Abstract:
A control system includes an auto-stop module, an auto-start module, and a starter module. The auto-stop module stops an engine when a brake pedal position is greater than a threshold position and a transmission is in a drive gear. The auto-start module starts the engine when the brake pedal position is less than a minimum position and the engine stop is initiated. When the engine start is initiated and an engine speed is greater than zero, the starter module engages a pinion gear of a starter with a ring gear of an engine by reciprocally actuating the pinion gear N times between a retracted position and an extended position, wherein N is an integer greater than two.

Description:
FIELD 
       [0001]    The present disclosure relates to a gear engagement control system and method for engaging gears rotating at different speeds. 
       BACKGROUND 
       [0002]    The background description provided herein is for the purpose of generally presenting the context of the disclosure. Work of the presently named inventors, to the extent it is described in this background section, as well as aspects of the description that may not otherwise qualify as prior art at the time of filing, are neither expressly nor impliedly admitted as prior art against the present disclosure. 
         [0003]    Hybrid propulsion systems typically include a first torque generator, such as an internal combustion engine (ICE), and a second torque generator, such as an electric machine (EM). Each can provide torque to a driveline to propel a vehicle. Various configurations of hybrid powertrains can be used, including a strong hybrid powertrain, a mild hybrid powertrain and/or other hybrid types. In a strong hybrid powertrain, the EM can drive the driveline directly, without transferring torque through a component of the ICE. 
         [0004]    In a mild hybrid configuration, the EM is coupled with the ICE, such as through the front end accessory drive. Torque generated by the EM is transferred to the driveline through the ICE. An exemplary mild hybrid powertrain includes a belt alternator starter (BAS) system. In the BAS system, the EM is coupled to the ICE via a traditional belt and pulley configuration, which drives other accessory components including, but not limited to, pumps and compressors. 
         [0005]    When coupled together, these technologies are capable of providing further fuel savings. One efficiency improvement included in hybrid propulsion systems is the engine start-stop function. During periods when a conventional engine would be idling, the hybrid system stops the engine to increase fuel savings. When the system senses that the driver is about to request the vehicle to accelerate, the hybrid system restarts the engine and may assist the engine in the subsequent vehicle acceleration. 
       SUMMARY 
       [0006]    A control system includes an auto-stop module, an auto-start module, and a starter module. The auto-stop module stops an engine when a brake pedal position is greater than a threshold position and a transmission is in a drive gear. The auto-start module starts the engine when the brake pedal position is less than a minimum position and the engine stop is initiated. When the engine start is initiated and an engine speed is greater than zero, the starter module engages a pinion gear of a starter with a ring gear of an engine by reciprocally actuating the pinion gear N times between a retracted position and an extended position, wherein N is an integer greater than two. 
         [0007]    A method includes initiating rotation of a first gear and engaging the first gear with a second gear rotating at a different speed by reciprocally actuating the first gear N times between a retracted position and an extended position, wherein N is an integer greater than two. 
         [0008]    In still other features, the systems and methods described above are implemented by a computer program executed by one or more processors. The computer program can reside on a tangible computer readable medium such as but not limited to memory, nonvolatile data storage, and/or other suitable tangible storage mediums. 
         [0009]    Further areas of applicability of the present disclosure will become apparent from the detailed description provided hereinafter. It should be understood that the detailed description and specific examples are intended for purposes of illustration only and are not intended to limit the scope of the disclosure. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0010]    The present disclosure will become more fully understood from the detailed description and the accompanying drawings, wherein: 
           [0011]      FIG. 1  is a functional block diagram illustrating an exemplary vehicle system according to the present disclosure; 
           [0012]      FIG. 2  is a functional block diagram illustrating an exemplary engine control system according to the present disclosure; and 
           [0013]      FIG. 3  is a flow diagram illustrating an exemplary method for controlling an engine system according to the present disclosure. 
