JP2018071355A - Crank angle calculation device for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To further enhance crank angle detection accuracy.SOLUTION: A crank angle calculation device for an internal combustion engine which performs pre-mixed compression self-ignited combustion comprises: a crank angle sensor 61 constituted to detect a crank angle; a cylinder inner pressure sensor constituted to detect a cylinder inner pressure; and an electronic control unit 50 which has a storage section constituted to preliminarily store a prediction value of a maximum cylinder inner pressure crank angle when the pre-mixed compression self-ignited combustion is performed, a detection section detecting an actual value of the maximum cylinder inner pressure crank angle by the crank angle sensor and the cylinder inner pressure sensor when the pre-mixed compression self-ignited combustion is performed, and a correction section constituted to correct output of the crank angle sensor on the basis of a deviation between the actual value of the maximum cylinder inner pressure crank angle and the prediction value thereof.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a crank angle calculation device for an internal combustion engine.

  The actual dead center position of the piston is detected, the reference crank angle position is corrected according to the actual dead center position information, and the interval from the corrected reference crank angle position to the position where the in-cylinder pressure becomes maximum is measured. Thus, an internal combustion engine that obtains the crank angle at which the in-cylinder pressure becomes maximum is known (see, for example, Patent Document 1). In Patent Document 1, when the internal combustion engine is in a non-explosion operation state such as a fuel cut, that is, a position where the in-cylinder pressure becomes maximum during motoring is detected and set as the actual dead center position of the piston.

JP 63-009679 A

  However, since the amount of intake air is relatively small during motoring, the change in in-cylinder pressure is relatively small. As a result, the detection accuracy of the in-cylinder pressure may be low due to noise or the like, and therefore the detection accuracy of the crank angle may be low. Further, considering that the crank angle detection accuracy can be increased by repeatedly performing the correction operation, in Patent Document 1 in which the correction operation is performed only during motoring, the crank angle detection accuracy may not be sufficiently increased. .

  According to the present invention, a crank angle calculation device for an internal combustion engine in which premixed compression self-ignition combustion is performed, the crank angle sensor configured to detect the crank angle, and the in-cylinder pressure is configured. An in-cylinder pressure sensor, an electronic control unit, and a storage unit configured to store in advance a maximum in-cylinder pressure crank angle prediction value when premixed compression auto-ignition combustion is performed; A detection unit for detecting a maximum cylinder pressure actual crank angle value by the crank angle sensor and the cylinder pressure sensor when premixed compression self-ignition combustion is performed, the cylinder maximum pressure crank angle actual value, and the cylinder maximum pressure. An internal control unit comprising: an electronic control unit comprising: a correction unit configured to correct an output of the crank angle sensor based on a deviation from a predicted crank angle value. Crank angle calculation device is provided.

  The calculation accuracy of the crank angle can be further increased.

1 is an overall view of a vehicle control device. It is a fragmentary sectional view of an internal combustion engine. It is a figure which shows the map of the correction coefficient kC. It is a diagram for demonstrating the maximum in-cylinder pressure crank angle. It is a figure which shows the map of the largest in-cylinder pressure crank angle estimated value (theta) PmHP at the time of HCCI combustion mode. It is a flowchart for performing crank angle calculation control of the Example by this invention.

  FIG. 1 shows an overall view of a vehicle control apparatus according to an embodiment of the present invention. Referring to FIG. 1, the vehicle control apparatus includes an internal combustion engine 1. The internal combustion engine 1 includes an engine body 2 having a plurality of, for example, four cylinders 2a. The cylinder 2 a is connected to a surge tank 4 through an intake branch pipe 3, and the surge tank 4 is connected to an outlet of a compressor 6 c of an exhaust supercharger 6 through an intake duct 5. The inlet of the compressor 6 c is connected to the air cleaner 8 through the intake air introduction pipe 7. An air flow meter 9 for detecting the amount of intake air is disposed in the intake air introduction pipe 7. A cooler 10 for cooling the intake air and a throttle valve 11 are sequentially arranged in the intake duct 5.

