JPH08303307A - Exhaust air reflux controller of internal combustion engine - Google Patents

Abstract

PURPOSE: To remove foreign matter adhered on a valve element so as to maintain the smooth open and close operations of the valve element by reciprocating the valve element in a condition in which torque is increased after an engine stops. CONSTITUTION: When an engine stops, a control unit makes speed of a stepping motor 31 later than ordinary speed to increase torque and moves a valve element 26 from the fully opened position to the fully closed position in this condition. Consequently, foreign matter adhered on a valve shaft 26A comes into contact with the other end face 43A of a dust cover 43 and is scraped off. Moreover, the valve element 26 stops in a condition in which it is slightly opened at small degree of opening θ after the cleaning work ends, and the condition is held due to detent torque of the stepping motor 31. Consequently, it is possible to prevent a seat part 26C from adhering on a 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. The oil content, carbon, etc. in the exhaust gas gradually adhere to the outer surface of the valve body (more specifically, the surface of the valve shaft), and may eventually be solidified by baking (so-called deposit occurs). Further, in the EGR control valve, since the clearance between the valve body and the seal portion provided outside the valve body is small, the foreign matter adhered to the valve body and solidified is within a minute clearance between the seal portion and the foreign body. If it gets in, a biting phenomenon (shaft stick) may occur, which may impede the smooth opening / closing operation of the valve element.

Here, even if oil or carbon adheres to the surface of the valve body, the adhesion force is small before it is solidified by the high temperature. Therefore, the valve body is repeatedly fully opened and fully closed. Most foreign matter is scraped off when the valve body passes through the seal. Therefore, the driving force is originally large,
In a negative pressure type EGR control valve that frequently repeats full opening and full closing, it is easy to remove carbon and the like adhering to the valve body, and thus the above-mentioned trapping phenomenon is unlikely to occur.

However, in an electrically controlled EGR control valve using a stepping motor, the valve opening is controlled more finely on the basis of the engine speed and the engine load. There is a case where the valve body is only opened up to this time, and in this case, foreign matter such as carbon adhering to the valve body can only be partially removed. Therefore, while the EGR control device using the electrically controlled EGR control valve can realize an appropriate EGR rate according to the operating conditions of the engine, there is a possibility that foreign matter such as carbon adhering to the valve body cannot be sufficiently removed. , The biting phenomenon may occur.

On the other hand, although the oil content and carbon in the exhaust gas adhere to the surface of the seat and the valve seat of the valve body, the carbon and the like adhered to the seat adhere to the valve body and the valve seat. That is, there is a possibility that a so-called “sticking phenomenon” may occur and smooth opening / closing operation of the valve element may be hindered. That is, after the engine is stopped, the EGR control valve is closed and the seat portion is brought into close contact with the valve seat. Therefore, the seat portion is adhered to the valve seat due to carbon or the like attached during the operation of the engine, which is required for opening the valve. The torque may increase or the valve opening operation may not be performed smoothly.

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 valve body may be caught by the contracting valve seat. . 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 an object thereof is to smooth the opening / closing operation of the exhaust gas recirculation control valve even when foreign matter such as carbon adheres to the valve body. The present invention provides an exhaust gas recirculation control device for an internal combustion engine. Another object of the present invention is to stabilize the opening / closing operation of the exhaust gas recirculation control valve by periodically and automatically removing foreign matter attached to the valve body. A further object of the present invention is to provide an exhaust gas recirculation control device for an internal combustion engine, which is capable of avoiding the adhered state between the valve body and the valve seat and improving the degree of freedom in flow rate characteristics.

[0011]

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 that is provided in the middle of the recirculation passage and opens and closes a valve body that is inserted into an annular member by a motor, and an exhaust gas that controls 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, comprising: recirculation control means, wherein when the engine is stopped, foreign matter adhering to the valve body is transferred to the annular body in a state in which the torque of the motor is increased above the torque during normal operation. The present invention is characterized in that stop processing means for moving the member in a removable direction is provided.

Further, specifically, a stepping motor is used as the motor, and the stop processing means makes the drive speed of the stepping motor slower than the normal drive speed when the engine is stopped. It is preferable to move the valve body from the fully open position to the fully closed position.

Further, a stepping motor is used as the motor, and when the engine is stopped, the stop processing means fully opens the valve body in a state in which the drive speed of the stepping motor is slower than the normal drive speed. After moving from the position to the fully closed position, it is more preferable to stop with a predetermined small opening.

