JP2011132930A - Ignition system of gas fuel internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To suppress the deterioration of the exhaust properties and drivability in a gas fuel internal combustion engine. <P>SOLUTION: An ignition system of the gas fuel internal combustion engine is provided with an ignition means that ignites a gas fuel, and an ignition timing correction means (S106) that advances the ignition timing to the gas fuel by the ignition means when the inert gas concentration of the gas fuel is high compared to when the inert gas concentration of the gas fuel is low. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an ignition system for a gas fuel internal combustion engine.

  Patent Document 1 discloses a technology for controlling a fuel injection amount according to a representative value of a calorific value determined according to a gas composition of a gas fuel and an octane number determined according to the gas composition of the gas fuel in a control device for a gas fuel internal combustion engine. A technique for controlling the ignition timing according to the representative value is disclosed.

There is a possibility that an inert gas such as CO ₂ or N ₂ is mixed in the gas fuel. When the inert gas is mixed into the gas fuel, the air-fuel ratio of the air-fuel mixture is affected according to its concentration. However, even when the inert gas concentration of the gas fuel changes, the air-fuel ratio of the air-fuel mixture can be controlled to a desired value by performing feedback control using an A / F sensor.

JP-A-10-61460 JP-A-8-093564 JP 2001-193571 A

  When the inert gas concentration of the gas fuel changes, it also affects the combustion state when the gas fuel burns. For example, when the inert gas concentration of the gas fuel increases, the combustion speed during combustion of the gas fuel decreases. For this reason, the inert gas concentration of the gas fuel increases excessively, which may cause deterioration of exhaust properties and drivability.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a technique capable of suppressing deterioration of exhaust properties and drivability in a gas fuel internal combustion engine.

  In the gas fuel internal combustion engine, the present invention corrects the ignition timing according to the inert gas concentration of the gas fuel.

More specifically, the ignition system for a gas fuel internal combustion engine according to the present invention is:
Ignition means for igniting the gas fuel;
Ignition timing correction means for advancing the ignition timing of the gas fuel by the ignition means when the inert gas concentration of the gas fuel is high compared to when the inert gas concentration of the gas fuel is low;
It is characterized by providing.

  According to the present invention, the ignition timing is advanced when the inert gas concentration of the gas fuel increases and the combustion speed during combustion of the gas fuel decreases. Thereby, the deterioration of the combustion state accompanying an increase in the inert gas concentration can be suppressed. As a result, it is possible to suppress the deterioration of exhaust properties and drivability.

The ignition system for a gas fuel internal combustion engine according to the present invention may further include a determination unit that determines whether or not the inert gas concentration of the gas fuel is higher than a predetermined concentration. Here, the predetermined concentration is a value set in advance as an upper limit value of the inert gas concentration at which the combustion speed during combustion of the gas fuel falls within an allowable range.

  In the above case, the ignition timing correction means may advance the ignition timing of the gas fuel by the ignition means when the determination means determines that the inert gas concentration of the gas fuel is higher than a predetermined concentration.

  The ignition system for a gas fuel internal combustion engine according to the present invention may further include at least one of an injection amount command value correction unit, a rotation speed acquisition unit, and a pressure acquisition unit. The injection amount command value correcting means corrects the command value of the fuel injection amount for the fuel injection valve of the gas fuel internal combustion engine so as to adjust the torque of the gas fuel internal combustion engine to the target torque. The rotation speed acquisition means acquires the rotation speed of the gas fuel internal combustion engine. The pressure acquisition means acquires the pressure of the gas fuel injected from the fuel injection valve.

  In the above-described case, the determination means has an increase correction amount of the fuel injection amount command value by the injection amount command value correction means that is greater than a predetermined threshold value, and the rotational speed of the gas fuel internal combustion engine acquired by the rotation speed acquisition means. When the fluctuation amount is smaller than a predetermined threshold value or when the pressure of the gas fuel acquired by the pressure acquisition means is within a predetermined normal range and the fluctuation amount is smaller than the predetermined threshold value, the inert gas of the gas fuel It may be determined that the concentration is higher than a predetermined concentration. Further, when both the rotational speed acquisition means and the pressure acquisition means are provided, the determination means obtains the rotational speed when the increase correction amount of the command value of the fuel injection amount by the injection amount command value correction means is larger than a predetermined threshold. The fluctuation amount of the rotational speed of the gas fuel internal combustion engine acquired by the means is smaller than a predetermined threshold, the pressure of the gas fuel acquired by the pressure acquisition means is within a predetermined normal range, and the fluctuation amount is predetermined. It may be determined that the inert gas concentration of the gas fuel is higher than a predetermined concentration when the value is smaller than the threshold value.

