JP2013151880A - Fuel injection system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To achieve a high-precision control of a fuel gas injection amount.SOLUTION: A fuel injection system includes: a first control device for outputting a first pulse signal specifying an energization period of a liquid fuel injection valve; and a second control device for generating a second pulse signal specifying an energization period of a gas fuel injection valve utilizing the first pulse signal. The second control device includes: an intake air volume estimation means for estimating an intake air volume of a cylinder based on the first pulse signal; and an energization period setting means for setting the energization period of the gas fuel injection valve based on the intake air volume.

Description

 The present invention relates to a fuel injection system.

  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 this bi-fuel system, the existing electronic control device that controls the gasoline injection amount outputs a gasoline pulse that defines the energization time of the gasoline injector to the new electronic control device, while the new electronic control device A gas pulse that defines the energization time of the gas injector is generated using the pulse (see Patent Document 1 below).

  In the following Patent Document 1, a gas flow effective index time is calculated by multiplying a gasoline pulse by a coefficient for gas fuel injection, and a fuel flow rate index is calculated by multiplying the engine rotation speed obtained from the gasoline pulse and the gasoline effective injection time. And a technique for correcting an error in the gas fuel injection amount due to a change in fuel injection pressure caused by a change in the fuel flow rate is disclosed by correcting the gas fuel effective injection time based on the fuel flow rate index. Yes.

JP 2008-38871 A

  In the above prior art, since the gas fuel effective injection time is calculated by directly multiplying the gasoline pulse by the coefficient for gas fuel injection, there is a possibility that the error of the gas fuel injection amount becomes large.

 The present invention has been made in view of the above-described circumstances, and includes a first control device that outputs a first pulse signal that defines the energization time of a liquid fuel injection valve, and gaseous fuel using the first pulse signal. An object of the present invention is to realize a highly accurate control of a gaseous fuel injection amount in a fuel injection system including a second control device that generates a second pulse signal that defines an energization time of an injection valve.

 In order to achieve the above object, in the present invention, as a first solving means related to a fuel injection system, a first control device that outputs a first pulse signal that defines an energization time of a liquid fuel injection valve; And a second control device that generates a second pulse signal that defines the energization time of the gaseous fuel injection valve using a pulse signal, wherein the second control device is based on the first pulse signal. A means is provided that includes an intake air amount estimation unit that estimates the intake air amount of the cylinder, and an energization time setting unit that sets an energization time of the gaseous fuel injection valve based on the intake air amount.

 Further, in the present invention, as a second solving means related to the fuel injection system, in the first solving means, the intake air amount estimating means determines the pulse width of the first pulse signal as the energization of the liquid fuel injection valve. An energization time measuring means for measuring time, and a liquid fuel pressure correction time, a liquid fuel temperature correction time, and an invalid energization time of the liquid fuel injection valve from the energization time of the liquid fuel injection valve measured by the energization time measurement means A liquid fuel injection amount calculating means for calculating a liquid fuel injection amount based on a value obtained by removing the fuel, and the liquid fuel injection amount calculated by the liquid fuel injection amount calculating means and a theoretical air-fuel ratio of the liquid fuel, And an intake air amount calculating means for calculating the intake air amount based on the above.

 According to the present invention, as a third solving means related to the fuel injection system, in the first or second solving means, the energization time setting means is the intake air estimated by the intake air amount estimating means. A gaseous fuel injection amount calculating means for calculating a gaseous fuel injection amount on the basis of the amount and a theoretical air-fuel ratio of the gaseous fuel, and the gaseous fuel based on the gaseous fuel injection amount calculated by the gaseous fuel injection amount calculating means Basic energization time calculation means for calculating the basic energization time of the injection valve, and the basic energization time calculated by the basic energization time calculation means are corrected based on the temperature and pressure of the gaseous fuel, and obtained after the correction. Means for adding a final energization time for calculating the final energization time of the gaseous fuel injection valve by adding the invalid energization time of the gaseous fuel injection valve to the value is adopted.

