Patent Publication Number: US-11022059-B2

Title: Abnormality determination apparatus for internal combustion engine

Description:
CROSS REFERENCES TO RELATED APPLICATIONS 
     The present application claims priority under 35 U.S.C. § 119 to Japanese Patent Application No. 2019-021331, filed Feb. 8, 2019, entitled “Abnormality Determination Apparatus for Internal Combustion Engine.” The contents of this application are incorporated herein by reference in their entirety. 
     TECHNICAL FIELD 
     The present disclosure relates to an abnormality determination apparatus for an internal combustion engine in which an intake passage upstream of a supercharger and a crankcase are connected by a breather line. 
     BACKGROUND 
     Such an abnormality determination apparatus for an internal combustion engine is described as a second embodiment in Japanese Unexamined Patent Application Publication No. 2017-078378. In such a case where the connection portion of the breather line to the intake passage has come off, the connection portion serves as an opening end portion for the air column of the intake passage, thus causing the resonant frequency of the air column to change. Focusing on this fact, this abnormality determination apparatus for an internal combustion engine monitors the magnitude of the pulsation of the intake flow rate in the intake passage to determine whether the connection portion of the breather line has come off. 
     In the above-described conventional abnormality determination apparatus, if the load on the internal combustion engine temporarily fluctuates due to disturbance or the like, the pulsation of the intake flow rate fluctuates to a large extent. For this reason, there is a possibility that the above-described conventional abnormality determination apparatus erroneously determines whether the connection portion of the breather line has come off. 
     SUMMARY 
     It is desirable to precisely determine the abnormality of a breather line of an internal combustion engine without being affected by disturbance or the like. 
     A first aspect of the disclosure proposes an abnormality determination apparatus for an internal combustion engine in which an intake passage upstream of a supercharger and a crankcase are connected by a breather line, including: an intake flow rate detection unit that detects an intake flow rate in the intake passage; and an abnormality determination unit that determines abnormality of the breather line, wherein the abnormality determination unit accumulates a time for which a rotation second-order component of a fluctuation waveform of the intake flow rate is equal to or more than a threshold over a predetermined period of time and determines the abnormality of the breather line when the accumulated value is less than a predetermined accumulation threshold. 
     According to the configuration of the first aspect, it is possible to precisely determine the abnormality of the breather line based on the rotation second-order component of the fluctuation waveform of the intake flow rate, which is unlikely to be affected by fluctuation in load on the internal combustion engine due to disturbance or the like. 
     A second aspect of the disclosure proposes an abnormality determination apparatus for an internal combustion engine in which in addition to the configuration of the first aspect, the rotation second-order component is calculated by multiplying the fluctuation waveform of the intake flow rate by a sine wave and a cosine wave corresponding to an angular velocity of a crank, followed by integration. 
     According to the configuration of the second aspect, it is possible to easily calculate the rotation second-order component of the fluctuation waveform of the intake flow rate. 
     Note that an air flow meter  16  in an embodiment corresponds to the intake flow rate detection unit of the disclosure. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The advantages of the disclosure will become apparent in the following description taken in conjunction with the following drawings. 
         FIG. 1  is a diagram illustrating the configuration of an internal combustion engine including an abnormality determination apparatus for a breather line of one embodiment. 
         FIG. 2  is a block diagram of the abnormality determination apparatus for the breather line of one embodiment. 
         FIGS. 3A and 3B  are explanatory diagrams for change in position of a piston associated with the rotation of a crankshaft of one embodiment. 
         FIG. 4  is an explanatory diagram of procedure of determining abnormality of the breather line of one embodiment. 
         FIG. 5  describes bandpass filter for extracting only the rotation second-order component from the fluctuation in the intake flow rate in the intake passage. 
     
