WO2009001206A2

WO2009001206A2 - Intake apparatus for multi-cylinder internal combustion engine

Info

Publication number: WO2009001206A2
Application number: PCT/IB2008/001685
Authority: WO
Inventors: Koji Honda; Takashi Kawase; Takashi Fukunaga; Kenji Isaka; Takatoshi Hattori
Original assignee: Toyota Jidosha Kabushiki Kaisha
Priority date: 2007-06-28
Filing date: 2008-06-27
Publication date: 2008-12-31
Also published as: WO2009001206A3; JP2009008020A

Abstract

A dividing wall (13) is provided which divides the inside of a surge tank (10), and a communication hole (17) which is always open is formed in the dividing wall (13) in a location upstream of an upstream-most branching portion, from among branching portions in the surge tank (10) to intake manifolds of a multi-cylinder internal combustion engine, and downstream of an upstream end (13a) of the dividing wall (13), which is provided downstream of a throttle valve.

Description

INTAKE APPARATUS FOR MULTI-CYLINDER INTERNAL COMBUSTION

ENGINE

BACKGROUND OF THE INVENTION

1. Field of the Invention

[0001] The invention relates to an intake apparatus for a multi-cylinder internal combustion engine.

2. Description of the Related Art

[0002] The reciprocating motion of pistons and the opening and closing of intake valves create areas of high and low pressure air flowing through an intake pipe. The difference between the two pressures creates a pulse which generates pressure waves that travel through the intake pipe. When there is a high pressure area of this pulse in the intake port right before the intake valve doses, air at that high pressure air is forced into the cylinder, which creates a kind of supercharging effect that improves the charging efficiency of air into the combustion chamber, and thus the torque generated by the internal combustion engine.

[0003] This kind of supercharging effect created by the intake pulse (hereinafter simply referred to as "intake pulse-generated supercharging effect") is only obtained in a limited engine speed range (hereinafter also referred to as "RPM range"). However, because the cycle of the intake pulse is determined by the length and sectional area of the intake pipe, the RPM range in which the intake pulse-generated supercharging effect is able to be obtained can be changed by adjusting these parameters. For example, when it is desirable to improve torque performance in the high RPM range, the intake pipe is tuned so that it is shorter and larger in diameter to make the intake pulse cycle shorter. Also, when it is desirable to improve torque performance in the low RPM range, the intake pipe is tuned so that it is longer and smaller in diameter to make the intake pulse cycle longer.

[0004] Japanese Patent Application Publication No. 2002-242681 (JP-A-2002-242681), however, describes technology for obtaining such an intake pulse-generated supercharging effect over a wider engine speed range. The technology described in JP-A-2002-242681 is a variable induction system that obtains the intake pulse-generated supercharging effect described above in a plurality of engine speed ranges by varying the effective length of the intake pipe. The variable induction system described in JP-A-2002-242681 does this by dividing the inside of a surge tank into two air chambers using a dividing wall, and providing a valve (i.e., a variable induction valve) that selectively allows and prevents communication between the two air chambers in the surge tank that are divided by the dividing wall. Opening and closing this variable induction valve switches the effective length of the intake pipe between long and short according to the engine speed, thus enabling the intake pulse-generated supercharging effect to be obtained in both the low RPM range and the high RPM range.

[0005] However, even if such a variable induction system is employed, the engine speed range in which the intake pulse-generated supercharging effect is able to be achieved is limited for each effective length of the intake pipe that is switched between long and short. Therefore, to further increase the engine speed range in which the intake pulse-generated supercharging effect can be obtained, it is necessary to be able to switch the effective length of the intake pipe among at least three lengths. However, this would result in a more complex apparatus and increased manufacturing costs due to the need for a plurality of variable induction valves and the like.

SUMMARY OF THE INVENTION

[0006] This invention thus provides an intake apparatus for a multi-cylinder internal combustion engine in which an intake pulse-generated supercharging effect can be obtained more effectively with a simple structure.