 According to the present invention, the first control device that outputs the first pulse signal that defines the energization time of the liquid fuel injection valve, and the second that defines the energization time of the gaseous fuel injection valve using the first pulse signal. A fuel injection system including a second control device for generating a pulse signal, wherein the second control device estimates an intake air amount of the cylinder based on a first pulse signal input from the first control device; Since the energization time of the gaseous fuel injection valve is set based on the estimation result, it is possible to realize highly accurate control of the gaseous fuel injection amount.

It is a schematic structure figure of fuel injection system A concerning this embodiment. Among the functions of the 2nd-ECU 4, functions that are effective during gas operation are shown in a block diagram.

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). And a gaseous 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 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, for example, 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 an electromagnetic valve attached to the intake pipe so that, for example, the injection port is exposed toward the intake port of the engine, and 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 (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.

 1st-ECU3 (1st control apparatus) is the gasoline injection amount (liquid fuel injection amount) which should be injected from the gasoline injector 13 based on the various sensor signals input from the various sensors (illustration omitted) which detect an engine driving | running state. And a gasoline pulse signal (first pulse signal) that defines the energization time of the gasoline injector 13 (hereinafter referred to as gasoline injector energization time) is generated based on the calculation result, and is 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.

 Specifically, when the 2nd-ECU 4 recognizes that gasoline is selected as the fuel to be used for engine operation based on the fuel switching signal input from the fuel switch 5 (that is, during gasoline operation), The gasoline pulse signal input from the 1st-ECU 3 is output to the gasoline injector 13 as it is.

 In addition, when the 2nd-ECU 4 recognizes that gas fuel is selected as the fuel used for engine operation (that is, during gas operation), the 2nd-ECU 4 opens the shut-off valve 23 to the gas injector 26 from the gas tank 21. Gas gas signal (second pulse signal) that starts energizing time of the gas injector 26 (hereinafter referred to as gas injector energizing time) using the gasoline pulse signal input from the 1st-ECU 3 is started. ) And output to the gas injector 26.

 The fuel change-over switch 5 is a switch that enables the fuel to be changed by a user's manual operation. Whether the liquid fuel is selected as the state of the switch, that is, the fuel used for engine operation, or the gaseous fuel is selected. A fuel switching signal indicating whether or not the fuel is being output is output to the 2nd-ECU 4.

 Next, the operation of the fuel injection system A configured as described above, particularly the operation during gas operation will be described in detail with reference to FIG.

 FIG. 2 is a block diagram showing functions that are effective during gas operation among the functions of the 2nd-ECU 4. As shown in FIG. 2, the 2nd-ECU 4 has an intake air amount estimation unit 41 (estimating the intake air amount of the cylinder based on a gasoline pulse signal input from the 1st-ECU 3 as a function that is effective during gas operation. (Intake air amount estimation means) and a gas injector energization time setting unit 42 (energization time setting means) for setting the gas injector energization time based on the intake air amount.

  Note that the 1st-ECU 3 does not depend on the state of the fuel selector switch 5 (that is, regardless of the gasoline operation or the gas operation) while the engine is operating, and the gasoline injector 13 at each fuel injection timing based on various sensor signals. The gasoline injection amount to be injected is calculated based on the calculation result, and a gasoline pulse signal for defining the gasoline injector energizing time based on the calculation result, that is, a gasoline pulse signal having a pulse width corresponding to the gasoline injector energizing time is generated and sent to the 2nd-ECU 4 Output.

 The intake air amount estimation unit 41 of the 2nd-ECU 4 has a gasoline injector energization time measurement unit 41a as a function for estimating the intake air amount of the cylinder based on the gasoline pulse signal input from the 1st-ECU 3 as described above. A gasoline fuel pressure correction time estimation unit 41b, a gasoline fuel temperature correction time estimation unit 41c, a gasoline injector invalid energization time estimation unit 41d, a gasoline injection amount calculation unit 41e, and an intake air amount calculation unit 41f are included.

 First, the gasoline injector energization time measurement unit 41a (energization time measurement means) measures the pulse width of the gasoline pulse signal input from the 1st-ECU 3 as the gasoline injector energization time, and the measurement result is sent to the gasoline injection amount calculation unit 41e. Output.

