Motor unit

A motor unit includes a bearing rotatably holding a shaft, and a housing accommodating a rotor, a stator, and the bearing. The housing has an opening, a cover closing the opening and fixed to the housing, and an annular member that has an annular shape when viewed from the axial direction and is provided independently from the bearing. The cover includes an accommodation portion accommodating the annular member, one or more ribs disposed radially outward of the accommodation portion when viewed from the axial direction, and one or more fixing points fixed to the housing. The one or more ribs extend outward from the accommodation portion. When viewed from the axial direction, for at least one of the ribs, the fixing point is formed on an extension line extending outward from the rib in a direction in which the rib extends.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present invention claims priority under 35 U.S.C. § 119 to Japanese Patent Application No. 2021-027971 filed on Feb. 24, 2021, the entire content of which is incorporated herein by reference.

FIELD OF THE INVENTION

The present invention relates to a motor unit.

BACKGROUND

Conventionally, a rotating machine having a casing accommodating a rotating shaft and an end plate provided on one end of the casing in the axial direction is known.

Here, when the annular member is accommodated in the end plate, vibration is transmitted from the casing to the annular member via the end plate, and the annular member may vibrate relative to the end plate. In this case, there is a risk of noise.

SUMMARY

An exemplary motor unit of the present invention includes a rotor that includes a shaft rotatable around a rotation axis, a stator, a bearing that rotatably holds the shaft, and a housing that accommodates the rotor, the stator, the bearing and has an opening on an axial one side, a cover that closes the opening and is fixed to the housing, and an annular member that has an annular shape when viewed from an axial direction and is provided independently from the bearing.

The cover includes an accommodation portion that protrudes from an axial one side outer face to the axial one side, is recessed from an axial other side outer face to the axial one side, and accommodates the annular member, one or more ribs that protrude from the axial one side outer face of the cover to the axial one side, and are disposed radially outward of the accommodation portion when viewed from the axial direction, and one or more fixing points fixed to the housing.

The one or more ribs extend outward from the accommodation portion. When viewed from the axial direction, for at least one of the ribs, the fixing point is formed on an extension line extending outward from the at least one rib in a direction in which the at least one rib extends.

DETAILED DESCRIPTION

In the present specification, a direction parallel to a rotation axis J2of a rotor21of a motor2is referred to as an “axial direction” of a motor unit1. The axial one side X1and the axial other side X2are defined as shown in the drawings. Additionally, the radial direction orthogonal to the rotation axis J2is simply referred to as “radial direction”, and the circumferential direction around the rotation axis J2is simply referred to as “circumferential direction”.

The motor unit1according to the exemplary embodiment of the present invention will be described below with reference to the drawings.FIG.1is a schematic diagram of the motor unit1according to an embodiment.FIG.2is a partially exploded perspective view including a shaft22. Note thatFIG.1is merely the conceptual diagram, and a layout and a dimension of each unit are not necessarily identical to a layout and a dimension of each unit of the actual motor unit1.

The motor unit1is mounted on a vehicle such as a hybrid vehicle (HV), a plug-in hybrid vehicle (PHV), and an electric vehicle (EV) in which at least the motor is used as a power source. The motor unit1is used as the power source of the vehicle.

As illustrated inFIG.1, the motor unit1has the motor2, a housing5, and a ring brush6. The housing5accommodates the motor2. Additionally, the motor unit1further has a gear unit3connected to the axial other side T of the shaft22and accommodated in the housing5.

The motor2is a DC brushless motor. The motor2is driven by electric power from an inverter (not shown). The motor2includes the rotor21that rotates around the rotation axis J2extending in the horizontal direction, and a stator25located radially outward of the rotor21. That is, the motor unit1has the stator25. That is, the motor2is an inner rotor type motor in which the rotor21is rotatably disposed inward of the stator25.

An electric power is supplied to the stator25, and thus, the rotor21rotates. The rotor21includes a shaft22, a rotor core23, and a rotor magnet24. The rotor21rotates around the rotation axis J2extending in the horizontal direction.

The shaft22extends around the rotation axis J2extending horizontally and in the vehicle width direction. The shaft22rotates around the rotation axis J2. That is, the motor unit1has the rotor21including the shaft22that is rotatable around the rotation axis J2.

In the motor unit1of the present embodiment, a lubricating oil CL as a coolant to be described later flows through a hollow portion221of the shaft22. For this reason, the shaft22has therein the hollow portion221penetrating along the rotation axis J2, and has an inlet220through which the lubricating oil CL flows into the hollow portion221to the axial other side.

The shaft22is rotatably supported by the housing5through a first bearing41, a second bearing42, a third bearing43, and a fourth bearing44to be described later. That is, the bearings41,42,43, and44are fixed to the housing5to rotatably support the shaft22.

Note that the shaft22can be divided into a portion in a motor accommodation space501and a portion in a gear unit accommodation space502. When the shaft22is dividable, the divided shafts22can adopt a screw coupling using a male screw and a female screw, for example. Alternatively, the divided shafts22may be joined by a fixing method such as press fitting or welding. When the fixing method such as press-fitting or welding is used, serrations combining recesses and protrusions extending in the axial direction may be used. With such a configuration, it is possible to reliably transmit the rotation. Additionally, the shaft22may be formed as a single member.

