Abstract:
A device capable of reducing an erroneous operation with a simple configuration in which, when two or more conductors M 1,  M 2,  M 3  (three of them in FIG. 1) are attracted by three or more magnets  1 a,  1 b,  1 c,  1 d (four of them in FIG. 1), the conductors M 1,  M 2,  M 3  are electrically connected between the respective magnets to bring a series circuit  3  into conduction that causes an electric current Is to flow, whereby an electric signal (voltage) Vs(=V) indicating the detection of the conductors M 1,  M 2,  M 3  is output.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    1. Field of the Invention  
           [0002]    The present invention relates to a conductor detecting device. More specifically, the invention relates to a conductor detecting device which has a simple structure and can reduce erroneous operations.  
           [0003]    2. Description of the Related Art  
           [0004]    A gearbox accommodating gears is filled with a lubricating oil. When the gears are driven, the gears in mesh produce fine particles or fragments as metal powder or metal shards, which are mingled in the lubricating oil.  
           [0005]    A bearing box which accommodates a bearing is also filled with the lubricating oil. When a shaft is driven, fine particles or fragments are produced as metal powder or metal shards from the sliding surfaces of the bearing and the shaft and are mingled in the lubricating oil.  
           [0006]    The fine particles or fragments of the gears may be caught by the normal gears or clog a lubricating oil passage in the bear box, causing an adverse effect. And, when the abrasion or damage of the bearing proceeds, the drive of the shaft is adversely affected.  
           [0007]    Therefore, detection of the metal powder or metal shards mingled in the lubricating oil enables to judge whether a level of abrasion or damage of the gears or bearing has exceeded a prescribed level.  
           [0008]    The gears and bearing are made of metal and are conductors. Accordingly, the gearbox or the bearing box is provided with a metal detecting device for detecting a conductor such as metal powder, metal shards or the like produced due to abrasion or chipping out of the gears or bearing.  
           [0009]    [0009]FIG. 7 is a diagram showing a structure of a conventional metal detecting device  72  which is disposed in a gearbox.  
           [0010]    The metal detecting device  72  is provided with a detecting section  71 . The detecting section  71  is provided with two magnets  70   a ,  70   b , which attract metal powder or metal shard M and are disposed with a space between them so to be electrically insulated. In the detection section  71 , electric current Ix, which indicates the detection of the metal powder or metal shard M, flows through a circuit when the magnets are electrically connected by the metal powder or metal shard M which is attracted by the two magnets  70   a ,  70   b . The current Ix is directly converted into a warning signal and output or processed as accumulated data, output warning signal or the like by an unshown controller. When the warning signal is output, it can be judged that the abrasion or damage of the gears has exceeded a prescribed level.  
           [0011]    When machining to produce the gears, swarf is produced. The swarf often stays on the gear surface even if the gear surface is washed. The swarf adhered to the gear surface is mingled into the lubricating oil.  
           [0012]    Furthermore, when the gearbox is being machined, cuttings are produced as metal powder or metal shards. Such cuttings might remain adhered to the inside surface of the gearbox even if the gearbox interior is washed. Therefore, the cuttings adhered to the inside surface of the gearbox are also mingled into the lubricating oil.  
           [0013]    There is also a possibility that when the bears are being checked for maintenance, a metal foreign material, which is different from the fine particles or fragments of the gears, is externally mingled into the lubricating oil in the gearbox.  
           [0014]    Here, the fine particles or fragments of the gears are attracted by the magnets  70   a ,  70   b  so to electrically connect the magnets, so that the current Ix flows, and the warning signal is output.  
           [0015]    But, the metal detecting device  72  is provided with only one detecting section  71 , so that the current Ix flows and the warning signal is output when the swarf, cuttings or metal foreign material is attracted to the magnets  70   a ,  70   b  to electrically connect the magnets.  