  According to this, it is possible to determine with higher accuracy whether or not the inert gas concentration of the gas fuel is higher than the predetermined concentration without separately providing a sensor for detecting the inert gas concentration.

  ADVANTAGE OF THE INVENTION According to this invention, the deterioration of exhaust property and drivability can be suppressed in a gas fuel internal combustion engine.

It is a figure which shows schematic structure of the gas fuel internal combustion engine which concerns on an Example, its fuel system, and an intake / exhaust system. It is a flowchart which shows the flow of the ignition timing control which concerns on an Example.

  Hereinafter, specific embodiments of the present invention will be described with reference to the drawings. The dimensions, materials, shapes, relative arrangements, and the like of the components described in the present embodiment are not intended to limit the technical scope of the invention to those unless otherwise specified.

<Example>
(Outline configuration)
FIG. 1 is a diagram showing a schematic configuration of a gas fuel internal combustion engine and its fuel system and intake / exhaust system according to the present embodiment. The internal combustion engine 1 is a vehicle driving engine that uses gasoline and compressed natural gas (hereinafter referred to as CNG) as fuel. The internal combustion engine 1 has four cylinders 2. Each cylinder 2 is provided with a spark plug 3. In this embodiment, the spark plug 3 corresponds to the ignition means according to the present invention.

  An intake manifold 4 and an exhaust manifold 5 are connected to the internal combustion engine 1. An intake passage 6 is connected to the intake manifold 4. An exhaust passage 7 is connected to the exhaust manifold 5. The four branch pipes of the intake manifold 4 are connected to the respective cylinders 2. Each branch pipe is provided with a gasoline injector 8 for injecting gasoline and a CNG injector 9 for injecting CNG.

  Each gasoline injector 8 is connected to a gasoline delivery pipe 10. One end of a gasoline supply passage 12 is connected to the gasoline delivery pipe 10, and the other end of the gasoline supply passage 12 is connected to a gasoline tank 13. A feed pump 14 is installed in the gasoline supply passage 12. Gasoline is supplied from the gasoline tank 13 to the gasoline delivery pipe 10 via the gasoline supply passage 12, and further, gasoline is supplied from the gasoline delivery pipe 10 to each gasoline injector 8.

  Each CNG injector 9 is connected to a CNG delivery pipe 11. One end of a CNG supply passage 15 is connected to the CNG delivery pipe 11, and the other end of the CNG supply passage 15 is connected to a CNG tank 16. A regulator 17 is installed in the CNG supply passage 15. CNG is supplied from the CNG tank 16 to the CNG delivery pipe 11 via the CNG supply passage 15, and further CNG is supplied from the CNG delivery pipe 11 to each CNG injector 9.

  The CNG delivery pipe 11 is provided with a pressure sensor 23 that detects the pressure of the CNG in the CNG delivery pipe 11 and a temperature sensor 24 that detects the temperature of the CNG. Further, a pressure sensor 25 that detects the pressure of CNG in the CNG supply passage 15 and a temperature sensor 26 that detects the temperature of the CNG are also provided upstream of the regulator 17 in the CNG supply passage 15.

  In the intake passage 6, an air cleaner 18, an air flow meter 22, and a throttle valve 19 are installed in this order. The exhaust passage 7 is provided with an exhaust purification catalyst 21 configured by an A / F sensor 27 that detects an air-fuel ratio of exhaust, a three-way catalyst, and the like.

  The internal combustion engine 1 is provided with an electronic control unit (ECU) 20. The ECU 20 is a unit that controls the operating state and the like of the internal combustion engine 1. An air flow meter 22, pressure sensors 23 and 25, temperature sensors 24 and 26, and an A / F sensor 27 are electrically connected to the ECU 20. Furthermore, a crank angle sensor 28 that detects the crank angle of the internal combustion engine 1 is also electrically connected to the ECU 20. Output signals from the sensors are input to the ECU 20. The ECU 20 derives the engine speed of the internal combustion engine 1 based on the output signal of the crank angle sensor 28.

  Further, the gasoline injectors 8, the CNG injectors 9, the feed pump 14, the regulator 17, and the throttle valve 19 are electrically connected to the ECU 20. These are controlled by the ECU 20.

  Note that the ignition system according to the present invention can be applied to an engine other than the engine configured as described above. For example, the present invention can be applied to an engine that uses only CNG as fuel, and can also be applied to an engine that directly injects fuel into a cylinder.

