JP2008190414A - Intake device of engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent the deterioration in combustion performance, by restraining dispersion in intake air between cylinders in a partial load area of an engine, in an intake device of the engine. <P>SOLUTION: Intake pipes 13 and 14 different in the intake passage length are arranged so that one end side is connected to a surge tank 12 and the multi-end side is connected to an air cleaner 11, respectively, and switching valves 21 and 22 are arranged in these intake pipes 13 and 14. The switching valve 21 and 22 are controlled for opening and closing by a controller 30. The controller 30 adjusts its opening by opening the two switching valves 21 and 22 when the engine is a partial load. Particularly when the engine is a low load, the opening of the two switching valves 21 and 22 is equalized, and when the engine is a medium load, the opening of the switching valves 21 and 22 is continuously changed in response to an engine load so that only one switching valve is put in an opening state in a high load. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an intake device for an engine, and particularly relates to the technical field of variable intake that performs intake with a variable intake passage length.

  2. Description of the Related Art Conventionally, many intake devices having a variable intake mechanism have been adopted as an intake device for an engine. As an example, an intake device disclosed in Patent Document 1 is known.

  The intake device disclosed in Patent Document 1 has one end connected to an air cleaner, the other end connected to a surge tank, one end connected to an air cleaner, and the other end connected to a surge tank. And a second intake pipe having a longer intake path than the first intake pipe, and a switching mechanism capable of switching the intake path from the air cleaner to the first intake pipe or the second intake pipe.

  Specifically, one end of each of the first and second intake pipes is connected to an air cleaner, while the other end of the second intake pipe having a longer intake passage length than the first intake pipe is connected to the first intake pipe. It is connected to. The intake device is configured to switch the intake path to the second intake pipe in the low engine speed range and the intake path to the first intake pipe in the middle engine speed range by a switching valve as a switching mechanism. Has been.

As a result, in the low and middle rotation range, the negative pressure wave generated with the start of intake is reversed by the surge tank or air cleaner as the opening end on the upstream side of the intake pipe and is returned to the intake port side as a sine wave. By utilizing the intake air, the intake air can be pushed into the cylinder and the charging efficiency of the intake air can be increased. In the present specification, the effect of reversing the pressure wave in the surge tank and returning to the intake port side is called an inertia effect, and the effect of reversing the pressure wave in the air cleaner and returning to the intake port side is called a resonance effect.
Japanese Patent Laid-Open No. 10-299490

  Incidentally, the charging efficiency of intake air can be improved by using the inertial effect and resonance effect of intake air as described above, or by reducing the ventilation resistance of the intake passage.

  Here, as a configuration for reducing the ventilation resistance in the intake passage, the surge tank is formed in a cylindrical shape extending in the direction in which the cylinders are arranged, and the intake pipes are connected to both ends of the surge tank, respectively. It is conceivable to eliminate the bending of the intake air when flowing into the surge tank. However, in such a configuration, since the length of the intake path in the surge tank is different for each cylinder, the variation in intake air among the cylinders increases.

  Such variation in intake air among cylinders greatly affects the combustion performance in the partial load region of the engine. Therefore, it is necessary to suppress the variation in intake air in the partial load region to prevent deterioration of the combustion performance.

  The present invention has been made in view of such a point, and an object of the present invention is to suppress a variation in intake air between cylinders in a partial load region of an engine in an engine intake device, thereby reducing combustion performance. It is to prevent.

  In order to achieve the above object, in the intake system for an engine according to the present invention, an open / close valve is provided in each of a long intake passage and a short intake passage, one end of which communicates with a surge tank and the other end communicates with an air cleaner. In the partial load region, both the on-off valves were opened, and the on-off valves were controlled so that the sum of the opening degrees of the two was a predetermined opening degree.

  Specifically, according to the first aspect of the present invention, a surge tank to which branch pipe portions of a plurality of cylinders are connected, and an intake passage length communicating with the surge tank on one end side and communicating with an air cleaner on the other end side are different. The present invention is directed to an engine intake device that includes a long intake passage and a short intake passage, and performs intake by switching the intake passage to at least one of the intake passages according to the engine rotation range.

