JP5101141B2 - Vacuum drying method and vacuum drying apparatus - Google Patents

Description

  The present invention relates to a vacuum drying technique suitable for drying mechanical parts.

  Machine parts are cleaned before painting and surface treatment. That is, dust, oil, iron powder, etc. attached to machine parts are removed by washing. In the old days, a solvent was used for the cleaning liquid, but nowadays, water or a water-based cleaning agent is used for the cleaning liquid because of the treatment of the waste liquid. The water-based cleaning agent is obtained by adding a surfactant or a solvent to water, and is mostly water. Hereinafter, water or an aqueous cleaning agent will be referred to as cleaning water.

  After cleaning, most of the cleaning water drops off from the workpiece, but a part remains in the form of adhering water. It is necessary to remove adhering water by the next step. Residual water is generally removed by a drying method. Natural drying, hot air drying, and vacuum drying are known as drying methods.

In particular, vacuum drying is advantageous in terms of thermal energy because it is not necessary to warm the workpiece to a high temperature, and heat distortion of the workpiece can be avoided. In recent years, attention has been focused on (see, for example, Patent Document 1). .
JP 2002-115966 A (page 3)

  In paragraph Nos. [0018] to [0019] of the third page of Patent Document 1, “(depressurized state)... Approximately, the boiling point of water rapidly decreases. The surface of the workpiece 24 is instantly dried by bumping and vaporizing ....... (work removal) When the drying process is completed, the decompression device 16 is stopped, the energization to the heater 20 is stopped, and the valves V1 to V1 are stopped. There is a description that “V5 is closed.

  In this description, it is not possible to specify the time point when the drying process is completed. That is, in the conventional vacuum drying method, the drying time is determined based on experiment and experience, and when this drying time is finished, it is recognized that the drying is finished. Since we don't want to produce poor drying, the actual drying time is 1.5 to several times longer than the time actually required.

  In this case, drying time becomes a bottleneck and productivity cannot be improved. Therefore, a technique capable of quantitatively grasping the truly necessary drying time is desired.

  An object of the present invention is to provide a technique capable of quantitatively grasping a truly necessary drying time.

The invention according to claim 1 is a vacuum drying method in which a work to which a part of cleaning water is attached is placed in a sealed container equipped with a vacuum pump, a vacuum gauge, and a heater, and the attached water is dried under reduced pressure. And
From the gas equation of state, the inner volume of the sealed container, the temperature in the sealed container kept constant by the heater, the molecular weight of water and the gas constant of moisture, the amount of water attached to the workpiece and the partial pressure of moisture Deriving a first equation in which the relationship of
A dry work model is placed in the sealed container, the sealed container is depressurized while maintaining a predetermined temperature with the heater, and the degree of vacuum when the degree of vacuum measured by the vacuum gauge becomes constant is set to a first pressure. And a process of
Adding the first pressure to the first equation to form a second equation;
In the workpiece, setting a permissible amount of adhering water;
A step of setting a pressure obtained from the allowable amount of adhering water and the second equation as a second pressure;
Put a work with water on it in the sealed container, depressurize the sealed container while maintaining a predetermined temperature with the heater, measure the degree of vacuum with the vacuum gauge when a predetermined time has elapsed from the start of decompression, A step of setting the degree to a third pressure;
Determining whether the third pressure is acceptable or not using the second pressure as a criterion;
It is characterized by comprising.

According to claim 2, the acceptability determining step, a repair possibility step of determining whether restoration directed to the work that is non if rated in the same step can, the work when it is determined that Y in this step A repairing process for repairing and a regeneration process for melting the workpiece when it is determined to be negative in the repairing / unstoring process are added.

  According to a third aspect of the present invention, the work is a torque converter case or a transmission case of an internal combustion engine transmission.

