JP2689100B2 - Stratified charge engine - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a stratified charge engine. 2. Description of the Related Art Conventionally, for the purpose of improving fuel efficiency and emission of an engine, only fuel required for ignition among fuels supplied to a combustion chamber in accordance with a load is unevenly distributed near an ignition device. Thus, a stratified charge engine capable of realizing lean combustion as a whole by enlarging the air-fuel ratio of only this portion to perform stratified combustion with improved ignitability is disclosed in, for example,
It is known as seen in JP-A No. 9-62807, JP-A-49-128109 and JP-A-51-1816. However, in the above stratified charge engine, stratified charge combustion is performed at a low load, and even during idle operation, the surroundings of the ignition device are the same as when the load is low. When the stratified combustion is performed mainly on the unevenly distributed fuel, there is a problem in combustion stability. That is, in the stratified combustion, the fuel consumption is improved by realizing lean combustion, and the fuel consumption is further improved by increasing the opening of the throttle valve to reduce pumping loss. When the same control is performed at the same time, the amount of intake air becomes larger than necessary even though the load is extremely low, and the pumping loss during the compression stroke becomes large. As a result, there is a possibility that rotation fluctuation during idle operation will increase, idle stability will decrease, and commercialability will decline. In view of the above circumstances, the present invention performs stratified combustion at low load and uniform combustion at high load to obtain good fuel efficiency and output performance and improve idle stability. It is intended to provide a stratified intake engine adapted to do so. A stratified charge engine according to the present invention is provided with a fuel supply means and an ignition device, performs stratified combustion at low load, performs uniform combustion at high load, and intake passage. An intake throttle means for controlling the opening area is provided to reduce the opening area of the intake passage by the intake throttle means during idle operation, while comparing the fuel injection timing by the fuel supply means with the injection timing during the stratified combustion. It is characterized in that it is provided with control means for controlling so as to correct the lead angle. At normal low load, stratified combustion is performed and the opening area of the intake passage is increased to perform lean combustion, while at high load, uniform combustion with an increased fuel injection amount is performed to increase output. At the time of idling, the intake air amount is reduced by the throttle operation of the intake throttle means to enrich the air-fuel ratio, and at the same time, the fuel injection timing is relatively advanced to promote the vaporization and atomization of the fuel to improve the combustibility and ignitability Improvements stabilize idle operation. Further, the exhaust gas temperature rises in accordance with the reduction of the intake air amount, and the warm-up property of the catalyst device is enhanced. According to the present invention, in the low load region,
Fuel is distributed unevenly around the ignition device in the combustion chamber to perform layered combustion to dilute the air-fuel ratio, and fuel consumption is improved by lean combustion, while fuel is dispersed and uniform in the high load operating range. Combustion can be performed to ensure good high-power operation without generating smoke. Further, during idle operation, enrichment of the air-fuel ratio and promotion of vaporization and atomization of fuel can be promoted to improve combustibility and ignitability, improve idle stability, and enhance commercialability. Also, as the exhaust gas temperature rises secondarily,
Early warm-up of the catalyst device can be achieved. Embodiments of the present invention will be described below with reference to the drawings. <First Embodiment> This embodiment is shown in FIGS. 1 to 5, and an example in which the fuel supply means is composed of a first fuel supply means for stratification and a second fuel supply means for dispersion. It is shown. In the engine shown in FIG. 1, 1 is a combustion chamber of a general open chamber shape having no sub chamber formed above a piston 2, 3 is an intake passage for introducing intake air into the combustion chamber 1, 4 Indicates an exhaust passage through which exhaust gas is discharged from the combustion chamber 1, reference numeral 5 indicates an intake valve, reference numeral 6 indicates an exhaust valve, and reference numeral 7 indicates a catalyst device interposed in the exhaust passage 4. In the combustion chamber 1, an ignition device 8 using a spark plug is provided, and a stratification fuel injection nozzle 9 for supplying fuel around the ignition device 8 is also provided.
