JP2006019894A - Waterproof visual sensor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a waterproof visual sensor provided with a function capable of positively preventing dew condensation on a transparent window plate fitted into a photographing window without relying on a moisture absorbent such as silica gel or requiring advanced airtightness. <P>SOLUTION: In the sensor, a heat generator such as a power element or a power source unit is housed in a waterproof case in which the transparent window plate is fitted into the photographing window. The appropriate number of pores for communicating the inside to the outside are provided on the appropriate portion of the case at a position near the transparent window between the transparent window plate and the heat generator. Further, the pores are closed with an air permeable film having a function of allowing humidity to pass while preventing water molecules of a liquid from passing. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a waterproof visual sensor in which a heating element such as a power element and a power supply unit is housed in a waterproof case in which a transparent window plate is fitted in a photographing window.

  An amplifier-separated type visual sensor including a sensor head unit that functions as a camera and an amplifier unit that performs various appearance inspections based on images obtained from the sensor head unit has been known (for example, Patent Document 1). reference). This type of visual sensor is widely applied to the appearance inspection of industrial products and various foods. Above all, in the European food industry, visual inspection of food is carried out using a lot of visual sensors, and due to the nature of the industry, equipment for food transport lines including visual sensors is installed every day work is completed. It is a common practice to keep clean by washing with water discharge.

  Therefore, in a visual sensor used in this type of food production line, a waterproof case in which a heating element such as a power element or a power supply unit is housed in a waterproof case in which a transparent window plate is fitted in a photographing window. A type sensor head is applied.

  By the way, in this type of waterproof visual sensor, although the waterproof structure is applied, the internal air expands due to a heating element such as a power element or a power source housed in the inside. Repeated contraction and the so-called breathing action prevent moisture (water molecules) from entering from the joints of cables and cases, no matter how appropriate the waterproof structure is. Therefore, in the waterproof visual sensor placed in a low temperature environment, the water vapor dissolved in the warmed air in the case is rapidly cooled by contacting the transparent window plate fitted in the shooting window, It has been pointed out that water droplets adhere to the inner surface of the transparent window plate and cause fogging on the transparent window plate due to so-called condensation.

By the way, in a waterproof camera in which condensation is likely to occur, as a means for optically preventing condensation, one that forms a sealed space between the first transparent member and the second transparent member is known. (For example, refer to Patent Document 1). As another method, a method in which a hygroscopic agent such as silica gel is accommodated in a camera case is also known.
JP 2002-277945 A

  However, with the structure described in Patent Document 1 described above, it is not always easy to maintain a completely sealed structure, and thus a sufficient solution has not been provided.

  In addition, even in the case of containing a hygroscopic agent such as silica gel, the capacity of the hygroscopic agent is limited, and eventually the problem of losing the hygroscopic performance and requiring frequent replacement has been pointed out. Yes.

  This invention has been made by paying attention to the above-mentioned problems in the conventional anti-condensation measures, and its purpose is to rely on a hygroscopic agent such as silica gel or to require a high degree of airtightness, An object of the present invention is to provide a waterproof visual sensor having a function capable of reliably preventing condensation on a transparent window plate fitted in a photographing window.

  Other objects and operational effects of the present invention will be easily understood by those skilled in the art by referring to the following description of the specification.

  The waterproof visual sensor of the present invention is configured by housing a heating element such as a power element and a power supply unit in a waterproof case in which a transparent window plate is fitted in a photographing window. Here, since the waterproof case also functions as a camera, it is a matter of course that photographing optical parts such as a photographing optical system and a two-dimensional imaging element are accommodated.

In addition, an appropriate number of pores communicating between the inside and outside of the case are opened at appropriate positions of the case between the transparent window plate and the heating element and in the vicinity of the transparent window plate, and these pores are liquid. while blocking the passage of water molecules, the passage of water vapor is closed by breathable film having the function of allowing.

According to this structure, both inside and outside of the waterproof case, in the vicinity of particularly transparent window plate, while the passage of water molecules of the liquid prevents the passage of water vapor through a breathable film having a function to allow vent Therefore, the temperature difference between the inside and outside of the transparent window plate is eliminated, thereby preventing condensation on the inner surface of the transparent window plate.

Thus, in the present invention, rather than increasing the airtightness of the inner and outer waterproof case, even while ensuring breathable by water intrusion molecules of the liquid prevents the temperature difference of the case inside and outside, In particular, the temperature difference between the inside and the outside of the transparent window plate is eliminated as much as possible to prevent condensation on the inner surface of the transparent window plate. At this time, if the pores that allow the air flow are opened in the case near the heating element such as the power element or the power supply unit, the outside air that has flowed in is immediately warmed. Although the temperature cannot be lowered sufficiently, in the present invention, since the pores are opened in the case as close to the transparent window plate as possible, and the air near the inner surface of the transparent window plate is cooled by the inflowed air, It is possible to prevent condensation more effectively.