           [0016]    Thus, the metal detecting device  72  had an erroneous operation that a warning signal was output because the current Ix flows when swarf, cuttings or metal foreign material, which is mingled in the same manner as the fine particles or fragments of the gears, is attracted by the magnets  70   a ,  70   b  to electrically connect the magnets.  
           [0017]    For example, Japanese Utility Model Laid-Open Publication No. SHO61-3466 discloses a metal detecting device which is provided with a plurality of detecting sections.  
           [0018]    [0018]FIG. 8 is a diagram showing the metal detecting device described in Japanese Utility Model Laid-Open Publication No. SHO61-3466.  
           [0019]    Metal detecting device  83  of FIG. 8 is configured to have a parallel circuit  82  by disposing a plurality of detecting sections (magnet devices)  81 , each of which has two magnets  80   a ,  80   b  disposed with a space between them to attract metal (magnetic foreign material). According to this metal detecting device  83 , when metal is attracted to any one of the plural detecting sections  81 ,  81 , . . . , the parallel circuit  82  is brought into conduction, and a current indicating the detection of metal flows through the circuit.  
           [0020]    The metal detecting device  83  of FIG. 8 is configured to improve its reliability of metal detection by disposing the plural detecting sections  81 . Therefore, according to this conventional metal detecting device  83 , the swarf, cuttings or metal foreign material, which is mingled in the same manner as the fine particles or fragments of the gears, is detected without fail. Thus, the problem of causing an erroneous operation remains unsolved.  
           [0021]    For example, the conventional metal detecting device  83  can remedy an erroneous operation by incorporating a logical circuit or performing a judging process by inputting output signals of the plural detecting sections  81 ,  81 , . . . , to the controller and, when metal is detected by any one of the plural detecting sections  81 ,  81 , . . . , judging that metal is not detected, and when metal is detected by two or more detecting sections  81 ,  81 , . . . , judging that metal is detected.  
           [0022]    But, addition of the controller to a conventional metal sensor has a disadvantage that the structure become complex and the cost becomes high.  
         SUMMARY OF THE INVENTION  
         [0023]    The present invention has been achieved under the above circumstances, and it is an object of the invention to reduce an erroneous operation by a simple structure.  
           [0024]    To achieve the above object, a first aspect of the invention is directed to a conductor detecting device which detects conductors by attracting the conductors to a plurality of magnets, wherein three or more magnets are disposed with spaces between the respective magnets to configure a series circuit; and the conductors are attracted by the three or more magnets so to be electrically connected between the respective magnets to bring the series circuit into conduction, and an electric signal indicating the detection of the conductors is output.  
           [0025]    The first aspect of the invention will be described with reference to FIG. 1.  
           [0026]    According to the first aspect of the invention, when two or more conductors M 1 , M 2 , M 3  (three conductors in FIG. 1) are attracted to three or more magnets  1   a ,  1   b ,  1   c ,  1   d  (four magnets in FIG. 1), the conductors M 1 , M 2 , M 3  are electrically connected between the respective magnets, and a series circuit  3  is brought into conduction to cause a current Is to flow. Thus, an electric signal (voltage Vs (=V) indicating the detection of the conductors M 1 , M 2 , M 3  is output.  
           [0027]    According to the first aspect of the invention, when two or more conductors are attracted between the three or ore magnets, the series circuit  3  is brought into conduction for the first time to output the electric signal Vs (=V). Therefore, when only one of the mingled swarf, cuttings or metal foreign material is attracted between the magnets, the electric signal Vs (=V) is not output, and when two or more metals are attracted between three or more magnets, the electric signal Is is output, so that an erroneous operation due to the attraction of one foreign material or the line is not caused.  
           [0028]    By disposing the three or more magnets  1   a ,  1   b ,  1   c ,  1   d  with a space between them to configure the series circuit  3 , an erroneous operation can be prevented, and addition of a controller to a metal sensor is not needed unlike a conventional art, so that the structure can be made simple, and the cost can be reduced.  
           [0029]    A second aspect of the invention relates to the first aspect of the invention, wherein the three or more magnets are arranged around the outer periphery of a rod member.  
