JP2001132557A - Egr device provided with reed valve - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an EGR device provided with a reed valve having a good durability, capable of preventing fatigue failure of a reed according to a judging reference of collision speed as well as newly setting the collision speed when the reed is seated, on a judging reference in relation to the fatigue of the reed of the reed valve provided in the EGR device. SOLUTION: In the EGR device wherein an EGR passage 4 in which an EGR valve 5 for controlling an EGR gas quantity Ge is dispose is connected to an intake passage 3 from an exhaust passage 2 of an engine 1, and the reed valve 10 for allowing flow of the direction from the exhaust passage 2 to the intake passage 3 and for blocking flow of the reverse direction is disposed in the EGR passage 4; the reed valve 10 is formed in such a constitution that reed seating speed V when the reed 14 collides with the valve seat 16 at the time of closing the reed valve 10 is set in the range S of 3.0 m/s and less.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an EGR device having a reed valve for a turbocharged diesel engine or the like.

[0002]

2. Description of the Related Art In measures against exhaust gas from engines such as diesel engines, the combustion temperature is reduced by recirculating a part of the exhaust gas, which is an inert gas, to the intake air in order to reduce the amount of NOx emitted from the exhaust gas. It is known that EGR (exhaust gas recirculation), which suppresses NOx generation by keeping it low, is effective.
It is widely used.

[0003] In a diesel engine, EGR must be performed even in a high-load region where a large amount of NOx is emitted in order to increase the effect of reducing NOx. However, in a high-supercharged engine using a high-efficiency turbocharger, as shown in FIG. 7, in a region A where the engine speed is low and medium and the load is medium and high, the boost pressure is low. Since (intake pressure) Pbm becomes higher than exhaust pressure Pem,
It becomes difficult to recirculate part of the exhaust gas to the intake side as EGR gas.

However, in the region A where the EGR is difficult, even if the average pressure is the boost pressure Pbm> the exhaust pressure Pem, as shown in FIG. 8, the boost pressure Pb <the exhaust pressure Pe is instantaneously caused by the exhaust pulsation. There is a portion X indicated by oblique lines. In other words, if the pulsation phenomenon of the exhaust pressure is used, the EGR can be performed for each short time, so that the EG
A reed valve is provided in the R passage so that EGR is performed in the X portion of the area A.

The reed valve prevents backflow from the supply side to the exhaust side when the boost pressure Pb> exhaust pressure Pex, thereby preventing deterioration of engine combustion and preventing deterioration of engine performance. , On the other hand, the boost pressure P
b <Open the reed valve only when the exhaust pressure Pex
By performing R, NOx is reduced.

Then, in this case, as shown in FIG.
In the case of an inline 6 cylinder, the exhaust manifold 2 is
The rear three cylinders are divided into two, and an EGR passage 4, an EGR valve 5, and a reed valve 10 are provided in two systems, and only the cylinders whose exhaust pulsations are close in phase so that exhaust pulsations between the cylinders do not cancel each other. Collectively, the cylinders whose exhaust pulsation phases are close to each other are separated so that the pulsation effect can be maximized.

With this system, an EGR rate of 10% or more can be obtained in a region A where EGR has not been performed at all, and NOx can be greatly reduced.

As shown in FIG. 2, the reed valve 10 is provided in the EGR passage 4 by providing a case 11 in the EGR passage 4 and a reed 14 and a stopper 12 outside the case 11. It is attached with a bolt 13 passed through a bolt hole 14a so as to be on the outside.

[0009]

However, the lead 14 of the reed valve 10 collides with the valve seat 16 when the reed valve 10 is closed, and this collision repeats as the reed valve 10 opens and closes. There is a problem that occurs.

[0010] This fatigue fracture is caused by the stress repeatedly generated when the lead 14 is seated, and as shown in FIG.
The tip of 14 is cracked, and this part is eventually chipped off. As a result, the crack or missing portion of the lead 14
The R gas leaks and the function of the check valve cannot be fulfilled.

