JP7298185B2 - bi-fuel vehicle - Google Patents

Description

The present invention relates to a bi-fuel vehicle that runs by switching between two types of fuel.

A bi-fuel vehicle runs by switching different fuels, such as gasoline and compressed natural gas (hereinafter referred to as CNG), and supplying them to an internal combustion engine. For example, CNG has the characteristics of higher fuel efficiency and less amount of harmful substances (nitrogen oxides, carbon dioxide, sulfur oxides, etc.) in exhaust gas than gasoline. Therefore, in bi-fuel vehicles that use gasoline and CNG, effects such as improved fuel efficiency and improved exhaust gas performance due to reduced consumption of gasoline can be expected.

Japanese Patent Application Laid-Open No. 2004-211610

In recent years, an increasing number of vehicles have an idling stop function that automatically stops the engine when a predetermined stop condition is met. Vehicles with an idling stop function have more opportunities to restart the engine from a stopped state. Therefore, the load on the starter for starting the engine and the battery that supplies power to the starter tends to increase.

A problem unique to bi-fuel vehicles is that each fuel has different characteristics such as starting performance. If the engine is started with a fuel with low starting performance, it will take a long time to crank, placing a heavy burden on the starter and battery. It may take. For example, since CNG has lower starting performance than gasoline, it may not be suitable as a starting fuel depending on the state of the battery and starter. On the other hand, there is also a demand to use CNG as effectively as possible because of its excellent fuel efficiency and exhaust gas performance. In particular, if the gasoline with high starting performance is always selected at the time of restarting, it will be disadvantageous in terms of fuel efficiency.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a bi-fuel vehicle having excellent starting performance and fuel efficiency of an internal combustion engine.

The present invention provides an internal combustion engine that can use a first fuel with relatively high starting performance and a second fuel with relatively high fuel efficiency, and automatically stops the internal combustion engine when a predetermined automatic stop condition is satisfied. and a control unit that restarts the internal combustion engine when a predetermined restart condition is satisfied while the internal combustion engine is stopped; and a rechargeable battery that supplies electric power to a starting device that starts the internal combustion engine. In the bi-fuel vehicle, the controller performs restart control to select the fuel to be used for restarting the internal combustion engine based on the state of the battery .
In one aspect, the control unit restarts the internal combustion engine using the first fuel when the battery has reached a predetermined degree of deterioration, and when the battery has not reached the predetermined degree of deterioration, The second fuel is used to restart the internal combustion engine.
In another aspect, the control unit restarts the internal combustion engine using the first fuel when the electric power consumption of the electric load other than the starting device is greater than a predetermined value in the automatic stop state of the internal combustion engine. If the amount of electric power used by the electric loads other than the starting device is smaller than a predetermined value, the internal combustion engine is restarted using the second fuel.

According to the present invention, it is possible to obtain a bi-fuel vehicle excellent in starting performance and fuel efficiency of the internal combustion engine by appropriately selecting the fuel to be used for restarting the internal combustion engine based on the state of the battery.

1 is a configuration diagram of a bi-fuel vehicle according to an embodiment; FIG. 4 is a flow chart showing restart control of the bi-fuel vehicle according to the present embodiment; FIG. 4 is a flow chart showing a modification of the restart control of the bi-fuel vehicle according to the present embodiment; FIG. 4 is a graph showing the difference in restart threshold for each fuel;

Hereinafter, this embodiment will be described in detail with reference to the accompanying drawings. First, referring to FIG. 1, components of a bi-fuel vehicle according to the present embodiment will be described. For convenience of explanation, FIG. 1 is simplified for explaining the technology of the present disclosure, and it is assumed that a vehicle normally has components even if they are not shown.

The bi-fuel vehicle 10 of the present embodiment switches between the first fuel F1 and the second fuel F2 having different fuel characteristics and supplies them to the engine 11, which is an internal combustion engine, to drive the engine 11. FIG. An engine ECU (Electrical Control Unit) 12 is provided as a control section that controls the engine 11 and related equipment. A battery 13 is provided as a power source for supplying electric power to the electrical system of the bi-fuel vehicle 10 .

The first fuel F1 and the second fuel F2 differ in starting performance when starting the engine 11, and the first fuel F1 has higher engine starting performance than the second fuel F2. In this embodiment, liquid gasoline fuel is used as the first fuel F1, and gaseous CNG (compressed natural gas) fuel is used as the second fuel F2. In terms of fuel characteristics other than starting performance, the second fuel F2 (CNG) is superior in fuel efficiency to the first fuel F1 (gasoline), and the amount of harmful substances in the exhaust gas after combustion is small (exhaust gas performance is expensive). The bi-fuel vehicle 10 has two fuel supply systems that supply these two types of fuels F<b>1 and F<b>2 to the engine 11 .

A first fuel tank 20, a first fuel line 21, a fuel pump 22, a pump motor 23, and a first injector 24 are provided as a fuel supply system for the first fuel F1. A liquid first fuel F<b>1 (gasoline) is stored in the first fuel tank 20 . The first fuel line 21 is a line that conveys the first fuel F<b>1 from the first fuel tank 20 to the first injector 24 . The fuel pump 22 is a pump driven by a pump motor 23 , and pumps the first fuel F<b>1 through the first fuel line 21 to the first injector 24 . The first injector 24 injects the first fuel F1 into an intake port (not shown) or a combustion chamber (not shown) of the engine 11 . The first fuel F1 injected from the first injector 24 mixes with air taken into the engine 11 from an intake system (not shown) to form an air-fuel mixture.

