JP3267896B2 - In-cylinder direct injection internal combustion engine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a direct injection internal combustion engine for directly injecting high pressure fuel from a fuel pump into a combustion chamber.

[0002]

2. Description of the Related Art There is an in-cylinder direct fuel injection internal combustion engine in which the combustion system is changed between stratified charge combustion and premixed combustion in accordance with operating conditions to achieve a balance between demands for improved fuel efficiency and increased output. That is, stratified charge combustion is performed at low load and low speed, and fuel consumption is improved by operating with a leaner air-fuel mixture in total. An output is obtained (for example, see Japanese Patent Application Laid-Open No. 2-169834).

[0003] In a conventional in-cylinder direct fuel injection internal combustion engine that switches between stratified combustion and premixed combustion, the ignition method is common regardless of the combustion method. The ignition method includes a single ignition method and a multiple ignition method. In the single ignition method, a charge current to the primary winding of the ignition coil is formed to generate a charging current.
By supplying one pulse signal to the primary side of the ignition coil, a high-voltage current is formed on the secondary side, and one ignition spark is formed, thereby performing ignition. However, in the in-cylinder direct fuel injection internal combustion engine that switches between stratified combustion and premixed combustion, the adoption of the single ignition method makes it difficult to perform an appropriate ignition operation at the time of stratified combustion. That is, in stratified combustion, it is necessary to perform ignition when a rich mixture exists near the ignition gap, but this timing is slightly changed, and in the single ignition system in which the ignition spark is formed only once at the time of ignition, It was difficult to match this timing, and there was a risk that the intended ignition operation could not be performed.

In the multiple ignition system, a series of alternating pulse signals are applied to the primary side of an ignition coil to form a high voltage current in an alternate direction on the secondary side to form a series of ignition sparks. Is disclosed in JP-A-62-139948. According to this method, the possibility that an ignition spark is formed when a rich portion of the air-fuel mixture reaches the spark plug electrode is increased, and the ignitability can be improved.

[0005]

In the conventional system, the ignition system was common to both stratified combustion and premixed combustion. When the one-time ignition method is adopted, the ignition in the stratified combustion method is not ideally performed as described above. In order to ideally perform ignition in the stratified combustion system, if the multiple ignition system is adopted, the air-fuel mixture is always homogeneous in the premixed system,
Since reliable ignition can be performed with a single ignition spark, the adoption of the multiple ignition method results in the use of wasteful electric energy for ignition, and there is a possibility that efficiency may be deteriorated accordingly.

SUMMARY OF THE INVENTION In view of the problems of the prior art, an object of the present invention is to realize an ideal ignition operation not only when operating in a stratified combustion system but also when operating in a premixing system. I do.

[0007]

The present invention employs the technical means of claim 1 to solve the above problems. According to this technical means, the switching of the ignition method is performed depending on whether the internal combustion engine is in the operation of performing premixed combustion or in the operation of performing stratified combustion, realizing ideal ignition operation and improving efficiency. The demand for improvement can be harmonized.

According to the technical means of the present invention, the ignition system for premixed combustion is a single ignition system, and the ignition system for stratified combustion is a multiple ignition system. An ignition operation can be realized. Claim 3
According to the technical means of the present invention, the ignition timing is controlled at the time of premix combustion according to the combustion state, and the fuel injection timing is controlled at the time of stratified combustion, thereby realizing more ideal combustion of the internal combustion engine. Can be achieved.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS In FIG. 1 schematically showing an internal combustion engine according to an embodiment of the present invention, 10 is a cylinder block, 12 is a piston, 13 is a crankshaft, 14 is a cylinder head, 16 is a combustion chamber, 17 Is an ignition plug, 18 is an intake valve, 20 is an intake port, 21 is a fuel injection valve, 22 is an exhaust valve, 24 is an exhaust port, 26 is an intake manifold, 28
Is a throttle valve, 29 is an accelerator pedal, and 30 is an air flow meter.

The fuel injection valve 21 is provided so as to open to the combustion chamber 16, and is connected to a fuel tank 38 via a fuel pipe 32, a fuel pump 34, and a fuel pipe 36. The fuel pump 34 is connected to the crankshaft 13 via a belt transmission mechanism (not shown), the rotation of the crankshaft 13 is transmitted to the fuel pump, and the fuel from the fuel tank 38 is supplied to the fuel injection valve 21.
And is directly injected into the combustion chamber 16 when the valve is opened.

