JP4802881B2 - Fuel supply device for internal combustion engine - Google Patents

Description

  The present invention relates to a fuel supply device for an internal combustion engine.

In recent years, an internal combustion engine that uses gaseous fuel such as CNG (Compressed Natural Gas) as a fuel for the internal combustion engine (hereinafter also referred to as “CNG engine”) or a plurality of fuels (for example, CNG, gasoline, etc.) An internal combustion engine (hereinafter also referred to as “bi-fuel engine”) that can be switched and used has been proposed.

  By the way, when a CNG engine is restarted after a short time stop of an internal combustion engine, or when gasoline is used as a fuel in a bi-fuel engine, a delivery pipe (hereinafter referred to as “fuel supply”) that supplies CNG to a fuel injection valve. In some cases, the temperature of CNG remaining inside the tube is excessively increased by radiation heat from the internal combustion engine. In such a case, there is a possibility that the normal operation of the fuel injection valve is hindered by excessively increasing the pressure inside the delivery pipe.

In this regard, in a bi-fuel engine in which CNG and gasoline can be selected and used, when gasoline is used as fuel, CNG is injected from the fuel injection valve and the fuel is extracted to remove the fuel. A technique for reducing the injection pressure has also been proposed (see, for example, Patent Document 1).
JP 2003-314317 A JP 2004-346904 A JP 2004-36458 A JP 9-317513 A

  However, if the fuel is withdrawn from the fuel injection valve for injecting CNG over the period when gasoline is used as the fuel for the internal combustion engine as in the above prior art, the CNG is changed when the fuel is switched to CNG. You have to wait until the pressure rises to a pressure where it can be injected. For this reason, the response at the time of switching the fuel deteriorates, and there are cases where the fuel is not switched smoothly or the internal combustion engine is not started smoothly.

  The present invention has been made in view of the above-described prior art, and an object of the present invention is to suppress an excessive increase in the pressure inside the fuel supply pipe in an internal combustion engine that can use gaseous fuel as fuel. Thus, it is to provide a technique capable of more smoothly supplying fuel to the internal combustion engine.

In order to achieve the above object, the fuel supply device for an internal combustion engine of the present invention employs the following means. That is, the fuel supply device for an internal combustion engine according to the present invention comprises:
A gaseous fuel injection valve for injecting gaseous fuel as fuel for the internal combustion engine;
A gaseous fuel supply pipe for supplying the gaseous fuel to the gaseous fuel injection valve;
A communication passage communicating the intake passage of the internal combustion engine and the gaseous fuel supply pipe;
Gaseous fuel introduction means for causing the gaseous fuel inside the gaseous fuel supply pipe to flow through the communication passage and lead to the intake passage when the pressure of the gaseous fuel supply pipe is higher than a predetermined pressure;
It is characterized by providing.

  In the fuel supply apparatus for an internal combustion engine configured as described above, the gaseous fuel stored in the fuel tank is regulated and stored in the gaseous fuel supply pipe, and then supplied to the gaseous fuel injection valve. And in the state where the gaseous fuel is continuously injected from the gaseous fuel injection valve, the gaseous fuel inside the gaseous fuel supply pipe is always replaced with new gaseous fuel, so that the internal combustion engine can be used for a short period of time. Even if it receives the radiant heat of the engine or the like, there is no possibility that the temperature of the gaseous fuel will rise excessively.

  However, for example, in a state where the gaseous fuel stays inside the gaseous fuel supply pipe, the gaseous fuel may be excessively heated by radiant heat from the internal combustion engine. In such a case, the internal pressure in the gaseous fuel supply pipe excessively rises due to thermal expansion of the gaseous fuel, which may make it difficult to open the gaseous fuel injection valve. In addition, the gaseous fuel in this invention can illustrate CNG (compressed natural gas), for example.

  On the other hand, the fuel supply device for an internal combustion engine according to the present invention includes a communication passage that connects the intake passage and the gaseous fuel supply pipe. The gaseous fuel introducing means causes the gaseous fuel inside the gaseous fuel supply pipe to flow through the communication passage and guide it to the intake passage when the pressure of the gaseous fuel supply pipe is higher than a predetermined pressure. As a result, the internal pressure of the gaseous fuel supply pipe can be reduced by reducing the residual amount of the gaseous fuel in the gaseous fuel supply pipe.

  Thereby, it can suppress that the internal pressure of the said gaseous fuel supply pipe becomes higher than predetermined pressure, and can operate the said gaseous fuel injection valve more smoothly. Further, there is no possibility that the gaseous fuel leaks from the gaseous fuel injection valve due to excessive increase in the internal pressure of the gaseous fuel supply pipe.

  In order to guide the gaseous fuel from the gaseous fuel supply pipe to the intake passage, for example, a communication portion between the gaseous fuel supply pipe and the communication passage, a middle of the communication passage, or the communication passage and the intake passage. An open / close valve may be provided at a communication portion or the like, and the open / close valve may be opened / closed according to the pressure of the gaseous fuel supply pipe.

  In the fuel supply device for an internal combustion engine according to the present invention, the gaseous fuel can be guided to the intake passage using a pressure difference between the intake passage and the gaseous fuel supply pipe. Therefore, it is not necessary to repressurize the gaseous fuel, such as when returning the gaseous fuel to the fuel tank.

