JP2007040208A - Controller for internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a controller for an internal combustion engine capable of increasing detection precision of a crank angle during reference time of pulse signal. <P>SOLUTION: This controller for the internal combustion engine calculates division time (ΔTi-1)/n by dividing time ΔTi-1 at the preceding period equally into n (six) parts, decides a crank angle at such timing Ti_k (k=1, 2 to n-1) that predetermined number of division times elapse from reference time i of pulse signal at a period at this time as a basic intermediate crank angle θi_k, calculates a crank angle θi_k' at which predetermined parameter related to a condition in a cylinder at the timing Ti_k becomes equal to the parameter at reference time of pulse signal at the period at this time or before it, and compares the calculated crank angle θi_k' with the basic crank angle θi_k to determine whether the basic crank angle θi_k is correct or not. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a control device for an internal combustion engine, and more particularly, to a control device for an internal combustion engine that executes various processes and controls using a crank angle value of the internal combustion engine.

  The crank angle of the internal combustion engine is detected using a crank angle sensor, and control is performed using the detected crank angle value, or various processes (angle synchronization processing) are performed in synchronization with the crank angle. A control device for an internal combustion engine is known. In particular, the signal obtained by the crank angle sensor is a pulse signal generated at a predetermined crank angle cycle, and the rising timing of the pulse signal is normally set to the reference time (trigger timing) of the pulse signal.

  There are also cases where it is desired to recognize the crank angle between the reference times of two pulse signals, or to execute a predetermined process, typically an interrupt process, in synchronization with such intermediate crank angle timing. Therefore, a process called multiplication that divides the time between the reference times into a plurality of times may be executed. Note that interrupt processing is performed when a CPU (microprocessor) is required to perform processing with a higher priority level than the processing routine currently being executed, or when processing needs to be performed according to some external timing. Is called.

  For example, Patent Document 1 discloses that an interrupt request signal generated by an interrupt generation circuit is divided and / or multiplied by a frequency divider / multiplier circuit to change an interrupt request signal generation cycle, and an interrupt request signal is generated at an arbitrary timing. An interrupt control device that generates software and reduces the load of software processing is disclosed.

JP 2003-131890 A

  By the way, when determining the intermediate crank angle during such a reference time, conventionally, the time from the previous pulse to the current pulse (not the angle) is measured, and the divided time is obtained by dividing the time by n. It is assumed that when a predetermined number m of divided time has elapsed from the pulse reference time, an angle obtained by multiplying the angle obtained by dividing the crank angle period by n into the predetermined number m has elapsed from the pulse reference time.

  However, according to this, since the intermediate crank angle in the current cycle is determined using the time of the previous cycle, the determined intermediate crank angle may cause an error with respect to the true crank angle. For example, when the time between the pulse reference times changes momentarily as the engine speed changes, such as when the internal combustion engine is accelerating, the time length between the previous cycle and the current cycle is different. The angle will deviate from the true crank angle. Thus, with the conventional method, it is difficult to accurately detect the crank angle during the pulse reference time, and it is difficult to execute processing and control using such an accurate crank angle value. There's a problem.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a control device for an internal combustion engine that can improve the detection accuracy of a crank angle during a reference time of a pulse signal.

  One form of a control device for an internal combustion engine according to the present invention is a pulse signal generating means for generating a pulse signal at a predetermined crank angle cycle, and a pulse signal generated at a current cycle from a reference time of a pulse signal generated at a previous cycle. A division time calculation means for calculating a division time by dividing the time until the reference time into n, and a crank angle at a timing when a predetermined number of division times have elapsed from the reference time of the pulse signal in the current cycle as a basic intermediate crank angle The basic intermediate crank angle determining means to be determined and the crank angle at which the predetermined parameter related to the in-cylinder state is equal to the parameter at the reference time of the pulse signal in the current or previous period is calculated. The calculation means compares the calculated crank angle with the basic crank angle to determine whether the basic crank angle is correct or not. Characterized in that a constant determining means.

Preferably, the parameter is PV ^kappa (where, P is cylinder pressure, V is cylinder volume, kappa is a predetermined constant), and further comprises a cylinder pressure sensor which detects the cylinder pressure, the in the timing parameters PV ^κ uses the in-cylinder pressure value detected by the in-cylinder pressure sensor at the timing, and the parameter PV ^κ at the reference time of the pulse signal in the current or previous period is the in-cylinder pressure sensor at the reference time. And the cylinder pressure value corresponding to the crank angle at the reference time is used.

