JP2010053813A - Hydrogen internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To suitably remove a toxic substance included in exhaust gas, in a hydrogen internal combustion engine. <P>SOLUTION: This hydrogen internal combustion engine has a cylinder 140 for providing motive power by burning hydrogen and generating ammonia NH3, an exhaust passage 160 for exhausting the exhaust gas including the ammonia to the outside from the inside of the cylinder, and an exhaust emission control means 170 arranged in the exhaust passage and removing nitrogen oxides NOx included in the exhaust gas by reducing by the ammonia. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a technical field of a hydrogen internal combustion engine that obtains power of, for example, a vehicle by burning hydrogen.

  Some hydrogen internal combustion engines of this type convert energy generated by burning hydrogen into power. Hydrogen is burned after being mixed with air in the cylinder. The exhaust gas generated at this time contains nitrogen oxide (NOx), which is considered harmful. For this reason, a hydrogen internal combustion engine has been proposed that includes exhaust purification means for purifying nitrogen oxides contained in the exhaust (see Patent Document 1). As an exhaust purification means, for example, one that purifies nitrogen oxides by using ammonia as a reducing agent has been proposed (see Patent Document 2).

JP 2007-303321 A JP-A-9-004441

  However, when ammonia is used for the exhaust gas purification means, it is often required to separately provide a device for storing ammonia, a device for generating ammonia, etc. in order to add ammonia as a reducing agent. These devices take up space and increase the overall size of the internal combustion engine. For example, precious metal that is a catalyst for generating ammonia and a relatively complicated mechanism for realizing a high-pressure state that allows reaction are used. This increases the cost. That is, the above-described technique has a technical problem that various inconveniences may occur in practice.

  The present invention has been made in view of the above-described problems, for example, and an object thereof is to provide a hydrogen internal combustion engine that can suitably purify harmful substances contained in exhaust gas.

  In order to solve the above problems, a hydrogen internal combustion engine of the present invention is a cylinder that generates power by burning hydrogen and generates ammonia, and an exhaust that exhausts exhaust gas containing ammonia from the inside to the outside of the cylinder. A passage, and an exhaust purification means that is provided in the exhaust passage and purifies the nitrogen oxides contained in the exhaust by being reduced by the ammonia.

  According to the hydrogen internal combustion engine of the present invention, during operation, the hydrogen supplied into the cylinder is mixed with air and burned. A hydrogen internal combustion engine is mounted on a vehicle such as an automobile, and energy generated by combustion is used as power. When hydrogen is burned, nitrogen oxides are produced with water. For this reason, the exhaust gas discharged from the cylinder of the hydrogen internal combustion engine contains nitrogen oxides which are harmful substances.

  In the present invention, particularly, hydrogen is combusted, whereby hydrogen (H) reacts with nitrogen (N) contained in the air in the cylinder to generate ammonia (NH3). The ammonia is typically generated when the air-fuel ratio is rich (that is, under an excessive fuel supply atmosphere), whereas the above-described nitrogen oxides are generated when the air-fuel ratio is lean (that is, In an oxygen excess supply atmosphere). Therefore, if the air-fuel ratio is adjusted, either nitrogen oxide or ammonia can be selectively generated. However, both nitrogen oxide and ammonia may be generated simultaneously. The ammonia produced here is discharged out of the cylinder as exhaust, similarly to nitrogen oxides.

  Exhaust gas purification means for purifying harmful substances contained in the exhaust gas is provided in an exhaust path through which the exhaust gas discharged from the cylinder passes. In the exhaust purification means, nitrogen oxides contained in the exhaust are purified using ammonia as a reducing agent. Specifically, nitrogen and water are generated by a reaction between nitrogen oxides generated in a lean atmosphere and ammonia generated in a rich atmosphere.

  In the present invention, in particular, as described above, ammonia that functions as a reducing agent is generated by the combustion of hydrogen in the cylinder. Therefore, even without providing a tank for storing ammonia, an ammonia generator for generating ammonia, or the like, Exhaust gas purification using ammonia can be performed. That is, it is possible to effectively purify the exhaust gas while suppressing space saving and cost increase of the entire internal combustion engine.

