JPH04353265A - Secondary air introduction passage for internal combustion engine - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a passageway for introducing secondary air into an intake port bypassing a throttle valve in an internal combustion engine.

0002

[Prior Art] For example, in an electronically controlled fuel injection engine in an internal combustion engine, the required fuel injection amount is approximately proportional to the intake manifold internal pressure, and the intake manifold internal pressure detected by a pressure sensor is The fuel injection amount is controlled in accordance with the engine rotation speed. Further, in the case of the above engine, a constant electric signal is always obtained by the throttle valve opening sensor, and the fuel is cut off during deceleration based on this signal. Therefore, if the idling speed is adjusted using the throttle valve, the throttle valve opening sensor must be calibrated in response to changes over time, which tends to make it difficult to maintain the accuracy of the throttle valve opening signal. . Therefore, idling control is usually performed by closing the throttle valve and adjusting the air flow rate of the secondary air introduction passage that bypasses the throttle valve.

[0003] Such secondary air introduction devices include a fast idle valve that opens only when the water temperature is low in response to the water temperature to increase the idling speed when the engine is cold, and a first idle valve that opens only when the water temperature is low, and a first idle valve that increases the idling speed when the engine is cold, and a first idle valve that opens only when the water temperature is low. There is an electronic control valve that adjusts the air-fuel ratio to keep the idling speed at an appropriate level, and an auxiliary air intake valve that compensates for the air flow rate during cranking. The one provided with each of these control valves is Utility Application No. 1-1 filed by the same applicant.
It is proposed in the specification of No. 04079. According to this structure, the throttle body is connected to a surge tank as an air chamber provided on the upstream side of the intake manifold, and the peripheral wall of the surge tank includes an air increase passage when the machine is cold, an auxiliary air introduction passage when starting, An idle rotation correction air introduction passage and a starting auxiliary air introduction passage are provided.

However, some of the above-mentioned secondary air introduction passages have a small inner diameter and a short passage length. In this case, a problem arises in that relatively high frequency intake noise is generated when air passes through the secondary air introduction passage.

[0005]

[Problems to be Solved by the Invention] The present invention has been made to improve these inconveniences, and its main purpose is to reduce the intake noise generated when secondary air passes through the secondary air introduction passage. The object of the present invention is to provide a secondary air introduction passage that can be reduced.

[0006]

SUMMARY OF THE INVENTION According to the present invention, it is an object of the present invention to provide a passage for introducing secondary air into an intake port bypassing a throttle valve in an internal combustion engine. Provided is a secondary air introduction passage for an internal combustion engine, characterized in that the secondary air introduction passage is provided with a muffler in order to reduce intake noise generated when the secondary air passes through the secondary air introduction passage. This is achieved by In particular, it is preferable that the muffling device is provided on the intake upstream side of a control valve that selectively opens and closes the secondary air introduction passage depending on the operating state.

[0007]

[Function] In this way, when an expansion chamber is provided as a noise muffling device, the secondary air goes around into the expansion chamber and intake noise is reduced, and for example, it resonates with an opposite phase to the intake noise. When a resonance chamber formed in this manner is provided, intake noise is canceled out and reduced. In particular, by providing a silencer on the upstream side of the control valve that selectively opens and closes the secondary air introduction passage, the sound generated from the control valve when the throttle valve is closed can be removed from the fresh air introduction port on the upstream side of the intake air. It can be prevented from coming out.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings. FIG. 1 schematically shows an intake system of an engine to which the present invention is applied. For example, an intake manifold 3 connected to the intake port 2 of each cylinder in an engine body 1 consisting of an in-line five-cylinder engine includes a throttle body 4 for adjusting the air flow rate and a throttle body 4 for removing dust from the atmosphere. An air cleaner 5 is connected thereto. Between the upstream side of the throttle valve 6 in the throttle body 4 and the most upstream side of the intake manifold 3, there is a space between the upstream side of the throttle valve 6 and the most upstream side of the intake manifold 3. A plurality of bypass passages are provided whose degree of communication is individually controlled depending on the state.

