Low-speed end braking speed reduction hub motor integrated system and control method

Abstract

The invention relates to a speed reduction hub motor integrated system for low-speed end braking and a control method, and belongs to the technical field of automobile drive.The system comprises a sun gear, a planetary gear, a bearing, a wheel shaft and a motor shell, the planetary gear is fixed to the wheel shaft through the bearing, and the motor shell is fixed to the sun gear through the bearing; the planetary gear is meshed with an inner gear ring fixed on the motor shell to establish linkage; and the sun gear adopts a bevel gear structure and is meshed with the planetary gear. The hub motor solves the problems that the integration degree of a speed reducer, a motor and a brake of an existing hub motor is not high, the internal space is still not fully utilized, and the design of part of parts is redundant.

Description

Technical Field

[0001] The present invention relates to the field of automobile drive technology, and in particular to a deceleration hub motor integrated system for low-speed end braking and a control method. Background Art

[0002] With the continuous advancement of electric vehicle technology, in-wheel motor technology is also constantly innovating and upgrading. In the field of passenger cars, the limited axial and radial space between the rim and the suspension system limits the size of the drive motor, reduction mechanism and brake. In order to adapt to changing driving conditions and meet performance requirements, it is necessary to study the contradiction between torque demand and power unit volume, and find effective ways to improve the torque density of the in-wheel motor system. At present, most in-wheel motor systems have problems with complex structure and large unsprung weight, which makes it difficult to achieve lightweight, high strength and low noise requirements while ensuring performance. Summary of the invention

[0003] In view of this, it is necessary to provide a reduction hub motor integrated system and control method for low-speed end braking to solve the problems that the reducer, motor and brake of the existing hub motor are not integrated to a high degree, the internal space is still not fully utilized, and some components are designed redundantly.

[0004] In order to solve the above problems, the present invention provides a low-speed end braking reduction hub motor integrated system, comprising a sun gear, a planetary gear, a bearing, a wheel shaft and a motor housing, wherein the planetary gear is fixed to the wheel shaft through the bearing, and the planetary gear is meshed with an inner gear ring fixed to the motor housing to establish linkage; The sun gear adopts a helical gear structure and meshes with the planetary gears.

[0005] In a possible implementation, it also includes a rotor bracket, an angular contact ball bearing and a locking nut, the end of the rotor bracket has a stepped structure, the stepped structure is recessed toward the interior of the rotor bracket, the rotor bracket is fixed to the motor housing through the angular contact ball bearing, and the end of the angular contact ball bearing is fixed to the motor housing through the locking nut.

[0006] In a possible implementation, it also includes an outer planetary carrier, a planetary carrier inner plate and a fixing bolt, the bearing is sleeved on the wheel axle, one side of the wheel axle abuts the outer planetary carrier, and the other side of the wheel axle is connected to the planetary carrier inner plate, and the fixing bolt passes through the planetary carrier inner plate and is threadedly connected to the wheel axle.

[0007] In a possible implementation, a tapered roller bearing is further included, and a central axis extends from the center of the outer planetary carrier, and the central axis is connected and fixed to the tapered roller bearing on the inner side of the wheel.

[0008] In a possible implementation, a locking nut is further included, the tapered roller bearing is sleeved on the end of the center shaft, the locking nut is threadedly connected to the end of the center shaft to limit the axial movement of the tapered roller bearing, and the gap between the center shaft and the rotor bracket is not less than 1 mm.

[0009] In a possible implementation, a deep groove ball bearing is further included, and the outer planet carrier is fixed to the motor housing through the deep groove ball bearing.

[0010] In a second aspect, the present invention further provides a control method for a low-speed end braking reduction hub motor integrated system, which is applied to the low-speed end braking reduction hub motor integrated system as described in any one of the above items, comprising: Get vehicle speed and slip rate information; Determine the total braking force currently required by the vehicle based on vehicle speed and slip rate information; The braking method and energy recovery method are determined based on the relationship between the maximum regenerative braking force of the front and rear axle motors and the required total braking force.