In claim 4, a vacuum drying apparatus that puts a work on which a part of the cleaning water adheres to a sealed container, and dries the adhered water under reduced pressure.
The vacuum dryer is a sealed container that contains the workpiece, a vacuum pump that depressurizes the inside of the sealed container, a heater that heats the inside of the sealed container, a thermometer that measures the temperature inside the sealed container, and a thermometer that uses this thermometer. The temperature controller that controls the output of the heater so that the measured temperature becomes a constant temperature, a vacuum gauge that measures the pressure inside the sealed container, and the degree of vacuum measured by this vacuum gauge are read, and based on this degree of vacuum Ri Do and a calculation and control unit for determining the drying of said workpiece,
In the calculation / control unit,
From the gas equation of state, the inner volume of the sealed container, the temperature in the sealed container kept constant by the heater, the molecular weight of water and the gas constant of moisture, the amount of water attached to the workpiece and the partial pressure of moisture Deriving a first equation in which the relationship of
A dry work model is placed in the sealed container, the sealed container is depressurized while maintaining a predetermined temperature with the heater, and the degree of vacuum when the degree of vacuum measured by the vacuum gauge becomes constant is set to a first pressure. And a process of
Adding the first pressure to the first equation to form a second equation;
In the workpiece, setting a permissible amount of adhering water;
The second pressure is set through a process group consisting of a step of setting the amount of the adhering adhering water and the pressure obtained from the second formula as the second pressure,
Such a calculation / control unit
Put a work with water on it in the sealed container, depressurize the sealed container while maintaining a predetermined temperature with the heater, measure the degree of vacuum with the vacuum gauge when a predetermined time has elapsed from the start of decompression, A step of setting the degree to a third pressure;
As a criterion the second pressure, through said third acceptance determining process pressure, a process group consisting of, have a function of determining acceptability of dry characterized Rukoto.

In the invention according to claim 1, the degree of vacuum (third pressure) is measured at the time of drying under reduced pressure, and if this pressure is higher than the judgment reference pressure (second pressure), the drying is successfully finished. judge.
The second pressure as the determination reference pressure is determined in advance from the performance of the sealed container and the vacuum pump and the allowable amount of adhering water. Therefore, the judgment reference pressure has a good correlation with the truly necessary drying time.

  Therefore, according to the present invention, the truly necessary drying time can be quantitatively grasped, and since the determination is made based on such a determination reference pressure, it is not necessary to extend the drying time. As a result, the wet workpiece can be efficiently dried.

According to the second aspect of the present invention, the step of determining whether or not the product is acceptable includes a repairability determining step, a repairing step of repairing the workpiece when it is determined to be acceptable in this step, and a regeneration step.
The work turned to the repairing process is repaired, and a pass / fail determination is made again through the process group according to claim 1.
The work turned to the regenerating process is melted, formed and regenerated into a new work.

  That is, it is a common case that a defect occurs in relation to a complicated shape portion of a workpiece formed into a specific shape. For workpieces that have been judged to be insufficiently dried, there may be burrows due to poor molding. If the work determined to be insufficiently dried can be repaired by visual confirmation, the work is repaired and washed again in the repairing process, and the reduced-pressure drying method according to claim 1 is performed.

For work that has been judged to be insufficiently dried, if the cause of inadequate drying by visual confirmation, for example, if it is found that there is a burrow, repair is impossible or the cause of insufficient drying cannot be identified After passing through the process etc., the reduced-pressure drying method of Claim 1 is implemented.
By having the process of Claim 2, it is a very important process which manufactures a corresponding | compatible workpiece | work very efficiently and also reduces the discard of material from an ecological viewpoint.

According to a third aspect of the present invention, the work is a torque converter case or a transmission case of an internal combustion engine transmission.
In particular, the torque converter case or the transmission case of the internal combustion engine transmission has a complicated structure, and the ribs of the corresponding metal are intricately erected on the metal plate. It is a difficult task even for the elderly.
Claim 3 in which the operator does not need to carry out visual drying confirmation is an excellent method by which anyone can carry out the process.

