JP4576198B2 - Gas engine with EGR system - Google Patents

Description

  According to the present invention, a mixed gas of gaseous fuel and air is supplied from a supply port to a combustion chamber, and spark discharge is generated in the mixed gas by an ignition plug provided in the combustion chamber so that the mixed gas is ignited and burned. It is related with the gas engine with an EGR system which was made to eject the EGR gas toward the outer peripheral part in a combustion chamber.

  A mixed gas formed by injecting gas fuel into a supply passage from a gas injection device connected to the gas fuel supply passage is supplied to the combustion chamber, and the spark plug provided in the combustion chamber supplies the mixed gas into the mixture gas. A gas engine having an EGR system in which EGR is mixed in an air supply and supplied to an engine combustion chamber through an air supply pipe in a gas engine configured to ignite and discharge the mixed gas by spark discharge. One technique is proposed in Japanese Patent Application Laid-Open No. 10-141144.

  In such a technique, the cylinder head is provided with an ignition plug-side air supply port and a liner-side air supply port, and from the ignition plug-side air supply port, air supply consisting only of the original air-fuel ratio is supplied in the vicinity of the ignition plug, From the liner side air supply port, supply air that is mixed with EGR gas in the vicinity of the inner wall surface of the cylinder to form a two-layer air sphere in the cylinder to achieve normal ignition and increase of the knocking limit. Yes.

JP-A-10-141144

In a gas engine equipped with an ignition device, if the ignition timing of the ignition plug is advanced, the combustion efficiency is improved and the fuel consumption rate is reduced, but there is a conflicting phenomenon that knocking is likely to occur.
Further, in the gas engine with an EGR system, as shown in FIG. 11, when the EGR amount (EGR rate) in the supply air is increased, NO _x (nitrogen oxide) is reduced, and the knocking limit is increased, so that knocking hardly occurs. It is known that

  From this knowledge, in the technique of the above-mentioned patent document 1 (Japanese Patent Laid-Open No. 10-141144), the air supply comprising only the original air-fuel ratio in the vicinity of the spark plug from the spark plug side air supply port provided in the cylinder head. From the liner-side air supply port, supplying air mixed with EGR gas in the vicinity of the inner wall surface of the cylinder, normal ignition by supplying air from the spark plug-side air supply port to the vicinity of the spark plug, and the liner The EGR gas from the side air supply port is increased in the knocking limit due to the mixed air supply.

However, in such a conventional technique, in order to supply the EGR gas mixed supply air from the liner side air supply port, it is necessary to install a mixer for mixing fresh air and EGR gas in the supply passage. The device is complicated and expensive.
In this conventional technique, the EGR gas mixture supply air is supplied from the liner side air supply port to the inner wall surface of the cylinder, that is, to the outer periphery of the combustion chamber. The EGR gas mixture supply air is supplied to the combustion chamber. Since it is only supplied near the outer periphery, a mixed gas of fresh air and EGR gas is supplied to the end gas that is distributed near the outer periphery in the combustion chamber and is likely to cause knocking due to self-ignition. reducing effect of increasing effect and nO _X in the knock limit is not sufficiently obtained due to the supply of the EGR gas into the end gas.
And so on.

SUMMARY OF THE INVENTION In view of the problems of the prior art, the present invention provides a gas engine having an EGR system configured to ignite and combust a mixed gas by means of a spark plug. providing EGR gas sufficient knock limit increasing effect and NO _X EGR system with a gas engine which reduction effect can be obtained in accordance with the supply of while satisfactorily retaining the ignition combustion performance for the purpose of.

The present invention achieves such an object. First, as a reference technique , a mixed gas of gaseous fuel and air is supplied from a supply port to a combustion chamber, and sparks are introduced into the mixed gas by an ignition plug provided in the combustion chamber. In a gas engine configured to discharge and ignite and burn the mixed gas, EGR gas (exhaust gas recirculation) diverted from the exhaust gas in the exhaust passage is ejected toward the outer peripheral portion of the combustion chamber. A technique is proposed in which a gas jet passage is provided and the oxygen concentration at the outer peripheral portion of the combustion chamber is made lower than the oxygen concentration at the central portion in the combustion chamber by the EGR gas jetted from the EGR gas jet passage .

