JPH0343380Y2 - - Google Patents

Description

[Detailed Description of the Invention] (Industrial Application Field) The present invention relates to an improvement of an engine intake system equipped with a pressure-responsive switching means for changing the natural frequency of an air column in an intake system.

(Prior Art) Conventionally, in the intake system of an engine, a negative pressure wave (pressure wave of negative pressure) generated with the start of intake is reflected at the opening end of the intake passage to the atmosphere or the intake expansion chamber on the upstream side of the intake passage, and a positive pressure wave ( The so-called intake inertia takes advantage of the fact that the positive pressure wave (positive pressure liquid) is returned toward the intake port, and the positive pressure wave reaches the intake port just before the intake valve closes, pushing the intake air into the combustion chamber. It is known to increase the filling efficiency of intake air by means of effects. When using such technology, if the shape of the intake passage is constant, the oscillation period of the pressure wave generated in the intake passage matches the opening and closing period of the intake valve, and the intake inertia effect is enhanced. Limited to a specific rotation range.

For this reason, conventionally, as seen in JP-A-56-115819, the length of the intake passage is changed depending on the engine speed, for example, the intake passage for each cylinder is divided into two parts at the upstream part. A long passage and a short passage are formed by branching, and the upstream ends of these passages are opened to an intake expansion chamber, etc., and a control valve is provided in the short passage, and this control valve is opened in a high rotation range. In this way, the effective length of the intake passage is shortened (see Figure 6 of the above-mentioned publication), and the natural frequency of the air column in the intake system is changed to reduce the inertial effect of the intake air in the low and high rotation ranges. An intake device has been proposed that increases the

(Problems to be Solved by the Invention) By the way, in an intake system such as the above-mentioned proposed example, the control valve as a switching means for changing the natural frequency of the air column of the intake system according to the operating state of the engine is as follows:
Normally, the throttle valve is opened and closed using a pressure-responsive member such as a diaphragm device whose operating pressure is intake negative pressure downstream of the throttle valve.

However, in high load ranges where the throttle valve opening is large and the intake air is not throttled much, the intake negative pressure downstream of the throttle valve approaches atmospheric pressure, making it impossible for the pressure-responsive member to reliably introduce the intake negative pressure. Therefore, there is a problem in that the switching operation of the switching means (the opening/closing operation of the control valve by the pressure responsive member) cannot be performed accurately and reliably.

The present invention was devised in view of these points, and its purpose is to ensure accurate and stable operation of the switching means, even in a high load range where the throttle valve opening is large and the intake air is not throttled much. It's about doing.

(Means for Solving the Problems) In order to achieve the above object, the solving means of the present invention includes an independent intake passage for introducing fresh air into the cylinder, and an intake passage connected to the upstream side of the independent intake passage. An intake expansion chamber that converts a negative pressure wave generated in an independent intake passage into a positive pressure wave, a switching means that changes the natural frequency of the air column of the intake system into at least two states, and a positive pressure to be introduced. and a pressure-responsive member that operates the switching means based on the differential pressure between the air pressure and the negative pressure, the upstream end of which is connected to the intake expansion chamber, and the downstream end of which is connected to the pressure-responsive member. a positive pressure passage connected to the intake expansion chamber for supplying the positive pressure of the intake expansion chamber to the pressure responsive member; an upstream end connected to the independent intake passage and a downstream end connected to the pressure responsive member; a negative pressure passage for supplying the negative pressure of the independent intake passage to the pressure responsive member; and a negative pressure passage that is interposed in the negative pressure passage and stores the negative pressure flowing from the independent intake passage. The structure includes a negative pressure reserve tank that allows pressure to flow out to the pressure responsive member side.

