JPH08319911A - Intake device for 4-cycle engine - Google Patents

Abstract

PURPOSE: To reduce intake gas noises during running caused when the vibration noises of air which is supercharged by air pressure during running are ejected from the front end of a vehicle and to reduce valve noises of a check valve of a second air supply system to an exhaust port and thereby to improve the efficiency of reducing noises as a whole intake device. CONSTITUTION: An intake air expansion room 33 of a specified volume is connected to a ram duct 19 for intaking air as a closed circuit and a second air expansion room 44 of a specified volume is disposed in a second air supply passageway 41 to an exhaust port from an air cleaner 20, thereby reducing intake gas noises in a specified range of frequencies and valve noises in a specified range of frequencies caused by a check valve 42 for introducing the second air.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an intake system for a four-cycle engine, and more specifically, it takes in combustion air by using traveling wind pressure, and transfers a part of the taken-in air to an exhaust port through a check valve. The present invention relates to a four-cycle engine intake device configured to be supplied as secondary air.

[0002]

2. Description of the Related Art In a four-cycle engine for a vehicle such as a motorcycle, a three-wheeled vehicle, a four-wheeled vehicle, or an automobile, the combustion air is taken in by using traveling wind pressure, and a part of the taken-in air is non-returned. An intake device configured to supply secondary air through a valve to the exhaust port may be used.

In general, an intake system for taking in combustion air by using traveling wind pressure introduces air from an air intake port on which traveling wind pressure acts into an air cleaner through a ram duct, and the air cleaner passes through a carburetor or a fuel injection unit to an engine. It is configured to be supplied to the inside (combustion chamber). Documents disclosing this type of intake device include, for example, Japanese Utility Model Laid-Open No. 5-46686.

Further, as one of the exhaust emission control devices, by supplying air (secondary air) to the exhaust port of the engine, the high temperature exhaust gas immediately after the exhaust valve is used to utilize unburned components (CO
A secondary air system (exhaust gas combustion system) for reburning (e.g., etc.) to complete combustion (conversion to CO ₂ ) is used. This secondary air system generally forms a secondary air supply path from the air cleaner to the exhaust port, and opens an air intake valve (check valve) in the middle thereof in response to a negative pressure component of the pressure wave in the exhaust pipe. Is adopted. A document disclosing a secondary air system of this type is, for example, Japanese Utility Model Publication No. 55-53693.

[0005]

However, in a four-cycle engine in which the secondary air system is used in combination with an intake device that takes in combustion air by using the traveling wind pressure, the intake flow in the ram duct causes Since the valve noise resulting from the operation of the check valve of the secondary air system is added to the intake noise generated, a measure for further reducing these noises is required.

The present invention has been made in view of the above technical problem, and an object of the present invention is to generate vibration noise of supercharged air by using traveling wind pressure, which is generated from the tip of a vehicle during traveling. Intake air noise can be effectively reduced, and the valve noise due to the opening / closing operation of the check valve for introducing the secondary air into the exhaust port can also be effectively reduced. An object is to provide an intake system for a four-cycle engine that can be efficiently reduced.

[0007]

DISCLOSURE OF THE INVENTION The present invention relates to a four-cycle engine which uses combustion air to take in combustion air and supplies a part of the taken-in air as secondary air to an exhaust port through a check valve. In the intake device, a constant volume intake expansion chamber is connected as a closed circuit in the ram duct between the air intake port and the air cleaner, and a constant volume secondary air is provided in the middle of the secondary air supply path between the air cleaner and the exhaust port. The object is achieved by providing an expansion chamber to reduce intake noise in a specific frequency range and reduce valve noise in a specific frequency range due to the operation of the check valve.

[0008]

Embodiments of the present invention will be described below with reference to the drawings. The same reference numerals denote the same or corresponding parts throughout the drawings. FIG. 10 shows a 4 with an intake device according to the invention
FIG. 3 is a left side view of a motorcycle with a cycle engine partially broken away. In FIG. 10, front wheels 11 and rear wheels 12 are suspended in front of and behind the body frame 10 via front and rear forks (not shown), and a 4-cycle engine 13 is attached to the center of the body frame 10. ing. A fuel tank 14 and a seat 15 are attached to the upper portion of the vehicle body frame 10, and are covered by cowlings 16 from the front surface of the vehicle body to both front half portions.

