JP2005214079A - Start and stop control methods for bi-fuel engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a start control method for a bi-fuel engine capable of securely starting the engine in low temperatures and a stop control method therefor while suppressing the deterioration of fuel economy and discharge of unburned HC. <P>SOLUTION: The bi-fuel engine can inject and supply a gas fuel and a liquid fuel independently of each other. In the cold start of the engine with the gas fuel, when the amount of the liquid fuel is less than a specified value, the gas fuel is jetted from a gas fuel jetting valve 120 after blank injection control is performed. When the amount of the liquid fuel is equal to or more than the specified value, the gas fuel is jetted from the gas fuel jetting valve without performing the blank injection control for starting. When the amount of the liquid fuel is less than a specified value when stopping the low temperature operation after the operation with the gas fuel, after a pressure release control is performed, the engine is stopped. When the amount of the liquid fuel is equal to or more than the specified value, the jetting of the gas fuel is stopped without performing the pressure release control to stop the engine. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a start control method and a stop control method for a bi-fuel engine, and more particularly to a start control method and a stop control method suitable for low temperatures.

  2. Description of the Related Art Recently, in automobiles and the like, gaseous fuel such as compressed natural gas (CNG) is attracting attention in place of liquid fuel such as gasoline and light oil from the viewpoint of air pollution control and resource saving. However, in the case of CNG, its energy density is lower than gasoline etc. (about 20-30% of gasoline), so vehicles equipped with engines that use CNG are compared to vehicles equipped with engines that use gasoline. The cruising range is short. In addition, due to delays in infrastructure development, the number of filling stations is not sufficient, and there are concerns about long-distance movement. In view of this, a dual fuel that can be supplied to the engine by switching at least one of the gaseous fuel and the liquid fuel, that is, a bi-fuel engine has been proposed.

  As such a bi-fuel engine, for example, the one described in Patent Document 1 is known. In this bi-fuel engine, in order to suppress discharge of unburned gas due to fuel adhesion at the time of cold start, gaseous fuel is injected from the gaseous fuel injection valve until the engine changes from a cold state to a predetermined warm-up state. After the predetermined warm-up state, the fuel is switched and controlled to inject liquid fuel from the liquid fuel injection valve.

  On the other hand, in order to improve the startability of the engine by eliminating sticking of the gaseous fuel injection valve at a low temperature due to the characteristics of the gaseous fuel in an engine using only the gaseous fuel, although it is not a bi-fuel engine. In Patent Document 2, when the engine temperature is equal to or lower than a predetermined value, the drive signal of the gaseous fuel injection valve is set to a larger current than in the normal time and the energization time is lengthened to eliminate sticking. Is disclosed.

  Furthermore, in Patent Document 3, in an engine using only gaseous fuel, in order to be able to release the sticking (adhesion) of the gaseous fuel injection valve at the start of cryogenic temperature, gaseous fuel injection is performed when the engine is stopped. A pressure relief control is performed to open and close the gaseous fuel injection valve and the communication path so as to reduce the fuel pressure applied to the valve, and at the time of start-up, a test valve that opens the gaseous fuel injection valve with the communication path closed ( A technique is disclosed in which control is performed.

JP 2000-213394 A JP-A-10-227248 Japanese Patent Laid-Open No. 2000-274312

  By the way, also in low temperature start control in a bi-fuel engine, when using gas such as CNG as fuel, there is a problem of sticking of the above-described gaseous fuel injection valve as in the case of an engine using only gaseous fuel. Therefore, it is conceivable to start with a liquid fuel at the time of starting at a low temperature. However, in the case of liquid fuel, since it takes time to evaporate, that is, vaporize after being supplied by injection, it is necessary to increase the injection supply amount in anticipation of this, and it is necessary to inject such liquid fuel. In all starting operations, an increase in unburned components due to liquid fuel adhering to the port and the wall surface of the combustion chamber is observed, leading to deterioration in fuel consumption and emission of unburned HC. Therefore, it is preferable to start with a gaseous fuel that does not have the problem of such fuel adhesion.

