JP2003056412A - Exhaust recirculation device for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reliably capture a foreign material scraped in the course of exhaust or from an exhaust recirculation control valve 7, thereby preventing the intervention of a foreign material between a valve element 29 and a valve seat 27. SOLUTION: An exhaust recirculation control valve 7 has a valve element 29 that moves in a vertical direction by a stepping motor, and exhaust gas flows from an exhaust inlet 26 downward of a valve seat 27 to a sideward exhaust outlet 28. An exhaust recirculation passage 4 in upstream has a first passage part 34 almost in a horizontal direction and a second passage part 35 almost in a vertical direction, and the bottom of the second passage part 35 is blocked up by a plug 37 to form a recessed part 36 for capturing a foreign material. The foreign material flowing from the first passage part 34 collides with a side face of the part 35, the element 29 or the seat 27 and drops to be collected in the recessed part 36. During startup of the engine, the valve element 29 operates as full close-full open-full close, thereby removing the intervening foreign material and dropping it in the recessed part 36.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement of an exhaust gas recirculation device that returns a part of exhaust gas of an internal combustion engine to an intake system.

[0002]

2. Description of the Related Art As is well known, an exhaust gas recirculation device for an internal combustion engine is provided with an exhaust gas recirculation passage provided so as to connect an exhaust passage and an intake passage of the internal combustion engine, and a midway portion of the exhaust gas recirculation passage. An exhaust gas recirculation control valve is provided, and the exhaust gas recirculation control valve controls the amount of exhaust gas recirculation, and thus the exhaust gas recirculation rate, to be optimum according to engine operating conditions. As the exhaust gas recirculation control valve, a mechanical type (negative pressure type) using a diaphragm has been widely used in the past, but recently, a valve body is moved up and down by a motor, for example, a stepping motor to control the opening degree. The electric control type exhaust gas recirculation control valve configured to do so is being widely used.

In the electrically controlled exhaust gas recirculation control valve using such a stepping motor, the exhaust gas recirculation ratio control according to the engine operating conditions can be easily realized by open loop control, but unlike the mechanical type. However, since there is a period in which the opening degree is maintained at a very small degree, there is a problem that foreign matter such as carbon particles and cutting powder in the exhaust gas is caught. That is, when these foreign matters are caught between the valve seat and the valve body, the valve body cannot be seated completely, which may cause stepping out of the stepping motor and eventually defective exhaust gas recirculation control. .

In order to suppress the inflow of foreign matter into such an exhaust gas recirculation control valve, there is conventionally known Japanese Unexamined Patent Publication No. 2000-170608.
In the publication, a recess for catching foreign matter is provided in the exhaust gas recirculation passage on the inlet side of the exhaust gas recirculation control valve, and a relatively heavy foreign matter flowing along the wall surface from the upstream side to the lower side is dropped into the recess. Such a configuration is disclosed.

[0005]

However, in the structure described in the above publication, it is mainly intended to prevent foreign matter flowing from the upstream side toward the exhaust gas recirculation control valve in the middle of the passage, Foreign matter that has collided with the body and dropped downward, or foreign matter dropped from the valve body due to the vertical movement of the valve body,
It cannot always be reliably captured.

Therefore, as described in, for example, Japanese Unexamined Patent Publication No. 8-303307, there is provided an apparatus having a structure in which the valve body is positively moved up and down to scrape off the foreign matter adhering to the valve body. If applied, the scraped foreign matter will be scattered without being captured, and will enter the exhaust gas recirculation control valve again,
It may be caught between the valve seat and the valve body.

Further, in the above-mentioned conventional device, it is not taken into consideration that the foreign matters collected in the concave portion are discharged to the outside. Therefore, since the foreign matters in the concave portion increase with time, the concave portion is also caused by the traveling vibration or the like. There is a problem that foreign matter is scattered from the inside and gets caught between the valve seat and the valve body.

