JP2835088B2 - Engine intake system - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention uses the pressure oscillation of an intake system to
The present invention relates to an intake device for an engine in which intake efficiency at the time of low rotation is improved.

[Conventional technology]

2. Description of the Related Art Conventionally, in an intake device for an engine, a method of adjusting the opening / closing timing of an intake valve according to the rotation speed of the engine in order to obtain high output has been known. For example, Japanese Patent Application Laid-Open No. 61-65036 discloses a configuration in which the opening / closing timing of an intake valve is controlled so that the opening timing of a low rotation is earlier than that of a high rotation. In such a configuration, even at a low rotation speed, the amount of intake air can be increased by effectively utilizing the inertia effect, and high output is achieved over the entire rotation range.

[Problems to be solved by the invention]

However, in the above-described conventional technology, the overlap period in which both the intake valve and the exhaust valve are open is lengthened by accelerating the opening / closing timing of the intake valve during low rotation. Therefore, during the overlap period, the combustion gas generated by the previous combustion remains without being completely exhausted, and the residual gas warms fresh air introduced from the intake valve, so that knocking is likely to occur. Further, since an increase in the filling amount is limited by the residual gas, it has been difficult to further improve the filling efficiency.

[Means for solving the problem]

In order to solve the above problem, an intake device for an engine according to the present invention includes an intake port for introducing fresh air to a combustion chamber, and an exhaust port for extracting combustion gas from the combustion chamber. The intake system is formed by an independent intake passage connected to the discontinuous cylinders via the intake port, a collective passage that collects the independent intake passages, and an extended passage that communicates with the collective passage. The intake timing is controlled so that both the valve opening and valve closing timings are earlier than when the engine is running at a high speed, and the overlap period in which both the intake port and the exhaust port are open is lower than when the engine is at a high speed. In the intake device of the engine that is set to be larger at the time of rotation, the intake air is drawn during the overlap period over the entire rotation range of the low rotation range of the engine. To act positive pressure in the vicinity of the intake port by the pressure vibration of the natural frequency of the intake system is characterized in that it is set to be variable in accordance with the rotational speed of the engine.

Further, the intake device for an engine according to the invention of claim 2 is:
In order to solve the above-mentioned problem, the intake device for an engine according to claim 1, wherein the intake device for a six-cylinder engine includes two collective passages each of which is an independent intake passage for three cylinders. The natural frequency of the intake system is such that positive pressure acts on the vicinity of the intake port via the two collecting passages due to the pressure vibration of the intake system during the overlap period of each cylinder over the entire rotation range of the low engine speed range of the engine. Is variably set according to the engine speed.

(Operation)

According to the configuration of the first aspect, at the time of low rotation, the timing of intake is earlier than at the time of high rotation, so that the overlap period is longer. However, during this overlap period over the entire rotation range of the low rotation range of the engine, such that a positive pressure acts near the intake port due to the pressure oscillation of the intake system,
Since the natural frequency of the intake system is variably set according to the engine speed, the residual gas generated by the previous combustion is pushed out through the exhaust port by the above positive pressure, and scavenging is more effectively performed. It can be carried out. Therefore, it is possible to improve the filling efficiency and increase the output in the low rotation speed range. Further, by improving the scavenging effect, it is possible to suppress the occurrence of knocking at the time of low rotation without increasing the temperature of the fresh air introduced into the combustion chamber.

According to the configuration of claim 2, the configuration of claim 1 is applied to a six-cylinder engine, and by providing two collecting passages in which independent intake passages of three cylinders are gathered, during the overlap period of each cylinder. Positive pressure is applied to the vicinity of the intake port via two collecting passages due to the pressure vibration of the intake system. Therefore, the same operation as that of the first aspect is exhibited.

