Torque sensor, mid-mounted motor and electric-assisted bicycle

Abstract

The present invention provides a torque sensor, a mid-mounted motor and an electric-assisted bicycle, which relate to the technical field of power-assisted bicycles and are designed to solve the problems of low precision and large space occupation of torque sensors of existing electric-assisted bicycles. The torque sensor includes a torsion bar sleeved on a central axis and a strain gauge fixed to the torsion bar, a first circumferential limit structure for limiting the circumferential relative rotation of the two is arranged between the torsion bar and the central axis, a second circumferential limit structure for limiting the circumferential relative rotation of the two is arranged between the output shaft and the torsion bar, wherein the central axis is radially supported on the housing of the mid-mounted motor, and an axial limit structure for limiting the axial relative movement of the two is arranged between the central axis and the housing. The mid-mounted motor includes the above-mentioned torque sensor. The electric-assisted bicycle includes the above-mentioned mid-mounted motor. The torque sensor provided by the present invention has high measurement precision and small space occupation, and can meet the use requirements of electric-assisted bicycles.

Description

Technical Field

[0001] The present invention relates to the technical field of power-assisted bicycles, and in particular to a torque sensor, a mid-mounted motor and an electric power-assisted bicycle. Background Art

[0002] Electric power-assisted bicycles have been widely used due to their convenient operation and low pollution. Usually, electric power-assisted bicycles are equipped with torque sensors, and the controller of the electric power-assisted bicycle can judge the actual working conditions according to the torque value detected by the torque sensor to achieve a better power-assisted effect.

[0003] However, the torque sensors used in existing electric-assisted bicycles are mostly magnetoelectric torque sensors or strain gauge torque sensors. The former is easily affected by the magnetic field of the mid-mounted motor movement when in use, and has low measurement accuracy; the latter, when in use, attaches the strain gauge to the elastic shaft and obtains the torque by measuring the deformation of the elastic shaft. This torque measurement method requires adding couplings at both ends of the elastic shaft to protect the elastic shaft, which results in a large space occupation and a large weight, and cannot well meet the use requirements of the mid-mounted motor for electric-assisted bicycles. Summary of the invention

[0004] The first object of the present invention is to provide a torque sensor to solve the technical problems of the existing torque sensors of electric-assisted bicycles having low accuracy and occupying a large space.

[0005] The torque sensor provided by the present invention is used to measure the torque transmitted from the central shaft of the mid-mounted motor to the output shaft. The torque sensor includes a torsion bar sleeved on the central shaft and a strain gauge fixed to the torsion bar. A first circumferential limiting structure for limiting the circumferential relative rotation of the two is arranged between the torsion bar and the central shaft, and a second circumferential limiting structure for limiting the circumferential relative rotation of the two is arranged between the output shaft and the torsion bar, wherein the central shaft is supported on the housing of the mid-mounted motor along its radial direction, and an axial limiting structure for limiting the axial relative movement of the two is arranged between the central shaft and the housing.

[0006] Further, the axial limiting structure includes a first limiting portion and a second limiting portion which are arranged on the central axis at axial intervals along the central axis, and at least one of the first limiting portion and the second limiting portion is detachably fixedly connected to the central axis, wherein along the first axial direction, the central axis abuts against the box shell through the first limiting portion; along the second axial direction, the central axis abuts against the box shell through the second limiting portion.

[0007] Furthermore, the first limiting portion includes a retaining spring installed on the central axis, and the second limiting portion includes a shoulder arranged on the central axis.

[0008] Furthermore, the first end of the torsion bar is matched with the central shaft via a spline, and the splines matching the torsion bar and the central shaft form the first circumferential limiting structure.

[0009] Furthermore, the torque sensor also includes an electric control box, which is relatively fixed to the torsion bar, and a circuit board is arranged in the electric control box, the strain gauge is electrically connected to the circuit board, and the circuit board is electrically connected to the controller of the mid-mounted motor.

