Strain wave gearing

Abstract

This invention provides a harmonic gear device with a small and compact mechanism that can maintain the assembled state of the parts and requires little space. The harmonic gear device (1) comprises three parts: an internal gear (2), a cup-shaped external gear (3), and a harmonic generator (4); and a temporary fixing fixture (9). The temporary fixing fixture (9) is connected and fixed to the output shaft (6) of the external gear (3) by a temporary fixing bolt (10), and to the input shaft (5) of the cam plate (41) of the harmonic generator (4) by a temporary fixing center bolt (11). The temporary fixing fixture (9) engages with the output shaft (6) and the input shaft (5) to maintain the assembled state of the three parts (2, 3, 4). The harmonic gear device (1) eliminates the need for position adjustment of the three parts during motor assembly. After the harmonic gear device (1) has been assembled into the motor, the space required to install the harmonic gear device (1) can be reduced by removing the temporary fixing fixture (9) from the harmonic gear device (1).

Description

Technical Field

[0001] The present invention relates to a harmonic gear device provided to users in a unit state in which three parts, namely an internal gear, an external gear and a harmonic generator, are assembled. Prior Art

[0002] A harmonic gear system is basically composed of three parts: a rigid internal gear, a flexible external gear, and a harmonic generator. Assembly of a harmonic gear system involves attaching the harmonic generator to the motor shaft and then inserting the harmonic generator, already attached to the motor shaft, into the internally attached external gear. Furthermore, positioning of the installed harmonic generator, such as centering and axial positioning, is necessary. To simplify assembly at the user's site, the harmonic gear system is sometimes supplied as a pre-assembled unit with all three parts pre-adjusted.

[0003] Such unit products are disclosed in Patent Documents 1 and 2, for example. The harmonic gear unit described in Patent Document 1 features a sealed structure with an input shaft supported by a bearing mechanism to simplify assembly work with motors and other components. The bearing mechanism maintains the assembled state of the three components and prevents undesirable consequences such as positional displacement of the harmonic generator during product transport, which could damage other components such as the oil seal. [Prior Art Literature] [Patent Document]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2014-74450 [Patent Document 2] Japanese Utility Model Registration No. 3187367 Summary of the Invention

[0005] [Problems to be solved by the invention]

[0006] The harmonic gear unit, which is preassembled from three parts, incorporates support mechanisms such as bearings to maintain the assembled state of the three parts, particularly the assembly of the harmonic generator and the external gear. Furthermore, a coupling mechanism is incorporated to facilitate assembly to the motor shaft and other components. The incorporation of support and coupling mechanisms significantly increases the size and weight of the unitized harmonic gear unit, requiring additional installation space. This, in turn, presents challenges such as increased rotational loss and increased manufacturing costs, which must be addressed.

[0007] In view of this, the main object of the present invention is to provide a harmonic gear device having a small and compact structure that can maintain the assembled state of parts and can be constructed with a smaller installation space. [Methods for solving the problem]

[0008] To solve the above-mentioned problems, the harmonic gear device of the present invention is configured such that a temporary fixing jig is used to maintain the assembled state of the structural parts before assembling the device such as a motor, and the temporary fixing jig can be removed after being assembled into the device.

[0009] Furthermore, the harmonic gear device of the present invention is configured such that, in the axial direction of the harmonic gear device, if the side of the harmonic gear device that is assembled to the motor to be assembled is regarded as the input side, and the other side is regarded as the output side, then the assembly and removal of the temporary fixing jig and the assembly of the input shaft to the motor shaft can all be performed from the output side.

[0010] In addition, the present invention's harmonic gear device is configured such that a temporary fixing bolt for connecting a temporary fixing jig to the input shaft of the harmonic gear device is used to attach a shaft connecting and fixing bolt instead of a temporary fixing bolt, thereby connecting and fixing the input shaft of the harmonic gear device to the rotating shaft (motor shaft) of the device to be assembled.

