JP2732050B2 - 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,
As described in JP-A-9-62807, JP-A-49-128109 and JP-A-51-1816. [0003] In the stratified charge engine, stratified charge combustion is performed at a low load. In the stratified charge charge combustion engine, the throttle amount of the intake passage is reduced to reduce the amount of intake air. The amount of air is increased and the air-fuel mixture is unevenly distributed around the ignition device to improve fuel efficiency by realizing stable combustion with the lean air-fuel mixture. When the air-fuel ratio increases, an air-fuel mixture is present, the air utilization rate is reduced, and smoke is generated. [0004] In this respect, in a high load state, uniform combustion in which fuel is dispersed and supplied to the entire combustion chamber improves the air utilization rate, so that a large output can be obtained as a whole. It is necessary to smoothly shift the combustion mode between the combustion and the uniform combustion under a high load without impairing the operation performance. In other words, depending on the load at which uniform combustion is started, the injected fuel is dispersed throughout the combustion chamber, so that it is too lean in view of the air-fuel ratio, impairing the ignitability and combustibility of the homogeneous mixture. Become. In particular, in the case of an engine in which an air-fuel ratio leaner than the stoichiometric air-fuel ratio (excess air ratio λ = 1) is set to a low / medium load region from the viewpoint of improving fuel efficiency, the fuel efficiency is also reduced by reducing the pumping loss. Since the output control is performed based on the fuel injection amount, the occurrence of misfire becomes a problem when starting the fuel supply for uniform combustion. In view of the above circumstances, the present invention controls both the generation of smoke and the occurrence of misfire while controlling the engine output by the fuel injection amount to reduce lean combustion and pumping loss in a wide operating range. Accordingly, it is an object of the present invention to provide a stratified intake engine in which the engine output is smoothly changed in the entire operation range to obtain good operation performance. The stratified charge engine of the present invention has a swirl generating means for generating swirl in the combustion chamber by introducing intake air into the combustion chamber, and a load detecting means for detecting a load on the engine. Means, a fuel supply means for supplying fuel into the combustion chamber, and an ignition device for igniting an air-fuel mixture in the combustion chamber. At low load, the supply fuel is unevenly distributed around the ignition device by the swirl generation means and the fuel supply means. While stratified combustion is performed by igniting and igniting, at high load, the supplied fuel is dispersed throughout the combustion chamber and ignited to perform uniform combustion, and the amount of fuel supplied to the combustion chamber is reduced. The engine output is gradually increased in accordance with the load increase, and the engine output is controlled. A transition region for supplying the fuel to be distributed and the fuel dispersed throughout the combustion chamber is provided, and the excess air ratio λ is set to be larger than 1 over the entire transition region. The excess ratio λ is set to be small, and the fuel supply amount for stratified combustion is reduced as the excess air ratio λ decreases in the transition region, and the fuel supply for uniform combustion is completed at the end of the transition. The fuel cell system further comprises control means for controlling the fuel supply means so as to make the fuel supply amount smaller than the fuel supply amount. It is preferable that the control means supplies a small amount of fuel for stratified combustion at the end of the transition region. On the other hand, it is preferable that the control means sets the fuel supply amount into the combustion chamber with the increase in load so that the rate of change from the stratified combustion region to the transition region is constant and continuously increased. is there. According to the stratified charge engine of the present invention as described above, in a low load region, the stratified charge is supplied unevenly around the ignition device in the combustion chamber with the generation of swirl. By performing combustion, fuel efficiency can be improved by lean combustion, but in the high-load operation range, it is possible to disperse fuel and perform uniform combustion to ensure good high-output operation without generating smoke. it can. Further, in the transition region of the intermediate load from the stratified combustion in the low load region to the uniform combustion in the high load region, both the fuel supply for the stratified combustion and the fuel supply for the uniform combustion are performed. In the region where the excess air ratio λ is larger than 1 and the excess air ratio λ is set to decrease as the load increases, the air-fuel mixture is unevenly distributed around the ignition device due to swirl generation in the region where uniform combustion starts. While ensuring sufficient fire, the swirling of the fuel for uniform combustion also improves the mixing with the air in the combustion chamber, and secures the ignitability and combustibility of a uniform mixture by promoting vaporization and atomization. be able to. In the transition region, the excess air ratio λ
As the fuel supply for stratified combustion is reduced as the fuel supply becomes smaller, and is made smaller than the fuel supply for uniform combustion at the end of the transition, the fuel for uniform combustion is increased as the load increases. The supply amount increases, the air utilization rate of the entire combustion chamber increases, and the engine output increases. And, since the uneven distribution of the fuel around the ignition device is enhanced by the swirl, the air-fuel ratio of the uniform mixture in the entire combustion chamber gradually increases, and as a result, the local air-fuel ratio around the ignition device tends to increase. However, since the amount of fuel supplied for stratified combustion is reduced as the excess air ratio λ of the entire combustion chamber is reduced, switching to uniform combustion without forming an over-enriched air-fuel mixture does not involve generation of smoke. It is possible to smoothly shift to high-output operation and obtain good operation performance. Embodiments of the present invention will be described below with reference to the drawings. This embodiment is shown in FIGS. 1 to 5 and shows an example in which the fuel supply means is constituted by a first fuel supply means for stratification and a second fuel supply means for dispersion. In the engine shown in FIG. 1, reference numeral 1 denotes a general open-chamber combustion chamber having no sub-chamber formed above a piston 2; 3 denotes an intake passage for introducing intake air into the combustion chamber 1; Denotes an exhaust passage for discharging exhaust gas from the combustion chamber 1, 5 denotes an intake valve, 6 denotes an exhaust valve, and 7 denotes a catalyst device provided in the exhaust passage 4. The combustion chamber 1 is provided with an ignition device 8 using a spark plug, and a stratification fuel injection nozzle 9 for supplying fuel around the ignition device 8.
