JP6079793B2 - Multi-fuel engine fuel control system - Google Patents

Description

  The present invention belongs to a technical field related to a fuel control device for a multi-fuel engine.

  Conventionally, for example, as shown in Patent Document 1, a multi-fuel engine that can use a first fuel and a second fuel (hydrogen and gasoline in Patent Document 1) is known.

  Further, Patent Document 2 has a problem of dilution of engine oil with fuel. Since dilution with fuel tends to occur on the high load side of the engine and hardly occurs on the high rotation side, the degree of dilution of engine oil has increased. Sometimes, it is disclosed that the engine operating point is changed to a high rotation side and / or a light load side to suppress dilution of engine oil by fuel.

JP 2008-128032 A JP 2008-297984 A

  By the way, in the multi-fuel engine that can use the first fuel and the second fuel, if one of the first fuel and the second fuel is a hydrogen fuel, the ignitability of the hydrogen fuel is good. Lean operation can be performed and low fuel consumption can be achieved.

  However, hydrogen fuel is a fuel that generates a large amount of water during combustion. The generated water adheres to the combustion chamber wall without being discharged into the exhaust system when the engine is cold, and the attached water burns. Enter the oil pan from the chamber and dilute the engine oil. As the engine operating time becomes longer, the degree of dilution of the engine oil with moisture increases, and when the degree of dilution exceeds a certain level, the lubrication performance of the engine oil decreases too much. The engine performance will be adversely affected.

  Here, as in Patent Document 2, even if the engine operating point is changed when the degree of dilution of the engine oil becomes high, as long as hydrogen fuel is used, the engine oil due to the moisture generated by the combustion is changed. It is difficult to suppress dilution. In particular, if hydrogen fuel is continuously used when the engine is cold, dilution of the engine oil with water proceeds, and the lubricating performance of the engine oil is surely lowered.

  The present invention has been made in view of such points, and an object of the present invention is to provide a variety of engines that can suppress deterioration in lubrication performance of engine oil while improving fuel efficiency. It is an object of the present invention to provide a fuel control device for a fuel engine.

  In order to achieve the above object, the present invention is directed to a fuel control device for a multi-fuel engine configured to be capable of supplying a first fuel and a second fuel, and the first fuel is hydrogen. The second fuel is a fuel that generates less water during combustion and has a lower lean combustion air-fuel ratio than the first fuel, and injects the first fuel to be supplied to the engine. A fuel injection valve, a second fuel injection valve for injecting the second fuel to be supplied to the engine, a dilution degree detecting means for detecting the degree of dilution of the engine oil by moisture, and the first and second Control means for controlling the operation of the fuel injection valve, wherein the control means supplies the first and second fuels in a low dilution state where the dilution degree by the dilution degree detection means is lower than a predetermined dilution degree. Predetermined While controlling the first and second fuel injection valves to supply the engine in a ratio and to make the combustion air-fuel ratio in the combustion chamber of the engine higher than the lean-air combustion air-fuel ratio of the second fuel In the high dilution state where the dilution degree by the dilution degree detecting means is equal to or higher than the predetermined dilution degree, the ratio of the supply amount of the first fuel to the engine is reduced more than in the low dilution state. The first fuel ratio reduction control for controlling the first and second fuel injection valves is configured to be executed.

  With the above configuration, in the low dilution state, the first fuel (hydrogen) and the second fuel made up of a fuel that generates a small amount of moisture during combustion and has a low lean-limit combustion air-fuel ratio with respect to the first fuel. To the engine at a predetermined ratio, the combustion air-fuel ratio in the combustion chamber of the engine can be set to a higher (lean) air-fuel ratio than the lean-limit combustion air-fuel ratio of the second fuel. Good fuel efficiency can be obtained. Further, since the ratio of the supply amount of the first fuel (hydrogen) to the engine is reduced in the high dilution state than in the low dilution state, the amount of water generated during the combustion of the first and second fuels is reduced. The dilution of the engine oil due to the moisture can be suppressed, and deterioration of the lubrication performance of the engine oil can be suppressed. The combustion air-fuel ratio in the high dilution state is a value between the lean air-fuel ratio of the second fuel and the combustion air-fuel ratio in the low dilution state, and the ratio of the first fuel supply amount is The smaller the value, the lower the value. (When only the second fuel is supplied to the engine, the lean air-fuel ratio of the second fuel may be set).

  The fuel control apparatus for the multi-fuel engine further includes engine water temperature detecting means for detecting a temperature of the cooling water of the engine, and the control means has a temperature of the cooling water by the engine water temperature detecting means lower than a predetermined temperature. It is preferable that the first fuel ratio reduction control is executed at the time of the high dilution state.

