Driving device for carriage

A driving device for a carriage includes a motor, a speed reducer, and a mecanum wheel. The speed reducer decelerates the power input from the motor and outputs a decelerated power. The mecanum wheel is rotated by the decelerated power output from the speed reducer. The speed reducer includes a speed reducing unit, a carrier, and a case. The speed reducing unit receives the power from the motor. The carrier supports the speed reducing unit. The case is rotatable relative to the carrier. The mecanum wheel is fixed on the case or the carrier.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is based on and claims the benefit of priority from Japanese Patent Application Serial No. 2017-026352 (filed on Feb. 15, 2017), the contents of which are hereby incorporated by reference in their entirety.

TECHNICAL FIELD

The present invention relates to a driving device for a carriage.

BACKGROUND

Mecanum wheels are known as traveling wheels. A mecanum wheel includes a wheel body and a plurality of rollers rotatably mounted on the outer periphery of the wheel body. Each of the rollers is supported on the wheel body so as to be rotatable around a rotation axis oblique to the rotation axis of the wheel body. A mecanum wheel having such a distinctive structure can be used as a traveling wheel of a carriage, so as to fabricate a carriage that can move in directions other than the font-rear direction of a carriage body.

However, because of the complex construction and movement, a mecanum wheel is subjected to loads in a complex manner. In particular, it is predicted that a mecanum wheel is subjected to loads in a plurality of directions. Designing and manufacturing a mecanum wheel that withstands such loads have been considered to be complicated and difficult. As a result, carriages including a mecanum wheel are not used widely.

SUMMARY

The present invention addresses the above problem, and one object thereof is to provide a driving device for a carriage including a mecanum wheel. A driving device for a carriage according to the present invention comprises: a motor; a speed reducer that decelerates power input from the motor and outputs a decelerated power; and a mecanum wheel to be rotated by the decelerated power output from the speed reducer, wherein the speed reducer includes a speed reducing unit that receives the power from the motor, a carrier that supports the speed reducing unit, and a case rotatable relative to the carrier, and the mecanum wheel is fixed on the case or the carrier.

It is also possible that the speed reducer further includes a pair of bearings disposed between the carrier and the case, and the pair of bearings receive both a thrust load and a radial load between the carrier and the case.

It is also possible that at least a part of the speed reducer is disposed inside the mecanum wheel in radial directions from a rotation axis of the mecanum wheel.

It is also possible that the case of the speed reducer is press-fitted into the mecanum wheel.

It is also possible that the speed reducer further includes a pair of bearings disposed between the carrier and the case, at least a part of the speed reducer is disposed inside the mecanum wheel in radial directions from a rotation axis of the mecanum wheel, and at least a part of the mecanum wheel is positioned between load centers of the pair of bearings in an axial direction parallel to the rotation axis of the mecanum wheel.

It is also possible that the speed reducer further includes a pair of bearings disposed between the carrier and the case, at least a part of the speed reducer is disposed inside the mecanum wheel in radial directions from a rotation axis of the mecanum wheel, and a center of the mecanum wheel corresponds to a center of load centers of the pair of bearings in an axial direction parallel to the rotation axis of the mecanum wheel.

It is also possible that the speed reducer further includes a pair of bearings disposed between the carrier and the case, and the pair of bearings are cylindrical roller bearings having rolling elements that are rotatable around an axis parallel to a rotation axis of the mecanum wheel.

According to the present invention, a driving device for a carriage including a mecanum wheel can be provided with a sufficient strength.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The first embodiment of the present invention will now be described with reference to the attached drawings. The accompanying drawings are simplified and the elements in the drawings are not necessarily drawn to scale, and the dimensional ratio between the elements and shapes of the elements may be different from the actual ones. However, from such simplified drawings, the embodiments described below and other embodiments of the present invention would be sufficiently understood by those skilled in the art.

First Embodiment

FIG. 1is a perspective view of a driving device for a carriage, according to a first embodiment of the present invention.FIG. 2is a sectional view of a motor of the driving device shown inFIG. 1along the rotation axis thereof.

As shown inFIG. 1andFIG. 2, the driving device10includes a motor20, a speed reducer30, and a mecanum wheel40. The speed reducer30decelerates the power (i.e., rotation) input from the motor20and outputs the decelerated power. The mecanum wheel40is rotated by the output from the speed reducer30.

As shown inFIG. 2, the speed reducer30includes a speed reducing unit31, a carrier32, and a case33. The speed reducing unit31receives the power (rotation) from the motor20. The carrier32supports the speed reducing unit31. The case33is capable of moving relative to the carrier32. In the example shown inFIG. 2, the speed reducer30further includes a base34that supports the motor20.

