JP2568250B2 - Engine valve timing controller - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a valve timing control device for controlling opening / closing timing of intake / exhaust valves in an engine, particularly an engine including a supercharger.

(Prior Art) Conventionally, for example, as disclosed in JP-A-62-87615, a supercharger is provided in an intake passage of an engine, and the intake air is supercharged by the operation of the supercharger. A supercharged engine in which the output torque of the engine is increased by increasing the intake charge amount for the cylinder is widely and generally known.

Then, in the engine equipped with this supercharger, by utilizing the high supercharging pressure of the intake air that is supercharged in the high load range, and setting a large overlap of the intake / exhaust stroke in the high load range, The supercharged intake air pushes out the high-temperature residual exhaust gas in the combustion chamber in the cylinder toward the exhaust side to enhance the scavenging effect, suppress the rise in intake air compression temperature due to the residual exhaust gas, and raise the knocking limit to compress the intake air. It is possible to set a high ratio to improve fuel efficiency.

However, on the other hand, in a low load region such as idling of the engine, the intake negative pressure becomes large, so that exhaust gas is blown back into the intake passage and the combustibility deteriorates. Therefore, the intake / exhaust stroke overlaps. Needs to be small.

By the way, at least in the high-load high-speed range, the intake valve closing timing and piston top dead center timing are set by delaying the intake valve closing timing in order to compensate for the decrease in the scavenging effect due to the increase in back pressure. It is conceivable to reduce the effective compression ratio determined by and increase the effective expansion ratio determined by the piston top dead center timing and the exhaust valve opening timing to prevent knocking and suppress the exhaust gas temperature rise. .

(Problems to be solved by the invention) However, in that case, as described above, in order to suppress the blowback of the exhaust gas to the intake system in the low load range, the valve timing of the intake valve is delayed so that the intake / exhaust stroke is reduced. When the overlap is reduced, the closing timing of the intake valve originally set on the delay side is further delayed, so that the effective compression ratio is significantly reduced. As a result, although the residual exhaust gas is reduced due to the reduction of the overlap, the compression temperature is extremely lowered, the combustibility is deteriorated, and good combustion stability cannot be obtained.

It is an object of the present invention to improve the valve timing control mechanism of the engine in the case of increasing the scavenging effect by increasing the overlap between the intake / exhaust strokes at the time of high load of the engine, and thereby to improve the effect at low load of the engine. It is intended to reduce the residual exhaust gas by reducing the overlap in the intake / exhaust stroke while avoiding an extreme decrease in the compression ratio.

(Means for Solving the Problems) In order to achieve the above object, a solution of the present invention includes:
The valve timing of the exhaust valve of the engine is made variable, and when the engine load is low, the valve timing of the exhaust valve is controlled to be behind the high load.

Specifically, the configuration of the present invention is as shown in FIG.
In the engine 1 equipped with the supercharger 14 that supercharges the intake air,
At least valve timing changing means 28 for changing the valve timing of the exhaust valve 7 for opening and closing the exhaust port 9 of the cylinder 5 is provided.

Further, the load detection means 32 for detecting the engine load and the output of the load detection means 32 are received, and at the time of high load of the engine 1, at least the period θ _EC from the piston top dead center to the closing time of the exhaust valve 7 is intake. The valve timing of the exhaust valve 7 is lower than the valve timing at the time of high load when the load is low so that the period from the opening of the valve 6 to the top dead center of the piston becomes longer than θ _{IO and the} valve timing of the exhaust valve is delayed. Also, a control means 30 for controlling the valve timing changing means 28 is provided so as to be on the advance side.

(Operation) With the above configuration, in the present invention, the load state of the engine 1 is detected by the load detecting means 32.
The valve timing changing means 28 is controlled by the control means 30 receiving the output to 32, and the valve timing of the exhaust valve 7 is changed. That is, when the engine 1 is under a heavy load, the valve timing of the exhaust valve 7 is delayed, so that the overlap of the intake / exhaust stroke becomes long, and the exhaust gas remaining in the cylinder 5 is exhausted by the intake air supercharged by the supercharger 14. It can be pushed out to the side effectively and the scavenging effect can be enhanced.

In that case, the exhaust valve 7 is set so that at least the period θ _EC from the piston top dead center to the closing of the exhaust valve 7 is longer than the period θ _IO from the opening of the intake valve 6 to the piston top dead center. The valve timing of is adjusted. Therefore, as in the opposite case (θ _IO ≧ θ _EC ), the intake / exhaust stroke overruns without setting the opening timing of the intake valve 6 with a fixed valve timing by advancing significantly before the piston top dead center. The lap can be increased, and thus the scavenging effect can be ensured satisfactorily.

On the other hand, in the low load range such as idling of the engine 1,
The valve timing of the exhaust valve 7 is changed to be ahead of the valve timing at the time of the high load. Therefore, the overlap between the intake / exhaust strokes is reduced, and the blowback of exhaust gas to the intake side is suppressed.

