JP2008175159A - Dual fuel engine control system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a dual fuel engine that selectively uses first or second fuel by switching, in which a torque variation is suppressed upon the switching of the fuels, while easing a change in combustion noises, and thereby prevents uncomfortable feeling from being given to passengers. <P>SOLUTION: Upon the switching from hydrogen fuel (the first fuel) having a tendency to increase a torque, to gasoline (the second fuel), an opening of a throttle valve 11 is basically reduced to perform a torque balancing. A throttle opening is maintained during a predetermined period immediately after the switching, while easing combustion by a retard angle of ignition timing and the like. The torque variation and the change in the combustion noises are suppressed thereby. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a control apparatus for a dual fuel engine that can be used by switching between two fuels, and more particularly, to a transient control procedure at the time of fuel switching.

Conventionally, as this type of dual fuel engine, an engine that is mounted on an automobile as disclosed in, for example, Patent Document 1 and can be used by switching between CNG (compressed natural gas) and gasoline is known. When the fuels having different properties are switched and used, the engine torque may fluctuate due to the switching, which may cause an uncomfortable feeling to the occupant. When a shock occurs, the fuel is switched.
JP 2001-193511 A

  However, when the fuel is switched by taking advantage of the operation of the transmission as in the conventional example, even if there is a situation where it is originally preferable to switch the fuel due to demands such as fuel consumption and emission, Unless the machine is operating, the fuel cannot be switched.

  In this regard, it is conceivable to control the engine torque so that the engine torque becomes substantially the same before and after the fuel change by changing the intake charge amount of the engine, but in this way the torque is adjusted by controlling the intake charge amount. However, although the torque fluctuations associated with the fuel change were substantially eliminated, a new problem was found that the change in the combustion noise before and after the change made the passenger feel uncomfortable.

  The present invention has been made in view of such a point, and the object of the present invention is to change the fuel by devising a transitional control procedure when switching the fuel during operation of the dual fuel engine. It is intended to prevent the passenger from feeling uncomfortable by suppressing the change in combustion noise while suppressing the torque fluctuation associated with the vehicle.

  In order to achieve the above object, in the control device according to the present invention, when switching from the first fuel to the second fuel, which tends to increase the torque relatively, the torque matching is basically performed by the intake charge reduction control. However, during a predetermined period immediately after switching, the control for reducing the intake charge amount is suppressed, and the fluctuation in torque is suppressed by slowing down the combustion.

  Specifically, according to the first aspect of the present invention, the first and second fuels can be switched and used, and the first fuel can be used even if the intake charge amount into the combustion chamber is the same when the second fuel is used. It is intended for a dual fuel engine control device that can obtain a higher torque than when using the engine. And a fuel switching means for switching the used fuel from one of the first and second fuels to the other when a predetermined condition is satisfied, and the second fuel to the second fuel during operation of the engine by the fuel switching means. Torque control means for controlling at least the intake charge amount so that the engine torque is substantially the same before and after the changeover to the fuel, and immediately after the changeover to the second fuel by the fuel changeover means. The predetermined period of time is provided with combustion slowing control means for slowing down the combustion so as to suppress the control of the intake charge amount by the torque control means and to reduce the increment of the engine torque thereby.

  With the above configuration, when the fuel is switched from the first fuel to the second fuel by the fuel switching means during operation of the dual fuel engine, the torque control is basically performed so that the engine torque is substantially the same before and after the switching. At least the intake charge amount is controlled by the means. That is, when switching from the first fuel to the second fuel, which tends to increase the torque, the increase in torque is suppressed by reducing the intake charge amount.

  Here, when switching from the first fuel to the second fuel, the combustion pressure tends to increase, and as a result, the combustion noise generated by the engine also increases. If it is made to decrease, the peak of the compression pressure (before ignition) of the intake air in the combustion chamber decreases, but the increase in pressure due to subsequent combustion does not become so small, so the combustion noise does not become so small.

  With regard to this point, in the above-described configuration, during the predetermined period immediately after the fuel switching, the reduction control of the intake charge amount is suppressed by the combustion slowing-down control means so that the peak of the compression pressure in the combustion chamber before ignition does not decrease so much. On the other hand, the combustion is slowed down to suppress an increase in pressure due to the combustion pressure. As a result, an increase in engine torque can be suppressed, an increase in combustion noise immediately after fuel switching can be effectively suppressed, and a change in combustion noise before and after switching becomes gentle so that passengers do not feel uncomfortable. become.

