JP4424283B2 - Spark ignition internal combustion engine - Google Patents

Description

  The present invention relates to a knocking suppression technique in a spark ignition type internal combustion engine.

  In a spark ignition type internal combustion engine, it is generally known to retard the ignition timing as a method of suppressing knocking during high-load operation. However, since retarding the ignition timing worsens combustion, leading to a reduction in output and exhaust emissions, there is a need for a technique for suppressing knocking that does not depend on the retarding of the ignition timing.

  Knocking occurs when unburned gas is compressed into burned gas in the end gas region and its temperature and pressure reach autoignition conditions. Therefore, it is considered that knocking can be suppressed if the combustion chamber can be cooled so that the gas temperature in the end gas region does not reach the self-ignition condition.

As a technique for cooling the combustion chamber to lower the gas temperature, for example, as disclosed in Patent Document 1, it is known to inject water directly into the combustion chamber. Water itself has a low temperature, and when it is vaporized, it takes heat (vaporization latent heat) from the surrounding gas, so that the gas temperature in the combustion chamber can be effectively reduced.
JP-A-10-54306 JP 2000-220482 A JP-A-8-177497 JP 2004-346832 A

  However, when water is injected into the combustion chamber, not all of the injected water becomes steam and is discharged from the combustion chamber. Some water adheres to the cylinder wall surface before being vaporized and is mixed with alcohol on the cylinder wall surface. If a part of water is mixed into the alcohol every time the water is injected, the alcohol may become clouded or emulsified, and the lubricating performance of the internal combustion engine may deteriorate.

  The present invention has been made in order to solve the above-described problems, and spark ignition that can suppress knocking by lowering the gas temperature in the combustion chamber without adversely affecting the operation performance of the internal combustion engine. An object is to provide an internal combustion engine.

In order to achieve the above object, the first invention provides
An alcohol injection valve capable of directly injecting alcohol into the combustion chamber;
Control means for injecting alcohol from the alcohol injection valve in accordance with the occurrence of knocking;
It is characterized by having.

According to a second invention, in the first invention,
Means for detecting or predicting knocking,
The control means injects alcohol from the alcohol injection valve when knocking is detected or predicted.

According to a third invention, in the second invention,
The control means is characterized by gradually increasing the amount of alcohol injected from the alcohol injection valve when knocking is detected or predicted even after injection of alcohol.

According to a fourth invention, in the third invention,
The control means stops the increase of the alcohol injection amount when the alcohol injection amount from the alcohol injection valve reaches a predetermined amount, and when knocking is detected or predicted even after the increase of the alcohol injection amount is stopped. The ignition timing is gradually retarded.

According to a fifth invention, in any one of the first to fourth inventions,
A fuel injection valve for injecting alcohol-containing fuel;
Separation supply means for taking out alcohol from the alcohol-containing fuel supplied to the fuel injection valve and supplying the taken alcohol to the alcohol injection valve;
It is characterized by having.

According to a sixth invention, in the fifth invention,
The separation supply unit has a storage unit that stores alcohol taken out from the alcohol-containing fuel, and supplies the alcohol stored in the storage unit to the alcohol injection valve.

A seventh invention is the invention according to any one of the first to sixth inventions,
The alcohol injection valve is characterized by injecting alcohol along an inner wall surface of the combustion chamber.

  According to the first invention, alcohol is injected into the combustion chamber in accordance with the timing of occurrence of knocking, whereby the combustion chamber is cooled by the latent heat of vaporization of alcohol, and the gas temperature can be reduced to suppress knocking. . Since alcohol has a larger latent heat of vaporization per unit weight than water, gasoline, etc., the cooling effect by injecting alcohol is extremely high. Further, as a result of turbulence in the gas in the combustion chamber caused by the injection of alcohol, there is an effect that the combustion speed is increased and knocking is suppressed.

  In addition, when water is injected into the combustion chamber, water that has not been vaporized may be mixed with the lubricating oil, which may cause the lubricating oil to become cloudy or reduce the lubricating performance due to emulsion, but alcohol has a low boiling point. Because it is easy to vaporize, it is unlikely to cause cloudiness or emulsion like in the case of spraying water. That is, according to the first invention, knocking can be suppressed without adversely affecting the lubrication performance of the internal combustion engine as in the case of injecting water.

