Abstract:
A lubricant deterioration sensor mounted in a machine to detect deterioration of a lubricant of the machine, the sensor comprising a white LED for emanating white light, an RGB sensor that detects colors of received light, a clearance forming member in which an oil clearance for intrusion of the lubricant is formed, and a support member that supports the white LED, the RGB sensor, and the clearance forming member; and wherein the clearance forming member allows passage of the light emitted from the white LED, and the oil clearance is placed along an optical path from the white LED to the RGB sensor.

Description:
TECHNICAL FIELD 
     The invention relates to an optical sensor for detecting deterioration of a machine lubricant. 
     BACKGROUND ART 
     As a lubricant deterioration sensor, an oil deterioration sensor in which an oil intrusion clearance for intrusion of a lubricant is formed on an optical path from an infrared LED (Light Emitting Diode) to a photodiode has been known. The oil deterioration sensor detects an amount of light which exits from the infrared LED and is absorbed by the lubricant in the oil intrusion clearance based on an amount of light received by the photodiode, and determines a degree of deterioration of the lubricant that correlates to the detected amount of absorbed light (see; for instance, Patent Documents 1 and 2). 
     However, the oil deterioration sensor described in Patent Documents 1 and 2 can detect a concentration of insoluble substance in the lubricant as a degree of deterioration of the lubricant but has a problem that types of contaminants in the lubricant can not be specified. 
     As a technique for specifying a type of contaminant in a lubricant, a technique in which a light is irradiated to a membrane filter by an LED after filtration of a lubricant is known. In the technique, a light reflected from contaminants on the membrane filer is converted by a light receiving element into RGB digital values, and types of the contaminants in the lubricant are specified according to the converted RGB digital values (see; for instance, Non-Patent Documents 1 and 2). 
     CITATION LIST 
     Patent Documents 
     Patent Document 1: JP-A-7-146233 
     Patent Document 2: JP-A-10-104160 
     Non-Patent Document 1: Tomohiko YAMAGUCHI, four others, “Method for determining hues of contaminants in a lubricant,” Engineering Department of Fukui University, Study Report March 2003, Vol. 51, No. 1, pp. 81 to 88. 
     Non-Patent Document 2: Tomonori HONDA, “Technique for diagnosing and inspecting deterioration of a lubricant,” Academic Journal of Precision Engineering, 2009, Vo. 75, No. 3, pp. 359-362 
     SUMMARY OF INVENTION 
     Technical Problem 
     However, in the techniques described in Non-Patent Documents 1 and 2, it is needed to sample a lubricant from a machine and to filter the sample by a membrane filter. Accordingly, the techniques have a problem that an instancy is inferior. 
     Accordingly, an object of the present invention is to provide a lubricant deterioration sensor capable of instantly specifying types of contaminants in a lubricant of a machine. 
     Solution to Problem 
     An optical sensor, comprising: 
     a light emitting element for emanating light; 
     a light receiving element for detecting the light, disposed adjacent to the light emitting element; 
     a clearance forming member forming a fluid clearance in which a fluid enters; 
     a support member supporting the light emitting element, the light receiving element and the clearance forming member; 
     an optical path surrounding member, wherein 
     the clearance forming member is transmissive so that the light emitted from the light emitting element, 
     the fluid clearance is provided on an optical path from the light emitting element to the light receiving element, and 
     the optical path surrounding member surrounds at least a portion of the optical path. 
     By means of the configuration, the optical sensor of the invention detects colors from light of, among white light rays emitted from the white light emitting element, wavelengths that are not absorbed by contaminants in the fluid at the fluid clearance by use of the color light receiving element, so that colors of the contaminants in the fluid of the machine can be instantly detected. In other words, the optical sensor of the invention can instantly specify, on the basis of the colors detected by the color light receiving element, types of contaminants in the fluid of the machine. Further, the optical path surrounding member covers the optical path so as to suppress effects by disturbance, thus the detection accuracy can be improved. 
     In the lubricant deterioration sensor according to the present invention, 
     a space provided on the optical path between the light emitting element and the clearance forming member may be formed by a hole, and 
     a space provided on the optical path between the light receiving element and the clearance forming member may be formed by a hole. 
     By means of the configuration, the optical path can be prevented from occurring a diffused reflection, thus the detection accuracy can be improved. 