  Preferably, when the determination unit determines that the calculated crank angle is different from the basic intermediate crank angle, the correction unit corrects the basic intermediate crank angle based on the calculated crank angle. Is further provided.

  Preferably, the apparatus further includes means for executing predetermined processing or control based on the crank angle value corrected by the correction means.

  Preferably, the number of cylinders of the internal combustion engine is 3 or more.

  In another aspect of the control device for an internal combustion engine according to the present invention, a pulse signal generating means for generating a pulse signal at a predetermined crank angle period and a reference time of the pulse signal generated at the previous period are generated at the current period. The divided time calculation means for calculating the divided time by dividing the time until the reference time of the pulse signal into n, and the in-cylinder state at the timing when a predetermined number of divided times have elapsed from the reference time of the pulse signal in this cycle And calculating a crank angle such that the calculated parameter is equal to a parameter at the reference time of the pulse signal in the current or previous period, and calculating the calculated crank angle. Crank angle determining means for determining the crank angle at the timing is provided.

  According to the present invention, it is possible to realize a control device for an internal combustion engine that can improve the accuracy of crank angle detection during the reference time of a pulse signal.

  Hereinafter, a preferred embodiment of the present invention will be described with reference to the accompanying drawings.

  The control device for an internal combustion engine in the present embodiment directly controls various control amounts (ignition timing, etc.) of the engine based on in-cylinder information detected by the in-cylinder information detection means, unlike a normal control device. The present inventor has intensively studied to enable highly accurate control of the internal combustion engine while reducing the calculation load, and as a result, a control method for the internal combustion engine using such in-cylinder information. I came up with a new idea. In the conventional method, there is a map control in which the control amount that seems to be optimal for each operating state of the engine is obtained by an experiment or the like in advance and mapped, and each map value is applied during actual engine operation to control the engine. It was general. In contrast, the method developed by the present inventor directly detects the combustion state in the cylinder during engine operation, and performs various controls so as to adjust the detected combustion state to a predetermined optimum combustion state. The amount is to be controlled. According to this new method, it is possible to greatly simplify the process of creating various maps, that is, the adaptation, which has conventionally required a lot of time and labor, and to greatly shorten the development period. There is.

  In-cylinder information representative of such in-cylinder combustion state is typically in-cylinder pressure. Therefore, as means for detecting in-cylinder information, in-cylinder pressure detecting means, specifically, in-cylinder pressure sensor is typical. is there. In addition, since the combustion in the cylinder is a chemical reaction and ions are generated during combustion, this ion generation amount is used as in-cylinder information, and an ion current detection device that outputs a current corresponding to this ion generation amount is provided in the cylinder. It can be used as inside information detection means. In any case, the in-cylinder information and the means for detecting this are not limited to these. For example, the in-cylinder information may be indirectly detected as well as the in-cylinder pressure sensor and the ion current detection device in which the detection unit is exposed in the cylinder.

  The control amount to be controlled is typically a combustion start timing (ignition timing for a gasoline engine, ignition timing for a diesel engine), a fuel injection amount, a fuel injection timing, etc., but is not limited to these, for example, a valve overlap amount Or the amount of air sucked into the cylinder may be used. As an example, the case of the combustion start time will be mainly described below.

The inventor has determined that the in-cylinder pressure detected by the in-cylinder pressure sensor and the in-cylinder volume at the time of detection of the in-cylinder pressure to enable highly accurate control of the combustion start timing in the cylinder of the internal combustion engine. It came to pay attention to the control parameter calculated based on it. More specifically, the inventors set P (θ) as the in-cylinder pressure detected by the in-cylinder pressure detecting means when the crank angle is θ, and the in-cylinder volume when the crank angle is θ as V (Θ) where the specific heat ratio is κ, the in-cylinder pressure P (θ) and the value V (θ) ^κ , which is the power of the in-cylinder volume V (θ) by the specific heat ratio (predetermined index) ^κ The control parameter P (θ) V (θ) ^κ (hereinafter referred to as “PV ^κ ” as appropriate) obtained as a product was noted. Then, the present inventor first has a correlation as shown in FIG. 1 between the change pattern of the heat generation amount Q in the cylinder of the internal combustion engine with respect to the crank angle and the change pattern of the control parameter PV ^κ with respect to the crank angle. I found out. In FIG. 1, −360 °, 0 °, and 360 ° correspond to the top dead center, and −180 ° and 180 ° correspond to the bottom dead center.

