JP2015042848A - Exhaust gas recirculation device of engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress wear caused by collision between a valve element and a valve seat in an exhaust gas recirculation valve.SOLUTION: An EGR device comprises: an EGR passage 17 for letting a part of the exhaust gas, which is discharged from a combustion chamber 16 of an engine 1 to an exhaust passage 5, flow into an intake passage 3 as EGR gas to recirculate into the combustion chamber 16; an EGR valve 18 for regulating an EGR gas flow rate in the EGR passage 17; various sensors 51, 52; and an electronic control unit (ECU) 50 for controlling the EGR valve 18 on the basis of rotation speed and a load of the engine. The EGR valve 18 includes a valve seat 33, a valve element 32 provided to be seatable on the valve seat 33, and a DC motor 31 for moving the valve element 32 to the valve seat 33. The ECU 50 calculates a target opening for the EGR valve 18 on the basis of the rotation speed and load of the engine detected by the various sensors 51, 52, and when the target opening is equal to or smaller than a predetermined minute opening, performs control for prohibiting valve opening of the EGR valve 18 and fully closing the exhaust gas recirculation valve 18.

Description

  The present invention relates to an exhaust gas recirculation device for an engine which causes a part of engine exhaust gas to flow into an intake passage as exhaust gas recirculation gas and recirculate to the engine.

  Conventionally, this type of technology has been employed in, for example, automobile engines. An exhaust gas recirculation (EGR) device guides part of exhaust gas after combustion discharged from an engine combustion chamber to an exhaust passage as EGR gas to the intake passage through the EGR passage and flows through the intake passage. It is mixed with intake air and returned to the combustion chamber. EGR gas flowing through the EGR passage is adjusted by an EGR valve provided in the EGR passage. By this EGR, nitrogen oxide (NOx) in the exhaust gas can be mainly reduced, and fuel efficiency can be improved at the time of partial load of the engine.

  The engine exhaust is either free of oxygen or lean. Therefore, by mixing a part of the exhaust gas with the intake air by EGR, the oxygen concentration in the intake air decreases. For this reason, in the combustion chamber, fuel burns in a state where the oxygen concentration is low, so that the peak temperature at the time of combustion is lowered and the generation of NOx can be suppressed. In a gasoline engine, the pumping loss of the engine can be reduced even when the throttle valve is closed to some extent without increasing the oxygen content in the intake air by EGR.

  Here, recently, in order to further improve the fuel efficiency of the engine, it is conceivable to perform EGR in the entire operation region of the engine, and it is required to realize a large amount of EGR. In order to realize a large amount of EGR, it is necessary to increase the inner diameter of the EGR passage, or increase the outer diameter of the valve body of the EGR valve and the flow passage opening area of the valve seat, compared to the conventional techniques.

  For example, Patent Document 1 described below describes an EGR device configured to remove deposits (deposits) attached to a valve seat and a valve body of an EGR valve at an early stage. In this EGR device, when the amount of deposit adhering to the valve body or the like of the EGR valve is estimated and it is determined that the estimated amount has reached a necessary amount for removal, the EGR gas flow rate in the EGR passage is a predetermined upper limit value. The valve body is opened and closed in a range (for example, a minute opening range) necessary for removing the deposit from the fully closed position on the condition that it is in a smaller flow rate range. Here, it is possible to assume a large amount of EGR for this EGR apparatus.

JP 2007-239680 A

  However, when the diameter of the EGR valve increases with the increase in mass EGR, the weight of the valve increases inevitably, and there is a concern that the reliability of the vibration of the valve during operation of the engine may be reduced. That is, in the minute opening range of the EGR valve, the clearance between the valve body and the valve seat is small, so when the valve body vibrates due to the influence of engine vibration, the valve body repeatedly collides with the valve seat, May cause wear. When the wear occurs, there is a concern that an unnecessary gap may be generated between the valve body and the valve seat when fully closed, or an error may occur in the EGR gas flow rate between the valve body and the valve seat when the valve is minutely opened. In particular, when the valve body becomes heavier with the increase in mass EGR, vibration and amplitude increase, and wear between the valve body and the valve seat may increase.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an exhaust gas recirculation device for an engine that can suppress wear due to a collision between a valve body and a valve seat with respect to the exhaust gas recirculation valve. It is to provide.

