Patent Publication Number: US-7588020-B2

Title: Oil separator

Description:
BACKGROUND OF THE INVENTION 
   The present invention relates to an oil separator that separates oil contained in blow-by gas of an engine. 
   Conventionally, blow-by gas returning devices are known that return blow-by gas, which leaks out from combustion chambers of an engine to a crankcase, to an intake passage, thereby ventilating the crankcase. Blow-by gas contains oil mist. When the oil mist collects on the inner surface of the intake passage, foreign matter contained in intake air adheres to the oil mist, which may cause formation of deposit. Accordingly, oil separators have been proposed that separates and recovers oil mist in blow-by gas. For example, an oil separator disclosed in Japanese Laid-Open Patent Publication No. 9-88544 blows blow-by gas that has flowed into the oil separator through an inlet port on a plurality of diverting plates located in a blow-by gas passage, thereby recovering oil mist on the diverting plates through a drain port. On the other hand, the oil separator allows the blow-by gas, from which oil mist has been separated, to flow from an outlet port to an intake passage. 
   In the oil separator of the above publication, oil mist on the diverting plates is guided to the drain port while the blow-by gas is diverted along a blow-by gas passage. Therefore, the direction along which the oil mist is guided and the direction along which the blow-by gas flows intersect with each other, which may splash the oil mist anew. Such repeated splashing of oil mist reduces the recovery rate of oil mist. As a result, blow-by gas containing a considerable amount of oil mist is returned to the intake passage. 
   SUMMARY OF THE INVENTION 
   Accordingly, it is an objective of the present invention to provide an oil separator capable of preventing oil that has been separated from blow-by gas from being repeatedly splashed. 
   To achieve the foregoing objective, one aspect of the present invention provides an oil separator for separating oil contained in blow-by gas from the blow-by-gas. The oil separator includes a casing, a separation mechanism, and a drain port. The casing has an inlet port through which blow-by gas flows into the oil separator, and an outlet port through which the blow-by gas flows out of the oil separator. The casing defines a blow-by gas passage extending to connect the inlet port and the outlet port to each other. The separation mechanism is located in the blow-by gas passage. The separation mechanism traps oil in blow-by gas, thereby separating the oil from the blow-by gas. The drain port is formed in the casing, and drains the separated oil. The outlet port is located in one of side portions of the casing that are located in opposite ends. The drain port is located in the other one of the side portions. 
   Another aspect of the present invention provides an oil separator for separating oil contained in blow-by gas from the blow-by gas. The separator includes a casing, a separation mechanism, and a drain port. The casing has an inlet port through which blow-by gas flows into the oil separator, and an outlet port through which the blow-by gas flows out of the oil separator. The casing defines a blow-by gas passage extending to connect the inlet port and the outlet port to each other. The separation mechanism is located in the blow-by gas passage. The separation mechanism traps oil in blow-by gas, thereby separating the oil from the blow-by gas. The drain port is formed in the casing, and drains the separated oil. The drain port opens in a direction opposite to a direction of flow of blow-by gas from the separation mechanism toward the outlet port. 
   Other aspects and advantages of the invention will become apparent from the following description, taken in conjunction with the accompanying drawings, illustrating by way of example the principles of the invention. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention, together with objects and advantages thereof, may best be understood by reference to the following description of the presently preferred embodiments together with the accompanying drawings in which: 
       FIG. 1  is a diagrammatic view illustrating an engine having a blow-by gas returning device according to one embodiment of the present invention; 
       FIG. 2  is a cross-sectional view illustrating the oil separator provided in the blow-by gas returning device shown in  FIG. 1 ; 
       FIG. 3A  is a cross-sectional view taken along line  3 A- 3 A of  FIG. 2 ; 
       FIG. 3B  is a cross-sectional view taken along line  3 B- 3 B of  FIG. 2 ; and 
       FIG. 4  is a cross-sectional view illustrating an oil separator according to another embodiment of the present invention. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   A blow-by gas returning device according to one embodiment of the present invention will now be described with reference to  FIGS. 1 to 3 . 