  In addition, ammonia itself used for the reduction of nitrogen oxides is a harmful substance, but ammonia is decomposed when exhaust purification is performed, as is the case with nitrogen oxides. That is, it can be considered that the exhaust purification means in the present invention has a function of purifying both nitrogen oxides and ammonia, which are harmful substances contained in the exhaust.

  As described above, according to the hydrogen internal combustion engine of the present invention, nitrogen oxide can be reduced using ammonia generated when hydrogen is burned. Therefore, it is possible to suitably purify harmful substances contained in the exhaust.

  In one aspect of the hydrogen internal combustion engine of the present invention, the pressure adjusting means capable of adjusting the pressure in the cylinder, and the pressure adjusting means are controlled so that the pressure in the cylinder is higher than in normal operation. And pressure control means for generating more ammonia in the cylinder than in the normal operation.

  According to this aspect, the cylinder is provided with the pressure adjusting means, and the pressure in the cylinder can be adjusted. The pressure adjusting means adjusts the pressure in the cylinder by changing the intake pressure, the compression ratio, the heat generation timing, and the like, for example. The pressure adjusting means is controlled by the pressure control means. That is, the pressure in the cylinder is adjusted by giving any instruction to the pressure adjusting means from the pressure control means.

  If the pressure in the cylinder is increased by the pressure adjusting means during normal operation of the internal combustion engine, a reaction in which ammonia is generated easily occurs, and as a result, the amount of ammonia generated increases. The “normal operation” here means a state in which combustion for obtaining power efficiently is performed in an internal combustion engine without considering the generation of ammonia. It refers to combustion in a lean state. This is the same in the following embodiments.

  As the amount of ammonia produced in the cylinder increases, the amount of ammonia supplied to the exhaust purification means also increases. For this reason, in the state where the pressure in the cylinder is increased, the reduction of nitrogen oxides in the exhaust gas purification means is performed efficiently, and the exhaust gas can be purified more effectively.

  The pressure control means detects the concentration of ammonia or nitrogen oxide contained in the exhaust gas, for example, and when the amount of ammonia is small relative to the nitrogen oxide and the exhaust gas purification cannot be performed properly, the pressure control means By controlling this, the pressure in the cylinder is increased. Thereby, the purification of the exhaust gas in the exhaust gas purification means is made more appropriate. Conversely, when the amount of ammonia is large relative to nitrogen oxides, the pressure adjusting means may be controlled to reduce the pressure in the cylinder.

  In another aspect of the hydrogen internal combustion engine of the present invention, the temperature adjusting means capable of adjusting the temperature in the cylinder and the temperature adjusting means are controlled so as to lower the temperature in the cylinder than during normal operation. Thus, the apparatus further includes temperature control means for generating more ammonia in the cylinder than in the normal operation.

  According to this aspect, the cylinder is provided with the temperature adjusting means, and the temperature in the cylinder can be adjusted. The pressure adjusting means adjusts the temperature in the cylinder by, for example, lowering the intake air temperature using an intercooler, an EGR (Exhaust Gas Recirculation) cooler, or the like, or injecting liquid hydrogen into the cylinder. The temperature adjusting means is controlled by the temperature control means. That is, the temperature in the cylinder is adjusted by giving some instruction from the temperature control means to the temperature adjusting means.

  If the temperature in the cylinder is lowered by the temperature adjusting means during normal operation of the internal combustion engine, a reaction in which ammonia is generated easily occurs, and as a result, the amount of ammonia generated increases. As the amount of ammonia produced in the cylinder increases, the amount of ammonia supplied to the exhaust purification means also increases. For this reason, when the temperature in the cylinder is lowered, the reduction of nitrogen oxides is efficiently performed in the exhaust gas purification means, and the exhaust gas can be purified more effectively.

  The temperature control means detects, for example, the concentration of ammonia or nitrogen oxide contained in the exhaust gas, and when the amount of ammonia is small relative to the nitrogen oxide and the exhaust gas cannot be appropriately purified, the temperature control means By controlling this, the temperature in the cylinder is lowered. Thereby, the purification of the exhaust gas in the exhaust gas purification means is made more appropriate. Conversely, when the amount of ammonia is larger than the nitrogen oxide, the temperature adjusting means may be controlled to increase the temperature in the cylinder.

