JP2004116398A - Internal combustion engine using hydrogen and method for operating the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a technology for reducing NOx in emission gas while securing sufficient efficiency of an internal combustion engine and preventing inconvenience of increase of hydrogen consumption. <P>SOLUTION: Gasoline injection quantity and hydrogen injection quantity required for generating request torque are established in controlling a driving condition of an engine (step S120). Each of the injection quantity is established to be a predetermined ratio as a ratio of a condition that quantity of NOx in emission gas is sufficiently low. Under a low load condition, injection control of gasoline and hydrogen is carried out to actually inject the quantity established above (step S140). Under a high load condition, injection controls are carried out with controlling hydrogen injection quantity at a predetermined upper limit value and EGR is carried out (step S150). At this time, if quantity of NOx exceeds a predetermined value, quantity of EGR gas is increased until NOx is sufficiently reduced (step S160-S180). <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a hydrogen-using internal combustion engine using hydrogen gas together with a hydrocarbon fuel as a fuel for combustion, and a method of operating the same.
[0002]
[Prior art]
In an internal combustion engine that uses gasoline as fuel, by supplying hydrogen gas in addition to gasoline, the lean limit of the combustion reaction can be expanded, so that nitrogen oxides (NOx) in exhaust gas can be further reduced. It is known to be. When lean combustion is performed by adding hydrogen as described above, the combustion temperature is reduced, so that energy loss due to heat release in the internal combustion engine is reduced, and the effect of improving the efficiency of the internal combustion engine is also obtained. Further, when performing lean combustion, the throttle valve is opened more widely, so that energy loss (pump loss) when the internal combustion engine performs intake can be reduced, which also has the effect of improving the efficiency of the internal combustion engine. Can be When NOx is reduced by further supplying hydrogen in addition to gasoline as fuel, it is known that the degree of NOx reduction can be sufficiently ensured by increasing the ratio of the hydrogen supply amount to a certain level or more. Have been.
[0003]
As another method for reducing NOx in exhaust gas exhausted from an internal combustion engine, a method of recirculating exhaust gas exhausted from a combustion chamber to an intake side (exhaust gas recirculation (EGR)) is also known. By recirculating the exhaust gas to the intake side, the combustion temperature decreases, so that the NOx amount in the exhaust gas is reduced. Further, when performing such EGR, under a certain condition where the air-fuel ratio takes a predetermined value, by performing simultaneously with the operation of supplying hydrogen in addition to gasoline, the exhaust gas NOx amount can be further reduced. (For example, see Patent Document 1).
[0004]
[Patent Document 1]
JP-A-10-306750
[Patent Document 2]
JP-A-59-43939
[Patent Document 3]
JP-A-53-70219
[0005]
[Problems to be solved by the invention]
However, when reducing NOx by supplying hydrogen, if hydrogen is supplied at a sufficient ratio to the supplied gasoline amount to reduce the amount of NOx in the exhaust gas, the higher the load request, the more hydrogen is supplied. It is necessary to increase the amount. Therefore, when the load fluctuation is large and the available hydrogen amount is limited, as in the case of using a gasoline engine as a power source for driving a vehicle, in order to secure a cruising distance, It is required to reduce the consumption of methane as much as possible. Further, when NOx is reduced by EGR, supply of exhaust gas to the intake side may cause unstable combustion, resulting in deterioration of drivability and a decrease in output, which may cause a reduction in efficiency. there were.
[0006]
SUMMARY OF THE INVENTION The present invention has been made to solve the above-described conventional problems, and reduces the NOx in exhaust gas and prevents inconveniences such as an increase in hydrogen consumption while ensuring sufficient efficiency in an internal combustion engine. The purpose is to provide the technology for.
[0007]
[Means for Solving the Problems and Their Functions and Effects]
In order to achieve the above object, the present invention is a hydrogen-using internal combustion engine using hydrogen gas together with a hydrocarbon fuel as a fuel for combustion,
A combustion chamber,
A hydrocarbon fuel supply unit for supplying hydrocarbon fuel to the combustion chamber,
A hydrogen supply unit that supplies hydrogen gas to the combustion chamber,
In response to a load request, a hydrocarbon fuel supply amount supplied from the hydrocarbon fuel supply unit, and a supply fuel amount control unit that determines a hydrogen gas supply amount supplied from the hydrogen supply unit,
An exhaust gas supply unit that supplies a part of the internal combustion engine exhaust gas to the combustion chamber;
With
The fuel supply amount control unit,
When it is assumed that the hydrocarbon fuel supply amount and the hydrogen gas supply amount are set in accordance with the load request such that the ratio of the hydrogen gas supply amount to the hydrocarbon fuel supply amount becomes a predetermined value, the hydrogen gas When the supply amount is equal to or less than a predetermined upper limit value, the set hydrogen gas supply amount and the hydrocarbon fuel supply amount are set to the amounts to be actually supplied, and when the hydrogen gas supply amount exceeds the predetermined upper limit value, the predetermined amount is set. The upper limit is the amount of hydrogen gas to be actually supplied,
The gist of the invention is that the exhaust gas supply section supplies the exhaust gas when the hydrogen gas supply amount exceeds the predetermined upper limit value when the above assumption is made.