According to this reference technique, in a high NO _X generation amount is large and self-ignition property remaining in the outer peripheral portion of the combustion chamber end gas, by allowed to intensively jetting the EGR gas from the EGR gas ejection passage, the A region where oxygen concentration is reduced by EGR gas is formed on the outer periphery of the combustion chamber.
On the other hand, in the vicinity of the center of the combustion chamber where the ignition plug is installed, fresh air that does not contain EGR gas, that is, a lean mixture of fuel gas and air, is supplied from the air supply port. As a result, the combustion chamber has a layered gas distribution in which a gas region having good ignition combustibility is formed in the vicinity of the center portion, and an oxygen concentration reduction region by EGR gas is formed in the outer peripheral portion.

Therefore, the ignition plug ignites and burns the gas mixture with good ignition combustibility near the center, so that the ignition combustibility is maintained well, and this ignition flame has a high flame propagation speed to move the combustion chamber in the radial direction. And can be propagated to the oxygen concentration lowering region in the outer peripheral portion, and the ignition performance improves the combustion performance of the end gas in the outer peripheral portion including the EGR gas in a low oxygen atmosphere.
Thus, while maintaining high combustion efficiency in the entire combustion chamber, NO _X generation amount is suppressed at the time of combustion of end gas in the outer peripheral portion, and further the less residual self-ignitability of the large gas on the outer peripheral portion or eliminated for The occurrence of knocking is suppressed and the knocking limit is increased.

In this reference technique , specifically, the following two configurations are preferable.
(1) The EGR gas ejection passage is directed to the peripheral wall of the air supply port so that the EGR gas ejected from the EGR gas ejection passage when the air supply valve is opened reaches the outer peripheral portion in the combustion chamber. Open.
(2) An EGR gas ejection passage is constituted by an EGR gas ejection pipe provided inside the air supply port, and the EGR gas ejection pipe is ejected from the EGR gas ejection pipe when the air supply valve is opened. Opens in the air supply port so as to reach the outer periphery of the combustion chamber.
With this configuration, the direction of the EGR gas ejection pipe can be set freely to some extent inside the air supply port, so that the directivity in the target EGR gas ejection direction is increased, and the target outer peripheral portion is accurately set. Can be supplied with EGR gas.

According to the present invention, in the gas engine, a plurality of EGR gas ejection passages for ejecting EGR gas (exhaust gas recirculation gas) diverted from the exhaust gas in the exhaust passage toward the outer peripheral portion in the combustion chamber is provided per cylinder. The plurality of EGR gas ejection passages are opened in different directions in the combustion chamber, and the oxygen concentration at the outer peripheral portion of the combustion chamber is determined by the EGR gas ejected from the EGR gas ejection passage in the center of the combustion chamber. Configure to lower the oxygen concentration of the site ,
Further, two of the plurality of EGR gas ejection passages are provided per one air supply port, and the two EGR gas ejection passages are directed in opposite directions in the combustion chamber so that the two EGR ejection passages are mutually connected. It is characterized by opening in the reverse direction.

According to this invention, a plurality of EGR gas ejection passages per cylinder opened in different directions in the combustion chamber, more specifically two per gas supply port, are provided and directed in opposite directions. Since the EGR gas is jetted in the opposite direction to the end gas at the outer peripheral portion of the combustion chamber from the EGR gas ejection passage opened in this manner, the disturbance of the mixed gas due to the EGR gas in the combustion chamber is promoted, and the flame in the combustion chamber The propagation speed is increased, and the combustion performance in the low oxygen atmosphere of the end gas in the outer peripheral portion containing the EGR gas is further improved.

The present invention also provides an EGR gas ejection passage for ejecting EGR gas (exhaust gas recirculation gas) diverted from the exhaust gas in the exhaust passage toward the outer peripheral portion of the combustion chamber in the gas engine, and the EGR gas ejection An EGR valve that adjusts the EGR gas flow rate in the passage, a knocking sensor that detects the knocking strength in the gas engine, and an allowable knocking strength in which the knocking strength detection value is preset based on the knocking strength detection value from the knocking sensor And a controller for controlling the opening degree of the EGR valve so as to increase the EGR gas flow rate when exceeding the EGR gas flow rate, and the EGR gas whose flow rate is controlled by the EGR valve and ejected from the EGR gas ejection passage. Lower the oxygen concentration at the outer periphery of the chamber than the oxygen concentration at the center of the combustion chamber. Characterized by being configured to so that.
In this invention, preferably, a plurality of EGR gas ejection passages provided with the EGR valve are provided per cylinder, and the plurality of EGR gas ejection passages are opened in different directions in the combustion chamber, The controller is configured to individually control the opening degree of each EGR valve so that the EGR gas flow rates in the plurality of EGR gas ejection passages are individually increased when the knocking strength detection value exceeds the allowable knocking strength. To do.

