JPH04194331A - Valve-timing controller apparatus for engine - Google Patents

Abstract

PURPOSE:To promote warming of an engine to improve the exhaust gas purification performance, by making small the valve overlap amount throughout all operational region during a cold time period of the engine when the engine is in a low-revolution/low-load state. CONSTITUTION:An amount of valve overlap can be made variable by a variable valve timing mechanism 5. When the engine is in a low-revolution/low-load region, ECU 13 controls the variable valve timing mechanism 5 to make small the amount of valve overlap. By this, generating EGR amount is reduced with the result that the combustion temperature and exhaust temperature are raised. Consequently, engine warming is promoted whereby the exhaust gas purification performance is improved.

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 an engine having a variable valve timing mechanism, as disclosed in Japanese Patent Application Laid-open No. 61-65036, in order to reduce pumping loss and improve fuel efficiency, the engine is operated in a light load operating range. In some cases, the amount of valve overlap is increased.

(Problem to be Solved by the Invention) However, in the above conventional example, in the idle region where the engine speed is low and the intake pipe pressure is low, and in the vicinity of the idle region, residual gas deteriorates combustibility and the engine operating state deteriorates. There is a problem with instability.

In particular, when the engine is cold, there is a problem in that the catalyst temperature decreases and the catalyst becomes inactive due to a decrease in the in-cylinder temperature and gas temperature due to deterioration of combustion.

(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. In other words, in an engine that is equipped with a variable valve timing means to vary the amount of valve overlap, the amount of valve overlap is made small when the engine is running at low speeds and under light load, and when the engine is cold, the amount of valve overlap is reduced throughout the entire operating range. It is characterized by a small amount.

Another feature is that the valve overlap amount is reduced when the engine is running at low speeds and under light load, and the region where the valve overlap amount is reduced when the engine is cold is expanded compared to when the engine is warm.

(Function) In the above configuration, when the engine is cold, the valve overlap amount is made small in all operating ranges to give top priority to warming up the engine.

Furthermore, when the engine is cold, the area in which the valve overlap amount is smaller than when the engine is warm is expanded to ensure engine stability.

(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 (not shown) is sliding in a cylinder 20 formed in an engine body 1, and an intake boat 8 and an exhaust boat 9 are supported in the cylinder 20. In addition, the intake valve 3 and the exhaust valve 2
open and close the intake boat 8 and exhaust boat 9, respectively. The opening/closing drive is performed by a cam mechanism 4, which changes the opening/closing timing of the exhaust valve 2 or the intake valve 3 by means of a variable valve timing mechanism 5, as will be described later.

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 portion 4a is selectively switched according to a control signal from the engine control unit (ECU) 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 catalyst 11 is located downstream of the exhaust boat 9. The intake air amount at the air urometer 10 is input to the ECU 3 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 temperature from the cooling water temperature sensor (not shown) is also EC.
It is input to Ul3.

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, ECU l
3 stores a valve overlap amount switching map, etc., which will be described later, in a built-in memory 13a.

FIG. 2 is a diagram showing a switching pattern of the amount of valve overlap (hereinafter referred to as valve overlap) by a general variable valve timing mechanism.

In each switching pattern shown in the figure, the left side is an exhaust valve (abbreviated as Ex), and the right side is an intake valve (In).

(abbreviated as ) respectively correspond to the lift curves. The horizontal axis represents the crank angle, where TDC means top dead center and BDC means bottom dead center. Moreover, the vertical axis is the valve lift (lift amount).

To explain the individual switching patterns, Fig. 2 (a
) to (C) show patterns in which the amount of valve overlap is switched by changing the phase of the cam that drives the valve,
FIGS. 2(d) to 2(f) show patterns in which the amount of valve overlap is changed by using two cams.

In addition, FIGS. 2(a) and 2(d) show that only the valve timing of the exhaust valve is operated in order to switch the valve overlap amount, and FIG. 2(b) shows that only the valve timing of the exhaust valve is operated.

In (e), only the valve timing of the intake valve is operated. Further, FIGS. 2(c) and 2(f) show a pattern in which the valve overlap amount is changed by operating the valve timings of both the exhaust valve and the intake valve.

Next, switching of the valve overlap amount in the apparatus of this embodiment will be described in detail.

FIG. 3(a) is a valve overlap switching map when the engine is warm according to this embodiment, and shows the interrelationship of valve overlap with engine rotational speed Ne and intake pipe pressure pb. Further, FIG. 3(b) shows a valve overlap amount switching pattern according to this embodiment, which corresponds to the switching pattern shown in FIG. 2(d).

FIG. 4 is a flowchart showing the valve timing control procedure in this embodiment. In the same figure, ECU
l3 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 or not the engine is being warmed up by comparing the temperature Twj with the cooling water temperature Twj that determines whether the engine has warmed up.

If the determination in step S4 is No, that is, the cooling water temperature Tw is higher than the warm-up completion determination temperature Twj, the process proceeds to step S5, and the valve overlap amount shown in FIG. 3(a) is determined assuming that the engine is in a warm state. Read the valve timing V setting value from the switching map. In other words, when the engine is at low speed and the intake pipe pressure is low (light load), in other words, when the engine is near idle, or when the engine speed is low to medium and the intake pipe pressure is high (high (corresponding to the shaded area in Fig. 3 (a)), the valve overlap amount is set small (pattern following the Ex and A timings in Fig. 3 (b)), and in other operating regions, the valve overlap amount is set to small. The setting value corresponding to the process of increasing the value (pattern according to the Ex and B timings in FIG. 3(b)) is read out.

