JP4934106B2 - engine - Google Patents

Description

  The present invention includes, as a combustion chamber, a main chamber facing the piston, and a sub chamber communicating with the main chamber via an injection hole, and a sub fuel supply path for supplying fuel gas to the sub chamber includes The present invention relates to an engine provided with a check valve that opens due to a pressure drop in the sub chamber and allows supply of fuel gas to the sub chamber.

In recent years, the introduction of a cogeneration system using a gas engine using natural gas as fuel has been promoted from the viewpoint of environment and economy. And since the system using a gas engine has high power generation efficiency, it has become the mainstream of a natural gas cogeneration system. In the cogeneration system, gas engines have been put into practical use from a small size of 1 kW class to a large size of several MW class, and different engine types and combustion methods are adopted depending on the size of the engine.
For example, in a medium-sized cogeneration system of 1-2 MW class, a high efficiency can be realized, so that a sub-chamber type spark ignition lean mirror cycle engine has become mainstream. The sub-chamber type engine includes a combustion chamber called a sub chamber communicating with the main chamber via an injection hole in addition to a normal combustion chamber called a main chamber. Then, the intake valve is opened in the intake stroke, the lean mixture is introduced into the main chamber, the fuel gas is introduced into the sub chamber, and the intake stroke and the lean mixture, etc. that flowed from the main chamber into the sub chamber through the nozzle holes in the compression stroke An air-fuel mixture is formed by mixing the fuel gas supplied to the sub chamber. Then, the air-fuel mixture formed in the sub chamber is spark-ignited by an ignition plug and burned, and a flame jet is injected from the sub chamber to the main chamber through the nozzle hole, and the lean air-fuel mixture formed in the main chamber is combusted. It is configured to let you. Therefore, as compared with a single-chamber engine having only a normal combustion chamber, it is possible to realize lean combustion in which the fuel gas is burned in a lean state with respect to air as a whole combustion chamber, and high efficiency is achieved. be able to.

As such a sub-chamber engine, there has been provided a mechanical on-off valve in a sub-fuel supply path for supplying fuel gas to the sub-chamber and a control device for controlling the opening / closing operation of the mechanical on-off valve. (For example, refer to Patent Document 1). In conventional sub-chamber engines, those provided with the above-described mechanical on-off valves have been the mainstream, but in recent years, those provided with check valves instead of mechanical on-off valves are being put into practical use. (For example, refer to Patent Document 2). This is because the configuration with a check valve is simpler than the mechanical on-off valve that opens and closes with an external driving force, making it easier to manufacture, reducing size and reducing costs. It is because it can plan.
This check valve has a structure in which the fuel gas does not flow in the reverse direction from the sub chamber to the sub fuel supply passage, and the fuel gas can be allowed to flow in the forward direction from the sub fuel supply passage to the sub chamber. ing. The check valve is in a closed state by bringing a valve body such as a ball into contact with the valve seat by the biasing force of the spring. When the pressure in the sub chamber decreases as the piston moves down during the intake stroke and the pressure difference between the upstream side and the downstream side of the check valve becomes a certain value or more, the pressure is increased in a direction against the biasing force of the spring. By acting, the valve body is separated from the valve seat to be opened, and the fuel gas is supplied to the sub chamber.

JP 2003-278548 A JP 2001-3753 A

  In an engine in which a check valve is provided in the auxiliary fuel supply path, the check valve is opened when the pressure difference between the upstream side and the downstream side of the check valve in the auxiliary fuel supply path exceeds a certain value. Accordingly, the pressure in the sub chamber decreases as the piston moves down during the intake stroke, and the check valve opens, so that fuel gas can be supplied to the sub chamber during the intake stroke. However, the pressure in the sub chamber decreases due to the exhaust of the combustion exhaust gas during the exhaust stroke, and the check valve may be opened during the exhaust stroke. When the check valve is opened during the exhaust stroke, the fuel gas supplied to the sub chamber is supplied from the sub chamber to the main chamber via the nozzle hole, and enters the exhaust path as unburned hydrocarbons without burning. It will be discharged. As a result, the amount of unburned hydrocarbons increases, leading to a decrease in engine efficiency.

  The present invention has been made paying attention to such a point, and an object thereof is to provide an engine capable of reducing the amount of unburned hydrocarbons and improving the engine efficiency.

