JP2007270716A - Diagnostic system of valve timing control device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To delicately determine a change in the valve timing more than a conventional determination, in an engine 1 mounted with VVT 13 capable of varying the operation timing of intake to exhaust valves 11 and 12. <P>SOLUTION: This diagnostic system has an ion current detecting circuit 33 detecting an ion current generated in a combustion chamber 6 of the engine 1, and integrates an ion current value detected on and after TDC in the combustion chamber 6, and estimates an internal EGR quantity on the basis of the ignition timing, filling efficiency ce and an engine speed ne in addition to an ion parameter Ip with a crank angle position integrated up to a predetermined rate of its total integral value as an evaluation value (the ion parameter Ip). A VVT phase, that is, the valve timing is estimated from the estimated internal EGR quantity, to thereby diagnose failure of a VVT control system. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a diagnosis of a valve timing control device that changes the operation timing of at least one of an intake valve and an exhaust valve of an engine, and in particular, obtains a combustion state of an engine from an ionic current and thereby estimates an operation timing of the valve. Regarding technology.

  Conventionally, as disclosed in, for example, Patent Document 1, in an engine in which the operation state of the intake or exhaust valve is switched between the low speed side and the high speed side, an ionic current generated in the combustion chamber after ignition of the air-fuel mixture is It is known to detect whether the actual valve timing is on the low speed side or the high speed side by comparing with the ion current waveform on the low speed side or the high speed side stored in advance. ing.

  That is, in general, the ion current is thought to be generated using ions generated by combustion as a medium, and the manner of generation varies depending on the combustion state, so the waveform of the ion current is the low speed side of the valve timing. It will change with the switching on the high speed side.

Therefore, in the above-mentioned document, the ion current waveform is measured and stored in advance for each of the low speed side and high speed side valve timings, and this is compared with the waveform of the ion current detected during engine operation. Thus, it is determined whether the actual valve timing is on the low speed side or the high speed side. Based on this determination result, malfunction or failure of the valve timing control device can be detected.
Japanese Patent Application Laid-Open No. 08-21295

  By the way, in recent years, in order to increase the intake charge efficiency in the entire engine operation region, a variable phase valve timing control device in which the valve timing is continuously changed according to the change of the operation state is becoming widespread. In an engine equipped with such a thing, there is a demand for determining whether the valve timing is advanced or retarded, that is, whether the valve timing is changed.

  However, the diagnostic device of the conventional example only determines whether the detected ion current waveform matches the low speed side or the high speed side that is stored in advance, so that the valve timing advances. It is not possible to judge the angle and the slow angle. This is because the conventional example is intended for a two-stage switching type engine in which the valve timing is switched to either the low speed side or the high speed side, and no further determination is required.

  In this regard, the inventor of the present application diligently studied the meaning of the ion current waveform, and as a result, noticed that the shape of the latter half of the waveform has a high correlation with the valve timing and completed the present invention. It is. That is, when the valve timing is changed, the valve overlap period of the intake and exhaust gas changes accordingly, and the amount of burnt gas (internal EGR) remaining in the combustion chamber also changes, which makes combustion more active. Or become sluggish.

  For example, as the amount of internal EGR increases, the combustion becomes slower as a whole, so that the ion current waveform becomes lower as a whole, but the internal EGR, which is a burnt gas, has a considerably high temperature. The combustion (initial combustion) is rather promoted, and there is not much change in the first half of the ion current waveform reflecting the state of the initial combustion.

  On the other hand, the initial combustion state as described above is not reflected in the latter half of the ion current waveform, and a high mountain appears when combustion is active as a whole, while it becomes low and smooth when combustion is slow. is there.

  Thus, focusing on the fact that the first half of the ion current waveform has a low correlation with the internal EGR amount, while the second half has a high correlation with the internal EGR amount, the object of the present invention is to correlate with the internal EGR amount. The purpose is to make it possible to determine a change in a certain valve timing more finely than in the past.

  In order to achieve the above object, the present invention determines the state of residual burned gas (internal EGR) based on the ionic current value detected on the retard side from the vicinity of the compression top dead center in the combustion chamber, Thereby, the change state of the valve timing is determined.

  Specifically, the invention of claim 1 is a diagnostic device for a valve timing control device that controls the operation timing of at least one of the intake and exhaust valves of an engine, and detects ions that generate an ion current generated in the combustion chamber of the engine. Valve operation by the valve timing control device based on the current detection means and the ion current value detected by the ion current detection means over a specific period on the retard side from the compression top dead center in the combustion chamber Determination means for determining a timing change state.

  With the above configuration, the ion current generated in the combustion chamber during the operation of the engine is detected by the ion current detection means, and in particular based on the ion current value detected over a specific period on the retard side from the vicinity of the compression top dead center. That is, based on the information included in the latter half of the ion current waveform, the change state of the valve operation timing is determined by the determination means.

  This eliminates information on the first half of the ion current waveform having a low correlation with the internal EGR, and accurately determines the state of the internal EGR highly correlated with the information based on the information on the second half of the ion current waveform. Therefore, the change timing of the valve timing corresponding to the state of the internal EGR can be determined more finely and accurately than in the past.

  More specifically, for example, the ion current values detected over the entire specified period are integrated, the crank angle position where up to a predetermined ratio of the total integrated value is integrated is specified, and the specified crank angle position is specified. The change timing of the valve timing may be determined based on the above (invention of claim 2). It can be determined that the more the crank angle position specified in this way is on the retard side, the more slowly the combustion is, and the greater the internal EGR amount, and the greater the overlap between the intake and exhaust valves. Can do.

  In particular, when the engine is of a spark ignition type, the valve timing can be estimated based on at least the crank angle position and the ignition timing specified as described above (the invention of claim 3). That is, the period from the ignition of the air-fuel mixture to the specific crank angle position is considered to represent the overall activity and slowness of combustion, and based on this, the amount of internal EGR and hence the valve timing can be estimated. .

