JPH11280522A - Start control device for cylinder injection engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress a change of torque and realize smooth starting of an engine, by adjusting combustion timing while improving ignition and combustion in starting the cylinder injection engine. SOLUTION: In a multi-cylinder four cycle cylinder injection engine provided with an injector 18 directly injecting fuel in a combustion chamber in each cylinder, an ECU60 controlling fuel injection from the injector 18 and ignition timing by a spark plug 15 is provided. This ECU60, when the engine is in a low speed condition from starting of an engine start, injects fuel from the injector 18 relating to the same cylinder to be divided into a compression stroke latter period and an expansion stroke also controls ignition so as to be performed in a period between fuel injection in a compression stroke latter period and fuel injection in an expansion stroke as starting time torque change adjusting control.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a start control device for controlling a fuel injection timing and the like so as to smoothly start an in-cylinder injection engine.

[0002]

2. Description of the Related Art Conventionally, in a spark ignition type engine (gasoline engine) in which ignition is performed by a spark plug, an injector having a tip facing a combustion chamber is provided so as to inject fuel directly into the combustion chamber, and a low rotation speed low 2. Description of the Related Art There is known an in-cylinder injection engine in which a fuel is injected from an injector in a compression stroke in a specific operation region such as a load so that a combustible air-fuel mixture is unevenly distributed in the vicinity of an ignition plug to perform stratified combustion to improve fuel efficiency. ing.

As a control at the start of this type of engine, for example, as disclosed in Japanese Patent Application Laid-Open No. Sho 60-56146, fuel is injected in a compression stroke during engine cranking in order to enhance ignitability. In this case, stratified charge combustion is performed, and after cranking, fuel is injected in an intake stroke in order to prevent smoldering of an electrode of a spark plug.

[0004]

The reciprocating engine has a problem that a torque fluctuation is caused by a negative torque in a compression stroke, and the torque fluctuation is liable to increase particularly at the start of an extremely low engine speed. However, even with the apparatus disclosed in Japanese Patent Application Laid-Open No. 60-56146, the problem of torque fluctuation at the time of starting cannot be solved.

To explain this problem in detail, in a four-stroke engine, intake, compression, expansion, and exhaust strokes are sequentially performed in accordance with the reciprocating operation of a piston in a cylinder. , A positive torque is applied to the output shaft via the shaft. However, in the compression stroke, a negative torque is generated as the compression pressure increases, and this negative torque increases in the latter half of the compression stroke. Then, the negative torque and the positive torque act with a time lag to produce a torque fluctuation, and the torque fluctuation increases at the time of starting the engine at a very low speed where the time interval becomes long (particularly at the time of cranking). easy.

[0006] Such a torque fluctuation at the time of starting the engine is not preferable in terms of feeling and the like. In particular, in a hybrid vehicle in which the engine and the motor are used separately and the engine is operated intermittently while the vehicle is operating, the engine may be started regardless of the driver's will during driving or the like,
The torque fluctuation in such a case gives the driver a sense of incongruity,
Worse feeling.

[0007] In order to suppress the above-mentioned torque fluctuation, it is only necessary to generate a positive torque in another cylinder that cancels out a negative torque generated in some cylinders in a multi-cylinder engine.

[0008] However, such a function is difficult to obtain with a conventional engine. That is, for example, in a four-cylinder four-stroke engine, when the first cylinder is in the compression stroke, the strokes of the respective cylinders are shifted, such as the expansion stroke of the second cylinder, the intake stroke of the third cylinder, and the exhaust stroke of the fourth cylinder. When the first cylinder is generating a large negative torque in the latter half of the compression stroke, a positive torque cannot be obtained in the third and fourth cylinders in the intake stroke and the exhaust stroke, and the second cylinder does not generate a large torque in the expansion stroke. Since the positive torque due to the combustion is attenuated in the latter half, the above negative torque cannot be sufficiently canceled.