  In order to achieve the above object, an invention according to claim 1 is directed to an exhaust gas recirculation passage in which a part of exhaust discharged from an engine combustion chamber to an exhaust passage flows into the intake passage as exhaust gas recirculation gas and is recirculated to the combustion chamber. An exhaust gas recirculation valve that adjusts the flow rate of the exhaust gas recirculation gas in the exhaust gas recirculation passage, the exhaust gas recirculation valve, a valve seat, a valve body that can be seated on the valve seat, and a valve body that moves relative to the valve seat Driving means for operating the engine, operating state detecting means for detecting the operating state of the engine, and control means for controlling the exhaust gas recirculation valve based on the operating state detected by the operating state detecting means. In the engine exhaust gas recirculation device, the control means obtains a target opening degree related to the exhaust gas recirculation valve based on the detected operating state, and when the target opening degree is equal to or less than a predetermined minute opening degree, Opening prohibited by prohibiting valve opening And intent to control the valve is fully closed.

  According to the configuration of the above invention, the target opening degree related to the exhaust gas recirculation valve is obtained by the control unit based on the operation state detected by the operation state detection unit. Further, when the target opening is equal to or less than a predetermined minute opening, the opening of the exhaust gas recirculation valve is prohibited and the exhaust gas recirculation valve is controlled to be fully closed by the control means. Therefore, in the opening range where the target opening is less than or equal to the predetermined minute opening, the exhaust gas recirculation valve is prohibited from opening and the exhaust gas recirculation valve is fully closed, so that there is a clearance between the valve body and the valve seat. The valve body does not collide with the valve seat under the influence of engine vibration.

  In order to achieve the above object, according to a second aspect of the present invention, in the first aspect of the present invention, the detected operating state includes a rotational speed and a load of the engine, and the control means has a minute opening degree. The purpose is to set according to the engine speed and load.

  According to the configuration of the above invention, in addition to the operation of the invention described in claim 1, the vibration of the valve body of the exhaust gas recirculation valve becomes larger as the engine speed and load become higher. Here, the upper limit of the minute opening at which opening of the exhaust gas recirculation valve is prohibited is set by the control means in accordance with the rotational speed and load of the engine, that is, the magnitude of the vibration of the valve body. Therefore, when the vibration of the valve body is reduced, it is not necessary to increase the upper limit of the minute opening more than necessary.

  According to the first aspect of the present invention, the exhaust gas recirculation valve can suppress wear due to the collision between the valve body and the valve seat, and can ensure the reliability of the exhaust gas recirculation valve.

  According to the second aspect of the invention, in addition to the effect of the first aspect of the invention, the exhaust gas recirculation gas flow rate can be accurately controlled in the engine operating region where the exhaust gas recirculation valve requires resolution. Thus, it is possible to ensure both the resolution and the reliability of the exhaust gas recirculation valve.

The schematic block diagram which shows the gasoline engine system which concerns on 1st Embodiment and contains the EGR apparatus of the engine with a supercharger. Sectional drawing which concerns on 1st Embodiment and is a part of EGR channel | path, and expands and shows the part in which an EGR valve is provided. The flowchart which shows an example of the processing content of EGR control concerning 1st Embodiment. 6 is a time chart showing the behavior of (a) engine load and (b) target opening when the engine speed NE is constant according to the first embodiment. The flowchart which shows an example of the processing content of EGR control in connection with 2nd Embodiment. The map referred in order to obtain | require the micro opening degree according to 2nd Embodiment according to an engine speed and engine load. The map referred in order to obtain | require the micro opening degree according to 2nd Embodiment according to an engine speed and engine load.

