JP7729183B2 - Motor lubrication structure - Google Patents

Description

This invention relates to a lubrication structure for supplying cooling and lubricating oil to a motor (motor-generator) used as a driving power source in hybrid vehicles, electric vehicles, and the like.

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 located 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.

Japanese Patent Application Laid-Open No. 2021-116855

The electric motor cooling structure 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 such as that 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 being supplied. However, this churning loss can be reduced by, for example, 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 energy consumed by the heater.

As such, there is still room for improvement in reducing oil churning losses and improving mechanical efficiency when using oil to cool and lubricate a motor or a transaxle that incorporates a motor.

This invention was conceived in response to the above technical challenges, and aims to provide a motor lubrication structure that can appropriately and easily reduce oil churning loss and improve mechanical efficiency.

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 side of the first coil end in the rotational axis direction, a second bearing supporting an end of the rotating shaft on the side of the second coil end in the rotational axis direction, a parking gear arranged on the first coil end side of the motor in the rotational axis direction and rotating integrally with the rotating shaft, and a front bearing on the side of the rotating shaft on the side of the first coil end in the rotational axis direction. a protective cover provided between the first coil end and the parking gear to protect the first coil end; a casing that houses the motor, the first bearing, the second bearing, the parking gear, and the protective cover; and an oil supply passage disposed in the casing above the first coil end and the second coil end in the vertical direction, for allowing oil supplied from outside to flow in the direction of the rotation axis and for causing the oil to drip 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 A lubrication structure for a motor that lubricates a first bearing and the second bearing, wherein the protective cover has a plate-shaped, annular main body portion disposed opposite the first coil end in the direction of the rotation axis, and an arc-shaped, plate-shaped 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 and extending in the direction of the rotation axis from below the first coil end to above the parking gear to above the first bearing, and a plurality of oil grooves formed along the direction of the rotation axis on an upper surface of the receptacle portion, and a portion of the oil grooves extending toward the first coil end and the parking gear are oil-received by the oil-receiving portion. an oil hole is formed through the main body portion, communicating with the portion extending above the gear to the end face of the first bearing; the oil groove and the oil hole form a plurality of guide oil passages; the oil is dripped from the supply oil passage onto the first coil end to cool the first coil end, and then the oil that drips from the first coil end to the lower side is captured by the upper surface of the receiver portion ; the oil captured by the receiver 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 allowed to drip from the end face of the receiver portion towards the first bearing.

In this invention, the receiver portion and the guide oil passage may be formed between the first coil end and the parking gear in the vertical direction, preventing the oil from dripping onto the parking gear and allowing the oil to flow above the first bearing.

The present invention may further include a guide plate provided between the second coil end and the second bearing in the vertical direction. 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 oil supply 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 drip from above the second bearing toward the second bearing (i.e., guiding the oil to the second bearing).

The present invention may also include 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 speed reduction mechanism arranged coaxially with the motor and amplifying the output torque of the motor and transmitting it to the differential gear.The drive shafts, differential gear, and speed reduction mechanism in this invention may be configured to be housed in the casing together with the motor (thus forming a "single-shaft transaxle" with the motor incorporated as an integral part).

The motor lubrication structure of this invention uses oil supplied into the casing to cool the motor's coil ends. 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, the motor lubrication structure of this invention features a protective cover for protecting the motor's coil end (first coil end) that includes a pan portion for capturing oil dripping from the first coil end and an oil guide passage for guiding the oil captured in the pan portion to the first bearing. Specifically, the protective cover in the motor lubrication structure of this invention is integrally formed with the pan portion described above, and the oil guide passage described above is formed in the pan portion. The pan portion is positioned below the first coil end and captures the oil that has risen in temperature after cooling the first coil end. The oil captured in the pan portion then passes through the oil guide passage and is supplied to the first bearing, which supports 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.

As described above, the receptacle portion and guide oil passage provided in the protective cover 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 portion 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.

In addition, a guide plate with a similar configuration to the receptacle 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 like the first bearing.

Accordingly, the motor lubrication structure of this invention does not require the installation of a special heater or other device to heat the oil; instead, it simply requires the installation of a receptacle and an oil guide passage in an existing protective cover, allowing heated, low-viscosity oil to be supplied to the bearings. This makes it possible to appropriately and easily effectively reduce oil churning loss, thereby improving the mechanical efficiency of the motor.

