Planetary reducer structure with external torque sensor

Abstract

The utility model discloses a two -stage planetary reducer structure of external torque sensor, including lower box, gear ring casing, inner tooth circle, drawboard and external torque sensor. Inner tooth circle is fixed in gear ring casing, and gear ring casing is rotatably connected with lower box through bearing assembly, and the drawboard is fixedly installed to the outside of inner tooth circle, and the external torque sensor is connected with the drawboard, and the torque of inner tooth circle is monitored. The reducer is two -stage structure, and the inner tooth circle contains first -stage and second -stage gear ring part, and is engaged with first -stage and second -stage planetary gear respectively, and the first sun gear input, and the first planet carrier connects the second sun gear, and the second planet carrier passes through the output shaft and exports, and the parts are coaxially arranged. The structure realizes the micro - rotation of inner tooth circle through the split design, and is convenient for external monitoring, and need not to disassemble the core part, is applicable to medium - large - size reducer, reduces the maintenance cost, and promotes the reliability.

Description

Technical Field

[0001] This utility model relates to the field of mechanical engineering, particularly to planetary gear transmission technology in mechanical transmission, specifically to a planetary reducer structure that can be connected to an external torque sensor. Background Technology

[0002] Two-stage planetary gear reducers, with their high transmission ratio, compact structure, and high torque output, are widely used in industrial automation, wind power generation, robotics, and mining machinery. Their core structure includes a first-stage and a second-stage planetary gear system, each stage consisting of a sun gear, planet gears, an internal ring gear, and a planet carrier. The first-stage sun gear receives input power, drives the planet carrier via the planet gears, connects to the second-stage sun gear, and finally outputs power through the second-stage planet carrier, achieving speed reduction and torque amplification. The internal ring gear is typically fixed to the housing or lower gearbox, providing responsive torque. This design simplifies manufacturing and assembly, is suitable for high-load applications, and can achieve transmission ratios exceeding 100:1. According to market data, the global planetary gear reducer market is worth over $100 billion, with an annual growth rate of approximately 6%, and the demand for torque monitoring is increasing to support overload protection and intelligent control.

[0003] However, torque monitoring faces significant challenges in two-stage planetary gearboxes. Traditional methods, such as attaching strain gauges to the output shaft, are suitable for small, single-stage equipment, but in medium to large two-stage systems, the measurement error can reach 5%-10% due to the large shaft diameter and inter-stage vibration interference. Another method utilizes magnetoelastic sensors to measure torque by detecting changes in the magnetic field on the shaft, offering high accuracy (0.1% error), but requires embedding in the shaft, making installation complex. Furthermore, in multi-stage systems, the error can increase to 15% due to vibrations and electromagnetic interference from the first stage. In addition, in existing designs, the internal gear ring is usually fixed to the housing and cannot rotate relative to it, making it difficult for external sensors to directly acquire its torque. Built-in sensor solutions require interfaces to be reserved during the design phase, limiting standardized production, and maintenance requires disassembling multiple stages, leading to downtime losses.

[0004] In high-load scenarios, such as robot joints (where overload can cause jamming) or wind power systems (where abnormal torque can lead to gear breakage), real-time monitoring of the internal gear ring torque is crucial. Studies show that the torque difference between two-stage systems can reach 30%, and monitoring only the output shaft while ignoring the internal gear ring's response torque can easily lead to missed overload hazards. Existing technologies sometimes attempt to optimize load balancing or sealing performance through floating internal gear rings, but do not address torque monitoring; axial sensor solutions require multiple sensors in multi-stage systems, increasing size and cost. Traditional patch methods suffer from decreased accuracy in large equipment due to shaft complexity, while magnetoelastic solutions are limited in application due to high cost and environmental sensitivity.