     In the lubricant deterioration sensor according to the present invention, 
     the light emitting element and the light receiving element may be accommodated in the optical path surrounding member at a position opposite to the clearance forming member. By means of the configuration, the light emitting element and the light receiving element can be protected from being affected from the thermal of the fluid, thus the detection accuracy can be improved. 
     In the lubricant deterioration sensor according to the present invention, the clearance forming member may have two rectangular prisms each of which has the reflection surface for bending the optical path, so that the optical path is bent by the reflection surfaces of the two rectangular prisms, and the oil clearance may be formed between the two rectangular prisms. 
     The configuration makes it possible to miniaturize the lubricant deterioration sensor of the invention by means of a simple configuration including a smaller number of parts. 
     The lubricant deterioration sensor according to the present invention may further include a screw portion configured to fix the optical sensor to a mating member, wherein the optical path surrounding member is disposed inside of the screw portion. 
     By means of the configuration, the configuration makes it possible to miniaturize the lubricant deterioration sensor of the invention by means of a simple configuration including a smaller number of parts 
     In the lubricant deterioration sensor according to the present invention, 
     a width of a space on the optical path between the light emitting element and the clearance forming member at a side of the clearance forming member may be shorter than a width of the space at a side of the light emitting element, and 
     the optical path between the light emitting element and the clearance forming member and the optical path between the light receiving element and the clearance forming member may extend in a direction in which the optical sensor is inserted to a mating member. 
     By means of the configuration, the activity for assembling can be improved. 
     In the lubricant deterioration sensor according to the present invention, a groove surrounding an opening of a space on the optical path between the light emitting element and the clearance forming member may be formed on a surface of the supporting member to which the clearance forming member is attached. By means of the configuration, the adhesive for attaching the clearance forming member can be prevented from irrupting into the space on the optical path. 
     An optical sensor, comprising: 
     a light emitting element that emits a light; 
     a light receiving element that detects the light; 
     a transmissive part that includes an incident surface to which the light is incident from the light emitting element and an exit surface from which the light incident on the incident surface, and defines a gap, into which a lubricant enters, in an optical path from the incident surface to the exit surface; and 
     a first narrowing part that narrows the optical path from the light emitting element to the incident surface. 
     The first narrowing part may include a first part defining a first hole in which the light emitting element is accommodated; and a second part defining a second hole which communicates the first hole with the incident surface and has a first narrowed portion, and an area of the optical path in the first narrowed portion may be smaller than an area of the optical path in the first hole. 
     The optical sensor may further comprise a second narrowing part that narrows the optical path from the exit surface to the light receiving element. 
     The second narrowing part may include a third part defining a third hole in which the light receiving element is accommodated; and a fourth part defining a fourth hole which communicates the third hole with the exit surface and has a second narrowed portion. An area of the optical path in the second narrowed portion may be smaller than an area of the optical path in the third hole. 
     The optical sensor may be configured such that: 
     the transmissive part includes a first rectangular prism and a second rectangular prism, 
     the first rectangular prism has:
         a first incident surface which is the incident suface;   a first exit surface orthogonal to the first incident surface;   a first reflection surface which is an inclined surface with respect to an apex angle being right angle and which bends the optical path of the light incident on the first incident surface;   a pair of first side surfaces which sandwitch the first incident surface, the first exit surface and the first reflection surface,       

     the second rectangular prism has:
         a second incident surface which opposes the first exit surface;   a second exit surface which is orthogonal to the second incident surface and which is the exit surface;   a second reflection surface which is an inclined surface with respect to an apex angle being right angle and which bends the optical path of the light incident on the second incident surface;   a pair of first side surfaces which sandwitch the first incident surface, the first exit surface and the first reflection surface,       

     at least one of the first rectangular prism and the second rectangular prism is an object to be fixed, 
     the optical sensor includes a wall to which a surface including the side surfaces is fixed, in the object to be fixed. 
     The optical sensor may further comprise a supporting member which supports the light emitting element, the light receiving element and the transmissive part. The supporting member may include the first narrowing part. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a front view of a lubricant deterioration sensor of one embodiment of the invention. 
         FIG. 2  is a front cross sectional view of the lubricant deterioration sensor shown in  FIG. 1 . 
