JPS595768B2 - Forced scavenging internal combustion engine - Google Patents

Description

Detailed Description of the Invention The present invention divides the intake system of an internal combustion engine into two systems, introduces pressurized air from the second intake system from the exhaust stroke to the intake stroke,
By scavenging the residual gas in the cylinder and giving a swirl to the intake air, the air-fuel ratio of the air-fuel mixture including this pressurized air becomes the output air-fuel ratio, which improves the output per engine weight, especially low-speed output, and improves fuel economy. The present invention relates to a forced scavenging internal combustion engine designed to improve performance and exhaust performance.

Conventionally, the intake system of an internal combustion engine is divided into two systems, with a main intake valve and a second auxiliary intake valve.The main intake valve takes in normal air-fuel mixture, and the auxiliary intake valve takes in atmospheric air or air-fuel mixture. is inhaled during the engine intake stroke, and the valve arrangement is considered so that there is a partially rich mixture and a lean mixture in the combustion chamber, and the mixture is particularly rich near the ignition plug, and on average as a whole. A number of applications have already been submitted to efficiently burn lean air-fuel mixtures and improve engine exhaust measures.

In addition, with a similar structure, secondary air is introduced into the combustion chamber through an auxiliary valve during the engine's expansion stroke, and harmful he, c is generated before the exhaust gas is discharged to the exhaust port.

There are also engines that burn .

Of these, in the former case, the auxiliary mixture is taken in at partial load, especially under atmospheric pressure, so the effect of lean mixture operation is recognized in the low load and low rotation range, but a large amount of residual gas remains in the cylinder. The remaining idle link and combustion instability in the deceleration region have not been sufficiently resolved.

Further, as a result of thorough experiments, it was found that the latter has almost the same effect as introducing secondary air into the exhaust port.

In both cases, improvement in output fuel efficiency under high loads is not considered at all.

There is also a system that simply supplies pressurized air to the combustion chamber during the exhaust stroke for the sole purpose of scavenging residual gas, but although this allows scavenging, it cannot burn a lean air-fuel mixture.

Therefore, in the present invention, the intake system is divided into two systems like these, but pressurized air is injected from one auxiliary intake system so as to create a swirl from the exhaust stroke to the intake stroke, and the residual gas in the cylinder is Forced scavenging internal combustion improves fuel efficiency and exhaust performance by making combustion more efficient during partial loads, idling, and deceleration, and improves output by adding pressurized air at full throttle output. It provides institutions.

The present invention will be explained below with reference to Examples.

In Figures 1 and 2, 1 is a combustion chamber, 2 is a main intake boat to which normal air-fuel mixture is supplied, 3 is a main intake valve that opens and closes this main intake boat 2, 4 is a spark plug, and 5 is an exhaust gas. In the ports, 6 is an exhaust valve that opens and closes the exhaust port 5, 7 is an auxiliary intake boat provided in a separate system from the intake boat 2, and 8 is an auxiliary intake valve that opens and closes this auxiliary intake boat 7, which will be described later. Air from the supply device is injected and supplied into the combustion chamber 1 from the engine exhaust stroke to the intake stroke, and residual exhaust residue in the combustion chamber 1 is discharged from the exhaust port 5.

In FIG. 1, 9 is an exhaust pipe, 10 is an auxiliary intake pipe, 11 is a piston, and 12 is a cylinder bed.

As a pressurized air supply device, an air pump 13 driven in synchronization with the crankshaft of the engine is provided, and air sucked in via an air cleaner 14 is supplied to the check valve 1.
5 to the surge tank 16, and then from the air flow control device 17 to the auxiliary intake pipe 10, the air is pressurized to at least atmospheric pressure or higher (according to experiments, 1.2
When pressurized to about 2.0 ky/i, it was effective from 1 to 5 considering engine output loss).

The air flow control device 17 measures engine speed, suction negative pressure, venturi negative pressure, exhaust pressure, throttle opening, and an intake air amount measuring device (for example, the output of an air flow meter in an electronic fuel injection device). The amount of air introduced from the auxiliary intake valve 8 is controlled based on signals such as (injection output) (or any combination of these, for example, a combined signal of engine speed and suction negative pressure).