  It should be noted that when a predetermined period immediately after the fuel switching elapses, it is preferable to control the intake charge amount to gradually decrease and the combustion speed to gradually increase, so that the combustion can be performed while maintaining the engine torque. The sound can be changed gradually.

  In order to slow down the combustion as described above, specifically, the ignition timing of the engine is relatively retarded (Claim 2), or the recirculation amount of the exhaust gas is relatively increased (Claim 3). Or the air-fuel ratio of the engine can be made relatively lean (Claim 4). Here, “relatively” does not mean that it is compared with that before the fuel switch, but it is compared with the control target value that is originally set corresponding to the operating state of the engine after the switch to the second fuel. It means that.

  Particularly preferable as the combustion slowing-down control means is to appropriately control the engine control parameters such as the exhaust gas recirculation amount and the air-fuel ratio including at least the ignition timing. And a catalyst temperature detecting means for detecting that the temperature of the catalyst disposed in the exhaust system of the engine is equal to or lower than a predetermined temperature, and switching from the first fuel to the second fuel is performed when the catalyst temperature is equal to or lower than the predetermined temperature. If so, it is preferable to retard at least the ignition timing by the combustion slowing-down control means for a predetermined period immediately after the switching. By so doing, the exhaust temperature rises due to the retard of the ignition timing, and the activation of the catalyst can be promoted.

  Further, when the engine is mounted on a vehicle, an operation input means for performing an operation for switching fuel by an occupant of the vehicle is provided, and an operation to the operation input means is performed as a fuel switching condition by the fuel switching means. It is preferable that the fuel can be switched in accordance with the occupant's will as including the input.

  In this case, it is preferable that the combustion slowing-down control means is used when conditions other than the operation input (for example, predetermined conditions in accordance with engine load, rotation speed, acceleration request, emission request, etc.) are satisfied. Therefore, the control of the intake charge amount by the torque control means is suppressed and the combustion is slowed down. In other words, when the fuel is switched according to the will of the occupant, the occupant hardly feels discomfort even if the combustion sound changes. In this case, by not slowing down the combustion, there is a problem such as deterioration in fuel consumption. It prevents it in advance.

  Further, when the fuel is switched according to the will of the occupant, it can be considered that the torque fluctuation is allowed, so that the torque control means itself is only applied when other conditions other than the operation input to the operation input means are satisfied. The intake charge amount for torque adjustment can be controlled (claim 7).

  As described above, according to the dual fuel engine control device of the present invention, when switching from the first fuel, which tends to increase the torque, to the second fuel, the torque adjustment is basically performed by controlling the reduction of the intake charge amount. However, during the predetermined period immediately after switching, the control for reducing the intake charge amount is suppressed, and the fluctuation in torque is suppressed by slowing down the combustion. , So that the passengers do not feel uncomfortable.

  In particular, when the catalyst temperature is low, at least a predetermined period immediately after the fuel switching, the ignition timing is retarded to slow down the combustion so that the exhaust temperature can be raised and the activation of the catalyst can be promoted.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. It should be noted that the following description of the preferred embodiment is merely illustrative in nature, and is not intended to limit the present invention, its application, or its use.

(Embodiment 1)
FIG. 1 shows a main configuration of an engine control apparatus A according to an embodiment of the present invention. An engine 1 is mounted on an automobile, and hydrogen fuel (corresponding to a first fuel) and gasoline (first fuel) having different properties as fuel. It is a so-called dual fuel engine that can be used by switching between two fuels. Hydrogen fuel tends to cause abnormal combustion such as pre-ignition compared to gasoline, so it is necessary to reduce the air-fuel ratio considerably or to recirculate a large amount of exhaust gas to suppress abnormal combustion. As shown in an example in FIG. 2, even when used at the same opening degree and the same engine speed, that is, when the intake charge amount is the same, the engine torque is higher when using gasoline than when using hydrogen fuel, as shown in an example in FIG. .

