JPS63208609A - Fuel injection type engine - Google Patents

Abstract

PURPOSE:To improve evaporation and combustion of fuel by leading burnt gas into a mixing chamber provided in a cylinder heat in an exhaust stroke, producing mixed gas by injecting fuel, and supplying the mixed gas from the chamber to a combustion chamber in a compression stroke. CONSTITUTION:While an engine is operating, a suction and exhaust valve 5 is opened and closed by rotation of a cam shaft 8, and an ignition plug 7 is ignited. In this case, fuel is injected from a nozzle 12 to a mixing chamber 11 from a suction stroke through a compression stroke. In a compression stroke, a piston 13 in a chamber 11 is lowered, so pressure in the chamber 11 is supplied to a communicating passage 24 so as to increase 1st valve body 27 of an opening/closing valve 25 against a spring 30. Thus fuel in the chamber 11 is pushed out into a combustion chamber 4 with gas. In an exhaust stroke, 2nd valve body 28 is moved up against a spring 33 to release the communicating passage 24. Thus part of burnt gas in the combustion chamber 4 is led into the chamber 11 through the communicating passage 24.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a fuel-injected engine, and more particularly to a fuel-injected engine in which fuel is injected into a mixing chamber communicating with a combustion chamber.

(Prior art) Engines that use fuel injection nozzles to supply fuel include those in which the fuel injection nozzles are installed in the intake manifold and those in which the fuel injection nozzles are installed directly in the combustion chamber. There is a problem in that the fuel injected from the nozzle tends to adhere to the inner wall surface of the intake boat, the intake valve, etc., and the latter also has the problem that it is not possible to ensure sufficient mixing time between the fuel injected from the nozzle and the air in the combustion chamber. .

Therefore, in either type, the formation of an air-fuel mixture or the vaporization of fuel are not performed well.

To deal with this, conventionally known methods have been known in which the intake boat is formed in a helical shape to promote the vaporization of fuel or the formation of an air-fuel mixture by forming a swirl of intake air in the combustion chamber during the intake stroke. ing. Also, JP-A-55-1
According to Japanese Patent No. 19911, a diesel engine is constructed so that a strong swirl is formed in a combustion chamber at the end of a compression stroke when fuel is injected from a fuel injection nozzle. This is done by providing an air storage chamber in the cylinder block that stores part of the intake air under high pressure, and communicating the storage chamber with the combustion chamber via an on-off valve, which is opened during the compression stroke. As a result, high-pressure air is injected into the combustion chamber from the air storage chamber to form a swirl within the combustion chamber. According to this, a stronger swirl can be obtained at the end of the compression stroke when fuel is injected, compared to the conventional system in which a swirl is formed during the intake stroke.

(Problems to be Solved by the Invention) However, since the conventional methods described above simply utilize swirl, it cannot be said that the vaporization of the fuel or the formation of an air-fuel mixture is necessarily performed well. In the case of diesel engines that use light oil with poor vaporization as fuel, the fuel is not vaporized sufficiently, so the required thermal efficiency and output performance cannot be obtained, and incomplete combustion causes an increase in the HC content in the exhaust gas. was inviting.

The present invention addresses the above-mentioned actual situation in fuel-injected engines, and effectively utilizes the thermal energy of burned gas in the combustion chamber in engines equipped with spark plugs, such as gasoline engines or spark-assist diesel engines. By utilizing this, the purpose is to promote the vaporization of fuel and form a good air-fuel mixture, thereby improving thermal efficiency or output performance, and reducing the HC content in exhaust gas.

(Means for Solving the Problems) In order to achieve the above object, a fuel injection engine according to the present invention is characterized by being configured as follows.

