JP4255876B2 - In-cylinder pressure detector - Google Patents

Description

  The present invention relates to an apparatus for detecting an in-cylinder pressure of an internal combustion engine. More specifically, the present invention relates to an in-cylinder pressure detection apparatus that corrects a drift of a detected in-cylinder pressure and detects a more accurate in-cylinder pressure.

  Conventionally, a cylinder (cylinder) of an internal combustion engine is provided with an in-cylinder pressure sensor that detects a pressure in the cylinder (hereinafter referred to as an in-cylinder pressure). The in-cylinder pressure detected by the sensor is used for controlling the internal combustion engine.

  A sensor using a piezoelectric element is known as an in-cylinder pressure sensor. This sensor detects the rate of change of in-cylinder pressure. As shown in FIG. 19, the change rate of the in-cylinder pressure detected by the in-cylinder pressure sensor 100 is typically integrated by the integration circuit 101. The output of the integration circuit 101 is used as the in-cylinder pressure.

  When a piezoelectric element is used, there is generally a hysteresis characteristic in the relationship between the change in the in-cylinder pressure and the output of the in-cylinder pressure sensor. Further, as the temperature of the piezoelectric element increases, the output of the in-cylinder pressure sensor also increases. When such an in-cylinder pressure sensor is mounted on an internal combustion engine, the output of the in-cylinder pressure sensor varies depending on the heat generated from the internal combustion engine. As a result, the in-cylinder pressure waveform output from the integration circuit may cause a “deviation”, that is, a drift as shown in FIG.

  When such a drift occurs, it becomes difficult to accurately detect the in-cylinder pressure. Also, the output of the in-cylinder pressure sensor is typically analog to digital (A / D) converted for subsequent computer processing. When a drift component is included in the output of the in-cylinder pressure sensor, there is a possibility that the correlation is lost between the output of the in-cylinder pressure sensor that is an analog value and the digital value after the A / D conversion of the output.

Patent Document 1 below discloses a technique for resetting an integration circuit as a technique for correcting such drift. Referring to FIG. 21, the switching element 112 is closed at a predetermined timing of each combustion cycle. When the element is closed, the potential difference before and after the capacitor 113 disappears, so that the output of the operational amplifier 114 is reset to the reference value. In response to this reset operation, the drift is removed.
JP-A-7-280686

  FIG. 22 shows an in-cylinder pressure waveform output from the integration circuit when the reset operation as described above is performed. The reset operation is performed at times t1, t2, t3, t4 and t5. It can be seen that the waveform 115 resulting from such a reset operation is superimposed on the in-cylinder pressure waveform. As a result, a discontinuous frequency characteristic appears in the in-cylinder pressure waveform before and after the reset operation. Due to such discontinuous frequency characteristics, undesired frequency components are mixed in the subsequent computer processing using the in-cylinder pressure. This reduces the accuracy of control of the internal combustion engine. Even if such a reset operation is performed, the drift increases between the reset operations, that is, during one combustion cycle.

  Therefore, there is a need for a technique for preventing drift in the detected in-cylinder pressure without performing such a reset operation.

  According to one aspect of the present invention, an in-cylinder pressure detecting device integrates an in-cylinder pressure sensor that outputs a signal corresponding to a rate of change in an in-cylinder pressure of an internal combustion engine, and an output signal of the in-cylinder pressure sensor, thereby calculating an in-cylinder pressure. And integrating means for calculating, and correcting means for correcting the in-cylinder pressure with a drift correction term for removing drift in the in-cylinder pressure to calculate a corrected in-cylinder pressure.

  According to one embodiment of the present invention, the in-cylinder pressure output from the integrating means is further sampled in the first cycle, and the drift amount is calculated based on the sampled in-cylinder pressure. The drift correction term is calculated by oversampling in a cycle shorter than one cycle and averaging the oversampled drift amount. The correcting means subtracts the drift correction term from the in-cylinder pressure output from the integrating means to calculate a corrected in-cylinder pressure.

  In one embodiment, the drift amount is calculated by subtracting a predetermined reference value from the sampled in-cylinder pressure. In one embodiment, the first cycle is a cycle in which the intake stroke in the combustion cycle of the internal combustion engine arrives, and the predetermined reference value is the pressure in the intake pipe in the intake stroke.

  According to another embodiment of the present invention, the corrected in-cylinder pressure is further sampled in the first cycle, the drift amount is calculated based on the sampled corrected in-cylinder pressure, and the drift amount is Oversampling is performed in a cycle shorter than the above cycle, the oversampled drift amount is averaged, and the drift correction term is calculated so as to converge the averaged drift amount to zero. The drift correction term is fed back to the correction means. The correcting means corrects the in-cylinder pressure output from the integrating means with the feedback drift correction term, and calculates the corrected in-cylinder pressure.