           [0030]    The second aspect of the invention will be described with reference to FIG. 2.  
           [0031]    According to the second aspect of the invention, the three or more magnets  1   a ,  1   b ,  1   c ,  1   d  are arranged around the outer periphery of the rod member  20 .  
           [0032]    A third aspect of the invention relates to the first aspect of the invention, wherein the three or more magnets are arranged concentrically.  
           [0033]    The third aspect of the invention will be described with reference to FIGS.  4 ( a ), ( b ).  
           [0034]    According to the third aspect of the invention, three or more magnets  40   a ,  40   b ,  40   c  are arranged concentrically.  
           [0035]    A fourth aspect of the invention relates to the first aspect of the invention, wherein the three or more magnets are arranged in a circumferential direction.  
           [0036]    The fourth aspect of the invention will be described with reference to FIG. 5.  
           [0037]    According to the fourth aspect of the invention, three or more magnets  50   a ,  50   b ,  50   d ,  50   d  are arranged in a circumferential direction.  
           [0038]    A fifth aspect of the invention relates to the first aspect of the invention, wherein the three or more magnets are arranged in parallel.  
           [0039]    The fifth aspect of the invention will be described with reference to FIG. 6.  
           [0040]    According to the fifth aspect of the invention, three or more magnets  60   a ,  60   b ,  60   c  are arranged in parallel. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0041]    [0041]FIG. 1 is an electric circuit diagram showing an embodiment of the present invention;  
         [0042]    [0042]FIG. 2 is a diagram showing a first layout example of magnets of FIG. 1;  
         [0043]    [0043]FIG. 3 is a diagram showing a state that a monitoring voltage varies according to a duration elapsed after driving equipment;  
         [0044]    FIGS.  4 ( a ) and  4 ( b ) are diagrams showing a second layout example of the magnets of FIG. 1;  
         [0045]    [0045]FIG. 5 is a diagram showing a third layout example of the magnets of FIG. 1;  
         [0046]    [0046]FIG. 6 is a diagram showing a fourth layout example of the magnets of FIG. 1;  
         [0047]    [0047]FIG. 7 is a diagram showing a conventional art; and  
         [0048]    [0048]FIG. 8 is a diagram showing a conventional art different from FIG. 7. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0049]    Now, embodiments of the conductor detecting device to which the present invention pertains will be described with reference to the accompanying drawings. It is assumed in the following embodiments that the conductor detecting device is a metal detecting device which detects metal mingled in a lubricating oil due to abrasion of metallic gears.  
         [0050]    [0050]FIG. 1 is an electric circuit diagram showing the metal detecting device of this embodiment.  
         [0051]    As shown in FIG. 1, the metal detecting device is broadly comprised of four magnets  1   a ,  1   b ,  1   c ,  1   d , a power supply  4 , an output resistor  5 , electric signal wires  2   a ,  2   b  and a series circuit  3 .  
         [0052]    The series circuit  3  is configured of the four magnets  1   a ,  1   b ,  1   c ,  1   d , the power supply  4  and the output resistor  5  which are connected in series.  
         [0053]    The magnets  1   a ,  1   b ,  1   c ,  1   d  are separately arranged to detect conductor metals M 1 , M 2 , M 3 . In this embodiment, it is assumed that M 1  is not fine particles or fragments of the gears but swarf (or cuttings, metal foreign materials), and M 2 , M 3  are fine particles or fragments of the gears.  
         [0054]    It is assumed that a gap between the magnets  1   a  and  1   b , a gap between the magnets  1   b  and  1   c  and a gap between the magnets  1   c  and  1   d  are respectively set to such a level that a worn or damaged level of gears has exceeded a prescribed threshold value.  
         [0055]    The positive terminal of the power supply  4  is connected to the magnet  1   c  through the electric signal wire  2   a . And, the negative terminal of the power supply  4  is connected to the magnet Id through the electric signal wire  2   b  and the output resistor  5 .  
