A driver for a balanced driving system of an electric bicycle

Abstract

A driver of a balanced driving system of an electric bicycle, the main structure of which is composed of a transmission shaft and a driving shaft, the two shafts form a cross-shaped structure with a shaft intersection angle of 90 degrees, and a bevel gear pair is used for transmission, and the bevel main and passive gears are respectively located on the transmission shaft and the driving shaft. A telescopic structure is arranged on the transmission shaft so that the spring steel wire flexible shaft always maintains reasonable straightness and tightness during operation; a mechanical transmission resistance blocking structure is arranged on the driving shaft so that the axial extrusion force and bending force generated when the driving wheel is running will not be transmitted to the bevel passive gear, so that the working conditions of the balanced driving functional unit remain stable; a torque limiting structure is arranged on the driving shaft so that the proportional torsion angle of the spring steel wire flexible shaft during operation is less than or equal to its rated value.

Description

Technical Field

[0001] The invention discloses a driver for a balanced driving system of an electric bicycle, belonging to the technical field of two-wheeled electric vehicles, and relates to a driver for a balanced driving system of a two-wheeled electric vehicle. Background Art

[0002] The motor of existing electric bicycles is integrated with the rear wheel, the rotor of the motor is the rear wheel hub, and the main shaft of the motor is the rear wheel axle. The disadvantages of this driving method are: the vehicle consumes a lot of electricity when driving, and the vehicle has a short cruising range. When the vehicle starts and accelerates, the battery will discharge with a large current. The impact of this instantaneous large current discharge on the battery will reduce the service life of the battery. The electric bicycle balance drive system consists of three parts: a motor, a balance drive functional unit, and a drive device. An electric bicycle using a balance drive system can significantly reduce its energy consumption when driving and significantly increase its cruising range. When the electric bicycle uses a balance drive system, the battery discharge current is small when the vehicle starts and accelerates, and the battery will not be affected by the impact caused by the large current discharge, so the service life of the battery can be significantly extended.

[0003] There is a spring steel wire flexible shaft with a length of 1 to 1.5 meters in the balance drive system of an electric bicycle. When driven, the spring steel wire flexible shaft will undergo proportional torsion deformation, and its proportional torsion angle must be less than the maximum allowable proportional torsion angle of the spring steel wire flexible shaft. If the driving torque of the vehicle is too large, causing the proportional torsion deformation of the spring steel wire flexible shaft to exceed its maximum allowable proportional torsion angle, the spring steel wire flexible shaft will fail due to excessive torsion deformation. During the vehicle driving process, the spring steel wire flexible shaft must maintain a moderate degree of tightness to maintain smooth power transmission. Since the length of the spring steel wire flexible shaft will change with the size of its proportional torsion angle, the tightness of the spring steel wire flexible shaft must be dynamically adjusted with the size of its proportional torsion angle. In view of the above problems, it is necessary to develop a driving device for an electric bicycle balance drive system that has an overload protection function and can dynamically adjust the tightness of the spring steel wire flexible shaft, so that the balance drive system can be better applied to electric bicycles.

[0004] The driving motor of the existing electric bicycle is integrated with the rear wheel. When the power is turned on, the electromagnetic torque between the permanent magnet inside the motor and the wire winding directly collides with the rolling resistance torque acting on the rear wheel, converting part of the electric energy into the work done by the rear wheel to overcome its rolling resistance torque, and at the same time, part of the electric energy is converted into energy consumed by vehicle vibration and noise along with power rebound. When the electric bicycle adopting the balance drive system is running, there will be no power rebound. Its power is output by the motor and transmitted to the power input shaft of the driver through the balance drive functional unit. The balance torque output by the power output end of the balance drive functional unit is a driving torque that changes continuously and smoothly, and its value is also small. The size of the mechanical resistance torque of the balance drive system of the electric bicycle and the stability of its operation change are very sensitive to the impact of the vehicle's cruising range. The lower the mechanical loss of the driving device of the balance drive system of the electric bicycle, the more significantly the above advantages of the vehicle balance drive system can be brought into play. Therefore, it is necessary to develop a driver with small mechanical resistance torque and stable operation change suitable for the balance drive system of the electric bicycle, so as to keep the driving performance of the balance drive system of the electric bicycle better, so that the electric bicycle has a higher cruising range. A patent has been applied for the related electric bicycle balance drive system (patent application number: 2022104776054). Summary of the invention

[0005] 1. Working principle of vehicle balance drive An electric bicycle balance drive system adopts a balance drive working principle to realize vehicle driving. The vehicle balance drive working principle is composed of six mechanisms, namely, torque balance mechanism, one-way power transmission mechanism, power decomposition mechanism, acceleration mechanism, optimal load mechanism, and power balance mechanism. Among them, the torque balance mechanism provides the basic technical conditions for energy conversion in the vehicle driving process, and the one-way power transmission mechanism, power decomposition mechanism, acceleration mechanism, optimal load mechanism, and power balance mechanism are the ways of energy conversion in the vehicle driving process.

[0006] A balanced driving working principle for a vehicle has a most basic mechanical device as its carrier, which is called a balanced driving working model. The working model consists of three parts, namely a power device, a balanced driving functional unit, and a driving wheel, and the three are located on the same central axis. The power input end of the balanced driving functional unit is connected to the power output end of the power device and keeps synchronous rotation, and the power output end of the balanced driving functional unit is connected to the power input end of the driving wheel and keeps synchronous rotation. The balanced driving functional unit is composed of a flexible shaft and a blocking flywheel. The blocking flywheel is located between the power output end of the power device and the power input end of the flexible shaft. The power input end of the blocking flywheel is the power input end of the balanced driving functional unit. The power output end of the blocking flywheel is connected to the power input end of the flexible shaft and keeps synchronous rotation. The power output end of the flexible shaft is the power output end of the balanced driving functional unit. The flexible shaft in the balanced driving functional unit is an ideal flexible shaft, which has a sufficiently large proportional torsion angle and has a torsional elastic modulus that fully matches the vehicle mass carried by the driving wheel, the output power of the power device, and the output torque.

[0007] In the working principle of balanced drive, the basic definition of flexible shaft is: an elastic body with the ability to undergo proportional torsional deformation around the same central axis has two ways of transmitting power at the same time during the power transmission process, namely, the synchronous rotation of each particle on the flexible shaft elastic body around its central axis and the asynchronous rotation generated by the elastic torsional deformation between each cross section on the flexible shaft elastic body. The synchronous rotation transmits synchronous power, and the asynchronous rotation transmits asynchronous power. The torsional deformation angles at the two ends of the flexible shaft elastic body are proportional to the magnitude of the torque acting on the two ends, which conforms to Hooke's law.

[0008] An electric bicycle balance drive system is a drive system suitable for electric bicycles that is developed and designed based on a balance drive working model and combined with the structural characteristics and usage requirements of electric bicycles. Its purpose is to increase the range of electric bicycles and the service life of batteries under the same battery conditions.

[0009] It should be pointed out that the working principle of balanced drive is applicable to all vehicles that walk on the ground with wheels. The balanced drive system of each type of vehicle is developed and designed based on the balanced drive working model as a prototype, and at the same time, it should be combined with their own structural characteristics and usage requirements. Therefore, the structures of balanced drive systems of different types of vehicles are different. As an elastic element, the flexible shaft is the core component of the balanced drive system. During the power transmission process, the flexible shaft generates a wave of metal atoms from its power input end to the power output end through its proportional torsional deformation. This atomic wave is a continuous and uninterrupted periodic fluctuation. This atomic wave decomposes the power at the input end into two forces, synchronous and asynchronous. The asynchronous power is transmitted through this atomic wave. This atomic wave can store or release asynchronous power according to the needs of vehicle driving. The sensitivity of the flexible shaft to decompose asynchronous power and the stability of the flexible shaft to transmit asynchronous power depend on the torsional deformation elastic modulus and the uniformity of torsional deformation of the flexible shaft, and are related to factors such as the material chemical composition, metallographic structure, grain size, distribution and morphology of non-metallic impurities, cross-sectional structural dimensions and length of the flexible shaft.

[0010] A balanced drive system for electric bicycles is the first application of the balanced drive working principle on a vehicle. The first problem to be solved is to find a suitable elastic element as a flexible shaft and verify the authenticity of the balanced drive working principle through experiments. The authenticity test verification of the balanced drive working principle includes: the stability of the driving wheel operation when the flexible shaft is used to transmit power and the verification of the balanced drive effect. The stability of the driving wheel operation means that the driving wheel is running continuously without short pauses during operation; the balanced drive effect is the increase in the driving wheel's cruising range compared with existing vehicles.

[0011] Spring steel wire is an elastic body with a solid cylindrical structure. When its diameter is small, it has a larger proportional torsional deformation angle. The rated total mass of an electric bicycle is usually less than 200 kg, and its rolling friction resistance torque when running at a constant speed on a flat road is usually less than 2 Nm. This resistance torque value is consistent with the proportional torsional deformation torque value of a spring steel wire with a smaller diameter. Therefore, spring steel wire can be used as a flexible shaft of an electric bicycle's balance drive system.

[0012] The first step of the verification work is to use spring steel wire as the flexible shaft, design and manufacture a bench test device based on the basic structure of the balanced drive working model. In the bench test, different resistance torques are applied to the drive wheel, so that the spring steel wire flexible shaft is always in a proportional torsional deformation state and keeps changing within a certain range. The bench test shows that the speed of the drive wheel changes asynchronously with the speed of the motor, and the drive wheel runs continuously and smoothly.