  According to the present invention, since the drift component can be removed without performing the reset operation, it is possible to prevent a discontinuous frequency characteristic from appearing in the in-cylinder pressure waveform.

  According to this invention, the drift is removed from the in-cylinder pressure calculated based on the output of the in-cylinder pressure sensor at predetermined time intervals. By using the in-cylinder pressure from which the drift is removed, the correlation between the output of the in-cylinder pressure sensor and the digital value after A / D conversion of the output is maintained.

  According to one embodiment of the present invention, the drift correction term is calculated in a cycle shorter than the first cycle in which the in-cylinder pressure is calculated. Since the drift is removed from the in-cylinder pressure according to such a short cycle, it is possible to avoid an increase in the drift in the in-cylinder pressure over the first cycle.

  Next, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is an overall configuration diagram of an internal combustion engine (hereinafter referred to as an engine) and its control device according to an embodiment of the present invention.

  An electronic control unit (hereinafter referred to as “ECU”) 1 includes an input interface 1a that receives data sent from each part of the vehicle, a CPU 1b that executes calculations for controlling each part of the vehicle, and a read-only memory (ROM) ) And a random access memory (RAM) 1c and an output interface 1d for sending control signals to various parts of the vehicle. The ROM of the memory 1c stores a program for controlling each part of the vehicle and various data. A program for in-cylinder pressure detection according to the present invention is stored in the ROM. The ROM may be a rewritable ROM such as an EPROM. The RAM is provided with a work area for calculation by the CPU 1b. Data sent from each part of the vehicle and control signals sent to each part of the vehicle are temporarily stored in the RAM.

  The engine 2 is, for example, a 4-cycle engine. The engine 2 may include a variable compression ratio mechanism.

  The engine 2 is connected to an intake pipe 4 via an intake valve 3 and connected to an exhaust pipe 6 via an exhaust valve 5. The intake valve 3 and the exhaust valve 5 may be a continuously variable valve system. A fuel injection valve 7 that injects fuel in accordance with a control signal from the ECU 1 is provided in the intake pipe 4. Alternatively, the fuel injection valve 7 may be provided in the combustion chamber 8.

  The engine 2 sucks an air-fuel mixture of air sucked from the intake pipe 4 and fuel injected from the fuel injection valve 7 into the combustion chamber 8. The combustion chamber 8 is provided with a spark plug 9 that discharges a spark in accordance with an ignition timing signal from the ECU 1. The air-fuel mixture is combusted by the spark emitted by the spark plug 9.

  The in-cylinder pressure sensor 15 is buried in a portion of the spark plug 9 that contacts the cylinder. Alternatively, when the fuel injection valve 7 is provided in the combustion chamber 8, the in-cylinder pressure sensor 15 may be buried in a portion of the fuel injection valve 7 that contacts the cylinder. The in-cylinder pressure sensor 15 generates a signal corresponding to the rate of change of the in-cylinder pressure in the combustion chamber 8 and sends it to the ECU 1.

  The engine 2 is provided with a crank angle sensor 17. The crank angle sensor 17 outputs a CRK signal and a TDC signal, which are pulse signals, to the ECU 1 as the crankshaft 11 rotates.

  The CRK signal is a pulse signal output at a predetermined crank angle. The ECU 1 calculates the rotational speed NE of the engine 2 according to the CRK signal. The TDC signal is a pulse signal output at a crank angle related to the TDC position of the piston 10.

  A throttle valve 18 is provided in the intake pipe 4 of the engine 2. The opening degree of the throttle valve 18 is controlled by a control signal from the ECU 1. A throttle valve opening sensor (θTH) 19 connected to the throttle valve 18 supplies a signal corresponding to the opening of the throttle valve 18 to the ECU 1.

  The intake pipe pressure (Pb) sensor 20 is provided on the downstream side of the throttle valve 18. The intake pipe pressure Pb detected by the Pb sensor 20 is sent to the ECU 1.

  A signal sent to the ECU 1 is passed to the input interface 1a and converted to analog / digital (A / D). The CPU 1b processes the digital signal according to a program stored in the memory 1c, and generates a control signal for sending to the actuator of the vehicle. The output interface 1d sends these control signals to the actuators of the fuel injection valve 7, the spark plug 9, the throttle valve 18, and other mechanical elements.

