Patent Description:
In <CIT>, a wheel drive device including a rotating body including a wheel, a fixed body that rotates relative to the rotating body, a seal member that is disposed between the rotating body and the fixed body and seals a sealing space containing a lubricant, and an oil receiving member that receives the lubricant that has leaked beyond the seal member is disclosed. In <CIT>, a planetary gear device including an internal gear, a planetary gear engaging with the internal gear, a sun gear positioned at a center of the internal gear and engaging with the planetary gear, a planetary carrier rotatably supporting the planetary gear in a state in which the planetary gear engages with the internal gear and the sun gear, a bearing inner cylinder comprising the internal gear on an inner circumferential surface, a bearing coaxially fitting in an outer circumference of the bearing inner cylinder, an output shaft outer cylinder coaxially fitting in an outer circumference of the bearing, and an output shaft end plate that fixes the planetary carrier and that is supported by the output shaft outer cylinder is disclosed.

The inventors of the present application have found a new idea for reducing axial dimensions of the entire wheel drive device while increasing a storage volume of the lubricant by the oil receiving member.

One of objects of the present invention is to provide a technique capable of reducing the axial dimensions of the entire wheel drive device while increasing the storage volume of the lubricant by the oil receiving member.

The aforementioned object is achieved by wheel devices according to the independent claims.

A first form of the present invention is disclosed in the independent claim <NUM>.

A second form of the present invention is disclosed in the independent claim <NUM>.

Particular embodiments of the present invention are disclosed in the appended dependent claims.

It is noted that, due to the nature of a "relative rotation", it is equivalent to say that the rotating body rotates relative to the fixed body or that the fixed body rotates relative to the rotating body.

According to the present invention, it is possible to reduce the axial dimensions of the entire wheel drive device while increasing the storage volume of the lubricant by the oil receiving member.

Hereinafter, embodiments will be described. The same reference numerals are added to the same components, and duplicated description will be omitted. In each drawing, components are omitted, enlarged, or reduced as appropriate for convenience of explanation. The drawings shall be viewed according to the orientation of the reference numerals.

<FIG> is referred to. A wheel drive device <NUM> is attached to a vehicle body <NUM> such as a transport cart and is used to drive a wheel <NUM>. The transport cart is, for example, an automatic guided vehicle (AGV), an autonomous mobile robot (AMR), or the like. A use of the wheel drive device <NUM> of the present disclosure is not limited to the transport cart, and can be applied to various vehicles, such as a forklift and a self-propelled service robot.

The wheel drive device <NUM> includes a motor <NUM>, a speed reducer <NUM> to which input rotation is input from an output shaft 16a of the motor <NUM>, a wheel <NUM> to which output rotation is output from the speed reducer <NUM>, and an attachment member <NUM> that is disposed between the motor <NUM> and the speed reducer <NUM> and is attached to the vehicle body <NUM>. Hereinafter, a direction along a rotation center line CL1 of the wheel <NUM> is referred to as an axial direction, and a radial direction and a circumferential direction having the rotation center line as the center of a circle are simply referred to as a radial direction and a circumferential direction.

The motor <NUM> includes a tubular-shaped motor frame 16b and a pair of covers 16c and 16d that cover opening end portions of the motor frame 16b. The pair of covers 16c and 16d include a load-side cover 16c disposed on the speed reducer <NUM> side and a counter load-side cover 16d disposed on a side opposite to the speed reducer <NUM>.

The attachment member <NUM> forms an annular shape as a whole. The attachment member <NUM> includes an attachment portion 22a for attaching to the vehicle body <NUM>. The attachment portion 22a in the present embodiment protrudes outwardly in the radial direction from the motor <NUM>. The attachment member <NUM> is attached to the vehicle body <NUM> by being connected to an attached portion 12a by a bolt (not illustrated) in a state where the attachment portion 22a is abutted against the attached portion 12a provided on the vehicle body <NUM>. The attached portion 12a may be provided on a component 12b to be attached to the vehicle body <NUM>, or may be provided on the vehicle body <NUM> itself.

<FIG> is referred to. The speed reducer <NUM> includes an input shaft <NUM> to which input rotation is input from the output shaft 16a of the motor <NUM>, a reduction mechanism <NUM> that decelerates the input rotation transmitted from the input shaft <NUM> and that converts the input rotation into output rotation, a casing <NUM> that accommodates the reduction mechanism <NUM>, and carriers 30A and 30B disposed inside the casing <NUM> in the radial direction are provided. The input shaft <NUM> is connected to the output shaft 16a of the motor <NUM> using a joint member <NUM> such as a spline joint.