In the above-described in-cylinder injection type engine, the fuel injection timing into the combustion chamber can be variously changed, and the injection timing and the ignition timing are adjusted so that the combustion timing is shifted at the time of engine start to suppress torque fluctuation. It is conceivable to adjust the combustion timing, but simply adjusting the combustion timing so as to shift the combustion timing deteriorates the ignitability and makes it difficult to perform good combustion.

The present invention has been made in view of the above circumstances, and aims to realize a smooth start of an engine by suppressing the torque fluctuation by adjusting the timing of the combustion while satisfactorily performing ignition and combustion at the time of engine start. It is an object of the present invention to provide a start-up control device for a direct injection type engine that can perform the following.

[0011]

In order to achieve the above object, the present invention relates to a multi-cylinder four-cycle in-cylinder injection engine in which an injector for directly injecting fuel into a combustion chamber is provided in each cylinder. And a control means for controlling the fuel injection and the ignition timing from the injector according to the determination by the start determination means. Sometimes, when starting torque fluctuation adjustment control,
The fuel injection from the injector to the same cylinder is performed separately in the latter stage of the compression stroke and the expansion stroke, and the ignition is performed at the timing between the fuel injection in the latter stage of the compression stroke and the fuel injection in the expansion stroke. Is what it is.

According to this device, when the above-described torque fluctuation adjustment control at the time of the start is being performed, first, the air-fuel mixture formed near the spark plug in the injection at the latter stage of the compression stroke is ignited immediately thereafter and burns. By using this as a fire before the end of the combustion, the mixture is burned by the fuel injection in the expansion stroke, so that ignitability and combustibility are ensured, and a positive torque is given until a relatively late stage of the expansion stroke. . Therefore,
In a multi-cylinder four-stroke engine in which the compression stroke of some cylinders and the expansion stroke of other cylinders overlap, the negative torque generated in the cylinder in the compression stroke is canceled by the torque obtained in the cylinder in the expansion stroke, The torque fluctuation at the time of starting is suppressed.

In particular, when the engine has four or more cylinders, the compression stroke of some cylinders and the expansion stroke of other cylinders largely overlap, so that the effect of suppressing the torque fluctuation at the start as described above is good. Is obtained.

In the apparatus according to the present invention, the timing of fuel injection in the latter stage of the compression stroke in the torque fluctuation adjustment control at the time of starting by the control means is changed so as to be earlier as the temperature becomes lower in accordance with the engine temperature. By increasing the time for vaporizing and atomizing the fuel from the injection to the ignition of the fuel, deterioration of the ignitability at low temperatures is suppressed.

Further, by changing the fuel injection timing of the expansion stroke in the starting torque fluctuation adjustment control by the control means so as to be advanced as the temperature becomes lower in accordance with the engine temperature, the injection in the latter half of the compression stroke and the injection in the expansion stroke are changed. Is properly adjusted to ignite the fuel injected during the expansion stroke,
Good combustion is achieved.

If the closing timing of the intake valve during the start-time torque fluctuation adjustment control by the control means is set to a time late enough to cause the backflow of intake air from the combustion chamber to the intake port, the compression stroke The negative torque at is reduced. Moreover, since the fuel is directly injected into the combustion chamber after the compression stroke, the fuel is not blown back and adheres to the port wall surface.

The torque fluctuation adjustment control at the start by the control means may be performed, for example, until the engine speed becomes higher than the cranking speed and lower than the idling speed to a predetermined speed. During cranking, torque fluctuation adjustment control at the time of starting is performed to suppress torque fluctuation.

In this case, the control means includes:
It is preferable to control so as to inject fuel in the compression stroke during a rapid increase in the engine speed from the engine speed exceeding the predetermined engine speed to the completion of the start. While the combustibility is ensured by the stratified combustion, the increase in the rotation speed can be appropriately regulated by adjusting the torque by controlling the fuel injection amount.