(Function) With the above configuration, there is a positive pressure passage for supplying the positive pressure of the intake expansion chamber to the pressure responsive member, a negative pressure passage for supplying the negative pressure of the independent intake passage to the pressure responsive member, and a negative pressure passage for supplying the negative pressure of the independent intake passage to the pressure responsive member. The intake expansion chamber is equipped with a negative pressure reserve tank that stores the negative pressure that flows in from the independent intake passage and drains the stored negative pressure to the pressure-responsive member side. Since almost no negative pressure waves are generated even in
The positive pressure is reliably supplied from the intake expansion chamber to the pressure responsive member through the positive pressure passage, and the negative pressure generated in the independent intake passage in the action area of the inertial effect of the intake air is stored in a negative pressure reserve tank. Negative pressure stored in the negative pressure reserve tank is supplied to the pressure responsive member. Therefore, negative pressure is reliably supplied from the negative pressure reserve tank to the pressure responsive member even in a high engine load range where the negative pressure in the independent intake passage approaches atmospheric pressure and it is difficult to obtain negative pressure from the independent intake passage.

(Example) Hereinafter, an example of the present invention will be described in detail based on the drawings.

1 to 3 show a first embodiment in which the present invention is applied to a four-cylinder, four-cycle engine. In the figure, reference numeral 1 denotes an engine body consisting of a cylinder block 2, a cylinder head 3, etc. In the engine body 1, four cylinders 4, first to fourth cylinders, are formed in series in the longitudinal direction. cylinder 4
A combustion chamber 5 is formed in each.

Reference numeral 6 denotes an independent intake device provided independently for each cylinder, and each independent intake passage 6 is connected to each cylinder via an intake port 7 formed in the cylinder head 3 and constituting the downstream end of the independent intake passage 6. It opens into the combustion chamber 5 of the cylinder 4. Reference numeral 8 denotes an intake expansion chamber made of a substantially rectangular cylindrical tank extending parallel to the longitudinal direction of the engine. It is divided into a first volume chamber 8a with a large volume and a second volume chamber 8b with a relatively small volume located below. The flow end portions of each of the independent intake passages 6 are connected to the first volume chamber 8a of the intake expansion chamber 8 with substantially the same passage length. An intake pipe 10 for introducing outside air is connected to one end surface of the first volume chamber 8a, and a throttle valve 11 for controlling the amount of intake air is disposed inside the intake pipe 10. Although not shown, a supercharger (for example, an exhaust turbo supercharger, a supercharging pump chamber) for supercharging intake air is provided upstream of the throttle valve 11, and the throttle valve 11 is pressurized by the supercharger. The intake air that has been throttled and introduced into the first volume chamber 8a is supplied to the combustion chamber 5 of each cylinder 4 via each independent intake passage 6. Further, the intake port 7 is provided with an intake valve 12 .

The second passage 1 from the middle of each independent intake passage 6
3 are branched, and the respective second passages 13, 13,...
The other ends are connected to the second volume chamber 8b of the intake expansion chamber 8 with substantially the same passage length, and
As a result, the second passage 13 is expanded by the second volume chamber 8b.
The independent intake passages 6, 6, . . . communicate with each other via the respective independent intake passages 6, 6, .

Further, each second passage 13 is provided with a control valve 14 as a switching means for opening and closing the second passage 13, and each control valve 14 is connected to the intake expansion chamber 8.
It is integrally and interlockably fixed to a valve shaft 15 extending parallel to the longitudinal direction. A valve lever 22 is fixed to the shaft end of the valve shaft 15, and the control valve 1 is connected to the valve lever 22.
A diaphragm device 16 as a pressure-responsive member for opening and closing 4 is connected thereto. The diaphragm device 16 is connected to the valve lever 22 by a rod 2.
1, and a first chamber 1 defined by the diaphragm 18.
9 and a second chamber 20, and a spring 24 which is compressed into the first chamber 19 and biases the diaphragm 18 in the direction in which the control valve 14 opens. The first chamber 19 is communicated via a negative pressure passage 23 with the downstream portion 6b of the independent intake passage 6 on which intake negative pressure acts, and the second chamber 20 is connected to the positive pressure passage 25.
The first and second chambers 19 and 20 of the diaphragm device 16 are in communication with the negative pressure from the independent intake passage 6 as their operating pressure. Positive pressure from the first volume chamber 8a is introduced in the same direction as the control valve 14 in its closing direction.

