JP2004340065A - Control device for hydrogen engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent generation of backfire or the like due to EGR (emission gas recirculation) in a hydrogen engine and improve fuel consumption by reducing NOx. <P>SOLUTION: If it is judged that the combustion temperature of the hydrogen engine 10 is low, an internal EGR amount is increased and an ignition timing correction amount is set to spark advance side (steps S101 to S104). As a result, generation of the backfire or the like caused by ignition speed-down in the hydrogen engine 10 can be prevented and NOx can be reduced, thus improving fuel consumption. If it is judged that the combustion state of the hydrogen engine 10 is degraded, on the other hand, the internal EGR amount is decreased and the ignition timing correction amount is set to lag side (steps S105 to S108). As a result, the EGR amount in the hydrogen engine 10 can be restrained from being excessively supplied, thus preventing degradation of drivability due to backfire or the like. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a hydrogen engine control device for recirculating exhaust gas in a hydrogen engine using hydrogen fuel.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, in a hydrogen engine using hydrogen fuel, the fuel is ignited by touching a wall surface (for example, an intake valve) in a combustion chamber where the temperature of the hydrogen fuel becomes high, or the hydrogen fuel is ignited before ignition. There is a phenomenon that a backfire or the like easily occurs. This is due to the property that hydrogen fuel has a very high lean burn limit and a minimum ignition energy as compared with gasoline fuel. For this reason, exhaust gas recirculation (hereinafter simply referred to as “EGR”), which is well-known in gasoline engines, for the purpose of reducing NOx (nitrogen oxides) is difficult and is not usually performed. Was the current situation.
[0003]
[Problems to be solved by the invention]
By the way, in the EGR of the gasoline engine, the setting is such that the EGR amount is set to be small in a low load / low rotation region and the EGR amount is increased in a high load / high rotation range. This is because, due to the characteristic that gasoline has a low lean burn limit, if the EGR amount is increased at a low load and a low rotation speed, the combustion state is deteriorated, and the drivability is deteriorated.
[0004]
However, as described above, the hydrogen fuel used in the hydrogen engine has a higher lean combustion limit than gasoline fuel, so that a large amount of EGR is possible, and it is desired to implement EGR to reduce NOx and improve fuel efficiency. The request was strong.
[0005]
In order to satisfy such a demand, there is a problem that backfire or the like due to the above-mentioned early ignition must not be caused.
[0006]
Accordingly, the present invention has been made to solve such a problem, and is intended for a hydrogen engine capable of reducing NOx and improving fuel efficiency while preventing the occurrence of backfire or the like due to EGR (exhaust gas recirculation) in the hydrogen engine. The task is to provide a control device.
[0007]
[Means for Solving the Problems]
According to the hydrogen engine control device of the first aspect, when the combustion temperature determination means determines that the combustion temperature of the hydrogen engine is low, EGR (exhaust gas recirculation) is performed by the recirculation control means. And the like, while reducing NOx and improving fuel economy.
[0008]
According to the second aspect of the present invention, when the combustion temperature of the hydrogen engine is determined to be low by the combustion temperature determining means, the ignition timing is advanced by the ignition timing control means simultaneously with the EGR by the recirculation control means. This prevents the occurrence of backfire or the like in conjunction with the decrease in the ignition speed, thereby reducing NOx and improving fuel efficiency.
[0009]
The combustion temperature determining means in the hydrogen engine control device determines that the combustion temperature in the hydrogen engine is low when the load detecting means detects a low load and the rotation speed detecting means detects a low rotation. As a result, the combustion temperature of the hydrogen engine can be determined to be high or low, so that a sensor or the like for detecting the actual combustion temperature can be omitted, and a simple and inexpensive system can be constructed.
[0010]
In the recirculation control means in the hydrogen engine control device according to claim 4, after the load detecting means detects at least one of the high load for a predetermined period or more and the high speed for a predetermined period or more by the rotation speed detecting means, the operating condition is detected. Even if a low load is detected by the load detecting means and a low rotation is detected by the rotational speed detecting means, the EGR in the hydrogen engine is prohibited for a predetermined period. That is, it is considered that the combustion temperature is high immediately after the high load of the hydrogen engine for a predetermined period or more and the high speed rotation for a predetermined period or more, and the combustion temperature is surely lowered by prohibiting the EGR for a predetermined period. When this happens, the EGR is started again, so that drivability is prevented from deteriorating due to backfire or the like.