A fuel injection pump 10 is connected to the stratification fuel injection nozzle 9 to form a first fuel supply means 11. On the other hand, the intake passage 3 is provided with a second fuel supply means 13 by means of a dispersion fuel injection nozzle 12 for supplying the fuel into the combustion chamber 1 in a distributed manner. Further, a throttle valve 14 is provided downstream of the dispersion fuel injection nozzle 12, and the throttle valve 14 is provided with an actuator 15 (not interlocked with an accelerator operation) for opening and closing the throttle valve 14. An intake throttle means 20 for controlling the opening area of the intake air flow control device 3 to regulate the amount of intake air is provided. As shown in FIG. 2, the downstream side portion of the intake passage 3 is curved so that the intake air is introduced from the tangential direction of the combustion chamber 1, and the swirl S along the circumferential direction is introduced into the combustion chamber 1. The generated swirl port is used to sufficiently mix the ignited fuel supplied from the stratification fuel injection nozzle 9 of the first fuel supply means 11 and ignited by the igniter 8 with the air, and burn the flame. It is propagated to the entire chamber 1 to sufficiently burn the entire injected fuel. The operation of the fuel injection pump 10 of the first fuel supply means 11, the fuel injection nozzle 12 for dispersion of the second fuel supply means 13 and the actuator 15 of the intake throttle means 20 is controlled by the control means 16. The control means 16 receives a load signal from the load detection means 17 which detects the required load of the engine by, for example, an accelerator sensor, and a detection signal from a water temperature sensor 18 which detects when the engine is cold, for example, by the cooling water temperature. Along with receiving the engine rotation signal from the engine rotation sensor 19 and the like, the fuel injection amount and fuel injection timing from the stratification fuel injection nozzle 9 and the fuel injection amount from the dispersion fuel injection nozzle 12 are respectively controlled, and the throttle valve The closing operation timing of 14 is controlled. According to the detection signal of the water temperature sensor 18, the control means 16 operates the intake throttle means 20 to close the throttle valve 14 to reduce the intake air amount when the cooling water temperature is lower than the set value. The second fuel supply means 13 supplies a predetermined amount of dispersed fuel.
Similarly, during idle operation, the intake throttle means 20 is operated to close the throttle valve 14 to reduce the intake air amount, and the fuel injection timing by the first fuel supply means 11 is advanced from the injection timing during stratified combustion. Is. Further, the fuel supply amount control corresponding to the load by the control means 16 receives the signal from the load detection means 17, and the second fuel supply means 13 is used in the normal operation region in the low / medium load region below the set load. The supply of the dispersed fuel is stopped, the stratified fuel is supplied by the first fuel supply means 11 to perform stratified combustion, the supply amount is increased according to the increase of the load, and the supply amount of the stratified fuel is increased when the set load is exceeded. To reduce. On the other hand, the dispersed fuel by the second fuel supply means 13 starts to be supplied at a load equal to or higher than the load in the vicinity of the set load, compensates for the decrease in the amount of the stratified fuel by the first fuel supply means 11, and provides a total supply according to the increase in the load. The amount of the dispersing fuel is increased so that the amount increases, and the stratified combustion shifts to uniform combustion. At this time, the injection amount and the number of injections for each injection are set in accordance with the engine speed. That is, the first corresponding to the load of the engine
The fuel supply amount control by the fuel supply means 11 and the second fuel supply means 13 is performed as shown in FIG. FIG. 3 shows the variation of the fuel supply amount Q with respect to the variation of the load together with the variation of the excess air ratio λ. The throttle valve 14 is basically in the fully opened state, the intake air amount is constant, and the load increases. However, the fuel supply amount Q is increased to reduce the excess air ratio λ, that is, the air-fuel ratio is increased to perform output control. In the fuel supply amount Q, the fuel in the region I is supplied from the first fuel supply means 11, and the fuel in the region II is supplied from the second fuel supply means 13. First fuel supply means 1
The supply of the stratified fuel according to 1 increases with an increase in the load below the set load at the point A, whereas when the load exceeds the set load A, the fuel supply from the first fuel supply means 11 decreases,
At the time of a high load exceeding the point B, a small amount of injection is continued to prevent the stratification fuel injection nozzle 9 from being clogged with carbon and from being heated. On the other hand, the supply of the dispersed fuel by the second fuel supply means 13 is started at a load equal to or higher than the set load at the point A, and when the load increases from this, the decrease in the supply of the stratified fuel by the first fuel supply means 11 is compensated. At the same time, the increased fuel is supplied in response to the increase in the load as a whole. The set load at the point A is set so that the excess air ratio λ at that point is equal to or less than the excess air ratio λ at the ignition limit at which even a homogeneous mixture can be ignited, and the load at the point B is set. Is set to a load state in which the excess air ratio λ at that time is equal to or higher than the excess air ratio λ at which the air utilization rate decreases due to stratified combustion and smoke starts to be generated. Therefore, below the point A, the fuel is a stratified combustion region in which the fuel is unevenly distributed around the ignition device 8 of the combustion chamber 1, and above the point B, the fuel is dispersed and supplied to the entire combustion chamber 1. In the uniform combustion region, a region between A and B is a transition region from the stratified combustion region to the uniform combustion region. The timing of starting the supply of the dispersed fuel by the second fuel supply means 13 does not coincide with the set load A point that reduces the supply of the stratified fuel by the first fuel supply means 11, and the phase in the vicinity of this point A It suffices to start the supply under a load condition that is mixed up. Further, the switching between the stratified fuel supply by the first fuel supply means 11 and the distributed fuel supply by the second fuel supply means 13 is made to gradually decrease and increase as described above, and the set load points A and B. You may make it switch on / off in the load state between the points. Next, FIG. 4 shows the injection timing (injection start timing) of the stratified fuel by the first fuel supply means 11 with respect to the load fluctuation.
