Electrically assisted bicycle with central shaft torque sensor based on strain principle

Abstract

The application discloses a middle shaft type torque sensor of an electrically-assisted bicycle based on a strain principle, which comprises an outer tube, a middle shaft rotatably supported and installed in the outer tube through a left bearing and a right bearing, the left bearing being installed in a left port of the outer tube, a strain part being formed at a right end of the outer tube, the right bearing being installed in a right bearing installation hole formed in the strain part; two stress beams are processed on the strain part, the two stress beams comprising a front stress beam and a rear stress beam, and a deformation cavity being formed between the front stress beam and the rear stress beam; a stress transmission bump is formed at the center of the front stress beam and tightly abuts against the outer circle of the right bearing, two suspended areas being symmetrically processed on the stress transmission bump; a metal thimble is installed at the center of the deformation cavity, a strain gauge is attached to the rear stress beam, and a PBC electric plate is installed on the outer tube. The application has the advantages of simple structure, collection of only the instantaneous thrust of the middle shaft during riding, reduction of interference and continuous and accurate measurement of the change of the stress of the middle shaft.

Description

TECHNICAL FIELD

[0001] The present application relates to the design technology of the middle shaft type torque sensor of the electrically assisted bicycle, in particular to a middle shaft type torque sensor of the electrically assisted bicycle based on the strain principle. BACKGROUND

[0002] In this era of nationwide fitness and green travel, cycling has been popular among more and more people because of its natural sports field and aerobic exercise. Because the infrastructure work in China is very good, the total mileage of the pavement is the first in the world, and the asphalt road conditions are good, making the cycling in China develop vigorously. As a new type of bicycle, the electrically assisted bicycle can intelligently provide power according to the user's effort, effectively reduce the user's fatigue, and ensure the riding experience and safety. The electrically assisted bicycle is used for walking, exercise and other purposes, which has been paid more and more attention in recent years.

[0003] The torque sensor, as a component for sensing the user's effort on the electrically assisted bicycle, is a crucial part of the entire electrically assisted bicycle system. As an input end, the accuracy of the torque sensor directly affects the judgment of the controller and the user experience. The commonly used sensors on the market include speed sensors, pseudo torque sensors and torque sensors. The speed sensor can only sense the speed of the user's pedaling or the speed of the bicycle running, and cannot effectively feedback the user's intention; the pseudo torque sensor simulates the user's effort signal by processing the speed signal, which is better than the speed sensor, but still cannot accurately feedback; the torque sensor measures the size of the user's pedaling force and the pedaling speed (the torque sensor generally includes a speed sensor) when the user rides, and can accurately feedback (the controller adjusts the motor output power according to the torque signal) according to the user's intention (the size of the effort). Torque sensors are increasingly accepted by electrically assisted bicycle systems. SUMMARY

[0004] The technical problem to be solved by the present application is to provide a middle shaft type torque sensor of the electrically assisted bicycle based on the strain principle, which has the advantages of simple structure, accurate measurement and convenient installation.

[0005] The technical scheme adopted by the present application to solve the above technical problems is:

[0006] A kind of electric power-assisted bicycle central shaft type torque sensor based on strain principle, including outer tube and the central shaft of being supported rotationally in the outer tube by left bearing and right bearing, left bearing is positioned and installed in the left port of outer tube, the right end of outer tube is integrally formed with strain part, right bearing is tightly fitted and installed in the right bearing installation hole formed in strain part;Two stress beams facing the rear of electric power-assisted bicycle are processed on strain part, two stress beams include front stress beam and rear stress beam, and long strip-shaped deformation cavity is formed between front stress beam and rear stress beam;The center of front stress beam is formed with stress transfer lug that is closely contacted with the outer circle of right bearing, and the upper and lower of stress transfer lug are symmetrically processed with two overhanging areas that are not contacted with the outer circle of right bearing;Metallic stylus for transmitting the thrust of front stress beam to rear stress beam is installed in the center of deformation cavity, strain gauge for detecting the stress deformation of rear stress beam is attached on rear stress beam, and PBC electric board connected with the electric signal of strain gauge is installed on outer tube.