    
    
     DETAILED DESCRIPTION 
     Hereinafter, an embodiment of the disclosure will be described based on  FIGS. 1 to 4 . 
     As illustrated in  FIG. 1 , on an intake passage  12  of an in-line four-cylinder 4-cycle internal combustion engine  11  to be mounted on an automobile, disposed are: an air cleaner  15 , which removes dust in intake air; an air flow meter  16 , which measures the intake flow rate; a supercharger  17  composed of a turbocharger or a supercharger, which pressurizes the intake air; and a throttle valve  18 , which adjusts the intake flow rate by narrowing the intake passage  12 , in this order from an inlet  13  at the upstream end in the flow direction of the intake air toward an intake manifold  14  at the downstream end in the flow direction of the intake air. A portion of the intake passage  12  between the air flow meter  16  and the supercharger  17  and a crankcase  19  of the internal combustion engine  11  are connected by a breather line  20 . The intake manifold  14  and the crankcase  19  of the internal combustion engine  11  are connected by a positive crankcase ventilation (PCV) line  21 , and a middle portion of the PCV line  21  is opened and closed by a PCV valve  22 . 
     Part of the fuel component contained in the intake air flows from the combustion chamber of the internal combustion engine  11  into the crankcase  19  through a gap between a piston and a cylinder as a blow-by gas, which is returned to the intake passage  12  through the breather line  20  or is returned to the intake passage  12  through the PCV line  21 . The fuel component contained in the blow-by gas is thus prevented from being released to the atmosphere. 
     Specifically, when the PCV valve  22  is opened during natural aspiration in which the supercharger  17  is not activated, the atmospheric pressure acts on the intake passage  12  upstream of the throttle valve  18  while the intake negative pressure of the internal combustion engine  11  acts on the intake passage  12  downstream of the throttle valve  18 . Hence, the intake air in the intake passage  12  upstream of the throttle valve  18  flows through the breather line  20  into the crankcase  19 . From the crankcase  19 , the intake air together with the blow-by gas is returned into the intake manifold  14  through the PCV line  21 . The blow-by gas together with the intake air is eventually supplied into the combustion chamber of the internal combustion engine  11 . 
     Moreover, at the time of supercharging in which the supercharger  17  is activated, the supercharging pressure acts on the intake passage  12  downstream of the supercharger  17 . Once the PCV valve  22  is closed, the supercharging pressure is prevented from escaping through the PCV line  21  into the crankcase  19 . The blow-by gas in the crankcase  19  is sucked out into the intake passage  12  by the negative pressure generated upstream of the activated supercharger  17 . From the intake passage  12 , the blow-by gas together with the intake air is supplied into the combustion chamber of the internal combustion engine  11  through the intake passage  12 . 
     In a case where during the supercharging of the internal combustion engine  11 , a first connection portion  23  at which the breather line  20  is connected to the intake passage  12  comes off or a second connection portion  24  at which the breather line  20  is connected to the crankcase  19  comes off, the blow-by gas flowing through the breather line  20  from the crankcase  19  toward the intake passage  12  is possibly released to the atmosphere. For this reason, it is necessary to detect such abnormality of the breather line  20  and issue an alert. 
     As illustrated in  FIG. 2 , to an abnormality determination unit  30  formed of an electronic control unit that determines abnormality of the breather line  20 , the air flow meter  16  and an alert unit  32  are connected. The alert unit  32  is formed of a liquid crystal panel provided on an instrument panel, for example. 
     Next, the action of the embodiment including the above-described configuration will be described. 
     As illustrated in  FIG. 3A , a piston  33  of the internal combustion engine  11  is connected to a crankshaft  35  by a connecting rod  34 . The height of the piston  33  (the position in the direction of movement of the piston  33 ) changes as a function of the rotational position of the crankshaft  35  and the oscillation position of the connecting rod  34 . That is, the fluctuation in the height of the piston  33  attributable to the rotation of the crankshaft  35  is a rotation first-order fluctuation in which the height fluctuates once per revolution of the crankshaft  35 . On the other hand, the fluctuation in the height of piston  33  attributable to the oscillation of the connecting rod  34  is a rotation second-order fluctuation in which the height fluctuates twice per revolution of the crankshaft  35 . 
