JP3721775B2 - In-cylinder injection engine start control device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a start control device that controls fuel injection timing and the like so that a smooth engine start can be performed in a direct injection engine.
[0002]
[Prior art]
Conventionally, in a spark ignition engine (gasoline engine) that is ignited by a spark plug, an injector with a tip facing the combustion chamber is provided so that fuel is directly injected into the combustion chamber, and a specific operation such as low rotation and low load is provided. 2. Description of the Related Art An in-cylinder injection engine is known in which in the region, fuel is injected from a injector in a compression stroke to cause flammable mixture to be unevenly distributed in the vicinity of a spark plug to perform stratified combustion to improve fuel efficiency.
[0003]
Further, as a control at the start of this type of engine, for example, as disclosed in Japanese Patent Application Laid-Open No. 60-56146, during engine cranking, fuel is injected in a compression stroke in order to improve ignitability, and stratification is performed. It is known that combustion is performed and fuel is injected in the intake stroke to prevent smoldering of the electrode of the spark plug after cranking is completed.
[0004]
[Problems to be solved by the invention]
By the way, in a reciprocating engine, torque fluctuation caused by negative torque in the compression stroke occurs, and there is a problem that torque fluctuation tends to increase especially at the time of engine start with a very low engine speed. Even a device such as that shown in the Japanese Patent Publication cannot solve the problem of torque fluctuation at the start.
[0005]
Specifically, in a four-cycle engine, intake, compression, expansion, and exhaust strokes are sequentially performed according to the reciprocating operation of the piston in the cylinder, and an explosion immediately after compression top dead center causes the piston to pass through the piston. Although a positive torque is applied to the output shaft, a negative torque is generated as the compression pressure increases in the compression stroke, and this negative torque increases in the latter half of the compression stroke. The negative torque and the positive torque act with a time lag, resulting in torque fluctuation. The torque fluctuation increases at the time of engine start (particularly during cranking) at a very low speed where the time interval is long. easy.
[0006]
Such torque fluctuation at the start of the engine is not preferable in terms of feeling and the like. In particular, in a hybrid vehicle in which the engine and motor are used properly and the engine is intermittently operated during vehicle operation, the engine may be started regardless of the driver's will during driving. Torque fluctuations make the driver feel uncomfortable and worsen the feeling.
[0007]
In order to suppress the above torque fluctuation, it is only necessary to generate a positive torque in other cylinders so as to cancel the negative torque in some cylinders in a multi-cylinder engine.
[0008]
However, such an operation is difficult to obtain with a conventional engine. That is, for example, in a four-cylinder four-cycle engine, when the first cylinder is in the compression stroke, the second cylinder is in the expansion stroke, the third cylinder is in the intake stroke, and the fourth cylinder is in the exhaust stroke. When the first cylinder is in the latter half of the compression stroke and generates a large negative torque, the third and fourth cylinders in the intake stroke and the exhaust stroke cannot obtain a positive torque, and the second cylinder has an expansion stroke. The negative torque cannot be sufficiently canceled because the positive torque due to combustion is attenuated in the second half.
[0009]
In the in-cylinder injection engine, the fuel injection timing into the combustion chamber can be variously changed, and the injection timing and the ignition timing are adjusted so as to suppress the torque fluctuation by shifting the combustion timing when starting the engine. However, the ignitability is deteriorated simply by adjusting the combustion timing to be shifted, and it becomes difficult to perform good combustion.
[0010]
In view of such circumstances, the present invention is a cylinder capable of suppressing the torque fluctuation by adjusting the timing of combustion while making the ignition and combustion satisfactorily performed at the time of engine start, and realizing a smooth engine start. An object of the present invention is to provide a start control device for an internal injection engine.
[0011]
[Means for Solving the Problems]
  In order to achieve the above object, the present invention provides a start discriminating means for discriminating an engine start time in a multi-cylinder four-cycle in-cylinder injection engine in which an injector for injecting fuel directly into a combustion chamber is provided in each cylinder. Control means for controlling the fuel injection and ignition timing from the injector according to the determination by the start determination means, and this control means is a torque fluctuation adjustment control at start-up when the engine is in a low rotation state from the start of engine start. As described above, the fuel injection from the injector for the same cylinder is performed separately in the latter half of the compression stroke and the expansion stroke, and the ignition is performed at a timing between the fuel injection in the latter half of the compression stroke and the fuel injection in the expansion stroke. becomeTherefore, the starting torque fluctuation adjustment control by this control means is performed until the engine speed is higher than the cranking speed and lower than the idle speed.Is.