       
    
    
     DETAILED DESCRIPTION 
       [0014]    The following description is merely exemplary in nature and is in no way intended to limit the disclosure, its application, or uses. For purposes of clarity, the same reference numbers will be used in the drawings to identify similar elements. As used herein, the phrase at least one of A, B, and C should be construed to mean a logical (A or B or C), using a non-exclusive logical or. It should be understood that steps within a method may be executed in different order without altering the principles of the present disclosure. 
         [0015]    As used herein, the term module refers to an Application Specific Integrated Circuit (ASIC), an electronic circuit, a processor (shared, dedicated, or group) and memory that execute one or more software or firmware programs, a combinational logic circuit, and/or other suitable components that provide the described functionality. 
         [0016]    As discussed above, a hybrid propulsion system may include an engine stop-start function that stops an engine during conventional engine idle periods and restarts the engine when a driver is about to request acceleration. A gear engagement control system and method of the present disclosure enables both hybrid and non-hybrid propulsion systems to restart a moving engine using a conventional starter. A pinion gear of the starter is actuated between retracted and extended positions in a quick dithering or pulsed sequence. At the same time, rotation of the pinion gear may be initiated by activating a motor in the starter. Actuating the pinion gear when initiating rotation of the pinion gear simulates spring loading the pinion gear to prevent gear teeth collision. 
         [0017]    Conventional propulsion systems crank an engine using a starter by actuating a pinion gear of the starter from a retracted position to an extended position and then maintaining the pinion gear in the extended position. In such systems, mechanical modifications to the starter may be necessary in order to avoid gear teeth collisions. These modifications may include beveling the gear teeth to provide angled surfaces for meshing teeth to readily slide into engagement, spring loading the pinion gear along a line of centers between the pinion gear and a ring gear of the engine, and clutching the pinion gear and ring gears to control and reduce the relative velocities of the gears. 
         [0018]    The gear engagement techniques of the present disclosure enable restarting an engine using a conventional starter without costly modifications. More generally, these techniques enable engagement between any electronically-actuated gear and another gear rotating at a different speed. 
         [0019]    Referring now to  FIG. 1 , an exemplary vehicle system  10  according to the present disclosure is shown. The vehicle system  10  includes a powertrain  12  controlled by a control module  14 . The powertrain  12  includes a powerplant  16  that produces drive torque that is transmitted through a transmission  18  to a drivetrain  20  to drive wheels  22  of the vehicle. The powerplant  16  may be a hybrid powerplant that includes a hybrid drive system  24  coupled with an internal combustion engine  26  that is engaged with a starter  28 . As such, drive torque may be supplied by the hybrid drive system  24 , the engine  26 , or a combination thereof. Alternatively, the powerplant  16  may not include the hybrid drive system  24  and drive torque may be supplied by the engine  26 . 
         [0020]    A starter  28  may be selectively engaged with the engine  26 . The starter  28  is operable to supply torque to crank and thereby start the engine  26 . One or more components of the starter  28  may be disengaged from the engine  26  while the engine  26  is running. 
         [0021]    The control module  14  controls operation of various components of the powertrain  12  including, but not limited to, the powerplant  16  and the transmission  18 . The control module  14  may control the operation based on inputs received from various sensors, as discussed herein. The control module  14  may control the drive torque produced by the powerplant  16  based on sensors that monitor one or more driver interface devices. 
         [0022]    The vehicle operator may manipulate a brake pedal  30  to regulate vehicle braking. In turn, a brake position sensor  32  may generate a brake pedal position signal that is communicated to the control module  14 . The brake pedal position signal may indicate a brake pedal position that increases as braking increases. The control module  14  may generate a brake control signal based on the brake pedal position signal. A brake system (not shown) may adjust braking based on the brake control signal to regulate vehicle speed. 
         [0023]    The vehicle operator may manipulate a gear lever  34  to select a gear (not shown) of the transmission  18 . In turn, a gear selection sensor  36  may generate a gear selection signal that is communicated to the control module  14 . The gear selection signal may indicate a gear (e.g., park, reverse, neutral, drive, low, high) of the transmission  18  that is selected by the vehicle operator. The control module  14  may generate a gear control signal based on the gear selection signal. The transmission  18  adjusts the gear selected based on the gear control signal to regulate transmission gear shifting. 
