JP6219609B2 - Engine start control device - Google Patents

Description

  The present invention relates to an engine start control device.

  Conventionally, after an engine is started, for example, by controlling the ignition timing, it has been widely practiced to stabilize, for example, the idling engine speed or to activate the exhaust purification catalyst early. (For example, refer to Patent Documents 1 and 2).

  Here, Patent Document 1 discloses a control of an internal combustion engine that allows the engine speed to converge to a target speed at an early stage while suppressing rotational fluctuations at the time of cold start, and enables early activation of the catalyst device. An apparatus is disclosed. This internal combustion engine control device can perform ignition timing retard control for warming up the catalyst device and engine speed feedback control by ignition timing to converge the engine speed to the target engine speed during cold start. A control device for an internal combustion engine, which compares the ignition timing with the comparison means for comparing the final ignition timing and the retard lower limit value during the execution of the rotational speed feedback control by the ignition timing, and the comparison result by the comparison means. And target speed changing means for changing the target speed in the speed feedback control. The control device for the internal combustion engine increases the target rotational speed by a predetermined number when the final ignition timing reaches the retardation lower limit, and the difference between the final ignition timing and the retardation lower limit becomes a predetermined angle advance side. When exceeding, by reducing the target rotational speed by a predetermined number, the engine rotational speed can be converged to the target rotational speed early and the catalyst device can be activated early at the time of cold start while suppressing the rotational fluctuation. .

  Further, in Patent Document 2, when the temperature of the internal combustion engine is lower than a predetermined temperature, the ignition timing is feedback controlled so that the engine rotational speed matches the target rotational speed, and when the temperature of the internal combustion engine is equal to or higher than the predetermined temperature. Is an internal combustion engine ignition control system that performs retarding control for retarding the ignition timing by a predetermined amount from a specified target ignition timing, and the internal combustion engine is configured to change the predetermined temperature according to the altitude of the place where the internal combustion engine is used. An engine ignition control system is disclosed. By the way, the fuel is more easily vaporized as the atmospheric pressure becomes lower. However, according to the ignition control system of the internal combustion engine, even when the altitude at which the internal combustion engine is used is high (that is, the atmospheric pressure is low), Effects such as early activation of the exhaust emission control device can be obtained.

JP 2008-190428 A JP 2008-255875 A

  However, from the cranking state in which the engine is cranked by the starter motor, the initial combustion (first explosion) is followed by a complete explosion, and the engine speed during the engine speed rises rapidly (initial engine start). In the technology such as Patent Document 1 and Patent Document 2 described above, the control is not considered. For this reason, for example, engine stability is deteriorated, emission at start-up is deteriorated due to variations in engine friction between engines (individual differences), fuel properties (e.g., easiness of evaporation), and the like. There was a fear.

  The present invention has been made to solve the above-mentioned problems, and can reduce fluctuations in the engine starting at the initial stage of engine startup caused by engine-to-engine fluctuations and fuel property fluctuations, improving starting stability, and An object of the present invention is to provide an engine start control device capable of improving emission at the time of start.

  An engine start control device according to the present invention includes a rotational position detecting means for detecting a rotational position of a crankshaft of an engine, and an engine at an arbitrary crank angle based on the rotational position of the crankshaft detected by the rotational position detecting means. The engine speed at a predetermined timing is predicted based on a speed acquisition means for obtaining an instantaneous speed that is the speed of rotation, and the instantaneous speed at a predetermined angle before the compression top dead center of the next ignition cylinder to be ignited next. Predicted rotation speed calculating means for obtaining a predicted rotation speed, storage means for storing a preset target rotation increase profile at engine start, and a target rotation increase profile stored by the storage means at a predetermined timing Target speed setting means for setting the target speed and ignition timing control for controlling the ignition timing of the engine And the ignition timing control means is configured such that when the engine is started, the predicted rotational speed obtained by the predicted rotational speed calculating means matches the target rotational speed set by the target rotational speed setting means. The ignition timing is controlled.

  According to the engine start control apparatus of the present invention, when the engine is started, the predicted engine speed that is predicted based on the instantaneous engine speed and the target engine speed that is set based on the target engine speed increase profile are obtained. The ignition timing is controlled so as to match. Therefore, in the initial stage of engine start, the engine speed can be increased along a preset target rotation increase profile. As a result, it is possible to reduce the rotational increase variation at the initial stage of engine starting due to the engine friction variation between the engines and the fuel property variation, and it becomes possible to improve the starting stability and the emission at the time of starting.

  In the engine start control device according to the present invention, the ignition timing control means calculates the ignition timing correction amount based on the difference between the predicted rotation speed and the target rotation speed, and corrects the ignition timing of the next ignition cylinder. preferable.

  In this case, since the ignition timing is corrected based on the difference between the predicted rotational speed and the target rotational speed, the engine rotational speed can be matched with the target rotational speed without delay. Thus, the engine speed can be increased along the target rotation increase profile without delay.