[0007] A first aspect of the invention relates to an intake apparatus for a multi-cylinder internal combustion engine. This intake apparatus includes a surge tank, and a dividing wall that divides the inside of the surge tank into a first air chamber to which a first intake manifold for a first cylinder group of the multi-cylinder internal combustion engine is connected, and a second air chamber to which a second intake manifold for a second cylinder group is connected. The dividing wall has a communication hole that is always open located upstream of an upstream-most branching portion, from among branching portions to the first intake manifold and the second intake manifold, and downstream of an upstream end of the dividing wall, which is provided downstream of a throttle valve.

[0008] When the inside of the surge tank is divided into two air chambers by the dividing wall, the effective length of the intake pipe is from- the intake port of each cylinder to the upstream end of the dividing wall. With the foregoing structure, a communication hole is provided in the dividing wall. In this case, pressure waves generated at the intake port of each cylinder by the reciprocating motion of the piston and the opening and closing of the intake valves travel upstream through the intake manifold for those cylinders and the air chamber in the surge tank to which that intake manifold is connected. Some of the pressure waves are reflected by the communication hole formed in the dividing wall and return to the intake port The remaining pressure-waves that pass through the communication hole, however, continue to travel upstream where they are reflected by the upstream end of the dividing wall and return to the intake port. Accordingly, two series of pressure waves, i.e., the pressure waves reflected by the communication hole and the pressure waves reflected by the upstream end of the dividing wall, return to the intake ports when the communication hole is formed in the dividing wall. Therefore, with the foregoing structure, the intake pulse-generated supercharging effect when the effective length of the intake pipe is from the intake ports to the communication hole, and the intake pulse-generated supercharging effect when the effective length of the intake pipe is from the intake ports to the upstream end of the dividing wall, are able to be obtained simultaneously. As a result, the width of the RPM range in which the intake pulse-generated supercharging effect can be obtained increases. Furthermore, a greater supercharging effect can be obtained by superimposing the two intake pulses. [0009] The intake apparatus may also include a variable induction valve which is provided downstream of the communication hole and opens and closes to selectively allow and prevent communication between the first air chamber and the second air chamber.

[0010] With the structure described above, it is possible to change the RFM range within which the intake pulse-generated supercharging effect can be obtained by changing the effective length of the intake pipe by opening and closing the variable induction valve. That is, when the variable induction valve is closed, the intake pulse-generated supercharging effect yielded by the two effective lengths of intake pipe can be obtained simultaneously, as described above. Also, when the variable induction valve is open, an intake pulse-generated supercharging effect yielded as a result of making the effective length of the intake pipe be from the intake port of each cylinder to the surge tank can be obtained. Because an intake apparatus that employs a variable induction system having such a variable induction valve already has a dividing wall that divides the inside of the surge tank, the intake pulse-generated supercharging effect can be more effectively obtained by making only a minor change to the structure, which simply involves forming a communication hole in the dividing wall.

[0OU] The multi-cylinder internal combustion engine may be a V-type internal combustion engine having a left bank and a right bank. Further, the first cylinder group may be arranged in the left bank and the second cylinder group may be arranged in the right bank.

[0012] Accordingly, the intake apparatus may be applied to a V-type internal combustion engine.

BRIEF DESCRIPTION OF THE DRAWINGS

[0013] The foregoing and further objects, features and advantages of the invention will become apparent from the following description of example embodiments with reference to the accompanying drawings, wherein like numerals are used to represent like elements and wherein: FIG 1 is a schematic perspective view of a structure, shown transparent, of a surge tank unit of an intake apparatus for a multi-cylinder internal combustion engine according to an example embodiment of the invention;

FIG 2 is a schematic view of the structure of the intake apparatus according to the example embodiment;

FIG 3A is a schematic view of the structure of the intake apparatus according to the example embodiment;

FIG 3B is a schematic view of a structure of an intake apparatus according to a first comparative example (Comparative example 1);

FIG 3C is a schematic view of a structure of an intake apparatus according to a second comparative example (Comparative example 2); and

FIG 4 is a graph showing the torque characteristics of an internal combustion engine employing the intake apparatus according to the example embodiment, the torque characteristics of an internal combustion engine employing the intake apparatus according to Comparative example 1 and the torque characteristics of an internal combustion engine employing the intake apparatus according to Comparative example 2.

