Wave gear unit

Abstract

The present invention provides a wave gear device. The wave gear device includes a spline having a top surface, a bottom surface, an outer surface, and an inner surface. A plurality of spline teeth extend from the inner surface toward a central axis. A wave generator is rotatably disposed in the spline. A belt assembly extends around the wave generator and includes a plurality of belt teeth that extend radially outward, whereby the total number of belt teeth is less than the total number of spline teeth. An output member defines a recess that accommodates the wave generator and the belt assembly, whereby in response to rotational movement from the wave generator, the output member rotates in the same direction as or in the opposite direction to the wave generator. A bearing assembly is disposed between the wave generator and the belt assembly and includes a plurality of needles, each of the plurality of needles extending parallel to the central axis. A vehicle lifting system including a wave gear device is also disclosed.

Description

Technical Field

[0001] The present invention relates generally to a strain wave gear arrangement, and more particularly to a strain wave gear arrangement for use with a vehicle lift system. Background Art

[0002] Harmonic drives are well known in the art. Typically, a harmonic drive is a single-stage gear transmission with three main components. These components are referred to as a circular spline, a flexspline, and a wave generator. The circular spline is a circular, rigid sun gear with teeth on its inner surface. The flexspline is a thin-walled, cup-shaped member with teeth on its outer surface, designed to mesh with the teeth of the circular spline. The flexspline is radially flexible and torsionally rigid, and has fewer teeth and a smaller radius than the circular spline. The wave generator is a noncircular cam that fits inside the flexspline and deforms it, causing some of its teeth to mesh with those of the circular spline while leaving other teeth completely disengaged. Each complete rotation of the wave generator causes the flexspline to travel around the circular spline at a rate equal to the difference between the number of teeth on the flexspline and the number of teeth on the circular spline. For example, if the circular spline has 100 teeth and the flexspline has 98 teeth, each rotation of the wave generator will cause the flexspline to travel a distance equal to two teeth around the circular spline. For example, if the circular spline has 100 teeth, the flexspline has 98 teeth, and the output member has 98 teeth, each rotation of the wave generator will cause the flexspline to travel a distance equal to two teeth around the circular spline. In this case, the output member rotates in the opposite direction of the wave generator. Alternatively, if the circular spline has 98 teeth, the flexspline has 98 teeth, and the output member has 100 teeth, each rotation of the wave generator will similarly cause the flexspline to travel a distance equal to two teeth around the circular spline. In this case, the output member rotates in the same direction as the wave generator.

[0003] Industries that benefit from harmonic drive gearing include semiconductors, machine tools, factory automation, robotics, medical devices, and aerospace. Medical applications that benefit from harmonic drive gearing include hospital beds, rehabilitation equipment, and MRI / CAT scan gantries. Other uses for harmonic drives include radiation therapy equipment, imaging camera positioning, and surgical robots. Robots used in semiconductor component manufacturing use harmonic drives to accurately position wafers for handling, loading, unloading, inspection, and testing. Military and aerospace applications for harmonic drive gearing include communications, military surveillance, and weather satellites, several deep space probes, telescopes including the Hubble Space Telescope, and the International Space Station. Harmonic drives are used to accurately control antenna and compass gimbals, align scientific instruments, adjust apertures and solar panels, and open and close hatches and doorways.

[0004] These applications require high positioning accuracy, repeatability, and low vibration. Harmonic drive gear sets are ideal for precision applications requiring a compact design and a high torque-to-weight ratio. They are capable of achieving positioning accuracy of less than 1 arc minute and repeatability of + / - 5 arc seconds without the benefit of output stage feedback.

[0005] Conventional designs for harmonic drive gearing involve a flexspline with two fewer teeth than a circular spline and an elliptical wave generator designed to cause the flexspline teeth to mesh with the circular spline teeth in two regions (diametrically opposed and corresponding to the major axis of the ellipse). The minor axis of the wave generator is short enough to allow the flexspline teeth to completely disengage along the minor axis and to allow for a one-tooth length difference between the circular spline and the flexspline in the non-contact region. The torque capacity of the gear system is equal to the shear force required to cause the contacting teeth to fail. This, therefore, allows for a "ratcheting torque" under which the flexspline can slide one tooth relative to the circular spline. This increases the number of contacting teeth and, therefore, the torque capacity and torsional stiffness. However, this situation significantly increases the forces on the flexspline, significantly shortening its fatigue life. Furthermore, it throws the system off balance, significantly increasing noise and vibration, and reducing positioning accuracy.

[0006] U.S. Patent No. 3,906,527 discloses a harmonic drive gear assembly of this type. The harmonic drive gear assembly includes a spline having a top surface, a bottom surface, an outer surface, and an inner surface. The top surface and the bottom surface are axially spaced apart from each other. The outer surface and the inner surface extend annularly about a central axis and connect the top surface to the bottom surface. A plurality of spline teeth extend from the inner surface toward the central axis. A wave generator is rotatably disposed in the spline.

[0007] Therefore, there is a need to provide a harmonic drive that minimizes motor size, is adaptable to different vehicle architectures, is lightweight, and has low noise, vibration, and harshness (NVH). Summary of the Invention

[0008] The present invention provides a wave gear device that is lightweight and compact. The present invention also provides a wave gear device that is easy to assemble. The present invention further provides a wave gear device with reduced noise, vibration and harshness (NVH).

[0009] One aspect of the present invention provides a wave gear device. The wave gear device includes a spline having a top surface, a bottom surface, an outer surface, and an inner surface, the top surface and the bottom surface being axially spaced apart from each other, and the outer surface and the inner surface extending annularly about a central axis and located between the top surface and the bottom surface, with a plurality of spline teeth extending from the inner surface toward the central axis. The wave gear device also includes: a wave generator rotatably disposed in the spline and including an eccentric core; and a belt assembly extending around the wave generator. The belt assembly includes an annular base defining a plurality of belt teeth extending radially outward and configured to engage the spline teeth, whereby the total number of the belt teeth is less than the total number of the spline teeth. The wave gear device further includes a bearing assembly disposed between the wave generator and the belt assembly and including a plurality of needles, each of the plurality of needles extending parallel to the central axis; and an output member engaging the belt assembly and defining a recess that accommodates the wave generator and the belt assembly.

