Abstract:
An automatic transmission utilizes a shift support system using combination of coupled clutch assemblies with a fluid drive and a gear system to provide multi-speed ratios with one reverse ratio without excessive heat generation. The fluid drive has an impeller and a turbine, and each coupled clutch assembly has two respective inputs from the fluid drive impeller and turbine with one output to the gear system. Each coupled clutch assembly provides possibilities of either connection or disconnection for engine to alternatively obtain different gear ratio speeds, or drive both odd and even gears at the same time for a smooth shift transition. Utilization of the shift support system with torque transmitting elements to provide connections between different gear sets allows the transmission to be operated in higher reliability and less complicated control than dual clutch transmission with similar efficiency.

Description:
REFERENCE CITED  
       [0001]    
       
         
               
               
               
               
             
           
               
                   
               
               
                   
               
             
             
               
                 5,106,352 A 
                 April 1992 
                 Lepelletier 
                 475/280 
               
               
                 5,950,781 A 
                 September 1999 
                 Adamis, et al. 
                 192/3.61 
               
               
                 6,463,821 B1 
                 October 2002 
                 Reed, Jr., et al 
                  74/330 
               
               
                 6,571,654 B2 
                 June 2003 
                 Forsyth 
                  74/339 
               
               
                 6,656,078 B1 
                 December 2003 
                 Raghavan, et al. 
                 475/276 
               
               
                 6,715,597 B1 
                 April 2004 
                 Buchanan, et al. 
                 192/70.12 
               
               
                 6,852,059 B2 
                 February 2005 
                 Lee, et al. 
                 475/286 
               
               
                   
               
             
          
         
       
     