[0005] Limitations of existing technologies include: fixed internal gear ring restricts external monitoring access; complex shafts in medium and large-sized equipment result in low accuracy of patch methods; and complex and costly installation and maintenance of built-in sensors. In the context of Industry 4.0, flexible external connection solutions are needed to support intelligent control. This invention, through a split gear ring housing and bearing design, allows the internal gear ring to rotate slightly relative to the lower housing, enabling external sensors to monitor the torque of the internal gear ring. It is suitable for medium and large-sized two-stage reducers, balancing structural rigidity and monitoring flexibility. Utility Model Content

[0006] In view of this, the present invention aims to provide a two-stage planetary reducer structure with an external torque sensor, solving the problems of inconvenient torque monitoring, complex installation, and limited accuracy caused by a fixed internal gear ring. Through a split gear ring housing design, the internal gear ring can rotate, allowing the external sensor to directly monitor the torque of the internal gear ring, dynamically control the input, and improve the safety of medium and large-sized reducers.

[0007] To achieve the above objectives, this utility model provides the following technical solution: A planetary reducer structure with an external torque sensor includes a lower housing, a gear ring housing, an internal gear ring, a pull plate, and an external torque sensor. The internal gear ring is fixed to the gear ring housing, and the gear ring housing is rotatably connected to the lower housing via a bearing assembly. The pull plate is fixedly installed on the outer side of the internal gear ring, and the external torque sensor is connected to the pull plate to monitor the torque of the internal gear ring.

[0008] Furthermore, the planetary reducer has a two-stage structure, including a first-stage planetary gear system and a second-stage planetary gear system; the internal gear ring includes a first-stage gear ring portion and a second-stage gear ring portion, which mesh with the first-stage planetary gears and the second-stage planetary gears, respectively.

[0009] Furthermore, the first-stage planetary gear system includes a first sun gear, a first planet gear, and a first planet carrier, and the second-stage planetary gear system includes a second sun gear, a second planet gear, and a second planet carrier. The first sun gear serves as the input end, the first planet carrier is fixedly connected to the second-stage sun gear, and the second planet carrier serves as the output end.

[0010] Furthermore, the lower housing is provided with an output shaft that rotates with it, and the output shaft is connected to the second planetary carrier.

[0011] Furthermore, the first sun gear, the second sun gear, the output shaft, and the lower housing are all arranged coaxially.

[0012] The beneficial effects of this utility model are as follows: This invention significantly improves the performance and applicability of a two-stage planetary gear reducer from a structural optimization perspective. Firstly, the split design optimizes the traditional one-piece housing into a combined structure where the lower housing is fixed and the gear ring housing is rotatable. The internal gear ring is fixed to the gear ring housing and rotates relative to the lower housing via a bearing assembly. This optimization avoids the rigid constraint of the internal gear ring being directly fixed to the lower housing, granting it rotational freedom. This allows an external torque sensor to directly respond to changes in the internal gear ring torque via a pull plate, without requiring invasive modifications to the core transmission components. Compared to traditional designs, this structure reduces assembly complexity and improves monitoring accuracy to within 1%, far superior to the 5%-10% error of the shaft-end strain gauge method. This optimization is particularly suitable for medium to large-sized gear reducers, where increased shaft diameter leads to increased interference in traditional monitoring. This structure integrates the torque acquisition point via an external pull plate, simplifying the sensor installation path and shortening installation time.

[0013] Secondly, the optimization of the two-stage transmission structure is reflected in the coaxial arrangement and inter-stage connection. The first sun gear, second sun gear, output shaft, and lower housing are coaxial, ensuring a compact layout and efficient power transmission. The first planetary carrier is directly fixed to the second sun gear, avoiding additional couplings and reducing vibration transmission and energy loss. Simultaneously, the optimized design of the pull plate fixed to the outside of the internal gear ring allows for more direct torque signal transmission. The resistance provided by the sensor only acts on the micro-rotation part, without interfering with planetary gear meshing and output shaft rotation. This structure separates monitoring and transmission functions, optimizing overall rigidity and dynamic response. In high-load scenarios (such as wind power systems), it can capture real-time fluctuations in the internal gear ring torque and support dynamic input adjustment.

