JP2004346842A - Start control method for bi-fuel engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a start control method for a bi-fuel engine for suppressing worsening of fuel economy and the exhaust of unburnt HC by making effective use of remaining gaseous fuel even when residual pressure in a container becomes control pressure or lower. <P>SOLUTION: In the bi-fuel engine capable of performing independent injection supply of gaseous fuel into a cylinder through a gaseous fuel cylinder injection valve 120 and liquid fuel into an intake passage through a liquid fuel intake passage injection valve 130, when residual pressure in a gaseous fuel container is the control pressure of a regulator 126 or higher, the gaseous fuel is injected in a compression stroke into the cylinder by the gaseous fuel cylinder injection valve 120, and when residual pressure in the gaseous fuel container is lower than the control pressure of the regulator 126 and not lower than the cylinder injectable lowest pressure, the gaseous fuel is injected into the cylinder by the gaseous fuel cylinder injection valve 120 by changing the injection timing to start the bi-fuel engine. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a bi-fuel engine start control method.
[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. This bi-fuel engine is a bi-fuel engine that can supply at least one of gas fuel and liquid fuel to the engine. During normal operation, the bi-fuel engine supplies gas fuel to the engine and stops supplying liquid fuel, and When the gas fuel amount becomes smaller than the lower threshold value, the liquid fuel is supplied to the engine and the gas fuel supply is stopped.
[0004]
[Patent Document 1]
JP-A-11-294212
[0005]
[Problems to be solved by the invention]
By the way, in the case of using a gas such as CNG as fuel in a bi-fuel engine, in order to effectively utilize the characteristics and extend the cruising distance, in the compression stroke, CNG is injected and supplied directly into a cylinder to perform stratified combustion. Preferably. For this reason, the filling pressure PF (for example, 20 MPa) in the container of CNG is usually reduced to a pressure (for example, 5 MPa) that can be controlled and injected by a regulator so that it can be directly injected into the cylinder. . When the residual pressure in the container is in the range of 20 to 5 MPa, direct injection in the cylinder in the compression stroke is possible without any problem, and CO by super-lean combustion by stratified combustion is possible. ₂ Etc. 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.
[0006]
However, as described in the prior art, when the remaining amount of the gaseous fuel becomes lower than the lower threshold, the liquid fuel is supplied and the supply of the gaseous fuel is stopped. If the engine is operated while switching to the above, there is a problem that the gas fuel remaining in the gas fuel container and having a lower threshold value or less cannot be used. This means that the gas fuel remaining in the gas fuel container becomes a waste capacity and the utilization efficiency of the gas fuel container is low.
[0007]
In addition, in the start after switching to the liquid fuel, in general, it takes time from the supply of the liquid fuel by injection to the evaporation, that is, the vaporization, so that the injection supply amount is increased in anticipation of this. I have. Therefore, when starting by injecting such liquid fuel, an increase in unburned components due to the liquid fuel adhering to the port and the wall surface of the combustion chamber is observed, which leads to deterioration of fuel efficiency and emission of unburned HC. There's a problem. This tendency is particularly remarkable at a low temperature start.
[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, to deteriorate fuel efficiency and to discharge unburned HC. It is an object of the present invention to provide a bi-fuel engine start control method capable of suppressing the occurrence of a fuel.
[0009]
[Means for Solving the Problems]
A start control method for a bifuel engine according to one embodiment of the present invention that solves the above-mentioned problems includes a method of injecting gaseous fuel into a cylinder via a gas fuel in-cylinder injection valve and injecting liquid fuel through a liquid fuel intake passage injection valve. In a bi-fuel engine capable of independently injecting and supplying to the passage, when the residual pressure in the container of the gaseous fuel is equal to or higher than the regulated pressure of the regulator, the gaseous fuel is injected into the cylinder by the gaseous fuel in-cylinder injection valve. On the other hand, when the residual pressure in the container of the gaseous fuel is less than the regulation pressure of the regulator and is equal to or higher than the minimum in-cylinder injectable pressure, the gaseous fuel is injected by the gaseous fuel in-cylinder injection valve. It is characterized in that the fuel is injected into the cylinder by changing the injection timing and is started.
[0010]
According to this configuration, when the residual pressure in the container of the gaseous fuel is equal to or higher than the regulated pressure of the regulator, and when the pressure is less than the regulated pressure of the regulator and equal to or more than the minimum in-cylinder injectable pressure, the gaseous fuel enters the cylinder. Since the fuel is injected and started, there is no adhesion of a wall surface due to the liquid fuel, and the deterioration of fuel efficiency and the emission of unburned HC are suppressed. Further, the residual gaseous fuel can be effectively used.
[0011]
Here, at the time of the start, an injection period and a timing are determined based on the residual pressure of the gaseous fuel in the container, and the gaseous fuel is injected during the determined injection period and the timing, while the engine is warmed up at a predetermined time. After entering the state, it is preferable to switch to the operation using the liquid fuel.
[0012]
This makes it possible to easily inject gaseous fuel, and it is not necessary to increase the amount of liquid fuel, so that deterioration in fuel efficiency and emission of unburned HC are suppressed.
[0013]
A start control method for a bi-fuel engine according to another embodiment of the present invention that solves the above-mentioned problems includes a gas fuel in a cylinder through a gas fuel in-cylinder injection valve, and a liquid fuel through a liquid fuel intake passage injection valve. In a bi-fuel engine that can independently supply and supply fuel to the intake passage, a gas fuel intake passage injection valve that supplies the gas fuel to the intake passage is further provided, and a residual pressure in the container of the gas fuel is controlled by a regulator pressure. When it is above, while the gaseous fuel is started by injecting the compression stroke into the cylinder by the gaseous fuel in-cylinder injection valve, the in-cylinder residual pressure of the gaseous fuel is less than the in-cylinder injectable minimum pressure, and When the pressure is equal to or higher than the intake passage injectable minimum pressure, the gaseous fuel is injected into the intake passage by the gaseous fuel intake passage injection valve and started.