     FIG. 1  illustrates an engine  1  having the blow-by gas returning device. A main body  2  of the engine  1  has a plurality of cylinders  3  (only one is shown). A piston  4  is located in each cylinder  3  to reciprocate. An intake manifold (intake passage)  5  is connected to the engine main body  2 . The interior of the intake manifold  5  communicates with the interior of the cylinders  3 , or combustion chambers. A valve chamber  6  is defined in an upper portion of the engine main body  2 . The valve chamber  6  accommodates a camshaft (not shown), which actuates intake valves and exhaust valves. The engine main body  2  includes a crankcase  7  located below the cylinders  3 . The engine main body  2  also includes a first guide passage  8  and a second guide passage  9  that connect the crankcase  7  with the valve chamber  6 . 
   In the engine main body  2 , an oil separator  10  is located above the valve chamber  6 . The oil separator  10  has an inlet port  10   a  that communicates with the valve chamber  6 . The oil separator  10  also has an outlet port  10   b  and a drain port  10   c . The oil separator  10  traps oil mist contained in blow-by gas flowing in through the inlet port  10   a , and discharges the purified blow-by gas (blow-by gas from which oil mist is removed) through the outlet port  10   b . The oil separator  10  drains the oil mist trapped in the oil separator  10  through the drain port  10   c . The outlet port  10   b  and the intake manifold  5  are connected to each other by a pipe  11 . A PCV valve  12 , which is an electromagnetic valve, is located in the pipe  11 . The PCV valve  12  is opened and closed, thereby connecting and disconnecting the outlet port  10   b  and the intake manifold  5  with respect to each other. 
   Next, the flow of blow-by gas will be described. When, during the operation of the engine  1 , the internal pressure of the intake manifold  5  becomes a negative pressure and the PCV valve  12  is opened, blow-by gas that leaks through a space between the piston  4  and the inner wall of the cylinder  3  is guided to the inlet port  10   a  of the oil separator  10  via the crankcase  7 , the first guide passage  8 , and the valve chamber  6  as illustrated by arrows of solid lines in  FIG. 1 . 
   The blow-by gas that has flowed into the oil separator  10  through the inlet port  10   a  is purified because oil mist contained in the blow-by gas is trapped by the oil separator  10 . The purified blow-by gas flows out through the outlet port  10   b , and is guided the intake manifold  5  through the pipe  11 . Unburned fuel contained in the blow-by gas that has flowed into the intake manifold  5  is drawn into the cylinder  3  and burned. 
   On the other hand, the oil mist trapped in the oil separator  10  is drained through the drain port  10   c  as shown by arrows of dotted lines in  FIG. 1 , and reaches an oil pan  13  located below the crankcase  7  via the second guide passage  9  and the crankcase  7 . The interior of the crankcase  7  communicates with the atmosphere through an unillustrated passage. 
   The internal structure of the oil separator  10  will now be described with reference to  FIGS. 2 to 3B . The oil separator  10  includes a casing  21 , which is provided with the inlet port  10   a , the outlet port  10   b , and the drain port  10   c.    
   The casing  21  has side portions located at opposite ends. The inlet port  10   a  and the outlet port  10   b  are located in one of the side portions (the left side portion as viewed in  FIG. 2 ). The drain port  10   c  is located in the other one of the side portions (the right side portion as viewed in  FIG. 2 ). A blow-by gas passage  22  is defined in the interior of the casing  21  by a dividing portion  21   a . The blow-by gas passage  22  is U-shaped as a whole and includes through passage sections (first to third passage sections)  23 ,  24 , and  25 . The inlet port  10   a  and the outlet port  10   b  are connected to each other by the blow-by gas passage  22 . The drain port  10   c  is formed in the casing  21  to be located at a turned section of the blow-by gas passage  22 . The drain port  10   c  opens in a different direction (substantially, opposite direction) from the opening direction of the outlet port  10   b  (see  FIG. 3B ). In other words, the drain port  10   c  opens in a different direction (substantially, opposite direction) from a direction in which blow-by gas flows out the outlet port  10   b.    
