Main electric-motor for vehicle

A first bearing box has, in one end face perpendicular to a direction along a rotor shaft and farther from a fan, an air outlet for air taken in through an air inlet to exit. A flow channel is defined between an outer peripheral surface of a cylindrical portion of the first bearing box continuous with the end face and a frame. A value obtained by dividing a distance between an outer periphery of blades in the fan and the air outlet by an outer radius of the blades is greater than or equal to a threshold.

TECHNICAL FIELD

The present disclosure relates to a self-ventilation main motor for vehicles.

BACKGROUND ART

A squirrel-cage induction motor is used as a main motor for driving an electric railway vehicle. A squirrel-cage rotor conductor included in the squirrel-cage induction motor includes a rotor core having slots on the outer periphery in the direction along a rotor shaft, and rod-like rotor bars received in the slots, and short-circuit rings as annular conductors bonded on both ends of the rotor bars. An alternating current flows through a stator coil received in a slot on a stator core thereby generating a rotating magnetic field. The squirrel-cage rotor conductor interlinks with the rotating magnetic field thereby generating an induced electromotive voltage. The induced electromotive voltage causes an induced current to flow through the squirrel-cage rotor conductor forming a closed circuit, and a magnetic pole is generated in the rotor core. The magnetic pole in the rotor core and the magnetic pole in the rotating magnetic field interact with each other subjecting the rotor core to a force in a direction tangent to the outer peripheral surface of the rotor core. This force is the output torque from the rotor shaft.

A current flowing through the stator coil and the rotor conductor causes a copper loss that is equivalent to the product of a resistance value of the conductor and the square of the current value. Such a copper loss increases the temperature in the stator coil and the rotor conductor. A magnetic flux resulting from a current flowing through the stator coil and the rotor conductor passes through the stator core and the rotor core.

An alternating magnetic flux, passing through the stator core and the rotor core, causes an iron loss and increases the temperature in the stator core and the rotor core. Any harmonic components in the voltage and the current fed to the main motor causes a harmonic loss and increases the temperature in the stator coil, the rotor conductor, the stator core, and the rotor core. As described above, various losses increase the interior temperature of the main motor during the operation of the main motor.

To cool the inside of the main motor during operation, the main motor includes a fan attached to the rotor shaft of the main motor, and has an air inlet at a position opposite to the fan from the core to take in exterior air through a housing, and an air outlet at a position outside the outer periphery of the fan to allow the interior air to exit. The rotor rotates to rotate the fan during the operation of the main motor, thereby producing a pressure difference between the outer periphery and the inner periphery of the blades in the fan. The pressure difference draws air through the air inlet to flow through an air passage in the rotor core and a gap between the rotor core and the stator core, and to exit through the air outlet. The air taken in through the air inlet cools the inside of the main motor.

The air taken in through the air inlet and exiting through the air outlet collides with an edge of the air outlet, thereby generating exhaust noise. A main motor for railway vehicles described in Patent Literature 1 includes a bracket with a negative pressure relief hole on one end of a frame that receives a stator on the inner periphery. The frame has, in a lower portion of the frame end, an outlet for air from an exhaust fan. At an inner surface of the bracket, a first narrow gap is left between the outer periphery of the negative pressure relief hole and the exhaust fan to reduce noise generated through the relief hole out of the motor.

CITATION LIST

Patent Literature

SUMMARY OF INVENTION

Technical Problem

Patent Literature 1 describes the motor with a larger air outlet and including an exhaust fan with a larger outer diameter. Although selecting an exhaust fan with a larger outer diameter increases the flow rate of air taken into the main motor to improve cooling performance, the fan generates larger exhaust noise. Although a main motor operating at a higher rotation speed increases the flow rate of air taken into the main motor to improve cooling performance, the motor also generates larger exhaust noise. Although selecting a fan with a smaller outer diameter to increase the distance between the outer periphery of the blades in the fan and the air outlet can reduces the exhaust noise, the fan draws less air into the main motor and lowers cooling performance.

