Electric drive system of tracked vehicle

Abstract

An electric drive system of a tracked vehicle, the electric drive system comprising a housing (1), an electric motor (5) and a coaxial speed reducer (10), wherein the electric motor (5) and the coaxial speed reducer (10) are integrated in the housing (1); the electric motor (5) comprises an electric motor shaft (4), the electric motor shaft (4) being an electric motor torque output end and being connected to an input shaft of the speed reducer; the coaxial speed reducer (10) is a planetary gearset speed reduction mechanism, the planetary gearset speed reduction mechanism comprising an input shaft and an output shaft (12), the output shaft (12) being connected to a track driving sprocket; and the electric motor shaft (4), the input shaft and the output shaft (12) have the same axis. The planetary gearset speed reduction mechanism of the coaxial speed reducer (10) may be of a planetary gear configuration with double gears which are coaxially and fixedly connected, so as to form a coaxial speed reduction structure with a large reduction ratio, so that the entire system has a higher integration level, higher power density and smaller size.

Description

Electric drive system for tracked vehicles Technical Field

[0001] The invention discloses an electric drive system for a tracked vehicle, which belongs to the technical field of tracked vehicle drive technology according to the International Patent Classification (IPC). Background Art

[0002] With the advancement of electric drive technology, an increasing number of tracked vehicles are powered by electric motors, including pure electric tracked vehicles, fuel cell tracked vehicles, extended-range electric tracked vehicles, and series hybrid tracked vehicles. The track electric drive system consists of a drive motor, a reduction gear, a lubrication and cooling system, and a housing. The housing is mounted on the vehicle body, and its output shaft directly drives the track drive wheels, eliminating the need for a drive axle. This simplifies the vehicle's overall structure, increases chassis space, and enables complex vehicle dynamics control. The drive motor is the power source, outputting torque. Typically, a vehicle's drive wheels require relatively high torque, with speeds ranging from several hundred to one or two thousand rpm. Meanwhile, electric motors typically have limited torque, with speeds ranging from several thousand to 10,000 rpm. The solution to this problem is to add a torque reduction and torque multiplication mechanism that reduces the motor speed while increasing torque several or even dozens of times.

[0003] Many electric drive systems use reducers with a reduction ratio of around 10, which requires motors with high torque, resulting in high cost, volume and weight.

[0004] For example, a tracked vehicle has a maximum speed of 40 km / h, a track drive wheel radius of 180 mm, and a torque requirement of 1000 Nm. If the motor-reducer ratio is 10:1, the motor torque is 100 Nm and the motor speed is 6000 rpm. If the reducer ratio is 20:1, the motor torque drops to 50 Nm and the motor speed is 12000 rpm. If the reducer ratio is 30:1, the motor torque is 33.3 Nm and the motor speed is 18000 rpm.

[0005] As can be seen, increasing the reduction ratio can reduce the motor torque requirement, thereby reducing the motor weight and size, which is very important for the motor drive system. Usually, the interior space of tracked vehicles is very small, so reducing the size of the motor is very important.

[0006] It is also important to reduce the volume of the crawler drive system and reduce the space it occupies, which is also a topic that needs to be studied in the field of technology.

[0007] Chinese document CN219883830U discloses a track electric drive system comprising a motor and a reducer. The motor and reducer are separated, and the reducer input and output shafts are perpendicular to each other. In this system, the motor outputs power through the motor shaft, which then enters the reducer through the reducer input shaft. After deceleration and torque increase, the system outputs torque through the output shaft, driving the track drive wheels. This separation of the motor and reducer results in a low level of integration and occupies a large space, compromising space required for payload.

