JP3840470B2 - Oil mist detection device - Google Patents

Description

  The present invention relates to a light scattering type oil mist detection device that detects oil mist generated by lubricating oil being heated by bearing overheating or the like in an internal combustion engine, and more particularly to an oil mist detection device that is suitably used in a marine internal combustion engine. Is.

  There are mainly two conventional apparatuses for optically measuring the oil mist concentration, the light transmission absorption type and the light scattering type.

  As shown in FIG. 8, in the light transmission and absorption type, the light emitting element and the light receiving element are opposed to each other with an appropriate distance, and the presence or absence of oil mist between the elements is detected by attenuation of transmitted light due to light absorption. For this reason, the light transmission window is greatly affected by dirt or the like, and may malfunction due to light attenuation due to dirt or the like. For example, assuming that 20% of the maximum received light amount received by the light receiving element from the light emitting element in the normal state is the amount attenuated by the oil mist generated at the maximum, 10% of the received light amount is attenuated by dirt or the like. Even if there is no oil mist, the judging means such as a computer will judge that 50% of the maximum amount of oil mist has occurred. In this way, in the light transmission absorption type, even if it is a little dirt, it malfunctions, more specifically, it recognizes that it has occurred even though oil mist has not occurred and leads to false alarms, so fresh air etc. Regular calibration and maintenance by is indispensable.

  On the other hand, as the light scattering type, as shown in FIG. 9, a method of detecting scattered light from oil mist is considered. In this method, in the absence of oil mist, the light emitted from the light emitting element does not enter the light receiving element in principle. Therefore, the oil mist has some change in sensitivity to dirt on the window. There is a merit that it is hard to be influenced by detection. In other words, even if 5% of the amount of received light is attenuated due to dirt or the like, it is possible to detect that the amount of generated oil mist has decreased by 5%, and the detection judgment will be greatly confused as in the light transmission absorption method described above. Absent. As described above, the light scattering type can exhibit the above-described effects when the space into which the oil mist is introduced is large and the light scattered on the inner wall of the space can be ignored.

  However, if the space into which the oil mist is introduced is small, for example, the light emitting element and the light receiving element cross each other at approximately 90 degrees, so that the scattered light on the inner wall of the space is large in the light receiving element even in the absence of oil mist. Incident light (this is referred to as base light), and the output level due to the base light may fluctuate due to contamination, resulting in malfunction. For example, as shown in FIG. 10, when dirt occurs, the output level (zero point) due to the base light decreases, and therefore even if the output value increases due to scattered light due to oil mist, the sum can reach the alarm level. In some cases, the occurrence of oil mist may be reported. Therefore, conventionally, as shown in Patent Document 1, some corrections are performed using a complicated configuration.

  Furthermore, in any of the systems described above, the light emitting element and the light receiving element must be separated from each other to some extent. Therefore, if they are attached to one casing in advance, the casing becomes larger, and if they are separated, the engine is attached to the engine or the like. In addition to complicated installation, there may be a problem in accuracy of the mounting position between the light emitting element and the light receiving element.

In order to solve such problems, the present inventor has developed a compact hollow casing which is devised so that the light emitting element and the light receiving element can be mounted close to each other, and the hollow casing is installed in the crankcase of the internal combustion engine. A light-scattering oil mist detection device is being developed so that it can be protruded and attached.
Japanese Patent No. 3263805

  However, when installed in a position where it is difficult to receive oil splashes, such as a 2-cycle engine, the above-mentioned ones are less likely to interfere with operation, but they are susceptible to oil splashes during normal operation, such as a 4-cycle engine. When it is attached to the position, the oil splash directly enters the casing, and there is a possibility that the oil mist cannot be normally detected due to the influence.

  Therefore, the present invention has a structure in which oil splashes do not easily enter the casing, and in an environment where a large amount of oil splashes, the structure is simple and the structure is simple, for a long period of time and reliably. The main object of the present invention is to provide a light scattering type oil mist detection device capable of stably detecting oil mist.

