JP2620871B2 - Engine intake system - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention is provided with a variable intake mechanism for supercharging by controlling an intake pipe shape variable means provided in the middle of an intake passage according to an operation state. The present invention also relates to an intake system for an engine in which a dynamic effect of intake can be enjoyed in a wide engine speed range by controlling the variable intake mechanism.

(Description of the Related Art) In an intake device for an engine, a charging efficiency is increased by utilizing a so-called dynamic effect of intake pressure, which is a fluctuation of intake pressure caused by an opening / closing operation of an intake valve, thereby improving output. Modified engines are known.

In this case, the rotational speed range in which the intake dynamic effect can be obtained is limited to a certain range corresponding to the natural frequency of the intake system. In view of this point, there is also known an engine structure in which the natural frequency of the intake system is changed according to the operating state in order to obtain the intake dynamic effect in a wide engine speed range.

For example, in Japanese Patent Application Laid-Open No. 60-14169, a switching valve is provided in the intake passage, and the switching valve is opened and closed according to the operating condition to change the natural frequency of the intake resonance system, thereby changing the rotational speed. On the other hand, there is disclosed an intake device that obtains output characteristics having two output peak values.

Further, an intake device for an engine having means for changing two or more natural frequencies of the intake system has also been proposed. In this way, if the natural frequency of the intake system is changed according to a change in the rotational speed, The output can be improved in a wide range of rotation speed.

(Problems to be Solved) However, if the means for switching the natural frequency of the intake system is configured so that the output can be improved in a wide rotation speed range as described above, the weight of the control system increases, and the followability of the switching is increased. As a result, there is a problem that a shock based on the natural frequency switching operation occurs.

This problem becomes remarkable especially when the rotational speed change is large.

The present invention has been made in view of such circumstances, and has as its object to provide an engine intake device that can solve the above-described shock problem based on an intake system switching operation. .

(Means for Solving the Problems) An object of the present invention is to control a valve element provided in the intake passage in accordance with the engine speed so that the natural frequency of the intake system is synchronized over a wide engine speed range. In an intake system for an engine provided with a variable intake mechanism for changing the natural frequency of the intake system, the natural frequency of the intake system is tuned in the wide engine speed range in an operating state where the change in the engine speed is small. By controlling the valve element of the variable intake mechanism, when the engine is in a no-load state or in an operation state in which the engine speed change is large, the control of the valve element is fixed or limited to thereby restrict the characteristic of the intake system. The variable control of the frequency can be achieved by an intake device for an engine, which is characterized by fixing or limiting.

In this case, in a preferred embodiment, the fixed position of the valve body can be arbitrarily set in the operating state where the change in the engine speed is large.

A variable intake mechanism according to the present invention includes an on-off valve for switching at least two resonance systems provided in an intake system, and an intake communication area provided separately from the on-off valve and in which intake air is introduced in conjunction with the on-off valve. From a control valve that changes

In the present invention, fixing the control of the valve element means that the valve element is immediately fixed at the position, and limiting the control of the valve element means, for example, fixing the valve element after slightly rotating the valve element. Say the case.

(Operation) According to the present invention, the natural frequency of the intake system to which the intake air is introduced is changed by controlling the variable intake mechanism so that the tuning speed is included in each operation region in accordance with the change in the operation state. Let it.

Then, in a no-load state in which no output is requested and in an operation state in which the rotational speed fluctuates greatly, that is, when the transmission is in a low speed stage, the control of the variable intake mechanism is fixed or the control amount thereof is limited.

(Explanation of Example) Hereinafter, an example of the present invention will be described with reference to the drawings.

FIG. 1 is a schematic view of an intake system for an engine according to one embodiment of the present invention. An engine 1 is a V-type six-cylinder engine having first to sixth cylinders 2a to 2f.

The first cylinder 2a and the third cylinder 2 in which the ignition order is not continuous
c, the fifth cylinder 2e is arranged in the first cylinder 1a, and the second cylinder 2b, the fourth cylinder 2d, and the sixth cylinder 2f are arranged in the second bank 1b.