  In another aspect of the hydrogen internal combustion engine of the present invention, the oxygen concentration adjusting means capable of adjusting the oxygen concentration in the cylinder, and the oxygen concentration adjustment so as to lower the oxygen concentration in the cylinder than during normal operation. The apparatus further comprises oxygen concentration control means for generating more ammonia in the cylinder than in the normal operation by controlling the means.

  According to this aspect, the cylinder is provided with the oxygen concentration adjusting means, and the oxygen concentration in the cylinder can be adjusted. The oxygen concentration adjusting means adjusts the oxygen concentration, for example, by increasing the amount of exhaust gas recirculated by the EGR system or by separating oxygen by cooling the intake air with liquid hydrogen or the like. The oxygen concentration adjusting means is controlled by the oxygen concentration control means. That is, the oxygen concentration in the cylinder is adjusted by giving some instruction from the oxygen concentration control means to the oxygen concentration adjusting means.

  During normal operation of the internal combustion engine, if the oxygen concentration in the cylinder is lowered (that is, made rich) by the oxygen concentration adjusting means, a reaction in which ammonia is generated easily occurs. Increased amount of ammonia. As the amount of ammonia produced in the cylinder increases, the amount of ammonia supplied to the exhaust purification means also increases. For this reason, when the oxygen concentration in the cylinder is low, the reduction of nitrogen oxides in the exhaust gas purification means is performed efficiently, and the exhaust gas can be purified more effectively.

  The oxygen concentration control means detects, for example, the concentration of ammonia or nitrogen oxide contained in the exhaust gas. If the amount of ammonia is small relative to the nitrogen oxide and the exhaust gas cannot be appropriately purified, the oxygen concentration control means By controlling the adjusting means, the oxygen concentration in the cylinder is lowered. Thereby, the purification of the exhaust gas in the exhaust gas purification means is made more appropriate. Conversely, when the amount of ammonia is larger than the nitrogen oxide, the oxygen concentration adjusting means may be controlled to increase the oxygen concentration in the cylinder.

  Note that the pressure adjusting means and the pressure control means, the temperature adjusting means and the temperature control means, and the oxygen concentration adjusting means and the oxygen concentration control means in each aspect described above may be used in combination. In other words, a plurality of parameters among the pressure, temperature, and oxygen concentration may be controlled. In such a case, since the effect of increasing ammonia is duplicated, more ammonia can be generated. Therefore, it is possible to suitably supply ammonia to the exhaust purification unit.

  The operation and other advantages of the present invention will become apparent from the best mode for carrying out the invention described below.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

<First Embodiment>
First, the configuration of the hydrogen internal combustion engine according to the present embodiment will be described with reference to FIG. FIG. 1 is a schematic view showing the overall configuration of the hydrogen internal combustion engine according to this embodiment.

  In FIG. 1, the hydrogen internal combustion engine according to this embodiment includes an air flow meter 110, a throttle 120, an intake pipe 130, a plurality of cylinders 140, a hydrogen injection valve 150, an exhaust pipe 160, a selective reduction catalyst ( SCR (Selective Catalytic Reduction) 170, hydrogen tank 210, hydrogen supply pipe 220, main stop valve 230, pressure regulating valve 240, EGR pipe 310, EGR cooler 320, EGR valve 330, and exhaust temperature sensor 410 And an oxygen concentration sensor 420 and an ECU (Electronic Control Unit) 500.

  The intake pipe 130 is provided with an air flow meter 110 that detects the amount of air taken in and a throttle 120 that adjusts the amount of air taken in. The air flow meter 110 has a form called a hot wire type, for example, and is configured to be able to directly measure the mass flow rate of the sucked air. The throttle 120 is opened and closed in accordance with, for example, an accelerator pedal operation by a vehicle driver, and the amount of air taken in can be adjusted in accordance with the opening. Although not shown here, an air cleaner for removing dust and the like in the intake air is typically provided upstream of the air flow meter 110. Further, a supercharger for compressing and supplying air and an intercooler for cooling the compressed intake air may be provided.