Furthermore, the motor lubrication structure of this invention can be applied to a transaxle with a single-shaft structure, in which, for example, a reduction gear mechanism, differential gear, and left and right drive shafts are arranged coaxially with the motor and housed together in a casing. Therefore, in this way, oil churning loss can be effectively reduced, making it possible to construct a transaxle with good power transmission efficiency.

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. 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. 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. FIG. 1 is a perspective view showing a conventional general protective cover that does not have a receptacle portion and an oil guide passage. 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.

Embodiments of the present invention will be described with reference to the drawings. Note that the embodiments shown below are merely examples of how the present invention can be realized and are not intended to limit the scope of the present invention.

The motor lubrication structure according to an embodiment of the present invention can be applied to a transaxle (or motor drive unit) with an integrated motor, as shown in FIG. 1, for example. The transaxle TA shown in FIG. 1 is a so-called single-shaft transaxle, 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, together with the motor 1, constitutes a so-called motor drive unit.

Motor 1 is mounted as a driving force source on electric vehicles such as hybrid vehicles and electric automobiles. Motor 1 is an electric motor such as 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. Motor 1 is also an electric motor with power generation capabilities, i.e., a motor-generator, and also functions as a generator that generates electricity when driven by external torque.

The motor 1 is a so-called inner rotor motor, consisting of a stator 1a fixed to the casing 7, a rotor 1b positioned 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 the coil (not shown) that make up 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 of the present invention, the coil end on the side closer to the parking gear 6 (described later) in the direction of the rotation axis AL (right side in FIG. 1) is referred to as the first coil end 1d, and the coil end on the opposite side (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, etc. The protective cover 9 is fixed to the stator 1a or the casing 7. Details of this protective cover 9 will be described later. The rotating shaft 1c of the rotor 1b is hollow, and the drive shaft 3, described below, is disposed within 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 supporting the end 1f of the rotating shaft 1c on the first coil end 1d side (right side in Figure 1) in the direction of the rotation axis AL is referred to as the first bearing 10, and the bearing supporting the opposite end 1g of the rotating shaft 1c on the second coil end 1e side (left side in Figure 1) in the direction of the rotation axis AL is referred to as the second bearing 11.

Drive shafts 2 and 3 are arranged coaxially with motor 1, i.e., on the rotational axis AL, facing each other on the left and right sides in the direction of rotational axis AL. In the example shown in Figure 1, the drive shaft on the right side in the direction of rotational axis AL is drive shaft 2, and the drive shaft on the left side in the direction of rotational axis AL is drive shaft 3.

The differential gear 4 is arranged coaxially with the motor 1 and drive shafts 2 and 3, i.e., on the rotation axis AL. The differential gear 4 is similar to conventional differential gears commonly used and is composed of a 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. 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 the reduction mechanism 5, which will be described later.

The reduction mechanism 5 is arranged coaxially with the motor 1 and 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 Figure 1, the reduction mechanism 5 is composed of a planetary gear mechanism using a so-called stepped pinion. Specifically, the reduction mechanism 5 is composed of 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 composed of 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 reduction mechanism 5 and is connected to the differential case 4a of the differential gear 4 (it is formed integrally with the differential case 4a). Therefore, the torque of the carrier 5d is transmitted to the differential gear 4.

Therefore, because the ring gear 5b is fixed so that it cannot 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 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.

The parking gear 6 is located on the first coil end 1d side of the motor 1 in the direction of the rotational axis AL (to the right in Figure 1). Specifically, the parking gear 6 is located between the first coil end 1d and the first bearing 10 in the direction of the rotational axis AL. The parking gear 6 is attached to the end 1f of the rotating shaft 1c of the motor 1. The parking gear 6 and the rotating shaft 1c rotate together. As a component of the electric vehicle's parking lock mechanism (not shown), the parking gear 6 meshes with the parking pole 6a to prevent rotation of the rotating shaft 1c and the drive shafts 2 and 3.

The casing 7, which serves as a "motor case," houses the motor 1, first bearing 10, second bearing 11, parking gear 6, and protective cover 9. Furthermore, the casing 7, which serves as a "transaxle case," houses the drive shafts 2 and 3, differential gear 4, and reduction gear mechanism 5, along with the motor 1.

The cooling pipe 8 is installed inside the casing 7, vertically above the first coil end 1d and the second coil end 1e (upper side in Figure 1). The cooling pipe 8 corresponds to the "oil supply passage" in this embodiment of the invention, and allows oil supplied from the outside to flow in the direction of the rotational axis AL and drips the oil vertically downward (lower side in Figure 1) at a predetermined location in the direction of the rotational axis AL. As shown in Figure 3 (described below), the cooling pipe 8 in particular drips oil from a position immediately above the first coil end 1d and the second coil end 1e in the vertical direction toward the first coil end 1d and the second coil end 1e.

