Abstract:
According to the invention, the filter is fixed to the engine block by screwing it to an attached connecting sleeve. The connecting sleeve contains a bypass valve, in the form of a tubular piston sliding in a through-passage and pushed against an intermediate shoulder by a spring. By sliding, the piston opens or closes a radial passage establishing direct communication between the inlet passage and the through-passage of the device. If the filter element of the filter is clogged, the pressure rise in the inlet passage causes the piston to move and the radial passage to open to reduce the pressure rise and ensure a satisfactory flow of oil. This reduces pressure rises upstream of the filter and ensures sufficient lubrication of the engine even in the case of clogging of the filter.

Description:
TECHNICAL FIELD OF THE INVENTION 
       [0001]    The present invention concerns circuits for distributing oil in heat engines such as internal combustion engines. 
         [0002]    Internal combustion engines comprise moving parts such as pistons, crankshafts, etc., which must be fed continuously with lubricating and/or cooling oil. 
         [0003]    For this, engines include a pressurized oil supply device, taking oil from a sump in the lower portion of the engine, pressurizing the oil by means of a pump to feed it into a network for distributing oil to the moving parts of the engine, the oil then returning to the sump. 
         [0004]    During operation, because of wear of the various moving parts and the oil, particles are found in suspension in the lubricating and cooling oil, and it is necessary to filter the oil to prevent the propagation of these particles, which can be abrasive, to the moving parts of the engine. A filter capable of blocking the particles in suspension is provided for this purpose, in the circuit between the pump and the oil distribution network. 
         [0005]    These particles progressively clog the filter in operation, which causes a progressive increase in the head loss in the filter. This results in a progressive reduction of the oil pressure in the passages downstream of the filter, and a simultaneous reduction in the rate of flow of oil to the moving parts of the engine. The problem also arises when starting under wintry conditions. In this case, the high viscosity of the oil makes the resistance to flow of the filter much higher and the oil pressure downstream of the filter decreases. The reduction in the oil pressure downstream of the filter risks leading to the destruction of the engine if the lubrication of the moving parts of the engine becomes insufficient or if the cooling of the engine becomes insufficient. The increase in the head loss tends to increase the pressure upstream of the filter. This upstream pressure can become prohibitive, with the risk of breaking certain parts such as seals or the filter. Any such breaking of seals suddenly interrupts the lubrication of the engine and also leads to its virtually immediate destruction. 
         [0006]    To avoid these problems, there has for a long time been provision for fitting the filters in the oil distribution circuit so that they are interchangeable. Periodically changing the filter in principle avoids it becoming clogged beyond a threshold that would cause either pipes to burst or insufficient lubrication. The filters are generally fitted interchangeably to the engine block by means of a connecting sleeve screwed into the end of an oil distribution passage in the engine block and having a threaded section onto which a threaded section of the filter is screwed. 
         [0007]    The operation of changing the filters is left to the assessment and the good intentions of the user, however, and the risk therefore remains of leaving a filter in place for too long and it becoming excessively clogged. 
         [0008]    The greatest risk is the excessive increase in pressure in the pipes upstream of the filter, in the case of excessive clogging of the filter. To reduce this risk, connecting a relief valve between the pipe upstream of the filter and the sump has already been envisaged. In the case of the upstream pressure exceeding a particular alarm threshold, the relief valve opens and conveys oil directly from the outlet of the pump to the sump, thereby reducing the pressure in the upstream pipe. However, it is clear that the quantity of oil that passes through the filter is then reduced commensurately, which accentuates the phenomenon of reduced lubrication and cooling of the moving parts of the engine, again with the risk of destruction of the engine. 
         [0009]    To avoid this risk, fitting a bypass valve into the interchangeable filter directly, between the filter inlet and its outlet, has been proposed. The valve then bypasses the filter element of the filter. In the case of excessive clogging of the filter element, the valve opens and conveys oil directly from the filter inlet to its outlet. This assures conduction of a sufficient quantity of oil to lubricate the engine, which simultaneously reduces any pressure rise upstream of the filter. 
