JPH061053B2 - Engine intake system - Google Patents

Description

TECHNICAL FIELD The present invention relates to an intake device for an engine in which a combustion mixture is stratified and filled in a combustion chamber, and in particular, ensures stratification in a low load region. is there.

(Prior Art) As a conventional example of such an intake system for an engine, as shown in Japanese Utility Model Laid-Open No. 58-94820, only air or a lean air-fuel mixture is burned at the beginning of the intake stroke of the piston. By supplying the mixture to the combustion chamber and supplying the rich mixture in the latter stage, a rich stratified mixture can be formed in the upper part near the spark plug in the combustion chamber, and as a result, the mixture is lean as a whole. However, there are some that are designed to ignite reliably.

And for the above stratification, one supplies a rich air-fuel mixture,
The other is provided with main and auxiliary intake passages for supplying a lean mixture or air, and with main and auxiliary intake valves for opening and closing these intake passages at a predetermined timing, and the downstream end of the auxiliary intake passage is It opens in the intake passage upstream of the main intake valve.

In the case of such stratification, particularly reliable stratification is required in the low load region in order to reliably maintain the ignition characteristics and improve the fuel efficiency by making the fuel lean. However, no such measures have been taken.

That is, to describe the one described in the above publication, this one supplies a lean air-fuel mixture (or air) in the early stage of the intake stroke by using the main and auxiliary intake passages with different intake valve opening periods, and in the latter stage of the intake stroke. Although the rich air-fuel mixture is supplied, the intake air flow rate adjustment according to the load is similarly performed in the main and auxiliary intake passages. Therefore, even if the load changes, there is no means for changing the ratio of the lean air-fuel mixture in the early stage of the intake stroke and the rich air-fuel mixture in the latter stage of the intake stroke. Therefore, no special measures have been taken to enhance stratification at low load and suppress stratification at high load.

(Object of the Invention) The present invention has been made in view of the above circumstances, and a low load is achieved by forming the main intake passage with the primary and secondary intake passages and opening the auxiliary intake passage in the primary intake passage. The purpose is to perform reliable stratification in the area.

(Structure of the Invention) According to the present invention, a main intake passage connected to a combustion chamber, a main intake valve that opens this main intake passage in an intake stroke of an engine, and a downstream end of the main intake passage upstream of the main intake valve are opened. An air-fuel mixture supply device that supplies a lean air-fuel mixture or air to the other intake passage while supplying a rich air-fuel mixture to the sub-intake passage and one of the main and sub intake passages, and a sub-opener that opens and closes the sub-intake passage. The auxiliary intake valve is opened and closed so that the lean air-fuel mixture or air is supplied to the combustion chamber at least early in the opening period of the main intake valve and the combustion air-fuel mixture is stratified and supplied. In the engine intake device configured as described above, the main intake passage is formed by a primary intake passage and a secondary intake passage that is closed when the load is low, and the primary intake passage has a passage diameter smaller than that of the secondary intake passage. And above The configuration is such that a swirl is generated in the air-fuel mixture supplied to the combustion chamber, and the auxiliary intake passage is opened to the primary intake passage.

With this configuration, the rich air-fuel mixture and the lean air-fuel mixture or the air can be stratified and supplied to the combustion chamber from the primary intake passage whose passage diameter is narrowed. Therefore, in particular, the secondary intake passage is closed and the primary intake passage is closed. The effect becomes remarkable at low load when intake is mainly performed.

(Embodiment) An embodiment of the present invention will be described below with reference to FIGS.

