JPH0674746B2 - Engine intake system - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an engine intake device including a timing valve between a supercharging auxiliary intake port and a surge tank.

(Prior Art) Conventionally, in an intake system of an engine, a surge tank is provided in a supercharging passage communicating with a supercharging auxiliary intake port opening to a combustion chamber, and a rotary valve is provided between the surge tank and the auxiliary intake port. A technique in which a rotary valve regulates the period for introducing supercharged air with respect to the opening / closing period of the auxiliary intake port is known, for example, as disclosed in JP-A-55-66616. is there.

The above-mentioned rotary valve is used to perform supercharging at the end of the intake stroke that does not hinder the natural intake when using both the natural intake and the supercharge. However, if the overlap period between the auxiliary intake port and the main intake port that performs natural intake is long, intake blowback will occur in the main intake port. The longer period causes a larger mechanical loss, which causes a reduction in output.

(Object of the Invention) In view of the above circumstances, the present invention is an intake device for an engine, which utilizes the pressure fluctuation associated with the opening and closing of a timing valve to improve the intake charging efficiency without increasing the blowback of intake air and the mechanical loss. It is intended to provide.

(Structure of the Invention) An intake device of the present invention has a main intake port and an auxiliary intake port, and a supercharger, a surge tank, and a timing valve are provided in this order from upstream in a supercharging passage communicating with the auxiliary intake port. For connecting the supercharger and the auxiliary intake port in the latter half of the intake stroke, the length of the supercharging passage from the surge tank to the timing valve is determined by the engine speed and the timing valve opening period. The wavelength is determined, and the primary reflected wave and the secondary reflected wave are set such that the half-wave phase of the fundamental wavelength is different, and the substantial ratio of the opening period and the closing period of the timing valve is 2: 1, At a specific engine speed, the open / close cycle of the timing valve and the vibration cycle of the vibration system between the surge tank are matched, and the pressure change during the opening period of the timing valve and its reflected wave are combined. It is characterized in that the pressure fluctuation due to the standing wave is generated so as to be low at the initial stage of opening of the timing valve and high at the final stage.

According to the present invention, the length of the supercharging passage from the surge tank to the timing valve is obtained, the basic wavelength of the supercharging passage is obtained from the engine speed and the timing valve opening period, and the primary reflected wave is obtained. By setting the secondary reflected wave so that the half-wave phase of the fundamental wavelength is different, and by forming the substantial ratio of the opening period and the closing period of the timing valve to 2: 1, opening and closing of the rotary valve Pressure fluctuation due to
The intake vibration system, which is set by setting the length, diameter, surge tank volume, etc. of the supercharging passage upstream of the rotary valve, is synchronized at a specific engine speed, and pressure fluctuations due to the opening of the timing valve and its reflected wave The combined standing wave can be generated, and its pressure fluctuation can be generated with a characteristic that it is low at the beginning of the timing valve opening and high at the end, which allows the intake air to be blown back without increasing mechanical loss. The pressure can be increased to improve the filling efficiency.

Embodiment An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is an overall configuration diagram of an engine having an intake device.

Each cylinder 2 provided in the engine body 1 of the four-cylinder engine E is provided with an auxiliary intake port 3 for supercharging, a main intake port 4 for natural intake, and an exhaust port 5 respectively. Each of the ports 3, 4, and 5 is opened / closed at a predetermined opening / closing timing by an intake / exhaust valve (not shown).

A supercharging passage 6 is connected to the auxiliary intake port 3 to supply supercharging air, and a natural intake passage 7 is connected to the main intake port 4 to perform natural intake. The upstream ends of the supercharging passage 6 and the natural intake passage 7 are connected to an air cleaner 9 via an air flow meter 8.

A supercharger 11 using an air pump is provided in the supercharging passage 6,
An intercooler 12 that cools the pressurized air is disposed downstream of the supercharger 11, and a surge tank 13 that temporarily stores the pressurized air is interposed. Further, between the surge tank 13 and the auxiliary intake port 3, a rotary valve 18 constituted by a rotary cylinder 19 is provided as a timing valve, and the surge valve 13 between the surge tank 13 and the rotary valve 18 is connected. The supply passage 6 is set to have a length that generates a constant pressure wave at an arbitrary rotation speed (preferably 2 / 3N or more) below the rated rotation speed N. A relief passage 14 that connects the surge tank 13 and the upstream side of the supercharger 11 is provided, and a relief valve 15 that regulates the upper limit pressure of the surge tank 13 is provided in the relief passage 14.

