Harmonic differential type small tooth difference speed reducer

Abstract

The utility model discloses a harmonic differential type small-tooth-difference speed reducer, and belongs to the field of machinery. The structure comprises an outer gear ring, a double-sided planetary gear ring, a sun gear and an eccentric circumferential cam, a double-sided planetary gear ring is adopted to be meshed with an outer gear ring and a sun gear at the same time under the constraint of a cam disc; the input shaft and the output shaft are in a strict speed reduction relation: under the condition that the outer gear ring is selected to be static, when the inner teeth of the double-sided planetary gear ring and the sun gear are meshed and roll for a circle, the angle corresponding to the tooth number difference value between the inner teeth and the sun gear is formed; when the outer teeth of the double-sided planetary gear ring and the inner teeth of the outer gear ring are meshed and roll for a circle, the double-sided planetary gear ring and the outer gear ring rotate by an angle corresponding to a tooth number difference value; numerical values of the two parties show an offset trend; the sun shaft or the outer gear ring can be selected to be static, so that the reduction ratio is larger than that of a small-tooth-difference mechanism meshed by a single gear, and the relation between the reduction ratio and the tooth height is not large; the device can be widely used in the machinery industry.

Description

[Technical Field]

[0001] The present invention belongs to the field of mechanical technology. Specifically, it is an improved harmonic gear reducer with a small tooth difference, which realizes a gear reduction structure with a high reduction ratio under a large tooth profile through differential motion. [Background Art]

[0002] Brief Introduction to Harmonic Reducer Technology:

[0003] The harmonic reducer originated abroad in the 1950s and began to be developed in China in the 1960s and 1970s. Many manufacturers now specialize in its production and have formed a series. It is widely used in industries such as electronics, aerospace, and robotics. Due to its unique advantages, its application in the chemical industry is also gradually increasing. In fact, this technology is an evolution based on the original technology of small tooth difference in the 1920s. English: harmonic gear drive. Definition: It mainly consists of four basic components: a wave generator, a flexible gear, a flexible bearing, and a rigid gear. A harmonic drive reducer is a gear drive that relies on the wave generator assembled with a flexible bearing to cause the flexible gear to produce controllable elastic deformation and mesh with the rigid gear to transmit motion and power. Applied disciplines: Mechanical Engineering (first-level discipline); Transmission (second-level discipline); Gear Transmission (third-level discipline). The harmonic gear drive reducer is a new type of reducer developed based on the principle of planetary gear drive. Harmonic gear drive (referred to as harmonic drive).

[0004] The wave generator H is a rod-shaped component with rolling bearings at both ends to form rollers, which are tightly pressed against the inner wall of the flexible gear 1. The flexible gear is a thin-walled gear that can produce large elastic deformation, and its inner hole diameter is slightly smaller than the major axis of the wave generator. The wave generator is the component that causes the flexible gear to produce controllable elastic deformation. When the wave generator is installed in the flexible gear, it forces the cross-section of the flexible gear to change from the original circular shape to an elliptical shape. The teeth near the two ends of the major axis are fully meshed with the teeth of the rigid gear, while the teeth near the two ends of the minor axis are completely disengaged from the rigid gear. The teeth in other sections of the circumference are in a transitional state between meshing and disengagement. When the wave generator rotates continuously in the direction shown in the figure, the deformation of the flexible gear continuously changes, causing the meshing state between the flexible gear and the rigid gear to also continuously change, from engagement, meshing, disengagement, separation, and then re-engagement... repeating in a cycle, thereby realizing the slow rotation of the flexible gear relative to the rigid gear in the opposite direction of the wave generator H. During operation, the rigid gear is fixed, and the wave generator is driven by a motor to rotate. The flexible gear is the driven wheel, outputting rotation to drive the load to move. During the transmission process, the number of cycles of deformation of a certain point on the flexible gear when the wave generator rotates one week is called the wave number, denoted by n. Commonly used are double-wave and triple-wave types. The stress of the flexible gear in double-wave transmission is smaller, the structure is relatively simple, and it is easy to obtain a large transmission ratio. Therefore, it is the most widely used type.