       TECHNICAL FIELD  
       [0002]     This invention relates to automatic transmissions, in particular used in motor vehicles, comprising conventional gearsets controlled by frictional elements, such as clutches coupled with a fluid drive that utilizes fluid that subjects to slip and drive without harsh shift feel, and gear shifting devices, such as synchronizers.  
       BACKGROUND OF THE INVENTION  
       [0003]     Conventional powertrain system used in a passenger vehicle is comprised of an engine, multi-speed transmission and a differential or final drive system. The premier function of transmission extends the operating range of the vehicle by allowing the engine to perform by means of its torque range several times higher than the engine torque as the transmission ratio increases and also allows the engine to perform its output speed range higher than engine speed as transmission ratio reduces, such as in the overdrive speed.  
         [0004]     With advent of six speed automatic transmissions (U.S. Pat. Nos. 5,106,352 and 6,656,078), the step size between ratios is reduced and the shift quality of the transmission by making the ratio interchanges is substantially improved comparing with three and four speed transmissions. Multi-speed transmissions, such as six speed automatic transmissions, also have advantages over fewer speed transmissions, such as three and four speed automatic transmissions, to achieve desirable fuel economy to generate maximum power.  
         [0005]     Such multi-speed transmissions still use the conventional torque converter for comfort shifting, but have quite low mechanical efficiency. Torque converters typically include impeller assemblies that are operatively connected with input shaft from an internal combustion engine, a turbine assembly that is fluidly connected with the impeller assembly and a stator or reactor assembly. These assemblies together form a substantially toroidal flow passage for kinetic fluid in the torque converter. Each assembly includes a plurality of blades or vanes that act to convert mechanical energy to hydrokinetic energy and back to mechanical energy. The stator assembly of a conventional torque converter is locked against rotation in one direction but is free to spin about an axis in the direction of rotation of the impeller assembly and turbine assembly. When the stator assembly is locked against rotation by so called one-way clutch, the torque is multiplied by the torque converter. During torque multiplication, the output torque is greater than the input torque for the torque converter. However, when there is no torque multiplication, the torque converter becomes a fluid coupling. Torque converter slip exists when the speed ratio is less than 1.0. The inherent slip reduces the efficiency of the torque converter. Although lock-up device is usually equipped in newly developed transmissions, only a few of gears can be locked up for saving energy and avoiding noise and vibration problems. Its overall efficiency is still low as long as the torque converter is used. Therefore, the method used to enhance the performance by increasing number of speeds almost reaches its limits and the torque converter is considered as a big technical barrier.  
         [0006]     Automated manual transmission (AMT), another type of automatic shifting transmission used in motor vehicles, improves the efficiency by removing the torque converter. Such automated manual transmissions (U.S. Pat. No. 6,571,654) typically include a plurality of power-operated actuators that are controlled by a transmission controller or some type of electronic control unit (ECU) to automatically shift synchronized clutches that control the engagement of meshed gear wheels traditionally found in manual transmissions. It does the function of interchanging the speed ratio by automatically disengaging the clutch disc, choosing the right gear ratio, shifting to the gear and engaging clutch automatically. However, this shifting procedure causes discontinuous torque delivery and harsh shift feel to the passengers. This discomfort characteristics is the major drawback to prevent it from wide applications in motor vehicles, although the efficiency can be as good as manual transmissions.  
         [0007]     Transmission using twin-clutch, known as dual clutch transmission (U.S. Pat. Nos. 5,950,781 and 6,463,821), also removes the torque converter to improve the mechanical efficiency. The dual clutch structure has two coaxially and cooperatively configured clutches that derive power input from a singular engine crankshaft. It consists of two independent transmission systems that have two concentric driving shafts, one is hollow and the other is solid within the hollow shaft. The first, third and fifth driving gears are on one of the driving shafts and the second, forth and sixth gears are on the other shaft. The third shaft is a driven shaft that has all the driven gears on it. The gear shifting operation is activated by dogs and sliding sleeves on driving and driven shafts. When a gear is shifted to the next gear for ratio interchange, it engages one of the clutches while the other is still in engagement. Due to the two-clutch engagement at the same time, one of them or both of them must create relative slip motion to prevent it from damaging the components in the system while the output speed takes the transition for a gradual change to the next gear. The shifting operation can give comfort feel that is similar to the one by using torque converter. The dual clutch transmission soon receives increasing popularity in the applications of passenger cars. The drawback of dual clutch transmission is that controlling and regulating the automatically actuated dual clutch transmission to achieve the desired vehicle passenger comfort goals is a complicated matter. There are a large number of events to be properly executed in terms of time for each shift to occur smoothly and efficiently. In addition, the clutch assembly working within the dual clutch transmission case generates a considerable amount of heat (U.S. Pat. No. 6,715,597). Especially, when the vehicle starts to launch and heavily loaded pressure acts on the clutch discs while slip is required for smooth transition (U.S. Pat. No. 6,463,821). The slip in dual clutch is quite high comparing to that in conventional automatic transmissions in which the clutch slip is limited between driving and driven clutch discs. These conventional automatic transmissions, either using planetary gear sets or parallel shafts with external gear sets, usually have an uncontrolled way to dissipate the heat that is generated from torque converter, clutches, gears and actuators, etc., by using a transmission fluid cooler. It has been proven to be reliable and economic for long time operations through the reduced pump pressure to circulate the flow. However, in the dual clutch transmission, since more heat can be generated in a short time, this cooling methodology is unable to serve the system to maintain the required fluid temperature. The requirements for the materials in friction elements are also high and the way to cool the transmission fluid and its control procedures are much more complicated (U.S. Pat. No. 6,715,597). Although dual clutch transmission provides high mechanical efficiency and comfort shifting quality, these disadvantages only allow it to be used in limited types of lighter duty vehicles. In addition, it leads to lower reliability than the conventional automatic transmissions unless more advanced materials and more complicated system with additional cooling device are used to ensure acceptable service life and reliable operation.  
