Patent Publication Number: US-7900610-B2

Title: Switching valve for EGR cooler

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is based upon and claims the benefit of priority from each of the prior Japanese Patent Application No. 2008-298883 filed on Nov. 24, 2008, the entire contents of which are incorporated herein by reference. 
     TECHNICAL FIELD 
     The present invention relates to an EGR cooler for cooling EGR gas in an engine and more particularly to a switching valve for an EGR cooler to switch a flow direction of EGR gas with respect to an EGR cooler. 
     BACKGROUND ART 
     Heretofore, as a technique of the above type, there is known an exhaust gas heat-exchanger disclosed in Patent Literature 1 mentioned below.  FIG. 10  is a cross sectional view of part of this heat-exchanger. This heat-exchanger includes a hollow shell  61  having an internal space and an exhaust gas manifold  62  fixed at one end of the shell  61 . The exhaust gas manifold  62  includes a first exhaust gas chamber  64  and a second exhaust gas chamber  65  adjacent to each other with a baffle plate  63  interposed therebetween. The exhaust gas chamber  64  includes an exhaust gas inlet  66  and the exhaust gas chamber  65  includes an exhaust gas outlet  67 , respectively. The first and second exhaust chambers  64  and  65  are partitioned by the baffle plate  63  and a flap valve element  68 . The flap valve element  68  is placed to be rotatable at its one end about a pin  69 . As shown by a solid line in  FIG. 10 , while the flap valve element  68  is placed in a closed position to close an opening  70  of the baffle plate  63 , exhaust gas flowing in the first exhaust gas chamber  64  is allowed to flow into the shell  61  and then flow into the second exhaust gas chamber  65  via the shell  61  without directly flowing into the second exhaust gas chamber  65 . On the other hand, as shown by a broken line in  FIG. 10 , while the flap valve element  68  is placed to open the opening  70 , the exhaust gas flowing in the first exhaust gas chamber  64  is allowed to directly flow into the second exhaust gas chamber  65 . As above, a flow direction of the exhaust gas is switched between a flow direction passing through the shell  61  and a flow direction not passing through the shell  61 . 
     CITATION LIST 
     Patent Literature 
     Patent Literature 1: Japanese national publication No. 2003-520922 
     SUMMARY OF INVENTION 
     Technical Problem 
     However, in the heat-exchanger disclosed in Patent Literature 1, the exhaust gas manifold  62  has to be formed with the opening  70  in the single baffle plate  63  separating the two exhaust gas chambers  64  and  65 . Thus, the exhaust gas manifold  62  could not be produced integrally by simply removing a mold. In particular, the opening  70  of the baffle plate  63  needs to be formed in a separate step. This results in an increase in the number of processes by just that much, leading to a cost increase. 
     The present invention has been made to solve the above problems and has a purpose to provide a switching valve for an EGR cooler to facilitate integral molding by mold removal. 
     Solution to Problem 
     To achieve the above purpose, one aspect of the present invention provides a switching valve for EGR cooler, the valve being to be provided in the EGR cooler to switch a flow direction of EGR gas with respect to the EGR cooler, the valve comprising: a valve housing molded by a mold and to be fixed to the EGR cooler; an inflow chamber formed in the valve housing so that EGR gas flows therein from an upstream side of the valve housing; a first passage formed in the valve housing to be adjacent to the inflow chamber through a first partition wall and to communicate with inside of the EGR cooler; a first communication hole formed in the first partition wall to provide communication between the inflow chamber and the first passage; an outflow passage through which EGR gas flows out of the valve housing to a downstream side thereof; a second passage formed in the valve housing to communicate with the outflow passage and be adjacent to the inflow chamber through a second partition wall, and communicate with the inside of the EGR cooler; a second communication hole formed in the second partition wall to provide communication between the inflow chamber and the second passage; a third partition wall dividing the first passage from the second passage, the first partition wall, the second partition wall, and the third partition wall being continuous to each other at a joined portion, forming a Y-shaped cross section; and a valve element placed to be swingable about a point near the joined portion between the first partition wall and the second partition wall, the valve element being swung to selectively close the first communication hole and the second communication hole, and the first partition wall and the second partition wall being slanted with respect to a mold-removing direction of a mold that forms the inflow chamber, and the third partition wall being almost parallel to a mold-removing direction of another mold that forms the first passage and the second passage. 