  In addition to the internal EGR, the combustion state of the engine also affects the so-called external EGR and the amount of intake charge combined with fresh air, the flow strength in the combustion chamber, the temperature of the combustion chamber, etc. In order to estimate the EGR amount and the valve timing, it is preferable to further consider the engine operating state.

  If the valve timing can be estimated in this way, it is compared with a target value of the valve timing in the valve timing control device, and a failure notification means for diagnosing a failure related to the valve timing control device and notifying it is provided. (Invention of claim 4). By so doing, it is possible to accurately diagnose a failure in the valve timing control device and notify it early.

  For example, when the valve timing control device includes a variable mechanism that can change the valve operation timing and a control unit that controls the variable mechanism, the failure notification unit includes a mechanical deviation of the variable mechanism, and the control. It is preferable to make a diagnosis and report by discriminating the abnormality of the means (invention of claim 5). In this way, it is possible to appropriately respond according to the failure state.

  More preferably, it is provided with valve timing correction means for correcting the control by the valve timing control device based on the valve operation timing estimated as described above so as to approach the target value. 6 invention). By this correction, the valve timing is optimized.

  Alternatively, on the basis of the valve operation timing estimated as described above, for example, if it is shifted to the side where the overlap of the intake and exhaust valves becomes larger, the valve is advanced, and if it is shifted, the valve is retarded. Thus, it is possible to provide ignition timing correction means for correcting the ignition timing of the engine (invention of claim 7). In this way, the ignition timing corresponding to the actual internal EGR amount is corrected to an appropriate ignition timing, thereby not only responding to the failure of the valve timing control device but also reducing the effect of changes in the internal EGR amount due to cycle fluctuations. Thus, the engine operating efficiency can be increased.

  As described above, according to the diagnostic apparatus of the valve timing control device of the present invention, based on the ion current value detected over a specific period on the retard side from the vicinity of the compression top dead center in the combustion chamber of the engine. That is, the information on the first half of the ion current waveform having a low correlation with the internal EGR is excluded, and the state of the internal EGR having a high correlation with this is accurately determined based on the information contained in the second half of the ion current waveform. Therefore, the change state of the valve operation timing corresponding to the state of the internal EGR can be determined more finely than in the past.

  Based on the change state of the valve operation timing thus determined, a failure of the valve timing control device can be accurately diagnosed and notified at an early stage, and an appropriate response according to the failure state can be performed.

Further, according to the determined change state of the valve operation timing, it can be corrected so as to approach the target value, or the ignition timing can be corrected, thereby improving the engine operating efficiency.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. It should be noted that the following description of the preferred embodiment is merely illustrative in nature, and is not intended to limit the present invention, its application, or its use.

(Schematic configuration of the engine)
FIG. 1 schematically shows an engine 1 according to an embodiment having a diagnostic device according to the present invention. In this example, the engine 1 includes a plurality of cylinders 2, 2,... (Only one is shown in the figure) in series. Is a spark ignition type engine. As shown in the drawing, the upper end of the cylinder 2 opens to the upper end surface of the cylinder block 3 and is closed by the lower surface of the cylinder head 4 mounted thereon. A piston 5 is fitted in the cylinder 2 so as to be able to reciprocate. A combustion chamber 6 is defined between the upper surface of the piston 5 and the lower surface of the cylinder head 4. On the other hand, a crankshaft (not shown) is disposed in the crankcase below the piston 5 and is connected to the piston 5 by a connecting rod.

  The cylinder head 4 is provided with an ignition plug 7 for each cylinder 2, and an electrode at the tip of the cylinder head 4 faces the combustion chamber 6, while a base end portion of the ignition plug 7 is connected to an ignition circuit 8. The ignition circuit 8 includes an igniter 8a composed of a power transistor and an ignition coil 8b, as shown only in FIG. 2 (a), and receives a control signal from a PCM 30 (to be described later) for each cylinder 2. The ignition plug 7 is energized at this timing (ignition timing). In this example, an ion current detection circuit 33 is connected to the ignition circuit 8 so that the ion current can be detected as shown in FIG. 5B, which will be described later.

  The cylinder head 4 is formed with an intake port 9 and an exhaust port 10 so as to open toward the combustion chamber 6 for each cylinder 2, and each port opening is opened and closed by a cam shaft. Intake and exhaust valves 11 and 12 (intake and exhaust valves) are provided. Although not shown in the figure, one camshaft is provided on each of the intake side and the exhaust side, and is connected to the crankshaft by a common cam chain. The intake shaft is synchronized with the rotation of the crankshaft. The intake and exhaust valves 11 and 12 are opened and closed at predetermined timings by rotating the side and exhaust side camshafts, respectively (see FIG. 3).

  Further, in this example, a phase variable mechanism 13 (Variable Valve Timing or less) capable of continuously changing the phase with respect to the rotation of the crankshaft within a predetermined angle range (for example, 40 to 60 ° CA) is applied to the intake-side camshaft. VVT 13 is attached, and the lift curve In of the intake valve 11 is changed to the advance side and the retard side by the VVT 13 as schematically shown in FIG. . Along with this, as shown in the figure, the overlap period of the exhaust valve 12 with the lift curve Ex changes, whereby the amount of burnt gas (hereinafter referred to as internal EGR) remaining in the combustion chamber 6 also changes.

  Specifically, as shown in FIG. 2 (b), the VVT 13 is arranged so as to cover the rotor 13a assembled to the front end portion of the intake side camshaft and the rotor 13a, and the cam chain is wound around the rotor 13a. The casing 13c is fixed to the sprocket 13b. Four vanes projecting radially outward are provided on the outer periphery of the rotor 13a, while four partition walls extending inward are provided on the inner periphery of the casing 13c. A plurality of hydraulic working chambers 13d, 13e,... Are formed between the vane and the partition wall.

  Then, a rotation input inputted to the sprocket 13b from a cam chain (not shown) is transmitted to the intake camshaft through the casing 13c, the hydraulic working chambers 13d and 13e, and the rotor 13a. At that time, the hydraulic pressure of the engine oil supplied to the hydraulic working chambers 13d, 13e,... Is adjusted by an oil control valve 13f (hereinafter referred to as OCV), so that the rotor 13a and the casing 13c, that is, the camshaft and the sprocket. The relative rotational position of 13a is changed, and the rotational phase of the cam shaft with respect to the crankshaft (hereinafter referred to as VVT phase) is changed.