[0012]
  According to this device, when the starting torque fluctuation adjustment control is performed, the air-fuel mixture formed in the vicinity of the spark plug by the injection in the latter half of the compression stroke is first ignited and burned immediately thereafter, and the combustion ends. By using this as a fire type before, the air-fuel mixture by fuel injection in the expansion stroke is combusted, so that a positive torque is applied until a relatively late stage of the expansion stroke while ensuring ignitability and combustibility. Therefore, in a multi-cylinder four-cycle engine in which the compression strokes of some cylinders and the expansion strokes of other cylinders overlap, the negative torque generated in the cylinders in the compression stroke is canceled out by the torque obtained in the cylinders in the expansion stroke. Thus, torque fluctuation at the time of starting is suppressed.The torque fluctuation adjustment control at the time of starting by the control means is performed until the engine speed reaches a predetermined speed that is higher than the cranking speed and lower than the idling speed. Torque fluctuation adjustment control is performed to suppress torque fluctuation.
[0013]
In particular, if the engine has four or more cylinders, the compression stroke of some cylinders and the expansion stroke of other cylinders greatly wrap, so that the effect of suppressing the torque fluctuation at the start as described above can be obtained satisfactorily. .
[0014]
In the apparatus of the present invention, if the timing of fuel injection in the latter half of the compression stroke in the starting torque fluctuation adjustment control by the control means is changed so as to be earlier as the temperature becomes lower according to the engine temperature, the injection from the latter half of the compression stroke is started at lower temperatures. By increasing the fuel vaporization and atomization time until ignition, deterioration of ignitability at low temperatures is suppressed.
[0015]
Further, if the timing of the fuel injection in the expansion stroke in the starting torque fluctuation adjustment control by the control means is changed so as to be advanced as the temperature decreases according to the engine temperature, the interval between the injection in the latter half of the compression stroke and the injection in the expansion stroke Is adjusted appropriately, and ignition and combustion of the fuel injected in the expansion stroke are performed satisfactorily.
[0016]
Further, if the closing timing of the intake valve during the start-up torque fluctuation adjustment control by the control means is set to a timing that is slow enough to cause the return of intake air from the combustion chamber to the intake port, the negative pressure in the compression stroke can be reduced. Torque is reduced. Moreover, since the fuel is directly injected into the combustion chamber after the compression stroke, the fuel does not blow back and adhere to the port wall surface.
[0018]
  Also,Preferably, the control means performs control so that fuel is injected during the compression stroke during a period of rapid increase in the engine speed from the time when the engine speed exceeds the predetermined speed until the start is completed. During the number increase period, flammability is ensured by stratified combustion, and the increase in the rotation speed can be appropriately regulated by adjusting the torque by controlling the fuel injection amount.
[0019]
Further, the starting torque fluctuation adjustment control by the control means may be performed for a predetermined time from the start of cranking of the engine. In this way, the predetermined cranking start from the start of cranking that tends to cause a feeling of deterioration due to torque fluctuation is performed. Over time, torque fluctuations are suppressed.
[0020]
The device of the present invention is effective when applied to a hybrid vehicle that includes an engine and a motor, and the engine is intermittently operated during vehicle operation. In this case, when the engine is started except for engine operation due to sudden acceleration. It is preferable that the control means is configured to perform the starting torque fluctuation adjustment control. In this way, when starting the engine due to sudden acceleration, the starting torque fluctuation adjustment control is stopped and priority is given to securing torque for sudden acceleration, and torque fluctuation is suppressed during other engine starting.
[0021]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0022]
FIG. 1 schematically shows the overall structure of an in-cylinder injection engine to which the present invention is applied. In this figure, the engine body 1 has a plurality of cylinders, for example, four cylinders 2a to 2d (see FIG. 2), and each cylinder has a combustion chamber above a piston 4 inserted in a cylinder bore. 5 is formed. An intake port 7 and an exhaust port 8 are opened in the combustion chamber 5, and these ports 7 and 8 are opened and closed by an intake valve 9 and an exhaust valve 10, respectively.