These bypass passages are attached to the intake manifold 3 and the throttle body 4, respectively.
A slow air passage 8 equipped with a variable jet 7 to define a basic idling air flow rate, and a fast idle valve 10 connected to a thermowax 9 to close when the cooling water temperature exceeds a predetermined value. It is equipped with an increase passage 11 and an electronic control valve 12 for adjusting the flow rate of bypass air to the intake manifold 3 so as to always maintain an appropriate idling rotation speed according to the operation of the air conditioner or the increase or decrease in electrical load. Correction air introduction passage 13
and an auxiliary air introduction passage 15 equipped with an auxiliary air valve 14 that operates in response to the intake negative pressure in order to compensate for insufficient intake flow due to low intake negative pressure during cranking. In order to inject fuel into the intake port 2 integrated into the cylinder head, a fuel injection valve 16 is provided near the connection portion of the intake port 2 with the intake manifold 3. The electronic control valves 12 are each controlled by an output signal from an electronic control circuit 17.

FIG. 2 shows in detail the intake manifold 3 portion of a five-cylinder engine to which the present invention is applied. The intake manifold 3 has independent intake branch pipes 20a for each cylinder.
~20e, and the upstream end of each intake branch pipe 20a~20e has an elongated box shape along the cylinder row direction and is configured as an air chamber common to all cylinders, which is sufficient to absorb intake pulsation. A surge tank 18 having a volume of A throttle body 4 having a throttle valve 6 therein is connected to one end of the surge tank 18.
Similar to known engines, the amount of intake air can be controlled by operating the accelerator pedal.

In a part of the peripheral wall of the throttle body 4, there are two passages 21a and 21b communicating between the intake upstream side of the throttle valve 6 and the joint surface side with respect to the surge tank 18, to constitute the bypass passage. It is formed. The surge tank 18 has the two passages 21a and 21 at the joint surface of the flange 18a for connecting the throttle body 4.
Two passages 23a and 23b are provided, each aligned with and communicating with the opening of b.

In addition, the intake branch pipe 20a of the surge tank 18
Mounting seats 19a, 19b, and 19c for the first idle valve 10, electronic control valve 12, and auxiliary air valve 14 described above are provided on the wall surface 18b on the side opposite to the side 20e. The surge tank 18 has its wall surface 18
After extending toward b, as shown in FIG.
A protrusion 24 is provided that extends to . One of the above passages 2
3a is the passage 21 provided in the throttle body 4;
It is formed in the protruding portion 24 so as to communicate with the first idle valve 10 and to open into the fast idle valve 10 mounting seat 19a provided at the intermediate portion of the wall surface 18b. Both passages 2
A cold air increase passage 11, which is a bypass passage, is formed by 1a and 23a.

Further, the surge tank 18 is provided with a protrusion 27 in the same manner as described above so as to extend from the end on the mounting side of the throttle body 4 to the end on the opposite side. The other passage 23b is connected to the throttle body 4
communicates with the passage 21b provided in the wall surface 18b.
An electronic control valve 12 provided near the throttle body 4 of
The auxiliary air valve 14 is provided near the end of the mounting seat 19b and the wall surface 18b on the side opposite to the throttle body 4 side.
It is formed in the protruding portion 27 so as to open to the mounting seat 19c. These passages 21b and 23b form a correction air introduction passage 13 and an auxiliary air introduction passage 15, which are bypass passages.

The mounting seat 19b has an opening 25 for communicating the inside of the fast idle valve 10 in the mounted state with the passage 23a, and an opening 25 for communicating the inside of the fast idle valve 10 in the mounted state with the passage 23a.
An opening 26 for communicating between the inside of the surge tank 18 and the inside of the surge tank 18
and is provided. Further, the mounting seat 19a has an opening 28 branching from the passage 23b to communicate the inside of the electronic control valve 12 in the installed state with the passage 23b, and an opening 28 branching from the passage 23b.
An opening 29 is provided for communicating the inside of the surge tank 18 with the inside of the surge tank 18. Further, the mounting seat 19c is provided with an opening 30 for communicating the inside of the auxiliary air valve 14 to be installed and the passage 23b, and an opening 31 for communicating the inside of the auxiliary air valve 14 and the inside of the surge tank 18. ing.