[0007] To optimize the above technical solution, the specific measures taken also include:

[0008] The peripheral surface of the above-mentioned outer tube is formed with a concave circuit board mounting position adjacent to the stress beam of the strain part, and the PBC electric board is fixed in the circuit board mounting position of the outer tube by an adhesive; the PBC electric board has a cable connector, and the strain part is formed with a cable clamping groove fixedly fitted with the cable connector.

[0009] The above-mentioned central shaft is fixedly fitted with a magnetic ring rotating synchronously with the central shaft, and the magnetic ring has 24 to 32 pairs of magnetic poles around it; the PBC electric board is provided with a main control chip and a Hall element for detecting the rotational speed of the central shaft by detecting the change of the magnetic poles of the magnetic ring.

[0010] The center of the above-mentioned deformation cavity is formed with a positioning arc-shaped groove for positioning and installing the metallic stylus.

[0011] The right end surface of the above-mentioned strain part is processed with a positioning pin hole, and a positioning pin is fitted in the positioning pin hole for positioning and cooperating with the slot of the five-way pipe of the electric power-assisted bicycle.

[0012] The above-mentioned strain part is provided with a right end cover for preventing dust from entering the right bearing installation hole, and the right end cover is fixedly installed on the strain part by three cross screws.

[0013] The left port of the above-mentioned outer tube is processed with a clamping spring slot, and a hole stop ring for preventing the axial movement of the left bearing is clamped in the clamping spring slot.

[0014] The outer periphery of the left end of the above-mentioned outer tube is processed with external threads, and the left end of the outer tube is screw-fitted with a left bowl for locking and fixing the outer tube on the five-way pipe of the electric power-assisted bicycle through external threads.

[0015] The two ends of the middle shaft are shaped into square heads, and the square heads are internally threaded; a left crank is installed on the square head of the left end of the middle shaft, and an integrated toothed disc crank is installed on the square head of the right end of the middle shaft.

[0016] Compared with the prior art, the outer tube of the application is integrally formed with a strain part, the strain part is provided with two stress beams in front and back, a metal thimble is arranged between the two stress beams, the front stress beam abuts against the right bearing, when the electrically assisted bicycle is ridden, the tension generated by the chain is converted into a thrust by the middle shaft and acts on the right bearing, the right bearing transmits the thrust to the front stress beam, the front stress beam deforms and extrudes the metal thimble, the metal thimble transmits the thrust to the rear stress beam, the rear stress beam is provided with a strain gauge, the strain gauge transmits the electrical signal generated by the change of the surface stress of the rear stress beam to the PBC electric panel, and the PBC electric panel processes the signal and outputs it through a cable connector. The application has simple structure, only collects the instantaneous thrust of the middle shaft when ridden, reduces interference, and can continuously and accurately measure the change of the force of the middle shaft. BRIEF DESCRIPTION OF DRAWINGS

[0017] Figure 1 is one of the three-dimensional structure schematic diagrams of the application;

[0018] Figure 2 is the second three-dimensional structure schematic diagram of the application;

[0019] Figure 3 is the sectional view of the application;

[0020] Figure 4 is the exploded view of the application;

[0021] Figure 5 is the three-dimensional structure schematic diagram of the outer tube of the application;

[0022] Figure 6 is the right view of the application after removing the right end cover;

[0023] Figure 7 is one of the assembly schematic diagrams of the application and the electrically assisted bicycle five-way pipe;

[0024] Figure 8 is the second assembly schematic diagram of the application and the electrically assisted bicycle five-way pipe. DETAILED DESCRIPTION

[0025] The embodiments of the application are further described in detail below with reference to the accompanying drawings.

[0026] Figures 1 to 8 is the structure and assembly schematic diagram of the application.

[0027] The reference signs are: hole check ring D, five-way pipe G, deformation cavity K, positioning arc-shaped groove K1, cross screw L, left crank P1, integrated toothed disc crank P2, suspended area Q, external thread W, cable connector X, left bearing Z1, right bearing Z2, outer tube 1, circuit board mounting position 1a, cable clamping groove 1b, strain part 11, right bearing mounting hole 11a, front stress beam 12, rear stress beam 13, stress transmission block 121, middle shaft 2, square head 21, internal threaded hole 21a, metal thimble 3, strain gauge 4, PBC electric plate 5, magnetic ring 6, positioning pin 7, right end cover 8, left toothed bowl 9.

