JP2008050954A - Gas fuel internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a gas fuel internal combustion engine, in particular, with respect to a hydrogen self-ignition internal combustion engine allowing self-ignition operation taking hydrogen as fuel, which can provide high efficiency and low noise by optimizing the fuel injection timing of the self-ignition internal combustion engine utilizing gas fuel. <P>SOLUTION: In a gas fuel internal combustion engine which allows self-ignition operation by gas fuel, an operating condition/state of the internal combustion engine is obtained (Step 100). On the basis of the operating condition/state of the internal combustion engine, the self-ignition timing of the internal combustion engine and the injection period of gas fuel are calculated (Steps 102, 104). On the basis of the self-ignition timing and an injection period, the fuel injection start timing of gas fuel is specified so as to execute combustion for optimizing engine efficiency (Step 106). <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a gas fuel internal combustion engine, and more particularly to a hydrogen self-ignition internal combustion engine capable of performing a self-ignition operation using hydrogen as a fuel.

  Conventionally, it is known to use hydrogen which is a gas fuel as a fuel for an internal combustion engine. Hydrogen can be combusted sufficiently even in an extremely thin air-fuel mixture with a combustible range of 4 to 75% in volume ratio and an excess air ratio of about 4 or more. For this reason, when hydrogen is used as a fuel for an internal combustion engine, power can be taken out even at a very lean air-fuel ratio, and so-called super-lean burn operation becomes possible.

According to the super lean burn operation, the throttle can be substantially fully opened, so that the pump loss can be reduced and the cooling temperature can be reduced because the combustion temperature is lowered. By reducing the pump loss and the cooling loss, the efficiency of the internal combustion engine is improved, and high-efficiency operation with excellent fuel efficiency becomes possible. Furthermore, the reduction of the combustion temperature, it is possible to suppress the generation amount of the NO _X to approximately zero, also, by using hydrogen as fuel, there is no generation of CO ₂ and CO. Therefore, the super lean burn operation using hydrogen makes it possible to realize complete zero emission.

JP-A-10-238374 JP-A-2005-139985 JP-A-7-189848

  By the way, hydrogen has a wider flammable range than liquid fuel such as gasoline. For this reason, when hydrogen is used as a fuel for an internal combustion engine, it is conceivable to use a self-ignition system instead of a normal spark ignition system.

  However, in the self-ignition operation using hydrogen as fuel, it is difficult to control the fuel injection timing. Since hydrogen gas has a much larger volume than liquid fuel with the same calorific value, the fuel injection period must be set longer, but if a large amount of fuel is injected before self-ignition, rapid premix combustion Combustion noise caused by is a problem. Further, since a large amount of hydrogen diffuses into the combustion chamber, unburned hydrogen due to premixed combustion increases.

  On the other hand, if the diffusion combustion period is set to be long, the combustion pressure in the later stage of combustion is lowered, so the problem of reduction in efficiency becomes significant. As described above, in the self-ignition operation using hydrogen as a fuel, the fuel injection timing greatly affects the efficiency of the internal combustion engine, the combustion noise, and the like.

  The present invention has been made to solve the above-described problems, and is designed to optimize the fuel injection timing of a self-ignition internal combustion engine using gas fuel so that high efficiency and low noise can be realized. An object is to provide a fuel internal combustion engine.

In order to achieve the above object, a first invention is a gas fuel internal combustion engine capable of self-ignition operation with gas fuel,
Self-ignition timing estimating means for estimating the self-ignition timing of the internal combustion engine based on the operating condition / state of the internal combustion engine;
An injection period calculating means for calculating an injection period of the gas fuel based on an operating condition / state of the internal combustion engine;
Injection start timing determining means for determining the injection start timing of the gas fuel based on the self-ignition timing and the injection period;
It is characterized by providing.

The second invention is the first invention, wherein
The internal combustion engine is a hydrogen internal combustion engine that uses hydrogen gas as gas fuel.

The third invention is the first or second invention, wherein
The injection start time determining means is
The shorter the injection period is, the longer the injection start time is specified.

The fourth invention is the invention according to any one of the first to third inventions,
Compression ratio adjusting means for adjusting the compression ratio of the internal combustion engine;
A self-ignition target timing calculating means for calculating a self-ignition target timing of the internal combustion engine based on the operating condition / state of the internal combustion engine;
Control means for operating the compression ratio adjusting means so that the self-ignition time becomes the self-ignition target time;
Is further provided.

The fifth invention is the fourth invention, wherein
The control means includes
Including first comparison means for comparing the self-ignition time with the self-ignition target time;
When the self-ignition timing is later than the self-ignition target time, the compression ratio adjusting means is operated so that the compression ratio becomes large.

The sixth invention is the fourth invention, wherein
The control means includes
Including first comparison means for comparing the self-ignition time with the self-ignition target time;
When the self-ignition timing is earlier than the self-ignition target time, the compression ratio adjusting means is operated so that the compression ratio becomes small.

