JP2015232280A - Multiple-fuel engine fuel injection control unit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fuel injection control unit of a multiple-fuel engine 10 configured so that a first fuel and a second fuel that are both gaseous fuels can be supplied to the engine 10, capable of suppressing a reduction in an intake air quantity while easily laying out fuel injection valves injecting the first fuel and the second fuel, respectively.SOLUTION: A second fuel is a fuel higher in ignitability and lower in heating value per unit mass than a first fuel, the first fuel is injected to an intake passage 14 of an engine 10 from a first fuel injection valve 17, and the second engine is directly injected into a combustion chamber of the engine 10 from a second fuel injection valve 18.

Description

  The present invention belongs to a technical field related to a fuel injection control device of a multi-fuel engine configured to be capable of supplying a first fuel and a second fuel, both of which are gaseous fuels.

  Conventionally, a multi-fuel engine using a first fuel and a second fuel is known. For example, in Patent Document 1, gasoline (liquid fuel) and hydrogen gas are used as fuel. In Patent Document 1, gasoline (liquid fuel) is injected into the intake passage of the engine, while hydrogen gas is directly injected into the combustion chamber of the engine.

JP 2006-105088 A

  By the way, when both the first fuel and the second fuel are gaseous fuels, when either one of the first fuel and the second fuel is injected into the intake passage of the engine, the liquid fuel and Unlike, there is a problem that the intake air amount decreases.

  On the other hand, when both the fuels are directly injected into the combustion chamber of the engine from the viewpoint of securing the intake air amount, the first fuel injection valve that injects the first fuel and the second fuel that injects the second fuel. It is necessary to arrange the injection valves so that their fuel discharge ports face the combustion chamber. In this case, the layout of the first and second fuel injection valves that are larger than the fuel injection valves that inject liquid is larger. Increased chance of difficulty.

  The present invention has been made in view of such a point, and an object of the present invention is to provide a fuel for a multi-fuel engine configured to be capable of supplying a first fuel and a second fuel, both of which are gaseous fuels. An object of the injection control apparatus is to suppress the reduction of the intake amount as much as possible while easily laying out the fuel injection valves for injecting the first fuel and the second fuel, respectively.

  In order to achieve the above object, the present invention is directed to a fuel injection control device for a multi-fuel engine configured to be capable of supplying both a first fuel and a second fuel that are both gaseous fuels. The fuel is a fuel that is highly ignitable with respect to the first fuel and has a low calorific value per unit mass, and a first fuel injection valve that injects the first fuel into the intake passage of the engine; A second fuel injection valve for directly injecting the second fuel into the combustion chamber of the engine, and the first fuel and the second fuel during the operation of the engine regardless of the operating state of the engine. Both are provided with a control means for controlling the operation of the first fuel injection valve and the second fuel injection valve in order to supply both to the engine.

  With the above configuration, the first fuel injection valve and the second fuel injection valve can be laid out more easily than the configuration in which the first fuel and the second fuel are directly injected into the combustion chamber of the engine. In addition, since the first fuel has a higher calorific value per unit mass than the second fuel, a high engine output can be obtained even if the amount of the first fuel injected by the first fuel injection valve is reduced. It becomes like this. As a result, of the fuel distribution ratio between the first fuel injected from the first fuel injection valve and the second fuel injected from the second fuel injection valve, the fuel distribution ratio of the first fuel is By reducing the engine output within a range that can ensure the engine output (increasing the fuel distribution ratio of the second fuel), it is possible to suppress the reduction of the intake air amount as much as possible. Furthermore, the ignitability of the fuel can be improved by increasing the fuel distribution ratio of the second fuel.

  In one embodiment of the fuel injection control device of the multi-fuel engine, the fuel injection control device further includes a throttle valve that is disposed upstream of the first fuel injection valve in the intake passage and adjusts the amount of intake air into the combustion chamber. The control means controls the operation of the throttle valve in addition to the operation of the first fuel injection valve and the second fuel injection valve. The throttle valve is fully opened, From the first fuel injected from the first fuel injector and the second fuel injector so that a target output torque can be obtained with a target rotational speed within a predetermined rotational speed region including the maximum efficiency point. A fuel distribution ratio with the second fuel to be injected is set, the first fuel is injected from the first fuel injection valve so as to achieve the set fuel distribution ratio, and the second fuel injection valve More injecting the second fuel It is configured to perform a target rotational speed control.

  As a result, even if the target output torque (required output) of the engine is changed, by changing the fuel distribution ratio of the first fuel and the second fuel, the engine can be operated within a predetermined engine speed range with good engine efficiency. Can continue to drive. Further, the pumping loss can be suppressed by fully opening the throttle valve. Therefore, fuel consumption can be improved.

  In the case of the configuration of the one embodiment, a catalyst that is disposed in the exhaust passage of the engine and purifies the exhaust gas of the engine, and a catalyst activity that detects whether the catalyst is in an active state or an inactive state. / Inactive detection means, and the control means executes the target rotational speed control when the catalytic activity / inactivity detection means detects the active state of the catalyst, while the catalytic activity / inactivity detection means When the inactive state of the catalyst is detected by, the fuel distribution rate of the first fuel is reduced while maintaining the opening degree of the throttle valve and the combustion air-fuel ratio in the combustion chamber relative to the detection of the active state of the catalyst. It is preferable that the catalyst activation control is performed to move the engine operating point to the high rotation side so that the engine output is maintained.