That is, the oil mist detection device according to the present invention is disposed so as to face the outside of the casing having the oil mist introduction chamber disposed in the crankcase of the internal combustion engine and the translucent window provided in the oil mist introduction chamber. A light emitting means and a light receiving means, and irradiates light from the light emitting means to a predetermined detection area in the oil mist introduction chamber through the light transmission window, and the irradiation light strikes oil mist existing in the detection area. Oil mist is detected when the light receiving means receives the scattered light generated through the light transmission window, and at least a part of the wall forming the oil mist introduction chamber is opened with a gap. An inner wall through-hole and an outer wall for introducing oil mist into the interior at different positions of the inner wall and the outer wall, which are constituted by the arranged inner and outer walls Has established a hole respectively, between the outer wall through hole and the inner wall through-hole, further establishes flow preventing wall for the oil droplets that have entered from the outer wall through hole is prevented from flowing into the inner wall of the through hole It is characterized by .

In such a case, the oil mist introduction chamber is connected to the outside crankcase through a non-linear path via the inner wall through hole, the gap and the outer wall through hole. It is possible to prevent the splash from entering the oil mist introduction chamber. Moreover, since the introduction and diffusion of the oil mist into the interior is not inhibited at all, it is possible to detect the oil mist normally without the influence of the oil splash. Further, since it is only necessary to provide the outer wall and the inner wall, the structure is simple and the size can be reduced. Furthermore, it is possible to prevent the oil splash that has entered from the outer wall through hole from being transmitted through the outer surface of the inner wall and entering the oil mist introduction chamber from the inner wall through hole.

An oil mist detection device according to the present invention is disposed so as to face an outer side of a casing having an oil mist introduction chamber disposed in a crankcase of an internal combustion engine and a translucent window provided in the oil mist introduction chamber. The light emitting means and the light receiving means are radiated from the light emitting means to the predetermined detection area in the oil mist introduction chamber through the light transmission window, and the irradiation light is applied to the oil mist existing in the detection area. The oil mist is detected by the light receiving means receiving the scattered light generated through the light transmission window, and at least a part of the wall forming the oil mist introduction chamber is opened with a gap. The inner wall through-hole and the outer wall through-hole for introducing the oil mist into the inner wall and the outer wall at different positions from each other. Provided holes respectively, which inner wall through hole and the outer wall through holes, characterized in that configured to overlap partially.
In such a case, the oil mist introduction chamber is connected to the outside crankcase through a non-linear path via the inner wall through hole, gap and outer wall through hole. It is possible to prevent the splash from entering the oil mist introduction chamber. Moreover, since the introduction and diffusion of the oil mist into the interior is not inhibited at all, it is possible to detect the oil mist normally without the influence of the oil splash. Further, since it is only necessary to provide the outer wall and the inner wall, the structure is simple and the size can be reduced. Furthermore, since the oil mist can reach the detection region more directly, the oil mist generated in the crankcase can reach the detection region as soon as possible, and a detection time delay can be prevented.

  As an effective installation position of the inflow prevention wall, it is desirable to provide it between the outer wall through-hole opened upward and the inner wall through-hole located near or below.

  In order to prevent a detection time delay, it is necessary that the oil mist generated in the crankcase reaches the detection region as soon as possible. For this purpose, an outer wall through-hole and an inner wall through-hole opened downward in the vicinity of the detection region are provided so that the penetration of oil droplets that mainly pour down from above is prevented, while the through-holes partially overlap. A configuration in which the oil mist reaches the detection region more directly is preferable.

  In order to make the effect more conspicuous, it is preferable that the inner wall through-hole opened downward in the vicinity of the detection region opens to substantially the side of the detection region.

  The oil droplets that have entered the inside through the outer wall through hole become oil droplets and accumulate in the lower part of the casing. In order to discharge this, it is preferable that the outer wall through hole is provided at least in the lower part of the outer wall. Of course, oil droplets may also enter the inner wall, albeit slightly. For the discharge, it is more preferable to provide an inner wall through hole at the lower portion of the inner wall. Furthermore, it is also effective to form an external discharge path for preventing oil accumulation below the transparent window.

  As a specific embodiment, there can be mentioned one in which the casing has a cylindrical shape, the tip of which protrudes into the crankcase, and is attached so that the axis is horizontal, for example.

  If the oil mist introduction chamber side of the translucent window is covered with an oil repellent film, oil droplets are difficult to adhere even when the oil mist concentration is high and the amount of oil splash is large, and the oil droplets adhered to the translucent window Since the opportunity to detect scattering due to is reduced, more accurate detection can be performed.

  If the oil mist introduction chamber side of the translucent window is covered with an oleophilic film, even if the oil mist concentration is low and the amount of oil splash is large, fogging due to the mist of the translucent window is prevented, and a slight amount of base light It is possible to prevent a false alarm from occurring due to the rise of

  An embodiment of the present invention will be described below with reference to the drawings.

