JPH08303308A - Exhaust air reflux controller of internal combustion engine - Google Patents

Abstract

PURPOSE: To prevent a seat section from adhering on a valve seat member closely in advance by not closing a valve element completely and holding it at a predetermined small degree of opening after an engine stops. CONSTITUTION: When an engine stops, a control unit makes a valve element 26 apart from a valve seat member 28 slightly through a stepping motor and sets a degree of opening of an EGR control valve to a predetermined small degree of opening θ. After that, electricity is not supplied to the stepping motor, but the position of the valve element 26 is held due to detent torque of the stepping motor against spring force of a valve spring 30. Consequently, it is possible to prevent a seat part 26C from adhering on the valve seat member 28.

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 an internal combustion engine, which recirculates a part of exhaust gas in an exhaust gas passage to an intake gas passage, and more particularly to an exhaust gas recirculation control valve for opening and closing a valve body by a motor. The present invention relates to an exhaust gas recirculation control device for an internal combustion engine.

[0002]

2. Description of the Related Art Generally, an internal combustion engine of an automobile is provided with an exhaust gas recirculation control device for returning a part of exhaust gas to an intake passage and adding it to a mixture to lower a combustion temperature and suppress NOx generation. It is provided (hereinafter, “exhaust gas recirculation” is abbreviated as EGR).

This type of EGR control device includes an EGR passage provided so as to communicate between an exhaust passage and an intake passage, and an EG
An EGR control valve provided in the middle of the R passage,
The EGR rate is controlled by adjusting the valve opening of the R control valve. As the EGR control valve, for example, as shown in Japanese Patent Application Laid-Open No. 2-78765, a mechanical type or negative pressure type that opens and closes a valve body by displacing a diaphragm by using suction negative pressure, and, for example, Japanese Patent Application Laid-Open No. As described in JP-A-2-238162, an electrically controlled type in which a valve element is electrically driven by a stepping motor is known, but in recent years, an appropriate EGR according to an engine speed and an engine load is known. In order to realize the rate with a simple open loop, etc., the one using a stepping motor is relatively widely used.

Then, in the EGR control device according to the prior art, an appropriate EGR rate is obtained based on the engine speed and the engine load, and the valve opening for achieving this EGR rate is calculated to calculate the EG.
The opening degree of the R control valve is controlled.

[0005]

By the way, when the EGR control valve is opened to recirculate a part of the exhaust gas to the intake air, the exhaust gas flows around the valve body into the intake passage. Oil components in the exhaust gas and adhesive components such as carbon gradually adhere to the valve seat and valve seat. For this reason, after the engine is stopped, the valve element and the valve seat are adhered by the adhesive component, so-called "sticking phenomenon" may occur, and smooth opening / closing operation of the valve element may be hindered.

That is, the valve body is always closed by the spring force of the valve spring so that the EGR control valve does not open due to exhaust pressure (pressure in the exhaust passage) regardless of whether it is mechanical type or electric control type. Since the normally-closed structure that urges in the direction is adopted, when the engine stops, the EGR control valve closes, and the seat portion of the valve element comes into close contact with the valve seat. Therefore, the seat portion may adhere to the valve seat due to the adhesive component such as carbon that adheres during engine operation, which may increase the torque required to open the valve or the valve opening operation may not be performed smoothly. There is. In particular, when the adhesive component is solidified by the residual heat of the engine or the like, a strong torque is required to separate the valve body from the valve seat.

Further, after the engine is stopped, the temperature lowers and the valve seat contracts. Therefore, depending on the angle (taper angle) of the seat portion, the contracting valve seat may cause the valve body to be bitten. . Therefore, in general, the valve element is formed with a large seat angle, that is, an obtuse angle.
If the seat angle is increased as a measure to prevent the valve body from getting caught, the EGR amount will change significantly even if the valve opening degree changes slightly, so that appropriate flow rate characteristics cannot be obtained and the usability is low. There is also. In other words, since the settable flow rate characteristic is determined from the viewpoint of preventing the valve element from being caught due to contraction, the degree of freedom of the flow rate characteristic is low.