[0014]
According to this configuration, when the residual pressure in the container of the gaseous fuel is less than the in-cylinder injectable minimum pressure and equal to or more than the intake passage injectable minimum pressure, the gaseous fuel is injected into the intake passage and started. In addition, the liquid fuel does not adhere to the wall surface and the like, and the deterioration of fuel efficiency and the emission of unburned HC are suppressed, and the residual gas fuel up to a lower pressure can be effectively used.
[0015]
Here, it is preferable that the gas fuel intake passage injection valve is connected via a low pressure regulator to a line branched from a line downstream of a high pressure regulator provided downstream of the gas fuel container.
[0016]
In this way, a constant pressure adjusted by the low-pressure regulator is exerted on the gas fuel intake passage injection valve, so that the control of the gas fuel injection supply amount is relatively simple only by changing the parameters of the injection period. Can be done.
[0017]
When the residual pressure of the gaseous fuel in the container is less than the minimum in-cylinder injectable pressure or less than the intake passage injectable minimum pressure, the liquid fuel is injected into the intake passage by a liquid fuel intake passage injection valve and started. Is preferred.
In this way, the starting is reliably performed.
[0018]
A start control method for a bi-fuel engine according to still another embodiment of the present invention that solves the above-described problems includes a method of injecting gaseous fuel into a cylinder by a gas fuel in-cylinder injection valve and injecting liquid fuel by a liquid fuel intake passage injection valve. In a bi-fuel engine capable of independently supplying and supplying fuel to a passage, a two-fluid fuel injection valve capable of simultaneously supplying the liquid fuel and the gaseous fuel to the intake passage is provided instead of the liquid fuel intake passage fuel injection valve. Connecting a line branched from a line downstream of a high-pressure regulator provided downstream of the gaseous fuel container to the two-fluid injection valve, and when the residual pressure of the gaseous fuel in the container is equal to or higher than the regulated pressure of the high-pressure regulator. Starts the injection by injecting the gaseous fuel into the cylinder by the gaseous fuel in-cylinder injection valve during the compression stroke, and reduces the residual pressure of the gaseous fuel in the container to the high pressure regime. When the pressure becomes lower than the regulating pressure of the gas generator, the fuel injection is started by injecting the liquid fuel and the gaseous fuel by the two-fluid injection valve while controlling the injection period according to the residual pressure of the gaseous fuel in the container. And
[0019]
According to this configuration, when the residual pressure of the gaseous fuel in the container becomes less than the regulated pressure of the high-pressure regulator, the injection period is controlled in accordance with the residual pressure of the gaseous fuel in the container, and the two-fluid injection valve controls the liquid fuel. The fuel and the gaseous fuel are injected to start the fuel injection, so that the atomization of the liquid fuel is promoted by using the gaseous fuel reduced to a pressure at which the in-cylinder injection cannot be performed. Thereby, vaporization is promoted and wall adhesion is suppressed, so that a required air-fuel mixture is easily formed, and starting can be performed without performing the fuel increase necessary for low-temperature starting using only liquid fuel. .
[0020]
Here, a low-pressure regulator is further interposed in the line branched from the line downstream of the high-pressure regulator, and the residual pressure of the gaseous fuel in the container is less than the regulated pressure of the high-pressure regulator, and the low-pressure regulator When the pressure is equal to or more than the regulated pressure, it is preferable to start by injecting gaseous fuel by the two-fluid injection valve.
[0021]
In this way, since a constant pressure adjusted by the low-pressure regulator is exerted on the two-fluid injection valve, the control of the injection supply amounts of the liquid fuel and the gaseous fuel can be relatively achieved only by changing the parameters of the injection period. Easy to do.
[0022]
Furthermore, a start control method for a bi-fuel engine according to still another embodiment of the present invention that solves the above-mentioned problems includes a method of injecting gaseous fuel into a cylinder by a gas fuel in-cylinder injection valve and injecting liquid fuel by a liquid fuel intake passage injection valve. A gas fuel intake passage injection valve for supplying the gaseous fuel to the intake passage so as to collide with the spray of the liquid fuel intake passage injection valve in the bi-fuel engine capable of independently supplying the fuel in the passage; Connecting a line branched from a downstream line of a high-pressure regulator provided downstream of the gaseous fuel container to the gaseous fuel intake passage injection valve so that the residual pressure of the gaseous fuel in the container is equal to or higher than the regulated pressure of the high-pressure regulator. In some cases, the gaseous fuel is injected into the cylinder by the gaseous fuel in-cylinder injection valve during the compression stroke to start the fuel tank, When the pressure is less than the regulated pressure of the high-pressure regulator, while controlling the injection period in accordance with the residual pressure of the gaseous fuel in the container, the gaseous fuel intake passage is used to supply the gaseous fuel by the injection valve and the liquid fuel intake passage. It is characterized in that each of the liquid fuels is injected and started by an injection valve.
[0023]
According to this configuration, when the residual pressure of the gaseous fuel in the container is less than the regulated pressure of the high-pressure regulator, the spray of the gaseous fuel injected by the gaseous fuel intake passage injection valve and the liquid fuel injected from the liquid fuel intake passage injection valve Atomization of the liquid fuel, so that atomization of the liquid fuel is promoted. Thereby, vaporization is promoted and wall adhesion is prevented, so that a required air-fuel mixture can be easily formed, and starting can be performed without performing a fuel increase necessary for low-temperature starting using only liquid fuel. Also, the starting time is reduced. Further, gaseous fuel whose residual pressure in the container is lower than the regulated pressure of the high-pressure regulator can be effectively used.
[0024]
Here, a low-pressure regulator is further interposed in the line branched from the line downstream of the high-pressure regulator, and the residual pressure of the gaseous fuel in the container is less than the minimum in-cylinder injectable pressure, and the low-pressure regulator When the pressure is equal to or more than the adjustment pressure, it is preferable that the gas fuel be injected into the intake passage by the gas fuel intake passage injection valve and the liquid fuel be injected into the intake passage by the liquid fuel intake passage injection valve to be started.
[0025]
In this way, a constant pressure adjusted by the low-pressure regulator is exerted on the gas fuel intake passage injection valve, so that the control of the gas fuel injection supply amount is relatively simple only by changing the parameters of the injection period. Can be done.
[0026]
After the engine has reached a predetermined warm-up state, it is preferable to stop the injection of the gaseous fuel and switch to the operation using the liquid fuel.
[0027]
With this configuration, after the residual pressure of the gaseous fuel in the container is reduced, the remaining gaseous fuel can be used efficiently while suppressing the deterioration of the fuel efficiency and the emission of unburned HC due to the liquid fuel at the time of low temperature start.
[0028]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.
[0029]
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.
[0030]
The engine 100 in FIG. 1 includes a gaseous fuel supply system and a liquid fuel supply system, and uses CNG as gaseous fuel and gasoline as liquid fuel. The gaseous fuel supply system includes a CNG in-cylinder injection valve 120 arranged so as to be able to inject into the combustion chamber 105 in the cylinder. The CNG in-cylinder injection valve 120 is a gas fuel container mounted on a vehicle via a CNG supply line 122. Is connected to the CNG cylinder 124. In the CNG supply line 122, a fuel cutoff valve and a high-pressure regulator 126 (not shown) are arranged (note that high pressure here means a relative difference from low pressure, which will be described later; It is not used in).
[0031]
The CNG filled in the CNG cylinder 124 at the filling pressure PF (for example, 20 MPa) is reduced to a constant high adjustment pressure PH (for example, 5 MPa) by the high-pressure regulator 126. In a normal engine control state, this high pressure is maintained. The CNG in-cylinder injection valve 120 injects the fuel into the cylinder at the compression stroke with the adjustment pressure PH. The high adjustment pressure PH is a pressure at which in-cylinder injection can always be performed in the compression stroke regardless of the operation state, and from this point, it may be referred to as a normal injection pressure in the following description.
[0032]
Similarly, the liquid fuel supply system includes a gasoline injection valve 130 disposed so as to be able to inject into an intake passage in the intake manifold 110, and the gasoline injection valve 130 is mounted on a liquid fuel container mounted on a gasoline supply line 132. Is connected to the gasoline tank 134 as Further, a fuel pump 133 is arranged in the gasoline supply line 132. Each of the CNG in-cylinder injection valve 120 and the gasoline injection valve 130 is controlled based on an output signal from the electronic control unit 300.
[0033]
An electronic control unit (hereinafter, referred to as an ECU) 300 is composed of a digital computer, and as is well known, a ROM (read only memory), a RAM (random access memory), and a CPU (microcontroller) interconnected via a bidirectional bus. Processor), a B-RAM (backup RAM) constantly connected to a power supply, an input port, an output port, and the like.
[0034]
Further, 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 connected to the intake manifold 110. In the CNG supply line 122 at the outlet of the CNG cylinder 124, a CNG residual pressure sensor 141 that generates 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 gasoline tank 134 is provided. The output voltages of these sensors 140, 141, and 142 are input to the input ports of ECU 300 via the corresponding AD converters. Further, the input port includes a rotation speed sensor 143 that generates an output pulse representing the engine rotation speed N, a throttle opening sensor 144 that detects a rotation angle of the throttle valve 115, and an accelerator opening that detects the amount of depression of an accelerator pedal. The sensor 145 and the like are connected. On the other hand, the output ports of the ECU 300 are connected to the ignition plug 109, the step motor 114, the CNG in-cylinder injection valve 120, the fuel pump 133, the gasoline injection valve 130, and the like, respectively, via the corresponding drive circuits.
[0035]
In the first embodiment of the present invention having the above configuration, for example, fuel is supplied to the engine 100 according to a start-time fuel injection control routine shown in FIG. This control routine is executed by interruption every predetermined set crank angle when the ignition switch is turned on and the starter is operated.
[0036]
First, in step S21, the residual pressure of the CNG fuel is checked. That is, it is determined whether or not the residual pressure P in the CNG cylinder 124 detected by the CNG residual pressure sensor 141 is equal to or higher than the high adjustment pressure PH that is reduced and adjusted by the high pressure regulator 126.
[0037]
If it is determined in step S21 that the residual pressure P in the CNG cylinder 124 is equal to or higher than the high adjustment pressure PH, the process proceeds to step S22, in which CNG is injected into the cylinder from the CNG in-cylinder injection valve 120 to be described later in a compression stroke. Thus, normal engine start and operation control are performed. On the other hand, if it is determined in step S21 that the residual pressure P in the CNG cylinder 124 is lower than the high adjustment pressure PH, the process proceeds to step S23, and the residual pressure P in the CNG cylinder 124 is further reduced to the in-cylinder injectable minimum pressure PS. It is determined whether or not: Here, the in-cylinder injectable minimum pressure PS (for example, 0.8 MPa) means that it is impossible to inject the in-cylinder only in the compression stroke with the entire amount of fuel required in accordance with the operating state. However, this is a pressure at which in-cylinder injection can be performed when a suction stroke is applied. When the residual pressure P in the CNG cylinder 124 is higher than the in-cylinder injectable minimum pressure PS, the process proceeds to step S24 to enter the CNG residual pressure start and operation mode.
[0038]
Here, when the residual pressure P of CNG is equal to or higher than the high adjustment pressure PH of the high-pressure regulator 126, the normal engine start and operation control by injecting CNG into the cylinder in the compression stroke from the CNG in-cylinder injection valve 120 is described. explain. In the engine 100 shown in FIG. 1, data relating to the injection timing and the injection period of the fuel injected from the CNG in-cylinder injection valve 120 and the gasoline injection valve 130 are respectively stored in an operating state of the engine 100, for example, a surge tank indicating an engine load. A function of the absolute pressure PM in the engine 111 and the engine speed N is stored in the ROM in advance in the form of a map. Here, the injection period of CNG is a period necessary for injecting CNG into the cylinder in a compression stroke by a required amount under the high adjustment pressure PH set to be reduced by the high-pressure regulator 126. The gasoline injection period is a period necessary for injecting gasoline by a required amount into the suction passage in a suction stroke under a constant pressure increased by the fuel pump 133.
[0039]
In the CNG start and operation mode, stratified combustion is performed by injecting CNG into the cylinder during the compression stroke to improve fuel efficiency. On the other hand, in the gasoline start and operation mode described later, the engine is started by injecting gasoline in the intake stroke, and thereafter, uniform combustion is performed in the stoichiometric air-fuel ratio or in the lean region.
[0040]
In the starting and operation mode based on CNG residual pressure in step S24, in the present embodiment, in-cylinder injection by CNG in-cylinder injection valve 120 changes the injection period and timing according to residual pressure P in CNG cylinder 124. Done. That is, in the start and operation mode based on the CNG residual pressure, since the residual pressure P of the CNG is lower than the high adjustment pressure PH of the high pressure regulator 126, the high pressure regulator 126 no longer operates and the injection is performed with the CNG residual pressure P itself. It is necessary to do so. The residual pressure P of CNG supplied to the CNG in-cylinder injection valve 120 changes (decreases) according to consumption. Therefore, in the actual control, it is necessary to experimentally obtain the CNG amount required for the start-up and subsequent operation in advance in correspondence with the residual pressure P of CNG that is less than the high adjustment pressure PH described above. The injection period and timing are stored in the form of a map, and in-cylinder injection by the CNG in-cylinder injection valve 120 is performed in the suction stroke and / or the compression stroke in accordance with the map.
[0041]
Further, from the state of the start and the operation mode by the CNG residual pressure in step S24, the process proceeds to step S25, and it is determined whether the warming-up of the engine 100 is completed. Until the warm-up is completed, the CNG residual pressure operation mode is continued. When the warm-up is completed, the process proceeds to step S27 described later, and the operation is switched to the operation using gasoline. That is, the mode is switched to the injection supply to the intake passage or the intake port 106 by the gasoline injection valve 130.
[0042]
On the other hand, if it is determined in step S23 that the residual pressure P of CNG is equal to or lower than the in-cylinder injectable minimum pressure PS, the process proceeds to step S26, in which the engine is started using gasoline. That is, only gasoline fuel is injected and supplied into the intake passage or the intake port 106 during the intake stroke by the gasoline injection valve 130, and is started. Data relating to the injection timing and injection period of the fuel injected from the gasoline injection valve 130 is stored in the ROM in advance in the form of a map corresponding to the gasoline starting state of the engine 100 as described above. , A predetermined amount of gasoline is injected and supplied. When the start is completed, the process proceeds to step S27, and the operation is switched to the above-described operation using gasoline.
[0043]
Next, a second embodiment of the present invention will be described with reference to FIGS. The second embodiment is different from the above-described first embodiment in that, in addition to the CNG in-cylinder injection valve 120, a CNG intake passage injection valve 121 arranged to be able to inject into the intake passage in the intake manifold 110 is provided. Further, the CNG supply branch line 123 is branched from the CNG supply line 122 downstream of the high-pressure regulator 126 and connected to the CNG intake passage injection valve 121. Note that the gasoline injection valve 130 and the CNG intake passage injection valve 121 are arranged in the intake passage in such a relationship that the sprays collide with each other. Since the other configuration is the same as that of the first embodiment, the same portions are denoted by the same reference numerals, and redundant description will be avoided.
[0044]
Therefore, in the second embodiment of the present invention, fuel is supplied to the engine 100 in accordance with, for example, a start-time fuel injection control routine shown in FIG. This control routine is executed by interruption every predetermined set crank angle when the ignition switch is turned on and the starter is operated, as in the first embodiment.
[0045]
First, in step S41, the residual pressure of the CNG fuel is checked. That is, it is determined whether or not the residual pressure P in the CNG cylinder 124 detected by the CNG residual pressure sensor 141 is equal to or higher than the high adjustment pressure PH that is reduced and adjusted by the high pressure regulator 126.
[0046]
If it is determined in step S41 that the residual pressure P in the CNG cylinder 124 is equal to or higher than the high adjustment pressure PH, the process proceeds to step S42, in which CNG is injected into the cylinder from the CNG in-cylinder injection valve 120 during the compression stroke. Thus, normal engine start and operation control are performed.