[0011] In a possible implementation, the braking mode and the energy recovery mode are determined according to the magnitude relationship between the maximum regenerative braking force of the front and rear axle motors and the required total braking force, including: If the maximum regenerative braking force of the front and rear axle motors is greater than the required total braking force, the braking force will be fully provided by the motors; If the maximum regenerative braking force of the rear axle motor is less than the required total braking force, the excess maximum regenerative braking force is transferred to the front axle to ensure maximum energy recovery; If the sum of the maximum regenerative braking forces of the front and rear axle motors is greater than the required total braking force, friction braking force is used for supplementary braking.

[0012] In a possible implementation, the method further includes: The maximum regenerative braking force of the front and rear axle motors is dynamically adjusted in real time according to the battery SOC and motor status.

[0013] In a possible implementation, the method further includes: Determine the energy recovery strategy based on the electric braking speed.

[0014] The beneficial effects of the present invention are as follows: the integrated reduction hub motor mainly includes three parts: the motor, the NGW planetary gear reducer and the disc brake. The axial dimension compression of the reduction hub motor is achieved by limiting the axial dimensions of the three parts, reducing redundant components, and making full use of the staggered arrangement of the axial space. In addition, a pair of tapered roller bearings are selected to offset the axial force generated by the helical gears, and a pair of angular contact ball bearings are used to support the motor housing and the rotor bracket to maintain the stability and support strength of the motor housing. The planetary frame part adopts a deep groove ball bearing to connect with the reducer housing. The deep groove ball bearing can maintain a certain clearance, so that the planetary gears are floatingly distributed, ensuring the load-balanced characteristics of the planetary gears. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 A schematic structural diagram of an embodiment of a reduction hub motor integrated system with low-speed end braking provided by the present invention; Figure 2 A flow chart of an embodiment of a control method for a deceleration hub motor integrated system with low-speed end braking provided by the present invention; Figure 3 A flow chart of a vehicle braking posture judgment strategy in a control method for a reduction hub motor integrated system for low-speed end braking provided by the present invention; Figure 4 In the control method of the deceleration hub motor integrated system for low-speed end braking provided by the present invention, an optimized front and rear axle braking force distribution limit control line; in, Figure 1 In: 1-outer planetary carrier, 2-reducer seal, 3-wheel bolts, 4-planetary gear shaft, 5-cassette oil seal, 6-wheel bolts, 7-inner gear ring, 8-motor rotor bracket and sun gear integration, 9-motor housing, 10-motor housing fixing bolts, 11-spokes, 12-secondary hub, 13-brake caliper, 14-brake disc, 15-planetary gear, 16-planetary gear bearing, 17-bearing gasket, 18-planetary carrier inner plate, 19-planetary carrier fixing bolts, 20-reducer housing, 21-motor housing fixing bolts, 22-angular contact ball bearing, 23-rotor bracket locking nut, 24-tapered roller bearing, 25-motor shaft locking nut. DETAILED DESCRIPTION

[0016] The preferred embodiments of the present invention are described in detail below in conjunction with the accompanying drawings, wherein the accompanying drawings constitute a part of this application and are used together with the embodiments of the present invention to illustrate the principles of the present invention, but are not used to limit the scope of the present invention.

[0017] A specific embodiment of the present invention discloses a low-speed end braking reduction hub motor integrated system, including a sun gear, a planetary gear, a bearing, a wheel shaft and a motor housing, see Figure 1, the reducer, brake and motor are highly integrated into one design, wherein: the planetary gear is fixed to the wheel shaft through the bearing, and the planetary gear is meshed with the inner gear ring fixed to the motor housing to establish linkage; The sun gear adopts a helical gear structure and meshes with the planetary gears.

[0018] In this embodiment, power is transmitted to the rotor bracket via the motor, and then transmitted to the three planetary gears via the sun gear integrated with the rotor bracket. The three planetary gears are evenly distributed in the inner gear ring. The planetary gears are transmitted to the wheel bolts on the outer plate of the planetary bracket through the planetary gear bearings and the planetary gear shafts. The wheel bolts are connected to the wheel hub to realize power transmission.