[0010] The beneficial effects brought by the torque sensor of the present invention are:

[0011] The torque sensor provided by the present invention is used to measure the torque transmitted from the central shaft of the central motor to the output shaft, and includes a torsion bar and a strain gauge, wherein the torsion bar is sleeved on the central shaft, and a first circumferential limit structure is provided between the torsion bar and the central shaft, the first circumferential limit structure is used to limit the circumferential relative rotation of the torsion bar and the central shaft, and the strain gauge is fixed to the torsion bar; a second circumferential limit structure is provided between the output shaft and the torsion bar, the second circumferential limit structure is used to limit the circumferential relative rotation of the output shaft and the torsion bar. In addition, the central shaft is supported on the box shell along its radial direction, and an axial limit structure is provided between the central shaft and the box shell, and the axial limit structure is used to limit the central shaft from moving relative to the box shell along its axial direction.

[0012] Taking the torque sensor used in the mid-mounted motor of an electric power-assisted bicycle as an example, when it is necessary to measure the torque transmitted from the central shaft of the mid-mounted motor to the output shaft, the central shaft rotates, and under the action of the first circumferential limiting structure, the torsion bar rotates with the central shaft; under the action of the second circumferential limiting structure, the output shaft rotates with the torsion bar. In the above process, since the central shaft is supported by the box shell along its radial direction, during the operation of the mid-mounted motor, the radial force received by the central shaft will be transmitted to the box shell, which will be carried by the box shell, and will not cause radial interference to the torsion bar; at the same time, since an axial limiting structure is provided between the central shaft and the box shell for limiting the axial relative movement of the two, the axial force received by the central shaft is also transmitted to the box shell, which will be carried by the box shell, and thus will not cause axial interference to the torsion bar. Therefore, the strain gauge arranged on the torsion bar can more accurately measure the torque transmitted from the central shaft to the output shaft, has strong anti-interference ability, and high measurement accuracy.

[0013] In addition, the above-mentioned structural form of arranging a torsion bar between the middle shaft and the output shaft to transmit torque and fixing the strain gauge on the torsion bar to realize torque measurement does not require additional coupling arrangement, occupies a small space, has a compact layout, and is light in weight, which can well meet the use requirements of the mid-mounted motor for electric power-assisted bicycles.

[0014] The second object of the present invention is to provide a mid-mounted motor to solve the technical problems of the torque sensor of the existing electric-assisted bicycle having low accuracy and occupying a large space.

[0015] The mid-mounted motor provided by the present invention includes a clutch and the above-mentioned torque sensor, the clutch is sleeved on the central shaft and is loosely matched with the central shaft, and the outer periphery of the clutch can be supported on the inner periphery of the output shaft in a clutchable manner; the second end of the torsion bar is matched with the clutch through a spline, and when the clutch is in the engaged state, the spline used to make the torsion bar and the clutch match each other forms the second circumferential limiting structure.

[0016] Further, along the axial direction of the central shaft, the first limiting portion of the torque sensor is located between the clutch and the torsion bar, and the first limiting portion abuts against the clutch along a first axial direction.

[0017] Furthermore, the mid-mounted motor also includes a first bearing, a second bearing and a third bearing, wherein the inner rings of the first bearing and the second bearing are fixedly mounted on the output shaft, and the outer rings are fixedly arranged on the housing; the third bearing is located at the end of the torsion bar away from the clutch, the inner ring of the third bearing is fixedly mounted on the central shaft, and the outer ring is fixedly arranged on the housing.

[0018] Furthermore, a supporting cover plate is fixedly arranged inside the housing, and the supporting cover plate divides the inner cavity of the housing into a first cavity and a second cavity. Transmission teeth are fixedly arranged on the outer periphery of the output shaft, and the transmission teeth are located in the first cavity. The electrical control box of the torque sensor is located in the second cavity.

[0019] Further, the box shell includes a box body and a box cover arranged in sequence along a first axial direction, the box cover is detachably fixedly connected to the box body, and the supporting cover plate is fixedly connected to the box cover, wherein the outer ring of the first bearing is fixedly set on the box cover, the outer ring of the second bearing is fixedly set on the supporting cover plate, and the first bearing and the second bearing are respectively arranged on both sides of the transmission tooth; the outer ring of the third bearing is fixedly set on the box body.

[0020] The beneficial effects brought by the mid-mounted motor of the present invention are:

[0021] By arranging a clutch and the torque sensor in the central motor, wherein the clutch is sleeved on the central shaft and is loosely matched with the central shaft, and the outer periphery of the clutch is clutchably supported on the inner periphery of the output shaft. The second end of the torsion bar is matched with the clutch through a spline to limit the relative rotation of the torsion bar and the clutch in the circumferential direction.