[0013] The second step of the verification work is to design and manufacture a balance drive system that can be installed on an electric bicycle for bench testing based on the basic structure of the balance drive working model and the bench test device used in the first step of the verification work. The purpose of this bench test is to verify the effect of the balance drive on the electric bicycle. Under the rated load, the rolling friction resistance torque of the driving rear wheel of the existing electric bicycle when riding at a constant speed on a flat asphalt road is usually 1.5 Nm to 2 Nm. In this bench test, the resistance torque loaded on the driving rear wheel of the electric bicycle is 2 Nm, and an ordinary 48-volt lead-acid battery is used as the power source. The speed of the driving rear wheel of the electric bicycle is equivalent to the speed of the electric bicycle when riding at a speed of 7 km / h to 15 km / h on the road. The minimum diameter of the spring steel wire used as the flexible shaft is determined based on the technical parameters such as the resistance torque loaded on the driving rear wheel, the elastic modulus of the spring steel wire, and the maximum allowable proportional torsion angle. In the bench test, the spring steel wire with the smallest diameter is first used as the flexible shaft. The cruising range of the electric bicycle running on the bench is tested in a complete discharge cycle of the battery. The spring steel wire flexible shaft of each diameter is tested for two complete discharge cycles of the battery, and the cruising range is the average of the two test values. In the bench test, the diameter of the spring steel wire used as the flexible shaft is increased successively, and its corresponding cruising range is tested respectively. In the bench test, as the diameter of the spring steel wire used as the flexible shaft increases successively, the cruising range of the electric bicycle will decrease accordingly. The bench test cruising range of the electric bicycle using the spring steel wire flexible shaft with the smallest diameter reaches 300 kilometers, and the bench test cruising range of the electric bicycle using the spring steel wire flexible shaft with the largest diameter reaches 120 kilometers. The smaller the diameter of the spring steel wire flexible shaft, the smaller its elastic modulus. In a fluctuation cycle of the motor output power, the spring steel wire flexible shaft will undergo a relatively large proportional torsional deformation, thereby being able to more effectively reduce the impact of the power wave and convert the excess power into the elastic deformation potential energy of the spring steel wire flexible shaft. Therefore, the smaller the diameter of the spring steel wire flexible shaft used in the electric bicycle, the longer its mileage in the bench test and the better its balanced drive effect.

[0014] The balancing torque generated by the spring steel wire flexible shaft of the electric bicycle balance drive system is a driving torque with power processing function. During the vehicle driving process, the balancing torque remains continuous and uninterrupted, and decomposes the power into synchronous power and asynchronous power. The synchronous power is generated and transmitted by the synchronous rotation of the spring steel wire flexible shaft, and its driving function is to keep the vehicle moving at a constant speed; the asynchronous power is generated and transmitted by the asynchronous rotation of the spring steel wire flexible shaft, and its driving function is to accelerate the vehicle. In the process of the spring steel wire flexible shaft decomposing the asynchronous power, an atomic wave will be formed on the spring steel wire flexible shaft, and the asynchronous power will be transmitted from the power input end of the spring steel wire flexible shaft to its power output end. Under the action of the balancing torque, the spring steel wire flexible shaft can adapt to the power needs of the vehicle drive and store excess power or release the required power.

[0015] Existing electric bicycles use 48V lead-acid batteries as power sources. At an ambient temperature of 25°C, the range of riding on a flat asphalt road is 40 kilometers. According to the test data verified in the second step, under the same battery conditions, the range of electric bicycles equipped with a balance drive system under bench test conditions is 3 to 6.5 times that of existing electric bicycles. The application of the balance drive working principle to electric bicycles has a significant effect on improving the range of electric bicycles.

[0016] A design scheme for a balanced drive system for an electric bicycle was formed after the above verification work was carried out, and the feasibility of the design scheme was increased through the above bench test process. In the absence of precedents, a design scheme for a balanced drive system for an electric bicycle needs to go through a long trial production and verification process.

[0017] The application of the balanced drive working principle to electric bicycles is an innovative technology in the field of two-wheeled electric vehicle technology. The motor of existing electric bicycles is integrated with the driving rear wheel. During riding, the rolling friction resistance torque of the driving rear wheel and the impact force of the road on the driving rear wheel directly collide with the electromagnetic field inside the motor. In such a driving process, the efficiency of energy conversion is very low and the driving performance of the vehicle is also poor. A balanced drive functional unit is set between the motor and the driving rear wheel of the electric bicycle that adopts the balanced drive working principle. The power input therein is decomposed and processed and the power is transmitted to the driver located at the rear wheel hub. In this way, the rolling friction resistance torque of the driving rear wheel and the impact force of the road on the driving rear wheel are avoided from directly colliding with the electromagnetic field inside the motor, thereby significantly improving the efficiency of energy conversion and significantly improving the driving performance of the vehicle.

[0018] 2. Automatic retractable function of the transmission shaft of a driver of an electric bicycle balance drive system The driver of an electric bicycle balance drive system adopts a cross-axis structure, and its main structure is composed of two shafts with an axis angle of 90 degrees. One of the shafts is the drive shaft, that is, the rear wheel shaft of the electric bicycle. The other shaft is the transmission shaft, that is, the power input shaft of the driver. The power is input from the transmission shaft and transmitted to the drive shaft through a bevel gear pair with an axis angle of 90 degrees located on the transmission shaft and the drive shaft, and drives the rear wheel to rotate.

[0019] The transmission shaft of the driver of the balanced driving system of an electric bicycle is located on one side of the center line of the front and rear wheels of the electric bicycle, and is located on the same straight line with the spring steel wire flexible shaft of the balanced driving system and the central axis of the motor. The power input end of the transmission shaft is connected to the power output end of the spring steel wire flexible shaft. During the balanced driving process, the spring steel wire flexible shaft is always in a proportional torsional deformation state. When the stress and strain distribution on each cross section of the spring steel wire flexible shaft is continuous and uniform and the stress and strain between each cross section present a continuous and stable change, the atomic wave generated by the proportional torsional deformation on the spring steel wire flexible shaft can smoothly decompose and transmit asynchronous power, and can timely and effectively convert the excess power into the elastic deformation potential energy of the spring steel wire flexible shaft, and can timely and effectively release the power required for vehicle driving. The spring steel wire flexible shaft of the balanced driving system of an electric bicycle should maintain the above-mentioned balanced driving effect. Its ideal working state should be that the centers of each cross section of the spring steel wire flexible shaft should be located on the same straight line, that is, the central axis of the spring steel wire flexible shaft should remain in a straight line, and there is no bending stress between each cross section of the spring steel wire flexible shaft. In order to solve the above technical problems and enable the spring steel wire flexible shaft to smoothly decompose and transmit asynchronous power and effectively realize its balanced driving function, the following technical measures are adopted on the transmission shaft of the driver of an electric bicycle balanced driving system.

[0020] When the spring steel wire flexible shaft rotates, its two ends will yaw, resulting in alternating bending stress on the cross section of the spring steel wire flexible shaft. In order to effectively eliminate the alternating bending stress, a cross-axis universal joint is arranged between the power output end of the spring steel wire flexible shaft and the power input end of the transmission shaft, and its front and rear ends are respectively connected to the power output end of the spring steel wire flexible shaft and the power input end of the transmission shaft, and the direction adjustment function of the universal joint eliminates the alternating bending stress generated on the cross section of the spring steel wire flexible shaft when it rotates.

[0021] The transmission shaft (power input shaft) of the driver of the balance drive system of an electric bicycle is a hollow shaft, and a spring steel wire flexible shaft passes through the central inner hole of the shaft, and there is a large gap between the inner hole wall and the outer circumferential surface of the spring steel wire flexible shaft. The front end of the cross-axis universal joint is tightly connected to the end of the spring steel wire flexible shaft, and the rear end of the cross-axis universal joint is a flat shaft with a non-circular cross-section. The rear end of the cross-axis universal joint is connected to the end of the extension sleeve through a sliding sleeve, and the flat shaft at the rear end of the cross-axis universal joint is inserted into the flat hole in the center of the sliding sleeve. There is a clearance fit between the flat shaft and the flat hole, and the two can move axially, but cannot rotate relative to each other. That is, the spring steel wire flexible shaft transmits torque to the transmission shaft through the sliding sleeve, and at the same time, the end of the spring steel wire flexible shaft can maintain axial free movement. A cross-axis universal joint is also arranged at the front end of the spring steel wire flexible shaft. The structure of the cross-axis universal joint is the same as that of the cross-axis universal joint at the rear end of the spring steel wire flexible shaft. The rear end of the universal joint is tightly connected with the front end of the spring steel wire flexible shaft. The front end of the universal joint is a flat shaft with a non-circular cross section. The flat shaft at the front end of the universal joint is inserted into the flat hole of the sliding sleeve at the front end of the extension sleeve. There is a clearance fit between the flat shaft and the flat hole. The two can move axially, but cannot rotate relative to each other. A deflection control bushing is arranged in the middle section of the spring steel wire flexible shaft. There is a unilateral gap of 1 mm to 2 mm between the outer circumferential surface of the spring steel wire flexible shaft and the inner hole wall of the bushing. Through such an arrangement, the power output by the motor is transmitted to the spring steel wire flexible shaft via the extension sleeve. The spring steel wire flexible shaft only bears torque force over the entire axial length of the spring steel wire flexible shaft, and does not bear axial force and bending force. The axial position of the spring steel wire flexible shaft can move freely within a certain range. The length of the spring steel wire flexible shaft can be automatically extended and retracted when transmitting power.

