Patent Publication Number: US-2021188074-A1

Title: Transmission-mounted combined energy recovery drive

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims priority to and the benefit of U.S. Provisional Patent Application No. 62/728,425, filed Sep. 7, 2018, the content of which is incorporated by reference in its entirety. 
    
    
     STATEMENT REGARDING FEDERALLY-SPONSORED RESEARCH OR DEVELOPMENT 
     This invention was made with government support under Department of Energy Contract No. DE-EE0007761 awarded by the Department of Energy. The government has certain rights in this invention. 
    
    
     TECHNICAL FIELD 
     The present disclosure relates generally to the field of energy recovery drive systems. 
     BACKGROUND 
     An energy recovery drive is a device designed to improve overall efficiency of a powertrain system by utilizing energy that would be otherwise lost. Some energy recovery drives utilize a motor-generator, which is a device that performs the functions of both a motor and an alternator (e.g., starting the engine and generating power for the electrical system). For example, the motor-generator can facilitate regenerative braking to recover energy that would otherwise be lost due to braking. During regenerative braking, the motor-generator operates as a generator to provide braking torque to the powertrain to convert the vehicle&#39;s kinetic energy to electrical energy, which can be stored in a battery for later use. The motor-generator can use the stored electrical energy to start the engine and to power (in part or in whole) the powertrain at an efficiency that is typically higher than that of an engine itself. 
     Waste heat recovery (“WHR”) systems are another type of energy recovery drive system. WHR systems capture a portion of the waste heat generated by an engine to perform useful work. Some WHR systems utilize a Rankine cycle (“RC”). The RC is a thermodynamic process in which heat is transferred to a working fluid in an RC circuit. The working fluid is pumped to a boiler where it is vaporized. The vapor is passed through an expander and then through a condenser, where the vapor is condensed back to a fluid. The expanding working fluid vapor causes the expander to rotate, thereby converting the waste heat energy to mechanical energy. The mechanical energy may be transmitted to engine system components, such as a pump, a compressor, a generator, etc. 
     Hybrid electric vehicles (“HEVs”) use both an engine and a motor-generator to drive the powertrain. HEVs can be classified into different categories based on their effected functions. In mild hybrid systems, the motor-generator assists the engine in driving the powertrain, but cannot fully drive the powertrain on its own. In full hybrid systems (also referred to as strong hybrid systems), the motor-generator can also drive the powertrain on its own without the engine. 
     HEVs can also be classified into different categories based on the configuration of the hybrid drive system. In parallel hybrid drive systems, the motor-generator and the engine contribute to driving the powertrain independently of one another. The powertrain can be driven by the engine, the motor-generator, or both. In parallel mild hybrid systems, the powertrain can be driven by the engine or by both the engine and the motor-generator; the powertrain cannot be driven by the motor-generator alone. 
     SUMMARY 
     Various embodiments relate to energy recovery drive systems. An example energy recovery drive system includes a motor-generator that is structured to selectively operate in a motor mode and a generator mode. The motor mode provides kinetic energy from electrical energy. The generator mode generates electrical energy from kinetic energy. A first shaft is operatively coupled to a transmission power take-off (“PTO”) shaft. A second shaft is operatively coupled to the motor-generator and to an alternative power source. The energy recovery drive system is controllably operated in a plurality of operating modes. In a first operating mode, the motor-generator is in torque providing engagement with each of the first and second shafts. In a second operating mode, the motor-generator is in torque receiving engagement with each of the first and second shafts. In a third operating mode, which the motor-generator is in torque communicating engagement with the second shaft and is disengaged from transferring torque to the first shaft and from receiving torque from the first shaft. 
     Various other embodiments relate to powertrain systems for a parallel mild hybrid vehicles. An example powertrain system includes an engine and a transmission having a PTO shaft. A master clutch controllably and selectively couples the engine and the transmission. A combined energy recovery drive is operatively coupled to the PTO shaft of the transmission and to an alternative power source. The combined energy recovery drive is structured to generate energy from inertia of the parallel mild hybrid vehicle when the engine is decoupled from the transmission via the master clutch. 
