JPH0128265Y2 - - Google Patents

Description

[Detailed description of the invention] (Field of industrial application) The present invention relates to an engine intake system, and in particular,
The present invention relates to an intake system for an engine in which the length of the intake pipe and the opening/closing timing of the intake valve are changed to improve output.

(Prior Art) Generally, in an engine, air intake is performed intermittently, so that air column vibration occurs in the intake air, and this air column vibration affects the amount of intake air, that is, the engine output. This air column vibration is determined by intake system parameters such as intake pipe length, diameter, and collection volume.

In an engine with the above intake system specifications constant, the air column vibration is set to be optimal under the specified operating conditions, and the air column vibration has an advantage at a specified rotation speed relative to the intake air amount It works, but it actually works against me in other areas.

Therefore, for example, as seen in Utility Model Application Publication No. 57-22629, the intake pipe on the downstream side of the surge tank in the intake passage was made into a telescopic structure, and its length was changed according to the engine speed, thereby improving the filling efficiency due to the inertia effect. Techniques have been proposed to improve output performance.
The above technology utilizes the so-called inertial supercharging effect in which the air column in the intake pipe is accelerated by the negative pressure generated within the cylinder at the beginning of the intake stroke, and the intake air is forced into the cylinder by the reverse pressure wave generated at the open end. It is something that exists.

There is also a technology that attempts to improve output by changing the opening/closing timing of the intake valve depending on the engine speed and load. In this case, if both of them are switched at the same time, the output characteristics will suddenly increase, causing a torque shock (acceleration shock) and making it impossible to obtain smooth drivability (acceleration).

Regarding the switching of the intake pipe length and timing, for example, during acceleration operation when the engine speed increases and the load increases, the intake pipe length is shortened from a long state, and the opening and closing timing of the intake valve is delayed, so that the exhaust valve When operating so that the overlap between the two is small, switching both at the same time will cause a positive torque shock as described above, but the change in filling amount when only the timing is changed while the intake pipe length remains long. is shown in Figure 4. As shown by the broken line in Figure 4, the state after the change is such that the filling amount decreases near the intake valve opening time IO and the intake valve closing time IC, resulting in a decrease in output and a negative torque shock. . In other words, the intake pipe length is normally set short to synchronize with high engine speeds, and in this state, it is possible to improve output by delaying the opening and closing timing of the intake valve, but if the intake pipe length remains long, the timing is limited. If delayed, the output will be reduced as described above.

On the other hand, FIG. 5 shows the change in the filling amount when only the intake pipe length is shortened while the opening/closing timing of the intake valve is kept constant. As shown by the broken line in FIG. 5, the state after the change increases the filling amount and increases the output, and it has been found that if the timing is further changed, the output increases.

(Purpose of the invention) In view of the above circumstances, the present invention aims to obtain a smooth transition of operating conditions without causing a large torque shock when changing the intake pipe length and the opening/closing timing of the intake valve, and to change the intake pipe length. The object of the present invention is to provide an intake system for an engine that maximizes the intake inertia effect of the engine and improves output over a wide range.

(Structure of the invention) The intake system of the invention includes an intake pipe length changing means for changing the intake pipe length at a predetermined engine speed, and a timing changing means for changing the opening/closing timing of the intake valve depending on the engine speed and load. , when entering a specific operating range in which both the intake pipe length and intake valve opening/closing timing are switched,
The present invention is characterized in that after the intake pipe length is changed by the intake pipe length changing means by the control means, the opening/closing timing of the intake valve is changed by the timing changing means.

(Effects of the invention) According to the invention, in addition to expanding the intake inertia effect by changing the intake pipe length, by changing the opening and closing timing of the intake valve, a greater output improvement effect is obtained, and both By controlling the intake pipe length and then changing the timing when transitioning to the switching region, smooth driving performance can be obtained without causing torque shock, and a good inertial supercharging effect can be obtained to increase the width of the engine. The output can be effectively improved within this range.

(Example) Hereinafter, an example of the present invention will be described with reference to the drawings.
FIG. 1 is a sectional front view of main parts of a multi-cylinder engine equipped with an intake device.