     As illustrated in  FIG. 3B , in the in-line four-cylinder 4-cycle internal combustion engine  11 , the pistons  33  of the #1 cylinder and the #4 cylinder operate at the same phase while the pistons  33  of the #2 cylinder and the #3 cylinder operate at a different phase shifted by 180° from the above phase. Hence, the internal pressure fluctuation of the crankcase  19  attributable to the oscillations of the four connecting rods  34  is a rotation second-order fluctuation in which the internal pressure fluctuates twice per revolution of the crankshaft  35 . 
     When the rotation second-order fluctuation is generated in the internal pressure of the crankcase  19  as described above, the pressure fluctuation is transmitted to the intake passage  12  through the breather line  20 , causing the rotation second-order fluctuation in the intake flow rate in the intake passage  12 . The present embodiment is configured to determine the abnormality of the breather line  20  based on the rotation second-order fluctuation in the intake flow rate generated in the intake passage  12 . 
     Note that the number of cylinders of the internal combustion engine  11  to which the embodiment is applied is not particularly limited. However, in a V-type 6-cylinder internal combustion engine, the pressure fluctuations in the internal pressure of the crankcase  19  due to the movements of 6 pistons  33  cancel out, so that the fluctuations in the internal pressure of the crankcase  19  are relatively small. Hence, the present disclosure is favorably applicable to the in-line four-cylinder internal combustion engine  11 . 
     Next, the procedure of determining the abnormality of the breather line  20  will be described based on  FIG. 4 . 
     The determination of the abnormality of the breather line  20  of the present embodiment is executed when the flow rate of the intake air detected by the air flow meter  16  is a predetermined value or more and the internal combustion engine  11  is being operated with a load of a predetermined value or more. This is because when the internal combustion engine  11  is being operated with a small load, the fluctuation in the intake flow rate in the intake passage  12  is small, making it difficult to obtain the amount of fluctuation necessary to determine abnormality with high precision. 
     First, in Step S 1 , the fluctuation in the intake flow rate in the intake passage  12  is detected by the air flow meter  16 . As described above, a periodic pressure fluctuation is generated in the crankcase  19  by the movement of the piston  33 . This periodic pressure fluctuation is transmitted to the intake passage  12  through the breather line  20  connected to the crankcase  19 , generating the fluctuation in the intake flow rate. The fluctuation in the intake flow rate in the intake passage  12  contains the rotation first-order component, the rotation second-order component, and rotation third-order and higher-order components. However, since the rotation third-order and higher-order components are small, the rotation first-order component and the rotation second-order component are dominant. 
     In subsequent Step S 2 , only the rotation second-order component in the fluctuation in the intake flow rate in the intake passage  12  is extracted using a bandpass filter. 
     The principle of the bandpass filter for extracting only the rotation second-order component from the fluctuation in the intake flow rate in the intake passage  12  will be described below. 
     As illustrated in  FIG. 5  ([Math. 1]), if a value obtained by multiplying a certain fluctuation waveform of the intake flow rate in the intake passage  12  detected by the air flow meter  16  by the second-order sine wave is added for each phase, the X component of the rotation second-order component of the certain waveform is obtained. If a value obtained by multiplying the certain waveform by the second-order cosine wave is added for each phase, the Y component of the rotation second-order component of the certain waveform is obtained. 
     To be more specific, the certain waveform f(t) may be expressed as [Math. 2], summation of sine waves sin(ωt), sin(2ωt), sin(3ωt), . . . and cosine waves cos(ωt), cos(2ωt), cos(3ωt), . . . in accordance with Fourier series expansion. Here, the angular frequency ω has one cycle with 720 deg corresponding to two rotations of the crankshaft  35 .
 
