Patent Publication Number: US-2023140511-A1

Title: Park pawl control with redundant power sources for e-securement systems for battery electric vehicles

Description:
FIELD 
     The present application generally relates to battery electric vehicles (BEVs) and, more particularly, to techniques for park pawl control with redundant power sources for electronic securement (e-securement) for BEVs. 
     BACKGROUND 
     A park pawl system comprises a park pawl that is selectively engaged/disengaged (e.g., to a toothed wheel) to physically lockup a driveline of a vehicle. In battery electric vehicles (BEVs), such as those including an electric drive module (EDM) for propulsion, park electronic securement (e-securement) can be a potential drivability issue. This may occur when the BEV is in drive/neutral/reverse and there is an electrical system malfunction that prevents the park pawl system from being controlled. Conventional solutions to this problem include the addition of excess hardware, such as additional electric motor(s) and spring loads, but this could significantly increase costs and cause packaging/weight issues and reduce reliability and longevity, which could be particularly problematic for lighter weight BEVs with less powerful propulsion systems. Accordingly, while such conventional park e-securement systems do work well for their intended purpose, there exists an opportunity for improvement in the relevant art. 
     SUMMARY 
     According to one example aspect of the invention, a park electronic securement (e-securement) system for a battery electric vehicle (BEV) is presented. In one exemplary implementation, the system comprises an electrical vehicle control unit (EVCU) configured to control operation of the BEV and comprising a power inverter module (PIM) for command of a park pawl system of the BEV, an electrical system comprising (i) a high voltage battery configured to power one or more electric motors of the BEV, (ii) a DC-DC converter configured to step-down a voltage of the high voltage battery to a redundant power source voltage, and (iii) a low voltage battery configured to power at least the EVCU, and a connection between the EVCU and the park pawl system, wherein the EVCU is configured to when there is at least one of a plurality of malfunctions of the electrical system, receive power from the redundant power source voltage and command either the park pawl system or an electric park brake to transition the BEV to a park state, and when there are none of the plurality of malfunctions of the electrical system, receive power from the low voltage battery for control of the park pawl system to transition the BEV to the park state when requested. 
     In some implementations, the EVCU is configured to command the electric park brake to transition the BEV to the park state when one of the plurality of electrical system malfunctions is present indicating the connection between the EVCU and the park pawl system is open or broken. In some implementations, the EVCU is configured to control the PIM to command the park pawl system to transition the BEV to the park state when one of the plurality of electrical system malfunctions is present indicating a ground short at the connection between the EVCU and the park pawl system. In some implementations, the EVCU is configured to control the PIM to command to the park pawl system to transition the BEV to the park state when one of the plurality of electrical system malfunctions is present indicating a ground short of the entire BEV. In some implementations, the connection comprises an H-bridge between the EVCU and the park pawl system, the H-bridge comprising four metal-oxide semiconductor field-effect transistors (MOSFETs). In some implementations, the system further comprises an isolating fuse between the first and second bridges. In some implementations, the isolating fuse is an approximately 200 ampere fuse. In some implementations, the redundant power source voltage and a voltage of the low voltage battery are each approximately 12 volts. 
     According to another example aspect of the invention, a park electronic securement (e-securement) method for a battery electric vehicle (BEV) is presented. In one exemplary implementation, the method comprises providing an electrical vehicle control unit (EVCU) configured to control operation of the BEV and comprising a power inverter module (PIM) for command of a park pawl system of the BEV, providing an electrical system comprising (i) a high voltage battery configured to power one or more electric motors of the BEV, (ii) a DC-DC converter configured to step-down a voltage of the high voltage battery to a redundant power source voltage, and (iii) a low voltage battery configured to power at least the EVCU, providing a connection between the EVCU and the park pawl system, detecting, by the EVCU, whether at least one of a plurality of malfunctions of the electrical system are present, when there is at least one of a plurality of malfunctions of the electrical system, receiving, by the EVCU, power from the redundant power source voltage and commanding, by the EVCU, either the park pawl system, via the PIM, or an electric park brake to transition the BEV to a park state, and when there are none of the plurality of malfunctions of the electrical system, receiving, by the EVCU, power from the low voltage battery for controlling, by the EVCU of the park pawl system to transition the BEV to the park state when requested. 
