JPH0396651A - Exhaust gas reflux controller of diesel engine - Google Patents

Abstract

PURPOSE:To properly perform EGR control by detecting variation of intake swirl strength, and adjusting EGR quantity in response to an engine operation condition based on the detection signal in the case that abnormality is found at a member for controlling a variable swirl means. CONSTITUTION:At respective sub-intake passages 8 connected to intake ports 3 in cylinders 2 of an engine 1, flow sensors 10 are arranged at the upstream side of control valves 9. A lift quantity of each EGR valve 12 is adjusted by controlling at least each actuator 17 based on the detection signal of at least each flow sensor 10. In this case, the lift quantity of the EGR valves 12 is adjusted according to a specified map corresponding to an operation condition of the engine 1. Consequently, even if abnormality occurs in the control valves 9 to vary flow quantity of intake air which passes through sub-intake passages 8, which results in that a swirl ratio is varied, adjustment of the EGR quantity in response hereto is properly performed.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an exhaust gas recirculation (EGR) control device for a diesel engine equipped with variable swirl means capable of changing the strength of intake swirl generated within a combustion chamber. .

(Prior technology) E as a NOx reduction system for diesel engines
There is a GR system. This EGR system generally includes an exhaust gas recirculation flow control valve (EGR valve) in the exhaust gas recirculation passage (EGR passage) that communicates the exhaust passage and intake passage of the engine, and adjusts the lift amount of the EGR valve based on the engine speed and the engine speed. The system controls the engine load according to the engine load and changes the EGRI according to the engine operating condition, thereby reducing NOx emissions over a wide operating range. In addition, in direct injection diesel engines, combustion improvement using intake swirl is performed depending on the engine speed and engine load, so the intake port is set to generate intake swirl in the combustion chamber. It is known that a sub-intake passage is provided for introducing intake air into the intake boat in a direction that weakens or strengthens the intake swirl.

Furthermore, as disclosed in JP-A-63-309721, for example, a system has been proposed in which exhaust gas is introduced into the intake boat from the sub-intake passage to perform EGR control and variable swirl control at the same time. It has been done. By the way, in direct injection diesel engines, it has been considered to use the heat of EGR gas to heat the combustion chamber at low speeds and low loads.
In other words, the idea is to heat the combustion chamber by introducing recirculated exhaust gas and improve the ignitability of the fuel at low engine speeds and low loads, when the heat generated by combustion is small and it is difficult to maintain the combustion chamber wall surface at a high temperature. It is being done. In this case, if the force of the intake air swirl is strong, a small amount of fuel will be diffused by the swirl and the ignitability will deteriorate, so it is desirable to have a small swirl ratio (the swirl ratio is the number of revolutions of intake air per revolution of the engine). (The higher the swirl ratio, the stronger the swirl). On the other hand, at high rotation speeds and high loads, it is desired to increase the swirl ratio as much as possible to increase the air utilization rate, that is, to improve the output while suppressing the generation of smoke. In this case, the amount of heat generated by combustion is sufficiently large compared to when the load is low, so the amount of EGR may be small in order to heat the combustion chamber. EGRIg like this
In a diesel engine equipped with a control means and a variable swirl means, the EGR valve installed in the EGR passage is not only controlled according to the engine speed and engine load, but also the amount of EGR is finely controlled according to changes in the swirl ratio. It is desirable to be able to adjust the However, in conventional engines of this type, both the lift amount of the control valve for adjusting the swirl ratio and the opening degree of the control valve for adjusting the EGR amount are set according to the engine rotation speed and engine load. If the control valve for adjusting the swirl ratio has deteriorated over time or has malfunctioned, the flow rate of intake air flowing through the auxiliary intake passage changes, and as a result, the swirl ratio fluctuates. , because the lift amount of the EGR valve cannot be adjusted accordingly, NO,! emissions will increase, and N
Even if the amount of OX emissions can be reduced, there is a problem in that HC emission characteristics, smoke characteristics, fuel efficiency characteristics, etc. deteriorate.

