Bi-fuel vehicles

Abstract

To provide a bi-fuel vehicle that can suppress deterioration of combustion stability and exhaust gas characteristics. [Solution] The system includes a gasoline tank 4 for storing liquid fuel gasoline, a gas fuel tank 5 for storing gaseous fuel CNG, a fuel switching device 6 that switches the fuel injected into the combustion chamber of each cylinder of the engine 2 between the gasoline stored in the gasoline tank 4 and the CNG stored in the gas fuel tank 5, and an ECU 8 that controls an idle stop that automatically stops the engine 2 when a preset automatic stop condition is met and restarts the engine 2 when a preset restart condition is met, and prohibits fuel switching of the engine 2 for a predetermined period after the restart of the engine 2 which has been automatically stopped by the idle stop.

Description

Technical Field

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

Background Art

[0002] Patent Document 1 describes a vehicle equipped with a bi-fuel engine capable of switching and using a plurality of fuels, and having a control unit that controls an idling stop for automatically stopping the engine when a preset automatic stop condition is satisfied and restarting the engine when a preset restart condition is satisfied.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In a bi-fuel vehicle that implements an idling stop, for example, fuel switching may occur due to driver operation or the like during the restart of the engine. However, if fuel switching is performed during the transient period of engine restart, control such as fuel injection becomes complicated, and there is a risk that combustion stability and exhaust gas characteristics deteriorate.

[0005] Therefore, an object of the present invention is to provide a bi-fuel vehicle capable of suppressing deterioration of combustion stability and exhaust gas characteristics.

Means for Solving the Problems

[0006] To solve the above problems, the present invention provides a bi-fuel vehicle equipped with an engine that switches between multiple fuels, comprising a control unit that controls an idle stop that automatically stops the engine when a preset automatic stop condition is met and restarts the engine when a preset restart condition is met, wherein the control unit prohibits switching the fuel of the engine for a predetermined period after the restart of the engine that has been automatically stopped by the idle stop. [Effects of the Invention]

[0007] Thus, according to the present invention, it is possible to suppress deterioration of combustion stability and exhaust gas characteristics. [Brief explanation of the drawing]

[0008] [Figure 1] Figure 1 is a schematic diagram of a bi-fuel vehicle according to one embodiment of the present invention. [Figure 2] Figure 2 is a graph showing an example of a predetermined value for the total amount of air in a bi-fuel vehicle according to one embodiment of the present invention. [Figure 3] Figure 3 is a flowchart showing the procedure for fuel switching in a bi-fuel vehicle according to one embodiment of the present invention. [Figure 4] Figure 4 is a flowchart showing the procedure for preventing fuel switching in a bi-fuel vehicle according to one embodiment of the present invention. [Figure 5] Figure 5 is a time chart showing the operation of fuel switching by fuel switching processing and fuel switching prohibition processing in a bifuel vehicle according to one embodiment of the present invention. [Modes for carrying out the invention]

[0009] A bifuel vehicle according to one embodiment of the present invention is a bifuel vehicle equipped with an engine that switches between multiple fuels, and includes a control unit that controls an idle stop that automatically stops the engine when a preset automatic stop condition is met and restarts the engine when a preset restart condition is met, and the control unit is configured to prohibit the switching of the engine's fuel for a predetermined period after the restart of the engine that has been automatically stopped by the idle stop.

[0010] As a result, the bi-fuel vehicle according to one embodiment of the present invention can suppress deterioration of combustion stability and exhaust gas characteristics. [Examples]

[0011] A bi-fuel vehicle according to an embodiment of the present invention will be described in detail below with reference to the drawings.

[0012] In Figure 1, a bi-fuel vehicle 1 according to one embodiment of the present invention is composed of an engine 2 as an internal combustion engine, a transmission 3, a notification unit 7, and an ECU (Electronic Control Unit) 8 as a control unit.

[0013] Engine 2 has multiple cylinders. In this embodiment, engine 2 is configured to perform a series of four strokes for each cylinder, consisting of an intake stroke, a compression stroke, an expansion stroke, and an exhaust stroke.

[0014] Engine 2 is connected to a starter 21. The starter 21 is connected to the crankshaft of engine 2 via a belt (not shown). When power is supplied, the starter 21 rotates, causing the crankshaft to rotate and providing the engine 2 with rotational force for starting.