In FIG. 1, the solid line shows the in-cylinder pressure detected at a predetermined minute crank angle in a predetermined model cylinder and the value obtained by raising the in-cylinder volume at the time of detection of the in-cylinder pressure by a predetermined specific heat ratio κ. This is a plot of the control parameter PV ^κ which is the product. In FIG. 1, the broken line is calculated and plotted with the heat generation amount Q in the model cylinder as Q = ＱdQ based on the following equation (1). In either case, for simplicity, κ = 1.32.
dQ / dθ = {dP / dθ · V + κ · P · dV / dθ} / {κ-1} (1)

As can be seen from the results shown in FIG. 1, the change pattern of the heat generation amount Q with respect to the crank angle and the change pattern of the control parameter PV ^κ with respect to the crank angle are almost the same (similar), and in particular, Before and after the start of combustion (ignition or ignition) of the air-fuel mixture (for example, a range from about −180 ° to about 135 ° in FIG. 1), the change pattern of the heat generation amount Q and the change pattern of the control parameter PV ^κ It can be seen that it agrees very well.

In one aspect of the present invention, the cylinder pressure detected by the cylinder pressure detecting means is utilized using the correlation between the newly generated in-cylinder heat generation amount Q and the control parameter PV ^κ, and the cylinder Based on the control parameter PV ^κ calculated from the in-cylinder volume at the time of detecting the internal pressure, the ratio of the heat generation amount up to a predetermined timing between the two points with respect to the total heat generation amount between the two points A combustion rate (MFB) is determined. Here, if the combustion ratio in the cylinder is calculated based on the control parameter PV ^κ , the combustion ratio in the cylinder can be accurately obtained without requiring high-load calculation processing. That is, as shown in FIG. 2, the combustion rate obtained based on the control parameter PV ^κ (see the solid line in the figure) is substantially the same as the combustion rate obtained based on the heat generation rate (see the broken line in the figure). To do.

In FIG. 2, the solid line represents the combustion ratio at the timing when the crank angle = θ in the model cylinder described above, calculated according to the following equation (2), and plotted based on the detected in-cylinder pressure P (θ). Is. However, for simplicity, κ = 1.32.
MFB = {P (θ) V (θ) ^κ− P (−120 °) · V (−120 °) ^κ } / {P (120 °) · V (120 °) ^κ− P (−120 °) · V (−120 °) ^κ } × 100 (%)
... (2)

  In FIG. 2, the broken line indicates the combustion ratio at the timing when the crank angle = θ in the above model cylinder, according to the above equation (1) and the following equation (3), and the detected in-cylinder pressure P (θ). Calculated based on the above and plotted. Also in this case, for simplicity, κ = 1.32.

And in one form of this invention, the combustion ratio calculated ^| required based on the control parameter PV ( ^kappa) calculated from the cylinder pressure detected by the cylinder pressure detection means and the cylinder volume at the time of the said cylinder pressure detection The combustion start timing (spark ignition timing or compression ignition timing) in the cylinder is controlled so that the value matches the target value. That is, when the combustion state in the cylinder is optimal, in other words, when the combustion is started from the optimal combustion start timing (MBT), the combustion ratio at a certain crank angle can be obtained experimentally or empirically. Therefore, by controlling the combustion start timing in the cylinder so that the actual combustion ratio at the constant crank angle matches the target value, and by controlling other control amounts, combustion in the cylinder Can be optimized.

In one embodiment of the present invention, the in-cylinder combustion state is optimal when the combustion ratio reaches 50% when the crank angle θ is 8 ° after compression top dead center. However, this value can take various values depending on the engine. Therefore, from the equation (2) and the control parameter PV ^κ at the time when the crank angle θ is −120 °, 8 ° and 120 °, the actual combustion ratio at the time when the crank angle θ is 8 ° after compression top dead center is measured. The measured value is calculated and compared with the target value of 50%. If the measured value is larger than the target value, the combustion start timing is retarded because the combustion start timing is too early, and the measured value is smaller than the target value. If the combustion start timing is too late, the combustion start timing is advanced. Thus, only the crank angle and the in-cylinder pressure at three points (−120 °, 8 ° and 120 °) are detected, and the calculation is only a simple calculation according to the equation (2). Note that the in-cylinder volume is uniquely determined from the crank angle, and these can be said to be equivalent. Therefore, the control amount of the engine can be controlled by extremely simple detection and calculation, and the calculation load and control load can be remarkably reduced.