  According to the second aspect, since alcohol is injected when knocking is actually detected or when knocking is predicted, knocking can be suppressed by using alcohol efficiently.

  According to the third aspect, by gradually increasing the alcohol injection amount until knocking is suppressed, knocking can be reliably suppressed while suppressing the amount of alcohol used.

According to the fourth aspect of the invention, when the alcohol injection amount reaches the specified amount, the knocking suppression method is switched from the increase in the alcohol injection amount to the retard of the ignition timing, so that the alcohol due to excessive consumption of alcohol Knocking can be reliably suppressed while preventing deterioration of exhaust emission due to shortage of the remaining amount or enrichment of the air-fuel ratio.

  According to the fifth aspect, since the alcohol necessary for suppressing knocking can be taken out from the alcohol-containing fuel of the raw fuel, it is not necessary to install the alcohol separately from the raw fuel, and the space can be saved.

  According to the sixth aspect of the invention, the alcohol supplied to the alcohol injection valve is stored in the storage unit, and therefore, when knocking is detected or when knocking is predicted, alcohol is extracted from the alcohol-containing fuel. Without waiting for this, alcohol can be quickly injected into the combustion chamber.

  According to the seventh aspect, by injecting alcohol along the inner wall surface of the combustion chamber, it is possible to effectively cool only the end gas region without cooling the center of the combustion chamber, and more effectively knocking. Can be suppressed.

Embodiment 1 FIG.
The first embodiment of the present invention will be described below with reference to FIGS.

  FIG. 1 is a diagram showing a schematic configuration of a spark ignition type internal combustion engine as Embodiment 1 of the present invention. The internal combustion engine according to the present embodiment is a spark ignition type four-stroke engine using alcohol-containing gasoline as fuel, and has a plurality of cylinders (not shown). The internal combustion engine according to this embodiment includes a cylinder block 6 in which a piston 8 is disposed, and a cylinder head 4 assembled to the cylinder block 6. A space from the upper surface of the piston 8 to the cylinder head 4 forms a combustion chamber 10 of each cylinder.

  A knock sensor 76 is attached to the cylinder block 6. Knock sensor 76 detects a knocking vibration (knocking signal) transmitted from combustion chamber 10 to cylinder block 6 and outputs a signal corresponding to the knocking vibration. As the knock sensor 76, either a resonance type or a non-resonance type may be used.

  An intake passage 20 and an exhaust passage 30 are connected to the combustion chamber 10 of each cylinder. An intake valve 12 for controlling the communication state is provided at a connection portion between the combustion chamber 10 and the intake passage 20, and an exhaust valve 14 for controlling the communication state is provided at a connection portion between the combustion chamber 10 and the exhaust passage 30. ing. A spark plug 16 is attached to the top of the combustion chamber 10 so as to protrude into the combustion chamber 10.

  An air cleaner 22 is provided at the upstream end of the intake passage 20, and air is taken into the intake passage 20 via the air cleaner 22. An air flow meter 72 that outputs a signal corresponding to the amount of intake air is disposed downstream of the air cleaner 22 in the intake passage 20. An electronically controlled throttle 24 is disposed downstream of the air flow meter 72. A gasoline injector 26 for supplying alcohol-containing gasoline as fuel to the combustion chamber 10 is attached to the downstream portion of the intake passage 20. The gasoline injector 26 is provided for each cylinder.

  A catalyst 32 is disposed in the exhaust passage 30. The exhaust gas discharged from the combustion chamber 10 is purified when passing through the catalyst 32 and then discharged into the atmosphere. An oxygen sensor 78 that outputs a signal corresponding to the oxygen concentration in the exhaust gas is disposed upstream of the catalyst 32 in the exhaust passage 30.

  The internal combustion engine according to the present embodiment includes an alcohol injector (alcohol injection valve) 40 capable of directly injecting alcohol into the combustion chamber 10. The alcohol injector 40 is attached to the cylinder head 4 so that its injection port faces the inside of the combustion chamber 10. The alcohol injector 40 is provided for each cylinder. FIG. 2 is a view in which a form of spraying alcohol by the alcohol injector 40 is viewed in a cross section of the combustion chamber 10. As shown in this figure, the alcohol injector 40 injects the alcohol along the inner wall surface 10 a of the combustion chamber 10 rather than toward the center of the combustion chamber 10.

