Bi-fuel vehicle

Abstract

To provide a bi-fuel vehicle capable of preventing vehicle behavior from becoming unstable.SOLUTION: In a bi-fuel vehicle in which an engine is automatically stopped when a predetermined automatic stop condition is established, and restarted when a predetermined restart condition is established, fuel switching between two types of fuel supplied to the engine is prohibited from being performed during the period from when the predetermined restart condition is established until it is determined that an engine speed has stabilized (S2 to S4), and when it is determined that the engine speed has stabilized, fuel switching is permitted (S5).SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a bi-fuel vehicle. [Background technology]

[0002] Conventionally, Patent Document 1 proposes a technology for a vehicle having an internal combustion engine capable of using two different fuels and a control unit that automatically stops the internal combustion engine when predetermined automatic stop conditions are met and restarts the internal combustion engine when predetermined restart conditions are met, where if the control unit decides to change the fuel used by the internal combustion engine while the internal combustion engine is automatically stopped, it switches the fuel used after the restart is completed. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2020-169603 A Summary of the Invention [Problem to be solved by the invention]

[0004] However, in the conventional technology described above, if the fuel is switched when the engine speed is not stable after restarting the internal combustion engine, there is a risk that the vehicle behavior may become unstable, and there is still room for improvement.

[0005] The present invention has been made in consideration of the above circumstances, and has an object to provide a bi-fuel vehicle that is capable of preventing the vehicle behavior from becoming unstable. [Means for solving the problem]

[0006] The bi-fuel vehicle of the present invention has an engine that can use two different types of fuel as driving fuel, a fuel changeover switch that is operated to switch the fuel supplied to the engine between the two types of fuel, and a control unit that automatically stops the engine when a predetermined automatic stop condition is met and restarts the engine when a predetermined restart condition is met.The bi-fuel vehicle performs fuel changeover that switches the fuel supplied to the engine between the two types of fuel in response to the operation of the fuel changeover switch, and the control unit is configured to prohibit the fuel changeover from the time the predetermined restart condition is met until it is determined that the engine rotation speed has stabilized, and to permit the fuel changeover when it is determined that the engine rotation speed has stabilized. Effect of the Invention

[0007] The present invention can provide a bi-fuel vehicle that can prevent the vehicle behavior from becoming unstable. [Brief description of the drawings]

[0008] [Figure 1] FIG. 1 is a schematic diagram of a vehicle to which a bi-fuel vehicle according to an embodiment of the present invention is applied. [Diagram 2] FIG. 2 is a flowchart showing a fuel switching limiting operation of a bi-fuel vehicle according to an embodiment of the present invention. [Diagram 3] FIG. 3 is a timing diagram showing a first example of the state of each part when the fuel switch limiting operation of the bi-fuel vehicle according to the embodiment of the present invention is executed. [Figure 4] FIG. 4 is a timing diagram showing a second example of the state of each part when the fuel switch limiting operation of the bi-fuel vehicle according to the embodiment of the present invention is executed. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] A bi-fuel vehicle according to one embodiment of the present invention has an engine that can use two different types of fuel as driving fuel, a fuel changeover switch that is operated to change the fuel supplied to the engine between the two types of fuel, and a control unit that automatically stops the engine when a predetermined automatic stop condition is met and restarts the engine when a predetermined restart condition is met, and is a bi-fuel vehicle that performs fuel changeover that changes the fuel supplied to the engine between the two types of fuel in response to the operation of the fuel changeover switch, and is characterized in that the control unit prohibits fuel changeover from the time when the predetermined restart condition is met until it is determined that the engine rotation speed has stabilized, and permits fuel changeover when it is determined that the engine rotation speed has stabilized. This makes it possible for the bi-fuel vehicle according to one embodiment of the present invention to prevent the vehicle behavior from becoming unstable. EXAMPLES

[0010] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A bi-fuel vehicle according to an embodiment of the present invention will now be described with reference to the drawings.

[0011] As shown in FIG. 1, a vehicle 1 includes an engine 2, a starter 3, an engine controller (hereinafter, simply referred to as “EG-ECU”) 4, and a display 5.

[0012] The engine 2 is configured as a bi-fuel engine that can switch between two different types of fuel as a driving fuel. In this embodiment, the engine 2 can switch between gasoline and CNG (Compressed natural gas) as a driving fuel.

[0013] The fuel for the engine 2 may be two different types of fuel. For example, diesel or hydrogen may be used instead of gasoline, and LPG (Liquefied Petroleum Gas) may be used instead of CNG.

[0014] The engine 2 is formed with a plurality of cylinders. The engine 2 generates power by performing a series of four strokes, which are an intake stroke, a compression stroke, an expansion stroke, and an exhaust stroke, for each cylinder. In this embodiment, the vehicle 1 is driven by the power generated by the engine 2.

