WO2013125278A1

WO2013125278A1 - Fuel injection system

Info

Publication number: WO2013125278A1
Application number: PCT/JP2013/051151
Authority: WO
Inventors: 喬士日平; 隆幸島津
Original assignee: 株式会社ケーヒン
Priority date: 2012-02-23
Filing date: 2013-01-22
Publication date: 2013-08-29
Also published as: JP2013174137A

Abstract

A fuel injection system comprising a first control device for outputting a first pulse signal stipulating the charging time of a liquid fuel injection valve, and a second control device for generating a second pulse signal stipulating the charging time of a gas fuel injection valve on the basis of the first pulse signal during gas fuel injection and outputting the second pulse signal to the gas fuel injection valve. When the occurrence of a fuel cut is detected during the gas fuel injection, the second control device implements a cleaning mode for outputting the first pulse signal inputted from the first control device to the liquid fuel injection valve after the fuel cut has ended.

Description

Fuel injection system

The present invention relates to a fuel injection system.
This application claims priority based on Japanese Patent Application No. 2012-037740 for which it applied to Japan on February 23, 2012, and uses the content here.

Conventionally, as a technology for improving the fuel efficiency and environmental protection performance of a vehicle, there is a bi-fuel system that selectively switches between liquid fuel such as gasoline and gaseous fuel such as compressed natural gas (CNG) and supplies it to a single engine. Are known. This bi-fuel system is often constructed by adding a new gas injection system to an existing gasoline injection system in order to reduce development costs.

In the following Patent Document 1, a gasoline pulse (a pulse signal having a pulse width corresponding to a gasoline injection amount and used to drive a gasoline injector) output from an existing ECU that controls the gasoline injection amount is disclosed as a new ECU. And a technique for converting a gasoline pulse into a gas pulse having a pulse width suitable for gas fuel (a pulse signal used for driving a gas injector) by this new ECU.

Also, in the bi-fuel system, when operation with liquid fuel continues for a long time, that is, when operation with a gas injector is not performed for a long time, deposits may adhere to the gas injector and clogging may occur. Patent Document 2 listed below discloses a technique for performing gas injector clogging prevention control, that is, gas fuel injection by a gas injector when the fuel cut control is being performed and the in-cylinder temperature is lower than the self-ignition temperature of the gas fuel. Has been. Although not disclosed in the following Patent Document 1, in general, when operation with liquid fuel is not performed for a long time, deposits may adhere to the liquid fuel injector and clogging may occur.

Japanese National Table No. 6-502472 Japanese Unexamined Patent Publication No. 2011-220284

When applying the injector clogging prevention technique described in Patent Document 2 to the system configuration described in Patent Document 1, it is not desired to change the existing ECU from the viewpoint of reducing development costs. Therefore, it is necessary to determine whether or not the condition that the fuel cut control is being performed and the in-cylinder temperature is lower than the auto-ignition temperature is satisfied, and if the condition is satisfied, it is necessary to provide a function of performing control to prevent clogging of the injector .

In that case, since the gasoline pulse is not output from the existing ECU during the fuel cut, the new ECU cannot output the gas pulse, and liquid fuel injection (clogging prevention control) by the liquid fuel injector cannot be performed. Further, in Patent Document 2, the in-cylinder temperature is estimated by an arithmetic expression using intake air temperature, cooling water temperature, engine speed, and the like (see paragraph 0049 in Patent Document 2). If added, calculation processing becomes complicated and the load on the CPU becomes heavy.

The aspect which concerns on this invention is made | formed in view of the situation mentioned above, the 1st control apparatus which outputs the 1st pulse signal which prescribes | regulates the energization time of a liquid fuel injection valve, and the said 1st pulse at the time of gaseous fuel injection A fuel injection system comprising: a second control device that generates a second pulse signal that defines an energization time of a gaseous fuel injection valve based on the signal and outputs the second pulse signal to the gaseous fuel injection valve; without estimating the in-cylinder temperature An object of the present invention is to prevent clogging of a liquid fuel injection valve.