         FIG. 3A  it is a front view of a support member shown in  FIG. 1 , and  FIG. 3B  is a front cross sectional view of the support member shown in  FIG. 1 . 
         FIG. 4A  it is a side view of the support member shown in  FIG. 1 , and  FIG. 4B  is a side cross sectional view of the support member shown in  FIG. 1 . 
         FIG. 5A  is a plan view of the support member shown in  FIG. 1 , and  FIG. 5B  is a bottom view of the support member shown in  FIG. 1 . 
         FIG. 6A  is a front view of a holder shown in  FIG. 1 , and  FIG. 6B  is a front cross sectional view of the holder shown in  FIG. 1 . 
         FIG. 7A  is a side view of the holder shown in  FIG. 1 , and  FIG. 7B  is a side cross sectional view of the holder shown in  FIG. 1 . 
         FIG. 8A  is a plan view of the holder shown in  FIG. 1 , and  FIG. 8B  is a bottom view of the holder shown in  FIG. 1 . 
         FIG. 9  is a view showing an optical path from a white LED to an RGB sensor shown in  FIG. 2 . 
         FIG. 10A  is a front cross sectional view of a cover shown in  FIG. 1 , and  FIG. 10B  is a side cross sectional view of the cover shown in  FIG. 1 . 
         FIG. 11A  is a plan view of the cover shown in  FIG. 1 , and  FIG. 11B  is a bottom view of the cover shown in  FIG. 1 . 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     An embodiment of the invention is hereunder described by reference to the drawings. 
     First, a configuration of a lubricant deterioration sensor of the embodiment is described. 
       FIG. 1  is a front view of an optical sensor  10  of the embodiment.  FIG. 2  is a front cross sectional view of the lubricant deterioration sensor  10  mounted in a machine  90 . In this embodiment, the optical sensor is used as a lubricant deterioration sensor  10 . 
     As shown in  FIGS. 1 and 2 , the lubricant deterioration sensor  10  is an apparatus for detecting deterioration of a lubricant  91  of the machine  90  mounted in the machine  90 . Although in the present embodiment this sensor  10  is used for the oil or the lubricant as an example, the sensor  10  can be used for any other fluid. 
     The lubricant deterioration sensor  10  includes a support member  20  that is made of an aluminum alloy for supporting respective parts of the lubricant deterioration sensor  10 , a holder  30  that is secured to the support member  20  with a screw  11  and that is made of an aluminum alloy; a clearance forming member  40  that is retained by the holder  30 , an electronic parts group  50  outfitted with a circuit board  51  that is secured to the support member  20  with screws  12 , and a cover  60  that is secured to the support member  20  with a screw  13  and that is made of an aluminum alloy. 
     The clearance forming member  40  is made up of two rectangular glass prisms  41  and  42 , and an oil clearance  40 a that is a clearance for intrusion of the lubricant  91  is formed between the two rectangular prisms  41  and  42 . 
     The electronic parts group  50  includes a white LED  52  mounted on the circuit board  51 , an RGB sensor  53  mounted on the circuit board  51 , a circuit board  54  placed opposite the white LED  52  and the RGB sensor  53  with reference to the circuit board  51 , a plurality of columns  55  for anchoring the circuit board  51  and the circuit board  54 , a circuit board  56  placed opposite the circuit board  51  with reference to the circuit board  54 , a plurality of columns  57  for securing the circuit board  54  and the circuit board  56 ; and a connector  58  mounted opposite the circuit board  54  with reference to the circuit board  56 . A plurality of electronic parts are mounted on the circuit board  51 , the circuit board  54 , and the circuit board  56 . Further, the circuit board  51 , the circuit board  54 , and the circuit board  56  are electrically connected to each other. 
     The lubricant deterioration sensor  10  is equipped with an O ring  14  for preventing leakage of the lubricant  91  from a clearance between the support member  20  and the machine  90  and an O ring  15  for preventing leakage of the lubricant  91  from a clearance between the support member  20  and the holder  30 . 
       FIG. 3A  is a front view of the support member  20 .  FIG. 3B  is a front cross sectional view of the support member  20 .  FIG. 4A  is a side view of the support member  20 .  FIG. 4B  is a side cross sectional view of the support member  20 .  FIG. 5A  is a plan view of the support member  20 .  FIG. 5B  is a bottom view of the support member  20 . 