The speed reducer <NUM> in the present embodiment is an eccentric oscillation type speed reducer. The input shaft <NUM> of the speed reducer <NUM> is a crankshaft having at least one (here, two) eccentric body <NUM>. Eccentric phases of a plurality of eccentric bodies <NUM> are offset from each other. The input shaft <NUM> and the eccentric body <NUM> may be either separate or integral.

The reduction mechanism <NUM> of the eccentric oscillation type speed reducer includes an external gear <NUM> that oscillates by the eccentric body <NUM> and an internal gear <NUM> that meshes with the external gear <NUM>. The external gear <NUM> is individually provided corresponding to each of the plurality of eccentric bodies <NUM>, and is supported by the eccentric body <NUM> to be relatively rotatable through an eccentric body bearing <NUM>. The internal gear <NUM> in the present embodiment includes an internal gear main body 38a integrated with the casing <NUM>, and an outer pin 38b provided on an inner peripheral portion of the internal gear main body 38a and constituting internal teeth.

The carriers 30A and 30B are disposed on one side in the axial direction of the reduction mechanism <NUM>. The carriers 30A and 30B in the present embodiment include a first carrier 30A disposed on one side in the axial direction and a second carrier 30B disposed on the other side in the axial direction. The carriers 30A and 30B are connected through a connection member <NUM> such as a pin. The carriers 30A and 30B support the input shaft <NUM> through an input bearing <NUM>. A main bearing <NUM> is disposed between the casing <NUM> and the carriers 30A and 30B.

The speed reducer <NUM> described above includes an output member <NUM> to which output rotation is transmitted from the reduction mechanism <NUM> and outputting the output rotation, and a fixing member <NUM> that rotates relative to the output member <NUM> when the output member <NUM> rotates. The fixing member <NUM> is fixed to the vehicle body <NUM> through the attachment member <NUM>. The output member <NUM> in the present embodiment forms a tubular shape as a whole. The output member <NUM> in the present embodiment is the casing <NUM> and the fixing member <NUM> is the carriers 30A and 30B. Alternatively, the output member <NUM> may be either the carrier 30A or the carrier 30B, and the fixing member <NUM> may be the casing <NUM>.

The wheel <NUM> travels on a traveling surface by being rotated by the output rotation output from the output member <NUM>. For example, the traveling surface is a floor surface of a building, a rail, or the like. The wheel <NUM> includes a wheel member <NUM> that is connected to the output member <NUM> by using bolts or the like, and a ground contact member <NUM> that is attached to an outer peripheral portion of the wheel member <NUM>. The wheel member <NUM> forms a tubular shape as a whole. The ground contact member <NUM> contacts the traveling surface when the wheel <NUM> travels. The ground contact member <NUM> in the present embodiment is a tire. Specific examples of the ground contact member <NUM> are not particularly limited, and in addition, a roller for an omni wheel, a roller for a mecanum wheel, or the like may be used.

The attachment member <NUM> functions as an adapter that connects the motor <NUM> and the speed reducer <NUM>. The attachment member <NUM> is connected to a flange portion (not illustrated) provided on a load-side cover 16c of the motor <NUM> using a bolt (not illustrated). The attachment member <NUM> is connected to the fixing member <NUM> of the speed reducer <NUM> using a bolt B. The attachment member <NUM> is connected to the fixing member <NUM> in a state in which a side surface portion of the attachment member <NUM> is abutted against a side surface portion of the fixing member <NUM>. Accordingly, the attachment member <NUM> is attached to the vehicle body <NUM> in a state in which each of the motor <NUM> and the speed reducer <NUM> is supported. The attachment member <NUM> is provided with a through-hole 22b that penetrates in the axial direction, and the output shaft 16a of the motor <NUM> and the input shaft <NUM> of the speed reducer <NUM> are inserted through the through-hole 22b.