[0010] Another aspect of the present invention is to provide a wave gear device. The wave gear device includes a spline having a top surface, a bottom surface, an outer surface, and an inner surface, wherein the top surface and the bottom surface are axially spaced apart from each other, and the outer surface and the inner surface extend annularly about a central axis and are located between the top surface and the bottom surface, with a plurality of spline teeth extending from the inner surface toward the central axis. The wave gear device also includes a wave generator rotatably disposed in the spline and including an eccentric core; and a belt assembly extending around the wave generator, the belt assembly including a back sleeve and an annular base defining a plurality of belt teeth extending radially outward to engage the spline teeth, whereby the total number of the belt teeth is less than the total number of the spline teeth. The wave gear device also includes a bearing assembly disposed between the wave generator and the belt assembly; and an output member engaging the belt assembly and defining a recess for accommodating the wave generator and the belt assembly.

[0011] Another aspect of the present invention provides a wave gear device. The wave gear device includes a spline having a top surface, a bottom surface, an outer surface, and an inner surface, the top surface and the bottom surface being axially spaced apart from each other, the outer surface and the inner surface extending annularly about a central axis and positioned between the top surface and the bottom surface, a plurality of spline teeth extending from the inner surface toward the central axis. The wave gear device also includes a wave generator rotatably disposed in the spline and including an eccentric core defining an indentation; and a belt assembly extending around the wave generator, the belt assembly including an annular base defining a plurality of belt teeth extending radially outward to engage the spline teeth, whereby the total number of the belt teeth is less than the total number of the spline teeth. The wave gear device further includes a clad sleeve surrounding the eccentric core of the wave generator, the clad sleeve including a tab configured to engage a notch in the eccentric core to prevent relative rotation between the eccentric core and the clad sleeve; a bearing assembly disposed between the clad sleeve and the belt assembly; and an output member engaging the belt assembly and defining a recess that accommodates the wave generator and the belt assembly. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Other advantages of the present invention will be readily appreciated as they become better understood by reference to the following detailed description considered in conjunction with the accompanying drawings, in which:

[0013] Figure 1 is a top perspective view of a wave gear device constructed according to one embodiment of the present invention;

[0014] Figure 2 This is an exploded view of the wave gear unit;

[0015] Figure 3 A wave gear device according to an embodiment of the present invention is Figure 1 a cross-sectional perspective view of the assembly along line 3-3;

[0016] Figure 4 is a perspective view of a belt used in a wave gear device according to one embodiment of the present invention;

[0017] Figure 5 yes Figure 4 A partial enlarged view of the belt in ;

[0018] Figure 6 is a top perspective view of a wave gear device constructed in accordance with an alternative embodiment of the present invention;

[0019] Figure 7 yes Figure 6 A bottom perspective view of a wave gear device;

[0020] Figure 8 is a cross-sectional perspective view of a damper comprising a vehicle lifting system including a wave gear arrangement;

[0021] Figure 9 is an exploded view of a wave gear device constructed according to another embodiment of the present invention;

[0022] Figure 10 It is a bottom perspective view of the wave gear device;

[0023] Figure 11 It is a top perspective view of the wave gear device;

[0024] Figure 12 is an exploded view of a wave gear device constructed according to another embodiment of the present invention;

[0025] Figure 13 is an exploded view of a chain for a wave gear device according to aspects of the present disclosure;

[0026] Figure 14 is an exploded view of a wave gear device constructed according to another embodiment of the present disclosure;

[0027] Figure 15 is a perspective view of a wave generator according to aspects of the present disclosure; and

[0028] Figure 16 is a perspective view of a chain assembly for a wave gear device according to aspects of the present disclosure. DETAILED DESCRIPTION

[0029] Referring to the drawings, wherein like reference numerals designate corresponding parts throughout the several views, Figure 1 1. A wave gear arrangement 20 constructed in accordance with one embodiment of the present invention is generally shown in FIG.

[0030] like Figures 1 to 3As best shown, the wave gear device 20 includes a spline 22, a wave generator 24, a belt assembly 26, and an output member 28. The spline 22 has a top surface 30, a bottom surface 32, an outer surface 34, and an inner surface 36. The top surface 30 and the bottom surface 32 are parallel to each other and spaced apart from each other. The outer surface 34 and the inner surface 36 extend annularly about the central axis A and connect the top surface 30 and the bottom surface 32. The spline 22 includes a projection 38 located on the inner surface 36 and adjacent to the top surface 30, radially inward toward the central axis A, and annular about the central axis A. The projection 38 also extends along the inner surface 36 from the top surface 30 toward the bottom surface 32 to a distal end 40 spaced apart from the bottom surface 32. The projection 38 includes a plurality of spline teeth 42 extending radially inward from the inner surface 36 and along the projection 38 and circumferentially spaced apart from each other. According to one embodiment of the present invention, each of the plurality of spline teeth 42 has a substantially trapezoidal shape to present a first tooth profile.

[0031] The wave generator 24 is rotatably disposed in the spline 22 to engage with the spline 22. The wave generator 24 has a base 44 and a top 46. The base 44 has a generally elliptical shape and extends about a central axis A. The top 46 has a generally circular shape and extends outward from the base 44. A protrusion 48 extends outward from the top 46 parallel to the central axis A. The wave generator 24 defines a bore 50 extending through the top 46 and the base 44 along the central axis A. The belt assembly 26 extends around the base 44. The belt assembly 26 includes an annular base defining a plurality of belt teeth 52. The plurality of belt teeth 52 extend radially outward and are configured to engage with the spline teeth 42. In other words, the belt teeth 52 diametrically mesh with the spline teeth 42, whereby the total number of belt teeth 52 is less than the total number of spline teeth 42. According to an embodiment of the present invention, the difference between the total number of spline teeth 42 and the total number of belt teeth 52 is equal to 2 or 4. Because the total number of teeth 52 is less than the total number of spline teeth 42, this creates a reduction ratio between the rotational speed of the rotor and the rotational speed of the wave generator 24. In some embodiments, the annular base comprises a band of elastic material, such as an elastomeric material, which can be formed into a single continuous loop. Alternatively or additionally, the annular base can comprise a chain having a plurality of links, each link defining one of the teeth.