[0008] Patent document CN 207218453 discloses an electric drive system design that integrates a motor, a reducer, and a differential into one, thereby improving the system's integration. The reducer is a two-stage parallel shaft gear reducer with a maximum speed ratio of about 25. The motor shaft outputs power to the input shaft of the reducer, which is decelerated and torque-increased by two stages of the reducer and then output through the differential. Some tracked electric drive systems are similar to this system, with two-stage parallel shaft gear reduction, but no differential is required. This integrated motor and reducer system improves the space occupied problem. The reducer uses a parallel shaft gear mechanism, and the driving gear shaft and the driven gear shaft are parallel to each other; usually the system requires a larger reduction ratio, so the driven gear has a larger diameter, which increases the lateral dimension and is L-shaped when viewed from the side. Therefore, the space utilization of drive systems of this shape still has room for improvement.

[0009] All vehicles are equipped with brakes. Tracked vehicles typically have brakes mounted on the output drive shaft of the track drive system. Brake discs are mounted on the electric drive system's drive shaft, while calipers are mounted on the vehicle chassis. Alternatively, brake hubs are mounted on the drive wheels, while brake pads are mounted on the vehicle chassis. Regardless of the type of brake, it requires axial space and increases axial length. Summary of the Invention

[0010] In view of the shortcomings of the existing technology, the present invention provides an electric drive system for tracked vehicles. Through the integrated design of the motor and the reduction mechanism, the reduction mechanism adopts a coaxial structure of the input shaft and the output shaft, which reduces the system volume and improves the space utilization rate inside the vehicle.

[0011] To achieve the above object, the present invention is achieved through the following technical solutions:

[0012] A tracked vehicle electric drive system includes a housing, a motor and a coaxial reducer, wherein the motor and the coaxial reducer are integrated in the housing.

[0013] The motor includes a motor shaft, which is the motor torque output end and is connected to the input shaft of the coaxial reducer;

[0014] The coaxial reducer is a planetary gear reduction mechanism, which includes an input shaft and an output shaft, and the output shaft is connected to the crawler drive wheel;

[0015] The motor shaft, input shaft and output shaft are coaxial.

[0016] Furthermore, the planetary gear reduction mechanism includes a sun gear, several planetary gears, a planetary carrier, a support ring gear, and an output ring gear. The sun gear is connected to the input shaft, which is connected to the motor shaft. The planetary gear shafts are mounted on the planetary carrier. The planetary gears rotate about their own axes while simultaneously following the shaft in orbit around the axis of the planetary carrier. The planetary gears cooperate with the support ring gear and the output ring gear, respectively. The output ring gear is connected to the output shaft to output torque. The planetary gears include a first gear and a second gear that are coaxially and fixedly connected. The first gear meshes with the fixed support ring gear, and the second gear meshes with the output ring gear. The output ring gear is connected to the output shaft to form the output shaft of the reduction mechanism.

[0017] The working process of the tracked vehicle electric drive system is as follows: the motor rotor outputs torque, which is transmitted to the sun gear through the motor shaft. The sun gear meshes with the first gear of the planetary gear and exerts force on the meshing point; the first gear meshes with the support ring gear. Because the support ring gear rotates at zero speed, the meshing point speed is zero, which is called the instantaneous center of motion; the second gear of the planetary gear is fixedly connected to the first gear coaxially and moves with it; the second gear meshes with the output ring gear, and the meshing point of the output ring gear moves in the tangential direction; the output ring gear is connected to the output shaft and drives the output shaft to rotate;

[0018] Input / output speed ratio of tracked vehicle electric drive system:

[0019] The number of teeth or effective radius of the sun gear is represented by S; the number of teeth or effective radius of the first gear is represented by P1; the number of teeth or effective radius of the second gear is represented by P2; the speed of the sun gear is represented by n S The speed of the output ring gear is expressed as n R2 .

