WO2017130543A1

WO2017130543A1 - Bifuel engine system

Info

Publication number: WO2017130543A1
Application number: PCT/JP2016/084749
Authority: WO
Inventors: 文人中谷; 雄司菱田
Original assignee: 愛三工業株式会社
Priority date: 2016-01-26
Filing date: 2016-11-24
Publication date: 2017-08-03
Also published as: JP2017133396A

Abstract

This bifuel engine system is provided with: multi-point injection (MPI) type gasoline injectors (22) which are located in the vicinity of each cylinder of a multi-cylinder engine (1), and which correspondingly inject gasoline into each cylinder; a single-point injection (SPI) type compressed natural gas (CNG) injector (32) which is located in a position away from each cylinder of the engine (1), and which injects CNG into an intake manifold (13); and an electronic control device (ECU) (50) for controlling the gasoline injectors (22) and the CNG injector (32) in accordance with the operation state of the engine (1). When it is determined that acceleration is demanded of the engine (1) during CNG operation, the ECU (50) controls the gasoline injectors (22) and the CNG injector (32) in order to switch from CNG operation to gasoline operation.

Description

Bi-fuel engine system

The present invention relates to a bi-fuel engine system configured to switch and supply gasoline and gas fuel as fuel to a multi-cylinder engine for operation.

Conventionally, as this type of technology, for example, a control method for a bi-fuel engine described in Patent Document 1 is known. In this control method, a gasoline injector that injects gasoline into an intake pipe in the vicinity of an engine cylinder (cylinder), and a CNG injector that injects CNG as gas fuel into an intake pipe away from the engine cylinder via a hose. In addition, a gasoline injector and a CNG injector are switched and used by a changeover switch, and the engine is operated by gasoline or CNG. In this control method, when the gasoline switch is switched from the gasoline injector to the CNG injector while the gasoline injector is operating by injecting gasoline, the gasoline injection from the gasoline injector and the CNG injection from the CNG injector are performed. It is designed to overlap. As a result, when the operation using gasoline is switched to the operation using CNG, the fuel can be switched without any trouble without causing dilution of CNG due to an increase in the volume of the hose or the like.

JP 2015-17594 A

By the way, in the bi-fuel engine described in Patent Document 1, acceleration may be required for the engine during operation by CNG. However, in the technique described in Patent Document 1, the CNG injector injects CNG at a position away from each cylinder of the engine. For this reason, even if the amount of CNG injection is increased during acceleration, it takes time for the increased amount of CNG to reach the cylinder, which may cause a delay in response to acceleration.

Here, in order to construct a bi-fuel engine at a lower cost, it is conceivable to use a single point injection (SPI) system for the injection of gas fuel such as CNG. Thus, it is expected that the degree of freedom for mounting the bi-fuel engine on the vehicle can be increased by using the gas fuel injection in the SPI system. On the other hand, in the SPI method, there is a possibility that a delay in response occurs in the increased injection at the time of acceleration, or the fuel distribution to each cylinder is deteriorated.

FIG. 6 shows a conventional bi-fuel engine (a) CNG or gasoline operation during engine acceleration, (b) engine speed NE, (c) throttle opening TA, (d) change in throttle opening. The behavior of ΔTA and (e) air-fuel ratio A / F is shown by a time chart. In FIG. 6, when the throttle opening degree TA and the change amount ΔTA of the throttle opening degree change at time t1 (see FIGS. 6C and 6D) and the engine is requested to accelerate, the operation by CNG changes. (See FIG. 6A), the CNG injection is increased in accordance with the throttle opening degree TA. However, when the CNG injection is performed by the SPI method at a position away from each cylinder, a delay occurs until the CNG reaches each cylinder, and the engine speed increases to NE between times t2 and t3. Or the air-fuel ratio A / F becomes lean (see FIG. 6E).

The present invention has been made in view of the above circumstances, and an object thereof is a bi-fuel engine system configured to supply gas fuel to an engine by using the SPI method, from during operation with gas fuel. An object of the present invention is to provide a bi-fuel engine system that can improve the acceleration response of an engine.