Therefore, the present invention has been made in view of the above problems of the prior art, and enables smooth opening / closing operation of the exhaust gas recirculation control valve even when the adhesive component in the exhaust gas adheres to the valve body. It is an object of the present invention to provide an exhaust gas recirculation control device for an internal combustion engine. Another object of the present invention is to provide an exhaust gas recirculation control device for an internal combustion engine, which avoids the adhered state between the valve body and the valve seat and can improve the degree of freedom of the flow rate characteristic.

[0009]

Therefore, the structure adopted by the exhaust gas recirculation control device for an internal combustion engine according to the present invention is an exhaust gas recirculation passage provided so as to connect an exhaust passage and an intake passage of the engine, and this exhaust gas recirculation passage. An exhaust gas recirculation control valve provided in the middle of the recirculation passage for opening and closing the valve body by a motor, and an exhaust gas recirculation control means for controlling the opening degree of the valve body by outputting a control signal to the exhaust gas recirculation control valve. An exhaust gas recirculation control device for an internal combustion engine, characterized in that valve closing processing means for stopping the valve element at a predetermined small opening when the engine is stopped is provided.

Further, the valve closing processing means, when the engine is stopped, moves the valve body to the fully closed position and then stops the engine in a state where it is separated from the fully closed position by a predetermined small opening degree. Is preferred.

Further, a stepping motor which generates a predetermined detent torque in a non-excited state is used as the motor, and the valve closing processing means stops the valve body at a predetermined small opening degree, and then the stepping motor is operated. It is desirable to stop the energization of.

[0012]

[Function] During engine operation, exhaust gas flows into the intake passage through the periphery of the valve body, so oil components in the exhaust gas and sticky components such as carbon are deposited on the valve seat and seat. Adhere to. Therefore, if the valve element is completely closed by the spring force of the valve spring after the engine is stopped, the valve element may stick to the valve seat member due to the adhesive component.

However, according to the first aspect of the present invention, the valve closing means stops the valve body with a predetermined small opening when the engine is stopped, so that the valve body does not adhere to the valve seat. As a result, the sticking phenomenon can be prevented in advance.

When the engine is stopped, the valve element is moved to the fully closed position and then stopped with a predetermined small opening from the fully closed position. It is possible to prevent the sticking phenomenon while confirming the fully closed position after the engine is stopped.

Further, according to the constitution of claim 3, a stepping motor for generating a predetermined detent torque in a non-excited state is used, and after the valve body is stopped at a predetermined small opening, the energization of the stepping motor is stopped. For example, it is possible to efficiently maintain the small opening degree of the valve body by using detent torque or the like.

[0016]

Embodiments of the present invention will now be described in detail with reference to FIGS.

1 to 8 relate to an exhaust gas recirculation control system for an internal combustion engine according to a first embodiment of the present invention, and FIG.
FIG. 1 is a configuration explanatory view showing an overall configuration of a GR control device, in which a cylinder 1 of an internal combustion engine is gas-liquid tightly covered by a cylinder head 2, and a combustion chamber 4 formed by the cylinder head 2 and a piston 3 The intake passage 5 and the exhaust passage 6 are connected. The intake passage 5 is provided with an air flow meter 7 for detecting the intake air amount, a throttle valve 8 for adjusting the intake air amount, and a fuel injection valve 9 in this order from the upstream side. On the other hand, the exhaust passage 6
A catalytic converter and an air-fuel ratio sensor, which are not shown, are provided on the downstream side of the.

The intake passage 5 and the exhaust passage 6 are connected by an EGR passage 10 as an exhaust gas recirculation passage. The EGR passage 10 is made of, for example, a heat-resistant tube, and the inflow side connection port 10A is connected in the middle of the exhaust passage 6 between the exhaust port and the catalytic converter, while the outflow side connection port 10B is an EGR control valve. Intake passage 5 via 11
Connected in the middle of. That is, more accurately, EG
The R passage 10 is located on the exhaust passage 6 side and is located on the exhaust passage 6 side.
C (portion between the inflow side connection port 10A and the EGR control valve 11) and the intake side passage 10D located on the intake passage 5 side
(Portion between the EGR control valve 11 and the outlet side connection port 10B).

