JP2000274266A - Engine and knocking suppression method therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress generation of knockings in an engine, increase a compression ratio and improve engine efficiency. SOLUTION: This engine has main cylinders 1 and a control cylinder 10, each for taking in fuel and oxygen-containing gas for combustion and allowing combustion of the mixture 20 inside it to maintain rotation of a crankshaft 6 in common with the cylinders 1, 10, and a control exhaust gas supply means A for supplying exhaust gas exhausted from the control cylinder 10 into the main cylinders 1.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an engine which inhales fuel and oxygen-containing gas for combustion, burns an air-fuel mixture inside, and maintains the rotation of a crankshaft. The present invention relates to a technique for maintaining a preferable operation state.

[0002]

2. Description of the Related Art Engines, which are internal combustion engines, are roughly classified into a spark ignition engine (Otto cycle engine) and a diesel engine which injects liquid fuel into compressed air. In the case of a conventional diesel engine, the compression power of the injected fuel is large and the mechanism is complicated, so the overwhelming majority is a spark ignition engine (hereinafter referred to as SI engine). SI
The engine feeds a mixture of air (an example of an oxygen-containing gas for combustion) and fuel into a cylinder, compresses the mixture in the cylinder, and then forcibly ignites with a spark plug. By the way, it is known that the efficiency of the engine increases as the compression ratio increases. However, in the case of the SI engine, when the compression ratio is increased, knocking occurs.
Can be suppressed to the extent. Knocking is a phenomenon in which an unburned portion spontaneously burns before a spark-ignited flame spreads over the entire region of the cylinder to generate a shock wave.

[0003]

SUMMARY OF THE INVENTION In view of the foregoing, an object of the present invention is to provide a technique for suppressing the occurrence of knocking of an engine, increasing the compression ratio, and improving the efficiency of the engine. I do.

[0004]

In order to achieve the above object, an engine according to the present invention inhales a fuel and an oxygen-containing gas for combustion, and performs internal combustion. A main cylinder and a control cylinder that burn the air-fuel mixture to maintain the rotation of the crankshaft and share the crankshaft, and supply exhaust gas discharged from the control cylinder into the main cylinder. A control exhaust gas supply means is provided. In the engine, in order to improve the combustion efficiency, it is important to suppress knocking and increase the compression ratio. In order to suppress this knocking, in the present invention, a control cylinder is provided separately from the main cylinder, and the control exhaust gas supply means supplies exhaust gas discharged from the control cylinder to the main cylinder. I have. Mixing the exhaust gas after combustion into the main cylinder reduces the ignitability of the air-fuel mixture that is taken into the main cylinder due to the decrease in oxygen concentration, thereby suppressing knocking due to premature ignition in the main cylinder. it can.
This means that even if the main cylinder is set to a high compression ratio, knocking is unlikely to occur, so that the compression ratio of the main cylinder can be increased to improve efficiency,
This also increases the efficiency of the engine.

Further, in order to further suppress knocking and further improve the efficiency of the engine, the following configuration can be adopted. That is, as described in claim 2, operating condition setting means for setting operating conditions of the control cylinder to operating conditions at which exhaust gas containing incomplete combustion components is discharged from the control cylinder is provided. Is preferred. Knocking is a phenomenon in which an unburned portion of the air-fuel mixture is adiabatically compressed and self-ignites during the progress of the flame from the spark plug, and the air-fuel mixture is prematurely ignited. In the reaction leading to self-ignition by adiabatic compression, first, it is understood that hydrocarbons as fuel are thermally decomposed by adiabatic compression to form formaldehyde, and the formaldehyde is consumed by reaction with OH radicals to reach self-ignition. ing. From this, when formaldehyde is supplied to the air-fuel mixture that is taken into the main cylinder, the reaction time until auto-ignition can be lengthened, and as a result, auto-ignition of the unburned portion due to adiabatic compression is prevented, Knocking can be suppressed.

Therefore, in the engine of the present invention, the operating condition of the control cylinder is set by the operating condition setting means, and the control cylinder is operated under the condition that the exhaust gas containing the incompletely combusted component is discharged. The air-fuel mixture supplied to the service cylinder is exhausted as exhaust gas in the course of complete combustion, that is, in a state containing formaldehyde. By mixing the exhaust gas containing a large amount of formaldehyde into the main cylinder by the control exhaust gas supply means, the air-fuel mixture in the main cylinder becomes a state containing a large amount of the formaldehyde, and the adiabatic compression does not completely consume the formaldehyde, and the unburned portion is not consumed. Since self-ignition by adiabatic compression does not occur, knocking can be suppressed as a result. With this configuration, the compression ratio of the main cylinder can be set large, and the efficiency of the engine can be improved. Further, in order to make the exhaust gas discharged from the control cylinder contain a large amount of untwisted components, the compression ratio of the control cylinder is set to be small, or the fuel concentration of the air-fuel mixture supplied to the control cylinder is reduced. It becomes possible by operating the control cylinder under conditions such as leaning.

