Research on Principle and Torque Transmission Model of Magneto-rheological Fluid Dual-clutch
Magneto-rheological fluid dual-clutch transmission (MRDCT) uses Magneto-rheological fluid (MRF) to replace the traditional friction to transmit torque. By controlling the current in the coil of the dual clutch, the magnetic flux density is changed, and the separation and combination of the dual clutch is realized. Based on the characteristics of MRF and MFC, MRDC is proposed. The principle of MRDC is introduced. The torque transmission models of plate-style and cylindrical MRDC are established and the torque transmission formulas are driven. Introduction MRF is a typical intelligent material controlled by magnetic field. MRF can shift into Bingham plastic solid from liquid state under the magnetic field in millisecond level. Interest in magnetorheological fluids derives from their ability to provide simple, quiet, rapid-response interfaces between electronic controls and mechanical systems[1-3]. Apply this effect of MRF to the design of the DCT, put forward a new type of transmission: MRDCT. It has simple structure, no wear, low energy consumption, fast response, overload protection and good controllability. Principle Analysis MRDCT is to put the two single composite clutch together, it also using magnetorheological effect. Like MRFC, MRDCT can divided into plate-style and cylindrical. Take cylindrica type of MRDCT as example, the principle as shown in Fig. 1. The whole device includes the drive shaft, the input tube, the output tube, coil, MRF, bearings, seals, etc. Double clutch input shaft and input tube processing as a whole, as the connection part of the engine, to input power. There are two output clutchs. In order to deliver more torque, it designed to cylindrica. Two clutch and the input tube form two airtight work area. Two clutch transmit power by two axis which connected to the gearbox. In the work area, the gaps between the cylinder piece is full of MRF, by the sealing device sealing. Two coils arranged set type on input tube, and the control mode are independent of each other. Figure 1. Principle of cylindrica type of MRDCT. Torque Calculation Model of MRDCT A lot of research for the calculation of the torque of the single cylinder (disc) has been carried out by scholars.MRDCT, is combined two magnetorheological clutch together, but requires each clutch torque can independently transfer target. Therefore, starting with a single clutch, the torque transfer model of double clutch is obtained. The Model of Cylinder MRDCT For an idealized single cylinder clutch, volume invariant, steady flow and flow rate is a function of radius, the transfer torque can be predigested as follows: 2 2 2 2 1 2 2 1 1 2 2 1 2 2 2 2 2 1 2 1 4 ln( / ) 4 ( ) B Lr r r r Lr r T r r r r            (1) Where L is the axial length of the magneticrheological work area, m; r1, r2 are inner and outer radius of magnetorheological region, m; 1  , 2  are the angular velocity of the inner and outer radius of the corresponding, rad/s; B  is the shear yield stress, Pa; η is liquid viscosity, Pa·s. When there is multiple cylinder nested, form n work area, the total torque value is the superposition of the transfer torque of each working area: 2 2 2 2 1 2 2 1 1 2 2 1 2 2 2 2 1 1 2 1 2 1 4 ln( / ) 4 ( ) n n i i i i i i i i all Bi i i i i Lr r r r Lr r T nT r r r r               (2) Due to a different location, two single clutch of magnetorheological axial length and tube sheet number is different. The axial length of two clutches work area respectively L1, ,L2, number of working space respectively for n1, n2. the torque of the computational model diagram is as shown in Fig. 2. Figure 2. The model of Multi-cylindrical MRDCT. Assume that magnetic separation between the two clutch ideal condition, namely no electromagnetic interference. The torque of clutch 1 as follows: 1 1 2 2 2 2 1 1 2 2 1 1 1 2 2 1 1 2 2 2 2 1 1 2 1 2 1 4 ln( / ) 4 ( ) n n i i i i i i i i Bi i i i i L r r r r L r r T r r r r              (3) The torque of clutch 2 as follows: 2 2 2 2 2 2 2 1 2 2 1 2 1 2 2 1 2 2 2 2 2 1 1 2 1 2 1 4 ln( / ) 4 ( ) n n j j j j j j j j Bj j j j j L r r r r L r r T r r r r              (4) Where ri1, ri2 are inner and outer radius of magnetorheological region of clutch1, rj1, rj2 are inner and outer radius of magnetorheological region of clutch2, m. To multi-cylindrical MRDCT, the axial length and the rotating radius of the two single clutch are different. In general, in order to make the two clutch to transmit the same target torque, in the design of can through the use of different working area that different cylinder numbers, or change the magnetic induction intensity by changing the coil turn numbers. The Model of Disc MRDCT For an idealized single disc clutch, volume invariant, steady flow and flow rate is a function of radius, transfer torque as follows: 3 3 4 4 2 1 2 1 2 1 2 ( ) ( )( ) 3 2 B T r r r r h           (5) Where h is the distance between the two disc, m; r1, r2 are inner and outer radius of magnetorheological region, m; 1  , 2  are the angular velocity of the inner and outer radius of the corresponding, rad/s; B  is the shear yield stress, PA; η is liquid viscosity Pa·s. If the pair of main and driven disc is n, the total torque for the clutch can deliver: 3 3 4 4 2 1 2 1 2 1 1 2 ( ) ( )( ) 3 2 n all B i i i i i i T nT r r r r h                   (6) Multi-disc MRDCT is similar to Multi-cylindrical MRDCT. the district of two clutch disc space are h1, h2, the pair of main, driven disc are n1, n2, the torque calculation model diagram is as shown in Fig. 3. Figure 3. The model of Multi-cylindrical MRDCT. Assume that magnetic separation between the two clutch ideal condition, namely there do not have electromagnetic interference. The torque of clutch 1 is: 1 3 3 4 4 1 2 1 2 1 2 1 1 1 2 ( ) ( )( ) 3 2 n B i i i i i i T r r r r h                  (7) The torque of clutch 2 is: 2 3 3 4 4 2 2 1 2 1 2 1 1 2 2 ( ) ( )( ) 3 2 n B i i i i i i T r r r r h                  (8) Where ri1, ri2 are inner and outer radius of magnetorheological region, m. Due to the different arrangement position, the size of the working area of the two clutch may also be different. Therefore, design can increase the torque transfer value by increasing the area is small clutch, driven disk log.; can also increase the number of windings increasing the magnetic induction intensity in order to achieve a target torque transfer. Due to the characteristics of the work can be appropriate to improve the connection 1 retaining clutch torque transmission capability, increase the reserve coefficient.