Therefore, when the intake pressure is higher than the exhaust pressure, E
The fresh air flows back into the GR passage 4 so that the combustion deteriorates. Also, the reed 14 is damaged, and the fragments pass through the EGR passage 4 to clog the EGR cooler 6. If it is sucked into the engine, the engine may be damaged and may cause an internal failure.

Therefore, when designing the reed valve 10, it is very important to prevent the fatigue fracture of the reed 14.

However, the reed 14 is a reed valve
10 and further incorporated as part of the engine.Moreover, it is exposed to relatively high temperature EGR gas. While colliding.
Therefore, in order to measure this, even if a strain gauge is attached to the back surface of the tip portion of the lead 14, it is peeled off, and it is very difficult to measure the stress generated by the collision of the broken portion of the lead 14. .

Therefore, it is difficult to measure or estimate the magnitude of the repetitive stress, and a clear stress value cannot be obtained. Therefore, it is important to prevent the fatigue fracture of the lead 14, There is a problem that occurrence of fatigue fracture cannot be predicted using an SN curve (stress-repetition number curve) for a repeated load.

On the other hand, the present inventors have determined that the repetitive stress σ
As a result of trial and error searching for an alternative to
A strain gauge 21 is attached to a portion of the lead 14 shown in FIG. 5 which avoids the tip of the lead 14, and a collision speed V when the lead 14 collides with the valve seat 16 is estimated by calculation from a time change of the strain at this portion. When the correlation between the collision velocity V and the fatigue fracture of the lead 14 was examined, data close to an SN curve as shown in FIG. 6 could be obtained.

The collision velocity V and the repetitive stress σ
Considering the relationship, the collision speed V is equal to the collision force F
And the impulse F × t, which is the product of the collision time t and
Since the collision force F is directly proportional to the repetition stress σ, it was presumed that the collision speed V had a relationship close to a proportional relationship with the repetition stress σ.

Based on this finding, the present inventors use the collision velocity V, which can be measured and estimated relatively easily, as a reference for fatigue strength instead of the repetitive stress σ, which is extremely difficult to measure. After adjusting the lead lift, the spring constant of the lead, the static clearance of the lead, etc. based on the standard,
It has been found that a reed and a reed valve having excellent durability can be manufactured relatively easily.

The present invention has been made in order to solve the above-mentioned problems based on this finding. It is an object of the present invention to provide a criterion for determining the fatigue failure of a reed valve reed provided in an EGR device. It is an object of the present invention to provide an EGR device provided with a reed valve having excellent durability which can newly provide a collision speed at the time of seating of a lead and can prevent a fatigue fracture of a lead in accordance with a criterion of the collision speed.

[0019]

An EGR device with a reed valve for achieving the above object is provided with an EGR passage provided with an EGR valve for controlling an EGR gas amount from an exhaust passage of an engine to an intake passage. A reed valve connected to the EGR passage and provided with a reed valve for allowing a flow in the direction from the exhaust passage to the intake passage and for preventing a flow in the reverse direction, wherein the reed valve is closed by closing the reed valve. It is characterized in that the reed seating speed at which the reed collides with the valve seat at the time of the valve is set to a range of 3.0 m / s or less.

That is, in evaluating the durability of the reed, there is a correlation between the durability of the reed and the seating speed of the reed. Therefore, the stress of the portion of the reed valve that collides with the valve seat at the tip of the reed is measured. Instead of calculating and evaluating based on the stress, the evaluation is performed based on the lead seating speed, and the lead seating speed is adjusted by adjusting the lead lift, the spring constant of the lead, the static clearance of the lead, etc. 3.0m / s
It is characterized by being kept within the allowable limits in the following ranges.

As shown in FIGS. 3 to 5, the lead seating speed is determined by attaching a strain gauge 21 to a portion of the reed valve 10 which does not collide with the valve seat 16 at a portion other than the tip of the lead 14,
From the temporal change of the strain measured by the strain gauge 21 and the shape including the length and warpage of the lead 14, the collision speed V when the tip of the lead 14 collides with the valve seat 16, that is, the lead seating speed V, The calculated lead seating speed V is used as a criterion for designing the fatigue strength of the lead 14.