The air intake port 1 is provided at the left and right running wind pressures (dynamic pressures) on the front surface of the cowling 16.
8 and 18 (only one side is shown) are formed, and the combustion air (engine intake air) taken in from each air intake 18, 18 is introduced into the air cleaner 20 through the left and right ram ducts 19 and 19 (only one side is shown). ,further,
An air-fuel mixture is created while flowing from the air cleaner 20 through a venturi portion (a part of the intake passage 22) 23 of a carburetor 21, and the created air-fuel mixture is supplied into a cylinder (combustion chamber) through an intake port of the engine 13. It

In the illustrated example, one air intake port 18 and one ram duct 19 are provided on the left and right sides (two in total), but this may be provided at one desired position, or at three or more positions. May be provided. Also,
In the case of a multi-cylinder engine, the number of cylinders that share one air cleaner 20 can be arbitrarily selected. That is,
One or more air cleaners shared by one or more cylinders may be used.

FIG. 1 is a plan view of an embodiment of an intake system for a 4-cycle engine to which the present invention is applied, and FIG. 2 is a vertical sectional view of an embodiment of an intake system for a 4-cycle engine to which the present invention is applied. is there. This embodiment shows the case of a four-cylinder engine, and in this embodiment, air is supplied from one air cleaner 20 to four cylinders A, B, C and D.

In FIGS. 1, 2 and 10, the intake device of the engine 13 includes two air intake ports 18, 18 formed on the front portion of the cowling 16 at the left and right, and cowling from these air intake ports. Left and right ram ducts (suction ducts) 19 that extend inside the vehicle body along the inner surface of 16.
19, an air cleaner 20 to which the rear ends of these ram ducts are connected, and an intake passage 22 at the outlet of the air cleaner.
A carburetor 21 connected via a suction port 25 formed in a cylinder head 24 of the engine 13 (FIG. 5)
And an intake passage 22 that connects the carburetor 21 and the intake port 25 to each other, and mixes fuel in the carburetor 21 with a desired air-fuel ratio to produce an engine 1
3 to the combustion chamber 26 (FIG. 5).

The air intakes 18, 18 have a desired projected area when viewed from the front, and the outside air positively applies the traveling wind pressure (ram pressure) to the ram ducts 19, 19 and the air cleaner 20. It is designed to be tucked in and supercharged. In this way, an intake device of a four-cycle engine is configured that takes in combustion air by using traveling wind pressure and fills the combustion chamber of the engine 13 with the air-fuel mixture created by the carburetor 21.

The air cleaner 20 has an element (filter element) in a cleaner case 27 having left and right inlets to which the left and right suction ducts 19 are connected and an outlet communicating with the intake passage 22 side of the carburetor 21. A filter 28 is attached, and the inside of the case 27 is divided into an element upstream side (dirty side) 29 and an element downstream side (clean side) 30. In addition, in this embodiment, as shown in FIG.
In the middle of 9, a surge tank 31 having a volume of 2.0 times or more, preferably 3.0 to 4.0 times, the engine displacement is formed.

The surge tank 31 temporarily reduces the flow velocity of air introduced at high speed by using traveling wind pressure (for example, 5 m / s or less) to separate rainwater and the like from intake air, and the rainwater is air cleaner. It is for preventing the intrusion into the inside of 20. A drain 32 is provided at the bottom of the surge tank 31 for discharging rainwater and the like separated from intake air and captured and collected.

FIG. 3 is a sectional view taken along line 3-3 in FIG. 1 and 3, an intake expansion chamber 33 of a constant volume is connected as a closed circuit in the middle of each ram duct 19, that is, in the illustrated embodiment, at a position adjacent to the ram duct 19 on the downstream side of the surge tank 31. . The intake expansion chamber 33 constitutes an intake resonator that resonates with the vibration of the air flow in the ram duct 19 (air vibration) to reduce the sound pressure level of the intake noise of a specific frequency. The intake expansion chamber 33 is connected to the ram duct 19 by a connecting pipe 34.
Connected through. B in FIG. 3 indicates the center of the vehicle body.