<First Embodiment>
Hereinafter, a first embodiment of an engine exhaust gas recirculation device (EGR device) according to the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a schematic configuration diagram showing a gasoline engine system including an EGR device for an engine with a supercharger in this embodiment. This engine system includes a reciprocating engine 1. An intake passage 3 is connected to the intake port 2 of the engine 1, and an exhaust passage 5 is connected to the exhaust port 4. An air cleaner 6 is provided at the inlet of the intake passage 3. A supercharger 7 for boosting the intake air in the intake passage 3 is provided in the intake passage 3 downstream of the air cleaner 6 between the exhaust passage 5 and the intake passage 3.

  The supercharger 7 includes a compressor 8 disposed in the intake passage 3, a turbine 9 disposed in the exhaust passage 5, and a rotating shaft 10 that connects the compressor 8 and the turbine 9 so as to be integrally rotatable. The supercharger 7 rotates the turbine 9 by the exhaust gas flowing through the exhaust passage 5 and integrally rotates the compressor 8 via the rotary shaft 10 to boost the intake air in the intake passage 3, that is, perform supercharging. It is like that.

  An exhaust bypass passage 11 that bypasses the turbine 9 is provided in the exhaust passage 5 adjacent to the supercharger 7. A waste gate valve 12 is provided in the exhaust bypass passage 11. By adjusting the exhaust gas flowing through the exhaust bypass passage 11 by the waste gate valve 12, the exhaust gas flow rate supplied to the turbine 9 is adjusted, the rotational speeds of the turbine 9 and the compressor 8 are adjusted, and supercharging by the supercharger 7 is performed. The pressure is adjusted.

  In the intake passage 3, an intercooler 13 is provided between the compressor 8 of the supercharger 7 and the engine 1. The intercooler 13 is for cooling the intake air that has been pressurized by the compressor 8 to a high temperature. A surge tank 3 a is provided in the intake passage 3 between the intercooler 13 and the engine 1. An electronic throttle device 14 that is an electric throttle valve is provided in the intake passage 3 downstream from the intercooler 13 and upstream from the surge tank 3a. The electronic throttle device 14 detects a butterfly throttle valve 21 disposed in the intake passage 3, a DC motor 22 for opening and closing the throttle valve 21, and an opening degree (throttle opening degree) TA of the throttle valve 21. And a throttle sensor 23 for performing the operation. The electronic throttle device 14 is configured such that the opening degree of the throttle valve 21 is adjusted by the throttle valve 21 being opened and closed by the DC motor 22 in accordance with the operation of the accelerator pedal 26 by the driver. As the configuration of the electronic throttle device 14, for example, the basic configuration of the “throttle device” described in FIGS. 1 and 2 of JP 2011-252482 A can be employed. The exhaust passage 5 downstream from the turbine 9 is provided with a catalytic converter 15 as an exhaust catalyst for purifying exhaust.

  The engine 1 is provided with an injector 25 for injecting and supplying fuel to the combustion chamber 16. Fuel is supplied to the injector 25 from a fuel tank (not shown). The engine 1 is provided with a spark plug 29 corresponding to each cylinder. Each spark plug 29 is ignited by receiving a high voltage output from the igniter 30. The ignition timing of each spark plug 29 is determined by the high voltage output timing from the igniter 30. The spark plug 29 and the igniter 30 constitute an ignition device.

  In this embodiment, the EGR device for realizing a large amount of EGR is a low-pressure loop type, and a part of the exhaust discharged from the combustion chamber 16 of the engine 1 to the exhaust passage 5 is flowed to the intake passage 3 as EGR gas. An exhaust gas recirculation passage (EGR passage) 17 for recirculation to the combustion chamber 16 and an exhaust gas recirculation valve (EGR valve) 18 provided in the EGR passage 17 for adjusting the flow of EGR gas in the EGR passage 17 are provided. The EGR passage 17 is provided between the exhaust passage 5 downstream from the catalytic converter 15 and the intake passage 3 upstream from the compressor 8. That is, a part of the exhaust gas flowing through the exhaust passage 5 flows as EGR gas to the intake passage 3 through the EGR passage 17 and recirculates to the combustion chamber 16. Connected to. Further, the inlet 17 b of the EGR passage 17 is connected to the exhaust passage 5 downstream from the catalytic converter 15.

