CN117704024A - Vehicle drive axle with differential active control function and control method thereof - Google Patents

Abstract

The invention discloses a vehicle drive axle with an active differential control function and a control method thereof, wherein the vehicle drive axle comprises a differential auxiliary motor; a driving wheel; and a transmission for transmitting power to the drive wheels and a planetary gear train for transmitting power from the auxiliary motor to the differential gear; the transmission includes differential gears, side gears, and differential cases, the differential gears being intermeshed with each other and with the respective corresponding side gears, the differential gears being disposed on the differential cases. The auxiliary motor is connected with the differential gear through the planetary gear train. The auxiliary motor can adjust output torque and steering according to the control method, so that active distribution of power at two ends of the drive axle is realized. The invention can assist the vehicle to turn, realize the limited slip of the differential mechanism when the vehicle has a slip trend, play the role of the differential mechanism lock when the vehicle slips, and greatly improve the escaping capability of the vehicle.

Description

A vehicle drive axle with differential active control function and its control method

Technical field

The present invention generally relates to a vehicle drive axle with a differential active control function and a control method thereof. In particular, the differential can be actively controlled in a complex road environment to enable the vehicle to have better driving performance.

Background technique

The power of the engine is transmitted to the driving wheels through transmission devices, which include clutches, transmissions, drive shafts and drive axles. The drive axle is the last assembly of the transmission chain. The drive axle is generally composed of a reducer and a differential.

When the car is turning, since the turning radii of the inner and outer wheels are different, the rotation speed of the inner and outer wheels is required to be different during the turn and the rotation speed of the outer wheels is higher than the rotation speed of the inner wheels. Therefore, the differential is a transmission device that creates a difference in the speed of the inner and outer wheels when turning, and rationally distributes torque to the left and right wheels when turning, allowing the vehicle to turn smoothly.

The main function of the differential is to distribute the driving force from the power source to the drive wheels on both sides. When the vehicle is traveling in a straight line, the same driving force is distributed to the wheels on both sides, so the wheels on both sides also have the same rotational speed. When the vehicle turns, the differential performs differential speed so that the left and right wheels obtain different speeds, thereby ensuring that the vehicle can turn smoothly.

Usually, a differential is composed of planetary gears, planetary carriers or differential cases, side gears and other components. The power input by the engine is transmitted to the differential, directly acts on the differential case, and is then transmitted through the planetary gears. to the left and right half shafts, which drive the wheels. Generally, the design of the differential should satisfy the rotation speed of the left and right half shafts and the rotation speed of the differential case equal to twice. When the vehicle is traveling in a straight line, the rotation speed of the left and right half shafts is equal to that of the differential case, and the left and right wheels are rigidly connected by a shaft. When the vehicle turns, the internal gears of the differential move relative to each other, causing the outer wheel speed to increase and the inner wheel speed to decrease.

The ordinary differential has an obvious shortcoming, that is, when one wheel slips or spins, the differential will transfer most of the power to the slipping or spinning wheel, making the vehicle unable to drive normally and losing a lot of power. Therefore, in order to prevent this situation from happening, people invented the limited-slip differential. When the vehicle slips, it can rigidly connect the left and right half-shafts, so that the power is evenly distributed to the wheels on both sides and helps the vehicle get out of trouble.

The main problems with current differentials are: although the limited-slip differential that requires manual control is technically simple and reliable, it is expensive, has a short service life, and is inconvenient to use. The active limited-slip differential can only work when the speed difference between the wheels on both sides reaches a set value, and cannot prevent the vehicle from skidding.

With the rapid development of motor control technology, it has become possible to use motors to control differentials. Compared with ordinary mechanical limited-slip differentials, the use of motor-controlled differentials can reduce the impact generated during operation, and compared with active limited-slip differentials, it can prevent vehicle slipping in advance.

Contents of the invention

In order to solve the problems existing in the existing limited-slip differential, the present invention provides a vehicle drive axle with a differential active control function and a control method thereof, so that the vehicle can adjust the differential speed in complex road environments and changing weather conditions. Based on the working characteristics of the differential, the vehicle's slipping tendency is judged based on the actual situation, so that the motor controls the differential slip limit in advance, thereby preventing the vehicle from slipping. In addition, the motor-controlled differential can not only control the differential slip, but also assist the vehicle in turning, which is a function that ordinary differential locks do not have.

