Patent Description:
For example, <CIT> discloses a cooling structure for a rotating electric machine (electric motor). Conventionally, a drive unit in which a rotating electric machine and a transmission are integrated is also known. Furthermore, reference shall be made to documents <CIT>, <CIT>, <CIT> and <CIT>, all of which disclose drive units with rotating electric machines, transmissions and cooling structures.

When the drive unit is provided with a cooling structure, it is preferable to provide a cooling structure capable of cooling both the rotating electric machine and the transmission. In this case, a cooling structure that does not become complicated is required.

An object of the present invention is to solve the aforementioned problem.

According to claim <NUM> of the present invention, a drive unit is provided. The drive unit includes a rotating electric machine including a rotating electric machine casing, a transmission including a transmission casing and integrated with the rotating electric machine, and a cooling structure configured to cool the rotating electric machine and the transmission, wherein the cooling structure includes a first cooling passage configured to cool the rotating electric machine and a second cooling passage configured to cool the transmission, and the first cooling passage and the second cooling passage are in communication with each other, and a common coolant flows through the first cooling passage and the second cooling passage.

According to claim <NUM>, since the first cooling passage and the second cooling passage communicate with each other and a common coolant flows through the first cooling passage and the second cooling passage, the cooling structure of the drive unit can be simplified.

A drive unit <NUM> shown in <FIG> includes a rotating electric machine <NUM>, a transmission <NUM> integrated with the rotating electric machine <NUM>, and a cooling structure <NUM> for cooling the rotating electric machine <NUM> and the transmission <NUM>. The drive unit <NUM> is used in a state in which a rotation axis AX (hereinafter simply referred to as "axis AX") of the rotating electric machine <NUM> is directed in the vertical direction. The term "vertical direction" includes not only an exact vertical direction but also a direction slightly inclined with respect to the vertical direction. Although the use of the drive unit <NUM> is not particularly limited, it can be used as a power source for driving a propeller <NUM> of a vertical take-off and landing aircraft, for example (see <FIG>).

The rotating electric machine <NUM> is an electric motor. The rotating electric machine <NUM> includes a shaft <NUM> that is rotatably supported, a rotor <NUM> fixed to the shaft <NUM>, a stator <NUM> surrounding the rotor <NUM>, and a rotating electric machine casing <NUM> accommodating the shaft <NUM>, the rotor <NUM>, and the stator <NUM>.

The rotor <NUM> is disposed on an axis AX of the rotating electric machine <NUM>. Although not shown in detail, the rotor <NUM> includes a rotor core made of laminated steel plates, for example, and magnets fixed to the rotor core. The shaft <NUM> and the rotor <NUM> rotate integrally. The rotor <NUM> is rotatably supported by bearings <NUM> and <NUM> disposed at one end and another end of the rotating electric machine casing <NUM>, respectively.

The stator <NUM> is formed in a hollow cylindrical shape, and is fixed to the inner circumferential surface of the rotating electric machine casing <NUM>. Although not shown in detail, the stator <NUM> includes a stator core and coils retained by the stator core. Electric power is supplied from a battery (not shown) to the stator <NUM>, a current flows through the coils, and a magnetic field is generated, whereby the rotor <NUM> and the shaft <NUM> are rotationally driven.

The rotating electric machine casing <NUM> has a cylindrical circumferential wall portion <NUM> surrounding the stator <NUM>, a ceiling portion <NUM> constituting one end portion (upper end portion) of the rotating electric machine casing <NUM>, and a bottom wall portion <NUM> constituting another end portion (lower end portion) of the rotating electric machine casing <NUM>. The circumferential wall portion <NUM> has a circumferential wall body <NUM> in which a spiral groove <NUM> is formed on an outer circumferential surface thereof, and a cylindrical cover <NUM> surrounding the circumferential wall body <NUM>.

The rotating electric machine <NUM> is provided with a first cooling passage <NUM> of the cooling structure <NUM>. The first cooling passage <NUM> cools the rotating electric machine <NUM>. A coolant is supplied to the first cooling passage <NUM>. The coolant is, for example, a liquid coolant. The liquid coolant is, for example, water or antifreeze liquid.