  The predetermined pressure is an upper limit pressure allowed for the gaseous fuel supply pipe for smoothly operating the gaseous fuel injection valve, and may be obtained experimentally in advance. Further, the predetermined pressure is, for example, preset and higher than the pressure at which the gaseous fuel flows from the fuel tank of the internal combustion engine into the gaseous fuel supply pipe, and malfunction may occur in the gaseous fuel injection valve. The pressure may be a pressure that allows for a predetermined margin.

  In addition, the gaseous fuel introduction means supplies the gaseous fuel over a period from when the internal pressure of the gaseous fuel supply pipe becomes higher than the predetermined pressure until it becomes equal to or lower than a second predetermined pressure lower than the predetermined pressure. The gas fuel supply pipe may lead to the intake passage.

Here, even if the gaseous fuel in the gaseous fuel supply pipe is heated by the radiant heat of the internal combustion engine or the like, the internal pressure of the gaseous fuel supply pipe operates on the gaseous fuel injection valve for the time being. It may be a pressure that does not reach a pressure at which a defect may occur. For example, the second predetermined pressure may be an upper limit pressure set when the gaseous fuel is regulated and supplied from the fuel tank to the gaseous fuel supply pipe.

  Then, after the internal pressure of the gaseous fuel supply pipe has sufficiently decreased, there is no possibility that the gaseous fuel injection valve will be difficult to open, so the gaseous fuel can be injected from the gaseous fuel injection valve. . Further, the gaseous fuel introduced into the intake passage by the gaseous fuel introduction means can be used as fuel for combustion of the internal combustion engine, and fuel consumption for combustion of the internal combustion engine is deteriorated. It becomes possible to suppress.

  When the internal combustion engine is stopped and restarted and the pressure of the gaseous fuel supply pipe is higher than the predetermined pressure, the gaseous fuel is introduced into the intake passage by the gaseous fuel introducing means. You may guide.

  That is, when the internal combustion engine is stopped, the gaseous fuel stays inside the gaseous fuel supply pipe without being injected from the gaseous fuel injection valve. In such a case, the temperature may be excessively increased by radiant heat from the internal combustion engine. For example, when the internal combustion engine is stopped for a short period after continuing high-speed running and then restarted, etc. The temperature of the gaseous fuel is often very high.

  On the other hand, in the fuel supply apparatus for an internal combustion engine according to the present invention, when the pressure of the gaseous fuel supply pipe is higher than the predetermined pressure when the internal combustion engine is stopped and restarted, the gaseous fuel introduction is performed. By means, the pressure of the gaseous fuel supply pipe can be reduced. Therefore, the opening / closing operation of the gaseous fuel injection valve can be performed more smoothly.

Further, in the fuel supply device for an internal combustion engine according to the present invention, a fuel introduction amount estimation means for estimating an introduction amount of the gaseous fuel guided from the gaseous fuel supply pipe to the intake passage by the gaseous fuel introduction means,
Gaseous fuel injection amount correction means for correcting the injection amount of the gaseous fuel injected from the gaseous fuel injection valve based on the introduction amount of the gaseous fuel estimated by the fuel introduction amount estimation means;
May be provided.

  As described above, the gaseous fuel introduced from the gaseous fuel supply pipe to the intake passage by the gaseous fuel introducing means can be used as fuel for combustion of the internal combustion engine. Therefore, the gaseous fuel injection amount correction means corrects the injection amount of the gaseous fuel injected from the gaseous fuel injection valve based on the introduction amount of the gaseous fuel estimated by the fuel introduction amount estimation means.

  That is, the injection amount of the gaseous fuel newly injected from the gaseous fuel injection valve can be corrected to be reduced in accordance with the introduced amount of the gaseous fuel introduced into the intake passage by the gaseous fuel introduction means. As a result, it is possible to suppress deterioration of fuel consumption and emission and so-called torque level difference caused by excessive gas fuel being supplied to the combustion chamber of the internal combustion engine.

  In addition, the fuel introduction amount estimation means is configured to control the gaseous fuel based on a change in internal pressure or temperature in the gaseous fuel supply pipe when the gaseous fuel is introduced into the intake passage by the gaseous fuel introduction means. The amount introduced may be estimated.

Further, the present invention can be applied to an internal combustion engine that can be used by switching a plurality of fuels as long as gaseous fuel can be used as the fuel of the internal combustion engine, and the following configurations can be exemplified. . That is, the fuel supply device for an internal combustion engine in the present invention is
The internal combustion engine can be used by switching a plurality of fuels including at least the gaseous fuel, and individual fuel supply means for supplying the plurality of fuels to the internal combustion engine for each of the plurality of fuels With
In the case where any one of the plurality of fuels is supplied to the internal combustion engine by the fuel supply means, before the fuel supplied to the internal combustion engine is switched to the gaseous fuel, the gaseous fuel introduction means may Fuel may be guided to the intake passage.

  According to the above configuration, the fuel supply means for supplying the fuel to the internal combustion engine is provided for each of the plurality of fuels. Therefore, even when the internal combustion engine is in operation, the gaseous fuel may not be continuously injected from the gaseous fuel injection valve in a state where the fuel is supplied from any of the plurality of fuel supply means. The gaseous fuel staying in the gaseous fuel supply pipe may be excessively heated and the internal pressure of the gaseous fuel supply pipe may be higher than the predetermined pressure.

