JP2010059866A - Device for detecting variation among cylinders - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a device for detecting a variation among cylinders which can accurately determine whether the variation among cylinders is present or not. <P>SOLUTION: The device for detecting the variation among cylinders includes a drive means 20 having an internal combustion engine 10, a fuel injection device 11, an exhaust manifold 12, an oxygen sensor 16, and an operating condition control means 18. The device for detecting the variation among cylinders further includes parameter acquisition means S104-S107 for acquiring a parameter P based on a detection waveform S which is the waveform of the output signal output within a specified time TL and an average waveform H obtained by moving-averaging the output signal output within a specified time TL and a determination means S109 for determining whether a variation among the cylinders 10a is present or not based on the parameter P and a threshold G1. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an inter-cylinder variation detection device.

  The inter-cylinder variation detection device includes an internal combustion engine having a plurality of cylinders, a fuel injection device that is provided in the internal combustion engine and injects fuel into each cylinder, and an exhaust gas that is connected to the internal combustion engine and collects an exhaust passage that communicates with each cylinder. The present invention is applied to driving means including an exhaust manifold having a collecting portion (for example, Patent Document 1).

  In this driving means, the oxygen concentration detection means disposed in the exhaust collecting portion outputs an output signal corresponding to the oxygen concentration in the exhaust gas flowing through the exhaust collecting portion, and the operating condition control means determines the fuel based on the output signal. The air-fuel ratio is changed by feedback control of the injection device. A conventional inter-cylinder variation detection device applied to this driving means uses the angle of a crank that is linked to the combustion cycle of each cylinder in order to determine the presence or absence of variation between the cylinders.

JP 2007-23917 A

By the way, since the demand for purifying the exhaust gas of the internal combustion engine has become more severe, the inter-cylinder variation detection device is required to be able to more accurately determine whether or not there is variation among the cylinders. Yes.

  The present invention has been made in view of the above-described conventional situation, and an object to be solved is to provide an inter-cylinder variation detection device that can more accurately determine the presence / absence of variation between cylinders.

An inter-cylinder variation detection device of the present invention includes an internal combustion engine having a plurality of cylinders, a fuel injection device that is provided in the internal combustion engine, and injects fuel into the cylinders, and is connected to the internal combustion engine. An exhaust manifold having an exhaust collecting portion where exhaust passages leading to the exhaust passage gather;
An oxygen concentration detecting means disposed in the exhaust collecting portion and outputting an output signal corresponding to the oxygen concentration in the exhaust gas flowing through the exhaust collecting portion at every sampling time;
An inter-cylinder applied to a drive means comprising: an operating condition control means for changing the air-fuel ratio by the fuel injection device between the rich side and the lean side while performing feedback control of the fuel injection device based on the output signal A variation detection device,
Parameter acquisition means for acquiring a parameter based on a detection waveform that is a waveform of the output signal output within a predetermined time and a moving average of the output signal output within the predetermined time; and
And determining means for determining whether or not there is a variation between the cylinders based on the parameter and the threshold value.

  In the inter-cylinder variation detecting device of the present invention, the output signal of the oxygen concentration detecting means changes accordingly by changing the air-fuel ratio between the rich side and the lean side in the feedback control state. The parameter acquisition means acquires a parameter based on a detection waveform that is a waveform of an output signal output within a predetermined time and an average waveform obtained by moving and averaging the output signals output within a predetermined time.

  Here, when there is variation among the cylinders, the detection waveform, which is a waveform obtained by continuously connecting the output signals, is disturbed. On the other hand, since the average waveform obtained by moving and averaging the output signals becomes a smoother waveform than the detected waveform, both are greatly different. On the other hand, when there is no variation among the cylinders, the detection waveform is not disturbed as a whole. For this reason, the average waveform obtained by moving and averaging the detected waveforms is not so different from the detected waveform. For this reason, the parameters acquired by the parameter acquisition means have different values depending on the presence or absence of variation between cylinders. For this reason, the determination means can determine the presence / absence of variation among the cylinders based on the parameter and the threshold value.

  Therefore, the inter-cylinder variation detecting device of the present invention can determine the presence / absence of variation among the cylinders using the output signal of the oxygen concentration detection means, and as a result, the presence / absence of variation between the respective cylinders compared to the conventional case. More accurate determination can be made.

  In the inter-cylinder variation detecting apparatus of the present invention, the parameter is preferably an integrated value of absolute values of differences between the detected waveform and the average waveform at each sampling time.