         [0010]    However, there is then the problem that correct operation of the device necessitates always having available a filter provided with a bypass valve. On changing the filter, if the user fits a filter that is not provided with any such bypass valve, the safety function is then absent, and the risks associated with progressive excessive clogging of the filter are encountered again. 
         [0011]    It has been proposed more recently to fit the bypass valve inside a connection interface disposed between the filter and the engine block. In this case, the connection interface includes an axial through-passage that conveys oil from the filter to an outlet passage in the engine block and contains the bypass valve and a bypass passage. 
         [0012]    The oil bypass device, which provides the safety function of maintaining sufficient oil pressure in the engine and a safety function of reducing any pressure rise upstream of the filter, then works correctly whatever the filter that the user fits to the engine, whether that be a filter fitted with a bypass valve or a filter without any such bypass valve. As a result, the security functions of maintaining sufficient oil pressure in the engine and of reducing any pressure rise upstream of the filter no longer depend on the intentions or attention of the user. 
         [0013]    Structures of the above type are described in the documents GB 2 164 395 A, DE 40 37 628 A, GB 1 595 051 A and EP 0 473 261 A. In all cases, the bypass valve comprises at least one closure part that selectively closes an orifice of the bypass pipe and can be moved along the longitudinal axis of the orifice, being urged toward the orifice by a return coil spring or a return leaf spring. 
         [0014]    Clearly these known devices do not have the sufficient reliability that might be expected of a safety device. In particular, because of the particular conditions of use of the valves in the presence of a fluid that is charged with impurities and that must be filtered, risks of failure remain in the case of soiling of the closure part or the orifice, or in the case of the closure part adopting an off-center position as a result of deformation of the return leaf springs: the seal is then no longer provided, an uncontrolled leak occurs, and the filtering becomes insufficient. The defective seal is aggravated by the fact that even partial opening of a displacement valve of this type increases the area of the valve subjected to the high fluid pressure, and therefore is further conducive to its opening. 
       STATEMENT OF THE INVENTION 
       [0015]    An object of the present invention is to design a safety device that assures improved reliability of operation, avoiding the risks of failure of the safety valve in the case of soiling, and avoiding the risks of failure by deformation of the return leaf springs. 
         [0016]    To achieve the above and other objects, the invention proposes an oil bypass device, comprising a bypass valve in a bypass passage, the bypass valve being adapted to assume the open state in the presence of a differential pressure higher than a particular bypass valve triggering threshold, the oil bypass device being integrated into a connecting sleeve adapted to be fitted to an engine block and to receive an interchangeable engine oil circuit filter, the connecting sleeve having an axial through-passage for conveying oil from the filter to an outlet passage of the engine block and containing the bypass valve and the bypass passage, the bypass passage being adapted to bypass a filter element of the filter. 
         [0017]    According to the invention, the connecting sleeve comprises:
       in the axial passage, an inlet bore, an outlet bore with a diameter less than the diameter of the inlet bore, and an intermediate shoulder connecting the inlet bore and the outlet bore,   at least one radial passage establishing communication between the inlet bore and an inlet passage of the engine block,   a tubular piston mounted so as to slide axially in the inlet bore and pushed against the intermediate shoulder by a return spring to close the radial passage,   the tubular piston including, on an outlet section of its exterior surface, an external annular recess with a radial facet which, in a closure position, is in line with the radial passage of the connecting sleeve.       
 
         [0022]    The valve structure with a tubular piston, which moves transversely relative to the longitudinal axis of the orifice, is much less sensitive to any blockage caused by accumulation of particles carried by the fluid to be filtered. This prevents sealing defects. 
         [0023]    Moreover, the area of the piston on which the differential fluid pressure generates a driving force in its direction of movement is the only radial facet of the external annular recess, and its area is not modified by the total or partial closing of the valve. This results in a further reduction of any risk of sealing defects. 
