Patent Publication Number: US-2007107691-A1

Title: Relief valve

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
      The present application claims priority under 35 USC 119 to Japanese Patent Application No. 2005-329856 filed on Nov. 15, 2005 the entire contents of which are hereby incorporated by reference.  
     BACKGROUND OF THE INVENTION  
      1. Field of the Invention  
      The present invention relates to a relief valve including: a cylindrical valve housing which is attached to an engine body so as to longitudinally extend continuously with a relief passage communicating with an ejection port of an oil pump and provided in the engine body. An outlet is provided in an axially intermediate portion thereof. A valve body is slidably fitted to the valve housing so as to allow the relief passage to communicate with the outlet as an oil pressure in the relief passage becomes equal to and exceeds a predetermined oil pressure. A skirt is formed in an umbrella shape so as to surround the valve housing and has an upper end portion fixed to the valve housing above the outlet in order to guide oil discharged from the outlet downwardly.  
      2. Description of Background Art  
      A relief valve is known, for example, in Japanese Patent Application No. 2001-207818, in which a valve housing is covered with an umbrella-like skirt below an outlet of the valve housing in order to prevent bubbles from being generated when oil discharged from the outlet is returned into an oil reservoir formed in a lower portion of an engine body.  
      Since it is required that an internal combustion engine be compact, it is not easy to change an inclination angle and size of the skirt so as to increase a flow passage area between the valve housing and the skirt in order to exert a reliable defoaming function in response to an increase in an amount of the oil discharged from the outlet of the relief valve and also to an increase in an ejection pressure thereof.  
     SUMMARY AND OBJECTS OF THE INVENTION  
      Tlt is an object of the present invention to provide a relief valve adapted to be capable of exerting a reliable defoaming function in response to an increase in the amount of oil discharged from the outlet and also to the increase of the ejection pressure thereof while avoiding a size increase of the skirt shape.  
      According to an embodiment of the present invention, a relief valve includes a cylindrical valve housing which is attached to an engine body so as to longitudinally extend continuously with a relief passage communicating with an ejection port of an oil pump and being provided in the engine body. An outlet is provided in an axially intermediate portion thereof. A valve body is slidably fitted to the valve housing so as to allow the relief passage to communicate with the outlet in response to oil pressure in the relief passage becoming equal to and exceeding a predetermined oil pressure. A skirt is provided which is formed in an umbrella shape so as to surround the valve housing and has an upper end portion fixed to the valve housing above the outlet in order to guide oil discharged from the outlet downward. An annular recessed portion is formed on an outer circumference of the intermediate portion of the valve housing below the outlet.  
      According to an embodiment of the present invention, a lower end of the skirt is disposed at a position corresponding to the intermediate portion of the annular recessed portion.  
      According to an embodiment of the present invention, an upper end portion of the valve housing, the upper end portion forming an inlet, is fluid-tightly fitted to the relief passage, and a receiving portion for receiving a lower end of the valve housing is provided in the engine body.  
      In accordance with an embodiment of the present invention, the annular recessed portion is formed on the outer circumference of the intermediate portion of the valve housing. Thus, a size increase of the shape of the skirt can be avoided, a flow passage area between the valve housing and the skirt can be increased, and a reliable defoaming function can be exerted in response to an increase in an amount of oil discharged from the outlet and also to an increase of an ejection pressure thereof. In addition, the annular recessed portion is formed on the outer circumference of the intermediate portion of the valve housing below the outlet, and a high pressure on the relief passage side is not applied to the valve housing below the outlet. Accordingly, the forming of the annular recessed portion does not damage the strength of the valve housing, thus making it possible to contribute to a weight reduction of the relief valve.  
      Moreover, in accordance with an embodiment of the present invention, the discharged oil which flows between the valve housing and the skirt can be guided by a lower end of the annular recessed portion, and can be discharged so as to spread radially. Thus, a defoaming effect can be enhanced.  