[0008]

The invention according to claim 1 is
An exhaust gas recirculation passage provided so as to connect the exhaust passage and the intake passage of the internal combustion engine, and an opening of the valve body with respect to a valve seat that is provided in the middle of the exhaust gas recirculation passage and is controlled by vertical movement of the valve body. In an exhaust gas recirculation device for an internal combustion engine, comprising an exhaust gas recirculation control valve, an exhaust gas recirculation passage upstream of the exhaust gas recirculation control valve extends in a substantially horizontal direction below a valve seat of the exhaust gas recirculation control valve. A first passage portion and a second passage portion extending from the first passage portion in a substantially vertical direction and having an upper end reaching the valve seat, and a projected area of the valve element at a lower end of the second passage portion. It is characterized in that a concave portion for capturing foreign matter having a larger area is provided.

Exhaust gas taken from the exhaust passage into the exhaust gas recirculation passage passes through the first passage portion and into the second passage portion in about 9 degrees.
It bends 0 degrees toward the valve seat and flows through the gap between the valve seat and the valve body. Here, when the flow of the exhaust gas bends from the first passage portion to the second passage portion, the relatively heavy foreign matter in the exhaust gas is separated, and further, the flow upward in the second passage portion causes the foreign matter to move to the valve body. And it collides with a valve seat and is separated. These separated foreign substances surely fall into a lower concave portion having an area larger than the projected area of the valve body and are not scattered to the outside.

A more specific aspect of the present invention is characterized in that the bottom of the recess is constituted by a removable plug.

In this structure, foreign matter in the recess can be discharged by removing the plug.

According to the third aspect of the invention, the recess is formed by closing the lower end of the work hole required for assembling the exhaust gas recirculation control valve with a plug.

In many cases, the exhaust gas recirculation control valve requires a working hole coaxial with the moving direction of the valve body for processing the valve seat and assembling the valve body. In the present invention, by closing the lower end of the work hole with a plug, a concave portion for capturing foreign matter is formed. Then, if the plug can be attached and detached with a screw or the like, foreign matter in the recess can be discharged.

As described in claim 4, it is desirable that a wool-like foreign matter collecting member is arranged in the recess. The foreign matter collecting member is made of, for example, steel wool or glass wool, and the foreign matter that has fallen into the recess is not collected and scattered.

Further, it is preferable that the foreign matter collecting member is fixedly supported by a perforated plate disposed above the foreign matter collecting member. This perforated plate is preferably
It is provided along the lower surface of the first passage portion and supports the foreign matter collecting member in the recess without disturbing the exhaust flow flowing through the first passage portion.

The exhaust gas recirculation system according to claim 6 further comprises, in addition to the normal exhaust gas recirculation control, foreign matter removal control means for performing a foreign matter removal operation for forcibly moving the valve body at least once to the fully open position. It is characterized by being.

By the foreign matter removing operation described above, the foreign matter caught between the valve body and the valve seat and the foreign matter such as carbon adhering to the valve body are positively removed. Then, as described above, this foreign substance falls downward and is captured in the recess.

As described in claim 7, it is desirable that the foreign matter removal control means repeatedly perform a full stroke movement from the fully closed position to the fully open position of the valve body a plurality of times as the foreign matter removal operation. For example, it moves from fully closed → fully opened → fully closed. It may be repeated many times.

In the invention of claim 8, the foreign matter removal control means executes the foreign matter removal operation after the internal combustion engine is stopped.

In the invention of claim 9, the foreign matter removal control means executes the foreign matter removal operation immediately before the start of the internal combustion engine.

[0021]

According to the exhaust gas recirculation system for an internal combustion engine of the present invention, the foreign matter in the exhaust flowing toward the exhaust gas recirculation control valve or the foreign matter dropped from the exhaust gas recirculation control valve is reliably collected in the recess, and the valve body It is possible to avoid the occurrence of biting between the valve seat and the valve seat.

In particular, by combining with a device for performing a positive foreign matter removing operation as claimed in claims 6 to 8, the foreign matter removed from the valve body or the valve seat is captured in the concave portion.
It does not scatter again to cause biting.

Further, by constructing the bottom of the recess with a detachable plug as in claim 2, it is possible to discharge the foreign matter accumulated inside and to collect the foreign matter collecting member in the recess. Also when mounting, it is easy to install or replace.

[0024]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings.

