JPH05215001A - Warming-up promoting device for engine - Google Patents

Abstract

PURPOSE:To improve fuel consumption performance and warming-up of an engine by high temperature exhaust gas. CONSTITUTION:An engine has a bypass passage 17 which bypasses a throttle valve 16 arranged in an intake passage 11, and an ISC valve 18 which is installed in the bypass passage 17. A throttle valve 26 is provided in an exhaust passage 22, while a driving actuator 28 is provided for driving the throttle valve 26. An engine cooling water temperature and an engine load, etc., are detected by sensor groups 25. A control unit U controls an exhaust valve timing variable mechanism 7 and the driving actuator 28 under a loadless, low speed and cold condition, such that a valve overlapping time is elongated and the throttle valve 26 is throttled compared to a hot condition.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an engine warm-up promoting device which accelerates engine warm-up.

[0002]

In Japanese Patent Laid-Open No. 62-67244, a bypass passage for bypassing a throttle valve is provided in an intake system,
A technique is disclosed in which a bypass valve for adjusting the amount of intake air is provided in the bypass passage to adjust the engine speed in the no-load low speed region.

Further, Japanese Patent Laid-Open No. 2-115537 discloses a valve opening in which both the intake valve and the exhaust valve are open.
There is a disclosure of valve-overlap period changing means for changing the wrapping period.

Further, Japanese Patent Laid-Open No. 1-159431 discloses an exhaust valve timing variable mechanism for changing the valve timing of the exhaust valve. By the way, this exhaust valve timing mechanism is designed to change the opening timing of the exhaust valve, so that the exhaust valve is opened at a later timing when cold than when warm.

[0005]

By the way, when the engine is cold, the combustion state inside the engine is unstable and the harmful components in the exhaust gas also tend to increase. Therefore, shortening the time required for warming up the engine is effective as a countermeasure for emission itself.

Therefore, an object of the present invention is to provide an engine warm-up promoting device which improves the engine warm-up property.

[0007]

In order to achieve the above object, the present invention adopts the following constitution. That is,

A bypass passage for bypassing a throttle valve arranged in the intake system, and a bypass passage interposed in the bypass passage,
In an engine provided with a bypass valve for adjusting the engine speed in the no-load low-speed region, a valve-overlap period changing means for changing the period of the valve-overlap in which both the intake valve and the exhaust valve are open. A throttle adjusting means for adjusting the throttle valve arranged in the exhaust system, a warm-up detecting means for detecting a warm-up state of the engine, an operating state detecting means for detecting an operating state of the engine, and the operating-state detecting means. And a signal from the warm-up detection means, the engine operating state is a no-load low-rotation state, and when the engine is cold, the valve overlap period is extended as compared to when the engine is warm, and the throttle valve is throttled. And a control means for changing to.

[0009]

With the above-described structure, the throttle valve is changed in the throttle direction when the engine is cold in the no-load low-rotation state, so that the exhaust work of the engine increases and the opening degree of the bypass valve increases to compensate for this. As a result, the intake amount increases, that is, the fuel injection amount increases, the temperature of the exhaust gas discharged from the engine rises, and the heat of the exhaust gas is used to raise the temperature of the engine cooling water passing through the cylinder head. Will be done. In addition, at this time, the valve overlap period is extended at the same time, so that the residual gas in the engine is increased and the vaporization and atomization of the fuel is promoted. Therefore, it is possible to improve the engine warm-up property while improving the fuel economy.

[0010]

Embodiments of the present invention will be described below with reference to the accompanying drawings. In FIG. 1, reference numeral 1 is 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
Has two intake ports and two exhaust ports that open to the combustion chamber (not shown), and these ports are opened and closed by the intake valve 3 or the exhaust valve 4.

The valve operating system for driving the intake valve 3 and the exhaust valve 4 to open and close will be described. The intake valve 3 is opened and closed by the 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 has a first valve timing (the timing shown by the one-dot chain line in FIG. 2) and a second valve timing (the solid line in FIG. 2) by the variable valve timing mechanism 7 attached to the exhaust camshaft 6. It is possible to switch to the timing shown by.

Comparing the first valve timing with the second valve timing, the second valve timing shows that the valve closing timing is delayed compared with the first valve timing, and the exhaust valve is closed late. Then, 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.
Is being expanded.