  In other words, between the rotor 13a and the casing 13c of the VVT 13, advance hydraulic working chambers 13d, 13d,... And retard hydraulic working chambers 13e, 13e,. When the hydraulic pressure in the advance side working chambers 13d, 13d,... Is increased by the hydraulic control by the OCV 13f, the rotor 13a is rotated in the direction of rotation of the camshaft (indicated by an arrow in the figure) with respect to the casing 13c. As a result, the VVT phase is changed to the advance side, and the opening timing and the closing timing of the intake valve 11 are relatively changed to the advance side.

  On the contrary, when the hydraulic pressure in the retard side working chambers 13e, 13e,... Is increased by the hydraulic control by the OCV 13f, the rotor 13a is rotated with respect to the casing 13c in the direction opposite to the rotating direction of the camshaft. The phase is changed to the retard side, and the opening timing and the closing timing of the intake valve 11 are changed to the retard side.

  Returning to FIG. 1, an intake passage 15 is disposed on one side of the cylinder head 4 (left side in the figure) so that the downstream end communicates with the intake port 9. The upstream end of the intake passage 15 is connected to an air cleaner 16 for filtering fresh air introduced from the outside. From there, an air flow sensor 17 for detecting the intake air flow rate in order toward the downstream side, and an electric motor 18a. A throttle valve 18 that throttles the intake passage 15 by being driven by and an injector 19, 19, ... (only one is shown in the figure) for supplying fuel to each cylinder 2 is disposed.

  On the other hand, on the opposite side of the cylinder head 4 (the right side in FIG. 1), an exhaust passage 20 communicates with the exhaust port 10 and exhausts burnt gas (exhaust gas) from the combustion chamber 6 in each cylinder 2. It is arranged. In this exhaust passage 20, in order from the upstream side, an oxygen concentration sensor (hereinafter referred to as O2 sensor) 21 for detecting the air-fuel ratio of the air-fuel mixture based on the oxygen concentration in the exhaust gas, and a catalyst for purifying the exhaust gas A converter 22 is provided.

  Further, an exhaust gas recirculation passage 24 (hereinafter referred to as an EGR passage) for recirculating a part of the exhaust gas to the intake air passage 15 is branched and connected to the exhaust passage 20 upstream of the O2 sensor 21. The downstream end of the passage 24 communicates with the intake passage 15 on the downstream side of the throttle valve 18. An electric flow control valve 25 (hereinafter referred to as EGR valve) whose opening degree can be adjusted is disposed near the downstream end of the EGR passage 24, and exhaust gas recirculated through the EGR passage 24 (hereinafter referred to as external EGR). The flow rate is adjusted.

  Furthermore, a crank angle sensor 26 comprising an electromagnetic pickup or the like for detecting the rotation angle (crank angle) of the crankshaft is provided in the crankcase below the cylinder block 3 of the engine 1. The crank angle sensor 26 is an electromagnetic pickup that outputs a signal corresponding to the passage of a convex portion provided on the outer peripheral portion thereof as the rotor 27 attached so as to rotate integrally with the end portion of the crankshaft is rotated. It consists of a coil 26. Further, a water temperature sensor 28 for detecting the temperature state of the cooling water is provided on the water jacket (not shown) of the cylinder block 3.

  Output signals from the airflow sensor 17, the O2 sensor 21, the crank angle sensor 26, the water temperature sensor 28, etc. are input to a PCM (Power-train Control Module) 30, respectively. As is well known, the PCM 30 includes a CPU, ROM, RAM, an I / O interface circuit, etc. In addition to the sensors, a cam angle sensor 31 that detects at least the rotation angle (rotation position) of the intake camshaft. And an accelerator opening sensor 32 that detects the amount of operation of the accelerator pedal, respectively, to receive signals output from the accelerator pedal.

  The PCM 30 determines the operating state of the engine 1 based on the signals input from the sensors and controls the operation of the engine 1 accordingly. That is, the PCM 30 outputs an ignition timing control signal for each cylinder 2 to the ignition circuit 8, and outputs a signal for controlling the intake flow rate to the throttle valve 18, and the injector 19 for each cylinder 2. ,... Are output to the EGR valve 25 to control the amount of exhaust gas (external EGR) circulating to the intake system through the EGR passage 24. Is output.

  Further, the PCM 30 outputs a signal for changing the operation timing (valve timing) of the intake valve 11 to the VVT 13 (OCV 13 f) according to the operating state of the engine 1. In this valve timing control, valve timings that increase the intake charge efficiency ce are obtained in advance by experiments or the like corresponding to the operating state of the engine 1, a control map is created, and the engine operating state is determined from this control map. The valve timing control target value corresponding to is read, and signals from the crank angle sensor 26 and the cam angle sensor 31 are fed back to perform phase control of the VVT 13.

  In other words, the PCM 30 includes a VVT control unit 30a (control means) that changes the intake valve timing by controlling the VVT phase by the operation of the OCV 13f functionally according to the control program stored in the memory. The VVT control unit 30a and the VVT 13 constitute a valve timing control device.

  By the way, even if the valve timing is controlled while feedbacking the signals from the crank angle sensor 26 and the cam angle sensor 31, the rotor 13a of the VVT 13 is assembled to the cam shaft as in this embodiment. In this case, the operation timing of the intake valve 11 may slightly shift due to this assembly error, and if it is large, the combustibility of the engine 1 may be lowered.

  In addition, the operation of the VVT 13 may be restricted due to clogging of the hydraulic circuit, or an abnormality may occur in either the crank angle sensor 26 or the cam angle sensor 31, and the valve timing may be controlled by erroneous control. This greatly deviates from the target value, resulting in a significant decrease in combustibility.