  In this embodiment, the engine 1 is a so-called rotary engine, and, as shown in FIG. 1, a rotor housing chamber 3 surrounded by a bowl-shaped rotor housing 2 having a trochoid inner peripheral surface and a side housing (not shown). A substantially triangular rotor 4 is accommodated and configured, and three working chambers (combustion chambers) are formed on the outer peripheral side thereof. In this embodiment, the engine 1 is integrated with the two rotor housings 2 so as to be sandwiched between the three side housings, and the two rotors are housed in the two rotor housing chambers 3 formed therebetween. FIG. 1 shows the two rotor accommodating chambers 3 in an unfolded state.

  The rotor 4 is supported so as to make a planetary rotational movement with respect to the eccentric shaft 5 penetrating the side housing, and the seal portions respectively disposed at the three tops of the outer periphery are respectively trochoidal inner peripheral surfaces of the rotor housing 2. Rotating around the eccentric ring of the eccentric shaft 5 while revolving, and revolving around the axis of the eccentric shaft 5. Then, during one revolution (revolution), the three working chambers formed between the tops of the rotor 4 move in the circumferential direction, and perform the strokes of intake, compression, expansion (combustion), and exhaust. The rotational force generated thereby is output from the eccentric shaft 5 via the rotor 4.

  In each rotor accommodating chamber 3 of the engine 1, two spark plugs 6, 6 are provided in the vicinity of the short axis of the rotor housing 2, so that an air-fuel mixture is obtained at a predetermined timing (ignition timing) for each working chamber. It is supposed to be ignited. On the other hand, an injector 7 for hydrogen fuel is provided in the vicinity of the long axis of the rotor housing 2 so as to inject hydrogen fuel supplied from a hydrogen fuel tank (not shown) into the working chamber from the intake to the compression stroke.

  Each rotor accommodating chamber 3 communicates with an intake passage 8 so as to open toward the working chamber in the intake stroke, and an exhaust passage 9 so as to open toward the working chamber in the exhaust stroke. Are communicating. Although not shown, an air cleaner and an air flow sensor are disposed on the upstream side of the intake passage 8, while the downstream side of the intake passage 8 branches into two and communicates with each rotor accommodating chamber 3 as described above. is doing.

  A throttle valve 11 that is driven by an actuator 10 such as a stepping motor and adjusts the cross-sectional area (valve opening degree) of the passage is disposed in the intake passage 8 before branching, thereby restricting the flow of intake air. The flow rate is adjusted. In addition, injectors 12 and 12 for injecting gasoline supplied from a gasoline fuel tank (not shown) are arranged in the intake passage 8 on the downstream side of the branch portion.

  On the other hand, the upstream side of the exhaust passage 9 is composed of an exhaust manifold branched so as to communicate with each rotor housing chamber 3 as described above, and downstream of the exhaust collecting portion, HC, CO, NOx, etc. in the exhaust A three-way catalyst 13 for purifying harmful components is disposed (a variety of catalysts other than the three-way catalyst can be used). The catalyst 13 is provided with a sensor 14 (hereinafter referred to as a catalyst temperature sensor) for detecting the temperature thereof, and an upstream side of the catalyst 13 is used for detecting the air-fuel ratio state of the exhaust gas based on the oxygen concentration in the exhaust gas. A sensor 15 (exhaust sensor) is provided.

  Further, an exhaust gas recirculation passage 16 (hereinafter referred to as an EGR passage) for returning a part of the exhaust gas to the intake air passage 8 is branched and connected to the exhaust passage 9 upstream of the exhaust sensor 15. The downstream end of 16 communicates with the intake passage 8 on the downstream side of the throttle valve 11. Near the downstream end of the EGR passage 16, an electromagnetic flow control valve 17 (hereinafter referred to as EGR valve) for adjusting the flow rate of the exhaust gas (hereinafter referred to as EGR gas) to be recirculated is disposed.

  The spark plug 6, the actuator 10 of the throttle valve 11, the EGR valve 17, and the injectors 4 and 12 for hydrogen fuel and gasoline are respectively controlled by a powertrain control module 20 (hereinafter referred to as PCM 20). It is like that.