[0011] In the harmonic gear device of the present invention, a temporary fixing jig is used to maintain the assembled state of the three components of the harmonic gear device, particularly the internal gear, external gear, and harmonic generator. This prevents the three components from shifting during transportation of the harmonic gear device, thus avoiding undesirable consequences such as unnecessary loads on other components such as the oil seal due to positional shifting.

[0012] Furthermore, when assembling the wave gear unit into the target device, the positional adjustment of the three parts is largely unnecessary, simplifying the assembly process. The temporary fixtures used to maintain the three parts in their assembled state are removed from the wave gear unit once it has been assembled into the target device. This reduces installation space, contributing to a more compact and compact device. Furthermore, since both the wave gear unit assembly and temporary fixture removal can be performed from a single direction, the assembly process is significantly more convenient.

[0013] Furthermore, the shaft-connecting bolts used to connect and secure the input shaft to the motor shaft being assembled can be installed instead of the temporary fixing bolts used to connect and secure the temporary fixing jig to the input shaft of the wave gear unit. This makes the coupling mechanism used to connect the input shaft to the motor shaft smaller and more compact. Simple diagram description

[0014] [Figure 1] (A) is a schematic longitudinal sectional view showing a harmonic gear device incorporating the present invention, and (B) is an explanatory diagram showing the meshing state of an internal gear and an external gear. [Figure 2] (A) is a schematic longitudinal sectional view of the wave gear unit with the temporary fixing jig removed, and (B) is a perspective view showing the input shaft. [Figure 3] (A) to (D) are illustrations showing the steps for removing the temporary fixing jig. Implementation Method

[0015] Referring to Figures 1 and 2 , an embodiment of a harmonic gearing device incorporating the present invention will be described. The harmonic gearing device 1 comprises a rigid internal gear 2; a flexible external gear 3, coaxially arranged inside the internal gear 2 and formed into a cup shape; a harmonic generator 4, coaxially arranged inside the external gear 3; an input shaft 5, coaxially fixed to the harmonic generator 4; an output shaft 6, coaxially fixed to the external gear 3; a main bearing 7, which supports the output shaft 6 (external gear 3) for relative rotation with the internal gear 2; and an end plate 8. The harmonic gearing device 1 also comprises a temporary fixing jig 9 for maintaining the internal gear 2, external gear 3, and harmonic generator 4, which have been assembled and positioned relative to each other, in their respective positions. The temporary fixing jig 9 is fastened to the output shaft 6 by a plurality of temporary fixing bolts 10 and to the input shaft 5 by a single temporary fixing center bolt 11. In the following description, in the direction along the central axis 1a of the wave gear device 1, that is, in the axial direction, the side where the end plate 8 is located is referred to as the input side of the axial direction, and the side where the temporary fixing jig 9 is located is referred to as the output side of the axial direction.

[0016] The internal gear 2 is a circular annular member with a rectangular cross-section, with internal teeth 21 formed on its circular inner circumference. The external gear 3 comprises a cylindrical body 32, which is flexible in the radial direction and has external teeth 31 that mesh with the internal teeth 21 of the internal gear 2; a diaphragm 33 extending radially inward from the rear end of the cylindrical body 32; and a rigid annular hub 34 formed on the inner circumference of the diaphragm 33. The harmonic generator 4 comprises a rigid annular cam plate 41; and a harmonic generator bearing 43 mounted on the elliptical outer circumference (non-circular outer circumference) of the cam plate 41. The harmonic generator 4 is embedded inside the cylindrical body 32 of the external gear 3, bending the cylindrical body 32 into an elliptical shape, causing the external teeth 31 to partially mesh with the internal teeth 21.

[0017] The input shaft 5 extends through the center hole of the cam plate 41 of the harmonic generator 4. The input shaft 5 is a hollow shaft with a disc-shaped flange 51 integrally formed on its outer circumference. The cam plate 41 of the harmonic generator 4 is coaxially connected and fixed to the outer circumference of the disc-shaped flange 51. Although the input shaft 5 is a separate component from the cam plate 41 in this example, the cam plate 41 and the input shaft 5 can also be formed as a single integral part.