In order to achieve this object, a characteristic configuration of an engine according to the present invention includes, as a combustion chamber, a main chamber facing a piston, and a sub chamber communicating with the main chamber via an injection hole, the sub chamber In the engine, the auxiliary fuel supply passage for supplying fuel gas to the engine is provided with a check valve that opens due to a pressure drop in the auxiliary chamber and allows the supply of the fuel gas to the auxiliary chamber.
The main fuel supply passage that supplies fuel gas to the intake passage that supplies fresh air to the main chamber is provided with a gas control valve that can freely open and close the main fuel supply passage, and the sub fuel supply passage includes the main fuel supply passage. The gas control valve is configured to branch from between the gas control valve in the supply passage and the connection portion to the intake passage, and controls the opening / closing operation of the gas control valve to control the supply timing of the fuel gas to the intake passage. A gas supply timing control means is provided.

According to this characteristic configuration, the auxiliary fuel supply path branches from between the gas control valve and the connection point to the intake path in the main fuel supply path, so the gas control valve for intermittently supplying the fuel gas to the intake path is provided. By utilizing this, the supply of the fuel gas to the auxiliary fuel supply path can be interrupted, and the configuration can be simplified. The gas supply timing control means controls the opening / closing operation of the gas control valve, so that the fuel gas supply timing to the sub chamber can be controlled while the fuel gas supply timing to the intake passage can be controlled. . For example, the gas supply timing control means controls the gas so that the gas control valve is closed during the exhaust stroke and the gas control valve is opened during periods when combustion in the main chamber is good during other periods. The opening / closing operation of the valve can be controlled. Therefore, it is possible to prevent the fuel gas from being supplied to both the intake passage and the sub chamber during the exhaust stroke while improving the combustion in the main chamber. Therefore, the supply of the fuel gas to the sub chamber can be prevented during the exhaust stroke, and the fuel gas can be prevented from being discharged into the exhaust passage as unburned hydrocarbon without burning.
From the above, while effectively simplifying the configuration by effectively using the gas control valve, it is possible to reduce the amount of unburned hydrocarbons and improve the engine efficiency.

  According to a further characteristic configuration of the engine according to the present invention, the gas supply timing control means includes the gas control valve so that a set period from the late exhaust stroke to the intake stroke is a supply timing of the fuel gas to the intake passage. It is in the point comprised so that the opening-and-closing operation | movement of may be controlled.

  According to this characteristic configuration, the fuel gas is supplied to both the intake passage and the sub chamber during the set period from the late stage of the exhaust stroke to the intake stroke by the gas supply timing control means. By supplying the fuel gas to both the intake passage and the sub chamber during this set period, combustion in the main chamber can be improved and a suitable air-fuel mixture can be formed in the sub chamber. The mixture can be accurately ignited. In addition, during the period other than the set period, the gas supply timing control means controls the gas control valve to the closed state, so that the fuel gas can be prevented from being supplied to the sub chamber, and the unburned carbonization can be prevented without burning the fuel gas. It can be prevented that hydrogen is discharged into the exhaust passage.

  According to a further characteristic configuration of the engine according to the present invention, a plurality of the combustion chambers are provided, and the main fuel supply path and the sub fuel supply path are provided for each of the plurality of combustion chambers. Branching from between the gas control valve in the main fuel supply passage to the other combustion chamber and the connection point to the intake passage with different rotation phases of the crankshaft performing various strokes of intake, compression, combustion / expansion, and exhaust The point is that it is configured to do.

For example, there is a case where the supply timing of the fuel gas to the intake passage for realizing the optimal combustion in the main chamber does not exist within the set period during the intake stroke late to the intake stroke. In this case, the auxiliary fuel supply passage for a certain combustion chamber is provided so as to branch from the main fuel supply passage for the same combustion chamber, and the supply timing of the fuel gas to the intake passage is set for a set period from the late stage of the exhaust stroke to the intake stroke. Then, there is a possibility that optimum combustion cannot be realized in the main chamber.
Therefore, according to this characteristic configuration, the auxiliary fuel supply path is provided so as to branch from the main fuel supply path to other combustion chambers having different rotation phases of the crankshaft for performing various strokes of intake, compression, combustion / expansion, and exhaust. As a result, for a certain combustion chamber, the timing for supplying the fuel gas to the intake passage and the timing for allowing the fuel gas to be supplied to the sub chamber can be made different. Therefore, for a certain combustion chamber, the fuel gas supply timing to the intake passage can be set to a period other than the set period during the intake stroke from the late exhaust stroke, while being able to achieve optimum combustion in the main chamber. The supply timing of the fuel gas to the sub chamber can be set within the set period during the intake stroke from the late exhaust stroke.

