JPH04284130A - Intake control device for internal combustion engine - Google Patents

Abstract

PURPOSE:To low keep the temperature of air supplied into an engine cylinder in the case of an internal combustion engine provided with a mechanical supercharger. CONSTITUTION:Air discharge passage 18 is branched from an intake air duct 13 in the downstream of a mechanical supercharger 17 to communicate with the atmosphere through a silencer 19. A discharge flow control valve 20 is provided in the air discharge passage 18. An opening of this discharge flow control valve 20 is controlled to a target opening determined by an operational condition of an engine.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an air intake control device for an internal combustion engine.

0002

[Prior Art] An engine-driven mechanical supercharger is arranged in an engine intake passage, and the intake passage upstream of the mechanical supercharger and the intake passage downstream of the mechanical supercharger are connected to each other via a bypass passage. In addition, a two-stroke internal combustion engine in which a bypass control valve is disposed in the bypass passage is known (Utility Model Application No. 1983-130).
(See Publication No. 631). In such a two-stroke internal combustion engine, when the bypass control valve opens, a portion of the intake air discharged from the mechanical supercharger is returned via the bypass passage into the intake passage upstream of the mechanical supercharger. Thus, by controlling the opening degree of the bypass control valve, the amount of air supplied into the engine cylinder can be controlled.

0003

However, the temperature of the intake air is increased when it passes through the mechanical supercharger, and thus high temperature air is discharged from the mechanical supercharger. Therefore, as mentioned above, if a part of the intake air discharged from the mechanical supercharger is returned to the intake passage upstream of the mechanical supercharger via the bypass passage, the heated intake air will be used to regenerate the mechanical supercharger. The air discharged from the mechanical supercharger to be heated in the machine is further heated, and this heated air is returned to the upstream side of the mechanical supercharger via the bypass passage again. The temperature of the air discharged from the mechanical supercharger is further increased. As a result, the temperature of the air supplied into the engine cylinder increases, thus causing problems such as knocking and self-ignition.

Further, a mechanical supercharger usually consists of a roots-type pump, and when such a roots-type pump is used, the pressure on the discharge side of the supercharger pulsates, unlike a supercharger consisting of an exhaust turbocharger. Therefore, if the upstream and downstream sides of a mechanical turbocharger are connected to each other via a bypass passage, the pressure pulsations generated on the discharge side of the turbocharger will propagate to the air cleaner via the bypass passage, and this pressure pulsation will cause the air cleaner to There is also the problem that air cleaners and the like generate vibration noise due to their vibration.

[0005]

[Means for Solving the Problems] In order to solve the above problems, according to the present invention, an engine-driven mechanical supercharger is arranged in the engine intake passage, and the intake passage downstream of the mechanical supercharger is The exhaust flow control valve is communicated with the atmosphere through an exhaust passage, and an exhaust flow control valve is provided in the air exhaust passage to control the opening of the exhaust flow control valve to a target opening determined by the engine operating state.

[0006]

[Operation] A part of the air discharged from the mechanical supercharger is released into the atmosphere without being returned to the upstream side of the mechanical supercharger.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows a case where the present invention is applied to a two-stroke diesel engine with a pre-chamber. Referring to Figure 1, 1 is the diesel engine body, 2 is the piston, 3 is the cylinder head, 4 is the main chamber, 5 is the intake valve, 6 is the intake port, 7 is the exhaust valve, 8 is the exhaust port, 9 is the sub Reference numeral 10 indicates a fuel injection valve disposed within the auxiliary chamber 9. Each intake port 6 is connected to a common intercooler 12 via a corresponding branch pipe 11, and the inlet of the intercooler 12 is connected to an air cleaner 14 via an intake duct 13. Disposed within the intake duct 13 are a throttle valve 16 connected to an accelerator pedal 15 and a mechanical supercharger 17 driven by the engine. The opening degree of the throttle valve 16 increases as the amount of depression of the accelerator pedal 15 increases.

An air exhaust passage 18 branches off from the intake duct 13 between the intercooler 12 and the mechanical supercharger 17.
This air exhaust passage 18 is communicated with the atmosphere via a muffler 19. An exhaust flow control valve 20 is disposed within the air exhaust passage 18 . In the embodiment shown in FIG. 1, the exhaust flow rate control valve 20 includes a negative pressure chamber 22 isolated from the atmosphere by a diaphragm 21, and a valve body 23 connected to the diaphragm 21 to control the amount of air flowing in the air exhaust passage 18. Be equipped. The negative pressure chamber 22 of the discharge flow rate control valve 20 is connected to the negative pressure conduit 24.
It is also connected to an engine-driven negative pressure pump 26 via an electromagnetic switching valve 25 that can communicate with the atmosphere. This electromagnetic switching valve 25
is controlled based on the output signal of the electronic control unit 30. Further, each exhaust port 8 is connected to a common exhaust manifold 27.

The electronic control unit 30 is composed of a digital computer, and includes a ROM (read only memory) 32, a RAM (random access memory) 33, a CPU (microprocessor) 34, and an input port 35, which are interconnected by a bidirectional bus 31. and an output port 36. The accelerator pedal 15 is equipped with a load sensor 40 that generates an output voltage proportional to the amount of depression of the accelerator pedal 15.
is attached, and the output voltage of this load sensor 40 is inputted to the input port 35 via the AD converter 37. Also,
In the negative pressure conduit 24 of the discharge flow rate control valve 20, there is an absolute pressure sensor 4 that generates an output voltage proportional to the absolute pressure in the negative pressure chamber 22.
1 is arranged, and the output voltage of this absolute pressure sensor 41 is AD
It is input to input port 35 via converter 38 . Further connected to the input port 35 is a rotational speed sensor 42 that generates an output pulse representing the engine rotational speed. On the other hand, the output port 36 is connected to the electromagnetic switching valve 25 via a drive circuit 39.

