JP5895570B2 - Gas engine control system - Google Patents

Description

  The present invention relates to a gas engine control system, and more particularly to a control system that can be suitably used for a stationary gas engine of a cogeneration system.

  For example, in a cogeneration system, a stationary small gas engine using natural gas as a fuel is used. As the gas engine, a port injection engine having a simple configuration is generally adopted due to cost restrictions and the like. Yes. Further, the above gas engine employs lean combustion in order to improve operating efficiency, and even when using natural gas with low ignitability, the mixture gas is stratified in the combustion chamber so that the natural gas is suitably lean burned. Various technologies are being studied such as

  As a technique for stratifying an air-fuel mixture in a combustion chamber, for example, in Patent Document 1, in a port injection type engine, a configuration is adopted in which an intake valve is closed after a piston passes a bottom dead center. When in the vicinity, the fuel is injected into the intake port by the fuel injection valve so that the fuel around the spark plug is relatively concentrated.

JP 2004-353463 A

  However, the technique of Patent Document 1 is applicable to liquid fuel (gasoline etc.) having a high volumetric energy density, but is not applicable to gas fuel such as natural gas having a volumetric energy density smaller than that of liquid fuel. Have difficulty. This is because in order to inject and supply fuel required by the engine (fuel equivalent to liquid fuel) with gaseous fuel during a limited period when the piston is near bottom dead center, the injection rate of gaseous fuel must be It must be greatly increased. For this purpose, it is necessary to make the opening area of the fuel injection valve very large or make the supply pressure of the gas fuel as high as that of the direct injection engine, resulting in an increase in cost.

  The main object of the present invention is to provide a gas engine control system capable of optimizing combustion in a gas engine without causing an increase in cost.

  Hereinafter, means for solving the above-described problems and the effects thereof will be described.

  In the gas engine control system according to the present invention, the gas engine is provided in the intake port (11a) and opens and closes the intake side opening of the combustion chamber, and the gas supplied from the fuel supply source (L1). A fuel supply device (14) for supplying fuel to the intake passage portion (12) upstream of the intake port and a fuel supply to the fuel supply device are supplied by a separate system, and fuel at a predetermined injection pressure is supplied to the intake port. A fuel injection valve (15) for injecting the fuel and an ignition plug (26) for generating an ignition spark in the combustion chamber. In addition, the fuel injection valve is provided in the intake port so that fuel is injected toward the spark plug through an open gap portion formed by opening the intake valve.

  The gas supply control means, as a fuel amount required for one combustion of the gas engine, a first fuel amount (Q1) supplied to the intake passage portion by the fuel supply device, and a second fuel injected to the intake port by the fuel injection valve The amount (Q2) is calculated, and the fuel amount control of the fuel supply device and the fuel injection valve is performed based on the respective fuel amounts (fuel amount control means). Further, the fuel injection timing is controlled so that fuel is injected by the fuel injection valve in the latter half of the intake valve opening period (injection timing control means).

  There is a concern that a gas engine using a gas fuel such as city gas using natural gas as a raw material has low combustion stability. In this regard, as described above, the fuel supply device and the fuel injection valve are provided, and the fuel injection valve injects fuel toward the spark plug through the open gap portion due to the opening of the intake valve, Further, since fuel is injected by the fuel injection valve in the latter half of the intake valve opening period, an equivalence ratio distribution is formed in the combustion chamber after the intake valve is closed, and the air-fuel mixture around the spark plug is reduced. Can be thickened locally. Thereby, the ignitability in the combustion chamber of the gas fuel can be improved, and consequently the combustion stability can be improved.

  The fuel supply to the gas engine is performed by two systems of a fuel supply device and a fuel injection valve, and the fuel supply by the fuel injection valve is limited to a part of the fuel amount (total fuel amount) required for one combustion. It is done. Therefore, even if the fuel injection timing by the fuel injection valve is limited to the latter period of the intake valve opening period, a desired amount of fuel can be injected and supplied by the fuel injection valve in the limited period. As described above, combustion in the gas engine can be optimized without increasing the cost.

