JP4277280B2 - Crank angle measuring device and measuring method - Google Patents

Description

  The present invention relates to a crank angle measuring device and a measuring method for measuring a crank angle of an internal combustion engine.

  In general, in various internal combustion engines, a crank angle of an output shaft (crankshaft) is detected using a crank angle sensor, and the crank angle is used to determine the rotational speed of the internal combustion engine or to set an ignition timing or the like. Used. A sensor used for detecting the crank angle is a magnetic sensor or a photoelectric sensor including a rotor plate (signal plate) fixed to the crankshaft, and is generally built in a distributor. In this case, the detection accuracy of the crank angle by the crank angle sensor greatly depends on the processing accuracy and mounting accuracy of the distributor and the rotor plate. In addition, electromagnetic noise from ignition plugs, injectors, and vibration noise of the internal combustion engine itself are easily superimposed on the output signal of the crank angle sensor. Therefore, in practice, the detection value of the crank angle sensor and the actual crank angle (true value) often deviate.

  Conventionally, as a technique for improving the detection accuracy of the crank angle, a crank angle sensor using a crank angle corresponding to a peak of in-cylinder pressure detected in a state where fuel supply to the combustion chamber (in-cylinder) is stopped. Is known (see, for example, Patent Document 1 and Patent Document 2). Under such a method, the crank angle corresponding to the peak of the in-cylinder pressure detected in a state where the fuel supply is stopped is considered to correspond to the compression top dead center. Then, a deviation (correction amount) between the crank angle and the detected value of the crank angle sensor corresponding to the compression top dead center is obtained, and the detected value of the crank angle sensor is corrected using this deviation.

Japanese Patent Laid-Open No. 3-47471 JP-A-8-28338

  However, the timing at which the fuel supply to the combustion chamber can be stopped during the operation of the internal combustion engine is limited. Under the above-described conventional method, the detection of the crank angle sensor is not performed unless such timing is reached. The value will not be corrected. For this reason, there has been a demand for a technique that can correct the detection value of the crank angle sensor immediately after the engine is started or when fuel is supplied to the combustion chamber.

  Therefore, an object of the present invention is to provide a crank angle measuring device and a measuring method that enable highly accurate measurement of the crank angle of an internal combustion engine at a desired timing.

  A first crank angle measuring device according to the present invention is a crank angle measuring device that is applied to an internal combustion engine that generates power by burning a mixture of fuel and air in a combustion chamber, and measures the crank angle of the internal combustion engine. The in-cylinder pressure detecting means for detecting the in-cylinder pressure in the combustion chamber, the determining means for determining the combustion chamber in the compression stroke, and the combustion chamber determined to be in the compression stroke by the determining means Based on the detected value of the in-cylinder pressure detecting means corresponding to the temporary crank angle of the point, the crank angle that minimizes the deviation of the heat generation amount between the two points is set to the in-cylinder pressure at one of the two points during the compression stroke. And calculating means for calculating the corresponding true crank angle.

  Further, it is preferable that the calculating means calculates a crank angle that minimizes the deviation of the heat generation amount by using a product of a value detected by the in-cylinder pressure detecting means and a value obtained by raising the in-cylinder volume by a predetermined index.

  Furthermore, a first crank angle measuring device according to the present invention includes a crank angle sensor that detects a crank angle of an internal combustion engine, and a crank angle sensor based on a crank angle that minimizes a deviation in heat generation and a temporary crank angle. It is preferable to further include a correction amount calculating means for calculating a correction amount for correcting the detected value, and a means for correcting the correction amount calculated by the correction amount calculating means according to the temperature of the internal combustion engine.

  A first crank angle measuring method according to the present invention is a crank angle measuring method that is applied to an internal combustion engine that generates power by burning a mixture of fuel and air in a combustion chamber, and measures the crank angle of the internal combustion engine. The combustion chamber in the compression stroke is determined, and the combustion chamber determined to be in the compression stroke is determined based on the measured values of the in-cylinder pressure corresponding to the two temporary crank angles in the compression stroke. The crank angle that minimizes the deviation of the heat generation amount between the two is calculated as the true crank angle corresponding to the in-cylinder pressure at one of the two points during the compression stroke.