         [0056]    The series circuit  3  is configured by disposing the four magnets  1   a ,  1   b ,  1   c ,  1   d  with a space among them as described above. It is assumed that a voltage of the power supply  4  is V, a resistance among all the magnets (which is called as a detection section resistance) is Rs, the output resistor is R, and voltages of both ends of the output resistor  5  (called as monitoring voltage) are Vs.  
         [0057]    When the magnets  1   a  and  1   b , the magnets  1   b  and  1   c  and the magnets  1   c  and  1   d  are electrically connected by the metals M 1 , M 2  and M 3 , the series circuit  3  is brought into conduction, and electric current Is which indicates the detection of the metals M 1 , M 2 , M 3  passes through the series circuit  3 . Thus, the monitoring voltage Vs at either end of the output resistor  5  becomes the voltage Vs (=V) corresponding to the electric current Is as described later. When the monitoring voltage Vs becomes the voltage Vs (=V) corresponding to the current Is, a warning signal is output to the outside.  
         [0058]    [0058]FIG. 2 shows a layout example of the magnets  1   a ,  1   b ,  1   c ,  1   d.    
         [0059]    As shown in FIG. 2, the magnets  1   a ,  1   b ,  1   c ,  1   d  are arranged around the outer periphery of a cylindrical rod member  20 . The magnets  1   a ,  1   b ,  1   c ,  1   d  are arranged in a longitudinal direction of the rod member  20 . The electric signal wires  2   a ,  2   b  are disposed in a hollow section of the rod member  20 .  
         [0060]    Then, an operation of the metal detecting device shown in FIG. 1 will be described with reference to FIG. 1, FIG. 2 and FIG. 3. FIG. 3 is a diagram showing a state that the monitoring voltage Vs is varied according to a time elapsed after the gears are driven.  
         [0061]    It is assumed that swarf M 1  is suddenly mixed into the lubricating oil at an initial stage when the gears are started to drive. The swarf M 1  is attracted to the magnets  1   a ,  1   b  within a period of time T 0  to time T 1 , and the magnets  1   a ,  1   b  are electrically connected by the swarf M 1 . But, the magnets  1   b  and  1   c  and the magnets  1   c  and  1   d  are not electrically connected. Therefore, the series circuit  3  is not brought into conduction, and the electric current Is does not flow. The monitoring voltage Vs at this time will be described.  
         [0062]    When electrical connection is not established between the magnets  1   b  and  1   c  and between the magnets  1   c  and  1   d , the detecting section resistance Rs is as follows:  
         Rs=∞  (1)  
         [0063]    The monitoring voltage Vs is determined as follows:  
           Vs= ( R/R+Rs )· V   (2)  
         [0064]    Therefore, from the above expressions (1) and (2), the monitoring voltage Vs when no electrical connection is established between the magnets  1   b  and  1   c  and between the magnets  1   c  and  1   d  is determined as follows:  
         Vs≈0  (3)  
         [0065]    When the monitoring voltage Vs is 0, a warning signal is not output to the outside. Specifically, when the swarf M 1  is mingled in the lubricating oil within a period of from drive starting time point T 0  to conducting time point T 1 , error detection resulting in the output of a warning signal can be prevented.  
         [0066]    Then, it is assumed that the gears are gradually worn and fine particles M 2 , M 3  are produced and mingled into the lubricating oil. The fine particles M 2 , M 3  are attracted between the magnets  1   b  and  1   c  and between the magnets  1   c  and  1   d  at time T 1 , and the electrical connection is established between the magnets  1   b  and  1   c  and between the magnets  1   c  and  1   d  by the fine particles M 2 , M 3 . And, the magnets  1   a  and  1   b  have been electrically connected by the swarf M 1 .  
         [0067]    Thus, when the electrical connection is established between the magnets  1   a  and  1   b , between the magnets  1   b  and  1   c  and between the magnets  1   c  and  1   d , the series circuit  3  is brought into conduction, and the electric current Is flows it. The monitoring voltage Vs at the time will be considered.  