The rotor core23is formed by laminating thin electromagnetic steel plates. The rotor core23is a columnar body extending along the axial direction. A plurality of rotor magnets24is fixed to the rotor core23. The plurality of rotor magnets24is disposed along the circumferential direction with magnetic poles disposed alternately.

The stator25includes a stator core26, a coil27, and an insulator (not illustrated) interposed between the stator core26and the coil27. The stator25is held by the housing5. The stator core26has a plurality of magnetic pole teeth (not shown) extending radially inward from an inner circumferential face of an annular yoke.

The coil27is formed by winding an electric wire around the magnetic pole teeth. The coil27is connected to an inverter unit (not shown) through a bus bar (not shown). The coil27includes a coil end protruding from the axial end face of the stator core26. The coil end protrudes in the axial direction relative to the end portion of the rotor core23of the rotor21.

A resolver28is attached to the axial one side end portion of the shaft22. The resolver28detects the position of the rotor21, that is, the rotation angle. As illustrated inFIG.2, the resolver28has a resolver stator281and a resolver rotor282. The resolver stator281is fixed to a later-described bearing holder52of the housing5. The resolver rotor282is fixed to the shaft22.

The resolver stator281has an annular shape, and the resolver rotor282has a disk shape. An inner circumferential face of the resolver stator281and an outer circumferential face of the resolver rotor282face each other in the radial direction. The resolver stator281periodically detects the position of the resolver rotor282when the rotor21rotates.

As a result, the resolver28acquires information on the position of the rotor21from the information on the position of the resolver rotor282.

Additionally, a bus bar (not shown) is disposed at the axial one side end portion inside the housing5. The bus bar connects an inverter unit (not illustrated) and the coil27and supplies an electric power to the coil27. Electric power is supplied to the coil27from the axial one side.

The gear unit3has a plurality of gears and is accommodated in the housing5. As described above, the gear unit3is connected to the shaft22at the axial other side. The gear unit3has a deceleration portion31and a differential portion32.

A deceleration portion31is connected to the shaft22. The deceleration portion31transmits the torque output from the motor2to the differential portion32. The deceleration portion31reduces the rotation speed of the motor2according to the reduction ratio and increases the torque output from the motor2according to the reduction ratio.

The deceleration portion31is a speed reducer of a parallel-axis gearing type, in which center axes of gears are disposed in parallel with each other. The deceleration portion31has a first gear311which is an intermediate drive gear, a second gear312which is an intermediate gear, a third gear313which is a final drive gear, and an intermediate shaft314.

The first gear311is disposed on an outer circumferential face of the shaft22. In the motor unit1of the present embodiment, the first gear311and the shaft22are formed of a single member. The first gear311rotates around the rotation axis J2together with the shaft22. The intermediate shaft314extends along an intermediate axis J4parallel to the rotation axis J2. Both end portions in the axial direction of the intermediate shaft314are rotatably supported by the housing5through bearings.

The second gear312and the third gear313are disposed on the intermediate shaft314. The second gear312meshes with the first gear311. The third gear313meshes with a ring gear321of the differential portion32. The torque of the shaft22is transmitted from the first gear311to the second gear312. Then, the torque transmitted to the second gear312is transmitted to the third gear313through the intermediate shaft314. The torque transmitted to the third gear313is transmitted to the ring gear321of the differential portion32. In this manner, the deceleration portion31transmits the torque output from the motor2to the differential portion32. The number of gears, the gear ratios of the gears, and so on can be modified in various manners according to the desired reduction ratio.

The differential portion32transmits the torque output from the motor2to an output shaft33. The output shaft33is attached to each of the left and right sides of the differential portion32. For example, the differential portion32has a function of transmitting the same torque to the left and right output shafts33while absorbing the difference in speed between the left and right drive wheels, that is, the output shafts33when the vehicle turns. The output shaft33protrudes to the outside of the housing5. A drive shaft (not shown) connected to a drive wheel of the vehicle is connected to the output shaft33.

In addition to these, the gear unit3may have a parking mechanism (not shown) that locks the vehicle when the operation of the motor unit1is stopped.

The housing5includes a housing body51, a bearing holder52, and a gear unit accommodation portion53. The housing body51, the bearing holder52, and the gear unit accommodation portion54are formed of, for example, a conductive material such as iron, aluminum, or an alloy thereof, in other words, metal, but are not limited thereto. Note that the housing body51, the bearing holder52, the gear unit accommodation portion54, and a cover8to be described later may be formed of the same material or may be formed of different materials. In order to suppress contact corrosion of dissimilar metals at the contact portion, it is preferable to form the parts with the same material.

The housing body51has a first tube portion511, a partition wall portion512, and a protrusion513. The first tube portion511is a tubular body extending in the axial direction. The stator core26is fixed inside the housing body51. Further, inside the first tube portion511, the axial one side part of the shaft22, the rotor core23, and the rotor magnet24are disposed. That is, the housing5accommodates the rotor21and the stator25. The first tube portion511has an opening on the axial one side.