[0014] Other advantages, objectives, and features of this invention will be set forth in part in the description which follows, and in part will be apparent to those skilled in the art from the following examination and study, or may be learned from practice of this invention. The objectives and other advantages of this invention can be realized and obtained through the following description. Attached Figure Description

[0015] To make the objectives, technical solutions, and advantages of this utility model clearer, the preferred embodiments of this utility model will be described in detail below with reference to the accompanying drawings, wherein: Figure 1 This is a schematic diagram of the overall structure of the planetary reducer with an external torque sensor in this utility model.

[0016] Reference numerals in the attached diagram: 1-First sun gear; 2-Internal gear ring; 3-Pull plate; 4-External torque sensor; 5-Gear ring housing; 6-First bearing; 7-Lower housing; 8-Second bearing; 9-Output shaft. Detailed Implementation

[0017] The following specific examples illustrate the implementation of this utility model. Those skilled in the art can easily understand other advantages and effects of this utility model from the content disclosed in this specification. This utility model can also be implemented or applied through other different specific embodiments, and various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of this utility model. It should be noted that the illustrations provided in the following embodiments are only schematic representations of the basic concept of this utility model. Unless otherwise specified, the following embodiments and features can be combined with each other.

[0018] The accompanying drawings are for illustrative purposes only and are schematic diagrams, not actual pictures. They should not be construed as limiting the present invention. To better illustrate the embodiments of the present invention, some parts in the drawings may be omitted, enlarged, or reduced, and do not represent the actual product dimensions. It is understandable to those skilled in the art that some well-known structures and their descriptions may be omitted in the drawings.

[0019] In the accompanying drawings of this utility model, the same or similar reference numerals correspond to the same or similar components. In the description of this utility model, it should be understood that if terms such as "upper," "lower," "left," "right," "front," and "rear" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, they are only for the convenience of describing this utility model and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, the terms used to describe positional relationships in the drawings are only for illustrative purposes and should not be construed as limiting this utility model. For those skilled in the art, the specific meaning of the above terms can be understood according to the specific circumstances.

[0020] Example 1: Two-stage planetary reducer for robot joints This embodiment describes a medium-sized two-stage planetary reducer for robot joints, designed with a transmission ratio of 80:1 and a rated output torque of 500 Nm. The structure is as follows: Figure 1 As shown, it includes a lower housing 7, a gear ring housing 5, an internal gear ring 2, a first-stage planetary gear system, a second-stage planetary gear system, an output shaft 9, a pull plate 3, and an external torque sensor 4. The internal gear ring 2 is fixed to the gear ring housing 5 and includes a first-stage gear ring portion and a second-stage gear ring portion. It adopts a helical tooth structure to improve meshing smoothness.

[0021] The first-stage planetary gear system includes a first sun gear 1, three first planet gears, and a first planet carrier. The second-stage planetary gear system includes a second sun gear, three second planet gears, and a second planet carrier. The first sun gear 1 serves as the input end. The first planet carrier is fixedly connected to the second sun gear, and the second planet carrier is connected to the output shaft 9 via a spline. The gear ring housing 5 is rotatably connected to the lower housing 7 via a first bearing 6 (upper needle roller bearing) and a second bearing 8 (lower needle roller bearing), ensuring that the internal gear ring 2 rotates slightly relative to the lower housing 7. The pull plate 3, made of high-strength alloy, is fixed to the outside of the internal gear ring 2 and connected to an external torque sensor 4 via bolts. The other end of the sensor is fixed to an external bracket.

[0022] The lower housing 7 is fixed to the robot base, and the first sun gear 1, the second sun gear, the output shaft 9 and the lower housing 7 are arranged coaxially.

[0023] During operation, the motor drives the first sun gear 1, and the power is transmitted to the second sun gear via the first planetary carrier. The second planetary carrier drives the joint movement through the output shaft 9. The internal gear ring 2 experiences a slight rotation tendency due to force, and the external torque sensor 4 detects the torque through the pull plate 3, with a monitoring accuracy of 0.8%. The torque data is fed back to the PLC control system, which dynamically adjusts the input torque to prevent joint overload. Tests show that under a 500Nm load, the monitoring error is <1.5%, and the transmission efficiency is >96%, meeting the requirements of high precision and fast response for the robot.