  A second crank angle measuring device according to the present invention is applied to an internal combustion engine that generates power by burning a mixture of fuel and air in a combustion chamber, and is a crank angle measuring device that measures the crank angle of the internal combustion engine. An in-cylinder pressure detecting means for detecting the in-cylinder pressure in the combustion chamber, and an in-cylinder pressure estimating means for estimating the in-cylinder pressure at a plurality of predetermined points based on a detection value of the in-cylinder pressure detecting means at one point during the compression stroke. And calculating means for approximately calculating a crank angle corresponding to a predetermined reference point based on the in-cylinder pressure at a plurality of points estimated by the in-cylinder pressure estimating means.

  The in-cylinder pressure estimating means also calculates the product of the in-cylinder pressure at one point during the compression stroke and the value obtained by raising the in-cylinder volume at the one point during the compression stroke to a power of a predetermined index. The in-cylinder pressure at a plurality of points is preferably calculated by dividing the product by a value raised to a predetermined exponent.

  Furthermore, a second crank angle measuring device according to the present invention is based on a crank angle sensor for detecting a crank angle of an internal combustion engine, a crank angle approximately calculated by a calculation means, and a crank angle corresponding to a reference point. It is preferable to further include a correction amount calculation unit that calculates a correction amount for correcting the detection value of the crank angle sensor, and a unit that corrects the correction amount calculated by the correction amount calculation unit according to the temperature of the internal combustion engine.

  The second crank angle measuring method according to the present invention is applied to an internal combustion engine that generates power by burning a fuel / air mixture in a combustion chamber, and is a crank angle measuring method for measuring the crank angle of the internal combustion engine. The in-cylinder pressure at a plurality of predetermined points is estimated based on the actually measured value of the in-cylinder pressure at one point during the compression stroke, and the predetermined reference point is handled based on the estimated value of the in-cylinder pressure at the plurality of points. The crank angle is approximately calculated.

  According to the present invention, it is possible to realize a crank angle measuring device and a measuring method that enable highly accurate measurement of the crank angle of an internal combustion engine at a desired timing.

The present inventor has conducted intensive research to enable highly accurate measurement of the crank angle of an internal combustion engine. In the process, first, the in-cylinder pressure detected by the in-cylinder pressure detecting means and the in-cylinder pressure are measured. Attention has been focused on control parameters calculated based on the cylinder volume at the time of detection. More specifically, the inventor sets 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 product of the in-cylinder pressure P (θ) and the value V ^κ (θ) obtained by raising the in-cylinder volume V (θ) by the specific heat ratio (predetermined index) κ. The control parameter P (θ) · V ^κ (θ) (hereinafter referred to as “PV ^κ ” as appropriate) obtained as follows. Then, the inventor has shown that the change pattern of the heat generation amount Q in the combustion chamber 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 have a correlation as shown in FIG. I found it. 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 predetermined minute crank angles 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 indicates the heat generation amount Q in the model cylinder based on the heat generation rate equation: dQ / dθ = {dP / dθ · V + κ · P · dV / dθ} / {κ-1}. , Q = ∫dQ. In either case, for simplicity, κ = 1.32.

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 of the air-fuel mixture (at the time of spark ignition for a gasoline engine and at the time of compression ignition for a diesel engine) (for example, in the range from about −180 ° to about 135 ° in FIG. 1) It can be seen that the change pattern of the control parameter PV ^κ agrees very well.

On the other hand, the compression stroke of the internal combustion engine, that is, the period from when the intake valve is fully closed until the compression top dead center is reached, can be regarded as a substantially adiabatic process. Since the heat generation amount in the combustion chamber of the engine is theoretically constant, the deviation of the heat generation amount Q between two predetermined points during the compression stroke is theoretically zero. Further, if the correlation between the heat generation amount Q and the control parameter PV ^κ described above is used, a predetermined two points (crank angle) during the compression stroke (from the time when the intake valve is fully closed until the compression top dead center is reached). When the deviation (absolute value) of the heat generation amount Q between two points where x becomes x, x + Δx) is ΔQ _PV ,

