JPH04194330A - Valve timing controller for engine - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a valve timing control device for an engine.

(Prior art) Conventionally, in a gasoline engine for a car, when the engine is cold at the initial stage of startup, the temperature of the engine itself is low (there are many unburned hydrocarbons generated in the cylinders, and the temperature of the catalyst is also low. Therefore, the temperature of the catalyst is low. Because of the poor purification performance of
The engine speed is increased until the coolant temperature reaches a predetermined temperature, causing the engine temperature to rise faster.

Additionally, by locating the catalyst immediately after the exhaust manifold, the temperature of the catalyst increases faster.

(Problem to be Solved by the Invention) However, in the conventional example described above, even if the engine speed is increased or the catalyst installation position is changed, a large amount of harmful exhaust gas is emitted when the engine is initially cold. There is.

(Means for Solving the Problems) The present invention has been made for the purpose of solving the above-mentioned problems, and includes the following configuration as a means for solving the above-mentioned problems. That is, in an engine valve timing control device including a valve timing variable means,
When the engine is cold, the exhaust valve opens later than when the engine is warm, and the exhaust valve opens after the bottom dead center of the piston.

(Function) In the above configuration, the piston compresses and heats the burnt gas, and the burnt gas stays in the combustion chamber for a long period of time, thereby functioning to promote warming up of the engine body.

(Embodiments) Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 is a diagram showing the configuration of essential parts of an engine valve timing control device (hereinafter referred to as the device) according to an embodiment of the present invention. In the figure, a piston is sliding in a cylinder 20 formed in an engine body l.
An intake boat 8 and an exhaust port 9 are supported on the cylinder 20 . Further, the intake valve 3 and the exhaust valve 2 open and close the intake boat 8 and the exhaust port 9, respectively. The opening/closing drive is performed by a cam mechanism 4, and this cam mechanism 4 is
As will be described later, the opening/closing timing of the exhaust valve 2 or the intake valve 3 is changed by the variable valve timing mechanism 5.

The cam portion 4a of the cam mechanism 4 is composed of cams having two different phases, and the variable valve timing mechanism 5
The cam of the cam part 4a is selectively switched according to a control signal from the engine control part (EC, U) 13.

An air flow meter 10 is provided upstream of the intake boat 8, and a throttle valve 15 is provided downstream thereof. Further, a turbocharger 17 is provided on the downstream side of the exhaust port 9.
, and catalyst 11 are located. The intake air amount from the air flow meter 10 is input to the ECU 13 as an intake air amount signal, and the boost pressure from the boost pressure sensor 14, the catalyst temperature from the catalyst temperature sensor 12, and the cooling water from a cooling water temperature sensor (not shown) are inputted to the ECU 13. The temperature is also input to the ECU 13.

The ECU 13 sends an ignition time control signal to the distributor and outputs a valve timing control signal to the variable valve timing mechanism 5. Also, ECU13
stores valve timing switching patterns and the like in a built-in memory 13a.

Next, switching of valve timing in the apparatus of this embodiment will be explained.

FIGS. 2(a) and 2(b) are diagrams schematically showing the interrelationship between opening and closing of the valve and piston position in the device of this embodiment, and FIG. , and a diagram showing a valve timing switching pattern during warm operation.

In the valve timing switching pattern shown in FIG. 2(C), the left side corresponds to the lift curve of the exhaust valve (abbreviated as Ex), and the right side corresponds to the lift curve of the intake valve (abbreviated as In). The horizontal axis represents the crank angle, and T
DC means top dead center and BDC means bottom dead center. Moreover, the vertical axis is the valve lift (lift amount).

FIG. 3 is a flowchart showing the valve timing control procedure in this embodiment. In the same figure, ECU
13 is the engine rotation speed Ne in step S1, the intake pipe pressure pb in step S2, and the cooling water temperature T in step S3.
Enter w. Then, in step S4, the cooling water temperature Tw
It is determined whether the engine is being warmed up by comparing the temperature T w j with the temperature T w j that determines whether the engine is warmed up.

If the determination in step S4 is No, that is, if the cooling water temperature Tw is higher than the temperature Twj at which warm-up completion is determined, the engine is determined to be in a warm state and the process proceeds to step S5, in which the exhaust valve 2
For this, the warm valve timing shown in FIG. 2(c) is selected. That is, as shown in FIG. 2(a), the exhaust valve 2 is opened to discharge exhaust gas before the piston 16 moves to the bottom dead center (BDC).

If the determination in step S4 is YES, the engine is assumed to be in a cold state and the process proceeds to step S6, where the cold state timing shown in FIG. 2(C) is selected as the valve timing. That is, exhaust gas discharge starts after the bottom dead center of the piston 16.

In step S7, the ECU 13 outputs a control signal to the variable valve timing mechanism 5 according to the valve timing selected in step S5 or step S6.

In this way, when the valve timing is cold, the amount of combustion gas that the piston 16 must push out and exhaust is larger than when it is warm (and it receives more energy from the piston 16. Therefore, the exhaust gas temperature also increases). As the catalyst warms up, the exhaust gas purification performance improves.

In addition, since the combustion gas remains in the cylinder for a long time, warming up of the engine body is promoted, and the amount of harmful exhaust gas generated in the cylinder is reduced.

As explained above, according to this embodiment, when the engine is cold, the exhaust valve opening timing is set after the bottom dead center of the piston to compress and heat the burnt gas, and the burnt gas after combustion in the cylinder This has the effect of increasing the length of time the engine stays in the engine, thereby promoting warm-up of the engine itself.

It should be noted that the present invention is not limited to the above embodiments,
The valve timing subsection according to the present invention is more effective when applied to, for example, a turbo engine.

If the engine is equipped with a turbo, the exhaust resistance is high, and the exhaust temperature is increased by compression heating of the piston and frictional heat caused by the exhaust resistance. Therefore, this increase in exhaust gas temperature promotes warming up of the catalyst.

(Effects of the Invention) As explained above, according to the present invention, by opening the exhaust valve after the piston bottom dead center when the engine is cold, the burnt gas is compressed and the combustion chamber is compressed. The longer residence period of burnt gas has the effect of promoting warm-up of the engine.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the main part configuration of an engine valve timing control device according to an embodiment of the present invention, and FIGS. Figure 2 (C) is a diagram showing valve timing switching patterns when the engine is cold and when the engine is warm, and Figure 3 is a diagram showing the valve timing control procedure in the example. It is a flowchart which shows. In the diagram, 1...engine body, 2...exhaust valve, 3...
- Intake valve, 4... Cam mechanism, 5... Variable valve timing mechanism, 6... Distributor, 8... Intake boat, 9... Exhaust boat, 12... Catalyst temperature sensor, 14. ... Boost pressure sensor, 16... Piston, 17... Turbocharger, 20... Cylinder. Patent 8 applicant Mazda Motor Corporation jJ”ml 4m, 4!,, 711b I JP
, Y factor = (C) Figure 2

Claims (1)

[Scope of Claims] In an engine valve timing control device including a valve timing variable means, when the engine is cold, the opening timing of the exhaust valve is delayed compared to when the engine is warm, and the opening timing of the exhaust valve is adjusted to the piston. A valve timing control device for an engine, characterized in that the timing is set after bottom dead center.