     In some implementations, the method further comprises commanding, by the EVCU, the electric park brake to transition the BEV to the park state when one of the plurality of electrical system malfunctions is present indicating the connection between the EVCU and the park pawl system is open or broken. In some implementations, the method further comprises commanding, by the EVCU via the PIM, the park pawl system to transition the BEV to the park state when one of the plurality of electrical system malfunctions is present indicating a ground short at the connection between the EVCU and the park pawl system. In some implementations, the method further comprises commanding, by the EVCU via the PIM, the park pawl system to transition the BEV to the park state when one of the plurality of electrical system malfunctions is present indicating a ground short of the entire BEV. In some implementations, the connection comprises an H-bridge between the EVCU and the park pawl system, the H-bridge comprising four metal-oxide semiconductor field-effect transistors (MOSFETs). In some implementations, the method further comprises providing an isolating fuse between the first and second bridges. In some implementations, the isolating fuse is an approximately 200 ampere fuse. In some implementations, the redundant power source voltage and a voltage of the low voltage battery are each approximately 12 volts. 
     Further areas of applicability of the teachings of the present application will become apparent from the detailed description, claims and the drawings provided hereinafter, wherein like reference numerals refer to like features throughout the several views of the drawings. It should be understood that the detailed description, including disclosed embodiments and drawings referenced therein, are merely exemplary in nature intended for purposes of illustration only and are not intended to limit the scope of the present disclosure, its application or uses. Thus, variations that do not depart from the gist of the present application are intended to be within the scope of the present application. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    is a functional block diagram of a battery electric vehicle (BEV) comprising an example park electronic securement (e-securement) system according to the principles of the present application; 
         FIGS.  2 A- 2 B  are electrical diagrams of two different architectures for the example park e-securement system of  FIG.  1    according to the principles of the present application; and 
         FIG.  3    is a flow diagram of an example park e-securement method for a BEV capable of operation during a plurality of different electrical system malfunctions according to the principles of the present application. 
     
    
    
     DESCRIPTION 
     As previously mentioned, park electronic securement (e-securement) issues could potentially occur when a battery electric vehicle (BEV) is in drive/neutral/reverse and there is an electrical system malfunction that prevents a park pawl system from being controlled. Conventional solutions to this problem include the addition of excess hardware, such as additional electric motor(s) and spring loads, but this could drastically increase costs and causes packaging/weight issues, which could be particularly problematic for lighter weight BEVs with less powerful propulsion systems. 
     Accordingly, improved park e-securement systems and methods are presented. In a first embodiment, a park e-securement system provides for park e-securement via the park pawl system or a separate electric park brake (EPB) during a plurality of different electrical system malfunctions. In this first embodiment, this is achieved with no additional hardware by stepping-down a voltage from the high voltage battery of the BEV using its direct current to direct current (DC-DC) converter, thereby providing a redundant power source voltage (e.g., in place of the low voltage battery of the BEV) at no additional costs. In a second embodiment, this is achieved with a separate low voltage backup battery and battery charger at slightly increased costs and packaging size/weight. 
     Referring now to  FIG.  1   , a functional block diagram of a BEV  100  having an example park e-securement system according to the principles of the present application is illustrated. The BEV  100  generally comprises an electrified powertrain  104  configured to generate (via an electric drive module, or EDM) drive torque to a driveline  108  for propulsion. It will be appreciated that the electrified powertrain  104  could have other suitable configurations. The electrified powertrain  104  generally comprises one or more electric motors  112 , a high voltage battery system  116  for powering the electric motor(s)  112 , and a DC-DC converter  120 . While the DC-DC converter  120  is generally shown as part of the electrified powertrain  104 , it will be appreciated that the DC-DC converter  120  could be located separately from the electrified powertrain  104 . An electrified vehicle control unit (EVCU)  124  is configured to control operation of the BEV  100 . 