In consideration of the aforementioned circumstances, an objective of the present disclosure is to reduce exhaust noise while improving cooling performance of a main motor for a vehicle.

Solution to Problem

In order to attain the aforementioned objective, a main motor for a vehicle according to the disclosure includes a frame fixed to the boogie in the vehicle, a rotor shaft received in the frame, a rotor core, a rotor conductor, a stator core, a stator coil, a first bearing box, a second bearing box, and a fan. The rotor core is fitted on the rotor shaft and rotatable integrally with the rotor shaft. The rotor conductor is retained in the rotor core. The stator core is attached to an inner peripheral surface of the frame and faces an outer peripheral surface of the rotor core across a gap. A stator coil is retained in the stator core. The first bearing box and the second bearing box are attached to the frame and face each other in a direction along the rotor shaft across the rotor core and the stator core. The first bearing box and the second bearing box each retain a bearing supporting the rotor shaft in a rotatable manner. The fan is attached to the rotor shaft between the first bearing box and the rotor core and rotatable integrally with the rotor shaft. The fan includes blades. The frame has, in a portion of the frame to which the second bearing box is attached or in a portion of the frame facing the second bearing box, an air inlet for taking in exterior air around the frame. The first bearing box has, in an end face of the first bearing box that is one of end faces perpendicular to the direction along the rotor shaft and is farther from the fan, an air outlet for air taken in through the air inlet to exit. The first bearing box includes a cylindrical portion continuous with the end face farther from the fan. The cylindrical portion has an outer peripheral surface facing the inner peripheral surface of the frame across a gap defining a flow channel for the air. The air taken in through the air inlet passes through the gap between the outer peripheral surface of the rotor core and the stator core, the fan, and the flow channel between the outer peripheral surface of the cylindrical portion of the first bearing box and the inner peripheral surface of the frame and exits through the air outlet. A value obtained by dividing a distance between an outer periphery of the blades in the fan and the air outlet by an outer radius of the blades is greater than or equal to a threshold.

Advantageous Effects of Invention

The main motor for a vehicle according to the above aspect of the present disclosure includes the bearing box with the air outlet in the end face, and is provided with a value obtained by dividing the distance between the outer periphery of the blades in the fan and the air outlet by the outer radius of the blades to greater than or equal to the threshold thereby reducing exhaust noise while improving cooling performance inside the vehicle main motor.

DESCRIPTION OF EMBODIMENTS

Embodiments of the present disclosure are described in detail with reference to the drawings. The same or corresponding components in the figures are given the same reference numerals.

FIG. 1is a cross-sectional view of a main motor for a vehicle according to Embodiment 1 of the present disclosure.FIG. 1is a cross-sectional view taken along a plane parallel to a rotor shaft3.FIG. 2is a side view of the main motor for a vehicle according to Embodiment 1. A vehicle main motor100includes a frame2fixed to a vehicle, the rotor shaft3received in the frame2, a first bearing box4and a second bearing box6attached to the frame2, a rotor core8fitted on the rotor shaft3, a stator core9attached to the inner peripheral surface of the frame2, and a fan10attached to the rotor shaft3. Z-axis refers to a vertical direction, X-axis refers to the traveling direction of the vehicle on which the vehicle main motor100is mounted, and Y-axis is a direction perpendicular to X-axis and Z-axis. The rotor shaft3extends in X-axis direction in the vehicle main motor100when fixed on, for example, a vehicle body. The rotor shaft3extends in Y-axis direction in the vehicle main motor100when fixed on, for example, a bogie in a vehicle. The vehicle main motor100is mounted on, for example, an electric railway vehicle. InFIG. 1and subsequent figures, X-axis, Y-axis, and Z-axis indicate the respective directions of the vehicle main motor100when mounted on a bogie in a vehicle.