  In a preferred embodiment, the waterproof case may be a case of the sensor head portion of the amplifier-separated visual sensor. According to such a configuration, it becomes easy to increase the distance between the transparent window plate and the heating element such as the power element and the power supply unit by making the case of the sensor head part into an elongated cross-sectional cylindrical shape in the optical axis direction. The rate at which the air flowing in from the pores is heated by the heating element can be reduced, the inner surface of the transparent window plate can be more effectively cooled, and condensation on the inner surface of the transparent window plate can be effectively prevented.

  In a preferred embodiment, an appropriate number of pores may be opened on the side of the case close to the transparent window plate. According to such a configuration, pores for air circulation can be easily secured even when the cross-sectional shape of the case is substantially the same as that of the transparent window plate.

  In a preferred embodiment, the breathable film may be attached to the inner surface of the case so as to cover the pores. According to such a structure, since the raw material of a breathable film is accommodated in the inner surface of a case and is not visible from the outside, the appearance is not impaired.

  In a preferred embodiment, a breathable film may be attached to the outer surface of the case so as to cover the pores. According to such a configuration, there is an advantage that it is resistant to external water pressure even when it is subjected to water discharge cleaning or the like.

In a preferred embodiment, the breathable film may be a polytetrafluoroethylene resin porous membrane. Here, the polytetrafluoroethylene (PTFE) resin porous membrane has hundreds of millions of fine pores per 1 cm ² and simultaneously exhibits waterproof / dustproof properties and air permeability, as well as water repellency, heat resistance and chemical resistance. Excellent characteristics such as heat resistance, weather resistance, and electrical characteristics. Therefore, the functions of gas permeability, water vapor permeability, and waterproofing can be sufficiently exhibited.

  According to the present invention, an appropriate number of pores communicating between the inside and outside of the case are opened at appropriate positions of the case between the transparent window plate and the heating element and in the vicinity of the transparent window plate, and water molecules are contained in the pores. The passage of water vapor is blocked by a breathable film that has the function of allowing it, so even when the waterproof visual sensor is placed in a low temperature environment, the inside of the transparent window plate In the vicinity, the flow of gas inside and outside is ensured, thereby eliminating the temperature difference between the inside and outside of the both sides of the transparent window plate, and reliably preventing condensation on the inner surface of the transparent window plate.

  In the following, a preferred embodiment of the present invention will be described in detail with reference to the accompanying drawings.

  FIG. 1 shows an external perspective view of the entire visual sensor to which the present invention is applied. As shown in the figure, the entire visual sensor includes an amplifier unit 1 and a sensor head unit 2. The amplifier unit 1 has a rectangular case 11. On the surface (front surface) of the case 11, an image display 12 and an operation unit cover 13 made of a liquid crystal device are provided. The operation unit cover 13 is hinged and can be opened and closed. When the operation unit cover 13 is opened, various operation keys appear inside. A DIN rail mounting groove 14 is drawn out on the back surface (back surface) of the case 11, a receptacle 15 is drawn out on the top surface, and an electric cord 16 is drawn out on the bottom surface. A connecting connector cover 17 is provided on both side surfaces of the case 11. The connecting connector cover 17 is slidably opened and closed. When the connecting connector cover 17 is opened, a connecting connector for connecting the amplifier units 1 adjacent to each other appears.

  The sensor head unit 2 has a waterproof sealed case 21. The case 21 has a square section that is elongated in the optical axis direction. The case 21 has a main body case 21a and a tip case 21b. An electronic circuit board is mounted in the main body case 21a. Although not shown, a heating element such as a power source or a communication power transistor is also mounted on the board in addition to a two-dimensional image sensor such as a CCD. Has been. On the other hand, the front end case 21b has a photographing window 22 on the front surface thereof closed with a transparent window plate 22a, and the front end case 22 has a lens barrel front end M that accommodates an optical system such as a photographing lens. And eight light emitting diodes D1-D8 for illumination are accommodated so that the circumference | surroundings may be surrounded.

  In the figure, the transparent window plate 22a fitted into the photographing window 22 is removed. That is, a photographing window 22 is drawn out on the front side of the case 21 and an electric cord 23 is drawn out from the rear side, and a front end connector of the electric cord 23 is coupled to the receptacle 15 of the amplifier unit 1, thereby Data transmission between the amplifier unit 1 and the sensor head unit 2 can be performed via the cord 23.

Next, the dew condensation preventing structure, which is a main part of the present invention, will be described. As shown in FIG. 3, a recessed portion 32 is provided on one of the four surfaces constituting the inner peripheral surface 31 of the tip end case 21a. As shown in an enlarged view in FIG. 4, five pores 37 a to 37 e are opened in the recessed portion 32. In the figure, a pore 37a is formed at the center, and four pores 37b to 37e are opened at 90 ° intervals so as to surround the pore 37a. The diameter of the pores is set to about 1.0 mm to 1.5 mm. The recessed portion 32 is formed by slightly denting the inner peripheral surface 31, and the shape thereof is a front rear circular shape. As shown in FIG. 3, the air permeable film 33 is attached to the concave portion 32 so as to block the pores 37 a to 37 e. As the air permeable film 33, a polytetrafluoroethylene (PTFE) resin porous film is adopted as an example. This porous PTFE resin membrane has hundreds of millions of fine pores per 1 cm ² and exhibits waterproof / dustproof properties and air permeability at the same time. Furthermore, this porous PTFE resin membrane has excellent characteristics such as water repellency, heat resistance, chemical resistance, weather resistance, electrical properties, etc., and is extremely useful for exhibiting gas permeability, water vapor permeability, and waterproofness. It is suitable for. Specifically, for example, Microtex (registered trademark) manufactured by NITTO DENKO can be employed.