That is, the cylinder head is provided with a mixing chamber that communicates with the combustion chamber via a communication passage, a fuel injection nozzle is installed in the chamber, a piston is provided in the chamber to increase or decrease its volume, and the communication passage is connected to the mixing chamber. Equipped with an on-off valve that opens and closes. Then, the on-off valve is opened during the exhaust stroke and the compression stroke, and the fuel injection nozzle is closed during the valve opening period of the on-off valve from the open period during the exhaust stroke to the open period during the compression stroke. The fuel injection device is configured to inject fuel into a mixing chamber, and to move a piston in the chamber in a direction in which the volume of the chamber decreases during an opening period during a compression stroke of the on-off valve.

(Function) According to the above configuration, the on-off valve opens the communication path between the combustion chamber and the mixing chamber during the exhaust stroke, so that part of the burnt gas in the combustion chamber flows into the mixing chamber as the piston moves upward. As a result, the inside of the chamber becomes a high energy state due to the thermal energy of the burnt gas and the kinetic energy of the flow caused by the pushing. Then, after the exhaust stroke shifts to the intake stroke and the on-off valve is opened, fuel is injected from the fuel injection nozzle into the mixing chamber, and this fuel is mixed with the burned gas in the chamber. Thermal energy and kinetic energy result in rapid and reliable vaporization and mixing, forming a good mixture within the chamber.

After that, when the intake stroke shifts to the compression stroke, the on-off valve is opened again and at the same time, the piston in the mixing chamber moves in the direction of decreasing the volume of the chamber.
The air-fuel mixture formed in the chamber as described above is forced into the combustion chamber. Then, this air-fuel mixture is further mixed with fresh air in the combustion chamber, and then ignited by the spark plug at the end of the compression stroke and combusted. In this case, the fuel in the air-fuel mixture pushed out from the mixing chamber into the combustion chamber is completely combusted within the combustion chamber because the fuel has already been sufficiently vaporized.

(Example) Examples of the present invention will be described below.

As shown in FIG. 1, the engine according to this embodiment includes a cylinder block 1, a piston 2 fitted into a cylinder surface 1a formed in the block 1, and a piston 2 that is not attached to the upper surface of the cylinder block 1. It has a combustion chamber 4 defined by a cylinder head 3, and an intake and exhaust boat 6 communicating with the combustion chamber 4 through intake and exhaust valves 5, 5 in the cylinder head 3.
．． 6 (only one shown) is formed. Further, an ignition plug 7 is mounted on the cylinder head 3 so that the ignition part 7a at the tip faces the combustion chamber 4, and a camshaft 8 is disposed in the upper part of the cylinder head 3. Suction and exhaust cams 8a, 8a provided on the shaft 8 are actuated by the rotation of the shaft 8 through the tappets 9, 9 and the valve spring 10.
10, the plates and the exhaust valves 5, 5 are opened at predetermined timings, respectively.

Furthermore, a mixing chamber 11 is provided in the cylinder head 3.
A fuel injection nozzle 12 is installed from the side so as to face the inside of the chamber 11, and a piston 13 that moves up and down to increase and decrease the volume of the chamber 11 is fitted into the chamber 11. There is. This piston 13 is moved up and down by a driving cam 8b provided on the camshaft 8 via a rocker arm 14 and a bushing rod 15. In other words, when the rocker arm 14 is in contact with the non-lifting part of the cam 8b, the piston 13
The bushing rod 15 is held at the upper end position by a spring 18 between a spring retainer 16 fixed to the upper end and a cover member 17 fixed to the cylinder head 3. The chamber 11 is moved downwardly to reduce the volume of the chamber 11.

In this embodiment, one stopper for regulating the upper end position of the piston 13 is moved up and down by a motor 20 via a pinion 21 and a rack 22. In other words, the maximum volume of the chamber 11 can be adjusted. still,
In order to make the upper end position of the piston 13 variable with respect to a fixed position of the bushing rod 15, a spring 23 is interposed at the connection portion between the bushing rod 15 and the piston 13.