[0011]
In the recirculation control means in the hydrogen engine control device according to the fifth aspect, the internal EGR amount in the hydrogen engine can be simplified as necessary by varying the valve overlap amount of the intake valve and the exhaust valve by the variable valve timing control mechanism. Can be changed to
[0012]
In the recirculation control means of the control apparatus for a hydrogen engine according to the sixth aspect, when the combustion state determination means determines that the combustion state of the hydrogen engine has deteriorated, the EGR amount in the hydrogen engine is reduced. As a result, excessive supply of the EGR amount is suppressed, and deterioration of drivability due to backfire or the like is prevented.
[0013]
In the combustion state determination means in the hydrogen engine control device of the seventh aspect, the deterioration of the combustion state is determined based on the fluctuation amount of the engine speed of the hydrogen engine by the rotation speed / speed detection means. As described above, since the deterioration of the combustion state of the hydrogen engine can be easily determined, an inexpensive system can be constructed.
[0014]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described based on examples.
[0015]
FIG. 1 is a schematic configuration diagram showing a hydrogen engine to which a hydrogen engine control device according to one example of an embodiment of the present invention is applied and peripheral devices thereof.
[0016]
In FIG. 1, reference numeral 10 denotes a hydrogen engine comprising a four-cycle four-cylinder fueled by hydrogen. Air introduced into an intake passage 11 of the hydrogen engine 10 is purified by an air cleaner 12 from an upstream side, and supplied to an air flow meter 13. After being adjusted by the throttle valve 14, the fuel gas is mixed with hydrogen fuel injected and supplied from the injectors 18 a to 18 d corresponding to each cylinder through the intake manifold 17 and supplied to each cylinder as a predetermined mixture. Then, ignition and combustion are performed at a predetermined timing. Here, the ignition system of each cylinder is omitted. The throttle opening of the throttle valve 14 is detected by a throttle opening sensor 15, and the intake pressure in the intake passage 11 downstream of the throttle valve 14 is detected by an intake pressure sensor 16.
[0017]
An intake valve 19 disposed in each cylinder of the hydrogen engine 10 is opened and closed by an intake camshaft 20. The intake side camshaft 20 is provided with an intake side variable valve timing control mechanism 21. Further, the exhaust valves 24 arranged in each cylinder of the hydrogen engine 10 are opened and closed by an exhaust camshaft 25. The exhaust side camshaft 25 is provided with an exhaust side variable valve timing control mechanism 26. In addition, 22 is an intake side cam position sensor, 23 is a crank position sensor, and 27 is an exhaust side cam position sensor. Exhaust gas from each cylinder of the hydrogen engine 10 passes from an exhaust manifold 28 through an exhaust passage 29, and is exhausted after NOx and the like are purified by a catalytic converter 30 disposed on the way.
[0018]
The hydrogen fuel stored in the high-pressure fuel tank 31 is converted into low-pressure fuel by a pressure reducing regulator 34 via a fuel cutoff valve 33, adjusted by a fuel adjusting mechanism 35, and opened and closed by a differential pressure with the intake manifold 17. Injection is supplied to each cylinder by injectors 18a to 18d. The fuel pressure in the high-pressure fuel tank 31 is detected by a fuel pressure sensor 32.
[0019]
An ECU (Electronic Control Unit) 40 includes a CPU as a central processing unit for executing various known arithmetic processing, a ROM for storing a control program and a control map, a RAM for storing various data, and a B / U. (Backup) It is configured as a logic operation circuit including a RAM, an input circuit, an output circuit, and a bus line connecting them.