[0047]
On the other hand, if it is determined in step S41 that the residual pressure P in the CNG cylinder 124 is lower than the high adjustment pressure PH, the process proceeds to step S43, and the residual pressure P in the CNG cylinder 124 is further reduced to the minimum intake pressure PL. It is determined whether or not: The intake passage injectable minimum pressure PL is a pressure at which the entire fuel amount required for starting can be injected into the intake passage in the intake stroke. When the residual pressure P in the CNG cylinder 124 is higher than the intake passage injectable minimum pressure PL, the process proceeds to step S44 to enter the start and operation mode by the CNG residual pressure.
[0048]
In the starting and operation mode using the CNG residual pressure in step S44, in the present embodiment, the injection into the intake passage or the intake port 106 by the CNG intake passage injection valve 121 is performed according to the residual pressure P in the CNG cylinder 124. Performed at different times and periods. That is, in the start and operation mode based on the CNG residual pressure, since the residual pressure P of the CNG is lower than the high adjustment pressure PH of the high pressure regulator 126, the high pressure regulator 126 no longer operates and the injection is performed with the CNG residual pressure P itself. It is necessary to do so. Therefore, in the actual control, the CNG required for the start-up and subsequent operation is experimentally determined in advance in accordance with the residual pressure P of the CNG that is lower than the high adjustment pressure PH and higher than the intake passage injectable minimum pressure PL. The injection period and timing required to obtain the amount are stored in the form of a map, and according to this, the injection into the intake passage or the intake port 106 by the CNG intake passage injection valve 121 is performed in the intake stroke, Start up and run.
[0049]
Further, from the state of the start and the operation mode based on the CNG residual pressure in step S44, the process proceeds to step S45, and it is determined whether the warm-up of the engine 100 is completed. Until the warm-up is completed, the CNG residual pressure operation mode is continued. When the warm-up is completed, the process proceeds to step S47 described later, and the operation is switched to the operation using gasoline. That is, the mode is switched to the injection supply to the intake passage or the intake port 106 by the gasoline injection valve 130.
[0050]
On the other hand, if it is determined in step S43 that the residual pressure P of CNG is equal to or lower than the intake passage injectable minimum pressure PL, the process proceeds to step S46, in which the engine is started using gasoline. That is, only gasoline fuel is injected and supplied into the intake passage or the intake port 106 during the intake stroke by the gasoline injection valve 130, and is started. Data relating to the injection timing and injection period of the fuel injected from the gasoline injection valve 130 is stored in the ROM in advance in the form of a map corresponding to the gasoline starting state of the engine 100 as described above. , A predetermined amount of gasoline is injected and supplied. When the start is completed, the process proceeds to step S47, and the above-described operation using gasoline is performed.
[0051]
Further, in the third embodiment of the present invention, as shown in FIG. 5, the high-pressure regulator 126 is connected to a CNG supply branch line 123 branched from a CNG supply line 122 downstream of the high-pressure regulator 126 in the second embodiment. A low-pressure regulator 127 for adjusting the pressure to a low adjustment pressure PL lower than the high adjustment pressure PH by the regulator 126 is provided. This low adjustment pressure PL is not necessarily required to be equal to the above-described minimum intake passage injection possible pressure PL. However, from the viewpoint of effectively utilizing the CNG fuel remaining in the CNG cylinder 124 to the end, in the present embodiment, , Are set equal.
[0052]
In the third embodiment of the present invention, the fuel is supplied to the engine 100 substantially in accordance with the above-described start-time fuel injection control routine shown in FIG. However, the difference is that, in step S44, in the second embodiment, the CNG intake pressure P supplied to the CNG intake passage injection valve 121 is changed (decreased) according to consumption, and the CNG intake pressure is changed. While the injection period and timing of the passage injection valve 121 are changed, the third embodiment supplies the CNG intake passage injection valve 121 with the low adjustment pressure PL by the low-pressure regulator 127. Since the regulated constant supply pressure is exerted, the CNG is injected and supplied simply in accordance with data stored only in the form of a map and for only the injection period in consideration of the engine water temperature condition and the like.
[0053]
Note that the start and operation mode based on the CNG residual pressure is obtained by replacing the CNG residual pressure P with the intake passage injectable minimum pressure PL in step S43 of the flowchart of FIG. 4 in the second embodiment. By the comparison between the residual pressure P of CNG and the low adjustment pressure PL by the low pressure regulator 127, the operation is continued until the residual pressure P of CNG becomes the low adjustment pressure PL. That is, the determination in step S43 is performed until it is determined that the residual pressure P of CNG is equal to or lower than the low adjustment pressure PL. When the remaining pressure P becomes equal to or lower than the low adjustment pressure PL, the process proceeds to step S46, and the gasoline is started.
[0054]
In the third embodiment, the constant low adjustment pressure PL adjusted by the low pressure regulator 127 is exerted on the CNG intake passage injection valve 121, so that it is necessary in the second embodiment. Controlling the CNG injection amount is relatively simple by simply changing the parameter of the injection period by the CNG intake passage injection valve 121 without considering the change in the injection amount depending on the change in the magnitude of the CNG residual pressure P. As described above.
[0055]
Next, a fourth embodiment of the present invention will be described with reference to FIGS. This fourth embodiment is different from the second embodiment shown in FIG. 3 in that gasoline and CNG are simultaneously or separately supplied to the intake passage instead of the gasoline injection valve 130 and the CNG intake passage injection valve 121. Alternatively, a two-fluid injection valve 135 capable of supplying an injection to the intake port 106 is provided. The two-fluid injection valve 135 is connected to a gasoline supply line 132 in which a fuel pump 133 is interposed, and is branched from a CNG supply line 122 downstream of the high-pressure regulator 126 as in the second embodiment. The CNG supply branch line 123 is connected. Since the other configuration is the same as that of the above-described second embodiment, FIG. 6 shows only the main part including the changed part, and the same part is denoted by the same reference numeral to avoid redundant description.