An intake port 3 and an exhaust port 4 are opened in the combustion chamber 2 of each cylinder of the engine 1.
An intake valve 5 and an exhaust valve 6 are disposed at the opening to the combustion chamber 2 . The intake passage 7 communicating with the intake port 3 includes a surge tank 9, is branched downstream of the surge tank 9, and is connected to each cylinder independently, and is provided with a fuel injection nozzle 10.

The surge tank 9 is formed by a casing 11 and a cylindrical rotating member 12 rotatably installed inside the casing 11. A pipe length changing means 13 is configured. This casing 11
forms an intake manifold fastened to the cylinder head 15 of the engine 1, and extended portions of the intake passages 7 connected to each cylinder are formed along the circumferential direction of the casing 11, corresponding to each cylinder. Further, the cylindrical outer circumferential surface of the rotating member 12 partitions its internal space and the intake passage 7 on the outer circumference, and the intake passage 7 for the adjacent cylinders of the casing 11
Each intake passage 7 is made independent for each cylinder in contact with the inner wall surface of the cylinder. Intake air flows into the cylindrical rotating member 12 from one end of the center thereof, and communicates with the intake passage 7 for each cylinder through a communication port 12a opened on the circumferential surface of the rotating member 12. The communication position between the internal space and the intake passage 7 changes depending on the position, and each intake passage 7 serves as an independent intake passage from the surge tank 9 to each cylinder.
It is configured so that its length is variable.

A drive motor 16 is connected to the rotating member 12 to change its rotational position, and the length of the intake pipe is changed by the rotation of the rotating member 12. The drive motor 16 is controlled by a control means 17.
It is driven and controlled by a control signal from a control unit.

On the other hand, the cylinder head 15 of the engine 1 is provided with a valve operating mechanism 18 that controls the opening and closing of the intake valve 5 and the exhaust valve 6. The valve operating mechanism 18 is provided with a timing changing means 19 that variably controls the valve timing of the intake valve 5 and the exhaust valve 6 to change the overlapping period thereof.

The valve mechanism 18 has intake side and exhaust side camshafts 20 and 21 that are rotationally driven by a crankshaft (not shown) of the engine 1,
The rotation of the camshafts 20 and 21 opens and closes the intake valve 5 and the exhaust valve 6 via the tappets 22 and 22. The tappets 22, 22 are fitted into and held by rotating members 23, 24 so as to be slidable in the vertical direction. The camshafts 20 and 21 are rotatably supported so as to allow mutual rotation, and are rotatable around the camshafts 20 and 21. The rotating members 23 and 24 are connected to the camshafts 20 and 21 depending on the operating condition of the engine.
A step motor 26 is attached which is oscillated by a rack and pinion through a rotating shaft 25 about the rotation axis of the timing changing means 19. The step motor 26 of the timing changing means 19 is also driven and controlled by a control signal from the control means 17 (control unit).

When the rotary shaft 25 is rotationally driven by the operation of the step motor 26, the rotation members 23 and 24 on the intake side and the exhaust side are rotated in opposite directions, and the rotation member 23 on the intake side is rotated by the camshaft 20.
is rotated in the same direction as the rotation direction (clockwise rotation). When the rotating members 23, 24 are rotated, the tappets 22, 22 also move together with the rotating members 23, 24, and the contact position of the cam surface and the upper surface of the tappets 22, 22 with respect to a specific angular position of the camshafts 20, 21 is determined. The rotational direction of the camshafts 20 and 21 changes to a lag side on the intake side and a lead side on the exhaust side, so that the overlap between the intake valve 5 and the exhaust valve 6 becomes smaller.

The control means 17 includes an engine rotation speed signal from a rotation speed sensor 27 and a load sensor 28.
The load signal from (intake negative pressure sensor) is input,
The control means 17 controls the opening and closing of the intake valve 5 and the exhaust valve 6 by the intake pipe length changing means 13 and the timing changing means 19, corresponding to the engine speed and load range as shown in FIG. This is to adjust the timing. That is, in FIG. 2, the set engine speed N and the set load P
On the other hand, in high load/low rotation speed range A, the intake pipe length is lengthened to set the standard overlap, and in high load/high rotation speed range B, the intake pipe length is shortened to make the overlap smaller than the standard overlap. In the low load/low rotational speed range C, the intake pipe length is lengthened to reduce the overlap, and in the low load/high rotational speed range D, the intake pipe length is shortened to reduce the overlap.

