Patent Publication Number: US-2012025642-A1

Title: Rotating electric machine

Description:
TECHNICAL FIELD 
     The present invention relates to a rotating electric machine, and more particularly relates to a rotating electric machine having a permanent magnet embedded therein. 
     BACKGROUND ART 
     In a rotating electric machine having a permanent magnet embedded therein, a rare-earth magnet is occasionally used as the permanent magnet in order to realize high efficiency and size reduction. In particular, an Nd (neodymium) magnet having a considerably high magnetic characteristic is used occasionally. Such an Nd magnet is excellent in magnetic characteristic, but is poor in temperature characteristic because holding power becomes deteriorated as temperature increases (thermal demagnetization). In the Nd magnet, the deterioration of the holding power causes such a problem that the magnet is demagnetized in an irreversible manner because of an external anti-magnetic field. This problem results in deterioration of performance of the rotating electric machine. Hence, a cooling structure for the permanent magnet to be used in the rotating electric machine becomes important in terms of temperature control in the permanent magnet. 
     For the cooling structure of a rotating electric machine, a technique for allowing a cooling oil supplied from a rotor shaft to flow through a cavity between a rotor and an end plate and discharging the cooling oil out of a discharge port at an outer peripheral side of the end plate has conventionally been proposed (see, e.g., Japanese Patent Laying-Open No. 2005-006429 (Patent Literature 1)). Moreover, a technique for providing an oil passage in a rotor and cooling a magnet by an oil flow has been proposed (see, e.g., Japanese Patent Laying-Open No. 2008-178243 (Patent Literature 2)). 
     CITATION LIST 
     Patent Literature 
     
         
         PTL 1: Japanese Patent Laying-open No. 2005-006429 
         PTL 2: Japanese Patent Laying-open No. 2008-178243 
       
    
     SUMMARY OF INVENTION 
     Technical Problem 
     When a discharge port for a cooling oil is provided near the outermost periphery of an end plate, oil flowed into the cavity between the rotor and the end plate is sent toward the discharge port by centrifugal force, and is discharged out of the discharge port directly. This raises a problem in that an oil pool is not formed in the cavity, so that an oil flow to be in contact with the rotor and a magnet is not formed, leading to the impossibility of effective cooling by oil. 
     When the discharge port for a cooling oil is provided at the inner peripheral side, an oil pool is formed in the cavity at the outer peripheral side relative to the discharge port in the cavity. However, oil pooled in this oil pool is pressed against the outer peripheral side by centrifugal force, leading to a high internal pressure. This raises a problem in that oil newly supplied to the cavity cannot enter the oil pool, and the supplied oil is discharged without replacing the oil in the oil pool, as a result of which the oil in the oil pool cannot be replaced, so that oil cooling cannot work effectively. 
     The present invention was made in view of the above-described problems, and has a main object to provide a rotating electric machine that can be improved in cooling performance. 
     Solution to Problem 
     A rotating electric machine of the present invention includes a rotation shaft provided so as to be rotatable, a rotor secured to the rotation shaft, a permanent magnet embedded in the rotor, an end plate holding the rotor, and a partition plate arranged between the rotor and the end plate. The end plate includes an annular plate portion arranged to be spaced from the rotor in an axial direction and secured to the rotation shaft, and a tubular portion protruding from an outer edge of the annular plate portion toward the rotor to abut on an axial end surface of the rotor. The partition plate is arranged to be spaced from both of the annular plate portion and the rotor in the axial direction so as to form a first space between the rotor and the partition plate and a second space between the annular plate portion and the partition plate. A coolant passage communicating with the first space is formed in the rotation shaft. A communication passage allowing the first space and the second space to communicate with each other is formed in the partition plate at a radially outer side relative to the permanent magnet. A through hole extending through the annular plate portion in the axial direction is formed in the annular plate portion at a radially inner side relative to the permanent magnet. 
     In the above-described rotating electric machine, the communication passage may be formed at the outermost peripheral part of the partition plate in a radial direction. 
     In the above-described rotating electric machine, the communication passage may be formed so as to correspond to the permanent magnet in circumferential position. 
     In the above-described rotating electric machine, a protruding portion protruding into the first space may be formed on at least one of the partition plate and the rotor. 
     In the above-described rotating electric machine, the protruding portions may be formed into a fin shape extending along the radial direction, and may be arranged at a greater spacing at a circumferential position where the permanent magnet is embedded. 