     As shown in  FIGS. 1 to 5B , the support member  20  includes a screw section  21  secured to a tapped hole  90   a  of the machine  90 , a hexagonal tool contact  22  that is to be gripped with a tool when the screw section  21  is rotated with respect to the tapped hole  90   a  of the machine  90 , and a holder housing section  23  for housing the holder  30 . Moreover, the support member  20  are formed with a hole  24  for insertion of the white LED  52 , a hole  25  for insertion of the RGB sensor  53 , two holes  26  for insertion of the screw  11 , two tapped holes  27  for insertion of the screws  12 , and two tapped holes  28  for insertion of the screw  13 . 
     The support member  20  supports the white LED  52  and the RGB sensor  53  by way of the circuit board  51 . The support member  20  supports the clearance forming member  40  by way of the holder  30 . 
       FIG. 6A  is a front view of the holder  30 .  FIG. 6B  is a front cross sectional view of the holder  30 .  FIG. 7A  is a side view of the holder  30 .  FIG. 7B  is a side cross sectional view of the holder  30 .  FIG. 8A  is a plan view of the holder  30 .  FIG. 8B  is a bottom view of the holder  30 .  FIG. 9  is a view showing an optical path  10   a  from the white LED  52  to the RGB sensor  53 . 
     As shown in  FIGS. 1 and 2  and  FIGS. 6A to 9 , the holder  30  includes a prism housing  31  that houses the rectangular prism  41 , a prism housing  32  that houses the rectangular prism  42 , and an LED housing  33  that houses the white LED  52 . The holder  30  are formed with a hole  34  for the RGB sensor  53 , a hole  35  that establishes mutual communication between the prism housing  31  and the LED housing  33 , a hole  36  that establishes mutual communication between the prism housing  32  and the hole  34 , two tapped holes  37  for screw-engagement of the screw  11 , a groove  38  to which the O ring  15  fits, an annular groove  39   a  for preventing an adhesive which fixes the rectangular prism  41  to the prism housing  31  from entering the hole  35 , and an annular groove  39   b  for preventing an adhesive which fixes the rectangular prism  42  to the prism housing  32  from entering the hole  36 . The grooves  39   a ,  39   b  for preventing the adhesive from entering the holes  35 ,  36  may be provided on the support member  20 . 
     The prism housing  31  includes two walls  31   a  between which the rectangular prism  41  is to be inserted. The walls  31   a  fix the rectangular prism  41  by means of an adhesive. The prism housing  32  includes two walls  32   a  between which the rectangular prism  42  is to be inserted. The walls  32   a  fix the rectangular prism  42  by means of an adhesive. 
     The holder  30  surrounds at least a portion of the optical path  10   a  from the white LED  52  to the RGB sensor  53  by means of the LED housing  33 , the hole  35 , the prism housing  31 , the prism housing  32 , the hole  36 , the hole  34 , making up an optical path surrounding member of the invention. The grooves  39   a ,  39   b  for preventing the adhesive from entering the holes  35 ,  36  may be provided on the optical path surrounding member. 
     A surface of the holder  30  is treated by antireflection; for instance, mat black anodized aluminum treatment. 
     As shown in  FIG. 9 , the oil clearance  40   a  of the clearance forming member  40  is placed on the optical path  10   a  from the white LED  52  to the RGB sensor  53 . 
     The rectangular prisms  41  and  42  are transmissive so that light emitted from the white LED  52  transmits therethrough. The rectangular prism  41  has an incident surface  41   a  on which light emitted by the white LED  52  falls, a reflection surface  41   b  that reflects the light fell on the incident surface  41   a , to thus make a 90-degree turn of a traveling direction of light, and an exit surface  41   c  from which the light reflected by the reflection surface  41   b  exits. The rectangular prism  42  has an incident surface  42   a  on which light exited from the exit surface  41   c  of the rectangular prism  41  falls, a reflection surface  42   b  that reflects the light fell on the incident surface  42   a , to thus make a 90-degree turn of a traveling direction of light, and an exit surface  42   c  from which the light reflected by the reflection surface  42   b  exits. 