[0015] The starter 3 includes a motor and a pinion gear. The starter 3 rotates the motor to rotate the crankshaft of the engine 2 via the pinion gear, thereby providing the engine 2 with a rotational force at the time of starting.

[0016] The EG-ECU4 is composed of a computer unit equipped with a CPU (Central Processing Unit), a RAM (Random Access Memory), a ROM (Read Only Memory), a flash memory for storing backup data, etc., an input port, and an output port.

[0017] The ROM of this computer unit stores various constants, various maps, and the like, as well as a program for causing the computer unit to function as the EG-ECU 4. That is, the CPU executes the program stored in the ROM using the RAM as a working area, whereby the computer unit functions as the EG-ECU 4 in this embodiment.

[0018] Various sensors are connected to the input port of the EG-ECU 4, including an engine speed sensor 21 that detects the rotation speed of the engine 2 (hereinafter simply referred to as "engine speed"), a brake stroke sensor 23 that detects the amount of operation of the brake pedal 22, an accelerator opening sensor 25 that detects the amount of operation of the accelerator pedal 24 (hereinafter simply referred to as "accelerator opening"), a vehicle speed sensor 26 that detects the vehicle speed, and a fuel selector switch 27 that is operated to switch the fuel supplied to the engine 2 between gasoline and CNG.

[0019] The output port of the EG-ECU 4 is connected to various control objects including a starter 3, a display 5, a first injector 31 that supplies gasoline to the engine 2, a second injector 32 that supplies CNG to the engine 2, and an ignition device 33 that ignites in the combustion chamber of the engine 2.

[0020] The EG-ECU 4 controls various control targets connected to the output port based on information obtained from various sensors connected to the input port. The EG-ECU 4 functions as a control unit 40 that automatically stops the engine 2 when a predetermined automatic stop condition is met, and restarts the engine 2 when a predetermined restart condition is met.

[0021] In this embodiment, when the engine 2 is running, the accelerator opening detected by the accelerator opening sensor 25 is substantially zero, the brake stroke detected by the brake stroke sensor 23 is equal to or greater than a predetermined amount, and the vehicle speed detected by the vehicle speed sensor 26 is equal to or less than a predetermined value (e.g., 7 km / h), the EG-ECU 4 determines that the automatic stop condition is met and automatically stops the engine 2 by stopping the supply of fuel by the first injector 31 and the second injector 32 and the ignition by the ignition device 33.

[0022] In addition, when the brake stroke detected by the brake stroke sensor 23 becomes substantially zero or the accelerator opening detected by the accelerator opening sensor 25 becomes equal to or greater than a predetermined value while the engine 2 is automatically stopped, the EG-ECU 4 determines that the restart conditions are met and restarts the engine 2 by rotating the crankshaft of the engine 2 using the starter 3 and then starting the supply of fuel by the first injector 31 or the second injector 32 and ignition by the ignition device 33.

[0023] When the fuel selector switch 27 is operated, the EG-ECU 4 performs fuel switching to control the first injector 31 and the second injector 32 so as to switch the fuel supplied to the engine 2 between gasoline and CNG.

[0024] The EG-ECU 4 prohibits fuel switching from when the restart condition is satisfied until it is determined that the engine speed is stable, and permits fuel switching when it is determined that the engine speed is stable. In this embodiment, the EG-ECU 4 determines that the engine speed is stable when the rate of change in the engine speed detected by the engine speed sensor 21 falls within a certain range.

[0025] When fuel switching is prohibited, the EG-ECU 4 notifies the user that fuel switching is prohibited, and when fuel switching is permitted, notifies the user that fuel switching is permitted.

[0026] For example, when fuel switching is prohibited, the EG-ECU 4 notifies the driver by displaying that fuel switching is prohibited on the display 5, and when fuel switching is permitted, the EG-ECU 4 notifies the driver by displaying that fuel switching is permitted on the display 5. Note that the EG-ECU 4 may notify the driver by displaying the information on the display 5, but may also notify the driver by sound from a speaker, lighting a lamp, or the like.

[0027] In this way, when fuel switching is prohibited, a notification that fuel switching is prohibited is provided, and when fuel switching is permitted, a notification that fuel switching is permitted is provided, thereby preventing unnecessary operation of the fuel changeover switch 27 and allowing the fuel changeover switch 27 to be operated at an appropriate timing.

[0028] The fuel switch limiting operation of the EG-ECU 4 configured as above will be described with reference to Fig. 2. The fuel switch limiting operation described below is repeatedly executed while the EG-ECU 4 is in operation.

[0029] First, in S1, the EG-ECU 4 determines whether the engine 2 is in an automatically stopped state. If it is determined in S1 that the engine 2 is in an automatically stopped state, the EG-ECU 4 executes the process of S2. If it is determined in S1 that the engine 2 is not in an automatically stopped state, the EG-ECU 4 ends the fuel switching limiting operation.