FIG. 1 shows the overall structure of an exhaust gas recirculation system according to the present invention. An internal combustion engine 1 is connected with an intake passage 2 and an exhaust passage 3 and the exhaust passage 3 is connected to the exhaust passage 3.
An exhaust gas recirculation passage 4 made of a metal pipe is provided so as to connect the intake passage 2 with the intake passage 2. A throttle valve 5 and an air flow meter 6 are arranged in the intake passage 2, but the exhaust gas recirculation passage 4 is provided with a throttle valve 5
Is connected to the downstream side.

An exhaust gas recirculation control valve 7 for controlling the amount of exhaust gas recirculation introduced from the exhaust gas passage 3 into the intake air passage 2 is interposed in the exhaust gas recirculation passage 4. The exhaust gas recirculation control valve 7 is
As will be described later, the stepping motor is used to change the opening degree, and the exhaust gas recirculation rate according to the engine operating condition is obtained by the engine control unit 8 that performs various controls of the entire internal combustion engine 1. like,
The opening is controlled. It should be noted that the engine control unit 8 receives detection signals from various sensors indicating engine operating conditions such as a throttle opening sensor 9, an air flow meter 6, a crank angle sensor 10, and a water temperature sensor 11 as well as operating signals. A start signal is input from the ignition key switch 12 in order to detect a start operation by a person.

FIG. 2 is a cross-sectional view showing the details of the exhaust gas recirculation control valve 7. The exhaust gas recirculation control valve 7 is a housing 21, which is an upper motor housing 22, an intermediate housing 23, and a lower lower part. The housing 24 and the housing 24 are provided, and are vertically integrated with each other so as to form a substantially cylindrical shape as a whole. The lower housing 24 has a central hole 25 penetrating up and down, the lower end of which serves as an exhaust inlet 26, and an annular valve seat 27 is attached thereto. An exhaust outlet 28, which is connected to the exhaust gas recirculation passage 4 on the downstream side, that is, near the intake passage 2, is opened on the side surface of the center hole 25.

The valve seat 27 has a tapered seating surface that spreads outward, that is, downward, and the seating surface is formed with a valve element 29 configured as a so-called outward-opening poppet valve.
Sits from the outside. The valve shaft 30 of the valve element 29 extends upward along the centers of the lower housing 24 and the intermediate housing 23, and the upper end portion thereof is a rotor of a stepping motor (not shown) housed in the motor housing 22. It is linked through a screw mechanism. That is, the valve shaft 30 linearly moves up and down by the rotational movement of the stepping motor, and the opening degree between the valve body 29 and the valve seat 27 changes. A first gas seal 31 and a second gas seal 32 for sealing the valve shaft 30 are arranged on the lower surface of the motor housing 22 and the upper surface of the lower housing 24, respectively, through which the valve shaft 30 penetrates. Coil springs 33 provided between the seals 31 and 32 press the housings 22 and 24, respectively.

An exhaust gas recirculation passage 4 upstream of the exhaust gas recirculation control valve 7 is connected to the exhaust gas inlet 26 of the lower housing 24. More specifically, the exhaust gas recirculation passage 4 includes a first passage portion 34 extending in a substantially horizontal direction at a position below the valve seat 27 of the exhaust gas recirculation control valve 7, and the first passage portion 3.
4 and a second passage portion 35 extending in a substantially vertical direction and having an upper end connected to the exhaust inlet 26, and a lower end of the second passage portion 35 is higher than an intersection portion with the first passage portion 34. It extends downward, and this extension is a recess 36 for capturing foreign matter. The second passage portion 35, and thus the concave portion 36, have a diameter substantially equal to that of the central hole 25 of the lower housing 24, and thus have an opening area larger than the projected area of the valve body 29. In this embodiment, the first
The passage portion 34 and the second passage portion 35 are made of metal pipes connected in a substantially T-shape, and a flange portion 38 for fixing to the lower housing 24 is provided at the upper end of the second passage portion 35. The lower end of the second passage portion 35 forming the recess 36 is closed by press-fitting a metal plug 37 having a substantially U-shaped cross section.