     One primary control aspect of the EVCU  124  is to control the electrified powertrain  104  to generate a desired amount of drive torque to meet a driver demand (e.g., input via an accelerator pedal). The EVCU  124  is typically powered by a low voltage battery  128 , which could also be utilized to power one or more accessory loads  132  of the BEV  100 . Another control aspect of the EVCU  124  is that it comprises a power inverter module (PIM)  136  (e.g., switches/relays for generating control signal(s)) for command of a park pawl system  140  of the BEV  100 . 
     In one exemplary implementation, the park pawl system  140  comprises an actuator (e.g., an electric motor) that, in response to signal(s) generated by the PIM  136  to drive a threaded spindle (e.g., supported by a ball bearing) on which a threaded nut is mounted, and the threaded nut is rotationally fixed by a sleeve and moves in a direction of the actuator and releases a cone that is pre-loaded by a compression spring, and the cone pushes a park pawl thereby rotating it around a pin towards a park lock wheel (e.g., a toothed wheel) to lockup the driveline  108  and transition the BEV  100  to a “park state” (fully stopped and e-secured). 
     The high voltage battery  116 , the DC-DC converter  120 , and the low voltage battery  128  are also generally referred to as an electrical system  148  of the BEV  100 . For example, the electrical system  148  could comprise the high and low voltage buses connected to these devices with the DC-DC converter  120  operating therebetween. There are a plurality of different electrical system malfunctions that could occur in the BEV  100 , which will now be described in greater detail. In some of these malfunction scenarios, the park pawl system  140  may be unable to be adequately controlled/commanded by the EVCU  124 . In these cases, as will be described more fully below, the EVCU  124  could actuate a separate electric park brake  144  via a brake system module (BSM)  148  that applies braking force to stop the driveline  108  (but does not physically lock it up like the park pawl system  140 ). For this reason, the e-securement systems and methods of the present application could be limited to lighter weight BEVs where the maximum weight (BEV+maximum expected load, or a “worst-case” scenario) would be able to be held stationary by the electric park brake  144 , even on a steep grade/hill. For heavier BEV applications, the electric park brake  144  alone could be insufficient for this. 
     Referring now to  FIGS.  2 A- 2 B , electrical diagrams of two different architectures  200 ,  250  for the example park e-securement system of  FIG.  1    according to the principles of the present application are illustrated. In  FIG.  2 A , there is no additional hardware required as previously described. This architecture  200  comprises a park pawl H-bridge  204  including four metal-oxide semiconductor field-effect transistors (MOSFETs)  208  (e.g., N-type MOSFETs) that connect between the park pawl system  140  and two half-bridges bridges of the EVCU  124 . In one exemplary implementation, the park pawn H-bridge is configured to allow for separate or isolated powering of the park pawl system  140  during the various malfunction scenarios described herein. An isolating fuse  212  (e.g., ˜200 amperes) is disposed between these two bridges external to the EVCU  124  (e.g., in a power distribution center, or PDC) for electrical isolation. As previously discussed, there are a plurality of different electrical system malfunctions that could occur, which will now be discussed in greater detail. 
     In a first example malfunction, an open or broken connection  216  between the EVCU  124  and the park pawl system  140  occurs. During this malfunction, the BEV  100  is still capable of continued driving, but the park pawl system  140  would otherwise not be engaged once the BEV  100  is stopped. Because this connection  216  is open or broken, no reliable communication to the park pawl system  140  is achievable. Thus, the EVCU  124  in this malfunction scenario would command the electric park brake  144  to engage for park e-securement. 