Further, as described in claim 3,
Preferably, the incomplete combustion component is formaldehyde in an amount of 5 to 30,000 ppm based on the air-fuel mixture taken into the main cylinder. 5 ppm to the exhaust gas discharged from the control cylinder and to the air-fuel mixture taken into the main cylinder
By containing the above formaldehyde, formaldehyde is not completely consumed in the adiabatic compression in the main cylinder, and the unburned part does not reach self-ignition due to the adiabatic compression, so that knocking can be suppressed. By controlling the formaldehyde content to 30,000 ppm or less, the control cylinder can be realized with a simple configuration.

Furthermore, in such an engine, it is preferable that the control cylinder is a cylinder that performs combustion by compressing and igniting the air-fuel mixture. In other words, the control cylinder operates as a so-called compression self-ignition engine without a spark plug, that is, without a spark plug. For example, by setting the compression ratio to a small value, formaldehyde, which is an intermediate product of adiabatic compression, is largely contained in the exhaust gas. The exhaust gas containing formaldehyde can be mixed into the main cylinder by control exhaust gas supply means, knocking of the main cylinder can be suppressed, and the engine efficiency can be reduced with a simple configuration. Can be improved.

According to a conventional method for suppressing knocking in an engine, a fuel and an oxygen-containing gas for combustion are taken in and a mixture is burned inside to maintain the rotation of the crankshaft. A main cylinder and a control cylinder are provided so as to share the crankshaft, and the exhaust gas discharged from the control cylinder is supplied into the main cylinder, and the exhaust gas discharged from the control cylinder is It is supplied to the main cylinder to suppress knocking of the main cylinder. In this way, by supplying exhaust gas from at least one control cylinder provided in the engine to the other main cylinders, the air-fuel mixture sucked into the main cylinders is in a condition in which self-ignition due to adiabatic compression is unlikely to occur, resulting in an excess. Knocking due to premature firing can be suppressed, and the efficiency of the engine can be improved.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The basic structure of an engine 100 according to the present invention will be described with reference to FIG. The engine 100 is a multi-cylinder engine in which four main cylinders 1 are arranged with a common crankshaft 6. The main cylinder 1 is a spark ignition engine that supplies intake air 20 of a mixture of fuel and air into a cylinder 3 through an intake passage 9, and ignites intake air 20 compressed by a piston 4 with a spark plug 7. Then, the rotation of the crankshaft 6 is maintained via the connecting rod 5, and the exhaust 21 after combustion in the main cylinder 1 is discharged to the outside via the exhaust passage 8. Such a configuration is similar to that of a normal multi-cylinder engine. In such an engine, it is effective to increase the compression ratio as much as possible in order to improve the efficiency of the engine. However, when the compression ratio is increased, the intake air after the adiabatic compression becomes high temperature, and before the flame spark ignited by the spark plug 7 spreads to the entire area of the cylinder 3, the unburned portion self-ignites and burns, generating a shock wave. This causes knocking, which causes engine damage and lowers engine efficiency.

In the reaction leading to auto-ignition by adiabatic compression, first, hydrocarbons as fuel are thermally decomposed by adiabatic compression to generate formaldehyde, and the formaldehyde is consumed by reaction with OH radicals to reach auto-ignition. I know that. From this, when about 10000 ppm of formaldehyde is supplied into the intake air 20 supplied to the main cylinder 1, the reaction time until self-ignition can be lengthened, and as a result, self-ignition of the unburned portion by adiabatic compression In this application, about 10,000 ppm of formaldehyde is supplied into the intake air supplied to the main cylinder 1 as will be described later.

That is, the engine 100 includes a control cylinder 10 having a piston 14 connected to the crankshaft 6 by a connecting rod 15, similarly to the main cylinder 1. The control cylinder 10 adopts a configuration of a compression ignition engine, supplies intake air 20 into a cylinder 13 through an intake passage 19, compresses and ignites an air-fuel mixture by a piston 14, and controls the combustion after combustion. Exhaust gas 22 for controlling exhaust gas passage 11
It is configured to be discharged to.

The operating conditions of the control cylinder 10 are as follows:
The control exhaust gas 22 is set so that formaldehyde as an incompletely combustible component is contained. Specifically, the compression ratio of the control cylinder 10 is set to a value that does not result in sufficient compression auto-ignition combustion, for example, sufficient compression. When performing self-ignition combustion, that is, while the compression ratio of a normal compression self-ignition engine is about 18, the compression ratio of the control cylinder 10 is set to about 15, and is adiabatically compressed by the piston 14. The air-fuel mixture does not burn sufficiently and is discharged to the control exhaust gas passage 11 as control exhaust gas containing incompletely combusted components. Therefore,
By operating the control cylinder 10 under such operating conditions, the control exhaust gas 22 in the control exhaust gas passage 11
It will contain a lot of formaldehyde.

