JPS5918530B2 - Internal combustion engine intake system - Google Patents

Description

[Detailed description of the invention] The present invention relates to an intake system for an internal combustion engine.

Usually, particularly in gasoline engines, the intake boat is formed into a boat shape with low fluid resistance in order to increase charging efficiency during high-speed, high-load operation and thereby obtain sufficient output.

However, when such a boat shape is used, during high-speed, high-load operation, a naturally occurring and quite strong turbulence is generated in the combustion chamber, so the combustion speed can be sufficiently increased, but during low-speed, low-load operation, sufficient turbulence does not occur within the combustion chamber. Therefore, there is a problem that the combustion rate cannot be sufficiently increased.

Methods of generating strong turbulence during low-speed, low-load operation include making the intake boat a helical shape or using a shroud valve to forcefully generate a swirling flow within the combustion chamber. There is a problem in that charging efficiency decreases during high-speed, high-load operation due to increased resistance.

Therefore, in order to increase the combustion rate during low-speed, low-load operation while ensuring high charging efficiency during high-speed, high-load operation, the intake boat must be formed into a boat shape with low fluid resistance, and at the same time, a powerful You have to try to cause some disturbance.

Furthermore, as a method of improving combustion during low-speed, low-load operation, in addition to generating strong turbulence within the combustion chamber, there is also a method of promoting vaporization of the fuel.

That is, during low-speed, low-load operation, the flow rate of air flowing through the venturi section of the carburetor is slow, and therefore the relative velocity between the injected fuel and the air flow is slow, making it impossible to atomize the fuel sufficiently, and as a result, a large amount of fuel is is a liquid one! - is supplied into the combustion chamber, which is one of the causes of deteriorating combustion and deteriorating exhaust emissions.

On the other hand, as is well known, knocking is more likely to occur when the engine is operating at low speeds and high loads, so in order to prevent this knocking, the ignition timing is usually delayed during low speed and high load operations.

However, delaying the ignition timing in this manner not only worsens the fuel consumption rate but also reduces engine output.

Another method for preventing such knocking is to generate strong turbulence within the combustion chamber during low-speed, high-load operation.

In this way, in order to increase the combustion rate during low-speed, low-load operation with a small amount of intake air, and furthermore to prevent knocking during low-speed, high-load operation with a relatively small amount of intake air, it is necessary to increase the combustion rate when the amount of intake air is small. It is necessary to create a strong disturbance in the room.

In this way, as an internal combustion engine that can generate strong turbulence in the combustion chamber when the amount of intake air is small while ensuring high charging efficiency during high-speed, high-load operation of the engine with a large amount of intake air, A second throttle valve is provided in each intake branch passage of the flow, and each communication branch passage communicating with each intake branch passage downstream of the second throttle valve is connected to a common communication passage, and the second throttle valve is connected to a common communication passage. A negative pressure responsive throttle valve driving device connected to the valve is provided, and the pressure between the negative pressure generated in the intake passage between the carburetor throttle valve and the second throttle valve and the negative pressure generated in the common communication passage. The applicant has proposed an internal combustion engine equipped with a negative pressure control valve that controls the negative pressure applied to the negative output of the negative pressure-responsive throttle cell drive device in response to the pressure difference so that the pressure difference remains constant. There is.

As mentioned above, this internal combustion engine takes in the opening of the second throttle valve by controlling the opening of the second throttle valve so that the pressure difference between the upstream side and the downstream side of the second throttle valve is maintained constant. Increase the size according to the increase in air volume,
This is intended to ensure high charging efficiency during high-load, high-speed operation of the engine with a large amount of intake air, while also causing the air-fuel mixture to be ejected from the communicating branch passage when the amount of intake air is low, creating strong turbulence within the combustion chamber. ing.

However, this internal combustion engine actually has a problem in that the pressure difference between the upstream side and the downstream side of the second throttle valve cannot be maintained accurately and constant at all times.

