A strain gauge based central shaft type torque sensor

Abstract

The utility model discloses a kind of central shaft type torque sensors based on strain gauge, including middle tube, middle shaft and strain gauge, middle shaft is rotatably supported and is arranged in middle tube by left bearing and right bearing;Left port of middle tube is formed with left bearing positioning cavity, right port of middle tube is formed with right bearing positioning cavity;Middle tube is equipped with a cantilever beam of cantilever structure, the cantilever beam is formed by the arc spring piece of only left end integrally connected with middle tube, which is divided from the side of middle tube towards the chain tension direction;The inside surface center of cantilever beam right end is formed with strain boss, strain boss and the outer surface of right bearing contact and cooperate, and the clearance is formed between the upper and lower sides of cantilever beam and right bearing with strain boss;Strain gauge is pasted on the outside surface of cantilever beam.The utility model is simple in structure, less required components, low in processing difficulty, and can guarantee the accuracy of data detection.

Description

Technical Field

[0001] This utility model relates to the manufacturing technology of a central axis torque sensor, and in particular to a central axis torque sensor based on a strain gauge. Background Technology

[0002] In today's era of national fitness and green travel, cycling, with its natural setting and aerobic exercise, has become increasingly popular. my country's excellent infrastructure, boasting the world's longest paved road network and superior asphalt road conditions, has fueled the rapid development of cycling in the country. As a new type of bicycle, the electric-assist bicycle, compared to traditional unassisted bicycles and pure electric two-wheelers, intelligently provides power based on the user's effort, effectively reducing fatigue while ensuring a better riding experience and safety.

[0003] Torque sensors, as components that sense the force exerted by the user on an e-bike, are a crucial part of the entire e-bike system. As an input terminal, the accuracy of the torque sensor directly affects the controller's judgment and the user experience. Currently, the three most commonly used sensors in e-bikes on the market are speed sensors, pseudo-torque sensors, and torque sensors. Speed ​​sensors can only sense the user's pedaling speed or the bicycle's running speed, and cannot effectively provide feedback on the user's intentions; pseudo-torque sensors simulate the user's force signals by processing speed signals, offering a better experience than speed sensors, but still cannot provide accurate feedback; torque sensors measure the magnitude of the force exerted by the user's feet and pedaling speed (torque sensors generally include speed sensors), and can accurately provide real-time feedback based on the user's intentions (force exertion) (the controller adjusts the motor's output power based on the torque signal). Torque sensors are being increasingly widely adopted in e-bike systems. Summary of the Invention

[0004] The technical problem to be solved by this utility model is to provide a central axis torque sensor based on strain gauges that is simple in structure, easy to install, and can ensure the continuity and accuracy of signal transmission, in light of the current state of the prior art.

[0005] The technical solution adopted by this utility model to solve the above-mentioned technical problems is as follows: A strain gauge-based axial torque sensor includes a central tube, a central shaft, and strain gauges. The central shaft is rotatably supported within the central tube via left and right bearings. A left bearing positioning cavity is formed inside the left end of the central tube, and a right bearing positioning cavity is formed inside the right end of the central tube. A cantilever beam with a cantilever structure is provided on the central tube near the right end. The cantilever beam is composed of an arc-shaped spring piece that is integrally connected to the central tube only at its left end, which is divided from the side of the central tube facing the direction of chain tension. A strain gauge protrusion is formed at the center of the inner surface of the right end of the cantilever beam. The strain gauge protrusion contacts and cooperates with the outer peripheral surface of the right bearing. An clearance area is formed between the upper and lower sides of the strain gauge protrusion and the right bearing on the cantilever beam. The strain gauge is attached to the outer surface of the cantilever beam.

[0006] To optimize the above technical solution, the specific measures also include: On the side of the aforementioned central tube opposite to the cantilever beam, a bracket mounting opening is formed. An electrical board bracket is fitted into the bracket mounting opening. A circuit board connected to the strain gauge circuit is fixedly mounted on the electrical board bracket. The circuit board is connected to a data output line.