[0005] Basic Characteristics:

[0006] *In a high load-carrying capacity harmonic drive, the tooth-to-tooth meshing is a surface contact. Coupled with a relatively large number of simultaneously meshing teeth (contact ratio), the load per unit area is small, and the load-carrying capacity is higher than that of other transmission forms.

[0007] *Large transmission ratio: The transmission ratio of a single-stage harmonic gear drive can reach i = 70 - 500.

[0008] *Small size and light weight.

[0009] *High transmission efficiency and long service life.

[0010] *Smooth transmission, no impact, no noise, and high motion accuracy.

[0011] *Since the flexspline bears a large alternating load, higher requirements are imposed on the fatigue strength, machining, and heat treatment of the flexspline material, and the process is complex.

[0012] Brief introduction to the original technology of a small tooth difference:

[0013] In a small tooth difference planetary gear drive, the tooth difference is usually 1 - 4. The external gear is mounted on the input shaft of the reducer through bearings and an eccentric sleeve. To balance part of the inertial force and improve the load-carrying capacity, usually two external gears are used, and there are two eccentrics on the eccentric sleeve and they are 180° apart. The internal gear mostly remains stationary. The output mechanism transmits the rotation of the external gear to the output shaft through pin shafts and keeps its angular velocity unchanged. Commonly used output mechanisms include pin shaft type and floating disk type, etc.

[0014] Structure and principle:

[0015] The small tooth difference planetary drive is an evolved form of the ordinary planetary drive. Its structure is simpler than that of the ordinary planetary drive and includes an internal gear ring, a planetary carrier, planetary gears, and a disk-shaped output shaft. In this structure, the planetary carrier is the driving part and the planetary gears are the driven parts, which is the opposite of the ordinary planetary drive.

[0016] The structure of the double universal coupling not only has a large axial dimension but also cannot be used in the case of multiple planetary gears, and it is now basically not used. The most widely used is the pin hole type disk-shaped output mechanism. A number of pin holes are evenly distributed along the circumference on the spoke plate of the planetary gear, and the same number of cylindrical pins are evenly distributed at the corresponding positions on the disk of the output shaft. The cylindrical pins are inserted into the pin holes of the planetary gear. The center distance between the internal gear ring and the planetary gear (i.e., the eccentricity of the planetary carrier) must be equal to the difference between the radius of the pin hole and the radius of the pin shaft, so as to ensure that the pin hole and the pin shaft always remain tangent, and the planetary gear can push the disk-shaped output shaft to rotate at the same speed and in the same direction. At this time, the centers of the internal gear ring, the planetary gear, the pin hole, and the pin shaft just form a parallelogram.

[0017] Applications of the small tooth difference planetary drive:

[0018] Planetary drives are widely used in planetary speed reducers for power transmission, and they have the advantages of compact size design, light weight, and large transmission power. The less tooth difference planetary drive is a special type of planetary drive. The movement of the planetary gear is a compound movement of self-rotation and revolution, and the calculation of its transmission ratio is relatively complex. It is divided into single-stage drive and multi-stage drive: The transmission ratio generally adopted for the involute less tooth difference single-stage drive is above 20 to 100, and the efficiency is 0.8 to 0.9. Its gears can be processed by general gear machine tools. If the number of teeth of the external gear is Z0 and the number of teeth of the internal gear is Zb, then when the internal gear is fixed, the transmission ratio ib of the input shaft and the output shaft is -Z0 / (Zb - Z0); when the output shaft (F) is stationary, the transmission ratio iF of the input shaft and the internal gear is Zb / (Zb - Z0). The smaller the tooth difference between the internal and external gears, the larger the transmission ratio obtained for each stage of transmission. However, when the tooth difference is reduced to a certain extent, for example, when using standard involute gears with a pressure angle of 20°, when the number of teeth of the internal gear is less than 180 and the tooth difference is less than 5 to 7, tooth profile overlapping interference will occur in the internal meshing gears. The solution is to adopt stub teeth and perform appropriate modification.

[0019] Main disadvantages of harmonic reducer technology:

[0020] * The flexspline deforms periodically, thus generating alternating stress, making it prone to fatigue failure.

[0021] * It has a large moment of inertia and starting torque and is not suitable for low-power tracking drives.

[0022] * It cannot be used in occasions where the transmission speed ratio is less than 35.

