JP2004239114A - Device and method of controlling fuel supply for bi-fuel engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To effectively utilize residual pressure in a container and elongate a cruising distance of a vehicle mounting a bi-fuel engine thereon, even when the residual pressure is a predetermined pressure or less. <P>SOLUTION: In the bi-fuel engine, a residual pressure detection sensor 141 detecting residual pressure in a gaseous fuel container 124, and a remaining amount detection sensor 142 detecting a remaining amount in a liquid fuel container 134, are provided. When the residual pressure is the predetermined pressure or less and the remaining amount is the predetermined amount or less, a control for changing ignition timing is performed so that gaseous fuel can be injected into a cylinder. Therefore, the residual gaseous fuel in the container is effectively utilized for elongating the cruising distance. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a fuel supply control device and method for a bifuel engine.
[0002]
[Prior art]
2. Description of the Related Art In recent years, gaseous fuels such as compressed natural gas (CNG) have attracted attention in automobiles and the like in place of liquid fuels such as gasoline and light oil from the viewpoint of suppressing air pollution and saving resources. However, in the case of CNG, the energy density is lower than that of gasoline or the like (about 20 to 30% of gasoline). Therefore, a vehicle equipped with an engine using CNG has a higher efficiency than a vehicle equipped with an engine using gasoline. Short cruising range. In addition, due to the delay of infrastructure development, the number of filling stations is not enough, and there is concern about long-distance travel. Therefore, a dual fuel that can supply at least one of the gaseous fuel and the liquid fuel to the engine, that is, a bifuel engine has been proposed.
[0003]
As such a bifuel engine, for example, one described in Patent Document 1 is known. When the internal pressure of the LPG cylinder drops to a predetermined pressure or lower (the remaining amount decreases), the bifuel engine is automatically switched to gasoline to continue the operation.
[0004]
Further, in the fuel supply control device for a bifuel engine described in Patent Document 2, when the remaining amount of the gaseous fuel is equal to or less than the first set value, the supply fuel is switched to the liquid fuel, and when the fuel supply is switched to the liquid fuel. I try to limit the engine output. In this manner, the driver is urged to supply gaseous fuel.
[0005]
[Patent Document 1]
JP-A-2-21368
[Patent Document 2]
JP 2002-38986 A
[0006]
[Problems to be solved by the invention]
In a bi-fuel engine, when gas such as CNG is used as fuel, in order to effectively utilize its characteristics and extend the cruising distance, it is necessary to directly inject CNG into a cylinder to perform stratified combustion. preferable. For this reason, the filling pressure (for example, 20 MPa) of CNG in a container is usually reduced to a pressure (for example, 5 MPa) that can be controlled and injected by a regulator so that the CNG can be directly injected into the cylinder. When the residual pressure in the vessel is in the range of 20 to 5 MPa, direct injection into the cylinder is possible without any problem. ₂ Can be expected to be reduced. In the stratified combustion, a rich air-fuel mixture and a lean air-fuel mixture are formed in a stratified form in a combustion chamber, and first, a portion of the rich air-fuel mixture is ignited, and the flame also burns the lean air-fuel mixture. This aims to improve the fuel consumption rate (hereinafter referred to as fuel efficiency) by burning a lean mixture as a whole while avoiding complete combustion and misfire.
[0007]
However, as described in the related art, when the remaining amount of the gaseous fuel is reduced, only by switching to the liquid fuel or limiting the engine output, the CNG of 5 MPa or less remaining in the CNG container is used. There is a problem that you can not. This is particularly remarkable in the case of long-distance operation, since, after switching to liquid fuel, if the remaining amount of the liquid fuel becomes a predetermined value or less, further cruising operation becomes impossible. .
[0008]
Therefore, an object of the present invention is to make it possible to effectively use the residual gaseous fuel even when the residual pressure of the gaseous fuel in the container becomes equal to or lower than a predetermined pressure, and to extend the cruising distance of the vehicle with the bifuel engine. It is an object of the present invention to provide an apparatus and a method for controlling a fuel supply of a bifuel engine.