The seventh invention is the invention according to any one of the first to sixth inventions,
An ignition auxiliary device disposed in a combustion chamber of the internal combustion engine;
A self-ignition permissible timing calculating means for calculating a self-ignition permissible time of the internal combustion engine based on the operating condition / state of the internal combustion engine;
An ignition assisting means for activating the ignition assisting device when not igniting by the self-ignition allowable time;
Is further provided.

The eighth invention is the seventh invention, wherein
The ignition assisting means is
Including a second comparison means for comparing the self-ignition time with the self-ignition allowable time;
The ignition assisting device is operated when the self-ignition timing is later than the self-ignition allowable time.

The ninth invention is the seventh invention, wherein
The ignition assisting means is
In-cylinder pressure acquisition means for acquiring the in-cylinder pressure of the internal combustion engine;
Determination means for determining the presence or absence of self-ignition based on the in-cylinder pressure;
It is characterized by providing.

  According to the first aspect of the present invention, in a gas fuel internal combustion engine capable of compression self-ignition operation using gas fuel, injection is performed based on the self-ignition timing and the injection period specified based on the operation condition / operation state of the internal combustion engine. The start time can be specified. The engine efficiency varies depending on the combustion mode and the combustion state. Therefore, according to the present invention, the injection start timing can be specified based on the self-ignition timing and the injection period so that the combustion with the optimum engine efficiency is performed.

  According to the second invention, the present invention can be implemented by a hydrogen internal combustion engine that uses hydrogen gas as the gas fuel.

  According to the third invention, the injection start timing is specified so that the injection is started at a later timing as the fuel injection period is shorter. For this reason, according to the present invention, a situation in which a large amount of fuel is injected before ignition can be avoided, and the generation of combustion noise and unburned hydrogen due to rapid premixed combustion can be suppressed.

  According to the fourth aspect of the invention, the compression ratio is adjusted so that the self-ignition timing specified based on the operating conditions and operating conditions of the internal combustion engine becomes the self-ignition target timing. For this reason, according to the present invention, the time of heat generation is always appropriate by surely performing self-ignition at the self-ignition target time, and high-efficiency operation can be realized.

  According to the fifth aspect, the compression ratio is adjusted based on a comparison between the self-ignition timing and the self-ignition target timing. That is, when the self-ignition time is later than the self-ignition target time, the target compression ratio is set high in order to advance the self-ignition time. For this reason, according to the present invention, self-ignition can be surely performed at the self-ignition target time.

  According to the sixth aspect of the invention, the compression ratio is adjusted based on a comparison between the self-ignition timing and the self-ignition target timing. That is, when the self-ignition time is earlier than the self-ignition target time, the target compression ratio is set low in order to delay the self-ignition time. For this reason, according to the present invention, self-ignition can be surely performed at the self-ignition target time.

  According to the seventh aspect, when the self-ignition does not occur before the self-ignition allowable time, the ignition is assisted by the ignition assisting device. For this reason, according to this invention, even if it is a case where self-ignition does not occur, highly efficient driving | operation is realizable by making it ignite reliably.

  According to the eighth aspect, the operation of the ignition assisting device is executed based on a comparison between the self-ignition time and the self-ignition allowable time. That is, when the self-ignition timing is later than the self-ignition allowable time, there is a high possibility that self-ignition will not occur, and thus the ignition assist device is operated. For this reason, according to the present invention, even when there is a high possibility that self-ignition will not occur, it is possible to reliably ignite.

  According to the ninth aspect, the operation of the ignition assist device is executed based on the in-cylinder pressure of the internal combustion engine. In the case of self-ignition, the in-cylinder pressure increases rapidly. For this reason, according to the present invention, the presence or absence of self-ignition can be reliably detected based on the in-cylinder pressure, and can be reliably ignited when self-ignition is not occurring.

  Several embodiments of the present invention will be described below with reference to the drawings. In addition, the same code | symbol is attached | subjected to the element which is common in each figure, and the overlapping description is abbreviate | omitted. The present invention is not limited to the following embodiments.

Embodiment 1 FIG.
[Hardware configuration]
FIG. 1 is a diagram for explaining the configuration of the embodiment of the present invention. As shown in FIG. 1, the gas fuel internal combustion engine 10 of this embodiment is a hydrogen engine that uses hydrogen as the gas fuel. The hydrogen engine 10 includes a cylinder block 14 in which a piston 12 is disposed, and a cylinder head 16 assembled to the cylinder block 14. A space surrounded by the inner walls of the cylinder block 14 and the cylinder head 16 and the upper surface of the piston 12 forms a combustion chamber 18. Although only one combustion chamber 18 is shown in FIG. 1, the hydrogen engine 10 is configured as a multi-cylinder engine having a plurality of combustion chambers 18.

  An intake passage 20 for introducing air into the combustion chamber 18 is connected to the combustion chamber 18. 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. A throttle 24 for adjusting the amount of air taken into the combustion chamber 18 is disposed in the intake passage 20. An air flow meter 26 for measuring the amount of intake air is attached upstream of the throttle 24 in the intake passage 20. An intake valve 28 for controlling a communication state between the intake passage 20 and the combustion chamber 18 is provided at a connection portion between the intake passage 20 and the combustion chamber 18.

