The electrified transmission system is increasingly adopting a high speed scheme because it has the highest power density to relieve quality. Since its input speed is high, especially for bridge deceleration, new challenges are put forward in terms of efficiency, load carrying capacity, and noise-vibration-pulling (NVH) characteristics. Under the leadership of the German Munich Institute of Technology Gears and Transmission Structure (FZG), the Speed2e cooperation project has studied this on a high-performance transmission system. The research results of the project will help pure electric vehicles (BEV ) Reach the development goal.
The SPEED2E cooperation project jointly promoted by the German Federal Economics and Energy (BMWI) and Transmission Technology Research Association (FVA) is to develop and study high-speed transmission systems for electrified automotive operating speeds up to 30000 r / min. In addition to the main unit of the cooperative project, Germany Munich Institute of Technology Gears and Transmission Structure (FZG), Hanno Wales, Institute of Machine Structure and Tribology, Institute of Transmission System and Power Electronics, Research Institute, Dam Shi Tower Specar Engineering Machinery Institute of Mechanical and Electrical System, Magna Gtruck, and Tentz System Engineering companies are partners for this project. Under the SPEED2E Cooperation Project Framework, a new type of transmission system based on two electrical transmission units and a transmission unit with two parallel branch transmission is investigated, and one of the parallel branch drives can be shifted. The layout of the prototype is intentionally designed to have a strong function, so that the possibility of extensive test research in the efficiency and lubrication and vibration characteristics at the highest operating speed. In the final stage of this three-year cooperation project, experimental research was carried out on the FZG universal test bench.
1 power transmission scheme
This power transmission system is designed on the basis of a C-stage front wheel drive sample that can reach 160 km / h. This bridge transmission (Figs. 1 and 2) composed of two branch transmission (Figs. 1 and 2) is driven by the same permanent magnet synchronous motor as the two speeds up to 30000 r / min. The branch transmission I (TGI) is designed to drive the two-stage front wheel drive transmission of 21 to be 21, and reaches 160 km / h at the maximum speed of the motor. In addition, the 3-stage branch transmission II (TGII) has two gear, i.e., the initial transmission ratio is 32 and the high-efficiency gear transmission ratio of 15. The two branch transmissions are mechanically coupled through a shared differential. Since its structure has a strong function, there is a shift that is uninterrupted. In addition, the flexible power distribution on both branch transmission provides the likelihood of implementing a shift policy that improves energy efficiency or reduces operational noise radiation.
(A)
(B)
Figure 1 Schematic diagram of the dynamic transmission system (a)
And its gear system (B)
Figure 2 Car Bridge Transmission
2 transmission structure and meshing design
The transmission aluminum housing consists of 3 parts, and is designed to be two branch transmission in the co-working work of the project partner Magna-Gottrak, which can be easily assembled / disintegrate on the test stage. A finite element model is based on the verification of static and dynamic bearing capabilities in accordance with the machine parts intensity (FKM) procedures. The bearing support generated by meshing is carried out as the basis for carrying capacity verification. In order to more accurately determine the bearing support, when the Rikor software applied to the FVA is calculated, the housing stiffness is reduced in the repeated process, and the housing bearing housing can be enhanced by a finite element based deformation analysis. Make it to ensure the smallest tilt in the carrier shaft.
Due to the speed condition restriction, a higher requirement for the hybrid main bearing of the transmission input stage and the prestressed X arrangement. FZG is designed for TG1 input stage and manufactures several meshing programs (Figure 3) to study various meshing geometry on high input speed for efficiency and vibration characteristics. All scenarios have the same wheelbase so that it can easily modify the meshing scheme of the required trial. The benchmark scheme is designed in accordance with the technical status of automatic transmission and has good load carrying capacity and no incentive geometric performance.
In order to improve efficiency, a low loss meshing scheme is used, which can reduce the sliding component of the mesh to minimum due to the very small tooth profile. Since the running speed tends to be increasing, in principle, it is no longer necessary to ensure the inclination of the meshing in principle (in the tangent to each other in the tangent direction). If the excitation frequency (depending on the number of meshing teeth) is small, then this condition can basically be resistant.