Reference numeral 40 schematically represents an ignition device.
This igniter 40 is functionally means for performing ignition by a single ignition method and means 4 for performing ignition by a multiple ignition method.
4 and a changeover switch 46 for switching between these ignition means 42 and 44. The single ignition means 42 is an ignition system in which only one spark is formed at one timing (crank angle position) in one cycle of the internal combustion engine, and ignition is performed by the single ignition. At the time of high load, the ignition operation by the ignition means 42 is performed once. On the other hand, the multiple ignition means 4
Reference numeral 4 denotes an ignition system in which a series of sparks are formed over a certain crank angle range in one cycle of the internal combustion engine.
At the time of low load, ignition by the multiple ignition means 44 is performed.

A control device 50 is provided as a microcomputer system for fuel injection control and ignition control. A signal from each sensor is input to the control device 50. The sensors include an air flow meter 30, which measures the amount of air taken into the internal combustion engine, a throttle sensor 52, which detects the opening of the throttle valve 28, a crank angle sensor 54, which detects the angular position of the crankshaft 13, and an air-fuel ratio sensor 55. Is shown. The control device 50 executes necessary calculations based on signals from these sensors, forms a fuel injection signal to the fuel injection valve 21 and an ignition signal by the ignition device 40, and operates the switch 46 to execute the one-time ignition means 42. And the multiple ignition means 44 is switched.

FIG. 2 illustrates the premixed combustion system and the stratified combustion system in relation to the difference in fuel injection timing.
In the premixed combustion system shown in (a), the fuel injection from the fuel injection valve 21 is performed in the middle of the supply stroke in which the piston 12 moves toward the bottom dead center as shown in (a). Therefore, when the piston is at the end of the intake stroke indicated by the bottom dead center in (b), the fuel is unevenly distributed near the crown of the piston 12, but the fuel shifts to the compression stroke, and the piston 12 moves to (c) and (d). ), The distribution of fuel in the combustion chamber becomes uniform. A spark is formed on the electrode of the ignition plug 17 near the top dead center of the piston 12 at the end of the compression stroke, and the mixture is ignited. In the present invention, the ignition in the premixed combustion system is performed by the single ignition means 42. That is, the spark for ignition is formed only once at a predetermined position.

On the other hand, in the stratified combustion system shown in (b), fuel injection has not yet been performed at the piston positions (a) and (b) during the intake stroke, and the piston 12 has moved to near the top dead center in the compression stroke. Fuel injection is performed at the position (d), so that a locally rich mixture portion is formed near the electrode of the spark plug 17, that is, stratification is performed. At the stage of stratification (e), the formation of an ignition spark takes place. In the present invention, the ignition in the stratified combustion system is performed by the multiple ignition means 44. That is, a series of sparks are formed by the ignition signal at the spark plug electrode, and the formation of a rich mixture and the formation of the spark at the spark plug electrode match.

Next, the single ignition means 42 and the multiple ignition means 4 constituted by the functional blocks 40 and 46 of FIG.
4 will be described with reference to FIG. That is, the ignition coil 60 includes a primary iron core 60-1 and a secondary iron core 60-2. The primary iron core 60-1 has a primary coil 60-3, and the secondary iron core 60-2.
Is wound with a secondary coil 60-4. Ignition transistors 60-5 and 60-6 are provided on the primary side of the ignition coil. The transistor 60-5 has a collector connected to one end of the primary coil 60-3 via a diode 60-7 and an emitter connected to the transistor 60-. The collector of the transistor 60-6 is connected to the other end of the primary coil 60-3 via the diode 60-8. The collectors of the transistors 60-5 and 60-6 are grounded and connected to the center of the primary coil 60-3 via the power supply 60-9. On the other hand, the secondary coil 60-4
Has one end connected to the spark plug 17 and the other end grounded.

In the operation of the ignition device shown in FIG. 3, at the time of single ignition, as shown in FIG.
One ignition pulse is supplied to one base of the 60-6. That is, in the example of FIG. 3A, an ignition pulse is supplied to the transistor 60-6. Then, when the ignition signal switches from High to Low, a high voltage is generated in the secondary coil 60-4, and an ignition spark P is formed. That is, in the case of single ignition, the ignition pulse goes high only once in the cycle, and spark formation is performed only once. On the other hand, FIG. 3B shows the case of multiple ignition, in which an ignition signal having an opposite phase consisting of N pulses is applied to the bases of the ignition transistors 60-5 and 60-6. Therefore, each time the ignition signal switches from High to Low, positive and negative high voltages are generated alternately, and a series of ignition sparks P,
P 'is formed.

