JP5035088B2 - engine - Google Patents

Description

  The present invention relates to an engine that performs premixed compression ignition combustion.

  In a spark ignition type engine, it is known to dilute an air-fuel mixture at low load to improve thermal efficiency and suppress fuel consumption. There is a limit to the dilution of the air-fuel mixture from the viewpoint of combustion stability. If the air-fuel mixture is diluted beyond this limit, the combustion becomes unstable due to misfire and the emission deteriorates.

  In the past, many technological developments have been made to expand the lean combustion region of the air-fuel mixture to the low load side. In recent years, as one of them, development and practical use of an engine employing premixed compression ignition combustion (self-ignition combustion) in which an air-fuel mixture is self-ignited by a compression action of a piston are awaited. With regard to this self-ignition combustion, many technical problems still remain until practical use, such as control of ignition near the top dead center and suppression of combustion noise caused by rapid heat generation.

  Here, an engine described in Patent Document 1 is known as a technique for solving the problem of ignitability related to self-ignition combustion.

In the engine described in Patent Document 1, a homogeneous mixture of gasoline is formed in the combustion chamber, and a hydrogen gas having a relatively high octane number and hardly self-igniting is injected near the top dead center of the compression stroke. A gas mixture of hydrogen gas is formed around Then, the air-fuel mixture is ignited and burned by the spark plug. By this combustion expansion, the air-fuel mixture in the unburned region in the combustion chamber is compressed and self-ignited.
JP 2004-036538 A

  The engine described in Patent Document 1 has an advantage that not only can the air-fuel mixture self-ignite, but also the timing of self-ignition combustion can be controlled by adjusting the ignition timing using a spark plug.

  However, in the engine described in Patent Document 1, since hydrogen gas is locally distributed around the spark plug, there is the following problem regarding emission.

  That is, there is a limit in ensuring ignition by the spark plug in order to make the hydrogen gas mixture lean. For this reason, it is necessary to set the concentration of hydrogen gas in the air-fuel mixture to be relatively high. As a result, NOx generation is unavoidable in the combustion of hydrogen gas at a high temperature, and the emission deteriorates. In addition, since the compression of the air-fuel mixture in the unburned region is performed by the combustion expansion of locally distributed hydrogen gas, self-ignition occurs sequentially from the point where the ignition point is reached, and self-ignition occurs simultaneously in the entire combustion chamber. It is difficult to produce. In particular, when the load is low, self-ignition cannot be caused in the region near the wall surface, and the amount of unburned components discharged increases.

  Accordingly, the present invention has been made paying attention to such problems, and an object thereof is to provide an engine that can achieve both high thermal efficiency by promoting self-ignition combustion and reduction of emissions.

The engine of the present invention includes a first fuel having a higher self-ignition property than gasoline, a second fuel having a higher combustion rate than gasoline, a lower self-ignition property than the first fuel, and a lower combustion rate than the second fuel. A supply means for supplying fuel so as to form an air-fuel mixture containing the third fuel in the combustion chamber; an ignition means for igniting the air-fuel mixture; and a control means for controlling the supply means and the ignition means. The means is characterized in that the supply ratio of each fuel is adjusted so that the ignited air-fuel mixture undergoes self-ignition combustion after flame propagation combustion, and the air-fuel mixture in the combustion chamber is ignited by the ignition means .

  According to the present invention, the supply ratio of the first fuel having high self-ignitability and the second fuel having a high combustion speed is adjusted so that the air-fuel mixture is self-ignited and combusted after flame propagation combustion. In addition, self-ignition combustion can be performed without forming an air-fuel mixture, and high thermal efficiency can be realized. Therefore, it is possible to suppress the deterioration of the emission accompanying the formation of the air-fuel mixture.

  Further, according to the present invention, the compression action due to the combustion expansion can be quickly generated in the entire combustion chamber. Therefore, the self-ignition of the air-fuel mixture due to the action of the first fuel can be caused in the entire combustion chamber, and the discharge of unburned components from the region near the wall surface can be suppressed.

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

(First embodiment)
FIG. 1 is a schematic configuration diagram of an engine according to the first embodiment.

  Referring to FIG. 1, the engine 100 includes a cylinder block 11 and a cylinder head 12.

  A cylinder 19 is formed in the cylinder block 11. The piston 13 is slidably inserted into the cylinder. A combustion chamber 14 is formed by the wall surface of the cylinder 19, the piston 13, and the lower surface of the cylinder head 12.

  The cylinder head 12 is formed with an intake port 15 </ b> A of an intake passage 15 communicating with one side of the combustion chamber 14. An intake valve 16 is provided in the intake port 15A. When the intake valve 16 is opened, air from which dust or the like has been removed by the air cleaner is sucked into the combustion chamber 14.

  Further, the cylinder head 12 is formed with an exhaust port 17A of an exhaust passage 17 communicating with the other side of the combustion chamber 14. An exhaust valve 18 is provided in the exhaust port 17A. When the exhaust valve 18 is opened, the exhaust after combustion is discharged from the combustion chamber 14.

  The intake valve 16 and the exhaust valve 18 described above are opened and closed by valve gears 161 and 181, respectively. The valve gears 161 and 181 are configured as camshafts whose angular phases with respect to the crankshaft are fixed.

  In the cylinder head 12, a fuel injection valve 21 is installed in the center near the cylinder center line, and a spark plug 25 is installed adjacent to the fuel injection valve 21. In the engine 100, in addition to the fuel injection valve 21, fuel injection valves 22 and 23 are provided as means for supplying fuel. These fuel injection valves 22 and 23 are arranged on the cylinder head 12 so as to inject fuel into the intake port.

  The fuel injection valves 21 to 23 are supplied with fuel having different properties. Among these fuel injection valves 21 to 23, the fuel injection valve 22 disposed at a position farthest from the combustion chamber 14 is a normal paraffin (hereinafter referred to as “n-paraffin”) having high self-ignitability as the first fuel. Is supplied. In addition, hydrogen gas having a high combustion rate is supplied as the second fuel to the fuel injection valve 23 disposed at a position closer to the combustion chamber 14 than the fuel injection valve 22. And the gasoline with a high octane number is supplied to the fuel injection valve 21 arrange | positioned in the center part of the cylinder head 12 as a 3rd fuel. The burning rate is the fastest for hydrogen gas, and is almost the same for gasoline and n-paraffin. Further, the self-ignitability is highest for n-paraffin, and decreases in the order of gasoline and hydrogen gas.