The present invention employs the following aspects in order to achieve the above object.
(1) An aspect according to the present invention includes a first control device that outputs a first pulse signal that defines an energization time of a liquid fuel injection valve; and a gaseous fuel injection valve based on the first pulse signal during gaseous fuel injection. A second control device that generates a second pulse signal that defines the energization time of the gas and outputs the second pulse signal to the gaseous fuel injection valve, wherein the second control device provides fuel during the gaseous fuel injection. When the occurrence of a cut is detected, a cleaning mode is implemented in which the first pulse signal input from the first control device is output to the liquid fuel injection valve after the fuel cut is completed.

(2) In the aspect of (1), the second control device returns to the gaseous fuel injection when the number of times of liquid fuel injection by the liquid fuel injection valve reaches a predetermined value by performing the cleaning mode. May be.

(3) In the above aspect (1) or (2), the second control device may perform the cleaning mode on condition that the engine speed is within a predetermined range after the fuel cut is completed. .

(4) In any one of the aspects (1) to (3), the second control device generates and terminates the fuel cut based on the presence or absence of the first pulse signal input from the first control device. May be judged.

In the aspect which concerns on this invention, when the 2nd control apparatus detects generation | occurrence | production of the fuel cut at the time of gaseous fuel injection, it is cleaning after the completion | finish of the said fuel cut, ie, the output of the 1st pulse signal by the 1st control apparatus restarted. Since the mode is executed, the liquid fuel injection valve can be cleaned (liquid fuel injection) without any problem. Moreover, in the aspect which concerns on this invention, since liquid fuel injection is implemented after completion | finish of a fuel cut, it is not necessary to estimate in-cylinder temperature in order to prevent fuel self-ignition during a fuel cut unlike the prior art. Therefore, according to the aspect of the present invention, it is possible to prevent clogging of the liquid fuel injection valve without estimating the in-cylinder temperature.

It is a schematic structure figure of fuel injection system A concerning this embodiment. 3 is a flowchart showing an injector clogging prevention process performed by a 2nd-ECU 4; 7 is a timing chart showing how the gas pulse signal and the gasoline pulse signal output from the 2nd-ECU 4 during gas operation change due to the injector clogging prevention process.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
FIG. 1 is a schematic configuration diagram of a fuel injection system A according to the present embodiment. The fuel injection system A is a bi-fuel system that selectively switches between liquid fuel (for example, gasoline) and gaseous fuel (for example, compressed natural gas) and supplies it to a single engine (not shown). A gas fuel supply system 2, a 1st-ECU (Electronic Control Unit) 3, a 2nd-ECU 4, and a fuel changeover switch 5.

The liquid fuel supply system 1 includes a gasoline tank 11, a gasoline supply pipe 12, and a gasoline injector 13 (liquid fuel injection valve). The gasoline tank 11 is a corrosion-resistant container that stores gasoline as liquid fuel, and has a built-in pump and regulator (not shown) that sucks the gasoline and sends it to the gasoline supply pipe 12.

The gasoline supply pipe 12 is a pipe for delivering gasoline from the gasoline tank 11 to the gasoline injector 13. The gasoline injector 13 is, for example, an electromagnetic valve (for example, a solenoid valve) mounted on the intake pipe so that the injection port is exposed toward the intake port of the engine, and corresponds to a gasoline pulse signal input from the 2nd-ECU 4. A predetermined amount of gasoline is injected.

The gaseous fuel supply system 2 includes a gas tank 21, a high pressure gas supply pipe 22, a shutoff valve 23, a regulator 24, a low pressure gas supply pipe 25, a gas injector 26 (gaseous fuel injection valve), and a gas fuel pressure sensor 27. And a gas fuel temperature sensor 28.

The gas tank 21 is a high pressure vessel filled with compressed natural gas (CNG) as gaseous fuel. The high-pressure gas supply pipe 22 is a high-pressure pipe for delivering high-pressure gas fuel from the gas tank 21 to the regulator 24. The shut-off valve 23 is an electromagnetic valve inserted in the high-pressure gas supply pipe 22 and opens or closes according to a shut-off valve drive signal input from the 2nd-ECU 4.

