JPS6217092B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an engine intake system, and in particular, a sub-throttle valve that closes only at low load is provided downstream of the main throttle valve, and a sub-intake passage that bypasses the sub-throttle valve. The present invention relates to an improvement in an intake device that increases the combustion rate by utilizing the swirl effect of high-speed intake air (or mixture) passing through a sub-intake passage. In particular, the present invention allows intake air to be taken in from the auxiliary intake passage not only during idling operation but also during other low-load operations. The present invention relates to an intake system for an engine, in which intake air is opened to a main intake passage in between, passes through a main throttle valve, and is guided to a sub-intake passage.

Conventionally, in the above-mentioned type of intake system, the sub-throttle valve, like the main throttle valve of the carburetor, is biased to the closed position by a return spring or the like, and the return spring is only pressed when necessary during operation. The valve was opened by applying a force that resisted the valve closing force.

According to this conventional type, it is possible to operate the opening and closing of the sub-throttle valve in conjunction with the opening and closing of the main throttle valve, but it is not possible to control the opening and closing by the intake negative pressure in the main intake passage. Another problem is that the sub-throttle valve is closed when the engine is stopped, which blocks the fuel wall flow in the main intake passage during a cold start, making it impossible to supply a rich mixture suitable for starting. There was a problem with this point. The reason why the opening/closing control using the intake negative pressure is difficult is that when the intake negative pressure is small such as during normal operation, the auxiliary throttle valve must be opened by going against the return spring. This is because an opposite operating force is required. SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to make the sub-throttle valve a normally open type, thereby enabling direct opening/closing control using intake negative pressure, thereby solving the above-mentioned drawbacks of the conventional throttle valve.

That is, the engine intake device according to the present invention includes a main intake passage communicating with a combustion chamber via an intake valve, a main throttle valve provided in the main intake passage, and a main intake passage connected to the main intake passage downstream of the main throttle valve. a sub-throttle valve that is provided in the passage and closes during low-load operation; an outlet that opens into the main intake passage downstream of the sub-throttle valve and upstream of and near the intake valve; and an outlet that opens into the main intake passage on the upstream side of the sub-throttle valve. The combustion chamber has a sub-intake passage with an inlet opening into the combustion chamber, and during low-load operation, intake air is drawn into the combustion chamber only from the sub-intake passage. The throttle valve is a normally open type having means for biasing the valve to the valve position, and is provided with means for closing the sub-throttle valve by negative intake pressure in the main intake passage during low-load operation.

In this case, a return spring biases the sub-throttle valve in the direction of the opening position, and a return spring is connected to the sub-throttle valve and presses against the return spring when the intake negative pressure becomes greater than a predetermined value. It is preferable to use a diaphragm that displaces the throttle valve to the closed position because the structure can be simplified.

Note that the return spring includes a compression spring disposed in contact with the diaphragm so as to bias the diaphragm against the intake negative pressure;
Alternatively, it is possible to use a tension spring or the like attached to bias the sub-throttle valve to the open position.

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a diagram showing the main parts of an engine having an intake system according to the present invention. The upper surface of the piston 14 fitted into the engine cylinder 12 and the cylinder head 15
A combustion chamber 16 is defined between the two, and an ignition plug 18, an intake valve 20, and an exhaust valve 22 are provided in the combustion chamber. Cams 24 and 26 are provided in the upper part of the cylinder head 15 to control the opening and closing of the intake valve and the exhaust valve. Exhaust from the exhaust valve 22 is exhausted through an exhaust passage 28.

Reference numeral 30 indicates a two-barrel type carburetor forming part of the intake system, the intake port of which is connected to the main intake passage 32, that is, passage sections 32A, 32B, 32.
It communicates with the intake valve 20 through C. A main throttle valve 34 is provided in the main intake passage to control the amount of air-fuel mixture supplied. The structure of the carburetor 30 including this main throttle valve is substantially the same as that of a well-known structure.

