Patent Description:
In <CIT><CIT>, a wheel drive device including an output member and a wheel member connected to the output member is disclosed. The output member and the wheel member include a spigot fitting portion in which an outer peripheral spigot surface and an inner peripheral spigot surface are spigot-fitted. <CIT> and <CIT> respectively disclose a wheel drive device falling within the wording of the pre-characterizing portion of claim <NUM> of the present application. The article "Fretting Corrosion or False Brinelling?" by Douglas Godfrey discloses that fretting corrosion is prevented by using lubricants containing an antiwear additive.

Fretting wear is likely to occur at the spigot fitting portion between the output member and the wheel member. The inventors of the present application have found a new idea for suppressing the fretting wear at the spigot fitting portion.

One of objects of the present disclosure is to provide a technique capable of suppressing fretting wear at a spigot fitting portion between an output member and a wheel member.

According to the invention as claimed in claim <NUM>, a wheel drive device includes an output member, and a wheel that includes a wheel member whereby the wheel member is connected to the output member, in which the output member and the wheel member include a spigot fitting portion in which an outer peripheral spigot surface, which is provided in one of the output member and the wheel member, and an inner peripheral spigot surface, which is provided in the other, are spigot-fitted, an anti-fretting agent is applied to the spigot fitting portion, and a seal member that prevents leakage of the anti-fretting agent is disposed between the output member and the wheel member.

According to the invention as claimed in claim <NUM>, it is possible to suppress the fretting wear at the spigot fitting portion between the output member and the wheel 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 drive source <NUM>, a speed reducer <NUM> to which input rotation is input from an output shaft 16a of the drive source <NUM>, and a wheel <NUM> to which output rotation is output from an output member <NUM> of the speed reducer <NUM>. For example, the drive source <NUM> is a motor, a gear motor, an engine, or the like. In addition to this, the wheel drive device <NUM> includes an attachment member <NUM> that is attached to the vehicle body <NUM> and supports each of the drive source <NUM> and the speed reducer <NUM>. Hereinafter, a direction along a rotation center line CL1 of the output member <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.

<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 drive source <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 28A and 28B disposed inside the casing <NUM> in the radial direction are provided.

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 <NUM> 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 34a integrated with the casing <NUM>, and an outer pin 34b provided on an inner peripheral portion of the internal gear main body 34a and constituting internal teeth.

The carriers 28A and 28B are disposed on one side in the axial direction of the reduction mechanism <NUM>. The carriers 28A and 28B in the present embodiment include a first carrier 28A disposed on one side in the axial direction and a second carrier 28B disposed on the other side in the axial direction. The carriers 28A and 28B are connected through a connection member <NUM> such as a pin. The carriers 28A and 28B support the input shaft <NUM> through an input bearing <NUM>. A main bearing <NUM> is disposed between the casing <NUM> and the carriers 28A and 28B.

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. 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>, but the carriers 28A and 28B may be used in place of the casing <NUM>. Details of the output member <NUM> will be described later.

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>, 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. Details of the wheel member <NUM> will be described later. 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.

An operation of the wheel drive device <NUM> described above will be described. In a case where the input rotation is input from the drive source <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 the 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.

<FIG> will be referred to. Hatching is omitted in the following drawings. One of the output member <NUM> and the wheel member <NUM> is an inner member <NUM>, and the other is an outer member <NUM>. In the present embodiment, the inner member <NUM> is the output member <NUM>, and the outer member <NUM> is the wheel member <NUM>. At least a part of the inner member <NUM> is disposed inward of the outer member <NUM> in the radial direction.

An insertion hole <NUM> into which the inner member <NUM> is inserted toward one side in the axial direction (here, a counter motor side) is provided on an inner peripheral surface of the outer member <NUM>. The insertion hole <NUM> includes an opening portion 54a that opens toward the other side in the axial direction (here, a motor side).

The inner member <NUM> and the outer member <NUM> respectively include axial abutment portions 56A and 56B that abut in the axial direction. The inner member <NUM> includes a first axial abutment portion 56A, and the outer member <NUM> includes a second axial abutment portion 56B that abuts against the first axial abutment portion 56A in the axial direction. In the present embodiment, the first axial abutment portion 56A is provided on a side surface portion of a first protrusion portion 58A that protrudes outwardly in the radial direction on an outer peripheral surface of the inner member <NUM>. In addition, the second axial abutment portion 56B is provided on a side surface portion of the second protrusion portion 58B that protrudes inwardly in the radial direction on the inner peripheral surface of the outer member <NUM>.

