Circular-arc and straight-line combined conjugate internal gear pair

Abstract

The application discloses a circular-arc and straight-line combined conjugate internal gear pair and belongs to the technical field of machinery. The single-side tooth profile of the external gear in the disclosed internal gear pair is formed by sequentially and smoothly connecting the end points of a circular arc A1B1, a circular arc B1C1, a straight-line segment C1D1, a circular arc D1E1 and a circular arc E1F1, and all the connecting positions are geometrically first-order continuous. The inner gear ring tooth profile is a conjugate envelope curve formed by the corresponding tooth profile segments of the external gear through meshing movement, and the tooth profile segments A2B2, B2C2, C2D2, D2E2 and E2F2 are geometrically first-order continuous at the joint end points. The external gear and the inner gear ring are eccentrically meshed to form the internal gear pair. The internal gear pair reduces the tooth surface sliding friction and meshing impact, improves the tooth root strength, stabilizes the fluid dynamic oil film and is quiet in operation. The internal gear pair can be applied to mechanical devices such as gear pumps, gear motors, speed reduction transmission devices and engineering mechanical hydraulic systems and industrial fluid conveying equipment, and has high universality.

Description

Technical Field

[0001] This invention relates to the field of gear transmission technology, and is particularly applicable to hydraulic power machinery. Specifically, it discloses a conjugate internal meshing gear pair combining circular arcs and straight lines, focusing on the development and design of the tooth profiles of the external gear and the internal gear ring. This gear pair can be widely adapted to internal meshing gear hydraulic pumps, internal meshing gear hydraulic motors, etc. Background Technology

[0002] Internal gear pairs are widely used in various hydraulic power and mechanical transmission devices such as hydraulic gear pumps, hydraulic gear motors, reduction transmission mechanisms, and fluid conveying equipment. They rely on the meshing of internal and external gears to achieve power transmission and volumetric oil transfer, offering advantages such as compact structure, smooth operation, and good self-priming capability. Currently, the industry mainstream uses involute internal gear pairs in large quantities. However, conventional involute internal gear pairs have several shortcomings under high-pressure, high-speed, and continuous operating conditions: 1. During the meshing process, the sliding friction on the tooth surface is large and the contact stress on the tooth surface is relatively high. Long-term high-pressure operation can easily lead to pitting and scuffing wear on the tooth surface, thus limiting the service life of the gear. 2. The meshing area is prone to forming a closed oil trap volume. The compression and expansion of the trapped oil will bring vibration, noise, pressure shock, and large flow pulsation, which is not conducive to the stable operation of high-precision hydraulic systems. 3. Involute gears have a minimum number of teeth limit. Small number of teeth makes them prone to undercut, which makes it impossible to further reduce the size of the gear and restricts the miniaturization design of equipment. 4. Conventional general-purpose linear conjugate internal meshing gear pairs have a coarse profile design, a short effective contact area, an unreasonable tooth root transition structure, insufficient bending strength under heavy loads, and are prone to tooth root cracking under high-pressure conditions, resulting in excessive internal leakage and decreased volumetric efficiency. The lack of geometric continuity in the tooth profile reduces the meshing allowance, affecting the overlap ratio, and can also subtly induce problems such as noise, pulsation, vibration, and wear, thus affecting the quality of use. Existing designs are mostly tailored to a single operating condition of gear pumps, resulting in narrow tooth profile adaptability and an inability to adapt to various devices such as hydraulic motors and reducers. Furthermore, most mainstream market solutions directly copy standard tooth profile curves without specific research and optimization of the tooth root, tooth tip, and meshing straight section. Therefore, the industry urgently needs an internal meshing gear pair with good versatility, excellent flexibility, less wear, lower noise, higher load capacity, and adaptability to multiple devices and scenarios. Summary of the Invention

[0003] Based on the above-mentioned shortcomings, this invention discloses a conjugate internal meshing gear pair combining circular arcs and straight lines.

[0004] The aforementioned gear pairs can be applied in hydraulic gear pumps, hydraulic gear motors, engineering hydraulic systems, speed reduction transmission devices, and industrial fluid conveying equipment. In these applications, internal meshing gear pairs exhibit characteristics such as stable and regular meshing lines, uniform tooth surface contact stress distribution, low tooth root bending stress, good load adaptability, stable hydrodynamic oil film, ultra-quiet operation, low vibration amplitude, small transmission pulsation, and good temperature adaptability, representing the future direction of gear technology.