The attachment member <NUM> and the motor <NUM> include a motor-side spigot joint portion <NUM> in which a first inner peripheral spigot surface 56a and a first outer peripheral spigot surface 56b are spigot-fitted. In the present embodiment, the first inner peripheral spigot surface 56a is provided on the attachment member <NUM>, and the first outer peripheral spigot surface 56b is provided on the load-side cover 16c of the motor <NUM>, but the reverse is also possible. The attachment member <NUM> and the fixing member <NUM> of the speed reducer <NUM> include a speed reducer-side spigot joint portion <NUM> in which a second inner peripheral spigot surface 58a and a second outer peripheral spigot surface 58b are spigot-fitted. In the present embodiment, the second inner peripheral spigot surface 58a is provided on the fixing member <NUM> and the second outer peripheral spigot surface 58b is provided on the attachment member <NUM>, but the reverse is also possible.

An operation of the wheel drive device <NUM> described above will be described. In a case where the input rotation is input from the motor <NUM> to the input shaft <NUM> of the speed reducer <NUM>, the reduction mechanism <NUM> operates. In a case where the reduction mechanism <NUM> operates, the output rotation decelerated with respect to the input rotation from the reduction mechanism <NUM> is transmitted to the output member <NUM>. In a case where the output rotation is transmitted to the output member <NUM>, the wheel <NUM> rotates together with the output member <NUM>, and the wheel <NUM> travels on the traveling surface.

In a case where the eccentric oscillation type speed reducer <NUM> is used as in the present embodiment, in a case where the input shaft <NUM> (crankshaft) rotates, the eccentric body <NUM> causes the external gear <NUM> to oscillate so that the center of the external gear <NUM> rotates around a rotation center line CL1 of the output member <NUM>. In a case where the external gear <NUM> is oscillated, meshing positions of the external gear <NUM> and the internal gear <NUM> change in the circumferential direction. Accordingly, each time the input shaft <NUM> rotates once, one of the external gear <NUM> and the internal gear <NUM> (here, the internal gear <NUM>) rotates by a difference in the number of teeth between the external gear <NUM> and the internal gear <NUM>. The axial rotation component is transmitted to the output member <NUM> as output rotation.

The wheel drive device <NUM> described above includes a rotating body <NUM> including the wheel <NUM>, a fixed body <NUM> that rotates relative to the rotating body <NUM> when the rotating body <NUM> rotates, and a seal member <NUM> that is disposed between the rotating body <NUM> and the fixed body <NUM> and that seals a sealing space <NUM> containing a lubricant <NUM>. In the present embodiment, the rotating body <NUM> is the wheel <NUM> and the output member <NUM> (casing <NUM>), and the fixed body <NUM> is the fixing member <NUM> (carriers 30A and 30B) and the attachment member <NUM>.

The sealing space <NUM> is provided as an internal space of the wheel drive device <NUM>. In the sealing space <NUM> in the present embodiment, the reduction mechanism <NUM> of the speed reducer <NUM> is accommodated and is provided at least at a location surrounded by the casing <NUM> and carriers 30A and 30B. The sealing space <NUM> in the present embodiment is sealed by a seal cover <NUM> that closes a counter motor-side opening portion of the tubular-shaped casing <NUM> and an oil seal 16e that is disposed between the output shaft 16a of the motor <NUM> and the load-side cover 16c, in addition to the seal member <NUM>. The lubricant <NUM> is used for lubricating the reduction mechanism <NUM>. The lubricant <NUM> in the present embodiment is a lubricating oil, but may be grease or the like.

The seal member <NUM> in the present embodiment is disposed between the casing <NUM> which is a part of the rotating body <NUM> and the second carrier 30B which is a part of the fixed body <NUM>. The seal member <NUM> is a contact type seal such as a lip seal and an O-ring, and is a lip seal in this case. The seal member <NUM> is composed of an elastic body such as rubber.

<FIG> and <FIG> are referred to. The wheel drive device <NUM> includes an oil receiving member <NUM> that receives the lubricant <NUM> that has leaked beyond the seal member <NUM>. Leakage beyond the seal member <NUM> as used herein means that the lubricant <NUM> leaks outward from the sealing space <NUM> containing the lubricant <NUM> through the location where the seal member <NUM> is disposed.

The oil receiving member <NUM> is provided on the attachment member <NUM> which is a part of the fixed body <NUM>. The oil receiving member <NUM> in the present embodiment is integrally molded as a part of the same member as a mating member <NUM> (here, the attachment member <NUM>) to which the oil receiving member <NUM> is provided, but it may be provided separately from the mating member <NUM>.