The first bearing box4and the second bearing box6face each other in Y-axis direction across the rotor core8and the stator core9. The first bearing box4and the second bearing box6respectively retaining bearings5and7to support the rotor shaft3in a rotatable manner are attached to the frame2. In the example shown inFIG. 1, the frame2has an opening in one face of the frame2perpendicular to Y-axis direction. The first bearing box4is fastened to the frame2in Y-axis direction to close the opening. The frame2has a through-hole in the other face of the frame2perpendicular to Y-axis direction. The second bearing box6is fastened to the frame2surrounding the through-hole in Y-axis direction to close the through-hole. The rotor core8is fitted on the rotor shaft3and is rotatable integrally with the rotor shaft3. The stator core9faces the outer peripheral surface of the rotor core8across a gap. The fan10includes blades11. The fan10is attached to the rotor shaft3between the first bearing box4and the rotor core8and is rotatable integrally with the rotor shaft3.

The frame2has, in a portion receiving the second bearing box6or in a portion facing the second bearing box6, an air inlet21to take in exterior air. InFIG. 1, the air inlet21is formed in an upper surface of the frame2in the vertical direction, but may be formed at another location. The air inlet21may be formed in an end face of the frame2perpendicular to the rotor shaft3and receiving the second bearing box6. The first bearing box4has, in an end face41of the first bearing box4that is one of end faces perpendicular to Y-axis direction and is farther from the fan10, an air outlet42for air taken in through the air inlet21to exit. In the example shown inFIG. 1, the end face41is fastened to the frame2in Y-axis direction. The first bearing box4includes a cylindrical portion43continuous with the end face41and having an outer peripheral surface facing the inner peripheral surface of the frame2across a gap defining an air flow channel20. In the example shown in Embodiment 1, the cylindrical portion43of the first bearing box4extends in the direction along the rotor shaft3. The cylindrical portion43of the first bearing box4defines the flow channel20with a constant cross-sectional area along a plane perpendicular to Y-axis direction to prevent a vortex due to the cylindrical shape.

The rotor core8has, on the outer periphery, slots cut in the direction along the rotor shaft3to receive rotor bars12. Each rotor bar12has both ends bonded to short-circuit rings13that are conductors with annular cross sections perpendicular to Y-axis direction for electrically connecting the rotor bars12together. The rotor core8has an air passage14for air flowing. The stator core9receives stator coils15.

To smooth a change in the direction of the air flow, the frame2may include an air guide16on the inner peripheral surface as shown inFIG. 1. The inclusion of the air guide16reduces a turbulence or a vortex that can occur when direction of the air flow is changed, and reduces air pressure loss. Reducing the air pressure loss increases air intake, and thus improves cooling performance.

FIG. 3is a diagram illustrating the flow of air in the main motor for a vehicle according to Embodiment 1. InFIG. 3, the solid arrows indicate a flow of air in the vehicle main motor100shown inFIG. 1. The rotor shaft3rotates during the operation of the vehicle main motor100. The rotor shaft3rotates to rotate the fan10fitted on the rotor shaft3. The fan10rotates to produce a pressure difference between the inner periphery and the outer periphery of the blades11, drawing in air through the air inlet21. In the example illustrated inFIG. 3, exterior air around the vehicle main motor100is taken into the vehicle main motor100through the air inlet21. The air taken into the vehicle main motor100flows through the gap between the outer peripheral surface of the rotor core8and the stator core9, and through the air passage14and reaches the fan10. The air from the fan10passes through the flow channel20and exits through the air outlet42. As described above, exterior air around the vehicle main motor100is taken into the vehicle main motor100and flows through the inside of the vehicle main motor100and out of the vehicle main motor100to cool the inside of the vehicle main motor100. The air exiting through the air outlet42generates exhaust noise. The structure of the vehicle main motor100that reduces such exhaust noise is described.