  FIG. 2 is a diagram illustrating an example of attachment of the in-cylinder pressure sensor 15. A spark plug 9 is screwed into the screw hole 22 of the cylinder head 21. A sensor element portion 25 of the in-cylinder pressure sensor is sandwiched with a washer 26 between a mounting seat surface 23 of the spark plug of the cylinder head 21 and the spark plug washer portion 24. The sensor element unit 25 is composed of a piezoelectric element.

  Since the sensor element unit 25 is tightened as a washer for the spark plug 9, a predetermined tightening load is applied to the sensor element unit 25. When the pressure in the combustion chamber 8 changes, the load applied to the sensor element unit 25 changes. The in-cylinder pressure sensor 15 detects a change in load with respect to the predetermined tightening load as a change in in-cylinder pressure.

  The principle of the present invention will be described with reference to FIG. FIG. 3A shows the output of the in-cylinder pressure sensor 15, that is, the rate of change Vps of the in-cylinder pressure.

In order to detect the in-cylinder pressure, the output Vps of the in-cylinder pressure sensor is integrated as shown in Expression (1). A waveform of the in-cylinder pressure Pcyl ′ obtained by integration is shown in FIG. As indicated by the line 81, a drift appears in the in-cylinder pressure Pcyl ′.

  In the present invention, the drift indicated by the line 81 is calculated. The in-cylinder pressure is corrected so that the calculated drift is removed from the in-cylinder pressure Pcyl '. The corrected in-cylinder pressure Pcyl does not include drift. A waveform of the corrected in-cylinder pressure Pcyl is shown in FIG.

  Several examples according to the present invention will be described below. In the following example, the time is measured using the crank angle. Therefore, each processing such as sampling and calculation is performed in synchronization with the crank angle. Alternatively, the time may be timed using other parameters. Alternatively, a timer or the like may be provided to perform each process at a predetermined time interval.

  FIG. 4 is a block diagram of the in-cylinder pressure detecting device according to the first embodiment of the present invention. The in-cylinder pressure detecting device is typically realized in the ECU 1. The functions realized by the blocks shown are typically realized by a computer program. Alternatively, these functions may be realized by hardware, software, firmware, and a combination thereof (the same applies to the following block diagrams). The output of the in-cylinder pressure sensor 15 is converted from analog to digital and is input to the in-cylinder pressure detection device as Vps.

  The integrator 31 integrates the output of the in-cylinder pressure sensor 15, that is, the change rate Vps of the in-cylinder pressure, as shown in the above equation (1), and calculates the in-cylinder pressure Pcyl '.

  The correction device 32 corrects the in-cylinder pressure Pcyl 'so that the drift is removed from the in-cylinder pressure Pcyl', and calculates the corrected in-cylinder pressure Pcyl. This correction is repeatedly performed at predetermined time intervals. Accordingly, the drift is removed from the in-cylinder pressure Pcyl 'at every predetermined time interval.

  In the first embodiment, the integration by the integration device 31 and the correction by the correction device 32 are performed with a period of Tk shorter than Tn equal to the length of one combustion cycle. Preferably, Tk is determined so as to coincide with the length of a cycle in which the output of the in-cylinder pressure sensor is converted from analog to digital. By doing so, every time the output of the in-cylinder pressure sensor is obtained as the digital value Vps, the in-cylinder pressure Pcyl 'can be corrected so as to remove the drift.

  FIG. 5 is a detailed block diagram of the correction device 32. Sampling by the sampling circuit 35 is performed with a period of Tn equal to the length of one combustion cycle. The sampling circuit 35 samples the in-cylinder pressure Pcyl 'at a predetermined crank (CRK) angle of each combustion cycle. Preferably, the in-cylinder pressure Pcyl 'is sampled at a predetermined crank angle during the intake stroke. The in-cylinder pressure sample Psample obtained by the sampling is held in the sampling circuit 35 until the next sampling. FIG. 6 shows the waveform of the in-cylinder pressure sample Psample.

  In response to the in-cylinder pressure sample Psample generated by the sampling circuit 35, the drift amount calculation circuit 36 executes the equation (2) to calculate the drift amount Pdft.

Drift amount Pdft = In-cylinder pressure Psample−reference value (2)
The reference value is preferably set so as to indicate the in-cylinder pressure when there is no influence of drift. In this embodiment, the output Pb of the intake pipe pressure sensor 20 (FIG. 1) sampled at the same timing as the sampling by the sampling circuit 35 is used as the reference value. Since the intake valve is open during the intake stroke, the in-cylinder pressure and the intake pipe pressure become substantially the same pressure if there is no influence of drift. That is, the value obtained by subtracting the intake pipe pressure Pb from the in-cylinder pressure sample Psample represents the drift amount Pdft accumulated during the combustion cycle.