         [0068]    When the electrical connection is established between the magnets  1   a  and  1   b , between the magnets  1   b  and  1   c  and between the magnets  1   c  and  1   d , the detecting section resistance Rs is determined as follows:  
         Rs≈0  (4)  
         [0069]    The monitoring voltage Vs is determined from the above expression (2) (Vs=(R/R+Rs)·V).  
         [0070]    Thus, from the above expression (2) and (4), when the electrical connection is established between the magnets  1   a  and  1   b , between the magnets  1   b  and  1   c  and between the magnets  1   c  and  1   d , the monitoring voltage Vs is determined as follows:  
         Vs≈V  (5)  
         [0071]    When the monitoring voltage Vs is V, a warning signal is output to the outside. Namely, when the gears are worn and their worn level exceeds a prescribed limit, the warning signal is output.  
         [0072]    Similarly, when a gear is chipped and the fragments M 2 , M 3  are attracted between the magnets  1   b  and  1   c  and between the magnets  1   c  and  1   d , the warning signal is also output.  
         [0073]    According to this embodiment described above, the series circuit  3  is brought into conduction for the first time when the three metals M 1 , M 2 , M 3  are attracted between the magnets (between the magnets  1   a  and  1   b ,  1   b  and  1   c , and  1   c  and  1   d ), the monitoring voltage Vs becomes the power voltage V, and the warning signal is output. Therefore, the attraction of only one of the mingled swarf, cuttings and metal foreign material M 1  between the magnets  1   a  and  1   b  does not output a warning signal. The warning signal is output only when the two metals M 2 , M 3  are attracted between the magnets  1   b  and  1   c  and between the magnets  1   c  and  1   d . Thus, an erroneous operation due to the attraction of a single foreign material or the like can be prevented.  
         [0074]    According to this embodiment, an erroneous operation can be prevented by the series circuit  3  configured by disposing the four magnets  1   a ,  1   b ,  1   c  and  1   d  with spaces therebetween. And, a controller is not required to be added to a metal sensor unlike a conventional art, so that the structure can be simplified, and the cost can be reduced.  
         [0075]    In this embodiment, it is assumed that the four magnets  1   a ,  1   b ,  1   c ,  1   d  are disposed to attract the three magnets M 1 , M 2 , M 3 .  
         [0076]    But, the present invention can dispose at least three magnets to attract at least two metals M 1 , M 2 .  
         [0077]    For example, when three magnets  1   a ,  1   b ,  1   c  are disposed and two metals M 1 , M 2  are attracted between two magnets (between the magnets  1   a  and  1   b  and between the magnets  1   b  and  1   c ), the series circuit  3  is brought into conduction for the first time, the monitoring voltage Vs becomes the power voltage V, and the warning signal is output. Attraction of at least one of the mingled swarf, cuttings and metal foreign material M 1  between the magnets  1   a  and  1   b  does not output the warning signal. And, only when the other metal M 2  is attracted between the magnets  1   b  and  1   c , the warning signal is output, so that an erroneous operation due to the attraction of a single foreign material or the like can be prevented.  
         [0078]    As shown in FIG. 2, the magnets  1   a ,  1   b ,  1   c ,  1   d  are arranged around the outer periphery of the cylindrical rod member  20  but they may be arranged in any form. For example, magnets  40   a ,  40   b ,  40   c  may be arranged concentrically as shown in FIGS.  4 ( a ) and  4 ( b ).  
         [0079]    [0079]FIG. 4( a ) is a perspective diagram showing an appearance of a sensor which has the magnets  40   a ,  40   b ,  40   c  arranged concentrically, and FIG. 4( b ) is a sectional diagram taken along line A-A of FIG. 4( a ).  