  Furthermore, if the intake valve timing changes, the overlap period with the exhaust side also changes, and the amount of internal EGR also changes, but this internal EGR is once exhausted and then sucked back into the cylinder 2. Exhaust gas is also included, and the amount is not constant even if the valve overlap is the same. That is, the internal EGR amount undergoes periodic fluctuations (so-called cycle fluctuations) even during steady operation of the engine 1, which may adversely affect the combustibility and the like.

  In view of these points, in the engine 1 of this embodiment, the ion current generated in the combustion chamber 6 after ignition is detected by the ion current detection circuit 33 connected to the ignition circuit 8 as described above. A change in the state, and hence a change in the internal EGR rate, is estimated, and a failure of the VVT 13 is diagnosed based on the estimation result, or ignition timing correction control is performed.

(Estimation of VVT phase by ion current)
First, the concept of obtaining an evaluation value Ip (hereinafter referred to as ion parameter) having a high correlation with the internal EGR rate from the detected ion current value will be described. Conventionally, the ion current is considered to be generated using ions generated by combustion as a medium. In this embodiment, as shown in FIG. An ion current detection circuit 33 is connected.

  In the illustrated example, the ion current detection circuit 33 includes a power supply capacitor 33a connected in series to the end opposite to the ignition plug 7 on which the secondary side of the ignition coil 8b is grounded, and a detection circuit 33b. When the spark plug 7 is energized by the operation of 8a (ignition), a circuit is constituted by the electric charge stored in the power supply capacitor 33a and the ions generated in the combustion chamber 6, and a current flows, and this current is detected. The circuit 33b detects it. A signal from the detection circuit 33b is output to the PCM 30.

  The value of the ion current detected in this manner changes with the progress of the crank angle after ignition as schematically shown in FIG. 4B, and the waveform usually has two peaks in the first half and the second half. appear. The ionic current represented in the first half of the mountain is thought to be based on ions (radicals) present on the flame surface that expand as the flame nuclei grow after the mixture has ignited. It is strongly influenced by the speed of the combustion chamber and the flow strength of the combustion chamber. That is, the first half of the mountain becomes steeper as the initial combustion becomes active, and its peak advances.

  On the other hand, the ion current expressed in the latter half of the mountain is not only ions (radicals) generated by the combustion reaction itself as described above, but also NOx present in the burned gas is thermally ionized as the temperature of the combustion chamber rises. It is thought that the generated ions are also used as a medium, and the peak appears at the crank angle position where the temperature of the combustion chamber becomes the highest, and as a whole, the higher the combustion is, the lower the lower it is. .

  Then, as described above, with the change in valve timing, when the internal EGR amount increases, for example, when the overlap period of intake and exhaust changes, the combustion slows down as a whole, so that the ion current waveform is low overall. However, since the internal EGR, which is a burned gas, has a considerably high temperature, the combustion of the air-fuel mixture immediately after ignition (initial combustion) is rather accelerated, and the ion current that reflects this initial combustion state There is not much change in the first half of the waveform.

  On the other hand, the peak of the second half of the ion current waveform does not reflect the state of the initial combustion as described above, and becomes higher and steep as the combustion is active as a whole, while it becomes lower as the combustion becomes slower. Therefore, if the internal EGR state is to be determined, it is better to exclude the information on the first half of the mountain that has a low correlation with the internal EGR and to make the determination based on the information contained in the second half of the ion current waveform. It is done.

  Therefore, in this embodiment, as schematically shown in FIG. 4, the latter half of the ion current waveform, that is, a specific period on the retard side from the compression top dead center (TDC) (in the example of the figure, the exhaust valve 12 of the exhaust valve 12). If the ion current value detected until the valve opening timing EVO) is integrated, and the total integrated value (corresponding to the area of the range shown by hatching in the figure) is set to a range of 10 to 90% The crank angle position accumulated up to “good” is used as an evaluation value representing the activity and slowness of the entire combustion, that is, the ion parameter Ip.

  FIG. 5 (a) shows the ignition timing and VVT phase (intake side valve timing) with the crank angle position where up to 50% of the total integrated value of ion current in the specific period is integrated as the ion parameter Ip. It is the experimental data which showed the change of the ion parameter Ip corresponding to the change of. In the figure, the solid line graph shows the case where the ignition timing is relatively advanced, the broken line graph shows the case where the ignition timing is relatively retarded, and the alternate long and short dash line graph shows an intermediate ignition between them. The case is in time.

  According to the figure, if the ignition timing is the same, the ion parameter Ip moves to the retard side as the VVT phase is on the advance side and the overlap between the intake and exhaust is larger, and the internal EGR amount It can be seen that the increase slows down the combustion as a whole. Further, when the ignition timing is represented on the horizontal axis as shown in FIG. 5B, it can be seen that the ion parameter Ip moves to the retard side as the ignition timing is retarded. From both figures, it can be said that the VVT phase can be obtained based on the ion parameter Ip.

  Here, the data shown in FIG. 5 is for the low rotation and low load region of the engine 1, but it has been found that similar characteristics can be obtained even in the middle and high rotation regions of the engine. However, the combustion state of the engine 1 is influenced not only by the internal EGR but also by the so-called external EGR and the intake charge amount into the cylinder 2 combined with fresh air, the flow strength in the combustion chamber 6, and the temperature of the combustion chamber 6. Therefore, if the VVT phase is to be obtained quantitatively based on the ion parameter Ip, it is necessary to consider the operating state of the engine 1 in addition to the ignition timing.

  Therefore, in this embodiment, as shown in an example in FIG. 6 (a), medium and high loads in the engine operation range defined by the load of the engine 1 (the charging efficiency ce in the figure) and the rotational speed ne. A plurality of grid points (x, y) are set at appropriate intervals in a range excluding the area. Then, in the engine operating state corresponding to each lattice point, as shown in FIG. 5, data representing the correlation between the ion parameter Ip, the ignition timing, and the VVT phase is obtained by experiments.