[0009]
[Means for Solving the Problems]
The fuel supply control device for a bifuel engine according to one embodiment of the present invention that solves the above-described problem can independently supply and supply gaseous fuel to a cylinder and liquid fuel to an intake passage communicating with the cylinder or the cylinder. In a bi-fuel engine, residual pressure detecting means for detecting the residual pressure of the gaseous fuel in the container, residual amount detecting means for detecting the residual amount of the liquid fuel in the container, and when the residual pressure in the container is a predetermined pressure or less. And, when the remaining amount in the container is equal to or less than a predetermined amount, the injection timing is set such that the in-cylinder injection of the gaseous fuel is enabled according to the residual pressure level in the gaseous fuel container and the compression pressure in the cylinder. And in-cylinder injection timing control means for performing change control.
[0010]
According to this configuration, when the residual pressure in the container is equal to or less than the predetermined pressure and the remaining amount in the container is equal to or less than the predetermined amount, the in-cylinder injection timing control means controls the residual pressure level in the gas fuel container and the compression pressure in the cylinder. Accordingly, the injection timing is controlled so as to enable the in-cylinder injection of the gaseous fuel, so that the gaseous fuel can be injected into the cylinder even if the residual pressure in the container is equal to or lower than the predetermined pressure. As a result, the cruising distance can be extended by effectively utilizing the gaseous fuel remaining in the container.
[0011]
Further, it is preferable that the in-cylinder injection timing control means changes and controls the injection timing such that the in-cylinder injection of the gaseous fuel is completed before the compression pressure in the cylinder becomes higher than the residual pressure level.
[0012]
In this case, the gaseous fuel remaining in the container can be effectively used, and in addition, the gaseous fuel necessary for good combustion without deterioration of the emission can be reliably supplied.
[0013]
Further, the in-cylinder injection timing control means may control to change the injection timing during the compression stroke when the residual pressure in the container is higher than the maximum compression pressure in the cylinder, and during the intake stroke when the residual pressure is low.
[0014]
In this way, gaseous fuel remaining in the container can be effectively used, and in addition, stratified combustion by injection in the compression stroke and stoichiometric air-fuel ratio or homogeneous lean combustion by injection in the intake stroke can improve fuel efficiency. it can.
[0015]
Further, when the residual pressure in the container is equal to or less than a predetermined pressure and the remaining amount in the container is equal to or less than a predetermined amount, a warning unit may be provided for warning that the mode has shifted to the gas fuel residual pressure operation mode. .
[0016]
In this way, the driver can be encouraged to replenish the gaseous fuel and the liquid fuel, which is practically convenient.
[0017]
In addition, a fuel supply control device for a bifuel engine according to another embodiment of the present invention that solves the above-described problem has a gas fuel in a cylinder and a liquid fuel in a cylinder or an intake passage that communicates with the cylinder. In a bi-fuel engine capable of supplying an injection, a residual pressure detecting means for detecting a residual pressure of the gaseous fuel in the container, a residual amount detecting means for detecting a residual amount of the liquid fuel in the container, and the residual pressure in the container being predetermined. Switching pressure adjusting means for switching the supply path of the gaseous fuel and adjusting the pressure to a second predetermined pressure lower than the predetermined pressure when the remaining pressure in the container is equal to or lower than the predetermined pressure. And in-cylinder injection timing control means for changing and controlling the injection timing so that the injected gas fuel is injected into the cylinder during the intake stroke.
[0018]
According to this configuration, when the residual pressure in the container is equal to or less than the predetermined pressure and the remaining amount in the container is equal to or less than the predetermined amount, the supply path of the gaseous fuel is switched by the switching pressure adjusting means, and (2) The injection timing is adjusted by the in-cylinder injection timing control means to change the injection timing so that the adjusted gaseous fuel is injected into the cylinder during the intake stroke. As a result, the gaseous fuel remaining in the container can be more effectively used, and the cruising distance can be greatly extended. In addition, the stoichiometric air-fuel ratio or homogeneous lean combustion by injection in the intake stroke results in the effect of improving fuel efficiency because stratified combustion is not included, but control using an engine control map or the like is possible, and control can be simplified. And cost reduction can be expected.
[0019]
Furthermore, a fuel supply control device for a bi-fuel engine according to still another embodiment of the present invention that solves the above-mentioned problem is configured such that a gas fuel is provided in a cylinder, and a liquid fuel is provided in an intake passage that communicates with the cylinder or the cylinder. In a bi-fuel engine capable of injecting and supplying, the residual pressure detecting means for detecting the residual pressure in the container of the gaseous fuel, the residual amount detecting means for detecting the residual amount of the liquid fuel in the container, and the residual pressure in the container. When the pressure is equal to or less than a predetermined pressure and the remaining amount in the container is equal to or less than a predetermined amount, a pressure increasing means for increasing the pressure in the supply path of the gaseous fuel; Operation control means for performing operation.