A second fuel tank 25, a second fuel line 26, an electromagnetic valve 27, and a second injector 28 are provided as a fuel supply system for the second fuel F2. In the second fuel tank 25, gaseous second fuel F2 (CNG) is stored in a high pressure state. The second fuel line 26 is a line that conveys the second fuel F2 from the second fuel tank 25 to the second injector 28 . The solenoid valve 27 is a normally closed solenoid valve, and when closed, blocks the delivery of the second fuel F2 to the second injector 28 side. When the solenoid valve 27 is opened by energization, the second fuel F2 is sent to the second injector 28 through the second fuel line 26 . Since the required fuel pressure on the engine 11 side is lower than the filling pressure of the second fuel tank 25, the high-pressure second fuel F2 in the second fuel tank 25 is depressurized by a regulator (not shown), It is supplied to injector 28 . The second injector 28 injects the second fuel F2 into an intake port (not shown) or a combustion chamber (not shown) of the engine 11 . The second fuel F2 injected from the second injector 28 mixes with air taken into the engine 11 from the intake system to form an air-fuel mixture.

An occupant driving the bi-fuel vehicle 10 can operate the fuel selection switch 14 to select either the first fuel F<b>1 or the second fuel F<b>2 to be supplied to the engine 11 . Further, it is also possible to automatically select the fuel to be supplied to the engine 11 by the control from the engine ECU 12 without depending on the operation of the passenger. The selected fuel is consumed to start the engine 11 and run the bi-fuel vehicle 10 . In both cases of manual selection and automatic selection, the engine ECU 12 controls the two fuel supply systems to supply the selected fuel to the engine 11 . Specifically, in the fuel supply when the use of the first fuel F1 is selected, a drive signal is sent from the engine ECU 12 to the pump motor 23 to drive the fuel pump 22, and the engine ECU 12 supplies fuel from the first injector 24. The injection timing and injection amount of the first fuel F1 are controlled. In the fuel supply when the use of the second fuel F2 is selected, a signal is sent from the engine ECU 12 to the solenoid valve 27 to open the solenoid valve 27, and the engine ECU 12 supplies the second fuel F2 from the second injector 28. Injection timing and injection quantity are controlled.

The engine 11 has a spark plug 30 inside the combustion chamber. The engine ECU 12 controls the ignition timing of the spark plug 30, and the ignition of the spark plug 30 ignites and burns the air-fuel mixture in the combustion chamber. Combustion of the air-fuel mixture causes a piston (not shown) to reciprocate within a cylinder (not shown) of the engine 11 , and the reciprocating motion of the piston is converted into rotational motion of the crankshaft 31 .

Rotation of the crankshaft 31 is transmitted to the transmission 32 . A clutch 33 is provided between the crankshaft 31 and the transmission 32 and is operable in an engaged state and a disengaged state. Rotational force is transmitted from the crankshaft 31 to the transmission 32 in the engaged state of the clutch 33 . . The transmission 32 changes the speed of the rotation transmitted from the crankshaft 31 and transmits it to the drive shaft 34, and the drive wheels 35 connected to the drive shaft 34 rotate to cause the bi-fuel vehicle 10 to travel.

A vehicle speed sensor 37 detects the rotational speed of the rotating parts after the transmission 32 such as the drive shaft 34 and the drive wheels 35 . A value detected by the vehicle speed sensor 37 is transmitted to the engine ECU 12 , and the vehicle speed of the bi-fuel vehicle 10 is calculated based on the value detected by the vehicle speed sensor 37 . A cooling system (not shown) for cooling the engine 11 is provided, and the temperature of cooling water in the cooling system is measured by a water temperature sensor 38 and the measured value is transmitted to the engine ECU 12 . The engine ECU 12 determines vehicle information such as the running state of the bi-fuel vehicle 10 and the driving state of the engine 11 by using the vehicle speed sensor 37, the water temperature sensor 38, and the like.

The bi-fuel vehicle 10 of the present embodiment is a manual transmission (MT) vehicle in which the gear stage of the transmission 32 is changed by manual operation. An occupant's operation related to traveling of the bi-fuel vehicle 10 is input via an accelerator pedal 40 , a clutch pedal 41 , a brake pedal 42 and a change lever 43 . Although not shown, a steering wheel is provided as means for steering the wheels.

An output request for the engine 11 is generated by operating the accelerator pedal 40 . An operation amount (accelerator opening) of the accelerator pedal 40 by the passenger is detected by an accelerator opening sensor 44 . Depending on the magnitude of the output demand based on the accelerator opening detected by the accelerator opening sensor 44, the engine ECU 12 controls the injection timing and injection amount of the fuel from the first injector 24 and the second injector 28, The engine 11 is driven by controlling the ignition timing, the amount of air taken in by the intake system, and the like.