  In the engine 100, both n-paraffin and hydrogen gas are obtained using gasoline as a raw fuel. The gasoline is stored in the fuel tank 31. The fuel tank 31 is provided with a low-pressure fuel pump 32. The gasoline in the fuel tank is sucked up by the low-pressure fuel pump 32 and supplied to the fuel separator 33.

  In the fuel separator 33, the n-paraffin component in gasoline is subjected to membrane separation. The separated n-paraffin component is supplied to the fuel reformer 34.

  The fuel reformer 34 is configured as a device that extracts hydrogen from the n-paraffin component by a dehydrogenation reaction using a catalyst. Part of the n-paraffin component supplied to the fuel reformer 34 is used for this dehydrogenation reaction, and the others pass through the fuel reformer 34 and are supplied to the fuel injection valve 22. In the fuel reformer 34, hydrogen is separated from a part of the supplied n-paraffin component, and hydrogen gas is taken out. Hydrogen gas is supplied to the fuel injection valve 23 by the gas fuel pump 35. The n-paraffin component used in the dehydrogenation reaction is transformed into a fuel having low autoignition characteristics represented by an aroma component by separating hydrogen. The aroma component after the dehydrogenation reaction is returned to the fuel separator 33, and is supplied to the fuel injection valve 21 by the high-pressure fuel pump 36 together with the remaining gasoline from which the n-paraffin component has been membrane-separated.

  The operations of the fuel injection valves 21 to 23 and the spark plug 25 described above are controlled by signals from an engine control unit (hereinafter referred to as “ECU”) 41. In the ECU 41, as a detection signal indicating the engine operating state, a signal from the accelerator sensor 51 that detects the amount of operation of the accelerator pedal by the driver, a signal for each reference crank angle and unit crank angle from the crank angle sensor 52, and an engine A signal or the like from the temperature sensor 53 that detects the temperature of the cooling water is input. The ECU 41 executes predetermined calculations related to engine control based on various input signals, and controls various operations of various engine control devices including the fuel injection valves 21 to 23 and the spark plug 25. A command signal is output.

  The operation of the ECU 41 will be described with reference to FIG. FIG. 2 is a flowchart showing fuel injection control by the ECU 41.

  In step S101, the ECU 41 reads the accelerator opening APO, the engine speed Ne, and the coolant temperature Tw as the engine operating state. The accelerator opening APO is calculated based on the operation amount of the accelerator pedal detected by the accelerator sensor 51. Further, the engine speed Ne is calculated based on a signal from the crank angle sensor 52.

  In step S102, the ECU 41 determines a region to which the engine operating state belongs based on the read operating state. This determination is made with reference to an operation region map as shown in FIG. This operation region map is created in advance based on the results of experiments and the like and stored in the ECU 41. When the engine operating state is in the low load / low rotation speed region A, a lean homogeneous mixture is formed in the combustion chamber using the three fuel injection valves 21-23. In order to form a homogeneous air-fuel mixture, the fuel injection valve 21 injects gasoline during the intake stroke, and the fuel injection valves 22 and 23 inject n-paraffin and hydrogen gas during the exhaust stroke. In contrast, when the engine operating state is in the high load or high rotation speed region B, gasoline is directly injected into the combustion chamber by the fuel injection valve 21 during the intake stroke, and a homogeneous air / fuel mixture having a stoichiometric air / fuel ratio is obtained. It forms in the combustion chamber.

  Returning to FIG. 2, in step S <b> 103, the ECU 41 calculates the injection amount Qf <b> 1 of n-paraffin by the fuel injection valve 22 according to the engine operating state. When the engine operating state is in the region B, the injection amount Qf1 is set to zero in order to stop the operation of the fuel injection valves 22, 23 other than the fuel injection valve 21 that supplies gasoline.

  In step S104, the ECU 41 calculates the hydrogen gas injection amount Qf2 from the fuel injection valve 23 in accordance with the engine operating state. When the engine operating state is in the region B, the injection amount Qf2 is set to zero for the same reason as in step S103.

  In step S105, the ECU 41 calculates the gasoline injection amount Qf3 from the fuel injection valve 21 in accordance with the engine operating state.

  In step S106, the ECU 41 drives the fuel injection valve 22 at a predetermined time during the exhaust stroke or the intake stroke to inject n-paraffin having an injection amount Qf1 into the intake port.

  In step S107, the ECU 41 drives the fuel injection valve 23 at a predetermined time during the exhaust stroke or the intake stroke to inject hydrogen gas of the injection amount Qf2 into the intake port.

  In step S108, the ECU 41 drives the fuel injection valve 21 at a predetermined time during the intake stroke to inject gasoline of the injection amount Qf3 into the combustion chamber.

  Next, the air-fuel mixture formed by the fuels injected from the fuel injection valves 21 to 23 in the low load / low rotation speed region A will be described with reference to FIGS. 4 and 5.

  FIG. 4A shows the ratio (supply ratio) Ffrac of each calorific value (J) of n-paraffin, hydrogen gas and gasoline in the total injection amount Qtotal of fuel supplied to the engine 100. FIG. 4B shows the relationship between the engine load Ld and the excess air ratio Lamd as the entire air-fuel mixture.

  In the engine 100, as shown in FIG. 4B, as the engine load Ld decreases, the excess air ratio Lamd is increased to form a leaner homogeneous mixture in the combustion chamber. As for the fuel ratio Ffrac, as shown in FIG. 4A, the ratio of n-paraffin and hydrogen gas is increased and the ratio of gasoline is decreased as the engine load Ld decreases.

  For example, when the engine load Ld is the low load Ld1, the total fuel injection amount is determined so that the excess air ratio Lamd is 3. In this case, the hydrogen gas supply ratio Ffrac is set to 0.4, and the n-paraffin supply ratio Ffrac is set to 0.6. In contrast, when the engine load Ld is the high load Ld2, the total fuel injection amount is determined so that the excess air ratio Lamd is 2. In this case, the hydrogen gas supply rate Ffrac is set to 0.3, the n-paraffin supply rate Ffrac is set to 0.21, and the gasoline supply rate Ffrac is set to 0.49.

