JPS59120771A - Exhaust gas recirculation control method of diesel engine - Google Patents

Abstract

PURPOSE:To prevent the occurrence of which smoke by increasing the exhaust gas recirculation flow when the suction pressure downstream a suction throttle section becomes a predetermined value or lower in a Diesel engine performing suction throttling during an idle operation. CONSTITUTION:When an engine is in operation, a control device 25 controls to open both negative pressure control valves 21, 22 and fully open an auxiliary suction throttle valve 16 during the warmup operation with the detected temperature of the cooling water by a water temperature sensor 28 at a predetermined value or lower, and to open only the negative pressure control valve 22 and half-open the auxiliary suction throttle valve 16 after the warmup is completed. Furthermore, the control device determines the standard EGR gas flow Qe based on outputs of an acceleration sensor 29 and a rotation speed sensor 26. When the detected value Pi of the suction pipe negative pressure by a suction pressure sensor 26 is predetermined value or lower and there is a fear of the occurrence of white smoke, a pulse signal with a duty ratio in response to the flow with the flow augmentation quantity DELTAQe increasing in response to the reduction of the suction pressure added to the said flow Qe is applied to a negative pressure control valve 43 to control the opening of an EGR valve 34.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an exhaust gas recirculation control method for an easel engine used in a vehicle such as an automobile, and more specifically to a method for controlling exhaust gas recirculation in a diesel engine whose intake air is throttled during idle operation. It concerns the control method.

In diesel engines used in vehicles such as automobiles, it is effective to perform so-called exhaust gas recirculation, in which a portion of the exhaust gas is returned to the engine intake system, in order to reduce NOx in the exhaust gas. has long been known, and this exhaust gas recirculation is a system that replaces part of the excess intake air drawn into the engine combustion chamber with exhaust gas according to the engine load, or in other words, the amount of fuel injection. It is done in flow rate.

In diesel engines used in vehicles such as automobiles, in order to eliminate vibrations during idling, an intake throttle valve installed in the middle of the engine intake system throttles the intake air during idling to reduce the amount of air intake into the engine. It has been known for some time that it is effective to limit the engine speed, and in view of this, a diesel engine that throttles the intake air during idling operation has already been proposed. If intake throttling is performed during idling operation, the idling vibration of the engine will be reduced, but the intake pressure will decrease (), and white smoke will be more likely to be generated due to incomplete combustion of fuel. When throttling is performed, the intake pressure may drop beyond the allowable value as the atmospheric pressure drops, and white smoke may be generated.

The present invention aims to provide an exhaust gas recirculation control method that can prevent the generation of white smoke as described above. It is characterized in that the intake pressure in the intake passage downstream of the intake throttle section is detected, and when the intake pressure is below a predetermined value, the exhaust gas recirculation flow rate is increased.

According to the exhaust gas recirculation control method of the present invention, when the intake pressure is below a predetermined value, that is, when there is a risk of white smoke being generated, the intake pressure is increased by increasing the exhaust gas recirculation flow rate. , the intake air temperature during compression increases and white smoke generation is prevented.

The invention will now be described in detail by way of example embodiments with reference to the accompanying drawings.

FIG. 1 shows an embodiment of a diesel engine equipped with an exhaust gas recirculation control device implementing the exhaust gas recirculation control method according to the present invention. In the figure, 1 indicates a diesel engine, which has a cylinder bore 2, a piston 3 is slidably received in the cylinder bore, and a combustion chamber 4 is defined above the piston 3. There is. The Diegel engine 1 has a swirl chamber 6 communicating with the combustion chamber 4 through a nozzle 5, and liquid fuel for diesel engines is injected into the swirl chamber from a fuel injection nozzle 7. Teru. The diesel engine 1 takes air into the combustion chamber 4 through an intake throttle device 8 and an intake manifold 9 through an intake port (not shown), and discharges exhaust gas from the combustion chamber 4 through an exhaust port 10 to an exhaust manifold 11. The intake boat and the exhaust port 10 are each opened and closed by a poppet valve, and in FIG. 1, only the exhaust poppet valve is shown by reference numeral 12.