According to this invention, the knocking sensor detects the knocking strength in the engine and inputs the detected knocking strength to the controller. The controller compares the knocking strength detection value with a preset allowable knocking strength, and the knocking strength detection value is allowed. When the knocking strength is exceeded, the opening degree of the EGR valve is increased to increase the EGR gas flow rate, and when the knocking strength is less than the allowable knocking strength, the EGR gas flow rate is decreased to reduce the EGR gas flow rate to a flow rate close to the allowable knocking strength. I can drive.
Further, as shown in FIG. 11, when the EGR gas flow rate increases, the combustion period becomes longer and the engine performance deteriorates. Therefore, it is possible to perform an operation that reliably avoids the occurrence of knocking while preventing a decrease in engine performance due to a prolonged combustion period due to an excessive EGR gas flow rate.

In this invention, preferably, the controller includes means for delaying the ignition timing of the spark plug when the knocking strength detection value exceeds a preset allowable knocking strength.
According to this structure, when the knocking strength detection value exceeds the allowable knocking strength in addition to the effect of preventing the occurrence of knocking by maintaining the EGR gas flow rate above the gas flow rate corresponding to the allowable knocking strength as described above. The effect of preventing the occurrence of knocking by controlling the ignition plug so as to delay the ignition timing is superimposed, and a stable operation that avoids further occurrence of knocking can be realized.

As described above, according to the present invention , the ignition plug ignites and burns a mixed gas having good ignition combustibility in the vicinity of the center portion, so that the ignition combustibility is maintained well, and the ignition flame is kept at a high flame propagation speed. Thus, the combustion chamber can be diffused in the radial direction and propagated to the oxygen concentration lowering region in the outer peripheral portion. By this ignition flame, the combustion performance in the low oxygen atmosphere of the end gas of the outer peripheral part containing EGR gas is improved.

Thus, while maintaining high combustion efficiency in the entire combustion chamber, NO _X generation amount is suppressed at the time of combustion of end gas in the outer peripheral portion, and further the less residual self-ignitability of the large gas on the outer peripheral portion or eliminated for , the knocking limit is increased occurrence of knocking is suppressed, while suppressing the suppressing NO _X generation amount generated constantly knocking can run the engine with retention of high thermal efficiency.
Further, according to the present invention, an EGR gas injection passage for injecting EGR gas toward the outer peripheral portion in the combustion chamber is provided with an extremely simple and low-cost apparatus in which the EGR gas injection passage is provided in the peripheral wall of the supply port or in the supply port. Te, while suppressing suppressing NO _X generation amount of occurrence of the knocking, such as can provide a gas engine which retained high thermal efficiency.

  Furthermore, according to the present invention, the knocking strength detection value is compared with a preset allowable knocking strength, and when the knocking strength detection value exceeds the allowable knocking strength, the opening degree of the EGR valve is increased and the EGR gas flow rate is increased. When the EGR gas flow rate is decreased and the EGR gas flow rate is decreased below the allowable knocking strength, the EGR gas flow rate can be operated at a flow rate close to the allowable knocking strength, thereby extending the combustion period due to the excessive EGR gas flow rate. It is possible to perform an operation that reliably avoids the occurrence of knocking while preventing a decrease in engine performance.

  Hereinafter, the present invention will be described in detail with reference to the embodiments shown in the drawings. However, the dimensions, materials, shapes, relative arrangements, and the like of the component parts described in this example are not intended to limit the scope of the present invention only to specific examples unless otherwise specified. Only.