   A separation mechanism  30  is located in the blow-by gas passage  22 , specifically, between the first passage section  23  and the second passage section  24 . The separation mechanism  30  traps oil mist in blow-by gas, and drains the oil mist through the drain port  10   c . The separation mechanism  30  includes a restriction plate  31  having a plurality of holes  31   a , and a trapping plate  32  for trapping oil mist in blow-by gas, and a backflow prevention plate  33  that prevents oil from flowing back from the drain port  10   c . The drain port  10   c  is also a component of the separation mechanism  30 . 
   As shown in  FIGS. 3A and 3B , the casing  21  is inclined such that the inlet port  10   a  and the outlet port  10   b  are located higher than the drain port  10   c . The third passage section  25  of the blow-by gas passage  22  is located downstream of the separation mechanism  30 , and higher than the separation mechanism  30 . On the other hand, the second passage section  24  of the blow-by gas passage  22 , which is located upstream of the third passage section  25 , is located lower than the restriction plate  31  and the trapping plate  32  of the separation mechanism  30 . In a horizontal cross-section shown in  FIG. 2 , the width D 1  of the third passage section  25  is less than the width D 2  of the second passage section  24 . That is, the cross-sectional area of the third passage section  25  is smaller than the cross-sectional area of the second passage section  24 . The outlet port  10   b  is located in an upper surface of the casing  21 , and opens upward so that blow-by gas flows out upward along a vertical direction (see  FIG. 3B ). 
   Next, the flow of blow-by gas and the flow of oil mist in the oil separator  10  will be described. During the operation of engine  1 , when the internal pressure of the intake manifold  5  becomes a negative pressure and the PCV valve  12  is open, blow-by gas flows into the casing  21  through the inlet port  10   a , and flows out through the outlet port  10   b.    
   The flow of blow-by gas in the casing  21  is shown by arrows of solid lines in  FIGS. 2 to 3B . Blow-by gas containing oil mist flows into the first passage section  23  of the blow-by gas passage  22  from the inlet port  10   a , and the flow is restricted by the holes  31   a  of the restriction plate  31 . That is, by passing through the holes  31   a , the flow velocity of the blow-by gas is increased. The blow-by gas with an increased flow velocity collides against the trapping plate  32 , so that some of the oil mist contained in the blow-by gas collects on the trapping plate  32  and condenses. On the other hand, the blow-by gas, from which some of the oil mist has been separated, turns around as shown by an arrow of solid lines in  FIG. 2  after passing by the trapping plate  32 . The oil mist that remains in the blow-by gas has a relatively great mass, and its direction of flow cannot be easily changed due to the inertia. Therefore, when the blow-by gas turns around, the oil mist in the blow-by gas collides against a wall surface  21   c  of the casing  21  having the drain port  10   c  and a wall surface  33   a  of the backflow prevention plate  33 , and collects on the wall surfaces  21   c ,  33   a . The blow-by gas, from which oil mist has been further removed by the wall surfaces  21   c ,  33   a , passes through the second passage section  24  and reaches the third passage section  25 . Since the cross-sectional area of the third passage section  25  is smaller than the cross-sectional area of the second passage section  24 , the flow velocity of blow-by gas is increased in the third passage section  25 . The blow-by gas then flows upward out of the outlet port  10   b.    