         [0024]    In practice, the connecting sleeve can comprise:
       a threaded fixing section, adapted to be screwed into a threaded end section of the outlet passage of the engine block,   a threaded receiver section, adapted to have an axial threaded fixing section of the filter screwed into it,   an intermediate abutment section, of greater diameter, abutting axially against a connecting face of the outlet passage of the engine block, and against which a connecting wall of the filter abuts around a central outlet orifice of the filter.       
 
         [0028]    This reproduces the usual structure of the connecting sleeves of known filters, so that no modification to the filters themselves is necessary for the purposes of the invention. 
         [0029]    Another aspect of the invention proposes an engine fitted with an oil bypass device as defined hereinabove and comprising:
       a sump receiving an oil reserve,   a pump taking oil from the sump and sending it under pressure to the inlet of the filter via an inlet passage in the engine block,   an outlet passage in the engine block for receiving the oil at the outlet of the filter and for conveying it via an oil distribution network to the moving parts of the engine, from which it is recovered and returned to the sump,   the filter engaged over the connecting sleeve which is itself provided with an oil bypass device with a radial passage and a tubular piston sliding axially for selectively establishing communication between the inlet passage and the outlet passage if the differential pressure between the inlet and the outlet of the filter element of the filter exceeds a particular bypass valve triggering threshold.       
 
         [0034]    The presence of the oil bypass device of the invention remains compatible with the presence of a relief valve between the inlet passage (at the output of the pump) and the sump. The relief valve operates if the oil pressure in the inlet passage exceeds a particular alarm threshold, and maintains the pressure substantially at that alarm threshold. In the oil bypass device of the invention, the bypass valve is preferably sized to convey a sufficient rate of flow of oil to lubricate the engine correctly if the oil pressure difference between the upstream and downstream sides of the filter is equal to the particular alarm threshold, i.e. in the case of blocking of the filter and triggering of the relief valve. 
     
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0035]    Other objects, features and advantages of the present invention will emerge from the following description of particular embodiments, given with reference to the appended figures, in which: 
           [0036]      FIG. 1  shows diagrammatically the general structure of an engine lubricating and cooling circuit fitted with an oil bypass device of the present invention; 
           [0037]      FIG. 2  is a view in longitudinal section of a known filter system comprising a filter connected to a sump by a threaded fixing sleeve; 
           [0038]      FIG. 3  shows, also in longitudinal section, a filtering system fitted with an oil bypass device according to one embodiment of the invention, with the bypass valve closed; 
           [0039]      FIG. 4  is a partial view in section to a larger scale with the oil bypass device from  FIG. 3  closed; and 
           [0040]      FIG. 5  shows the filter system from  FIG. 3  in its bypass configuration. 
       
    
    
     DESCRIPTION OF PREFERRED EMBODIMENTS 
       [0041]    Consider first  FIG. 1 , which shows the general structure of an oil distribution circuit for cooling and lubricating moving parts of an engine. 
         [0042]    The engine comprises, in the lower portion, a sump  1  that receives and contains an oil reserve  2 . A pump  3  takes oil from the sump  1  and sends it under pressure in a distribution passage to an oil distribution network  4  that directs the oil to the moving parts such as the pistons  5  of the engine and the vital parts such as the crankshaft bearings of the engine. The oil then returns to the sump via a return passage  6 . 
         [0043]    In the distribution passage, a filter  7  is inserted between the pump  3  and the oil distribution network  4 . The filter  7  is interchangeable, and thus is connected in a removable and sealed manner between an inlet passage  8  and an outlet passage  9  of the distribution pipe. 
         [0044]    A bypass valve  10  is connected between the inlet passage  8  and the outlet passage  9  by a bypass passage  11 . A relief valve  12  provides selective communication between the inlet passage  8  and the sump  1  if the pressure in the inlet passage  8  exceeds a particular alarm threshold. 
         [0045]    The filter  7  is removably fitted to the engine block in the manner to be described with reference to the subsequent figures. 