FIG. 10 is an overall configuration diagram of a direct ignition gas engine provided with an EGR system to which the present invention is applied.
10, 100 is an engine, 101 is a cylinder of the engine (6 cylinders in this example), 112 is a crankshaft, 103 is an air supply manifold, 114 is an air supply pipe, 104 is an exhaust manifold, and 105 is an exhaust pipe. 111 is an air cleaner, 113 is a fuel gas supply pipe, 110 is a gas mixing device that mixes fuel gas from the fuel gas supply pipe 113 with air that has passed through the air cleaner 111 to generate a lean mixture, and 109 is supplied to the engine 100 A throttle valve for adjusting the flow rate of the lean air-fuel mixture.

Reference numeral 102 denotes an EGR pipe branched from the exhaust pipe 105 and connected to the air supply pipe 114 to recirculate a part of exhaust gas (EGR gas) flowing through the exhaust pipe 105 to the air supply pipe 114, and the EGR pipe 102 includes the EGR pipe 102. An EGR cooler 107 that cools the EGR gas and an EGR valve 108 that adjusts the flow rate of the EGR gas are installed.
A controller 50 controls the opening and closing of the throttle valve 109 and the EGR valve 108 and also controls the ignition timing of the ignition plug (see FIG. 1) of each cylinder.
The present invention relates to an improvement of an EGR system in a direct ignition gas engine having such a configuration.

FIG. 1 is a main part configuration diagram including a sectional view around a combustion chamber in a direct ignition gas engine with an EGR system according to a first embodiment of the present invention, and FIG. 2 is a schematic plan view (explanatory view) around the combustion chamber. 3 is a comparison diagram of the EGR effect in the first embodiment.
In FIG. 1, 121 is an engine piston, 129 is a cylinder head, 123 is a cylinder liner, 122 is a combustion chamber defined by an upper surface of the piston 121 and a lower surface of the cylinder head 129, 120 is an air supply port, and 125 is An air supply valve that opens and closes the air supply port 120, 126 is an exhaust port, and 127 is an exhaust valve that opens and closes the exhaust port 126.
Reference numeral 128 denotes an ignition plug that is attached to a central portion of the combustion chamber of the cylinder head 129 (123b is the center of the cylinder) and sparks discharge to the mixed gas in the combustion chamber 122.

Reference numeral 5 denotes an engine speed detector that detects the speed (engine speed) of the engine 100 (see FIG. 10), and reference numeral 6 denotes a load detector that detects a load (engine load) of the engine 100. Reference numeral 2 denotes a knocking sensor that detects knocking in the engine 100, and is preferably configured to detect the in-cylinder pressure of the engine 100 to detect the knocking intensity.
Reference numeral 50 denotes a controller that performs a control operation described later. The detected value of the engine speed from the engine speed detector 5, the detected value of the engine load from the load detector 6, and the detected value of knocking from the knocking sensor 2 are input to the controller 50, and the controller 50 performs a control operation as will be described later based on these detected values, and controls the ignition timing of the spark plug 128 based on the result.

In FIG. 1, reference numeral 1 denotes an EGR gas ejection passage bored in the cylinder head 129. As shown in FIG. 10, an EGR valve 108 is branched from the exhaust pipe 105 and adjusts the flow rate of the EGR cooler 107 and EGR gas. Is connected to an EGR pipe 102 where EGR gas is installed, and EGR gas is introduced through the EGR pipe 102.
The EGR gas ejection passage 1 is formed on the peripheral wall 120a of the air supply port 120, and the EGR gas ejected from the EGR gas ejection passage 1 when the air supply valve 125 is opened, Specifically, as shown in FIG. 2, the opening is directed so as to reach the end gas having a high self-ignitability staying along the cylinder liner inner surface 123a of the outer peripheral portion.

During the operation of the direct ignition gas engine, as shown in FIG. 10, the fuel gas supplied through the fuel gas supply pipe 113 is mixed with the air that has passed through the air cleaner in the gas mixing device 110 to become a lean air-fuel mixture. The lean air-fuel mixture passes through the air supply port 120 and is introduced into the combustion chamber 122 when the air supply valve 125 is opened.
When the air supply valve 125 is opened, the EGR gas stays from the EGR gas ejection passage 1 along the cylinder liner inner surface 123a in the outer peripheral portion of the combustion chamber 122 as indicated by the arrow S1 in FIGS. The gas is intensively ejected into the highly ignitable end gas. By the supply of the EGR gas, an oxygen concentration reduction region Z (see FIG. 2) due to the EGR gas is formed at the outer peripheral portion along the cylinder liner inner surface 123a of the combustion chamber 122.