[0020]
According to this configuration, when the residual pressure in the container is equal to or less than the predetermined pressure and the remaining amount in the container is equal to or less than the predetermined amount, the pressure in the gas fuel supply path is increased by the pressure increasing means, and the pressure is increased by the operation control means. Since the gaseous fuel operation is performed by injecting the supplied gaseous fuel into the cylinder, the gaseous fuel remaining in the container can be more effectively used without deteriorating the fuel efficiency, and the cruising distance can be greatly extended.
[0021]
The pressure increasing means may include a pressure increasing pump provided in a gas fuel supply path between a regulator provided downstream of the gas fuel container and a fuel injection valve.
[0022]
Further, the pressure increasing means may include a movable piston disposed in the gaseous fuel container and an actuator for moving the piston.
[0023]
Further, the pressurizing means may include a balloon made of a gas-permeable and highly elastic material, which is provided in the gaseous fuel container, and an air pump for supplying high-pressure air to the balloon.
[0024]
A fuel supply control method for a bi-fuel engine according to another embodiment of the present invention that solves the above-described problem is to independently supply fuel by injecting gaseous fuel into a cylinder and supplying liquid fuel to an intake passage communicating with the inside of the cylinder or the cylinder. In a possible bifuel engine, the residual pressure of the gaseous fuel in the container is detected, the remaining amount of the liquid fuel in the container is detected, and the residual pressure in the container is equal to or less than a predetermined pressure, and the residual amount in the container is at a predetermined level. When the amount is equal to or less than the fixed amount, the injection timing is changed and controlled according to the residual pressure level in the gaseous fuel container and the compression pressure in the cylinder so as to enable the in-cylinder injection of the gaseous fuel.
[0025]
Here, it is preferable that the injection timing is changed and controlled so that the in-cylinder injection of the gaseous fuel is completed before the compression pressure in the cylinder becomes higher than the residual pressure level.
[0026]
Further, when the residual pressure in the container is higher than the maximum compression pressure in the cylinder, the injection timing may be changed to a compression stroke, and when the residual pressure is lower than the maximum compression pressure in the cylinder, the injection timing may be changed and controlled.
[0027]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.
[0028]
First, an outline of a bifuel engine 100 to which the present invention is applied will be described with reference to FIG. 101 is an engine body, 102 is a cylinder block, 103 is a cylinder head, 104 is a piston, 105 is a combustion chamber, 106 is an intake port, 107 is an exhaust port, and 109 is a spark plug arranged at the top of the combustion chamber 105. Is shown. The intake port 106 is connected to a surge tank 111 via an intake manifold 110, and the surge tank 111 is connected to an air cleaner 113 via an intake duct 112. A throttle valve 115 driven by a step motor 114 is arranged in the intake duct 112. On the other hand, the exhaust port 107 is connected to a NOx storage catalytic converter 118 via an exhaust manifold 116 and an exhaust pipe 117.
[0029]
The engine 100 shown in FIG. 1 includes a gas fuel supply system and a liquid fuel supply system, and uses CNG as a gas fuel and gasoline as a liquid fuel. The gaseous fuel supply system includes a CNG injection valve 120 disposed so as to be able to inject into the combustion chamber 105 in the cylinder. The CNG injection valve 120 is connected to a CNG cylinder 124 as a gaseous fuel container mounted on the vehicle via a CNG supply pipe 122. It is connected. A fuel cutoff valve and a regulator 126 (not shown) are arranged in the CNG supply pipe 122. CNG filled in the CNG cylinder 124 at a filling pressure (for example, 20 MPa) is reduced to a predetermined set pressure PR (for example, 5 MPa) by the regulator 126. In a normal engine control state, the CNG is kept at this set pressure PR. The CNG is injected into the cylinder from the injection valve 120. The set pressure PR may be referred to as a normal injection pressure in the following description.
[0030]
Similarly, the liquid fuel supply system includes a gasoline injection valve 130 disposed so as to be able to inject into the intake passage in the intake manifold 110, and the gasoline injection valve 130 is connected to a liquid fuel container mounted on the vehicle via a gasoline supply pipe 132. It is connected to a gasoline tank 134. Note that a fuel pump (not shown) is disposed in the gasoline supply pipe 132. These CNG injection valve 120 and gasoline injection valve 130 are controlled based on output signals from electronic control unit 300, respectively. The gasoline injection valve 130 may be arranged so as to be able to directly inject into the combustion chamber 105 in the cylinder, like the CNG injection valve 120.