The regulator 24 is a pressure reducing valve disposed on the downstream side of the shutoff valve 23, and decompresses the high pressure gas fuel supplied from the gas tank 21 to a desired pressure when the shutoff valve 23 is opened to the low pressure gas supply pipe 25. Send it out. The low-pressure gas supply pipe 25 is a low-pressure piping for delivering low-pressure gas fuel from the regulator 24 to the gas injector 26. The gas injector 26 is, for example, an electromagnetic valve mounted on the intake pipe so that the injection port is exposed toward the intake port of the engine. The gas injector 26 injects a predetermined amount of gas fuel according to a gas pulse signal input from the 2nd-ECU 4. To do.

The gas fuel pressure sensor 27 detects the internal pressure of the low pressure gas supply pipe 25 (ie, the gas fuel pressure on the low pressure side) from the regulator 24, and outputs a gas fuel pressure signal indicating the detection result to the 2nd-ECU 4. . The gas fuel temperature sensor 28 detects the internal temperature (low pressure gas fuel temperature) of the low pressure gas supply pipe 25 and outputs a gas fuel temperature signal indicating the detection result to the 2nd-ECU 4.

The 1st-ECU 3 (first control device) calculates a gasoline injection amount based on various sensor signals indicating engine operation states input from various sensors (not shown) and is necessary for obtaining the gasoline injection amount. An energization time of the gasoline injector 13 (hereinafter referred to as a gasoline injector energization time) is calculated, and a gasoline pulse signal (first pulse signal) having a pulse width set to the gasoline injector energization time is generated and output to the 2nd-ECU 4 .

The 2nd-ECU 4 (second control device) includes a gas fuel pressure signal input from the gas fuel pressure sensor 27, a gas fuel temperature signal input from the gas fuel temperature sensor 28, and a gasoline pulse input from the 1st-ECU 3. Based on the signal and the fuel switching signal input from the fuel switch 5, energization control of the gasoline injector 13, the gas injector 26 and the shutoff valve 23 is performed.

When the 2nd-ECU 4 recognizes that gasoline is selected as the fuel to be used based on the fuel switching signal input from the fuel switch 5, the 2nd-ECU 4 shifts to the gasoline injection mode (liquid fuel injection mode) while When it is recognized that the gas is selected, the gas injection mode (gaseous fuel injection mode) is entered.

The 2nd-ECU 4 calculates the energization time of the gas injector 26 (hereinafter referred to as gas injector energization time) based on the gasoline pulse signal input from the 1st-ECU 3, and opens the shut-off valve 23 in the gas injection mode. The gas fuel supply from the gas tank 21 to the gas injector 26 is started and a gas pulse signal (second pulse signal) whose pulse width is set to the gas injector energizing time is output to the gas injector 26, while in the gasoline injection mode. A gasoline pulse signal is output to the gasoline injector 13.

The fuel change-over switch 5 is a switch that enables the fuel to be changed by a manual operation of the user, and indicates the state of the switch, that is, a fuel that indicates whether gasoline is selected as the fuel to be used or whether gas is selected. A switching signal is output to the 2nd-ECU 4.

Next, the operation of the fuel injection system A configured as described above will be described in detail.
When the engine is in operation, the 1st-ECU 3 does not depend on the state of the fuel changeover switch 5 (that is, regardless of gasoline operation or gas operation), and each fuel injection timing is based on the engine operation state recognized from various sensor signals. The gasoline injection amount to be injected from the gasoline injector 13 is calculated at the same time, the gasoline injector energization time necessary for obtaining the gasoline injection amount is calculated, and a gasoline pulse signal whose pulse width is set to the gasoline injector energization time is generated. And output to the 2nd-ECU 4.

In the case of a 4-cycle engine, it is necessary to perform fuel injection once while the crankshaft rotates twice. Therefore, every time the crankshaft rotates twice, a gasoline pulse having a predetermined pulse width is transferred from the 1st-ECU3 to the 2nd-ECU4. A signal is output once.

The 2nd-ECU 4 measures the pulse width of the gasoline pulse signal input from the 1st-ECU 3 as described above as the gasoline injector energization time, and uses the gasoline injector energization time as a flow characteristic of the gas injector 26, gas fuel pressure, and gas fuel. By correcting based on the temperature, the gas injector energization time is calculated.