FIG. 4is a cross-sectional view of a main motor for a vehicle. A vehicle main motor500shown inFIG. 4differs from the vehicle main motor100according to Embodiment 1 of the present disclosure in that a frame52outside the outer periphery of blades57in a fan56has an air outlet54. A first bearing box55and the second bearing box6face each other in Y-axis direction across the rotor core8and the stator core9. The first bearing box55and the second bearing box6respectively retaining bearings5and7to support the rotor shaft3in a rotatable manner are attached to the frame52. The fan56includes the blades57. The fan56is attached to the rotor shaft3between the first bearing box55and the rotor core8and is rotatable integrally with the rotor shaft3. The vehicle main motor500includes an air guide58for guiding air from the fan56toward the air outlet54. The inclusion of the air guide58prevents air from the fan56from reaching an air inlet side of the fan56again after being redirected toward the stator coil15. A flow channel59is defined between the face of the first bearing box55perpendicular to Y-axis direction and the air guide58.

FIG. 5is a diagram illustrating the flow of air in the main motor for a vehicle. InFIG. 5, the solid arrows indicate the flow of air in the vehicle main motor500shown inFIG. 4. The rotor shaft3rotates during the operation of the vehicle main motor500. The rotor shaft3rotates to rotate the fan56fitted on the rotor shaft3. The fan56rotates to produce a pressure difference between the inner periphery and the outer periphery of the blades57, drawing in air through an air inlet53. The air taken into the vehicle main motor500flows through the gap between the outer peripheral surface of the rotor core8and the stator core9, and through the air passage14and reaches the fan56. The air from the fan56passes through the flow channel59and exits through the air outlet54. The air exiting through the air outlet54generates exhaust noise.

FIG. 6is a partial cross-sectional view of the main motor for a vehicle.FIG. 6is an enlarged view of an area B shown inFIG. 4. The distance between the outer periphery of the blades57in the fan56, that is an end of the blades57nearer to the air outlet54, and the air outlet54is referred to as L1, and the outer radius of the blades57is referred to as R1. As the distance L1is smaller with respect to the outer radius R1, the air has a larger velocity distribution when reaching the air outlet54. This increases the likelihood that a turbulence or a vortex occurs as the air collides with the edge of the air outlet54. A turbulence or a vortex can increase exhaust noise. As the distance L1is larger with respect to the outer radius R1, the air has a smaller velocity distribution when reaching the air outlet54. This decreases the likelihood that a turbulence or a vortex occurs as the air collides with the edge of the air outlet54. In other words, when the gap ratio defined as L1/R1changes, the magnitude of exhaust noise changes.

FIG. 7is a graph showing an example relationship between the gap ratio and a noise level ratio. The level of the exhaust noise during the operation of the vehicle main motor500is measured with a known noise meter. The noise level ratio inFIG. 7is a ratio obtained by dividing the measurement value (dB) obtained with the noise meter by a target value (dB) for the exhaust noise level. In other words, the exhaust noise with a noise level ratio of 1 matches the target value for the noise level. The measurement value indicating the exhaust noise represents a maximum value among the measurement values obtained during a predetermined period. InFIG. 7, the horizontal axis shows the gap ratio and the vertical axis shows the noise level ratio. The graph shown inFIG. 7shows a fitted curve representing a relationship between the gap ratio and the noise level ratio derived from the gap ratio and the noise level ratio calculated using a measurement value indicating the noise level. The fitted curve inFIG. 7is obtained by measuring exhaust noise for different vehicle main motors500including the blades57with varying outer peripheries in the fan56and thus having different distances between the outer periphery of the blades57in the fan10and the air outlet54. The measurement results are then used to calculate the exhaust noise at the same air flow rate. As shown inFIG. 7, increasing the gap ratio enables reducing the exhaust noise. The distance between the rotor shaft3and the air outlet54cannot be increased due to space limitation for the vehicle main motor500. Thus, to increase the gap ratio, the outer radius of the blades57is to be reduced. However, the blades57with a reduced outer radius can lower cooling performance, and can increase the temperature in the vehicle main motor500.

