JPH04179825A - Control apparatus for engine - Google Patents

Abstract

PURPOSE:To increase the air utilizing efficiency and achieve high output, by lessening, in a region of load higher than a specified load, the overlap between an opening period and an exhaust period of a first intake port capable of providing a strong swirl generation force in accordance with increase of engine load. CONSTITUTION:To a combustion chamber 1 of an engine are opened a first intake port 3 having a strong swirl generation force and a second intake port 4 having a weak swirl generation force. Further, a shutter valve 11 opens or closes an intake passage 10 communicated with the second intake port 4 while, on the other hand, a valve opening/closing timing varying means 9 can vary the opening/closing timing for an intake valve for independently opening or closing the first intake port 3. In this case, a control unit 17 controls the valve opening/closing varying means 9 in a manner that the overlap between the opening period and the exhaust period of the first intake port 3, in a region of load higher than a specified load, is lessened in accordance with an increase in the engine load. Since this suppresses an increase in the residual gas, the air utilizing efficiency is enhanced and a high output can be achieved.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention relates to an engine having a plurality of intake ports for one cylinder, and in particular, an engine including an intake port with a strong swirl-generating force and an intake port with a weak swirl-generating force. The present invention relates to a control device for an engine.

(Prior Art) Conventionally, for example, as described in Japanese Patent Publication No. 59-51647, two independent intake ports are opened in the combustion chamber of an engine, one of which has a strong swirl generation force, By using the other intake port with weak swirl generation force and low passage resistance, and at low load, intake air is introduced only from the intake port with strong swirl generation force, creating a strong swirl inside the combustion chamber to vaporize and atomize the fuel. The engine is designed to increase charging efficiency by introducing intake air from both intake ports at high loads, thereby ensuring combustion stability at low loads and increasing output at high loads. is proposed.

(Problem to be solved by the invention) By the way, the basic requirements for an engine are as follows:
Combustion stability at low loads including idle.

There are low emissions, low fuel consumption, high output, etc., but for combustion stability and high output, as mentioned above, intake boats with strong swirl generation power and intake ports with weak swirl generation power are used depending on the operating condition. This can be achieved to some extent by doing this, and by promoting the vaporization and atomization of fuel by swirling in this way, it becomes possible to operate with a lean air-fuel mixture, and therefore fuel efficiency at low loads is improved. However, it is important to reduce emissions, especially NOx, and
Regarding fuel efficiency improvement under high loads, the above-mentioned conventional means alone cannot achieve sufficient effects.

In order to reduce NOx, the so-called internal EGR is achieved by overlapping the intake and exhaust timing, causing exhaust gas to flow back to the intake boat side and remain in the combustion chamber.
It is necessary to make the most of the effect of the air-fuel mixture, and in order to reduce fuel consumption, it is advantageous to operate with as lean a mixture as possible, so that knocking does not occur even when driving with a lean mixture. However, it is still necessary to use internal EGR to suppress the combustion rate. However, in the conventional device mentioned above, if the internal EGR is not effective and the valve overlap is simply set to a large value, the air utilization rate will decrease and high output will not be obtained under high load. arise.

The present invention has been made in view of the above-mentioned problems, and uses a plurality of intake ports to ensure combustion stability due to swirl at low loads and improve output at high loads, and to stabilize combustion due to this swirl. The objective of the present invention is to provide an engine control device that can achieve both combustion stability, low emissions, low fuel consumption, and high output by balancing the reduction of NOx and fuel consumption by internal EGR with the improvement of fuel efficiency and output. do.

(Means for Solving the Problems) An engine control device according to the present invention has a first intake port that opens into the combustion chamber of the engine and has a strong swirl-generating force, and a second intake port that opens into the combustion chamber and has a weak swirl-generating force. An intake port, a shutter valve that opens and closes an intake passage communicating with a second intake port, a valve timing variable means that varies the opening and closing timing of the intake valve that independently opens and closes the first intake port, and an opening degree of the shutter valve. shutter valve control means that increases the amount of air in response to an increase in engine load, and valve timing that reduces the overlap between the open period of the first intake port and the exhaust/air period in a region above a predetermined load as the engine load increases. The valve timing control means is characterized by comprising a valve timing control means for controlling the variable means.