  A plurality of cylinders 140 are provided downstream of the intake pipe 130, and the intake air is supplied into the plurality of cylinders 140. The cylinder 140 is configured so that hydrogen is supplied from the hydrogen tank 210 via the hydrogen supply pipe 220. The hydrogen supply pipe 220 is provided with a main stop valve 230 for controlling the supply of hydrogen and a pressure regulating valve 240 capable of finely adjusting the supply of hydrogen. That is, whether or not hydrogen is supplied into the cylinder 140 is controlled by opening and closing the main stop valve 230, and the amount of hydrogen supplied into the cylinder 140 is adjusted by the opening of the pressure regulating valve 240. Hydrogen supplied through the hydrogen supply pipe 220 is injected into the cylinder 140 from the hydrogen injection valve 150.

  Further, the cylinder 140 is provided with an intake valve and an exhaust valve (not shown), and the opening / closing timing of each can be controlled. That is, by making the intake and exhaust timing variable, the compression ratio in the cylinder 140 can be controlled.

  Here, the case where all of the plurality of cylinders 140 use hydrogen as fuel will be described, but it is sufficient that at least one cylinder 140 uses hydrogen as fuel. That is, a cylinder 140 using hydrogen as fuel and a cylinder using liquid fuel such as gasoline or alcohol, gas fuel other than hydrogen, or the like may be mixed.

  An exhaust pipe 160, which is an example of the “exhaust path” of the present invention, is provided downstream of the cylinder 140, and exhaust generated in the cylinder 140 during combustion is guided to the outside. The exhaust pipe 160 is provided with a selective reduction catalyst 170 which is an example of the “exhaust purification means” of the present invention, and purifies harmful substances contained in the exhaust. In the selective reduction catalyst 170, for example, the reaction shown in the following chemical formulas (1) and (2) occurs to purify the exhaust.

6NO + 4NH ₃ → 5N ₂ + 6H ₂ O (1)
6NO ₂ + 8NH ₃ → 7N ₂ + 12H ₂ O (2)
That is, nitrogen and water are produced by the ammonia produced during combustion acting as a reducing agent on NOx, which is a harmful substance contained in exhaust gas.

  The exhaust pipe 160 is provided with an EGR pipe 310 so as to branch off, and a part of the exhaust can be recirculated to the intake side. The EGR pipe 310 is provided with an EGR cooler 320 to cool the recirculated EGR. The EGR cooler 320 can also use liquid hydrogen as a refrigerant. An EGR valve 330 is provided between the EGR pipe 310 and the intake pipe 130 to control the amount of EGR introduced from the EGR pipe 310 to the intake pipe 130 by opening and closing.

  When EGR is introduced, for example, combustion is performed in a state where the oxygen concentration is low, so that the amount of NOx emission is reduced. In addition, the fuel consumption rate is improved due to a decrease in pumping loss during intake.

  An exhaust temperature sensor 410 and an oxygen concentration sensor 420 are provided downstream of the selective reduction catalyst 170 in the exhaust pipe 160. Further, an intake air temperature sensor, an intake pressure sensor, an in-cylinder pressure sensor, or the like may be provided as means for detecting each parameter during the internal combustion period.

  The ECU (Electronic Control Unit) 500 includes a pressure control unit 510 which is an example of the “pressure control unit” of the present invention, a temperature control unit 520 which is an example of the “temperature control unit” of the present invention, and the “oxygen control unit” of the present invention. An oxygen concentration control unit 530 that is an example of the “concentration control means” is configured to control the operation of each part in the hydrogen internal combustion engine. That is, the ECU 500 functions as an electronic control unit that controls the overall operation of the hydrogen internal combustion engine.

  Next, the operation of the hydrogen internal combustion engine according to this embodiment will be described with reference to FIG.

  In FIG. 1, during operation of the hydrogen internal combustion engine according to the present embodiment, air is supplied from the intake pipe 130 to the plurality of cylinders 140 and hydrogen serving as fuel is supplied from the hydrogen supply pipe 220. The supplied air and hydrogen are mixed in the cylinder 140 and burned. The energy generated by the combustion is converted into power such as a piston (not shown) and used as power for a vehicle on which a hydrogen internal combustion engine is loaded.