  The cylinder 2 a is connected to the inlet of the turbine 6 t of the exhaust supercharger 6 through the exhaust manifold 12. The outlet of the turbine 6t is connected to the catalyst 14 through the exhaust pipe 13. The upstream and downstream of the turbine 6 t are connected to each other by a waste gate valve 15. An air-fuel ratio sensor 16 for detecting the air-fuel ratio is disposed in the exhaust pipe 13. The surge tank 4 and the exhaust manifold 12 are connected to each other by an exhaust gas recirculation (hereinafter referred to as EGR) passage 17. An EGR control valve 18 for controlling the amount of EGR gas and a cooler 19 for cooling the EGR gas are disposed in the EGR passage 17. The combustion order of the internal combustion engine 1 is, for example, 1-3-4-2.

  FIG. 2 shows in detail an internal combustion engine 1 according to an embodiment of the present invention. Referring to FIG. 2, 30 is a cylinder block, 31 is a cylinder head, 32 is a piston, 33 is a combustion chamber, 34 is an intake port, 35 is an intake valve, 36 is a valve operating mechanism of the intake valve 35, 37 is an exhaust port, 38 is an exhaust valve, 39 is a variable valve mechanism of the exhaust valve 38, 40 is a fuel injection valve disposed substantially at the center of the combustion chamber 33, 41 is a spark plug disposed adjacent to the fuel injection valve 40, and 42 is a combustion chamber. In-cylinder pressure sensors arranged in the cylinder 33 are shown. The in-cylinder pressure sensor 42 is provided in at least one cylinder 2a.

  Referring again to FIG. 1, the electronic control unit 50 comprises a digital computer and is connected to each other by a bidirectional bus 51, a ROM (Read Only Memory) 52, a RAM (Random Access Memory) 53, a CPU (Microprocessor) 54, An input port 55 and an output port 56 are provided. Output voltages of the air flow meter 9, the air-fuel ratio sensor 16, and the in-cylinder pressure sensor 42 are input to the input port 55 via the corresponding A / D converters 57. Further, a load sensor 60 that generates an output voltage proportional to the amount of depression of the accelerator pedal 59 is connected to the accelerator pedal 59, and the output voltage of the load sensor 60 is input to the input port 55 via the corresponding AD converter 57. The Further, a crank angle sensor 61 configured to detect a crank angle and a cam position sensor 62 configured to detect an angular position of a cam that drives an intake valve, for example, are connected to the input port 55. . The crank angle sensor 61 and the cam position sensor 62 will be described later. In the embodiment according to the present invention, the crank angle is set to 0 ° when the first cylinder is at the compression top dead center. On the other hand, the output port 56 is connected to the variable valve mechanism 39 of the cylinder 2a, the fuel injection valve 40 and the spark plug 41, the actuator of the throttle valve 11, the wastegate valve 15, and the EGR control valve via the corresponding drive circuits 58, respectively. 18 respectively.

  In the embodiment according to the present invention, the crankshaft rotor is fixed to the crankshaft of the internal combustion engine 1, and 34 protrusions provided at intervals of, for example, 10 degrees and a missing tooth portion are formed on the outer periphery of the crankshaft rotor. Has been. The crank angle sensor 61 described above includes, for example, an electromagnetic pickup, and is disposed facing the crankshaft rotor. Therefore, every time the protrusion of the crankshaft rotor passes the crank angle sensor 61, the crank angle sensor 61 generates an output pulse. On the other hand, when the missing tooth portion of the crankshaft rotor passes the crank angle sensor 61, the interval between the output pulses becomes longer. In other words, the crank angle sensor 61 outputs a signal representing a missing tooth portion, that is, a missing tooth signal.

  In the embodiment according to the present invention, for example, the camshaft rotor is fixed to the camshaft of the valve operating mechanism 36 of the intake valve 35, and one protrusion is formed on the outer periphery of the camshaft rotor. The cam position sensor 62 described above includes, for example, an electromagnetic pickup, and is disposed facing the cam shaft rotor. Therefore, every time the protrusion of the camshaft rotor passes the cam position sensor 62, the cam position sensor 62 generates an output pulse.