  As shown in FIGS. 1 and 2, the oil mist detection device 1 according to the present embodiment is attached to a crankcase C of a marine diesel engine, for example, and oil generated inside the crankcase C due to bearing overheating or the like. Used to detect mist.

  Specifically, this includes a cylindrical detection portion 11 that is attached to the mounting hole C1 provided in the wall of the crankcase C so as to protrude from the outside so that the tip side protrudes substantially horizontally inside the crankcase C. And a rectangular parallelepiped control unit 12 connected to the base end of the detection unit 11.

  As schematically shown in FIG. 3, the detection unit 11 forms an oil mist introduction chamber 61 configured to be able to introduce and diffuse oil mist inside at the distal end side, and a sensor housing chamber 66 at the proximal end side. The casing 6 is provided. The oil mist introduction chamber 61 and the sensor storage chamber 66 are partitioned by a transparent window W formed of a transparent plate material, and the light emitting means 2 and the light receiving means 3 are disposed at positions facing the transparent window W of the sensor storage chamber 66. They are arranged side by side.

  The light emitting means 2 is, for example, an LED whose light emitting surface is arranged toward the light transmitting window W, and in the present embodiment, a light emitting means 2 that emits light in a wavelength band that matches the particle diameter of oil mist is used. Of course, other light emitting means 2 such as LD (laser diode) may be used. The light receiving means 3 is, for example, a PD (photodiode) whose light receiving surface is arranged toward the light transmitting window W, and outputs an electric signal having a value corresponding to the intensity of light received on the light receiving surface. Of course, other light receiving means such as a CCD may be used.

  The light emitting means 2 and the light receiving means 3 are arranged in parallel so that the optical axis of the light LB to be irradiated and the optical axis of the light LS to be received are substantially parallel to each other. As schematically shown in FIG. 6 are partitioned by a partition plate 43 arranged along the 6 axis 6C. And by the 1st refracting means 41 arrange | positioned between the light emission surface of the light emission means 2, and the translucent window W, the irradiation light LB emitted from the light emission means 2 bends to the light reception means 3, and as shown in FIG. The detection area S set near the central axis 6C of the oil mist introduction chamber 61 is irradiated through the light transmission window W. On the other hand, the scattered light LS generated when the irradiation light LB strikes the oil mist present in the detection region S passes through the light transmission window W and then passes through the light receiving surface of the light receiving means 3 as shown in FIG. It is bent by the second refracting means 42 disposed between the light window W and received by the light receiving means 3. The first refracting means 41 and the second refracting means 42 have a semicircular shape obtained by halving a circular convex lens by a straight line passing through its optical axis (center), and a light shielding member 44 having a thin plate shape is provided in the semicircular shape. It arrange | positions so that it may be inserted | pinched between split surfaces. Further, the inner surface of the front end of the casing 6 is formed in a tapered surface so as to have a conical shape, and even if the scattered light LS enters the front end side of the oil mist introduction chamber 61, it is internally reflected a number of times. And absorbs it (does not reflect as stray light).

  In this way, the scattered light LS received by the light receiving means 3 is converted into a detection signal that is an electrical signal corresponding to the intensity thereof, transmitted to the control unit 12 through a preamplifier circuit, etc., and in an oil mist state A lamp display is displayed. The detection signal can be transmitted to a main control device (not shown) via a cable.

  Therefore, in this embodiment, as shown in FIGS. 4 to 7, the side circumferential portion of the wall body 62 forming the oil mist introduction chamber 61 is composed of an inner wall 63 and an outer wall 64 having a gap 65 therebetween. It has a double wall structure. Then, the inner wall through hole 8 and the outer wall through hole 7 for introducing oil mist into the inner wall 63 and the outer wall 64 at different positions are penetrated in the thickness direction, respectively, and a gap 65 between the through hole and the inner and outer walls is provided. The oil mist can be led out and introduced into the oil mist introduction chamber 61 via the. Here, the mutually different positions include a positional relationship in which a part thereof overlaps in addition to a positional relationship in which the inside is not visible when viewed from the outside, that is, a positional relationship in which there is no overlapping portion.

  Specifically, each through hole will be described in detail below.

  For example, four outer wall through holes 7 are arranged above the center (hereinafter referred to as first outer wall through holes 7 (1)) and four are arranged below the center (of which the tip Two disposed at the central portion are the second outer wall through hole 7 (2), one disposed at the central portion is the third outer wall through hole 7 (3), and one disposed at the proximal end is the fourth outer wall. Through holes 7 (4)).