     The incident surface  41   a , the reflection surface  41   b , and the exit surface  41   c  of the rectangular prism  41 , and the incident surface  42   a , the reflection surface  42   b , and the exit surface  42   c  of the rectangular prism  42  are optically polished. The reflection surface  41   b  of the rectangular prism  41  and the reflection surface  42   b  of the rectangular prism  42  each are covered with an aluminum evaporated film. In order to protect the aluminum evaporated film that has a low degree of hardness and adhesion, the aluminum evaporated film is further coated with an SiO 2  film. 
     The optical path  10   a  is bent at 90-degree angle on the reflection surface  41   b  of the rectangular prism  41 , further is bent at 90-degree angle also on the reflection surface  42   b  of the rectangular prism  42 . To be specific, the optical path  10   a  is bent at 180 degrees angle by the clearance forming member  40 . 
     A distance between the exit surface  41   c  of the rectangular prism  41  and the incident surface  42   a  of the rectangular prism  42  is a length of the oil clearance  40   a . The length of the oil clearance  40   a  is 1 millimeter for instance. When the length of the oil clearance  40   a  is too short, contaminants in the lubricant  91  become difficult to flow through the oil clearance  40   a  appropriately, so that a degree of detection accuracy of a color of the contaminants in the lubricant  91  deteriorates. In the meantime, when the length of the oil clearance  40   a  is too long, light emitted from the white LED  52  is too absorbed by the contaminants in the lubricant  91  in the oil clearance  40   a  to reach the RGB sensor  53 , so that the degree of detection accuracy of the color of the contaminants in the lubricant  91  also deteriorates. Consequently, it is preferable that the length of the oil clearance  40   a  be appropriately set such that the degree of detection accuracy of the color of the contaminants in the lubricant  91  improves. 
     The white LED  52  is an electronic part that emits white light and makes up a light emitting element of the invention. For instance, NSPW500GS-K1 manufactured by Nichia Corporation, can be used as the white LED  52 . Although in the present embodiment the white LED  52  is used as the light emitting element, the light emitting element can be any other light emitting device. The light emitted by the light emitting element is preferably visible light, but may be light having wavelength other than the visible light. 
     The RGB sensor  53  is an electronic part that detects a color of received light and makes up a color light receiving element of the invention. For instance, S9032-02 manufactured by Hamamatsu Photonics K.K. can be used as the RGB sensor  53 . 
     As shown in  FIG. 2 , the connector  58  is connected to a connector  59  of an external device of the lubricant deterioration sensor  139   a  and is fed with electric power from the external device by way of a connector  95 . A detection result of the lubricant deterioration sensor  10  is output to the external device as an electric signal by way of the connector  95 . 
       FIG. 10A  is a front cross sectional view of the cover  60 .  FIG. 10B  is a side cross sectional view of the cover  60 .  FIG. 11A  is a plan view of the cover  60 .  FIG. 11B  is a bottom view of the cover  60 . 
     As shown in  FIGS. 1, 2, 10A to 11B , the cover  60  has a hole  61  for insertion of the connector  58  and two holes  62  for insertion of the screw  13 . 
     A surface of the cover  60  is treated by antireflection; for instance, mat black anodized aluminum treatment. 
     The optical sensor  10  includes a first narrowing part that narrows the optical path  10   a  from the light emitting element  52  to the incident surface  41   a.    
     The first narrowing part includes a first part defining a first hole in which the light emitting element  52  is accommodated, a second part defining a second hole which communicates the first hole with the incident surface  41   a  and has a first narrowed portion. An area of the optical path  10   a  in the first narrowed portion is smaller than an area of the optical path  10   a  in the first hole. 
     The optical sensor  10  includes a second narrowing part that narrows the optical path  10   a  from the exit surface  42   c  to the light receiving element  53 . 
     The second narrowing part includes a third part defining a third hole in which the light receiving element  53  is accommodated, and a fourth part defining a fourth hole which communicates the third hole with the exit surface  42   c  and has a second narrowed portion. An area of the optical path  10   a  in the second narrowed portion is smaller than an area of the optical path  10   a  in the third hole. 
     The first rectangular prism  41  has a first incident surface which is the incident surface  41   a , a first exit surface  41   c  orthogonal to the first incident surface  41   a , a first reflection surface  41   b  which is an inclined surface with respect to an apex angle being right angle and which bends the optical path  10   a  of the light incident on the first incident surface  41   a , a pair of first side surfaces which sandwich the first incident surface  41   a , the first exit surface  41   c  and the first reflection surface  41   b.    