[0031]
The electronic control unit 300 is composed of a digital computer, and is connected to a ROM (Read Only Memory) 320, a RAM (Random Access Memory) 330, a CPU (Microprocessor) 340, and a power supply connected to each other via a bidirectional bus 310. B-RAM (backup RAM) 350, input port 360, and output port 370.
[0032]
A pressure sensor 140 that generates an output voltage proportional to the absolute pressure in the surge tank 111 is attached to the surge tank 111. In the CNG supply pipe 122 at the outlet of the CNG cylinder 124, a CNG residual pressure sensor 141 for generating an output voltage proportional to the residual CNG amount in the CNG cylinder 124, that is, the residual pressure, is disposed. A gasoline remaining amount sensor 142 that generates an output voltage proportional to the remaining gasoline amount in the inside is provided. The output voltages of these sensors 140, 141 and 142 are input to the input port 360 via the corresponding AD converter 380, respectively. The input port 360 is connected to a rotation speed sensor 143 that generates an output pulse indicating the engine rotation speed N. On the other hand, the output port 370 is connected to the ignition plug 109, the step motor 114, the CNG injection valve 120, and the gasoline injection valve 130 via the corresponding drive circuits 390, respectively.
[0033]
In the first embodiment of the present invention having the above configuration, for example, fuel is supplied to the engine 100 according to a fuel injection control routine shown in FIG. This control routine is executed by interruption every predetermined set crank angle. First, in step S21, the remaining amounts of CNG and gasoline fuel are checked. That is, the residual pressure P in the CNG cylinder 124 detected by the CNG residual pressure sensor 141 is equal to the predetermined pressure PS (in this embodiment, the regulator 126 is a pressure capable of always performing in-cylinder injection during the compression stroke regardless of the operation state. Is higher than the set pressure PR which is set to reduce the pressure, ie, the normal injection pressure is adopted), or the remaining gasoline amount V in the gasoline tank 134 detected by the gasoline remaining amount sensor 142 is determined. It is determined whether or not it is larger than a predetermined amount VS (in the present embodiment, almost 0 is adopted).
[0034]
If it is determined in step S21 that the remaining pressure P in the CNG cylinder 124 is higher than the predetermined pressure PS or the remaining gasoline amount V in the gas tank 134 is larger than the predetermined amount VS, Then, the process proceeds to step S22, where normal engine control described later is performed. On the other hand, when the residual pressure P in the CNG cylinder 124 is equal to or lower than the predetermined pressure PS and the residual gasoline amount V in the gasoline tank 134 is equal to or lower than the predetermined amount VS in the determination in step S21, the process proceeds to step S23. Enter the CNG residual pressure operation mode. At the same time, a warning light is turned on to urge the driver to replenish CNG and gasoline.
[0035]
Here, the normal engine control when the residual pressure P of CNG is higher than the predetermined pressure PS and the remaining gasoline amount V is higher than the predetermined amount VS will be described. In the engine 100 of FIG. 1, data relating to the injection timing and the injection time of the fuel injected from the CNG injection valve 120 and the gasoline injection valve 130 are respectively stored in the surge tank 111 indicating the operating state of the engine 100, for example, the engine load. As a function of the absolute pressure PM and the engine speed N, it is stored in the ROM 320 in the form of a map in advance. The CNG injection time is a time required for injecting CNG into the cylinder in a compression stroke or a suction stroke by a required amount under a set pressure PR set to be reduced by the regulator 126. The gasoline injection time is a time required for injecting gasoline into a suction passage in a suction stroke by a required amount under a constant pressure increased by a fuel pump. In the CNG operation mode, stratified combustion is performed to improve fuel efficiency, or homogeneous combustion is performed depending on operation conditions. On the other hand, in the gasoline operation mode, homogeneous combustion is performed in a stoichiometric air-fuel ratio or a lean region.