The partition wall portion512expands radially inward from the axial other side end portion of the first tube portion511. The partition wall portion512is provided with a through hole514penetrating along the rotation axis J2. The through hole514has a circular cross section, and its center line overlaps with the rotation axis J2. Then, the shaft22penetrates the through hole514. The shaft22penetrating the through hole514is rotatably supported by the partition wall portion512through the second bearing42and the fourth bearing44. The motor unit1has bearings42,44that rotatably hold the shaft22. The second bearing42is disposed on the axial one side of the partition wall portion512, and the fourth bearing44is disposed on the axial other side of the partition wall portion512. As a result, since the shaft22is rotatably supported at an intermediate portion in the axial direction, deflection, warpage, and the like of the shaft22are curbed when the shaft22rotates. The housing5accommodates the bearings42,44.

The protrusion513has a flat plate shape and extends vertically downward from the axial other side of an outer circumferential face of the first tube portion511. In the motor unit1according to the present embodiment, the first tube portion511, the partition wall portion512, and the protrusion513are formed of a single member. The partition wall portion512and the protrusion513form a side plate portion510that closes the axial one side end portion of the gear unit accommodation portion54.

A first drive shaft passage hole515is formed in the protrusion513. The first drive shaft passage hole515is a hole axially penetrating the protrusion513. The output shaft33penetrates the first drive shaft passage hole515in a rotatable state. An oil seal (not shown) is provided between the output shaft33and the first drive shaft passage hole515to curb leakage of the lubricating oil CL. An axle (not shown) that rotates the wheel is connected to the tip end of the output shaft33.

The bearing holder52expands in the radial direction. The bearing holder52is fixed to the axial one side of the first tube portion511. While the bearing holder52can be fixed to the first tube portion511with a screw, for example, the method is not limited thereto, and a method of firmly fixing the bearing holder52to the first tube portion511, such as screwing or press-fitting, can be widely used.

As a result, the bearing holder52is electrically connected to the housing body51. Here, the term “two members are electrically connected” includes a case where the two members are physically in contact with each other and can be electrically conducted, and also includes a case where the two members are close to each other to an extent of being substantially at the same potential. That is, electrically connected members have the same or substantially same potential. Hereinafter, in a case where there is electrical connection, a similar configuration is assumed. In the motor unit1of the present embodiment, the housing body51and the bearing holder52have the same potential.

Additionally, the first tube portion511and the bearing holder52are in close contact with each other. Here, close contact means to have such a sealing property that the lubricating oil CL inside the housing5does not leak to the outside and that foreign matters such as external water, dust, and the like do not enter. Close contact refers to a similar configuration hereinafter.

The bearing holder52has an opening521recessed from the axial one side face of the bearing holder52to the axial other side. That is, the housing5has an opening on the axial one side. A through hole520penetrating in the axial direction is formed in a bottom face of the opening521. The center of the through hole520coincides with the rotation axis J2, and the shaft22penetrates the through hole520. The axial one side end portion of the shaft22is disposed inside the opening521.

The first bearing41is disposed on the axial other side of the bearing holder52. The housing5accommodates the bearing41. The shaft22penetrating the through hole520is rotatably supported by the bearing holder52through the first bearing41. The bearing41rotatably holds the shaft22.

The resolver stator281of the resolver28is fixed to the inside of the opening521. That is, the resolver stator281is fixed to the bearing holder52. When the resolver stator281is disposed in the bearing holder52, the center line thereof coincides with the rotation axis J2. Then, the resolver stator281is fixed to the bearing holder52by a screw (not shown). Note that the fixing of the resolver stator281to the bearing holder52is not limited to a screw, and a fixing method, such as press-fitting and bonding, that can firmly fix the resolver stator281to the bearing holder52can be widely used.

In the motor unit1, the shaft22penetrates the through hole514at the axial other side relative to the rotor core23, and penetrates the through hole520at the axial one side in relative to the rotor core23. Then, both sides of the shaft22across the rotor core23in the axial direction are rotatably supported by the housing5through the first bearing41and the second bearing42. At this time, the shaft22is rotatable about the rotation axis J2.

The cover8is attached to the axial one side of the bearing holder52. The cover8covers the axial one side of the opening521of the bearing holder52, and is in close contact with the bearing holder52. That is, the motor unit1has the cover8that closes the opening and is fixed to the housing5. Additionally, the bearing holder52and the cover8are electrically connected. For this reason, the cover8and the housing body51have the same potential.

The cover8has an accommodation portion80. The accommodation portion80protrudes from the axial one side outer face to the axial one side, and is recessed from the axial other side outer face to the axial one side. The accommodation portion80accommodates the ring brush6(annular member) to be described later. The detailed configuration of the cover8will be described later.

A region that is enclosed by covering the opening521of the bearing holder52with the cover8and fixing the cover8to the bearing holder52is an accommodation space55. In a state where the stator25of the motor2is accommodated in the first tube portion511, the bearing holder52is attached to the axial one side of the first tube portion511, and the cover8is attached to the axial one side of the bearing holder52. As a result, the axial one side end portion of the shaft22is accommodated in the accommodation space55. Then, a contacted portion61is formed at the axial one side end portion of the shaft22. That is, the housing5has the accommodation space55in which the contacted portion61of the shaft22is accommodated. Further, the accommodation space55is formed between the cover8and the bearing holder52.

