Abstract:
Joint portions to which tubes are coupled are provided with a pair of connector portions which are engaged/disengaged in accordance with the engagement/disengagement of the joint portions. Further, a detection circuit is provided which detects the non-conduction state between terminals provided at the connection portions. The detection circuit is arranged to output an alarm signal when the state between the terminal metal members is non-conductive. Thus, when one of the joint portions disengages, the corresponding one of the connector portions also disengages, so that the state between the terminal metal members becomes non-conductive and the alarm signal is generated.

Description:
This is a Continuation of application Ser. No. 09/698,000 filed Oct. 27, 2000 now U.S. Pat. No. 6,532,931. The entire disclosure of the prior application is hereby incorporated by reference herein in its entirety. 
    
    
     BACKGROUND OF THE INVENTION 
     The present invention relates to a system for detecting the disengagement of a joint portion provided in a feedback path for blowby gas. 
     The blowby gas is generated when the mixture gas of the fuel and the air leaks from a portion between the cylinder and the piston of an engine. For example, in the engine for an automobile, the blowby gas is collected and fed back to an intake path of the engine so as to prevent the blowby gas from being emitted in the atmosphere. 
     When performing the maintenance of the engine room of an automobile, a pipe for feeding back the blowby gas is sometimes removed or disengaged. 
     However, in the prior art, even when the pipe is kept in the disengaged state, the engine operates and an alarm indication etc. for notifying the removal or disengagement of the pipe is not made. Thus, there may arise such a matter that a driver operates the engine without noticing that the pipe is disengaged thereby to emit the blowby gas in the atmosphere. 
     SUMMARY OF THE INVENTION 
     Accordingly, the invention has been made in view of the aforesaid problem of the prior art, and an object of the invention is to provide a disengagement detection system for a joint portion which can detect the disengagement of the joint portion provided at a feedback path for blowby gas. 
     The Invention of Aspect  1   
     A disengagement detection system for a joint portion according to aspect  1  is arranged in a manner that in the disengagement detection system wherein a feedback path for deeding back blowby gas to an intake path of an engine is formed by coupling a plurality of cavities, the disengagement detection system is characterized in that 
     joint portions provided at each of a pair of the cavities and mutually coupled are provided with a pair of connector portions which are engaged/disengaged in accordance with engagement/disengagement of the joint portions, respectively, 
     a detection means is provided for detecting a non-conduction state between terminal metal members provided at the connector portions, and 
     the detection means outputs a disengagement detection signal when a state between the terminal metal members is non-conductive. 
     The Invention of Aspect  2   
     The invention as in aspect  2  is characterized in that in the disengagement detection system for a joint portion according to aspect  1 , 
     plural pairs of the connector portions are provided, 
     the detection means includes a switch circuit which is closed only when all the connector portions are coupled to partner-side connector portions, respectively, and all the terminal metal members are conductively coupled mutually, and 
     the detection means detects that a state between the terminal metal members having been mutually coupled at one of the connector portions becomes non-conductive when the switch circuit is opened. 
     The Invention of Aspect  3   
     The invention as in aspect  3  is characterized in that in the disengagement detection system for a joint portion according to aspect  2 , 
     the cavity having two the connector portions is provided with a pair of electric paths for connecting, between the two connector portions, the pair of terminal metal members provided at the two connector portions, and 
     the pair of electric paths are arranged to flow currents in opposite direction when sad switch circuit is closed. 
     Action and Effects of the Invention 
     The Invention of Aspect  1   
     According to the arrangement of aspect  1 , when the joint portion is disengaged, the connector portion is also disengaged, so that the state between the terminal metal members provided at the connector portions becomes non-conductive. The detection means detects such a non-conductive state thereby to output the disengagement detection signal. Thus, a diver can notice that the joint portion is disengaged. 
     The Invention of Aspect  2   
     According to the arrangement of aspect  2 , in the case where a plurality of the joint portions are provided at the feedback path for the blowby gas, when even one of the joint portions is disengaged, the switch circuit is opened. Thus, the disengagement of the joint portion can be detected. 
     The Invention of Aspect  3   
     According to the arrangement of aspect  3 , currents flow in opposite direction in the pair of the electric paths provided in the cavity to constitute outward and homeward paths of the switch circuit, respectively. Thus, the configuration of the switch circuit along the cavity can be simplified as compared with the case where only the outward path is provided between the connector portions provided at the cavity and the homeward path is provided in another portion. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a schematic diagram showing a feedback path for blowby gas according to an embodiment of the invention. 