  The EGR passage 17 is provided with an EGR cooler 20 for cooling the EGR gas flowing through the passage 17. In this embodiment, the EGR valve 18 is disposed in the EGR passage 17 downstream of the EGR cooler 20.

  FIG. 2 is an enlarged sectional view showing a part of the EGR passage 17 where the EGR valve 18 is provided. As shown in FIGS. 1 and 2, the EGR valve 18 is configured as a poppet valve and as an electric valve. That is, the EGR valve 18 includes a valve body 32 that is driven by a DC motor 31 corresponding to an example of the driving means of the present invention. The valve body 32 has a substantially conical shape, and is provided so as to be seated on a valve seat 33 provided in the EGR passage 17. The DC motor 31 includes an output shaft 34 that is configured to be able to reciprocate (stroke) in a straight line. A valve body 32 is fixed to the tip of the output shaft 34. The output shaft 34 is supported by a housing constituting the EGR passage 17 via a bearing 35. The opening degree of the valve body 32 with respect to the valve seat 33 is adjusted by moving the output shaft 34 of the DC motor 31 in a stroke. The output shaft 34 of the EGR valve 18 is provided so as to be able to perform a stroke movement by a predetermined stroke L1 from a fully closed state in which the valve body 32 is seated on the valve seat 33 to a fully open state in which the valve body 32 contacts the bearing 35. . In this embodiment, in order to realize a large amount of EGR, the opening area of the valve seat 33 is enlarged as compared with the conventional technique. Accordingly, the diameter of the valve body 32 is increased. As a configuration of the EGR valve 18, for example, a basic configuration of “EGR valve” described in FIG. 1 of JP 2010-275941 A can be adopted.

  In this embodiment, in order to execute fuel injection control, ignition timing control, intake air amount control, EGR control, and the like according to the operating state of the engine 1, the injector 25, the igniter 30, the DC motor 22 of the electronic throttle device 14, and The DC motor 31 of the EGR valve 18 is controlled by an electronic control unit (ECU) 50 in accordance with the operating state of the engine 1. The ECU 50 stores in advance a central processing unit (CPU), a predetermined control program and the like, various memories for temporarily storing a calculation result of the CPU, and the like, an external input circuit connected to these parts, and an external And an output circuit. The ECU 50 corresponds to an example of a control unit of the present invention. An igniter 30, an injector 25, and DC motors 22 and 31 are connected to the external output circuit. The external input circuit is connected to various sensors 27 and 51 to 55 corresponding to an example of the operating state detecting means of the present invention for detecting the operating state of the engine 1 including the throttle sensor 23, and various engine signals are inputted. It has come to be.

  Here, in addition to the throttle sensor 23, an accelerator sensor 27, an intake pressure sensor 51, a rotation speed sensor 52, a water temperature sensor 53, an air flow meter 54, and an air-fuel ratio sensor 55 are provided as various sensors. The accelerator sensor 27 detects an accelerator opening ACC that is an operation amount of the accelerator pedal 26. The intake pressure sensor 51 detects the intake pressure PM in the surge tank 3a. That is, the intake pressure sensor 51 detects the intake pressure PM in the surge tank 3a downstream from the throttle valve 21. The rotational speed sensor 52 detects the rotational angle (crank angle) of the crankshaft 1a of the engine 1 and detects the change in the crank angle as the rotational speed (engine rotational speed) NE of the engine 1. The water temperature sensor 53 detects the cooling water temperature THW of the engine 1. The air flow meter 54 detects the intake air amount Ga flowing through the intake passage 3 immediately downstream of the air cleaner 6. The air-fuel ratio sensor 55 is provided in the exhaust passage 5 immediately upstream of the catalytic converter 15, and detects the air-fuel ratio A / F in the exhaust.

  In this embodiment, the ECU 50 controls the EGR valve 18 in order to execute the EGR control in accordance with the operation state of the engine 1 in the entire operation region of the engine 1. Further, the ECU 50 normally controls the opening of the EGR valve 18 based on the operating state detected during the acceleration operation or the steady operation of the engine 1, and the EGR valve 18 when the engine 1 is stopped, idle operation, or deceleration operation. Is controlled to close the valve.

