JPH0361613A - Intake device for engine - Google Patents

Abstract

PURPOSE:To speedily scavenge the residual gas from the inside of a combustion chamber by setting the characteristic frequency in an intake system so that each positive ressure acts into the vicinity of an intake port by the pressure vibration in the intake system during the overlap period at the low revolution. CONSTITUTION:An intake system consists of independent intake passages 21-26, collecting passages 27 and 28 and a passage 29, and main intake 30 and 31. Control is performed so that the intake timing in the low revolution speed of an engine is set to make earlier than that in the high revolution speed. In this case, the main intake passages 30 and 31 are formd in spiral shape, and connected by the communication passages 38-41 in the prescribed intervals is turn from the upstream side, and the communication passages 38-41 are opened and closed by the opening/closing operation of the opening/closing valves 42-45. Therefore, the positive pressure acts in the vicinity of the intake ports 9-14 by the pressure vibration in the intake system, during the overlap period in the low revolution operation. Therefore, the residual gas formed in the preceding combustion is pushed out through the exhaust ports 15-20 by the positive pressure, and scavenging can be carried out effectively.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to an engine intake system that improves intake air filling efficiency at low engine speeds by utilizing pressure vibrations in the intake system.

[Conventional technology]

2. Description of the Related Art Conventionally, in an engine intake system, a method has been known in which the opening and closing timing of an intake valve is adjusted according to the rotational speed of the engine in order to obtain high output. For example, Japanese Unexamined Patent Publication No. 61-65036 discloses a configuration in which the opening/closing timing of the intake valve is controlled to be earlier at low rotations than at high rotations. With this configuration, even at low rotation speeds, it is possible to effectively utilize the inertia effect to increase the intake air filling amount, and high output is achieved over the entire rotation range.

[Problem to be solved by the invention]

However, with the above conventional technology, by advancing the opening/closing timing of the intake valve at low engine speeds, the overlap period during which both the intake valve and the exhaust valve are open becomes longer. The combustion gas generated by the combustion of the engine remains without being completely exhausted, and this residual gas warms the fresh air introduced from the intake valve, making it more likely to cause knocking. Further, since the increase in the filling amount is restricted by the residual gas, it has been difficult to further improve the filling efficiency.

[Means to solve the problem]

In order to solve the above-mentioned problems, an engine intake device according to the present invention includes an intake port for introducing fresh air into a combustion chamber and an exhaust port for leading out combustion gas from the combustion chamber, and the intake device has a non-continuous intake order. An intake system is formed by an independent intake passage connected to the cylinder via the intake port, a collective passage that brings together the independent supply passages, and an extension passage that leads to the collective passage. In an engine intake system, the pressure in the intake system is controlled to be faster than that at high engine speeds, and during the overlap period when the intake port and exhaust port are both open at low engine speeds, It is characterized in that the natural frequency of the intake system is set so that positive pressure acts near the intake port due to vibration.

[For production]

According to the above configuration, the overlap period becomes longer at low engine speeds because the intake timing is earlier than at high engine speeds. However, during this overlap period, the natural frequency of the intake system is set so that positive pressure acts near the intake port due to pressure oscillations in the intake system, so the residual gas generated from the previous combustion is Positive pressure forces the air out through the exhaust port, allowing for more effective scavenging. Therefore, it is possible to improve charging efficiency and achieve high output in a low rotation range. In addition, the improved scavenging effect prevents the fresh air introduced into the combustion chamber from becoming too hot.
It is possible to suppress the occurrence of knocking that occurs at low rotation speeds.

[Embodiment 1] An embodiment in which the present invention is applied to a V-type six-cylinder engine will be described below with reference to FIGS. 1 to 8.

As shown in FIG. 1, bank 1 of a V-type engine includes cylinders 3 to 5, while bank 2 includes cylinders 6 to 8. Intake is performed in the order of cylinder 3 → cylinder 6 → cylinder 4 → cylinder 7 → cylinder 5 → cylinder 8. For the cylinders 3 to 8,
Intake ports 9-14 are provided, and exhaust ports 15-20 are provided. These intake ports 9-1
4 and exhaust ports 15 to 20 are opened and closed at predetermined timings by intake valves and exhaust valves (not shown), respectively. The intake timing is determined by the timing of opening and closing of the intake valve, and is set to be earlier when the engine is rotating at a low speed of 3000 rpm or less than when the engine is rotating at a high speed higher than 300 rpm. The opening/closing timing of the intake valves is switched by a known method, such as changing the phase angle of the camshaft or opening and closing the intake and exhaust valves using different rocker arms at low and high rotations.