      Furthermore, in accordance with an embodiment of the present invention, the valve housing is thrust downward by a liquid pressure of the relief passage and the annular recessed portion is formed on the intermediate portion of the valve housing. Accordingly, a seated area of the lower end of the valve housing on the receiving portion provided in the engine body can be set relatively large while increasing a flow passage area between the valve housing and the skirt. Thus, a large load can be avoided from being concentratedly applied to the lower end of the valve housing and the valve housing can be reliably attached to the engine body.  
      Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
      The present invention will become more fully understood from the detailed description given hereinbelow and the accompanying drawings which are given by way of illustration only, and thus are not limitative of the present invention, and wherein:  
       FIG. 1  is a side view of an internal combustion engine;  
       FIG. 2  is an enlarged longitudinal cross-sectional side view of main portions of  FIG. 1 ; and  
       FIG. 3  is a cross-sectional view along a line  3 - 3  of  FIG. 2 . 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
      A description will be made below of a mode for carrying out the present invention based on an embodiment of the present invention, which is shown in the accompanying drawings.  
      As illustrated in  FIG. 1 , an engine body  5  includes a cylinder axis inclined upwardly to the front that is mounted on a vehicle body frame of a motorcycle. The engine body  5  includes a cylinder block  8  integrally having a cylinder barrel  6  and an upper case  7  continuous with a lower portion of the cylinder barrel  6 . A lower case  9  is coupled to a lower portion of the cylinder block  8  so as to construct a crankcase  10  in cooperation with the upper case  7 . An oil pan  11  is coupled to a lower portion of the lower case  9 , that is, to a lower portion of the crankcase  10 . A cylinder head  12  is coupled to an upper portion of the cylinder block  8  with a head cover  13  coupled to an upper portion of the cylinder head  12 . A coupling surface  14  between the upper case  7  and the lower case  9  is set so as to be inclined downwardly to the front in a state where the engine  5  is mounted on the motorcycle.  
      Between the upper case  7  and the lower case  9 , which form the crankcase  10 , a crankshaft  15  is provided that includes an axis that is rotatably supported along a vehicle width direction of the motorcycle. To the crankshaft  15 , rotational power from a starter motor  16  attached to the upper case  7  is inputted through a starter gear transmission mechanism  17 .  
      An output of the crankshaft  15  is shifted by a gear transmission  18  and is transmitted to a rear wheel as a driving wheel. The transmission  18  is composed by providing gear trains between a main shaft  19  and a counter shaft  20 . The gear trains are capable of selectively establishing a plurality of speeds. The main shaft  19  has an axis parallel to the crank shaft  15 , and is rotatably supported between the upper case  7  and the lower case  9 . The counter shaft  20  has an axis parallel to the main shaft  19 , and is rotatably supported by the lower case  9 .  
      Onto one end of the main shaft  19 , a starting clutch  21  interposed between the crankshaft  15  and the main shaft  19  is attached. When the starting clutch  21  turns to an engaged state in response to a shifting operation of a rider, power from the crankshaft  15  is transmitted to the main shaft  19 .  
      Between the cylinder head  12  and the head cover  13 , a valve mechanism  24  including an intake camshaft  22  and an exhaust camshaft  23  is housed. To the intake camshaft  22  and the exhaust camshaft  23 , which are supported rotatably by the cylinder head  12 , the rotational power of the crankshaft  15  is transmitted, which is reduced by half in speed by the timing transmission means  26  including a timing chain  25 .  
      Referring to  FIG. 2  in combination, to the lower case  9  in the crankcase  10 , an oil pump  28  having a rotation axis parallel to the crankshaft  15  is attached. An endless chain  32  is wound around a drive sprocket  31  fixed to the main shaft  19  of the gear transmission  18 , and around a driven sprocket  30  fixed to a rotation shaft  29  of the oil pump  28 .  
      Oil reserved in an oil reservoir  33  formed in the oil pan  11  is drawn up by the oil pump  28  through an oil strainer  34 . In the lower case  9 , an ejection passage  35  that extends parallel to the coupling surface  14  between the upper case  7  and the lower case  9  is provided so as to communicate with an ejection port  36  of the oil pump  28 . Thus, oil from the oil pump  28  is ejected to the ejection passage  35 . In addition, a relief passage  37  which is perpendicularly branched from the ejection passage  35  extends downwardly so as to allow an upper end portion thereof to communicate with the ejection passage  35  provided in the lower case  9 . By a function of a relief valve  38  connected to the relief passage  37 , the pressure of the oil in the ejection passage  35  is maintained to be constant.  