[0032] The output member 28 defines a recess 54 for accommodating the wave generator 24 and the belt assembly 26. The output member 28 engages the belt assembly 26. Thus, in response to rotational motion from the wave generator 24, the output member 28 rotates in the same direction as or opposite to the wave generator 24. Accommodating the wave generator 24 in the recess 54 of the output member 28 makes the wave gear device 20 more compact and allows for easy assembly of the wave gear device 20. The output member 28 includes a generally circular base plate 56 disposed on the central axis A and in abutting relation with the belt assembly 26 and the wave generator 24. The base plate 56 has an outer periphery 58 extending annularly about the central axis A. A wall 60 extends axially from the base plate 56 along the outer periphery 58 and is configured to engage the spline 22. The wall 60 includes a plurality of spaced-apart wall teeth 62 that extend radially toward the central axis A to engage the belt assembly 26, allowing the output member 28 to rotate at the same speed as the belt assembly 26 and the wave generator 24. The wall teeth 62 have a second tooth profile that is different from the first tooth profile of the spline teeth 42 to allow the output member 28 to rotate at the same speed as the belt and wave generator 24. According to one embodiment of the present invention, each of the wall teeth 62 has a generally triangular shape to exhibit the second tooth profile. The output member 28 includes a collar 64 that extends annularly outward from the base plate 56 about the central axis A to define a recess 54 extending about the central axis A between the collar 64, the base plate 56, and the wall 60. The collar 64 extends through the bore 50 and defines a hole 66 that extends along the central axis A.

[0033] Figures 4 to 7 An alternative embodiment of the present invention is illustrated. Figures 4 and 5 As best illustrated, each of the plurality of teeth 52 includes a metal insert 68 disposed therein to provide reinforcement and rigidity to the teeth 52. The metal insert 68 extends through the belt assembly 26 along the central axis A to an insert end 70 spaced apart from the belt assembly 26. Figures 6 and 7 As best illustrated, the base plate 56 defines an aperture 72 disposed about the central axis A to receive the insert end 70 to couple the output member 28 to the wave generator 24 and the belt assembly 26 for rotation therewith.

[0034] In operation, a rotational motion or torque load input is first introduced into the wave gear device 20 via the wave generator 24. It should be understood that this input can be applied via an electric motor or any other source of rotational motion. According to one embodiment of the present invention, the protrusion 48 of the wave generator 24 can be coupled to an electric motor or source of rotational motion to allow the wave generator 24 to introduce rotational motion into the wave gear device 20. As the wave generator 24 rotates within the spline 22, the belt assembly 26 deforms in response to the motion of the wave generator 24 and slides around the wave generator 24. As the belt assembly 26 slides around the wave generator 24, the upper half of the belt teeth 52 mesh with the spline teeth 42. Because the total number of belt teeth 52 is less than the total number of spline teeth 42, the rotational speed of the wave generator 24 is reduced as the wave generator 24 rotates within the spline 22. Furthermore, as the belt assembly 26 slides around the wave generator 24, the lower half of the belt teeth 52 mesh with the wall teeth 62. Because the total number of wall teeth 62 is equal to the total number of belt teeth 52, the output member 28 rotates in the same direction as or opposite to the direction of rotation of the wave generator 24. Therefore, as the belt teeth 52 engage both the spline teeth 42 and the wall teeth 62, shear forces are generated due to the introduction of torque loads. According to one embodiment of the present invention, the belt assembly 26 can be made of an elastomeric material (e.g., rubber). Since the belt assembly 26 is made of an elastomeric material, it can withstand shear forces generated by rotational motion or the introduction of torque loads, thereby reducing the noise, vibration, and harshness (NVH) levels of the wave gear device.

[0035] Another aspect of the present invention provides a vehicle lifting system 74. Figure 8 1 , a vehicle lift system 74 constructed in accordance with one embodiment of the present invention is generally illustrated.

[0036] The vehicle lift system 74 may be used in conjunction with the vehicle's dampers 76. It will be appreciated that the dampers 76 may be hydraulic dampers or magnetorheological (MR) dampers. Figure 8 As best illustrated in FIG. , the damper 76 includes a housing 78 having a generally cylindrical shape disposed on a central axis A. The housing 78 extends between a first end 80 and a second end 82 and defines fluid chambers 84, 86 extending therebetween for containing a working fluid. It will be appreciated that the working fluid may be a hydraulic fluid or an MR fluid. A mounting ring 88 having a generally circular shape is attached to the first end 80 of the housing 78 for attachment to a vehicle.

[0037] A piston 90, slidably disposed in fluid chambers 84, 86, divides fluid chambers 84, 86 into a compression chamber 84 and a rebound chamber 86. Compression chamber 84 extends between first end 80 of housing 78 and piston 90. Rebound chamber 86 extends between second end 82 of housing 78 and piston 90. A rod guide 92, disposed in rebound chamber 86, is attached to second end 82 of piston 90 to close fluid chambers 84, 86. A piston rod 94 extends along central axis A through rod guide 92 and into rebound chamber 86, and is attached to piston 90 to move piston 90 along central axis A between a compression stroke and a rebound stroke. The compression stroke is defined as movement of piston rod 94 and piston 90 toward first end 80 of housing 78. The rebound stroke is defined as movement of piston rod 94 and piston 90 toward second end 82 of housing 78.