[0008]
With such a configuration, when the load request is relatively small, hydrogen gas is supplied to the internal combustion engine in addition to the hydrocarbon fuel so that the ratio of the hydrogen gas supply amount to the hydrocarbon fuel supply amount becomes a predetermined value. Therefore, it becomes possible to sufficiently reduce the NOx amount in the exhaust gas by performing the lean combustion. Furthermore, by performing lean combustion, energy loss and pump loss due to heat release can be reduced, and the efficiency of the internal combustion engine can be improved. Further, when the load request is relatively large, the hydrogen gas supply amount is set to the predetermined upper limit value, so that the consumption amount of the hydrogen gas can be suppressed. When the load demand is relatively large, the EGR is further performed, so that the NOx amount in the exhaust gas can be sufficiently reduced. Even in the case where EGR is performed as described above, by supplying hydrogen gas in addition to hydrocarbon fuel, it is possible to stably perform combustion in a leaner state, thereby improving the efficiency of the internal combustion engine. Can be obtained.
[0009]
In the hydrogen-using internal combustion engine of the present invention,
A NOx sensor for detecting an amount of nitrogen oxides in exhaust gas discharged from the combustion chamber,
The exhaust gas supply unit may further increase the amount of the exhaust gas supplied to the combustion chamber when the amount of the nitrogen oxide detected by the NOx sensor exceeds a predetermined amount.
[0010]
With such a configuration, when the load demand is relatively large, the amount of exhaust gas supplied to the combustion chamber is made sufficiently large, so that the amount of NOx in the exhaust gas can be sufficiently reduced. At this time, since a hydrogen gas is further supplied to the combustion chamber in addition to the hydrocarbon fuel, a good combustion state can be obtained even if the amount of exhaust gas subjected to EGR is increased until the amount of NOx in the exhaust gas is sufficiently reduced. It can be maintained.
[0011]
Further, in the hydrogen-using internal combustion engine of the present invention,
The apparatus further includes a torque fluctuation detection unit that detects a fluctuation in torque output by the internal combustion engine,
When the magnitude of the torque fluctuation detected by the torque fluctuation detecting section exceeds a predetermined value, the supplied fuel amount control section may further increase the actually supplied hydrogen gas amount.
[0012]
With such a configuration, the amount of hydrocarbon fuel or hydrogen gas supplied to the combustion chamber becomes insufficient due to some inconvenience, or the combustion state becomes insufficient due to an excessive amount of exhaust gas supplied to the combustion chamber. Even if it deteriorates, such a combustion state can be immediately improved.
[0013]
In the hydrogen-using internal combustion engine of the present invention,
The hydrogen supply unit may supply a hydrogen gas containing substantially no other component.
[0014]
With such a configuration, since there is no possibility that other components deteriorate the combustion state, even in a leaner (high air-fuel ratio) state, combustion can be performed without any trouble. By increasing the air-fuel ratio, it is possible to sufficiently obtain the effect of reducing NOx in exhaust gas. Here, the hydrogen gas containing substantially no other component may be, for example, a hydrogen gas having a hydrogen concentration of 90% or more.
[0015]
In the hydrogen-using internal combustion engine of the present invention,
The hydrocarbon is gasoline;
The predetermined value, which is a ratio of the hydrogen gas supply amount to the hydrocarbon fuel supply amount, may be a value corresponding to a calorific value ratio of 20% or more.
[0016]
With such a configuration, when the ratio of the actually supplied hydrogen gas amount to the actually supplied hydrocarbon fuel amount becomes 20% or more in terms of the calorific value ratio, the NOx amount in the exhaust gas becomes substantially zero. It is possible to do.
[0017]
In the hydrogen-using internal combustion engine of the present invention,
Depending on the supply amount of the hydrocarbon fuel and the supply amount of the hydrogen gas, the intake amount of the air used for combustion is adjusted so that a predetermined amount of air is taken in as a condition for sufficiently reducing the amount of nitrogen oxides in the exhaust gas. An intake air amount control unit for controlling may be further provided.
[0018]
By controlling the intake air amount in this manner, the effect of reducing the NOx amount in the exhaust gas can be sufficiently enhanced. In order to further reduce the amount of NOx in the exhaust gas, the amount of intake air may be set so that the air-fuel ratio becomes higher within a range where the combustion reaction in the combustion chamber proceeds without hindrance. When controlling the amount of intake air in this way, it is desirable to control, for example, the amount of NOx in exhaust gas to be 1 g / kWh or less.
[0019]
The present invention can be realized in various forms other than the above, and for example, can be realized in a form such as an operation method of an internal combustion engine.
[0020]
BEST MODE FOR CARRYING OUT THE INVENTION
Next, embodiments of the present invention will be described in the following order based on examples.
A. Overall configuration of the device:
B. Driving behavior:
C. effect:
D. Modification:
[0021]
A. Equipment configuration:
FIG. 1 is an explanatory diagram illustrating a schematic configuration of an engine 10 including a control device according to one embodiment of the present invention. As is well known, the operation principle of an engine is to burn fuel in a combustion chamber, convert combustion heat generated at that time into mechanical work, and output it as power. The engine 10 illustrated in FIG. 1 is mounted on a vehicle as a power source for driving the vehicle, and includes a cylinder block 11 provided with a cylindrical cylinder, a cylinder head 20 mounted on an upper portion of the cylinder block 11, and A combustion chamber is formed by the piston 12 slidably assembled inside the cylinder.
