Device and method for exhaust gas recirculation

Abstract

A device is provided for exhaust gas recirculation (EGR), in particular in diesel engines, from the exhaust gas tract into the fresh air path of the engine, wherein a cooling device connected to the cooling system of the engine is provided within an EGR section as an exhaust-gas (EG)/coolant heat exchanger, with which an EGR valve for proportioning the EG recirculation rate is associated. The EGR valve is connected to a coolant, and the cooling device comprises an EG pre-cooler and an EG main cooler connected downstream of the EG pre-cooler. The EGR valve is installed between the EG pre-cooler and the EG main cooler in a valve housing between the EG pre-cooler and the EG main cooler. A method for EGR is provided as well.

Claims

1. A device for exhaust-gas recirculation (EGR) from the exhaust-gas train into the fresh-air path of the engine, wherein a cooling device connected to the cooling system of the engine is provided within an EGR section as an exhaust-gas (EG)/coolant heat exchanger, with which an EGR valve (6) for proportioning the EG recirculation rate is associated, wherein: the cooling device comprises an EG pre-cooler (3) and an EG main cooler (5) that follows it spatially, wherein the EGR valve (6) is installed in a valve housing (4) disposed between the EG pre-cooler and the EG main cooler, wherein the valve housing (4) is connected with a separate cooling path (8c) for external cooling of the EGR valve (6) and wherein a further cooling path (8d) is provided for cooling electrical components in the interior of the EGR valve.

2. The device of claim 1, wherein the EG pre-cooler (3) and the valve housing (4) are configured as a one-part component.

3. The device of claim 1, wherein the EG pre-cooler (3) and/or the EG main cooler (5) each have a multi-part housing (3a, 3b; 5a, 5b).

4. The device of claim 3, wherein a housing part (3b; 5a) of the pre-cooler (3) and/or of the main cooler (5) that follows the valve housing (4), in each instance, is configured in one piece with the valve housing (4).

5. The device of claim 4, wherein a heat exchanger insert part in the manner of an EG pipe bundle (14, 15) is installed in the housings (3a, 3b; 5a, 5b), in each instance.

6. The device of claim 1, wherein a coolant connector (18) forms the coolant inflow to the valve housing (4), that the EG pre-cooler (3) is connected with the valve housing (4) and provided with a coolant drain (11) to the EG main cooler (5).

7. The device of claim 6, wherein the valve housing (4) is provided with further coolant drains (19) to the engine cooling system and/or other heat exchangers on the engine side.

8. The device of claim 7, wherein the EG pre-cooler (3) has separate cooling channels for EG cooling, for conducting the coolant, which channels extend in the longitudinal direction of the EG pre-cooler (3).

9. The device according of claim 1, wherein a coolant connector (10) forms the coolant inflow to the EG pre-cooler (3), the coolant drain (11) of which connector is directly connected with the EG main cooler (5), the coolant drain (13) of which, in turn, is connected with the engine cooling system.

10. A method for exhaust-gas recirculation (EGR), wherein: the exhaust gas (EG) branched off from the exhaust-gas train of the engine, within an EGR section, is sent, in series, first through an EG pre-cooler (3), then, for proportioning of the EG recirculation rate and its distribution, through an EGR valve (6), and finally through an EG main cooler (5), wherein the EG main cooler follows the EG pre-cooler spatially, the cooling water branched off from the cooling system of the engine, as a coolant, is first conducted in series through the EG pre-cooler (3), afterward through the EG main cooler (5), and at least one partial amount of the branched-off cooling water is conducted for external cooling of the EGR valve (6) through a valve housing (4) that accommodates the EGR valve (6) and that is disposed between the EG pre-cooler and the EG main cooler and additionally through the interior of the EGR valve (6).

11. The method of claim 10, wherein the branched-off partial amount of the cooling water is branched off to heat exchangers on the engine side, which are present outside of the EGR section.

12. The method of claim 10, wherein the exhaust gas is branched off from the exhaust-gas manifold (1) of the engine and cooled by about 250 to 300 C. in the EG pre-cooler (3).

13. The method of claim 12, wherein the exhaust gas is cooled to an exit temperature <100 C. in the EGR section.

14. The method of claim 10, wherein cooling water branched off from the cooling system of the engine is withdrawn on the pressure side, behind the cooling-water pump of the engine.

Description

BRIEF DESCRIPTION OF THE DRAWING

(1) In the following, exemplary embodiments of the invention will be explained using the drawing. This shows:

(2) FIG. 1 shows, in a schematic representation, an EGR section with an EG pre-cooler and an EG main cooler, each configured in one piece.

(3) FIG. 2 shows a spatial representation of an embodiment according to FIG. 1, in a perspective, outside view,

(4) FIG. 3 shows the embodiment of FIG. 2, partly in section,

(5) FIG. 4 shows a schematic representation of an EGR section, with an EG pre-cooler and an EG main cooler, each configured in divided form,

(6) FIG. 5 shows a spatial representation of an embodiment according to FIG. 4, in a perspective outside view, and

(7) FIG. 6 shows, in a schematic representation, an embodiment variant of FIG. 4.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

(8) FIG. 1, in a schematic representation, shows an EGR section following an exhaust-gas manifold, from which the engine exhaust gas 7 is conducted to the outside by way of the exhaust-gas system (not shown). The exhaust-gas manifold 1 possesses a branch 2, by way of which a partial exhaust gas stream 7a is conducted to an EG pre-cooler 3, afterward deflected by 90 in an EGR valve housing 4, and conducted to the intake manifold (not shown) of the engine by way of a downstream EG main cooler 5, as a cooled-down partial exhaust gas stream 7b.