  In the embodiment according to the present invention, the crankshaft rotor is formed so that the missing tooth portion faces the crank angle sensor 61 when the first cylinder and the fourth cylinder are at the compression top dead center. Further, the camshaft rotor is formed so that the protrusion faces the cam position sensor 62 when the first cylinder is at the compression top dead center. Therefore, it can be seen that when the missing tooth signal is output from the crank angle sensor 61 and the pulse is output from the cam position sensor 62, the crank angle is 0 °. Further, the crank angle CA is known in accordance with the sequentially generated output pulses. Further, the engine speed Ne can be determined from the time from when the missing tooth signal is output from the crank angle sensor 61 to when the next missing tooth signal is output, that is, the time required for one revolution of the crankshaft.

  On the other hand, the internal combustion engine 1 according to the embodiment of the present invention has a combustion mode between an SI combustion mode in which spark ignition (SI) combustion is performed and an HCCI combustion mode in which premixed compression auto-ignition (HCCI) combustion is performed. Switchable. In the SI combustion mode, fuel is injected during the intake stroke, whereby a substantially homogeneous premixed gas is formed in the combustion chamber 33. The premixed gas is then ignited by a spark plug 41 and burned by flame propagation. In the embodiment according to the present invention, the air-fuel ratio in the SI combustion mode is set to approximately the stoichiometric air-fuel ratio.

  On the other hand, in the HCCI combustion mode, fuel injection is performed during the intake stroke, whereby a substantially homogeneous premixed gas is formed in the combustion chamber 33. This premixed gas is then compressed as the piston 32 rises, thereby self-igniting and burning. In this case, it is considered that the temperature of the premixed gas at a number of positions in the combustion chamber 33 reaches the self-ignition temperature almost simultaneously, and combustion is started almost simultaneously at the number of positions. Thus, in the HCCI combustion mode, the ignition action by the spark plug 41 is not performed apart from the auxiliary ignition. In the embodiment according to the present invention, the air-fuel ratio in the HCCI combustion mode is set to be leaner than the stoichiometric air-fuel ratio.

  In the HCCI combustion mode, since the air-fuel ratio can be made lean enough to the extent that SI combustion cannot be performed, fuel consumption can be reduced. Further, since the combustion period is shorter than that in the SI combustion mode, the thermal efficiency can be increased. Furthermore, since the combustion temperature is lower than in the SI combustion mode, the generation of NOx can be limited.

  In order to perform premixed compression self-ignition combustion, it is necessary to maintain the in-cylinder temperature at a temperature at which the premixed gas can self-ignite. In the embodiment according to the present invention, in the HCCI combustion mode, the exhaust valve 38 is opened twice in the exhaust stroke and the intake stroke by the variable valve mechanism 39 of the exhaust valve 38. In this way, the high temperature exhaust gas is returned from the exhaust manifold 12 into the combustion chamber 33 during the intake stroke, so that the in-cylinder temperature is maintained high. On the other hand, in the SI combustion mode, the exhaust valve 38 is opened once in the exhaust stroke. Note that the variable valve mechanism 39 of the embodiment according to the present invention can switch between a cam having one cam peak and a cam having two cam peaks.

  In the embodiment according to the present invention, the combustion mode is set to one of the SI combustion mode and the HCCI combustion mode according to the engine operating state such as the engine load and the engine speed. In one example, the combustion mode is set to the SI combustion mode at the time of high load and high rotation, and the combustion mode is set to the HCCI combustion mode at the time of low load and low rotation.

In the internal combustion engine 1 according to the embodiment of the present invention, the crank angle θ is calculated, and the fuel injection timing, the ignition timing, and the like are controlled using the crank angle θ. Here, in the embodiment according to the present invention, the crank angle θ is calculated using the following equation (1).
θ = θA + kC (1)

  In Expression (1), θA represents the actual crank angle value, and kC represents the correction coefficient.

  The actual crank angle value θA is the output of the crank angle sensor 61, that is, the actual crank angle detected by the crank angle sensor 61.