     Advantageous Effects of Invention 
     According to the above configuration, the valve housing of the switching valve is formed with the first partition wall having the first communication hole and the second partition wall having the second communication hole. This makes it possible to facilitate integral molding of the switching valve by mold removal using a molding mold. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a cross sectional view of an EGR cooler device in a first embodiment; 
         FIG. 2  is a cross sectional view showing a state where a joint pipe is removed from the EGR cooler device in the first embodiment; 
         FIG. 3  is a plan view of a switching valve in the first embodiment; 
         FIG. 4  is a cross sectional view of the switching valve in the first embodiment; 
         FIG. 5  is a cross sectional view showing a relationship between a valve housing and a mold for molding the housing; 
         FIG. 6  is a cross sectional view of an EGR cooler in a second embodiment; 
         FIG. 7  is a plan view of a switching valve in the second embodiment; 
         FIG. 8  is a cross sectional view of the switching valve in the second embodiment; 
         FIG. 9  is a cross sectional view showing a relationship between a valve housing and a mold for molding the housing; and 
         FIG. 10  is a cross sectional view showing a part of a heat-exchanger in a prior art. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     First Embodiment 
     A detailed description of a first preferred embodiment of a switching valve for an EGR cooler embodying the present invention will now be given referring to the accompanying drawings. 
       FIG. 1  is a cross sectional view of an EGR cooler device  1 . In use, this device is oriented with respect to “Top” and “Bottom” as shown in  FIG. 1 . This device  1  includes an EGR cooler  2 , a switching valve  4  fixed to the EGR cooler  2  through a gasket  3  to switch a flow direction of EGR gas with respect to the EGR cooler  2 , and a joint pipe  5  attached to the switching valve  4 . The EGR cooler  2  and the switching valve  4  are fastened to each other with bolts or the like (not shown) and similarly the switching valve  4  and the joint pipe  5  are fastened to each other with bolts or the like (not shown).  FIG. 2  is a cross sectional view showing a state where the joint pipe  5  is removed from the EGR cooler device  1 . 
     The EGR cooler  2  has an opening  6  at one end and an almost cup shape internally having a gas chamber  7 . The EGR cooler  2  has a double walled structure by an inner casing  8  and an outer casing  9 . Between the casings  8  and  9 , a water chamber  10  is formed to circulate cooling water. The EGR cooler  2  is provided with two pipe joints  11  and  12  each extending outward. Through those pipe joints  11  and  12 , the cooling water is supplied to and discharged from the water chamber  10 . 
       FIG. 3  is a plan view of the switching valve  4 .  FIG. 4  is a cross sectional view of the switching valve  4 . The switching valve  4  includes a valve housing  16 . A flange  16   a  is integrally formed at a rear end of the valve housing  16 . The valve housing  16  internally includes the inflow chamber  17 , a first partition wall  18 , a first passage  19 , a first communication hole  20 , an outflow passage  21 , a second passage  23 , a second partition wall  22 , a second communication hole  24 , and a third partition wall  25 . EGR gas will flow in the inflow chamber  17  from an upstream side of the valve housing  16 . The first passage  19  is adjacent to the inflow chamber  17  through the first partition wall  18  and communicates with the inside of the EGR cooler  2 . The first communication hole  20  is formed in the first partition wall  18  to provide communication between the inflow chamber  17  and the first passage  19 . The outflow passage  21  allows the EGR gas to flow out of the valve housing  16  to a downstream side thereof. The second passage  23  communicates with the outflow passage  21 , and is adjacent to the inflow chamber  17  through the second partition wall  22 , and communicates with the inside of the EGR cooler  2 . The second communication hole  24  is formed in the second partition wall  22  to provide communication between the inflow chamber  17  and the second passage  23 . The third partition wall  25  divides the first passage  19  from the second passage  23 . 