In claim 4, a vacuum drying apparatus that puts a work on which a part of the cleaning water adheres to a sealed container, and dries the adhered water under reduced pressure.
The vacuum dryer is a sealed container that contains the workpiece, a vacuum pump that depressurizes the inside of the sealed container, a heater that heats the inside of the sealed container, a thermometer that measures the temperature inside the sealed container, and a thermometer that uses this thermometer. The temperature controller that controls the output of the heater so that the measured temperature becomes a constant temperature, a vacuum gauge that measures the pressure inside the sealed container, and the degree of vacuum measured by this vacuum gauge are read, and based on this degree of vacuum Ri Do and a calculation and control unit for determining the drying of said workpiece,
In the calculation / control unit,
From the gas equation of state, the inner volume of the sealed container, the temperature in the sealed container kept constant by the heater, the molecular weight of water and the gas constant of moisture, the amount of water attached to the workpiece and the partial pressure of moisture Deriving a first equation in which the relationship of
A dry work model is placed in the sealed container, the sealed container is depressurized while maintaining a predetermined temperature with the heater, and the degree of vacuum when the degree of vacuum measured by the vacuum gauge becomes constant is set to a first pressure. And a process of
Adding the first pressure to the first equation to form a second equation;
In the workpiece, setting a permissible amount of adhering water;
The second pressure is set through a process group consisting of a step of setting the amount of the adhering adhering water and the pressure obtained from the second formula as the second pressure,
Such a calculation / control unit
Put a work with water on it in the sealed container, depressurize the sealed container while maintaining a predetermined temperature with the heater, measure the degree of vacuum with the vacuum gauge when a predetermined time has elapsed from the start of decompression, A step of setting the degree to a third pressure;
As a criterion the second pressure, through said third acceptance determining process pressure, a process group consisting of, have a function of determining acceptability of dry characterized Rukoto.

Conventionally, since the drying state has been carried out by visual confirmation , individual differences among workers are likely to occur, and work efficiency has been reduced due to excessive drying time.
In this regard, in the present invention, the dry state is determined by the degree of vacuum. Therefore, there is no worry that individual differences among workers occur, the drying time can be optimized, and work efficiency can be improved.

The calculation / control unit measures the degree of vacuum (third pressure) at the time of drying under reduced pressure, and determines that drying has been successfully completed if this pressure is higher than the judgment reference pressure (second pressure). To do.
The second pressure as the determination reference pressure is determined in advance from the performance of the sealed container and the vacuum pump and the allowable amount of adhering water. Therefore, the judgment reference pressure has a good correlation with the truly necessary drying time.

  Therefore, according to the present invention, the truly necessary drying time can be quantitatively grasped, and since the determination is made based on such a determination reference pressure, it is not necessary to extend the drying time. As a result, the wet workpiece can be efficiently dried.

The best mode for carrying out the present invention will be described below with reference to the accompanying drawings. The drawings are viewed in the direction of the reference numerals.
FIG. 1 is a principle view of a vacuum drying apparatus according to the present invention. A vacuum drying apparatus 10 includes a sealed container 12 having a lid 11 and a work such as a torque converter case or a mission case provided in the sealed container 12. 13, a work stand 14 that supports 13, a drain pipe 15 that drains water from the bottom of the sealed container 12, a vacuum pump 16 that depressurizes the inside of the sealed container 12, a heater 17 that warms the inside of the sealed container 12, and the inside of the sealed container 12. A thermometer 18 that measures the temperature of the heater 17, a temperature controller 19 that controls the output of the heater 17 so that the temperature measured by the thermometer 18 becomes a constant temperature (for example, 50 ° C.), and the pressure inside the sealed container 12. A vacuum gauge 21 to be measured and the degree of vacuum measured by the vacuum gauge 21 are read, and the vacuum pump 16 is operated based on a predetermined time set by a setting device 22 such as a keyboard. An arithmetic and control unit 23 during performing a series of operations described below a vacuum pump 16 with stop after a lapse of a display unit 24 for displaying the result of the drying, made of.

Next, the vacuum drying method of the present invention will be described.
As is well known, the equation of state of gas is given by the following equation.

(1) A numerical value is put into M, R, T, and V in the equation to obtain a relational expression between the partial pressure p of water and the mass w of water. The relational expression (“first expression”) is shown below.