     Advantageous Effects of Invention 
     According to the rotating electric machine of the present invention, the rotating electric machine can be improved in cooling performance. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a sectional view showing a rotating electric machine according to a first embodiment of the present invention. 
         FIG. 2  is an enlarged sectional view enlargedly showing part of the rotor shown in  FIG. 1 . 
         FIG. 3  is a partial sectional perspective view of an end plate. 
         FIG. 4  is a sectional view showing a state in which a coolant is pooled in a first space. 
         FIG. 5  is a sectional view showing a state in which the coolant is pooled in a second space. 
         FIG. 6  is a sectional view showing, from a different angle, a state in which the coolant is pooled in the first space and the second space. 
         FIG. 7  is a schematic view showing the shape of a partition plate of a second embodiment. 
         FIG. 8  is a sectional view of a rotor with the partition plate shown in  FIG. 7  disposed therein. 
         FIG. 9  is an enlarged sectional view enlargedly showing part of a rotor of a rotating electric machine of a third embodiment. 
         FIG. 10  is a sectional view of the rotor taken along the line X-X shown in  FIG. 9 . 
         FIG. 11  is an enlarged sectional view enlargedly showing part of a rotor of a rotating electric machine of a fourth embodiment. 
         FIG. 12  is a sectional view of the rotor taken along the line XII-XII shown in  FIG. 11 . 
         FIG. 13  is an enlarged sectional view enlargedly showing part of a rotor of a rotating electric machine of a fifth embodiment. 
         FIG. 14  is a sectional view of the rotor taken along the line XIV-XIV shown in  FIG. 13 . 
         FIG. 15  is an enlarged sectional view enlargedly showing part of a rotor of a rotating electric machine of a sixth embodiment. 
         FIG. 16  is a sectional view of the rotor taken along the line XVI-XVI shown in  FIG. 15 . 
         FIG. 17  is a sectional view showing a variation of a protruding portion formed on an axial end surface of the rotor. 
         FIG. 18  is an enlarged sectional view enlargedly showing part of a rotor of a rotating electric machine of an eighth embodiment. 
         FIG. 19  is a sectional view of the rotor taken along the line XIX-XIX shown in  FIG. 18 . 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     Hereinafter, embodiments of the present invention will be described referring to the drawings. In the drawings, identical or corresponding parts are shown with an identical reference numeral, and description thereof will not be repeated. 
     It is noted that, in embodiments as will be described below, each component is not necessarily essential for the present invention unless otherwise specified. When number, amount and the like are mentioned in the embodiments below, such number and the like are for illustration unless otherwise specified, and the scope of the present invention is not necessarily limited to such number, amount and the like. 
     First Embodiment 
       FIG. 1  is a sectional view showing a rotating electric machine  100  according to an embodiment of the present invention. Rotating electric machine  100  shown in the drawing is mounted on a hybrid vehicle having, as power sources, an internal combustion engine such as a gasoline engine or a diesel engine, and a motor supplied with electric power from a chargeable and dischargeable secondary cell (battery). Rotating electric machine  100  represents a motor generator having at least one of the function as a motor supplied with electric power to generate driving force and the function as a power generator (generator). 
     As shown in  FIG. 1 , rotating electric machine  100  includes a rotation shaft  58 , a rotor  10  and a stator  50 . Rotor  10  is secured to rotation shaft  58  extending along a center line  101 . Rotation shaft  58  is provided so as to be rotatable together with rotor  10  about center line  101 , which is an imaginary center line of rotation of rotation shaft  58 , by a magnetic field generated in stator  50 . 
     Rotor  10  includes a rotor core  11  and a permanent magnet  21  that is embedded in rotor core  11 . That is, rotating electric machine  100  is an IPM (Interior Permanent Magnet) motor. Rotor core  11  has a cylindrical shape along center line  101 . Rotor core  11  is composed of a plurality of electromagnetic steel plates  12  laminated in an axial direction (the direction along centerline  101  indicated by a double-headed arrow DR 1  in  FIG. 1 ). 
     Stator  50  is arranged on the outer circumference of rotor  10 . Stator  50  includes a stator core  51  and a coil  55  wound around stator core  51 . Stator core  51  is composed of a plurality of electromagnetic steel plates  52  laminated in the axial direction along center line  101 . It is noted that rotor core  11  and stator core  51  are not limited to the electromagnetic steel plates, but may be integrally molded by, for example, a dust core. 