In the rotary valve 18, a tubular body 19 is rotatably supported in the supercharging passage 6 about a rotary shaft 20, and an opening 19a corresponding to each cylinder 2 is provided on an outer peripheral portion of the tubular body 19. .
A pulley 21 is fixed to one end of the rotary shaft 20, and is linked to an output shaft 22 of the engine E via a timing belt 23. The downstream ends of the branch passages 6a having one ends corresponding to the openings 19a of the cylindrical body 19 are connected to the auxiliary intake ports 3 of the respective cylinders 2. A control valve 25 for controlling the supercharging amount is provided in each of the branch passages 6a. The control valve 25 is operated in cooperation with, for example, a throttle valve (not shown), and its opening is adjusted according to the load or the like.

The rotary valve 18 has an opening period in which one of the openings 19a communicates with the branch passage 6a on the downstream side with respect to the rotation of the tubular body 19, and communication between all the openings 19a and the branch passages 5a is closed. It is configured such that the substantial ratio with the closing period is an integer ratio of 2: 1. That is, in the opening 19a arranged on the circumference of the cylinder 19 so as to sequentially communicate with the branch passages 6a of each cylinder 2 in accordance with the intake order thereof, the opening 19a in the circumferential direction The size of the opening angle is the opening period, and the period until this opening 19a is closed and the next opening 19a is in communication is the closing period,
The opening angle is set to have a predetermined ratio.

That is, as shown in FIG. 3, when the intake sequence (ignition sequence) is the 1-3-4-2 cylinder, the opening timing of the rotary valve 18 is first the opening 19a for the first cylinder at the angle IO ₁ . open closed at an angle IC _1, followed by the opening 19a is closed by an angle IC ₃ opens at an angle IO ₃ for the third cylinder,
Similarly, the opening 19a for the fourth cylinder is intended to close an angle IC ₄ open at an angle IO ₄ (omitted for the second cylinder). Then, from the opening timing IO to the closing timing IC, the initial portion at the beginning of opening and the final portion at the end of closing actually open the opening 19a.
Since it does not work effectively even when opened, the ratio of the effective opening period I excluding the ineffective portion a to the closing period II including the ineffective period a is set to 2: 1 and the rotation angle of the output shaft 22 is set. The opening period I is set to 120 ° and the closing period II is set to 60 °.

The opening timing of the opening 19a is basically the main intake port 4
The valve is opened at the end of the intake stroke of the natural aspiration by, and the supercharging pressure is applied only at this time to perform supercharging.
In the setting of the effective opening period I and the closing period II, the error in setting the integer ratio is, for example, 120 ° ± 2
0 ° and 60 ± 20 ° are acceptable.

In addition, as shown by the chain line in FIG.
It is possible to make the opening period variable by partitioning the entrance portion of the branch passage 6a communicating with the opening 19a in the rotational direction of the rotary valve 18 and disposing the shutter valve 26 on one side.
When the shutter valve 26 is closed, the opening angle of the opening 19a is substantially reduced. When the opening period I at the time of low speed is shortened, the effective opening period I is 120 ° and the closing period II is 60 ° at the time of high speed when the shutter valve 26 is opened.
So, while the ratio is 2: 1, the shutter valve 26
In the low speed range in which is closed, the effective opening period I is set to 90 °, the closing period II is set to 90 °, and the ratio of the two is set to 1: 1.

According to the above configuration, a pressure fluctuation caused by opening / closing the rotary valve 18 is generated in the upstream supercharging passage 6, and is reflected between the surge tank 13 and the rotary valve 18.
And at a specific engine speed, surge tank
The vibration period (fundamental wavelength) of the vibration system of the supercharging passage 6 obtained from the length of the supercharging passage 6 from 13 to the rotary valve 18 (supercharging passage length) and the opening period of the rotary valve 18, and the rotary valve 18 A standing wave is generated by the pressure change at the time of opening and the combined wave of the reflected wave, that is, the opening / closing cycle of the rotary valve 18 and the vibration cycle of the vibration system with the surge tank 13 coincide with each other. When a standing wave, which is a composite wave of the pressure change at the time of opening and its reflected wave, is generated and becomes a resonance state, the intake pressure from the rotary valve 18 to the auxiliary intake port 3 is relatively low at the beginning of opening and then gradually increases. Supercharger
It becomes higher than the discharge pressure by 11, the amount of supply air increases, the intake charging efficiency increases, and the output can be further improved in addition to the supercharging effect.