  On the other hand, according to the present invention, before the fuel supplied to the internal combustion engine is switched to the gaseous fuel, the gaseous fuel can be guided to the intake passage by the gaseous fuel introducing means. Therefore, it is possible to switch the fuel to the gaseous fuel after sufficiently reducing the pressure of the gaseous fuel supply pipe, so that the opening and closing operation of the gaseous fuel injection valve can be performed more smoothly.

  In the present invention, examples of the plurality of fuels including at least the gaseous fuel include a combination of CNG and gasoline. Further, the types of the fuels themselves do not have to be different from the plurality of fuels. Therefore, only CNG is used as the fuel, and the present invention can be applied even when the CNG is individually supplied from a plurality of fuel supply systems. In such a case, a communication passage that connects the gaseous fuel supply pipe and the intake passage may be provided for each fuel supply system. Examples of the fuel supply means include a fuel injection valve (injector) and a carburetor (carburetor).

  By the way, when the plurality of fuels are, for example, a combination of CNG and gasoline, and the pressure of the gaseous fuel supply pipe is higher than the predetermined pressure when the internal combustion engine is stopped and restarted, Gasoline may be selected as the fuel for the internal combustion engine.

  In such a case, even if the pressure of the gaseous fuel supply pipe is being reduced by guiding the gaseous fuel to the intake passage by the gaseous fuel introduction means, the gasoline is removed from the fuel supply means. The internal combustion engine can be supplied. Therefore, the internal combustion engine can be started more quickly.

Further, in the present invention, a fuel introduction amount estimation means for estimating an introduction amount of the gaseous fuel guided from the gaseous fuel supply pipe to the intake passage by the gaseous fuel introduction means,
A fuel supply amount correction unit that corrects the supply amount of any of the plurality of fuels by the fuel supply unit based on the introduction amount of the gaseous fuel estimated by the fuel introduction amount estimation unit may be provided.

  Accordingly, the supply amount of any of the plurality of fuels can be corrected to decrease in accordance with the introduction amount of the gaseous fuel guided to the intake passage. As a result, it is possible to suppress deterioration of fuel consumption and emission due to excessive fuel being supplied to the combustion chamber of the internal combustion engine and so-called torque step.

According to the present invention, in an internal combustion engine that can use gaseous fuel as fuel, it is possible to suppress the pressure inside the fuel supply pipe from rising excessively and to supply the fuel more smoothly to the internal combustion engine.

  The best mode for carrying out the present invention will be exemplarily described in detail below with reference to the drawings. It should be noted that the dimensions, materials, shapes, relative arrangements, and the like of the components described in this embodiment are intended to limit the technical scope of the invention only to those unless otherwise specified. is not.

  FIG. 1 is a diagram illustrating a schematic configuration of an internal combustion engine 1 including a fuel supply device according to the present embodiment and a fuel supply system thereof. In FIG. 1, the internal combustion engine 1 and a part of its exhaust system are omitted.

  The internal combustion engine 1 is a four-cylinder CNG fuel engine having four cylinders 2. An intake branch pipe 3 is connected to the internal combustion engine 1, and each branch pipe of the intake branch pipe 3 communicates with a combustion chamber of each cylinder 2 via an intake port (not shown).

  The internal combustion engine 1 is also provided with a CNG fuel tank 30 filled with high-pressure CNG fuel. The CNG fuel tank 30 is connected to one end of a CNG fuel supply passage 31, and the other end of the CNG fuel supply passage 31 is connected to a CNG delivery pipe 32.

  A regulator 33 is provided in the CNG fuel supply passage 31, and the pressure of the CNG fuel is adjusted to a pressure within a preset range by the regulator 33. In the CNG fuel supply passage 31, a CNG pressure sensor 31a and a CNG temperature sensor 31b are arranged between the CNG fuel tank 30 and the regulator 33, and the remaining CNG is detected by the CNG pressure sensor 31a and the CNG temperature sensor 31b. The amount is detected. A CNG fuel injection valve 35 is attached to each intake branch pipe 3 leading to each cylinder 2, and each CNG fuel injection valve 35 is connected to a CNG delivery pipe 32.

  With such a configuration, the CNG fuel filled in the CNG fuel tank 30 is supplied to the CNG delivery pipe 32 through the CNG fuel supply passage 31. The CNG fuel is supplied from the CNG delivery pipe 32 to each CNG fuel injection valve 35. The CNG fuel injection valve 35 supplies the CNG fuel supplied from the CNG delivery pipe 32 to the branch pipes of the intake branch pipe 3 by the valve opening operation, and stops the supply by the valve closing operation. Accordingly, the CNG delivery pipe 32 corresponds to a gaseous fuel supply pipe in this embodiment.

  The CNG delivery pipe 32 is provided with a CNG delivery pipe pressure sensor 32a for detecting the pressure in the CNG delivery pipe 32 and a CNG delivery pipe temperature sensor 32b for detecting the temperature in the CNG delivery pipe 32. ing. Further, the CNG delivery pipe 32 and the intake branch pipe 3 communicate with each other via a relief pipe 36. The connection portion of the relief pipe 36 to the CNG delivery pipe 32 is normally closed and opened when necessary. A relief valve 37 is provided.

