GB2260574A - Engine intake silencer with variable resonator capacity - Google Patents

Abstract

The capacity of the resonator tube 6 communicating with the air cleaner intake tube 4 is variable by controlling operation of the valves 8a, 8b. The engine speed dependent voltage from a frequency to voltage convener 16 is fed to comparators 20a. 20b which operate switches 22a, 22b controlling solenoid coils (28. Fig. 2) of valve actuators 24a, 24b. Below 3000 rpm both valves are open, between 3 and 4000 rpm valve 8a is open and 8b closed and above 4000 rpm both valves are closed. <IMAGE>

Description

L,.).' INTAKE SILENCER OF THE VARIABLE TYPE FOR USE IN MOTOR VEHICLE The

present invention relates to an intake silencer and more in particular to an intake silencer for reducing noise generated from an air intake system of motor vehicle engine.

The generation of noise from an engine system used for a motor vehicle is caused by the engine system itself, a piston system or an Litake system. Among them, noise from the intake system is generated coming from the difference between the inner pressure and the outer pressure of a combustion chamber when an intake valve being opened or closed. It is transmitted therefrom to an air cleaner and then dispersed toward the outside.

The intake noise is influenced by the frequency, generally the low frequency, related with the revolution number of an engine.

As well-known, noise generated due to the low frequency should be eliminated if possible since it resonates a vehicle 1 1 body itself to produce noise inside the motor vehicle.

Kawamura's US Patent No. 4,136,756 provides a suction air muffler for motorcycle effective to prevent producing noise which would otherwise be produced by air drawn by suction into the inlet of the motorcycle. Takails US Patent No. 4,350,223 provides a silencer for reducing noise produced by air drawn into the engine such that a resonance chamber is placed on a conduct connected to an air cleaner and porous metal tubes connect the space inside the chamber to the conduct. Hanzawa et all US Patent No. 4,800,985 proposes an intake air silencer including a side branch tube which is flexible at least partially for installation in a limited space, placed on an intake tube connected to an air cleaner to reduce noise.

As described above, many kinds of silencers for reducing the air intaking noise into the engine have been commercially used.

Generally, they are divided into two types. one is a side branch type silencer, which can reduce noise by virtue of the mutually interfering of sonic waves according to quarter wave filter 2 theory. Another is a cavity type silencer, which can silence noise by changing a wave energy of a sonic wave into a going and coming energy at the inside of a resonance chamber.

The present invention is related with an improvement of the side branch type silencer. FIG. 5 shows a basic structure of the side branch type silencer. The resonance chamber B is formed on an air intake tube in the form of connecting with each other, so that, when the air intaking noise arrives at the inside of the intake tube, it resonates the resonance chamber B. The mutual interference between resonating wave and noise occurs therein thereby reducing noise.

The engine provided with the silencer of this type is known to obtain the improved horse power and fuel consumption ratio as a graph shown in FIG. 6 since the path of the intake tube with a limited space has the sufficient amount of existed therein, air thereby causing the high charging efficiency of air drawn into the inside of a cylinder. The theoretical reduction of noise frequency of the side branch type silencer can represent F = C/4L :3 as a formula. C is an acoustic velocity and L is the length of the resonance chamber. This formula means that the effective length of the resonance chamber can be variable to widen the reducible low frequency region. Thus, if the length or the capacity of the resonance path varies with the change of the RPM sensor of the engine, the preferred efficiency of noise reduction can be obtained.

Japanese Specification No. 86-41815 proposes the silencer of the variable type such that some short and long pipes connect the path of the intake tube with the resonance box and entrances of the pipes are provided with the opened and closed valves. Each opened and closed valve gears with the revolution of the engine thereby forming the simple structure and effectively reducing noise independently of the change of the engine revolution.

However, the pipes interposed between the intake path and the resonance box can not help having a large size unfit for the limited engine chamber. Japanese Specification No. 61-41813 provides the silencer such that a piston placed at the inside of 4 the resonance tube slides by a stepping motor corresponding to the engine revolution thereby increasing and/or decreasing the cavity of the resonance chamber, so that such problem can be solved.