[0038] Actuator 96 is attached to housing 78 to change the height of the vehicle, allowing the vehicle to adapt to different driving modes. Actuator 96 includes a threaded shaft 98, a threaded bushing 100, and a plurality of bushing ball bearings 102. Threaded shaft 98, which has a generally tubular shape, is attached to the outer surface of housing 78 and extends annularly about central axis A between a first open end 104 and a second open end 106. First open end 104 is positioned adjacent to first end 80 of housing 78 and attached to housing 78. Second open end 106 is axially spaced apart from first end 80 and attached to housing 78. A generally circular snap ring 108 is positioned adjacent to first open end 104 between threaded shaft 98 and housing 78 and extends about central axis A to secure threaded shaft 98 to housing 78. In other words, threaded shaft 98 is fixed to housing 78 and extends annularly about housing 78. Threaded bushing 100, disposed about threaded shaft 98, is rotatable about central axis A and axially movable along threaded shaft 98. The threaded bushing 100 extends between a major end 110 and a minor end 112. The major end 110 of the threaded bushing 100 is positioned adjacent to a first open end 104 of the threaded shaft 98. The minor end 112 of the threaded bushing 100 is positioned axially spaced from the second open end 106. A plurality of bushing ball bearings 102 are positioned between the threaded bushing 100 and the threaded shaft 98 to allow the threaded bushing 100 to rotate about the threaded shaft 98 and to convert the rotational motion of the threaded bushing 100 into axial motion along the threaded shaft 98.

[0039] A cover 114 having a generally tubular shape is disposed about a central axis A and radially spaced from the threaded bushing 100. The cover 114 extends along the central axis A between a proximal end 116 and a distal end 118, wherein the proximal end 116 is located adjacent the main end 110 of the threaded bushing 100 and the distal end 118 is located adjacent the secondary end 112 of the threaded bushing 100. The cover 114 and the threaded bushing 100 together define a compartment 120 extending about the central axis A between the cover 114 and the threaded bushing 100. An end plate 122 extends radially inward from the proximal end 116 to the main end 110 and is in abutting relation with the main end 110. A plurality of fasteners 124 are disposed adjacent the proximal end 116 of the cover 114 and extend through the cover 114 and the end plate 122 to attach the end plate 122 to the cover 114. A spring seat 126 disposed in the compartment 120 extends between the distal end 118 of the cover 114 and the secondary end 112 of the threaded bushing 100. The spring seat 126 is attached to the cover 114 and the threaded bushing 100 to accommodate a coil spring (not shown) that extends helically around the housing 78. A plurality of bolts 128 are disposed adjacent the distal end 118 of the cover 114 and extend through the cover 114 and the spring seat 126 to attach the spring seat 126 to the cover 114. A plurality of cover ball bearings 128 are disposed between the spring seat 126 and the threaded bushing 100 to allow the threaded bushing 100 to rotate about the spring seat 126.

[0040] An electric motor 130 is disposed in the compartment 120 and is coupled to the threaded bushing 100 for providing rotational motion to the threaded bushing 100 so as to move the threaded bushing 100 axially along the threaded shaft 98 to raise and lower the height of the vehicle. In other words, the electric motor 130 initiates the rotational motion to raise and lower the height of the vehicle. The electric motor 130 includes a rotor 132 having a generally tubular shape, which is disposed adjacent to the auxiliary end 112 of the threaded bushing 100 and is rotatable about a central axis A. A main body 134 having a cylindrical shape is disposed about the rotor 132 and extends annularly about the central axis A. A pair of bobbins 136 axially spaced apart from each other and adjacent to the main body 134 extend annularly about the central axis A, sandwiching the main body 134 between the pair of bobbins 136. Each of the spools 136 includes a coil 138 extending about a central axis A that is electrically connected to a power source to provide current to the coil 138 , thereby generating a magnetic field to rotate the rotor 132 within the compartment 120 .

[0041] The wave gear device 20 is configured to be positioned in the compartment 120 and coupled to the main end 110 of the threaded shaft 98 and the rotor 132 to reduce the rotational speed of the rotor 132 and increase the torque of the electric motor 130 to rotate the threaded bushing 100 about the central axis A. According to one embodiment of the present invention, the spline 22 is provided in the compartment 120, adjacent to the rotor 132, and attached to the cover 114. The wave generator 24 is rotatably disposed in the spline 22 to engage with the electric motor 130 to transmit the rotational motion of the rotor 132 to the threaded shaft 98. A protrusion 48 extending outward from the top 46 of the wave generator 24 couples the wave generator 24 to the rotor 132 of the electric motor 130 for rotational motion therewith.

[0042] Output member 28 housing wave generator 24 and belt assembly 26 is coupled to threaded bushing 100 to transfer rotational motion of rotor 132 to threaded bushing 100. Output member collar 64 extends about central axis A and is coupled to threaded bushing 50 for rotation therewith.

[0043] During operation, to raise and lower the height of the vehicle, the electric motor 130 initiates rotational motion to the wave gear arrangement 20 via the rotor 132. In response to the rotational motion of the rotor 132, the wave generator 24, coupled to the rotor 132, rotates along with the rotor 132. Because the total number of belt teeth 52 is less than the total number of spline teeth 42, the wave generator 24 reduces the rotational speed of the rotor 132 as it rotates within the spline 22. Furthermore, because the wave generator 24 engages the output member 28, the output member 28 rotates along with the wave generator 24. Because the total number of wall teeth 64 equals the total number of belt teeth 52, the output member 28 can rotate at the same speed as the wave generator 24. Consequently, the threaded bushing 100 attached to the output member 28 rotates along with the output member 28 at the same rotational speed as the wave generator 24 and moves axially along the threaded shaft 98 to raise and lower the height of the vehicle.

[0044] Figures 9 to 11 A wave gear device 200 constructed according to another embodiment of the present invention is illustrated. The wave gear device 200 includes a spline 202, a wave generator 204, a belt assembly 206, and an output member 208. The spline 202 has a top surface 210, a bottom surface 212, an outer surface 214, and an inner surface 216. The top surface 210 and the bottom surface 212 are spaced apart from each other. The outer surface 214 and the inner surface 216 extend about a central axis A, connecting the top surface 210 and the bottom surface 212. The spline 202 includes a plurality of spline teeth 218 that extend radially inward from the inner surface 216 toward the central axis A and are circumferentially spaced apart from each other. According to an embodiment of the present invention, each of the plurality of spline teeth 218 can have a generally trapezoidal shape to present a first tooth profile.