The oil receiving member <NUM> in the present embodiment includes an axial wall portion 80a that extends in the axial direction from the mating member <NUM> in which the oil receiving member <NUM> is provided, and an outer wall portion 80b that protrudes inwardly in the radial direction from an outer end portion of the axial wall portion 80a. The oil receiving member <NUM> is provided to protrude in the axial direction from the mating member <NUM> as a whole.

At least a part of the oil receiving member <NUM> is disposed inside an axial recessed portion <NUM> formed in one of the rotating body <NUM> and the fixed body <NUM> (here, the rotating body <NUM>). Hereinafter, one of the rotating body <NUM> and the fixed body <NUM> in which the axial recessed portion <NUM> is formed is referred to as a recessed portion forming body <NUM>. The axial recessed portion <NUM> is formed outwardly in the radial direction from the seal member <NUM> in the recessed portion forming body <NUM>. The axial recessed portion <NUM> is recessed from a side surface portion of the recessed portion forming body <NUM> toward one side in the axial direction (here, a counter motor side), and is continuous in an annular shape. The axial recessed portion <NUM> forms a radial gap 84c between an upper surface portion 84a and a lower surface portion 84b of the axial recessed portion <NUM>, and the oil receiving member <NUM> is disposed in the radial gap 84c. The axial recessed portion <NUM> in the present embodiment is formed between the output member <NUM> and the wheel member <NUM>, which are a part of the rotating body <NUM>.

The oil receiving member <NUM> includes a receiving recessed portion <NUM> having a concave shape for receiving the lubricant <NUM>. The receiving recessed portion <NUM> in the present embodiment is formed inside the axial wall portion 80a and the outer wall portion 80b. The receiving recessed portion <NUM> in the present embodiment is configured as an annularly continuous groove portion. The receiving recessed portion <NUM> forms an oil reservoir <NUM> that stores the lubricant <NUM> received by the oil receiving member <NUM>. The oil reservoir <NUM> in the present embodiment is provided below a lower end position Pa at an inner peripheral end portion of the outer wall portion 80b of the oil receiving member <NUM>.

The receiving recessed portion <NUM> includes a bottom surface portion 88a and a pair of side surface portions 88b and 88c provided on both sides of the bottom surface portion 88a in the axial direction. The pair of side surface portions 88b and 88c include an inner surface portion 88b on the mating member <NUM>, which is provided integrally with the oil receiving member <NUM>, and an outer surface portion 88c on the side opposite to the mating member <NUM>. In the present embodiment, the inner surface portion 88b is composed of the mating member <NUM>, and the outer surface portion 88c is composed of the oil receiving member <NUM>. As described above, the receiving recessed portion <NUM> of the oil receiving member <NUM> may be at least partially constituted by the oil receiving member <NUM>, and partially constituted by the mating member <NUM>.

The wheel drive device <NUM> includes a lubricant propagation member <NUM> through which the lubricant <NUM> that has leaked from the seal member <NUM> propagates. In <FIG>, a propagation path of the lubricant <NUM> is schematically indicated by an arrow Da. The lubricant propagation member <NUM> is a casing <NUM> and forms the above-described axial recessed portion <NUM> in the present embodiment. The lubricant <NUM> that has leaked from the seal member <NUM> propagates through an outer surface portion of the lubricant propagation member <NUM> by at least its own weight. The lubricant propagation member <NUM> includes, as a propagation location of the lubricant <NUM>, an outer surface portion 91a located outwardly in the radial direction from the seal member <NUM> and an axial surface portion 91c that extends inwardly in the axial direction from an outer peripheral edge portion 91b of the outer surface portion 91a. The axial surface portion 91c is provided with the upper surface portion 84a of the axial recessed portion <NUM> forming the radial gap 84c. The oil receiving member <NUM> is disposed below the propagation location of such lubricant <NUM>, and can receive the lubricant <NUM> dripping from the propagation location.

The lubricant propagation member <NUM> includes a guide portion <NUM> provided on the axial surface portion 91c that is a position facing the oil receiving member <NUM> inwardly in the radial direction. The guide portion <NUM> includes a large outer diameter portion 92a provided on the axial surface portion 91c and a small outer diameter portion 92b provided on the axial surface portion 91c inwardly in the axial direction from the large outer diameter portion 92a. An outer diameter R92b of the small outer diameter portion 92b is smaller than an outer diameter R92a of the large outer diameter portion 92a. The guide portion <NUM> in the present embodiment is configured by providing a recessed portion in the axial surface portion 91c at a location of the small outer diameter portion 92b. In addition, it may be configured by providing a protrusion at a location of the axial surface portion 91c that becomes the large outer diameter portion 92a, or may be configured by gradually reducing the outer diameter of the axial surface portion 91c inwardly in the axial direction. In the present embodiment, the large outer diameter portion 92a and the small outer diameter portion 92b constituting the guide portion <NUM> are provided in a range over the entire circumference of the axial surface portion 91c.

