JP5728818B2 - Control device for gas fuel engine - Google Patents

Description

  The present invention relates to a control device for a gas fuel engine.

  Automotive engines that use compressed natural gas (CNG) as gas fuel have been developed. As a technology related to a CNG engine, Patent Document 1 discloses that in a cylinder direct injection type CNG engine that directly injects CNG into a cylinder, the differential pressure between the maximum combustion pressure and the fuel injection pressure falls below a limit differential pressure. Furthermore, there is described a technique for ensuring the sealing performance of the in-cylinder injector by changing the ignition timing and the air-fuel ratio to lower the combustion pressure to the target combustion pressure.

  Since gas fuel such as CNG has a large volume change (density change) due to temperature as liquid fuel such as gasoline and light oil, the injection amount (injection time) is corrected according to the temperature of the gas fuel.

JP 2005-113698 A JP 2005-240581 A JP 2000-087771 A

  Since the gas fuel has a larger volume than the liquid fuel, the temperature of the gas fuel greatly affects the temperature of the entire air-fuel mixture. Therefore, the temperature of the gas fuel affects the combustibility of the air-fuel mixture. For example, if the temperature of the gas fuel is reduced, the combustion speed is slowed down and mixing with air is not performed well, so that combustion is worsened and exhaust performance and fuel consumption performance may be reduced. is there. Although liquid fuels such as gasoline and light oil lower the temperature of the air due to latent heat when the state changes (vaporizes), the effect of the fuel temperature itself on the temperature of the entire mixture is small. It is a phenomenon.

  By the way, in an engine using gas fuel, the gas fuel stored at a high pressure in the gas tank is decompressed by a regulator and then supplied to the fuel injection valve via the delivery pipe. Since the temperature of the gas fuel decreases due to the adiabatic expansion during the decompression, the temperature of the gas fuel during the injection becomes lower than the temperature of the gas tank. The temperature of the gas fuel at the time of injection varies depending on conditions such as a source pressure value (temperature in the gas tank) and a flow rate, and in some cases, combustion may be deteriorated for the above reason.

  This invention is made | formed in view of this point, and it aims at providing the control apparatus which can suppress the deterioration of combustion in a gas fuel engine.

The present invention for solving the above problems is as follows.
A control device for a gas fuel engine operated by combustion of gas fuel,
Fuel injection means for supplying gas fuel to the gas fuel engine;
Ignition means for igniting a mixture of gas fuel and air in a cylinder of the gas fuel engine;
Fuel temperature detection means for detecting the temperature of the gas fuel injected from the fuel injection means;
Ignition timing control means for controlling the ignition timing by the ignition means;
With
The ignition timing control means includes an ignition timing correction means for advancing the ignition timing when the temperature of the gas fuel detected by the fuel temperature detection means is equal to or lower than a predetermined reference temperature compared to the case where it is not. Is a control device for a gas fuel engine.

  According to the present invention, when the temperature of the gas fuel is equal to or lower than the reference temperature, the ignition timing is corrected to the advance side. Therefore, the temperature of the gas fuel is lowered to such a degree that the combustion may be deteriorated. However, deterioration of combustion can be suppressed. In addition, since the temperature of the gas fuel injected from the fuel injection valve, which directly affects the temperature of the air-fuel mixture, is used as the temperature of the gas fuel, it is possible to appropriately determine whether or not the ignition timing advance correction is necessary. , Combustion deterioration can be suitably suppressed.

  For example, a delivery pipe that accumulates gas fuel at a predetermined pressure and distributes it to the fuel injection means, and a regulator that decompresses the gas fuel taken out from a tank that stores the gas fuel to the predetermined pressure and supplies it to the delivery pipe The fuel temperature detecting means may detect the temperature of the gas fuel in the delivery pipe.

  As a result, even when the temperature of the gas fuel decreases due to adiabatic expansion during decompression by the regulator, the temperature of the gas fuel is detected by the fuel temperature detecting means, and if the detected gas fuel temperature is lower than the reference temperature, ignition is performed. Since the timing advance correction is performed, it is possible to suitably suppress the deterioration of combustion.

  In the above configuration, the predetermined reference temperature is a value determined based on the lower limit value of the gas fuel temperature at which it can be determined that the deterioration of combustion does not occur, and is experimentally determined in consideration of the required exhaust performance and fuel consumption performance. Is done. The reference temperature may be a certain fixed value, or may be a variable value according to the engine operating conditions (for example, the injection amount and the rotational speed). In this case, the ignition timing correction means may include reference temperature setting means for setting the reference temperature to a value corresponding to the operating state of the gas fuel engine.