As shown in FIGS. 3 and 4, a protrusion 32 is integrally provided on the lower surface of the surge tank 18 in the longitudinal direction from the vicinity of the throttle body 4. . A side branch 33 in the shape of a blind alley branching from the passage 23a near the branching passage toward the opening 28 is formed within the protruding portion 32 as a muffling device.

Next, the operation of the above embodiment will be explained. When the auxiliary air valve 14 is in the open state, the passage 21b
, the passage 23b and its opening 30, the inlet and outlet of the auxiliary air valve 14, and the communication hole 31 with the inside of the surge tank 18. By the way, this auxiliary air valve 14 is set to be kept open by negative pressure during cranking. Therefore, during cranking, sufficient air bypasses the throttle valve 6 and is supplied into the intake pipe, improving startability.

When the engine completely explodes and the intake negative pressure reaches a predetermined value, and the cooling water temperature is below the predetermined value, that is, in a cold state, the first idle valve 1 is closed by the contraction of the thermowax 9.
0 opens, passage 21a, passage 23a and its opening 25,
The cold air increase passage 11, which is composed of the inlet and outlet of the first idle valve 10 and the communication hole 26 with the inside of the surge tank 18, communicates with each other, increasing the air flow rate and increasing the idling speed when the engine is cold. .

As the engine warms up, the first idle valve 10 closes and the engine reaches normal idling speed. During steady operation, the passage exclusively through the electronic control valve 12,
That is, the openings 2 of the passage 21b, the passage 23a, and their branch passages.
8. The idling rotational speed is corrected in the correction air introduction passage 13, which is constituted by the inlet and outlet of the electronic control valve 12, and the communication hole 29 with the inside of the surge tank 18.

Incidentally, when the secondary air passes through the correction air introduction passage 13, intake noise is generated, and the peak of the intake noise can be actually measured or estimated. In addition, in the side branch 33, the opening area to the passage 23a, the pipe length corresponding to the straight pipe section from the opening to the interior of the side branch 33, and the volume of the side branch 33 are designed. By changing the correction air introduction passage 13
The phase and frequency of the resonance frequency with respect to the peak frequency of the intake sound passing through the passage 23b can be arbitrarily set. By the way, when the cross-sectional area of the passage is small and the passage length is long, high-frequency sound is generated. High frequency sound is
It is relatively unpleasant, and its propagation is highly linear and difficult to attenuate.

According to the present invention, by setting the shape of the side branch 33 so as to generate a resonant frequency with an opposite phase, which is a phase shifted by half a cycle from the peak frequency,
The peak frequency of the unpleasant high-frequency sound of the intake air is canceled out, and the intake noise is reduced. The side branch 33 in the above embodiment is integrally molded using a core when die-casting the surge tank 18, which is a part of the intake manifold 3, and is integrated with the surge tank 18. , space-saving and compact. Note that a resonator chamber or an expansion chamber may be provided in place of the side branch 33.

Furthermore, as shown in FIG. 5, the passage 23b
A hose joint 34 is provided on the hose plug 34.
A tube 35 whose free end is closed with a blind stopper may be connected to the tube. In this way, a resonance chamber similar to that of the side branch 33 can be formed by the tube 35, and even if there is not enough installation space for the side branch 33, it can be accommodated, and the area around the secondary air introduction passage can be suitably used. It can be made more compact. Further, by using an elastomer material as the material of the tube 35, an effect of absorbing the sound radiated from the passage 23b is produced.

By the way, the sound generated from the electronic control valve 12 when the throttle valve 6 is closed is heard outside through the fresh air inlet of the intake duct. According to the present invention, since the side branches 33 and tubes 35 constituting the muffling device are installed on the intake upstream side of the electronic control valve 12 as described above, the sound flowing from the electronic control valve 12 toward the intake upstream side is , the sound is suitably muted in the middle.

