JPS623125A - Air intake device for direct injection type diesel engine - Google Patents

Abstract

PURPOSE:To facilitate fuel combustion and reduce the occurrence of smoke for an engine wherein an open/close valve is provided at an air intake passage and opened in the course of a suction stroke at a low speed and load condition, by providing a control means for actuating said valve even in a low speed and high load range. CONSTITUTION:In an engine wherein a limiting device for introducing suction air is provided at an air intake passage 8 for limiting an air flow into a combustion chamber 3 until the half-way of a suction stroke and causing the sudden introduction of air into said chamber 3 in the course of a suction stroke for adiabatic compression through the operation of an open/close valve 10, it is made possible to change over the open/close valve 10 by the actuating device 11 thereof as controlled through a control means 12, so that said valve 10 will be in a working condition and a stop condition wherein operation stops and the air intake passage 8 is open through-out a suction stroke. And the control means 12 is made active at a relatively low speed and particular operation range at a low load side, while said valve 10 is so controlled as to be operable at a low speed and high load range, regardless of said particular operation range.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention increases the intake air temperature by adiabatic compression in order to promote starting of a diesel engine and improve emissions. This invention relates to an intake device designed to be strengthened.

(Prior Art) Conventionally, as shown in Japanese Utility Model Application Publication No. 59-107936, in order to improve the ignitability at the time of starting a diesel engine, the intake air supplied to the combustion chamber is compressed adiabatically to raise the intake air temperature. An intake device (starting promotion device) is known. This device has an on-off valve in the intake passage that opens during the intake stroke. Specifically, an intake throttle valve is provided in the main intake passage, and an on-off valve is provided in the bypass intake passage that bypasses the intake throttle valve. , during low-load operating conditions from startup to warm-up, the intake throttle valve throttles the main intake passage, and the valve mechanism or pressure-responsive valve opens the on-off valve in the middle of the intake stroke. I'm trying to get it working. The operation of the on-off valve restricts the intake air into the combustion chamber until the middle of the intake stroke, and rapidly introduces the intake air into the combustion chamber from the middle of the intake stroke to perform adiabatic compression. According to this device,
It improves ignitability and combustibility, and also helps reduce white smoke and HC. Furthermore, compared to the case where the intake air is heated by an air heater, a large amount of energy is not consumed as electric power, and the temperature of the intake air can be efficiently raised in the combustion chamber.

By the way, in conventional devices of this type, the opening/closing valve is operated only at low speeds, low loads, and low temperatures (in the case of the above-mentioned publication, during startup and warm-up), when the temperature during ignition and combustion is difficult to rise. The on-off valve is used to promote adiabatic compression of the intake air, and to promote startup and prevent misfires in such cases.

On the other hand, in direct-injection diesel engines, there is a demand to strengthen the intake swirl in order to promote fuel atomization and increase the combustion rate at low rotation speeds and high loads.
To meet this requirement, conventional measures have been taken such as providing a swirl-generating boat in the intake system, and as a result, the intake passage and the intake boat have a complicated structure.

(Objective of the Invention) In view of the above circumstances, the present invention utilizes an on-off valve provided to raise the intake air temperature by adiabatic compression of the intake air, and improves the speed at low rotation and high load ranges without complicating the intake boat etc. The present invention provides an intake system for a direct injection diesel engine that can enhance intake swirl.

(Structure of the Invention) The present invention provides an on-off valve in the intake passage for each cylinder of an engine, and switches the on-off valve from a closed state to an open state in the middle of the intake stroke in a specific operating range on the relatively low rotation and low load side. In the intake system of a direct injection diesel engine, which operates the 1mrll valve to rapidly introduce intake air from the middle of the intake stroke to perform adiabatic compression, there are It is equipped with a control means that operates the on-off valve in the low rotation and high load range.

In other words, in addition to operating the on-off valve to perform adiabatic compression of the intake air in the operating range where the temperature during ignition and combustion is difficult to rise, swirl is created by operating the on-off valve even at low rotation speeds and high loads. The aim is to strengthen the

(Embodiment) FIG. 1 shows a first embodiment of the present invention. In the same figure,
Reference numeral 1 designates a cylinder constituting each cylinder of a direct injection diesel engine, and a combustion chamber 3 is formed above a piston 2 inside the cylinder, and this combustion chamber 3 includes an intake boat 5 equipped with an intake valve 4; An exhaust boat 7 equipped with an exhaust valve 6 is open. An intake passage 8 is communicated with the intake boat 5,
Further, an exhaust passage 9 is communicated with the exhaust boat 7.

Then, the introduction of intake air into the combustion chamber 3 is restricted to the intake passage 8 by an on-off valve 10 until the middle of the intake stroke, and the intake air is rapidly introduced into the combustion chamber 3 from the middle of the intake stroke to perform adiabatic compression. An intake air introduction regulating device is provided.

