Patent Publication Number: US-2016227677-A1

Title: Electric power converter

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is based on and claims the benefit of priority from earlier Japanese Patent Application No. 2015-15204 filed Jan. 29, 2015, the description of which is incorporated herein by reference. 
     TECHNICAL FIELD 
     The present disclosure relates to an electric power converter having a semiconductor module and a reactor. 
     BACKGROUND 
     An electric power converter, which generates power for driving a hybrid car or an electric vehicle, for example, has a reactor constituting a booster circuit for boosting a power supply voltage. 
     With the increase of the current supplied to the electric power converter, heat generation of not only semiconductor modules but the reactor tends to increase. 
     Therefore, an electric power converter provided with a cooler for cooling a reactor with semiconductor modules has been proposed (refer to Japanese Patent Application Laid-Open Publication No. 2014-138012, for example). 
     However, a coil of the reactor is embedded in a core in the electric power converter disclosed in the Publication No. &#39;012. 
     That is, the coil is covered with the core. 
     Thus, although the reactor is in contact with the cooler, the core is interposed between the coil and the cooler. 
     Hence, the coil that is a main heat source of the reactor is difficult to cool efficiently. 
     As a result, there is a problem that it is difficult to improve the heat dissipation efficiency of the reactor. 
     SUMMARY OF THE DISCLOSURE 
     An embodiment provides an electric power converter having excellent cooling efficiency of a reactor. 
     An electric power converter in a first aspect includes a semiconductor module having a built-in semiconductor element therein, a reactor having a coil made of a conductor and a core, which is made of a magnetic material, that covers at least a portion of an outside of the coil, and a cooler for cooling the semiconductor module and the reactor. 
     The cooler has a coolant passage member having a coolant flow path, and the coil of the reactor has an exposed coil portion exposed from the core. 
     The exposed coil portion is in contact with the coolant passage member, the core has a core end face disposed flush with the exposed coil portion, and both the exposed coil portion and the core end face are in surface contact with the coolant passage member. 
     In the electric power converter mentioned above, the reactor is incorporated in the stacked body in a state of being sandwiched between cooling tubes, which are coolant passage members, from both sides in the stacking direction. 
     Thereby, it is possible to cool the reactor from both sides in the stacking direction. 
     In addition, the coil has the exposed coil portions, and the exposed coil portions are in contact with the cooling tubes. 
     Thereby, the heat of the coils can be dissipated directly to the cooling tubes from the exposed coil portions. 
     In other words, since it is possible to directly cool the coil that is the main heat source in the reactor by the cooler, it is possible to improve the cooling efficiency of the reactor. 
     As described above, according to the present disclosure, it is possible to provide an electric power converter having excellent reactor cooling efficiency. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       In the accompanying drawings: 
         FIG. 1  shows a plan view of an electric power converter in a first embodiment; 
         FIG. 2  shows a sectional view taken along a line II-II in  FIG. 1 ; 
         FIG. 3  shows a perspective view of a stacked body in the first embodiment; 
         FIG. 4  is a plan view of the stacked body in a state with one of divided core members removing in the first embodiment; 
         FIG. 5  shows a perspective view of a reactor in the first embodiment; 
         FIG. 6  shows a exploded perspective view of the reactor in first embodiment; 
         FIG. 7  is a plan view of a stacked body in a state with one of divided core members removed in a second embodiment; and 
         FIG. 8  is a plan view of a stacked body in a state with one of divided core members removed in a third embodiment. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     First Embodiment 
     An embodiment of an electric power converter will be described with reference to  FIGS. 1 to 6 . 
     As shown in  FIGS. 1 to 4 , an electric power converter  1  includes semiconductor modules  2  having built-in semiconductor elements therein, a reactor  3  having a coil  31  made of a conductor and a core  32 , which is made of a magnetic material, that covers at least a portion of an outside of the coil  31 , and a cooler  4  for cooling the semiconductor modules  2  and the reactor  3 . 
     The cooler  4  has a plurality of cooling tubes  41 , which are coolant passage members, stacked with the semiconductor modules  2  and the reactor  3 . 
     The respective semiconductor modules  2  and the reactor  3  are sandwiched by the cooling tubes  41  from both sides in a stacking direction X. 
     A stacked body  11  composed of the semiconductor modules  2 , the reactor  3  and the cooling tubes  41  is pressed in the stacking direction X. 
     The reactor  3  is incorporated into the stacked body  11  in a state where an axial direction Z of the coil  31  is perpendicular to the stacking direction X. 
     As shown in  FIGS. 2, 4, and 5 , the coil  31  has exposed coil portions  311  that are exposed at least in one of the stacking directions X from the core  32 . 