[0022] When the electric bicycle balance drive system is running, the balance torque of the spring steel wire flexible shaft maintains a dynamic balance state with the driving resistance torque of the electric bicycle. The vehicle driving resistance torque includes the uniform driving resistance torque and the accelerated driving resistance torque. During the vehicle driving process, the vehicle driving resistance torque is constantly changing, and the balance torque of the spring steel wire flexible shaft also changes accordingly. When the balance torque of the spring steel wire flexible shaft is in an increasing trend, its axial length is in a shortening trend; when the balance torque of the spring steel wire flexible shaft is in a decreasing trend, its axial length is in a lengthening trend. During the vehicle driving process, the axial length of the spring steel wire flexible shaft will change within a certain range (about 2 mm). When the electric bicycle balance drive system is running, a drive shaft of a driver of an electric bicycle balance drive system can move back and forth along its central axis as the balance torque of the spring steel wire flexible shaft changes. Thereby, the straightness and tightness of the spring steel wire flexible shaft are kept reasonable.

[0023] 3. Power transmission of a driver of an electric bicycle balance drive system 1. Vehicle movement principle Regardless of the size of the mass and structure of the vehicle that moves on the ground, the principle of vehicle movement is the same. We can regard the wheel model of the vehicle movement principle as a driving wheel rotating around its central axis and rolling along the ground at the same time, and the vehicle mass carried by the driving wheel is regarded as a mass point located at the center point of the driving wheel.

[0024] According to the wheel model of the vehicle motion principle, the mass point at the center of the driving wheel (the vehicle mass carried by the driving wheel) generates a gravity perpendicular to the ground, which generates a rolling friction resistance torque between the ground and the driving wheel in the opposite direction of the driving wheel's rotation. One end of the central axis of the driving wheel is the power input end. When the input driving torque gradually increases to equal the rolling friction resistance torque of the driving wheel, the driving wheel begins to rotate. At this time, the torque acting on the central axis of the driving wheel is composed of the driving torque and the rolling friction resistance torque. When the driving wheel rotates at a constant speed, the driving torque and the rolling friction resistance torque of the driving wheel are equal in magnitude and act in opposite directions.

[0025] The motion of the driving wheel consists of two kinds of motion, one of which is the linear motion of the mass point of the vehicle carried by the driving wheel at the center point of the driving wheel (hereinafter referred to as the bearing mass point); the other is the rotation of the driving wheel around its central axis, and the linear velocity of any mass point on the outer edge of the driving wheel is equal to the linear motion velocity of the bearing mass point. When the driving torque is greater than the rolling friction resistance torque of the driving wheel, the driving wheel will accelerate its rotation, and the bearing mass point at its center point will also accelerate, moving along the original linear motion direction at an accelerated speed, and the linear motion direction of the bearing mass point is equal to the linear acceleration of the tangent direction of the circle at any point on the outer edge of the driving wheel. At this time, the bearing mass point generates an inertial force due to the accelerated motion, which acts on the center point of the driving wheel in the opposite direction to the linear motion direction of the bearing mass point. The inertial force generates an inertial resistance torque acting on the driving wheel, and the direction of the inertial resistance torque is opposite to the direction of the driving torque and the same as the direction of the rolling friction resistance torque of the driving wheel. When the driving wheel is in an accelerated rotational motion state and the vehicle mass carried by the load-bearing mass at its center point is also in an accelerated linear motion, the resistance torque acting on the driving wheel is equal to the sum of the rolling friction resistance torque of the driving wheel and the inertial resistance torque generated by the acceleration of the load-bearing mass. The greater the driving torque, the greater the acceleration of the load-bearing mass, and the greater the inertial resistance torque generated by the acceleration of the vehicle mass carried by the load-bearing mass. As the driving torque continues to increase, when the sum of the inertial resistance torque generated by the acceleration of the vehicle mass carried by the load-bearing mass and the rolling friction resistance torque of the driving wheel is greater than the maximum adhesion between the driving wheel and the ground, the driving wheel will slip and only rotate around its central axis, and the load-bearing mass at the center point of the driving wheel will remain in its original position and will not move in a straight line.

[0026] In the actual movement of the vehicle, the motion trajectory of the center point of the driving wheel is not a straight line, but a spatial curve. The ideal driving torque input by the power input end of the driving wheel center axis is that its size always remains equal to the resistance torque of the driving wheel. The resistance torque acting on the driving wheel is a synthetic torque, which is composed of the rolling friction resistance torque of the driving wheel and the inertial resistance torque generated by the acceleration of the vehicle mass carried by the load-bearing mass point. The magnitude of the rolling friction resistance torque is equal to the product of the gravity of the vehicle mass carried by the load-bearing mass point and the rolling friction coefficient of the road surface where the driving wheel is located. In this product, the gravity of the vehicle mass carried by the load-bearing mass point is a constant, and the rolling friction coefficient of the road surface where the driving wheel is located is a variable, but the change trend of this variable is gentle. In the smaller rotation angle range of the driving wheel, the product can also be regarded as a constant. During the vehicle driving process, the work done by the driving wheel to overcome the rolling friction resistance torque changes linearly with the vehicle speed. The inertial resistance torque and the acceleration of the load-bearing mass point are mutually dependent, and its magnitude is also proportional to the acceleration of the load-bearing mass point. Here, the difference between the driving torque and the rolling friction resistance torque is called the acceleration torque. According to Newton's second law of motion, the acceleration of the load-bearing mass point is proportional to the acceleration torque. The acceleration torque is associated with multiple variable parameters such as the intensity and frequency of the power wave and the road conditions where the driving wheel is located. The change trend between the kinetic energy increased by the acceleration of the load-bearing mass point and the speed is nonlinear. Therefore, the change trend between the movement speed of the load-bearing mass point and the inertial resistance torque is also nonlinear.

[0027] During the operation of the driving wheel, two forms of energy conversion will occur simultaneously. One of the energy conversions is that the driving wheel overcomes the rolling friction resistance torque and does work. In this energy conversion process, the power consumed by the driving wheel keeps the load-bearing mass in a uniform motion state. Another energy conversion is that the driving wheel overcomes the inertial resistance torque of the load-bearing mass acceleration and does work. In this energy conversion process, the power consumed by the driving wheel is converted into the kinetic energy of the load-bearing mass increased by acceleration, and the linear movement speed of the load-bearing mass increases. It can be seen from this that the ideal input power at the power input end of the driving wheel center axis is that when the driving wheel is running at a uniform speed, the input torque of the power is equal to the rolling friction resistance torque acting on the driving wheel, the speed input from the power input end is synchronized and equal to the speed of the driving wheel, and the input power changes linearly. When the driving wheel accelerates, the power input end of the driving wheel center axis needs to input two powers at the same time, one of which makes the driving wheel run at a uniform speed at an existing speed, and this power changes linearly. The other power makes the driving wheel take the existing speed as the initial velocity and produces an acceleration, and its change trend changes nonlinearly. When the driving wheel is running at a reduced speed, the power input from the power input end is less than the work done by the driving wheel to overcome the rolling friction resistance torque. At this time, the inertia moment generated by the deceleration of the load-bearing mass point at the center point of the driving wheel has the same direction of action as the driving torque at the power input end. As the speed of the driving wheel decreases, the kinetic energy of the load-bearing mass point is converted into the work done by the driving wheel to overcome the rolling friction resistance torque. During the process of the driving wheel running at a reduced speed, the acceleration of the load-bearing mass point at the center of the driving wheel is a negative value. At this time, there are still two forces acting on the driving wheel, one of which comes from the power input end of the driving wheel center axis, and the other comes from the kinetic energy of the load-bearing mass point.

[0028] Existing vehicles use a rigid synchronous transmission mode, and the input power of the power input end of the transmission device is synchronized and equal to the output power of the power output end. The power wave output by the power device directly collides with the rolling friction resistance torque of the drive wheel and the vehicle mass carried by the load-bearing mass. Under normal circumstances, the frequency of the power wave output by the vehicle power device is relatively high. The power wave converts its energy into the work done by the drive wheel to overcome the rolling friction resistance torque in the form of a collision impact. When the power wave is strong, part of its energy will also be converted into the kinetic energy generated by the acceleration of the vehicle mass carried by the load-bearing mass in the form of a collision impact. Under the condition of rigid synchronous transmission, the power wave output by the vehicle power device converts its energy into the work done by the drive wheel to overcome the rolling friction resistance torque and the kinetic energy of the vehicle mass carried by the load-bearing mass in the form of a collision impact, and is accompanied by a part of power rebound. The stronger the power wave output by the power device, the more power will rebound. This power rebound will reduce the power output efficiency of the vehicle power device and cause vibration and noise in the vehicle transmission device. Under the condition of rigid synchronous transmission, the power input end of the central axis of the driving wheel can only input a power wave, which realizes its power decomposition and energy conversion in the form of collision impact, and is accompanied by power rebound.