  The alcohol injected by the alcohol injector 40 is alcohol fractionated from alcohol-containing gasoline, such as ethanol or methanol. The internal combustion engine according to this embodiment includes a fractionator 50 for fractionating alcohol from alcohol-containing gasoline. The fractionator 50 is connected to a fuel tank 42 that stores alcohol-containing gasoline by a fuel supply line 52. The alcohol-containing gasoline in the fuel tank 42 is sucked up by a pump 44 disposed in the fuel supply line 52 and supplied to the fractionator 50. The pump 44 may be a mechanical pump driven by the internal combustion engine body 2 or an electric pump driven by a motor.

  Cooling water before returning to the radiator 60 through the engine body 2 is introduced into the fractionator 50. In the fractionator 50, heat exchange is performed between the alcohol-containing gasoline supplied to the fractionator 50 by the pump 44 and the cooling water after passing through the engine body 2. Since the boiling point of alcohol (ethanol or methanol in this embodiment) is 90 ° C. or less, the alcohol is fractionated from the alcohol-containing gasoline by exchanging heat with cooling water.

  The alcohol injector 40 is connected to the fractionator 50 by an alcohol supply line 56. A pump 48 is disposed in the alcohol supply line 56. The alcohol fractionated from the alcohol-containing gasoline in the fractionator 50 is sucked up by the pump 48 and compressed to a predetermined pressure higher than the combustion gas pressure in the combustion chamber 10 before being supplied to the alcohol injector 40. The pump 48 may be a mechanical pump driven by the internal combustion engine body 2 or an electric pump driven by a motor. In this embodiment, the fractionator 50, the alcohol supply line 56, and the pump 48 constitute the “separation supply means” according to the first invention. The pump 48 is provided with a relief valve (not shown). The relief valve opens when the alcohol pressure on the downstream side of the pump 48 reaches a predetermined relief pressure. Connected to the relief valve is a return line 58 for returning alcohol released from the alcohol supply line 56 to the fuel tank 42 when the relief valve is opened.

  The gasoline injector 26 is connected to the fractionator 50 by a gasoline supply line 54. A pump 46 is disposed in the gasoline supply line 54. The alcohol-containing gasoline obtained by fractionating some of the alcohol contained therein is sucked up from the fractionator 50 by the pump 46 and supplied to the gasoline injector 26. The pump 46 may be a mechanical pump driven by the internal combustion engine body 2 or an electric pump driven by a motor. The pump 46 is provided with a relief valve (not shown). The relief valve opens when the gasoline pressure on the downstream side of the pump 46 reaches a predetermined relief pressure. Connected to the relief valve is a return line 58 for returning alcohol-containing gasoline released from the gasoline supply line 54 to the fuel tank 42 when the relief valve is opened.

  Further, the internal combustion engine according to the present embodiment includes an ECU (Electronic Control Unit) 70 as its control device. Various devices such as the spark plug 16, the throttle 24, the gasoline injector 26, and the alcohol injector 40 are connected to the output side of the ECU 70. Various sensors such as a crank angle sensor 74 that outputs a signal corresponding to the rotation angle of the crankshaft 18 are connected to the input side of the ECU 70 in addition to the knock sensor 76, the air flow meter 72, and the oxygen sensor 78 described above. Yes. The ECU 70 controls each device according to a predetermined control program based on the output of each sensor.

  One of the controls of the internal combustion engine executed by the ECU 70 is knocking suppression control for suppressing knocking. The ECU 70 detects the occurrence of knocking based on a signal output from the knock sensor 76, and executes knocking suppression control. The contents of the knocking suppression control executed by the ECU 70 in the present embodiment can be described with reference to FIG. FIG. 3 is a flowchart showing a routine of knocking suppression control executed by the ECU 70. Since knocking is related to the ignition timing, in this routine, the knocking suppression control is executed together with the ignition timing control.