  An engine start control device according to the present invention includes an initial combustion detection unit that detects whether or not initial combustion has occurred from a cranking state, and a counter that counts the number of ignitions after the initial combustion is detected by the initial combustion detection unit. And the target rotation increase profile is set as a target increase rotation speed map that defines the relationship between the engine warm-up state, the number of ignitions counted by the counting means, and the rotation increase amount of the engine rotation speed, Preferably, the target rotational speed setting means searches the target ascending rotational speed map based on the number of ignitions counted by the counting means, and sets the target rotational speed according to the acquired rotational increase amount.

  In this way, after the first combustion is detected, the target rotational speed is set for each ignition (combustion). Therefore, it is possible to control the engine speed so as to coincide with the target speed for each ignition. Therefore, it is possible to increase the engine speed along the target rotation increasing profile without delay and with high accuracy.

  In the engine start control apparatus according to the present invention, it is preferable that the target ascending engine speed map is set in consideration of standard engine friction and standard fuel properties.

  In this way, it is possible to appropriately set the target ascent rotation speed map (target rotation ascent profile).

  In the engine start control device according to the present invention, the rotation speed acquisition means is based on the rotation position of the crankshaft detected by the rotation position detection means in addition to the instantaneous rotation speed, and the average engine rotation speed during a predetermined crank angle. Before the initial combustion detection means calculates the stroke average rotational speed, the instantaneous rotational speed is determined according to the engine warm-up state and the engine warm-up state. After detecting the initial combustion depending on whether or not the added value with the determination threshold value set according to is exceeded, and calculating the stroke average rotational speed, the instantaneous rotational speed becomes the stroke average rotational speed. It is preferable to detect whether or not initial combustion has occurred depending on whether or not the addition value with the determination threshold has been exceeded.

  In this way, it is possible to reliably detect the initial combustion without delay even before or after the stroke average rotational speed is calculated. In addition, since the cranking rotation speed and the determination threshold are set according to the engine warm-up state, it is possible to detect the initial combustion with higher accuracy in consideration of the friction at the time of engine start.

  In the engine start control device according to the present invention, it is preferable that the ignition timing control means is set so that the reference ignition timing before correction at the time of engine start is retarded from MBT.

  In this way, the output torque can be increased or decreased by correcting the ignition timing with respect to the reference ignition timing. Therefore, increasing the output torque by advancing the ignition timing to adjust the rotation increase amount to the increase side, and decreasing the output torque by retarding the ignition timing to decrease the rotation increase amount. It becomes possible to adjust.

  According to the present invention, it is possible to reduce the variation in the engine rotation at the initial stage of engine starting due to the engine friction variation between the engines and the fuel property variation, and to improve the starting stability and the emission at the time of starting. .

It is a figure showing composition of an engine to which an engine starting control device concerning an embodiment is applied. It is a figure which shows the example of a cranking stroke average rotation speed initial value table, and a combustion determination threshold value table. It is a figure which shows the example of a target raise rotation speed map. It is a figure which shows the example of a prediction rotation speed map. It is a figure which shows the example of an ignition timing correction amount map. It is a timing chart which shows an example of changes, such as instantaneous number of rotations at the time of engine starting, stroke average number of rotations, prediction number of rotations, target number of rotations, and ignition timing correction value. It is a figure for demonstrating the area which calculates the ignition timing of each cylinder, and an engine speed.

  DESCRIPTION OF EMBODIMENTS Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings. In addition, in each figure, the same code | symbol is attached | subjected to the same element and the overlapping description is abbreviate | omitted.

  First, the configuration of an engine 10 to which the engine start control device according to the embodiment is applied will be described with reference to FIG. FIG. 1 is a diagram illustrating a configuration of an engine 10 to which an engine start control device is applied.

  The engine 10 is, for example, a horizontally opposed four-cylinder gasoline engine. In the engine 10, air sucked from the air cleaner 16 is throttled by an electronically controlled throttle valve (hereinafter simply referred to as “throttle valve”) 13 provided in the intake pipe 15, passes through the intake manifold 11, and enters the engine 10. It is sucked into each formed cylinder. Here, the amount of air taken in from the air cleaner 16 is detected by an air flow meter 14 disposed between the air cleaner 16 and the throttle valve 13. A vacuum sensor 30 for detecting the pressure in the intake manifold 11 (intake pipe negative pressure) is disposed inside the collector portion (surge tank) constituting the intake manifold 11. Further, the throttle valve 13 is provided with a throttle opening sensor 31 that detects the opening of the throttle valve 13.

  In the vicinity of the intake port 22 communicating with the intake manifold 11, an injector 12 for injecting fuel is attached to each cylinder. The injector 12 injects the fuel sucked up by the feed pump and sent out from the fuel tank into the intake port 22. Further, a spark plug 17 that ignites the air-fuel mixture and an igniter built-in coil 21 that applies a high voltage to the spark plug 17 are attached to the cylinder head of each cylinder. In each cylinder of the engine 10, an air-fuel mixture of the sucked air and the fuel injected by the injector 12 is ignited by the spark plug 17 and burned. The exhaust gas after combustion is exhausted through the exhaust pipe 18.