To this end, a meshing test (lower critical) scheme for 13 teeth active pinion with very few teeth is designed. In addition, there is a possibility that it may be to analyze the engagement vibration characteristics at resonance or on the upper critical operation. To this end, the upper critical meshing geometry adopts the possible maximum number of teeth (restrictions on the minimum modulus in the predetermined wheelbase and the predetermined tool database), which is the largest, in addition to reducing the transmission The ratio in order to achieve a smaller mass ratio between the active pinion and the gear to reduce the richestability.
Figure 3 Meshing test scheme of branch transmission I
3 test device and test range
In order to completely analyze the high speed transmission, the measuring axis for measuring torque and rotational speed is integrated at the transmission inlet and outlet, and thereby also installed an injection lubricating apparatus for transmission lubrication to ensure flexible use of low viscosity lubricants. The transmission parts are supplied, while the oil volume flow is distributed according to the demand of the lubricating mesh and the rolling bearing through the flow control valve. Before the entire drive system is installed on the FZG universal test bench, the two branch transmission are first trials in Munich (TGI) and Hannover (TGII), respectively.
Munich's test content is to analyze the vibration and efficiency of TGI, and for this purpose, only the TGI meshing gear train of the corresponding meshing test is mounted in the transmission housing, and the closed differential (Fig. 4 and Figure 5) are mounted. In order to evaluate the vibration condition, solid sound and air sound measurement were performed. Solid symbol measurements To install a plurality of acceleration sensors on the gear housing. The Hannover test focuses on the detection of the electric synchronous claw clutch and analysis of the distribution of the lubricant of TGII, and uses the TGII housing cover made of plexiglass, so that it is possible to use a high-speed camera to shoot a fluid and oil pool splashing oil. Distributed status.
Figure 4 Test device for branch transmission I
Figure 5 Low loss meshing test of branch transmission I
4 meshing test vibration characteristics
Figure 6 shows the contrast of each of the schemes relative to the rotational speed averaging solid sound period, which is the same acceleration sensor, which is the same acceleration sensor, which is the same acceleration sensor, by the same acceleration sensor, for each of the engagement tests. The direction was measured. The test plan until the highest design speed is 30000 r / min. The frequency of the rotation tooth mesh can be identified according to its active pinion teeth and the higher order than its higher order. The first order of the pulling frequency of the low loss scheme is high, which is due to the relatively high meshing stiffness, which causes the dynamic wheel tooth. Further, a side frequency band has occurred around the wheel tooth meshing frequency, which is caused by a high rotation meshing frequency and the degree deviation.
The lower critical scheme also exhibits high solid sound at higher order engagement frequencies, so this indicates that due to the reduced number of teeth, it is designed to achieve no vibration performance. The upper critical scheme has a low solid sound level similar to the reference scheme. Due to the limitations of working principle, the motor is greatly reduced in high-speed speed and no incentive meshing geometry, and the meshing resonance is very small, and the relatively small level is super high.
Therefore, the usual design goal may have limitations in order to avoid meshing the overall resonance. These tests confirmed the meshing characteristics designed according to the current technical level facilitates reducing noise. The geometric design of the geometric optimization of the number of teeth is also advantageous in acoustic performance during higher speeds, as they have a high-calorie mezzer frequency, and it is difficult to detect. The lower critical scheme is the worst in terms of acoustic performance, because the harmonics of the wheel tooth meshing frequency have a high level, and the excitation frequencies under all test speed are lower, which are in the audible frequency range, so it can confirm this It is disadvantageous to avoid meshing resonance.
Figure 6 measured when the speed accelerated under full load
Solid sound average secting comparison
5 conclusions and prospects
The SPEED2E cooperation project has confirmed the feasibility of the high-speed transmission system for electric vehicles in principle. In the final phase of the entire transmission system of the project creation and test, the transmission structure of the operating policy power branch is shown in the efficiency and NVH characteristics, and then in the next Speed4e partner project can be famous with the famous Industrial partners together, further develop the results, developed into a highly integrated drive system. Read more
Our other product:
