Patent Publication Number: US-2018037205-A1

Title: Vehicle regenerative air brake system

Description:
TECHNICAL FIELD 
     This disclosure relates to a regenerative air brake system for a vehicle. The regenerative air brake system may be selectively employed to reduce the load on the vehicle&#39;s friction braking system and increase the amount of energy that can be reclaimed during vehicle deceleration. 
     BACKGROUND 
     The need to improve the energy efficiency of automotive vehicles has been well documented. Efforts have therefore been undertaken to reclaim energy that would otherwise be lost to the environment as waste heat during vehicle operation. For example, regenerative braking systems are known that reclaim energy through braking by repurposing an electric motor as an electric generator. However, these systems typically lack effectiveness during sudden braking conditions at high speeds. 
     SUMMARY 
     A vehicle according to an exemplary aspect of the present disclosure includes, among other things, a vehicle body and a regenerative air brake system disposed inside the vehicle body. The regenerative air brake system includes a conduit, a turbine positioned in the conduit, and an electrical generator operatively connected to the turbine and positioned remotely from the conduit. 
     In a further non-limiting embodiment of the foregoing vehicle, the conduit includes an inlet at a front of the vehicle body and an outlet at a rear of the vehicle body. 
     In a further non-limiting embodiment of any of the foregoing vehicles, the conduit at least partially extends through an engine compartment of the vehicle body. 
     In a further non-limiting embodiment of any of the foregoing vehicles, the conduit at least partially extends through a chassis of the vehicle body. 
     In a further non-limiting embodiment of any of the foregoing vehicles, the conduit includes a branch having an inlet, and a door is movable to open and close the inlet. 
     In a further non-limiting embodiment of any of the foregoing vehicles, the inlet is located near a wheel well of the vehicle body. 
     A further non-limiting embodiment of any of the foregoing vehicles includes an actuator configured to move the door between a first position and a second position to open and close the inlet. 
     In a further non-limiting embodiment of any of the foregoing vehicles, the conduit includes a first branch having a first inlet and a second branch having a second inlet, and the first branch and the second branch meet at a junction of the conduit. The junction is upstream from the turbine. 
     In a further non-limiting embodiment of any of the foregoing vehicles, the turbine includes a stator and a rotor. 
     In a further non-limiting embodiment of any of the foregoing vehicles, the electrical generator feeds electricity to an electrical system of the vehicle. 
     A further non-limiting embodiment of any of the foregoing vehicles includes a friction braking system. The regenerative air brake system and the friction braking system cooperate to decelerate the vehicle. 
     A further non-limiting embodiment of any of the foregoing vehicles includes a control system adapted to activate the regenerative air brake system during vehicle deceleration. 
     A method according to an exemplary aspect of the present disclosure includes, among other things, activating a regenerative air brake system of a moving vehicle during vehicle braking events to assist in decelerating the moving vehicle. 
     A further non-limiting embodiment of the foregoing method includes activating the regenerative air brake system if a requested deceleration rate exceeds a threshold deceleration rate. 
     A further non-limiting embodiment of any of the foregoing methods includes activating the regenerative air brake system if a current vehicle speed exceeds a threshold vehicle speed. 
     A further non-limiting embodiment of any of the foregoing methods includes activating the regenerative air brake system if an inferred amount of airflow passing through the regenerative air brake system exceeds a threshold amount of airflow. 
     In a further non-limiting embodiment of any of the foregoing methods, the vehicle braking events occur when a friction braking system of the moving vehicle has been activated. 
     A further non-limiting embodiment of any of the foregoing methods includes utilizing a turbine to extract energy from airflow communicated through a conduit of the regenerative air brake system, and powering an electrical generator using the energy extracted from the airflow. 
     A further non-limiting embodiment of any of the foregoing methods includes opening a door at an inlet of the conduit to allow the airflow to enter the conduit. 
     A further non-limiting embodiment of any of the foregoing methods includes deactivating the regenerative air brake system during non-braking events. 
     The embodiments, examples, and alternatives of the preceding paragraphs, the claims, or the following description and drawings, including any of their various aspects or respective individual features, may be taken independently or in any combination. Features described in connection with one embodiment are applicable to all embodiments, unless such features are incompatible. 
     The various features and advantages of this disclosure will become apparent to those skilled in the art from the following detailed description. The drawings that accompany the detailed description can be briefly described as follows. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  schematically illustrates a vehicle. 
         FIG. 2  schematically illustrates a regenerative air brake system of a vehicle. 
         FIG. 3  schematically illustrates a regenerative air brake system according to another embodiment of this disclosure. 
         FIG. 4  schematically illustrates a regenerative air brake system according to yet another embodiment of this disclosure. 
         FIG. 5  schematically illustrates an exemplary control strategy for controlling a regenerative air brake system of a vehicle. 
     
    
    
     DETAILED DESCRIPTION 
     This disclosure describes a vehicle regenerative air brake system. The regenerative air brake system includes a conduit, a turbine positioned in the conduit, and an electrical generator operatively connected to the turbine. The regenerative air brake system is selectively activated to reclaim energy during braking events, assist in decelerating the moving vehicle, or both. In some embodiments, the regenerative air brake system is automatically activated in response to actuating a friction braking system of the vehicle. These and other features are discussed in greater detail in the following paragraphs of this detailed description. 
       FIG. 1  schematically illustrates a vehicle  10  traveling in a direction D along a roadway  12 . Although an exemplary component relationship of the vehicle  10  is illustrated in  FIG. 1 , this illustration is highly schematic and is not intended to limit this disclosure. In other words, the placement and orientation of the various components of the vehicle  10  could vary from vehicle to vehicle. 
     The vehicle  10  could include a traditional drivetrain or an electrified drivetrain. In addition, the vehicle  10  is depicted in this non-limiting embodiment as a car. However, trucks, cars, vans, or any other type of automotive vehicles could also benefit from the teachings of this disclosure. 
     The exemplary vehicle  10  includes a powertrain having one or more power sources  14 . In a first non-limiting embodiment, the power source  14  is an engine if the vehicle  10  includes a traditional drivetrain. In another non-limiting embodiment, the power source  14  is an electric machine (i.e., an electric motor, generator, or combined motor/generator) if the vehicle  10  includes an electrified drivetrain. In yet another non-limiting embodiment, the power source  14  includes both an engine and an electric machine if the vehicle  10  includes a hybrid drivetrain. The power source(s)  14  generate torque to drive one or more sets of drive wheels  16  of the vehicle  10 . 
     The vehicle  10  includes a friction braking system  18  for decelerating the drive wheels  16  in order to bring the vehicle  10  to a stop, or to arrest its motion. For example, the friction braking system  18  may operate to slow the speed of the drive wheels  16  by applying one or more friction elements (e.g., brake pads, shoes, etc., not shown in schematic depiction of  FIG. 1 ). Application of the friction elements converts the kinetic energy of the moving drive wheels  16  into heat to inhibit motion of the vehicle  10 . The friction braking system  18  is activated by depressing a brake pedal  50  located within the passenger compartment of the vehicle  10 . The brake pedal  50  is typically depressed by an operator&#39;s foot in order to activate the friction braking system  18  and decelerate the vehicle  10 . Although not shown, the vehicle  10  could additionally include a regenerative engine braking system. 
     The vehicle  10  is additionally equipped with a regenerative air brake system  20 . The regenerative air brake system  20  may be used in combination with the friction braking system  18  to decelerate the vehicle  10 . In a non-limiting embodiment, the regenerative air brake system  20  generates electricity during braking events by reclaiming energy from airflow that passes through the vehicle  10 . Various exemplary regenerative air brake systems are discussed in greater detail below. 
       FIG. 2  details an exemplary regenerative air brake system  20 . The regenerative air brake system  20  could be employed within the vehicle  10  of  FIG. 1  or any other vehicle. In a non-limiting embodiment, the regenerative air brake system  20  includes a conduit  22 , a turbine  24 , and an electrical generator  26 . 
     The conduit  22  establishes a hollow passage that extends entirely or partially through the vehicle  10 . The conduit  22  is positioned inside a vehicle body  28 , or structural frame, of the vehicle  10 . The conduit  22  is considered “inside” the vehicle body  28  in that it is not mounted to an exterior portion of the vehicle  10  but instead is an internal component of the vehicle  10 . In a non-limiting embodiment, portions of the conduit  22  pass through hollow sections of a chassis  25  of the vehicle  10 . In another non-limiting embodiment, portions of the conduit  22  extend through an engine compartment  34  of the vehicle  10 . 
     The conduit  22  includes an inlet  30  and an outlet  32 . An airflow F may enter the conduit  22  through the inlet  30  and may be expelled from the conduit  22  through the outlet  32 . In a non-limiting embodiment, the inlet  30  is disposed at a front of the vehicle body  28 , whereas the outlet  32  is disposed at a rear of the vehicle body  28 . The exact conduit design shown in  FIG. 2  is not intended to be limiting, and it should be understood that other configurations are contemplated within the scope of this disclosure. 
     The turbine  24  is mounted within the conduit  22  at a location between the inlet  30  and the outlet  32 . The exact mounting location of the turbine  24  can vary depending on various design aspects associated with the vehicle  10 , including but not limited to the amount of airflow F that is permitted to pass through the conduit  22 . The turbine  24  includes a stator  36  and a rotor  38 . The stator  36  is a stationary component and the rotor  38  is a movable component. For example, the stator  36  controls the speed and direction of the airflow F as it is communicated through the conduit  22  toward the rotor  38 , and the rotor  38  rotates to extract work (i.e., energy) from the airflow F. 
     The electrical generator  26  is operably connected to the turbine  24 , and in particular to the rotor  38 , via a drive shaft  40 . The energy extracted from the airflow F by the rotor  38  drives the electrical generator  26  to generate electricity which can be fed back into an electrical system  54  of the vehicle  10 , for example. In a non-limiting embodiment, the electrical generator  26  is mounted at a location remote from the conduit  22 . Stated another way, unlike the turbine  24 , the electrical generator  26  is not mounted within the conduit  22 . 
     A control system  42  is adapted to control activation and deactivation of the regenerative air brake system  20  during movement of the vehicle  10  in the direction D along the roadway  12 . The control system  42  could be part of an overall vehicle system controller (VSC) or could be a separate control system that communicates with the VSC. The control system  42  includes one or more control modules  44  equipped with executable instructions for interfacing with and commanding operation of various components of the regenerative air brake system  20 . In another non-limiting embodiment, each control module  44  of the control system  42  includes a processing unit  46  and non-transitory memory  48  for executing the various control strategies and modes of the regenerative air brake system  20 . One exemplary control strategy of the regenerative air brake system  20  is discussed below with reference to  FIG. 5 . 
     In a non-limiting embodiment, the control system  42  is adapted to activate the regenerative air brake system  20  if the friction braking system  18  (see  FIG. 1 ) of the vehicle  10  has been activated. This may be referred to as a braking event. In a non-limiting embodiment, the control system  42  monitors a position of the brake pedal  50  to determine whether or not the friction braking system  18  has been activated. The brake pedal  50  may be selectively depressed by a driver to decelerate the vehicle  10  using the friction braking system  18 . The brake pedal  50  may be an electronic device that includes a sensor  52  for indicating a pedal position when the brake pedal  50  is actuated. The sensor  52  may generate a pedal position signal S 1  that is communicated to the control system  42  as pressure is applied to the brake pedal  50 . The pedal position signal S 1  is indicative of an amount of pressure applied to the brake pedal  50 , and may be used by the control system  42  to determine whether or not to activate the regenerative air brake system  20  in order to augment decelerating the vehicle  10 . Additional exemplary functions of the control system  42  include monitoring the current speed of the vehicle  10 , estimating the amount of airflow F passing through the conduit  22  of the regenerative air brake system  20 , etc. 
     When the regenerative air brake system  20  is activated, airflow F is communicated freely through the conduit  22  to the turbine  24 . The airflow F passing through the turbine  24  exerts a force on the turbine  24  which arrests movement of the vehicle  10  via increased drag. Thus, in a non-limiting embodiment, the regenerative air brake system  20  acts as an aeronautical air brake to aid in decelerating the vehicle  10 . 
