JP3190411B2 - Engine intake air control system - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an intake air amount control device for an engine.

[0002]

2. Description of the Related Art As an engine intake air amount control device,
As disclosed in Japanese Patent Application Laid-Open No. 63-198747, on the assumption that the intake air amount is adjusted so that the engine speed becomes the target speed in the no-load low-speed range, the ignition timing is reduced during the cold start. And thereby performing a rapid warm-up.

As disclosed in Japanese Patent Application Laid-Open No. 62-667, an intake air amount control device for an engine adjusts the intake air amount so that the engine speed becomes a target speed in a no-load low-speed region. On the premise that the ignition timing is retarded at the time of no-load low rotation, the ignition timing is corrected to the advance side at the time of starting. In this case, at the time of starting, the drop in the engine speed can be reduced based on the increase in the intake air amount from the time of no-load low rotation, and a smooth start can be achieved.

[0004]

However, from the viewpoint of energy saving, it is preferable to drive a vehicle as large as possible with a small displacement engine.
In order to prevent a so-called engine stall, startability (prevention of a drop in engine speed) is the most important problem. Therefore, it is expected that higher startability can be obtained than in the case of the intake air amount control device.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an engine intake air amount control device capable of further improving startability.

[0006]

In order to achieve the above object, the present invention provides an intake system which has a correspondence with the fuel injection amount so that the engine speed becomes a target speed in a no-load low-speed region. An intake air amount control device for an engine having an intake air amount adjusting means for adjusting an air amount, a catalyst provided in an exhaust system for purifying exhaust gas, and an exhaust resistance adjusting means provided in the exhaust system for increasing or decreasing exhaust resistance. Ignition timing adjusting means for adjusting the ignition timing, starting state detecting means for detecting the starting state of the vehicle, operating state detecting means for detecting the operating state of the engine, the operating state detecting means and the starting state detecting means When the operating state of the engine is in the no-load low-speed state, the exhaust resistance is increased and the ignition timing is retarded based on the intake air amount adjusting means. While allowed to increase the incoming air volume, it is constituted that and a control means for shifting the ignition timing to the advance side while reducing the exhaust resistance at the time of starting.

[0007]

With the above configuration, in the no-load low-rotation state, the exhaust work of the engine increases and the torque decreases with the increase of the exhaust resistance (exhaust pressure) and the retard of the ignition timing. Since the intake air amount adjusting means increases the intake air amount, when the vehicle starts moving, the exhaust resistance is reduced and the ignition timing is shifted to the advance side. The increase in the exhaust work based on the start-up torque and the like appear as an increase in the starting torque, so that a drop in the engine speed can be suppressed. In addition, the internal EGR is generated based on the increase in the exhaust resistance in the no-load low-rotation state, and the internal EGR increases the temperature in the cylinder, thereby improving the fuel vaporization and atomization at the time of starting. Become. Therefore, the flammability is improved, and the starting torque is also increased from that viewpoint. As a result, a drop in the engine speed is further suppressed, and accordingly, the startability is further improved. Further, in the no-load low-rotation state, the intake air amount adjusting means increases the intake air amount in order to compensate for the increase in the exhaust work of the engine and the decrease in the torque based on the increase in the exhaust resistance and the retard of the ignition timing. As the intake air amount increases, the fuel injection amount increases, the temperature of exhaust gas discharged from the engine rises, and the catalyst can be activated early.

[0008]

Embodiments of the present invention will be described below with reference to the accompanying drawings. In FIG. 1, reference numeral 1 denotes an engine body, and the engine body 1 is an in-line four-cylinder engine in which four cylinders 2 are arranged in series. And each cylinder 2
In FIG. 1, a spark plug P is exposed to a combustion chamber (not shown), and two intake ports and two exhaust ports are opened. These ports are opened and closed by an intake valve 3 or an exhaust valve 4.

The valve system for opening and closing the intake valve 3 and the exhaust valve 4 will be described. The intake valve 3 is opened and closed by an intake camshaft 5 at a predetermined timing in synchronization with the rotation of the engine output shaft. On the other hand, the exhaust valve 4 is controlled by a variable valve timing mechanism 7 attached to the exhaust camshaft 6 to a first valve timing (a timing indicated by a chain line in FIG. 2) and a second valve timing (a solid line in FIG. 2). ).