The amount of air is preferably sufficient to completely expel the residual gas in the cylinder, and therefore the minimum required amount is equal to the residual gas.

The ratio of residual gas in the cylinder to the amount of intake air changes depending on the engine load, and is generally 15-30% at idle due to valve overlap, and 30% or more during deceleration, due to residual gas remaining in the intake and exhaust system. At high speeds and high loads, the amount of air is as low as 3 to 8 due to the inertia of the intake and exhaust valves, so the amount of air should be controlled within an appropriate range by considering the valve timing of the intake and exhaust valves, which will be described later. Decide to do so.

Therefore, specifically, the pressurized air passage area of the air flow rate control device 17 is controlled based on the signal indirectly representing the amount of intake air.

By doing so, even if the amount of intake air is the same, a large amount of pressurized air is introduced into the low load area where there is a lot of residual gas, and it becomes possible to introduce enough pressurized air to accurately replace the residual gas.

Next, as shown in FIG. They may be placed on the same side (Fig. 2 A and C) or on different sides (Fig. 2 Opening).

Then, as the pressurized air from the auxiliary intake valve 8 generates a swirl within the combustion chamber 1, a guide means 18 is formed on the auxiliary intake valve 8 or the auxiliary intake boat 7 [Fig. ].

In Fig. 2A, a guide means 18 (shroud 18a) is provided on the auxiliary intake valve 7 to generate a swirl as shown by the arrow, efficiently expelling residual gas from almost the entire cylinder, and at the same time the main intake valve 7. A vortex is also generated in the air-fuel mixture flowing from the intake valve 3, causing turbulence and increasing the combustion speed to improve combustion efficiency.

In FIG. 2C, the auxiliary intake boat 7 is curved in plan view, and the angle of inflow into the combustion chamber 1 in the vertical plane is made as small as possible to form a guide means 18b for generating a vortex flow.

Figure 2 The ports are intake and exhaust valves 3, 5 and auxiliary intake valve 8 as shown in the figure.
Because of this arrangement, a swirl is generated naturally and the above-mentioned purpose can be achieved without the need for any special swirl means.

The suction efficiency from the auxiliary intake valve 8 has little direct effect on the engine output, so even if the suction efficiency decreases due to the installation of these vortex generation guide means 18, there is almost no decrease in the output, and therefore, Combustion efficiency can be significantly improved by making every effort to increase the intake efficiency of the air-fuel mixture taken in from the main intake valve 3 side, and by creating a swirl in the air-fuel mixture flow as described above using auxiliary pressurized air. .

As shown in FIGS. 3 and 4, the auxiliary intake valve 8 begins to open in the latter half of the exhaust stroke, expelling residual gas from the combustion chamber 1 until the exhaust valve 6 closes, and in the first half of the intake stroke. Close the valve.

As mentioned above, the residual gas amount, which is approximately a function of the intake air amount and suction negative pressure, can be precisely replaced with pressurized air.1 This eliminates changes in the air-fuel ratio and residual gas amount due to changes in the pressurized air amount. In particular, it becomes possible to operate in a lean region where these changes have a large effect on engine performance.

In addition, in order to improve the output of the engine, this auxiliary intake valve 8
It is preferable to delay the valve closing timing and increase the amount of air in the combustion chamber 1 as described later.

First, the opening timing of the main intake valve 3 is approximately the same as in a normal engine or slightly delayed.

Especially for engines with poor scavenging, good results can be obtained by delaying the closing timing of the exhaust valve 6.

Preferably, as shown in FIG. 8, the opening/closing timing of the auxiliary intake valve 8 (or the relative valve timing of the main intake valve 3 and exhaust valve 6) is made variable, so that the exhaust valve is lower when fully open than when under partial load. It is preferable to set the overlap time with 6 and the valve opening period to be long to increase output at full open output and improve exhaust performance and fuel efficiency at partial load.

