JP2014190311A - Fuel injection control device for bi-fuel internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fuel injection control device for a bi-fuel internal combustion engine which is capable of suppressing deterioration of drivability due to a difference in fuel property that is caused by a fuel fill.SOLUTION: When at least one of a first fuel and a second fuel is supplied, at the time that an engine is started after the supply, an internal combustion engine is started with the fuel having a larger ratio in the fuels before the supply which are contained in the fuels after the supply.

Description

  The present invention relates to a fuel injection control device for a bi-fuel internal combustion engine.

  Conventionally, a bi-fuel internal combustion engine that can use two types of fuel is known. For example, the bi-fuel internal combustion engine disclosed in Patent Document 1 can use gasoline and CNG (Compressed Natural Gas) as supply fuel. This bi-fuel internal combustion engine is provided with a dedicated fuel system for supplying gasoline and CNG separately. For this reason, this bi-fuel internal combustion engine can select gasoline or CNG as the supply fuel.

JP 2002-038980 A JP 2008-259933 A JP 2004-346911 A

  By the way, some gasolines are mixed with ethanol. Ethanol is known to have a lower calorific value than gasoline. For this reason, when the mixing ratio of gasoline and ethanol is different, the component composition, that is, the fuel property is different, and the calorific value is different. Moreover, although the main component of CNG is methane, it is known that this CNG is different in fuel properties depending on its production area, production time, season, etc., and its calorific value is different. Thus, the properties of the fuel used in the internal combustion engine are not necessarily constant.

  For this reason, when the above-mentioned bi-fuel internal combustion engine is replenished, a fuel having a different property from the remaining fuel may be replenished. In this case, the calorific value of the fuel before replenishment is different from the calorific value of the fuel after replenishment, and the combustion state in the internal combustion engine changes. As a result, there is a concern that drivability will be adversely affected. In particular, at the time of start-up after replenishing fuel, combustion is performed by the air-fuel ratio learned by the fuel before replenishment, so this effect appears remarkably.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a fuel injection control device for a bi-fuel internal combustion engine that can suppress a deterioration in drivability due to a difference in fuel properties. .

In order to achieve the above object, a first invention is a fuel injection control device for a bi-fuel internal combustion engine,
In a fuel injection control device for a bi-fuel internal combustion engine that uses a first fuel and a second fuel having different properties as supply fuels,
When at least one of the first fuel and the second fuel is replenished, the fuel with the larger proportion of the fuel before replenishment included in the fuel after replenishment when starting the engine after replenishment is used. An internal combustion engine is started.

  In addition, in the second invention according to the first invention, the switching from the fuel used at the start to the other fuel is set based on at least one of the engine speed, the load factor, and the throttle change amount. It is performed in the operation area.

  The third aspect of the invention relates to the learning of the properties of the fuel used at the start in the air-fuel ratio feedback control based on the output of the air-fuel ratio sensor provided in the exhaust passage after the engine is started in the first or second invention. And switching to the other fuel is prohibited until the learning is completed.

  According to a fourth aspect of the present invention, in any one of the first to third aspects, the air-fuel ratio is based on an output of an air-fuel ratio sensor provided in the exhaust passage after switching from the fuel used at the start to the other fuel. In the feedback control, the characteristics of the fuel after switching are learned.

  According to a fifth aspect, in any one of the first to fourth aspects, the first fuel is a liquid fuel.

  According to a sixth aspect, in any one of the first to fifth aspects, the second fuel is a gaseous fuel.

  According to the first invention, it is possible to start with the fuel having the smaller change in the fuel property. For this reason, the deterioration of the drivability at the time of engine starting by the difference in fuel property can be suppressed.

  According to the second invention, switching can be performed in an operation region suitable for switching fuel. For this reason, the shock which generate | occur | produces at the time of fuel switching can be reduced.

  According to the third aspect of the invention, it is possible to reliably perform learning control for the fuel used at the time of starting. For this reason, the learning value of the parameter for performing the optimal combustion for the fuel used at the start can be reliably calculated. As a result, after switching from the fuel used at the start to the other fuel, when switching to the fuel at the start again, optimal combustion can be performed immediately.

  According to the fourth aspect of the invention, it is possible to reliably perform the learning control for the fuel that is not used at the time of starting.