  The fuel amount control means may calculate the first fuel amount and the second fuel amount so that the first fuel amount is greater than the second fuel amount (claim 2).

  According to the above configuration, most of the fuel amount required for combustion of the gas engine is covered by the fuel supply of the fuel supply device, and the remaining part is covered by the fuel injection of the fuel injection valve. In this case, considering that the fuel injection valve injects fuel toward the spark plug through the opening gap portion due to the opening of the intake valve as described above, the fuel injection amount by the fuel injection valve is as follows. Even if the amount is relatively small, the ignitability in the combustion chamber can be improved. Therefore, fuel consumption can be improved by minimizing the fuel injection amount.

The block diagram which shows the outline of the engine control system in embodiment of invention. A time chart for explaining fuel supply operation at the time of engine operation. The flowchart which shows a fuel supply control process. The block diagram which shows the outline of an engine control system in another embodiment.

  DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, an embodiment of the invention will be described with reference to the drawings. This embodiment is embodied about the small gas engine used for a cogeneration system, and the engine is used as an engine for power generation. The gas engine of the present embodiment is a stationary engine, and is operated using city gas (natural gas mainly composed of methane) supplied from the city gas supply facility to the cogeneration system as fuel.

  In FIG. 1, an engine 10 is a spark ignition type multi-cylinder gas engine, and an intake pipe 12 and an exhaust pipe 13 are connected to an engine body 11. The intake pipe 12 is provided with a gas supply valve 14 that supplies (discharges) gas fuel (city gas) supplied through the gas pipes L <b> 1 and L <b> 2 into the intake pipe 12. The gas supply valve 14 corresponds to a fuel supply device, and the amount of fuel supplied to the intake pipe 12 is adjusted by adjusting the valve opening of the gas supply valve 14 during engine operation.

  Of the gas pipes L1 and L2, the upstream gas pipe L1 is a feed pipe that feeds gas fuel from a gas storage tank or the like as a gas supply source to the building where the cogeneration system is installed. The pipe L1 corresponds to the fuel supply source. In this system, gas fuel is supplied in a low pressure state near atmospheric pressure, and the gas supply pressure, that is, the gas pressure supplied to the gas supply valve 14 is 110 kPa, which is slightly higher than atmospheric pressure. (About 1.1 atmospheres).

  The gas supply valve 14 is a proportional control having a gas passage through which gas fuel flows, a valve body that can variably adjust the opening area of the gas passage, and a drive unit such as a solenoid that drives the valve body to a desired lift position. It is a valve, and the gas supply amount (gas release amount) into the intake pipe 12 is adjusted by changing the passage opening area according to the valve body lift amount. In this case, the gas supply amount into the intake pipe 12 is increased by increasing the passage opening area, and the gas supply amount into the intake pipe 12 is decreased by reducing the passage opening area. The gas supply valve 14 is provided upstream of the manifold portion that distributes the intake air to each cylinder in the intake pipe 12, that is, at the intake pipe collection portion. The gas supply valve 14 is preferably provided downstream of a throttle valve (not shown) and discharges gas fuel into the intake pipe 12 by intake negative pressure.

  In an engine operating state in which the engine 10 is in operation, fresh air flowing from the upstream side of the intake pipe and gas fuel supplied by the gas supply valve 14 are mixed in the intake pipe 12 and the mixture is taken into the intake air. It is fed to the downstream side of the pipe.

  The intake port 11a of the engine body 11 is provided with an electromagnetically driven fuel injection valve 15 as second fuel supply means. An electrically driven compressor 17 is connected to the fuel injection valve 15 via a pipe 16, and gas fuel pressurized to a predetermined injection pressure by the compressor 17 is injected from the fuel injection valve 15 into the intake port 11a. Is done. That is, gas fuel is supplied to the fuel injection valve 15 in a separate system from the fuel supply to the gas supply valve 14. The compressor 17 pressurizes the gas fuel supplied from the gas pipe L2 to, for example, 200 to 300 kPa (about 2 to 3 atmospheres). The fuel injection valve 15 opens and closes according to the injection signal, and the fuel injection amount is adjusted according to the length (pulse length) of the injection signal.