[0018] The output shaft 6 is coaxially connected and fixed to the annular hub 34 of the externally toothed gear 3 from the output side. The output shaft 6 is a disc-shaped member with a center hole 61 of the same diameter as the center hole 35 of the hub 34. The main bearing 7 is located on the outer circumference of the output shaft 6. The main bearing 7 is formed of a cross roller bearing, with its inner ring 71 integrally formed with the output shaft 6. The inner ring 71 can also be manufactured as a separate component from the output shaft 6 and coaxially connected and fixed to the outer circumference of the output shaft 6. The outer ring 72 of the main bearing 7 is located on the output side of the internally toothed gear 2 and coaxially connected and fixed to the internally toothed gear 2. The rollers are rollably inserted into the raceway groove formed between the inner ring 71 (output shaft 6) and the outer ring 72. The gap between the inner ring 71 (output shaft 6) and the outer ring 72, which is open toward the output side, is sealed by the output-side oil seal 12. End plate 8 is located on the input side of internal gear 2 and is fixedly connected to it. The input-side end 52 of input shaft 5 passes through the center hole 81 of end plate 8 and protrudes toward the input side. The gap between the outer circumference of input shaft 5 and the inner circumference of the center hole of end plate 8 is sealed by an input-side oil seal 13.

[0019] The temporary fixing jig 9 is positioned on the output side of the output shaft 6. It comprises a cylindrical portion 91 sized to fit into the center hole 61 of the output shaft 6; and a disc-shaped flange 92 that radially expands outward from the output-side end of the cylindrical portion 91. The outer diameter of the flange 92 is approximately the same as that of the output shaft 6. The end surface of the flange 92 facing the output shaft 6 forms a stepped end surface 93, the inner circumference of which protrudes toward the output shaft 6. This stepped end surface 93 is formed to complement the stepped end surface 62 of the output shaft 6.

[0020] Bolt holes 94 for attaching temporary fixing bolts 10 are formed on the outer periphery of the flange of the temporary fixing jig 9. Bolt holes 94 are arranged circumferentially at regular (constant) angular intervals and extend axially through the outer periphery of the flange. In this example, bolt holes 94 are formed at two locations. Bolt locking holes 63 extending axially are formed in the outer periphery of the stepped end surface 62 of the output shaft 6 at locations corresponding to the bolt holes 94. The temporary fixing jig 9 is coaxially connected and fixed to the output shaft 6 by inserting the temporary fixing bolts 10 through the bolt holes 94 from the output side and locking them into the bolt locking holes 63.

[0021] The circular center hole 95 in the cylindrical portion 91 of the temporary fixing jig 9 serves as a bolt hole for inserting the temporary fixing center bolt 11 from the output side. The circular center hole 95 has a circular inner circumferential surface portion with a smaller diameter midway along its axial direction, forming an annular stepped surface 96 facing the output side and an annular stepped surface 97 facing the input side. The head of the temporary fixing center bolt 11 engages with the annular stepped surface 96. Furthermore, the output-side end portion 53 of the input shaft 5 is coaxially inserted into the circular center hole 95 from the input side. The center hole portion of the output-side end portion 53 serves as a bolt locking hole 55 into which the temporary fixing center bolt 11 is locked and secured. The temporary fixing jig 9 is coaxially connected and secured to the input shaft 5 by the temporary fixing center bolt 11, which is inserted through the circular center hole 95 from the output side and locked and secured in the bolt locking hole 55.

[0022] Here, the front end face 54 of the output-side end portion 53 of the input shaft 5 abuts against the annular stepped surface 97 (axial positioning surface) of the circular center hole 95 of the temporary fixing jig 9, thereby fixing the axial position of the input shaft 5. Furthermore, as shown in Figure 2(B), the outer circumferential surface 56 of the output-side end portion 53 of the input shaft 5 is formed into a D-shaped cutout shape with both radially opposite portions of the circular outer circumferential surface cut into flat surfaces. The inner circumferential surface 98 (rotational positioning surface) on the input side of the circular center hole 95 of the temporary fixing jig 9 is a D-shaped cutout shape complementary to the outer circumferential surface 56 of the input shaft 5. Both radially opposite portions of the circular inner circumferential surface protrude inwardly to form flat surfaces. This locking mechanism secures the rotational position of the input shaft 5.

