JPH0654109B2 - Engine fuel supply - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a fuel supply system for an engine. In particular, the present invention provides a fuel for an engine having an intake system in which two intake passages communicating with the same combustion chamber are provided, and one of the intake passages is provided with a control valve that closes the passage when the load is low. Regarding the feeding device.

(Prior Art) An intake passage of an engine is composed of a primary intake passage and a secondary intake passage that communicate with the same combustion chamber, and a control valve that closes the passage is provided in the secondary intake passage during high load operation. It is well known that an engine is designed to intake air only from the primary intake passage during low / medium load operation.
No. 167254 can be mentioned. This type of engine can increase the flow velocity of the intake air to strengthen the intake swirl in the combustion chamber even during low-to-medium load operation where the intake air amount is relatively small, and the swirl strength can be increased according to the opening of the control valve. At the same time that the control can be performed, the effect of improving the atomization state of the fuel can be expected, so that the low / medium load operation can be performed with a relatively lean mixture. As an engine of this type, as disclosed in Japanese Utility Model Laid-Open No. 167254/1982, in addition to the structure in which the primary and secondary intake passages are opened to the combustion chamber by separate intake ports, both intake passages are provided. A configuration in which the combustion chamber is opened through a common intake port is also known.

(Problems to be Solved by the Invention) In the engine of the type described above, controlling the fuel supply so as to obtain a satisfactory operation over the entire operating region cannot be said to be completely solved,
There is room for improvement. That is, in order to ensure stable combustion in a low load operation range and to operate with a lean air-fuel mixture as much as possible, it is possible to improve fuel consumption characteristics and reduce harmful components in exhaust gas, particularly CO and HC. In order to reduce the amount of nitrogen oxides in exhaust gas, it is strongly desired to be able to operate with a lean air-fuel mixture while ensuring smooth acceleration / deceleration even in the medium-load operation region. By the way. Also, during high load operation, the high output required for the engine must be generated, and the transition of operation is smooth even when the above-mentioned control valve transitions from the closed state to the open state or vice versa. It is desirable to be carried out. In the engine disclosed in Japanese Utility Model Laid-Open No. 57-167254, the fuel injection valve is provided in both the primary and secondary intake passages. However, simply providing two fuel injection valves in each intake passage. , I do not get enough satisfactory results.

Therefore, it is an object of the present invention to provide a fuel supply system for an engine having the above-described two intake passages so that a favorable operating condition can be obtained over the entire operating range.

(Means for Solving Problems) In the present invention, in order to solve the above problems, two fuel injection valves are provided in the intake system, one of the fuel injection valves has a large injection angle type, and the other fuel injection valve has a large injection angle. The injection valve has a small injection angle, and the operation of these fuel injection valves is related to the opening and closing of the control valve in the secondary intake passage. That is, the control valve is operated so that it opens in the medium / high load operating region of the engine and closes in the low load operating region, and the control valve closes in the low load operating region, and the control valve is open but the load is relatively low. Only the fuel injection valve with a large injection angle is operated in the operating region, and the fuel injection valve with a small injection angle is operated in the high load operating region. In this case, it is preferable that the fuel injection valve with the large injection angle is arranged in the primary intake passage and the other fuel injection valve is arranged in the secondary intake passage. Further, the fuel injection valve having a large injection angle may be operated even in the high load operation region.

(Operation) In the present invention, the fuel injection valve having a large injection angle operates during low / medium load operation. The fuel injection valve having a large injection angle has a relatively small fuel injection amount, but has a good atomization effect of the fuel, and therefore improves the mixing with air and improves the combustion state. As a result, combustion is stable under low load operation, and operation with a lean mixture becomes possible. Further, even during the medium load operation, the fuel is stable, so that the operation with the lean air-fuel mixture in the region where the generation of nitrogen oxide is small becomes possible. Further, during high load operation, the fuel injection valve having a small injection angle operates, and a large amount of fuel required for high output can be supplied.

(Effect) As described above, in the present invention, fuel is supplied to the low load region where the secondary intake passage is closed by the fuel injection valve having a large injection angle and high atomization efficiency, so that stable combustion is ensured. Therefore, it is possible to improve fuel efficiency and reduce harmful components in exhaust gas. Further, even in the medium load range where the control valve is opened, the fuel injection valve with a large injection angle is operated, so operation with a lean air-fuel mixture is possible, the generation of nitrogen oxides can be suppressed, and in the high load range, the injection angle is increased. A small amount of fuel injection valve can supply a sufficient amount of fuel according to the output demand. Therefore, the present invention provides satisfactory operation over the entire operating region of the engine.

(Embodiment) First, referring to FIG. 1 and FIG. 2, the engine 1 is
A cylinder block 2 having a cylinder bore 2a and a cylinder head 3 attached to the upper end of the cylinder block 2.
And a piston 4 that reciprocates in the cylinder bore 2a of the cylinder block 2, and a combustion chamber 5 is formed in the cylinder head 3. The cylinder head 3 is formed with a primary intake port 6, a secondary intake port 7 and an exhaust port 8. The primary intake port 6 is provided with a primary intake valve 9, the secondary intake port 7 is provided with a secondary intake valve 10, and the exhaust port 8 is provided with an exhaust valve 11. The primary intake port 6 is connected to the primary intake passage 12, and the secondary intake port 7 is connected to the secondary intake passage 13. Intake passage 1
2 and 13 are connected to a common surge tank 14, and this surge tank 14 is connected to a main intake passage 15. The main intake passage 15 has a throttle valve 16 and an air cleaner 17 is provided at the upstream end. Further, an air flow sensor 18 is arranged in the main intake passage 15 on the downstream side of the air cleaner 17. A control valve 19 is provided in the secondary intake passage 13.