The output member <NUM> and the wheel member <NUM> are connected by a connection member <NUM>. The output member <NUM> and the wheel member <NUM> in the present embodiment are connected by the connection member <NUM> at the respective axial abutment portions 56A and 56B. The connection member <NUM> in the present embodiment is a bolt, but may also be a rivet, a pin, or the like. A plurality of the connection members <NUM> are disposed with a space in the circumferential direction. The inner member <NUM> and the outer member <NUM> include an insertion hole <NUM> for inserting the connection member <NUM>. In the present embodiment, the insertion hole <NUM> of the inner member <NUM> is a female screw hole, and the insertion hole <NUM> of the outer member <NUM> is a non-screw hole. The connection member <NUM> is inserted into the insertion holes <NUM> of the inner member <NUM> and the outer member <NUM> in the axial direction, and connects the inner member <NUM> and the outer member <NUM> in a state in which the respective axial abutment portions 56A and 56B are abutted.

The inner member <NUM> and the outer member <NUM> include a spigot fitting portion <NUM> in which an outer peripheral spigot surface <NUM> and an inner peripheral spigot surface <NUM> are spigot-fitted. The outer peripheral spigot surface <NUM> is provided on an outer peripheral surface of the inner member <NUM> (here, the output member <NUM>), and the inner peripheral spigot surface <NUM> is provided on the inner peripheral surface of the outer member <NUM> (here, the wheel member <NUM>). The wheel member <NUM> is connected in a state in which the output member <NUM> and the wheel member <NUM> are spigot-fitted at the spigot fitting portion <NUM>.

An anti-fretting agent <NUM> is applied to the spigot fitting portion <NUM>. It can also be said that the anti-fretting agent <NUM> is applied to the outer peripheral spigot surface <NUM> and the inner peripheral spigot surface <NUM>. In <FIG>, hatching is applied to an application location of the anti-fretting agent <NUM>. The anti-fretting agent <NUM> has a function of preventing fretting wear caused by contact between the outer peripheral spigot surface <NUM> and the inner peripheral spigot surface <NUM>. Specific examples of the anti-fretting agent <NUM> are not particularly limited, and a liquid lubricant such as wax, oil, and fatty acid may be used in addition to a solid lubricant such as molybdenum disulfide and graphite, for example. In a case where the solid lubricant is used as the anti-fretting agent <NUM>, a mixture of the solid lubricant in a form of powder and a lubricating oil such as grease and oil may be used as the anti-fretting agent <NUM>.

A seal member <NUM> that prevents the anti-fretting agent <NUM> from leaking into an external space is disposed between the inner member <NUM> and the outer member <NUM>. For example, the seal member <NUM> is a contact type seal such as an O-ring and a lip seal, and here, the seal member <NUM> is the O-ring. The seal member <NUM> in the present embodiment is composed of an elastic body such as rubber. This seal member <NUM> is disposed between the inner member <NUM> and the outer member <NUM> with elastic deformation. The seal member <NUM> is disposed on one side in the axial direction with respect to the spigot fitting portion <NUM>, and prevents the anti-fretting agent <NUM> from leaking to the one side in the axial direction.

Each of the inner member <NUM> and the outer member <NUM> includes a pair of radial facing portions <NUM> facing each other in the radial direction. The spigot fitting portion <NUM> is provided on the pair of radial facing portions <NUM>. The seal member <NUM> is disposed between the pair of radial facing portions <NUM>. In the present embodiment, the radial facing portion <NUM> of the inner member <NUM> is provided on an outermost diameter portion <NUM> having the largest outer diameter in an axial range facing the inner peripheral surface of the outer member <NUM> in the radial direction. The radial facing portion <NUM> of the outer member <NUM> is provided at a position overlapping the radial facing portion <NUM> of the outermost diameter portion <NUM> in the radial direction.

At least one of the inner member <NUM> and the outer member <NUM> is provided with a recessed portion <NUM> that accommodates the seal member <NUM>. The recessed portion <NUM> is provided as an annularly continuous groove portion. Accordingly, by accommodating the seal member <NUM> in one recessed portion <NUM> of the inner member <NUM> and the outer member <NUM>, the seal member <NUM> can be mounted to the one recessed portion <NUM>. The recessed portion <NUM> in the present embodiment is provided on the outer peripheral surface of the inner member <NUM> (here, the output member <NUM>), and the seal member <NUM> can be mounted to the inner member <NUM>. Accordingly, when the wheel drive device <NUM> is assembled, the seal member <NUM> is less likely to come off than when the seal member <NUM> is accommodated in the recessed portion <NUM> of the outer member <NUM>, so that good workability can be obtained.