[0019] The motor rotor bracket 8 in the embodiment of the present invention minimizes the axial material and reduces its axial size under the premise of meeting the strength requirement, and designs the sun gear of the planetary gear reducer and its end into an integrated structure to reduce the number of connecting parts, and sets a special step on the other side of the rotor bracket end, and separates and fixes it from the motor housing 9 extending thereto through a pair of angular contact ball bearings 22, and the end of the bearing is axially fixed by a special locking nut 23. The sun gear adopts a helical gear design to mesh with the planetary gear 15 to reduce the vibration noise during meshing, and the planetary gear is fixed to the planetary gear shaft 4 through the planetary gear bearing 16, and meshes with the inner gear ring 7 fixed to the motor housing 9, and the two ends of the planetary gear shaft are fixed to the planetary carrier plate, and the inner plate 18 of the planetary carrier plate is locked with the planetary shaft 4 through the central planetary carrier fixing bolt 19, and the axial fixing gaskets 17 on both sides of the planetary gear bearing 16 are locked to achieve the axial fixation of the planetary gear bearing 16, and the other side of the planetary gear shaft 4 is connected to the outer planetary carrier plate 1 to achieve support. Wheel bolts 3 and planetary shaft support holes are arranged on the outer planetary carrier plate respectively, and the axial dimension is reduced on the basis of ensuring the design strength of the planetary carrier plate. A central axis extends from the center of the outer planetary carrier plate to the inner side of the wheel and is fixed with a pair of tapered roller bearings 24. The pair of tapered roller bearings 24 offset the axial force generated when the helical gears are meshed and support the motor housing 9. The end of the central axis is fixed by a locking nut 25 to prevent the axial movement of the tapered roller bearing 24. The central axis and the motor rotor bracket are integrated with the sun gear and separated by a 1mm gap. The outer planetary carrier plate 1 is fixed to the motor housing 9 through a deep groove ball bearing 6. The deep groove ball bearing 6 can achieve floating distribution of the three planetary gears 15 and achieve load-balanced performance. In order to reduce the volume of the hub motor and reduce the weight, the motor housing and the reducer housing are designed to be shared as one, that is, the motor housing is also the reducer housing. The outer side of the deep groove ball bearing is axially sealed and fixed by a box-type 5 oil seal. In order to realize the processing and installation of the motor housing, it is processed in blocks and spliced ​​into a motor as a whole by fixing bolts 10 during installation. The motor housing separates the planetary gear and the rotor bracket, and is connected to the rotor bracket through an oil seal 2. The inner side of the motor housing is fixed to a specific hole of the suspension through a fixing bolt 21 to maintain static support. The secondary hub connected to the wheel spoke extends to the inner side of the wheel and is connected to a special annular brake disc at 12 evenly distributed fixing holes on it. A brake caliper fixed to the suspension is installed on the brake disc, forming the mechanical brake part of the reduction hub motor. While achieving parking brake, it also supplements the mechanical brake in emergency situations such as insufficient electric brake performance or electric brake failure.

[0020] Specifically, in Figure 1In the figure, the motor: the motor housing 9 is connected by bolts 10. The motor stator 8 is bonded to the motor housing 9, and the wheel hub and the auxiliary wheel hub are connected by welding. Reducer: The two oil seals are installed at the gap with interference fit, the planetary gears, the planetary gear bearings and the planetary gear shafts are all assembled with interference fit, the tapered roller bearings 24 and 1 are interference fit, and the axial positioning is determined by 25. The inner plate of the planetary carrier is connected to the planetary shaft by bolts 19, the wheel bolts 3 are interference fit on the planetary carrier plate, the inner gear ring is interference fit on the motor housing (reducer housing), the bearing 22 is locked and fixed axially by 23, and the radial direction adopts interference fit. Bearing 6 adopts interference fit.

[0021] Based on the above-mentioned low-speed end braking deceleration hub motor integrated system, the embodiment of the present invention also provides a control method for the low-speed end braking deceleration hub motor integrated system, please refer to Figure 2 ,include: S201, obtaining vehicle speed and slip rate information; S202, determining the total braking force currently required by the entire vehicle according to the vehicle speed and slip rate information; S203, determining a braking method and an energy recovery method according to the relationship between the maximum regenerative braking force of the front and rear axle motors and the required total braking force.