     The aforementioned first partition wall  18 , second partition wall  22 , and third partition wall  25  are joined to each other at a joined portion  26  in a Y-shaped cross section as shown in  FIGS. 1 ,  2 , and  4 . A flap valve element  27  is placed to be swingable about a point near the joined portion  26  between the first partition wall  18  and the second partition wall  22 . This valve element  27  is driven by an actuator (not shown) separately provided. When this valve element  27  is brought into surface contact with the first partition wall  18  or the second partition wall  22 , the first communication hole  20  and the second communication hole  24  are selectively closed. Specifically, when the valve element  27  closes the first communication hole  20 , the second communication hole  24  is opened. On the other hand, when the valve element  27  closes the second communication hole  24 , the first communication hole  20  is opened. When the valve element  27  closes the first communication hole  20  as shown by a solid line in  FIG. 1 , EGR gas flowing from the upstream side into the inflow chamber  17  is allowed to flow out through the outflow passage  21  via the second communication hole  24  and the second passage  23  as indicated by solid lines with arrows without passing through the gas chamber  7  of the EGR cooler  2 . On the other hand, when the valve element  27  closes the second communication hole  24  as shown by a chain double dashed line in  FIG. 1 , the EGR gas flowing from the upstream side into the inflow chamber  17  is allowed to flow through the gas chamber  7  of the EGR cooler  2  as indicated by double dashed lines with arrows, in which the EGR gas is cooled, and then the EGR gas is allowed to flow out through the outflow passage  21  via the second passage  23 . 
       FIG. 5  is a cross sectional view showing a relationship between the valve housing  16  and a first mold  31  and a second mold  32  for molding the housing  16 . The housing  16  is made of metal such as aluminum by use of the first and second molds  31  and  32 . The first mold  31  is configured to mainly form the inflow chamber  17  of the housing  16 . The second mold  32  is configured to mainly form the first passage  19  and the second passage  23  of the housing  16 . The first mold  31  is integrally formed with molding parts  31   a  and  31   b  for forming the first communication hole  20  and the second communication hole  24 . Both the molds  31  and  32  are clamped and between them molten metal is supplied. Thus, the first partition wall  18 , second partition wall  22 , and third partition wall  25  are formed continuously in the Y-shaped cross section. In addition, the first partition wall  18  and the second partition wall  22  are formed with the first communication hole  20  and the second communication hole  24  respectively. Herein, the first partition wall  18  and the second partition wall  22  are slanted in a bifurcated form with respect to a mold-removing direction F 1  of the first mold  31  that forms the inflow chamber  17 . The third partition wall  25  is almost parallel to a mold-removing direction F 2  of the second mold  32  that forms the first passage  19  and the second passage  23 . Furthermore, the first to third partition walls  18 ,  22 , and  25  are configured so that an inflow direction F 3  of EGR gas from the gas chamber  7  of the EGR cooler  2  to the second passage  23  intersects with an outflow direction F 4  of EGR gas through the outflow passage  21  as shown in  FIG. 2 . Herein, the outflow passage  21  is formed separately from the inflow chamber  17 , first passage  19 , and second passage  23 . 
     The first to third partition walls  18 ,  22 , and  25  are configured so that an inflow direction F 5  of EGR gas from the upstream side into the inflow chamber  17  and an outflow direction F 6  of EGR gas from the first passage  19  into the gas chamber  7  of the EGR cooler  2  are almost parallel to each other as shown in  FIG. 2 . Furthermore, the gas chamber  7  of the EGR cooler  2  is configured to direct the flow of EGR gas in a curved path like “U” as shown in  FIGS. 1 and 2 . An inflow port of the EGR cooler  2  for allowing EGR gas to flow in the gas chamber  7  is connected to the first passage  19 . An outflow port of the EGR cooler  2  for EGR gas to flow out of the gas chamber  7  is connected to the second passage  23 . During use of the EGR cooler device  1 , moreover, as shown in  FIG. 1 , the valve housing  16  is oriented so that the EGR gas outflow direction F 4  through the outflow passage  21  is directed to the “Bottom”. 
     As shown in  FIG. 1 , the joint pipe  5  has a function of introducing EGR gas into the inflow chamber  17  of the switching valve  4  and a function of connecting with an external EGR pipe. The joint pipe  5  is therefore provided with an inlet  35  for introducing EGR gas and a diffusion chamber  36  having a semispherical shape with a larger diameter than the inlet  35 . The shape and size of an opening of the diffusion chamber  36  is equal to an entrance of the inflow chamber  17  of the switching valve  4 . A front end and a rear end of the joint pipe  5  are formed with flanges  5   a  and  5   b  respectively. Accordingly, EGR gas introduced in the inlet  35  of the joint pipe  5  is allowed to diffuse in the diffusion chamber  36  and smoothly flow in the inflow chamber  17  of the switching valve  4 . The front-side flange  5   a  is connected to an EGR pipe continuous with an exhaust passage of an engine. 