As described above, in the transaxle TA incorporating the motor 1, the oil supplied to the casing 7 cools the coil ends 1d and 1e of the motor 1. At the same time, the oil supplied to 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 supply of lubricating oil. For example, as shown in FIG. 2, in a conventional configuration, relatively low-temperature (high-viscosity) oil 12 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. Note that in the conventional configuration shown in FIG. 2, components or parts having the same configuration and function as those in the motor lubrication structure of 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.

In accordance with this embodiment of the motor lubrication structure, as shown in FIG. 3, the protective cover 9 for protecting the first coil end 1d of the motor 1 is provided with a receptacle portion 9a for capturing oil 12 dripping from the first coil end 1d, and an oil guide passage 9b for guiding the oil 12 captured in the receptacle portion 9a to the first bearing 10. In other words, the protective cover 9 of the motor lubrication structure in this embodiment of the invention is integrally formed with the receptacle portion 9a described above, and the oil guide passage 9b described above is formed in the receptacle portion 9a.

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

As described above, the guide oil passage 9b is formed on the upper surface 9c of the tray portion 9a, extending in the direction of the rotation axis AL. Specifically, as shown in Figure 5, the guide oil passage 9b is formed from an oil hole 9d for circulating 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 opens onto the end face of the tray portion 9a, and the oil 12 that enters the oil groove 9e from this point drips toward the first bearing 10.

As a result, the oil 12 captured in the receptacle 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. By supplying the first bearing 10 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.

As shown in FIG. 3, the receiver portion 9a and guide oil passage 9b provided on the protective cover 9 as described above are positioned between the first coil end 1d and the parking gear 6 in the vertical direction, and across 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 reduces the adhesion of the oil 12 to the parking gear 6. This makes it easy to 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.

Furthermore, in the motor lubrication structure according to this embodiment of the present invention, as shown in FIG. 3, a guide plate 13 having a configuration similar to the receptacle portion 9a and guide oil passage 9b described above is provided for the second bearing 11, which 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 described above. 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.

Accordingly, the motor lubrication structure of this invention does not require the installation of a special heater or the like to heat the oil 12; instead, it simply requires the installation of a receptacle portion 9a and an oil guide passage 9b, as shown in Figure 5, on an existing protective cover 9', as shown in Figure 4, to supply heated, low-viscosity oil 12 to the bearings 10, 11. This makes it possible to appropriately and easily effectively reduce the agitation loss of the oil 12, thereby improving the mechanical efficiency of the motor 1.

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 the reduction gear mechanism 5, differential gear 4, and left and right drive shafts 2, 3 are arranged coaxially with the motor 1 and housed together in a casing 7. Therefore, in this manner, it is possible to effectively reduce churning loss of the oil 12 and construct a transaxle TA with good power transmission efficiency.

1 Motor 1a (Motor) Stator 1b (Motor) Rotor 1c (Motor) Rotating Shaft (Rotor Shaft)
1d First coil end (of motor) 1e Second coil end (of motor) 1f End (of rotating shaft) 1g End (of rotating shaft) 2 Drive shaft 3 Drive shaft 4 Differential gear 4a Differential case (of differential gear) 4b Side gear (of differential gear) 4c Differential pinion (of differential gear) 4d Pinion shaft (of differential gear) 5 Reduction mechanism 5a Sun gear (of differential gear) 5b Ring gear (of differential gear) 5c Stepped pinion (of differential gear) 5d Carrier (of differential gear) 5e Large diameter pinion (of stepped pinion) 5f Small diameter pinion (of stepped pinion) 6 Parking gear 6a Parking pole (of parking lock mechanism) 7 Casing 8 Cooling pipe (oil supply passage)
9 Protective cover 9a Receptacle portion (of protective cover) 9b Guide oil passage (of protective cover) 9c Upper surface (of receptacle portion) 9d Oil hole (of guide oil passage) 9e Oil groove (of guide oil passage) 9' Protective cover (of conventional shape) 10 First bearing 11 Second bearing 12 Oil 13 Guide plate AL Rotation axis TA Transaxle (or motor drive unit)

Claims (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 ;
A lubrication structure for a motor, characterized in that the oil captured in the receiving portion is caused to flow through the multiple guide oil passages in the direction of the rotation axis to the upper side of the first bearing, and is caused to drip from the end face of the receiving portion toward the first bearing.