  In the first step 100 of the routine shown in FIG. 3, the current engine speed and throttle opening are acquired. The engine speed can be obtained from the signal of the crank angle sensor 74, and the throttle opening can be obtained from a command value supplied from the ECU 70 to the electronic control throttle 24. In the next step 102, an appropriate ignition timing corresponding to the acquired engine speed and throttle opening, that is, an ignition timing (MBT) at which the output is maximized, is obtained, and the internal combustion engine is operated at the appropriate ignition timing.

  In step 104, it is determined whether or not knocking has occurred based on a signal output from the knock sensor 76. If knocking has not occurred, this routine ends. If knocking has occurred, the processing of steps 106 to 110 is executed as knocking suppression control.

  In step 106, alcohol is directly injected into the combustion chamber 10 from the alcohol injector 40 in accordance with the timing of occurrence of knocking (time when knocking is most likely to occur after TDC). The alcohol injected from the alcohol injector 40 is vaporized by the combustion heat in the combustion chamber 10, and burns in the same manner as the alcohol-containing gasoline that is the fuel. The ignition timing is unchanged, and the operation at the appropriate ignition timing set in step 102 is continued.

  Alcohol has a lower temperature than the surrounding combustion gas and takes heat away from the surrounding gas when vaporized. Moreover, the latent heat of vaporization per unit weight of alcohol is extremely higher than that of water or gasoline. Therefore, by directly injecting alcohol into the combustion chamber 10, the inside of the combustion chamber 10 can be effectively cooled, and knocking can be suppressed by lowering the gas temperature. Moreover, since the alcohol is injected along the inner wall surface 10a of the combustion chamber 10, only the end gas region can be effectively cooled without cooling the center of the combustion chamber 10 and deteriorating combustion. Further, as a result of the turbulence in the gas in the combustion chamber 10 caused by the injected alcohol particles, there is an effect that the combustion speed is increased and knocking is suppressed.

  In the next step 108, the presence or absence of knocking after alcohol injection is determined based on the signal output from the knock sensor 76. If knocking still occurs after alcohol injection, the setting of the amount of alcohol injected from the alcohol injector 40 is corrected to the increase side in the next step 110. In the next process of step 106, the increased amount of alcohol is directly injected from the alcohol injector 40 into the combustion chamber 10. By increasing the alcohol injection amount, the cooling effect of the combustion chamber 10 is enhanced and the knocking suppression effect is also improved. The increase in the alcohol injection amount is continued until knocking does not occur in the determination in step 108, and this routine ends when knocking does not occur.

  As described above, by executing the routine shown in FIG. 3, the gas temperature in the combustion chamber 10 can be lowered by the cooling effect due to the latent heat of vaporization of alcohol, and knocking can be suppressed. Further, since the alcohol injection amount is gradually increased until knocking is suppressed, knocking can be reliably suppressed while suppressing the amount of alcohol used.

  In addition, when water is injected into the combustion chamber 10 as in the prior art, water that has not been vaporized is mixed with the lubricating oil (engine oil), thereby reducing the lubricating performance due to the cloudiness of the lubricating oil and the emulsion. However, if alcohol is injected as in this embodiment, alcohol has a low boiling point and is easy to vaporize, so there is a possibility that the lubricating oil may become cloudy or emulsified like water is injected. Is low. That is, according to the internal combustion engine according to the present embodiment, there are advantages that the influence on the lubrication performance of the internal combustion engine is small as in the case of injecting water, and knocking can be more effectively suppressed.

  Furthermore, according to the internal combustion engine according to the present embodiment, the alcohol necessary for suppressing knocking can be fractionated from the alcohol-containing gasoline as the raw fuel, so there is an advantage that it is not necessary to separately install alcohol. Since the amount of alcohol necessary for suppressing knocking is small compared to the fuel injection amount, even if the alcohol is fractionated from the raw fuel, the alcohol content of the raw fuel is not significantly changed.

Embodiment 2. FIG.
Next, a second embodiment of the present invention will be described with reference to FIG.

  The spark ignition type internal combustion engine as the second embodiment of the present invention can be realized by causing the ECU 70 to execute the routine shown in FIG. 4 instead of the routine shown in FIG. 3 in the first embodiment. In the routine shown in FIG. 4, processes having the same contents as those in the routine shown in FIG. In addition, overlapping description of the processing having already been described is omitted.