  Thus, the output torque of the engine can be reduced by reducing the fuel distribution ratio of the first fuel having a high calorific value without reducing the opening of the throttle valve. Here, since the intake air amount increases due to the decrease in the fuel distribution ratio of the first fuel and the combustion air-fuel ratio is maintained, the total fuel injection amount of the first and second fuels increases, but basically The injection amount of the first fuel having a high calorific value decreases, and the output torque of the engine decreases. However, the engine output is maintained as the operating point of the engine moves to the high rotation side. Therefore, the operating point of the engine can be moved to the operating point on the high speed side without changing the engine output without causing deterioration in fuel consumption due to the throttle valve opening being reduced. When the engine is operated at a high speed in this way, the flow rate of the exhaust gas increases, so that the amount of heat radiation in the portion between the exhaust opening of the combustion chamber and the catalyst in the exhaust passage decreases, and the exhaust gas gains momentum. Since the catalyst is in good contact with the catalyst, the catalyst is easily activated. Further, by moving to an operating point where the efficiency of the engine is lowered, the amount of waste heat increases and the temperature of the exhaust gas also rises, making it easier to activate the catalyst.

  When the control means is configured to execute the catalyst activation control as described above, the catalyst is a NOx storage reduction catalyst, and the NOx storage reduction catalyst converts NOx in the exhaust gas of the engine. The NOx occluded is stored in a lean air-fuel ratio atmosphere, and the occluded NOx is stored in a rich air-fuel ratio atmosphere and an atmosphere in which the temperature of the NOx occlusion reduction catalyst is higher than a predetermined temperature higher than the activation temperature of the NOx occlusion reduction catalyst. And a NOx occlusion amount detection means for detecting the NOx occlusion amount of the NOx occlusion reduction catalyst, and a catalyst temperature detection means for detecting the temperature of the NOx occlusion reduction catalyst, wherein the control means comprises: When the activation state of the catalyst is detected by the catalyst activity / inactivity detection means, the NOx occlusion amount by the NOx occlusion amount detection means is less than a first predetermined amount. The target engine speed control is performed so that the engine is in a lean operation in which the NOx occlusion reduction catalyst occludes NOx and the NOx emission amount from the combustion chamber is equal to or less than a preset set amount. When the active state of the catalyst is detected, the NOx occlusion amount of the NOx occlusion reduction catalyst is not less than the first predetermined amount, and the temperature of the catalyst by the catalyst temperature detecting means is not less than the predetermined temperature. In some cases, the operation of the first fuel injection valve, the second fuel injection valve, and the throttle valve is controlled so that the engine is in a rich operation in which the NOx storage reduction catalyst releases the stored NOx. Further, the control means is configured to detect the inactive state of the catalyst by the catalyst activity / inactivity detection means and to the NOx occlusion amount detection means. When the NOx occlusion amount is equal to or greater than a second predetermined amount that is less than the first predetermined amount, the catalyst activation control is executed, and even when the inactive state of the catalyst is detected, the NOx occlusion amount is When the amount is smaller than the second predetermined amount, it is preferable that the target rotational speed control is executed.

  Thus, before the NOx occlusion amount reaches the first predetermined amount in the NOx occlusion reduction catalyst, the catalyst activation control is executed to activate the NOx occlusion reduction catalyst, and the temperature of the NOx occlusion reduction catalyst exceeds the predetermined temperature. As a result, if the NOx occlusion amount reaches the first predetermined amount, the NOx release condition has already been established, and NOx can be released immediately. The second predetermined amount is as close as possible to the first predetermined amount, and the NOx occlusion amount is made to be the first predetermined amount by executing the catalyst activation control from the time when the NOx occlusion amount becomes the second predetermined amount. The amount of NOx occlusion reduction catalyst may be set to an amount that allows the temperature of the NOx occlusion reduction catalyst to be equal to or higher than a predetermined temperature. As described above, the engine rotation control for catalyst activation is performed by executing the catalyst activation control only when the NOx occlusion amount approaches the amount (first predetermined amount) at which NOx must be released. Can be suppressed as much as possible.

  In the case of the configuration of the one embodiment, the engine is an engine with a supercharger, and the intake opening that opens to the combustion chamber of the engine is fully closed in the compression stroke, and the control means is When the engine is at a rotational speed between its start and a predetermined rotational speed lower than the target rotational speed, the fuel distribution ratio of the first fuel is configured to be smaller than a predetermined value. It is preferable.

  That is, in the so-called intake slow closing configuration in which the intake opening is fully closed in the compression stroke, the output torque of the engine is reduced due to a decrease in the effective compression ratio, but the output torque is not reduced by the supercharger. can do. Further, in the configuration of the intake air late closing, the first fuel injected from the first fuel injection valve and the intake air tend to be returned from the combustion chamber to the intake passage through the intake opening in the compression stroke. However, it can be prevented by the supercharging pressure by the supercharger. Here, when the engine is at a low engine speed between the start and a predetermined speed, the supercharging pressure by the supercharger is low. The first fuel injected from the fuel injection valve and the intake air are returned from the combustion chamber to the intake passage through the intake opening. On the other hand, since the fuel injected from the second fuel injection valve is normally injected after the intake opening is closed, it is not returned to the intake passage. Therefore, at a low engine speed until the predetermined speed is reached when the engine is started, the amount of fuel returned to the intake passage is reduced by making the fuel distribution ratio of the first fuel smaller than a predetermined value. As a result, it is possible to suppress a decrease in engine output caused by returning fuel to the intake passage.