     The airflow F passing through the conduit  22  eventually passes through the turbine  24 . Since the airflow F typically passes though the conduit  22  at constant subsonic speeds and therefore behaves like an incompressible flow, the stator  36  of the turbine  24  may be provided to modify the properties (speed, temperature, direction, etc.) of the airflow F so additional work can be extracted from the airflow F by the rotor  38 . The energy extracted from the airflow F by the rotor  38  is used to power the electrical generator  26  for generating electricity. 
     The energy reclaimed from the airflow F during vehicle deceleration can be used for various purposes. For example, in a vehicle powered solely by an internal combustion engine, the reclaimed energy can be used to reduce the load on the alternator and reduce fuel consumption of the engine. In an alternative embodiment, such as for hybrid and all-electric vehicles, the reclaimed energy can be used to power various components of the vehicle, or can be used to aid vehicle propulsion, thus increasing available energy and overall vehicle efficiencies. 
       FIG. 3  illustrates another exemplary regenerative air brake system  120 . The regenerative air brake system  120  is similar to the regenerative air brake system  20  of  FIG. 2  but includes a slightly modified conduit  122  for directing airflow F through the regenerative air brake system  120 . The distinctions between the non-limiting embodiments of  FIGS. 2 and 3  should become apparent in view of the following details of the regenerative air brake system  120 . 
     In a non-limiting embodiment, the regenerative air brake system  120  includes a conduit  122 , a turbine  124 , and an electrical generator  126 . The conduit  122  is positioned inside a vehicle body  28  of the vehicle  10  and includes multiple branches  160  that direct the airflow F toward the turbine  124 . Although two branches  160  are shown in  FIG. 3 , the conduit  122  could include any number of branches. 
     Each branch  160  establishes an inlet  130  for directing the airflow F into the conduit  122 . In a non-limiting embodiment, the inlets  130  are positioned near wheel wells  162  of the vehicle  10 , although other inlet locations are also contemplated. A door  164  may be selectively moved to open or close the inlet  130 . Each door  164  includes an actuator  166  for moving the door  164  between the closed and open positions. The actuator  166  could include a mechanical device, an electrical device, or any other actuating device capable of moving the door  164  to open and close the inlet  130 . 
     The conduit  122  further includes an outlet  132 . The airflow F may be expelled from the conduit  122  through the outlet  132  after energy has been extracted from the airflow F by the turbine  124 . In a non-limiting embodiment, the outlet  132  is disposed at a rear of the vehicle body  28 . However, other outlet locations are also contemplated within the scope of this disclosure. 
     Airflow F entering into each branch  160  mixes with airflow F from other branches at a junction  168  prior to passing to the turbine  124 . The turbine  124  may be mounted at any location downstream from the junction  168 . 
     The turbine  124  includes a stator  136  and a rotor  138 . The stator  136  controls the speed and direction of the airflow F as it is communicated through the conduit  122  toward the rotor  138 , and the rotor  138  rotates to extract energy from the airflow F. 
     The electrical generator  126  is operably connected to rotor  138  via a drive shaft  140 . The energy extracted from the airflow F by the rotor  138  drives the electrical generator  126  for generating electricity. Energy is thus reclaimed during vehicle deceleration and can be used to power various vehicle loads. 
     A control system  142  of the regenerative air brake system  120  is adapted to activate/deactivate the regenerative air brake system  120 . In a non-limiting embodiment, the control system  142  activates the regenerative air brake system  120  if the friction braking system  18  (see  FIG. 1 ) of the vehicle  10  has been activated and deactivates the regenerative air brake system  120  if the friction braking system  18  has been deactivated. For example, if the friction braking system  18  is activated, the control system  142  commands the actuators  166  to move the doors  164  to an open position, thus allowing airflow F to enter into the inlets  130  of the branches  160 . The airflow F entering the conduit  122  eventually passes through the turbine  124 , thus exerting a force on the turbine  124  which arrests movement of the vehicle  10  via increased drag. In addition, the energy extracted from the airflow F by the rotor  138  may be used to generate electricity within the electrical generator  126 . The control system  142  commands the actuators  166  to move the doors  164  to a closed position, thus closing off the inlets  130 , once the friction braking system  18  has been deactivated. 
