JP2658217B2 - Exhaust gas recirculation device - Google Patents

Description

The present invention relates to an exhaust gas recirculation device for recirculating exhaust gas from an exhaust system of an engine to an intake system.

"Prior art" An exhaust gas recirculation device is generally provided with a housing provided with an exhaust gas recirculation passage communicating an intake system and an exhaust system of an engine, a diaphragm case attached to the housing, and provided in the diaphragm case. A diaphragm formed to define a pressure chamber in the diaphragm case;
A valve connected to the diaphragm and moved forward and backward, and connected to and separated from a valve seat provided in the housing to open and close the exhaust gas recirculation passage.

Since high-temperature recirculated exhaust gas flows in the housing, the diaphragm is heated by heat conducted from the housing through the diaphragm case and also by radiant heat from the engine. In particular, in recent years, due to an increase in the amount of recirculated exhaust gas due to the tightening of exhaust gas regulations, or an increase in the temperature of recirculated exhaust gas due to downsizing of the engine design, the temperature of the diaphragm becomes high and the durability decreases. Tend.

Therefore, conventionally, an exhaust gas recirculation device in which a cooling water passage is formed in the housing and cooling water is circulated through the cooling water passage to cool the housing, thereby preventing the temperature of the diaphragm from becoming high. Has been proposed.

"Problems to be Solved by the Invention" However, in the conventional device in which the cooling water passage is provided in the housing, as shown in the test results later, the result is that the recirculated exhaust gas is cooled and the diaphragm is cooled. When the recirculated exhaust gas is cooled, deposits tend to adhere to various parts.

Further, generally, since the housing is formed by casting, not only the size of the housing is increased and the weight is increased, but also the structure of the mold is complicated, resulting in an increase in cost.

"Means for Solving the Problems" In view of such drawbacks, the present invention provides an exhaust gas recirculation device including a housing provided with an exhaust gas recirculation passage communicating between an intake system and an exhaust system of an engine; A diaphragm case which is attached to the housing via an insulator and at least a part of which is formed of a cast product, a diaphragm which is provided in the diaphragm case and defines a pressure chamber in the diaphragm case, and which is connected to the diaphragm; A valve that is moved forward and backward to open and close the exhaust gas recirculation passage by being brought into contact with and separated from a valve seat provided in the housing, and a pipe buried in a diaphragm case that is the cast product. The inside is a cooling water passage.

[Operation] According to the above configuration, the diaphragm case itself accommodating the diaphragm can be cooled more directly, so that the diaphragm is cooled without substantially cooling the recirculated exhaust gas as shown in the test results later. Can be
Thereby, the diaphragm can be efficiently cooled while preventing the generation of the deposit.

In addition, since at least a part of the diaphragm case is made of a cast product and the pipe in which the cooling water passage is formed is embedded, the cooling water passage is formed directly in the cast product. As a result, it is possible to reliably prevent water leakage.

"Example" Hereinafter, the present invention will be described with reference to the illustrated example.
In FIG. 2 and FIG. 2, a passage 2 which is curved upward from a horizontal direction and opens upward is formed in a housing 1, and a passage 3 is continuously provided from an upper portion of the passage 2 to the right.
The two passages 2 and 3 form a substantially U-shaped exhaust gas recirculation passage 4. The opening in the horizontal part of the passage 2 is an exhaust gas inlet 4a, and the opening of the passage 3 is an exhaust gas outlet 4b. The exhaust gas inlet 4a is connected to the exhaust system of the engine, Each is connected to the intake system of the engine.

A diaphragm case 12 composed of a lower case 10 fixed to the housing 1 with screws 9 via an insulator 8 and an upper case 11 connected to the housing 1 is provided at an opening opening above the passage 2. . In the illustrated embodiment, the lower case 10 is manufactured by casting, and the upper case 11 is manufactured by pressing.

A diaphragm 13 is accommodated in the diaphragm case 12, and an outer peripheral portion of the diaphragm 13 is sandwiched between the lower case 10 and the upper case 11, so that the negative pressure chamber 14 is vertically larger in the diaphragm case 12. An air pressure chamber 15 is defined. The negative pressure chamber 14 is connected to an intake system of an engine (not shown) via a conduit 16,
The atmospheric pressure chamber 15 is communicated with the atmosphere through an opening (not shown) formed in the lower case 10.

