JPH07163954A - Cleaning method and cleaner - Google Patents

Abstract

PURPOSE:To provide a cleaning method and a cleaner in which uniform cleaning quality is obtained irrespective of the state of individual workpieces. CONSTITUTION:A workpiece 4 is immersed in cleaning liquid 3 in a cleaning tank 5 and cleaned. The cleaning liquid 3 is fed into the cleaning tank 5 and the cleaning liquid 3 contaminated with oil component foreign matter, etc,. is discharged outside the cleaning tank 5. The electrical conductivity of the cleaning liquid 3 in the cleaning tank 5 is measured. When the variation in electrical conductivity within a prescribed time becomes not more than a prescribed criteria of judgement, the termination of the cleaning is decided otherwise, when the variation in electrical conductivity within a prescribed time disappears, the termination of the cleaning is judged. The cleaning liquid 3 is filtered at the outside of the cleaning tank 5 and circulated. A cleaner 1 consists of the cleaning tank 5, cleaning liquid feeding means 9 and a cleaning liquid discharge means 8. An electrical conductivity measuring means 20 is installed in the cleaning tank 5, and a termination deciding means 21 is installed. A cleaning liquid circulating means 10 for connecting the cleaning liquid discharge means 8 and the cleaning liquid feeding means 9 is formed, and the cleaning liquid circulating means 10 is provided with a cleaning liquid filtration means 12. An ultrasonic vibrator 2 is installed in the bottom part of the cleaning tank 50.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and a cleaning device for immersing a work in a cleaning liquid contained in a cleaning tank and cleaning it by ultrasonic cleaning or the like.

[0002]

2. Description of the Related Art Conventionally, a work such as a molded product is immersed in a cleaning liquid stored in an ultrasonic cleaning tank having an ultrasonic vibrator at the bottom, and ultrasonic waves are radiated from the ultrasonic vibrator to the cleaning liquid. There is known an ultrasonic cleaning method of cleaning by doing. In such an ultrasonic cleaning method, an excellent cleaning effect can be obtained by using a cleaning liquid from which dissolved gas has been degassed.By changing the degree of degassing depending on the work, deburring or sticking to the work surface It is possible to clean the solid foreign matter such as the material scraps, the solid foreign matter such as the material scraps adhered to the surface of the work through the oil, or the oil itself.

In the above ultrasonic cleaning method, oil and foreign matters removed from the work by cleaning the work are mixed in the cleaning liquid, and if left alone, the cleaning ability of the cleaning liquid is lost in a short time. Therefore, usually, the cleaning liquid is taken out of the ultrasonic cleaning tank and filtered to remove oil and foreign substances mixed in the cleaning liquid, and is circulated to the ultrasonic cleaning tank as a clean cleaning liquid. The cleaning ability is maintained.

In the ultrasonic cleaning method, the work is immersed in the cleaning liquid for a predetermined cleaning time for cleaning. The cleaning time is empirically determined according to the form of the work, and since the cleaning liquid is always kept in a clean state as described above, it is possible to set the cleaning time in advance. Therefore, the work can be efficiently washed under certain conditions.

However, if the cleaning is performed in accordance with the cleaning time set in advance, the cleaning time becomes constant regardless of the state of the individual work, so that the cleaning quality of each work may be uneven. is there.

[0006]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a cleaning method and a cleaning apparatus which can eliminate such inconvenience and obtain uniform cleaning quality regardless of the state of each work. .

[0007]

In order to achieve the above object, the cleaning method of the present invention is such that when a workpiece is immersed in the cleaning liquid contained in the cleaning tank for cleaning, the cleaning liquid is supplied to the cleaning tank. In the cleaning method of supplying the cleaning liquid mixed with the oil removed by the cleaning of the work, foreign matter, etc. to the outside of the cleaning tank, measuring the electric conductivity of the cleaning liquid in the cleaning tank, It is characterized in that the end of the cleaning is judged when the magnitude of the change in the electric conductivity becomes equal to or smaller than a predetermined judgment value.