 f= 1+ a   1  sin(ω t )+ b   1  cos(ω t )+ a   2  sin(2 ωt )+ b   2  cos(2 ωt )+ . . .  [Math. 2]
 
     When the [Math. 2] is multiplied by the sine wave sin(ωt), followed by integration, only the Fourier coefficient a1 of the angular frequency sine wave is left as shown in [Math. 3]. 
     
       
         
           
             
               
                 
                   
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     Similarly, when the [Math. 2] is multiplied by the cosine wave cos(ωt), followed by integration, only the Fourier coefficient b1 of the angular frequency cosine wave is left. It is thus possible to easily obtain the rotation second-order component of the certain waveform f(t) from these Fourier coefficients a1 and b1. 
     Once the rotation second-order component in the fluctuation in the intake flow rate in the intake passage  12  is extracted in Step S 2  as described above, a time T for which a peak portion of the rotation second-order component in the fluctuation in the intake flow rate in the intake passage  12  is equal to or more than a predetermined threshold is accumulated over a predetermined period of time (for example, 2 to 10 seconds) in Step S 3 . If the accumulated value is equal to or more than an accumulation threshold, the breather line  20  is determined to be normal. If the accumulated value is less than the accumulation threshold, the breather line  20  is determined to be abnormal and the alert unit  32  is activated to notify a passenger of that effect. 
     The reason why it is possible to determine whether the breather line  20  is normal or abnormal from the accumulated value of the time T for which the rotation second-order component in the fluctuation in the intake flow rate in the intake passage  12  is equal to or more than the predetermined threshold is as described below. In a case where the breather line  20  is normal and is not in communication with the atmosphere, the pressure fluctuation of the crankcase  19  is transmitted as it is to the intake passage  12  from the breather line  20  and the resulting fluctuation in the intake flow rate in the intake passage  12  is detected by the air flow meter  16 . Hence, if the detected fluctuation in the intake flow rate in the intake passage  12  is large, that is, if the peak portion of the intake flow rate is equal to or more than the threshold, it is possible to determine that the breather line  20  is not in communication with the atmosphere and is normal. On the other hand, if the breather line  20  has come off the first or second connection portion  23  or  24  or is broken in a middle thereof, the breather line  20  communicates with the atmosphere and the fluctuation in the intake flow rate in the intake passage  12  is reduced. Hence, if the detected fluctuation in the intake flow rate is small, that is, if the peak portion of the intake flow rate is likely to be less than the threshold, it is possible to determine that the breather line  20  is in communication with the atmosphere and is abnormal. 
     Meanwhile, consider a case where the magnitude of the fluctuation in the intake flow rate in the intake passage  12  is evaluated. If the intake flow rate fluctuates to a positive value and a negative value, merely accumulating the intake flow rate over a predetermined period of time results in incorrect evaluation because the positive and negative values cancel out. In view of this, as in the present embodiment, accumulating the time T for which the peak portion of the fluctuation in the intake flow rate is equal to or more than the predetermined threshold over the predetermined period of time makes it possible to correctly evaluate the magnitude of the fluctuation in the intake flow rate and conduct the abnormality determination with high precision. 
     In addition, if the load on the internal combustion engine  11  fluctuates due to disturbance or the like, the rotation first-order component of the fluctuation in the intake flow rate in the intake passage  12  also fluctuates. However, since the rotation second-order component is hardly affected, it is possible to increase the determination precision and prevent erroneous determination from occurring by conducting the abnormality determination on the breather line  20  base on the rotation second-order component. 
     Although the embodiment of the disclosure has been described so far, various modifications in design may be made without departing from the scope of the disclosure. 
     For example, the number of cylinders of the internal combustion engine  11  is not limited to the four in the embodiment. 
     Moreover, although the breather line  20  is connected to the crankcase  19  in the embodiment, it is also possible to achieve the advantageous effect of the disclosure by causing the internal space of the crankcase  19  and the internal space of a head cover to communicate and connecting the breather line  20  to the head cover. Hence, an embodiment in which the breather line  20  is connected to another space that communicates with the crankcase  19  is also encompassed by the scope of the disclosure. Although a specific form of embodiment has been described above and illustrated in the accompanying drawings in order to be more clearly understood, the above description is made by way of example and not as limiting the scope of the invention defined by the accompanying claims. The scope of the invention is to be determined by the accompanying claims. Various modifications apparent to one of ordinary skill in the art could be made without departing from the scope of the invention. The accompanying claims cover such modifications.