The control unit 12 as "exhaust gas recirculation control means" for centrally electrically controlling the engine is a CPU
It is configured as a microcomputer system including an arithmetic circuit such as the above, a memory circuit such as ROM and RAM, and an input / output circuit. On the input side of the control unit 12, an air flow meter 7, a throttle sensor 13 for detecting the throttle opening of a throttle valve 8,
A crank angle sensor 14 for detecting the engine speed,
A water temperature sensor 15 for detecting the cooling water temperature of the engine, an ignition switch 16 and the like are connected, and a fuel injection valve 8 and an EGR are provided on the output side of the control unit 12.
The control valve 11 is connected to a spark plug 17 or the like for igniting the air-fuel mixture (the wiring between the fuel injection valve 8 and the spark plug 17 is not shown). Further, the control unit 12 refers to an EGR control map (not shown) formed in the memory circuit to determine the EGR rate (valve opening degree of the EGR control valve 11) based on the engine speed and the engine load. It has a normal control unit 12A for controlling and a valve closing process unit 12B as a "valve closing process means" for controlling the valve opening degree after the engine is stopped, which will be described later, as its internal functions.

Next, referring to FIGS. 2 and 3, the EGR
A preferred specific example of the control valve 11 will be described. That is, FIG. 2 shows an enlarged view of the EGR control valve 11 in the closed state, and FIG. 3 shows an enlarged view of the EGR control valve 11 in the opened state.
Reference numeral 1 denotes an electrically controlled flow control valve including a housing 21, a valve body 26, a stepping motor 31 and the like, which will be described later. Note that the upper side in the figure will be referred to as “one side”, and the lower side in the figure will be referred to as “other side”.

The housing 21 is a stepping motor 3
1 side housing 21A which accommodates 1 and the other side housing 21B which accommodates the valve body 26, and each of these housings 21
A housing 21C, which connects A and 21B in the axial direction (vertical direction), is divided into three parts.
A, 21B and 21C are assembled by bolts 22. Further, the other side housing 21B has an inlet 23 connected to the exhaust side passage 10C of the EGR passage 10,
Outflow port 2 connected to intake side passage 10D of GR passage 10
4 are formed in the radial direction so that they are vertically separated from each other and are orthogonal to each other. The inlet port 23 and the outlet port 24 are formed in the axial direction of the other side housing 21B.
It is connected via 5.

A valve body 26 is provided in the valve body accommodation hole 25 of the other housing 21B so as to be movable in the axial direction.
The valve body 26 includes a small-diameter rod-shaped valve shaft 26A coaxially inserted into the valve body accommodation hole 25, a valve portion 26B integrally formed on the other end side of the valve shaft 26A, and the valve portion 26B. The seat portion 26C is integrally formed on the outer surface of the sheet with a predetermined taper angle to form an open-type poppet valve.

Further, the valve shaft 26A of the valve body 26 is inserted through a gas seal 27 fitted on one side of the valve body accommodation hole 25 and a dust cover 43, which will be described later, through a minute clearance (not shown) to form a seat. The portion 26C comes into contact with the valve seat member 28 fitted to the other side of the valve body accommodation hole 25 from the other side in the axial direction. Further, a thin disk-shaped spring receiving member 29 is fixed to one end side of the valve shaft 26A, and the valve body 2 is provided between the spring receiving member 29 and one end side of the gas seal 27.
A valve spring 30 for urging 6 in a valve closing direction (one side direction) with a predetermined spring force is provided.

A stepping motor 31 is housed in the one-side housing 21A, and the stepping motor 31 is vertically separated from the rotor 32 arranged coaxially with the valve body 26 on the outer peripheral side of the rotor 32. It is configured as a PM type stepping motor from the two stators 33 provided as above.