FIG. 8is a partial cross-sectional view of the main motor for a vehicle according to Embodiment 1.FIG. 8is an enlarged view of an area A shown inFIG. 1. A value obtained by dividing the distance L2between the outer periphery of the blades11in the fan10and the air outlet42by the outer radius R2of the blades11is greater than or equal to a threshold. Considering the relationship between the gap ratio and the noise level ratio shown inFIG. 7, the threshold may be 0.3 or greater. More specifically, the value obtained by dividing the distance L2between the outer periphery of the blades11and the air outlet42by the outer radius R2of the blades11may be 0.3 or greater. The vehicle main motor100according to Embodiment 1 of the present disclosure is provided with the value obtained by dividing the distance L2between the outer periphery of the blades11in the fan10and the air outlet42by the outer radius R2of the blades11greater than or equal to the threshold, and thus can reduce exhaust noise. The vehicle main motor100with the flow channel20extending in Y-axis direction can have the blades11with a larger outer radius than the outer radius of the blades57in the vehicle main motor500inFIG. 6, without increasing the length of the vehicle main motor100in Z-axis direction. More specifically, having the flow channel20extending in Y-axis direction to increase the gap ratio, the vehicle main motor100reduces exhaust noise while improving cooling performance.

FIG. 9is a cross-sectional view of the main motor for a vehicle according to Embodiment 1. The rotor shaft3of the vehicle main motor100receives a coupling61that transfers the rotation of the vehicle main motor100to a drive device. The coupling61is attached to the rotor shaft3at a position where a portion of the outer peripheral surface of the coupling61faces the inner peripheral surface of the first bearing box4of the vehicle main motor100. More specifically, a portion of the outer peripheral surface of the coupling61is covered with the first bearing box4. This prevents any scattered debris from entering a gap between the vehicle main motor100and the coupling61while the vehicle is traveling, and prevents damage on the vehicle main motor100as well as on the coupling61.

As described above, the vehicle main motor100according to Embodiment 1 of the present disclosure includes the first bearing box4with the air outlet42in the end face41, and is provided with the value obtained by dividing the distance between the outer periphery of the blades11in the fan10and the air outlet42by the outer radius of the blades11to greater than or equal to the threshold to reduce exhaust noise while improving cooling performance inside the vehicle main motor100.

FIG. 10is a cross-sectional view of a main motor for a vehicle according to Embodiment 2.FIG. 11is a partial cross-sectional view of the main motor for a vehicle according to Embodiment 2.FIG. 11is an enlarged view of an area C shown inFIG. 10. A vehicle main motor200according to Embodiment 2 further includes a first airflow regulating plate22extending in Y-axis direction on an outer peripheral surface of a cylindrical portion43of the first bearing box4, in addition to the components in the vehicle main motor100according to Embodiment 1. The vehicle main motor200may include any number of first airflow regulating plates22.FIG. 12is a partial cross-sectional view of the main motor for a vehicle according to Embodiment 2.FIG. 12is a cross-sectional view taken along line A-A inFIG. 11. In the example shown inFIG. 12, a plurality of first airflow regulating plates22is circumferentially arranged at regular intervals on the outer peripheral surface of the cylindrical portion43of the first bearing box4. The inclusion of the first airflow regulating plates22reduces the velocity components of air flowing through the flow channel20in the rotational direction about the rotor shaft3. When the air flowing obliquely in the rotational direction about the rotor shaft3with respect to Y-axis direction collides with the edge of the air outlet42, an air vortex forms and generates exhaust noise. The first airflow regulating plates22reduce the velocity components of air flowing through the flow channel20in the rotational direction about the rotor shaft3. The first airflow regulating plates22thus rectify air flow reaching the air outlet42into substantially laminar flow. The substantially laminar flow reaching the air outlet42prevents an air vortex and reduces exhaust noise.

In the example shown inFIG. 12, a plurality of first airflow regulating plates22is circumferentially arranged at regular intervals on the outer peripheral surface of the cylindrical portion43of the first bearing box4. In some embodiments, the first airflow regulating plates22may be circumferentially arranged at irregular intervals on the outer peripheral surface of the cylindrical portion43of the first bearing box4. The first airflow regulating plates22circumferentially arranged at irregular intervals on the outer peripheral surface of the cylindrical portion43of the first bearing box4reduce resonance produced in the vehicle main motor200, and prevent an increase in the exhaust noise due to resonance.