[0005] The technical solution adopted by this invention to solve the above-mentioned technical problems is as follows: A pair of internal meshing gears is developed, including an external gear and an internal gear ring. The working tooth profile of the external gear is composed of several circular arcs and a straight line segment, which are sequentially arranged with their end points overlapping and smoothly connected. All tooth profile segments satisfy geometric first-order continuity at their connection points, and all have a common tangent at the connection points. The tooth profile of the internal gear ring is the conjugate envelope curve formed by the corresponding circular arcs and straight line segments in the tooth profile of the external gear under meshing motion. The external gear is located in the inner cavity of the internal gear ring, and the central axes of the external gear and the internal gear ring are offset by a certain distance to form an internal meshing conjugate gear pair.

[0006] Compared with existing technologies, the key feature of this invention lies in the composition and connection method of the tooth profile. The tooth profile segments comprising the tooth profile include several circular arcs and a straight line, all of which satisfy geometric first-order continuity at their connection points and share a common tangent (G1 continuity, i.e., tangential continuity) at these points. The entire tooth profile has no inflection points or sharp angles. This not only eliminates the stress concentration problem at the tooth root, greatly improving load adaptability, but also helps to form a fluid lubricating oil film during gear meshing, reducing the risk of surface wear. It also effectively ensures the sealing performance of the gear meshing.

[0007] After conducting comparative experiments in multiple batches and scenarios, the following results were obtained: The aforementioned internal meshing gear pair has a very small oil trapping capacity due to the meshing and sealing of the tooth profile, and will not experience the sudden rise and fall of oil pressure, cavitation, vibration and other working conditions caused by oil trapping in traditional involute gears, thus almost eliminating the oil trapping phenomenon. When the aforementioned internal meshing gear pair is applied to a hydraulic pump, the fluid output will be extremely stable with very low pulsation, and valves and oil pipes will not easily resonate and loosen. The aforementioned internal meshing gear pairs are used in hydraulic pumps, hydraulic motors, etc. The performance degradation rate during long-term durability testing is much lower than that of conventional gear pairs. They are durable and do not easily wear out under high-temperature hydraulic oil conditions, thus preventing internal leakage from increasing. Internal leakage can be completely controlled. The aforementioned internal meshing gear pair is used in hydraulic oil pumps. Compared with piston pumps, precision vane pumps, etc., it has a higher tolerance for impurities in hydraulic oil, thus having better anti-fouling performance, making it more suitable for ordinary industrial hydraulic oil conditions, and lowering the maintenance threshold. The aforementioned tooth profile structure features smooth meshing and pressure relief without drastic volume changes, ensuring stable pressure holding. It is suitable for injection molding machines and precision machine tools that require continuous pressure stabilization, and the servo system consumes less energy. The aforementioned tooth profile segments are precisely conjugate, exhibiting a uniform variation in inter-tooth volume and good flow consistency across high and low speeds. The tooth profiles also feature smooth, tangential connections, resulting in minimal meshing impact vibration and low vibration amplitude. The aforementioned external gears have a thicker tooth root, higher bending strength, and are less prone to tooth breakage under high pressure, thus having a superior load-bearing capacity. The aforementioned internal meshing gear pair has uniform force distribution on its tooth profile and better radial force balance, which results in a smaller bearing load and makes the bearing less prone to damage under high pressure. The aforementioned internal meshing gear pair has a compact structure and is lighter in weight, making it very suitable for installation in confined spaces in machine tools and equipment; The aforementioned internal meshing gear pairs are used in hydraulic systems, exhibiting good low-speed stability and eliminating severe noise, cavitation, and whistling at high speeds. The aforementioned meshing contact points of the gear profiles can form a stable hydrodynamic oil film, resulting in low frictional loss, lower heat generation, and less likelihood of the oil temperature exceeding the standard during long-term continuous operation. This reduces problems such as oil aging and seal failure, and also extends the life of the gear pair. The aforementioned internal meshing gear pairs are highly compatible with lubricating oil, ordinary hydraulic oil, and some low-temperature media, and are applicable to machine tools, rubber and plastic machinery, engineering machinery, and automated production lines. Attached Figure Description