Note that this change in valve timing can be realized by known means such as making the camshaft slidable and tilting the cam surface in the direction of the sliding force.

Next, it will be explained in more detail, including its effect.

The auxiliary intake valve 8 opens from the exhaust stroke to the intake stroke of the engine, and air pressurized to at least atmospheric pressure is supplied into the combustion chamber 1 from the auxiliary intake pipe 10.

At this moment, the combustion gas in the cylinder is expelled by this pressurized air, and when the exhaust valve 6 closes, almost no residual gas remains and is replaced with fresh air.

As the residual gas that does not participate in combustion decreases, the combustion efficiency improves accordingly, producing the effects described below.

First, when the engine is at full throttle output, the residual gas in the cylinder is generally 10 or more in the low-speed rotation range, causing a reduction in low-speed torque, while it is not so large in the high-speed rotation range, at 3 to 8 ratio.

However, before the air-fuel mixture is fully taken in from the main intake boat 2, most of the residual gas is expelled, and the air-fuel mixture in the combustion chamber 1, including the fresh air that remains as residual gas, becomes the output air. So that the ratio is (A/F Ki 12-14),
If the main mixture is set in advance to be too rich at full throttle output, 1
Since the energy generated by the explosion increases accordingly, the torque also increases compared to the conventional one, as shown in FIG.

According to experiments, the low speed torque increases by 5 to 15 times, and the maximum torque increases by about 5 factors, which means that the cylinder stroke volume increases by 5 to 1 factor.
This corresponds to an increase of 5% by 1, making it a very practical and easy-to-use engine with a large output compared to the engine weight.

Next, during partial load, it is preferable to use exhaust recirculation, especially in the sense of reducing NOx, but since there is almost no residual gas in the cylinder, the actual exhaust recirculation rate in the combustion chamber 1 is reduced. The control is now largely due to flow control in the exhaust recirculation passage, thus reducing fluctuations due to residual gas and providing effective NOx reduction without compromising engine stability.

Since swirl occurs due to pressurized air flow during partial load as will be described later, the aim is to improve fuel efficiency and reduce nc and co through lean mixture combustion.

Therefore, the air-fuel mixture taken in from the main intake boat 2 is not as rich as in the case of full-open power operation described above, and the air-fuel ratio in the combustion chamber 1, including the air replaced with residual gas, is higher than the stoichiometric air-fuel ratio. Set it so that you get a lean mixture.

Combustion of the lean air-fuel mixture is performed stably by giving swirl and turbulence to the pressurized air flowing in from the auxiliary intake valve 8, as shown in FIG.

Furthermore, since the air-fuel ratio is made thinner than the stoichiometric air-fuel ratio, the oxidation effect of Re and Co occurs without introducing secondary air into the exhaust system.

Since there is no residual gas, combustion is faster, which improves fuel efficiency.

Regarding the effect of reducing NOx, since the relatively high temperature residual gas is replaced with outside air at almost room temperature, the increase in the mixture temperature becomes smaller, and if the combustion speed remains the same, the maximum combustion temperature decreases, so the generation of NOx is reduced. will be suppressed by that amount.

In addition, changing the air-fuel ratio of the main air-fuel mixture between full throttle output and partial load can be done by controlling a power pulp device, etc., similar to a normal internal combustion engine, and one echo is replaced by residual gas. It can be said that there are some improvements in air-fuel ratio control (conventionally, the air-fuel ratio of only the intake air-fuel mixture was controlled) in response to fresh air.

When the suction negative pressure is large and the residual gas in the cylinder increases to about 15-30%, such as when the engine is idling or decelerating, the proportion of combustible air-fuel mixture in the combustion chamber 1 decreases, and the engine loses stability. This makes it easy to misfire.

For this reason, it is difficult to make the air-fuel mixture lean in conventional engines, and the practical air-fuel ratio limit is usually around the stoichiometric air-fuel ratio.

However, according to the present invention, this rapidly increasing residual gas can be completely replaced with fresh air, so for the same reason as in the case of partial load mentioned above, combustion is stabilized and fuel consumption is reduced by several times compared to the conventional method as shown in Figure 7. Improve step by step.