At this time, since the valve timing of the exhaust valve 7 is corrected to the advanced side, the effective compression ratio does not extremely decrease as in the case where the valve timing of the intake valve 6 is corrected to the delayed side. It is possible to secure good combustion stability in the low load region.

(Embodiment) An embodiment of the present invention will be described below with reference to the drawings starting from FIG.

FIG. 2 shows the overall construction of an embodiment of the present invention, in which 1 is an engine equipped with a cylinder block 2 and a cylinder head 3, and a cylinder 4 in which a piston 4 is reciprocally fitted. 5, 5, ... (Cylinder) are formed. On the other hand, the cylinder head 3 is formed with intake / exhaust ports 8 and 9 communicating with the respective cylinders 5, and the intake / exhaust ports 8 and 9 are opened / closed by intake / exhaust valves 6 and 7, respectively. The intake port 8 constitutes the downstream end of the intake passage 10, and the upstream end of the intake passage 10 is connected to the air cleaner 11. In the middle of the intake passage 10, from the upstream side, an air flow meter 12 that detects the intake air amount, a throttle valve 13 that throttles and opens the intake passage 10, and a mechanical supercharger that is driven by the engine 1 to supercharge intake air. Feeder 14
And a surge tank are provided, which is located directly above the supercharger 14 /
The downstream intake passage 10 is connected by a bypass passage 15 that relieves the intake air supercharged by the supercharger 14 to the upstream side of the supercharger 14, and this bypass passage 15 controls the amount of intake relief. A control valve 16 is provided. Reference numeral 17 is an injector for injecting and supplying fuel into the intake port 8.

The intake / exhaust valves 6 and 7 are respectively the camshaft 18 and
Opening and closing are driven by cams 20 and 21 on 19. The camshafts 18 and 19 are rotatably supported by the cylinder head 3 and have timing pulleys 22 and 2 attached to one end thereof.
It is rotationally driven by a crankshaft (not shown) of the engine 1 through a timing belt (not shown) wound around the pulley 3 and the pulleys 22 and 23. The exhaust-side cam shaft 19 is axially separated into a drive-side shaft 19a and a driven-side shaft 19b in the vicinity of the timing pulley 23, and the opposite end outer peripheries of the separated both shafts 19a and 19b have different directions. Spiral splines 24, 25 that swivel around are formed, and a sleeve 26 driven by a stepping motor 27 is slidable in the axial direction by a spline (not shown) on the inner periphery of the spline 24, 25. It is externally fitted, and by moving the sleeve 26 in the axial direction by the stepping motor 27, the driven shaft 19b is relatively rotated with respect to the driving shaft 19a, so that the valve timing of the exhaust valve 7 is changed. The valve timing changing mechanism 28 is configured.

The stepping motor 27 that drives the sleeve 26 is a CP
The operation is controlled by the control unit 30 with a built-in U. The control unit 30 includes a rotation sensor 31 for detecting the number of revolutions of the engine 1 and a load sensor 32 as a load detecting means for detecting the engine load based on the intake air amount and the like.
Each output signal of and is input.

In the control unit 30, advance control of the valve timing of the exhaust valve 7 is performed according to the control procedure shown in FIG. That is, first, in the first step S ₁ the engine speed detected by the rotation sensor 31 and the engine load detected by the load sensor 32 are respectively input, and in the next step S ₂ , based on a preset map. To set the valve timing advance angle of the exhaust valve 7. As shown in FIG. 5, this map divides the operating region of the engine 1 into a low-speed low-load region, that is, an idling region and other regions including a high-speed high-load region.
6 (a), the valve timing is delayed, and at least the period θ from the top dead center (TDC) of the piston 4 to the closing time (EC) of the exhaust valve 7 is increased in the high speed and high load region. _EC is set to be longer than the period θ _IO from when the intake valve 6 is opened (IO) to when the piston 4 is at top dead center (TDC) (θ _EC > θ _IO ), while in the idling region, As shown in FIG. 6B, the valve timing is set to be on the advance side of the valve timing in the high speed and high load region.

Next, in step S ₃ , the stepping motor 27 is operated to the set advance value, and then the process is ended.

Therefore, in this embodiment, the control unit
30 receives the output of the load sensor 32, and at the time of high load of the engine 1, at least the period θ _EC from the piston top dead center to the closing of the exhaust valve 7 is from the opening of the intake valve 6 to the piston top dead center. The valve timing of the exhaust valve 7 is delayed so that it becomes longer than the period θ _IO until the time, and the valve timing of the exhaust valve 7 is set to the lead side of the valve timing at the time of high load when the load is low. Control means for controlling the timing changing mechanism 28 is configured.

