Hard gear harmonic reducer

Abstract

According to the method for designing the harmonic reducer through the hard gears, the two layers of rolling bodies are clamped between the tooth grooves of the inner hard gear and the tooth grooves of the outer hard gear, the two layers of rolling bodies fluctuate in the radial direction, and therefore the higher torque, the longer service life and the higher reliability are achieved through the transmission method. And the contact parts of all parts in the torque transmission path are always in rolling contact.

Description

Technical Field

[0001] The invention relates to a transmission device of a speed changer, and belongs to the technical field of machinery. Background Art

[0002] Currently known harmonic reducers use flexible gears that require continuous radial deformation. Because this design easily fatigues the material, the torque they can withstand is small and their lifespan is short. U.S. Patent [US9297442B1] discloses a device that uses an endless chain structure instead of the gears in the reducer as the transmission mechanism. However, in this device, torque is transmitted by the pin 112 or pin 218 in the chain, and the component in contact with the pin in this structure is the pin disk 118 or the roller 219. Due to the rotation of the roller or the pin, sliding friction inevitably exists at the contact point, and this friction cannot be eliminated. In addition, Chinese patent [CN2022109777833] discloses a pendulum shaft transmission mechanism using a two-layer endless chain as the transmission medium between two gears. In this mechanism, the outer and inner rolling elements roll at different speeds. For example, when the outer rolling element rolls one tooth on the gear tooth surface, the inner rolling element needs to roll two teeth on the gear tooth surface. Therefore, an oil wedge between the two rolling elements is required to eliminate sliding friction between the two layers. If the oil wedge fails, sliding friction is inevitable.

[0003] In order to solve the above problems, the present invention is proposed. Summary of the Invention

[0004] A hard gear harmonic reducer is characterized by comprising at least two gears with different numbers of teeth, gear A1 and gear B1, with the two gears having the same axial center. A ring consisting of two layers of rolling elements is installed between the two gears. The first layer of rolling elements meshes with gear A1, and the second layer of rolling elements meshes with gear B1, allowing thrust to be transmitted between the two layers of rolling elements. Furthermore, a wave generator is provided, which, driven by an input shaft, propels the two layers of rolling elements to engage and disengage between gears A1 and B1. Due to the different numbers of teeth on the two gears, a reduction transmission is achieved. Compared to known harmonic reducers, the present invention uses a combination of two layers of rolling elements and hard gears to replace the radial deformation of the flexspline, thereby eliminating material fatigue and reducing torque. Furthermore, during radial motion, the two-layered ring of rolling elements experiences rolling friction with gears A1 and B1.

[0005] A further advantage is that since there is no pendulum shaft structure, the axes of gears A1 and B1 are the same and fixed, and the rolling of the two layers of rolling elements can be synchronized. Even if the oil wedge between the two layers of rolling elements fails, sliding friction will not occur. At this point, the main contact components in the reducer can achieve rolling contact.

[0006] The purpose of the present invention is to invent a harmonic reducer with higher torque and longer service life, wherein the contact parts of various components in the torque transmission path are all rolling contacts.

[0007] Furthermore, in order to maintain rolling contact between the rolling elements and the gear contact surface, the following data was obtained through modeling and experimental testing: the number of teeth of gear A1 is the same as the number of rolling elements in contact with it, and the tooth profile curve of gear A1 is a circular arc curve. The radius of the circular arc curve is R1, and the radius of the rolling element in contact with it is R2, then R1 ≥ 1.06 × R2. The purpose is to avoid the rolling elements and gear tooth surfaces from sticking or deforming under heavy loads and then biting, thereby maintaining rolling contact. The value of 1.06 was obtained in experiments based on existing commonly used materials and extreme operating conditions. Under extreme operating conditions, the lubricant will coke and combine with tiny debris generated during operation to form hard lumps, which will accelerate the wear of the reducer and even cause it to get stuck. However, when the value is greater than 1.06, the situation improves significantly.

[0008] In the present invention, various combinations of the number of teeth on gears A1 and B1 and the number of rolling elements in each layer are possible, including but not limited to the following: when the number of teeth on the inner gear located on the outer ring is N, the number of teeth on the center gear is N-2, and the number of rolling elements in each layer of the two layers is N; or, when the number of teeth on the inner gear located on the outer ring is N+2, the number of teeth on the center gear is N, and the number of rolling elements in each layer of the two layers is N. In both of these combinations, the number of teeth on gears A1 and B1 is not a prime number. The purpose of not having a prime number of teeth is to enable the gears to be quickly machined using a grinder with multiple grinding heads, thereby reducing production costs.