An independent intake passage 6 is located in the middle of the negative pressure passage 23.
A negative pressure reserve tank 26 is interposed to store the negative pressure introduced from the negative pressure reserve tank 2.
A check valve 27 is provided at the connection port on the independent intake passage 6 side of 6 to allow only the inflow of negative pressure from the independent intake passage 6 to the negative pressure reserve tank 26, and to block the outflow of negative pressure in the opposite direction. is installed. As a result, the negative pressure generated in the independent intake passage 6 is stored in the negative pressure reserve tank 26 in the area where the inertial effect of intake air acts, and the negative pressure stored in the negative pressure reserve tank 26 is transferred to the negative pressure passage 23. The first chamber 19 is supplied through the first chamber 19 .

In addition, the negative pressure reserve tank 26 and the first chamber 1
The negative pressure passage 23 between the first chamber 19 and the negative pressure reserve tank 26 has a negative pressure position and a first
The chamber 19 is opened to the atmosphere and the negative pressure reserve tank 2 is opened.
A first three-way solenoid valve 28 is interposed to close the negative pressure passage 23 on the 6 side and take an open position to the atmosphere to keep the negative pressure reserve tank 26 in a sealed state.

On the other hand, a check valve 29 is provided in the middle of the positive pressure passage 25 to allow only positive pressure to flow from the first volume chamber 8a to the second chamber 20, and to prevent positive pressure from flowing in the opposite direction. is interposed. In addition, the check valve 29
The positive pressure passage 25 between the second chamber 20 and the second chamber 20 has a positive pressure position that communicates the second chamber 20 with the first volume chamber 8a, and a positive pressure passage that opens the second chamber 20 to the atmosphere and connects the second chamber 20 with the first volume chamber 8a. A second three-way solenoid valve 30 is interposed, which takes an atmosphere open position and closes the positive pressure passage 25.

And the first and second three-way solenoid valves 28, 30
A control unit 31 is connected to the engine, and the control unit 31 receives a signal from a rotation speed sensor 32 that detects the engine rotation speed, and controls the first and second three-way solenoid valves 28 and 30 according to the engine rotation speed. control the operation. Specifically, the control unit 31 controls as follows.
That is, during low rotation (for example, below 5000 rpm), the first three-way solenoid valve 28 is placed in the negative pressure position, and the second
By positioning the three-way solenoid valves 30 in positive pressure positions, the negative pressure in the negative pressure reserve tank 26 is introduced into the first chamber 19, and the first volume chamber 8a is introduced into the second chamber 20.
The diaphragm 18 is biased in the valve closing direction (in the direction of the arrow) against the spring force of the spring 24 by the pressure acting in the valve closing direction, and the control valve 14 is closed via the rod 21. On the other hand, by positioning both the first and second three-way solenoid valves 28 and 30 to the atmosphere open position during high rotation (for example, 5000 rpm or more), both the first chamber 19 and the second chamber are exposed to the atmosphere. As a result, the diaphragm 18 is returned to the valve opening direction by the spring force of the spring 24, and the control valve 14 is opened via the rod 21. Therefore, the switching mechanism 33 that changes the effective length of the independent intake passage of each cylinder 4 and changes the natural frequency of the air column according to the engine operating condition is configured by each of the means described above. Note that the opening/closing operation of the control valve 14 according to the engine speed may be performed at least in a high load range where engine output is required, and the control valve 14 may be in the open or closed state at low loads. It may be maintained in a valve state.