         [0046]      FIG. 2  shows the usual structure of the interchangeable filters as connected to the engine block. In this figure, there is seen the engine block portion  13  that is to receive the filter  7  and that comprises the end sections of the inlet passage  8  and the outlet passage  9 . The engine block  13  has a fixing face  14  provided with an annular chamber  15  into which the inlet passage  8  discharges. The outlet passage  9  terminates in a tubular cylindrical tip  16  projecting into the annular chamber  15  and terminating at a connecting face  18  set back from the fixing face  14 . Inside the tubular cylindrical tip  16 , the outlet passage  9  terminates in a threaded end section  17 . 
         [0047]    The filter  7  comprises an exterior tubular blind envelope  19 , closed at its first end  20 , and receiving at its second end a connecting and fixing wall  21  having a central outlet orifice  22  and one or more peripheral inlet orifices  23 . The peripheral inlet orifices  23  face the annular chamber  15  of the inlet passage  8 . The central outlet orifice  22  faces the outlet passage  9 . Around the central outlet orifice  22 , the connecting and fixing wall  21  includes an interior skirt forming an axial threaded fixing section  22   a.    
         [0048]    Inside the tubular blind envelope  19  is a tubular filter element  24  accommodated between a central space  25  and a peripheral space  26 , the ends of the filter element  24  being closed by two sealed flanges  27  and  28 . 
         [0049]    An annular seal  29  is disposed between the connecting and fixing wall  21  and the fixing face  14 , around the annular chamber  15 . 
         [0050]    The filter  7  is fixed and connected by a connecting sleeve  30  attached to the engine block  13 . The connecting sleeve  30  comprises a threaded fixing section  31  adapted to be screwed and stuck into the threaded end section  17  of the tubular cylindrical tip  16  of the engine block  13 . 
         [0051]    At the opposite end, the connecting sleeve  30  includes a threaded receiver section  32  adapted to have the axial threaded fixing section  22   a  of the filter  7  screwed into it. 
         [0052]    The connecting sleeve  30  further comprises an intermediate abutment section  33 , of larger diameter than the threaded receiver section  32  and the threaded fixing section  31 , and intended to abut axially against the connecting face  18  of the tubular cylindrical tip  16  of the engine block  13 , against which the transverse connecting and fixing wall  21  abuts around the central outlet orifice  22  of the filter  7 . 
         [0053]    Finally, the connecting sleeve  30  includes an axial through-passage  36  for the passage of oil. 
         [0054]    The axial dimension of the intermediate abutment section  33  is chosen to compress the seal  29  sufficiently when the filter  7  is in position on the engine block  13 . 
         [0055]    In operation, oil arrives via the inlet passage  8 , as indicated by the arrow  34 , and then penetrates into the peripheral space  26  of the filter  7  on passing through the peripheral inlet orifice  23 , passes through the filter element  24  as indicated by the arrow  35 , is recovered in the central space  25  and then passes through the through-passage  36  of the connecting sleeve  30  to escape into the outlet passage  9  as indicated by the arrow  37 . 
         [0056]    In this known structure, oil is always allowed to flow in the through-passage  36  of the connecting sleeve  30 . 
         [0057]    The filter  7  itself can contain a check valve or a bypass valve, which are not represented in the figure. 
         [0058]    Consider now  FIGS. 3 to 5 , which show the device according to the invention. 
         [0059]    In this device, only the interior of the connecting sleeve  30  is modified. Thus all the other components of the known device from  FIG. 2  are seen again, and those components are identified in  FIGS. 3 to 5  with the same reference numbers. For this reason, these common components will not be described again. 
         [0060]    In particular, the exterior shape of the connecting sleeve  30  from  FIG. 3  is the same as the exterior shape of this sleeve in  FIG. 2 , in particular with regard to the dimensions of the threaded fixing section  31  and the threaded receiver section  32 . 
         [0061]    As in the known structure, the connecting sleeve  30  includes a through-passage  36  providing permanent communication between the central space  25  of the filter  7  and the outlet passage  9 . 
         [0062]    In the embodiment shown in  FIGS. 3 to 5 , the axial through-passage  36  of the connecting sleeve  30  comprises two successive sections, namely an inlet bore  38  and an outlet bore  39 , which are coaxial with respect to each other. The outlet bore  39  has a diameter smaller than the diameter of the inlet bore  38 . An intermediate shoulder  40  connects the inlet bore  38  to the outlet bore  39 , and thus constitutes an annular seat oriented toward the filter  7 . 