According to one aspect of the present invention, a vehicle drive axle with a differential active control function is provided. The drive axle includes an auxiliary motor; a transmission device, the transmission device is a differential, and the output is connected to a half shaft. , the input terminal is connected with the auxiliary motor, and the control unit. And the control unit controls the auxiliary motor to control the transmission device according to the vehicle speed and the difference in rotation speed of the two wheels.

According to another aspect of the present invention, a control method for active differential control is also provided, which adjusts the rotation speed and direction of the auxiliary motor according to different situations, thereby controlling the working conditions of the differential gear in the differential, and realizing active differential control. The torque is distributed to the left and right axle shafts by the device. The method is as follows:

Determine the current vehicle speed and the difference in rotational speed of the wheels on both sides.

When the vehicle speed is not zero, there is a large speed difference between the wheels on both sides, and it is within the allowable range of the setting, the auxiliary motor will assist the differential to perform differential speed, drive the differential gear to rotate, and transfer torque from the low-speed side half shaft Shifted to the high-speed side half shaft, thereby improving the vehicle's steering characteristics. The torque provided by the auxiliary motor increases as the speed difference between the wheels on both sides increases, and also decreases as it decreases.

When the vehicle speed is not zero, there is a large speed difference between the wheels on both sides and it is approaching the set allowable critical value, the auxiliary motor will operate to hinder the differential speed, causing the speed of the differential gear to decrease and improving the differential limit in advance. slippery properties, thereby helping the vehicle prevent skidding. The torque provided by the auxiliary motor increases as the speed difference between the wheels on both sides increases, and also decreases as it decreases.

When the vehicle speed is zero and there is a large speed difference between the wheels on both sides and exceeds the set value, the auxiliary motor will run quickly to block the differential speed, causing the speed of the two differential gears to drop to zero. There is no speed difference between the shafts, which is equivalent to a rigid connection between the half shafts on both sides. The torque is evenly distributed to the left and right half shafts, so that the vehicle has better anti-skid performance and can get rid of slipping as soon as possible.

Optionally, when the differential is in a stable operating state, the rotational speed of the differential gear is constant, and the sum of the driving torques of all loads on the differential gear is zero. By applying an additional driving torque to the differential gear to change the force on the half shafts on both sides, the torque distribution of the left and right output shafts of the differential can be achieved. During the operation of the differential, the differential gear is subject to the force given to it by the left and right half shafts, the torque of the left and right half shafts driving the differential gears, friction torque and additional driving torque. The torque of the left and right half-shaft drive differential gears and the size and direction of the additional drive torque will affect the working characteristics of the differential. Therefore, different control methods are used for the additional drive torque to achieve various additional functions of the differential. .

When the torque of the left and right side shaft gears driving the differential gears is in the opposite direction to the additional driving torque, the additional driving torque offsets part of the driving torque on the differential gears, the speed of the differential gears decreases, and the speed difference of the side gears decreases. Small to achieve limited slip or differential lock function. In this case, when the torque of the differential gear driven by the left and right half shafts is greater than the additional driving torque, the difference in driving torque of the half shafts on both sides decreases, and the difference in speed between the left and right half shafts decreases. At this time, the differential has a limited slip function. ; When the torque of the left and right half shafts driving the differential gears is equal to the additional driving torque, there is no speed difference between the half shafts on both sides, which is equivalent to a rigid connection of the two sides of the half shafts; when the torque of the left and right half shafts driving the differential gears is less than the additional driving torque , the differential gear will rotate in the opposite direction, which is inconsistent with the actual application.

When the torque of the left and right side shaft drive differential gears and the extra drive torque are in the same direction, the extra torque and the torque of the left and right side shaft drive differentials drive the differential gear to rotate and transfer the torque from the low speed half shaft to High-speed half shafts, thereby improving the vehicle's steering characteristics. In this case, when the torque of the differential gears driven by the left and right half shafts is greater than the additional driving torque, the force exerted on the half shafts by the differential gears acting on both sides of the half shafts is reduced, and part of the torque is transferred from the low speed side to the low speed side. The high-speed side, but the driving force obtained by the high-speed side wheels is still less than that of the low-speed side wheels; when the torque of the left and right half shafts driving the differential gears is equal to the additional driving torque, the force acting on the differential gears on both sides of the half shafts to the half shafts The magnitude becomes zero, part of the torque is transferred from the low-speed side to the high-speed side, and the torque obtained by the wheels on both sides is equal; when the torque of the left and right half-shaft drive differential gears is less than the additional drive torque, the differential gears acting on both sides of the half-shafts The direction of the force given to the axle shaft changes, and part of the torque is transferred from the low-speed side to the high-speed side. The differential gear will assist in driving the high-speed side wheel. Under turning conditions, the outside wheel will obtain greater driving force than the inside wheel, making the vehicle The turning radius is reduced.

Preferably, the additional drive torque in the method is provided by an auxiliary motor.

Preferably, the method measures the driving speed of the car and the difference in rotation speed of the two wheels at predetermined time intervals.

Optionally, the selected method is completed in advance when the car leaves the factory and controls the steering and provided torque of the auxiliary motor for different vehicle speeds and wheel speed differences on both sides.

By adopting the differential active control method of the present invention, the working performance of the differential of the vehicle can be optimized in real time, thereby improving the driving performance of the vehicle, improving the turning performance and preventing the vehicle from slipping.

Description of the drawings

The foregoing and other aspects of the present invention will be more fully understood from the following detailed description in conjunction with the following drawings. It should be noted that the proportions of the drawings may be different for the purpose of clear explanation, but this will not affect the understanding of the present invention. In the attached picture:

Figure 1 schematically shows a block diagram of the differential active control system;

Figure 2 schematically shows a schematic diagram of an embodiment of a vehicle drive axle with a differential active control function as shown in Figure 1;

Figure 3 schematically shows a flow chart of the differential active control method according to the present invention.

Detailed ways

In the various drawings of this application, structurally identical or functionally similar features are designated by the same reference numerals.

Figure 1 schematically shows a block diagram of a vehicle drive axle with differential active control function of the present invention. The system includes a power source 1 that provides power to the entire transmission 3 . The auxiliary motor 2 is always connected to the components in the transmission device 3 and affects the power distribution of the transmission device 3 to the drive wheels 4 on both sides under the control of the vehicle control unit 5 . The vehicle control unit 5 can respectively control the auxiliary motor 2 and monitor the rotational speed difference of the driving wheels 4 on both sides. For example, it can control the magnitude and direction of the output torque of the auxiliary motor 2 in real time based on the demand obtained by monitoring the rotational speed difference of the driving wheels 4 on both sides.

In addition, the power source of the present invention can be a fuel engine or an electric motor. Therefore, those skilled in the art should understand that the vehicle with differential control function referred to in this application can be either a fuel vehicle or an electric vehicle. car.

As shown in Figure 2, in the transmission device, the side gear 18 meshes with the differential gear 1, and the differential gear 1 meshes with the differential gear 4. The differential gear 4 is fixedly connected with the planet gear 5, the differential gear 4 meshes with the side gear 16, the planet gear 5 meshes with the ring gear 6 and the ring gear 14, the ring gear 6 also meshes with the planet gear 7, and the planet gear 7 meshes with the sun The wheel 12 meshes, and the sun gear 12 is fixedly connected to the vehicle body, the planetary gear 7 is connected to the planet carrier 8, the ring gear 14 meshes to the planetary gear 9, the planetary gear 9 meshes to the sun gear connected to the auxiliary motor 11, and the planetary gear 9 meshes to the planetary gear 9. 8 frames are connected. Both differential gear 1 and differential gear 4 are installed on the differential case 15 . In this way, torque can be transmitted from the differential case 15 to the driving wheels 10 and 19 via the differential gears 1 and 4, the side gears 16 and 18. Among them, the planet gear 7 and the planet gear 9 have the same parameters, and the sun gear 12 and the sun gear connected to the auxiliary motor 11 have the same parameters.

When the driving wheel 10 and the driving wheel 19 rotate at the same speed, the differential gear 1 and the differential gear 4 only revolve with the differential case and do not rotate. At this time, the planetary gear 5 is equivalent to being fixedly connected to the ring gear 14 and the ring gear 6. Therefore, the movement conditions of the planet gear 6 and the planet gear 8 are the same, the sun gear 12 and the sun gear connected to the auxiliary motor 11 have the same movement conditions, and since the sun gear 12 is fixedly connected to the vehicle body and the rotation speed is zero, it is connected to the auxiliary motor 11 The sun gear speed is also zero. This ensures that when the differential gear 1 and the differential gear 4 do not rotate, the auxiliary motor 11 does not work. When the auxiliary motor 11 works, the torque of the auxiliary motor 11 is transmitted to the planetary gear 9, and then to the ring gear 14, and then to the planetary gear 5 from the ring gear 14, and finally to the differential gear 4. Shaft gear 16 and side gear 18.