Each of the intake ports 9 to 14 has an independent intake passage 2.
1 to 26 are connected, and fresh air flowing through the independent intake passages 21 to 26 is introduced into a combustion chamber (not shown) via intake ports 9 to 14. On the other hand, independent exhaust passages (not shown) are connected to the exhaust ports 15 to 20, respectively, so that the combustion gas in the combustion chamber is
15 to 20, and is further discharged to the outside via an exhaust system including the independent exhaust passage.

The independent intake passages 21 to 26 are connected to the collective passage 27, and the independent intake passages 21 to 23 are connected to the collective passage 27.
is connected to the collective passage 28. Gathering aisles 27 and 28
The downstream sides communicate with each other through a passage 29, while the upstream sides communicate with main intake passages 30 and 31, respectively. At the boundary between the collective passages 27 and 28 and the passage 29, there are on-off valves 32 and 32, which are driven to open and close by an actuator 46, which will be described later.
33 are provided. The main intake passages 30 and 31 come together on the upstream side and communicate with a common intake passage 34. This common intake passage 34 is provided with a throttle valve 35 near the gathering part of the main intake passages 30 and 31, and a throttle valve 35
An air flow meter 36 is provided further upstream from the air flow meter 36, and the most upstream portion thereof is connected to an air cleaner 37.

In addition, the above-mentioned independent intake passages 21 to 26, collective passage 27,
28, passage 29, and main intake passages 30 and 31 constitute an intake system in the intake device.

Furthermore, the passage 29 and the main intake passages 30 and 31 correspond to extended passages in the intake system.

The above intake system includes intake ports 9 to 14 and exhaust port 1.
During the period when ports 5 to 20 are both open, that is, during the overlap period, pressure vibrations in the intake system cause intake ports 9 to 14 to open.
Its natural frequency is set so that positive pressure acts nearby. Therefore, in this embodiment, the main intake passages 30, 3
1 to communicate with each other through communicating portions provided at a plurality of different positions, the communicating positions and the intake ports 9 to
14 to obtain the required natural frequency. In this case, since the opening and closing periods of the intake ports 9 to 14 differ depending on the engine rotation speed, the communication position of the main intake passages 30 and 31 is moved closer to the intake ports 9 to 14 as the engine rotation speed increases. It is made variable.

In addition, when increasing torque at low rotation speeds by the resonance effect, the lower the rotation speed, the higher the torque tends to be obtained at the resonance tuned rotation speed, but on the other hand, the torque changes sharply in the low rotation range, The range of rotational speeds in which torque greater than a predetermined value can be obtained becomes narrower. For this reason, the main intake passage 30
- If the number of communication parts 31 is small, the drop in torque becomes large when switching the communication of each communication part, and large fluctuations in noise occur. Therefore, ideally, when installing an intake system equipped with the above-mentioned intake system on an actual vehicle, in order to obtain stable torque characteristics in the low rotation range, it is necessary to
It is desirable to provide a large number of communication parts between 0. However, in reality, it is necessary to reduce the number of communication parts as much as possible in consideration of cost, control required for communication switching, and the like. For this reason, in this embodiment, at least two communication portions are provided,
The switching of these communications is performed at wider intervals as the engine rotational speed increases, and is performed within a range of ±20% from the resonance tuning rotational speed.

Next, the configuration of an intake system that satisfies the above conditions will be described.

As shown in FIGS. 2(a) and 2(b), the main intake passages 30 and 31 in the intake system have a spiral shape, and communicating passages 38 are provided as communicating portions at predetermined intervals from the upstream side. .about.41. As shown in FIG. 1, the communication passages 38 to 41 each have an on-off valve 42.
- 45 are provided, and the communication passages 38 - 41 are opened and closed by the opening and closing operations of these on-off valves 42 - 45 .

The actuators 46 for driving the on-off valves 42 to 45 and the on-off valves 32 and 33 are configured so that the engine rotational speed detected by the rotational speed detection sensor 47 is different from some rotational speeds preset in the comparison section 48. The height is compared, and if the detected rotational speed is higher than a certain set rotational speed, one of the on-off valves 42 to 45 and on-off valves 32 and 33 corresponding to the set rotational speed is opened. In other words, when the on-off valves 32, 33, 42 to 45 are driven as described above and the rotational speed of the engine changes from low to high speed, the communication passage 38 → communication passage 39 → communication passage 40 → communication passage 41 → passage They open in sequence in the order of 29, and close in the reverse order when the engine speed changes from high to low.

