WO2008065936A1

WO2008065936A1 - Alcohol-fuel internal combustion engine

Info

Publication number: WO2008065936A1
Application number: PCT/JP2007/072496
Authority: WO
Inventors: Daisuke Uchida
Original assignee: Toyota Jidosha Kabushiki Kaisha
Priority date: 2006-11-27
Filing date: 2007-11-21
Publication date: 2008-06-05
Also published as: JP2008133726A

Abstract

An alcohol-fuel internal combustion engine in which catalyst deterioration can be prevented by lowering the temperature of the exhaust gas while diminishing wasteful energy consumption. An alcohol and a fossil fuel are normally supplied according to a given standard mixing proportion. However, when the temperature of the catalyst has exceeded a given standard temperature or is expected to exceed the standard temperature, the alcohol is fed in a larger amount than the feed amount determined from the standard mixing proportion.

Description

Specification

Alcohol fuel internal combustion engine

Technical field

TECHNICAL FIELD [0001] The present invention relates to an alcohol fuel internal combustion engine that uses a mixed fuel in which alcohol and fossil fuel are mixed.

Background art

In recent years, a mixed fuel obtained by mixing alcohol and fossil fuel has attracted attention as an alternative fuel for fossil fuels such as gasoline and light oil. Patent Documents 2 and 3 disclose techniques related to an alcohol fuel internal combustion engine using such a fuel. The techniques disclosed in Patent Documents 2 and 3 are specifically related to an exhaust gas purification technique in an alcohol fuel internal combustion engine.

[0003] Alcohol-fueled internal combustion engines also use a catalyst for purification of exhaust gas. The catalyst activates its purifying ability as the temperature rises. If the temperature rises too high, precious metal sintering occurs and the performance deteriorates. The temperature of the catalyst rises as the catalyst receives heat from the exhaust gas. Therefore, in order to prevent the deterioration of the catalyst, such as is necessary force ^s suppress the temperature of the exhaust gas flowing into the catalyst so that the catalyst from overheating.

[0004] Patent Document 1 discloses a technique for preventing deterioration of a catalyst due to overheating.

In the technique disclosed in Patent Document 1, when the operating range of the internal combustion engine is in a specific high temperature range (catalyst degradation high temperature range), the fuel injection amount is increased from an amount determined from the target air-fuel ratio. When fuel is vaporized, it takes heat (vaporization latent heat) from the surrounding gas. Therefore, if the fuel injection amount is increased, the latent heat of vaporization can be increased accordingly, and the gas temperature in the combustion chamber can be effectively reduced.

Patent Document 1: Japanese Unexamined Patent Publication No. 2006-70891

Patent Document 2: Japanese Patent Laid-Open No. 2-199214

Patent Document 3: Japanese Utility Model Publication No. 3-19420

Disclosure of the invention Problems to be solved by the invention

[0005] However, the fuel increased in the catalyst degradation high temperature region in the technique described in Patent Document 1 is effective for cooling the exhaust gas, but does not contribute to the output of the internal combustion engine. That is, the energy that the fuel has is wasted. Force S that needs to be surely prevented from deterioration of the catalyst due to overheating S, want to minimize wasteful energy consumption

[0006] The present invention has been made to solve the above-described problems, and relates to an alcohol-fueled internal combustion engine capable of preventing deterioration of a catalyst by lowering exhaust temperature while suppressing wasteful energy consumption.

Means for solving the problem

[0007] In order to achieve the above object, the first invention includes a catalyst for purifying exhaust gas generated by combustion of the mixed fuel by burning a mixed fuel in which alcohol and fossil fuel are mixed. Alcohol fuel internal combustion engine,

Supply means for supplying alcohol and fossil fuel in accordance with a predetermined basic mixing ratio; and when the temperature of the catalyst exceeds a predetermined upper limit temperature or when it is predicted that the upper limit temperature is exceeded, the alcohol supply amount is set to Alcohol supply amount correction means for increasing the supply amount determined from

It is characterized by having!