According to the differential active control method of the present invention, the vehicle control unit of the car can determine the magnitude and direction of the auxiliary motor output torque based on the determined vehicle speed and the rotation speed difference of the wheels on both sides.

For traditional differential locks, they are generally aimed at limiting the speed difference of the driving wheels on both sides after the car slips. Moreover, traditional differential locks generally produce a certain impact during their operation, and cannot prevent the car from slipping. However, the differential active control method of the present invention can reduce impact, prevent slippage in time, and can also improve the turning performance when the vehicle turns.

Figure 3 schematically shows a flow chart of a differential active control method according to one embodiment of the present invention.

First, in step S1, determine the current speed of the car and the difference in rotational speed of the driving wheels on both sides.

In step S2, it is determined whether the differential auxiliary motor needs to run according to the current working conditions. Whether the auxiliary motor is running can be determined by factors such as the current vehicle speed, the difference in rotational speed of the driving wheels on both sides, the accelerator pedal position, the braking position, the cruise setting, the vehicle's uphill or downhill status, etc. This work can be performed by the vehicle control unit, for example. To be done.

If the determination result of step S2 is "yes", in step S3, the vehicle control unit determines whether the difference in rotational speed of the driving wheels on both sides of the vehicle is within the allowable range based on the difference in rotational speed of the driving wheels on both sides.

If the determination result of step S3 is "yes", then step S4 may determine that the steering of the auxiliary motor is to assist the differential to perform differential speed, and then calculate the output torque of the auxiliary motor based on the speed difference and the vehicle speed.

The specific implementation steps of step S4 are as follows.

First, the direction of rotation of the planetary gear 5 connected to the auxiliary motor is determined based on the positive and negative of the wheel speed difference Δn on both sides, thereby determining the direction of the output torque of the auxiliary motor. Since the larger the speed difference is, the greater the torque output by the auxiliary motor should be, and the maximum torque T _max that the auxiliary motor can output is a certain value. Therefore, the output speed of the auxiliary motor at this time can be calculated by linear interpolation based on the current speed difference. moment.

For example, assuming that the rotational speed difference on both sides is Δn ₁ and Δn ₁ <0, it can be seen from Δn=n ₂ -n ₁ that when the rotational speed difference is less than zero, the rotation direction of the planetary wheel 5 is opposite to that of the wheels on both sides. Let Δn′ ₁ = |Δn ₁ |, since Δn′ ₁ is between the set speed difference Δn _min1 and Δn _max1 , the auxiliary motor needs to assist the differential speed, so it can be determined that the output torque direction of the auxiliary motor should be in line with the planetary gear steering On the contrary, it is the same as the steering of the wheels on both sides. The auxiliary motor output torque T=T _max ×(Δn′ ₁ -Δn _min1 )/(Δn _max1 -Δn _min1 ). Further assuming that Δn ₁ =-400r, Δn _min1 =200r, Δn _max1 =800r, T _max =200N·m, it can be determined that the direction of the auxiliary motor output torque is the same as the wheel steering, and the auxiliary motor output torque T = T _max × ( Δn′ ₁ -Δn _min1 )/(Δn _max1 -Δn _min1 )=200×(400-200)/(800-200)=66.67N·m. Among them, n ₁ represents the speed of differential gear 1, n ₂ represents the speed of differential gear 4, Δn _min1 is the minimum speed difference at which the auxiliary motor assists the differential to start working, and Δn _max1 is the maximum speed difference at which the auxiliary motor assists the differential to work. , T _max is the maximum output torque of the auxiliary motor itself, which is a parameter that has been determined in advance by the auxiliary motor itself. For example, it is stored in the corresponding auxiliary motor memory and can be called directly when needed.

If the judgment result of step S2 is "no", step S1 will be executed again after a period of time.

If the judgment result of step S3 is "no", then step S5 may determine that the auxiliary motor assists the differential in limiting slip, and then calculates the output torque of the auxiliary motor based on the rotation speed difference and the vehicle speed.

The specific steps of step S5 are as follows.