  Alternatively, a pressure value calculated based on an output of an air flow sensor provided in the intake pipe may be used as the reference value.

  FIG. 7 shows an example of the drift amount Pdft. The in-cylinder pressure sample Psample1 sampled at time t1 during the intake stroke in the first combustion cycle is held in the sampling circuit 35 until the next in-cylinder pressure sample is obtained. The difference from the intake pipe pressure Pb sampled at time t1 is the drift amount Pdft1 for the first combustion cycle. Similarly, the in-cylinder pressure sample Psample2 sampled at time t2 during the intake stroke in the second combustion cycle is held in the sampling circuit 35 until the next in-cylinder pressure sample is obtained. The difference from the intake pipe pressure Pb sampled at time t2 is the drift amount Pdft2 for the second combustion cycle. Thus, the drift amount Pdft is calculated for each combustion cycle.

  Returning to FIG. 5, the oversampling circuit 37 oversamples the drift amount Pdft to generate a sample of the drift amount Pdft. The moving average circuit 38 averages samples of the drift amount Pdft. These operations will be specifically described with reference to FIG.

  FIG. 8A shows an example of the waveform of the drift amount Pdft calculated by the drift amount calculation circuit 36 in each combustion cycle (that is, in a cycle of Tn). The oversampling circuit 37 oversamples the drift amount Pdft with a period of Tk shorter than Tn.

The sampling number m in one combustion cycle is (Tn / Tk). Each time a new sample is obtained by oversampling, the moving average circuit 38 averages the samples Pdft (k− (m−1)) to Pdft (k) according to the equation (3). k represents an operation cycle. Thus, the drift amount Pcyl_comp per time Tk is calculated.

  A line 82 as shown in FIG. 8B shows an example of the drift amount Pcyl_comp thus obtained. Note that the line 82 corresponds to the line 81 shown in FIG.

  Returning to FIG. 5, the correction circuit 39 receives the drift amount Pcyl_comp per time Tk as a drift correction term. The correction circuit 39 corrects the in-cylinder pressure Pcyl 'by subtracting the drift correction term Pcyl_comp from the in-cylinder pressure Pcyl', and calculates a corrected in-cylinder pressure Pcyl. The corrected in-cylinder pressure Pcyl indicates an in-cylinder pressure that does not include drift, as described with reference to FIG.

  Thus, every time the output of the in-cylinder pressure sensor is obtained as the digital value Vps, the in-cylinder pressure Pcyl 'is corrected by the drift correction term Pcyl_comp. Since the length of the period Tk is shorter than the length of the combustion cycle, accumulation of drift in the in-cylinder pressure can be avoided over one combustion cycle.

  In the above embodiment, the moving average method is used to average the oversampled samples of the drift amount. Alternatively, other filtering (eg, a low pass filter) may be used.

  In the above embodiment, the reference value Pb is subtracted from the in-cylinder pressure Pcyl 'in order to calculate the drift amount Pdft. Alternatively, the in-cylinder pressure Pcyl 'during the intake stroke may be used as the drift amount Pdft without subtracting the reference value Pb. This is because, in the intake stroke (particularly, near the start of the intake stroke), the pressure appearing in the in-cylinder pressure sensor is typically considered to be caused by drift. However, by using the reference value, in particular, by setting the intake pipe pressure Pb as the reference value, the drift amount Pdft can be calculated more accurately, and the accuracy of the absolute value of the in-cylinder pressure Pcyl after drift correction is increased. be able to.

  FIG. 9 is a diagram showing a more detailed operation of the sampling circuit 35 of FIG. FIG. 9A shows the in-cylinder pressure Pcyl ′ output from the integrating device 31.

  The sampling circuit 35 includes an up counter. The up counter value Dcnt is shown in FIG. The up-counter is reset to zero at the start of the intake stroke of each combustion cycle, that is, when the crank angle becomes zero. The up counter counts according to the crank signal from the crank angle sensor 17 (FIG. 1).

  In one embodiment, the crank signal is output every time the crankshaft rotates once. The crank signal is output 720 times during one combustion cycle. Therefore, the up counter counts from 0 to 720 in each combustion cycle.

  FIG. 9B further shows a waveform indicating the crank angle Dsample where the in-cylinder pressure Pcyl 'should be sampled. The value of the crank angle Dsample is determined in advance. The sampling circuit 35 compares the value Dcnt of the up counter with the crank angle Dsample.

  As shown in FIG. 9C, when the value Dcnt of the up counter matches the crank angle Dsample, a sample signal Tsample having a predetermined value (for example, 1) is output. When the value Dcnt of the up counter does not match the predetermined value Dsample, a sample signal Tsample having a zero value is generated.