  As a result, when the temperature of the cooling water of the engine is lower than the predetermined temperature, that is, at a temperature at which moisture generated during combustion of the first and second fuels is not discharged into the exhaust system and is easily mixed into the engine oil. In some cases, by executing the first fuel ratio reduction control, dilution of the engine oil by the moisture can be effectively suppressed. Further, when the temperature of the engine cooling water is equal to or higher than the predetermined temperature, the water is discharged to the exhaust system and the engine oil is diluted by the water without performing the first fuel ratio reduction control. There is almost no. Accordingly, when the engine coolant temperature is equal to or higher than the predetermined temperature, the first fuel can be supplied to the engine at the same ratio as in the low dilution state even in the high dilution state. Good fuel efficiency can be obtained as in the low dilution state.

  When the first fuel ratio reduction control is executed when the temperature of the cooling water is lower than the predetermined temperature and in the highly diluted state as described above, the second fuel is ignited more than the first fuel. The control means relates to the degree of dilution until the complete explosion of the engine when starting the engine when the temperature of the cooling water by the engine water temperature detecting means is lower than the predetermined temperature. Preferably, the first fuel is mainly supplied to the engine and the first fuel ratio reduction control is executed in the high dilution state after the complete explosion of the engine.

  That is, since the second fuel is a fuel having lower ignitability than the first fuel, when the first fuel ratio reduction control is executed at the start of the engine when the temperature of the engine coolant is lower than the predetermined temperature, Combustion becomes quite unstable, making it difficult to start the engine. On the other hand, when starting the engine when the temperature of the cooling water of the engine is lower than the predetermined temperature, the first fuel is mainly supplied to the engine until the engine completes explosion, so that good engine startability is achieved. Can be secured.

  Further, when the first fuel ratio reduction control is executed when the temperature of the cooling water is lower than the predetermined temperature and in the highly diluted state, the second fuel is more ignitable than the first fuel. The fuel is low and has a high calorific value per unit volume, and when the first fuel ratio reduction control is executed, the control means has a light load that is a load smaller than a predetermined load. It is preferable that the ratio of the supply amount of the first fuel to the engine is increased more than when the load is not less than the predetermined load.

  That is, in the light load operation that is smaller than the predetermined load when the temperature of the cooling water of the engine is lower than the predetermined temperature, the combustion stability may be deteriorated. At this time, the first fuel with high ignitability is deteriorated. When the first fuel ratio reduction control for reducing the ratio of the supply amount is executed, the combustion stability is further deteriorated. Therefore, when the first fuel ratio reduction control is executed during such a light load operation, the ratio of the first fuel supply amount to the engine is increased compared to when the engine load is equal to or higher than the predetermined load. By doing so, it is possible to ensure the combustion stability when executing the first fuel ratio reduction control in the light load operation. In addition, by executing the first fuel ratio reduction control, the ratio of the second fuel supply amount, which has a higher calorific value per unit volume than the first fuel, increases compared to the low dilution state. The engine can be warmed up early to be in a warm state, and when the engine is warm, the water in the engine oil can be evaporated, so that it can be quickly returned to a low dilution state.

  Further, when the first fuel ratio reduction control is executed when the temperature of the cooling water is lower than the predetermined temperature and in the highly diluted state, the second fuel is more ignitable than the first fuel. The fuel is low and has a high calorific value per unit volume, and the control means has a medium load or a high load when the engine load is a predetermined load or higher when the first fuel ratio reduction control is executed. In some cases, the engine may be configured to supply only the second fuel.

  As a result, even when the temperature of the engine coolant is lower than the predetermined temperature, the combustion can be stabilized even when the first fuel is not supplied to the engine at the time of medium load or high load operation where the combustion is stable. There is no problem in performance, and the engine can be warmed up to a warm state as soon as possible by supplying only the second fuel.

  As described above, according to the fuel control device for a multi-fuel engine of the present invention, good fuel efficiency is obtained in the low dilution state, and moisture generated during the combustion of the first and second fuels in the high dilution state. It is possible to suppress the engine oil from being diluted and to prevent the lubrication performance of the engine oil from deteriorating.

1 is a schematic view of a vehicle equipped with a multi-fuel engine that is fuel-controlled by a fuel control device 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 graph which shows the hydraulic characteristic of engine oil. It is a graph which shows the relationship between the excess air ratio (lambda) and NOx discharge | emission amount from an engine when making it burn with an engine about hydrogen gas, natural gas, and these mixed gas A, B, and C. FIG. Regarding hydrogen gas, natural gas, and mixed gas A, B, and C thereof, the relationship between the excess air ratio λ and the engine output torque and the excess air ratio λ and the thermal efficiency of the engine when the engine is burned It is a graph which shows a relationship. It is a flowchart which shows the processing operation at the time of engine starting by the control unit, and driving | operation.