[0024] Example 2: Two-stage planetary gearbox for wind power systems This embodiment focuses on a large two-stage planetary gearbox in a wind power system, designed with a transmission ratio of 120:1 and a rated output torque of 2000 Nm. The structure is as follows: Figure 1 As shown, it includes a lower housing 7, a gear ring housing 5, an internal gear ring 2, a first-stage planetary gear system, a second-stage planetary gear system, an output shaft 9, a pull plate 3, and an external torque sensor 4. The internal gear ring 2 is fixed to the gear ring housing 5 and includes a first-stage gear ring portion and a second-stage gear ring portion. It adopts a spur gear structure to simplify manufacturing.

[0025] The first-stage planetary gear system includes a first sun gear 1, four first planet gears, and a first planet carrier. The second-stage planetary gear system includes a second sun gear, four second planet gears, and a second planet carrier. The first sun gear 1 serves as the input end. The first planet carrier is fixedly connected to the second sun gear, and the second planet carrier is connected to the output shaft 9 via a flange. The gear ring housing 5 is rotatably connected to the lower housing 7 via a first bearing 6 (upper double-row tapered roller bearing) and a second bearing 8 (lower double-row tapered roller bearing), accommodating micro-rotation under high loads. The pull plate 3 is made of high-strength steel and welded to the outside of the internal gear ring 2, connecting to an external torque sensor 4 (magnetoelastic type). The sensor is fixed to an external base.

[0026] The lower housing 7 is fixed to the wind turbine tower, and the first sun gear 1, the second sun gear, and the output shaft 9 are arranged coaxially.

[0027] During operation, the wind turbine drives the first sun gear 1, and the power is amplified in two stages and transmitted to the generator via the output shaft 9. The torque of the internal gear ring 2 is transmitted to the external torque sensor 4 through the pull plate 3, with a monitoring accuracy of 1%. The data is integrated into the IoT system for remote diagnostics. If abnormal torque (such as exceeding the 2000Nm limit) is detected, the control system reduces the input power to prevent damage to the blades or gears. Tests show that under a 2000Nm load, the monitoring error is <2%, the transmission efficiency is >95%, and the system reliability is improved by 30%.

[0028] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of this utility model and are not intended to limit it. Although this utility model has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solution of this utility model without departing from the spirit and scope of this technical solution, and all such modifications or substitutions should be covered within the scope of the claims of this utility model.

Claims

1. A planetary reducer structure with an external torque sensor, characterized in that, It includes a lower housing, a gear ring housing, an inner gear ring, a pull plate, and an external torque sensor; the inner gear ring is fixed on the gear ring housing, and the gear ring housing is rotatably connected to the lower housing through a bearing assembly; the pull plate is fixedly installed on the outer side of the inner gear ring, and the external torque sensor is connected to the pull plate to monitor the torque of the inner gear ring.

2. The planetary reducer structure with an external torque sensor according to claim 1, characterized in that, The planetary reducer has a two-stage structure, including a first-stage planetary gear system and a second-stage planetary gear system; the internal gear ring includes a first-stage gear ring portion and a second-stage gear ring portion, which mesh with the first-stage planetary gears and the second-stage planetary gears, respectively.

3. The planetary reducer structure with an external torque sensor according to claim 2, characterized in that, The first-stage planetary gear system includes a first sun gear, a first planet gear, and a first planet carrier. The second-stage planetary gear system includes a second sun gear, a second planet gear, and a second planet carrier. The first sun gear serves as the input end, the first planet carrier is fixedly connected to the second-stage sun gear, and the second planet carrier serves as the output end.

4. The planetary reducer structure with an external torque sensor according to claim 3, characterized in that, The lower housing is equipped with an output shaft that rotates with it, and the output shaft is connected to the second planetary carrier.

5. The planetary reducer structure with an external torque sensor according to claim 4, characterized in that, The first sun gear, the second sun gear, the output shaft, and the lower housing are all arranged coaxially.

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