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 in the V-type engine
, Cylinders 6 to 8 are provided in the bank 2, and cylinders 6 to 8 are provided in the bank 2. These cylinders 3 to 8 correspond to cylinder 3 → cylinder 6 → cylinder 4 → cylinder 7 → cylinder 5. → Intake is performed in the order of the cylinders 8. The cylinders 3 to 8 are provided with intake ports 9 to 14, and are provided with exhaust ports 15 to 20. The intake ports 9 to 14 and the exhaust ports 15 to 20 are opened and closed at predetermined timing by intake and exhaust valves (not shown). The timing of intake is determined by the timing of opening and closing the intake valve. For example, the intake timing is set to be faster 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 3000 rpm.
The opening / closing timing of the intake valve is switched by a well-known method such as changing the phase angle of the camshaft or opening / closing the intake valve and the exhaust valve by different rocker arms at low rotation and high rotation.

The intake ports 9 to 14 have independent intake passages 21 respectively.
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 the intake ports 9 to 14. On the other hand, exhaust port 15-20
Are connected to respective independent exhaust passages (not shown), and the combustion gas in the combustion chamber is led out through exhaust ports 15 to 20 and further to the outside through an exhaust system including the independent exhaust passages. It is being discharged.

In the independent intake passages 21 to 26, the independent intake passages 21 to 23 are connected to the collective passage 27, and the independent intake passages 24 to 26 are connected to the collective passage 28.
It is connected to the. Collective passages 27 and 28 have passage 29 on the downstream side.
And the upstream side is the main intake passage
It leads to 30 and 31. On the boundary between the collecting passages 27 and 28 and the passage 29, on-off valves 32 and 33 that are opened and closed by being driven by an actuator 46 described later are provided. Main intake passage 30
31 are gathered on the upstream side and communicate with the common intake passage 34. The common intake passage 34 is provided with a throttle valve 35 near the confluence of the main intake passages 30 and 31 and a throttle valve 35
An air flow meter 36 is provided further upstream of the air conditioner, and the most upstream portion is connected to an air cleaner 37. The independent intake passages 21 to 26, the collective passages 27 and 28, the passages
An intake system in the intake device is constituted by 29 and the main intake passages 30 and 31. Also, the passage 29 and the main intake passage
Reference numerals 30 and 31 correspond to extended passages in the intake system.

The intake system includes an intake port 9 to 14 and an exhaust port 15
The natural frequency is set such that a positive pressure acts on the intake ports 9 to 14 in the vicinity of the intake ports 9 to 14 due to the pressure oscillation of the intake system during a period in which the intake valves 20 to 20 are open, that is, an overlap period. Therefore, in the present embodiment, the main intake passages 30 and 31 are communicated with each other by communication portions provided at a plurality of different positions, thereby changing the distance between the communicated position and the intake ports 9 to 14, The required natural frequency has been obtained.
In this case, the intake ports 9 to
Since the opening and closing periods of the ports 14 are different, the communication positions of the main intake passages 30 and 31 are made variable so as to approach the intake ports 9 to 14 as the engine speed increases.

Further, when increasing the torque at the time of low rotation by the resonance effect, a high torque tends to be obtained at the resonance tuning rotation speed as the rotation is low, but on the other hand, the torque changes sharply in a low rotation range, The range of the rotational speed at which a torque equal to or larger than a predetermined value is obtained is narrowed. Therefore, the main intake passage 30
If the number of the communication portions 31 is small, when switching the communication of each communication portion, the drop of the torque becomes large and the noise fluctuates greatly. Therefore, ideally, when an intake device having the above-described intake system is mounted on an actual vehicle, in order to obtain a stable torque characteristic in a low rotation range, the main intake passage 30 is required.
It is desirable to provide a large number of communication portions between the 31 and switch the communication between the communication portions so that the communication portions at positions communicate with each other in accordance with the rotation speed of the engine. However, in practice, it is necessary to reduce the number of communication parts as much as possible in consideration of cost, control required for switching communication, and the like. For this reason, in the present embodiment, at least two communication portions are provided, and the communication is switched at a wider interval as the rotation speed of the engine increases, and within a range of ± 20% from the resonance tuning rotation speed. I'm trying to do it.