An air-fuel ratio sensor 19 that outputs a signal corresponding to the oxygen concentration in the exhaust gas is attached to the exhaust pipe 18. As the air-fuel ratio sensor 19, an O ₂ sensor that detects the exhaust air-fuel ratio on and off is used. As the air-fuel ratio sensor 19, a linear air-fuel ratio sensor (LAF sensor) that can detect the exhaust air-fuel ratio linearly may be used.

Further, an exhaust purification catalyst 20 is disposed downstream of the air-fuel ratio sensor 19. The exhaust purification catalyst 20 is a three-way catalyst, which simultaneously oxidizes hydrocarbons (HC) and carbon monoxide (CO) in the exhaust gas and reduces nitrogen oxides (NOx) to produce harmful gas components in the exhaust gas. Is purified to harmless carbon dioxide (CO ₂ ), water vapor (H ₂ O) and nitrogen (N ₂ ).

  The exhaust pipe 18 is provided with an exhaust gas recirculation device (hereinafter referred to as an “EGR (Exhaust Gas Recirculation) device”) 40 that recirculates a part of the exhaust gas discharged from the engine 10 to the intake pipe 15 of the engine 10. It has been. The EGR device 40 includes an EGR pipe 41 that communicates the exhaust pipe 18 and the intake pipe 15 of the engine 10 and an EGR valve 42 that is disposed on the EGR pipe 41 and adjusts an exhaust gas recirculation amount (EGR flow rate). ing. The opening degree of the EGR valve 42 is controlled by an electronic control device 50 described later according to the operating state of the engine 10.

  In addition to the air flow meter 14, the air-fuel ratio sensor 19, the vacuum sensor 30, and the throttle opening sensor 31 described above, a cam angle sensor 32 for determining the cylinder of the engine 10 is attached in the vicinity of the camshaft of the engine 10. . A crank angle sensor 33 for detecting the rotational position of the crankshaft 10a is attached in the vicinity of the crankshaft 10a of the engine 10. Here, for example, a timing rotor 33a in which protrusions of 34 teeth with two teeth missing are formed at an interval of 10 ° is attached to the end of the crankshaft 10a, and the crank angle sensor 33 is connected to the timing rotor 33a. The rotational position of the crankshaft 10a is detected by detecting the presence or absence of the protrusion. That is, the crank angle sensor 33 corresponds to the rotational position detection means described in the claims. As the cam angle sensor 32 and the crank angle sensor 33, for example, an electromagnetic pickup type is used.

  These sensors are connected to an electronic control unit (hereinafter referred to as “ECU”) 50. Further, the ECU 50 includes a water temperature sensor 34 that detects the temperature of the cooling water of the engine 10, an oil temperature sensor 35 that detects the temperature of the lubricating oil, and an accelerator pedal that detects the amount of depression of the accelerator pedal, that is, the opening of the accelerator pedal. Various sensors such as an opening sensor 36 are also connected.

  The ECU 50 includes a microprocessor that performs calculations, a ROM that stores programs for causing the microprocessor to execute each process, a RAM that stores various data such as calculation results, and a backup RAM in which the stored contents are held by a 12V battery. And an input / output I / F and the like. The ECU 50 also includes an injector driver that drives the injector 12, an output circuit that outputs an ignition signal, a motor driver that drives an electric motor that opens and closes the electronically controlled throttle valve 13, and the like.

  In the ECU 50, the cylinder is determined from the output of the cam angle sensor 32, and the engine speed is obtained from the output of the crank angle sensor 33. Further, in the ECU 50, based on the detection signals input from the various sensors described above, various types such as the intake air amount, the intake pipe negative pressure, the accelerator pedal opening, the air-fuel ratio of the air-fuel mixture, and the water temperature and oil temperature of the engine 10 are provided. Information is acquired. Then, the ECU 50 comprehensively controls the engine 10 by controlling the fuel injection amount, the ignition timing, and various devices such as the throttle valve 13 based on the acquired various pieces of information.

  Further, the ECU 50 changes from the cranking state in which the engine 10 is cranked by the starter motor to the initial combustion (initial explosion) and shifts to the complete explosion, and the engine speed rapidly rises (that is, the engine starting initial stage). By adjusting the ignition timing of the engine and controlling the engine speed, the engine speed is increased along a preset target speed increasing profile. Therefore, the ECU 50 functionally includes a rotational speed acquisition unit 51, a storage unit 52, an initial combustion detection unit 53, a counting unit 54, a target rotational speed setting unit 55, a predicted rotational speed calculation unit 56, and an ignition timing control unit 57. ing. In the ECU 50, when the program stored in the ROM is executed by the microprocessor, the rotational speed acquisition unit 51, the initial combustion detection unit 53, the counting unit 54, the target rotational speed setting unit 55, the predicted rotational speed calculation unit 56, Each function of the ignition timing control unit 57 is realized.

  The rotational speed acquisition unit 51 obtains an instantaneous rotational speed Nreal that is an engine rotational speed at an arbitrary crank angle based on a temporal change in the rotational position of the crankshaft 10 a detected by the crank angle sensor 33. That is, the rotation speed acquisition unit 51 functions as a rotation speed acquisition unit described in the claims. In the present embodiment, the instantaneous rotational speed Nreal is calculated for each crank pulse (for example, every 10 °) from the time between the crank pulses. For example, in the case where a hybrid vehicle or the like is provided with a resolver, the instantaneous rotational speed Nreal may be acquired using the resolver.