On the other hand, the mixing chamber 1 in the cylinder head 3
A communication passage 24 is provided between the combustion chamber 1 and the combustion chamber 4, and an on-off valve 25 is provided to open and close the communication passage 24. The on-off valve 25 includes a hollow first valve body 27 that is vertically slidably fitted into a valve hole 26 formed in the cylinder head 3;
A second valve body 28 is also fitted into the hollow portion of the valve body 28 so as to be vertically slidable. The first valve body 27 is biased downward by a spring 30 installed between its upper end surface and a plug 29 fixed to the upper end of the valve hole 26, and normally the lower end is attached to the valve seat member 31. Although the communication path 24 is closed by being in contact with the pressure receiving surface 27a, the chamber 1
When pressure is applied from 1@ through the communication path 24, it moves upward against the spring 30, and the lower end surface separates from the valve seat member 31, opening the communication path 24.

Further, the second valve body 28 is configured to communicate with and block communication between the first axial passage hole 27b and the second radial passage hole 27c following the hollow portion of the first valve body 27. A spring 33 installed between the upper end surface and the plug 32 fixed to the upper end of the hollow portion of the first valve body 27 causes the lower end surface to come into contact with the stepped portion formed in the hollow portion of the first valve body 27. In this state, the first valve body 27 and
The space between the second through holes 27b and 27c is blocked. When pressure is applied to the lower end surface from the combustion chamber 4 through the first through hole 27b, the first through hole is moved upward against the spring 33. The second communication holes 27b and 27c are made to communicate with each other, and at this time, the first valve body 27
Even if it is closed, the above 1. Second through holes 27b, 27c
The communication path 24 is opened through the.

Next, the operation of the above embodiment will be explained.

When the engine is running, the intake and exhaust valves 5 are
, 5 are opened and closed at predetermined timing, and the spark plug 7
is ignited at a predetermined timing to execute the intake, compression, expansion, and exhaust strokes. In this case, fuel or air-fuel mixture is supplied to the combustion chamber 4 as follows.

That is, as shown in FIG. 2, fuel is injected from the fuel injection nozzle 12 into the mixing chamber 11 from the intake stroke to the first half of the compression stroke, and during the compression stroke, fuel is injected into the mixing chamber 11 as shown by the symbol (A) in FIG. As the piston 13 in the chamber 11 moves downward and the volume of the chamber 11 is reduced, the pressure of the gas in the chamber 11 increases, and as shown by the symbol (b), the pressure flows through the communication path 24. The first valve body 27 of the opening/closing valve 25 is moved upward against the spring 30 through the opening/closing valve 25, thereby causing the fuel injected into the chamber 11 to flow into the combustion chamber 4 together with the gas in the chamber 11.
It is pushed out.

However, in the on-off valve 25, when the pressure of the burnt gas in the combustion chamber 4 increases due to the upward movement of the piston 2 during the exhaust stroke, the second valve body 28 that receives this pressure is moved by the spring 3.
3 in the first valve body 27, as shown by reference numeral (C) in FIG. The communication path 24 is opened through the second communication holes 27b and 27c. Also, at this time, the sign (
As shown in (d), the piston 13 in the mixing chamber 11 moves upward and the volume of the chamber 11 increases, so
A part of the burnt gas in the combustion chamber 4 is introduced into the chamber 11 through the communication passage 24 without being discharged to the outside from the exhaust boat. In this case, this burnt gas has a high temperature and flows into the chamber 11 with great force, so that the inside of the chamber 11 becomes in a high energy state due to the thermal energy and kinetic energy of the burnt gas.

