JPS6113082B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement in an engine intake valve device that controls the lift amount of an engine intake valve, and particularly relates to an improvement when the engine is cold.

Conventionally, a valve train that opens and closes an engine's intake valve is equipped with a control device that controls the amount of lift of the intake valve according to the engine load. By increasing the amount, when the engine is operating at low load, the intake air flow is throttled and the intake air velocity is increased, increasing combustion efficiency, while when the engine is operating at high load, the intake resistance is reduced, increasing charging efficiency, and improving output. An intake valve device for an engine has been proposed. (For example, see Japanese Utility Model Application Publication No. 113010/1983.) By the way, in an engine equipped with such an intake valve device, if the same lift amount control is performed when the engine is cold as when it is warmed up, the In addition to poor fuel vaporization and atomization and poor combustion stability, which are similar to the cold engine characteristics, especially during low-load operation, intake resistance increases due to a decrease in lift amount and intake negative pressure decreases. Since the differential pressure between the intake passage and the float chamber becomes smaller, the fuel from the nozzle is not sprayed vigorously into the intake passage, and its atomization is not promoted, which further worsens fuel vaporization and atomization, resulting in fuel stability. There was a problem that sex became significantly worse.

Therefore, the present invention has been made in view of such problems, and in an engine equipped with the above-described intake valve device, when the engine is cold, the lift amount of the intake valve is set to be larger than when the engine is warmed up. ,
By increasing the intake negative pressure when the engine is cold,
By increasing the differential pressure between the intake passage and the float chamber, the fuel from the nozzle is forcefully jetted into the intake passage and atomized, thereby promoting vaporization and atomization of the fuel and improving combustion stability when the engine is cold. It is an object of the present invention to provide an intake valve device for an engine that can be improved.

Hereinafter, the present invention will be described in detail based on embodiments shown in the drawings.

In FIG. 1, 1 is a cylinder block, 2 is a cylinder head, 3 is a combustion chamber formed within the cylinder head 2, 4 is an intake port that opens into the combustion chamber 3, and 5 is an intake air port that opens and closes the intake port 4. valve, 6
is an intake valve valve operating device that opens and closes the intake valve 5 in synchronization with the rotation of the engine. Reference numeral 7 designates an intake manifold connected to the intake port 4, and the intake manifold 7 and the intake port 4 form an intake passage 8 communicating with the combustion chamber 3. 9 is a throttle valve disposed in the intake passage 8;
10 is an exhaust port that opens into the combustion chamber 3, and 11 is an exhaust valve that opens and closes the exhaust port 10.

The valve train 6 includes an intake valve cam 13 fixed to a camshaft 12 which is rotationally driven in synchronization with the rotation of the engine, and a shaft 14 supported in the cylinder head 2 so as to be axially parallel to the camshaft 12. a cam follower 1 whose base is swingably supported and slides into contact with the cam surface of the intake valve cam 13;
5 and the bracket portion 15a of the cam follower 15.
an arm 18 having one end pivotally supported by a pin 16 and having an adjuster screw 17 at the other end that abuts the upper end of the valve shaft 5a of the intake valve 5;
A rotatable roller 1 that contacts an arcuate surface 18a provided on the upper surface of the arm 18 to form a swing fulcrum A of the arm 18.
9, a fulcrum displacement mechanism 20 constituting a variable lift amount control device that displaces the roller 19 relative to the arm 18 according to the operating state of the engine, and a fulcrum displacement mechanism 20 fixed to the upper end of the valve shaft 5a of the intake valve 5. A spring 22 is interposed between the spring receiving washer 21 and the cylinder head 2, and biases the intake valve 5 in the closing direction, and also biases the cam follower 15 so as to be in constant sliding contact with the cam surface of the intake valve cam 13. It consists of
Intake valve cam 1 due to rotational drive of camshaft 12
3 rotates the cam follower 15 to the shaft 14.
The arm 18 is caused to swing around the axis, and the arm 18 is
The valve shaft 5a of the intake valve 5 resists the spring force of the spring 22 via the adjusting screw 17 at the other end of the arm 18 by swinging about the point of contact with the roller 19 (swing fulcrum A). It is configured to open and close the intake valve 5 by pushing it down or lifting it up by the spring force of the spring 22.

The fulcrum displacement mechanism 20 also includes a shaft 23 rotatably supported within the cylinder head 2;
A lever portion 24 that is fixed to the shaft 23 and swings as the shaft rotates; a roller 19 that is rotatably supported at the lower part of the lever portion 24 so as to come into contact with the arcuate surface 18a of the arm 18; and the shaft 23.
a worm gear 26 that meshes with the gear 25; a reversible motor 27 that drives the worm gear 26 forward and backward; and the reversible motor 2.
The control circuit 28 includes a control circuit 28 that controls the drive of the engine 7 according to the operating state of the engine, and the control circuit 28 receives a load detection signal _S1 that detects the engine load from, for example, the intake negative pressure in the intake passage 8 and the engine rotation speed. The rotation speed detection signal _S2 etc. detected is input,
In response to the load detection signal S ₁ and rotation speed detection signal S ₂ , the control circuit 28 determines the operating state of the engine, and depending on the operating state of the engine, the reversible motor 2
7 in normal or reverse rotation, the reversible motor 27 drives the gear 25 via the worm gear 26,
The roller 19 supported on the lever part 24 is moved to the arm 18.
The lever ratio of the arm 18 is changed to change the lift amount of the intake valve 5. Therefore, when the engine is operated at low load, the lever of the arm 18 is changed. While the ratio is changed to be smaller on the adjuster screw 17 side and the lift amount of the intake valve 5 is set smaller,
During high load operation of the engine, the lever ratio on the adjuster screw 17 side of the arm 18 is changed to increase, thereby setting the lift amount of the intake valve 5 to a large value.