  The feature of the routine shown in FIG. 4 is that a restriction is imposed on the amount of alcohol injected from the alcohol injector 40. In other words, while the knocking occurs, the alcohol injection amount is gradually increased, but when the alcohol injection amount reaches the specified amount, the subsequent increase is prohibited and the alcohol injection amount is limited to the specified amount. It is said. Further, when knocking continues even after the increase in the alcohol injection amount is stopped, the ignition timing is retarded as knocking suppression control.

  Specifically, the routine shown in FIG. 4 will be described. In step 108, when it is determined that knocking still occurs after the alcohol injection, prior to the correction of the alcohol injection amount to the increase side by the processing of step 110, The process of step 112 is performed. In step 112, it is determined whether or not the current alcohol injection amount has reached a specified amount. The alcohol injection amount may be directly measured with a flow meter, or may be calculated from the injector driving time and pressure. The prescribed amount of the alcohol injection amount is preferably determined in consideration of the alcohol fractionation speed in the fractionator 50 and the influence of the alcohol injection on the exhaust emission.

  If the result of determination in step 112 is that the alcohol injection amount has not yet reached the specified amount, the setting of the alcohol amount injected from the alcohol injector 40 is corrected to the increase side (step 110). In the next process of step 106, the increased amount of alcohol is directly injected from the alcohol injector 40 into the combustion chamber 10. The increase in the alcohol injection amount is continued until knocking does not occur in the determination in step 108 or until the alcohol injection amount reaches the specified amount in the determination in step 112.

  As a result of the determination in step 112, when the alcohol injection amount reaches the specified amount, the subsequent increase in the alcohol injection amount is prohibited and the alcohol injection amount is limited to the specified amount. Then, step 114 is selected as the next processing. In step 114, the ignition timing is corrected to the retard side by a predetermined angle. That is, after the alcohol injection amount reaches the specified amount, knocking is suppressed by retarding the ignition timing.

  In the next step 116, the presence or absence of knocking after retarding the ignition timing is determined based on the signal output from the knock sensor 76. If knocking still occurs after the ignition timing is retarded, the process of step 114 is performed again, and the ignition timing is further corrected to the retard side by a predetermined angle. The retard of the ignition timing is continued until knocking does not occur in the determination of step 116, and this routine ends when knocking does not occur.

  As described above, according to the internal combustion engine according to the present embodiment, when the alcohol injection amount reaches the specified amount, the knocking suppression method is switched from the increase in the alcohol injection amount to the retard of the ignition timing. Further, knocking can be reliably suppressed while preventing a shortage of alcohol remaining due to the alcohol consumption exceeding the fractionation capability of the fractionator 50 and deterioration of exhaust emission due to enrichment of the air-fuel ratio. Further, since the gas temperature in the combustion chamber 10 can be lowered by the alcohol injection, the retard amount of the ignition timing is small, so that the decrease in output and the deterioration of exhaust emission due to the retard of the ignition timing can be suppressed. .

Embodiment 3 FIG.
Next, a third embodiment of the present invention will be described with reference to FIGS.

  FIG. 5 is a diagram showing a schematic configuration of a spark ignition type internal combustion engine as the third embodiment of the present invention. Like the internal combustion engine according to the first embodiment, the internal combustion engine according to the present embodiment is a spark ignition type four-stroke engine using alcohol-containing gasoline as fuel. In FIG. 5, the same components as those in the internal combustion engine shown in FIG. In addition, overlapping description of the components already described is omitted.

  First, differences in configuration between the internal combustion engine according to the present embodiment and the internal combustion engine according to the first embodiment will be described. The internal combustion engine according to this embodiment includes an alcohol spare tank 64 on an alcohol supply line 56 that connects the alcohol injector 40 and the fractionator 50. The pump 48 is disposed between the alcohol preliminary tank 64 and the alcohol injector 40. With such a configuration, the alcohol fractionated by the fractionator 50 is temporarily stored in the alcohol preliminary tank 64. At the time of alcohol injection, the alcohol is sucked up from the alcohol preliminary tank 64 by the pump 48 and supplied to the alcohol injector 40.