A normally open sub-throttle valve 40 that is closed only during low-load operation is provided downstream of the main throttle valve 34 . This sub-throttle valve is mechanically connected to a diaphragm 44 in a diaphragm device 42 via a connecting member 46. A negative pressure introducing chamber 48 is defined above the diaphragm of the diaphragm device (in FIG. 1), and the chamber 48 is connected to the main throttle valve 34 through a line 50.
It communicates with the main intake passage on the more downstream side, that is, the intake negative pressure generation region. A compression spring 52 is disposed within the negative pressure introduction chamber 48 and abuts against the diaphragm 44 to bias it downward (in FIG. 1). Therefore, if the intake negative pressure is less than a predetermined value or there is no intake negative pressure, the diaphragm 44 is displaced downward by the spring 44,
The sub-throttle valve 40 connected thereto is always held in the open position. That is, the diaphragm spring 52 is also used as a return spring for the normally open sub-throttle valve 40. On the other hand, when the intake negative pressure increases during low-load operation including idling and reaches a predetermined value or more, the diaphragm 44 moves upward and closes the sub-throttle valve 40 connected thereto.

A sub-intake passage 60 is provided to bypass the sub-throttle valve 40. The outlet 62 of the auxiliary intake passage opens into the main intake passage 32 at a position near the upstream side of the intake valve 20. On the other hand, an inlet 64 of the sub-intake passage 60 is provided between the main throttle valve 34 and the sub-throttle valve 40. The cross-sectional area of the auxiliary intake passage is suitably about one-tenth of the cross-sectional area of the main intake passage.

FIGS. 2 to 5 are diagrams showing an air intake device of the present invention having other configurations. This intake device has the main throttle valve 34 and the sub-throttle valve 40 connected by a link mechanism 70 having lost motion, and the sub-throttle valve 40
A tension spring 72 urges the opening position.
This differs from the intake device shown in FIG. 1 in that it is additionally provided, but the other configurations are substantially the same.

FIG. 2 is a diagram showing the state of the intake system before starting the engine. There is no intake negative pressure before the engine starts, that is, when the engine is stopped. Therefore, the inside of the negative pressure introducing chamber 48 of the diaphragm device 42 is at atmospheric pressure, and the diaphragm 44 is maintained at the lower position (in FIG. 2) by the spring 52. Therefore, the sub-throttle valve connected to the diaphragm 44 is in the open position as in the case of FIG. In the configuration shown in FIG. 2, a tension spring 72 is further provided, and this spring also urges the sub-throttle valve 40 to the open position (see FIG. 4).

FIG. 3 is a diagram showing a state when the engine is started and then is operated at a low load, and a large intake negative pressure is applied. During this low-load operation, a large intake negative pressure is introduced into the negative pressure introducing chamber of the diaphragm device 42, and the diaphragm 44 is moved by the spring 52 by the negative pressure.
and 72 and is sucked upward. For this reason,
The sub-throttle valve 40 connected to the diaphragm is moved to the closed position. Details of the mounting portion of the sub-throttle valve 40 during low-load operation shown in FIG. 3 are shown in FIG. 5.

However, in the configurations shown in FIGS. 2 to 5,
The main throttle valve 34 and the sub-throttle valve 40 are connected by a link mechanism 70 having a lost motion or elongated hole engagement connecting member 74 . Main throttle valve 34
is opened from the closed or small opening position shown in FIG. 3, and when the opening increases to normal operation or output operation, the link mechanism 70 moves in the direction of arrow A in FIGS. 3 and 5.
Move in the direction shown. The other end of the link mechanism is an arm 7 rotatably supported on the shaft of the sub-throttle valve 40.
6, and the arm 76 is adapted to engage with a hook 78 fixed to the shaft of the sub-throttle valve when the sub-throttle valve 40 is closed (FIG. 5). . Therefore, if the opening operation of the sub-throttle valve 40 is delayed, such as when the opening degree of the main throttle valve 34 is suddenly increased, the opening operation of the sub-throttle valve 40 is mechanically performed via the link mechanism 70 in accordance with the movement of the main throttle valve 34. It has become possible to do so.