By operating the clutch pedal 41, the connection state of the clutch 33 is changed. The clutch 33 is engaged when the clutch pedal 41 is not depressed and the clutch 33 is disengaged when the passenger depresses the clutch pedal 41 . An operation amount (clutch stroke) of the clutch pedal 41 is detected by a clutch stroke sensor 45 . The engagement state of the clutch 33 is identified in the engine ECU 12 based on the detection signal from the clutch stroke sensor 45 .

By operating the brake pedal 42, the braking operation by the brake mechanism 36 is performed. When the passenger depresses the brake pedal 42 , the pedaling force is amplified by a brake booster (not shown) and transmitted to the brake mechanism 36 . Brake mechanism 36 then decelerates the rotation of the wheels through mechanical frictional contact to reduce the speed of bi-fuel vehicle 10 . An operation amount (brake stroke) of the brake pedal 42 is detected by a brake stroke sensor 46 .

The shift stage of the transmission 32 is selected by operating the change lever 43 . The change lever 43 has a neutral position in which none of the gear stages in the transmission 32 is selected, and power is not transmitted from the transmission 32 to the drive shaft 34 in the neutral position. When the change lever 43 is operated from the neutral position to select a gear stage, the transmission 32 operates via a shift device (not shown) to switch to the corresponding gear stage. A shift sensor 47 detects the shift position and neutral position selected by the change lever 43 .

The stopped engine 11 is started by being given initial rotation by a starter 50, which is an electric engine starting device. The starter 50 includes a motor (not shown) driven by power supply from the battery 13, and when a start signal is input to the starter 50 from the engine ECU 12, the motor rotates a rotating shaft (not shown). Rotation of the rotation shaft of the starter 50 is transmitted to the crankshaft 31 via gears, and the engine 11 is started when the crankshaft 31 starts rotating.

Battery 13 is a rechargeable secondary battery. In this embodiment, a lead-acid battery is used as the battery 13 . A generator 51 (alternator) that generates power using the rotational power of the crankshaft 31 is provided, and the battery 13 is charged with the power generated by the generator 51 . A current sensor 52 that detects the current input to and output from the battery 13, a voltage sensor 53 that detects the voltage across the terminals of the battery 13, and a temperature sensor 54 that detects the temperature of the battery 13 are provided. Signals from the respective sensors 52, 53 and 54 are transmitted to the engine ECU 12, and the state of the battery 13 is calculated and determined. Specific information indicating the state of the battery 13 includes the state of charge (SOC), the accumulated discharge amount, the depth of discharge (DOD), the degree of deterioration (state of health: SOH), and the like. can be calculated. The state of charge (SOC) is the remaining capacity obtained by subtracting the discharge amount from the fully charged state of the battery 13 . The degree of deterioration using SOH as an index is 100% when the battery 13 is new, and the deterioration progresses gradually due to charging/discharging and aging.

The battery 13 supplies operating power to the pump motor 23, the electromagnetic valve 27, the spark plug 30, the starter 50, and the like. In addition to these electrical components related to driving the engine 11 , the bi-fuel vehicle 10 has an electrical load 55 to which power is supplied from the battery 13 . The electric load 55 is a group of components of an electrical system in general that consumes electric power, and includes, for example, an air conditioner, a car navigation system, a headlight, and various other auxiliary devices. The engine ECU 12 uses a current sensor 52 to measure the amount of electric power that changes based on the state of use of various electric loads 55 and the state of the bi-fuel vehicle 10 .

The engine ECU 12 automatically stops the engine 11 to enter an idling stop state when a predetermined automatic stop condition (idling stop condition) is satisfied while the engine 11 is running. It is determined whether the automatic stop condition is established based on occupant operation information obtained by the accelerator opening sensor 44, clutch stroke sensor 45, brake stroke sensor 46, etc., and vehicle information obtained by the vehicle speed sensor 37, water temperature sensor 38, etc. be done. For example, the vehicle speed is equal to or less than a predetermined vehicle speed, the occupant is not operating a steering wheel (not shown), the brake pedal 42 is depressed, the change lever 43 is in the neutral position, and the clutch pedal 41 is in the neutral position. When all of the conditions that the pedal is not depressed and that the accelerator opening is equal to or less than a predetermined opening are satisfied, it is determined that the automatic stop condition is satisfied, and the engine 11 is automatically stopped by the control of the engine ECU 12. .

Further, the engine ECU 12 restarts the engine 11 when a predetermined restart condition is satisfied during idling stop. In addition to the operation information of the passenger and the vehicle information described above, the state of the battery 13 is also included in the determination of whether the restart condition is satisfied. For example, when the change lever 43 is in the neutral position, the steering wheel is operated, the clutch pedal 41 is depressed, the brake pedal 42 is not depressed, and a predetermined time has passed since the engine 11 was automatically stopped. The engine 11 is automatically restarted under the control of the engine ECU 12 when any one of the following conditions is satisfied: that the time has elapsed, that the discharge of the battery 13 has progressed beyond a predetermined level, or the like. The reason why the state of the battery 13 is included in the restart conditions is to prevent the battery 13 from being over-discharged because the generator 51 does not generate power when the engine 11 is stopped.

Note that the automatic stop conditions and restart conditions regarding the idling stop illustrated above are examples in the case of a manual transmission (MT) vehicle, and the details of each condition are not limited to the above examples.