  The experimental data thus obtained is organized, and the ion parameter Ip (Ip-1, Ip-2,..., Ip-b) and the ignition timing (Igt-1, Igt-2,. ..., Igt-a) and a calculation map for obtaining the VVT phase is created and electronically stored in the memory of the PCM 30. In this way, the ion parameter Ip is calculated from the ion current value detected during operation of the engine 1, and based on the ion parameter Ip and the ignition timing, the calculation map corresponding to the engine operating state at that time is referred to. , VVT phase can be obtained quantitatively.

  Incidentally, the engine operating state corresponding to the grid point (x, y) in FIG. 6 (a) may be dealt with by data interpolation. Further, for example, the outside air temperature, the engine water temperature, the atmospheric pressure, the air-fuel ratio, the VVT 13 The ion parameter Ip and the VVT phase obtained thereby may be corrected in accordance with the operating state of Further, when obtaining the ion parameter Ip, the external EGR is preferably constant, and more preferably stopped if possible.

-Calculation of ion parameters-
FIG. 7 is a flowchart specifically showing the procedure for obtaining the ion parameter Ip from the detected value of the ion current as described above. This flow is executed for each combustion cycle of each cylinder 2 when the control of the VVT 13 is executed by the VVT control unit 30a of the PCM 30 after the engine is warmed up (VVT execution flag is on), for example.

  In step SA1 after the start shown in the figure, after ignition, at least signals from the crank angle sensor 26, the cam angle sensor 31 and the ionic current detection circuit 33 are input to determine whether or not ignition noise has disappeared, that is, whether or not the ignition has ended. At the same time, it is determined whether or not compression top dead center (TDC) has been reached. If either determination is NO, the process returns. If both determinations are YES and ignition ends and TDC is reached, the process proceeds to step SA2 and detected. After the stored ion current value is stored in the memory in association with the crank angle, the process proceeds to step SA3.

  In step SA3, it is determined whether or not the valve opening timing EVO of the exhaust valve 12 has been reached. Until this time is reached, the process returns to step SA2, and the crank angle position and the ionic current value are determined at predetermined time intervals (for example, 0.1 milliseconds). Are stored in the memory in association with each other, and if EVO is reached, the process proceeds to step SA4 to calculate the ion parameter Ip. That is, the total accumulated value of the ion current stored so far is obtained, and the crank angle position where up to 50% is accumulated is specified as the ion parameter Ip.

  Then, the process proceeds to step SA5, and if the VVT control is being executed and the flag is on, the process returns to step SA1 to continue the above process (continue the process), while if the VVT control execution flag is off, the process is continued. NO is determined to be NO and the control ends (END).

-Estimation of VVT phase-
Next, the procedure for estimating the current VVT phase using the ion parameter Ip calculated as described above is shown in the first half of the flowchart of FIG. In step SB1 after the start as shown in the figure, it is determined whether or not a predetermined condition for diagnosing the VVT 13 is satisfied. For example, if the engine is cold or the engine is in a high load operation range, NO is determined and the process returns. For example, if the diagnosis condition is satisfied in the warm air-fuel ratio feedback region, the determination is YES, the process proceeds to step SB2, the VVT diagnosis flag indicating that the diagnosis of VVT 13 is performed is turned on, and the process proceeds to step SB3.

  In step SB3, referring to the calculation map of FIG. 6 as described above based on the ion parameter Ip calculated as in the flow of FIG. 7, the engine operating state (ce, ne), and the ignition timing, The current VVT phase is estimated (calculation of the actual VVT phase VP). Further, based on signals from the crank angle sensor 26 and the cam angle sensor 31, the monitor value avta of the VVT phase calculated by the VVT control unit 30a of the PCM 30 is read from the memory.

  In the subsequent step SB4, the VVT phase estimated value VP estimated in step SB3 and the monitor value avta read from the memory are stored as a set, and in the subsequent step SB5, the VVT phase estimated value VP and the monitor value avta are stored. It is determined whether or not a set of data has been collected as much as necessary for the diagnosis of VVT 13. If NO is collected, the process returns to step SB3 and the procedure of steps SB3 and SB4 is repeated while necessary data is collected. If YES is determined, the process proceeds to step SB6 and later to perform a failure diagnosis of the VVT 13.

  The determination as to whether or not necessary data has been collected in step SB5 can be made, for example, by determining whether the VVT phase monitor value avta is lower than the lower limit value avta-mn set in advance on the retard side and set in advance on the advance side. Change to the value avta-mx or more, that is, the VVT 13 has operated in a sufficiently wide range from the advance side to the retard side, and the VVT phase estimation value VP and the monitor value avta collected during that time What is necessary is just to determine with YES, when satisfy | filling both conditions that the number of data sets is more than predetermined number.

  That is, as schematically shown in FIG. 9 (a), the control of the VVT 13 is started by the VVT control unit 30a of the PCM 30 while the vehicle is running (VVT execution flag is on), and then the engine 1 is warmed up (the engine water temperature is reduced). As the VVT 13 diagnosis condition is established (VVT diagnosis flag is turned on) and the diagnosis of the VVT 13 is started as described above, the vehicle is If the running state changes variously, and the VVT 13 operates over a sufficiently wide range, and the data of the set of the estimated value VP and the monitor value avta of the phase is collected as much as necessary, the following is obtained. Then, the failure of the VVT 13 is diagnosed.

-VVT failure diagnosis-
Next, failure diagnosis of the VVT 13 performed based on the data of the set of the VVT phase estimated value VP and the monitor value avta obtained as described above will be described with reference to FIG. As shown in the figure, a graph (VVT operating characteristic graph) representing the correlation between the monitor value avta and the estimated value VP based on the ion parameter Ip from the lower limit value avta-mn to the upper limit value avta-mx of the VVT phase monitor value avta is obtained. If there is no failure in both the VVT 13 main body and the control system including the sensor and the hydraulic circuit, the two are almost coincident with each other and become a straight line graph indicated by a one-dot chain line in the figure.