  In the combustion in the cylinder 140, for example, in the combustion in the case where the air-fuel ratio is in a lean state, the reactions shown in the following chemical formulas (3) and (4) occur.

2H ₂ + 2O ₂ + N ₂ → 2H ₂ O + 2NO (3)
2H ₂ + 3O ₂ + N ₂ → 2H ₂ O + 2NO ₂ (4)
Further, in combustion when the air-fuel ratio is in a rich state, a reaction as shown in the following chemical formula (5) occurs.

5H ₂ + O ₂ + N ₂ → 2H ₂ O + 2NH ₃ (5)
That is, NOx or ammonia is generated along with water by combustion. The NOx and ammonia are discharged out of the cylinder 140 as exhaust, and are led to the selective reduction catalyst 170 via the exhaust pipe 160. In the selective reduction catalyst 170, as described above, nitrogen and water are generated by ammonia acting as a reducing agent on NOx. That is, the concentrations of NOx and ammonia in the exhaust are reduced extremely effectively.

  However, during normal operation in which priority is given to combustion efficiency, for example, combustion in a lean state is often performed, so that the amount of ammonia produced is smaller than the amount of NOx produced. That is, ammonia that can sufficiently reduce the generated NOx is not generated, and NOx in the exhaust gas may not be appropriately purified. On the other hand, in the hydrogen internal combustion engine according to the present embodiment, it is possible to increase the amount of ammonia produced by controlling each parameter during operation.

  Hereinafter, the operation when increasing the amount of ammonia produced in the hydrogen internal combustion engine according to the present embodiment will be described with reference to FIGS. 2 to 7 in addition to FIG. In addition, below, operation | movement of each site | part is demonstrated separately for every parameter controlled in order to increase the production amount of ammonia.

  First, the case where the pressure in the cylinder 140 is controlled will be described with reference to FIGS. FIG. 2 is a flowchart showing the operation when controlling the cylinder pressure in the hydrogen internal combustion engine according to the present embodiment. FIG. 3 is a timing chart showing the change of the controlled parameter in time series (part 2). 1).

  In FIG. 2, in the hydrogen internal combustion engine according to the present embodiment, during operation, it is first determined whether or not ammonia for purifying NOx is insufficient (step S11). Whether or not ammonia is insufficient is determined by the ECU 500 based on, for example, the concentration of ammonia in the cylinder 140, the concentration of NOx contained in the exhaust gas after passing through the selective reduction catalyst 170, or the like. Or you may determine by the time etc. which the combustion in the lean state estimated that there is much quantity of NOx produced | generated is performed continuously.

  If it is determined that the ammonia is insufficient (step S11: YES), the pressure control unit 510 in the ECU 500 performs control to increase the intake pressure (step S12). The pressure control unit 510 performs control so as to increase the compression ratio (step S13) and further advance the heat generation timing (step S14) either continuously or in parallel. Note that the processing from step S12 to step S14 has the effect of increasing the pressure in the cylinder 140 by being performed alone. That is, the pressure in the cylinder 140 increases if at least one of the intake pressure increase, compression ratio increase, and heat generation timing advance is performed. However, the pressure in the cylinder 140 can be effectively increased by performing a plurality of controls among the increase of the intake pressure, the increase of the compression ratio, and the advance angle of the heat generation timing. Further, as long as the pressure in the cylinder 140 can be increased, a method other than the method described above may be used.

  In FIG. 3, the pressure control unit 510 performs control so that the opening degree of the throttle 120 is increased in order to increase the intake pressure. That is, the throttle 120 can be said to be an example of the “pressure adjusting means” in the present invention. In this way, more air is introduced into the intake pipe 130 and the intake pressure rises. In the case where a supercharger or the like is provided, the intake pressure can also be increased by increasing the compression rate of the air supplied from the supercharger.

  The pressure control unit 510 controls the VVT (Variable Valve Timing) system to advance in order to increase the compression ratio. That is, the opening / closing timing of the intake valve and the exhaust valve provided in the cylinder 140 is changed to the advance direction. When a variable compression mechanism is provided, the compression ratio can be increased by directly controlling the variable compression mechanism.