[0017] The center frequency (resonance frequency) f _r of the frequency band sound pressure level is significantly reduced by providing the intake expansion chamber 33, the volume V of the intake expansion chamber 33, the diameter of Ramudakuto 19 (circular cross-section Other than the equivalent diameter) D,
It is determined by the diameter d of the connecting pipe 34 and the length L of the connecting pipe 34, and the attenuation amount at each frequency (as a variable) is also obtained from these specifications and frequency. That is, if the speed of sound is C,
It can be expressed by f _r = C / 2π (G / V) ^0.5 . Here, G is a correction coefficient, and in this embodiment, G = 0.25.
It becomes πd ² /(L+1.6d/2). Also, assuming that the attenuation amount of each frequency f is A, A = 10log [1 + {(G
V) obtained in ^{_{0.5 / 2S 0} 2 / {}} f / f r -f r / f} 2. Here, an S ₀ = πD ^2/4.

In FIG. 2, 35 is a crankcase, 3
6 is a cylinder, 37 is a head cover, 38 is an exhaust pipe, 3
9 indicates a radiator, respectively. Further, in the engine 13 of the present embodiment, by supplying a part of the air taken in from the ram duct 19 to the exhaust port as secondary air, the high temperature exhaust gas immediately after the exhaust valve is used to extract the unburned component of the exhaust gas ( CO etc. is re-combusted to complete combustion (CO ₂
An exhaust gas purification device (secondary air system = exhaust gas combustion system) 40 for purifying the exhaust gas by the conversion into

FIG. 4 is a side view of the exhaust gas purification device (secondary air system) 40, and FIG. 5 is the exhaust gas purification device 40.
FIG. 3 is a vertical sectional view showing the overall configuration of Next, the exhaust gas purification device 40 whose detailed structure is shown in FIG. 5 will be described. In FIGS. 2, 4 and 5, the secondary air system 40 forms a secondary air supply passage 41 from the clean side 30 of the air cleaner 20 to the exhaust port, and checks in the middle of the secondary air supply passage 41. A valve type check valve (air intake valve) 42 is provided.

The check valve 42 is formed of a leaf valve in the illustrated example, and has a structure that opens in response to the negative pressure component of the pressure wave in the exhaust pipe 38 or the exhaust port 43. In the illustrated example, the check valve 42 is attached to the cylinder head 24 or the head cover 37, and the secondary air supply passage 41 is a rubber hose between the air cleaner 20 and the check valve 42 in the illustrated example. And the cylinder head 24 is formed between the check valve 42 and the exhaust port 43.
It is formed by the passage inside.

In FIGS. 2, 4 and 5, the secondary air supply passage 4 from the air cleaner 20 to the exhaust port 43.
In the middle of 1, the secondary air expansion chamber 44 and the negative pressure switching valve 45 are provided at a position between the air cleaner 20 and the check valve 42 in the secondary air supply passage 41 in the illustrated example.
In the illustrated example, the secondary air expansion chamber 44 is mounted at a position adjacent to the negative pressure switching valve 45 on the upstream side.

The negative pressure switching valve 45 normally allows secondary air to flow, but a portion of the intake passage 22 closer to the engine than the carburetor 21 (such as the intake port 2) when the engine brake is applied.
(Including No. 5), it closes and operates to shut off the secondary air supply passage 41 when a strong negative pressure is generated. The reason for providing the negative pressure switching valve 45 is that the exhaust port 4 is used during deceleration operation.
This is to prevent an explosion (backfire) that may occur due to an extra unburned component in the exhaust gas when fresh air (fresh air) is supplied to 3.

The secondary air expansion chamber 44 is for reducing valve noise of a specific frequency (mechanical noise generated when the valve is opened / closed) due to the opening / closing operation of the check valve 42 during engine operation, and is constant. It is formed as a volumetric expander silencer. 6 and 7 are vertical sectional views showing the internal structures of the secondary air expansion chamber 44 and the negative pressure switching valve 45. FIG. 6 shows the state when the negative pressure switching valve 45 is open, and FIG. The respective states when the negative pressure switching valve 45 is closed are shown.

In FIG. 6, the arrow D indicates the air cleaner 20.
From the secondary air expansion chamber 44 to the negative pressure switching valve 45, the arrow E represents the secondary air flow from the secondary air expansion chamber 44 to the negative pressure switching valve 45, and the arrow F represents the negative pressure switching valve 45. 2 shows a secondary air flow passing therethrough towards the check valve 42. An arrow G in FIG. 7 indicates an intake port 25 of the engine 13.
A state in which a strong negative pressure generated in the engine side region is introduced from the carburetor 21 in the intake passage 22 is shown.