[0022] Take the use of the mid-mounted motor in an electric-assisted bicycle as an example for explanation. When the electric-assisted bicycle is running in a mode combining electricity and manpower, the clutch and the output shaft are in a combined state. At this time, the output shaft obtains power through the following paths: the middle shaft is driven by manpower to rotate, and under the action of the first circumferential limit structure, the torsion bar rotates with the middle shaft, and the torsion bar further outputs the rotational force to the clutch, and the clutch outputs the power to the output shaft; at the same time, the electric power is input from the output shaft to drive the output shaft to rotate, that is, the output shaft obtains both manpower and electricity. When the electric-assisted bicycle is running in electric mode, the clutch and the output shaft are in a separated state. At this time, the output shaft only obtains electric power, and the electric power drives the output shaft to rotate, and the electric-assisted bicycle runs in electric mode.

[0023] The setting of the clutch enables the power output of the mid-mounted motor to have two different modes, meeting the functional requirements of the electric-assisted bicycle. In addition, due to the use of the torque sensor, the torque measurement accuracy is high, so that the electric-assisted bicycle can accurately know the driver's driving intention during driving; and, because the torque sensor occupies a small space, the structure of the mid-mounted motor is relatively compact.

[0024] The third object of the present invention is to provide an electric-assisted bicycle to solve the technical problems that the torque sensor of the existing electric-assisted bicycle has low accuracy and occupies a large space.

[0025] The electric power-assisted bicycle provided by the present invention comprises the above-mentioned mid-mounted motor.

[0026] The beneficial effects brought by the electric power-assisted bicycle of the present invention are:

[0027] By arranging the above-mentioned mid-mounted motor in the electric-assisted bicycle, the electric-assisted bicycle accordingly has all the advantages of the above-mentioned mid-mounted motor, which will not be described in detail here. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying creative work.

[0029] Figure 1 A structural front view of a mid-mounted motor provided in an embodiment of the present invention;

[0030] Figure 2 for Figure 1 AA section view in (the mid-mounted motor is a partial structural diagram).

[0031] Description of reference numerals:

[0032] 100-middle shaft; 200-output shaft; 300-torque sensor; 400-clutch; 500-housing; 600-first limit part; 800-support cover plate;

[0033] 110-first external spline; 120-second limiting portion;

[0034] 210- transmission tooth;

[0035] 310-torsion bar; 311-first internal spline; 312-second external spline; 320-strain gauge; 330-electrical control box;

[0036] 410-second internal spline;

[0037] 510-box cover; 520-box body;

[0038] 710-first bearing; 720-second bearing; 730-third bearing; 740-fourth bearing;

[0039] 810-Limiting boss. DETAILED DESCRIPTION

[0040] In order to make the above-mentioned objects, features and advantages of the present invention more clearly understood, the specific embodiments of the present invention are described in detail below in conjunction with the accompanying drawings. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0041] Figure 1 The front view of the structure of the mid-mounted motor provided in this embodiment, Figure 2 for Figure 1 AA section view in (the central motor is a partial structural representation). Figure 1 and Figure 2 As shown, this embodiment provides a mid-mounted motor, which includes a clutch 400 and a torque sensor 300, wherein the clutch 400 is used to control the engagement and separation of the middle shaft 100 and the output shaft 200, and the torque sensor 300 is used to measure the torque transmitted from the middle shaft 100 of the mid-mounted motor to the output shaft 200.

[0042] For details, please refer to Figure 2The torque sensor 300 includes a torsion bar 310 sleeved on the central axis 100 and a strain gauge 320 fixed to the torsion bar 310, a first circumferential limiting structure for limiting the circumferential relative rotation of the torsion bar 310 and the central axis 100 is arranged between the torsion bar 310 and the central axis 100, a second circumferential limiting structure for limiting the circumferential relative rotation of the output shaft 200 and the torsion bar 310 is arranged between the output shaft 200 and the torsion bar 310, wherein the central axis 100 is radially supported by the housing 500 of the central motor, and an axial limiting structure for limiting the axial relative movement of the central axis 100 and the housing 500 is arranged between the central axis 100 and the housing 500.