In addition, in order to improve combustion stability, especially during idling and deceleration, including during partial load, the main intake valve 3 adjusts the intake timing of the air-fuel mixture taken in from the main intake boat 2 to or from top dead center. By setting the cylinder to start opening later than the cylinder, it is possible to wait for the residual gas to be expelled and reduce mixing with residual gas in the cylinder as much as possible.
By delaying the end of opening of the auxiliary intake valve 8 compared to when the output is fully open, pressurized air is blown until near the end of the intake stroke, which tends to cause swirl and turbulence in the air mixture flow, and accelerates combustion.

The variable valve timing control is based on various signals such as suction negative pressure, engine rotational speed, exhaust pressure, throttle opening, exhaust pressure throttle opening, or intake air amount measuring device, or an appropriate combination of these signals. This is done by, for example, sliding the aforementioned camshaft using a hydraulic actuator.

By the way, in order to make the scavenging of residual gas by supplying pressurized air most effective, which is the gist of the present invention, from the exhaust stroke to the intake stroke, by the time the piston reaches the top dead center, It is preferable to set the cam profile or valve timing of the auxiliary intake valve 8 so as to introduce at least about 50 parts or more of the total amount of auxiliary air.

Since the exhaust valve 6 closes together with the opening operation of the auxiliary intake valve 8, scavenging of residual gas becomes worse as the exhaust valve 6 approaches the top dead center where it is almost closed.

Further, when the main intake valve 3 is opened, the residual gas flows back into the intake system due to the negative pressure in the intake manifold, so that scavenging of the residual gas is similarly impaired.

Therefore, in order to improve the scavenging efficiency of residual gas, it is preferable to increase the amount of air introduced when the auxiliary intake valve 8 begins to open, and to expel as much residual gas as possible before the main intake valve 3 opens.

Furthermore, as described above, when the main intake valve 3 is opened, the pressurized air creates a swirl turbulence in the air mixture flowing in from the main intake valve 3.

When the opening degree of the auxiliary intake valve 8 is throttled to increase the flow velocity, the combustion velocity can be effectively increased in conjunction with the guide means 18 for generating swirl.

Therefore, as shown in FIG. 5A, the opening characteristics of the auxiliary intake valve 8 are most preferably such that the flow rate is large at the initial stage of opening.
The lift diagram is set so that approximately 50% or more of the total flow rate is introduced before the top dead center, and a high-speed flow is obtained by the throttle in the latter half of the valve opening.

However, if more than 50% of the total air can be introduced before reaching top dead center, the auxiliary air may be introduced with a substantially uniform small valve lift amount during the full valve opening period, as shown in Figure 5. .

As a means for supplying pressurized air to this auxiliary intake system, a pressurized air supply device including an air pump 13v is shown.1 This is equipped with an exhaust pressure turbo operated by exhaust pressure in the exhaust system, and is driven by this exhaust pressure turbo. It is also possible to supply compressed air from an air compressor to the auxiliary intake pipe 10.

Note that as the air pump 13, it is possible to use various mechanical air pumps in addition to the commonly used vane type air pump.

First, the amount of introduced air is controlled by a surge tank 16 to maintain a constant pressure, and an air flow rate control device 17 that responds to a signal based on the operating state of the engine allows the air to be replaced at least immediately with residual gas that varies depending on the operating state. However, the flow rate may be controlled by increasing the introduction pressure according to the engine rotation speed.

An auxiliary intake valve 8 controls the amount of pressurized air introduced.
The effective diameter of the main intake valve 3 is set to be smaller than that of the main intake valve 3, but even within this range, it is relatively large when emphasis is placed on low-speed output, and conversely, it is set small when emphasis is placed on engine stability under partial load. good.

The above embodiment was explained assuming that the engine is equipped with a carburetor.
It is of course possible to apply the present invention to an engine equipped with a fuel injection device, and the present invention can also be applied to an engine which uses liquid fuel such as gasoline as well as liquefied gas such as propane or butane as fuel.