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

  FIG. 1 is a schematic diagram of a vehicle 1 equipped with a multi-fuel engine 10 (hereinafter referred to as an engine 10) that is fuel-controlled by a fuel control device according to an embodiment of the present invention. The vehicle 1 is a so-called range extender EV vehicle (also referred to as a vehicle having a series hybrid system (series hybrid vehicle)), and includes an engine 10, a generator 20 driven by the engine 10 to generate electric power, A high-voltage / large-capacity battery 30 in which the power generated by the generator 20 is stored (charged), and the generated power of the generator 20 driven by the engine 10 and the stored power (discharged power) of the battery 30 A drive motor 40 that is driven by both or only the discharge power of the battery 30 is provided. In the present embodiment, the generator 20 is a motor generator having a function of a motor, and the engine 10 is driven (cranked) by the generator 20 as a motor to start the engine 10. .

  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, and 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 requested to accelerate the vehicle 1. Sometimes, the engine 10 is started and 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 a power generation engine used to drive the generator 20 to generate power. 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 as fuels. The hydrogen gas corresponds to the first fuel, and the natural gas corresponds to the second fuel composed of a fuel that generates less moisture during combustion and has a lower lean combustion air-fuel ratio than the first fuel. The second fuel is not limited to natural gas but may be propane or butane, for example. The second fuel is also preferably a fuel having a lower ignitability than the first fuel (hydrogen gas) and a higher calorific value per unit volume, and natural gas, propane and butane are fuels suitable for such fuel. It is. The second fuel is not limited to gaseous fuel, but may be liquid fuel.

  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 a compressor 85a of an exhaust turbocharger 85 to be described later), the intake passage 14 is driven by a throttle valve actuator 90 such as a stepping motor and has a cross-sectional area ( A throttle valve 16 for adjusting the valve opening) 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). In engine control described later in this embodiment, the throttle valve 16 is fully opened.

  Hydrogen ports from which hydrogen gas from the hydrogen tank 70 and natural gas from the CNG tank 71 are respectively injected into the intake passage 14 in each branch passage downstream of the branch portion of the intake passage 14. An injection valve 17A and a CNG port injection valve 17B are provided. The hydrogen gas and natural gas injected by the hydrogen and CNG port injection valves 17A and 17B, respectively, are mixed with air and supplied to the working chamber in the intake stroke. The hydrogen and CNG port injection valves 17A and 17B are used when the engine 10 is extremely cold (the temperature of the engine coolant is considerably low even when the engine is cold). This is a fuel injection valve that is used only at the time of starting at a temperature lower than the lower temperature), and is used for the hydrogen and CNG direct injection valves that will be described later at the time of starting other than extremely cold and during operation of the engine 10. Fuel (hydrogen gas and natural gas) is directly injected into the combustion chamber from 18A and 18B. In other words, when the engine 10 is extremely cold, the fuel injection openings of the hydrogen and CNG direct injection valves 18A and 18B may be blocked by freezing of water generated by fuel combustion. Therefore, fuel is injected from the hydrogen and CNG port injection valves 17A and 17B exceptionally at the time of start-up during extremely cold. When starting and operating the engine 10, fuel is injected only from the hydrogen and CNG port injection valves 17A and 17B, or the hydrogen and CNG direct injection valves 18A and 18B and the hydrogen and CNG are injected. It is also possible to inject fuel from the port injection valves 17A and 17B. Conversely, the hydrogen and CNG port injection valves 17A and 17B can be eliminated. In the following description, it is assumed that fuel (hydrogen gas and natural gas) is injected from the hydrogen and CNG direct injection valves 18A and 18B.

  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 occluded in a lean air-fuel ratio atmosphere, and the occluded NOx is released in a rich air-fuel ratio atmosphere to cause the NOx to react with HC and CO in the exhaust gas. Have the function of reducing

  In each rotor housing 11 (each cylinder), a hydrogen direct injection valve 18A for directly injecting hydrogen gas from the hydrogen tank 70 into the working chamber (combustion chamber) in the compression stroke of the rotor accommodating chamber 11a; CNG direct injection valve 18B for directly injecting natural gas from the CNG tank 71 into the working chamber (combustion chamber) in the compression stroke of the rotor accommodating chamber 11a, and hydrogen and CNG direct injection valves 18A, 18B Two spark plugs 19 for igniting the injected hydrogen gas and natural gas are provided. Hydrogen gas and natural gas are injected and supplied to the engine 10 (combustion chamber) at substantially the same volume ratio (both about 50%) except when the engine is cold and in a highly diluted state described later.

  In the present embodiment, the hydrogen direct injection valve 18A (exceptionally, the hydrogen port injection valve 17A) corresponds to the first fuel injection valve that injects the first fuel to be supplied to the engine 10, and is directly connected to the CNG direct injection valve. The injection valve 18 </ b> B (exceptionally the CNG port injection valve 17 </ b> B) corresponds to a second fuel injection valve that injects the second fuel to be supplied to the engine 10.

  The engine 10 is provided with an exhaust turbocharger 85 that supercharges intake air into the working chamber (combustion chamber) in the intake stroke in each rotor accommodating chamber 11a of the engine 10. The exhaust turbocharger 85 includes a compressor 85 a disposed on the downstream 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. And a turbine 85b disposed in the turbine. 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 on the downstream side of the compressor 85a in the intake passage 14, and then in the intake chamber in each rotor accommodating chamber 11a via each branch path. Inhaled.