Next, an outline of the operation of the control device value 50 is shown in FIG.
This will be described with reference to the flowchart of FIG. That is, step S1
Indicates the determination of the premixed combustion zone or the stratified combustion zone. FIG. 5 shows the division of the stratified combustion region and the premixed combustion region with respect to the internal combustion engine speed and the load. As can be seen from this figure, stratified combustion is performed on the low rotation speed / low load side, and premixed combustion is performed on the high rotation speed / high load side. That is, the rotation speed of the internal combustion engine can be determined from the interval between the crank angle pulse signals from the crank angle sensor 54. On the other hand, the load of the internal combustion engine can be grasped from the opening degree of the throttle valve 28 detected by the throttle sensor 52, and the determination of the stratified combustion region or the premixed combustion region is made based on the detected rotation speed and load at that time. It can be carried out. In step S2, it is determined whether or not the operation range determined in step S1 is a premixed combustion range. When it is determined that the current time is within the premixing range, the process proceeds to step S3, where the ignition means is selected once. That is, the control device 50
, A signal for switching the switching means 46 to the ignition means 42 once is output. That is, as shown in FIG. 3 (a), an ignition signal is supplied once to one transistor, in the figure, the transistor 60-6, and a high voltage is generated in the secondary coil at the time of switching from High to Low, A spark for ignition is formed once on the electrode.

On the other hand, if it is determined in step S2 that the combustion zone is not the premixed combustion zone, the combustion zone is a stratified combustion zone, and step S4
The controller 50 outputs a signal for switching the switching means 46 to the multiple ignition means 44 side. That is, FIG.
As shown in (b), an ignition signal of opposite phase is supplied to the bases of the transistors 60-5 and 60-6, and each time the high-to-low transition occurs, the secondary coil 60-2 is supplied with an alternate high-voltage. A voltage is generated and a series of sparks for ignition are formed on the electrodes.

FIG. 6 explains the operation of the multiple ignition means selected in the stratified combustion region in comparison with the single ignition. That is, the fuel F is injected from the fuel injection valve 21 toward the vicinity of the electrode 17A of the spark plug 17. In the case of multiple ignition, as shown in (a), a series of ignition operations are performed near the compression top dead center, and a series of different crank angle positions (b)
In (e), a spark f is formed on the electrode. In the figure, fuel F is
Here, ignition is performed to meet the spark f at the position (d). Although the timing at which the fuel F from the fuel injection valve 21 comes to the position of the spark plug electrode is slightly shifted, since the spark f is formed at a series of positions by the operation of the multiple ignition means, the fuel encounters any spark. Therefore, reliable ignition can be realized. On the other hand, in the case of stratified combustion, if the ignition is performed once as shown in (b), the spark f is only formed at the position of (d), and the timing at which the fuel F from the fuel injection valve section 21 comes to the electrode site. Fuel F
Can not meet the spark f, and there is a possibility that an ignition mistake may occur.

In the second embodiment, the combustion state is determined in each of the single ignition in the premixed combustion and the multiple ignition in the stratified combustion. If the optimum combustion is not obtained, the premixed combustion in which the single ignition is performed is performed. In this case, the ignition timing is corrected (retardation of the ignition timing), and in the case of stratified charge combustion in which multiple ignitions are performed, the fuel injection timing is corrected. This embodiment is similar in hardware configuration to FIG. However, signals from knock sensor 70 and in-cylinder pressure sensor 72 provided in the internal combustion engine are used in control device 50 to detect the combustion state. Here, knock sensor 70 forms an electric signal according to mechanical vibration of the internal combustion engine main body, as is well known. The in-cylinder pressure sensor 72 is provided in the combustion chamber 16 and generates an electric signal according to the pressure in the combustion chamber.

FIG. 7 is a flowchart for explaining the operation of the second embodiment. This flowchart includes step S1
Step S4 does not differ from Step S1 to Step S4 in the flowchart of FIG. 4 in the first embodiment. That is, when it is determined from the rotation speed and load of the internal combustion engine that high-mixing combustion is to be performed at a high revolution and high load, the single ignition means 4
2 is performed, and one ignition signal is supplied to one of the transistors 60-5 and 60-6 in one cycle as described in FIG. 3A, and ignition is performed by one spark. On the other hand, when it is determined that stratified combustion is to be performed at a low rotation speed and a low load, the ignition signals of opposite phases having a plurality of pulses are output from the transistors 60-5 and 60-6 as described in FIG.
And a series of multiple sparks are formed and ignited. Then, in the premixed combustion operation range, after selection of the ignition means 42 once, it is determined in step S5 whether or not optimal combustion is being performed. This determination is made by detecting a vibration corresponding to knocking of the internal combustion engine based on a signal from knock sensor 70 accompanying the ignition operation, and determining whether the vibration is greater than a predetermined value. Alternatively, the fluctuation of the in-cylinder pressure is detected by the in-cylinder pressure sensor 72, and it can be determined whether or not the internal combustion engine is optimally burning based on whether or not the fluctuation is larger than a predetermined value. If it is determined that the internal combustion engine is performing optimal combustion, step S6 is bypassed, that is,
The ignition timing remains unchanged. On the other hand, when it is determined by the knock sensor 70 or the in-cylinder pressure sensor that the internal combustion engine is not performing optimal combustion, the process proceeds to step S6, and the ignition timing is controlled in a direction for improving the combustibility, that is, in a retard direction. If the flammability is improved due to the ignition timing retard control, the determination in step S5 is eventually switched to an affirmative determination, and thereafter the ignition timing is not corrected any further.