     Moreover, the exposed coil portions  311  are in contact with the cooling tubes  41 . 
     That is, the exposed coil portions  311  are in contact with the cooling tubes  41  without an intervention of the core  32 . 
     The exposed coil portions  311  may be in contact with the cooling tubes  41  directly, or may be in contact through members having thermal conductivity. 
     Further, the coil  31  is formed by winding a conductor wire with an insulating film on its surface, and there exist electrically insulating films on the exposed coil portions  311 . 
     As shown in  FIGS. 2, and 4 to 6 , the coil  31  has the exposed coil portions  311  on both sides in the stacking direction X. 
     The core  32  includes outer leg portions  321  disposed on an outer peripheral side of the coil  31 , inner leg portions  322  disposed on an inner peripheral side of the coil  31 , and base portions  323  that connect the outer leg portions  321  and the inner leg portions  322 . 
     The outer leg portions  321  are disposed at positions in a width direction Y that is perpendicular to both the stacking direction X and the axial direction Z relative to the coil  31 . 
     In the present specification, the stacking direction X and the axial direction Z mean the stacking direction of the stacked body  11  and the axial direction of the coil  3 , respectively. 
     Moreover, the width direction Y means a direction perpendicular to both the stacking direction X and the axial direction Z. 
     As shown in  FIG. 6 , the core  32  of the reactor  3  is formed of a pair of divided core members  320  that are divided in the axial direction Z. 
     In other words, the core  32  is a so-called EE core, and each of the divided core members  320  has a substantially E-shaped cross section that is perpendicular to the stacking direction X of the stacked body  11 . 
     That is, each of the divided core members  320  has a substantially flat plate-like base portion  323 , a pair of outer leg portions  321  protruding in the axial direction Z from both ends of the base portion  323 , and the inner leg portion  322  protruding from a center of the base portion  323  in the same direction as the outer leg portions  321 . 
     Then, the core  32  is formed by joining the pair of divided core members  320  so as protruding sides of the outer leg portions  321  and the inner leg portions  322  to face each other. 
     As shown in  FIGS. 2 and 4 , the core  32  has core end faces  324  disposed flush with the exposed coil portions  311 , and both the exposed coil portions  311  and the core end faces  324  are in surface contact with the cooling tubes  41 . 
     The core  32  (the divided core members  320 ) is formed by compacting a soft magnetic powder such as iron powder, for example. 
     It should be noted that the materials and production method of the core  32  are not particularly limited as long as it is made of a soft magnetic material. 
     As shown in  FIG. 6 , the coil  31  is formed by winding a rectangular conductor helically in a state that a major surface of the conductor faces the axial direction Z. 
     In other words, the coil  31  is wound in a so-called edge-wise winding. 
     In addition, the rectangular conductor is formed by forming an insulating film such as enamel on a surface thereof. 
     Further, the coil  31  is formed by forming a flat surface on each end face of the coil  31  in the stacking direction X, and these flat surfaces are the exposed coil portions  311 . 
     Moreover, another flat surface is formed on each end face of the coil  31  in the width direction Y. 
     As shown in  FIG. 4 , a length of the coil  31  in the stacking direction X is larger than a length of the coil  31  in the width direction Y. 
     Moreover, as shown in  FIGS. 5 and 6 , the coil  31  has a pair of terminals  312  protruding in the same direction in the axial direction Z. 
     As shown in  FIGS. 1 to 3 , the pair of terminals  312  are drawn out from a side of the coil  31  closer to the semiconductor modules  2 . 
     As shown in  FIGS. 2 and 4 , the coil  31  is matched with the core  32  in a state in which the inner leg portions  322  of the core  32  are inserted in an inner peripheral side of the coil  31 . 
     In other words, the coil  31  is disposed in a state so as to wound around the inner leg portions  322  of the core  32 . 
     Further, as shown in  FIG. 6 , insulating members  33  for electrically insulating the coil  31  and the core  32  are interposed between the coil  31  and the core  32 . 
     A pre-molded resin molding as the insulating member  33 , for example, may be assembled together with the coil  31  and the core  32 . 
     Moreover, after the matching of the coil  31  and the core  32 , a liquid resin may be filled and solidified in a gap between the coil  31  and the core  32 . 
     Furthermore, the insulating member  33  may also be other aspects such as an insulating paper, for example. 
     The insulating members  33  are disposed in a state of being in contact with the coil  31  and the core  32 . 
     Then, at least in the stacking direction X, the coil  31  abuts the inner leg portions  322  via the insulating members  33 , and is configured such that a load in the stacking direction X is transmitted between the coil  31  and the inner leg portions  322 . 