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 including a dispersing fuel injection nozzle 12 for dispersing and supplying fuel into the combustion chamber 1. Further, a throttle valve 14 is provided downstream of the dispersion fuel injection nozzle 12, and an actuator 15 for electrically opening and closing the throttle valve 14 (not linked to the accelerator operation).
Are provided to form intake throttle means 20 for controlling the opening area of the intake passage 3 to regulate the amount of intake air. As shown in FIG. 2, the downstream portion of the intake passage 3 is curved to introduce intake air from a tangential direction of the combustion chamber 1 and to form a swirl S in the combustion chamber 1 along its circumferential direction. A swirl port (swirl generating means) is formed, and the swirl causes the ignition fuel supplied from the stratification fuel injection nozzle 9 of the first fuel supply means 11 and ignited by the ignition device 8 to be sufficiently mixed with air. With
The flame is propagated to the entire combustion 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 dispersing fuel injection nozzle 12 of the second fuel supply means 13, and the operation of the actuator 15 of the intake throttle means 20 are controlled by control means 16. The control means 16 receives a load signal from a load detection means 17 for detecting a required load of the engine by, for example, an accelerator sensor, and a detection signal from a water temperature sensor 18 for detecting when the engine is cold, for example, by a cooling water temperature. At the same time, it receives the engine rotation signal from the engine rotation sensor 19 and controls the fuel injection amount and the fuel injection timing from the stratification fuel injection nozzle 9 and the fuel injection amount from the dispersion fuel injection nozzle 12, respectively. 14 to control the closing operation timing. The control means 16 operates the intake throttle means 20 to close the throttle valve 14 in response to the detection signal of the water temperature sensor 18 when the cooling water temperature is equal to or lower than the set value to reduce the intake air amount. The second fuel supply means 13 supplies a predetermined amount of dispersed fuel. The control of the fuel supply amount corresponding to the load by the control means 16 is performed by the second fuel supply means 13 in a normal operation range in a low / medium load range below a set load upon receiving a signal from the load detection means 17. The supply of the dispersed fuel is stopped, the stratified fuel is supplied by the first fuel supply means 11 to perform stratified combustion, and the supply amount is increased in accordance with the increase in the load. This is to reduce the supply amount. 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 type corresponding to the engine load
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 starts at a load equal to or higher than the set load at the point A, and when the load increases further, the decrease in the supply of the stratified fuel by the first fuel supply means 11 is compensated for. At the same time, it supplies the increased fuel in response to the increase in the load as a whole. The load set at the point A is set so that the excess air ratio λ at that time is equal to or less than the ignition limit excess air ratio λ that can ignite even a homogeneous mixture, 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 becomes equal to or higher than the excess air ratio λ at which the air utilization rate decreases due to the stratified combustion and smoke starts to be generated. The excess air ratio λ is 1 or more below the point B, and the fuel supply amount increases as the load increases, and the excess air ratio λ decreases. Therefore, below the point A, the fuel is distributed in a stratified combustion region around the ignition device 8 in the combustion chamber 1, and above point B, the fuel is dispersed and supplied to the entire combustion chamber 1. In the uniform combustion region to be performed, a section from A to B is a transition region from the stratified combustion region to the uniform combustion region, and both the stratified combustion fuel and the uniform combustion fuel are supplied. The start timing of the supply of the dispersed fuel by the second fuel supply means 13 does not coincide with the set load A point at which the supply of the stratified fuel by the first fuel supply means 11 is reduced. The supply may be started under the changed load state. Next, FIG. 4 shows the injection timing (injection start timing) of the stratified fuel by the first fuel supply means 11 in response 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 advanced earlier (small amount injection) as the process shifts to the area where the dispersion of the point B is performed beyond the point A.