In this embodiment, this intake air introduction regulating device is a rotary valve type on-off valve that is linked to the engine output shaft and opens in the middle of the intake stroke. 11. The on-off valve drive device 11 includes an on-off valve 1
By incorporating interlocking shutoff means (not shown) that can stop the valve 10 in the open state or variable opening/closing timing means that can change the opening/closing timing so that the opening/closing valve 10 is open during the entire intake stroke, The CPU is capable of stopping the operating function of the on-off valve 10 at a specific time, and the control means 12 can control the engine.

Reference numeral 12 denotes a control means such as a microcomputer, etc. The on-off valve driving device 11 is controlled based on an on-off valve drive control signal 11' corresponding to the operating state, whereby the on-off valve 10 is in an operating state and its operating function is stopped and the intake air is turned off. It is possible to switch to a deactivation state in which the passage is open throughout the entire intake stroke.

In this control means 12, the operating range of the on-off valve 10 is set in advance as shown in FIG.゛In other words, in Fig. 2, the vertical axis is the engine load,
・The horizontal axis represents the engine speed, and the curve R shows the line of maximum load. In this figure, the shaded area A,
B is the operating range of the on-off valve 10, and the operating range on the relatively low-speed, low-load side, where the temperature during ignition combustion is inherently difficult to rise, is the operating range A of the on-off valve 10 for increasing the intake air temperature. At the same time, the operating region on the low-speed, high-load side is defined as the operating region B of the on-off valve 10 for swirl reinforcement. These areas A and B are stored in advance in the memory within the control means 12 as a map. Note that the operating range A of the on-off valve 10 for increasing the intake air temperature may be corrected so as to expand at low temperatures depending on the cooling water temperature and the like.

A control lever opening signal 13, an engine rotation speed signal 14, and an engine cooling water i signal 15 corresponding to the engine load are input to the 611111 means 12, and the control means 12 is set as described above with these input values. Based on the map of the operating region, the on-off valve drive device is configured to put the on-off valve 10 into the operating state when the operating state is in the operating region A or B of the on-off valve 10, and keep the on-off valve 10 in the non-operating state at other times. It controls @11.

The operation of the intake device configured in this way will be explained next.

In region A of relatively low rotation and low load, where the temperature during ignition and combustion naturally tends to be low, the open/close valve 1o is operated and adiabatic compression of the intake air is performed, so that the intake air temperature rises.
This temperature increase facilitates starting and improves emissions. In other words, the opening/closing valve 10 is closed until the middle of the intake stroke to restrict the introduction of intake air into the combustion chamber 3, and from the middle of the intake stroke, the opening/closing valve 10 is opened and a large amount of intake air is suddenly introduced into the combustion chamber 3. This causes adiabatic compression of the intake air and increases the intake air temperature. At relatively low rotation speeds and low loads, this increase in intake air temperature contributes to the dead weight of combustibility.
Misfires are prevented and the generation of white smoke, HC, etc. is suppressed.

Further, the on-off valve 10 is operated even in the region B of low rotation and high load, and the operation of the on-off valve 10 at this time is useful for promoting combustion by strengthening swirl and thereby preventing smoke generation. In other words, as shown in FIG. 3, the opening timing to of the on-off valve 10 is delayed from the opening timing 1.0 of the intake valve, and the negative pressure generated in the cylinder during this time causes the opening timing to of the on-off valve 10 to be delayed.
Closing timing of the intake valve from o 1. Since intake air is rapidly introduced during the period up to C, the intake flow rate is significantly increased (solid line D) compared to when intake air is introduced during the entire intake stroke (dashed line C), and the intake swirl is strengthened. Ru.

At low rotation speeds and high loads, the intake swirl is strengthened in this way, which improves fuel atomization and mixing with air, increases the combustion rate, and promotes combustion, resulting in the generation of smoke. is prevented. In addition, at low rotation speeds, the intake stroke time is relatively long and there is a time margin to secure the intake air filling amount, so by adjusting the opening timing of the 1ml1fl valve 10 to be delayed by this margin, Intake air filling required during low rotation and high load 1
It is possible to strengthen the intake swirl while ensuring the amount of intake air.

Other embodiments of the on-off valve and the valve driving device of the present invention will be described with reference to FIGS. 4 and 5. FIG.