In switching the opening/closing of the on-off valves 32, 33, 42-45, the rotational speed difference type N0 from the minimum resonance tuned rotational speed Nr until the on-off valve 42 opens, and the on-off valve 43-45 and the on-off valve after the on-off valve 42 opens, Assuming that the rotational speed differences when 32 and 33 open sequentially are N+, Nz, Ni, and N4, their magnitude relationships are set as follows.

No <Nl <N2 <N3 <N4 However, No is twice the rotational speed difference ΔN determined by engine characteristics and the like.

In the above configuration, the engine rotation speed is 300 Qrpm.
In the following low rotation range, the opening/closing timing of the intake valve and the exhaust valve is advanced, as shown by curve C in FIG. 6, than in the curved high rotation range, and the overlap period becomes longer. On the other hand, in the intake system, pressure oscillations occur, and the pressure waves are reflected by one of the communication passages 38 to 41 and the passage 29 that communicate with the intake ports 9 to 14 at a position closest to the intake ports 9 to 14, resulting in positive pressure. . For example, the pressure waves generated by the main intake passage 30 shown in FIG. 7(a) are
As shown in (c), it acts on intake ports 9 to 11 during the overlap period in cylinders 3 to 5. Although not shown, the pressure waves generated by the main intake passage 31 also act on the intake ports 12 to 14 during the overlap period in the same manner as described above. Normally, when the overlap period becomes long in the low rotation range, problems such as unstable combustion occur, but in this example, the combustion gas remaining without being exhausted during the overlap period is removed by the positive pressure. The scavenging effect can be improved by pushing out the air, and the above-mentioned inconveniences can be solved. Moreover, the amount of intake air can be increased by positive pressure, and the filling efficiency can be improved.

By the way, the intake ports 9 to 14 and the exhaust ports 15 to
Since the opening/closing time of 20 varies depending on the engine speed, positive pressure is applied to the intake ports 9 to 14 by varying the natural frequency of the intake system.

In this case, as shown in FIG. 8, when the rotational speed increases from the lowest resonance tuning rotational speed Nr, the torque decreases, but when the rotational speed reaches Nr+N, the communication path 38 opens and the torque increases again. Subsequently, when the engine rotational speed increases from the communication of the communication passage 38 by the rotational speed difference N, the communication passage 39 becomes open, and thereafter, as the engine rotational speed sequentially increases at intervals of the rotational speed difference NZ, Nz, Na. The communication passage 40, the communication passage 41, and the passage 29 communicate with each other. Moreover, the communication passages 38 to 41 and the passage 29 communicate within a range of each resonance tuning rotation speed within ±20%. Therefore, the communication path 38
41 and the passage 29 communicate with each other, it is possible to suppress a large drop in torque and fluctuations in noise.

The main intake passages 30 and 31 are shown in FIGS. 2(a) and (
The shape is not limited to that shown in b), and depending on the required length, for example, shapes as shown in FIGS. 3 to 5 can be considered. The main intake passages 30 and 31 shown in FIGS. 3(a) and (b) have a bent and overlapping shape, and are suitable for cases where they are formed with a slightly long length. FIGS. 4(a) and ( The main intake passages 30 and 31 shown in b) are -
It has a spiral shape that is long in the direction, and is suitable when it is formed quite long. The main intake passages 30 and 31 shown in FIGS. 5(a) and 5(b) are curved at two places and have a shape resembling an oval, and are suitable for being formed relatively short. However, these main intake passages 30 and 31 are also
Communication can be switched in the same way as shown in Figures (a) and (b).

[Embodiment 2] Next, another embodiment of the present invention will be described based on FIGS. 2 to 9. It should be noted that members having the same functions as those in the first embodiment are denoted by the same reference numerals, and their explanations will be omitted.

As shown in FIG. 9, the intake system in this embodiment has independent intake passages 21 to 2 between intake ports 9 to 14 provided in each cylinder 3 to 8 of the engine and main intake passages 30 and 31.
6 is provided in the same manner as in the first embodiment, but is different in that the downstream sides of the main intake passages 30 and 31 are not communicated with each other. In this case as well, in order to apply positive pressure to the intake ports 9 to 14 during the overlap period in the low rotation region, the main intake passages 30 and 31 are arranged as shown in FIGS. 2 to 5 depending on the required length. It is formed into the shape shown in . And the communication passage 38~ provided between the main intake passages 30 and 31.
Although not shown, the opening and closing of 41 is controlled in the same manner as the intake system shown in FIG.