  However, if starting with gaseous fuel is always performed at low temperature starting, it is necessary to perform the above-described depressurization control or trial valve opening control, which consumes the gaseous fuel wastefully and deteriorates fuel consumption. Will be invited. On the other hand, as a result of avoiding the above-described depressurization control and trial valve opening control, if the starting is poor, the vehicle cannot run, so this must be avoided completely.

  Accordingly, an object of the present invention is to provide a start control method and a stop time control method for a bi-fuel engine that can reliably start at a low temperature while suppressing deterioration of fuel consumption and emission of unburned HC. is there.

  A bifuel engine start control method according to an aspect of the present invention that solves the above-described problems is a bifuel engine that can separately inject and supply gaseous fuel and liquid fuel. When the fuel is less than the predetermined value, after performing the idle driving control, the fuel gas is injected by the gaseous fuel injection valve and started. On the other hand, when the liquid fuel is higher than the predetermined value, the gas is discharged without performing the idle driving control. The fuel is injected by a gaseous fuel injection valve and started.

Here, when the injection of the gaseous fuel by the gaseous fuel injection valve fails without performing the idling control, it is preferable to start by injecting the liquid fuel by the liquid fuel injection valve.
In addition, after an engine will be in a predetermined | prescribed warm-up state, you may switch to the driving | operation by gaseous fuel.

  Further, a bifuel engine stop control method according to another aspect of the present invention that solves the above-described problem is a bifuel engine that can independently inject and supply gaseous fuel and liquid fuel. When the liquid fuel is less than the predetermined value at the time of low temperature stop, the pressure release control is performed and then stopped.On the other hand, when the liquid fuel is higher than the predetermined value, the injection of the gaseous fuel is stopped without performing the pressure release control. It is characterized by being stopped.

  According to the start control method for a bi-fuel engine according to one aspect of the present invention, when the liquid fuel is less than a predetermined value at the time of cold start with the gaseous fuel, the idle driving control is performed, and then the gaseous fuel is injected with the gaseous fuel. It is injected and started by a valve. Therefore, starting at a low temperature is surely performed. On the other hand, when the liquid fuel is greater than or equal to a predetermined value, the gas fuel is started by being injected by the gas fuel injection valve without performing idling control, so that the fuel consumption is deteriorated without wasteful consumption of the gas fuel. There is nothing.

Here, when the injection of the gaseous fuel by the gaseous fuel injection valve fails without performing the idle driving control, the liquid fuel is injected by the liquid fuel injection valve and started. Therefore, starting at a low temperature is surely performed.
In addition, according to the form which switches to the operation | movement with gaseous fuel after an engine will be in a predetermined | prescribed warm-up state, the cruising range can be expanded using the characteristic of gaseous fuel effectively.

  Further, according to the stop control method for a bi-fuel engine according to another aspect of the present invention, when the liquid fuel is less than a predetermined value at the time of low temperature stop after operation with gaseous fuel, the stop is performed after the pressure release control is performed. Therefore, the next starting failure that must be started with gaseous fuel can be avoided. On the other hand, when the liquid fuel is equal to or higher than the predetermined value, the injection of the gaseous fuel is stopped without performing the depressurization control, so that the fuel efficiency is not deteriorated without consuming the gaseous fuel wastefully.

Embodiments of the present invention will be described below with reference to the accompanying drawings.
First, an outline of a bi-fuel 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 disposed at the top of the combustion chamber 105. Show. 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 disposed in the intake duct 112.

  The engine 100 in FIG. 1 includes a gaseous fuel supply system and a liquid fuel supply system. In the present embodiment, CNG is used as the gaseous fuel and gasoline is used as the liquid fuel. The gaseous fuel supply system includes a plurality of CNG injection valves 120 arranged to be able to inject fuel into the combustion chamber 105 in each cylinder, and the plurality of CNG injection valves 120 are connected to a delivery pipe 121 having a common fuel chamber. It is connected. The delivery pipe 121 is further connected to a CNG cylinder 124 as a gas fuel container mounted on a vehicle via a CNG supply line 123 provided with a delivery cutoff valve 122. A fuel cutoff valve and regulator 126 (not shown) are arranged near the outlet of the CNG cylinder 124 of the CNG supply line 123.