      In addition, to lubricated portions of the engine body  5 , such as between crank journal walls  39  . . . and the crankshaft  15 , which the crankcase  10  includes, the oil is supplied from a main gallery  40  provided in the lower case  9  of the crankcase  10 . The main gallery  40  is connected to the ejection passage  35  through an oil filter  41  and an oil cooler  42 .  
      More specifically, the oil ejected from the oil pump  28  is pressure-regulated by the relief valve  38 , and as shown by arrows in  FIG. 2 , is cleaned by the oil filter  41 , is then cooled by the oil cooler  42 , and is guided to the main gallery  40 .  
      Referring to  FIG. 3  in combination, the relief valve  38  includes a cylindrical valve housing  44  which is attached between the lower case  9  and oil pan  11  of the engine body  5  so as to longitudinally extend continuously with the relief passage  37  and includes outlets  43  . . . provided in axially intermediate portions thereof. A valve body  45  is slidably fitted to the valve housing  44  so as to allow the relief passage  37  to communicate with the outlets  43  . . . as the oil pressure in the relief passage  37  becomes equal to and exceeds a predetermined oil pressure. A skirt  46  is formed in an umbrella shape in a portion surrounding the outlets  43  . . . and has an upper end portion fixed to the valve housing  44  above the outlets  43  . . . in order to guide the oil discharged from the outlets  43  . . . downward.  
      The relief passage  37  is provided in the lower case  9  so as to longitudinally extend so that a lower end thereof opens to the oil reservoir  33  side. An upper end portion of the valve housing  44 , which forms an inlet  47 , is fluid-tightly fitted to the lower end portion of the relief passage  37  so as to allow the inlet  47  to communicate with the relief passage  37 . More specifically, an O-ring  48  is attached to an outer circumference of the valve housing  44  in a fitted portion of the valve housing  44  to the relief passage  37 .  
      In the oil pan  11  in the engine body  5 , a receiving portion  49  projects upwardly that receives a lower end of the valve housing  44 . The receiving portion  49  is formed into a cylindrical shape so as to longitudinally extend upwardly. Since the coupling surface  14  between the upper case  7  and the lower case  9  is inclined downwardly to the front, and the valve housing  44  coaxially continues with the relief passage  37  perpendicularly branched from the ejection passage  35  extending parallel to the coupling surface  14 . An upper end surface of the receiving portion  49  is formed in an inclined manner so as to perpendicularly abut on the lower end of the valve housing  44 . In addition, a notch  55  is provided in a part along a circumferential direction of the receiving portion  49 .  
      The outlets  43  . . . are provided on the axially intermediate portions of the valve housing  44  so as to be located below the lower case  9  when the upper end portion of the valve housing  44  is fluid-tightly fitted to the lower case  9  so as to coaxially continue with the relief valve  37 . The valve body  45  slidably fitted to the valve housing  44  so as to switch the communication/shutoff between the inlet  47 . The outlets  43  . . . are formed into a closed-end cylindrical shape in which an upper end is closed.  
      In addition, above the outlets  43  . . . , into the valve housing  44 , a stopper pin  50  having an axis along one diameter line thereof is inserted. An upper limit position of the valve body  45  is regulated in such a manner that the upper-end closed portion thereof abuts on the stopper pin  50 , and the valve body  45  located at the upper limit position makes a shutoff between the inlet  47  and the outlets  43  . . . .  
      Moreover, a disk-like retainer  52  is inserted into a lower portion of the valve housing  44  so that a downward movement thereof can be regulated by a snap ring  51  attached to an inner surface of the lower end of the valve housing  44 . A valve spring  53  which urges the valve body  45  upward is compressed between the retainer  52  and the valve body  45 . Then, when a force in a valve opening direction, which presses the valve body  45  downward by the oil pressure in the inlet  47  communicating with the relief passage  37 , exceeds a force in a valve closing direction, which urges the valve body  45  upwardly by the valve spring  53 , the valve body  45  moves downwardly so as to allow the inlet  47  to communicate with the outlets  43  . . . . More specifically, the oil pressures in the relief passage  37  and the ejection passage  35  are maintained to be constant by the function of the relief valve  38 .  