BRIEF DESCRIPTION OF THE DRAWINGS It is a schematic block diagram for demonstrating the structure of the system of Embodiment 1 of this invention. In this embodiment, it is a flowchart of the control routine performed by ECU at the time of engine starting.

Embodiment 1 FIG.
[System Configuration of Embodiment 1]
FIG. 1 is a schematic configuration diagram for explaining the configuration of the system according to the first embodiment of the present invention. The system shown in FIG. 1 includes an engine 10. An engine 10 shown in FIG. 1 is a spark ignition type four-cycle reciprocating engine.

  The engine 10 includes four cylinders 56. The cylinder 56 is formed in the cylinder block 55. Each cylinder 56 is provided with a spark plug 48. In the present invention, the number of cylinders and the cylinder arrangement are not limited to this.

  A flywheel 50 is attached to an end portion of a crankshaft (not shown) provided in the engine 10. When combustion occurs, the crankshaft rotates and the flywheel 50 rotates accordingly. A crank angle sensor 52 is provided in the vicinity of the flywheel 50 in order to detect the rotation of the flywheel 50.

  An intake passage 11 is connected to the cylinder 56. The intake passage 11 includes an air cleaner 12 at the inlet. An air flow sensor 14 is provided in the intake passage 11 downstream of the air cleaner 12 in order to detect the intake air amount. An electronically controlled throttle valve 16 is provided in the intake passage 11 downstream of the air flow sensor 14.

  An exhaust passage 54 is connected to the cylinder 56. An air-fuel ratio sensor 58 is attached in the exhaust passage 54, and a catalyst 60 is further provided downstream thereof. The air-fuel ratio sensor 58 here is an air-fuel ratio sensor in a broad sense. Specifically, it may be an oxygen sensor or an all-range air-fuel ratio sensor.

  The engine 10 in the present embodiment is a bi-fuel engine that can supply two types of fuel. Of the two types of fuel, one is liquid fuel gasoline and the other is gaseous fuel CNG. Since these fuels are supplied separately, these fuels are not supplied simultaneously. The engine 10 includes two independent fuel systems for supplying these fuels. Hereinafter, the structure of each fuel system will be described in detail.

  The structure of the fuel system for supplying gasoline will be described. The gasoline is stored in the gasoline tank 42. The gasoline tank 42 is provided with a level sensor 43 for measuring the remaining amount of stored gasoline. A gasoline supply passage 46 is attached to the gasoline tank 42 in order to supply gasoline from the inside of the gasoline tank 42 to the outside. A feed pump 44 is provided in the gasoline supply passage 46. A gasoline delivery pipe 22 is connected to the end of the gasoline supply passage 46. The gasoline delivery pipe 22 is provided with gasoline injectors 26 according to the number of cylinders 56. The gasoline injector 26 is installed so that the injection port faces the intake passage 11.

  A fuel system for supplying CNG will be described. CNG is filled in the CNG tank 36. A CNG supply passage 40 is attached to the CNG tank 36. A CNG supply passage 40 near the CNG tank 36 is provided with a supply passage pressure sensor 32 and a supply passage temperature sensor 34 in order to measure the remaining amount of CNG. A regulator 30 is provided in the CNG supply passage 40 downstream of the supply passage pressure sensor 32 and the supply passage temperature sensor 34. The regulator 30 is provided to adjust the downstream pressure to be constant. A CNG delivery pipe 28 is provided at the end of the CNG supply passage 40 downstream of the regulator 30. The delivery pipe 28 for CNG is provided with a pressure sensor 18 inside the delivery pipe and a temperature sensor 20 inside the delivery pipe. The CNG delivery pipe 28 is provided with CNG injectors 24 according to the number of cylinders 56. The CNG injector 24 is installed so that the injection port faces the intake passage 11.