  As shown in FIG. 9D, in response to the output of the sample signal Tsample having a predetermined value, the sampling circuit 35 samples the in-cylinder pressure Pcyl 'to obtain the in-cylinder pressure sample Psample. The in-cylinder pressure sample Psample is held in the sampling circuit 35 while the sample signal Tsample having a zero value is being output. As described above, the in-cylinder pressure sample Psample is generated with a period of Tn equal to the length of the combustion cycle.

  FIG. 10 shows the correction device 32 shown in the in-cylinder pressure detection device of FIG. 4 according to the second embodiment of the present invention. The main difference from the correction apparatus shown in FIG. 5 is that a controller 50 is provided.

  The sampling circuit 45 samples the corrected in-cylinder pressure Pcyl. The sampling method is the same as that of the sampling circuit 35 shown in FIG. 5, and the sample Psample is held in the sampling circuit 45. However, it should be noted that the sampling target of the sampling circuit 35 is the corrected in-cylinder pressure Pcyl while the sampling target of the sampling circuit 45 is the corrected in-cylinder pressure Pcyl '. This is because the controller 50 described below needs to use a waveform reflecting the drift correction term Pcyl_comp_SLD output from the controller (that is, the corrected in-cylinder pressure Pcyl) as an input.

  Drift amount calculation circuit 46, oversampling circuit 47 and moving average circuit 48 operate in the same manner as drift amount calculation circuit 36, oversampling circuit 37 and moving average circuit 38 shown in FIG.

  The controller 50 calculates the drift correction term Pcyl_comp_SLD so that the drift amount Pcyl_comp per time Tk converges to the target value Pcyl_comp_cmd. The correction circuit 49 corrects the in-cylinder pressure Pcyl 'by adding the drift correction term Pcyl_comp_SLD to the in-cylinder pressure Pcyl', and calculates the corrected in-cylinder pressure Pcyl.

  In this embodiment, since the control is performed so that the difference between the in-cylinder pressure Pcyl and the intake pipe pressure Pb during the intake stroke is eliminated, the target value Pcyl_comp_cmd is zero. As described above, the reference value Pb may not be subtracted from the in-cylinder pressure sample Psample. In this case, the intake pipe pressure Pb sampled during the intake pipe stroke is set to the target value Pcyl_comp_cmd.

  The controller 50 performs the response assignment control with a period of Tk shorter than the length Tn of the combustion cycle, and converges the drift amount Pcyl_comp.

  The response designation type control is a control capable of designating the convergence speed of the control amount (here, the drift amount Pcyl_comp) to the target value. According to the response assignment control, the drift amount Pcyl_comp can be converged to zero at a desired speed without causing an overshoot. In this embodiment, simple sliding mode control is used as response designation control.

  FIG. 11 is a more detailed block diagram of the controller 50. In order to implement the response designation type control, the switching function setting unit 52 sets a switching function σ as shown in Expression (4). Enc indicates a deviation between the drift amount Pcyl_comp (k) calculated for the corrected in-cylinder pressure Pcyl (k) and the target value Pcyl_comp_cmd, as shown in the equation (5). Here, k represents an operation cycle.

σ (k) = Enc (k) + POLE · Enc (k−1) (4)
Enc (k) = Pcyl_comp (k) −Pcyl_comp_cmd
(5)
POLE is a response specifying parameter of the switching function σ and defines the convergence speed of the drift amount Pcyl_comp. POLE is preferably set to satisfy -1 <POLE <0.

  The equation with the switching function σ (k) = 0 is called an equivalent input system and defines the convergence characteristic of the drift amount. When σ (k) = 0, Expression (4) can be expressed as Expression (6).

Enc (k) = − POLE · Enc (k−1) (6)
Here, the switching function will be described with reference to FIG. Expression (6) is represented by a line 61 on a phase plane in which the vertical axis is Enc (k) and the horizontal axis is Enc (k−1). This line 61 is called a switching line. It is assumed that an initial value of a state quantity (Enc (k−1), Enc (k)) consisting of a combination of Enc (k−1) and Enc (k) is represented by a point 62. The response designation type control operates to place the state quantity represented by the point 62 on the switching line 61 and restrain it on the switching line 61.

  According to the response designation type control, by holding the state quantity 62 on the switching line 61, the state quantity can be converged to the origin 0 on the phase plane very stably without being affected by disturbance or the like. it can. In other words, by constraining the state quantities (Enc (k−1), Enc (k)) to a stable system without input shown in Equation (6), the disturbance Enc is made robust and the deviation Enc is made zero. It can be converged.

