JPH078814Y2 - Engine intake and exhaust pipe structure - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial field of application) The present invention relates to an intake / exhaust pipe structure for an engine, which utilizes intake or exhaust pulsating pressure to increase intake efficiency or exhaust efficiency and improve engine output. It is a thing.

(Prior Art) Conventionally, for example, in an intake system of an engine, a negative pressure wave generated at the start of intake is reflected by the atmosphere on the upstream side of the intake passage of the engine or the open end of a surge tank (expansion chamber) to become a positive pressure wave. By using the fact that the positive pressure wave reaches the intake port just before the intake valve is closed and the intake air is pushed in, the so-called intake inertia effect enhances the intake charging efficiency. is there.

By the way, in this case, if the length or shape of the intake passage is constant, it is specified that the intake inertia effect is enhanced by the matching between the vibration cycle of the pressure wave generated in the intake passage and the opening / closing cycle of the intake valve. Will be limited only to the speed range. Therefore, for example, as disclosed in Japanese Patent Laid-Open No. 60-164619, the length of the intake passage can be changed according to the engine speed range, and the intake passage for each cylinder of the engine can be changed. Is bifurcated upstream to form a long first passage and a short second passage, and the upstream ends of these passages are opened to the surge tank or the intake expansion chamber, respectively, and the short second passage is formed. An opening / closing valve is provided at the passage-side opening of the intake valve so that the effective length of the intake passage is shortened by opening this opening / closing valve in the high rotation range, and the opening / closing valve is closed in the low rotation range to close the intake passage. An engine intake system has been proposed in which the effective length is extended and thus the inertial effect of intake air is enhanced in the low speed region and the high speed region depending on the engine speed region.

On the other hand, in the case where the engine intake device is configured as described above, particularly when the intake inertia effect is sufficiently obtained in the low engine speed range without increasing the volume of the surge tank or the intake expansion chamber too much, As is clear from the following equation (Helmholtz resonance equation), it is necessary to particularly increase the length L of the intake passage.

However, a: sound velocity f: cross-sectional area of passage V: volume of expansion chamber L: length of passage However, the space of the engine room in an automobile is physically limited, and inevitably a compact engine is required. Therefore, in general, the intake passage is normally installed in a state of being bent in a substantially U shape as shown in FIG. 7, for example.

That is, in FIG. 7, reference numeral E is an engine, a first intake passage 51 having a long passage distance is connected to an intake port 60 of the engine E through an intake manifold 50, and the first intake passage 51 is further connected. The passage 51 is curved in a U shape,
A surge tank that functions as a pressure wave reversal part at its tip
54 is provided.

On the other hand, the second passage 55 having a short passage distance forms its passage space as an intake expansion chamber for pressure wave reversal, and communicates with the straight pipe portion of the first passage 51 to open, and the opening 52 position The on-off valve 53 described above is provided in the.

(Problems to be solved by the invention) However, when the first intake passage 51 is bent in a U shape as shown in FIG. 7, at least two curved portions A and B are formed in the intake passage. (And the curved part
The bending radii of A and B become smaller as the installation space occupied by the first intake passage 51 is made smaller), and as a result, the intake flow is at the inner peripheral side of the bending portions A and B. Separation occurs and a vortex flow is generated as indicated by symbol V,
Substantially the flow passage area becomes small, which becomes a resistance to the intake air flow. The generation of the eddy flow of the working fluid in the curved passage and the increase in resistance due to the generation of the eddy flow occur not only in the intake passage but also in the exhaust passage. That is, in the engine, the pulsating pressure of the working fluid (exhaust gas) may be used on the exhaust side to improve the exhaust efficiency, and in that case, the example of the intake passage has been described. As described above, when the first exhaust passage and the second exhaust passage communicating with the pressure reversing portion are provided as the exhaust passages, and the exhaust passage side having a long passage length is curved and formed,
It is conceivable that eddy flow occurs due to separation of exhaust gas on the inner peripheral side of the curved portion, which causes increase in exhaust resistance (exhaust efficiency decrease).