  On the other hand, the correction coefficient kC is for correcting the actual crank angle value θA, and is set to zero when it is not necessary to correct the actual crank angle value θA. In the embodiment according to the present invention, the correction coefficient kC is determined according to the engine operating state. In one example, the correction coefficient kC is stored in the RAM 53 in the form of a map shown in FIG. 3 as a function of the engine load L and the engine speed Ne.

In the embodiment according to the present invention, the correction coefficient kC is calculated using the following equation (2).
kC = θPmHP−θPmHA (2)

  In Expression (2), θPmHP represents the maximum in-cylinder pressure crank angle predicted value in the HCCI combustion mode, and θPmHA represents the maximum in-cylinder pressure crank angle actual value in the HCCI combustion mode.

  In the embodiment according to the present invention, as shown in FIG. 4, the crank angle θ at which the in-cylinder pressure P becomes the maximum value Pm in one combustion cycle is referred to as the maximum in-cylinder pressure crank angle θPm. In addition, the actual maximum cylinder pressure crank angle actual value represents the actual value of the maximum cylinder pressure crank angle θPm, that is, the actual maximum cylinder pressure crank angle θPm detected by the crank angle sensor 61 and the cylinder pressure sensor 42. Further, the predicted maximum in-cylinder pressure crank angle represents a predicted value of the maximum in-cylinder pressure crank angle θPm, that is, the maximum in-cylinder pressure crank angle θPm predicted in the engine operating state when the actual maximum in-cylinder pressure crank angle is detected. ing. Therefore, the actual maximum cylinder pressure crank angle value θPmHA in the HCCI combustion mode represents the actual maximum cylinder pressure crank angle θPm detected by the crank angle sensor 61 and the cylinder pressure sensor 42 in the HCCI combustion mode, and the HCCI combustion mode. The predicted maximum in-cylinder pressure crank angle θPmHP at the time represents the maximum in-cylinder pressure crank angle θPm predicted in the HCCI combustion mode in the engine operating state when the above-described maximum in-cylinder pressure crank angle actual value θPmHA is detected.

  In the embodiment according to the present invention, the maximum in-cylinder pressure crank angle predicted value θPmHP in the HCCI combustion mode is determined according to the engine operating state. In one example, the maximum in-cylinder pressure crank angle predicted value θPmHP in the HCCI combustion mode is obtained in advance by experiments and stored in advance in the ROM 52 as a function of the engine load L and the engine speed Ne in the form of a map shown in FIG. Has been.

  That is, in the embodiment according to the present invention, the correction coefficient kC is calculated based on the deviation between the maximum in-cylinder pressure crank angle predicted value θPmHP in the HCCI combustion mode and the maximum in-cylinder pressure crank angle actual value θPmHA in the HCCI combustion mode. This deviation is expressed, for example, in the form of a difference (= θPmHP−θPmHA). In another embodiment (not shown), the above-described deviation is expressed in the form of a ratio (= θPmHA / θPmHP), for example.

  The deviation between the maximum in-cylinder pressure crank angle predicted value θPmHP in the HCCI combustion mode and the maximum in-cylinder pressure crank angle actual value θPmHA in the HCCI combustion mode is the actual crank angle detected by the crank angle sensor 61, that is, the actual crank angle. It represents the error between the value θA and the true crank angle. Therefore, by correcting the actual crank angle value θA with the correction coefficient kC, this error can be eliminated and the true crank angle can be calculated.

  Moreover, according to the inventor of the present application, it has been confirmed that when HCCI combustion is performed, combustion is more stable than when other combustion is performed, and thus variation in in-cylinder pressure is small. Therefore, the crank angle actual value θA is corrected by correcting the crank angle actual value θA based on the deviation between the maximum in-cylinder pressure crank angle predicted value θPmHP in the HCCI combustion mode and the maximum in-cylinder pressure crank angle actual value θPmHA in the HCCI combustion mode. The actual value θA can be corrected more accurately.

  In the embodiment according to the present invention, the maximum in-cylinder pressure crank angle actual value θPmHA is calculated when HCCI combustion is stable. In other words, when HCCI combustion is unstable, the maximum in-cylinder pressure crank angle actual value θPmHA is not calculated, and the correction coefficient kC is not calculated. Therefore, the correction coefficient kC can be calculated more accurately, and the actual crank angle value θA can be corrected more accurately.