[0015] This engine 2 is supplied with one fuel selected from two types of fuels, namely, gasoline as a liquid fuel and CNG (Compressed Natural Gas) (LPG (Liquefied Petroleum Gas) may also be used) as a gaseous fuel, which are injected into the combustion chamber of each cylinder. The engine 2 includes a gasoline supply system that supplies gasoline stored in the gasoline tank 4 into the combustion chamber, and a gas fuel supply system that supplies CNG stored at high pressure in the gas fuel tank 5 into the combustion chamber.

[0016] The fuel switching device 6 switches the fuel injected into the combustion chamber of each cylinder of the engine 2. The fuel switching device 6 switches the fuel injected into the combustion chamber of each cylinder of the engine 2 between gasoline stored in the gasoline tank 4 and CNG stored in the gas fuel tank 5 under the control of the ECU 8.

[0017] The transmission 3 shifts the rotation output from the engine 2 and drives the drive wheels 10 via the drive shaft 11. The transmission 3 includes a constant-mesh transmission mechanism composed of a parallel-axis gear mechanism (not shown). The transmission 3 is adapted to select a gear position in the transmission mechanism according to an operation of a shift lever (not shown) by the driver.

[0018] The transmission 3 takes one of the following states according to the operation of the shift lever: for example, a gearshift state of 1st to 5th speeds corresponding to a predetermined gear ratio, a neutral state in which the rotation output from the engine 2 is not transmitted to the drive shaft 11, and a reverse state for reversing the bifuel vehicle 1.

[0019] A dry single-plate clutch 31, for example, is provided between the engine 2 and the transmission 3, and the clutch 31 connects or disconnects the power transmission between the engine 2 and the transmission 3.

[0020] The transition between the connected state and the disconnected state of the power transmission in this clutch 31 corresponds to the depression position of the clutch pedal 81, that is, the clutch stroke.

[0021] When the clutch pedal 81 is not depressed, the clutch 31 is in the engaged state, and the rotation of the crankshaft is transmitted to the transmission 3.

[0022] On the other hand, when the clutch pedal 81 is depressed, the clutch 31 is in the disengaged state, and the transmission of power from the crankshaft to the transmission 3 is cut off.

[0023] A clutch pedal switch 82 is provided on the clutch pedal 81. The clutch pedal switch 82 detects whether the clutch 31 is in the disengaged state.

[0024] The notification unit 7 is composed of, for example, a monitor device, a speaker, a lamp, a meter, a buzzer, etc., and notifies the driver of various information through vision, hearing, etc.

[0025] The ECU 8 is composed of a computer unit including a CPU (Central Processing Unit), a RAM (Random Access Memory), a ROM (Read Only Memory), a flash memory for storing backup data, an input port, and an output port.

[0026] In the ROM of this computer unit, a program for making the computer unit function as the ECU 8 is stored together with various constants, various maps, etc.

[0027] That is, by the CPU executing the program stored in the ROM using the RAM as a work area, this computer unit functions as the ECU 8 in this embodiment.

[0028] In addition to the aforementioned clutch pedal switch 82, various sensors such as a fuel selection switch 9, an accelerator opening sensor 84, a brake switch 86, a vehicle speed sensor 87, an air flow sensor 88, and a water temperature sensor 89 are connected to the input port of the ECU 8.

[0029] The fuel selection switch 9 accepts the driver's input and outputs a signal to select either gasoline or CNG as the fuel to be injected into the combustion chamber of each cylinder of the engine 2. The ECU 8 switches the fuel injected into the combustion chamber of each cylinder of the engine 2 according to the signal from the fuel selection switch 9.

[0030] The accelerator pedal position sensor 84 detects the accelerator pedal position, which is the degree to which the accelerator pedal 83 is opened by the driver. The brake switch 86 detects whether or not the brake pedal 85 has been pressed by the driver. The vehicle speed sensor 87 detects the speed of the bi-fuel vehicle 1 from the rotational speed of the drive wheels 10, etc.

[0031] The airflow sensor 88 detects the intake air volume, which is the flow rate of the intake air from the engine 2. The water temperature sensor 89 detects the engine water temperature, which is the temperature of the coolant in the engine 2.