(Ignition timing correction control)
The inert gas concentration of CNG tends to vary depending on the country or region. When the inert gas concentration of CNG increases excessively, the combustion state deteriorates due to a decrease in the combustion speed when CNG burns. As a result, there is a risk of deteriorating exhaust properties and drivability. In this embodiment, when CNG is used as a fuel in order to suppress such deterioration of exhaust properties and drivability accompanying an increase in the inert gas concentration of CNG, ignition is performed according to the inert gas concentration. Control to correct the time.

  Specifically, it is determined whether the inert gas concentration of CNG is higher than a predetermined concentration. When it is determined that the CNG inert gas concentration is higher than the predetermined concentration, the ignition timing by the spark plug 3 is advanced from the normal time (that is, when the CNG inert gas concentration is equal to or lower than the predetermined concentration). . Here, the predetermined concentration is an upper limit value of the inert gas concentration at which the combustion speed during the combustion of CNG falls within an allowable range. Such a predetermined concentration can be set in advance based on experiments or the like.

  Even when the inert gas concentration of CNG increases and the combustion speed decreases, the deterioration of the combustion state can be suppressed by advancing the ignition timing. As a result, it is possible to suppress the deterioration of exhaust properties and drivability.

(Inert gas concentration determination)
Next, a method for determining whether the inert gas concentration of CNG is higher than a predetermined concentration according to the present embodiment will be described. In this embodiment, (a) the increase correction amount of the command value of the CNG injection amount output from the ECU 20 to the CNG injector 9 is larger than a predetermined threshold value, and (b) is derived based on the output signal of the crank angle sensor 28. (C) the pressure of the CNG detected by the pressure sensor 23 is within a predetermined normal range, and the amount of fluctuation is a predetermined threshold value. Is smaller than the predetermined concentration, it is determined that the CNG inert gas concentration is higher than the predetermined concentration.

  When the CNG inert gas concentration increases, the torque of the internal combustion engine 1 decreases unless the CNG injection amount from the CNG injector 9 increases. Therefore, in this case, in order to adjust the torque of the internal combustion engine 1 to the target torque, the command value of the CNG injection amount output from the ECU 20 to the CNG injector 9 is corrected to be increased. Therefore, as shown in (a) above, when the increase correction amount of the command value of the CNG injection amount is larger than a predetermined threshold value, it can be determined that there is a high possibility that the inert gas concentration of CNG is higher than the predetermined concentration.

  However, when the actual injection amount with respect to the command value of the CNG injection is reduced as a result of problems such as clogging of the CNG injector 9 in the CNG injection system, the command value of the CNG injection amount is increased as described above. It is corrected. Therefore, in order to distinguish between an increase in the CNG inert gas concentration and a malfunction of the CNG injection system, it is determined whether or not the conditions (b) and (c) are satisfied.

  When a malfunction occurs in the CNG injection system, the variation in the amount of CNG injection actually injected from the CNG injector 9 may increase. When the variation in the CNG injection amount becomes large, the fluctuation amount of the engine speed of the internal combustion engine 1 increases. On the other hand, even if the command value of the CNG injection amount is corrected to increase due to an increase in the inert gas concentration of CNG, the variation of the CNG injection amount does not increase, so the engine of the internal combustion engine 1 caused by this The fluctuation amount of the rotation speed is small. Therefore, as shown in (b) above, when the fluctuation amount of the engine rotation speed of the internal combustion engine 1 derived based on the output signal of the crank angle sensor 28 is smaller than a predetermined threshold, a problem occurs in the CNG injection system. It can be judged that there is a high possibility of not.

Further, when a malfunction occurs in the regulator 17 in the CNG injection system, the pressure of the CNG detected by the pressure sensor 23 becomes a value different from the normal value, or the amount of fluctuation thereof increases. Therefore, as shown in the above (c), when the CNG pressure detected by the pressure sensor 23 is within the predetermined normal range and the fluctuation amount is smaller than the predetermined threshold value, the malfunction of the regulator 17 does not occur. It can be judged that the possibility is high.

  From the above, when all of the above conditions (a) to (c) are satisfied, the determination can be made with high accuracy by determining that the inert gas concentration of CNG is higher than the predetermined concentration.

  Each threshold value is determined in advance based on an experiment or the like as a value that allows each of the above determinations, and is stored in the ECU 20.

  In the present embodiment, a sensor for detecting the inert gas concentration of CGN may be installed in the CNG injection system. However, since the CNG injection system is under high pressure, it is difficult to provide such a sensor. According to the determination method as described above, it is possible to determine with higher accuracy whether or not the inert gas concentration of CNG is higher than a predetermined concentration without separately providing such a sensor.