As a result of the ejection of EGR gas from the EGR gas ejection passage 1 as described above, the oxygen (O ₂ ) concentration distribution in the combustion chamber 122 is obtained from a uniform distribution as shown in FIG. , B, the O ₂ concentration near the center is large, and the outer peripheral portion along the cylinder liner inner surface 123a becomes an oxygen concentration decrease region Z in which the O ₂ concentration is decreased.
That is, when the EGR gas is ejected from the EGR gas ejection passage 1, fresh air that does not contain EGR gas, that is, fuel gas and air is supplied from the supply port 120 in the vicinity of the center of the combustion chamber 122 where the ignition plug 128 is installed. As a result, the combustion chamber 122 is formed with a gas region having a good ignition combustion property near the center, and an outer peripheral portion is formed. A layered gas distribution is formed in which an oxygen concentration reduction region Z due to EGR gas is formed.

Then, under such a layered gas distribution, as shown in FIG. 1, a spark discharge is generated in the lean air-fuel mixture near the center of the combustion chamber 122 by the spark plug 128 attached to the center of the combustion chamber of the cylinder head 129. Then, an ignition flame is generated by igniting the lean air-fuel mixture in the part. The ignition flame continue to spread toward the outer peripheral portion of the combustion chamber 122 in the radial direction, the low NO _X combustion at a low oxygen atmosphere at the end gas is carried out in an oxygen concentration reduction region Z of the outer peripheral portion.

In the controller 50, the ignition timing of the spark plug 128 is advanced according to the increase in the engine speed detected by the engine speed detector 5 or the increase in the engine load detected by the load detector 6. Control to do.
Further, the controller 50 calculates the knocking strength based on the knocking detection value from the knocking sensor 2, compares the knocking strength detection value with a preset allowable knocking strength, and calculates the knocking strength detection value. Is controlled to advance the ignition timing of the spark plug 128 until the detected knocking strength value is equal to or lower than the allowable knocking strength.

Therefore, according to the first embodiment, the ignition plug 128 ignites and burns the mixed gas having good ignition combustibility in the vicinity of the center portion, so that the ignition combustibility is kept good, and this ignition flame is transmitted with high flame propagation. The inside of the combustion chamber 122 can be diffused in the radial direction at a speed and can be propagated to the oxygen concentration lowering region Z in the outer peripheral portion, and by this ignition flame, in the low oxygen atmosphere of the outer end gas including the EGR gas. The combustion performance is improved.
Thus, while maintaining high combustion efficiency in the entire combustion chamber 122, NO _X generation amount is suppressed at the time of combustion of end gas in the outer peripheral portion, further comprises or eliminated less residual self-ignitability of the large gas on the outer peripheral portion Therefore, the occurrence of knocking is suppressed and the knocking limit, that is, the allowable knocking strength can be increased.

FIG. 4 is a view corresponding to FIG. 1 showing a second embodiment of the present invention.
In the second embodiment, the EGR gas ejection passage is constituted by the EGR gas ejection pipe 3 provided inside the air supply port 120. The EGR gas ejection pipe 3 is configured so that the EGR gas ejected from the EGR gas ejection pipe 3 when the air supply valve 125 is opened is the outer peripheral portion in the combustion chamber 122, specifically as shown in FIG. In addition, the opening is directed toward the end gas having a high self-ignitability that stays along the cylinder liner inner surface 123a of the outer peripheral portion.
According to the second embodiment, since the direction of the EGR gas ejection pipe 3 can be set to some extent freely inside the air supply port 120, the directivity in the target EGR gas ejection direction is increased, and the target and EGR gas can be accurately supplied into the end gas at the outer peripheral portion.
Other configurations and operational effects are the same as those of the first embodiment shown in FIGS. 1 to 3, and the same members or elements are denoted by the same reference numerals.