  FIG. 5 is obtained by converting the supply ratio Ffrac of each fuel shown in FIG. 4A to a fuel injection amount Qf that correlates with the heat generation amount (J).

  Since the excess air ratio Lamd increases as the engine load Ld decreases, the total fuel injection amount Qtotal increases with a decrease in the engine load Ld, as can be seen from the fuel injection amount Qf correlated with the heat generation amount shown in FIG. Decrease. However, in order to increase the supply ratio of n-paraffin and hydrogen gas with respect to the decrease in engine load Ld, these injection amounts Qf1 and Qf2 increase regardless of the decrease in engine load Ld. In region A, the supply ratios of three types of fuels with different combustion characteristics are adjusted, so that while maintaining the fuel concentration as a whole, in other words, maintaining the engine output, It can be adjusted, and combustion with desired characteristics can be realized.

  As shown in FIG. 5, the occurrence of knocking is suppressed by decreasing the injection amount Qf1 of n-paraffin as the engine load Ld increases. Further, when the engine load Ld increases, the total fuel injection amount Qtotal also increases. Therefore, it is possible to stabilize the ignition regardless of the hydrogen gas, so that the hydrogen gas injection amount with respect to the increase in the engine load Ld. Decrease Qf2. Therefore, in the region A, as the engine load Ld increases, the combustion in the form of promoting the self-ignition combustion gradually shifts to the spark ignition combustion.

  Combustion of the air-fuel mixture formed in the combustion chamber in the low load / low rotational speed region A is achieved as follows.

  When the engine operating state is in the region A, n-paraffin having a high autoignition property and hydrogen gas having a high combustion speed are diffused together with gasoline throughout the combustion chamber 14 to form a homogeneous air-fuel mixture. This homogeneous air-fuel mixture has a high self-ignitability and a high combustion rate. When this homogeneous air-fuel mixture is ignited by the spark plug 25, the air-fuel mixture burns and burns even in a lean state due to the action of hydrogen gas having a high combustion speed, and the flame expands to the air-fuel mixture in the combustion chamber. During the flame propagation combustion as described above, the air-fuel mixture in the unburned portion is compressed by the combustion expansion and reaches the self-ignition combustion by the action of n-paraffin having a high self-ignitability. As described above, in the engine 100, the homogeneous air-fuel mixture in the combustion chamber is subjected to flame propagation combustion in the first half of combustion and self-ignition combustion in the second half of combustion.

  When the engine operating state is in a high load or high rotation speed region B, the stoichiometric air-fuel ratio homogeneous mixture formed in the combustion chamber is ignited by the spark plug 25 and burns and propagates in flame.

  As described above, in the engine 100 of the present embodiment, the following effects can be obtained.

  In the engine 100, an n-paraffin that self-ignites and burns a homogeneous mixture containing n-paraffin with high self-ignitability and hydrogen gas with a high combustion rate after the ignited mixture undergoes flame propagation combustion. And formed after adjusting to the supply ratio of hydrogen gas. External energy is supplied to the homogeneous air-fuel mixture by the spark plug 25, the air-fuel mixture is flame-propagated and combusted by the action of hydrogen gas, and the air-fuel mixture is compressed by combustion expansion, so that the action of n-paraffin with high self-ignitability To auto-ignite the mixture. As described above, since the self-ignition combustion of the air-fuel mixture is promoted, the self-ignition combustion can be stably performed even at a low load, and high thermal efficiency can be realized.

  Further, in the engine 100, a lean homogeneous mixture is ignited by the spark plug 25. However, since hydrogen gas is a fuel having a higher combustion speed than gasoline, the mixture does not misfire due to the action of hydrogen gas. Can be burned. Therefore, unlike the conventional method, it is not necessary to form a fuel-rich air-fuel mixture and self-ignite, and the deterioration of emissions can be suppressed.

  Furthermore, the flame of the burned air-fuel mixture quickly expands throughout the combustion chamber by the action of hydrogen gas having a high combustion speed. Therefore, the compression action by the combustion expansion can be quickly obtained in the entire combustion chamber including the region close to the wall surface of the combustion chamber 14. Thereby, the air-fuel mixture can be self-ignited and combusted in the entire combustion chamber, and emission of unburned components can be suppressed.

  The supply ratio Ffrac of n-paraffin and hydrogen gas in the total fuel injection amount Qtotal may be changed according to the cooling water temperature Tw. When the cooling water temperature Tw is low as indicated by the two-dot chain line in FIG. 4A, the supply ratio Ffrac of n-paraffin and hydrogen gas is increased as compared with the case after the completion of warming indicated by the solid line. Thereby, regardless of the warm-up state of engine 100, the combustion speed and self-ignitability of the air-fuel mixture can be maintained and combustion can be stabilized.

  Further, the fuel supply ratio Ffrac is not only increased linearly with a decrease in the engine load Ld, but is also increased in a quadratic function as shown in FIGS. 6 (A) and 6 (B). Also good. FIG. 6A shows an increase in the increase amount per unit change amount of the engine load Ld as the load Ld of the engine 100 decreases at each supply ratio of n-paraffin and hydrogen gas.

(Second Embodiment)
FIG. 7 is a schematic configuration diagram of the engine 100 of the second embodiment. The configuration of the engine 100 of the second embodiment is substantially the same as that of the first embodiment. Here, parts or parts different from the first embodiment will be described. About a common part etc., the same code | symbol is attached | subjected and description is abbreviate | omitted.

  The engine 100 of the second embodiment differs from the first embodiment in the configuration of the combustion chamber and the fuel system.

  That is, in the engine 100, a main combustion chamber 141 separated by the cylinder head 12 and the piston 13 and a sub-combustion chamber 142 having a constant volume separated by a portion other than the main combustion chamber 141 and the injection hole 142a are formed. The The sub-combustion chamber 142 is for forming a flame torch ejected from the nozzle hole 142a into the main combustion chamber 141 by combustion of the air-fuel mixture in the sub-combustion chamber.