Next, the first pressure is obtained by the following procedure using the vacuum drying apparatus 10 shown in FIG.
The work 13 is sun-dried in advance and sufficiently dried. This dried product is called a work model 26. The work model 26 is placed in the hermetic container 12, the hermetic container 12 is depressurized while being kept at a predetermined temperature (50 ° C.) by the heater 17, and the degree of vacuum is continuously measured by the vacuum gauge 21. The inner volume of the sealed container 12 is 325.2 liters, and the exhaust speed of the vacuum pump 16 is 6,410 liters per minute.

FIG. 2 is a decompression graph obtained with a work model, in which the horizontal axis indicates the exhaust time corresponding to the vacuum pump operating time, and the vertical axis indicates the degree of vacuum.
When the evacuation time was 0, the vacuum gauge reading was 1.0 atm (atmospheric pressure), but the evacuation time shifted from low vacuum to high vacuum as the evacuation time passed. However, from about 25 seconds, the pressure became constant at 0.031 atm. Such a pressure is called the degree of vacuum.

  In FIG. 1, when the lid 11 is opened, the atmosphere enters the sealed container 12, and a trace amount of substances contained in the atmosphere adheres to the sealed container 12 and the work stand 14. These minute amounts of substances, such as organic substances, evaporate from the surface when high vacuum is applied, and fill the sealed container 12 as gas.

Such gas generation is, for example, inundation entering from a hole opened in the bottom of the boat. For example, the vacuum pump 16 is a drainage pump that scrapes water accumulated in the boat.
Inundation cannot be stopped, but if the capacity of the drainage pump is high, the level of the inundation (water level) can be lowered. The level of flooding (water level) becomes constant when the drainage pump and the flooding are balanced. The water level that became constant corresponds to the degree of vacuum.
This degree of vacuum varies depending on the size and structure of the sealed container.

  In the above example, the degree of vacuum reached 0.031 atm. This 0.031 atm is referred to as “first pressure”.

The first equation described above is an equation in an ideal state. The first pressure is an actual value determined from the sealed container 12 and the vacuum pump 16 to be used. Therefore, the first expression is corrected with the first pressure, and specifically, the first pressure is applied to the right side of the first expression. The obtained formula is called the second formula.

  FIG. 3 is a graph showing the relationship between the amount of adhering water and the degree of vacuum, and is a graph of the second equation described above. That is, by substituting 5, 10, and 15 for w, p can be obtained and a graph can be drawn.

By the way, although it is desired that the amount of adhering water is “0”, if the humidity in the atmosphere is high, moisture in the atmosphere adheres to the work taken out from the sealed container. Therefore, it is not practical to set the amount of attached water to “0”. The exhaust time must also be extended.
Therefore, the amount of adhering water allowed is determined in consideration of the dryness required from the contents of the next process (painting, chemical conversion treatment, etc.).

  Suppose that the amount of adhering water allowed is 5 g (grams). Then, as shown in the graph, the corresponding degree of vacuum is 0.054 atm. This pressure is called “second pressure”.

The process so far is summarized as follows.
The relationship between the amount of water adhering to the workpiece and the partial pressure of moisture from the equation of state of gas, the volume of the sealed vessel, the temperature inside the sealed vessel kept constant by the heater, the molecular weight of water and the gas constant of moisture Deriving a first equation wherein:
A process of putting a dried work model in a sealed container, depressurizing the sealed container while maintaining a predetermined temperature with a heater, and setting the degree of vacuum when the degree of vacuum measured with a vacuum gauge becomes constant as the first pressure When,
Adding the first pressure to the first equation to form the second equation;
Setting the amount of adhering water allowed in the workpiece;
The amount of adhering water allowed and the step of setting the pressure determined from the second equation to the second pressure were carried out.
The process so far is a preparation process group.

Next, the pass / fail determination of the dry state performed in the automobile production line will be described.
A wet workpiece (for example, a torque converter case or a transmission case) 13 is placed in the sealed container 12 of FIG. 1, and the sealed container 12 is decompressed while being kept at a predetermined temperature (50 ° C.) by the heater 17. When a predetermined time (for example, 25 seconds) elapses from the start of pressure reduction, the vacuum degree is measured by the vacuum gauge 21. This degree of vacuum is referred to as “third pressure”.