[0008] The second invention is the same as the first invention,

The alcohol supply amount correction means predicts the temperature of the catalyst under each supply amount of alcohol and fossil fuel determined from the basic mixing ratio, and the alcohol supply amount increases as the predicted temperature is higher than the upper limit temperature. It is characterized by increasing the amount correction.

[0009] A third invention is the first or second invention,

It is further characterized by further comprising fossil fuel supply amount correction means for reducing the fossil fuel supply amount from the supply amount determined from the basic mixing ratio so that the excess air ratio does not change before and after the correction of the alcohol supply amount.

[0010] A fourth invention is the third invention, in which

The fuel supply means may be configured so that the excess air ratio is constant or substantially constant. It is characterized by supplying alcohol and fossil fuel according to the combined ratio! /.

[0011] A fifth invention is the invention according to any one of the first to fourth inventions,

It further comprises an intake air amount adjusting means for adjusting the intake air amount so that the torque of the internal combustion engine does not change before and after the correction of the alcohol supply amount.

[0012] A sixth invention is the first or second invention,

The fossil fuel supply amount correction means further reduces the fossil fuel supply amount from the supply amount determined from the basic mixing ratio so that the torque of the internal combustion engine does not change before and after the correction of the alcohol supply amount. It is said.

[0013] A seventh invention is the invention according to any one of the first to fourth inventions,

It further comprises ignition timing adjusting means for adjusting the ignition timing so that the torque of the internal combustion engine does not change before and after the correction of the alcohol supply amount.

[0014] In order to achieve the above object, an eighth invention comprises a catalyst for purifying exhaust gas generated by combustion of the mixed fuel by burning a mixed fuel in which alcohol and fossil fuel are mixed. Alcohol fuel internal combustion engine,

Fuel supply means for supplying a mixed fuel obtained by mixing alcohol and fossil fuel;

Alcohol concentration correction means for making the concentration of alcohol in the mixed fuel higher than a predetermined basic alcohol concentration when the temperature of the catalyst exceeds a predetermined upper limit temperature or when it is expected to exceed the upper limit temperature; ,

It is characterized by having!

[0015] A ninth invention is the eighth invention, wherein

The alcohol concentration correction means predicts the temperature of the catalyst under the basic alcohol concentration, and increases the alcohol concentration correction as the predicted temperature is higher than the upper limit temperature. Les.

[0016] The tenth invention is the eighth or ninth invention, wherein

It further comprises fuel supply amount correction means for increasing the supply amount of the mixed fuel so that the excess air ratio does not change before and after the correction of the alcohol concentration. [0017] An eleventh aspect of the invention is the tenth aspect of the invention,

The fuel supply means supplies the alcohol and the fossil fuel according to the basic mixing ratio so that the excess air ratio is constant or substantially constant.

[0018] A twelfth invention is any one of the eighth to eleventh inventions,

It further comprises an intake air amount adjusting means for adjusting the intake air amount so that the torque of the internal combustion engine does not change before and after the correction of the alcohol concentration.

[0019] In a thirteenth invention according to the eighth or ninth invention,

It is further characterized by further comprising a fuel supply amount correction means for increasing the supply amount of the mixed fuel so that the torque of the internal combustion engine does not change before and after the correction of the alcohol concentration.