[0023]
The intake valve 9 and the exhaust valve 10 are opened and closed by a valve operating mechanism including camshafts 11 and 12. The valve operating mechanism for the intake valve 9 is provided with a variable valve timing device 13 that can change the opening / closing timing of the intake valve 9.
[0024]
A spark plug 15 is disposed at the center of the combustion chamber 5, and the tip of the plug faces the combustion chamber 5. The spark plug 15 is connected to the ignition coil 16.
[0025]
In addition, the tip of the injector 18 faces the combustion chamber 5 from the side, and fuel is directly injected into the combustion chamber 5 from the injector 18. The injector 18 of each cylinder is connected to a delivery pipe 21 of the fuel circuit 20. The fuel circuit 20 includes a fuel supply passage 22 and a return passage 23 connected to the delivery pipe 21, and an in-tank fuel pump 25, filters 26 and 27, and a high-pressure fuel pump are provided between the fuel tank 24 and the fuel supply passage 22. 28, a high-pressure side pressure regulator 29 and a low-pressure side pressure regulator 30 are disposed between the return passage 23 and the fuel tank 24, and a passage (not shown) that bypasses the high-pressure side pressure regulator 29. And a bypass valve 31 for opening and closing the passage.
[0026]
The fuel pressure can be changed by operating the bypass valve 31. That is, when the bypass valve 31 is closed while the high-pressure fuel pump 28 is operating, the fuel pressure is adjusted to a predetermined high pressure by the pressure adjusting action of the high-pressure pressure regulator 29, and the bypass valve 31 is opened. In some cases, the high pressure side pressure regulator 29 does not substantially function, and the fuel pressure is adjusted to a predetermined low pressure by the pressure regulating action of the low pressure side pressure regulator 30.
[0027]
An intake passage 40 and an exhaust passage 41 are connected to the engine body 1. In the intake passage 40, an air cleaner 43, an air flow sensor 44, a throttle valve 45 driven by a motor 46, and a surge tank 47 are provided in this order from the upstream side. A throttle opening sensor 48 that detects the opening of the throttle valve 45 is provided. Further, an ISC passage 50 that bypasses the throttle valve 45 is provided, and an ISC valve 51 that controls the air flow rate of the passage is provided in the ISC passage 50.
[0028]
An independent intake passage 53 for each cylinder is provided downstream of the surge tank 47, and each independent intake passage 53 communicates with the intake port 7 of each cylinder. Each independent intake passage 53 is provided with a swirl control valve 54. The swirl control valve 54 is driven by an actuator 55 such as a step motor to open and close, and the intake swirl is controlled by the opening and closing operation. ing.
[0029]
On the other hand, the exhaust passage 41 detects the air-fuel ratio by detecting the oxygen concentration in the exhaust gas.₂A sensor 57 is provided, and an exhaust gas purifying catalyst 58 is provided downstream thereof.
[0030]
Reference numeral 60 denotes an engine control unit (ECU). The ECU 60 includes the air flow sensor 44, the throttle opening sensor 48, and the O₂The detection signals a, b, and c from the sensor 57 are input, and the crank angle signal d and the cylinder discrimination signal e for detecting the engine speed and the like are input from the distributor 61 interlocked with the camshaft 12. Detection signals f, g, h from an accelerator opening sensor 62 that detects the opening (accelerator pedal depression amount), an intake air temperature sensor 63 that detects the temperature of intake air, a water temperature sensor 64 that detects the temperature of engine coolant, and the like. Is also entered.
[0031]
Further, the ECU 60 outputs a signal j for controlling fuel injection to the injector 18 via the injector drive unit 66, and also outputs a signal k for controlling the ignition timing to the ignition coil 16, and also drives the throttle valve. A signal l for controlling the throttle opening is output to the motor 46 through the throttle drive unit 67, a signal m for controlling the ISC valve 51, a signal n for controlling the bypass valve 31 of the fuel circuit, and a valve timing variable device A signal o etc. for controlling 13 is also output.