If the measured third pressure is 0.06 atm, it exceeds the second pressure of 0.054 atm as a criterion for determination, so the determination fails (insufficiently dried).
Moreover, if the measured 3rd pressure is 0.04 atm, since it has fallen below the 2nd pressure 0.054 atm as a criteria, determination will be a pass (it is dry enough).

The above operation will be described again in the flow.
FIG. 4 is a flowchart for explaining the procedure up to the determination of whether or not the drying is successful, and sets the amount w of adhering water allowed in step number (hereinafter, ST) 01. By substituting this w into the second equation (p = 0.0045w + 0.031), the second pressure p2 is determined (ST02). Further, the drying time t1 is set with reference to FIG. 2 (ST03) . A suitable drying time t1 is 25 seconds.

In ST04, the wet work is put into the sealed container, and the operation of the vacuum pump is started (ST05). When the exhaust time (vacuum pump operation time) t2 reaches a predetermined t1, the vacuum pump is stopped (ST07). The third pressure (pressure in the sealed container) p3 at that time is measured (ST08).
The calculation / control unit 23 shown in FIG. 1 checks whether or not the third pressure p3 is equal to or lower than the second pressure p2 (ST09).

  If the third pressure p3 is equal to or lower than the second pressure p2, it is determined to pass (ST10), and if not, it is determined to fail (ST11), and this is displayed on the display unit 24 of FIG.

The allowable amount of adhering water (ST01) is appropriately set depending on the atmospheric pressure, humidity, size of the workpiece, size of the sealed container, and the like.
The same applies to the drying time t1 in ST03.

As described above, in the present invention, the degree of vacuum (third pressure) when the vacuum pump is stopped is compared with the second pressure so that the quality of drying can be determined.
The operation time of the vacuum pump can be shortened to the minimum necessary time with reference to FIG. Conventionally, a long drying time that has been extended to the safe side can be changed to a short drying time in the present invention. As a result, productivity can be greatly increased.

Preferably, the next step is continued in (A) of ST11 in FIG.
FIG. 5 is a flowchart showing the repair availability process and subsequent steps. In ST12, it is determined whether or not the work that has been rejected can be repaired (step of repairability).
If it is determined that the process is acceptable, the process is transferred to a repair process (ST13) for repairing the workpiece. Alternatively, if it is determined that the repair is not possible, the process is turned to the regeneration process (ST14) for melting the workpiece.

The work sent to the repairing process is repaired, and the pass / fail judgment of the drying of the present invention is performed again.
The work turned to the regenerating process is melted, formed and regenerated into a new work.

  That is, it is a common case that a defect occurs in relation to a complicated shape portion of a workpiece formed into a specific shape. For workpieces that have been judged to be insufficiently dried, there may be burrows due to poor molding. If the work judged to be insufficiently dried can be repaired by visual confirmation, it is repaired and washed again in the repair process, and the reduced-pressure drying method is carried out.

For work that has been judged to be insufficiently dried, if the cause of inadequate drying by visual confirmation, for example, if it is found that there is a burrow, repair is impossible or the cause of insufficient drying cannot be identified The vacuum drying method is carried out after passing through the steps.
By having the process of FIG. 5, it is an extremely important process for manufacturing the workpiece very efficiently and reducing the disposal of materials from the viewpoint of ecology.

If the workpiece is a torque converter case or a transmission case of an internal combustion engine transmission, the structure is complicated, and the ribs of the corresponding metal are intricately erected on the metal plate. It is difficult even for a skilled worker to visually determine the dry state after drying such a torque converter case or mission case.
According to the present invention, it is not necessary for the operator to perform visual drying confirmation, and anyone can perform the process.

  Although the method of the present invention is suitable for determining the drying of automobile parts, it can be applied to other machine parts.

  The reduced-pressure drying method of the present invention is suitable for drying automobile parts.