[0007] A magnetic ring is fixedly mounted on the central axis at the position corresponding to the circuit board, and a Hall element for detecting changes in the magnetic poles of the magnetic ring is installed on the circuit board.

[0008] The outer circumferential surface of the right end of the aforementioned middle tube is formed with an annular positioning shoulder for positioning with the right end of the bicycle bottom bracket. An annular rib is formed on the outer circumferential surface of the middle part of the middle tube, and an external thread is formed on the outer circumferential surface of the left end of the middle tube.

[0009] The left end of the aforementioned center tube is equipped with a left threaded cup for locking and fixing the center tube in the bicycle bottom bracket tube. The left threaded cup is formed with an internal thread for engaging with the external threaded helix at the left end of the center tube.

[0010] The left end of the aforementioned middle tube is fitted with a left retaining ring to prevent the left bearing from dislodging from the left bearing positioning cavity, and the right end of the middle tube is fitted with a right retaining ring to prevent the right bearing from dislodging from the right bearing positioning cavity.

[0011] A shim is provided between the right retaining ring and the right bearing as described above.

[0012] The root of the cantilever beam connected to the central tube is provided with curved holes to prevent stress concentration.

[0013] Compared with existing technologies, this invention features a cantilever beam with a cantilever structure at the right end of the central tube. The cantilever beam is formed by an arc-shaped spring piece, with only its left end integrally connected to the central tube, cut from the side of the central tube facing the direction of chain tension. A strain gauge protrusion is formed at the center of the inner surface of the right end of the cantilever beam, which contacts and cooperates with the outer circumferential surface of the right bearing. A clearance zone is formed between the cantilever beam and the right bearing on the upper and lower sides of the strain gauge protrusion. Compared with other central axis torque sensors on the market, this invention requires fewer parts, has lower processing difficulty, simplifies the product structure, and reduces production costs while ensuring measurement accuracy. Attached Figure Description

[0014] Figure 1 This is a schematic diagram of the structure of this utility model; Figure 2 This is an exploded view of this utility model; Figure 3 This is the right view of the present invention; Figure 4 This is a three-dimensional structural schematic diagram of the present invention; The attached diagrams are labeled as follows: left retaining ring K1, right retaining ring K2, clearance zone Q, left bearing Z1, right bearing Z2, central tube 1, curved hole 1a, cantilever beam 11, strain gauge 111, annular positioning shoulder 12, annular rib 13, central shaft 2, strain gauge 3, circuit board bracket 4, circuit board 5, magnetic ring 6, left toothed cup 7, gasket 8, data output line 9. Detailed Implementation

[0015] The embodiments of this utility model will be described in further detail below with reference to the accompanying drawings.

[0016] Figures 1 to 4 This is a schematic diagram of the structure of this utility model. As shown in the figure, this utility model discloses a central axis torque sensor based on strain gauges. The central axis torque sensor includes a central tube 1, a central axis 2, and strain gauges 3. The central axis 2 is rotatably supported by a left bearing Z1 and a right bearing Z2 and passes through the central through hole of the central tube 1. A left bearing positioning cavity is formed in the left port of the central through hole of the central tube 1, and the left bearing Z1 is positioned and installed in the left bearing positioning cavity. In order to prevent the left bearing Z1 from falling out of the left bearing positioning cavity, a left retaining spring K1 for holes is also installed in the left port of the central tube 1. A right bearing positioning cavity is formed in the right port of the central through hole of the central tube 1, and the right bearing Z2 is positioned and installed in the right bearing positioning cavity. Similarly, in order to prevent the right bearing Z2 from falling out of the right bearing positioning cavity, a right retaining spring K2 for holes is installed in the right port of the central tube 1. At the same time, in order to eliminate gaps and prevent the central axis 2 from moving axially, this utility model also provides a shim 8 between the right retaining spring K2 and the right bearing Z2.