[0020] The present invention discloses an electric drive system for a tracked vehicle, which utilizes a motor coupled to a planetary gear reducer. The motor shaft, input shaft, and output shaft are coaxially connected, with an outer contour close to a cylinder and a regular shape, resulting in high space utilization within the vehicle. The planetary gear reduction mechanism of the coaxial reducer in the present invention can be a coaxially fixed double-gear planetary gear structure, forming a coaxial reduction structure with a large reduction ratio, thereby achieving higher system integration, greater power density, and smaller size. The planetary gear reduction mechanism of the reducer in the present invention can also be a two-stage planetary gear reduction mechanism, with the output shaft of the first-stage planetary gear reduction mechanism serving as the input shaft of the second-stage planetary gear reduction mechanism. The two-stage planetary gear reduction mechanisms are connected in series, and the speed ratios are multiplied to obtain the input / output speed ratio of the electric drive system. Both planetary gear reduction mechanisms can further integrate vehicle brakes, using wet multi-disc brakes, and are integrated with the motor and coaxial reducer, greatly improving system integration and reducing the space occupied by the electric drive and brakes. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] FIG1 is a schematic structural diagram of an embodiment of the present invention.

[0022] FIG2 is a schematic diagram of an embodiment of the present invention.

[0023] FIG3 is a schematic diagram of the integrated brake of the present invention.

[0024] FIG4 is a schematic structural diagram of another embodiment of the present invention.

[0025] FIG5 is a schematic diagram of an integrated brake according to another embodiment of the present invention. DETAILED DESCRIPTION

[0026] The present invention will be further described below in conjunction with the accompanying drawings:

[0027] Embodiment: Referring to Figures 1 to 5, a tracked vehicle electric drive system includes a housing 1, a motor 5, and a coaxial reducer 10. The motor 5 and coaxial reducer 10 are integrated within the housing 1. The motor includes a stator 2, a rotor 3, and a rotor shaft, i.e., a motor shaft 4. The motor shaft 4 is the torque output terminal and is connected to the input shaft of the coaxial reducer. The coaxial reducer is a planetary gear reduction mechanism comprising an input shaft and an output shaft 12, which is connected to the track drive wheels. The motor shaft 4, input shaft, and output shaft 12 are three coaxial. The planetary gear reduction mechanism of the coaxial reducer in the present invention can be a coaxially fixed double-gear planetary gear structure, or a two-stage planetary gear reduction mechanism, ultimately forming a high reduction ratio reduction structure, which improves overall system integration, increases power density, and reduces size. Both planetary gear reduction mechanisms can further integrate vehicle brakes, such as wet multi-disc brakes or other brakes, integrated with the motor and coaxial reducer, significantly improving system integration and reducing the space occupied by the electric drive and brakes.

[0028] In order to further illustrate this application scheme, the specific description is as follows

[0029] Implementation 1:

[0030] Referring to Figure 1, the tracked vehicle motor drive system includes a housing 1, a motor 5, and a reducer (coaxial reducer 10). The housing 1 is connected to the vehicle body and is non-rotating. All components mounted on or fixedly connected to the housing are non-rotating and, for clarity, are referred to as fixed. The motor 5 includes a stator 2 and a rotor 3. The stator is fixedly mounted on the housing 1 and cannot rotate. The motor rotor shaft, i.e., the motor shaft 4, is supported by bearings and can rotate relative to the stator / housing. The reducer 10 includes a sun gear 6, several planetary gears 7, a planetary carrier 8, a support ring gear 9, and an output ring gear 11. The sun gear 6 is connected to an intermediate shaft as an input shaft and is connected to the motor rotor shaft. The planetary gears 7 are composed of a first gear 7-1 and a second gear 7-2 coaxially connected. The planetary gears 7 are mounted on a planetary carrier 8, which is coaxial with the motor rotor and sun gear. The planetary gears 7 rotate about their own axes while simultaneously orbiting around the axis of the planetary carrier. The output ring gear 11 is connected to an output shaft 12, which is connected to the track drive wheels.

[0031] The input shaft of the reducer mechanism is directly or indirectly connected to the sun gear 6. There are several pairs of planetary gears, each of which is fixedly connected by two coaxial gears. The one that meshes with the sun gear is called the input planetary gear, namely the first gear 7-1, and the other is called the output planetary gear, namely the second gear 7-2. The shafts of these planetary gears are fixedly mounted on the planet carrier 8. There are two ring gears, one is the support ring gear 9, and the other is the output ring gear 11. Connection method: the motor rotor 3 is connected to the sun gear 6; the sun gear 6 meshes with the input planetary gear (first gear 7-1) in the planetary gear pair; the input planetary gear (first gear 7-1) is also meshed with the support ring gear 9; the input planetary gear (first gear 7-1) is fixedly connected to the output planetary gear (second gear 7-2), driving the output planetary gear (second gear 7-2) to rotate, which includes revolution and rotation; the output planetary gear (second gear 7-2) meshes with the output ring gear 11.