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 case, the cranking which is liable to deteriorate the feeling due to the torque fluctuation. The torque fluctuation is suppressed for a predetermined time from the start.

The device of the present invention is effective to be applied to a hybrid vehicle having an engine and a motor in which the engine is operated intermittently during operation of the vehicle. In this case, the operation of the engine due to sudden acceleration is excluded. Preferably, the control means is configured to perform the start-time torque fluctuation adjustment control when the engine is started. In this manner, when the engine is operating due to sudden acceleration, the torque variation adjustment control at the time of starting is stopped, and priority is given to securing torque for sudden acceleration, and torque variation is suppressed at other times when the engine is started.

[0021]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 schematically shows the overall structure of a direct injection engine to which the present invention is applied. In this figure, an engine body 1 has a plurality of cylinders,
It has cylinders 2a to 2d (see FIG. 2), and in each of the cylinders, a combustion chamber 5 is formed above a piston 4 inserted into a cylinder bore. An intake port 7 and an exhaust port 8 are opened in the combustion chamber 5, and these ports 7, 8 are opened and closed by an intake valve 9 and an exhaust valve 10, respectively.

The intake valve 9 and the exhaust valve 10 are opened and closed by a valve operating mechanism including camshafts 11 and 12 and the like. The valve 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.

In the center of the combustion chamber 5, a spark plug 15
Is disposed, and the tip of the plug faces the combustion chamber 5. This ignition plug 15 is connected to an ignition coil 16.

The front end of the injector 18 faces the side of the combustion chamber 5, and fuel is directly injected from the injector 18 into the combustion chamber 5. The injector 18 of each cylinder is connected to the 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 a fuel pump 25, filters 26 and 27, and a high-pressure fuel pump 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 provided between the return passage 23 and the fuel tank 24, and a passage (not shown) that bypasses the high pressure side pressure regulator 29 is provided. ) And a bypass valve 31 for opening and closing this passage.

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 operation of the high-pressure side pressure regulator 29, and the bypass valve 31 is opened. In such a case, 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 adjusting operation of the low-pressure side pressure regulator 30.

Further, 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 for detecting the opening of the throttle valve 45 is provided. Further, an ISC passage 50 that bypasses the throttle valve 45 is provided. The ISC passage 50 is provided with an ISC valve 51 that controls an air flow rate in this passage.

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. A swirl control valve 54 is provided in each independent intake passage 53. The swirl control valve 54 is opened and closed by being driven by an actuator 55 such as a step motor, and the opening and closing operation controls the intake swirl. ing.

On the other hand, in the exhaust passage 41, the air-fuel ratio is detected by detecting the oxygen concentration in the exhaust gas.
_Two sensors 57 are provided, and an exhaust gas purifying catalyst 58 is provided downstream thereof.

Reference numeral 60 denotes a control unit (ECU) for controlling the engine. The ECU 60 receives the detection signals a, b, and c from the air flow sensor 44, the throttle opening sensor 48, and the O ₂ sensor 57, and receives a signal from the distributor 61 linked to the camshaft 12 to detect the engine speed. Angle signal d and cylinder discrimination signal e are input, an accelerator opening sensor 62 for detecting an accelerator opening (accelerator pedal depression amount), an intake air temperature sensor 63 for detecting a temperature of intake air,
Detection signals f, g, and h from a water temperature sensor 64 and the like for detecting the temperature of the engine cooling water are also input.

Also, the ECU 60 supplies the injector 1
A signal j for controlling fuel injection is output to the ignition coil 16 via an injector drive unit 66, a signal k for controlling ignition timing is output to the ignition coil 16, and a throttle valve driving motor 46 is output to the throttle valve driving motor 46. A signal 1 for controlling the throttle opening is output via the 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, a signal o for controlling the variable valve timing device 13, and the like. Is also output.