  That is, the PCM 20 includes at least a vehicle speed sensor 21 for detecting a traveling speed (vehicle speed) of an automobile, an accelerator pedal (see FIG. 5), in addition to signals from the airflow sensor, the catalyst temperature sensor 14 and the exhaust sensor 15 described above. A signal is input from an accelerator opening sensor 22 for detecting an operation amount (not shown), a fuel switching switch 23 (operation input means) for performing an operation for switching fuel by an occupant, and the like.

  Based on these input signals, the PCM 20 calculates the torque required for the engine 1, controls the opening of the throttle valve 11 so as to obtain this required torque, and controls the intake charge amount into each working chamber. At the same time, the fuel injection amount from the injectors 4 and 12 is controlled so as to obtain an appropriate air-fuel ratio. Further, the PCM 20 energizes the spark plug 6 at an appropriate timing (ignition timing) for each working chamber, and EGR so that the ratio of fresh air (air) and EGR gas in the intake air is appropriate. The opening degree of the valve 17 is controlled.

  Further, the PCM 20 selects either hydrogen fuel or gasoline according to the operation of the fuel changeover switch 23. If hydrogen fuel is used, the injector 4 is selected. If gasoline is used, the injector 12 is selected. Operate. Further, if the fuel switch 23 is operated even while the engine 1 is in operation, the PCM 20 switches the fuel to be used from one of hydrogen fuel and gasoline to the other.

  By the way, as described above, the engine 1 of this embodiment has the same throttle opening and the same engine rotation speed (that is, even in the same operation state), compared to when using hydrogen fuel when using gasoline. The engine torque is increased, and when the fuel is switched during the engine operation as described above, it is preferable that a large torque fluctuation does not occur before and after the switching.

  Therefore, basically, when switching from hydrogen fuel, which tends to increase torque, to gasoline, the opening degree of the throttle valve 11 is made smaller than the original control target value for a while after the switching, so that the working chamber The amount of intake air charged into the engine is relatively reduced. On the contrary, the opening of the throttle valve 11 may be relatively increased for a while after switching from gasoline to hydrogen fuel so that the intake charge amount increases.

  However, if the intake charge amount is reduced by correcting the throttle control after switching from hydrogen fuel to gasoline, there is almost no fluctuation in engine torque before and after the fuel switch, while the combustion sound generated by the engine 1 suddenly increases. On the other hand, passengers may feel uncomfortable because they grow.

  That is, since the combustion pressure is larger when using gasoline than when hydrogen fuel is used, torque tends to increase and combustion noise tends to increase. As shown in FIG. 3A, the peak of the compression pressure of the intake air (before ignition) decreases while the pressure increase ΔP due to the subsequent combustion is too small. Because it must not be, the combustion noise does not become too small.

  Therefore, in this embodiment, the control of the throttle valve 11 is suppressed for a predetermined period immediately after switching to gasoline so that the compression pressure peak hardly decreases as shown in FIG. Combustion is slowed down by timing delay etc., and the increase in engine torque is suppressed by suppressing the pressure increase after ignition. By doing so, the pressure increase ΔP due to combustion is reduced, and the combustion noise is reduced even when gasoline is used, as in the case of hydrogen fuel.

  The specific control procedure for fuel switching by the PCM 20 will be described below with reference to FIGS. 4 to 6. First, in step SA1 of the flow in FIG. 4, a signal (switch signal) from the fuel switching switch 23 is input. In subsequent step SA2, it is determined whether or not a switching operation has been performed. If this determination is NO and the switching operation is not performed, the process returns. On the other hand, if the determination is YES and the switching operation is performed, the process proceeds to step SA3, and it is determined whether or not the fuel is switched from hydrogen fuel to gasoline. If this determination is NO and switching from gasoline to hydrogen fuel, detailed description is omitted, but switching from gasoline to hydrogen fuel is performed according to a predetermined procedure.

  On the other hand, if switching from hydrogen fuel to gasoline (YES in step SA3), the process proceeds to step SA4, and signals from the vehicle speed sensor 21 and the accelerator opening sensor 22 are input. In the subsequent step SA5, a signal from the catalyst temperature sensor 14 is input, and in step SA6, it is determined whether the catalyst temperature is equal to or lower than the activation temperature. If this determination is NO and the catalyst 13 is activated, the process proceeds to step SA10 described later. On the other hand, if the determination is YES and the catalyst 13 is not activated, the process proceeds to step SA7, and is read from a preset table and read from the target ignition. Decide when.