  The combustion chamber 18 is connected to an exhaust passage 30 for discharging the combustion gas in the combustion chamber. A purification catalyst 32 is disposed in the exhaust passage 30 and the exhaust gas is purified by the purification catalyst 32 and then discharged into the atmosphere. An oxygen sensor 34 for measuring the oxygen concentration in the exhaust gas is attached upstream of the purification catalyst 32. An exhaust valve 36 for controlling a communication state between the exhaust passage 30 and the combustion chamber 18 is provided at a connection portion between the exhaust passage 30 and the combustion chamber 18.

  Further, an in-cylinder injection valve 40 and an in-cylinder pressure sensor 52 are disposed in the combustion chamber 18. The in-cylinder injection valve 40 is connected to a hydrogen supply device 42 via a hydrogen supply pipe 44. Specific examples of the hydrogen supply device 42 include a hydrogen tank that stores hydrogen, a reformer that reforms a hydrocarbon-based fuel to generate hydrogen, or a hydrogen storage means such as a metal hydride. In the hydrogen engine of the present embodiment, the type of the hydrogen supply device 42 is not limited. A pump 46 that pumps hydrogen to the in-cylinder injection valve 40 is disposed in the hydrogen supply pipe 44. The pump 46 compresses hydrogen to a pressure that can be sufficiently injected even in the vicinity of the compression TDC. When a high-pressure hydrogen tank is used as the hydrogen supply device 42 and the storage pressure is higher than the injection pressure, a regulator may be used instead of the pump 46.

  The hydrogen engine 10 of the present embodiment is provided with an ECU (Electronic Control Unit) 70 as its control device. Various devices such as the in-cylinder injection valve 40 and the throttle 24 described above are connected to the output portion of the ECU 70. In addition to the above-described air flow meter 26, oxygen sensor 34, and in-cylinder pressure sensor 52, various sensors such as a crank angle sensor 48 and a water temperature sensor 50 are connected to the input unit of the ECU 70. The ECU 70 drives each device according to a predetermined control program based on the output of each sensor.

[Operation of Embodiment 1]
Next, the operation of the first embodiment will be described. The hydrogen engine 10 of the present embodiment is an engine that uses hydrogen as a fuel and can burn an air-fuel mixture by self-ignition. The combustion mode of the hydrogen engine 10 includes premixed combustion and diffusion combustion. Specifically, first, hydrogen injected from the in-cylinder injection valve 40 is mixed with air in the combustion chamber 18 to generate a combustible mixture. When the combustible air-fuel mixture in the combustion chamber 18 is compressed and reaches the self-ignition temperature, self-ignition occurs almost simultaneously at several locations of the combustible air-fuel mixture, and premixed combustion in which the combustible air-fuel mixture burns rapidly is performed. Next, after the premixed combustion, hydrogen gas is continuously injected into the burning flame, so that diffusion combustion is performed in which hydrogen burns while being diffusely mixed with air.

  The shorter the fuel injection period until premixed combustion (hereinafter referred to as “premixed period”), that is, the earlier the self-ignition timing, the smaller the fuel injection amount before premixed combustion. It is suppressed and combustion noise can be reduced. Moreover, since the amount of hydrogen diffusing into the combustion chamber is small, generation of unburned hydrogen can be suppressed.

  However, as described above, since hydrogen gas has a significantly larger volume than liquid fuel with the same calorific value, the fuel injection period Af must be set longer, but if the premixing period is increased, The combustion noise and unburned hydrogen mentioned above are problems.

  On the other hand, if the diffusion combustion period is set to be long, the combustion pressure in the later stage of combustion is lowered, so the problem of reduction in efficiency becomes significant. As described above, in the self-ignition operation using hydrogen as a fuel, the fuel injection timing greatly affects the efficiency of the internal combustion engine, the combustion noise, and the like.

That is, in the above-described self-ignition combustion including premixed combustion and diffusion combustion, there is a fuel injection start timing at which self-ignition timing at which the engine efficiency is optimum corresponds to the injection period Af. Therefore, in the first embodiment, the optimum fuel injection start crank angle θs is calculated according to the following arithmetic expression, and fuel injection is executed.
Injection start crank angle θs = auto-ignition temperature reaching crank angle θai−advance amount Δθ (1)

  Here, the self-ignition temperature reaching crank angle θai is a compression crank angle at which the combustible air-fuel mixture in the combustion chamber 18 becomes a temperature at which self-ignition is possible, and is a value estimated based on the operating condition and operating state of the hydrogen engine 10. It is. Further, the advance amount Δθ is a value defined as an advance amount from the self-ignition temperature reaching crank angle θai.