An embodiment of an engine according to the present invention will be described with reference to the drawings.
[First Embodiment]
As shown in FIG. 1, the engine 1 is configured by connecting a cylinder head 2, a cylinder block 3, a crankcase (not shown), and an oil pan (not shown) so as to overlap each other. An intake valve 4 and an exhaust valve 5 that can be freely opened and closed are provided. The piston 6 is slidably accommodated in the cylinder block 3, and the reciprocating operation force of the piston 6 is transmitted from the crank mechanism 7 to the crankshaft 8 and output as rotational power. Although not shown, the power from the crankshaft 8 is transmitted to a camshaft or the like that opens and closes the intake valve 4 and the exhaust valve 5.

  As the combustion chamber N, a main chamber 9 facing the upper surface of the piston 6 on the lower surface side of the cylinder head 2 and a sub chamber 11 communicating with the main chamber 9 through the injection hole 10 are provided. The engine 1 uses a fuel gas such as a gaseous fuel gas or a city gas, and in the main chamber a lean mixture of fuel gas and air (a mixture of air and a small amount of fuel gas) is taken in the intake stroke. 9, fuel gas is supplied to the sub chamber 11, and a lean air-fuel mixture is flowed from the main chamber 9 into the sub chamber 11 through the nozzle hole 10 in the compression stroke to form a gas mixture in the sub chamber 11. The air-fuel mixture combusted in the sub chamber 11 by ignition with the ignition plug 16 of the chamber 11 is configured to be injected as a flame jet F into the main chamber 9 through the nozzle hole 10.

  Although one combustion chamber N is shown in FIG. 1, the engine 1 is composed of a multi-cylinder engine having a plurality of pistons 6 and a plurality of combustion chambers N. Then, the engine 1 transmits the driving force from the crankshaft 8 to a generator (not shown) to generate electric power, and recovers exhaust heat from the engine via a heat medium so that it can be supplied to a heat consuming terminal or the like. Used in cogeneration systems.

  An intake passage 12 for supplying fresh air that is a lean air-fuel mixture is provided in the main chamber 9, and a main fuel supply passage 13 for supplying fuel gas to the intake passage 12 is provided. The main fuel supply path 13 is provided with a gas control valve 14 that is supplied with fuel gas at a constant pressure and that can freely open and close the main fuel supply path 13. The gas control valve 14 is configured as a valve capable of high-speed response, and is configured to control the fuel gas concentration distribution of the lean air-fuel mixture supplied to the main chamber 9 by controlling the opening / closing operation of the gas control valve 14. Has been. Although not shown, the intake passage 12 is provided with a throttle valve, a supercharger that supercharges air, and the like on the upstream side of the connection point with the main fuel supply passage 13.

  The sub chamber 11 is formed inside a base 15 having a nozzle hole 10 formed at the lower end, and the base 15 is supported by the cylinder head 2 with the lower end protruding into the main chamber 9. An ignition unit 17 having an ignition plug 16 is provided at the upper part of the base 15, and the ignition plug 16 is provided so that its ignition point 16 a is located in the sub chamber 11.

  The auxiliary fuel supply passage 18 for supplying the fuel gas to the auxiliary chamber 11 branches from the gas control valve 14 and the connection portion to the intake passage 12 in the main fuel supply passage 13 so as to guide the fuel gas to the auxiliary chamber 11. It is configured. The auxiliary fuel supply path 18 extends from the outside of the ignition unit 17 toward the inside thereof and communicates with the auxiliary chamber 11. The auxiliary fuel supply path 18 is configured in a narrow tubular shape whose width is narrower than that of the main fuel supply path 13. For example, the pipe diameter of the auxiliary fuel supply path 18 can be about 1/10 of the pipe diameter of the main fuel supply path 13. And although illustration is abbreviate | omitted, in the auxiliary fuel supply path 18, the opening adjustment valve is provided upstream from the non-return valve 19, and the main fuel supply path 13 is adjusted by adjusting the opening degree of the opening adjustment valve. The ratio of the fuel gas supplied to the fuel gas and the fuel gas supplied to the auxiliary fuel supply path 18 can be set to a desired ratio.

  The auxiliary fuel supply passage 18 is provided with a check valve 19 that opens due to a pressure drop in the auxiliary chamber 11 and allows supply of fuel gas to the auxiliary chamber 11. The check valve 19 is in a closed state by bringing a valve body such as a ball into contact with the valve seat by a biasing force of a spring, and the pressure difference between the upstream side and the downstream side is greater than a certain value due to the pressure drop of the sub chamber 11. Then, pressure acts in a direction against the urging force of the spring, the valve body is separated from the valve seat and is opened, and the supply of fuel gas to the sub chamber 11 is allowed.