  In addition to the instantaneous rotational speed, the rotational speed acquisition unit 51 calculates the average engine rotational speed during a predetermined crank angle based on a temporal change in the rotational position of the crankshaft 10a detected by the crank angle sensor 33. The average rotation speed is calculated. In the present embodiment, the bottom dead center BDC at the end of the combustion stroke (expansion stroke) (in the case of a four-cylinder engine), a crank with a BBDC of 10 ° with respect to the compression stroke top dead center TDC of the compression stroke of the next cylinder. At the time of signal input, the stroke average rotational speed NaveT180_BBDC10 is calculated based on the stroke time T180 in the 180 ° period before the signal input (that is, BTDC10 ° CA to BBDC10 ° CA).

  Here, as shown in FIG. 7, the ignition order of the engine 10 is the first cylinder (# 1), the third cylinder (# 3), the second cylinder (# 2), the fourth cylinder (# 4). ) In this order. Therefore, the stroke average rotational speed NaveT180_BBDC10 is, for example, in the section from BTDC10 ° CA to BBDC10 ° CA of the first cylinder (# 1) (that is, from BTDC10 ° CA of the first cylinder (# 1) to the third cylinder (##). 3) based on the time taken to rotate to BTDC 10 ° CA). The instantaneous rotational speed Nreal and the stroke average rotational speed NaveT180_BBDC10 acquired by the rotational speed acquisition unit 51 are output to the initial combustion detection unit 53, the predicted rotational speed calculation unit 56, and the ignition timing control unit 57.

  The storage unit 52 includes, for example, the above-described ROM and the like, and stores a preset target rotation increase profile at the time of starting the engine in addition to the above-described program. That is, the storage unit 52 functions as a storage unit described in the claims. Here, the target rotation increase profile includes the engine coolant temperature indicating the warm-up state of the engine 10 (hereinafter simply referred to as “water temperature”), and the number of ignitions after the initial combustion counted by the counter 54 (details will be described later). And a target ascending engine speed map that defines the relationship between the engine speed and the engine speed increase amount. The storage unit 52 also stores various tables and maps such as a cranking stroke average rotation speed initial value table, a combustion determination threshold value table, a predicted rotation speed map, a target increase rotation speed map, and an ignition timing correction amount map. Yes. Details of these tables and maps will be described later.

  The initial combustion detection unit 53 detects whether or not initial combustion has occurred from the cranking state. That is, the initial combustion detection unit 53 functions as initial combustion detection means described in the claims.

  More specifically, the initial combustion detection unit 53 determines the engine warm-up state (water temperature) before the stroke average rotation speed is calculated, that is, until the first stroke average rotation speed is calculated from the start of cranking. ) The cranking stroke average rotation speed initial value (cranking stroke average rotation speed) set in accordance with () and the combustion determination threshold value (determination threshold value) set in accordance with the engine warm-up state (water temperature). Is the initial combustion determination rotational speed (threshold), and it is determined that the initial combustion has been detected when the instantaneous rotational speed exceeds the initial combustion determination rotational speed (threshold).

  Here, how to set the initial combustion determination rotational speed (threshold value) will be described in more detail. The ROM of the ECU 50 stores a table (cranking stroke average rotation speed initial value table) that defines the relationship between the water temperature of the engine 10 and the cranking stroke average rotation speed initial value, and is based on the water temperature of the engine 10. By searching the cranking stroke average rotation speed initial value table, the cranking stroke average rotation speed initial value is acquired.

  Here, an example of the cranking stroke average rotation speed initial value table is shown by a solid line in FIG. In FIG. 2, the horizontal axis represents the water temperature (° C.) of the engine 10, and the vertical axis represents the cranking stroke average rotation speed initial value (rpm). Here, the cranking stroke average rotational speed initial value is set in consideration of the standard engine friction at the starting water temperature and the stroke average rotational speed during cranking in the state of the battery or starter. Therefore, the cranking stroke average rotational speed initial value table is set so that the cranking stroke average rotational speed initial value gradually increases as the water temperature increases, as shown by the solid line in FIG.

  Similarly, the ROM of the ECU 50 stores a table (combustion determination threshold value table) that defines the relationship between the water temperature of the engine 10 and the combustion determination threshold value, and the combustion determination threshold value table is searched based on the water temperature of the engine 10. By doing so, a combustion determination threshold value is acquired. Here, an example of the combustion determination threshold value table is shown by a broken line in FIG. In FIG. 2, the horizontal axis is the water temperature (° C.) of the engine 10, and the vertical axis is the combustion determination threshold value (rpm). The combustion determination threshold value table is set so that the combustion determination threshold value gradually increases as the water temperature increases, as indicated by a broken line in FIG.