Can be expressed as

Here, in general, there is a slight deviation between the detected value of the crank angle sensor and the actual crank angle (true value). Therefore, if x and x + Δx in the above equation (1) are temporary values that are not true values (temporary crank angles in the compression stroke), the measured values of the in-cylinder pressure corresponding to the temporary crank angles x and x + Δx Even if P (x) and P (x + Δx) and in-cylinder volumes V (x) and V (x + Δx) are substituted into the right side of the above equation (1), ΔQ _PV does not become zero. In contrast, the measured values P (x) and P (x + Δx) of the in-cylinder pressure corresponding to the temporary crank angle x and x + Δx are substituted into the right side of the above equation (1), and the in-cylinder volume is set to V ( Substituting as θ) and V (θ + Δx) and changing θ (crank angle) in the range from the fully closed intake valve to the compression top dead center, when θ reaches a certain value, (1 ) ΔQ _PV shown by the equation is minimum (ideally zero). The crank angle that minimizes ΔQ _PV can be regarded as a true crank angle corresponding to the actual measurement value P (x).

The first embodiment according to the present invention utilizes such novel knowledge. That is, under the first mode of the present invention, the combustion chamber in the compression stroke is determined, and the combustion chamber determined to be in the compression stroke is related to the two temporary crank angles (x and x + Δx in the compression stroke). ) Is calculated based on the measured values (P (x) and P (x + Δx)) of the in-cylinder pressure to minimize the deviation ΔQ _PV of the heat generation amount between the two points. Is the true crank angle corresponding to the in-cylinder pressure P (x) at one of the two points (crank angle x) during the compression stroke.

  Thus, under the first embodiment of the present invention, if the combustion chamber in the compression stroke is determined, a crank angle close to the true value is obtained even before the peak of the in-cylinder pressure is detected. be able to. Therefore, according to the first aspect of the present invention, the correction amount for favorably correcting the detected value of the crank angle sensor is calculated at a desired timing such as immediately after the engine is started, and the crank angle of the internal combustion engine is highly accurate. Measurement can be performed.

Further, as described above, the crank angle that minimizes the deviation ΔQ _PV of the heat generation amount is calculated using the product of the detected value of the in-cylinder pressure detecting means and the value obtained by raising the in-cylinder volume to a predetermined exponent. And preferred. Furthermore, it is preferable that a correction amount for correcting the detected value of the crank angle sensor is calculated based on the crank angle that minimizes the deviation ΔQ _PV in the heat generation amount and the temporary crank angle (= x). The amount is preferably corrected according to the temperature of the internal combustion engine represented by, for example, the engine coolant temperature. Thereby, the correction amount of the crank angle sensor can be made closer to the true value.

By the way, the compression stroke and the expansion stroke after the intake valve of the internal combustion engine is fully closed until the exhaust valve is opened can be regarded as a substantially adiabatic process. Then, after the intake valve is fully closed, the measured value of the in-cylinder pressure at one point (crank angle = θ ₀ ) during the compression stroke until ignition is performed (combustion is started) is obtained. P (θ ₀ ), the in-cylinder volume at one point during the compression stroke is V (θ ₀ ), and there are a plurality of intervals from the fully closing of the intake valve to the opening of the exhaust valve (compression stroke and expansion stroke). If the in-cylinder pressure and the in-cylinder volume at the point are P (θ ₁ ), P (θ ₂ ), P (θ ₃ ), V (θ ₁ ), V (θ ₂ ), V (θ ₃ ), The relationship shown in equation (2) is established. However, P (θ ₁ ), P (θ ₂ ), and P (θ ₃ ) basically correspond to the compression pressure during so-called motoring (during cranking or deceleration) and are affected by combustion. Minute (combustion pressure) is not included (if in-cylinder pressure during combustion, the effect due to combustion is corrected).

If the relationship of the above equation (2) is used, a plurality of points (crank angles = θ ₁ , θ ₂ , θ _{3) in} the compression stroke and the expansion stroke after the intake valve is fully closed until the exhaust valve is opened. ) In-cylinder pressure is expressed as shown in the following equations (3) to (5).