  The first outer wall through-hole 7 (1) is a circular one provided at an oblique upper portion of the outer wall 64, two at the same position in the axis 6C direction at the distal end and two at the same position in the axis 6C direction at the proximal end. Is arranged.

  The second outer wall through hole 7 (2) is provided at an oblique lower portion of the outer wall 64 and has the same shape as the first outer wall through hole 7 (1). And it arrange | positions directly under the said 1st outer wall through-hole 7 (1) provided in the front-end | tip part.

  The third outer wall through hole 7 (3) is provided at the lowermost part of the outer wall 64, and has a circular shape with a larger diameter than the first outer wall through hole 7 (1).

  The fourth outer wall through-hole 7 (4) has an oval shape extending in the circumferential direction from the lowermost part of the outer wall 64 to the diagonally lower part, and is disposed at the base end of the outer wall 64. The fourth outer wall through hole 7 (4) is provided almost immediately below the third outer wall through hole 7 (3).

  The inner wall through-holes 8 are, for example, four circular ones at the tip (hereinafter referred to as first inner wall through-hole 8 (1)) and one circular one at the base end (hereinafter referred to as second inner wall). (Referred to as a through hole 8 (2)) and one oval shape (hereinafter referred to as a third inner wall through hole 8 (3)).

  The first inner wall through-holes 8 (1) are arranged at a total of four locations, the uppermost part, both sides, and the lowermost part of the inner wall 63, and the first inner wall through-holes 8 (1) Two outer wall through-holes 7 (2) and the axis 6C are at the same position, and are set at different positions in the circumferential direction. These do not overlap at all with the first outer wall through hole 7 (1) and the second outer wall through hole 7 (2).

  The second inner wall through hole 8 (2) is disposed at the uppermost part of the inner wall 63, and is located at the same position in the axis 6C direction as that of the base end portion of the first outer wall through hole 7 (1). Thus, the positions are set at different phases in the circumferential direction. The second inner wall through-hole 8 (2) does not overlap at all with the first through-hole.

  The third inner wall through hole 8 (3) has an oval shape extending in the circumferential direction from the lowermost part of the inner wall 63 to the side, and is closer to the tip than the fourth outer wall through hole 7 (4). It is provided and is configured to partially overlap with the fourth outer wall through-hole 7 (4).

  Further, in this embodiment, the first outer wall through-hole 7 (1), which is the outer wall through-hole 7 that opens upward, and the inner wall through-hole 8 located near or below the first outer wall through-hole 7 enter from the outer wall through-hole 7. An inflow prevention wall 10 is provided to prevent the splashed oil from flowing into the inner wall through hole 8. The inflow prevention wall 10 is a plate-like member that is interposed between the inner surface of the outer wall 64 and the outer surface of the inner wall 63 and closes the gap 65.

  Specifically, between the first outer wall through hole 7 (1) and the first inner wall through hole 8 (1) located on both sides thereof, and the first outer wall through hole 7 (1). ) Between the second inner wall through hole 8 (2) and the third inner wall through hole 8 (3) located on both sides thereof.

  The inflow prevention wall 10 provided between the first outer wall through hole 7 (1) and the first inner wall through hole 8 (1) located at the top of the inner wall 63 is a straight line extending in the direction of the axis 6C. It is plate-shaped. The inflow prevention wall 10 provided between the first outer wall through hole 7 (1) and the first inner wall through hole 8 (1) located on the side of the inner wall 63 is located above the first inner wall through hole 8 (1). In a side view, curved or bent shape, provided with an upper cover portion 10A that covers the side wall and a side cover portion 10B that is suspended from one end of the upper cover portion 10A and covers the side of the first inner wall through hole 8 (1). It is.

  The inflow prevention wall 10 provided between the base end portion of the first outer wall through hole 7 (1) and the second inner wall through hole 8 (2) has a linear plate shape extending in the direction of the axis 6C. is there. The inflow prevention wall 10 provided between the first outer wall through hole 7 (1) and the third inner wall through hole 8 (3) is located above the third inner wall through hole 8 (3). A side view, curved or bent shape provided with an upper cover portion 10A for covering and a side cover portion 10B hanging from one end of the upper cover portion 10A and covering the side of the third inner wall through-hole 8 (3). is there. In this embodiment, the side cover portion 10B extends so as to be continuous with the side cover portion 10B of the inflow preventing wall 10 on the back side so as to completely cover the side edge portion of the third inner wall through-hole 8 (3). It is composed.