  In FIG. 2, reference numeral 111 denotes an oil pan that stores engine oil. Engine oil in the oil pan 111 is supplied to each part of the engine 10 by an oil pump 112 driven by the engine 10, and then returns to the oil pan 111 again. .

  The vehicle 1 includes a battery current / voltage sensor 101 that detects a current flowing in 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 an occupant of the vehicle 1 (accelerator opening by an occupant'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 It faces the formed water jacket (not shown) and flows through the water jacket. Engine water temperature sensor 106 for detecting the temperature of the engine coolant (engine water temperature), the pressure in the hydrogen tank 70 (that is, the hydrogen gas remaining amount in the hydrogen tank 70), and the pressure in the CHG tank 71 (that is, in the CNG tank 71) A tank pressure sensor 107 (which is provided separately for the hydrogen tank 70 and the CNG tank 71), and an air flow sensor 108 for detecting the intake air flow rate sucked into the intake passage 14. The oil level sensor 109 for detecting the oil level in the oil pan 111, the oil pressure sensor 110 for detecting the supply pressure (hydraulic pressure) of the engine oil by the oil pump 112, and the heating device described later, An operation switch 55 for operating and operating the heating device, operation control of the engine 10, A control unit 100 that performs like (operation control words generator 20 and the drive motor 40) operation control of the second inverter 50, 51 is provided. The rotation angle sensor 104 also serves as an engine rotation speed sensor that detects the rotation speed of the engine 10.

  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, an oil level sensor. 109, various information signals from the oil pressure sensor 110, the operation switch 55, and the like are 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.

  Then, based on the input signal, the control unit 100 controls the throttle valve actuator 90, the hydrogen port injection valve 17A, the CNG port injection valve 17B, the hydrogen direct injection valve 18A, the CNG direct injection valve 18B, and A control signal is output to the spark plug 19 to control the engine 10, and a control signal is output to the first and second inverters 50 and 51 to control the generator 20 and the drive motor 40. The control unit 100 includes a hydrogen direct injection valve 18A (exceptionally a hydrogen port injection valve 17A) as a first fuel injection valve, and a CNG direct injection valve 18B (as a second fuel injection valve). Exceptionally, it constitutes a control means for controlling the operation of the CNG port injection valve 17B).

  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, the control unit 100 selects the first mode when the SOC of the battery 30 is higher than the predetermined capacity, and the acceleration request of the vehicle 1 more than the predetermined even if the SOC of the battery 30 is higher than the predetermined capacity. In the case where the required output of the drive motor 40 based on the signals from the accelerator opening sensor 102 and the vehicle speed sensor 103 is large as in the case where there is, 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 confirms whether or not there is an operation request for the engine 10 based on the required output of the drive motor 40 and the SOC value of the battery 30, and the operation request for the engine 10 is If there is, the engine 10 is cranked by the generator 20 as a motor to start the engine 10, and the engine 10 is operated to cause the generator 20 to generate power after the start.

  When the engine 10 is operated in response to a power generation request, the control unit 100 basically performs a steady operation unless there is a request for acceleration of the vehicle 1 or more. When the control unit 100 operates in a steady state at the time of a power generation request in this manner, the control unit 100 operates at a medium load or a high load that is a load higher than a predetermined load and in a predetermined rotation speed region. In the present embodiment, the predetermined rotational speed region is an efficient region including the highest efficiency point of the engine 10 (for example, 1800 rpm to 2200 rpm). In the present embodiment, the predetermined rotational speed region is basically operated at 2000 rpm. On the other hand, the control unit 100 sets the target rotational speed of the engine 10 to a higher value as the required output of the drive motor 40 is larger when the acceleration request of the vehicle 1 exceeds a predetermined value.

  In the present embodiment, the engine 10 is requested to be operated when the power generation is requested when the engine 10 is stopped, and when the engine 10 is stopped when there is no power generation request. This is when heating is requested by the occupant's operation switch 55.

  That is, the vehicle 1 is provided with a device for heating the passenger compartment of the vehicle 1 using the cooling water of the engine 10. This heating device may be incorporated as an air conditioner. This heating device has a heater core that performs heat exchange between the air blown into the passenger compartment and the cooling water, and the operation switch 55 that is operated by a passenger of the vehicle 1 to operate the heating device. Operation information of the operation switch 55 is input to the control unit 100. If there is no power generation request and the engine 10 is stopped, and the heating request is made by the operation switch 55, the control unit 100 starts the engine 10 and warms the cooling water of the engine 10. At this time, the control unit 100 operates the engine 10 with a light load that is a load smaller than the predetermined load. That is, the cooling water of the engine 10 is warmed by operating the engine 10 while generating power slightly by the generator 20.