[0022]
The cylinder block 11 is provided with a combustion pressure sensor 42 for detecting the combustion pressure in the combustion chamber. The cylinder head 20 has an intake valve 22 for sucking air into the combustion chamber, an exhaust valve 21 for discharging exhaust gas from the combustion chamber, a spark plug 23, and an injector 35 for injecting fuel. Is provided. The injector 35 is an electromagnetic valve that is driven to open and close by power supply control to inject fuel. The injector 35 is provided with a pressure sensor 57, and is supplied with fuel pressurized to a predetermined pressure by a gasoline high-pressure pump 58. The fuel injected from the injector 35 evaporates in the combustion chamber and mixes with the air introduced through the intake valve 22 to form an air-fuel mixture. The cylinder head 20 is provided with an intake manifold 30 for guiding air to the combustion chamber and an exhaust manifold 16 for guiding exhaust gas discharged from the combustion chamber.
[0023]
The intake manifold 30 is connected to an air cleaner 34 via a surge tank 31 and an intake passage 32. When the outside air passes through the air cleaner 34, foreign matter is removed by an element provided in the air cleaner. An air flow meter 33 for detecting an intake air amount is provided in the intake passage 32 on the downstream side of the air cleaner 34. Further, an EGR valve 38 for introducing exhaust gas discharged from the combustion chamber is provided between the air flow meter 33 and the surge tank 31 in the intake passage 32. As described above, the EGR is to recirculate the exhaust gas discharged from the combustion chamber to the intake side. The operation of the EGR executed in the present embodiment will be described later in detail. Further, a hydrogen injector 39 for injecting hydrogen gas is mounted between the EGR valve 38 and the surge tank 31 in the intake passage 32. The hydrogen injector 39 is connected via a hydrogen flow path 54 to a hydrogen tank 50 that stores hydrogen. A hydrogen pump 52 is provided in the hydrogen flow path 54, and a pressure sensor is provided in a connection portion between the hydrogen tank 50 and the hydrogen flow path 54, and hydrogen pressurized to a predetermined pressure by the hydrogen pump 52 is The hydrogen is supplied to the hydrogen injector 39. The hydrogen injector 39 is an electromagnetic valve that is opened / closed and driven to inject hydrogen by energization control. The hydrogen injected from the hydrogen injector 39 is mixed with the air in the intake passage 32 and supplied to the combustion chamber.
[0024]
A throttle valve 36 for adjusting the amount of air flowing into the combustion chamber is provided in the intake manifold 30 on the downstream side of the surge tank 31. The throttle valve 36 is driven to open and close by a throttle motor 37 so that a desired amount of intake air is realized in the engine 10.
[0025]
The exhaust manifold 16 has a NOx sensor 59 and is connected to the catalytic converter 54. The exhaust gas discharged from the engine 10 contains nitrogen oxides (NOx) generated by the reaction of nitrogen in the air, and the NOx sensor 59 detects the amount of NOx in the exhaust gas. The catalytic converter 54 includes a catalyst for purifying exhaust gas discharged from the engine 10. That is, a three-way catalyst that oxidizes hydrocarbons (HC) and carbon monoxide (CO), which are incomplete combustion components in the exhaust gas, and reduces NOx is provided. The exhaust gas purified by the catalytic converter 54 by the action of the catalyst is discharged into the atmosphere.
[0026]
Further, the exhaust manifold 16 is provided with an EGR flow path 44 which is a flow path branched therefrom. In the engine 10 of the present embodiment, an operating state in which a part of the exhaust gas discharged from the combustion chamber is recirculated (EGR) to the combustion chamber in addition to the intake air taken in from the outside can be selected. . Part of the exhaust gas is supplied from the above-described EGR valve 38 into the intake passage 32 through the EGR flow path 44 and mixed with the intake air. By performing the valve opening control of the EGR valve 38, the gas amount (EGR gas amount) circulated to the combustion chamber is adjusted.
[0027]
The piston 12 is connected to a crankshaft 17 via a crank mechanism. When the crankshaft 17 rotates, the rotational motion is converted into a reciprocating linear motion by the function of the crank mechanism, and the piston 12 slides up and down in the cylinder. The movement of the piston 12 moving up and down is converted into a rotational movement of the crankshaft 17 by the crank mechanism. When the piston 12 descends with the exhaust valve 21 closed and the intake valve 22 opened, air and fuel in the intake manifold 30 flow from the intake valve 22 into the combustion chamber. Next, the intake valve 22 is closed to raise the piston 12 to compress the intake air-fuel mixture, and then, when a spark is blown from the ignition plug 23, the air-fuel mixture compressed by the piston 12 explosively burns, causing the piston 12 to burn. Push down. This force is converted into rotational motion by the crank mechanism, and is output from the crankshaft 17 as power. A crank angle sensor 41 for detecting a rotational position of the crankshaft is provided at a tip of the crankshaft 17.
[0028]
An electronic control unit (ECU) 40 controls the overall operation of the engine 10, such as fuel injection control, ignition timing control, and EGR control. The ECU 40 is a logical operation circuit configured by connecting a central processing unit (hereinafter, CPU), a ROM, a RAM, an input / output circuit, and the like to each other by a bus.