5 to 7, a negative pressure switching valve 45
Is composed of a negative pressure sensitive on-off valve that opens and closes the valve body 47 by the movement of the diaphragm 46. Normally, it is in the open (circulation) state of FIG. 6 by the urging force of the spring 48. When a strong negative pressure is generated in the intake port 25, the diaphragm 46 moves the spring 48.
By moving to the left in the drawing against the above, the operation is performed so as to be in the closed (blocked) state of FIG. 7.

In FIGS. 6 and 7, 49 is a shaft connecting the diaphragm 46 and the valve body 47, and 50 is a negative pressure chamber communicating with the intake port 25 so that negative intake pressure acts on the diaphragm 46. And 51 is an atmosphere communication chamber formed on the opposite side of the diaphragm 46. An air outlet 52 of the negative pressure switching valve 45 is connected to the check valve 42 via a secondary air supply passage 41 composed of a rubber hose or the like. In addition, the negative pressure chamber 50 has a tube 53.
Is connected to the intake port 25 of the engine via.

5 to 7, the secondary air expansion chamber 44
Is connected to the inlet of the negative pressure switching valve 45, and the inlet of the secondary air expansion chamber 44 is connected to the clean side 30 of the air cleaner 20 via a secondary air supply passage 41 composed of a rubber hose or the like. There is. The secondary air expansion chamber 44 forms a silencer for reducing valve noise of a specific frequency caused by the opening / closing operation of the check valve 42 that opens / closes in response to a pressure wave in the exhaust port 43, As shown in the drawing, a pipe-shaped inlet member 55 is fixed to the inlet-side end surface of the closed case 54 forming the expansion chamber, and a pipe-shaped outlet member 56 is fixed to the outlet-side end surface.

In FIG. 5, reference numeral 57 designates an intake valve.
Reference numeral 8 is an exhaust valve, 59 is a piston, 60 is an intake valve cam that controls opening / closing of the intake valve 57, and 61 is an exhaust valve cam that controls opening / closing of the exhaust valve 58.

According to the embodiment described above, the combustion air is taken in from the air intake port 18 provided in the front surface in the traveling direction by using the traveling wind pressure, and a part of the taken-in air is subjected to the negative pressure wave in the exhaust port 43. In a four-cycle engine intake device that supplies secondary air to the exhaust port 43 as a secondary air by a check valve 42 that opens in response to a pressure component, a constant volume is provided in the ram duct 19 between the air intake port 18 and the air cleaner 20. The intake expansion chamber 33 is connected as a closed circuit to reduce intake noise in a specific frequency range, and
By providing a secondary air expansion chamber 44 having a constant capacity in the middle of the secondary air supply passage 41 for introducing secondary air from the air cleaner 20 to the exhaust port 43, a specific frequency caused by the operation of the check valve is provided. Since it is configured to reduce the valve noise in the region, the vibration noise of the supercharged air that utilizes the traveling wind pressure is directly emitted from the tip of the vehicle, which effectively reduces the intake noise during traveling. Also, the valve noise caused by the opening / closing operation of the check valve for introducing the secondary air into the exhaust port can be effectively reduced, and the noise of the entire intake system can be efficiently reduced. An engine intake system is provided.

FIG. 8 is a graph showing the frequency characteristics of the noise level (sound pressure level) and the measurement result of the overall value of the intake device having the intake expansion chamber and the intake device having no intake expansion chamber according to the present invention. The measurement of FIG. 8 is 600c.
Motorcycle with c engine is 50km in 3rd speed
The solid line shows the case of the motorcycle equipped with the intake expansion chamber according to the present invention, and the chain line shows the case without the intake expansion chamber. FIG.
As is clear from the graph of Fig. 3, by providing the intake expansion chamber according to the present invention, a specific frequency (125H in this example)
noise level in the vicinity of z) can be effectively reduced,
The overall value can also be effectively reduced.

FIG. 9 is a graph showing the frequency characteristics of the noise level (sound pressure level) and the measurement result of the overall value of the intake device having the secondary air expansion chamber according to the present invention and the intake device having no secondary air expansion chamber. Is. The measurement of FIG.
It was carried out under the condition that the 600 cc engine was operated at 1050 rpm under no load, the solid line represents the case of the motorcycle equipped with the secondary air expansion chamber according to the present invention, and the chain line represents the case without the secondary air expansion chamber. Indicates. By providing the secondary air expansion chamber according to the present invention, as shown in the graph of FIG. 9, the noise level in the region of about 250 Hz to about 2000 Hz can be effectively reduced, and the overall value is also effectively reduced. can do.