That is, in this internal combustion engine, the above-mentioned negative pressure control valve has a high pressure chamber and a low pressure chamber separated by a control diaphragm, and these high pressure chambers and low pressure chambers are connected to the intake air on the upstream side and downstream side of the second throttle valve, respectively. A valve chamber is connected to the negative pressure generation area of the pipe, and a valve chamber is further attached to the high pressure chamber through a partition wall, and an atmosphere communication control valve is provided in the valve chamber to control the opening and closing of an atmosphere communication boat opened in the valve chamber. The control valve is connected to the control diaphragm by passing through the partition wall, and the valve chamber is connected to the negative end of the negative pressure responsive throttle valve drive device on the one hand, and the second throttle valve through the negative pressure conduit on the other hand. It is connected to the negative pressure generation area of the intake pipe on the upstream side, and when the pressure difference between the high pressure chamber and the low pressure chamber deviates from a predetermined value, the control diaphragm moves and the atmosphere communication control valve controls the air bleed action from the atmosphere communication boat. Thereby, the negative pressure applied to the negative chamber of the negative pressure responsive throttle valve drive device is controlled, and the second throttle valve is driven and controlled so that the pressure difference between the high pressure chamber and the low pressure chamber becomes a predetermined value. ing.

In this negative pressure control valve, in order to prevent pressure leakage between the high pressure chamber and the valve chamber, the partition wall that separates these compartments is composed of a separation diaphragm, and the valve rod of the atmospheric communication control valve is connected to the separation diaphragm. It is fixed through the center part.

However, the negative pressure acting on the high pressure chamber from the mosquito is from near atmospheric pressure to -
550m71Hg, whereas the negative pressure generated inside the valve chamber is maintained in the range of -100yuiHg to -1150Hg, so the pressure difference between the atmospheric pressure chamber and the valve chamber fluctuates greatly depending on changes in engine load. do.

For this purpose, if a separation diaphragm is provided as described above, the separation diaphragm will forcibly move the atmosphere communication control valve in response to changes in the engine load, disrupting the air bleed control action from the atmosphere communication boat, and as a result, the 2
It becomes difficult to maintain a constant pressure difference between the upstream side and the downstream side of the throttle valve at all times.

SUMMARY OF THE INVENTION An object of the present invention is to provide an intake device that can maintain a constant pressure difference across a second throttle valve at all times while ensuring high filling efficiency when the amount of intake air is large.

Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.

Referring to FIG. 1 and FIG. 2, 1 is a cylinder block, 2 is a piston that reciprocates within the cylinder block 1,
3 is a cylinder head fixed on the cylinder block 1, 4 is a combustion chamber, and 5ay5b.

5c, 5d are intake boats, 6a#6bj6cj6d are intake valves, 7a, 7b, 7c, 7d are exhaust ports, 8a, 8
b, 8c, and 8d indicate exhaust valves, and an ignition plug (not shown) is arranged in the combustion chamber 4.

In addition, in FIG. 2, 9a, t9b, t9c, and t9d indicate the first cylinder, the second cylinder, the third cylinder, and the fourth cylinder, respectively.

As shown in FIGS. 1 and 2, the intake manifold 10
A carburetor 11 having a carburetor throttle valve 12 is mounted on the manifold gathering portion 10a of the vehicle, and this carburetor throttle valve 12 is connected to an accelerator pedal provided in the vehicle cab.

On the other hand, the intake manifold 10 is fixed to the cylinder head 3 via a spacer 13, and a second throttle valve 14 is provided in the spacer 13 corresponding to each cylinder.

These second throttle valves 14 share a common throttle shaft 1.
5, and this throttle shaft 1 is fixed as shown in FIG.
The tip of the arm 16 fixed to the end of the arm 5 is connected to a control rod 18 of a diaphragm type throttle valve drive device 17.

This throttle valve drive device 17 has a negative pressure chamber 20 and an atmospheric pressure chamber 21 separated by a diaphragm 19, and a control rod 18 is fixed to the diaphragm 19.

In addition, a compression spring 2 for pressing the diaphragm is provided in the negative pressure chamber 20.
2 is inserted.

Furthermore, as shown in FIG. 1, a diaphragm type negative pressure control valve 23 is provided alongside the throttle valve drive device 17.

This negative pressure control valve 23 has a diaphragm retainer 25 that is movable within its maggot 24, and a low pressure chamber 27 and a high pressure chamber 28 separated by a diaphragm 26.

Further, a retainer guide chamber 29 is formed within the housing 24, and the small diameter head of the diaphragm retainer 25 is slidably fitted into this retainer guide chamber 29.