  In addition, in this embodiment, the sensor housing chamber 66 and the oil mist introduction chamber 61 in the casing 6 are formed separately from each other for the purpose of assembly and manufacturing, and are connected by fitting them. Oil easily collects below the translucent window W, which is a portion. Therefore, a groove which is the external discharge path 13 is formed in the wall body 62 of this portion and connected to the fourth outer wall through-hole 7 (4) so that the oil can be smoothly drained.

  According to the present embodiment configured as described above, even when a large amount of oil splashes on the upper portion of the casing 6, for example, when priming of the lubricating oil is performed when the engine is started or stopped, the upward outer wall through-hole 7 is used. The oil splash that has entered is blocked by the inflow prevention wall 10 and is discharged from the outer wall through hole 7 provided in the lower part without entering the inner wall through hole 8. Accordingly, it is possible to reliably prevent oil droplets from entering the detection region S. On the other hand, since the oil mist can reach the detection region S via the outer wall through-hole 7, the gap 65, and the inner wall through-hole 8, it is possible to normally detect the oil mist by eliminating the influence of oil splashes. Can do.

  In particular, in this embodiment, as shown in FIGS. 4 to 7, the oil mist is caused by convection and diffusion in the engine, mainly through a fourth outer wall through hole 7 (4) and a third inner wall through hole provided in the lower part of the casing 6. The detection area S is reached via 8 (3). Thus, the fourth outer wall through hole 7 (4) and the third inner wall through hole 8 (3) are provided in the vicinity of the detection region S. In particular, the third inner wall through hole 8 (3) is located on the side of the detection region S. In addition, the oil mist reaches the detection region S more directly from the outside due to the overlap of the long holes, and the detection time does not hinder the oil mist from reaching the detection region S. Delay can be prevented. Moreover, since the outer wall through-hole 7 and the inner wall through-hole 8 are provided in plural at the tip and upper part of the oil mist introduction chamber 61, the oil mist can be replaced efficiently.

  Furthermore, since the fourth outer wall through-hole 7 (4) and the third inner wall through-hole 8 (3) are opened downward, even if oil splashes from above, the oil splash does not enter inside. . The position of the fourth outer wall through-hole 7 (4) and the third inner wall through-hole 8 (3) in the axial direction is slightly different even with respect to a slight amount of oil splashing from below due to rebound, etc. The impact is minimal. In addition, the plate body 10 standing upright on the lower base end side of the third inner wall through-hole 8 (3) in FIG. 4 is a prevention wall C for preventing oil splashing from obliquely downward toward the light-transmitting plate. is there.

  In addition, the area of the third and fourth outer wall through-holes 7 (4) provided at the lowermost part of the outer wall 64 is made larger than the total area of the first outer wall through-holes 7 (1) opening upward, for example. Therefore, oil does not accumulate in the oil mist introduction chamber 61.

  The present invention is not limited to the above embodiments.

  For example, the position, shape, number, and the like of the inner and outer wall through holes are not limited to the above-described embodiment, and the positions may be shifted so that the oil splash does not directly enter the oil mist introduction chamber. The same applies to the inflow prevention wall, and it is particularly preferable that the inflow prevention wall be disposed at a location where there are many oil splashes.

  Of course, the shape, material, and the like of the casing are not limited to the above embodiment.

  Further, for example, in the case of a diesel engine of a medium and high speed four-cycle type, an oil mist detection device is attached at a position where it is easy to receive oil splashes, and the oil mist concentration during normal operation is also high. As an oil mist detection device for high concentration, it is possible to make it difficult to adhere dirt on the light-transmitting window, particularly by covering the optical window with an oil-repellent film. According to this method, the number of baffle plates of the inner wall member can be reduced, and the structure for preventing splashing can be simplified.

  When an oil repellent film is used, the oil mist may condense on the translucent window and cause fogging. This fogging usually causes light scattering on the slight window surface and raises the base light as a disturbance. In the case of a low-speed two-cycle type among diesel engines, an oil mist detection device is attached at a position where it is difficult to receive oil splashes, and the concentration during normal operation is low. Therefore, since the alarm point is also set low, a malfunction may occur due to a slight rise in the base light. Therefore, in this case, in order to prevent this, an oleophilic film may be used as a protective coating for the transparent window. This prevents clouding of the surface due to condensation of oil mist, and enables stable detection of oil mist.