[0032] Meanwhile, the output port of the ECU8 is connected to various control devices, including the aforementioned fuel switching device 6, notification unit 7, and starter 21, as well as injectors (not shown). The injectors supply fuel to the engine 2. The ECU8 controls the starting and stopping of the engine 2, output torque, etc., by controlling the starter 21 and injectors.

[0033] The ECU8 controls the idle stop function, which stops engine 2 when a preset automatic stop condition is met and restarts engine 2 when a preset restart condition is met.

[0034] The conditions for automatic stopping include, for example, the vehicle speed being below a predetermined speed, the transmission 3 being in neutral, the brake pedal 85 being depressed, the clutch pedal 81 not being depressed, and the accelerator opening being below a predetermined opening, all of which must be met. On the other hand, the conditions for restarting include, for example, the transmission 3 being in neutral, and at least one of the following being met, such as the clutch pedal 81 being depressed or the brake pedal 85 not being depressed.

[0035] In this embodiment, the ECU 8 prohibits fuel switching for the engine 2 during a predetermined period after the restart of the engine 2, which has been automatically stopped by the idle stop function.

[0036] For example, the ECU8 prohibits fuel switching for engine 2 during the period from when engine 2, which has been automatically stopped by the idle stop function, starts to restart until engine 2 reaches a fully combusted state.

[0037] The fully ignited state of engine 2 means that it can operate using only engine fuel even without the starter 21 being driven.

[0038] For example, ECU8 prohibits fuel switching for engine 2 after engine 2 has fully combusted, until the accumulated air volume of engine 2 exceeds a predetermined value, or until the feedback correction amount for engine 2's fuel learning falls within a predetermined range.

[0039] The cumulative air volume is the total amount of air drawn into engine 2 from the start of engine 2's restart. The predetermined value for the cumulative air volume is a value that ensures combustion stability and exhaust gas characteristics do not deteriorate.

[0040] The predetermined range of the fuel learning feedback correction amount is the range of the fuel learning feedback correction amount that ensures that combustion stability and exhaust gas characteristics do not deteriorate.

[0041] The ECU8 varies a predetermined value for the accumulated air volume according to the engine coolant temperature at the start of restarting engine 2. The ECU8 increases the predetermined value for the accumulated air volume as the engine coolant temperature decreases. The predetermined value for the accumulated air volume may also be varied according to the engine oil temperature instead of the engine coolant temperature.

[0042] The predetermined value of the accumulated air volume is set, for example, as shown in Figure 2. In Figure 2, for example, the line indicated by A represents the change in the predetermined value of the accumulated air volume when the fuel used during restart is CNG, and the line indicated by B represents the change in the predetermined value of the accumulated air volume when the fuel used during restart is gasoline.

[0043] The ECU8 may also prohibit fuel switching for engine 2 during the automatic stop period, from the start of automatic stopping of engine 2 due to the idle stop function until the start of restarting engine 2.

[0044] The ECU8 informs the driver via the notification unit 7 that fuel switching is prohibited. If the ECU8 attempts to switch fuels by operating the fuel selection switch 9 while fuel switching is prohibited, the notification unit 7 will notify the driver that the fuel switching has been suspended, and the suspended fuel switching will be automatically executed once fuel switching is permitted.

[0045] The fuel switching process by the ECU8 of the bi-fuel vehicle 1 according to this embodiment, configured as described above, will be explained with reference to Figure 3. The fuel switching process described below is initiated when a fuel switching request occurs. A fuel switching request occurs when the driver operates the fuel selection switch 9 or during the engine 2 control process of the ECU8.

[0046] In step S1, the ECU8 determines whether the fuel state maintenance request, which will be processed later, is a fuel state maintenance request.

[0047] If the ECU 8 determines that the fuel state maintenance request is indeed a fuel state maintenance request, it executes the process in step S2. If the ECU 8 determines that the fuel state maintenance request is not a fuel state maintenance request, it executes the process in step S3.

[0048] In step S2, the ECU8 determines whether the current fuel system is functioning correctly.

[0049] If the ECU8 determines that the current fuel system is functioning correctly, it executes the process in step S1. If the ECU8 determines that the current fuel system is not functioning correctly, it executes the process in step S3.