         [0008]     The objective of this invention is to provide a new transmission system by overcoming the disadvantages in automatic transmissions, automated manual transmissions (AMT) and dual clutch transmissions. By using suitable combination of reliable fluid drive and coupled clutches, it provides similar mechanical efficiency as in automated manual transmissions (AMT) and dual clutch transmissions, comfort shift quality and efficient heat dissipation as widely used in conventional automatic transmissions, low material requirements for the friction elements and reliable operation with reduced control complexity.  
       SUMMARY OF THE INVENTION  
       [0009]     It is an object of the present invention to provide automatic transmissions using a shift support system for multi-step forward speed ratios and one reverse speed ratio.  
         [0010]     In one aspect of the present invention, the transmission incorporates a gear system, a shift support system and engageable torque-transmitting components.  
         [0011]     In another aspect of the present invention, the gear system contains first and second gear subsystems.  
         [0012]     In another aspect of the present invention, the first and second gear subsystems have one common output shaft and have first and second input shafts, respectively.  
         [0013]     In another aspect of the present invention, shift support system contains two coupled clutch assemblies and a fluid drive.  
         [0014]     In another aspect of the present invention, each coupled clutch assembly has first and second coupled clutches.  
         [0015]     In another aspect of the present invention, each clutch in the coupled clutch assembly has driving and driven clutch discs.  
         [0016]     In another aspect of the present invention, the driven clutch discs of first and second clutches in each coupled clutch assembly are continuously coupled.  
         [0017]     In another aspect of the present invention, the fluid drive contains an impeller and a turbine.  
         [0018]     In another aspect of the present invention, each coupled clutch assembly enables either the first clutch driving disc connection with the fluid drive impeller or no connection.  
         [0019]     In another aspect of the present invention, each coupled clutch assembly enables either the second clutch driving disc connection with the fluid drive turbine or no connection.  
         [0020]     In another aspect of the present invention, driven clutch discs of the first coupled clutch assembly continuously connects with the input shaft of the first gear subsystem.  
         [0021]     In another aspect of the present invention, driven clutch discs of the second coupled clutch assembly continuously connects with the input shaft of second gear subsystem.  
         [0022]     In another aspect of the present invention, first of four engageable torque-transmitting components selectively connects the first or third driving gears with input shaft in the first gear subsystem.  
         [0023]     In another aspect of the present invention, second of four engageable torque-transmitting components selectively connects the second driving gear in the first gear subsystem or fifth driving gear in the second gear subsystem with the common output shaft of the gear system.  
         [0024]     In another aspect of the present invention, third of four engageable torque-transmitting components selectively connects the fourth or sixth driving gears in the second gear subsystem with the output shaft of the gear system.  
         [0025]     In another aspect of the present invention, fourth of four engageable torque-transmitting components selectively connect the reverse driving gear with input shaft in the first gear subsystem.  
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0026]      FIG. 1  is a schematic representation of a six speed automatic transmission using a shift support system.  
         [0027]      FIG. 2  is a schematic representation for the first gear in the transmission described in  FIG. 1 .  
         [0028]      FIG. 3-1  is a schematic representation of the first shifting stage: preparation for gear shifting from gear  1  to gear  2 : shift to 2 nd  gear under no load while 1 st  gear is still engaged.  
         [0029]      FIG. 3-2  is a schematic representation of the second shifting stage: first transition for gear shifting from gear  1  to gear  2 : 2 nd  gear engages with fluid drive while 1 st  gear is still engaged.  
         [0030]      FIG. 3-3  is a schematic representation of the third shifting stage: the second transition for gear shifting from gear  1  to gear  2 : 1 st  gear is disengaged while engaged 2 nd  gear is driven by fluid drive.  
         [0031]      FIG. 3-4  is a schematic representation of the fourth shifting stage: completion of gear shifting from gear  1  to gear  2 : fluid drive engagement is removed and 2 nd  gear is directly driven by the engine.  
         [0032]      FIG. 4  is a synchronizer engagement schedule.  
         [0033]      FIG. 5-1  is a schematic representation for gear shifting from odd gear to even gear. (a) Shift preparation (b) First transition (c) Second transition (d) Shift completion  
         [0034]      FIG. 5-2  is a schematic representation for gear shifting from even gear to odd gear. (a) Shift preparation (b) First transition (c) Second transition (d) Shift completion  
         [0035]      FIG. 6-1  is rotating speed difference between fluid drive impeller and turbine when up shift.  
         [0036]      FIG. 6-2  is rotating speed difference between fluid drive impeller and turbine when down shift.  
         [0037]      FIG. 7  is a schematic representation of a four speed automatic transmission using a shift support system.  
         [0038]      FIG. 8  is a schematic representation of a five speed automatic transmission using a shift support system.  
         [0039]      FIG. 9  is a schematic representation of a seven speed automatic transmission using a shift support system.  
     