[0020] The fourteenth invention is the invention according to any one of the eighth to eleventh inventions,

It further comprises ignition timing adjusting means for adjusting the ignition timing so that the torque of the internal combustion engine does not change before and after the correction of the alcohol concentration. The invention's effect

[0021] According to the first invention, the supply amount of alcohol is increased in a situation where the catalyst may be deteriorated due to overheating. By increasing the amount of alcohol supplied, the combustion chamber can be cooled by the latent heat of vaporization of alcohol. Alcohol contains oxygen in its composition, so it burns quickly. For this reason, the gas temperature in the combustion chamber when the exhaust valve is opened can be relatively lowered. As a result, it is possible to reduce the temperature of the exhaust gas flowing into the catalyst. Compared to fossil fuels, alcohol has a large latent heat of vaporization per unit weight! /, So compared to increasing the fossil fuel supply amount! /, An increase in amount can provide the same cooling effect. it can. Moreover, since alcohol generates less heat per unit weight than fossil fuel, much less energy is wasted to obtain the same cooling effect than when fossil fuel is increased. . That is, according to the first aspect of the invention, it is possible to suppress waste of energy while reliably preventing deterioration of the catalyst due to overheating. [0022] According to the second invention, the risk of catalyst deterioration due to overheating is high! /, And the increase in the amount of alcohol supplied is increased, so that deterioration of the catalyst due to overheating can be more reliably prevented. .

[0023] According to the third invention, the fossil fuel supply amount is reduced in accordance with the increase in the alcohol supply amount, so that the change in the excess air ratio can be prevented, and the emission due to the change in the excess air ratio can be prevented. It is possible to prevent the catalyst from being deteriorated due to overheating without deteriorating the catalyst.

[0024] According to the fourth aspect of the invention, the purification efficiency in the catalyst is maintained by controlling the supply amounts of alcohol and fossil fuel so that the excess air ratio is always kept constant or substantially constant. Touch with force S.

[0025] According to the fifth aspect, the intake air amount is adjusted in accordance with the increase in the alcohol supply amount, whereby the torque change of the internal combustion engine can be prevented, and the drivability deteriorates due to the torque change. It is possible to prevent deterioration of the catalyst due to overheating without incurring.

[0026] According to the sixth aspect of the invention, the fossil fuel supply amount is reduced in accordance with the increase in the alcohol supply amount, so that the torque change of the internal combustion engine can be prevented, and the drivability deteriorates due to the torque change. It is possible to prevent deterioration of the catalyst due to overheating without incurring.

[0027] According to the seventh invention, the ignition timing is adjusted in accordance with the increase in the alcohol supply amount, whereby the torque change of the internal combustion engine can be prevented and the drivability is deteriorated due to the torque change. It is possible to prevent deterioration of the catalyst due to overheating.

[0028] According to the eighth invention, in a situation where there is a risk of catalyst deterioration due to overheating, the concentration of alcohol in the mixed fuel is corrected to increase. Since alcohol has a large latent heat of vaporization per unit weight, the combustion chamber can be cooled by the latent heat of vaporization of alcohol by increasing the concentration of alcohol. Alcohol contains oxygen in its composition, so it burns quickly. For this reason, the gas temperature in the combustion chamber when the exhaust valve is opened can be made relatively low. As a result, it is possible to reduce the temperature of the exhaust gas flowing into the catalyst. Furthermore, since alcohol generates less heat per unit weight than fossil fuel, the energy that is wasted to obtain the same cooling effect is much higher than when the combustion temperature is lowered by increasing the amount of fossil fuel. Less. In other words, according to the tenth invention, energy waste is suppressed while reliably preventing deterioration of the catalyst due to overheating. That's the power S.

[0029] According to the ninth aspect, the higher the risk of catalyst deterioration due to overheating, the higher the concentration of alcohol in the mixed fuel, so that deterioration of the catalyst due to overheating can be more reliably prevented.

[0030] According to the tenth invention, the supply amount of the mixed fuel is increased before and after the correction of the alcohol concentration, whereby the change in the excess air ratio can be prevented, and the change in the excess air ratio can be prevented. It is possible to prevent deterioration of the catalyst due to overheating without causing deterioration of the mission.

[0031] According to the first aspect of the invention, the purification efficiency in the catalyst is maintained by controlling the supply amounts of alcohol and fossil fuel so that the excess air ratio is always kept constant or substantially constant. That's the power S.

