JPH0737768B2 - Intake device for 4-cycle multi-cylinder engine - Google Patents

Description

The present invention relates to an intake system for a four-cycle multi-cylinder engine,
Particularly, it relates to the structure of the intake passage connected to the cylinder.

[Prior art]

In this type of engine, a conventional primary intake passage and a high-speed secondary intake passage are made to communicate with a cylinder having a plurality of intake ports, and the secondary intake passage is opened / closed in conjunction with the engine speed. It is known that a normally open switching valve is provided to change the passage length of the intake passage according to the operating conditions of the engine.

[Problems to be solved by the invention]

However, since the length of the regular primary intake passage is set according to the intake inertia at low speed, the intake flow rate flowing through the primary intake passage near the saturation point as the load increases and the rotational speed increases. In other words, during the transition period in which the switching valve starts to open, the length of the primary intake passage does not properly match the flow of intake air, and it was impossible to effectively use the intake inertia. Therefore, as indicated by the broken line in FIG. 3, there is a problem that the torque temporarily drops at the time of shifting to the high rotation and high load operation.

The present invention has been made under such circumstances, and it is possible to obtain a high torque over the entire operating range, and further to make the communication passage short and simple, and to make the primary and secondary An object of the present invention is to obtain a compact intake system for a four-cycle multi-cylinder engine that does not require a space for installing a communication passage around the intake passage.

[Means for solving problems]

In order to achieve the above-mentioned object, the present invention has a plurality of cylinders arranged in parallel with a space between each other, and a plurality of intake ports respectively connected to the combustion chambers of these cylinders, and the intake air of each combustion chamber is A normal primary intake passage that supplies intake air over the entire operating range and a secondary intake passage that supplies intake air only during high-speed or high-load operation are connected to the mouth, and these primary intake passage and secondary intake passage are connected. It is premised on a 4-cycle multi-cylinder engine arranged in parallel with each other.

Then, among the plurality of cylinders, the intake timings of the adjacent cylinders are made different from each other, and the primary intake passages of the adjacent cylinders are arranged between the secondary intake passages of the adjacent cylinders so that the primary intake air The passages are arranged side by side, and these adjacent primary intake passages are communicated with each other via a communication passage, and a normally closed type control that is opened when the engine speed reaches a rotation range higher than planned It features a valve.

[Action]

According to this configuration, when the engine shifts to high-speed or high-load operation, the control valve is opened and the low-speed primary intake passages are communicated with each other, so that when one cylinder enters the intake stroke, A pressure difference occurs between the primary intake passages,
The intake air also flows into the primary intake passage during the intake stroke from the primary intake passages of the other cylinders. Therefore, the impedance from the outside air inlet to the open end of the communication passage is reduced, which means that the equivalent pipe length of the primary intake passage is substantially shortened, and the passage length of the primary intake passage is smaller than that of the conventional one. It becomes a good fit to the flow. Therefore, not only the intake resistance is reduced, but also a large amount of intake air can be sent to the cylinder by effectively utilizing the supercharging effect based on the intake inertia. Therefore, the drop in torque at the time of shifting to high-speed or high-load operation is reduced, and high torque can be obtained over the entire operating range.

Further, according to the above configuration, since the primary intake passages connected via the communication passage are adjacent to each other, the communication passage may be arranged between the primary intake passages, and the secondary intake passage is largely bypassed. No need. Therefore, the communication passage can be formed in a short straight line, and the intake resistance is suppressed accordingly, so that the intake air in the primary intake passage that is out of the intake stroke can be efficiently guided into the primary intake passage during the intake stroke. You can

Moreover, since the communication passage is accommodated between the two adjacent primary intake passages, the communication passage does not greatly extend around the primary intake passage and the secondary intake passage. Therefore, it is not necessary to secure a dedicated space for arranging the communication passage around the primary and secondary intake passages, and the entire intake device can be made compact.

Example of Invention

The present invention will be described below based on an embodiment shown in the drawings.

In the figure, reference numeral 1 is a cylinder block, 2 is a cylinder head,
Reference numeral 3 denotes a piston, and in the cylinder block 1, cylinders 4 and 4, for example, are arranged side by side in a line. The combustion chamber 5 located at the top of the cylinders 4 has three intake ports 6 and two exhaust ports 7 as shown in FIG. 1, and these intake ports 6 and exhaust ports 7 are The intake valve 8 and the exhaust valve 9 are opened and closed at predetermined timings.

In FIG. 2, reference numeral 10 is an intake camshaft, and 11 is an exhaust camshaft.