[0028] The application discloses a middle shaft type torque sensor of an electric power-assisted bicycle based on a strain principle, which comprises an outer tube 1 capable of being inserted into a five-way pipe G of the electric power-assisted bicycle in a rotation-preventing mode, a middle shaft 2 being rotatably supported in the outer tube 1 through left and right bearings Z1 and Z2, the inner circles of the left and right bearings Z1 and Z2 being positioned and matched with the middle shaft 2, so that the middle shaft 2 can rotate freely relative to the outer tube 1. Figure 3 As shown in the figure, in order to prevent the left bearing Z1 from moving axially, a clamping spring groove is further formed in the left bearing mounting cavity of the left end port of the outer tube 1, and a hole check ring D matched with the left bearing Z1 is clamped in the clamping spring groove. The focus of the application is that the right end of the outer tube 1 is fixedly installed with or integrally formed with a strain part 11, the diameter of the strain part 11 is greater than that of the five-way pipe G of the electric power-assisted bicycle, so that the left side surface of the strain part 11 can be matched with the right end port of the five-way pipe G in a positioning mode after the middle shaft type torque sensor is installed on the five-way pipe G. Figure 6It can be clearly seen that two stress beams are machined on the strain part 11, the stress beams are arranged in relative vertical to the chain of the electric bicycle, and the outer ends of the stress beams are all directed to the rear of the electric bicycle. The two stress beams include a front stress beam 12 and a rear stress beam 13, and the front stress beam 12 and the rear stress beam 13 are arranged in interval, and the interval between the front stress beam 12 and the rear stress beam 13 forms a long strip-shaped deformation cavity K. In order to ensure that the thrust borne by the right bearing Z2 can be accurately transmitted to the front stress beam 12, the center of the front stress beam 12 is shaped in close contact with the stress transmission protrusion 121 on the outer circle of the right bearing Z2, and the upper and lower of the stress transmission protrusion 121 are symmetrically machined with two overhanging areas Q which are not in contact with the outer circle of the right bearing Z2, the overhanging areas Q are communicated with the right bearing mounting hole 11a, so that the contact surface of the front stress beam 12 and the right bearing Z2 is avoided in the tension direction except the stress transmission protrusion 121, thereby ensuring that the stress can be transmitted to the rear of the vehicle through the front stress beam 12. The center of the deformation cavity K of the present application is installed with a connecting piece for realizing two-stage stress transmission in a close fit manner, and the thrust borne by the front stress beam 12 can be accurately transmitted to the rear stress beam 13 through the connecting piece. Herein, the connecting piece of the present application is preferably a metal thimble 3, and the metal thimble 3 is cylindrical, and the contact surface of the metal thimble 3 with the rear stress beam 13 is relatively small, so that the metal thimble 3 can better transmit the thrust borne by the front stress beam 12 to the rear stress beam 13 after being extruded by the deformation of the front stress beam 12, so that the plane of the rear stress beam 13 changes, and the plane of the rear stress beam 13 is attached with a strain gauge 4 for detecting the stress deformation of the rear stress beam 13. The outer tube 1 of the present application is also installed with a PBC electric board 5 connected with the electric signal of the strain gauge 4, and the PBC electric board 5 is installed with at least a main control chip and a Hall element for signal processing. Figure 2 and Figure 3 As shown in the figures, the both ends of the middle shaft 2 are shaped with square heads 21, and the square heads 21 are machined with internal thread holes 21a. Figure 7 and Figure 8 As can be seen, the left end of the middle shaft 2 is mounted with a left crank P1 through the square head 21 in a manner of preventing rotation, and the right end of the middle shaft 2 is mounted with an integrated toothed disc crank P2 through the square head 21 in a manner of preventing rotation. Screws can be installed in the internal thread holes 21a, and the left crank P1 and the integrated toothed disc crank P2 can be fixed on the middle shaft 2 in a manner of preventing disengagement through the screws. The toothed disc of the integrated toothed disc crank P2 can be connected with the chain. When the rider rides, the pedaling of the rider makes the chain tensioned, and the chain transmits the pedaling torque to the middle shaft 2 through the toothed disc, so that the middle shaft 2 generates a rearward thrust, and the middle shaft 2 transmits the thrust to the right bearing Z2, and then to the front stress beam 12, the metal thimble 3, and finally to the rear stress beam 13. After the strain gauge 4 attached to the rear stress beam 13 senses the change of the plane stress of the rear stress beam 13, the electric signal is transmitted to the PBC electric board 5, and the main control chip on the PBC electric board 5 can output the processed signal after the received electric signal is processed.