     Coil  55  is electrically connected to a control device  70  by way of a three-phase cable  60 . Three-phase cable  60  consists of a U-phase cable  61 , a V-phase cable  62  and a W-phase cable  63 . Coil  55  consists of a U-phase coil, a V-phase coil and a W-phase coil, and U-phase cable  61 , V-phase cable  62  and W-phase cable  63  are connected to terminals of these three coils, respectively. 
     An ECU (Electrical Control Unit)  80  mounted on the hybrid vehicle sends, to control device  70 , a torque command value to be output from rotating electric machine  100 . Control device  70  generates a motor control current for outputting a torque designated based on the torque command value, and feeds the motor control current to coil  55  through three-phase cable  60 . 
     An end plate  25  is provided so as to be opposed to axial end surfaces  13 ,  14  located at the opposite ends of rotor  10  in the axial direction. End plate  25  holds the laminated structure of electromagnetic steel plates  12  constituting rotor  10  in the axial direction. When ends of electromagnetic steel plates  12 , which are opposed to permanent magnet  21 , are magnetized, a force will be exerted so as to separate electromagnetic steel plates  12  from each other by action of a magnetic force. However, arranging end plate  25  to hold the laminated structure of electromagnetic steel plates  12  prevents electromagnetic steel plates  12  from being separated from each other. End plate  25  is fixed to rotation shaft  58  by any method such as screwing, caulking or pressure fitting to be integrally rotatable, and makes a rotational movement along with rotation of rotation shaft  58 . 
     A partition plate  29  is arranged between axial end surfaces  13 ,  14  of rotor  10  and end plate  25 . Partition plate  29  is formed so as not to be relatively movable with respect to rotation shaft  58  in the axial direction. 
     Rotation shaft  58  is formed to be hollow. A coolant passage  31  is formed inside rotation shaft  58 . Coolant passage  31  is formed such that a coolant, represented by a cooling oil, for cooling permanent magnet  21  can flow therethrough. Coolant passage  31  includes an axial passage  32  extending in the axial direction so as to involve center line  101 . Coolant passage  31  also includes a radial passage  33  provided in communication with axial passage  32  and extending in a radial direction of rotation shaft  58 . 
     A cavity communicating with radial passage  33  is formed between end plate  25  and axial end surface  13 ,  14  of rotor  10 . This cavity forms a coolant passage  41 . Coolant passage  41  is formed such that the coolant for cooling permanent magnet  21  can flow therethrough. End plate  25  has a through hole  48  formed therein that extends through end plate  25  in the axial direction so as to allow coolant passage  41  to communicate with the outside. 
     As shown by arrows in  FIG. 1 , the coolant for cooling permanent magnet  21  is transferred from a pump not shown, passes through axial passage  32  and radial passage  33 , and is introduced into coolant passage  41 . The coolant supplied to coolant passage  41  can be discharged from coolant passage  41  via through hole  48 . 
       FIG. 2  is an enlarged sectional view enlargedly showing part of rotor  10  shown in  FIG. 1 .  FIG. 3  is a partial sectional perspective view of end plate  25 . As shown in  FIGS. 2 and 3 , end plate  25  includes a disc-shaped annular plate portion  26  and a tubular portion  27  protruding from an outer edge  26   a  of annular plate portion  26 . A hole  26   b  is formed in the central portion of annular plate portion  26 . Rotation shaft  58  is inserted through this hole  26   b  to allow annular plate portion  26  to be secured to rotation shaft  58 , so that end plate  25  is fixed to rotation shaft  58 . 
     As shown in  FIG. 2 , annular plate portion  26  is arranged to be separated from axial end surface  13  of rotor  10  in the axial direction. Tubular portion  27  protrudes from annular plate portion  26  toward axial end surface  13  of rotor  10 . A circular leading end surface  27   a  (see  FIG. 3 ) of tubular portion  27  abuts on axial end surface  13  of rotor  10 , so that the laminated structure of electromagnetic steel plates  12  is held in the axial direction. 