  In addition, the present invention is not limited to the above illustrated example, and various modifications can be made without departing from the spirit of the present invention.

  According to the present invention described in detail above, the oil mist introduction chamber is connected to the outside of the crankcase through a non-linear path via the inner wall through hole, the gap, and the outer wall through hole. It is possible to prevent the generated oil splash from entering the oil mist introduction chamber. Moreover, since the introduction and diffusion of the oil mist into the interior is not inhibited at all, it is possible to detect the oil mist normally without the influence of the oil splash. Further, since it is only necessary to provide the outer wall and the inner wall, the structure is simple and the size can be reduced, and a long-life, easy-to-handle and inexpensive device is possible.

1 is an overall perspective view showing an entire oil mist detection device according to an embodiment of the present invention. Usage state explanatory drawing which shows the usage state of the oil mist detection apparatus in the embodiment. The typical longitudinal end figure which shows the internal structure of the oil mist detection apparatus in the embodiment. The cross-sectional view which shows the structure of the wall body of the oil mist detection apparatus in the embodiment from a front direction. The longitudinal cross-sectional view which shows the structure of the wall body of the oil mist detection apparatus in embodiment of this invention from upper direction. FIG. 5 is a cross-sectional view taken along line A-A ′ in FIG. 4. B-B 'line sectional drawing in FIG. The principle explanatory drawing explaining the detection principle of a light transmissive absorption type oil mist detection apparatus. The principle explanatory drawing explaining the detection principle of a light-scattering type oil mist detection apparatus. The principle explanatory drawing explaining the detection principle of the conventional light scattering type oil mist detection apparatus.

Explanation of symbols

C ... Crankcase 61 ... Oil mist introduction chamber 6 ... Casing W ... Translucent window 2 ... Light emitting means 3 ... Light receiving means S ... Detection area LB ... Irradiation light LS ... scattered light 62 ... wall body 65 ... gap 63 ... inner wall 64 ... outer wall 8 ... inner wall through hole 7 ... outer wall through hole 1 ... oil mist detection device 10 ... Inflow prevention wall 13 ... External discharge path

Claims (9)

A casing having an oil mist introduction chamber disposed in a crankcase of an internal combustion engine, and a light emitting unit and a light receiving unit disposed so as to face an outer side of a translucent window provided in the oil mist introduction chamber. Means for irradiating light to a predetermined detection region in the oil mist introduction chamber through the light transmission window and scattering light generated when the irradiation light hits the oil mist present in the detection region through the light transmission window. The light receiving means detects oil mist by receiving light,
An inner wall for introducing at least a part of a wall body forming the oil mist introduction chamber from an inner wall and an outer wall arranged with a gap and introducing oil mist into the inner wall and the outer wall at different positions. A through hole and an outer wall through hole are provided,
An oil is further provided between the outer wall through-hole and the inner wall through-hole, and an inflow prevention wall for preventing oil droplets entering from the outer wall through-hole from flowing into the inner wall through-hole. Mist detection device. The detection region downward is provided an outer wall through hole and an inner wall through hole is opened in the vicinity, they through hole oil mist detecting apparatus according to claim 1, characterized in that configured to overlap partially. 3. The oil mist detection device according to claim 1, wherein the inflow prevention wall is provided between an outer wall through-hole that opens upward and an inner wall through-hole located near or below the outer wall through-hole. The oil mist detection device according to claim 2 or 3, wherein an inner wall through-hole opened downward in the vicinity of the detection region opens to substantially a side of the detection region. The outer wall through hole, at least the outer wall oil mist detecting apparatus according to claim 1, 2, 3 or 4 wherein is provided in the lower part of the. Oil mist detection apparatus according to claim 1, 2, 3, 4 or 5, wherein forming the external discharge path to prevent oil sump beneath the transparent window in the wall. Casing a cylindrical shape, the tip portions oil mist detecting apparatus according to claim 2, 3, 4, 5 or 6, wherein those mounted to protrude into the crankcase. Oil mist detection apparatus according to claim 1,2,3,4,5,6 or 7, wherein the oil mist introduction chamber side of said light transmitting window is covered with oil repellency film. Oil mist detection apparatus according to claim 1,2,3,4,5,6 or 7, wherein the oil mist introduction chamber side of the light transmitting window covered with a lipophilic film.