JPS6316803Y2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a variable valve timing control device for intake and exhaust valves of a turbocharged internal combustion engine.

Turbocharging is widely known as a system that supercharges intake air using the energy contained in exhaust gas, and contributes to improving fuel efficiency by increasing horsepower per engine weight.

By the way, in diesel engines, when engine output is not required, such as in a low engine load range, the excess ratio of air to injected fuel is large, so the supply of supercharging air by the turbocharger is rather a compression process during the compression stroke. It only increases the loss and can even be said to be unnecessary.

The amount of air sucked into the cylinder can be controlled by changing the timing of opening and closing the intake and exhaust valves. Therefore, in such a low-load operating range, for example, by shortening the opening/closing period of the intake valve, it is possible to prevent more air than necessary from being drawn into the cylinder.

By the way, when supercharging is performed using a turbocharger, the rotation of the turbocharger increases in proportion to the exhaust energy, that is, as the engine rotation increases.
Since the amount of supercharging is also proportional to this, the optimal required opening/closing timing of the intake and exhaust valves also changes depending on the characteristics of the engine, and this has a large effect on engine performance.

Previous attempts have been made to variably control the opening and closing timing of intake and exhaust valves depending on the operating conditions.
Numerous proposals (for example, the applicant's 1983-
No. 103385), but there is no way to control the valve timing in relation to the characteristics of the turbocharger, and even if it is variable control, the control accuracy is generally rough, and in combination with the turbocharger, it is difficult to control the valve timing depending on the operating condition. There was nothing that could be controlled accurately.

This invention was developed with a focus on these points, and uses a microcomputer to variably control the opening and closing timing of the intake and exhaust valves according to the operating conditions, making full use of the characteristics of turbochargers. Reduce compression loss at
It is an object of the present invention to provide a variable control device for intake and exhaust valves that increases output in a high load range.

Hereinafter, embodiments of the present invention will be described based on the drawings.

In FIG. 1, 1 indicates a diesel engine body, 2 an intake passage, 3 an exhaust passage, and 4 a turbocharger.

The turbocharger 4 has an exhaust turbine 5 interposed in the exhaust passage 3, and drives an intake compressor 6 coaxially therewith.

7 indicates an intake valve, and 8 indicates an exhaust valve. As shown in FIG. 2, a cam 10 that drives the intake and exhaust valves 7 and 8 (in this case, only the intake valve cam is shown) is fixed to a camshaft 11, and the camshaft 11 is axially moved by an actuator 24 to a link 25. is moved through the
It is held in that position by an oil lock hydraulic cylinder 12.

The cam profile is formed differently as the cam 10 is displaced in the axial direction, so that the opening/closing timing of the intake valve 7 can be changed.

In other words, the cam follower 13 contacts the cam 10, and the lift that changes as the cam 10 rotates.
It is transmitted from a rocker arm (not shown) to the intake valve 7 via the push rod 14, and when the profile in contact with the cam follower 13 changes due to the movement of the cam 10, the opening/closing timing can be changed.

The camshaft 11 is rotated in synchronization with engine rotation by a rotation drive means (not shown).

In the hydraulic cylinder 12, pressure oil is selectively supplied from a hydraulic source via an oil lock valve 17 to an oil chamber 16 partitioned by a piston 15 connected to the camshaft 11, and when the oil lock valve 17 is closed, the piston 15 is closed. is locked in oil and receives the thrust of the camshaft 11.

The oil lock valve 17 is controlled to open and close based on control signals from the microcomputer 20.

When the microcomputer 20 receives signals from a rotational speed sensor 21 that detects the engine rotational speed and a load sensor 22 that detects the load, the microcomputer 20 selects one of the optimal intake and exhaust valve opening/closing timings determined in advance according to the operating state. , selects a value corresponding to the rotational speed and load at that time, controls the operation of the actuator 24 so as to obtain the opening/closing timing, and moves the camshaft 11 via the drive link 25.

Note that as the actuator 24, for example, an electromagnetic solenoid or the like is used.

Next, to explain the operation, when the engine is under low load, the supercharging air from the turbocharger 4 only increases the compression work and becomes unnecessary, but in such an operating range, the microcomputer 20 The camshaft 11 is displaced via the actuator 24 so that the opening period of the valve 7 is shortened.

Since the profile of the cam 10 changes as it moves in the axial direction, the opening period of the intake valve 7 via the cam follower 13 is shortened, and the amount of air sucked into the cylinder is reduced.

Note that when the actuator 24 is driven, the oil lock valve 17 is opened, and the hydraulic cylinder 12 allows hydraulic oil to enter and exit the oil chamber 16 in accordance with the axial movement of the camshaft 11.

When the displacement of the camshaft 11 stops, the oil lock valve 17 closes to lock the oil in the oil chamber 16 partitioned by the piston 15, and the camshaft 11 generated by contact between the cam 10 and the cam follower 13
receives thrust force.

Therefore, the actuator 24 only needs to generate a driving force when the camshaft 11 is displaced, and when the oil lock is released, the camshaft 11 automatically returns to the initial position by the thrust force.

When the required air amount increases, such as when the load is high, the opening period of the intake valve 7 is lengthened, and the amount of valve overlap with the exhaust valve 8 is also increased.
The microcomputer 20 controls the operation of the actuator 24 to increase the intake and exhaust efficiency, causing the engine to exert high output.

As described above, according to the present invention, since the opening/closing timing of the intake and exhaust valves is variably controlled according to the operating conditions, in combination with a turbocharger, the engine can be operated to achieve the best thermal efficiency in all regions. Fuel efficiency and output performance can be further improved.

[Brief explanation of the drawing]

FIG. 1 is a schematic configuration diagram including a turbocharger of the present invention, and FIG. 2 is a configuration diagram of a valve train. 1... Diesel engine body, 2... Intake passage, 3... Exhaust passage, 4... Turbo charger,
7...Intake valve, 8...Exhaust valve, 10...
Cam, 11...Camshaft, 12...Oil lock cylinder, 13...Cam follower, 17...
...oil lock valve, 20...microcomputer, 24...actuator.

Claims (1)

[Scope of utility model registration request] It is equipped with a turbocharger that rotates an intake compressor that supercharges intake air by an exhaust turbine driven by exhaust pressure, and is also equipped with an engine rotation speed and load detection means that detects the cam lift as the cam of the intake and exhaust valve is displaced in the axial direction. At the same time, the camshaft with this cam attached thereto is supported freely in the axial direction, and a locking hydraulic cylinder is interlocked with the end of the camshaft, and an actuator is provided to drive the camshaft in the axial direction. A variable intake/exhaust valve control device comprising a microcomputer that controls the operation of the actuator and the oil lock valve of the hydraulic cylinder based on the detected engine speed and load.