Subsequently, the configuration of the 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 are provided as communication portions at predetermined intervals in order from the upstream side.
They are interconnected by 38-41. As shown in FIG. 1, the communication passages 38 to 41 are provided with opening / closing valves 42 to 45, respectively.
38 to 41 are opened and closed.

The actuators 46 for driving the opening / closing valves 42 to 45 and the opening / closing valves 32 and 33 are arranged such that the rotation speed of the engine detected by the rotation speed detection sensor 47 is different from some of the rotation speeds set in advance in the comparing section 48 and the height. If the detected rotational speed is higher than a certain set rotational speed, one of the on-off valves 42 to 45 and the on-off valves 32 and 33 corresponding to the set rotational speed is opened. In other words, the on-off valves 32, 33,
42 to 45 are driven as described above, and when the rotation speed of the engine changes from low to high, the communication passage 38 → the communication passage 39 → the communication passage 40 → the communication passage 41 → the communication passage 29 is sequentially opened in this order, When the engine speed changes from high to low, the engine closes in the reverse order.

In switching between opening and closing of the on-off valves 32, 33, 42 to 45, the rotation speed difference from the minimum resonance tuning rotation speed Nr to the opening of the on-off valve 42 is N ₀ , and the on-off valves 43 to 45 and The rotation speed difference when the valves 32 and 33 are sequentially opened is N ₁ ,
Assuming N ₂ , N ₃ , and N ₄ , these magnitude relationships are set as follows.

N ₀ <N ₁ <N ₂ <N ₃ <N ₄ where N ₀ is a value obtained by doubling the rotation speed difference ΔN determined by the engine characteristics and the like.

In the above configuration, in the low rotation range where the engine rotation speed is 3000 rpm or less, the opening and closing timing of the intake valve and the intake valve is advanced as compared with the case of the high rotation range indicated by the curve D as shown by the curve C in FIG. The overlap period becomes longer.
On the other hand, in the intake system, pressure vibration is generated, and the pressure wave is reflected by one of the communication passages 38 to 41 and the passage 29 communicating at the position closest to the intake ports 9 to 14, and becomes a positive pressure. . For example, the main intake passage 30 shown in FIG.
Causes the pressure waves to act on the intake ports 9 to 11 of the cylinders 3 to 5 during the overlap period, as shown in FIGS. Although not shown, the pressure wave generated by the main intake passage 31 also acts on the intake ports 12 to 14 during the overlap period as described above. Normally, if the overlap period is long in the low rotation speed range, inconveniences such as unstable combustion occur.In the case of this embodiment, however, the combustion gas remaining without being discharged during the overlap period is reduced by the positive pressure. It can be pushed out to improve the scavenging effect, and the above-mentioned inconvenience can be solved. Further, the intake pressure can be increased by the positive pressure, and the charging efficiency can be improved.

By the way, the intake ports 9 to 14 and the exhaust ports 15 to 20
The opening and closing time varies depending on the engine speed,
On the other hand, by changing the natural frequency of the intake system, positive pressure is applied to the intake ports 9-14. In this case, as shown in FIG. 8, when the rotation speed increases from the minimum resonance tuning rotation speed Nr, the torque decreases, but the rotation speed decreases.
Upon reaching the nr + N ₀ communicated with the communication passage 38, again a torque is increased. Subsequently, when the engine rotational speed increases by a rotation speed difference N ₁ from the communication of the communication passage 38 communicates with the communication passage 39, and later,
As the engine rotation speed sequentially increases at intervals of the rotation speed differences N ₂ , N ₃ , N ₄ , 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 with each other within a range of ± 20% of each resonance tuning rotation speed. Therefore, when the communication paths 38 to 41 and the path 29 communicate with each other, it is possible to suppress a large drop in torque and fluctuation in noise.