  By acquiring the parameters as described above, the inter-cylinder variation detecting device can further highlight the difference in parameters according to the presence or absence of the inter-cylinder variation, and as a result, the operational effects of the present invention can be more reliably ensured. Can be played.

  In the inter-cylinder variation detection device of the present invention, the oxygen concentration detection means outputs a voltage value corresponding to a state where the air-fuel ratio is rich or lean with respect to the theoretical air-fuel ratio from the oxygen concentration in the exhaust gas. It may be a lambda type oxygen sensor that outputs as a signal.

  In this case, in this inter-cylinder variation detection device, when the air-fuel ratio is changed between the rich side and the lean side in the feedback control state, the waveform of the output signal of the lambda type oxygen sensor corresponds to a high voltage value corresponding to the rich side (for example, 1V) and a low voltage value corresponding to the lean side (for example, about 0V) periodically. In particular, when the air-fuel ratio is near the boundary between the rich side and the lean side, in other words, when the waveform of the output signal changes from a high voltage value to a low voltage value or from a low voltage value to a high voltage value. The voltage value changes steeply in a short time.

  Even when a lambda-type oxygen sensor that outputs such an output signal is employed, the parameter acquired by the parameter acquisition unit based on the detected waveform and the average waveform has different values depending on the presence or absence of variation between cylinders. For this reason, this inter-cylinder variation detecting device can surely enjoy the effects of the present invention.

  DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments embodying the present invention will be described below with reference to the drawings.

  As shown in FIG. 1, the inter-cylinder variation detection apparatus of the embodiment includes an on-vehicle four-cylinder gasoline engine (hereinafter simply referred to as “engine”) 10 and an engine which are an example of an embodiment of an internal combustion engine having a plurality of cylinders. 10 is applied to a drive unit 20 including a fuel injection device 11, an exhaust manifold 12, an oxygen sensor 16, and an operation condition control unit 18. Before describing the inter-cylinder variation detecting device in detail, the driving means 20 will be described.

  The engine 10 has a well-known configuration and has four cylinders 10a. Each cylinder 10a has a combustion chamber (not shown). The combustion chamber is provided with an intake valve (not shown) for introducing a mixed gas of fuel and air and an exhaust valve (not shown) for exhausting exhaust gas from the combustion chamber.

  An intake manifold 13 is connected to the engine 10. The intake manifold 13 has an intake manifold portion 13b in which an intake passage 13a communicating with the intake valve of each cylinder 10a is collected.

  An electromagnetically driven fuel injection device 11 is attached to the intake passage 13a. The fuel injection device 11 is disposed so as to inject fuel from a discharge hole (not shown) drilled at the tip of the fuel injection device 11 toward the intake valve of each cylinder 10a. The fuel injected from the discharge hole of the fuel injection device 11 and the air flowing through the intake passage 13a through the intake manifold 13b are mixed to form a mixed gas, and this mixed gas is formed in each cylinder 10a as the intake valve is opened. Are introduced into a combustion chamber for combustion.

  An exhaust manifold 12 is connected to the engine 10. The exhaust manifold 12 has an exhaust collecting portion 12b in which exhaust passages 12a communicating with the exhaust valves of the respective cylinders 10a are gathered. When the mixed gas introduced into the combustion chamber of each cylinder 10a burns, it is discharged to the outside through the exhaust passage 12a and the exhaust collecting portion 12b as exhaust gas when the exhaust valve is opened. A well-known catalyst and a silencer are provided on the downstream side of the exhaust manifold 12.

  A lambda type oxygen sensor (hereinafter simply referred to as “oxygen sensor”) 16 is disposed in the exhaust collecting portion 12b. The oxygen sensor 16 determines a voltage value corresponding to a state where the air-fuel ratio is richer or leaner than the stoichiometric air-fuel ratio from the concentration of oxygen in the exhaust gas flowing through the exhaust collecting portion 12b. An output signal is output to the means 18 every sampling time (for example, 1 millisecond). The oxygen sensor 16 corresponds to oxygen concentration detection means.

  The oxygen sensor 16 is a known oxygen sensor using a zirconia solid electrolyte. When the air-fuel ratio of the exhaust gas is richer than the stoichiometric air-fuel ratio, a corresponding high voltage value (about 1 V) is used as an output signal. Output. On the other hand, when the air-fuel ratio of the exhaust gas is leaner than the stoichiometric air-fuel ratio, the oxygen sensor 16 outputs a corresponding low voltage value (about 0 V) as an output signal. In particular, when the air-fuel ratio is near the boundary between the rich side and the lean side, in other words, when the waveform of the output signal changes from a high voltage value to a low voltage value or from a low voltage value to a high voltage value. The voltage value changes steeply in a short time.