[0029] In the embodiments, by Figure 5 As can be seen, a recessed circuit board mounting position 1a is formed on the circumferential surface of the outer tube 1 at the stress beam adjacent to the strain section 11. The PBC board 5 is fixed in the circuit board mounting position 1a of the outer tube 1 using adhesive. A cable connector X is led out from the PBC board 5, which is used to facilitate the signal output after processing. In order to facilitate the fixing of the cable connector X and prevent damage to the PBC board 5, a cable slot 1b is formed on the strain section 11 to fix and fit with the cable connector X.

[0030] In the embodiments, as shown Figure 3 As shown, a magnetic ring 6 is fixedly mounted on the central shaft 2 of this invention. The magnetic ring 6 can rotate synchronously with the central shaft 2. One circumference of the magnetic ring 6 contains multiple pairs of magnetic poles, preferably 24 to 32 pairs. When the magnetic ring 6 rotates with the central shaft 2, the Hall element on the PBC circuit board 5 can detect the rotational speed of the central shaft 2 by the change in the S / N poles of the magnetic ring 6, thereby measuring the rider's pedaling speed. The Hall element also transmits the measured data signal to the main control chip on the PBC circuit board 5, which processes the received signal and outputs the result.

[0031] In this embodiment, in order to prevent the metal ejector pin 3 from shifting in the deformation cavity K, a positioning arc groove K1 is formed at the center of the deformation cavity K for positioning and installing the metal ejector pin 3.

[0032] In the embodiment, a positioning pin hole is machined on the right end face of the strain section 11 of the present invention, and a positioning pin 7 is inserted through the positioning pin hole. A groove is opened on the bottom tube G of the electric-assisted vehicle, and the positioning pin 7 can be inserted into the groove of the bottom tube G to position the installation direction of the central axis torque sensor and prevent the central axis torque sensor from rotating in the bottom tube G.

[0033] In the embodiments, from Figure 1 and Figure 2 As can be seen from the image, the strain gauge 11 is equipped with a right end cover 8. The right end cover 8 prevents dust from entering the right bearing mounting hole 11a, thereby ensuring the operating environment of the right bearing Z2. The strain gauge 11 has three threaded holes, and the right end cover 8 is fixedly mounted on the strain gauge 11 with three Phillips head screws L.

[0034] In this embodiment, an external thread W is machined on the outer circumferential surface of the left end of the outer tube 1, and a left threaded cup 9 is screwed onto the left end of the outer tube 1 via the external thread W. The left threaded cup 9 allows the outer tube 1, i.e., the entire central axis torque sensor, to be locked and fixed onto the bottom bracket G of the electric-assisted bicycle. When assembling the central axis torque sensor of this invention with the bottom bracket G of the electric-assisted bicycle frame, it is not necessary to machine threads on the bottom bracket G as with traditional torque sensors; the bottom bracket G can be installed directly as a round tube.

[0035] The present application is installed, first look at the orientation of the stress beam, then the left end of the outer tube 1 from the right port of the five-way pipe G inserted, and the positioning pin hole of the strain part 11 aligns the slot of the electric bicycle five-way pipe G, and then the positioning pin 7 is inserted into the positioning pin hole and the slot of the five-way pipe G, and the outer tube 1 is positioned. After the outer tube 1 is positioned, the stress beam is opposite to the vertical direction of the electric bicycle chain, and finally the left block 9 is tightened with a wrench, and the middle shaft type torque sensor is fixed.