(1) In order to achieve the above object, one aspect of the present invention is a bi-fuel engine system configured to switch and supply gasoline and gas fuel as fuel to a multi-cylinder engine. In order to supply gasoline to the engine, gasoline supply means adopting a multi-point injection (MPI) system for injecting gasoline corresponding to each cylinder in the vicinity of each cylinder, and supplying gas fuel to the engine Therefore, gas fuel supply means adopting a single point injection (SPI) system for injecting gas fuel into the intake passage at a position away from each cylinder, gasoline supply means according to the operating state of the engine, and Control means for controlling the gas fuel supply means, and the control means is provided to the engine during operation with gas fuel. When it is determined that the speed is required, in order to switch to operation using gasoline operation with gaseous fuel, and the spirit of controlling the gasoline supply means and the gas fuel supply means.

According to the configuration of (1) above, when the engine is requested to accelerate during operation using gas fuel, the operation is switched from operation using gas fuel to operation using gasoline, and the engine is accelerated by operation using gasoline. Therefore, even if the SPI system that injects the fuel gas into the intake passage at a position distant from each cylinder is adopted as the gas fuel supply means, the gasoline corresponding to each cylinder in the vicinity of each cylinder during engine acceleration. Gasoline is supplied to each cylinder with good responsiveness by the MPI type gasoline supply means for injecting fuel.

(2) In order to achieve the above object, in the configuration of (1) above, when the control means determines that a return from the cut off of the supply of the gas fuel is requested during the operation using the gas fuel, the operation using the gas fuel is performed. In order to switch from gasoline operation to gasoline operation, it is preferable to control the gasoline supply means and the gas fuel supply means.

According to the configuration of (2) above, in addition to the operation of the configuration of (1) above, when a return from gas fuel supply interruption (gas fuel cut) is requested during operation with gas fuel, Switching from driving to driving with gasoline, the engine is driven with gasoline. Therefore, even if the gas fuel supply means adopts the SPI method in which fuel gas is injected into the intake passage at a position away from each cylinder, it corresponds to each cylinder in the vicinity of each cylinder when returning from the gas fuel cut. Then, the gasoline is supplied to each cylinder with good responsiveness by the MPI type gasoline supply means for injecting the gasoline.

According to the configuration of (1) above, in the bi-fuel engine system configured to supply gas fuel to the engine using the SPI method, it is possible to improve the acceleration response of the engine during operation with gas fuel. it can.

According to the configuration of (2) above, in addition to the effect of the configuration of (1) above, a decrease in engine rotation is suppressed when returning from a gas fuel cut during operation with gas fuel, and engine stall is prevented. be able to.

1 is a schematic configuration diagram illustrating a bi-fuel engine system mounted on an automobile according to an embodiment. The flowchart which shows the content of the fuel-injection control at the time of acceleration during CNG driving | operation concerning one Embodiment. The flowchart which shows the content of the fuel-injection control at the time of F / C return | return during CNG driving | operation concerning one Embodiment. According to one embodiment, (a) driving with CNG or gasoline during engine acceleration, (b) engine rotation speed, (c) throttle opening, (d) amount of change in throttle opening, (e) acceleration determination, (F) Injection estimation frequency and (g) Time chart showing air-fuel ratio behavior. According to one embodiment, (a) driving with CNG or gasoline, (b) engine speed, (c) estimated number of injections, (d) fuel cut return determination and (e) air-fuel ratio at the time of return from CNG cut Time chart showing behavior. According to the conventional example, (a) operation with CNG or gasoline during engine acceleration, (b) engine rotation speed, (c) throttle opening, (d) change in throttle opening, and (e) air-fuel ratio behavior A time chart showing.

Hereinafter, an embodiment embodying a bi-fuel engine system according to the present invention will be described in detail with reference to the drawings.