FIG. 1 shows the structure of an intake system for an engine, where 1 is an engine, 2 is a cylinder, 3 is a piston, 4 is a cylinder head, and a combustion chamber 5 is formed below the cylinder head 4. Reference numeral 6 is a spark plug, and 7 is a main intake passage connected to the combustion chamber 5. In the present embodiment, a rich air-fuel mixture is supplied. Reference numeral 8 is a main intake valve that opens the main intake passage 7 in the intake stroke of the engine, and 9 is a sub intake passage having a downstream end opened to the main intake passage 7 upstream of the main intake valve 8 and supplied with a lean air-fuel mixture or air. In this embodiment, air is supplied. Reference numeral 10 is an auxiliary intake valve formed of a solenoid valve that opens and closes the auxiliary intake passage 9 in synchronization with the crankshaft of the engine. The auxiliary intake valve 10 is provided in the main intake passage 7 downstream of the opening of the auxiliary intake passage 9. Air (or lean air-fuel mixture ... The same applies hereinafter) is supplied in the early and late stages of the opening period of the valve 8, and the auxiliary intake passage 9 is supplied so that the rich air-fuel mixture is supplied in the middle period of the opening period of the main intake valve 8. Open and close. In addition, the auxiliary intake valve 1
0 opens in the primary intake passage 14 described later.

11 is a vaporizer (mixture supply device) for supplying a rich mixture to the main intake passage 7, 12 is an exhaust passage, 13 is an exhaust valve, 14,
Reference numeral 15 denotes a primary and secondary intake passage formed in the main intake passage 7. The primary intake passage 14 has a passage diameter narrower than that of the secondary intake passage 15 and is opened tangentially to the combustion chamber 5. The air-fuel mixture is swirled to facilitate stratification, and the secondary intake passage 15 opens toward the upper surface of the piston substantially parallel to the center of the cylinder 2 without swirling. It is configured to introduce intake air.

Reference numeral 16 is a swirl control valve which is interlocked so as to close when the opening of the main throttle valve 17 is below a certain level, that is, when the load is low. It is supplied from the passage 14 to enhance the swirl effect. 18 is a sub throttle valve, 19 is a main intake passage 7 and a sub intake passage 9
In the present embodiment, only the air is supplied to the auxiliary intake passage 9 by the air cleaner provided on the upstream side of the. Reference numeral 20 is a preheating means for heating the rich air-fuel mixture supplied from the main intake passage 7 to raise the atomization state of the fuel, 2
Reference numerals 1 and 22 respectively denote a heater and a cooler for cooling or heating the lean air-fuel mixture or air from the auxiliary air intake passage 9, which are temperature sensors 2 for detecting the temperature of the preheating means 20.
3 is selectively used by the damper 24a driven by the switching means 24 which operates based on the signal of FIG. That is, when the engine is warm, the lean air-fuel mixture or air from the auxiliary intake passage 9 is cooled by the cooler 22 to increase the specific heat ratio to improve the output, and when the engine is cold, it is heated by the heater 21 to promote atomization.

Reference numeral 25 is a control means using a microcomputer, which receives an oxygen sensor 26 provided in the exhaust passage 12, a fully open switch signal of the main throttle valve 17, a crank angle signal of the engine, etc., and inputs the main intake valve 8 and the auxiliary intake valve 10. Etc. are controlled as described above. A specific example of this will be described later. Two
Reference numeral 7 is a leakage passage of the auxiliary intake valve 10 for smoothing the flow.

The opening / closing timing of the main intake valve 8 and the auxiliary intake valve 10 is set to the second
It will be described with reference to the drawings. In Figure 2, BDC is bottom dead center,
TDC is the top dead center, 108 is the opening of the main intake valve 8,
0, 110H and 110L indicate the opening degree of the auxiliary intake valve 10 by 11
Reference numeral 3 indicates the opening degree of the exhaust valve 13. 110H is for a high load and 110L is for a low load. When the load is low, the opening timing of the auxiliary intake valve 10 is advanced in order to prevent the rich air-fuel mixture from blowing back from the main intake valve 8. The opening operation (110, 110H, etc.) of the auxiliary intake valve 10 is designed to open at the beginning and the end of the opening period of the main intake valve 8. And combustion chamber 5
At the beginning of the opening period of the main intake valve 8, the air introduced into the primary intake passage 14 of the main intake passage 7 from the auxiliary intake passage 9 by the opening (110) of the auxiliary intake valve 10 is mainly discharged from the carburetor 11. The rich air-fuel mixture is supplied as a lean air-fuel mixture (lean) by being mixed with the rich air-fuel mixture supplied through the intake passage 7, and during the middle period of the opening period of the main intake valve 8, the rich air-fuel mixture (rich) is discharged from the main intake passage 7. In the latter half of the opening period of the main intake valve 8, air is mixed by the opening (110H, 110L) of the auxiliary intake valve 10 in the same manner as described above, and a lean mixture is supplied.

