JP2009150331A - Engine egr valve control device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an engine EGR valve control device for reducing gas flow noises in opening an EGR valve while minimizing the influences on exhaust gas. <P>SOLUTION: In the case where engine operating conditions are in a gas flow noise reduction required region, two-stage operation control device performs ramp control to gently open the EGR valve 26 at a predetermined opening speed for a predetermined time when starting the opening of the EGR valve 26 from a fully closed condition. After finishing the ramp control, it quickly opens the EGR valve up to a target opening. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an engine exhaust gas recirculation system, and more particularly to an engine EGR valve control device that suppresses the deterioration of exhaust gas and the generation of noise (air flow noise) when the EGR valve is opened. is there.

Conventionally, in an EGR device such as an automobile engine, a part of exhaust gas is returned to an intake passage via an EGR passage (EGR passage) and supplied to a combustion chamber. By controlling the recirculation amount (EGR amount) of the exhaust gas, it is possible to secure a good combustion state and promote exhaust gas purification. In addition, there is an example of EGR valve control in which the EGR valve is opened from the fully closed state to the target opening degree in order to prevent smoke discharge due to EGR excessive recirculation. As an example of this, in Patent Document 1, if the exhaust gas recirculation region condition is met at the time of cancellation of the exhaust, when the exhaust gas recirculation is started, the opening degree of the EGR valve first opens stepwise to a predetermined opening degree, and then the time elapses. With this, the target opening degree is achieved when the exhaust pressure is sufficiently lowered and the exhaust pressure is sufficiently reduced.
JP 2000-337172 A

  However, in the technique such as Patent Document 1, when the EGR valve starts to open from the fully closed state, if the opening degree change is large, EGR gas flows suddenly due to the pressure difference between the front and rear of the EGR valve, and airflow noise is generated as annoying noise. In particular, when the EGR valve is opened stepwise at a stroke up to a predetermined opening degree, there is a problem that EGR gas flows at a stroke at the beginning of opening the EGR valve and airflow noise is likely to be generated.

    This invention is made in view of such a subject, and provides the engine EGR valve control apparatus which can reduce the airflow sound at the time of valve opening of an EGR valve, suppressing increase of NOx as much as possible. Objective.

  In order to achieve the above object, an EGR valve control device for an engine according to claim 1 is an exhaust gas recirculation device that recirculates a part of the exhaust gas flowing through the exhaust passage of the engine to the intake passage side via the EGR valve. When the EGR valve starts to open from the fully closed state, the EGR valve is controlled to be gradually opened at a predetermined opening speed, and after the ramp control is completed, the EGR valve is quickly reached to the target opening. It is characterized by performing control to open the valve.

  According to a second aspect of the present invention, the ramp control is performed when the engine is rotating at a low speed and is not performed when the engine is rotating at a high speed.

  Further, the invention according to claim 3 is characterized in that the lamp control is performed when the engine is under a low load and is not performed when the engine is under a high load.

  Furthermore, the invention according to claim 4 provides a correlation map in which an air flow noise reduction effect area obtained in advance by experimental values from the valve opening speed and a predetermined time from the fully closed state to the end of lamp control is provided, Accordingly, the EGR valve control is performed by setting the valve opening speed and the predetermined time from the correlation map.

  Further, in the invention according to claim 5, when the opening degree when the EGR valve is fully opened is 100%, the predetermined valve opening speed is 40 to 60% / sec, and the predetermined time is 900 to 1300 msec. It is a feature.

  Further, the invention described in claim 6 is characterized in that the lamp control is performed in a transient operation state such as during rapid acceleration.

  Therefore, according to the EGR valve control device for an engine of the present invention as set forth in claim 1, the EGR gas is prevented from abruptly flowing by being controlled by ramp control when the EGR valve starts to open from the fully closed state. As a result, generated airflow noise is reduced. At the same time, since there is no sudden decrease in the excess air ratio at the beginning of opening the EGR valve, the discharge of smoke is also suppressed. Furthermore, since the EGR valve is controlled to be opened to the target opening immediately after the end of the lamp control, the EGR can be applied and the increase in NOx due to the lamp control can be suppressed.

