JPS6019971Y2 - engine intake system - Google Patents

Description

[Detailed description of the invention] The invention provides a low-load intake passage equipped with a low-load carburetor and a high-load intake passage equipped with a high-load carburetor that are each independently opened into the combustion chamber of the engine. The improvement of the intake characteristics of the so-called multiple intake system, especially in the area where only the low-load carburetor is used (hereinafter referred to as the area where only the carburetor is used).

) to the combined use area of low-load and high-load vaporizers (hereinafter referred to as the combined use area).

) is concerned with improving the air-fuel mixture supply characteristics during the transition period.

Traditionally, this type of dual intake device has been well known.
At low to medium loads, including engine idling, only the small-diameter low-load intake passage is used to increase the air-fuel mixture flow velocity.
While promoting vaporization and atomization of the fuel, when the engine is under high load, the air-fuel mixture is also supplied from the high-load intake passage to improve output, so to speak, to obtain intake characteristics that match the operating conditions of the engine. It has the advantage of being able to

The above-mentioned dual intake device is, for example, a diaphragm device that utilizes the venturi negative pressure of the low-load carburetor and opens the throttle valve of the high-load carburetor when the venturi negative pressure reaches a set value. There is a known type in which the air-fuel mixture is started to be supplied from the high-load carburetor when activated.

By the way, this type of dual intake system uses the venturi negative pressure of the low-load carburetor to start supplying the air-fuel mixture from the high-load carburetor, so it can be used from a single use area to a combined use area. During the transition period, the opening timing of the throttle valve of the high-load carburetor is delayed, and as a result, the air-fuel mixture becomes insufficient.
As shown by the solid line B in the figure, it has been recognized that there is a problem that causes a decrease in engine output during the transition period.

This is because in a dual intake system, the cross-sectional area of the low-load intake passage is narrowed in order to increase the air-fuel mixture flow rate, so the effect of the passage resistance of the low-load intake passage becomes noticeable just before entering the above combination area. This is due to the fact that the venturi negative pressure of the low-load carburetor reaches a saturated state, so the venturi negative pressure obtained as a signal is small.

For this reason, in the past, the eccentricity of the throttle valve shaft of the high-load carburetor was set small in order to open the throttle valve of the high-load carburetor with a small venturi negative pressure, or the eccentricity of the throttle valve shaft of the high-load carburetor was set small, or the spring incorporated in the diaphragm device was A system has been proposed in which the spring force is set to a small value, but in that case, the return of the throttle valve deteriorates, resulting in a problem of deterioration of engine performance.

Therefore, the present invention can supply the necessary air-fuel mixture at the time of transition from the single use area to the combination use area without worsening the return of the throttle valve, and can prevent a decrease in engine output during the transition period. Its purpose is to provide intake systems for engines.

Therefore, in the present invention, an auxiliary mixture supply passage is provided that opens into the high-load intake passage downstream of the throttle valve of the high-load carburetor, and an on-off valve is provided in the middle of the passage. A detection device is provided to detect the timing of transition to the transition region, and when the throttle valve of the high-load carburetor is closed at least at the transition timing, the opening/closing valve is actuated by the detection signal of the detection device to open the auxiliary mixture supply passage. The basic feature is that the auxiliary air-fuel mixture is supplied to the high-load intake passage downstream of the throttle valve of the high-load carburetor.

Hereinafter, the present invention will be specifically explained with reference to the illustrated embodiments.

In Fig. 1, 1 is an air cleaner, 2 is a low-load carburetor 3 (hereinafter simply referred to as the P-side carburetor), and a high-load carburetor 4.
5 is an intake manifold connected to the duplex carburetor 2, 6 is a cylinder head, and 7 is a combustion chamber 8 inside together with the cylinder head 6. In the cylinder body that defines the intake manifold 5, an intake passage 5p with a small passage cross-sectional area and an intake passage 5S with a large passage cross-sectional area are separated by a partition wall 9. The former intake passage 5p is connected to the P side carburetor 3. Intake passage 3p
and an internal intake passage 6p with a small passage cross-sectional area separated by a separation wall 10 in the cylinder head 6,
A low-load intake passage 11 (hereinafter referred to as the P-side intake passage) supplies the air-fuel mixture supplied by the P-side carburetor 3 to the combustion chamber 8.

) to form.

Similarly, the latter intake passage 5s is supplied by the S side carburetor 4 together with the intake passage 4s of the S side carburetor 4 and the internal intake passage 6s with a large passage cross-sectional area separated by a separation wall 10 in the cylinder head 6. A high-load intake passage 12 (hereinafter referred to as an S-side intake passage) supplies the air-fuel mixture to the combustion chamber 8 independently of the P-side intake passage 11.