(Means for Solving Problems) The present invention has been made for the purpose of solving the above problems, and connects a pressure reversal portion and a cylinder, and forms at least one bending portion in the middle thereof. And the first passage,
An intake passage of the cylinder is provided, which has a second passage, one end side of which communicates with the first passage through an on-off valve and the other end of which communicates with the pressure reversing portion and which has an intake passage length shorter than that of the first passage. Alternatively, the pulsating pressure generated in the exhaust stroke is used, and the intake / supercharging or forced exhaust corresponding to the rotation range is performed in a plurality of rotation ranges of the engine by opening / closing the opening / closing valve in a predetermined engine rotation range. In the intake / exhaust pipe structure of the engine, one end side of the second passage is connected to the first passage on the inner peripheral side of the curved portion of the first passage, while the opening / closing valve is located at a position facing the communication portion. It is arranged.

(Operation) According to the above means, first, since the connecting portion of the second passage to the first passage is provided on the inner circumferential side of the curved portion of the first passage, the connecting portion of the first passage is provided. A space corresponding to the passage diameter of the second passage is formed inside the curved portion, whereby the passage cross-sectional area of the first passage is substantially expanded to the inside of the passage generating the eddy flow. The eddy flow, which is the main cause of the increase in flow resistance, is absorbed in the opening space of the second passage, and as a result, the energy loss (bend loss) of intake air or exhaust gas generated in the curved portion of the first passage is suppressed to the minimum. The decrease in intake and exhaust efficiency is prevented.

Next, in this configuration, since the opening / closing valve that opens / closes the second passage is installed so as to face the communication portion of the second passage with respect to the first passage, the opening / closing valve is the second passage. Unlike the case of being arranged closer to the upstream side of the other end, a dead volume is not formed at the downstream end of the second passage when the on-off valve is closed, and unnecessary pressure reversal action is not caused. Therefore, a reliable intake inertia effect at low speed can be obtained.

(Embodiment) FIGS. 1 to 3 show an embodiment (first embodiment) when the present invention is applied to an intake pipe of an engine.

First, FIG. 3 shows a schematic configuration of the entire structure of the embodiment, and a symbol E is an engine. The engine E is, for example, a four-cylinder four-cycle engine, and first to fourth cylinders 4a to 4d are formed in an engine body 1 including a cylinder block 2 and a cylinder head 3 shown in FIG. Combustion chambers 6a to 6d are formed in the cylinders 4a to 4d, respectively, above the pistons 5a to 5d, and the combustion chambers 6a to 6d are formed.
The intake ports 7a to 7d and the exhaust ports 8a to 8d are opened in 6d, and the intake valves 9a to 9d and the exhaust valves 10a to 10d are installed in the respective ports 7a to 7d and 8a to 8d as shown in FIG. ing. A spark plug (not shown) is provided in each of the combustion chambers 6a to 6d.
Is equipped with.

In the intake ports 7a to 7d of the cylinders 4a to 4d, the main air intake passages (corresponding to the first passage in the utility model registration claim) 12a to 12d for the respective cylinders that are independent of each other are provided with the downstream ends. As shown in FIG. 1, the upstream sides of the respective main intake passages 12a to 12d communicate with each other and are curved upward in a substantially U-shape,
The upstream ends thereof are commonly connected to the surge tanks 13, respectively. Then, outside air is introduced into the surge tank 13 from an air cleaner (not shown) via the intake introducing pipe 15, and a throttle valve 17 is arranged in the middle of the intake introducing pipe 15. In addition, each of the above main intake passages 12
Fuel injection valves 19a to 19d connected to the fuel supply passage 18 are disposed near the downstream ends of a to 12d.

Further, one of the U-shaped curved portions A and B of the main intake passages 12a to 12d, for example, the A curved portion on the intake downstream side, has a branch port that branches from each of the main intake passages 12a to 12d. Branching passages (corresponding to the second passage in the utility model registration claim) 22a to 22d for connecting the respective main intake passages 12a to 12d to each other via 21a to 21d are connected. In this embodiment, in order to make the intake system more compact, the surge expansion chamber 13a having a relatively large capacity is formed in the surge tank 13 provided in the intake system, while the main intake passage 12a to The branch passages 22a to 22d having the intake expansion chamber 20 having a relatively small capacity are formed so as to be located in the inner space of the curved portion 12d, and the main intake passages 12a to 12d are formed at the lower ends of the branch passages 22a to 22d. The branch inlets 21a to 21d communicating with the respective main inlet passages 12a to 12d are first curved upward from the formation positions of the branch inlets 21a to 21d, and the upstream end side thereof is further curved laterally. The surge tank 13 is opened at the upper part of the intake expansion chamber 13a. As shown in FIG. 1, the upstream curved portions of the main intake passages 12a to 12d are formed substantially parallel to each other along the circumferential surface of the surge tank 13 in the vertical direction, and the intake expansion of the surge tank 13 is expanded in advance. The upstream expansion portion of the chamber 13a and the outside main intake passages 12a to 12d and the intake expansion chamber 20 of the branch passages 22a to 22d.
Of the branch passages 22a to 22d and the downstream main intake passages 12a to 12d outside thereof.
The intake pipe parts constituting the above are integrally molded, and these intake pipe parts are connected to each other through the flange part 24, whereby a sufficiently compact intake system is formed. In this case, the intake expansion chamber 13a is the first pressure reversal portion in the scope of utility model registration claim, and the intake expansion chamber 20a
Corresponds to the second pressure reversal section.