In the cleaning method of the present invention, the end of the cleaning may be determined when the fluctuation of the electric conductivity within the predetermined time has disappeared.

Further, the cleaning method of the present invention is characterized in that the cleaning liquid in which the oil content, the foreign matter and the like are mixed is filtered outside the cleaning tank and is circulated to the cleaning tank as the clean cleaning liquid.

The cleaning method of the present invention comprises a cleaning tank for containing a cleaning liquid, a cleaning liquid supply means for supplying a clean cleaning liquid to the cleaning tank when the workpiece is immersed in the cleaning tank for cleaning, and the cleaning of the work. In a cleaning device comprising a cleaning liquid discharge means for discharging a cleaning liquid mixed with oil, foreign matter, etc. removed by means of the cleaning liquid discharge means to the outside of the cleaning tank, the cleaning tank is provided with an electric conductivity measuring means for measuring the electric conductivity of the cleaning liquid. A cleaning means provided with an end judging means for judging the end of the cleaning when the magnitude of the fluctuation of the electric conductivity of the cleaning liquid measured by the electric conductivity measuring means within a predetermined time is less than a predetermined judgment value. It can be implemented advantageously by the device.

In the cleaning apparatus, the cleaning liquid circulating means for connecting the cleaning liquid discharging means and the cleaning liquid supplying means to circulate the cleaning liquid taken out from the cleaning tank by the cleaning liquid discharging means to the cleaning tank by the cleaning liquid supplying means. Is provided
The cleaning liquid circulating means is provided with a cleaning liquid filtering means for filtering the oil and foreign matters. Further, the cleaning apparatus is characterized in that an ultrasonic transducer is provided at the bottom of the cleaning tank.

[0012]

When the work is cleaned in the cleaning liquid contained in the cleaning tank, the oil and solid foreign matter removed from the work are mixed in the cleaning liquid. At this time, while supplying a clean cleaning liquid to the cleaning tank, the cleaning liquid mixed with the oil removed by the cleaning of the workpiece and solid foreign matter is discharged to the outside of the cleaning tank. The amount of foreign matter in the cleaning tank increases once immediately after the start of cleaning the work, but gradually decreases, and the cleaning liquid in the cleaning tank is returned to a clean state again.

Since the oil and solid foreign matter mediate the transfer of electric charges in the cleaning liquid, the conductivity of the cleaning liquid increases or decreases according to the amounts of the oil and solid foreign matter in the cleaning liquid. That is, the extremely low conductivity in the clean cleaning liquid before cleaning the work sharply increases immediately after the cleaning of the work is started, and the oil and solids mixed in the cleaning liquid from the work as the cleaning progresses. When the amount of foreign matter is gradually decreased, the amount becomes gradually lower.

Therefore, when the electric conductivity of the cleaning liquid in the cleaning tank is measured, the electric conductivity that once increased turns to decrease, and the magnitude of the fluctuation of the electric conductivity within a predetermined time becomes less than a predetermined judgment value. In this case, it is determined that the oil and solid foreign matter mixed in the cleaning liquid have been discharged, and that there is no more new mixing, and the end of the cleaning is judged at that point.

In the cleaning method of the present invention, the judgment is facilitated by determining the end of the cleaning when the fluctuation of the electric conductivity within a predetermined time is eliminated.

In the cleaning method of the present invention, the cleaning liquid mixed with the oil, foreign matter, etc. is filtered outside the cleaning tank and circulated as the clean cleaning liquid to the cleaning tank so that it is contained in the cleaning liquid in the cleaning tank. The amount of the oil and the solid foreign matter to be generated is reduced, and the end of the cleaning is judged from the electric conductivity of the cleaning liquid in the same manner as described above. Further, by circulating the cleaning liquid as described above, the cleaning liquid can be repeatedly used, and the cost is reduced.