) is formed. On the other hand, 13 is the throttle valve 1 of the S side carburetor 4.
Diaphragm device for opening and closing 5, 16 is P side, S
This is a venturi negative pressure introduction passage provided in the partition wall 2a separating the side carburetors 3 and 4, and the passage 16 is connected to the venturi portions 17 and 18 of the P side carburetor 3 and the S side carburetor 4, respectively, on the P side and the S side. Venturi negative pressure outlets 19, 20 (the S-side negative pressure outlet 20 is provided to ensure that the throttle valve 15 of the S-side carburetor 4 is opened after the throttle valve 15 of the S-side carburetor 4 is opened). There is.

), and the P side venturi negative pressure taken out is connected to the negative pressure conduit 21.
is introduced into the negative pressure chamber 13a of the diaphragm device 13 through the diaphragm device 13.

The diaphragm device 13 includes a negative pressure chamber 13a and an atmospheric chamber 13.
The actuating rod 13d has a base fixed to a diaphragm 13c that partitions the S-side carburetor 4, and a tip connected to the tip of an opening/closing lever 22 fixed to the outer shaft end of the eccentric valve shaft 15a of the throttle valve 15 of the S-side carburetor 4. , P introduced into the negative pressure chamber 13a
When the side venturi negative pressure reaches the set value or more, the negative pressure chamber 13
The actuating rod 13d is pulled in by overcoming the set load of the spring 13e compressed in the inside a, and the opening/closing lever 22 is swung to open the throttle valve 15 of the S side carburetor 4.

Further, the upstream side of 25 communicates with the fuel passage 26 of the P-side carburetor 3 and the air passage 29 opened to the P-side intake passage 11 upstream of the venturi section 17 of the P-side carburetor 3, and the downstream side of the 25 communicates with the S-side carburetor 4. An auxiliary mixture supply passage 27 is a diaphragm type opening/closing valve device provided in the middle of the auxiliary mixture supply passage 25, and an operating rod 27b is connected to the diaphragm 27a. When the auxiliary mixture supply passage 5 is opened by operating the on-off valve 28 supported through the auxiliary mixture supply passage 25, the auxiliary mixture supply passage 25 receives the mixture of air and fuel introduced from the air passage 29 and the fuel passage 26. It is supplied to the S-side intake passage 12.

The diaphragm type on-off valve device 27 is a diaphragm 27
The first section separated by a. Second negative pressure chamber 27pw27s
The first negative pressure chamber 27p has a throttle valve 14 of the P side carburetor 3.
A first valve having a negative pressure outlet 30 in the downstream P-side intake passage 11
While communicating with the negative pressure conduit 31, S is connected to the second negative pressure chamber 27s.
A second negative pressure conduit 33 having a negative pressure outlet 32 is communicated with the S side intake passage 12 downstream of the throttle valve 15 of the side carburetor 4 .

Now, the pressure difference ΔP1 between the intake negative pressure Pα acting on the negative pressure outlet 30 and the intake negative pressure Pβ acting on the negative pressure outlet 32 is the first negative pressure chamber 27p and the second negative pressure chamber 27s. Considering the differential pressure ΔP that occurs between the
4), this differential pressure ΔP increases as the number of rotations of the engine increases and peaks at the transition period from the single use area to the combined use area.

Therefore, by appropriately setting the set load of the spring 27c compressed in the second negative pressure chamber 27s of the tire flam type opening/closing valve device 27 to a value appropriately smaller than the peak value of the differential pressure ΔP, the above-mentioned transition can be achieved. The opening/closing valve 28 supported on the operating rod 27b can be opened only at the specified time.

In the above configuration, when the engine uses only the P side carburetor 3 at low, medium load, low and medium speeds, the throttle valve 15 of the S side carburetor 4 remains fully closed), and the P side carburetor 3 The air-fuel mixture supplied from the P-side carburetor 3 according to the opening degree of the throttle valve 14 flows down at a high flow velocity through the P-side intake passage 11 with a narrowed passage cross-sectional area, so that atomization and vaporization of the fuel are promoted. On the other hand, it flows into the combustion chamber 8 from the intake hole 36 opened by the intake valve 35 while maintaining its flow velocity, and a swirl is created in the combustion chamber 8, so that the combustion performance of the engine can be improved. .

Next, in the independent use area of the P side carburetor 3, the throttle valve 14 of the P side carburetor 3 is fully opened and the engine speed is increased, and when the transition period to move to the combined use area is reached, the P side negative pressure outlet There is a relatively large pressure difference ΔP between the intake negative pressure Pα acting on the S side negative pressure outlet 30 and the intake negative pressure Pβ acting on the S side negative pressure outlet 32.
occurs.