  On the other hand, for example, the rotor 13a of the VVT 13 is assembled so as to be shifted in the rotational direction with respect to the camshaft, and as a result, the operation timing of the intake valve 11 is either the advance side or the retard side. When they are deviated, the estimated value VP of the VVT phase based on the ion parameter Ip is uniformly deviated to the advance side or the retard side irrespective of the magnitude of the monitor value avta, and the graph of the VVT operating characteristic in this case Is as shown by the solid line in the figure.

  Further, when an abnormality occurs in the crank angle sensor 26 or the cam angle sensor 31 used for controlling the VVT 13, the monitor value avta calculated based on the signals from these sensors is a value that differs greatly from the actual VVT phase. However, in this case, there is no correlation between the monitor value avta and the estimated value VP as shown in the graph of the VVT operating characteristics, and it is considered that the value becomes irregular.

  Therefore, a graph of the VVT operating characteristics as described above is actually obtained, and based on this, a failure of the VVT 13 and its control system is distinguished and diagnosed. The specific procedure of this diagnosis is shown in the latter half of the flowchart of FIG. 8, and first, based on the data of the estimated value VP and the monitor value avta of the VVT phase collected in steps SB3 to SB5 as described above. In step SB6, a graph of the VVT operating characteristics as described above is obtained by, for example, regression analysis.

  In subsequent step SB7, deviations (VVT phase deviations) ΔVP @ mx and ΔVP @ mn of the estimated value VP from the monitor value avta are obtained on the advance side and the retard side of the VVT phase from the graph of the VVT operating characteristics. In the example of the figure, ΔVP @ mx and ΔVP @ mn are respectively obtained at the upper limit and lower limit of the monitor value avta. If the estimated value VP is larger than the monitor value avta, the deviation becomes a positive value, and conversely, the estimated value VP Is smaller than the monitor value avta, the deviation becomes a negative value. However, the larger the absolute value of the deviation, the more the VVT phase is shifted.

  Therefore, in the following step SB8, first, it is determined whether the absolute values of the VVT phase shifts ΔVP @ mx and ΔVP @ mn on each of the advance side and the retard side are equal to or less than a predetermined failure determination value: determination ΔVP. If the amount is equal to or less than the determination value (YES), the process proceeds to step SB9, where it is determined that there is no failure, and the control ends (end). On the other hand, if the absolute value of any one of the VVT phase shifts ΔVP @ mx and ΔVP @ mn exceeds the determination ΔVP (NO), the process proceeds to step SB10, and this time the VVT on each of the advance side and the retard side It is compared whether the phase shifts ΔVP @ mx and ΔVP @ mn are substantially the same value (ΔVP @ mx≈ΔVP @ mn?).

  If the determination is YES, it means that the VVT phase shift ΔVP is substantially the same over a wide range from the advance side to the retard side, and the VVT operating characteristic is indicated by a solid line in FIG. 9 (b). Therefore, the process proceeds to step SB11, where it is determined that the assembly displacement of the VVT 13 with respect to the camshaft is informed, and the control ends (end).

  On the other hand, if the determination in step SB10 is NO, the VVT phase shift ΔVP indicates an irregular value, and the correlation shown in the graph appears between the estimated value VP of the VVT phase and the monitor value avta. Therefore, in this case, it is determined that an abnormality has occurred in the crank angle sensor 26 or the cam angle sensor 31 that outputs a signal for calculating the monitor value avta, and this is notified (the abnormality of the control system is notified). ), The control ends (end).

  Thus, the occurrence of a failure in the VVT phase control is diagnosed and notified by discriminating the mechanical assembly deviation of the VVT 13 itself and the abnormality of its control system, so that an appropriate response according to the state of the failure can be obtained. It becomes possible. That is, when the cause of the failure is a mechanical assembly deviation of the VVT 13 itself, as is apparent from the graph of FIG. 9B, the VVT phase is uniformly shifted to the advance side or the retard side. The target value of VVT phase control may be corrected uniformly so that this deviation is eliminated.

  Specifically, as shown in an example of the flow of correction control in FIG. 10, first, in step SB13 after the start, it is determined whether or not the assembly deviation of VVT 13 has been determined in steps SB10 and SB11 of the flow of FIG. If NO in which the assembly deviation has not been determined, the control ends (end). On the other hand, if YES in which the assembly deviation has been determined, the process proceeds to step SB14, where the average value of the VVT phase deviation ΔVP caused by the assembly deviation is obtained. (In the example of the figure, average values of VVT phase shifts ΔVP @ mx and ΔVP @ mn on each of the advance side and the retard side are obtained).

  In step SB15, the target value (phase control value) of VVT phase control performed by the VVT control unit 30a of the PCM 30 is corrected by the average value of the phase shift ΔVP obtained in step SB14 (that is, Then, the control target value is shifted to the advance side or the retard side accordingly), and thereafter the correction control is ended (END). If the VVT phase control is corrected so that the influence of the assembly deviation is eliminated in this way, the intake valve timing becomes more appropriate, and the operating efficiency of the engine 1 is improved.

  A crank in which the ion current values detected after TDC in the combustion chamber 6 of the engine 1 are integrated by the flow of FIG. 7 and the first half of the flow of FIG. 8, and up to a predetermined ratio of the total integrated value is integrated. The determination unit 30b is configured to identify the angular position (ion parameter Ip) and thereby determine the change state of the VVT phase. In this embodiment, the determination means 30b is configured to estimate the VVT phase, that is, the intake valve timing based on the ion parameter Ip and the ignition timing and further considering the engine operating state.

  Further, the VVT phase (estimated value VP) estimated by the determination means 30b of the PCM 30 and the monitor value avta (corresponding to the target value of VVT phase control) are compared by the procedure in the latter half of the flow of FIG. A failure notification means 30c is configured to diagnose and diagnose a failure related to control based on a mechanical shift of the VVT 13 itself and an abnormality of the control system, and notify the diagnosis.

  Further, according to the flow of FIG. 11, the VVT phase control, that is, the control of the intake valve timing is performed in accordance with the deviation ΔVP between the VVT phase (estimated value VP) estimated by the determining means 30b of the PCM 30 and the monitor value avta. A valve timing correction means 30d for correcting the above is configured.