  The surge tank is provided so as to extend in the direction in which the branch pipe portions are arranged, and the long intake passage is communicated with one end side of the surge tank, while the short intake air is provided with the other end side. The long communication passage is provided with a first on-off valve, and the short intake passage is provided with a second on-off valve. When the engine is partially loaded, the first and second on-off valves are provided. And an opening / closing valve control means for controlling the opening and closing of the first and second opening / closing valves so that the sum of the opening degrees of the two is a predetermined opening degree capable of supplying a necessary intake air amount to each cylinder. It shall be provided. Here, the partial load means a low load and a medium load smaller than a high load.

  With this configuration, in the partial load region of the engine, the first and second on-off valves provided in the two intake passages having different intake passage lengths are opened, and the sum of the opening degrees of both is required for each cylinder. Since the opening / closing control is performed so that the predetermined amount of intake air can be supplied, it is possible to reduce the variation in intake air for each cylinder as compared with the case where intake is performed only from one intake passage. That is, even if the two intake passages have a so-called side entry structure that communicates with both ends of the surge tank, variations in intake air can be suppressed by adopting the above-described configuration.

  In the above-described configuration, the on-off valve control means is configured to make the first and second on-off valves have the same opening degree in the low load range in the low rotation range and middle rotation range of the engine. (Second invention).

  As described above, when the engine is in a low and middle load range, for example, when idling, the combustion performance is greatly affected by the variation in intake air, so the first and second on-off valves are set to the same opening degree. As a result, the variation in intake air can be more reliably suppressed.

  Further, the on-off valve control means increases the opening degree of the first on-off valve and decreases the opening degree of the second on-off valve in response to an increase in engine load in the middle load region in the low engine speed range. In the high load region, only the first on-off valve is fully opened. On the other hand, in the middle rotation region of the engine, the opening degree of the second on-off valve is increased in response to an increase in engine load in the medium load region. It is preferable that the opening degree of the first on-off valve is reduced and only the second on-off valve is fully opened in the high load region (third invention).

  As a result, in the high load region in the low / medium speed region of the engine, only the first on-off valve or the second on-off valve is fully opened, and intake is performed from either the long intake passage or the short intake passage. Thus, the charging efficiency of intake air can be increased by the resonance effect in each passage. In these engine rotation ranges, in the middle load range, as the engine load increases from the low load range where the opening amounts of the first and second on-off valves are equal as described above, the opening degree of one on-off valve increases. Therefore, by opening / closing the first and second on / off valves so that the opening of the other on / off valve becomes smaller, the opening / closing of the on / off valve changes abruptly between the low load region and the high load region. Can be prevented. Therefore, even when the engine load changes, it is possible to prevent variations in intake air among cylinders as much as possible.

  Further, it is preferable that the on-off valve control means is configured so that the first and second on-off valves have the same opening degree in the high engine speed range (fourth invention). Thus, by making the opening degree of the first and second on-off valves equal, it is possible to suppress variations in intake air between the cylinders in the high engine speed range. Here, in the high engine speed range where the intake air charging efficiency is increased by utilizing the inertia effect of the intake air, the volume of the space upstream of the cylinders only needs to be increased. Even if the opening degree is made equal, the charging efficiency of intake air is not deteriorated. Therefore, with the above-described configuration, it is possible to suppress variations in intake air without deteriorating intake charging efficiency in a high engine speed range.

  Further, it is preferable that the on-off valve control means is configured to fully open the first and second on-off valves for a predetermined period when the engine is accelerated (fifth invention). During engine acceleration, the two on-off valves are temporarily fully opened, and as much intake as possible is performed from the two intake passages, so that the torque response during acceleration can be improved. Here, the predetermined period means, for example, a period during which the engine is accelerated or a part of the period.

  According to the present invention, the long intake passage and the short intake passage, each having one end communicating with the surge tank and the other end communicating with the air cleaner, are provided with the on-off valves, respectively, and the first and second on-off valves are provided in the partial load region of the engine. By controlling the opening and closing of the on-off valve so that the sum of the opening degrees of the two reaches a predetermined opening degree, it is possible to prevent variations in intake air, and the combustion performance deteriorates when the engine is partially loaded. Can be prevented.

