JP2840603B2 - 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. [0008] A stratified charge engine according to the present invention is provided with a load detecting means for detecting a load of the engine, a fuel supply means for supplying fuel to a combustion chamber, and a fuel supply means. At the time of low load, while performing stratified combustion by supplying and igniting fuel at a later stage so that the combustible mixture is unevenly distributed around the ignition device from the fuel supply means at low load,
When the load is high, the fuel is supplied and ignited early so that the combustible air-fuel mixture is dispersed throughout the combustion chamber to perform uniform combustion, and the fuel injection amount supplied to the combustion chamber is increased according to the load increase. While gradually increasing and controlling the engine output, between the stratified combustion region by the late fuel injection at the low load and the uniform combustion region by the early fuel injection at the high load, the early fuel injection and the late fuel injection A transition region for performing both fuel injections is provided, and the excess air ratio λ is set so as to be greater than 1 over the entire transition region. In this transition region, the excess air ratio λ is set so as to decrease as the load increases. Further, the increase rate of the early fuel injection accompanying the increase in the load in the transition area is increased to be equal to or more than the increase rate of the entire fuel injection, and the transition area accompanying the load increase is increased. And control means for controlling the fuel supply means so that the late fuel injection amount becomes smaller than the early fuel injection amount at the end of the process. [0009] Another stratified charge engine of the present invention includes load detecting means for detecting a load on the engine, fuel supply means for supplying fuel to the combustion chamber, and an ignition device disposed in the combustion chamber. At low load, fuel is supplied and ignited in a later stage so that the combustible mixture is unevenly distributed around the ignition device from the fuel supply means, and stratified combustion is performed. Between the stratified combustion region by the late fuel injection at the time of low load and the uniform combustion region by the early fuel injection at the time of high load. A transition region for performing both early fuel injection and late fuel injection is provided, and the excess air ratio λ is set to be larger than 1 over the entire stratified combustion region. At the same time, the ratio of the late fuel injection amount to the total fuel injection amount supplied into the combustion chamber decreases in the transition region as the excess air ratio λ decreases. In this manner, a control means for controlling the fuel supply means is provided. According to the stratified charge engine of the present invention as described above, in the low load range, the fuel is supplied by the late fuel injection so that the combustible mixture is unevenly distributed around the ignition device in the combustion chamber. By performing the supplied stratified combustion, fuel efficiency is improved by lean combustion, but in a high-load operation range, uniform combustion in which fuel is supplied so that the combustible mixture is dispersed throughout the combustion chamber by early fuel injection. As a result, good high-power operation can be ensured without generating smoke. Furthermore, in the transition region from the stratified combustion in the low load region to the uniform combustion in the high load region, both late fuel injection for stratified combustion and early fuel injection for uniform combustion are performed, and in this transition region, By setting the excess air ratio λ to be greater than 1 and to decrease the excess air ratio λ with an increase in the load, in the region where uniform combustion is started, the latter-stage fuel injection is continued to become a fire around the ignition device. By diversifying the air-fuel mixture and securing the time until ignition by early fuel injection to promote the vaporization and atomization of the fuel, the ignitability and combustibility of a uniform air-fuel mixture with a lean air-fuel ratio are ensured. be able to. Further, the increase rate of the early fuel injection accompanying the increase in the load in the transition region is increased to be equal to or more than the increase ratio of the entire fuel injection, and the late fuel injection amount is reduced at the end of the transition region accompanying the load increase. By reducing the amount of early fuel injection, the amount of early fuel injection increases with an increase in load, the air utilization rate of the entire combustion chamber increases, and the engine output increases. As a result, the air-fuel ratio of the homogeneous air-fuel mixture dispersed throughout the combustion chamber gradually increases, and as a result, the local air-fuel ratio where the stratified air-fuel mixture unevenly distributed by the late fuel injection around the igniter and the uniform air-fuel mixture overlaps increases. In the lean air-fuel ratio region where the ratio of the late fuel injection amount to the total fuel injection amount is small and the excess air ratio λ of the entire combustion chamber to which the entire fuel injection amount is supplied is 1 or more, there is a tendency. Therefore, the operation can be smoothly shifted to high-power operation without generating smoke, and good operation performance can be obtained. Further, according to another stratified charge engine of the present invention, the early fuel injection and the late fuel injection are performed between a stratified combustion region in which the excess air ratio λ is greater than 1 and a uniform combustion region under a high load. In the transition region where both fuel injections are performed, the excess air ratio λ is set to decrease as the load increases, and the ratio of the late fuel injection amount to the total fuel injection amount decreases as the excess air ratio λ decreases. As a result, when the fuel amount is increased in response to the increase in the load from the low load region, if the late fuel injection amount for the stratified combustion is directly increased, the rich mixture exists in a part of the combustion chamber. In order to reduce the air usage rate and generate smoke, the later-stage fuel injection quantity is reduced as the excess air rate λ is reduced, the early fuel injection quantity is increased and uniform dispersion is promoted to increase the air usage rate. Improve and reduce smoke While it is possible to change the combustion mode. 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. The swirl port 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, and the flame is burned. The fuel 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 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 late fuel injection from the first fuel supply means 11 to perform stratified combustion, and the supply amount is increased according to the increase in the load. In the region, the supply amount of the stratified fuel is reduced. On the other hand, the dispersed fuel by the early fuel injection from the second fuel supply means 13 is:
Supply is started at a load equal to or higher than the load in the vicinity of the set load, and the amount is increased at an increase rate equal to or greater than the increase rate of the total fuel injection amount so as to compensate for the decrease amount of the stratified fuel by the first fuel supply means 11. In this case, the supply amount of the dispersing fuel is increased so that the total supply amount is increased, and the stratified combustion is shifted to the 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 by the late fuel injection from the first fuel supply means 11, and the fuel in the region II is supplied by the early fuel injection from the second fuel supply means 13. The supply of stratified fuel by the first fuel supply means 11 increases as the load increases below the set load at point A, while the fuel supply from the first fuel supply means 11 decreases when the load exceeds point A. When the load is higher than 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 between A and B is a transition region from the stratified combustion region to the uniform combustion region, and the stratified combustion fuel and the uniform combustion fuel are separately injected twice. 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 by a predetermined amount (late period) than the ignition timing near the compression top dead center, and the injected fuel is increased. The ignition is performed in a state where the ignition device 8 is effectively unevenly distributed around the ignition device 8. As the shift to the region where the dispersion of the point B is performed beyond the point A is performed, the injection timing is advanced and the injection (small amount injection) is performed at an earlier timing, and the uneven distribution of the fuel injected from the first fuel supply means 11 is reduced. It is made small and 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, 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, in the normal operation region at a low / medium load below the set load A point, the stratified combustion by the late fuel injection is performed to obtain good ignitability. Fuel efficiency is improved by enabling lean combustion in which the excess air ratio λ is 1 or more, and at the same time, in this stratified region, the amount of intake air is kept constant without closing the throttle valve 14 and fuel supply by the first fuel supply means 11 is performed. By controlling the output by the amount,
Pumping loss associated with the throttle operation of the throttle valve 14 can be significantly reduced, and fuel efficiency is further improved. In the transition region from the set load A point to the point B, the early fuel injection and the late fuel injection are performed, and the early fuel injection is increased to shift from stratified combustion to uniform combustion. In the high-load operation region beyond the above, high-output operation is performed without generating smoke by increasing the air utilization rate as uniform combustion, and combustion in each combustion mode is performed in all regions to achieve stratified combustion. Good operation performance can be achieved by transition to uniform combustion, 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