Is performed to reduce the uneven distribution of the fuel injected from the first fuel supply means 11 and to distribute the fuel 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, in FIG. 4, the ignition timing is set to be substantially constant with respect to the load fluctuation, but this may be changed so that the ignition timing is advanced in accordance with the increase in 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. When the engine is cold, as shown by the dashed line in FIG. 5, the engine is throttled over a wide range in a low-to-medium load region. Thus, the excess air ratio is reduced and the air-fuel ratio is made rich. In addition, the throttle valve 14 is controlled to close so as to prevent the catalyst temperature from decreasing during deceleration when the fuel supply is stopped and to improve the engine braking performance. Therefore, according to the stratified charge engine of the above-described embodiment, stratified combustion is performed to obtain good ignitability, and the excess air ratio λ In the stratified region, the intake air amount is kept constant without closing the throttle valve 14, and the output control is performed by the fuel supply amount by the first fuel supply means 11 at the same time. Is performed, the pumping loss accompanying the throttle operation of the throttle valve 14 can be significantly reduced, and the fuel efficiency is further improved. In the transition region from the point A to the point B exceeding the set load A, both the stratified combustion fuel and the uniform combustion fuel are supplied, and the ratio of the uniform combustion fuel is increased to increase the uniform combustion fuel from the stratified combustion. After the transition to combustion, in the high-load operation range beyond the point B, the air utilization is increased as uniform combustion to perform high-power operation without generating smoke.
Good driving performance can be achieved in all areas, and fuel efficiency can be improved by reducing pumping loss. Further, when the engine is cold, the fuel is supplied by the second fuel supply means 13 for dispersing and supplying the fuel to the entire combustion chamber, or the fuel injection timing by the first fuel supply means 11 is advanced to allow the fuel to be injected into the combustion chamber 1. In addition, uniform combustion is performed so that the fuel supplied to the fuel cell is dispersed, and the throttle valve 14 is closed by the intake throttle means 20 to reduce the amount of intake air to enrich the air-fuel ratio of the dispersed fuel. Is secured. In the above embodiment, the dispersing fuel injection nozzle 12 is interposed in the middle of the intake passage 3, but may be disposed so as to open into the combustion chamber 1. The injection timing of the dispersed fuel directly supplied to the combustion chamber 1 is
The injection is set to be completed between the intake stroke and the initial stage of the compression stroke.
In this case, uniform combustion is obtained by uniformly dispersing the gas in the chamber. Further, in the above embodiment, the amount of decrease in the amount of intake air by the intake throttle means 20 or the degree of equalization tendency due to advance of the injection timing is changed and adjusted according to the cooling water temperature, that is, the degree of the engine cold state. Alternatively, the amount of intake air may be increased as the temperature rises, and the combustion may return to stratified combustion.

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 control of a fuel supply amount with respect to a load together with an excess air ratio in the example of FIG. 1; FIG. 5 is a characteristic diagram showing an opening degree of a throttle valve with respect to a load change in the example of FIG. 1. [Description of References] 1 Combustion chamber 3 Intake passage 8 Ignition device 9 Stratification 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

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 swirl generating means for generating a swirl in the combustion chamber by introducing intake air into the combustion chamber, a load detecting means for detecting a load of the engine, a fuel supply means for supplying fuel to the combustion chamber, and an air-fuel mixture in the combustion chamber. An ignition device that ignites the fuel, and performs stratified combustion by eccentrically igniting the supplied fuel around the ignition device by the swirl generating means and the fuel supply means at low load, while supplying fuel to the entire combustion chamber at high load. A stratified charge engine that performs uniform combustion by dispersing and igniting, and gradually increases a fuel supply amount supplied to a combustion chamber in accordance with an increase in load to control an engine output; A fuel supply that is distributed unevenly around the ignition device and a fuel that is dispersed throughout the combustion chamber are supplied to the intermediate load region where the combustion shifts from the stratified combustion to the uniform combustion region. A region is provided, and the excess air ratio λ is set to be larger than 1 over the entire region of the transition region. In this transition region, the excess air ratio λ is set to decrease with an increase in load. Control means for controlling the fuel supply means so as to reduce the fuel supply amount for stratified combustion as the excess air ratio λ decreases and to make the fuel supply amount for uniform combustion smaller at the end of the transition. A stratified charge engine comprising: 2. The stratified charge engine according to claim 1, wherein the control means supplies a small amount of fuel for stratified combustion at the end of the transition region. 3. 2. The control device according to claim 1, wherein the control unit sets the amount of fuel supplied into the combustion chamber with the increase in load so that the rate of change is constant and continuously increased from the stratified combustion region to the transition region. 3. A stratified charge engine as described.