JPS60224928A - Suction system for supercharged engine - Google Patents

Abstract

PURPOSE:To make improvements in charging efficiency at a low-speed range, by specifying the length of a passage at the downstream of an expansion chamber in a main suction passage in particular, in case of a device installing a timing valve, which is operated so as to supercharge an engine at suction stroke closing time, in the downstream of a supercharger in a supercharging passage. CONSTITUTION:A suction passage 11 is branched off into a main suction passage 12 and a supercharging passage 13 from its midway, while a throttle valve 17 and an expansion chamber 18 both are installed in this main suction passage 12. On the other hand, a vane type supercharger 20, a supercharged air control valve 22 and a timing valve 23 are all installed in the supercharging passage 13. In the above-mentioned, the length of the main suction passage 12 at the downstream of the expansion chamber 18 is set so as to cause a compressional wave to be added to the vicinity of a main suction port 14 at suction stroke closing time by means of a suction inertial effect at an engine low-speed range of less than 3,000 r.p.m. With this constitution, suction pressure in and around a main suction port 4 is raised up, preventing the prefiring of supercharged air from occurring, whereby charging efficiency is improved.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention forms a main intake passage and a supercharging passage to the right of the supercharger, and a supercharging passage downstream of the supercharger that is synchronized with engine rotation. This invention relates to an intake system for a supercharged engine that is equipped with a timing valve that opens and closes at different times.

(Prior Art) Conventionally, as shown in Japanese Patent Publication No. 58 ``511 J 4 '''i. A main intake passage and a supercharging passage leading to the supercharging are formed, and the intake bow 1 at the downstream end of the intake passage
- and the supercharging port h at the downstream end of the supercharging passage are opened into the combustion chamber, and a timing valve that opens and closes to perform supercharging at the end of the intake stroke is installed in the supercharging passage where the supercharging flow is separate. J/,: An engine intake device is known. According to this intake system, supercharged air is supplied from the supercharging passage to the combustion chamber in addition to natural intake air from the main intake passage, and the output f1 of the engine can be improved.

In this intake system, supercharging is performed at the end of the intake stroke, but when the timing valve starts to shorten, the main intake port is completely closed. Therefore, in order to increase charging efficiency, it is necessary to prevent supercharged air from blowing back into the main intake passage between the time the timing valve starts opening and the main intake boat closes. There is a demand for Iζ. When the intake air flow velocity in the intake passage is high, blowback is suppressed, but when the engine speed is low, the intake air flow velocity is low, so it is desirable to take measures to prevent blowback even more actively. was.

(Objective of the Invention) In view of the above circumstances, the present invention has been devised to prevent the supercharged air supplied from the supercharging passage to the combustion chamber at the end of the intake stroke from blowing back into the main intake passage in the low speed range of the engine. The engine is designed to increase the charging efficiency at low speeds and reduce the output of the supercharged engine, thereby reducing the intake cost of 1 yen.

(Structure of the Invention) The present invention forms a main intake passage and a supercharging passage having a supercharger, and installs a timing valve downstream of the supercharger that opens and closes to perform supercharging at the end of the intake stroke. In an engine equipped with a fuel supply passage, at least one of the length of the main intake passage downstream of the enlarged chamber formed in the main intake passage or the length of the communication passage between cylinders including the main intake passage should be determined in the low speed range. The compression wave is set so that a compression wave is sent to the vicinity of the main intake passage opening of the cylinder at the end of the intake stroke. In the low speed range of the engine, there is a compression wave (2J) designed to prevent the supercharged air from blowing back into the main intake passage.

(Embodiment) FIG. 1 shows a first embodiment of the present invention. In this figure, 1 is a cylinder C of one engine, a piston 2 is housed inside A, and a combustion chamber 3 is formed above this piston 2. A main intake boat 4, a supercharging boat T-5, and an IR boat 6 are opened in this combustion chamber 3, and these boats 4 to 6 are provided with an intake valve 7, a supercharging intake valve 8J3
and 11 valves 9 are respectively equipped.

11 is an intake passage, and from the middle of the
The main intake passage 12 communicates with the first intake boat 4, and the supercharging passage 13 communicates with the supercharging boat 5. An air cleaner 14 and an air flow meter 15 are disposed in the intake passage 11 upstream of the branch point between the main intake passage 12 and the supercharging passage 13.
In response to the IC intake air flow detected by the meter 15, the M air intake installed in the main intake passage 12, etc.
Fuel injection m from V (not shown) is controlled.

