JPH0574689B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an intake system for a diesel engine that improves ignitability and facilitates starting, especially when cold.

(Prior art) In modern diesel engines, by effectively utilizing adiabatic compression to raise the intake air temperature,
A device designed to promote startup has been proposed. That is, as shown in Japanese Utility Model Application No. 55-165935, the intake air is throttled during the intake stroke to maintain a high negative pressure in the cylinder, while the exhaust valve is opened from the end of the intake stroke to the beginning of the compression stroke. A system has been proposed in which exhaust gas is sucked all at once into the cylinder under high negative pressure, and the temperature of the intake air is raised by the adiabatic compression effect of the sucked exhaust gas.

However, with the above-mentioned conventional type, exhaust gas, which is an inert gas, is inhaled even when the load is high.
There is a problem that the output decreases under high loads. In addition, if the above-mentioned conventional type is configured to inhale exhaust gas only at low rotation speeds,
Another problem arises in that the valve mechanism becomes extremely complicated.

Therefore, in order to obtain adiabatic compression without using exhaust gas, the applicant has provided a timing valve in the intake passage of the engine, and uses this timing valve to close the intake passage at the beginning of the intake stroke. This creates a high negative pressure inside the cylinder, and at the end of the intake stroke, the intake passage is opened and fresh air is introduced all at once into the cylinder, which has a high negative pressure.This new air introduced all at once creates heat insulation. We have developed something that performs compression.

By the way, some engine intake passages are designed as swirl intake passages, such as helical ports, in order to generate swirl within the combustion chamber, but this swirl intake passage has a large intake resistance, so its throttling loss or the suction speed is lowered, which becomes an unfavorable cause in carrying out the adiabatic compression described above. That is, if the intake resistance is large, the force and time required to introduce new fuel into the cylinder (combustion chamber), which has a high negative pressure, becomes longer, which causes a reduction in the adiabatic compression effect.

(Object of the Invention) The present invention is based on the premise that adiabatic compression is performed without using exhaust gas by using the above-mentioned timing valve, and the present invention is directed to a device equipped with a swirl intake passage. Another object of the present invention is to provide an intake system for a diesel engine that can prevent the adiabatic compression effect from being reduced by the swirl intake passage.

(Structure of the Invention) In order to achieve the above-mentioned object, in the present invention, in addition to the swirl intake passage, a directional intake passage with low intake resistance is provided as the intake passage opening into the combustion chamber. The intake passage is provided with the above-mentioned timing valve for adiabatic compression, and the swirl intake passage is provided with a shutter valve that opens and closes it. When the control device operates the timing valve to perform adiabatic compression, the shutter valve is closed to prevent intake from the swirl intake passage.

(Example) In FIG. 1, 1 is the main body of a diesel engine, which is a reciprocating type engine in which a combustion chamber 5 is defined by a cylinder block 2, a cylinder head 3, and a piston 4 that reciprocates within the cylinder block 2. It is said to belong to

An intake port 6 formed in the cylinder head 3 is opened in the combustion chamber 5.
are opened and closed by the intake valve 7 at known timings in synchronization with the rotation of the engine. This intake port 6 is connected to the primary intake ports 8 and 2.
Secondary intake port 9
is a so-called helical port, and the intake valve 7
By generating a swirl around the stem 7a, swirled intake air is introduced into the combustion chamber 5. Further, the primary intake port 8 has a smaller effective opening area than the secondary intake port 9, and is formed in a substantially straight line so as to reduce suction resistance. It has been merged into 9. In the embodiment, the engine main body 1 is of a so-called Mann type (evaporative combustion type) which is a direct injection type, and therefore, a cavity 10 is formed on the top wall of the piston 5 to allow air to flow from the secondary intake port 9. The fuel from the fuel injection valve 11 is made to flow on a thin film along the inner peripheral wall of the cavity 1010 while being assisted by the swirled intake air.

A branch pipe 12a of an intake manifold 12 is connected to the intake port 6, and the branch pipe 12a is divided into a primary passage 13 and a secondary passage 14 having a larger effective opening area by a partition wall 12b. has been completed. Of course, the primary passage 13 is connected to the primary intake port 8, and both 8 and 13 constitute the directional intake passage A, and the secondary passage 14 is connected to the secondary intake port 9, and the secondary passage 14 is connected to the secondary intake port 9. Both 9 and 14 constitute a swirl intake passage B. A negative pressure opening/closing valve C as a timing valve is disposed in the directional intake passage A,
In addition, a shutter valve 15 is provided in the swirl intake passage B.
is installed. As shown in FIG. 3, this negative pressure on-off valve C includes a shutter plate 16 held between the cylinder head 3 and the intake manifold 12, and a casing 17 integrated therewith. A valve chamber 19 is defined within the casing 17 by a partition wall 18, and a communication port 20 formed in the shutter plate 16 communicates between the valve chamber 19 and the downstream side of the negative pressure on/off valve C. The valve chamber 19 and the upstream side of the negative pressure on/off valve C are communicated through the communication port 21 . The communication port 20 formed in the shutter plate 16 is opened and closed by a valve body 22 slidably held by the partition wall 18.
The valve body 22 is connected to a diaphragm 23 stretched inside the casing 17, and is normally urged by a return spring 24 in a direction to close the communication port 20 when seated on the shutter plate 16.