In such an intake system,
35 is the intake expansion chamber 8, each independent intake passage 6,
6... and each of the second passages 13, 13... The structure 35 is an intake system structure for forming the intake expansion chamber 8 (the first volume chamber 8a and the second volume chamber 8b).
The tank part 36 that constitutes the tank part 36 extends from the upper side of the tank part 36 opposite to the engine side to the side and lower sides of the tank part 36, bypassing the periphery of the tank part 36, and a part of its constituent wall, that is, the side wall and Upstream portions 6a, 6 of each independent intake passage 6, 6... using the lower wall
integral intake pipe portions 37, 37, which are integrally formed so that their upstream ends open at the upper side of the tank portion 36 (first volume chamber 8a); and the respective integral intake pipe portions 37, 37. ... branching and extending for each cylinder from the lower side toward the engine side, each independent intake passage 6,
The branch intake pipe portions 38, 38, . . . forming the downstream portions 6b, 6b, .
The tank portion 36 near the branch intake pipe portion 38 of
A communication pipe portion 39 that integrally forms a second passage 13 that communicates the middle of each independent intake passage 6 with the second volume chamber 8b by using the lower wall of the constituent walls of the second volume chamber 8b; 39... and each of the above-mentioned branch intake pipe sections 38, 3
8, and a flange portion 40 that connects the tips of the engine body 1 with the flange portion 40.
On the other hand, with the independent intake passage downstream portion 6b of each branch intake pipe section 38 aligned with the intake port 7 of each cylinder 4, bolts 41, 41... are inserted from the side and tightened to connect the engine body 1. Fixed. Further, the upper part of the engine-side side of the tank portion 36 is formed to bulge toward the engine to ensure a sufficient volume of the first volume chamber 8a.

Further, the downstream side portion 6b of the independent intake passage and each intake port 7 of each of the branched intake pipe portions 38 are formed to extend substantially linearly from diagonally upward toward the combustion chamber 5 and open into the combustion chamber 5. There is. The downstream portion 6 of the independent intake passage of each branch intake pipe portion 38
An injection valve mounting hole 42 is formed in the upper part near the downstream end of the fuel injection valve 43, and the tip injection port of the fuel injection valve 43 is inserted and fixed into the mounting hole 42 via a seal ring 42a. The installation direction of the mounting hole 42 and the fuel injection valve 43 is such that the fuel from the injection valve 43 is injected toward the intake valve 12 of the fuel chamber 5, and each fuel injection valve 43, 43... It is communicatively connected to a fuel supply pipe 44 arranged parallel to the longitudinal direction of the engine. As a result, the fuel injection valve 43 is installed in a lying state almost along the branch intake pipe section 38, and the intake expansion chamber 8 is located on the extension line g of the center line of the fuel injection valve 43.
(Tank portion 36) is located close to fuel injection valve 43 and fuel supply pipe 44.

Further, a control valve 14 is disposed in the second passage 13 of each communication pipe section 39, and the intake expansion chamber 8
(Tank portion 36) is located on the center extension line g of the fuel injection valve 43, so the intake system structure 35
is located at a position below the center extension line g in the tank portion 36 and at each of the second passages 13, 13.
A dividing plane along the longitudinal direction of the intake expansion chamber 8 at the position of the partition plate 9 between the second volume chamber 8b of the intake expansion chamber 8 including... and the first volume chamber 8a of the intake expansion chamber 8. The upper divided body 35a is formed by being divided into upper and lower parts by the tank part 36, and the upper half part of the tank part 36 and the upper half part of each integral intake pipe part 37, 37... are integrally molded, and the lower part of the tank part 36 half part, lower half part of integral intake pipe parts 37, 37..., each branch intake pipe part 38,
38..., each communicating tube part 39, 39... and a lower divided body 35b integrally formed with a flange part 40, both divided bodies 35a, 35b are joined via the partition plate 9, and bolts 45, 45 ... are inserted from below and tightened to form an airtight connection.