1 is a principle diagram of a vacuum drying apparatus according to the present invention. It is the decompression graph obtained with the work model. It is a graph which shows the relationship between the quantity of adhesion water, and a vacuum degree. It is a flowchart explaining the procedure to the pass / fail determination of drying. It is a flow chart after the repair availability process and thereafter.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 ... Vacuum drying apparatus, 12 ... Airtight container, 13 ... Work (wet work), 16 ... Vacuum pump, 17 ... Heater, 18 ... Thermometer, 19 ... Temperature controller, 21 ... Vacuum gauge, 22 ... Setting device, 23 ... calculation / control unit, 24 ... display unit, 26 ... work model (dry work).

Claims (4)

A vacuum drying method in which a work to which a part of cleaning water is attached is placed in a sealed container equipped with a vacuum pump, a vacuum gauge, and a heater, and the attached water is dried under reduced pressure.
From the gas equation of state, the inner volume of the sealed container, the temperature in the sealed container kept constant by the heater, the molecular weight of water and the gas constant of moisture, the amount of water attached to the workpiece and the partial pressure of moisture Deriving a first equation in which the relationship of
A dry work model is placed in the sealed container, the sealed container is depressurized while maintaining a predetermined temperature with the heater, and the degree of vacuum when the degree of vacuum measured by the vacuum gauge becomes constant is set to a first pressure. And a process of
Adding the first pressure to the first equation to form a second equation;
In the workpiece, setting a permissible amount of adhering water;
A step of setting a pressure obtained from the allowable amount of adhering water and the second equation as a second pressure;
Put a work with water on it in the sealed container, depressurize the sealed container while maintaining a predetermined temperature with the heater, measure the degree of vacuum with the vacuum gauge when a predetermined time has elapsed from the start of decompression, A step of setting the degree to a third pressure;
Determining whether the third pressure is acceptable or not using the second pressure as a criterion;
A vacuum drying method comprising the steps of:   In the pass / fail judgment step, a repair propriety step for judging whether or not repair is possible for a work rejected in the same step, and a repair step for repairing the work if it is judged acceptable in this step The reduced-pressure drying method according to claim 1, further comprising a regeneration step of dissolving the workpiece when it is determined to be negative in the repairability determination step.   3. The reduced-pressure drying method according to claim 1, wherein the workpiece is a torque converter case or a transmission case of an internal combustion engine transmission. A vacuum drying device that puts a work with a part of the washing water in a sealed container and dries the attached water under reduced pressure.
The vacuum dryer is a sealed container that contains the workpiece, a vacuum pump that depressurizes the inside of the sealed container, a heater that heats the inside of the sealed container, a thermometer that measures the temperature inside the sealed container, and a thermometer that uses this thermometer. The temperature controller that controls the output of the heater so that the measured temperature becomes a constant temperature, a vacuum gauge that measures the pressure inside the sealed container, and the degree of vacuum measured by this vacuum gauge are read, and based on this degree of vacuum Comprising a calculation / control unit that determines the drying of the workpiece,
In the calculation / control unit,
From the gas equation of state, the inner volume of the sealed container, the temperature in the sealed container kept constant by the heater, the molecular weight of water and the gas constant of moisture, the amount of water attached to the workpiece and the partial pressure of moisture Deriving a first equation in which the relationship of
A dry work model is placed in the sealed container, the sealed container is depressurized while maintaining a predetermined temperature with the heater, and the degree of vacuum when the degree of vacuum measured by the vacuum gauge becomes constant is set to a first pressure. And a process of
Adding the first pressure to the first equation to form a second equation;
In the workpiece, setting a permissible amount of adhering water;
The second pressure is set through a process group consisting of a step of setting the amount of the adhering adhering water and the pressure obtained from the second formula as the second pressure,
Such a calculation / control unit
Put a work with water on it in the sealed container, depressurize the sealed container while maintaining a predetermined temperature with the heater, measure the degree of vacuum with the vacuum gauge when a predetermined time has elapsed from the start of decompression, A step of setting the degree to a third pressure;
A reduced-pressure drying apparatus having a function of determining whether or not drying is performed through a process group including a step of determining whether or not the third pressure is acceptable using the second pressure as a criterion.

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