The case33and the base34have a substantially cylindrical shape and extend in the direction of the rotation axis Ax of the motor20. A body21of the motor20is mounted on one end of the base34via a fastening member (not shown). On the other end of the base34, there is fixed one end of the case33via a fastening member51such as a bolt.

Inside the case33and the base34in the radial directions from the rotation axis Ax, there is provided an input shaft35that extends in the direction of the rotation axis Ax. Further, inside the case33in the radial directions from the rotation axis Ax, there are provided the speed reducing unit31and the carrier32.

The input shaft35serves as an input gear that inputs power from the motor20to the speed reducing unit31. More specifically, one end of the input shaft35is connected to an output shaft25of the motor20. This enables the input shaft35to rotate around the rotation axis Ax integrally with the output shaft25of the motor20. Thus, the power (rotation) output from the motor20is transmitted to the input shaft35. The input shaft35inputs, at the other end thereof, the power from the motor20to the speed reducing unit31.

The body21and the output shaft25of the motor20are removably mounted on the base34and the input shaft35, respectively. Therefore, the motor20can be replaced when necessary.

The speed reducing unit31decelerates power (rotation) that is input from the input shaft35and transmits the power with an increased torque to the carrier32or the case33. In the example shown inFIG. 2, the case33is fixed on the base34, and therefore, the speed reducing unit31transmits the power to the carrier32to rotate the carrier32.

In the example shown inFIG. 2, the speed reducer30is configured as an eccentric oscillating speed reducer, and the speed reducing unit31constitutes an eccentric oscillating gear. An eccentric oscillating speed reducer typically has a small backlash that makes it possible to reduce malfunctions of the whole driving device10. The speed reducer30is not limited to an eccentric oscillating speed reducer but may be other types of speed reducers. For example, the speed reducer30may be a planetary gear speed reducer or may be constituted by a speed reducing structure in which a planetary gear speed reducer and an eccentric oscillating speed reducer are combined together. Alternatively, the speed reducer30may be constituted by other desired types of speed reducing structures. When the speed reducer30is a planetary gear speed reducer, the speed reducing unit31constitutes a planetary gear.

The carrier32retains the speed reducing unit31. Further, the carrier32is connected to the case33via a pair of bearings60a,60bdisposed between the carrier32and the case33, so as to be rotatable relative to the case33. In the example shown inFIG. 2, the speed reducing unit31meshes with the case33fixed stationary, and therefore, the carrier32rotates around the rotation axis Ax at a reduced rotation speed along with the speed reducing unit31. The carrier32is also restrained by the pair of bearings60a,60bfrom moving in the direction of the rotation axis Ax relative to the case33.

The pair of bearings60a,60balso withstand the loads imparted to the carrier32and the case33. When the carriage includes a mecanum wheel, a thrust load and a radial load may be imparted to the carrier32and the case33from the mecanum wheel. The thrust direction mentioned herein refers to the direction in which the rotation axis Ax extends. The radial direction mentioned herein refers to the radial directions from the rotation axis Ax. The pair of bearings60a,60bcan receive both the thrust load and the radial load between the carrier32and the case33. Since the pair of bearings60a,60bthus configured are disposed between the carrier32and the case33, the thrust load and the radial load are prevented from being transmitted to components of the speed reducer30such as the speed reducing unit31. As a result, the life span of the speed reducer30can be elongated. In the example shown inFIG. 2, the bearings60a,60bare angular ball bearings each including track rings61a,61band arrays of spherical rolling elements62a,62benclosed between the track rings61a,61b.

The pair of bearings60a,60bare not limited to angular ball bearings but may be other types of bearings. For example, the pair of bearings60a,60bmay be cylindrical roller bearings having rolling elements that are rotatable around an axis parallel to the rotation axis Bx of the mecanum wheel40described later. In this case, the pair of bearings60a,60bcan receive at least the radial load. As a result, the radial load is prevented from being transmitted to components of the speed reducer30such as the speed reducing unit. As a result, the life span of the speed reducer30can be elongated. In an example described later in which the speed reducer30is disposed inside the mecanum wheel40, the thrust load imparted to the elements constituting the speed reducer30is small, while the radial load imparted to the same is large. Therefore, a cylindrical roller bearing is suitable since it has rolling elements that are rotatable around an axis parallel to the rotation axis Bx of the mecanum wheel40.

On the other end of the carrier32, there is fixed a connector80via a fastening member53such as a bolt. The connector80connects the mecanum wheel40to the carrier32. A wheel body41of the mecanum wheel40described later is fixed to the connector80via a fastening member52such as a bolt. The connector80is designed to the dimensions of the mecanum wheel40and the speed reducer30so as not to have an unnecessary clearance formed between the mecanum wheel40and the speed reducer30. The connector80is also designed in consideration of the size and direction of the load imparted to the mecanum wheel40during traveling of the carriage, so as to have a strength enough to withstand the load. Naturally, the speed reducer30and the fastening member53for fixing the connector80to the speed reducer30are also designed in consideration of the dimensions of the mecanum wheel40and the size and direction of the load imparted to the mecanum wheel40. That is, in this embodiment, the whole driving device10is designed in consideration of the size and direction of the load imparted to the mecanum wheel40.