     Partition plate  29  is arranged to be separated from both of annular plate portion  26  of end plate  25  and axial end surface  13  of rotor  10  in the axial direction. The cavity between end plate  25  and axial end surface  13  of rotor  10  is partitioned by partition plate  29 . Partition plate  29  partitions the space surrounded by annular plate portion  26 , tubular portion  27 , axial end surface  13  of rotor  10 , and the outer peripheral surface of rotation shaft  58  in the axial direction to be divided into two, thereby forming a first space  42  between rotor  10  and partition plate  29  and a second space  43  between annular plate portion  26  and partition plate  29 . 
     First space  42  is defined by axial end surface  13  of rotor  10  and a surface of partition plate  29  opposed to rotor  10 . Second space  43  is defined by surfaces of annular plate portion  26  and partition plate  29  opposed to each other. The outer peripheral surface of rotation shaft  58  defines the radially innermost wall surfaces of first space  42  and second space  43 . The inner peripheral surface of tubular portion  27  defines the radially outermost wall surfaces of first space  42  and second space  43 . 
     Partition plate  29  is formed into a disc shape smaller in diameter than the inner diameter of tubular portion  27 . Partition plate  29  is arranged such that the outer edge of partition plate  29  is opposed to tubular portion  27 . A communication passage  44  is formed between the outermost peripheral part of partition plate  29  most distant from center line  101  in the radial direction (the direction indicated by a double-headed arrow DR 2  in  FIG. 2  and orthogonal to the axial direction) and tubular portion  27 . Communication passage  44  is formed to extend through partition plate  29  in the axial direction so as to allow first space  42  and second space  43  to communicate with each other. 
     Through hole  48  extending through annular plate portion  26  in the axial direction is formed in annular plate portion  26  of end plate  25 . Through hole  48  allows outer space opposite to rotor  10  relative to annular plate portion  26  and second space  43  to communicate with each other. 
     A hole portion is formed in rotor core  11  so as to extend through rotor core  11  along the axial direction of the cylindrical shaft. Permanent magnet  21  is inserted into this hole portion to be embedded in rotor  10 . Permanent magnet  21  is arranged to extend through rotor  10  in the axial direction such that axial end surface  23  of permanent magnet  21  is exposed in first space  42 . 
     First space  42 , communication passage  44 , second space  43 , and through hole  48  constitute coolant passage  41 . Radial passage  33  formed within rotation shaft  58  communicates with first space  42 . First space  42  is connected to radial passage  33 . As shown in  FIG. 2 , communication passage  44  is formed at the radially outer side relative to permanent magnet  21 . Through hole  48  is formed at the radially inner side relative to permanent magnet  21 . 
       FIG. 4  is a sectional view showing a state in which the coolant is pooled in first space  42 .  FIG. 5  is a sectional view showing a state in which the coolant is pooled in second space  43 .  FIG. 6  is a sectional view showing, from a different angle, a state in which the coolant is pooled in first space  42  and second space  43 .  FIGS. 4 and 5  show the section orthogonal to the axial direction of rotor  10 .  FIG. 6  shows the section along the axial direction of rotor  10 . It is noted that  FIG. 4  is a sectional view of rotor  10  taken along the line IV-IV shown in  FIG. 6 , and  FIG. 5  is a sectional view of rotor  10  taken along the line V-V shown in  FIG. 6 . Arrows shown in  FIGS. 4 to 6  indicate the coolant flow. 
     As shown in  FIGS. 4 and 6 , the coolant supplied to radial passage  33  via axial passage  32  within rotation shaft  58  flows to the radially outer side by the action of centrifugal force generated by rotation of rotor  10 . The coolant flows through radial passage  33  into first space  42 , passing through communication port  34  that allows radial passage  33  and first space  42  to communicate with each other. The coolant flows in first space  42  to the radially outer side while being in contact with axial end surface  13  of rotor  10  and the surface of partition plate  29  opposed to rotor  10 , to arrive at axial end surface  23  of permanent magnet  21  exposed in first space  42 . Since the coolant flows while being in contact with axial end surface  23  of permanent magnet  21 , axial end surface  23  of permanent magnet  21  is cooled by the coolant. 
     As shown in  FIG. 6 , the coolant arrived at the outermost peripheral part in the radial direction in first space  42  flows into second space  43  passing through communication passage  44  formed at the outermost peripheral part of partition plate  29 . The coolant flows in second space  43  to the radially inner side, arrives at through hole  48  formed in annular plate portion  26 , and is discharged out of through hole  48  to the outside. 