The second aspect of the present invention utilizes such knowledge. That is, under the second embodiment of the present invention, a predetermined number of points (crank angles = θ ₁ , θ ₂ , θ) are based on the actually measured value P (θ ₀ ) of the in-cylinder pressure at one point during the compression stroke. ₃ ), the in-cylinder pressure is estimated. Based on the estimated values P (θ ₁ ), P (θ ₂ ), and P (θ ₃ ) of the in-cylinder pressure at the plurality of points, a predetermined top dead center or the like is determined. The crank angle corresponding to the reference point is approximately calculated by, for example, Gaussian approximation processing.

Under such a second embodiment of the present invention, if the measured value P (θ ₀ ) of the in-cylinder pressure at one point in the compression stroke is obtained, even before the peak of the in-cylinder pressure is detected. A crank angle close to the true value can be obtained. Therefore, according to the second embodiment of the present invention, it is possible to calculate a correction amount for satisfactorily correcting the detection value of the crank angle sensor at a desired timing and to perform highly accurate measurement of the crank angle of the internal combustion engine. It becomes possible.

The in-cylinder pressures P (θ ₁ ), P (θ ₂ ), and P (θ ₃ ) at a plurality of points are the in-cylinder pressure P (θ ₀ ) at one point during the compression stroke and one point during the compression stroke. Is the product of the in-cylinder volume V (θ ₀ ) raised to the power of the predetermined index κ, and the in-cylinder volume V (θ ₁ ), V (θ ₂ ) or V (θ ₃ ) is raised to the power of the predetermined index κ Preferably, it is calculated by dividing by the value obtained. Further, it is preferable that a correction amount for correcting the detected value of the crank angle sensor is calculated based on the approximately calculated crank angle and the crank angle corresponding to the reference point. It is preferable that the correction is made according to the temperature of the internal combustion engine represented by the water temperature or the like. Thereby, the correction amount of the crank angle sensor can be made closer to the true value.

  Hereinafter, the best mode for carrying out the present invention will be specifically described with reference to the drawings.

  FIG. 2 is a schematic configuration diagram showing an internal combustion engine equipped with a crank angle measuring device 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. 2, the internal combustion engine 1 is preferably 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 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. In addition, an intake valve Vi that opens and closes an intake port and an exhaust valve Ve that opens and closes an exhaust port are provided for each combustion chamber 3 in the cylinder head of the internal combustion engine 1. Each intake valve Vi and each exhaust valve Ve are opened and closed by a valve operating mechanism (not shown) having a variable valve timing function. Further, the internal combustion engine 1 has a number of spark plugs 7 corresponding to the number of cylinders, and the spark plugs 7 are disposed in the cylinder heads so as to face the corresponding combustion chambers 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. 2, 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.

  Further, as shown in FIG. 2, the internal combustion engine 1 has a plurality of injectors 12, and the injectors 12 are disposed in the cylinder head so as to face the corresponding combustion chambers 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 and the like described above are electrically connected to an 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, etc., all not shown. Various sensors such as an air flow meter AFM for detecting the intake air amount and a water temperature sensor 13 for detecting the engine coolant temperature are electrically connected to the ECU 20 via an A / D converter (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, the valve operating mechanism, etc. so as to obtain a desired output based on the detection values of various sensors. To control.

  As shown in FIG. 2, the sensors connected to the ECU 20 further include a crank angle sensor 14. The crank angle sensor 14 is a magnetic sensor or a photoelectric sensor including a rotor plate (signal plate) fixed to the crankshaft, and provides a pulse signal indicating the rotation angle of the crankshaft to the ECU 20. Further, the internal combustion engine 1 has in-cylinder pressure sensors (in-cylinder pressure detecting means) 15 including a semiconductor element, a piezoelectric element, an optical fiber detection element, or the like, corresponding to the number of cylinders. 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 provides the ECU 20 with a voltage signal (a signal indicating a detected value) corresponding to the pressure (in-cylinder pressure) applied to the pressure receiving surface in the combustion chamber 3. The detected values of the crank angle sensor 14 and each in-cylinder pressure sensor 15 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. The ECU 20 that receives signals from the crank angle sensor 14 and the in-cylinder pressure sensor 15 uses the detection values of the sensors for controlling the internal combustion engine 1.

