Motor lubrication structure

Abstract

To provide a motor lubrication structure which enables reduction of stirring loss of an oil to be achieved easily to improve mechanical efficiency.SOLUTION: In a motor lubrication structure, an oil 12 dropped from a supply oil passage 8 in a casing 7 cools a coil end 1d of a motor 1 and lubricates bearings 10, 11 supporting a rotary shaft of the motor 1. A protection cover 9 of the coil end 1d is formed with: a tray part 9a which captures the oil 12 which is dropped from the supply oil passage 8 to the coil end 1d to cool the coil end 1d and then is dropped downward from the coil end 1d, and a guide oil passage 9b which causes the oil 12 captured by the tray part 9a to flow to an area above the bearing 10 in a rotation axis direction AL and causes the oil 12 to be dropped from the area above the bearing 10 toward the bearing 10.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to a lubrication structure for supplying oil for cooling and lubrication to a motor (motor generator) used as a driving power source for hybrid vehicles, electric vehicles, etc. [Background technology]

[0002] Patent Document 1 describes an invention related to an electric motor cooling device that aims to improve spatial efficiency in the arrangement of oil passages that supply oil to the electric motor and reduce driving losses of the electric motor. The electric motor described in Patent Document 1 is configured to transmit torque to left and right drive shafts disposed in a hollow portion of the motor shaft via a reducer and a differential gear. The electric motor cooling device includes an oil seal that seals between the differential gear case and the outer peripheral surface of the drive shaft, an internal drive shaft oil passage formed inside the drive shaft, an oil inlet hole formed in the drive shaft on the differential gear side relative to the oil seal to allow oil to flow from the differential gear to the internal drive shaft oil passage, and an oil outlet hole formed in the drive shaft on the electric motor side relative to the oil seal to allow oil to flow from the internal drive shaft oil passage to the inside of the motor shaft. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent Publication No. 2021-116855 Summary of the Invention [Problem to be solved by the invention]

[0004] The cooling structure for an electric motor described in Patent Document 1 supplies cooling oil to the electric motor housed together with a reducer using a stepped-pinion planetary gear mechanism and a differential gear within a so-called transaxle casing, which houses both the reducer and the differential gear. In a transaxle incorporating an electric motor as described in Patent Document 1, the electric motor is cooled with oil as described above, and the oil supplied into the casing lubricates the rotating and sliding parts of the transaxle, such as the gears of the reduction mechanism and the bearings of the rotating shaft. Among the rotating parts within the transaxle, the motor's rotating shaft (rotor shaft) rotates at high speed, resulting in significant churning loss in the bearings supporting the motor's rotating shaft due to the oil supply. To address this, for example, the churning loss can be reduced by heating the supplied oil with a heater to reduce the oil's viscosity. However, this increases costs due to the heater and reduces efficiency due to the heater's energy consumption.

[0005] As described above, when a motor or a transaxle incorporating a motor is cooled and lubricated with oil, there is still room for improvement in reducing oil churning loss and improving mechanical efficiency.

[0006] The present invention was devised in light of the above technical problems, and aims to provide a lubrication structure for a motor that can appropriately and easily reduce oil churning loss and improve mechanical efficiency. [Means for solving the problem]

[0007] In order to achieve the above object, the present invention provides a motor (mounted as a driving force source in an electric vehicle or a hybrid vehicle), a first coil end and a second coil end respectively protruding from both ends of the motor in a rotational axis direction of a rotating shaft (rotor shaft) of the motor, a first bearing supporting an end of the rotating shaft on the first coil end side in the rotational axis direction, a second bearing supporting an end of the rotating shaft on the second coil end side in the rotational axis direction, a parking gear disposed on the first coil end side of the motor in the rotational axis direction and rotating integrally with the rotating shaft, and a bearing between the first coil end and the parking gear in the rotational axis direction. a casing that houses the motor, a first bearing, a second bearing, a parking gear, and the protective cover; and an oil supply passage that is arranged in the casing vertically above the first coil end and the second coil end, and that causes oil supplied from an external source to flow in the direction of the rotation axis and drips the oil downward in the vertical direction at a predetermined location in the direction of the rotation axis, wherein the oil dripping from the oil supply passage cools the motor and lubricates the first bearing and the second bearing, and the protective cover is the rotor has a plate-like, annular main body portion disposed opposite the first coil end in the direction of the rotation axis; and an arc-shaped, plate-like receptacle portion formed in a predetermined range along the circumferential direction of an inner periphery of the main body portion above in the vertical direction, the receptacle portion extending in the direction of the rotation axis from below the first coil end to above the parking gear to above the first bearing, wherein a plurality of oil grooves are formed in an upper surface of the receptacle portion along the direction of the rotation axis, and an oil hole is formed through the main body portion to connect a portion of the oil groove extending toward the first coil end with a portion extending above the parking gear to an end face of the first bearing, and a plurality of guide oil passages are formed by the oil groove and the oil hole, The oil is dropped from the supply oil passage onto the first coil end to cool the first coil end, and then the oil is passed from the first coil end to the On the bottom The dripped oil is poured into the tray. On the top of the part The oil trapped in the receiving pan is then guided to the first bearing in the direction of the rotation axis. Upper side and causes the oil to flow through the plurality of guide oil passages. From the end face of the tray The method is characterized in that the liquid is dropped from the nozzle toward the first bearing.