  In this embodiment, the ECU 20 that corrects the command value of the CNG injection amount for the CNG injector 9 to adjust the torque of the internal combustion engine 1 to the target torque corresponds to the injection amount command value correcting means according to the present invention. The ECU 20 that derives the engine speed of the internal combustion engine 1 based on the crank angle sensor 28 and the output signal of the crank angle sensor 28 corresponds to the rotation speed acquisition means according to the present invention. The pressure sensor 23 corresponds to a pressure acquisition unit according to the present invention.

(Ignition timing control flow)
Here, the flow of the ignition timing control according to the present embodiment will be described based on the flowchart shown in FIG. This flow is stored in advance in the ECU 20 and is repeatedly executed by the ECU 20 at predetermined intervals during the operation of the internal combustion engine 1. Further, the correction control of the command value of the CNG injection amount for the CNG injector 9 for adjusting the torque of the internal combustion engine 1 to the target torque is performed by another control flow. The correction amount of the command value for the CNG injection amount in the correction control is stored in the ECU 20.

  In this flow, in step S101, it is determined whether or not the internal combustion engine 1 is operated using CNG as fuel. If an affirmative determination is made in step S101, then the process of step S102 is executed. On the other hand, if a negative determination is made in step S101, the process of step S107 is executed next. In step S107, the execution of this flow is temporarily stopped without correcting the ignition timing.

  In step S102, it is determined whether or not the command value is increased and corrected in the correction control of the command value of the CNG injection amount for the CNG injector 9, and the increase correction amount ΔQcng is greater than a predetermined threshold value ΔQcng0. If an affirmative determination is made in step S102, the process of step S103 is executed next, and if a negative determination is made, the process of step S107 is executed next.

  In step S103, it is determined whether or not the fluctuation amount ΔNe of the engine rotational speed of the internal combustion engine 1 derived based on the output signal of the crank angle sensor 28 is smaller than a predetermined threshold value. The fluctuation amount ΔNe of the engine rotation speed is calculated as, for example, the difference between the maximum value and the minimum value of the engine rotation speed during a predetermined period during steady operation. If an affirmative determination is made in step S103, the process of step S104 is executed next. If a negative determination is made, the process of step S107 is executed next.

In step S104, it is determined whether or not the pressure Pcng of the CNG detected by the pressure sensor 23 is within a predetermined normal range and the fluctuation amount ΔPcng is smaller than a predetermined threshold value ΔPcng0. The CNG pressure fluctuation amount ΔPcng is calculated, for example, as the difference between the maximum value and the minimum value of the CNG pressure during a predetermined period during steady operation. If an affirmative determination is made in step S104, the process of step S105 is executed next. If a negative determination is made, the process of step S107 is executed next.

  In step S105, it is determined that the inert gas concentration Cing of CNG is higher than the predetermined concentration Cing0. In this case, next, in step S106, the ignition timing by the spark plug 3 is advanced. Thereafter, the execution of this flow is temporarily stopped.

  In step S106, when the advance timing of the ignition timing by the spark plug 3 is to be corrected, it is determined in advance from the ignition timing when the inert gas concentration Cing of CNG is equal to or lower than the predetermined concentration Cing0, that is, when the advance angle correction is not performed. It may be advanced by a certain angle. Further, the value of the CNG inert gas concentration Cing may be calculated based on the increase correction amount ΔQcng of the command value of the CNG injection amount, and the advance amount of the ignition timing may be determined based on the value. In this case, the advance amount of the ignition timing increases as the inert gas concentration Cing of CNG increases. The relationship between the inert gas concentration Cing of CNG and the advance amount of the ignition timing can be determined in advance based on experiments or the like.

  In the present embodiment, the ECU 20 that executes steps S102 to S105 in the above flow corresponds to the determination unit according to the present invention. Moreover, ECU20 which performs step S106 in the said flow is equivalent to the ignition timing correction means which concerns on this invention.

  In the present embodiment, as described above, (a) the increase correction amount of the command value of the CNG injection amount issued from the ECU 20 to the CNG injector 9 is larger than a predetermined threshold, and (b) the crank angle sensor 28 The fluctuation amount of the engine rotation speed of the internal combustion engine 1 derived based on the output signal is smaller than a predetermined threshold, and (c) the CNG pressure detected by the pressure sensor 23 is within a predetermined normal range. Then, when all of the fact that the fluctuation amount is smaller than the predetermined threshold is established, it is determined that the inert gas concentration of CNG is higher than the predetermined concentration. However, when (a) and (b) are established, or when (a) and (c) are established, it may be determined that the inert gas concentration of CNG is higher than a predetermined concentration.