  In addition, the control unit 100 detects the degree of dilution of the engine oil by moisture based on the oil pressure that is detected by the oil pressure sensor 110 and that is the supply pressure of the engine oil from the oil pump 112. That is, since the oil pump 112 is driven by the engine 10, the hydraulic pressure increases as the engine speed increases, as shown in FIG. As the engine oil is diluted with moisture, the gradient of the hydraulic characteristic line becomes smaller.

  Therefore, when the engine 10 is idling (no-load operation), the control unit 100 determines that the engine oil dilution degree is greater than or equal to a predetermined dilution level when the oil pressure by the oil pressure sensor 110 is less than or equal to a predetermined pressure. It is determined that a certain high dilution state has been reached. The predetermined dilution is such that if the oil is further increased, the lubrication performance of the engine oil deteriorates too much and adversely affects the performance of the engine 10. For example, the dilution rate of the engine oil with water is 30%. is there. In this case, when the engine 10 is idling, the control unit 100 enters a high dilution state when the oil pressure by the oil pressure sensor 110 reaches or falls below the oil pressure characteristic line where the dilution ratio is 30%. It is determined that it has become. In this way, the hydraulic pressure sensor 110 constitutes a dilution degree detection means for detecting the degree of dilution of the engine oil with moisture. As will be described later, the predetermined dilution is provided with hysteresis.

  The water that dilutes the engine oil burns hydrogen gas and natural gas when the engine 10 is operating when the engine water temperature by the engine water temperature sensor 106 (engine water temperature detection means) is lower than the predetermined temperature. The longer the operation time when the engine is cold, the more the engine oil is diluted with moisture. Further, since natural gas is a fuel that generates less water during combustion than hydrogen gas, engine oil is diluted mainly by the water generated by the combustion of hydrogen gas.

  As another form of detecting the degree of dilution of the engine oil, the control unit 100 operates when the engine 10 is operating when the engine is cold and the operation time is a predetermined time (the engine water temperature reaches the predetermined temperature). It is also possible to calculate the integrated value of the cold short-time operation time that was less than the time) In this case, the control unit 100 constitutes the dilution degree detecting means. The greater the integrated value is, the higher the degree of dilution is. The control unit 100 determines that the highly diluted state has been reached when the integrated value is equal to or greater than a predetermined value.

  Alternatively, the degree of dilution of the engine oil may be detected by the oil level sensor 109. That is, the oil level in the oil pan 111 is increased by the amount of water mixed in the engine oil after the cold engine operation compared to before the operation, so the degree of dilution is detected by the increase change amount. can do. In this case, the oil level sensor 109 constitutes the dilution degree detecting means. The greater the integrated value of the oil level increase change accompanying the operation when the engine is cold, the higher the degree of dilution. When the integrated value exceeds a predetermined value, the control unit 100 It is determined that a highly diluted state has been reached.

  In the low dilution state where the engine oil dilution degree is lower than the predetermined dilution degree, the control unit 100 supplies hydrogen gas and natural gas at a predetermined ratio (in the present embodiment, approximately the same volume ratio as described above). Thus, the hydrogen and CNG direct injection valves 18A and 18B are controlled so as to be supplied to the engine 10 and to make the combustion air-fuel ratio in the combustion chamber of the engine 10 higher than the lean air-fuel ratio of natural gas. Hereinafter, this control is referred to as normal control.

  Here, FIG. 4 shows the excess air ratio λ and the engine 10 when hydrogen gas, natural gas, and mixed gas A, B, C thereof are burned by the engine 10 (rotation speed 2000 rpm, throttle valve 16 fully opened). The relationship with the NOx emission amount from (combustion chamber) is shown. The mixed gas A has hydrogen gas and natural gas at substantially the same volume ratio (both are about 50%), and the mixed gas B has a larger volume ratio of hydrogen gas than the mixed gas A, The mixed gas C has a volume ratio of hydrogen gas larger than that of the mixed gas B. FIG. 5 shows the relationship between the excess air ratio λ and the output torque of the engine 10 when the above-mentioned gases shown in FIG. 4 are burned by the engine 10 (rotation speed 2000 rpm, throttle valve 16 fully opened), and air. The relationship between excess ratio (lambda) and the thermal efficiency of the engine 10 is shown. Here, natural gas is injected from the CNG direct injection valve 18B, and hydrogen gas is injected from the hydrogen port injection valve 17A. In this case, the magnitude of the output torque is larger than when hydrogen gas and natural gas are injected from the hydrogen and CNG port injection valves 17A and 17B or the hydrogen and CNG direct injection valves 18A and 18B, respectively. Although the above changes, the trend of the above relationship does not change greatly.

  From FIG. 4 and FIG. 5, the lean air limit combustion air-fuel ratio (here, excess air ratio λ) of natural gas is 1.6, and even if the excess air ratio λ is larger than this, stable ignition is achieved. I can't do it. 4 and 5, the excess air ratio λ is only up to 2.7, but the lean excess air excess ratio λ of hydrogen gas is about 3. In FIGS. 4 and 5, the results when the excess air ratio λ of hydrogen gas is lower than 1.8 are omitted.