Here, the air introduced in the latter period does not enter the combustion chamber 5 as a lean air-fuel mixture, and is set in the range of the amount that remains in the main intake passage 7 downstream of the opening of the auxiliary intake passage.

By opening and closing the auxiliary intake valve 10 in this way, lean and rich stratification is formed in the combustion chamber 5 from below.
Also in the next stroke, the lean air-fuel mixture accumulated in the main intake passage 7 in the previous stroke enters earlier and the same stratification as described above is performed.

In the auxiliary intake passage 9, the diameter of the main intake passage 7 is reduced,
In addition, the swirl control valve 16 in the secondary intake passage 15 is closed when the load is low, and the auxiliary intake valve 10 is open because the opening is formed in the primary intake passage 14 that is configured to provide a swirl action. The rich air-fuel mixture and the air are surely stratified in the primary intake passage 14 having a narrow width, and the stratified air-fuel mixture is swirled to give combustion chamber 5
Is supplied to. Further, when the auxiliary intake valve 10 is closed, only the rich air-fuel mixture is swirled from the primary intake passage 14 and supplied to the combustion chamber 5. As described above, when the load is low, the primary intake passage 14 and the auxiliary intake passage 9 are favorably stratified with the secondary intake passage 15 closed.

On the other hand, when the load is high, the secondary intake passage 15 is opened, and the ratio of the flow rate of the air-fuel mixture having a constant air-fuel ratio from the carburetor 11 to the secondary intake passage 15 increases. The effect of changing the air-fuel ratio is relatively decreased by 9 and the stratification effect is suppressed.

Next, a specific configuration for controlling the opening / closing timing of the auxiliary intake valve 10 will be described with reference to FIGS. 3 and 4. FIG. 3 shows the control means 2
5 shows a concrete example, and FIG. 4 shows signal waveforms of respective parts in FIG. In these figures, 28 is a crank angle signal generating means and 29 is a reference signal generating means. The crank angle signal is input to a pulse counter 30 and reset by a reset circuit 31 by a predetermined reference signal. The output A of the pulse counter 30 is input to the comparison circuits 33, 34, 35, 36 via the D / A converter 32, and the set values 37, 3 are set.
Compared with 8, 39, 40, outputs B, C, E, respectively
Get F. Output B is ON when the set value is 37 or less, output C
Becomes ON when the value is equal to or greater than the set value 38, and the output D is obtained by the AND circuit 41. Similarly, the output G is obtained from the outputs E and F by the AND circuit 42. And OR from outputs D and G
The output H is obtained by the circuit 43. This output H is input to the solenoid 10a that drives the auxiliary intake valve 10 via the gate circuit 44 and the OR circuit 45. Due to the output H in the first half, the opening timing of the auxiliary intake valve 10 in the early stage of the opening period of the main intake valve 8 is the opening timing of the auxiliary intake valve 10 in the latter half of the opening period of the main intake valve 8 due to the output H in the latter half. Is determined.

The output of the OR circuit 48 of the start switch 46 and the throttle valve fully open switch 47 is input to the gate circuit 44, and the OR circuit 45 ORs the deceleration switch 49 and the signal passed through the timer 51 of the ignition switch 50.
The signal from the circuit 52 is input. The gate circuit 44 is for closing the auxiliary intake valve 10 to make a rich air-fuel mixture (rich) at the time of starting and high load, and the OR circuit 45.
Is for opening the auxiliary intake valve 10 in order to make the air-fuel mixture lean during deceleration and for a certain time after the ignition is cut off.