, the L2 main intake passage 12 is provided with a throttle valve 17 that is opened and closed by operating the accelerator, and an enlarged chamber (lige tank) downstream of the throttle valve 17.
18 are formed. M/j The supercharging passage 13 has the supercharging 1
Fi20 is the installation number, and this supercharger 20 consists of, for example, a vane type air pump driven by the output shaft 21 of the engine. This supercharging 8120 may be operated in conjunction with the output shaft 21 of the engine at all times, but by being connected to the output shaft 21 via a clutch mechanism, it can be stopped at low loads when supercharging is not necessary. You may also leave it as such.

A supercharging air control valve 22 is arranged in the supercharging passage 13 downstream of the supercharging 11120 to control the supercharging port according to the load of the engine. A timing valve 23 is provided downstream from the 〇-tally valve. In addition, the supercharging passage 131 described in -1- is a relief passage that relieves excess supercharging air between the supercharging air 8!20 and the supercharging air control valve 22 to the -L flow side of the supercharger 20. 24 is formed, and a check valve type relief valve 25 is provided in the middle of this relief passage 24. The figure shows the relationship between the opening and closing timing of the main intake valve 8 J3 J and the timing valve 23.
As shown in the figure, the opening starts just before TDC (Top Dead Center) and closes after BDC (Bottom Dead Center). In addition, as shown by line 8'c, the supercharging intake valve 8 has a slightly delayed opening timing and closing timing compared to the main intake valve 7.
It's sea urchin. Further, the timing valve 23 is opened at least before the supercharging intake valve 8 is closed at the end of the intake stroke, as shown by line C], and the timing valve 23 is opened at least before the supercharging intake valve 8 is closed.
It will be closed on or after 5-)
The timing valve 23 and the supercharging intake valve 8 are designed so that supercharging air is supplied to the combustion chamber only while they are open. The opening period of this timing valve 23 is the main intake valve 7.
Some parts of the opening period have been delayed.

In this J: shape structure, the length of the main intake passage 12 downstream of the enlarged chamber 18 is set in advance so that a compression wave is applied to the vicinity of the main intake boat 4 at the end of the intake stroke due to the so-called intake inertia effect in the low speed range of the engine. is set. In other words, during the intake stroke in which the main intake valve 7 is closed, the expansion wave (negative pressure wave) generated as the piston 2 descends propagates in the main intake passage 12 at a speed equal to the velocity of sound plus the flow velocity, and is compressed in the expansion chamber 18. The compression wave is reversed and reflected by waves (positive pressure waves), but the timing at which this compression wave returns to the vicinity of the main intake boat 4 is related to the length of the main intake passage 12 downstream of the expansion chamber 18, and is related to the engine rotation. Varies depending on number. Therefore, when the speed is in the low speed range, the expansion chamber 1
The length of the main intake passage 12 downstream of the main intake passage 8 is set.

Here, the low speed range is 1 or higher than the idle speed and 3.00 Or
Refers to the rotation speed region below pm.

In the case of an intake system configured in this way, at the end of the intake stroke, the supercharging air flows as shown by curve G in FIG. is supplied to the combustion chamber 3.

During the period during which supercharging air is supplied, during which the 1st intake valve 7 is opened, the 1st intake valve 7 is opened.
There is a possibility that it will be blown back. On the other hand, the intake pressure near the intake boat 4 is as shown by the curved line in FIG.
After the valve is opened, the pressure gradually decreases from around 1' D C, and after reaching 0 pressure in the middle of the intake stroke, the negative pressure gradually decreases. , intake line Pi! The intake pressure at the end of the period becomes as shown by the two-point gl line Da, and when the main intake valve 7 is closed, the pressure increases somewhat due to the action of the intake flow, but at low speeds the intake flow rate is low, so the above pressure 1 stomach is small,
The blowback effect due to the intake air flow itself is poor. Therefore, there is a tendency for supercharged air to blow back at low speeds.

On the other hand, when the above-mentioned intake frI effect is maintained in the low speed range, the solid line portion D
As shown in b, the intake pressure near the main intake boat 4 increases, preventing supercharged air from blowing back, thereby increasing charging efficiency. Therefore, the relationship between engine speed and output torque when the intake inertia effect is not provided is shown in Figure 4 with 2 fish boxes mE, and when the intake inertia effect is provided in the low speed range, the solid line " As shown in , the output torque is increased in the low speed range.