In the stratified combustion operation range, after selecting the multiple ignition means in step S4, it is determined in step S7 whether optimal combustion is being performed. This determination also detects the vibration corresponding to the knocking of the internal combustion engine based on the signal from the knock sensor 70 in the same manner as in step S5, and detects whether the vibration is greater than a predetermined value or detects the fluctuation of the in-cylinder pressure with the in-cylinder pressure sensor 72. It can be determined whether or not the internal combustion engine is performing optimal combustion based on whether or not the variation is greater than a predetermined value. If it is determined that the internal combustion engine is burning optimally,
S8 is bypassed, that is, the fuel injection timing remains unchanged. On the other hand, if it is determined by the knock sensor 70 or the in-cylinder pressure sensor that the internal combustion engine is not performing optimal combustion, the process proceeds to step S8.
The fuel injection timing is controlled in a direction to improve the combustibility. This determination is made, for example, by changing the injection timing by a small amount in one direction (for example, in the retard direction), and thereby improving the combustion (whether or not the fluctuation range detected by the knock sensor becomes smaller). If it is determined that the combustion is improved, the fuel injection timing is continuously corrected in the same direction. If the injection timing is changed in one direction, the combustion is deteriorated in the opposite direction. (Angular direction), the fuel injection timing is changed by a small amount, and the fuel injection timing that optimizes the combustibility is obtained by such an operation. If the combustibility is improved due to the control of the fuel injection timing, the judgment in the next step S7 is eventually switched to an affirmative judgment, after which no further correction of the fuel injection timing is performed.

In step S8, correction of the ignition timing can be used in addition to correction of the fuel injection timing.
In this case, control can be performed such that the interval between the fuel injection timing and the ignition timing is constant. That is, by controlling the fuel injection timing, the timing at which the rich portion of the air-fuel mixture arrives at the spark plug electrode changes, and accordingly the ignition timing is changed, and the interval between the two is maintained constant. Even when the fuel injection timing is changed, a series of sparks are formed on the ignition plug electrode at the timing when the rich portion of the air-fuel mixture arrives at the electrode, so that reliable ignition can be realized. Note that the injection timing and the ignition timing can be controlled independently.

FIG. 8 shows a third embodiment. At the time of premixed combustion 81 as shown in FIG. 2A, the dwell angle of the ignition signal 82 is reduced, and a discharge 85 with small discharge energy is performed. At the time of stratified combustion 83 as shown in FIG. By increasing the dwell angle of the ignition signal 84 and performing a discharge 86 with a large discharge energy to extend the discharge period, the discharge is continued during a period in which stratification is performed (a period in which the air-fuel mixture exists near the spark gap). To improve the probability of inputting energy to the air-fuel mixture and prevent misfire.

FIG. 9 shows a fourth embodiment. (A) of FIG.
At the time of premixed combustion as shown by, the SW91 is connected to the SW91a side, the number of turns of the primary coil is increased, and
The discharge ratio of the secondary coil is reduced to perform discharge with a small discharge energy (FIGS. 8 and 85). During stratified charge combustion as shown in FIG. 2B, SW91 is connected to SW91b side, and the number of turns of the primary coil is changed. The discharge ratio is increased by increasing the turns ratio between the primary coil and the secondary coil to increase the discharge energy (86 in FIGS. 8 and 86), thereby extending the discharge period. The discharge is continued during the period when the gas mixture exists), the energy input probability to the air-fuel mixture is improved, and misfire is prevented.