  The CNG filled in the CNG cylinder 124 with the filling pressure PF (for example, 20 MPa) is decompressed to a certain regulated pressure PH (for example, 5 MPa) by the regulator 126, and in the normal engine control state, this regulated pressure PH. Therefore, it is injected in the compression stroke from the CNG injection valve 120 as the gaseous fuel injection valve into the cylinder. This adjustment pressure PH is a pressure at which in-cylinder injection can always be performed in the compression stroke regardless of the operating state. From this point, it may be referred to as normal injection pressure in the following description.

  Similarly, the liquid fuel supply system includes a gasoline injection valve 130 serving as a liquid fuel injection valve disposed in an intake passage in the intake manifold 110 so as to be capable of injection. The gasoline injection valve 130 is connected via a gasoline supply line 132. It is connected to a gasoline tank 134 as a liquid fuel container mounted on the vehicle. Further, a fuel pump 133 is disposed in the gasoline supply line 132. These CNG injection valve 120 and gasoline injection valve 130 are controlled based on output signals from electronic control unit 300, respectively.

  The electronic control unit (hereinafter referred to as ECU) 300 is a digital computer, and as is well known, a ROM (Read Only Memory), a RAM (Random Access Memory), and a CPU (Microcontroller) connected to each other via a bidirectional bus. Processor), a B-RAM (backup RAM) that is always connected to a power source, an input port, an output port, and the like.

  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 123 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 amount of remaining gasoline in the gasoline tank 134 is disposed. The output voltages of these sensors 140, 141, and 142 are respectively input to the input ports of ECU 300 via 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 the rotation angle of the throttle valve 115, and an accelerator opening that detects the amount of depression of the accelerator pedal. A sensor 145, a coolant temperature sensor 146 for detecting the engine coolant temperature, a fuel temperature sensor 147 for detecting the fuel temperature of the CNG cylinder 124, and the like are connected. On the other hand, the output ports of the ECU 300 are connected to the spark plug 109, the step motor 114, the CNG injection valve 120, the delivery cutoff valve 122, the fuel pump 133, the gasoline injection valve 130, and the like via corresponding drive circuits. .

  In the embodiment of the present invention for the bi-fuel engine configured as described above, for example, fuel is supplied to the engine 100 in accordance with the start-time fuel injection control routine shown in FIG. This control routine is executed by interruption every predetermined crank angle when the ignition switch is turned on and the starter is operated.

  First, in step S201, when the starter is turned on from the standby state, the process proceeds to step S202, and it is determined whether or not the start is a low temperature. Although it is possible to determine whether or not the engine is cold starting based on the engine coolant temperature, the engine oil temperature, or the intake air temperature, which is representative of the engine temperature, in the present embodiment, the detection from the coolant temperature sensor 146 is performed. Depending on the value, this is done depending on whether or not this is a predetermined value (for example, 0 ° C.) or less.

  If it is determined in step S202 that the engine is not cold start, i.e., "NO", the process proceeds to step S210, in which gasoline is supplied from the gasoline injection valve 130 to the intake port 106, or the CNG injection valve 120 to CNG in the cylinder. Normal engine start and operation control is performed by injecting and supplying the fuel in the compression stroke. It should be noted that normal engine start and operation control other than the low temperature start are not included in the gist of the present invention, and thus detailed description thereof is omitted.

  On the other hand, if it is determined in step S202 that the start is low, that is, "YES", the process proceeds to step S203, and it is determined whether or not the CNG fuel operation mode is selected. Here, the CNG fuel operation mode is a switching / switching in which the fuel to be used is switched automatically or in response to the intention of the driver in order to effectively exhibit the characteristics of the bi-fuel engine. In a bi-fuel engine equipped with a selection system, the mode of operation selected to use CNG fuel. Normally, driving with CNG fuel is advantageous from the viewpoint of suppressing deterioration of fuel consumption and emission of unburned HC. Therefore, the CNG fuel operation mode is set, and the process proceeds to step S204 after step S203. However, when the driver is not in the CNG fuel operation mode, that is, when the gasoline operation mode is selected, the process proceeds to step S211 and normal engine start and operation control with gasoline, which will be described later, is performed.