The intake throttle device 8 includes a main intake throttle valve 14 that opens and closes the main intake passage 13, and a sub-intake throttle valve 16 that opens and closes a sub-intake passage 15 provided to bypass the main intake passage 13. The main intake throttle valve 14 is drivingly connected to the accelerator pedal 17, and is located at the fully open position as shown in the figure when the accelerator pedal 17 is released, and opens as the amount of the accelerator pedal 17 is increased. It looks like this. The auxiliary intake throttle valve 16 is drivingly connected to a double diaphragm device 18, and when atmospheric pressure is introduced into both diaphragm chambers 19 and 20, it is located in the fully open position as shown in the figure, and when atmospheric pressure is introduced into the diaphragm chamber 19. When negative pressure is introduced into the diaphragm chamber 20, it is located at the open position, and when negative pressure is introduced into both the diaphragm chambers 19 and 20, it is located at the fully open position.

The diaphragm chambers 19 and 20 each have a negative pressure control valve 21.2.
2, negative pressure and atmospheric pressure are selectively introduced. The negative pressure control valves 21 and 22 are both electromagnetic negative pressure control valves, and when energized, the negative pressure of the negative pressure tank 23 is introduced into the diaphragm chamber 19 or 20, and when not energized, atmospheric pressure is introduced into the diaphragm chamber 19 or 20. It is set to be introduced. The negative pressure control valves 21 and 22 are energized and controlled by a control device 25, which will be described later.

The exhaust manifold 11 includes an exhaust gas intake boat 31.
The intake manifold 9 is provided with an exhaust gas injection port 32, and the exhaust gas intake boat 31 is provided with a conduit 33,
An exhaust gas recirculation control valve 34 and a conduit 35 are connected to the υ1 gas injection boat 32 in communication.

The exhaust gas recirculation control valve 34 includes a valve element 37 that opens and closes the valve port 36 and is connected by a valve rod 38 to a die hair phragm device 39 and negatively connected to a diaphragm chamber 41 provided on one side of the diaphragm 40. When no pressure is introduced, the valve port 36 is pushed down by the spring force of the compression coil spring 42, and on the other hand, when negative pressure is introduced into the diaphragm chamber 41, it resists the spring force of the compression coil spring 42. 36 to the valve port 1.
It is designed to open depending on the magnitude of the negative pressure.

Negative pressure and atmospheric pressure are selectively introduced into the diaphragm chamber 41 by a negative pressure control valve 43. The negative pressure control valve 43 is an electromagnetic negative pressure control valve, and when energized, Ω1f
Negative pressure in the tank 23 is introduced into the diaphragm chamber 41, and atmospheric pressure is introduced into the diaphragm chamber 41 when not energized, and the energized state and de-energized state are repeated by receiving a pulse signal of a predetermined frequency. Therefore, negative pressure is supplied to the diaphragm chamber 41, which increases as the duty ratio of the pulse increases.

The control device 25 controls the energization of the negative pressure control valve 43 .

The control device 25 is an electric type such as a microcomputer, and receives information about the engine speed from the rotation speed sensor 26, information about opening/closing from the engine switch 27, and information about the engine cooling water temperature from the water temperature sensor 28. The sensor 29 provides information regarding the amount of depression of the accelerator pedal 17, and the intake pressure sensor 30 provides information regarding the intake pressure in the intake passage downstream of the intake throttle device 8, based on the intake flow. The control valves 21, 22 and 43 are configured to control energization.

The control I device 25 operates the negative pressure control valves 21 and 22 when the engine switch 27 is closed and the engine cooling water temperature detected by the water temperature sensor 28 is below a predetermined value, for example 60°C.
When the engine cooling water temperature is above a predetermined value, only the negative pressure control valve 22 is energized. Both negative pressure control valves 21 and 22 are energized until the time elapses.

By controlling the energization to the negative pressure control valves 21 and 22 as described above, the auxiliary intake throttle valve 16 is brought to the fully open position when the engine is warmed up, and is brought to the half open position after the engine is warmed up. When stopped, it is brought to the fully open position. During idling, the accelerator pedal 17 is released and the main intake throttle valve 14 is in the fully open position, and at this time, intake air is throttled by taking air only through the auxiliary intake passage 15. By controlling the opening position of the sub-intake throttle valve 16 as described above, the idle intake throttle becomes larger after warm-up is completed than during warm-up.