Moreover, by providing means for reducing the air-fuel ratio in accordance with an increase in engine load in addition to the above configuration, reduction in fuel consumption can be achieved more effectively.

(Function) In an operating range where the engine load is low, the shutter valve closes and the intake air from the second intake port is cut off. A strong swirl is generated within the combustion chamber by introducing intake air from the first intake port. As a result, the swirl promotes vaporization and atomization of the fuel, improving combustion stability at low loads including idle. Also, at this time, internal EGR is performed due to the overlap between the opening period of the first intake port and the exhaust period, and the EGR effect causes N
Ox is reduced.

Furthermore, when the load increases, the shutter valve is opened and intake air is also introduced from the second intake port, and the degree of opening is increased in accordance with the increase in load, thereby weakening the swirl in the combustion chamber, and Filling efficiency is improved. Further, at this time, the open period of both intake ports overlaps with the exhaust period, so that the amount of residual gas increases. The internal EGR effect reduces NOx, and the swirl is weakened and residual gas increases, thereby suppressing the combustion rate. Therefore, knocking is less likely to occur, and operation at a relatively lean air-fuel ratio is possible.

Furthermore, as the load increases further, the opening degree of the Nyatter valve increases, which weakens the swirl even further, resulting in higher charging efficiency and lower combustion noise. Further, at this time, the overlap between the opening period of the first intake port and the exhaust period is reduced in accordance with an increase in the load. As a result, the increase in residual gas is suppressed, the air utilization rate is improved, and high output is achieved.

(Example) Examples will be described below based on the drawings.

FIG. 1 is an overall system diagram of an embodiment of the present invention. As schematically shown in the figure, the combustion chamber 1 of the engine is equipped with an ignition plug 2 at a substantially central position, and two intake ports 3.4 opening at opposing positions with the ignition plug 2 in between.
Furthermore, two exhaust ports 5 and 6 are provided which are 90 degrees apart from the intake boats 3 and 4 and open at opposing positions with the ignition plug 2 in between. Here, one intake boat 3
is a helical port with a strong swirl-generating force, and an electromagnetic fuel injection valve 8 is provided in an intake passage 7 communicating with the helical port. Further, a valve device (not shown) for opening and closing the intake boat 3 is provided with a knob timing variable mechanism 9. It should be noted that the variable valve timing mechanism 9 is a well-known mechanism. Also, the other intake boat 4 is a relatively straight low swirl port with low passage resistance, and the intake passage 10 communicating with this port is provided with a butterfly type Nyatter valve 11.

A negative pressure actuator 12 that opens and closes the shutter valve 11 is connected to the shutter valve 11, and a three-way solenoid valve 14 is interposed in the middle of a negative pressure passage 13 that introduces operating negative pressure into the negative pressure chamber 12a of the actuator 12. ing. The negative pressure actuator 12 is operated by the balance between the negative pressure introduced into the negative pressure chamber 12a and the biasing force of the spring 12b, and the larger the negative pressure, the more the shutter valve 11
Drive to the open side.

Each of the above-mentioned intake passages 7. communicates with the two intake boats 3.4.
IO is formed by branching from an upstream intake passage 15 that communicates with an air cleaner (not shown), and a throttle valve 16 is disposed in the middle of the upstream intake passage 15.

Above fuel injection valve 8. Three-way solenoid valve 14. The actuators of the variable valve timing mechanism 9 and the variable valve timing mechanism 9 are each controlled by a control unit 17. Therefore, the control unit 17 receives an idle signal from an idle switch 18 attached to the throttle valve 16, an intake pipe pressure signal from a boost sensor 19 provided downstream of the throttle valve 16, and the like. Engine speed signal from a rotation sensor (not shown).

An intake air amount signal etc. from an air flow meter is input.

The variable valve timing mechanism 9 includes two types of cams to change the open period of the intake boat 3 in two stages, and the control unit 17 controls the selection of the two types of cams.
done by. That is, two types of cams are shown in FIG. 2: cam 1. Cam 2 has the valve lift characteristics shown in cam 2, and the exhaust period (E
Valve lift (cam l) with small overlap with
) is used, and in a region equal to or lower than the intake pipe pressure (PB), a valve lift (cam 2) that has a large overlap with the exhaust period (EX) is used. Note that the open period of the other intake boat 4 with low swirl is the same as that of the cam 2 described above.