[0043] When it is necessary to measure the torque transmitted from the central shaft 100 of the central motor to the output shaft 200, the central shaft 100 rotates, and under the action of the first circumferential limiting structure, the torsion bar 310 rotates following the central shaft 100; under the action of the second circumferential limiting structure, the output shaft 200 rotates following the torsion bar 310. In the above process, since the central shaft 100 is supported by the box shell 500 in its radial direction, during the operation of the central motor, the radial force received by the central shaft 100 will be transmitted to the box shell 500, and the box shell 500 will bear the load, without causing radial interference to the torsion bar 310; at the same time, since an axial limiting structure for limiting the axial relative movement of the central shaft 100 and the box shell 500 is provided between the central shaft 100 and the box shell 500, the axial force received by the central shaft 100 is also transmitted to the box shell 500, and the box shell 500 will bear the load, so that the torsion bar 310 will not be caused axial interference. Therefore, the strain gauge 320 disposed on the torsion bar 310 can more accurately measure the torque transmitted from the central shaft 100 to the output shaft 200 , has strong anti-interference performance, and has high measurement accuracy.

[0044] In addition, the above-mentioned structure in which the torsion bar 310 is arranged between the middle shaft 100 and the output shaft 200 to transmit torque and the strain gauge 320 is fixed to the torsion bar 310 to realize torque measurement does not require additional coupling arrangement, occupies a small space, has a compact layout, and is light in weight, which can well meet the use requirements of electric assisted bicycles.

[0045] Please continue to refer to Figure 2 In the central motor, the clutch 400 is sleeved on the middle shaft 100 and is loosely matched with the middle shaft 100. The outer periphery of the clutch 400 can be clutched and supported on the inner periphery of the output shaft 200 to cut off the power of the output shaft 200 outputting the positive direction rotation to the middle shaft 100 and the power of the middle shaft 100 outputting the output shaft 200 to the reverse direction rotation. The first end of the torsion bar 310 is splined with the middle shaft 100, and the second end of the torsion bar 310 is also splined with the clutch 400. The spline used to match the torsion bar 310 with the middle shaft 100 forms a first circumferential limit structure, and in the engaged state of the clutch 400, the spline used to match the torsion bar 310 with the clutch 400 forms a second circumferential limit structure.

[0046] The example of using the mid-mounted motor for an electric-assisted bicycle is used for explanation. When the electric-assisted bicycle is running in a mode combining electric power and manpower, the clutch 400 and the output shaft 200 are in a combined state. At this time, the output shaft 200 obtains power through the following path: the middle shaft 100 is driven by manpower to rotate, and under the action of the first circumferential limit structure, the torsion bar 310 rotates with the middle shaft 100, and the torsion bar 310 further outputs the rotational force to the clutch 400, and the clutch 400 outputs the power to the output shaft 200; at the same time, the electric power is input from the output shaft 200 to drive the output shaft 200 to rotate, that is, the output shaft 200 obtains both manpower and electric power. When the electric-assisted bicycle is running in an electric mode, the clutch 400 and the output shaft 200 are in a separated state. At this time, the output shaft 200 only obtains electric power, and the output shaft 200 is driven to rotate by the electric power, and the electric-assisted bicycle runs in an electric mode.

[0047] The setting of the clutch 400 enables the power output of the mid-mounted motor to have two different modes, meeting the functional requirements of the electric-assisted bicycle. In addition, due to the use of the torque sensor 300, the torque measurement accuracy is high, so that the electric-assisted bicycle can accurately know the driving intention of the driver during driving; and, because the torque sensor 300 occupies a small space, the structure of the mid-mounted motor is relatively compact.

[0048] It should be noted that, in the present embodiment, the clutch 400 is a mechanical clutch, and its working principle is similar to that of the wedge-type one-way clutch in the prior art. When the middle shaft 100 rotates in a first direction, the clutch 400 and the output shaft 200 are in a coupled state, and when the middle shaft 100 rotates in a second direction, the clutch 400 and the output shaft 200 are in a separated state, thereby realizing power input and power cutoff from the middle shaft 100 to the output shaft 200.

[0049] Please continue to refer to Figure 2 In this embodiment, specifically, the first end of the torsion bar 310 is provided with a first internal spline 311, and the middle shaft 100 is provided with a first external spline 110 at a position corresponding to the first end of the torsion bar 310, and the first external spline 110 and the first internal spline 311 are loosely matched to form a first circumferential limit structure; the second end of the torsion bar 310 is provided with a second external spline 312, and the clutch 400 is provided with a second internal spline 410, and the second internal spline 410 and the second external spline 312 are loosely matched to form a second circumferential limit structure. The first circumferential limit structure and the second circumferential limit structure are used to realize power transmission from the middle shaft 100 to the output shaft 200 when the clutch 400 is engaged.