Next, to describe the operation of the above embodiment, each control valve 14 is closed by the switching mechanism 33, and the second passage 13 is closed, thereby allowing the second volume chamber 8b to communicate with the independent intake passages 6, 6... In the state in which the intake stroke of each cylinder 4 is blocked, the negative pressure wave generated in the intake stroke of each cylinder 4 is propagated to the first volume chamber 8a and reflected there.
In other words, as the negative pressure waves and their reflected waves propagate through a relatively long passage, the oscillation period (natural frequency) of these pressure waves matches the intake valve opening/closing period in the low rotation range. The inertia effect of the intake air in the area is enhanced, and the intake air filling efficiency is increased. On the other hand, the switching mechanism 33 opens each of the control valves 14 to open the second passage 13, and each independent intake passage 6,
6... In a state where they are in communication with each other, the negative pressure waves generated during the intake stroke of each cylinder 4 are reflected in the second volume chamber 8b via the second passage 13, and the negative pressure waves and reflected waves are propagated. By shortening the passage length, the oscillation period (natural frequency) of the pressure wave matches the intake valve opening/closing period in the high rotation range, increasing the intake inertia effect. The propagated pressure waves also act effectively through the second volume chamber 8b, greatly increasing the filling efficiency in the high rotation range. Therefore, at least in the high load region, the control is performed at a lower rotation speed than a predetermined rotation speed corresponding to the intermediate rotation speed between the above-mentioned low rotation speed range and high rotation speed range where the intake inertia effect can be obtained. By closing the valve 14 and opening the control valve 14 at higher rotation speeds, the intake air filling efficiency can be increased over the entire rotation range and the output can be improved. In particular, the intake air filling efficiency in the high rotation range can be further improved by the pressure propagation effect between the cylinders, compared to the conventional case where the intake passage was simply shortened to increase the inertia effect. .

The sizes of the first and second volume chambers 8a and 8b that are suitable for effectively exerting the above-mentioned effects are such that the first volume chamber 8a has a capacity of 0.5 times or more of the displacement, and the second volume has a capacity of 0.5 times or more of the displacement. It is desirable that the capacity of the chamber 8b is 1.5 times or less than the exhaust volume. Further, it is desirable that the second volume chamber 8b has a smaller capacity than the first volume chamber 8a, and that the cross-sectional area of the second volume chamber 8b is larger than the cross-sectional area of each independent intake passage 6.

In this case, the diaphragm device 16 that opens and closes the control valve 14 in the switching mechanism 33 is
In the low load range, the first chamber 19 of the diaphragm device 16 is supplied with negative pressure from the independent intake passage 6, and the second chamber 20 is supplied with positive pressure from the first volume chamber 8a, so that the control valve 14 is In the high load range, the opening degree of the throttle valve 11 increases and the intake negative pressure in the independent intake passage 6 approaches atmospheric pressure. Negative pressure is supplied from the negative pressure reserve tank 26 that stores negative pressure in the action area, and positive pressure is supplied to the second chamber 20 from the first volume chamber 8a where almost no negative pressure waves are generated. Control valve 14
is closed.

Further, in this case, the intake expansion chamber 8 (the first volume chamber 8a and the second volume chamber 8
b) Tank portion 36 and each independent intake passage 6
The integral intake pipe section 37 that constitutes the upstream section 6a of each independent intake passage 6, the branched intake pipe section 38 that constitutes the downstream section 6b of each independent intake passage 6, and the communication pipe section 39 that constitutes each second passage 13, Each independent intake passage 6 detours around the intake expansion chamber 8 and
(tank part 36), and each second passage 13 is integrally formed with a part of the wall that constitutes the intake expansion chamber 8 (second volume chamber 8b). Therefore, in order to obtain the required length of the independent intake passage 6 and the required volumes of the first and second volume chambers 8a and 8b of the intake expansion chamber 8, these intake systems can be made compact and small. It is possible to sufficiently secure the above-mentioned required length and required volume within a limited space (engine room), and it is possible to improve vehicle mountability.

Further, the fuel injection valve 43 is connected to the branch intake pipe portion 38.
The fuel injector is mounted near the downstream end of the independent intake passage 6, that is, on the downstream side of the independent intake passage 6, toward the combustion chamber 5 in order to supply the injected fuel to the combustion chamber 5 with good response while ensuring good atomization. It is necessary that the tank portion 36 (intake expansion chamber 8) of the intake system structure 35 be located close to the center extension line g of the valve 43, and that the control valve 14 be disposed in each of the second passages 13. It is. Therefore, the intake system structure 35 is located at a position below the center extension line g in the tank portion 36, that is, on the branch intake pipe portion 38 side, and along the longitudinal direction of the intake expansion chamber 8 at the position of the partition plate 9. The upper divided body 35a and the lower divided body 35 are arranged vertically on the ivy dividing surface.
The lower divided body 35
b is attached to the engine body 1 at its flange portion 40 by tightening bolts 41 from the side, and then each branch intake pipe portion 38 of the lower divided body 35b is attached.
Each fuel injection valve 43 is inserted into the injection valve mounting hole 42 from the direction of the central extension line g of the fuel injection valve 43 and fixed to the lower division body 35b.
At the same time, the control valve 14 is inserted into the second passage 13 of each communication pipe portion 39 of the lower divided body 35b from above.
are inserted and fixed to the valve shaft 15, and then the upper divided body 35a is fitted to the lower divided body 35b with the partition plate 9 interposed therebetween, and both 35a, 35b are tightened by tightening the bolts 45 from below. By joining them together, it is possible to ensure good moldability, and it is possible to easily assemble the upper and lower divided bodies 35a, 35b. can be easily assembled, and good assembly performance can be ensured.