The invention has the advantage of minimizing the size of the silencer. However, since a tool of the piston type slides riding on a screw rod rotated by the stepping motor, the complex structure can be formed. Especially, the piston can not be rapidly changed immediately when the revolution number of the engine is changed thereby causing the poor efficiency of noise reduction thouch in a moment.

k, Accordingly, the feature of the present invention is a silencer with a side branch which can rapidly change its capacity according to the revolution number of the engine though it has the simple structure and the small size. The present invention comprises a signal processing part, a signal comparing part and a valve driving part. In the signal processing part, a RPM sensor modulates a waveform obtained by detecting the revolution number of the engine and a F/V converter changes it thereafter emitting a signal to the signal comparing part. In the signal comparing part, a plurallty of comparators emit the opened and closed signal to a valve driver by comparing a output signal emitted from the signal processing part with a basic signal. In the valve driving part, when the corresponding valve driver turns on or off by virtue of the signal emitted from the corresponding comparator, a corresponding actuator opens or closes the corresponding valve dividing the inside of the side branch. Thus, such processing steps help to reduce noise.

Further features and advantages of the present invention will be apparent in the following detailed description in connection with the accompanying drawings, in which:

FIG. 1 is a gist view of a silencer related with the present invention; FIGS. 2A & 2B are a sectional side view showing an opening 6 and closing operation of FIG. 1; FIG. 3 is a flow diagram explaining a operating order of a controller of FIG. 1; 4 i.

FIG. 4 is a graph of the comparison of noise reducing efficiency between the present invention and the conventional silencer; FIG. 5 is a sectional view of an embodiment of the conventional silencer;and FIG. 6 is a graph explaining the horse power and the fuel consumption ratio of FIG. 5.

FIG. 1 shows a silencer according to an embodiment of the present invention, which is incorporated in an automatic internal combustion engine(not shown). The silencer includes an air passage tube 4 serving as an intake tube. The air intake tube 4 is connected to an air cleaner 2. The silencer also includes a side branch tube 6 which is connected to the lower side of the air intake tube 4. The side branch tube 6 comprises a first valve 7 8a and a second valve Bb -tiD t;ititm its inside by stages.

The change of the capacity cDzrespcmcling to the and/or closing -the fi:rst and second valve -will be shown as f ollows:

Change of Capacity maximum- Mejium - opened and Clowed State of 'Valve 7-i-xst valve Second Valve opened minimum - closed A conventional RPM -tens6r 12- connected to a crank axis of the engine detacts its zevolution n.imber to emit pulse to. an signal procetssor 14 of- aL signal processing pw(:-!( 3.0. IC modulates pulse therefrom into Wave.shape to apply Loa]?/IT converter 16 It change the modulated 'wave into voltage. to ami a signal comparing part 18 as-a output signal. The a i g.!,g 1 C9qr-aring part 18 comprises a first compArator 20a co=ected.to_the f i r-st valve and a'second conparator 20b connected tn '-he basic voltage is differently applied tD each The basic voltage(Vrefl) of the first comparator(20a).1s,iegs -han a ! - t-.

that of the second comparator(20b). Thus, only when the output signal more than the basic voltage is applied thereto, a signal is outputted to a valve driving part 22. The valve driving part 22 is operated according to the signal emitted from the comparators 20a,20b. The valve driving part 22 comprises a first switching element 22a into which the signal emitted from the first comparator 20a is inputted and a second switching element 22b into which the signal emitted from the second comparator 20b is inputted. A conventional switching transistor is appropriate for the switching element. when the signal therefrom turns on the switching ilements 22a,22b, they output the driving voltage (Vcc). The valve driving part also comprises a first and second actuator 24a,24b connected to the first and second valve 8a,8b at the end of outputting.

FIGS. 2A & 2B shows a connection of the first actuator 24a to the corresponding first valve 8a as example. FIG. 2A shows a opened state of the valve Sa.

The actuator 24a comprises a push rod 26 for sliding at the 9 center of its inside and a magnetiFed coil 28 wound around the push rod 26. An elastic spring 30 wound on the push rod exposed outside the actuator 24a Is supported by a spring sheet 32. The end -of the pus;.i rod 26 is linked with an arm 36 fixed on the supporting axis 34 enabling the first valve 8a to rotate. When the push rod 26 is influenced by the elastic spring tc protrude the outside thereby rotating the arm, the first valve Sa opens the entrance o_2 the side branch 6. The rotation angle of the valve Sa makes a right angle with.the insid of the side branch 6 and that is regulated by a stopper 38,40 projected on the valve 8a.. When the first switching element 22a is turned on at the opened state of the valve $a, the magnetized coil 28 of the ictuator 24a is supplied with the voltage for the valve Ba to be adhered as shown in PIG. 2B.

At that time, whereas the reactionary energy is saved in the elastic. spring 30# the arm 36 alosRs-the first valve 8a by totating it. When the first switching element 22a is again turned offt the push rod 26 returns to the original position by the JL 0 0 applied reactionary energy of the elastic spring 30 due to the magnetized coil 28's losing the adhering power. Thus, the first valve 8a is opened. The above description can be applied to the second valve 8b as well.