  FIG. 2 is a map showing a relationship established between the injection period Af and the advance amount Δθ. The map of FIG. 2 shows that the advance amount Δθ tends to be smaller as the injection period Af is shorter, in the entire autoignition temperature reaching crank angle θai. As the advance amount Δθ, a value corresponding to the self-ignition temperature reaching crank angle θai and the injection period Af is specified according to the tendency of the map.

  According to the above equation (1), the injection start crank angle θs is calculated by subtracting the advance amount Δθ from the self-ignition temperature reaching crank angle θai. Therefore, the shorter the injection period Af, that is, the smaller the injection amount, the smaller the advance amount from θai, and eventually the injection start crank angle θs becomes a crank angle that is retarded from θai. Therefore, since the fuel injection start timing can be adjusted so that the injection amount for the premixed combustion is not too large, the generation of combustion noise and unburned hydrogen can be suppressed, and highly efficient operation is realized. be able to.

[Specific Processing in Embodiment 1]
Next, with reference to FIG. 3, the specific content of the process performed in this Embodiment is demonstrated. FIG. 3 is a flowchart of a routine in which the ECU 70 executes a process for supplying hydrogen gas to the hydrogen engine 10.

  In the routine shown in FIG. 3, first, the operating conditions and operating state of the hydrogen engine 10 are input (step 100). Here, specifically, the engine speed Ne, the injection amount Qf, the injection pressure Qp, the intake air temperature Ti, the EGR rate Re, the water temperature Tw, and the like are input as operating conditions or operating states in the hydrogen engine 10.

  Next, the self-ignition temperature reaching crank angle θai is estimated (step 102). The self-ignition temperature reaching crank angle θai is a value estimated as a compression crank angle that reaches a temperature at which the combustible air-fuel mixture in the combustion chamber 18 can self-ignite based on the operating condition and operating state of the hydrogen engine 10. Specifically, the self-ignition temperature reaching crank angle θai is estimated based on the operating condition and operating state input in step 100 above.

  Next, the injection period Af is calculated (step 104). The injection period Af is a crank angle period of hydrogen injection. Specifically, the calculation is based on the engine speed Ne, the injection amount Qf, and the injection pressure Qp input in step 100 above.

  In the routine shown in FIG. 3, next, the injection start crank angle θs is calculated (step 106). Here, specifically, first, the advance amount Δθ is specified. The advance amount Δθ is in accordance with the map shown in FIG. 2 described above, and the advance angle amount Δθ corresponding to the self-ignition temperature reaching crank angle θai estimated in step 102 and the injection period Af calculated in step 104. Identified from Next, the self-ignition temperature reached crank angle θai estimated in step 102 and Δθ are substituted into the equation (1), and the injection start crank angle θs is calculated.

  As described above, according to the first embodiment, the fuel injection start timing can be adjusted so that the fuel injection amount before the premix combustion is not too large, and the premix combustion can be performed. For this reason, operation with high efficiency is possible and generation of unburned hydrogen can be suppressed.

  Further, according to the first embodiment described above, as the injection period Af becomes shorter, the advance amount Δθ is calculated as a negative value. In such a case, fuel injection is started at a retarded angle side relative to the self-ignition temperature reaching crank angle θai, and rapid combustion due to premixed combustion is suppressed, and combustion noise can be reduced.

  By the way, in Embodiment 1 mentioned above, although the hydrogen engine is used as a gas fuel internal combustion engine, the gas fuel internal combustion engine used is not restricted to this. That is, this embodiment may be executed in a gas fuel internal combustion engine that uses a gas fuel other than hydrogen gas. This also applies to other embodiments described below.

  In the first embodiment described above, the self-ignition temperature reaching crank angle θai is the “self-ignition timing” in the first invention, and the injection start crank angle θs is the “injection start timing” in the first invention. Each corresponds. Further, when the ECU 70 executes the process of step 102, the “self-ignition timing estimating means” in the first invention executes the process of step 104, thereby causing the “injection” in the first invention. The “period calculation means” executes the processing of step 106, thereby realizing the “injection start timing determination means” in the first aspect of the present invention.

Embodiment 2. FIG.
[Features of Embodiment 2]
Next, a second embodiment of the present invention will be described with reference to FIG. The system of the present embodiment can be realized by causing the ECU 70 to execute a routine shown in FIG. 4 to be described later using the hardware configuration shown in FIG.

  In the first embodiment described above, in order to calculate the injection start crank angle θs, the self-ignition temperature reaching crank angle θai estimated based on the operating conditions and the like is used. Here, it is preferable that θai be an ignition crank angle at which combustion is theoretically optimal in thermal efficiency (hereinafter referred to as “self-ignition temperature attainment target crank angle θaiR”).

  However, the self-ignition temperature reaching crank angle θai varies depending on the operating state. For this reason, it is difficult to set various operating conditions so that θai always becomes the self-ignition temperature reaching target crank angle θaiR.