  In this embodiment, the ECU 50 controls the electronic throttle device 14 based on the accelerator opening ACC in order to drive the engine 1 in response to a driver's request. Further, the ECU 50 controls to open the electronic throttle device 14 based on the accelerator opening ACC during acceleration operation or steady operation of the engine 1 and closes the electronic throttle device 14 when the engine 1 is stopped or decelerated. It has become. As a result, the throttle valve 21 is opened during acceleration or steady operation of the engine 1 and closed when the engine 1 is stopped or decelerated.

  Here, in the low-pressure loop type EGR device in this embodiment, the valve body 32 of the EGR valve 18 increases in diameter and weight as the mass EGR is increased, so that the reliability of the vibration of the valve body 32 during operation of the engine 1 is improved. There is concern about the decline. In particular, there is a concern about wear occurring between the two 32 and 33 due to the valve body 32 colliding with the valve seat 33 due to vibration in a minute opening range. Therefore, in this embodiment, the ECU 50 performs the following EGR control in order to prevent wear caused by a collision between the valve body 32 and the valve seat 33.

  FIG. 3 is a flowchart showing an example of the processing content of EGR control. When the processing shifts to this routine, first, in step 100, the ECU 50 takes in the cooling water temperature THW from the detection value of the water temperature sensor 53.

  Next, in step 110, the ECU 50 takes in the engine rotational speed NE and the engine load KL based on the detection values of the intake pressure sensor 51 and the rotational speed sensor 52. The ECU 50 can determine the engine load KL from the relationship between the intake pressure PM and the engine speed NE.

  Next, in step 120, the ECU 50 determines whether or not the coolant temperature THW is higher than a predetermined value Th1. Here, for example, “70 ° C.” can be applied as the predetermined value Th1. If the determination result is negative, the ECU 50 proceeds to step 210. If the determination result is affirmative, the ECU 50 proceeds to step 130.

  In step 210, the ECU 50 executes forced EGR cut control and returns the process to step 100. That is, the ECU 50 controls the EGR valve 18 to be fully closed in order to forcibly cut (shut off) the EGR.

  On the other hand, in step 130, the ECU 50 obtains the target opening degree Tegr of the EGR valve 18 based on the engine speed NE and the engine load KL. The ECU 50 can obtain the target opening degree Tegr corresponding to the engine speed NE and the engine load KL by referring to a predetermined map.

  Next, at step 140, the ECU 50 determines whether or not the valve opening flag XEGRON is “1”. The valve opening flag XEGRON is set to “1” when the EGR valve 18 is opened, and is set to “0” when the EGR valve 18 is closed. If the determination result is affirmative, the ECU 50 proceeds to 150. If the determination result is negative, the ECU 50 proceeds to step 160.

  In step 150, the ECU 50 determines whether or not the target opening degree Tegr is equal to or less than a predetermined minute opening degree B1. If the determination result is affirmative, the ECU 50 proceeds to step 170. If this determination result is negative, the ECU 50 proceeds to step 200.

  On the other hand, in step 160 after shifting from step 140, the ECU 50 determines whether or not the target opening degree Tegr is equal to or smaller than a predetermined minute opening degree A1 (> B1). If the determination result is affirmative, the ECU 50 proceeds to step 170. If this determination result is negative, the ECU 50 proceeds to step 200.

  In step 170 after shifting from step 150 or step 160, the ECU 50 sets the target opening degree Tegr to “0”.

  Next, in step 180, the ECU 50 resets the valve opening flag XEGRON to “0”.

  On the other hand, in step 200 after shifting from step 150 or step 160, the ECU 50 sets the valve opening flag XEGRON to “1”.

  In step 190 after shifting from step 180 or step 200, the ECU 50 controls the EGR valve 18 to the target opening degree Tegr and returns the process to step 100. Here, when the target opening degree Tegr is “0”, the ECU 50 controls the EGR valve 18 to be fully closed. When the target opening degree Tegr becomes a predetermined value other than “0”, the ECU 50 controls the opening of the EGR valve 18.