Further, in the engine 100, as a means for supplying fuel, a fuel injection valve 23 is installed at the center of the cylinder head 12 near the cylinder center line. The fuel injection valve 23 injects hydrogen gas having a high combustion speed into the auxiliary combustion chamber 142. Further, the fuel injection valves 21 and 22 are arranged on the cylinder head 12 so as to inject fuel into the intake port of the intake passage 15.
The fuel injection valve 21 injects gasoline having a high octane number. The fuel injection valve 22 injects n-paraffin having high self-ignitability.

  Both n-paraffin and hydrogen gas are obtained using gasoline as a raw fuel, and the gasoline as the raw fuel is stored in the fuel tank 31 as in the first embodiment.

  FIG. 8 is a flowchart showing fuel injection control by the ECU 41.

  In step S201, the ECU 41 reads the accelerator opening APO, the engine speed Ne, and the coolant temperature Tw as the engine operating state.

  In step S202, the ECU 41 determines a region to which the engine operation state belongs based on the read operation state.

  When the engine operating state is in the low load / low rotational speed region A of FIG. 3, the fuel injection valves 21 and 22 are used to form a lean homogeneous mixture containing gasoline and n-paraffin in the main combustion chamber. At the same time, hydrogen gas is injected into the auxiliary combustion chamber by the fuel injection valve 23. In the compression stroke, the lean homogeneous mixture formed in the main combustion chamber 141 flows into the sub-combustion chamber as the piston 13 rises, so that the mixture of n-paraffin, gasoline, and hydrogen gas is contained in the sub-combustion chamber. It is formed.

  In contrast, when the engine operating state is in the high load or high rotational speed region B, only the fuel injection valve 21 is used to form a stoichiometric air-fuel ratio homogeneous mixture in the main combustion chamber.

  In step S203, the ECU 41 calculates the injection amount Qf4 of n-paraffin by the fuel injection valve 22 according to the engine operating state. When the engine operating state is in region B, the injection amount Qf4 is set to zero.

  In step S204, the ECU 41 calculates the hydrogen gas injection amount Qf5 from the fuel injection valve 23 in accordance with the engine operating state. When the engine operating state is in the region B, the injection amount Qf5 is set to zero.

  In step S205, the ECU 41 calculates the gasoline injection amount Qf6 from the fuel injection valve 21 according to the engine operating state.

  In step S206, the ECU 41 drives the fuel injection valve 22 at a predetermined time during the exhaust stroke or the intake stroke to inject n-paraffin having an injection amount Qf4 into the intake port.

  In step S207, the ECU 41 drives the fuel injection valve 23 at a predetermined time during the compression stroke to inject hydrogen gas of the injection amount Qf5 into the auxiliary combustion chamber.

  In step S208, the ECU 41 drives the fuel injection valve 21 at a predetermined timing during the exhaust stroke or the intake stroke to inject gasoline of the injection amount Qf6 into the intake port.

  Next, with reference to FIGS. 9 and 10, the air-fuel mixture formed in the main combustion chamber in the region A by the gasoline and n-paraffin injected from the fuel injection valves 21 and 22 will be described. Further, the hydrogen gas injected into the auxiliary combustion chamber will be described with reference to FIG.

  FIG. 9A shows a supply ratio (a ratio of heat generation amount) Ffrac of each fuel in a total injection amount Qtotal of n-paraffin and gasoline supplied to the engine 100. FIG. 9B shows the relationship between the engine load Ld and the excess air ratio Lamd as the entire air-fuel mixture.

  In the engine 100, as shown in FIG. 9B, the excess air ratio Lamd is increased as the engine load Ld decreases. This causes combustion with a lean homogeneous mixture. In this air-fuel mixture, as shown in FIG. 9A, the n-paraffin supply ratio Ffrac increases as the engine load Ld decreases. On the contrary, the gasoline supply ratio Ffrac decreases as the engine load Ld decreases. For example, at high load Ld2, the n-paraffin supply rate Ffrac is set to 0.3, and the gasoline supply rate Ffrac is set to 0.7. On the other hand, at low load Ld1, the n-paraffin supply rate Ffrac is set to 1.0, and the gasoline supply rate Ffrac is set to 0.

  FIG. 10 is obtained by converting the fuel supply ratio Ffrac shown in FIG. 9A to a fuel injection amount Qf correlated with the heat generation amount.

  Since the excess air ratio Lamd is increased as the engine load Ld is decreased, the total fuel injection amount Qtotal is decreased with respect to the decrease in the engine load Ld as shown in FIG. However, since the ratio of n-paraffin to the decrease in engine load Ld is increased, the injection amount Qf4 of n-paraffin increases as the engine load Ld decreases. Thereby, in the homogeneous air-fuel mixture formed in the main combustion chamber 141, the self-ignitability obtained by the action of n-paraffin can be adjusted.

  The injection amount Qf5 of hydrogen gas injected into the auxiliary combustion chamber 142 is adjusted according to the engine load Ld as shown in FIG. The hydrogen gas injection amount Qf5 is increased as the engine load Ld decreases. By the action of the hydrogen gas, the combustion speed of the air-fuel mixture formed in the auxiliary combustion chamber can be adjusted.

  In the engine 100 of the present embodiment, combustion is achieved as follows.

  When the engine operating state is in the region A, n-paraffin having high self-ignitability is diffused together with gasoline throughout the main combustion chamber to form a homogeneous air-fuel mixture. In the compression stroke, the air-fuel mixture in the main combustion chamber flows into the sub-combustion chamber through the injection holes 142a as the piston 13 moves up. Since the air-fuel mixture in the main combustion chamber flowing into the sub-combustion chamber 142 is lean, hydrogen gas having a high combustion speed is supplied into the sub-combustion chamber in order to ensure ignitability. When external energy is supplied to the air-fuel mixture in the auxiliary combustion chamber by the spark plug 25, even if the air-fuel mixture flowing from the main combustion chamber 141 into the auxiliary combustion chamber 142 is lean, the action of hydrogen gas causes the auxiliary air in the auxiliary combustion chamber. The air-fuel mixture burns and propagates. By this combustion, a flame torch that is ejected from the nozzle hole 142a to the main combustion chamber 141 is formed. A flame torch with hydrogen gas having a high combustion speed spreads quickly throughout the main combustion chamber. The supply ratio of n-paraffin with high self-ignitability and hydrogen gas with a fast combustion rate is adjusted to a supply ratio such that the air-fuel mixture in the main combustion chamber is self-ignited and burned after flame propagation combustion by a flame torch with hydrogen gas. Yes. Therefore, the homogeneous air-fuel mixture in the main combustion chamber is ignited by the flame torch, flame propagation combustion, and self-ignition combustion by combustion expansion.