  The initial cranking stroke average rotational speed initial value and the combustion determination threshold value are added to set the initial combustion determination rotational speed (threshold value). It should be noted that the parameters that define the cranking stroke average rotation speed initial value and the combustion determination threshold value only need to be indicators of the warm-up state of the engine. For example, oil temperature or the like may be used instead of the water temperature. .

  On the other hand, after the calculation of the stroke average rotation speed is started, the initial combustion detection unit 53 sets the stroke average rotation speed as the cranking stroke average rotation speed, and calculates the stroke average rotation speed (cranking stroke average rotation speed) and the combustion. The addition value to the determination threshold is set as the initial combustion determination rotational speed (threshold), and it is determined that the initial combustion is detected when the instantaneous rotational speed exceeds the initial combustion determination rotational speed (threshold). Here, since the calculation methods of the stroke average rotation speed and the combustion determination threshold value are as described above, detailed description thereof is omitted here. In addition, after the first combustion is detected, the update of the cranking stroke average rotational speed is stopped. The detection result of the initial combustion detection unit 53 is output to the counting unit 54.

  The counting unit 54 is a counter that counts (counts) the number of ignitions (the number of combustions) after the initial combustion is detected by the initial combustion detection unit 53. That is, the counting unit 54 functions as counting means described in the claims.

  More specifically, when the initial combustion is detected by the initial combustion detection unit 53, the counting unit 54 measures at an intermediate point in the expansion stroke (compression stroke of the next ignition cylinder) (BTDC 70 ° in the present embodiment). The numerical value (counter value) is 1. After the first combustion is detected, the count value is incremented every reference point during the expansion stroke (compression stroke of the next ignition cylinder), that is, every ignition (every combustion). Note that the count value counted by the counting unit 54, that is, the number of ignitions after the initial combustion detection is output to the target rotation number setting unit 55.

  The target rotation speed setting unit 55 is based on the target rotation increase profile (target increase rotation speed map) stored in the storage unit 52 and the number of ignitions after the initial combustion detection (combustion frequency) counted by the counting unit 54. Thus, the target rotational speed at a predetermined timing (in this embodiment, at the end of the expansion stroke (compression top dead center of the next ignition cylinder)) is set. That is, the target rotational speed setting unit 55 functions as a target rotational speed setting unit described in the claims.

  Here, how to set the target rotation speed will be described. In the ROM of the ECU 50, a map that defines the relationship between the water temperature (° C.) of the engine 10, the number of ignitions after the first combustion detection (the number of combustions), and the target ascending speed for each number of ignitions (target ascending speed map) Is stored, and the target ascending engine speed for each ignition is obtained by searching the target ascending engine speed map based on the water temperature of the engine 10 and the number of ignitions.

  Here, an example of the target ascending rotation speed map is shown in FIG. In FIG. 3, the horizontal axis represents the water temperature (° C.) of the engine 10, and the vertical axis represents the number of ignitions (the number of combustions) (times) after the first combustion detection. In the target ascent speed map, the target ascent speed is given for each combination (grid point) of the engine water temperature and the number of ignitions. The target ascent speed map (target speed ascent profile) is set in consideration of the standard engine friction of the applied engine and the standard fuel property (evaporation property) of the fuel used. In other words, the target increase rotational speed map is set as a map in which the engine rotational increase pattern in a standard state is defined by the engine water temperature and the number of ignitions (the number of combustions).

  The target rotational speed setting unit 55 searches the target upward rotational speed map based on the water temperature of the engine 10 and the number of ignitions counted by the counting unit 54 to acquire the target upward rotational speed, and the initial combustion is detected. Using the cranking stroke average rotation speed of the previous stroke as the initial value, the target rotation speed (target rotation) with respect to the ignition frequency (combustion frequency) is added for each ignition frequency (combustion frequency). Ascending profile). The target rotational speed set by the target rotational speed setting unit 55 is output to the ignition timing control unit 57.

  The predicted rotational speed calculation unit 56 is set to a predetermined angle before the compression top dead center (TDC) of the cylinder to be ignited next (next ignition cylinder) (in this embodiment, set to BTDC 70 ° (in the middle of the expansion stroke of the combustion cylinder)). Based on the instantaneous rotational speed at, the engine rotational speed (that is, the predicted rotational speed) at a predetermined timing (in this embodiment, the compression top dead center of the next ignition cylinder (at the end of the combustion stroke of the cylinder ignited this time)) is predicted. The predicted rotational speed calculation unit 56 predicts the rotational speed at the end of the compression stroke of the next cylinder to be ignited (that is, near the ignition timing) while the instantaneous rotational speed is rising due to combustion. Functions as the predicted rotation speed calculation means described in the claims.

  More specifically, in the ROM of the ECU 50, a map (prediction) that defines in advance the relationship between the water temperature of the engine 10, the instantaneous rotational speed at BTDC 70 °, and the predicted rotational speed at the compression top dead center of the next ignition cylinder. (Revolution speed map) is stored, and the predicted rotation speed calculation unit 56 searches the predicted rotation speed map based on the acquired water temperature and instantaneous rotation speed of the engine 10 and compresses the top dead center of the next ignition cylinder. Get the predicted rotation speed at.

