Abstract:
A control device of an engine includes an adjustment mechanism and a controller. The adjustment mechanism is configured to adjust an intake air amount. The controller is configured to save a first learning value in a volatile storage medium, the first learning value being obtained by learning an operation amount of the adjustment mechanism when the engine is idle. The controller is configured to control the adjustment mechanism according to the first learning value. The controller is configured to save a second learning value in a non-volatile storage medium, the second learning value being equal to the first learning value. The controller is configured to correct the first learning value using the second learning value after the first learning value is cleared.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The present invention relates to a control device and a control method of an engine. 
         [0003]    2. Description of Related Art 
         [0004]    It is known that the intake air amount of an engine, mounted on a vehicle, is adjusted by the throttle valve. Continued use of an engine may form a deposit on the throttle valve, sometimes resulting in a decrease in the intake air amount even when the throttle angle remains the same. Meanwhile, technology has been developed to correct the throttle angle according to the number of engine stalls or the engine speed and to store the resulting learning value for preventing permanent performance degradation. 
         [0005]    The stored learning value may be cleared to the initial value, when the battery is removed or replaced for vehicle maintenance. In this case, if the throttle valve is replaced or cleaned, a desired air amount can be obtained sufficiently; however, if a deposit is remains formed on the throttle valve, the air intake amount will be insufficient. 
         [0006]    As one of the methods to avoid the insufficiency of the intake air amount, Japanese Patent Application Publication No. 2010-127212 (JP 2010-127212 A) discloses a method. According to this method, if the learning value is cleared, the throttle valve is controlled so that the insufficiency of the intake air amount can be avoided when the engine is started later. 
       SUMMARY OF THE INVENTION 
       [0007]    An increase in the throttle angle could avoid a stall but may result in an excessive engine speed. 
         [0008]    The present invention provides a control device and a control method of an engine that can maintain a proper intake air amount even after the learning value is cleared. 
         [0009]    According to a first aspect of the present invention, a control device of an engine includes an adjustment mechanism and a controller. The adjustment mechanism is configured to adjust an intake air amount. The controller is configured to save a first learning value in a volatile storage medium. The first learning value is obtained by learning an operation amount of the adjustment mechanism when the engine is idle. The controller is configured to control the adjustment mechanism according to the first learning value. The controller is configured to save a second learning value in a non-volatile storage medium. The second learning value is equal to the first learning value. The controller is configured to correct the first learning value using the second learning value after the learning value saved in the volatile storage medium is cleared. 
         [0010]    The second learning value stored in the non-volatile storage medium is not cleared even when the battery is removed and the power supply is stopped. Therefore, even when the first learning value stored in the volatile storage medium is cleared, the second learning value stored in the non-volatile storage medium can be used to operate the adjustment mechanism based on the operation amount obtained from the result of learning. Thus, the above configuration ensures an appropriate intake air amount even after the learning value is cleared. 
         [0011]    In the control device, the controller may be configured to stop updating of the second learning value after the first learning value is cleared. This allows the second learning value in the non-volatile storage medium to be maintained at the value before the first learning value in the volatile storage medium is cleared. 
         [0012]    In the control device, the controller may be configured to correct, the first learning value if, after the first learning value is cleared, the operation amount of the adjustment mechanism is an operation amount corresponding to an initial value of the first learning value and an output torque of the engine is smaller than a predetermined value. This allows the adjustment mechanism to be controlled suitably using the second learning value, obtained from the learning result, if the adjustment mechanism cannot be controlled properly by the first learning value that is initialized to the initial value. 
         [0013]    In the control device, the controller may be configured to correct the first learning value if, after the first learning value is cleared, the operation amount of the adjustment mechanism is an operation amount corresponding to an initial value of the first learning value and the engine is not be started. This allows the adjustment mechanism to be controlled suitably using the second learning value, obtained from the learning result, if the adjustment mechanism cannot be controlled properly by the first learning value that is initialized to the initial value. 
         [0014]    In the control device, the controller may be configured to correct the first learning value by adding a difference between the second learning value and the first learning value to the first learning value. This allows the cleared learning value to be returned to the first learning value before it is cleared. 
         [0015]    According to a second aspect of the present invention, a control method of an engine including an intake air amount adjustment mechanism, the control method includes: saving a first learning value in a volatile storage medium, the first learning value being obtained by learning an operation amount of the adjustment mechanism when the engine is idle; controlling the adjustment mechanism according to the first learning value; saving a second learning value in a non-volatile storage medium, the second learning value being equal to the first learning value; and correcting the first learning value using the second learning value after the first learning value is cleared. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0016]    Features, advantages, and technical and industrial significance of exemplary embodiments of the invention will be described below with reference to the accompanying drawings, in which like numerals denote like elements, and wherein: 
           [0017]      FIG. 1  is a general diagram showing a vehicle in an exemplary embodiment of the present invention; 
           [0018]      FIG. 2  is a collinear diagram showing the relation among the number of rotations established by a power split mechanism in the exemplary embodiment; 
           [0019]      FIG. 3  is a general diagram showing an engine in the exemplary embodiment: and 
           [0020]      FIG. 4  is a flowchart showing the processing executed by an EFI-ECU in the exemplary embodiment. 