By the way, as described above, of the fuels selected and used in the bi-fuel vehicle 10, the second fuel F2 has the characteristic that it is more difficult to start the engine 11 than the first fuel F1. Therefore, when the engine 11 is started with the second fuel F2 selected as the fuel to be supplied to the engine 11, there is a possibility that the current discharge of the battery 13 will increase and the starter 50 will wear out due to long-term cranking. . In particular, this problem becomes conspicuous when the engine 11 is automatically stopped and restarted with a relatively high frequency, such as when idling is stopped. Bi-fuel vehicle 10 of the present embodiment selects an appropriate fuel and restarts engine 11 according to the state of battery 13 while engine 11 is stopped. Conditions and control for fuel selection when starting the engine 11 will be described below.

Reference is made to the amount of charge in the battery 13 as a first selection criterion for battery status. In the following, the case where the state of charge (SOC) indicating the remaining capacity is used as an index of the amount of charge of the battery 13 will be described as an example. During cranking by the starter 50, the battery 13 needs to instantaneously supply a large current, and a voltage drop occurs in the battery 13 for a short period of time. At this time, the lower the amount of charge in the battery 13, the greater the amount of voltage drop when the engine 11 is started, and the driving force of the starter 50 is reduced. Further, if a large amount of electric power is discharged in a state where the charge amount has decreased, the progress of deterioration of the battery 13 is accelerated.

Therefore, when the charge amount of the battery 13 is smaller than a predetermined value, the engine ECU 12 selects the use of the first fuel F1 with high starting performance to start the engine 11 . By using the first fuel F1, the starting performance of the engine 11 can be ensured even when the driving force of the starter 50 is reduced for a short period of time. In addition, the use of the first fuel F1 completes start-up early and reduces the time required for cranking, thereby reducing the discharge amount of the battery 13 during cranking and suppressing the progress of deterioration of the battery 13. .

When the amount of charge of the battery 13 is greater than the predetermined value, the engine ECU 12 selects the use of the second fuel F2 and starts the engine 11 . If the charge amount of the battery 13 is sufficiently secured, the amount of voltage drop when the starter 50 is driven can be kept small, and the driving force of the starter 50 is secured, and the engine 11 can be reliably started by cranking in a short time. can be started. Fuel efficiency is improved by using the second fuel F2.

The degree of deterioration of the battery 13 is referred to as a second selection criterion for the battery state. In the following, the case of using SOH as an index of the degree of deterioration of the battery 13 will be described as an example. If the deterioration of the battery 13 progresses, problems such as being unable to cope with long-time cranking by the starter 50 may occur. Therefore, it is necessary to reduce the load on the battery 13 to suppress further deterioration, and to reliably start the engine 11 in a short driving time of the starter 50 .

When the degree of deterioration of the battery 13 is smaller than a predetermined value (deterioration progresses), the engine ECU 12 selects the use of the first fuel F<b>1 with high starting performance to start the engine 11 . By using the first fuel F1, cranking by the starter 50 is completed in a short time with a low load. As a result, the amount of discharge of the battery 13 during cranking can be reduced, and progress of deterioration of the battery 13 can be suppressed. In addition, by suppressing the progress of deterioration of the battery 13, it contributes to ensuring the starting performance from the next time onward.

When the degree of deterioration of the battery 13 is greater than a predetermined value (deterioration has not progressed), the engine ECU 12 selects the use of the second fuel F2 and starts the engine 11 . Sufficient electric power can be supplied to the starter 50 by the battery 13 whose deterioration has not progressed, and the engine 11 can be reliably started, and the fuel consumption performance is improved by using the second fuel F2.

As a third selection criterion for the battery state, the amount of electric power used by the electric load 55 of the vehicle other than the starter 50 is referred to. When the amount of electric power used by the electric load 55 is high, when cranking is performed by the starter 50, the amount of electric power supplied to the starter 50 decreases by the amount allocated to the other electric loads 55, resulting in power shortage. tendencies arise. The starter 50 driven in a low power state takes a long time to increase the revolution of the engine 11 and complete the cranking. If the starter 50 is driven for a long time, it will be damaged due to heat generation. In addition, after the engine 11 is restarted, before the battery can be charged by the power generated by the generator 51, the electric load 55, which consumes a large amount of electric power, is discharged further, causing the voltage of the battery 13 to drop. Deterioration may be accelerated.

Therefore, when the power consumption of the battery 13 is greater than a predetermined value while the engine 11 is stopped, the engine ECU 12 selects the use of the first fuel F1 with high starting performance to start the engine 11 . By using the first fuel F1, cranking is completed in a short period of time, the starter 50 is prevented from being driven for a long period of time, and consumption of the starter 50 is suppressed. In addition, suppressing consumption of the starter 50 contributes to ensuring the starting performance from the next time onward. Moreover, deterioration of the battery 13, which is heavily burdened by the electric load 55, can be prevented.

When the power consumption of the battery 13 is smaller than a predetermined value while the engine 11 is stopped, the engine ECU 12 selects the use of the second fuel F2 to start the engine 11 . Since a sufficient amount of power to be supplied to the starter 50 is ensured without excessive power being allocated to other electric loads 55, the rotation of the engine 11 can be quickly increased by the starter 50 to complete cranking. Therefore, even when the second fuel F2 is used, damage to the starter 50 and overdischarge of the battery 13 due to long-time driving can be prevented. Fuel efficiency is improved by using the second fuel F2.

