JPH03100314A - Exhaust system control device of internal combustion engine - Google Patents

Abstract

PURPOSE:To improve engine stability by cooling a long exhaust pipe in a manner, wherein a corresponding parameter difference between exhaust mass flow amounts in a plurality of exhaust pipes of different pipe length is in not more than a predetermined value, from detection of an exhaust flow speed. CONSTITUTION:Physical quantity detecting means 5, 6, constituted of full pressure pickups 7, 9 and static pressure pickups 8, 10, are respectively mounted to exhaust manifolds 2, 3. Here in a control unit 11, a parameter corresponding to a mass flow amount of exhaust is calculated being based on outputs of the physical quantity detecting means 5, 6 in accordance with a program stored in a memory in the interior. A control value of exhaust system control, in which a difference between the exhaust mass flow amounts in the exhaust manifolds 2, 3 in each bank is in not more than a predetermined value, is calculated with a control signal output to an electric motor-driven fan 12. Thus by rotating the electric motor-driven fan 12 being based on the control signal, air is fed to the exhaust manifold 2 of long pipe length to cool it. Accordingly, the exhaust mass flow amount is increased with engine stability improved.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to an exhaust system control device for an internal combustion engine, and more particularly, the present invention relates to an exhaust system control device for an internal combustion engine. The present invention relates to an exhaust system control device that improves engine stability by detecting flow velocity and cooling the long exhaust pipe side.

(Prior art) Generally, in internal combustion engines such as four-stroke engines,
The volumetric efficiency, which is the ratio between the volume of the air-fuel mixture taken into the combustion chamber and the stroke volume of the internal combustion engine, greatly affects the output characteristics of the engine. It is known that it is affected by the system configuration and engine speed.

For this purpose, devices for controlling the exhaust system have been developed. For example, a device similar to the conventional exhaust system control device for this type of internal combustion engine is described in Japanese Patent Application Laid-Open No. 153424/1983 [for Multi-Cylinder Engines]. There is a device called "Performance Improvement Method".

With this device, the valve timing overramp angle of cylinders with long exhaust pipes is set to be larger than the valve timing overramp angle of cylinders with short exhaust pipes, thereby improving performance without making any changes to the intake or exhaust pipes, etc. The intention is to improve the

(Problem to be Solved by the Invention) However, in such conventional devices, the difference in tube length is equalized by a bulb overramp, so although the output performance can be approximately equalized, the valve Because the timing is manipulated, there is a large rebound in the output, which impairs engine stability, especially idling stability.

It should be noted that, in principle, it is better for the overramp angle of the valve timing to be small during idling, but this is contrary to the above-mentioned conventional device. The above phenomenon is due to the fact that when the exhaust pipe lengths are different, the filling efficiency of the cylinder on the long exhaust passage side becomes low, which not only deteriorates engine stability but also the output, but conventionally, countermeasures against idle stability have been taken. There will be.

(Objective of the Invention) Therefore, an object of the present invention is to increase the exhaust mass flow rate and improve engine stability by detecting the exhaust flow velocity and cooling the long exhaust passage based on this information.

(Means for Solving the Problems) In order to achieve the above object, the exhaust system control device for an internal combustion engine according to the present invention detects a physical quantity related to the flow velocity of exhaust gas in an internal combustion engine having a plurality of exhaust pipes with different pipe lengths. The means a and the calculating means for calculating a parameter corresponding to the mass flow rate of exhaust gas based on the output of the physical quantity detecting means a include a long exhaust pipe such that the difference in exhaust mass flow rate in the plurality of exhaust pipes is equal to or less than a predetermined value. and a cooling means d that cools the long exhaust pipe based on the output of the control means C.

(Operation) In the present invention, parameters corresponding to exhaust mass flow rates in a plurality of exhaust pipes are calculated by directly detecting the exhaust flow velocity, and long exhaust pipes are cooled so that the difference between the two becomes equal to or less than a predetermined value.

Therefore, cooling improves the filling efficiency of the cylinders on the exhaust pipe side, equalizes performance among the cylinders, and improves engine stability.

(Example) Hereinafter, the present invention will be explained based on the drawings.

2 to 6 are diagrams showing one embodiment of an exhaust system control device for an internal combustion engine according to the present invention, and are examples in which the present invention is applied to a V-type six-cylinder engine. In FIG. 2, l is a V-type 6-cylinder engine, and six cylinders represented by #1 to #6 are arranged in a V-shape for each bank (first bank and second bank). The three cylinders in the first bank on the left side of the figure are connected to the exhaust manifold 2, and the three cylinders in the second bank on the right side are connected to the exhaust manifold 3. The exhaust manifolds 2.3 join in the middle and are combined into one exhaust front tube 4.
The exhaust gas from each cylinder is discharged to the outside through.

The exhaust manifolds 2.3 have different pipe lengths corresponding to each bank, and the exhaust manifold 2 on the first bank side has a longer pipe length than the exhaust manifold 13 on the second bank side.

The exhaust manifolds 2 and 3 are each provided with physical quantity detection means 5.6, which detect physical quantities related to the exhaust flow velocity in each bank (in this embodiment, the static pressure and total pressure of intake air).
It is designed to detect.

Here, the physical quantity detection means 5 is constituted by a total pressure pickup 7 and a static pressure pickup 8 attached to the exhaust manifold 2, as shown in FIG. These are for measuring the flow velocity of exhaust gas in the exhaust manifold 2 by applying the principle of a so-called pitot tube. Specifically, as shown in FIG. 4, for example, a voltage element 7a at the tip,
8a is provided, and the static pressure P and total pressure (total pressure) P2 of the exhaust gas are measured by the voltage elements 7a and 8a, converted into electrical signals, and taken out to the outside. Note that the structure of the other physical ff1Ji2 output means 6 is the same as that of the physical quantity detection means 5,
Total pressure pinkup and static pressure pisoqua.