Moreover, the upper divided body 35a and the lower divided body 3
5b is achieved by tightening the bolts 45 from below, while ensuring good assemblability, the upper part of the engine side side of the tank part 36 (intake expansion chamber 8) is secured. There is also the advantage that a sufficient volume of the intake expansion chamber 8, particularly the first volume chamber 8a, can be secured. The second volume chamber 8b is arranged in parallel with the first volume chamber 8a by vertically disassembling the tank portion 36 of the intake system structure 35 with the partition plate 9, and
Since a part of the constituent wall (partition plate 9) is shared, the intake system can be made more compact.

FIG. 4 shows a second embodiment of the present invention, and shows the first embodiment of the invention.
In the embodiment, the intake expansion chamber 8 is divided into a first volume chamber 8a and a second volume chamber 8a.
It is divided into a volume chamber 8b to obtain an intake inertia effect in each of the low rotation range and high rotation range, and to further increase the intake air filling efficiency by propagating pressure waves between cylinders, especially in the high rotation range. The second embodiment is an example in which the intake inertia effect is simply increased in the low rotation range and the high rotation range, as in the conventional example.
(The same parts as in the first embodiment (FIGS. 1 to 3) are given the same reference numerals, and detailed explanation thereof will be omitted).

That is, in the lower wall of the tank part 36 that constitutes the intake expansion chamber 8 in the intake system structure 35, the second passages 13, 13, . , each second passage 13
A control valve 1 that opens and closes depending on the engine operating condition.
4 is provided, and the switching mechanism 33 maintains the control valve 14 in the closed state in the low engine speed range, and transfers the pressure waves generated in each cylinder 4 to the intake expansion chamber 8 through a relatively long independent intake passage 6. By propagating the pressure wave through the engine, the vibration period of the pressure wave and the intake valve opening/closing period are matched, increasing the intake inertia effect in the low rotation range. On the other hand, in the high rotation range, the control valve 14 is opened to communicate the middle part of each independent intake passage 6 to the intake expansion chamber 8 via the second passage 13, thereby making the propagation path of the pressure wave relatively short. The oscillation cycle of the pressure wave and the intake valve opening/closing cycle are matched in the high rotation range to enhance the intake inertia effect.

In this case as well, as shown in the figure, the negative pressure of the independent intake passage 6 is supplied to the first chamber 19 of the diaphragm device 16 in the switching mechanism 33, and the negative pressure of the independent intake passage 6 is supplied to the diaphragm device 16 in the switching mechanism 33.
The positive pressure of the intake expansion chamber 8 is introduced into each of the valves so that the response direction matches the valve closing direction, and as in the first embodiment, the intake inertia effect is reliably achieved in the low rotation range. be able to.

In addition to the above-mentioned embodiments, the present invention also includes the above-mentioned first embodiment.
The partition plate 9 in the embodiment has upper and lower first volume chambers 8a.
A communication hole is provided to communicate between the upper and lower volume chambers 8a and 8b, and the intake air filling efficiency is further increased by utilizing intake pressure vibration between the upper and lower volume chambers 8a and 8b in the low rotation range. It is also applicable to systems.