[0032]
The ECU 60 has a function as start determination means for determining when the engine is started and a function as control means for controlling fuel injection and ignition timing in accordance with the determination by the start determination means. As a starting torque fluctuation adjustment control, when the engine is in a low rotation state from the start of the engine, fuel injection from the injector for the same cylinder is divided into the latter half of the compression stroke and the expansion stroke, and the ignition is compressed as described above. The fuel injection is performed at a time between the fuel injection in the latter half of the stroke and the fuel injection in the expansion stroke.
[0033]
The apparatus of the present invention is effective when applied to a hybrid vehicle using both an engine and a motor. An example of the hybrid system is shown in FIG.
[0034]
In this figure, a torque converter 71 on the input side of the continuously variable transmission 70 is connected to the output shaft of the engine body 1, while an axle 73 is connected to the output side of the continuously variable transmission 70 via a final reduction gear 72. In addition, a motor / generator 74 is connected. An alternator 76 is connected to the front end side of the output shaft of the engine body 1 via a belt 75 or the like. The motor / generator 74 and the alternator 76 are connected to a battery 79 via inverters 77 and 78.
[0035]
A hybrid system control controller (ECU 60 in FIG. 1 or a controller not shown) separates the engine and the motor / generator 74 for driving the vehicle according to the driving state of the vehicle. For example, the engine is stopped and the motor / generator 74 is controlled so as to operate as a motor during low-speed traveling or at the beginning of acceleration, and the engine is controlled to operate in other operating states.
[0036]
FIG. 3 is a flowchart showing an example of start control performed in the ECU 60. The process shown in this flowchart starts when engine start is started when a predetermined engine operating condition is satisfied, for example, during driving of the hybrid vehicle. Note that hybrid system control, including determination of engine operating conditions and control of engine operation and stop in accordance with it, and determination of motor operating conditions and control of motor operation and stop in accordance with that, are not shown. This is done by a control routine.
[0037]
When the processing shown in the flowchart of FIG. 3 starts in response to the start of engine start, first, in step S1, the engine speed ne obtained from the crank angle signal, the accelerator opening degree accel detected by the accelerator opening degree sensor 62, and the water temperature sensor 64. The water temperature Tw detected by is read. Subsequently, in step S2, it is determined whether or not the engine speed ne is higher than the first set speed N1 (predetermined speed). The first set rotational speed N1 is set to a rotational speed slightly higher than the cranking rotational speed (for example, 300 rpm). Accordingly, when the determination in step S2 is NO, the cranking state is established. When this determination is YES Means that the engine speed is higher than the cranking state.
[0038]
When the determination in step S2 is NO, as the starting torque fluctuation adjustment control, each fuel injection amount is determined so that the fuel injection from the injector is performed in two stages, the latter half of the compression stroke and the expansion stroke. The second pulse width and the second pulse width are calculated (steps S3 and S4), and the first and second injection timings are calculated (steps S3 and S4). In this case, the first injection timing is the latter stage of the compression stroke, the second injection timing is the expansion stroke, and the first and second injection timings and the pulse widths define the correspondence between these and the water temperature in advance. It is calculated according to the detected value of the water temperature Tw by the table.
[0039]
The relationship between the first and second injection timings and the water temperature is set as shown in FIG. That is, the first injection timing is changed in accordance with the water temperature in the range of the latter half of the compression stroke, and the second injection timing is changed in the range of the expansion stroke, both of which are advanced as the water temperature decreases.
[0040]
Further, as the starting torque fluctuation adjustment control when the determination in step S2 is NO, the ignition timing is set between the first injection timing and the second injection timing (step S7).
[0041]
If the determination in step S2 is YES, the water temperature T is determined in step S8._W It is determined whether or not the temperature is higher than the set temperature T1. If it is warm, based on the determination of whether or not it is a stratified region (step S9), if it is a stratified region, the stratified mode is set (step S10), and if not stratified region, the uniform mode is set (step S11). ). Here, the stratification region means an operation region suitable for performing stratified combustion. For example, a predetermined operation region on the low rotation and low load side is set as a stratification region in advance. The stratified mode is a mode for controlling the fuel injection timing and the ignition timing so that ignition is performed in a state in which fuel is injected from the injector in the compression stroke and the air-fuel mixture is unevenly distributed in the vicinity of the spark plug. Is a mode in which the fuel injection timing and ignition timing are controlled so that ignition is performed in a state where fuel is injected from the injector during the intake stroke and fuel is uniformly diffused throughout the combustion chamber.