      The skirt  46  integrally includes, in order from an upper end thereof a small-diameter cylindrical portion  46   a  press-fitted to the valve housing  44 , a tapered portion  46   b  which allows a small-diameter end thereof to coaxially continue with a lower end of the small-diameter cylindrical portion  46   a  and is formed to be larger in diameter as going downward and a large-diameter cylindrical portion  46   c  which coaxially continues with a lower end, that is, a large-diameter end of the tapered portion  46   b . The small-diameter cylindrical portion  46   a  is fixed to the valve housing  44  by press fitting and the like so as to cover both ends of the stopper pin  50  in order to inhibit the stopper pin  50  from separating from the valve housing  44 . The valve housing  44  is surrounded by the tapered portion  46   b  and large-diameter cylindrical portion  46   c  of the skirt  46 , and the tapered portion  46   b  and the large-diameter cylindrical portion  46   c  form the umbrella shape surrounding the valve housing  44 .  
      In addition, an annular recessed portion  54  is formed on an outer circumference of the intermediate portion of the valve housing  44  below the outlets  43  . . . . A lower end of the skirt  46 , that is, a lower end of the large-diameter cylindrical portion  46   c  is disposed at a position corresponding to the intermediate portion of the annular recessed portion  54 .  
      Next, a description will be made of functions of this embodiment. In order to prevent bubbles from being generated when the oil discharged from the outlets  43  . . . provided in the valve housing  44  of the relief valve  38  is returned into the oil reservoir  33  in the oil pan  11 , the upper end portion of the skirt  46  formed into the umbrella shape so as to surround the outlets  43  . . . is fixed to the valve housing  44  above the outlets  43  . . . . Moreover, the annular recessed portion  54  is formed on the outer circumference of the intermediate portion of the valve housing  44  below the outlets  43  . . . . Therefore, it is possible to avoid a size increase of the shape of the skirt  46  and to increase a flow passage area between the outlets  43  . . . and the skirt  46 . Thus, a reliable defoaming function can be exerted in response to an increase in an amount of the oil discharged from the outlets  43  . . . and also to an increase in an ejection pressure thereof. In addition, the annular recessed portion  54  is formed on the outer circumference of the intermediate portion of the valve housing  44  below the outlets  43  . . . , and a high pressure on the relief passage  37  side is not applied to the valve housing  44  below the outlets  43  . . . . Accordingly, the forming of the annular recessed portion  54  does not damage the strength of the valve housing  44 . Thus, it is possible to reduce the weight of the relief valve  38 .  
      Moreover, the lower end of the skirt  46  is disposed at the position corresponding to the intermediate portion of the annular recessed portion  54 . Accordingly, the discharged oil which flows between the valve housing  44  and the skirt  46  can be guided by the lower end of the annular recessed portion  54 , and can be discharged so as to spread radially, and a defoaming effect can be enhanced.  
      Moreover, the upper end portion of the valve housing  44 , which forms the inlet  47 , is fluid-tightly fitted to the relief passage  37 , the receiving portion  49  which receives the lower end of the valve housing  44  is provided in the oil pan  11 , and the valve housing  44  is thrust on the receiving portion  49  side by the liquid pressure of the relief passage  37 . Furthermore, the annular recessed portion  54  is formed on the intermediate portion of the valve housing  44 . Accordingly, a seated area of the lower end of the valve housing  49  on the receiving portion  49  can be set relatively large while increasing a flow passage area between the valve housing  44  and the skirt  46 . Thus, a large load can be avoided from being concentratedly applied to the lower end of the valve housing  44 , and the valve housing  44  can be reliably attached to the engine body  5 .  
      The invention being thus described, it will be obvious that the same may be varied in many ways. Such variations are not to be regarded as a departure from the spirit and scope of the invention, and all such modifications as would be obvious to one skilled in the art are intended to be included within the scope of the following claims.