  Further, according to the second invention, the opening degree of the first and second on-off valves is made equal in the low and middle engine speed range and the low load range of the engine, which greatly affects the combustion performance due to variations in intake air. Therefore, variations in intake air can be more reliably prevented, and deterioration of combustion performance can be more reliably prevented.

  According to the third aspect of the invention, in the low engine speed range, the first on-off valve is opened and the second on-off valve is closed in response to an increase in engine load in the medium load region, and the first on-off valve is closed in the high load region. Only the on-off valve is opened, and in the middle rotation range of the engine, the second on-off valve is opened and the first on-off valve is closed in response to an increase in engine load in the middle load region, and the second on-off valve is opened in the high load region. Only the open state can be prevented, so that the opening of the on-off valve can be prevented from changing suddenly between the low load region and the high load region of the engine, and variations in intake and response delays can be prevented. It can be prevented as much as possible.

  Further, according to the fourth aspect of the invention, in the high engine speed range, the opening degree of the first and second on-off valves is made equal so that the intake air variation is prevented without deteriorating the intake charging efficiency. be able to.

  According to the fifth aspect of the present invention, when the engine is accelerated, the first and second on-off valves are fully opened for a predetermined period, so that the torque response during acceleration can be improved.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. It should be noted that the following description of the preferred embodiment is merely illustrative in nature and is not intended to limit the present invention, its application, or its use.

-Overall configuration-
FIG. 1 shows a schematic configuration of an intake device 1 of an internal combustion engine (engine) according to the present embodiment. In FIG. 1, reference numeral 2 denotes a plurality of cylinders 3, 4, 5 communicating with the intake device 1. , 6 (4 cylinders in this embodiment) is formed. Reference numerals 3a, 4a, 5a, and 6a indicate intake ports, and reference numerals 3b, 4b, 5b, and 6b indicate exhaust ports, respectively.

  The intake device 1 includes an air cleaner 11 for purifying air taken in from a duct (not shown), a surge tank 12 disposed between the air cleaner 11 and the engine 2, the surge tank 12 and the air cleaner 11, Are provided with intake pipes 13 and 14 (long intake passage and short intake passage), and branch pipe portions 15, 16, 17 and 18 for connecting the surge tank 12 and the engine 2. In the intake device 1, the negative pressure pressure wave generated when the intake of each cylinder 3, 4, 5, 6 of the engine 2 is started is inverted at the opening end on the intake upstream side to become a sine wave, and the intake port 3 a , 4a, 5a, and 6a, the so-called intake inertia effect or resonance effect is used to push the intake air into the cylinder, thereby improving the intake charging efficiency. Here, the inertial effect is that the pressure wave is reversed in the surge tank 12 and returned to the intake ports 3a, 4a, 5a, 6a. The pressure wave is reversed in the air cleaner 11 and the intake ports 3a, 4a, 5a, 6a. Returning to the side is called a resonance effect.

  Specifically, each of the branch pipe portions 15, 16, 17, 18 communicates with the intake ports 2 b, 2 b,... Of the engine 2 on one end side, and is connected to the surge tank 12 on the other end side. The internal space of the surge tank 12 is communicated. The surge tank 12 is a cylindrical member formed so as to extend along the arrangement direction of the branch pipe portions 15, 16, 17, 18, and the branch pipe portions 15, 16, 17, 18 are formed on the side surfaces thereof. However, the intake pipes 13 and 14 are connected to both ends, respectively. That is, in this embodiment, the intake device 1 has a so-called side entry structure in which the intake pipes 13 and 14 communicate with the surge tank 12 from both ends. Further, the surge tank 12 is formed in a small capacity so that a pressure wave generated with the start of intake air passes through and is reversed by the air cleaner 11 on the upstream side of the intake air in the low and middle rotation range of the engine 2.

  The intake pipes 13 and 14 are provided with switching valves 21 and 22 (first and second on-off valves) that also function as throttle valves, respectively. The switching valves 21 and 22 are control valves configured to perform opening / closing control based on an output signal from a controller 30 (open / close valve control means) such as an ECU. As will be described in detail later, the controller 30 is configured to change the opening degree of the switching valves 21 and 22 in accordance with the rotational speed of the engine and the required torque.