  As shown in FIG. 4, if the excess air ratio λ is the same, the natural gas has a smaller NOx emission than the hydrogen gas, and the mixed gas A, B, C has a larger volume ratio of the natural gas (hydrogen gas It can be seen that the smaller the volume ratio), the smaller the NOx emissions. That is, when the volume ratio of hydrogen gas in the hydrogen gas or mixed gas is large, the NOx emission amount increases. However, when the volume ratio of hydrogen gas in the hydrogen gas or mixed gas is large, the lean combustion air-fuel ratio becomes high, so the NOx emission can be reduced by increasing the combustion air-fuel ratio in the combustion chamber. .

  Therefore, in the present embodiment, the combustion air-fuel ratio (excess air ratio λ) at the time of the normal control, the NOx emission amount from the engine 10 is only the natural gas, and the lean air-fuel ratio (λ = 1.6). Therefore, the lean air-fuel ratio is made substantially the same as the NOx emission amount when burning. In this embodiment, the lean air-fuel ratio is obtained at the point Q2 where the line parallel to the horizontal axis passing through the point Q1 of λ = 1.6 on the natural gas line in FIG. The value of λ (ie, λ = 1.9) is obtained.

  On the other hand, in the high dilution state, the control unit 100 sets the hydrogen and CNG direct injection injectors 18A and 18B to reduce the volume ratio of the supply amount of hydrogen gas to the engine 10 more than in the low dilution state. The first fuel ratio reduction control to be controlled is executed. That is, in the high dilution state, the volume ratio of the supply amount of hydrogen gas that generates a large amount of water during combustion is reduced (the volume ratio of the supply amount of natural gas that generates a small amount of water during combustion is increased). ) To suppress dilution of engine oil due to moisture generated during combustion of hydrogen gas and natural gas. The combustion air-fuel ratio (excess air ratio λ) at the time of the first fuel ratio reduction control is the lean air-fuel ratio (λ = 1.6) of the natural gas and the combustion air-fuel ratio (λ = 1) in the low dilution state. .9), the lower the volume ratio of the supply amount of hydrogen gas, the lower the value (when only natural gas is supplied to the engine 10, the combustion air-fuel ratio at the lean limit of natural gas) Or a slightly lower combustion air-fuel ratio (for example, λ = 1.4).

  In the present embodiment, the control unit 100 executes the first fuel ratio reduction control when the engine water temperature by the engine water temperature sensor 106 is lower than the predetermined temperature and in the high dilution state, and in the high dilution state. Even so, when the engine water temperature is equal to or higher than the predetermined temperature, the normal control is executed. This is because when the engine water temperature is equal to or higher than the predetermined temperature, the water generated during the combustion of hydrogen gas and natural gas is discharged to the exhaust system without performing the first fuel ratio reduction control. This is because engine oil rarely dilutes. The first fuel ratio reduction control may be executed in the high dilution state regardless of the engine water temperature.

  Further, in the present embodiment, the control unit 100, when starting the engine 10 when the engine water temperature is lower than the predetermined temperature, supplies hydrogen gas to the engine 10 until the complete explosion of the engine 10 regardless of the degree of dilution. The low water temperature start control that is mainly supplied is executed, and after the complete explosion of the engine 10, the first fuel ratio reduction control is executed in the high dilution state, while the low dilution is executed after the complete explosion of the engine 10. In the state, the normal control is executed. The volume ratio of the amount of hydrogen gas supplied to the engine 10 during the low water temperature start control is preferably 80% to 100% (in this embodiment, 100%). The combustion air-fuel ratio (excess air ratio λ) at the time of the low water temperature start-up control is such that the combustion air-fuel ratio (λ = 1.9) in the low-dilution state and the lean-air-limit combustion air-fuel ratio (λ = 3) However, it is preferable that the value is not too high from the viewpoint of ensuring good engine startability.

  On the other hand, when the engine water temperature is equal to or higher than the predetermined temperature, the control unit 100 executes the normal control both when the engine 10 is started and during operation.

  In the present embodiment, the volume ratio of the amount of hydrogen gas supplied to the engine 10 during the first fuel ratio reduction control is determined according to whether the load on the engine 10 is a light load that is smaller than a predetermined load. Change accordingly. Specifically, the control unit 100 performs the predetermined load when the load of the engine 10 is the light load (that is, when a heating request without a power generation request) is performed during the execution of the first fuel ratio reduction control. The volume ratio of the supply amount of hydrogen gas to the engine 10 is increased as compared with the above-described medium load or high load. The volume ratio of hydrogen gas to the engine 10 during light load operation is preferably 10% to 30% (in this embodiment, 20%).