[0023] By attaching and securing the temporary fixing jig 9 to the input shaft 5 and the output shaft 6 in this manner, the harmonic generator 4 assembled to the input shaft 5 is maintained in its fitted state within the externally toothed gear 3 assembled to the output shaft 6. This also maintains the meshing state between the externally toothed gear 3 and the internally toothed gear 2 facilitated by the harmonic generator 4. This maintains the assembled state of the three components during transport of the harmonic gear unit 1, preventing adverse consequences such as excessive loads on other components, such as the input-side oil seal 13, due to axial misalignment, eccentricity, or tilting. Furthermore, since the assembled state is maintained, assembly work into a target device, such as a motor, is simplified, eliminating the need for component position adjustment.

[0024] (Jig removal steps) 3(A) to 3(D) are explanatory diagrams showing the steps of removing the temporary fixing jig 9 when the wave gear device 1 is assembled with the temporary fixing jig 9 and transported to the installation location.

[0025] First, as shown in Figure 3(A), the harmonic gear device 1, with the temporary fixing jig 9 already attached, is assembled to the motor housing 101 of the motor 100 to be assembled. The end plate 8, which regulates the input-side end surface of the harmonic gear device 1, is positioned on the motor housing 101 (motor-side assembly flange). The harmonic gear device 1 is assembled to the motor housing 101 by inserting connecting bolts (not shown) through bolt holes 15 extending through the internal gear 2 forming the housing of the harmonic gear device 1, the outer ring 72 of the main bearing 7, and the end plate 8. The distal end of the motor shaft 102 is coaxially inserted into the center hole of the input-side end 52 of the input shaft 5 of the harmonic gear device 1. A bolt locking hole 105 is formed on the distal end surface of the motor shaft 102, into which a central connecting bolt 104, used to connect and secure the motor shaft 102 to the input shaft 5 of the harmonic gear device 1, is locked.

[0026] On the output side of the wave gear unit 1, the head of temporary fixing center bolt 11 is exposed from the output side within the circular center hole 95 of temporary fixing jig 9, which is already assembled on the output side of the wave gear unit 1. As shown in Figure 3(B), temporary fixing center bolt 11 is removed, releasing the connection between temporary fixing jig 9 and input shaft 5.

[0027] Next, the input shaft 5 of the wave gear device 1 is fastened to the motor shaft 102 using a shaft-connecting center bolt 104, replacing the temporary fixing center bolt 11. As shown in Figure 3(C), on the output side of the wave gear device 1, the shaft-connecting center bolt 104 is inserted through the circular center hole 95 of the temporary fixing jig 9 and into a bolt-locking hole 105 formed at the front end of the motor shaft 102. The input shaft 5 of the wave gear device 1 is coaxially connected and fixed to the motor shaft 102. As a result, the wave gear device 1 is assembled to the motor 100, with the temporary fixing jig 9 maintaining the assembled state of the three components. During assembly, there is no need to adjust the position of the external gear 3 or the harmonic generator 4.

[0028] After this, as shown in Figure 3(D), on the output side of the wave gear device 1, the temporary fixing bolts 10 securing the temporary fixing jig 9 to the output shaft 6 are loosened, and the temporary fixing jig 9 is removed from the output shaft 6 toward the output side. An O-ring groove 66 is formed on the output-side step end face 62 of the output shaft 6 of the wave gear device 1, and an O-ring 67 is inserted therein. A load-side member (not shown) is assembled to the output-side end face 65 of the output shaft 6 via the O-ring 67.