       
    
    
     DETAILED DESCRIPTION OF EMBODIMENTS 
       [0021]    An exemplary, embodiment of the present invention is described below with reference to the drawings. In the description below, the like reference numeral is given to the like component. The components having the like reference numeral have the like name and the like function and, therefore, the repetitive description will not be given. 
         [0022]    Referring to  FIG. 1 , a vehicle includes an engine  10 , a first motor generator  11 , a second motor generator  12 , a power split mechanism  13 , a reduction gear,  14 , and a driving battery  15 . The power train of this vehicle includes the engine  10 , the first motor generator  11 , and the second motor generator  12 . 
         [0023]    The vehicle travels by the driving force from at least one of the engine  10  and the second motor generator  12 . 
         [0024]    The engine  10 , first motor generator  11 , and second motor generator  12  are connected via the power split mechanism  13 . The motive power generated by the engine  10  is divided into two paths by the power split mechanism  13 . One is a path for driving the wheels via the reduction gear  14 . The other is a path for generating electric power by driving the first motor generator  11 . 
         [0025]    The first motor generator  11  is a three-phase AC rotary electric machine that includes a U-phase coil, a V-phase coil, and a W-phase coil. The first motor generator  11  generates electricity by the motive power of the engine  10  divided by the power split mechanism  13 . The electric power generated by the first motor generator  11  is used for different purposes depending on the traveling state of the vehicle or the State Of Charge (SOC) of the driving battery  15 . For example, when the vehicle is traveling in the usual state, the electric power generated by the first motor generator  11  is used directly as the electric power for driving the second motor generator  12 . On the other hand, when the SOC of the driving battery  15  is lower than a predetermined value, the electric power generated by the first motor generator  11  is stored in the driving battery  15 . 
         [0026]    When starting the engine  10 , the first motor generator  11  functions as a motor and cranks the engine  10 . During cranking, the first motor generator  11  generates a torque to increase the engine speed. 
         [0027]    The second motor generator  12  is a three-phase AC rotary electric machine that includes a U-phase coil, a V-phase coil, and a W-phase coil. The second motor generator  12  is driven by at least one of the electric power stored in the driving battery  15  and the electric power generated by the first motor generator  11 . 
         [0028]    The driving force of the second motor generator  12  is transmitted to the wheels via the reduction gear  14 . In this manner, the second motor generator  12  assists the engine  10  in driving the vehicle or drives the vehicle by the driving force obtained from the second motor generator  12  itself. 
         [0029]    During the regenerative braking of the vehicle, the second motor generator  12 , which is driven by the wheels via the reduction gear  14 , operates as a generator. This allows the second motor generator  12  to operate as a regenerative brake that converts braking energy to electric power. The electric power generated by the second motor generator  12  is stored in the driving battery  15 . 
         [0030]    The power split mechanism  13  is composed of a planetary gear that includes a sun gear, a pinion gear, a carrier, and a ring gear. The pinion gear is engaged with the sun gear and the ring gear. The carrier supports the pinion gear so that it can rotate on its axis. The sun gear is coupled to the rotation axis of the first motor generator  11 . The carrier is coupled to the crankshaft of the engine  10 . The ring gear is coupled to the rotation axis of the second motor generator  12  and to the reduction gear  14 . 
         [0031]    The engine  10 , first motor generator  11 , and second motor generator  12  are coupled via the power split mechanism  13  composed of the planetary gear. This configuration establishes the relation of the number of rotations among the engine  10 , first motor generator  11 , and second motor generator  12  as shown by the straight line in the collinear diagram in  FIG. 2 . 
         [0032]    Returning to  FIG. 1 , the driving battery  15  is a battery pack composed of a plurality of cells. The driving battery  15  is composed of battery modules in each of which a plurality of cells are integrated. A plurality of battery modules are connected in series. An example of the driving battery  15  is a lithium ion battery. The voltage of the fully charged driving battery  15  is about 200V. 
         [0033]    In this exemplary embodiment, the engine  10  is controlled by an electronic fuel injection (EFI)-electronic control unit (ECU)  300 . The first motor generator  11  and the second motor generator  12  are controlled by a motor generator (MG)-ECU  400 . The EFI-ECU  300  and the MG-ECU  400  are connected to a powertrain manager (PM)-ECU  500  in such a way that two-way communication is possible. 