 Here, in the gasoline injector energization time, the basic energization time (gasoline injector basic energization time) calculated from the gasoline injection amount and the gasoline fuel pressure correction time for correcting the change in density of the gasoline fuel due to the pressure change. And a gasoline fuel temperature correction time for correcting a change in density of gasoline fuel due to a temperature change, and an energization time that does not actually contribute to gasoline injection (the time from the start of energization of the gasoline injector 13 to the completion of valve opening; the gasoline injector) Invalid energization time).

 In order to accurately calculate the gasoline injection amount by the gasoline injection amount calculation unit 41e, and thus to accurately calculate the intake air amount by the intake air amount calculation unit 41f, the gasoline fuel pressure correction time is calculated from the gasoline injector energization time. It is necessary to cancel (remove). This is because the 1st-ECU 3 adds or subtracts the gasoline fuel pressure correction time, that is, the time that does not affect the gasoline injection amount, with respect to the gasoline injector basic energization time calculated from the gasoline injection amount as pressure correction of the gasoline fuel. Because.

  Therefore, the gasoline fuel pressure correction time estimation unit 41b estimates the gasoline fuel pressure correction time included in the gasoline injector energization time, and outputs the estimation result to the gasoline injection amount calculation unit 41e. For the estimation of the gasoline fuel pressure correction time, for example, the gasoline fuel pressure correction time may be calculated from a predetermined arithmetic expression based on the current engine operating state grasped from various sensor signals, or The gasoline fuel pressure correction time corresponding to the current engine operating state may be searched using table data indicating the correlation with the gasoline fuel pressure correction time.

 Further, in order to accurately calculate the gasoline injection amount by the gasoline injection amount calculation unit 41e, and thus to accurately calculate the intake air amount by the intake air amount calculation unit 41f, the gasoline fuel temperature correction is performed from the gasoline injector energization time. Need to cancel time. This is because the 1st-ECU 3 adds or subtracts the gasoline fuel temperature correction time, that is, the time that does not affect the gasoline injection amount, to the gasoline injector basic energization time calculated from the gasoline injection amount as the temperature correction of the gasoline fuel. Because.

 Therefore, the gasoline fuel temperature correction time estimation unit 41c estimates the gasoline fuel temperature correction time included in the gasoline injector energization time, and outputs the estimation result to the gasoline injection amount calculation unit 41e. As a method for estimating the gasoline fuel temperature correction time, a method similar to the gasoline fuel pressure correction time described above can be used.

 Further, in order to accurately calculate the gasoline injection amount by the gasoline injection amount calculation unit 41e, and thus to accurately calculate the intake air amount by the intake air amount calculation unit 41f, the gasoline injector invalid energization from the gasoline injector energization time. Need to cancel time. This is because, depending on the engine operating state, the gasoline injector basic energization time may not vary even though the gasoline injector invalid energization time has increased or decreased.

 Therefore, the gasoline injector invalid energization time estimation unit 41d estimates the gasoline injector invalid energization time included in the gasoline injector energization time, and outputs the estimation result to the gasoline injection amount calculation unit 41e. As a method for estimating the gasoline injector invalid energization time, a method similar to the gasoline fuel pressure correction time described above can be used.

 The gasoline injection amount calculating unit 41e (liquid fuel injection amount calculating means) cancels the gasoline fuel pressure correction time, the gasoline fuel temperature correction time, and the gasoline injector invalid energization time from the gasoline injector energization time (that is, the gasoline injector invalid energization time). The gasoline injection amount is calculated based on the basic injector energization time, and the calculation result is output to the intake air amount calculation unit 41f.

 Specifically, the gasoline injection amount calculation unit 41e subtracts the gasoline fuel pressure correction time, the gasoline fuel temperature correction time, and the gasoline injector invalid energization time from the gasoline injector energization time (gasoline fuel pressure correction time, gasoline fuel temperature correction time). Thus, the gasoline injector basic energization time is calculated, and the gasoline injection amount is calculated from the gasoline injector basic energization time based on the flow rate characteristics of the gasoline injector 13 measured in advance.