     As shown in  FIGS. 1 to 4 , the cooler  4  is formed by stacking a plurality of cooling tubes  41  and each of them are connected to each other by connecting pipes  42  in vicinities of both end portions of the cooling tube  41  in the width direction Y. 
     Further, a coolant inlet pipe  431  for introducing a coolant to the cooler  4  and a coolant outlet pipe  432  for discharging the coolant from the cooler  4  are disposed at one end of the cooler  4  in the stacking direction X. 
     A side in which the coolant inlet pipe  431  and the coolant outlet pipe  432  are disposed is referred to as a front of the cooler  4  (stacked body  11 ) and an opposite side as a rear for the sake of convenience in the various embodiments. 
     The stacked body  11  is formed by disposing the semiconductor modules  2  respectively to a plurality of gaps formed between the plurality of cooling tubes  41  in the cooler  4 . 
     Among the gaps between the cooling tubes  41  in the cooler  4 , the reactor  3  is disposed in the rearmost gap. 
     The gap where the reactor  3  is disposed has a larger length in the stacking direction X than the gaps where the semiconductor modules  2  are disposed. 
     Therefore, the connecting pipes  42  connecting the cooling tubes  41  sandwiching the reactor  3  are longer than the other connecting pipes  42 . 
     As shown in  FIGS. 2  and  FIG. 4 , the reactor  3  is in surface contact with the pair of cooling tubes  41  at a pair of exposed coil portions  311  and a pair of core end faces  324 , respectively. 
     In other words, cooling surfaces of the cooling tubes  41 , which are flat surfaces, are in surface contact with both the exposed coil portions  311  and the core end surface  324  that are flush flat surfaces. 
     Then, the cooling tubes  41 , and the exposed coil portions  311  and the core end faces  324  are in close contact in a state of being pressed in the stacking direction X to each other. 
     In addition, the semiconductor modules  2  and the cooling tubes  41  are also being pressed in a state of surface contacting with each other. 
     The coolant introduced from the coolant inlet pipe  431  passes through the connecting pipes  42  y and is distributed to each cooling tube  41 , and flows in a longitudinal direction of the cooling tube  41  through coolant flow paths inside the cooling tube  41  (i.e., in the width direction Y). 
     Then, while flowing through the cooling tubes  41 , the coolant exchanges heat with the semiconductor modules  2  and the reactor  3 . 
     The coolant of which the temperature is raised by the heat exchange passes through the connecting pipes  42  on a downstream side appropriately and is guided to the coolant outlet pipe  432 , the discharged from the cooler  4 . 
     As for the coolant, for example, a natural coolant such as ammonia or water, water mixed with ethylene glycol-based antifreeze, a fluorocarbon-based coolant such as FLUORINERT (registered trademark), another fluorocarbon-based coolant such as HCFC123 or HFC134a, a methanol, an alcohol-based coolant such as an alcohol, or a ketone-based coolant such as acetone can be used. 
     As shown in  FIGS. 1 and 2 , the stacked body  11  is pressed in the stacking direction X. 
     That is, the electric power converter  1  is formed by disposing the stacked body  11  in the case  12 , and disposing a pressing member  13  at a rear end side of the stacked body  11 . 
     The pressing member  13  is pressing a rear end face  111  of the stacked body  11  in the stacking direction X toward the front. 
     The pressing member  13  is, for example, a leaf spring, and is interposed between the rear end face  111  of the stacked body  11  and an inner wall surface  121 , which faces the rear end surface  111 , of the case  12  in a state of being compressed elastically deformed in the stacking direction X. 
     Note that the manner of construction or arrangement of the pressing member  13  is not particularly limited. 
     The electric power converter  1  is mounted on an electric vehicle or a hybrid vehicle, and is used as an inverter for converting a source power to a driving power required for driving a motor, for example. 
     Next, functions and effects of the present embodiment will be described. 
     In the electric power converter  1 , the reactor  3  is incorporated in the stacked body  11  in a state where being sandwiched between the cooling tubes  41  from both sides in the stacking direction X. 
     Thereby, it is possible to cool the reactor  3  from both sides in the stacking direction X. 
     In addition, the coil  31  has the exposed coil portions  311 , and the exposed coil portions  311  are in contact with the cooling tubes  41 . 
     Thereby, the heat of the coils  31  can be dissipated directly to the cooling tubes  41  from the exposed coil portions  311 . 
     In other words, since it is possible to directly cool the coil  31  that is the main heat source in the reactor  3  by the cooler  4 , it is possible to improve the cooling efficiency of the reactor  3 . 
     In addition, the coil  31  has the exposed coil portions  311  on both sides in the stacking direction X. 
     Thus, it is possible to perform the heat dissipation of the coil  31  efficiently from both sides in the stacking direction X. 