[0017] from Figure 4As can be clearly seen, the central tube 1 of this invention has a cantilever beam 11 with a cantilever structure near its right end. The cantilever beam 11 is composed of an arc-shaped spring piece that can expand elastically, with only its left end integrally connected to the central tube 1. This arc-shaped spring piece is actually formed by dividing a portion of the side of the central tube 1 facing the direction of chain tension. Only one side of the arc-shaped spring piece remains connected to the central tube 1, while the other three sides form a gap with the central tube 1. The right end of the cantilever beam 11 extends to the right bearing positioning cavity, thus transforming the originally closed-loop right bearing positioning cavity into a semi-enclosed bearing positioning cavity. Figure 3 It can be seen that ( Figure 3 (The arrow in the diagram indicates the direction of chain tension). A strain gauge protrusion 111 is formed at the center of the inner surface of the right end of the cantilever beam 11 of this invention. This strain gauge protrusion 111 contacts and engages with the outer circumferential surface of the right bearing Z2. A clearance zone Q is formed between the strain gauge protrusion 111 and the right bearing Z2 on both the upper and lower sides of the cantilever beam 11. Only the strain gauge protrusion 111 contacts the right bearing Z2; the rest of the cantilever beam 11 is in clearance. This allows the central shaft 2 to accurately transmit the chain tension it bears to the cantilever beam 11 through the right bearing Z2, causing the cantilever beam 11 to bend elastically under stress. Strain gauges 3 of this invention are attached to the outer surface of the cantilever beam 11. There can be one or more sets of strain gauges 3. The strain gauges 3, attached to the cantilever beam 11, convert the deformation of the cantilever beam 11 under stress into an electrical signal output. This utility model features a cantilever beam 11 with a cantilever structure on the central tube 1. Only the strain gauge 111 of the cantilever beam 11 contacts the right bearing Z2, while the rest of the beam is designed to be open. Therefore, the structure is simple, easy to process, and highly responsive, ensuring the continuity and accuracy of signal transmission.

[0018] In the embodiments, as shown Figure 1 and Figure 2 As shown, a bracket mounting opening is formed on the side of the central tube 1 opposite to the cantilever beam 11. "Opposite" here refers to the circumferential direction; the cantilever beam 11 is 180 degrees away from the bracket mounting opening. An electrical board bracket 4 is fitted into the bracket mounting opening. A circuit board 5, connected to the strain gauge 3, is fixedly mounted on this bracket 4. The circuit board 5 is connected to a data output line 9. The strain gauge 3 can feed back the electrical signal generated by deformation to the circuit board 5. The circuit board 5 has a processing chip. The processing chip processes the received electrical signal internally and then outputs the processed signal externally through the data output line 9.

[0019] In this embodiment, a magnetic ring 6 is fixedly mounted on the central shaft 2 at a position corresponding to the circuit board 5. A Hall element for detecting changes in the magnetic poles of the magnetic ring 6 is installed on the circuit board 5. The magnetic ring 6 consists of 36 pairs of magnetic poles and can rotate synchronously with the central shaft 2. The Hall element can detect the rotational speed and direction of the central shaft 2 by the changes in the magnetic poles.

[0020] In the embodiments, as shown Figure 1 As shown, the outer circumferential surface of the right end of the middle tube 1 of this invention is formed with an annular positioning shoulder 12 for positioning and cooperating with the right end of the bicycle bottom bracket. An annular rib 13 is formed on the outer circumferential surface of the middle part of the middle tube 1, and an external thread is formed on the outer circumferential surface of the left end of the middle tube 1. The annular rib 13 can enhance the mechanical strength of the middle tube 1.