[0020]
Here, as various sensors, the intake air amount from the air flow meter 13, the throttle opening from the throttle opening sensor 15, the intake pressure from the intake pressure sensor 16, and the intake camshaft 20 from the intake cam position sensor 22. The cam position, the crank position of the crankshaft (not shown) from the crank position sensor 23, the cam position of the exhaust camshaft 25 from the exhaust cam position sensor 27, the fuel pressure in the high pressure fuel tank 31 from the fuel pressure sensor 32, and the like. The detection signal is input to the input circuit of the ECU 40. Control signals are output from the output circuit of the ECU 40 to the intake-side variable valve timing control mechanism 21, the exhaust-side variable valve timing control mechanism 26, the fuel cutoff valve 32, the pressure reducing regulator 33, the fuel adjustment mechanism 34, and the like as various actuators. .
[0021]
The intake-side camshaft 20 is displaced by the intake-side variable valve timing control mechanism 21 such that the deviation of the intake-side cam position sensor 22 from the crank position sensor 23 becomes a predetermined crank angle [° CA (Crack Angle)]. Opening / closing timing is advanced / retarded. The exhaust-side camshaft 25 is displaced by the exhaust-side variable valve timing control mechanism 26 so that the deviation of the exhaust-side cam position sensor 27 from the crank position sensor 23 becomes a predetermined crank angle [° CA]. The timing is advanced / retarded. Then, an internal EGR amount described later is set by a valve overlap amount based on the opening / closing timing of the intake valve 19 by the intake side variable valve timing control mechanism 21 and the opening / closing timing of the exhaust valve 24 by the exhaust side variable valve timing control mechanism 26. .
[0022]
Next, a description will be given with reference to FIG. 5 based on a flowchart of FIG. 2 showing a processing procedure of the EGR control in the ECU 40 used in the control device for a hydrogen engine according to one example of the embodiment of the present invention. Here, FIG. 5 is a time chart showing transition states of various sensor signals, various control amounts, and the like corresponding to the processes of FIG. 2 and FIGS. 3 and 4 described later. Note that this EGR control routine is repeatedly executed by the ECU 40 at predetermined time intervals.
[0023]
In FIG. 2, first, in step S101, a combustion temperature determination process described later is executed. Next, the process proceeds to step S102, where it is determined whether the combustion temperature is low. When the determination condition of step S102 is satisfied, that is, when it is determined that the combustion temperature in the hydrogen engine 10 is low (from time t0 to time t3 and time t6 shown in FIG. 5), the process proceeds to step S103, and the intake-side variable valve is operated. The internal EGR amount by the timing control mechanism 21 and the exhaust side variable valve timing control mechanism 26 is increased by a predetermined amount. Next, the process proceeds to step S104, and a correction amount from the current ignition timing to the advance side is set as an ignition timing correction amount according to the internal EGR amount increased in step S103.
[0024]
Next, the process proceeds to step S105, and a combustion state determination process described later is executed. Next, the process proceeds to step S106, and it is determined whether the combustion state has deteriorated. When the determination condition in step S106 is satisfied, that is, when it is determined that the combustion state in the hydrogen engine 10 is deteriorated (time t1 to time t2 shown in FIG. 5), the process proceeds to step S107, and the intake-side variable valve timing is performed. The internal EGR amount by the control mechanism 21 and the exhaust-side variable valve timing control mechanism 26 is reduced by a predetermined amount. Next, the process proceeds to step S108, and a correction amount from the current ignition timing to the retard side is set as the ignition timing correction amount according to the internal EGR amount reduced in step S107.
[0025]
On the other hand, when the determination condition in step S102 is not satisfied, that is, when it is determined that the combustion temperature in the hydrogen engine 10 is high, or when the determination condition in step S106 is not satisfied, that is, when the combustion state in the hydrogen engine 10 is good. When it is determined, this routine ends without performing any operation.
[0026]
Next, a description will be given with reference to FIG. 5 based on a flowchart of FIG. 3 showing a processing procedure of the combustion temperature determination in FIG.
[0027]
In FIG. 3, in step S201, it is determined whether the intake pressure PM [kPa] detected by the intake pressure sensor 16 as a load on the hydrogen engine 10 exceeds a predetermined value A. When the determination condition of step S201 is satisfied, that is, when the intake pressure PM as the load of the hydrogen engine 10 exceeds the predetermined value A and is large (time t4 to time t5 shown in FIG. 5), the process proceeds to step S202, and the counter Ti is reset. "+1" is incremented. Next, the process proceeds to step S203, and it is determined whether or not the counter Ti exceeds a predetermined value B. When the determination condition of step S203 is satisfied, that is, when the counter Ti exceeds the predetermined value B and is large, the process proceeds to step S204, where it is determined that the hydrogen engine 10 is in a high load state for a predetermined period and the combustion temperature is high, and this routine is executed. finish.