  As described above, according to the fuel injection control device for a multi-fuel engine of the present invention, the second fuel is a fuel having high ignitability with respect to the first fuel and low calorific value per unit mass, The first fuel injection valve injects the first fuel into the intake passage of the engine, and the second fuel injection valve injects the second fuel directly into the combustion chamber of the engine. Compared to the configuration in which the fuel and the second fuel are directly injected into the combustion chamber, the first fuel injection valve and the second fuel injection valve can be easily laid out and injected from the first fuel injection valve. Of the fuel distribution ratio between the first fuel and the second fuel injected from the second fuel injection valve, the fuel distribution ratio of the first fuel is reduced within a range in which the engine output can be secured, Suppress the reduction of intake air as much as possible It is possible.

1 is a schematic view of a vehicle equipped with a fuel injection control device for a multi-fuel engine according to an embodiment of the present invention. It is a block diagram which shows the structure of the engine of the said vehicle, and its control system. It is a flowchart which shows the first half part of the processing operation at the time of the engine driving | operation by a control unit. It is a flowchart which shows the latter half part of the processing operation at the time of the engine driving | operation by a control unit.

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

  FIG. 1 is a schematic view of a vehicle 1 equipped with a fuel injection control device for a multi-fuel engine according to an embodiment of the present invention. The vehicle 1 is a so-called range extender EV vehicle (which can be said to be a series type hybrid vehicle in a broad sense), and includes an engine 10, a generator 20 driven by the engine 10 to generate electric power, and the generator The high-voltage and large-capacity battery 30 in which the power generated by the battery 20 is stored (charged), and both the generated power of the generator 20 driven by the engine 10 and the stored power (discharge power) of the battery 30 or And a drive motor 40 that is driven only by the discharge power of the battery 30 (in this embodiment, it is basically driven only by the discharge power of the battery 30 as will be described later). In the present embodiment, the engine 10 is started by a starter motor (not shown). However, the generator 20 may be changed to a motor generator, and the engine 10 may be started by driving the motor generator as a motor. Is possible.

  A first inverter 50 is provided between the generator 20 and the battery 30, and a second inverter 51 is provided between the battery 30 and the drive motor 40. The first inverter 50 and the second inverter 51 are connected to each other, and the battery 30 is connected to the connection line. The power generated by the generator 20 is supplied to the battery 30 via the first inverter 50 and also supplied to the drive motor 40 via the first and second inverters 50 and 51. Discharged power from the battery 30 is supplied to the drive motor 40 via the second inverter 51.

  The drive motor 40 is basically driven by the discharge power of the battery 30. When the output of the drive motor 40 is insufficient with only the discharge power of the battery 30, such as when the vehicle 1 is accelerated, the engine 10 is started. Thus, the power generated by the generator 20 is also supplied to the drive motor 40. The output of the drive motor 40 is transmitted to the drive wheels 61 (the left and right front wheels steered by the steering wheel 62) via the differential device 60, whereby the vehicle 1 travels.

  The drive motor 40 is capable of generating regenerative power, and operates as a generator when the vehicle 1 is decelerated, so that the battery 30 is charged with the generated power (regenerative power). When the remaining capacity (SOC) of the battery 30 falls below a predetermined capacity, the engine 10 is started and the battery 30 is charged with the generated power of the generator 20. The predetermined capacity is a capacity that is higher than the level that requires urgently required charging of the battery 30, and is a capacity that can be maintained at an appropriate level that is not too low and not too high as the remaining capacity of the battery 30. is there. The battery 30 can be externally charged by a power source external to the vehicle 1.

  The engine 10 is used only for power generation by the generator 20. The engine 10 is a multi-fuel engine configured such that hydrogen gas stored in the hydrogen tank 70 and natural gas (CNG) stored in the CNG tank 71 can be supplied to the engine 10 as fuel. . Natural gas corresponds to a first fuel, and hydrogen gas corresponds to a second fuel that has high ignitability to natural gas and a low calorific value per unit mass.

  As shown in FIG. 2, the engine 10 is a twin-rotor (two-cylinder) rotary piston engine, and is roughly arranged in a rotor housing chamber 11 a formed in two saddle-shaped rotor housings 11 (inside cylinders). Each of the triangular rotors 12 is accommodated. The two rotor housings 11 are integrated with the side housings so as to be sandwiched between three side housings (not shown), and each rotor housing chamber 11a is composed of each rotor housing 11 and the side housings on both sides thereof. Is formed. In FIG. 2, the two rotor housings 11 (two cylinders) are shown in an unfolded state, and the eccentric shafts 13 respectively drawn in the central portions in the two rotor housings 11 are the same.

  Each of the rotors 12 has apex seals (not shown) at the apexes of the triangles, and the apex seals are in sliding contact with the inner surface of the trochoid of the rotor housing 11. Three working chambers (corresponding to combustion chambers) are defined in 11a (each cylinder). Each rotor 12 rotates around the eccentric shaft 13 in a state where the three apex seals of the rotor 12 are in contact with the inner peripheral surface of the trochoid of the rotor housing 11, and around the axis of the eccentric shaft 13. To revolve around. While the rotor 12 makes one revolution, the working chambers formed between the tops of the rotor 12 move in the circumferential direction, and the intake, compression, expansion (combustion), and exhaust strokes are performed. The rotating force is output from the eccentric shaft 13 as the output shaft through the rotor 12.

  An intake passage 14 is connected to each of the rotor accommodating chambers 11a so as to communicate with an intake opening that opens to the working chamber in the intake stroke, and communicates with an exhaust opening that opens to the working chamber in the exhaust stroke. An exhaust passage 15 is connected to the front. There is one intake passage 14 on the upstream side, but on the downstream side, the intake passage 14 branches into two branch passages and communicates with each of the rotor accommodating chambers 11a. On the upstream side of the branch portion of the intake passage 14 (upstream side of the port injection valve 17 described later), a cross-sectional area (valve opening degree) of the intake passage 14 is driven by a throttle valve actuator 90 such as a stepping motor. A throttle valve 16 for adjustment is provided. The throttle valve 16 adjusts the amount of intake air into each rotor accommodating chamber 11a (the working chamber in the intake stroke).