[0032] According to the twelfth aspect, the intake air amount is adjusted before and after the correction of the alcohol concentration, whereby the torque change of the internal combustion engine can be prevented and the drivability deteriorates due to the torque change. It is possible to prevent deterioration of the catalyst due to overheating.

[0033] According to the thirteenth invention, the amount of the mixed fuel supplied is increased before and after the correction of the alcohol concentration, whereby the torque change of the internal combustion engine can be prevented, and the driveability deteriorates due to the torque change. It is possible to prevent catalyst deterioration due to overheating without incurring

[0034] According to the fourteenth invention, the ignition timing is adjusted before and after the correction of the alcohol concentration, whereby a change in the torque of the internal combustion engine can be prevented, and the deterioration of the driver ability due to the change in the torque is not caused. It becomes possible to prevent deterioration of the catalyst due to overheating. Brief Description of Drawings

FIG. 1 is a schematic diagram of a system of an alcohol fuel internal combustion engine as an embodiment of the present invention.

FIG. 2 is a time chart showing the contents of engine control for preventing catalyst overheating performed in the embodiment of the present invention.

FIG. 3 is a time chart showing the contents of engine control for making the excess air ratio constant executed in the embodiment of the present invention. FIG. 4 is a time chart showing the contents of engine control for making the torque executed in the embodiment of the present invention constant.

Explanation of symbols

[0036] 2 Engine body

4 Air intake passage

6 Exhaust passage

8 slots

10 Catalyst

12 Fuel injection valve

14 Gasoline tank

16 Alcohol fuel tank

18 Gasoline pump

20 Alconole fuel pump

22 Compounding equipment

30 Control unit

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a schematic view of a system of an alcohol fuel internal combustion engine as an embodiment of the present invention. As shown in this figure, an intake passage 4 and an exhaust passage 6 are connected to a main body (hereinafter, engine main body) 2 of an alcohol fuel internal combustion engine. A throttle 8 is disposed in the intake passage 4, and a fuel injection valve 12 is attached downstream of the throttle 8. Although only one fuel injection valve 12 is shown in the figure, this is for simplification of the figure, and in reality, the fuel injection valve 12 is provided for each cylinder. A catalyst 10 for purifying exhaust gas is disposed in the exhaust passage 6.

[0038] This system is provided with a gasoline tank 14 in which gasoline is stored, and an alcohol mixed fuel tank 16 in which a mixed fuel of alcohol and gasoline (hereinafter, alcohol mixed fuel) is stored. The alcohol-mixed fuel in the alcohol-mixed fuel tank 16 is adjusted to a predetermined alcohol concentration in advance. The gasoline in the gasoline tank 14 is pumped 1 It is sucked up by 8 and supplied to the compounding device 22. The alcohol mixed fuel in the alcohol mixed fuel tank 16 is sucked up by the pump 20 and supplied to the blending device 22. The blending device 22 is a device that adjusts the alcohol concentration of the alcohol mixed fuel (in other words, the mixing ratio of alcohol and gasoline) by mixing gasoline with the alcohol mixed fuel. The alcohol mixed fuel whose alcohol concentration is adjusted by the blender 22 is supplied to the fuel injection valve 12 and injected from the fuel injection valve 12 into the engine body 2.

In addition, this system is provided with a control device 30 that controls the operation of the system. Various devices such as the fuel injection valve 12, the blending device 22, and the throttle 8 are connected to the output unit of the control device 30. The fuel injection amount can be adjusted by controlling the fuel injection valve 12. It is possible to adjust the alcohol concentration of the alcohol-mixed fuel by controlling the blending device 22. The intake air amount can be adjusted by controlling the throttle 8. Various information relating to the operating state of the engine body 2 such as the accelerator opening, the engine speed, and the intake air temperature is input to the input unit of the control device 30. The control device 30 controls each device according to a predetermined control program based on these various information!

