JPH06257517A - Exhaust gas reflux controller and control method for internal combustion engine - Google Patents

Abstract

PURPOSE:To supply the optimum EGR quantity even when the temperature of an EGR valve is in a transient condition. CONSTITUTION:A reflux pipe 4 for circulating the exhaust gas of an internal combustion engine 1 to an intake pipe 2 via an EGR(exhaust gas reflux) valve 5 is provided and a temperature detection means 9 is provided at the EGR valve 5. And controllers 6, 8 are also provided for calculating the opening of the EGR valve 5 based on rotational speed and a fuel injection quantity of the internal combustion engine 1, and for opening/closing the EGR valve 5 based on the calculated result.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exhaust gas recirculation control device for recirculating exhaust gas to an intake pipe in an internal combustion engine to control a combustion temperature in a cylinder.

[0002]

2. Description of the Related Art An example of a conventional exhaust gas recirculation control system for an internal combustion engine will be described with reference to FIG. 3. An intake pipe 2 and an exhaust pipe 3 are connected to a diesel engine 1. The diesel engine 1 operates by burning a mixture of air sucked into the cylinder via the intake pipe 2 and fuel gas injected into the cylinder in the cylinder. Further, the exhaust gas generated by the combustion in the cylinder is exhausted via the exhaust pipe 3.

The intake pipe 2 and the exhaust pipe 3 are connected via a recirculation pipe 4, and an EGR valve 5 is interposed in the recirculation pipe 4. The opening / closing operation of the EGR valve 5 is controlled by a vacuum regulation valve 6, and the vacuum regulation valve 6 is supplied with a negative pressure from a vacuum pump 7 which operates based on the operation of the diesel engine 1.

The vacuum regulation valve 6 is controlled based on an output signal of an electronic control unit (hereinafter referred to as ECU) 8, and the ECU 8 has a detection signal SGr for detecting the rotation speed of the diesel engine 1 and an in-cylinder A detection signal SGf for detecting the amount of fuel injected into the engine is input.

Therefore, the ECU is determined based on the rotation speed of the diesel engine 1 and the fuel injection amount into the cylinder.
A control signal is output from 8 to the vacuum regulation valve 6. The vacuum regulation valve 6 controls the negative pressure supplied to the EGR valve 5 based on its control signal, and the EGR valve 5 has its opening adjusted based on the negative pressure supplied from the vacuum regulation valve 6. .

In such an exhaust gas recirculation control device,
The exhaust gas recirculation amount (EGR amount) is set as follows. That is, as shown in FIG. 4, the ECU 8 controls the opening degree of the EGR valve 5 via the vacuum regulation valve 6 based on the fuel injection amount F and the engine speed R which fluctuate based on the throttle operation.

The solid curve in the upper part of FIG. 4 is a curve showing the maximum fuel injection amount at each engine speed R,
The state of the engine during normal operation exists in the area below this solid line.

Then, for example, when the engine speed R is in the low speed region based on the arbitrary fuel injection amount F, E
The GR amount increases as the engine speed increases, and the limit value for the fuel injection amount F is set by the smoke limit line L1 which is the maximum value in a range where smoke is not generated as exhaust gas. That is, when the EGR amount is too large, the fuel gas in the cylinder is in an incomplete combustion state and black smoke is generated. Further, if an appropriate amount of EGR is supplied, the combustion temperature in the cylinder is suppressed and NOx generation is suppressed.

Further, when the engine speed R shifts to a high speed region, the EGR amount decreases with an increase in the engine speed R, and the limit value is the maximum value within a range where the EGR valve 5 is not destroyed by high temperature. It is set to the temperature limit line L2. That is, when the engine speed R becomes high and the amount of exhaust gas passing through the EGR valve 5 per unit time increases, the temperature of the EGR valve 5 rises. If the temperature of the EGR valve 5 exceeds the limit value, normal operation of the EGR valve 5 may be hindered. Further, in such a high rotation region, the temperature limit line L2 becomes lower than the smoke limit line L1.

[0010]

In the exhaust gas recirculation control device as described above, the EGR amount is set only on the basis of the fuel injection amount F and the engine speed R.

On the other hand, as shown in FIG. 5, when the EGR valve 5 is in the off state, that is, in the closed state, the temperature T of the EGR valve 5 does not rise, and when the EGR valve 5 is turned on and opened. The temperature T of the EGR valve 5 rises.

That is, based on the detection signals SGr and SGf, the EGR valve 5 is turned off from the state where the EGR valve 5 is turned off.
When the R valve 5 is turned on, the time tk in the transient state until the temperature T of the EGR valve 5 reaches the steady temperature corresponding to the fuel injection amount F and the engine speed R is 10.
It takes about 20 minutes.