In the cleaning apparatus of the present invention, when the workpiece is cleaned by immersing the work in the cleaning liquid contained in the cleaning tank, the cleaning liquid supply means supplies the cleaning liquid to the cleaning tank while the cleaning liquid is supplied. The cleaning liquid mixed with oil, foreign matter, and the like removed from the work by the discharging means is discharged to the outside of the cleaning tank. Then, the electric conductivity of the cleaning liquid in the cleaning tank is measured with time by the electric conductivity measuring means provided in the cleaning tank, and the magnitude of the fluctuation of the electric conductivity within a predetermined time becomes a predetermined judgment value or less. When this happens, the end determination means determines the end of the cleaning.

In the cleaning device, a cleaning liquid circulating means for connecting the cleaning liquid discharging means and the cleaning liquid supplying means is provided, and a cleaning liquid filtering means for filtering the oil content, foreign matters and the like is provided in the cleaning liquid circulating means, whereby the cleaning liquid is provided. The cleaning solution taken out from the cleaning tank by the discharging means is filtered by the filtering means to remove the oil and foreign matters, and is circulated to the cleaning tank by the cleaning solution supply means as a clean cleaning solution.

In the cleaning apparatus of the present invention, an ultrasonic vibrator is provided at the bottom of the cleaning tank, and when ultrasonic cleaning is performed,
Particularly advantageously used. According to the ultrasonic cleaning, the oil, foreign matter and the like adhering to the work are rapidly removed, and the cleaning liquid discharging means discharges the oil out of the cleaning tank, thereby obtaining an excellent cleaning effect. Since the ultrasonic cleaning is performed extremely quickly, the change in the electric conductivity of the cleaning liquid can be easily grasped, and the end of the ultrasonic cleaning can be reliably determined.

[0020]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, the cleaning method and cleaning apparatus of the present invention will be described in more detail with reference to the accompanying drawings. FIG. 1 is a schematic diagram showing an example of the configuration of the cleaning apparatus of the present invention,
FIG. 2 is a graph showing the relationship between the cleaning time, the amount of oil residue, and the current value.

As shown in FIG. 1, the ultrasonic cleaning apparatus 1 of this embodiment is provided with an ultrasonic vibrator apparatus 2 at the bottom, and an ultrasonic vibrator is provided when a work 4 is immersed in the cleaning liquid 3 supplied into the tank. An ultrasonic cleaning tank 5 that irradiates the cleaning liquid 3 with ultrasonic waves from the device 2 to clean the work 4, and an overflow when the work 4 is immersed in the ultrasonic cleaning tank 5 provided adjacent to the ultrasonic cleaning tank 5. Overflow tank 6 for containing cleaning liquid 3
The ultrasonic cleaning tank 5 and the overflow tank 6 are connected by an inclined drainage path 7.

Further, the ultrasonic oscillator device 2 has an ultrasonic oscillator (not shown) housed in a sealed container made of stainless steel, and the ultrasonic oscillator is based on an ultrasonic signal sent from an external ultrasonic oscillator. And emits a predetermined ultrasonic wave. The surface of the ultrasonic transducer device 2 is plated with nickel in order to protect it from erosion caused by ultrasonic waves.

On the side surface of the ultrasonic cleaning tank 5, a cleaning liquid outlet 8 and a cleaning liquid supply port 9 are provided so as to face each other, and the cleaning liquid outlet 8 and the cleaning liquid supply port 9 are provided outside the ultrasonic cleaning tank 5. The cleaning liquid 3 in the ultrasonic cleaning tank 5 is circulated from the cleaning liquid outlet 8 through the conduit 10 to the cleaning liquid supply port 9 by the pump 11 which is connected through the conduit 10 and is connected to the cleaning liquid supply port 9 through the conduit 10. It has become. The cleaning liquid take-out port 8 and the cleaning liquid supply port 9 are supplied to the ultrasonic cleaning tank 5 by the cleaning liquid 3 supplied from the ultrasonic cleaning tank 5 or supplied to the ultrasonic cleaning tank 5. A rectifying device (not shown) is incorporated to form a laminar flow parallel to.

The conduit 10 is provided with a filter 12 downstream of the pump 18 so as to filter out solid foreign matters such as oil content, burrs, and material scraps mixed in the cleaning liquid 3 by cleaning the work 4. .