The first cooling passage <NUM> has an inlet passage <NUM>, a spiral passage <NUM>, and a discharge passage <NUM>. The inlet passage <NUM> introduces the coolant into the rotating electric machine casing <NUM>. The inlet passage <NUM> is provided in a lower portion of the rotating electric machine casing <NUM> in a use state in which the axis AX of the rotating electric machine <NUM> is directed in the vertical direction. In the present embodiment, the inlet passage <NUM> is formed in an inlet port <NUM> provided in the lower portion of the cylindrical cover <NUM>. A supply line <NUM> of a coolant circulation device <NUM> is connected to the inlet port <NUM>.

As shown in <FIG>, the spiral passage <NUM> extends spirally, with the axis AX of the rotating electric machine <NUM> as the center, in the circumferential wall portion <NUM> of the rotating electric machine casing <NUM> on the downstream side of the inlet passage <NUM>.

As shown in <FIG>, in the present embodiment, the spiral passage <NUM> is formed between the circumferential wall body <NUM> and the cylindrical cover <NUM>. A lower end of the spiral passage <NUM> is an upstream end of the spiral passage <NUM>. An upper end of the spiral passage <NUM> is a downstream end of the spiral passage <NUM>.

The discharge passage <NUM> discharges the coolant that has passed through the spiral passage <NUM> from the rotating electric machine casing <NUM>. The discharge passage <NUM> penetrates an end wall portion (ceiling portion <NUM>) constituting one end portion of the rotating electric machine casing <NUM> in a use state in the axial direction of the rotating electric machine <NUM>.

The transmission <NUM> is fixed to one end portion (ceiling portion <NUM>) of the rotating electric machine <NUM>. In the present embodiment, the transmission <NUM> is configured as a planetary gear unit. In the present embodiment, the transmission <NUM> is disposed coaxially with the rotating electric machine <NUM>. The transmission <NUM> includes a sun gear <NUM> fixed to one end (upper end) of the shaft <NUM> of the rotating electric machine <NUM>, and a plurality of planetary gears <NUM> meshing with the sun gear <NUM>.

The transmission <NUM> further includes a carrier <NUM> for supporting a plurality of planetary gears <NUM>, an output shaft <NUM> fixed to the carrier <NUM>, and an internal gear <NUM> meshing with the plurality of planetary gears <NUM>. The output shaft <NUM> is disposed coaxially with the shaft <NUM>. A load (for example, the propeller <NUM> shown in <FIG>) is coupled to the output shaft <NUM>. The transmission <NUM> further includes a transmission casing <NUM> which accommodates the sun gear <NUM>, the planetary gear <NUM>, the carrier <NUM>, the output shaft <NUM> and the internal gear <NUM>. The internal gear <NUM> is formed on an inner circumferential surface of the transmission casing <NUM>. The configuration of the transmission <NUM> is not limited to the planetary gear unit, and other transmission mechanisms may be used.

Lubricating oil circulates inside the transmission <NUM>. The transmission <NUM> has an oil reservoir portion <NUM> for storing the lubricating oil. The oil reservoir portion <NUM> is provided in a lower portion of the transmission casing <NUM>. The oil reservoir portion <NUM> is formed in an annular shape centered about the axis AX of the rotating electric machine <NUM>. Although details are not shown, a lubricating oil circulation mechanism is provided inside the transmission casing <NUM> to recover lubricating oil from the oil reservoir portion <NUM> and to inject (spray) the lubricating oil from above a gear train (sun gear <NUM>, planetary gear <NUM> and internal gear <NUM>). A pump for recovering the lubricating oil from the oil reservoir portion <NUM> may be, for example, a cam-type pump mechanically interlocked with the rotation of the shaft <NUM>.

The cooling structure <NUM> further includes a second cooling passage <NUM> for cooling the transmission <NUM>. The first cooling passage <NUM> and the second cooling passage <NUM> communicate with each other, and a common coolant flows through the first cooling passage <NUM> and the second cooling passage <NUM>. The first cooling passage <NUM> and the second cooling passage <NUM> are arranged in series. In the present embodiment, the first cooling passage <NUM> is disposed upstream of the second cooling passage <NUM>. Specifically, the second cooling passage <NUM> is formed by a gap provided between the rotating electric machine casing <NUM> and the transmission casing <NUM>.