[0056]
The two-fluid injection valve 135 used here is a so-called air (gas) assist injection valve utilizing a method of atomizing a liquid by a high-speed airflow (for example, Japanese Patent Application Laid-Open No. 5-263726, JP-A-5-187342, JP-A-5-263726, JP-A-11-270444, and the like) can be used. It is used by connecting the gas side inlet to the CNG supply branch line 123. The two-fluid injection valve 135 used in this embodiment is of a type that can independently control the injection of CNG and gasoline.
[0057]
In the fourth embodiment of the present invention having the above-described configuration, fuel is supplied to the engine 100 in accordance with, for example, a start-time fuel injection control routine shown in FIG. This control routine is executed by interruption every predetermined set crank angle as in the previous embodiment.
[0058]
Therefore, first, in step S71, the residual pressure of the CNG fuel is checked. That is, it is determined whether the residual pressure P in the CNG cylinder 124 is equal to or higher than the high adjustment pressure PH. If it is determined in step S71 that the residual pressure P in the CNG cylinder 124 is equal to or higher than the high adjustment pressure PH, the process proceeds to step S72, in which CNG is injected from the CNG in-cylinder injection valve 120 into the cylinder during the compression stroke. Thus, normal engine start and operation control are performed.
[0059]
On the other hand, if it is determined in step S71 that the residual pressure P in the CNG cylinder 124 is lower than the high adjustment pressure PH, the process proceeds to step S73, in which it is determined whether the pressure is equal to or lower than the intake passage injectable minimum pressure PL. When the residual pressure P in the CNG cylinder 124 is higher than the intake passage injectable minimum pressure PL, the process proceeds to step S74, and the CNG residual pressure start and operation mode are entered.
[0060]
In the starting and operation mode using the CNG residual pressure in step S74, in the present embodiment, the in-cylinder injection by the CNG in-cylinder injection valve 120 is not performed, and the two-fluid injection valve 135 supplies the injection to the intake passage or the suction port 106. Is performed. In this case, regarding the CNG injection in the two-fluid injection valve 135, the predetermined pressure is not higher than the high adjustment pressure PH of the high-pressure regulator 126 because the CNG residual pressure P is lower than the high adjustment pressure PH of the high-pressure regulator 126 as in the case of the second embodiment. During the period, it is necessary to inject with the CNG residual pressure P itself.
[0061]
Therefore, in the actual control, the amount of CNG that can be injected by the two-fluid injection valve 135 is experimentally determined in advance in accordance with the residual pressure P of CNG that is less than the high adjustment pressure PH, and corresponds to the starting condition of the engine 100. In order to obtain the total amount of fuel in the engine required for the starting condition, the injection period of gasoline by the two-fluid injection valve 135 is stored in the form of a map. In any case, the gasoline injection period of the two-fluid injection valve 135 is determined such that gasoline is injected in an amount that compensates for the decrease in the CNG injection amount due to the decrease in the residual pressure P of CNG. Thus, in the fourth embodiment, the atomization of the gasoline is atomized by mixing the gasoline and the CNG by utilizing the CNG reduced to a pressure at which the normal in-cylinder injection cannot be performed. Promoted. As a result, the gasoline fuel is quickly vaporized, so that the generation of the air-fuel mixture is promoted without being attached to the intake passage or the wall surface of the combustion chamber. Therefore, the residual CNG fuel can be effectively used, and as a result of ignition and stable combustion, the fuel can be started without increasing the amount of fuel required for low-temperature start with only the liquid fuel.
[0062]
Further, from the state of the start and the operation mode based on the CNG residual pressure in step S74, the process proceeds to step S75, and it is determined whether the warm-up of the engine 100 is completed. Until the warm-up is completed, the operation mode using the CNG residual pressure is continued. When the warm-up is completed, the process proceeds to step S77 described later, and the operation is switched to the operation using gasoline. That is, the mode is switched to the injection supply to the intake passage or the suction port 106 by the two-fluid injection valve 135.
[0063]
The start and operation mode based on the CNG residual pressure is continued until the residual pressure P of the CNG reaches the intake passage injection minimum pressure PL as shown in the flowchart of FIG. That is, the determination is made in step S73 until the residual pressure P of the CNG is determined to be equal to or lower than the intake passage injectable minimum pressure PL. The start is switched to. When starting the gasoline, only the gasoline fuel is injected and supplied into the intake passage or the intake port 106 by the two-fluid injection valve 135 during the intake stroke. As described above, data relating to the injection timing and injection period of gasoline fuel injected from the two-fluid injection valve 135 is stored in the ROM in advance in the form of a map corresponding to the starting conditions of the engine 100, as described above. A predetermined amount of gasoline is injected and supplied based on the data. When the startup is completed, the process proceeds to step S77, in which only gasoline is injected from the two-fluid injection valve 135, and the above-described operation using only gasoline is performed.
[0064]
Next, a fifth embodiment of the present invention will be described with reference to FIG. The fifth embodiment is different from the fourth embodiment in that a CNG supply branch line 123 branched from a CNG supply line 122 downstream of the high-pressure regulator 126 and connected to the two-fluid injection valve 135 includes: That is, a low-pressure regulator 127 for adjusting the pressure to a low adjustment pressure PL lower than the high adjustment pressure PH by the high-pressure regulator 126 is provided.