  Next, an embodiment of a control device for an internal combustion engine that executes such control will be specifically described.

  FIG. 3 is a schematic configuration diagram showing an internal combustion engine according to the present invention. The internal combustion engine 1 shown in FIG. 1 generates power by burning a fuel / air mixture in a combustion chamber 3 formed in a cylinder block 2 and reciprocating a piston 4 in the combustion chamber 3. Is. Although only one cylinder is shown in FIG. 3, the internal combustion engine 1 is configured as a multi-cylinder engine, and the internal combustion engine 1 of the present embodiment is configured as a four-cylinder engine, for example. The internal combustion engine 1 of the present embodiment is a spark ignition internal combustion engine, more specifically a gasoline engine.

  The intake port of each combustion chamber 3 is connected to the intake pipe 5 via an intake manifold, and the exhaust port of each combustion chamber 3 is connected to the exhaust pipe 6 via an exhaust manifold. The cylinder head of the internal combustion engine 1 is provided with an intake valve Vi for opening and closing the intake port and an exhaust valve Ve for opening and closing the exhaust port for each cylinder, that is, for each combustion chamber 3. Each intake valve Vi and each exhaust valve Ve are opened and closed by a valve mechanism VM having a variable valve timing function. Further, the internal combustion engine 1 has a spark plug 7 for each cylinder, and the spark plug 7 is disposed in the cylinder head so as to face the corresponding combustion chamber 3.

  The intake pipe 5 is connected to a surge tank 8 as shown in FIG. An air supply pipe L1 is connected to the surge tank 8, and the air supply pipe L1 is connected to an air intake port (not shown) via an air cleaner 9. A throttle valve (electronically controlled throttle valve in this embodiment) 10 is incorporated in the middle of the supply pipe L1 (between the surge tank 8 and the air cleaner 9). On the other hand, as shown in FIG. 3, a front-stage catalyst device 11 a including a three-way catalyst and a rear-stage catalyst device 11 b including a NOx storage reduction catalyst are connected to the exhaust pipe 6.

  Furthermore, as shown in FIG. 3, the internal combustion engine 1 has an injector 12 for each cylinder, and the injector 12 is disposed in the cylinder head so as to face the corresponding combustion chamber 3. Each piston 4 of the internal combustion engine 1 is configured as a so-called deep dish top surface type, and a recess 4a is formed on the upper surface thereof. In the internal combustion engine 1, fuel such as gasoline is directly injected from each injector 12 toward the recess 4 a of the piston 4 in each combustion chamber 3 in a state where air is sucked into each combustion chamber 3. As a result, in the internal combustion engine 1, the fuel / air mixture layer is formed (stratified) in the vicinity of the spark plug 7 so as to be separated from the surrounding air layer. And stable stratified combustion can be performed. The internal combustion engine 1 of the present embodiment is described as a so-called direct injection engine, but is not limited to this, and the present invention can be applied to an intake pipe (intake port) injection type internal combustion engine. Not too long.

  Each of the spark plugs 7, the throttle valve 10, the injectors 12, the valve operating mechanism VM and the like described above are electrically connected to an electronic control unit (hereinafter referred to as ECU) 20 that functions as a control device for the internal combustion engine 1. The ECU 20 includes a CPU, a ROM, a RAM, an input / output port, a storage device, and the like, all not shown. As shown in FIG. 3, various sensors including the crank angle sensor 14 of the internal combustion engine 1 are electrically connected to the ECU 20 via an A / D converter or the like (not shown). The ECU 20 uses the various maps stored in the storage device and the spark plug 7, the throttle valve 10, the injector 12, and the valve mechanism VM so that a desired output can be obtained based on detection values of various sensors. Control etc.