In the gas injection mode, the 2nd-ECU 4 generates a gas pulse signal whose pulse width is set to the gas injector energizing time and outputs the gas pulse signal to the gas injector 26 with the shut-off valve 23 opened. Thus, a required amount of gas fuel is injected from the gas injector 26 according to the engine operating state.

On the other hand, the 2nd-ECU 4 outputs the gasoline pulse signal input from the 1st-ECU 3 to the gasoline injector 13 as it is in the gasoline injection mode. Thereby, the gasoline fuel of the quantity requested | required according to an engine driving | running state is injected from the gasoline injector 13. FIG.

Here, if the gas fuel operation is continued for a long time, deposits (for example, compressor oil used when filling the gas fuel) may adhere to the gasoline injector 13 and clogging may occur. Accordingly, the 2nd-ECU 4 performs an injector clogging prevention process shown in the flowchart of FIG. 2 in order to prevent the gasoline injector 13 from clogging. Note that the 2nd-ECU 4 repeatedly performs the injector clogging prevention process shown in FIG. 2 at a constant control cycle.

As shown in FIG. 2, when the 2nd-ECU 4 starts the injector clogging prevention process, it first determines whether or not the gas operation is currently being performed (whether or not it is in the gas injection mode) (step S1). In step S2, the process proceeds to step S2. On the other hand, in the case of “No”, the present injector clogging prevention process is ended (EXIT).

If “Yes” in step S1, the 2nd-ECU 4 determines whether the fuel is currently being cut (step S2). If “Yes”, the process proceeds to step S3, while “No”. In this case, the process proceeds to step S5. Here, when the fuel cut is in progress, the output of the gasoline pulse signal by the 1st-ECU 3 stops, so the 2nd-ECU 4 determines whether the fuel is being cut based on the presence or absence of the gasoline pulse signal input from the 1st-ECU 3 ( That is, it is determined whether or not a fuel cut has occurred and ended.

The 2nd-ECU 4 determines whether or not the current engine speed is within a predetermined range if “Yes” in the above step S2 (step S3). If “No”, the present injector clogging prevention process is performed. On the other hand, in the case of “Yes”, after the execution of the cleaning mode is permitted, the present injector clogging prevention processing is ended (step S4). Here, a crank pulse signal output from a crank sensor (not shown) (a pulse signal having a period required for the crankshaft to rotate a predetermined angle) is input to the 2nd-ECU 4 (see FIG. 1). The 2nd-ECU 4 calculates the engine speed from this crank pulse signal.

Note that the “predetermined range” of the engine speed indicates a speed range in which the gas injection can be safely switched to the gasoline injection. For example, in the high speed range, gas / gasoline injection cannot be switched at the same time, and there is a possibility that both injections or missing injections may occur, or a circuit failure may occur due to switching of injected fuel. The injection fuel is not switched at the rotational speed. In addition, since switching in a lower rotational range than the idling speed may cause instability of combustion, for example, when the idling speed is 600 rpm, the injected fuel is used at an engine speed of 500 rpm or less. Is not switched.

The 2nd-ECU 4 determines whether or not the execution of the cleaning mode is permitted in the case of “No” in step S2, that is, when the fuel cut is completed (step S5). On the other hand, the present injector clogging prevention process is terminated, while in the case of “Yes”, the process proceeds to step S6.
Then, if “Yes” in step S5, that is, if the execution of the cleaning mode is permitted, the 2nd-ECU 4 determines whether the number of gasoline injections (number of liquid fuel injections) by the gasoline injector 13 has reached a predetermined value. If “No”, the process proceeds to step S7, while if “Yes”, the process proceeds to step S8.

The 2nd-ECU 4 outputs the gasoline pulse signal input from the 1st-ECU 3 to the gasoline injector 13 if “No” in step S6, that is, if the number of gasoline injections by the gasoline injector 13 has not reached the predetermined value. A cleaning mode is performed (step S7). Thereby, the gasoline injection by the gasoline injector 13 is implemented, and the deposit adhering to the gasoline injector 13 can be removed (cleaned). The “predetermined value” of the number of gasoline injections is set to the number of times that the deposit adhered to the gasoline injector 13 can be sufficiently removed by the gasoline injection.