       FIG. 4  illustrates yet another exemplary regenerative air brake system  220 . In a non-limiting embodiment, the regenerative air brake system  220  includes a conduit  222 , a turbine  224 , and an electrical generator  226 . The conduit  222  is positioned inside a vehicle body  28  of the vehicle  10  and includes multiple branches  260  that direct the airflow F toward the turbine  224 . Each branch  260  includes an inlet for directing the airflow F into the conduit  222 . In a non-limiting embodiment, a first inlet  230 A is positioned at a front of the vehicle body  28 , a second inlet  230 B is positioned near a first wheel well  262 A of the vehicle body  28 , and a third inlet  230 C is positioned near a second wheel well  262 B of the vehicle body  28 . A door  264  may be selectively moved to open or close at least the second inlet  230 B and the third inlet  230 C, in a further non-limiting embodiment. 
     The conduit  222  further includes an outlet  232 . The airflow F may be expelled from the conduit  222  through the outlet  232  after energy has been extracted from the airflow F by the turbine  224 . In a non-limiting embodiment, the outlet  232  is disposed at a rear of the vehicle body  28 . However, other outlet locations are also contemplated. 
     Airflow F entering into each branch  260  mixes with airflow F from other branches at a junction  268  prior to passing to the turbine  224 . A stator  236  of the turbine  224  controls the speed and direction of the airflow F, and the rotor  238  rotates to extract energy from the airflow F. The energy extracted from the airflow F by the rotor  238  drives the electrical generator  226  for generating electricity. 
     A control system  242  is adapted to activate/deactivate the regenerative air brake system  220 . In a non-limiting embodiment, the control system  242  activates the regenerative air brake system  220  if the friction braking system  18  (see  FIG. 1 ) of the vehicle  10  has been activated and deactivates the regenerative air brake system  220  if the friction braking system  18  has been deactivated. 
       FIG. 5 , with continued reference to  FIGS. 1-4 , schematically illustrates a control strategy  300  for determining whether to activate the regenerative air brake system  20 . Although the exemplary control strategy  300  is described with reference to the air brake system  20  of  FIG. 2 , it is equally applicable to the regenerative air brake systems  120 ,  220  of  FIGS. 3 and 4 , respectively. In a non-limiting embodiment, the control system  42  of the regenerative air brake system  20  is programmed with one or more algorithms adapted to execute the exemplary control strategy  300 , or any other control strategy. In another non-limiting embodiment, the control strategy  300  is stored as executable instructions in the non-transitory memory  48  of the control module  44  of the control system  42 . 
     The control strategy  300  begins at block  302 . At block  304 , the control strategy  300  determines whether a braking event, or vehicle deceleration, has been requested. Braking events occur when the friction braking system  18  has been actuated to begin decelerating the vehicle  10 . In a non-limiting embodiment, the control system  42  of the regenerative air brake system  20  detects the braking event by analyzing the pedal position signal S 1  received from the brake pedal  50 . The brake pedal  50  thus directly controls activation of the friction braking system  18  and indirectly controls activation of the regenerative air brake system  20 . 
     The control strategy  300  proceeds to block  306  if a braking event has been detected at block  304 . At this block, the control system  42  may undertake a series of system analyses for determining whether or not to activate the regenerative air brake system  20 . In a first non-limiting embodiment, the control system  42  compares a requested deceleration rate, which can be derived from the pedal position signal S 1 , to a threshold deceleration rate to determine whether to activate the regenerative air brake system  20 . In another non-limiting embodiment, the control system  42  compares a current vehicle speed to a threshold vehicle speed to determine whether to activate the regenerative air brake system  20 . In yet another non-limiting embodiment, the control system  42  estimates an amount of airflow F passing through the conduit  22  to determine whether to activate the regenerative air brake system  20 . The amount of airflow F passing through the conduit  22  may be inferred based on feedback from a tachometer of the turbine  24 , based on feedback from pressure sensors positioned within the conduit  22  and which provide an estimate of the density of the airflow F, or based on inferred ambient temperatures which provide an estimate of the density of the airflow F. The control system  42  may analyze one or more of the deceleration rate, the current vehicle speed, and the estimate of the airflow F passing through the conduit  22  when determining whether or not to activate the regenerative air brake system  20 . 