In addition to the starter 50 and the electric load 55, the pump motor 23 associated with the supply of the first fuel F1 and the solenoid valve 27 associated with the supply of the second fuel F2 also consume power during operation. The second fuel F2, which is a gaseous fuel, is blocked from being delivered to the second injector 28 side by the normally closed electromagnetic valve 27 when the supply to the engine 11 is blocked. Therefore, when starting the engine 11 using the second fuel F2 as the fuel, it is necessary to supply the second fuel F2 to the second injector 28 by energizing and opening the electromagnetic valve 27 before the starter 50 is driven. be. The first fuel F1, which is a liquid fuel, remains in the first fuel line 21 in a state where the supply to the engine 11 is cut off, and the amount of initial injection from the first injector 24 can be secured, so the engine 11 can be started. After that, the fuel pump 22 may be driven according to the amount of fuel used. Therefore, when starting the engine 11 using the first fuel F<b>1 as the fuel, the pump motor 23 can be operated at a later timing than the electromagnetic valve 27 . That is, in the initial stage of starting the engine 11, the fuel supply system for the first fuel F1 is easier to suppress the power consumption than the fuel supply system for the second fuel F2. The fuel to be used can be set in consideration of the difference in power consumption at the earliest stage in the fuel supply system in consideration of each of the above selection criteria.

Next, the flow of engine restart control according to the present embodiment will be described with reference to the flowchart of FIG. The following control contents are repeatedly executed at a predetermined time.

In step S1-1, it is determined whether the engine is in the idling stop state. If the automatic stop condition described above is satisfied and the idling stop state is established (YES), the process proceeds to step S1-2. If it is not in the idling stop state (NO), the control flow exits because there is no request to restart the engine 11 .

At step S1-2, it is determined whether the charge amount of the battery 13 is smaller than a predetermined value. As described above as the first selection criterion regarding the battery state, when the charge amount of the battery 13 is low, the amount of voltage drop increases when the starter 50 is driven, which may result in insufficient driving force for starting. . Further, discharging a large amount of power when the charge amount is low greatly accelerates deterioration of the battery 13 . In step S1-2, the possibility of such an adverse effect occurring is determined, and if the charge amount of the battery 13 is smaller than the predetermined value (YES), it is determined that the charge amount is insufficient, and the process proceeds to step S1-3. If it is determined that the charge amount of the battery 13 is greater than the predetermined value and the charge amount is sufficient (NO), the process proceeds to step S1-7.

In step S1-3, it is determined whether the amount of electric power used by the electrical load 55 during idling stop is greater than a predetermined value. As described above as the third selection criterion regarding the battery state, when the amount of electric power used by the electric load 55 is large, the amount of electric power supplied to the starter 50 decreases, requiring long-time cranking. Excessive burden. Further, there is a possibility that the discharge of the battery 13 progresses too much before the charging by the power generation of the generator 51 can be started after the engine 11 is restarted. The possibility of such adverse effects occurring is determined in step S1-3, and if the amount of electric power used by the electric load 55 is greater than a predetermined value (YES), it is determined that the amount of electric power supplied to the starter 50 is insufficient. Then, the process proceeds to step S1-4. If it is determined that the amount of electric power used by the electric load 55 is smaller than the predetermined value and that a sufficient amount of electric power can be supplied to the starter 50 (NO), the process proceeds to step S1-8.

At step S1-7, it is determined whether the degree of deterioration of the battery 13 is equal to or less than a predetermined value. As described above as the second selection criterion related to the battery state, if the deterioration of the battery 13 progresses, it is not possible to cope with long-time cranking by the starter 50, and the deterioration of the battery 13 is likely to progress further. become. In step S1-7, the possibility of occurrence of such adverse effects is determined, and if the degree of deterioration of the battery 13 is smaller than a predetermined value (deterioration has progressed) (YES), the process proceeds to step S1-3. If the degree of deterioration of the battery 13 is greater than the predetermined value (deterioration has not progressed) (NO), the process proceeds to step S1-8.

At step S1-4, use of the first fuel (gasoline) is selected. At step S1-8, use of the second fuel (CNG) is selected. That is, the amount of charge of the battery 13 (first selection criterion), the degree of deterioration of the battery 13 (second selection criterion), and the amount of electric power used by the electric load 55 (third selection criterion) are used to grasp the status of the battery 13. When it is determined that the starting performance should be emphasized by referring to it as an index, the first fuel with good starting performance is selected. On the other hand, when it is determined from these indices that the battery state allows the engine 11 to be started without any problem with the second fuel, the second fuel with good fuel efficiency is selected.

After selecting the fuel to be supplied to the engine 11 in step S1-4 or step S1-8, it is determined in step S1-5 whether the conditions for restarting the engine 11 are satisfied. If any of the above-described restart conditions (occupant operation information, vehicle information, battery discharge state, etc.) are satisfied (YES), the process proceeds to step S1-6 to supply the selected fuel to the engine 11. The engine 11 is restarted. If the restart condition does not hold (NO), exit from the control flow without restarting.