     Through hole  48  is opened in a portion located at the radially inner side relative to permanent magnet  21 . Accordingly, as shown in  FIGS. 5 and 6 , a coolant pool  19  in which the coolant is pooled is formed in first space  42  and second space  43  at the outer peripheral side relative to the radial position at which through hole  48  is formed. 
     With the structure of the present embodiment, the outer peripheral side of partition plate  29  is sank in the coolant pooled in coolant pool  19 . This causes a difference between the gas pressure in first space  42  and the gas pressure in second space  43 , the gas pressure in first space  42  being relatively higher. The coolant flow is thus produced in coolant pool  19  as well, as a result of which the coolant flows without stagnation to flow from first space  42  to second space  43  via communication passage  44 , and is discharged out of through hole  48 . 
     That is, according to the present embodiment, formation of coolant pool  19  always brings axial end surface  23  of permanent magnet  21  having a low thermal resistance into contact with the coolant. Also, formation of the coolant flow without stagnation such that the coolant is not retained within coolant pool  19  allows the coolant at a low temperature to be always supplied to axial end surface  23  of permanent magnet  21 . Permanent magnet  21  can thus be cooled efficiently, which can prevent permanent magnet  21  from causing thermal demagnetization that would result from temperature rise and prevent permanent magnet  21  from deteriorating in holding power. 
     Moreover, disposing partition plate  29  between rotor  10  and end plate  25  enables formation of coolant pool  19  and formation of the coolant flow in coolant pool  19 , so that an effective method of cooling permanent magnet  21  with an easy structure can be provided. End plate  25  is configured by a combination of disc-shaped annular plate portion  26  and sleeve-shaped tubular portion  27 , partition plate  29  is of disc shape, and end plate  25  and partition plate  29  can be molded easily, which can reduce the manufacturing cost and simplify the manufacturing process of rotating electric machine  100 . 
     Coolant pool  19  is formed at the outer peripheral side relative to the radial position at which through hole  48  is formed. That is, if the position of through hole  48  in the radial direction is changed, the depth of coolant pool  19  can be freely changed. By changing the depth of coolant pool  19 , a surface area of axial end surface  13  of rotor  10  always covered with the coolant can be changed freely. Therefore, the coverage by which the coolant covers rotor  10  can be changed freely in accordance with the cooling performance required by rotor  10 . Since this change in coverage can be achieved only by changing the position of through hole  48  in the radial direction, any coverage can be obtained easily, without increasing the manufacturing cost of rotating electric machine  100 . 
     Through hole  48  out of which the coolant is discharged to the outside is formed at the radially inner side of end plate  25 . This controls centrifugal force to be exerted on the coolant scattering out of through hole  48 , which can minimize the loss generated when the coolant is discharged. In addition, the coolant flowed out of through hole  48  can be prevented from entering the clearance between rotor  10  and stator  50 , which can avoid increase in rubbing loss during rotation of rotor  10 . 
     Second Embodiment 
       FIG. 7  is a schematic view showing the shape of partition plate  29  of a second embodiment.  FIG. 8  is a sectional view of rotor  10  with partition plate  29  shown in  FIG. 7  disposed therein. The section shown in  FIG. 8  is a section of rotor  10  taken in the axial direction along the line IV-IV shown in  FIG. 6  and viewed toward partition plate  29  in the opposite direction of the line IV-IV. While partition plate  29  of the first embodiment is formed into a disc shape, partition plate  29  of the second embodiment shown in  FIG. 7  differs from that of the first embodiment in that a plurality of notches  29   a  are formed at the outer edge. 
     With reference to  FIG. 8 , partition plate  29  is positioned in the circumferential direction (the direction along the arc of cylindrical rotation shaft  58  or tubular portion  27 , indicated by a double-headed arrow DR 3  shown in  FIG. 8 ) such that notches  29   a  are arranged at the radially outer side relative to permanent magnet  21 . At this time, partition plate  29  is attached to rotation shaft  58  so as not to be relatively rotatable, and partition plate  29  is configured to rotate integrally with rotor  10  so that the relative positions of permanent magnet  21  and notches  29   a  in the circumferential direction do not change. Partition plate  29  is formed to have an outer diameter equal to or slightly smaller than the inner diameter of tubular portion  27  such that the outer peripheral part at which no notch  29   a  is formed abuts on the inner peripheral surface of tubular portion  27 . 