[0032] Working principle of the tracked vehicle motor drive system: the motor rotor 3 outputs torque, which is transmitted to the sun gear 6 through the rotor shaft, i.e., the motor shaft 4; the sun gear 6 meshes with the first gear 7-1 of the planetary gear and applies force to the meshing point; the meshing points on both sides move at the same speed; the first gear 7-1 of the planetary gear meshes with the support ring gear 9. Since the speed of the support ring gear 9 is zero, the meshing point speed is zero, which is called the instantaneous center of motion; the second gear 7-2 of the planetary gear is coaxially fixedly connected to the first gear 7-1 and moves with it; the second planetary gear 7-2 meshes with the output ring gear 11, driving the meshing point of the output ring gear 11 to move in the tangential direction, or driving the output ring gear 11 to rotate; the output ring gear 11 is connected to the output shaft 12, driving the output shaft to rotate.

[0033] Referring to FIG2 , the number of teeth or effective radius of the sun gear 6 is represented by S; the number of teeth or effective radius of the first planetary gear 7-1 is represented by P1; the number of teeth or effective radius of the second planetary gear 7-2 is represented by P2; the number of teeth or effective radius of the support ring gear 9 is represented by R1; and the number of teeth or effective radius of the output ring gear 11 is represented by R2. The following geometric relationship exists: R1=S+2P1……(1)

[0034] and R2=S+P1+P2……(2)

[0035] The sun gear 6 is used as the input shaft and rotates clockwise at a speed of n. S , the sun gear 6 is meshed with the first gear 7-1 of the planetary gear at point A, and the linear velocity of point A is n S S: that is, v A =n S ·S.

[0036] The sun gear 6 drives the first gear 7-1 of the planetary gear to move. The first gear 7-1 moves in a plane, and point B on the first gear 7-1 meshes with the sun gear 6. The movement speed of point B is equal to that of point A: v B =v A =n S ·S.

[0037] Point C on the first gear P1 meshes with point D on the support gear ring R1, and they move at the same speed. The support gear ring R1 is connected to the housing and is stationary and does not rotate. The speed of each point is zero, so: v C =v D =0.

[0038] From the perspective of kinematics, the first gear 7-1 of the planetary gear is in plane motion. The instantaneous velocity of point C is zero, which is the instantaneous center. The second gear 7-2 of the planetary gear is connected to the first gear 7-1 as a whole. They move in plane together and rotate around the instantaneous center. The linear velocity of the point E where the second gear 7-2 meshes with the output ring gear 11 is determined by the law of plane motion: its linear velocity v E The ratio of the linear velocity of point B on the first gear 7-1 to line segment CB is equal to the ratio of the linear velocity of point B on the first gear 7-1 to line segment CB: The linear velocity of the meshing point F between the output ring gear 11 and the second gear 7-2 is: The speed of the output ring gear 11 is:

[0039] In summary, the input / output speed ratio of the tracked vehicle motor drive system is:

[0040] For example, if S=18, R1=66, R2=60, P1=24, and P2=18, then R1=S+2P1 and R2=S+P1+P2. The speed ratio is calculated as: Spd Ratio=26.67.

[0041] During engineering design, the gear shift design and other technologies can be used. Based on the geometric relationship R1 = S + 2P1 and R2 = S + P1 + P2, the ring gears R1 and R2 can be increased or decreased by one tooth, that is: R1 = S + 2P1 ± 1 R2 = S + P1 + P2 ± 1

[0042] For example, if S = 21, R1 = 90, R2 = 78, P1 = 34, P2 = 22, then the formula calculates Spd Ratio = 20.78, and the actual speed ratio is 20.86, with an error of 0.40%. In this case, the error of formula (3) is very small, less than 1%, and it can still be used.