     Based on the system analyses described above, the control strategy  300  determines whether the regenerative air brake system  20  would be effective to either assist in decelerating the vehicle  10  or to generate electricity at block  308 . If YES, the control strategy  300  activates the regenerative air brake system  20  at block  310 , and thus begins extracting energy from the airflow F with the rotor  38  of the turbine  24  to power the electrical generator  26 . As part of this activation, the control strategy  300  may also determine how much of the capacity (between 0% and 100%) of the regenerative air brake system  20  should be utilized. This determination may again be based on series of system analyses associated with block  306 . In a non-limiting embodiment, the capacity may be determined using one or more look-up tables stored in the non-transitory memory  48  of the control system  42 . 
     In further non-limiting embodiments, activation and deactivation of the regenerative air brake system  20  may be controlled as follows. The resistance provided by the regenerative air brake system  20  depends on the energy extracted from the airflow F, which is first extracted by the turbine  24  and then mechanically transferred to the electrical generator  26 . The resistance provided by the electrical generator  26 , which translates to the resistance to the airflow F by the turbine  24 , is directly related to the electrical current generated. Therefore, the regenerative air brake system  20  can be activated or deactivated by having the control system  42  modulate the generated current. While the regenerative air brake system  20  is deactivated, the electrical generator  26  is, in essence, disconnected, and the rotor  38  spins freely. Upon activation of the regenerative air brake system  20 , the control system  42  engages the electrical generator  26 , and as the current is generated the electrical generator  26 , and therefore the turbine  24 , will resist the airflow F and brake the vehicle  10  as it extracts energy from the airflow F. 
     In a first non-limiting embodiment, the control system  42  uses a form of signal modulation to regulate the current produced by the electrical generator  26 . The control system  42  thus may vary the proportion of braking capacity that is requested from the regenerative air brake system  20  from 0% to 100%. The signal modulation strategy may utilize electrical relays, such as a pulse-width modulation methodology. In another non-limiting embodiment, the control system  42  uses an electrical relay to connect and disconnect the electrical generator  26  in accordance with activation and deactivation of the regenerative air brake system  20 . In yet another non-limiting embodiment, the turbine  24  and the electrical generator  26  may be mechanically connected and disconnected in accordance with the activation and deactivation of the regenerative air brake system  20 . Various mechanical components such as clutches, gears, etc. may be used to mechanically connect and disconnect the electrical generator  26 . 
     The regenerative air brake system  20  is deactivated during non-braking events. Once deactivated, the control strategy  300  may return to block  302 . 
     The regenerative air brake systems of this disclosure reduce the load on the vehicle&#39;s friction braking system and increase the amount of energy that can be reclaimed during vehicle decelerations. The energy reclaimed during the braking events helps compensate for energy that is otherwise lost to the environment (e.g., as waste heat) as the vehicle decelerates. The regenerative air brake systems are especially effective at high speeds when sudden deceleration is necessary. 
     Although the different non-limiting embodiments are illustrated as having specific components or steps, the embodiments of this disclosure are not limited to those particular combinations. It is possible to use some of the components or features from any of the non-limiting embodiments in combination with features or components from any of the other non-limiting embodiments. 
     It should be understood that like reference numerals identify corresponding or similar elements throughout the several drawings. It should be understood that although a particular component arrangement is disclosed and illustrated in these exemplary embodiments, other arrangements could also benefit from the teachings of this disclosure. 
     The foregoing description shall be interpreted as illustrative and not in any limiting sense. A worker of ordinary skill in the art would understand that certain modifications could come within the scope of this disclosure. For these reasons, the following claims should be studied to determine the true scope and content of this disclosure.