[0009] Furthermore, the design schemes of the tooth profile curves of gears A1 and B1 include but are not limited to the following schemes: the tooth profile curve of at least one gear contains a circular arc curve, or the tooth profile curve of at least one gear contains a cycloid, or the tooth profile curve of at least one gear contains an elliptical curve, including one or more combinations of the above schemes.

[0010] According to the reducer disclosed in the present invention, a reduction gear can be designed, which is characterized by: comprising at least three gears, gear A1, gear B1 and gear B2, wherein the three gears have the same axial position, wherein gear B1 and gear B2 have the same number of teeth and are respectively located at the two ends of the shaft, gear A1 has a different number of teeth from the above two gears, and a wave generator is located in the middle position between gear B1 and gear B2. The wave generator drives two layers of rolling elements to engage with the three gears at the same time, wherein gear B1 and gear B2 are fixed and do not rotate, and gear A1 drives the output shaft to rotate.

[0011] A reduction gear device can also be designed based on the reducer disclosed in the present invention, characterized in that two wave generators are located at opposite ends of a shaft and rotate synchronously, with gears A1 and B1 positioned between the two wave generators, with their tooth surfaces facing each other. The wave generators drive two layers of rolling elements to mesh with two gears, one of which is fixed and does not rotate, while the other drives the output shaft to rotate.

[0012] The reducer disclosed in the present invention has a further improvement: at least one of the two layers of rolling elements in the ring is composed of a chain, or the two layers of rolling elements are composed of two ring-shaped chains, with the rolling elements of different layers in direct contact. This improvement differs from known chain drives or sprocket drives. In the present invention, two adjacent rolling elements are simultaneously engaged in the tooth grooves of two gears, and torque is primarily transmitted directly by the two adjacent rolling elements. The chain's connecting piece is primarily responsible for positioning the rolling elements, and the force it is subjected to is very small. Therefore, during long-term use, the chain's connecting piece is less likely to stretch, and its service life is also extended.

[0013] In order to prevent the ring chain from moving in the axial direction, the present invention provides a solution as follows: the ring chain includes a connecting piece connecting each chain link, and the edge of the connecting piece is protruding. The protruding portion is located at both ends of the edge of the gear tooth profile in the axial section of the gear. Its purpose is to serve as a retaining edge to limit the ring chain from falling off in the axial direction.

[0014] The wave generator of the present invention contacts the ring formed by the two layers of rolling elements through the third layer of rolling elements and the flexible annular material. This structure is used to ensure that the wave generator is in rolling contact with the two layers of rolling elements during rotation.

[0015] The hard gear harmonic speed reducer of the present invention can be combined with various engines to form a power output module. The engines may include but are not limited to: an axial flux motor, an outer rotor motor, an inner rotor motor, or a turbine.

[0016] The hard gear harmonic reducer of the present invention can be used in various mechanical transmission systems, and its application scenarios include but are not limited to propeller drive or hub drive or mechanical joints, where mechanical joints include but are not limited to rotary joints of industrial machinery, or wearable robotic arms, or human-machine collaborative mechanical devices, or robotic arms, or vehicle steering systems, or aircraft steering rudder transmission systems, or ship steering rudder transmission systems.

[0017] The technical advantages and protection scope of the present invention will be more clearly understood with reference to the accompanying drawings. The accompanying drawings and accompanying descriptions are intended to specifically illustrate the advantages of the present invention, and the specific examples therein are not intended to limit the protection scope of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Explanation of symbols in the figure: A1 - outer ring No. 1 internal tooth gear; B1 - center No. 1 gear; B2 - center No. 2 gear; C - cross-sectional position; D1 - first layer of rolling elements in the two layers of rolling elements; D2 - second layer of rolling elements in the two layers of rolling elements; D3 - third layer of rolling elements; E - wave generator; E1 - flexible annular structure; F1 - first bearing; F2 - second bearing; F3 - third bearing; F4 - fourth bearing; F5 - fixed shaft; H1 - rotor of the motor; H2 - stator of the motor; O - axis position; J - chain connecting piece.

[0019] Figure 1 This is a hard gear harmonic reducer designed based on the principles disclosed in the present invention, and this reducer and an outer rotor motor are combined into a power output module. The figure is an axial cross-sectional view of the module.

[0020] Figure 2 yes Figure 1 Radial cross-section view at the mid-section position C1.

[0021] Figure 3 yes Figure 1 Radial cross-section view at the mid-section position C2.

[0022] Figure 4 These are two axial views of the two-layer rolling element structure of the present invention. DETAILED DESCRIPTION

[0023] The advantages of the present invention and preferred embodiments of the present invention are described with reference to the accompanying drawings. Specific examples are provided to illustrate the advantages of the present invention and are not intended to limit the scope of protection of the present invention.