[0043] In the present invention, the vehicle brake can be integrated into the motor drive system. Specifically, a brake 13 can be installed on the input or output shaft 12 (see Figure 3). Brake 13 is preferably a wet multi-disc brake, but other brake types are also possible. Alternatively, the brake can be installed on the planetary carrier 8.

[0044] The invention discloses a coaxial transmission speed reduction mechanism with a large speed reduction ratio, which is used in a motor drive system of a tracked vehicle.

[0045] The innovative features of the electric drive system for tracked vehicles of the present invention are as follows:

[0046] 1. Electric drive system for tracked vehicles with integrated motor and reducer.

[0047] 2. The electric drive system with a coaxial reducer has a simple external shape, which is convenient for layout in the vehicle and facilitates the utilization of internal space.

[0048] 3. The motor drive system for a high-reduction-ratio tracked vehicle includes a housing, motor, and reduction gear. The housing is a relatively stationary, non-rotating component connected to the vehicle body and chassis via a suspension. The motor consists of a stator and rotor. The stator is fixedly mounted to the housing, and the rotor shaft (motor shaft) is the output shaft for the motor torque and is connected to the input shaft of the reduction gear. The reduction gear input shaft is connected to the center / fixed-axis gear (sun gear), which meshes with several planetary gears. The planetary gears each rotate around their own axis, which is mounted on a planetary carrier and revolves around the planetary carrier's axis. The planetary carrier rotates around its own axis, but does not require a physical shaft or bearing support. These planetary gears also mesh with an internal gear ring (support gear) fixed to the housing. Each planetary gear is coaxially fixed to another gear and rotates at the same speed. The planetary gear secondary meshes with the second internal gear ring (output gear), which serves as the output shaft of the reduction gear. The output shaft is connected to the track drive wheels, driving the vehicle.

[0049] 4. The use of wet multi-disc brakes, integrated with the motor and large reduction ratio coaxial reducer, greatly improves system integration and reduces the space occupied by the electric drive and brake.

[0050] The beneficial effects of the present invention are as follows:

[0051] Compared with the system in which the motor, reducer and brake are separated, this system integrates the three into one and has a small size.

[0052] Compared with the reduction mechanism with parallel shaft transmission, the present invention adopts a coaxial reducer, which has a high transmission density, a small size, a regular shape, is easy to install and arrange inside the vehicle, and occupies a small space.

[0053] Compared with the single-row planetary gearbox reduction mechanism: the reduction ratio of the single-row planetary gearbox is limited by the system structure and component processing technology, and generally does not exceed 5 (i.e., 5:1); this system can achieve a much larger reduction ratio. The tracked vehicle electric drive system of the present invention has a speed ratio of 15 to 40 or even higher, the requirements for the matching motor are reduced, the motor torque is smaller, the speed is increased, the motor cost, volume and weight are reduced, and the efficiency is improved.

[0054] Implementation 2:

[0055] Referring to Figure 4, a tracked vehicle electric drive system includes a housing 1, a motor, and a coaxial reducer, with the motor and coaxial reducer integrated within the housing. The motor includes a stator 2 and a rotor 3. Unlike Implementation 1, the coaxial reducer utilizes a two-stage planetary gear set, each with a reduction ratio of 3 to 5 times. The output shaft of the first stage serves as the input shaft of the next stage. The two stages are connected in series, and the speed ratios are multiplied to achieve a speed ratio of 10 to 25 times. Each stage planetary gear set includes a sun gear, a planetary carrier, planetary gears, and a supporting ring gear. For example, the front stage planetary gear set includes a matching sun gear 6, planetary gears 7, planetary carrier 8, and a front supporting ring gear 9. The secondary stage planetary gear set includes a matching rear sun gear 14, rear planetary gears 15, rear planetary carrier 16, and a rear supporting ring gear 17. The output shaft of the rear planetary carrier serves as the system's output shaft 12.