   The flow of oil mist collected on the trapping plate  32  shown by arrows of broken lines in  FIGS. 2 to 3A . The oil mist collected on the trapping plate  32  condenses to form liquid oil  26 , and flows down on a front surface  32   a  of the trapping plate  32  and reaches a bottom surface  21   b  of the casing  21 . After reaching the bottom surface  21   b , the oil  26  is guided to the drain port  10   c  after streaming on the bottom surface  21   b , which is inclined relative to a horizontal plane. The oil mist collected on the wall surface  21   c  of the casing  21  and the wall surface  33   a  of the backflow prevention plate  33  flows down to the bottom surface  21   b  of the casing  21 , and is guided to the drain port  10   c  after streaming on the bottom surface  21   b . The oil  26 , which has been guided to the drain port  10   c , is recovered to the oil pan  13  from the drain port  10   c  via the second guide passage  9 . 
   In the oil separator  10  configured as described above, the draining direction of the oil mist and the discharging direction of the blow-by gas are significantly different from each other, and the oil mist separated from the blow-by gas by the separation mechanism  30  is prevented from being raised and repeatedly splashed by the flow of the blow-by gas. In a portion where blow-by gas contacts the oil  26  spread on the bottom surface  21   b  of the casing  21 , the oil  26  is possibly raised and repeatedly splashed by the flow of the blow-by gas. Therefore, the second passage section  24 , which is adjacent to and downstream of the separation mechanism  30 , preferably has a relatively large cross-sectional area so that the flow velocity is reduced in the second passage section  24 . On the other hand, in the third passage section  25 , which is located above the separation mechanism  30 , the oil  26  hardly exists on the bottom surface  21   b  of the casing  21 . Thus, even if the cross-sectional area of the third passage section  25  is relatively reduced to increase the flow velocity of the blow-by gas, the oil  26  is unlikely to be repeatedly splashed. 
   The above described embodiment provides the following advantages. 
   (1) The outlet port  10   b  is located in one of the opposite side portions of the casing  21 . The drain port  10   c  is located in the other one of the opposite side portions of the casing  21 . The drain port  10   c  opens in a direction opposite to the direction of flow of blow-by gas from the separation mechanism  30  toward the outlet port  10   b . The blow-by gas from which oil is separated by the trapping plate  32  is guided to the outlet port  10   b , and oil mist collected on the trapping plate  32  is guided to the drain port  10   c  located in a side opposite to the side of the outlet port  10   b . Therefore, the draining direction of oil mist and the discharging direction of blow-by gas are greatly different from each other. Therefore, the blow-by gas is prevented from contacting the oil  26  spread on the bottom surface  21   b  of the casing  21 . Accordingly, oil mist is prevented from raised and repeatedly splashed by the flow of the blow-by gas. 
   (2) The outlet port  10   b  and the drain port  10   c , which are located in the opposite side portions of the casing  21 , are separated from each other by a great distance. Therefore, oil accumulated in the drain port  10   c  is suppressed from flowing out from the outlet port  10   b  as much as possible. 
   (3) The drain port  10   c  opens in a direction opposite to the second and third passage sections  24 ,  25 , through which blow-by gas flows after oil mist has been removed therefrom. Therefore, the draining direction of oil mist and the discharging direction of blow-by gas can be significantly different from each other. This prevents oil mist from raised and repeatedly splashed by the flow of blow-by gas. 
   (4) The inlet port  10   a  and the outlet port  10   b  are located in the same side portion of the casing  21  so that the blow-by gas passage  22  has a U-shape. The drain port  10   c  is provided in the casing  21  to be located at the turned section of the blow-by gas passage  22 . When blow-by gas turns around, oil mist contained the blow-by gas collides against the wall surface  21   c  of the casing  21  and the wall surface  33   a  of the backflow prevention plate  33  located at the turned section of the blow-by gas passage  22 , and is readily guided to the drain port  10   c . Therefore, oil mist is reliably separated from blow-by gas with a relatively compact structure. 
   (5) The drain port  10   c  is located in the turned section of the U-shaped blow-by gas passage  22 . Therefore, the oil  26  accumulated in the turned section of the blow-by gas passage  22  is efficiently drained from the drain port  10   c.    