As explained above, the present invention provides air flow from the auxiliary intake system provided separately from the main intake system, from the exhaust stroke to the intake stroke of the engine.
Pressurized air is introduced into the combustion chamber to expel the residual gas to the exhaust port.1 This increases the ratio of the combustible mixture to the cylinder volume by the amount that the residual gas is replaced with fresh air. While increasing the power at full throttle output, it also eliminates combustion instability caused by a sudden increase in residual gas during partial load, idle link, and deceleration.
HC improves fuel efficiency and ensures stable combustion even when the air-fuel mixture is diluted at the same time.

It is also possible to reduce harmful exhaust gas components such as CO.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal cross-sectional view of the present invention, FIG. 2A and C are bottom views of the combustion chamber, FIG. 3 is an explanatory diagram showing pulp timing, and FIG.
Fig. 5 A 20 is an explanatory diagram showing the opening characteristics of the auxiliary intake valve, Fig. 6 is an explanatory diagram showing the fully open output characteristics of the present invention in comparison with the conventional one, and Fig. 7 is an explanatory diagram showing the fuel consumption at idling of the present invention. FIG. 8 is an explanatory diagram showing an example in which the valve timing of the auxiliary intake valve is variable. 1... Combustion chamber, 2... Main intake boat,
3... Main intake valve, 4... Spark plug, 5...
...Exhaust port, 6...Exhaust valve, 7...
...Auxiliary intake boat, 8...Auxiliary intake valve,
10... Auxiliary intake pipe, 13... Air pump, 16... Surge tank, 17...
...Air flow rate control device, 18...Guiding means for generating eddies.

Claims (1)

[Scope of Claims] 1. In a reciprocating internal combustion engine, in addition to the main intake system that supplies the air-fuel mixture to the combustion chamber, an auxiliary intake system is provided that has a guide means for creating a vortex in the air-fuel mixture within the combustion chamber, A pressurized air supply device is connected to this auxiliary intake system, and the auxiliary intake valve provided in the auxiliary intake system is opened near the top dead center of the engine from the exhaust stroke to the intake stroke, and pressurized air is introduced. The forced scavenging internal combustion system is characterized in that the auxiliary intake system is provided with an air flow rate control device that inputs a signal that changes according to the engine intake air amount and increases the pressurized air introduction amount according to the increase in the intake air amount. institution. 2 The amount of pressurized air introduced from the auxiliary intake system is set to be at least 50% or more of the total amount introduced by the time the top dead center is reached near the end of the exhaust stroke.
Forced scavenging internal combustion engine as described in . 3. Claim 1 in which the relative valve timing between the auxiliary intake valve and the main intake valve and/or exhaust valve is configured to be variable.
The forced scavenging internal combustion engine according to item 1 or 2. 4. Forced scavenging according to claim 3, in which the overlap between the auxiliary intake valve and the exhaust valve is increased when the engine is fully open, and the overlap between the auxiliary intake valve and the main intake valve is increased when the engine is at partial load. Internal combustion engine. 5. The auxiliary intake valve or the auxiliary intake port is provided with a guide means for creating a vortex in the mixture flow in the combustion chamber that is directed toward the exhaust valve from a direction far from the exhaust valve. Forced scavenging internal combustion engine according to any one of Item 4. 6. The forced scavenging internal combustion engine according to any one of claims 1 to 5, wherein the air-fuel mixture in the combustion chamber is set to be richer than the stoichiometric air-fuel ratio when the engine is fully open. 7. The air-fuel mixture in the combustion chamber when the engine is partially loaded is set to be thinner than the stoichiometric air-fuel ratio.
The forced scavenging internal combustion engine according to any one of items 6 to 6. 8. A forced scavenging internal combustion engine according to any one of claims 1 to 7, comprising an air pump as a pressurized air supply device. 9. The forced scavenging internal combustion engine according to any one of claims 1 to 7, comprising an exhaust turbo-driven air compressor as the pressurized air supply device.