[0028]
On the other hand, when the determination condition of step S201 is not satisfied, that is, when the intake pressure PM as the load of the hydrogen engine 10 is smaller than the predetermined value A (before time t4 and after time t5 shown in FIG. 5), or at step S203. If the determination condition is not satisfied, that is, if the counter Ti is smaller than the predetermined value B, the process proceeds to step S205. In step S205, it is determined whether the engine speed Ne [rpm] based on the crank position signal from the crank position sensor 23 exceeds a predetermined value C. When the determination condition of step S205 is satisfied, that is, when the engine speed Ne of the hydrogen engine 10 exceeds the predetermined value C and is high (time t3 to time t5 shown in FIG. 5), the process proceeds to step S206, and the counter Si is set to “+1”. Is incremented. Next, the process proceeds to step S207, and when the counter Si exceeds the predetermined value D and is large, the process proceeds to step S204, where it is determined that the hydrogen engine 10 is in the high rotation state for a predetermined period and the combustion temperature is high, and this routine is terminated. I do.
[0029]
On the other hand, when the determination condition of step S205 is not satisfied, that is, when the engine rotation speed Ne of the hydrogen engine 10 is lower than the predetermined value C (before time t3 and after time t5 shown in FIG. 5), or the determination condition of step S207 Is not satisfied, that is, when the counter Si is smaller than the predetermined value D, the process proceeds to step S208. In step S208, it is determined whether a predetermined time or more has elapsed after the previous high combustion temperature determination. If the determination condition in step S208 is satisfied, that is, if a predetermined time or more has elapsed after previously determining that the combustion temperature was high, the process proceeds to step S209, where it is determined that the combustion temperature is low, and this routine ends. On the other hand, if the determination condition in step S208 is not satisfied, that is, if a predetermined time or more has not elapsed since the combustion temperature was previously determined to be high, the routine ends without performing any operation.
[0030]
As described above, even if the engine rotational speed Ne once exceeds the predetermined value C or the intake pressure PM once exceeds the predetermined value A, and if both become lower than the predetermined value, the combustion temperature is not immediately determined to be low. The combustion temperature low determination is not performed until the delay time (time t5 to time t6 shown in FIG. 5) as a predetermined time elapses, that is, until the actual combustion temperature is considered to be low, so that the EGR is prohibited. .
[0031]
Next, a description will be given with reference to FIG. 5 based on the flowchart of FIG. 4 showing the processing procedure of the combustion state determination in FIG.
[0032]
In FIG. 4, in step S301, the previous engine speed Ne (i-1) is subtracted from the current engine speed Ne (i) based on the crank position signal from the crank position sensor 23, and the engine speed fluctuation amount ΔNe [ rpm] is calculated. Next, the process proceeds to step S302, and it is determined whether the engine speed fluctuation amount ΔNe calculated in step S301 exceeds a predetermined value E. When the determination condition of step S302 is satisfied, that is, when the engine speed fluctuation amount ΔNe exceeds the predetermined value E and is large (time t1 to time t2 shown in FIG. 5), the process proceeds to step S303, and the combustion state is deteriorated. Is determined, and this routine ends. On the other hand, when the determination condition of step S302 is not satisfied, that is, when the engine speed fluctuation amount ΔNe is smaller than the predetermined value E, the process proceeds to step S304, the combustion state is determined to be good, and this routine ends.
[0033]
As described above, the control apparatus for a hydrogen engine according to the present embodiment includes the hydrogen engine 10 using hydrogen as fuel, the combustion temperature determination means achieved by the ECU 40 that determines the combustion temperature of the hydrogen engine 10, and the hydrogen engine 10. When it is determined by the ignition timing control means achieved by the ECU 40 for controlling the ignition timing and the combustion temperature determination means that the combustion temperature is low, EGR (exhaust gas recirculation) of the hydrogen engine 10 is carried out at the same time as the ignition. Recirculation control means achieved by the ECU 40 which also advances the ignition timing by the timing control means.