[0050] In step S3, ECU8 performs a fuel switch. After completing the process in step S3, ECU8 terminates the fuel switch process.

[0051] The fuel switching prohibition process by the ECU8 of the bi-fuel vehicle 1 according to this embodiment will be explained with reference to Figure 4. The fuel switching prohibition process described below is started when the ECU8 starts operating and is executed at a predetermined time interval.

[0052] In step S11, the ECU8 determines whether or not engine 2 is automatically stopped due to idle stop.

[0053] If the ECU 8 determines that engine 2 is automatically stopped due to idle stop, it executes the process in step S15. If the ECU 8 determines that engine 2 is not automatically stopped due to idle stop, it executes the process in step S12.

[0054] In step S12, the ECU8 determines whether or not engine 2 is in the process of restarting.

[0055] If ECU8 determines that engine 2 is restarting, it executes the process in step S15. If ECU8 determines that engine 2 is not restarting, it executes the process in step S13.

[0056] In step S13, the ECU8 determines whether the fuel learning feedback correction amount is within a predetermined range.

[0057] If the ECU 8 determines that the fuel learning feedback correction amount is within a predetermined range, it executes the process in step S14. If the ECU 8 determines that the fuel learning feedback correction amount is not within a predetermined range, it executes the process in step S15.

[0058] In step S14, the ECU8 determines whether the accumulated amount of air is equal to or greater than a predetermined value.

[0059] If the ECU8 determines that the accumulated air volume is equal to or greater than a predetermined value, it executes the process in step S11. If the ECU8 determines that the accumulated air volume is not equal to or greater than a predetermined value, it executes the process in step S15.

[0060] In step S15, the ECU8 changes the fuel state maintenance request to fuel state maintenance. After executing the process in step S15, the ECU8 terminates the fuel switching prohibition process.

[0061] The operation resulting from this fuel switching process and fuel switching prohibition process will be explained with reference to Figure 5.

[0062] At time t1, when the automatic stop condition for engine 2 is met and idle stop is activated, the fuel state maintenance request becomes fuel state maintenance, the engine speed decreases, and engine 2 stops at time t2.

[0063] At time t3, even if the driver operates the fuel selection switch 9 to switch fuels, the fuel switch will not be performed because the fuel state maintenance request is for fuel state maintenance.

[0064] At time t4, if the conditions for restarting engine 2 are met and the idle stop function is not activated, engine 2 will restart, its rotational speed will increase, and at time t5, engine 2 will fully ignite.

[0065] Subsequently, the accumulated air volume increases, the fuel learning feedback correction amount also increases, and at time t6, bi-fuel vehicle 1 starts moving and its speed increases.

[0066] At time t7, the accumulated air volume exceeds a predetermined value, and the fuel learning feedback correction amount also falls within a predetermined range. As a result, the fuel state maintenance request is changed to a fuel switching permission, and the fuel switching operation performed by the driver, which had been pending at time t3, is executed.

[0067] Thus, in this embodiment, the ECU 8 prohibits fuel switching for the engine 2 during a predetermined period after the restart of the engine 2, which has been automatically stopped by the idle stop function.

[0068] This prevents deterioration of combustion stability and exhaust gas characteristics by prohibiting fuel switching during the transient period of engine 2, such as during restart.

[0069] Furthermore, the ECU8 prohibits fuel switching for engine 2 during the period between the restart of engine 2, which has been automatically stopped by the idle stop function, and when engine 2 reaches a fully combusted state.

[0070] As a result, during the restart of engine 2, which is a transient period in which engine speed and load fluctuate significantly, prohibiting fuel switching can suppress deterioration of combustion stability and exhaust gas characteristics.

[0071] Furthermore, ECU8 prohibits fuel switching for engine 2 after engine 2 has fully combusted, until the accumulated air volume of engine 2 exceeds a predetermined value, or until the feedback correction amount for engine 2's fuel learning falls within a predetermined range.

[0072] This allows the system to determine whether combustion stability and exhaust gas characteristics can be guaranteed by referring to the cumulative amount of air. If these conditions cannot be met, fuel switching is prohibited, thereby preventing deterioration of combustion stability and exhaust gas characteristics.

[0073] Furthermore, by allowing fuel switching only after fuel learning is complete, appropriate control can be performed to ensure combustion stability and exhaust gas characteristics through fuel injection and air volume control the next time the same fuel is switched to.