In the above embodiment, the present invention is applied automatically.
Although the case where it is applied to a wheeled vehicle has been described, the present invention is not limited to the automatic 3,
A vehicle that runs with a four-cycle engine, such as a four-wheeled vehicle or an automobile, can be similarly applied and the same effect can be obtained. The present invention also relates to the engine 1
It can be similarly applied regardless of the number of three cylinders, the number of air intake ports 18 and the number of ram ducts 19, the number of air cleaners 20, the number of carburetors 21, and the like, and the same effect is obtained.

[0033]

As is apparent from the above description, according to the present invention, the combustion air is taken in by using the traveling wind pressure,
2 of a part of the taken-in air to the exhaust port via the check valve
In a 4-cycle engine intake device that supplies as secondary air, an intake expansion chamber with a constant volume is connected as a closed circuit in the middle of a ram duct between the air intake and the air cleaner, and a secondary air supply path between the air cleaner and the exhaust port is connected. Since a secondary air expansion chamber having a constant capacity is provided in the middle of the above, the intake noise in the specific frequency range is reduced and the valve noise in the specific frequency range due to the operation of the check valve is reduced.
Vibration noise of supercharged air using traveling wind pressure is effectively reduced from the intake noise during traveling generated by being emitted from the tip of the vehicle, and a check valve for introducing secondary air into the exhaust port is also provided. Provided is an intake device for a four-cycle engine, which can effectively reduce the valve noise caused by the opening / closing operation and can effectively reduce the noise of the intake device as a whole.

[Brief description of drawings]

FIG. 1 is a partially cutaway plan view of an embodiment of an intake device for a 4-cycle engine to which the present invention is applied.

FIG. 2 is a vertical cross-sectional view of an embodiment of an intake device for a 4-cycle engine to which the present invention is applied.

3 is a cross-sectional view taken along line 3-3 in FIG.

FIG. 4 is a side view showing a secondary air system for purifying exhaust gas of an intake device of a four-cycle engine to which the present invention is applied.

FIG. 5 is a vertical cross-sectional view showing a configuration of a secondary air system for purifying exhaust gas of an intake device of a 4-cycle engine to which the present invention is applied.

FIG. 6 is a vertical cross-sectional view showing a secondary air introduction state of the secondary air expansion chamber and the negative pressure switching valve in FIG.

7 is a vertical cross-sectional view showing a state where the secondary air expansion chamber and the negative pressure switching valve in FIG. 5 are shut off from the secondary air.

FIG. 8 is a graph showing measurement results of noise level frequency characteristics and overall values of an intake device having an intake expansion chamber and an intake device having no intake expansion chamber according to the present invention.

FIG. 9 is a graph showing measurement results of noise level frequency characteristics and overall values of an intake device having a secondary air expansion chamber and an intake device having no secondary air expansion chamber according to the present invention.

FIG. 10 is a partially cutaway left side view of a motorcycle equipped with a 4-cycle engine having an intake device to which the present invention is applied.

[Explanation of symbols]

 10 body frame 13 engine 16 cowling 18 air intake 19 ram duct 20 air cleaner 21 carburetor 22 intake passage 23 venturi section 24 cylinder head 25 intake port 26 combustion chamber 28 element (filter) 30 clean side 31 surge tank 33 intake expansion chamber 34 connection Pipe 40 Secondary air system (exhaust gas purification device) 41 Secondary air supply passage 42 Check valve (air intake valve) 43 Exhaust port 44 Secondary air expansion chamber 45 Negative pressure switching valve 53 Tube 54 Sealing case 55 Inlet member 56 Outlet Element

Claims (1)

[Claims] 1. An air intake port of a four-cycle engine intake device which takes in combustion air by using traveling wind pressure and supplies a part of the intake air as secondary air to an exhaust port through a check valve. A fixed volume intake expansion chamber is connected as a closed circuit in the ram duct between the air cleaner and the air cleaner, and a secondary air expansion chamber with a constant volume is installed in the middle of the secondary air supply path between the air cleaner and the exhaust port. An intake system for a four-cycle engine, which reduces intake noise in a frequency range and reduces valve noise in a specific frequency range due to the operation of the check valve.