Here, when the first valve timing is compared with the second valve timing, the second valve timing is the same as the exhaust late closing whose valve closing timing is delayed as compared with the first valve timing. When the second valve timing is selected, the valve overlap period (O / L) in which both the intake valve and the exhaust valve are in the open state.
Has been expanded.

An intake system 10 of the engine body 1 has a common intake passage 11 arranged in order from the upstream side to the downstream side.
, A surge tank 12 as an intake expansion chamber, and an independent intake passage 13. The common intake passage 11 has an air cleaner 14, an air flow meter 15, and a throttle valve in order from the upstream side to the downstream side. 16, a fuel injection valve (not shown) and the like are disposed, and a bypass passage 17 that bypasses the throttle valve 16 is provided in the common intake passage 11, and an intake speed that controls an idle speed is provided in the bypass passage 17. An ISC valve 18 is provided as air amount adjusting means. Since the specific contents of the idle speed control using the ISC valve 18 are the same as those in the conventional art, the details are omitted.

The exhaust system 20 of the engine body 1 is composed of an exhaust manifold 21 and a common exhaust passage 22. The common exhaust passage 22 has a pre-three-way purifying exhaust gas in order from upstream to downstream. A catalyst 23, an exhaust gas reservoir 24, a throttle valve 26, a main three-way catalyst 27, a variable silencer 29, and the like are provided. The throttle valve 26 is driven by a drive actuator 28.

Reference numeral U shown in FIG. 1 is a control unit constituted by, for example, a microcomputer, and includes a CPU, a ROM, a RAM, and the like, as is known. In addition to a signal indicating the amount of intake air from the air flow meter 15, the control unit U receives an engine cooling water temperature, an engine load, an engine speed, and a start signal from the sensor group 25 (for example, in the case of an AT car, the D range state ( In addition, various signals indicating that the brake OFF is detected in the brake ON state) are input. On the other hand, control unit U
, A control signal is output to the ISC valve 18, the variable exhaust valve timing mechanism 7, the drive actuator 28, the spark plug P, and the like.

Next, control contents of the control unit U will be described. In the throttle control no-load low rotation region of the throttle valve 26, the throttle valve 26 is throttled, and is fully opened at the time of starting. This is because, when the exhaust resistance (exhaust pressure) is increased in the no-load low-speed state, the exhaust work of the engine increases, and the ISC valve 18 increases the intake air amount to compensate for this. At this time, by reducing the exhaust resistance, an increase in the exhaust work based on the increase in the exhaust resistance is expressed as an increase in the starting torque, and the drop in the engine speed is suppressed. Moreover, not only that, the internal EGR based on the increase in the exhaust resistance in the no-load low-rotation state raises the temperature in the cylinder, thereby improving the vaporization and atomization of the fuel at the time of starting.
The aim is to improve the flammability and increase the starting torque from that viewpoint. As a result, a drop in the engine speed is further suppressed, and accordingly, the startability is further improved. Specifically, the throttle limit of the throttle valve 26 in the no-load low-rotation state is a state in which the throttle valve 26 is opened 5 deg from the fully closed state. About 400mm
Hg has been around. Although this value varies depending on the engine, it is determined based on the thermal reliability, and when the throttle is large, the exhaust pressure greatly changes even if the throttle is slightly changed. In addition, the throttle amount of the throttle valve 26 is reduced as the temperature is lower. This is because when the throttle valve 26 is throttled,
To compensate for the increase in engine exhaust work, IS
Since the opening degree of the C valve 18 is increased to increase the intake air amount, that is, the fuel injection amount, and the temperature of the exhaust gas discharged from the engine 1 becomes higher, the heat of the cylinder head ( A large amount of heat is transmitted to the cooling water passing through the cooling water passage in the head, thereby promoting warm-up of the engine 1, thereby stabilizing the combustion state at an early stage and suppressing the exhaust gas from containing harmful components. That is. In the present embodiment, the pre- and main three-way catalyst 2
3, 27, in particular, the pre-three-way catalyst 23 is activated early and exerts its catalytic action within a short period of time to start purifying the exhaust gas.