Further, when a stepping motor is used as the motor, and the stop processing means restarts the engine during the stop processing in which the valve element is moved from the fully open position to the fully closed position, the stepping motor in normal time is used. It is desirable to fully close it at the driving speed of.

Further, the exhaust gas recirculation control valve is provided with a housing, a valve body provided in the housing so as to be movable in the axial direction, and provided on one side of the housing to move the valve body in the axial direction. Therefore, it is preferable to have a stepping motor that separates from and seats on the valve seat, and a dust cover of a substantially conical cylindrical shape that is fitted onto the valve body in the vicinity of the outer peripheral side thereof.

[0016]

Since the exhaust gas flows into the intake passage through the periphery of the valve body during operation of the engine, foreign matter such as oil or carbon in the exhaust gas may adhere to the outer surface of the valve body. However, since the stop processing means increases the motor torque after the engine is stopped and moves the valve body in the direction in which the foreign material can be removed by the annular member, the foreign matter attached to the valve body is removed every time the engine is stopped. Therefore, it is possible to prevent the phenomenon of biting between the valve body and the seal portion. That is, when the valve body moves in the direction of being housed in the seal portion, the foreign matter attached to the valve body comes into contact with the tip surface of the seal portion and is scraped off. That is, "the direction in which foreign matter can be removed by the annular member" means the valve closing direction in the case of the outer opening type that opens the valve seat from the outside, and the direction of the inner opening type that opens the valve seat from the inside. Is in the valve opening direction. In other words,
It can also be defined as "the direction in which the valve body is housed in the annular member".

Further, according to the structure of claim 2, wherein the valve body is moved from the fully open position to the fully closed position in a state where the driving speed of the stepping motor is slower than that in the normal time, the torque is reduced by decreasing the driving speed. Can be increased,
The surface of the valve body can be cleaned with this torque increased.

Further, according to the constitution of claim 3, the valve body is moved from the fully open position to the fully closed position with the driving speed of the stepping motor being slower than in the normal state, and then stopped at a predetermined small opening. For example, valve body surface (valve shaft surface)
It is possible to remove the foreign matter adhering to the valve body and prevent the valve body and the valve seat from adhering to each other due to the foreign matter adhering to the seat portion at the tip of the valve body.

Further, when the engine is restarted while the valve body is moved from the fully open position to the fully closed position, the valve body is fully closed at the driving speed of the stepping motor in normal time. For example, while the valve body is being cleaned, this cleaning work does not affect the restart of the engine, which improves usability.

Further, the housing, the valve element provided in the housing so as to be movable in the axial direction, and the stepping element provided on one side of the housing for moving the valve element in the axial direction to separate from and seat on the valve seat. According to the configuration of claim 5, which uses the exhaust gas recirculation control valve having a motor and a dust cover having a substantially conical cylindrical shape that is fitted around the outer peripheral side of the valve body, the concrete conical cylindrical shape is used. The dust cover can scrape off foreign matter adhering to the valve body surface.

[0021]

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

1 to 7 relate to an exhaust gas recirculation control device 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 electrically centrally 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. The normal control unit 12A for controlling and the stop processing unit 12B as "stop processing means" for controlling the cleaning operation after the engine is stopped, which will be described later, are provided 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 receiving hole 25 of the other side 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 to one side of the valve body accommodation hole 25 and a dust cover 43 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, it rotates forward and reverse by a predetermined normal speed S _N and a predetermined normal torque T _N by a number corresponding to the number of pulses, and this rotational force Is the rotor shaft 35
The valve body 26 opens and closes by being converted into a linear motion by. To be more precise, normally, the speed and torque at the time of valve closing are different from those at the time of valve opening, and the speed at the time of valve closing is faster, but in the present embodiment, no particular distinction is made.
An example will be described in which the valve is driven at the same normal speed S _N and torque T _N when the valve is open and when the valve is closed. Further, as shown in the characteristic diagram of FIG. 4, 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. Note that T _{H in} FIG. 4 is a holding torque.