[0042]
In step S8, the water temperature T_W When it is determined that the engine temperature is cold below the set temperature T1, it is determined in step S12 whether or not the engine speed ne is higher than the second set speed N2. The second set rotational speed N2 is a rotational speed close to the idle rotational speed (for example, about 600 rpm). When the determination in step S12 is NO, the engine speed ne is between the first set speed N1 and the second set speed N2, and the speed until the engine is shifted from the cranking state to the operating state after the start is completed. In this case, the process proceeds to step S10 to enter the stratification mode. When the determination in step S12 is YES, the uniform mode is set (step S13).
[0043]
After the processing in steps S3 to S7 or the mode setting in any of steps S10, S11, and S13, the first injection and the second injection from the injector are performed in steps S14 and S15. In this case, when the processing of steps S3 to S7 is performed, the first injection and the second injection are actually performed according to the setting, but when the mode setting in any of steps S10, S11, S13 is performed, In principle, only the first injection is performed in the intake stroke or the compression stroke, and the second injection is set to zero.
[0044]
According to the apparatus of the present embodiment as described above, fuel is produced in the cranking period T1 from the start of starting shown in FIG. 5, the period T2 of engine speed increase after cranking, and the period T3 after completion of starting. Control of injection and the like is appropriately changed, torque fluctuation during cranking is reduced, and the transition from the start to the operation state after the start is performed smoothly.
[0045]
That is, during the cranking period T1 from the start of engine startup until the first set speed N1 is reached, fuel injection is performed in the latter half of the compression stroke and the expansion stroke, and ignition is performed between the two injections. (Steps S3 to S7). In such a control state, first, the air-fuel mixture formed in the vicinity of the spark plug in the first injection in the latter half of the compression stroke is ignited immediately after top dead center, so that ignition and combustion are favorably performed. Before completion, the mixture is burned by using this as a fire type by the second fuel injection. In this way, while ensuring ignitability and combustibility, a positive torque is applied until the middle or later stage of the expansion stroke by combustion of the air-fuel mixture by the second fuel injection.
[0046]
In this case, the first injection timing and the ignition timing are set to timings suitable for ignition and combustion, combustion by the first fuel injection continues until the second fuel injection, and negative torque as described later is applied. What is necessary is just to set the space | interval of the 1st injection and the 2nd injection, the ratio of the injection quantity, etc. so that moderate torque for canceling may be obtained by the 2nd fuel injection.
[0047]
Also, when the engine temperature is low, if the time from fuel injection to ignition is short, vaporization and atomization worsen and the ignitability tends to deteriorate, but as control according to the engine temperature (water temperature) at the time of engine start As in the above embodiment, as the water temperature is lower, the first fuel injection timing is advanced in order to increase the time for vaporization and atomization, and the water temperature is also lower in the second fuel injection timing accordingly. If it is made earlier, the mixture is ignited and burned by the first injection, and the mixture is ignited and burned by the second injection using this as a fire type, even when the temperature is low.
[0048]
By controlling the fuel injection and ignition timing in the cranking period T1 as described above, a multi-cylinder (generally, four or more cylinders) 4 in which the latter half of the compression stroke of one cylinder and the expansion stroke of another cylinder overlap. In the cycle engine, the positive torque applied in the cylinder in the expansion stroke cancels out the negative torque generated in the cylinder in the compression stroke. This operation will be specifically described with reference to FIG. 6 by taking the case of a four-cylinder four-cycle engine as an example.
[0049]
As shown in this figure, in a four-cylinder four-cycle engine, intake, compression, expansion, and exhaust strokes are sequentially performed in each cylinder, and cranks are performed in the order of the first cylinder, the third cylinder, the fourth cylinder, and the second cylinder. By shifting the stroke of each cylinder by 180 degrees in angle, the expansion stroke of the first cylinder and the compression stroke of the third cylinder, the expansion stroke of the third cylinder and the compression stroke of the fourth cylinder, the expansion stroke of the fourth cylinder, The compression stroke of the two cylinders, the expansion stroke of the second cylinder, and the compression stroke of the first cylinder lap.