[0023] * For harmonic drives using a roller wave generator (free deformation wave), its instantaneous transmission ratio is not a constant.

[0024] * The heat dissipation condition is poor.

[0025] Main disadvantages of less tooth difference reducer technology:

[0026] * The torque it can bear decreases sharply with the reduction of tooth height and is prone to fatigue failure.

[0027] * The speed ratio change is not as large as that of the harmonic reducer.

[0028] * The mechanical structure is relatively complex and the cost is relatively high. [Summary of the Invention]

[0029] The object of the present invention: Combine the principles of the harmonic reducer and the less tooth difference reducer to create a reducer that integrates the advantages of both.

[0030] The characteristics of the present invention: Compact structure, high transmission efficiency and transmission frequency, and long service life.

[0031] The key technology of the present invention: An eccentric circumferential cam is adopted to generate the first harmonic wave, which drives the double-sided planetary gear to perform associated planetary motion, thereby obtaining the deceleration of the mechanism.

[0032] Specific invention content:

[0033] The structure of the harmonic differential planetary reducer with few teeth difference includes: an external gear ring, a double-sided planetary gear ring, a sun gear, and an eccentric circumferential cam. Among them, the external gear ring and the sun gear are coaxial, and the double-sided planetary gear ring is constrained by the cam disc (equivalent to the planetary support) and meshes with the external gear ring and the sun gear simultaneously. That is, the inner teeth of the double-sided planetary gear ring mesh with the sun gear, and the outer teeth of the double-sided planetary gear ring mesh with the external gear ring. Mathematically, it is: the maximum distance between the pitch circles of the external gear ring and the sun gear is equal to the maximum distance between the inner teeth and the outer teeth of the double-sided planetary gear ring. This enables the double-sided planetary gear ring to mesh with the external gear ring and the sun gear simultaneously.

[0034] The assembly relationship is as follows: The function of the cam disc is equivalent to the planetary support, the planetary shaft is the rotating shaft of the double-sided planetary gear ring, and the cam disc constrains the planetary shaft to revolve around the sun shaft like a crankshaft. In this way, the cam disc is like a harmonic generator, emitting a cycle of harmonic waves every revolution. When the external gear ring is fixed as a part of the housing, the sun gear serves as the output shaft, and the cam disc (equivalent to the planetary support) serves as the input shaft. When the sun gear is the fixed part, the external gear ring serves as the output shaft. The input shaft and the output shaft can be reversed and used as a speed increaser.

[0035] Working principle: When the external gear ring is stationary, there will be a strict deceleration relationship between the input shaft and the output shaft. Let the number of teeth of the inner teeth of the double-sided planetary gear ring be A, the number of teeth of the outer teeth be B, the number of teeth of the sun gear be C, and the number of teeth of the external gear ring be D. Under the meshing relationship constraint, D > B and A > C. It can be obtained that when the inner teeth of the double-sided planetary gear ring mesh and roll with the sun gear for one week, the angle corresponding to the number of teeth |D - B| (the angle corresponding to the difference in the number of teeth) is turned between the inner teeth and the sun gear. Similarly, when the outer teeth of the double-sided planetary gear ring mesh and roll with the inner teeth of the external gear ring for one week, the angle corresponding to the number of teeth |A - C| (the angle corresponding to the difference in the number of teeth) is turned between the double-sided planetary gear ring and the external gear ring. The direction relationship is judged as: the rotation direction obtained by the rolling meshing between the double-sided planetary gear ring and the sun gear is opposite to the rotation direction obtained by the rolling meshing between the double-sided planetary gear ring and the external gear ring. That is, there is a tendency of rotational cancellation, and even the rotational speed of the double-sided planetary gear ring becomes zero. When the sun shaft is stationary, according to the relative motion relationship, the situation is the same as the above deceleration value but in the opposite direction.

[0036] Therefore, the reduction ratio of this case will be larger than that of single-gear meshing, enabling a high reduction ratio to be obtained without excessive increase in the number of teeth:

[0037] The reduction ratio is approximately: A / [|A - C| - |D - B|]; By appropriately adjusting the values of A, B, C, and D, the difference between (A - C) and (D - B) will be much smaller than C and D; Therefore, establishing a large reduction ratio has little to do with the size of the tooth height. A larger tooth height is beneficial for bearing capacity and efficiency, and the mechanical stability is also much better.