  The system configuration of the first embodiment includes an ECU 100 (Engine Control Unit) that controls the operating state of the engine 10. On the input side of the ECU 100, an air flow sensor 14, a delivery pipe pressure sensor 18, a delivery pipe temperature sensor 20, a supply passage pressure sensor 32, a supply passage temperature sensor 34, a level sensor 43, a crank angle sensor 52, and an empty Various sensors such as the fuel ratio sensor 58 are electrically connected to each other. ECU 100 detects the operating state of engine 10 based on signals input from various sensors. For example, the ECU 100 calculates the engine speed based on the output value from the crank angle sensor 52. The ECU 100 calculates the intake air amount based on the output value of the air flow sensor 14. ECU 100 calculates the load factor based on the engine speed and the intake air amount. The ECU 100 calculates the air / fuel ratio (A / F) based on the output value of the air / fuel ratio sensor 58.

  Various actuators such as a throttle valve 16, a CNG injector 24, a gasoline injector 26, a feed pump 44, and a spark plug 48 are electrically connected to the output side of the ECU 100. The ECU 100 outputs signals for operating various actuators according to the operating state. For example, the ECU 100 changes the opening degree of the throttle valve 16 in order to obtain an intake air amount corresponding to the operating state. The ECU 100 adjusts the opening timing of the injection port of the CNG injector 24 or the gasoline injector 26 in order to obtain a fuel injection amount corresponding to the operating state. Hereinafter, a flow in which gasoline and CNG are supplied to the engine 10 when the ECU 100 operates various actuators in each fuel system will be described in detail.

  A flow in which gasoline is supplied to the engine 10 will be described. The gasoline in the gasoline tank 42 is pumped from the gasoline tank 42 to the gasoline supply passage 46 when the feed pump 44 is operated. The pumped-up gasoline is supplied to the gasoline delivery pipe 22 from the gasoline supply passage 46. The gasoline in the gasoline delivery pipe 22 is injected toward the intake passage 11 when the injection port of the gasoline injector 26 is opened. At this time, the ECU 100 calculates the valve opening timing of the gasoline injector 26 from the fuel injection amount corresponding to the operating state, and drives the gasoline injector 26 according to the valve opening timing. The injected gasoline is supplied into the cylinder 56 together with fresh air and used for combustion.

  A flow in which CNG is supplied to the engine 10 will be described. The CNG in the CNG tank 36 is supplied to the CNG delivery pipe 28 after passing through the CNG supply passage 40. CNG in the CNG delivery pipe 28 is injected toward the intake passage 11 when the injection port of the CNG injector 24 is opened. At this time, the ECU 100 calculates the valve opening timing of the CNG injector 24 based on the fuel injection amount corresponding to the operating state and the respective outputs from the delivery pipe pressure sensor 18 and the delivery pipe temperature sensor 20, and the opening timing is calculated. The CNG injector 24 is driven according to the valve timing. The injected CNG is supplied into the cylinder 56 together with fresh air and used for combustion.

  In the engine 10 in the present embodiment, fuel property learning control (hereinafter simply referred to as “learning control”) is performed by air-fuel ratio feedback control. Specifically, first, the air-fuel ratio sensor 58 detects the oxygen concentration contained in the exhaust gas generated when gasoline or CNG is burned. Next, the ECU 100 calculates the air / fuel ratio based on the oxygen concentration detected by the air / fuel ratio sensor 58. The ECU 100 learns the fuel properties based on the deviation between the calculated air-fuel ratio and the target air-fuel ratio. More specifically, a feedback correction coefficient suitable for the properties of the currently used fuel is learned from the deviation of the air-fuel ratio. By performing the learning control, it is possible to perform the optimal combustion according to the change in the fuel property.

  However, in the learning control described above, the learning value cannot be calculated until the output value of the air-fuel ratio sensor 58 is stabilized after the combustion is started after the engine is started. In addition, the air-fuel ratio sensor 58 used for learning control is activated by warming up. For this reason, it is not possible to calculate the learning value for the currently supplied fuel immediately after the cold start until the warm-up is completed. For this reason, when the engine is started, combustion is performed based on the learned value learned during the previous operation. Then, when fuel is replenished between the previous operation and the current start, the difference in fuel properties before and after replenishment may cause the startability to deteriorate due to the difference.

  The above-mentioned problem is a problem that occurs both in an engine that uses a single type of fuel and in a bi-fuel engine like this embodiment. However, in the case of a bi-fuel engine, either one of the fuels may not be replenished. In such a case, it is possible to start with fuel that has not been replenished. Further, even when both are replenished, the fuel with the smaller change in fuel properties before and after replenishment can be used for starting.