Since the intake device of the present invention has the configuration and operation described above, the following effects can be obtained.

The main intake passage is provided with a main throttle valve and a sub-throttle valve downstream of the main throttle valve. It has an outlet that opens into the passage, and an inlet that opens into the main intake passage on the upstream side of the sub-throttle valve.During low-load operation, the sub-throttle valve closes and intake air is drawn only through the sub-intake passage.
Since the intake air is drawn only through the intake passage even during low-load operation, the intake air flow rate can be increased even during low-load operation, and the swirl of intake air within the combustion chamber can be strengthened, thereby improving the combustion state. In particular, in the present invention, the auxiliary throttle valve 40, which operates to close only during low negative operation including idling, is always urged to the open position by the return springs 52, 72, etc., so that the auxiliary throttle valve is not opened or closed. The operation can now be performed using intake negative pressure. Therefore, it has become possible to control the sub-throttle valve extremely easily.

In other words, when the intake negative pressure is high during low-load operation, this negative pressure suction force can be used to close the sub-throttle valve, and when the suction negative pressure is low during high-load operation, the valve is automatically returned to the open position. be able to.

In addition, the sub-throttle valve can be automatically opened both when the engine is stopped (before starting) and when the main throttle valve is open (from normal operation to fully open), making it possible to open the sub-throttle valve automatically. It can be matched to your requirements.

Furthermore, when the intake negative pressure increases during deceleration, the sub-throttle valve can be operated to close, and when the intake negative pressure decreases during acceleration, the valve can be opened automatically. It is possible to ensure that the original requirements are met.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of the main parts of an engine equipped with the intake system of the present invention, and FIG. Figure 3 is a sectional view of the main parts showing the same state as in Figure 2 during low load operation after starting the engine, Figure 4 is a side view showing details of the sub-throttle valve mounting part in the state of Figure 2, and Figure 5. The figure is a side view showing details of the sub-throttle valve mounting part in the state shown in FIG. 3. In each figure, the same reference numbers indicate the same or corresponding parts, 12...engine cylinder, 14...piston, 15...cylinder head, 20...intake valve,
30... Carburetor, 32... Main intake passage, 32A,
32B, 32C... Passage portion of main intake passage, 34
...Main throttle valve, 40...Sub-throttle valve, 42...Diaphragm device, 44...Diaphragm, 48...
Negative pressure introduction chamber, 52... compression spring (return spring), 60... auxiliary intake passage, 62... outlet,
64... Inlet, 70... Link mechanism, 72... Tension spring (return spring), 74... Lost motion type connecting member, respectively.

Claims (1)

[Scope of Claims] 1. A main intake passage communicating with a combustion chamber via an intake valve, a main throttle valve provided in the main intake passage, and a main throttle valve provided in the main intake passage downstream of the main throttle valve. a sub-throttle valve that closes during low-load operation; an outlet that opens into the main intake passage on the downstream side of the sub-throttle valve and also upstream of and near the intake valve; and an outlet that is upstream of the sub-throttle valve and downstream of the main throttle valve. In an intake system for an engine, the engine has a sub-intake passage having an inlet opening into the main intake passage, and intake air is drawn into the combustion chamber only from the sub-intake passage during low-load operation. The intake valve of the engine is characterized in that the valve is a normally open type having means for biasing the valve to the open position, and means is provided for closing the sub-throttle valve by intake negative pressure in the main intake passage during low load operation. Device. 2. In the above item 1, the means for closing the sub-throttle valve includes a return spring that biases the sub-throttle valve in the direction of the opening position, and a return spring that is connected to the sub-throttle valve and that closes the sub-throttle valve when the intake negative pressure exceeds a predetermined value. An intake system for an engine, comprising a diaphragm that displaces the sub-throttle valve to a closed position against the return spring when the diaphragm increases in size. 3. The engine intake system according to item 2, wherein the return spring is a compression spring arranged to bias the diaphragm against the intake negative pressure. 4. The engine intake system according to item 2, wherein the return spring is a tension spring that urges the sub-throttle valve to an open position.