     Still other embodiments relate to a method of recovering or providing energy in a parallel mild hybrid vehicle. A combined energy recovery drive is coupled to a transmission of an engine via a first shaft, the first shaft in rotational communication with a first gear train. The combined energy recovery drive is coupled to an alternative power source via a second shaft, the second shaft in rotational communication with a second gear train. The first shaft is selectively coupled to the second shaft via a master clutch, an engaged position of the master clutch comprising the master clutch in rotational communication with the first shaft and the second gear train, and a disengaged position of the master clutch comprising the master clutch not in rotational communication with the first shaft and the second gear train. 
     These and other features, together with the organization and manner of operation thereof, will become apparent from the following detailed description when taken in conjunction with the accompanying drawings, wherein like elements have like numerals throughout the several drawings described below. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The details of one or more implementations are set forth in the accompanying drawings and the description below. Other features, aspects, and advantages of the disclosure will become apparent from the description, the drawings, and the claims. 
         FIG. 1  is rear perspective view of a powertrain system, according to an example embodiment. 
         FIG. 2  is a front perspective view of a transmission and an energy recovery drive system of the powertrain system of  FIG. 1 , with the transmission grayed out to highlight the energy drive system. 
         FIG. 3  is a side elevational view of the energy recovery drive system of  FIG. 2 . 
         FIG. 4  is a block diagram of the powertrain system of  FIG. 1  including the energy recovery drive system of  FIGS. 2 and 3 . 
         FIGS. 5A-5C  illustrate various operating modes of the energy recovery drive system of  FIGS. 2-4 , according to various example embodiments. 
     
    
    
     It will be recognized that some or all of the figures are schematic representations for purposes of illustration. The figures are provided for the purpose of illustrating one or more implementations with the explicit understanding that they will not be used to limit the scope or the meaning of the claims. 
     DETAILED DESCRIPTION 
     In various conventional parallel mild hybrid systems, the motor-generator is coupled directly to the engine. As such, it is not possible to decouple the engine and the motor-generator and still regenerate energy. For example, it is not possible to generate power via “engine-off coasting,” in which the engine is shut off and decoupled from the transmission, and energy is generated from the inertia of the vehicle and/or from an alternative power source (e.g., a WHR turbine). Some full hybrid systems include a clutch between the motor and the engine to achieve this function. However, in engine-driven mild hybrid systems, space constraints and costs prohibit this arrangement. 
     Various embodiments relate to combined engine recovery drive systems. An example energy recovery drive system is mounted on a transmission of a mild hybrid system and is structured to recover energy from multiple sources, such as from the powertrain and from an alternative power source, such as a WHR system. In some embodiments, the energy recovery drive system includes a motor-generator that is operatively coupled to a PTO shaft of the transmission. This configuration allows the motor-generator to be disengaged from the engine via a master clutch of the transmission, thereby enabling the energy recovery drive system to regenerate power even when the engine is shut off, such as via vehicle inertia during engine-off coasting and via the alternative power source. 
     According to various embodiments, the combined energy recovery system is structured as a three-way system with interfaces to a motor-generator, an alternative power source (e.g., a WHR turbine), and a transmission PTO shaft. More specifically, the combined energy recovery system is structured to operate in various operating modes that allows power flow in any one of the following configurations: (1) from the transmission and the alternative power source to the motor-generator; (2) from the motor-generator and the alternative power source to the transmission; and (3) from the alternative power source to the motor-generator or from the motor-generator to the alternative power source, but not to the transmission. 
     According to various embodiments, the combined energy recovery drive system is structured as a standalone assembly that can be simply bolted to the back of a transmission with minimal modification required to the stock transmission design. 
     According to various embodiments, the combined energy recovery drive system is in transmission fluid communicating engagement with the transmission. In such embodiments, the combined energy recovery drive system utilizes transmission fluid for lubrication and cooling. This feature operates to minimize weight and complexity of the combined energy recovery drive system, and also improves operational efficiency of the combined energy recovery drive system. 
       FIG. 1  is rear perspective view of a powertrain system  100 , according to an example embodiment. In some embodiments, the powertrain system  100  is utilized in a mild hybrid electric vehicle. The powertrain system  100  includes an engine  102 , a transmission  104 , and an energy recovery drive system  106 . The engine  102  is operatively coupled to the transmission  104  so as to transfer torque and power to the transmission  104 . The transmission  104  includes one or more gear trains structured to controllably adjust speed and torque from the engine  102  to a driveshaft (not shown) to power a vehicle or stationary device (e.g., a genset). The energy recovery drive system  106  is operatively coupled to the transmission  104 . The energy recovery drive system  106  is structured to regenerate energy recovered from the powertrain system  100  and/or from an alternative power source, and to transmit energy to the powertrain system  100 . 