         [0024]    The control module  14  may implement the gear engagement techniques of the present disclosure. The starter  28  may be a conventional starter and the control module  14  may execute an engine stop-start function. The control module  14  may stop the engine  26  during conventional engine idle periods and restart the engine  26  when a driver is about to request acceleration. When restarting the engine  26  at engine speeds greater than zero, the control module  14  may engage a pinion gear of the starter  28  with a ring gear of the engine  26  by actuating the pinion gear between retracted and extended positions in a quick dithering or pulsed sequence. Actuating the pinion gear in this manner causes the pinion gear to behave as though the pinion gear were spring-loaded along a line of centers between the pinion gear and the ring gear. 
         [0025]    Referring now to  FIG. 2 , the engine  26  may be one of several configurations including, but not limited to, the reciprocating type as discussed herein. The engine  26  produces drive torque by combusting a mixture of air and fuel in cylinders (not shown). Air may be drawn into the engine  26  through a throttle (not shown) that controls the amount of air entering the engine  26 . Fuel may be supplied by a fuel system (not shown) that controls the amount of fuel supplied to the cylinders. The air-fuel mixture may be ignited by a spark ignition system (not shown), providing combustion that supplies energy to the cylinders. 
         [0026]    Pistons (not shown) may reciprocate within the cylinders in response to the combustion and transmit drive torque to a crankshaft  38 . The crankshaft  38  rotates in response to the drive torque and may transmit the drive torque to the transmission  18  of  FIG. 1 . A crankshaft position sensor (CPS)  40  may sense rotation of the crankshaft  38  and generate a crankshaft position sensor signal in response to the rotation of the crankshaft  38 . 
         [0027]    The starter  28  may include a motor/actuator assembly  42  connected to the crankshaft  38  by a gear train  44 . The motor/actuator assembly  42  may include a motor  46  and an actuator  48 . The motor  46  may supply torque that is transmitted to the crankshaft  38  via the gear train  44 . The actuator  48  may control whether the torque generated by the motor  46  is transmitted to the crankshaft  38 . In various configurations, discussed in further detail below, the actuator  48  may be operable to selectively couple the motor  46  and one or more components of the gear train  44  with the crankshaft  38 . 
         [0028]    The gear train  44  may include a driven member  50  and a driving member  52 . The driven member  50  may be fixed to rotate with the crankshaft  38  and may be rotatably driven by the driving member  52 . The driving member  52  may be coupled to the motor/actuator assembly  42  and may be configured to be engaged and disengaged with the driven member  50  at engine speeds of zero and above. In this regard, the driven member  50  may be a ring gear of the engine  26  and the driving member  52  may be a pinion gear of the starter  28 . 
         [0029]    When engaged with the driven member  50 , the driving member  52  may transmit the torque supplied by the motor/actuator assembly  42  to the driven member  50 . The actuator  48  may provide for the engagement and disengagement between the driven and driving members  50 ,  52 . The motor/actuator assembly  42  may be activated to provide for the engagement of the driven and driving members  50 ,  52  and may be deactivated to provide for the disengagement of the driven and driving members  50 ,  52 . 
         [0030]    The motor/actuator assembly  42  and the gear train  44  may be arranged in ring and gear configuration. In this configuration, the driven member  50  may include a flywheel of the engine  26  having a ring gear and the driving member  52  may include a pinion gear of the starter  28  that meshes with the ring gear. The pinion gear may be a retractable pinion gear that meshes with the ring gear when extended and disengages from the ring gear when retracted. In such an arrangement, the actuator  48  of the motor/actuator assembly  42  may control the extension and retraction of the pinion gear. 
         [0031]    Referring still to  FIG. 2 , an exemplary implementation of the control module  14  in an exemplary engine control system  100  for the engine  26  is shown. The control module  14  may include a speed determination module  102 , an auto-stop module  104 , an auto-start module  106 , and a starter module  108 . The speed determination module  102  determines a rotational speed (RPM) of the engine  26 . The speed determination module  102  may determine the engine RPM based on the signal generated by a crankshaft position sensor  40 . 