[0029]
Such control by the ECU 40 is performed by the ECU 40 detecting various operating conditions such as the accelerator opening, the engine speed, and the intake air amount operated by the driver, and according to various programs stored in the ROM, the throttle motor 37 and the ignition motor. This is performed by driving the plug 23, the injector 35, the hydrogen injector 39, and the like. The accelerator opening is detected by an accelerator opening sensor 44 provided on the accelerator pedal. The engine rotation speed is calculated based on the detection signal of the crank angle sensor 41 provided on the crankshaft 17 described above. Further, the intake air amount is obtained based on a detection signal of an air flow meter 33 provided in the intake passage 32.
[0030]
The fuel injection control is to inject an appropriate amount of fuel in accordance with the amount of air introduced into the combustion chamber, thereby adjusting the air-fuel ratio (air-fuel ratio) of the air-fuel mixture formed in the combustion chamber to an appropriate value. This is control to keep the value. In the present embodiment, as the control of the fuel injection amount, the amount of gasoline injected from the injector 35 and the amount of hydrogen injected from the hydrogen injector 39 are controlled.
[0031]
The ignition timing control is a control for blowing a spark at an appropriate timing in accordance with the rise of the piston 12. The EGR control is a control for reducing a NOx in the exhaust gas by circulating a predetermined amount of the exhaust gas discharged from the combustion chamber to the combustion chamber.
[0032]
B. Driving behavior:
FIG. 2 is a flowchart illustrating a NOx reduction processing routine that is repeatedly executed at a predetermined cycle in the ECU 40 while the engine 10 of the present embodiment is operating. When this routine is executed, first, the ECU 40 acquires the rotation speed and the accelerator opening of the engine 10 (step S100). When the rotation speed and the accelerator opening of the engine 10 are acquired, the ECU 40 calculates the required torque of the engine 10 based on these (step S110), and determines the gasoline injection amount, the hydrogen injection amount, and the intake air amount as Q respectively. _G '(Cc / st), Q _H '(Cc / st), P' is set (step S120).
[0033]
FIG. 3 is a diagram showing the result of examining the amount of NOx in exhaust gas at that time by injecting gasoline and hydrogen at various ratios in the same engine as the embodiment. In FIG. 3, the intake air amount is changed under each condition where the gas / water ratio is varied, and when the NOx concentration in the exhaust gas becomes the lowest, that is, the intake air amount (air-fuel ratio) is optimal. The measured value when this happens is the NOx amount in the exhaust gas under that condition. Therefore, in each measurement result shown in FIG. 3, the air-fuel ratio at the time of measurement is not always the same. The optimum value of the intake air amount will be further described. If hydrogen is supplied to the engine in addition to gasoline, the combustion reaction can proceed at a higher air-fuel ratio without any problem. At this time, as long as the combustion reaction proceeds without hindrance, increasing the air amount as much as possible can further reduce the NOx amount in the exhaust gas by lowering the combustion temperature. However, if the amount of air is excessive, inconveniences such as misfires will occur. Therefore, the optimum value of the intake air amount can be regarded as the maximum value of the intake air amount within a range in which the combustion reaction proceeds without hindrance.
[0034]
As shown in FIG. 3, when the intake air amount (air-fuel ratio) is adjusted to the optimum value, the ratio of hydrogen to gasoline is 30% or more in terms of the calorific value (the ratio of the calorific value of hydrogen to the total heat amount is 22% or more). When the value corresponds to, the NOx amount in the exhaust gas can be made substantially zero. Therefore, in this embodiment, the gasoline injection amount set value Q is set in step S120 so that the ratio of the hydrogen injection amount to the gasoline injection amount becomes 30% in terms of the calorific value ratio. _G 'And hydrogen injection amount setting Q _H '
[0035]
In the present embodiment, the required torque in the engine 10 and the corresponding gasoline injection amount, hydrogen injection amount, and intake air amount are stored in the ECU 40 as a map in advance. That is, the amount of fuel (gasoline injection amount and hydrogen injection amount at which the heat amount ratio becomes the above value) required to convert thermal energy into mechanical work in the engine 10 to obtain a predetermined required torque, and the intake air at this time The optimal value of the quantity is stored in advance for the required torque. As described above, the optimum value of the intake air amount is a value determined experimentally. In step 120, based on the required torque calculated in step S110, the gasoline injection amount set value Q _G ', Hydrogen injection amount set value Q _H 'And the intake air amount set value P' are determined.
[0036]
Next, the hydrogen injection amount Q set in step S120 _H 'And the predetermined reference value Q ₀ (Cc / st) (step S130). Where the reference value Q ₀ Is a value preset as the upper limit value of the hydrogen injection amount and stored in the ECU 40.
[0037]
In step S130, the hydrogen injection amount set value Q _H 'Is the reference value Q ₀ If it is determined to be less than or equal to, the hydrogen injection amount Q _H (Cc / st), gasoline injection amount Q _G (Cc / st) and the intake air amount P are respectively determined by the Q set in step S120. _H ', Q _G 'And P'. Further, the opening of the EGR valve 38 (EGR opening) is determined to be zero, that is, the EGR gas amount is determined to be zero. Then, a drive signal is output to the hydrogen injector 39, the injector 35, the throttle motor 37, and the EGR valve 38 so that the injection amount and the gas amount become the above values (step S140). Note that a throttle opening for obtaining a predetermined intake air amount is experimentally set in advance in accordance with the rotation speed of the engine 10 and stored in the ECU 40 as a map. Therefore, in step S140, the throttle opening is determined by referring to the map based on the engine speed detected in step S100 and the intake air amount P determined in step S120, and the throttle motor 37 is driven. ing.