  According to the above control, the ECU 50 obtains the target opening degree Tegr related to the EGR valve 18 based on the detected operating state, that is, the engine rotational speed NE and the engine load KL. When the target opening degree Tegr is equal to or less than the predetermined minute opening degrees A1 and B1, the ECU 50 prohibits the opening of the EGR valve 18 and controls the EGR valve 18 to be fully closed.

  FIG. 4 is a time chart showing the behavior of (a) engine load KL and (b) target opening degree Tegr when the engine speed NE is constant. In FIG. 4, the engine load KL increases between time t1 and time t6, becomes constant between time t6 and time t7, and decreases between time t7 and time t12. Accordingly, when the engine load KL becomes the first map value map1 at times t2 and t11, the first target value tegr1 (0) is obtained as the target opening degree Tegr, and at time t4 and t9, the engine load is calculated. When KL becomes the second map value map2, the second target value tegr2 is obtained as the target opening degree Tegr. When the engine load KL becomes the third map value map3 at times t5 and t8, the target opening degree A third target value tegr3 is obtained as Tegr. Here, the target value between the first target value tegr1 and the second target value tegr2 and the target value between the second target value tegr2 and the third target value tegr3 are obtained by complementary calculation, respectively. Can do.

  In FIG. 4, as shown in (a), between time t2 and time t3 when the engine load KL increases, the conventional target opening degree Tegr is equal to the engine load KL as shown by a two-dot chain line in (b). Increase with the increase. On the other hand, in the present embodiment, as indicated by a thick line in (b), when the target opening degree Tegr is equal to or less than a predetermined minute opening degree A1 between time t2 and time t3, the target opening degree Tegr is Set to “0”. That is, the target opening degree Tegr is set to “0” in the opening range where the target opening degree Tegr obtained from the map is equal to or smaller than the minute opening degree A1.

  On the other hand, as shown in FIG. 4A, between time t10 and time t11 when the engine load KL decreases, the conventional target opening degree Tegr is the engine load as shown by the two-dot chain line in FIG. Decreases as KL decreases. On the other hand, in the present embodiment, as indicated by a thick line in (b), when the target opening degree Tegr is equal to or smaller than a predetermined minute opening degree B1 between time t10 and time t11, the target opening degree Tegr is Set to “0”. That is, the target opening degree Tegr is set to “0” in the opening range where the target opening degree Tegr obtained from the map is equal to or smaller than the minute opening degree B1.

  According to the engine EGR device in this embodiment described above, the target opening degree Tegr related to the EGR valve 81 based on the engine rotation speed NE and the engine load KL detected by the intake pressure sensor 51 and the rotation speed sensor 52 is determined by the ECU 50. Is required. When the target opening degree Tegr is equal to or less than the predetermined minute opening degrees A1, B1, the ECU 50 prohibits the opening of the EGR valve 18 and controls the EGR valve 18 to be fully closed. Accordingly, in the opening range where the target opening degree Tegr is equal to or less than the predetermined minute opening degrees A1 and B1, the opening of the EGR valve 18 is prohibited and the EGR valve 18 is fully closed. The clearance between the valve body 32 and the valve seat 33 is not affected by the vibration of the engine 1. For this reason, about the EGR valve 18, the abrasion by the collision between the valve body 32 and the valve seat 33 can be suppressed. As a result, the reliability of the flow characteristics can be ensured for the EGR valve 18.

Second Embodiment
Next, a second embodiment of the engine exhaust gas recirculation apparatus according to the present invention will be described in detail with reference to the drawings.

  In each embodiment described below, the same components as those in the first embodiment are denoted by the same reference numerals, description thereof is omitted, and different points are mainly described.

  This embodiment is different from the first embodiment in terms of processing contents of EGR control. FIG. 5 is a flowchart showing an example of processing contents of EGR control in this embodiment. The flowchart of FIG. 5 differs from the flowchart of FIG. 3 in that the process of step 135 is provided between step 130 and step 140.