  The operating condition control means 18 is a control program stored in the memory of the engine control electronic control unit. When the engine 10 is started and the engine control electronic control unit starts controlling the engine 10, the engine control electronic The CPU in the control unit executes the operating condition control means 18. Then, the operating condition control means 18 performs arithmetic processing based on the output signal of the oxygen sensor 16. Then, by performing feedback control of the fuel injection device 11, the injection amount of the fuel injection device 11 is adjusted, and the air-fuel ratio is kept in a desired range.

  Although not described, the engine 10 includes various sensors such as an intake manifold negative pressure sensor that detects a negative pressure in the intake manifold 13, a water temperature sensor that detects an engine water temperature, and a crank angle sensor that detects an engine crank angle. These output signals are also appropriately input to the engine control electronic control unit and used for controlling the engine 10.

  In this engine 10, the operating condition control means 18 calculates the air-fuel ratio based on the output signal of the oxygen sensor 16, and feeds back the fuel injection amount for each cylinder 10a so that the calculated air-fuel ratio matches the target value. Control. At this time, the injection amount is corrected based on the engine speed, the engine load, and the like to calculate the final injection amount, and the fuel injection device 11 is controlled by the final injection amount.

  The air-fuel ratio feedback control described above controls the fuel injection amount (air-fuel ratio) of each cylinder based on the air-fuel ratio information detected by the exhaust collecting portion 12b of the exhaust manifold 12, but in reality, each cylinder 10a. Every time the air-fuel ratio varies. For this reason, the presence / absence of variation between the cylinders 10a is determined by the inter-cylinder variation detection device of the present embodiment. Details thereof will be described below.

  The inter-cylinder variation detection apparatus of the present embodiment is constituted by an “inter-cylinder variation determination” program 17 (steps S101 to S109 shown in FIG. 2). The “inter-cylinder variation determination” means program 17 is stored in the memory of the engine control electronic control unit. When the engine 10 is started and the engine control electronic control unit starts control of the engine 10, the CPU in the engine control electronic control unit starts parallel processing of the “inter-cylinder variation determination” program 17. The “inter-cylinder variation determination” program 17 may be appropriately executed when necessary.

  When the CPU in the engine control electronic control unit starts the “inter-cylinder variation determination” program 17, first, in step S101, the timer-T and the parameter P are reset as initial settings. The timer-T starts counting from the time when it is reset, and continues counting until a predetermined time TL (for example, several hundred milliseconds to several tens of seconds) is reached. Further, the timer-T is reset every time the operating condition flag becomes “OFF” in the next step S102.

  Next, the process proceeds to step S102, and it is determined whether or not the operating condition flag is “ON”. Here, the operating condition flag changes the air-fuel ratio of the fuel injection device 11 between the rich side and the lean side while the operating condition control means 18 performs feedback control of the fuel injection device 11 based on the output signal of the oxygen sensor 16. “ON” is set when the state is reached, and “OFF” is set otherwise. As a specific example in which the operation condition flag is “ON”, there is a case where the engine speed and the load are in a constant state. An example of the waveform of the output signal of the oxygen sensor 16 when the operating condition flag is “ON” is shown by a solid line as a detection waveform S in the third row from the top of FIG.

  In the case of “No” in step S102, the process returns to step S101, and steps S101 to S102 are repeated until the operating condition suitable for the inter-cylinder variation determination is reached.

  On the other hand, if “Yes” in step S102, the process proceeds to step S103, and the inter-cylinder variation determination is turned on.

  Next, the process proceeds to step S104, where the output signals output from the oxygen sensor 16 at every sampling time are sequentially acquired, and the detection waveform S, which is a waveform obtained by continuously connecting the output signals, is acquired.

  Next, the process proceeds to step S105, and the average waveform H is obtained by moving and averaging the output signals constituting the detection waveform S. A specific method of the moving average is well known in the fields of mathematics, information processing, etc., and will not be described. However, the output signal constituting the detection waveform S is set to a cycle of two engine revolutions (a cycle of variation between the cylinders 10a). ) Is preferably used for moving average. The average waveform H is preferably corrected so that the phase shift is small when the phase shift with respect to the detection waveform S is large. As shown in the third row from the top in FIG. 3, the average waveform H (shown by a broken line superimposed on the detection waveform S) is a smoother waveform than the detection waveform S.

  Next, the process proceeds to step S106, and the absolute value Z of the difference between the detected waveform S and the average waveform H at each sampling time is calculated. An example of the absolute value Z is shown in the fourth row from the top in FIG.

