Uninterrupted Shift Transmission and Its Shift Characteristics Kegang Zhao, Yanwei Liu, Xiangdong Huang, Rongshan Yang, and Jianjun Wei

374 IEEE/ASME TRANSACTIONS ON MECHATRONICS, VOL. 19, NO. 1, FEBRUARY 2014 Uninterrupted Shift Transmission and Its Shift Characteristics Kegang Zhao, Yanwei Liu, Xiangdong Huang, Rongshan Yang, and Jianjun Wei Abstract—A novel transmission concept, the uninterrupted shift but suffers from bad shift quality due to the shift torque in- transmission (UST), is introduced in this paper, which retains most terruption [4], [5]. DCT concept could be predigested as the of the components common or similar to normal automated trans- combination of two AMTs working in turns [6]. Thus, DCT has missions such as automated manual transmission or dual clutch transmission, but offers an uninterrupted torque from engine to two alternating power routes from the engine to wheels, making wheels during the shifting process with the so-called multimode it possible to achieve no or shorter torque interruption during controllable shifters. An UST dynamic model is established to ana- gearshifts [6], [7]. lyze UST’s shift characteristics. The special control logic involving In a long time, AT has been the dominator in the world for the engine, clutch and transmission are put forward to improve its smooth shift quality, and AMT has gained some ground in UST’s shift quality, and are applied in the simulation model us- ing MATLAB/Simulink tools. To validate the simulation model the market of commercial vehicles for its low cost and high and the control logic, a proto test bench has been designed and efficiency. In recent years, DCT functioning as a no torque built with corresponding data acquisition system and controlling interrupt type of AMT has started to be applied in compact and equipment. Finally UST’s torque uninterrupted functionality dur- midsize cars in Europe primarily and then in Asia. ing shift, effectiveness of the proposed control logic and validity of AT and DCT can achieve smooth drivability without or with the proposed dynamic model have all been verified experimentally. shorter torque interruption during gearshifts, which is real- Index Terms—Control logic, one-way clutch, shift quality, unin- ized mainly by clutch–clutch overlapping control [8]–[10]. The terrupted shift transmission. smooth clutch–clutch overlapping control needs the proper and accurate control processes, otherwise it will cause undesirable I. INTRODUCTION torque interruption or oscillations [11], [12]. So the higher con- HE transmission is a speed ratio switching device between trol precision makes the real cost significantly increased, and T engine and wheels. The manual transmission (MT) is the the abrasion of clutches would lower the shift reliability. most efficient transmission available, with 97% efficiency over If a transmission could embody the merits of AMT, DCT, and a representative drive cycle [1]. Its main weakness is requiring AT without their demerits, it would be a tempting option for much attention and work of the driver for shifts for operat- both passenger and commercial vehicles. ing the clutch on each gear shift. The automatic transmission The UST (uninterrupted shift transmission) [13], [14] seems operates shifts automatically with the choices of gears deter- a potential one, which retains most of the components common mined by a transmission control unit (TCU) to maximize fuel or similar to AMT/DCT for low cost, and could achieve com- economy, drivability and shift quality, as well as reduce en- parable shift quality with AT/DCT for its uninterrupted shift gine emission [2]. Automatic transmissions in the market today characteristics. One of its distinct breakthroughs is to realize mainly include planetary-automatic transmission (AT), auto- ON/OFF control gearshift instead of clutch–clutch overlapping mated manual transmission (AMT) and dual clutch transmission control gearshift as in AT and DCT. (DCT). With planetary train, wet clutches and torque converter, This paper is organized as follows. In Section II, the UST AT is relatively complicated, expensive and less efficient [3]. concept and its key component’s working characteristics are in- AMT is easy to manufacture and as highly efficient as MT, troduced, and its gearshift principle is also explained. In Section III, the modeling of UST driveline is presented, which is to be Manuscript received July 16, 2011; revised November 11, 2011, June 29, used to study control logic and shift characteristics. In Section 2012, and September 20, 2012; accepted November 4, 2012. Date of publica- IV, the UST shift process is analyzed and the control logic of tion January 30, 2013; date of current version January 17, 2014. Recommended engine, clutch and transmission is proposed. In Section V, based by Technical Editor J. Wang. This work was supported by the National Natural Science Foundation of China under Grant 50805049. on the MATLAB/Simulink software platform, the simulation K. Zhao and