──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Haruo Okimoto 3-1 Shinchi, Fuchu-cho, Aki-gun, Hiroshima Mazda Co., Ltd. (72) Inventor Seiko Kono 3-1 Shinchi, Fuchu-cho, Aki-gun, Hiroshima Matsu (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) JP-A-58-158331 (JP, A) JP-A-52-54651 (JP, Y2) (58) Fields investigated (Int. Cl. ⁶ , DB name) F02D 41/00-45/00 F02B 17/00

Claims (1)

(57) [Claims] A load detecting means for detecting an engine load; a fuel supply means for supplying fuel to the combustion chamber; and an ignition device disposed in the combustion chamber. While stratified combustion is performed by supplying fuel and igniting late so that air is unevenly distributed, uniform combustion is performed by supplying fuel and igniting early so that the combustible mixture is dispersed throughout the combustion chamber at high load. A stratified charge engine, wherein the amount of fuel injected into the combustion chamber is gradually increased in accordance with an increase in load to control engine output; and Between the uniform combustion region by early fuel injection at high load,
A transition region for performing both early fuel injection and late fuel injection is provided, and the excess air ratio λ is set to be greater than 1 over the entire transition region. λ is set to be small, and the rate of increase in early fuel injection with an increase in load in the transition area is increased to be equal to or greater than the rate of increase in all fuel injections, and at the end of the transition area with an increase in load. A stratified charge engine, further comprising control means for controlling the fuel supply means such that the late fuel injection amount is smaller than the early fuel injection amount. 2. A load detecting means for detecting an engine load; a fuel supply means for supplying fuel to the combustion chamber; and an ignition device disposed in the combustion chamber. While stratified combustion is performed by supplying fuel and igniting late so that air is unevenly distributed, uniform combustion is performed by supplying fuel and igniting early so that the combustible mixture is dispersed throughout the combustion chamber at high load. A stratified charge engine, wherein between the stratified combustion region by late fuel injection at the time of low load and the uniform combustion region by early fuel injection at the time of high load,
A transition region for performing both early fuel injection and late fuel injection is provided, and the excess air ratio λ is set to be greater than 1 over the entire stratified combustion region. In the transition region, the ratio of the late fuel injection amount to the total fuel injection amount supplied into the combustion chamber is decreased so that the excess air ratio λ decreases. A stratified charge engine comprising control means for controlling the means.