  Here, an example of the predicted rotation speed map is shown in FIG. In FIG. 4, the horizontal axis is the water temperature (° C.) of the engine 10, and the vertical axis is the instantaneous rotational speed (rpm) of the engine 10. In the predicted rotational speed map, predicted rotational speed data is given for each combination (grid point) of the engine water temperature and the instantaneous rotational speed. For example, the predicted rotational speed data is used to estimate the rotational speed reduction amount of the instantaneous rotational speed at the end of the stroke from the relationship among the engine rotational speed, rotational energy generated by the engine rotation part inertia, compression work, and work due to friction. Can be obtained. Note that the predicted rotational speed calculated by the predicted rotational speed calculation unit 56 is output to the ignition timing control unit 57.

  The ignition timing control unit 57 controls the ignition timing of the engine 10. More specifically, the ignition timing control unit 57 calculates an optimal ignition timing and energization time according to the operating state of the engine 10 (for example, the engine speed and the air amount) at a reference point (for example, BTDC 70 °), When the ignition timing comes, an ignition signal is output to the igniter built-in coil 21. The igniter built-in coil 21 generates a high voltage based on the ignition signal and applies it to the electrode of the spark plug 17. The spark plug 17 ignites a spark with the applied high voltage and burns the air-fuel mixture in the combustion chamber.

  Further, when the ignition timing control unit 57 starts the engine 10, the predicted rotational speed obtained by the predicted rotational speed calculation unit 52 matches the target rotational speed set by the target rotational speed setting unit 54. Control ignition timing. That is, the ignition timing control unit 57 sets the reference ignition timing before correction at the start of the engine to a setting retarded from the MBT (for example, 70% torque ignition timing), and based on the difference between the predicted engine speed and the target engine speed. Then, the ignition timing correction amount is calculated, and the ignition timing of the next ignition cylinder is corrected. The ignition timing control unit 57 functions as ignition timing control means described in the claims.

  Here, how to obtain the ignition timing correction amount will be described. The ROM of the ECU 50 stores a map (ignition timing correction amount map) that defines the relationship between the predicted rotation speed (rpm), the difference between the predicted rotation speed and the target rotation speed (rpm), and the ignition timing correction amount. The ignition timing correction amount of the next ignition cylinder is acquired by searching the ignition timing correction amount map based on the predicted rotation speed and the difference between the predicted rotation speed and the target rotation speed.

  An example of the ignition timing correction amount map is shown in FIG. In FIG. 5, the horizontal axis represents the predicted rotational speed (rpm), and the vertical axis represents the difference (rpm) between the predicted rotational speed and the target rotational speed. In the ignition timing correction amount map, ignition timing correction amount data is provided for each combination (lattice point) of the predicted rotation speed and the difference between the predicted rotation speed and the target rotation speed. In the ignition timing correction amount map, the ignition timing correction amount is set so that the ignition timing is advanced when the predicted rotational speed is lower than the target rotational speed, and the predicted rotational speed is higher than the target rotational speed. The ignition timing correction amount is set so that the ignition timing is retarded.

  That is, for example, when the friction is high and the rotation increase is slightly delayed, the ignition timing control unit 57 advances the ignition timing to compensate for the rotation increase. Further, the ignition timing control unit 57 advances the ignition timing to compensate for the rotation increase even when the fuel tends to be slightly heavy (not easily evaporated) and the torque is difficult to be generated. In this way, the ignition timing control unit 57 determines whether or not the engine speed has increased according to the target rotation increase profile for each combustion (ignition) at a time, and ignites the next ignition cylinder. By sequentially controlling so as to correct the time, the predicted rotational speed and the target rotational speed are made to coincide. As a result, the engine speed increases along the target rotation increase profile.

  Next, the operation of the engine start control device will be described with reference to FIG. FIG. 6 is a timing chart showing an example of changes in the instantaneous rotational speed, the stroke average rotational speed, the predicted rotational speed, the target rotational speed, the ignition timing correction value, and the like when the engine is started. The horizontal axis in FIG. 6 is the crank angle (°), and the vertical axis is the instantaneous rotational speed (rpm: intermediate solid line), stroke average rotational speed (rpm: intermediate solid line), cranking stroke average rotational speed. (Rpm: broken line), initial combustion determination rotational speed (rpm: dotted line), target rotational speed (rpm: one-dot chain line), predicted rotational speed (rpm: two-dot difference line), number of ignition (combustion) after initial combustion detection (time) : Thin solid line), ignition timing correction value (°: thick solid line).

  First, when the starter motor is driven and cranking is started, output of the instantaneous rotational speed is started at a crank angle of 90 °. Thereafter, the instantaneous rotational speed repeats the rotation increase due to the combustion of the air-fuel mixture and the increase in the cylinder pressure, the engine friction after the exhaust valve opens and the cylinder pressure decreases, and the rotation decrease due to the compression of the next ignition cylinder. .