Plates are placed above and below the center of the diaphragm 13
The plates 20 and 21 are overlapped, and the plates 20 and 21 and the diaphragm 13 are integrally connected by a liner 22 and a nut 23. One end of an operating rod 24 is connected to the shaft portion of the retainer 22 by penetrating the other end thereof. The other end of the operating rod 24 is slidably penetrated by a bush 25 closing an upper opening of the passage 2 so that the exhaust gas can be recirculated. A valve 26 is formed to protrude into the circulation passage 4 and is integrally formed with the protruding end.

The valve 26 is urged downward by a compression spring 27 elastically mounted between the upper case 11 and the diaphragm 13, and is normally seated on a valve seat 28 provided in the housing 1, and is connected to the exhaust gas recirculation passage 4. Is closed.

In the illustrated embodiment, however, a pipe 32 having a U-shape in a horizontal plane and having both ends bent downward in advance is embedded in the lower case 10 manufactured by the casting, and the inside of the pipe 32 is cooled. The water passage 33 is provided. One end 32a of the pipe 32 is communicated with, for example, an outlet-side cooling water passage of an engine block, and the other end 32b is communicated with a suction part of a water pump.
The cooling water is circulated through

Therefore, according to the above configuration, the cooling water passage 33
Effectively cuts off the heat conducted from the housing 1 to the diaphragm 13 through the lower case 10, and cools the lower case 10 itself, so that the radiant heat to the diaphragm 13 caused by the heating thereof, and Since the conduction heat conducted from the bush 25 to the diaphragm 13 via the operating rod 24 is effectively suppressed, the diaphragm 13
Can be prevented from becoming high in temperature.

Next, effects of the present invention will be described based on test results shown in the following table.

As shown in the above test results, without cooling, the diaphragm temperature is as high as 260 ° C., and also in the prior art in which the housing is cooled,
Even if a large amount of cooling water of 7000 ml per minute is circulated, the diaphragm temperature can only be reduced to 200 ° C., whereas in the device of the present invention, it is possible to drastically reduce to 140 ° C. with 500 ml of cooling water per minute. .

In particular, comparing the outlet temperature of the recirculated exhaust gas, when the housing is cooled, the cooling directly lowers the temperature of the recirculated exhaust gas, thereby indirectly suppressing the temperature rise of the diaphragm. In particular, when the temperature of the recirculated exhaust gas decreases, deposits tend to adhere to the downstream side. On the other hand, it is understood that the apparatus of the present invention hardly cools the recirculated exhaust gas and efficiently and directly cools the diaphragm itself.

Further, in the above embodiment, in order to form the cooling water passage 33, it is only necessary to simultaneously embed the pipe 32 curved into a required shape at the time of casting the lower case 10, and the pipe 32 is originally formed of water. Since leakage does not occur, leakage of cooling water can be reliably prevented as compared with the case where the cooling water passage 33 is formed directly in the lower case 10 of a cast product.

Although the cooling water passage 33 is desirably provided in the lower case 10 as in the above-described embodiment, if the upper case 11 is a cast product, the upper case
11 may be provided.

[Effects of the Invention] As described above, according to the present invention, it is possible to cool the diaphragm more efficiently than in the past, prevent cooling of the recirculated exhaust gas, and deposit It is possible to obtain the effect that the adhesion can be prevented and the leakage of the cooling water can be surely prevented.

[Brief description of the drawings]

FIG. 1 is a plan view showing an embodiment of the present invention, and FIG. 2 is a sectional view. 1 ... housing, 4 ... exhaust gas recirculation passage 10 ... lower case, 11 ... upper case 13 ... diaphragm, 12 ... diaphragm case 14 ... negative pressure chamber, 15 ... atmospheric pressure chamber 24 ... Actuating rod, 26… Valve 28… Valve seat, 32… Pipe 33 …… Cooling water passage

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Kuniharu Suzuki 3-65, Midorigaoka, Toyota-shi, Aichi Prefecture Inside Daitoyo Kogyo Co., Ltd. (72) Inventor Yoshiaki Kitagawa 3-65, Midorigaoka, Toyota-shi Toyota City, Aichi Pref. 56) References Japanese Utility Model Showa Sho 62-108560 (JP, U)

Claims (1)

(57) [Claims] 1. A housing provided with an exhaust gas recirculation passage communicating an intake system and an exhaust system of an engine, and a diaphragm case attached to the housing via an insulator and at least a part of which is formed of a cast product. A diaphragm provided in the diaphragm case to form a pressure chamber in the diaphragm case; and a reciprocating exhaust gas which is connected to the diaphragm and operated forward and backward to be brought into contact with and separated from a valve seat provided in the housing. An exhaust gas recirculation apparatus comprising: a valve for opening and closing a passage; and a pipe buried in a diaphragm case as the casting, and further comprising a cooling water passage in the pipe.