Further, in the case of “Yes” in the above step S6, that is, when the number of gasoline injections by the gasoline injector 13 reaches a predetermined value, the 2nd-ECU 4 performs gas injection for gas operation (ie, gas injection for gas operation). Returning to the output of the gas pulse signal to the gas injector 26 (step S8). Then, the 2nd-ECU 4 ends the present injector clogging prevention process after completing the permission to perform the cleaning mode (step S9).

To summarize the above-described injector clogging prevention processing, when the 2nd-ECU 4 detects the occurrence of a fuel cut during gas injection, the engine speed is within a predetermined range after the fuel cut ends (the injection fuel can be switched safely). When the cleaning mode is performed on the condition that the number of gasoline injections by the gasoline injector 13 reaches a predetermined value due to the execution of the cleaning mode, the operation returns to the gas injection.

FIG. 3 is a timing chart showing how the gas pulse signal and the gasoline pulse signal output from the 2nd-ECU 4 change during the gas operation by such an injector clogging prevention process. As shown in FIG. 3, the gas pulse signal is output from the 2nd-ECU 4 to the gas injector 26 during the gas operation, but the output of the gas pulse signal stops during the fuel cut, and after the fuel cut ends, the cleaning mode As a result, the 2nd-ECU 4 outputs a gasoline pulse signal to the gasoline injector 13 and returns to gas injection when the number of gasoline injections reaches a predetermined value.

As described above, in this embodiment, when the 2nd-ECU 4 detects the occurrence of a fuel cut during gas injection, the cleaning mode is performed after the fuel cut ends, that is, after the output of the gasoline pulse signal by the 1st-ECU 3 is resumed. Since it carries out, cleaning (gasoline injection) of the gasoline injector 13 can be carried out without any problem. Moreover, in this embodiment, since gasoline injection is performed after the end of the fuel cut, it is not necessary to estimate the in-cylinder temperature in order to prevent fuel self-ignition during the fuel cut as in the prior art. Therefore, according to the present embodiment, it is possible to prevent clogging of the gasoline injector 13 without estimating the in-cylinder temperature.

In addition, this invention is not limited to the said embodiment, Of course, you may change embodiment in the range which does not deviate from the meaning of this invention. For example, the present invention can be applied to a bi-fuel system that selectively switches a gaseous fuel other than CNG and a liquid fuel other than gasoline and supplies the fuel to a single engine.

A ... fuel injection system, 1 ... liquid fuel supply system, 2 ... gaseous fuel supply system, 3 ... 1st-ECU (first control device), 4 ... 2nd-ECU (second control device), 5 ... fuel changeover switch, 13 ... gasoline injector (liquid fuel injection valve), 26 ... gas injector (gas fuel injection valve)

Claims

A first control device that outputs a first pulse signal that defines an energization time of the liquid fuel injection valve;
A second control device that generates a second pulse signal that defines an energization time of the gaseous fuel injection valve based on the first pulse signal during gaseous fuel injection and outputs the second pulse signal to the gaseous fuel injection valve. There,
When the second control device detects the occurrence of a fuel cut during the gaseous fuel injection, the second control device outputs the first pulse signal input from the first control device to the liquid fuel injection valve after the fuel cut ends. A fuel injection system that performs a cleaning mode.
The said 2nd control apparatus returns to the said gaseous fuel injection, when the frequency | count of the liquid fuel injection by the said liquid fuel injection valve reaches predetermined value by implementation of the said cleaning mode, The said fuel control device is returned to the gaseous fuel injection. Fuel injection system.
3. The fuel injection system according to claim 1, wherein the second control device performs the cleaning mode on condition that an engine speed is within a predetermined range after the fuel cut is completed.
The first control device according to any one of claims 1 to 3, wherein the second control device determines the occurrence and end of the fuel cut based on the presence or absence of the first pulse signal input from the first control device. The fuel injection system according to item.