[0045] Wave generator 204 is rotatably disposed within spline 202. Wave generator 204, having a generally annular shape, extends about central axis A. According to embodiments of the present invention, wave generator 204 may have an elliptical shape. Wave generator 204 defines a bore 220 extending through wave generator 204 along central axis A. Belt assembly 206 extends around wave generator 220. Belt assembly 206 includes an annular shape defining a plurality of belt teeth 222 that extend radially outward and are configured to engage with spline teeth 218. In other words, belt teeth 222 diametrically mesh with spline teeth 218, whereby the total number of belt teeth 222 is less than the total number of spline teeth 218. According to embodiments of the present invention, the difference between the total number of spline teeth 218 and the total number of belt teeth 222 is equal to 2 or 4. Because the total number of belt teeth 222 is less than the total number of spline teeth 218, this creates a reduction ratio between the rotational speed of the rotor and the rotational speed of wave generator 204. In some embodiments, the endless base comprises a band of elastic material which may be formed as a single-piece continuous loop.Alternatively or additionally, the endless base may comprise a chain having a plurality of links, each link defining one of said teeth.

[0046] The output member 208 defines a recess 224 for receiving the wave generator 204 and the belt assembly 206. The output member 208 engages the belt assembly 206, whereby, in response to rotational movement of the wave generator 204, the output member 208 rotates in the same direction as or in the opposite direction of the wave generator 204. Accommodating the wave generator 204 in the recess 224 of the output member 208 makes the wave gear device 200 more compact and allows for easy assembly of the wave gear device 200. The output member 208 includes a generally circular base plate 226 disposed on the central axis A and in abutting relation with the belt assembly 206 and the wave generator 204. The base plate 226 has a periphery 228 extending annularly about the central axis A. A wall 230 extends axially from the base plate 226 along the periphery 228 to engage the spline 202.

[0047] Wall 230 includes a plurality of spaced-apart wall teeth 232 extending radially toward central axis A to engage belt assembly 206 and allow output member 208 to rotate at the same speed as belt assembly 206 and wave generator 204. Wall teeth 232 have a second tooth profile that is different from the first tooth profile of spline teeth 218 to allow output member 208 to rotate at the same speed as belt assembly 206 and wave generator 204. According to an embodiment of the present invention, each of the plurality of wall teeth 232 has a generally triangular shape to exhibit the second tooth profile. Output member 208 includes a collar 234 positioned radially inward from wall 230 and extending annularly about central axis A to define a recess 224 extending about central axis A between collar 234, base plate 226, and wall 230. A plurality of connecting members 236 extend radially outward from collar 234 and couple to base plate 228 to connect collar 234 to base plate 226. The collar 234 extends through the bore 220 and defines an aperture 238 extending along the central axis A.

[0048] Each of the plurality of teeth 222 includes a metal insert 240 disposed therein to provide reinforcement and rigidity to the teeth 222. The metal insert 240 extends through the belt assembly 206 along the central axis A to an insert end 242 spaced apart from the belt assembly 206. The insert end 242 meshingly engages with the wall teeth 232 to transfer the rotational motion of the wave generator 204 to the output member 208.

[0049] The belt assembly 206 can be configured as a chain 244 including a plurality of links 246, each having a similar or identical configuration. The links 246 are connected to one another to form a continuous loop. Each of the links 246 defines a corresponding one of the belt teeth 222. The wave generator 204 can define a plurality of orifices 248 for coupling the wave generator 204 to a drive member, such as an electric motor. The collar 234 includes a plurality of engagement members 250 that are circumferentially spaced apart from one another and extend radially inward toward the central axis A to engage the shaft and transmit the rotational motion of the electric motor to the shaft. The outer surface 214 of the spline 202 defines a plurality of channels 252 extending from the top surface 210 to the bottom surface 212, the plurality of channels 252 being circumferentially spaced apart from one another.

[0050] In operation, an input of rotational motion or torque load is first introduced into the wave gear device 200 via the wave generator 204 via an electric motor or any other source of rotational motion. According to an embodiment of the present invention, the plurality of apertures 250 of the wave generator 204 can be coupled to an electric motor or source of rotational motion to allow the wave generator 204 to introduce rotational motion into the wave gear device 200. As the wave generator 204 rotates within the spline 202, the belt assembly 206 deforms in response to the motion of the wave generator 204 and slides around the wave generator 204. As the belt assembly 206 slides around the wave generator 204, the belt teeth 222 mesh with the spline teeth 218. Because the total number of belt teeth 222 is less than the total number of spline teeth 218, the rotational speed of the wave generator 204 decreases as the wave generator 204 rotates within the spline 202. Additionally, as the belt assembly 206 slides around the wave generator 204, the insert end 242 of the metal insert 240 meshes with the wall teeth 232. Because the total number of wall teeth 232 equals the total number of belt teeth 222, the output member 208 can rotate at the same speed as the wave generator 204.

[0051] Therefore, due to the engagement of the belt teeth 222 with both the spline teeth 218 and the wall teeth 232, shear forces are generated due to the introduction of torque loads. According to one embodiment of the present invention, the belt assembly 206 can be made of an elastomeric material (e.g., rubber). Since the belt assembly 206 is made of an elastomeric material, the belt assembly 206 can withstand the shear forces generated by the introduction of rotational motion or torque loads, thereby reducing the noise, vibration, and harshness (NVH) levels of the wave gear device 200.

[0052] Figure 12 A wave gear device 300 constructed according to another embodiment of the present disclosure is illustrated. The wave gear device 300 includes a spline 302, a wave generator 304, a belt assembly 306, and an output member 308. The spline 302 has a top surface 310, a bottom surface 312, an outer surface 314, and an inner surface 316. The top surface 310 and the bottom surface 312 are spaced apart from each other. The outer surface 314 and the inner surface 316 extend about a central axis A to connect the top surface 310 and the bottom surface 312. The spline 302 includes a plurality of spline teeth 318 that extend radially inward from the inner surface 316 toward the central axis A and are circumferentially spaced apart from each other. According to an embodiment of the present disclosure, each of the plurality of spline teeth 318 can have a generally trapezoidal shape to present a first tooth profile.