The ring brush6and the resolver28are disposed side by side along the rotation axis J2in the accommodation space55. At this time, the ring brush6and the contacted portion61provided at the axial one side end portion of the shaft22face each other in the radial direction. Details of the ring brush6and the contacted portion61will be described later.

A cover member56(seeFIG.2) is attached to the axial one side end portion of the shaft22. The cover member56is disposed on the axial one side relative to the resolver rotor282. The cover member56covers the resolver rotor282from the axial one side. The cover member56is fixed between the resolver rotor282fixed to the shaft22and the contacted portion61, and covers part of the resolver rotor282from the axial one side. By covering part of the resolver rotor282with the cover member56, it is possible to curb intrusion of wear powder or the like of the ring brush6or the contacted portion61into the resolver28. As a result, the motor unit1can be driven stably for a long period of time.

The gear unit accommodation portion54has a recessed shape that is open to the axial one side. The gear unit accommodation portion54has a second tube portion541and a blockage unit542. The axial one side end portion of the second tube portion541is attached to the side plate portion510. The second tube portion541has a shape overlapping an outer edge portion of the side plate portion510in the axial direction. The second tube portion541is fixed to the side plate portion510while being in close contact with and in electrical contact with the side plate portion510.

The second tube portion541is fixed to the side plate portion510by screwing, for example, but the method is not limited thereto. For example, a fixing method capable of firmly fixing the second tube portion541to the side plate portion510, such as welding or press-fitting, can be widely used. An opening of the gear unit accommodation portion54is covered by the side plate portion510.

The second tube portion541and the blockage unit542are formed of a single member. The blockage unit542has a plate shape extending radially inward from the axial other side end portion of the second tube portion541. A space surrounded by the second tube portion541, the blockage unit542, and the side plate portion510is the gear unit accommodation space502. The axial other side end portion of the shaft22is rotatably supported by the blockage unit542through the third bearing43. The bearing43rotatably holds the shaft22. The housing5accommodates the bearing43.

A second drive shaft passage hole543is formed in the blockage unit542. The second drive shaft passage hole543is a hole axially penetrating the blockage unit542. The output shaft33penetrates the second drive shaft passage hole543in a rotatable state. An oil seal (not shown) is provided between the output shaft33and the second drive shaft passage hole543to curb leakage of the lubricating oil CL. An axle (not shown) that rotates the wheel is connected to the tip end of the output shaft33. Note that the output shaft33rotates about a differential axis J5.

The inside of the housing5is filled with the lubricating oil CL for lubricating gears and bearings of the gear unit3. In the motor unit1, the oil is also used for cooling the motor2. That is, the lubricating oil CL for lubricating the motor unit1is a coolant for cooling the motor.

As illustrated inFIG.1, the lubricating oil CL is stored in a lower region of the gear unit accommodation space502. That is, a coolant (lubricating oil CL) for cooling the stator25is stored inside the housing5. Part of the differential portion32is immersed in the lubricating oil CL stored in the lower region of the gear unit accommodation space502. The lubricating oil CL stored in the lower region of the gear unit accommodation space502is taken up by the operation of the differential portion32and diffused into the gear unit accommodation space502. The oil diffused into the gear unit accommodation space502is supplied to each gear disposed inside the gear unit accommodation space502and used for lubrication. Additionally, part of the lubricating oil CL diffused into the gear unit accommodation space502is also supplied to each bearing and used for lubrication.

As illustrated inFIG.1, an oil reserve tray57is disposed in an upper region of the gear unit accommodation space502. The oil reserve tray57opens upward. The taken lubricating oil CL moves upward in the gear unit accommodation space502and flows into the oil reserve tray57.

The lubricating oil CL accumulated in the oil reserve tray57flows into the hollow portion221of the shaft22from the inlet220of the shaft22at the axial other side end portion through an oil supply path (not shown). The lubricating oil CL in the hollow portion221of the shaft22flows to the axial one side. The lubricating oil CL having flowed through the hollow portion221is sprayed toward the stator25. As a result, the lubricating oil CL cools the stator25.

Since the shaft22has a tubular shape, even when the lubricating oil CL is caused to flow into the hollow portion221of the shaft22, the lubricating oil CL can be drawn from the inlet220by negative pressure generated by the airflow flowing out to the axial one side during rotation of the shaft22. As a result, the lubricating oil CL can be supplied to the entire motor2, and the motor2can be cooled stably. Hence, the motor2can be driven stably.

The motor unit1has a coolant circulation unit7that circulates the lubricating oil CL. The coolant circulation unit7includes a pipe portion71, a pump72, an oil cooler73, and a motor oil reservoir74.

The pipe portion71is a pipe formed in the housing5. The pipe portion71connects the pump12and the motor oil reservoir74disposed inside the first tube portion511, and supplies the lubricating oil CL to the motor oil reservoir74. The pump72sucks the lubricating oil CL stored in the lower region of the gear unit accommodation space502. The pump72is an electric pump, but is not limited thereto. For example, the motor unit1may be driven using part of the output of the output shaft33.