(Purpose of the Invention) Therefore, the present invention provides a diesel engine equipped with an EGR amount adjusting means and a variable swirl means, and even when a control member in the variable swirl means deteriorates or breaks down due to aging, the present invention provides accurate EGR control. An object of the present invention is to provide an EGR control device that can perform control.

(Structure of the Invention) The EGR control device according to the present invention includes a flow rate sensor or a flow rate sensor that detects changes in the strength of intake swirl in the intake system, and based on the output signal of this sensor, controls the EGR amount adjustment means to operate the engine. It is characterized by being controlled in accordance with the state.

(Effects of the Invention) According to the present invention, the flow rate or flow velocity of the intake air actually flowing through the sub-intake passage is detected by the flow rate sensor or the flow rate sensor, and the EGR amount is adjusted based on this detection signal. Even if a control member in the device deteriorates or breaks down due to changes over time, it is possible to adjust the EGR amount accordingly, reducing NO and emissions without causing deterioration of HC emission characteristics, smoke characteristics, etc. It has the effect of reducing

(Embodiments) Hereinafter, embodiments of the present invention will be described with reference to the drawings.

In FIG. 1, reference numeral 1 denotes an engine body, which is configured as an in-line four-cylinder type engine having four cylinders (combustion chambers) 2. Each cylinder 2 has an intake boat 3 and an exhaust boat 4 opening therein. An independent intake passage 5a branched from the common intake passage 5 is connected to the intake port 3, and an independent exhaust passage 6a branched from the common exhaust passage 6 is connected to the exhaust port 4. The intake boat 3 is a helicopter port, and the intake air that has passed through the intake boat 3 is supplied into the combustion chamber 2 while generating a swirl that swirls counterclockwise in the figure. A sub-intake passage 8 is led out from each independent intake passage 5a. The downstream end of this sub-intake passage 8 opens into the intake boat 3, but its opening position and direction are such that the intake swirl flowing through the intake port 3 is weakened by the intake air supplied from the sub-intake passage 8. location and orientation. That is, in the case of this embodiment, the opening position of the auxiliary intake passage 8 is near the downstream end of the intake port 3, and the opening position of the auxiliary intake passage 8 is approximately in front of the intake air from the independent intake passage 5a where the intake air from the auxiliary intake passage 8 is swirled. is oriented to impinge on the air and weaken the intake swirl.

As shown in FIG. 2, each sub-intake passage 8 is provided with a control valve 9 for opening and closing the sub-intake passage 8 to adjust the swirl ratio.Furthermore, on the upstream side of this control valve 9, A flow rate sensor 10 is provided to detect the flow rate of intake air passing through the sub-intake passage 8. An EGR passage 11 for recirculating part of the exhaust gas into the independent intake passage 5a is provided between each independent exhaust passage 6a and the independent intake passage 5a. An EGR valve 12 for controlling external EGRf in each of the two is disposed.

On the other hand, based on the over-ramp of the opening period of the intake and exhaust valves (not shown) from the end of the exhaust stroke to the beginning of the intake stroke in each cylinder 2, exhaust gas is pulled back to the combustion chamber by intake negative pressure to perform internal EGR. The common intake passage 5 is provided with an intake throttle valve 13, and the common exhaust passage 5 is provided with an intake throttle valve 13.
The passage 6 is provided with an exhaust shank valve 14. The control valves 9 that open and close the auxiliary intake passage 8 to adjust the swirl ratio are operated all at once by a common actuator 16 that is driven by a control signal output from the control unit 15. Each is actuated by a separate actuator l7, and the intake throttle valve 13 and the exhaust shutter valve l4 are also actuated by one actuator 18.