[0050] In the present embodiment, since the first external spline 110 and the first internal spline 311 as well as the second external spline 312 and the second internal spline 410 are connected by clearance fit, there is a certain clearance to allow a small amount of processing and assembly errors, and the radial force and axial force acting on the central axis 100 are completely borne by the housing 500, so that the central axis 100 will not interfere with the torsion bar 310 after being subjected to external forces.

[0051] Please continue to refer to Figure 2 In this embodiment, the torque sensor 300 also includes an electric control box 330. Specifically, the electric control box 330 is relatively fixed to the torsion bar 310. A circuit board is arranged in the electric control box 330. The strain gauge 320 is electrically connected to the circuit board, and the circuit board is electrically connected to the controller of the central motor.

[0052] When in use, the strain gauge 320 feeds back the electrical signal changes caused by its own deformation to the circuit board, and then feeds back to the controller through the circuit board to obtain the driving intention under various actual working conditions. By setting the circuit board in the electric control box 330, the circuit board is protected and the risk of short circuit and other faults of the circuit board is reduced. In addition, the relatively fixed setting of the electric control box 330 and the torsion bar 310 allows the electric control box 330 to rotate synchronously during the rotation of the torsion bar 310, thereby avoiding the entanglement of the signal line or the failure of the connection.

[0053] It should be noted that, in this embodiment, "electrical connection" includes not only using a signal line to achieve connection between two components, but also using a wireless signal transmission method to achieve connection between two components. Specifically, the wireless signal transmission can be achieved through a Bluetooth module.

[0054] Please continue to refer to Figure 2 In this embodiment, the central motor further includes a first bearing 710, a second bearing 720 and a third bearing 730, wherein the inner rings of the first bearing 710 and the second bearing 720 are fixedly mounted on the output shaft 200, and the outer rings of the first bearing 710 and the second bearing 720 are fixedly arranged on the housing 500; the third bearing 730 is located at the end of the torsion bar 310 away from the clutch 400, and the inner ring of the third bearing 730 is fixedly mounted on the middle shaft 100, and the outer ring of the third bearing 730 is fixedly arranged on the housing 500. In addition, the clutch 400 is supported on the output shaft 200 through the fourth bearing 740, specifically, the inner ring of the fourth bearing 740 is fixedly mounted on the outer peripheral surface of the clutch 400, and the outer ring of the fourth bearing 740 is installed on the inner peripheral surface of the output shaft 200.

[0055] In the central motor, the clutch 400 and the central shaft 100 are clearance-matched, and the clutch 400 is also supported on the output shaft 200 through the fourth bearing 740. At the same time, the output shaft 200 is supported on the housing 500 through the first bearing 710 and the second bearing 720, so it can be regarded as that the central shaft 100 is supported on the housing 500 at a single point; the other end of the central shaft 100 is provided with a third bearing 730, so that the other end of the central shaft 100 is supported on the housing 500 through the third bearing 730. Therefore, both ends of the central shaft 100 are supported on the housing 500, that is, the radial force on the central shaft 100 can be transmitted to the housing 500, and the torsion bar 310 will not be interfered with due to the radial force on the central shaft 100.

[0056] Please continue to refer to Figure 2 In this embodiment, a support cover plate 800 is fixedly provided inside the housing 500. Specifically, the support cover plate 800 divides the inner cavity of the housing 500 into a first cavity and a second cavity. A transmission tooth 210 is fixedly provided on the outer periphery of the output shaft 200. The transmission tooth 210 is located in the first cavity, and the electric control box 330 of the torque sensor 300 is located in the second cavity.

[0057] By providing the support cover plate 800 in the housing 500, the inner cavity is separated, which to a certain extent prevents the grease of the transmission gear 210 in the first cavity from being thrown into the second cavity and causing interference to the torque sensor 300, thereby affecting the measurement result.