  The pressure control unit 510 performs control so that the ignition timing by a spark plug or the like provided in the cylinder 140 is advanced in order to advance the heat generation timing. Further, if the timing for injecting hydrogen from the hydrogen injection valve 150 is advanced, the heat generation timing can be advanced more effectively.

  Returning to FIG. 2, after the control by the pressure control unit 510 is performed, the ECU 500 determines again whether or not ammonia is insufficient (step S15). If it is determined that ammonia is not insufficient (step S15: NO), the pressure control unit 510 controls the intake pressure to decrease (step S16), and the compression ratio is controlled to decrease. (Step S17), the heat generation timing is controlled to be retarded (Step S18). That is, as shown in FIG. 3, the valve timing and ignition timing by the throttle 120 and the VVT system are set to the original values, and the normal operation is resumed.

  The control for increasing the pressure in the cylinder 140 by the pressure control unit 510 may be performed only for a predetermined period set in advance. That is, it may be set to return to normal operation after a predetermined period of time has passed, regardless of whether ammonia is deficient. At this time, if a predetermined period is set based on the amount of ammonia that increases by increasing the pressure, ammonia can be generated more suitably.

  On the other hand, when it is determined that the ammonia is insufficient even after the pressure control unit 510 performs the control from step S12 to step S14 (step S15: YES), the controlled intake pressure, compression ratio and The heat generation time is maintained. Alternatively, control may be performed such that the intake pressure and the compression ratio are further increased or the heat generation timing is advanced.

  As described above, by controlling each part by the pressure control unit 510, the pressure of the cylinder 140 can be temporarily increased. During the control, hydrogen combustion is performed in a high-pressure field, and the amount of ammonia produced can be increased, so that harmful substances in the exhaust gas can be more suitably purified.

  Next, the case where the temperature in the cylinder 140 is controlled will be described with reference to FIGS. 4 and 5. FIG. 4 is a flowchart showing the operation when controlling the in-cylinder temperature in the hydrogen internal combustion engine according to the present embodiment, and FIG. 5 is a timing chart showing the change of the controlled parameter in time series (part 2). 2). In addition, below, the part which overlaps with the case where the pressure in the cylinder 140 mentioned above is controlled shall be abbreviate | omitted suitably.

  In FIG. 4, the hydrogen internal combustion engine according to the present embodiment first determines whether or not ammonia for purifying NOx is insufficient during operation (step S21). Here, if it is determined that the ammonia is insufficient (step S21: YES), the temperature control unit 520 in the ECU 500 performs control so as to lower the intake air temperature (step S22). The temperature control unit 520 controls to inject liquid hydrogen into the cylinder 140 continuously or in parallel (step S23). It should be noted that the processing in step S22 and step S23 has the effect of lowering the temperature in the cylinder 140 by being performed alone. That is, if any one of the intake air temperature decrease and the liquid hydrogen injection is controlled, the temperature in the cylinder 140 decreases. However, the temperature in the cylinder 140 can be effectively reduced by controlling both the reduction of the intake air temperature and the injection of liquid hydrogen. Further, as long as the temperature in the cylinder 140 can be lowered, a method other than the method described above may be used.

  The change in the temperature in the cylinder 140 can be detected by, for example, an exhaust temperature sensor 410 (see FIG. 1) provided in the exhaust pipe 160.

  In FIG. 5, the temperature control unit 520 controls, for example, the EGR cooler 320 and an intercooler (not shown) in order to lower the intake air temperature. That is, the temperature of the intake air temperature is lowered by controlling the cooling effect of the EGR cooler 320, the intercooler, or the like to be higher. Therefore, the EGR cooler 320 can be said to be an example of the “temperature adjusting means” in the present invention. Note that liquid hydrogen may be used as a refrigerant for lowering the intake air temperature.

  Further, the temperature control unit 520 performs control so that liquid hydrogen injection into the cylinder 140 is started. Alternatively, control is performed so as to increase the amount of liquid hydrogen that has already been injected. Thereby, the temperature in the cylinder 140 is directly cooled.