  A port injection valve 17 (first fuel injection valve) for injecting natural gas supplied from the CNG tank 71 into the intake passage 14 is provided in each branch passage downstream of the branch portion of the intake passage 14. It is arranged. The natural gas injected by the port injection valve 17 is supplied to the working chamber in the intake stroke in a state of being mixed with air (premixed state).

  Two exhaust passages 15 are provided on the upstream side so as to communicate with the respective rotor accommodating chambers 11a, but are joined together on the downstream side. A low temperature active three-way catalyst 81 and a NOx occlusion reduction catalyst 82 for purifying exhaust gas are disposed downstream of the merging portion of the exhaust passage 15. The low temperature active three-way catalyst 81 is a three-way catalyst having a catalyst activation temperature lower than that of the NOx storage reduction catalyst 82, and is disposed upstream of the NOx storage reduction catalyst 82. In FIG. 2, arrows shown in the intake passage 14 and the exhaust passage 15 indicate the flow of intake and exhaust.

  The NOx occlusion reduction catalyst 82 is configured, for example, by supporting a NOx occlusion agent such as barium (Ba) or potassium (K) on a carrier containing a noble metal such as platinum (Pt) or palladium (Pd). The NOx in the exhaust gas of the engine 10 is stored in a lean air-fuel ratio atmosphere, and the stored NOx is stored in the rich air-fuel ratio atmosphere and the temperature of the NOx storage-reduction catalyst 82 is the activity of the NOx storage-reduction catalyst 82. The NOx is released under an atmosphere at a predetermined temperature higher than the gasification temperature and is reduced to react with HC and CO in the exhaust gas to reduce.

  In each rotor housing 11 (each cylinder), a direct injection valve 18 (second cylinder) that directly injects hydrogen gas supplied from the hydrogen tank 70 into the working chamber (combustion chamber) in the compression stroke of the rotor accommodating chamber 11a. And two spark plugs 19 for igniting the natural gas injected from the port injection valve 17 and the hydrogen gas injected from the direct injection valve 18.

  The fuel distribution rate of natural gas, which is the mass ratio of the fuel injection amount by the port injection valve 17 to the total fuel injection amount by the port injection valve 17 and the direct injection valve 18 (hereinafter referred to as port injection ratio), and the total fuel injection The fuel distribution rate of hydrogen gas, which is the mass ratio of the fuel injection amount by the direct injection valve 18 to the amount (hereinafter referred to as the direct injection ratio), is basically the normal power generation operation (target rotational speed control) described later. Although the target output torque is set to be obtained, the port injection ratio and the direct injection ratio change as described later.

  In the present embodiment, the intake opening is configured to be opened and closed by the rotor 12 and fully closed during the compression stroke (so-called intake late closing configuration). In such a configuration of slow intake closing, the output torque of the engine 10 decreases due to a decrease in the effective compression ratio, but a turbocharger 85 is provided in order to prevent the output torque from decreasing. Further, in the configuration of the slow intake closing, the natural gas injected from the port injection valve 17 and the intake air are about to return from the working chamber to the intake passage 14 through the intake opening in the compression stroke. This can be prevented by the supercharging pressure by the supercharger 85.

  The turbocharger 85 includes a compressor 85 a disposed on the upstream side of the throttle valve 16 in the intake passage 14 and a downstream side of the merging portion in the exhaust passage 15 and an upstream side of the three-way catalyst 81. It is comprised with the arrange | positioned turbine 85b. The turbine 85b is rotated by the exhaust gas flow, and the rotation of the turbine 85b activates the compressor 85a connected to the turbine 85b to compress the air taken into the intake passage 14. The compressed air is cooled by an intercooler 86 disposed downstream of the compressor 85 a in the intake passage 14.

  The vehicle 1 includes a battery current / voltage sensor 101 that detects a current flowing into and out of the battery 30 and a voltage of the battery 30, and an accelerator that detects an amount of depression of an accelerator pedal by a driver of the vehicle 1 (accelerator opening by a driver's operation). An opening sensor 102, a vehicle speed sensor 103 that detects the vehicle speed of the vehicle 1, a rotation angle sensor 104 that is provided on the eccentric shaft 13 and detects the rotation angle position of the eccentric shaft 13, and a low-temperature active three-way catalyst in the exhaust passage 15 An air-fuel ratio sensor 105 (configured by a linear O2 sensor in this embodiment) that is disposed between the turbine 81 and the turbine 85 b and detects the air-fuel ratio of the exhaust gas of the engine 10, and the rotor housing 11 Facing the formed water jacket (not shown), the water jacket An engine water temperature sensor 106 for detecting the temperature of engine cooling water flowing in the engine (engine water temperature), a pressure in the hydrogen tank 70 (that is, a hydrogen gas remaining amount in the hydrogen tank 70), and a pressure in the CHG tank 71 (that is, a CNG tank). 71, a tank pressure sensor 107 for detecting the remaining amount of natural gas), an air flow sensor 108 for detecting the intake flow rate sucked into the intake passage 14, the operation control of the engine 10, and the first and second inverters 50. , 51 (that is, the operation control of the generator 20 and the drive motor 40) and the like. The rotational angle sensor 104 also serves as an engine rotational speed sensor that detects the rotational speed of the engine 10 (hereinafter referred to as engine rotational speed).