Reference numeral 53 is a boost signal for detecting the load of the engine, and this signal is input to the set values 39 and 40 via the set value correction circuit 54 to change the timing of the outputs E and F, that is, the output H of the latter half. With this, proper stratification is performed according to the load condition of the engine.

The signal from the oxygen sensor 26 is input to the comparison circuit 55,
The value is compared with the set value 56, and is input to the set value 37 via the integration circuit 57 and the set value correction circuit 58. Accordingly, the closing timing of the pulse H in the first half of opening the auxiliary intake valve 10 is changed according to the oxygen concentration of the exhaust gas in the exhaust passage 12. As a result, the state of the exhaust gas can be fed back to electrically control the auxiliary intake valve, and thus the air-fuel ratio control can be performed.

It should be noted that in the above-described embodiment, the case where the auxiliary intake valve 10 is opened in the early and late stages of the opening period of the main intake valve 8 has been described. A small amount must be provided so that the lean air-fuel mixture or air is not supplied, and considering the diffusion action in the combustion chamber, at least the initial auxiliary intake valve 1 is required for stratification.
It only needs to have a valve open of zero.

Further, in the above embodiment, the rich air-fuel mixture is supplied to the main intake passage 7 and the air is supplied to the sub-intake passage 9, but, conversely, air is supplied to the main intake passage 7 and the sub-intake passage 9 is richly mixed. By supplying air, the opening timing of the auxiliary intake valve 10 is set to the main intake valve 8
Even if the valve is opened in the middle of the valve opening period, the same effect as described above can be obtained.

As described above, according to the engine intake system of the present invention, the auxiliary intake passage opened and closed by the auxiliary intake valve is connected upstream of the main intake valve that opens and closes the main intake passage, and the air-fuel mixture in the combustion chamber is connected. In which the main intake passage is formed of a primary intake passage and a secondary intake passage that is closed when the load is low, the primary intake passage has a passage diameter smaller than that of the secondary intake passage. Since the swirl is generated in the mixture that is throttled and is supplied to the combustion chamber, and the secondary intake passage is opened in this primary intake passage, the primary intake air is closed in the state where the secondary intake passage is closed. At low load when intake air is supplied from the passage to the combustion chamber, it is ensured that the rich air-fuel mixture and the lean air-fuel mixture or air are stratified and supplied through the primary intake air passage.

[Brief description of drawings]

FIG. 1 is a configuration diagram of an intake system for an engine according to an embodiment of the present invention, FIG. 2 is a timing chart showing opening states of a main intake valve and an auxiliary intake valve in the intake system, and FIG. FIG. 4 is a configuration diagram of control means for controlling the valve, and FIG. 4 is a waveform diagram of output pulses in the control means. DESCRIPTION OF SYMBOLS 1 ... Engine, 2 ... Cylinder, 5 ... Combustion chamber, 7 ... Main intake passage, 8 ... Main intake valve, 9 ... Sub intake passage, 10 ... Sub intake valve, 11 ... Vaporizer (mixture supply device), 14 ... Primary intake passage, 15 ... Secondary intake passage.

Claims (1)

[Claims] 1. A main intake passage connected to a combustion chamber, a main intake valve that opens the main intake passage in an intake stroke of an engine, and a sub intake passage having a downstream end opened to the main intake passage upstream of the main intake valve. And a mixture supply device that supplies a rich mixture to either one of the main and sub intake passages and a lean mixture or air to the other intake passage, and an auxiliary intake valve that opens and closes the auxiliary intake passage. The auxiliary intake valve is configured to open and close so that a lean air-fuel mixture or air is supplied to the combustion chamber at least early in the opening period of the main intake valve, and the combustion air-fuel mixture is stratified and supplied. In the intake passage of the engine, the main intake passage is formed by a primary intake passage and a secondary intake passage that is closed when the load is low, and the primary intake passage has a passage diameter narrowed as compared with the secondary intake passage, and In the combustion chamber A structure that causes a swirl in the gas mixture to be fed, and an intake device of an engine, characterized in that the auxiliary air intake passage was opened in the primary intake passage above.