In FIG. 1, 29 is a cylinder block, and 30 is a piston.

The operation of the control means 17 will be explained based on the flowchart shown in FIG. After the start, data on the engine speed and load are read in step S1, and it is determined in step S2 whether the operating region based on this data is region B in FIG. This judgment
If YES, it is in the B area, it is determined in step S3 whether or not the last time was in the A area, and if NO, it is determined in step S5 whether the flag IF has been reset to 0. If the judgment in step S3 is YES and the area is A, the flag IF is set to 1 in step S4, a timer is started, and the process proceeds to step S5.

If the determination in step S5 is NO, that is, if the previous time was in area A and the current transition is to area B, it is determined whether the timer started in step S4 is less than the first set value _t1 , and if it is less than _t1 , In step S7, a control signal for shortening the intake pipe length is output to the intake pipe length changing means 13. On the other hand, when the timer is greater than or equal to _t1 , it is determined in step S8 whether the timer is less than the second set value _t2 , and when it is less than _t2 , a control signal for reducing the overlap is output to the timing changing means 19 in step S9. ,
When t is ₂ or more, the flag IF is set in step S10.
is reset to 0 and the timer is stopped. According to the above flow, when transitioning from region A to region B, the intake pipe length is first shortened, and then the opening/closing timing of the intake valve 5 and exhaust valve 6 is changed so as to reduce the overlap.

Next, if the judgment in step S2 is NO and the judgment in step S5 is YES, and in an operating state other than the transition from area A to area B, step S
In step S11, it is determined whether the area is A, and in step S12, it is determined whether it is the C area.
YES), S13 increases the intake pipe length.
At the same time, S is increased based on the overlap.
There are 14 items. Also, area C (YES in S12)
In this case, S15 increases the length of the intake pipe and S16 decreases the overlap. Furthermore, when in the B and D regions (NO in S12), along with S17 which shortens the intake pipe length,
This is to reduce the overlap (S18).

According to the embodiment described above, when the operating state shifts to an operating range in which both the intake pipe length and intake valve opening/closing timing are changed due to changes in engine speed and load, the timing is changed after changing the intake pipe length. By trying to improve the output by doing so, smooth output improvement can be achieved.
Good drivability can be ensured.

In the above embodiment, the opening/closing timing of both the intake valve and the exhaust valve is changed, but the opening/closing timing of only the intake valve may be changed. Further, the intake pipe length changing mechanism may be modified in design as appropriate in addition to the mechanism using the rotating member described above.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional front view of essential parts of an engine having an intake system according to an embodiment of the present invention, FIG. 2 is an explanatory diagram showing switching control characteristics of intake pipe length and timing with respect to engine speed and load operating range, FIG. 3 is a flowchart showing the operation of the control means;
Figure 4 is a characteristic diagram showing the change in filling amount when the intake valve opening/closing timing is delayed with a long intake pipe length.
FIG. 5 is a characteristic diagram showing the change in the filling amount when the intake pipe length is shortened with the timing constant. DESCRIPTION OF SYMBOLS 1... Engine, 2... Combustion chamber, 5... Intake valve, 7... Intake passage, 9... Surge tank, 13
... Intake pipe length changing means, 17 ... Control means, 19
...Timing change means, 27...Rotational speed sensor, 28...Load sensor.

Claims (1)

[Scope of utility model registration request] The engine is equipped with an intake pipe length changing means for changing the intake pipe length at a predetermined engine speed. The present invention is characterized by providing a control means for controlling the opening/closing timing of the intake valve by the timing changing means after controlling the intake pipe length by the intake pipe length changing means when a specific operating range is reached in which both the opening and closing timings are switched. Engine intake system.