[0034]
That is, when it is determined that the combustion temperature of the hydrogen engine 10 is low, the ignition timing is advanced at the same time as the EGR is performed. This makes it possible to prevent the occurrence of backfire and the like in conjunction with the decrease in the ignition speed of the hydrogen engine, to reduce NOx and to improve fuel efficiency.
[0035]
Further, the control device for a hydrogen engine of the present embodiment includes an intake pressure sensor 16 as a load detecting means for detecting an intake pressure PM as a load of the hydrogen engine 10, and a rotational speed detection for detecting an engine rotational speed Ne of the hydrogen engine 10. The combustion temperature determining means provided by the ECU 40 includes a crank position sensor 23 as a means, and when the intake pressure sensor 16 detects a low load and the crank position sensor 23 detects a low rotation, the combustion temperature is low. Is determined. This makes it possible to determine whether the combustion temperature in the hydrogen engine 10 is high or low and to omit a sensor or the like for detecting the actual combustion temperature, so that a simple and inexpensive system can be constructed.
[0036]
The recirculation control means achieved by the ECU 40 of the hydrogen engine control device according to the present embodiment provides a high load in which the counter Ti exceeds a predetermined value B for a predetermined period when the intake pressure PM by the intake pressure sensor 16 is high, that is, a high load. After the intake pressure or at least one of the high-speed operation conditions in which the counter Si exceeds a predetermined value D is detected for a predetermined period when the engine rotation speed Ne by the crank position sensor 23 is higher than the predetermined value D, the low intake pressure by the intake pressure sensor 16 and the crank Even if low rotation is detected by the position sensor 23, the EGR is prohibited for a delay time as a predetermined period. That is, it is considered that the combustion temperature is high immediately after the high intake pressure of the hydrogen engine 10 for a predetermined period or more, and immediately after the high rotation for a predetermined period or more, and the combustion is reliably performed by prohibiting the EGR for the delay time. Since the EGR is started again when the temperature decreases, it is possible to prevent the drivability from being deteriorated due to backfire or the like.
[0037]
Further, the control apparatus for a hydrogen engine according to the present embodiment includes an intake camshaft 20 as a driven shaft for opening and closing an intake valve 19 and an exhaust valve 24 from a crankshaft (not shown) as a drive shaft of the hydrogen engine 10 and an exhaust side. An intake-side variable valve timing control mechanism 21 and an exhaust-side variable valve timing control mechanism 26 that are provided in a driving force transmission system that transmits driving force to the camshaft 25 and that can freely change the opening and closing timing of the intake valve 19 and the exhaust valve 24 are provided. The recirculation control means achieved by the ECU 40 performs internal EGR by changing the valve overlap amount by the intake-side variable valve timing control mechanism 21 and the exhaust-side variable valve timing control mechanism 26. Thereby, the internal EGR amount in the hydrogen engine 10 can be easily changed as needed.
[0038]
Furthermore, the control apparatus for a hydrogen engine according to the present embodiment includes a combustion state determination unit that is achieved by the ECU 40 that determines the combustion state of the hydrogen engine 10. When the deterioration of the combustion state is determined by the combustion state determination means, the EGR amount is reduced. As a result, the supply of an excessive amount of EGR to the hydrogen engine 10 can be suppressed, and deterioration of drivability due to backfire or the like can be prevented.
[0039]
In addition, the control device for a hydrogen engine according to the present embodiment includes a crank position sensor 23 as a rotation speed detection unit that detects the engine rotation speed Ne of the hydrogen engine 10. The determination of the deterioration of the combustion state is made based on the engine speed fluctuation amount ΔNe by the crank position sensor 23. As a result, deterioration of the combustion of the hydrogen engine 10 can be easily determined, and an inexpensive system can be constructed.
[0040]
In the above embodiment, the internal EGR amount with respect to the hydrogen engine 10 is increased / decreased by using the intake side variable valve timing control mechanism 21 and the exhaust side variable valve timing control mechanism 26 as the EGR control. However, the present invention is not limited to this, and the external EGR amount can be increased / decreased from the exhaust passage side to the intake passage side using a known external EGR mechanism.・ Effect can be expected.