FIG. 1 is a schematic configuration diagram showing a bi-fuel engine system mounted on an automobile in this embodiment. The multi-cylinder engine 1 explodes and burns a combustible mixture of fuel and air supplied through an intake passage 2 in a combustion chamber of each cylinder 3, and exhausts the burned exhaust gas through the exhaust passage 4. Discharge outside. As a result, the engine 1 operates the piston 5 to rotate the crankshaft 6 to obtain power.

The intake passage 2 includes an air cleaner 11, an electronic throttle device 12, and an intake manifold 13 in that order from the inlet side. The air cleaner 11 cleans the air taken into the intake passage 2. The electronic throttle device 12 adjusts the amount of air (intake amount) Ga that flows through the intake passage 2 and is sucked into the combustion chamber of each cylinder 3. The electronic throttle device 12 drives the throttle valve 15 to open and close by a motor 14. A throttle sensor 41 provided in the electronic throttle device 12 detects an opening degree (throttle opening degree) TA of the throttle valve 15 and outputs an electric signal corresponding to the detected value. The intake manifold 13 distributes the intake air flowing through the intake passage 2 to each cylinder 3.

The bi-fuel engine system of this embodiment is configured to switch and supply gasoline and compressed natural gas (CNG) as fuel to the multi-cylinder engine 1 and operate, and a gasoline supply device 21 for supplying gasoline. The fuel supply device 20 includes a CNG supply device 31 that supplies CNG. In this embodiment, CNG corresponds to an example of the gas fuel of the present invention. The gasoline supply device 21 includes a plurality of gasoline injectors 22 provided corresponding to the respective cylinders 3, a gasoline tank 23 for supplying gasoline to each gasoline injector 22, a gasoline line 24, a gasoline pump 25, and a delivery pipe 26. Is provided. The gasoline injector 22 employs a port injection type and a multi-point injection (MPI) method in which gasoline is injected into the intake port 7 corresponding to each cylinder 3 in the vicinity of each cylinder 3 of the engine 1. This corresponds to an example of the gasoline supply means of the present invention. The gasoline tank 23 stores gasoline. The gasoline pump 25 pumps gasoline from the gasoline tank 23 to the gasoline line 24. The gasoline pumped to the gasoline line 24 is supplied to each gasoline injector 22 via the delivery pipe 26. The supplied gasoline is injected into each intake port 7 and supplied to each cylinder 3 by controlling each injector 22.

The CNG supply device 31 includes one CNG injector 32, and a CNG cylinder 33 and a CNG line 34 for supplying CNG to the injector 32. The CNG injector 32 employs a single point injection (SPI) system for injecting CNG into the intake manifold 13 at a position distant from each cylinder 3 of the engine 1, and the gas fuel supply means of the present invention. It corresponds to an example. The CNG line 34 is provided with a main valve 35, a shut-off valve 36, and a CNG regulator 37. The main valve 35 is composed of an electromagnetic valve that is opened and closed to control the supply and shutoff of CNG from the CNG cylinder 33 to the CNG line 34. The shut-off valve 36 is composed of an electromagnetic valve that is opened and closed to control the flow of CNG. The CNG regulator 37 adjusts CNG fed to the CNG injector 32 to a predetermined pressure. CNG supplied from the CNG cylinder 33 to the CNG injector 32 through the CNG line 34 is injected into the intake manifold 13 by the control of the CNG injector 32, and is supplied to each cylinder 3 through each intake port 7.

1st CNG pressure sensor 61 for detecting the pressure of CNG in the part is provided in CNG line 34 downstream from main valve 35. A delivery pipe 38 is provided on the CNG line 34 between the CNG regulator 37 and the CNG injector 32. The delivery pipe 38 is provided with a second CNG pressure sensor 62 for detecting the CNG pressure in the pipe 38 and a CNG temperature sensor 63 for detecting the temperature of the CNG in the pipe 38. When both the main valve 35 and the shutoff valve 36 are opened, CNG is supplied from the CNG cylinder 33 to the CNG injector 32 via the CNG line 34 and the like. On the other hand, when the main valve 35 or the shutoff valve 36 is closed, CNG is not supplied to the CNG injector 32.