         [0080]    As shown in FIG. 4( a ), the magnets  40   a ,  40   b ,  40   c  are concentrically arranged on a flat surface  41   a  of a disc member  41 . The flat surface  41   a  of the disc member  40  is immersed in a lubricating oil. An electric signal wire  42   a  is connected to the magnet  40  at the center of the concentric circles and an electric signal wire  42   b  is connected to the magnet  40   c  at the outermost position of the concentric circles. The magnets  40   a ,  40   b ,  40   c  correspond to the magnets  1   a ,  1   b ,  1   c ,  1   d  of FIG. 1, and the electric signal wires  42   a ,  42   b  correspond to the electric signal wires  2   a ,  2   b  of FIG. 1. Therefore, when the metals M 1 , M 2  are attracted between the magnets  40   a  and  40   b  and between the magnets  40   b  and  40   c  respectively, electric current Is flows through the electric signal wires  42   a ,  42   b , the monitoring voltage Vs becomes the power voltage V, and the warning signal is output to the outside.  
         [0081]    Magnets  50   a ,  50   b ,  50   c    50   d  may be arranged in a circumferential direction as shown in FIG. 5.  
         [0082]    The magnets  50   a ,  50   b ,  50   c ,  50   d  are arranged in the circumferential direction on a flat surface  51  a of a disc member  51  as shown in FIG. 5. The flat surface  51  a of the disc member  51  is immersed in a lubricating oil. An electric signal wire  52   a  is connected to the magnet  50   a , and an electric signal wire  52   b  is connected to the magnet  50   c.    
         [0083]    The magnets  50   a ,  50   b ,  50   c ,  50   d  correspond to the magnets  1   a ,  1   b ,  1   c ,  1   d  of FIG. 1, and electric signal wires  52   a ,  52   b  correspond to the electric signal wires  2   a ,  2   b  of FIG. 1. Therefore, when the metals M 1 , M 2  are attracted between the magnets  50   a  and  50   b  and between the magnets  50   b  and  50   c , the electric current Is flows through the electric signal wires  52   a ,  52   b , the monitoring voltage Vs become the power voltage V, and the warning signal is output to the outside. And, when metals M 1 , M 2  are attracted between the magnets  50   a  and  50   d  and between the magnets  50   d  and  50   c  respectively, the electric current Is flows through the electric signal wires  52   a ,  52   b , the monitoring voltage Vs becomes the power voltage V, and the warning signal is output to the outside.  
         [0084]    As shown in FIG. 6, magnets  60   a ,  60   b ,  60   c  may be arranged in parallel.  
         [0085]    The magnets  60   a ,  60   b ,  60   c  are arranged in parallel on a flat surface  61   a  of a disc member  61  as shown in FIG. 6. The flat surface  61   a  of the disc member  61  is immersed in a lubricating oil. An electric signal wire  62   a  is connected to the magnet  60   a , and an electric signal wire  62   b  is connected to the magnet  60   c.    
         [0086]    The magnets  60   a ,  60   b ,  60   c  correspond to the magnets  1   a ,  1   b ,  1   c ,  1   d  of FIG. 1, and the electric signal wires  62   a ,  62   b  correspond to the electric signal wires  2   a ,  2   b  of FIG. 1. Therefore, when the metals M 1  and M 2  are attracted between the magnets  60   a  and  60   b  and between the magnets  60   b  and  60   c , the current Is flows through the electric signal wires  62   a ,  62   b , the monitoring voltage Vs becomes the power voltage V, and the warning signal is output to the outside.  
         [0087]    In the embodiment described above, it was assumed that abrasion of the metallic gears was detected, but the invention can also be applied to a case of detecting the abrasion of metallic bearings.  
         [0088]    In this embodiment, it was assumed that metal in a lubricating oil was detected, but the invention can also be applied to the detection of metal in a hydraulic oil of a hydraulic machine. Furthermore, the invention may be applied to the detection of metal mingled into a coolant for cooling an engine other than the detection in oil. And, the invention can also be applied to the detection of a general conductor other than metal.