Y. Liu are with the Guangdong Key Laboratory of Vehicle En- model is built and shift processes are simulated to evaluate the gineering, South China University of Technology, Guangzhou 510640, China. control logic developed. In Section VI, the validation experi- (e-mail: [email protected]; [email protected]). X. Huang (corresponding author) is with the Guangdong Key Laboratory mental bench is described and experimental results are shown of Vehicle Engineering, South China University of Technology, Guangzhou and analyzed. Conclusions that synthesize the results of this 510640, China, and also with the Automotive Engineering Institute, Guangzhou paper are reported in Section VII. Automobile Group Company, Ltd., Guangzhou 510640, China (e-mail: [email protected]). R. Yang and J. Wei are with the Automotive Engineering Institute, Guangzhou II. UST CONCEPT Automobile Group Company, Ltd., Guangzhou 510640, China (e-mail: yangrs@ gaei.cn; [email protected]). A. Uninterrupted Shift Transmission Color versions of one or more of the figures in this paper are available online at http://ieeexplore.ieee.org. The structural layout of uninterrupted shift transmission Digital Object Identifier 10.1109/TMECH.2012.2235183 (UST) could be similar to that of AMT or DCT. In the 1083-4435 © 2013 IEEE. Personal use is permitted, but republication/redistribution requires IEEE permission. See http://www.ieee.org/publications standards/publications/rights/index.html for more information. ZHAO et al.: UNINTERRUPTED SHIFT TRANSMISSION AND ITS SHIFT CHARACTERISTICS 375 Fig. 1. Schematic layout of a four-speed AMT-like UST. Fig. 3. Roller-type controllable one-way clutch. (a) Structure of COWC. (b) COWC in the enabled mode. (c) COWC in the disabled mode. ωo i which is the relative rotate speed of the outer race and the Fig. 2. Spring–damper model of an OWC. inner race, and is given as t AMT-like UST for example, the conventional frictional clutch, Toc = nk ωo i dt + ncωo i (1) 0 parallel shafts, gearsets, etc. are retained, but synchronizers of the forward gears are replaced by the so-called multimode con- where n is the number of wedging components, k is the spring trollable shifters (MCSs), as a four-speed UST schematically constant, and c is the damper coefficient. shown in Fig. 1. Engine torque transmitted by the clutch flows The controllable OWC (COWC) is the OWC that can be alternatively into the MCSs that are connected correspondingly controlled to work in two modes: the enabled mode and the to the driving gear of the forward gear pairs. disabled mode. When enabled, COWC functions as a normal The shift of reverse gear is realized by a synchronizer in OWC, which wedges in one direction and freewheels in the this case. And the shifts between forward gears are realized by other direction. When disabled, it freewheels in both directions. MCSs, while the torque intervention assistance is performed COWCs also exist in various types. A roller-type COWC is through engine and clutch control by the control unit. shown in Fig. 3, with (a) showing its components, (b) showing its enabled mode, and (c) showing its disabled mode. It consists of an outer race, an inner race, several rollers, a control ring and B. Multimode Controllable Shifter a group of claws. The control ring is operated by a fork, just In fact, the multimode controllable shifter (MCS) is a special like the synchronizer in AMT. Axial movement of the control type of bidirectionally controllable one-way clutch (COWC), or ring determines the relative location of the rollers and claws to the combination of two normal COWCs in opposite directions. realize the enabled or disabled mode. Concretely, in the enabled OWCs are applied widely to selectively transmit power from mode, the rollers are not restricted by the claws and run into the one race to the other race [15]–[17]. According to the relative narrow location shown in Fig. 3(b), so that the COWC functions rotating direction of the inner race and the outer race, OWC has as a normal OWC. In the disabled mode, the rollers are restricted two states of operation: the wedged state and the freewheel state. in the wide location shown in Fig. 3(c) by the claws, so that the OWC transmits torque in one direction of the relative rotation COWC freewheels in both directions. of one race to the other in the wedged state. When the relative The COWC operation is shown in Fig. 4. The real line in- rotation direction of the two races reverses, OWC is released dicates the enabled mode, and the broken line indicates the from the wedged state and runs into the freewheel state. OWCs disabled mode. The spindle of control ring penetrates guide slot exist in various types, such as roller-type, sprag-type and ratchet- in claw and guide slot in inner race, so the axial movement of the type [17], with all types having an inner race and an outer race, control ring changes the relative location of claw and inner race. and the same functions.

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