  The control unit 100 is a controller based on a well-known microcomputer, and includes a central processing unit (CPU) that executes a program, a memory that is configured by, for example, a RAM or ROM, and stores a program and data, and an electrical signal An input / output (I / O) bus. The control unit 100 includes a battery current / voltage sensor 101, an accelerator opening sensor 102, a vehicle speed sensor 103, a rotation angle sensor 104, an air-fuel ratio sensor 105, an engine water temperature sensor 106, a tank pressure sensor 107, an air flow sensor 108, and the like. An information signal is input.

  The generator 20 transmits information on the voltage and current generated by the generator 20 to the control unit 100. The control unit 100 inputs the information and generates power generated by the generator 20 from the information. (Power generation amount) is detected.

  The drive motor 40 transmits information on the rotational speed of the drive motor 40 and information on the regenerative power generation voltage and regenerative power generation current generated by the drive motor 40 to the control unit 100, and the control unit 100 transmits the information. The input is used to control the operation of the drive motor 40.

  Based on the input signal, the control unit 100 outputs a control signal to the throttle valve actuator 90, the port injection valve 17, the direct injection valve 18, and the spark plug 19 to control the engine 10, and Control signals are output to the first and second inverters 50 and 51 to control the generator 20 and the drive motor 40. The control unit 100 constitutes control means for controlling the operation of the port injection valve 17, the direct injection valve 18 and the throttle valve 16. In the present embodiment, the control unit 100 controls the port injection valve 17 and the direct injection valve 18 to supply both natural gas and hydrogen gas to the engine 10 during operation of the engine 10 regardless of the operating state of the engine 10. Control the operation of

  The control unit 100 controls the first and second inverters 50 and 51 to generate power from the generator 20 and the first mode in which the drive motor 40 is driven only with the discharged power from the battery 30 with the engine 10 stopped. A second mode in which the drive motor 40 is driven with the discharge power from the battery 30 while charging the battery 30 with the power, and a third mode in which the drive motor 40 is driven with the power from both the battery 30 and the generator 20. Switch to the mode. In this third mode, all of the power generated by the generator 20 is supplied to the drive motor 40, and a part of the power generated by the generator 20 is supplied to the drive motor 40 while the rest is supplied to the battery 30. Is included.

  The control unit 100 detects the remaining capacity (SOC) of the battery 30 based on the current flowing into and out of the battery 30 and the voltage of the battery 30 detected by the battery current / voltage sensor 101. Then, when the SOC of the battery 30 is higher than the predetermined capacity, the control unit 100 selects the one mode. Even if the SOC of the battery 30 is higher than the predetermined capacity, the control unit 100 opens the accelerator due to a driver's acceleration request or the like. When the required output of the drive motor 40 based on the signals from the degree sensor 102 and the vehicle speed sensor 103 is large, the third mode is selected. Further, the control unit 100 selects the second mode when the SOC of the battery 30 is not more than the predetermined capacity. It should be noted that when the remaining amount of hydrogen gas in the hydrogen tank 70 by the tank pressure sensor 107 is equal to or lower than a preset first set value, or the remaining amount of natural gas in the CNG tank 71 is set to a second preset value. The first mode is selected when the set value or less is reached.

  When the engine 10 is in a stopped state, the control unit 100 checks the presence or absence of a power generation request based on the required output of the drive motor 40 and the SOC value of the battery 30, and when there is a power generation request, the starter motor Then, the engine 10 is started, and the engine 10 is operated to cause the generator 20 to generate power.

  Below, the processing operation at the time of the driving | operation of the engine 10 by the control unit 100 is demonstrated based on the flowchart of FIG.3 and FIG.4.

  In the first step S1, signals from various sensors are read, and in the next step S2, the required output of the drive motor 40 is calculated based on the signals from the accelerator opening sensor 102 and the vehicle speed sensor 103.

  In the next step S3, the presence or absence of a power generation request is confirmed based on the required output of the drive motor 40 and the SOC of the battery 30, and in the next step S4, it is determined whether or not there is a power generation request.

  When the determination in step S4 is NO, the process returns to step S1, while when the determination in step S4 is YES, the process proceeds to step S5 and the engine 10 is started.

  In the next step S6, it is determined whether or not the engine 10 has increased to a predetermined rotational speed (a rotational speed lower than a rotational speed (for example, 1800 rpm) within a predetermined rotational speed region described later) from the start, and this step S6. When the determination is NO, the routine proceeds to step S7, where the port injection ratio is made smaller than the first predetermined value, and the direct injection ratio is made larger than the second predetermined value (the direct injection ratio is changed to the port injection ratio). The sum of the ratio and the direct injection ratio is 100%). Thereby, the port injection ratio is basically smaller than that in the normal power generation operation described later. Thereafter, the process returns to step S6.

  Here, at a low engine speed until the predetermined speed is reached, the supercharging pressure by the turbocharger 85 is low. Therefore, in the configuration of the intake air late closing as described above, the engine is injected from the port injection valve 17. Natural gas and the sucked air are returned from the working chamber to the intake passage 14 through the intake opening in the compression stroke. On the other hand, the fuel injected from the direct injection valve 18 is injected after the intake opening is closed, and therefore is not returned to the intake passage 14. Therefore, at a low engine speed until the predetermined speed is reached when the engine 10 is started, the amount of fuel returned to the intake passage 14 is reduced by making the port injection ratio smaller than the first predetermined value, A reduction in the output of the engine 10 due to the return of fuel to the intake passage 14 is suppressed.