  In this embodiment, since the phase space related to the switching function σ is two-dimensional, the switching line is represented by a straight line 61. When the phase space is three-dimensional, the switching line is represented by a plane, and when the phase space is four or more dimensions, the switching line becomes a hyperplane.

  The response designation parameter POLE can be variably set. By adjusting the response designation parameter POLE, the convergence speed of the deviation Enc can be designated.

  Referring to FIG. 13, reference numerals 65, 66, and 67 indicate convergence speeds of the deviation Enc when the response designation parameter POLE is -1, -0.8, and -0.5, respectively. As the absolute value of the response designation parameter POLE decreases, the convergence speed of the deviation Enc increases.

Returning to FIG. 11, the reaching law calculation unit 53 calculates the reaching law input Urch represented by the proportional term of the switching function σ, as shown in Expression (7). The reaching law input Urch is an input for placing the state quantity on the switching line. The adaptive law calculation unit 54 calculates an adaptive law input Uadp represented by the integral term of the switching function σ, as shown in Expression (8). The adaptive law input Uadp is an input for placing the state quantity on the switching line while suppressing the steady-state deviation. Krch and Kadp are feedback gains, which are determined in advance by simulation or the like. The adder 55 adds the reaching law input Urch and the adaptive law input Uadp as shown in Expression (9). Thus, the drift correction term Pcyl_comp_SLD is calculated.

  As shown in FIG. 10, the drift correction term Pcyl_comp_SLD (k) is fed back to the correction circuit 49. The correction circuit 49 adds the received drift correction term Pcyl_comp_SLD (k) to the in-cylinder pressure Pcyl '(k + 1) obtained in the next cycle to calculate the corrected in-cylinder pressure Pcyl (k + 1). The drift correction term Pcyl_comp_SLD (k + 1) is calculated again based on the corrected in-cylinder pressure Pcyl (k + 1) and fed back to the correction circuit 49.

  With reference to FIG. 14, the effect of using response designation control will be described. FIG. 14A shows the waveform of the drift amount Pcyl_comp output from the moving average circuit 38 in the first embodiment described above. As indicated by reference numerals 71 to 73, discontinuity occurs in the waveform. This is because the drift amount Pdft is calculated for each combustion cycle. That is, this is because the calculated drift amount Pdft is constant over time Tn. If the in-cylinder pressure Pcyl 'is corrected with the drift amount Pcyl_comp represented by such a discontinuous waveform, discontinuity may appear in the waveform of the corrected in-cylinder pressure Pcyl. This may not be preferable in the process of frequency-resolving the corrected in-cylinder pressure waveform. Such a discontinuity can be eliminated by using response designating control.

  FIG. 14B shows the drift correction term Pcyl_comp_SLD calculated by the controller 50. For comparison, the drift amount Pcyl_comp shown in FIG. 14A is shown by a dotted line.

  Since the drift correction term Pcyl_comp_SLD is calculated asymptotically to the target value (zero value) by the response designation control, the drift correction term Pcyl_comp_SLD is obtained as a continuous waveform. Since the waveform of the drift correction term Pcyl_comp_SLD has no discontinuity, it is possible to avoid an undesirable discontinuity from appearing in the waveform of the in-cylinder pressure Pcyl.

  Next, a process for calculating the in-cylinder pressure Pcyl according to the second embodiment will be described with reference to FIGS.

  FIG. 15 shows a flowchart of a process for calculating the drift amount Pdft. As described above, this process is performed with a period of Tn. n indicates an operation cycle.

  In step S1, as described with reference to FIG. 9, when the up counter value Dcnt reaches the crank angle Dsample at which the in-cylinder pressure is to be sampled, the process is started (S1). As described above, in one embodiment, the process is initiated at a predetermined timing during the intake stroke of each combustion cycle.

  In step S2, the corrected in-cylinder pressure Pcyl is sampled to obtain an in-cylinder pressure sample Psample. Further, the output Pb from the intake pipe pressure sensor is sampled. In step S3, the difference between the in-cylinder pressure sample Psample and the intake pipe pressure Pb is calculated as the drift amount Pdft.

  FIG. 16 shows a flowchart of a process for calculating the corrected in-cylinder pressure Pcyl. This process is performed with a period of Tk. k represents an operation cycle.

  In step S11, the output Vps of the in-cylinder pressure sensor 15 is read (that is, the output of the in-cylinder pressure sensor 15 is sampled to obtain a digital value Vps). In step S12, an integration routine (FIG. 17) is performed. By this integration routine, the output Vps of the in-cylinder pressure sensor is integrated, and the in-cylinder pressure Pcyl 'is calculated.