     In addition, the pressing force (sandwiching force) from the pair of cooling tubes  41  that sandwich the reactor  3  can be received in the coil  31 . 
     In other words, the coil  31  acts in the role of a beam with respect to the pressing force applied to the reactor  3 . 
     In general, it is possible to incorporate the reactor  3  into the stacked body  11  without being reinforced by a separate member particularly by being configured to receive the pressing force by the coil  31  that has a higher strength than the core  32 . 
     As a result, a reduction of the number of parts and a miniaturization can be easily realized. 
     Further, the core  32  has the outer leg portions  321 , the inner leg portions  322 , and the base portions  323 , and the outer leg portions  321  are disposed at the positions in the width direction Y with respect to the coil  31 . 
     Thereby, the rigidity of the coil  31  in the stacking direction X can also be increased by the inner leg portions  322  disposed inside the coil  31 . 
     As a result, it is possible to improve the strength of the reactor  3  with respect to the pressing force. 
     In addition, it is possible to sufficiently secure the magnetic circuit of the reactor  3 , and thus it is possible to secure a sufficient inductance. 
     Further, the core  32  has the core end faces  324  disposed flush with the exposed coil portions  311 , and both the exposed coil portions  311  and the core end faces  324  are in surface contact with the cooling tubes  41 . 
     This makes it possible to further improve the strength of the reactor  3  with respect to the pressing force in the stacking direction X. 
     Moreover, since it is possible to dissipate the heat to the cooling tubes  41  also from the core  32  in addition to the coil  31 , it is possible to further improve the cooling efficiency of the reactor  3 . 
     As described above, according to the present embodiment, it is possible to provide the electric power converter having excellent reactor cooling efficiency. 
     Second Embodiment 
     It should be appreciated that, in the second embodiment and the subsequent embodiments, components identical with or similar to those in the first embodiment are given the same reference numerals unless otherwise indicated so, and repeated structures and features thereof will not be described in order to avoid redundant explanation. 
     As shown in  FIG. 7 , the exposed coil portions  311  protrude in the stacking direction X more than the core end surface  324  does in the electric power converter  1  according to the present embodiment. 
     The pair of exposed coil portions  311  are respectively disposed further away from the outer side than the pair of core end faces  324  are in the stacking direction X. 
     Then, the reactor  3  is in contact with the cooling tubes  41  at the exposed coil portions  311 , while the core end faces  324  are not in contact with the cooling tubes  41 . 
     That is, clearances are formed between the core end surfaces  324  and the cooling tubes  41 . 
     The remainder is the same as the first embodiment. 
     Since the exposed coil portions  311  protrude in the stacking direction X more than the core end faces  324  do in the present embodiment, the exposed coil portions  311  can be reliably brought into contact with the cooling tubes  41 . 
     In other words, even if there is some lengthal tolerance, the exposed coil portions  311  may be disposed reliably at both ends of the reactor  3  in the stacking direction X. 
     Then, the pressure from the cooling tubes  41  can be received reliably at the exposed coil portions  311 . 
     As a result, it is possible to reliably improve the cooling efficiency of the reactor  3 , and also it is possible to dispose the reactor  3  stably between the cooling tubes  41 . 
     The remainder has the same functions and effects as in the first embodiment. 
     Third Embodiment 
     As shown in  FIG. 8 , the reactor  3  is disposed so that a lateral direction (a short side direction) of the coil  31  is in the stacking direction X when viewed from the axial direction Z in the electric power converter  1  of the present embodiment. 
     That is, the length of the coil  31  of the reactor  3  in the stacking direction X is shorter than the length of the coil  31  in the width direction Y. 
     Then, the exposed coil portions  311  are formed on both sides in the lateral direction of the coil  31 . 
     The remainder is the same as first embodiment. 
     Since the exposed coil portions  311  are formed on both sides in the lateral direction of the coil  31 , it is possible to obtain larger areas of the exposed coil portions  311  in the present embodiment. 
     As a result, heat dissipation of the coil  31 , as well as the cooling efficiency of the reactor  3  can be improved. 
     Moreover, since the exposed coil portions  311  are disposed on both sides in the lateral direction of the coil  31 , heat transferring distances from each portion of the coil  31  to the exposed coil portions  311  tend to be shorter. 
     From this point of view, the heat dissipation of the coil  31 , as well as the cooling efficiency of the reactor  3  can be improved. 
     The remainder has the same functions and effects as in the first embodiment. 
     The present disclosure is not limited to the above embodiments; however, various modifications are possible within the scope of the present disclosure. 
     For example, a position at which the reactor in the stacked body is disposed is not limited to the gap at the rear end of the stacked body  11 , but may be other positions such as a gap at the front end of the stacked body  11 .