JP2000145484A - Valve unit of supercharged engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a simply structured valve unit which is capable of improving fuel efficiency by performing optimal control of the air charge amount irrespective of operation state of the engine. SOLUTION: A supercharged engine is provided with a turbo-charger and a cam shaft 2 for driving intake valve and exhaust valve. The supercharged engine is provided with a timer 6 for changing rotational phase of the cam shaft 2 with respect to the crank shaft 1, and a control unit 5 for controlling the timer 6 in response to the operation state of the engine. As a result, the excessive amount of air supply is restrained at the high rotational area or low load area while securing the air charge amount at the other area. Accordingly, the fuel efficiency of the supercharged engine can be improved by performing optimal control of the air charge amount.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a valve train for a supercharged engine, and more particularly, to a valve train suitable for improving fuel efficiency by optimally controlling an air supply amount irrespective of an operating state of an engine. It is.

[0002]

2. Description of the Related Art As a conventional valve operating device for an engine, there is a valve operating device in which a closing timing of an intake valve is delayed or a valve lift is increased in a high-speed operation range to increase an air supply amount.

However, when such a valve train is directly applied to a turbocharged engine, in particular, to a turbocharged engine with an intercooler, excessive supply of air during operation in a high speed range or a low load range is provided. As a result, there is a problem that fuel efficiency is deteriorated. Further, in the conventional valve gear, since only the opening / closing timing of either the intake valve or the exhaust valve is controlled, the effect of improving the fuel consumption by controlling the opening / closing timing of the valve is significantly improved. There was also a problem that it was not possible.

[0004]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and has a simple structure capable of improving fuel efficiency by optimally controlling the amount of air supply regardless of the operating state of the engine. It is an object to provide a valve device.

[0005]

SUMMARY OF THE INVENTION In order to solve the above problems, the present invention provides a turbocharged engine having a camshaft for driving an intake valve and an exhaust valve while providing a turbocharger. A timer for changing the rotation phase is provided, and a control unit for controlling the timer in response to an operating state of the engine is provided.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a schematic configuration diagram showing one embodiment of a valve system for a supercharged engine according to the present invention, and shows a crankshaft 1 of an engine equipped with a turbocharger (not shown) and a cam and an exhaust valve for driving an intake valve (not shown). The camshafts 2 each having a cam for driving the same are linked via a sprocket 3, a timing chain 4, and a timer 6 controlled by a control unit 5. Accordingly, the opening and closing timings of the intake valve and the exhaust valve are simultaneously controlled in response to the timing (phase) of the camshaft 2 controlled by the timer 6.

The control unit 5 receives various kinds of operation information represented by the engine speed and load output from a sensor (not shown), determines the operation state of the engine, and controls the timer 6. Also. Timer 6
This is for changing the rotation phase of the camshaft 2 with respect to the crankshaft 1 based on a control signal output from the control unit, and a conventionally known hydraulic timer, electronic timer, or the like is used.

In the valve system for a supercharged engine having the above-described structure, the camshaft 2 is driven to rotate by the crankshaft 1 when the engine is operated.
An intake valve and an exhaust valve (not shown) are each driven to open at predetermined times.

When it is determined that the engine is operating, for example, in a medium speed / medium load range based on various operation information output from a sensor (not shown), the control unit 5 outputs a non-operation signal to the timer 6. I do. Therefore, in this state, the timer 6 does not perform the advancing operation, and the camshaft 2
Rotates in exactly the same phase as the crankshaft 1, and, for example, opens the intake valve and the exhaust valve at the same timing as in the prior art, as shown by the solid line in FIG.

That is, during operation in the medium speed / medium load region where the timer does not advance, the intake valve is opened from just before the exhaust top dead center to immediately after the intake bottom dead center as in the conventional case. Improve fuel efficiency by securing air supply.

When the intake valve closing timing is set immediately after the intake bottom dead center as described above, when the engine is operated in a high speed region where the supercharging efficiency is high or in a low load region where a large amount of fuel is not supplied. In some cases, the intake air amount is increased more than necessary, and fuel efficiency may be reduced.