The main intake passages 30 and 31 are not limited to those shown in FIGS. 2 (a) and 2 (b). For example, as shown in FIGS. 3 to 5, depending on the required length. Such a shape is conceivable. The main intake passages 30 and 31 shown in FIGS. 3 (a) and 3 (b) have bent and overlapped shapes and are suitable for a case where they are formed slightly longer. The main intake passages 30 and 31 shown in FIGS. 4 (a) and 4 (b) have a spiral shape that is long in one direction and are suitable for a case where the main intake passages are formed to be considerably long. The main intake passages 30 and 31 shown in FIGS. 5 (a) and 5 (b) are curved at two locations and have a shape similar to an ellipse, and are suitable when formed relatively short. However, the communication between these main intake passages 30 and 31 is switched similarly to those shown in FIGS. 2 (a) and 2 (b).

Embodiment 2 Next, another embodiment of the present invention will be described with reference to FIGS. The members having the same functions as in the first embodiment are denoted by the same reference numerals, and the description thereof will be omitted.

As shown in FIG. 9, the intake system in this embodiment includes intake ports 9 to 14 provided in each of the cylinders 3 to 8 of the engine.
And the independent intake passages 21 to 26 are provided between the main intake passages 30 and 31 as in the first embodiment, but the downstream sides of the main intake passages 30 and 31 are not connected. Are different in that Also in this case, in order to apply a positive pressure to the intake ports 9 to 14 during the overlap period in the low rotation region, the main intake passage
30 and 31 are formed in a shape as shown in FIGS. 2 to 5 according to the required length. And the main intake passage 30
Opening and closing of the communication passages 38 to 41 provided between the 31s is controlled in the same manner as in the intake system shown in FIG.

Further, in the present invention, since it is sufficient that the natural frequency of the intake system can be changed as required, the main intake passages 30 and 31 having the same shape as the above are assembled as shown by a two-dot chain line in the drawing. It may be provided downstream of the passages 27 and 28.
Alternatively, the communication passages 38 to 41 in the main intake passages 30 and 31 are
They may be provided separately on the upstream and downstream sides. In this case, the main intake passage 30 provided downstream of the collecting passages 27 and 28
31 is connected or closed at its ends, and provided with on-off valves 32 and 33, respectively. In addition, the main intake passage 30 provided downstream of the collective passages 27 and 28
The communication passages 38 to 41 are provided between the valves 31 and 31 from the on-off valves 32 and 33 to the downstream side, but are omitted in the drawing for simplicity.

In such a configuration, at the time of low rotation, as shown in FIG. 6, the opening / closing timing of the intake valve is advanced, and even if the overlap period becomes longer, as shown in FIG. Positive pressure acts on the intake ports 9-11 of
Similarly, a positive pressure acts on the intake ports 12-14. Therefore, similarly to the first embodiment, the scavenging effect can be improved, and the occurrence of knocking in a low rotation range can be suppressed, and the charging efficiency can be improved. Further, since the opening / closing timing of the on-off valves 32, 33, 42 to 45 is set as shown in FIG. 8, when the passage 29 and the communication passages 38 to 41 are opened and closed, a large drop in torque and fluctuation of noise are generated. Can be suppressed.

〔The invention's effect〕

As described above, the intake device for an engine according to the first aspect of the present invention includes the intake port for introducing fresh air into the combustion chamber and the exhaust port for extracting combustion gas from the combustion chamber, and the cylinders in which the intake sequence is not continuous. The intake system is formed by an independent intake passage connected via the intake port, an aggregate passage for gathering the independent intake passages, and an extended passage leading to the aggregate passage, and the intake timing at the time of low engine rotation is adjusted. Both the valve opening and valve closing timings are suppressed so as to be earlier than at the time of high engine speed,
In the intake system of an engine, in which the overlap period in which both the intake port and the exhaust port are open is set to be larger at low engine speeds than at high engine speeds, the engine overlaps over the entire low engine speed range. During the period, the natural frequency of the intake system is variably set in accordance with the engine speed so that a positive pressure acts near the intake port due to the pressure vibration of the intake system.