[0041]
Further, in the above embodiment, the correction amount of the ignition timing to the advance side / retard side is set at the same time as the increase / decrease of the EGR amount as the EGR control. However, the present invention is not limited to this, and may be only the increase / decrease of the EGR amount.
[0042]
In the above embodiment, the intake pressure PM detected by the intake pressure sensor 16 is used as the load of the hydrogen engine 10. However, the present invention is not limited to this. For example, the amount of intake air detected by the controller 13 may be used.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram showing a hydrogen engine to which a control device for a hydrogen engine according to an embodiment of the present invention is applied and peripheral devices thereof.
FIG. 2 is a flowchart illustrating a processing procedure of EGR control in an ECU used in the hydrogen engine control device according to one example of the embodiment of the present invention.
FIG. 3 is a flowchart illustrating a processing procedure for determining a combustion temperature in FIG. 2;
FIG. 4 is a flowchart showing a processing procedure for determining a combustion state in FIG. 2;
FIG. 5 is a time chart showing transition states of various sensor signals, various control amounts, and the like corresponding to the processes of FIGS. 2 to 4;
[Explanation of symbols]
Reference Signs List 10 Hydrogen engine 16 Intake pressure sensor 19 Intake valve 20 Intake side camshaft 21 Intake side variable valve timing control mechanism 22 Intake side cam position sensor 23 Crank position sensor 24 Exhaust valve 25 Exhaust side camshaft 26 Exhaust side variable valve timing control mechanism 27 Exhaust cam position sensor 40 ECU (electronic control unit)

Claims (7)

A hydrogen engine powered by hydrogen,
Combustion temperature determination means for determining a combustion temperature of the hydrogen engine;
A recirculation control unit for recirculating exhaust gas of the hydrogen engine when the combustion temperature determination unit determines that the combustion temperature is low. A hydrogen engine powered by hydrogen,
Combustion temperature determination means for determining a combustion temperature of the hydrogen engine;
Ignition timing control means for controlling the ignition timing of the hydrogen engine,
Recirculation control means for recirculating the exhaust gas of the hydrogen engine when the combustion temperature determination means determines that the combustion temperature is low, and at the same time advancing the ignition timing by the ignition timing control means. A control device for a hydrogen engine. Load detection means for detecting a load on the hydrogen engine,
Rotation speed detection means for detecting the engine rotation speed of the hydrogen engine,
3. The combustion temperature judging means judges that the combustion temperature is low when a low load is detected by the load detecting means and a low rotation is detected by the rotational speed detecting means. 3. The control device for a hydrogen engine according to 1. The recirculation control unit detects a low load by the load detection unit after detecting at least one operation condition of a high load for a predetermined period or more by the load detection unit or a high rotation for a predetermined period or more by the rotation speed detection unit. 4. The hydrogen engine control device according to claim 3, wherein the recirculation of the exhaust gas is prohibited for a predetermined period even when a low speed is detected by a load and the rotation speed detection unit. A driving force transmission system that transmits driving force from a driving shaft of the hydrogen engine to a driven shaft that opens and closes at least one of an intake valve and an exhaust valve, and controls an opening / closing timing or a lift amount of the intake valve or the exhaust valve. Equipped with a variable valve timing control mechanism that can be changed,
3. The hydrogen engine control device according to claim 1, wherein the recirculation control unit recirculates the exhaust gas by changing a valve overlap amount by the variable valve timing control mechanism. . A combustion state determination unit that determines a combustion state of the hydrogen engine;
3. The hydrogen engine according to claim 1, wherein the recirculation control unit reduces the recirculation amount of the exhaust gas when the combustion state determination unit determines that the combustion state has deteriorated. 4. Control device. A rotation speed detection unit that detects an engine rotation speed of the hydrogen engine,
The control apparatus for a hydrogen engine according to claim 6, wherein the combustion state determination unit determines the deterioration of the combustion state based on a variation amount of the engine rotation speed by the rotation speed detection unit.

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