[0029] 2. Power required to drive the vehicle In the principle of vehicle motion, the mass of the vehicle carried by the driving wheel can be regarded as a particle, which is located at the center point of the driving wheel and has the same mass as the mass of the vehicle carried by the driving wheel. Two kinds of motion will occur during the vehicle driving process, namely the rotational motion of the driving wheel around its center point and the motion of the particle carried by the driving wheel at its center point along a straight line parallel to the ground. The motion of the load-bearing particle located at the center point of the driving wheel can also be decomposed into uniform motion and accelerated motion. In the process of the load-bearing particle maintaining uniform motion, the input power of the driving wheel is converted into the work done by the driving wheel to overcome the uniform speed driving resistance. In the process of the accelerated motion of the load-bearing particle, the input power of the driving wheel is converted into the kinetic energy increased by the accelerated motion of the load-bearing particle.

[0030] Two different forms of energy conversion occur during vehicle driving, namely, the energy conversion required for the vehicle to travel at a constant speed at a given speed and the energy conversion required for the vehicle to accelerate at a given speed as an initial speed. The first form of energy conversion is the conversion of the input power of the driving wheel into the work done by the driving wheel to overcome its constant speed resistance. The mathematical equation is that the work done by the driving wheel to overcome its constant speed resistance is equal to the product of the constant speed resistance of the driving wheel and the existing speed of the driving wheel. The constant speed resistance of the driving wheel can be derived and converted based on the rolling friction resistance torque of the driving wheel. Here, for the convenience of analysis, the air resistance of the vehicle can be ignored. The constant speed resistance torque of the driving wheel is equal to the rolling friction resistance torque of the driving wheel, that is, the product of the gravity of the particle and the rolling friction coefficient of the driving wheel. This value can be regarded as a constant. In the above mathematical equation, the input power of the driving wheel changes linearly with the existing speed of the driving wheel. When the input torque of the driving wheel is synchronized and equal to the uniform speed resistance torque of the driving wheel, the input power of the driving wheel is equal to the work done by the driving wheel to overcome its uniform speed resistance. That is, the power output by the vehicle power device can be synchronized and transmitted to be equal to the work done by the driving wheel to overcome its uniform speed resistance.

[0031] The kinetic energy of the particle carried by the driving wheel is equal to its mass multiplied by the square of its velocity divided by 2. Based on this, the mathematical equation for the relationship between the kinetic energy increased by the accelerated motion of the particle and the velocity of the particle can be derived. This equation is a quadratic equation. The relationship between the kinetic energy increased by the accelerated motion of the particle carried by the driving wheel and the velocity of the particle carried by the driving wheel is nonlinear, and the relationship curve between the two is a quadratic curve. The power device used in existing vehicles usually generates and outputs power through the rotational motion of the swivel around its central axis, and the waveform of its power wave is similar to or close to a sine wave. Under the condition of synchronous power transmission, the power device used in existing vehicles cannot generate and output a power wave with a waveform exactly the same as the above quadratic curve, and it is also impossible to achieve that the input power of the driving wheel is equal to the kinetic energy increased by the accelerated motion of the particle carried by the driving wheel.

[0032] In summary, two forms of energy conversion occur during vehicle driving. The first form of energy conversion is that the input power of the driving wheel is converted into the work done by the driving wheel to overcome its uniform speed resistance; the second form of energy conversion is that the input power of the driving wheel is converted into the kinetic energy increased by the accelerated motion of the mass carried by the driving wheel. The first form of energy conversion can achieve the equality of the input power of the driving wheel and the work done by the driving wheel to overcome its uniform speed resistance through synchronous power transmission; the second form of energy conversion cannot achieve the equality of the input power of the driving wheel and the kinetic energy increased by the accelerated motion of the mass carried by the driving wheel through synchronous power transmission.

[0033] Under the existing vehicle power technology conditions, the ideal vehicle drive system should be to set a power processing unit between the vehicle power device and the drive wheel. The unit will correct the waveform of the power wave input by the power device and store excess energy or release the required energy. The power processing unit will then output uniform power and acceleration power to the drive wheel. The uniform power is equal to the work done by the drive wheel to overcome the uniform resistance, and the acceleration power is equal to the kinetic energy increased by the accelerated motion of the mass carried by the drive wheel.

[0034] 3. Formation of asynchronous power When the spring steel wire flexible shaft is in a static torsion state, the metal atoms in its elastic body will displace along a fixed trajectory and undergo proportional torsional deformation. This deformation is usually considered uniform, and the time sequence of the deformation process is also ignored. Since the metallographic structure of the spring steel wire flexible shaft is uneven, the stress and strain distribution inside it is uneven. The uneven deformation of the spring steel wire flexible shaft will not affect the applicability of Hooke's law, that is, when the deformation is kept within a certain range, the torque at the two ends of the spring steel wire flexible shaft is proportional to its torsion angle.

[0035] The spring steel wire flexible shaft is in a state of rotation when transmitting power, and a pair of equal and opposite balanced torques are always applied to its two ends. Under the action of balanced torque, the movement of each particle in the elastic body of the spring steel wire flexible shaft can be decomposed into synchronous rotation and asynchronous rotation around its central axis. These two kinds of rotational motion decompose the input power into synchronous power and asynchronous power. The synchronous power keeps the vehicle moving at a constant speed, and the asynchronous power makes the vehicle accelerate. The input power and output power at the two ends of the spring steel wire flexible shaft are not synchronously equal.

[0036] When the two ends of the spring steel wire flexible shaft (power input end and power output end) rotate asynchronously, this end face rotation will cause the fluctuation of atoms in the spring steel wire flexible shaft elastic body and form atomic waves. The propagation speed of this atomic wave in the spring steel wire flexible shaft elastic body is similar to the propagation speed of sound waves in the iron rod. When the length of the spring steel wire flexible shaft is 1 meter to 1.5 meters, the time required for this atomic wave to propagate from one end of the spring steel wire flexible shaft to the other end is 0.2 milliseconds to 0.3 milliseconds. The asynchronous rotation of the power input end of the spring steel wire flexible shaft converts the excess input power into the elastic deformation potential energy of the spring steel wire flexible shaft elastic body, and the asynchronous rotation of the power output end of the spring steel wire flexible shaft converts the elastic deformation potential energy of the spring steel wire flexible shaft elastic body into the kinetic energy increased by the acceleration of the vehicle. The elastic deformation potential energy of the spring steel wire flexible shaft elastic body changes with the balance torque at the two ends of the spring steel wire flexible shaft. The greater the balance torque, the greater the elastic deformation potential energy. Under normal circumstances, the speed of an electric bicycle is less than 35 kilometers per hour, and the speed of its driving wheel is less than 600 revolutions per minute. If the transmission ratio of the balance drive system of an electric bicycle is 1 to 2, the speed of its driving wheel is less than 1200 revolutions per minute. The speed of the asynchronous rotation of the two ends of the spring steel wire flexible shaft is less than the speed of its driving wheel. According to the current speed of the electric bicycle, the angular velocity of the asynchronous rotation of the two ends of the spring steel wire flexible shaft should be less than 7 degrees per millisecond. Relative to such a small angular velocity of asynchronous rotation, the propagation speed of the atomic wave in the elastic body of the spring steel wire flexible shaft is fast enough, and the asynchronous power can be continuously and smoothly transmitted in the elastic body of the spring steel wire flexible shaft, and its energy conversion process can be continuously and smoothly realized.

[0037] 4. Power input of a driver of an electric bicycle balance drive system Two supporting bearings are arranged on the transmission shaft of the driver of the balanced driving system of an electric bicycle. The front bearing is a sliding bearing, which is located in a cylinder on one side of the driving shaft, and its central axis intersects the central axis of the driving shaft vertically; the rear bearing is a single-row radial ball bearing, which is located in the bearing seat of the gear box of the driver. The outer circumferential surface of the transmission shaft and the inner holes of the above two bearings are clearance-matched, and the transmission shaft can move forward and backward along its central axis. The conical driving gear is sleeved on the outer circumferential surface of the transmission shaft through its central hole and maintains an interference fit, and its tail end face is abutted against the end face of the inner ring of the rear end bearing, so that the axial positioning of the conical driving gear can be maintained during operation. The interference fit between the center hole of the conical driving gear and the outer circumferential surface of the transmission shaft prevents relative rotation between the two. The front end of the rear extension sleeve is sleeved on the outer circumferential surface of the end of the transmission shaft, and four pins are evenly distributed in the circumferential direction. The four pins prevent relative rotation between the transmission shaft and the rear extension sleeve, and the axial positioning between the two can also be maintained. The end of the spring steel wire flexible shaft is axially slidably connected to the sleeve at the end of the rear extension sleeve through a universal joint. The end of the universal joint can slide freely in the axial direction of the inner hole of the sleeve, but cannot rotate relatively. The power output by the motor is transmitted to the rear extension sleeve through the spring steel wire flexible shaft through the universal joint at its end, and then to the transmission shaft.

[0038] 5. A drive shaft of a drive of a balance drive system of an electric bicycle The rotational motion of the power output end of the spring steel wire flexible shaft is synthesized by synchronous rotational motion and asynchronous rotational motion, and is transmitted to the drive shaft through the transmission shaft and the cone driving gear respectively. During the transmission process, the synchronous rotational motion and the asynchronous rotational motion of the synthesized rotational motion remain independent and do not affect each other. The rotational motion of the driving wheel on the driving shaft can also be decomposed into uniform rotational motion and accelerated rotational motion. The uniform rotational motion refers to the existing angular velocity of the driving wheel at any time point during the vehicle's driving process; the accelerated rotational motion refers to the angular acceleration of the driving wheel with the existing angular velocity as the initial velocity at any time point during the vehicle's driving process. The synchronous rotational motion and asynchronous rotational motion output from the power output end of the spring steel wire flexible shaft are transmitted to the cone driven gear through the transmission shaft and the cone driving gear respectively. The synchronous rotational motion occurs simultaneously with the uniform rotational motion of the driving wheel and remains equal in magnitude, and the asynchronous rotational motion occurs simultaneously with the accelerated rotational motion of the driving wheel and remains equal in magnitude.