  That is, in the light load operation when the engine water temperature is lower than the predetermined temperature, the combustion stability may be deteriorated. At this time, the volume ratio of the supply amount of hydrogen gas having high ignitability is decreased. When the first fuel ratio reduction control is executed, the combustion stability is further deteriorated. Therefore, when the first fuel ratio reduction control is performed during such a light load operation, the volume ratio of the hydrogen gas to the engine 10 is increased compared to during the medium load or high load operation, thereby stabilizing the combustion. Ensure sex. Further, the execution of the first fuel ratio reduction control increases the volume ratio of the supply amount of natural gas, which has a higher calorific value per unit volume than hydrogen gas, as compared with the low dilution state. 10 can be warmed up early to be in a warm state.

  Further, the control unit 100 supplies only natural gas to the engine 10 by setting the volume ratio of hydrogen gas to the engine 10 to 0% during the middle load or high load operation during the execution of the first fuel ratio reduction control. To do. In medium or high load operation, there is no problem in combustion stability even if hydrogen gas is not supplied to the engine 10 at all, and the engine 10 is warmed up as soon as possible by supplying only natural gas. Can be warm. When the engine 10 is warm, water in the engine oil can be evaporated. The volume ratio of hydrogen gas to the engine 10 during medium-load or high-load operation may be smaller than the volume ratio of hydrogen gas to the engine 10 during light-load operation, but is 0% as described above. Is most preferred.

  In the present embodiment, the predetermined dilution which is the dilution at the boundary between the low dilution state and the high dilution state (boundary dilution when switching between the first fuel ratio reduction control and the normal control) is set. Is provided with hysteresis, and the predetermined dilution degree when switching from the first fuel ratio reduction control to the normal control is the predetermined dilution degree when switching from the normal control to the first fuel ratio reduction control. The level is lower than the degree (in the example of FIG. 3, the dilution rate is 30%) and is hardly diluted with moisture (for example, the dilution rate is 3%). That is, once the above-described highly diluted state is reached, the engine oil dilution level is set to a highly diluted state unless the engine oil dilution level falls below, for example, a 3% dilution rate level. The low dilution state is set. Conversely, once the low dilution state is reached, the dilution level of the engine oil is low, for example, unless the dilution rate is 30% or higher, and when the dilution rate is 30% or higher. Furthermore, the high dilution state is obtained.

  Next, processing operations when the engine 10 is started and operated by the control unit 100 will be described based on the flowchart of FIG.

  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, based on the required output of the drive motor 40 and the SOC of the battery 30, the presence or absence of an operation request for the engine 10 is confirmed. In the next step S4, it is determined whether or not there is an operation request for the engine 10. judge.

  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 whether or not the engine water temperature by the engine water temperature sensor 106 is lower than the predetermined temperature. Determine whether.

  When the determination in step S5 is NO, the process proceeds to step S6, and the normal control (both the volume ratio of hydrogen gas and natural gas is set to about 50%) is performed both at the time of starting and operation of the engine 10. Then, the process proceeds to step S13. On the other hand, when the determination in step S5 is YES, the process proceeds to step S7 to determine whether or not the engine 10 has already been started.

  When the determination in step S7 is NO, the process proceeds to step S8, the low water temperature start control is executed, and then the process proceeds to step S9. On the other hand, if the determination in step S7 is yes, the process proceeds directly to step S9.

  In step S9, the degree of dilution of the engine oil is the predetermined dilution level (for example, when the engine is currently in a low dilution state, the dilution rate is, for example, 30%. When the engine oil is currently in a high dilution state, the dilution rate is, for example, 3%. If the determination in step S9 is NO, the process proceeds to step S6. If the determination in step S9 is YES, the process proceeds to step S10. Proceed to

  In step S10, it is determined whether or not the load on the engine 10 is light (whether there is no power generation request and there is a heating request). When the determination in step S10 is NO, the process proceeds to step S11, and the first fuel ratio reduction control (the hydrogen gas volume ratio is set to 0% and the natural gas volume ratio is set to 100%) is executed. Thereafter, the process proceeds to step S13. On the other hand, when the determination in step S10 is YES, the process proceeds to step S12 to execute the first fuel ratio reduction control (the hydrogen gas volume ratio is set to 20% and the natural gas volume ratio is set to 80%). Then, the process proceeds to step S13.

  In step S13, signals from various sensors are newly read to check whether or not there is an engine request, and it is determined whether or not there is no engine operation request. When the determination in step S13 is NO, the process returns to step S5. On the other hand, when the determination in step S13 is YES, the process proceeds to step S14, the engine 10 is stopped, and then the process returns.

  When the engine 10 is stopped, the degree of dilution of the engine oil is the predetermined dilution level (when the engine 10 is currently in a low dilution state, for example, the dilution rate is 30%, and when the engine oil is currently in a high dilution state, for example, The dilution state (low dilution state or high dilution state) is determined according to whether or not the dilution rate is 3% or more, and the dilution state is stored in the memory. For example, when the engine 10 is operated for a long time and changes from the high dilution state to the low dilution state during the engine warm state, the low dilution state is stored, and the next step immediately after the start of the engine 10 is performed. The predetermined dilution level in the determination of S9 is a level at a dilution rate of 30%. On the other hand, if it is stored as the high dilution state, the predetermined dilution in the determination of step S9 immediately after the start of the next engine 10 becomes a level of 3% dilution.