       FIG. 2  is a front perspective view of the transmission  104  and the energy recovery drive system  106  of the powertrain system  100  of  FIG. 1 , with the transmission  104  deemphasized to highlight the energy recovery drive system  106 . The energy recovery drive system  106  includes a motor-generator  108 , an alternative power source drive  110 , a first shaft  114 , a first gear train  116 , a second gear train  118 , and a clutch assembly  120 . 
     The motor-generator  108  is operatively coupled to the transmission  104  via the first shaft  114 . The motor-generator  108  is also operatively coupled to the alternative power source drive  110  via a second shaft (not shown). In some embodiments, the first shaft  114  is a PTO shaft of the transmission  104 . The first gear train  116  is structured to adjust the speed and torque of energy transmitted between the motor-generator  108  and the second shaft. The second gear train  118  is structured to adjust the speed and torque of energy transmitted between the motor-generator  108  and the first shaft  114 . The first and second gear trains  116 ,  118  are arranged as a parallel axis gear train. By structuring the first and second gear trains  116 ,  118  in this manner and optimizing the gear ratios of the first and second gear trains  116 ,  118 , the energy recovery drive system  106  can be optimized such that each power source, including the transmission  104 , the motor-generator  108 , and the alternative power source coupled to the alternative power source drive  110 , are operated at their individual peak efficiencies. In other embodiments, the first and second gear trains  116 ,  118  are arranged in other configurations, such as a planetary arrangement. The clutch assembly  120  is structured to selectively couple and decouple the alternative power source drive  110 , the second shaft  130 , and the motor-generator  108  from the first shaft  114  and the transmission  104 . 
       FIG. 3  is a side elevational view of the energy recovery drive system  106  of  FIG. 2 . As shown in  FIG. 3 , first gear train  116  includes a first gear  124  and a second gear  126 . The first gear  124  and the second gear  126  are in meshed engagement with each other. The motor-generator  108  includes a drive shaft  128  operatively coupled to the first gear  124 . The second gear  126  is operatively coupled to a second shaft  130 . The second shaft  130  is a unitary shaft that extends between the first gear  124  and the alternative power source drive  110 . Various other components, including a first bearing (not shown) of a rear bearing housing  132 , the clutch assembly  120 , and a second bearing (not shown) of a front bearing housing  134  are also coupled to the second shaft  130 , which extends therethrough. 
     The clutch assembly  120  includes a clutch housing  136 , a clutch basket  138 , and an integrated gear  140 . The clutch housing  136  includes a clutch hub (not shown) fixedly coupled to (e.g., splined to) the second shaft  130  so as to co-rotate with the second shaft  130 . The integrated gear  140  is fixedly coupled to the clutch basket  138 . The integrated gear  140  is rotationally coupled to the second shaft  130  such that the integrated gear  140  is capable of rotating freely relative to the second shaft  130 . 
     The clutch assembly  120  is controllable between an engaged position and a disengaged position. For example, in some embodiments, the clutch assembly  120  includes a plurality of friction plates, clutch springs that force the friction plates together, and an actuator. In some embodiments, the clutch assembly  120  is in a normally engaged position, absent external force applied thereto. In the engaged position, the clutch basket  138  is coupled to the clutch hub such that the clutch basket  138  and the integrated gear  140  co-rotate with the second shaft  130 . In the engaged position, torque is transferred to and from the transmission  104  via the first shaft  114 . In order to reach the disengaged position, the actuator forces the friction plates away from each other such that the clutch basket  138  is decoupled from the clutch hub so that the second shaft  130  rotates independently of the clutch basket  138  and the integrated gear  140 . In the disengaged position, no torque is transferred to or from and from the transmission  104  via the first shaft  114 . In some embodiments, the clutch assembly  120  includes a clutch position sensor (e.g., an inductive position sensor) to determine a current physical position of the clutch assembly  120 . 
     The clutch assembly  120  is positioned on the second shaft  130  between the first gear train  116  and the second gear train  118 . This location minimizes the torque provided to the clutch assembly  120 , which allows the clutch to have a compact package size. Typically, the operating speed at which a motor-generator or an alternative power source operates at peak efficiency is higher than the operating speed of the engine, the transmission, or the PTO shaft. As a result, gear trains in energy recovery drive systems are typically designed to step up the speed going from the transmission to the motor-generator and the alternate power source. This results in a progressive reduction in torque after each gear set. According to various embodiments, by positioning the clutch assembly  120  between the first gear train  116  and the second gear train  118 , and not right at the first shaft  114  (the PTO shaft), the clutch assembly  120  is exposed to lower torque and can be packaged in a smaller size compared to clutch assemblies in other arrangements. 