DETAILED DESCRIPTION OF THE EMBODIMENTS

[0014] Hereinafter, an example embodiment of an intake apparatus for a multi-cylinder internal combustion engine of the invention will be described in more detail with reference to FIGS. 1 to 4. Incidentally, in this example embodiment, the multi-cylinder internal combustion engine is a V-type six-cylinder internal combustion engine that has two banks (i.e., a left bank and a right bank) of three cylinders each.

[0015] FIG 1 is a schematic perspective view of a structure, shown transparent, of a surge tank unit used in an intake apparatus for a multi-cylinder internal combustion engine according to the example embodiment of the invention. As shown in the drawing, in this surge tank unit, connectors which connect to a throttle body and intake manifolds of the cylinders are integrally provided on a surge tank 10. That is, a connector 11 which connects to a throttle body having a throttle valve is provided on the side of the surge tank 10 of the surge tank unit, and six connectors 12a to 12f which connect to intake manifolds are provided on the front of the surge tank 10. Of the connectors 12a to 12f, the connectors that connect to an intake manifold for the three cylinders of the left bank of the engine (i.e., connectors 12a to 12c) are arranged in a row at the upper portion of the surge tank 10, and the connectors that connect to an intake manifold for the three cylinders of the right bank of the engine (i.e., connectors 12d to 12f) are arranged in a row at the lower portion of the surge tank 10. Incidentally, these connectors 12a to 12f essentially form upstream portions of the intake manifolds.

[0016] The inside of the surge tank 10 of this surge tank unit is divided into two chambers, i.e., an upper chamber and a lower chamber, by a dividing wall 13. That is, the surge tank 10 is divided into a first air chamber 14 formed in the upper portion of the surge tank 10, and a second air chamber IS formed in the lower portion of the surge tank 10. Similarly, the connector 11 of the surge tank unit is also divided into an upper portion and a lower portion by the dividing wall 13. The connectors 12a to 12c that connect to the intake manifold for the cylinders of the left bank of the engine are connected to the first air chamber 14, and the connectors 12d to 12f that connect to the intake manifold for the cylinders of the right bank of the engine are connected to the second air chamber IS. Furthermore, a variable induction valve 16 that opens and closes to selectively allow and prevent communication between the first air chamber 14 and the second air chamber IS is provided in the dividing wall 13 in the surge tank 10. Incidentally, in this example embodiment, the three cylinders of the left bank that are connected to the first air chamber 14 form a first cylinder group, and the three cylinders of the right bank that are connected to the second air chamber IS form a second cylinder group. Also, as shown in FIG 1, in this example embodiment, the surge tank is generally rectangular parallelepiped, with a first surface to which the connector 11 is connected being generally orthogonal to a second surface to which the connectors 12a to 12f are connected. The variable induction valve 16 is arranged closer to a surface opposing the first surface than it is to the first surface. [0017] In the intake apparatus of this example embodiment, a communication hole 17 which is always open is formed in the dividing wall 13 of the surge tank unit. This communication hole 17 is formed upstream of an upstream-most branching portion, from among branching portions in the surge tank 10 to the intake manifolds (Le., to the connectors 12a to 12f), and downstream of an upstream end 13a of the dividing wall 13, which is provided downstream of a throttle valve. Hie branching portions are the orifices in the surge tank 10 which lead to the intake manifolds, and the upstream-most branch portion is located at the most upstream of those orifices. Also, in this example embodiment, as shown in FIQ 1, the connector 11 is bent and the communication hole 17 is located upstream of the bent portion of the connector 11. Further, the communication hole 17 is arranged toward one side in the width direction of the connector 11, in particular, toward the inner side of the bent portion. Moreover, the communication hole 17 is an elongated hole in which the longitudinal direction thereof is substantially perpendicular to the direction of airflow in the connector 11. In this embodiment, the communication hole 17 has a rectangular shape with the longer sides extending perpendicular to the direction of airflow in the connector 11.

[0018] FIG 2 is a schematic view of the structure of the intake apparatus according to the example embodiment provided with this kind of surge tank unit. As shown in the drawing, the intake air path of the intake apparatus branches into two by the dividing wall 13 downstream of a throttle body 19 hi which a throttle valve 18 is arranged. Accordingly, intake air travels to the three cylinders of the left bank through the first air chamber 14 and the connectors 12a to 12c, while intake air travels to the three cylinders of the right bank through the second air chamber 15 and the connectors 12d to 12f.

