JPH0672536B2 - Engine intake system - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement of an intake device that performs intake using a pressure wave generated in an intake passage.

(Prior Art) Conventionally, an engine has been proposed in which dynamic effects of intake air, such as intake inertia and resonance effect, are utilized to improve the charging efficiency and thereby secure a high output.

However, when the effect of the pressure wave of the intake air is used to improve the charging efficiency, there are the following problems. When the engine speed decreases, the lowering speed of the piston decreases, and thus the negative pressure wave generated decreases, and the effect of improving the filling rate also decreases. In addition, the propagation of the pressure wave occurs at a constant velocity called sonic velocity, whereas the timing at which the effect of pushing the intake air by the pressure wave is desired changes depending on the engine speed, so the pressure wave in a wide rotational speed range is It is difficult to obtain the effect of improving the filling efficiency.

In view of such a situation, JP-A-55-107018 discloses that a supply air reservoir provided in an intake passage upstream of an intake valve and an intake passage communicating with a cylinder and the intake air passage are provided. An air supply control valve having a valve plate that rotates at the same speed as or one half the rotation speed of the crankshaft, and the communication between the cylinder and the air supply reservoir by the control valve according to the rotation speed of the crankshaft. An intake structure for an engine is disclosed which is controlled to obtain an effect of increasing a filling rate by a pressure wave of intake air in a wide range of rotation speed.

(Problems to be Solved by the Invention) Generally, an engine speed (hereinafter referred to as a tuned speed) at which a filling rate increasing effect by a pressure wave generated in an intake system can be obtained is expressed by the following relational expression.

Here, N: tuning rotation speed (rpm), θ _e : effective valve opening period (d
eg), ν: Natural frequency of intake system during intake valve opening period (H
z).

The effective valve opening period does not mean the valve opening period of the intake valve, but is the period during which the intake air is actually introduced into the cylinder, and in the structure disclosed in the above-mentioned JP-A-55-107018, Since the opening / closing period of the control valve is included within the range of the opening period of the intake valve, the effective opening period is when the air supply control valve is open. And the air control valve
During the period when the intake valve is open, the valve opening timing is changed according to the engine speed.
Therefore, in this configuration, the generation timing of the negative pressure wave can be shifted by controlling the opening timing of the intake control valve according to the rotation speed, so that the pressure wave can be generated in the engine speed range with a certain width. The effect of increasing the filling rate can be obtained. However, in the structure disclosed above,
The opening period of the intake control valve is always included in the opening period of the intake valve, regardless of the change in the engine speed.
The effective valve opening period θ _e in the equation (1) is constant, and the natural frequency ν of the system is also constant. Therefore, the rotational speed region in which the filling rate increasing effect is obtained is limited to the region obtained by changing the opening timing of the intake control valve in the range included in the opening period of the intake valve, and thus the rotational speed region is sufficiently wide. Therefore, the effect of increasing the filling efficiency cannot be obtained.

Further, in the above-mentioned structure, in the low rotation speed region, in order to generate a large negative pressure wave, the opening timing of the air supply control valve is delayed to delay the air supply start timing, but this causes a large pumping loss. Therefore, when the load is low, the adverse effect on fuel economy becomes significant.

Further, in the above structure, the effective valve opening period is substantially the valve opening period of the intake control valve having a smaller opening period than the intake valve, so that the intake control valve results in an increase in passage resistance.
In particular, there is a possibility that a sufficient intake air amount cannot be secured during high rotation and high load operation.

(Means for Solving the Problems) The present invention is configured to solve the above problems, and an intake device of the present invention includes an intake port opened and closed in synchronization with rotation of an engine, and the intake port. A control valve that is provided in the intake passage upstream of the port and that controls the intake passage to be opened after the opening timing of the intake port and after the intake top dead center to delay the intake start timing, and at the time of low engine load and high engine load. Releasing means for releasing the delay control of the control valve during rotation, and a reversing unit provided in the intake passage upstream of the control valve for reversing an intake negative pressure wave generated on the downstream side of the control valve when the control valve is opened. It has and. The release means releases the delay control by connecting the independent intake passages communicating with the cylinders to each other downstream of the control valve when the engine is under a low load and at a high speed.