The ECU 60 has a function as a start determining means for determining when the engine is started, and a function as a control means for controlling fuel injection and ignition timing according to the determination by the start determining means. Then, as the start-time torque fluctuation adjustment control, when the engine is in a low rotation state from the start of the engine start, the fuel injection from the injector to the same cylinder is performed separately in the latter half of the compression stroke and the expansion stroke, and the ignition is performed in the compression stroke. The fuel injection is performed at a timing between the fuel injection in the latter half of the stroke and the fuel injection in the expansion stroke.

The device of the present invention is effectively applied to a hybrid vehicle using both an engine and a motor. FIG. 2 shows an example of the hybrid system.

In this figure, an output shaft of the engine body 1 is connected to a torque converter 71 on the input side of a continuously variable transmission 70, while the output side of the continuously variable transmission 70 is connected to an axle via a final reduction device 72. 73 and a motor / generator 74 are connected. An alternator 7 is provided on the front end side of the output shaft of the engine body 1 via a belt 75 or the like.
6 are connected. The motor / generator 74 and the alternator 76 are connected to a battery 79 via inverters 77 and 78.

A controller for controlling the hybrid system (the ECU 60 in FIG. 1 or another controller not shown) controls the hybrid system in accordance with the driving state of the vehicle.
The engine and the motor / generator 74 are selectively used for driving the vehicle. For example, the engine is stopped during low-speed running or at the beginning of acceleration, and the motor / generator 74 is controlled so as to operate as a motor. Is controlled so that the engine operates in the operating state of.

FIG. 3 is a flowchart showing an example of the start control performed by the ECU 60. The process shown in this flowchart is started, for example, when the engine start is started when a predetermined engine operating condition is satisfied while the hybrid vehicle is operating, for example. The control of the hybrid system including the determination of the engine operating conditions and the control of the operation and stop of the engine corresponding thereto, and the determination of the motor operating conditions and the control of the operation and stop of the motor corresponding thereto are performed by different types of illustration other than those shown in FIG. This is performed by a control routine.

When the processing shown in the flowchart of FIG. 3 is started in response to the start of the engine start, first, at step S1
And the engine speed n obtained from the crank angle signal
e, the accelerator opening accel detected by the accelerator opening sensor 62 and the water temperature Tw detected by the water temperature sensor 64 are read. Subsequently, in step S2, it is determined whether or not the engine speed ne is higher than a first set speed N1 (predetermined speed). The first set speed N1 is a speed slightly higher than the cranking speed (for example, 300 rpm).
pm), so that the determination in step S2 is N
When it is O, it is in the cranking state, and this determination is YES.
Means that the engine speed is higher than the cranking state.

If the determination in step S2 is NO,
As the start-time torque fluctuation adjustment control, the first pulse width and the second pulse width for determining the fuel injection amount are calculated in order to perform the fuel injection from the injector in two stages, the latter half of the compression stroke and the expansion stroke ( Steps S3 and S4)
Is performed, and the first injection timing and the second injection timing 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 each of the first and second injection timings and each pulse width determines the correspondence between these and the water temperature in advance. The calculated value is calculated according to the detected value of the water temperature Tw using the table.

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 the range of the latter half of the compression stroke, and the second injection timing is changed in the range of the expansion stroke in accordance with the water temperature, but both are advanced as the water temperature becomes lower.

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] When the determination in Step S2 is YES, whether the time between high temperature than the water temperature T _W is the set temperature T1 is determined in step S8. Then, if it is a warm time, based on the determination (step S9) of whether or not it is a stratified region,
If it is a stratified region, the stratified mode is set (step S1).
0), if it is not a stratified region, a uniform mode is set (step S11). Here, the stratified region means an operation region suitable for performing stratified combustion, and, for example, a predetermined operation region on a low rotation speed and low load side is set in advance as a stratified region. The stratified mode is a mode in which fuel is injected from an injector in a compression stroke to control fuel injection timing and ignition timing so that ignition is performed in a state where an air-fuel mixture is unevenly distributed near an ignition plug. In this mode, the fuel is injected from the injectors during the intake stroke, and the fuel injection timing and the ignition timing are controlled so that the fuel is uniformly diffused throughout the combustion chamber and the ignition is performed.