The oil cooler73is disposed between the pump72of the pipe portion71and the motor oil reservoir74. That is, the lubricating oil CL sucked by the pump72is sent to the motor oil reservoir74passing the oil cooler73and through the pipe portion71. For example, a refrigerant such as water supplied from the outside is supplied to the oil cooler73. Then, heat is exchanged between the refrigerant and the lubricating oil CL to lower the temperature of the lubricating oil CL. Note that while the oil cooler73used herein is a liquid-cooled type using a refrigerant, the oil cooler73is not limited thereto, and may be a so-called air-cooled type that cools with traveling air of the vehicle. By using the oil cooler73, the temperature of the lubricating oil CL supplied to the motor oil reservoir74can be lowered, and the cooling efficiency of the motor2can be enhanced.

The motor oil reservoir74is a tray disposed in the upper region of the motor accommodation space501and opened upward. More specifically, the motor oil reservoir74is disposed vertically above the stator25in the motor accommodation space501. A dropping hole is formed in a bottom portion of the motor oil reservoir74, and the motor2is cooled by dropping the lubricating oil CL from the dropping hole. The dropping hole is formed above the coil end271of the coil27of the stator25, for example, and the coil27is cooled by the lubricating oil CL.

The ring brush6is in contact with the contacted portion61formed at the axial one side end portion of the shaft22. The contacted portion61is made of a material having higher conductivity than a bearing contact portion222in contact with the inner ring of the bearing of the shaft22. That is, the conductivity of the contacted portion61is higher than the conductivity of the bearing contact portion222in contact with the bearing41of the shaft22. The contacted portion61is in contact with a brush portion63described later of the ring brush6.

By making the conductivity of the contacted portion61higher than that of the bearing contact portion222in contact with the bearing41of the shaft22, most of the axial current generated in the shaft22can flow to the ring brush6in contact with the contacted portion61. As a result, a potential difference between the inner ring and the outer ring of the bearing can be curbed, and electric corrosion of the bearing can be curbed effectively. Note that although the first bearing41is described, the potential difference between the inner ring and the outer ring is similarly curbed and electric corrosion is curbed in other bearings as well.

Note that the contacted portion61is a conductive film of silver, copper, or the like, and is formed by applying a metal paste, for example. Note that the contacted portion61may be formed by a film forming method such as plating or vapor deposition, in addition to coating. The electric corrosion of the bearing will be described later. Additionally, when electrically conducted sufficiently to the ring brush6, the contacted portion61may be part of the shaft22.

The motor unit1has an annular shape when viewed from the axial direction, and has the ring brush6(annular member) provided independently from the bearings41to44. The annular member (ring brush6) is a member different from the bearing. The ring brush6has a conductive ring62and the brush portion63. The conductive ring62has an annular shape and is made of a conductive material such as metal. That is, the annular member (ring brush6) has the conductive ring62that has an annular shape and has conductivity. The conductive ring62is disposed inside the accommodation portion80of the cover8. The conductive ring62is fixed to the accommodation portion80by press fitting. That is, the annular member (ring brush6) is fixed to the accommodation portion80by press fitting. As a result, no adhesive is required for fixing the annular member, and it is possible to reduce materials and eliminate the man-hours for managing the adhesive. However, the fixing method is not limited to this, and a method capable of firmly fixing the conductive ring62to the accommodation portion80, such as adhesion or welding, can be widely adopted.

The brush portion63is a material that has conductivity and can be bent in the circumferential direction. The brush portion63is fixed to an inner circumferential face of the conductive ring62and is electrically connected to the conductive ring62. That is, the ring brush6is electrically connected to the housing5via the cover8. The annular member (ring brush6) has the brush portion63that is fixed to the radial inner circumferential face of the conductive ring62and has conductivity and is bendable in the circumferential direction.

The brush portion63protrudes radially inward. The length from the inner circumferential face of the conductive ring62to the radially inward tip end of the brush portion63is longer than the radial distance between the conductive ring62and the contacted portion61. For this reason, the radially inward tip end of the brush portion63elastically bends and is in contact with the contacted portion61.

Since the contacted portion61is formed on the outer circumferential face of the shaft22, the radially inward tip end of the brush portion63continues to contact the contacted portion61even when the shaft22moves in the axial direction. That is, even when the shaft22moves in the axial direction, the conducting state between the shaft22and the housing5is maintained.

In the present embodiment, a wire member made of carbon fiber is used as the brush portion63, but the present invention is not limited thereto. A wire member made of a member that is elastically deformable and has conductivity can be widely used. Additionally, the brush portion is not limited to the wire member, and may have a film shape having a width in the rotation axis J2direction and a thickness in the circumferential direction.

As illustrated inFIG.1, the axial one side end portion of the shaft22is rotatably supported by the bearing holder52through the first bearing41. The shaft22penetrates the through hole520and protrudes to the axial one side. Then, the resolver rotor282of the resolver28is attached to the axial one side of the shaft22relative to the through hole520.

When the ring brush6is attached to the accommodation portion8of the cover8, the radially inward tip end of the brush portion63of the ring brush6is in contact with the contacted portion61of the outer circumferential face of the shaft22. That is, the outer circumferential face of the shaft22is in contact with the brush portion63. Since the brush portion63deforms elastically, the radially inward tip end of the brush portion63deforms along the contacted portion61and is in contact with the contacted portion61, so that the brush portion63and the contacted portion61are electrically connected. As a result, the shaft22and the ring brush6are electrically connected.