That is, FIG. 4 shows pressure fluctuations associated with opening / closing of the rotary valve 18. For the effective opening period I of the rotary valve 18 shown by the broken line, this opening causes the pressure drop fluctuation A as shown by the thin solid line, and since the ratio with the closing period is 2: 1, its primary reflected wave B is It occurs with a delay of half a wavelength as indicated by the one-dot chain line. A secondary reflected wave C delayed by a half wavelength with respect to the primary reflected wave B is generated as shown by a chain double-dashed line. When these are combined, a standing wave D of the intake air is generated as shown by the thick solid line, and the pressure decreases in the initial stage of the opening period I of the rotary valve 18 and increases in the latter half. Therefore, the pressure fluctuation associated with the standing wave D having the above characteristics acts on the auxiliary intake port 3, so that the intake air to the main intake port 4 is overlapped with the main intake port 4 at the initial opening (supercharging). You can reduce the blowback. In addition, the supercharger 11
Even if is used, supercharging is suppressed at the time of overlap, and the suppressed supercharging is supercharged in the latter half of supercharging, so that an efficient supercharging characteristic can be obtained as a whole.

In the above embodiment, the passage length between the rotary valve 18 and the surge tank 13 is set so that the standing wave is generated at any rotation speed below the rated rotation speed N (preferably above 2 / 3N). Although it is fixed to a predetermined length, this passage length may be made variable so as to expand the range of tuning revolutions in which resonance occurs and expand the range in which the effect of improving the charging efficiency is obtained. That is, as the variable length mechanism, for example, a rotating body or a sliding body is provided in the middle of the passage so as to change the passage length, or a plurality of passages having different lengths are arranged side by side and these passages are switched. Those having a variable length can be appropriately adopted.

Further, in the above embodiment, the four-cylinder four-cycle engine has been described. However, in this four-cylinder four-cycle engine, the intake stroke of each cylinder starts at every 180 °, and the openings of the rotary valve 18 for each cylinder overlap. However, in a 6-cylinder engine, since the intervals are 120 °, opening and closing all cylinders with one rotary valve 18 causes overlapping of opening timings and pressure fluctuations due to opening and closing of the cylinders are reduced, thus improving filling efficiency. Since the effect is reduced, in the case of the six cylinders, it is sufficient to separate the cylinders into three cylinders and arrange the rotary valves in each cylinder. On the other hand, the present invention can also be applied to a rotary piston engine.

Further, when the vibration generated between the surge tank 13 and the rotary valve 18 and the supercharged air pulsation discharged by the positive displacement air pump of the supercharger 11 are synchronized, the pressure vibration in the resonance state becomes larger. Therefore, the intake charging efficiency can be improved.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of an engine having an intake device according to an embodiment of the present invention, FIG. 2 is a schematic configuration diagram of a rotary valve portion, FIG. 3 is a characteristic diagram showing opening / closing timing of the rotary valve, and FIG. The figure is an explanatory view showing pressure fluctuations associated with opening and closing of a rotary valve. E ... Engine, 1 ... Engine main body 2 ... Cylinder, 3 ... Auxiliary intake port 4 ... Main intake port, 5 ... Supercharging passage 6a ... Branch passage, 7 ... Natural intake passage 11 ... Excess Feeder, 13 …… Surge tank 18 …… Rotary valve 19 …… Cylinder, 19a …… Opening I …… Effective opening period, II …… Closed period

Claims (3)

[Claims] 1. A main intake port and an auxiliary intake port,
From the upstream to the supercharger, which communicates with the auxiliary intake port,
In an intake system for an engine in which a surge tank and a timing valve are provided in order, and the supercharger and the auxiliary intake port communicate with each other in the latter half of the intake stroke, the length of the supercharging passage from the surge tank to the timing valve is set to The fundamental wavelength of the supercharging passage is obtained from the rotation speed and the timing valve opening period, and the primary reflected wave and the secondary reflected wave are set so that the half-wavelength phase of the fundamental wavelength is different, and the opening period of the timing valve is An air intake system for engines characterized by a substantial ratio of 2: 1 to the closing period. 2. The substantial ratio of the opening period to the closing period of the timing valve is basically set to 2: 1 in the low speed range.
The intake system for an engine according to claim 1, wherein the intake system is 1: 1. 3. The intake system for an engine according to claim 1, wherein a length of a supercharging passage between the timing valve and the surge tank is variable.