     The second rectangular prism  42  has a second incident surface  42   a  which opposes the first exit surface  41   c , a second exit surface  42   c  which is orthogonal to the second incident surface  42   a  and which is the exit surface  42   c , a second reflection surface  42   b  which is an inclined surface with respect to an apex angle being right angle and which bends the optical path  10   a  of the light incident on the second incident surface  42   a , a pair of second side surfaces which sandwich the second incident surface  42   a , the second exit surface  42   c  and the second reflection surface  42   b.    
     At least one of the first rectangular prism  41  and the second rectangular prism  42  is an object to be fixed. The optical sensor  10  includes a wall to which a surface including the side surfaces is fixed, in the object to be fixed. 
     The support member  20  which supports the light emitting element  52 , the light receiving element  53  and the transmissive part  41 ,  42 . The support member  20  includes the first narrowing part. 
     Next, a method for assembling the lubricant deterioration sensor  10  is described. 
     First, an adhesive is applied to two surfaces of the surfaces of the rectangular prism  41  that contact the two walls  31   a  of the prism housing  31  as well as to an outer peripheral surface of the groove  39   a  that contacts the incident surface  41   a  of the rectangular prism  41  of the prism housing  31  of the holder  30 , whereby the rectangular prism  41  is secured to the prism housing  31  by means of the adhesive. In addition, an adhesive is applied to two surfaces of the surfaces of the rectangular prism  42  that contact the two walls  32   a  of the prism housing  32  as well as to an outer peripheral surface of the groove  39   b  which contacts the exit surface  42   c  of the rectangular prism  42  of the prism housing  32  of the holder  30 , whereby the rectangular prism  42  is secured to the prism housing  32  by means of the adhesive. Further, the white LED  52  is secured to the LED housing  33  of the holder  30  by means of the adhesive. 
     Next, the holder  30  outfitted with the O ring  15  is secured, by means of the screw  11 , to the holder housing  23  of the support member  20  outfitted with the O ring  14 . 
     The electronic parts group  50  into which various electronic parts except the white LED  52 ; namely, the circuit board  51 , the RGB sensor  53 , and the connector  58 , are previously assembled is secured to the support member  20  by the screws  12 , thereby the white LED  52  is soldered to the circuit board  51 . 
     Finally, the cover  60  is secured to the support member  20  by the screw  13 . 
     A method for mounting the lubricant deterioration sensor  10  to the machine  90  is now described. 
     First, the tool contact  22  of the support member  20  is pinched with a tool, and the screw  21  of the support member  20  is screwed into the tapped hole  90   a  of the machine  90 , whereby the lubricant deterioration sensor  10  is secured to the machine  90 . 
     The connector  95  of an external device of the lubricant deterioration sensor  10  is connected to the connector  58 . 
     Next, operation of the lubricant deterioration sensor  10  is described. 
     In the lubricant deterioration sensor  10 , white light is emitted from the white LED  52  by means of the electric power fed from an external device by way of the connector  58 . 
     The lubricant deterioration sensor  10  outputs amounts of RGB colors of light received by the RGB sensor  53  as an electric signal to an external device by way of the connector  58 . 
     The lubricant deterioration sensor  10  can also be separately equipped with a sensor other than the RGB sensor  53 . For instance, when a temperature sensor for detecting a temperature of the lubricant  91  is included in the electronic parts group  50 , the lubricant deterioration sensor  10  can output a temperature detected by the temperature sensor to an external device as an electric signal by way of the connector  58 . 
     As described above, the lubricant deterioration sensor  10  detects colors from light of, among white light rays emitted from the white LED  52 , wavelengths that are not absorbed by contaminants in the lubricant  91  in the oil clearance  40   a  by use of the RGB sensor  53 , so that colors of the contaminants in the lubricant  91  of the machine  91  can be instantly detected. In other words, the lubricant deterioration sensor can instantly specify, on the basis of the colors detected by the RGB sensor  53 , types and amounts of contaminants in the lubricant  91  of the machine  90  by use of an external device, like a computer. Incidentally, the lubricant deterioration sensor  10 , electronic parts that specify types and amounts of contaminants in the lubricant  91  of the machine  90  from the colors detected by the RGB sensor  53  can also be included in the electronic parts group  50 . 