  Further, the advance amount of the ignition timing by the ignition timing correction means is a value determined so as to suppress the deterioration of combustion when the gas fuel temperature is equal to or lower than the reference temperature. This advance amount may be a certain fixed value, or may be a variable value corresponding to the operating condition of the engine and the detected gas fuel temperature. In this case, the ignition timing correction means sets the advance amount of the ignition timing to a value corresponding to the operating state of the gas fuel engine and the temperature of the gas fuel detected by the fuel temperature detection means. Setting means may be included.

  The present invention can also be applied to a gas fuel engine including a port injection valve that injects and supplies gas fuel to an intake port. Further, the present invention can also be applied to a gas fuel engine provided with an in-cylinder direct injection valve that injects gas fuel directly into a cylinder. The present invention can also be applied to a bi-fuel engine that can be operated using gas fuel and / or gasoline as fuel. In this case, it is provided with gasoline fuel injection means for injecting and supplying gasoline into the intake port and / or the cylinder of the gas fuel engine, and the ignition means can ignite a mixture of gas fuel, gasoline and air in the cylinder. Just do it.

  ADVANTAGE OF THE INVENTION According to this invention, it becomes possible to provide the control apparatus which can suppress the deterioration of combustion in a gas fuel engine.

It is a figure which shows schematic structure of the gas fuel engine which concerns on an Example, a fuel system, an intake system, and an exhaust system. It is a flowchart showing the execution procedure of the ignition timing control of the gas fuel engine which concerns on an Example.

  Hereinafter, embodiments of the present invention will be described in detail. 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.

  In this embodiment, the present invention is applied to a gas fuel engine using compressed natural gas (CNG) as gas fuel. In addition, this invention can also apply this invention to the internal combustion engine which uses the natural gas which is primary fuel, such as liquefied petroleum gas (LPG), and petroleum gas, the coal conversion gas which is secondary fuel, and petroleum conversion gas. .

  FIG. 1 is a diagram illustrating a schematic configuration of a gas fuel engine, a fuel system, an intake system, and an exhaust system according to the present embodiment. The engine 1 is a vehicle driving engine that uses gasoline and compressed natural gas (hereinafter referred to as CNG) as fuel. The engine 1 has four cylinders 2. Each cylinder 2 is provided with a spark plug 3 (ignition means).

  An intake manifold 4 and an exhaust manifold 5 are connected to the 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 intake ports of the intake manifold 4 are connected to the cylinders 2 respectively. Each intake port is provided with a gasoline injector 8 (gasoline fuel injection means) for injecting gasoline and a CNG injector 9 (fuel injection means) 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 that accumulates CNG at a predetermined pressure. 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. The CNG supply passage 15 is provided with a regulator 17 for reducing the pressure of CNG taken out from the CNG tank 16. The CNG stored in the CNG tank 16 at a high pressure is decompressed by the regulator 17, and the CNG is supplied to the CNG delivery pipe 11 through the CNG supply passage 15. The CNG in the CNG delivery pipe 11 is distributed to each CNG injector 9.

  The CNG delivery pipe 11 is provided with a pressure sensor 23 for detecting the pressure of the CNG in the CNG delivery pipe 11 and a temperature sensor 24 (fuel temperature detection means) for detecting 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 from the upstream side. The exhaust passage 7 is provided with an A / F sensor 27 that detects the air-fuel ratio of the exhaust. An exhaust purification catalyst 21 composed of a three-way catalyst or the like is installed downstream of the A / F sensor 27.

  The engine 1 is provided with an electronic control unit (ECU) 20. The ECU 20 is a unit that controls the operating state of the engine 1 and the like. 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. Further, a crank angle sensor 28 that detects the crank angle of the 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 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 operated using only CNG as fuel, and can also be applied to an in-cylinder direct injection type engine in which fuel is directly injected into a cylinder.

  Since CNG, which is a gaseous fuel, has a larger volume than gasoline, which is a liquid fuel, the temperature of the CNG greatly affects the temperature of the entire air-fuel mixture formed in the cylinder 2. Therefore, the temperature of CNG injected from the CNG injector 9 affects the combustibility of the air-fuel mixture. For example, when the temperature of CNG injected from the CNG injector 9 is lowered, the combustion speed is slowed down and mixing with air is not performed well, so that combustion is deteriorated and exhaust performance and fuel consumption performance are lowered. It can be a cause. On the other hand, although gasoline, which is a liquid fuel, lowers the temperature of air due to latent heat when the state changes (vaporizes), the temperature of the gasoline itself injected from the gasoline injector 8 has little influence on the temperature of the entire mixture.