[0040] As one of the engine controls executed by the control device 30, there is fuel control for preventing the catalyst 10 from overheating. Since the temperature of the catalyst 10 is increased by supplying heat from the exhaust gas to the catalyst 10, it is necessary to suppress the temperature increase of the exhaust gas in order to prevent the catalyst 10 from being overheated. As an effective method, it is effective to cool the combustion chamber using the latent heat of vaporization when the fuel is vaporized. In the engine control, which is the power of this embodiment, alcohol is used instead of gasoline as fuel for cooling the combustion chamber. That is, the alcohol injection amount is increased.

[0041] Since alcohol contains oxygen in its composition, it has a higher combustion rate than gasoline. Thereby, the gas temperature in the combustion chamber when the exhaust valve is opened can be relatively lowered, and as a result, the temperature of the exhaust gas flowing into the catalyst 10 can be lowered. Compared to fossil fuels such as gasoline, alcohol has a large latent heat of vaporization per unit weight. Therefore, compared with the case of increasing the injection amount of gasoline, the same cooling effect can be obtained with a small increase amount. However, alcohol is more expensive than gasoline Since the amount of heat generated per unit weight is small, the amount of energy that is wasted to obtain the same cooling effect is much smaller than when the amount of gasoline injected is increased.

[0042] As described above, if the combustion chamber is cooled by using the alcohol contained in the alcohol-mixed fuel, it is possible to prevent waste of energy while reliably preventing the catalyst 10 from being overheated. Hereinafter, the contents of the engine control executed in the present embodiment will be described more specifically with reference to FIGS.

FIG. 2 is a time chart showing the contents of engine control for preventing overheating of the catalyst 10. FIG. 2 shows the relationship between the alcohol concentration of the alcohol mixed fuel adjusted by the blending device 22 and the temperature of the catalyst 10. The alcohol concentration indicated by a broken line in FIG. 2 is a basic value of the alcohol concentration adjusted by the blending device 22. This basic value is determined from comprehensive viewpoints such as fuel consumption rate, torque, and exhaust emission. Usually, the mixing ratio of alcohol and gasoline is adjusted so that the alcohol concentration becomes the basic value.

[0044] The change in the catalyst temperature indicated by the broken line in FIG. 2 indicates the change in the catalyst temperature when the internal combustion engine is operated with the alcohol concentration maintained at the basic value. If the alcohol concentration is kept at the basic value at all times, the catalyst temperature may rise due to the rise in exhaust temperature during high-speed and high-load operation, and the upper limit temperature may be exceeded. The upper limit temperature is the upper limit of the temperature at which thermal degradation of the catalyst 10 can be avoided if it is less than that, and if the catalyst temperature exceeds the upper limit temperature, the possibility of degradation of the catalyst 10 due to overheating becomes extremely high. End up.

Therefore, in the engine control according to the present embodiment, as shown by the solid line in FIG. 2, when the catalyst temperature is expected to exceed the upper limit temperature at the basic value, the alcohol concentration is set to the basic value. Also set a higher value. By increasing the alcohol concentration of the alcohol blended fuel, the amount of alcohol fuel injected is relatively increased. As a result, the combustion chamber can be cooled by the vaporization latent heat of the alcohol to lower the exhaust temperature, and the catalyst temperature is prevented from exceeding the upper limit temperature. The change in catalyst temperature shown by the solid line in Fig. 2 shows the change in catalyst temperature when the alcohol concentration is changed, as shown by the solid line.

[0046] Specifically, the control device 30 determines the alcohol concentration from a multidimensional map with the engine load and the engine speed as axes. Whether the catalyst temperature exceeds the upper limit This is because the engine can be operated in the operating range. In the high load range, the exhaust gas temperature increases as the combustion heat increases. In addition, in the high speed range, the amount of heat per unit time that the catalyst 10 receives from the exhaust gas increases as the flow rate of the exhaust gas increases. For this reason, when the internal combustion engine is in a high rotation and high load range, the catalyst temperature is likely to exceed the upper limit temperature. Therefore, the control device 30 sets the alcohol concentration to a value higher than the basic value when the internal combustion engine is operated in a specific operating region on the high rotation and high load side, and sets the alcohol concentration to the basic value in other operating regions. It is set to a value.