When the lubricant <NUM> tries to propagate inwardly in the axial direction in the axial surface portion 91c of the lubricant propagation member <NUM>, it becomes difficult for the lubricant <NUM> to climb from the large outer diameter portion 92a to the small outer diameter portion 92b. Therefore, the lubricant <NUM> can be held by the large outer diameter portion 92a of the guide portion <NUM> by blocking the propagation of the lubricant <NUM> in the large outer diameter portion 92a of the guide portion <NUM>. The guide portion <NUM> can guide the lubricant <NUM> held by itself to the oil receiving member <NUM> in a direction Db by separating the lubricant <NUM> by its own weight, rotation, or the like. That is, the guide portion <NUM> of the lubricant propagation member <NUM> holds the lubricant <NUM> by blocking the propagation of the lubricant <NUM> at a position facing the oil receiving member <NUM> inwardly in the radial direction, and guides the held lubricant <NUM> to the oil receiving member <NUM> by separating it.

Accordingly, it is possible to reduce the amount of the lubricant <NUM> that tries to pass inwardly in the axial direction at a position that faces the oil receiving member <NUM> inwardly in the radial direction in the lubricant propagation member <NUM>. In this example, the lubricant <NUM> trying to pass inwardly in the axial direction leaks into the external space <NUM> after passing through the upper surface portion 84a of the axial recessed portion <NUM>, the bottom portion, the lower surface portion 84b, and the side surface portion of the wheel member <NUM>, as indicated by an arrow Dc. That is, after passing through the position facing the oil receiving member <NUM> inwardly in the radial direction in the lubricant propagation member <NUM>, the lubricant <NUM> leaks into the external space <NUM> after passing through an outer surface portion of a member (here, the wheel member <NUM>) that is integrated with the lubricant propagation member <NUM> below the oil receiving member <NUM>. By providing the above-described guide portion <NUM>, it is possible to reduce the amount of the lubricant <NUM> leaking into the external space <NUM>.

<FIG> is referred to. In <FIG>, hatching is applied to a part of a propagation location <NUM> of the lubricant <NUM> that has leaked from the seal member <NUM>. The lubricant propagation member <NUM> in the present embodiment is a part of the rotating body <NUM>. Therefore, the lubricant <NUM> that has leaked from the seal member <NUM> propagates to a range continuous in the circumferential direction from the propagation location of the lubricant <NUM> by its own weight in the lubricant propagation member <NUM>, by the rotation of the lubricant propagation member <NUM>. The propagation location <NUM> of the lubricant <NUM> due to this rotation includes the outer surface portion 91a and an axial surface portion 91c of the lubricant propagation member <NUM> located outwardly in the radial direction from the seal member <NUM>. The oil receiving member <NUM> of the present embodiment is provided in an annular shape so as to surround the propagation location <NUM> of the lubricant <NUM> which is a part of the lubricant propagation member <NUM> from the outside in the radial direction. Accordingly, when the lubricant <NUM> splashes from the propagation location <NUM> of the lubricant <NUM> of the lubricant propagation member <NUM> by the rotation of the rotating body <NUM>, it is possible to receive the lubricant <NUM> by the oil receiving member <NUM>. As a result, leakage of the splashed lubricant <NUM> into the external space <NUM> can be suppressed.

Effects of the wheel drive device <NUM> described above will be described.

At least a part of the oil receiving member <NUM> is disposed inside the axial recessed portion <NUM> formed in one of the rotating body <NUM> and the fixed body <NUM>. Therefore, as compared with a case where the axial recessed portion <NUM> is not formed in the recessed portion forming body <NUM>, an axial dimension L80 (refer to <FIG>) of the oil receiving member <NUM> can be increased by the amount of the oil receiving member <NUM> disposed in the axial recessed portion <NUM>, and the storage volume of the lubricant can be increased accordingly. Here, the ability to increase the storage volume of the lubricant means that the volume of the oil reservoir <NUM> of the oil receiving member <NUM> can be increased. Further, as compared with a case where the axial dimension L90 of the same oil receiving member <NUM> is secured without forming the axial recessed portion <NUM> in the recessed portion forming body <NUM>, the axial dimension of the entire wheel drive device <NUM> can be reduced. As a result, it is possible to reduce the axial dimensions of the entire wheel drive device <NUM> while increasing the storage volume of the lubricant by the oil receiving member <NUM>.