[0058] Please continue to refer to Figure 2 In this embodiment, the box shell 500 includes a box body 520 and a box cover 510 arranged in sequence along the first axial direction, wherein the box cover 510 and the box body 520 are detachably fixedly connected, the supporting cover plate 800 is fixedly connected to the box cover 510, the outer ring of the first bearing 710 is fixedly set on the box cover 510, the outer ring of the second bearing 720 is fixedly set on the supporting cover plate 800, and the first bearing 710 and the second bearing 720 are respectively arranged on both sides of the transmission gear 210, and the outer ring of the third bearing 730 is fixedly set on the box body 520.

[0059] In this embodiment, the support cover plate 800 is provided with a limiting boss 810, and the support cover plate 800 is assembled with the box cover 510 through the limiting boss 810. Since the support cover plate 800 is fixedly connected to the box cover 510, and the first bearing 710 is supported on the box cover 510, and the second bearing 720 is supported on the support cover plate 800, the output shaft 200 is stably supported, and the influence on the output shaft 200 caused by the deformation of the box body 520 is avoided.

[0060] Please continue to refer to Figure 2The axial limiting structure includes a first limiting portion 600 and a second limiting portion 120 which are arranged on the central axis 100 at intervals along the axial direction of the central axis 100. Specifically, the first limiting portion 600 is detachably fixedly connected to the central axis 100. Figure 2 The middle axis 100 is in contact with the box shell 500 through the first limiting portion 600; along the second axial direction ( Figure 2 The middle shaft 100 is in contact with the box housing 500 through the second limiting portion 120. The first limiting portion 600 is located between the clutch 400 and the torsion bar 310.

[0061] When the middle shaft 100 is subjected to a force in the first axial direction, that is, Figure 2 When a force is applied to the left, the force transmission path is: central axis 100 - first limit portion 600 - clutch 400 - inner ring of fourth bearing 740 - ball of fourth bearing 740 - outer ring of fourth bearing 740 - output shaft 200 - inner rings of first bearing 710 and second bearing 720 - balls of first bearing 710 and second bearing 720 - outer rings of first bearing 710 and second bearing 720 - case cover 510 and support cover plate 800. That is to say, the force applied to central axis 100 along the first axial direction will eventually be transmitted to case shell 500, and will not cause interference to torsion bar 310 along the first axial direction.

[0062] When the middle shaft 100 is subjected to a force in the second axial direction, that is, Figure 2 When a force is applied to the right, the force transmission path is: central axis 100 - second limiting portion 120 - inner ring of the third bearing 730 - ball of the third bearing 730 - outer ring of the third bearing 730 - housing 520. That is to say, the force applied to the central axis 100 along the second axial direction will eventually be transmitted to the housing 500, and will not cause interference to the torsion bar 310 along the second axial direction.

[0063] Please continue to refer to Figure 2 In this embodiment, the first position-limiting portion 600 includes a retaining spring installed on the central axis 100, and the second position-limiting portion 120 includes a shaft shoulder provided on the central axis 100. Specifically, the central axis 100 is provided with an annular groove, and the retaining spring is provided in the annular groove. The arrangement of the first position-limiting portion 600 and the second position-limiting portion 120 is simple in structure and easy to arrange.

[0064] In other embodiments, the first limiting portion 600 and the second limiting portion 120 may be both configured as a retaining spring structure, that is, the first limiting portion 600 and the second limiting portion 120 are both detachably fixedly connected to the central axis 100 .

[0065] In addition, this embodiment also provides an electric-assisted bicycle, which includes the above-mentioned mid-mounted motor.

[0066] By arranging the above-mentioned mid-mounted motor in the electric-assisted bicycle, the electric-assisted bicycle accordingly has all the advantages of the above-mentioned mid-mounted motor, which will not be described in detail here.

[0067] Although the present invention is disclosed as above, the present invention is not limited thereto. Any person skilled in the art can make various changes and modifications without departing from the spirit and scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the scope defined by the claims.

[0068] Finally, it should be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the term "comprises" or any other variant thereof is intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, the elements defined by the sentence "comprises a ..." do not exclude the presence of other identical elements in the process, method, article or device including the elements.

[0069] In the above embodiments, the descriptions of directions such as “left” and “right” are all based on the drawings.