  Therefore, in the second embodiment, in the hydrogen engine capable of adjusting the compression ratio, the compression ratio is adjusted so that the self-ignition temperature reaching crank angle θai becomes the self-ignition temperature reaching target crank angle θaiR. More specifically, when θai is retarded from θaiR, the compression ratio is adjusted to be higher, and conversely, when θai is advanced from θaiR, the compression ratio is The compression ratio is adjusted to be lower. As a result, it is possible to control so that θai always becomes θaiR, so that self-ignition can be performed at a crank angle at which the thermal efficiency is optimal, and the heat generation time is always kept appropriate, realizing high-efficiency operation. be able to.

  The actual compression ratio can be adjusted to the target compression ratio by changing the closing timing of the intake valve 28. Since the valve timing changing method is not a main part of the present invention and is a known method, detailed description thereof is omitted here.

[Specific Processing in Second Embodiment]
Next, with reference to FIG. 4, the specific content of the process performed in this Embodiment 2 is demonstrated. FIG. 4 is a flowchart of a routine in which the ECU 70 executes a process for supplying hydrogen gas to the hydrogen engine 10.

  In the routine shown in FIG. 4, first, the operating conditions and operating state of the hydrogen engine 10 are input (step 200). Specifically, the actual compression ratio ε of the hydrogen engine 10 is input in addition to the process similar to the process of step 100 shown in FIG. More specifically, the actual compression ratio ε is calculated based on the output signal of the in-cylinder pressure sensor 52.

  Next, the self-ignition temperature reaching crank angle θai is estimated (step 202). Here, specifically, θai is estimated based on the operation condition and the operation state input in step 200. Next, the injection period Af is calculated (step 204). Here, specifically, the same processing as step 104 shown in FIG. 3 is executed. Next, the injection start crank angle θs is calculated (step 206). Here, specifically, the same processing as step 106 shown in FIG. 3 is executed.

  In the routine shown in FIG. 4, next, the self-ignition temperature reaching target crank angle θaiR is calculated (step 208). Specifically, θaiR is calculated based on the injection period Af and the engine speed Ne.

  Next, it is determined whether or not the self-ignition temperature reaching crank angle θai is retarded from the self-ignition temperature reaching target crank angle θaiR (step 210). When the compression ratio is adjusted, θai can be changed to the advance side or the retard side. For this reason, when it is determined in the above step 210 that θai is on the retard side with respect to θaiR, the compression ratio is adjusted so that θai is shifted to the advance side (step 212). Here, specifically, a value obtained by adding the amount of change Δε of the compression ratio corresponding to the retardation of θai to the actual compression ratio ε input in step 200 is set as the target compression ratio εt. The

  On the other hand, if it is determined in step 210 that θai is on the more advanced side than θaiR, the compression ratio is adjusted so that θai is shifted to the retarded side (step 214). Specifically, a value obtained by subtracting the amount of change Δε of the compression ratio corresponding to the advance angle of θai from the actual compression ratio ε input in step 200 is set as the target compression ratio εt. Is done.

  As described above, according to the second embodiment, the actual compression ratio is adjusted so that the self-ignition temperature reaching crank angle θai becomes the self-ignition temperature reaching target crank angle θaiR. For this reason, the position of heat generation in combustion becomes appropriate, the fuel injection timing is optimized, and high-efficiency operation can be realized.

  In the second embodiment described above, the target compression ratio εt is set so that θai becomes θaiR, and the actual compression ratio is adjusted to the target compression ratio by changing the closing timing of the intake valve 28. However, the adjustment method of the actual compression ratio is not limited to this. That is, in an internal combustion engine that can mechanically change the in-cylinder volume, the in-cylinder volume may be adjusted so that the actual compression ratio becomes the target compression ratio.

  In the second embodiment described above, the self-ignition temperature reaching crank angle θai is the “self-ignition timing” in the first invention, and the injection start crank angle θs is the “injection start timing” in the first invention. Each corresponds. Further, when the ECU 70 executes the process of step 202, the “self-ignition timing estimating means” in the first aspect of the invention executes the process of step 204, thereby the “injection” in the first aspect of the invention. The “period calculation means” executes the processing of step 206 described above, thereby realizing the “injection start timing determination means” in the first aspect of the present invention.

  In the second embodiment described above, the self-ignition temperature reaching target crank angle θaiR corresponds to the “self-ignition target time” in the fourth aspect of the invention, and the ECU 70 executes the processing of step 208 above. As a result, the “self-ignition target timing calculation means” in the fourth aspect of the invention executes the process of step 210, so that the “first comparison means” of the fifth aspect of the invention performs the process of step 210. By executing, the “first comparing means” in the sixth aspect of the present invention is realized.

Embodiment 3 FIG.
[Features of Embodiment 3]
Next, a third embodiment of the present invention will be described with reference to FIGS. The system of the present embodiment can be realized by causing the ECU 70 to execute a routine shown in FIG. 6 to be described later using the hardware configuration shown in FIG.

  The gas fuel internal combustion engine of the third embodiment is a hydrogen engine that uses hydrogen as the gas fuel as in the first embodiment. FIG. 5 is a diagram showing a schematic configuration of the hydrogen engine 60 of the present embodiment. In FIG. 5, the same parts as those of the hydrogen engine 10 shown in FIG. 1 are denoted by the same reference numerals, and detailed description thereof is omitted or simplified.