  A control device 20 that controls the operation of the spark plug 16 and the like to control the engine 1 is provided, and a detection signal from a timing sensor 21 that measures the rotation angle of the crankshaft 8 is input to the control device 20. It is configured as follows. For example, the timing sensor 21 is configured to detect the rotation angle of the crankshaft 8 by electromagnetically detecting the position of a tooth portion of a gear-like magnetic body provided on the crankshaft 8.

  The control device 20 is provided with gas supply timing control means 23 for controlling the opening / closing operation of the gas control valve 14 in order to control the supply timing of the fuel gas to the intake passage 12. The gas supply timing control means 23 controls the gas control valve so that the set period from the late exhaust stroke to the intake stroke becomes the supply timing of the fuel gas to the intake passage 12 in order to achieve optimal combustion in the main chamber 9. 14 is configured to control the opening and closing operation. As shown in FIG. 2, the gas supply timing control means 23, for example, supplies fuel to the intake passage 12 when the rotation angle of the crankshaft 8 immediately after the exhaust valve 5 is closed is between 10 ° and 90 °. The opening / closing operation of the gas control valve 14 is controlled so that the gas supply timing is reached. As a result, in the intake stroke, the gas control valve 14 is opened, so that fuel gas can be supplied to the intake passage 12, and the check valve 19 is opened due to the pressure drop in the sub chamber 11 caused by the lowering of the piston 6. Thus, the fuel gas can also be supplied to the sub chamber 11. In the compression stroke, the combustion / expansion stroke, and the exhaust stroke, the gas control valve 14 is closed, and the pressure upstream of the check valve 19 in the auxiliary fuel supply passage 18 can be kept low. Therefore, even if the check valve 19 is opened in the exhaust stroke, it is possible to prevent the fuel gas from being supplied to the sub chamber 11 and being exhausted without being combusted.

The engine 1 is configured to sequentially perform intake, compression, combustion / expansion, and exhaust strokes by opening and closing the intake valve 4 and the exhaust valve 5 in the same manner as a normal four-stroke internal combustion engine.
In the intake stroke, the intake valve 4 is opened and the piston 6 descends, whereby fresh air that is a lean air-fuel mixture is sucked into the main chamber 9 from the intake passage 12. At this time, the gas control valve 14 is controlled in an open state, and the sub chamber 11 also decreases in pressure with a decrease in pressure in the main chamber 9, so that the pressure difference between the upstream side and the downstream side of the check valve 19 is constant. When the value exceeds the value, the check valve 19 is opened, and the fuel gas is supplied to the sub chamber 11.
In the compression stroke, the gas control valve 14 is controlled to be closed, and the piston 6 ascends with the intake valve 4 closed, thereby compressing the lean air-fuel mixture in the main chamber 9. At this time, the lean air-fuel mixture flows from the main chamber 9 to the sub-chamber 11 through the nozzle hole 10, and the fuel gas and the lean air-fuel mixture supplied in the sub fuel supply path 18 are mixed, An air-fuel mixture having a high concentration of fuel gas is formed in the sub chamber 11. As for the check valve 19, the pressure of the sub chamber 11 increases as the piston 6 rises, and the check valve 19 is closed, and the supply of fuel gas to the sub chamber 11 is stopped.
Based on the detection signal of the timing sensor 21, the control device 20 activates the spark plug 16 at the ignition timing (set timing near top dead center or near top dead center), and performs spark ignition in the sub chamber 11.
In the combustion / expansion stroke, the combustion gas burned in the sub chamber 11 is injected as a flame jet F into the main chamber 9 through the nozzle hole 10, thereby burning the lean air-fuel mixture in the main chamber 9. In 9, the combustion gas is expanded and the piston 6 is lowered.
In the exhaust stroke, the exhaust valve 5 is opened and the piston 6 is raised, so that the combustion exhaust gas is exhausted to the exhaust passage 22. At this time, the gas control valve 14 is controlled in the closed state, so that it is possible to prevent the fuel gas from being supplied to the sub chamber 11 and exhausted without being combusted.

  As described above, the engine according to the present invention controls the opening / closing operation of the gas control valve 14 so that the fuel gas is supplied to the intake passage 12 when the rotation angle of the crankshaft 8 is between 10 ° and 90 °. By doing so, the emission amount of unburned hydrocarbons can be reduced and the engine efficiency can be improved. The engine according to the present invention has an unburned hydrocarbon concentration in the exhaust gas of 1/3 and a power generation efficiency of 0 compared with a conventional engine in which the check valve 19 is simply provided in the auxiliary fuel supply passage 13. .It has been confirmed by experiment that it has improved by 5 points. This experiment was performed using an engine having a bore diameter of 180 mm, a piston stroke of 230 mm, 12 cylinders, a displacement of 70.2 liters, a rotational speed of 1200 rpm, and a power generation output of 800 kW.