  Therefore, in step S204, it is determined whether or not the gasoline amount is greater than or equal to a predetermined value. The predetermined amount of gasoline is determined from the viewpoint of whether or not traveling to the nearest gas station or filling station is sufficiently possible. The gasoline amount being less than the predetermined value means that the gasoline amount was less than the predetermined value even when the engine was stopped last time. Therefore, in order to surely start with CNG fuel regardless of gasoline fuel, the pressure release control at the time of stop, which will be described later, is performed at the time of the previous stop, so when the gasoline amount is less than a predetermined value, Proceeding to step S212, CNG idle driving start control, which will be described in detail later, is executed. On the other hand, when the gasoline amount is equal to or greater than the predetermined value, the process proceeds to step S205, and normal start control in CNG fuel injection is performed. In the normal start control in this CNG fuel injection, in the present embodiment, a predetermined drive signal is sent from the ECU 300 to the CNG injection valve 120, and CNG is injected and supplied from the CNG injection valve 120 into the cylinder in the compression stroke. The start control by is performed. The data regarding the injection timing and the injection period of the starting fuel injected from the CNG injection valve 120 are respectively the absolute pressure PM in the surge tank 111 representing the temperature state of the engine 100 and the engine load, the engine speed N, and the like. Is stored in the ROM in advance in the form of a map. Here, the CNG injection period is a period required to inject CNG into the cylinder by the required amount under the normal injection pressure set by the regulator 126 under a reduced pressure.

  After the normal start control in the CNG fuel injection in step S205 is performed, the process proceeds to step S206, and it is determined whether or not the CNG fuel injection is failed. That is, in normal start control in CNG fuel injection, a fail signal IJf that is generated when the CNG injection valve 120 is not driven for some reason (such as sticking) even though the drive signal is sent from the ECU 300. Is detected by the ECU 300 and determined. The determination of whether or not the CNG fuel injection is failed is performed, for example, when a drive signal is sent to the CNG injection valve 120 once or twice and a fail signal IJf is generated. When the fail signal IJf is issued, the process proceeds to step S207, where the control is performed by switching to gasoline.

  In this starting control by gasoline, the engine is started by injecting gasoline in the intake stroke, and thereafter, uniform combustion by the stoichiometric air-fuel ratio or lean region is performed. Data relating to the injection timing and injection period of the fuel injected from the gasoline injection valve 130 at the time of starting is also stored in advance in the form of a map in the ROM. The gasoline injection period is a period required to inject gasoline into the intake passage in the intake stroke under a constant pressure boosted by the fuel pump 133.

  After the engine is started by injecting gasoline in step S207, the process proceeds to step S208, and it is determined whether or not the engine 100 has been warmed up. The determination as to whether or not the warm-up has been completed is made based on a detected value from the coolant temperature sensor 146 based on whether or not the warm-up is a predetermined value (for example, 50 ° C.) or more. Such a predetermined value is obtained by experiments as a temperature at which the cause of sticking of the CNG injection valve 120 is eliminated. When the warm-up is completed, the process proceeds to step S209, and the operation is switched to the operation by CNG injection.

  Next, normal engine start-up and operation control with gasoline performed in step S211 when the CNG fuel operation mode is not selected, that is, the gasoline operation mode is selected in the determination in step S203 described above will be described. In the normal engine start-up and operation control with gasoline, only gasoline fuel is injected and supplied into the intake passage or intake port 106 in the intake stroke by the gasoline injection valve 130. As described above, the data relating to the injection timing and the injection period of the fuel injected from the gasoline injection valve 130 are stored in the ROM in advance in the form of a map corresponding to the gasoline start state of the engine 100. On the basis of this, a predetermined amount of gasoline is injected and supplied.