     FIG. 2 is a sectional view showing an insertion side joint portion, a first receiving side joint portion and connector portions provided therein. 
     FIG. 3 is an exploded perspective view showing the insertion side joint portion and the first receiving side joint portion. 
     FIGS. 4A to  4 C are sectional side views showing the procedure for attaching the insertion side joint portion to a tube. 
     FIG. 5 is a perspective view showing a second receiving side joint portion. 
     FIG. 6 is a sectional side view showing the state where the insertion side joint portion is coupled to the second receiving side joint portion. 
     FIG. 7 is a perspective view showing the state where the insertion side joint portions are attached to both ends of the tube. 
     FIG. 8 is a perspective view showing the state where the insertion side joint portion and the first receiving side joint portion are coupled to each other. 
     FIG. 9 is a sectional side view showing the state where the insertion side joint portion and the first receiving side joint portion are coupled to each other. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The embodiment of the invention will be explained with reference to FIGS. 1 to  9 . 
     FIG. 1 shows a part of a feed back path for feeding back the blowby gas which is provided at the engine of an automobile. The feedback path is formed by tubes  14  which connect between a crank case  11  capable of generating the blowby gas and an intake duct  12  to the engine within the engine. 
     More specifically, first receiving side joint portions  13  are provided at three portions in total, that is, two portions of the crank case  11  and one portion of the intake duct  12 . Each of the tubes  14  is provided at its both ends with insertion side joint portions  15 . The insertion side joint portion  15  on the one end side of each of the tubes  14  is coupled to the first receiving side joint portion  13  and the insertion side joint portion  15  on the other end side of each of the tubes  14  is coupled to a T-shaped second receiving side joint portion  16 . 
     The insertion side joint portion  15  is formed by composite resin and arranged in a manner as shown in FIG. 2 that a female connector portion  52  is protruded toward the side direction from a main body pipe  51  which is fitted and fixed to the tube  14 . The constituent parts of the insertion side joint portion  15  are shown in FIG.  3 . That is, the main body pipe  51  includes a small diameter portion  53 , a middle diameter portion  54  and a large diameter portion  55  sequentially from the tube  14  side. A disengagement prevention projection  56  is formed at the tip end of the small diameter portion  53  and an engagement groove  57  is formed between the middle diameter portion  54  and the large diameter portion  55 . 
     At the tip end of the large diameter portion  55  on the side thereof away from the middle diameter portion  54 , a flange  58  is formed so as to expand toward the side direction. As shown in FIG. 2, the large diameter portion  55  has a duplicated structure in a manner that piping portions  20 ,  40  provided at the partner-side joint portions  13 ,  16  are fitted into the clearance between an outer cylindrical wall  55 V and an inner cylindrical wall  55 W of the large diameter portion. The inner cylindrical wall  55 W is slightly protruded to the forward direction from the outer cylindrical wall  55 V. An O ring  71  is fittingly coupled at the position near the tip end of the portion of the inner cylindrical wall  55 W which is covered by the outer cylindrical wall  55 V. 
     The main body pipe  51  is sequentially fitted with a rotation body  59  and a fastening sleeve  61  from the small diameter portion  53  side. A lock ring  60  is fitted to the external surface of the fastening sleeve  61 . 
     The fastening sleeve  61  is provided at its one end with a flange  62 , and further provided with a plurality of slits  61 A extending in the axial direction which are formed at the end portion thereof on the flange  62  side, whereby the flange  62  side of the fastening sleeve can be expanded and shrunk in the radial direction. 
     A pair of flexible pieces  63  (only one of the flexible pieces is shown in FIG. 3) are provided at the end portion of the fastening sleeve  61  on the side opposite to the flange  62 . The fastening sleeve  61  is fitted to the main body pipe  51  from the flexible pieces  63  side in a manner that the tip end projections  63 A provided at the flexible pieces  63  engage with the engagement groove  57  of the main body pipe  51 , so that the fastening sleeve is prevented from being disengaged. 