   (6) The outlet port  10   b  is located in the upper surface of the casing  21 , and opens upward so that blow-by gas flows out upward along a vertical direction. Oil mist contained in blow-by gas has a relatively large mass, and therefore does not easily flow vertically upward due to the action of gravity. Therefore, oil mist is suppressed from flowing out through the outlet port  10   b  as much as possible. 
   (7) The cross-sectional area of the third passage section  25 , which is located downstream of and higher than the separation mechanism  30 , is smaller than the cross-sectional area of the second passage section  24 , which is located lower than the restriction plate  31  and the trapping plate  32  of the separation mechanism  30 . In the third passage section  25 , the oil  26  hardly exists on the bottom surface  21   b  of the casing  21 . Thus, even if the cross-sectional area of the third passage section  25  is relatively reduced to increase the flow velocity of the blow-by gas, the oil  26  is unlikely to be repeatedly splashed. Therefore, the size of the oil separator is reduced by reducing the cross-sectional area of the third passage section  25 , while suppression the repeated splash of oil. 
   The above illustrated embodiment may be modified as follows. 
   In the embodiment of  FIGS. 1 to 3B , the blow-by gas passage  22  is U-shaped. However, the blow-by gas passage  22  may have a different shape. For example, in an oil separator  40  shown in  FIG. 4 , an L-shaped blow-by gas passage is formed in the casing  21 . The oil separator  40  separates oil mist in blow-by gas that has flowed in through the inlet port  10   a  by means of the trapping plate  32 , and guides the purified blow-by gas to the outlet port  10   b  located in a side portion of the casing  21  (see arrows of solid lines). On the other hand, the separated oil mist is guided to the drain port  10   c , which is located in port  10   b  (see arrow of broken line). This configuration also greatly differentiates the draining direction of oil mist and discharging direction of blow-by gas from each other, and suppresses repeated splash of oil mist. 
   In the embodiment of  FIGS. 1 to 3B , the drain port  10   c  is located in the turned section of the U-shaped blow-by gas passage  22 , and opens in a direction opposite to the second and third passage sections  24 ,  25 . However, the drain port  10   c  may be located downstream of or upstream of the turned section of the blow-by gas passage  22 , and may open in an arbitrary direction. 
   In the embodiment of  FIGS. 1 to 3B , the outlet port  10   b  is located in the upper surface of the casing  21 , and opens upward. However, the outlet port  10   b  may be located in a surface other than the upper surface of the casing  21 , and open in a direction other than an upward direction. 
   In the illustrated embodiments, the casing  21  is inclined such that the inlet port  10   a  and the outlet port  10   b  are located higher than the drain port  10   c . However, the casing  21  does not need to be inclined, and the inlet port  10   a  and the outlet port  10   b  may be located at the same height as or lower than the drain port  10   c.    
   In the embodiment of  FIGS. 1 to 3B , the cross-sectional area of the third passage section  25 , which is located downstream of and higher than the separation mechanism  30 , is smaller than the cross-sectional area of the second passage section  24 , which is located lower than the third passage section  25 . However, if there is no possibility of repeated splash of oil mist, the cross-sectional area of the second passage section  24  may be reduced such that the cross-sectional area of the second passage section  24  is equal to the cross-sectional area of the third passage section  25 . 
   In the illustrated embodiments, the single trapping plate  32  is used. However, two or more trapping plates  32  may be provided. The trapping plate  32  does not need to be shaped as a plate, but may have a different shape as long as it traps oil mist. 
   In the illustrated embodiments, the restriction plate  31  and the trapping plate  32  are located upstream of the turned section of the blow-by gas passage. However, the restriction plate  31  and the trapping plate  32  may be located downstream of the turned section. 
   Therefore, the present examples and embodiments are to be considered as illustrative and not restrictive and the invention is not to be limited to the details given herein, but may be modified within the scope and equivalence of the appended claims.