Therefore, in the above embodiment, the engine speed is detected by the rotation sensor 31 and the engine load is detected by the load sensor 32, and the exhaust valve 7 is detected by the control unit 30 based on the engine speed and the load.
Is set, and the stepping motor 27 of the valve timing changing mechanism 28 is operated and controlled to reach the set value, and the valve timing of the exhaust valve 7 is changed. Then, in the high speed and high load region of the engine 1, the valve timing is as shown in FIG.
Valve timing is delayed. Therefore, the overlap between the intake / exhaust strokes becomes longer, and the residual exhaust gas in the cylinder 5 can be effectively pushed out to the exhaust port 9 by the intake air supercharged by the supercharger 14 to enhance the scavenging effect. You can

At that time, at least the period θ _EC from the piston top dead center (TDC) to the exhaust valve 7 closing (EC) is from the intake valve 6 opening (IO) to the piston top dead center (TDC). Since it is set to be longer than the period θ _IO , conversely, the period θ _EC from the piston top dead center (TDC) to the valve closing (EC) of the exhaust valve 7 is (when the intake valve 6 is opened ( (IO) to piston top dead center (TDC), if the period is θ _IO or less (θ _IO ≧ θ _EC ), increase the opening timing of the intake valve 6 with fixed valve timing before piston top dead center. The overlap of the intake / exhaust strokes can be increased without advancing and setting, and thus the scavenging effect can be ensured satisfactorily.

On the other hand, in the low load range such as idling of the engine 1,
The valve timing of the exhaust valve 7 is changed so as to be ahead of the valve timing at the time of the high load,
The overlap of the intake / exhaust stroke is reduced, the blowback of intake air is suppressed, and good combustibility can be secured.

At that time, since the valve timing of the exhaust valve 7 is corrected to the advanced side, the effective compression ratio does not extremely decrease as in the case of correcting the valve timing of the intake valve 6 to the delayed side, and the combustion stability is improved. Can be secured.
Therefore, it is possible to reduce the amount of residual exhaust gas by reducing the overlap in the intake / exhaust stroke while avoiding an extreme decrease in the effective compression ratio when the engine 1 is under a low load.

In the above embodiment, only the valve timing of the exhaust valve 7 is changed by the valve timing changing mechanism 28, but it is possible to provide a changing mechanism for changing the valve timing on the intake valve 6 side as well. In that case, the valve timing change amount of the exhaust valve 7 is made larger than that of the intake valve, and the above condition, that is, at least the time θ from piston top dead center (TDC) to exhaust valve 7 closing time (EC) is θ. _It suffices to satisfy the condition that _EC is longer than the period θ _IO from the time when the intake valve is opened (IO) to the time when piston top dead center (TDC).

(Effects of the Invention) As described above, according to the present invention, a supercharger for supercharging intake air is provided, and the intake / exhaust stroke overlap is increased in a high load range to obtain a scavenging effect by supercharging pressure of intake air. In this engine, the valve timing of the exhaust valve of the engine is made variable, and when the engine load is low, the valve timing of the exhaust valve is controlled to be more advanced than under high load. While avoiding the extreme reduction of the effective compression ratio at low load of
It is possible to reduce the residual exhaust gas by reducing the overlap in the exhaust stroke.

[Brief description of drawings]

FIG. 1 is a diagram showing the configuration of the present invention. FIG. 2 and the following drawings show an embodiment of the present invention, FIG. 2 is a vertical sectional view schematically showing the overall structure thereof, FIG. 3 is a plan view showing a valve timing changing mechanism, and FIG. 4 is a control unit. Fig. 5 is a flow chart showing the valve timing advance control procedure of the exhaust valve in Fig. 5, Fig. 5 is a characteristic diagram showing a region in which the exhaust valve valve timing advance control is performed, and Fig. 6 is an intake / fluctuation accompanying a change in the engine operating state. It is a figure which shows the change of the valve opening period of an exhaust valve. 1 ... Engine, 4 ... Piston, 5 ... Cylinder, 6 ...
Intake valve, 7 ... Exhaust valve, 9 ... Exhaust port, 14
…… Supercharger, 28 …… Valve timing change mechanism (valve timing change means), 30 …… Control unit (control means), 32 …… Load sensor (load detection means), θ
_EC : Period from top dead center of piston to closing of exhaust valve, θ _IO ...... Period from opening of intake valve to top dead center of piston.

 ─────────────────────────────────────────────────── --- Continuation of the front page (72) Inventor Hidefumi Fujimoto 3-3 Shinchi, Fuchu-cho, Aki-gun, Hiroshima Mazda Corporation (56) References JP-A-63-297729 (JP, A) JP-A-61 -232335 (JP, A) JP 61-185628 (JP, A) JP 60-166717 (JP, A)

Claims (1)

(57) [Claims] 1. An engine equipped with a supercharger for supercharging intake air, comprising valve timing changing means for changing valve timing of an exhaust valve for opening and closing at least an exhaust port of a cylinder, and load detecting means for detecting engine load. Receiving the output of the load detecting means, at least when the engine is under high load, the period from the piston top dead center to the exhaust valve closing is longer than the period from the intake valve opening to the piston top dead center. In order to delay the valve timing of the exhaust valve, a control means for controlling the valve timing changing means is provided so that the valve timing of the exhaust valve is on the advance side of the valve timing at the time of the high load when the load is low. An engine valve timing control device characterized by the above.