In the above-mentioned structure, among the foreign matters contained in the exhaust gas flowing through the first passage portion 34, the foreign matters such as cutting powder having a relatively large weight are crossed with the second passage portion 35. At that time, it tries to go straight, collides with the side wall surface of the second passage portion 35, and falls downward. Also, some foreign matter flows from the first passage portion 34 along the second passage portion 35,
It collides with the lower surfaces of the valve seat 27 and the valve element 29 and falls.
These foreign matters are collected in the recess 36. Further, as will be described later, the valve body 2 is operated as a foreign matter removing operation while the engine is stopped.
9 may move from the fully closed state to the fully open state and then to the fully closed state again. With this foreign matter removing operation, the valve body 29 and the valve shaft 3
The foreign matter adhering to 0 or the foreign matter caught in the valve seat 27 is scraped off. This foreign matter also has a recess 36.
Be sure to be captured within. When the foreign matter enters the recess 36, the main flow of exhaust gas passes above the recess 36 as shown by the arrow in FIG. 3, so that the foreign matter 39 collected in the recess 36 by this exhaust flow. Will never fly again.

Next, the embodiment shown in FIG. 4 shows an example in which a foreign matter collecting member 41 formed by appropriately rolling metal wool is arranged in the recess 36. The foreign matter collecting member 41 is inserted into the second passage portion 35 from below when the plug 37 is press-fitted. It should be noted that the foreign matter collecting member 41 has a concave portion 36.
Although it may be fixed to the inner wall surface of the device by some means, for example, if the foreign substance collecting member 41 is formed to be slightly larger than the diameter of the second passage portion 35 and is press-fitted, it is practically used. Sufficient fixed holding is possible.

According to the construction in which the foreign matter collecting member 41 is provided as described above, the foreign matter 39 that has fallen into the recess 36 is entangled with the foreign matter collecting member 41 made of metal wool as shown in the drawing, and is reliably collected. Scattering due to vibration can be prevented.

Next, in the embodiment shown in FIG. 5, the plug 37 for closing the lower surface of the recess 36 is of a screw type so that it can be easily attached and detached. That is, a female screw portion is formed on the inner periphery of the lower end of the second passage portion 35 forming the recess 36, and the plug 37 has a male screw portion 37a and a hexagonal portion 37b. It is detachably screwed to the section. Therefore, at the time of periodic inspection, etc., this plug 3
By removing 7, the foreign matter accumulated in the recess 36 can be easily discharged. The foreign matter collecting member 41 described above is used.
Of course, it is also possible to use together.

Next, FIG. 6 shows a further different embodiment of the present invention. In this embodiment, a part of the exhaust gas recirculation passage 4 on the upstream side of the exhaust gas recirculation control valve 7, that is, the first passage portion 34 and the second passage portion 35, is formed integrally with the lower housing 24 of the exhaust gas recirculation control valve 7. There is. That is, the lower housing 24 is extended downward so as to form the second passage portion 35, and is integrally formed in a shape in which the first passage portion 34 is branched laterally. The upstream exhaust gas recirculation passage 4 made of a metal pipe is connected to the flange portion 42 at the end of the first passage portion 34.

The lower end of the second passage portion 35 is also the first end.
The plug 37 extends downward from the intersection with the passage 34, and the plug 37 closes the opening of the lower surface of the passage 34 to form a recess 36 for capturing foreign matter. In this embodiment, the plug 37 is also of a screw type that is detachably screwed, and has a hexagonal hole 37c that engages with a wrench. In addition, a mesh-shaped perforated plate 45 is attached to the upper surface of the recess 36, that is, the opening that opens to the bottom surface of the first passage portion 34. Between the perforated plate 45 and the plug 37,
A foreign matter collecting member 41 made of metal wool is arranged. More specifically, a step portion 46 for positioning the perforated plate 45 is provided at the upper end opening position of the recessed portion 36, and the perforated plate 4 is inserted from below with the plug 37 removed.
5 and the foreign matter collecting member 41 are sequentially inserted, and finally the plug 37 is tightened to fix the porous plate 45 and the foreign matter collecting member 41 in the recess 36.
In the structure in which the lower housing 24 and the first and second passage portions 34 and 35 are integrated as described above, a working hole is required for processing the valve seat 27 and assembling the valve body 29. In the example, the lower end opening closed by the plug 37 is simultaneously used as a working hole.