The diaphragm 23 allows the casing 17 to
A negative pressure chamber 25 defined therein is communicated with the downstream side of the negative pressure on/off valve C via a negative pressure introduction path 22 formed in the valve body 22, and the negative pressure in the negative pressure chamber 25 is maintained at a predetermined level. When the pressure rises to the valve opening pressure, the diaphragm 23 moves to the left against the return spring 24 as shown in FIG.
The communication port 20 is opened further apart.

The shutter valve 15 is opened and closed by a negative pressure actuator 27.
For this reason, a negative pressure chamber 27b defined by a diaphragm 27a linked to the shutter valve 15
However, through the electromagnetic switching valve 28, the negative pressure pump 2
9 is connected. By switching the switching valve 28 and introducing negative pressure into the negative pressure chamber 27b,
The shutter valve 15 is closed against the return spring 27c, and conversely, the shutter valve 15 is opened by introducing atmospheric air into the negative pressure chamber 27b. Of course, this shutter valve 15
is open, the intake air only flows through the swirl intake passage B, and the negative pressure on/off valve C remains closed at all times, that is, the operation of the negative pressure on/off valve C is stopped, and conversely, the shutter valve 15 is closed. When this happens, the negative pressure on-off valve C operates to perform adiabatic compression.

The switching of the switching valve 28, that is, the accompanying opening operation of the shutter valve 15 (negative pressure opening/closing valve C)
(operation stoppage) and closing operation (operation of the negative pressure on-off valve C) are the control unit 30 as a control device.
This was done by The control unit 30 receives an engine rotational speed signal S ₁ , an engine load signal S ₂ , and an engine coolant temperature signal S ₃ .
The shutter valve 15 is closed and the negative pressure on/off valve C is operated only when the operating range shown by the hatching in FIG. It is designed to let you do so. The above operating range is determined by considering the reliability (limit of followability) of the negative pressure on-off valve C regarding the engine speed, and by taking into consideration that the oxygen content in the combustion chamber 5 will not be insufficient regarding the engine load. Each has been decided.

The effect of the above configuration will be explained.
First, whether or not to perform adiabatic compression, that is, the opening/closing control of the shutter valve 15 will be explained based on the flowchart shown in FIG.

First, in step 50, the cooling water temperature signal _S3 is input, and in step 51, it is determined whether or not this cooling water temperature is -5 DEG C. or lower. When the cooling water temperature is -5 DEG C. or lower, the ignitability is poor, that is, starting is difficult, so the shutter valve 15 is closed in step 52.

Next, in steps 53 and 54, the engine speed signal _S1 and the engine load signal _S2 are sequentially inputted, and in step 55, the negative pressure on/off valve C described above is inputted.
It is determined whether or not it is within the operating range. If it is determined that it is within this operating range, step 53 is performed.
In order to continue operating the negative pressure on/off valve C, the shutter valve 15 is kept in the closed position. Also,
If it is determined that it is not within this operating range, the step
56, the shutter valve 15 is placed in the open position.

In addition, in step 51, the cooling water temperature is -5℃.
If the value exceeds 1, it is assumed that the environment is favorable for ignitability, and the process returns to step 50.

Next, regarding adiabatic compression, that is, negative pressure on/off valve C
Let us explain the effect of .

First, before starting the engine, the communication port 20 of the negative pressure on-off valve C is closed by the valve body 22, and the directional intake passage A is closed. When the engine is cranked from this state, the negative pressure within the combustion chamber 5 increases as the piston 5 descends. When the negative pressure in the combustion chamber 5 increases to a predetermined level, that is, the valve opening pressure as described above, the communication port 20 is opened and the intake air is introduced into the combustion chamber 5 at once. The inhaled air is adiabatically compressed. Due to this adiabatic compression,
The intake air temperature is increased by several tens of degrees, and this increase in intake air temperature facilitates smooth ignition and engine starting, and ensures stable combustion after ignition. Of course, the air sucked in before the negative pressure on/off valve C (the communication port 20 of it) opens is the air in the directional intake passage A on the downstream side of the negative pressure on/off valve C and the swirl intake passage on the downstream side of the shutter valve 15. This is the air inside B. and,
The introduction of fresh air at once by opening the negative pressure on/off valve C is carried out through the directional intake passage A, which has low suction resistance, so that adiabatic compression is effectively performed.