A degassing device 13 for degassing the dissolved gas of the cleaning liquid 3 is provided downstream of the filter 12 in the conduit 10. The degassing device 13 is a vacuum degassing device that introduces the cleaning liquid 3 into a depressurized sealed tank and releases the dissolved gas in the cleaning liquid 3 into the depressurized space in the sealed tank to degas it, a hollow fiber gas separation membrane. And a cleaning liquid 3 are circulated in the hollow fiber gas separation membrane, and the outside of the hollow fiber gas separation membrane is decompressed to separate the dissolved gas in the cleaning liquid 3 through the hollow fiber gas separation membrane. A membrane module or the like is used.

The cleaning liquid 3 is degassed by the degassing device 13, and its dissolved oxygen concentration is adjusted in the range of 0.01 to 5 ppm depending on the form of the work 4 or the purpose of cleaning. still,
Since the ultrasonic cleaning device 1 is used in the air, the cleaning liquid 3
The gas dissolved in is actually air, but the composition of air is almost constant at oxygen: nitrogen≈1: 4, so the dissolved oxygen concentration is used as an index indicating the total dissolved gas concentration.

At the bottoms of the ultrasonic cleaning tank 5 and the overflow tank 6, conduits 14a, 14 for discharging the cleaning liquid 3 are respectively provided.
b is provided, and the discharge conduits 14a and 14b are connected to the conduit 10 on the upstream side of the pump 11. Further, the conduit 10 branches the auxiliary conduit 15 downstream of the deaerator 13,
The auxiliary conduit 14 is connected to an auxiliary supply port 16 provided at the top of the ultrasonic cleaning tank 5. A valve 17 is provided in each of the conduit 10, the discharge conduits 14a and 14b, and the auxiliary conduit 15.
Is provided so that the flow rate of each conduit can be adjusted. A heater 18 is provided at the bottom of the ultrasonic cleaning tank 5 so that the cleaning liquid 3 can be heated if necessary.

In the ultrasonic cleaning apparatus 1 shown in FIG. 1, a DC 12V power source 19 is provided outside, is connected to the electrode plates 19a and 19b immersed in the ultrasonic cleaning tank 5, and is connected in series with the DC power source 19. The electric current of the cleaning liquid 3 is measured by the current detection circuit 20. In addition, the current detection circuit 20
Is connected to an end judging means 21 for judging the end of cleaning of the work 4 based on the magnitude of the fluctuation of the electric conductivity within a predetermined time.

Further, the ultrasonic cleaning apparatus 1 includes a work 4
Moving means 22 for transferring and discharging the ultrasonic wave to the ultrasonic cleaning device 1,
Elevating means 23 for transferring the work 4 conveyed by the moving means 22 and immersing it in the ultrasonic cleaning tank 5 is provided, and the end determining means 21 is connected to the elevating means 23 to control its operation. It has become like.

Next, a cleaning method by the ultrasonic cleaning apparatus 1 of the present embodiment will be described by taking as an example the case of cleaning the vane (made of iron) of the compressor as the work 4.
The vane of the compressor is subjected to double-side lapping with # 1500 abrasive grains (average particle diameter 8.0 μm) and mineral oil, and the abrasive grains and material scraps are attached to the surface together with the mineral oil.

In the cleaning method of the present embodiment, first, the vane (workpiece 4) stored in a stainless steel storage basket (not shown) is transferred from the previous step to the ultrasonic cleaning device 1 by the moving means 22 and stored therein. The basket is transferred to the lifting means 23. Then, the elevating means 23 descends, and the vanes (workpieces 4) housed in the storage basket are placed in the ultrasonic cleaning tank 5.
Is immersed in. Then, the end determination means 21 is activated, and immediately the electric current detection circuit 20 starts measuring the electric conductivity of the cleaning liquid 3.