         [0034]    The PM-ECU  500  outputs a command signal to the EFI-ECU  300  about the target output and the target torque of the engine  10 . The PM-ECU  500  also outputs a command signal to the MG-ECU  400  about the generation power of the first motor generator  11  and the driving power of the second motor generator  12 . This means that the PM-ECU  500  regarded as a controller that integrally controls the power train of the vehicle. 
         [0035]    Referring to  FIG. 3 , the following describes the engine  10  more in detail. Although  FIG. 3  shows an inline four-cylinder gasoline engine, as the engine  10 , the present invention is not limited to such an engine this but is applicable to various types of engines such as a V6 engine or a V8 engine. 
         [0036]    The engine  10  is an internal combustion engine. As shown in  FIG. 3 , the engine  10  includes four cylinders  112 . Each cylinder  112  is connected to a common surge tank  30  via a corresponding intake manifold  20 . The surge tank  30  is connected to an air cleaner  50  via an air intake duct  40 . 
         [0037]    A throttle valve  70 , driven by an electric motor  60 , is provided in the air intake duct  40 . The throttle valve  70  is controlled so that the throttle angle TA is changed according to a change in the accelerator position. When the engine  10  is idle, the throttle angle is controlled by the idle speed control (ISC) so that the engine speed becomes equal to the target idling speed. The idle-time throttle angle TAISC is corrected according to the driving condition of the engine. 
         [0038]    For example, if the idle-time engine speed is lower than a threshold NE 1 , the idle-time throttle angle TAISC is corrected so that it is increased by a predetermined value. Conversely, if the idle-time engine speed is higher than a threshold NE 2 , the idle-time throttle angle TAISC is corrected so that it is decreased by a predetermined value. 
         [0039]    When the predetermined learning condition is satisfied, a first learning value EQG of the idle-time throttle angle TAISC, or the intake airflow rate learning value, is calculated. For example, if the idle-time throttle angle TAISC becomes higher than a threshold TAISC 1 , the first learning value EQG is increased by a predetermine value. Conversely, if the idle-time throttle angle TAISC becomes lower than a threshold TAISC 2 , the first learning value EQG is decreased by a predetermine value. The first learning value EQG is calculated in this manner. The method for correcting the idle-time throttle angle TAISC and the method for calculating the first learning value EQG are not limited to those described above. 
         [0040]    Each cylinder  112  is coupled to a common exhaust manifold  80 , which is coupled to a three-way catalyst converter  90 . For each cylinder  112 , a spark plug  110  and an injector  120 , which injects fuel into the intake port and/or the intake passage, are provided. The spark plug  110  and the injector  120  are controlled based on the output signal from the electronic fuel injection (EFI)-ECU  300 . 
         [0041]    Each injector  120  is connected to a delivery pipe  130 , which is connected to an electric-motor-driven fuel pump  150  via a fuel pressure regulator  140 . The fuel pressure regulator  140  is configured to return a part of the fuel, discharged from the fuel pump  150 , to a fuel tank  200  if the fuel pressure of the fuel, discharged from the fuel pump  150 , becomes higher than a predetermined fuel pressure setting. This configuration therefore prevents the pressure of the fuel, supplied to the injector  120 , from becoming higher than the fuel pressure setting. 
         [0042]    A pipe  210 , connected to the fuel pump  150 , is inserted in the fuel tank  200 . The fuel pump  150  sucks the fuel, stored in the fuel tank  200 , via the pipe  210 . The larger the number of rotations of the fuel pump  150  is, the larger the fuel suction amount of the fuel becomes. 
         [0043]    The EFI-ECU  300 , configured by a digital computer, includes a clock  310 , a read-only memory (ROM)  320 , a volatile random access memory (RAM)  330 , a non-volatile RAM  332 , and a central processing unit (CPU)  340 . 
         [0044]    The ROM  320  stores a program executed by the EFI-ECU  300 . The volatile RAM  330  stores, for example, the first learning value EQG of the idle-time throttle angle TAISC. The non-volatile RAM  332  stores, for example, a second learning value EQGDEP that is updated to a value equal to the first learning value EQG. Unless inhibited, the second learning value EQGDEP is updated at a regular interval so that its value becomes equal to the first learning value EQG. 
         [0045]    The CPU  340  executes the program stored in the ROM  320  and, using the values stored in the RAM  330  and the RAM  332 , controls the throttle angle TA and the fuel injection amount. 
         [0046]    In this exemplary embodiment, the EFI-ECU  300  is powered by an auxiliary battery  302 . Therefore, when the auxiliary battery  302  is removed for repairing the vehicle, the first learning value EQG, stored in the volatile RAM  330 , is cleared to the initial value. That is, the first learning value EQG is reset in such a case. On the, other′ hand, the second learning value EQGDEP stored in the non-volatile RAM  332  is not cleared. 