The control valve of the present invention is opened later than the intake top dead center, that is, TDC at the time of low rotation and high load operation, thereby generating a large pressure wave and exerting the effect of pushing the intake air at the end of the intake stroke. There is. In this case, the opening timing of the control valve may be constant, or may be changed stepwise or continuously according to changes in the engine speed and load. The delay control of the intake start timing by the control valve is
It is designed to be released at the time of low load and at the time of high rotation. According to the present invention, the releasing means is provided with a bypass passage that bypasses the control valve, and connects the bypass passage to the independent intake passage to each cylinder downstream of the control valve,
When the load is low and the rotation speed is high, the bypass valve provided in the bypass passage is opened to introduce the intake air from the bypass passage. In addition, a bypass passage that connects the independent intake passages for the respective cylinders on the downstream side of the control valve to each other is provided, and a bypass valve is installed in the passage, and this valve is opened during low load and high rotation, and intake air for other cylinders is opened. The intake air may be introduced through the passage. Further, in the intake system of the present invention, the reversing unit for reversing the negative pressure wave of the intake air generated on the downstream side when the control valve is opened is provided on the upstream side of the control valve. The reversing portion may be formed by forming a volume portion having a constant volume in the intake passage common to each cylinder, or an intake pipe of a cylinder in which the phase of the generated negative pressure wave is shifted by a half wavelength. It is also possible to connect them so that they face each other.

According to the present invention, the control valve is controlled so as to be opened later than the intake top dead center during the operation at low and medium speeds and medium and high loads, and a large negative pressure is provided in the intake passage downstream of the control valve. A pressure wave
This negative pressure wave propagates upstream in the intake passage and is inverted at the reversing portion to become a positive pressure wave. This positive pressure wave propagates downstream as a reflected wave and exerts an effect of pushing intake air into the combustion chamber at the end of the intake stroke. Due to this effect, the engine according to the present invention can ensure a high charging efficiency, and thus can improve the output.

According to the present invention, it is found that the delay control by the control valve at the time of high rotation is rather harmful as a result of increasing the passage resistance, and in addition to the intake introduction performed via the control valve, Intake air is also introduced from the path of (3) to substantially cancel the delay control by the control valve. This extends the effective valve opening period, that is,
In the above equation (1), θ _e becomes large, the passage resistance is reduced, a large amount of intake air can be introduced, and the natural frequency is such that the tuning speed of the pressure wave can be obtained in such an operating region. By configuring the intake system as described above, the dynamic effect of intake air can be obtained together, and the charging efficiency can be further improved.

In addition, since the pumping loss at the time of low load increases and the fuel consumption is adversely affected, the delay control is similarly canceled. Therefore, according to the present invention, it is possible to secure a sufficient intake amount at the time of high rotation, and
It is also possible to prevent a decrease in fuel consumption when the load is low.

Further, in a preferred aspect of the present invention, the intake start timing is delayed by delaying the valve opening timing of the control valve according to the operating conditions such as engine rotation and engine load, thereby controlling the effective valve opening period. . That is, the above equation (1) At, θ _e is changed according to the operating state. As a result, the tuning rotation speed can be obtained in a wide rotation speed region, and the desired effect of increasing the charging efficiency by the pressure wave can be obtained in each of different rotation regions.

(Description of Embodiments) Hereinafter, embodiments of the present invention will be described with reference to the drawings.