This retainer guide chamber 29 is connected to the high pressure chamber 28 via the negative pressure port 30, and therefore the negative pressure in the retainer guide chamber 29 is always equal to the negative pressure in the high pressure chamber 28.

On the other hand, a spring retainer 32 adjustable by an adjusting screw 31 is provided in the low pressure chamber 27, and a compression spring 33 for pressing the diaphragm is inserted between the spring retainer 32 and the diaphragm retainer 25.

Further, the negative pressure control valve 23 has a retainer guide chamber 29 and a valve chamber 3 arranged in the housing 24 with a partition wall 34 separating the valve chamber 3.
5, and an air hole 36 opens in this valve chamber 35.

A valve body 37 facing the air hole 36 is inserted into the valve chamber 35, and the valve body 37 is constantly pressed downward by the spring force of the compression spring 38.

On the other hand, a communication hole 39 is formed on the partition wall 34, and a control rod 40 supported by the diaphragm retainer 25 passes through the communication hole 39.

As shown in FIG. 1, the tip of the control rod 40 can protrude into the valve chamber 35, and the tip of the control rod 40 can also come into contact with the valve body 37.

Furthermore, an annular diaphragm having a small cross-sectional area is formed between the inner wall surface of the communication hole 39 and the outer peripheral surface of the control rod 40 .

Furthermore, the valve chamber 35 is connected to the negative royal chamber 20 via a negative pressure conduit 41, while the high pressure chamber 28 is connected to the upstream side of the second throttle valve 14 via a negative pressure conduit 42.

On the other hand, as shown in FIGS. 1 and 2, the spacer 13
A common communication passage 43 extending in the longitudinal direction of the cylinder head 3 is formed in the lower side of the cylinder head 3, and this common communication passage 43 and the intake bows 5a, 5b of each cylinder.

5c and four communication branch paths 44a connecting the insides of Sd.

44b, 44c, 44d are formed within the cylinder head 3.

Each of these communication branches 44a, 44b. 44c and 44d are directed toward the gap formed between the intake valve and its valve seat when the intake valve is opened.

Further, the low pressure chamber 27 of the negative pressure control valve 23 is connected to the common communication path 43 via a negative pressure conduit 45.

Figure 3 shows the intake bow of each cylinder during engine operation) 5a,
5b, 5c, and 5d are shown.

In Fig. 3, the horizontal axis θ indicates the crank angle, and the vertical axis indicates the pressure in the intake port near the back of the intake valve bulk portion (hereinafter referred to as intake port pressure), and each reference line A
, B, C, and D indicate atmospheric pressure.

In addition, curves E, F, G, and H are for each intake port 5a.
5b, 5c, and 5d, and arrows I, J, and L indicate the opening period of each intake valve 6ay6b, 6c, and 6d of the corresponding intake port.

Focusing on the No. 1 cylinder in Fig. 3, the pressure inside the intake port is positive in the crank angle range M immediately after the intake valve opens, and then in the crank angle range N when the piston is descending. It can be seen that the pressure becomes negative pressure, and then when the piston starts to rise, the pressure inside the intake port becomes positive pressure again.

Therefore, if we pay attention to the crank angle range P of the first and second cylinders in FIG. It can be seen that the pressure is positive.

Furthermore, in the crank angle range Q of the 2nd and 4th cylinders, when the pressure inside the 2nd cylinder's intake bow) 5b is negative pressure, the pressure inside the 4th cylinder's intake bow) 5d becomes positive pressure, and the pressure inside the 3rd cylinder and In the crank angle range R of the 4th cylinder, when the pressure inside the 4th cylinder's intake bow) 5b is negative pressure, the pressure inside the 3rd cylinder's intake bow) 5c' becomes positive pressure, and the pressure inside the 1st and 3rd cylinders becomes positive. In the crank angle range S, the intake bow of the 3rd cylinder) 5
It can be seen that when the pressure inside c is negative pressure, the pressure inside intake bow 5a of cylinder No. 1 becomes positive pressure.

Therefore, if we pay attention to the No. 1 and No. 2 cylinders, in the first half of the intake stroke in the No. 1 cylinder, the intake bow) Sa and the
The intake bow) 5 due to the pressure difference with the intake bow) 5b of the number cylinder
It can be seen from b that the air-fuel mixture is supplied into the intake air chamber Sa via the communication branch path 44b, the common communication path 43, and the communication branch path 44a.