In the region where stratification is performed below the set load at the point A, the injection timing is set to a timing earlier than the ignition timing near the compression top dead center by a predetermined amount, and the injected fuel is set to the ignition device 8. Ignition is performed in a state where it is effectively unevenly distributed around. The injection timing is advanced and the injection is performed at an earlier timing as the transition to the area where the dispersion of the point B is performed beyond the point A is performed.
The uneven distribution of the fuel injected from the fuel supply means 11 is reduced so that the fuel is dispersed throughout the combustion chamber 1. In addition, when the load is extremely low such as during idling, the fuel injection timing and the ignition timing are slightly advanced from those in the stratified combustion to improve the stability. When the engine is cold, the second
Instead of supplying the dispersed fuel by the fuel supply means 13,
By advancing the fuel injection timing by the first fuel supply means 11 in the same manner as at the time of the high load, the injection is completed at an early timing from the intake stroke to the early stage of the compression stroke, and the intake air in the combustion chamber 1 thereafter is completed. The fuel may be dispersed by the flow of the air to obtain uniform combustion. Further, although the ignition timing is set to be substantially constant with respect to the load fluctuation in FIG. 4, this may be changed so that the ignition timing is advanced according to the increase of the load. On the other hand, the intake throttle means 2 by the control means 16
As shown in FIG. 5, the opening / closing control of the throttle valve 14 of 0 is basically performed with the throttle valve 14 fully opened to perform a non-throttle operation. This is to reduce the intake air amount by making it smaller. Further, when the engine is cold, as shown by the chain line in FIG. 5, the range is narrowed down in a low / medium load range, and as the load decreases, the opening is made smaller to reduce the intake air amount. Thus, the excess air ratio is reduced and the air-fuel ratio is made rich. In addition, the throttle valve 14 is controlled to be closed in order to prevent the catalyst temperature from decreasing during deceleration while the fuel supply is stopped and to improve the engine braking performance. Therefore, according to the stratified charge engine of the above-described embodiment, in the normal operation region under the set load A point or lower at the low / medium load, stratified combustion is performed to obtain good ignitability and lean combustion is possible. As a result, the fuel consumption is improved, and at the same time, in this stratified region, the throttle valve 14 is not closed, the intake air amount is made constant, and the output control is performed by the fuel supply amount by the first fuel supply means 11. Pumping loss accompanying the throttle operation of the valve 14 can be significantly reduced, and fuel economy is further improved. Further, in the high load operation range exceeding the set load point A, the stratified combustion is changed to the uniform combustion to increase the air utilization rate and the high output operation is performed without the generation of smoke. Good driving performance in all areas and improved fuel economy by reducing pumping loss. Further, during idle operation, the fuel injection timing by the first fuel supply means 11 is advanced from that during the stratified combustion to promote vaporization and atomization of the injected fuel to improve combustibility, and the intake throttle means 20 is used. The throttle valve 14 is closed to reduce the intake air amount to enrich the air-fuel ratio, thereby improving idle stability. Further, when the engine is cold, the fuel is supplied by the second fuel supply means 13 for distributing the fuel to the entire combustion chamber or the fuel injection timing by the first fuel supply means 11 is advanced to advance the inside of the combustion chamber 1. In addition to performing uniform combustion so as to disperse the fuel supplied to the intake air, the intake throttle means 20 closes the throttle valve 14 to reduce the intake air amount and enrich the air-fuel ratio of the dispersed fuel, thereby improving the warm-up property. Has been secured. The second fuel supply means 13 may supply the dispersed fuel to the intake passage 3 by using a carburetor, instead of the fuel injection method by the dispersion fuel injection nozzle 12. In the above embodiment, the second fuel supply means 1