[0030] In S2, the EG-ECU 4 determines whether or not the restart condition of the engine 2 is satisfied. If it is determined in S2 that the restart condition of the engine 2 is satisfied, the EG-ECU 4 executes the process of S3. If it is determined in S2 that the restart condition of the engine 2 is not satisfied, the EG-ECU 4 executes the process of S2.

[0031] That is, when the EG-ECU 4 determines in S2 that the restart condition of the engine 2 is not satisfied, the fuel switching limiting operation goes into a standby state in which it waits for the restart condition of the engine 2 to be satisfied.

[0032] In S3, the EG-ECU 4 prohibits fuel switching and notifies the user that fuel switching is prohibited. After executing the process of S3, the EG-ECU 4 executes the process of S4. In S4, the EG-ECU 4 determines whether the engine speed is stable.

[0033] If it is determined in S4 that the engine speed is stable, the EG-ECU 4 executes the process of S5. If it is determined in S4 that the engine speed is not stable, the EG-ECU 4 executes the process of S4. That is, if the EG-ECU 4 determines in S4 that the engine speed is not stable, the fuel switching limiting operation goes into a standby state to wait for the engine speed to stabilize.

[0034] In S5, the EG-ECU 4 permits the fuel switching and notifies the user that the fuel switching is permitted. After executing the process of S5, the EG-ECU 4 ends the fuel switching limiting operation.

[0035] Hereinafter, the state of each part of the vehicle 1 when the EG-ECU 4 executes a deceleration operation will be described with reference to FIG.

[0036] 3 shows, from the top, the transitions of the engine speed, the automatic stop state of the engine 2, the inhibition state of fuel switching, the operation state of the fuel selector switch 27, and the fuel used and supplied to the engine 2.

[0037] At time t1, when the automatic stop condition of the engine 2 is satisfied, the engine 2 is automatically stopped by the EG-ECU 4. Therefore, in the figure, the automatic stop state of the engine 2 is turned ON.

[0038] When the fuel changeover switch 27 is operated at time t2, fuel changeover is performed because fuel changeover is not prohibited. In the example shown in Fig. 3, the fuel supplied to the engine 2 is changed from CNG to gasoline (denoted as "PETROL" in the figure) at time t2. That is, at time t2, the first injector 31 is controlled so as to be able to inject fuel, and the second injector 32 is controlled by the EG-ECU 4 so as not to inject fuel.

[0039] At time t3, when the fuel selector switch 27 is operated, fuel switching is performed because fuel switching is not prohibited. In the example shown in Fig. 3, the fuel supplied to the engine 2 is switched from gasoline to CNG at time t3. That is, at time t3, the second injector 32 is controlled to be able to inject fuel, and the first injector 31 is controlled by the EG-ECU 4 not to inject fuel.

[0040] At time t4, when the restart condition of the engine 2 is satisfied, the engine 2 is restarted by the EG-ECU 4 and fuel switching is prohibited. Therefore, even if the fuel changeover switch 27 is operated at time t5 and time t6, fuel switching is not performed because the fuel changeover is prohibited.

[0041] At time t7, when the EG-ECU 4 determines that the engine speed has stabilized, fuel switching is permitted. Therefore, when the fuel selector switch 27 is operated at time t8, fuel switching is performed because fuel switching is not prohibited. In the example shown in Fig. 3, at time t8, the fuel supplied to the engine 2 is switched from CNG to gasoline.

[0042] As described above, the bi-fuel vehicle of this embodiment prohibits fuel switching from the time when the restart conditions for engine 2 are met until it is determined that the engine speed has stabilized, and once it is determined that the engine speed has stabilized, fuel switching is permitted, thereby making it possible to prevent unstable vehicle behavior such as poor starting, engine stall, deterioration of NVH performance, etc.

[0043] In the above embodiment, an example has been described in which fuel switching is not performed even if the fuel changeover switch 27 is operated in a state in which fuel switching is prohibited. In contrast, the bi-fuel vehicle according to this embodiment may be configured to hold fuel switching when the fuel changeover switch 27 is operated in a state in which fuel switching is prohibited, and to execute the held fuel switching when fuel switching is permitted, as shown in FIG.

[0044] Fig. 4, like Fig. 3, shows the states of the various parts of the vehicle 1. When the automatic stop condition for the engine 2 is met at time t11, the engine 2 is automatically stopped by the EG-ECU 4. When the fuel selector switch 27 is operated at time t12, the fuel supplied to the engine 2 is switched from CNG to gasoline.