[0050]
In the cranking period T1, the fuel injection (P1, P2 in FIG. 6) and the ignition timing (IG in FIG. 6) are controlled as described above, for example, in the expansion stroke of the first cylinder. The applied positive torque cancels the negative torque generated in the compression stroke of the third cylinder, and similarly between the third cylinder and the fourth cylinder, between the fourth cylinder and the second cylinder, and between the second cylinder and the second cylinder. Even in the case of one cylinder, the positive torque given by the cylinder in the expansion stroke cancels the negative torque generated in the cylinder in the compression stroke.
[0051]
Therefore, torque fluctuation during cranking is suppressed and feeling is improved. In particular, in a hybrid vehicle such as that shown in FIG. 2, the engine is started regardless of the driver's will, for example, during the transition from the motor operating state to the engine operating state even during traveling. In particular, it is possible to prevent the driver from feeling uncomfortable due to torque fluctuation.
[0052]
Next, in the period T2 after cranking in which the engine speed ne is higher than the first set speed N1, fuel injection or the like is controlled so as to give torque for increasing the engine speed. In the present embodiment, when the engine speed ne is between the first set speed N1 and the second set speed N2, the stratified mode is set in both the cold time and the warm time, and fuel injection is performed in the compression stroke. Then, stratified combustion is performed. Then, by appropriately controlling the fuel injection amount in this stratification mode, the transition to the operation state after the start is completed is performed smoothly.
[0053]
In other words, in a general engine, the engine speed rapidly increases after cranking as shown by a two-dot chain line in FIG. 5, and once it overshoots, it becomes the speed after starting. When the engine is started regardless of the will of the engine, the engine speed is required to be adjusted so as to avoid a sudden engine speed increase and overshoot because such a fluctuation in the engine speed gives the driver a sense of incongruity. . However, when the engine speed is lower than the second set rotational speed N2, the intake air amount reaches a saturated state even when the throttle opening is small, and it is difficult to control the intake air amount. Since it is necessary to supply fuel corresponding to the amount of intake air, it is difficult to control the engine output.
[0054]
On the other hand, when the stratified mode is set in the period T2, the engine output is appropriately controlled by controlling the fuel injection amount even at a low speed when flammability is ensured by stratified combustion in an excessive air state and the intake air amount is difficult to control. Thus, as shown by the solid line in FIG. 5, the engine speed increase can be moderated moderately, overshoot can be prevented, and the engine can be smoothly shifted to the state after starting.
[0055]
In addition, after the engine speed is higher than the second set speed T2 and the start-up is completed (period T3 in FIG. 5), in the cold mode, the fuel is injected in the intake stroke. As a result, vaporization and atomization of the fuel are promoted, and the combustibility is enhanced. In warm mode, the stratified mode or the uniform mode is selected according to the operation region.
[0056]
FIG. 7 is a flowchart showing a second embodiment of the start control. In this embodiment, in addition to the control (steps S1 to S15) similar to the first embodiment shown in FIG. 3, the closing timing of the intake valve during the start time torque fluctuation adjustment control is changed from the combustion chamber to the intake port. The variable valve timing device 13 is controlled so that the timing is late enough to cause the intake air to blow back, for example, the crank angle is set to about 100 ° ABDC.
[0057]
That is, in this flowchart, following the processing up to step S15, it is determined in step S16 whether or not the engine speed ne is higher than the second set speed N2, and if it is equal to or less than the second set speed N2, step S17. Thus, the variable valve timing device (VVT) 13 is closed late (timing is slow enough to cause the return of intake air from the combustion chamber to the intake port), and if higher than the second set rotational speed N2, the variable valve timing device (VVT) ( VVT) 13 is the normal control.
[0058]
According to this embodiment, when the engine is started, the closing timing of the intake valve is delayed and the effective compression ratio is reduced, so that the negative torque generated in the compression stroke is reduced. Etc., torque fluctuations are suppressed. In addition, since the fuel is directly injected into the combustion chamber after the compression stroke during the engine start, the fuel is not blown back and adheres to the wall of the port even if it is closed late in this way. The combustion stability at the time is ensured.