  An intake valve 21 and an exhaust valve 22 are provided in the intake port 11a and the exhaust port 11b of the engine body 11, respectively. The intake valve 21 opens and closes the intake side opening of the combustion chamber 25, and the exhaust valve 22 opens and closes the exhaust side opening of the combustion chamber 25. These valves 21 and 22 are opened and closed according to the rotation of the cam shafts 23 and 24, and the air in the intake pipe 12 is introduced into the combustion chamber 25 by the opening operation of the intake valve 21, and the opening operation of the exhaust valve 22 is performed. Exhaust gas after combustion is discharged to the exhaust pipe 13.

  A spark plug 26 is attached to the engine body 11 for each cylinder. The ignition plug 26 is provided at a position that is substantially in the center of the combustion chamber 25 in the head portion of the engine body 11, and is attached with the ignition electrode exposed in the combustion chamber 25. A high voltage is applied to the ignition plug 26 at a desired ignition timing through an ignition device 27 including an ignition coil. By applying this high voltage, a spark discharge is generated between the opposing electrodes of each spark plug 26, and the air-fuel mixture in the combustion chamber 25 is ignited and used for combustion. In addition, the engine body 11 is provided with a piston 28 that reciprocates in the engine cylinder, and a crankshaft 29 that rotates in accordance with the reciprocation of the piston 28.

  The exhaust pipe 13 is provided with a catalyst 31 for purifying the exhaust gas. The catalyst 31 is made of an oxidation catalyst, for example. In addition, the exhaust pipe 13 is provided with an equivalence ratio sensor 32 that detects the equivalence ratio (= fuel-air ratio) of the air-fuel mixture on the upstream side of the catalyst.

  The ECU 40 is composed mainly of a well-known microcomputer comprising a CPU 40a and a memory 40b comprising a ROM, a RAM, etc., and executes various control programs stored in the ROM, so that the engine can be operated according to the engine operating state each time. 10 various controls are executed. Specifically, in addition to the equivalence ratio sensor 32 described above, the ECU 40 is connected to a rotation speed sensor 41 that detects the engine rotation speed, and a load sensor 42 that detects an intake pipe pressure as an engine load. Detection signals of the sensors are sequentially input to the ECU 40. It is also possible to detect the required amount of power generation in the cogeneration system as the engine load. The ECU 40 controls the gas fuel supply amount by the gas supply valve 14, the fuel injection amount and fuel injection timing by the fuel injection valve 15, the ignition timing by the spark plug 26, and the like based on these input various detection signals. The command value is calculated, and the driving of the gas supply valve 14, the fuel injection valve 15, the ignition device 27, and the like is controlled based on the control command value.

  The control of the gas supply valve 14 will be described. The gas supply valve 14 supplies gas fuel to the intake pipe 12 while maintaining the gas pressure supplied from the gas pipes L1 and L2, that is, in a low pressure state. The valve opening, that is, the passage opening area is controlled according to the required amount of fuel supply. In the present embodiment, the valve opening degree of the gas supply valve 14 is controlled according to the duty ratio, and the ECU 40 calculates a duty command value according to the required amount of fuel supply, and the duty command value Thus, the state of the gas supply valve 14 is controlled.

  On the other hand, the fuel injection valve 15 injects the gas fuel at a higher pressure than the gas fuel supplied from the gas pipes L1 and L2, and can secure a predetermined injection rate. The injection time is controlled in accordance with the required amount of fuel injection.

  Here, city gas used as gas fuel has a low volumetric energy density because its gas supply pressure is low. Further, since the city gas is primarily controlled only in the amount of heat and not ignitable, the ignitability of the engine 10 varies. Due to these factors, there is a concern about deterioration of combustion stability in the engine 10 using city gas as fuel. In addition, in city gas, other combustible gases, such as LPG, are mixed for heat amount adjustment.