The other end of the rotor 32 is the bearing 3
A substantially cylindrical holder 32A rotatably supported by
And a cylindrical permanent magnet 32B provided on the outer peripheral side of the holder 32A. A plurality of magnetic poles (N poles, S poles) are alternately magnetized in the circumferential direction in the permanent magnet 32B. . A rotor shaft 35 is provided on the inner peripheral side of the holder 32A so as to be movable in the axial direction, and the other end side of the rotor shaft 35 is inserted into a bush 36 so that the valve shaft 26
It is in contact with one end side of A. That is, the rotor shaft 35
Is for converting the rotational movement of the rotor 32 into an axial movement via a spiral groove, and its rotation is restricted by a spring pin 37. Further, a spring bearing member 38 having a small diameter is provided at a substantially middle portion of the rotor shaft 35, and between the spring bearing member 38 and one end side of the bush 36,
A spring 39 is provided to prevent rattling due to backlash of the threaded portion of the rotor shaft 35.

On the other hand, each of the stators 33 provided on the outer peripheral side of the rotor 32 so as to be vertically separated from each other is a bobbin 33A, a winding 33B wound around the bobbin 33A, and a bobbin 33A.
A first stator plate 33C formed in a substantially U-shaped half-section so as to surround the outer side of the first stator plate, and a second stator plate 33C formed in an annular shape so as to substantially cover the opening side of the first stator plate 33C. It is composed of a stator plate 33D. Further, each winding 33B is composed of, for example, three independent windings, and each stator 33 is combined with a phase difference of 90 °. Further, an annular center plate 40 is provided between each of the stators 33. The center plate 40 positions each of the stators 33 and prevents magnetic interference with each other. The windings 33B of each stator 33 are respectively connected to terminals 41, and each of these terminals 41 extends into a connector portion 42 formed integrally with the one-side housing 21A.

The stepping motor 31 is
When a pulse signal is applied from the control unit 12 via the terminal 41, as shown in FIG. 4, a positive speed V _SN and a normal torque _TN are set to a positive value corresponding to the number of pulses. The valve body 26 opens and closes by rotating in reverse and converting this rotational force into linear motion by the rotor shaft 35. To be more precise, normally, the speed and torque during normal operation are different between when the valve is closed and when it is opened.
Although the speed when the valve is closed is faster, in this embodiment,
No particular distinction is made and the same normal speed S _N when the valve is open and when it is closed
Also, the case of driving with the torque T _N will be described as an example.
Further, the stepping motor 31 has a characteristic that the torque decreases as the speed increases, and generates a predetermined detent torque T _D when there is no excitation. In addition,
T _{H in} FIG. 4 is a holding torque.

On the other end side of the gas seal 27, a valve shaft 26A is provided.
A dust cover 43 having a substantially conical cylindrical shape is provided on the outer peripheral side of the. The dust cover 43 is provided to prevent foreign matter attached to the valve shaft 26A from entering the gas seal 27. For example, the outer diameter of the valve shaft 26A is made of a material having at least heat resistance such as stainless steel. It is formed in a substantially conical cylinder shape having an inner diameter slightly larger than that, and is fixed to the other end side of the gas seal 27 so that the other end surface 43A of the smaller diameter faces the valve portion 26B side of the valve body 26. . Further, the dust seal 43 is provided in the exhaust introduction system (exhaust side passage 10C, inflow port 23, valve body accommodation hole 25, outflow port 2).
4, the height dimension is set such that the other end surface 43A is in the vicinity of one side of the outflow port 24 in order to prevent an increase in the flow path resistance of the intake side passage 10D).

The plug 44 is for sealing the opening formed when the valve body accommodation hole 25 is bored in a gas-liquid tight manner, and is fixed to the other side housing 21B by a knock pin or the like (not shown). . An upper plate 45 provided between one end side of the holder 32A and the inner surface side of the one side housing 21A.
Serves as a guide plate for guiding the holder 32A. A corrugated washer 46 is provided between the other end of the bearing 34 and the intermediate housing 21C, and the corrugated washer 46 axially supports the outer race of the bearing 34. Further, the nipple 47 formed so as to project radially outward from the outer surface side of the intermediate housing 21C is for forming a cooling water passage.