The second cooling passage <NUM> is formed so as to surround the axis AX of the rotating electric machine <NUM>. The second cooling passage <NUM> is formed along the oil reservoir portion <NUM>. A groove <NUM> surrounding the axis AX is formed in an upper surface of the ceiling portion <NUM> of the rotating electric machine casing <NUM>. The groove <NUM> and a lower surface of the transmission casing <NUM> form the second cooling passage <NUM>. The lower surface of a bottom wall <NUM> of the oil reservoir portion <NUM> is a part of the lower surface of the transmission casing <NUM>. Therefore, the second cooling passage <NUM> is formed by the lower surface of the bottom wall <NUM> of the oil reservoir portion <NUM> and the groove <NUM>. As shown in <FIG>, the second cooling passage <NUM> (groove <NUM>) extends in a C-shape so as to surround the axis AX of the rotating electric machine <NUM>. It should be noted that the shape of the second cooling passage <NUM> (groove <NUM>) is not limited to the C-shape (arc shape) as long as it follows the oil reservoir portion <NUM>. When viewed from the axial direction of the rotating electric machine <NUM>, the second cooling passage <NUM> (groove <NUM>) may have a polygonal shape surrounding the axis AX or may have a wave shape extending so as to surround the axis AX.

As shown in <FIG>, the drive unit <NUM> further includes an inner seal member <NUM> and an outer seal member <NUM> disposed between the rotating electric machine <NUM> and the transmission <NUM>. The inner seal member <NUM> is disposed inside the second cooling passage <NUM> extending in an arc shape (C-shape) and between the rotating electric machine <NUM> and the transmission <NUM>. The outer seal member <NUM> is disposed outside the second cooling passage <NUM> and between the rotating electric machine <NUM> and the transmission <NUM>. The inner seal member <NUM> and the outer seal member <NUM> are sandwiched and held between the rotating electric machine casing <NUM> and the transmission casing <NUM>. The inner seal member <NUM> and the outer seal member <NUM> are disposed concentrically with respect to the axis AX.

As shown in <FIG>, the transmission casing <NUM> has a communication passage <NUM> that connects the first cooling passage <NUM> and the second cooling passage <NUM>. An upstream end of the communication passage <NUM> is connected to the downstream end (discharge passage <NUM>) of the first cooling passage <NUM> on a radially-outward side of the outer seal member <NUM>. A downstream end of the communication passage <NUM> is connected to the second cooling passage <NUM> between the inner seal member <NUM> and the outer seal member <NUM> (see <FIG>). The downstream end of the communication passage <NUM> is connected to an upstream end of the second cooling passage <NUM>. The communication passage <NUM> is formed in an L-shape (a V-shape with the top facing upward).

An annular joint member <NUM> is disposed straddling the downstream end of the first cooling passage <NUM> and the upstream end of the communication passage <NUM>. The joint member <NUM> is liquid-tightly fitted to the rotating electric machine casing <NUM> via a seal member <NUM> and is liquid-tightly fitted to the transmission casing <NUM> via a seal member <NUM>. A hollow portion of the joint member <NUM> communicates with the first cooling passage <NUM> and the communication passage <NUM>.

As shown in <FIG>, the transmission casing <NUM> further includes an outlet passage <NUM> for discharging the coolant that has passed through the second cooling passage <NUM> from the transmission casing <NUM>. An upstream end of the outlet passage <NUM> is connected to a downstream end of the second cooling passage <NUM>. The outlet passage <NUM> opens at an outlet port <NUM> provided in the transmission casing <NUM>.

As shown in <FIG>, the outlet passage <NUM> and the communication passage <NUM> form a multi-level crossing. Specifically, the outlet passage <NUM> extends above the communication passage <NUM>.