  In the present embodiment, the engine 10 is caused to perform lean combustion with an equivalence ratio of, for example, 0.5. This equivalence ratio = 0.5 is leaner than the equivalence ratio (about 0.6 to 0.7) generally set in consideration of combustion stability in a small natural gas engine, and is equivalent in the cogeneration system. While the operation cost can be reduced by making the ratio even leaner, there is still a concern in terms of combustion stability. In addition, the merit of being able to reduce the amount of NOx in the exhaust can be obtained by making the equivalence ratio leaner.

  Therefore, in the present embodiment, as described above, the fuel supply to the engine 10 is performed by the two fuel supply means in order to achieve combustion stability using city gas as the gas fuel and setting the equivalence ratio to 0.5. Is going to do. In particular, the fuel injection of the fuel injection valve 15 locally concentrates the fuel around the spark plug in the combustion chamber 25 to perform so-called stratification. That is, an equivalence ratio distribution is formed in the combustion chamber 25 by the gas fuel injected from the fuel injection valve 15 to improve the ignitability of the fuel.

  Specifically, the fuel injection valve 15 is connected to the intake port 11a so that fuel is injected toward the spark plug 26 (specifically, near the plug ignition electrode) through the opening gap portion of the intake valve 21 opened. Is provided. As fuel injection control of the fuel injection valve 15, fuel injection is performed in the latter half of the valve opening period of the intake valve 21. Thereby, the distribution of the equivalence ratio is formed in the combustion chamber 25, and the ignitability at the time of ignition by the spark plug 26 is improved.

  FIG. 2 is a time chart for explaining the fuel supply operation during engine operation. FIG. 2 shows the valve lift of the intake valve 21 and the exhaust valve 22, the valve opening degree of the gas supply valve 14, the injection signal of the fuel injection valve 15, and the ignition signal with the horizontal axis as the crank angle position. . The valve lift, the injection signal, and the ignition signal show the behavior for one cylinder.

  The gas supply valve 14 is maintained in an open state during engine operation, and fuel is continuously supplied to the collecting portion of the intake pipe 12. In this case, the valve opening degree of the gas supply valve 14 is adjusted according to the engine operating state every time. When the intake valve 21 is opened in the intake stroke, gas fuel flows into the combustion chamber 25 of each cylinder through the manifold portion of the intake pipe 12. In the state shown in the figure, the gas supply valve 14 is held at a constant opening.

  On the other hand, the fuel injection valve 15 is driven to open in response to an injection signal for each cylinder during the latter half of the opening period of the intake valve 21, and fuel injection at the intake port 11a is performed as the valve is opened. In this case, in particular, the fuel injection start timing (t1 in the figure) is controlled based on the valve closing timing and the injection time TA so that the fuel injection ends at the valve closing timing (t2 in the figure) of the intake valve 21. It is like that. For example, the start timing of fuel injection is controlled at a timing within a period from BTDC 270 ° CA to BTDC 230 ° CA.

  Then, after fuel injection, ignition by the spark plug 26 is performed at a timing t3 near the compression TDC. In this case, in the combustion chamber 25, the gas fuel supplied from the gas supply valve 14 is uniformly filled, and the area around the spark plug is locally concentrated by the gas fuel injected from the fuel injection valve 15. The equivalence ratio distribution is formed. And the ignition with the spark plug 26 is implemented with respect to the locally concentrated fuel, so that the ignitability of the gas fuel is good.

  FIG. 3 is a flowchart showing the fuel supply control process. This process is repeatedly executed by the ECU 40 at, for example, a predetermined time period.

  In FIG. 3, in step S11, the engine operating state such as the engine speed, the engine load (for example, the intake pipe pressure), and the equivalence ratio is read. The required fuel amount is calculated. This required fuel amount is a fuel amount corresponding to the required torque of the engine 10. At this time, the basic fuel amount is calculated based on the engine rotational speed and the engine load, the basic fuel amount is corrected based on the deviation amount of the actual equivalent ratio with respect to the target equivalent ratio, and the corrected result is used as the final required fuel amount. The amount of fuel. Regarding the equivalence ratio control, in the present embodiment, the target equivalence ratio is set to 0.5, and the required fuel amount is calculated so that the lean combustion is performed at the equivalence ratio = 0.5.