  If the engine speed reaches the predetermined speed and the determination in step S6 is YES, the process proceeds to step S8 where the throttle valve 16 is fully opened and the combustion air-fuel ratio A in the working chamber (combustion chamber) is reached. The total fuel injection amount is set so that / F becomes 2.3 (feedback control is performed by the output of the air-fuel ratio sensor 105), and the engine speed Ne is a predetermined speed including the maximum efficiency point of the engine 10. The target output torque can be obtained with a target rotational speed (2000 rpm in this embodiment) within the region (within the rotational speed region where the efficiency of the engine 10 is maximum or close to the maximum) (that is, corresponding to the power generation amount to be generated). Set the port injection ratio and direct injection ratio, and set the total fuel injection amount, port injection ratio and direct injection so that the target engine output can be obtained. So as to be morphism ratio, injecting natural gas from the port injection valve 17 and executes the target rotational speed control for injecting the hydrogen gas from the direct injection injector 18. Hereinafter, the operation of the engine 10 in step S8 is referred to as a normal power generation operation. In this normal power generation operation, the fuel injected from the port injection valve 17 is not returned to the intake passage 14 due to the boost pressure by the turbocharger 85. In this embodiment, during the operation of the engine 10 (including the time of starting), the throttle valve 16 is always in the fully open state as in the normal power generation operation.

  In the normal power generation operation, basically, the NOx storage reduction catalyst 82 is in the active state (the low temperature active three-way catalyst 81 is also in the active state), and the NOx storage amount of the NOx storage reduction catalyst 82 is the first place. This operation is performed when the amount is less than the fixed amount. In this operation, the NOx storage reduction catalyst 82 stores the NOx in the engine 10 and the amount of NOx discharged from the working chamber becomes equal to or less than a preset set amount. In order to achieve such a lean operation (A / F = 2.3), the target rotation speed control is executed. The first predetermined amount is an amount close to a level at which NOx can no longer be occluded, and is an amount that requires the occluded NOx to be released. The NOx occlusion amount of the NOx occlusion reduction catalyst 82 can be calculated from the operation history of the engine 10, and the control unit 100 integrates the NOx occlusion amount based on the operation state during the operation of the engine 10. Therefore, the control unit 100 constitutes NOx occlusion amount detection means for detecting the NOx occlusion amount of the NOx occlusion reduction catalyst 82.

  In the next step S9, it is determined whether or not the engine water temperature by the engine water temperature sensor 106 is equal to or higher than a first predetermined temperature. The first predetermined temperature is a temperature corresponding to the temperature at which the NOx storage reduction catalyst 82 is activated. That is, in step S9, it is determined whether or not the NOx storage reduction catalyst 82 is in an active state, and the engine water temperature sensor 106 detects whether the NOx storage reduction catalyst is in an active state or an inactive state. Thus, the catalyst activity / inactivity detection means is configured.

  When the determination in step S9 is YES, the process proceeds to step S10, and it is determined whether or not the NOx occlusion amount of the NOx occlusion reduction catalyst 82 is smaller than the first predetermined amount. If the determination in step S9 is yes, the process directly returns. That is, the normal power generation operation is performed as it is.

  When the determination in step S9 is NO, the process proceeds to step S11, in which it is determined whether or not the NOx occlusion amount of the NOx occlusion reduction catalyst 82 is equal to or greater than a second predetermined amount that is less than the first predetermined amount. The second predetermined amount is a value as close as possible to the first predetermined amount, and the NOx occlusion amount is executed by performing catalyst activation control, which will be described later, when the NOx occlusion amount becomes the second predetermined amount. Before the first predetermined amount is reached, the engine water temperature is set to a second predetermined temperature higher than the first predetermined temperature (that is, the temperature of the NOx storage reduction catalyst 82 is set to the predetermined temperature or higher). Use as much as possible. The second predetermined temperature is a temperature corresponding to the predetermined temperature at which NOx can be released as the temperature of the NOx storage reduction catalyst 82. The engine water temperature sensor 106 also constitutes catalyst temperature detection means for detecting the temperature of the NOx storage reduction catalyst 82 in addition to the catalyst activity / inactivity detection means. As the catalyst temperature detecting means, a temperature sensor for detecting the temperature of the NOx storage reduction catalyst 82 may be provided in the NOx storage reduction catalyst 82 instead of the engine water temperature sensor 106. In this case, the temperature sensor is connected to the catalyst activity / It is also preferable to use as inactive detection means.

  If the determination in step S11 is NO, the process directly returns. That is, even when the inactive state of the NOx storage reduction catalyst 82 is detected, when the NOx storage amount of the NOx storage reduction catalyst 82 is smaller than the second predetermined amount, the normal power generation operation (the target rotational speed control) is performed. Do.

  On the other hand, when the determination in step S11 is YES, the process proceeds to step S12 to determine whether or not the vehicle 1 is stopped based on a signal from the vehicle speed sensor 103. The stop here is a vehicle speed that can be considered to be substantially stopped in addition to the vehicle speed being zero, and the vehicle driver feels uncomfortable due to an increase in engine rotation due to the execution of catalyst activation control described later. Including the case where the vehicle speed is such that The vehicle speed sensor 103 constitutes vehicle stop detection means for detecting the stop of the vehicle 1. Note that the determination in step S12 is not always necessary and can be eliminated.