  In step S13, the drift amount Pdft (n) obtained in step S3 (FIG. 15) is oversampled. In step S14, as shown in the above equation (3), m sample values obtained by oversampling, that is, Pdft (k) to Pdft (k− (m−1)) are moving averaged, and time A drift amount Pcyl_comp per Tk is calculated.

  In step S15, simple response designation control is performed to calculate a drift correction term Pcyl_comp_SLD. In step S16, the drift correction term Pcyl_comp_SLD is added to the in-cylinder pressure Pcyl 'obtained from the integrating device to calculate the corrected in-cylinder pressure Pcyl.

  FIG. 17 shows a flowchart of the integration process in step S12 of FIG. In step S21, how much time (seconds) the actual period Tk is actually calculated is calculated. As described above, in this embodiment, the time is measured using the crank angle. For example, the processing performed “in the cycle of Tk” is performed “every time the crank angle advances by D (for example, 0.25 degrees)”. The time length corresponding to the crank angle period D actually varies according to the engine speed. Therefore, in each cycle, it is preferable to calculate the actual time length of the cycle Tk based on the detected engine speed and to calculate the corrected in-cylinder pressure based on the time length.

  If the engine speed NE (k) detected this time indicates the rotation speed of the crankshaft per minute, the rotation speed of the crankshaft per second is (NE (k) / 60). On the other hand, if the output Vps of the in-cylinder pressure sensor is sampled for each crank angle of D, the number of samplings per one rotation of the crankshaft is 360 / D.

  Therefore, the frequency H (Hz) at which the output Vps of the in-cylinder pressure sensor is sampled is expressed by Expression (10).

H = (NE (k) × 360 / D) / 60 = (6 × NE (k)) / D
(10)
Therefore, the actual time length Tk (k) of the current cycle is calculated by Expression (11). Here, the unit of Tk (k) is second.

Tk (k) = 1 / H = D / (6 × NE (k)) (11)
Steps S22 and S23 show integration processing. In step S22, a change amount ΔPcyl ′ (k) of the in-cylinder pressure per time Tk (k) is calculated. Since the output Vps (k) of the in-cylinder pressure sensor represents the change rate of the in-cylinder pressure Pcyl ′, the change amount ΔPcyl ′ (k) of the in-cylinder pressure per time Tk (k) is calculated as shown in Expression (12). Is done. By using the actual time length Tk (k), the change amount ΔPcyl ′ of the in-cylinder pressure can be calculated more accurately.

ΔPcyl ′ (k) = Vps (k) × Tk (k) (12)
In step S23, the in-cylinder pressure change ΔPcyl ′ (k) calculated in step S22 per time Tk (k) is added to the previous value Pcyl ′ (k−1) of the in-cylinder pressure. This time value Pcyl ′ (k) is calculated.

  Alternatively, the in-cylinder pressure Pcyl 'may be calculated at a predetermined time interval without being synchronized with the crank angle. For example, it can be implemented so as to synchronize with a timer set with a predetermined time. In such a case, the predetermined time interval is set to the actual time length Tk (k). The in-cylinder pressure Pcyl ′ can be calculated so as to be synchronized with other parameters, but in this case as well, the change amount ΔPcyl ′ of the in-cylinder pressure is calculated in consideration of the actual time length of the period Tk. preferable.

  FIG. 18 shows a flowchart of the response designation type control in step S15 (FIG. 16). In step S31, a deviation Enc (k-1) between the previous value Pcyl_comp (k-1) of the drift amount per time Tk and the target value Pcyl_comp_cmd is calculated. In step S32, a deviation Enc (k) between the current value Pcyl_cmp (k) of the drift amount per time Tk and the target value Pcyl_comp_cmd is calculated.

  In step S33, the switching function σ is calculated according to the above equation (4). In step S34, the reaching law input Urch is calculated according to the above equation (7).

  In step S35, the switching function σ (k) is added to the previous value G (k−1) of the integrated value of the switching function to calculate the current value G (k) of the integrated value of the switching function. In step S36, the adaptive law input Uadp is calculated according to the above equation (8). In step S37, the control input to the correction device 31, that is, the drift correction term Pcyl_comp_SLD is calculated according to the above equation (9).

  Alternatively, the drift correction term Pcyl_comp_SLD may be calculated using a control method different from the response assignment type control, such as a backstepping method or optimal control.

  The present invention is applicable to a general-purpose internal combustion engine (such as an outboard motor).