  Next, the process proceeds to step S107, where the absolute value Z is integrated, and the integrated value is set as the parameter P. An example of the parameter P is shown in the fifth row from the top in FIG.

  Next, the process proceeds to step S108, and it is determined whether or not the timer-T is equal to or longer than the predetermined time TL (whether or not the timer-T has counted up).

  If “Yes” in step S108, it means that there is no variation among the cylinders 10a (“OK”), so the process returns to step S101 and the above-described processing is repeated.

  On the other hand, if “No” in step S108, the process proceeds to step S109 to determine whether or not the parameter P is equal to or greater than the threshold value G1. Here, the threshold value G1 is a value set so that a large number of parameters P when there is a variation between the cylinders 10a and a parameter P when there is no variation between the cylinders 10a are collected and distinguished from each other. It is.

  In the case of “No” in step S109, it is in the midst of the cylinder-to-cylinder variation determination, and since the presence or absence of variation between the cylinders 10a is uncertain, the process returns to step S102 and steps S102 to S109 are repeated. When returning to step S102, if the operating condition of the engine changes midway and the operating condition flag is “OFF”, the process returns to step S101, and the inter-cylinder variation determination is canceled midway.

  On the other hand, if “Yes” in step S109, the process proceeds to step S110, the timer T is stopped, and it is determined that there is variation among the cylinders 10a (“NG”).

  After step S110, it is possible to eliminate the variation among the cylinders 10a by receiving the determination of “NG” and adjusting the fuel injection amount of the fuel injection device 11 as appropriate.

  Here, a specific example of the processing in steps S101 to S110 described above will be described with reference to FIG.

  The periodically varying detection waveform S shown in the third row from the top in FIG. 3 shows an example of a waveform in which the output signal of the oxygen sensor 16 is continuously connected. In this embodiment, a lambda type oxygen sensor is employed as the oxygen sensor 16. For this reason, when the air-fuel ratio is changed between the rich side and the lean side in the feedback control state, the waveform S of the output signal of the oxygen sensor 16 has a high voltage value (1 V) corresponding to the rich side and a low value corresponding to the lean side. It changes periodically between voltage values (0V). In particular, when the air-fuel ratio is in the vicinity of the boundary between the rich side and the lean side, in other words, when the waveform S of the output signal changes from 1 V side to 0 V side or from 0 V side to 1 V side, The voltage value changes steeply in a short time.

  In the above case, as shown in the uppermost stage of FIG. 3, the operating condition flag is switched from “OFF” to “ON”, so the routine proceeds from step S102 to step S103, and the inter-cylinder variation determination is set to the ON state.

  As shown in the second row from the top in FIG. 3, steps S102 to S109 are repeated until the timer-T reaches a certain time TL. Meanwhile, in steps S104 to S107, the absolute value Z of the difference between the detected waveform S and the average waveform H at each sampling time is calculated, and as shown in the fifth row from the top in FIG. A certain parameter P is acquired.

  Then, until the timer-T reaches a certain time TL, as shown in the third row from the top in FIG. 3, the detection waveform S is not disturbed so much, as shown in the fifth row from the top in FIG. The parameter P does not exceed the threshold G1. In this case, it is determined that there is no variation (“OK”) among the cylinders 10a.

  On the other hand, the detection waveform S is particularly disturbed on the rich side after the timer-T is reset for a certain time TL and until the second time for a certain time TL (indicated by an arrow R in FIG. 3). As shown in the fifth row from the top in FIG. 3, the parameter P is equal to or greater than the threshold value G1. In this case, it is determined that there is a variation between the cylinders 10a ("NG").

  In this way, the inter-cylinder variation detection device of the embodiment can accurately determine the presence or absence of variation between the cylinders 10a.

  In steps S104 to S107, the parameter P is set based on the detection waveform S that is the waveform of the output signal output within the predetermined time TL and the average waveform H obtained by moving average of the output signal output within the predetermined time T. It corresponds to the parameter acquisition means to acquire.

  Step S109 corresponds to determination means for determining whether or not there is variation among the cylinders 10a based on the parameter P and the threshold value G1.

  Here, the inter-cylinder variation detecting device of the embodiment is applied to the driving unit 20 described above, and includes parameter acquisition units S104 to S107 and a determination unit S109.