A radial gap <NUM> that is adjacent to the spigot fitting portion <NUM> in the axial direction is provided between the pair of radial facing portions <NUM>. A part of the radial gap <NUM> is closed by the seal member <NUM>. The radial gap <NUM> includes an opening end portion 74a that is provided between end portions of the pair of radial facing portions <NUM> and opens in the axial direction. In a case where the inner member <NUM> and the outer member <NUM> are provided with the recessed portion <NUM> that accommodates the seal member <NUM>, the radial gap <NUM> is provided at a location excluding the recessed portion <NUM>. By providing the radial gap <NUM> between the pair of radial facing portions <NUM>, an axial dimension L1 of the spigot fitting portion <NUM>, which causes fretting wear in the pair of radial facing portions <NUM>, can be shortened by the amount of an axial dimension L2 of the radial gap <NUM>. As a result, the fretting wear can be suppressed as compared with a case where the radial gap <NUM> is not provided between the pair of radial facing portions <NUM>.

A gap between the pair of radial facing portions <NUM> in the radial gap <NUM> is wider than a gap between the pair of radial facing portions <NUM> in the spigot fitting portion <NUM>. The radial dimension R74 of the radial gap <NUM> is smaller than a thickness dimension R70 of the seal member <NUM>. Here, the thickness dimension R70 refers to a radial dimension obtained by subtracting an inner diameter dimension from an outer diameter dimension of the seal member <NUM>.

The seal member <NUM> is provided at an intermediate position of the radial gap <NUM> in the axial direction. It can be said that the seal member <NUM> is not provided at the opening end portion 74a of the radial gap <NUM>. Accordingly, the radial gap <NUM> can be widened with respect to the seal member <NUM> on the side opposite to the spigot fitting portion <NUM> in the axial direction, rather than the disposition position of the seal member <NUM> being the opening end portion 74a of the radial gap <NUM>. As a result, it becomes difficult for only a foreign matter having a dimension smaller than the radial gap <NUM> to reach the seal member <NUM> from the external space, and the seal member <NUM> can be protected from contact with a foreign matter having a large dimension.

The axial abutment portions 56A and 56B of the output member <NUM> and the wheel member <NUM> are disposed on the side opposite to the seal member <NUM> in the axial direction with respect to the spigot fitting portion <NUM>. At least one of the first axial abutment portion 56A and the second axial abutment portion 56B (both in the present embodiment) may satisfy this condition. Accordingly, the axial abutment portions 56A and 56B abutting against each other can prevent the anti-fretting agent <NUM> from leaking to the spigot fitting portion <NUM> on the side opposite to the seal member <NUM> in the axial direction. As a result, other seal members for preventing leakage of the anti-fretting agent <NUM> can be omitted. In addition, by adopting the bolt as the connection member <NUM>, the axial abutment portions 56A and 56B can be brought into close contact with each other by tightening force of the bolt. As a result, the leakage of the anti-fretting agent <NUM> can be effectively suppressed by the axial abutment portions 56A and 56B abutting against each other.

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

The anti-fretting agent <NUM> is applied to the spigot fitting portion <NUM> between the output member <NUM> and the wheel member <NUM>. Accordingly, the fretting wear at the spigot fitting portion <NUM> can be suppressed. As a result, durability of the wheel drive device <NUM> can be improved.

The seal member <NUM> that prevents the leakage of the anti-fretting agent <NUM> is disposed between the output member <NUM> and the wheel member <NUM>. Accordingly, the scattering of the anti-fretting agent <NUM> into an external space <NUM> can be suppressed. As a result, a state in which the anti-fretting agent <NUM> is applied to the spigot fitting portion <NUM> can be maintained for a long period of time, and the fretting wear suppression effect by the anti-fretting agent <NUM> can be exhibited for a long period of time. In addition, the seal member <NUM> can suppress intrusion of foreign matters from the external space <NUM> into the spigot fitting portion <NUM>.

Next, other features of the wheel drive device <NUM> will be described. Between the output member <NUM> and the wheel member <NUM>, a radial load is transmitted. In a case where a function of transmitting the radial load is exclusively exhibited in the spigot fitting portion <NUM>, it is preferable that the axial dimension L1 of the spigot fitting portion <NUM> is made longer in order to reduce a contact pressure at the spigot fitting portion <NUM>. On the other hand, in the present embodiment, the function of transmitting the radial load between the output member <NUM> and the wheel member <NUM> is exclusively exhibited by a plurality of connection members <NUM> in place of the spigot fitting portion <NUM>. In addition, the spigot fitting portion <NUM> in the present embodiment is exclusively used to position the output member <NUM> and the wheel member <NUM> in the radial direction.