Ignition timing control In this embodiment, ignition timing control is also taken into account.
Basically, the ignition timing is set based on the basic fuel injection amount and the engine speed as in the conventional case, and various corrections are made to the basic ignition timing to set the final ignition timing. It is determined. On the premise of the above, in the present embodiment, the ignition timing is retarded in the no-load low-speed rotation region, and the ignition timing is shifted to the advance side at the time of starting. This is because, when the ignition timing is retarded, the ISC valve 18 increases the opening degree to increase the intake air amount to compensate for the reduction in torque accompanying the ignition timing, and tries to maintain the idle rotation speed. The starting torque is being increased by shifting the timing to the advance side.
Specifically, the retard amount of the ignition timing is 1 before compression top dead center.
It is set to 10 deg from 0 deg to 0 deg. The retard amount is determined in consideration of the lead angle responsiveness and the flammability during the retard.

During the valve timing control of the exhaust valve, the second timing (open: 50 deg BBDC, closed: 15 deg ATD) in the low-load, low-speed rotation state
C) is selected and in other states the first timing (open; 50 deg BBDC, closed; 5 deg ATD)
C) is selected. This is to expand the valve overlap period in the no-load low-speed state to promote the internal EGR action described in the throttle control of the throttle valve 26, that is, to promote the vaporization and atomization of the fuel by increasing the residual gas. . The valve timing of the intake valve is open; 5 deg.
BBDC, closed; 50 degABDC.

Next, as a specific example, a displacement of 1.5 (l)
Startability (from 1000 rpm to 250 rpm) with a displacement of 3 (l) (hereinafter referred to as 3 (l) engine) using an engine (hereinafter referred to as a 1.5 (l) engine).
m. 750r. p. m. Will be described. As is apparent from FIG.
When the (l) and 3 (l) engines are kept at the same engine speed and the same load is applied, the drop of the engine speed is larger in the 1.5 (l) engine.
In 1.5 (l) engine, in order to obtain a the start, since friction loss is about twice is required intake air charging amount Q ₂ 'is about twice for Q ₁ in FIG. 4 . That is, in the engine 1.5 (l) engine, drive resistor P _f is almost identical with the corresponding rotation range, 1
000r. p. m. The amount of intake air (the amount of intake air) used to consume torque for the engine reaches the engine stall at (Equation 1), but in order to avoid the engine stall, it is 750 r. p. m. If the engine speed落込free up, Q ₂ is required.

(Equation 1) That is, (Equation 2), which is about 750 r. p. m. If the engine is allowed to start with a drop in engine speed up to 1000 r.p.m. p. m.
When nothing is done (without exhaust throttle and ignition timing retard)
At least 50% higher than the intake charge of 1.
Five times the intake charge is required.

(Equation 2)

This ensures the throttling action of the throttle valve 26 and the retard action of the ignition timing. That is, since the intake air filling amount based on the throttle action of the throttle valve 26 has an upper limit of 400 mmHg exhaust pressure as described above based on the throttle, as shown in FIG.
From the reference filling amount (discharge pressure 0 mmHg ignition timing 10 degB
It is about 1.3 times the intake charge amount at the time of TDC.

On the other hand, the intake charge based on the retard action of the ignition timing is about 1.2 times the reference charge from FIG. 5 because the retard amount is 10 deg.
Therefore, from both of the above, about 1.
This means that the intake air amount is five times as large.

In addition, it is needless to say that the throttle action of the throttle valve 26 occupies a large specific gravity with respect to the retard action of the ignition timing in comparison with the amount of intake air. As a result, the internal EGR function also works, and the decrease in the engine speed is 750 r.
p. m. Up to a higher engine speed, ie approximately 800 r.p.m. p. m. It is considered that the vehicle will start.

As shown in FIG. 6, the present embodiment is different from the ideal embodiment b in comparison with the conventional case c in such a series of changes in the rotational speed (engine speed), the amount of intake air, and the throttle opening. Is shown. Based on the contents of this embodiment of FIG. 6, as shown in FIG. 7, at the time of starting, the starting torque is increased, and the startability is further improved.