The intake system of the engine 1 has an intake manifold 3a corresponding to the first bank 1a and an intake manifold corresponding to the second bank 1b.
3b.

From the intake manifolds 3a and 3b, the intake port 4a of each cylinder
Branch intake passages 5a to 5f communicating with .about.4f extend. An air cleaner 7 is provided at an upstream end of the intake passage 6 at a position upstream of the intake manifolds 3a and 3b, and an air flow meter 8 is provided at a downstream side thereof.

A throttle valve 9 is provided downstream of the air flow meter 8.

Downstream of the branch portion of the intake passage 6 and upstream of the position where the branch intake passages 5a to 5f to the respective cylinders are provided, a communication passage 10 communicating the two intake manifolds 3a and 3b is provided.
A butterfly valve type opening / closing valve 11 for communicating or blocking the passage 10 is arranged in the passage 10.

The downstream ends of the intake manifolds 3a and 3b communicate with each other through a communication path 12. At both ends of the communication path 12, a pair of variable control valves 13a and 13b that operate in synchronization are arranged.

As shown in FIG. 2, the variable control valves 13a and 13b include a fan-shaped valve element 14 supported on a common rotary shaft 14a.

A gear 14b meshing with the drive gear 15a of the drive motor 15 is mounted on the rotating shaft 14a, and is rotated by the power of the motor 15.

In addition, the inside of the communication path 12 is partitioned in the longitudinal direction,
Thereby, three communication paths 12a, 12b, and 12c are formed.

As the fan-shaped valve element 14 rotates, the communication path
The area of the twelve communication passages changes, and accordingly, the natural frequency of the resonance system of the intake air changes.

The device of the present invention includes these on-off valve 11 and variable control valve 13.
A control unit 16 for controlling a drive motor 15 for a and 13b is provided.The control unit 16 receives an engine speed, a symbol indicating on / off of a clutch, and a signal indicating a position of a gear position of a transmission. It has become so.

Then, the control unit 16 calculates the signal to control the motor 15 for the on-off valve 11 and the variable control valves 13a and 13b, and changes the natural frequency of the intake system so that the synchronized rotation exists in the operation state. It is made to let.

The control of the device having the above structure will be described.
FIG. 3 is a flowchart showing an example of control by the control unit 16.

In FIG. 3, the control unit 16 first reads the engine speed, the state of the clutch, and the gear position.

When the clutch is on and the shift speed is high, the variable control valve 13 is controlled in accordance with the engine speed.
a, 13b and the on-off valve 11 are controlled to change the natural frequency of the intake system.

That is, when the engine speed is low, the control unit 16 closes the on-off valve 11 to shut off the communication passage 10, and also completely closes the variable control valves 13a and 13b to shut off the communication passage 12.

Therefore, the resonance system of the intake air in this case is as shown by the solid line in FIG. That is, the pressure wave of the intake air is
At the branching point, and becomes a positive pressure wave to give a resonance effect.

 In this case, the cycle of the positive pressure wave is the longest.

Next, when the engine speed rises to a predetermined range, the control unit 16 drives the motor 15 to rotate the variable control valves 13a and 13b to open the communication passage 12.

In this case, since the communication passage 12 is divided into three as described above, the natural frequency of the intake system changes in three stages according to the amount of rotation of the variable control valves 13a and 13b. Then, the cycle of the positive pressure wave becomes shorter as the communication paths 12a, 12b, and 12c become in communication.

This is based on the fact that the volume of the resonance system of the intake air increases as the communication state of the communication passage 12 increases.

Accordingly, the resonance system in the case where the communication path 12 is completely in communication is as shown in FIG.

Furthermore, when the rotation speed increases, the control unit
16 closes the variable control valves 13a and 13b and opens the on-off valve 11.

Thereby, the inversion position of the positive pressure wave becomes the communication path 10,
The resonance system becomes as shown by the solid line in FIG. 6, and the natural frequency further increases.

Next, when the rotation speed further increases, the control unit 16 starts opening the variable control valves 13a and 13b. Accordingly, the natural frequency of the resonance system also increases in three stages as described above.