[0036]
In the fuel supply control of the engine 100 according to the present embodiment, the operation in the CNG operation mode is performed until the residual pressure P of CNG reaches the predetermined pressure PS. The mode is switched to the operation mode. Then, in the gasoline operation mode, when the remaining gasoline amount V becomes equal to or less than the predetermined amount VS, the above-described CNG residual pressure operation mode is entered. In this CNG residual pressure operation mode, since the residual pressure P of CNG is lower than the predetermined pressure PS equal to the set pressure PR of the regulator 126, the regulator 126 does not operate any longer, and the injection can be performed with the CNG residual pressure P itself. Required.
[0037]
Here, returning to the control routine of FIG. 2, after entering the CNG residual pressure operation mode, it is determined in step S24 whether or not the compression stroke injection is possible at the CNG residual pressure P. This determination is made based on the CNG residual pressure P lower than the predetermined pressure PS and the compression pressure PC in the cylinder. The compression pressure PC in the cylinder varies according to the operating state. That is, more specifically, the basic pressure waveform that maximizes the TDC position according to the compression ratio and valve timing of the engine 100 is, as shown in FIG. 3A, the magnitude of the amount of intake air confined in the cylinder, in other words, It fluctuates according to the operating state. A curve connecting the maximum values of the compression pressure PC is as shown in FIG. Here, the curve a is a curve connecting the maximum pressure values of, for example, 5 MPa corresponding to the predetermined pressure PS, the curve b is 4.5 MPa, and the curve c is 4 MPa, for example. The compression pressure PC is stored in the ROM 320 in advance in the form of a map as a function of the engine operating state.
[0038]
Therefore, in the present embodiment, the injection timing is changed and controlled in accordance with the CNG residual pressure P and the compression pressure PC so that the in-cylinder injection in the compression stroke of CNG becomes as possible as possible, thereby improving fuel efficiency. That is, the CNG residual pressure P is compared with the compression pressure PC in the engine operating state in which the control routine is executed, and if the CNG residual pressure P is in an operation region higher than the compression pressure PC, the process proceeds to step S25. The injection timing is changed and controlled to perform in-cylinder injection in the compression stroke. For example, when the maximum value of the compression pressure PC is in a light-load low-speed operation region bounded by a curve c in FIG. 3B and the CNG residual pressure P is a residual pressure corresponding to the curve b, In the operation region surrounded by the curves b and c, in-cylinder injection is performed in the compression stroke of CNG. The injection timing is controlled so that the in-cylinder injection of CNG ends before the compression pressure PC in the cylinder becomes higher than the CNG residual pressure P.
[0039]
On the other hand, if it is determined in step S24 that the in-cylinder injection in the compression stroke is not possible, the process proceeds to step S26, and the in-cylinder injection in the intake stroke with the lower CNG residual pressure P is performed. The injection timing is changed and controlled. As described above, in the first embodiment of the present invention, even when the CNG residual pressure P becomes lower than the predetermined pressure PS, the supply of the CNG fuel to the engine 100 can be continuously performed. CNG can be used effectively. Moreover, since in-cylinder injection is performed as much as possible in the compression stroke, fuel efficiency can be improved by stratified combustion, which means that the cruising distance of the vehicle equipped with the bifuel engine is increased.
[0040]
Next, a second embodiment of the present invention will be described with reference to FIGS. The second embodiment is different from the first embodiment in that when the CNG residual pressure operation mode is entered, the CNG supply path is switched and the second predetermined pressure PS ′ (which is lower than the predetermined pressure PS). For example, there is provided switching pressure adjusting means for adjusting the pressure to 0.8 MPa) and in-cylinder injection timing control means for changing and controlling the injection timing so as to inject the adjusted CNG into the cylinder during the intake stroke. The rest of the configuration is the same as that of the first embodiment, and a duplicate description will be omitted.
[0041]
Therefore, in FIG. 4, a second CNG supply pipe 123 including a second regulator 127 is provided as a switching pressure adjusting means in a form bypassing the regulator 126 of the CNG supply pipe 122, and a switching valve 129 is provided at a branch portion thereof. ing.
[0042]
In the second embodiment of the present invention, for example, fuel is supplied to the engine 100 according to a fuel injection control routine shown in FIG. This control routine is executed by interruption every predetermined set crank angle as in the first embodiment. Steps S51 to S53 are the same as steps S21 to S23 of the control routine in the first embodiment, where the remaining amounts of CNG and gasoline fuel are checked, and whether normal engine control or CNG residual pressure operation mode control is performed. Is determined. Then, in step S53, the CNG residual pressure operation mode is entered, and after the warning light is turned on, the process proceeds to step S54, and the switching valve 129 is switched to the second CNG supply pipe 123. Further, the process proceeds to step S55, in which the injection timing is adjusted so that the CNG adjusted to the second predetermined pressure PS ′ (for example, 0.8 MPa) lower than the predetermined pressure PS by the second regulator 127 is injected into the cylinder during the intake stroke. Be changed.