  As shown in FIG. 1, the intake pipes 13 and 14 have a longer intake passage length in the first intake pipe 13 (long intake passage) than in the second intake pipe 14 (short intake passage). It is provided as follows. That is, the air cleaner 11 is positioned on the second intake pipe 14 side with respect to the surge tank 12, and the first intake pipe 13 is partly in the cylinder axial direction of the cylindrical surge tank 12 ( It extends in the extending direction) and is connected to the air cleaner 11. Here, the first intake pipe 13 is set to an intake passage length that allows a resonance effect to be obtained in the low rotation range of the engine 2. On the other hand, the second intake pipe 14 is set to an intake passage length such that the resonance effect can be obtained in the middle rotation range of the engine 2.

  By changing the length of the intake pipes 13 and 14 in this way, when the intake air is pushed into the cylinders 3, 4, 5 and 6 using the resonance effect of the intake air, the resonance effect is generated in different engine rotation ranges. Thus, torque can be improved in a wide engine rotation range.

  Further, as shown in FIG. 1, the intake pipes 13 and 14 have an annular shape as a whole, with one end connected to the end of the surge tank 12 and the other end connected to the air cleaner 11. Thus, by connecting the two intake pipes 13 and 14 to one air cleaner 11 and omitting one air cleaner 11, the intake device 1 can be miniaturized and the cost can be reduced. In addition, by making the intake pipes 13 and 14 annular as described above, the entire intake device 1 becomes compact, and the intake device 1 can be compactly arranged in a narrow engine room.

  Further, the intake pipes 13 and 14 are formed such that the first intake pipe 13 having a longer intake passage length has a smaller passage cross-sectional area than the second intake pipe 14. Thus, by reducing the passage cross-sectional area, the resonance effect of intake air can be more reliably obtained in the low rotation range. Therefore, the rotational range in which the resonance effect can be obtained can be changed also by such a difference in passage cross-sectional area, and the torque can be improved more reliably in a wide rotational range. The switching valves 21 and 22 provided in the intake pipes 13 and 14 have a first switching valve 21 rather than the second switching valve 22 in accordance with the size of the passage sectional area of the intake pipes 13 and 14 as described above. The bore diameter may be formed to be smaller. In such a configuration, as will be described in detail later, intake air leakage when the first switching valve 21 is in the closed state can be suppressed, and the intake air resonance effect can be obtained more reliably.

-Variable intake-
Next, the operation of variable intake in the intake device 1 having the above-described configuration will be described below with reference to FIGS. Note that the variable intake operation of the intake device 1 is performed by the opening / closing control of the switching valves 21 and 22 by the controller 30, and the opening / closing control varies depending on the load and the rotational speed of the engine 2. In the case of a high load, a description will be given for each engine speed range in each load state, divided into partial loads. Here, each engine rotation range is divided into low, middle and high rotation ranges as shown in FIG.

(High load condition)
When the engine 2 has a high load, in order to obtain as much torque as possible, the intake charging efficiency is increased in each engine rotation range using the inertia effect and the resonance effect of the intake air.

  Specifically, when the rotation speed of the engine 2 is in a low rotation range, the first switching valve 21 of the first intake pipe 13 having a long intake passage length is opened as shown in FIG. On the other hand, the second switching valve 22 of the second intake pipe 14 having a short intake passage length is closed. As a result, intake is performed only by the first intake pipe 13, and the resonance effect of the intake can be obtained in the low rotation region I of the engine 2 as indicated by a solid line (a) in FIG. 4. Therefore, the intake charging efficiency can be increased in the low rotation region I of the engine 2, and the torque can be improved in the region I.

  When the rotation speed of the engine 2 is in the middle rotation range, as shown in FIG. 2, the second switching valve 22 of the second intake pipe 14 having a short intake passage length is opened, while the intake passage length is increased. The first switching valve 21 of the long first intake pipe 13 is closed. As a result, intake is performed only by the second intake pipe 14, and the resonance effect of the intake can be obtained in the middle rotation region II of the engine 2 as indicated by a broken line (b) in FIG. Accordingly, the charging efficiency of intake air can be increased in the middle rotation region II of the engine 2, and the torque can be improved in the region II.