The speed S _C and the torque T _C during cleaning are
The torque is required to scrape off foreign matter such as oil and carbon adhering to the surface of the valve shaft 26A of the valve body 26 with the dust cover 43, and is set so that the cleaning process can be completed in a minimum time. . That is, for example, since carbon or the like is not solidified immediately after being adhered, it can be removed with a weak torque of about 0.1 kg, but when foreign matter is baked and solidified over time, a torque of about 0.5 kg is required. Therefore, while the cleaning torque T _C needs to be set to about 0.5 kg or more, if the speed S _C is decreased to increase the torque T _C , the cleaning work time becomes longer and the engine restarts. There is a possibility that it will affect

Therefore, the cleaning speed S _C and torque T _C
Is set to the minimum torque required for foreign matter removal (for example, speed S _C = 50-60 pps). However, the torque required for removing foreign matter varies depending on the diameter size of the rotor shaft 35, and the specific relationship between speed and torque varies depending on the size of the stepping motor 31, the driving method, and the like. It is an example, and the present invention is not limited thereto. The torque - speed characteristics because it has a certain degree of temperature dependence, it is more preferable to set the speed S _C and the torque T _C during cleaning in consideration of this.

At the other end 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 for removing foreign matter adhering to the valve shaft 26A to prevent foreign matter from entering the gas seal 27. For example, a material having at least heat resistance such as stainless steel is used to remove the foreign matter from the valve shaft 26A. It is formed in a substantially conical tubular shape having an inner diameter dimension slightly larger than the outer diameter dimension, 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. Has been done. In other words, the dust cover 43 is formed in an inverted conical cylinder shape so that the small-diameter other end surface 43A faces the valve portion 26B. Also, this dust seal 4
In order to prevent an increase in the flow path resistance of the exhaust introduction system (including the exhaust side passage 10C, the inflow port 23, the valve body housing hole 25, the outflow port 24, and the intake side passage 10D), the other end face 43A flows. The height of the outlet 24 is set so as to reach the vicinity of one side thereof. Here, in the present embodiment, the dust cover 43 constitutes an “annular member”, but when the dust cover 43 is omitted, the gas seal 27 becomes an “annular member”.

The plug 44 covers the opening formed when the valve body accommodation hole 25 is bored in a gas-liquid tight manner, and is fixed to the other 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 stop 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 the next 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, so the process proceeds to step 3 and the drive torque of the stepping motor 31 is set. That is, in step 3, as shown in FIG. 4, the speed of the stepping motor 31 is increased from the normal speed S _N to the cleaning speed S _C , so that the torque is changed from the normal torque T _N to the cleaning time. The torque T _{C of} is increased.

Then, in step 4, the valve body 26 is moved to the fully open position with the torque increased, and in step 5 that follows, the valve body 26 is fully opened from the fully open position with the torque similarly increased. Move to closed position. As the valve body 26 reciprocates, foreign matter such as oil and carbon adhering to the surface of the valve body 26 is scraped off by the dust cover 43, and removed and cleaned. However, although the foreign matter removal range is limited to the lift range of the valve body 26, there is no particular inconvenience because the valve shaft 26A outside the lift range does not enter the gas seal 27. As will be described later, when the engine is restarted during the stop process shown in FIG. 5, the stop process is immediately interrupted and the normal process unit 12A performs the normal process.

Next, the operation of this embodiment will be described with reference to the operation explanatory diagram of FIG.

First, when the engine starts at a certain time t ₁ ,
The normal control unit 12A of the control unit 12 determines the valve opening (EGR) from the EGR control map based on the engine speed N and the load T _P (specifically, basic injection amount T _P = intake air amount Q / rotation speed N). Rate) and until the operation of the engine is stopped at a certain time t ₂ , the valve opening degree of the EGR control valve 11 is set as the operating condition of the engine with the speed _SN at the normal time and the torque _TN at the normal time. Open loop control accordingly. If the engine operating conditions are outside the EGR control range, 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 control unit 12 once outputs the EG at the normal speed S _C.
The R control valve 11 is closed, and then the stop processing unit 12B performs the stop processing described above with FIG. 5 in an open loop. That is, the stop processing unit 12B sets the speed of the stepping motor 31 to the cleaning speed S _C slower than the normal speed S _N after the EGR control valve 11 is fully closed at the time t ₃ , thereby performing the stepping operation. The torque of the motor 31 is increased to the torque T _C at the time of cleaning, and in this state, the valve body 26 of the EGR control valve 11 is moved to the fully open position as shown in the enlarged view of the main part of FIG. 7.