[0043]
In general, when the injection pressure is low to inject a gas (gas) such as CNG, the time required to inject the required amount of gas is long, but a compression pressure is generated in the intake stroke. Instead, the required amount of gas can be injected in a short time even with the injection pressure such as the second predetermined pressure PS 'having a relatively low pressure as described above. However, as a result of the injection in the intake stroke, stratified combustion cannot be performed in the combustion chamber 105, so that the effect of improving fuel efficiency is reduced. However, control using an engine control map or the like corresponding to an operation state can be performed. Can be simplified and cost reduction can be expected.
[0044]
Further, a third embodiment of the present invention will be described with reference to FIGS. The third embodiment is different from the above-described first and second embodiments in that, when the CNG residual pressure operation mode is entered, the pressure increasing means for increasing the pressure in the CNG supply path, and the increased CNG And operation control means for performing gaseous fuel operation by injecting into the cylinder. The other configurations are the same as those of the first and second embodiments, so that the same components are denoted by the same reference numerals, and redundant description will be avoided.
[0045]
Therefore, in FIG. 6, in the third embodiment of the present invention, a pressure increasing means includes a pressure increasing pump 210 disposed downstream of the regulator 126 of the CNG supply pipe 122 and a pressure sensor 212 disposed further downstream thereof. . The boost pump 210 and the pressure sensor 212 are connected to the above-described electronic control unit 300 so that the pressure of CNG boosted by the boost pump 210 becomes, for example, a predetermined pressure PS equal to the set pressure PR by the regulator 126. Feedback controlled.
[0046]
In the third embodiment of the present invention, for example, fuel is supplied to the engine 100 according to a fuel injection control routine shown in FIG. This control routine is executed by interruption every predetermined set crank angle similarly to the first and second embodiments. Steps S71 to S73 are the same as steps S21 to S23 and steps S51 to S53 of the control routine in the first and second embodiments, respectively, where the remaining amounts of CNG and gasoline fuel are checked, and normal engine control is performed. Or the CNG residual pressure operation mode control is determined. Then, in step S73, the operation enters the CNG residual pressure operation mode, the warning light is turned on, and the process proceeds to step S74. In step S74, the boost pump 210 is driven, and the residual pressure P of the CNG cylinder 124, which is lower than the predetermined pressure PS, is increased. Then, in step S75, it is determined whether or not the boosted CNG has reached the predetermined pressure PS, and in the state where the pressure has reached the predetermined pressure PS, the process proceeds to step S76, and normal CNG operation control is performed. The normal CNG operation control is a state in which the injection pressure of CNG is sufficient, and in-cylinder injection in the compression stroke can be performed at an injection timing according to the operation state.
[0047]
Further, fourth and fifth embodiments of the present invention will be described with reference to FIGS. The fourth and fifth embodiments of the present invention use still another form of the boosting means using the booster pump in the above-described third embodiment of the present invention, and are conceptually common. Will be explained. More specifically, the fourth and fifth embodiments of the present invention have a common feature in that the decrease in the pressure in the CNG cylinder 124 due to the consumption of CNG is directly compensated for by the pressure increasing means.
[0048]
That is, in the fourth embodiment of the present invention, as shown in FIG. 8, a piston 222 is slidably provided in a CNG cylinder 124, and an actuator 220 for moving the piston 222 is provided. .
[0049]
Further, in the fifth embodiment of the present invention, as shown in FIG. 9, a balloon 232 made of a gas-permeable and highly elastic material is provided in a CNG cylinder 124, and high-pressure air is supplied to the balloon 232. An air pump 230 is provided. The actuator 220 and the air pump 230 are connected to the above-described electronic control unit 300, and are feedback-controlled so that the pressure in the CNG cylinder 124 becomes the normal injection pressure based on the detection of the pressure by the CNG residual pressure sensor 141. In addition, what is supplied into the balloon 232 is not limited to high-pressure air, but may be another fluid that can be used as appropriate.