[0074] Furthermore, the lower the engine water temperature when engine 2 is restarted, the larger the predetermined value for the accumulated air volume will be.

[0075] This ensures combustion stability and exhaust gas characteristics by allowing fuel switching only after a sufficient amount of accumulated air has been secured when the engine water temperature is low.

[0076] Furthermore, if the engine water temperature is high, promptly allowing a fuel switch can reduce the discomfort caused by the discrepancy between the fuel selected by the driver and the actual fuel being used.

[0077] Additionally, ECU8 prohibits fuel switching for engine 2 while engine 2 is automatically shut down. This prevents the deterioration of restartability caused by the timing of fuel switching and engine 2 restart overlapping. In addition, the opening and closing of valves for fuel switching is eliminated, improving quietness.

[0078] Furthermore, the ECU8 informs the driver via the notification unit 7 that fuel switching is prohibited.

[0079] This allows the driver to recognize that fuel switching is prohibited, and reduces the sense of unease caused by the discrepancy between the fuel the driver expects to use and the actual fuel used.

[0080] Furthermore, if the driver attempts to switch fuels while fuel switching is prohibited, the ECU8 notifies the driver via the notification unit 7 that the fuel switching has been suspended, and then automatically executes the suspended fuel switching after the fuel switching is permitted.

[0081] This allows the driver to recognize that the fuel switching operation has been suspended, thus reducing the sense of unease caused by the discrepancy between the fuel the driver expects to use and the actual fuel used.

[0082] Furthermore, by automatically executing the previously pending fuel change once permission for fuel change is granted, the inconvenience experienced by the driver due to the need for repeated operation can be minimized.

[0083] In this embodiment, an example has been described in which the ECU 8 performs various judgments and calculations based on various sensor information. However, the invention is not limited to this, and the bi-fuel vehicle 1 may be equipped with a communication unit capable of communicating with an external device such as an external server, and various judgments and calculations may be performed by the external device based on detection information from various sensors transmitted from the communication unit, and the judgment and calculation results may be received by the communication unit and used to perform various controls.

[0084] While embodiments of the present invention have been disclosed, it will be apparent to those skilled in the art that modifications can be made without departing from the scope of the invention. All such modifications and equivalents are intended to be included in the following claims. [Explanation of Symbols]

[0085] 1. Bi-fuel vehicle 2 engines 6. Fuel switching device 7 Hochi Department 8 ECU (control unit) 9. Fuel Selection Switch 88 Airflow Sensor 89 Water temperature sensor

Claims

1. A bi-fuel vehicle equipped with an engine that switches between and uses multiple fuels, The system includes a control unit that controls an idle stop function, which automatically stops the engine when a preset automatic stop condition is met and restarts the engine when a preset restart condition is met. The control unit prohibits the switching of the engine's fuel during a predetermined period after the restart of the engine, which has been automatically stopped by the idle stop function, in a bi-fuel vehicle.

2. The bi-fuel vehicle according to claim 1, wherein the control unit prohibits switching the engine's fuel during the period from when the engine, which has been automatically stopped by the idle stop, is restarted until the engine reaches a fully combusted state.

3. The bi-fuel vehicle according to claim 1, wherein the control unit prohibits switching the engine's fuel after the engine has finished combustion until the accumulated air volume of the engine exceeds a predetermined value, or until the feedback correction amount of the engine's fuel learning falls within a predetermined range.

4. The bi-fuel vehicle according to claim 3, wherein the lower the engine water temperature at the time of restarting the engine, the larger the predetermined value of the accumulated air volume.

5. The control unit prohibits switching the engine's fuel while the engine is automatically stopped, as described in claim 1 for the bi-fuel vehicle.

6. It is equipped with a notification unit that broadcasts various kinds of information, The bi-fuel vehicle according to any one of claims 1 to 5, wherein the control unit notifies the driver via the notification unit that fuel switching is prohibited.

7. The bi-fuel vehicle according to claim 6, wherein the control unit, when a driver performs a fuel switching operation while fuel switching is prohibited, notifies the driver via the notification unit that the execution of the fuel switching has been suspended, and automatically executes the suspended fuel switching after the fuel switching is permitted.

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