[0038]
In step S140, when the drive signal is output as described above, the process proceeds to step S180 to detect the torque. The processing after step S180 will be described later.
[0039]
In step S130, the hydrogen injection amount set value Q 'is set to the predetermined reference value Q ₀ If it is determined that the hydrogen injection amount Q _H Is the reference value Q ₀ Is determined. Also, the gasoline injection amount Q _G Is the gasoline injection amount set value Q set in step S120. _G Is determined to be larger than '(Q _G = Q _G '+ Α). Here, the gasoline injection amount set value Q _G Α, which is an increment for ', is for correcting the gasoline injection amount in order to obtain the required torque calculated in step S110. That is, the hydrogen injection amount Q _H With the hydrogen injection amount set value Q _H Q less than ' ₀ This is an additional amount for compensating for a decrease in output energy due to the above-mentioned suppression by increasing the gasoline injection amount. Further, the intake air amount P is determined to be P ′ set in step S120. Further, the opening degree of the EGR valve 38 is determined to be a predetermined opening degree B%. Then, a drive signal is output to the hydrogen injector 39, the injector 35, the throttle motor 37, and the EGR valve 38 so that the injection amount and the gas amount become the above values (step S150). The control of the intake air amount is performed by determining the throttle opening with reference to a predetermined map based on the detected engine rotation speed and the determined intake air amount P, similarly to step S140. .
[0040]
In the above description, one of steps S140 and S150 is performed after steps S120 and S130. However, actually, these steps are not performed separately. In the engine 10, as a map for determining the hydrogen injection amount based on the required torque, the upper limit of the hydrogen injection amount is initially set to Q so that these determinations can be made simultaneously. ₀ There is a map that is set to keep it low. That is, if the ratio of the hydrogen injection amount to the gasoline injection amount is set to 30% in terms of the calorific value ratio, the hydrogen injection amount Q _H 'Is the reference value Q ₀ Is exceeded, the hydrogen injection amount is Q ₀ However, as the gasoline injection amount, maps are prepared in which the amounts that make up the required torque by supplementing the hydrogen injection amount are stored. And the hydrogen injection amount Q _H Is the reference value Q ₀ For the required torque set in the above, the hydrogen injection amount Q at that time is also _H And gasoline injection quantity Q _G Is stored. Further, a map for setting the throttle opening based on the engine rotation speed when the EGR opening is B% is stored. _H Is the reference value Q ₀ Is set, the throttle opening is set with reference to this map.
[0041]
Next, a detection signal is obtained from the NOx sensor 59 (step S160), and the detected NOx amount in the exhaust gas is compared with a predetermined reference value C (ppm) (step S170). Here, the predetermined reference value C is an upper limit value allowable as the amount of NOx in the exhaust gas, and is set in advance and stored in the ECU 40.
[0042]
If it is determined in step S170 that the NOx amount in the exhaust gas is equal to or smaller than the predetermined reference value C, the process proceeds to step S180 to detect the torque. The processing after step S180 will be described later.
[0043]
When it is determined in step S170 that the NOx amount in the exhaust gas is larger than the predetermined reference value C, the EGR opening is set as the opening obtained by adding the increasing amount F% to the opening B% determined in step S150. It is determined again (step S180). Here, the increase amount F% is a value set in advance as a minimum increase amount of the EGR opening when the EGR gas amount is increased. When the EGR opening is determined again and the EGR valve 38 is driven in this way, the process returns to step S160 and repeats the processing from step S160. When the amount of EGR gas recirculated to the combustion chamber is increased in this manner, the NOx concentration in the exhaust gas decreases due to a decrease in the combustion temperature. Therefore, here, the control of increasing the EGR opening by F% is repeated until the NOx amount in the exhaust gas becomes equal to or less than the reference value C. Since the air-fuel ratio changes by increasing the EGR opening in step S180, a configuration in which the intake air amount is corrected is also possible. Also, by increasing the EGR opening degree, the correspondence relationship between the engine rotation speed, the intake air amount, and the throttle opening degree also changes, so that it is possible to make a correction for this. However, since the increase amount F% is set to a very small value and has little influence on the intake air amount, in this embodiment, the correction of the intake air amount (throttle opening) is not performed.
[0044]
After step S140 or after it is determined in step S170 that the NOx amount is equal to or less than the reference value C, the output torque of the engine 10 is detected, and the magnitude of the torque fluctuation is set to the reference value D (Nm). A comparison is made (step S190). If the combustion state in the engine 10 is disturbed, the torque fluctuation increases. The reference value D is preset and stored in the ECU 40 as a reference value for determining that the combustion state in the engine 10 is proceeding without hindrance.