The first airflow regulating plates22may each have a uniform height in the direction perpendicular to the rotor shaft3, or may have a larger height toward the air outlet42. The first airflow regulating plate22having a larger height toward the air outlet42in the direction perpendicular to the rotor shaft3more effectively rectifies air flow toward the air outlet42, and prevents an increase in the exhaust noise.

As described above, the vehicle main motor200according to Embodiment 2 of the present disclosure includes the first airflow regulating plates22arranged on the outer peripheral surface of the cylindrical portion43of the first bearing box4to reduce exhaust noise.

FIG. 13is a cross-sectional view of a main motor for a vehicle according to Embodiment 3.FIG. 14is a partial cross-sectional view of the main motor for a vehicle according to Embodiment 3.FIG. 14is an enlarged view of an area D shown inFIG. 13. A vehicle main motor300according to Embodiment 3 includes a main frame23and a joint frame24, in place of the frame2in the vehicle main motor100according to Embodiment 1. The stator core9is attached to the inner peripheral surface of the main frame23. The joint frame24is adjacent to the main frame23in Y-axis direction. The first bearing box4is attached to the joint frame24. In the example shown inFIG. 13, the main frame23has a through-hole in one face of the main frame23perpendicular to Y-axis direction. The second bearing box6is fastened to the main frame23surrounding the through-hole in Y-axis direction to close the through-hole. The main frame23has an opening at the other face perpendicular to Y-axis direction. The joint frame24is fastened to the main frame23in Y-axis direction. The flow channel20is defined between the outer peripheral surface of the cylindrical portion43of the first bearing box4and the inner peripheral surface of the joint frame24. In the example shown inFIG. 13, the air guide16is arranged on the inner peripheral surface of the main frame23. The air guide16has an end nearer the air outlet42at the joint between the main frame23and the joint frame24.

The vehicle main motor300further includes second airflow regulating plates25extending in Y-axis direction on the inner peripheral surface of the joint frame24defining the flow channel20together with the outer peripheral surface of the cylindrical portion43of the first bearing box4. The vehicle main motor300may include any number of second airflow regulating plates25.FIG. 15is a partial cross-sectional view of the main motor for a vehicle according to Embodiment 3.FIG. 15is a cross-sectional view taken along line B-B inFIG. 14. In the example shown inFIG. 15, a plurality of second airflow regulating plates25is circumferentially arranged at regular intervals on the inner peripheral surface of the joint frame24. Similarly to the first airflow regulating plates22, the inclusion of the second airflow regulating plates25reduces the velocity components of air flowing through the flow channel20in the rotational direction about the rotor shaft3. When the air flowing obliquely in the rotational direction about the rotor shaft3with respect to Y-axis direction collides with the edge of the air outlet42, an air vortex forms and generates exhaust noise. The inclusion of the second airflow regulating plates25reduces the velocity components of air flowing through the flow channel20in the rotational direction about the rotor shaft3. The second airflow regulating plates25thus rectify air flow into substantially laminar flow when reaching the air outlet42. The substantially laminar flow reaching the air outlet42prevents an air vortex and reduces exhaust noise.

In the example shown inFIG. 15, a plurality of second airflow regulating plates25is circumferentially arranged at regular intervals on the inner peripheral surface of the joint frame24. In some embodiments, the second airflow regulating plates25may be circumferentially arranged at irregular intervals on the inner peripheral surface of the joint frame24. The second airflow regulating plates25circumferentially arranged at irregular intervals on the inner peripheral surface of the joint frame24reduce resonance produced in the vehicle main motor300, and prevent an increase in the exhaust noise due to resonance.

The second airflow regulating plates25may each have a uniform height in the direction perpendicular to the rotor shaft3, or have a larger height toward the air outlet42. The second airflow regulating plate25having a larger height toward the air outlet42in the direction perpendicular to the rotor shaft3more effectively rectifies air flow toward the air outlet42, and prevents an increase in the exhaust noise.