  When the pressure in the CNG delivery pipe 32 detected by the CNG delivery pipe pressure sensor 32a excessively rises, the relief valve 37 is opened to relieve the CNG fuel to the intake branch pipe 3. . As a result, the residual amount of gaseous fuel in the CNG delivery pipe 32 is reduced, and the pressure of the CNG delivery pipe 32 is reduced. Therefore, the CNG delivery pipe 32, the relief pipe 36, and the relief valve 37 constitute a part of the gaseous fuel introduction means in this embodiment.

  Next, the intake branch pipe 3 is connected to an intake pipe 4, and the intake pipe 4 is connected to an air cleaner box 5. An air flow meter 6 that outputs an electrical signal corresponding to the amount of intake air flowing through the intake pipe 4 is attached to the intake pipe 4 downstream of the air cleaner box 5.

  An intake throttle valve 7 for adjusting the flow rate of the intake air flowing through the intake pipe 4 is provided downstream of the air flow meter 6 in the intake pipe 4.

  In the intake system of the internal combustion engine 1 configured as described above, the intake air that has flowed into the air cleaner box 5 is removed from dust, dust, and the like in the intake air by an air cleaner (not shown) in the air cleaner box 5 and then the intake pipe. 4, the flow rate is adjusted by the intake throttle valve 7 as necessary and flows into the intake branch pipe 3. The intake air flowing into the intake branch pipe 3 is distributed to the combustion chamber of each cylinder 2 through each branch pipe. And it burns by using the CNG fuel injected from each gaseous fuel injection valve 35 as an ignition source.

  On the other hand, an exhaust branch pipe 8 is connected to the internal combustion engine 1, and each branch pipe of the exhaust branch pipe 8 communicates with the combustion chamber of each cylinder 2 via an exhaust port (not shown). The exhaust branch pipe 8 is connected to the exhaust pipe 9 on the downstream side.

The internal combustion engine 1 and its fuel supply system configured as described above include an electronic control unit (ECU) 50 for controlling the internal combustion engine 1 and the fuel supply system.
Is attached. The ECU 50 is a unit that controls the operation state of the internal combustion engine 1 in accordance with the operation conditions of the internal combustion engine 1 and the driver's request, and also performs control related to the fuel supply system of the internal combustion engine 1.

  The ECU 50 supplies fuel such as sensors relating to the control of the operating state of the internal combustion engine 1 such as the air flow meter 6, CNG pressure sensor 31 a, CNG temperature sensor 31 b, CNG delivery pipe pressure sensor 32 a, CNG delivery pipe temperature sensor 32 b, etc. Sensors related to system control are connected via electrical wiring, and their output signals are input to the ECU 50.

  On the other hand, the intake throttle valve 7, the CNG fuel injection valve 35, the relief valve 37, and the like are connected to the ECU 50 through electric wiring so that the ECU 50 can control the above-described parts.

  The ECU 50 includes a CPU, a ROM, a RAM, and the like. The ROM stores a program for performing various controls of the internal combustion engine 1 and a map storing data. Here, the control for reducing the pressure in the CNG delivery pipe 32 is one of the programs stored in the ROM of the ECU 50. Therefore, the ECU 50 constitutes a part of the gaseous fuel introducing means, the fuel introduction amount estimating means, and the gaseous fuel injection amount correcting means in this embodiment.

  In the fuel supply device for an internal combustion engine configured as described above, the temperature of the CNG fuel supplied to the inside of the CNG delivery pipe 32 rises due to the radiant heat of the internal combustion engine 1 or the like. When the CNG fuel injection from the CNG fuel injection valve 35 is stopped, the CNG fuel stays in the CNG delivery pipe 32, and the temperature rise of the CNG fuel becomes significant. For example, it is conceivable that the temperature of the CNG fuel is excessively increased when the internal combustion engine 1 is stopped for a short period of time after continuing high speed travel and then restarted.

Then, the internal pressure of the CNG delivery pipe 32 rises excessively, and the CNG fuel injection valve 35
If the force with which the CNG fuel presses the valve of the CNG fuel injection valve 35 becomes larger than the force for opening the valve, the opening / closing operation of the CNG fuel injection valve 35 may not be performed smoothly.

  Therefore, in order to prevent the opening of the CNG fuel injection valve 35 from becoming difficult, in the fuel supply device for the internal combustion engine in this embodiment, when the internal pressure of the CNG delivery pipe 32 rises excessively, the CNG fuel The internal pressure of the CNG delivery pipe 32 is reduced by circulating the relief pipe 36. Below, the control for reducing the pressure in the CNG delivery pipe 32 is demonstrated.

  FIG. 2 is a flowchart showing a startup pressure reduction routine for reducing the pressure in the CNG delivery pipe 32 during startup in the fuel supply device of the internal combustion engine 1 according to this embodiment. This routine is a program stored in the ROM in the ECU 50 and is executed every time the internal combustion engine 1 is started.