[0045]
Here, detection of the output torque in the engine 10 will be described. In the engine 10, the torque is detected by measuring the rotation speed of the engine. Hereinafter, the principle of torque detection will be briefly described with reference to FIG. FIG. 4 is an explanatory diagram showing how the engine speed and output torque change in a so-called four-cylinder engine having four combustion chambers. The rotation speed of the engine actually fluctuates with the crank angle even when the engine is operated in a steady state. Such fluctuations occur because the intake stroke, the compression stroke, the expansion stroke, and the exhaust stroke are repeatedly performed in each combustion chamber with slightly different phases. FIG. 4A shows how the engine rotation speed varies with the crank angle. FIG. 4B shows how the output torque fluctuates with respect to the crank angle. FIG. 4C shows four steps for the first cylinder and the pressure in the combustion chamber for each cylinder. In each cylinder, energy is output only at the beginning of the expansion stroke, and energy is consumed in the other cylinders. Therefore, as one of the cylinders enters the expansion stroke, the output torque of the engine 10 increases, thereby increasing the engine rotation speed. Therefore, the output torque can be calculated based on the rate of change of the engine rotation speed. When the combustion reaction proceeds without hindrance, both the engine speed and the output torque fluctuate within a predetermined fluctuation range. However, when a malfunction occurs in the combustion state, the desired torque is not output from the cylinder in which the malfunction has occurred, so that the output torque exhibits an abnormal fluctuation exceeding the predetermined fluctuation range. Actually, a difference between the engine rotation speeds measured at two points corresponding to a predetermined crank angle is obtained, and when the difference is equal to or more than a predetermined value, it is determined that the magnitude of the torque fluctuation is equal to or more than a predetermined reference value. can do. The output torque of the engine 10 may be detected based on the detection signal of the combustion pressure sensor 42 or may be directly detected by providing a torque sensor, in addition to the detection based on the engine rotation speed.
[0046]
When it is determined in step S190 that the magnitude of the torque fluctuation is equal to or smaller than the reference value D, this routine ends. When it is determined in step S190 that the magnitude of the torque fluctuation exceeds the reference value D, a value obtained by adding the increase amount G (cc / st) to the hydrogen injection amount determined in the previous step is used as the hydrogen injection amount. The amount is newly determined (step S200). That is, this step S200 corresponds to the hydrogen injection amount Q in step S140. _H = Q _H If it is a process after it is determined as', the hydrogen injection amount Q _H = Q _H '+ G is determined again. Also, this step S200 corresponds to the hydrogen injection amount Q in step S150. _H = Q ₀ If it is a process after it is determined, the hydrogen injection amount Q _H = Q ₀ + G is determined again. Here, the increase amount G is a value set in advance as a minimum increase amount when increasing the hydrogen injection amount. As described above, it is considered that the large torque fluctuation indicates that the combustion state is inconvenient. Therefore, in this embodiment, the combustion state is improved by increasing the hydrogen injection amount.
[0047]
In step S200, the hydrogen injection amount Q _H Is increased, the process returns to step S160, and the processes in and after step S160 are executed. By increasing the hydrogen injection amount, it is considered that the fuel amount is secured and the combustion state is improved. However, since the combustion chamber becomes richer, the NOx concentration in the exhaust gas may increase. is there. Therefore, after increasing the hydrogen injection amount in step S200, the NOx amount in the exhaust gas is detected, and it is confirmed whether the NOx amount in the exhaust gas is within an allowable range. When the amount of NOx in the exhaust gas exceeds the allowable amount, the amount of the EGR gas to be circulated is increased to reduce the amount of NOx in the exhaust gas. As described above, the problem of the magnitude of the torque fluctuation is improved by increasing the hydrogen injection amount, and when there is an increase in the NOx amount due to this, the NOx amount is improved by increasing the EGR gas amount. When the magnitude of the torque fluctuation finally becomes equal to or smaller than the reference value D in step S190, the present routine ends.
[0048]
C. effect:
According to the engine 10 of the present embodiment configured as described above, it is possible to achieve an improvement in efficiency and a reduction in NOx in exhaust gas while suppressing the consumption of hydrogen. That is, since hydrogen is used in addition to gasoline as fuel, combustion can be performed in a leaner state, and NOx in exhaust gas can be reduced. Further, as described above, the efficiency of the internal combustion engine can be improved by suppressing energy loss and pump loss due to heat release. At this time, when the load is low (the required torque is equal to or less than a predetermined value), the NOx amount in the exhaust gas can be extremely reduced by using the gasoline injection amount and the hydrogen injection amount at a predetermined ratio. In addition, when the load is high (the required torque exceeds a predetermined value), the supply amount of hydrogen is set to the predetermined upper limit value, so that the consumption amount of hydrogen can be suppressed. Further, by further performing the EGR, the NOx amount in the exhaust gas can be sufficiently reduced. Therefore, even if the load fluctuates greatly, it is possible to keep the amount of NOx in the exhaust gas sufficiently small and to keep the efficiency of the internal combustion engine sufficiently high while suppressing the consumption of hydrogen as a whole. it can.
[0049]
D. Modification:
The present invention is not limited to the above-described embodiment, but can be implemented in various modes without departing from the gist of the invention, and for example, the following modifications are possible.
[0050]
D1. Modification 1
In the above embodiment, the ratio of the hydrogen injection amount to the gasoline injection amount was set to a value corresponding to 30% in terms of the calorific value to make the NOx amount in the exhaust gas almost zero, but different ratios were set. Is also good. For example, a lower value may be set so that the heat amount ratio becomes a value corresponding to 20% or 25%. Actually, in particular, when the load (required torque in the engine) is small, the NOx amount in the exhaust gas can usually be made sufficiently close to zero even if the ratio of the hydrogen injection amount is made lower.