[0039] However, there are multiple rotating bodies on the drive shaft. In addition to transmitting torque, there are also axial forces and bending forces interacting with each other. The interaction forces between these rotating bodies will change the synchronous rotation and asynchronous rotation of the cone driven gear, reducing the transmission efficiency. The driving shaft is provided with rotating bodies such as cone driven gear, bell-shaped driving sleeve, driving wheel hub, etc. The theoretical central axis of its rotation is the central axis of the driving shaft. The cone driven gear transmits power to the driving wheel hub through the bell-shaped driving sleeve. In actual application, due to the manufacturing and assembly errors of parts and components, and the slight bending elastic deformation of the driving shaft, the rotational center axes of the cone driven gear, bell-shaped driving sleeve, driving wheel hub and other rotating bodies are not on the same straight line, but each has its own rotational center axis. If the three rotating bodies on the driving shaft are rigidly connected into a combined rotating body and made to rotate synchronously, since there is a certain eccentricity between the actual rotational center axis of each rotating body and its common rotational center axis, axial force and bending force will be generated between the rotating bodies when transmitting power, thereby forming a mechanical resistance wave. In addition, when the vehicle is driving, the interaction between the vehicle load and the road support force causes the drive wheel to produce a yaw motion within a certain range. This yaw motion of the drive wheel hub will also cause axial force and bending force between the rotating bodies on the drive shaft, thereby generating another mechanical resistance wave.

[0040] The rolling resistance of the rear wheel of an electric bicycle under normal driving conditions is usually less than 2 Nm. The power consumption of an electric bicycle using a balanced drive system is only 20% to 30% of that of an existing electric bicycle when its mechanical loss is ignored, which has a significant energy-saving effect. The mechanical loss of the driver of an electric bicycle balanced drive system has a significant impact on the vehicle's balanced drive effect and its cruising range. Only by reducing the mechanical loss of the driver to a certain value (less than 10% of the normal driving energy consumption of existing vehicles) can the electric bicycle using a balanced drive system maintain a good balanced drive effect and a high cruising range (greater than 3 times the cruising range of existing vehicles). In order to reduce the mechanical resistance of the driver and reduce the power consumption caused by the mechanical resistance, it is necessary to design the rotating body on the drive shaft of the driver and its connection method in a targeted manner.

[0041] The driving hub and the bell-shaped driving sleeve on the driving shaft form a rotating assembly and have the same central axis of rotation; the cone driven gear on the driving shaft is an independent rotating body and has its own independent central axis of rotation. A ball universal joint is arranged between the hub rotating assembly and the cone driven gear, and the cone driven gear can smoothly transmit the torque to the driving hub through the universal joint. The axial extrusion force and bending force generated by the yaw motion of the hub and its eccentric moment will not be transmitted to the cone driven gear. The cone driven gear on the driving shaft has its own independent rotation center axis and will not be subjected to the axial extrusion force and bending force from the driving wheel hub. When transmitting power, the active and passive cone gears can maintain a stable and reasonable meshing gap and transmit power efficiently (mechanical transmission efficiency is greater than 95%). The synchronous power and asynchronous power output from the power output end of the spring steel wire flexible shaft are smoothly transmitted to the driving wheel hub through the transmission shaft and the cone active and passive gear pair respectively. The synchronous power is equal to the work done by the driving wheel to overcome the uniform speed resistance, and the asynchronous power is equal to the kinetic energy increased by the load-bearing mass of the driving wheel when it accelerates, thereby realizing balanced driving of the vehicle.

[0042] The left and right ends of the drive shaft of the driver of an electric bicycle balance drive system are externally threaded, and nuts are used to fasten the drive shaft to the open grooves on the left and right sides of the rear fork of the electric bicycle. The conical passive gear, bell-shaped drive sleeve, rear wheel hub, and other parts are mounted on the drive shaft, and the design center axis coincides with the center axis of the drive shaft. The conical active gear transmits power to the conical passive gear, and then to the bell-shaped drive sleeve, and then the bell-shaped drive sleeve drives the rear wheel hub to rotate the rear wheel. Due to errors in the manufacturing and assembly of parts, the rotation centers of the conical passive gear, bell-shaped drive sleeve, and rear wheel hub are not on the same center axis. This eccentric error will generate mechanical transmission resistance during the vehicle driving process. The mechanical transmission resistance presents regular periodic changes. Every time the rear wheel hub rotates one circle, it completes a fluctuation change cycle. Therefore, the periodic change frequency of the mechanical transmission resistance wave is the same as the synchronous speed of the conical passive gear, bell-shaped drive sleeve, and rear wheel hub. Under the condition of balanced driving, the power output end of the spring steel wire flexible shaft will undergo synchronous rotation and asynchronous rotation. Its synchronous rotation transmits synchronous power, and its asynchronous rotation transmits asynchronous power. Therefore, the power output by the bevel driving gear on the transmission shaft includes both synchronous and asynchronous power.

[0043] The fluctuation frequency of the asynchronous power transmitted from the power output end of the spring steel wire flexible shaft to the bevel driving gear on the transmission shaft is equal to the synchronous speed of the spring steel wire flexible shaft, that is, the synchronous speed of the bevel driving gear on the transmission shaft. The mechanical transmission resistance wave and the asynchronous power wave on the drive shaft are both periodically changing waves, and the ratio of their fluctuation frequencies is approximately equal to the transmission ratio of the bevel gear pair. The two waves are closely related, and the mechanical transmission resistance wave will significantly weaken the intensity of the asynchronous power wave. Under balanced driving conditions, the asynchronous power on the drive shaft is used to accelerate the vehicle. This acceleration mechanism is an important function of the balanced drive system of the electric bicycle. The mechanical transmission resistance wave on the drive shaft will directly reduce the balanced drive function of the balanced drive system of the electric bicycle and increase the power consumption of the vehicle. In order to solve the above technical problems, a ball universal joint is arranged between the bevel driven gear and the bell-shaped driving sleeve on the driving shaft. The universal joint is located in the center hole of the bell-shaped driving sleeve, and the outer circumferential surface thereof is interference fit with the center hole wall of the bell-shaped driving sleeve. When the vehicle is driven, the two will not rotate relative to each other. Two protrusions are evenly distributed on the right end face of the ball universal joint, and a ball is installed on the four sides of the two protrusions through a blind hole respectively. Two grooves are also evenly distributed on the tail port of the bevel driven gear on the driving shaft. The protrusions and the grooves are embedded in each other, and the side of the groove maintains point contact with the ball. When the bevel driven gear rotates around its center, its tail can swing freely in the axial and radial directions, and transmit torque through the point contact between the side of its groove and the ball. In this way, when the bevel driven gear rotates, it will not be affected by the yaw motion generated when the driving hub and the bell-shaped driving sleeve rotate, and the mechanical transmission resistance wave can be effectively eliminated.

[0044] 4. Torque limiting function of a driver of an electric bicycle balance drive system When the existing electric bicycle is running, its power is driven by a collision impact. The driving torque acting on the rear wheel hub presents discontinuous fluctuations, and its fluctuation amplitude is also high. When the vehicle is in an accelerated driving state, the amplitude of this impact torque will increase significantly, and its peak value will usually be greater than 8 Nm. Under balanced driving conditions, when the electric bicycle is running, the balance torque at the power output end of the spring steel wire flexible shaft of its balanced driving system and the vehicle driving resistance torque acting on the rear wheel hub always maintain a dynamic balance state, and the power output to the drive shaft is decomposed into uniform power and acceleration power. These two powers realize energy conversion in a balanced manner under the action of the balance torque, and there will be no collision impact phenomenon. Therefore, the driving torque acting on the rear wheel hub will be significantly reduced. When the electric bicycle is running on a flat road, the balance drive torque of its balance drive system is usually less than 2 Nm; when the electric bicycle is accelerating on a flat road, the balance drive torque of its balance drive system is usually less than 6 Nm. During the driving process of the electric bicycle balance drive system, the spring steel wire flexible shaft is always in a proportional torsional deformation state, and the range of fluctuation of stress and strain on its cross section should be kept within a moderate and reasonable range. The results of the bench test of the electric bicycle balance drive system show that when the stress on the cross section of the spring steel wire flexible shaft is less than 30% of its yield stress, the electric bicycle balance drive system can obtain a better balance drive effect, and the fatigue resistance service life of the spring steel wire flexible shaft is also high. According to the balance drive torque required by the electric bicycle balance drive system under normal driving conditions and the 30% yield strength of the spring steel wire flexible shaft, the material and diameter of the spring steel wire used in the spring steel wire flexible shaft can be determined. In the actual use of electric bicycles, it is inevitable that abnormal use conditions such as sudden braking, crossing obstacles, and accelerating too fast will occur. When these abnormal use conditions occur, the impact torque acting on the spring steel wire flexible shaft increases sharply, causing the stress on the cross section of the spring steel wire flexible shaft to exceed its yield strength and produce permanent plastic deformation. After the spring steel wire flexible shaft undergoes permanent plastic deformation, the balance drive function of the electric bicycle balance drive system will be reduced, and the fatigue resistance service life of the spring steel wire flexible shaft will also be reduced. In order to solve the above technical problems, a torque limiting structure is provided on the driving shaft. When the resistance torque acting on the driving wheel is greater than the torque limiting value of the torque limiting structure, relative rotation will occur between the conical passive gear on the driving shaft and the driving wheel hub. At this time, the driving torque acting on the driving wheel hub is equal to the torque limiting value of the torque limiting structure. Through such a setting, when the electric bicycle is used abnormally, the stress on the cross section of the spring steel wire flexible shaft can be kept less than 30% of its yield stress, so that the balance driving function of the balance driving system of the electric bicycle remains stable and sustainable, and the spring steel wire flexible shaft will not produce permanent plastic deformation and has a high fatigue resistance service life.