[0008] Figure 1 This is a front view of the external gear in an embodiment of the present invention; Figure 2 This is a partially enlarged view of the external gear tooth profile in an embodiment of the present invention; Figure 3 This is an enlarged view of a portion of the first circular arc A1B1 and the second circular arc B1C1 of the external gear tooth profile in an embodiment of the present invention; Figure 4 This is an enlarged view of the third arc D1E1 and the fourth arc E1F1 of the external gear tooth profile in an embodiment of the present invention; Figure 5 This is a front view of the internal gear ring according to an embodiment of the present invention; Figure 6 This is a partial enlarged view of the tooth profile of the internal gear ring in an embodiment of the present invention; Figure 7 This is an enlarged view of the partial curves A2B2 and B2C2 of the internal gear ring profile in an embodiment of the present invention; Figure 8 This is an enlarged view of the partial curves C2D2, D2E2, and E2F2 of the internal gear ring in an embodiment of the present invention; Figure 9 , Figure 10 This is an assembly drawing of the internal meshing gear pair according to an embodiment of the present invention; Figure 11 This is an integral drawing of the gear shaft according to an embodiment of the present invention. Detailed Implementation

[0009] The present invention will be further described below with reference to the accompanying drawings and embodiments: An arc-shaped, straight-line conjugate internal gear pair includes an external gear and an internal gear ring. The external gear has a number of teeth evenly arranged circumferentially, and all teeth have completely identical tooth profiles. The internal gear ring has a number of internal teeth evenly arranged circumferentially, and all internal teeth have completely identical tooth profiles.

[0010] like Figure 1 , Figure 2 , Figure 3 , Figure 4 As shown, the tooth profile segments of the single-sided working tooth profile of the external gear include: a first circular arc A1B1, a second circular arc B1C1, a straight line segment C1D1, a third circular arc D1E1, and a fourth circular arc E1F1, which are sequentially connected by overlapping end points. The end point of the first circular arc A1B1 coincides with the beginning point of the second circular arc B1C1, that is, they coincide at point B1, and have a common tangent at point B1, with the tangent point being geometrically first-order continuous. The end point of the second circular arc B1C1 coincides with the beginning point of the straight line segment C1D1, that is, they coincide at point C1, and have a common tangent at point C1, with the tangent point being geometrically first-order continuous. The end point of the straight line segment C1D1 coincides with the beginning point of the third circular arc D1E1, that is, they coincide at point D1, and have a common tangent at point D1, with the tangent point being geometrically first-order continuous. The endpoint of the third arc D1E1 coincides with the starting point of the fourth arc E1F1, that is, they coincide at point E1, and there is a common tangent at point E1, with the tangent point being geometrically first-order continuous.

[0011] The second circular arc B1C1, the straight line segment C1D1, and the third circular arc D1E1 of the external gear tooth profile are symmetrical on the left and right sides. The first circular arc A1B1 is the tooth root arc, and the fourth circular arc E1F1 is the tooth tip arc.

[0012] like Figure 5 , Figure 6 , Figure 7 , Figure 8As shown, the working tooth profile of the internal gear ring is the conjugate envelope curve formed by each tooth profile segment in the working tooth profile of the external gear under meshing motion. It includes: the conjugate envelope curve A2B2 formed by the first circular arc A1B1 under meshing motion; the conjugate envelope curve B2C2 formed by the second circular arc B1C1 under meshing motion; the conjugate envelope curve C2D2 formed by the straight line segment C1D1 under meshing motion; the conjugate envelope curve D2E2 formed by the third circular arc D1E1 under meshing motion; and the conjugate envelope curve E2F2 formed by the fourth circular arc E1F1 under meshing motion. A2B2, B2C2, C2D2, D2E2, and E2F2 have their beginning and end points coincide and are smoothly connected, exhibiting geometric first-order continuity at the connecting endpoints.

[0013] like Figure 9 , Figure 10 As shown, the external gear is located in the inner cavity of the internal gear ring. The central axis of the external gear and the central axis of the driven internal gear ring are offset by a certain distance, and the two are paired to form an internal meshing conjugate gear pair.