(Ignition timing correction control)
Next, the ignition timing correction performed based on the VVT phase (estimated value VP) estimated as described above will be described. That is, in general, the ignition timing is set so that the engine operating efficiency is maximized while avoiding knocking or the like, and at this time, the peak of the cylinder internal pressure appears at 15-20 ° CA after compression top dead center (ATDC). However, when the internal EGR amount deviates from the target value due to the above-described deviation in VVT phase control or due to cycle fluctuation, and the combustion becomes slow, for example, the peak of the cylinder internal pressure is retarded. To the side, the efficiency will be reduced.

  Therefore, in this embodiment, by correcting the ignition timing based on the VVT phase (estimated value VP) estimated from the ion parameter Ip as described above, even if the internal EGR amount deviates from the target value, the peak of the cylinder internal pressure Appears in the above-mentioned desirable range so as to suppress a decrease in the operating efficiency of the engine 1.

  That is, as schematically shown in FIG. 11 corresponding to FIG. 5 (b), for example, it is determined from the current ignition timing (actual Igt) of the engine 1 and the target VVT phase of control (which may be the monitor value avta). When the ion parameter Ip (actual Ip) obtained from the detected value of the ion current is on the advance side with respect to a, and the actual VVT phase (estimated value VP) is estimated from the corresponding point b, VVT Even if the phases are different, if the ignition timing is retarded to the appropriate Igt so that the value of the ion parameter Ip is substantially the same as the point a (point c in the figure), the combustion speed increases due to the deviation of the internal EGR amount. Even if it is, the peak of the cylinder internal pressure appears in the desired range as described above by retarding the ignition timing accordingly.

  A specific procedure for correcting the ignition timing as described above will be described below with reference to the flowchart of FIG. 12. First, in step SC1 after the start, it is determined whether or not the VVT control is being executed, and the VVT execution flag is turned on. If it is being executed, the routine proceeds to step SC2, where an ignition timing correction flag indicating that the ignition timing is to be corrected is turned on, and the routine proceeds to step SC3.

  In step SC3, the actual VVT phase is calculated (estimation of the actual VVT phase) as in step SB3 of the flow of FIG. 8, and the estimated actual VVT phase (estimated value VP) and, for example, the monitor value avta are calculated. Based on the current ignition timing (actual Igt), an appropriate ignition timing (appropriate Igt) is calculated as described with reference to FIG. For this calculation, an arithmetic map as shown in FIG. 6B may be used.

  Subsequently, in step SC4, the ignition timing deviation ΔIgt between the actual Igt and the appropriate Igt is calculated (ΔIgt = appropriate Igt−actual Igt). In step SC5, the current ignition timing is corrected to correct the ignition timing. The offset value Igtofs added to the control value (actual Igt) is calculated and added to the basic control target value Igtpcmseq corresponding to the operating state of the engine 1 to calculate the next control value of the ignition timing. (Step SC6). Note that ΔIgt (−1) and Igtofs (−1) both indicate values in the previous control cycle.

  That is, in this embodiment, as schematically shown in FIG. 13 (a), in order to correct the basic control target value Igtpcmseq set in advance corresponding to the operating state of the engine 1. The offset value Igtofs is always added to determine the ignition timing control value, and the offset value Igtofs is updated in accordance with the ignition timing deviation ΔIgt obtained for each control cycle. Yes.

  Thus, by controlling the ignition timing by adding the offset value Igtofs to the basic control target value Igtpcmseq, even if the basic control target value Igtpcmseq changes due to a change in the operating state of the engine 1, First, ignition timing control in which the offset value Igtofs is reflected is performed, and the influence of individual variations of the engine 1 can be reduced. Further, by correcting the ignition timing in accordance with the deviation ΔIgt, the influence of the change in the internal EGR amount due to the deviation of the VVT phase control and the cycle fluctuation is reduced, and the operating efficiency of the engine 1 is increased.

  FIG. 13 (b) shows that the VVT control unit 30a of the PCM 30 starts the control of the VVT 13 (VVT control execution flag is turned on) while the vehicle is running, and the ignition timing correction is started as described above. FIG. 6 schematically shows a change in the appropriate Igt obtained based on the estimated value VP and a change in the actual Igt that follows this change. For example, due to the cycle fluctuation of the internal EGR amount, the appropriate Igt as shown by the solid line in FIG. When I changes, the actual Igt also changes to follow this change (indicated by a one-dotted line in the figure), and it can be seen that the deviation between the two gradually decreases.

  Then, while the VVT control is being executed (YES in step SC7 in FIG. 12), the procedure of steps SC3 to SC6 is repeated. On the other hand, if the VVT control is ended (VVT execution flag is OFF), NO is determined in step SC7 and the step is performed. Proceeding to SC8, the ignition timing correction flag is turned off, and the control ends (end).

  Based on the VVT phase (estimated value VP) estimated by the determination means 30b of the PCM 30, that is, the valve operation timing of the intake air according to the flow of FIG. The ignition timing correction means 30e is configured to correct the ignition timing so that the ignition timing is shifted to the retarded side if the shift is reversed.

  Therefore, according to the diagnostic device of the valve timing control device of the engine 1 according to this embodiment, based on the ionic current value detected on the retard side from the TDC in the combustion chamber 6 in the cylinder 2, that is, with the internal EGR. Since the information of the first half part of the ion current waveform having a low correlation is excluded, the state of the internal EGR having a high correlation with this can be accurately determined based on the information contained in the second half part of the ion current waveform. The VVT phase corresponding to the EGR state, that is, the operation timing of the intake valve 11 can be determined more finely than before.

  At that time, the crank angle position obtained by integrating up to a predetermined ratio of the total integrated value of the ion current in the specific period is used as an evaluation value (ion parameter Ip), and in addition to the ion parameter Ip, the ignition timing, the charging efficiency ce, and the engine Since the VVT phase can be accurately estimated on the basis of the rotational speed ne, the estimation result distinguishes the VVT control system failure from the assembly error of the VVT 13 itself and the abnormality of the control system, and makes a detailed and accurate diagnosis. Accordingly, it is possible to notify at an early stage, thereby making it possible to take an appropriate response according to the failure state.