  Further, the internal combustion engine according to the present embodiment includes a gasoline spare tank 62 on a gasoline supply line 54 that connects the gasoline injector 26 and the fractionator 50. The pump 46 is disposed between the gasoline spare tank 62 and the gasoline injector 26. With such a configuration, the alcohol-containing gasoline obtained by fractionating some of the alcohol contained therein by the fractionator 50 is temporarily stored in the gasoline spare tank 62. At the time of gasoline injection, the alcohol-containing gasoline is sucked up from the gasoline spare tank 62 by the pump 46 and supplied to the gasoline injector 26.

  Further, the internal combustion engine according to this embodiment includes a bypass line 68 that bypasses the fractionator 50 and directly connects the fuel tank 42 and the gasoline injector 26. A pump 66 is disposed in the bypass line 68. When this pump 66 is operated, alcohol-containing gasoline as fuel can be supplied directly from the fuel tank 42 to the gasoline injector 26. The pump 66 may be a mechanical pump driven by the internal combustion engine body 2 or an electric pump driven by a motor.

  As described above, the internal combustion engine according to the present embodiment includes the alcohol spare tank 64, the gasoline spare tank 62, the bypass line 68, and the pump 66 that are not provided in the internal combustion engine according to the first embodiment. The other configuration is the same as that of the internal combustion engine according to the first embodiment. The form of alcohol sprayed by the alcohol injector 40 is the same as that in the first embodiment, and the alcohol is injected along the inner wall surface of the combustion chamber 10.

  Next, the knocking suppression control executed by the ECU 70 in the internal combustion engine according to the present embodiment will be described. FIG. 6 is a flowchart illustrating a routine of knocking suppression control that is executed by the ECU 70. Since knocking is related to the ignition timing, in this routine, the knocking suppression control is executed together with the ignition timing control.

  In the first step 200 of the routine shown in FIG. 6, the current engine speed and throttle opening are acquired. The engine speed can be obtained from the signal of the crank angle sensor 74, and the throttle opening can be obtained from a command value supplied from the ECU 70 to the electronic control throttle 24. In the next step 202, an appropriate ignition timing according to the acquired engine speed and throttle opening, that is, an ignition timing (MBT) at which the output becomes maximum is obtained. Then, alcohol-containing gasoline (mixed fuel) is injected from the gasoline injector 26 at an appropriate fuel injection timing, and the ignition plug 16 is ignited at an appropriate ignition timing.

  In the internal combustion engine of the present embodiment, two lines 52 and 54 that pass through the fractionator 50 and two lines 68 that bypass the fractionator 50 are provided as lines for supplying fuel from the fuel tank 42 to the gasoline injector 26. There is a line. The ECU 70 has a function of selectively switching these two lines. In a situation where knocking has not occurred, the bypass line 68 is selected, and alcohol-containing gasoline is supplied directly from the fuel tank 42 to the gasoline injector 26. When the bypass line 68 is selected, the pumps 44, 46 and 48 are stopped.

  In step 204, it is determined whether or not knocking has occurred based on a signal output from the knock sensor 76. If knocking has not occurred, this routine ends. If knocking has occurred, the processing of steps 206 to 214 is executed as knocking suppression control.

  In step 206, the operation of the pumps 44, 46 and 48 is started, and conversely, the operation of the pump 66 is stopped. As a result, the line for supplying fuel to the gasoline injector 26 is switched from the bypass line 68 to the lines 52 and 54 via the fractionator 50. At the next fuel injection, the alcohol-containing gasoline in the gasoline spare tank 62 is sucked up by the pump 46 and supplied to the gasoline injector 26.

  In step 208, alcohol is directly injected into the combustion chamber 10 from the alcohol injector 40 in accordance with the timing of occurrence of knocking (time when knocking is most likely to occur after TDC). Alcohol stored in the alcohol reserve tank 64 is supplied to the alcohol injector 40. The alcohol injected from the alcohol injector 40 is vaporized by the combustion heat in the combustion chamber 10, and burns in the same manner as the alcohol-containing gasoline that is the fuel. Note that the ignition timing is unchanged, and the operation at the appropriate ignition timing set in step 202 is continued.

  In addition, when the operation of the pump 44 is started, alcohol-containing gasoline is supplied from the fuel tank 42 to the fractionator 50. In step 210, the alcohol-containing gasoline is fractionated in the fractionator 50. Alcohol fractionated from the alcohol-containing gasoline is stored in the alcohol spare tank 64. The remaining alcohol-containing gasoline from which alcohol has been fractionated is stored in the gasoline reserve tank 62.