[0047] In addition, the control device 30 increases the correction amount with respect to the basic value of the alcohol concentration as the operating range of the internal combustion engine is on the high rotation high load side. If the alcohol concentration is maintained at the basic value, the maximum temperature of the catalyst 10 is predicted to exceed the upper limit temperature as the operating range of the internal combustion engine is on the high rotation high load side. In other words, the risk of deterioration of the catalyst 10 due to overheating increases with increasing rotation and load. Therefore, by changing the correction amount for the basic value of the alcohol concentration according to the operating range of the internal combustion engine as described above, it becomes possible to more reliably prevent the deterioration of the catalyst 10 due to overheating.

[0048] By the way, since alcohol contains oxygen in the composition, if the alcohol concentration is increased while the injection amount of the alcohol mixed fuel injected from the fuel injection valve 12 is kept constant, the fuel amount is insufficient with respect to the air amount. Will happen. In order to prevent the emission from deteriorating, it is necessary to keep the excess air ratio constant before and after the change in the alcohol concentration.

FIG. 3 is a time chart showing the contents of engine control for making the excess air ratio constant. FIG. 3 shows the relationship between the alcohol concentration of the alcohol mixed fuel adjusted by the blending device 22, the injection amount of the alcohol mixed fuel injected from the fuel injection valve 12, and the excess air ratio. As shown by the broken line in Fig. 3, when the fuel injection amount is always constant (constant with respect to the predetermined intake air amount), if the alcohol concentration is increased above the basic value, the excess air ratio also changes from the basic value to the lean side. It will come off. The basic value of the excess air ratio is set to a value at which the exhaust gas purification efficiency by the catalyst 10 is maximized, specifically to 1. If the excess air ratio can be maintained at 1, high oxidation efficiency can be obtained by offsetting the oxidizing component and the reducing component contained in the exhaust gas.

[0050] In the engine control according to the present embodiment, the alcohol concentration is increased from its basic value to a high concentration. When the correction is made to the degree side, as shown by the solid line in FIG. 3, the injection amount of the alcohol-mixed fuel by the fuel injection valve 12 is also increased. The higher the alcohol concentration is! /, The higher the basic value, the greater the fuel injection amount increase correction. This prevents fuel shortage relative to the air volume when the alcohol concentration is increased, and maintains the excess air ratio at a constant value (basic value) before and after the change in alcohol concentration.

[0051] In Fig. 3, a change in the amount of alcohol to be injected and a change in the amount of gasoline to be injected are shown in accordance with changes in the alcohol concentration and the fuel injection amount. As described above, changing the alcohol concentration and the fuel injection amount means increasing the alcohol injection amount while decreasing the gasoline injection amount. Increasing the alcohol injection amount increases the cooling effect in the combustion chamber, and reducing the gasoline injection amount makes it possible to maintain the excess air ratio at a constant value.

Next, engine control for making the torque constant before and after the alcohol concentration correction will be described. As mentioned earlier, alcohol has a lower calorific value per unit weight than gasoline. For this reason, if the alcohol concentration is increased while the injection amount of the alcohol mixed fuel injected from the fuel injection valve 12 is kept constant, the energy obtained by the combustion of the fuel decreases, and the torque of the internal combustion engine decreases. In order to prevent deterioration of drivability, it is necessary to keep the torque constant before and after the change in alcohol concentration.