The ultrasonic cleaning tank 5 contains a weak alkaline cleaning agent 5
% Tap water is supplied as the cleaning liquid 3, and the cleaning liquid 3 is taken out from the cleaning liquid take-out port 8 by the pump 11 and is passed through the filter 10 and the deaerator 13 by the conduit 10 to the cleaning liquid feed port 9 and the auxiliary feed port 16. To the ultrasonic cleaning tank 5. The circulation is performed by the ultrasonic cleaning tank 5
The cleaning liquid 3 is discharged and supplied at a volume of about 0.25 to 0.95% / sec. In this embodiment, 60
For an ultrasonic cleaning tank 5 having a volume of 1 liter, 0.
The cleaning liquid 3 of 25 liter / sec is discharged and supplied.

Next, ultrasonic waves are radiated from the ultrasonic vibrator housed in the ultrasonic vibrator device 2 to the cleaning liquid 3 to ultrasonically clean the work 4. The ultrasonic wave output 600
w, frequency 25 kHz, density 1 w / cm ² .

When the ultrasonic cleaning of the work 4 is started, the cleaning liquid 3 is degassed so as to have the above-mentioned dissolved oxygen concentration, so that a shock wave due to the collapse of cavitation is generated in the work 4.
Of the oil, and solid foreign matters attached through the oil are removed from the surface of the work 4 and mixed into the cleaning liquid 3. Then, the oil and solid foreign matter are removed by the cleaning liquid 3
Since the transfer of electric charge is mediated therein, the conductivity of the cleaning liquid 3 is increased, and the current detection circuit 20 causes the electrode plates 19a and 19b
It is detected as an increase in current during the period.

The cleaning liquid 3 is supplied to the cleaning liquid outlet 8 as described above.
After being taken out from the container, filtered by the filter 12, and circulated from the cleaning liquid supply port 9 and the auxiliary supply port 16 to the ultrasonic cleaning tank 5, oil and solid foreign matter removed as the cleaning of the work 4 progresses. When the water content decreases, the cleaning liquid 3 in the ultrasonic cleaning tank 5 is gradually cleaned, and the cleaning liquid 3
The electric conductivity of is gradually reduced. This gradual decrease in conductivity is measured by the current detection circuit 20 over time, and the end determination means 2
It is output to 1. Then, when the end judging means 21 detects that the fluctuation of the electric conductivity has disappeared within a predetermined time, it judges that the cleaning is completed and raises the elevating means 23 to raise the storage basket by the ultrasonic cleaning tank 5. Pull up from.

Next, the raised storage basket is transferred from the elevating means 23 to the transfer means 22 and carried out of the ultrasonic cleaning apparatus 1, and the cleaning operation is completed.

In the washing operation, the amount of oil residue of the work 4 was continuously measured with time, and the results shown in Table 1 below were obtained. The amount of the oil residue was determined by extracting the oil adhering to the work 4 with carbon tetrachloride and measuring the oil concentration in a predetermined amount of carbon tetrachloride by the infrared absorption method.

[0038]

[Table 1]

From Table 1, it is clear that when the cleaning time is 30 seconds or more, the residual amount of oil adhered to the work 4 becomes a trace amount of oil adhered before cleaning, and can be treated as a good product. is there.

Next, the current value of the cleaning liquid 3 between the electrode plates 19a and 19b measured by the current detecting circuit 20 as the electric conductivity of the cleaning liquid 3 at each time corresponding to the cleaning time in Table 1 is shown in Table 2 below. Show.

[0041]

[Table 2]

It can be seen from Table 2 that the current value, which became sharply high immediately after the cleaning was started, gradually decreased as the cleaning progressed, and the amount of oil adhering to the work 4 became a trace amount after 30 seconds and reached 1.5 mA. It is clear that the fluctuation disappears. This is because, immediately after the cleaning is started, oil, abrasive grains, material scraps, and the like are mixed in the cleaning liquid 3, and the number of mediatoring the transfer of electric charges in the cleaning liquid 3 is rapidly increased. Since it is circulated and filtered by the filter 12, oil content, abrasive grains, material scraps and the like in the cleaning liquid 3 are gradually reduced, and it is considered that the oil content adhering to the work 4 becomes constant as it becomes a trace amount. be able to.