         [0063]    At least one radial passage  41  is provided in the intermediate abutment section  33 . The radial passage  41  provides communication between the inlet bore  38  of the through-passage  36  and the annular chamber  15  of the inlet passage  8 . 
         [0064]    A tubular piston  42  is mounted so as to slide axially in the inlet bore  38  and is pushed toward the engine block  13  by a return coil spring  43 . The return coil spring  43  is a compression spring disposed between the tubular piston  42  and a fixing key  44  engaged in the inlet bore  38 . 
         [0065]    The tubular piston  42  slides with a small clearance in the inlet bore  38 , so as to provide some degree of seal. 
         [0066]    The spring  43  pushes the tubular piston  42  against the intermediate shoulder  40 . In this position, as shown in  FIG. 3 , it blocks the radial passage  41 , preventing direct flow of oil from the inlet passage  8  toward the outlet passage  9 . 
         [0067]    Consider now  FIG. 5 , showing the state of the device assuming serious clogging of the filter element  24  of the filter  7 . 
         [0068]    In this state, because of the clogging of the filter  7 , the pressure P 1  in the inlet passage  8  is much higher than the pressure P 2  in the outlet passage  9 . 
         [0069]    If the pressure difference P 1 −P 2  is greater than a bypass valve triggering threshold, the tubular piston  42  is pushed toward the filter  7  against the return force of the spring  43 . In this position, the tubular piston  42  is moved away from the radial passage  41  and allows oil to flow directly from the inlet passage  8  toward the through-passage  36  and the outlet passage  9 . 
         [0070]    In this position, the direct flow of oil through the radial passage  41  causes a reduction in the pressure P 1  in the inlet passage  8 , providing the function of reducing any pressure rise, and enables sufficient oil to flow toward the outlet passage  9  to lubricate and cool the engine. 
         [0071]    The tubular piston  42  and the return spring  43  in the connecting sleeve  30  thus constitute a bypass valve (valve  10  in  FIG. 1 ), bypassing the filter  7  via the radial passage  41  and the outlet bore  39  which themselves constitute a bypass passage (bypass passage  11  in  FIG. 1 ). 
         [0072]    Consider now  FIG. 4 , which shows to a larger scale the elements of the bypass device according to the invention. 
         [0073]    The tubular piston  42  includes, over an outlet section of its exterior surface, an external annular recess  42   a  limited axially by a facet  42   b . In a closure position, the external annular recess  42   a  is in line with the radial passage  41  of the connecting sleeve  30 . As a result, a pressure rise in the radial passage  41 , coming from the inlet passage  8 , produces a differential thrust on the facet  42   b  and therefore moves the tubular piston  42  against the return force exerted by the spring  43 , i.e. upward in  FIG. 4 . 
         [0074]    As represented in the figures, a plurality of passages like the radial passage  41  are preferably provided, distributed at the periphery of the through-passage  36 , in order to ensure a sufficient rate of flow of oil to the engine in case of opening of the bypass valve, i.e. in case of blocking of the filter  7 . 
         [0075]    The force of the spring  43  will be chosen to cause the bypass valve  10  to open if the differential pressure P 1 −P 2  reaches a particular threshold for triggering the bypass valve  10 . 
         [0076]    Generally, the bypass valve  10  will be open before the relief valve  12  opens ( FIG. 1 ). 
         [0077]    A coarse filter can be added upstream of the radial passages  41  in order to prevent the passage of excessively large particles that could damage the components of the engine. In one practical embodiment, this kind of filter could be a cylinder with a pierced peripheral wall, engaged axially over the intermediate abutment section  33  of the connecting sleeve  30  so as to be disposed at the inlet of each radial passage  41 . 
         [0078]    The present invention is not limited to the embodiments that have been described explicitly, and includes the various variations and generalizations thereof within the scope of the following claims.