[0038] Furthermore: This speed reducer can be used in multiple stages.

[0039] The technical progress of the present invention: It has the advantages of high precision, high reduction ratio, and high service life in the case of having no flexible components. [BRIEF DESCRIPTION OF THE DRAWINGS]

[0040] The present invention will be further described below in conjunction with the preferred embodiments of the present invention with reference to the accompanying drawings:

[0041] Figure 1 Explosion and overall schematic diagram of the harmonic differential planetary speed reducer with few teeth difference.

[0042] Figure 2 Schematic diagram of the explosion assembly relationship between the double-sided planetary gear ring and the cam disc.

[0043] Figure 3 Schematic diagram of the synchronous meshing cross-section of the double-sided planetary gear ring, the sun gear, and the external gear ring

[0044] Figure 4 Schematic diagram of the external gear ring structure

[0045] Description of the reference numerals in the drawings:

[0046] 1 Double-sided planetary gear ring

[0047] 1-1 External teeth

[0048] 1-2 Internal teeth

[0049] 1-3 Gear ring bracket

[0050] 1-4 Concentric shaft hole

[0051] 2 Sun gear

[0052] 2-1 Output shaft

[0053] 2-2 Sun teeth

[0054] 3 End cover

[0055] 4 External gear ring (also the housing)

[0056] 4-1 Internal gear

[0057] 4-2 Shaft hole

[0058] 5 Sun axis (sun shaft)

[0059] 6 Eccentric Circumferential Cam (Harmonic Disk, Similar to Crankshaft)

[0060] 6-1 Cam Disk

[0061] 6-2 Input Shaft

[0062] 7 Cam Axis (Planetary Axis) [Specific Embodiment]

[0063] As Figure 1 , Figure 2 , Figure 3 , Figure 4 shown:

[0064] The structure of a kind of harmonic differential planetary gear reducer includes: external gear ring (also acting as the housing) (4), double-sided planetary gear ring (1), sun gear (2), eccentric circumferential cam (6) (harmonic disk, similar to crankshaft), end cover (3); among which, the external gear ring (4) also acts as the housing and has an internal tooth (4-1) structure; the double-sided planetary gear ring (1) has internal teeth (1), external teeth (2), gear ring support (1-3) and concentric shaft hole (1-4); the internal gear (2) is coaxially and rigidly connected with the output shaft (3); the input shaft (6-2) on the eccentric circumferential cam (6) and the cam disk (6-1) are eccentrically connected by two shafts, the two shafts are parallel and have a spacing, and the cam disk (6-1) is in sliding fit with the concentric shaft hole (1-4) of the double-sided planetary gear ring (1), and can be constrained by bearings, allowing the cam disk (6-1) to rotate freely;

[0065] The sun gear (2) has an output shaft (2-1) and sun teeth (2-2).

[0066] Assembly relationship: The end cover (3) and the external gear ring (4) form the housing of the reducer; the output shaft (2-1) of the sun gear (2) passes through the central hole of the end cover (3) and can rotate freely; the input shaft (6-2) on the eccentric circumferential cam (6) passes through the shaft hole (4-2) of the external gear ring (4); the internal teeth (1-1) of the double-sided planetary gear ring (1) mesh with the sun gear (2), and at the same time, the external teeth (1-2) mesh with the internal teeth of the external gear ring (4) on the other side; for the meshing relationship, see Figure 3 , the sun axis (5) is coaxial with the external gear ring (4), the cam axis (7) is parallel to the sun axis (5), and as the gear ring support (1-3) is driven by the eccentric circumferential cam (6), the cam axis (7) revolves around the sun axis (5).