[0065]
When the CNG fuel residual pressure P in the CNG cylinder 124 becomes lower than the high adjustment pressure PH of the high-pressure regulator 126 and becomes equal to or higher than the low adjustment pressure PL of the low-pressure regulator 127, At the same time, the CNG fuel is injected and supplied by the two-fluid injection valve 135 and is started. Since the other configuration is the same as that of the above-described fourth embodiment, FIG. 8 shows only the main part including the changed part, and the same part is denoted by the same reference numeral to avoid redundant description.
[0066]
In the fifth embodiment of the present invention having the above configuration, the fuel is supplied to the engine 100 substantially according to the above-described fuel injection control routine at the time of starting shown in FIG. However, the difference is that in step S74, in the fourth embodiment, the two-fluid injection is performed in accordance with the fact that the residual pressure P of CNG supplied to the two-fluid injection valve 135 changes (decreases) with consumption. The CNG injection period and timing by the valve 135 are changed and supplied. In the fifth embodiment, however, the constant pressure adjusted to the low adjustment pressure PL by the low pressure regulator 127 is applied to the two-fluid injection valve 135. , The CNG and gasoline are injected and supplied simply in accordance with data stored only in the form of a map and for only the injection period in consideration of the engine water temperature condition and the like.
[0067]
Note that the start and operation mode based on the CNG residual pressure is obtained by replacing the CNG residual pressure P with the intake passage injectable minimum pressure PL in step S73 of the flowchart of FIG. 7 in the fourth embodiment. By the comparison between the residual pressure P of CNG and the low adjustment pressure PL by the low pressure regulator 127, the operation is continued until the residual pressure P of CNG becomes the low adjustment pressure PL. That is, the determination is performed in step S73 until the residual pressure P of CNG is determined to be equal to or lower than the low adjustment pressure PL. When the remaining pressure P becomes equal to or lower than the low adjustment pressure PL, the process proceeds to step S76, and the gasoline is started.
[0068]
Also in the fifth embodiment, since the constant low adjustment pressure PL adjusted by the low pressure regulator 127 is applied to the two-fluid injection valve 135, CNG required in the fourth embodiment is required. By simply changing the parameters of the injection period of CNG and gasoline by the two-fluid injection valve 135 without considering the change of the injection amount depending on the change of the residual pressure P, the injection amount of CNG and gasoline is changed. As described above, the control can be performed relatively easily.
[0069]
Further, a sixth embodiment and a seventh embodiment of the present invention will be described. In the sixth embodiment, in addition to the CNG in-cylinder injection valve 120, a CNG intake passage injection valve 121 arranged so as to be able to inject into the intake passage in the intake manifold 110 is provided, and the gasoline injection valve 130 and the CNG intake passage injection are provided. As shown in FIG. 3, the valve 121 and the valve 121 are arranged in the intake passage in such a manner that the sprays collide with each other. . More specifically, when the CNG residual pressure P in the CNG cylinder 124 is lower than the high adjustment pressure PH of the high-pressure regulator 126, the injection period from the CNG intake passage injection valve 121 is controlled in accordance with the CNG residual pressure P. , The CNG intake passage injection valve 121 is used to start the CNG fuel, and the gasoline fuel valve 130 is used to start the gasoline fuel by colliding the fuel spray with each other.
[0070]
In the seventh embodiment of the present invention, the CNG supply branch line 123 to which the CNG intake passage injection valve 121 of the above-described sixth embodiment is connected is connected to the CNG supply branch line 123 at a low pressure lower than the high adjustment pressure PH by the high pressure regulator 126. It differs from the sixth embodiment only in that a low-pressure regulator 127 for adjusting the pressure to the adjustment pressure PL is provided.
[0071]
The sixth embodiment and the seventh embodiment are different from the above-described fourth embodiment and the fifth embodiment, respectively, only in the form of each injection valve. Therefore, the description about the fourth embodiment and the fifth embodiment will be referred to respectively, and redundant description will be avoided. However, in addition, in the fourth and fifth embodiments, the CNG fuel and the gasoline fuel are injected and supplied by the two-fluid injection valve 135, whereas in the sixth and seventh embodiments, The difference is that the CNG intake passage injection valve 121 and the gasoline injection valve 130 arranged in the intake passage in such a relation that the sprays collide with each other, the sprays collide with each other and are injected and supplied.
[0072]
Also in these sixth and seventh embodiments, since the gasification of gasoline is promoted, the vaporization is promoted and the adhesion to the wall is suppressed, so that the required mixture can be easily formed. Done. Therefore, the starting can be performed without performing the necessary fuel increase at the time of the low temperature starting using only gasoline, and the starting time is also reduced.
[0073]
In the above-described embodiments, an example has been described in which CNG is used as the gaseous fuel and gasoline is 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 start-time fuel injection control routine according to the first embodiment of the present invention.
FIG. 3 is an overall diagram showing second and sixth embodiments of the present invention.
FIG. 4 is a flowchart showing an example of a start-time fuel injection control routine according to the second and third embodiments of the present invention.
FIG. 5 is a diagram of a main part showing third and seventh embodiments of the present invention.
FIG. 6 is a diagram of a main part showing a fourth embodiment of the present invention.
FIG. 7 is a flowchart illustrating an example of a start-time fuel injection control routine according to fourth and fifth embodiments of the present invention.
FIG. 8 is a diagram of a main part showing a fifth embodiment of the present invention.