     According to the aforementioned embodiment, the valve housing  16  of the switching valve  4  is configured such that the first partition wall  18 , the second partition wall  22 , and the third partition wall  25  are continuous with each other at the joined portion  26  in the Y-shaped cross section, the first partition wall  18  and the second partition wall  22  are slanted in a bifurcated form with respect to the mold-removing direction F 1  of the first mold  31  that forms the inflow chamber  17 , and the third partition wall  25  is almost parallel to the mold-removing direction F 2  of the second mold  32  that forms the first passage  19  and the second passage  23 . Therefore, as shown in  FIG. 5 , when the first mold  31  forming the inflow chamber  17  is to be removed from the molded housing  16 , the mold  31  can be easily separated from the first partition wall  18  and the second partition wall  22 . When the second mold  32  forming the first passage  19  and the second passage  23  is to be removed from the molded housing  16 , the mold  32  can be easily separated from the third partition wall  25 . Furthermore, one of the molds  31  and  32 , i.e., the first mold  31  is formed with the molding parts  31   a  and  31   b  for forming the communication holes  20  and  24  respectively as shown in  FIG. 5 . In the molding of the first and second partition walls  18  and  22 , the communication holes  20  and  24  are made at the same time when the molds  31  and  32  are removed from the housing  16 . Consequently, since the partition walls  18  and  22  having the communication holes  20  and  24  are formed in the valve housing  16 , such configuration can facilitate integral molding by removal of the molds  31  and  32 . In the present embodiment, therefore, the number of processes can be reduced, thereby saving a manufacturing cost of the switching valve  4  by just that much, as compared with the configuration that the communication holes  20  and  24  are formed in an additional process. 
     In the present embodiment, as shown in  FIG. 2 , the EGR gas inflow direction F 5  into the inflow chamber  17  of the valve housing  16  and the EGR gas outflow direction F 6  out of the first passage  19  are almost parallel to each other, so that the EGR gas flow direction does not much change. Thus, pressure loss of the EGR gas flowing from the switching valve  4  to the EGR cooler  2  is reduced and accordingly the flow amount of the EGR gas allowed to pass through the EGR cooler  2  can be increased. 
     In the present embodiment, in use of the EGR cooler device  1  shown in  FIG. 1 , the valve housing  16  is oriented so that the direction F 4  of EGR gas flowing out through the outflow passage  21  is directed to the “Bottom”. This orientation allows flocculated water to flow down out of the housing  16  through the outflow passage  21  without staying in the second passage  23  of the housing  16  and the gas chamber  7  of the EGR cooler  2 . The EGR cooler  2  and the housing  16  can therefore be prevented from corroding. 
     Second Embodiment 
     Next, a second embodiment of a switching valve for an EGR cooler according to the present invention will be described below with reference to the accompanying drawings. 
     In the following description, similar or identical parts or components to those in the first embodiment are given the same reference signs as those in the first embodiment. The following explanation is focused on differences from the first embodiment. 
       FIG. 6  is a cross sectional view of an EGR cooler device  41  in this embodiment. The orientation of this device  41  with respect to “Top” and “Bottom” in use is as shown in  FIG. 6 . This device  41  includes the EGR cooler  2  and a switching valve  42  fixed to the cooler  2  to switch the flow direction of EGR gas with respect to the cooler  2 . The EGR cooler  2  and the switching valve  42  are fastened to each other with bolts (not shown) or the like through the gasket  3 . 
       FIG. 7  is a plan view of the switching valve  42 .  FIG. 8  is a cross sectional view of the switching valve  42 . The switching valve  42  in the second embodiment is different from the switching valve  4  in the first embodiment in that the valve  42  integrally has the function of the joint pipe  5  instead of eliminating the joint pipe  5  in the first embodiment. The valve housing  16  in the second embodiment includes an introduction passage  43  extending from the inflow chamber  17  to the upstream side. For this introduction passage  43 , the housing  16  is integrally formed with a cylindrical joint pipe portion  16   b  in a front end portion. A front end of this joint pipe portion  16   b  is formed with a flange  16   c . Other configurations in this embodiment are basically identical to those in the first embodiment. 