FIG. 5 is a view corresponding to FIG. 1 showing a third embodiment of the present invention, and FIG. 6 is a schematic plan view (explanatory view) around the combustion chamber.
In the third embodiment, two EGR gas ejection passages are provided for one air supply port 120, and the two EGR gas ejection passages are opened in the combustion chamber 122 in opposite directions. Yes.
That is, in FIGS. 5 to 6, of the two EGR gas ejection passages provided in each of the air supply ports 120, one EGR gas ejection passage 1 is connected to the peripheral wall 120 a of the air supply port 120. When the air valve 125 is opened, the EGR gas ejected from the EGR gas ejection passage 1 stays along the cylinder liner inner surface 123a on the upstream side of the air supply air from the air supply valve 125 as indicated by the arrow S1 in FIG. Opening is directed so as to be ejected into the end gas.
Further, the EGR gas ejection pipe 3 which is the other EGR gas ejection passage is configured such that the EGR gas ejected from the EGR gas ejection pipe 3 when the air supply valve 125 is opened corresponds to the air supply valve as indicated by the arrow S2 in FIG. An opening is directed toward the end gas staying along the cylinder liner inner surface 123a on the downstream side of the air supply flow from 125.

According to the third embodiment, two EGR gas ejection passages opened in opposite directions in the combustion chamber 122, that is, provided in the supply port 120, are directed in opposite directions. The EGR gas ejection passage 1 and the EGR gas ejection pipe 3 that are opened cause the EGR gas to be ejected in opposite directions into the end gas at the outer peripheral portion in the combustion chamber 122, so that the EGR gas in the combustion chamber 122 Disturbance of the mixed gas is promoted.
Thereby, the flame propagation speed in the combustion chamber 122 is increased, and the combustion performance in the low oxygen atmosphere of the end gas in the outer peripheral portion including the EGR gas is further improved.
Other configurations and operational effects are the same as those of the first embodiment shown in FIGS. 1 to 3, and the same members or elements are denoted by the same reference numerals.

FIG. 7 is a diagram corresponding to FIG. 1 showing a fourth embodiment of the present invention, FIG. 8 is an operation explanatory diagram of the fourth embodiment, and FIG. 9 is a control block diagram of the fourth embodiment.
In the fourth embodiment, the EGR gas ejection passage 1 and the EGR gas ejection pipe 3 in the third embodiment are connected to the first and second EGR gas flow rates in the EGR gas ejection pipe 3 and the EGR gas ejection passage 1. 2 EGR valves 7 and 8 are provided, and the opening degree of the first and second EGR valves 7 and 8 is changed according to the detected value of the knocking strength, and the EGR gas flow rate from the EGR gas ejection pipe 3 and the EGR gas ejection passage 1 is changed. I have control.

That is, in FIG. 7, 7 is a first EGR valve that is provided in the EGR gas ejection pipe 3 of the third embodiment and controls the flow rate of the EGR gas ejected from the EGR gas ejection pipe 3, and 8 is that of the third embodiment. This is a second EGR valve that is provided in the EGR gas ejection passage 1 and controls the flow rate of the EGR gas ejected from the EGR gas ejection passage 1.
Reference numeral 5 denotes an engine speed detector that detects the speed (engine speed) of the engine 100 (see FIG. 10), and reference numeral 6 denotes a load detector that detects a load (engine load) of the engine 100. Reference numeral 2 denotes a knocking sensor that detects knocking in the engine 100, and is preferably configured to detect the in-cylinder pressure of the engine 100 to detect the knocking intensity.
Reference numeral 50 denotes a controller that performs a control operation described later. The detected value of the engine speed from the engine speed detector 5, the detected value of the engine load from the load detector 6, and the detected value of knocking from the knocking sensor 2 are input to the controller 50, and the controller 50 performs a control operation as will be described later based on these detection values, and controls the opening degree of the first EGR valve 7 and the second EGR valve 8 and the ignition timing of the spark plug 128 based on the result. .

Next, the control operation of the fourth embodiment will be described with reference to FIG.
The knocking detection value from the knocking sensor 2 is input to the knocking intensity comparison unit 55 of the controller 50 to calculate the knocking intensity.
Further, the detected value of the engine speed from the engine speed detector 5 and the detected value of the engine load from the load detector 6 are input to an ignition timing calculating unit 53 and an EGR amount calculating unit 54 described later. .
56 is an allowable knocking strength setting unit, and the relationship between the allowable knocking strength, that is, the knocking limit and the EGR gas flow rate Q is set so that the EGR gas flow rate Q increases as the knocking strength increases.
In the knocking strength comparison unit 55, the detected value of the knocking strength is compared with the allowable knocking strength set in the allowable knocking strength setting unit 56, and the comparison results are compared with the ignition timing calculation unit 53 and the EGR amount calculation unit. 54.