The internal space S surrounded by the base34, the case33, and the carrier32is sealed by a seal portion70. The seal portion70in the embodiment includes a first seal element71that seals between the base34and the input shaft35, and a second seal element72that seals between the case33and the carrier32. The speed reducing unit31and the bearings60a,60bare disposed in the internal space S sealed and closed by the seal portion70.

Next, the mecanum wheel will be described.

As shown inFIG. 1, the mecanum wheel40includes a wheel body41and a plurality of barrel-shaped rollers42rotatably mounted on the periphery of the wheel body41. Each of the rollers42is supported on the wheel body41so as to be rotatable around a rotation axis By oblique to the rotation axis Bx of the wheel body41. The rotation axis By of the rollers42extends at an angle of about 45° with respect to the rotation axis Bx of the mecanum wheel40.

In the example shown inFIG. 2, the mecanum wheel40is fixed on the connector80of the carrier32such that rotation axis Bx of the mecanum wheel40is aligned with the rotation axis Ax of the carrier32. When the speed reducing unit31is configured to rotate the case33as in an example described later, the mecanum wheel40may be fixed on the case33so as to rotate along with the case33.

The driving device10thus configured is mounted on a carriage body (not shown) to construct a carriage. It should be noted that the driving device10is applicable to all kinds of carriages in which power from the motor20is transmitted to the wheel40via the speed reducer30. For example, the driving device10of the invention can be applied not only to carriages that require assistance by an operator during traveling but also to carriages (i.e., an unmanned conveyance vehicle) such as AGVs (Automatic Guided Vehicles) or RGVs (Rail Guided Vehicles) that do not require assistance by an operator during traveling.

As described above, the driving device10for a carriage according to the first embodiment includes a motor20, a speed reducer30, and a mecanum wheel40. The speed reducer30decelerates the power input from the motor20and outputs the decelerated power. The mecanum wheel40is rotated by the output from the speed reducer30. The speed reducer30includes a speed reducing unit31, a carrier32, and a case33. The speed reducing unit31receives the power from the motor20. The carrier32supports the speed reducing unit31. The case33is rotatable relative to the carrier32. The mecanum wheel40is fixed on the case33or the carrier32.

In this driving device, the speed reducer30can be provided with a sufficient strength, and the mecanum wheel40can be connected to the motor20via the speed reducer30. Further, speed reducers30having various strengths and sizes may be previously designed or prepared to significantly reduce the burden of complicated strength calculation and designing and manufacturing based on the strength calculation in application of the mecanum wheel40. According to the embodiment, the speed reducer30or the whole driving device10can be designed in consideration of the dimensions of the mecanum wheel40and the size and direction of the load imparted to the mecanum wheel40.

In the first embodiment, the speed reducer30further includes a pair of bearings60a,60bdisposed between the carrier32and the case33. The pair of bearings60a,60breceive both the thrust load and the radial load between the carrier32and the case33. As a result, the thrust load and the radial load can be prevented from being transmitted to components of the speed reducer30such as the speed reducing unit31. As a result, the life span of the speed reducer30can be elongated.

Alternatively, it is also possible that the speed reducer30further includes a pair of bearings60a,60bdisposed between the carrier32and the case33, and the pair of bearings60a,60bare cylindrical roller bearings having rolling elements that are rotatable around an axis parallel to the rotation axis Bx of the mecanum wheel40. In this case, the pair of bearings60a,60bcan receive the radial load.

As a result, the radial load is prevented from being transmitted to components of the speed reducer30such as the speed reducing unit31. As a result, the life span of the speed reducer30can be elongated.

Second Embodiment

Next, the second embodiment of the present invention will now be described with reference toFIG. 3. The second embodiment is substantially the same as the first embodiment except that at least a part of the speed reducer is disposed inside the mecanum wheel and that the mecanum wheel is fixed on the case, not on the carrier. In the following description of the second embodiment, the same elements as in the first embodiment will be denoted by the same reference numerals and detailed descriptions thereof will be omitted. Further, when it is obvious that the advantages obtained in the first embodiment can also be obtained in this embodiment, the description of the advantages may be omitted.

In the driving device100shown inFIG. 3, the speed reducing unit31of the speed reducer30is configured to transmit power to the case33. More specifically, in the example shown inFIG. 3, the case33is not fixed on the base34, but the carrier32is fixed on the base34via a fastening member55such as a bolt. As a result, the speed reducing unit31is configured to transmit power to the case33so as to rotate the case33.