[0021] In this embodiment, the left end of the middle tube 1 is provided with a left threaded cup 7, which is formed with an internal thread for engaging with the external thread of the left port of the middle tube 1. During installation, the middle tube 1 is inserted into the right port of the bicycle bottom bracket, and the annular positioning shoulder 12 of the middle tube 12 is positioned and engaged with the plane of the right port of the bicycle bottom bracket. Then, the middle tube 1 is locked and fixed in the bicycle bottom bracket by engaging with the external thread of the left port of the middle tube 1 through the left threaded cup 7.

[0022] In this embodiment, the root of the cantilever beam 11 connected to the central tube 1 is provided with a curved hole 1a to prevent stress concentration.

[0023] The above embodiments provide a systematic and detailed description of the present utility model. These are merely preferred embodiments of the present utility model and are not intended to limit the present utility model. For those skilled in the art, the present utility model can have various modifications and variations. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present utility model should be included within the protection scope of the present utility model.

Claims

1. A strain gauge-based axial torque sensor, comprising a central tube (1), a central shaft (2), and a strain gauge (3), wherein the central shaft (2) is rotatably supported within the central tube (1) via a left bearing (Z1) and a right bearing (Z2); a left bearing positioning cavity is formed within the left port of the central tube (1), and a right bearing positioning cavity is formed within the right port of the central tube (1); characterized in that: The central tube (1) has a cantilever beam (11) with a cantilever structure at the right end near the central tube (1). The cantilever beam (11) is composed of an arc-shaped spring piece that is only integrally connected to the central tube at its left end, which is divided from the side of the central tube (1) facing the direction of chain tension. A strain gauge (111) is formed at the center of the inner side of the right end of the cantilever beam (11). The strain gauge (111) contacts and cooperates with the outer peripheral surface of the right bearing (Z2). An clearance area (Q) is formed between the upper and lower sides of the strain gauge (111) and the right bearing (Z2). The strain gauge (3) is attached to the outer side of the cantilever beam (11).

2. A strain gauge-based central axis torque sensor according to claim 1, characterized in that: The central tube (1) has a bracket mounting opening formed on the side opposite to the cantilever beam (11). A circuit board bracket (4) is installed in the bracket mounting opening. A circuit board (5) connected to the strain gauge (3) is fixedly installed on the circuit board bracket (4). A data output line (9) is connected to the circuit board (5).

3. A strain gauge-based central axis torque sensor according to claim 2, characterized in that: A magnetic ring (6) is fixedly mounted on the central shaft (2) at the position corresponding to the circuit board (5), and a Hall element for detecting the change of magnetic poles of the magnetic ring (6) is installed on the circuit board (5).

4. A strain gauge-based central axis torque sensor according to claim 3, characterized in that: The outer peripheral surface of the right end of the middle tube (1) is formed with an annular positioning shoulder (12) for positioning with the right end of the bicycle bottom bracket. The outer peripheral surface of the middle part of the middle tube (1) is formed with an annular rib (13). The outer peripheral surface of the left end of the middle tube (1) is formed with an external thread.

5. A strain gauge-based central axis torque sensor according to claim 3, characterized in that: The left end of the middle tube (1) is provided with a left thread cup (7) for locking the middle tube (1) in the bicycle bottom bracket tube. The left thread cup (7) is formed with an internal thread for engaging with the external thread of the left end of the middle tube (1).

6. A strain gauge-based central axis torque sensor according to claim 5, characterized in that: The left port of the middle tube (1) is fitted with a left retaining ring (K1) to prevent the left bearing (Z1) from coming out of the left bearing positioning cavity, and the right port of the middle tube (1) is fitted with a right retaining ring (K2) to prevent the right bearing (Z2) from coming out of the right bearing positioning cavity.

7. A strain gauge-based central axis torque sensor according to claim 6, characterized in that: A shim (8) is provided between the right retaining ring (K2) and the right bearing (Z2).

8. A strain gauge-based central axis torque sensor according to claim 7, characterized in that: The root of the cantilever beam (11) connected to the central tube (1) is provided with a curved hole (1a) to prevent stress concentration.

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