[0024] Figure 1 This is a hard-gear harmonic reducer designed based on the principles disclosed in this invention. This reducer is combined with an outer rotor motor to form a power output module. The figure shows an axial cross-section of this module. A fixed shaft F5 is located in the center of the figure and serves as the fixed shaft for the outer rotor motor. The motor's stator H2, center gear No. 1 B1, and center gear No. 2 B2 are fixedly connected to this shaft. The motor's rotor H1 is mounted on this shaft via bearings No. 3 F3 and No. 4 F4. A wave generator E is fixedly mounted on the motor's rotor H1. The outer side of the wave generator E is surrounded by a third-layer rolling element D3. A flexible annular structure E1 is located outside the third-layer rolling element D3. This flexible annular structure E1 is in direct contact with the second-layer rolling element D2. The second-layer rolling element meshes with the center gears B1 and B2, and also with the first-layer rolling element D1. The first-layer rolling element D1 meshes with the outer ring gear No. 1 A1.

[0025] Figure 2 yes Figure 1Radial cross-section view at the mid-section position C1. Figure 2 The center is axis O, which serves as the axis of the motor and all gears in the hard gear harmonic reducer. Around axis O is fixed axis F5, which is securely connected to the motor stator H2. Stator H2 is secured to the motor rotor H1, which is securely connected to the wave generator E. The wave generator's outer layer is the third layer of rolling elements D3, which are in contact with the second layer of rolling elements D2 via a flexible annular structure E1. Together, the second layer of rolling elements D2 and the first layer of rolling elements D1 form what is referred to as a two-layer rolling ring in this invention. The first layer of rolling elements D1 meshes with outer ring gear A1.

[0026] Figure 3 yes Figure 1 Radial cross-section view at the mid-section position C2. Figure 3 The center is the axis O, which is the axis of the motor and also the axis of all gears in the hard gear harmonic reducer. The outer periphery of the axis O is the fixed axis F5, the outer layer of the fixed axis F5 is fixedly connected to the motor stator H2, the outer layer of the motor stator H2 is the motor rotor H1, and the outer layer of the motor rotor H1 is the center No. 1 gear B1. Figure 1 As can be seen, there is no contact between center gear B1 and motor rotor H1, and center gear B1 is fixed to fixed shaft F5. The second layer of rolling elements D2 is in contact with center gear B1. Together with the first layer of rolling elements D1, these second layer of rolling elements D2 form what is referred to as a two-layered ring in this invention. The first layer of rolling elements D1 meshes with outer ring gear A1.

[0027] The following combination Figure 1 、 Figure 2 、 Figure 3 To illustrate the operation mode and advantages of the case of the present invention. Figure 2 It can be seen that the radial cross section of the wave generator E is elliptical or oblong. When the wave generator E rotates with the fixed motor rotor H1, it will push the two layers of rolling elements to move radially. Figure 3 It can be seen that the ring composed of two layers of rolling elements meshes with gears A1 and B1 at the same time. Since the two gears have different numbers of teeth, a reduction transmission is generated.

[0028] Figure 1 The center gear No. 2 B2 and the center gear No. 1 B1 are installed on both sides of the wave generator E, and the two center gears have the same number of teeth and the corresponding positions of the teeth are also the same. This design can effectively balance the circumferential overturning force generated by the rolling body during the engagement process with the gear.

[0029] according to Figure 2 and Figure 3 It can be seen that when Figure 2 The motor rotor H1 in the circuit rotates clockwise. Figure 3 Rolling element D2 and rolling element D1 at the marked position move radially. These two rolling elements are directly engaged between the tooth grooves of gears B1 and A1. As the two layers of rolling elements move radially outward, torque is transmitted between the two gears through the rolling elements. Unlike conventional chain drives or sprocket drives, the connecting plate requires almost no force during torque transmission.

[0030] Figure 4 These are two axial views of the two-layer rolling element structure of the present invention. Figure 4 The upper part shows that only the first layer of rolling elements D1 of the two layers is composed of chains. Between the links of the chain, the second layer of rolling elements D2 is installed below the connecting piece J. The second layer of rolling elements D2 has no connecting piece. Figure 4 The lower part shows that the two layers of rolling elements are composed of two chains.

[0031] Other specific cases can also be designed based on the reducer principle proposed in the present invention. Application scenarios include but are not limited to being combined with a turboshaft engine to form a power module, or being combined with an electric motor to form a power module. The electric motor can be an axial flux motor, an outer rotor motor, or an inner rotor motor.