  In this table, as shown in FIG. 5A, for example, the target ignition timing when using gasoline is set in association with the difference in engine torque when using hydrogen fuel, so that this torque difference is eliminated. The ignition timing is retarded to reduce the engine torque. If the required torque to the engine 1 when using each of hydrogen fuel and gasoline is calculated from the vehicle speed and accelerator opening read in step SA4, the control target value of the ignition timing corresponding to this torque difference is calculated from the table. Can be read.

  The required torque for the engine 1 is obtained from the control map preset for each of the hydrogen fuel and gasoline based on the current vehicle traveling speed and the accelerator opening, and the power transmission system. The torque to be generated by the engine 1 is obtained by performing a necessary correction calculation in consideration of the loss of torque on the road and the driving loss of the auxiliary equipment of the engine 1.

  In step SA8, the injectors 4 and 12 to be operated for each rotor accommodating chamber 3 are switched from the hydrogen fuel injector 4 to the gasoline injector 12, and the throttle is maintained until a predetermined period (for example, 5 seconds) elapses. While maintaining the opening of the valve 11, the ignition timing is controlled to be the target ignition timing determined in step SA7. That is, by retarding the ignition timing from the original control target value when using gasoline, the combustion is slowed down so that the engine torque becomes substantially the same as before fuel switching (when using hydrogen fuel).

  If the predetermined period elapses after the fuel is switched, the process proceeds to step SA9, and thereafter, the opening of the throttle valve 11 is gradually decreased over a preset time (for example, about 1 minute), while the ignition timing is increased. Are gradually advanced to return them to the original control target values when using gasoline, and then return.

  That is, as shown in the time chart of FIG. 6, at the time of switching from hydrogen fuel to gasoline, the opening degree of the throttle valve 11 is maintained for a predetermined period (˜t1) immediately after the switching, and only by retarding the ignition timing. The engine torque is suppressed by suppressing the torque fluctuation of the engine 1 and preventing the combustion noise from suddenly increasing, and thereafter gradually reducing the opening of the throttle valve 11 while gradually returning the ignition timing (t1 to t2). The combustion noise is gradually changed while maintaining.

  Thus, if the ignition timing is retarded relatively, the temperature of the exhaust gas rises, so that the temperature increase of the inactive catalyst 13 can be promoted and the activation thereof can be promoted. Note that not only ignition timing retard control but also air-fuel ratio and EGR correction control as in step SA10 described below may be used in combination to slow down combustion.

  On the other hand, in step SA10 which has been determined that the catalyst 13 has been activated in step SA6, it is read from a preset table in the same manner as in step SA7, and the target air-fuel ratio or target EGR amount (EGR gas amount) is read. Target flow). An example of this table is shown in FIGS. 5B and 5C. In this table, control target values for the air-fuel ratio and the EGR amount are set in association with the torque difference in the same manner as the target ignition timing table.

  In the subsequent step SA11, the injectors 4 and 12 are switched in the same manner as in step SA8, and while the opening of the throttle valve 11 is maintained until a predetermined period elapses, the air-fuel ratio is made leaner or EGR increased, That is, at least one of them is controlled to slow down combustion. Thereafter, the process proceeds to step SA12, and the opening degree of the throttle valve 11 is decreased in the same manner as in step SA9. On the other hand, the air-fuel ratio and the EGR amount are gradually returned to the original control target values, and then returned.

  Fuel switching means 20a for switching the fuel to be used from one of hydrogen fuel and gasoline to the other when the fuel switching switch 23 is operated in accordance with steps SA8 and SA11 of the flow (when a predetermined condition is satisfied). Thus, the steps SA9 and SA12 constitute torque control means 20b for controlling the charging amount of the intake air so that the engine torque becomes substantially the same before and after switching from hydrogen fuel to gasoline.

  In steps SA8 and SA11, the control of the intake charge amount is suppressed for a predetermined period immediately after switching to gasoline, and the ignition timing is retarded so as to reduce the increase in engine torque caused by this, or Combustion slowing control means 20c that slows down the combustion by slowing the fuel ratio or increasing the EGR amount is also configured.