  Here, the detection accuracy of the crank angle by the crank angle sensor 14 greatly depends on the processing accuracy and mounting accuracy of the rotor plate and the like, and the output signal of the crank angle sensor includes electromagnetic waves from the spark plug 7 and the injector 12. Noise and vibration noise of the internal combustion engine 1 itself are easily superimposed. Therefore, in practice, the detection value of the crank angle sensor 14 and the actual crank angle (true value) often shift. In view of this point, in the present invention, a crank angle measuring device that enables highly accurate measurement of the crank angle of the internal combustion engine 1 by correcting the detection value of the crank angle sensor 14 by the in-cylinder pressure sensor 15 or the ECU 20 or the like. Is configured.

  Next, a method for calculating a correction amount for correcting the detection value of the crank angle sensor 14 in the internal combustion engine 1 will be described with reference to FIG.

When calculating the correction amount for correcting the detection value of the crank angle sensor 14 according to the routine of FIG. 3, the ECU 20 first determines the predetermined time based on the signal generated from each in-cylinder pressure sensor 15 every predetermined time. The variation ΔP of the in-cylinder pressure between the combustion chambers 3
ΔP = P _{k + 1} −P _k
(S10, S12). However, P _k indicates a value of the in-cylinder pressure indicated by a signal given from any of the in-cylinder pressure sensors 15 to the ECU 20 at a certain timing, and k is an integer of 1 or more. Then, when the fluctuation amount ΔP is obtained, the ECU 20 determines whether or not the fluctuation amount ΔP exceeds a predetermined threshold value Pr (S14).

  When the ECU 20 repeatedly executes the processes of S12 and S14 and determines that the fluctuation amount ΔP exceeds the threshold value Pr in any combustion chamber 3 (S14), the ECU 20 has the fluctuation amount ΔP higher than the threshold value Pr. It is determined that the combustion chamber 3 is in the compression stroke, and the in-cylinder pressure measured values P (x) and P corresponding to the predetermined temporary crank angles x and x + Δx are determined for the combustion chamber 3 from a predetermined storage area. (X + Δx) is read (S16). In the present embodiment, the provisional crank angle x is selected from between the fully closed state of the intake valve and the compression top dead center, for example, 20 °. Δx is, for example, 10 °, which is the same as the sampling period of each in-cylinder pressure sensor 15, and in S16, the values of P (20 °) and P (30 °) of the target combustion chamber 3 are predetermined storage areas. Read from.

When the measured values P (x) and P (x + Δx) of the in-cylinder pressure corresponding to the temporary crank angle x and x + Δx are read, the ECU 20 displays the measured value P (x = 20 [deg.] And P (x + [Delta] x = 30 [deg.]), And the in-cylinder volume is substituted as V ([theta]) and V ([theta] + [Delta] x) to change [theta] in the range from the fully closed intake valve to the compression top dead center. Thus, the crank angle that minimizes the deviation ΔQ _PV of the heat generation amount is calculated as the true crank angle corresponding to the actually measured value P (x) (S18). In the present embodiment, the values of V ^κ (θ) and V ^κ (θ + Δx) are calculated in advance and stored in the storage device. In S18, the ECU 20 reads V ^κ (θ) and V ^κ from the storage device. by executing repetitive calculations (theta + [Delta] x) values sequentially read out of is substituted into the right side of the equation (1), to calculate the true crank angle of the Delta] Q _PV minimized.

  When the true crank angle corresponding to the actual measurement value P (x) is calculated, the ECU 20 takes the deviation between the true crank angle and the temporary crank angle x, thereby correcting the detected value of the crank angle sensor 14. α is calculated (S20). As described above, by executing the routine of FIG. 3 at a desired timing, a correction amount for favorably correcting the detected value of the crank angle sensor 14 is calculated, and high-accuracy measurement of the crank angle of the internal combustion engine 1 is performed. It becomes possible to execute. According to the routine of FIG. 3, if the combustion chamber 3 in the compression stroke is determined, a crank angle close to the true value can be obtained even before the peak of the in-cylinder pressure is detected. The routine 3 is particularly effective when executed at the start of the internal combustion engine 1 where the position (crank angle) of the piston 4 in each combustion chamber 3 is unknown. As a result, the crank angle can be accurately measured immediately after the internal combustion engine 1 is started.