In step S8, the water temperature T _W is set to the set temperature T.
When it is determined that the engine is in the cold state of 1 or less, the engine speed ne is increased to the second set speed N2 in step S12.
It is determined whether it is higher. The second set rotation speed N2
Is a rotation speed close to the idle rotation speed (for example, about 600 rpm). If 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 engine speed ne is changed from the cranking state to the operating state after the start is completed. This means that the vehicle is climbing, and in this case, the process proceeds to step S10 and the stratified mode is set. The determination in step S12 is YE
When S is reached, the mode is set to the uniform mode (step S1).
3).

After the processing in steps S3 to S7 or the mode setting in any of steps S10, S11, and S13, in steps S14 and S15, 1
The second injection and the second injection are performed. In this case, after the processing of steps S3 to S7, the first injection and the second injection are actually performed according to the setting,
After the mode setting in any of 10, S11, and S13, only the first injection is performed in the intake stroke or the compression stroke in principle, and the second injection is set to 0.

According to the apparatus of the present embodiment as described above,
Cranking period T1 from the start of start shown in FIG.
And the period T2 of the engine speed increase after cranking
And the period T3 after the start is completed, the control of the fuel injection and the like is appropriately changed, the torque fluctuation during cranking is reduced, and the transition from the start to the operating state after the start is performed smoothly.

That is, during the cranking period T1 from the start of the engine until the engine reaches the first set number of revolutions N1, fuel is injected during the latter half of the compression stroke and the expansion stroke, and during the two injections. Control is performed so that ignition is performed (steps S3 to S7). In such a control state, first, in the first injection in the latter half of the compression stroke, the air-fuel mixture formed in the vicinity of the ignition plug is ignited immediately after the top dead center, whereby good ignition and combustion are performed. Before the termination, the mixture is used as a fire to burn the air-fuel mixture by the second fuel injection. In this way, while ensuring the ignitability and the combustibility, a positive torque is given by the combustion of the air-fuel mixture by the second fuel injection until the middle or late stage of the expansion stroke.

In this case, the first injection timing and the ignition timing are set to timings suitable for ignition and combustion, the combustion by the first fuel injection continues until the second fuel injection, and a negative The interval between the first injection and the second injection, the ratio of the injection amount, and the like may be set so that an appropriate torque for canceling the second torque can be obtained by the second fuel injection.

Further, when the temperature of the engine is low, if the time from fuel injection to ignition is short, vaporization and atomization worsen and the ignitability tends to deteriorate, but depending on the engine temperature (water temperature) when the engine is started. As in the above embodiment, as the water temperature is lower, the first fuel injection timing is advanced to increase the vaporization and atomization time as the water temperature is lower, and the second fuel injection timing is correspondingly increased. If the water temperature is made earlier as the water temperature is lower, the ignition and combustion of the air-fuel mixture by the first injection and the ignition and combustion of the air-fuel mixture by the second injection using the same as the ignition are performed well even at a low temperature.

By controlling the fuel injection and ignition timing during the cranking period T1 as described above, a multi-cylinder engine (generally four or more cylinders) in which the latter part of the compression stroke of some cylinders and the expansion stroke of other cylinders overlap. In the four-stroke engine of (4), an effect is obtained in which the positive torque given to the cylinder in the expansion stroke cancels the negative torque generated in the cylinder in the compression stroke. This operation will be specifically described with reference to FIG. 6 taking a four-cylinder four-cycle engine as an example.