  In the next step 212, the presence or absence of knocking after alcohol injection is determined based on the signal output from the knock sensor 76. If knocking still occurs after alcohol injection, the setting of the amount of alcohol injected from the alcohol injector 40 is corrected to the increase side in the next step 214. Moreover, the fraction of alcohol in the fractionator 50 is also increased in accordance with the increase in the amount of alcohol. In the next process of step 208, the increased amount of alcohol is directly injected from the alcohol injector 40 into the combustion chamber 10. By increasing the alcohol injection amount, the cooling effect of the combustion chamber 10 is enhanced and the knocking suppression effect is also improved. The increase in the alcohol injection amount is continued until knocking does not occur in the determination in step 212, and this routine ends when knocking does not occur.

  As described above, according to the internal combustion engine according to the present embodiment, since alcohol is stored in the alcohol preliminary tank 64, when knocking occurs, the alcohol is fractionated from the alcohol-containing gasoline in the fractionator 50. Without waiting for this, alcohol can be rapidly injected into the combustion chamber 10. According to the internal combustion engine according to the present embodiment, even if the fractionation is started after the knocking is detected, the fractionator 50 does not always have to be operated, and energy for fractionation is saved. can do.

  However, in order to perform alcohol injection using the alcohol in the alcohol reserve tank 64, it is necessary to always store a sufficient amount of alcohol in the alcohol reserve tank 64. Since the alcohol-containing gasoline in the gasoline reserve tank 62 is used for fuel injection after the line is switched until the pump 44 is started, a sufficient amount of alcohol-containing gasoline is always in the gasoline reserve tank 62. It needs to be stored. Therefore, the ECU 70 also executes the storage amount optimization control described below in conjunction with the knocking suppression control in order to keep the storage amount in the spare tanks 62 and 64 appropriately.

  FIG. 7 is a flowchart showing a storage amount optimization control routine executed by the ECU 70. In the first step 300 of the routine shown in FIG. 7, the current temperature of the cooling water and the amount of storage in each of the reserve tanks 62 and 64 are acquired. The cooling water temperature acquired here is the temperature of the cooling water before leaving the engine body 2 and entering the fractionator 50. The coolant temperature can be acquired from a signal from a temperature sensor (not shown). The amount of storage in each of the reserve tanks 62 and 64 can be acquired by measuring the liquid level, for example.

  In the next step 302, the acquired cooling water temperature is compared with the boiling point of the alcohol. If the cooling water temperature has not risen sufficiently, such as during a cold start, and is below the alcohol boiling point, this routine ends. In this case, even if the separator 50 is operated, the heat exchange necessary to separate the alcohol from the alcohol-containing gasoline cannot be performed. If the cooling water temperature is higher than the alcohol boiling point, the determination in step 304 is made.

  In step 304, it is determined whether or not the amount of alcohol stored in the alcohol reserve tank 64 is smaller than a reference value, and whether or not the amount of gasoline stored in the gasoline reserve tank 62 is smaller than a reference value. Each reference value is determined in consideration of the fractionation speed in the fractionator 50 and the injection amount of each injector 26, 40. As a result of the determination, when the amount of storage in any of the reserve tanks 62 and 64 is equal to or greater than the respective reference value, this routine ends.

  As a result of the determination in step 304, when the stored amount is smaller than the reference value in either one of the two spare tanks 62 and 64, the operation of the pump 44 is started regardless of whether knocking has occurred or not. Then, the alcohol-containing gasoline is supplied from the fuel tank 42 to the fractionator 50. Then, the alcohol-containing gasoline is fractionated in the fractionator 50 (step 306). Alcohol fractionated from the alcohol-containing gasoline is stored in the alcohol reserve tank 64, and the remaining alcohol-containing gasoline from which alcohol has been fractionated is stored in the gasoline reserve tank 62. The fractional distillation of the alcohol-containing gasoline is continued until the storage amount becomes equal to or higher than the reference value in the determination in step 304, and the routine ends when the amount becomes higher than the reference value.