FIG. 4 is a time chart showing the contents of engine control for making the torque constant. FIG. 4 shows the relationship between the alcohol concentration of the alcohol mixed fuel adjusted by the blending device 22, the opening of the throttle 8, and the torque. The change in the intake air amount corresponds to the change in the throttle opening. The injection amount of the alcohol-mixed fuel injected from the fuel injection valve 12 is determined according to the intake air amount so that the excess air ratio becomes a basic value! Therefore, as shown by the broken line in FIG. 4, if the throttle opening is constant, the intake air amount and the fuel injection amount are kept constant. In this case, if the alcohol concentration is increased, a torque drop occurs as shown by the broken line in FIG.

[0054] In the engine control, which is the power of the present embodiment, when the alcohol concentration is corrected from its basic value to the increasing side, the throttle opening is increased as shown by the solid line in FIG. Alcoa The higher the valve concentration is than the basic value, the greater the correction of the throttle opening. This prevents a decrease in combustion energy when the alcohol concentration is increased, and keeps the torque constant before and after the change in alcohol concentration.

As described above, according to the engine control described with reference to FIG. 2, it is possible to reliably prevent deterioration of the catalyst 10 due to overheating while suppressing waste of energy. In the present embodiment, the control device 30 executes the engine control described with reference to FIG. 2, so that the “alcohol supply amount correcting means”, the eighth and The “alcohol concentration correction means” according to the ninth aspect of the invention has been realized!

[0056] Further, by combining the engine control described with reference to FIG. 2 with the engine control described with reference to FIG. 2, the engine control described with reference to FIG. 3 can be performed by overheating without causing deterioration of emissions due to a change in the excess air ratio. It becomes possible to prevent the deterioration of the catalyst 10. In the present embodiment, the control device 30 executes each engine control described with reference to FIG. 2 and FIG. 3, so that the “fossil fuel supply amount correcting means” according to the third invention and the tenth invention The “fuel supply amount correcting means” is realized.

[0057] Further, by combining the engine control described with reference to FIG. 2 with the engine control described with reference to FIG. 4, it is possible to prevent deterioration of the catalyst due to overheating without causing deterioration of drivability due to torque change. It becomes possible. In the present embodiment, the control device 30 executes each engine control described with reference to FIGS. 2 and 3, so that the “intake air amount adjusting means” according to the sixth invention and the twelfth invention are achieved. The "intake air amount adjustment means" is realized.

[0058] Further, by combining the engine control described using FIG. 2 with the engine control described using FIG. 3 and the engine control described using FIG. It is possible to prevent the deterioration of the catalyst 10 due to overheating without incurring both deterioration of the drive and deterioration of drivability due to torque change.

[0059] While 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.

[0060] As a method of preventing the torque change of the internal combustion engine, in accordance with the increase in alcohol concentration It is effective to advance the ignition timing. Increasing the alcohol concentration increases the octane number, so knocking in a high load range can be avoided. This means that the ignition timing can be advanced. If the ignition timing can be advanced, it is possible to suppress a decrease in torque due to an increase in alcohol concentration.

[0061] If the excess air ratio can be ignored, the torque change of the internal combustion engine before and after the correction of the alcohol concentration is increased by increasing the injection amount of the alcohol mixed fuel injected from the fuel injection valve 12. Can also be prevented. In other words, the fuel injection amount is adjusted so that the torque is constant, instead of making the excess air ratio constant. In this case, the overall fuel injection amount is increased, but the breakdown is that the gasoline injection amount is decreased with respect to the increase in the alcohol injection amount. This is because the increase in torque associated with the increase in alcohol is offset by the decrease in gasoline injection.

In the above embodiment, the catalyst temperature is predicted from the engine speed and the engine load. However, the temperature of the exhaust gas may be measured by a temperature sensor, and the catalyst temperature may be predicted from the exhaust temperature. Alternatively, the temperature of the catalyst may be measured directly by attaching a temperature sensor to the catalyst 10.

[0063] Further, the first to seventh inventions can also be applied to an alcohol fuel internal combustion engine that is separately provided with an alcohol injection valve for injecting alcohol and a fossil fuel injection valve for injecting fossil fuel such as gasoline.