  Thereafter, in step S13, the fuel amount Q1 supplied by the gas supply valve 14 and the fuel amount Q2 injected by the fuel injection valve 15 are distributed with respect to the calculated required fuel amount. The fuel amount Q1 is the amount of fuel supplied into the combustion chamber 25 during the opening period of the intake valve 21 among the fuel supplied by the gas supply valve 14, and the fuel amount Q2 is determined by the fuel injection valve 15 for each cylinder. This is the amount of fuel injected.

  In this embodiment, most of the amount of fuel necessary for combustion in each cylinder is supplied by the gas supply valve 14 and the remaining part is supplied by the fuel injection valve 15. For example, Q1: Q2 = 8: 2. In this embodiment, the distribution ratio of the fuel amounts Q1 and Q2 is set to a predetermined ratio, but the ratio is appropriately changed to 9: 1, 7: 3, etc. in addition to Q1: Q2 = 8: 2. In short, it is only necessary that Q1> Q2.

  Thereafter, in step S14, the required opening of the gas supply valve 14 is calculated based on the fuel amount Q1 calculated in step S13. In subsequent step S15, the required opening of the gas supply valve 14 is converted into an opening command value (duty command value), and the opening command value is output to the gas supply valve 14.

  In step S16, the injection time by the fuel injection valve 15 is calculated based on the fuel amount Q2 calculated in step S13. In the subsequent step S17, the injection timing by the fuel injection valve 15 is calculated. At this time, the fuel injection start timing is calculated based on the valve closing timing and the injection time so that the fuel injection ends at the valve closing timing of the intake valve 21. Finally, in step S18, an injection command value (injection pulse) is calculated based on the injection time and the injection timing, and the injection command value is output to the fuel injection valve 15.

  According to the embodiment described in detail above, the following excellent effects can be obtained.

  There is a concern that the engine 10 using low-pressure city gas as fuel has low combustion stability. In this regard, as described above, the fuel injection valve 15 injects fuel toward the spark plug 26 through the opening gap portion due to the opening of the intake valve 21, and further in the later stage in the valve opening period of the intake valve 21. Since gas fuel is injected by the fuel injection valve 15, an equivalence ratio distribution can be formed in the combustion chamber 25 after the intake valve 21 is closed, and the air-fuel mixture around the spark plug can be locally concentrated. As a result, the ignitability of the gas fuel in the combustion chamber 25 can be improved, and consequently the combustion stability can be improved.

  The fuel supply to the engine 10 is performed by two systems of the gas supply valve 14 and the fuel injection valve 15, and the fuel supply by the fuel injection valve 15 is one of the required fuel amount (total fuel amount) required for one combustion. Limited to department. Therefore, even if the fuel injection timing by the fuel injection valve 15 is limited to the later stage of the valve opening timing of the intake valve 21, it is possible to supply a desired amount of fuel by the fuel injection valve 15 during the limited period. Become. As described above, combustion in the engine 10 can be optimized without causing an increase in cost.

  As a stationary engine, high efficiency can be achieved, so the efficiency of the cogeneration system can be improved. Therefore, the energy cost can be greatly improved.

  As a gas engine for cogeneration, there is a prior art that stabilizes combustion by increasing the energy required for ignition by using technologies such as gas high pressure direct injection, light oil ignition, and sub-chamber structure in large engines. To do. However, in such prior art, a complicated and expensive configuration is indispensable, and a mounting space is also required, so that there is a problem that it is difficult to use with a small engine having a small cylinder diameter. In this regard, according to the configuration of the present embodiment, desired combustion performance can be realized without using a complicated and expensive configuration.