  When this routine is executed, first, in S101, the pressure Pc in the CNG delivery pipe 32 is acquired based on the value detected by the CNG delivery pipe pressure sensor 32a of the internal combustion engine 1 according to this embodiment. When the processing of S101 ends, the process proceeds to S102.

  In S102, it is determined whether or not the pressure Pc in the CNG delivery pipe 32 is higher than the allowable limit pressure Pc1. Here, the allowable limit pressure Pc1 is the upper limit pressure allowed for the CNG delivery pipe 32, and is obtained experimentally in advance. Specifically, for example, a pressure that is higher than the upper limit pressure that is set when CNG fuel is regulated by the regulator 33 and that allows for a certain margin in the pressure that may cause malfunction of the CNG fuel injection valve 35 may be used. good.

  When the pressure Pc in the CNG delivery pipe 32 is equal to or lower than the allowable limit pressure Pc1, it is determined that the pressure at which it is difficult to open the CNG fuel injection valve 35 has not been reached, and this routine is temporarily terminated. On the other hand, when the pressure Pc in the CNG delivery pipe 32 is higher than the allowable limit pressure Pc1, it is determined that it is difficult to open the CNG fuel injection valve 35, and the process proceeds to S103.

  In S103, the ECU 50 fully closes the intake throttle valve 7, and in S104, the ECU 50 opens the relief valve 37. When the relief valve 37 is opened, the CNG fuel in the CNG delivery pipe 32 is relieved to the intake branch pipe 3 via the relief pipe 36. Therefore, the pressure Pc in the CNG delivery pipe 32 can be reduced. Further, when the CNG fuel is relieved to the intake branch pipe 3, the intake throttle valve 7 is fully closed in the above-described S103, so that the relieved CNG fuel flows back through the intake branch pipe 3 to the outside of the internal combustion engine 1. Is prevented from diffusing. When the process of S104 ends, the process proceeds to S105.

  In S105, the pressure Pc in the CNG delivery pipe 32 is acquired again, and it is determined whether or not the pressure Pc in the CNG delivery pipe 32 is equal to or lower than the set upper limit pressure Pc2. Here, the set upper limit pressure Pc2 is an upper limit pressure that is allowed when CNG fuel is injected from the CNG fuel injection valve 35 provided in the CNG delivery pipe 32, and may be obtained experimentally in advance. Specifically, for example, the upper limit pressure set when the CNG fuel is regulated by the regulator 33 may be used.

When the pressure Pc in the CNG delivery pipe 32 exceeds the set upper limit pressure Pc2, it is determined that the CNG fuel injection valve 35 may be difficult to open, and the state after the process of S104 is Will continue. That is, the state where the relief valve 37 is opened is continued until the pressure Pc in the CNG delivery pipe 32 becomes equal to or lower than the set upper limit pressure Pc2, and the process of reducing the pressure Pc in the CNG delivery pipe 32 is continued.

  On the other hand, when the pressure Pc in the CNG delivery pipe 32 is equal to or lower than the set upper limit pressure Pc2, there is no risk that it will be difficult to open the CNG fuel injection valve 35 even if the CNG fuel injection valve 35 is opened. The determination is made and the process proceeds to S106.

  In S106, the relief valve 37 is closed by the ECU 50. As a result, relief of CNG fuel from the CNG delivery pipe 32 to the intake branch pipe 3 is stopped, and the process of reducing the pressure Pc in the CNG delivery pipe 32 ends. When the process of S106 ends, the process proceeds to S107.

  In S107, the relief amount Rq of the CNG fuel relieved from the CNG delivery pipe 32 by the processes from S104 to S106 is acquired. Specifically, for example, the relief amount Rq may be derived from detection values obtained by the CNG delivery pipe pressure sensor 32a and the CNG delivery pipe temperature sensor 32b. Further, the relief amount Rq may be derived by reading from a map in which the relationship between the change amount of the CNG delivery pipe pressure sensor 32a and the CNG delivery pipe temperature sensor 32b and the relief amount Rq is stored. Therefore, the CNG delivery pipe pressure sensor 32a and the CNG delivery pipe temperature sensor 32b correspond to fuel introduction amount estimation means in this embodiment. When the process of S107 ends, the process proceeds to S108.

  In S108, the opening degree of the intake throttle valve 7 is adjusted by the ECU 50. The opening degree of the intake throttle valve 7 at this time is the opening degree of the intake throttle valve 7 required when the internal combustion engine 1 is started, and may be obtained experimentally in advance. Then, when the process of S108 ends, the process proceeds to S109.

  In S109, the ECU 50 obtains the CNG fuel correction amount Qrc based on the CNG fuel relief amount Rq. The CNG fuel correction amount Qrc is a fuel injection amount for correcting a CNG fuel injection amount Qbc (hereinafter referred to as “CNG basic injection amount Qbc”) injected from the CNG fuel injection valve 35 when this routine is not executed. . In this embodiment, the CNG fuel relieved in the intake branch pipe 3 is combusted in the combustion chamber (not shown), so the CNG basic injection amount Qbc is corrected to be reduced. Specifically, for example, the CNG fuel correction amount Qrc may be equal to the CNG fuel relief amount Rq. Therefore, in this embodiment, the ECU 50 constitutes part of the gaseous fuel injection amount correction means together with the CNG fuel injection valve 35.