Referring to FIG. 1 and FIG. 2, the engine 1 of this example is
It is a four-cylinder engine, and four cylinder bores 3 are formed in the cylinder block 2, and a piston 4 is reciprocally arranged in each cylinder bore 3. A cylinder head 5 is coupled above the cylinder block 2, and a space formed by a space above the piston of the cylinder bore 3 and a lower recess of the cylinder head 5 constitutes a combustion chamber 6. An intake port 7 and an exhaust port 8 are opened in the combustion chamber 6, and an intake passage 9 and an exhaust passage 10 are formed in the cylinder head 5 so as to communicate with the intake port 7 and the exhaust port 8. An intake valve 11 is associated with the intake port 7, and an exhaust valve 12 is associated with the exhaust port 8. Further, a spark plug 12a is arranged on the cylinder head 5 so that its tip portion projects into the combustion chamber. A manifold is connected to the intake passage 9 of each cylinder, a fuel injection nozzle 12b is attached in the vicinity of this connection portion, and the intake passages 9 join upstream to form a main intake passage 13 and extend further upstream. An air cleaner is provided at the upstream end of the main intake passage 13.
14 is installed, an air flow meter 15 for measuring the intake air flow rate is provided downstream of the air cleaner 14, and a volume part 16 having a constant volume for inverting the negative pressure wave generated in the intake system is provided on the downstream side thereof. Is provided. Further, in the main intake passage 13, a throttle valve 17 is arranged,
A cylindrical rotary valve 18 as shown in FIG. 3 is rotatably arranged at a branch portion downstream of the throttle valve.
The intake passage 9 to each cylinder downstream of the branch portion is provided with a bypass passage 19
By-pass valves 20 are attached to the connecting portions of the bypass passage 19 and the intake passages 9, respectively. The upstream side of the bypass passage 19 is connected between the branch portion of the main intake passage 13 and the throttle valve 17. An opening 21 that communicates with the intake passage 9 of each cylinder at a predetermined rotation position is provided on the peripheral wall of the rotary valve 18 for each cylinder. In this example, ignition is 1-3-4-2
Therefore, the opening positions for the first and fourth cylinders and the opening positions for the second and third cylinders are formed with the same orientation in order to avoid mutual interference of intake air. As shown in FIG. 1, the rotary shaft 18 a of the rotary valve 18 is connected to the pulley 2 via an advance mechanism 22.
Connected to 3. The pulley 23 is connected via a belt 26 to a drive pulley 25 attached to the end of the crankshaft 24. In this example, the pulley 23 and the pulley 25 have the same diameter, so that they rotate at the same speed. The advance mechanism 22 includes a helical gear 27 attached to the end of the rotary shaft 23a of the pulley 23 and a rotary valve.
A helical gear 28 attached to the end of the rotary shaft 18a of 18 and arranged to face the helical gear 27 on the pulley 23 side;
An adjusting piece 29 that meshes with both helical gears 27 and 28 is provided. The adjusting piece 29 can change the meshing position with the helical gears 27 and 28 in the rotation axis direction of the rotary valve 18, and when the adjusting piece 29 moves in the axial direction and the meshing position changes, the helical gear 27, The relative rotation position with 28 changes,
As a result, the amount of advance angle is changed. An actuator 30 is provided to adjust the axial position of the adjustment piece 29, and the actuator is preferably operated by a command signal from a control unit 31 including a microcomputer. There is. In this example, a signal indicating the engine speed is input to the control unit 31, and the control unit 31 determines the advance amount according to the speed signal, and advances it via the actuator 30. Drives the angular mechanism 22. The control unit 31 is also adapted to receive an engine load signal, and the control unit 31 controls the bypass valve 20 according to the rotation speed and the load value.
A command signal for opening the bypass valve 20 is output to the actuator 20a in a predetermined operation region.

In the above structure, in this example, the rotary valve 18 rotates at the same speed as the crankshaft 24. Therefore, the rotary valve 18
The timing at which the opening 21 of the cylinder communicates with the intake passage 9 of each cylinder, that is, the opening period of the rotary valve 18,
It corresponds to 11 valve opening periods. In this example, intake air is actually introduced into the combustion chamber 6 while the intake valve 11 is open and the rotary valve 18 is open. Therefore, this period is the effective valve opening period. Referring to FIG. 4 together, the opening period of the rotary valve 18 is adapted to be changed according to the engine speed. When the rotation speed increases, the rotary valve 18 is rotated as shown by the broken line in the figure. The valve opening timing of 18 is set so as to approach the valve opening timing of the intake valve 11. On the other hand, when the engine speed is low, the valve opening timing of the rotary valve 18 is shifted to the delay side by the operation of the advance mechanism 22 as shown by the solid line in the figure. When the rotary valve 18 opens, intake air is actually introduced into the combustion chamber 6, but at the time of opening this, the rotary valve
A negative pressure wave of intake air is generated on the downstream side of 18. This negative pressure wave
It propagates upstream through the intake passage 13 and reaches the volume 16. In the volume part 16, the negative pressure wave is inverted and becomes a positive pressure wave, and the intake passage
It propagates inside 13 to the downstream side and finally reaches the combustion chamber 6.

In this example, the intake system is configured so that the positive pressure wave reaches the combustion chamber 6 at the end of the intake stroke, and thus the intake pressure pushing effect of the positive pressure wave is utilized to achieve high intake efficiency. Trying to get. Then, as the amplitude of the negative pressure wave generated when the rotary valve 18 is opened is larger, a larger reversal positive pressure wave is generated, and as a result, it can be seen that a large effect of increasing the charging efficiency can be obtained. In the low rotation speed in which the generated negative pressure wave tends to be small, the valve opening timing of the rotary valve 18 is delayed compared with the high rotation speed, and a larger negative pressure wave is formed. Further, the engine speed at which the effect of increasing the filling rate by the pressure wave is obtained, that is, the tuning speed N (rpm)
Is expressed as N = θ _e · ν / 6 as a function of the effective valve opening period θ _e (deg) and the natural frequency ν (Hz) of the intake system. In the device of this example, the advance mechanism 22 is Since the effective valve opening period θ _e is changed according to the rotation speed change, the tuning rotation speed can be obtained over a wide rotation speed range, and as a result, a wide rotation speed range from low rotation speed to middle rotation speed can be obtained. Thus, the effect of increasing the filling rate can be obtained.