Next, when the valve body 26 reaches the fully open position at time t ₄ , the stop processing unit 12B causes the stepping motor 31
Is reversed and the torque T _C is increased, the valve 26
Move to the fully closed position. As a result, as shown in FIG. 7, while the foreign matter DP such as carbon attached to the valve shaft 26A of the valve body 26 comes into contact with the other end surface 43A of the dust cover 43 and is scraped off, the valve body 26 closes at time t ₅ . Speak.

On the other hand, when the engine is restarted at a certain time t ₆ during the stop processing, as shown by the chain double-dashed line in FIG.
The speed of the stepping motor 31 is returned to the normal speed S _N , and the valve body 26 is promptly displaced in the valve closing direction.
Close the valve at ₇ . After that, although not shown, the normal control by the normal control unit 12A is performed.

According to the present embodiment configured as described above,
The following effects are obtained.

First, when the engine is stopped, the valve body 26 inserted into the dust cover 43, which is an annular member, is inserted into the dust cover 43 while the torque of the motor 31 is increased above the torque T _N under normal conditions. Since the stop processing unit 12B for moving the foreign matter in the direction capable of removing foreign matter (valve closing direction) is provided, as shown in FIG. 7, every time the engine is stopped, the valve body 2
Foreign matter such as carbon attached to the surface of the valve shaft 26A of No. 6 can be removed and cleaned. As a result, it is possible to prevent foreign matter adhering to the valve shaft 26A from entering the gas seal 27 and causing a biting phenomenon, and it is possible to maintain a smooth opening / closing operation of the valve body 26.

Secondly, when the engine is stopped, the stop processor 12B makes the valve body 26 fully closed from the fully open position with the drive speed of the stepping motor 31 slower than the normal drive speed S _N. Since the structure is moved to the position, when the engine is stopped, it is possible to easily increase the torque more than the torque T _N at the normal time to reciprocate the valve body 26, thereby removing foreign matter.

Thirdly, when the engine is restarted during the stop processing in which the valve body 26 is moved from the fully open position to the fully closed position, the stop processing unit 12B operates the valve body 26 at the normal speed S _N. Since the valve is closed, the cleaning work by the stop process does not affect the restart of the engine, and the usability is improved.

Fourthly, the EGR control valve 11 is provided with a housing 21, a valve body 26 movably provided in the housing 21 in the axial direction, and a valve body 26 provided on one side of the housing 21. The stepping motor 31 for moving the valve seat member 28 in and out of the valve seat member 28, and the valve body 2
6 has a substantially conical cylindrical dust cover 43 that is fitted close to the outer peripheral side of the valve 6, the valve body 26 is reciprocated with a high torque T _C after the engine is stopped. The dust cover 43 can effectively scrape off the adhered foreign matter.

Fifth, in the present embodiment, the dust cover 43
Is formed in a substantially conical tube shape, and the other end surface 43A having a small diameter is opposed to the valve portion 26B of the valve body 26, so that the stress generated when a foreign object contacts the other end surface 43A is applied to the one end surface side having a large diameter. By dispersing, the foreign matter can be reliably scraped off, and the durability and the like of the dust cover 43 can be improved.

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. The feature of this embodiment is that the valve body is not completely closed after the cleaning operation of the valve body is completed, but is held at a predetermined small opening degree.

That is, FIG. 8 is an explanatory view showing the overall configuration of the EGR control device according to the present embodiment, and the control unit 51 of the present embodiment is similar to 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 stop processing unit 51B as a "stop processing unit" are provided. However, as will be described later, the stop processing unit 51B of the present embodiment causes the EGR control valve 11 to complete after the cleaning work after the engine is stopped.
This is different from the above-described embodiment in that the valve opening degree is maintained at a predetermined small opening degree.

Next, the stop processing of this embodiment will be described with reference to the flowchart of FIG.
Performs the same processing as steps 1 to 5 described with reference to FIG. 5, and in step 11, the ignition switch 1
After reading 6 in step 12, it is determined whether or not the ignition switch 16 is turned off. In step 13, the speed of the stepping motor 31 is increased from the normal speed S _N to the cleaning speed S _C. Let

As a result, the torque of the stepping motor 31 increases from the torque T _{N in the} normal state to the torque T _C in the cleaning. In this state, in step 14, the valve body 26 is moved to the fully open position, and the next step is performed. At 15, the valve body 26 is moved to the fully closed position. As a result, as described in the first embodiment, as shown in FIG. 11, the foreign matter DP adhering to the valve shaft 26A comes into contact with the other end surface 43A of the dust cover 43 and is scraped off to clean the valve shaft 26A. The work is done automatically.