In addition, in the adiabatic compression mentioned above, as is clear from the explanation so far, fresh air with a pressure almost equal to atmospheric pressure enters the combustion chamber, which is in a negative pressure state, all at once. The air existing in the combustion chamber and the air that entered earlier are compressed by the air that enters later, thereby increasing the temperature of the intake air. As the negative pressure on/off valve C opens and the pressure in the combustion chamber increases, the negative pressure on/off valve C is eventually closed, but during the period from opening to closing of the negative pressure on/off valve C, sufficient adiabatic compression is achieved. The following effects can be obtained. Of course, since a large amount of air is not required at the time of starting, even if the opening period of the negative pressure on-off valve C is short, there is no problem in ensuring the amount of air necessary for ignition.

After the engine is started, the shutter valve 15 is opened when the cooling water temperature exceeds -5 DEG C. or when the operating state is outside the operating range shown in FIG. As a result, the intake air is taken in from the swirl intake passage B having a large effective opening area without being subjected to resistance from the negative pressure on-off valve C, so that horsepower is improved and a swirl is generated in the combustion chamber 5. Therefore, it is also preferable in terms of improving combustion.

In addition, when a negative pressure on-off valve C is provided for each cylinder in a multi-cylinder engine, and the ignition timing overlaps with the opening timing of the intake valve 7 between adjacent cylinders, one negative pressure By setting the opening pressure of the on-off valve C so that other negative pressure on-off valves C do not open when the on-off valve C is open, so-called intake air interference can be prevented and adiabatic compression can be performed effectively.

FIG. 7 shows another embodiment of the present invention, in which the same components as in the previous embodiment are given the same reference numerals, and their explanation will be omitted.

In this embodiment, as a configuration having two intake valves, a directional intake passage A and a swirl intake passage B are opened into the combustion chamber 5 completely separately and independently, and both A and B are separated from each other by separate intake valves. It is designed to be opened and closed by. By adopting such a configuration, the degree of freedom in the arrangement relationship between both intake passages A and B is increased compared to the above embodiment, and each intake passage A or B can fully demonstrate its original function. . Note that 31 in the figure is an exhaust port.

Although the embodiments have been described above, the present invention is not limited thereto, and includes, for example, the following cases.

For example, the timing valve may be of a butterfly type, and its opening/closing timing may be controlled by the control unit 30. Further, the timing valve may be a rotary valve, and by synchronizing the timing valve with engine rotation, the opening/closing timing may be set to a predetermined value.

The timing valve may be operated even when the engine is under high load or at high engine speed.

Timing valves may be provided only for some cylinders. That is, for example, in a four-cylinder diesel engine, a timing valve can be provided for one cylinder or two cylinders, and in this way, the timing valve is provided for all cylinders. Thus, the work required to operate the timing valve can be reduced. Note that when one cylinder completely explodes, the remaining cylinders will also completely explode, and when multiple timing valves are provided, if they are installed for cylinders whose ignition timings are not adjacent to each other, the intake air A decrease in the efficiency of adiabatic compression due to interference can be inevitably prevented.

The present invention is applicable not only to reciprocating engines but also to rotary piston engines.

(Effects of the Invention) As is clear from the above, the present invention has the following advantages:
Since fresh air is used instead of exhaust gas as the gas used for adiabatic compression, the engine starts smoothly by improving ignition performance while preventing output loss during high loads. In addition, there is no need to make the valve operating mechanism for the exhaust valve particularly complicated, and the structure can be simplified.

Additionally, in addition to the swirl intake passage with high suction resistance that generates swirl to improve combustion, we have also provided a directional intake passage with low suction resistance.
Intake air is introduced for adiabatic compression through this directional intake passage with low intake resistance, so adiabatic compression is effectively performed, improving ignition performance and improving engine starting, especially when cold. It can be done.

[Brief explanation of drawings]

FIG. 1 is a longitudinal sectional view showing one embodiment of the present invention. FIG. 2 is a simplified plan sectional view of the intake port portion in FIG. 1. FIG. 3 and FIG. 4 are cross-sectional views showing a specific example of a negative pressure on-off valve as a timing valve and its operation. FIG. 5 is a diagram showing an example of an operating range in which a negative pressure on-off valve as a timing valve is operated. FIG. 6 is a flowchart showing an example of controlling the shutter valve and the associated negative pressure on/off valve as a timing valve. FIG. 7 is a simplified plan sectional view of a main part showing another embodiment of the present invention. 1: Engine body, 5: Combustion chamber, 6: Intake port, 7: Intake valve, 8: Primary intake port, 9: Secondary intake port, 12: Intake manifold, 13: Primary passage, 14: Secondary passage , 15: Shutter valve,
27: Actuator, 30: Control unit, A: Directional intake passage, B: Swirl intake passage, C: Negative pressure opening/closing valve (timing valve).

Claims (1)

[Scope of Claims] 1. A directional intake passage and a swirl intake passage, each of which opens into a combustion chamber, and which is disposed in the directional intake passage and is closed for a predetermined period at the beginning of the intake stroke, and during the intake stroke after the predetermined period has elapsed. The engine is characterized by comprising: a timing valve that opens when the swirl intake passage is opened; a shutter valve that is disposed in the swirl intake passage and opens and closes the swirl intake passage; and a control device that closes the shutter valve at least when the engine is cold started. Diesel engine intake system.