[0053] The wave generator 304 is rotatably disposed in the spline 302. The wave generator 304 has a generally annular shape and extends about a central axis A. According to an embodiment of the present disclosure, the wave generator 304 may have an elliptical shape. The wave generator 304 defines a bore 320 extending through the wave generator 304 along the central axis A. The belt assembly 306 extends around the wave generator 304.

[0054] The belt assembly 306 can be configured as a chain 344 comprising a plurality of links 345, each having a similar or identical configuration. The links 345 are connected to one another to form a continuous loop. Each of the links 345 includes a support plate 346 facing the center of the continuous loop and two first tubular portions 347 attached to the support plate and facing outward from the center of the continuous loop. The first tubular portions 347 are coaxial with one another and spaced apart by a distance approximately equal to the axial length of each first tubular portion 347. Each link 345 also includes two second tubular portions 348 attached to the support plate and facing outward from the center of the continuous loop in an opposite direction from the first tubular portions 347. The second tubular portions 348 are coaxial with one another and spaced apart by a distance approximately equal to the axial length of each second tubular portion 348.

[0055] The first tubular portion 347 of a given one of the links 345 in the chain 344 is configured to interweave with the second tubular portion 348 of the next adjacent link 345 in the chain 344. A link pin 340 extends through the first tubular portion 347 of one of the links 345 and the interwoven second tubular portion 348 of the next adjacent link 345, thereby coupling the two links 345 of the chain together. The link pin 340 also serves to provide reinforcement and rigidity to the belt teeth 322. Each stack of connected first and second tubular portions 347, 348 defines the belt teeth 322 of the chain 344. Thus, the belt teeth 322 extend radially outward to engage with the spline teeth 318. That is, the belt teeth 322 mesh diametrically with the spline teeth 318, resulting in a total number of belt teeth 322 being less than the total number of spline teeth 318. Figure 13 An exploded view of the chain 344 is shown.

[0056] According to one embodiment of the present invention, the difference between the total number of spline teeth 318 and the total number of belt teeth 322 is equal to 2 or 4. Because the total number of belt teeth 322 is less than the total number of spline teeth 318, this can create a reduction ratio between the rotational speed of the rotor and the rotational speed of the wave generator 304.

[0057] The output member 308 defines a recess 324 for accommodating the wave generator 304 and the belt assembly 306. The output member 308 engages the belt assembly 306, whereby, in response to rotational motion from the wave generator 304, the output member 308 rotates in the same direction as or opposite to the wave generator 304. Accommodating the wave generator 304 in the recess 324 of the output member 308 makes the wave gear device 300 more compact and allows for easy assembly of the wave gear device 300. The output member 308 includes a generally circular base plate 326 disposed on the central axis A and in abutting relation with the belt assembly 306 and the wave generator 304. The base plate 326 has a periphery 328 extending annularly about the central axis A. A wall 330 extends outwardly from the periphery 328 about the central axis A to engage the spline 302. Wall 330 includes a plurality of spaced-apart wall teeth 332 extending radially outward from wall 330 toward central axis A to engage with belt assembly 306 and allow output member 308 to rotate at the same speed as belt assembly 306 and wave generator 304. Wall teeth 332 may have a second tooth profile that is different from the first tooth profile of spline teeth 318 to allow output member 308 to rotate at the same speed as belt assembly 306 and wave generator 304. According to an embodiment of the present disclosure, each wall tooth 332 of the plurality of wall teeth 332 has a generally triangular shape to exhibit the second tooth profile. Output member 308 defines a through-hole 334 having a generally circular shape, located on central axis A, and communicating with bore 320.

[0058] The wave generator 304 can define a plurality of apertures 350 for coupling the wave generator 304 to a drive member, such as an electric motor. The base plate 326 includes a plurality of engagement members 352 that are circumferentially spaced apart from one another and extend radially inward toward the central axis A to engage the shaft and transmit the rotational motion of the electric motor to the shaft. The wave generator 304 includes a flange 352 positioned adjacent the apertures 348, extending radially outward from the wave generator 304 and annularly about the central axis A. The flange 352 abuts the spline 302 to sandwich the spline 302 between the output member 308 and the wave generator 304 and prevent axial movement of the spline 302.

[0059] In operation, an input of rotational motion or torque load is first introduced into the wave gear device 300 via the wave generator 304 via an electric motor or any other source of rotational motion. According to an embodiment of the present disclosure, the plurality of apertures 350 of the wave generator 304 can be coupled to an electric motor or source of rotational motion, thereby allowing the wave generator 304 to introduce rotational motion into the wave gear device 300. As the wave generator 304 rotates within the spline 302, the belt assembly 306 deforms in response to the motion of the wave generator 304 and slides around the wave generator 304. As the belt assembly 306 slides around the wave generator 304, the belt teeth 322 mesh with the spline teeth 318. Because the total number of belt teeth 322 is less than the total number of spline teeth 318, the rotational speed of the wave generator 304 is reduced as the wave generator 304 rotates within the spline 302. Furthermore, as the belt assembly 306 slides around the wave generator 304, the belt assembly 306 also meshes with the wall teeth 332. Because the total number of wall teeth 332 is equal to the total number of belt teeth 322, the output member 308 rotates in the same direction as or opposite to the direction of rotation of the wave generator 304. Therefore, since the belt teeth 322 engage both the spline teeth 318 and the wall teeth 332, shear forces are generated due to the introduction of torque loads. According to one embodiment of the present disclosure, the belt assembly 306 can be made of an elastomeric material (e.g., rubber). By making the belt assembly 306 of an elastomeric material, the belt assembly 206 can withstand shear forces generated by rotational motion or the introduction of torque loads, thereby reducing the noise, vibration, and harshness (NVH) levels of the wave gear device 300.