  If the determination in step S12 is YES, the process returns as it is (performs the normal power generation operation). On the other hand, if the determination in step S12 is NO, the process proceeds to step S13, and port injection is performed for the normal power generation operation. The ratio is decreased and the direct injection ratio is increased (the sum of the port injection ratio and the direct injection ratio is 100%), and the operating point of the engine 10 is moved to the higher rotation side than the normal power generation operation. Then return. That is, when the inactive state of the NOx occlusion reduction catalyst 82 is detected, and when the NOx occlusion amount of the NOx occlusion reduction catalyst 82 is equal to or greater than the second predetermined amount, the NOx occlusion reduction is performed while the vehicle 1 is stopped. When the active state of the catalyst 82 is detected, while maintaining the opening degree of the throttle valve 16 and the combustion air-fuel ratio in the working chamber, the port injection ratio is decreased and the operating point of the engine 10 is increased so that the engine output is maintained. The catalyst activation control to move to the rotation side is executed. Thus, even if the opening degree of the throttle valve 16 is not reduced (even when it is fully opened), the output torque of the engine can be reduced by reducing the port injection ratio. Here, since the intake amount increases due to the decrease in the port injection ratio and the combustion air-fuel ratio is maintained, the total fuel injection amount of natural gas and hydrogen gas increases, but basically the natural gas with a high calorific value. As the fuel injection amount decreases, the output torque of the engine decreases. However, the engine output is maintained as the operating point of the engine 10 moves to the high rotation side. It should be noted that the engine speed after moving to the high speed side is basically higher than or equal to the engine speed within the predetermined engine speed range, and the efficiency of the engine 10 at this time depends on the normal power generation. It is lower than when driving.

  By executing the catalyst activation control, the operating point of the engine 10 is moved to the operating point on the high speed side without changing the engine output without causing deterioration of fuel consumption due to the throttle valve 16 being throttled down. Can do. When the engine 10 is operated at a high speed in this way, the flow rate of the exhaust gas increases, so that the amount of heat radiation in the portion between the exhaust opening of the combustion chamber and the catalyst in the exhaust passage 15 decreases, and the exhaust gas. However, the NOx occlusion reduction catalyst 82 is vigorously contacted, so that the NOx occlusion reduction catalyst 82 is easily activated. Further, by moving to an operating point where the efficiency of the engine 10 becomes low, the amount of waste heat increases and the temperature of the exhaust gas also rises, making it easier to activate the NOx storage reduction catalyst 82.

  When the determination in step S10 is NO, the process proceeds to step S14, and whether or not the engine water temperature by the engine water temperature sensor 106 is equal to or higher than the second predetermined temperature (that is, the temperature of the NOx storage reduction catalyst 82 is the predetermined temperature). Whether or not).

  If the determination in step S14 is NO, the process returns as is (performs the normal power generation operation). On the other hand, if the determination in step S14 is YES, the process proceeds to step S15, and the combustion empty in the working chamber (combustion chamber) is reached. The total fuel injection amount is set so that the fuel ratio A / F becomes 0.9 (feedback control is performed by the output of the air-fuel ratio sensor 105), and the engine speed Ne is the same target speed as the target speed control. The port injection ratio and the direct injection ratio are set so that the same target output torque as in the target rotational speed control can be obtained with 2000 rpm (that is, the same target engine output as in the target rotational speed control can be obtained). It is set from the port injection valve 17 so that the set total fuel injection amount, port injection ratio and direct injection ratio are set. Injecting gas and injecting the hydrogen gas from the direct injection injector 18. That is, when detecting the active state of the NOx storage reduction catalyst 82, when the NOx storage amount of the NOx storage reduction catalyst 82 is not less than the first predetermined amount and the temperature of the NOx storage reduction catalyst 82 is not less than the predetermined temperature, The operation of the port injection valve 17, the direct injection valve 18 and the throttle valve 16 is controlled so that the engine 10 is in a rich operation in which the NOx occlusion reduction catalyst 82 releases the occluded NOx.

  In the next step S16, it is determined whether or not a predetermined time has elapsed since the start of the rich operation. The predetermined time is a time required for releasing substantially the entire amount of NOx stored in the NOx storage reduction catalyst 82. If the determination in step S16 is NO, the operation in step S16 is repeated. If the determination in step S16 is YES, the process returns to step S8 (executes the normal power generation operation).

  Therefore, in this embodiment, natural gas is injected into the intake passage 14 of the engine 10 by the port injection valve 17, and the direct injection valve 18 has high ignitability with respect to natural gas and low calorific value per unit mass. Since the hydrogen gas is directly injected into the combustion chamber of the engine 10, the port injection valve 17 and the direct injection valve 18 are easily laid out as compared with the configuration in which both natural gas and hydrogen gas are directly injected into the combustion chamber. can do. Further, since natural gas has a higher calorific value per unit mass than hydrogen gas, a high engine output can be obtained even if the amount of natural gas injected by the port injection valve 17 is reduced. As a result, by reducing the port injection ratio within a range in which the engine output can be secured (increasing the hydrogen injection ratio), it is possible to suppress the reduction of the intake amount as much as possible. Furthermore, the ignitability of the fuel can be improved by increasing the hydrogen injection ratio.

  The present invention is not limited to the embodiment described above, and can be substituted without departing from the spirit of the claims.

  For example, in the above embodiment, the engine 1 is a multi-fuel rotary engine that uses natural gas and hydrogen gas as fuel, but it may be a reciprocating engine that uses natural gas and hydrogen gas as fuel, both of which are gaseous fuels. As long as the first fuel and the second fuel are used and the second fuel is a fuel that has high ignitability to the first fuel and a low calorific value per unit mass, any fuel can be used. However, the present invention can be applied.

  Moreover, in the said embodiment, although the engine 1 and its fuel-injection control apparatus were mounted in the range extender EV vehicle (series type hybrid vehicle), not only this but any other provided with an engine and a vehicle drive motor It can also be mounted on a hybrid vehicle of such a type, or can be mounted on a vehicle driven only by an engine.