In this embodiment, the foreign material collecting member 41 is securely held in the recess 36 by the perforated plate 45, and the interference between the main exhaust flow and the foreign material collecting member 41 can be avoided. Further, similarly to the above-described embodiment, the plug 37
The foreign matter accumulated inside can be easily discharged by removing.

Next, the foreign matter removal control executed by the engine control unit 8 for the exhaust gas recirculation control valve 7 will be described with reference to the flowchart of FIG. The foreign matter removal in this embodiment is mainly intended to remove foreign matter such as cutting powder adhered to the surfaces of the valve body 29 and the valve shaft 30 in a relatively dry state, and therefore, not immediately after the engine is stopped. , Just before the engine starts. That is, immediately after the stop, since viscous oil components such as unburned gas and lubricating oil components remain on the valve element 29 and the valve seat 27, foreign matter adheres in a wet state, and the foreign matter adheres from the valve element 29 or the valve seat 27. Hard to drop off. Therefore, the foreign matter is removed at the next start when the oil is evaporated to some extent. In the engine stopped state before starting, the exhaust gas recirculation control valve 7 is generally fully closed.

First, in step 1, after starting the control, it is confirmed that the ignition key switch is turned on, and the process proceeds to step 2. In step 2, the stepping motor is instructed to the step number at which the exhaust gas recirculation control valve 7 has the maximum opening degree, and the valve element 29 is set to the fully open position. After that, the routine proceeds to step 3, where the stepping motor is driven so that the valve body 29 is fully closed. This generally indicates a step number less than the step number corresponding to the fully closed position, and drives the stepping motor until mechanically fully closed. Then, in step 4, initialization of the stepping motor control, that is, learning of the fully closed position is performed. Thus, the foreign matter removal by the forced movement of the valve element 29 is completed, and the routine proceeds to step 5, where the cranking of the engine by the starter motor, that is, the actual start is started.

In this way, the valve element 29 is fully reciprocated by full stroke, fully open, and fully closed.
Even if a relatively large foreign matter is caught between the valve element 29 and the valve seat 27, it is easily removed and falls into the recess 36 below. Further, since it is executed before the actual start, it does not adversely affect the drivability of the engine. Moreover, when the operation is performed not at the time immediately after the stop but at the time of starting, the oil component having a viscosity that generally causes the foreign matter to adhere is evaporated to some extent, and the foreign matter is in a dry state. The foreign matter that has been caught in between is more reliably removed. In addition, fully closed → fully open →
The operation of fully closing may be repeated a plurality of times.

Next, FIG. 8 is a flow chart showing a different embodiment of the foreign matter removal control. In this embodiment, after confirming that the ignition key switch is turned on in step 1, the process proceeds to step 1A, where it is determined whether a predetermined time (for example, 8 hours) has elapsed since the engine was stopped. To do. Then, if the predetermined time or more has elapsed, the process proceeds to step 2. Each step except step 1A is basically the same as the above-described embodiment, and step 2
Then, the stepping motor is instructed to the step number at which the exhaust gas recirculation control valve 7 has the maximum opening degree, and the valve body 29 is set to the fully open position. After that, the routine proceeds to step 3, where the stepping motor is driven so that the valve body 29 is fully closed. This generally indicates a step number less than the step number corresponding to the fully closed position, and drives the stepping motor until mechanically fully closed. Then, in step 4, initialization of the stepping motor control, that is, learning of the fully closed position is performed. Thus, the foreign matter removal by the forced movement of the valve element 29 is completed, and the routine proceeds to step 5, where the cranking of the engine by the starter motor, that is, the actual start is started. On the other hand, if the predetermined time has not elapsed in step 1A, it is considered that the evaporation of the oil component that causes the foreign matter to adhere has not progressed sufficiently, and the valve element 29 is not forcibly reciprocated. As a result, cranking of the engine is started immediately.