[0051]
D2. Modified example 2:
In the above embodiment, when performing control to reduce the amount of NOx in the exhaust gas, the load state is divided into two stages of a low load state and a high load state. However, the load state is divided into more stages. Is also good. For example, the load state may be controlled in three stages: a low load state, a medium load state, and a high load state. That is, in the low load state, as in the low load state of the embodiment, a desired torque can be output, and the ratio of the hydrogen injection amount to the gasoline injection amount becomes a predetermined value (for example, 30%). The injection amount is determined to reduce the NOx amount. Then, in the middle load state, the gasoline injection amount is determined while suppressing the hydrogen injection amount to the first upper limit, and EGR is performed so that the NOx amount is sufficiently reduced. In the high load state, the gasoline injection amount is determined by suppressing the hydrogen injection amount to the second upper limit value larger than the first upper limit value, and EGR is performed so that the NOx amount is sufficiently reduced. With such a configuration, the upper limit of the hydrogen injection amount is provided in a plurality of stages, and the EGR is performed efficiently, so that the effect of suppressing the hydrogen consumption can be further enhanced. The upper limit value of the hydrogen injection amount in the high load state may be set to an amount that allows the combustion reaction to proceed without any problem even when the EGR gas amount is increased until the NOx amount becomes sufficiently small at the maximum load. . Therefore, by using the first upper limit value that is smaller than such an upper limit value determined according to the maximum load in the medium load state, it is possible to reduce the hydrogen consumption as a whole. .
[0052]
D3. Modification 3:
In the embodiment, after the hydrogen injection amount is increased in step S200, the NOx amount in the exhaust gas is detected, and the EGR opening is adjusted as necessary. However, after the step S200, the NOx amount is adjusted. Is not possible. This is because the amount of additional hydrogen required to suppress torque fluctuations is usually very small so as not to affect the A / F (ratio between the amount of air and the amount of fuel). Thus, the combustion state can be improved by setting the hydrogen increase amount G to an extremely small value that does not affect the A / F, and the NOx increase amount in the exhaust gas at this time is ignored. Can be. In this case, after increasing the hydrogen injection amount in step S200, the process may return to step S190 and check the magnitude of the torque fluctuation again.
[0053]
D4. Modification 4:
In the embodiment, the three-way catalyst is disposed on the exhaust side. However, an oxidation catalyst may be used instead of the three-way catalyst. Conventionally, when reducing NOx by EGR, it has been difficult to reduce the NOx amount to a sufficient level because it is necessary to refrain from the EGR gas amount in order to secure combustion. Therefore, usually, NOx is further reduced by the three-way catalyst in the subsequent stage. When combustion is ensured by adding hydrogen according to the present invention, a sufficient amount of EGR gas can be used so that NOx can be sufficiently reduced. Therefore, NOx can be sufficiently reduced without using the latter catalyst. In this case as well, although HC is contained in the exhaust gas, an oxidation catalyst may be used instead of a three-way catalyst, so that the present invention can be easily applied to an internal combustion engine that performs lean combustion as described above.
[0054]
D5. Modification 5:
In the embodiment, gasoline is injected into the combustion chamber (direct injection), and hydrogen is injected into the intake passage 32 (port injection), but various modifications are possible. Either direct injection or port injection can be selected for each of the gasoline injection position and the hydrogen injection position.
[0055]
Further, in the embodiment, the supply position of the EGR gas is set to the upstream side of the surge tank 31 to ensure the mixed state of the EGR gas and the air. However, the EGR gas may be supplied from a different position. . If the EGR gas is supplied from a further downstream side, the temperature of the gas introduced into the combustion chamber can be further increased, and the fuel efficiency can be improved.
[0056]
D6. Modification 6:
In the embodiment, the hydrogen tank 50 is provided to supply hydrogen to the combustion chamber. However, hydrogen generated by reforming gasoline may be supplied to the combustion chamber. However, the reformed gas usually has a hydrogen concentration of about 21% and further contains CO and nitrogen. The use of CO as fuel for combustion leads to a decrease in combustion efficiency. Also, supplying reformed gas containing nitrogen (inert gas) to the combustion chamber is the same as supplying hydrogen and EGR simultaneously. Therefore, when the load is relatively small, in order to obtain the effect of improving the efficiency by adding hydrogen more sufficiently, when using a reformed gas, CO is supplied before being supplied to the internal combustion engine. It is desirable to perform a step of removing or increasing the purity of hydrogen.
[Brief description of the drawings]
FIG. 1 is an explanatory diagram illustrating a schematic configuration of an engine 10 including a control device according to an embodiment of the present invention.
FIG. 2 is a flowchart illustrating a NOx reduction processing routine.
FIG. 3 is a diagram showing the result of examining the amount of NOx in exhaust gas at that time by injecting gasoline and hydrogen at various ratios.
FIG. 4 is an explanatory diagram showing a state in which a rotation speed and an output torque of the engine change in a four-cylinder engine.