[0014] like Figure 1 , Figure 9 , Figure 10 As shown, an assembly through hole is opened at the center of the external gear, through which the drive shaft passes, and circumferential positioning is achieved by a flat key or spline. When this structure is applied, external power drives the drive shaft (6) to rotate, and the drive shaft drives the external gear to rotate synchronously through a flat key (7) or spline. The external gear relies on the tooth profile formed by the first circular arc A1B1, the second circular arc B1C1, the straight line segment C1D1, the third circular arc D1E1, and the fourth circular arc E1F1 to interact with the curves A2B2, B2C2, C2D2, and D2E on the internal gear ring. 2、 The gear meshing transmission formed by E2F2 completes torque transmission. The external gear and drive shaft can be a separate, detachable structure, allowing for easy removal and replacement of the gear without needing to replace the entire drive shaft. Alternatively, it can be designed as a gear-shaft structure where the gear and shaft are integrated, such as... Figure 11 As shown, both types can participate in meshing normally.

[0015] The illustrations in this embodiment only provide a set of tooth profiles and tooth ratios for use with an internal gear pump as a reference. Specific gear parameters, tooth ratios, eccentricity, etc., should be adjusted according to the application scenario and working conditions. As long as the tooth profile combination curve described in the independent claims is used during application, smooth meshing, low pulsation, and ultra-quiet operation can be achieved.

Claims

1. A conjugate internal meshing gear pair consisting of a circular arc and a straight line, comprising an external gear and an internal gear ring. Its characteristics are: The tooth profile of the external gear consists of several circular arcs and a straight line. Adjacent tooth profile segments satisfy geometric first-order continuity at their connection points and share a common tangent. The external gear has a number of teeth evenly distributed circumferentially, and all teeth have identical tooth profile structures. The internal gear ring has a number of internal teeth evenly distributed circumferentially, and all internal teeth have identical tooth profile structures. The single-sided tooth profile of the external gear is formed by the first circular arc A1B1, the second circular arc B1C1, the straight line segment C1D1, the third circular arc D1E1, and the fourth circular arc E1F1, whose beginning and end points coincide and are smoothly connected. Adjacent tooth profile segments satisfy geometric first-order continuity at their connection points and share a common tangent. The working tooth profile of the internal gear ring is the conjugate envelope curve formed by the meshing motion of the tooth profile segments in the working tooth profile of the external gear. The external gear and the internal gear ring are paired to form an internal meshing conjugate gear pair. The external gear is located inside the internal gear ring cavity, and the central axis of the external gear and the central axis of the internal gear ring are offset by a certain distance. The tooth profile segments of the external gear working tooth profile include: a first circular arc A1B1, a second circular arc B1C1, a straight line segment C1D1, a third circular arc D1E1, and a fourth circular arc E1F1. The endpoint of the first circular arc A1B1 coincides with the starting point of the second circular arc B1C1, that is, they coincide at point B1. They satisfy geometric first-order continuity at point B1 and have a common tangent at point B1. The endpoint of the second circular arc B1C1 coincides with the starting point of the straight line segment C1D1, that is, they coincide at point C1. They satisfy geometric first-order continuity at point C1 and have a common tangent at point C1. The endpoint of the straight line segment C1D1 coincides with the starting point of the third circular arc D1E1, that is, they coincide at point D1. They satisfy geometric first-order continuity at point D1 and have a common tangent at point D1. The endpoint of the third circular arc D1E1 coincides with the starting point of the fourth circular arc E1F1, that is, they coincide at point E1. They satisfy geometric first-order continuity at point E1 and have a common tangent at point E1. The second circular arc B1C1, the straight line segment C1D1, and the third circular arc D1E1 in the tooth profile segments of the external gear are symmetrical on both sides. The first circular arc A1B1 is the root circular arc, and the fourth circular arc E1F1 is the tip circular arc. The tooth profile segments of the working tooth profile of the internal gear ring include: the conjugate envelope curve A2B2 formed by the meshing motion of the first circular arc A1B1, the conjugate envelope curve B2C2 formed by the meshing motion of the second circular arc B1C1, the conjugate envelope curve C2D2 formed by the meshing motion of the straight line segment C1D1, the conjugate envelope curve D2E2 formed by the meshing motion of the third circular arc D1E1, and the conjugate envelope curve E2F2 formed by the meshing motion of the fourth circular arc E1F1. A2B2, B2C2, C2D2, D2E2, and E2F2 have their first and last endpoints coincide and are smoothly connected, and are also geometrically first-order continuous at the connecting endpoints.

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