[0008] In addition, the receiving tray portion and the guide oil passage in this invention may be formed between the first coil end and the parking gear in the vertical direction, and may be configured to prevent the oil from dripping onto the parking gear and to allow the oil to flow up to the upper part of the first bearing.

[0009] Furthermore, the present invention may further include a guide plate provided between the second coil end and the second bearing in the vertical direction, and the guide plate in this invention may further include a receptacle portion (of the guide plate) that captures the oil that drips downward from the second coil end after dripping from the supply oil passage onto the second coil end to cool the second coil end, and a guide oil passage (of the guide plate) that causes the oil captured in the receptacle portion to flow to above the second bearing in the direction of the rotation axis and drips from above the second bearing towards the second bearing (i.e., guiding the oil to the second bearing).

[0010] The present invention may also comprise left and right drive shafts arranged coaxially with the motor and facing each other on the left and right in the direction of the rotation axis, a differential gear arranged coaxially with the motor and causing differential rotation of the left and right drive shafts, and a reduction mechanism arranged coaxially with the motor and amplifying the output torque of the motor and transmitting it to the differential gear, and the drive shafts, differential gear, and reduction mechanism in this invention may be configured to be housed in the casing together with the motor (thus forming a ``single-shaft structure transaxle'' in which the motor is integrally incorporated). [Effects of the Invention]

[0011] In the motor lubrication structure of the present invention, oil supplied into the casing cools the motor's coil end. At the same time, the oil supplied into the casing lubricates the bearings supporting the motor's rotating shaft. Because the motor's rotating shaft rotates at high speed, churning loss inevitably occurs in the bearings supporting the rotating shaft due to the lubricating oil supplied. In contrast, in the motor lubrication structure of the present invention, a protective cover for protecting the motor's coil end (first coil end) has a pan portion that captures oil dripping from the first coil end and a guide oil passage that guides the oil captured in the pan portion to the first bearing. Specifically, the protective cover in the motor lubrication structure of the present invention is integrally formed with the pan portion, and the guide oil passage is formed in the pan portion. The pan portion is positioned below the first coil end and captures the oil whose temperature has increased after cooling the first coil end. The oil captured in the pan portion then passes through the guide oil passage and is supplied to one of the first bearings supporting the motor's rotating shaft. As a result, the first bearing can be supplied with oil whose temperature has increased and whose viscosity has decreased after cooling the first coil end.By supplying the first bearing with oil that has a lower viscosity than conventional oil (compared to oil supplied without cooling the coil end), oil agitation loss can be reduced.

[0012] The receptacle and guide oil passage provided in the protective cover as described above are positioned vertically between the first coil end and the parking gear and across the parking gear in the direction of the rotation axis. This allows oil that drips from the first coil end and is captured in the receptacle to be guided to the first bearing without dripping onto the parking gear, preventing or minimizing oil from adhering to the parking gear. This makes it easy to reduce churning loss caused by oil adhering to the parking gear, which rotates with the motor's rotating shaft.

[0013] Furthermore, a guide plate having a configuration similar to that of the receptacle portion and guide oil passage can be provided for the second bearing, which supports the motor's rotating shaft on the opposite side of the motor from the first bearing. This allows oil whose temperature has increased and whose viscosity has decreased after cooling the second coil end to be easily supplied to the second bearing, just as with the first bearing.

[0014] Therefore, with the motor lubrication structure of this invention, heated, low-viscosity oil can be supplied to the bearings with a simple configuration that simply provides a pan and an oil guide passage in an existing protective cover, without the need for a special heater or the like to heat the oil. This makes it possible to appropriately and easily effectively reduce oil churning loss, thereby improving the mechanical efficiency of the motor.