    
     DESCRIPTION OF PREFERRED EMBODIMENTS  
       [0040]     Referring to the drawings, wherein like characters represent the same or corresponding components throughout the several views, there is shown in  FIG. 1 , a powertrain system  1  having a conventional engine, a six-speed transmission  2 , and a conventional final drive mechanism  3 .  
         [0041]     The six-speed transmission  2  includes a shift support system  40 , which includes two coupled clutch assemblies  41  and  42  and a fluid drive  43 , and a gear system, which includes first subsystem  10  and second subsystem  20 . The fluid drive  43  includes impeller  43   a , which is continuously interconnected with the output shaft of engine, and the turbine  43   b , which is selectively interconnected with either coupled clutch assemblies  41  or  42  or both. The first gear subsystem includes a hollow shaft  101  with gears  105 ,  106 ,  107  and  108 , in which gears  105 ,  106  and  108  are free to rotate, but  107  is fixed on  101 . The second gear subsystem also includes a shaft  201 , which goes through shaft  101 , and gears  204 ,  205  and  206 , which are fixed on  201 . Two synchronizers,  103  and  104 , are included in the first gear subsystem  10  and other two synchronizers,  202  and  203 , are included in the second gear subsystem  20 . Shaft  30  is an output shaft, in which driven gears  111 ,  207 ,  208  and  209  are installed for free rotating and driven gear  109 ,  110 ,  112  are fixed. Shaft  102  can be a fixed shaft without rotation to support an idler gear  123 .  
         [0042]     The synchronizer,  103 , can be controlled to make three possible connections described as follows:  
         [0043]     1. Connection between gear  105  and shaft  101   
         [0044]     2. Connection between gear  106  and shaft  101   
         [0045]     3. No connection  
         [0046]     Another synchronizer  104  on shaft  101  can also be controlled to make two possible connections described as follows:  
         [0047]     1. Connection between gear  108  and shaft  101   
         [0048]     2. No connection  
         [0049]     Another synchronizer  202  on shaft  30  can also be controlled to make three possible connections described as follows:  
         [0050]     1. Connection between gear  111  and shaft  30   
         [0051]     2. Connection between gear  207  and shaft  30   
         [0052]     3. No connection  
         [0053]     Another synchronizer  203  can be controlled to make three possible connections described as follows:  
         [0054]     1. Connection between gear  208  and shaft  30   
         [0055]     2. Connection between gear  209  and shaft  30   
         [0056]     3. No connection  
         [0057]     The gear,  123 , which is free to rotate on shaft  104 , serves as an idler that rotates for the purpose of changing the rotation direction of  112 .  
         [0058]     Shaft  30  serves as an output shaft to give the rotation speed and torque to the final drive mechanism, which usually includes reduction gears and differential system.  
         [0059]     First coupled clutch assembly  41  includes two clutches, in which their driven discs are coupled each other to be connected with shaft  101 . The two inputs are from fluid drive impeller  43   a  and turbine  43   b , respectively. They can be connected or disconnected independently as the controlled hydraulic pressure changes. Therefore, four possible connections can be generated between the driving and driven discs described as follows:  
         [0060]     1. Fluid drive impeller  43   a  connects with shaft  101   
         [0061]     2. Fluid drive turbine  43   b  connects with shaft  101   
         [0062]     3. Both fluid drive impeller  43   a  and turbine  43   b  connect with shaft  101   
         [0063]     4. No connection  
         [0064]     Second coupled clutch assembly  42  has the same configuration as  41 , but has the single output to shaft  201 . It also has four possible connections described as follows:  
         [0065]     1. Fluid drive impeller  43   a  connects with shaft  201   
         [0066]     2. Fluid drive turbine  43   b  connects with shaft  201   
         [0067]     3. Both fluid drive impeller  43   a  and turbine  43   b  connect with shaft  201   
         [0068]     4. No connection  
         [0069]     As results of the arrangement of two coupled clutch assemblies and fluid drive of the present invention, the transmission system is alternatively engaged to provide odd number and even number speed ranges, respectively.  
         [0070]     As mentioned above, the first and second coupled clutch assemblies  41  and  42  are alternatively engaged for transmitting power from engine to either gear subsystem  10  or gear subsystem  20 . The first and second coupled clutch assemblies  41  and  42  are controlled electronically, and the coupled clutch assemblies  41  and  42  in disengaged or engaged combinations with fluid drive gives maintained shift quality and facilitates transfer of power from one transmission subsystem to another.  
         [0071]     The above description can be illustrated by an example in which the transmission shifts from first gear to the second gear. At the beginning, the first gear is used for the engine to give rotating speed and torque to shaft  101  through coupled clutch assembly  41 . The power is delivered from the synchronizer  103  to gear  105 . As shown in  FIG. 2 , since gear  105  engages with gear  109  for the first gear ratio and  109  and  112  are fixed on shaft  30 , the power is delivered from shaft  30  to final drive mechanism. The coupled clutch assembly  42  is also engaged to drive shaft  201  under no load. The following four steps is described in details for gear shift process:  
         [0072]     Step 1: Preparation for shift. First, electronic control system (omitted from the figure) gives command to disengage the second couple clutch assembly  42  and then use synchronizer  202  to make connection between gear  207  and shaft  30  under no load. After that, the second coupled clutch assembly  42  is used to connect fluid drive turbine  43   b  with shaft  201 . At this moment, although gear  105  engages with gear  109  for the first gear ratio and gear  204  engages with gear  207  for the second gear ratio, there is no interference between the gears because fluid drive has fluid slip between impeller  43   a  and turbine  43   b . The output speed is still the first gear speed, shown in  FIG. 3-1 .  
         [0073]     Step 2: The first transition. The electronic control system gives command to disengage the coupled clutch assembly  41 . Since the first gear has no load, synchronizer  103  can be disengaged after disengagement of  41 . The fluid drive turbine  43   b  drives the second gear through the engagement of gear  204  and gear  207 . The output speed gradually increases by the fluid drive, shown in  FIG. 3-2 .  
         [0074]     Step 3: The second transition. The electronic control system gives command to operate second coupled clutch assembly  42  to gradually connect fluid drive impeller  43   a  with shaft  201 , shown in  FIG. 3-3 . At the same time, the connection between shaft  201  and fluid drive turbine  43   b  is maintained to provide the second gear speed. At the moment, the fluid drive loses its function since the impeller  43   a  and turbine  43   b  have the same speed.  
         [0075]     Step 4: Completion of shift. The electronic control system gives command to operate second coupled clutch assembly  42  to gradually disconnect fluid drive turbine  43   b  with shaft  201 . At the moment, the impeller  43   a  drives the second gear directly through the engagement of synchronizer  202  and connection between gears  204  and  207 , shown in  FIG. 3-4 . First coupled clutch assembly  41  connects fluid drive turbine  43   b  with shaft  101  for preparation to next gear under no load.  
         [0076]     In this manner, shift quality is maintained with smooth transition for gear ratio change from one to the other in the automatic transmission, while providing better fuel economy with no torque interrupts. Unlike torque converter to drive a motor vehicle frequently to cause low efficiency in conventional automatic transmissions, direct drive is used to drive a motor vehicle and fluid drive in the present invention is just used for shifting gears.  
         [0077]     Similarly, above steps for shifting gears, except launching and the reverse gear, are also valid for shifting one gear to the adjacent gear. By changing the synchronizer&#39;s positions, different gear ratios can be achieved.  FIG. 4  shows the positions of four synchronizers for the engagement schedule to generate different gear ratios.  
         [0078]     It is the same principle for the gears to shift from even number gears to odd number gears, but the engagement and disengagement for coupled clutch assemblies is in a different order. The difference between to shift from odd number gears to even number gears and to shift from even number gears to odd number gears using shift support system  40  can be illustrated in  FIGS. 5-1  and  5 - 2 .  
         [0079]     Shift from an odd gear to an even gear: 
        1. Preparation for shifting. Disconnect the first coupled clutch assembly  42  and then use synchronizer to connect the even gear with shaft  30  under no load. Then, second coupled clutch assembly  42  reconnects the fluid drive turbine  43   b  with shaft  201 , shown in  FIG. 5-1   a.       2. The first transition. First coupled clutch assembly  41  disengages and the fluid drive turbine  43   b  drives the even gear, shown in  FIG. 5-1   b.       3. The second transition. Second coupled clutch assembly  42  to gradually connect fluid drive impeller  43   a  to shaft  201 . The fluid drive impeller  43   a  and turbine  43   b  drive the even gear at the same time, shown in  FIG. 5-1   c.       4. Completion of shifting. Second coupled clutch assembly  42  disconnects the fluid drive turbine  43   b  with shaft  201  and the impeller  43   a  drives the even gear directly, shown in  FIG. 5-1   d.          
 