  In particular, in this embodiment, the catalyst temperature detecting means 20d for detecting that the temperature of the catalyst 13 disposed in the exhaust system of the engine 1 is equal to or lower than a predetermined temperature is constituted by step SA6, and the combustion slowing control means 20c. The ignition timing is retarded when the catalyst temperature is equal to or lower than a predetermined temperature.

  The functions of the fuel switching means 20a, torque control means 20b, combustion slowing control means 20c, and catalyst temperature detection means 20d are all realized by the CPU of the PCM 20 executing a control program as shown in FIG. In this sense, it can be said that the PCM 20 includes the respective means in the form of a software program.

  Therefore, according to the control apparatus A for the dual fuel engine according to this embodiment, when switching from hydrogen fuel to gasoline, which tends to increase the engine torque, the throttle valve 11 is set so that the engine torque is substantially the same before and after that. While controlling the opening and controlling the intake charge amount for each working chamber of each rotor accommodating chamber 3, the ignition timing is delayed while maintaining the opening of the throttle valve 11 for a predetermined period immediately after switching. Torque fluctuations can be sufficiently suppressed by slowing the combustion by leaning the angle or the air-fuel ratio or increasing the EGR amount.

  If the engine torque is reduced by slowing down the combustion while maintaining the opening of the throttle valve 11, the peak of the compression pressure in the working chamber does not decrease as shown by the broken line graph in FIG. On the other hand, the increase in pressure due to combustion is reduced, and the combustion noise is reduced even when gasoline is used, as in the case of using hydrogen fuel. Therefore, the change in the combustion sound before and after the fuel switching can be alleviated, and the occupant does not feel uncomfortable.

(Embodiment 2)
FIG. 7 shows the procedure of fuel switching control executed by the PCM 20 in the engine control apparatus A according to Embodiment 2 of the present invention. In the second embodiment, the fuel switching is controlled even when a predetermined condition is established based on the signal from the catalyst temperature sensor 14 in addition to the signal from the fuel switching switch 23. The configuration itself is the same as that of the first embodiment, and the same members are denoted by the same reference numerals, and the description thereof is omitted.

  Then, the flow of FIG. 7 starts when the ignition is turned on, and a signal from the catalyst temperature sensor 14 is input in the first step SB1, and in the subsequent step SB2, it is determined whether or not the catalyst temperature is equal to or lower than the activation temperature. If this determination is NO and the catalyst 13 is activated, the process proceeds to step SB3 to input a signal (switch signal) from the fuel changeover switch 23, and in the subsequent step SB4, the fuel corresponding to the switch signal is selected, Return.

  That is, if the catalyst 13 is activated, the fuel is switched according to the operation of the fuel switch 23 as in the first embodiment, but at this time, the torque of the engine 1 is not adjusted. This is because it is considered that when the occupant switches the fuel according to his / her own will, it is unlikely that the passenger will feel uncomfortable even if torque fluctuation occurs.

  On the other hand, if the determination in step SB2 is YES and the catalyst 13 is inactive, the process proceeds to step SB5 and hydrogen fuel is selected. Since the concentration of harmful components generated during the combustion of hydrogen fuel is much lower than that during gasoline combustion, the emission does not deteriorate much even if the catalyst 13 is inactive. Therefore, if the catalyst 13 is inactive, the exhaust emission can be reliably reduced by selecting the hydrogen fuel regardless of the operation of the fuel changeover switch 23.

  Subsequently, in step SB6, a signal from the catalyst temperature sensor 14 is input again, and in step SB7, it is determined whether the catalyst temperature is equal to or lower than the activation temperature. While this determination is YES and the catalyst 13 is inactive, the process returns to step SB6. On the other hand, if the catalyst 13 is activated and the determination is NO, the process proceeds to step SB8, and this time it is determined whether the fuel corresponding to the switch signal is gasoline. . If this determination is NO, the routine returns. On the other hand, if the determination is YES and gasoline is designated by the switch operation, the hydrogen fuel is switched to gasoline in the following steps SB9-12.

  That is, first, in step SB9, the signals from the vehicle speed sensor 21 and the accelerator opening sensor 22 are input in the same manner as in step SA4 of the flow shown in FIG. 4 (Embodiment 1), and in step SB10, the same step SA7 is performed. , Read from a preset table and correct the target ignition timing, target air-fuel ratio or target EGR amount, that is, at least one of these three control parameters, in order to slow down the combustion, as in SA10 Determine the control target value.

