump; a control operation function of opening the vacuum cleaning and drying tank to the atmosphere and returning it to an atmospheric pressure state after the vacuum drying; It is equipped with a single-bath sealed vacuum washer-dryer, characterized in that the internal volume of the pressure absorption tank and the degree of vacuum are set so that the internal pressure of the pressure absorption tank after collecting the exhaust gas is maintained at a reduced pressure below atmospheric pressure.

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