Similarly, during the intake stroke of the 2nd cylinder, the intake bow of the 4th cylinder)
5d to communication branch path 44d, common communication path 43, communication branch path 4
The air-fuel mixture is supplied into the intake boat 5b via 4b,
During the intake stroke of the No. 3 cylinder, the air-fuel mixture is supplied from the intake boat 5c of the No. 3 cylinder to the intake boat Sd of the No. 4 cylinder, and during the intake stroke of the No. 3 cylinder, the air-fuel mixture is supplied from the intake boat 5a of the No. 1 cylinder to the
The air-fuel mixture is supplied into the intake bow 5c of the number cylinder.

In this way, during the intake stroke of each cylinder, the communication branches 44a correspond to each other.

44b, 44c, and 44d to each intake boat 5a.

The air-fuel mixture is supplied into 5b, 5c, and Sd due to the pressure difference within the intake boat.

As mentioned above, the air-fuel mixture is supplied to the intake boat where negative pressure is generated due to the pressure difference between the positive pressure and negative pressure generated in the intake port, but the positive pressure generated in the intake port is due to the second throttle. It is greatly affected by the opening degree of the valve 14.

That is, when the opening degree of the second throttle valve 14 is large, the positive pressure generated in the intake boat 5a due to the blowback action immediately escapes into the intake manifold 10 and is attenuated immediately. When the opening degree of the intake port 14 is large, the positive pressure generated within the intake port 5a becomes extremely small.

On the other hand, when the opening degree of the second throttle valve 14 is small, the second
The positive pressure generated in the intake boat 5a by the throttling action of the throttle valve 14 is maintained within the intake boat 5a without being significantly attenuated.

Therefore, when the opening degree of the second throttle valve 140 is small, for example, the positive pressure in the intake bow Sb is maintained without attenuation, so that the pressure difference between the negative pressure and the negative pressure in the intake bow Sb of the cylinder under the intake stroke is large. As a result, the air-fuel mixture is blown out from the communication branch 44a into the intake boat 5a at high speed.

On the other hand, each cylinder's intake boat 5 a s 5 b p 5
The negative pressure generated in the cy5d fluctuates as shown in FIG. As shown by curve Y in the figure, it becomes extremely small during pressure fluctuations.

In FIG. 4, the vertical axis P indicates the pressure within the common communication path 43, the horizontal axis θ indicates the crank angle, and the reference line X indicates atmospheric pressure.

During engine operation, negative pressure is generated within the intake manifold 10 downstream of the carburetor throttle valve 12, and this negative pressure is transferred to the negative pressure conduit 42.
It is applied to the high pressure chamber 28 of the negative pressure control valve 23 via.

On the other hand, the intake boats 5a, 5 downstream of the second throttle valve 14
b, 5c, and 5d, there is a second
A larger negative pressure is generated on the upstream side of the throttle valve 14,
This large negative pressure is transferred to the negative pressure control valve 23 via the negative pressure conduit 45.
is added to the low pressure chamber 27.

At this time, the pressure difference between the pressure in the intake manifold 10 upstream of the second throttle valve 14 and the pressure in the common communication passage 43, that is, the pressure difference between the high pressure chamber 28 and the low pressure chamber 27, is determined by the spring force of the compression spring 33. When the set pressure difference is greater than the set pressure difference, the diaphragm 26 moves downward against the compression spring 33, and as a result, the valve body 37 closes the communication hole 39 and opens the atmospheric hole 36.

As a result, air flows into the negative pressure chamber 20 of the throttle valve drive device 17.
When the negative pressure in the negative pressure chamber 20 becomes smaller, the diaphragm 19 is lowered by the spring force of the compression spring 22, and the second throttle valve 14 is thus rotated in the direction of the arrow.

As a result, the negative pressure downstream of the second throttle valve 14 becomes smaller and the negative pressure inside the common communication passage 43 becomes smaller, and accordingly, the pressure difference between the high pressure chamber 28 and the low pressure chamber 27 becomes smaller than the set pressure difference. The diaphragm 26 is moved upward by the spring force of the compression spring 33, and as a result, the valve body 37 closes the air hole 36 and opens the communication hole 39, as shown in FIG.