However, the EGR amount is set only on the basis of the fuel injection amount F and the engine speed R. As a result, even when the EGR valve 5 is just turned on from the off state, if the engine speed R is in the high rotation range, E
Although the temperature T of the GR valve 5 is low, the EGR amount is determined based on the preset temperature limit line L2. Therefore, it becomes possible to supply only an EGR amount much smaller than the EGR amount that can be supplied by the EGR valve 5, and NO
There is a problem that x cannot be suppressed effectively.

The present invention has been made in view of the above problems, and an object thereof is to provide an exhaust gas recirculation control device capable of supplying an optimum EGR amount even when the temperature of the EGR valve is in a transient state. To provide.

[0015]

In order to achieve the above object, the present invention is provided with a recirculation pipe for recirculating exhaust gas of an internal combustion engine to an intake pipe through an EGR valve, and the EGR valve is provided with a temperature detecting means. A control device that is provided, calculates the opening degree of the EGR valve based on the detection signal of the temperature detection means, the rotation speed of the internal combustion engine, and the fuel injection amount, and opens and closes the EGR valve based on the calculation result. Is provided.

Further, an internal combustion engine is provided with a recirculation pipe for recirculating exhaust gas to an intake pipe via an EGR valve, and the exhaust gas recirculation for controlling the opening degree of the EGR valve based on the rotational speed of the internal combustion engine and the fuel injection amount. In the control method, the EG
When the temperature of the R valve is detected and the rotation speed of the internal combustion engine is equal to or higher than a predetermined value, the rotation speed and the fuel injection amount are determined based on the detected temperature of the EGR valve and a preset limit temperature of the EGR valve. The recirculation possible region of the exhaust gas calculated by the above is changed.

[0017]

The opening of the EGR valve is calculated on the basis of the detection signal of the temperature detecting means, the rotational speed of the internal combustion engine and the fuel injection amount. Therefore, when the temperature of the EGR valve has not reached the limit temperature, the optimum amount of exhaust gas corresponding to the temperature of the EGR valve is recirculated to the intake pipe.

[0018]

1 and 2 show an embodiment of the present invention. The same components as those in the conventional example will be described with the same reference numerals.

As shown in FIG. 1, a diesel engine 1
An intake pipe 2 and an exhaust pipe 3 are connected to. The intake pipe 2
And the exhaust pipe 3 are connected via a return pipe 4, and the return pipe 4
An EGR valve 5 is interposed in the. The opening / closing operation of the EGR valve 5 is controlled by a vacuum regulation valve 6, and the vacuum regulation valve 6 is supplied with a negative pressure from a vacuum pump 7.

The vacuum regulation valve 6 is E
Controlled based on the output signal of the CU 8, the ECU 8 is supplied with the signals SGr and SGf for detecting the rotational speed R of the diesel engine 1 and the fuel injection amount F into the cylinder.

The EGR valve 5 is provided with a temperature sensor 9, and the temperature sensor 9 outputs a temperature signal SGt based on the temperature of the EGR valve 5 to the ECU 8. Therefore, the ECU 8 outputs a control signal to the vacuum regulation valve 6 based on the detection signal SGr of the rotational speed R of the diesel engine 1, the detection signal SGf of the fuel injection amount F, and the detection signal SGt of the temperature sensor 9.

The vacuum regulate valve 6 controls the negative pressure supplied to the EGR valve 5 based on its control signal, and the EGR valve 5 has its opening degree changed based on the negative pressure supplied from the vacuum regulate valve 6. Adjusted.

In such an exhaust gas recirculation control device,
The EGR amount is set as follows. That is, FIG.
As shown in (4), the ECU 8 sends a signal via the vacuum regulate valve 6 based on the fuel injection amount F based on the accelerator pedal depression amount, the engine speed R, and the detection signals SGr, SGf, SGt based on the temperature of the EGR valve 5. The opening degree of the EGR valve 5 is controlled.

The solid curve in the upper part of FIG. 2 is a curve showing the maximum fuel injection amount at each engine speed R, as in the prior art. Then, in the state where the engine speed R is in the low speed region, the EGR amount is set to the smoke limit line L1 which increases with the increase of the engine speed R.