  The fuel amount Q1 supplied by the gas supply valve 14 and the fuel amount Q2 injected by the fuel injection valve 15 are calculated so as to satisfy Q1> Q2. In this case, considering that the fuel injection valve 15 injects fuel toward the spark plug 26 through the opening gap portion due to the opening of the intake valve 21 as described above, the fuel by the fuel injection valve 15 Even if the injection amount is relatively small, the ignitability in the combustion chamber 25 can be improved. Therefore, fuel consumption can be improved by minimizing the fuel injection amount.

  The fuel amounts Q1 and Q2 are calculated so that the engine 10 performs lean combustion. As described above, the fuel injection of the fuel injection valve 15 forms an equivalence ratio distribution in the combustion chamber 25 (that is, stratifies in the combustion chamber 25), thereby improving the combustion stability during lean combustion. It is done. In this case, the lean limit in the engine 10 can be increased, and for example, leaning can be performed up to an equivalence ratio of about 0.5. Further, by reducing the equivalence ratio (increasing the excess air ratio), the combustion temperature can be lowered, thereby reducing the NOx amount.

  With reference to the closing timing of the intake valve 21, the fuel injection timing is controlled so that the fuel injection is completed at the closing timing. According to this configuration, the fuel injected from the fuel injection valve 15 can surely flow into the combustion chamber 25 while slowing the fuel injection within the valve opening period of the intake valve 21 as much as possible. Thereby, it becomes an advantageous configuration in forming an equivalence ratio distribution in the combustion chamber 25 (that is, stratifying the inside of the combustion chamber 25).

  The fuel gas pressurized by the compressor 17 is injected into the intake port by the fuel injection valve 15. According to this configuration, gas fuel is supplied to the gas supply valve 14 and the fuel injection valve 15 from the same gas pipe L1 (fuel supply source). In this case, the gas pipe L1 (fuel supply source) only needs to have one fuel system, and even if the fuel supply to the combustion chamber 25 is performed in two systems, the configuration is made as simple as possible. Can be suppressed.

  In the compressor 17, the gas fuel may be pressurized to such an extent that the injected fuel at the intake port can reach the spark plug 26 with the momentum of injection (injection force), and the pressurized pressure may be about several atmospheres. Therefore, realization with a simple configuration is possible.

(Other embodiments)
You may change the said embodiment as follows, for example.

  In the above embodiment, the gas fuel is pressurized to a predetermined injection pressure by the compressor 17 and the pressurized fuel is injected from the fuel injection valve 15. However, this may be changed as shown in FIG. In FIG. 4, as a difference from the configuration of FIG. 1, a gas cylinder 51 that stores fuel at a pressure corresponding to a predetermined injection pressure is provided instead of the compressor 17. The gas cylinder 51 is a pressure vessel that stores high-pressure gas or liquefied gas, and for example, DME (dimethyl ether) is stored at 200 kPa. The gas cylinder 51 stores a fuel having a component different from that of the gas fuel (city gas) supplied from the gas pipe L1, and the fuel stored in the gas cylinder 51 is a gas supplied from the gas pipe L1. It has better ignitability than fuel.

  In this case, the fuel injection valve 15 injects the fuel supplied from the gas cylinder 51 at the intake port. As the control of the fuel injection amount and fuel injection timing of the fuel injection valve 15, the same control as described above is performed.

  According to the above configuration, as a configuration in which the gas fuel is supplied to the fuel injection valve 15 at a pressure higher than that of the gas fuel supplied from the gas pipe L1 (fuel supply source), a pressurizing unit such as the compressor 17 is unnecessary. Thus, the configuration can be simplified. Further, the fuel injected by the fuel injection valve 15 can be a gas fuel different from the fuel supplied from the gas pipe L1. Therefore, when optimizing the combustion stability, it is possible to appropriately select which gas fuel is injected by the fuel injection valve 15.

  Further, since the fuel stored in the gas cylinder 51 (that is, the fuel injected by the fuel injection valve 15) is more ignitable than the gas fuel supplied from the gas pipe L1, the spark plug 26 Ignition can be improved. Thereby, combustion stability can be improved further. The fuel stored in the gas cylinder 51 (the fuel injected by the fuel injection valve 15) may be a gas fuel having a cetane number larger than that of city gas, and may be LPG in addition to DME.