Further, the opening / closing valve 25a is provided at each of the branch ports 21a to 21d.
25d are provided, and the opening / closing valves 25a to 25d are controlled by a predetermined control circuit (not shown) that operates by receiving the output of the engine speed detecting means, and the engine speed is less than the set value via the actuator 26. It is controlled to be closed in the low speed range and opened in the high speed range where the engine speed is equal to or higher than the set value.

The on-off valves 25a-2
The opening / closing operation of 5d may be performed at least during a high load when engine output is particularly required, while the opening / closing valves 25a to 25d may be maintained in an open state or a closed state at a low load. You may Further, in the above embodiment, the intake expansion chamber 13a of the surge tank 13 and the intake expansion chamber 20 of the branch passages 22a to 22d are integrally formed, but the intake expansion chamber 13a and the intake passages of the branch passages 22a to 22d are expanded. Room 2
It may be formed separately from 0.

According to this intake pipe structure, the negative pressure wave generated in the intake stroke of each cylinder of the engine in the state where the opening / closing valves 25a to 25d provided in the respective branch ports 21a to 21d of the respective intake passages 12a to 12d are closed. Is propagated to the intake expansion chamber 13a of the surge tank 13 and reflected there, that is, the negative pressure wave and its reflected wave propagate through a relatively long passage, so that the oscillation cycle of the pressure wave in the low speed range is increased or decreased. The inertial effect of intake is enhanced by matching the cycle. That is, the relationship between the engine speed and the intake charge efficiency in this state is as shown by the curve A in FIG. 4, and the intake charge efficiency is sufficiently increased in the low speed range. On the other hand, in the state where the on-off valves 25a to 25d are opened, the negative pressure wave generated in the intake stroke is reflected in the intake expansion chamber 20 of the branch passages 22a to 22d and the negative pressure wave and the reflection are generated, as described later in detail. By reducing the length of the passage used for wave propagation, the intake inertia effect in the high speed range is enhanced, and the pressure wave propagated from other cylinders also effectively acts in this operating range. That is, the relationship between the engine speed and the intake charge efficiency at high load in this state is as shown by the curve B in FIG. 4, and the charge efficiency in the high speed range is enhanced.

Therefore, at least when the load is high, the opening / closing valves 25a to 25d are closed on the lower speed side with the rotation speed No corresponding to the point where the curves A and B intersect, and the opening / closing valve 25a on the higher speed side. By opening ~ 25d, the intake charging efficiency is increased in all speed ranges and the engine output is effectively improved. In particular, the intake charging efficiency in the high-speed range is higher than that in the conventional case where the intake passage is simply shortened to increase the intake inertia effect (curve C), as compared with the conventional case, in which mutual pressure propagation action due to communication between the cylinders occurs. Will be further enhanced in.

In that case, since the branch passages 22a to 22d are located on the inner peripheral side of the curved portion A of the intake passages 12a to 12d and the branch openings 21a to 21d are formed, the branch openings 21a to 21d.
Due to the existence of the curved portion A, the passage cross-sectional area of the portion of the curved portion A is substantially enlarged, and the eddy flow generated in the inner peripheral side portion of the curved portion A is the branch ports 21a to 21d of the branch passage 22. Will be absorbed in. Therefore, each intake passage 12a-1
Even if the curved portion A is present in 2d, such an energy loss (bend loss) does not occur, and the effect of improving the intake charging efficiency can be more effectively obtained.

Next, FIG. 5 and FIG. 6 show a second embodiment (applied to the intake pipe) of the present invention, in which the intake upstream side curved portion B of each of the intake passages 12a to 12d downstream of the surge tank 13 is provided. Branch passage 22
It is characterized in that branch ports 21a to 21d of a to 22d are formed.