In exhibiting such positioning function, the axial dimension L1 of the spigot fitting portion <NUM> may be short. Rather, as a countermeasure against fretting wear, it is preferable that the axial dimension L1 of the spigot fitting portion <NUM>, which causes the fretting wear, is shortened. In addition, as the axial dimension L1 of the spigot fitting portion <NUM> becomes shorter, frictional resistance is less likely to occur in a case where the inner member <NUM> is inserted into the insertion hole <NUM> of the outer member <NUM>.

From such a viewpoint, it is preferable that the axial dimension L1 of the spigot fitting portion <NUM> is set to a size that is equal to or less than half the total dimension (= L1 + L2) of the axial dimension L1 of the spigot fitting portion <NUM> and the axial dimension L2 of the radial gap <NUM>. Although a lower limit value is not particularly limited, for example, <NUM> or more may be a lower limit value, and preferably <NUM> or more may be a lower limit value. Accordingly, the axial dimension L1 of the spigot fitting portion <NUM> can be shortened as compared with a case where the axial dimension L1 of the spigot fitting portion <NUM> is set to a size that is more than half of the total dimension (= L1 + L2). As a result, the occurrence of fretting wear can be suppressed as compared with such a case. In addition, as compared with such a case, the workability in a case where the inner member <NUM> is inserted into the insertion hole <NUM> of the outer member <NUM> can be improved. The axial dimension L1 of the spigot fitting portion <NUM> may have a size that is more than half of the total dimension (= L1 + L2).

As described above, the seal member <NUM> is mounted to the outer peripheral surface of the inner member <NUM>. To realize this, in the present embodiment, the seal member <NUM> is accommodated in the recessed portion <NUM> provided on the outer peripheral surface of the inner member <NUM>. Specific examples for mounting the seal member <NUM> is not particularly limited, and tightening, fitting, or the like may be used.

<FIG> and <FIG> are referred to. In a case where the inner member <NUM> is inserted into the insertion hole <NUM>, the inner member <NUM> passes through the opening portion 54a of the insertion hole <NUM> and then is moved until the first axial abutment portion 56A abuts against the second axial abutment portion 56B of the outer member <NUM>.

Here, a relief recessed portion <NUM> is provided on the inner peripheral surface of the outer member <NUM> to reduce the frictional resistance of the seal member <NUM> in a case where the inner member <NUM> is inserted into the insertion hole <NUM>. In a case where the relief recessed portion <NUM> is provided on the inner peripheral surface of the outer member <NUM>, the relief recessed portion <NUM> is provided between a contact location <NUM> of the seal member <NUM> with respect to the inner peripheral surface of the outer member <NUM> and the opening portion 54a of the insertion hole <NUM>. In the present embodiment, the relief recessed portion <NUM> is provided between the radial facing portion <NUM> of the outer member <NUM> and the opening portion 54a of the insertion hole <NUM>. The relief recessed portion <NUM> is provided to be recessed outwardly in the radial direction from the contact location <NUM> of the seal member <NUM> on the inner peripheral surface of the outer member <NUM>. An inner diameter R80a of the relief recessed portion <NUM> may be set to a size capable of avoiding contact with the seal member <NUM> mounted on the inner member <NUM>. For example, the axial dimension L80 of the relief recessed portion <NUM> is larger than an axial dimension L70 of the seal member <NUM>.

Accordingly, the frictional resistance of the seal member <NUM> can be reduced as compared with a case where the relief recessed portion <NUM> is not provided on the inner peripheral surface of the outer member <NUM>. As a result, it becomes easier to insert the inner member <NUM> into the insertion hole <NUM> of the outer member <NUM>, and good workability can be obtained.

<FIG> and <FIG> are referred to. The seal member <NUM> in the present embodiment is mounted on the inner peripheral surface of the outer member <NUM> in place of the outer peripheral surface of the inner member <NUM>. To realize this, the recessed portion <NUM> that accommodates the seal member <NUM> is provided on the inner peripheral surface of the outer member <NUM>.