The turns ratio may be varied by changing the number of turns of the secondary coil. FIG. 10 shows a fifth embodiment.
During premixed combustion 101 as shown in FIG. 2A, the initial energy input to the air-fuel mixture is increased by increasing the spark gap and increasing the capacity component, and the stratification as shown in FIG. At the time of combustion 102, the spark gap is reduced and the induction component is increased to extend the discharge period, improve the probability of inputting energy to the air-fuel mixture, and prevent misfire.

At this time, the spark gap may be made variable by the center electrode or the ground electrode. Further, as the means for making the variable, for example, a motor 103 or a solenoid 104 may be used.

[Brief description of the drawings]

FIG. 1 is an overall schematic diagram of an internal combustion engine of the present invention.

FIG. 2 is a diagram showing a series of different positions (a) of a piston in a fuel distribution state between a premixed combustion system (a) and a stratified combustion system.
It is a figure demonstrated by (e).

FIG. 3 is a diagram illustrating a single ignition system (a) and a multiple ignition system (b) in an embodiment of the present invention.

FIG. 4 is a flowchart illustrating the operation of the first embodiment of the present invention.

FIG. 5 is a diagram illustrating the division between stratified combustion and premixed combustion with respect to the internal combustion engine speed and load.

FIG. 6 is a schematic diagram illustrating an ignition operation when each of a multiple ignition system (a) and a single ignition system (b) is employed in stratified combustion.

FIG. 7 is a flowchart illustrating the operation of the second embodiment of the present invention.

FIG. 8 is a timing chart showing a third embodiment in which the ignition energy is changed depending on the magnitude of the dwell angle.

FIG. 9 is a schematic view of an ignition device according to a fourth embodiment.

FIG. 10 is a schematic view showing a fifth embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 16 ... Combustion chamber 17 ... Spark plug 40 ... Ignition device 42 ... Single ignition means 44 ... Multiple ignition means 46 ... Changeover switch 50 ... Control device 70 ... Combustion pressure sensor 72 ... Knock sensor

──────────────────────────────────────────────────続 き Continuation of front page (51) Int.Cl. ⁷ Identification code FI F02D 43/00 301 F02D 43/00 301A 301J F02P 3/045 303 F02P 3/045 303F 5/15 13/00 301J 13/00 301 H01T 13/26 H01F 38/12 F02P 5/15 B H01T 13/26 H01F 31/00 501C (72) Inventor: Kimitaka Saito 14 Iwatani, Shimoba Kakucho, Nishio City, Aichi Pref. Tatsuo Kobayashi 1 Toyota Town, Toyota City, Aichi Prefecture Inside Toyota Motor Corporation (56) References JP-A-8-246878 (JP, A) JP-A 4-179859 (JP, A) JP-A 4-179860 (JP, A) JP-A-4-362276 (JP, A) JP-A-10-318108 (JP, A) JP-A-9-32651 (JP, A) −35284 (JP, U) Japanese Utility Model 5-1826 (JP, U) (58) Fields investigated (Int. Cl. ⁷ , DB name) F02P 15/10 F02B 17/00 F02D 41/02 F02D 41/34 F02D 41/04 F02D 43/00 F02P 3/045 F02P 5/15 F02P 13/00 H01F 38/12 H01T 13/26

Claims (4)

(57) [Claims] An in-cylinder direct injection for supplying fuel in a different manner between an intake stroke injection during an operation in which premix combustion is to be performed and a compression stroke injection in an operation to perform stratified combustion according to operating conditions of an internal combustion engine. In an internal combustion engine, the turns ratio of the primary coil and the secondary coil is made variable during premixed combustion and stratified combustion so that the ignition method is variable according to the operating conditions, and the turns ratio is reduced during premixed combustion. An in-cylinder direct injection internal combustion engine characterized by reducing discharge energy and increasing the turns ratio during stratified combustion to increase discharge energy and extend the discharge period. 2. An in-cylinder direct injection for supplying fuel in a different manner between an intake stroke injection during operation in which premixed combustion is to be performed and a compression stroke injection in operation in which stratified combustion is to be performed according to operating conditions of an internal combustion engine. In an internal combustion engine, the spark gap of the spark plug is varied between premixed combustion and stratified combustion so that the ignition method can be varied according to the operating conditions. An in-cylinder direct injection internal combustion engine characterized in that a spark gap is reduced during stratified combustion and an induction component is mainly used. 3. The method according to claim 2, wherein the spark gap of the spark plug is changed by a solenoid.
In-cylinder direct injection type internal combustion engine according to 1. 4. A combustion state detecting means for controlling an ignition timing during premix combustion and a fuel injection timing during stratified combustion according to the combustion state. An in-cylinder direct injection internal combustion engine according to any one of the preceding claims.