  In the embodiment according to the present invention, whether HCCI combustion is stable is determined as follows. That is, the variance value σθPmHA of the maximum in-cylinder pressure crank angle actual value θPmHA within a certain period in the HCCI combustion mode is calculated. Specifically, the maximum in-cylinder pressure crank angle actual value θPmHA is detected or calculated for a plurality of combustions within a certain period, and the variance value σθPmHA of these maximum in-cylinder pressure crank angle actual values θPmHA is calculated. This variance value σθPmHA has a correlation with the difficulty of self-ignition. That is, for example, when the combustion is shifted to the retard side or when the combustion speed is slow (when the intake air temperature is low, the octane number of the fuel is higher than the designated fuel, etc.), the dispersion value σθPmHA increases. Therefore, a small dispersion value σθPmHA is an indicator that HCCI combustion is stable. In another embodiment (not shown), instead of the dispersion value σθPmHA, the dispersion value of the maximum value Pm of the in-cylinder pressure P, the dispersion value of the in-cylinder pressure change rate maximum value dP / dθ, or the maximum in-cylinder pressure change rate A dispersion value of the crank angle θ giving the value dP / dθ is used.

  Further, the maximum value dP / dθ of the change rate of the in-cylinder pressure within the above-described fixed period is calculated. Specifically, the maximum value of the change rate of the in-cylinder pressure is detected or calculated for a plurality of combustions within a certain period, and dP / dθ is calculated by averaging these change rate maximum values. It should be noted that the maximum value of the in-cylinder pressure change rate is calculated by averaging the values before and after the maximum value of the in-cylinder pressure change rate in another example. This in-cylinder pressure change rate maximum value dP / dθ correlates with the likelihood of self-ignition. That is, for example, when the combustion is shifted to the advance side or when the combustion speed is high (when the intake air temperature is high, the octane number of the fuel is lower than the designated fuel, etc.), the maximum in-cylinder pressure change rate dP / dθ is growing. Therefore, a small in-cylinder pressure change rate dP / dθ is an indicator that HCCI combustion is stable. In another embodiment (not shown), instead of the above-mentioned maximum in-cylinder pressure change rate dP / dθ, the maximum value Pm of the in-cylinder pressure P, the maximum in-cylinder pressure crank angle θPm, or the maximum in-cylinder pressure change rate. A crank angle θ that gives dP / dθ is used.

  Next, when the above-described dispersion value σθPmHA is smaller than a predetermined threshold value σθPmHth and the maximum in-cylinder pressure change rate dP / dθ is smaller than a predetermined threshold rate (dP / dθ) th. HCCI combustion is determined to be stable, otherwise HCCI combustion is determined to be unstable. As a result, it can be accurately determined whether or not HCCI combustion is stable. Therefore, the correction coefficient kC can be calculated more accurately. In another embodiment (not shown), it is determined whether or not HCCI combustion is stable based on the dispersion value σθPmHA without being based on the maximum in-cylinder pressure change rate dP / dθ. In yet another embodiment (not shown), the determination is made based on the in-cylinder pressure change rate maximum value dP / dθ without being based on the dispersion value σθPmHA.

  Further, in the embodiment according to the present invention, the correction coefficient kC is learned. Specifically, when the correction coefficient kC is newly calculated, the correction coefficient kC stored in the RAM 53 is updated using the newly calculated correction coefficient kC. In this case, the engine operating state that gives the updated correction coefficient kC includes the maximum in-cylinder pressure crank angle predicted value θPmHP in the HCCI combustion mode and the maximum in-cylinder pressure crank angle in the HCCI combustion mode in order to newly calculate the correction coefficient kC. The actual value θPmHA is the same as the calculated engine operating state.

  Thus, in the embodiment according to the present invention, the correction coefficient kC is calculated or updated using the maximum in-cylinder pressure crank angle actual value θPmHA in the HCCI combustion mode. That is, since the correction coefficient kC is calculated or updated when the change in the cylinder pressure is relatively large, the calculation accuracy of the cylinder pressure is improved. In addition, since the calculation frequency of the maximum in-cylinder pressure crank angle actual value θPmHA in the HCCI combustion mode is high, the correction coefficient kC can be calculated more accurately. Therefore, the calculation accuracy of the crank angle is further improved. Furthermore, since the crank angle is calculated more accurately, fuel injection timing control, ignition timing control, etc. based on the crank angle can be performed more accurately.