  Returning to FIG. 4, after the control by the temperature control unit 520 is performed, the ECU 500 determines again whether or not ammonia is insufficient (step S24). Here, if it is determined that the ammonia is not insufficient (step S24: NO), the temperature control unit 520 performs control to increase the intake air temperature (step S25), and liquid hydrogen into the cylinder 140 is obtained. Control is performed so as to stop the injection (step S26). That is, as shown in FIG. 5, each controlled parameter is set to the original value, and the normal operation is resumed.

  The control for reducing the temperature in the cylinder 140 by the temperature control unit 520 may be performed only for a predetermined period set in advance. That is, it may be set to return to normal operation after a predetermined period of time has passed, regardless of whether ammonia is deficient. At this time, if a predetermined period is set based on the amount of ammonia increasing by lowering the temperature, ammonia can be generated more suitably.

  On the other hand, if it is determined that the ammonia is insufficient even after the temperature control unit 520 performs the control in steps S22 and S23 (step S24: YES), the controlled intake air temperature and liquid hydrogen are determined. The injection amount is maintained. Alternatively, control may be performed so that the intake air temperature is further lowered or more liquid hydrogen is injected.

  As described above, by controlling each part by the temperature control unit 520, the temperature of the cylinder 140 can be temporarily reduced. During the control, hydrogen combustion is performed in a low temperature field, and the amount of ammonia produced can be increased, so that harmful substances in the exhaust gas can be more suitably purified.

  Next, the case where the oxygen concentration in the cylinder 140 is controlled will be described with reference to FIGS. FIG. 6 is a flowchart showing the operation when controlling the in-cylinder oxygen concentration in the hydrogen internal combustion engine according to this embodiment, and FIG. 7 is a timing chart (time series) showing changes in the controlled parameters. Part 3).

  In FIG. 6, the hydrogen internal combustion engine according to the present embodiment first determines whether or not ammonia for purifying NOx is insufficient during operation (step S31). Here, if it is determined that ammonia is insufficient (step S31: YES), the oxygen concentration control unit 530 in the ECU 500 performs control so as to increase the EGR amount (that is, the amount of exhaust gas to be recirculated) ( Step S32). The oxygen concentration control unit 530 performs control so that the intake air is cooled by liquid hydrogen continuously or in parallel (step S33). It should be noted that the processing of step S32 and step S33 has the effect of reducing the oxygen concentration in the cylinder 140 by being performed alone. That is, if any one of the increase of the EGR amount and the cooling of the intake air is performed, the oxygen concentration in the cylinder 140 decreases. However, by controlling both the increase of the EGR amount and the cooling of the intake air, the oxygen concentration in the cylinder 140 can be effectively reduced. Further, as long as the oxygen concentration in the cylinder 140 can be reduced, a method other than the method described above may be used.

  The change in the oxygen concentration in the cylinder 140 can be detected by, for example, an oxygen concentration sensor 420 (see FIG. 1) provided in the exhaust pipe 160.

  In FIG. 7, the oxygen concentration control unit 530 controls the EGR valve 330 so as to increase the opening degree in order to increase the EGR amount. That is, the EGR valve 330 is an example of the “oxygen concentration adjusting unit” in the present invention. Further, the same effect can be obtained by increasing the opening of an exhaust throttle valve (not shown) or increasing the cooling effect of the EGR cooler 320.

  Further, the oxygen concentration control unit 530 increases the amount of liquid hydrogen serving as a refrigerant in order to cool the intake air. By cooling the intake air, oxygen in the intake air is separated. As a result, the oxygen concentration in the intake air is reliably reduced.

  Returning to FIG. 6, after the control by the oxygen concentration control unit 530 is performed, the ECU 500 determines again whether or not ammonia is insufficient (step S34). If it is determined that ammonia is not insufficient (step S34: NO), the oxygen concentration control unit 530 performs control so as to decrease the EGR amount (step S35), and cools the intake air. Control is performed to reduce the amount of liquid hydrogen (step S36). That is, as shown in FIG. 7, the controlled parameters are set to their original values, and the normal operation is resumed.

  The control for reducing the oxygen concentration in the cylinder 140 by the oxygen concentration control unit 530 may be performed only for a predetermined period set in advance. That is, it may be set to return to normal operation after a predetermined period of time has passed, regardless of whether ammonia is deficient. At this time, if a predetermined period is set based on the amount of ammonia that increases by lowering the oxygen concentration, ammonia can be generated more suitably.