[0022] In this embodiment, in order to maintain a good braking effect and ensure the energy recovery efficiency, it is necessary to reasonably design the motor feedback braking control strategy. The control strategy designed in the embodiment of the present invention mainly meets the following two conditions: (1) ensuring the absolute safety of vehicle braking. (2) maximizing the regenerative braking energy feedback. In order to effectively achieve the above goals, the designed regenerative braking control strategy should reasonably distribute the braking torque of the whole vehicle according to different braking scenarios. When distributing the braking torque of the front and rear axles of the braking vehicle, it is also necessary to flexibly distribute the electric braking force of the coaxial hub motor and the traditional friction braking force.

[0023] Specifically, first, the slip ratio S is introduced as an irrelevant factor to ensure the braking efficiency of the vehicle during unconventional braking. When the slip ratio is 0.2, the lateral and longitudinal adhesion coefficients of the vehicle are at a large position. When it is greater than, the lateral adhesion coefficient decays rapidly. In order to avoid wheel locking and increase the adhesion utilization of the wheel to the ground, the upper limit of the slip ratio is set to 0.2. When the set value is exceeded, the ABS starts to work and the regenerative braking mode is turned off; when S<0.2, electrical energy continues to be recovered. Based on vehicle braking safety, in order to ensure the effectiveness of energy recovery, the specified motor feedback braking speed threshold must also be met. And the power battery SOC <90%. Vehicle braking posture identification strategy process Figure 2 shown.

[0024] The electric brake speed threshold is set to 260rpm, that is, when the speed is higher than the threshold, the vehicle will recover energy. The relationship between the maximum braking torque, speed and power is:

[0025] (1) Vehicle speed influencing factors Related research shows that when the vehicle speed is low, that is, when the motor speed is low, the electromotive force generated inside the motor is relatively low and unstable, which may cause unstable situations such as electric brake failure. The motor feedback braking speed threshold is set, and the motor speed influencing factor is introduced at the same time. .

[0026] (2) Charging current and power battery SOC During the energy recovery process, the charging current value of the power battery is positively correlated with the braking torque of the hub motor, which can be expressed as:

[0027] (3) Factors affecting motor failure In order to ensure that the motor plays an effective role in vehicle feedback braking, the motor failure factor is introduced , in order to further correct the electric braking torque of the vehicle during the feedback braking process, which can be simply expressed as:

[0028]

[0029] That is, stage 1: when the vehicle is in braking or sliding state, the vehicle controller calculates the braking intensity z under this working condition based on the current vehicle speed and time, and the regenerative braking controller solves the required total braking force of the whole vehicle. Based on the required braking force of the vehicle, the braking strength coefficient, and the force analysis of the ideal vehicle braking dynamics module with the front and rear wheels locked at the same time, the ideal front and rear axle braking force distributed according to the I curve can be obtained by further formula 9. and At the same time, the brake controller module calculates the maximum regenerative motor power that can be provided by the corresponding single front and rear wheels based on the current vehicle operation status, power battery SOC, etc. and .

[0030]

[0031] Figure 4 In the OP section, the front and rear axle braking forces are distributed along the I curve. That is, the braking mode 1 is entered: the braking force required by the vehicle is only provided by the front and rear axle hub motors.

[0032]

[0033]

[0034] The hydraulic braking force is involved in braking, which will inevitably cause energy loss. However, when the assembly parameters are matched, the working power of the electric wheel of the front axle is greater than that of the rear axle, that is, under the same braking intensity, the maximum regenerative braking force provided by the front axle is greater than that of the rear axle. At this moment, in order to ensure the efficiency of braking recovery, the control strategy will distribute the torque exceeding the maximum electric braking force of the rear axle to the front axle when the braking force is distributed according to the I curve, that is, This part of the braking force is distributed to the front axle until the front axle electric braking force reaches its peak, at which time the front and rear axle mechanical braking forces do not participate in the work. In this mode, the optimization strategy enables the wheel hub motor on the rear axle to participate in the regenerative braking to the maximum extent, while enabling the wheel hub motor on the front axle to participate more in the regenerative braking, so that the overall efficiency of the power generation system is improved as a whole, and ensures that the PQ segment of the distribution curve is still between the ECE regulations and the I curve, that is, the optimization distribution control strategy is based on the braking stability of the vehicle, so as to maximize the benefits of regenerative braking energy recovery.