[0056] Referring to Figure 5 , a vehicle brake can be integrated into the motor drive system. Specifically, a brake 13, preferably a wet multi-disc brake, can be installed on the input or output shaft 12. Alternatively, the brake can be installed on the planet carrier 8 of the first-stage planetary gearbox.

[0057] The above records are only examples of the technical content of this creation. Any modifications and changes made by anyone familiar with this technology using this creation are within the patent scope claimed by this creation, and are not limited to those disclosed in the examples.

Claims

1. An electric drive system for a tracked vehicle, characterized in that: It includes a housing, a motor and a coaxial reducer, wherein the motor and the coaxial reducer are integrated in the housing; The motor includes a motor shaft, which is the motor torque output end and is connected to the input shaft of the reducer; The coaxial reducer is a planetary gear reduction mechanism, which includes an input shaft and an output shaft, and the output shaft is connected to the crawler drive wheel; The motor shaft, input shaft and output shaft are coaxial.

2. The electric drive system for a tracked vehicle according to claim 1, characterized in that: The planetary gear reduction mechanism includes a sun gear, several planetary gears, a planetary carrier, a supporting ring gear, and an output ring gear. The sun gear is connected to the input shaft, which is connected to the motor shaft; the shafts of the planetary gears are installed on the planetary carrier, and the planetary gears rotate around their own axes and at the same time follow the shaft to revolve around the axis of the planetary carrier; the planetary gears cooperate with the supporting ring gear and the output ring gear respectively, and the output ring gear is connected to the output shaft for outputting torque.

3. The electric drive system for a tracked vehicle according to claim 2, characterized in that: The planetary gear includes a first gear and a second gear which are coaxially fixedly connected. The first gear is engaged with a supporting ring gear which is fixed. The second gear is engaged with an output ring gear which is connected to an output shaft to form an output shaft of a reduction mechanism.

4. The electric drive system for a tracked vehicle according to claim 1, characterized in that: A vehicle brake is provided on the input shaft, output shaft or planetary carrier shaft of the coaxial reducer. The brake is integrated with the motor and the coaxial reducer to improve system integration and reduce the space occupied by the electric drive and the brake.

5. The electric drive system for a tracked vehicle according to claim 4, characterized in that: The vehicle brakes use wet multi-disc brakes.

6. The electric drive system for a tracked vehicle according to any one of claims 1 to 4, characterized in that: The working process of the tracked vehicle electric drive system is as follows: the motor includes a stator and a matching rotor. The motor rotor outputs torque, which is transmitted to the sun gear through the motor shaft. The sun gear meshes with the first gear of the planetary gear and exerts force on the meshing point; The first gear meshes with the support ring gear. Since the support ring gear rotates at zero speed, the meshing point has zero speed, which is called the instantaneous center of motion. The second gear of the planetary gear is coaxially fixed to the first gear and moves with it. The second gear meshes with the output ring gear, and the meshing point of the output ring gear moves in the tangential direction. The output ring gear is connected to the output shaft and drives the output shaft to rotate. Input / output speed ratio of tracked vehicle electric drive system: The number of teeth or effective radius of the sun gear is represented by S; the number of teeth or effective radius of the first gear is represented by P1; the number of teeth or effective radius of the second gear is represented by P2; the speed of the sun gear is n S , the speed of the output ring gear is n R2 .

7. The electric drive system for a tracked vehicle according to claim 1, characterized in that: The planetary gear reduction mechanism is a two-stage planetary gear mechanism, and the output shaft of the first stage planetary gear mechanism serves as the input shaft of the second stage planetary gear mechanism; the two stages planetary gear mechanisms are connected in series, and the speed ratios are multiplied.

8. The electric drive system for a tracked vehicle according to claim 7, characterized in that: Also included is a vehicle brake that is integrated into the motor drive system.

9. The electric drive system for a tracked vehicle according to claim 8, characterized in that: A vehicle brake is installed on the input shaft or output shaft of the coaxial reducer, or a brake is installed on the planet carrier of the first-stage planetary gearbox.

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