Although the embodiments have been described above, the present invention includes the following embodiments. In the exhaust system 20, a throttle valve 26 is provided downstream of the main three-way catalyst 27 so that the effective area of the exhaust passage is reduced by the throttle valve 26 when the engine is cold. According to this, the temperature of the pre- and main three-way catalysts 23 and 127 rises earlier in the cold state in the no-load low-speed state based on the above-described operation. The variable silencer 29 is used as exhaust resistance adjusting means by switching its path. The throttle 16 is used as intake air amount adjusting means in a no-load low-speed region.

[0023]

As is apparent from the above description, according to the present invention, it is possible to provide an engine intake air amount control device capable of further improving the startability. Further, the catalyst can be activated early.

[Brief description of the drawings]

FIG. 1 is an overall configuration diagram of an engine according to an embodiment.

FIG. 2 is a diagram showing valve timing in the embodiment.

FIG. 3 is a characteristic diagram showing a relationship between an exhaust pressure and a throttle opening degree of a throttle valve 26.

FIG. 4 is a diagram illustrating the operation of the embodiment.

FIG. 5 is a characteristic diagram showing the effects of ignition timing and exhaust pressure on intake air charge.

FIG. 6 is a diagram showing a change over time of a rotation speed, an intake air filling amount, and a throttle opening;

FIG. 7 is an explanatory diagram illustrating an increase in starting torque when the throttle valve is opened from a closed state.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Engine main body 7 Exhaust valve timing variable mechanism 17 Bypass passage 18 ISC valve 20 Exhaust system 22 Common exhaust passage 25 Sensor group 26 Throttle valve 28 Drive actuator U Control unit O / L Valve overlap period

──────────────────────────────────────────────────続 き Continuation of front page (51) Int.Cl. ⁷ Identification code FI F02D 41/06 310 F02D 41/06 310 320 320 43/00 301 43/00 301B 301K 301Z F02P 5/15 F02P 5/15 E ( 58) Field surveyed (Int.Cl. ⁷ , DB name) F02D 9/00-11/10 F02D 13/00-28/00 F02D 29/00-29/06

Claims (5)

(57) [Claims] 1. A fuel injection amount and a correspondence relationship are set so that an engine speed becomes a target speed in a no-load low-speed region.
In an intake air amount control device for an engine having an intake air amount adjusting means for adjusting an intake air amount, a catalyst provided in an exhaust system for purifying exhaust gas, and an exhaust resistance provided in the exhaust system for increasing / decreasing exhaust resistance. Adjusting means, ignition timing adjusting means for adjusting ignition timing, starting state detecting means for detecting the starting state of the vehicle, operating state detecting means for detecting the operating state of the engine, the operating state detecting means and the starting state Receiving the signal from the detection means, the
Sometimes, the exhaust resistance is increased and the ignition timing is
The intake air based on the intake air amount adjusting means is retarded.
While increasing the air volume, the exhaust resistance is reduced when starting.
Control means for shifting the ignition timing to the advanced side, and an intake air amount control device for an engine. 2. The intake air amount control device for an engine according to claim 1, wherein the engine is a water-cooled engine. 3. The engine according to claim 1, further comprising: a warm-up detection unit that detects a warm-up state of the engine, wherein the control unit increases the exhaust resistance in the no-load low-rotation state as the engine becomes colder. An intake air amount control device for an engine, which is set. 4. A valve overlap period changing means for changing a period of a valve overlap in which both an intake valve and an exhaust valve are in an open state, and a warm-up detecting a warm-up state of the engine. Wherein the control means is set so as to increase the valve-overlap period when the engine is in a no-load low-rotation state during a warm state. Engine intake air amount control device. 5. The apparatus according to claim 3, further comprising a valve overlap period changing means for changing a valve overlap period in which both the intake valve and the exhaust valve are open. An intake air amount control device for an engine, wherein the period of valve overlap is set to be increased when the engine operation state is a no-load low rotation state.