     Further, as shown in FIG. 4A, the fastening sleeve  61  is at first in such a state that the lock ring  60  is disposed at the end portion on the flexible pieces  63  side. In this state, the diameter of the end portion of the fastening sleeve is enlarged on the flange  62  side and the tube  14  is inserted in the clearance between the fastening sleeve  61  and the main body pipe  51  (refer to FIG.  4 B). Then, as shown in FIG. 4C, when the lock ring  60  is moved to the flange  62  side, the tube  14  is sandwiched between the fastening sleeve  61  and the main body pipe  51  to prevent the tube from being disengaged. In this respect, the lock ring  60  does not restore to the original position since engaging recess portions  65  thereof engage with projections  64  provided at the flange  62  side of the fastening sleeve  61 . 
     As shown in FIG. 3, the rotation body  59  is provided with a prism portion  67  which is extended in the side direction from the external periphery of a cylindrical portion  66  to be fitted on the outer periphery of the main body pipe  51 . The cylindrical portion  66  is sandwiched between the flange  58  of the main body pipe  51  and the end portion of the fastening sleeve  61  engaged with the engagement groove  57 . Accordingly, the rotation body is held in such a state that it can rotate relative to the main body pipe  51  but can not move in the axial direction. 
     The female connector portion  52  is provided at the tip end of the prism portion  67 . As shown in FIG. 2, the female connector portion  52  is provided with a hood portion  68  directed to the partner-side joint portion. A pair of female type terminal metal members  70  (only one of the terminal metal members is shown in FIG. 2) are housed side by side within a terminal housing portion  69  which extends to the open side from the inner surface of the hood portion  68 . 
     Then, the explanation will be made as to the first receiving side joint portion  13  provided at the crank case  11  and the intake duct  12 . As shown in FIG. 2, the first receiving side joint portion  13  is formed by assembling a connector block  30  made of composite resin to the piping portion  20  made of composite resin. The piping portion  20  is provided with a horizontal pipe  22  extended in the left and right direction in the figure from the intermediate portion of a main body pipe  21  which extends in the upward and downward direction in the figure. A circular cylindrical portion  31  hanging down from the connector block  30  is fitted within the upper end opening  21 A of the main body pipe  21 , and a base portion  32  provided at the base end side of the circular cylindrical portion  31  is fixed to the opening edge of the upper end opening  21 A by an oscillation fusing process. An O ring  23  is attached to the outer periphery of the circular cylindrical portion  31  hanging down from the connector block  30 , whereby the upper end of the main body pipe  21  is completely closed. 
     An O ring  24  is attached to the outer periphery of the lower end of the main body pipe  21  of the piping portion  20  in a manner that the O ring is fitted in a watertight state into a hole  25  which is formed by penetrating the wall of each of the intake duct  12  and the crank case  11 , whereby the inner space of the piping portion  20  communicates with the inner space of each of the intake duct  12  and the crank case  11 . 
     The connector block  30  extends in the left and right direction in FIG. 2 from the circular cylindrical portion  31  and is provided at its both ends with a first male connector portion  33  and a second male connector portion  34 . The male connector portions  33 ,  34  are provided with hood portion  33 A,  34 A, respectively. The hood portion  33 A of the first male connector portion  33  disposed in the left side in FIG. 2 is opened in the same direction as the horizontal pipe  22 . A pair of bus bars  35  (only one of the bus bars  35  is shown in FIG. 2) are extended in parallel within the connector block  30 . The both end portions of these bus bars  35  extend to the open side from the inner surface of the hood portion  33 A,  34 A to constitute male terminals  33 B,  34 B, respectively. More specifically, in the first male connector portion  33 , the male terminal  33 B is laid on a supporting table  33 C which protrudes to the inner side from the upper wall of the hood portion  34 A so that the contact surface of the male terminal is directed downward in FIG.  2 . In contrast, in the second male connector portion  34 , the male terminal  34 B extends in a cantilever or overhang fashion. A locking projection portion  34 C is formed on the external upward surface of the hood portion  34 A of the second male connector portion  34 , and a lock arm  75 R provided at a female connector  75  of the partner-side joint portion engages with the locking projection portion  34 C. 
     The T-shaped second receiving side joint portion  16  will be explained based on FIG.  5 . The second receiving side joint portion  16  is also formed by assembling a connector block  41  made of composite resin to the piping portion  40  mad of composite resin. The piping portion  40  is formed by T-shaped three interconnection pipes  42  (same configuration as the horizontal pipe  22  of the first receiving side joint portion  13 ) extending in three direction. A receiving recess portion  43  having an opening portion directed upward in FIG. 5 is provided at the common base end portion of the interconnection pipes  42  of the piping portion  40 . A circular cylindrical portion  44  hanging down from the connector block  41  is fitted within the receiving recess portion  43  and fixed by an oscillation fusing process like the first receiving side joint portion  13 . 