  The above-mentioned CNG basic injection amount Qbc is necessary for setting the air-fuel ratio to a preset target air-fuel ratio (for example, stoichiometric) in accordance with the intake air amount acquired from the output signal from the air flow meter 6, for example. The fuel injection amount may be used. When the process of S109 is completed, the process proceeds to S110.

  In S <b> 110, CNG fuel of the post-CNG corrected injection amount Qc that is the corrected fuel injection amount is injected from the CNG fuel injection valve 35. When the processing of S110 ends, this routine is once ended.

As described above, the CNG fuel in the CNG delivery pipe 32 is excessively heated when the internal combustion engine 1 according to this embodiment is started, and the pressure Pc in the CNG delivery pipe 32 is changed to the CNG fuel injection valve 35. The pressure Pc in the CNG delivery pipe 32 is reduced by relieving the CNG fuel from the CNG delivery pipe 32 to the intake branch pipe 3 even when it is higher than the allowable limit pressure Pc1 that may make it difficult to open the valve. can do. Therefore, when CNG fuel is injected from the CNG fuel injection valve 35, the opening operation of the CNG fuel injection valve 35 is prevented from becoming difficult, so that fuel can be supplied to the internal combustion engine 1 more smoothly. It becomes possible. Further, since it is not necessary to remove the CNG fuel from the CNG fuel injection valve 35, it is possible to suppress the deterioration of the response when the CNG fuel is injected from the CNG fuel injection valve 35.

  Further, the CNG fuel that has been relieved in the air branch pipe 3 is used as fuel for burning the internal combustion engine 1, and the fuel injection amount that is injected from the CNG fuel injection valve 35 is corrected based on the relief amount Rq of the CNG fuel. can do. Accordingly, it is possible to suppress the deterioration of fuel consumption and emission and the occurrence of a torque step caused by supplying excessive CNG fuel to the combustion chamber of the internal combustion engine 1.

  In this embodiment, the relief valve 37 is opened to relieve the CNG fuel to the intake branch pipe 3, but this is not limited to full opening. Therefore, opening the relief valve 37 means that the opening degree of the relief valve 37 is set to an opening degree necessary for allowing the CNG fuel to flow out from the CNG delivery pipe 32 in order to reduce the pressure Pc in the CNG delivery pipe 32. It means to do.

  Next, an embodiment different from the first embodiment of the fuel supply device for the internal combustion engine 1 according to the present invention will be described. FIG. 3 is a diagram illustrating a schematic configuration of the internal combustion engine 1 including the fuel supply apparatus according to the present embodiment and a fuel supply system thereof. Here, the same or equivalent components as those of the fuel supply device of the first embodiment are denoted by the same reference numerals, and detailed description thereof is omitted.

  The internal combustion engine 1 according to the present embodiment is a so-called bi-fuel engine in which a CNG fuel system and a gasoline fuel system are separately provided as fuel supply systems, and CNG fuel and gasoline fuel can be selectively used. Hereinafter, a fuel supply apparatus of a gasoline fuel system will be mainly described.

  The internal combustion engine 1 is provided with a gasoline fuel tank 40 for storing gasoline. The gasoline fuel tank 40 is connected to a gasoline fuel supply passage 41, and the other end of the gasoline fuel supply passage 41 is connected to a gasoline fuel delivery pipe 42. The gasoline fuel supply passage 41 is provided with a pump 43 for pumping the gasoline fuel stored in the gasoline fuel tank 40 to the gasoline fuel delivery pipe 42. A gasoline fuel injection valve 45 is attached to each intake branch pipe 3 that communicates with each cylinder 2, and each gasoline fuel injection valve 45 is connected to a gasoline fuel delivery pipe 42.

  With such a configuration, the gasoline fuel in the gasoline fuel tank 40 is supplied to the gasoline fuel delivery pipe 42 through the gasoline fuel supply passage 41. The gasoline fuel is supplied from the gasoline fuel delivery pipe 42 to the gasoline fuel injection valve 45. Further, the gasoline fuel injection valve 45 supplies the gasoline fuel supplied from the gasoline fuel delivery pipe 42 by the valve opening operation to each branch pipe of the intake branch pipe 3, and stops the supply by the valve closing operation. Therefore, the gasoline fuel injection valve 45 corresponds to the fuel supply means in this embodiment.

  In the fuel supply device of the internal combustion engine configured as described above, the CNG fuel system and the gasoline fuel system are provided as the fuel supply system. Therefore, when gasoline fuel is used as the fuel of the internal combustion engine 1 Even when the internal combustion engine 1 is in operation, the state where CNG fuel is not injected from the CNG fuel injection valve 35 is continued. In the state where the CNG fuel staying in the CNG delivery pipe 32 is excessively heated and the pressure Pc in the CNG delivery pipe 32 is higher than the allowable limit pressure Pc1, the fuel of the internal combustion engine 1 is used as gasoline. When a request to change from fuel to CNG fuel is made, it may be difficult to open and close the CNG fuel injection valve 35.

  Therefore, when gasoline fuel is used as the fuel of the internal combustion engine 1 according to this embodiment and the pressure Pc in the CNG delivery pipe 32 is higher than the allowable limit pressure Pc1, the pressure Pc in the CNG delivery pipe 32 is The control to reduce is demonstrated.