Since the lead 14 is configured as a cantilever, the change in the strain εy in the Y direction measured by the strain gauge 21 when the lead 14 is seated, that is, the time t of εy With respect to the differential value d (εy) / dt. Therefore, assuming that C is a proportional constant to a specific shape and a lead of a spring constant, V = C × d (εy) /
The lead seating speed V can be calculated as dt. The proportionality constant C can be obtained by a simple bending experiment or calculation of the reed 14 before the reed valve 10 is incorporated into the EGR passage.

The lead seating speed V is the same as the lead 14
Is the speed of collision with the valve seat 16, and theoretically, the impulse (F ×
t) is in a relationship proportional to the collision speed V, and it is presumed that the relationship is close to a proportional relationship with the repetition stress. Therefore, it seems that theoretical support is also possible, but in reality, the lead 14 is in a cantilever state and the collision time t needs to be considered. Without deriving an equation, the lead sitting speed V is selected as an index of fatigue failure from experimental experience.

The lead seating speed V is 3.0 m
The shape and spring constant of the lead are selected so as to fall within the fatigue fracture avoidance range S of / s or less. The fatigue fracture avoidance range S of the safe lead seating speed V of 3.0 m / s or less is:
These are numerical values supported by experiments performed by the inventors of the present invention, and a part of the experimental results is shown in FIG. According to FIG. 6, no fatigue failure occurs at 3.0 m / s or less and 3.0 m / s or less.
Above s, the result that fatigue fracture occurs is obtained, which supports the upper limit of 3.0 m / s.

The lower limit has no effect on the fatigue fracture and can be set freely. However, when the lead seating speed V is 0 m / s, the reed valve does not open and close, and the lead seating speed V becomes lower. If the response speed of the reed valve is extremely small, that is, if the response speed of the reed valve is too slow, a backflow occurs and the reed valve becomes unsuitable. Therefore, in reality, the lower limit is 0.1
m / s is preferred.

As described above, by configuring the reed valve with the lead seating speed V of the lead within the fatigue failure avoiding range S of 3.0 m / s or less, the fatigue failure of the lead can be prevented. Since the reed seating speed, which is relatively easy to calculate, is used as a criterion, the reed valve can be designed and manufactured relatively easily.

[0027]

Embodiments of the present invention will be described below with reference to the drawings.

As shown in FIG. 2, a reed valve 10 used in an EGR device provided with a reed valve according to an embodiment of the present invention includes a case 11 having a flat seating surface 16 in which a reed 14 and a stopper 12 are bolted. 13 fixedly formed. This lead
14 is formed with its proximal end fastened and its distal end free.

In the present invention, the reed valve
The lead seating speed V, which is the collision speed at the time when the tip of the lead 14 collides with the valve seat 16, is determined by experiment or calculation. As shown in FIG. 6, the lead seating speed V is 3.0 m / s. Select the shape of the lead 14, such as the length, width, thickness, and warpage, and the spring constant, etc., so as to fall within the fatigue fracture avoidance range S described below. Also, select the shape and location of the valve seat 16 and the stopper 12. The reed 14 and the reed valve 10 are formed by setting the above.

The reed seating speed V of the reed valve 10 is, as shown in FIGS. 3 to 5, determined by attaching a strain gauge 21 to a portion of the reed valve 10 other than the tip of the reed 14.
It can be calculated from the temporal change in the distortion of the portion that does not collide with the shape and the shape including the length and warpage of the lead 14.

The reed valve 10 is, for example, as shown in FIG.
Is provided in the EGR passage 4 of the EGR device as shown in FIG.
When the GR valve 5 is opened to perform EGR, the reed valve 10 is operated according to the differential pressure between the exhaust pressure Pex and the boost pressure Pb.
Is opened and closed, and when the exhaust pressure Pex> the boost pressure Pb, the valve is opened to perform EGR, and conversely, the exhaust pressure Pex <the boost pressure P
In the case of b, the valve is closed to prevent the backflow of fresh air Ai.