  As described above, the CNG supplied to the CNG injector 9 is obtained by decompressing the CNG stored in the CNG tank 16 at a high pressure by the regulator 17. Since the temperature of the CNG decreases due to the adiabatic expansion during the pressure reduction, the temperature of the CNG injected from the CNG injector 9 becomes lower than the original pressure value (the temperature in the CNG tank 16). The temperature of CNG at the time of injection from the CNG injector 9 varies depending on conditions such as a source pressure value and a flow rate, and in some cases, combustion may deteriorate.

  Therefore, in the gas fuel engine of the present embodiment, when the temperature of the CNG in the CNG delivery pipe 11 detected by the temperature sensor 24 is equal to or lower than the predetermined reference temperature, the ignition by the spark plug 3 is compared to the case where it is not. The timing was corrected to the advance side. The temperature of CNG in the CNG delivery pipe 11 is good combustibility even when the temperature of the entire air-fuel mixture is lowered due to the temperature drop of CNG by correcting the ignition timing to the advance side. This makes it possible to prevent the deterioration of exhaust emission and fuel consumption due to poor combustion.

  Here, the reference temperature is a value determined based on the lower limit value of the CNG temperature at which it can be determined that the deterioration of combustion does not occur, and is experimentally determined in consideration of required exhaust performance and fuel consumption performance. The reference temperature may be set to a certain constant value (for example, 0 ° C.), or a map or an arithmetic expression for determining the reference temperature according to the operating state (injection amount or rotation speed) of the engine 1 is stored in the ECU 20. The variable value may be set in accordance with the obtained operating state of the engine 1.

Further, the advance amount of the ignition timing by the ignition timing correction is a value determined so that deterioration of combustion can be suppressed when the CNG temperature is equal to or lower than the reference temperature. The advance amount may be set to a constant value (for example, 2 ° CA), or a map or an arithmetic expression that determines the advance amount in accordance with the operating state (injection amount or rotational speed) of the engine 1 is stored in the ECU 20. It may be set to a variable value according to the obtained operating state of the engine 1.

  FIG. 2 is a flowchart showing an execution procedure of ignition timing control of the gas fuel engine according to the present embodiment. The processing of this flowchart is repeatedly executed by the ECU 20 at predetermined intervals while the engine 1 is operating.

  In step S101, the ECU 20 acquires the operating state of the engine 1. For example, the engine speed, CNG, and gasoline injection amount can be acquired as indices representing the operating state of the engine 1.

  In step S102, the ECU 20 sets a basic ignition timing. The basic ignition timing is an ignition timing determined in advance so as to satisfy the required exhaust performance and fuel consumption performance in a normal state where the temperature of the CNG is higher than the reference temperature. The basic ignition timing is stored in the ECU 20 as a map for determining the basic ignition timing from the rotation speed and the injection amount of the engine 1, and is acquired in step S101 and the basic ignition timing is calculated from the map based on the rotation speed and the injection amount. be able to.

  In step S103, the ECU 20 acquires the temperature of the CNG in the CNG delivery pipe 11. The temperature of CNG is detected by the temperature sensor 24.

  In step S104, the ECU 20 acquires a reference temperature. As described above, the reference temperature is obtained by a map or an arithmetic expression based on a certain fixed value or the rotational speed and injection amount of the engine 1 acquired in step S101. The ECU 20 that performs the processing of this step functions as the reference temperature setting means of the present invention.

  In step S105, the ECU 20 determines whether or not the CNG temperature acquired in step S103 is equal to or lower than the reference temperature acquired in step S104. When it is determined that the temperature of the CNG is equal to or lower than the reference temperature, the ECU 20 proceeds to step S106, and when it is determined that the temperature of the CNG is higher than the reference temperature, the ECU 20 proceeds to step S108.

  In step S106, the ECU 20 acquires the advance amount of the ignition timing. As described above, the advance amount is obtained by a map or an arithmetic expression based on a certain fixed value or the rotation speed and injection amount of the engine 1 acquired in step S101. The ECU 20 that performs the processing of this step functions as the advance amount setting means of the present invention.

  In step S107, the ECU 20 corrects the ignition timing. That is, the timing advanced by the advance amount acquired in step S106 with respect to the basic ignition timing set in step S102 is set as the ignition timing for ignition control.

  In step S108, the ECU 20 does not correct the ignition timing, sets the basic ignition timing set in step S102 as the ignition timing for ignition control, and proceeds to step S109.