         [0084]     Shift from an even gear to an odd gear: 
        1. Preparation for shifting. Disconnect second coupled clutch assembly  41  and use synchronizer to connect the odd gear with shaft  30  under no load. Then, first coupled clutch assembly  41  reconnects the fluid drive turbine  43   b  with shaft  101 , shown in  FIG. 5-2   a.       2. The first transition. Second coupled clutch assembly  42  disengages and the fluid drive turbine  43   b  drives the odd gear, shown in  FIG. 5-2   b.       3. The second transition. First coupled clutch assembly  41  gradually connects fluid drive impeller  43   a  with shaft  101 . The fluid drive impeller  43   a  and turbine  43   b  drive the odd gear at the same time, shown in  FIG. 5-2   c.       4. Completion of shifting. First coupled clutch assembly  41  disconnects the fluid drive turbine  43   b  with shaft  101  and the fluid drive impeller  43   a  drives the odd gear directly, shown in  FIG. 5-2   d . Second coupled clutch assembly  42  connects with fluid drive turbine  43   b  under no load to prepare for next gear.        
 
         [0089]     During launching or reverse gear shifting using shift support system  40 , only three steps are needed. The launching procedures are described as follows: 
        1. Preparation for launching. Synchronizer  103  connects the first gear to shaft  30  under no load. Then, first coupled clutch assembly  41  connects the fluid drive turbine  43   b  with shaft  101 .     2. The transition. First coupled clutch assembly  41  to gradually connect fluid drive impeller  43   a  with shaft  101 . The fluid drive impeller  43   a  and turbine  43   b  drive the first gear at the same time.     3. Completion. First coupled clutch assembly  41  disconnects the fluid drive turbine  43   b  with shaft  101  and the fluid drive impeller  43   a  drives the first gear directly. Second coupled clutch assembly  42  connects with fluid drive turbine  43   b  under no load to prepare for next gear.        
 