In the high engine speed region, the control valve itself gives the effect of restricting the passage, and if the control to shift the rotary valve to the delay side is performed as described above, the passage resistance increases and the high filling amount is increased. Will be an adverse effect on the securing of.
Therefore, in this example, when the rotation speed is high, the actuator 20a
Is operated to open the bypass valve 20 so that the intake air is also introduced from the bypass passage 19 and is substantially a rotary valve.
The delay control by 18 is canceled. As a result, it is possible to solve the problem that intake air shortage occurs at high rotation speeds. Further, when the control is performed such that the opening timing of the rotary valve 18 is delayed at a relatively low engine speed and a low load, the pumping loss increases, and the deterioration of fuel efficiency becomes remarkable.
Similarly, the bypass valve 20 is opened, and intake air is also introduced from the bypass passage 19 to substantially cancel the delay control of the rotary valve 18.

Referring to FIG. 5, another embodiment of the present invention is shown. In this embodiment, the intake passage 13 upstream of the rotary valve 18 is shown.
The bypass passage 19 that connects the independent intake passages 9 to each other is not provided, and the communication passage 19 that connects the independent intake passages 9 to each other is provided on the downstream side of the rotary valve 18. Therefore, in the structure of this example, when the bypass valve 20 is opened, the independent intake passages are in communication with each other. The ignition sequence of the engine of this example is 1-3-4-2, and the opening 21 of the rotary valve 18 has the same orientation for the first and fourth cylinders and for the second and third cylinders. Has become. Therefore, the rotary valve 18
Since the first and fourth cylinders and the second and third cylinders are opened at the same timing, the intake valve 11 and the rotary valve 18 are opened at the timings shown in FIG. Therefore, when the bypass valve 20 is opened and the independent intake passages 9 are in communication with each other, the next intake stroke is performed for the cylinder that is currently performing the intake stroke as shown by the arrow in FIG. Independent intake passage 9 and communication passage for the cylinder
Intake air is supplied through 19a. Since this intake air is introduced in the first half of the intake stroke, even if the valve opening timing of the control valve is shifted to the delay side, the valve opening period is substantially extended and the intake shortage can be resolved.

In addition, in the above embodiments, the example in which the present invention is applied to the reciprocating engine has been described, but the present invention can also be applied to the rotary piston engine in the same manner.

[Brief description of drawings]

1 is an overall schematic view of an engine according to an embodiment of the present invention, FIG. 2 is a partial sectional view of the engine of FIG. 1, FIG. 3 is a perspective view of a rotary valve, and FIG. 5 is a graph showing the valve opening timing, FIG. 5 is a schematic diagram of an engine according to another embodiment of the present invention, and FIG. 6 is a graph showing the valve timing of the engine of FIG. 1 ... Engine, 2 ... Cylinder block, 3 ... Cylinder bore, 4 ... Piston, 5 ... Cylinder head, 6 ... Combustion chamber, 9 ... Intake passage, 10 ... Exhaust passage, 13 ... Main intake Passage, 14 ... Air cleaner, 15 ... Air flow meter, 16 ... Volume, 17 ... Throttle valve, 18 ... Rotary valve, 19 ... Bypass passage, 19a ... Communication passage, 20 ... Bypass valve, 22 …… Advance mechanism, 31 …… Control unit.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Junzo Sasaki 3-1, Shinchi Fuchu-cho, Aki-gun, Hiroshima Prefecture Mazda Co., Ltd. (72) Inventor Kazunori Tominaga 3-3 Shinchi, Fuchu-cho, Aki-gun, Hiroshima Mazda Stock In the company

Claims (1)

[Claims] 1. An intake port opened and closed in synchronization with the rotation of an engine, and an intake passage provided upstream of the intake port, the intake passage being located after the opening timing of the intake port and after intake top dead center. A control valve that delays the opening intake start timing, a release means that releases delay control of the control valve when the engine is under low load and high rotation, and a control valve that is provided in the intake passage upstream of the control valve. And a reversing unit for reversing an intake negative pressure wave generated on the downstream side of the control valve when the valve is opened, and the releasing means communicates the independent intake passages to each cylinder downstream of the control valve when the engine is under a low load and at a high rotation speed. The engine intake system is characterized in that the delay control is released by doing so.