After that, when the intake stroke begins and the communication passage 24 is blocked by the second valve body 28 of the on-off valve 25, fuel is injected from the fuel injection nozzle 12 into the mixing chamber 11 as described above. However, at this time, the fuel is in chamber 1
The burnt gas in the chamber 11 is immediately and reliably vaporized by the thermal energy and kinetic energy, and a good air-fuel mixture is formed in the chamber 11. During the compression stroke, this air-fuel mixture is pushed out into the combustion chamber 4 as described above, and is further mixed with fresh air in the combustion chamber 4, and ignited by the spark plug 7 to be combusted. Since it is sufficiently vaporized in the mixing chamber 11 and well mixed with the burnt gas, it is completely combusted in the combustion chamber 4. This improves thermal efficiency or output performance, and reduces the HC content in the exhaust gas. Note that during combustion in the combustion chamber 4, there is burnt gas that was forced into the mixing chamber 11 during the exhaust stroke, so combustion occurs relatively slowly, which reduces NOx in the exhaust gas. The content will also be reduced.

Here, in this embodiment, the stopper 19 that regulates the upper end position of the piston 13 in the mixing chamber 11 is moved up and down by the motor 20, and when the engine is under high load, that is, when the amount of fuel injected from the fuel injection nozzle 12 is large, , the stopper 19 is moved upward. Therefore, when the load is high, the volume of the chamber 11 when the piston 13 is at the upper end position is increased compared to when the load is low.
The amount of burnt gas introduced into the chamber 11 or the energy of the burnt gas increases in accordance with the fuel injection amount, so that the fuel is always well vaporized and formed in the chamber 11. The concentration of the air-fuel mixture (air-fuel ratio) is also substantially constant regardless of the engine load, that is, the fuel injection amount.

In addition to the fuel injection nozzle 12 installed in the mixing chamber 11 as described above, an auxiliary fuel injection nozzle is provided on the intake boat or the intake manifold, as shown in FIG. In I, the fuel is injected only from the fuel injection nozzle 12 of the mixing chamber 11, and in the high rotation and high load region (2), fuel may be further supplied from the auxiliary fuel injection nozzle. In this way, the required fuel supply amount can be ensured at times of high rotation and high load, which require a large amount of fuel.

(Effects of the Invention) As described above, according to the present invention, part of the burnt gas is introduced into the mixing chamber provided in the cylinder head during the exhaust stroke, and fuel is injected into the burnt gas from the fuel injection nozzle. to form a mixture, and this mixture is supplied from the chamber to the combustion chamber during the compression stroke.
The fuel is immediately and reliably vaporized in the chamber by the thermal energy and kinetic energy of the burnt gas, forming a good air-fuel mixture. As a result, even in spark-assist diesel engines that use light oil with poor vaporization as fuel, complete combustion will occur within the combustion chamber, improving thermal efficiency or output performance and reducing the HC content in exhaust gas. Furthermore, the NOx content is also reduced due to the action of the burnt gas.

[Brief explanation of the drawing]

The drawings show an embodiment of the present invention. Fig. 1 is a sectional view showing the structure around the combustion chamber, and Fig. 2 shows the volume of the mixing chamber, the lift of the on-off valve, the fuel injection timing, and the ignition timing in relation to the combustion cycle. The time chart shown in FIG. 3 is a graph showing an example of fuel injection control with respect to the operating state of the engine. 3... Cylinder head, 4... Combustion chamber, 11...
Mixing chamber, 12...Fuel injection nozzle, 13
...Piston, 24...Communication passage, 25...Opening/closing valve.

Claims (1)

[Claims] (1) A mixing chamber provided in the cylinder head and communicated with the combustion chamber via a communication passage, a fuel injection nozzle that injects fuel into the chamber, and a piston provided in the chamber to increase or decrease its volume. and an on-off valve that opens and closes the communication passage, the on-off valve opens during the exhaust stroke and the compression stroke, and the fuel injection nozzle opens during the exhaust stroke and the compression stroke of the on-off valve. injecting fuel into the chamber during a valve-closing period between a valve-opening period;
A fuel injection engine characterized in that a piston in the chamber is configured to move in a direction in which the volume of the chamber decreases during a valve opening period during a compression stroke of the on-off valve.