[Explanation of symbols]
100 bi-fuel engine
120 CNG in-cylinder injection valve
121 CNG intake passage injection valve
122 CNG supply line
123 CNG supply branch line
124 CNG cylinder
126 High pressure regulator
127 Low pressure regulator
130 Gasoline injection valve
134 gasoline tank
141 CNG residual pressure sensor
142 Gasoline level sensor
300 Electronic control unit
PCNG residual pressure
PH high regulation pressure
PL Low adjustment pressure (minimum pressure that can be injected in the intake passage)
PS Minimum injectable cylinder pressure

Claims (10)

In a bi-fuel engine capable of independently injecting and supplying gaseous fuel into a cylinder via a gas fuel in-cylinder injection valve and liquid fuel to an intake passage via a liquid fuel intake passage injection valve,
When the residual pressure in the container of the gaseous fuel is equal to or higher than the regulated pressure of the regulator, the gaseous fuel is started by injecting the compression stroke into the cylinder by the gaseous fuel in-cylinder injection valve,
When the residual pressure in the container of the gaseous fuel is less than the regulated pressure of the regulator and is equal to or higher than the in-cylinder injectable minimum pressure, the gas fuel is injected into the cylinder by the gaseous fuel in-cylinder injection valve to change the injection timing. A start control method for a bifuel engine, which comprises injecting and starting. At the time of the start, while determining the injection period and timing based on the residual pressure in the container of the gaseous fuel, while injecting the gaseous fuel in the determined injection period and timing,
2. The start control method for a bi-fuel engine according to claim 1, wherein the operation is switched to the operation using the liquid fuel after the engine reaches a predetermined warm-up state. In a bi-fuel engine capable of independently injecting and supplying gaseous fuel into a cylinder via a gas fuel in-cylinder injection valve and liquid fuel to an intake passage via a liquid fuel intake passage injection valve,
A gas fuel intake passage injection valve for supplying the gas fuel to the intake passage is further provided,
When the residual pressure in the container of the gaseous fuel is equal to or higher than the regulated pressure of the regulator, the gaseous fuel is started by injecting the compression stroke into the cylinder by the gaseous fuel in-cylinder injection valve,
When the residual pressure in the container of the gaseous fuel is less than the in-cylinder injectable minimum pressure and is equal to or more than the intake passage injectable minimum pressure, the gaseous fuel is injected into the intake passage by the gaseous fuel intake passage injection valve. A start control method for a bi-fuel engine, which is started. The gas fuel intake passage injection valve is connected to a line branched from a line downstream of a high pressure regulator provided downstream of the gas fuel container via a low pressure regulator. Bi-fuel engine start control method. When the residual pressure in the container of the gaseous fuel is less than the in-cylinder injectable minimum pressure or less than the intake passage injectable minimum pressure, the liquid fuel is injected into the intake passage by a liquid fuel intake passage injection valve and started. 5. The start control method for a bifuel engine according to claim 1, wherein: In a bi-fuel engine, gas fuel can be independently injected and supplied to a cylinder by a gas fuel in-cylinder injection valve and liquid fuel to an intake passage by a liquid fuel intake passage injection valve.
In place of the liquid fuel intake passage injection valve, a two-fluid injection valve capable of simultaneously supplying the liquid fuel and the gaseous fuel to the intake passage is provided, and a line downstream of a high-pressure regulator provided downstream of the gaseous fuel container Is connected to the two-fluid injection valve,
When the residual pressure in the container of the gaseous fuel is equal to or higher than the regulated pressure of the high-pressure regulator, the gaseous fuel is started by injecting the compression stroke into the cylinder by the gaseous fuel in-cylinder injection valve,
When the residual pressure in the container of the gaseous fuel becomes lower than the regulated pressure of the high-pressure regulator, the liquid fuel and the gas are controlled by the two-fluid injection valve while controlling the injection period according to the residual pressure in the container of the gaseous fuel. A start control method for a bi-fuel engine, which starts by injecting fuel. A low-pressure regulator is further interposed in a line branched from a line downstream of the high-pressure regulator,
When the residual pressure in the container of the gaseous fuel is less than the regulated pressure of the high-pressure regulator and is equal to or greater than the regulated pressure of the low-pressure regulator, the fuel is started by injecting the gaseous fuel by the two-fluid injection valve. The start control method for a bi-fuel engine according to claim 6. In a bi-fuel engine, gas fuel can be independently injected and supplied to a cylinder by a gas fuel in-cylinder injection valve and liquid fuel to an intake passage by a liquid fuel intake passage injection valve.
A gas fuel intake passage injection valve for injecting the gaseous fuel into the intake passage so as to collide with the spray of the liquid fuel intake passage injection valve, and a line downstream of a high-pressure regulator provided downstream of the gas fuel container; Connected to the gas fuel intake passage injection valve,
When the residual pressure in the container of the gaseous fuel is equal to or higher than the regulated pressure of the high-pressure regulator, the gaseous fuel is started by injecting the compression stroke into the cylinder by the gaseous fuel in-cylinder injection valve,
When the residual pressure in the container of the gaseous fuel is less than the regulated pressure of the high-pressure regulator, while controlling the injection period in accordance with the residual pressure in the container of the gaseous fuel, the gaseous fuel is injected by the gaseous fuel intake passage injection valve, A start control method for a bi-fuel engine, wherein liquid fuel is injected and started by the liquid fuel intake passage injection valve. A low-pressure regulator is further interposed in a line branched from a line downstream of the high-pressure regulator,
When the residual pressure in the container of the gaseous fuel is lower than the minimum in-cylinder injectable pressure and equal to or higher than the adjustment pressure of the low-pressure regulator, the gaseous fuel is supplied to the liquid fuel by the gaseous fuel intake passage injection valve. 9. The start control method for a bi-fuel engine according to claim 8, wherein the engine is started by injecting into an intake passage by an intake passage injection valve. 10. The bi-fuel engine start control according to claim 3, wherein after the engine has reached a predetermined warm-up state, the injection of the gaseous fuel is stopped and the operation is switched to the operation using the liquid fuel. Method.

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