[0060] Figure 14 is an exploded view of a wave gear device 420 constructed in accordance with another embodiment of the present disclosure. Figure 14 The wave gear device 420 includes a wave generator 424 and a belt assembly 426 configured to wrap around and rotate around the wave generator 424. The wave gear device 420 also includes a top washer 428 that covers the belt assembly 426 to prevent the belt assembly 426 from moving away from the wave generator 424 in the axial direction. The wave generator 424 can be connected to the Figure 2 The wave generator assembly 26 of the wave gear device 20 functions similarly, and the belt assembly 426 can be used with Figure 2 The belt assembly 26 of the wave gear arrangement 20 functions similarly.

[0061] The wave generator 424 includes an eccentric core 430 having an outer wall 432 with an elliptical profile. The eccentric core 430 can be made of molded plastic. However, other materials, such as metal or composite materials, can be used. The eccentric core 430 defines two notches 434 on opposite sides of the outer wall 432, near its axial ends. The wave generator 424 also includes a cladding sleeve 440 made of a hard material, such as steel. The cladding sleeve 440 has a hollow, elongated cylindrical shape configured to cover the outer wall 432 of the eccentric core 430. The cladding sleeve 440 defines a flat outer surface 442 and two radially inwardly extending tabs 444. The tabs 444 of the cladding sleeve 440 are configured to engage corresponding notches in the notches 434 in the eccentric core 430 to retain the cladding sleeve 440 on the eccentric core 430 and prevent relative rotation therebetween.

[0062] The wave generator 424 also includes a bearing assembly 450 having a retainer 452 and a plurality of needles 454. Each of the needles 454 extends parallel to the axis of the eccentric core 430 and is spaced apart from one another and held in place by the retainer 452. The bearing assembly 450 is configured to extend around the flat outer surface 442 of the cladding sleeve 440. The bearing assembly 450 can be flexible to conform to the shape of the outer wall 432 of the eccentric core 430 as the belt 460 rotates around the wave generator 424.

[0063] The belt assembly 426 includes a belt 460 of an elastic material (e.g., rigid polyurethane) disposed around a support sleeve 462 of a rigid material (e.g., steel). The support sleeve 462 can be formed as a hollow cylinder with thin sidewalls. As the belt 460 rotates around the wave generator 424, the support sleeve 462 can be flexible to conform to the shape of the outer wall 432 of the eccentric core 430. In some embodiments, the elastic material of the belt 460 can be overmolded onto the support sleeve 462. The elastic material of the belt 460 can be attached to the support sleeve 462 by other means (e.g., using a friction fit, welding, using an adhesive, etc.).

[0064] In operation, the bearing assembly 450 may be sandwiched between the cladding sleeve 440 of the wave generator 424 and the support sleeve 462 of the belt assembly 426 , with the needle 454 rolling therebetween to provide a smooth fit with relatively low friction between the belt assembly 426 and the wave generator 424 .

[0065] Figure 15 is a perspective view of a wave generator 424 according to one aspect of the present disclosure.

[0066] Figure 164 is a perspective view of a chain assembly 470 according to one aspect of the present disclosure. The chain assembly 470 includes a chain 344 disposed about a support sleeve 462. The chain assembly 470, when used in conjunction with a wave generator 424 having a bearing assembly 450, can provide additional efficiency gains and / or load handling capabilities.

[0067] A wave gear device includes a spline having a top surface, a bottom surface, an outer surface, and an inner surface, the top surface and the bottom surface being axially spaced from each other, the outer surface and the inner surface extending annularly about a central axis and located between the top surface and the bottom surface, a plurality of spline teeth extending from the inner surface toward the central axis. The wave gear device also includes a wave generator rotatably disposed in the spline and including an eccentric core; and a belt assembly extending around the wave generator. The belt assembly includes an annular base defining a plurality of belt teeth extending radially outward and configured to engage the spline teeth, whereby the total number of the belt teeth is less than the total number of the spline teeth. The wave gear device also includes a bearing assembly disposed between the wave generator and the belt assembly and including a plurality of needles, each of the plurality of needles extending parallel to the central axis; and an output member engaging the belt assembly and defining a recess for accommodating the wave generator and the belt assembly.

[0068] In some embodiments, the endless base may comprise a band of elastic material. In some embodiments, the endless base comprises a chain having a plurality of links, each link of the plurality of links defining one of the teeth.

[0069] In some embodiments, the belt assembly further comprises a support sleeve, and wherein the plurality of needles of the bearing assembly are configured to roll along the support sleeve.

[0070] In some embodiments, the output member includes a base plate disposed in abutting relationship with the belt assembly and the wave generator, and the base plate includes a periphery extending annularly about the central axis.

[0071] In some embodiments, the wave gear device may further include a wall extending axially from the base plate along the periphery and configured to engage with the spline, wherein the wall may define a plurality of wall teeth spaced apart from each other, the plurality of wall teeth extending radially toward the central axis to engage with the belt assembly.

[0072] A wave gear device includes a spline having a top surface, a bottom surface, an outer surface, and an inner surface, the top surface and the bottom surface being axially spaced from each other and extending annularly about a central axis and located between the top surface and the bottom surface, with a plurality of spline teeth extending from the inner surface toward the central axis. The wave gear device also includes a wave generator rotatably disposed in the spline and including an eccentric core; and a belt assembly extending around the wave generator, the belt assembly including a support sleeve and an annular base defining a plurality of belt teeth extending radially outward to engage the spline teeth, whereby the total number of the belt teeth is less than the total number of the spline teeth. The wave gear device also includes a bearing assembly disposed between the wave generator and the belt assembly; and an output member engaging the belt assembly and defining a recess for accommodating the wave generator and the belt assembly.

[0073] In some embodiments, the support sleeve is made of steel.In some embodiments, the support sleeve is formed as a hollow cylinder.

[0074] In some embodiments, the endless base comprises a band of elastic material. In some embodiments, the band assembly comprises the band of elastic material overmolded onto the support sleeve. In some embodiments, the endless base comprises a chain having a plurality of links, each of the plurality of links defining one of the belt teeth.

[0075] In some embodiments, the output member includes a base plate disposed in abutting relationship with the belt assembly and the wave generator, and the base plate has a periphery extending annularly about the central axis.