The three-way solenoid valve 14 is switched to the atmosphere release position by a control signal from the control unit 17 during high load when the intake pipe pressure (PB) exceeds a predetermined value (P2). At this time, the shutter valve 11 is fully opened. In a region where the load is lower than that, the three-way solenoid valve 14 is switched to the negative pressure introducing position. At this time, the opening degree of the shutter valve II is determined by the negative pressure and spring characteristics. FIG. 3 shows the shutter valve 11 that is controlled according to the load in this way.
It shows the opening characteristics.

Further, the fuel injection valve 8 is driven and controlled by an injection pulse signal from a control unit 17. that time,
The pulse width that defines the fuel injection amount is basically set based on the engine rotational speed (NE) and the intake air amount (QA). Furthermore, in this embodiment, the pulse width is corrected so that the air-fuel ratio changes in two stages in response to an increase in engine load.

That is, in light load and steady medium load regions where the shutter valve 11 is fully closed (regions where the intake pipe pressure is lower than PI in FIG. 3), the air-fuel ratio is set to be thinner than the stoichiometric air-fuel ratio, and the shutter valve 11 is opened. In the steady high load and full load regions, the pulse width of the injection pulse signal is controlled so that the air-fuel ratio becomes approximately the stoichiometric air-fuel ratio.

FIG. 4 is a flowchart for executing actuator control of the variable valve timing mechanism 9 in the above embodiment. Note that 5l-S9 indicates each step.

When started, the engine speed (NE) and intake pipe negative pressure (FB) are read in step 81, and the idle switch signal (IDSW) is determined in step S2. And I.D.S.W.
If the signal is ON, the process goes to S3 to check whether the engine speed (NE) is lower than a predetermined value NEI. If NE<NEI, it is determined that it is idling, and in S4 it is determined that the cam 1 selection condition in FIG. 2 is satisfied, and in S5
Executes cam 1 selection by the actuator.

If it is determined that the IDSW signal is not ON in S2, it is determined in S6 whether PB is larger than PI in FIG. Executes cam 2 selection by the actuator.

When YES in S6 (i.e. FB>PI),
At S9, check whether FB is larger than P2 in Figure 3,
If YES (that is, PB>P2), go to S4,
Select cam l in S5. Also, No (i.e. P 1
<FB≦P2), the process goes to S7, and cam 2 is selected in S8.

(Effects of the Invention) Since the present invention is configured as described above, in an engine provided with a plurality of intake ports, it is possible to stabilize combustion at low load by swirl, improve output at high load, and reduce internal EG.
By balancing the reduction of NOx and fuel consumption by R,
Combustion stability, low emissions, low fuel consumption and high output can all be achieved.

[Brief explanation of the drawing]

Fig. 1 is an overall system diagram of one embodiment of the present invention, Fig. 2 is a control characteristic diagram of the variable valve timing mechanism in the same embodiment, Fig. 3 is an opening characteristic diagram of the shutter valve in the same embodiment, and Fig. 4 The figure is a flowchart for executing control in the same embodiment. l: combustion chamber, 3.4=intake port, 7, 10: intake passage, 8. Fuel injection valve, 9: Valve timing variable mechanism, 1
1 Nishiator valve, 12: Negative pressure actuator, 14:
Three-way solenoid valve, 17; control unit, 19
Niboost sensor. Agent Patent Attorney Jun Susumu Fuji −

Claims (2)

[Claims] (1) Opening and closing a first intake port with a strong swirl-generating force that opens into the combustion chamber of the engine, a second intake port with a weak swirl-generating force that opens into the combustion chamber, and an intake passage that communicates with the second intake port. a shutter valve that independently opens and closes the first intake port, a valve timing variable means that varies the opening and closing timing of the intake valve that independently opens and closes the first intake port, and a shutter valve control that increases the opening degree of the shutter valve in accordance with an increase in engine load. and valve timing control means for controlling the valve timing variable means to reduce the overlap between the open period and the exhaust period of the first intake port in accordance with an increase in engine load in a region of a predetermined load or more. An engine control device characterized by: (2) The engine control device according to claim 1, further comprising means for reducing the air-fuel ratio in response to an increase in engine load.