     The connector block  41  is formed in a T-shape in correspondence with the piping portion  40  and has three branched portions in parallel to the interconnection pipes  42 , respectively. A third male connector portion  45  having the same configuration as the first male connector portion  33  provided at the aforesaid first receiving side joint portion  13  is provided at the tip end of each of the three branched portions. 
     As shown in FIG. 5, three bus bars  46  are buried within the connector block  41 . The first bus bar  46 A of the three bus bars extends straightly between third male connector portions  45 X,  45 X directed in the opposite direction to each other to constitute a male terminal  47 A of one of the third male connector portions  45 X. The remaining two second bus bars  46 B,  46 B of the three bus bars are exposed at their one ends within the remaining third male connector portion  45 Y to constitute male terminals  47 C,  47 C placed side by side. Further, the bus bars  46 B,  46 B are bent perpendicularly in the opposite direction within the connector block  41  to constitute the remaining male terminals  47 B,  47 B of the third male connector portions  45 X,  45 X directed in opposite direction to each other. 
     The entirety of the system according to the embodiment will be explained while explaining the concrete example of the assembling procedure of the feedback path for blowby gas according to the embodiment. 
     First, as explained with reference to FIGS. 4A to  4 C, the insertion side joint portions  15  are attached to the both ends of each of the tubes  14 . Then, the terminal metal members  70  are fixedly attached to both ends of each of a pair of electric wires D 1  whose lengths are set to be almost equal to the tube  14  (see FIG.  2 ). Then, as shown in FIG. 7, these electric wires D 1  are laid along the tube  14 , and the terminal metal members  70  at the both ends of the electric wires D 1  are attached within the female connector portions  52  at the both ends of the tube  14 , respectively. In this manner, the three tubes  14  are prepared to which the insertion side joint portions  15  etc. are attached. 
     Thereafter, for example, the insertion side joint portions  15  at the one ends of the three tubes  14  are coupled to the three first receiving side joint portions  13  provided at the two portions of the crank case  11  and the one portion of the intake duct  12 , respectively. To this end, as shown in FIG. 2, the main body pipe  51  and the female connector portion  52  of the insertion side joint portion  15  are opposed and pushed to the horizontal pipe  22  and the first male connector portion  33  of the first receiving side joint portion  13 , respectively. Thus, the horizontal pipe  22  is inserted into the clearance between the outer cylindrical wall  55 V and the inner cylindrical wall  55 W formed at the main body pipe  51  of the insertion side joint portion  15 , so that the tube  14  is communicated with the crank case  11  or the intake duct  12 . Further, the connector portions  52 ,  33  are coupled to each other, so that the terminal metal member  70  of the female connector portion  52  is conductively coupled to the male terminal  33 B (the one terminal of the bus bar  35 ) of the first male connector portion  33 . 
     Then, the insertion side joint portion  15  at the other end of each of the tubes  14  is attached to the T-shaped second receiving side joint portion  16 . For this purpose, also the main body pipe  51  and the female connector portion  52  of the insertion side joint portion  15  are opposed to the interconnection pipe  42  and the third male connector portion  45  of the second receiving side joint portion  16 , respectively. In this respect, even when the tube  14  twists in the unexpected direction, both the main body pipe  51  and the female connector portion  52  can be easily opposed to both the interconnection pipe  42  and the third male connector portion  45 , respectively, by rotating the female connector portion  52  of the insertion side joint portion  15  around the main body pipe  51 . 
     In each of the tubes, when the insertion side joint portion  15  is pushed to the second receiving side joint portion  16  as shown in FIG. 6, the interconnection pipe  42  is inserted into the clearance formed at the main body pipe  51  of the insertion side joint portion  15 , whereby the three tubes  14  are mutually communicated. Further, the connector portions  52 ,  45  are coupled to each other, so that the terminal metal member  70  of the female connector portion  52  is conductively coupled to the male terminal (the end portion of the bus bar  46 ) of the third male connector portion  45 . 
     Then, as shown in FIG. 8, the female connector  75  is coupled to the second male connector portion  34  of each of the first receiving side joint portions  13  provided at the crank case  11 . A pair of female terminal metal members (not shown) are housed within the female connector  75 . These female terminal metal members are short-circuited by an electric wire D 2  and so both the male terminals  34 B,  34 B within the second male connector portion  34  are short-circuited. 