[0050]
In the fourth and fifth embodiments of the present invention, for example, fuel is supplied to the engine 100 according to a fuel injection control routine shown in FIG. This control routine is executed by interruption every predetermined set crank angle similarly to the first to third embodiments. Steps S101 to S103 are the same as steps S21 to S23, steps S51 to S53, and steps S71 to S73 of the control routine in the first to third embodiments, and a check of the remaining amount of CNG and gasoline fuel is performed. , It is determined whether the control is the normal engine control or the CNG residual pressure operation mode control. Then, in step S103, the CNG residual pressure operation mode is entered, and after the warning lamp is lit, the process proceeds to step S104, and as described above, the pressure in the CNG cylinder 124 is increased to the normal injection pressure, and the normal CNG operation is performed. Is performed.
[0051]
Here, the control in step S104 is performed by a boost / normal CNG operation control subroutine shown in FIG. That is, in step S111, the pressure P in the CNG cylinder 124 is detected by the CNG residual pressure sensor 141. Then, in step S112, it is determined whether or not the detected pressure P is higher than the normal injection pressure (this can be equal to the pressure PR set by the regulator 126 as described above). When the pressure P is lower than the normal injection pressure, the process proceeds to step S113, where the actuator 220 (or the air pump 230) is driven, and the piston 222 (or the balloon 232) is operated. Then, in step S114, the pressure P in the CNG cylinder 124 is detected again, and the process waits until the pressure P becomes higher than the normal injection pressure. When the pressure P is higher than the normal injection pressure in the determinations in step S112 and step S115, the process proceeds to step S116, and normal CNG operation is performed.
[0052]
According to the third to fifth embodiments of the present invention, the normal CNG operation in which the CNG boosted by the boosting means is injected into the cylinder during the compression stroke is performed. The CNG remaining in the CNG cylinder 124 can be more effectively used to the end, and the cruising distance can be greatly extended.
[0053]
In the embodiments described above, an example was described in which CNG was used as the gaseous fuel and gasoline was used as the liquid fuel. However, as the gaseous fuel, for example, natural gas and petroleum gas which are primary fuels, or coal conversion gas and oil conversion gas which are secondary fuels can be used. It is needless to say that hydrocarbons such as isooctane, hexane, heptane, light oil and kerosene, hydrocarbons such as butane and propane which can be stored in a liquid state, and methanol can be used as the liquid fuel.
[Brief description of the drawings]
FIG. 1 is a general diagram showing an outline of a bifuel engine to which the present invention is applied and a first embodiment.
FIG. 2 is a flowchart illustrating an example of a fuel injection control routine according to the first embodiment of the present invention.
3A is a graph showing a state of a change in a waveform of a compression pressure according to an operation state, and FIG. 3B is a graph showing a state of a change in a maximum value of a compression pressure according to an operation state.
FIG. 4 is a diagram showing a second embodiment of the present invention.
FIG. 5 is a flowchart illustrating an example of a fuel injection control routine according to a second embodiment of the present invention.
FIG. 6 is a diagram showing a third embodiment of the present invention.
FIG. 7 is a flowchart illustrating an example of a fuel injection control routine according to a third embodiment of the present invention.
FIG. 8 is a diagram showing a fourth embodiment of the present invention.
FIG. 9 is a diagram showing a fifth embodiment of the present invention.
FIG. 10 is a flowchart illustrating an example of a fuel injection control routine according to fourth and fifth embodiments of the present invention.
FIG. 11 is a flowchart illustrating an example of a subroutine for boost / normal CNG operation control in the fourth and fifth embodiments of the present invention.
[Explanation of symbols]
100 bi-fuel engine
120 CNG injection valve
124 CNG cylinder
129 Switching valve
130 Gasoline injection valve
134 gasoline tank
141 CNG residual pressure sensor
142 Gasoline level sensor
210 Boost pump
220 actuator
230 air pump
300 Electronic control unit

Claims (12)

In a bi-fuel engine, gas fuel can be injected into a cylinder, and liquid fuel can be independently injected and supplied to an intake passage communicating with the cylinder or the cylinder.