  In this inter-cylinder variation detection device, when there is variation between the cylinders 10a, the detection waveform S is disturbed. On the other hand, since the average waveform H is a smoother waveform than the detection waveform S, both are greatly different. On the other hand, when there is no variation among the cylinders 10a, the detection waveform S is not disturbed as a whole. For this reason, the average waveform H obtained by moving and averaging the detection waveform S and the detection waveform S are not so different. For this reason, the parameter P acquired by the parameter acquisition means S104 to S107 has different values depending on the presence or absence of variation between the cylinders 10a. For this reason, the determination unit S109 can determine whether or not there is a variation between the cylinders 10a based on the parameter P and the threshold value G1.

  Accordingly, the inter-cylinder variation detecting device of the embodiment can determine the presence / absence of variation between the respective cylinders 10a using the output signal of the oxygen sensor 16, and as a result, the presence / absence of variation between the respective cylinders 10a as compared with the related art. Can be determined with higher accuracy.

  In this inter-cylinder variation detecting device, the parameter P is an integrated value of the absolute value Z of the difference between the detected waveform S and the average waveform H at each sampling time. For this reason, this inter-cylinder variation detection device can further highlight the difference in the parameter P according to the presence or absence of variation between the cylinders 10a, and as a result, the effects of the present invention can be more reliably exhibited. it can.

  Further, since this cylinder-to-cylinder variation detection device employs a lambda-type oxygen sensor as the oxygen sensor 16, when the air-fuel ratio is in the vicinity of the boundary between the rich side and the lean side, the voltage value has a steep slope in a short time. Change.

  Even when the lambda type oxygen sensor 16 that outputs such an output signal is employed, the parameter P acquired by the parameter acquisition means S104 to S107 based on the detection waveform S and the average waveform H is a variation of each cylinder 10a. The value varies depending on the presence or absence. For this reason, this inter-cylinder variation detecting device can surely enjoy the effects of the present invention.

  While the present invention has been described with reference to the embodiments, it is needless to say that the present invention is not limited to the above-described embodiments and can be appropriately modified and applied without departing from the spirit thereof.

  For example, instead of the lambda-type oxygen sensor 16 of the embodiment, an all-region oxygen sensor that transmits an output signal corresponding to the entire region of oxygen concentration change may be employed.

  The present invention can be used for an internal combustion engine and driving means.

It is a schematic explanatory drawing which shows the variation detection apparatus between cylinders of an Example. 7 is a flowchart of an “inter-cylinder variation determination” program according to the inter-cylinder variation detection device of the embodiment. It is explanatory drawing which shows the transition of each parameter in connection with the variation detection apparatus between cylinders of an Example during the process of the "judgment variation determination" program.

Explanation of symbols

10 ... Internal combustion engine
DESCRIPTION OF SYMBOLS 10a ... Cylinder 11 ... Fuel-injection apparatus 12 ... Exhaust manifold 12a ... Exhaust passage 12b ... Exhaust collecting part 16 ... Oxygen concentration detection means (lambda type oxygen sensor)
17 ... "Cylinder variation determination" program 18 ... Operating condition control means 20 ... Drive means G ... Threshold P ... Parameter S104 to S107 ... Parameter acquisition means S109 ... Determination means S ... Detection waveform H ... Average waveform TL ... Constant time

Claims (3)

An internal combustion engine having a plurality of cylinders, a fuel injection device that is provided in the internal combustion engine and injects fuel into the cylinders, and an exhaust collection unit that is connected to the internal combustion engine and collects exhaust passages that communicate with the cylinders. An exhaust manifold having,
An oxygen concentration detecting means disposed in the exhaust collecting portion and outputting an output signal corresponding to the oxygen concentration in the exhaust gas flowing through the exhaust collecting portion at every sampling time;
An inter-cylinder applied to a drive means comprising: an operating condition control means for changing the air-fuel ratio by the fuel injection device between the rich side and the lean side while performing feedback control of the fuel injection device based on the output signal A variation detection device,
Parameter acquisition means for acquiring a parameter based on a detection waveform that is a waveform of the output signal output within a predetermined time and a moving average of the output signal output within the predetermined time; and
An inter-cylinder variation detection apparatus comprising: a determination unit that determines whether or not there is variation between the cylinders based on the parameter and the threshold value.   The inter-cylinder variation detection device according to claim 1, wherein the parameter is an integrated value of an absolute value of a difference between the detection waveform and the average waveform at each sampling time.   The oxygen concentration detection means outputs, as the output signal, a voltage value corresponding to a state where the air-fuel ratio is on the rich side or the lean side with respect to the stoichiometric air-fuel ratio from the oxygen concentration in the exhaust gas. The inter-cylinder variation detection device according to claim 1, wherein the device is a lambda type oxygen sensor.

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