  In step S107, the ECU 20 executes ignition control for performing ignition by the spark plug 3 in accordance with the ignition timing set in step S107 or step S108.

ECU20 which performs the above process functions as an ignition timing control means in the present invention. In particular, the ECU 20 that executes the processing from step S105 to step S108 functions as the ignition timing correction means in the present invention.

  According to the ignition timing control of the CNG engine according to the present embodiment, when it is determined that the temperature of the CNG is low enough to cause combustion deterioration, the ignition timing is corrected to advance, so that the combustion deterioration is reduced. It can suppress what happens. Therefore, even in the CNG engine configured as in the present embodiment in which the temperature of the CNG in the CNG tank 16 is inevitably lowered when the regulator 17 is depressurized, it is possible to ensure good combustibility. In addition, it is possible to suitably suppress deterioration of exhaust performance and fuel consumption performance.

  The embodiment in which the present invention is applied to the bi-fuel engine in which CNG and gasoline are injected and supplied to the intake port of the intake manifold 4 has been described above, but the present invention is a port injection valve that injects CNG to the intake port of the intake manifold 4. The present invention can be applied to a port injection type CNG engine having only a cylinder, or an in-cylinder direct injection type CNG engine having only an in-cylinder direct injection valve that directly injects CNG into each cylinder 2. In addition, when the present invention is applied to a bi-fuel engine using CNG and gasoline as fuel, any of CNG in-cylinder direct injection, CNG and gasoline in-cylinder direct injection, and gasoline only in-cylinder direct injection may be used.

DESCRIPTION OF SYMBOLS 1 ... Engine 2 ... Cylinder 3 ... Spark plug 4 ... Intake manifold 5 ... Exhaust manifold 6 ... Intake passage 7 ... Exhaust passage 8 ... Gasoline injector 9 ... CNG injector 10 .. gasoline delivery pipe 11 .. CNG delivery pipe 12 .. gasoline supply passage 13 .. gasoline tank 14 .. feed pump 15 .. CNG supply passage 16 .. CNG tank 17 .. regulator 18. Air cleaner 19 ・ ・ Throttle valve 20 ・ ・ ECU
21 .. Exhaust purification catalyst 22 .. Air flow meter 23 .. Pressure sensor 24 .. Temperature sensor 25 .. Pressure sensor 26 .. Temperature sensor 27 .. A / F sensor 28.

Claims (7)

A control device for a gas fuel engine operated by combustion of gas fuel,
Fuel injection means for supplying gas fuel to the gas fuel engine;
Ignition means for igniting a mixture of gas fuel and air in a cylinder of the gas fuel engine;
Fuel temperature detection means for detecting the temperature of the gas fuel injected from the fuel injection means;
Ignition timing control means for controlling the ignition timing by the ignition means;
With
The ignition timing control means includes an ignition timing correction means for advancing the ignition timing when the temperature of the gas fuel detected by the fuel temperature detection means is equal to or lower than a predetermined reference temperature compared to the case where it is not. A control device for a gas fuel engine. In claim 1,
The control device for a gas fuel engine, wherein the ignition timing correction means includes reference temperature setting means for setting the reference temperature to a value corresponding to an operating state of the gas fuel engine. In claim 1 or 2,
The ignition timing correction means includes an advance amount setting means for setting the advance amount of the ignition timing to a value corresponding to the operating state of the gas fuel engine and the temperature of the gas fuel detected by the fuel temperature detection means. A control device for a gas fuel engine, comprising: In any one of Claim 1 to 3,
The control device for a gas fuel engine, wherein the fuel injection means includes a port injection valve for supplying gas fuel to an intake port of the gas fuel engine. In any one of Claim 1 to 3 ,
The control apparatus for a gas fuel engine, wherein the fuel injection means includes an in-cylinder direct injection valve that supplies gas fuel directly into the cylinder. In any one of Claim 1 to 5,
A delivery pipe for accumulating gas fuel at a predetermined pressure and distributing it to the fuel injection means;
A regulator for reducing the gas fuel taken out from the tank for storing the gas fuel to the predetermined pressure and supplying it to the delivery pipe;
With
The control device for a gas fuel engine, wherein the fuel temperature detection means detects the temperature of the gas fuel in the delivery pipe. In any one of Claim 1 to 6,
The gas fuel engine is a bi-fuel engine operable by combustion of gas fuel and gasoline,
Gasoline fuel injection means for supplying gasoline into the intake port and / or cylinder of the gas fuel engine;
The control device for a gas fuel engine, wherein the ignition means is capable of igniting a mixture of gas fuel, gasoline and air in a cylinder.

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