As the on-off valve 10' in this embodiment, this on-off valve 10
An automatic valve type is used that automatically opens and closes when the negative pressure in the intake passage downstream becomes greater than a predetermined value, and the intake passage is divided into the main intake passage 8a and the auxiliary intake passage 8b. An intake throttle valve 20 driven by an actuator 21 controlled by the control means 12 is provided in the main intake passage 8a, and the auxiliary intake passage 8b is opened downstream of the intake throttle valve 20. With,
The above-mentioned automatic valve type on-off valve 1 is provided in this auxiliary intake passage 8b.
0' is provided. Further, as a means for rotating the intake throttle valve 20, an actuator 2 such as a diaphragm device is used.
1, a passage 22 for operating this, and a vacuum pump 23
A driving device including a switching valve 24 and the like is provided.

The switching valve 24 is controlled by the control means 12 so that the intake throttle valve 20 is opened when negative pressure is introduced from the vacuum pump 23 to the actuator 21 through the passage 22. □゛Also, open m
As shown in an enlarged view in FIG. 5, the valve 10' includes a valve body 32 provided in a valve chamber 30 and abutting a valve seat 31 from the upstream side;
A diaphragm 34 connected to this valve body 32 via a connecting shaft 33, two chambers 35 and 36 partitioned by this diaphragm 34, and a valve body 32 provided in one of the chambers 35 in the valve closing direction. A return spring 37 biases the
It consists of. The one chamber 35 has a communication hole 38 that passes through the valve body 32, the connecting shaft 33, and the diaphragm 34.
communicates with the sub-intake passage 8b downstream of the valve body 32 via
The other chamber 36 communicates with the upstream side of the auxiliary intake passage 8b, that is, a surge tank (not shown) via an opening 39, and is maintained at approximately atmospheric pressure.

Therefore, the n1 intake passage 8b downstream of the on-off valve 10'
The negative pressure inside is transmitted to the chamber 35 through the communication hole 38, and when this negative pressure is below a certain value, the valve body 32 is biased in the valve closing direction by the return spring 37, but when the negative pressure is constant When the value exceeds the value, the valve body 32 is opened against the biasing force of the return spring 37 via the diaphragm 34.

In the above configuration, the main intake passage 6 is controlled by the intake throttle valve 20.
When a is throttled, the piston 2 descends during the intake stroke, and the main and auxiliary intake passages 8a, which communicate with the combustion chamber 3,
When the negative pressure inside 8b increases above a certain value, the on-off valve 1
0' changes from the open state to the open state, and the intake air suddenly enters the combustion chamber 3.
is introduced to obtain an adiabatic compression effect. On the other hand, when the intake throttle valve 20 is open, almost no intake negative pressure is generated, so the operation of the on-off valve 10' is stopped and the on-off valve 1
'0' is kept closed.

Even in a device using such an on-off valve and an on-off valve driving device, the same functions as in the first embodiment can be achieved by controlling the opening and closing of the intake throttle valve 20 by the control means 12.

In addition to these embodiments, although not shown, an automatic valve type on-off valve as described above is rotatably provided in the intake passage, and when the on-off valve is in operation, it is interposed in the passage and opened and closed. There are various practical methods, such as a configuration in which the valve is rotated by an actuator so that it does not intervene in the passage when the valve is inactive.
Aspects may be adopted.

(Effects of the Invention) As described above, the present invention operates an on-off valve to perform adiabatic compression in the intake system of a direct injection diesel engine in order to increase the intake air temperature in a relatively low-speed and low-load operating region. At the same time, by operating the on-off valve even during low-speed, high-load conditions, the on-off valve is used to strengthen the swirl required for direct injection diesel engines at low speed and high loads. For this reason, in addition to the original role of this type of device, which is to increase the intake air temperature and promote starting, it also promotes combustion at low rotation speeds and high loads without the need for a complicated intake boat structure, and thereby reduces smoke. This makes it possible to reduce

[Brief explanation of drawings]

Fig. 1 is an overall configuration diagram of the intake system of a direct injection diesel engine according to an embodiment of the present invention, Fig. 2 is an explanatory diagram showing the operating range of the on-off valve, and Fig. 3 is a change in intake flow velocity due to the operation of the on-off valve. FIG. 4 is a sectional view of a main part showing another embodiment, and FIG. 5 is an enlarged sectional view of the on-off valve. 8...Intake passage, 10.10'...Opening/closing valve, 11
... Opening/closing valve drive device, 12... Control means. Patent applicant Mazda Corporation No. 1
Figure H also goes to C.

Claims (1)

[Claims] 1. An on-off valve is provided in the intake passage for each cylinder of the engine, and the on-off valve is operated to change from a closed state to an open state in the middle of the intake stroke in a specific operating range on the relatively low rotation and low load side; In the intake system of a direct-injection diesel engine, which operates the on-off valve to rapidly introduce intake air from the middle of the intake stroke to perform adiabatic compression, the on-off valve is operated in the low rotation and high load range, in addition to the above-mentioned specific operating range. An intake system for a direct injection diesel engine, characterized in that it is provided with a control means for operating it.