In the EGR amount calculation unit 54, when the knocking strength detection value exceeds the allowable knocking strength in the comparison result from the knocking strength comparison unit 55, the EGR gas flow rate is increased and set in the EGR amount setting unit 52. The increase amount of the EGR gas flow rate is added to the EGR gas flow rate corresponding to the detected value of the engine speed and the engine load, and input to the EGR valve control device 10.
In the EGR valve control device 10, the distribution amount Q1 of the first EGR valve 7 and the distribution amount Q2 of the second EGR valve 8 of the EGR gas flow rate Q are calculated.
In this case, in the EGR valve control apparatus 10, as shown in FIG. 8, the distribution amounts Q1 and Q2 of the EGR gas flow rate Q are changed according to the magnitude of the knocking strength (in this case, as the knocking strength increases, Q1 / Q2 is set to be small), the distribution amount Q2 of the EGR gas flow rate Q of the second EGR valve 8 in this example, for example, the EGR valve on the side where the effect of reducing the knocking strength increases as the knocking strength increases. Is controlled to increase.

  Therefore, when the comparison result that the detected value of the knocking intensity exceeds the allowable knocking intensity is input from the knocking intensity comparison unit 55, the EGR valve control device 10 corresponds to the knocking intensity as described above. A distribution amount Q1 of the first EGR valve 7 and a distribution amount Q2 of the second EGR valve 8 based on the distribution amount ratio of the EGR gas flow rate Q are calculated, and the opening degrees of the first EGR valve 7 and the second EGR valve 8 are determined by the EGR gas. The opening is controlled to correspond to the distribution amount Q1 of the flow rate and the distribution amount Q2 of the second EGR valve 8.

An ignition timing setting unit 51 retards the ignition timing of the spark plug 128 in relation to the engine speed or the engine load when the detected knocking strength exceeds the allowable knocking strength. It is set.
In the ignition timing calculation unit 53, the knocking strength detection value exceeds the allowable knocking strength from the relationship between the allowable knocking strength set in the ignition timing setting unit 51 and the ignition timing. The ignition circuit 9 is controlled so as to delay the ignition timing, and the ignition timing of the spark plug 128 is delayed by the ignition circuit 9. Thus, the ignition timing of the spark plug 128 is controlled to be retarded until the knocking intensity detection value becomes equal to or less than the allowable knocking intensity.

  According to the fourth embodiment, the knocking sensor 2 detects the knocking strength in the engine and inputs it to the controller 50. The controller 50 compares the knocking strength detection value with a preset allowable knocking strength, When the knocking strength detection value exceeds the allowable knocking strength, the opening degrees of the first EGR valve 7 and the second EGR valve 8 are determined based on the EGR gas flow rate Q1 of the EGR gas ejection pipe 3 on the first EGR valve 7 side and the second EGR valve 8. While controlling the amount of distribution with the EGR gas flow rate Q2 of the EGR gas ejection passage 1 on the side, the EGR gas flow rate is increased by decreasing the EGR gas flow rate when the EGR gas flow rate is lower than the allowable knocking strength. It can be operated at a flow rate close to knocking strength.

That is, as shown in FIG. 11, when the EGR gas flow rate increases, the combustion period becomes longer and the engine performance deteriorates. However, according to the fourth embodiment, the EGR gas flow rate is decreased when the EGR gas flow rate is lower than the allowable knocking strength. By controlling in this way, it is possible to perform an operation that reliably avoids the occurrence of knocking while preventing a decrease in engine performance due to a prolonged combustion period due to an excessive EGR gas flow rate.
Therefore, according to the fourth embodiment, the knocking strength detection value exceeds the allowable knocking strength in the effect of preventing the occurrence of knocking by maintaining the EGR gas flow rate above the gas flow rate corresponding to the allowable knocking strength. When the ignition timing of the spark plug is controlled so as to be delayed, the knocking prevention effect by superimposing can be superimposed to realize stable operation that avoids further knocking.