[0035]

[0036] Complement accordingly according to the composite control strategy. As the braking force increases, the braking force required by the vehicle increases. At this time, the braking efficiency and braking safety should be given priority. Therefore, the front and rear axle braking force distribution is based on Figure 4 The braking force is carried out in the middle RG section, that is, it follows the I curve distribution, which is mode 3. To avoid the front axle locking first, the QR section is designed to be parallel to the f line group and located on the left side of the f curve, and the braking force is 90% of the f curve.

[0037]

[0038] Based on the braking force allocated on the front and rear axles by the control strategy in the previous stage, the brake braking and electric braking are respectively distributed to each wheel hub motor on the front and rear axles.

[0039]

[0040] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by any technician familiar with the technical field within the technical scope disclosed by the present invention should be covered within the protection scope of the present invention.

Claims

1. A low-speed end braking reduction hub motor integrated system, characterized in that: Including sun gear, planetary gears, bearings, axles and motor housing; The planetary gear is fixed on the wheel shaft through the bearing, and the planetary gear is meshed with the inner gear ring fixed to the motor housing to establish linkage; The sun gear adopts a helical gear structure and meshes with the planetary gears.

2. The low-speed end braking reduction hub motor integrated system according to claim 1 is characterized in that: It also includes a rotor bracket, an angular contact ball bearing and a locking nut, wherein the end of the rotor bracket has a stepped structure, the stepped structure is recessed toward the inside of the rotor bracket, the rotor bracket is fixed to the motor housing through the angular contact ball bearing, and the end of the angular contact ball bearing is fixed to the motor housing through the locking nut.

3. The low-speed end braking reduction hub motor integrated system according to claim 2 is characterized in that: It also includes an outer planetary carrier, a planetary carrier inner plate and fixing bolts, the bearing is sleeved on the wheel axle, one side of the wheel axle abuts against the outer planetary carrier, and the other side of the wheel axle is connected to the planetary carrier inner plate, and the fixing bolts pass through the planetary carrier inner plate and are threadedly connected to the wheel axle.

4. The low-speed end braking reduction hub motor integrated system according to claim 3 is characterized in that: It also includes a tapered roller bearing. A central axis extends from the center of the outer planetary carrier. The central axis is connected and fixed to the tapered roller bearing on the inner side of the wheel.

5. The low-speed end braking reduction hub motor integrated system according to claim 4 is characterized in that: It also includes a locking nut, the tapered roller bearing is sleeved on the end of the central shaft, the locking nut is threadedly connected to the end of the central shaft to limit the axial movement of the tapered roller bearing, and the gap between the central shaft and the rotor bracket is not less than 1mm.

6. The low-speed end braking reduction hub motor integrated system according to claim 3 is characterized in that: It also includes a deep groove ball bearing, and the outer planet carrier is fixed to the motor housing through the deep groove ball bearing.

7. A control method for a low-speed end braking reduction hub motor integrated system, applied to the low-speed end braking reduction hub motor integrated system as described in any one of claims 1 to 6, characterized in that: include: Get vehicle speed and slip rate information; Determine the total braking force currently required by the vehicle based on vehicle speed and slip rate information; The braking method and energy recovery method are determined based on the relationship between the maximum regenerative braking force of the front and rear axle motors and the required total braking force.

8. The control method of the low-speed end braking reduction hub motor integrated system according to claim 7 is characterized in that: The braking mode and energy recovery mode are determined according to the relationship between the maximum regenerative braking force of the front and rear axle motors and the required total braking force, including: If the maximum regenerative braking force of the front and rear axle motors is greater than the required total braking force, the braking force will be fully provided by the motors; If the maximum regenerative braking force of the rear axle motor is less than the required total braking force, the excess maximum regenerative braking force is transferred to the front axle to ensure maximum energy recovery; If the sum of the maximum regenerative braking forces of the front and rear axle motors is greater than the required total braking force, friction braking force is used for supplementary braking.

9. The control method of the low-speed end braking reduction hub motor integrated system according to claim 7 is characterized in that: Also includes: The maximum regenerative braking force of the front and rear axle motors is dynamically adjusted in real time according to the battery SOC and motor status.

10. The control method of the low-speed end braking reduction hub motor integrated system according to claim 7, characterized in that: Also includes: Determine the energy recovery strategy based on the electric braking speed.

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