The above-described control in the flowchart of FIG. 2 selects the fuel for restarting in general without limiting the content of restart conditions from the idling stop state. A modification of control different from this will be described with reference to the flow chart of FIG. In this modification, the fuel is selected and the engine 11 is restarted only when a restart condition related to the battery 13 (hereinafter referred to as a battery restart condition) is met. The following control contents are repeatedly executed at a predetermined time.

In step S2-1, it is determined whether the engine is in the idling stop state. If the automatic stop condition described above is satisfied and the idling stop state is established (YES), the process proceeds to step S2-2. If it is not in the idling stop state (NO), exit from the control flow.

In step S2-2, it is determined whether a restart condition other than the battery restart condition (another restart condition) is established. The battery restart condition is a case where a request to restart the engine 11 is generated due to a decrease in the charge amount of the battery 13 (details will be described later), and restart requests for other reasons are different from other restart conditions. Become. For example, a restart request related to the vehicle operation by the passenger (depression of the clutch pedal 41, release of the brake pedal 42, steering wheel operation, etc.), a restart request after a predetermined time has passed since the engine 11 was automatically stopped, and the like. Another restart condition. If any one of these conditions is established, the restart condition other than the battery restart condition is assumed to be established (YES), and the routine proceeds to step S2-9, where the engine 11 is restarted. The restart in step S2-9 is performed by continuing to use the fuel that was used before idling stop, and fuel selection and switching are not executed. If the restart condition other than the battery restart condition is not satisfied (NO), the process proceeds to step S2-3.

At step S2-3, it is determined whether the degree of deterioration of the battery 13 is smaller than a predetermined value. The criteria and grounds for determination in step S2-3 are the same as in step S1-7 in FIG. 2 described above. If the degree of deterioration of the battery 13 is smaller than the predetermined value (deterioration has progressed) (YES), the process proceeds to step S2-4. If the degree of deterioration of the battery 13 is greater than the predetermined value (deterioration has not progressed) (NO), the process proceeds to step S2-10.

At step S2-4, it is determined whether the power consumption of the electric load 55 is greater than a predetermined value. The criteria and grounds for determination in step S2-4 are the same as in step S1-3 in FIG. 2 described above. If the amount of electric power used by the electric load 55 is greater than the predetermined value (YES), the process proceeds to step S2-5. If the electric power consumption of the electric load 55 is smaller than the predetermined value (NO), the process proceeds to step S2-10.

At step S2-5, use of the first fuel (gasoline) is selected. At step S2-10, use of the second fuel (CNG) is selected. In other words, the degree of deterioration of the battery 13 (second selection criterion) and the amount of electric power used by the electric load 55 (third selection criterion) are referred to as indicators for grasping the state of the battery 13, and the battery state in which the starting performance should be emphasized. If it is determined that the first fuel with good starting performance is selected, and if it is determined that the battery state is such that the engine 11 can be started without problems with the second fuel, the second fuel with good fuel efficiency is selected. .

After selecting the fuel to be supplied to the engine 11 in step S2-5 or step S2-10, the process proceeds to step S2-6. At step S2-6, a restart threshold is selected according to the selected fuel. The restart threshold is a boundary value at which the charge amount of the battery 13 decreases and battery charging from power generation by restarting the engine 11 is requested.

The restart threshold will be described with reference to FIG. Since the engine 11 is stopped during the idling stop and the battery 13 cannot be charged by driving the generator 51, the charge amount of the battery 13 decreases due to discharge as the time in the idling stop state elapses. continue. Since the first fuel F1 has higher starting performance than the second fuel F2, the engine 11 can be started by the starter 50 even when the charge amount of the battery 13 is relatively low. On the other hand, since the starting performance of the second fuel F2 is lower than that of the first fuel F1, it is necessary to start the engine 11 by the starter 50 from a state where the charge amount of the battery 13 is relatively high. Based on these conditions, a low restart threshold L is selected when starting the engine 11 using the first fuel F1. When starting the engine 11 using the second fuel F2, a high restart threshold H is selected. The restart threshold value L and the restart threshold value H may be set in advance as fixed values based on the characteristics of each fuel F1 and F2 and the performance of the battery 13, or may be calculated by the engine ECU 12 based on predetermined parameters. may be determined.

After selection of the restart threshold value in step S2-6, the process proceeds to step S2-7 to determine whether the battery restart condition is satisfied. Here, the amount of charge of the battery 13, which is the current detection value, is compared with the restart threshold. If the use of the first fuel F1 is selected in step S2-5, comparison is made with the lower restart threshold value L, and if the use of the second fuel F2 is selected in step S2-10 , with the higher restart threshold H. As a result of the comparison, if the amount of charge in the battery 13 is less than the restart threshold value (YES) in step S2-7, it is determined that the battery restart condition is satisfied, and the process proceeds to step S2-8, where the selected fuel is supplied to the engine 11. to restart the engine 11. When the engine 11 is restarted, the generator 51 is driven, the battery 13 is charged, and the low level of charge below the restart threshold is eliminated. If the amount of charge in the battery 13 is greater than the restart threshold value in step S2-7 (NO), it is determined that the battery restart condition is not met and there is no immediate need for battery charging, and restart is not performed. Exit control flow.