  Further, in the routine of FIG. 3, the correction amount α of the crank angle sensor 14 calculated in S20 is further corrected according to the engine coolant temperature detected by the water temperature sensor 13 (S22). That is, the deviation (deviation amount) between the true value of the crank angle and the crank angle detected by the crank angle sensor 14 also depends on the temperature of the internal combustion engine 1 typified by the coolant temperature or the like. A correlation as shown in FIG. 4 exists between the temperature of 1 (cooling water temperature) and the temperature-dependent component δ of the deviation (deviation amount).

  For this reason, in the present embodiment, a map that defines the relationship between the coolant temperature and the deviation amount δ is stored in advance in the storage device, and the ECU 20 is based on the detection value of the water temperature sensor 13 after the process of S20. Then, the temperature of the engine coolant is acquired, and the deviation amount δ corresponding to the acquired temperature of the engine coolant is read from the map. Then, the ECU 20 corrects the correction amount α calculated in S20 using the read deviation amount δ, stores it in a predetermined storage area, and ends the routine of FIG. Thus, by correcting the correction amount α of the crank angle sensor 14 according to the temperature of the engine coolant, the correction amount α of the crank angle sensor 14 can be made closer to the true value.

FIG. 5 is a flowchart for explaining another method for calculating the correction amount of the crank angle sensor 14 in the internal combustion engine 1 described above. The routine in FIG. 5 is executed as an alternative to the routine in FIG. 3, and the routine in FIG. 5 is executed when a predetermined condition is satisfied. When calculating the correction amount for correcting the detection value of the crank angle sensor 14 according to the routine of FIG. 5, first, the ECU 20 fully closes the intake valve Vi from a predetermined storage area for a predetermined one combustion chamber 3. After that, the measured value P (θ ₀ ) of the in-cylinder pressure at one point (crank angle = θ ₀ ) in the compression stroke until ignition is executed (combustion is started) is read ( S30). This measured value P (θ ₀ ) of the in-cylinder pressure is a reference in-cylinder pressure in the following processing, and in this embodiment, θ ₀ is set to −60 °, for example.

When the in-cylinder pressure P (θ ₀ ) as a reference is read in S30, the ECU 20 uses the relationships of the above equations (3) to (5) to fully close the intake valve Vi for the predetermined combustion chamber 3. Thereafter, in-cylinder pressures P (θ ₁ ), P (θ ₂ ), P at a plurality of points (crank angles = θ ₁ , θ ₂ , θ ₃ ) in the compression stroke and the expansion stroke until the exhaust valve Ve is opened. (Θ ₃ ) is calculated (estimated) (S32). In this embodiment, in S32, for example, in-cylinder pressures P (−10 °), P (0 °), P (10 when θ ₁ = −10 °, θ ₂ = 0 °, and θ ₃ = 10 °. °) is calculated. In this embodiment, since the combustion is performed in the combustion chamber 3 when the crank angle becomes θ ₃ = 10 °, the in-cylinder pressure P (θ ₃ ) estimated in S32 is Excludes (corrected) the influence of combustion (combustion pressure). Further, the crank angles θ ₁ , θ _2, and θ ₃ can be any plurality of points selected from an angle range that will include a value corresponding to the compression top dead center as a reference point.

Here, θ ₁ = −10 ° and the estimated value P (−10 °) of the in-cylinder pressure are represented as (θ ₁ , P ₁ ), and θ ₂ = 0 ° and the in-cylinder pressure P (0 °) are represented by (θ ₂ , P ₂ ), and θ = 10 ° and in-cylinder pressure P (10 °) are expressed as (θ ₃ , P ₃ ), these (θ ₁ , P ₁ ), (θ ₂ , P ₂ ) By executing Gaussian approximation using (θ ₃ , P ₃ ), an approximate value of the crank angle corresponding to the compression top dead center as the reference point can be obtained (S34).