  As shown in FIG. 5, in the hydrogen engine 60 of the present embodiment, a spark plug 62 is disposed in the combustion chamber 18. The spark plug 62 is connected to the output part of the ECU 70. The ECU 70 can perform ignition control of the spark plug 62 according to a predetermined program based on the output signal of each sensor.

[Operation of Embodiment 3]
In the first embodiment described above, the injection start crank angle θs is specified on the assumption that self-ignition starts when the crank angle reaches the self-ignition temperature reaching crank angle θai. However, depending on the operating conditions, it may be difficult to reach the self-ignition temperature easily, and θai may be very retarded. In such a case, it is assumed that self-ignition does not occur, and even if self-ignition occurs, combustion efficiency decreases due to a decrease in combustion pressure because the combustion timing shifts to the retard side.

  Therefore, in the third embodiment, when there is a possibility that self-ignition does not occur, spark assist by the spark plug 62 is executed. More specifically, the most retarded self-ignition crank angle (hereinafter referred to as “self-ignition allowable most retarded crank angle θaiD”) that can allow efficiency reduction is calculated, and θai is retarded from θaiD. In this case, the spark assist is executed. As a result, even when self-ignition is not performed, it is possible to reliably ignite, and it is possible to suppress a decrease in efficiency due to the ignition delay.

[Specific Processing in Embodiment 3]
Next, with reference to FIG. 6, the specific content of the process performed in this Embodiment 3 is demonstrated. FIG. 6 is a flowchart of a routine in which the ECU 70 executes processing for supplying hydrogen gas to the hydrogen engine 60.

  In the routine shown in FIG. 6, first, the operating condition and operating state of the hydrogen engine 60 are input (step 300). Next, the self-ignition temperature reaching crank angle θai is estimated (step 302). Next, the injection period Af is calculated (step 304). Next, the injection start crank angle θs is calculated (step 306). Specifically, the same processing as the processing of steps 100 to 106 shown in FIG. 3 is executed.

  In the routine shown in FIG. 6, next, the self-ignition allowable most retarded crank angle θaiD is calculated (step 308). Specifically, θaiD is calculated based on the injection period Af and the engine speed Ne.

  Next, it is determined whether or not the self-ignition temperature reaching crank angle θai is more retarded than the self-ignition allowable maximum delay crank angle θaiD (step 310). As described above, the self-ignition timing becomes retarded as the self-ignition temperature reaching crank angle θai shifts to the retard side, so that the problem of efficiency reduction due to a decrease in the combustion pressure appears remarkably. For this reason, when it is determined in step 310 that θai is on the retard side with respect to θaiD, the process proceeds to the next step and spark assist is executed (step 312). Here, specifically, the combustion of hydrogen is assisted by ignition by the spark plug 62.

  On the other hand, if it is determined in step 310 that θai is more advanced than θaiD, self-ignition is performed when the crank angle reaches θai, so that the spark assist is not executed and this routine is executed. Is terminated.

  As described above, according to the third embodiment, when it is determined that self-ignition will not occur before the self-ignition allowable most retarded crank angle θaiD that allows efficient combustion by self-ignition, the spark plug 62 Spark assist is performed. For this reason, even when it does not self-ignite, it becomes possible to ignite surely and to suppress efficiency fall.

  Further, according to the third embodiment, when the self-ignition is performed before the self-ignition allowable maximum delay crank angle θaiD, the spark assist is not executed. Combustion by self-ignition is ignited from a portion with a mixture ratio that is easy to burn, and therefore, unburned hydrogen due to partial oxygen shortage is less likely to be generated than forced ignition using a spark plug or the like. For this reason, generation | occurrence | production of unburned hydrogen can be suppressed to the minimum.

  By the way, in Embodiment 3 mentioned above, although it is supposed that the spark assist by the spark plug 62 is performed, the apparatus used for assist is not restricted to a spark plug. In other words, a glow plug, an air heater or the like may be used to assist in ignition by directly heating the combustible air-fuel mixture in the combustion chamber.

  In the third embodiment described above, the self-ignition temperature reaching crank angle θai is the “self-ignition time” in the first invention, and the injection start crank angle θs is the “injection start time” in the first invention. Each corresponds. In addition, when the ECU 70 executes the process of step 302, the “self-ignition timing estimating means” in the first invention executes the process of step 304, so that “injection” in the first invention is executed. The “period calculation means” executes the processing of step 306 above, thereby realizing the “injection start timing determination means” in the first aspect of the present invention.

  Further, in the third embodiment described above, the spark plug 62 is the “ignition assisting device” in the seventh invention, and the self-ignition allowable most retarded crank angle θaiD is the “self-ignition allowable timing” in the seventh invention. Respectively. Further, when the ECU 70 executes the process of step 308, the “self-ignition allowable timing calculation means” in the seventh invention executes the process of step 312 so that “ “Ignition assisting means” is realized.