[0029] As described above, the present embodiment of the harmonic gearing device 1 maintains the assembled state of its components, including the internal gear 2, external gear 3, and harmonic generator 4, using a temporary fixing jig 9 before assembly to the motor 100. This eliminates the need to adjust the positions of these three components when assembling the harmonic gearing device 1 to the motor 100, simplifying assembly.

[0030] Because the harmonic gear device 1 does not require a bearing mechanism to maintain the position of the harmonic generator 4 on the external gear 3, it achieves a unit structure that easily reduces the inertia of the input shaft 5. The temporary fixing jig 9 used to maintain the assembled state is removed after the harmonic gear device 1 is assembled to the motor 100. This reduces the installation space required for the harmonic gear device 1, contributing to the overall miniaturization, compactness, and weight reduction of the device in which it is incorporated.

[0031] For example, in the input shaft 5, shown in Figure 2(B), which is assembled with the cam plate 41 (wave plug) of the harmonic generator 4, the output-side shaft end 53 protruding toward the output side is eliminated, making the input shaft 5 flatter and lighter (lower inertia). In this case, a recessed portion with a D-shaped inner surface of a specific depth is formed on the output-side end face of the input shaft 5. This is accomplished by forming a portion of the cylindrical portion 91 of the temporary fixing jig 9 with a D-shaped outer surface that fits within the recessed portion.

[0032] Furthermore, in this embodiment of the wave gear device 1, the input shaft 5 and the motor shaft 102 are connected and secured by a shaft-connecting center bolt 104, which is provided in place of the temporary center bolt 11. This facilitates a smaller and more compact wave gear device 1 compared to configurations employing shaft couplings such as shaft couplings or spline shafts.

[0033] Furthermore, the assembly of the wave gear device 1 to the motor 100 and the removal of the temporary fixing jig 9 can be performed from the same side (the output side) of the wave gear device 1. This facilitates assembly of the wave gear device 1 to the motor 100 and allows for easy automated assembly of the wave gear device 1 at the user's site.

[0034] Furthermore, the harmonic gear device 1 of this embodiment forms a sealed unit equipped with an input-side oil seal 13 and an output-side oil seal 12. This eliminates the need for sealing components (such as oil seals) on the motor 100 side of the assembly. Furthermore, the structure of the input shaft 5 of the harmonic generator 4 of the harmonic gear device 1 can be tailored to the shaft connection structure of the motor shaft 102.

[0035] 1: Harmonic gear device 1a: Central axis 2: Internal gear 3: External gear 4: Harmonic Generator 5: Input shaft 6: Output shaft 7: Main bearing 8: End plate 9: Temporary fixation fixture 10: Temporarily fix the bolts 11: Temporarily fix the center bolt 12: Output side oil seal 13: Input side oil seal 15: Bolt hole 21: Internal teeth 31: External teeth 32:Tubular body 33: Diaphragm 34: Wheel Hub 35: Center hole 41: Cam plate 43: Harmonic generator bearing 51: Disc-shaped flange 52: Input side shaft end 53: Output side shaft end 54: front end 55: Bolt locking hole 56: Outer surface 61: Center hole 62: Step difference end face 63: Bolt locking hole 65: Output side end face 66: O-ring groove 67:O-ring 71: Inner Ring 72: Outer Ring 81: Center hole 91: cylindrical part 92: flange 93: Step difference end face 94: Bolt hole 95: Circular center hole 96: Circular step surface 97: Circular step surface 98: Inner Surface 100: Motor 101: Motor housing 102: Motor shaft 104: Center bolt for shaft connection 105: Bolt locking hole