As shown in this figure, in the four-cylinder four-stroke engine, the intake, compression, expansion, and exhaust strokes are sequentially performed in each cylinder, and the first, third, fourth, and second cylinders are used. In this order, the strokes of the cylinders are shifted by 180 ° in crank angle, so that 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, and the expansion of the fourth cylinder The stroke and the compression stroke of the second cylinder overlap, and the expansion stroke of the second cylinder and the compression stroke of the first cylinder overlap each other.

During 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, so that, for example, the first cylinder The positive torque given in the expansion stroke 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 third cylinder and the second cylinder. Also between the cylinder and the first cylinder, the positive torque given to the cylinder in the expansion stroke cancels the negative torque generated in the cylinder in the compression stroke.

Therefore, torque fluctuation during cranking is suppressed, and feeling is improved. In particular, in a hybrid vehicle as shown in FIG. 2, the engine is started irrespective of the driver's will during the transition from the motor operation state to the engine operation state even during driving, etc. Also, a situation in which the driver feels strange due to torque fluctuation is prevented.

Next, during a period T2 after cranking when the engine speed ne is higher than the first set speed N1, fuel injection or the like is controlled so as to apply a torque for increasing the engine speed. In the present embodiment, the engine speed ne is changed from the first set speed N1 to the second set speed N2.
Up to this time, the stratified mode is set in both the cold state and the warm state, and fuel injection is performed in the compression stroke to perform stratified combustion. Then, by appropriately controlling the fuel injection amount in the stratification mode, the transition to the operation state after the start is completed is smoothly performed.

That is, in the case of a general engine, the engine speed rapidly increases after cranking as shown by a two-dot chain line in FIG. In such a case, when the engine is started regardless of the driver's will, such fluctuations in the rotational speed will give the driver a sense of incongruity.Therefore, it is necessary to adjust the engine output so as to avoid a sudden increase in the rotational speed or overshoot. Required. However, when the engine speed is low at or below the second set rotation speed N2, the intake air amount reaches a saturated state even with a small throttle opening, and it is difficult to control the intake air amount. Since it is necessary to supply fuel corresponding to the amount of intake air to control the engine output, it is difficult to control the engine output.

On the other hand, if the stratified mode is set in the period T2, the combustibility is ensured by stratified combustion in an excessive air state, and the engine output is controlled by controlling the fuel injection amount even at a low speed where it is difficult to control the intake air amount. Can be appropriately adjusted, whereby the increase in the engine speed is moderately moderate as shown by the solid line in FIG. 5, and the overshoot is prevented, so that the state can be smoothly shifted to the state after the start.

When the engine speed is equal to the second set speed T
2 after the start is completed (period T in FIG. 5).
In 3), when the engine is in a cold state, the mode is set to a uniform mode in which the fuel is injected in the intake stroke, so that the vaporization and atomization of the fuel are promoted and the combustibility is enhanced. Further, at the time of warming, the stratified mode or the uniform mode is set according to the operation region.

FIG. 7 is a flowchart showing a second embodiment of the starting control. In this embodiment, the same control as in the first embodiment shown in FIG. 3 (Steps S1 to S15)
In addition, the valve closing timing of the intake valve during the start-time torque fluctuation adjustment control is set so as to be late enough to cause the backflow of the intake air from the combustion chamber to the intake port, for example, about ABDC 100 ° at the crank angle. The variable timing device 13 is controlled.

That is, in this flowchart, following the processing up to step S15, step S16
It is determined whether or not the engine speed ne is higher than the second set speed N2. If the engine speed ne is equal to or lower than the second set speed N2, the variable valve timing device (VVT) 13 is used in step S17.
Is closed late (a timing that is late enough to cause the backflow of intake air from the combustion chamber to the intake port), and if it is higher than the second set rotation speed N2, the variable valve timing device (VVT) 13 is set to normal control in step S18. You.