Even with such a configuration, the passage cross-sectional area of the bending portion B can be substantially enlarged as in the case of the first embodiment, so that the energy loss in the bending portion B can be suppressed to the minimum. It is possible to contribute to the improvement of the intake air charging efficiency.

In each of the above embodiments, the case of the intake pipe of the engine has been described as an example, but it goes without saying that the present invention can be similarly applied to the case of improving the exhaust porosity of the exhaust pipe of the engine. .

(Effect of the Invention) As described above, the present invention connects the pressure reversing portion and the cylinder, and forms the at least one curved portion in the middle of the first passage, and the one end side of the opening / closing valve. Through the first
And a second passage having the other end communicating with the pressure reversing portion and having a shorter intake passage length than the first passage, and utilizing the pulsating pressure generated in the intake or exhaust stroke of the cylinder. In the intake / exhaust pipe structure of the engine, the intake supercharging or the forced exhaust corresponding to the rotation range is performed in a plurality of rotation ranges of the engine by opening / closing the opening / closing valve in a predetermined engine rotation range. The one end side of the second passage is made to communicate with the passage of the first passage on the inner peripheral side of the curved portion of the first passage, while the opening / closing valve is arranged at a position facing the communication portion. is there.

Therefore, according to the present invention, first the second passage to the first passage is provided.
Since the connecting portion of the passage is provided on the inner side of the curved portion of the first passage, the space portion corresponding to the passage diameter of the second passage is provided inside the curved portion of the first passage. Is formed, whereby the passage cross-sectional area of the first passage is substantially expanded inside the passage generating the eddy flow, and the eddy flow, which is the main cause of the increase in flow resistance, is generated in the opening of the second passage. As a result of being absorbed in the space, energy loss (bend loss) of intake air or exhaust gas that occurs in the curved portion of the first passage is suppressed to a minimum, and a decrease in intake and exhaust efficiency is prevented.

Next, in this configuration, since the opening / closing valve that opens / closes the second passage is installed so as to face the communication portion of the second passage with respect to the first passage, the opening / closing valve is the second passage. Unlike the case of being arranged closer to the upstream side of the other end, a dead volume is not formed at the downstream end of the second passage when the on-off valve is closed, and unnecessary pressure reversal action is not caused. Therefore, a reliable intake inertia effect at low speed can be obtained.

[Brief description of drawings]

FIG. 1 is a front view of an intake pipe structure for an engine according to a first embodiment of the present invention, FIG. 2 is a sectional view of a passage connecting portion in the same embodiment, and FIG. 3 is an entire structure of the same embodiment. FIG. 4 is a schematic plan view showing the structure, FIG. 4 is a graph showing the relationship between the engine speed range and intake charge ratio in the same embodiment, and FIG. 5 is an intake pipe structure for an engine according to a second embodiment of the present invention. FIG. 6 is a sectional view of a passage connecting portion in the same embodiment, and FIG. 7 is a sectional view of a conventional engine intake pipe structure. 1 ... Engine body 2 ... Cylinder block 3 ... Cylinder head 4a-4d ... Cylinder 7a-7d ... Intake port 12a-12d ... Main intake passage (first passage) 13 ... Surge tank (First passage) 20 ...... Intake expansion chamber (second pressure reversal part) 21a to 21d ...... Branch ports 22a to 22d ...... Branch passages (second passage) 25a to 25d ...... Open / close valves A, B ... … Bent

Claims (1)

[Scope of utility model registration request] 1. A first passage formed by connecting a pressure reversal portion and a cylinder, and forming at least one curved portion in the middle thereof,
An intake passage of the cylinder is provided, which has a second passage, one end side of which communicates with the first passage through an on-off valve and the other end of which communicates with the pressure reversing portion and which has an intake passage length shorter than that of the first passage. Alternatively, the pulsating pressure generated in the exhaust stroke is used, and the intake / supercharging or forced exhaust corresponding to the rotation range is performed in a plurality of rotation ranges of the engine by opening / closing the opening / closing valve in a predetermined engine rotation range. In the intake / exhaust pipe structure of the engine, one end side of the second passage is connected to the first passage on the inner peripheral side of the curved portion of the first passage, while the opening / closing valve is located at a position facing the communication portion. An intake / exhaust pipe structure for an engine characterized by being provided.