Then, in step 16, the valve body 26 in the fully closed position is slightly opened and stopped to maintain a predetermined small opening degree, and then the energization of the stepping motor 31 is stopped to end the program. To do. When the engine is restarted after that, it is preferable to move the valve body 26 to the fully closed position and then perform the EGR control during normal operation in terms of initialization of position information and the like. However, if the valve element 26 is opened by a small opening θ
Even if the normal EGR control is started with the valve slightly opened, the valve opening θ is so small that it hardly affects the restart of the engine.

In this embodiment, the valve body 26 is slightly opened with the cleaning speeds S _C and T _C. However, the present invention is not limited to this, and the normal speeds S _N and T _N are not limited thereto. The valve may be slightly opened with. However, when the valve is opened at the cleaning speed S _C or the like, the control structure can be simplified because there is no need to switch the speed of the stepping motor 31.

Next, the operation of the present embodiment will be described with reference to the operation explanatory view of FIG. 10. 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. Normal EGR control by 51A is performed, and EGR
After the control valve 11 is closed at time t ₃ , the speed S _C during cleaning is
And that the torque T _C is reciprocated from the fully open position to the fully closed position is the same as in the first embodiment.

However, in this embodiment, at the time t ₅ , the valve body 2
After 6 reaches the fully closed position, 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 in which the predetermined small opening θ is maintained. More specifically, after the valve body 26 reaches the fully closed position at time t ₅ , the stop processing unit 51B causes the stepping motor 31 to have, for example, about 3 steps (the “step” here is the number of pulses). Only by reversely rotating the valve body 26 away from the fully closed position, as shown in FIG. 11, a state in which the valve 26 is slightly opened at a predetermined small opening θ is generated. Here, the predetermined small opening θ is
The seat portion 26C of the valve body 26 is preferably set to the minimum opening required to prevent the seat portion 26C of the valve body 26 from being adhered to the valve seat member 28 by an adhesive component such as oil or carbon. It is not limited, for example, 1 to 10
An appropriate value such as a step can be adopted.

Then, after slightly opening the valve element 26 at a predetermined small opening θ, the stop processing unit 51B stops energizing the stepping motor 31 to end the processing. If the valve body 26 is returned to the fully closed position by the spring force of the valve spring 30, the valve body 26 cannot be prevented from sticking to the valve seat member 28. 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. 12, the spring force of the valve spring 30 and the torque T _{S in the} valve closing direction generated by the valve spring 30 are in a proportional relationship, and with respect to this torque T _S ,
The detent torque T _D (holding force generated by the permanent magnet 32B) of the stepping motor 31 and the bearing 34
The starting torque T _B (more specifically, the total value of the holding force due to the frictional force of the bearing 34 and the frictional force generated in each of the other movable parts) opposes.

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.

[0062]

## 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.

[0063]

[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

[0064]

[Formula 3] T _S = (L / 2π) ・ η ₂・ F η ₂ = (tan θ−μ) / (tan θ (1 + μtan θ)) where L: pitch of conversion screw for linear movement F: valve spring 30 Spring force θ: Lead angle of conversion screw μ: Friction coefficient Also in this embodiment having such a configuration, the same effect as that of the above-described first embodiment can be obtained. In addition to this, the present embodiment has the following effects.

First, the stop processing unit 51B closes the valve body 26 from the fully open position to the fully closed position with the driving speed of the stepping motor 31 slower than the normal driving speed S _N when the engine is stopped. After moving to the position, a predetermined small opening θ
Since the foreign matter adhered to the valve shaft 26A can be scraped off by the dust cover 43, the foreign matter adhered to the seat portion 26C prevents the valve body 26 from adhering to the valve seat member 28. It can be surely prevented.

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
It is possible to maintain the smooth opening / closing operation of the. In other words, when the valve body 26 is fully closed after the engine is stopped as in the prior art, the valve body 26 and the valve seat member 28 stick to each other, so that the valve body 26 is resisted against this adhesive force. It is necessary to open the valve. Therefore, in the prior art, it is necessary to increase the torque of the stepping motor 31 in preparation for the "sticking phenomenon", but this requires a strong torque of, for example, about 1.5 kg, so that the stepping motor 31 becomes large. , The degree of freedom in mounting will be reduced. On the other hand, in this embodiment, since the valve body 26 is slightly opened after the engine is stopped, the "sticking phenomenon" does not occur essentially, and the mechanical structure is not modified at all and the cost is low. Thus, the EGR control can be stabilized.