Since the brush portion63is made of an elastically deformable material, the electrical connection between the shaft22and the ring brush6is maintained even when the shaft22rotates. For this reason, the shaft22and the housing5, that is, the inner ring attached to the shaft22and the outer ring attached to the housing5of each of the first bearing41to the fourth bearing44have the same potential, and electric corrosion of the bearing due to discharge generated based on the potential difference is curbed. As a result, variations in the rotation of the shaft22are suppressed, and the motor unit1can be driven stably for a long period of time. In other words, the life of the motor unit1can be prolonged.

Additionally, since the rotor21and the stator25of the motor2can be cooled stably with the lubricating oil CL, a decrease in output due to a temperature rise of the motor2can be curbed. That is, in the motor unit1, a decrease in output can be curbed over a long period of time.

As illustrated inFIG.1, the inner diameter of the axial one side end portion of the hollow portion221of the shaft22may be formed smaller than the inner diameter of the axial other side T. A step is formed at the axial one side of the hollow portion221. As a result, even when the shaft22is inclined so that the axial one side is lower than the axial other side, the flow of the lubricating oil CL is curbed by the step formed at the axial one side of the shaft22. As a result, it is possible to prevent the lubricating oil CL from entering into a space between the ring brush6and the contacted portion61from the axial one side of the shaft22to form an oil film, and to curb an increase in electric resistance between the housing5and the shaft22due to the oil film.

Next, the first embodiment of the cover8will be described. Hereinafter, for various embodiments of the cover8, an alphabet is added to “8” as a code for convenience.

FIG.3is a perspective view of a cover8A according to the first embodiment when viewed from the axial one side.FIG.4is a perspective view of the cover8A according to the first embodiment when viewed from the axial other side. The cover8A shown inFIGS.3and4is formed by die casting and is made of a material such as aluminum.

The cover8A has an accommodation portion80that protrudes from an axial one side outer face S1to the axial one side and is recessed from an axial other side outer face S2to the axial one side. The accommodation portion80is formed in a cylindrical shape in which the axial one side is closed around the rotation axis J2.

As shown inFIGS.3and4, the cover8has a plurality of ribs81. One rib81has a one side protrusion81A and an other side protrusion81B. The one side protrusion81A and the other side protrusion81B are disposed so as to face each other in the axial direction. The one side protrusion81A protrudes from the axial one side outer face S1of the cover8in the axial direction to the axial one side. The other side protrusion81B protrudes from the axial other side outer face S2of the cover8to the axial other side. In this way, since the one rib81is formed of the one side protrusion81A and the other side and the other side protrusion81B, the axial thickness of the rib81can be increased and the strength of the cover8can be improved. Further, since the cover8is formed by die casting, the one side protrusion81A and the other side and the other side protrusion81B can be formed. In this case, since the one side protrusion81A and the other side and the other side protrusion81B are each solid, the strength of the rib81can be improved.

The one side protrusion81A and the other side protrusion81B extend radially outward from the outer circumference of the accommodation portion80. That is, the rib81extends radially outward from the outer circumference of the accommodation portion80. In the cover8A shown inFIGS.3and4, the number of ribs81is eight as an example, but the number of ribs81may be plural other than eight or one. That is, the cover8A has one or more ribs81that protrude from the axial one side outer face S1of the cover8A to the axial one side and are disposed radially outward of the accommodation portion80when viewed from the axial direction. The plurality of ribs81extends radially from the accommodation portion80.

Cover8A has a plurality of fixing points82. The fixing points82are disposed along the outer edge of the cover8A. Here, the number of fixing points82is eight, which is the same as the number of ribs81. The number of fixing points82may be one when the number of ribs81is one. That is, the number of one or more ribs81is the same as the number of the one or more fixing points82.

In the cover8A, the fixing point82is a through hole through which a bolt penetrates in the axial direction. The cover8A is fixed to the bearing holder52by the bolt inserted into the fixing point82. That is, the cover8A has one or more fixing points82that are fixed to housing5.

A bolt accommodation portion821which is recessed to the axial other side and accommodates the head of the bolt is formed around the fixing point82(through hole). As a result, the axial position of the head of the bolt can be lowered, and the motor unit1can be miniaturized in the axial direction.

Further, the fixing point is not limited to a fixing point for bolting as described above, and may be a fixing point by welding, adhesion, crimping or the like, for example.

Here,FIG.5is a plan view of the cover8A as viewed from the axial one side. As shown inFIG.5, each rib81(one side protrusion81A) extends toward a fixing point82. More specifically, when viewed in the axial direction, a line segment extending from the rotation axis J2in the radial direction through the width center position of the rib81passes through the fixing point82. That is, the one or more ribs81extend outward from the accommodation portion80. For at least one of the ribs81, when viewed in the axial direction, the fixing point82is formed on an extension line extending outward from the rib81in the direction of in which the rib81extends.

Vibration is transmitted from the housing5to the fixing point82of the cover8A. When the rib81is not provided, the transmitted vibration is likely to be transmitted to the ring brush6accommodated in the accommodation portion80via the cover8A. As a result, the ring brush6vibrates relative to the cover8A, and noise is likely to be generated. On the other hand, in the present embodiment, since the ribs81are provided in the above-described manner, it is possible to suppress the transmission of vibration from the fixing point82to the ring brush6(annular member) and suppress noise. Further, since the rib81is formed of the one side protrusion81A and the other side protrusion81B, the transmission of vibration can be further suppressed.