First, determine the state of the vehicle based on the vehicle speed. If the vehicle speed is zero, it means that the vehicle has skidded. Then, the direction of the planetary gear 5 connected to the auxiliary motor is determined based on the positive or negative of the wheel speed difference Δn on both sides, thereby determining the auxiliary motor output torque. of steering. At this time, the required output torque of the auxiliary motor should be such that the differential gear 4 does not rotate. Then the torque M input by the auxiliary motor to the planetary wheel should satisfy M _d -M _f ≤M ≤ M _d -M _f , M=T/i. Where M _d is the driving torque acting on the differential gear 4, M _f is the friction torque acting on the differential gear 4, T is the auxiliary motor output torque, and i is the transmission ratio of the planetary gear train. Since M _d is very small when the wheel slips, M = M _f = K × T ₀ /2 can meet the requirements, where K is the locking coefficient of the differential and T ₀ is the differential input torque. If the vehicle speed is not zero, it means that the vehicle has a tendency to slip. Then, the direction of the planetary gear 5 connected to the auxiliary motor is determined based on the positive and negative difference Δn between the wheel speeds on both sides, thereby determining the direction of the output torque of the auxiliary motor. Since the greater the speed difference when the input power remains unchanged, the smaller the torque required to be output by the auxiliary motor is. Therefore, the output torque of the auxiliary motor is set to the minimum value T _min when the wheel is completely slipping. Since the auxiliary motor can output the maximum torque T _max It is known, so the output torque of the auxiliary motor at this time can be calculated by linear interpolation based on the current speed difference.

For example, when the vehicle speed is equal to zero, the speed difference between the driving wheels on both sides is Δn ₂ and Δn ₂ <0. From the fact that the vehicle speed is equal to zero and the speed difference between the driving wheels on both sides is greater than the allowable range, it can be judged that the vehicle has skidded. From Δn=n ₂ -n ₁ , we can know When the rotational speed difference is less than zero, the rotation direction of the planetary gear 5 is opposite to that of the slipping wheel. Let Δn′ ₂ = |Δn ₂ |. Since Δn′ ₂ exceeds the set speed difference, the auxiliary motor must assist the differential to limit slip. Therefore, it can be determined that the output torque direction of the auxiliary motor should be the same as the planetary gear steering, that is, the high-speed rotating wheel. Turn to the opposite. The auxiliary motor should output torque T = K × T _max /2/i. Furthermore, assuming that the vehicle speed is zero, the difference in rotational speed of the driving wheels on both sides is Δn ₂ =-2000r, K = 0.05, T _max = 2000N·m, i = 1, then it can be determined that the direction of the auxiliary motor output torque is opposite to the wheel steering. The motor should output torque T=K×T _max /2/i=0.05×2000/2/1=50N·m. Among them, T _max is the input torque of the differential in the first gear of the car, i is the transmission ratio of the planetary gear train, and K is the locking coefficient of the differential. The input torque and locking coefficient of the differential in the first gear of the car are parameters that have been determined in advance. For example, they are stored in the corresponding memory and can be called directly when needed.

For another example, when the vehicle speed is not zero and has a certain value, the difference in rotational speed of the driving wheels on both sides is Δn ₃ and Δn ₃ <0. Based on the fact that the vehicle speed is not zero and the difference in rotational speed of the driving wheels on both sides is greater than the allowable range, it can be judged that the vehicle has a tendency to skid and is in Set the speed difference between Δn _min2 and Δn _max2 , and then from Δn=n ₂ -n ₁ , it can be seen that when the speed difference is less than zero, the rotation direction of the planetary gear 5 is opposite to that of the slipping wheel. Let Δn′ ₃ = |Δn ₃ |. Since Δn′ ₃ exceeds the set speed difference, the auxiliary motor must assist the differential to limit slip. Therefore, it can be determined that the direction of the auxiliary motor output torque should be the same as the planetary gear steering, that is, the high-speed rotating wheel. Turn to the opposite. The output torque T of the auxiliary motor should be=T _min +K×(T _max -T _min )×(Δn _max2 -Δn ₃ )/(Δn _max2 -Δn _min2 ). Further assuming that the vehicle speed is not zero, the difference in rotational speed of the driving wheels on both sides is Δn ₃ =-1600r, K = 0.05, Δn _min2 = 1200r, Δn _max2 = 2000r, T _min = 50N·m, T _max = 200N·m, i = 1, then it can be determined that the direction of the output torque of the auxiliary motor is opposite to that of the wheel steering. The output torque of the auxiliary motor is T=T _min +K×(T _max -T _min )×(Δn _max2 -Δn ₃ )/(Δn _max2 - Δn _min2 )=50+(200-50)×(2000-1600)/(2000-1200)=125N·m. Among them, T _max is the input torque of the differential at this time, which is determined by the vehicle control unit, K is the locking coefficient of the differential, and i is the transmission ratio of the planetary gear train.