Further, in the driving device100shown inFIG. 3, at least a part of the speed reducer30is disposed inside the mecanum wheel40in the radial directions from the rotation axis Bx of the mecanum wheel40. In other words, at least a part of the speed reducer30is disposed in a region overlapping with the mecanum wheel40in the direction of the rotation axis Ax. More specifically, the case33of the speed reducer30is press-fitted into the mecanum wheel40. The wheel body41of the mecanum wheel40is fixed on the case33via a fastening member56such as a bolt, and the wheel body41is also supported at the inner periphery thereof by the case33. Naturally, the case33of the speed reducer30may be disposed inside the mecanum wheel40by a method other than press-fitting such as loose fitting.

Thus, since at least a part of the speed reducer30is disposed inside the mecanum wheel40, it is possible to reduce the dimension of the driving device100in the direction of the rotation axis Bx. In addition, it is possible to reduce the moment of force applied from the mecanum wheel40to the speed reducer30. As a result, the life span of the speed reducer30can be further elongated. Further, since the moment of force applied from the mecanum wheel40to the speed reducer30is reduced, it is possible to reduce the dimensions of the fastening member56for fixing the mecanum wheel40on the speed reducer30.

In the example shown inFIG. 3, at least a part of the mecanum wheel40is positioned between the load center Pa of the bearing60aand the load center Pb of the bearing60bin the axial direction parallel to the rotation axis Bx of the mecanum wheel40. The load centers Pa, Pb of the bearings60a,60brefer to the points at which the central axis Cx of the bearings60a,60bintersects the extensions of the vectors indicating a resultant of forces transmitted from the track rings61a,61bof the bearings60a,60bto the arrays of rolling members62a,62benclosed between the track rings61a,61b. Since at least a part of the mecanum wheel40is positioned between the load center Pa of the bearing60aand the load center Pb of the bearing60b, it is possible to effectively reduce the moment of force applied to the speed reducer30.

Further, in the example shown inFIG. 3, the center O of the mecanum wheel40corresponds to the center of the load centers Pa, Pb of the pair of bearings60a,60b. This makes it possible to set the moment of force applied from the mecanum wheel40to the speed reducer30at zero. As a result, the life span of the speed reducer30can be furthermore elongated.

In the example shown inFIG. 3, the internal space S surrounded by the base34, the case33, and the carrier32is sealed by a seal portion170. The seal portion170in the embodiment includes a first seal element171that seals between the base34and the input shaft35, a second seal element172that seals between the case33and the carrier32, and a third seal element173that seals the other end of the case33. The speed reducing unit31and the bearings60a,60bare disposed in the internal space S sealed and closed by the seal portion170.

In the driving device100for a carriage according to the second embodiment described above, at least a part of the speed reducer30is disposed inside the mecanum wheel40in the radial directions from the rotation axis Bx of the mecanum wheel40. This makes it possible to reduce the dimension of the driving device100in the direction of the rotation axis Bx. In addition, it is possible to reduce the moment of force applied by the mecanum wheel40to the speed reducer30. As a result, the life span of the speed reducer30can be further elongated. Further, since the moment of force applied from the mecanum wheel40to the speed reducer30is reduced, it is possible to reduce the dimensions of the fastening member56for fixing the mecanum wheel40on the speed reducer30.

The case33of the speed reducer30is press-fitted into the mecanum wheel40. Thus, the wheel body41of the mecanum wheel40is supported at the inner periphery thereof by the case33. As a result, the strength of the mecanum wheel40can be increased.

Further, at least a part of the mecanum wheel40is positioned between the load centers Pa, Pb of the pair of bearings60a,60bin the axial direction parallel to the rotation axis Bx of the mecanum wheel40. This makes it possible to more effectively reduce the moment of force applied from the mecanum wheel40to the speed reducer30. As a result, the life span of the speed reducer30can be furthermore elongated.

Further, the center O of the mecanum wheel40corresponds to the center of the load centers of the pair of bearings60a,60bin the axial direction parallel to the rotation axis Bx of the mecanum wheel40. This makes it possible to set the moment of force applied from the mecanum wheel40to the speed reducer30at zero. As a result, the life span of the speed reducer30can be furthermore elongated.

The invention is not limited to the above-described embodiments and modification examples. For example, various modifications may be made to the elements of the embodiments and the modification examples described above. The invention also encompasses embodiments including components and/or methods other than the above-described components and/or methods. The invention also encompasses embodiments not including some elements of the above-described components and/or methods. Further, advantageous effects of the invention are not limited to the above-described ones, and there may be a specific effect depending on a specific configuration of each embodiment.