FIG. 9 is a flowchart showing a further different embodiment of the foreign matter removal control. In this embodiment, instead of the above-mentioned step 1A, as step 1B, it is determined whether or not the cooling water temperature of the internal combustion engine 1 is below a predetermined temperature (for example, 40 ° C.). If the temperature is equal to or lower than the predetermined temperature, it means that a sufficient amount of time has passed since the last operation stop, and it is considered that the oil has evaporated and the foreign matter has dried. In step 2 and subsequent steps, the foreign matter removing operation is performed. On the other hand, if the cooling water temperature is higher than the predetermined temperature in step 1B, it is considered that the time has not elapsed since the engine was stopped and the evaporation of the oil component has not progressed sufficiently. It does not move back and forth. As a result, cranking of the engine is started immediately.

[Brief description of drawings]

FIG. 1 is a structural explanatory view showing an overall structure of an exhaust gas recirculation device according to the present invention.

FIG. 2 is a sectional view showing the exhaust gas recirculation control valve.

FIG. 3 is a sectional view similar to FIG. 2, showing a state in which the valve body is open.

FIG. 4 is a sectional view of an essential part of an exhaust gas recirculation control valve showing an embodiment provided with a foreign matter collecting member.

FIG. 5 is a cross-sectional view of a main part of an exhaust gas recirculation control valve showing an embodiment including a screw type plug.

FIG. 6 is a sectional view showing still another embodiment of the exhaust gas recirculation control valve.

FIG. 7 is a flowchart showing the flow of foreign matter removal control.

FIG. 8 is a flowchart showing another embodiment of foreign matter removal control.

FIG. 9 is a flowchart showing still another embodiment of foreign matter removal control.

[Explanation of symbols]

4 ... Exhaust gas recirculation passage 7 ... Exhaust gas recirculation control valve 27 ... Seat 29 ... Valve 34 ... 1st passage part 35 ... 2nd passage part 36 ... Recess 37 ... Plug 41 ... Foreign material collecting member 45 ... Perforated plate

Claims (9)

[Claims] 1. An exhaust gas recirculation passage which is provided so as to connect an exhaust passage and an intake passage of an internal combustion engine, and an opening of the valve body with respect to a valve seat, which is provided in the middle of the exhaust gas recirculation passage. In an exhaust gas recirculation system for an internal combustion engine, the exhaust gas recirculation control valve being controlled by a dynamic operation, wherein an exhaust gas recirculation passage upstream of the exhaust gas recirculation control valve is located below a valve seat of the exhaust gas recirculation control valve. It has a first passage portion that extends in a substantially horizontal direction and a second passage portion that extends in a substantially vertical direction from the first passage portion and has an upper end reaching the valve seat. An exhaust gas recirculation device for an internal combustion engine, comprising: a recess for trapping foreign matter having an area larger than the projected area of the valve element. 2. The exhaust gas recirculation system for an internal combustion engine according to claim 1, wherein the bottom of the recess is formed by a removable plug. 3. The exhaust gas recirculation system for an internal combustion engine according to claim 2, wherein the recess is formed by closing a lower end of a work hole required for assembling the exhaust gas recirculation control valve with a plug. 4. The exhaust gas recirculation device for an internal combustion engine according to claim 1, wherein a wool-like foreign matter collecting member is arranged in the recess. 5. The exhaust gas recirculation device for an internal combustion engine according to claim 4, wherein the foreign matter collecting member is fixedly supported by a perforated plate disposed above the foreign matter collecting member. 6. In addition to the normal exhaust gas recirculation control, foreign matter removal control means for executing a foreign matter removal operation for forcibly moving the valve body to the fully open position at least once is further provided. An exhaust gas recirculation device for an internal combustion engine according to any one of items 1 to 5. 7. The internal combustion engine according to claim 6, wherein the foreign matter removal control means repeatedly performs a full stroke movement from the fully closed position to the fully open position of the valve body a plurality of times as the foreign matter removal operation. Exhaust gas recirculation system for engines. 8. The exhaust gas recirculation system for an internal combustion engine according to claim 6 or 7, wherein the foreign matter removal control means executes the foreign matter removal operation after the internal combustion engine is stopped. 9. The exhaust gas recirculation system for an internal combustion engine according to claim 6, wherein the foreign matter removal control means executes the foreign matter removal operation immediately before starting the internal combustion engine.