  Furthermore, the CNG idling start control executed in step S212 when it is determined in step S204 that the gasoline amount is less than the predetermined value will be described with reference to the time chart of FIG. The CNG idle driving start control is a control performed in combination with a pressure relief control when the engine is stopped, which will be described later.

  Therefore, in this CNG idle driving start control, the delivery cutoff valve 122 is closed (see i in FIG. 4B), and the fuel pressure (delivery fuel pressure) in the delivery pipe 121 is 0 or less than a predetermined value (FIG. 4 ( B) (see j), the drive current is larger than usual during the drive period from when CNG injector 120 starts cranking (see FIG. 4 (B) b) to cylinder discrimination (see FIG. 4 (B) c). It is driven by a long drive signal (refer to FIGS. 4B to 4H, which is indicated as an injector in the figure). Thereby, this sticking of the CNG injection valve 120 sticking or sticking due to the low temperature is peeled off. Then, after cylinder discrimination, the delivery cutoff valve 122 is opened (see FIG. 4 (B) i), and the fuel amount at start is injected and started. In addition, as shown in FIG. 4A, the drive signal of the CNG injection valve 120 is a DCDC drive having a larger driving force in order to surely remove the fixation of the CNG injection valve 120 that is fixed or stuck. Control is performed so as to have a period Td, a battery voltage driving period Tb with a large driving force, and a holding current driving period Th for maintaining the valve open state.

  Note that after the CNG idle driving start control in step S212 and in the determination in step S206, if there is no failure in the injection from the CNG injection valve 120, the process proceeds to step S213, and the operation control in CNG is performed. Is called.

  Next, stop control of the present invention will be described. In the present embodiment, for example, the engine 100 is stopped according to the engine stop control routine shown in FIG. That is, in step S301, if it is determined from the standby state that the ignition switch is OFF, the process proceeds to step S302, and it is determined whether or not a low-temperature stop has occurred. This low-temperature stop determination is made based on a detection value from the fuel temperature sensor 147 that detects the fuel temperature of the CNG cylinder 124, whether or not this is below a predetermined value (for example, 0 ° C.). If it is determined in step S302 that the stop is not a low temperature, that is, "NO", the process proceeds to step S306, and normal stop control is performed by stopping the fuel being supplied.

  On the other hand, if it is determined in step S302 that the stop is at a low temperature, that is, "YES", the process proceeds to step S303, and it is determined whether or not the above-described CNG fuel operation mode is selected. Here, if the CNG fuel operation mode is not selected, that is, if the gasoline operation mode is “NO” due to the driver's intention, the process proceeds to step S307, and gasoline injection from the gasoline injection valve 130 to the intake port 106 is performed. Normal engine stop control is performed to stop the supply. On the other hand, when the CNG fuel operation mode is selected, it is determined in step S304 whether or not the gasoline amount is equal to or greater than a predetermined value. When the gasoline amount is equal to or greater than the predetermined value, that is, “YES”, the process proceeds to step S305, and normal stop control is performed by stopping the fuel supply from the CNG injection valve 120.

  By the way, if the determination in step S304 is “NO”, that is, if the gasoline amount is less than the predetermined value, this means that the next start must be performed with CNG fuel, and this start must be performed reliably. Therefore, it progresses to step S308 and CNG pressure relief control is performed. The CNG pressure release control will be described with reference to the time chart of FIG. Note that the CNG pressure release control is performed in combination with the idle driving control as described above.

  In this CNG pressure release start control, the delivery cutoff valve 122 is closed (see FIG. 5b) almost simultaneously with the ignition switch being turned off (see FIG. 5c). Then, while sending a drive signal to the CNG injection valve 120 and an ignition signal to the ignition plug 109 for a predetermined time (for example, about 1 second) (see f and g in FIG. 5), the ISC correction value and the ignition delay amount are set. Increase (see d and e in FIG. 5) to accelerate fuel consumption. As a result, the fuel pressure in the delivery pipe 121 is set to 0 or below a predetermined value (see FIG. 5a). As a result, as described above, the CNG fuel pressure at the time of starting is set to 0 or a predetermined value or less, and at the same time, the CNG injection valve 120 that is stopped due to the fuel pressure is prevented from sticking or sticking.