  The internal combustion engine 1 has an in-cylinder pressure sensor 15 including a semiconductor element, a piezoelectric element, an optical fiber detection element, or the like in each cylinder. Each in-cylinder pressure sensor 15 is disposed on the cylinder head so that the pressure receiving surface faces the corresponding combustion chamber 3, and is electrically connected to the ECU 20 via an A / D converter (not shown). Each in-cylinder pressure sensor 15 detects the in-cylinder pressure (relative pressure) in the corresponding combustion chamber 3 and gives a signal indicating the detected value to the ECU 20. Furthermore, the internal combustion engine 1 has an intake pressure sensor 16 that detects the pressure (intake pressure) of intake air in the surge tank 8 as an absolute pressure. The intake pressure sensor 16 is electrically connected to the ECU 20 via an A / D converter (not shown) or the like, and gives a signal indicating the detected absolute pressure of the intake air in the surge tank 8 to the ECU 20. The detection values of the crank angle sensor 14, each in-cylinder pressure sensor 15 and the intake pressure sensor 16 are sequentially given to the ECU 20 every minute time, and stored in a predetermined storage area (buffer) of the ECU 20 by a predetermined amount.

  Next, the detection of the crank angle by the crank angle sensor 14 will be described. A rotor 26 as shown in FIG. 4 (A) is fixed to the crankshaft of the internal combustion engine 1. 34 tooth protrusions 26a, which are only missing, are formed at a predetermined angle Δθ, for example, at intervals of 10 °. A crank angle sensor 14 composed of an electromagnetic pickup is disposed so as to face the protrusions 26a. The crank angle sensor 14 generates an output pulse every time the protrusion 26 a of the rotor 26 passes the crank angle sensor 27.

  That is, when the protrusion 26a of the rotor 26 approaches the crank angle sensor 14 and leaves the crank angle sensor 14, the crank angle sensor 14 outputs an output voltage whose potentials are opposite to each other as indicated by X in FIG. (Sensor output) V is generated. The sensor output V is waveform-shaped by an AD converter with a constant voltage as a reference, and as a result, a pulse signal that is a rectangular wave corresponding to the protrusion 26b of the rotor 26 as shown by Y in FIG. 4B is generated. , Input to the ECU 20. Thus, the ECU 20 can recognize the crank angle for each angle Δθ (10 °) from the pulse signal. This crank angle is a value obtained directly from the pulse signal and is an accurate value.

  In particular, a reference time is set for the pulse signal, and when the pulse signal rises in this embodiment, the reference time of the pulse signal is set. That is, the ECU 20 recognizes or detects an accurate crank angle for each Δθ at the time of reference of the pulse signal. Hereinafter, the reference time of the pulse signal is referred to as “pulse reference time”.

  Note that when the missing tooth portion 26b of the rotor 26 passes through the crank angle sensor 14, the interval between pulses increases as indicated by Z in FIG. For example, the ECU 20 determines the engine rotational speed N from the time from when the signal Z representing the missing tooth portion 26b is detected until the next signal Z is output, that is, the time required for one revolution of the crankshaft. In the present embodiment, the missing tooth portion 26b is formed so that, for example, the first cylinder or the fourth cylinder is at the compression top dead center when the missing tooth portion 26b faces the crank angle sensor 14.

By the way, in such a crank angle detection device, an accurate value can be directly detected for the crank angle at the pulse reference time, but an accurate value can be directly detected for the crank angle during the pulse reference time, that is, the intermediate crank angle. I cannot do it, and I have to rely on estimation. If the number of protrusions of the rotor 26 is increased, more crank angles can be detected accurately, but there are hardware limitations. On the other hand, when executing the control, it may be necessary to recognize or detect such an intermediate crank angle. That is, the control device of the present embodiment executes a predetermined interrupt process simultaneously with the arrival of a predetermined intermediate crank angle, and performs a predetermined process or control based on the value of the predetermined intermediate crank angle. It is supposed to run. In particular, in the control device using the parameter PV ^κ corresponding to the crank angle as in the present embodiment, it is necessary to recognize the crank angle at a cycle smaller than the basic cycle (10 °) of the crank angle obtained by the crank angle sensor 14. In addition, it is necessary to recognize an accurate intermediate crank angle closer to the true value. In other words, it is necessary to improve the resolution and accuracy of crank angle detection.