Furthermore, in each of the above embodiments, a single diaphragm device 16 is formed with a first chamber 19 into which intake negative pressure downstream of the throttle valve 11 is introduced, and a second chamber 20 into which positive pressure downstream of the supercharger is introduced. In this way, the function of the pressure-responsive member is that the operating pressure is the intake negative pressure downstream of the throttle valve 11, and the function of the pressure-responsive member is that the operating pressure is the positive pressure downstream of the supercharger. A separate pressure responsive member may also be provided. In addition, these two pressure-responsive members are configured to maintain one of the two states (the valve closed state in the embodiment) as in the above embodiment, and also to switch between the two states. It may be modified to have both functions.

Furthermore, as a means for opening and closing the control valve 14, various pressure-responsive actuators can be employed in addition to the diaphragm device 16 as in the above embodiment.

In addition to the pressure-responsive switching mechanism that switches the length of the passageway used for pressure wave propagation as in the above embodiments, the present invention also provides a The present invention can also be widely applied to various known switching mechanisms that change the natural frequency of the air column of the intake system into at least two states, such as by making the air column variable.

Furthermore, it goes without saying that the present invention is not limited to the four-cylinder engine as in the embodiments described above, but can also be applied to other multi-cylinder engines, such as five-cylinder engines and six-cylinder engines.

(Effect of the invention) As explained above, according to the intake device of the invention, there is a positive pressure passage for supplying the positive pressure of the intake expansion chamber to the pressure responsive member, and a negative pressure of the independent intake passage is supplied to the pressure responsive member. and a negative pressure reserve tank which is interposed in the negative pressure passage and stores the negative pressure flowing in from the independent intake passage side and causes the stored negative pressure to flow out to the pressure responsive member side. Therefore, in high engine load ranges, positive pressure is supplied from the intake expansion chamber, where almost no negative pressure waves are generated, to the pressure-responsive components through the positive pressure passage, and is also stored in the negative pressure reserve tank. Since negative pressure is supplied to the pressure-responsive material through the negative pressure passage, the switching means that changes the natural frequency of the air column in the intake system into at least two states can be operated reliably and accurately even in high engine load ranges. It can be made or held.

[Brief explanation of drawings]

The drawings illustrate embodiments of the present invention, and include FIGS. 1 to 3.
The figure shows the first embodiment, and FIG. 1 is - of FIG. 3.
A longitudinal side view along the line, Figure 2 is - of Figure 3.
FIG. 3 is a partially cut away plan view. FIG. 4 is a diagram corresponding to FIG. 1 showing the second embodiment. DESCRIPTION OF SYMBOLS 1... Engine body, 4... Cylinder, 6... Independent intake passage, 8... Intake expansion chamber, 8a... First volume chamber, 8b... Second volume chamber, 11... Throttle valve, 13... Second passage, 14... Control valve (switching means), 15... Valve shaft, 16... Diaphragm device, 18... Diaphragm, 19... First chamber, 20... Second chamber, 23... Negative pressure aisle, 25
... Positive pressure passage, 26 ... Negative pressure reserve tank, 2
7... Check valve, 29... Check valve, 31... Control unit, 32... Rotation speed sensor, 33...
...Switching mechanism.

Claims (1)

[Scope of utility model registration request] an independent intake passage for introducing intake air into the cylinder;
an intake expansion chamber that is connected to the upstream end of the independent intake passage and converts negative pressure waves generated in the independent intake passage into positive pressure waves; and an intake expansion chamber that sets the natural frequency of the air column of the intake system to at least two states. and a pressure responsive member that operates the switching means based on the differential pressure between the introduced positive pressure and the negative pressure, the upstream end of which is connected to the intake expansion chamber. and a positive pressure passage whose downstream end is connected to the pressure responsive member and for supplying the positive pressure of the intake expansion chamber to the pressure responsive member, and whose upstream end is connected to the independent intake passage and whose downstream end is connected to the pressure responsive member. is connected to the pressure-responsive member and supplies the negative pressure of the independent intake passage to the pressure-responsive member; An intake device for an engine, comprising a negative pressure reserve tank that stores pressure and causes the stored negative pressure to flow out to a pressure responsive member.