That is, under the routine of FIG. 5, the in-cylinder pressure is expressed by the following equation (6) (Gaussian function) that well reflects the characteristics when the crank angle is in the range of -10 ° to 10 °. Is assumed. In this case, P in Equation (6), that is, the in-cylinder pressure, becomes maximum when θ = m. Therefore, m that maximizes P is an approximate value of the crank angle corresponding to the compression top dead center. ). Further, when (θ ₁ , P ₁ ), (θ ₂ , P ₂ ) and (θ ₃ , P ₃ ) are respectively substituted into the equation (6) and the logarithm of both sides is taken, the following equation (7) is obtained. Thus, by solving the equation (7), an approximate value (= m) of the crank angle corresponding to the compression top dead center can be obtained. In Equation (7), d is a time constant, and K is a gain.

  When the approximate value (= m) of the crank angle corresponding to the compression top dead center is obtained for the target combustion chamber 3 by the process of S34, the ECU 20 calculates the obtained approximate value (= m) and the compression top dead center. The correction amount α for the detected value of the crank angle sensor 14 is calculated by taking the deviation from the crank angle corresponding to (0 ° in this embodiment) (S36). Further, also in the routine of FIG. 5, the engine cooling detected by the water temperature sensor 13 in the same manner as in S22 described above so that the correction amount α of the crank angle sensor 14 calculated in S36 is closer to the true value. Correction is made according to the temperature of the water (S38). The ECU 20 ends the routine of FIG. 5 when the correction amount α corrected in accordance with the temperature of the engine coolant in S38 is stored in a predetermined storage area.

As described above, according to the routine of FIG. 5, if the measured value P (θ ₀ ) of the in-cylinder pressure at one point in the compression stroke is obtained, the true value is obtained even before the peak of the in-cylinder pressure is detected. A crank angle close to can be obtained. Therefore, even when the routine of FIG. 5 is executed, it is possible to calculate a correction amount for satisfactorily correcting the detection value of the crank angle sensor 14 and to perform highly accurate measurement of the crank angle of the internal combustion engine 1. Become. In S30, the in-cylinder pressure P (θ ₀ ) may be read for all the combustion chambers 3 to obtain an average value, and the processes after S32 may be executed using the obtained average value. In S30, the in-cylinder pressure P (θ ₀ ) may be read for all the combustion chambers 3, and the processing after S32 may be executed for each combustion chamber 3 to obtain the correction amount α for each combustion chamber 3.

It is a graph which shows the correlation between control parameter PV ( ^kappa) used in this invention, and the amount of heat generation in a combustion chamber. It is a schematic block diagram of the internal combustion engine provided with the crank angle measuring device by this invention. 3 is a flowchart for explaining a method of calculating a correction amount for correcting a detection value of a crank angle sensor in the internal combustion engine of FIG. 2. It is a graph which shows the relationship between the temperature dependence of the temperature of an internal combustion engine, and the deviation of the true value of a crank angle, and the crank angle detected by a crank angle sensor. 6 is a flowchart for explaining another method for calculating a correction amount for correcting a detection value of a crank angle sensor in the internal combustion engine of FIG. 2.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Internal combustion engine 3 Combustion chamber 4 Piston 5 Intake pipe 6 Exhaust pipe 7 Spark plug 8 Surge tank 10 Throttle valve 11a, 11b Catalyst device 12 Injector 13 Water temperature sensor 14 Crank angle sensor 15 In-cylinder pressure sensor AFM Air flow meter Ve Exhaust valve Vi Intake valve

Claims (8)