  Therefore, in the present embodiment, a process called multiplication is performed to divide the time between pulse reference times into a plurality of times and increase the crank angle detection timing. This will be described below.

  FIG. 5 shows a pulse signal as shown in FIG. 4B, where the crank angle period of interest is called the current period and is denoted by the symbol i. The cycle immediately before the current cycle is referred to as the previous cycle, and is represented by the symbol i-1. Similarly, the cycle immediately after the current cycle is referred to as the next cycle and is represented by the symbol i + 1. The start time of each cycle is the rise time of the pulse signal, that is, the pulse reference time, and the length of each cycle is equal to Δθ = 10 ° in the unit of the crank angle, but due to the change of the engine speed in the unit of time And not necessarily equal. That is, the time length ΔTi−1 of the previous cycle and the time length ΔTi of the current cycle are not necessarily equal. In the present embodiment, multiplication for dividing one crank angle period into six parts will be described, but an arbitrary value can be adopted for the number of divisions n. Note that n can be arbitrarily set as a natural number of 2 or more.

  When recognizing the intermediate crank angle in the current cycle, the ECU 20 first measures the time length ΔTi−1 of the previous cycle with a built-in timer or the like, and divides it into six to divide time (ΔTi−1) / 6. Is calculated. Then, a time k × (ΔTi−1) obtained by multiplying the division time (ΔTi−1) / 6 by a predetermined number k (k = 1, 2,..., N−1) from the pulse reference time θi of the current cycle. ) / 6, the crank angle at the timing (referred to as intermediate timing) Ti_k is sequentially determined as five intermediate crank angles, ie, basic intermediate crank angles θi_k (θi_1, θi_2, θi_3, θi_4, θi_5). θi_k = θi + k × Δθ / n.

  By the way, with this method of simply determining the basic intermediate crank angle of the current cycle using the division time of the previous cycle, there is no particular problem when there is no change in rotational speed, such as during idle operation or constant speed operation, but acceleration When the time lengths of the previous cycle and the current cycle are different as in the case of time or deceleration, the obtained basic intermediate crank angle is not necessarily an accurate value equal to the true value. For example, during deceleration, the time length of the current cycle is longer than the previous cycle, and the basic intermediate crank angle θi_k deviates in a direction less than the true value as the basic intermediate crank angle θi_k increases from the pulse reference time θi. End up.

Therefore, whether the basic intermediate crank angle θi_k obtained in this way is determined as correct or not. The parameter PV ^κ related to the in-cylinder state is used for this correctness determination. As understood from the above description, it is assumed that the expression of adiabatic change: P ₁ V ₁ ^κ = P ₂ V ₂ ^κ (where κ is a specific heat ratio, 1.32 in the present embodiment) holds in the compression stroke. Therefore, the correct / incorrect determination is performed in the compression stroke. However, when the combustion is not executed, the equation also holds for the expansion stroke. In such a case, it is possible to make such a correct / incorrect determination in the expansion stroke.

The ECU 20 first acquires the in-cylinder pressure P (θi) detected by the in-cylinder pressure sensor 15 simultaneously with the arrival of the pulse reference time θi, and the in-cylinder volume V (θi) corresponding to the crank angle of the pulse reference time θi. Is calculated from a map or function equation stored in advance, and the parameter P (θi) V (θi) ^κ is calculated and stored in a predetermined storage area. Next, the ECU 20 acquires the in-cylinder pressure P (θi_k) detected by the in-cylinder pressure sensor 15 at the same time as the intermediate timing Ti_k is reached. The ECU 20 then calculates the following formula: P (θi) V (θi) ^κ = P (θi_k) V (θi_k ′) ^κ (4)
An in-cylinder volume V (θi_k ′) that satisfies the above is obtained, and a crank angle corresponding to the in-cylinder volume V (θi_k ′), that is, a reference intermediate crank angle θi_k ′ is calculated. Thereafter, the ECU 20 compares the reference intermediate crank angle θi_k ′ with the basic intermediate crank angle θi_k. If they are equal, the ECU 20 determines the basic intermediate crank angle θi_k as an accurate intermediate crank angle. The intermediate crank angle θi_k is determined as an inaccurate intermediate crank angle.

According to this, it is possible to estimate the more accurate intermediate crank angle θi_k ′ using the parameter PV ^κ, and it is also possible to estimate the basic intermediate crank angle θi_k tentatively determined based on the intermediate crank angle θi_k ′. It can be determined whether or not.