[0045] The torque limiting structure is composed of parts such as a bell-shaped drive sleeve, a friction plate, a friction disc, a disc spring, a pressure plate, and an adjusting nut. The bell-shaped drive sleeve is provided with two ends, large and small, and the friction plate, friction disc, disc spring, pressure plate, and adjusting nut are respectively mounted on the outer circumferential surface of the small end rod of the bell-shaped drive sleeve. Two left and right bearing fulcrums are provided on the drive shaft, wherein the left bearing is placed at the left end of the center hole of the wheel hub, and the right bearing fulcrum is provided with an inner ring bearing and an outer ring bearing, wherein the inner ring bearing is placed in the center hole of the large end of the bell-shaped drive sleeve, and the outer ring bearing is placed on the outer circumferential surface of the large end of the bell-shaped drive sleeve, and the outer circumferential surface of the outer ring bearing is installed in the center hole of the right end cover of the wheel hub. During the vehicle driving process, when the driving torque is less than the torque limiting value of the torque limiting structure, the inner ring bearing of the right bearing fulcrum of the drive shaft rotates relatively, and its outer ring bearing does not rotate relatively; when the driving torque is equal to or greater than the torque limiting value of the torque limiting structure, the inner ring bearing and the outer ring bearing of the right bearing fulcrum of the drive shaft both rotate relatively.

[0046] 5. Requirements for power transmission under vehicle balanced driving conditions The driving method of existing vehicles is that the power output by the power device is synchronously transmitted to the drive wheel through the rigid transmission parts, and collides with the drive wheel and the mass it carries. During the collision and impact process, the power is decomposed, part of which is converted into the work done by the drive wheel to overcome the uniform resistance and the kinetic energy increased by the acceleration of the mass carried by the drive wheel, and part of the power rebounds back to the drive system. Under the condition of vehicle collision and impact driving, the power output by the power device is greater than the sum of the work done by the drive wheel to overcome the uniform resistance and the kinetic energy increased by the acceleration of the mass carried by the drive wheel, and the energy transfer between the drive wheel, the transmission device, and the power device forms a two-way circulation loop. Under such conditions, there is no need to set specific technical requirements for vehicle power transmission.

[0047] The working principle of vehicle balance drive is that the vehicle drive system consists of three parts: power device, balance drive functional unit and drive wheel. The balance drive functional unit receives the power output by the power device, decomposes the power into uniform speed power and acceleration power after power processing, and outputs it to the drive wheel. Under the condition of balanced drive, the power is transmitted in one direction and no power rebound occurs. In practical applications, the drive wheel is driven by a drive device, in which rigid drive parts are provided. The uniform speed power and acceleration power output by the balance drive functional unit are transmitted through rigid transmission parts respectively, and the two are independent of each other and do not affect each other. Under the condition of the same vehicle mass and speed, if the mechanical loss of the vehicle drive system is ignored, the power required for balanced drive is about 10% of that of existing vehicles. It can be seen that the values ​​of uniform speed power and acceleration power output by the balance drive functional unit are small. In actual applications, transmission parts are subject to manufacturing, assembly, and slight elastic deformation. These factors will lead to mechanical transmission resistance in the process of power transmission. As the drive wheel runs, the mechanical transmission resistance fluctuates. These mechanical transmission resistance waves are large, and their intensity is often greater than the uniform power wave and acceleration power wave output by the balance drive functional unit. These resistance waves will seriously interfere with the transmission of the power wave, and even offset the power wave, resulting in a reduction in the vehicle's balanced drive effect. Therefore, the mechanical resistance should be minimized on the path of power transmission, and the transmission of mechanical resistance waves should be blocked between the balance drive functional unit and the drive wheel. Only in this way can the working mechanism of the balance drive functional unit run smoothly and maintain a good balance drive effect.

[0048] The main structure of the driver of an electric bicycle balance drive system is composed of a transmission shaft and a drive shaft. The two shafts form a cross-shaped structure with a shaft intersection angle of 90 degrees, and a bevel gear pair is used for transmission. The bevel active and passive gears are located on the transmission shaft and the drive shaft respectively. An electric bicycle balance drive system uses a spring steel wire flexible shaft, and its driver must not only reduce the mechanical transmission resistance and block the transmission of the mechanical transmission resistance wave between the balance drive functional unit and the drive wheel; at the same time, the spring steel wire flexible shaft must always maintain a reasonable straightness and tightness during operation; the spring steel wire flexible shaft must also be protected from the destructive effect of the overload impact load when the vehicle is overloaded, and its proportional torsion angle must always be kept within the rated range.

[0049] The tail of the transmission shaft of the driver of the balance drive system of an electric bicycle is connected with an extension sleeve, a sliding sleeve and a cross-axis universal joint are arranged in the central hole of the extension sleeve, a flat hole is arranged at the center of the sliding sleeve, the end surface of the sliding sleeve is welded to the end surface of the extension sleeve, the front end of the cross-axis universal joint is connected to the end of the spring steel wire flexible shaft, and the rear end flat shaft is inserted into the flat hole of the sliding sleeve in a clearance fit manner, and there is no relative rotation between the flat shaft and the flat hole, but axial sliding can occur. The spring steel wire flexible shaft is protected from axial extrusion force and bending force by the direction adjustment function of the universal joint; the torque is transmitted by the mutual cooperation of the flat shaft and the flat hole, and the axial length of the spring steel wire flexible shaft is freely extended and retracted with the change of the balance torque.

[0050] A driving shaft of a driver of a balanced driving system of an electric bicycle is provided with a bell-shaped driving sleeve, a ball universal joint is placed at the port of the center hole of the large end of the bell-shaped driving sleeve, and its outer circumferential surface is tightly fitted with the center hole wall by interference, and relative rotation does not occur between the two. Two convex claws are symmetrically arranged on the right side of the ball universal joint, and a steel ball is respectively arranged through a blind hole on the four side planes of the two convex claws, and its spherical surface is 1 mm to 2 mm higher than the side plane. Two open grooves are symmetrically arranged at the tail of the conical passive gear, and the two convex claws of the ball universal joint are respectively inserted into the two open grooves, and the four side planes of the open groove respectively maintain point contact with the steel ball surface, and the steel ball surface can roll in any direction on the side plane of the open groove. Only torque is transmitted between the conical passive gear and the bell-shaped driving sleeve through the ball universal joint, and the axial extrusion force and bending force generated when the driving wheel is running will not be transmitted to the conical passive gear, so that the working conditions of the balanced driving functional unit remain stable.

[0051] A bell-shaped driving sleeve is arranged on the driving shaft of a driver of a balanced driving system of an electric bicycle, and an adjusting nut, a disc spring, a pressure plate, a left friction plate, a friction disc and a right friction plate are arranged in sequence on the small end rod portion of the bell-shaped driving sleeve, a flat shaft is arranged on the left side of the small end rod portion of the bell-shaped driving sleeve, and the flat shaft is matched with the central flat hole of the pressure plate in a clearance, so that the two do not rotate relative to each other, but can move axially, and the pressure plate, the left friction plate, the friction disc and the right friction plate are pressed tightly on the end face of the pillow block in the middle of the bell-shaped driving sleeve by the axial pressure generated by the adjusting nut and the disc spring, and four friction surfaces are formed in sequence between the pressure plate and the end face of the pillow block, and the friction area of ​​the right side face of the pressure plate and the end face of the pillow block is larger than the friction area of ​​the left and right side faces of the friction disc Friction area, the limited torque value of the friction disk can be set by adjusting the nut. Two protrusions are symmetrically arranged at the outer edge of the friction disk and embedded in the corresponding grooves of the wheel hub end cover to prevent relative rotation between the two. When the driving wheel operates normally, the bell-shaped driving sleeve drives the wheel hub to rotate through four friction surfaces and with the inner ring bearing as the support; when the operating resistance torque of the driving wheel is greater than the limited torque value of the friction disk, the friction surfaces on the left and right sides of the friction disk will slip, and relative rotation will occur between the bell-shaped driving sleeve and the outer ring bearing. At this time, the acting torque between the clock-shaped driving sleeve and the wheel hub remains equal to the limited torque value of the friction disk, so that the proportional torsion angle of the spring steel wire flexible shaft is less than or equal to its rated value.