  FIG. 4 shows a gasoline fuel selection pressure reduction routine for reducing the pressure Pc in the CNG delivery pipe 32 before switching the fuel from the gasoline fuel to the CNG fuel in the fuel supply device of the internal combustion engine 1 according to this embodiment. It is a flowchart. This routine is a program stored in the ROM in the ECU 50, and is executed at predetermined intervals when gasoline fuel is selected as the fuel for the internal combustion engine 1.

  S201 and S202 in this routine correspond to S101 and S102 in the above-described start time pressure reduction routine, respectively, and detailed description thereof will be omitted.

  Further, in S202, when the pressure Pc in the CNG delivery pipe 32 is equal to or lower than the allowable limit pressure Pc1, it is determined that the pressure that makes it difficult to open the CNG fuel injection valve 35 has not been reached. finish. On the other hand, when the pressure Pc in the CNG delivery pipe 32 is higher than the allowable limit pressure Pc1, it is determined that it is difficult to open the CNG fuel injection valve 35, and the process proceeds to S203.

  In S203, the relief valve 37 is opened by the ECU 50. When the relief valve 37 is opened, the CNG fuel in the CNG delivery pipe 32 is relieved to the intake branch pipe 3 via the relief pipe 36. Therefore, the pressure Pc in the CNG delivery pipe 32 can be reduced. When the process of S203 ends, the process proceeds to S204.

  In S204, the relief amount Rq of the CNG fuel relieved from the CNG delivery pipe 32 is acquired. When the process of S204 ends, the process proceeds to S205.

  In S205, the ECU 50 acquires the gasoline fuel correction amount Qrg injected from the gasoline fuel injection valve 45 based on the CNG fuel relief amount Rq. Here, the correction amount Qrg of gasoline fuel is the amount of gasoline fuel necessary to generate energy equivalent to the energy generated when the CNG fuel of the relief amount Rq burns. Therefore, the gasoline fuel correction amount Qrg is determined so that the engine generated torque does not change before and after the relief of the CNG fuel. Then, when this routine is not executed, the gasoline fuel basic injection amount Qbg is corrected by subtracting the gasoline fuel correction amount Qrg from the gasoline fuel basic injection amount Qbg injected from the gasoline fuel injection valve 45. Therefore, in this embodiment, the ECU 50 constitutes part of the fuel supply amount correction means together with the gasoline fuel injection valve 45.

  Note that the gasoline fuel basic injection amount Qbg is required to set the air-fuel ratio to a preset target air-fuel ratio (for example, stoichiometric) in accordance with the intake air amount acquired from an output signal from the air flow meter 6, for example. A good fuel injection amount is also possible. Further, when the processing of S205 ends, the process proceeds to S206.

  In S <b> 206, the gasoline fuel with the corrected gasoline injection amount Qg, which is the corrected fuel injection amount, is injected from the gasoline fuel injection valve 45. Then, when the process of S206 ends, the process proceeds to S207.

In S207, the pressure Pc in the CNG delivery pipe 32 is acquired again, and it is determined whether or not the pressure Pc in the CNG delivery pipe 32 is equal to or lower than the set upper limit pressure Pc2. When the pressure Pc in the CNG delivery pipe 32 exceeds the set upper limit pressure Pc2, it is determined that it is difficult to open the CNG fuel injection valve 35, and the state after the process of S203 is continued. Is done. That is, the state where the relief valve 37 is opened is continued until the pressure Pc in the CNG delivery pipe 32 becomes equal to or lower than the set upper limit pressure Pc2, and the process of reducing the pressure Pc in the CNG delivery pipe 32 is continued.

  On the other hand, when the pressure Pc in the CNG delivery pipe 32 is equal to or lower than the set upper limit pressure Pc2, there is no risk that it will be difficult to open the CNG fuel injection valve 35 even if the CNG fuel injection valve 35 is opened. The determination is made and the process proceeds to S208.

  In S208, the relief valve 37 is closed by the ECU 50. Thereby, the CNG fuel in the CNG delivery pipe 32 is not relieved to the intake branch pipe 3, and the process of reducing the pressure Pc in the CNG delivery pipe 32 is ended. When the processing of S208 is completed, this routine is once ended.

  As described above, even when gasoline fuel is used as the fuel for the internal combustion engine 1 according to this embodiment and the pressure Pc in the CNG delivery pipe 32 is higher than the allowable limit pressure Pc1, the fuel to be used. By executing this routine before switching to CNG fuel, the pressure Pc in the CNG delivery pipe 32 can be reduced.

  Therefore, when the fuel is switched to the CNG fuel, the pressure Pc in the CNG delivery pipe 32 is prevented from being maintained in an excessively high pressure state, and after the fuel is switched to the CNG fuel, the injection valve of the CNG fuel injection valve 35 is opened. It becomes possible to prevent the valve from becoming difficult, and to supply the fuel to the internal combustion engine 1 more smoothly. Further, since it is not necessary to remove the CNG fuel from the CNG fuel injection valve 35 during the period in which the gasoline fuel is injected from the gasoline fuel injection valve 45, the fuel for the internal combustion engine 1 is switched from gasoline fuel to CNG fuel. It is possible to suppress the deterioration of the response and smoothly switch the fuel.