  As described above, when the rotational speed of the engine 2 is in the low-medium rotational range, one of the first and second switching valves 21 and 22 is closed. The first and second switching valves 21 and 22 are not completely closed even in the closed state, and a minute gap is left, and intake air leaks from the gap. For this reason, the pressure wave that is reversed by the air cleaner 11 is attenuated by the leakage of the intake air, and the resonance effect of the obtained intake air is reduced. Therefore, as shown by a broken line (thin line) in FIG. 5, the torque obtained in the low and middle rotation range is smaller than the ideal state. Since the intake air leakage increases as the bore diameter of the switching valve increases, as described above, the bore diameter of the first switching valve 21 provided in the first intake pipe 13 having a small passage cross-sectional area is large. By forming the first switching valve 21 so as to be smaller than the second switching valve 22 provided in the second intake pipe 14 having a large passage cross-sectional area, the first switching valve 21 has the same bore diameter. Intake leakage is reduced. Thereby, in the state where the first switching valve 21 is closed and the second switching valve 22 is opened, that is, in the middle rotation range of the engine 2, a sufficient intake air resonance effect can be obtained, and the torque can be improved more reliably. Can be achieved.

  When the rotation speed of the engine 2 is in the high rotation range, as shown in FIG. 3, both the first and second switching valves 21 and 22 are opened. As a result, intake is performed from both the first and second intake pipes 13 and 14, and intake resistance can be reduced and the intake upstream volume of each intake port 3a, 4a, 5a, 6a is increased. Therefore, the inertia effect of the intake air is obtained by the space upstream of the intake air. Therefore, as shown by the one-dot chain line (c) in FIG. 4, in the region (right end in the drawing) where the rotational speed is the highest in the high rotation region III of the engine 2, the configuration shown in FIGS. The torque can be increased compared to the solid line and the broken line).

  As described above, by performing the variable intake as described above, the torque can be improved in a wide rotation range of the engine 2.

  Further, in the side entry structure in which the intake pipes 13 and 14 are connected to both ends of the surge tank 12 as in the present embodiment, the intake passage lengths of the cylinders 3, 4, 5 and 6 in the surge tank 12 are as follows. However, as described above, when intake is performed from the first and second intake pipes 13 and 14 in the high speed range of the engine 2, the intake air amount varies between cylinders. It is possible to reduce the variation in intake air between cylinders in the high engine speed range.

  By the way, in general, as the capacity of the surge tank 12 increases, a greater inertial effect is obtained in the high rotation range of the engine 2, but conversely, a resonance effect is less likely to be obtained in the low and medium rotation range, and the throttle valve downstream. There is a problem that the volume of the air intake becomes larger and the response of intake air deteriorates.

  On the other hand, as in the present embodiment, the capacity of the surge tank 12 is reduced, and the first and second switching valves 21 and 22 are opened in the high speed range of the engine 2 to intake ports 3a, 4a and 5a. By increasing the capacity of the intake upstream space of 6a, it is possible to reliably obtain the resonance effect in the low and middle rotation range while preventing the deterioration of the response of the intake, and sufficient inertial effect in the high rotation range Obtainable.

  Next, a specific example of opening / closing control of the first and second switching valves 21 and 22 by the controller 30 is shown in FIG. FIG. 6 shows an example of changes in the opening degree of the first and second switching valves 21 and 22 when the rotational speed of the engine 2 is gradually increased with time.

  As in the example of FIG. 6, the controller 30 opens the first switching valve 21 when the rotation speed of the engine 2 is in the low rotation range I, and the first switch valve 21 when the rotation speed is in the middle rotation range II. The switching valve 21 is closed and the second switching valve 22 is opened. When the rotation speed of the engine 2 is in the high rotation range III, the first switching valve 21 is opened again. Thereby, as above-mentioned, a torque can be improved in the wide rotation area of the engine 2. FIG.