  Therefore, in the present embodiment, in the low dilution state, hydrogen gas and natural gas are supplied to the engine 10 at a predetermined volume ratio, so that the combustion air-fuel ratio in the combustion chamber of the engine 10 is reduced to the natural gas lean limit. It is possible to set the air / fuel ratio to be higher (lean) than the combustion air / fuel ratio. Further, in the high dilution state, the volume ratio of the supply amount of hydrogen gas to the engine 10 is reduced more than in the low dilution state (the first fuel ratio reduction control is executed). It is possible to reduce the amount of water generated at the time of combustion and suppress dilution of the engine oil by the water, thereby suppressing deterioration of the lubricating performance of the engine oil. Since the water in the engine oil evaporates when the engine 10 is in a warm state, even if the engine 10 is in a highly diluted state, the first fuel ratio reduction control can suppress the dilution of the engine oil with water. Eventually, it will return to a low dilution state.

  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 10 is a power generation engine used to drive the generator 20 in the series hybrid system to generate power. However, the engine 10 is an engine that drives the drive wheels 61 of the vehicle 1 ( Including an engine of a parallel hybrid system). Moreover, in the said embodiment, although the engine 10 was used as the rotary piston engine, it can also be set as a reciprocating 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 control device for a multi-fuel engine configured to be able to supply a first fuel and a second fuel, respectively.

10 Multi-fuel engine 18A Direct injection valve for hydrogen (first fuel injection valve)
18B CNG direct injection valve (second fuel injection valve)
100 Control unit (control means)
106 Engine water temperature sensor (engine water temperature detection means)
110 Oil pressure sensor (dilution degree detection means)

Claims (5)

A fuel control device for a multi-fuel engine configured to be able to supply a first fuel and a second fuel, respectively,
The first fuel is hydrogen;
The second fuel is a fuel that generates less moisture during combustion and has a lower lean combustion air-fuel ratio than the first fuel,
A first fuel injection valve for injecting the first fuel to be supplied to the engine;
A second fuel injection valve for injecting the second fuel to be supplied to the engine;
A dilution degree detection means for detecting the degree of dilution of the engine oil with moisture;
Control means for controlling the operation of the first and second fuel injection valves,
The control means includes
When the dilution degree by the dilution degree detecting means is in a low dilution state where the dilution degree is lower than a predetermined dilution degree, the first and second fuels are supplied to the engine at a predetermined ratio and the combustion air-fuel ratio in the combustion chamber of the engine While controlling the first and second fuel injection valves so as to make the fuel air ratio higher than the lean limit combustion air-fuel ratio of the second fuel,
In the high dilution state in which the dilution degree by the dilution degree detecting means is equal to or higher than the predetermined dilution degree, the first fuel supply amount ratio to the engine is reduced in order to reduce the ratio of the first fuel supply amount to the engine. A fuel control device for a multi-fuel engine, characterized in that the first fuel ratio reduction control for controlling the first and second fuel injection valves is executed. The fuel control apparatus for a multi-fuel engine according to claim 1,
An engine water temperature detecting means for detecting the temperature of the cooling water of the engine;
The control means is configured to execute the first fuel ratio reduction control when the temperature of the cooling water by the engine water temperature detection means is lower than a predetermined temperature and in the high dilution state. Fuel control device for multi-fuel engine. The fuel control apparatus for a multi-fuel engine according to claim 2,
The second fuel is a fuel having lower ignitability than the first fuel,
When the engine is started when the temperature of the cooling water by the engine water temperature detecting means is lower than the predetermined temperature, the control means is responsive to the engine until the complete explosion of the engine regardless of the degree of dilution. A fuel control apparatus for a multi-fuel engine, wherein one fuel is mainly supplied and the first fuel ratio reduction control is executed in the highly diluted state after the complete explosion of the engine. . The fuel control device for a multi-fuel engine according to claim 2 or 3,
The second fuel is a fuel having lower ignitability and higher calorific value per unit volume than the first fuel,
When the first fuel ratio reduction control is executed, the control means is configured so that when the engine load is a light load that is smaller than a predetermined load, the engine is more than the predetermined load. A fuel control apparatus for a multi-fuel engine, characterized in that the ratio of the first fuel supply amount is increased. The fuel control device for a multi-fuel engine according to claim 2 or 3,
The second fuel is a fuel having lower ignitability and higher calorific value per unit volume than the first fuel,
The control means supplies only the second fuel to the engine when the load of the engine is a medium load or a high load that is a load greater than or equal to a predetermined load during the execution of the first fuel ratio reduction control. A fuel control device for a multi-fuel engine, characterized in that it is configured as described above.

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