As these actuators 16 to 19, for example, negative pressure diaphragm type actuators that are controlled by a control valve provided in a negative pressure introduction passage are used. The control unit 15 receives an engine speed signal from an engine speed sensor 21 provided on the fuel injection bomb 20 and the amount of depression of the accelerator pedal, that is, the engine load, which is linked to the position of the control lever on the bomb 20. The accelerator opening signal from the accelerator opening sensor 22 to be detected, the flow rate signal from the flow rate sensor 10 provided in each sub-intake passage 8 and detecting the amount of intake air flowing through the sub-intake IL passage 8, and others are input, and the control is performed. The Unisoto 15 is configured to drive each actuator 16 to 19 based on input signals from these sensors 10, 21, and 22. Then, by controlling the actuator 16 to open and close the control valve 9 based on the engine speed and the accelerator opening, the flow rate of the intake air passing through the auxiliary intake ill passage 8 is controlled, and the swirl ratio is thereby adjusted as shown in FIG. It changes as shown in the graph below. Further, by controlling the actuator 17 and adjusting the lift amount of the EGR valve 12 based on the engine speed and the accelerator opening degree, the EGR rate changes as shown in the graph of FIG. 4. Furthermore, by adjusting the lift amount of the EGR valve 12 according to the mass control shown in FIG. 5 in accordance with the flow rate of intake air passing through the sub-intake passage 8 detected by the flow rate sensor 10, deterioration, failure, etc. can be prevented in the control valve 9. Even if this causes a change in the flow rate of intake air passing through the sub-intake passage 8 and thereby changes the swell ratio, the EGR amount can be immediately and accurately adjusted for each cylinder 2 in response to the change. In the above embodiment, the flow rate sensor 10 is used to detect the flow rate of the intake air flowing through the sub-intake passage 8, and the swirl ratio of the intake air is determined thereby. You may use it. Alternatively, the strength of the intake swirl may be directly measured using an intake swirl sensor.

Further, in the above embodiment, an EGR passage 11 equipped with an EGR valve I2 is provided between each independent exhaust Iil passage 6a and an independent intake passage 5a to perform external EGR control. For example, exhaust valve 1
The present invention can also be applied to the case where internal EGR control is performed using only EGR control.

Furthermore, the present invention provides an intake boat 3 instead of the auxiliary intake passage 8.
It can also be applied to engines equipped with variable swirl means in which an intake air flow changing plate is installed.

[Brief explanation of drawings]

FIG. 1 is an overall system diagram showing an embodiment of the present invention, FIG. 2 is a sectional view near the intake boat, FIGS. 3 and 4 are graphs showing the swirl ratio and EGR rate obtained by the present invention, and FIG. FIG. 5 is a map showing the relationship between the flow velocity of intake air flowing through the sub-intake passage and the EGR rate. 1--1 Engine body 2-1 Cylinder (combustion chamber) 3- Intake port 4- Exhaust port 5- Common intake passage
5a - independent intake passage 6 - - common exhaust passage 6a
・--Independent exhaust passage 8 - Sub-intake passage 9 - Swirl ratio adjustment control valve 10 - Flow rate sensor 1 1 --- E G R passage 1 2 - E G R valve 13 - = Intake throttle valve 1
4 - Exhaust shutter valve 5 - Control unit 6 - IL - Actuator ○1 Fuel injection bomb 1 - Engine speed sensor 2 - Accelerator opening sensor

Claims (1)

[Scope of Claims] A diesel engine equipped with an exhaust gas recirculation amount adjustment means for adjusting the amount of exhaust gas recirculation, and a variable swirl means provided in the intake system and capable of changing the strength of the intake swirl generated in the combustion chamber. In the engine, a flow rate sensor or a flow rate sensor is provided in the intake system to detect changes in the strength of the intake swirl, and the exhaust gas recirculation amount adjusting means is adjusted to correspond to the engine operating state based on the output signal of this sensor. 1. An exhaust gas recirculation control device for a diesel engine, comprising: control means for controlling the exhaust gas recirculation of a diesel engine.