[0045] At time t13, when the fuel changeover switch 27 is operated, the fuel supplied to the engine 2 is changed from gasoline to CNG. At time t14, when the restart condition of the engine 2 is satisfied, the engine 2 is restarted by the EG-ECU 4 and the fuel changeover is prohibited.

[0046] At time t15, when the fuel changeover switch 27 is operated, since fuel changeover is prohibited, the fuel changeover that would switch the fuel supplied to the engine 2 from CNG to gasoline is put on hold.

[0047] At time t16, when the EG-ECU 4 determines that the engine speed has stabilized, fuel switching is permitted, the pending fuel switching is executed, and the fuel supplied to the engine 2 is switched from CNG to gasoline.

[0048] In this way, if the fuel changeover switch 27 is operated while fuel changeover is prohibited, the fuel changeover is put on hold, and if fuel changeover is permitted while fuel changeover is on hold, the on-hold fuel changeover is executed, thereby reducing the trouble of having the driver operate the fuel changeover switch 27 again after fuel changeover is permitted.

[0049] In addition, when the fuel changeover switch 27 is operated while fuel changeover is prohibited, or when fuel changeover is put on hold, the EG-ECU 4 may notify the driver that fuel changeover has been put on hold, and when the put-on hold fuel changeover is executed, may notify the driver that the put-on hold fuel changeover has been executed. This configuration allows the driver to correctly understand the vehicle state, and prevents erroneous operation, etc.

[0050] In the above embodiment, the EG-ECU 4 determines that the engine speed is stable when the rate of change in the engine speed detected by the engine speed sensor 21 falls within a certain range.

[0051] In response to this, the EG-ECU 4 may be configured to determine that the engine speed is stable when the rate of change in the vehicle speed detected by the vehicle speed sensor 26 falls within a certain range while the power of the engine 2 is being transmitted to the wheels.

[0052] In addition, the EG-ECU 4 may be configured to determine that the engine speed has stabilized when the rate of change in the injection time of the first injector 31 or the second injector 32 that supplies fuel to the engine 2 falls within a certain range.

[0053] Also, the EG-ECU 4 may determine that the engine speed is stable when a predetermined fuel switching inhibition time has elapsed since the fuel switching was inhibited. For example, a map in which the fuel switching inhibition time is associated with the engine coolant temperature and the terminal voltage of the battery that supplies power to the starter 3 is stored in the ROM, and the EG-ECU 4 determines the fuel switching inhibition time based on this map.

[0054] The bi-fuel vehicle according to the present invention can be applied to vehicles having a manual transmission such as an MT (Manual Transmission), as well as vehicles having an automatic transmission such as a CVT (Continuously Variable Transmission), an AT (Automatic Transmission), a DCT (Dual-Clutch Transmissions), an AMT (Automated Manual Transmission), and an AGS (Auto Gear Shift).

[0055] The bi-fuel vehicle according to the present invention can be applied to a vehicle equipped with an ISG (Integrated Starter Generator). When the bi-fuel vehicle according to the present invention is applied to a vehicle equipped with an ISG, the ISG applies a rotational force to the engine 2 instead of the starter 3 when restarting the engine 2.

[0056] While the present invention has been disclosed by way of example, it will be apparent that modifications may be made to the present invention without departing from the spirit and scope of the present invention, and the present invention is disclosed with the understanding that equivalents of such modifications are intended to be included within the scope of the invention as defined by the appended claims. [Explanation of symbols]

[0057] 1 vehicle (bi-fuel vehicle) 2 Engine 27 Fuel selector switch 40 Control section

Claims

1. An engine that can use two different types of fuel as a driving fuel; a fuel selector switch that is operated to switch the fuel supplied to the engine between the two types of fuel; a control unit that automatically stops the engine when a predetermined automatic stop condition is satisfied and restarts the engine when a predetermined restart condition is satisfied, A bi-fuel vehicle that switches the fuel supplied to the engine between the two types of fuel in response to an operation of the fuel changeover switch, The control unit is prohibiting the fuel switching from when the predetermined restart condition is satisfied until it is determined that the engine speed has stabilized; A bi-fuel vehicle, wherein the fuel switching is permitted when it is determined that the engine rotation speed has stabilized.

2. 2. The bi-fuel vehicle according to claim 1, wherein the control unit, when the fuel switching is prohibited, notifies the driver that the fuel switching is prohibited.

3. The control unit is When the fuel changeover switch is operated in a state where the fuel changeover is prohibited, the fuel changeover is suspended, 3. The bi-fuel vehicle according to claim 1, wherein when the fuel switching is permitted while the fuel switching is on hold, the on-hold fuel switching is executed.

4. The control unit is When the fuel switching is suspended, a notification is given that the fuel switching is suspended; 4. The bi-fuel vehicle according to claim 3, wherein when the pending fuel switching is executed, a notification is given that the pending fuel switching has been executed.

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