[0019] When the variable induction valve 16 is open, thereby allowing communication between the fast air chamber 14 and the second air chamber 15, the effective length of the intake pipe is from the intake ports to the portion where the connectors 12a to 12f connect with the surge tank 10. Qn the other hand, when the variable induction valve 16 is dosed, thereby preventing communication between the first air chamber 14 and the second air chamber 15, the effective length of. the intake pipe would be from the intake ports to the upstream end 13a of the dividing wall 13 provided downstream of the throttle valve 18 if the communication hole 17 was not provided.

[0020] However, with this example embodiment, the communication hole 17 is formed in the dividing wall 13, as described above. In this case, the pressure waves generated at the intake ports of the cylinders by the reciprocating motion of the pistons and the opening and closing of the intake valves travel to the intake upstream side through the intake manifolds of those cylinders, the connectors 12a to 12f, and the air chambers (i.e., the first air chamber 14 and the second air chamber IS) in the surge tank 10. The transmitted pressure waves are partially reflected by the communication hole 17. That is, some of the pressure waves are reflected by the communication hole 17 formed in the dividing wall 13 and return to the intake ports, while the rest of the pressure waves that pass through the communication hole 17 continue to travel to the intake upstream side where they are reflected by the upstream end 13a of the dividing wall 13 and return to the intake ports.

[0021] Accordingly, in the example embodiment in which the communication hole 17 is formed in the dividing wall 13, the two series of pressure waves, i.e., the pressure waves reflected by the communication hole 17 and the pressure waves reflected by the upstream end 13a of the dividing wall 13, return to the intake ports when the variable induction valve 16 is closed. As a result, two wave pulses with different cycles are created, making it possible to simultaneously obtain the intake pulse-generated supercharging effect obtained when the effective length of the intake pipe is from the intake ports to the communication hole 17, and the intake pulse-generated supercharging effect obtained when the effective length of the intake pipe is from the intake ports to the upstream end 13a of the dividing wall 13. As a result, the width of the RPM range in which the intake pulse-generated supercharging effect can be obtained increases. In addition, an even greater supercharging effect can be obtained by superimposing these two intake pulses.

[0022] Here, the effects of the intake apparatus for a multi-cylinder internal combustion engine according to this example embodiment will now be described through a comparison with the following two configuration examples of intake apparatuses. FIG 3A is a schematic view of the structure of the intake apparatus according to the example embodiment, in which the communication hole 17 is formed in the dividing wall 13. FIG 3B is a schematic view of a structure of an intake apparatus according to a first comparative example (Comparative example 1), and FIG 3C is a schematic view of a structure of an intake apparatus according to a second comparative example (Comparative example 2). As shown in FIG 3B, the intake apparatus according to Comparative example 1 is provided with a dividing wall 13' having no communication hole. An upstream end 13a' of the dividing wall 13' is positioned where the communication hole 17 is formed in the intake apparatus of the example embodiment Also, as shown in FIG 3C, the intake apparatus according to Comparative example 2 is provided with a dividing wall 13" which also has no communication hole. An upstream end 13a" of the dividing wall 13" is positioned in the same place as the upstream end 13a of the dividing wall 13 of the intake apparatus of the example embodiment

[0023] FIG 4 is a graph showing the torque characteristics of an internal combustion engine employing the intake apparatus of the example embodiment, the torque characteristics of an internal combustion engine employing the intake apparatus of Comparative example 1, and the torque characteristics of an internal combustion engine employing the intake apparatus of Comparative example 2. When the effective length of the intake pipe is short, the engine speed range in which the intake pulse-generated supercharging effect can be obtained shifts to the high speed side. Therefore, as shown by the graph, the engine speed range in which the intake pulse-generated supercharging effect can be obtained is higher, and thus the engine speed at which maτinnim torque is obtained is higher, in the internal combustion engine employing the intake apparatus of Comparative example 1 in which the effective length of the intake pipe is shorter, than it is in the internal combustion engine employing the intake apparatus of Comparative example 2 in which the effective length of the intake pipe is longer.