[0052] VI. Structure of a driver for an electric bicycle balance drive system The balance drive system of the electric bicycle is set to be located on the right side of the vehicle, and the rear brake is located on the left side of the vehicle. A driver for the balance drive system of an electric bicycle consists of five parts: a telescopic transmission shaft, a drive shaft, a bevel gear pair, a mechanical transmission resistance blocking structure, and a torque limiting structure. The front end of the telescopic transmission shaft passes through a through hole on a cylinder located at the right end of the drive shaft, so that the central axis of the drive shaft intersects perpendicularly with the central axis of the telescopic transmission shaft. The active bevel gear of the bevel gear pair with an axis intersection angle of 90° is installed at the rear end of the telescopic transmission shaft, and its passive bevel gear is installed at the right end of the drive shaft.

[0053] A driver for a balanced driving system of an electric bicycle Figure 1 As shown, Figure 1 The middle part 1 is a spring steel wire flexible shaft. Figure 1 The middle piece 2 is the deflection control bushing. Figure 1 The middle part 3 is the transmission shaft. Figure 1 The middle part 4 is an oil seal. Figure 1 The middle part 5 is the rear fork. Figure 1 The middle piece 6 is a sliding bearing. Figure 1 The middle part 7 is the drive shaft. Figure 1 The middle part 8 is a conical driving gear, and the transmission shaft (part 3) is tightly connected to the conical driving gear through an interference fit, and no relative rotation occurs between the two. Figure 1 The middle part 9 is the gear box housing. Figure 1 The middle piece 10 is an adjusting sleeve, which is used to adjust the axial position of the bevel driving gear. Figure 1 The middle piece 11 is a single row radial ball bearing. Figure 1 The middle part 12 is an O-type rubber sealing ring. Figure 1 The middle part 13 is a bearing seat outer sleeve, which is welded into one piece with the gear box housing. Figure 1 The middle part 14 is a bearing seat, and its outer circumferential surface is clearance-matched with the inner hole of the bearing seat outer sleeve (part 13), and is sealed by an O-type rubber seal ring (part 12). The transmission shaft (part 3) is radially positioned by the front sliding bearing (part 6) and the rear single-row radial ball bearing (part 11), and is axially positioned by the adjustment sleeve (part 10). Figure 1 The middle part 15 is an oil seal, and the outer circumferential surface of the transmission shaft (part 3) is kept sealed by the front oil seal (part 4) and the rear oil seal (part 15). Figure 1 The middle piece 16 is a pin. Figure 1 The middle piece 17 is a bushing. Figure 1 The middle piece 18 is a threaded sleeve. Figure 1 The middle part 19 is an extension sleeve, and the front end of the extension sleeve (part 19) is sleeved on the tail of the transmission shaft (part 3) through the bushing (part 17), and the torque and axial positioning are transmitted through 4 evenly distributed pins (part 16). Figure 1 The middle piece 20 is a pin. Figure 1 The middle piece 21 is a cross-axis universal joint. Figure 1 The middle part 22 is a sliding sleeve. The front end of the cross-axis universal joint (part 21) is fastened to the end of the spring steel wire flexible shaft (part 1) through a pin shaft (part 20). The sliding shaft at its rear end is inserted into the inner sliding hole of the sliding sleeve (part 22). The outer circumferential surface of the sliding sleeve is placed in the inner hole at the end of the extension sleeve (part 19). The end surface of the sliding sleeve is fastened to the end surface of the extension sleeve by welding. Figure 1 The middle part 23 is an O-type rubber sealing ring. Figure 1 The middle piece 24 is a bevel driven gear. Figure 1 The middle part 25 is an oil seal sleeve. Figure 1 The middle part 26 is an oil seal. Figure 1 The middle piece 27 is a ball-type universal joint. Figure 1 The middle piece 28 is an inner ring bearing (single row radial ball bearing). Figure 1 The middle piece 29 is a friction disc. Figure 1 The middle part 30 is a friction plate. Figure 1 The middle part 31 is a disc spring. Figure 1 The middle piece 32 is an adjusting nut. Figure 1 The middle piece 33 is a single-row radial ball bearing. Figure 1 The middle part 34 is a brake drum. Figure 1 The middle part 35 is a brake disc. Figure 1 The middle piece 36 is the rear wheel hub. Figure 1 The middle piece 37 is a pressure plate. Figure 1 The middle piece 38 is an outer ring bearing (sliding bearing). Figure 1 The middle piece 39 is a bell-shaped drive sleeve. Figure 1 The middle part 40 is the wheel hub end cover. Figure 1 The middle part 41 is an O-type rubber sealing ring. Figure 1 The middle piece 42 is an adjustment sleeve. Figure 1 The middle piece 43 is a sliding bearing.

[0054] The extension sleeve (part 19) is cylindrical, with a central through hole along its central axis. Its front end is sleeved on the tail of the transmission shaft (part 3) through a bushing, and the central axis of the extension sleeve and the central axis of the transmission shaft are located on the same straight line. The end of the spring steel wire flexible shaft (part 1), the cross-axis universal joint (part 21), and the sliding sleeve (part 22) are placed in the central hole of the extension sleeve in a front-to-back order. The tail of the spring steel wire flexible shaft is fastened to the front end of the cross-axis universal joint through a pin (part 20), and the flat shaft at the rear end of the cross-axis universal joint is inserted into the central flat hole of the sliding sleeve. The two are clearance-fitted and will not rotate relative to each other, but the flat shaft can move axially in the flat hole. The end surface of the sliding sleeve is fastened to the end surface of the extension sleeve by welding.

[0055] When the drive shaft transmits torque, through the direction adjustment of the cross-axis universal joint, the eccentricity of the front and rear ends of the spring steel wire flexible shaft, the vibration of the vehicle and the slight elastic deformation will not generate extrusion force and bending force between the flat shaft and the flat hole. Only torque is transmitted between the flat shaft and the flat hole, and the flat shaft can move freely axially in the flat hole, so that the spring steel wire flexible shaft maintains reasonable straightness and tightness.

[0056] The bevel driven gear (part 24) is provided with a central through hole, and the driving shaft (part 7) passes through the central through hole. The outer circumferential surface of the sliding bearing (part 38) maintains an interference fit with the inner circumferential surface of the central through hole of the bevel driven gear. The inner hole of the sliding bearing and the outer circumferential surface of the corresponding section on the driving shaft are clearance fit. The bevel driven gear rotates on the driving shaft through the sliding bearing. Two open grooves are symmetrically provided at the end of the bevel driven gear. The ball universal joint (part 27) is placed at the front end of the inner hole of the large end of the bell-shaped driving sleeve (part 37). The outer circumferential surface of the ball universal joint and the inner hole wall of the bell-shaped driving sleeve are interference fit, and there is no relative rotation between the two. Two convex claws are symmetrically provided at the front end of the ball universal joint. A blind hole is provided on the front and rear sides of each convex claw. A steel ball is provided in each blind hole, and the vertex of the steel ball protrudes from the side plane by 1 mm to 2 mm. The claw at the front end of the ball universal joint is inserted into the open groove at the end of the conical passive gear and is axially positioned through a single-row radial ball bearing (item 28) and an adjustment sleeve (item 39). The steel ball on the side of the claw is in point contact with the side plane of the open groove and transmits torque. The apex of the steel ball can roll in any direction on the side plane of the open groove. Therefore, the yaw motion of the rear wheel hub (item 36) and the slight elastic bending deformation of the drive shaft will not form an extrusion force and bending force acting on the conical passive gear, and the conical passive gear can maintain its own independent rotation center axis during operation.

[0057] The single-row radial ball bearing (item 28) is an inner ring bearing, which is placed at the left end of the center hole of the large end of the bell-shaped drive sleeve. Its inner hole is mounted on the corresponding bearing neck of the drive shaft (item 7) and is maintained in axial positioning by a circlip and a pillow block.

[0058] The sliding bearing (part 37) is an outer ring bearing, and the inner hole of the bearing is dynamically fitted with the outer circumferential surface of the large end of the bell-shaped drive sleeve (part 39), and the outer circumferential surface of the outer ring bearing is tightly fitted with the central inner hole wall of the hub end cover (part 40). The outer circumferential surface of the large end of the bell-shaped drive sleeve and the hub end cover can rotate relative to each other through the outer ring bearing.

[0059] The friction plate (part 30) is divided into two left and right plates, and the friction disc (part 29) is placed between the left and right friction plates. The left friction plate, the friction disc, and the right friction plate are respectively mounted on the outer circumferential surface of the small end rod of the bell-shaped driving sleeve in a front-to-back order. Two protrusions (driving claws) are symmetrically arranged at the outer edge of the friction disc, and two opening grooves are correspondingly arranged at the left end surface of the wheel hub end cover. The two protrusions are respectively inserted into the two opening grooves, and there is no relative rotation between the two, but axial movement can occur.

[0060] The pressure plate (part 37), the disc spring (part 31), and the adjusting nut (part 32) are sequentially mounted on the outer circumferential surface of the small end rod of the bell-shaped drive sleeve. The right side of the pressure plate is in close contact with the friction plate, and the left side of the pressure plate is in close contact with the disc spring. The small end of the bell-shaped drive sleeve is provided with a section of flat shaft with external threads. The pressure plate is mounted on the section of flat shaft through its central flat hole. The pressure plate can move axially on the section of flat shaft, but will not rotate relative to the flat shaft. The adjusting nut presses the pressure plate, disc spring, left friction plate, friction disc, and right friction plate on the end plane of the outer cylindrical shaft platform of the bell-shaped drive sleeve along the central axis direction through a section of external threads at the small end of the bell-shaped drive sleeve. The pressing force applied by the disc spring to the left friction plate, friction disc, right friction plate, and end plane of the shaft platform can be adjusted by twisting the adjusting nut. The torque limit value of the torque limiting structure can be set through actual measurement.