(9) The EG pre-cooler 3 is configured as a single-part cast part, together with the EGR valve housing 4, and connected with the EG main cooler 5, which is also configured as a cast part, by way of a flange connected 4b, forming a seal. The EG main cooler 5 is also configured in one piece; it ends with a flange 5b for connecting with the intake manifold of the engine, not shown.

(10) Different cooling paths, which are all supplied by the cooling system of the engine, are shown with dark arrows, wherein the starting temperature of the engine oil cooler (not shown) approximately corresponds to the input temperature of the different cooling paths.

(11) According to FIG. 1, a first cooling path 8 gets into the interior of the valve housing 4 by way of a coolant connector 18. There, division of the cooling path 8 comes about, into a first cooling path 8a, which runs through the pre-cooler 3 and by way of the coolant exit 11, the output of which is passed on to the EG main cooler 5. The cooling water that has been heated in the pre-cooler 3 gets back, by way of the coolant exit 13 of the latter, into the cooling system of the engine through the coolant entry 12 of the EG main cooler 5, according to the arrow 8b.

(12) The branched-off exhaust gas stream 7a, the input temperature of which, into the pre-cooler 3, amounts to approximately 550 to 600 C., is cooled down by approximately 250 to 300 C. in the EG pre-cooler 3, and then exits from the EG main cooler 5 as an exhaust gas stream 7b having a temperature100 C., before it is conducted to the intake manifold of the engine.

(13) In the interior of the EGR valve housing 4, a partial stream 8c, which serves for cooling the valve housing 4, is branched off from the cooling path 8. In the interior of the housing, there is a cooling mantle 22 (cf. FIG. 3) for cooling a seat bracket 23 for accommodating a valve body of the EGR valve 6. The partial cooling water stream 8c is conducted back into the cooling system of the engine by means of a coolant exit 19.

(14) Furthermore, a further partial stream 8d is branched off in the interior of the valve housing 4, which stream flows through the interior of the EGR valve 6 for the purpose of cooling the electrical installed parts present there, and is connected with the cooling system of the engine by way of a coolant exit 20.

(15) FIG. 2, in a simplified spatial representation, shows an embodiment according to the principle of FIG. 1. There, the same components are identified with the reference symbols according to FIG. 1. In addition, a hose connection 21 is shown between the EG pre-cooler 3 and the EG main cooler 5. The two EG coolers 3, 5 follow one another at an angle of 90 degrees, as is evident in FIG. 1, wherein the angled piece is formed by the valve housing 4. The EG pre-cooler 3 is connected in one piece with the valve housing 4 that forms the angled piece, and it is advantageous if it is configured as a one-part cast piece.

(16) FIG. 3 shows further details relating to FIG. 2, namely the cooling mantle 22 of the valve housing 4, which has already been mentioned and serves to cool the seat bracket 23, in which the valve body 24 of the EGR valve 6 is accommodated.

(17) The coolant is connected with the interior of the EGR valve 6 for the purpose of cooling the electrical installations accommodated there, by way of bores 26 in the valve body 24. These installations serve for activation of a valve tappet 25, which is shown in its closed position relative to a valve seat 27 in FIG. 3, and regulates the gas stream 7a as a function of the passage opening.

(18) FIG. 4, in a schematic top view, shows an embodiment with a divided structure of the EG pre-cooler 3, of the EG main cooler 5, as well as a separate structure of the valve housing 4. Aside from the divided structure of the EG pre-cooler 3, in two housing halves 3a and 3b, as well as of the EG main cooler 5, in two housing halves 5a and 5b, FIG. 4 differs from FIG. 1 by a direct connection of a coolant path 9 branched off from the engine cooling system, to a coolant connector 10 of the housing part 3a of the EG pre-cooler 3. The coolant path 9 flows through the EG pre-cooler 3 and in this regard cools a heat-exchanger insert 14, which consists, for example, of a pre-fabricated pipe system for passing the partial exhaust gas stream 7a through. The EG main cooler is equipped with a similar pipe system 15, through which the partial exhaust gas stream 7a flows and exits from the EG main cooler 5 as a partial exhaust gas stream 7b, to be passed on into the fresh-air manifold of the engine. Furthermore, components shown in FIG. 4, which are the same as in FIG. 1, are provided with the same reference symbols. This also holds true for the spatial representation according to FIG. 5, which corresponds to the embodiment according to FIG. 4.

(19) FIG. 5, in a simplified form, shows a spatial representation of the embodiment according to FIG. 4. There, the same components are identified with the reference numerals according to FIG. 4. In addition, sprue eyes 30 are shown, which are provided either as a connector for a hose connection or are provided with a closure lid. Cast-on attachment eyes 28, 29 are provided as attachment points for further components.

(20) FIG. 6 shows a variant of FIG. 4, wherein the housing parts 3b and 5a are cast in one piece with the EGR valve housing 4 for cost reasons, thereby eliminating two individual cast parts and two flange seals.