[Second Embodiment]
In the first embodiment, the main fuel supply passage 13 and the auxiliary fuel supply passage 18 are provided for each of the plurality of combustion chambers, and the auxiliary fuel supply passage 18 is a gas control valve in the main fuel supply passage 13 for the same combustion chamber. 14 and a connection point with respect to the intake passage 12 are branched. In the second embodiment, instead of this configuration, the auxiliary fuel supply path 18 branches from between the connection point to the gas control valve 14 and the intake path 12 in the main fuel supply path 13 for the other combustion chambers. Has been. The plurality of combustion chambers are configured to vary the rotational phase of the crankshaft 8 that performs various strokes of intake, compression, combustion / expansion, and exhaust.

  FIG. 3 shows two combustion chambers of the first combustion chamber N1 and the second combustion chamber N2 among the plurality of combustion chambers. On the basis of FIG. 3, the auxiliary fuel supply path 18 is configured to branch from between the gas control valve 14 in the main fuel supply path 13 for the other combustion chambers and the connection location to the intake path 12. explain.

  For example, in the first combustion chamber N1, there is a case where the supply timing of the fuel gas to the intake passage 12 for realizing the optimal combustion in the main chamber 9 does not exist within the set period from the late exhaust stroke to the intake stroke. is there. Therefore, by providing the auxiliary fuel supply path 18 so as to branch from the main fuel supply path 13 to the second combustion chamber N2 having different rotational phases of the crankshaft 8 for performing various strokes, The fuel gas supply timing to the passage 12 and the fuel gas supply timing to the sub chamber 11 can be made different. Therefore, for the first combustion chamber N1, the supply timing of the fuel gas to the intake passage 12 can be set to a period other than the set period during the intake stroke to the intake stroke, and optimal combustion is performed in the main chamber 9. While being able to be realized, the supply timing of the fuel gas to the sub chamber 11 can be set within the set period from the latter stage of the exhaust stroke to the intake stroke.

[Another embodiment]
(1) In the first embodiment, the setting period for supplying the fuel gas to the intake passage 12 may be set in any way as long as it is in the range from the latter stage of the exhaust stroke to the intake stroke.

(2) In the first and second embodiments described above, the set period of time for supplying the fuel gas to the intake passage 12 can be a fixed period or can be changed. In the case of changing the set period, for example, the set period can be changed so as to obtain an optimum combustion state according to the combustion state in the main chamber 9.

  The present invention includes, as a combustion chamber, a main chamber facing the piston, and a sub chamber communicating with the main chamber via an injection hole, and a sub fuel supply path for supplying fuel gas to the sub chamber includes A check valve that opens due to a pressure drop in the sub chamber and allows the supply of fuel gas to the sub chamber is provided to reduce unburned hydrocarbon emissions and improve engine efficiency. Can adapt to any engine.

Schematic of the engine in the first embodiment Timing chart showing open / closed state of gas control valve in crankshaft rotation phase Schematic of the engine in the second embodiment

Explanation of symbols

6 piston 9 main chamber 10 nozzle hole 11 sub chamber 12 intake passage 13 main fuel supply passage 14 gas control valve 18 sub fuel supply passage 19 check valve 23 gas supply timing control means N combustion chamber

Claims (3)

As a combustion chamber, it comprises a main chamber facing the piston, and a sub chamber communicating with the main chamber via a nozzle hole,
The sub fuel supply path for supplying fuel gas to the sub chamber is an engine provided with a check valve that opens due to a pressure drop in the sub chamber and allows fuel gas to be supplied to the sub chamber. And
The main fuel supply passage for supplying fuel gas to the intake passage for supplying fresh air to the main chamber is provided with a gas control valve capable of opening and closing the main fuel supply passage,
The sub fuel supply path is configured to branch from between the gas control valve in the main fuel supply path and a connection point to the intake path,
An engine provided with gas supply timing control means for controlling the opening and closing operation of the gas control valve in order to control the supply timing of the fuel gas to the intake passage.   The gas supply timing control means is configured to control the opening / closing operation of the gas control valve so that the set period from the late exhaust stroke to the intake stroke is the supply timing of the fuel gas to the intake passage. The engine according to claim 1. A plurality of the combustion chambers;
The main fuel supply path and the sub fuel supply path are provided for each of the plurality of combustion chambers,
The auxiliary fuel supply passage is connected to the gas control valve and the intake passage in the main fuel supply passage to the other combustion chambers having different rotational phases of the crankshaft for performing intake, compression, combustion / expansion, and exhaust strokes. The engine according to claim 1, wherein the engine is configured to branch from between the parts.

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