A graph obtained by combining the results of Tables 1 and 2 is shown in FIG. As is clear from Table 1, Table 2 and FIG. 2, in this embodiment, the amount of oil residue attached to the work 4 is rapidly reduced by ultrasonic cleaning, and almost 30 seconds after the start of cleaning, almost no oil residue remains. Although it is a trace amount, the current value of the cleaning liquid 3 increases once after the start of cleaning and becomes constant after 30 seconds.
Then, since the fluctuation disappears after this time, the fluctuation of the current value can be easily grasped and the end of cleaning can be surely judged.

In the present embodiment, the current value did not change at all after 30 seconds from the start of cleaning, but the current value decreased with a gentle slope for a predetermined time, for example, for 30 seconds, and the fluctuation range was When the current value becomes equal to or lower than a predetermined current value, for example, 1 mA or less, it may be determined that the cleaning is completed, assuming that the cleaning effect is not substantially affected even if the cleaning is continued for a longer time.

In the ultrasonic cleaning apparatus 1 shown in FIG. 1, the current value of the cleaning liquid 3 between the electrode plates 19a and 19b immersed in the ultrasonic cleaning tank 5 is measured. When the stainless steel basket is dipped in to clean the work 4, the space for immersing the electrode plates 19a and 19b may not be obtained in order to efficiently use the volume of the ultrasonic cleaning tank 5. In such a case, the electrode plate 19
One of a and 19b may be replaced with a stainless steel basket or ultrasonic transducer device 2 in which the work 4 is housed, and the stainless steel basket or ultrasonic transducer device 2 may be used as an electrode plate. The stainless steel basket and ultrasonic transducer device 2 may be connected to the DC power source 19 to use the stainless steel basket and ultrasonic transducer device 2 as an electrode plate. When using the stainless steel basket and the ultrasonic transducer device 2 as an electrode plate, for example, the stainless steel basket is connected to the anode side of the DC power supply 19 and the ultrasonic transducer device 2 is connected to the cathode side of the DC power supply 19. To do.

Furthermore, when the ultrasonic cleaning tank 5 is made of a conductive material, the ultrasonic cleaning tank 5 may be used as an electrode. When the ultrasonic cleaning tank 5 is used as an electrode, the current value of the cleaning liquid 3 between the ultrasonic cleaning tank 5 and the work 4 or the ultrasonic transducer device 2 is measured, or the cleaning liquid 3 is connected to the electrode plate 1
Electrode plate 19a or 19b by immersing 9a or 19b
The current value of the cleaning liquid 3 between the ultrasonic cleaning tank 5 and the ultrasonic cleaning tank 5 is measured.

[0047]

As is apparent from the above, according to the cleaning method of the present invention, when cleaning a work, the electric conductivity of the cleaning liquid in the cleaning tank is measured and the cleaning liquid within a predetermined time is measured. By determining that the cleaning has been completed when the magnitude of the change in the electrical conductivity becomes equal to or less than a predetermined determination value, the cleaning can be completed at an appropriate time for each cleaning of each work. It is possible to obtain excellent cleaning quality with no variation between the two.

In the cleaning method of the present invention, the judgment can be easily performed by determining the end of the cleaning when the conductivity has not changed within a predetermined time.

In the cleaning method of the present invention, the oil content,
By filtering the cleaning liquid mixed with foreign substances and the like outside the cleaning tank, and circulating the cleaning liquid as the clean cleaning liquid in the cleaning tank,
Since the amount of the oil and solid foreign matter contained in the cleaning liquid in the cleaning tank is reduced, it is possible to determine the end of the cleaning from the electric conductivity of the cleaning liquid in the same manner as described above, and the cleaning liquid is repeatedly used. Therefore, the cost can be saved.