Further, in other words, normally, not only the EGR control valve 11 but also almost all control valves are fully closed or fully opened when their driving force (for example, current, pressure, etc.) is lost. However, it is the conventional general common sense that, even if an intermediate opening degree or a small opening degree is passed during driving, as in the present invention, when the driving force is lost, “the valve is substantially closed. However, the idea and viewpoint of setting a unique opening such as “small opening θ that is not in a fully closed state” was completely lacking. Therefore, in the related art, as described above, in order to prevent the sticking phenomenon, a direct mechanical solution such as adjusting the taper angle of the seat portion 26C and increasing the driving force of the stepping motor 31 is often appealed. This increases the cost and reduces the usability (for example, the degree of freedom in mounting the motor and the degree of freedom in setting the flow rate characteristic). On the other hand, the present invention defeats the conventional general idea that "the EGR control valve 11 should be fully closed or fully opened when the driving force is lost", and as a result, a sticking phenomenon is inherently achieved at a low cost. Has been resolved.

Secondly, since the valve element 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 element 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 this 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 without the battery power being 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 12, since the detent torque T _D is small, this detent torque T _D
When trying to keep the small opening θ depending on
It is necessary to remarkably increase the magnetic force of the permanent magnet 32B using an expensive material, 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, the "stop processing means 51B" is used.
When the engine is stopped, with the torque of the stepping motor 31 increased, the valve body 26 is moved by the annular member 43 in a direction in which foreign matter can be removed, and then a predetermined small opening θ
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".

In each of the above embodiments, after the engine is stopped,
The case where the valve body 26 is reciprocated at the slow cleaning speed S _C has been exemplified, but in the case of the outward opening type, the other end surface 43A of the dust cover 43 is mainly when the valve body 26 moves in the valve closing direction.
Since foreign matter is scraped off with, as shown in the modification of FIG.
The valve may be moved at a slow speed S _C only in the valve closing direction and at the normal speed S _N in the valve opening direction (in the case of the inward opening type, conversely, only the valve opening direction may be slowed down). Good).

In each of the above-described embodiments, the case where the valve element 26 is reciprocated only once has been described as an example, but the present invention is not limited to this and, for example, in consideration of the influence on restarting the engine or the like. However, it may be moved multiple times.

Further, as a drive source of the EGR control valve 11, in consideration of easiness of control, use of the detent torque T _D in a non-excited state, easiness of torque change, manufacturing cost, etc., PM using a permanent magnet is used. Although the type stepping motor 31 is preferable, the present invention is not limited to this, and any motor capable of changing the torque may be used. For example, a hybrid type stepping motor or the like may be used.

Therefore, in the second embodiment, "stop processing means 5"
1B, when the engine is stopped, in a state where the torque of the motor 31 is increased, the valve body 26 is moved by the annular member 43 in a direction capable of removing foreign matter, and then stopped at a predetermined small opening θ. It can also be understood as an "exhaust gas recirculation control device for an internal combustion engine". If such a grasp is made, the detent torque T _D cannot always be utilized, and therefore some energization may be required to maintain the small opening degree θ of the valve body 26, which leads to power consumption. Can't get enough effect in. However, even in this case, by adopting a low power consumption type motor, a secondary power supply means such as a solar power generation device or a large capacity battery, etc., the valve body 26 can be made small with relatively low energy consumption after the engine is stopped. It is possible to maintain the opening degree θ.

In each of the above embodiments, the case where the dust cover 43 as an annular member scrapes off foreign matter has been described as an example. However, the dust cover 43 is eliminated and the other end surface of the gas seal 27 as an annular member is omitted. Foreign matter may be removed with.

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

[0079]

As described in detail above, according to the exhaust gas recirculation control device for an internal combustion engine according to the present invention, after the engine is stopped, the torque of the motor is increased and the valve body is moved in a direction in which foreign matter can be removed by the annular member. Since it is configured to move, foreign matter attached to the valve body can be automatically removed every time the engine is stopped,
It is possible to prevent the "bite-in phenomenon" in advance and maintain a smooth opening / closing operation.