The 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.
And a surge tank 12 serving as an intake expansion chamber, and an independent intake passage 13, and in the common intake passage 11 from the upstream side to the downstream side, an air cleaner 14, an air flow meter 15, and a throttle valve in this order. 16, a fuel injection valve (not shown), etc. are arranged, and a bypass passage 17 for bypassing the throttle valve 16 is attached to the common intake passage 11. The bypass passage 17 has a bypass for controlling the idle speed. An ISC valve 18 as a valve is provided. Since the specific contents of the idle speed control using the ISC valve 18 are the same as the conventional ones, 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 purifies exhaust gas in order from the upstream side to the downstream side. A catalyst 23, an exhaust gas reservoir 24, a throttle valve 26, a main three-way catalyst 27, a silencer (not shown), etc. are arranged. Of these, the throttle valve 26 is adapted to be driven by a drive actuator 28.

Reference numeral U shown in FIG. 1 is a control unit composed of, for example, a microcomputer, and is provided with a CPU, a ROM, a RAM and the like as is known. To the control unit U, various signals representing engine cooling water temperature, engine load, etc. are input from the sensor group 25 in addition to the signal representing the intake air amount from the air flow meter 15. On the other hand, a control signal is output from the control unit U to the ISC valve 18, the exhaust valve timing changing mechanism 7, the drive actuator 28 and the like.

Valve Timing Control of Exhaust Valve The valve timing of the exhaust valve 4 is controlled based on the map shown in FIG. (1) No-load low rotation region I The valve timing is changed between warm and cold,
At the warm time, the first timing (timing shown by the one-dot chain line in FIG. 2: valve overlap is small) is selected,
On the other hand, the second timing (timing shown by the solid line in FIG. 2: large valve overlap) is selected during cold operation.

(2) High load low rotation and high load medium rotation region III In this region III, the valve timing of the exhaust valve is set to the first timing (small overlap),
The filling efficiency is improved.

(3) Region II other than the above regions I and III In this region II, the valve timing of the exhaust valve is set to the above second timing (large overlap), and in the low / medium load region, Fuel consumption improvement by increasing EGR, NO _x
In the high load range, the scavenging efficiency is increased and the output is improved.

Throttle Control of Throttle Valve 26 The throttle valve 26 is throttled when it is cold in the no-load low rotation region I (see FIG. 3), and its throttle state is, for example, a fully closed state.

Ignition timing control 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 added to the basic ignition timing. Then, the final ignition timing is determined. Then, on the premise of the above, in the present embodiment, the no-load low rotation region I
In FIG. 3, the cold ignition timing is set during cold, and the cold ignition timing is, as shown in FIG. 4, about 10 deg to about 20 deg after compression top dead center. It is said that.

That is, the contents of the ignition timing control will be described by limiting to the no-load low rotation speed region I. During warm time, ignition is performed before the compression top dead center (compression top dead center) as in the conventional case. Ignition is performed at a timing that is retarded more than the ignition timing at the time of warm time (about 10 deg before).

The above control contents are summarized as follows in the no-load low speed region I. Warm state Barubuo --overlap: state of the small throttle valve 26: open state ignition timing: time between the same cold as conventional Barubuo --overlap: state of the large stop valve 26: stop state ignition timing: larger Rita than during the warm - de

Therefore, in the no-load low rotation speed region I, the combustion stability is ensured under a small valve overlap period during the warm period. On the other hand, when cold,
In order to compensate for the increase in exhaust work of the engine due to the throttle of the throttle valve 26, the opening degree of the ISC valve 18 is increased to increase the intake air amount, that is, the fuel injection amount. Moreover, in the present embodiment, during this cold state, the combustion state becomes slower due to the increase in the residual gas accompanying the expansion of the valve overlap period, and at the same time, due to the retard of the ignition timing,
As shown in FIG. 4, the combustion state becomes a “afterburning” state in which the combustion state occurs in the latter half of the expansion stroke. On the other hand,
Due to the increase in the residual gas accompanying the expansion of the valve overlap period, the vaporization and atomization of the fuel is promoted.

Therefore, the temperature of the exhaust gas discharged from the engine 1 becomes high due to the cold control in the region I, and the high-temperature exhaust gas passes through the exhaust port, so that the cylinder is cooled. A large amount of heat is transferred to the head (cooling water that passes through the cooling water passage in the head), which also promotes warm-up of the engine 1.
Further, the pre- and main three-way catalysts 23 and 27 arranged in the exhaust system 20, especially the pre-three-way catalyst 23, are activated early,
The catalytic action is exerted within a short period of time to start purification of exhaust gas. Moreover, in this case, the fuel economy can be improved by promoting the vaporization and atomization of the fuel.

FIG. 5 shows another embodiment of the present invention. The mechanical structure of this embodiment is the same as that of the first embodiment (FIG. 1).