Claims

The scope of the claims

[1] In an alcohol fuel internal combustion engine equipped with a catalyst for purifying exhaust gas generated by combustion of a mixed fuel in which alcohol and fossil fuel are mixed, and purifying exhaust gas generated by the combustion of the mixed fuel,

Fuel supply means for supplying alcohol and fossil fuels according to a predetermined basic mixing ratio;

An alcohol supply amount correcting means for increasing the alcohol supply amount from a supply amount determined from the basic mixing ratio when the temperature of the catalyst exceeds a predetermined upper limit temperature or when the catalyst temperature is predicted to exceed the upper limit temperature;

An alcohol-fueled internal combustion engine comprising:

[2] The alcohol supply amount correcting means predicts the temperature of the catalyst under each supply amount of alcohol and fossil fuel determined from the basic mixing ratio, and the higher the predicted temperature is, the higher the upper limit temperature is. The alcohol-fueled internal combustion engine according to claim 1, wherein the correction of the alcohol supply amount is increased.

[3] The apparatus further comprises a fossil fuel supply amount correcting means for reducing the fossil fuel supply amount from the supply amount determined from the basic mixing ratio so that the excess air ratio does not change before and after the correction of the alcohol supply amount. The alcohol-fueled internal combustion engine according to claim 1 or 2.

[4] The fuel supply means may supply the alcohol and the fossil fuel according to the basic mixing ratio so that the excess air ratio is constant or substantially constant! 3. Alcohol-fueled internal combustion engine.

[5] Any one of claims 1 to 4, further comprising intake air amount adjusting means for adjusting the intake air amount so that the torque of the internal combustion engine does not change before and after the correction of the alcohol supply amount. 1. The alcohol fuel internal combustion engine according to item 1.

[6] The apparatus further comprises fossil fuel supply amount correction means for reducing the fossil fuel supply amount from the supply amount determined from the basic mixing ratio so that the torque of the internal combustion engine does not change before and after the correction of the alcohol supply amount. The alcohol-fueled internal combustion engine according to claim 1 or 2, wherein

[7] The ignition timing adjusting means for adjusting the ignition timing so that the torque of the internal combustion engine does not change before and after the correction of the alcohol supply amount.

The alcohol fuel internal combustion engine according to any one of 1 to 4;

[8] In an alcohol-fueled internal combustion engine equipped with a catalyst for purifying exhaust gas generated by combustion of a mixed fuel in which alcohol and fossil fuel are mixed, and purifying exhaust gas generated by the combustion of the mixed fuel,

An alcohol-fueled internal combustion engine comprising:

[9] The alcohol concentration correction means predicts the temperature of the catalyst under the basic alcohol concentration, and increases the alcohol concentration correction as the predicted temperature is higher than the upper limit temperature. 9. An alcohol-fueled internal combustion engine according to claim 8.

[10] The claim 8 or 9, further comprising fuel supply amount correction means for increasing the supply amount of the mixed fuel so that the excess air ratio does not change before and after the correction of the alcohol concentration. Alcohol fueled internal combustion engine.

[11] The fuel supply means may supply the alcohol and the fossil fuel according to the basic mixing ratio so that the excess air ratio may be constant or substantially constant! 10. Alcohol fuel internal combustion engine as described in 10.

[12] Any one of claims 8 to 11, further comprising intake air amount adjusting means for adjusting the intake air amount so that the torque of the internal combustion engine does not change before and after the correction of the alcohol concentration. 2. The alcohol fuel internal combustion engine according to item 1.

[13] The fuel supply amount correction means for increasing the supply amount of the mixed fuel so that the torque of the internal combustion engine does not change before and after the correction of the alcohol concentration. The alcohol-fueled internal combustion engine described.

[14] The torque of the internal combustion engine does not change before and after the alcohol concentration correction. The alcohol-fueled internal combustion engine according to any one of claims 8 to 11, further comprising ignition timing adjusting means for adjusting the ignition timing.