That is, when the throttle valve 14 of the P-side carburetor 3 is opened wide and the air-fuel mixture flow rate in the P-side intake passage 11 increases, the influence of passage resistance increases, and as a result, the The intake negative pressure immediately below the throttle valve 14, that is, the intake negative pressure Pα acting on the first negative pressure outlet 30, decreases relatively.

On the other hand, the intake negative pressure Pγ directly above the intake valve 35 is higher than the intake negative pressure Pα by the passage resistance of the P-side intake passage 11, and the intake negative pressure acting on the second negative pressure outlet 32 is higher than the intake negative pressure Pα by the passage resistance of the P-side intake passage 11. Pβ
Since the throttle valve 15 of the S side carburetor 4 is fully closed, the intake negative pressure Pγ directly above the intake valve 35 is equal to S, and as a result, the intake air acting on the first negative pressure outlet 30 Negative pressure Pα
is smaller than the intake negative pressure Pβ acting on the second negative pressure outlet 32, creating a significant pressure difference ΔP between them.

This differential pressure ΔP acts in the direction of opening the on-off valve 28 supported by the diaphragm on-off valve device 27, and eventually overcomes the set load of the spring 27c in the second negative pressure chamber 27s to open the on-off valve 28 and assist The mixture supply passage 25 is opened.

Therefore, the air-fuel mixture is supplied to the S-side intake passage 12 downstream of the throttle valve 15 of the S-side carburetor 4 via the auxiliary mixture supply passage 25 while the S-side throttle valve 15 remains fully closed. This assists the air-fuel mixture that cannot be handled by the P-side intake passage 11 alone.

During this transition period, the P side venturi negative pressure increases,
This rise is taken out from the P side venturi negative pressure outlet 19, and the negative pressure chamber 13a of the diaphragm device 13 opens and closes the throttle valve 15 of the S side carburetor 4 via the negative pressure introduction passage 16 and the negative pressure conduit 21. transmitted to.

As a result, the diaphragm 13c overcomes the set load of the spring 13e and is biased in the direction of retracting the supported operating rod 13d, opening the throttle valve 15 of the S-side carburetor 4 via the opening/closing lever 22, and opening the throttle valve 15 of the S-side carburetor 4. 4 starts supplying the air-fuel mixture with the opening operation of the throttle valve 15 of the S side carburetor 4, and shifts to the combined use area.

On the other hand, when shifting to the combination area, the negative intake pressure Pα directly below the P-side carburetor 3 throttle valve 14 of the P-side intake passage is
The air-fuel mixture gradually decreases as the flow velocity decreases due to the increase in passage area associated with the opening of the air-fuel mixture, and as a result, the air-fuel mixture also flows into the S-side intake passage 12. As a result, the intake negative pressure Pβ immediately below the throttle valve 15 of the S-side carburetor 4 becomes It relatively decreases, and the differential pressure ΔP between the two decreases.

Then, as the differential pressure ΔP decreases, the diaphragm type on-off valve 27 closes the supported on-off valve 28 as the set load of the spring 27c of the second negative pressure chamber 27s overcomes the differential pressure ΔP, and the auxiliary mixture supply passage 25 is fully closed again to stop supplying the auxiliary mixture.

Thereafter, the engine output can be ensured mainly by the necessary and sufficient air-fuel mixture supplied by the S-side carburetor 4.

Then, by supplying the auxiliary mixture during the transition period mentioned above,
The engine output is smoothly shifted to the combined use range without decreasing as shown by A in FIG. 2, and there is no temporary drop in engine output as shown by B in the prior art.

In the embodiment shown in FIG. 4, a diaphragm type on-off valve device 27' interposed in the middle of the auxiliary mixture supply passage 25 is connected to the intake valve downstream of the throttle valve 15 of the S-side carburetor 4 in the S-side intake passage 12. Pressure P
β, and the intake negative pressure Pβ is introduced into the negative pressure chamber 27's of the diaphragm type on-off valve device 27'.
Control is performed using the intake negative pressure Pα downstream of the throttle valve 14 of the P-side carburetor 3 in the P-side intake passage 11.

Therefore, the throttle valve 15 of the S side carburetor 4 in the S side intake passage 12
A negative pressure conduit 33' that leads the S side negative pressure outlet 32 set downstream to the negative pressure chamber 27'S of the diaphragm type on-off valve device 27'.
Connect the IJ-F passage 40 in the middle of the IJ
The atmosphere open end 40a of the IJ-F passage 40 is connected to the intake negative pressure outlet 3 downstream of the throttle valve 14 of the P side carburetor 3 of the P side intake passage 11.
The diaphragm device 41 is supported in an atmosphere opening chamber 41a of a diaphragm device 41 which is opened and closed by the intake negative pressure Pα acting on the air.