Next, based on the flowchart of FIG.
The valve closing processing operation according to this embodiment will be described.

First, in step (abbreviated as "S" in the figure) 1, an ignition switch ("IG" in the figure) is used.
The state of the switch 16 is abbreviated), and in step 2, it is monitored whether or not the ignition switch 16 is turned off. If "YES" is determined in this step 2, it means that the engine has stopped. Therefore, the process proceeds to step 3, and the opening degree of the valve element 26 is changed to a predetermined valve opening degree θ as shown in the enlarged view of the main part of FIG. Is set, and in the final step 4, the energization of the stepping motor 31 is stopped and the program ends. After that, when the engine is restarted, it is preferable to move the valve body 26 to the fully closed position and then perform the normal EGR control in terms of initialization of position information and the like. However, even if the normal EGR control is started while the valve body 26 is slightly opened with the small opening degree θ, the valve opening degree θ is so small that it has little influence on the restart of the engine.

Next, the operation of the present embodiment will be described with reference to the operation explanatory view of FIG. 7. First, when the engine is started at a certain time t ₁ , the normal control section 12A of the control unit 12 causes the engine rotation to start. The valve opening degree (EGR rate) is read from the EGR control map based on the number N and the load T _P (more specifically, basic injection amount T _P = intake air amount Q / rotational speed N), and at a certain time t ₂ , the engine opening Until the operation is stopped, the valve opening degree of the EGR control valve 11 is open-loop controlled according to the operating condition of the engine. The operating condition of the engine is E
If it is out of the GR control area, EGR is not performed.

When the ignition switch 16 is turned off at a certain time t ₂ and the operation of the engine is stopped, the valve closing processing section 12B of the control unit 12 sets the valve opening degree of the valve element 26 to a predetermined value via the stepping motor 31. After the valve body 26 achieves the predetermined small opening θ at time t ₃ , the energization of the stepping motor 31 is stopped and the process ends. More specifically, the valve closing processing unit 12B
Drives the stepping motor 31 to separate the valve body 26 from the fully closed position so that the valve body 26 may stop at a position separated from the fully closed position by 3 steps in pulse number, and as shown in FIG. The valve is slightly opened with a small opening θ of.

Here, the predetermined small opening θ is the valve body 26.
The sheet portion 26C of the sticky component D such as oil or carbon
Since it is preferable to set the opening degree to the minimum necessary to prevent the valve seat member 28 from being adhered to the valve seat member 28 by P, the distance is not limited to the above-described three-step separation dimension, and for example, 1 to 10 steps or the like. An appropriate value can be adopted.

After the valve body 26 is slightly opened (substantially closed but not completely closed) at a predetermined small opening θ, the valve closing processor 51B: The energization to the stepping motor 31 is stopped and the processing is terminated. After the energization is stopped, the valve body 26 is returned to the fully closed position by the spring force of the valve spring 30, so that the valve body 26 is not moved to the valve seat member 28. It cannot prevent sticking. Therefore, in the present embodiment, the detent torque T _D generated by the stepping motor 31 in the non-excited state is used to maintain the opening degree of the valve body 26 at the small opening degree θ after the power supply is stopped.

That is, as shown in the characteristic diagram of FIG.
The spring force of 0 and the torque T _{S in the} valve closing direction generated by the valve spring 30 are in a proportional relationship, and the detent torque T _S of the stepping motor 31 is related to the torque T _{S in the} valve closing direction.
_D (holding force generated by the permanent magnet 32B) and the starting torque T _B of the bearing 34 (specifically, the bearing 34
The total value of the holding force due to the frictional force and the frictional force generated in each of the other movable parts).

Therefore, as shown in the following formula 1, the total value T _{t of} the detent torque T _D and the starting torque T _B is, for example, 100.
If the torque T _{S in the} valve closing direction generated by the spring force of the valve spring 30 set to about 0 g is exceeded, the opening degree of the valve element 26 is small even if the power supply to the stepping motor 31 is stopped.
Is held, the difference between the total value T _t and closing direction of the torque T _S of the torque of the valve opening direction is the holding force of the valve body 26.