As shown in FIG. 2, the control device 25 determines the standard exhaust gas recirculation flow rate based on the amount of depression of the accelerator pedal 17 detected by the accelerator sensor 29 and the engine speed detected by the rotation speed sensor 26. Qe is calculated, and when the intake pressure Pi detected by the intake pressure sensor 30 is equal to or higher than a predetermined value A without the risk of white smoke generation, a pulse signal with a duty ratio corresponding to the standard exhaust gas recirculation flow 1MQe is negative. When the intake pipe negative pressure Pi applied to the pressure control valve 43 and detected by the intake pipe negative pressure sensor 30 is less than the predetermined value A, that is, when there is a risk of white smoke generation, the standard exhaust gas recirculation flow path is Increased exhaust gas recirculation @, which is obtained by adding the flow rate increase ω amount ΔQe that increases as the intake pressure decreases to Qe, as shown in FIG. It is designed to be applied to a negative pressure control valve 43.

By controlling the duty ratio of the pulse signal given to the negative pressure control valve 43 as described above, when the intake pressure is above a predetermined value, that is, when there is no risk of white smoke generation, the accelerator pedal is depressed and suspended. Exhaust gas recirculation is performed at a standard exhaust gas recirculation flow rate determined according to the engine speed, and this reduces NOx in the exhaust gas. When the intake pressure falls below a predetermined value, that is, when there is a risk of white smoke generation, exhaust gas recirculation is performed at a flow rate that is increased by a predetermined amount from the standard exhaust gas recirculation flow rate. In this way, when the intake pressure is lower than a predetermined value, the exhaust gas recirculation flow rate is increased, which causes the intake pressure to rise, and a large amount of relatively high-temperature exhaust gas flows into the engine combustion chamber, which reduces the compression rate. The intake air temperature increases and the generation of white smoke is avoided.

Although the present invention has been described in detail with respect to specific embodiments above, it will be appreciated by those skilled in the art that the present invention is not limited thereto and that various embodiments can be made within the scope of the present invention. It should be obvious.

[Brief explanation of the drawing]

FIG. 1 is a schematic configuration diagram showing 10 embodiments of an f easel engine equipped with an exhaust gas recirculation control device implementing the exhaust gas recirculation control method according to the present invention, and FIG. 2 is a schematic diagram showing the exhaust gas recirculation control method according to the present invention. Flow illustrating one implementation of the recirculation control method
y-17-1-1 FIG. 3 is a graph showing the characteristic of increasing the amount of exhaust gas recirculation flow in the exhaust gas recirculation control method according to the present invention. 1... Day pill engine, 2... Cylinder bore, 3...
... Piston, 4... Combustion chamber, 5... Nozzle, 6...
- Vortex chamber. 7... Combustion injection nozzle, 8... Intake throttle device, 10
...Intake manifold, 10...Exhaust port, 11
...Exhaust manifold, 12...Poppet h valve, 13
...Main intake passage, 14...Main intake throttle valve, 15...
・Sub-intake passage. 16... Sub-intake throttle valve, 17... Accelerator pedal,
18...Double diaphragm device, 19.20...
Diaphragm chamber, 21.22...Negative pressure control valve, 23.
... Negative pressure tank, 25... Control device, 26... Rotation speed sensor. 27... Engine switch, 28... Water temperature sensor, 29
...Accelerator sensor, 30...Intake pressure sensor, 3
1...Exhaust gas intake port 1~, 32...Exhaust gas injection port 1~. 33... Conduit, 34... Exhaust gas recirculation control valve, 3
5... Conduit, 36... Valve boat, 37... Valve element, 38... Valve rod, 39... Diaphragm device,
40...Diaphragm, 41...Diaphragm chamber,
42...Compression coil spring, 43...Negative pressure control valve patent applicant: Toyota Motor Corporation representative
Masaki Akashi, Patent Attorney Figure 1 Figure 3 Intake Pressure PL

Claims (1)

[Claims] An exhaust gas recirculation control method for a D-Hill engine that throttles the intake air during idling operation detects the intake pressure in the intake passage downstream of the intake throttle section in terms of intake flow, and detects when the intake pressure is below a predetermined value. An exhaust gas recirculation control method for a diesel engine, which is characterized by sometimes increasing the exhaust gas recirculation flow rate.