JPH0324565B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an intake system for a multi-cylinder engine.

[Prior art]

Recently, various development proposals have been made for vehicle engines that utilize so-called dynamic effects to efficiently supply intake air from the perspective of increasing engine output. For example, as shown in Japanese Utility Model Application Publication No. 57-92021, there is a system that supercharges intake air by utilizing the resonance effect of intake air vibration within an intake system. In other words, each cylinder is divided into two groups, with cylinders having non-adjacent ignition orders, and the two chambers corresponding to each group are communicated with each cylinder through an independent intake passage. Each upstream intake passage is connected to the chamber, and
A communication path is provided that directly communicates both chambers, and normally the valve provided in this communication path is closed to perform resonance supercharging, but when the engine is under low load, the valve is opened to stop resonance supercharging and reduce intake air. This is designed to reduce the pumping loss that occurs to obtain resonance, thereby preventing a drop in engine output.

Recently, there has been a trend in vehicle engines to use fuel injection devices instead of conventional carburetors as fuel supply devices from the perspective of improving fuel control accuracy. A system is adopted in which the amount of air is detected, the control unit calculates the amount of fuel to be injected according to this amount of intake air, and a corresponding fuel injection pulse is applied to the fuel injection valve to inject and supply fuel.

However, when a fuel injection device is provided in the device described in the above-mentioned conventional publication, for example, as is usually the case, an intake air amount sensor is provided on the upstream side of the chamber and a fuel injection valve is provided on the downstream side of the chamber, and fuel is injected according to the output of the intake air amount sensor. When the amount of fuel supplied from the valve is controlled, there is a problem in that the engine speed drops or the engine stalls when the engine is decelerated.

[Purpose of the invention]

SUMMARY OF THE INVENTION In view of these problems, it is an object of the present invention to provide an intake system for a multi-cylinder engine that can prevent deterioration of drivability during deceleration.

[Structure of the invention]

In order to prevent the deterioration of drivability during deceleration, the inventor of the present invention conducted extensive research into the mechanism by which the deterioration occurs, and as a result, discovered that the following causes the deterioration. That is, in the intake system for the multi-cylinder engine, the valve of the communication passage is opened when the engine is decelerating, and the chamber for one cylinder has a large volume. When the throttle valve is closed in this state, the engine speed will slowly decrease due to its inertia (see characteristic curve a in Figure 4), and the intake air amount detected by the intake air amount sensor will be lower than the throttle valve. It is thought that the amount of intake air passing through the chamber (see characteristic curve b in Figure 4) is approximately equal to the amount of intake air that is actually taken into the engine (see characteristic curve c in Figure 4).
(see characteristic curve d in Figure 4), and if the volume of the chamber is large as mentioned above, the pressure change is proportional to the pressure equivalent to the amount of intake air used to control the amount of fuel supplied in the control unit (see characteristic curve d in Figure 4). As a result, the air-fuel ratio of the mixture shifts to the lean side during the first half of deceleration (see section A in Figure 4), and to the rich side during the second half of deceleration (see section B in Figure 4). , the combustibility deteriorates, causing a drop in rotation and engine stalling as described above.

Therefore, in order to suppress the air-fuel ratio fluctuation during deceleration, it is considered that the valve of the communication passage should be closed during deceleration, and the volume of the chamber for one cylinder may be reduced to reduce the delay in pressure change in the chamber. However, in this case, if the valve in the communication passage is simply closed during deceleration, the intake negative pressure and
If there are variations in intake resistance, etc., there will be variations in the intake air distribution, resulting in variations in the air-fuel ratio between groups, which will increase unpleasant engine vibrations, which will occur at low engine speeds where the engine's inertia decreases. This is of particular concern.

Therefore, this invention divides cylinders that do not have adjacent firing orders into a plurality of groups, connects the intake passage of each cylinder to a chamber for each group, and provides a valve in the communication passage that communicates each chamber. In an intake system for a multi-cylinder engine in which this valve is opened during low load, an intake air amount sensor is provided upstream of the chamber, and a fuel injection valve downstream of the chamber is controlled based on its output.
During deceleration, the valve is forcibly closed when the rotational speed is above a predetermined rotational speed, which is higher than the idle rotational speed.

〔Example〕

Hereinafter, one embodiment of the present invention will be described with reference to the drawings.