[0038]

## EQU1 ## T _t = T _D + T _B > T _S Also, the detent torque T _D is expressed by the following formula 2, and the valve closing direction torque T _S is expressed by the following formula 3.

[0039]

[Formula 2] T _D = (1/2) · (B _g ² / μ ₀ ) · g · A _g · P where B _{g is} the magnetic flux density of the air gap μ _{0 is} the magnetic permeability of the air gap g is the air gap length _Ag : Magnetic pole cross-sectional area per pole P: Number of pole pairs

[0040]

## EQU3 ## T _S = (L / 2π) ・ η ₂・ F η ₂ = (tan θ−μ) / (tan θ (1 + μtan θ)) where L: pitch of conversion screw to linear motion F: valve spring 30 Spring force θ: Lead angle of conversion screw μ: Coefficient of friction In this embodiment having such a configuration, the following effects are achieved.

First, since the valve closing processing section 51B is configured to stop the valve body 26 at a predetermined small opening θ when the engine stops, as shown in FIG.
Due to the adhesive component DP attached to the valve body 26,
It can be surely prevented from being adhered to No. 8.

As a result, the "sticking phenomenon" between the valve element 26 and the valve seat member 28 is prevented, and the EGR control valve 11 is prevented.
It is possible to maintain the smooth opening / closing operation of the. In other words, when the valve body 26 is completely closed by the spring force of the valve spring 30 after the engine is stopped as in the prior art, the valve body 26 and the valve seat member 28 stick to each other. It is necessary to open the valve body 26 against this adhesive force.

Therefore, in the prior art, it is necessary to increase the torque of the stepping motor 31 in preparation for such a "sticking phenomenon", but this requires a strong torque of, for example, about 1.5 kg. 31
Becomes larger and the degree of freedom in mounting is reduced. On the other hand, in the present embodiment, since the valve element 26 is slightly opened by the predetermined small opening θ after the engine is stopped, the "sticking phenomenon" does not occur essentially, and the mechanical configuration is corrected. It is possible to stabilize the EGR control at low cost without adding the above.

Further, in other words, the EGR control valve 11 is normally constructed as a normally-closed type control valve that constantly urges the valve element 26 in the valve closing direction so that the EGR control valve 11 does not open due to exhaust pressure. Therefore, even in the case of an electrically controlled EGR control valve (inevitably in the case of a mechanical EGR control valve using negative pressure), when the engine is stopped, it is fully closed. It is a common technical common sense that even if an intermediate opening degree or a small opening degree is passed during driving, when the energization is stopped, “a small opening which is not a fully closed state but a substantially closed state is present when the energization is stopped. It completely lacked the idea and viewpoint of setting and maintaining a unique opening called "degree θ". Therefore, in the prior art,
As described above, in order to prevent the sticking phenomenon, it is often appealed to a direct and mechanical solution means such as adjusting the taper angle of the seat portion 26C and increasing the driving force of the stepping motor 31, but this increases the cost. In addition, the usability (for example, the degree of freedom in mounting the motor and the degree of freedom in setting the flow rate characteristic) is reduced. On the other hand, the present invention breaks the conventional general stereotype that "the EGR control valve 11 should be fully closed when the engine is stopped", thereby essentially solving the sticking phenomenon at a low cost. ing.

Secondly, since the valve body 26 is pulled away from the valve seat member 28 and stopped, even if the valve seat member 28 contracts due to a temperature decrease after the engine is stopped, the valve portion 26B of the valve body 26 is bitten by this. It will not get stuck. Therefore, the seat portion 2
Since it is not necessary to reduce the taper angle of 6C to an obtuse angle, it is possible to provide the taper angle with a degree of freedom and realize an appropriate EGR flow rate characteristic. That is, if the taper angle is set to an acute angle, the change in the flow path area per one-step signal can be reduced, so that an appropriate EGR flow rate characteristic can be easily realized.

Thirdly, in the present embodiment, since the stepping motor 31 is configured to maintain the small opening θ by utilizing the detent torque T _D generated in the non-excited state, the valve body is not consumed and the valve body is not consumed. 26 can be separated from the valve seat member 28.