[0024] In contrast, in the internal combustion engine employing the intake apparatus of the example embodiment, the communication hole 17 enables the intake pulse-generated supercharging effects obtained from two different effective lengths, Le., long and short, of the intake pipe to be obtained simultaneously. Therefore, the intake pulse-generated supercharging effect can be obtained in both the engine speed range in which the intake pulse-generated supercharging effect can be obtained when the intake apparatus of Comparative example 1 is employed, and the engine speed range in which the intake pulse-generated supercharging effect can be obtained when the intake apparatus of Comparative example 2 is employed. Furthermore, when the engine speed ranges in which the supercharging effect can be obtained overlap, the pulses superimpose resulting in an even greater supercharging effect and greater maximum torque. Incidentally, in the internal combustion engine employing the intake apparatus of the example embodiment, torque performance in the high engine speed range can also be improved by opening the variable induction valve 16 to make the effective length of the intake pipe even shorter.

[0025] Incidentally, in the intake apparatus for a multiple cylinder example embodiment according to the example embodiment, the engine speed range in which the intake pulse-generated supercharging effect can be obtained is able to be changed by adjusting the position and size of the communication hole 17. For example, forming the communication hole 17 farther downstream enables the engine speed at which maximum torque can be obtained to be shifted toward the high speed side. Also, increasing the size of the communication hole 17 increases the degree to which pressure waves are reflected by the communication hole 17, which also enables the engine speed at which maximum torque can be obtained to be shifted toward the high speed side.

[0026] The intake apparatus for a multi-cylinder internal combustion engine according to the example embodiment described above yields the following effects. In the example embodiment, the dividing wall 13 that divides the inside of the surge tank 10 is provided, and the communication hole 17 that is always open is formed in the dividing wall 13. The position in which the communication hole 17 is formed in the dividing wall 13 is upstream of the upstream-most orifice, from among the orifices in the surge tank 10 which lead to the intake manifolds (i.e., to the connectors 12a to 12f), and downstream of the upstream end 13a of the dividing wall 13, which is provided downstream of the throttle valve 18. In this way, with the intake apparatus for a multi-cylinder internal combustion engine of the example embodiment in which the communication hole 17 is formed in the dividing wall 13, the intake pulse-generated supercharging effect that is obtained when the effective length of the intake pipe is from the intake ports to the communication hole 17, and the intake pulse-generated supercharging effect that is obtained when the effective length of the intake pipe is from the intake ports to the upstream end 13a of the dividing wall 13, can be obtained simultaneously. As a result, the width of the engine speed range in which the intake pulse-generated supercharging effect can be obtained increases. In addition, an even greater supercharging effect can be obtained by superimposing these two intake pulses. Therefore, according to this example embodiment, the intake pulse-generated supercharging effect can be obtained more effectively by the simple structure in which the dividing wall 13 that divides the inside of the surge tank 10 is provided, and the communication hole 17 is simply formed in the dividing wall 13.

[0027] The intake apparatus of this example embodiment employs a variable induction system in which the dividing wall 13 that divides the surge tank 10 into the first air chamber 14 and the second air chamber 15 is provided, and the variable induction valve 16, which opens and closes to selectively allow and prevent communication between the first air chamber 14 and the second air chamber 15, is arranged in the dividing wall 13. Because an intake apparatus that employs this kind of variable induction system already has the dividing wall 13 that divides the inside of the surge tank 10, the only change that is needed is to simply form the communication hole 17 in the dividing wall 13.

[0028] Incidentally, the foregoing example embodiment may also be changed in the following ways. That is, in the example embodiment described above, the invention is applied to an intake apparatus that employs a variable induction system which has the variable induction valve 16 that opens and closes to selectively allow and prevent communication between the first air chamber 14 and the second air chamber 15, thereby changing the effective length of the intake pipe. Because an intake apparatus that employs this kind of variable induction system already has the dividing wall 13 that divides the inside of the surge tank 10, the only change that is needed is to simply form the communication hole 17 in the dividing wall 13. However, even with an intake apparatus that does not employ such a variable induction system, it is possible to simultaneously obtain the intake pulse-generated supercharging effects obtained from the two different effective lengths, i.e., long and short, of the intake pipe by providing a dividing wall portion that divides the surge tank and forming a communicating hole such as that described above in the dividing wall.