  Further, in the above-described third embodiment, the “second comparison means” in the seventh aspect of the present invention is realized by the ECU 70 executing the processing of step 310 described above.

Embodiment 4 FIG.
[Features of Embodiment 4]
Next, a fourth embodiment of the present invention will be described with reference to FIG. The system of the present embodiment can be realized by causing the ECU 70 to execute a routine shown in FIG. 7 described later using the hardware configuration shown in FIG.

  In the third embodiment described above, when the self-ignition temperature reaching crank angle θai is on the more retarded side than the self-ignition allowable most retarded crank angle θaiD that allows efficient combustion by self-ignition, the advance angle is larger than θaiD. It is determined that no self-ignition occurs on the side, and spark assist by the spark plug 62 is executed.

  However, the self-ignition temperature reaching crank angle θai is an estimated value calculated based on the operating condition and operating state, and when the current crank angle θ reaches θai, self-ignition is not always started, In some cases, auto-ignition may not occur.

  Therefore, in the fourth embodiment, whether or not combustion by self-ignition has been started is confirmed by detecting the in-cylinder pressure of the hydrogen engine 60. More specifically, when the start of self-ignition is not recognized in a period in which the current crank angle θ is on the advance side of the self-ignition allowable most retarded crank angle θaiD (that is, the in-cylinder pressure is a pressure pattern during combustion) (If this is not the case) Spark assistance will be executed. Thereby, the case where it does not self-ignite can be detected reliably, and ignition can be assisted reliably in such a case.

  Further, when the start of self-ignition is recognized by θaiD, the spark assist is not executed. As described in the third embodiment, combustion by self-ignition is ignited from a portion having a mixture ratio that is easy to combust. Therefore, unburned hydrogen due to partial oxygen shortage is smaller than forced ignition using a spark plug or the like. Hard to occur. For this reason, generation | occurrence | production of unburned hydrogen can be suppressed to the minimum, and it becomes possible to implement | achieve highly efficient driving | operation.

[Specific Processing in Embodiment 4]
Next, with reference to FIG. 7, the specific content of the process performed in this Embodiment 4 is demonstrated. FIG. 7 is a flowchart of a routine in which the ECU 70 executes a process for supplying hydrogen gas to the hydrogen engine 60.

  In the routine shown in FIG. 6, first, the operating condition and operating state of the hydrogen engine 60 are input (step 400). Next, the self-ignition temperature reaching crank angle θai is estimated (step 402). Next, the injection period Af is calculated (step 404). Next, the injection start crank angle θs is calculated (step 406). Specifically, the same processing as the processing of steps 100 to 106 shown in FIG. 3 is executed.

  In the routine shown in FIG. 7, next, the self-ignition allowable maximum delay crank angle θaiD is calculated (step 408). Here, specifically, the same processing as that in step 308 shown in FIG. 6 is executed.

  Next, the current crank angle θ is input (step 410). Here, specifically, the output signal of the crank angle sensor 48 is input. Next, it is determined whether or not the current crank angle θ is on the retard side with respect to the self-ignition allowable maximum retard crank angle θaiD (step 412). When θ is on the retard side with respect to θaiD, the routine proceeds to the next step, and it is determined whether or not combustion by self-ignition has been started (step 414). When combustion starts, the in-cylinder pressure rises rapidly. For this reason, the presence or absence of self-ignition can be accurately determined by monitoring the in-cylinder pressure. Here, specifically, it is determined whether or not the in-cylinder pressure detected by the in-cylinder pressure sensor 52 is similar to the pressure pattern during combustion.

  If combustion due to self-ignition is not confirmed in step 414, the process proceeds to the next step and spark assist is executed (step 416). Here, specifically, the same process as the process of step 312 shown in FIG. 6 is executed. On the other hand, if it is confirmed in step 414 that combustion due to self-ignition is confirmed, spark assist is not executed, and this routine is terminated.

  As described above, according to the fourth embodiment, when it is confirmed that the self-ignition is not performed up to the self-ignition allowable most retarded crank angle θaiD that allows efficient combustion by self-ignition, ignition is performed. Spark assist by the plug 62 is executed. For this reason, even when it does not self-ignite, it becomes possible to ignite surely, and a reduction in efficiency can be effectively suppressed.

  By the way, in Embodiment 4 mentioned above, although it is supposed that the spark assist by the spark plug 62 is performed, the apparatus used for assist is not restricted to a spark plug. In other words, a glow plug, an air heater or the like may be used to assist in ignition by directly heating the combustible air-fuel mixture in the combustion chamber.

  In Embodiment 4 described above, the self-ignition temperature reaching crank angle θai is the “self-ignition timing” in the first invention, and the injection start crank angle θs is the “injection start timing” in the first invention. Each corresponds. Further, when the ECU 70 executes the process of step 402, the “self-ignition timing estimating means” in the first aspect of the invention executes the process of step 404, so that the “injection” in the first aspect of the invention is performed. The “period calculation means” executes the processing of step 406, so that the “injection start timing determination means” in the first aspect of the invention is realized.