In this way, in order to ensure the starting performance and prevent deterioration of the battery 13, a threshold is set for the progress of discharge (decrease in the amount of charge) of the battery 13 during idling stop, and when the discharge progresses beyond the threshold Then, assuming that the battery restart condition is satisfied, the idling stop is forcibly interrupted and the engine 11 is restarted. By changing the threshold that determines the battery restart condition according to the selected fuel, the duration of the idling stop is maximized while ensuring startability, contributing to improved fuel efficiency. .

For example, if the engine 11 is restarted as soon as the battery charge amount falls below the restart threshold value H for the second fuel F2, regardless of the use of the first fuel F1 with high starting performance, The duration of the idling stop is shorter than when the engine is restarted when the restart threshold value L is reached. With the first fuel F1, startability can be ensured until the restart threshold value L is reached. Therefore, it is better to restart the engine after the restart threshold value L is reached, rather than using the restart threshold value H as an index. , The effect of fuel saving by idling stop is high.

In the above control, the engine restart control is performed using the state of charge (SOC) of the battery 13 as information indicating the state of charge of the battery as an indicator of the amount of charge. It is also possible to set That is, by using the values detected by the current sensor 52, the voltage sensor 53, the temperature sensor 54, and the like, the integrated discharge amount of the battery is estimated (calculated) while the bi-fuel vehicle 10 is running and during the idling stop. Then, the obtained integrated discharge amount of the battery is applied as the state-of-charge information (charge amount) in step S1-2 in FIG. It can be applied as information (charge amount) and compared with the restart threshold. From a similar point of view, it is also possible to refer to the depth of discharge (DOD) of the battery as information on the state of charge instead of the accumulated discharge amount of the battery. As described above, the information on the state of charge of the battery in the present invention may be based on either the power remaining in the battery or the power discharged by the battery. In addition, the amount of charge of the battery in the present invention does not mean only the remaining battery capacity in a narrow sense, but is a concept that includes the integrated amount of discharge from the battery and the depth of discharge.

Further, the progress of deterioration of the battery can be identified by using the battery voltage during idling stop instead of using the degree of deterioration (SOH) as an index. If the battery voltage is low with the same amount of charge, it can be determined that the deterioration of the battery is progressing. The degree of deterioration of the battery in the present invention can employ various indices as described above, and is not limited to a specific index.

As described above, the bi-fuel vehicle 10 of the present embodiment can operate the engine 11 based on the state of the battery 13 (the state of charge and deterioration of the battery 13 itself, the state of power supply from the battery 13 to the electric load 55). Perform restart control to select the fuel to be used for restart. Under conditions where the battery 13 is expected to be excessively discharged or degraded, the first fuel F1, which has excellent starting performance, is selected to achieve reliable engine restart with a low load. Under other conditions, the second fuel F2, which has excellent fuel efficiency, is selected to avoid the regular use of the first fuel F1 when the engine is restarted, thereby improving fuel efficiency. As a result, the bi-fuel vehicle 10 can achieve both starting performance and fuel efficiency.

It should be noted that the present invention is not limited to the above-described embodiments, and can be implemented with various modifications. In the above embodiment, the configuration, control, and the like shown in the accompanying drawings are not limited to this, and can be changed as appropriate within the scope of exhibiting the effects of the present invention. In addition, it is possible to carry out by appropriately modifying the present invention as long as it does not deviate from the scope of the purpose of the present invention.

In the above embodiment, gasoline and CNG are used together as fuels for the bi-fuel vehicle 10, but the combination of fuels in the bi-fuel vehicle to which the present invention is applied is not limited to this. For example, it is possible to select a combination of multiple types of fuels with different characteristics, such as light oil, liquefied natural gas (LNG), liquefied petroleum gas (LPG), and other alternative fuels. In other words, fuels that can be selectively used as in the above embodiment based on differences in starting performance and fuel efficiency can be widely applied.

Although the above-described embodiment exemplifies a manual transmission (MT) vehicle in which a stepped gear shift operation is performed manually, the bi-fuel vehicle of the present invention can be applied regardless of the type of transmission mechanism. For example, it can be applied to a vehicle equipped with an automatic transmission, and more specifically, a continuously variable transmission (CVT), a dual clutch transmission (DCT), a torque converter type automatic (AT), and an automatic transmission manual transmission. (AMT), and so on. Note that the conditions for automatically stopping the idling stop and the conditions for restarting are not limited to the conditions described in the above embodiment because they differ depending on the type of transmission mechanism.

In the above embodiment, the case of restarting the engine after idling stop has been described, but the present invention can also be applied to restarting after engine stall. That is, the present invention can be applied if the engine restart is in a form in which startability, battery load, etc. can be affected by fuel selection, and the factors leading to engine stop before restart are not uniform. good too.

Although the above embodiment is applied to a vehicle having only the engine 11, which is an internal combustion engine, as a power source for running, the present invention is applied to a vehicle (a so-called hybrid vehicle) that uses both an internal combustion engine and an electric motor as power sources. It is also possible to In this case, various types of hybrid vehicles are applicable, such as a type in which the electric motor alone can drive the vehicle, and a type in which the electric motor is used only to start the engine and assist the driving force of the engine. . In other words, the present invention can be widely applied to any bi-fuel vehicle that supplies a plurality of fuels to the internal combustion engine regardless of the presence or absence of an electric motor. Hybrid vehicles, which use the electric motor frequently while driving, are more likely to experience changes in the battery state than vehicles that run only on the internal combustion engine. The usefulness of the present invention is high.