The plurality of spark plugs 16 provided in the engine 1 corresponding to the respective cylinders 3 perform an ignition operation by receiving a high voltage output from the ignition coil 17. The ignition timing of each spark plug 16 is determined by the output timing of the high voltage from the ignition coil 17.

The catalytic converter 8 provided in the exhaust passage 4 purifies the exhaust discharged from the engine 1 to the exhaust passage 4. The oxygen sensor 43 provided in the exhaust passage 4 detects the oxygen concentration Ox in the exhaust discharged from the engine 1 to the exhaust passage 4 and outputs an electric signal corresponding to the detected value.

The rotational speed sensor 44 provided in the engine 1 detects the rotational speed of the crankshaft 6, that is, the engine rotational speed NE, and outputs an electrical signal corresponding to the detected value. A water temperature sensor 45 provided in the engine 1 detects the temperature (cooling water temperature) THW of the cooling water flowing inside the engine 1 and outputs an electrical signal corresponding to the detected value. In addition, the automobile is provided with a vehicle speed sensor 46 that detects the vehicle speed and outputs an electrical signal corresponding to the detected value.

In this embodiment, the electronic control unit (ECU) 50 inputs various signals output from the

various sensors

41, 43 to 46. Based on these input signals, that is, according to the operating state of the engine 1, the ECU 50 performs each fuel injector 22, CNG injector 32, and ignition coil in order to execute fuel injection control including ignition control and ignition timing control. 17 is controlled.

Here, the fuel injection control is to control the fuel injection amount and the fuel injection timing by controlling the

injectors

22 and 32 in accordance with the operating state of the engine 1. The air-fuel ratio control is a feedback control of the air-fuel ratio of the engine 1 to a predetermined target air-fuel ratio such as the theoretical air-fuel ratio by controlling the

injectors

22 and 32 based on the detection signal of the oxygen sensor 43. In this embodiment, the ECU 50 uses the gasoline to perform the idling operation immediately after the start of the engine 1 and the completion of the start as the use of gasoline and CNG in the fuel injection control, and then switches to the operation using the CNG. ing. The ignition timing control is to control the ignition timing by each spark plug 16 by controlling the ignition coil 17 according to the operating state of the engine 1.

In this embodiment, the ECU 50 corresponds to an example of the control means of the present invention. The ECU 50 has a known configuration including a central processing unit (CPU), a read only memory (ROM), a random access memory (RAM), a backup RAM, and the like. The ROM stores in advance predetermined control programs related to the various controls described above. The ECU 50 is configured to execute the various controls described above according to these control programs.

In addition, the driver's seat of the car is for selecting a gasoline mode that uses only gasoline for driving the engine 1, a CNG mode that uses only CNG, and a normal mode that selectively uses gasoline and CNG. A mode switch 66 is provided. Similarly, the driver's seat is provided with a mode lamp 67 for displaying whether the current driving is the gasoline mode, the CNG mode, or the normal mode. The mode switch 66 and the mode lamp 67 are connected to the ECU 50, respectively. The display of the mode lamp 67 is controlled by the ECU 50.

As described above, since the bi-fuel engine system of this embodiment employs the SPI method for CNG injection, the bi-fuel engine system can be configured relatively inexpensively and can increase the degree of freedom of mounting on the vehicle. However, by adopting the SPI method for the CNG injection, there is a risk that the arrival of the CNG, which is increased in quantity when the engine 1 is accelerated, may be delayed or the CNG distribution to each cylinder 3 may be deteriorated. . In addition, there is a risk that the CNG injected reaches the cylinders 3 at the time of return from the fuel cut, or the CNG distribution to the cylinders 3 is deteriorated. As a result, at the time of return from the fuel cut, the rotation of the engine 1 may be reduced, leading to an engine stall. Therefore, in this embodiment, the fuel injection control at the time of acceleration of the engine 1 during the CNG operation and the return from the fuel cut is improved as follows. FIG. 2 is a flowchart showing the content of fuel injection control during acceleration during CNG operation.