         [0032]    The auto-stop module  104  may receive the brake pedal position signal from the brake position sensor  32  and may receive the gear selection signal from the gear selection sensor  36 . The auto-stop module  104  generates an auto-stop signal to automatically stop the engine  26  (i.e., stop the engine  26  without a manual engine shutdown) during conventional engine idle periods. The auto-stop module  104  may generate the auto-stop signal based on the brake pedal position signal and the gear selection signal. For example, the auto-stop module  104  may generate the auto-stop signal when the brake pedal position signal indicates that the brake pedal position is greater than a threshold position and the gear selection signal indicates that the selected gear is drive. In addition, the auto-stop signal may be generated when a vehicle speed is zero. 
         [0033]    The auto-start module  106  may receive the brake pedal position signal from the brake position sensor  32  and may receive the auto-stop signal from the auto-stop module  104 . The auto-start module  106  generates an auto-start signal to automatically start the engine  26  (i.e., start the engine  26  without a manual engine startup) when a driver is about to request acceleration. 
         [0034]    The auto-start module  106  may generate the auto-start signal based on the brake pedal position signal and the auto-stop signal. For example, the auto-start module  106  may generate the auto-start signal when the brake pedal position signal indicates that the brake pedal position is less than a minimum position and the auto-stop signal indicates that an auto-stop is in progress. Alternatively, the auto-start module  106  may determine that an auto-stop is in progress based on the engine RPM determined by the speed determination module  102 . For example, the auto-start module  106  may determine that an auto-stop is in progress when the engine RPM is less than a predetermined engine run speed and the engine RPM is decreasing. 
         [0035]    The starter module  108  may receive the engine RPM from the speed determination module  102  and may receive the auto-start signal from the auto-start module  106 . The starter module  108  generates a starter activation signal that activates the starter  28  to crank and thereby start the engine  26 . The starter module  108  may generate the starter activation signal based on the engine RPM and the auto-start signal. For example, the starter module  108  may generate the starter activation signal when the engine RPM is greater than zero and the auto-start signal indicates that an auto-start has been initiated. In addition, the starter module  108  may generate the starter activation signal when the engine RPM is less than a maximum RPM. The maximum RPM may be predetermined (e.g., 400 RPM) such that the starter  28  is activated at low engine speeds to prevent damage to the driven and driving members  50 ,  52 . 
         [0036]    The starter activation signal may include a motor activation signal that initiates rotation of the motor  46  and an actuator activation signal that initiates actuation of the actuator  48 . The actuator activation signal may be varied to extend and retract the driving member  52 . For example, 12 and 0 volt signals may respectively extend and retract the driving member  52 . Rotation of the motor  46  may be initiated at the same time that actuation of the actuator  48  is initiated. Due to inertia, a starter motor response is typically almost one order of magnitude slower than a starter pinion response. Thus, initiating the motor  46  at the same time as initiating the actuator  48  may cause the driven and driving members  50 ,  52  to engage before the motor  46  begins to crank the engine  26 . 
         [0037]    The starter module  108  may vary the actuator activation signal to extend and retract the driving member  52  between a retracted position and an extended position. The extended position is a position in which the diving member  52  may engage the driven member  50 , and the retracted position is a position in which the diving member  52  is disengaged from the driven member  50 . The starter module  108  may actuate the driving member  52  from the retracted position to the extended position, from the extended position to the retracted position, and from the retracted position to the extended position. 
         [0038]    Alternatively, the starter module  108  may actuate the driving member  52  between the retracted and extended positions until the driven and driving members  50 ,  52  are engaged. The starter module  108  may determine that the driven and driving members  50 ,  52  are engaged based on an actuation position sensor (not shown) that detects a position of the driving member  52 . 
         [0039]    Whether the actuator activation signal actuates the driving member in a predetermined extended-retracted-extended sequence or in a retracted-extended sequence determined by engagement of the driven and driving members  50 ,  52 , thereafter the actuator activation signal may activate the starter  28  in a conventional continuous manner to crank and thereby start the engine  26 . The starter module  108  may stop generating the starter activation signal when the engine  26  is running. The starter module  108  may determine that the engine  26  is running when the engine RPM is greater than the predetermined engine run speed and the engine RPM is increasing. 