According to the second and third aspects of the present invention, the region where the airflow noise reduction is important in the engine rotation speed and the engine load condition (at the time of low speed and low load), and the NOx reduction is not required because the airflow noise reduction is unnecessary. It is possible to determine whether or not lamp control can be performed by dividing the priority area (at high speed and high load). The ramp control can be performed only with the engine operating conditions that are truly necessary to reduce airflow noise and increase NOx.
Furthermore, in the invention of claim 4, in consideration of the airflow noise reduction effect and the NOx increase suppression effect, the correlation between the valve opening speed and the predetermined time with the engine operating conditions (engine rotation speed and engine load) as parameters. Create a map. By using the correlation map, it is possible to set a good valve opening speed and the predetermined time under predetermined engine operating conditions (engine speed and engine load).

  Furthermore, in the invention according to claim 5, by optimizing the valve opening speed and the predetermined time (hereinafter referred to as duration), the NOx increases while greatly reducing the air flow noise when the EGR valve is opened. Can be suppressed as much as possible.

  Further, according to the sixth aspect of the invention, since the EGR valve lamp control is used in the transient operation state such as the rapid acceleration that is the operation condition in which the airflow noise is most likely to be generated, the effect can be further brought out.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

  FIG. 1 is an EGR control device embodied for a diesel engine. As shown in the figure, a supercharger 6 is provided in the intake passage 4 of the engine 2. Intake air taken from an air cleaner (not shown) is supercharged by the compressor 8 and then introduced into the combustion chamber 16 via the intercooler 10.

  An intake throttle valve 12 is disposed at an appropriate position in the intake passage 4. The intake throttle valve 12 includes a butterfly valve body 14 that is driven by a motor. The fresh air amount is controlled by opening and closing the butterfly valve body 14, and the exhaust gas recirculation amount (EGR amount) is also controlled.

  A turbine 22 coupled coaxially with the compressor 8 is provided in the exhaust passage 20 of the engine 2, and the turbine 22 is rotationally driven by the exhaust gas after combustion.

  The intake passage 4 and the exhaust passage 20 are connected by an EGR passage 24, and an EGR valve 26 is disposed at an appropriate position of the EGR passage 24. The EGR valve 26 includes a poppet valve body 28 that is driven by a motor, and the EGR amount is controlled by opening and closing the poppet valve body 28. The ECU 40 (electronic control unit) performs comprehensive control of the engine 2 including continuous control of the opening degree of the intake throttle valve 12 and the EGR valve 26.

  Various sensors such as an air flow sensor 30, an intake pressure sensor 32, an intake air temperature sensor 34, a rotation speed sensor 36, and an accelerator sensor 38 are connected to the input side of the ECU 40. The air flow sensor 30 outputs a voltage corresponding to the fresh air amount of the engine 2, the intake pressure sensor 32 detects the intake pressure, and the intake air temperature sensor 34 detects the intake air temperature. The rotational speed sensor 36 detects the rotational speed of the engine 2 and the accelerator sensor 38 detects the accelerator opening degree by the driver. On the other hand, various devices such as the fuel injection valve 18 are connected to the output side of the ECU 40 in addition to the intake throttle valve 12 and the EGR valve 26 described above.

  Here, the ECU 40 includes an injection control unit 42 that controls opening and closing of the fuel injection valve 18, and an EGR control unit 44 that controls opening and closing of the intake throttle valve 12 and the EGR valve 26. Then, the ECU 40 continuously controls the opening degree of the butterfly valve body 14 of the intake throttle valve 12 and the opening degree of the valve body poppet 28 of the EGR valve 26 so that the target excess air ratio λ becomes the target excess air ratio λ. Feedback control (λF / B control) is performed.

  Specifically, the injection control unit 42 sets the fuel injection amount from the rotational speed from the rotational speed sensor 36 and the accelerator opening from the accelerator sensor 38, and the fuel injection valve 18 is set based on these set values. The engine 2 is operated by driving control.

  Further, the EGR control unit 44 calculates a target excess air ratio λ based on the rotational speed and the fuel injection amount. On the other hand, the EGR control unit 44 calculates the actual EGR amount and the target excess air ratio λ based on the fresh air amount from the air flow sensor 30 and the like. Next, the deviation between the calculated target excess air ratio λ and the actual excess air ratio λ is fed back. Then, an instruction value is obtained from the control gain set by the PID control unit 48, and the rotation amount of the butterfly valve body 14 of the intake throttle valve 12 and the lift amount of the poppet valve body 28 of the EGR valve 26 are continuously determined by this instruction value. Control. As a result, the requested EGR amount is obtained and approaches the target excess air ratio λ.