According to the EGR device provided with the reed valve having the above-described structure, the reed seating speed V of the reed valve 10 is set to 3.0 m /
Since the lead 14 is formed within the safe fatigue fracture avoiding range S of not more than s, the lead 14 does not suffer from fatigue failure, and can prevent fatigue failure due to repeated collision of the lead 14 with the valve seat 16. Therefore, the lead 14 is damaged and the fragments are
An accident such as flowing into the passage 4 or the combustion chamber of the engine 1 can be prevented.

In addition, since the lead seating speed V is used as the evaluation standard of the fatigue strength instead of the repetitive stress which is difficult to measure, the fatigue strength can be evaluated by relatively simple measurement and calculation.

In a more specific numerical example, the lift of a lead having a width of 20 mm and a length of 43 mm is 6.9 m.
m to 3mm, lead thickness from 0.25mm to 0.3
05mm and lead material from SUS631 to GI
By changing to N6 (equivalent to SUS420J2), it was confirmed that the actual seating speed of the lead was within the safe fatigue fracture avoidance range S of 3.0 m / s or less.

[0035]

As described above, according to the EGR device having the reed valve of the present invention, the reed seating speed, which is the speed at which the reed collides with the valve seat, is 3.0 m / s or less. Since it is formed to be within the range, it is possible to prevent fatigue destruction due to repeated collision of the reed with the valve seat, and to prevent accidents such as breakage of the reed and debris flowing into the EGR passage and the inside of the engine. it can.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a supercharged engine showing an EGR device provided with a reed valve.

FIGS. 2A and 2B are diagrams showing a mounting state of a reed valve, FIG. 2A is a cross-sectional view of a mounting portion of the reed valve, FIG. 2B is a plan view showing a reed valve lead, and FIG. (D) is a perspective view of the case, and (e) is a perspective view after assembling the reed valve.

FIG. 3 is a front view of the reed valve showing an arrangement of a strain gauge for increasing a reed seating speed of the reed valve according to the present invention.

FIG. 4 is a sectional view taken along line WW of FIG. 3;

FIG. 5 is a perspective view of a lead showing an arrangement of a strain gauge for increasing a lead seating speed of the reed valve according to the present invention.

FIG. 6 is a diagram of an experimental result showing a relationship between a lead seating speed, the number of collisions, and a fatigue fracture strength.

FIG. 7 is a diagram illustrating the relationship between boost pressure and exhaust pressure with respect to engine torque and engine speed for explaining the operation of a reed valve.

FIG. 8 is a diagram illustrating a pulsating state of a boost pressure and an exhaust pressure with respect to a crank angle for explaining an operation of a reed valve.

FIG. 9 is a diagram showing the progress of the breakage of the reed of the reed valve.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Engine 2 Exhaust passage (exhaust manifold) 3 Intake passage 3a Intake manifold 4 EGR passage 5 EGR valve 10 Reed valve 14 Reed 16 Valve seat

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Masahide Kimura 1212 Abe, Ochiai-cho, Takahashi-shi, Okayama F-term in the Okayama Plant of Eagle Industry Co., Ltd. 3G062 AA01 AA05 CA08 EA09 ED10 GA14 GA22 3H058 AA15 BB27 CA20 EE05 EE15

Claims (1)

[Claims] 1. An engine according to claim 1, further comprising:
An EGR passage provided with an EGR valve for controlling the amount of GR gas is connected to the EGR passage, and a reed valve for allowing a flow in the direction from the exhaust passage to the intake passage and preventing a flow in the reverse direction is provided in the EGR passage. In the EGR device, the reed valve is
An EGR device equipped with a reed valve, wherein the reed seating speed at which the reed collides with the valve seat when the reed valve is closed is formed within a range of 3.0 m / s or less.