         [0040]    The starter activation signal may be a single activation signal that initiates rotation of the motor  46  and initiates actuation of the actuator  48 . The single activation signal may rotate the motor  46  and actuate the actuator  48  using either the predetermined extended-retracted-extended sequence or the retracted-extended sequence determined by engagement of the driven and driving members  50 ,  52 . Thereafter, the single activation signal may activate the starter  28  in a conventional continuous manner to crank and thereby start the engine  26 . The starter module  108  may stop generating the starter activation signal when the engine  26  is running. 
         [0041]    The actuator/single activation signals may actuate the actuator  48  between the retracted and extended positions at an actuation frequency. The actuation frequency may be predetermined to be different than a rotational frequency of the driven and driving members  50 ,  52  when engaged. For example, the actuation frequency may be higher than the rotational frequency. 
         [0042]    Referring now to  FIG. 3 , an exemplary method  200  for controlling the engine system  10  is shown. The method  200  may be implemented in one or more modules of the engine system  10 , such as the control module  14 , discussed above. For simplicity, the method  200  will be described with reference to the various components of the engine system  10 . 
         [0043]    At  202 , control activates the starter  28  in a conventional continuous manner to crank and thereby start the engine  26 . Control may activate the starter  28  in response to a request to start the engine  26 . During activation of the starter  28 , the starter  28  may engage the engine  26  and begin to supply torque to the engine  26  that increases engine speed. The control module  14  may continue to activate the starter  28  until the engine RPM increases above a predetermined engine run speed. The predetermined engine run speed may correspond to an engine RPM above which the engine  26  may continue to operate (i.e., run) on its own at startup without the continued assistance of the starter  28 . The predetermined engine run speed may be a function of one or more engine operating conditions such as, but not limited to, engine temperature. 
         [0044]    At  204 , control determines whether the engine  26  is running. Control proceeds to  206  when the engine  26  is running. Otherwise, control returns to  202  as shown. Control may determine whether the engine  26  is running by comparing the engine RPM and the predetermined engine run speed. For example, control may determine the engine  26  is running when the engine RPM is greater than the predetermined engine run speed and the engine RPM is increasing. 
         [0045]    At  206 , control determines whether a brake pedal position indicated by the brake position sensor  32  is greater than a threshold position and whether the selected gear indicated by the gear selection sensor  36  is drive. When the brake pedal position is greater than the threshold position and the selected gear is drive, indicating conventional engine idle conditions are present, control proceeds to  208 . At  208 , control initiates an auto-stop to automatically stop the engine  26 . Control proceeds to  210  when the auto-stop is in progress. 
         [0046]    At  210 , control determines whether the brake pedal position is less than a minimum position while the auto-stop is in progress. When the brake pedal position is less than the minimum position while the auto-stop is in progress, indicating acceleration is expected, control returns to  208 . Otherwise, control proceeds to  212 . At  212 , control initiates an auto-start to automatically start the engine  26 . Control proceeds to  214  when the auto-start is initiated. 
         [0047]    At  214 , control determines whether an engine speed is greater than zero when the auto-start is initiated. When the engine speed is greater than zero and the auto-start is initiated, control proceeds to  216  and  218 . Otherwise, control returns to  202  as shown. At  216 , control actuates the driving member  52  of the starter  28  between extended and retracted positions. Control may actuate the driving member  52  in an extended-retracted-extended sequence. Control may actuate the driving member  52  at an actuation frequency that is higher than a rotational frequency of the driven and driving members  50 ,  52  when engaged. At  218 , control initiates rotation of the motor  46  of the starter  28 . Control may perform  216  and  218  at the same time, and then may return to  202 . 
         [0048]    The broad teachings of the disclosure can be implemented in a variety of forms. Therefore, while this disclosure includes particular examples, the true scope of the disclosure should not be so limited since other modifications will become apparent to the skilled practitioner upon a study of the drawings, the specification, and the following claims.