As shown in <FIG>, a recovery line <NUM> of the coolant circulation device <NUM> is connected to the outlet port <NUM>. The coolant is introduced into a supply unit <NUM> of the coolant circulation device <NUM> via the recovery line <NUM>. Although not shown in detail, the supply unit <NUM> includes, for example, a heat exchanger for cooling the coolant and a pump for supplying the coolant to the first cooling passage <NUM> of the cooling structure <NUM>.

The supply unit <NUM> of the coolant circulation device <NUM> supplies the coolant to the first cooling passage <NUM> through the supply line <NUM>. The coolant is discharged from the rotating electric machine casing <NUM> after sequentially flowing through the inlet passage <NUM>, the spiral passage <NUM>, and the discharge passage <NUM> of the first cooling passage <NUM>. While the coolant flows through the spiral passage <NUM>, the rotating electric machine casing <NUM> is cooled by the coolant.

As shown in <FIG>, the coolant flows from the discharge passage <NUM> of the first cooling passage <NUM> to the communication passage <NUM> and then flows into the second cooling passage <NUM> via the communication passage <NUM>. As shown in <FIG>, the coolant flows along the C-shaped second cooling passage <NUM>. When the coolant flows through the second cooling passage <NUM>, the transmission casing <NUM> is cooled by the coolant. As shown in <FIG>, the coolant is discharged from the second cooling passage <NUM> through the outlet passage <NUM> to the outside of the transmission casing <NUM>. As shown in <FIG>, the coolant discharged from the transmission casing <NUM> is returned to the supply unit <NUM> via the recovery line <NUM> of the coolant circulation device <NUM>.

As shown in <FIG>, the drive unit <NUM> can be applied to a propeller device <NUM>. The drive unit <NUM> is not limited to a power source for the propeller device <NUM>, but can be used as a power source for other devices. The propeller device <NUM> is provided with the drive unit <NUM>, an accommodation member <NUM> for housing the drive unit <NUM>, and the propeller <NUM> connected to the transmission <NUM> of the drive unit <NUM>.

The propeller device <NUM> is used for a vertical take-off and landing aircraft, for example. Therefore, the rotating electric machine <NUM> is disposed such that the axis AX of the rotating electric machine <NUM> is directed in the vertical direction when the propeller device <NUM> is in use. The propeller device <NUM> may adopt a configuration in which the axis AX of the rotating electric machine <NUM> is directed substantially in the horizontal direction when the propeller device <NUM> is in use.

A fan <NUM> for generating an air flow in the accommodation member <NUM> is attached to a lower end of the shaft <NUM> of the rotating electric machine <NUM>, and blows air to a heat exchanger (not shown) of the supply unit <NUM>, for example. The propeller <NUM> has a propeller shaft <NUM> connected to an output shaft <NUM> of the transmission <NUM>, a hub <NUM> provided in an upper end of the propeller shaft <NUM>, and a plurality of blades <NUM> projecting radially outward from the hub <NUM>. It should be noted that the present invention can be applied to an aircraft, a ship, a vehicle such as a two-wheeled or four-wheeled vehicle, or the like by arranging the rotation axis of the output shaft <NUM> of the transmission <NUM> of the drive unit <NUM> to be directed in the horizontal direction.

According to the present embodiment, the following effects are obtained.

The cooling structure <NUM> of the drive unit <NUM> includes the first cooling passage <NUM> configured to cool the rotating electric machine <NUM> and the second cooling passage <NUM> configured to cool the transmission <NUM>. The first cooling passage <NUM> and the second cooling passage <NUM> are in communication with each other. Since the common coolant flows through the first cooling passage <NUM> and the second cooling passage <NUM>, the cooling structure <NUM> of the drive unit <NUM> can be simplified.

The first cooling passage <NUM> is disposed on an upstream side of the second cooling passage <NUM>. In the drive unit <NUM>, since the temperature of the rotating electric machine <NUM> tends to be higher than that of the transmission <NUM>, the rotating electric machine <NUM> can be effectively cooled by disposing the first cooling passage <NUM> on the upstream side of the second cooling passage <NUM>.

Since the second cooling passage <NUM> is formed by a gap provided between the rotating electric machine casing <NUM> and the transmission casing <NUM>, the second cooling passage <NUM> can be realized with a simple structure.