  In step SB11, as in steps SA8 and SA11 in the flow of FIG. 4, the injectors 4 and 12 to be used are switched and the opening of the throttle valve 11 is maintained until the predetermined period elapses. By retarding the timing, leaning the air-fuel ratio, or increasing the EGR, that is, correcting the at least one control parameter, the combustion is slowed down.

  If the predetermined period immediately after the fuel switching elapses, the process proceeds to step SB12, where the opening of the throttle valve 11 is gradually decreased over a preset time as in steps SA9 and SA12 of the flow of FIG. The ignition timing, the air-fuel ratio, and the EGR amount are gradually returned to the control target values when the gasoline is used, and then returned.

  That is, when the catalyst 13 is inactive, hydrogen fuel is selected even if gasoline is designated by the fuel changeover switch 23. Therefore, when the catalyst 13 is activated, the hydrogen fuel is automatically switched to gasoline. However, since this fuel switching does not depend on the occupant's operation, there is a risk that torque fluctuations or changes in combustion noise may cause the occupant to feel uncomfortable.

  Therefore, immediately after such automatic fuel switching, the combustion is slowed down by retarding the ignition timing, leaning the air-fuel ratio or increasing the EGR amount while maintaining the opening degree of the throttle valve 11 as in the first embodiment. By suppressing the change, torque fluctuations before and after switching and changes in combustion noise are suppressed. Thereafter, the combustion noise is gradually changed while maintaining the torque.

  Also in the flow of FIG. 7, the fuel switching means 20a and the combustion slowing control means 20c are configured by step SB11, and the torque control means 20b is configured by step SB12.

  The fuel switching means 20a of the second embodiment is in a state in which hydrogen fuel is selected because the catalyst 13 is inactive although gasoline is designated by the operation of the fuel switching switch 23. When the catalyst 13 is activated as the temperature rises (when a predetermined condition is satisfied), the hydrogen fuel is automatically switched to gasoline.

  In other words, the fuel switching means 20a of this embodiment includes an operation input to the fuel switching switch 23 as a condition for switching the fuel to be used. The torque control means 20b and the combustion slowing control means 20c are respectively fuel switching switches. Only when conditions other than the operation of 23 are satisfied, control for torque matching and combustion slowdown is performed.

  Therefore, according to the control apparatus A for the dual fuel engine according to the second embodiment, first, if the catalyst 13 is inactive, the exhaust emission can be reliably ensured by selecting the hydrogen fuel regardless of the operation of the fuel switch 23. Can be reduced. Then, when switching to gasoline automatically in accordance with the subsequent activation of the catalyst 13, the torque fluctuation can be sufficiently suppressed as in the first embodiment, and the change in the combustion sound becomes moderate, so that the passenger feels uncomfortable. Never remember.

(Other embodiments)
The configuration of the present invention is not limited to the first and second embodiments, and includes various other configurations. That is, in the first embodiment, as shown in step SA11 of the flow of FIG. 4, if the catalyst 13 is activated, the combustion is slowed down by leaning the air-fuel ratio or increasing the EGR. The ignition timing may be retarded.

  Further, in the second embodiment, as shown in steps SB3 and SB4 in the flow of FIG. 7, when the fuel is switched in accordance with the operation of the fuel switch 23 after the activation of the catalyst 13, the engine 1 is controlled by the control of the throttle valve 11. However, at this time, torque adjustment may be performed and only the combustion slowing control may not be performed.

  On the contrary, when the fuel is switched according to the operation of the fuel switch 23, both the torque adjustment and the slowing of the combustion can be performed.

  Further, in the first embodiment, the fuel switching is performed according to the operation of the fuel switching switch 23. In the second embodiment, the fuel switching is automatically performed in addition to the activation of the catalyst 13. However, the fuel is switched according to various other conditions, for example, in the case of a rapid acceleration operation in which the accelerator opening increases rapidly, or when the hydrogen fuel in the tank falls below a predetermined amount. be able to.

  Furthermore, in each of the above embodiments, it is possible to switch between gasoline and hydrogen fuel as the fuel used, but it is not limited to this, for example, compressed natural gas may be employed instead of hydrogen fuel, Light oil may be used instead of gasoline.