According to the present invention, in a gas engine having an EGR system that is configured to ignite and burn mixed gas by means of a spark plug, the ignition combustion performance by the spark plug is good with a simple structure and a low-cost device. It can be held to, provide adequate knock limit increasing effect and NO _X EGR system with a gas engine which reduction effect can be obtained in accordance with the supply of the EGR gas.

It is a principal part block diagram including sectional drawing around the combustion chamber in the direct ignition type gas engine with an EGR system which concerns on 1st Example of this invention. 2 is a schematic plan view (explanatory view) around a combustion chamber in the first embodiment. FIG. It is a comparison figure of the EGR effect in the 1st example. FIG. 3 is a view corresponding to FIG. 1 showing a second embodiment of the present invention. FIG. 6 is a view corresponding to FIG. 1 showing a third embodiment of the present invention. It is a schematic plan view (descriptive drawing) around the combustion chamber in the third embodiment. FIG. 6 is a view corresponding to FIG. 1 showing a fourth embodiment of the present invention. It is operation | movement explanatory drawing in the said 4th Example. It is a control block diagram in the fourth embodiment. It is a whole lineblock diagram of a direct ignition type gas engine provided with an EGR system to which the present invention is applied. It is operation | movement explanatory drawing regarding the EGR rate in each said Example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 EGR gas ejection path 2 Knocking sensor 3 EGR gas ejection pipe 5 Engine speed detector 6 Load detector 7 1st EGR valve 8 2nd EGR valve 50 Controller 100 Engine 120 Air supply port 121 Piston 122 Combustion chamber 125 Air supply valve 128 Ignition plug

Claims (4)

A gas mixture of gas fuel and air is supplied to a combustion chamber from an air supply port, and spark discharge is generated in the gas mixture by an ignition plug provided in the combustion chamber so that the gas mixture is ignited and combusted. In the gas engine, a plurality of EGR gas ejection passages for ejecting EGR gas (exhaust gas recirculation gas) diverted from the exhaust gas in the exhaust passage toward the outer peripheral portion of the combustion chamber are provided per cylinder. The EGR gas ejection passage is opened in different directions in the combustion chamber, and the oxygen concentration in the outer peripheral portion of the combustion chamber is determined from the oxygen concentration in the central portion of the combustion chamber by the EGR gas ejected from the EGR gas ejection passage. Is also configured to lower ,
Further, two of the plurality of EGR gas ejection passages are provided per one air supply port, and the two EGR gas ejection passages are directed in opposite directions in the combustion chamber so that the two EGR ejection passages are mutually connected. A gas engine with an EGR system that opens in the opposite direction .   2. The gas engine according to claim 1, wherein an EGR gas ejection passage for ejecting EGR gas (exhaust gas recirculation gas) diverted from the exhaust gas in the exhaust passage toward an outer peripheral portion in the combustion chamber, and the EGR gas ejection passage. An EGR valve for adjusting the EGR gas flow rate in the engine, a knocking sensor for detecting the knocking strength in the gas engine, and an allowable knocking strength in which the knocking strength detection value is preset based on the knocking strength detection value from the knocking sensor. A controller for controlling the opening degree of the EGR valve so as to increase the EGR gas flow rate when exceeding, and the flow rate is controlled by the EGR valve and the EGR gas ejected from the EGR gas ejection passage in the combustion chamber Decrease the oxygen concentration in the outer peripheral part from the oxygen concentration in the central part in the combustion chamber EGR system with a gas engine, characterized in that the sea urchin configuration. A plurality of EGR gas ejection passages provided with the EGR valve are provided per cylinder, the plurality of EGR gas ejection passages are opened in different directions in the combustion chamber, and the controller detects the knocking strength The opening degree of each EGR valve is individually controlled so that the EGR gas flow rates in the plurality of EGR gas ejection passages are individually increased when the value exceeds the allowable knocking strength. Item 3. A gas engine with an EGR system according to Item 2 .   4. The gas engine with an EGR system according to claim 3, wherein the controller includes means for delaying an ignition timing of the spark plug when the knocking strength detection value exceeds a preset allowable knocking strength.

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