  That is, for example, when the assembly deviation of the VVT 13 is determined as described above, if the control is corrected so as to eliminate the VVT phase deviation ΔVP caused by this, the valve timing is made more appropriate and the operation of the engine 1 is performed. Efficiency can be improved.

  Alternatively, the ignition timing can be corrected in accordance with the detected VVT phase shift ΔVP. In this way, the ignition timing is advanced or retarded in accordance with the actual internal EGR deviation, thereby causing the peak of the cylinder internal pressure. Can be caused to appear in a desirable range, so that not only the failure of the VVT control system can be dealt with, but also the influence of the change in the internal EGR amount due to the cycle fluctuation can be reduced, and the operating efficiency of the engine 1 can be improved. .

  In the diagnostic device of this embodiment, the state of the external EGR is determined based on the ion current value detected in a specific period after TDC in the combustion chamber 6 of the engine 1. Not only from the TDC, but from about 5 to 10 ° CA before and after that.

  Further, as the ion parameter Ip, a crank angle position in which up to a predetermined ratio (10 to 90%) of the total integrated value of the ion current in the specific period is used is not limited to this, but the predetermined ratio is integrated. The ion parameter Ip can be the slope, maximum value, etc. of the ion current waveform until it is generated.

  Further, in the above embodiment, in steps SB3 to SB5 of the flow of FIG. 8, the data of the set of the estimated value VP of the VVT phase and the monitor value avta is stored, and the VVT operation is performed after collecting this data for a predetermined number or more. Although a characteristic graph is identified and a fault diagnosis is performed based on the characteristic graph, the present invention is not limited to this. For example, in the same step SB4, the VVT phase shift ΔVP is calculated from the VVT phase estimated value VP and the monitor value avta, and the average value is calculated after collecting a predetermined number of data of the phase shift ΔVP. Depending on whether or not this is the determination value: determination ΔVP or less, it may be determined whether there is an assembly error.

  Furthermore, in the above-described embodiment, the VVT 13 is disposed on the intake side of the engine 1 and thereby the operation timing of the intake valve 11 is controlled. However, the present invention is not limited to this, and the VVT is disposed on the exhaust side. It may be a thing. Further, the configuration of the VVT is not limited to that of the above-described embodiment, and of course, it corresponds to various variable mechanisms of the type that changes the phase, and instead of or in addition to this, the intake and exhaust valves 11 and 12 The present invention can also be applied to an engine equipped with a variable valve mechanism in which the lift amount is variable and each valve is driven by hydraulic pressure or electromagnetic force.

1 is a schematic structural diagram of an engine provided with a diagnostic device for a valve timing control device according to an embodiment of the present invention. It is explanatory drawing which shows typically the structure (a) of an ion current detection circuit, and the ion current waveform (b) detected by this. It is explanatory drawing (a) which shows the lift curve of an intake / exhaust valve, and the fragmentary sectional view (b) which shows an example of the structure of VVT. It is explanatory drawing which shows the definition of an ion parameter typically. It is a graph which shows an ignition timing, a VVT phase, and the change of an ion parameter mutually matched. Explanation schematically showing a grid point (a) set in the engine operating region and a calculation map (b) for obtaining the VVT phase from the ion parameter and the ignition timing in the engine operating state corresponding to each grid point. FIG. It is a flowchart figure which shows the procedure of calculation of an ion parameter. It is a flowchart figure which shows the procedure of estimation of a VVT phase, and the failure diagnosis of a VVT control system based on this. It is explanatory drawing which shows the concept of the fault diagnosis of a VVT control system. It is a flowchart figure which shows the correction | amendment procedure of VVT control. It is explanatory drawing which shows the idea of ignition timing correction | amendment. It is a flowchart figure which shows the procedure of ignition timing correction | amendment. It is explanatory drawing which shows the procedure (a) of ignition timing correction | amendment, and the ignition timing (b) which changes by this.

Explanation of symbols

1 Engine 6 Combustion chamber 11 Intake valve
12 Exhaust valve
13 VVT (phase variable mechanism)
30 PCM
30a VVT controller (control means)
30b determination means 30c failure notification means 30d valve timing correction means 30e ignition timing correction means 33 ion current detection circuit (ion current detection means)

Claims (7)

A valve timing control device diagnostic device for controlling the operation timing of at least one of an intake valve and an exhaust valve of an engine,
Ion current detection means for detecting ion current generated in the combustion chamber of the engine;
Based on the ionic current value detected by the ionic current detection means over a specific period from the vicinity of the compression top dead center in the combustion chamber to the retarded angle side, the valve operation timing change state by the valve timing control device is changed. A diagnostic device for a valve timing control device comprising: a determination means for determining.   The determination unit integrates the ion current values detected over the entire specified period, specifies a crank angle position where up to a predetermined ratio of the total integrated value is integrated, and determines the valve operation timing based on the crank angle position. The diagnostic device according to claim 1, wherein the diagnostic device is configured to determine a change state. The engine is of spark ignition type,
The diagnostic device according to claim 2, wherein the determination means is configured to estimate a valve operation timing based on at least the specified crank angle position and ignition timing.   Comparing the valve operation timing estimated by the determination means with the target value of the valve operation timing in the valve timing control device, it comprises a failure notification means for diagnosing a failure related to the valve timing control device and notifying the failure. The diagnostic device according to claim 3. The valve timing control device includes a variable mechanism that can change the valve operation timing, and a control unit that controls the variable mechanism.
5. The diagnostic apparatus according to claim 4, wherein the failure notification means is configured to discriminate between a mechanical shift of the variable mechanism and an abnormality of the control means.   The valve timing correction means for correcting control of the valve operation timing by the valve timing control device based on the valve operation timing estimated by the determination means is provided. Diagnostic device. 6. The diagnostic apparatus according to claim 3, further comprising an ignition timing correction unit that corrects an ignition timing of the engine based on the valve operation timing estimated by the determination unit.

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