1 shows an intake system for a multi-cylinder engine according to an embodiment of the present invention shown in FIGS. 1 to 3; FIG. In the figure,
1 is a chamber, and the chamber 1 is defined by a partition wall 2 into a first chamber 3 and a second chamber 4. The upstream ends of intake manifolds (intake passages) 5a, 5b, and 5c extending to the first, third, and fifth cylinders in which the firing order is not consecutive are connected to the bottom surface of the first chamber 3,
The bottom surface of the second chamber 4 is connected to the upstream ends of intake manifolds (intake passages) 5d, 5e, and 5f extending to the second, fourth, and sixth cylinders, which are also not sequential in firing order. Here, it is assumed that the engine is ignited at every crank angle of 120° in the ignition order of the first, second, third, fourth, fifth, and sixth cylinders.

Further, the downstream end of the intake pipe 6 is connected to the side surface of the chamber 1 . The downstream end of this intake pipe 6 is formed into two upstream intake passages 7, 8, each of which is connected to the first chamber 3 of the chamber 1.
and the second chamber 4, and both the upstream intake passages 7, 8 form a first communication passage 9 that communicates the first chamber 3 and the second chamber 4 of the chamber 1. This first
The passage length L1 and the passage cross-sectional area S1 of the communication passage 9 are the first
The length and cross-sectional area are set such that resonance of intake air can be obtained in a low rotation range below the set rotation speed Ne1 and a high rotation range above the second set rotation speed Ne2.
Further, throttle valves 11a and 11b are provided in the upstream intake passages 7 and 8, respectively.

Further, an opening 10 is formed in the partition wall 2, and the opening 10 serves as a second communication passage that communicates the first chamber 3 and the second chamber 4 of the chamber 1 in parallel with the first communication passage 9. The passage length (thickness of the partition wall 2) L2 and passage cross-sectional area (area of the opening 10) S2 of the second communication passage are equal to or greater than the first set rotation speed Ne1 and the second set rotation speed
The length and cross-sectional area are set so that gas resonance can be obtained in the medium rotation range below Ne2. Also, this opening 1
0 is provided with a valve 12 that opens and closes it, and the valve 12 is opened and closed by an actuator 13.

Further, in the figure, reference numeral 14 has a rotation speed sensor that detects the engine rotation speed, 15 a throttle sensor that detects the throttle opening degree, and 16 a valve control map that uses the engine rotation speed and the throttle opening degree as parameters. It is a control circuit (valve control means) that receives the outputs of both sensors 14 and 15, reads an open signal or a close signal, and applies it to the actuator 13. Here, as shown in Fig. 3, the above valve control map shows that when the engine is under high load, the engine speed is in the low speed range below the first set value Ne1 and in the high speed range above the second set value Ne2. Close signal, open signal is stored in the middle rotation range from the first set value Ne1 to the second set value Ne2, and when the engine is under low load, the predetermined rotation speed Ne3 is higher than the idle rotation speed NeID during deceleration. Close signals are stored in the above areas, and open signals are stored in other areas. Note that in FIG. 3, curve a is the no-load line.

Further, 17 is an intake air amount sensor provided in the intake pipe 6 on the upstream side of the chamber 1 and detects the amount of intake air;
18 receives the output of the intake air amount sensor 17, creates a fuel injection pulse according to the amount of intake air, and sends it to the intake manifolds 5a to 5f on the downstream side of the chamber 1.
This is a control circuit (fuel control means) that controls the amount of fuel supplied from the fuel injection valve 19 to the fuel injection valve 19 provided near the downstream end.

Next, the operation will be explained.

When the engine operates, the output of the intake air amount sensor 17 is applied to the control circuit 18, and the circuit 18 creates a fuel injection pulse according to the amount of intake air, which is applied to the fuel injection valve 19 at a predetermined timing. Fuel is injected and supplied to each cylinder.
In addition, the rotation speed sensor 14 and the throttle sensor 15
Both outputs of are applied to a control circuit 16, which circuit 16
Then, an open signal or a close signal is read out from the valve control map (see FIG. 3) depending on the load condition and rotational condition of the engine, and is applied to the actuator 13 to open or close the valve 12.