  Moreover, in each said embodiment, although the engine 1 is a rotary engine, the control apparatus A of this invention is applicable also to a reciprocating engine, without being restricted to this. Furthermore, the vehicle on which the engine 1 is mounted is not limited to an automobile.

  As described above, the present invention can suppress the torque fluctuation when switching the fuel during the operation of the dual fuel engine, while also reducing the change in the combustion noise so as not to give the passenger a sense of incongruity. It is suitable as an engine for automobiles.

It is explanatory drawing which shows typically the principal part structure of the control apparatus of the dual fuel engine which concerns on Embodiment 1 of this invention. It is a figure which shows the relationship between throttle opening and the maximum torque of an engine by contrasting hydrogen fuel and gasoline. It is explanatory drawing which shows the change of the acupressure waveform in a working chamber. It is a flowchart figure which shows the control procedure of fuel switching. It is explanatory drawing which shows an example of the table for correction | amendment control of ignition timing, an air fuel ratio, and EGR amount. It is a time chart figure which shows the change of the throttle opening and ignition timing after switching from hydrogen fuel to gasoline. FIG. 5 is a view corresponding to FIG. 4 according to Embodiment 2 in which the fuel is automatically switched according to the activation of the catalyst.

Explanation of symbols

1 Dual fuel engine 13 Three-way catalyst (catalyst)
14 Catalyst temperature sensor (catalyst temperature detection means)
16 EGR passage (exhaust gas recirculation means)
17 EGR valve (exhaust gas recirculation means)
20 PCM: Powertrain control module 20a Fuel switching means 20b Torque control means 20c Combustion slowing control means 20d Catalyst temperature detection means 23 Fuel changeover switch (operation input means)

Claims (7)

The first and second fuels can be switched and used, and even when the second fuel is used, even if the intake charge amount to the combustion chamber is the same, a higher torque can be obtained than when the first fuel is used. A control device for a dual fuel engine,
Fuel switching means for switching the used fuel from one of the first and second fuels to the other when a predetermined condition is satisfied;
Torque control means for controlling at least the intake charge amount so that the engine torque becomes substantially the same before and after the switching when the fuel switching means switches from the first fuel to the second fuel during operation of the engine;
Combustion slowing that suppresses the control of the intake charge amount by the torque control means for a predetermined period immediately after switching to the second fuel by the fuel switching means, and slows down the combustion so as to reduce the increase in engine torque caused thereby. Control means;
A control device for a dual fuel engine, comprising: The control device according to claim 1,
The control device for a dual fuel engine, characterized in that the combustion slowing-down control means relatively retards the ignition timing of the engine. In the control device according to claim 1 or 2,
The engine is provided with exhaust gas recirculation means for recirculating part of the exhaust gas to the combustion chamber,
The control device for a dual fuel engine, wherein the combustion slowing-down control means relatively increases an exhaust gas recirculation amount by the exhaust gas recirculation means. The control device according to any one of claims 1 to 3,
The control apparatus for a dual fuel engine, characterized in that the combustion slowing-down control means makes the engine air-fuel ratio relatively lean. The control device according to claim 1,
A catalyst temperature detecting means for detecting that the temperature of the catalyst disposed in the exhaust system of the engine is equal to or lower than a predetermined temperature;
The combustion slowing-down control means controls a plurality of control parameters including engine ignition timing, and when the catalyst temperature detecting means detects that the catalyst temperature is equal to or lower than a predetermined temperature. A dual fuel engine control device characterized by relatively retarding at least the ignition timing of the engine. In the control device according to any one of claims 1 to 4,
The engine is mounted on the vehicle,
Comprising an operation input means for performing an operation for switching fuel by an occupant of the vehicle;
The fuel switching means includes an operation input to the operation input means as a predetermined condition for switching the used fuel,
The combustion slowing-down control means suppresses the control of the intake charge amount by the torque control means and slows down the combustion only when a condition other than the operation input to the operation input means is satisfied among the predetermined conditions. A control device for a dual fuel engine characterized by being a thing. The control device according to claim 6.
The torque control means controls the intake charge amount only when the conditions other than the operation input to the operation input means among the conditions for switching the fuel to be used are satisfied. Control device.

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