  Furthermore, an example of the injection drive monitoring control that is used together with the above-described embodiment to enable effective use of the advantages of the bi-fuel engine will be described with reference to the flowchart of FIG. In order to make this control effective, the driver's seat is provided with a display that can display an abnormality warning and a stop recommendation from the ECU 300, and the ECU 300 is a non-volatile memory B-RAM that does not lose its stored contents even after the ignition switch is turned off. (Backup RAM).

  When the injection drive monitoring control is started, first, in step S601, it is determined whether or not the already-described CNG fuel operation mode is selected. When the CNG fuel operation mode is selected, that is, when “YES”, the process proceeds to step S602, and it is determined whether or not the CNG fuel injection is failed. That is, in the normal drive control in the CNG fuel injection, the ECU 300 detects and determines the fail signal IJf that is generated when the CNG injection valve 120 is not driven for some reason despite the drive signal sent from the ECU 300. It is done. When the fail signal IJf is not issued, that is, when the fail signal IJf is OFF, the process proceeds to step S608, and normal operation control in CNG injection by injecting and supplying CNG into the cylinder in the compression stroke from the CNG injection valve 120 is performed. Done. On the other hand, when the fail signal IJf is ON, the process proceeds to step S603, and it is determined whether or not the gasoline amount is equal to or greater than a predetermined value. When the gasoline amount is less than the predetermined value, that is, when “NO”, the process proceeds to step S609, and the warning of the CNG injection valve 120 injection (ING) drive abnormality and the vehicle stop recommendation are displayed on the above-mentioned display. To be done. Conversely, when the gasoline amount is greater than or equal to the predetermined value, the process proceeds to step S604, where the gasoline is switched to, and then the CNG fuel injection is always prohibited in step S605, and the CNG injection valve 120 is injected (ING) to the driver in step S606. A warning of drive abnormality and a repair recommendation are displayed on the above-mentioned display. The CNG fuel injection always-inhibited measures and the injection (ING) drive abnormality warning and the repair recommendation are stored in the non-volatile memory described above, the CNG injection valve 120 is repaired, a special release signal, etc. The system is such that it will not be released unless entered. Along with such warnings and recommendations, normal operation control with gasoline fuel is performed in step S607.

  On the other hand, if the CNG fuel operation mode is not selected in step S601, that is, if “NO”, the process proceeds to step S610 to determine whether or not the gasoline fuel injection is failed. That is, in normal drive control in gasoline fuel injection, ECU 300 detects and determines a fail signal IJf that is generated when gasoline injection valve 130 is not driven for some reason even though a drive signal is sent from ECU 300. Is done. When the fail signal IJf is not generated, that is, when the fail signal IJf is OFF, the process proceeds to step S616, and normal operation control in gasoline injection is performed by supplying the fuel from the gasoline injection valve 130 to the intake port 106 in the intake stroke. Is called. On the other hand, when the fail signal IJf is ON, the process proceeds to step S611, and it is determined from the detection value from the CNG residual pressure sensor 141 whether the CNG amount is equal to or greater than a predetermined value. When the CNG amount is less than the predetermined value, that is, when “NO”, the process proceeds to step S617, and the warning of the injection (ING) drive abnormality of the gasoline injection valve 130 and the vehicle stop recommendation are displayed on the display. To be done. On the other hand, when the CNG amount is equal to or larger than the predetermined value, the process proceeds to step S612 and is switched to CNG. Next, the gasoline fuel injection is always prohibited in step S613, and the CNG injection valve 120 is injected into the driver in step S614 (ING). A warning of drive abnormality and a repair recommendation are displayed on the above-mentioned display. Note that the gasoline fuel injection always-inhibited measures and the warning of injection (ING) drive abnormality and the recommendation for repair are stored in the above-mentioned nonvolatile memory, and the gasoline injection valve 130 is repaired as in the case of CNG. However, unless a special release signal is input, the system is not released. Then, along with such warnings and recommendations, normal operation control with CNG fuel is performed in step S615.

