CROSS-REFERENCE TO RELATED APPLICATION

This application claims under 35 U.S.C. § 119(a) the benefit of priority to Japanese Patent Application No. 2018-136487 filed on Jul. 20, 2018, the entire contents of which are incorporated herein by reference.

BACKGROUND

(a) Technical Field

The present disclosure relates to a motor, and more particularly, to a motor to be used in a pure electric vehicle (EV) or a hybrid vehicle (HEV) and that efficiently suppresses a temperature increase.

(b) Background Art

A developed technique in the related art teaches a configuration in which cooling oil is pressure-fed to a flow passage formed in a shaft and is introduced into a clearance between an inner peripheral surface of a hole through which a shaft of a rotor core penetrates. The cooling oil is then introduced into an inner flow passage on an inner side of a permanent magnet and is discharged to an outer side of the rotor. However, since the cooling oil is discharged and circulated into a case, the cooling oil is forcibly injected between the rotor and a stator to generate a drag torque which causes a deterioration in efficiency of the motor. In addition, since the pump of the cooling oil is within the case, the temperature of the cooling temperature disadvantageously increases.

The above information disclosed in this section is merely for enhancement of understanding of the background of the disclosure and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.

SUMMARY

The present disclosure provides a cooling structure capable of efficiently cooling a rotor in a motor.

In one aspect, the present invention provides a motor that may include: a shaft rotatably supported on a case; a rotor having a rotor core to which a plurality of magnets may be provided on an outer periphery of the shaft and disposed to face a stator on the case side; and flow passages formed on the shaft and the rotor to allow cooling oil to pass through a core flow passage inside the rotor core from an introduction flow passage on a first side in an axial direction of the shaft and to flow to the introduction flow passage on a second side in the axial direction of the shaft, wherein an inlet in communication with the introduction flow passage and an outlet in communication with the introduction flow passage may be formed in the case.

In an exemplary embodiment, the introduction flow passage and the core flow passage may be connected to each other by a supply flow passage, the core flow passage and the introduction flow passage may be connected to each other by a discharge flow passage, the core flow passage and the core flow passage may be connected to each other by a return flow passage, and the supply flow passage and the discharge flow passage may be formed by branched flow passages which are branched into at least two. In addition, the branched flow channel may include the core flow channel provided in an odd number. Both sides of the rotor core may be disposed between end plates, and the supply flow passage and the discharge flow passage may be disposed on the end plate. The rotor core may have a structure in which a plurality of electronic steels are stacked by bonding and embedded in the electronic steel plates on which the magnets are stacked.

In particular, since the inlet in communication with the introduction flow passage and the outlet in communication with the discharge flow passage may be formed in the case, the cooling oil may be supplied from the outside of the case and returned to the outside of the case. The cooling oil may be cooled outside, and as a result the temperature in the motor may be efficiently reduced due to the cooled cooling oil. The flow passage may include the introduction flow passage on a first side in the axial direction of the shaft, the core flow passage inside the rotor core, and the discharge flow passage on a second side in the axial direction of the shaft. Since the flow passage may be formed in the shaft and the rotor core, the cooling oil may flow more smoothly in the flow passage, thereby efficiently reducing the temperature in the motor. Since no cooling oil is discharged into the case, the cooling oil may be forcibly injected between the rotor and the stator, thus preventing drag torque from being generated.

The introduction flow passage and the core flow passage may be connected to each other by the supply flow passage, the core flow passage and the discharge flow passage may be connected to each other by the discharge flow passage, the core flow passage and the core flow passage may be connected to each other by the return flow passage. The supply flow passage and the discharge flow passage may be the branched flow passages which are branched into at least two, such that the cooling oil may flow from one side to the other side without an extra core flow passage. For example, when the number of core flow passages is 10, if 10 core flow passages reciprocate in one cylinder, the outlet on the last core flow passage comes to the supply side. In other words, 11 core flow passages may be provided. However, when the core flow passage is divided into the routes of five and five two-system, one system may include five flow passages which are an odd number and thus, the outlet of the last core flow passage may come to the discharge side.

Since the number of core flow passages is an odd number, the branched flow passage does not require an extra core flow passage, and the outlet of the last core flow passage comes to the discharge side. For example, when the total number of core flow passages is 8, the number of core flow passages may be divided into a (five, three) two-system, and the number of core flow passages in each system may be set to be an odd number. When the core flow passages are divided into a (four, four) two-system, the outlet of the last core flow passage does not come to the discharge side.

Further, since both sides of the rotor core may be disposed between the end plates, both the supply passage and the discharge passage may be formed on the end plates. The end plate may have a circular plate body and thus, the supply flow passage and the discharge flow passage may extend in any direction from the center. The end plate may include a semicircular groove and a first side thereof may be closed by the end of the rotor core to thus form the supply passage and the discharge passage.

Since the plurality of electromagnetic steel plates may be stacked by the bonding, comparing the stacking of the electromagnetic steel plates by the bonding with the coupling by the caulking, the electromagnetic steel plates are not omitted from the clearance. Further, when receiving apertures are formed on the electromagnetic steel plates, the magnet may be embedded more easily. When the through apertures are formed on the electromagnetic steel plates, the core flow passage may be formed more easily.