When the process proceeds to this routine, in step 100, the ECU 50 determines whether or not the current mode is a normal mode in which gasoline and CNG are selectively used. The ECU 50 proceeds to step 110 when the determination result is affirmative, and returns the process to step 100 when the determination result is negative.

In step 110, the ECU 50 determines whether or not the current operation is CNG operation using CNG. If this determination result is affirmative, the ECU 50 proceeds to step 120, and if this determination result is negative, the ECU 50 proceeds to step 130.

In step 120, the ECU 50 determines whether a precondition for switching to gasoline is satisfied. For example, the ECU 50 determines that (a) the engine speed NE is within a predetermined range, (b) the throttle opening TA is within a predetermined range, and (c) a change amount ΔTA of the throttle opening TA is a predetermined value. Assuming that the above is the case, that is, when the engine 1 is accelerating, (d) the vehicle speed is equal to or higher than a predetermined value, and (e) the driving time using CNG is equal to or longer than a predetermined time, When all the conditions a) to (e) are satisfied, it is determined that the precondition for switching to gasoline is satisfied. The ECU 50 proceeds to step 150 when the determination result is affirmative, and returns the process to step 100 when the determination result is negative.

On the other hand, in step 130, the ECU 50 determines whether or not CNG operation is possible. The ECU 50 determines that the CNG operation is possible when the gasoline injection is performed a predetermined number of times or more after the acceleration of the engine 1 is started. The ECU 50 proceeds to step 140 when the determination result is affirmative, and returns the process to step 100 when the determination result is negative.

In step 140, the ECU 50 switches to CNG operation. That is, the ECU 50 permits the opening of the CNG injector 32 in order to inject CNG. Thus, CNG is injected from each CNG injector 32 at a predetermined timing.

From step 120, in step 150, the ECU 50 clears the estimated number of injections CEI to “0”. The ECU 50 estimates the number of injections by the gasoline injector 22 when the engine 1 is in operation.

Next, in step 160, the ECU 50 switches to gasoline operation. That is, the ECU 50 drives the gasoline pump 25 to inject gasoline, and permits the opening of each gasoline injector 22. As a result, gasoline is injected from each gasoline injector 22 at a predetermined timing. Thereafter, the ECU 50 returns the process to step 100.

According to the above control, when the ECU 50 determines that acceleration is required for the engine 1 during the operation by the CNG, the gasoline pump 25, the gasoline injector 22 and the CNG injector 32 are switched from the operation by the CNG to the operation by the gasoline. And to control. Specifically, the gasoline pump 25 is driven, the gasoline injector 22 is opened at a predetermined timing, and the CNG injector 32 is closed.

Next, FIG. 3 is a flowchart showing the content of fuel injection control at the time of fuel cut return during CNG operation. The time of fuel cut return during CNG operation means when CNG injection is once interrupted during CNG operation and then returned to CNG injection. The flowchart of FIG. 3 is the same as that of the flowchart of FIG. 2 in terms of the contents of

steps

100, 110, and 130-160. 3 is different from the flowchart of FIG. 2 in that the content of step 125 is different from step 120 of the flowchart of FIG. 2 and that step 200 is added between step 120 and step 150.

Therefore, when the processing shifts to this routine, the ECU 50 determines whether or not a precondition for switching to gasoline is satisfied in step 125 after executing the processing of step 100 and step 110. Here, for example, the ECU 50 is premised on (g) that the engine rotational speed NE is equal to or higher than a predetermined value, (h) that the vehicle speed is higher than or equal to a predetermined value, and (i) that the previous fuel cut is in progress. When all the conditions (g) to (i) are satisfied, it is determined that the precondition for switching to gasoline is satisfied. The ECU 50 proceeds to step 200 when this determination result is affirmative, and returns the process to step 100 when this determination result is negative.

In this embodiment, the ECU 50 determines in step 130 that the CNG operation is possible when gasoline injection is performed a predetermined number of times or more after the fuel cut of the engine 1 is restored.