  Therefore, conceptually expressed, the electronic control unit 50 of the embodiment according to the present invention is configured to store in advance the maximum in-cylinder pressure crank angle predicted value when the premixed compression auto-ignition combustion is performed. A storage unit, a detection unit for detecting the maximum cylinder pressure crank angle actual value by the crank angle sensor 61 and the cylinder pressure sensor 42 when the premixed compression self-ignition combustion is being performed, and the maximum cylinder pressure crank angle actual value. And a corrector configured to correct the output of the crank angle sensor 61 based on the deviation between the maximum in-cylinder pressure crank angle prediction value.

  FIG. 6 shows a routine for executing the crank angle detection control of the embodiment according to the present invention. This routine is executed by interruption every predetermined time. Referring to FIG. 6, in step 100, it is determined whether or not the HCCI combustion mode is being performed. When the HCCI combustion mode is being performed, the routine proceeds to step 101 where the above-described dispersion value σθPmHA is calculated. In the following step 102, it is determined whether or not the variance value σθPmHA is smaller than a predetermined threshold value σθPmHth. When σθPmHA <σθPmHth, the routine proceeds to step 103 where the above-mentioned in-cylinder pressure change rate maximum value dP / dθ is calculated. In the following step 104, it is determined whether or not the in-cylinder pressure change rate maximum value dP / dθ is smaller than a predetermined threshold rate (dP / dθ) th. When dP / dθ <(dP / dθ) th, the routine proceeds to step 105 where the maximum in-cylinder pressure crank angle predicted value θPmHP in the HCCI combustion mode is calculated from the map of FIG. In the following step 106, the maximum in-cylinder pressure crank angle actual value θPmHA in the HCCI combustion mode is calculated. In an example, the maximum in-cylinder pressure crank angle actual value θPmHA is calculated for each of the above-described multiple combustions, and the maximum in-cylinder pressure crank angle actual value θPmHA is calculated by averaging the maximum in-cylinder pressure crank angle actual value θPmHA. Is done. In the following step 107, the correction coefficient kC is calculated using the above equation (2). In the following step 108, the correction coefficient kC is learned. In the following step 109, the crank angle θ is calculated using the above equation (1).

  On the other hand, when the HCCI combustion mode is not performed at step 100, when σθPmHA ≧ σθPmHth at step 102, or when dP / dθ <(dP / dθ) th at step 104, the routine jumps to step 109. Accordingly, in this case, the correction coefficient kC is not calculated and learned.

  In the embodiment described so far, the correction coefficient kC and the maximum in-cylinder pressure crank angle predicted value θPmHP in the HCCI combustion mode are values determined according to the engine operating state. In another embodiment (not shown), the correction coefficient kC and the maximum in-cylinder pressure crank angle predicted value θPmHP in the HCCI combustion mode each take one value independent of the engine operating state.

1 Internal combustion engine 42 In-cylinder pressure sensor 50 Electronic control unit 61 Crank angle sensor

Claims (1)

A crank angle calculation device for an internal combustion engine in which premixed compression self-ignition combustion is performed,
A crank angle sensor configured to detect the crank angle;
An in-cylinder pressure sensor configured to detect in-cylinder pressure;
An electronic control unit,
A storage unit configured to store in advance a maximum in-cylinder pressure crank angle prediction value when premixed compression self-ignition combustion is performed;
A detection unit that detects a maximum cylinder pressure crank angle actual value by the crank angle sensor and the cylinder pressure sensor when premixed compression self-ignition combustion is performed;
A correction unit configured to correct the output of the crank angle sensor based on a deviation between the actual maximum cylinder pressure crank angle actual value and the estimated maximum cylinder pressure crank angle;
An electronic control unit comprising:
A crank angle calculation device for an internal combustion engine, comprising:

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