JPH04159428A - Exhaust gas purification device of internal combustion engine - Google Patents

Abstract

PURPOSE:To obtain increase in a temperature of a catalytic converter in an early stage and facilitate actuation of a catalyst remarkably by advancing an open timing of an exhaust valve after a cold start. CONSTITUTION:A variable valve timing actuator 15 which serves as a major a part of a variable timing mechanism is mounted on the front end part of a cam shaft 14 on the exhaust side in a DOHC type valve system, in an internal combustion engine having a catalytic converter 4 interposed in an exhaust passage 3, and a variable valve timing control valve 16 is arranged in an oil pressured passage led to the actuator 15. The variable valve timing control valve 16 is ON/OFF-controlled based on the detection signal of a water temperature sensor 17 by a control unit 18. When an internal combustion engine is started in its cold condition, the variable timing mechanism is controlled to a phase on lead side. Consequently, the pressure and the temperature of exhaust gas which flows into an exhaust system are increased, and the temperature of the catalytic converter 4 is increased in an early stage so that the converter may be activated.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention relates to an exhaust purification device for an internal combustion engine equipped with a catalytic converter in the exhaust system, and in particular to an exhaust purification device for reducing HC, etc. immediately after engine cold start. Regarding equipment.

(Prior art) It is known that harmful components such as HC contained in the exhaust gas of an internal combustion engine are generated in large quantities when the internal combustion engine is not sufficiently warmed up, that is, immediately after a cold start. However, when using a catalytic converter, which is a very common method, immediately after a cold start, the temperature of the catalytic converter does not rise to the catalyst activation temperature, so sufficient exhaust purification effect cannot be obtained, and HC etc. There is a problem that there is a risk that it may be discharged into the water.

Therefore, as seen in Japanese Patent Application Laid-Open No. 52-24616, it has been conventional practice to arrange a catalytic converter on the upstream side of the exhaust system, for example at the exhaust boat outlet, to speed up the temperature rise of the catalytic converter. It is considered.

(Problem to be solved by the invention) However, if the catalytic converter is placed upstream of the exhaust system as in the above conventional method, the temperature rises quickly immediately after startup, but at the same time, the catalytic converter becomes hot during high-speed, high-load operation, etc. The disadvantage is that the durability of the catalytic converter is significantly reduced due to continuous exposure to the catalytic converter.

Incidentally, Japanese Patent Application Laid-Open No. 127716 discloses a valve timing control device that switches the opening/closing timing of an exhaust valve to an advanced phase during high-load operation. Although it contributes to an increase in output, it cannot be expected to improve exhaust purification performance during cold conditions, and it has no effect, especially when low-load operation is continued.

(Means for Solving the Problems) An exhaust gas purification device for an internal combustion engine according to the present invention includes a temperature sensor for detecting the temperature of the internal combustion engine or the catalytic converter. , a variable valve timing mechanism that retards the opening timing of an exhaust valve, and control that controls the variable valve timing mechanism to an advanced phase until the temperature detected by the temperature sensor reaches a predetermined temperature after a cold start of the internal combustion engine. It is characterized by being equipped with a circuit.

(Operation) When the internal combustion engine is started in a cold state, the variable valve timing mechanism provided for the exhaust valve is controlled to an advanced phase.

In a four-stroke internal combustion engine, the exhaust valve opening timing is set in the middle of the expansion stroke, so if this timing is advanced, the pressure of the exhaust gas flowing into the exhaust system will increase, and the temperature of the exhaust gas will also increase. Therefore, the temperature of the catalytic converter rises early and becomes activated.

Then, when the temperature detected by the temperature sensor reaches a predetermined temperature,
The opening timing of the exhaust valve is returned to its normal phase.

(Example) Hereinafter, an example of the present invention will be described in detail based on the drawings.

FIG. 1 is a configuration explanatory diagram showing an embodiment of the present invention, in which 1 indicates an internal combustion engine, 2 indicates an intake passage thereof, and 3 indicates an exhaust passage thereof.