     The second gear train  118  includes the integrated gear  140  of the clutch assembly  120 , a third gear  142 , a fourth gear  144 , and a fifth gear  146 . The integrated gear  140  and the third gear  142  are in meshed engagement with each other. The fourth gear  144  and the fifth gear  146  are in meshed engagement with each other. The third gear  142  and the fourth gear  144  are operatively (e.g., fixedly) coupled to an idler shaft  148  so as to co-rotate with the idler shaft  148 . The idler shaft supported by a third bearing (not shown) of the rear bearing housing  132  and a fourth bearing of an idler bearing housing  150 . 
     The fifth gear  146  is operatively (e.g., fixedly) coupled to the first shaft  114  so as to co-rotate with the first shaft  114 . The first shaft  114  is supported by a fourth bearing (not shown) of a first shaft bearing housing  152 . 
       FIG. 4  is a block diagram of the powertrain system  100  of  FIG. 1  including the energy recovery drive system  106  of  FIGS. 2 and 3 . As shown in  FIG. 4 , the powertrain system  100  includes the engine  102 , the transmission  104 , and the energy recovery drive system  106 . The engine  102  is operatively coupled to the transmission  104  via a transmission master clutch  153 . The transmission  104  includes the first shaft  114  and a drive shaft  154 . The drive shaft  154  may power a final drive of a vehicle. As described above, the first shaft  114  is operatively coupled to the energy recovery drive system  106 . 
     The powertrain system  100  also includes an electrical system  155  operatively coupled to the energy recovery drive system  106 . More specifically, the electrical system  155  is operatively coupled to the motor-generator  108  and the powertrain supervisor controller  158 . According to various embodiments, the electrical system  155  includes batteries, an inverter, and power electronics to transmit electrical energy to and to receive electrical energy from the motor-generator  108 . It should be understood that the electrical system  155  may also be operatively coupled to other components of the powertrain system  100  and of a vehicle including the powertrain system  100 . 
     In addition to the components described in connection with  FIGS. 2 and 3 , the energy recovery drive system  106  also includes an alternative power source  156  and a powertrain supervisor controller  158 . The alternative power source  156  is operatively coupled to the alternative power source drive  110 . The alternative power source drive  110  operatively couples the alternative power source  156  to the motor-generator  108 . In some embodiments, the alternative power source  156  is a WHR turbine of a WHR system. However, the alternative power source  156  can be any type of power source. In some embodiments, the alternative power source drive  110  is a belt drive with pulleys coupled to the alternative power source  156  and to the second shaft  130 . In some embodiments, the alternative power source drive  110  may also be used as a PTO. 
     The powertrain supervisor controller  158  is structured to control various aspects of the energy recovery drive system  106 . The powertrain supervisor controller  158  is operatively and communicatively coupled to various components of the energy recovery drive system  106 , such as the motor-generator  108 , the clutch assembly  120 , the alternative power source  156 , the electrical system  155 , and various sensors and other components. Various aspects of control functionality of the powertrain supervisor controller  158  are discussed further below. 
     The powertrain supervisor controller  158  is also operatively and communicatively coupled to an engine control unit (“ECU”)  160  and a transmission control unit (“TCU”)  162 . The ECU  160  receives and analyzes input values from various sensors and controls various actuators and other devices to ensure optimal performance of the engine  102 . The TCU  162  similarly receives and analyzes input values from various sensors and controls various actuators and other devices to ensure optimal performance of the transmission  104 . 
     In some embodiments, the powertrain supervisor controller  158  is configured to monitor operation of the electrical system  155  and to control operation of the energy recovery drive system  106  based on operating conditions of the electrical system  155 . For example, in some embodiments, the powertrain supervisor controller  158  is configured to monitor state of charge of an electrical storage unit (e.g., a battery) of the electrical system  155  and to control operation of the energy recovery drive system  106  based on the monitored state of charge. In some embodiments, the powertrain supervisor controller  158  is configured to control a position of the clutch assembly  120  and/or the transmission master clutch  153  based on the monitored state of charge. For example, in some embodiments, the powertrain supervisor controller  158  is configured to switch from the first operating mode in which the motor-generator  108  is operating as a generator to the second operating mode in which the motor-generator  108  is operating as a motor in response to the state of charge exceeding a threshold value. 