As shown in FIG. 2, the first fuel injection valve 20 is provided in the primary intake passage 12, and the second fuel injection valve 21 is provided in the secondary intake passage 13.
Are provided respectively. The first fuel injection valve 20 is of a type having a large injection angle, and the second fuel injection valve 21 is of a type having a small injection angle. These fuel injection valves 20 and 21 are connected to a fuel supply passage 23 having a regulator 22 for adjusting the fuel pressure.

The above is a description of one cylinder, but in the case of a multi-cylinder engine, first and second fuel injection valves are provided in the primary and secondary intake passages of each cylinder, respectively. FIG. 1 shows these fuel injection valves with the same reference numerals.

A controller 24 is provided to control the operation of the fuel injection valves 20 and 21. The air flow rate signal from the air flow sensor 18 is input to the control device 24, and the throttle valve 1
6, the throttle valve opening signal from the opening sensor 25 and the crank angle signal from the crank angle sensor 26 are input. The control device 24 performs a calculation based on these input signals to generate a fuel injection signal according to engine operating conditions, and the fuel injection signal is given to the fuel injection valves 20 and 21.

The control valve 19 is interlocked with the throttle valve 16 by a communication mechanism (not shown), and starts to open when the throttle valve 16 opens a predetermined opening or more. That is, the control valve 19 is opened in the medium / high load region of engine operation. In the low load engine operating region, the control valve 19 is closed and the intake air is supplied to the combustion chamber 5 only from the primary intake passage 12. The primary intake port 6 is formed so as to guide the intake air tangentially to the combustion chamber 5, and the intake air flowing into the combustion chamber 5 from the primary intake port 6 forms a swirl in the combustion chamber 5. A spark plug 27 is attached to the cylinder head 3.
Is provided to ignite the air-fuel mixture in the combustion chamber 5 at an appropriate timing. The control device 24 gives an operation signal to the first fuel injection valve 20 in a low load region in which the control valve 19 is closed and in a medium load region in which the control valve 19 is open but the engine load is relatively low, and the fuel is injected into the fuel injection valve 20. Inject a jet. Then, at the time of high load operation, an operation signal is also given to the second fuel injection valve 21, and fuel injection is also performed from this injection valve 21. This control can be performed based on, for example, a map corresponding to the engine load and the engine speed, an example of which is shown in FIG. In FIG. 3, in region A, fuel injection is performed only by the first fuel injection valve 20, and in region B, both fuel injection valves 20, 21 perform fuel injection.

FIG. 4 shows the relationship between the engine load and the operable air-fuel ratio corresponding thereto. In the figure, the curve a shows the operable range when the control valve 19 is closed and fuel is supplied only by the first fuel injection valve 20. As is clear from the curve a, under this condition, it is possible to operate with a lean air-fuel mixture in a relatively low load region. Curve b
Indicates the operable range when the control valve 19 is opened and fuel is supplied only from the first fuel injection valve 20, and the curve c indicates when the control valve 19 is opened and fuel is also supplied from the second fuel injection valve 21. The respective operable areas are shown. As is apparent from the figure, by supplying fuel only from the first fuel injection valve 20 in the medium load operation range, the air-fuel ratio can be increased only in the range shown by the shaded area in the figure.

[Brief description of drawings]

FIG. 1 is a schematic sectional view of an engine showing an embodiment of the present invention, FIG. 2 is a bottom view seen from the inside of a cylinder head, FIG. 3 is a chart showing a control region of a fuel injection valve, and FIG. It is a chart showing the effect of the present invention. 2 ... Cylinder block, 3 ... Cylinder head, 6 ... Primary intake port, 7 ... Secondary intake port, 12 ... Primary intake passage, 13 ... Secondary intake passage, 16 ... Throttle valve, 19 ... ... control valve, 20 ... first fuel injection valve, 21 ... second fuel injection valve, 24 ... control device.

Claims (4)

[Claims] 1. A control valve having a primary intake passage and a secondary intake passage communicating with the same combustion chamber, the control valve being opened in the medium / high load operating region of the engine and closed in the low load operating region in the secondary intake passage. In an engine having an installed intake system, a first fuel injection valve having a large injection angle and a second fuel injection valve having a small injection angle
A fuel injection valve is arranged, and a control device is provided which operates only the first fuel injection valve in a low / medium load operation region of the engine and operates the second fuel injection valve in a high load operation region. And fuel supply system for the engine. 2. The fuel supply device for an engine according to claim (1), wherein the first fuel injection valve is arranged in the primary intake passage and the second fuel injection valve is arranged in the secondary intake passage. 3. The fuel supply device for an engine according to claim (1) or (2), wherein the primary and secondary intake passages are connected to a combustion chamber via separate intake ports. 4. The fuel supply device for an engine as defined in any one of the above items (1) to (3), wherein the control device operates the first fuel injection valve even in a high load operation region.