     The coolant flowing from first space  42  to second space  43  flows through notches  29   a  formed in partition plate  29 . That is, notches  29   a  of partition plate  29  constitute communication passage  44  that allows first space  42  and second space  43  to communicate with each other. By positioning partition plate  29  in the circumferential direction as described above, communication passage  44  is fanned so as to correspond to permanent magnet  21  in circumferential position. 
     The coolant supplied through radial passage  33  of rotation shaft  58  into first space  42  via communication port  34  flows into communication passage  44 . By specifying the position of communication passage  44 , the coolant flow in first space  42  can be created so as to ensure the coolant to flow while being in contact with axial end surface  23  of permanent magnet  21 . Therefore, permanent magnet  21  can be cooled more efficiently. 
     Third Embodiment 
       FIG. 9  is an enlarged sectional view enlargedly showing part of rotor  10  of rotating electric machine  100  of a third embodiment.  FIG. 10  is a sectional view of rotor  10  taken along the line X-X shown in  FIG. 9 . As shown in  FIGS. 9 and 10 , a protruding portion  90  protruding into first space  42  is formed in partition plate  29  of the third embodiment. Protruding portion  90  has a plurality of fin-shaped protruding portions  91  extending in the radial direction, as shown in  FIG. 10 . 
     Axial end surface  23  of permanent magnet  21  is exposed in first space  42 . Then, providing radial protruding portions  91  protruding into first space  42  can disturb the coolant flow in first space  42 , such as by producing a vortex or turbulence in first space  42 , since protruding portions  91  cause obstruction to the coolant flow flowing in first space  42  to the radially outer side. The coolant at a low temperature can thus be brought into contact with axial end surface  23  of permanent magnet  21  more efficiently, which can further improve permanent magnet  21  in cooling performance. 
     It is noted that partition plate  29  needs to be made of a non-magnetic material so as to prevent magnetic flux leakage, and partition plate  29  can be made of any non-magnetic material. For example, partition plate  29  can be formed using a thin plate of about 1 mm thick made of a metallic material, such as aluminium superior in workability. Since working is facilitated when aluminium is used, partition plate  29  can be easily molded into any shape by any machining such as press working. 
     Fourth Embodiment 
       FIG. 11  is an enlarged sectional view enlargedly showing part of rotor  10  of rotating electric machine  100  of a fourth embodiment.  FIG. 12  is a sectional view of rotor  10  taken along the line XII-XII shown in  FIG. 11 . As shown in  FIGS. 11 and 12 , protruding portion  90  protruding into first space  42  is formed in partition plate  29  of the fourth embodiment. Protruding portion  90  has a plurality of fin-shaped protruding portions  92  extending in the circumferential direction, as shown in  FIG. 12 . 
     Similarly to the third embodiment, by providing protruding portions  92 , the coolant flow in first space  42  can be disturbed, and the coolant at a low temperature can be brought into contact with axial end surface  23  of permanent magnet  21  more efficiently, which can further improve permanent magnet  21  in cooling performance. 
     Fifth Embodiment 
       FIG. 13  is an enlarged sectional view enlargedly showing part of rotor  10  of rotating electric machine  100  of a fifth embodiment.  FIG. 14  is a sectional view of rotor  10  taken along the line XIV-XIV shown in  FIG. 13 . As shown in  FIGS. 13 and 14 , protruding portion  90  protruding into first space  42  is formed in partition plate  29  of the fifth embodiment. Protruding portion  90  has a plurality of independently-formed protruding portions  93 , as shown in  FIG. 14 . 
     Similarly to the third embodiment, by providing protruding portions  93 , the coolant flow in first space  42  can be disturbed, and the coolant at a low temperature can be brought into contact with axial end surface  23  of permanent magnet  21  more efficiently, which can further improve permanent magnet  21  in cooling performance. 
     Sixth Embodiment 
       FIG. 15  is an enlarged sectional view enlargedly showing part of rotor  10  of rotating electric machine  100  of a sixth embodiment.  FIG. 16  is a sectional view of rotor  10  taken along the line XVI-XVI shown in  FIG. 15 . Unlike the third to fifth embodiments, partition plate  29  is in the form of flat plate in the sixth embodiment, and protruding portion  90  protruding from axial end surface  13  of rotor  10  into first space  42  is formed. Protruding portion  90  has a plurality of fin-shaped protruding portions  94  extending along the radial direction, as shown in  FIG. 16 . 