       FIGS. 5A-5C  illustrate various operating modes of the energy recovery drive system  106  of  FIGS. 2-4 , according to various example embodiments. The powertrain supervisor controller  158  is structured to control the energy recovery drive system  106  in the various operating modes based on conditions of the powertrain system  100 .  FIG. 5A  illustrates a first operating mode of the energy recovery drive system  106 . In the first operating mode, the motor-generator  108  is in torque receiving engagement with each of the first shaft  114  and the second shaft  130 . In other words, in the first operating mode, the motor-generator  108  receives energy along a first path  500  from the alternative power source drive  110  via the second shaft  130  and receives energy along a second path  502  from the engine  102  or the transmission  104  via the first shaft  114 . In the first operating mode, the motor-generator  108  operates as a generator to generate electrical energy from the received rotational energy. The clutch assembly  120  is in an engaged position. 
       FIG. 5B  illustrates a second operating mode of the energy recovery drive system  106 . In the second operating mode, the motor-generator  108  is in torque providing engagement with the first shaft  114  and the alternative power source drive  110  is also in torque providing engagement with the first shaft  114 . In other words, in the second operating mode, the motor-generator  108  provides energy along a third path  504  to the transmission  104  via the first shaft  114 . The alternative power source drive  110  also provides energy along a fourth path  506  to the transmission  104  via the second shaft  130 . In the second operating mode, the motor-generator  108  operates as a motor to provide energy to the transmission  104 . The clutch assembly  120  is in an engaged position. 
       FIG. 5C  illustrates a third operating mode of the energy recovery drive system  106 . In the third operating mode, the motor-generator  108  is in torque communicating engagement with the first shaft  114 . In other words, in the third operating mode, the motor-generator  108  receives energy along a fifth path  508  from the alternative power source drive  110  via the second shaft  130 . In the third operating mode, the clutch assembly  120  is disengaged so as to decouple the motor-generator  108  and the alternate power source drive  110  from the first shaft  114  and the transmission  104 . Therefore, the motor-generator  108  is able to generate energy in the third operating mode from torque received from the alternative power source drive  110  without requiring operation of the engine  102  or the transmission  104 . In addition, in the third operating mode, the motor-generator  108  is also able to provide torque to the second shaft  130  without requiring operation of the engine  102 . For example, the torque provided by the motor-generator  108  to the second shaft  130  may be used to power one or more accessories coupled to the second shaft  130  without requiring operation of the engine  102 . Therefore, the motor-generator  108  is also able to provide energy in the third operating mode to components coupled to the second shaft  130  without requiring operation of the engine  102  or the transmission  104 . As used herein, the phrase “torque communicating engagement” includes both torque providing engagement and torque receiving engagement. 
     Further to the above, in some configurations, the alternative power source  156  (e.g., a waste heat recovery turbine) also powers pumps that are coupled thereto. During start-up, there is typically not enough thermal energy for the alternative power source  156  to achieve a sufficient power output (e.g., a high enough turbine power) to power these pumps. Therefore, in some configurations, the energy recovery drive system  106  utilizes the motor-generator  108  or engine  102  (which is disconnected in third operating mode) to power the alternative power source  156  via the alternative power source drive  110 . In short, the motor-generator  108  does not only receive torque from alternative power source drive  110  but also provides torque to the alternative power source drive  110  in some scenarios. Additionally, the alternative power source drive  110  may be used to drive accessories other than the alternate power source  156 . 
     Reference throughout this specification to “one embodiment,” “an embodiment,” “an example embodiment,” or similar language means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the present invention. Thus, appearances of the phrases “in one embodiment,” “in an embodiment,” “in an example embodiment,” and similar language throughout this specification may, but do not necessarily, all refer to the same embodiment. 
     Accordingly, the present disclosure may be embodied in other specific forms without departing from its spirit or essential characteristics. The described embodiments are to be considered in all respects only as illustrative and not restrictive. The scope of the disclosure is, therefore, indicated by the appended claims rather than by the foregoing description. All changes which come within the meaning and range of equivalency of the claims are to be embraced within their scope.