After the magnitude and direction of the output torque of the auxiliary motor are determined, step S6 is executed to control the magnitude and direction of the output torque of the auxiliary motor.

In this way, no matter whether the car is turning, skidding or has a tendency to slip, the auxiliary motor can be controlled in time according to the differential auxiliary motor control method of the present invention, thereby improving the vehicle's driving performance by actively controlling the differential performance. And greatly improve the vehicle's ability to escape difficulties.

The above method of the present invention can be completed in real time in the drive control system, that is, at a certain time interval, the size and direction of the output torque of the auxiliary motor are determined based on the actual measured speed and the rotational speed difference of the wheels on both sides, and then repeated as shown in Figure 3 process, thereby ensuring that the differential auxiliary motor control method of the present invention can operate efficiently in real time according to real working conditions.

Of course, for vehicles that cannot provide real-time calculations, various working conditions can also be simulated before the differential active control system of the present invention leaves the factory, and then a control strategy can be formulated as shown in Figure 3, and then this control system can be The policy is stored in the vehicle control unit. When the car is actually driving, based on the real-time monitored working conditions, the pre-stored control strategy is called to control the auxiliary motor control differential system.

Although specific embodiments of the invention are described in detail herein, they are presented for purposes of illustration only and should not be construed as limiting the scope of the invention. Various substitutions, changes and modifications may be devised without departing from the spirit and scope of the invention.

Claims (14)

1. A vehicle drive axle with active control function of differential mechanism and control method thereof, the vehicle drive axle comprises a differential mechanism auxiliary motor; a driving wheel; a transmission for transmitting power to the drive wheels; the transmission device comprises differential gears and side gears, the differential gears are meshed with each other and with the corresponding side gears, and the auxiliary motor is connected with the differential gears through a planetary gear train. The auxiliary motor is capable of adjusting output torque and steering according to the control method to actively control the differential.

2. A device according to claim 1, characterized in that in the transmission the side gear 18 is in engagement with the differential gear 1 and the differential gear 1 is in engagement with the differential gear 4. The differential gear 4 is fixedly connected with the planetary gear 5, the differential gear 4 is meshed with the side gear 16, the planetary gear 5 is meshed with the gear ring 6 and the gear ring 14, the gear ring 6 is further meshed with the planetary gear 7, the planetary gear 7 is meshed with the sun gear 12, the sun gear 12 is fixedly connected with the vehicle body, the planetary gear 7 is connected with the planet carrier 8, the gear ring 14 is meshed with the planetary gear 9, the planetary gear 9 is meshed with the sun gear connected with the auxiliary motor 11, and the planetary gear 9 is connected with the planet carrier 8. The differential gear 1 and the differential gear 4 are both mounted on the differential case 15. So that torque can be transmitted from the differential case 15 to the driving wheels 10 and 19 via the differential gear 1 and 4, the side gears 16 and 18. Wherein the parameters of the planetary gear 7 and the planetary gear 9 are the same, and the parameters of the sun gear 12 and the sun gear connected with the auxiliary motor 11 are the same.

3. The transmission according to claim 1, wherein when the rotational speeds of the driving wheel 10 and the driving wheel 19 are the same, the differential gear 1 and the differential gear 4 are only rotated with the differential case and are not rotated, and then the planetary gear 5 is fixedly connected with the ring gear 14 and the ring gear 6, so that the movement of the planetary gear 6 and the planetary gear 8 is the same, the movement of the sun gear 12 and the sun gear connected with the auxiliary motor 11 is the same, and the rotational speed of the sun gear connected with the auxiliary motor 11 is zero because the rotational speed of the sun gear 12 fixedly connected with the vehicle body is zero. Thereby ensuring that the auxiliary motor 11 does not operate when the differential gear 1 and the differential gear 4 do not spin. When the auxiliary motor 11 is operated, the torque of the auxiliary motor 11 is transmitted to the planetary gears 9, then to the ring gear 14 from the planetary gears 9, then to the planetary gears 5 from the ring gear 14, and finally to the side gears 16 and 18 from the differential gear 4.