[0032] The present invention is applied in a mechanical transmission device, and its application scenarios include but are not limited to applications in propeller drive or hub drive or mechanical joints, where mechanical joints include but are not limited to rotary joints of industrial machinery, or wearable robotic arms, or human-machine collaborative mechanical devices, or robotic arms, or vehicle steering systems, or aircraft steering rudder transmission systems, or ship steering rudder transmission systems, or other various application scenarios, or other mechanical actuators, which are not listed here.

Claims

1. Hard gear harmonic reducer, which is characterized by: It includes at least two gears with different numbers of teeth, gear A1 and gear B1, and the two gears have the same axial position. A ring consisting of two layers of rolling elements is installed between the two gears. The first layer of rolling elements in the two layers of rolling elements meshes with gear A1, and the second layer of rolling elements meshes with gear B1. Thrust can be transmitted between the two layers of rolling elements. In addition, there is a wave generator. The wave generator can push the two layers of rolling elements to mesh or disengage between gear A1 and gear B1 under the drive of the input shaft. The number of rolling elements in one of the two layers of rolling elements is the same as the number of teeth of the gear meshing with it, and the minimum curvature radius of the tooth profile curve of the gear is R1, and the radius of the rolling element in contact with it is R2, R1 ≥ 1.06 × R2. Due to the different numbers of teeth of the two gears, reduction transmission is achieved.

2. The reducer according to claim 1, characterized in that: The number of teeth of gear A1 and gear B1 is not a prime number among natural numbers.

3. The reducer according to claim 1, characterized in that: There are multiple combinations of the number of teeth of gear A1 and gear B1 and the number of rolling elements in each layer, and the combinations include at least one of the following: when the number of teeth of the inner gear located on the outer ring is N, the number of teeth of the center gear is N-2, and the number of rolling elements in each layer of the two layers is N; or, when the number of teeth of the inner gear located on the outer ring is N+2, the number of teeth of the center gear is N, and the number of rolling elements in each layer of the two layers is N.

4. The reducer according to claim 1, wherein: The design schemes of the tooth profile curves of gears A1 and B1 include the following schemes: the tooth profile curve of at least one gear includes a circular arc curve, or the tooth profile curve of at least one gear includes a cycloid, or the tooth profile curve of at least one gear includes an elliptical curve, including one or more combinations of the above schemes.

5. According to the reducer described in claim 1, a reduction gear can be designed, which is characterized by: The design methods of the wave generator and the gear include one of the following two methods. The first is to include at least three gears, gear A1, gear B1 and gear B2, and the three gears have the same axial position, wherein gear B1 and gear B2 have the same number of teeth and are located at both ends of the shaft respectively. The wave generator is located in the middle position between gear B1 and gear B2. The wave generator drives two layers of rolling elements to engage with the three gears at the same time, wherein gear B1 and gear B2 are fixed and do not rotate, and gear A1 drives the output shaft to rotate; the second is to have two wave generators located at both ends of the shaft and rotate synchronously, and gear A1 and gear B1 are located between the two wave generators.

6. The reducer according to claim 1, characterized in that: In the ring composed of two layers of rolling elements, at least one layer of rolling elements is composed of a chain, or the two layers of rolling elements are composed of two ring-shaped chains, and the rolling elements of different layers are in direct contact.

7. The reducer according to claim 1, characterized in that: The two layers of rolling elements include an annular chain having connecting plates connecting the chain links. The edges of the connecting plates protrude, and the protruding portions exceed the edges of the gear tooth profiles in the axial direction of the gear. The purpose of the protruding portions is to serve as retaining edges to prevent the annular chain from falling off in the axial direction.

8. The reducer according to claim 1, characterized in that: The wave generator is in contact with the ring formed by the two layers of rolling elements through the third layer of rolling elements and the flexible annular material. This structure is used to ensure that the wave generator is in rolling contact with the two layers of rolling elements during rotation.

9. The transmission according to claim 1, characterized in that: The hard gear harmonic reducer cooperates with the engine to form a power output module. The engine can be any one of an axial flux motor, an outer rotor motor, an inner rotor motor or a turbine.

10. The reducer according to claim 1 or 2 or 3 or 4 or 5 or 6 or 7 or 8 or 9, characterized in that: The reducer is used in a transmission system, and its application scenarios include but are not limited to propeller drive or hub drive or mechanical joints, where mechanical joints include but are not limited to rotary joints of industrial machinery, or wearable robotic arms, or human-machine collaborative mechanical devices, or robotic arms, or vehicle steering systems, or aircraft steering rudder transmission systems, or ship steering rudder transmission systems.

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