  At the crank angle of 180 °, the discrimination of the cylinder is completed, and the output of the cranking stroke average rotation speed and the initial combustion determination rotation speed is started. The method for calculating the cranking stroke average rotational speed and the initial combustion determination rotational speed is as described above, and thus detailed description thereof is omitted here. Thereafter, the output of the stroke average rotational speed is started at a crank angle of 350 °. Here, the stroke average rotational speed is lower in the rotational speed (calculation result) because the calculation timing is delayed with respect to the instantaneous rotational speed and an expansion stroke in which the engine speed increases is included in the calculation period.

  At the crank angle of 360 °, intake of the first combustion cylinder is started, and at the crank angle of 720 °, the initial combustion cylinder is ignited, the air-fuel mixture burns (initial combustion), and the instantaneous rotational speed rises rapidly.

  At the crank angle of 830 ° (BTDC 70 °), the number of ignitions (the number of combustions) is set to 1. At this timing, since the predicted rotational speed (expected rotational speed at the end of the expansion stroke)> target rotational speed, −3 ° (retard) is set as the ignition timing correction amount, and the ignition timing of the next ignition cylinder is retarded. It is corrected to. Therefore, the output torque is reduced and the amount of increase in rotation is suppressed. At the crank angle of 890 °, the stroke average rotational speed increases with a delay.

  Next, at the timing of a crank angle of 1010 ° (BTDC 70 °), the number of ignitions (the number of combustions) is incremented and increased to 2. At this timing, since the predicted rotational speed (expected rotational speed at the end of the expansion stroke) <target rotational speed, + 4.5 ° (advance) is set as the ignition timing correction amount, and the ignition timing of the next ignition cylinder is advanced. Is corrected to the side. Therefore, the output torque is increased and the amount of increase in rotation is increased.

  Next, at the timing of a crank angle of 1190 ° (BTDC 70 °), the number of ignitions (the number of combustions) is incremented and increased to 3. Even at this timing, since the predicted rotational speed (expected rotational speed at the end of the expansion stroke) <target rotational speed, + 5.5 ° (advance) is set as the ignition timing correction amount, and the ignition timing of the next ignition cylinder is advanced. Is corrected to the side. Therefore, the output torque is increased and the amount of increase in rotation is increased.

  Next, at the timing of the crank angle 1370 ° (BTDC 70 °), the number of ignitions (the number of combustions) is incremented and increased to 4. Even at this timing, since the predicted rotational speed (expected rotational speed at the end of the expansion stroke) <target rotational speed, + 5 ° (advance angle) is set as the ignition timing correction amount, and the ignition timing of the next ignition cylinder is advanced to the advanced angle side. It is corrected. Therefore, the output torque is increased and the amount of increase in rotation is increased.

  Next, at the timing of the crank angle 1550 ° (BTDC 70 °), the number of ignitions (the number of combustions) is incremented and increased to 5. At this timing, since the predicted rotational speed (expected rotation speed at the end of the expansion stroke) matches the target rotational speed, ± 0 ° (retard) is set as the ignition timing correction amount.

  As described above, by starting each calculation before the end of the expansion stroke (compression stroke of the next ignition cylinder) and reflecting the correction to the ignition timing of the next ignition cylinder, the predicted rotational speed and the target rotational speed are matched. The engine speed increases along the target rotation increase profile.

  As described above in detail, according to the present embodiment, when the engine 10 is started, the predicted rotational speed that is predicted based on the instantaneous rotational speed and the target that is set based on the target rotational increase profile. The ignition timing is controlled so that the rotational speed matches. Therefore, in the initial stage of engine start, the engine speed can be increased along a preset target rotation increase profile. As a result, it is possible to reduce the variation in engine start-up (cranking-first explosion-complete explosion) due to engine friction variation between engines (individual differences) and fuel property variations, improving starting stability, and It becomes possible to improve the emission at start-up.

  According to this embodiment, since the ignition timing is corrected based on the difference between the predicted rotation speed and the target rotation speed, the engine rotation speed can be matched with the target rotation speed without delay. Thus, the engine speed can be increased along the target rotation increase profile without delay.

  Further, according to the present embodiment, after the first combustion is detected, the target rotational speed is set for each ignition (combustion). Therefore, it is possible to control the engine speed so as to coincide with the target speed for each ignition. Therefore, the engine speed can be increased along the target rotation increase profile without delay and with high accuracy.

  According to the present embodiment, the target ascent speed map (target speed ascent profile) is set in consideration of the standard engine friction of the applied engine and the standard fuel properties of the fuel used. The target ascent speed map (target speed ascent profile) can be set appropriately.

  Further, according to the present embodiment, before the stroke average rotational speed is calculated, the instantaneous rotational speed is set to the cranking rotational speed that is set according to the engine water temperature, and the combustion determination threshold value that is set according to the engine water temperature. Whether or not the initial combustion has occurred is detected depending on whether or not the addition value of the value exceeds the value, and after calculating the stroke average rotation speed, the instantaneous rotation speed is obtained by adding the stroke average rotation speed and the combustion determination threshold value. It is detected whether or not the first combustion has occurred depending on whether or not it has exceeded. Therefore, the initial combustion can be reliably detected without delay either before or after the stroke average rotational speed is calculated. Further, since the cranking rotation speed and the combustion determination threshold are set according to the engine water temperature (warm-up state), it is possible to detect the initial combustion with higher accuracy in consideration of the friction at the time of starting the engine. .