In the exhaust passage 3, a catalytic converter 4 using, for example, a three-way catalyst is installed on a relatively downstream side (for example, under the floor of the vehicle), and a muffler 5 is disposed further downstream. Further, an air-fuel ratio detection sensor 6 is installed upstream of the catalytic converter 4.

A throttle valve 7 is installed in the intake passage 2, and an air flow meter 8 of, for example, a hot wire type is installed upstream of the throttle valve 7.

Note that 9 is an air cleaner. In addition, the fuel injection valve lO supplies fuel to each cylinder toward the intake port of each cylinder.
is provided.

The internal combustion engine 1 is a D engine in which the intake valve 11 and the exhaust valve 12 are each driven by an independent camshaft 13.14.
It has an OHC type valve operating mechanism, and a variable valve timing actuator 15, which is a main part of the variable valve timing mechanism as will be described later, is attached to the front end of the exhaust side camshaft 14, and the actuator 15 A variable valve timing control valve 16 (see FIG. 2) is disposed in the hydraulic path leading to.

Further, in this embodiment, the cooling water temperature is detected as the engine temperature, and a water temperature sensor 17 for this purpose is attached to, for example, the water jacket of the internal combustion engine.

The control unit 18 configuring the control circuit of the variable valve timing mechanism uses a so-called microcomputer system, and turns on the variable valve timing control valve 16 of the variable valve timing mechanism based on the detection signal of the water temperature sensor 17. , is controlled to be OFF. The control unit 18 is also configured to comprehensively execute various controls of the internal combustion engine 1, such as air-fuel ratio control, that is, injection amount control of the fuel injection valve 10 and ignition timing control, based on detection signals from various sensors. It has become.

FIG. 2 shows details of the variable valve timing mechanism. The variable valve timing actuator 15 disposed at the front end of the camshaft 14 includes an inner cylinder 21 fixed to the camshaft 14 by a mounting port 24, and a cam pulley part 23 for a timing belt (not shown) on the outer periphery. The cup-shaped outer cylinder 22 is the main body, and both are arranged at a predetermined angle (
For example, they are fitted so that they can rotate relative to each other by about 10°. A ring-shaped piston 25 is interposed between the outer circumference of the inner cylinder 21 and the inner circumference of the outer cylinder 22.

This piston 25 has helical gear-like threads on its inner and outer circumferential surfaces, and these threads similarly mesh with threads formed on the outer circumferential surface of the inner cylinder 21 and the inner circumferential surface of the outer cylinder 22. Due to this helical gear-like engagement, the inner cylinder 21 and the outer cylinder 22 rotate relative to each other as the piston 25 moves in the axial direction. The cam pulley section 23 is linked to a crank pulley via a timing belt (not shown).

Further, the piston 25 is always urged forward by a return spring 26, and a hydraulic chamber 27 is defined between the piston 25 and the front end surface of the outer cylinder 22 so as to counteract this urging force. .

On the other hand, the camshaft 14 is provided with a lubricating oil passage 28 along the axial direction, and the hydraulic chamber 27 communicates with the lubricating oil passage 28 via an oil passage 29 in the mounting bolt 24. Further, high-pressure lubricating oil is constantly supplied to the lubricating oil passage 28 from the cylinder head side via a cam journal portion (not shown) and a communication hole 28a.

The variable valve timing control valve 16 is connected to the lubricating oil passage 2.
8 and the drain boat 35 on the low pressure side to ON/OFF control the hydraulic pressure acting on the variable valve timing actuator I5, and is a cylindrical valve case with a communication hole 30 opened. 31 and
a plunger 32 that slides inside the valve case 31 to open and close the communication hole 30; a return spring 33 that biases the plunger 32 in the direction in which the communication hole 30 is opened;
The solenoid 34 slides the plunger 32 in the closing direction against the biasing force of the return spring 33.

Next, the operation of the above embodiment will be explained.