In the above embodiment, the amount of charge of the battery 13, the degree of deterioration of the battery 13, and the amount of electric power used by the electric load 55 are used as indicators for grasping the status of the battery 13. FIG. It is also possible to grasp the battery state by means of indices other than these. For example, the battery state may be grasped from the length of time required to start the engine, the last regeneration time in a vehicle capable of regenerative power generation, operation information of an electric load supplied with power from the battery, and the like.

In the above embodiment, a lead-acid battery is used as the battery 13, but it is also possible to use a lithium-ion battery or the like as an in-vehicle power supply other than the lead-acid battery.

As described above, the bi-fuel vehicle according to the present invention can achieve both engine starting performance and fuel efficiency, and is particularly useful for vehicles in which battery usage conditions are likely to change and high-precision power management is required. is.

10: Bi-fuel vehicle 11: Engine (internal combustion engine)
12: Engine ECU (control unit)
13: Battery 20: First Fuel Tank 22: Fuel Pump 23: Pump Motor 24: First Injector 25: Second Fuel Tank 27: Solenoid Valve 28: Second Injector 31: Crankshaft 32: Transmission 33: Clutch 34: Drive shaft 35 : Drive wheel 36 : Brake mechanism 40 : Accelerator pedal 41 : Clutch pedal 42 : Brake pedal 43 : Change lever 50 : Starter (starting device)
51: Generator 55: Electric load F1: First fuel F2: Second fuel

Claims (7)

an internal combustion engine capable of using a first fuel with relatively high starting performance and a second fuel with relatively high fuel efficiency;
a control unit that automatically stops the internal combustion engine when a predetermined automatic stop condition is satisfied and restarts the internal combustion engine when a predetermined restart condition is satisfied in the automatic stop state of the internal combustion engine;
a rechargeable battery that powers a starting device that starts the internal combustion engine;
A bi-fuel vehicle comprising
The control unit performs restart control for selecting a fuel to be used for restarting the internal combustion engine based on the state of the battery,
The control unit restarts the internal combustion engine using the first fuel when the battery has reached a predetermined degree of deterioration,
A bi-fuel vehicle, wherein the internal combustion engine is restarted using the second fuel when the battery has not reached the predetermined degree of deterioration. an internal combustion engine capable of using a first fuel with relatively high starting performance and a second fuel with relatively high fuel efficiency;
a control unit that automatically stops the internal combustion engine when a predetermined automatic stop condition is satisfied and restarts the internal combustion engine when a predetermined restart condition is satisfied in the automatic stop state of the internal combustion engine;
a rechargeable battery that powers a starting device that starts the internal combustion engine;
A bi-fuel vehicle comprising
The control unit performs restart control for selecting a fuel to be used for restarting the internal combustion engine based on the state of the battery,
The control unit, in an automatic stop state of the internal combustion engine,
restarting the internal combustion engine using the first fuel when the amount of electric power used by an electric load other than the starting device is greater than a predetermined value;
A bi-fuel vehicle, wherein the internal combustion engine is restarted using the second fuel when the amount of electric power used by an electric load other than the starting device is smaller than the predetermined value. 3. The bi-fuel vehicle according to claim 1, wherein said first fuel is gasoline and said second fuel is compressed natural gas. The control unit
determining whether the amount of charge of the battery is smaller or larger than a predetermined value before determining whether the battery has reached the predetermined degree of deterioration;
restarting the internal combustion engine using the first fuel when the charge amount of the battery is smaller than the predetermined value;
determining whether or not the battery has reached the predetermined degree of deterioration when the amount of charge of the battery is greater than the predetermined value; The internal combustion engine is restarted using the first fuel, and the internal combustion engine is restarted using the second fuel when the battery has not reached the predetermined degree of deterioration. The bi-fuel vehicle according to claim 1 , wherein: The control unit
In the automatic stop state of the internal combustion engine, whether the charge amount of the battery is smaller than a predetermined value before determining whether the electric power consumption of the electric load other than the starter is larger or smaller than the predetermined value. determine whether it is greater than
When the amount of charge of the battery is smaller than the predetermined value, it is determined whether the amount of electric power used by the electric load other than the starter is larger or smaller than the predetermined value, and the power consumption of the electric load other than the starter is determined. When the amount of electric power used is greater than the predetermined value, the first fuel is used to restart the internal combustion engine, and the amount of electric power used by the electrical loads other than the starting device is smaller than the predetermined value. when restarting the internal combustion engine using the second fuel,
3. The bi-fuel vehicle according to claim 2, wherein the internal combustion engine is restarted using the second fuel when the charge amount of the battery is greater than the predetermined value. The predetermined restart condition includes a battery restart condition due to the state of charge of the battery falling below a restart threshold;
6. The control unit according to any one of claims 1 to 5 , wherein the control unit performs the restart control to select a fuel to be used for restarting the internal combustion engine only when the battery restart condition is satisfied. Bi-Fuel Vehicles as described in paragraph. The control unit sets the restart threshold lower when restarting the internal combustion engine using the first fuel than when restarting the internal combustion engine using the second fuel. The bi-fuel vehicle according to claim 6 , characterized in that:

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