[0067] Working principle: When the external gear ring (4) is stationary, there will be a strict deceleration relationship between the input shaft (6-2) and the output shaft (2-1). Assume that the number of teeth of the internal teeth (1-1) of the double-sided planetary gear ring (1) is A; the number of teeth of the external teeth (1-2) is B; the number of teeth of the sun gear (2) is C; and the number of teeth of the external gear ring (4) is D. Under the meshing constraint, it can be obtained that D > B and A > C. It can be concluded that when the internal teeth (1-1) of the double-sided planetary gear ring (1) mesh and roll one week with the sun gear (2), the angle corresponding to the number of teeth D - B (the angle corresponding to the difference in the number of teeth) is turned between the internal teeth (1-1) and the sun gear (2); similarly, when the external teeth (1-2) of the double-sided planetary gear ring (1) mesh and roll one week with the internal teeth (4-1) of the external gear ring (4), the angle corresponding to the number of teeth A - C (the angle corresponding to the difference in the number of teeth) is turned between the double-sided planetary gear ring (1) and the external gear ring (4). The direction relationship is judged as: the rotation direction obtained by the rolling meshing of the double-sided planetary gear ring (1) and the sun gear (2) is opposite to the rotation direction obtained by the rolling meshing of the double-sided planetary gear ring (1) and the external gear ring (4); that is, there is a tendency of rotational cancellation, and even the rotational combined speed of the double-sided planetary gear ring (1) becomes zero.

Claims

1. Harmonic differential small tooth difference reducer, including: Outer gear ring, double-sided planetary gear ring, sun gear, eccentric circular cam; the outer gear ring is coaxial with the sun gear, and the double-sided planetary gear ring is on the cam plate, which is equivalent to the planetary bracket constraint, and meshes with the outer gear ring and the sun gear at the same time; that is, the inner teeth of the double-sided planetary gear ring mesh with the sun gear; and the outer teeth of the double-sided planetary gear ring mesh with the outer gear ring; in mathematical terms, the maximum distance between the outer gear ring and the sun gear pitch circle is equal to the maximum distance between the inner teeth of the double-sided planetary gear ring and the outer teeth pitch circle; this allows the double-sided planetary gear ring to mesh with the outer gear ring and the sun gear at the same time; the role of the cam plate It is equivalent to the planetary carrier controlling the double-sided planetary gear ring to revolve, the planetary shaft is the rotating shaft of the double-sided planetary gear ring, and the cam plate constrains the planetary shaft to revolve around the sun shaft like a crankshaft; in this way, the cam plate is like a harmonic generator, emitting a cycle of harmonics every time it revolves; when the outer gear ring is fixed as a part of the housing, the sun gear serves as the output shaft, and the cam plate is equivalent to the planetary carrier, serving as the input shaft; and when the sun gear is a fixed part, the outer gear ring serves as the output shaft; the input shaft and the output shaft can be interchanged and reversible, and can be used as a speed increaser; Its characteristics are: The double-sided planetary gear ring is used to mesh with the outer gear ring and the sun gear under the constraint of the cam plate; the input shaft and the output shaft will present a strict reduction relationship: When the outer gear ring is stationary, the number of teeth of the inner teeth of the double-sided planetary gear ring is A; the number of teeth of the outer teeth is B; the number of teeth of the sun gear is C; the number of teeth of the outer gear ring is D; under the constraints of the meshing relationship, D is greater than B, and A is greater than C; it can be concluded that when the inner teeth of the double-sided planetary gear ring mesh with the sun gear and roll one circle, the inner teeth and the sun gear rotate by the angle corresponding to the number of teeth DB; similarly, when the outer teeth of the double-sided planetary gear ring mesh with the inner teeth of the outer gear ring and roll one circle, the double-sided planetary gear ring and the outer gear ring rotate by the angle corresponding to the number of teeth AC; the direction relationship is judged as follows: the rotation direction obtained by the rolling meshing of the double-sided planetary gear ring and the sun gear is The directions of rotation obtained by the rolling meshing of the double-sided planetary gear ring and the outer gear ring are opposite; that is, there is a trend of rotational cancellation, and even the combined rotation speed of the double-sided planetary gear ring is zero; when the sun shaft is selected to be stationary, according to the relative motion relationship, the situation is the same as the above-mentioned deceleration value, but in the opposite direction; therefore, this case will have a larger reduction ratio than the single-gear meshing, and a high reduction ratio can be obtained without excessively increasing the number of teeth: the reduction ratio is approximately: A / [|AC|-|DB|]; due to the appropriate adjustment of the values ​​of A, B, C, and D, the difference between (AC) and (DB) will be much smaller than that of C and D; therefore, establishing a larger reduction ratio has little to do with the size of the tooth height.

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