  When the engine operating state is in the region B, the fuel injection valve 21 injects an amount of gasoline corresponding to the stoichiometric air / fuel ratio to form a homogeneous air / fuel mixture having the stoichiometric air / fuel ratio in the main combustion chamber 141. In the compression stroke, a part of this homogeneous air-fuel mixture flows into the auxiliary combustion chamber 142 through the nozzle holes 142a. By supplying external energy to the air-fuel mixture in the auxiliary combustion chamber 142 by the spark plug 25, the air-fuel mixture in the auxiliary combustion chamber is combusted. Thereby, a flame torch is ejected from the nozzle hole 142a into the main combustion chamber, and the air-fuel mixture in the main combustion chamber is flame-propagated and combusted by the flame torch.

  As described above, in the engine 100 of the present embodiment, the following effects can be obtained.

  In the engine 100, the homogeneous air-fuel mixture formed in the combustion chamber is ignited by a flame torch from the nozzle hole 142a of the auxiliary combustion chamber 142. Since the air-fuel mixture has its self-ignitability promoted by the action of n-paraffin, the engine 100 can stably perform self-ignition combustion and achieve high thermal efficiency.

  Moreover, since n-paraffin is a highly self-igniting fuel, it is not necessary to form a strong flame torch in order to cause the air-fuel mixture to self-ignite and burn. Therefore, the disturbance in the main combustion chamber due to the flame torch can be suppressed, and a decrease in thermal efficiency due to cooling loss can be avoided.

  Furthermore, by supplying hydrogen gas having a high combustion rate to the auxiliary combustion chamber 142, the ignitability of the air-fuel mixture in the auxiliary combustion chamber can be improved, and more stable combustion can be realized. Since the hydrogen gas injection amount Qf5 is increased as the engine load Ld decreases, the ignitability can be maintained regardless of the engine load Ld, and the air-fuel mixture in the main combustion chamber can be stably self-ignited and combusted.

  As in the first embodiment, the n-paraffin supply ratio Ffrac in the total fuel injection amount Qtotal may be changed according to the cooling water temperature Tw. As shown by the two-dot chain line in FIG. 9, when the cooling water temperature Tw is low, the supply rate Ffrac of n-paraffin is increased as compared with the case after the completion of warming indicated by the solid line. Further, at the time of cooling, in addition to or instead of changing the supply ratio of n-paraffin, the hydrogen gas injection amount Qf5 may be increased as shown by a two-dot chain line in FIG.

(Third embodiment)
FIG. 12 is a schematic configuration diagram of an engine 100 according to the third embodiment.

  The basic configuration of the engine 100 of the third embodiment is substantially the same as that of the first embodiment, but differs in that fuel injection control is performed so that the combustion in the region A becomes more stable. That is, the injection amount of each fuel is corrected according to the combustion state of the air-fuel mixture, and the difference will be mainly described below.

  As shown in FIG. 12, engine 100 includes an in-cylinder pressure sensor 54 and a knock sensor 55.

  The in-cylinder pressure sensor 54 is provided in the cylinder block 11 and detects the pressure in the combustion chamber (in-cylinder pressure). A detection signal from the in-cylinder pressure sensor 54 is input to the ECU 41.

  The knock sensor 55 is installed in the cylinder block 11. Knock sensor 55 detects vibration generated in the engine body. A detection signal from knock sensor 55 is input to ECU 41.

  The ECU 41 determines the combustion state of the air-fuel mixture in the low load / low rotation speed region A based on the detection signals of the in-cylinder pressure sensor 54 and the knock sensor 55, and the injection amount of each fuel according to the combustion state Qf1 to Qf3 are corrected. Accordingly, the fuel injection amount correction control executed by the ECU 41 in the region A will be described with reference to FIGS.

  FIG. 13 is a flowchart showing the fuel injection amount correction control executed by the ECU 41. This control is performed at a constant cycle, for example, a cycle of 10 milliseconds when the engine operating state is in the region A.

  In step S301, the ECU 41 reads in-cylinder pressure P and knock level N as the engine operating state. The in-cylinder pressure P is calculated based on a detection signal from the in-cylinder pressure sensor 54. The knock level N is calculated based on the vibration amount detected by the knock sensor 55. The calculated in-cylinder pressure P and knock level N are stored as, for example, values (waveforms) with respect to time, and in each step described later, the in-cylinder pressure P at the time of flame propagation combustion or self-ignition combustion. And knock level N are read.

At step S302, ECU 41 determines whether the cylinder pressure P _A is smaller than the reference pressure P ₁ not when the air-fuel mixture in the combustion chamber is flame propagation combustion. If the in-cylinder pressure P _A is smaller than the reference pressure P ₁ , it is determined that flame propagation combustion in the first half of combustion has misfired, and the process proceeds to step S303. In contrast, if the in-cylinder pressure P _A is greater than the reference pressure P ₁ , it is determined that flame propagation combustion has occurred, and the process proceeds to step S304.

As the cylinder pressure P _A in the case that the flame propagation combustion, for detecting the cylinder pressure in the piston near the top dead center in the expansion stroke.

  In step S303, the ECU 41 executes flame propagation combustion misfire control in order to suppress misfire of flame propagation combustion. This flame propagation combustion misfire control will be described later with reference to FIG.

In step S304, the ECU 41 determines whether or not the in-cylinder pressure P _B when the air-fuel mixture in the combustion chamber undergoes self-ignition combustion is smaller than the reference pressure P ₂ . The reference pressure P ₂ is a value larger than the above-described reference pressure P ₁ . If the in-cylinder pressure P _B is smaller than the reference pressure P ₂ , it is determined that the self-ignition combustion in the second half of combustion has misfired, and the process proceeds to step S305. On the other hand, if the in-cylinder pressure P _B is greater than the reference pressure P ₂ , it is determined that self-ignition combustion is taking place, and the process proceeds to step S306.