Claims

1. A harmonic gear device comprising: a rigid internal gear; a flexible external gear coaxially disposed inside the internal gear and forming a cup shape; a harmonic generator coaxially disposed inside the external gear; a main bearing supporting the external gear in a state of relative rotation with respect to the internal gear, the external gear comprising: a cylindrical body flexible in a radial direction and having external teeth that mesh with the internal teeth of the internal gear; a diaphragm extending radially inward from one end of the cylindrical body; a rigid hub formed on the inner periphery of the diaphragm; the harmonic generator comprising: a rigid cam plate having an input shaft; a harmonic generator bearing mounted on the non-circular outer peripheral surface of the cam plate; the harmonic generator being embedded inside the cylindrical body of the external gear, the cylindrical body being flexed radially to partially mesh the external teeth with the internal teeth; the main bearing comprising: An outer ring is coaxially fixed to the aforementioned internal gear; an inner ring has an output shaft coaxially fixed to the aforementioned external gear's hub. The aforementioned harmonic generator is positioned on one side (input side) in the axial direction, and the aforementioned output shaft is positioned on the other side (output side), separated from the aforementioned hub by the aforementioned external gear. The device is characterized by: a temporary fixing fixture that holds the three components—the aforementioned internal gear, the aforementioned external gear, and the aforementioned harmonic generator—in a specific assembly state; a first temporary fixing bolt and a second temporary fixing bolt. The aforementioned input shaft has: an input-side shaft end that is connected and fixed to the motor shaft of the assembly object; and an output-side shaft end that is connected and fixed to the aforementioned temporary fixing fixture. The aforementioned temporary fixing fixture has: a disc-shaped flange located on the aforementioned output side relative to the aforementioned output shaft; a cylindrical portion protruding from the aforementioned disc-shaped flange through the central hole of the aforementioned output shaft and the central hole of the aforementioned hub toward the aforementioned input side; and a hollow portion extending through the aforementioned disc-shaped flange and the aforementioned cylindrical portion. The aforementioned cylindrical portion engages with the aforementioned output-side shaft end of the aforementioned input shaft and includes: an axial direction positioning surface for defining the axial position of the aforementioned harmonic generator relative to the aforementioned external gear; a rotation direction positioning surface for defining the rotation direction position; and a aforementioned temporary fixing fixture coaxially connected and fixed to the aforementioned output shaft by the aforementioned first temporary fixing bolt assembled from the aforementioned output side to the aforementioned disc-shaped flange, and coaxially connected and fixed to the aforementioned output-side shaft end of the aforementioned input shaft by the aforementioned second temporary fixing bolt installed from the aforementioned output side to the aforementioned hollow portion.

2. The harmonic gear device as described in claim 1, wherein the aforementioned axial direction positioning surface is an annular step surface facing the input side of the aforementioned hollow portion formed on the aforementioned input side of the aforementioned hollow portion of the aforementioned temporary fixing fixture; the front end face of the aforementioned input side shaft end of the aforementioned input shaft inserted into the aforementioned hollow portion abuts against the aforementioned annular step surface from the aforementioned input side; the aforementioned rotation direction positioning surface is formed on the inner circumferential surface of the aforementioned hollow portion of the aforementioned temporary fixing fixture on the aforementioned input side, and forms a shape in which a portion of the circular inner circumferential surface protrudes inward in the radial direction; and the outer circumferential surface of the aforementioned input side shaft end of the aforementioned input shaft inserted into the aforementioned hollow portion forms a shape complementary to the aforementioned rotation direction positioning surface.

3. The harmonic gear device as described in claim 1, further comprising: a shaft connecting bolt, installed in the aforementioned hollow portion after the aforementioned second temporary fixing bolt has been removed, for connecting and fixing the aforementioned input side shaft end of the aforementioned input shaft to the aforementioned motor shaft of the assembly object.

4. The harmonic gear device as described in claim 1 further comprises: an end plate fixed to the aforementioned internal gear from the aforementioned input side; an input-side oil seal; an output-side oil seal, wherein the aforementioned input-side shaft end of the aforementioned input shaft protrudes toward the aforementioned input side through the central hole of the aforementioned end plate, the gap between the inner circumferential surface of the aforementioned central hole of the aforementioned end plate and the outer circumferential surface of the aforementioned input-side shaft end is sealed by the aforementioned input-side oil seal, and the gap toward the aforementioned output-side opening formed between the aforementioned outer ring and the aforementioned inner ring of the aforementioned main bearing is sealed by the aforementioned output-side oil seal.

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