  When the reference intermediate crank angle θi_k ′ and the basic intermediate crank angle θi_k are different from each other, the ECU 20 corrects the basic intermediate crank angle θi_k. For example, the ECU 20 determines a value θi_k ′ obtained by adding a difference (θi_k′−θi_k) between θi_k ′ and θi_k to θi_k as a final intermediate crank angle after correction. Alternatively, the ECU 20 does not perform such a calculation and directly replaces θi_k with θi_k ′ and determines θi_k ′ as the final intermediate crank angle after correction.

Then, the ECU 20 executes predetermined processing or control using the final intermediate crank angle θi_k ′ thus obtained. Such processing or control includes various processing or control related to ignition timing control, fuel injection control, and the like. For example, in the case of the ignition timing control according to the present embodiment in which the combustion rate at 8 ° after compression top dead center is close to 50%, ignition is executed at the same time as or near the arrival of a certain intermediate crank angle θi_k ′. Further, the value of the intermediate crank angle θi_k ′ is used as θ in P (θ) V (θ) ^κ in the above equation (2). Further, when interrupt processing is executed at a certain intermediate timing Ti_k, θi_k ′ is used as a value representing the crank angle at this timing.

  By the way, the above equation (4) is established only in the compression stroke except for the situation where combustion is not performed. For this reason, it is possible to determine whether or not the intermediate crank angle is correct and correct only while one of the cylinders of the four-cycle engine (= 720 ° crank angle) is in the compression stroke. Normally, in an engine with four or more cylinders, either cylinder is always in a compression stroke during one cycle or one rotation of the engine, and therefore it is possible to always execute determination and correction of the intermediate crank angle. . Therefore, the present invention is preferably applied to an engine having four or more cylinders.

  Moreover, even if the engine has three cylinders, the present invention can be suitably applied as in the case of four or more cylinders. That is, according to the cycle diagram of the three-cylinder engine shown in FIG. 6, in the case of equidistant explosion, compression of each cylinder is started every 720 ° / 3 = 240 °. For example, the compression stroke of the # 1 cylinder is 0 to 180 °, the compression stroke of the # 2 cylinder is 240 to 420 °, and the compression stroke of the # 3 cylinder is 480 to 660 °. When this is viewed in one revolution of the engine, one of the cylinders is always in the compression stroke. Therefore, as in the case of four or more cylinders, it is possible to always execute the determination of whether the intermediate crank angle is correct or not, and the correction.

By the way, in this embodiment, the value P (θi) V (θi) ^κ at the time of pulse reference of the current cycle is used as the reference parameter PV ^κ . However, the present invention is not limited to this, and a pulse in a cycle before the current cycle is used. A reference value may be used. This is because even the value at the pulse reference time in the period before the current period satisfies the above expression (4) as long as it exists in the compression stroke. However, in view of the fact that the operating state of the engine may change, it is optimal to use the value of the current cycle as a target.

  The following may be considered as other embodiments of the present invention. According to the embodiment, the reference intermediate crank angle θi_k ′ and the basic intermediate crank angle θi_k are compared, and whether the basic intermediate crank angle θi_k is correct or not is determined. If they are different, the basic intermediate crank angle θi_k is determined as the reference intermediate crank angle. A method of correcting by the angle θi_k ′ was adopted. However, the value of the reference intermediate crank angle θi_k ′ may be determined directly as the intermediate crank angle to be obtained without going through such steps of comparison, determination, and correction.

That is, the ECU 20 first acquires the in-cylinder pressure P (θi) detected by the in-cylinder pressure sensor 15 simultaneously with the arrival of the pulse reference time θi, and at the same time, obtains the in-cylinder volume V (corresponding to the crank angle of the pulse reference time θi. The parameter P (θi) V (θi) ^κ is calculated by calculating θi) from a previously stored map or function equation, and stored in a predetermined storage area. Next, the ECU 20 acquires the in-cylinder pressure P (θi_k) detected by the in-cylinder pressure sensor 15 simultaneously with the arrival of the intermediate timing Ti_k (= θi + k × (ΔTi−1) / 6). The ECU 20 then calculates the following formula: P (θi) V (θi) ^κ = P (θi_k) V (θi_k ′) ^κ (4)
An in-cylinder volume V (θi_k ′) that satisfies is obtained, and a crank angle θi_k ′ corresponding to the in-cylinder volume V (θi_k ′) is calculated. This crank angle θi_k ′ is directly determined as the intermediate crank angle to be obtained.