  Further, the CNG fuel relieved in the intake branch pipe 3 can be used as fuel for burning the internal combustion engine 1, and the gasoline corrected based on the gasoline fuel correction amount Qrg corresponding to the relief amount Rq of the CNG fuel. The gasoline fuel with the corrected injection amount Qg can be supplied to the internal combustion engine 1. Therefore, it is possible to suppress the deterioration of fuel consumption and emission and the occurrence of a torque step due to excessive gasoline fuel being supplied to the combustion chamber of the internal combustion engine 1.

  In the internal combustion engine 1 according to the present embodiment, when the internal combustion engine 1 is started from a state where the operation of the internal combustion engine 1 is stopped, the pressure Pc in the CNG delivery pipe 32 is higher than the allowable limit pressure Pc1. The start time pressure reduction routine indicated by 2 may be executed, or the gasoline fuel selection pressure reduction routine indicated by FIG. 4 may be applied. Therefore, any of the above routines can be selected according to the fuel (CNG fuel, gasoline fuel) used for the fuel of the internal combustion engine 1. At that time, when gasoline fuel is selected as the fuel to be used for the internal combustion engine 1, the relief of the CNG fuel to the intake branch pipe 3 and the supply of the gasoline fuel to the combustion chamber can be performed simultaneously. Thus, the internal combustion engine 1 can be started quickly.

  In the present embodiment, the fuel supply apparatus according to the bi-fuel engine that can selectively use CNG fuel and gasoline fuel has been described. However, the present invention is not limited to the combination of the above fuels. For example, it can be applied to a combination of CNG fuel and LPG, hydrogen, dimethyl ether, etc., and even if the fuel to be used is only CNG fuel, the CNG fuel can be individually supplied from a plurality of different fuel supply systems. You may apply with respect to a fuel supply apparatus. Furthermore, three or more types of fuels may be used.

It is a figure which shows schematic structure of the internal combustion engine provided with the fuel supply apparatus which concerns on Example 1 of this invention, and its fuel supply system. 3 is a flowchart showing a starting pressure reduction routine in the internal combustion engine fuel supply apparatus according to the first embodiment. It is a figure which shows schematic structure of the internal combustion engine provided with the fuel supply apparatus which concerns on Example 2, and its fuel supply system. 6 is a flowchart showing a pressure reduction routine when gasoline fuel is selected in a fuel supply apparatus for an internal combustion engine according to a second embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Internal combustion engine 2 ... Cylinder 3 ... Intake branch pipe 4 ... Intake pipe 5 ... Cleaner box 6 ... Air flow meter 7 ... Intake throttle valve 8 ... Exhaust branch pipe 9 ... Exhaust pipe 30 ... CNG fuel tank 31 ... CNG fuel supply passage 31a ... CNG pressure sensor 31b ... CNG temperature sensor 32 ... CNG delivery pipe 32a ... CNG delivery pipe pressure Sensor 32b ... CNG delivery pipe temperature sensor 33 ... Regulator 35 ... CNG fuel injection valve 36 ... Relief pipe 37 ... Relief valve 40 ... Gasoline fuel tank 41 ... Gasoline fuel supply passage 42 ... gasoline fuel delivery pipe 43 ... pump 45 ... gasoline fuel injection valve 50 ... ECU

Claims (3)

A gaseous fuel injection valve for injecting gaseous fuel as fuel for the internal combustion engine;
A gaseous fuel supply pipe for supplying the gaseous fuel to the gaseous fuel injection valve;
A communication passage communicating the intake passage of the internal combustion engine and the gaseous fuel supply pipe;
The gaseous fuel inside the gas fuel supply pipe when the pressure of the gaseous fuel supply pipe is higher than the acceptable constant pressure at a pressure limit for operating the gas fuel injection valve in the communicating passage Gaseous fuel introduction means for circulating and leading to the intake passage;
An internal combustion engine fuel supply apparatus comprising:
The internal combustion engine can be used by switching a plurality of fuels including at least the gaseous fuel, and individual fuel supply means for supplying the plurality of fuels to the internal combustion engine for each of the plurality of fuels With
In the case where the fuel other than the gaseous fuel among the plurality of fuel to the internal combustion engine by said fuel supply means is supplied, when the pressure of the front SL gas fuel supply pipe is higher than the predetermined pressure, the A fuel supply device for an internal combustion engine, wherein the gaseous fuel is guided to the intake passage by gaseous fuel introduction means.   When the internal combustion engine is stopped and restarted, and when the pressure of the gaseous fuel supply pipe is higher than the predetermined pressure, the gaseous fuel is introduced into the intake passage by the gaseous fuel introducing means. The fuel supply device for an internal combustion engine according to claim 1. Fuel introduction amount estimation means for estimating the introduction amount of the gaseous fuel guided from the gaseous fuel supply pipe to the intake passage by the gaseous fuel introduction means;
The fuel supply amount correction means for correcting the supply amount of any of the plurality of fuels by the fuel supply means based on the introduction amount of the gaseous fuel estimated by the fuel introduction amount estimation means. Item 3. A fuel supply device for an internal combustion engine according to Item 1 or 2.

Images