Fourthly, in the present embodiment, not only the detent torque T _D of the stepping motor 31 but also the starting torque T _B of the bearing 34, which includes the frictional force of each movable part, is utilized. Since 26 is held at a predetermined small opening θ, the structure for holding the valve element 26 at a small opening θ can be optimized without unnecessarily increasing the size and cost of the stepping motor 31.

That is, as shown in FIGS. 4 and 8, since the detent torque T _D is small, an expensive material is used in order to maintain the small opening θ depending only on the detent torque T _D. Therefore, it is necessary to remarkably increase the magnetic force of the permanent magnet 32B or to increase the size of the stepping motor 31 itself. On the other hand, in the present embodiment, the drive mechanism of the valve body 26 is comprehensively examined and the starting torque T _B is also used, so that it is not necessary to increase the detent torque T _D, and it is simple and low cost. The small opening θ can be maintained.

Therefore, in this embodiment, "valve closing processing means 51B"
Is a predetermined small opening θ when the engine is stopped.
The internal combustion engine is characterized in that the small opening degree θ is maintained by the detent torque T _D of the stepping motor 31 and the starting torque T _B of each movable part in a state where the power supply to the stepping motor 31 is stopped. It is also possible to understand it as "the exhaust gas recirculation control device".

Next, a second embodiment of the present invention will be described with reference to FIGS. In this embodiment, the same components as those in the first embodiment described above are designated by the same reference numerals, and the description thereof will be omitted. A feature of this embodiment is that the valve body is completely closed after the engine is stopped and then set to a predetermined small opening.

That is, FIG. 9 is an explanatory view showing the overall configuration of the EGR control device according to this embodiment, and the control unit 51 of this embodiment also has the same structure as the control unit 12 described in the first embodiment. It is configured as a microcomputer system, and its internal function is not shown in FIG.
A normal control unit 51A based on the GR control map and a valve closing processing unit 51B as "valve closing processing means" are provided. However, as described below, the valve closing processing unit 51B of the present embodiment moves the valve body 26 to the fully closed position once after the engine is stopped, and then separates the valve body 26 by a predetermined small opening θ, as described in the above embodiment. Is different from.

Next, the valve closing process of this embodiment will be described with reference to the flowchart of FIG.
After reading the ignition switch 16 in step 12, it is determined in step 12 whether or not the ignition switch 16 is turned off. If the ignition switch 16 is turned off, the stepping motor 31 is driven in the next step 13, The valve body 26 is completely closed. Thereby, the control unit 51 can confirm the fully closed position.

Next, after the valve body 26 reaches the fully closed position, in step 14, the stepping motor 31 is reversed by a few steps to separate the valve body 26 from the valve seat member 28, and the EGR control valve 11 operates. The valve opening is set to a predetermined small opening θ. Finally, in step 15, the energization of the stepping motor 31 is stopped and the program ends.

Next, the operation of the present embodiment will be described with reference to the operation explanatory diagram of FIG. 11. First, the normal control unit is operated from the time when the engine is started at time t ₁ to the time when the engine is stopped at time t _2. The point that the normal EGR control by 51A is performed is the same as in the first embodiment.

However, in the present embodiment, after the engine is stopped, the valve body 26 is once moved to the fully closed position, and then at time t.
_{In step 3} , the stepping motor 31 is slightly rotated in the reverse direction to move the valve element 26 in the valve opening direction, and the processing is ended in a state where a predetermined small opening θ is maintained.

This embodiment, which is constructed in this way, can also obtain the same effects as the above-mentioned first embodiment. In addition to this, in the present embodiment, after the engine is stopped, the valve body 26 is closed once and then the valve seat member 28 is moved by a predetermined small opening θ.
Since it is configured to be separated from, the fully closed position can be confirmed each time the engine is stopped, and the next normal EGR control can be accurately performed in open loop.

In each of the above embodiments, the EGR control valve 1
Although the PM type stepping motor 31 using a permanent magnet is illustrated as the drive source of No. 1, the present invention is not limited to this.
Any motor may be used as long as it is a motor that generates the detent torque T _D after the power supply is stopped.