According to this embodiment, when the engine is started, the closing timing of the intake valve is set to the above-mentioned late closing to reduce the effective compression ratio, thereby reducing the negative torque generated in the compression stroke. Also, torque fluctuation in cranking or the like is suppressed. In addition, since the fuel is directly injected into the combustion chamber after the compression stroke during engine start, even if the fuel is lately closed, the fuel is not blown back and adheres to the port wall surface. The combustion stability at the time is ensured.

FIG. 8 is a flowchart showing a third embodiment of the start control. 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 that of the first embodiment shown in FIG. 3 is performed except when the engine is operated due to sudden acceleration, but the securing of torque is prioritized for a predetermined time from the start of acceleration when the engine is operated due to sudden acceleration. Control.

That is, in this flowchart, in step S101 subsequent to step S1, it is determined whether or not the accelerator opening change rate acceld is smaller than a predetermined sudden acceleration determination value A1, and the accelerator opening change rate acceld is rapidly determined. When the acceleration judgment value A1 or more is reached, the timer sets a predetermined time TM1.
Is set (step S102). The value of this timer decreases over time.

Next, in step S2, it is determined whether or not the engine speed ne is higher than the first set speed N1. If the engine speed ne is equal to or less than the first set speed N1, it is determined in step S103 whether or not the timer is "0". It is determined that when the timer is “0”, 1
The second and the second calculation of each pulse width and each injection timing and the setting of the ignition timing (Steps S3 to S7) are performed.

When the engine speed ne is higher than the first set speed N1, it is determined in step S8 whether or not the water temperature T _W is higher than the set temperature T1. The determination as to whether or not it is a stratified region and the selection of the stratified mode and the uniform mode (steps S9 to S11) are performed. If it is cold, the timer is set to "0" in step S104.
It is determined whether or not the engine speed ne is higher than the second set speed N2 when the timer is "0", and the uniform mode and the stratification mode are selected accordingly (steps S12 and S13). , S10) are performed.

If it is determined in step S103 that the timer is not "0", the stratification mode and the uniform mode are selected in accordance with the area determination in steps S9 to S11. When it is determined that the value is not "0", the process proceeds to step S13, and the uniform mode is selected.

According to this embodiment, even when the engine is started, the predetermined time during the rapid acceleration with a large accelerator opening change rate acceld is equal to the torque fluctuation adjustment control during cranking (steps S3 to S7) and after the cranking. The control for slowing the rise of the rotation speed is stopped, and the stratified mode and the uniform mode are selected according to the operating region and the water temperature so as to be advantageous for obtaining the torque.

Therefore, when the engine is operated by rapid acceleration such that the accelerator pedal is suddenly depressed, securing of the torque is prioritized and the driver's acceleration request is satisfied. When the engine is started other than during the rapid acceleration, the feeling is improved by suppressing the torque fluctuation as in the first embodiment.

The control at the time of starting by the apparatus of the present invention can be variously changed in addition to the examples shown in the above-mentioned flowcharts.

For example, in the example shown in each of the above-mentioned flowcharts, the starting torque fluctuation adjustment control (steps S3 to S7) is performed until the first set rotation speed is reached. A certain time (several seconds) from the start of cranking
Only the starting torque fluctuation adjustment control may be performed.

The present invention is particularly effective when applied to an engine of a hybrid vehicle. However, even when the present invention is applied to an engine other than a hybrid vehicle, the effect of suppressing the torque fluctuation at the start can be obtained. And is effective for improving the feeling.

[0069]

As described above, according to the present invention, when the engine is in a low rotation state from the start of the engine start, the fuel injection from the injector to the same cylinder is controlled in the latter stage of the compression stroke and the expansion stroke as the torque fluctuation control at the start. And the ignition is performed at a timing between the fuel injection in the latter stage of the compression stroke and the fuel injection in the expansion stroke, so that the compression stroke of some cylinders and that of other cylinders are performed. In a multi-cylinder 4-cycle in which the expansion stroke overlaps, at the time of engine start, negative torque generated in the cylinder in the compression stroke is canceled out by the torque caused by combustion in the cylinder in the expansion stroke during the expansion stroke, thereby suppressing torque fluctuation. The engine can be started smoothly.