Then, the intake air amount calculation unit 41f (intake air amount calculation means) calculates the intake air amount of the cylinder based on the gasoline injection amount calculated by the gasoline injection amount calculation unit 41e and the theoretical air-fuel ratio of gasoline, The calculation result is output to the gas injector energization time setting unit 42. The intake air amount can be calculated using the following equation (1). The intake air amount corresponding to the gasoline injection amount calculated this time may be searched using table data indicating the correlation between the gasoline injection amount and the intake air amount.
Intake air amount = gasoline injection amount x gasoline theoretical air-fuel ratio (1)

 The gas injector energization time setting unit 42 functions as a gas fuel injection amount calculation unit 42a, as a function for setting the gas injector energization time based on the intake air amount estimated by the intake air amount estimation unit 41 as described above. A gas injector basic energization time calculation unit 42b, a gas fuel pressure correction coefficient calculation unit 42c, a gas fuel temperature correction coefficient calculation unit 42d, a gas injector invalid energization time calculation unit 42e, and a gas injector energization time calculation unit 42f are included.

The gas fuel injection amount calculation unit 42a (gaseous fuel injection amount calculation means) calculates the gas fuel injection amount based on the intake air amount estimated by the intake air amount estimation unit 41 and the theoretical air-fuel ratio of the gas fuel, The calculation result is output to the gas injector basic energization time calculation unit 42b. The gas fuel injection amount can be calculated using the following equation (2). Note that the gas fuel injection amount corresponding to the intake air amount calculated this time may be searched using table data indicating the correlation between the intake air amount and the gas fuel injection amount.
Gas fuel injection amount = Intake air amount ÷ Theoretical air-fuel ratio of gas fuel (2)

  The gas injector basic energization time calculation unit 42b (basic energization time calculation means) uses the gas fuel injection amount calculated by the gas fuel injection amount calculation unit 42a based on the flow rate characteristics of the gas injector 26 measured in advance. The basic energization time (gas injector basic energization time) of the gas injector 26 is calculated, and the calculation result is output to the gas injector energization time calculation unit 42f.

  Here, in order to calculate an accurate gas injector energization time by the gas injector energization time calculation unit 42f, a gas fuel for correcting a volume variation of the gas fuel due to a pressure change with respect to the gas injector basic energization time. While performing pressure correction and gas fuel temperature correction for correcting the sonic fluctuation of the gas fuel due to temperature change, the energization time that does not actually contribute to gas injection (the time from the start of energization of the gas injector 26 to the completion of valve opening) It is necessary to add a gas injector invalid energization time).

  Therefore, the gas fuel pressure correction coefficient calculating unit 42c is a coefficient for correcting the gas fuel pressure during the basic gas injector basic energization time based on the gas fuel pressure on the low pressure side of the regulator 24 detected by the gas fuel pressure sensor 27. (Gas fuel pressure correction coefficient) is calculated, and the calculation result is output to the gas injector energization time calculation unit 42f.

The gas fuel pressure correction coefficient can be obtained from the ratio of the fluctuating pressure between the gas fuel pressure detected this time and the reference fuel pressure as a reference, according to Boyle's law equation (3) below. The gas fuel pressure correction coefficient corresponding to the gas fuel pressure detected this time may be searched using table data indicating the correlation between the gas fuel pressure and the gas fuel pressure correction coefficient.
Gas fuel pressure correction coefficient = V2 / V1 = P1 / P2 (3)
(V1: reference fuel volume, V2: fuel volume, P1: reference fuel pressure, P2: gas fuel pressure)

  Further, the gas fuel temperature correction coefficient calculating unit 42d is a coefficient for performing gas fuel temperature correction of the gas injector basic energization time based on the gas fuel temperature on the lower pressure side than the regulator 24 detected by the gas fuel temperature sensor 28. (Gas fuel temperature correction coefficient) is calculated, and the calculation result is output to the gas injector energization time calculation unit 42f.

  The gas fuel temperature correction coefficient can be obtained from the ratio of the fluctuating pressure between the gas fuel temperature detected this time and the reference fuel temperature serving as a reference, using the sound velocity equation of gas (4) below. The gas fuel temperature correction coefficient corresponding to the gas fuel temperature detected this time may be searched using table data indicating the correlation between the gas fuel temperature and the gas fuel temperature correction coefficient.