  By executing the above routine, a sufficient amount of alcohol can always be stored in the alcohol preliminary tank 64. Thereby, alcohol can be promptly supplied to the alcohol injector 40 when knocking occurs. In addition, since a sufficient amount of alcohol-containing gasoline can be always stored in the gasoline reserve tank 62, a necessary amount of alcohol is contained after the line is switched until the operation of the pump 44 is started. Gasoline can be supplied to the gasoline injector 26.

Others.
Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and modifications can be made without departing from the spirit of the present invention. For example, the following modifications may be made.

  In the above embodiment, knocking is detected based on a signal output from the knock sensor 76. However, the occurrence of knocking can also be predicted in advance from a change in the in-cylinder pressure. If knocking is predicted, the occurrence of knocking can be prevented in advance by directly injecting alcohol from the alcohol injector 40 into the combustion chamber 10. Further, when the internal combustion engine enters a specific operation state, for example, a high-load operation state, alcohol may be directly injected from the alcohol injector 40 into the combustion chamber 10 regardless of whether knocking has occurred. This also prevents knocking from occurring in advance.

  In the configuration shown in FIGS. 1 and 5, a heat exchanger may be disposed between the pump 48 and the alcohol injector 40. It is preferable to introduce the cooling water cooled by the radiator 60 into the heat exchanger. According to this, the alcohol whose temperature has been increased by being compressed by the pump 48 can be cooled by heat exchange with the cooling water, and the cooling effect when the alcohol is injected into the combustion chamber 10 can be enhanced.

  1 and 5, exhaust gas may be introduced into the fractionator 50 instead of the cooling water. Since the exhaust gas has a high temperature, alcohol can be fractionated from the alcohol-containing gasoline by exchanging heat between the exhaust gas and the alcohol-containing gasoline.

  In the above embodiment, the present invention is applied to a spark ignition type internal combustion engine that uses alcohol-containing gasoline as a fuel. However, the present invention is a spark ignition that uses a normal fuel (such as gasoline) that does not contain alcohol. The present invention can also be applied to an internal combustion engine. In that case, an alcohol tank storing alcohol may be mounted separately from the fuel tank, and the alcohol may be supplied directly from the alcohol tank to the alcohol injector. Although it is necessary to separately install an alcohol tank, the knocking suppression effect obtained by alcohol injection is the same as in the above embodiment.

1 is a diagram showing a schematic configuration of a spark ignition type internal combustion engine as Embodiment 1 of the present invention. FIG. It is a figure which shows the spraying form of alcohol by the alcohol injector shown in FIG. It is a flowchart shown about the routine of the knocking suppression control performed in Embodiment 1 of this invention. It is a flowchart shown about the routine of the knocking suppression control performed in Embodiment 2 of this invention. It is a figure which shows schematic structure of the spark ignition type internal combustion engine as Embodiment 3 of this invention. It is a flowchart shown about the routine of the knocking suppression control performed in Embodiment 3 of this invention. It is a flowchart shown about the routine of the storage amount optimization control performed in Embodiment 3 of this invention.

Explanation of symbols

4 Cylinder head 6 Cylinder block 8 Piston 10 Combustion chamber 16 Spark plug 20 Intake passage 26 Gasoline injector 30 Exhaust passage 40 Alcohol injector 42 Fuel tank 44, 46, 48, 66 Pump 50 Fractionator 52 Fuel supply line 54 Gasoline supply line 56 Alcohol supply line 58 Return line 60 Radiator 62 Gasoline spare tank 64 Alcohol spare tank 68 Bypass line 70 ECU
74 Crank angle sensor 76 Knock sensor

Claims (2)

An alcohol injection valve capable of directly injecting alcohol into the combustion chamber;
Control means for injecting alcohol from the alcohol injection valve in accordance with the occurrence of knocking;
A fuel injection valve for injecting alcohol-containing fuel;
Separation supply means for taking out alcohol from the alcohol-containing fuel supplied to the fuel injection valve and supplying the taken alcohol to the alcohol injection valve;
A spark ignition type internal combustion engine comprising: 2. The spark according to claim 1 , wherein the separation supply unit has a storage unit that stores alcohol taken out from the alcohol-containing fuel, and supplies the alcohol stored in the storage unit to the alcohol injection valve. Ignition internal combustion engine.

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