Further, as shown in FIG. 6, it is preferable to provide a throttle 36 by fitting, for example, an annular member into the passage 21b.
In this case, there is an effect of suppressing pulsations occurring in the passages 21b and 23b. This aperture 36 may be used in combination with one provided with the side branch 33 shown in FIG. 1, one provided with the tube 35 shown in FIG. 5, or the like. Further, as shown in FIG. 7, a tapered portion 37 formed by casting, drilling, or a combination thereof may be provided on the intake upstream side of the passage 21b. In this case, there is no need to use a separate member, so the number of parts does not increase.

Furthermore, instead of the throttle 36, for example, the passage 21
A metal gasket 38 having an inner diameter smaller than the inner diameter of b may be provided. In this case, as shown in FIG. 8, the metal part is exposed inside the passage 21b, and the outer peripheral part is held between the throttle body 4 via the composition sheet 39 or the like, or exposed inside the passage 21b. It is best to form the part so that it gradually bends in the direction of the air flow and narrows. By doing so, it is possible to suitably prevent vibration noise from being generated due to the intake air flow in the constricted portion of the gasket. Further, a similar effect can be obtained even if a filter is provided in place of the diaphragm 36.

Note that in this embodiment, the electronic control valve 12
When the intake passage 4a is closed, there is also an effect of reducing intake noise passing through the intake passage 4a. Further, by reducing the wave motion of the intake sound of the secondary air, it is possible to suppress the vibration of the valve body when the valve is opened, and the amount of incoming air can be adjusted with high precision.

[0026]

As described above, according to the present invention, for example, a resonant chamber capable of resonating in an opposite phase to the peak frequency of intake noise generated when secondary air passes through a secondary air introduction passage is provided. By providing it as a muffling device, the sound at the peak frequency is canceled out and intake noise is reduced. Further, by providing the muffling device on the intake upstream side of the control valve, it is possible to suitably reduce the noise generated from the control valve when the throttle valve is closed.

[Brief explanation of drawings]

FIG. 1 is an intake system diagram of an engine to which the present invention is applied.

FIG. 2 is a top view of the intake manifold.

FIG. 3 is a view taken in the direction of arrow III in FIG. 2;

FIG. 4 is a view taken along the arrow IV-IV line in FIG. 2;

FIG. 5 is an enlarged view of main parts showing a second embodiment to which the present invention is applied.

FIG. 6 is an enlarged view of main parts showing a modified embodiment based on the present invention.

FIG. 7 is an enlarged view of main parts showing another modified embodiment based on the present invention.

FIG. 8 is an enlarged view of main parts showing another modified embodiment based on the present invention.

[Explanation of symbols]

1 Engine body 2 Intake port 1a Cylinder head 1b Cylinder block 3 Intake manifold 4 Throttle body 4a Intake passage 5 Air cleaner 6 Throttle valve 7 Variable jet 8 Slow air passage 9 Thermo wax 10 First idle valve 11　Cold machine air increase passage 12 Electronic control valve 13 Correction air introduction passage 14 Auxiliary air valve 15 Auxiliary air introduction passage 16 Fuel injection valve 17 Electronic control circuit 18 Surge tank 18a Flange 18b Wall surface 19a-19c Mounting seat 20a-20e Intake branch pipe 21a, 21b passage 23a, 23b passage 24 Projection part 25 Opening 26 Communication hole 27 Projection part 28 Opening 29 Communication hole 30 Opening 31 Communication hole 32 Projection part 33 Side brunch 34 Hose joint 35 tube 36 Aperture 37 Taper part 38 Gasket 39 Composition sheet

Claims (2)

[Claims] 1. A passage for introducing secondary air into an intake port by bypassing a throttle valve in an internal combustion engine, the intake noise generated when the secondary air passes through the secondary air introduction passage. A secondary air introduction passage for an internal combustion engine, characterized in that the secondary air introduction passage is provided with a muffling device in order to reduce noise. 2. The internal combustion engine according to claim 1, wherein the muffling device is provided on the intake upstream side of a control valve that selectively opens and closes the secondary air introduction passage depending on the operating state. Engine secondary air introduction passage.