The oil receiving member <NUM> is provided on the attachment member <NUM>. Accordingly, a part of the heat generated by the motor <NUM> and the speed reducer <NUM> and transmitted to the attachment member <NUM> can be transmitted to the oil receiving member <NUM> from the attachment member <NUM>. Therefore, a surface area contributing to heat radiation to the air can be increased by the amount of the oil receiving member <NUM>. As a result, the amount of heat that is released to the air directly from the attachment member <NUM> and the oil receiving member <NUM> without passing through the vehicle body <NUM> can be increased, and the heat radiation of the wheel drive device <NUM> can be improved. In addition, since the amount of heat transmitted from the attachment member <NUM> to the vehicle body <NUM> out of the heat transmitted to the attachment member <NUM> can be reduced, the influence on the vehicle body <NUM> due to the heat generated by the motor <NUM> or the like can be reduced.

As described above, the oil receiving member <NUM> in the present embodiment functions as a heat radiating member for receiving a part of the heat transmitted to the attachment member <NUM> and radiating the heat to the external space <NUM>. From such a viewpoint, a part of the oil receiving member <NUM> may be provided at a position exposed to the external space <NUM> when viewed from the radial direction. Here, a part of the oil receiving member <NUM> means the axial wall portion 80a of the oil receiving member <NUM> in the present embodiment.

The oil receiving member <NUM> is provided on the fixed body <NUM>. Accordingly, the oil receiving member <NUM> can be maintained in a stationary state when the wheel <NUM> rotates, so that a state in which the lubricant <NUM> is stored can be stably maintained by the oil receiving member <NUM> without spilling.

Next, other features of the wheel drive device <NUM> will be described. <FIG> is referred to. The wheel drive device <NUM> includes a facing member <NUM> that is disposed to face the lubricant propagation member <NUM> that is a part of the rotating body <NUM> in the axial direction. The facing member <NUM> in the present embodiment is the attachment member <NUM> provided with the oil receiving member <NUM>, and is a part of the fixed body <NUM>. The facing member <NUM> is also disposed to face not only the lubricant propagation member <NUM> but also the seal member <NUM> in the axial direction. The bottom surface portion 88a of the oil receiving member <NUM> is inclined inwardly in the radial direction toward the facing member <NUM> in the axial direction. Advantages regarding the above will be described.

A case where the lubricant <NUM> which is splashed upward from the axial surface portion 91c of the lubricant propagation member <NUM> by the rotation of the rotating body <NUM> above the seal member <NUM> is received by the oil receiving member <NUM> is considered. In <FIG>, two propagation paths of the lubricant <NUM>, which is splashed upward in this way, are schematically indicated by arrows Dd and De. The propagation path in the present embodiment is indicated by the arrow Dd, and the propagation path in the reference embodiment is indicated by the arrow De. A solid line arrow in <FIG> indicates that the lubricant <NUM> propagates at a location visible in <FIG>, and a broken line arrow indicates that the lubricant <NUM> propagates at a hidden location in <FIG>.

The structure (not illustrated) of the reference embodiment assumes a case where the bottom surface portion 88a of the oil receiving member <NUM> is not inclined and is parallel to the axial direction. In this case, a case where the lubricant <NUM>, which is received by the bottom surface portion 88a of the oil receiving member <NUM> and is splashed upward, propagates on a side opposite to the facing member <NUM> in the axial direction is considered. In this case, as illustrated by the arrow De in <FIG>, as the lubricant <NUM> drips downward from the outer surface portion 88c of the oil receiving member <NUM>, the lubricant <NUM> returns to the axial surface portion 91c of the lubricant propagation member <NUM>. As a result, after propagating from an upper portion to a lower portion of the axial surface portion 91c of the lubricant propagation member <NUM>, the lubricant <NUM> propagates below the oil receiving member <NUM>, and a risk that the lubricant <NUM> leaks to the external space <NUM> is increased.