  An example of another application mode of the breathable film is shown in FIGS. In this example, a circular recessed portion 35 is provided on the outer peripheral surface 34 of the tip end case 21a, and as shown in FIG. 38e is opened. And the air permeable film 36 is stuck on it so that each pore 38a-38e in this recessed part 35 may be plugged up.

  In the method of sticking the air permeable film 33 shown in FIG. 3 and FIG. 4 to the inner peripheral surface 31, the air permeable film 33 cannot be seen from the outside hidden inside the case 21a. There are no advantages. On the other hand, in the case where the breathable film 36 is attached to the outer peripheral surface 34 of the case 21a shown in FIGS. 5 and 6, the appearance is slightly impaired, but the water is washed in the food production line. In addition, since the water pressure acts in a direction in which the air permeable film 36 is pressed against the outer peripheral surface 34 of the case, there is an advantage that the air permeable film 36 is hardly peeled off. In particular, in the example shown in FIG. 6, the recessed portion 35 is circular, and the air-permeable film 36 is firmly fitted into the inside, so that there is an advantage that it is less likely to be peeled off even by water discharge cleaning.

  Since the present invention has the above-described configuration, as shown in FIG. 7, the breathable films 33 and 36 are disposed between the transparent window plate 22a and the heating element H and in positions close to the transparent window plate 22a. Therefore, the inflowing air A1 and the outflowing air A2 freely pass through this, so that the temperature of the gas on the inner surface of the transparent window plate 22a gradually decreases, and the difference in temperature between the inside and outside of the transparent window plate is eliminated. It is possible to prevent the water droplets W1 and W2 from adhering to the inner surface of the 22a and so-called dew condensation. In FIG. 7, it seems that the water droplets W1 and W2 are condensed on the inner surface of the transparent window plate 22a, but it is the operational effect of the present invention that there is no such condensation.

  Since the present invention has the above-described configuration and operational effects, it maintains sufficient waterproofness even under the practice of the European food industry, which is washed out with water particularly when the work is completed for one day. However, since the condensation of the transparent window plate can be prevented, the unclearness of the photographed image due to the condensation and fogging of the transparent window plate eliminates the problems such as measurement errors and measurement impossibility, and always clear images. Therefore, the durability or reliability of this type of visual sensor can be remarkably improved.

1 is an external perspective view of an entire visual sensor to which the present invention is applied. It is the perspective view seen from the diagonal front of the sensor head part. It is explanatory drawing (the 1) of the sticking aspect of a breathable film. It is an enlarged view (the 1) of the pore in a recessed part. It is explanatory drawing (the 2) of the sticking aspect of a breathable film. It is an enlarged view (the 2) of the pore in a recessed part. It is operation | movement explanatory drawing of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Amplifier part 2 Sensor head part 11 Case 12 Image display 13 Operation part cover 14 DIN rail mounting groove 15 Receptacle 16 Electrical cord 17 Connection connector cover 21 Case 21a Body part case 21b Tip part case 22 Shooting window 22a Transparent window board 23 Electrical cord 31 Inner peripheral surface 32 Recessed portion 33 Breathable film 34 Outer peripheral surface 35 Recessed portion 36 Breathable film 37a-37e Fine pore 38a-38e Fine pore A1 Inflow air A2 Outflow air D1-D8 Light emitting diode H Heating element M Lens barrel Tip W1, W2 Water drop

Claims (6)

In a waterproof case where a transparent window plate is fitted in the shooting window, a heating element such as a power element or a power supply unit is accommodated.
There between the transparent window plate and the heating element, the case place close to the transparent window plate position has been opened pores of appropriate number communicating casing and out, and they pores passage of water molecules of the liquid A waterproof visual sensor characterized by being blocked by a breathable film having a function of allowing water vapor to pass therethrough.   The waterproof visual sensor according to claim 1, wherein the waterproof case is a case of a sensor head portion of an amplifier-separated visual sensor.   The waterproof visual sensor according to claim 1, wherein an appropriate number of pores are provided on a side surface of the case close to the transparent window plate.   The waterproof visual sensor according to any one of claims 1 to 3, wherein a breathable film is attached to the inner surface of the case so as to cover the pores.   The waterproof visual sensor according to any one of claims 1 to 3, wherein a breathable film is attached to the outer surface of the case so as to cover the pores.   The waterproof visual sensor according to claim 1, wherein the breathable film is a polytetrafluoroethylene resin porous membrane.

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