[0029] In this example embodiment, the intake apparatus is described as being applied to a V-type six-cylinder internal combustion engine, but the invention may also be similarly applied to an internal combustion engine of another configuration, hi other words, regardless of the configuration of the internal combustion engine, effects similar to those described above can be obtained by structuring the intake apparatus as follows: i) dividing the cylinders of a multi-cylinder internal combustion engine into a first cylinder group and a second cylinder group, with cylinders in which the intake pulse cycle is substantially similar grouped together, ii) providing a dividing wall to divide the inside of the surge tank into a first air chamber to which the connectors of an intake manifold for one cylinder group are connected, and a second air chamber to which the connectors of an intake manifold for the other cylinder group are connected, and iii) forming a communication hole that is always open in the dividing wall. Incidentally, the position in which this communication hole is formed is upstream of the upstream-most orifice, from among the orifices in the surge tank which lead to the intake manifolds, and downstream of the upstream end of the dividing wall, which is provided downstream of the throttle valve.

[0030] While some embodiments of the invention have been illustrated above, it is to be understood that the invention is not limited to the details of the illustrated embodiments, but may be embodied with various changes, modifications or improvements, which may occur to those skilled in the art, without departing from the spirit and scope of the invention.

Claims

CLAIMS:

1. An intake apparatus for a multi-cylinder internal combustion engine, comprising: a surge tank; and a dividing wall that divides the inside Qf the surge tank into a first air chamber to which a first intake manifold for a first cylinder group of the multi-cylinder internal combustion engine is connected, and a second air chamber to which a second intake manifold for a second cylinder group is connected, wherein the dividing wall has a communication hole that is always open located upstream of an upstream-most branching portion, from among branching portions in the surge tank to the first intake manifold and the second intake manifold, and downstream of an upstream end of the dividing wall, which is provided downstream of a throttle valve.

2. The intake apparatus according to claim 1, further comprising a variable induction valve which is provided downstream of the communication hole and opens and closes to selectively allow and prevent communication between the first air chamber and the second air chamber.

3. The intake apparatus according to claim 1, further comprising a connector for connecting the surge tank and a throttle body, wherein the dividing wall also divides the inside of the connector into a portion that is communicated with the first air chamber and a portion that is communicated with the second air chamber.

4. The intake apparatus according to claim 3, wherein the communication hole is in a portion of the dividing wall which divides the inside of the connector.

5. The intake apparatus according to claim 4, wherein the connector is bent, and the communication hole is located upstream of the bent portion of the connector.

6. The intake apparatus according to claim 4 or 5, wherein the communication hole is arranged toward one side in the width direction of the connector.

7. The intake apparatus according to claim S, wherein the communication hole is arranged toward the inner side of the bent portion of the connector.

8. The intake apparatus according to any one of claims 1 to 7, further comprising a first connector that connects the first cylinder group with the first air chamber, and a second connector that connects the second cylinder group with the second air chamber.

9. The intake apparatus according to claim 1, wherein the surge tank is generally rectangular parallelepiped, the intake apparatus further comprising: a connector that connects the surge tank with a throttle body, the connector being connected to a first surface of the surge tank; a first connector that connects the first cylinder group with the first air chamber; and a second connector that connects the second cylinder group with the second air chamber, wherein the first connector and the second connector are connected to a second surface of the surge tank, the second surface being substantially orthogonal to the first surface.

10. The intake apparatus according to claim 9, further comprising a variable induction valve which is provided in the dividing wall in a position downstream of the communication hole and is closer to a surface of the surge tank that is opposite the first surface of the surge tank than it is to the first surface, and opens and closes to selectively allow and prevent communication between the first air chamber and the second air chamber.

11. The intake apparatus according to any one of claims 1 to 10, wherein the communication hole is an elongated hole in which the longitudinal direction thereof is substantially perpendicular to the direction of airflow.

12. The intake apparatus according to any one of claims 1 to 11, wherein the multi-cylinder internal combustion engine is a V-type internal combustion engine having a left bank and a right bank, the first cylinder group being arranged in the left bank and the second cylinder group being arranged in the right bank.