In the cleaning apparatus of the present invention, when the workpiece is cleaned by immersing the workpiece in the cleaning liquid contained in the cleaning tank, the cleaning liquid supply means supplies a clean cleaning liquid to the cleaning tank while discharging the cleaning liquid. The cleaning liquid mixed with oil, foreign matter, etc. removed from the work by means is discharged to the outside of the cleaning tank, and the conductivity of the cleaning liquid in the cleaning tank is changed with time by the conductivity measuring means provided in the cleaning tank. By the above measurement, the end of the cleaning can be judged by the end judging means at the time when the magnitude of the fluctuation of the conductivity within the predetermined time becomes equal to or smaller than the predetermined judgment value.

In the cleaning device, the cleaning liquid circulating means for connecting the cleaning liquid discharging means and the cleaning liquid supplying means is provided, and the cleaning liquid filtering means for filtering the oil content, foreign matter and the like is provided in the cleaning liquid circulating means, whereby the cleaning liquid is obtained. The cleaning liquid taken out of the cleaning tank by the discharging means can be filtered by the filtering means and circulated to the cleaning tank by the cleaning liquid supply means as a clean cleaning liquid.

Further, in the cleaning apparatus of the present invention, when an ultrasonic transducer is provided at the bottom of the cleaning tank to perform ultrasonic cleaning, the ultrasonic cleaning is performed extremely quickly, so that the conductivity of the cleaning liquid is reduced. The fluctuation of the degree becomes clear. Therefore, the change in the electric conductivity can be easily grasped, and the end of the ultrasonic cleaning can be reliably determined.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing a configuration example of a cleaning device of the present invention.

FIG. 2 is a graph showing the relationship between the cleaning time, the amount of oil residue, and the current value.

[Explanation of symbols]

3 ... cleaning liquid, 5 ... cleaning tank, 8 ... cleaning liquid discharging means, 9 ... cleaning liquid supplying means, 10 ... cleaning liquid circulating means, 12 ... cleaning liquid filtering means, 20 ... conductivity measuring means, 21 ... end judging means.

Claims (6)

[Claims] 1. When a work is immersed in a cleaning liquid contained in a cleaning tank for cleaning, a clean cleaning liquid is supplied to the cleaning liquid and oil and foreign matters removed by cleaning the work are mixed. In the cleaning method of discharging the cleaning liquid to the outside of the cleaning tank, the conductivity of the cleaning liquid in the cleaning tank is measured,
A cleaning method, wherein the end of the cleaning is judged when the magnitude of the fluctuation of the electric conductivity within a predetermined time becomes equal to or smaller than a predetermined judgment value. 2. The cleaning method according to claim 1, wherein the end of the cleaning is judged when the fluctuation of the electric conductivity within the predetermined time disappears. 3. The cleaning method according to claim 1, wherein the cleaning liquid in which the oil content, foreign matter and the like are mixed is filtered outside the cleaning tank and circulated to the cleaning tank as the clean cleaning liquid. 4. A cleaning tank for containing a cleaning liquid, a cleaning liquid supply means for supplying a clean cleaning liquid to the cleaning tank when the workpiece is immersed in the cleaning tank for cleaning, and an oil content removed by cleaning the workpiece. A cleaning liquid discharging means for discharging the cleaning liquid mixed with foreign matters to the outside of the cleaning tank, wherein the cleaning tank is provided with an electric conductivity measuring means for measuring the electric conductivity of the cleaning liquid, and the electric conductivity measurement is performed. A cleaning method, characterized by further comprising: an end judging means for judging the end of the cleaning when the magnitude of the fluctuation of the electric conductivity of the cleaning liquid measured by the means within a predetermined time is equal to or smaller than a predetermined judgment value. apparatus. 5. A cleaning liquid circulating means for connecting the cleaning liquid discharge means and the cleaning liquid supply means to circulate the cleaning liquid taken out from the cleaning tank by the cleaning liquid discharge means to the cleaning tank by the cleaning liquid supply means, The cleaning apparatus according to claim 4, wherein the cleaning liquid circulating means is provided with cleaning liquid filtering means for filtering the oil, foreign matter and the like. 6. The cleaning apparatus according to claim 4, wherein an ultrasonic vibrator is provided at the bottom of the cleaning tank.