In step 200, the ECU 50 determines whether or not it is a return from the fuel cut (F / C). In this embodiment, the ECU 50 determines that the fuel has been returned from the fuel cut (F / C) when the estimated number of injection estimations CEI reaches a predetermined value. The ECU 50 proceeds to step 150 when the determination result is affirmative, and returns the process to step 100 when the determination result is negative.

Thereafter, the ECU 50 executes the processing of step 150 and step 160, and then returns the processing to step 100.

According to the above control, when the ECU 50 determines that a return from the fuel cut of the CNG is requested during the operation by the CNG, the ECU 50 switches from the operation by the CNG to the operation by the gasoline in order to switch from the operation by the CNG. The CNG injector 32 is controlled. Specifically, the gasoline pump 25 is driven, the gasoline injector 22 is opened at a predetermined timing, and the CNG injector 32 is closed.

According to the bi-fuel engine system of this embodiment described above, when the engine 1 is requested to accelerate during operation by CNG, operation from CNG is switched to operation by gasoline, and engine 1 is accelerated by operation by gasoline. Is done. Therefore, even if the SPI system for injecting CNG into the intake manifold 13 at a position away from each cylinder 3 is employed for the CNG injector 32, when the engine 1 is accelerated, it is in the vicinity of each cylinder 3 (intake port 7). Gasoline is supplied to each cylinder 3 with good responsiveness by the MPI type gasoline injector 22 that injects gasoline corresponding to each cylinder 3. For this reason, in the bi-fuel engine system configured to supply the CNG to the engine 1 by adopting the SPI method, it is possible to improve the acceleration response of the engine during operation by the CNG.

FIG. 4 shows a bi-fuel engine system according to this embodiment. (A) Operation with CNG or gasoline when the engine 1 is accelerated, (b) Engine rotational speed NE, (c) Throttle opening TA, (d) Throttle The behavior of the change amount ΔTA of the opening degree, (e) acceleration determination, (f) estimated number of injections CEI and (g) air-fuel ratio A / F is shown by a time chart. In FIG. 4, when the throttle opening degree TA and the change amount ΔTA of the throttle opening degree change at time t1 (see FIGS. 4C and 4D), the engine 1 is determined to be accelerated (FIG. 4E). (See FIG. 4 (a)), and the gasoline injection is increased according to the throttle opening degree TA. In this embodiment, since the MPI method is employed in which gasoline is injected in the vicinity of each cylinder 3 (intake port 7) corresponding to each cylinder 3, the injected gasoline is injected into each cylinder 3. Will be supplied immediately. For this reason, as shown in FIG. 4B surrounded by a broken-line ellipse, the engine speed NE increases without delay from time t2, and there is no problem in increasing the rotation of the engine 1. Further, as shown in FIG. 4 (g), the air-fuel ratio A / F also does not become lean between times t2 and t3. In this embodiment, in FIG. 4, when the estimated number of injections CEI cleared to “0” at time t1 reaches a predetermined value C1 at time t3, the operation from gasoline is returned to the operation by CNG. It has become.

In this embodiment, when the CNG is requested to return from the fuel cut during the operation by the CNG, the operation by the CNG is switched to the operation by the gasoline, and the engine 1 is operated by the gasoline. Therefore, even if the SPI system for injecting CNG into the intake manifold 13 at a position away from each cylinder 3 is adopted for the CNG injector 32, the vicinity of each cylinder 3 (intake port 7) when returning from CNG fuel cut. ), The gasoline is supplied to each cylinder 3 with good responsiveness by the MPI type gasoline injector 22 which injects gasoline corresponding to each cylinder 3. For this reason, in the bi-fuel engine system configured to supply the CNG to the engine 1 by adopting the SPI method, it is possible to suppress a decrease in the rotation of the engine 1 at the time of return from the fuel cut during the operation by the CNG, and to generate an engine stall. It can be prevented in advance.