  That is, after executing the processing of step 130, the ECU 50 obtains the minute opening (A1, B1) of the EGR valve 18 based on the engine speed NE and the engine load KL in step 135. Here, the ECU 50 obtains the minute opening degrees A1, B1 (A1> B1) according to the engine rotational speed NE and the engine load KL by referring to, for example, maps as shown in FIGS. it can. As shown in FIGS. 6 and 7, the minute openings A1 and B1 are set to increase as the engine speed NE and the engine load KL increase. This corresponds to the vibration of the valve body 32 of the EGR valve 18 becoming larger as the engine 1 is rotated at a higher speed and a higher load. Thereafter, the ECU 50 proceeds to step 140.

  According to the above control, in addition to the control of the first embodiment, the ECU 50 is configured to set the predetermined minute openings A1 and B1 according to the engine speed NE and the engine load KL.

  According to the EGR device for an engine in this embodiment described above, in addition to the effects of the EGR device of the first embodiment, the following effects are obtained. That is, generally, the vibration of the valve body 32 of the EGR valve 18 increases as the engine rotational speed NE and the engine load KL increase. This is because the vibration of the engine 1 increases as the engine 1 rotates at a higher load. Here, the upper limits of the minute openings A1 and B1 at which the opening of the EGR valve 18 is prohibited are set by the ECU 50 in accordance with the engine speed NE and the engine load KL, that is, the magnitude of the vibration of the valve body 32. That is, when the vibration of the valve body 32 becomes large, the upper limits of the minute openings A1 and B1 where the opening of the EGR valve 18 is prohibited are set in a relatively large opening range, and the vibration of the valve body 32 becomes small. In this case, the upper limits of the minute openings A1 and B1 at which the opening of the EGR valve 18 is prohibited are set in a relatively small opening range. Therefore, the EGR gas flow rate can be accurately controlled in the low rotation and low load operation region of the engine 1 where the resolution is required for the EGR valve 18, ensuring the resolution of the EGR valve 18, the valve body 32 and the valve seat. Thus, it is possible to achieve both the reliability with respect to the wear with 33.

  Note that the present invention is not limited to the above-described embodiments, and a part of the configuration can be changed as appropriate without departing from the spirit of the invention.

  (1) In each of the above embodiments, the exhaust gas recirculation device for an engine according to the present invention is embodied in a gasoline engine system, but may be embodied in a diesel engine.

  (2) In each of the above embodiments, the present invention is embodied in a low-pressure loop EGR device, but may be embodied in a high-pressure loop EGR device.

  The present invention can be used for an automobile engine regardless of, for example, a gasoline engine or a diesel engine.

1 Engine 3 Intake passage 5 Exhaust passage 16 Combustion chamber 17 EGR passage (exhaust gas recirculation passage)
18 EGR valve (exhaust gas recirculation valve)
31 DC motor (drive means)
32 Valve body 33 Valve seat 50 ECU (control means)
51 Intake pressure sensor (operating state detection means)
52 Rotational speed sensor (Operating state detection means)
53 Water temperature sensor (Operating state detection means)
NE Engine speed KL Engine load A1 Small opening B1 Small opening

Claims (2)

A part of the exhaust gas discharged from the engine combustion chamber to the exhaust passage flows as an exhaust recirculation gas to the intake passage to recirculate to the combustion chamber, and an exhaust recirculation passage;
An exhaust gas recirculation valve for adjusting the flow rate of the exhaust gas recirculation gas in the exhaust gas recirculation passage;
The exhaust gas recirculation valve includes a valve seat, a valve body provided so as to be seated on the valve seat, and drive means for moving the valve body relative to the valve seat;
An operating state detecting means for detecting the operating state of the engine;
In an exhaust gas recirculation device for an engine, comprising: control means for controlling the exhaust gas recirculation valve based on the operational state detected by the operational state detection means;
The control means obtains a target opening degree related to the exhaust gas recirculation valve based on the detected operating state, and opens the exhaust gas recirculation valve when the target opening degree is equal to or smaller than a predetermined minute opening degree. An exhaust gas recirculation device for an engine, wherein the exhaust gas recirculation valve is prohibited and controlled to be fully closed. The detected operating state includes the rotational speed and load of the engine,
2. The engine exhaust gas recirculation device according to claim 1, wherein the control unit sets the minute opening according to a rotation speed and a load of the engine.

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