  In addition, according to the present embodiment, since the reference ignition timing before correction at the time of engine start is set to retard from the MBT, the ignition timing is advanced or retarded with respect to the reference ignition timing, The output torque can be increased or decreased. Therefore, increasing the output torque by advancing the ignition timing to adjust the rotation increase amount to the increase side, and decreasing the output torque by retarding the ignition timing to decrease the rotation increase amount. It becomes possible to adjust.

  Although the embodiment of the present invention has been described above, the present invention is not limited to the above embodiment, and various modifications can be made. For example, in the above-described embodiment, the target rotational speed (target rotational increase profile) is compared with the instantaneous rotational speed (predicted rotational speed), but it may be configured to compare with the stroke average rotational speed. Further, the section for detecting the stroke average rotational speed is not limited to the above embodiment (BTDC 10 ° CA to BBDC 10 ° CA).

  In the above-described embodiment, a four-cylinder engine has been described as an example of the engine 10, but the present invention can also be applied to engines other than the four-cylinder engine. In the above embodiment, the case where the present invention is applied to a port injection type engine has been described as an example. However, the present invention combines an in-cylinder injection type engine, and in-cylinder injection and port injection. It can also be applied to engines.

  In the above embodiment, when the predicted rotational speed is obtained, the predicted rotational speed map is searched based on the instantaneous rotational speed and the engine water temperature. However, the prediction accuracy can be improved by dropping the phenomenon into a physical model and calculating. Good. Similarly, the ignition timing correction amount may be obtained by calculating the relationship between the ignition timing and the engine torque, the engine rotation part inertia, and the like in the physical model.

DESCRIPTION OF SYMBOLS 10 Engine 10a Crankshaft 13 Electronically controlled throttle valve 17 Spark plug 21 Igniter built-in coil 31 Throttle opening sensor 32 Cam angle sensor 33 Crank angle sensor 33a Timing rotor 34 Water temperature sensor 35 Oil temperature sensor 36 Accelerator pedal opening sensor 50 ECU
51 Rotational Speed Acquisition Unit 52 Storage Unit 53 Initial Combustion Detection Unit 54 Counting Unit 55 Target Rotational Speed Setting Unit 56 Predicted Rotational Speed Calculation Unit 57 Ignition Timing Control Unit

Claims (4)

Rotational position detection means for detecting the rotational position of the crankshaft of the engine;
Based on the rotational position of the crankshaft detected by the rotational position detecting means, a rotational speed acquisition means for obtaining an instantaneous rotational speed that is an engine rotational speed at an arbitrary crank angle;
Predicted rotational speed calculation means for predicting the engine rotational speed at a predetermined timing based on the instantaneous rotational speed before the compression top dead center of the next ignition cylinder to be ignited and calculating the predicted rotational speed;
Storage means for storing a preset target rotation increase profile at the time of engine start;
Target rotation speed setting means for setting a target rotation speed at the predetermined timing based on the target rotation increase profile stored by the storage means;
Ignition timing control means for controlling the ignition timing of the engine;
Initial combustion detection means for detecting whether or not initial combustion has occurred from the cranking state;
Counting means for counting the number of ignition after the initial combustion is detected by the initial combustion detection means ,
The rotational speed acquisition means obtains a stroke average rotational speed that is an average engine rotational speed during a predetermined crank angle based on the rotational position of the crankshaft detected by the rotational position detecting means in addition to the instantaneous rotational speed. ,
The initial combustion detection means includes
Before the stroke average rotational speed is calculated, the instantaneous rotational speed is an addition value of the cranking rotational speed set according to the engine warm-up condition and the determination threshold value set according to the engine warm-up condition. It is detected whether or not the first combustion has occurred depending on whether or not
After the stroke average rotational speed is calculated, it is detected whether or not the initial combustion has occurred depending on whether or not the instantaneous rotational speed has exceeded the added value of the stroke average rotational speed and the determination threshold,
The target rotation increase profile is set as a target increase rotation speed map that defines the relationship between the engine warm-up state, the number of ignitions counted by the counting means, and the rotation increase amount of the engine rotation speed,
The target rotation speed setting means searches the target increase rotation speed map based on the number of ignitions counted by the counting means, sets the target rotation speed according to the acquired rotation increase amount,
When the engine is started, the ignition timing control means performs ignition so that the predicted rotational speed obtained by the predicted rotational speed calculating means matches the target rotational speed set by the target rotational speed setting means. An engine start control device for controlling timing.   The ignition timing control means calculates an ignition timing correction amount based on a difference between the predicted rotational speed and the target rotational speed, and corrects the ignition timing of the next ignition cylinder. Engine start control device. 3. The engine start control device according to claim 1, wherein the target ascending engine speed map is set in consideration of standard engine friction and standard fuel properties. 4. It said ignition timing control means, start control system for engine according to any one of claims 1 to 3, characterized in that a setting which is retarded from the MBT the reference ignition timing before correction at the time of engine start.

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