[0015] Furthermore, the motor lubrication structure of the present invention can be applied to a single-shaft transaxle in which a reduction gear mechanism, a differential gear, and left and right drive shafts are arranged coaxially with the motor and housed together in a casing. As a result, it is possible to effectively reduce oil churning loss and configure a transaxle with good power transmission efficiency. [Brief explanation of the drawings]

[0016] [Figure 1] 1 is a cross-sectional view illustrating an example of a lubrication structure for a motor according to the present invention, showing a transaxle having a single shaft structure to which the lubrication structure for a motor according to the present invention is applied. FIG. [Figure 2] 1 is a cross-sectional view showing the flow of oil in a conventional lubrication structure that does not have a receptacle portion and an oil guide path, as a comparative example of the lubrication structure for a motor of the present invention. FIG. [Figure 3]This is a diagram for explaining the lubrication structure of the motor of this invention, and in particular shows an enlarged view of the oil supply passage, oil supply passage (cooling pipe), motor coil end, bearing, parking gear, receptacle portion provided on the protective cover, and guide plate in the lubrication structure, as well as a cross-sectional view showing the flow of oil supplied through the oil supply passage. [Figure 4] FIG. 1 is a perspective view showing a conventional general protective cover that does not have a receptacle portion and an oil guide passage. [Figure 5] FIG. 1 is a diagram for explaining the lubrication structure of the motor of the present invention, and is a perspective view showing a receptacle portion provided on the protective cover and an oil guide passage (oil hole, oil groove portion) formed in the receptacle portion. DETAILED DESCRIPTION OF THE INVENTION

[0017] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The following embodiments of the present invention will be described with reference to the accompanying drawings. Note that the following embodiments are merely examples of specific embodiments of the present invention and are not intended to limit the scope of the present invention.

[0018] The motor lubrication structure according to the embodiment of the present invention can be applied to a transaxle (or motor drive unit) with an integrated motor, as shown in Fig. 1. The transaxle TA shown in Fig. 1 is a transaxle with a so-called single-shaft structure, and includes a motor 1, left and right drive shafts 2 and 3, a differential gear 4, a reduction mechanism 5, and a parking gear 6, all of which are arranged on the same rotation axis AL, as well as a casing 7 that houses the motor 1, drive shafts 2 and 3, differential gear 4, reduction mechanism 5, and parking gear 6, and a cooling pipe (oil supply passage) 8. In other words, the transaxle TA shown in Fig. 1 is integrated with the motor 1 to form a so-called motor drive unit.

[0019] The motor 1 is mounted as a driving force source on electric vehicles such as hybrid vehicles and electric automobiles. The motor 1 is, for example, a permanent magnet synchronous motor or an induction motor, and functions as a prime mover that is driven by a supply of electric power to output torque. The motor 1 is also a motor-generator that has a power generation function, and also functions as a generator that generates electricity when driven by external torque.

[0020] The motor 1 is a so-called inner rotor motor and is composed of a stator 1a fixed to the casing 7, a rotor 1b disposed on the inner periphery of the stator 1a, and a rotating shaft (rotor shaft) 1c of the rotor 1b. The motor 1 also has coil ends 1d and 1e of a coil (not shown) constituting the stator 1a. The coil ends 1d and 1e protrude from both ends of the motor 1 (stator 1a) in the direction of the rotation axis AL. In this embodiment, the coil end on the side closer to a parking gear 6 (described later) in the direction of the rotation axis AL (the right side in FIG. 1) is referred to as the first coil end 1d, and the coil end on the opposite side (the left side in FIG. 1) is referred to as the second coil end 1e. The first coil end 1d is provided with a protective cover 9 to protect the first coil end from foreign matter and the like. The protective cover 9 is fixed to the stator 1a or the casing 7. Details of the protective cover 9 will be described later. The rotating shaft 1c of the rotor 1b is a hollow shaft, and a drive shaft 3, which will be described later, is disposed in the hollow portion. The rotating shaft 1c of the rotor 1b is rotatably supported at both ends in the direction of the rotation axis AL by bearings 10 and 11. In this embodiment of the present invention, the bearing that supports the end 1f of the rotating shaft 1c on the first coil end 1d side (right side in FIG. 1) in the direction of the rotation axis AL is referred to as the first bearing 10, and the bearing that supports the opposite end, i.e., the end 1g of the rotating shaft 1c on the second coil end 1e side (left side in FIG. 1) in the direction of the rotation axis AL, is referred to as the second bearing 11.