  On the other hand, the EGR control unit 44 performs open loop control at the time of forced regeneration when a particulate filter (DPF) is provided, for example, at the time of sudden acceleration of the vehicle or idling. Specifically, the EGR is performed with the amount of rotation of the butterfly valve body 14 and the opening degree of the EGR valve 26 for adjusting the opening degree of the intake throttle valve 12 appropriately from the fully open position according to each operation state described above. The lift amount of the poppet valve body 28 for preventing it from being output is output from the PID control unit 48. As described above, since the opening degree of the intake throttle valve 12 and the EGR valve 26 is respectively controlled open and is not corrected using the feedback signal, a desired excess air ratio can be obtained quickly.

  The EGR valve control of the embodiment will be described with reference to the flowchart of FIG. First, in step S201, it is determined whether or not the vehicle is in a transient operation such as sudden acceleration of the vehicle based on the input signal of the engine rotational speed from the rotational speed sensor 36 and the accelerator opening from the accelerator sensor 38. If YES, step S202 is performed. Proceed to

In step S202, the EGR valve is once fully closed (rapid valve closing control), and the process proceeds to step S203. The reason why the EGR valve is fully closed is to suppress the generation of smoke due to a sudden decrease in the excess air ratio.
Further, in step S203, it is determined whether or not the lamp control at the start of opening the EGR valve is possible based on the engine operating conditions (engine speed and engine load) described in detail later with reference to FIG. The process proceeds to S207 with NO, and step control is performed in which the valve is opened step by step from the fully closed position to the target opening degree. If YES, the process proceeds to S204, where the lamp control is performed with the optimum valve opening speed and duration determined using the map of FIG.

  After step S204, the process proceeds to step S205, where it is determined whether or not the lamp control is completed based on the duration. If NO, the process returns to step S204 to continue the lamp control, and if YES, the process proceeds to step S206. In step S206, step control is performed to open the valve from the valve opening position at the end of the lamp control to the target opening at once.

  FIG. 3 shows a time history of a state change in which the EGR valve opens from a fully closed state to a target opening. A solid line shows the present embodiment with lamp control, and a broken line shows an example of the prior art without lamp control. In the case of this embodiment, when the EGR valve starts to open from the fully closed state, the EGR valve is controlled to open slowly at the valve opening speed ΔL and the duration t, and after the lamp control is completed, The EGR valve is controlled to open quickly to the target opening.

  Therefore, without the conventional ramp control, it opens stepwise from the fully closed state to a target opening, so that the EGR gas flows to the intake side at once due to the pressure difference between the front and back of the EGR valve, that is, the pressure difference between the intake air and the exhaust gas. In contrast, the EGR valve opens slowly in this embodiment, so that EGR gas is prevented from flowing to the intake side at a stretch, and airflow noise is reduced.

  FIG. 4 shows an engine operating condition area map with and without a lamp in EGR valve control. In this embodiment, lamp control is performed at low speed and low load, and lamp control is not performed at high speed and high load. This is because, at the time of low speed and low load, the influence of the airflow noise is larger than the other noises, so that the EGR gas is prevented from flowing all at once as a result of the lamp control. . In the case of high speed and high load, the effect of airflow noise is smaller than other noises, and NOx reduction is prevented without performing lamp control because it is a region where NOx reduction is necessary to keep exhaust gas within the regulation value. Is.

  The curve shown in the figure shows an adjustment curve for smoothly shifting the opening / closing operation of the EGR valve when the EGR valve is controlled from the presence of the ramp control to the absence of the ramp control. The valve opening speed and duration may be controlled according to the load, or the valve opening speed is constant and the duration is gradually shortened, or the valve opening speed is increased and the duration is shortened. You may adjust. When the EGR valve is controlled from the absence of the lamp control to the presence, the control opposite to the control without the lamp control is performed.

    FIG. 5 shows an example of a correlation map showing the relationship between the optimum valve opening speed and duration of EGR ramp control. In this figure, the area A1 where the airflow noise reduction effect is large is an audible level at which the driver does not care about the airflow sound, and the area A2 during the airflow sound reduction effect is an acceptable level where the airflow sound can be heard, The airflow noise reduction effect small A3 is a level where the airflow sound is somewhat worrisome, and the airflow sound reduction effect cannot be confirmed in other areas.