The figure which shows schematically the engine and its control apparatus according to one Example of this invention. The figure which shows attachment of the cylinder pressure sensor according to one Example of this invention. The figure which shows the waveform of the corrected in-cylinder pressure from which (a) the output of the in-cylinder pressure sensor, (b) the in-cylinder pressure including a drift, and (c) drift were removed according to one Example of this invention. The block diagram of the cylinder pressure detection apparatus according to one Example of this invention. 1 is a block diagram of a correction device according to one embodiment of the present invention. The figure which shows the waveform of the cylinder pressure sample Psample according to one Example of this invention. The figure which shows the drift amount Pdft according to one Example of this invention. The figure which shows drift amount Pcyl_comp per time Tk according to one Example of this invention. The figure which shows the method of sampling in-cylinder pressure Pcyl 'according to one Example of this invention. The block diagram of the correction | amendment apparatus according to the other Example of this invention. FIG. 4 is a block diagram of a controller according to another embodiment of the present invention. The figure which shows the switching function of response designation | designated type control according to the other Example of this invention. The figure which shows the response designation | designated parameter of response designation | designated type control according to another Example of this invention. The figure which shows the discontinuity of the drift correction | amendment term when not using response designation | designated control according to one Example of this invention, and the continuity of the drift correction | amendment term when using (b) response designation | designated control. The flowchart of the process which calculates drift amount Pdft according to one Example of this invention. The flowchart of the process which calculates corrected cylinder pressure Pcyl according to one Example of this invention. The flowchart of the integration process according to one Example of this invention. The flowchart of response designation | designated type control according to one Example of this invention. A circuit that integrates the output of the in-cylinder pressure sensor according to the prior art. The figure which shows the drift of cylinder pressure. The circuit which integrates the output of a cylinder pressure sensor provided with the reset means according to a prior art. The figure which shows the influence on the cylinder pressure waveform by reset operation according to a prior art.

Explanation of symbols

1 ECU
2 Engine 8 Combustion chamber 15 In-cylinder pressure sensor

Claims (6)

An in-cylinder pressure sensor that outputs a signal corresponding to the rate of change of the in-cylinder pressure of the internal combustion engine;
Integrating means for calculating an in-cylinder pressure by integrating an output signal from the in-cylinder pressure sensor;
Means for sampling in-cylinder pressure output from the integrating means in a first cycle;
A means for calculating a drift amount based on the sampled in-cylinder pressure, the drift amount calculated this time being held until the next drift amount calculation ;
Means for oversampling the drift amount in a cycle shorter than the first cycle;
Means for averaging the oversampled drift amount and calculating a drift correction term for removing drift in the in-cylinder pressure;
Correction means for correcting the drift correction term by subtracting from the in-cylinder pressure output from the integration means, and calculating a corrected in-cylinder pressure;
An in-cylinder pressure detecting device. The means for calculating the drift amount further includes:
By subtracting a predetermined reference value from the sampled in-cylinder pressure, comprising means for calculating the drift amount, cylinder pressure detection device according to claim 1. The in-cylinder pressure detection according to claim 2 , wherein the first cycle is a cycle in which an intake stroke in a combustion cycle of the internal combustion engine arrives, and the predetermined reference value is a pressure in the intake pipe in the intake stroke. apparatus. An in-cylinder pressure sensor that outputs a signal corresponding to the rate of change of the in-cylinder pressure of the internal combustion engine;
Integrating means for calculating an in-cylinder pressure by integrating an output signal from the in-cylinder pressure sensor;
Correction means for correcting the in-cylinder pressure with a drift correction term for removing drift in the in-cylinder pressure, and calculating a corrected in-cylinder pressure;
Means for sampling the corrected in-cylinder pressure in a first cycle;
A means for calculating a drift amount based on the sampled corrected in-cylinder pressure, the drift amount calculated this time being held until the next drift amount calculation;
Means for oversampling the drift amount in a cycle shorter than the first cycle;
Means for averaging the oversampled drift amount;
Means for calculating the drift correction term so as to converge the averaged drift amount to zero;
Means for feeding back the drift correction term to the correction means,
The correcting means corrects the in-cylinder pressure output from the integrating means with the feedback drift correction term, and calculates the corrected in-cylinder pressure.
In-cylinder pressure detection device. The means for calculating the drift amount further includes:
The in-cylinder pressure detecting device according to claim 4 , further comprising means for subtracting a predetermined reference value from the sampled in-cylinder pressure to calculate the drift amount. The in-cylinder pressure detection according to claim 5 , wherein the first cycle is a cycle in which an intake stroke in a combustion cycle of the internal combustion engine arrives, and the predetermined reference value is a pressure in the intake pipe in the intake stroke. apparatus.

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