[0076] In some embodiments, the wave gear device further includes a wall extending axially from the base plate along the periphery and configured to engage the spline, and the wall defines a plurality of wall teeth spaced apart from each other, the plurality of wall teeth extending radially toward the central axis to engage with the belt assembly.

[0077] Another aspect of the present invention provides a wave gear device. The wave gear device includes a spline having a top surface, a bottom surface, an outer surface, and an inner surface, the top surface and the bottom surface being axially spaced apart from each other, and the outer surface and the inner surface extending annularly about a central axis and located between the top surface and the bottom surface, with a plurality of spline teeth extending from the inner surface toward the central axis. The wave gear device also includes a wave generator rotatably disposed in the spline and including an eccentric core defining a recess; and a belt assembly extending around the wave generator, the belt assembly including an annular base defining a plurality of belt teeth extending radially outward to engage the spline teeth, whereby the total number of the belt teeth is less than the total number of the spline teeth. The wave gear device also includes a cladding sleeve surrounding the eccentric core of the wave generator, the cladding sleeve including a tab configured to engage a recess in the eccentric core to prevent relative rotation between the eccentric core and the cladding sleeve; a bearing assembly disposed between the cladding sleeve and the belt assembly; and an output member engaging the belt assembly and defining a recess that accommodates the wave generator and the belt assembly.

[0078] In some embodiments, the notch is one of a plurality of notches in the eccentric core, and wherein the tab is one of a plurality of tabs, each tab of the plurality of tabs being configured to engage a corresponding one of the plurality of notches in the eccentric core. In some embodiments, the bearing assembly includes a plurality of needles configured to roll along the cladding sleeve.

[0079] In some embodiments, the belt assembly further comprises a support sleeve, and wherein the plurality of needle-like members of the bearing assembly are configured to roll along the support sleeve. In some embodiments, the endless base comprises a band of elastic material. In some embodiments, the endless base comprises a chain having a plurality of links, each of the plurality of links defining one of the belt teeth.

[0080] Obviously, in light of the above teachings, many modifications and variations of the present invention are possible, and these modifications and variations may be implemented in ways other than those specifically described while remaining within the scope of the appended claims. These foregoing descriptions should be interpreted as covering any combination in which the novel features of the present invention are put to use.

[0081] This application claims priority to U.S. provisional patent application serial number 63 / 228,971 filed on August 3, 2021.

Claims

1. A wave gear device, comprising: a spline having a top surface, a bottom surface, an outer surface, and an inner surface, the top surface and the bottom surface being axially spaced from one another and the outer surface and the inner surface extending annularly about a central axis and located between the top surface and the bottom surface, a plurality of spline teeth extending from the inner surface toward the central axis; a wave generator rotatably disposed in the spline and comprising an eccentric core; a belt assembly extending about the wave generator, the belt assembly including an annular base defining a plurality of belt teeth extending radially outward and configured to engage the spline teeth, whereby a total number of the belt teeth is less than a total number of the spline teeth; a cladding sleeve surrounding the eccentric core of the wave generator; a bearing assembly disposed between the wave generator and the belt assembly and comprising a plurality of needles, each needle of the plurality of needles extending parallel to the central axis, wherein the belt assembly further comprises a support sleeve, and wherein the plurality of needles of the bearing assembly are configured to roll between the support sleeve and the cladding sleeve to provide a smooth fit; and An output member engages the belt assembly and defines a recess that receives the wave generator and the belt assembly.

2. The wave gear device according to claim 1, wherein: The annular base includes a band of elastic material.

3. The wave gear device according to claim 1, wherein: The endless base includes a chain having a plurality of links, each of the plurality of links defining one of the teeth.

4. The wave gear device according to claim 1, wherein: The output member includes a base plate disposed in abutting relationship with the belt assembly and the wave generator and having a periphery extending annularly about the central axis.

5. The wave gear arrangement of claim 4, further comprising a wall extending axially from the base plate along the periphery and configured to engage the spline, in, The wall defines a plurality of wall teeth spaced apart from one another and extending radially toward the central axis for engagement with the belt assembly.

6. The wave gear device according to claim 1, wherein: The supporting sleeve is made of steel.

7. The wave gear device according to claim 1, wherein: The supporting sleeve is formed as a hollow cylinder.

8. The wave gear device according to claim 2, wherein: The strap assembly includes the strap of elastic material overmolded onto the support sleeve.

9. A wave gear device, comprising: a spline having a top surface, a bottom surface, an outer surface, and an inner surface, the top surface and the bottom surface being axially spaced from one another and the outer surface and the inner surface extending annularly about a central axis and located between the top surface and the bottom surface, a plurality of spline teeth extending from the inner surface toward the central axis; a wave generator rotatably disposed in the spline and including an eccentric core defining a recess; a belt assembly extending around the wave generator, the belt assembly including an annular base defining a plurality of belt teeth extending radially outwardly to engage the spline teeth, whereby a total number of the belt teeth is less than a total number of the spline teeth; a cladding sleeve surrounding the eccentric core of the wave generator, the cladding sleeve including a tab configured to engage the notch in the eccentric core to prevent relative rotation between the eccentric core and the cladding sleeve; a bearing assembly disposed between the cladding sleeve and the belt assembly, wherein the bearing assembly includes a plurality of needles configured to roll along the cladding sleeve, wherein the belt assembly further includes a support sleeve, and wherein the plurality of needles of the bearing assembly are configured to roll between the support sleeve and the cladding sleeve to provide a smooth fit; and An output member engages the belt assembly and defines a recess that receives the wave generator and the belt assembly.

10. The wave gear device according to claim 9, wherein: The notch is one of a plurality of notches in the eccentric core, and wherein the tab is one of a plurality of tabs, each tab of the plurality of tabs being configured to engage a corresponding one of the plurality of notches in the eccentric core.

11. The wave gear device according to claim 9, wherein: The annular base includes a band of elastic material.

12. The wave gear device according to claim 9, wherein: The endless base includes a chain having a plurality of links, each of the plurality of links defining one of the teeth.

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