In particular, in this start-time torque fluctuation adjustment control, the fuel injected in the latter half of the compression stroke is ignited, and then the mixture is used as an ignition source to combust the fuel-air mixture in the expansion stroke. Thus, a positive torque can be given in the expansion stroke while satisfactorily performing the combustion, and the torque fluctuation at the time of starting can be effectively suppressed.

[Brief description of the drawings]

FIG. 1 is a schematic diagram illustrating an example of an engine including a start control device according to 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 a start-time control.

FIG. 4 is a diagram showing a relationship between water temperature and fuel injection timing.

FIG. 5 is a diagram showing a temporal change of an engine speed at the time of starting.

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 the starting control.

FIG. 8 is a flowchart showing a third embodiment of the starting control.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Engine main body 2a-2d Cylinder 5 Combustion chamber 13 Variable valve timing device 15 Spark plug 18 Injector 60 Control unit 62 Accelerator opening sensor 64 Water temperature sensor

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code FI F02D 41/04 330 F02D 41/04 330L 335 335E 335J 43/00 301 43/00 301B F02P 5/15 F02P 5/15 E (72 ) Inventor Kiyotaka Mamiya 3-1, Shinchi, Fuchu-cho, Aki-gun, Hiroshima Mazda Co., Ltd.

Claims (9)

[Claims] In a multi-cylinder four-cycle in-cylinder injection engine in which an injector for directly injecting fuel into a combustion chamber is provided for each cylinder, a start discriminating means for discriminating engine start time, and a discrimination by the start discriminating means. Control means for controlling fuel injection and ignition timing from the injector in response to the start-up torque fluctuation control when the engine is in a low rotation state from the start of the engine.
The fuel injection from the injector to the same cylinder is performed separately in the latter stage of the compression stroke and the expansion stroke, and the ignition is performed at the timing between the fuel injection in the latter stage of the compression stroke and the fuel injection in the expansion stroke. A start control device for a direct injection type engine, comprising: 2. The start control apparatus for a direct injection engine according to claim 1, wherein the engine has four or more cylinders. 3. The fuel injection system according to claim 1, wherein the fuel injection timing in the latter stage of the compression stroke in the starting torque fluctuation adjustment control by the control means is changed in accordance with the engine temperature so as to be earlier as the temperature becomes lower. A control device for an in-cylinder injection engine according to the above description. 4. The in-cylinder 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 in accordance with the engine temperature so as to be earlier as the temperature becomes lower. Control system for injection engine. 5. The valve closing timing of the intake valve during the start-time torque fluctuation adjustment control by the control means is set to a time late enough to cause a return of intake air from the combustion chamber to the intake port. Item 5. The control device for a direct injection engine according to any one of Items 1 to 4. 6. The engine according to claim 1, wherein said control means controls the torque fluctuation at the time of starting until the engine speed becomes higher than the cranking speed and lower than the idle speed. A control device for a direct injection engine according to any one of claims 1 to 5. 7. The control means controls the fuel injection in a compression stroke during a rapid increase in the engine speed from when the engine speed exceeds the predetermined engine speed to when the engine is completely started. The control device for a direct injection engine according to claim 6, wherein 8. The control of an in-cylinder injection engine according to claim 1, wherein the starting torque fluctuation adjustment control by the control means is performed for a predetermined time from the start of cranking of the engine. apparatus. 9. A control device for an in-cylinder injection engine used in a hybrid vehicle including an engine and a motor, the engine being operated intermittently while the vehicle is operating, wherein the control is performed when the engine is started except when the engine is operated due to sudden acceleration. The control device for a direct injection engine according to any one of claims 1 to 8, wherein the control means is configured to perform the start-time torque fluctuation adjustment control.