By the way, the intake ports 6 of the cylinders 4 are gathered together in the cylinder head 2. A fuel injection valve 25 is provided in the gathering portion 12, and the intake passages 14 are provided at the open ends of the gathering portion 12, respectively. Are connected. The upstream end of the intake passage 14 is connected to the intake chamber 15, and a throttle valve 13 is provided at the intake inlet of the intake chamber 15.

The interior of the intake passage 14 is divided into a regular primary intake passage 16 and a high-speed secondary intake passage 17, and the passage cross-sectional area of this primary intake passage 16 is the passage cross-sectional area of the secondary intake passage 17. Is formed smaller than. Therefore, the primary intake passage 16 and the secondary intake passage 17 have different equivalent pipe lengths, and the equivalent pipe length of the primary intake passage 16 is determined to be long according to the intake inertia at low speed.

A butterfly-type switching valve 18 that constantly closes the intake passage 17 is provided in the middle of the secondary intake passage 17. The valve shaft 18a of the switching valve 18 is connected to, for example, an actuator (not shown) that uses an intake negative pressure as a drive source. Therefore, the switching valve 18 has a large opening of the throttle valve 13 or the engine speed. Is the preset speed N ₁
When the intake negative pressure increases, the valve is rotated in the opening direction.

Further, among the four cylinders 4, the cylinders 4, 4 adjacent to each other have a crank angle phase difference of 180 °, that is, intake timings are different from each other. The primary intake passages 16, 16 of these adjacent cylinders 4, 4 are parallel to each other, and the secondary intake passages 17, 17 of the adjacent cylinders 4, 4 are provided.
The primary intake passages 16 and 16 themselves are arranged side by side.

The primary intake passages 16, 16 of the cylinders 4, 4 with different intake timings are
As shown in FIG. 1, they are communicated with each other via a communication passage 19. The communication passage 19 is between the primary intake passages 16 and 16.
It extends linearly in a direction orthogonal to the intake passages 16, 16. The passage cross-sectional area of the communication passage 19 is determined by the primary intake passage.
It is set to be approximately equal to or larger than the cross-sectional area of 16 passages, and the butterfly-type control valve is provided in the middle of this communication passage 19.
20 are provided. The control valve 20 always closes the communication passage 19, and its valve shaft 20a is connected to the control mechanism 21 that is linked to the engine speed. In other words, the control mechanism 21 opens the control valve 20 when the engine speed reaches N ₂ which is lower than the engine speed at which the switching valve 18 starts to open. The rotation speed is detected from the ignition pulse of the ignition unit 22, for example.
Then, when this detection signal reaches a predetermined level, the control unit 23 gives an operation command signal to the servo motor 24 to sequentially rotate the valve shaft 20a in the opening direction according to the increase in the engine speed. The control valve 20 is fully opened when the engine speed is between N ₂ and N ₁ .

In such a configuration, during low-speed operation in which the engine speed does not reach N ₂ , both the switching valve 18 and the control valve 20 are closed, so the intake air whose flow rate is controlled by the throttle valve 13 is the primary intake passage 16 It is sucked into the combustion chamber 5 during the suction stroke through only. Therefore, as the intake flow velocity increases, the equivalent pipe length of the primary intake passage 16 is determined in accordance with the intake inertia at low speeds, so the supercharging effect based on the intake inertia is effectively used to burn a large amount of intake air. It can be fed into the chamber 5 and high torque is obtained.

On the other hand, when the engine speed reaches N ₂ and shifts to medium speed operation, the control mechanism 21 detects this and opens the control valve 20 according to the engine speed. Then, the primary intake passages 16, 16 between the cylinders 4, 4 having different intake timings communicate with each other, so that when one cylinder 4 enters the intake stroke, a pressure difference is generated between the primary intake passages 16, 16. The intake air in the other primary intake passage 16 flows into the primary intake passage 16 during the intake stroke via the communication passage 19. For this reason, the impedance between the intake chamber 15 and the open end of the communication passage 19 decreases, so that the equivalent pipe length of the primary intake passage 16 is substantially shortened in response to an increase in intake flow rate and flow velocity as compared with the case of low speed. It will be. As a result, even if the flow rate of the intake air flowing in the primary intake passage 16 approaches the saturation point, the primary intake passage 16
The passage length of (1) is well adapted to the flow of intake air, so that the intake resistance is reduced and the supercharging effect based on the intake inertia can be effectively used. Therefore,
A large amount of intake air can be continuously sent to the combustion chamber 5 at a low speed, and the torque drop is reduced as shown by the solid line in FIG.