When the engine speed R shifts to a high engine speed range, the EGR amount is set within a range of a plurality of temperature limit lines Lt1 to Ltn which are reduced as the engine speed R increases. The temperature limit lines Lt1 to Ltn fluctuate based on the detection signal SGt that detects the temperature of the EGR valve 5,
When the temperature of the valve 5 rises, the EGR amount decreases by moving toward the temperature limit line Ltn, and when the temperature of the EGR valve 5 decreases, the EGR amount increases by moving toward the temperature limit line Lt1. It is set.

In the exhaust gas recirculation control device thus constructed, the EGR amount is set at the smoke limit line L1 when the engine speed R is in the low engine speed region, and the EGR amount increases as the engine speed R increases. Will increase.

When the engine speed R shifts to a high engine speed range, the EGR amount becomes equal to the smoke limit line L1 and the temperature limit line Lt1.
It is set by either Ltn. That is, when the EGR valve 5 is turned on from the off state, the temperature T of the EGR valve 5 is still low, so the EGR amount is set by the temperature limit line Lt1. Therefore, since the temperature limit line Lt1 exceeds the smoke limit line L1 at most engine speeds R, the EGR amount is set substantially at the smoke limit line L1.

Further, the EGR valve 5 continues to be turned on,
When the temperature T of the EGR valve 5 rises, the temperature limit line sequentially shifts toward the same Ltn as the temperature T rises, and the EGR amount is set based on the temperature boundary line.

In the above embodiment, the detection signals SGr,
The SGf detection means was not described in detail. To give some examples, the direct detection means of the detection signal SGr is to provide a magnetic sensor close to the end of the gear directly connected to the crankshaft to convert the rotation of the crankshaft into a pulse signal. Existing means such as

Further, as an indirect detecting means, there is a means for detecting a negative pressure of intake air which fluctuates due to fluctuation of the engine speed by a pressure sensor. Examples of means for detecting the detection signal SGf include means for electrically detecting the depression amount of the accelerator pedal.

The detection signals SGr, S are not limited to these.
Other existing means may be used as the means for detecting Gf. As described above, in this exhaust gas recirculation control device, the EGR amount is set by the smoke limit line L1 and the plurality of temperature limit lines Lt1 to Ltn based on the temperature of the EGR valve 5. Therefore, when the engine speed R is in the high speed range, E
Since the optimum EGR amount corresponding to the temperature of the GR valve 5 can be set, NOx can be effectively suppressed.

[0032]

As described above in detail, the present invention is based on EGR.
Optimal EGR even when the valve temperature is in a transient state
It is possible to provide an exhaust gas recirculation control device for an internal combustion engine that is capable of supplying a large amount of gas, and has an excellent effect.

[Brief description of drawings]

FIG. 1 is a configuration diagram illustrating an exhaust gas recirculation control device according to an embodiment.

FIG. 2 is an explanatory diagram showing an operation of an exhaust gas recirculation control device according to an embodiment.

FIG. 3 is a configuration diagram showing an exhaust gas recirculation control device of a conventional example.

FIG. 4 is an explanatory diagram showing an operation of a conventional exhaust gas recirculation control device.

FIG. 5 is an explanatory diagram showing the relationship between the operation of the EGR valve and the temperature.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Diesel engine as an internal combustion engine, 2 ... Intake pipe, 4 ... Recirculation pipe, 5 ... EGR valve, 6 ... Vacuum regulation valve as a control device, 8 ... ECU as a control device, 9 ... As temperature detecting means Temperature sensor.

Claims (2)

[Claims] 1. A recirculation pipe for recirculating exhaust gas of an internal combustion engine to an intake pipe via an EGR valve is provided, and an opening degree of the EGR valve is calculated based on a rotational speed of the internal combustion engine and a fuel injection amount. In an exhaust gas recirculation control device that opens and closes an EGR valve based on a calculation result, the EGR valve is provided with a temperature detecting means, and based on a detection signal of the temperature detecting means and a rotation speed and a fuel injection amount of the internal combustion engine. An exhaust gas recirculation control device for an internal combustion engine, comprising a control device that calculates an opening degree of the EGR valve and opens and closes the EGR valve based on the calculation result. 2. An exhaust gas recirculation system in which an internal combustion engine is provided with a recirculation pipe for recirculating exhaust gas to an intake pipe via an EGR valve, and the opening degree of the EGR valve is controlled based on the rotational speed of the internal combustion engine and the fuel injection amount. In the control method, the temperature of the EGR valve is detected, and when the rotation speed of the internal combustion engine is equal to or higher than a predetermined value, the rotation speed is based on the detected temperature of the EGR valve and a preset limit temperature of the EGR valve. And an exhaust gas recirculation control method for an internal combustion engine, wherein the recirculation possible region of the exhaust gas calculated by the fuel injection amount is changed.