  The present invention is also applicable to a control device for an internal combustion engine that performs normal map control. The time when the pulse signal falls may be used as the reference time of the pulse signal. The present invention is also applicable to internal combustion engines other than gasoline engines, such as diesel engines.

It is a graph which shows the correlation with control parameter PV ( ^kappa) and the amount of heat generation in a combustion chamber. It is a graph which shows the correlation with the combustion rate calculated ^| required based on control parameter PV ( ^kappa) , and the combustion rate calculated ^| required based on a heat release rate. It is a schematic block diagram which shows the internal combustion engine containing the control apparatus by this invention. It is a figure regarding the detection of the crank angle by a crank angle sensor, (A) is the schematic of a crank angle sensor and a rotor, (B) is the signal output from a crank angle sensor, and the pulse obtained by shaping this Signal. It is a graph which shows each timing in a pulse signal. It is a cycle diagram of a 3 cylinder engine.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Internal combustion engine 2 Cylinder block 3 Combustion chamber 4 Piston 5 Intake pipe 6 Exhaust pipe 7 Spark plug 8 Surge tank 10 Throttle valve 12 Injector 14 Crank angle sensor 15 In-cylinder pressure sensor 16 Intake pressure sensor 20 Electronic control unit (ECU)
26 Rotor 26a Protrusion L1 Supply pipe Ve Exhaust valve Vi Intake valve VM Valve mechanism P In-cylinder pressure V In-cylinder volume

Claims (6)

Pulse signal generating means for generating a pulse signal at a predetermined crank angle period;
A divided time calculation means for calculating a divided time by dividing the time from the reference time of the pulse signal generated in the previous cycle to the reference time of the pulse signal generated in the current cycle into n equal parts;
Basic intermediate crank angle determining means for determining a crank angle at a timing at which a predetermined number of division times have elapsed from the reference time of the pulse signal in this cycle as a basic intermediate crank angle;
A calculation means for calculating a crank angle such that a predetermined parameter related to the in-cylinder state at that timing is equal to the parameter at the reference time of the pulse signal in the current or previous period;
A control device for an internal combustion engine, comprising: a determination unit that compares the calculated crank angle with the basic crank angle and determines whether the basic crank angle is correct or not. The parameter is PV ^κ (where P is in-cylinder pressure, V is in-cylinder volume, κ is a predetermined constant),
A cylinder pressure sensor for detecting the cylinder pressure;
The parameter PV ^κ at the timing uses an in-cylinder pressure value detected by the in-cylinder pressure sensor at the timing,
The in-cylinder volume corresponding to the in-cylinder pressure value detected by the in-cylinder pressure sensor at the time of the reference and the parameter PV ^κ at the reference time of the pulse signal in the current or previous period, and the crank angle at the reference time The control device for an internal combustion engine according to claim 1, wherein a value is used.   And a correction unit that corrects the basic intermediate crank angle based on the calculated crank angle when the determination unit determines that the calculated crank angle is different from the basic intermediate crank angle. The control apparatus for an internal combustion engine according to claim 1 or 2, characterized by the above-mentioned.   4. The control apparatus for an internal combustion engine according to claim 2, further comprising means for executing predetermined processing or control based on a value of the crank angle corrected by the correcting means.   5. The control device for an internal combustion engine according to claim 1, wherein the number of cylinders of the internal combustion engine is three or more. Pulse signal generating means for generating a pulse signal at a predetermined crank angle period;
A divided time calculation means for calculating a divided time by dividing the time from the reference time of the pulse signal generated in the previous cycle to the reference time of the pulse signal generated in the current cycle into n equal parts;
Calculates a predetermined parameter related to the in-cylinder state at a timing when a predetermined number of division times have elapsed from the reference time of the pulse signal in the current cycle, and the calculated parameter is the pulse signal in the current or previous cycle. An internal combustion engine control apparatus comprising: crank angle determining means for calculating a crank angle that is equal to a parameter at a reference time and determining the calculated crank angle as a crank angle at the timing.

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