[0021] The drive shafts 2 and 3 are arranged coaxially with the motor 1, i.e., on the rotational axis AL, facing each other on the left and right sides in the direction of the rotational axis AL. In the example shown in Fig. 1, the drive shaft on the right side in the direction of the rotational axis AL is referred to as drive shaft 2, and the drive shaft on the left side in the direction of the rotational axis AL is referred to as drive shaft 3.

[0022] The differential gear 4 is arranged coaxially with the motor 1 and the drive shafts 2 and 3, i.e., on the rotation axis AL. The differential gear 4 is similar to a conventional differential gear commonly used, and is composed of a so-called differential case 4a, a pair of (left and right) side gears 4b, a pair of differential pinions 4c, and a pinion shaft 4d. Each side gear 4b of the differential gear 4 is attached to the tip of the drive shafts 2 and 3, respectively, and therefore the differential gear 4 generates differential rotation between the left and right drive shafts 2 and 3. At the same time, the amplified output torque of the motor 1 is transmitted to the differential gear 4 via a reduction mechanism 5, which will be described later.

[0023] The reduction mechanism 5 is disposed coaxially with the motor 1 and the drive shafts 2 and 3, i.e., on the rotation axis AL. The reduction mechanism 5 amplifies the output torque of the motor 1 and transmits it to the differential gear 4. In the example shown in FIG. 1, the reduction mechanism 5 is configured as a planetary gear mechanism using a so-called stepped pinion. Specifically, the reduction mechanism 5 is configured from a sun gear 5a, a ring gear 5b, a stepped pinion 5c, and a carrier 5d. The sun gear 5a serves as the input member of the reduction mechanism 5 and is attached to the rotating shaft 1c of the motor 1. The sun gear 5a and the rotating shaft 1c rotate integrally. The ring gear 5b is fixed to the casing 7. The stepped pinion 5c is configured from a large-diameter pinion 5e and a small-diameter pinion 5f, which has a smaller diameter than the large-diameter pinion 5e. The large-diameter pinion 5e meshes with the sun gear 5a. The small-diameter pinion 5f meshes with the ring gear 5b. The carrier 5d supports the stepped pinion 5c so that it can rotate and revolve. The carrier 5d also serves as the "output member" of the speed reduction mechanism 5 and is connected to the differential case 4a of the differential gear 4 (formed integrally with the differential case 4a). Therefore, the torque of the carrier 5d is transmitted to the differential gear 4.

[0024] Therefore, because the ring gear 5b is fixed so as not to rotate, when torque is transmitted to the sun gear 5a and the sun gear 5a rotates, the rotation speed of the carrier 5d decreases relative to the rotation speed of the sun gear 5a in the reduction mechanism 5. In other words, the reduction mechanism 5 amplifies the output torque of the motor 1 input to the sun gear 5a and outputs it from the carrier 5d to the differential gear 4.

[0025] The parking gear 6 is disposed on the first coil end 1d side of the motor 1 in the direction of the rotation axis AL (on the right side in FIG. 1). Specifically, the parking gear 6 is disposed between the first coil end 1d and the first bearing 10 in the direction of the rotation axis AL. The parking gear 6 is attached to an end portion 1f of the rotating shaft 1c of the motor 1. The parking gear 6 and the rotating shaft 1c rotate integrally. The parking gear 6 is a component of a parking lock mechanism (not shown) of the electric vehicle, and prevents the rotating shaft 1c and the drive shafts 2 and 3 from rotating by meshing with a parking pole 6a.

[0026] The casing 7 serves as a so-called "motor case" and houses the motor 1, first bearing 10, second bearing 11, parking gear 6, and protective cover 9. Furthermore, the casing 7 serves as a so-called "transaxle case" and houses the drive shafts 2 and 3, differential gear 4, and reduction mechanism 5 together with the motor 1 and the like.

[0027] The cooling pipes 8 are installed inside the casing 7 vertically above the first coil ends 1d and the second coil ends 1e (upper side in Figure 1). The cooling pipes 8 correspond to the "oil supply passages" in this embodiment of the invention, and allow oil supplied from the outside to flow in the direction of the rotational axis AL and drip the oil vertically downward (lower side in Figure 1) at predetermined locations in the direction of the rotational axis AL. As shown in Figure 3 (described below), the cooling pipes 8 drip oil from a position immediately above the first coil ends 1d and the second coil ends 1e vertically toward the first coil ends 1d and the second coil ends 1e.