After the internal combustion engine 1 starts, if the cooling water temperature detected by the water temperature sensor 17 is below a predetermined temperature, the solenoid 34 is turned on based on the control signal from the control unit 18, and the communication hole 30 is closed. Ru. Therefore, the oil pressure in the lubricating oil passage 28 and, in turn, the oil pressure in the hydraulic chamber 27 becomes high, and the piston 25 slides against the biasing force of the return spring 26. As a result, the inner cylinder 21 is connected to the outer cylinder 22.
The exhaust side cam shirt 14 rotates relative to the crank angle, and the phase of the exhaust side cam shirt 14 changes to the leading side by about 10 degrees, for example.

Therefore, the opening/closing timing of the exhaust valve 12 is indicated by the broken line (A) in FIG.
As shown in , the timing is earlier than in the initial state, and as a result, the temperature of the exhaust gas flowing into the exhaust system becomes higher than in the case of normal opening/closing timing. As a result, the heating temperature of the catalytic converter 4 in the exhaust passage 3 is accelerated, and the activation temperature is reached early, thereby making it possible to purify the exhaust gas, especially HC, which becomes a problem at low temperatures.

Then, when the engine cooling water temperature reaches a predetermined temperature, the solenoid 34 of the variable valve timing control valve 16 is turned off, and the oil pressure in the lubricating oil passage 28 is released. Therefore,
The piston 25 returns to the initial position by the biasing force of the return spring 26, and the inner cylinder 21 rotates relative to the outer cylinder 22 in the opposite direction to reach the initial phase. In other words, the opening/closing timing of the exhaust valve is the normal opening/closing timing shown by the solid line (b) in FIG. 3, and excessively high temperature exhaust gas does not continue to be discharged.

FIG. 4 shows, as an example, the temperature rise characteristics of the catalytic converter 4 placed under the vehicle floor after a cold start, specifically the change in the catalytic converter population temperature, in comparison with a conventional one (solid line). It is. In this example, the exhaust valve opening/closing timing is controlled to the advanced phase until 30 seconds have elapsed from startup, but it is not possible to quickly raise the temperature of the catalytic converter 4 by controlling the phase in such a very short period of time. HC, etc. can be reduced.

In the above embodiment, the cooling water temperature is detected as the engine temperature, but oil temperature, exhaust temperature, etc. may be used instead. Alternatively, the temperature of the catalytic converter 4 itself may be detected to control the phase of the exhaust valve opening/closing timing.

(Effects of the Invention) As is clear from the above explanation, the exhaust purification device for an internal combustion engine according to the present invention aims to raise the temperature of the catalytic converter early by advancing the opening timing of the exhaust valve after a cold start. Therefore, activation of the catalyst is greatly promoted, and exhaust emissions, especially HC, which tend to increase when the engine temperature is low, can be significantly reduced. Furthermore, since the catalytic converter can be placed downstream of the exhaust system and is not exposed to excessively high temperatures, the durability of the catalytic converter is improved.

[Brief explanation of the drawing]

Fig. 1 is a configuration explanatory diagram showing one embodiment of the present invention, Fig. 2 is a sectional view showing a variable valve timing mechanism, Fig. 3 is a valve lift characteristic diagram of the intake and exhaust valves of this embodiment, and Fig. 4 is FIG. 3 is a characteristic diagram showing a change in the inlet temperature of the catalytic converter after a cold start in comparison with a conventional one. l... Internal combustion engine, 4... Catalytic converter, 14...
- Exhaust side camshaft, 15... Variable valve timing actuator, 16... Variable valve timing control valve, 17... Water temperature sensor, IS... Control unit. Figure 2 jU,)1

Claims (1)

[Claims] (1) In an exhaust gas purification system for an internal combustion engine equipped with a catalytic converter in the exhaust system, a temperature sensor that detects the temperature of the internal combustion engine or the catalytic converter, a variable valve timing mechanism that retards the opening timing of the exhaust valve, and an internal combustion engine An exhaust purification device for an internal combustion engine, comprising: a control circuit that controls the variable valve timing mechanism to an advanced phase until the temperature detected by the temperature sensor reaches a predetermined temperature after a cold start.