Note that as the in-cylinder pressure P _B during self-ignition combustion, the in-cylinder pressure in the vicinity of 15 ° after the piston top dead center in the expansion stroke is detected.

  In step S305, the ECU 41 executes self-ignition combustion misfire control in order to suppress misfire of self-ignition combustion. This self-ignition combustion misfire control will be described later with reference to FIG.

  In step 306 and step S307, the ECU 41 determines the knocking occurrence state.

At step S306, ECU 41 determines whether or not the knocking level N is smaller than the reference value N _1. If knock level N is smaller than reference value N ₁ , it is determined that knocking has not occurred, and the process ends. On the contrary, when the knocking level N is larger than the reference value N _1, it is determined that knocking has occurred, the flow goes to step S307.

At step S307, ECU 41 determines whether or not the knocking level N is smaller than the reference value N _2. The reference value N ₂ is a value larger than the above-described reference value N ₁ . If knock level N is smaller than reference value N ₂ , it is determined that weak knocking has occurred, and the process proceeds to step S308. In contrast, when knocking level N is larger than the reference value N ₂ determines that stronger knocking than the weak knocking is occurring, the flow goes to step S309.

  In step S308, the ECU 41 executes weak knocking control in order to suppress the occurrence of weak knocking. This weak knocking control will be described later with reference to FIG.

  In step S309, the ECU 41 executes strong knocking control in order to suppress the occurrence of strong knocking. This strong knocking control will be described later with reference to FIG.

  Correction control of each fuel injection amount executed by the ECU 41 when misfire suppression is performed will be described with reference to FIG. FIG. 14A shows the flame propagation combustion misfire control. FIG. 14B shows the self-ignition combustion misfire control.

  When it is determined that the flame propagation combustion is misfiring in the engine 100, the flame propagation combustion misfire control is executed as shown in FIG.

In step S331, the ECU 41 performs an increase correction by adding the correction value dQf1 _A to the n-paraffin injection amount Qf1.

At step S332, ECU 41 may increase corrected by adding a correction value DQf2 _A to the hydrogen gas injection amount Qf2.

At step S333, ECU 41 performs a decrease correction by subtracting a correction value DQf3 _A from the gasoline injection amount Qf3. This correction value dQf3 _A is set as a value that does not change the total calorific value at the time of air-fuel mixture combustion even if the n-paraffin and hydrogen gas are corrected to increase in quantity.

  When flame propagation combustion in the first half of the combustion of the air-fuel mixture is misfired, the hydrogen gas injection amount is corrected to increase to increase the combustion speed of the air-fuel mixture, and the n-paraffin injection amount is increased to correct the self-ignitability of the air-fuel mixture. To increase. Thereby, flame propagation combustion can be stabilized and self-ignition combustion can be performed more reliably.

ECU41 is constituted to repeat the control of steps S331~S333 until misfires flame propagation combustion can be suppressed, and sets the correction value dQf1 _A ~dQf3 _A of the fuel in accordance with the value of the cylinder pressure P _A You may comprise as follows.

  On the other hand, when it is determined that self-ignition combustion is misfiring in engine 100, self-ignition combustion misfire control is executed as shown in FIG.

In step S351, the ECU 41 adds the correction value dQf1 _B to the n-paraffin injection amount Qf1 to correct the increase.

In step S352, the ECU 41 reduces the correction value dQf3 _B from the gasoline injection amount Qf3 to correct the decrease. This correction value dQf3 _B is set as a value that does not change the total calorific value at the time of air-fuel mixture combustion even when the n-paraffin injection amount is corrected to increase.

  When the self-ignition combustion is misfired, the n-paraffin injection amount is corrected to be increased, and the self-ignition property of the air-fuel mixture is improved, so that the self-ignition combustion can be prevented from misfiring.

The ECU 41 is configured to repeat the control of steps S351 and S352 until self-ignition combustion misfire is suppressed, but is configured to set the correction values dQf1 _B and dQf3 _B according to the value of the in-cylinder pressure P _B. May be.

  Correction control of each fuel injection amount executed by the ECU 41 when knocking occurs will be described with reference to FIG. FIG. 15A shows the weak knocking control. FIG. 15B shows the strong knocking control.

  When it is determined that weak knocking has occurred in engine 100, weak knocking control is executed as shown in FIG.

At step S381, ECU 41 may increase corrected by adding a correction value DQf2 _C to the hydrogen gas injection amount Qf2.

At step S382, ECU 41 performs a decrease correction by subtracting a correction value DQf3 _C from the gasoline injection amount Qf3. This correction value dQf3 _C is set as a value that does not change the total calorific value during the combustion of the air-fuel mixture even if the hydrogen gas injection amount is corrected to increase.

  When weak knocking occurs, the hydrogen gas injection amount is corrected to increase and the combustion speed of the air-fuel mixture is increased, so the combustion period of the air-fuel mixture can be shortened and the occurrence of weak knocking can be suppressed.

The ECU 41 is configured to repeat the control of steps S381 and S382 until the weak knocking is suppressed, and is configured to set the correction value dQf2 _C and the correction value dQf3 _C according to the value of the knock level N. Also good.

  On the other hand, when it is determined that strong knocking has occurred in engine 100, control during strong knocking is executed as shown in FIG.

At step S391, ECU 41 performs a decrease correction by subtracting a correction value DQf1 _D from the injection amount Qf1 of n- paraffins.

At step S392, ECU 41 may increase corrected by adding a correction value DQf2 _D to the hydrogen gas injection amount Qf2.

At step S393, ECU 41 performs a decrease correction by subtracting a correction value DQf3 _C from the gasoline injection amount Qf3. This correction value dQf3 _C is set to a value that does not change the total calorific value at the time of air-fuel mixture combustion even if the n-paraffin injection amount is corrected to decrease and the hydrogen gas injection amount is increased.

  When strong knocking has occurred, the hydrogen gas injection amount is corrected to increase to increase the combustion speed of the air-fuel mixture, and the n-paraffin injection amount is corrected to decrease to reduce the self-ignitability of the air-fuel mixture. Thus, the self-ignition of the air-fuel mixture can be suppressed while shortening the combustion period of the air-fuel mixture, so that the occurrence of strong knocking can be suppressed.