  The gas injector invalid energization time calculation unit 42e calculates the gas injector invalid energization time from a predetermined arithmetic expression based on the battery voltage and the gas fuel pressure, and outputs the calculation result to the gas injector energization time calculation unit 42f. Note that the gas injector invalid energization time corresponding to the current battery voltage and gas fuel pressure may be searched using table data indicating the correlation between the battery voltage and gas fuel pressure and the gas injector invalid energization time.

  Then, the gas injector energization time calculation unit 42f (final energization time calculation means) multiplies the gas injector basic energization time by the gas fuel pressure correction coefficient and the gas fuel temperature correction coefficient, thereby correcting the gas fuel pressure and the gas fuel temperature. And the final gas injector energization time is calculated by adding the gas injector invalid energization time to the value obtained after the correction.

  When the 2nd-ECU 4 calculates the gas injector energizing time by the function that is effective during gas operation as described above, a gas pulse signal that defines the gas injector energizing time based on the calculation result, that is, a pulse corresponding to the gas injector energizing time. A gas pulse signal having a width is generated and output to the gas injector 26. Thus, a required amount of gas fuel is injected from the gas injector 26 according to the engine operating state.

  According to the present embodiment as described above, the 2nd-ECU 4 estimates the intake air amount of the cylinder based on the gasoline pulse signal input from the 1st-ECU 3, and the gas injector energization time (gas pulse) based on the estimation result. Since the signal pulse width is set, it is possible to realize highly accurate control of the amount of gas fuel injected from the gas injector 26.

  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.

  DESCRIPTION OF SYMBOLS A ... Fuel injection system, 3 ... 1st-ECU (1st control apparatus), 4 ... 2nd-ECU (2nd control apparatus), 13 ... Gasoline injector (liquid fuel injection valve), 26 ... Gas injector (gaseous fuel injection valve) , 41... Intake air amount estimation unit (intake air amount estimation means), 42... Gas injector energization time setting unit (energization time setting means), 41 a... Gasoline injector energization time measurement unit (energization time measurement means), 41 e. Injection amount calculation unit (liquid fuel injection amount calculation unit), 41f ... intake air amount calculation unit (intake air amount calculation unit), 42a ... gas fuel injection amount calculation unit (gaseous fuel injection amount calculation unit), 42b ... gas injector basics Energizing time calculating unit (basic energizing time calculating unit), 42f... Gas injector energizing time calculating unit (final energizing time calculating unit)

Claims (3)

A first control device that outputs a first pulse signal that defines the energization time of the liquid fuel injection valve, and a second pulse signal that generates a second pulse signal that defines the energization time of the gaseous fuel injection valve using the first pulse signal. A fuel injection system comprising two control devices,
The second control device includes:
Intake air amount estimating means for estimating the intake air amount of the cylinder based on the first pulse signal;
Energization time setting means for setting an energization time of the gaseous fuel injection valve based on the intake air amount;
A fuel injection system comprising: The intake air amount estimation means includes
Energization time measuring means for measuring the pulse width of the first pulse signal as the energization time of the liquid fuel injection valve;
Based on values obtained by removing the liquid fuel pressure correction time, the liquid fuel temperature correction time, and the invalid energization time of the liquid fuel injector from the energization time of the liquid fuel injector measured by the energization time measuring means. A liquid fuel injection amount calculating means for calculating the liquid fuel injection amount;
Intake air amount calculation means for calculating the intake air amount based on the liquid fuel injection amount calculated by the liquid fuel injection amount calculation means and the theoretical air-fuel ratio of the liquid fuel;
The fuel injection system according to claim 1, further comprising: The energization time setting means includes
Gaseous fuel injection amount calculating means for calculating a gaseous fuel injection amount based on the intake air amount estimated by the intake air amount estimating means and the theoretical air-fuel ratio of the gaseous fuel;
Basic energization time calculating means for calculating a basic energization time of the gaseous fuel injection valve based on the gaseous fuel injection amount calculated by the gaseous fuel injection amount calculating means;
The basic energization time calculated by the basic energization time calculating means is corrected based on the temperature and pressure of the gaseous fuel, and the final energization time of the gaseous fuel injection valve is added to the value obtained after the correction. Final energizing time calculating means for calculating energizing time of the gaseous fuel injection valve;
The fuel injection system according to claim 1, further comprising:

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