In this regard, according to the present embodiment, the bottom surface portion 88a of the oil receiving member <NUM> is inclined to approach inwardly in the radial direction toward the facing member <NUM>. Therefore, as illustrated by the arrow Dd, the lubricant <NUM> received by the bottom surface portion 88a of the oil receiving member <NUM> above the seal member <NUM> can be guided to a side of the facing member <NUM> by its own weight. The lubricant <NUM> guided to the side of the facing member <NUM> in this manner propagates downward on the side surface portion of the facing member <NUM>, and then is guided to the oil reservoir <NUM> of the oil receiving member <NUM>. That is, in a case where the lubricant <NUM>, which is splashed upward, is received by the bottom surface portion 88a of the oil receiving member <NUM>, after propagating the side surface portion of the facing member <NUM>, it can be guided to the oil reservoir <NUM> of the oil receiving member <NUM>. As a result, the lubricant <NUM>, which is splashed upward, propagates to the side opposite to the facing member <NUM>, so that it is possible to avoid a situation in which the lubricant <NUM> leaks to the external space <NUM>.

Next, modification examples of each component described so far will be described.

Specific examples of the speed reducer <NUM> are not particularly limited, and various reduction mechanisms can be applied, such as a bending meshing type speed reducer, a simple planetary gear type speed reducer, a traction drive, or the like, in addition to the eccentric oscillation type speed reducer. The type of the eccentric oscillation type speed reducer is not particularly limited. As an example of this, the center crank type in which the crankshaft (input shaft <NUM>) is disposed on the rotation center line of the wheel <NUM> has been described in the embodiment. In addition to this, it may be a distribution type in which a plurality of crankshafts are disposed at positions offset in the radial direction from the rotation center line of the wheel <NUM>. The type of the bending meshing type speed reducer is not particularly limited, and may be, for example, a cup type having one internal gear, a silk hat type, or the like in addition to a tubular type having two internal gears.

The axial recessed portion <NUM> may be formed in any one of the rotating body <NUM> and the fixed body <NUM>. The axial recessed portion <NUM> may be formed in the fixed body <NUM> in place of the rotating body <NUM>. It is assumed that, for example, a case where the axial recessed portion <NUM> is formed in the attachment member <NUM> that is the fixed body <NUM>. In addition to this, the axial recessed portion <NUM> may be formed in only one of the output member <NUM> and the wheel member <NUM>, which are the rotating body <NUM>. In addition, the output member <NUM> and the wheel member <NUM> may be integrally molded, in addition to a case where the output member <NUM> and the wheel member <NUM> are separately provided as in the embodiment.

Specific examples of the position and shape of the oil receiving member <NUM> are not particularly limited as long as the lubricant that has leaked beyond the seal member <NUM> can be received. For example, the oil receiving member <NUM> may be disposed only below the propagation location of the lubricant <NUM> by its own weight in the lubricant propagation member <NUM>. In this case, for example, the oil receiving member <NUM> may form a continuous arc shape in a circumferential range of about half a circumference below the propagation location of the lubricant <NUM> by its own weight. The bottom surface portion 88a of the oil receiving member <NUM> may not be inclined, or may be inclined outwardly in the radial direction toward the facing member <NUM>.

An example in which the mating member <NUM> provided with the oil receiving member <NUM> is a part of the fixed body <NUM> has been described, but the mating member <NUM> may be a part of the rotating body <NUM>. For example, it is assumed that the oil receiving member <NUM> is provided in any one of the output member <NUM> and the wheel member <NUM>, which are a part of the rotating body <NUM>.

Claim 1:
A wheel drive device (<NUM>) that drives a wheel (<NUM>), comprising:
a rotating body (<NUM>) including the wheel (<NUM>);
a fixed body (<NUM>) in which the rotating body (<NUM>) rotates relative to the fixed body (<NUM>);
a seal member (<NUM>) that is disposed between the rotating body (<NUM>) and the fixed body (<NUM>) and that seals a sealing space (<NUM>) containing a lubricant (<NUM>);
an oil receiving member (<NUM>) that receives the lubricant (<NUM>) that has leaked beyond the seal member (<NUM>); and
wherein at least a part of the oil receiving member (<NUM>) is disposed inside an axial recessed portion (<NUM>) formed in one of the rotating body (<NUM>) and the fixed body (<NUM>), characterized in that the wheel drive device further comprises a guide portion (<NUM>) that is provided at a position facing the oil receiving member (<NUM>) inwardly in a radial direction and that guides the lubricant (<NUM>) to the oil receiving member (<NUM>).