FIG. 5 shows a second embodiment of the invention, in which:
In the low speed range of the engine, so-called inter-cylinder intake air is used to prevent air from flowing back into the main intake passage. This figure shows a 2-air n4-cycle engine, in which main intake boats 4a, 4b, supercharging boats 5a, 5b, and exhaust ports 1-6a, 6b are opened to combustion ports 13a, 3b of each cylinder 1a, 1b, respectively. Main intake valve 7 on the boat
a, 7b, supercharging intake valves 8a, 8b, and exhaust valve 9a.

9b is equipped. Intake passage 12 +,
, L branch from the middle for each cylinder, and each intake passage branch part 12p+, 12b communicates with the intake boat 4a, 4b of each cylinder 1a, lb. Supply path 131. ), the supercharging air is branched from the exhaust port valve 22 to each cylinder (ia, 1b, respectively).
Supercharged boats 5a, 5bk, ? i! A timing valve 23a, 23b is installed in each supercharging passage branch portion 13a, 13b. The timing valves 23a and 23b are opened at the same timing fflL as the engine rotates, as in the first embodiment.

The length of the communication passage consisting of the main suction passage branch parts 12a and 12b between the mountain air 1s11a and 1b is the following: The compression wave is set so that a compression wave is applied near the 1st intake bow 1-f1 of the cylinder at the end of the intake stroke. At the intake port rfn OH, the intake air is compressed by the residual gas pressure in the combustion chamber, and the compression wave is sent to the intake boat of the other cylinder, and when the main intake boat of one cylinder is closed, due to the action of the intake air flow; A compression wave is generated and the compression wave is sent to the SL intake port of the other cylinder.Then, in the low engine speed range,
The length of the communication path is set so that the compression wave that occurs when the intake boat of one cylinder opens or the compression wave that occurs when the intake boat closes reaches the vicinity of the main intake boat of the other cylinder at the end of the intake stroke. ing.

Even if the inter-cylinder intake interference effect is utilized in this way, in the low speed range of the engine, compression waves are applied to each cylinder 1a and 1b near the main intake bows 1-4a and 4b at the end of the intake stroke, respectively. As in the case of the first embodiment, blowback of supercharged air is prevented and charging efficiency is increased.

In addition, an expansion chamber 28 is installed at each cylinder branch point of the main intake passage 12 as shown by the two-dot chain line in FIG.
You can also do this. Even in multi-cylinder engines with three or more cylinders, the main intake passage can be branched from the enlarged chamber for each air Fa to create an inter-cylinder intake interference effect between each cylinder in the low speed range. . Furthermore, it is also possible to simultaneously achieve the above-mentioned intake inertia effect and inter-cylinder intake interference effect in the low speed range, depending on the length of the enlarged chamber and the length of the intake passage branch. Furthermore, the timing valve 23
IJ The engine speed is high / it starts to get cold (even if the configuration is configured to open and close earlier).

(Effects of the Invention) As described above, the present invention has a timing valve installed in the supercharging passage to supply supercharging air from the supercharging passage to the combustion chamber at the end of the intake stroke. In the low speed range where supercharged air is easily blown back to the intake passage by /18, the I@1 of the cylinder at the end of the intake stroke. By applying a compression wave near the opening of the electrical passage, it is possible to prevent supercharged air from blowing back into the main intake passage, thereby increasing charging efficiency in the low speed range and increasing output. It is something that is.

[Brief explanation of the drawing]

- Fig. 1 is a schematic diagram showing a first embodiment of the present invention, and Fig. 2 is a diagram showing the opening/closing 11 of the main intake valve, supercharging intake valve, and timing valve.
．． ' An explanatory diagram showing the 1st stage, Figure 3 is 1-Intake bow 1- (
FIG. 4 is an explanatory diagram showing the relationship between engine speed and output torque, and FIG. 5 is a schematic diagram showing the ff12 embodiment. 1.1a, lb... cylinder, 12-4 intake passage, 13.
...Supercharging passageway, 18... Expansion chamber, 20... Supercharging bridge,
23...Timing valve. Patent applicant Higashi) I] - Industry Co., Ltd. 1

Claims (1)

[Claims] 1 and 21 intake passages, the turbocharger is placed on the right, and a filtration feed passage is formed, and a timing valve that opens and closes to perform supercharging at the end of the intake stroke is installed in the supercharging passage downstream of the turbocharger. In the S engine, at least one of the length of the main intake passage downstream of the enlarged chamber formed in the main intake passage or the length of the communication passage between the cylinders including the two main intake passages is adjusted during the intake stroke in the low speed range. An intake system for an engine with a filtration feed angle characterized by being set so that a compression wave is sent near the main intake passage opening 1 of the final stage cylinder.