[0036] The present application measures the torque by the strain principle. When the middle shaft 2 is subjected to the torsional torque of the pedal, the middle shaft 2 transmits the torsional torque received by the right bearing Z2 and the metal needle 3 to the strain gauge 4 in the form of a pushing force. The strain gauge 4 senses the change of the surface stress of the stress beam, and outputs after processing the signal by the PCB electric board 5.

[0037] The best embodiment of the present application has been illustrated, and various changes or modifications made by those skilled in the art will not deviate from the scope of the present application.

Claims

1. A strain-based torque sensor for a bottom bracket of an electric-assisted bicycle, comprising an outer tube (1) and a bottom bracket (2) rotatably supported and installed in the outer tube (1) by a left bearing (Z1) and a right bearing (Z2). The left bearing (Z1) is positioned in the left port of the outer tube (1). A strain section (11) is integrally formed at the right end of the outer tube (1). The right bearing (Z2) is tightly fitted in the right bearing mounting hole (11a) formed in the strain section (11). A recessed circuit board mounting position (1a) is formed on the circumferential surface of the outer tube (1) at the stress beam adjacent to the strain section (11). A fixed mounting on the bottom bracket (2) is provided. A magnetic ring (6) rotates synchronously with the central shaft (2); a PBC board (5) connected to the strain gauge (4) is mounted on the outer tube (1); the PBC board (5) is fixed in the circuit board mounting position (1a) of the outer tube (1) by adhesive; the PBC board (5) is provided with a main control chip and a Hall element for detecting the rotational speed of the central shaft (2) by detecting the change of magnetic poles of the magnetic ring (6); the strain section (11) is equipped with a right end cover (8) to prevent dust from entering the right bearing mounting hole (11a), and the right end cover (8) is fixed on the strain section (11) by three cross screws (L); its characteristics are: The strain section (11) is machined with two stress beams facing the rear of the electric bicycle. The two stress beams include a front stress beam (12) and a rear stress beam (13). A long strip-shaped deformation cavity (K) is formed between the front stress beam (12) and the rear stress beam (13). The center of the front stress beam (12) is formed with a stress transmission protrusion (121) that fits tightly against the outer circle of the right bearing (Z2). The stress transmission protrusion (121) has two suspended areas (Q) that are not in contact with the outer circle of the right bearing (Z2) and are symmetrically machined on its upper and lower sides. The center of the deformation cavity (K) is tightly fitted. The device is equipped with a connector for two-stage stress transmission. The connector is a metal pin (3). The metal pin (3) is cylindrical and is used to transmit the thrust borne by the front stress beam (12) to the rear stress beam (13). The center of the deformation cavity (K) is formed with a positioning arc groove (K1) for positioning and installing the metal pin (3). The strain gauge (4) is attached to the rear stress beam (13) to detect the stress deformation of the rear stress beam (13). The PBC board (5) has a cable connector (X) leading out. The strain section (11) has a cable slot (1b) formed to fix and fit with the cable connector (X). The magnetic ring (6) contains 24 to 32 pairs of magnetic poles around its circumference; a positioning pin hole is machined on the right end face of the strain section (11), and a positioning pin (7) is provided in the positioning pin hole for positioning and engaging with the slot of the bottom bracket (G) of the electric-assisted vehicle. A retaining ring groove is machined in the left port of the outer tube (1), and a retaining ring (D) for preventing the left bearing (Z1) from axially moving is fitted in the retaining ring groove; The outer circumferential surface of the left end of the outer tube (1) is machined with an external thread (W), and the left end of the outer tube (1) is screwed with a left thread cup (9) for locking the outer tube (1) onto the bottom bracket (G) of the electric bicycle through the external thread (W); The two ends of the central shaft (2) are formed with square heads (21), and the square heads (21) are machined with internal threaded holes (21a); ​​a left crank (P1) is installed on the square head (21) at the left end of the central shaft (2), and an integrated crank chainring (P2) is installed on the square head (21) at the right end of the central shaft (2).

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