However, 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 valve timing is set to a timing at which the amount of valve overlap is small in all operating regions. In other words, when the engine is cold, the catalyst temperature Tc is the warm-up completion determination temperature Tw.
Since the catalyst is not activated because it is lower than j, the valve timing for the exhaust valve is set in accordance with the Ex and A timings shown in FIG. 3(b).

In step S7, the ECU 13 sends a control signal to the variable valve timing mechanism 5 according to the valve timing v7 set in step S5 or step S6.

As explained above, according to this embodiment, when the engine is cold, the valve overlap amount is made small in all operating ranges, and when the engine is warm, the valve overlap amount is made small near the engine idle, thereby improving combustion. This has the effect of preventing the deterioration of engine speed, activating the catalyst, and stabilizing the engine condition near idle.

<Other Examples> Next, other examples according to the present invention will be described. still,
The engine valve timing control device according to this embodiment is the same as the device according to the first embodiment, so detailed explanation thereof will be omitted.

FIGS. 5(a) to 5(C) are diagrams for explaining switching of the valve overlap amount in this embodiment.

FIG. 5(a) is a valve overlap amount switching map when the engine is warm according to another embodiment, and FIG. 5(b) is a map for changing the valve overlap amount when the engine is warm.
is a valve overlap amount switching map when the engine is cold. These maps show the interrelationship of the valve overlap amount with respect to the engine rotational speed Ne and the intake pipe pressure pb. Moreover, FIG. 5(C) shows a valve overlap amount switching pattern according to another embodiment, and shows a second valve overlap amount switching pattern.
This corresponds to the switching pattern shown in Figure (a).

Next, the valve timing control procedure in this embodiment will be explained according to the flowchart shown in FIG. In the same figure, ECU1 3 sets the engine speed Ne at step Sll and the intake pipe pressure pb at step S12.
, the cooling water temperature Tw is input in step S13. Then, in step S14, the coolant temperature Tw is compared with the coolant temperature Twj for determining whether warming up is complete, and based on the comparison, it is determined whether the engine is being warmed up.

If the determination in step S14 is No1, that is, the cooling water temperature Tw
is higher than the warm-up completion determination temperature Twj, the process advances to step S15, and the engine is assumed to be in a warm state, and the valve timing is determined from the valve overlap amount switching map (map a) shown in FIG. 5(a). Read the setting value. In other words, when the engine is near idle or when the engine speed is low to medium and the intake pipe pressure is high, a map having a set value that makes the valve overlap amount small is selected.

However, if the determination in step S14 is YES, it is determined that the engine is in a cold state, and the process proceeds to step 816.
The valve overlap amount switching map shown in Figure (b) (
Map b) to valve timing V? In the map b shown in FIG. 5(b), which reads out the set value of FIG.
Compared to map a shown in a), the region where the valve overlap amount is small near the engine idle is expanded to take into consideration other operating regions when the engine is cold.

In step S17, the ECU 13 applies pressure to the variable valve timing mechanism 5 with a control signal corresponding to the pulse timing Vt set in step S15 or step S16.

As explained above, according to Honji's embodiment, when the engine is running at low speed and the intake pipe pressure is low, in a light load state, that is, near engine idle, the amount of valve overlap is reduced when the engine is cold compared to when the engine is warm. By widening the area where it is made small, there is an effect that the stability of the engine can be ensured.

(Effects of the Invention) As explained above, according to the present invention, by making the valve overlap amount variable depending on the engine condition and reducing the internal EGR amount, combustion temperature and exhaust gas temperature are increased, and warm-up temperature is increased. This has the effect of promoting the purification of exhaust gas and improving exhaust gas purification performance.

[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. 2(a) to (f) show switching of valve overlap amount by variable valve timing. Fig. 3(a) is a diagram showing a valve overlap amount switching map when the engine is warm according to the embodiment, and Fig. 3(b) is a diagram showing the valve overlap amount switching pattern according to the embodiment. FIG. 4 is a flowchart showing the valve timing control procedure in the embodiment, and FIG. 5(a) is a diagram showing a valve overlap amount switching map when the engine is warm according to another embodiment. , FIG. 5(b) is a diagram showing a valve overlap amount switching map when the engine is cold according to another embodiment, and FIG. 5(C) is a diagram showing a valve overlap amount switching pattern according to another embodiment. FIG. 6 is a flowchart showing a valve timing control procedure in another embodiment. 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 port, 12... Catalyst temperature sensor, 14... ...Boost pressure sensor, 20... cylinder. Patent 8 patent Mazda Motor Corporation Engine rotation difference - r'l Neyu Figure 3 (0) Ex, A tie fan Figure 3 (b) 1 engine rotation &7! Ne→ Kuma・Va0) Figure 5 (0) <Pine 7゛b> Figure 5 (b) Figure 5 (C)

Claims (2)

[Claims] (1) In an engine that is equipped with a valve timing variable means to vary the amount of valve overlap, the amount of valve overlap is small when the engine speed is low and the load is light, and when the engine is cold, the amount of valve overlap is made small over the entire operating range. An engine valve timing control device characterized by having a small size. (2) In an engine that is equipped with a valve timing variable means to vary the amount of valve overlap, the amount of valve overlap is smaller when the engine speed is low and the load is light, and when the engine is cold, the valve overlap is smaller than when the engine is warm. An engine valve timing control device characterized by expanding a region in which the amount of valve timing is small.