This allows the natural frequency of the intake system to vary according to the engine speed such that a positive pressure acts near the intake port due to the pressure vibration of the intake system over the entire rotation range of the low engine speed range during the overlap period. Therefore, when the engine is running at a low rotation speed with a long overlap period, the residual gas generated by the previous combustion is quickly scavenged from the combustion chamber, so that the scavenging effect can be further improved. Therefore, increasing the filling amount
It is possible to increase the output in the low rotation range, and to suppress the occurrence of knocking at low speed without increasing the temperature of the fresh air introduced into the combustion chamber.

As described above, the intake system for an engine according to the second aspect of the present invention is the intake system for an engine according to the first aspect, wherein the two intake passages are formed by integrating the independent intake passages of the three cylinders. An intake device for an engine of a cylinder, wherein positive pressure acts on the vicinity of an intake port via two collective passages due to pressure vibration of an intake system during an overlap period of each cylinder over an entire rotation range of a low rotation range of the engine. As described above, the natural frequency of the intake system is variably set in accordance with the engine speed.

As a result, in a six-cylinder engine provided with two collective passages from which the resonance effect can be greatly extracted, the amount of intake air can be further increased, and a high output in a low rotation range can be sufficiently achieved. There is an effect that the occurrence of knocking at low speed can be suppressed without increasing the temperature of the fresh air introduced into the chamber.

[Brief description of the drawings]

FIG. 1 shows one embodiment of the present invention, and is a schematic view showing a configuration of an intake device. FIG. 9 shows another embodiment of the present invention, and is a schematic view showing a configuration of an intake device. FIGS. 2 to 8 are common to both of the above embodiments. 2 (a) are diagrams showing the shape of the main intake passage as viewed in the direction of arrow A in FIGS. 1 and 9. FIG. 2 (b) are cross-sectional views showing the shape of the main intake passage as viewed in the direction of arrow B in FIGS. 1 and 9. FIG. FIG. 6 is a graph showing the relationship between the opening degree of the intake valve and the exhaust valve and the crank angle. FIG. 7 is an explanatory diagram showing a state in which the positive pressure wave is acting during the overlap period. FIG. 8 is a graph showing the relationship between the engine speed and the 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 a passage, and 30 and 31 are main intake passages (extended passages). , 32 ・ 33 ・ 42〜45
Is an on-off valve, and 38 to 41 are communication paths.

────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Mikiko Fujii 3-1, Shinchi, Fuchu-cho, Aki-gun, Hiroshima Prefecture Mazda Co., Ltd. (56) References JP-A-2-207133 (JP, A) (58) Field surveyed (Int. Cl. ⁶ , DB name) F02B 27/02

Claims (2)

(57) [Claims] 1. An independent intake passage having an intake port for introducing fresh air into a combustion chamber and an exhaust port for extracting combustion gas from the combustion chamber, the independent intake passage being connected to the cylinders whose intake sequence is not continuous through the intake port. An intake passage is formed by a collective passage for collecting independent intake passages and an extended passage leading to the collective passage, and the intake timing at low engine speeds is high when the engine opens and closes at high engine speeds. In the intake system of the engine, the overlap period in which both the intake port and the exhaust port are open is set to be larger at a low rotation speed than at a high rotation speed of the engine. During the overlap period, the intake system operates so that the positive pressure acts near the intake port due to the pressure oscillation of the intake system over the entire rotation range in the low rotation range. An intake device for an engine, wherein a natural frequency of an air system is variably set according to an engine speed. 2. An intake device for a six-cylinder engine provided with two collecting passages in which respective independent intake passages of three cylinders are collected.
During the overlap period of each cylinder, the natural frequency of the intake system is variably set in accordance with the engine speed so that a positive pressure acts near the intake port via the two collecting passages due to the pressure vibration of the intake system. The intake device for an engine according to claim 1, wherein the intake device is provided.