On the other hand, 29 is a cooling water passage formed near the elbow portion of the intake manifold 7 through which engine cooling water flows. A temperature sensor 30 is installed to detect the engine temperature (temperature), and an engine temperature detection signal _S3 from the temperature sensor 30 is input to the control circuit 28. Upon receiving the engine temperature detection signal _S3 , the control circuit 28 When the engine is cold, the intake valve 5 is lower than when it is warmed up.
The lift amount is set to be large. In other words, the lift amount of the intake valve 5 when the engine is cold is different from the lift amount characteristic when the engine is warmed up (characteristic in which the lift amount is set larger during high load operation than during low load operation) as shown in Fig. 2. The engine temperature is set to be higher when the intake negative pressure increases (that is, during low-load operation) than during warm-up, and when the load is kept constant as shown in Figure 3. The lift amount is set to increase as the height decreases.

Therefore, in the above embodiment, when the engine is normally warmed up, the lift amount of the intake valve 5 is the second.
As shown by the solid line in the figure, the engine temperature changes depending on the load; it is small during low-load operation, and increases as the load increases, and as shown by the solid line in Fig. 3, when the load is constant, the engine temperature changes. It has a characteristic that is constant for .

On the other hand, when the engine is cold, the temperature sensor 30
The lift amount of the intake valve 5 is determined by inputting the engine temperature detection signal _S3 to the control circuit 28.
As shown by the broken line in Figure 2, it changes depending on the load, but the lift amount during low-load operation is larger than during warm-up, and when the load is constant as shown by the broken line in Figure 3, The lift amount increases as the engine temperature decreases.

As a result, when the engine is cold, especially during low-load operation, the intake flow velocity increases due to the increase in the lift amount of the intake valve 5, and the intake negative pressure in the intake passage 8 increases. Since the differential pressure with the float chamber increases compared to when warmed up, the fuel from the nozzle is vigorously jetted into the intake passage 8 and becomes atomized, and the increase in negative pressure causes the fuel in the intake passage 8 to become atomized. Evaporability improves, resulting in fuel vaporization,
Atomization is significantly promoted and combustion stability can be improved.

Note that the present invention is not limited to the above-mentioned embodiment, but includes various other modifications. For example, in the above-mentioned embodiment, the fulcrum is used as a lift amount variable control device that varies the lift amount of the intake valve 5. Although the displacement mechanism 20 is used, it goes without saying that various other means and devices can be used.

Further, in the above embodiment, the temperature sensor 30 detects the temperature of the engine cooling water in the cooling water passage 29 and indirectly detects the engine temperature, but in other cases, the temperature sensor 30 detects the engine temperature directly or indirectly. Needless to say, a temperature sensor that detects the temperature may also be used.

Furthermore, an air flow meter may be provided in the intake passage 8 to detect the engine load based on the amount of intake air.

As explained above, according to the present invention, the valve train that opens and closes the intake valve is provided with a control device that controls the lift amount of the intake valve according to the engine load, so that when the valve is operated at high load or when the load is low, In an engine intake valve device that increases the lift amount of the intake valve, a temperature sensor is installed to detect the engine temperature, and the lift amount is set larger when the engine is cold than when it is warmed up. When the engine is cold, the increase in intake negative pressure promotes fuel vaporization and atomization to improve combustion stability, ensuring good combustion stability even when the engine is cold and has a lift variable means. It is something that can be done.

[Brief explanation of the drawing]

The drawings illustrate an embodiment of the present invention, and FIG. 1 is a schematic diagram of the overall configuration, FIG. 2 is a diagram showing the characteristics of the intake valve lift amount with respect to intake negative pressure, and FIG. 3 is a diagram showing the intake valve lift amount with respect to engine temperature. FIG. 3 is a diagram showing the characteristics of the lift amount. 3... Combustion chamber, 5... Intake valve, 6... Valve train, 8... Intake passage, 20... Fulcrum displacement mechanism, 2
8... Control circuit, 29... Cooling water passage, 30...
Temperature sensor, _S1 ...load detection signal, _S2 ...rotation speed detection signal, _S3 ...engine temperature detection signal.

Claims (1)

[Claims] 1 The valve train that opens and closes the intake valve is equipped with a control device that controls the lift amount of the intake valve according to the engine load, so that the lift amount of the intake valve is larger during high-load operation than during low-load operation. What is claimed is: 1. An intake valve device for an engine according to the present invention, wherein a temperature sensor is provided to detect the temperature of the engine, and a lift amount is set to be larger when the engine is cold than when the engine is warmed up.