Further, since the valve body is moved from the fully open position to the fully closed position in a state where the driving speed of the stepping motor is slower than the normal time, the torque can be easily increased by slowing the driving speed. The valve body surface can be cleaned with the torque increased.

Further, since the valve body is moved from the fully open position to the fully closed position with the driving speed of the stepping motor being slower than in the normal state, the valve body is stopped at a predetermined small opening, so that In addition to removing foreign matter adhering to the surface (surface of the valve shaft), foreign matter adhering to the seat portion at the tip of the valve body can prevent the valve body and valve seat from adhering to each other. By providing the taper angle with a degree of freedom, it is possible to easily obtain an appropriate flow rate characteristic.

Further, when the engine is restarted while moving the valve body from the fully open position to the fully closed position, the valve body is configured to be fully closed at the driving speed of the stepping motor in the normal time. While cleaning, this cleaning work does not affect the restart of the engine,
Usability is improved.

Further, the housing, the valve element provided in the housing so as to be movable in the axial direction, and the stepping element provided on the one side in the housing and moved in the axial direction to separate from and seat on the valve seat. Since the exhaust recirculation control valve having the motor and the substantially cone-shaped dust cover externally fitted close to the outer periphery of the valve body is used, the dust cover attached to the valve body surface by the substantially cone-shaped dust cover. Foreign matter can be scraped off efficiently.

[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 stop processing.

FIG. 6 is an operation explanatory view showing the operation of the valve body.

FIG. 7 is an enlarged sectional view showing a valve body and the like of an exhaust gas recirculation control valve.

FIG. 8 is a configuration explanatory view 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. 9 is a flowchart showing stop processing.

FIG. 10 is an operation explanatory view showing the operation of the valve body.

FIG. 11 is an enlarged view of a main part of the exhaust gas recirculation control valve when the valve is opened with a small opening.

FIG. 12 is a characteristic diagram showing a relationship between a spring force of a valve spring and a torque in a valve closing direction.

FIG. 13 is an operation explanatory diagram of an exhaust gas recirculation control device for an internal combustion engine according to a modified example of the present invention.

[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 ... Stop processing part (stop processing means) 21 ... Housing 26 ... Valve body 28 ... Valve seat member 31 ... Stepping motor 43 ... Dust cover 43A ... Other end surface

Claims (5)

[Claims] 1. An exhaust gas recirculation passage that connects an exhaust passage and an intake passage of an engine, and an exhaust gas recirculation valve that is provided in the middle of the exhaust gas recirculation passage and opens and closes a valve element that is inserted into an annular member by a motor. An exhaust gas recirculation control device for an internal combustion engine, comprising: a control valve; and an exhaust gas recirculation control means for controlling the opening degree of the valve element by outputting a control signal to the exhaust gas recirculation control valve. In the internal combustion engine, there is provided stop processing means for moving foreign matter adhering to the valve element in a direction in which the annular member can be removed by the annular member in a state where the torque of the motor is increased more than the torque during normal operation. Exhaust gas recirculation control device. 2. A stepping motor is used as the motor, and when the engine is stopped, the stop processing means fully opens the valve body in a state in which the drive speed of the stepping motor is slower than the normal drive speed. The exhaust gas recirculation control device for an internal combustion engine according to claim 1, wherein the exhaust gas recirculation control device is moved from a position to a fully closed position. 3. A stepping motor is used as the motor, and when the engine is stopped, the stop processing means fully opens the valve body in a state in which the drive speed of the stepping motor is slower than the drive speed during normal operation. The exhaust gas recirculation control device for an internal combustion engine according to claim 1, wherein the exhaust gas recirculation control device is stopped at a predetermined small opening after being moved from the position to the fully closed position. 4. A stepping motor is used as the motor, and when the stop processing means restarts the engine during the stop processing in which the valve element is moved from the fully open position to the fully closed position, the stepping motor in normal time is used. The exhaust gas recirculation control device for an internal combustion engine according to any one of claims 1 to 3, wherein the exhaust gas recirculation control device is fully closed at a driving speed of. 5. The exhaust gas recirculation control valve includes a housing,
A valve element provided in the housing so as to be movable in the axial direction, a stepping motor provided on one side of the housing for moving the valve element in the axial direction to separate from and seat on a valve seat, and the valve element. The exhaust gas recirculation control device for an internal combustion engine according to any one of claims 1 to 4, further comprising: a dust cover having a substantially conical cylindrical shape that is externally fitted close to the outer peripheral side thereof.