Specifically, the ring brush6is used as an annular member accommodated in the accommodation portion80. Since the vibration transmitted from the cover8A to the conductive ring62is larger than the vibration transmitted from the shaft22to the brush portion63, it is effective to suppress the vibration transmission by the rib81.

Further, as described above, since the number of ribs81is the same as the number of fixing points82, it is easy to suppress vibration in a well-balanced manner with respect to each fixing point82, and vibration of the cover8A is effectively suppressed. The number of ribs81does not necessarily have to match the number of fixing points82.

Further, as shown inFIG.5, the rib81includes a first rib811and a second rib812. A distance from a connection portion CN, of the first rib811, with the accommodation portion80to the fixing point82is longer than a distance from the connection portion CN, of the second rib812, with the accommodation portion80to the fixing point82. The first rib811is longer than the second rib812. When the above distance is long, the vibration of the cover8A tends to be large, but the vibration can be suppressed by increasing the length of the rib81. The combination of the first rib811and the second rib812may be other than the combination of the ribs81shown inFIG.5.

Further, as shown inFIG.5, the radially inner ends81T of the ribs81adjacent to each other in the circumferential direction do not come into contact with each other. As a result, it is possible to prevent the radially inner ends of the ribs from coming into contact with each other and the contact portion from acting as a vibration source.

Further, as shown inFIG.6, an axial height H from the axial one side outer face S1of the rib81(one side protrusion81A) continuously decreases toward an outer side. As a result, it is possible to suppress the warp of the cover8A when it is formed by die casting.

Here,FIG.7is a perspective view showing a state in which the ring brush6is accommodated in the accommodation portion80of the cover8A.FIG.8is a cross-sectional perspective view in the state ofFIG.7. Note thatFIGS.7and8show a state in which the ring brush6is accommodated in the accommodation portion80by press fitting.

Further crimping is performed in the state ofFIGS.7and8. At this time, at a plurality of locations in the circumferential direction of an axial other side end face80S of the accommodation portion80, the axial other side end face80S is pushed to the axial one side by a punch. As a result, as shown in the schematic cross-sectional view inFIG.9, a recess801is formed by a punch on the axial other side end face80S, and a deformed portion W1protruding radially inward is formed at an axial other side end portion of an inner circumferential side wall face80W of the accommodation portion80. The deformed portion W1and the conductive ring62of the ring brush6come into contact with each other, and the conductive ring62is pushed radially inward. As a result, it is possible to prevent the ring brush6from coming off in the axial direction. Specifically, when the accommodation portion80is formed by die casting, the accommodation portion80is thicker in the radial direction, so that the crimping as described above is effective.

The press-fitted ring brush6may be disposed on the axial one side relative to the deformed portion W1. As a result, normally, the ring brush6does not come into contact with the deformed portion W1, but even when the ring brush6moves in the axial direction, it comes into contact with the deformed portion W1, so that the ring brush6is prevented from coming off in the axial direction.

That is, the annular member (ring brush6) can come into contact with the deformed portion W1due to crimping of the wall face80W extending in the circumferential direction of the accommodation portion80. As a result, it is possible to prevent the annular member from coming off in the axial direction.

Further, it is desirable that the recesses801by the punch are disposed at equal intervals in the circumferential direction. That is, the plurality of deformed portions W1is disposed at equal intervals in the circumferential direction. As a result, the removal of the annular member can be further suppressed.

Next, the second embodiment of the cover8will be described.FIG.10is a perspective view of the cover8B according to the second embodiment when viewed from the axial one side.FIG.11is a perspective view of the cover8B according to the second embodiment when viewed from the axial other side. The cover8B shown inFIGS.10and11is formed by press molding and is made of a material such as iron.

In the cover8B according to the second embodiment, as in the first embodiment described above, a plurality of ribs81extending outward from the accommodation portion80is provided. The accommodation portion80and the rib81are formed by press molding. The accommodation portion80protrudes from the axial one side outer face of the cover8B to the axial one side, and is recessed from the axial other side outer face of the cover8B to the axial one side. Since the cover8B is formed by press molding, it is easy to form a structure in which the plate thickness of the cover8B including the rib81is almost constant. That is, the cover8B is formed by deforming one plate. As a result, the material of the cover8B can be reduced, and the cost can be reduced.

Here,FIG.12is a plan view of the cover8B as viewed from the axial one side. Each of the ribs813A to813C shown inFIG.12is one of the ribs81. As shown inFIG.12, for the rib813A, when viewed in the axial direction, a line segment Lc extending from the rotation axis J2in the radial direction through the width center position of the rib813A passes through the fixing point82, but for ribs81other than this rib, a similar line segment does not pass through the fixing point82. However, as shown inFIG.12, for ribs813B and813C, when viewed in the axial direction, extension lines L1and L2extending outward from the ribs813B and813C in a direction in which each of the ribs813B and813C extends (direction parallel to the radial direction) pass through the fixing point82. That is, for the ribs813A and813C, when viewed from the axial direction, the fixing points82are formed on the extension lines extending outward from the ribs813A to813C in the direction in which each of the ribs813A to813C extends. With such ribs813A to813C, it is possible to suppress the transmission of vibration from the fixing point82to the ring brush6.