The ECU 41 is configured to repeat the control of steps S391 to S393 until strong knocking is suppressed, but is configured to set the correction values dQf1 _{D to} dQf3 _D for each fuel according to the value of the knock level N. May be.

  As described above, the engine 100 of the present embodiment can obtain the following effects.

  In engine 100, when the engine operating state is in region A, the fuel injection amount is corrected according to the combustion state of the air-fuel mixture, so that the combustion state of the air-fuel mixture can be stabilized.

  The present invention is not limited to the above-described embodiment, and it is obvious that various modifications can be made within the scope of the technical idea.

  In the first embodiment, n-paraffin is injected into the intake passage by the fuel injection valve 22 and hydrogen gas by the fuel injection valve 23. However, these fuels are directly injected into the combustion chamber. Also good. By directly injecting n-paraffin, it is possible to avoid the occurrence of self-ignition before the premixing proceeds sufficiently. Further, by directly injecting hydrogen gas, it is possible to prevent the occurrence of backfire toward the intake passage 15.

  In the second embodiment, the auxiliary combustion chamber 142 is formed by installing a dedicated member or component. However, a recess is provided in the cylinder block 11 or the cylinder head 12, and the auxiliary combustion chamber 142 is formed by the recess. It may be.

In the third embodiment, the knocking determination is performed based on the detection value of the knock sensor 55, but the knocking determination may be performed based on the detection value of the in-cylinder pressure sensor 54. In this case, it is determined that weak knocking has occurred when the amplitude M of the in-cylinder pressure in the in-cylinder pressure waveform in the frequency band peculiar to knocking is larger than the reference value M _{1 and} smaller than the reference value M _2. determines that strong knocking is greater than the reference value M ₂ is generated.

In the third embodiment, the misfire determination is made by comparing the in-cylinder pressure detected by the in-cylinder pressure sensor 54 with the reference pressure. However, the amount of heat generated during combustion is calculated from the detected in-cylinder pressure, and this heat generation is calculated. You may make it determine misfire based on quantity. Then, when the calorific value Q _A calculated based on the in-cylinder pressure P during the period in which the air-fuel mixture undergoes flame propagation combustion is smaller than the reference calorific value Q ₁ , it is determined that the flame propagation combustion has misfired. When the calorific value Q _B calculated based on the in-cylinder pressure P during the self-igniting combustion period is smaller than the reference calorific value Q ₂ , it is determined that the self-igniting combustion has misfired.

Further, since the amount of change in the angular velocity of the crankshaft is smaller than that in the normal state at the time of misfire, the misfire may be determined based on this amount of change in angular velocity. The amount of change in angular velocity can be calculated based on the detection value of the crank angle sensor 52. Then, when the angular velocity change amount Δw _A during the period in which the air-fuel mixture is subjected to flame propagation combustion is smaller than the reference change amount Δw ₁ , it is determined that the flame propagation combustion has misfired. Further, if the angular velocity change amount Δw _B during the self-ignition combustion period is smaller than the reference change amount Δw ₂ , it is determined that the self-ignition combustion has misfired.

Furthermore, an ion current sensor may be provided in the spark plug 25, and misfire determination may be performed based on the ion current at the time of air-fuel mixture combustion. When the air-fuel mixture burns, cations are generated according to the combustion state, so that the ion current sensor detects an ionic current caused by the cations. If the ion current I _A during the period in which the air-fuel mixture is flame-propagating and combustion is smaller than the reference current value I ₁ , it is determined that flame-propagating combustion has misfired. Further, when the ion current I _B of the period of self-ignition combustion is smaller than the reference current value I ₂ determines that the self-ignition combustion misfire has occurred.

  In the first to third embodiments, the intake valve 16 may be driven by a variable valve mechanism. In this case, as shown in FIG. 16, the valve closing timing IVC of the intake valve 16 is advanced to the piston bottom dead center side with respect to the decrease in the engine load Ld. As a result, the effective compression ratio of the engine increases, so that the self-ignitability of n-paraffin can be increased and the self-ignition combustion of the air-fuel mixture can be stabilized.

  In the first to third embodiments, a compression ratio variable mechanism 71 that variably controls the mechanical compression ratio may be provided as shown in FIGS. In this case, as shown in FIG. 17, by increasing the mechanical compression ratio CR of the engine 100 with respect to the decrease in the engine load Ld, the action of the self-ignitability of n-paraffin can be increased, Self-ignition combustion can be stabilized. According to the variable control of the mechanical compression ratio, in addition to stabilizing the self-ignition, it is possible to obtain the effect of improving the thermal efficiency by increasing the mechanical compression ratio.

  In the first to third embodiments, a plurality of fuels having different properties are individually supplied to achieve predetermined autoignition properties and combustion rates. However, a plurality of fuels of different compositions prepared in advance so as to obtain a predetermined autoignition property and combustion speed are stored in individually provided fuel tanks, and these are switched to the engine 100 according to the operating state. You may make it supply.

  In the first to third embodiments, in addition to the fuel tank 31 for storing gasoline, a fuel tank for storing n-paraffin and a fuel tank for storing hydrogen gas are provided, and the fuel stored in each of these fuel tanks is stored in each tank. You may supply to a fuel injection valve.

  As the first fuel, in addition to n-paraffin, a fuel classified as having a high cetane number, such as light oil, dimethyl ether or diethyl ether, can be used.

  As the second fuel, in addition to hydrogen, a fuel having a high laminar combustion speed such as ethylene or acetylene can be used.