  Further, in the fourth embodiment described above, the spark plug 62 is the “ignition assist device” in the seventh invention, and the self-ignition allowable maximum delay crank angle θaiD is the “self-ignition allowable timing” in the seventh invention. Respectively. Further, when the ECU 70 executes the process of step 408, the “self-ignition allowable timing calculation means” in the seventh aspect of the invention executes the process of step 416, thereby “ “Ignition assisting means” is realized.

  Further, in the above-described fourth embodiment, the “in-cylinder pressure acquisition means” and the “determination means” according to the ninth aspect of the present invention are realized by the ECU 70 executing the processing of step 414.

It is a figure for demonstrating the structure of Embodiment 1 of this invention. 6 is a map showing a relationship established between an injection period Af and an advance amount Δθ. It is a flowchart of the routine performed in Embodiment 1 of the present invention. It is a flowchart of the routine performed in Embodiment 2 of this invention. It is a figure for demonstrating the structure of Embodiment 3 of this invention. It is a flowchart of the routine performed in Embodiment 3 of the present invention. It is a flowchart of the routine performed in Embodiment 4 of this invention.

Explanation of symbols

10, 60 Gas fuel internal combustion engine (hydrogen engine)
12 Piston 14 Cylinder block 16 Cylinder head 18 Combustion chamber 20 Intake passage 22 Air cleaner 24 Throttle 26 Air flow meter 28 Intake valve 30 Exhaust passage 32 Purification catalyst 34 Oxygen sensor 36 Exhaust valve 40 In-cylinder injection valve 42 Hydrogen supply device 44 Hydrogen supply pipe 46 Pump 48 Crank angle sensor 50 Water temperature sensor 52 In-cylinder pressure sensor 60 Hydrogen engine 62 Spark plug
Af Injection period
Ne engine speed
Qf Injection amount
Qp Injection pressure
Re EGR rate
Ti intake temperature
Tw Water temperature Δθ Lead angle amount ε Actual compression ratio εt Target compression ratio θai Auto-ignition temperature reaching crank angle θaiD Auto-ignition allowable retard angle crank angle θaiR Auto-ignition temperature reaching target crank angle θs Injection start crank angle
TDC (Top Dead Center)

Claims (9)

In a gas fuel internal combustion engine capable of compression self-ignition operation of gas fuel,
Self-ignition timing estimating means for estimating the self-ignition timing of the internal combustion engine based on the operating condition / state of the internal combustion engine;
An injection period calculating means for calculating an injection period of the gas fuel based on an operating condition / state of the internal combustion engine;
Injection start timing determining means for determining the injection start timing of the gas fuel based on the self-ignition timing and the injection period;
A gas-fueled internal combustion engine comprising:   The gas fuel internal combustion engine according to claim 1, wherein the internal combustion engine is a hydrogen internal combustion engine using hydrogen gas as gas fuel. The injection start time determining means is
The gas fuel internal combustion engine according to claim 1 or 2, wherein the shorter the injection period, the longer the injection start timing is specified. Compression ratio adjusting means for adjusting the compression ratio of the internal combustion engine;
A self-ignition target timing calculating means for calculating a self-ignition target timing of the internal combustion engine based on the operating condition / state of the internal combustion engine;
Control means for operating the compression ratio adjusting means so that the self-ignition time becomes the self-ignition target time;
The gas fuel internal combustion engine according to any one of claims 1 to 3, further comprising: The control means includes
Including first comparison means for comparing the self-ignition time with the self-ignition target time;
5. The gas fuel internal combustion engine according to claim 4, wherein when the self-ignition timing is later than the self-ignition target timing, the compression ratio adjusting means is operated so that the compression ratio becomes large. The control means includes
Including first comparison means for comparing the self-ignition time with the self-ignition target time;
5. The gas fuel internal combustion engine according to claim 4, wherein when the self-ignition timing is earlier than the self-ignition target time, the compression ratio adjusting means is operated so that the compression ratio becomes small. An ignition auxiliary device disposed in a combustion chamber of the internal combustion engine;
A self-ignition permissible time acquisition means for calculating a self-ignition permissible time of the internal combustion engine based on the operating condition / state of the internal combustion engine;
An ignition assisting means for activating the ignition assisting device when not igniting by the self-ignition allowable time;
The gas fuel internal combustion engine according to any one of claims 1 to 6, further comprising: The ignition assisting means is
Including a second comparison means for comparing the self-ignition time with the self-ignition allowable time;
The gas fuel internal combustion engine according to claim 7, wherein the ignition assisting device is operated when the self-ignition timing is later than the self-ignition allowable time. The ignition assisting means is
In-cylinder pressure acquisition means for acquiring the in-cylinder pressure of the internal combustion engine;
Determination means for determining the presence or absence of self-ignition based on the in-cylinder pressure;
The gas fuel internal combustion engine according to claim 7, further comprising:

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