  Thus, according to this injection drive monitoring control, normal operation is continued as it is if there is no abnormality in the injection drive, regardless of whether the fuel is operated with CNG or gasoline. Even when an abnormality occurs in one injection drive, the fuel is switched when the other fuel has a predetermined remaining amount value, so that the operation can be continued without any trouble even after the occurrence of the abnormality. Further, the use of the injection valve on which this abnormality has occurred is always prohibited, and a warning of an injection (ING) drive abnormality and a repair recommendation are given to the driver, resulting in a major failure. It is guaranteed that repairs will be performed early without any problems. Further, when this one abnormality occurs, when the other fuel does not reach a predetermined remaining amount value, a warning of this abnormality and the stop of the vehicle are recommended, so that damage can be minimized.

  In the above-described embodiment, the CNG fuel is injected and supplied directly into the cylinder in the compression stroke to perform stratified combustion, and the gasoline fuel is injected and supplied into the port in the intake stroke to perform homogeneous combustion. Both the gasoline fuel and the gasoline fuel may be injected into the cylinder or the port.

  Furthermore, in the embodiments described so far, an example in which CNG is used as the gaseous fuel and gasoline is used as the liquid fuel has been described. However, as the gaseous fuel, for example, natural gas and petroleum gas which are primary fuels, or coal conversion gas and petroleum conversion gas which are secondary fuels can be used. Needless to say, hydrocarbons such as isooctane, hexane, heptane, light oil, and kerosene, butanes that can be stored in a liquid state, hydrocarbons such as propane, and methanol can be used as the liquid fuel.

It is a whole line figure showing an outline of a bi-fuel engine to which the present invention is applied. It is a flowchart which shows an example of the starting control routine in this invention. It is a flowchart which shows an example of the stop control routine in this invention. It is a time chart for demonstrating start time blanking control, (A) shows the drive pattern of the drive signal of a CNG injection valve, (B) shows the operation timing of each part. It is a time chart for demonstrating stop pressure release control, and shows the operation timing of each part. It is a flowchart which shows an example of the control routine of the injection drive monitoring control which concerns on this invention.

Explanation of symbols

100 Bi-fuel engine 120 CNG injection valve 122 Delivery shut-off valve 123 CNG supply line 124 CNG cylinder 126 Regulator 130 Gasoline injection valve 134 Gasoline tank 141 CNG residual pressure sensor 142 Gasoline remaining amount sensor 146 Cooling water temperature sensor 147 Fuel temperature sensor 300 Electronic control unit

Claims (4)

In a bi-fuel engine that can inject and supply gas fuel and liquid fuel independently,
At the time of cold start with gaseous fuel, when the liquid fuel is less than a predetermined value, after performing idle driving control, the gaseous fuel is started by injecting with the gaseous fuel injection valve,
A start control method for a bi-fuel engine, wherein when the liquid fuel is equal to or greater than a predetermined value, the gas fuel is injected by the gas fuel injection valve without performing idling control.   2. The bi-fuel engine according to claim 1, wherein when the injection of the gaseous fuel by the gaseous fuel injection valve fails without performing the idling control, the liquid fuel is injected by the liquid fuel injection valve and started. Starting control method.   3. The start control method for a bi-fuel engine according to claim 2, wherein after the engine is in a predetermined warm-up state, the operation is switched to operation with gaseous fuel. In a bi-fuel engine that can inject and supply gas fuel and liquid fuel independently,
At the time of low-temperature stop after operation with gaseous fuel, when the liquid fuel is less than a predetermined value, after performing depressurization control, it is stopped,
A stop control method for a bi-fuel engine, wherein when the liquid fuel is equal to or greater than a predetermined value, injection of gaseous fuel is stopped and stopped without performing depressurization control.

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