[Explanation of symbols]
10 ... Engine
11 ... Cylinder block
12 ... Piston
16 Exhaust manifold
17 ... Crankshaft
20 ... Cylinder head
21 ... Exhaust valve
22 ... intake valve
23… Spark plug
30 ... intake manifold
31 ... Surge tank
32 ... intake passage
33 ... Air flow meter
34 ... Air cleaner
35 ... Injector
36 ... Throttle valve
37 ... Throttle motor
38… EGR valve
39… Hydrogen injector
40 ... ECU
41 ... Crank angle sensor
42 ... combustion pressure sensor
44 ... EGR channel
44 ... Accelerator opening sensor
50 ... hydrogen tank
52 ... hydrogen pump
54: Catalytic converter
54 ... hydrogen flow path
57… Pressure sensor
58… Gasoline high pressure pump
59… NOx sensor

Claims (7)

A hydrogen-using internal combustion engine using hydrogen gas together with a hydrocarbon fuel as a fuel for combustion,
A combustion chamber,
A hydrocarbon fuel supply unit for supplying hydrocarbon fuel to the combustion chamber,
A hydrogen supply unit that supplies hydrogen gas to the combustion chamber,
In response to a load request, a hydrocarbon fuel supply amount supplied from the hydrocarbon fuel supply unit, and a supply fuel amount control unit that determines a hydrogen gas supply amount supplied from the hydrogen supply unit,
An exhaust gas supply unit that supplies a part of the internal combustion engine exhaust gas to the combustion chamber,
The fuel supply amount control unit,
When it is assumed that the hydrocarbon fuel supply amount and the hydrogen gas supply amount are set in accordance with the load request such that the ratio of the hydrogen gas supply amount to the hydrocarbon fuel supply amount becomes a predetermined value, the hydrogen gas When the supply amount is equal to or less than a predetermined upper limit value, the set hydrogen gas supply amount and the hydrocarbon fuel supply amount are set to the amounts to be actually supplied, and when the hydrogen gas supply amount exceeds the predetermined upper limit value, the predetermined amount is set. The upper limit is the amount of hydrogen gas to be actually supplied,
The hydrogen-using internal combustion engine, wherein the exhaust gas supply unit supplies the exhaust gas when the hydrogen gas supply amount exceeds the predetermined upper limit when the assumption is made. The hydrogen-using internal combustion engine according to claim 1,
A NOx sensor for detecting an amount of nitrogen oxides in exhaust gas discharged from the combustion chamber,
The hydrogen-containing internal combustion engine, wherein the exhaust gas supply unit further increases the amount of exhaust gas supplied to the combustion chamber when the amount of nitrogen oxides detected by the NOx sensor exceeds a predetermined amount. The hydrogen-using internal combustion engine according to claim 1 or 2,
The apparatus further includes a torque fluctuation detection unit that detects a fluctuation in torque output by the internal combustion engine,
The supply-fuel-amount control unit is a hydrogen-using internal combustion engine that further increases the amount of hydrogen gas actually supplied when the magnitude of the torque fluctuation detected by the torque fluctuation detection unit exceeds a predetermined value. The hydrogen-using internal combustion engine according to any one of claims 1 to 3, wherein
A hydrogen-using internal combustion engine, wherein the hydrogen supply unit supplies hydrogen gas containing substantially no other component. The hydrogen-using internal combustion engine according to any one of claims 1 to 4,
The hydrocarbon is gasoline;
The hydrogen-using internal combustion engine, wherein the predetermined value, which is a ratio of the supply amount of the hydrogen gas to the supply amount of the hydrocarbon fuel, is a value corresponding to a calorific value ratio of 20% or more. The hydrogen-using internal combustion engine according to any one of claims 1 to 5,
Depending on the supply amount of the hydrocarbon fuel and the supply amount of the hydrogen gas, the intake amount of the air used for combustion is adjusted so that a predetermined amount of air is taken in as a condition for sufficiently reducing the amount of nitrogen oxides in the exhaust gas. A hydrogen-using internal combustion engine further comprising an intake air amount control unit for controlling. A method for operating a hydrogen utilizing internal combustion engine using hydrogen gas together with a hydrocarbon fuel as a fuel for combustion,
(A) determining a hydrocarbon fuel supply amount and a hydrogen gas supply amount to be supplied to a combustion chamber of the internal combustion engine according to a load request;
(B) supplying hydrocarbon fuel to the combustion chamber according to the determination in the step (a);
(C) supplying hydrogen gas to the combustion chamber according to the determination in the step (a);
(D) supplying a portion of the exhaust gas discharged from the internal combustion engine to the combustion chamber under predetermined conditions,
The step (a) comprises:
When it is assumed that the hydrocarbon fuel supply amount and the hydrogen gas supply amount are set in accordance with the load request such that the ratio of the hydrogen gas supply amount to the hydrocarbon fuel supply amount becomes a predetermined value, the hydrogen gas When the supply amount is equal to or less than a predetermined upper limit value, the set hydrogen gas supply amount and the hydrocarbon fuel supply amount are determined as amounts to be actually supplied, and when the hydrogen gas supply amount exceeds the predetermined upper limit value, Determining the predetermined upper limit value as the amount of hydrogen gas to be actually supplied,
The method (d) is a method of operating a hydrogen-using internal combustion engine, including the step of supplying the exhaust gas when the hydrogen gas supply amount exceeds the predetermined upper limit value when the assumption is made.

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