Then, in the high-load, low-speed range or the high-load, high-speed range of the engine, the valve 12 closes and the intake air in the chamber 1 flows at the primary or secondary natural frequency determined by the shape of the first communication passage 9, etc. The engine resonates, and each cylinder is efficiently resonantly supercharged. In addition, in the high load and medium speed range of the engine, the valve 12
opens, and the intake air in the chamber 1 now resonates at the primary natural frequency determined by the shape of the second communication passage 10, etc., and in this case as well, each cylinder is efficiently resonantly supercharged. .

On the other hand, in the low load range of the engine, the valve 12 is normally opened and intake air is supplied between the first chamber 3 and the second chamber 4 of the chamber 1 via the second communication passage 10. The pressure in the first chamber 3 and the pressure in the second chamber 4 become approximately equal, and approximately the same amount of intake air is supplied to each cylinder.

When the engine is decelerating, the valve 12 is forcibly closed at high speed, and each cylinder is connected to the first chamber 3 or second chamber 4 of the corresponding chamber 1.
When the engine rotates at low speeds, the valve 12 is opened and the intake air is supplied between the first chamber 3 and the second chamber 4 of the chamber 1, and an approximately equal amount of air is supplied to each cylinder. Intake air will be supplied.

In the device of this embodiment as described above, the valve is forcibly closed when the engine is decelerated at high speed, so the volume of the chamber for each cylinder can be reduced, and the delay in the change in intake pressure caused by the chamber volume can be reduced. This can reduce fluctuations in the air-fuel ratio of the air-fuel mixture and prevent deterioration in drivability such as drop in rotation and engine stalling.

In addition, this device opens the valve during low speed deceleration to correct the amount of intake air between the first and second chambers, so even if there are variations in intake negative pressure, intake resistance, etc. between groups. Even if there is a problem, approximately the same amount of intake air can be supplied to each cylinder, and unpleasant engine vibrations will not increase.

In the above embodiment, the inside of the chamber is divided into a first chamber and a second chamber by a partition wall, but the chamber may of course be formed separately in the present invention. Further, the number of chambers may be a plurality other than two.

In addition, in the above embodiment, the shapes of the first and second communication passages were set so that resonance of intake air could be obtained in the low, high and medium rotation ranges, but the present invention changes the shape of the first communication passages, etc. Accordingly, it may be set so that resonance of intake air is obtained in a predetermined rotation range, and the second communication path may simply communicate between the chambers.

〔Effect of the invention〕

As described above, according to the present invention, supercharging is performed using the resonance effect of intake air, and at low load, the valve provided in the communication path between the chambers is opened to stop resonance supercharging. In the intake system of an engine, an intake sensor is provided upstream of the chamber, and the fuel injection valve downstream of the chamber is controlled based on the output of the intake sensor.The valve is also Since it is forcibly closed, it is possible to suppress air-fuel ratio fluctuations in the high rotation range during deceleration, preventing deterioration of drivability such as drop in rotation and engine stalling, and also prevent intake air between groups in the low rotation range during deceleration. This has the effect of ensuring balance and preventing an increase in engine vibration.

[Brief explanation of drawings]

1 and 2 are a cross-sectional plan view and a cross-sectional side view of an intake system for a multi-cylinder engine according to an embodiment of the present invention, respectively, and FIG. 3 is a control circuit 1 in the above system.
6 is a diagram showing the opening/closing signal of No. 6, and FIG. 4 is a diagram showing changes in the engine speed, the amount of intake air passing through the throttle valve, the intake equivalent pressure, and the pressure in the chamber to explain the configuration of the present invention. 3, 4...1st room, 2nd room (chamba), 5a
~5f...Intake manifold (intake passage), 7,
8... Upstream intake passage, 10... Opening (communication passage),
12... Valve, 16... Control circuit (valve control means), 17... Intake air amount sensor, 18... Control circuit (fuel control means), 19... Fuel injection valve.

Claims (1)

[Claims] 1. When each cylinder is divided into a plurality of groups, with cylinders that do not have adjacent ignition orders as one group, the chamber provided corresponding to each group is independently communicated with the chamber corresponding to each cylinder. an intake passage, an upstream intake passage that communicates with each chamber, a communication passage that directly communicates the plurality of chambers, a valve provided in the communication passage, an intake air amount sensor provided upstream of the chamber, and an intake passage provided downstream of the chamber. a fuel control means for controlling the amount of fuel supplied from a fuel injection valve provided on the side according to the output of the intake air amount sensor; An intake system for a multi-cylinder engine, comprising valve control means for forcibly closing the valve in a range of a predetermined rotation speed or higher.