Therefore, at this time, the negative pressure in the negative pressure chamber 20 increases, so the diaphragm 19 rises against the compression spring 22, and the second throttle valve 14 rotates in the opposite direction to arrow A.

When the second throttle valve 14 rotates in the opposite direction of arrow A, the negative pressure on the downstream side of the second throttle valve 14 increases again, so that the valve body 37 closes the communication hole 39 and the air hole 3
6 is opened, and as a result, the second throttle valve 14 is rotated again in the direction of arrow A.

Such operations are repeated to maintain a constant pressure difference between the upstream side of the second throttle valve 14 and the common communication passage 43.

Note that the upstream side of the second throttle valve 14 and the common communication passage 43
The pressure difference to be maintained between the inside and the inside is the compression spring 3 of the negative pressure control valve 23
It can be set arbitrarily by the spring force of 3.

As mentioned above, the pressure difference between the upstream side of the second throttle 4jr14 and the common communication passage 43 is maintained constant, so when the amount of intake air is small, the opening degree of the second throttle valve 14 is small and the amount of intake air increases. It can be seen that the opening amount of the second throttle valve 14 increases accordingly.

On the other hand, during high-load operation when the carburetor throttle valve 12 is wide open, the negative pressure in the intake manifold 10 downstream of the carburetor throttle valve 12 becomes extremely small, so the high pressure chamber 28 and the low pressure chamber of the negative pressure control valve 23 27 is always smaller than the set pressure difference, thus the valve body 37
6 is closed and the communicating hole 39 is opened.

Therefore, at this time, the negative pressure chamber 20 of the throttle valve drive device 17
Negative pressure in the intake manifold 10 downstream of the carburetor throttle valve 12 is always applied inside the diaphragm 19, but since this negative pressure is extremely small as mentioned above, the diaphragm 19 is pushed to its lowest position by the spring force of the compression spring 22. As a result, the second throttle valve 14 is kept fully open.

In this way, when the amount of intake air is small, the opening degree of the second throttle valve 140 becomes small, but at this time, as mentioned above, the pressure difference between the positive pressure and the negative pressure between the intake ports becomes large. The air-fuel mixture is blown out at high speed into the intake port 5d.

As mentioned above, since the opening of the communication branch 44d is oriented toward the gap formed between the intake valve 6d and its valve seat when the intake valve is opened, the air-fuel mixture ejected from the communication branch 44d passes through the gap and is combusted. It flows into the chamber 4 at a high velocity.

As a result, a strong swirling flow as shown by the arrow W in FIG. 2 is generated in the combustion chamber 4, and the combustion speed is thus greatly increased.

On the other hand, when the amount of intake air increases, the second throttle valve 14 opens fully, so that high filling efficiency can be ensured.

Another embodiment is shown in FIGS. 5 and 6.

In this embodiment, the central part of the common communication passage 43 is the sub-intake passage 4.
6 into the intake manifold 10a.
connected to.

On the other hand, as shown in FIG. 5, a second common communication passage 48 is formed in the upper side of the spacer 13, and this second common communication passage 48 is connected to the second throttle valve 14 through a communication branch passage 49.
It is connected to each downstream intake port) 5a, 5b, 5c, and Sd.

This second common communication passage 48 is connected to the low pressure chamber 27 of the negative pressure control valve 23 via the negative pressure conduit 50, and thus, in this embodiment as well, when the amount of intake air is small, the second throttle valve 14 is closed. When the opening degree is small and the amount of intake air increases, the second throttle valve 14 is fully opened.

Therefore, when the amount of intake air is small, part of the air-fuel mixture formed in the carburetor 11 is transferred to the auxiliary intake passage 46 and the common communication passage 4.
3 and communication branches 44a, 44b, 44c, 44
It ejects into the intake ports 5a, sb t5c, and 5d through df.

As shown in FIGS. 5 and 6, these auxiliary intake passages 46, common communication passages 43, and communication branch passages 44a.

The cross-sectional area of 44b, 44c, and 44d is that of the intake ports 5a and 5.
The cross-sectional areas of the passages b, 5c, and 5d are much smaller, and therefore, the air-fuel mixture flows through these passages at a high speed, promoting vaporization of the fuel during this time.