The relief recessed portion <NUM> is provided on the outer peripheral surface of the inner member <NUM> in place of the inner peripheral surface of the outer member <NUM>. In a case where the relief recessed portion <NUM> is provided on the outer peripheral surface of the inner member <NUM>, the relief recessed portion <NUM> is provided between the contact location <NUM> of the seal member <NUM> with respect to the outer peripheral surface of the inner member <NUM> and the spigot fitting portion <NUM>. The relief recessed portion <NUM> is provided to be recessed inwardly in the radial direction from the contact location <NUM> of the seal member <NUM> on the outer peripheral surface of the inner member <NUM>. An outer diameter R80b of the relief recessed portion <NUM> may be set to a size capable of avoiding contact with the seal member <NUM> mounted on the outer member <NUM>. For example, the axial dimension L80 of the relief recessed portion <NUM> is larger than the axial dimension L70 of the seal member <NUM>.

Accordingly, as compared with a case where the relief recessed portion <NUM> is not provided on the outer peripheral surface of the inner member <NUM>, the frictional resistance of the seal member <NUM> can be reduced as in the first embodiment. In relation to such an effect, the seal member <NUM> may be mounted to one of the inner peripheral surface of the outer member <NUM> and the outer peripheral surface of the inner member <NUM>, and the relief recessed portion <NUM> may be provided on the other.

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 output member <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 output member <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.

One of the output member <NUM> and the wheel member <NUM> may be the inner member <NUM> having the outer peripheral spigot surface <NUM>, and the other may be the outer member <NUM> having the inner peripheral spigot surface <NUM>. To realize this, unlike the embodiment, the wheel member <NUM> may be the inner member <NUM>, and the output member <NUM> may be the outer member <NUM>.

The radial gap <NUM> that is adjacent to the spigot fitting portion <NUM> in the axial direction may not be provided between the pair of radial facing portions <NUM>. It can also be said that the axial range of the spigot fitting portion <NUM> may be adjacent to a range overlapping the seal member <NUM> in the radial direction.

The seal member <NUM> may be provided at the opening end portion 74a of the radial gap <NUM>.

The recessed portion <NUM> may be provided on at least one of the output member <NUM> and the wheel member <NUM>. The recessed portion <NUM> may be provided on both the inner peripheral surface of the outer member <NUM> and the outer peripheral surface of the inner member <NUM> unlike the embodiment. In addition, neither the output member <NUM> nor the wheel member <NUM> may have the recessed portion <NUM> that accommodates the seal member <NUM>.

The seal member <NUM> may be disposed individually on both sides in the axial direction with respect to the spigot fitting portion <NUM>. The seal member <NUM> may be disposed only on the side of the axial abutment portions 56A and 56B with respect to the spigot fitting portion <NUM> unlike the embodiment. Each of the output member <NUM> and the wheel member <NUM> may not include the axial abutment portions 56A and 56B.

Neither the inner member <NUM> nor the outer member <NUM> may be provided with the relief recessed portion <NUM>.

The above-described embodiments and modification examples are examples. The technical ideas that abstract, within the scope of the claims, the embodiments and modification examples should not be construed as being limited to the contents of the embodiments and modification examples. Many design changes such as the change, addition, and deletion of components can be made, within the scope of the claims, with respect to the contents of the embodiments and modification examples. In the above-described embodiments, the contents for which such design changes are possible are emphasized by adding the notation "embodiment". However, design changes are allowed, within the scope of the claims, even in the contents in which there is no such notation. Hatching applied to the cross section of the drawing does not limit the material of the hatched object. Structures and numerical values as mentioned in the embodiments and modification examples naturally include those that can be regarded as the same when manufacturing errors and the like are taken into consideration.

Any combination of the above components is also valid if it is within the scope of the claims. For example, any description of other embodiments may be combined, within the scope of the claims, with the embodiment, or the modification examples may be combined with any description of the embodiments and modification examples.

A component composed of a single member in an embodiment may be composed of a plurality of members.

Claim 1:
A wheel drive device (<NUM>) comprising:
an output member (<NUM>); and
a wheel (<NUM>) that includes a wheel member (<NUM>) whereby the wheel member (<NUM>) is connected to the output member (<NUM>),
wherein
the output member (<NUM>) and the wheel member (<NUM>) include a spigot fitting portion (<NUM>) in which an outer peripheral spigot surface (<NUM>) and an inner peripheral spigot surface (<NUM>) are spigot-fitted,
characterized in that
an anti-fretting agent (<NUM>) is applied to the spigot fitting portion (<NUM>), and
a seal member (<NUM>) that prevents leakage of the anti-fretting agent (<NUM>) is disposed between the output member (<NUM>) and the wheel member (<NUM>).