JPH02267319A - Intake device for diesel engine - Google Patents

Abstract

PURPOSE:To increase intake air resistance so as to enlarge the effect of an engine brake by controlling a variable swirl mechanism to strengthen intake air swirls in the non-injection region of fuel at the time of an engine being decelerated. CONSTITUTION:The intake port of an engine main body 1 is formed into a helical port, so that the intake air is fed into a combustion chamber 2 while generating swirls. Each branch passage 8b of an auxiliary intake passage 8 led out of an intake manifold 5 is so set as to weaken the above-mentioned swirls in its opening position and leading direction. The common passage 8a of the auxiliary intake air passage 8 is provided with a control valve 10 for opening/closing this common passage 8a, and the control valve 10 is controlled by a control unit 11 according to the varied operation region of the engine. In this case, the intake swirl is controlled to be strong in the non-injection region of fuel at the time of the engine being decelerated.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an intake VtW of a diesel engine having a variable swirl mechanism.

(Prior art) In a diesel engine, in order to improve combustion using intake swirl according to the engine speed, this intake swirl is applied to an intake port that is set to generate an intake swirl in the combustion chamber. It is known that a sub-passage is provided for introducing intake or exhaust gas into the intake boat in the direction of weakening or strengthening (Utility Model Application No. 591).
79241, JP-A-63-14082).

In a diesel engine equipped with such a variable swirl mechanism, the intake swirl is weakened in the low load region where the fuel injection amount is small to improve ignition performance, and the intake swirl is improved in the low rotation/noble @ region where the fuel injection amount is large but the intake flow velocity is slow. In this case, the intake swirl is strengthened to improve fuel sales. In addition, high rotation
In high-load regions, the intake swirl is weakened to increase the amount of intake air filling.

(Object of the invention) The present invention actively utilizes the variable swirl mechanism,
An object of the present invention is to provide an intake device for a diesel engine that can expand the effect of engine braking during deceleration.

(Structure of the Invention) The present invention is characterized in that the variable swirl mechanism is controlled B so that the intake swirl becomes strong in a fuel non-injection region during engine deceleration.

(Effect of the invention) If the intake swirl is made strong, the intake resistance becomes large.
By increasing the intake swirl in the non-fuel injection region during engine deceleration, the effect of engine braking can be expanded.

(Example) Hereinafter, an example of the present invention will be described based on the drawings.

In FIG. 1, reference numeral 1 denotes an engine main body, which is configured as an in-line four-cylinder type having four cylinders (combustion chambers) 2. An intake boat 3 and an exhaust boat 4 are open to each cylinder 2, respectively. A branch passage 5a of an intake manifold 5 is connected to the intake boat 3, and a branch passage 6a of an exhaust manifold 6 is connected to the exhaust boat 4. intake boat 3
The intake air that has passed through this intake boat 3 is supplied into the combustion chamber 2 while generating a swirl.

A sub-intake passage 8 is led out from the intake manifold 5. This sub-intake passage 8 consists of one common passage 8a and a number of branch passages 8b branched from this common passage 8a according to the number of cylinders, and the downstream end of each branch passage 8b opens to the intake boat 3. The opening position and direction of the zero branch passage 8b are such that the intake swirl flowing through the intake boat 3 is weakened by the intake air supplied from the branch passage 8b. That is, in the case of this embodiment, the opening position of the branch passage 8b is set near the downstream end of the intake boat 3, and the intake from the branch 1IIN8b collides almost head-on with the swirling intake air from the branch passage 5a. and is oriented to reduce intake swirl. A one-way valve 9 for preventing backflow of intake air is provided at the upstream end of each branch passage 8b, and a control valve lO for opening and closing the sub-intake passage 8 is further provided in the middle of the common passage 8a. It is arranged.

Reference numeral 11 denotes a control unit, into which an engine rotational speed signal, an accelerator opening signal (indicating a load), a needle valve lift amount, etc. are input. Based on these input signals, the control unit 11 reads the intake swirl strength suitable for each operating range from a swirl basic map as shown in FIG. 2, and turns the control valve 10 ON/OFF to adjust the intake swirl strength. change.

That is, in the low load region, the intake swirl is weakened by turning the control valve 10 ON (open) to create a weak swirl region.
In the low rotation/high load region, the intake swirl is strengthened by setting the control valve 10 to 0FF (closed) to create a swirl tjIII region. Control valve 10 is turned on in medium to high rotation and high load areas.
By setting it to (open), it becomes a weak swirl region. In addition, when the control unit 11 detects a no-fuel injection region from the accelerator opening degree and engine rotation speed in a fully closed state,
Turn on (close) the control valve IO to make the intake swirl strong,
This increases intake resistance and increases the effect of engine braking. Note that the non-fuel injection region may be detected by measuring the high-pressure pipe internal pressure of the fuel injection valve or the needle valve lift (l) of the direct injection nozzle.

FIG. 3 shows an example of a flowchart of an intake swirl control routine executed by the control unit 11.

In FIG. 3, the engine speed and the accelerator opening are detected in step Sl and step s2, and step S
In step 3, it is determined whether or not there is no fuel injection region.

When this determination is rNOJ, normal swirl control according to the basic map shown in FIG. 2 is performed in step s4, and when the determination in step S3 is rYEsJ, the control valve 1o is set to 0FF (closed) in step s5. It weakens the intake swirl, increases intake resistance, and expands the effect of engine braking.

In the configuration shown in FIG. 1 described above, the branch passage 8b of the 1iill intake passage 8 is provided in a direction that weakens the intake swirl, but on the contrary, it may be provided in a direction that strengthens the intake swirl.

[Brief explanation of drawings]

FIG. 1 is an overall system diagram showing one embodiment of the present invention, FIG. 2 is a basic swirl map, and FIG. 3 is a flowchart of an intake swirl control routine. 1-Engine body 2--Cylinder (combustion chamber) 3--
Intake boat 5--Intake manifold 5a-Branch passage 8a--Common passage sub-intake passage 10--Control valve 8b-Branch passage 1-Control unit

Claims (1)

[Claims] In a diesel engine intake system equipped with a variable swirl mechanism that can change the strength of intake swirl generated in a combustion chamber, the intake swirl becomes strong in a non-fuel injection region during engine deceleration. An intake system for a diesel engine, characterized in that the variable swirl mechanism is controlled as described above.