     In the lubricant deterioration sensor  10 , the reflection surfaces  41   b  and  42   b  for refracting the optical path  10   a  are formed on the clearance forming member  40 . Therefore, when compared with the configuration in which the optical path  10   a  from the white LED  52  to the RGB sensor  53  is straightforward, the entirety of the sensor can be miniaturized by placing the white LED  52  and the RGB sensor  53  in close proximity to each other. Further, in the lubricant deterioration sensor  10 , the clearance forming member  40  plays the role of bending the optical path  10   a  as well as the role of forming the oil clearance  40   a . Hence, when compared with a configuration separately provided with a member for refracting the optical path  10   a  instead of the clearance forming member  40 , the number of parts can be curtailed. 
     In particular, in the lubricant deterioration sensor  10 , the clearance forming member  40  is made up of the two rectangular prisms  41  and  42  on which there are formed the reflection surfaces  41   b  and  42   b  for effecting 90-degree refraction of the optical path  10   a . The optical path  10   a  is subjected to 180-degree refraction by means of the reflection surfaces  41   b  and  42   b  of the two rectangular prisms  41  and  42 , and the oil clearance  40   a  is formed between the two rectangular prisms  41  and  42 . Hence, the lubricant deterioration sensor can be miniaturized by means of a simple configuration that includes a smaller number of parts. 
     Further, the lubricant deterioration sensor  10  is equipped with the holder  30  that surrounds at least a portion of the optical path  10   a . The surface of the holder  30  is treated with antireflection processing. Hence, the RGB sensor  53  can be prevented from experiencing unwanted reflected light. Consequently, when compared with the configuration in which the RGB sensor  53  experiences unwanted reflected light, the lubricant deterioration sensor  10  can enhance the detection accuracy of colors of contaminants in the lubricant  91 . 
     In the lubricant deterioration sensor  10 , the surfaces of the clearance forming member  40  that form the oil clearance  40   a ; namely, the exit surface  41   c  of the rectangular prism  41  and the incident surface  42   a  of the rectangular prism  42 , can also be treated with oil repellent treatment. In the lubricant deterioration sensor  10 , when the exit surface  41   c  of the rectangular prism  41  and the incident surface  42   a  of the rectangular prism  42  are given oil repellent treatment, the exit surface  41   c  of the rectangular prism  31  and the incident surface  42   a  of the rectangular prism  42  are less susceptible to stains. Therefore a decrease in detection accuracy of colors of contaminants in the lubricant  91 , which would otherwise be caused by stains, can be prevented. 
     In the lubricant deterioration sensor  10 , the layout of the white LED  52  and the RGB sensor  53  may also be different from that described in the embodiment. For instance, in the lubricant deterioration sensor  10 , the optical path  10   a  from the white LED  52  to the RGB sensor  53  may also be straightforward. 
     In the lubricant deterioration sensor  10 , the optical path  10   a  can also be bended by means of a configuration other than the rectangular prism. 
     For instance, fluorine coating, a transparent silicone resin, and the like, are available as coating that makes it difficult for stains (sludge) in a lubricant to adhere. 
     The patent application is based on Japanese Patent Application JP-2010-269097 (filed on Dec. 2, 2010), the subject matter of which is incorporated herein by reference in its entirety. 
     INDUSTRIAL APPLICABILITY 
     The lubricant deterioration sensor of the invention enables instant specification of types of contaminants in a lubricant of a machine 
     REFERENCE SIGNS LIST 
       10  Lubricant Deterioration Sensor 
       10   a  Optical Path 
       20  Support Member 
       30  Holder (Optical Path Surrounding Member) 
       40  Clearance Forming Member 
       40   a  Oil Clearance 
       41  Rectangular Prism 
       41   b  Reflection Surface 
       41   c  Exit Surface (Surface that makes up Oil Clearance) 
       42  Rectangular Prism 
       42   a  Entrance Surface (Surface that makes up Clearance) 
       42   b  Reflection Surface 
       52  White Led (Light Emitting Element) 
       53  RGB Sensor (Color Receiving Element) 
       90  Machine 
       91  Lubricant