[0059]
FIG. 8 is a flowchart showing a third embodiment of the start control, and steps for performing the same processes as those in the flowchart of FIG. 3 are denoted by the same reference numerals. In this embodiment, the same control as in the first embodiment shown in FIG. 3 is performed except when the engine is operating due to sudden acceleration. However, priority is given to securing the torque for a predetermined time from the start of acceleration when the engine is operating due to sudden acceleration. Switching to proper control.
[0060]
That is, in this flowchart, in step S101 following step S1, it is determined whether or not the accelerator opening change rate acceld is smaller than a predetermined rapid acceleration determination value A1, and the accelerator opening change rate acceld is determined to be a rapid acceleration determination value. When A1 or more is reached, a predetermined time TM1 is set in the timer (step S102). The value of this timer decreases with time.
[0061]
Next, in step S2, it is determined whether or not the engine speed ne is higher than the first set speed N1, and if it is equal to or lower than the first set speed N1, it is determined whether or not the timer is "0" in step S103. When the timer is “0”, the first and second pulse widths and injection timings are calculated, and the ignition timing is set (steps S3 to S7).
[0062]
When the engine speed ne is higher than the first set speed N1, the water temperature T is determined in step S8._W It is determined whether or not the temperature is higher than the set temperature T1, and if it is warm, the determination as to whether or not it is a stratification region and the selection of the stratification mode and the uniform mode corresponding thereto are performed (steps S9 to S11). If it is cold, it is determined whether or not the timer is “0” in step S104, and it is determined whether or not the engine speed ne is higher than the second set speed N2 when the timer is “0”. The uniform mode and stratification mode are selected accordingly (steps S12, S13, S10).
[0063]
If it is determined in step S103 that the timer is not "0", the stratification mode and uniform mode are selected according to the region determination in steps S9 to S11, and the timer is not "0" in step S104. When it is determined that, the process proceeds to step S13 and the uniform mode is selected.
[0064]
According to this embodiment, even when the engine is started, the predetermined time during rapid acceleration with a large accelerator opening change rate acceld is the torque fluctuation adjustment control during cranking (steps S3 to S7) and the rotation speed after cranking. The control for slowing the rise is stopped, and the stratification mode and the uniform mode are selected according to the operation region and the water temperature so as to be advantageous for gaining torque.
[0065]
Therefore, when the engine is operating due to sudden acceleration in which the accelerator pedal is depressed suddenly, priority is given to securing torque and the driver's acceleration request is satisfied. When the engine is started other than during rapid acceleration, the feeling is improved by suppressing torque fluctuations as in the first embodiment.
[0066]
In addition, the control at the time of start-up by the apparatus of the present invention can be variously changed in addition to the examples shown in the respective flowcharts.
[0067]
For example, in the examples shown in the above flowcharts, the starting torque fluctuation adjustment control (steps S3 to S7) is performed until the first set rotational speed is reached. The torque fluctuation adjustment control at the start may be performed for a predetermined time (several seconds) from the start of cranking.
[0068]
Further, the present invention is particularly effective when applied to an engine of a hybrid vehicle. However, even when applied to an engine other than a hybrid vehicle, there is no change in that an effect of suppressing torque fluctuation at the start can be obtained. It is effective for improving the ring.
[0069]
【The invention's effect】
As described above, according to the present invention, when the engine is in a low rotation state from the start of engine start, fuel injection from the injector for the same cylinder is divided into the latter half of the compression stroke and the expansion stroke as start-up torque fluctuation adjustment control. At the same time, since ignition is performed at a time between the fuel injection in the latter half of the compression stroke and the fuel injection in the expansion stroke, the compression strokes of some cylinders and the expansion strokes of other cylinders overlap. In such a multi-cylinder 4 cycle, when starting the engine, the negative torque generated in the cylinder in the compression stroke is canceled out by the torque generated by the combustion during the expansion stroke in the cylinder in the expansion stroke, and the torque fluctuation is suppressed and the engine starts smoothly. Can be performed.