[0061] When the driving torque is less than the torque limit value of the torque limiting structure, the bell-shaped driving sleeve, the friction disc and the driving wheel hub keep rotating synchronously; when the resistance torque of the driving wheel hub is greater than the torque limit value of the torque limiting structure, relative sliding will occur between the friction disc and the friction plates on both sides of it. At this time, the bell-shaped driving sleeve and the friction disc rotate asynchronously, and the driving torque output by the bevel passive gear remains equal to or less than the torque limit value of the torque limiting structure, thereby keeping the proportional torsional deformation angle of the spring steel wire flexible shaft less than its maximum allowable proportional torsional angle. According to the test results, when the working stress on the cross section of the spring steel wire flexible shaft is less than 30% of its yield stress, the spring steel wire flexible shaft has a higher fatigue resistance and service life. Therefore, the torque limit value of the torque limiting structure can be set to the torque value corresponding to 30% of the yield stress of the cross section of the spring steel wire flexible shaft. Under normal vehicle driving conditions, the balance torque of the spring steel wire flexible shaft should be less than the torque value corresponding to 20% of the yield stress of the cross section of the spring steel wire flexible shaft.

[0062] During normal vehicle driving, power is transmitted to the bevel driven gear installed on the drive shaft through the active bevel gear installed on the transmission shaft, transmitted to the bell-shaped drive sleeve through the ball universal joint, transmitted to the friction plate through the left and right friction plates, and then transmitted to the drive wheel hub through the friction plate. BRIEF DESCRIPTION OF THE DRAWINGS

[0063] Figure 1 A driver for a balanced driving system of an electric bicycle Figure 2 A driver for a balanced driving system of an electric bicycle according to this embodiment Example

[0064] The driver of an electric bicycle balance drive system is installed on the rear fork of the vehicle, and its installation space is limited to the space between the rear fork gaps. Usually, the size of the rear fork gap of an electric bicycle is less than 220 mm, and its installation space is small. Therefore, the structure of the driver should be as simple and compact as possible while meeting the vehicle use requirements.

[0065] The active and passive bevel gear pair is the core component of the driver. The shaft angle of the bevel gear pair determines the basic structure of the driver. Setting the shaft angle of the bevel gear pair to 90° is more conducive to the structural layout and manufacturing and installation of the balanced drive system. The transmission ratio of the active and passive bevel gear pair of the driver is an important technical parameter of the balanced drive system. The larger the transmission ratio of the active and passive bevel gear pair of the driver, the smaller the torque transmitted by the spring steel wire flexible shaft of the balanced drive system, the smaller the diameter of the spring steel wire flexible shaft, the better the flexibility of the spring steel wire flexible shaft, the better the balanced drive effect of the balanced drive system, and the greater the ratio of the speed of the motor of the vehicle balanced drive system to the speed of the rear wheel. Since a part of the electric energy will be consumed in the current loop between the motor and the battery for each rotation of the motor, the greater the ratio of the speed of the motor of the vehicle balanced drive system to the speed of the rear wheel, the more electric energy will be consumed in the current loop between the motor and the battery for each rotation of the rear wheel, which is not conducive to improving the vehicle's cruising range and the service life of the battery. Under the condition of maintaining moderate flexibility of the spring steel wire flexible shaft of the vehicle's balanced drive system, the transmission ratio of the active and passive bevel gear pairs is selected as close to 1 as possible, which is more conducive to improving the vehicle's cruising range and the service life of the battery.

[0066] During the driving process of an electric bicycle, when the tire encounters an uneven road surface or a ditch on the ground, the rotation speed of the tire will instantly decrease or stop. At this time, the inertial force of the motor's rotating body will cause the spring steel wire flexible shaft to bear a torque exceeding the rated torque value of the motor, or even a torque exceeding the maximum allowable torque value of the spring steel wire flexible shaft. At this time, the torque limiting structure of the vehicle balance drive system driver needs to play its overload protection role to avoid the spring steel wire flexible shaft from failing due to excessive torsional deformation. The torque limiting value of the torque limiting structure can be changed by twisting the adjustment nut in the torque limiting structure. If the torque limiting value of the torque limiting structure is adjusted too small, the frequency of slippage of its friction disc will increase, which will affect the normal riding of the vehicle; if the torque limiting value of the torque limiting structure is adjusted too large, the protective effect of the torque limiting structure on the spring steel wire flexible shaft will be reduced. The torque limiting value of the torque limiting structure is an important technical parameter of the vehicle balance drive system driver. A reasonable torque limiting value of the torque limiting structure should be selected under the condition of maintaining the normal riding of the vehicle. Under normal circumstances, the torque limiting value should be 1.2 to 1.5 times the rated torque of the motor.

[0067] The basic parameters of the electric bicycle of this embodiment are: the vehicle curb mass is 95 kg, the rated load is 75 kg, the rated voltage of the motor is 48 volts, and the rated torque of the motor is 8 Nm.

[0068] The transmission ratio of the active and passive bevel gear pairs of the driver of the electric bicycle balance drive system of this embodiment is 1 to 1.5, the module of the bevel teeth is 2 mm, the number of teeth of the bevel driving gear is 30, and the number of teeth of the bevel passive gear is 45; the torque limiting value of the torque limiting device of the driver of the electric bicycle balance drive system is 1.2 times the rated torque of the motor, that is, 9.6 Nm.

[0069] A driver of the electric bicycle balance drive system of this embodiment is as follows Figure 2 As shown, in Figure 2 The opening size of the center rear fork is 200 mm, the thread diameters at the left and right ends of the drive shaft are M14 and M16 respectively, and the outer diameter of the drive shaft is 20 mm.

Claims

1. A driver for a balance drive system of an electric bicycle, characterized in that: The transmission shaft and driving shaft of a driver of a balanced driving system of an electric bicycle are in a cross structure, a telescopic structure is arranged on the transmission shaft, and a mechanical transmission resistance blocking structure and a torque limiting structure are arranged on the driving shaft respectively.

2. The driver of the electric bicycle balance drive system according to claim 1, characterized in that: The invention discloses a telescopic structure of a transmission shaft of a driver of a balanced driving system of an electric bicycle. A sliding sleeve and a cross-axis universal joint are arranged in the central hole of an extension sleeve, a flat hole is arranged at the center of the sliding sleeve, the end surface of the sliding sleeve is welded to the end surface of the extension sleeve, the front end of the cross-axis universal joint is connected to the end of a spring steel wire flexible shaft, and the rear end flat shaft is inserted into the flat hole of the sliding sleeve in a clearance fit manner. No relative rotation occurs between the flat shaft and the flat hole, but axial sliding can occur.

3. The driver of the electric bicycle balance drive system according to claim 1, characterized in that: A mechanical transmission resistance blocking structure of a drive shaft of a driver of a balanced drive system of an electric bicycle is that a ball-type universal joint is placed at the port of a central hole at the large end of a bell-shaped drive sleeve, and its outer circumferential surface is tightly fitted with the central hole wall by interference, and no relative rotation occurs between the two. Two cams are symmetrically arranged on the right side of the ball-type universal joint, and a steel ball is respectively arranged on the four side planes of the two cams through a blind hole, and the spherical surface of the steel ball is 1 mm to 2 mm higher than the side plane. Two open grooves are symmetrically arranged at the tail of a conical passive gear, and the two cams of the ball-type universal joint are respectively inserted into the two open grooves, and the four side planes of the open groove respectively maintain point contact with the steel ball surface, and the steel ball surface can roll in any direction on the side plane of the open groove.

4. The driver of the electric bicycle balance drive system according to claim 1, characterized in that: A torque limiting structure of a drive shaft of a driver of a balanced drive system of an electric bicycle is that an adjusting nut, a disc spring, a pressure plate, a left friction plate, a friction disc and a right friction plate are sequentially arranged on the small end rod of a bell-shaped drive sleeve; a flat shaft is provided on the left side of the small end rod of the bell-shaped drive sleeve, and is gap-matched with the central flat hole of the pressure plate; no relative rotation occurs between the two, but axial movement can occur; the pressure plate, the left friction plate, the friction disc and the right friction plate are pressed against the end face of the pillow block in the middle of the bell-shaped drive sleeve by the axial pressure generated by the adjusting nut and the disc spring, and four friction surfaces are sequentially formed between the pressure plate and the end face of the pillow block; the friction surfaces on the right side face of the pressure plate and the end face of the pillow block The friction area is larger than the friction area of ​​the left and right sides of the friction disk. The limited torque value of the friction disk can be set by adjusting the nut. Two protrusions are symmetrically arranged at the outer edge of the friction disk and embedded in the corresponding grooves of the wheel hub end cover to prevent relative rotation between the two. When the driving wheel operates normally, the bell-shaped driving sleeve drives the wheel hub to rotate through four friction surfaces and with the inner ring bearing as the support. When the operating resistance torque of the driving wheel is greater than the limited torque value of the friction disk, the friction surfaces on the left and right sides of the friction disk will slip, and relative rotation will occur between the bell-shaped driving sleeve and the outer ring bearing. At this time, the acting torque between the clock-shaped driving sleeve and the wheel hub remains equal to the limited torque value of the friction disk.

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