  Note that, at the time of transition, which is the moment of acceleration of the engine 2, as shown by the solid line in FIG. 7 (the left end in the figure), both of the switching valves 21 and 22 are momentarily opened. In this state, the inside of the surge tank 12 may be brought close to atmospheric pressure. By doing so, the torque can be increased with good responsiveness during acceleration. Then, after the switching valves 21 and 22 are opened only at the moment of acceleration as described above, one switching valve (second switching valve 22 in FIG. 7) is closed, and as described above, the engine 2 The switching valves 21 and 22 are controlled to open and close in accordance with the rotation range. The moment corresponds to a predetermined period of the present invention, and corresponds to, for example, part or all of the acceleration period of the engine 2.

  Here, FIG. 7 shows an example of the valve opening when the engine 2 is accelerated and the second switching valve 22 is opened for a moment when only the first switching valve 21 is opened. ing. In FIG. 7, a two-dot chain line indicates the opening degree of the second switching valve 22 when the engine 2 is not in an acceleration state. In the present embodiment, the case where the engine 2 is accelerated when only the first switching valve 21 is open has been described. However, the engine 2 is accelerated when only the second switching valve 22 is open. In such a case, the first switching valve 21 may be opened for a moment.

(Partial load)
Next, the variable intake operation of the intake device 1 when the engine 2 is partially loaded will be described with reference to FIGS.

  When the engine 2 has a partial load, stable combustion is required rather than torque improvement. That is, as described above, in the configuration as in the present embodiment in which the intake pipes 13 and 14 are connected to both ends of the surge tank 12, the variation in intake air between the cylinders is large, and the combustion performance is likely to deteriorate. In the case of a load other than a high load that requires improvement, intake is performed from both of the intake pipes 13 and 14 to eliminate variations in intake.

  Therefore, as shown in FIG. 8, the opening degree of the switching valves 21 and 22 is controlled according to the engine speed and load. That is, in the high speed range of the engine 2, both the switching valves 21 and 22 are opened regardless of the magnitude of the load, while in the low / medium speed range of the engine 2, only one of the switching valves is used at the time of high load as described above. In the case of other partial loads, intake is performed by opening both the switching valves 21 and 22. As a result, it is possible to suppress variations in intake air except in a low-medium rotation and high-load region where it is necessary to increase the charging efficiency of the intake air using the resonance effect of the intake air.

  FIG. 9 shows the change-over valve 21 with respect to the load change in the low rotation range (AA) of the engine 2 in FIG. 8 (load change when the load when the change-over valve 21 is fully opened is 100%). FIG. 10 shows the opening degrees of the switching valves 21 and 22 with respect to the engine speed in the high load region (BB) in FIG.

  As shown in FIG. 9, the switching valves 21 and 22 are controlled to be opened and closed so that the sum of the opening degrees of the two becomes an opening degree that can supply the intake air amount required by the cylinder. Specifically, when the engine 2 is in a low rotation range and has a low load, the opening degree of the switching valves 21 and 22 is the same, and intake is performed from the intake pipes 13 and 14 almost equally. This is because, when idling, there is a great influence on the deterioration of combustion performance due to variations in intake air. Therefore, the switching valves 21 and 22 are set to the same opening degree, and intake is performed from both the intake pipes 13 and 14, thereby ensuring more certainty. This is because it is necessary to suppress variation. When the engine 2 has a medium load, when the engine load gradually increases, the opening degree of the first switching valve 21 increases in accordance with the engine load, while the opening degree of the second switching valve 22 increases accordingly. When the engine 2 is small and the load is high, the first switching valve 21 is fully opened and the second switching valve 22 is closed.

  Although not particularly illustrated, in the middle rotation range of the engine 2, contrary to the above, the opening / closing control is performed so that the opening degree of the second switching valve 22 increases in accordance with the engine load. That is, in the low load region of the engine 2, the opening degree of the switching valves 21 and 22 is the same as described above. However, in the middle load region, the second switching valve 22 increases in accordance with the engine load. The opening degree of the first switching valve 21 gradually decreases, and in the high load region, the second switching valve 22 is fully opened and the first switching valve 22 is closed. Further, in the middle rotation region of the engine 2, as shown in FIG. 8, the region where both the first and second cut petals 21 and 22 are opened as the engine rotation speed increases is a low load range. It has become. This is because as the rotational speed of the engine 2 increases, the influence on the combustion performance due to variations in intake air becomes smaller.