Since the second cooling passage <NUM> extends in the circumferential direction of the rotating electric machine <NUM> so as to surround the axis AX of the rotating electric machine <NUM>, the transmission <NUM> can be efficiently cooled.

The annular inner seal member <NUM> and the annular outer seal member <NUM> are disposed between the rotating electric machine <NUM> and the transmission <NUM>. The inner seal member <NUM> is disposed inside the second cooling passage <NUM> extending in an arc shape, and the outer seal member <NUM> is disposed outside the second cooling passage <NUM>. Since the inner seal member <NUM> and the outer seal member <NUM> are provided, it is possible to simplify the sealing structure for preventing leakage of the coolant from the second cooling passage <NUM>.

As shown in <FIG>, the transmission casing <NUM> includes the communication passage <NUM> connecting the first cooling passage <NUM> and the second cooling passage <NUM>. The upstream end of the communication passage <NUM> is connected to the first cooling passage <NUM> on the radially-outward side relative to the outer seal member <NUM>. As shown in <FIG>, the downstream end of the communication passage <NUM> is connected to the second cooling passage <NUM> between the inner seal member <NUM> and the outer seal member <NUM>. In accordance with this configuration, the first cooling passage <NUM> and the second cooling passage <NUM> can be connected via the communication passage <NUM> without adopting a complicated sealing structure.

As shown in <FIG>, since the lubricating oil is cooled by the second cooling passage <NUM> formed along the oil reservoir portion <NUM> of the transmission <NUM>, the entire interior of the transmission <NUM> can be efficiently cooled by the lubricating oil circulating in the transmission <NUM>.

The first cooling passage <NUM> includes the spiral passage <NUM> extending spirally, with the axis AX of the rotating electric machine <NUM> as the center, in the circumferential wall portion <NUM> of the rotating electric machine casing <NUM>, and the discharge passage <NUM> configured to discharge the coolant having passed through the spiral passage <NUM> from the rotating electric machine casing <NUM>. The discharge passage <NUM> penetrates in the axial direction of the rotating electric machine casing <NUM>, the end wall portion constituting one end portion of the rotating electric machine casing <NUM> in the axial direction. In accordance with this configuration, the length of the discharge passage <NUM> can be shortened.

As shown in <FIG>, the second cooling passage <NUM> extends in a C-shape so as to surround the axis AX of the rotating electric machine <NUM>. The transmission casing <NUM> includes the communication passage <NUM> and the outlet passage <NUM>, and the communication passage <NUM> and the outlet passage <NUM> form a multi-level crossing. In accordance with this configuration, it is possible to increase the passage length of the C-shaped second cooling passage <NUM> and improve the cooling performance for the transmission <NUM>.

Claim 1:
A drive unit (<NUM>) comprising:
a rotating electric machine (<NUM>) including a rotating electric machine casing (<NUM>);
a transmission (<NUM>) including a transmission casing (<NUM>) and integrated with the rotating electric machine; and
a cooling structure (<NUM>) configured to cool the rotating electric machine and the transmission,
wherein the cooling structure includes a first cooling passage (<NUM>) configured to cool the rotating electric machine and a second cooling passage (<NUM>) configured to cool the transmission, and
the first cooling passage and the second cooling passage are in communication with each other, and a common coolant flows through the first cooling passage and the second cooling passage,
the second cooling passage is formed by a gap provided between the rotating electric machine casing and the transmission casing and extends in a C-shape in a circumferential direction of the rotating electric machine so as to surround an axis (AX) of the rotating electric machine,
the drive unit further comprises:
an inner seal member (<NUM>) having an annular shape and disposed inside the second cooling passage, between the rotating electric machine and the transmission; and
an outer seal member (<NUM>) having an annular shape and disposed outside the second cooling passage, between the rotating electric machine and the transmission,
the transmission casing includes a communication passage (<NUM>) connecting the first cooling passage and the second cooling passage,
an upstream end of the communication passage is connected to the first cooling passage on a radially-outward side relative to the outer seal member, and
a downstream end of the communication passage is connected to the second cooling passage between the inner seal member and the outer seal member.