It is a schematic block diagram of the engine of 1st Embodiment. It is a flowchart which shows fuel-injection control. It is a driving | operation area | region map for switching of a combustion form. It is a figure which shows the relationship between an engine load and the ratio of the emitted-heat amount of each fuel. It is a figure which shows the relationship between an engine load and the injection amount of each fuel. It is a figure which shows the relationship between an engine load and the ratio of the emitted-heat amount of each fuel. It is a schematic block diagram of the engine of 2nd Embodiment. It is a flowchart which shows fuel-injection control. It is a figure which shows the relationship between an engine load and the ratio of the emitted-heat amount of each fuel. It is a figure which shows the relationship between an engine load and the ratio of the emitted-heat amount of each fuel. It is a figure which shows the relationship between an engine load and the injection amount of hydrogen gas. It is a schematic block diagram of the engine of 3rd Embodiment. It is a flowchart which shows the injection quantity correction | amendment control of each fuel. It is a flowchart which shows the injection quantity correction | amendment control at the time of misfire suppression. It is a flowchart which shows the injection quantity correction | amendment control at the time of knocking suppression. It is an operation map used for variable control of valve timing of an intake valve. It is an operation map used for variable control of a compression ratio.

Explanation of symbols

13 Piston 14 Combustion chamber 141 Main combustion chamber 142 Subcombustion chamber 142a Injection hole 16 Intake valve 161 Valve operating device (valve timing control means)
21 Fuel injection valve (supply means)
22 Fuel injection valve (supply means)
23 Fuel injection valve (supply means)
25 Spark plug (ignition means)
31 Fuel tank 33 Fuel separator 34 Fuel reformer 41 Engine control unit (control means)
51 Accelerometer 52 Crank Angle Sensor 53 Cooling Water Temperature Sensor 54 In-Cylinder Pressure Sensor 55 Knock Sensor 71 Compression Ratio Variable Mechanism Step S302 Flame Propagation Combustion Misfire Determination Means Step S303 Self-ignition Combustion Misfire Determination Means Step S306 Knock Determination Means Step S307 Knocking Strength Determination means

Claims (18)

Including a first fuel having a higher self-ignition property than gasoline, a second fuel having a faster combustion rate than gasoline, and a third fuel having a lower self-ignition property than the first fuel and a slower combustion rate than the second fuel. a supply means for supplying fuel to the air-fuel mixture formed in the combustion chamber but,
Ignition means for igniting the air-fuel mixture;
Control means for controlling the supply means and the ignition means,
Wherein, engine ignited air-fuel mixture by adjusting the feed rate of the fuel to self-ignition combustion after a flame propagation combustion, characterized in that it ignited by the ignition means in the air-fuel mixture in the combustion chamber . 2. The engine according to claim 1, wherein a homogeneous mixture containing each fuel is formed in the entire combustion chamber, and the homogeneous mixture is ignited by the ignition means. Wherein, as the engine load decreases, it increases the supply proportions of the first fuel and second fuel, engine according to claim 2, characterized in that to reduce the feed rate of the third fuel. Further comprising cold state determination means for determining whether the engine is in a cold state,
When it is determined that the engine is in a cold state, the control means increases the supply ratio of the first fuel and the second fuel and decreases the supply ratio of the third fuel than when warming up. The engine according to claim 2 . Flame propagation combustion misfire determination means for determining whether flame propagation combustion is misfired,
Wherein, when the flame propagation combustion misfire has occurred, the supply proportions of the first fuel and the second fuel increases, claim claim 2, characterized in that to reduce the feed rate of the third fuel 4. The engine according to any one of 4 . A self-ignition combustion misfire determination means for determining whether the self-ignition combustion is misfiring,
Wherein, when the self-ignition combustion misfire has occurred, and increases the supply proportions of the first fuel, any of the preceding claims 2, characterized in that to reduce the feed rate of the third fuel The engine according to one. A knocking judging means for judging whether knocking has occurred or not,
Wherein, when the knocking is occurring, any one of claims 6 claims 2 to increase the feed rate of the second fuel, and wherein the reducing the feed rate of the third fuel Engine described in. A knocking strength judging means for judging the strength of knocking when knocking occurs,
Wherein when strong knocking than a reference value has occurred, according to claim 7 to increase the feed rate of the second fuel, and wherein the reducing the supply proportions of the first fuel and the third fuel Engine described in. A main combustion chamber whose volume changes as the piston moves;
A sub-combustion chamber having a constant volume and communicating with the main combustion chamber via the nozzle hole ;
An air-fuel mixture containing a first fuel having a higher autoignition property than gasoline is formed in the main combustion chamber, and an air-fuel mixture containing a second fuel having a higher combustion speed than gasoline is formed in the sub-combustion chamber. Supply means for supplying fuel to
Ignition means for igniting a homogeneous mixture containing the second fuel formed in the auxiliary combustion chamber ;
Control means for controlling the supply means and the ignition means,
The control means includes a first fuel and a first fuel so that the air-fuel mixture in the main combustion chamber undergoes self-ignition combustion after flame propagation combustion based on a flame torch caused by combustion of the air-fuel mixture in the sub-combustion chamber ignited by the ignition means. An engine characterized by adjusting a supply ratio of the second fuel. The supply means has a self-ignitability lower than that of the first fuel, a third fuel having a combustion speed slower than that of the second fuel, and a homogeneous mixture containing the first fuel and the third fuel in the main combustion chamber. The engine according to claim 9 , wherein the engine is supplied into the main combustion chamber so as to be formed. The engine according to claim 10 , wherein the control means increases the supply ratio of the first fuel and decreases the supply ratio of the third fuel as the engine load decreases. The engine according to claim 10 or 11 , wherein the control means increases the supply amount of the second fuel as the engine load decreases. Further comprising cold state determination means for determining whether the engine is in a cold state,
Wherein, when the engine is determined to be in the cold state than during the warm-up increases the supply proportions of the first fuel, claim, characterized in that to reduce the feed rate of the third fuel 10 The engine according to claim 12 . The engine according to claim 13 , wherein the control means increases the supply amount of the second fuel more than when warming up when it is determined that the engine is in a cold state. The engine according to any one of claims 2 to 14 , wherein the control means increases the excess air ratio of the homogeneous mixture as the engine load decreases. The engine according to any one of claims 1 to 15 , wherein the control means adjusts the fuel supply rate when the engine operating state is in a low load and low rotation speed range. As the engine load decreases, claim 16 claim 1, further comprising a valve timing control means to bring the closing timing of the intake valve in the piston bottom dead center timing so that the effective compression ratio is increased The engine according to one. The engine according to any one of claims 1 to 17 , further comprising a variable compression ratio mechanism that increases the mechanical compression ratio of the engine as the engine load decreases.

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