  As described above, in the middle load region in the low and middle rotation region of the engine, the switching valves 21 and 22 continuously connect the open / close state of the valve in the low load state and the open / close state of the valve in the high load state. Furthermore, since the switching valves 21 and 22 are controlled to open and close according to the engine load, it is possible to prevent the opening degree of the switching valves 21 and 22 from changing suddenly. As a result, it is possible to prevent deterioration of responsiveness when the switching valves 21 and 22 are opened and closed and increase in intake fluctuations.

  Also, as shown in FIG. 10, when the engine 2 is in a high load state and the engine speed increases, as described above, the first switching valve 21 is opened in the low rotation range and the above in the middle rotation range. The second switching valve 22 is opened, and the first and second switching valves 21 and 22 are opened in the high rotation range. When the switching valve is switched, since the switching valve gradually opens or closes, both the first and second switching valves 21 and 22 are open. An area is provided.

  In FIG. 8, in the high speed range of the engine 2, the opening degree of the switching valves 21 and 22 is the same, and both switching valves 21 and 22 are fully opened.

  As described above, according to this embodiment, one end side of the first and second intake pipes 13 and 14 having different intake passage lengths is connected to the surge tank 12, and the other end side is connected to the air cleaner 11, respectively. 13 and 14 are provided with switching valves 21 and 22, respectively, and in the partial load region of the engine 2, both the switching valves 21 and 22 are opened, and the sum of the opening degrees of both the valves provides the amount of intake required for each cylinder. A so-called side entry structure in which intake pipes 13 and 14 are connected to both ends of the surge tank 12 as in this embodiment in order to perform opening / closing control of the switching valves 21 and 22 so as to have a predetermined opening that can be supplied. Even so, the variation in intake air among the cylinders can be reduced. Therefore, even in the partial load state where the influence of the deterioration of the combustion performance due to the variation of the intake air is large, the above-described configuration can suppress the intake air variation among the cylinders and prevent the deterioration of the combustion performance. it can.

  Further, in the low load range in the low and medium rotation range of the engine 2, the first and second switching valves 21 and 22 have the same opening degree, so that variations in intake air between the cylinders can be more reliably prevented. . Therefore, even when the influence of variations in intake air is large, such as during idling, deterioration of combustion performance can be more reliably prevented.

  Further, in the middle load region in the low / medium rotation region of the engine 2, the open / close state of the switching valves 21, 22 in the low load region and the open / close state of the switching valves 21, 22 in the high load region are continuously connected. While the opening of one of the switching valves 21 and 22 gradually increases according to the engine load, the opening of the other switching valve 21 and 22 gradually decreases. It is possible to prevent the opening degree of the switching valves 21 and 22 from changing suddenly, and to prevent deterioration of responsiveness when the switching valves 21 and 22 are opened and closed, and increase in variation in intake air.

  Further, since the first and second switching valves 21 and 22 have the same opening degree in the high rotation range of the engine 2, it is possible to reduce intake air variations without deteriorating intake charge efficiency. That is, since the charging efficiency is improved by the inertia effect of the intake air in the high speed region of the engine 2, even if both the first and second switching valves 21 and 22 are opened in the high load region, the intake charging efficiency is deteriorated. I will not let you.

  Furthermore, when the engine 2 is accelerated, the first and second switching valves are fully opened for a predetermined period, so that the torque responsiveness during acceleration can be improved, and after the predetermined period has elapsed, the original opening / closing is performed. Since the process returns to the control, as described above, it is possible to improve the torque in each rotation region and load region, and to prevent deterioration of the combustion performance.

<< Other Embodiments >>
The configuration of the present invention is not limited to the above embodiment, but includes various other configurations. That is, in each of the above embodiments, the intake pipes 13 and 14 are connected to the single air cleaner 11 and formed in an annular shape. However, the present invention is not limited to this, and the intake pipes 13 and 14 are provided with air cleaners, respectively. 13 and 14 may be arranged linearly with respect to the surge tank 12.

  Moreover, in the said embodiment, although the engine 2 is a 4 cylinder structure, it is not restricted to this, A 6 cylinder or more may be sufficient.