On the other hand, the sixth
A strong swirling flow as shown by the arrow W in the figure is generated, and as a result, the burnup is greatly increased.

On the other hand, when the amount of intake air increases, the second throttle valve 14 is fully opened, and most of the air-fuel mixture flows through the intake manifold branch pipes and intake ports 5a, 5b, 5c, and 5, which have low flow resistance.
Since the fuel is supplied into the combustion chamber 4 through the valve d, high charging efficiency can be ensured.

As described above, according to the present invention, it is possible to greatly increase the combustion rate when the engine is running at low speed and low load while ensuring high charging efficiency when the engine is running at high speed and high load.

Furthermore, even when the engine is operating at low speed and high load, strong turbulence can be generated within the combustion chamber, thereby preventing knocking.

Further, since there is no need to provide a separation diaphragm that separates the high pressure chamber 28 and the valve chamber 35 as in the conventional case, the high pressure chamber 28
The pressure difference between the valve chamber 35 and the valve chamber 35, that is, the pressure difference before and after the second throttle valve 14, can be accurately maintained at a constant pressure difference regardless of the magnitude of the negative pressure in the high pressure chamber 28.

Furthermore, as shown in FIG. 4, the negative pressure applied to the low pressure chamber 21 of the negative pressure control valve 23 is small during fluctuations, so the valve body 37 vibrates violently every time negative pressure is generated in the intake port. Since there is no noise, noise can be prevented, the life can be improved, and moreover, the opening control of the second throttle valve can be performed stably.

In addition, in FIG. 1, a second common communication path 48 as shown in FIG. 5 is further provided in addition to the common communication path 43.
The low pressure chamber 27 of the negative pressure control valve 23 can also be connected to the common communication path.

[Brief explanation of the drawing]

FIG. 1 is a side sectional view of an internal combustion engine according to the present invention taken along line I-I in FIG. 2, FIG. 2 is a partially sectional plan view of FIG. 1, and FIG. 3 is a negative pressure inside the intake boat. A graph showing changes in the negative pressure in the common communication passage.
FIG. 6 is a side sectional view of another embodiment taken along line 2--v in the figure, and FIG. 6 is a partially sectional plan view of FIG. 5. 5a, 5b, 5c, 5d---Intake boat, 6ay6
b, 6c, 6d... Intake valve, 10... Intake manifold, 11... Carburetor, 12... Carburetor throttle valve, 14... Second throttle valve, 17... Throttle valve drive Device, 20... Negative pressure chamber, 23... Negative pressure control valve, 27... Low pressure chamber, 28... High pressure chamber, 35... Valve chamber, 36... Air hole, 37... Valve body, 43... common communication path, 44a. 44b, 44c, 44d series of branches, 48...
Second common communication path.

Claims (1)

[Scope of Claims] 1. A second throttle valve is provided in each intake branch passage downstream of the carburetor throttle valve, and each communication branch passage is provided in communication with each intake branch passage downstream of the second throttle valve. a negative pressure responsive throttle valve drive device connected to the common communication path and connected to the second throttle valve;
The internal combustion engine is provided with a negative pressure control valve that controls negative pressure applied to the negative pressure chamber of the negative pressure responsive throttle valve drive device in response to a pressure difference before and after the throttle valve so that the pressure difference becomes constant. The negative pressure control valve includes a high pressure chamber and a low pressure chamber separated by a diaphragm, and the high pressure chamber and the low pressure chamber are located in intake pipe negative pressure generation areas upstream and downstream of the second throttle valve, respectively. Further, a valve chamber is attached to the high pressure chamber of the negative pressure control valve via a partition wall, and a valve body is provided in the valve chamber for controlling the opening and closing of an air hole opened in the valve chamber, and the valve body is connected to the above-mentioned diamond. intake air of an internal combustion engine, the valve chamber being connected to the negative pressure chamber of the negative pressure responsive throttle valve drive device on the one hand and to the high pressure chamber via a throttle formed on the partition wall on the other hand; Device. 2. An intake system for an internal combustion engine according to claim 1, wherein the common communication passage is connected to the intake passage between the carburetor throttle valve and the second throttle valve.