[0070]
In particular, in this starting torque fluctuation adjustment control, since the fuel injected in the latter half of the compression stroke is ignited, this is used as a fire type so that the air-fuel mixture is combusted in the expansion stroke. A positive torque can be applied in the expansion stroke while performing well, and torque fluctuation suppression at the start can be effectively achieved.
[Brief description of the drawings]
FIG. 1 is a schematic view showing an example of an engine provided with a start control device of the present invention.
FIG. 2 is a schematic diagram of a drive system of a hybrid vehicle shown as an example of application of the present invention.
FIG. 3 is a flowchart showing a first embodiment of start-up control.
FIG. 4 is a diagram showing the relationship between water temperature and fuel injection timing.
FIG. 5 is a diagram showing a temporal change in engine speed at the start.
FIG. 6 is an explanatory diagram showing each stroke, fuel injection timing, and ignition timing of a four-cylinder four-cycle engine.
FIG. 7 is a flowchart showing a second embodiment of start-up control.
FIG. 8 is a flowchart showing a third embodiment of start-up control.
[Explanation of symbols]
1 Engine body
2a-2d cylinder
5 Combustion chamber
13 Valve timing variable device
15 Spark plug
18 Injector
60 Control unit
62 Accelerator position sensor
64 Water temperature sensor

Claims (8)

In a multi-cylinder four-cycle in-cylinder injection engine in which each cylinder is provided with an injector that directly injects fuel into the combustion chamber, start determination means for determining when the engine is started, and the injector according to the determination by the start determination means Control means for controlling the fuel injection and ignition timing of the engine, and this control means performs fuel injection from the injector for the same cylinder as a torque fluctuation adjustment control at start-up when the engine is in a low rotation state from the start of engine start. together causes divided into the compression stroke late and the expansion stroke, the ignition being adapted to carry out the time between the fuel injection of the fuel injection and the expansion stroke of the latter said compression stroke, when starting by the control means The torque fluctuation adjustment control is performed until the engine speed is higher than the cranking speed and lower than the idle speed. Start control apparatus for a cylinder injection type engine, characterized in that the.   2. The in-cylinder injection engine start control device according to claim 1, wherein the engine has four or more cylinders.   The in-cylinder injection according to claim 1 or 2, wherein the timing of fuel injection in the latter half of the compression stroke in the starting torque fluctuation adjustment control by the control means is changed so as to be advanced as the temperature becomes lower, according to the engine temperature. Type engine control device.   4. The control of a direct injection type engine according to claim 3, wherein the fuel injection timing of the expansion stroke in the starting torque fluctuation adjustment control by the control means is changed so as to be advanced as the temperature becomes lower according to the engine temperature. apparatus.   5. The closing timing of the intake valve during the start time torque fluctuation adjustment control by the control means is set to a timing that is late enough to cause the return of intake air from the combustion chamber to the intake port. The in-cylinder injection engine control device according to any one of the above. Said control means to claim 1 engine speed and controls as during abrupt rising period of the rotation speed to start completion from exceeding the predetermined rotational speed for injecting fuel in the compression stroke The control apparatus for a cylinder injection engine according to any one of claims 5 to 6. In a multi-cylinder four-cycle in-cylinder injection engine in which each cylinder is provided with an injector that directly injects fuel into the combustion chamber, start determination means for determining when the engine is started, and the injector according to the determination by the start determination means Control means for controlling the fuel injection and ignition timing of the engine, and this control means performs fuel injection from the injector for the same cylinder as a torque fluctuation adjustment control at start-up when the engine is in a low rotation state from the start of engine start. It is made to divide into the latter half of the compression stroke and the expansion stroke, and the ignition is made at the timing between the fuel injection in the latter half of the compression stroke and the fuel injection in the expansion stroke. the torque variation adjustment control, the braking of the direct injection engine you characterized in that to perform the cranking of the engine is started a predetermined time Apparatus. In-cylinder injection engine control device used in a hybrid vehicle equipped with an engine and a motor, and the engine is operated intermittently while the vehicle is operating, and the above-mentioned torque fluctuation at the time of engine startup excluding engine operation due to sudden acceleration The in-cylinder injection engine control device according to any one of claims 1 to 7 , wherein the control means is configured to perform adjustment control.

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