The valve timing of the exhaust valve 4 in this embodiment can be switched between the first timing and the second timing, as in the first embodiment.

Explaining only in the no-load low rotation region I, the valve timing of the exhaust valve 4 is the same first timing as the first embodiment (the timing shown by the one-dot chain line in FIG. -Small barp is selected,
On the other hand, during cold weather, the second timing shown by the solid line in FIG. 5 is selected. Here, as can be understood from FIG. 5, the valve timing in the cold state is delayed compared with the timing in the warm state (first timing), and the valve overlap period is expanded. There is. Further, the valve opening timing in the cold state is advanced as compared with that in the warm state so that the high temperature gas in the expansion stroke is discharged to the exhaust system 20. The temperature of the three-way catalyst 23 will rise more quickly due to the exhaust gas having a temperature higher than this.

Further, since the expansion of the valve overlap is realized by the late closing of the exhaust valve 4, the IS
It is possible to prevent the control amount of the C valve 18 from being forced. In other words, when the expansion of the valve overlap in the cold state is realized by advancing the opening timing of the intake valve 3 (changing the phase of the valve timing of the intake valve 3), the intake valve 3 can be correspondingly expanded. Since the valve closing timing becomes early, the intake amount decreases, and ISC is added to compensate for this.
The valve opening amount of the valve 18 becomes extremely large, and the ISC valve 18 (bypass passage 17) may not be able to completely compensate.

Although the embodiment of the present invention has been described above, the present invention is not limited to this and includes the following modifications. That is, in the exhaust system 20, a throttle valve may be arranged on the downstream side of the main three-way catalyst 27, and the effective area of the exhaust passage may be reduced by the throttle valve when it is cold. According to this, in the region I, when the engine is cold, the pre- and main three-way catalysts 2 are produced on the basis of the above-mentioned action.
3, 127 will have its temperature rise earlier.

[0030]

As is clear from the above description, according to the present invention, it is possible to improve the fuel economy and improve the warm-up of the engine by the high temperature exhaust gas.

[Brief description of 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 first embodiment.

FIG. 3 is a control map used for controlling the embodiment.

FIG. 4 is an explanatory view of the operation of the embodiment.

FIG. 5 is a diagram showing valve timing in the second embodiment.

[Explanation of symbols]

 1 engine body 2 cylinder 3 intake valve 4 exhaust valve 7 exhaust valve timing variable mechanism 10 intake system 11 common intake passage 16 throttle valve 17 bypass passage 18 ISC valve 20 exhaust system 22 common exhaust passage 23 pre-three-way catalyst 25 sensor group 26 throttle Valve 27 Main three-way catalyst 28 Drive actuator U Control unit O / L Valve overlap period

Claims (5)

[Claims] 1. An engine provided with a bypass passage for bypassing a throttle valve arranged in an intake system, and a bypass valve interposed in the bypass passage for adjusting an engine speed in a no-load low rotation region. , The valve overlap period changing means for changing the period of the valve overlap in which both the intake valve and the exhaust valve are in the open state, the throttle adjusting means for adjusting the throttle valve arranged in the exhaust system, and the engine A warm-up detecting means for detecting a warm-up state, an operating state detecting means for detecting an operating state of the engine, a signal from the operating state detecting means and the warm-up detecting means, and the operating state of the engine is no load low. In the rotating state, when cold, the period of valve overlap is extended as compared with during warm time, and the control means for changing the throttle valve in the throttle direction is provided. Warm-up facilitating device for an engine, characterized in that. 2. The warm-up promoting device for an engine according to claim 1, wherein the engine is a water-cooled engine. 3. The engine according to claim 1, wherein a catalyst for purifying exhaust gas is provided in an exhaust system of the engine, and the throttle valve is provided downstream of the catalyst. Engine warm-up promoting device. 4. The engine according to claim 1, further comprising exhaust timing variable means for changing a valve timing of an exhaust valve, the exhaust timing variable means being controlled by the control means so that the operating state of the engine is unloaded. An engine warm-up promoting device for an engine, which is in a low rotation state, and is configured to be an exhaust gas early opening mode in which an exhaust valve is opened earlier in a cold state than in a warm state. 5. The engine according to claim 1, wherein the valve overlap period changing means is constituted by an exhaust valve timing variable mechanism for switching the valve timing of the exhaust valve between a first valve timing and a second valve timing. When the operating state is in the no-load low rotation state, the first valve timing is set during the warm time, the second valve timing is set during the cold state, and the second valve timing is set to the first valve timing. In comparison, the engine warm-up promoting device is characterized in that the opening timing of the engine is early exhaust, and the closing timing of the engine is late.