When the variable control valves 13a and 13b and the on-off valve 11 are fully opened, a resonance system shown by a solid line in FIG. 7 is obtained.

Referring to FIG. 8, the on-off valve 11 and the variable control valves 13a, 1
The relationship between 3b and the output torque of the control engine is shown. The torque characteristic line a in FIG. 8A is a characteristic obtained in the case of the resonance system of FIG. 4, that is, the resonance system having the lowest natural frequency, and the characteristic line b is the resonance system of FIG.
This is a characteristic obtained in the case of a resonance system having the largest natural frequency.

As shown in FIG. 8 (b) and FIG. 8 (c), the natural frequencies are different depending on the combination of the opening / closing operation of the on-off valve 11 and the variable control valves 13a, 13b. A plurality of characteristic lines are obtained. In the control of the present embodiment, the natural frequency of the intake system is switched according to the change in the engine speed, so that the resonance effect of the intake air can be secured in the respective speed ranges, and the characteristic line c in FIG. The output can be increased as shown by.

In the control of this example, when the clutch is off and when the shift speed of the transmission is at a low speed, the above-described control is not performed, and the on-off valve 11 is set to the position indicated by d in FIG. The position and variable control valves 13a and 13b are fixed to the position e in FIG. 8C, that is, a position frequently used during acceleration.

This is because there is no output request when the clutch is off, and there is no need to perform natural frequency switching control. Is worsened and a shock occurs.

Therefore, in this case, regardless of the change in the engine speed, the on-off valve 11 is fixed at the position d in FIG. 8B and the variable control valves 13a and 13b are fixed at the position e in FIG. 8C. Therefore, the acceleration required in the low speed stage can be sufficiently exhibited.

However, the on-off valve 11 has a variable moment of inertia
Since it is smaller than a and 13b and has good followability, opening and closing may be controlled in accordance with a change in the number of revolutions.

Further, the fixing position is not limited to the above-described embodiment, and can be set arbitrarily. For example, the valve may be fixed to a position at the time of shifting to a low speed stage.

(Effect of the Invention) According to the present invention, it is possible to eliminate the shock caused by the natural frequency switching operation of the intake system that occurs when the rotational speed fluctuation is large, and to perform the proper natural frequency switching operation to effectively resonate. The effect can be obtained, and the output can be improved.

[Brief description of the drawings]

FIG. 1 is a schematic view showing an intake system of an engine according to one embodiment of the present invention, FIG. 2 is a cross-sectional view of a communication passage showing a variable control valve, and FIG. 3 is an example of control. 4 to 7 are conceptual diagrams showing a resonance system, and FIG. 8 is a graph showing an opening / closing operation of an on-off valve and a variable control valve, and a torque characteristic. 1 ... engine, 2a-2f ... cylinder, 3a, 3b ... intake manifold, 4a-4f ... intake passage, 5a-5f ... branch intake passage, 6 ... intake passage, 7 ... air cleaner, 8 …… Air flow meter, 9 …… Throttle valve, 10 …… Communication passage, 11 …… On-off valve, 12 …… Communication passage, 13a, 13b …… Variable control valve, 14 …… Valve body, 14a …… Rotary shaft , 14b …… Drive gear,
15 ... Drive motor, 16 ... Control unit.

Claims (2)

(57) [Claims] A valve body provided in the intake passage is controlled in accordance with the engine speed to change the natural frequency of the intake system so that the natural frequency of the intake system is synchronized in a wide engine speed range. In an intake device for an engine having a variable intake mechanism, the valve body of the variable intake mechanism is controlled such that the natural frequency of the intake system is tuned in the wide engine rotational speed range in an operating state where the change in the engine rotational speed is small, When the engine is in a no-load state or in an operation state in which the change in the engine speed is large, the variable control of the natural frequency of the intake system is fixed or limited by fixing or limiting the control of the valve body. An intake device for an engine, characterized by: 2. The intake system for an engine according to claim 1, wherein the fixed position of the valve body can be set arbitrarily in the operating state where the change in the engine speed is large.