In addition, in the present invention, since it is only necessary to be able to vary the natural frequency of the intake system according to the demand, as shown by the two-dot chain line in the figure, main intake passages 30 and 31 having the same shape as above are shown.
may be provided on the downstream side of the collection passages 27 and 28. Alternatively, the communication passages 38 to 41 in the main intake passages 30 and 31 may be distributed and provided on the upstream side and the downstream side. In this case, the main intake passages 30 and 31 provided on the downstream side of the collective passages 27 and 28 are either connected to each other at their ends or are closed, and each has an on-off valve 32.
・33 is provided. Note that between the main intake passages 30 and 31 provided on the downstream side of the collective passages 27 and 28, communication passages 38 to 41 are provided downstream from the on-off valves 32 and 33, but they are not shown in the figure for simplicity. I omitted it.

In such a configuration, as shown in FIG. 6, even if the opening/closing timing of the intake valve is advanced at low rotation speeds and the overlap period becomes longer, as shown in FIG. Positive pressure acts on the intake ports 9 to 11 of
Similarly, positive pressure acts on the intake ports 12-14. Therefore, as in the first embodiment, the scavenging effect can be improved, the occurrence of knocking in the low rotation range can be suppressed, and the charging efficiency can be improved. In addition, the timing of opening and closing of the on-off valves 32, 33, 42 to 45 is 8th.
Since the settings are as shown in the figure, it is possible to suppress large drops in torque and fluctuations in noise when the passage 29 and the communication passages 38 to 41 are opened and closed.

〔Effect of the invention〕

As described above, the engine intake device according to the present invention includes an intake port that introduces fresh air into a combustion chamber and an exhaust port that leads out combustion gas from the combustion chamber, and the intake device is provided with an intake port that introduces fresh air into a combustion chamber, and an exhaust port that leads out combustion gas from the combustion chamber. An intake system is formed by independent intake passages connected via ports, a collective passage that brings together the independent supply passages, and an extension passage leading to the collective passage. In an engine intake system that is controlled to speed up faster than when the engine is rotating, during the overlap period when the intake port and exhaust port are both open when the engine is running at low speed, the intake port is closed due to pressure vibrations in the intake system. The natural frequency of the intake system is set so that positive pressure acts nearby.

As a result, the natural frequency of the intake system is set so that positive pressure acts near the intake port due to pressure vibrations in the intake system during the overlap period, so when the engine is running at low speed during the long overlap period, By quickly scavenging residual gas generated from the previous combustion from within the combustion chamber, the scavenging effect can be further improved. Therefore, it is possible to increase the charging amount and achieve high output in the low rotation range, and the fresh air introduced into the combustion chamber does not become hot, suppressing the occurrence of knocking at low speeds. It has the effect of being able to

[Brief explanation of drawings]

FIG. 1 shows one embodiment of the present invention, and is a schematic diagram showing the configuration of an intake device. FIG. 9 shows another embodiment of the present invention, and is a schematic diagram showing the configuration of an intake device. 2 to 8 are common to both of the above embodiments. (a) of FIGS. 2 to 5 are views taken in the direction of arrow A in FIGS. 1 and 9, showing the shape of the main intake passage. (b) of FIGS. 2 to 5 are sectional views taken in the direction of arrow B in FIGS. 1 and 9, showing the shape of the main intake passage. FIG. 6 is a graph showing the relationship between the opening degrees of the intake valve and exhaust valve and the crank angle. FIG. 7 is an explanatory diagram showing how positive pressure waves act during the overlap period. FIG. 8 is a graph showing the relationship between engine speed and torque. 3 to 8 are cylinders, 9 to 14 are intake ports, 15 to 20 are exhaust ports, 21 to 26 are independent intake passages, 27 and 28 are collective passages, 29 is passage, 30 and 31 are main intake passages (extension passages) , 32, 33, 42 to 45 are on-off valves, and 38 to 4 1 are communication passages.

Claims (1)

[Claims] 1. An independent intake passage that is equipped with an intake port that introduces fresh air into the combustion chamber and an exhaust port that brings out combustion gas from the combustion chamber, and that is connected to cylinders whose intake order is not consecutive through the intake port, and an independent supply. An intake system is formed by a collection passage that brings passages together and an extension passage that leads to the collection passage, and the timing of intake during low engine speeds is controlled to be earlier than when the engine is at high rotations. In an engine intake system, during the overlap period when the intake port and exhaust port are both open at low engine speeds, the intake system is designed so that positive pressure acts near the intake port due to pressure vibrations in the intake system. An engine intake device characterized by having a set natural frequency.