A crank angle measuring device that is applied to an internal combustion engine that generates power by burning a mixture of fuel and air in a combustion chamber, and measures a crank angle of the internal combustion engine,
In-cylinder pressure detecting means for detecting in-cylinder pressure in the combustion chamber;
A discriminating means for discriminating the combustion chamber in the compression stroke;
With respect to the combustion chamber determined to be in the compression stroke by the determination means, the in- cylinder pressure detection means corresponding to two temporary crank angles (x, x + Δx) separated by a predetermined crank angle (Δx) during the compression stroke. The actually measured values (P (x), P (x + Δx)) of the detected in-cylinder pressure and the in-cylinder volumes (V (θ), V (θ + Δx)) at two points separated by a predetermined crank angle (Δx) are obtained. And calculating the deviation (ΔQ) of the heat generation amount between the two points, and the crank angle (θ) of the two in-cylinder volumes (V (θ), V (θ + Δx)) is fully closed. The crank angle (θ or θ + Δx) that minimizes the absolute value of the deviation (ΔQ) of the heat generation amount by changing in the range from the top dead center to the compression top dead center is obtained, and this crank angle is calculated at two points in the compression stroke. Calculated as the true crank angle corresponding to the cylinder pressure at either one Crank angle measurement apparatus comprising: a calculation means that.   The calculation means calculates a crank angle that minimizes the deviation of the heat generation amount, using a product of a detection value of the in-cylinder pressure detection means and a value obtained by raising the in-cylinder volume by a predetermined index. The crank angle measuring device according to claim 1. A crank angle sensor for detecting a crank angle of the internal combustion engine;
A correction amount calculating means for calculating a correction amount for correcting the detected value of the crank angle sensor based on the crank angle that minimizes the deviation of the heat generation amount and the temporary crank angle;
The crank angle measuring device according to claim 1 or 2, further comprising means for correcting the correction amount calculated by the correction amount calculating means according to the temperature of the internal combustion engine. A crank angle measuring method applied to an internal combustion engine that generates power by burning a fuel / air mixture in a combustion chamber, and measuring a crank angle of the internal combustion engine,
The combustion chamber in the compression stroke is determined, and the combustion chamber determined to be in the compression stroke corresponds to two temporary crank angles (x, x + Δx) separated by a predetermined crank angle (Δx) during the compression stroke. The measured value (P (x), P (x + Δx)) of the in-cylinder pressure detected by the in-cylinder pressure detecting means and the in-cylinder volume (V (θ), V (θ + Δx)) is used to calculate the deviation (ΔQ) of the heat generation amount between the two points, and the crank angle (θ) of the two in-cylinder volumes (V (θ), V (θ + Δx)) Is changed in the range from the fully closed state of the intake valve to the compression top dead center to obtain the crank angle (θ or θ + Δx) that minimizes the absolute value of the deviation (ΔQ) of the previous heat generation amount, and the crank angle is compressed as described above. True crank angle corresponding to in-cylinder pressure at one of the two points in the stroke Crank angle measurement method and calculating by. A crank angle measuring device that is applied to an internal combustion engine that generates power by burning a mixture of fuel and air in a combustion chamber, and measures a crank angle of the internal combustion engine,
In-cylinder pressure detecting means for detecting in-cylinder pressure in the combustion chamber;
In-cylinder pressure estimating means for estimating in-cylinder pressure at a plurality of predetermined points based on a detection value of the in-cylinder pressure detecting means at one point during the compression stroke;
Computational means for approximately calculating a crank angle corresponding to a predetermined reference point by executing Gaussian approximation processing based on in-cylinder pressure at the plurality of points estimated by the in-cylinder pressure estimating means. Crank angle measuring device.   The in-cylinder pressure estimation means is configured to calculate a product of an in-cylinder pressure at one point during the compression stroke and a value obtained by raising the in-cylinder volume at the one point during the compression stroke to a power of a predetermined index. 6. The crank angle measuring device according to claim 5, wherein an in-cylinder pressure at the plurality of points is calculated by dividing an internal volume by a value raised to the power of the predetermined index. A crank angle sensor for detecting a crank angle of the internal combustion engine;
Correction amount calculation means for calculating a correction amount for correcting the detected value of the crank angle sensor based on the crank angle approximately calculated by the calculation means and the crank angle corresponding to the reference point;
The crank angle measuring device according to claim 5 or 6, further comprising means for correcting the correction amount calculated by the correction amount calculating means according to the temperature of the internal combustion engine. A crank angle measuring method applied to an internal combustion engine that generates power by burning a fuel / air mixture in a combustion chamber, and measuring a crank angle of the internal combustion engine,
A crank corresponding to a predetermined reference point based on an estimated value of the in-cylinder pressure at the plurality of points based on an actually measured value of the in-cylinder pressure at one point during the compression stroke. A method of measuring a crank angle, wherein the angle is approximately calculated by executing a Gaussian approximation process .

Images