The fuel injection nozzle 12 for dispersion of No. 3 is interposed in the middle of the intake passage 3, but the fuel injection nozzle 12 for dispersion of this second fuel supply means 13 is used for the stratified fuel injection of the first fuel supply means 11. Like the nozzle 9, it may be arranged so as to open in the combustion chamber 1. In that case, the injection timing of the dispersed fuel directly supplied to the combustion chamber 1 by the second fuel supply means 13 is the above-mentioned first fuel. The injection is set to be completed earlier than the fuel injection timing by the supply means 11 and between the intake stroke and the initial stage of the compression stroke, and the fuel supplied by the second fuel supply means 13 is uniformly mixed in the combustion chamber 1 with the intake air. The fuel is supplied by the second fuel supply means 13 or the fuel injection timing by the first fuel supply means 11 is the same as that of the second fuel supply means 13 when the engine is cold. It is intended to obtain a uniform combustion with binary angle. <Second Embodiment> This embodiment is shown in FIGS. 6 to 9, and an example in which the fuel supply means is constituted by one fuel injection nozzle provided in the intake passage to switch between stratified combustion and uniform combustion. The control at the time of idling is not particularly shown, but is performed in the same manner as the previous example. In the engine shown in FIGS. 6 and 7,
Reference numeral 22 denotes a primary intake passage that opens to the primary intake port 23 of the combustion chamber 1, and 24 denotes 2 that also opens to the secondary intake port 25.
A secondary intake passage, 26 is an exhaust passage opened to an exhaust port 27, 28 is a primary intake valve, 29 is a secondary intake valve, 30 is an exhaust valve, and 8 is an ignition device by an ignition plug. The downstream side portion of the primary intake passage 22 is provided in a swirl port forming a swirl in the combustion chamber 1, and the upstream side merges with the secondary intake passage 24, and the intake throttle means 20 by the throttle valve 14 is provided. The intake air amount is regulated by the operation, and a swirl control valve 31 is provided in the secondary intake passage 24. A fuel injection nozzle 32 for injecting fuel from the valve gap toward the vicinity of the ignition device 8 in the combustion chamber 1 when the primary intake valve 28 is opened is provided in the primary intake passage 22. The fuel supply means 33 is arranged to constitute the fuel supply means 33. The fuel supply means 33 and the intake throttle means 20 are controlled by the same control means (not shown) as in the previous example.
The amount of fuel injected from the fuel injection nozzle 32, the injection timing, and the opening of the throttle valve 14 are controlled. The fuel supply means 33 is
The output control is performed by increasing the fuel supply amount according to the load, and the stratified combustion and the uniform combustion are switched by controlling the injection timing. That is, the fuel injection timing is performed as shown in FIG. 8, S indicates the injection start timing, and E indicates the injection end timing. Regarding the fuel injection timing in the stratified region below the set load corresponding to point A in FIG. 3 of the first embodiment, the fuel is injected at a late timing immediately before the primary intake passage 22 is closed at the end of the intake stroke, and the fuel is the primary fuel. It flows into the combustion chamber 1 through the opening gap of the intake valve 28, and the ignition device 8
Is distributed so as to be unevenly distributed around the engine, and even when the piston 2 rises in the compression stroke, the fuel is unevenly distributed in the upper part of the combustion chamber 1 to perform stratified combustion. At that time, the fuel injection end is set to a fixed time, the injection start is made earlier,
The injection amount is increased as the load increases. When the set load at the point A is exceeded, the injection timing is greatly advanced and accelerated, and when the load exceeds the point B, the injection end is made constant and the injection start is advanced to increase the load. The fuel injection from the beginning of the intake stroke causes the fuel that has flowed into the combustion chamber 1 to be dispersed throughout the combustion chamber 1 due to the flow of intake air, thereby performing uniform combustion. is there. Further, when the engine is cold, as shown by the chain line in FIG. 8, the injection timing (starting timing) is greatly advanced and accelerated even at a low load, so that the fuel accompanying the fuel supply from the beginning of the intake stroke is increased. Dispersion is used to achieve uniform combustion, and the injection amount is increased by making the injection start constant and delaying the injection end as the load increases. The swirl control valve 31 provided in the secondary intake passage 24 is opened from the setting A, the intake air is also supplied from the secondary intake passage 24, and is supplied from the primary intake passage 22. It prevents excessive swirl strength of intake air, suppresses combustion noise and knocking due to abnormal increase in combustion speed, and reduces intake resistance to improve intake efficiency. The opening of the throttle valve 14 in this embodiment is controlled as shown in FIG. In this example, the stratification of the fuel in the stratified region is reduced because the uneven distribution ratio around the ignition device 8 is reduced as compared with the case of the preceding example.