[0070] The above description of the disclosed embodiments enables one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A mid-mounted motor, characterized in that: The invention comprises a clutch (400) and a torque sensor (300), wherein the torque sensor is used to measure the torque transmitted from the middle shaft (100) of the middle motor to the output shaft (200) of the middle motor, wherein the torque sensor (300) is annular, and comprises a torsion bar (310) sleeved on the middle shaft (100) and a strain gauge (320) fixed on the torsion bar (310), wherein the torque sensor (300) further comprises an electric control box (330), wherein the electric control box (330) and the torsion bar (310) are relatively fixed; a first circumferential limiting structure for limiting the circumferential relative rotation of the torsion bar (310) and the middle shaft (100) is provided between the torsion bar (310) and the output shaft (200) and the torsion bar (310), wherein a second circumferential limiting structure for limiting the circumferential relative rotation of the torsion bar (310) and the output shaft (200) and the torsion bar (310) are provided between the torsion bar (310) and the output shaft (20 ... The central axis (100) is supported on the housing (500) of the central motor along its radial direction, and an axial limiting structure for limiting the axial relative movement of the central axis (100) and the housing (500) is provided between the central axis (100) and the housing (500), and the axial limiting structure comprises a first limiting portion (600) and a second limiting portion (120) which are arranged on the central axis (100) at intervals along the axial direction of the central axis (100); a supporting cover plate (800) is fixedly provided in the housing (500), and the supporting cover plate (800) divides the inner cavity of the housing (500) into a first cavity and a second cavity; a transmission tooth (210) is fixedly provided on the outer periphery of the output shaft (200), and the transmission tooth (210) is located in the first cavity, and the electric control box (330) of the torque sensor (300) is located in the second cavity; The clutch (400) is sleeved on the central shaft (100) and is loosely matched with the central shaft (100), and the outer periphery of the clutch (400) is supported on the inner periphery of the output shaft (200) in a disengageable manner; the second end of the torsion bar (310) is matched with the clutch (400) via a spline, and when the clutch (400) is in a coupled state, the spline used to make the torsion bar (310) and the clutch (400) match each other forms the second circumferential limiting structure.

2. The mid-mounted motor according to claim 1, characterized in that: At least one of the first limiting portion (600) and the second limiting portion (120) is detachably fixedly connected to the central axis (100), wherein along a first axial direction, the central axis (100) abuts against the box shell (500) via the first limiting portion (600); and along a second axial direction, the central axis (100) abuts against the box shell (500) via the second limiting portion (120).

3. The mid-mounted motor according to claim 2, characterized in that: The first limiting portion (600) comprises a retaining spring mounted on the central axis (100), and the second limiting portion (120) comprises a shaft shoulder arranged on the central axis (100).

4. The mid-mounted motor according to claim 1, characterized in that: The first end of the torsion bar (310) is matched with the central shaft (100) via a spline, and the spline used to make the torsion bar (310) and the central shaft (100) match each other forms the first circumferential limiting structure.

5. The mid-mounted motor according to claim 1, characterized in that: A circuit board is arranged in the electric control box (330), the strain gauge (320) is electrically connected to the circuit board, and the circuit board is electrically connected to the controller of the central motor.

6. The mid-mounted motor according to claim 1, characterized in that: Along the axial direction of the central axis (100), the first limiting portion (600) of the torque sensor (300) is located between the clutch (400) and the torsion bar (310), and the first limiting portion (600) abuts against the clutch (400) along the first axial direction.

7. The mid-mounted motor according to claim 1, characterized in that: The central motor further comprises a first bearing (710), a second bearing (720) and a third bearing (730), wherein the inner rings of the first bearing (710) and the second bearing (720) are fixedly mounted on the output shaft (200), and the outer rings are fixedly arranged on the housing (500); the third bearing (730) is located at an end of the torsion bar (310) away from the clutch (400), the inner ring of the third bearing (730) is fixedly mounted on the central shaft (100), and the outer ring is fixedly arranged on the housing (500).

8. The mid-mounted motor according to claim 7, characterized in that: The box shell (500) comprises a box body (520) and a box cover (510) which are sequentially arranged along a first axial direction, the box cover (510) is detachably fixedly connected to the box body (520), and the support cover plate (800) is fixedly connected to the box cover (510), wherein the outer ring of the first bearing (710) is fixedly arranged on the box cover (510), the outer ring of the second bearing (720) is fixedly arranged on the support cover plate (800), and the first bearing (710) and the second bearing (720) are respectively arranged on both sides of the transmission gear (210); and the outer ring of the third bearing (730) is fixedly arranged on the box body (520).

9. An electric power-assisted bicycle, characterized in that: Including the mid-mounted motor as described in any one of claims 1-8.

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