  The case where it is determined that the inert gas concentration of CNG is higher than the predetermined concentration when all of the above conditions (a) to (c) are satisfied as in the present embodiment. The determination accuracy becomes higher. However, it is possible to distinguish between an increase in the CNG inert gas concentration and a malfunction in the CNG injection system by determining whether or not one of the conditions (b) or (c) is satisfied. It is. Therefore, even in these cases, it is possible to determine whether or not the inert gas concentration of CNG is higher than the predetermined concentration without separately providing a sensor for detecting the inert gas concentration of CGN in the injection system of CNG.

(Other control)
When the inert gas concentration of CNG becomes higher than a predetermined concentration, the flammability of CNG is greatly reduced compared to the normal time. Therefore, in this embodiment, when it is determined that the CNG inert gas concentration is higher than the predetermined concentration, the upper limit value of the increase correction amount set in the correction control of the command value of the CNG injection amount for the CNG injector 9 is set. It may be eliminated or the upper limit value may be changed to a value larger than usual.

  Further, in this embodiment, when an EGR device that installs a part of the exhaust gas as EGR gas into the intake system is installed, if it is determined that the inert gas concentration of CNG is higher than a predetermined concentration, the intake air of EGR gas The introduction into the system may be stopped or the amount introduced may be reduced from the normal time. By using these controls together, deterioration of the combustion state of CNG can be suppressed with a higher probability.

DESCRIPTION OF SYMBOLS 1 ... Internal combustion engine 2 ... Cylinder 3 ... Spark plug 8 ... Gasoline injector 9 ... CNG injector 10-Gasoline delivery pipe 11-CNG delivery pipe 15-CNG supply passage 16 · · CNG tank 17 · · Regulator 19 · · Throttle valve 20 · · ECU
22. Air flow meter 23 Pressure sensor 24 Temperature sensor 27 A / F sensor 28 Crank angle sensor

Claims (5)

Ignition means for igniting the gas fuel;
Ignition timing correction means for advancing the ignition timing of the gas fuel by the ignition means when the inert gas concentration of the gas fuel is high compared to when the inert gas concentration of the gas fuel is low;
An ignition system for a gas-fueled internal combustion engine, comprising: A determination means for determining whether or not the inert gas concentration of the gas fuel is higher than a predetermined concentration;
The ignition timing correction means advances the ignition timing of the gas fuel by the ignition means when the determination means determines that the inert gas concentration of the gas fuel is higher than the predetermined concentration. The ignition system of the gas fuel internal combustion engine according to claim 1. Injection amount command value correcting means for correcting a command value of the fuel injection amount for the fuel injection valve of the gas fuel internal combustion engine in order to adjust the torque of the gas fuel internal combustion engine to a target torque;
A rotation speed acquisition means for acquiring the rotation speed of the gas fuel internal combustion engine,
The increase correction amount of the command value of the fuel injection amount by the injection amount command value correcting means is larger than a predetermined threshold value, and the fluctuation amount of the rotational speed of the gas fuel internal combustion engine acquired by the rotational speed acquiring means is a predetermined threshold value. 3. The ignition system for a gas fuel internal combustion engine according to claim 2, wherein the determination means determines that the inert gas concentration of the gas fuel is higher than the predetermined concentration when the gas fuel is smaller than the predetermined concentration. Injection amount command value correcting means for correcting a command value of the fuel injection amount for the fuel injection valve of the gas fuel internal combustion engine in order to adjust the torque of the gas fuel internal combustion engine to a target torque;
Pressure acquisition means for acquiring the pressure of the gas fuel injected from the fuel injection valve,
The increase correction amount of the command value of the fuel injection amount by the injection amount command value correcting means is larger than a predetermined threshold value, and the pressure of the gas fuel acquired by the pressure acquiring means is within a predetermined normal range and its fluctuation The ignition system for a gas fuel internal combustion engine according to claim 2, wherein when the amount is smaller than a predetermined threshold, the determination means determines that the inert gas concentration of the gas fuel is higher than the predetermined concentration. . A pressure acquisition means for acquiring the pressure of the gas fuel injected from the fuel injection valve;
The increase correction amount of the command value of the fuel injection amount by the injection amount command value correcting means is larger than the predetermined threshold value, and the fluctuation amount of the rotational speed of the gas fuel internal combustion engine acquired by the rotational speed acquiring means is the predetermined threshold value. And when the pressure of the gas fuel acquired by the pressure acquisition means is within a predetermined normal range and the fluctuation amount is smaller than a predetermined threshold value, the determination means The ignition system for a gas fuel internal combustion engine according to claim 3, wherein the gas concentration is determined to be higher than the predetermined concentration.

Images