The diaphragm device 41 includes an atmosphere opening chamber 41a provided with an atmosphere opening 41b, and a negative pressure conduit 3 connected to the P side negative pressure outlet 30.
The diaphragm 41d that partitions off the negative pressure chamber 41c communicated through 1' is used as a valve body for the tip opening 40a of the relief passage 40, and the throttle valve 14 of the P side carburetor 3 is sequentially operated to prevent the P side intake. When the negative pressure Pα reaches a set value or less, the diaphragm 41d closes the tip opening 40a by the spring force of a spring 41e compressed in the negative pressure chamber 41c, and the relief is stopped.

When relief to the atmosphere is stopped, the S-side intake negative pressure Pβ is directly introduced into the negative pressure chamber 27'S of the diaphragm type on-off valve device 27' through the negative pressure conduit 33', The diaphragm 27'a that partitions the negative pressure chamber 27'S and the negative pressure chamber 27'p overcomes the set load of the spring 27'c to open the on-off valve 28 supported on the operating loft 27'b, thereby opening the auxiliary mixture supply passage. 25 starts supplying the auxiliary air-fuel mixture to the S-side intake passage 12 downstream of the throttle valve 15 of the S-side carburetor 4.

The timing of starting and stopping the auxiliary air-fuel mixture can be determined by appropriately selecting the set load of the flap ring 41e in response to the decrease in the P-side intake negative pressure Pα during the transition period as described above.

This embodiment has no other differences from the previous embodiment except for the above points, so the same parts are given the same numbers and further explanation will be omitted.

As is clear from the detailed explanation above, the present invention provides an auxiliary mixture supply passage for guiding the auxiliary mixture to the S-side intake passage in a dual intake system for an engine, and also provides an on-off valve in the middle of the passage. On the other hand, a detection device is provided to detect the timing of transition from the single use area to the combined use area, and the opening/closing valve is actuated by the detection signal of the detection device when the vent valve of the high-load carburetor is closed at least during the transition period. The present invention provides an engine intake device in which an auxiliary air-fuel mixture is supplied to an S-side intake passage downstream of a throttle valve of an S-side carburetor.

Therefore, according to the present invention, the air-fuel mixture can also be supplementarily supplied from the S-side intake passage at the time of transition from the single use area to the combined use area, and the opening timing of the throttle valve of the S-side carburetor can be brought forward. It is possible to secure the necessary amount of air-fuel mixture without any change, and therefore, there is an advantage that a smooth transition is possible without causing a decrease in engine output during the transition period.

[Brief explanation of the drawing]

Fig. 1 is a cross-sectional explanatory diagram of essential parts showing one embodiment of an engine intake system according to the present invention, and Fig. 2 shows a transition from a single use area to a combined use area with engine rotational speed on the horizontal axis and engine torque on the vertical axis. Figure 3 is a graph showing torque changes over time, and shows the intake negative pressure Pα in the P-side intake passage and the intake negative pressure Pβ in the S-side intake passage with respect to the engine speed when the throttle valve of the P-side carburetor is fully open. FIG. 4 is a cross-sectional explanatory view of a main part similar to FIG. 1 showing another embodiment of the engine intake system according to the present invention. 3...P side carburetor, 4...S side carburetor, 11...P side intake passage, 12...S
Side intake passage, 13... Diaphragm device for opening and closing the throttle valve of the S side carburetor, 14... Throttle valve of the P side carburetor, 15... S side carburetor Throttle valve, 25...
...Auxiliary mixture supply passage, 27, 27'...Diaphragm type on-off valve device, 30...P side intake negative pressure outlet, 32...S side intake negative Pressure outlet.

Claims (1)

[Claims for Utility Model Registration] A low-load intake passage equipped with a low-load carburetor and a high-load intake passage equipped with a high-load carburetor are each independently opened into the combustion chamber. In an engine intake system, the engine intake system is equipped with a diaphragm device that is operated by negative pressure in a venturi section of a commercial carburetor and opens a throttle valve of the high-load carburetor when the negative pressure reaches a set value or more. An auxiliary mixture supply passage that opens into the high-load intake passage downstream of the throttle valve of the high-load carburetor and is equipped with an on-off valve, and a low-load and high-load carburetor from the area where only the low-load carburetor is used. A detection device is provided for detecting the timing of transition to the combined use area of the vaporizer, and at least when the throttle valve of the high-load vaporizer is closed during the transition period, the opening/closing valve is opened by the signal of the detection device to perform auxiliary mixing. An intake system for an engine, characterized in that an auxiliary air-fuel mixture is supplied to a high-load intake passage downstream of a throttle valve of a high-load carburetor from an air supply passage.