Residual pressure detecting means for detecting the residual pressure in the container of the gaseous fuel,
Remaining amount detecting means for detecting the remaining amount of the liquid fuel in the container,
When the residual pressure in the container is equal to or less than a predetermined pressure, and when the remaining amount in the container is equal to or less than a predetermined amount, the gaseous fuel in the cylinder depends on the residual pressure level in the gaseous fuel container and the compression pressure in the cylinder. In-cylinder injection timing control means for changing and controlling the injection timing so as to enable injection,
A fuel supply control device for a bifuel engine, comprising: The in-cylinder injection timing control means controls the injection timing so that the in-cylinder injection of the gaseous fuel ends before the compression pressure in the cylinder becomes higher than the residual pressure level. 2. The fuel supply control device for a bifuel engine according to claim 1. 2. The injection timing control means according to claim 1, wherein the in-cylinder injection timing control means changes the injection timing to a compression stroke when the residual pressure in the container is higher than a maximum compression pressure in the cylinder, and to an intake stroke when the residual pressure is low. 3. The fuel supply control device for a bifuel engine according to item 2. When the residual pressure in the container is equal to or less than a predetermined pressure and the remaining amount in the container is equal to or less than a predetermined amount, the apparatus further includes a warning unit that warns that the mode has shifted to the gas fuel residual pressure operation mode. Item 4. The fuel supply control device for a bifuel engine according to any one of Items 1 to 3. In a bi-fuel engine, gas fuel can be injected into a cylinder, and liquid fuel can be independently injected and supplied to an intake passage communicating with the cylinder or the cylinder.
Residual pressure detecting means for detecting the residual pressure in the container of the gaseous fuel,
Remaining amount detecting means for detecting the remaining amount of the liquid fuel in the container,
When the residual pressure in the container is equal to or less than a predetermined pressure and the remaining amount in the container is equal to or less than a predetermined amount, a switching pressure for switching the supply path of the gaseous fuel and adjusting the pressure to a second predetermined pressure lower than the predetermined pressure. Means,
In-cylinder injection timing control means for changing and controlling the injection timing so as to inject the regulated gaseous fuel into the cylinder during the intake stroke,
A fuel supply control device for a bifuel engine, comprising: In a bi-fuel engine, gas fuel can be injected into a cylinder, and liquid fuel can be independently injected and supplied to an intake passage communicating with the cylinder or the cylinder.
Residual pressure detecting means for detecting the residual pressure in the container of the gaseous fuel,
Remaining amount detecting means for detecting the remaining amount of the liquid fuel in the container,
When the residual pressure in the container is equal to or less than a predetermined pressure, and when the remaining amount in the container is equal to or less than a predetermined amount, a pressure increasing unit that increases the pressure in a supply path of the gaseous fuel,
Operation control means for performing the gas fuel operation by injecting the pressurized gas fuel into the cylinder,
A fuel supply control device for a bifuel engine, comprising: 7. The bi-fuel engine according to claim 6, wherein the pressure increasing means includes a pressure increasing pump disposed in a gas fuel supply path between a regulator and a fuel injection valve provided downstream of the gas fuel container. Fuel supply control device. 7. The fuel supply control device for a bi-fuel engine according to claim 6, wherein the pressure increasing means includes a movable piston disposed in a gaseous fuel container and an actuator for moving the piston. 7. The bi-fuel according to claim 6, wherein the pressure increasing means includes a balloon made of a highly gas-permeable and highly elastic material disposed in a gaseous fuel container, and an air pump for supplying high-pressure air to the balloon. Engine fuel supply control device. In a bi-fuel engine, gas fuel can be injected into a cylinder, and liquid fuel can be independently injected and supplied to an intake passage communicating with the cylinder or the cylinder.
Detecting the residual pressure in the container of the gaseous fuel,
Detecting the remaining amount of the liquid fuel in the container,
When the residual pressure in the container is equal to or less than a predetermined pressure and the remaining amount in the container is equal to or less than a predetermined amount, the cylinder of the gaseous fuel depends on the residual pressure level in the gaseous fuel container and the compression pressure in the cylinder. A fuel supply control method for a bi-fuel engine, characterized in that the injection timing is changed and controlled so that injection is possible. 11. The fuel for a bi-fuel engine according to claim 10, wherein an injection timing is controlled so as to terminate the in-cylinder injection of the gaseous fuel before the compression pressure in the cylinder becomes higher than the residual pressure level. Supply control method. The fuel for a bifuel engine according to claim 10 or 11, wherein the injection timing is controlled to be changed to a compression stroke when the residual pressure in the container is higher than the maximum compression pressure in the cylinder, and to an intake stroke when the residual pressure is lower than the maximum compression pressure in the cylinder. Supply control method.

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