       FIG. 9  is a cross sectional view showing a relationship between the valve housing  16  and a first mold  46  and a second mold  47  for molding the housing  16 . The first mold  46  is configured to mainly form the introduction passage  43  and the inflow chamber  17  of the housing  16 . The second mold  47  is configured to mainly form the first passage  19  and the second passage  23  of the housing  16 . The first mold  46  is integrally formed with molding parts  46   a  and  46   b  for forming the first communication hole  20  and the second communication hole  24 . Both the molds  46  and  47  are clamped and between them molten metal is supplied. Thus, the first partition wall  18 , second partition wall  22 , and third partition wall  25  are formed continuously in a Y-shaped cross section. In addition, the first partition wall  18  and the second partition wall  22  are formed with the first communication hole  20  and the second communication hole  24  respectively. Herein, the first partition wall  18  and the second partition wall  22  are slanted with respect to the mold-removing direction F 1  of the first mold  46  that forms the introduction passage  43  and the inflow chamber  17 . The third partition wall  25  is almost parallel to the mold-removing direction F 2  of the second mold  47  that forms the first passage  19  and the second passage  23 . Furthermore, the first to third partition walls  18 ,  22 , and  25  are configured so that an inflow direction of EGR gas from the gas chamber  7  of the EGR cooler  2  to the second passage  23  intersects with the outflow direction of the EGR gas through the outflow passage  21 . Herein, the outflow passage  21  is formed separately from the inflow chamber  17 , first passage  19 , and second passage  23 . 
     In the second embodiment, similarly to the first embodiment, when the first mold  46  forming the introduction passage  43  and the inflow chamber  17  is to be removed from the molded housing  16 , the first mold  46  can be easily separated from the first partition wall  18  and the second partition wall  22  as shown in  FIG. 9 . When the second mold  47  forming the first passage  19  and the second passage  23  is to be removed from the molded housing  16 , the second mold  47  can be easily separated from the third partition wall  25 . As shown in  FIG. 9 , furthermore, one of the molds  46  and  47 , i.e., the first mold  46  is formed with the molding parts  46   a  and  46   b  for forming the communication holes  20  and  24 . Accordingly, in the molding of the first and second partition walls  18  and  22 , the communication holes  20  and  24  are made simply at the same time when the molds  46  and  47  are removed from the housing  16 . Consequently, since the partition walls  18  and  22  having the communication holes  20  and  24  are formed in the valve housing  16 , such configuration can facilitate integral molding by removal of the molds  46  and  47 . In the present embodiment, therefore, the number of man-hours can be reduced, thereby saving a manufacturing cost of the switching valve  42  by just that much as compared with the configuration that the communication holes  20  and  24  are formed in an additional process. 
     Other operations and effects of the switching valve  42  in the second embodiment are the same as those of the switching valve  4  in the first embodiment. 
     The present invention is not limited to the aforementioned embodiment and may be embodied in other specific forms without departing from the spirit or essential characteristics thereof. 
     In the above embodiments, the first mold  31  or  46  and the second mold  32  or  47  are used to form the valve housing  16 . The molding parts  31   a  and  31   b  or  46   a  and  46   b  for forming the first and second communication holes  20  and  24  in the housing  16  are provided in only the first mold  31  or  46 . Alternatively, such molding parts may be provided in only the second mold or in both the first and second molds. 
     In the above embodiments, the valve housing  16  is made of metal such as aluminum. As an alternative, at least a valve housing of the switching valve may be made of resin, heat-hardening resin (bakelite-phenol resin), or others having a heat resistance property. The valve housing made of resin can have an internal surface in a mirror-smooth state as compared with the valve housing  16  made of metal. Thus, carbon particles or the like contained in EGR gas are hard to stick to such internal surface. In this case, a heat resistance property of the resin valve housing will not cause any problems only if it has an allowable temperature limit of about 200° C. 
     INDUSTRIAL APPLICABILITY 
     The present invention can be applied to an EGR device including an EGR cooler to be provided in an engine. 
     While the presently preferred embodiment of the present invention has been shown and described, it is to be understood that this disclosure is for the purpose of illustration and that various changes and modifications may be made without departing from the scope of the invention as set forth in the appended claims. 
     REFERENCE SIGNS LIST 
     
         
           1  EGR cooler device 
           2  EGR cooler 
           4  Switching valve 
           16  Valve housing 
           17  Inflow chamber 
           18  First partition wall 
           19  First passage 
           20  First communication hole 
           21  Outflow passage 
           22  Second partition wall 
           23  Second passage 
           24  Second communication hole 
           25  Third partition wall 
           26  Joined portion 
           27  Valve element 
           31  First mold 
           32  Second mold 
           41  EGR cooler device 
           42  Switching valve 
           46  First mold 
           47  Second mold 
         F 1  Mold-removing direction 
         F 2  Mold-removing direction 
         F 3  Inflow direction 
         F 4  Outflow direction 
         F 5  Inflow direction 
         F 6  Outflow direction