  The area A1 is an area where the valve opening speed ΔL = 45 to 55% / sec and the duration t = 1100 to 1250 msec when the opening degree when the EGR valve is fully opened is 100%, and the area A2 is The valve opening speed ΔL = 40 to 60% / sec and the duration t = 900 to 1300 msec (excluding the area A1). The region A3 is a region where the valve opening speed ΔL = 35 to 65% / sec and the duration t = 850 to 1350 msec (excluding the regions A1 and A2). According to the experimental results, the air flow noise when the EGR valve is opened is reduced by performing the minimum necessary ramp control with the valve opening speed ΔL = 40-60% / sec and the duration t = 900-1300 msec. However, it is possible to suppress the increase of NOx as much as possible, and more preferably, by controlling the valve opening speed ΔL = 45 to 55% / sec and the duration t = 1100 to 1250 msec, Sound can be greatly reduced.

  The area A4 shown in FIG. 5 is an area in which the lamp control of the EGR valve is too early to obtain a silencing effect, and the area A5 has a short duration of the lamp control of the EGR valve, so that the silencing effect is not obtained. A6 and A7 are regions that cannot be obtained, because the valve opening speed is low and the ramp control is completed before the EGR valve is fully opened, so that the silencing effect cannot be obtained and NOx also deteriorates. The region is a region where NOx deteriorates because the duration of the ramp control of the EGR valve is long, and the region A9 is almost fully opened by the lamp control alone, so the silencing effect cannot be obtained, and NOx also deteriorates. It is an area to do.

  The description of one embodiment of the present invention is finished above, but the present invention is not limited to the above embodiment, and various modifications can be made without departing from the spirit of the present invention. For example, in the case of transient operation such as sudden acceleration of the vehicle, the method of performing ramp control and step control of the EGR valve has been described, but in the case of forced regeneration or the case of idle operation when a particulate filter (DPF) is provided The same control may be performed. Further, in this embodiment, the step control that opens to the target opening at a time after the end of the lamp control has been described, but without opening the valve to the target opening at once, EGR is applied and NOx does not deteriorate. Valve control having a steep slope with respect to time may be performed.

It is a whole lineblock diagram showing the EGR control device concerning one embodiment of the present invention. It is a flowchart regarding EGR valve control by the control apparatus of FIG. It is time history which showed the opening-and-closing state of the EGR valve at the time of implementing lamp control in one embodiment of the present invention. It is an engine operation condition area | region map with and without EGR valve lamp control. It is a correlation map which shows the relationship between the optimal valve opening speed and duration of EGR valve lamp control.

Explanation of symbols

2 Engine 4 Intake passage 12 Intake throttle valve 20 Exhaust passage 24 EGR passage 26 EGR valve 40 ECU (Electronic Control Unit)
44 EGR controller

Claims (6)

  In an exhaust gas recirculation device that recirculates part of exhaust gas flowing through an exhaust passage of an engine to an intake passage through an EGR valve, when the EGR valve starts to open from a fully closed state, the EGR valve is opened to a predetermined value. An EGR valve control device for an engine, characterized in that a ramp control for gradually opening the valve at a speed is performed, and a control for opening the EGR valve to a target opening immediately after the completion of the ramp control is performed. .   2. The engine EGR valve control device according to claim 1, wherein the ramp control is performed when the engine is rotating at a low speed and is not performed when the engine is rotating at a high speed.   The engine EGR valve control device according to claim 1 or 2, wherein the ramp control is performed at a low load of the engine and is not performed at a high load.   A correlation map in which an airflow noise reduction effect area obtained in advance from experimental values is determined based on the valve opening speed and a predetermined time from the fully closed state to the end of lamp control is provided. The engine EGR valve control device according to claim 1, wherein the EGR valve control is performed by setting a speed and the predetermined time.   2. The engine according to claim 1, wherein when the opening degree of the EGR valve is fully opened is 100%, the predetermined valve opening speed is 40 to 60% / sec and the predetermined time is 900 to 1300 msec. EGR valve control device. The engine EGR valve control device according to claim 2 or 3, wherein the ramp control is performed in a transient operation state such as sudden acceleration.