11, and detects the total pressure P4 and static pressure P3, respectively.

The signal from the physical quantity detection means 5.6 is input to the control unit 11, which has functions as arithmetic means and control means, is mainly composed of a microcomputer, and is stored in an internal memory. The parameters corresponding to the exhaust mass flow rate are calculated based on the outputs of the physical quantity detection means 5 and 6 according to the program, and the exhaust system is controlled so that the difference in the exhaust mass flow rate in the exhaust manifolds 2.3 of each bank is equal to or less than a predetermined value. A control value S is calculated and a control signal S is output to the electric fan 12 (corresponding to cooling means). The electric fan 12 rotates based on a control signal S, and sends air to the long exhaust manifold 2 for cooling.

Next, the effect will be explained.

FIG. 5 is a flowchart showing a program for controlling the exhaust system, and this program is executed once every predetermined time.

First, in step S1, the static pressure Pl on the first bank side, the total pressure P
2 and the static pressure P3 and total pressure P4 on the second bank side, and in step S2, these total pressures P, , P, and static pressure P,
, P, the dynamic pressure of each bank is determined according to the following equation.

ρu+"=pz T)+ ■ ρuz""p4-p3 However, ρ: Density of exhaust uI: Exhaust flow velocity of the first bank u2: Exhaust flow velocity of the second bank The above formula is based on Bernoulli's theorem. It is well known that velocity can be determined from pressure.

Next, in step S3, the average value of the dynamic pressure of each bank is calculated, and these are designated as A and A2. The average value is determined by the usual arithmetic mean. Note that A and A2 correspond to parameters corresponding to the mass flow rate of exhaust gas. Next, in step S4, the difference between A2 and A is calculated according to the following formula: ΔA=A2-A.

In step S5, ΔA is compared with a predetermined value. ΔA is the difference between the average dynamic pressures of both banks, and the above comparison is performed in order to control this to a predetermined value or less. When ΔA>K, the electric fan 12 is driven (fan ON) in step S6, and the exhaust manifold 2 is cooled by air. On the other hand, when ΔA≦, the drive of the electric fan I2 is stopped (fan 0FF) in step St, and the routine ends.

The above process can reduce the difference in the mass flow rate of the exhaust gas between the two banks. Here, the mass flow rate refers to the mass of the flow rate per unit time, and the mass flow rate - u x ρ x B. However, U : Exhaust flow velocity B: Area of exhaust passage. Applying this to the first and second banks, tJ+ Xl)+ ×B+ =uz Xρ2 XB
2 However, B1: Passage area B2 of exhaust manifold 2
= Passage area ρ1 of exhaust manifold 3. ρ2: If 2, which is the density of exhaust air in each bank, is established, the filling efficiency of both banks becomes equal.

Here, since B,=B2, U,Xρl ==lJ2Xρ2.For example, when u,<u2, electric fan 1
2 to cool the exhaust manifold 2, the density ρ1 of the exhaust gas on the first bank side increases, and ρ1〉
It becomes ρ2. As a result, uI × ρI = l12
The condition X ρ2 is satisfied. As a result, the exhaust mass flow rate of the exhaust manifold 2 on the first bank side increases, the filling efficiency increases, the performance among the cylinders of each bank is made uniform, the engine stability is improved, and the output is also improved.

FIG. 6 is a graph showing the change in engine speed when the electric fan 12 is turned on at 0N10FF.As is clear from this figure, when the electric fan 12 is turned on, fluctuations in the engine speed are suppressed and engine stability is improved. will improve. This effect is particularly noticeable during idle, and greatly contributes to improving idle stability.

The application of the present invention is not limited to the type 6 six-cylinder engine as in the above embodiment, but can also be applied to other types of engines with different pipe lengths.

Further, other suitable means may be used for cooling, and the physical quantity detection means is not limited to a pitot tube, but may also use a resonator, for example.

(Effect) According to the present invention, a parameter corresponding to the mass flow rate of the exhaust gas is detected, and a long exhaust pipe is cooled so that the difference in the parameter among a plurality of exhaust pipes is equal to or less than a predetermined value. Therefore, the exhaust mass flow rate can be increased and engine stability can be improved.

[Brief explanation of drawings]

FIG. 1 is a basic conceptual diagram of the present invention, FIGS. 2 to 6 are diagrams showing an embodiment of an exhaust system control device for an internal combustion engine according to the present invention, FIG. 2 is an overall configuration diagram thereof, and FIG. 4 is a diagram showing the arrangement of the physical quantity detecting means, FIG. 4 is a diagram showing the configuration of the physical quantity detecting means, FIG. 5 is a flowchart showing the exhaust system control program, and FIG. 6 is a diagram for explaining the effect. It is a graph. I...Engine, 2.3...Exhaust manifold, 4...
Exhaust front tube, 5.6...physical quantity detection means, 7.9...total pressure big amplifier, 8.10...
... Static pressure pickup, 11 ... Control unit (calculating means, control means), 12 ... Electric fan (cooling means).

Claims (1)

[Scope of Claims] a) Physical quantity detection means for detecting a physical quantity related to the flow velocity of exhaust gas in an internal combustion engine having a plurality of exhaust pipes with different pipe lengths; b) A method for determining the mass flow rate of exhaust gas based on the output of the physical quantity detection means. a calculation means for calculating corresponding parameters; c) a control means for calculating a control value for cooling a long exhaust pipe so that the difference in exhaust mass flow rate in a plurality of exhaust pipes is equal to or less than a predetermined value; and d) a control means for calculating a control value. An exhaust system control device for an internal combustion engine, comprising a cooling means for cooling a long exhaust pipe based on output.