Further, although it is preferable that the detent torque T _D can be used, the detent torque T _D is not necessarily limited to this, and for example, a secondary power supply means such as a solar power generator or a holding battery may be provided, or in addition thereto. It is possible to hold the valve element 26 at a small opening θ by adopting a low power consumption type motor.

Further, in each of the above-mentioned embodiments, the so-called outward opening type EGR control valve 11 is illustrated, but the present invention is not limited to this.
It can be easily applied to an inward opening type EGR control valve.

[0060]

As described in detail above, according to the exhaust gas recirculation control device for an internal combustion engine according to the present invention, the valve closing processing means stops the valve body at a predetermined small opening when the engine stops. Due to the configuration, the valve body does not adhere to the valve seat,
The sticking phenomenon can be prevented in advance.

When the engine is stopped, the valve element is moved to the fully closed position and then stopped with a predetermined small opening from the fully closed position. It is possible to prevent the sticking phenomenon while confirming the position.

Further, since a stepping motor which generates a predetermined detent torque in a non-excited state is used and the valve body is stopped at a predetermined small opening degree, energization to the stepping motor is stopped, the detent torque, etc. It is possible to efficiently hold the small opening degree of the valve body by utilizing.

[Brief description of drawings]

FIG. 1 is a configuration explanatory view showing an overall configuration of an exhaust gas recirculation control device for an internal combustion engine according to a first embodiment of the present invention.

FIG. 2 is an enlarged sectional view showing an exhaust gas recirculation control valve in a closed state.

FIG. 3 is an enlarged view of an exhaust gas recirculation control valve in an open state.
It is a sectional view similar to FIG.

FIG. 4 is a characteristic diagram showing a relationship between speed and torque of a stepping motor.

FIG. 5 is a flowchart showing a valve closing process.

FIG. 6 is an enlarged sectional view showing a valve body and the like of an exhaust gas recirculation control valve.

FIG. 7 is an operation explanatory view showing the operation of the valve body.

FIG. 8 is a characteristic diagram showing a relationship between a spring force of a valve spring and a torque in a valve closing direction.

FIG. 9 is a configuration explanatory diagram showing an overall configuration of an exhaust gas recirculation control device for an internal combustion engine according to a second embodiment of the present invention.

FIG. 10 is a flowchart showing a valve closing process.

FIG. 11 is an operation explanatory view showing the operation of the valve body.

[Explanation of symbols]

5 ... Intake passage 6 ... Exhaust passage 10 ... EGR passage (exhaust gas recirculation passage) 11 ... EGR control valve (exhaust gas recirculation control valve) 12, 51 ... Control unit (exhaust gas recirculation control means) 12A, 51A ... Normal control part 12B, 51B ... valve closing processing section (valve closing processing means) 26 ... valve body 28 ... valve seat member 31 ... stepping motor

Claims (3)

[Claims] 1. An exhaust gas recirculation passage provided to connect an exhaust passage and an intake passage of an engine, an exhaust gas recirculation control valve provided in the middle of the exhaust gas recirculation passage for opening and closing a valve body by a motor, and the exhaust gas recirculation control valve. An exhaust gas recirculation control device for an internal combustion engine, comprising an exhaust gas recirculation control means for controlling the opening degree of the valve body by outputting a control signal to a recirculation control valve, wherein the valve body is controlled when the engine is stopped. An exhaust gas recirculation control device for an internal combustion engine, comprising valve closing processing means for stopping at a predetermined small opening. 2. The valve closing processing means, when the engine is stopped, moves the valve element to a fully closed position and then stops the engine with a predetermined small opening from the fully closed position. The exhaust gas recirculation control device for an internal combustion engine according to claim 1, wherein. 3. A stepping motor that generates a predetermined detent torque in a non-excited state is used as the motor,
The exhaust gas of the internal combustion engine according to claim 1 or 2, wherein the valve closing processing means stops the energization of the stepping motor after stopping the valve body at a predetermined small opening degree. Reflux control device.