  Since DME, LPG and the like are liable to be liquefied, fuel is supplied from the pressure vessel to the fuel injection valve 15 in a liquid state, injected from the fuel injection valve 15 and reaches the combustion chamber 25, and then the fuel is gasified It is also possible to make it.

  In the configuration of FIG. 4, the fuel property information of the fuel stored in the gas cylinder 51 is stored in the memory 40b (storage unit) in the ECU 40, and the fuel supply control is performed based on the fuel property information. It is good. For example, an EEPROM may be used as the memory 40b. Specifically, when the stored fuel in the gas cylinder 51 is DME, the property information of the DME is stored in the memory 40b. Desirably, for example, when city gas is used as the standard fuel, a fuel amount correction value corresponding to a difference in characteristics between the city gas and DME may be stored.

  Regarding the acquisition of fuel property information, code information such as a barcode may be attached to the outside of the gas cylinder 51 and the like, read by a reading device, and transmitted to the ECU 40 side. Alternatively, an IC memory storing fuel property information may be attached to the outside of the gas cylinder 51 and the information in the IC memory may be read by the ECU 40.

  According to the configuration in which the fuel property information is stored in the memory 40b in the ECU 40 as described above, in the case where the fuel stored in the gas cylinder 51 is different from the fuel supplied from the gas pipe L1, which fuel is used. Thus, the fuel supply control can be carried out after grasping whether or not they are different. In this case, the ECU 40 can appropriately control the equivalence ratio after accurately grasping the fuel properties in the ECU 40.

  In the above embodiment, after calculating the required fuel amount required for one combustion of the engine 10 (total fuel amount for each cylinder), the required fuel amount is converted into the fuel amount Q1 and fuel by the gas supply valve 14 at a predetermined distribution ratio. The fuel is distributed to the fuel amount Q2 by the injection valve 15, but this is changed. Specifically, instead of calculating the required fuel amount for each combustion, the fuel amount Q1 by the gas supply valve 14 and the fuel amount Q2 by the fuel injection valve 15 may be calculated separately. . For example, the fuel amount Q1 is calculated based on the engine speed and the engine load, while the fuel amount Q2 is calculated based on the feedback control amount of the equivalence ratio (or air-fuel ratio) (Q2 = base amount + feedback). Control amount). In this case, the distribution ratio of the fuel amounts Q1 and Q2 slightly varies, but as described above, it is possible to improve the combustion stability while performing the desired lean combustion.

  In the above embodiment, the injection start timing of the fuel injection valve 15 is controlled based on the valve closing timing and the injection time so that the fuel injection ends at the valve closing timing of the intake valve 21. It is also possible to change the predetermined timing in the intake stroke as the injection start timing of the fuel injection valve 15. In this case, BTDC 270 ° CA or later is set as the injection start timing of the fuel injection valve 15 so that fuel injection is performed in the latter half of the valve opening period of the intake valve 21.

  In the embodiment described above, the pressure applied by the compressor 17 (that is, the injection pressure of the fuel injection valve 15) may be set variably. For example, when the amount of fuel required for one combustion of the engine 10 exceeds a predetermined value, the pressure applied by the compressor 17 is increased. Alternatively, the target pressure is variably set so that the pressure applied by the compressor 17 increases as the fuel amount increases.

  In the system shown in FIGS. 1 and 4, a swirl (lateral vortex) may be generated in the combustion chamber 25, and gas fuel may be injected into the central portion of the swirl by the fuel injection valve 15. For example, a swirl forming mechanism such as a baffle plate may be provided in the intake port of the engine 10, and the swirl may be generated along the inner circumferential surface of the combustion chamber 25 by the swirl forming mechanism. In this case, the gas fuel supplied by the gas supply valve 14 becomes a swirl along the cylindrical inner peripheral surface of the combustion chamber 25, and fuel injection by the fuel injection valve 15 is performed toward the vicinity of the spark plug in the center portion. In the combustion chamber 25, an equivalence ratio distribution is formed (the combustion chamber 25 is stratified).