FIG. 3 shoT:7s a flow chart of the operation of a controller.

The frequency detected by the RPM sensor 12 is inputted to the F/A converter 16 to change the voltage, which is outputted to the comparator 18. At that time, the frequency is proportional to the voltage. so that if the revolution number of the engine is reduced, the voltage becomes lower or if the frequency is increased, the voltage becomes high.

Thus, the basic voltage(Vrefl) of the first comparator(20a) according to the subject embodiment of the present invention is less than the output voltage from the F/V converter 16 at the middle speed region of the engine. The basic voltage(Vref2) of the second comparator(20a) according to the subject embodiment of the present invention is higher than the output voltage from the F/V converter 16 at the lower speed region of the engine.

2L]L As a result, at the lower speed region, the signal is emitted to the and of the output of each comparator 20a, 20b to open each valves 8a,8b, so that the side branch 6 has the maximum capacity Ll. At the middle speed region, the only first comparator 20a emits the signal to open the only first valve 8a, so that the side branch 6 has the medium capacity L2. At the high speed region, each valve 8a,8b is closed for the side branch to have the minimum capacity L3.

More particularly, the lower speed region of the engine is under 300 RPM. The middle speed region is above 3000 RPM and under 4000 RPM. The high speed region is above 4000 RPM. The basic voltage (Vrefl) of the first comparator 20a is less than the output voltage of the F/V converter 16 at the middle speed region. The basic voltage (Vrefl) of the first comparator 20a is higher than the output voltage of the F/V converter 16 at the high speed region. The basic voltage (Vref2) of the second comparator 20b is higher than the output voltage of the F/V converter 16 at the lower speed region and is higher than the IL 2 1 output voltage of the F/V converter 16 at the middle speed region.

Thus, when both basic voltages are respectively set up, each comparator 20a,20b independently emits the signal according to the lower, middle or high speed region of the revolution number of the engine. As a result, at the lower speed region, each valve 8a,8b is opened, so that the side branch 6 has the maximum capacit7 Ll. At the middle speed region, the only first valve 8a is opened, so that the side branch 6 has the medium capacity L2. At the high speed region, each valve 8a,8b is closed for the side branch to have the minimum capacity L3.

FIG. 4 shows a measurement of noises divided as an overall noise and a second order noise at intervals of 1 meter, respectively generated from an engine without a silencer, an engine having a conventional silencer shown in FIG. 5 and an engine provided with a side branch type silencer of the present invention.

1 1 The present invention has the consistent efficiency of noise X 3 reduction independently of the change of the revolution number of the engine and is very effective to the reduction of the second order noise.

Thus, the present invention is simple in structure and small in size to easily install in a limited space of the engine. Also, the length of the side branch can rapidly vary with the change of the revolution number of the engine to obtain the good efficiency of noise reduction. Especially, when the side branch has a single and flexible type, the easier installation can be obtained.

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Claims (7)

1. An intake silencer of the variable type for use in a motor vehicle which can rapidly change its capacity according to the change of Ithe revolution number of an engine, comprises a side branch in which valves are disposed at the position by which the inside capacity is divided according to its step, a signal processing part which detects the revolution number of the engine and then outputs the voltage corresponding to the detected revolution numbar, a comparing part in which the outputted signal is compared wIth the reference signal and then signal is outputted respectively, said comparing part including a first and a second comparator which is dependent on a plurality of valves disposed at the side branch according to the step, and a valve driving part in which the first and second valves are respectively opened or closed by a first and a second actuators on the basis of the output signal of a first and a second switching element connected respectively to the output terminal of said a first and a second comparator.

3-5

2. The intake silencer as claimed in Claim 1, wherein valves disposed at its inside is a throttle valve or a butterfly valve.

3. The intake silencer as claimed in Claim 1, wherein in the signal comparing part, the voltage of the first comparator is less than that of the second comparator.

4. The intalkee silencer as claimed in Claim 1, wherein a conventional si,.-.itching element is used as a first and second switching element.

5. The intake silencer as claimed in Claim 1, wherein a first and second actuator respectively comprises a push rod for sliding at the center of its inside, a magnetized coil applied by the first and second switching element wound around the one side of the push rod and arms gearing the first and second valve by the push rod.

6. The intake silencer as claimed in Claim side branch is provided with a flexible tube.

1, wherein the

7. An intake silencer substantially as herebefore described with reference to and as illustrated by. Figures 1 to 4 of the accompanying drawings.

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