         [0093]     The reverse gear shifting can use the similar description by replacing the first gear with reverse gear from above.  
         [0094]     Based on above principle, multi-speed automatic transmissions using shift support system  40  can be derived into several types in order to be used in different applications. A four-speed automatic transmission, which includes a shift support system  140  and a gear system  120  containing two gear subsystems  1110  and  1120 , is shown in  FIG. 7 , a five-speed automatic transmission, which includes a shift support system  240  and a gear system  220  containing two gear subsystems  2110  and  2120 , is shown in  FIG. 8  and a seven-speed automatic transmission, which includes a shift support system  340  and a gear system  320  containing two gear subsystems  3110  and  3120 , is shown in  FIG. 9 .  
         [0095]     In summary, since an advantage is taken by replacing the dual clutch friction in a dual clutch transmission with non-contact fluid friction, the friction between clutch discs is greatly reduced with less heat generation. It is important for such friction reduction to prevent discs from wear and seizure failures with lower requirement of materials in order to ensure the system reliability and low cost. At the same time, good shift quality with continuous power transfer and passenger comfort can be achieved. Since fluid drive uses fluid to transfer speed and torque, its self-adaptive characteristics can maintain smoothness to avoid harsh shift feel so that the electronic control can be simpler. It is important to point out that the fluid drive is only used for shifting the gears and not used to drive the vehicle frequently as conventional automatic transmissions do. Therefore, high efficiency is achievable as being similar to automated manual transmission.