         [0047]    If the throttle valve  70  is replaced or cleaned when the first learning value EQG is cleared and, as a result, no deposit is formed on the throttle valve  70 , the intake air amount of the engine  10  may be suitable. 
         [0048]    In contrast, if the throttle valve  70  is neither replaced nor cleaned when the first learning value EQG is cleared and a deposit remains formed on the throttle valve  70 , the first learning value EQG, is returned to the initial value. This may results in the insufficient intake air amount of the engine  10 . In this exemplary, embodiment, the second learning value EQGDEP, stored in the non-volatile RAM  332 , is used to correct the first learning value EQG after it is cleared. 
         [0049]    Referring to  FIG. 4 , the following describes the processing executed by the EFI-ECU  300 . Note that the processing described below is executed repeatedly at a predetermined interval. Also note that the processing described below is executed after the engine  10  is started. 
         [0050]    In step  100  (hereinafter, step is abbreviated S), the EFI-ECU  300  determines whether the first learning value. EQG is cleared and whether a deposit is formed on the throttle valve  70  before the first learning value. EQG is cleared. For example, it is determined that the first learning value EQG is cleared and that a deposit is formed on the throttle valve  70  before the first learning value EQG, is cleared if the following four are satisfied: (1) the second learning value EQGDEP is larger than the initial value of the first learning value EQG, (2) the first learning value EQG is equal to or larger than the initial value of the first learning value EQG, (3) the learning of the throttle angle TAISC is not completed, and (4) the amount of the residual fuel is a predetermined value or larger. It is determined that the learning of the throttle angle TAISC is completed if the first learning value EQG is not changed for a predetermined time or longer. 
         [0051]    If the first learning value EQG is not cleared (NO in S 100 ) or if the first learning value EQG is cleared but a deposit is not formed′ on the throttle valve  70  before the first learning value EQG is cleared (NO in S 100 ), the second learning value EQGDEP is updated to the value equal to the first learning value EQG in S 102 . 
         [0052]    On the other hand, if the first learning value EQG is cleared and a deposit is formed on the throttle valve  70  before the first learning value EQG is cleared (YES in S 100 ), the update of the second learning value EQGDEP is inhibited in S 104 . After that, the correction amount of the first learning value EQG is calculated in S 106 . For example, the correction amount of the first learning value EQG is the difference between the second learning value EQGDEP and the first learning value EQG (second learning value EQGDEP−first learning value EQG). 
         [0053]    After that, in S 108 , the EFI-ECU  300  determines whether the intake air amount of the engine  10  is insufficient. At this time, because the first learning value EQG is cleared, the throttle angle TAISC is a value corresponding to the initial value of the first learning value EQG. That is, in controlling the throttle valve  70 , the throttle angle TAISC is determined based on the initial value of the first learning value EQG. 
         [0054]    For example, if the torque of the first motor generator  11  is a positive value (engine speed is increased) or if the actual torque of the engine  10  is smaller than a predetermined value, it is determined that the intake air amount is insufficient. The torque of the first motor generator  11 , if positive, indicates that the first motor generator  11  assists the engine  10  to maintain the engine speed of the engine  10  or to crank the engine  10  because the engine  10  cannot be started with the insufficient intake air amount. The actual torque of the engine  10  can be calculated from the throttle angle and the engine speed using the known technology. 
         [0055]    If the intake air amount is insufficient (YES in S 108 ) and, in addition, the intake air amount insufficiency time lasts a predetermine time or longer (YES in S 110 ), the correction amount calculated in S 106  as described above is added to the first learning value EQG in S 112 . The correction method of the first learning value EQG is not limited to this method. For example, the first learning value EQG may be corrected by increasing the value a predetermined amount at a time. If the intake air amount is insufficient, S 108  and S 110  are repeated until the intake air amount insufficiency time becomes a predetermined time or longer. 
         [0056]    If the intake air amount is insufficient even after the first learning value EQG is corrected (YES in S 114 ) and the intake air amount insufficiency time lasts a predetermined time or longer (YES in S 116 ), it is considered that a malfunction of the engine  10  is occurred due to a factor other than a deposit. In this case, the malfunction indicator lamp (not shown) is turned on in S 118 . It is possible to use two different malfunction indicator lamps, one for a case in which the torque of the first motor generator  11  is positive and the other for a case in which the actual torque of the engine  10  is lower than a predetermined value. If a sufficient intake air amount is reserved in S 108  and S 114 , the processing is once terminated. 
         [0057]    The embodiments disclosed herein are to be considered merely illustrative and not restrictive in any respect. The scope of the present invention is defined not by the foregoing description but by the appended claims, and it is intended that the scope of the present invention include all modifications that fall within the meaning and scope equivalent to those of the appended claims.