     Similarly to the third embodiment, by providing protruding portions  94 , the coolant flow in first space  42  can be disturbed, and the coolant at a low temperature can be brought into contact with axial end surface  23  of permanent magnet  21  more efficiently, which can further improve permanent magnet  21  in cooling performance. In addition, the surface area of rotor  10  exposed in first space  42  is increased because protruding portion  90  is formed on rotor  10 . This can increase the contact area of rotor  10  with the coolant flowing in first space  42 , which can further improve rotor  10  in cooling efficiency. 
     Seventh Embodiment 
       FIG. 17  is a sectional view showing a variation of protruding portion  90  formed on axial end surface  13  of rotor  10 . Protruding portion  90  of the seventh embodiment has a plurality of fin-shaped protruding portions  94  extending along the radial direction. While fin-shaped protruding portions  94  of the sixth embodiment are arranged uniformly in the circumferential direction, protruding portions  94  of the seventh embodiment are arranged at irregular spacings in the circumferential direction. Specifically, protruding portions  94  are arranged at a greater spacing at the circumferential position where permanent magnet  21  is embedded. 
     Then, the coolant is less likely to flow in the space at the circumferential position where spacing between adjacent protruding portions  94  is relatively small and where permanent magnet  21  is not disposed. In contrast, the coolant is more likely to flow in the space at the circumferential position where permanent magnet  21  is embedded, so that a greater amount of coolant comes into contact with permanent magnet  21 . Therefore, a passage of the coolant can be formed targeting at permanent magnet  21 , and the coolant at a low temperature can be brought into contact with axial end surface  23  of permanent magnet  21  more efficiently, which can further improve permanent magnet  21  in cooling performance. 
     Eighth Embodiment 
       FIG. 18  is an enlarged sectional view enlargedly showing part of rotor  10  of rotating electric machine  100  of an eighth embodiment.  FIG. 19  is a sectional view of rotor  10  taken along the line XIX-XIX shown in  FIG. 18 . In the first embodiment, partition plate  29  is formed to have an outer diameter smaller than the inner diameter of tubular portion  27 , and communication passage  44  is formed between partition plate  29  and tubular portion  27 , however, as shown in  FIGS. 18 and 19 , it may be configured such that a through hole extending through partition plate  29  along its thickness is formed at the outer peripheral part, and such that this through hole allows first space  42  and second space  43  to communicate with each other. 
     The through hole formed at the outer peripheral part of partition plate  29  is not limited to the circular hole shown in  FIG. 19 . For example, the through hole may be made as a long hole extending in the circumferential direction, and partition plate  29  may be positioned such that communication passage  44  formed by this long hole corresponds to permanent magnet  21  in circumferential position. This can ensure that the coolant flow is formed on axial end surface  23  of permanent magnet  21  similarly to the second embodiment, which allows permanent magnet  21  to be cooled more efficiently. 
     It is noted that, although the foregoing describes a rotating electric machine mounted on a hybrid vehicle and functioning as a driving source driving wheels and a power generator generating power with power of an engine or the like, the rotating electric machine of the present invention can also be mounted on a fuel-cell vehicle, an electric vehicle or the like, and utilized as a driving source driving wheels. 
     While the embodiments of the present invention are described above, the structures of the respective embodiments may be combined as appropriate. It should be understood that the embodiments disclosed herein are illustrative and non-restrictive in any respect. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims. 
     INDUSTRIAL APPLICABILITY 
     The rotating electric machine of the present invention is applicable particularly advantageously to a rotating electric machine mounted on a vehicle. 
     REFERENCE SIGNS LIST 
       10  rotor;  11  rotor core;  12 ,  52  electromagnetic steel plate;  13 ,  14 ,  23  axial end surface;  21  permanent magnet;  25  end plate;  26  annular plate portion;  26   a  outer edge;  26   b  hole;  27  tubular portion;  27   a  leading end surface;  29  partition plate;  29   a  notch;  31  coolant passage;  32  axial passage;  33  radial passage;  34  communication port;  41  coolant passage;  42  first space;  43  second space;  44  communication passage;  48  through hole;  50  stator;  51  stator core;  55  coil;  58  rotation shaft;  90 ,  91 ,  92 ,  93 ,  94  protruding portion;  100  rotating electric machine;  101  center line.