     Finally, as shown in FIG. 9, the female connector  75  is coupled to the second male connector portion  34  of the first receiving side joint portion  13  provided at the intake duct  12 . A pair of electric wires D 3 , D 3  coupled to a detection circuit  80  (see FIG. 1) are fixedly attached to a pair of female terminal metal members  76  (see FIG. 2) which are housed within the female connector  75 . The detection circuit  80  is arranged to output an alarm signal when the portion between a pair of detection terminals  81 A,  81 A coupled to these electric wires D 3 , D 3  is placed in an insulated state, while stop the alarm signal when the pair of the detection terminals are short-circuited. 
     The system according to the embodiment operates in the following manner. 
     When the ignition key of an automobile is turned on, the engine is started and simultaneously the detection circuit  80  is activated. In the case where all the tubes  14  constituting the feedback path for the blowby gas are coupled from one another by means of the respective joint portions, as shown in FIG. 1, the system is in a state that a closed circuit (which corresponds to “a switch circuit” of the invention and hereinafter called “a switch circuit C 1 ”) formed by the electric wires D 1  to D 3  and the bus bars  35 ,  46  is connected to the pair of detection terminals  81 A,  81 B of the detection circuit  80 . Thus, since the detection terminals  81 A,  81 B of the detection circuit  80  are short-circuited, the alarm signal is not outputted. In this case, for example, a small current flows from one of the detection terminals  81 A of the detection circuit  80  to the other detection terminal  81 B through the switch circuit C 1 . Thus, the opposite currents flow through the pair of the electric wires D 1 , D 1  disposed within the tubes  14 , respectively, thereby to form outward and homeward paths of the switch circuit C 1 . In this manner, since both the outward and homeward paths are provided in the tube  14 , the configuration of the switch circuit C 1  along the tube  14  according to the embodiment can be simplified as compared with the case where only the outward path is provided in the tube and the homeward path is provided in another portion. 
     In this manner, since the alarm signal is not delivered in a state where all the joint portions are coupled, the automobile can be driven normally. Thus, even when a load is applied to the engine and the blowby gas is generated, the blowby gas thus generated is sucked by the negative pressure of the intake duct  12  and feed back and hence prevented from being exhausted in the atmosphere. 
     When performing the maintenance of the automobile, the joint portions  13 ,  15 ,  16  are sometimes disengaged. In this respect, when these joint portions  13 ,  15 ,  16  are disengaged and then restored after the maintenance, if one of these joint portions is carelessly forgotten to be coupled, there arises a fear that the blowby gas may leak from the joint portion thus remained in a disengagement state when the blowby gas is generated. 
     However, since the connector portion at the joint portion thus disengaged is detached, the switch circuit C 1  is opened and so the portion between the detection terminals  81 A,  81 B of the detection circuit  80  is placed in an insulated state. In this state, when the ignition key is turned on to activate the detection circuit  80 , the alarm signal is outputted from the detection circuit  80 . Thus, a driver notices that one of the joint portions in the blowby gas feedback path is in a disengagement state. Accordingly, the blowby gas can be prevented from being exhausted in the atmosphere by coupling the joint portion thus remained in the disengagement state. 
     Thus, according to this embodiment, if the joint portion is disengaged, the connector portion is also disengaged. Since the detection circuit  80  outputs the alarm signal (signal detecting of disengagement), the driver notices that the joint portion is disengaged. Then, it is possible for the driver to take an immediate action so as to prevent from blowby gas being exhausted in the atmosphere. 
     Other Embodiments 
     The invention is not limited to the aforesaid embodiment, and for example, the embodiments explained below are also included within the technical field of the invention and further the invention may be modified in various manners without departing from the gist of the invention. 
     (1) Although, in the aforesaid embodiment, the female connector portion  52  provided at the insertion side joint portion  15  is arranged to be rotatable, this connector portion may be arranged not to be able to rotate. 
     (2) Although, in the aforesaid embodiment, the pair of the electric wires D 1  are disposed in each of the tubes  14  and the pair of the electric wires are used as the outward and homeward paths, respectively, one electric wire serving as an outward path may be disposed along the tube and the other electric wire serving as a homeward path may be disposed in a portion other than the tube. 
     (3) For example, the system may be arranged in a manner that the starter motor of the engine can not be operated when the joint portion is disengaged thereby to surely prevent the generation of the blowby gas.