4. A transmission according to claim 2, characterised in that the ring gear 7 has both an inner ring gear and an outer ring gear.

5. The method according to claim 1, wherein the invention provides a vehicle drive axle with an active differential control function and a control method thereof, so that the vehicle can actively control the differential under complex road surface environment and variable weather conditions, thereby improving the drivability of the vehicle.

6. The method of claim 1, wherein the control method adjusts the rotation speed and direction of the motor according to different conditions, thereby controlling the working condition of the planetary gears in the differential, and realizing the active allocation of the differential to the left and right axle shaft torque, the method comprises the following steps:

the current vehicle speed and the rotational speed difference of the wheels at the two sides are determined.

The auxiliary motor assists the differential to differential in a speed range which is not zero and has a large rotation speed difference between wheels at two sides, the differential is driven to rotate together, and torque is transferred from a low-speed side half shaft to a high-speed side half shaft, so that the steering characteristic of the vehicle is improved, and the differential is controlled to assist in turning on a rugged multi-curve road. The torque provided by the motor increases as the wheel speed difference increases and also decreases as it decreases.

When the speed of the vehicle is not zero, the wheels on two sides have larger rotation speed difference and exceed a set value, the auxiliary motor blocks the differential mechanism from differentiating, so that the rotation speed of the differential gear is reduced, the slip limiting performance of the differential mechanism is improved in advance, and the vehicle is helped to prevent slipping in rainy and snowy weather and on complex road surfaces. The torque provided by the auxiliary motor at a given power level is reduced as the difference between the rotational speeds of the wheels on both sides increases, and also increases as the difference decreases.

When the speed of the vehicle is zero, the wheels on the two sides have larger rotating speed difference and exceed a set value, the auxiliary motor rapidly runs to prevent the differential mechanism from differentiating, so that the two differential gears do not rotate, at the moment, the two half shafts have no rotating speed difference, which is equivalent to rigid connection of the two half shafts, and the torque is evenly distributed to the left half shaft and the right half shaft, so that the vehicle has better anti-skid performance and gets rid of the slipping condition as soon as possible.

7. The method of claim 6, wherein the rotational speed of the differential gear is constant when the differential is in a steady state operation, and the sum of all loads to the drive torque of the differential gear is zero. The left and right output shaft torque distribution of the differential can be realized by applying an additional driving torque on the differential gear to change the force applied to the two side half shafts. During operation of the differential, the differential gear is subjected to torque, friction torque and additional drive torque from the left and right axle shafts driving the differential gear. The torque of the differential gear driven by the left half shaft and the right half shaft and the magnitude and the direction of the additional driving torque influence the working characteristics of the differential, so that different control methods are adopted for the additional driving torque, and various additional functions of the differential can be realized.

8. The method of claim 7, wherein the additional drive torque is provided by an auxiliary motor.

9. The method of claim 6, wherein the method measures the running speed of the vehicle and the difference in rotational speeds of the two wheels at predetermined intervals.

10. The method of claim 6, which is completed in advance at the time of shipment of the automobile and controls steering of an auxiliary motor and the supplied torque for different vehicle speeds and both-side wheel speed differences.

11. The method of claim 10, wherein the control unit controls steering and torque of the motor.

12. The method of claim 6, according to another aspect of the present invention, there is also provided a vehicle differential active control system, the system comprising an auxiliary motor; the transmission device is a driving axle, the output of a differential mechanism in the transmission device is connected with a half shaft, the input end of the differential mechanism is connected with an auxiliary motor, and the control unit. And the control unit controls the auxiliary motor to control the differential mechanism according to the speed of the vehicle and the difference of the rotation speeds of the two wheels.

13. The method of claim 12, wherein the transmission is a gear transmission.

14. A vehicle drive axle with active control function of differential mechanism and control method thereof, the vehicle drive axle comprises a differential mechanism auxiliary motor; a driving wheel; and a transmission for transmitting power to the drive wheels and a planetary gear train for transmitting torque of the auxiliary motor to the differential gear; the transmission device comprises differential gears and side gears, the differential gears are meshed with each other and with the corresponding side gears, and the auxiliary motor is connected with the differential gears through a planetary gear train. The auxiliary motor is capable of adjusting output torque and steering according to the control method to actively control the differential. The vehicle is characterized by being a fuel oil vehicle, a hybrid electric vehicle and a pure electric vehicle.