  Note that, as the swirl forming means, a configuration in which the swirl is formed according to the operation of the intake valve 21 may be employed. For example, in the intake stroke, a swirl may be formed by opening one of the two intake valves provided for each cylinder and closing the other intake valve.

  In the above embodiment, the gas supply valve 14 is provided in the collecting portion (upstream side of the manifold portion) of the intake pipe 12, but this is changed so that the gas supply valve 14 is provided for each cylinder in the intake manifold. There may be.

  ・ In addition to city gas, combustible gas (mainly methane) generated from waste can be used as gas fuel supplied from a fuel supply source (gas piping, etc.). Moreover, you may make it apply to gas engines other than a stationary engine by using the gas cylinder which stores combustible gas as a fuel supply source.

  DESCRIPTION OF SYMBOLS 10 ... Engine (gas engine), 11a ... Intake port, 12 ... Intake pipe (intake passage part), 14 ... Gas supply valve (fuel supply device), 15 ... Fuel injection valve, 21 ... Intake valve, 25 ... Combustion chamber, 26 ... Spark plug, 40 ... ECU (gas supply control means, fuel amount control means, injection timing control means), L1 ... gas piping (fuel supply source).

Claims (6)

A gas engine (10) for causing combustion in the combustion chamber (25) using gas fuel, a gas supply control means (40) for controlling the supply mode of the gas fuel in the gas engine, and a pressure vessel for storing fuel ( 51), a gas engine control system comprising
The gas engine
An intake valve (21) provided in the intake port (11a) for opening and closing an intake side opening of the combustion chamber;
A fuel supply device (14) for supplying gas fuel supplied from a fuel supply source (L1) to the intake passage portion (12) upstream of the intake port;
A fuel injection valve (15) that is supplied with fuel separately from the fuel supply to the fuel supply device and injects fuel at a predetermined injection pressure at the intake port;
A spark plug (26) for generating sparks in the combustion chamber;
Have
The fuel injection valve is provided in the intake port so that fuel is injected toward the spark plug through an opening gap portion by opening the intake valve,
The gas supply control means includes
As a fuel amount required for one combustion of the gas engine, a first fuel amount (Q1) supplied to the intake passage portion by the fuel supply device, and a second fuel amount (Q2) injected into the intake port by the fuel injection valve And a fuel amount control means for performing fuel amount control of the fuel supply device and the fuel injection valve based on the respective fuel amounts;
Injection timing control means for controlling the fuel injection timing so that fuel is injected by the fuel injection valve in the latter half of the valve opening period of the intake valve;
A has,
The pressure vessel stores fuel at a pressure corresponding to the predetermined injection pressure;
Gas engine control characterized in that fuel is supplied in a liquid state from the pressure vessel to the fuel injection valve, and fuel supplied from the pressure vessel is injected at the intake port in the fuel injection valve. system.   2. The gas engine control system according to claim 1, wherein the fuel amount control unit calculates the first fuel amount and the second fuel amount such that the first fuel amount> the second fuel amount.   The gas engine control system according to claim 1, wherein the fuel amount control means calculates the first fuel amount and the second fuel amount so that lean combustion is performed in the gas engine.   4. The fuel injection timing control unit according to claim 1, wherein the injection timing control unit controls the fuel injection timing so that fuel injection is completed at the valve closing timing with reference to the valve closing timing of the intake valve. 5. Gas engine control system. The pressure vessel stores a fuel having a component different from that of the gas fuel supplied from the fuel supply source,
The gas engine control system according to any one of claims 1 to 4 , wherein the fuel stored in the pressure vessel is superior in ignitability to gas fuel supplied from the fuel supply source. The fuel property information of the fuel stored in the pressure vessel is stored in the storage unit (40b),
The gas engine control system according to any one of claims 1 to 5, wherein the gas supply control unit performs fuel supply control based on fuel property information stored in the storage unit.

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