No. 4 needs to be throttled so as to reduce the intake air amount, but its throttle opening is smaller than that of a conventional carburetor engine that performs output control by the air-fuel mixture charge amount as shown by the chain line, The pumping loss can be reduced. When the engine is cold, the throttle valve opening is reduced to about the opening indicated by the chain line to reduce the intake air amount and enrich the air-fuel ratio. Therefore, in this embodiment as well, lean combustion by layered combustion is performed at low load to improve fuel efficiency, while high output operation can be performed at high load without causing smoke due to uniform combustion. it can. Further, when the engine is cold, a good warm-up property is obtained by enriching the air-fuel ratio by reducing the intake air amount and dispersing the fuel by advancing the injection timing, and the temperature rises early. To activate the catalyst. In the control of the injection timing after warm-up in this embodiment, as shown in FIG. 8, the injection end is fixed (reference) and the injection start is advanced to increase the injection amount according to the load. Instead of this, the injection start timing may be fixed (reference) and the injection end may be advanced in accordance with the change in the load. Further, in both of the above-described embodiments, the degree of homogenization tendency is changed and adjusted depending on the cooling water temperature, that is, the degree of engine cooling state, by the amount of reduction of the intake air amount by the intake throttle means 20, or the advance of the injection timing. Alternatively, the intake air amount is increased as the temperature rises, and the stratified combustion is restored.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic configuration diagram of a stratified charge engine according to one embodiment of the present invention. FIG. 2 is a plan view schematically showing a combustion chamber in the example of FIG. FIG. 4 is a characteristic diagram showing the control of the fuel supply amount with respect to the load together with the excess air ratio in the example of FIG. 1; FIG. 5 is a characteristic view showing the opening of the throttle valve with respect to load fluctuation in the example of FIG. 1. FIG. 6 is a bottom view showing a partial cross section of a cylinder head in a stratified intake engine according to a second embodiment of the present invention. 7 is a cross-sectional view taken along the line VII-VII of FIG. 6; FIG. 8 is a characteristic diagram showing fuel injection timing control with respect to the load in the example of FIG. 6; Characteristic diagram showing control [Explanation of symbols] 1 Combustion chamber 3 intake passage 8 ignition device 9 stratified fuel injection nozzle 10 fuel injection pump 11 first fuel supply means 12 dispersion fuel injection nozzle 13 second fuel supply means 14 throttle valve 15 actuator 16 control means 17 load detection means 18 water temperature sensor 20 Intake throttle means 32 Fuel injection nozzle 33 Fuel supply means

   ────────────────────────────────────────────────── ─── Continuation of front page    (72) Inventor Haruo Okimoto               Pine, 3-1, Shinchi, Fuchu-cho, Aki-gun, Hiroshima               DA Co., Ltd. (72) Inventor Makoto Kono               Pine, 3-1, Shinchi, Fuchu-cho, Aki-gun, Hiroshima               DA Co., Ltd.                (56) References JP-A-51-1816 (JP, A)                 JP-A-54-47924 (JP, A)                 JP-A-56-151213 (JP, A)                 JP-A-57-62915 (JP, A)                 52-54651 (JP, Y2)

Claims (1)

(57) [Claims] A stratified combustion is provided by providing fuel supply means for supplying fuel into the combustion chamber and an ignition device arranged in the combustion chamber, and when the load is low, fuel is unevenly distributed around the ignition device from the fuel supply means to supply and ignite the fuel. On the other hand, in a stratified charge engine that performs uniform combustion by dispersing fuel in the combustion chamber and igniting it at high load, an intake throttle means for controlling the opening area of the intake passage is provided. A control means for reducing the opening area of the intake passage by the intake throttle means during idle operation, and controlling the fuel injection timing by the fuel supply means so as to advance the fuel injection timing relative to the injection timing during the stratified combustion. A stratified air supply engine characterized by being equipped. 2. The stratified charge engine according to claim 1, wherein the fuel supply unit directly injects fuel into the combustion chamber to perform stratified combustion. 3. The fuel supply means operates from the intake stroke to the beginning of the compression stroke.
To advance injection from the injection timing of stratified combustion so that the injection is completed in
Fuel is directly injected into the combustion chamber with uniform injection timing to achieve uniform combustion.
Stratified Charge engine according to claim 1, wherein the performing.