     In a second example malfunction, there is a short (e.g., 12 volts to ground) at or near the connection  216 , thereby resulting in the EVCU  124  losing power if only the low voltage battery  128  were present and cause the BEV  100  to lose propulsion as no power is fed to EVCU  124  and the BEV  100  would coast down. The park pawl system  140  also would not get engaged once the BEV  100  is stopped, and there again would be no reliable form of securement because the EVCU  124  (with no power) would be unable to control the park pawl system  140 . However, the redundant power source voltage from the DC-DC converter  120  is able to keep the EVCU  124  powered and functional for park e-securement. 
     In a third example malfunction, there is a short (e.g., 12 volts to ground) in the whole BEV  100 , during which the park e-securement system will still maintain functionality via the redundant power source voltage as described with respect to the second example malfunction scenario. In the architecture  250  of  FIG.  2 B , in contrast to  FIG.  2 A , there is some additional hardware required—a low voltage backup battery  262 , two fuses  266 , and a backup battery charger  270 . This architecture  250  will function the same way as the architecture  200  of  FIG.  2 A  with respect to the various example electrical system malfunction scenarios described above (e.g., open/broken connection  266  or other 12 volt to ground short), but at the cost of slightly increased costs (due to additional hardware) and packaging/weight. 
     In the illustrated architecture  250 , the park pawl H-bridge  254  comprises diodes  258   a ,  258   b  for the two bridges as the currents are lesser compared to the architecture of  FIG.  2 A . The DC-DC converter  120  is able to provide electrical energy to power the backup battery charger  270  to keep the low voltage backup battery  262  charged, which provides power to the H-bridge  254  via two fuses  266 . As previously discussed, the increased cost and packaging size/weight could be undesirable, particularly for compact lighter weight BEVs. 
     Referring now to  FIG.  3   , an example park e-securement method  300  for a BEV capable of operation during a plurality of different electrical system malfunctions according to the principles of the present application is illustrated. While the BEV  100  and its components are specifically referenced for illustrative/descriptive purposes, it will be appreciated that the method  300  could be applicable to any suitable BEV. At  304 , the EVCU  124  comprising the PIM  136  for control of the park pawl system  140  is provided. At  308 , the electrical system  148  comprising (i) the high voltage battery  116 , (ii) the DC-DC converter  120 , and (iii) the low voltage battery  128  is provided. At  312 , the connection  216 / 266  between the EVCU  124  and the park pawl system  140  is provided. 
     At  316 , a determination is made whether at least one of the plurality of malfunctions of the electrical system  148  are present. When false, the method  300  proceeds to  320  where normal control of the park pawl system  140  continues (e.g., because there is no 12 volt power loss from the low voltage battery  128 ) and the method  300  ends. When true, at  324  a determination is made whether the malfunction(s) include an open/broken connection  216 / 266 . When true, the method  300  proceeds to  328  where the EVCU  124 , powered by the redundant power source voltage from the DC-DC converter  120 , commands the electric park brake  144  to engage thereby stopping the BEV  100  for park e-securement and the method  300  ends. When false, the method  300  proceeds to  332  where the EVCU, again powered by the redundant power source voltage from the DC-DC converter  120 , commands (via the PIM  136 ) the park pawl system  140  to engage thereby stopping the BEV  100  for park e-securement and the method  300  ends. 
     It will be appreciated that the term “controller” as used herein refers to any suitable control device or set of multiple control devices that is/are configured to perform at least a portion of the techniques of the present application. Non-limiting examples include an application-specific integrated circuit (ASIC), one or more processors and a non-transitory memory having instructions stored thereon that, when executed by the one or more processors, cause the controller to perform a set of operations corresponding to at least a portion of the techniques of the present application. The one or more processors could be either a single processor or two or more processors operating in a parallel or distributed architecture. 
     It should also be understood that the mixing and matching of features, elements, methodologies and/or functions between various examples may be expressly contemplated herein so that one skilled in the art would appreciate from the present teachings that features, elements and/or functions of one example may be incorporated into another example as appropriate, unless described otherwise above.