As described above, the vehicle main motor300according to Embodiment 3 of the present disclosure includes the second airflow regulating plates25arranged on the inner peripheral surface of the joint frame24defining the flow channel20together with the outer peripheral surface of the cylindrical portion43of the first bearing box4to reduce exhaust noise.

FIG. 16is a cross-sectional view of a main motor for a vehicle according to Embodiment 4.FIG. 17is a partial cross-sectional view of the main motor for a vehicle according to Embodiment 4.FIG. 17is an enlarged view of an area E shown inFIG. 16. A vehicle main motor400according to Embodiment 4 further includes first airflow regulating plates22extending in Y-axis direction on an outer peripheral surface of a cylindrical portion43of a first bearing box4, similarly to the vehicle main motor200according to Embodiment 2, in addition to the components in the vehicle main motor300according to Embodiment 3. The vehicle main motor400may include any number of first airflow regulating plates22and second airflow regulating plates25.

FIG. 18is a partial cross-sectional view of the main motor for a vehicle according to Embodiment 4.FIG. 18is a cross-sectional view taken along line C-C inFIG. 17. In the example shown inFIG. 18, a plurality of first airflow regulating plates22and a plurality of second airflow regulating plates25are circumferentially arranged at regular intervals respectively on the outer peripheral surface of the cylindrical portion43of the first bearing box4and the inner peripheral surface of the joint frame24. In the same manner as in Embodiments 2 and 3, the inclusion of the first airflow regulating plates22and the second airflow regulating plates25reduces the velocity components of air flowing through the flow channel20in the rotational direction about the rotor shaft3. When the air flowing obliquely in the rotational direction about the rotor shaft3with respect to Y-axis direction collides with the edge of the air outlet42, an air vortex forms and generates exhaust noise. The inclusion of the first airflow regulating plates22and the second airflow regulating plates25reduce the velocity components of air flowing through the flow channel20in the rotational direction about the rotor shaft3. The first airflow regulating plates22and the second airflow regulating plates25thus rectify air flow into substantially laminar flow when reaching the air outlet42. The substantially laminar flow reaching the air outlet42prevents an air vortex and reduces exhaust noise.

In the example shown inFIG. 18, a plurality of first airflow regulating plates22and a plurality of second airflow regulating plates25are circumferentially arranged at regular intervals respectively on the outer peripheral surface and the inner peripheral surface defining the flow channel20. In some embodiments, a plurality of first airflow regulating plates22and a plurality of second airflow regulating plates25may be circumferentially arranged at irregular intervals on the outer peripheral surface and the inner peripheral surface defining the flow channel20respectively. The first airflow regulating plates22and the second airflow regulating plates25circumferentially arranged at irregular intervals on the outer peripheral surface and the inner peripheral surface defining the flow channel20reduce resonance produced in the vehicle main motor400, and prevent an increase in the exhaust noise due to resonance. Either the first airflow regulating plates22or the second airflow regulating plates25may be circumferentially arranged at regular intervals respectively on the outer peripheral surface and the inner peripheral surface defining the flow channel20, and the other plates may be circumferentially arranged at irregular intervals on the inner peripheral surface or the outer peripheral surface defining the flow channel20.

The first airflow regulating plates22and the second airflow regulating plates25may each have a uniform height in the direction perpendicular to the rotor shaft3, or may have a larger height toward the air outlet42. The first airflow regulating plate22and the second airflow regulating plate25each having a larger height toward the air outlet42in the direction perpendicular to the rotor shaft3more effectively rectify air flow toward the air outlet42, and prevent an increase in the exhaust noise.

As described above, the vehicle main motor400according to Embodiment 4 of the present disclosure includes the first airflow regulating plates22arranged on the outer peripheral surface of the cylindrical portion43of the first bearing box4and the second airflow regulating plates25arranged on the inner peripheral surface of the joint frame24defining the flow channel20together with the outer peripheral surface of the cylindrical portion43of the first bearing box4to reduce exhaust noise.

The present disclosure is not limited to the embodiments described above. The air inlet21may be formed in the face of the frame2perpendicular to Y-axis direction.

REFERENCE SIGNS LIST