  Accordingly, in the present invention, when the engine is started when fuel is replenished, the internal combustion engine is started with the fuel having the larger proportion of the fuel before replenishment contained in the fuel after replenishment. Thereby, it is possible to start using the fuel having the smaller change in the fuel property. As a result, deterioration of startability can be suppressed. Below, the process specifically performed by ECU100 is demonstrated.

[Starting control routine]
FIG. 2 is a flowchart of a control routine executed by the ECU 100 when the engine 10 is started in the present embodiment. In the routine shown in FIG. 2, it is first determined whether or not fuel has been replenished (S100). In S100, first, the ECU 100 determines whether or not gasoline has been refueled. The ECU 100 determines whether or not there is a difference in the output value of the level sensor 43 before and after starting. If there is a difference, it is determined that gasoline has been refueled. If there is no difference, it is determined that gasoline is not being refueled. Next, similarly, the ECU 100 determines whether or not CNG is filled. The ECU 100 determines whether there is a difference between the output values of the supply passage pressure sensor 32 and the supply passage temperature sensor 34 before and after the start. If there is a difference, it is determined that CNG filling has been performed. If there is no difference, it is determined that CNG is not filled. In this way, it is determined whether or not the fuel for both gasoline and CNG has been replenished.

  If it is determined in S100 that fuel has not been replenished, that is, both gasoline and CNG have not been replenished, this routine ends.

  On the other hand, if it is determined in S100 that fuel has been replenished, that is, at least one of gasoline and CNG has been replenished, it is determined whether or not the proportion of remaining fuel is greater for CNG than for gasoline. (S102). In S102, first, the ECU 100 calculates the ratio of remaining fuel in gasoline and CNG. The ratio of the remaining fuel here is a value obtained by dividing the fuel remaining before replenishment by the fuel after replenishment. For example, if 10 L of gasoline remains before replenishment and the gasoline becomes 50 L after replenishment, 10/50 = 0.2 is calculated, and this numerical value of 0.2 is the ratio of the remaining fuel in the gasoline It becomes. Similarly, the ratio of remaining CNG fuel is also calculated. By calculating the ratio of these remaining fuels, the ratio of the fuel before replenishment contained in the fuel after replenishment can be grasped. Next, the ECU 100 compares the ratio of the gasoline remaining fuel ratio and the CNG remaining fuel ratio. This makes it possible to predict the fuel with the larger change in fuel properties before and after replenishment. Note that when only one of gasoline and CNG is replenished, the ratio of the remaining fuel to the unsupplied fuel is 1.

  In S102, when it is determined that the proportion of fuel before replenishment in the fuel after replenishment is larger than gasoline, that is, the proportion of remaining fuel in CNG is larger than the proportion of remaining fuel in gasoline. In this case, starting by CNG is performed (S104). As a result, the engine can be started using CNG, which is the fuel with less change in fuel properties. As a result, it is possible to suppress the deterioration of drivability at the start. Next, it is determined whether or not the learning control of the CNG property is finished (S106). In this specification, the end of learning control means that the standard deviation (variation) of the most recent predetermined number of learning values calculated by learning control is equal to or less than a reference value. If it is determined that the learning control has not ended, this step is repeated.

  On the other hand, if it is determined in S102 that the gasoline is CNG or more with respect to the ratio of the fuel before replenishment in the fuel after replenishment, that is, if the ratio of the remaining fuel of gasoline is equal to or greater than the ratio of the remaining fuel of CNG, Is started (S108). As a result, it is possible to start using gasoline, which is the fuel with less change in fuel properties. As a result, it is possible to suppress the deterioration of drivability at the start. Next, it is determined whether or not the gasoline property learning control is finished (S110). If it is determined that the learning control has not ended, this step is repeated.

  When it is determined in S106 or S110 that the learning control has been completed, it is determined whether or not it is an operation region in which fuel can be switched (S112). The operating range in which the fuel can be switched is, for example, an operating range in which the engine speed is 500 to 3000 rpm, the load factor is 20 to 60%, and the change of the throttle valve 16 is within 5%, that is, low to medium speed and low This is a medium load operating range. By performing switching in an operation region suitable for such switching, it is possible to reduce a shock at the time of switching.