The control exhaust gas passage 11 is connected to the intake passage 9 on the side of the main cylinder 1, and the control exhaust gas 22 containing a large amount of formaldehyde flows through the intake passage 9 of the main cylinder 1 into the cylinder 3 of the main cylinder 1 Is supplied together with the intake air 20. Since the main cylinder 1 supplied with the mixed gas of the control exhaust gas 22 and the intake air 20 contains more formaldehyde than the case where only the intake air 20 is supplied, the main cylinder 1 consumes formaldehyde in the adiabatic compression process. Before the flame ignited by the spark plug 7 spreads over the entire area of the cylinder 3.
Since the unburned portion does not self-ignite and burn, knocking due to the flame of the self-ignition combustion is suppressed. With this configuration, the occurrence of knocking in the main cylinder 1 is suppressed. For example, even if the compression ratio is set to about 15 in order to improve the combustion efficiency of the main cylinder 1, the ignition plug 7 enables combustion by spark ignition, and a stable operating state can be maintained. The means for supplying the control exhaust gas 22 from the control cylinder 10 into the main cylinder 1 in order to suppress knocking is referred to as control exhaust gas supply means A.

[Other Embodiments] (A) As a fuel that can be used in the engine of the present invention, any hydrocarbon-based fuel such as city gas, gasoline, propane, methanol, and hydrogen can be used. (B) In generating the air-fuel mixture, the fuel may be mixed with a gas containing oxygen for combustion of the fuel. For example, air is generally used as the oxygen-containing gas for combustion. is there. However, as such a gas, it is possible to use, for example, an oxygen-enriched gas having an oxygen component content higher than that of air. (C) In the above embodiment, the description has been given in relation to a so-called four-cycle engine. However, the present invention is applicable to a two-cycle engine. (D) In the above-described embodiment, the structure in which the air-fuel mixture of fuel and air is sucked into the cylinder as intake air has been described. The invention of the present application is applicable to an engine having a fuel injector that injects fuel into a cylinder. (E) In the above embodiment, the control cylinder 10
Is operated under the condition that the control exhaust gas 22 contains an incomplete combustion component, and the control exhaust gas 22 is supplied to the main cylinder 1
The control exhaust gas 22 is supplied to the main cylinder 1 by supplying the control exhaust gas 22 to the main cylinder 1 even if the control cylinder 10 is not operating under the operating condition including the incomplete combustion component. As a result, the oxygen concentration of the air-fuel mixture decreases, and the combustibility of the air-fuel mixture decreases, so that knocking can be suppressed. (F) In the above embodiment, the control cylinder 10
Has been described as a compression self-ignition engine, the control cylinder 10 may be configured as an SI engine, or only the control engine may be configured as a two-cycle engine.

[0016]

Therefore, according to the above method, knocking can be suppressed in the engine, and the operating state of the engine can be improved.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration of an engine of the present application.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Main cylinder 3 Cylinder 4 Piston 5 Connecting rod 6 Crank 7 Spark plug 8 Exhaust passage 9 Intake passage 10 Control cylinder 11 Control exhaust gas passage 20 Intake 21 Exhaust 22 Control exhaust 100 Engine A Control exhaust gas supply means

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) F02D 19/12 F02D 19/12 Z F02M 25/07 570 F02M 25/07 570M 570Z (72) Inventor Koji Moriya 4-1-2 Hirano-cho, Chuo-ku, Osaka-shi, Osaka F-term in Osaka Gas Co., Ltd. (reference) 3G023 AA06 AA18 AB01 AC01 AC07 AF01 AF02 AG03 3G062 CA06 ED01 ED10 GA06 3G092 AA01 AA02 AA03 AA06 AA13 AA17 AB05 AB07 AB08 DC09 FA HD07X

Claims (5)

[Claims] 1. A fuel and an oxygen-containing gas for combustion are taken in, and
A main cylinder and a control cylinder that burn the air-fuel mixture to maintain the rotation of the crankshaft are provided with the crankshaft in common, and exhaust gas discharged from the control cylinder is supplied into the main cylinder. An engine provided with control exhaust gas supply means. 2. The engine according to claim 1, further comprising operating condition setting means for setting operating conditions of the control cylinder to operating conditions under which exhaust gas containing incomplete combustion components is discharged from the control cylinder. 3. The engine according to claim 2, wherein the incomplete combustion component is formaldehyde in an amount of 5 to 30,000 ppm based on the air-fuel mixture taken into the main cylinder. 4. The cylinder according to claim 1, wherein the control cylinder is a cylinder that performs combustion by compressing and igniting the air-fuel mixture.
The engine described in the section. 5. Intake of fuel and oxygen-containing gas for combustion,
A main cylinder and a control cylinder for burning the air-fuel mixture and maintaining the rotation of the crankshaft are provided sharing the crankshaft, and the exhaust gas discharged from the control cylinder is supplied into the main cylinder. An engine knocking suppression method comprising: supplying exhaust gas discharged from the control cylinder to the main cylinder to suppress knocking of the main cylinder.