  On the other hand, if it is determined that the ammonia is insufficient even after the oxygen concentration control unit 530 performs the control of step S32 and step S33 (step S34: YES), the controlled EGR amount and the liquid The amount of hydrogen is maintained. Alternatively, it may be controlled to further increase the EGR amount or cool the intake air by using more liquid hydrogen.

  As described above, the oxygen concentration of the cylinder 140 can be temporarily reduced by controlling each part by the oxygen concentration control unit 530. During the control, hydrogen combustion is performed in a low oxygen concentration field, and the amount of ammonia produced can be increased, so that harmful substances in the exhaust gas can be more suitably purified.

  As described above, according to the hydrogen internal combustion engine according to the present embodiment, the generation amount can be appropriately increased according to the shortage of ammonia. Therefore, it is possible to suitably purify harmful substances contained in the exhaust.

  Although the case where the pressure, temperature, and oxygen concentration in the cylinder 140 are controlled separately has been described above, these controls are typically performed simultaneously or continuously. This makes it possible to effectively increase the amount of ammonia produced. However, if at least one of the pressure, temperature, and oxygen concentration in the cylinder 140 is controlled, the effect of increasing the amount of ammonia produced can be obtained accordingly.

  The present invention is not limited to the above-described embodiment, and can be appropriately changed without departing from the gist or concept of the invention that can be read from the claims and the entire specification, and a hydrogen internal combustion engine with such a change Is also included in the technical scope of the present invention.

1 is a schematic diagram illustrating an overall configuration of a hydrogen internal combustion engine according to an embodiment. 4 is a flowchart illustrating an operation when controlling the pressure in the cylinder in the hydrogen internal combustion engine according to the embodiment. It is a timing chart (the 1) which shows the change of the controlled parameter in time series. 5 is a flowchart showing an operation when controlling the temperature in the cylinder in the hydrogen internal combustion engine according to the embodiment. It is a timing chart (the 2) which shows the change of the parameter controlled in time series. 5 is a flowchart showing an operation when controlling the in-cylinder oxygen concentration in the hydrogen internal combustion engine according to the embodiment. It is a timing chart (the 3) which shows the change of the parameter controlled in time series.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 110 ... Air flow meter, 120 ... Throttle, 130 ... Intake pipe, 140 ... Cylinder, 150 ... Hydrogen injection valve, 160 ... Exhaust pipe, 170 ... Selective reduction catalyst, 210 ... Hydrogen tank, 220 ... Between hydrogen supply, 230 ... Main stop Valve: 240 ... Pressure regulating valve, 310 ... EGR pipe, 320 ... EGR cooler, 330 ... EGR valve, 410 ... Exhaust temperature sensor, 420 ... Oxygen concentration sensor, 500 ... ECU, 510 ... Pressure controller, 520 ... Temperature controller, 530 ... Oxygen concentration control unit

Claims (4)

Cylinders that generate power and generate ammonia by burning hydrogen,
An exhaust path for exhausting the exhaust gas containing ammonia from the inside of the cylinder to the outside;
An exhaust gas purifying means provided in the exhaust path and purifying the exhaust gas by reducing nitrogen oxide contained in the exhaust gas with the ammonia. Pressure adjusting means capable of adjusting the pressure in the cylinder;
Pressure control means for generating more ammonia in the cylinder than in the normal operation by controlling the pressure adjusting means so that the pressure in the cylinder is higher than that in the normal operation. The hydrogen internal combustion engine according to claim 1. Temperature adjusting means capable of adjusting the temperature in the cylinder;
Temperature control means for generating more ammonia in the cylinder than in the normal operation by controlling the temperature adjusting means to lower the temperature in the cylinder than in the normal operation. The hydrogen internal combustion engine according to claim 1. Oxygen concentration adjusting means capable of adjusting the oxygen concentration in the cylinder;
Oxygen concentration control means for generating more ammonia in the cylinder than in normal operation by controlling the oxygen concentration adjusting means to lower the oxygen concentration in the cylinder than in normal operation. The hydrogen internal combustion engine according to claim 1.

Images