[0028] As described above, in the transaxle TA incorporating the motor 1, the oil supplied into the casing 7 cools the coil ends 1d and 1e of the motor 1. At the same time, the oil supplied into the casing 7 lubricates the bearings 10 and 11 supporting the rotating shaft 1c of the motor 1. Because the rotating shaft 1c of the motor 1 rotates at high speed, the bearings 10 and 11 supporting the rotating shaft 1c inevitably experience relatively large churning losses due to the lubricating oil supplied. For example, as shown in FIG. 2, in a conventional configuration, oil 12 with a relatively low temperature (high viscosity) drips from the top of the casing 7 and is supplied to the bearings 10 and 11. Therefore, in the conventional configuration, relatively large churning losses occur in the bearings 10 and 11. In the conventional configuration shown in FIG. 2, members or components having the same configurations and functions as those in the lubrication structure of the motor according to the embodiment of the present invention shown in FIG. 1 and FIG. 3 (described later) are designated by the same reference numerals as those used in FIGS. 1 and 3.

[0029] Therefore, in the motor lubrication structure according to the embodiment of the present invention, as shown in Figure 3, protective cover 9 for protecting first coil end 1d of motor 1 is provided with a receptacle portion 9a for capturing oil 12 dripping from first coil end 1d, and a guide oil passage 9b for guiding oil 12 captured in receptacle portion 9a to first bearing 10. In other words, protective cover 9 of the motor lubrication structure according to the embodiment of the present invention is integrally formed with receptacle portion 9a as described above, and receptacle portion 9a has guide oil passage 9b as described above formed therein.

[0030] As shown in FIG. 5, the tray portion 9a is a plate-shaped member curved along the inner periphery of the protective cover 9, and is formed integrally with the main body of the protective cover 9, as opposed to a conventional protective cover 9' as shown in FIG. 4. An oil guide passage 9b is formed in the vertical upper surface 9c of the tray portion 9a. The tray portion 9a is positioned vertically below the first coil end 1d (the lower side in FIG. 3). As a result, oil 12 supplied from the cooling pipe 8 to the first coil end 1d and passed through the first coil end 1d drips onto the tray portion 9a. Therefore, the tray portion 9a captures the oil 12, whose temperature has increased after cooling the first coil end 1d.

[0031] As described above, the guide oil passage 9b is formed in the upper surface 9c of the tray portion 9a so as to extend in the direction of the rotation axis AL. Specifically, as shown in Fig. 5, the guide oil passage 9b is formed by an oil hole 9d for circulating the oil 12 and an oil groove 9e. Therefore, the oil 12 captured in the tray portion 9a flows into the oil groove 9e of the guide oil passage 9b. The tip of the oil groove 9e is connected to an end face portion of the tray portion 9a so as to open, and the oil 12 that has entered the oil groove 9e from this portion drips toward the first bearing 10.

[0032] As a result, the oil 12 captured in the tray portion 9a passes through the guide oil passage 9b and is supplied to the first bearing 10, which supports the rotating shaft 1c of the motor 1. Therefore, the first bearing 10 can be supplied with oil 12 whose temperature has increased and whose viscosity has decreased after cooling the first coil end 1d. Because the first bearing 10 is supplied with oil 12 that has a lower viscosity than conventional oil (compared to oil supplied without cooling the coil end), churning loss of the oil 12 can be reduced.

[0033] As shown in FIG. 3 , the receiver portion 9a and guide oil passage 9b provided in the protective cover 9 as described above are disposed between the first coil end 1d and the parking gear 6 in the vertical direction and so as to straddle the parking gear 6 in the direction of the rotation axis AL. This allows the oil 12 that drips from the first coil end 1d and is captured by the receiver portion 9a to be guided to the first bearing 10 without dripping onto the parking gear 6. This prevents or suppresses the oil 12 from adhering to the parking gear 6. This makes it possible to easily reduce the churning loss that occurs when the oil 12 adheres to the parking gear 6, which rotates together with the rotating shaft 1c of the motor 1.

[0034] Furthermore, in the motor lubrication structure according to the embodiment of the present invention, as shown in Fig. 3, a guide plate 13 having a configuration similar to that of the tray portion 9a and guide oil passage 9b described above is provided for a second bearing 11 that supports the rotating shaft 1c of the motor 1 on the opposite side of the first bearing 10 (the left side of Fig. 3) across the motor 1. This allows oil 12, whose temperature has increased and whose viscosity has decreased after cooling the second coil end 1e, to be easily supplied to the second bearing 11, just as with the first bearing 10. Therefore, the second bearing 11 is supplied with oil 12 that has a lower viscosity than conventional oil (compared to oil supplied without cooling the coil end), thereby reducing churning loss of the oil 12.