A portion of the intake air discharged from the mechanical supercharger 17 is discharged into the atmosphere through an air discharge passage 18 and a muffler 19. The amount of air discharged into the atmosphere increases as the opening degree of the exhaust flow rate control valve 20 increases, and thus the amount of air supplied into the engine cylinder decreases as the opening degree of the exhaust flow rate control valve 20 increases. On the other hand, the electromagnetic switching valve 25 is controlled by its duty ratio, and as the duty ratio increases, the time during which the negative pressure chamber 22 is communicated with the negative pressure pump 26 becomes longer than the time during which the negative pressure chamber 22 is communicated with the atmosphere. Become. Therefore, it can be seen that as the duty ratio increases, the negative pressure in the negative pressure chamber 22 increases, and thus the opening degree of the discharge flow rate control valve 20 increases.

FIG. 2 shows the optimum opening degree of the discharge flow control valve 20,
That is, the target opening degree θ of the discharge flow rate control valve 20 is shown. As can be seen from FIG. 2, the target opening degree θ is a function of, for example, the depression amount L of the accelerator pedal 15 and the engine speed N. In FIG. 2, θ0 indicates the target opening θ is zero, that is, the discharge flow control valve 20 is fully closed, and θ1
, θ2, θ3, θ4, θ5, the opening degree of the discharge flow rate control valve 20 increases. Therefore, the smaller the depression amount L of the accelerator pedal 15 and the lower the engine speed N, the larger the target opening degree θ of the exhaust flow control valve 20 becomes. Also, from θ=θ0, the accelerator pedal 15
In a region where the amount of depression L is large or in a region where the engine speed N is high, the exhaust flow control valve 20 is maintained in a fully closed state. Note that the target absolute pressure PO in the negative pressure chamber 20 necessary to obtain the target opening degree θ shown in FIG. The data is stored in advance in the ROM 32 in the form of

FIG. 4 shows a control routine for the exhaust flow rate control valve 20, and this routine is executed by interruption at regular intervals. Referring to FIG. 4, first, in step 100, the target absolute pressure PO in the negative pressure chamber 22 is calculated from the relationship shown in FIG. 3 based on the output signal of the load sensor 40 and the engine speed N. Then step 101
Then, it is determined whether the absolute pressure PM in the negative pressure chamber 22 detected by the absolute pressure sensor 41 is greater than (PO+α). Here, α is a small constant value. PM≧(PM+
If α), proceed to step 102 and
The duty ratio DT of the control pulse supplied to 5 is increased by d, thus reducing the absolute pressure PM. On the other hand, if PM≧(PO+α), step 10
The process proceeds to step 3, where it is determined whether PM≦(PO−α), and when PM≦(PO+α), the process proceeds to step 104. In step 104, the duty ratio DT is decreased by d, thus increasing the absolute pressure PM. In this way, the absolute pressure PM in the negative pressure chamber 22 becomes (PO
−α)≦PM≦(PO+α).

In the embodiment shown in FIG.
All of the excess air heated by 7 is discharged into the atmosphere via an air discharge passage 18 and a muffler 19. Therefore, it is possible to prevent high temperature air from being supplied into the engine cylinder. Furthermore, in the embodiment shown in FIG. 1, the air supplied into the engine cylinder is cooled by the intercooler 12, but since the air temperature flowing into the intercooler 12 is low, there is no need to cool the intake air so much by the intercooler 12. , thus intercooler 1
2 can be made smaller. In addition, mechanical supercharger 17
Since the pressure pulsations generated on the discharge side of the air cleaner 14 do not propagate to the air cleaner 14, it is possible to prevent the air cleaner 14 and the like from vibrating and generating vibration noise. Moreover, although this pressure pulsation propagates within the air discharge passage 18, this pressure pulsation is attenuated within the muffler 19, and thus no noise is generated.

FIG. 5 shows another embodiment. In this embodiment, the exhaust manifold 27 includes an exhaust pipe 50 and a catalytic converter 51.
, exhaust pipe 52, sub-silencer 53, exhaust pipe 54, main silencer 5
5 and an exhaust pipe 56, and the exhaust air passage 18 is connected to the exhaust pipe 52 upstream of the sub-silencer 53. In this embodiment, as shown in FIG.
Not only is there an advantage that there is no need to provide a dedicated muffler for the exhaust pipe 56, but there is also an advantage that the concentration of smoke discharged from the exhaust pipe 56 can be lowered.

[0015]

[Effects of the invention] Since the temperature of the air supplied into the engine cylinder can be kept low, knocking and self-ignition can be prevented from occurring, and furthermore, the air cleaner etc. can be prevented from generating vibration noise. be able to.

[Brief explanation of the drawing]

FIG. 1 is an overall view of a two-stroke internal combustion engine.

FIG. 2 is a diagram showing a target opening degree of a bypass control valve.

FIG. 3 is a diagram showing target absolute pressure.

FIG. 4 is a flowchart for executing bypass control.

FIG. 5 is an overall view of a two-stroke internal combustion engine showing another embodiment.

[Explanation of symbols]

13...Intake duct 17...Mechanical supercharger 18...Air exhaust passage 20...Discharge flow control valve

Claims (1)

[Claims] Claim 1: An engine-driven mechanical supercharger is disposed in an engine intake passage, the intake passage downstream of the mechanical supercharger is communicated with the atmosphere via an air exhaust passage, and an exhaust flow rate is set in the air exhaust passage. An intake control device for an internal combustion engine that includes a control valve and controls the opening degree of an exhaust flow rate control valve to a target opening degree determined by the engine operating state.