FIG. 5 relates to the bi-fuel engine system of this embodiment. (A) Operation with CNG or gasoline, (b) Engine rotational speed NE, (c) Estimated number of injections CEI, d) Fuel cut (F / C) return determination and (e) Air-fuel ratio A / F behavior are shown in a time chart. In FIG. 5, when the fuel cut (F / C) return is determined (YES) at time t1 (see FIG. 5D), the operation is switched from the CNG operation to the gasoline operation (see FIG. 5A). ), Fuel is supplied to the engine 1 by gasoline injection. That is, the gasoline injected by the MPI gasoline injector 22 disposed in the vicinity of each cylinder 3 (intake port 7) is immediately supplied to each cylinder 3. Therefore, as shown in FIG. 5 (b), the decrease in the engine rotational speed NE is moderated between the times t1 and t2, and the engine 1 holds the rotation without being stalled. Further, as shown in FIG. 5E, the air-fuel ratio A / F does not become lean between times t1 and t2. In this embodiment, in FIG. 5, when the estimated number of injections CEI cleared to “0” at time t1 reaches a predetermined value C1 at time t2, the operation from gasoline is returned to the operation by CNG. It has become.

By the way, in this embodiment, it is configured to switch from driving by CNG to driving by gasoline at the time of acceleration during driving by CNG and return from fuel cut. On the other hand, at the time of acceleration during operation by CNG and at the time of return from the fuel cut, it is conceivable to switch from the operation by CNG to the operation by both CNG and gasoline, and it is considered that the acceleration response is also improved. However, when the engine 1 is operated with both CNG and gasoline, two types of fuel are consumed simultaneously, and the overall fuel consumption of the engine 1 is deteriorated. In this embodiment, since driving using both CNG and gasoline is not employed, it is possible to suppress the deterioration of the overall fuel consumption of the engine.

Note that the present invention is not limited to the above-described embodiment, and a part of the configuration can be appropriately changed and implemented without departing from the spirit of the invention.

(1) In the above embodiment, the port injection type gasoline injector 22 is used as the gasoline supply means, but a cylinder injection type gasoline injector can also be used. In this case, the same effect as that of the above embodiment can be obtained.

(2) In the above embodiment, CNG is used as the gas fuel, but liquefied petroleum gas (LPG) can also be used. In this case, the same effect as that of the above embodiment can be obtained.

(3) In the above embodiment, the throttle opening degree TA and the change amount ΔTA of the throttle opening degree are used for the acceleration determination, but the opening degree of the accelerator pedal operated to open and close the electronic throttle device 12 is detected. The opening degree and the amount of change in the opening degree can also be used. In this case, the responsiveness of the engine acceleration determination can be improved.

The present invention can be used in a bi-fuel engine system configured to switch and supply gasoline and gas fuel as fuel to a multi-cylinder engine.

1 Engine 2 Intake passage 3 Cylinder 13 Intake manifold 22 Gasoline injector (gasoline supply means)
32 CNG injector (gas fuel supply means)
50 ECU (control means)

Claims

A bi-fuel engine system configured to supply and operate gasoline and gas fuel as fuel for a multi-cylinder engine,
Gasoline supply means adopting a multi-point injection (MPI) system for injecting the gasoline corresponding to each cylinder in the vicinity of each cylinder in order to supply the gasoline to the engine;
Gas fuel supply means adopting a single point injection (SPI) system for injecting the gas fuel into the intake passage at a position away from each cylinder to supply the gas fuel to the engine;
Control means for controlling the gasoline supply means and the gas fuel supply means according to the operating state of the engine, and the control means is requested to accelerate the engine during operation with the gas fuel. When judged, the bifuel engine system controls the gasoline supply means and the gas fuel supply means in order to switch from the gas fuel operation to the gasoline operation.
When the control means determines that a return from the gas fuel supply interruption is requested during the operation with the gas fuel, the control means switches the operation with the gas fuel to the operation with the gasoline. The bi-fuel engine system according to claim 1, wherein the gas fuel supply means is controlled.