  The above-described embodiments are merely examples, and the scope of the present invention should not be interpreted in a limited manner. The scope of the present invention is defined by the scope of the claims, and all modifications and changes belonging to the equivalent scope of the claims are within the scope of the present invention.

  INDUSTRIAL APPLICABILITY The present invention is useful for a fuel injection control device for a multi-fuel engine configured to be able to supply a first fuel and a second fuel, both of which are gaseous fuels.

DESCRIPTION OF SYMBOLS 1 Vehicle 10 Multi-fuel engine 14 Intake passage 15 Exhaust passage 16 Throttle valve 17 Port injection valve (first fuel injection valve)
18 Direct injection valve (second fuel injection valve)
82 NOx storage reduction catalyst 85 Turbocharger 100 Control unit (control means) (NOx storage amount detection means)
106 Engine water temperature sensor (catalytic activity / inactivity detection means) (catalyst temperature detection means)

Claims (5)

A fuel injection control device for a multi-fuel engine configured to be capable of supplying a first fuel and a second fuel, both of which are gaseous fuels,
The second fuel is a fuel having high ignitability with respect to the first fuel and a low calorific value per unit mass,
A first fuel injection valve for injecting the first fuel into the intake passage of the engine;
A second fuel injection valve for directly injecting the second fuel into the combustion chamber of the engine;
During the operation of the engine, the first fuel injection valve and the second fuel injection valve are operated so as to supply both the first fuel and the second fuel to the engine regardless of the operation state of the engine. And a fuel injection control device for a multi-fuel engine. The fuel injection control device for a multi-fuel engine according to claim 1,
A throttle valve that is disposed upstream of the first fuel injection valve in the intake passage and adjusts the amount of intake air into the combustion chamber;
The control means controls the operation of the throttle valve in addition to the operation of the first fuel injection valve and the second fuel injection valve, and the throttle valve is fully opened to maximize the engine. The first fuel injected from the first fuel injection valve and the second fuel injection valve are injected so that a target output torque can be obtained at a target rotational speed within a predetermined rotational speed region including the efficiency point. The fuel distribution ratio with the second fuel to be set is set, the first fuel is injected from the first fuel injection valve so as to be the set fuel distribution ratio, and the second fuel injection valve is used. A fuel injection control device for a multi-fuel engine, characterized in that it is configured to execute target rotational speed control for injecting the second fuel. The fuel injection control device for a multi-fuel engine according to claim 2,
A catalyst disposed in an exhaust passage of the engine for purifying exhaust gas of the engine;
A catalyst activity / inactivity detection means for detecting whether the catalyst is in an active state or in an inactive state;
The control means executes the target rotation speed control when the catalyst activity / inactivity detection means detects the catalyst activation state, while the catalyst activity / inactivity detection means detects the catalyst inactivity state. When the activation state of the catalyst is detected, while maintaining the opening degree of the throttle valve and the combustion air-fuel ratio in the combustion chamber, the fuel distribution ratio of the first fuel is decreased and the engine output is maintained. A fuel injection control device for a multi-fuel engine, characterized in that the catalyst activation control for moving the operating point of the engine to a high rotation side is executed. The fuel injection control device for a multi-fuel engine according to claim 3,
The catalyst is a NOx storage reduction catalyst,
The NOx occlusion reduction catalyst occludes NOx in the engine exhaust gas in a lean air-fuel ratio atmosphere, and stores the occluded NOx in a rich air-fuel ratio atmosphere and the temperature of the NOx occlusion reduction catalyst is the NOx occlusion catalyst. It is released under an atmosphere of a predetermined temperature or higher higher than the activation temperature of the reduction catalyst,
NOx occlusion amount detection means for detecting the NOx occlusion amount of the NOx occlusion reduction catalyst;
Catalyst temperature detecting means for detecting the temperature of the NOx storage reduction catalyst,
When the NOx occlusion amount by the NOx occlusion amount detection means is less than a first predetermined amount when the catalyst activation state is detected by the catalyst activity / inactivity detection means, the control means causes the engine to occlude the NOx occlusion. In order to achieve a lean operation in which the reduction catalyst occludes NOx and the amount of NOx discharged from the combustion chamber is equal to or less than a preset set amount, the target rotational speed control is executed and the active state of the catalyst At the time of detection, when the NOx occlusion amount of the NOx occlusion reduction catalyst is not less than the first predetermined amount and the temperature of the catalyst by the catalyst temperature detecting means is not less than the predetermined temperature, the engine is occluded. The first fuel injection valve, the second fuel injection valve, and the slot are arranged in order to achieve a rich operation in which the reduction catalyst releases the stored NOx. Is configured to control the operation of the valve,
Further, the control means is a second predetermined amount when the inactive state of the catalyst is detected by the catalyst activity / inactivity detecting means and the NOx occlusion amount by the NOx occlusion amount detecting means is smaller than the first predetermined amount. When the above is true, the catalyst activation control is executed, and the target rotational speed control is executed when the NOx occlusion amount is smaller than the second predetermined amount even when the inactive state of the catalyst is detected. A fuel injection control device for a multi-fuel engine characterized by comprising: The fuel injection control device for a multi-fuel engine according to any one of claims 2 to 4,
The engine is an engine with a supercharger, and is configured such that an intake opening that opens into a combustion chamber of the engine is fully closed in a compression stroke,
The control means makes the fuel distribution ratio of the first fuel smaller than a predetermined value when the engine is at a rotational speed from the start to a predetermined rotational speed lower than the target rotational speed. A fuel injection control device for a multi-fuel engine characterized by comprising:

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