However, in this embodiment, when it is determined that the engine is operating in a high speed range or a low load range based on various types of operation information, the control unit 5 outputs an advance signal. Then, the timer 6 advances the timing to advance the closing timing of the intake valve, and in some cases, changes the timing before the intake bottom dead center as shown by the broken line in FIG.

Further, if the opening timing of the exhaust valve is advanced by the above-described advancement action, the PV of FIG.
As shown by the broken line in the diagram, the pressure (exhaust pressure) in the combustion chamber is rapidly reduced, and the amount of combustion gas remaining in the combustion chamber at the time of opening the intake valve is reduced. In FIG. 3, the circles indicate the valve opening point of the exhaust valve and the valve closing point of the intake valve when the camshaft 2 is not advanced, and the black circle indicates the exhaust when the camshaft 2 is advanced. 2 shows a valve opening point and a valve closing point of an intake valve.

That is, when the engine speed is low, the exhaust can be sufficiently exhausted even if the exhaust valve is opened late. In a high speed region, the camshaft 2 is advanced and the exhaust valve is opened. If the valve is opened early, the exhaust pressure can be reduced, thereby improving fuel efficiency.

When the engine speed is low, it is desired that the intake valve be closed as late as possible to secure the air supply amount. During operation in a low load range where no air is needed, the camshaft 2 is advanced to set the closing timing of the intake valve early, thereby reducing excess air supply and improving fuel efficiency. Can be.

Therefore, the camshaft 2 with respect to the crankshaft 1 responds to the engine speed and load.
By changing the rotational phase of the motor, the supply of excess air in the high-speed range or low-load range is suppressed, and the amount of air supply in other ranges is ensured. Since the supply amount can be optimally controlled, the fuel efficiency of the supercharged engine can be improved.

In the above embodiment, the timer is controlled based on the engine speed and load to change the phase of the camshaft. For example, the acceleration of the engine, the accelerator opening, the atmospheric pressure, the supercharging pressure or The advance angle can be corrected in accordance with various conditions such as the outside air temperature, and finer control can be performed.

When the control unit 5 and the timer 6 for changing the advance angle of the camshaft 2 stepwise are provided, these structures can be simplified, but the phase of the camshaft 2 is continuously changed. By providing the control unit 5 and the timer 6, the effect of improving fuel efficiency can be further enhanced.

Although the present invention is effective in improving the fuel efficiency of a turbocharged engine as described above, it is particularly effective when applied to a turbocharged engine with an intercooler having a high supercharging rate. A remarkable fuel efficiency improvement effect can be obtained.

[0020]

As is apparent from the above description, the present invention changes the phase of the camshaft in response to the operating state of the engine, thereby enabling the engine to operate in a high-speed region or a low-load region, which is a concern in a supercharged engine. Since the supply of excess air during operation is suppressed, the fuel supply can be improved by optimally controlling the air supply amount in the entire operation range.

Further, since the intended purpose can be achieved by simultaneously controlling the opening and closing timings of the intake valve and the exhaust valve, it is necessary to independently control the camshafts for driving both valves independently. Instead, the present invention can also be applied to an engine having a simple configuration in which both valves are driven by a common camshaft.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram showing an embodiment of a valve system for a supercharged engine according to the present invention.

FIG. 2 is a diagram showing opening and closing characteristics of a valve according to the embodiment shown in FIG. 1;

FIG. 3 shows the P of the supercharged engine according to the embodiment shown in FIG. 1;
It is a -V diagram.

[Explanation of symbols]

 Reference Signs List 1 crankshaft 2 camshaft 3 sprocket 4 timing chain 5 control unit 6 timer

Claims (1)

[Claims] In a supercharged engine provided with a camshaft for driving an intake valve and an exhaust valve while providing a turbocharger, a timer for changing a rotation phase of the camshaft with respect to the crankshaft is provided, and the operation state of the engine is controlled. A valve system for a supercharged engine, further comprising a control unit that controls the timer in response.