Further, when the engine speed reaches N ₁ and shifts to high speed operation, the switching valve 18 is opened. Therefore, the intake air is fed into the combustion chamber 5 not only from the primary intake passage 16 but also from the secondary intake passage 17 for high speed, so that the required intake amount in the high speed region can be sufficiently satisfied, and the high intake air continuously continues. Torque is obtained.

Further, according to the above configuration, since the primary intake passages 16, 16 connected via the communication passage 19 are arranged between the secondary intake passages 17, 17 and are adjacent to each other, the communication passage 19 is the primary passage. It may be arranged between the intake passages 16 and 16, and the secondary intake passages 17 and 17
Does not need to be detoured significantly. Therefore, the total length of the communication passage 19 can be shortened, and the communication passage 19 can be formed in a mere straight line shape. Therefore, the intake resistance is suppressed by that amount, and the primary intake passage 16 in one of the intake strokes that is out of the intake stroke is suppressed. The intake air can be efficiently guided into the primary intake passage 16 during the intake stroke.

In addition, the communication passage 19 includes two adjacent primary intake passages 16, 1
Since it is accommodated in the dead space generated between 6, the communication passage 19 does not greatly extend around the primary intake passages 16, 16 and the secondary intake passages 17, 17. Therefore, it is not necessary to secure a dedicated space for disposing the communication passage 19 around the primary and secondary intake passages 16 and 17, and there is an advantage that it contributes to downsizing of the entire intake device.

Incidentally, in carrying out the present invention, in place of the fuel injection valve, a carburetor of a forced opening / closing type which is forcibly opened / closed over the entire operating region in association with the throttle operation in the primary intake passage is provided, Provide a negative pressure responsive carburetor that is opened in the secondary intake passage when the intake negative pressure reaches or exceeds a preset value or when the opening of the carburetor reaches a higher opening than expected. Is also good.

Further, the number of intake ports is not limited to three, but may be two, and the cylinder arrangement may be V-shaped.

〔The invention's effect〕

According to the present invention described in detail above, the equivalent pipe length of the primary intake passage is shortened during the transition period to high-speed or high-load operation. Therefore, even at this time, the supercharging effect based on the intake inertia can be effectively used. As a result, a large amount of intake air can be sent to the cylinder in combination with the decrease in intake resistance. Therefore, the drop in torque is reduced, and high torque can be obtained over the entire operating range.

Further, when the primary intake passage is communicated via the communication passage, it is not necessary to largely detour the communication passage to the secondary intake passage, so that the total length of the communication passage can be shortened and the communication passage can be a straight line. Can be formed into a shape,
Intake resistance can be kept small. Therefore, the intake air in one of the primary intake passages that has deviated from the intake stroke can be efficiently guided into the primary intake passage during the intake stroke, and it is possible to prevent a torque drop during a transition period to high speed or high load operation. Will be more convenient.

In addition, since the communication passage does not need to greatly extend around the primary intake passage and the secondary intake passage, it is not necessary to secure a dedicated space for arranging the communication passage around these primary and secondary intake passages. However, there is an advantage that the entire intake device can be made compact.

BRIEF DESCRIPTION OF THE DRAWINGS The drawings show one embodiment of the present invention. FIG. 1 is a plan view of a cross section of an intake passage portion, FIG. 2 is an overall cross sectional view, and FIG. 3 is a characteristic showing a change in torque. It is a figure. 4 ... Cylinder, 5 ... Combustion chamber, 6 ... Intake port, 16 ...
Primary intake passage, 17 …… Secondary intake passage, 19 …… Communication passage, 20
...... Control valve.

Claims (1)

[Claims] 1. A plurality of cylinders arranged in parallel with a space between each other, and a plurality of intake ports respectively connected to the combustion chambers of the respective cylinders, wherein the intake ports of the respective combustion chambers have a whole operation range. A normal primary intake passage for supplying intake air to a secondary intake passage for supplying intake air only during high-speed or high-load operation is communicated, and the primary intake passage and the secondary intake passage are arranged in parallel with each other. In a four-cycle multi-cylinder engine, the intake timings of adjacent cylinders of the plurality of cylinders are different from each other, and the primary intake passages of the adjacent cylinders are arranged between the secondary intake passages of the adjacent cylinders. Due to
These primary intake passages are arranged side by side, and these adjacent primary intake passages are communicated with each other via a communication passage, and an opening operation is normally performed in this communication passage when the engine speed reaches a rotation range higher than expected. An intake system for a four-cycle multi-cylinder engine, which is provided with an open type control valve.