[0035] Therefore, according to the motor lubrication structure of the present invention, heated, low-viscosity oil 12 can be supplied to bearings 10, 11 with a simple configuration that simply provides a tray portion 9a and an oil guide passage 9b as shown in Figure 5 to an existing protective cover 9' as shown in Figure 4, without providing a special heater or the like for heating oil 12. As a result, it is possible to appropriately and easily effectively reduce the churning loss of oil 12, and ultimately improve the mechanical efficiency of motor 1.

[0036] Furthermore, as shown in Figure 1, the motor lubrication structure of this invention can be applied to a transaxle TA with a uniaxial structure in which a reduction gear mechanism 5, a differential gear 4, and left and right drive shafts 2, 3 are arranged coaxially with a motor 1 and housed together in a casing 7. Therefore, as described above, it is possible to effectively reduce the churning loss of oil 12 and configure a transaxle TA with good power transmission efficiency. [Explanation of symbols]

[0037] 1 motor 1a (Motor) Stator 1b (motor) rotor 1c (motor) rotating shaft (rotor shaft) 1d (Motor) 1st coil end 1e (Motor) Second Coil End 1f (rotation shaft) end 1g End (of rotating shaft) 2 drive shafts 3 drive shaft 4 differential gear 4a (differential gear) differential case 4b (differential gear) side gear 4c (differential gear) differential pinion 4d (differential gear) pinion shaft 5 Reduction mechanism 5a (differential gear) sun gear 5b (differential gear) ring gear 5c (differential gear) stepped pinion 5d (differential gear) carrier 5e (Stepped pinion) Large diameter pinion 5f (Stepped pinion) small diameter pinion 6 Parking gear 6a Parking pole (parking lock mechanism) 7 Casing 8 Cooling pipe (oil supply passage) 9 Protective cover 9a (Protective cover) tray 9b (protective cover) guide oil passage 9c (Top surface of the tray) 9d Oil hole (in the induction oil passage) 9e Oil groove (in the guide oil passage) 9' (traditional) protective cover 10 First bearing 11 Second bearing 12 Oil 13 Guidance plate AL rotation axis TA Transaxle (or motor drive unit)

Claims

[Claim 1] a motor; a first coil end and a second coil end protruding from both ends of the motor in the direction of the rotation axis of the rotary shaft of the motor; a first bearing supporting an end of the rotary shaft on the side of the first coil end in the direction of the rotation axis; a second bearing supporting an end of the rotary shaft on the side of the second coil end in the direction of the rotation axis; a parking gear disposed on the first coil end side of the motor in the direction of the rotation axis and rotating integrally with the rotary shaft; and a protective cover disposed between the first coil end and the parking gear in the direction of the rotation axis and protecting the first coil end. a casing that houses the motor, a first bearing, a second bearing, a parking gear, and a protective cover; and an oil supply passage that is arranged in the casing vertically above the first coil end and the second coil end, and that causes oil supplied from outside to flow in the direction of the rotation axis and drips the oil downward in the vertical direction at a predetermined location in the direction of the rotation axis, wherein the oil dripping from the oil supply passage cools the motor and lubricates the first bearing and the second bearing, the protective cover has a plate-like, annular main body portion disposed opposite the first coil end in the direction of the rotation axis, and an arc-shaped, plate-like receptacle portion formed in a predetermined range along the circumferential direction of an inner periphery of the main body portion above in the vertical direction, the receptacle portion extending in the direction of the rotation axis below the first coil end and above the parking gear to the upper side of the first bearing, a plurality of oil grooves formed along the rotation axis direction on an upper surface of the tray portion; an oil hole is formed through the main body portion to communicate a portion of the oil groove extending toward the first coil end and a portion of the oil groove extending above the parking gear to an end face of the first bearing, a plurality of guide oil passages are formed by the oil grooves and the oil holes; the oil dripping from the oil supply passage onto the first coil end to cool the first coil end, and then the oil dripping from the first coil end to the lower side is captured by an upper surface of the receiver portion; The oil captured by the tray portion is caused to flow through the plurality of guide oil passages to the upper side of the first bearing in the direction of the rotation axis, and is also caused to drip from an end face of the tray portion toward the first bearing. A motor lubrication structure characterized by the above.

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