Here,FIG.13is a perspective view showing a state in which the ring brush6is accommodated in the accommodation portion80of the cover8B.FIG.14is a cross-sectional perspective view in the state ofFIG.13. Note thatFIGS.13and14show a state in which the ring brush6is accommodated in the accommodation portion80by press fitting and a state in which the accommodation portion80is subjected to the crimping described later.

As shown inFIG.13, a plurality of deformed portions802due to crimping is disposed at equal intervals in the circumferential direction at the axial other side end portion of the accommodation portion80. As shown inFIG.14, the deformed portion802is formed by bending radially inward part of the axial other side end portion of the wall portion800W, included in the accommodation portion80, extending in the circumferential direction. The radially inward face of the deformed portion802is in contact with the conductive ring62of the ring brush6. As a result, the ring brush6is suppressed from coming off in the axial direction. Since the cover8B is formed by press molding, the radial thickness of the wall portion800W is thin, and it is easy to bend the wall portion800W.

The ring brush6may be disposed on the axial one side relative to the deformed portion802. In this case, normally, the ring brush6does not come into contact with the deformed portion802, but even when the ring brush6moves in the axial direction, the conductive ring62is in contact with the deformed portion802to prevent the ring brush6from coming off.

That is, the deformed portion802is provided at the axial other side end portion of the annular wall portion800W included in the accommodation portion80, and is bent radially inward. As a result, when the cover8is formed by press molding, the deformed portion802can be easily formed.

Next, the third embodiment of the cover8will be described.FIG.15is a perspective view of a cover8C according to the third embodiment when viewed from the axial one side.FIG.16is a perspective view of the cover8C according to the third embodiment when viewed from the axial other side. The cover8C shown inFIGS.15and16is formed by press molding as in the second embodiment.

Here,FIG.17is a plan view of the cover8C when viewed from the axial one side. Each of the ribs814A to814F shown inFIG.17is one of the ribs81. As shown inFIG.17, for the ribs814A to814C, when viewed in the axial direction, the line segment Lc extending from the rotation axis J2in the radial direction through the width center position of each of the ribs814A to814C passes through the fixing point82, but for ribs81other than these ribs, a similar line segment does not pass through the fixing point82. However, as shown inFIG.17, for ribs814D to814F, when viewed in the axial direction, extension lines L3to L5extending outward from the ribs814D to814F in a direction in which each of the ribs814D to814F extends (direction parallel to the radial direction) pass through the fixing point82. That is, for the ribs814A to814F, when viewed from the axial direction, the fixing points82are formed on the extension lines extending outward from the ribs814A to814F in the direction in which each of the ribs814A to814F extends. With such ribs814A to814F, it is possible to suppress the transmission of vibration from the fixing point82to the ring brush6.

Further, as shown inFIG.17, the width w of each of the ribs81at the same radial position is the same from the radial inner end to the radial outer end of each of all the plurality of ribs81. As a result, the transmission of vibration can be suppressed in a well-balanced manner in the circumferential direction.

Further, as shown inFIG.17, the width w of the rib81continuously decreases toward a radially outer side. As a result, when the cover8C is formed by press molding, it can be easily removed in the jig removal process.

Hereinafter, modifications of the first to third embodiments described above will be described.FIG.18is a schematic plan view of a cover8D according to the first modification when viewed from the axial one side.

As shown inFIG.18, each rib815A to815D bends and extends in the middle. For such ribs815A to815D, fixing points82are formed on extension lines L6to L9extending outward from the ribs815A to815D in the direction in which each of the ribs815A to815D extends when viewed from the axial direction. With such ribs815A to815D, it is possible to suppress the transmission of vibration from the fixing point82to the ring brush6accommodated in the accommodation portion80.

FIG.19is a schematic plan view of the cover8E according to the second modification when viewed from the axial one side.

As shown inFIG.19, the direction in which each rib816A to816D extends deviates from the radial direction. For such ribs816A to816D, the fixing point82is formed on the extension lines L10to L13extending outward from the ribs816A to816D in the direction in which each of the ribs816A to816D extends when viewed from the axial direction. With such ribs816A to816D, it is possible to suppress the transmission of vibration from the fixing point82to the ring brush6accommodated in the accommodation portion80.

FIG.20is a schematic plan view of the cover8F according to the third modification when viewed from the axial one side.

As shown inFIG.20, for all the ribs817A to817D, the center line passing through the width center position of each of the ribs does not pass through the fixing point82. However, also for such ribs817A to817D, the fixing point82is formed on the extension lines L14to L17extending outward from the ribs817A to817D in the direction in which each of the ribs817A to817D extends when viewed from the axial direction. With such ribs817A to817D, it is possible to suppress the transmission of vibration from the fixing point82to the ring brush6accommodated in the accommodation portion80.

The embodiments of the present invention are described above. Note that, the scope of the present invention is not limited to the above-described embodiments. The present invention can be implemented by making various modifications to the abovementioned embodiments without departing from the gist of the invention.

The present invention can be used, for example, as a drive motor for various vehicles.