  Moreover, in the said embodiment, while the opening degree of the 1st switching valve 21 is enlarged and the opening degree of the 2nd switching valve 22 is made small, as the engine load becomes large in the middle load low rotation area of the engine 2, Not limited to this, if the opening degree of the first and second switching valves 21 and 22 is equal in the low load region and only the first switching valve 21 is open in the high load region, the first The opening degree of the second switching valves 21 and 22 may be changed in any way.

  Furthermore, in the above-described embodiment, two intake paths are provided. However, the present invention is not limited to this, and three or more intake paths may be provided. In this case, the length of each intake passage is preferably set so that an intake resonance effect can be obtained in each engine rotation range. Thereby, the torque can be improved more precisely in a wide rotation range of the engine 2.

  As described above, the engine intake device according to the present invention can prevent variations in intake air between the cylinders by performing intake from the two intake pipes in the partial load region of the engine. This is particularly useful for an engine in which intake passages having different intake passage lengths communicate with both ends of the tank.

FIG. 3 is a schematic diagram showing valve control when the engine is in a high load low rotation region in the engine intake device according to the first embodiment. FIG. 2 is a view corresponding to FIG. 1 when the engine is in a high load mid-rotation region. FIG. 2 is a view corresponding to FIG. 1 when the engine is in a high-load high-rotation region. It is a figure which shows the relationship between an engine speed and a torque. FIG. 5 is a view corresponding to FIG. 4 when leakage from the switching valve in the closed state is taken into consideration. It is a figure which shows an example of the change of the opening degree of the switching valve when an engine speed is gradually enlarged with time. It is a figure which shows an example of the change of the opening degree of a switching valve at the time of accelerating when only one switching valve is an open state. It is a figure which shows the outline of the opening / closing control of the switching valve according to an engine speed and torque. It is a figure which shows the relationship between a load and the opening degree of a switching valve when an engine is a low rotational speed in FIG. 8 (AA). It is a figure which shows the relationship between an engine speed and the opening degree of a switching valve when an engine is high load in FIG. 8 (BB).

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Engine intake device 2 Engine 3, 4, 5, 6 Cylinder 3a, 4a, 5a, 6a Intake port 11 Air cleaner 12 Surge tank 13 1st intake pipe (long intake passage)
14 Second intake pipe (short intake passage)
15, 16, 17, 18 Branch pipe portion 21 First switching valve (first on-off valve)
22 Second switching valve (second on-off valve)
30 controller (open / close valve control means)

Claims (5)

A surge tank to which branch pipe portions of a plurality of cylinders are connected, and a long intake passage and a short intake passage having different intake passage lengths communicating with the surge tank on one end side and communicating with an air cleaner on the other end side. An engine intake device that performs intake by switching an intake path to at least one of the intake paths according to an engine rotation range,
The surge tank is provided so as to extend in the direction in which the branch pipe portions are arranged, and the long intake passage is communicated with one end side of the surge tank, while the short intake passage is provided with the other end side. Communicated,
The long intake passage is provided with a first on-off valve, and the short intake passage is provided with a second on-off valve,
When the engine is partially loaded, the first and second on-off valves are opened so that the sum of the opening amounts of the first and second opening / closing valves becomes a predetermined opening amount that can supply the necessary intake air amount to each cylinder. And an on-off valve control means for controlling on-off of the second on-off valve. In claim 1,
The engine is characterized in that the on-off valve control means is configured to make the first and second on-off valves have the same opening degree in a low load region in a low rotation region and a middle rotation region of the engine. Inhalation device. In claim 2,
The on-off valve control means includes
In the low engine speed range, the opening degree of the first on-off valve is increased and the opening degree of the second on-off valve is reduced in response to an increase in the engine load in the medium load range. While only the on-off valve is fully open,
In the middle rotation region of the engine, the opening degree of the second on-off valve is increased and the opening degree of the first on-off valve is reduced in response to an increase in engine load in the medium load region. An intake system for an engine, wherein only the on-off valve is configured to be fully open. In any one of Claim 1 to 3,
The engine intake device according to claim 1, wherein the on-off valve control means is configured to make the first and second on-off valves have the same opening degree in a high engine speed range. In any one of Claims 1-4,
The engine intake device according to claim 1, wherein the on-off valve control means is configured to fully open the first and second on-off valves for a predetermined period when the engine is accelerated.

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