  If it is determined in S112 that the operation region is not capable of fuel switching, this step is repeated.

  On the other hand, if it is determined in S112 that the operation region can be switched, it is determined whether there is a CNG operation request (S114). The CNG operation request is, for example, a signal output when the driver turns on a fuel switching selection switch. However, the CNG driving request is not limited to that by the driver. For example, the case where the ECU 100 switches the fuel according to the operating state is also included.

  If it is determined in S114 that there is a CNG operation request, it is determined whether or not the CNG operation is currently being performed (S116). When it is determined that the CNG operation is not currently being performed, the operation is switched to the CNG operation (S118).

  If it is determined in S116 that the CNG operation is being performed, or if the CNG operation is switched in S118, the CNG operation is executed (S120).

  Next, it is determined whether or not the CNG property learning control has ended (S122). If it is determined that the learning control has not ended, this step is repeated. When it is determined that the learning control has ended, this routine ends.

  On the other hand, when it is determined in S114 that there is no CNG operation request, it is determined whether or not the gasoline operation is currently being performed (S124). If it is determined that the gasoline operation is not currently being performed, the operation is switched to the gasoline operation (S126).

  If it is determined in S124 that the gasoline operation is being performed, or if the gasoline operation is switched in S126, the gasoline operation is executed (S128).

  Next, it is determined whether or not the gasoline property learning control is finished (S130). If it is determined that the learning control has not ended, this step is repeated. When it is determined that the learning control has ended, this routine ends.

  In the present embodiment, as shown in FIG. 1, the configuration in which both the CNG injector 24 and the gasoline injector 26 are port injection type has been described, but the present invention is not limited to this. For example, at least one of the CNG injector 24 and the gasoline injector 26 may be an in-cylinder injection type engine configuration.

  In addition, although gasoline has been described as an example of liquid fuel, the present invention is not limited to this. For example, the present invention may be applied to a bi-fuel engine that uses alcohol or a mixture of gasoline and alcohol.

  Moreover, although CNG was mentioned as an example and demonstrated as gaseous fuel, it is not limited to this. For example, the present invention may be applied to a bi-fuel engine using liquefied petroleum gas (LPG), hydrogen, dimethyl ether (DME), or the like.

10 Engine 14 Air Flow Sensor 16 Throttle Valve 22 Gasoline Delivery Pipe 24 CNG Injector 26 Gasoline Injector 28 CNG Delivery Pipe 32 Supply Passage Pressure Sensor 34 Supply Passage Temperature Sensor 36 CNG Tank 40 CNG Supply Passage 42 Gasoline Tank 43 Level Sensor 44 Feed pump 46 Gasoline supply passage 52 Crank angle sensor 58 Air-fuel ratio sensor 100 ECU

Claims (6)

In a fuel injection control device for a bi-fuel internal combustion engine that uses a first fuel and a second fuel having different properties as supply fuels,
When at least one of the first fuel and the second fuel is replenished, the fuel with the larger proportion of the fuel before replenishment included in the fuel after replenishment when starting the engine after replenishment is used. A fuel injection control device for a bi-fuel internal combustion engine characterized by starting an internal combustion engine.   2. The switching from the fuel used at the time of starting to the other fuel is performed in an operation region set based on at least one of the engine speed, the load factor, and the amount of change in throttle. A fuel injection control device for a bi-fuel internal combustion engine.   After starting the engine, in the air-fuel ratio feedback control based on the output of the air-fuel ratio sensor provided in the exhaust passage, learning of the properties of the fuel used at the start is performed and switching to the other fuel until the learning is completed The fuel injection control device for a bi-fuel internal combustion engine according to claim 1 or 2, wherein   After switching from the fuel used at the time of starting to the other fuel, in the air-fuel ratio feedback control based on the output of the air-fuel ratio sensor provided in the exhaust passage, learning of the properties of the fuel after switching is performed. Item 4. The fuel injection control device for a bi-fuel internal combustion engine according to any one of Items 1 to 3.   The fuel injection control device for a bi-fuel internal combustion engine according to any one of claims 1 to 4, wherein the first fuel is a liquid fuel.   The fuel injection control device for a bifuel internal combustion engine according to any one of claims 1 to 5, wherein the second fuel is a gaseous fuel.

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