WO2001051799A1

WO2001051799A1 - A device for recirculation of exhaust gases

Info

Publication number: WO2001051799A1
Application number: PCT/SE2001/000011
Authority: WO
Inventors: Ingemar Eriksson
Original assignee: Stt Emtec Ab
Priority date: 2000-01-07
Filing date: 2001-01-05
Publication date: 2001-07-19
Also published as: SE0000034D0; SE522759C2; TW482863B; SE0000034L; AU2720601A

Abstract

A device for recirculation of a portion of the exhaust gases from a combustion engine to an intake of the engine via an exhaust gas recirculation line (3a). In the device an intake channel (5a) to the engine has a venturi effect producing arrangement (6), which covers a first part (11) of the intake cross section area of the engine. The exhaust gas recirculation line (3a) is connected to the intake channel (5a). Furthermore, the device comprises a valve arrangement (13) arranged to regulate the flow through a second part (12) of the intake cross section area of the engine, which second part (12) is not covered by the venturi effect producing arrangement (6). This device intends to improve suction effect on the exhaust gas recirculation line (3a) and, via advantageous control of the valve arrangement (13), also ensure that an amount of exhaust gases sufficient for desired exhaust gas purification is recirculated at low load on the engine.

Description

A device for recirculation of exhaust gases

FIELD OF THE INVENTION

The present invention is related to a device for recirculation of a portion of the exhaust gases from a combustion engine to an intake of the engine via an exhaust gas recirculation line.

PRIOR ART

To reduce peak temperatures during combustion and by that re- strict formation of nitrogen oxide (NO_x) it is known since many years to recirculate a portion of the exhaust gases from a combustion engine to the intake system of said engine. This is usually called EGR (Exhaust Gas Recirculation).

The admixture of exhaust gases to the total intake flow to the combustion engine is different depending on the type and load of the engine in question. For instance, the intake flow to a fuel injection engine consists of air and recirculated exhaust gases and at a carburettor engine it consists of an air-fuel mixture and recirculated exhaust gases. However, it is usually recirculated such an amount of exhaust gases that it constitutes a relatively small part, typically 0-5%, of the total intake flow at high load on the combustion engine. At low load on the combustion engine, it is usual that the exhaust gases constitute a larger part, typically up to 30% and preferably in the upper part of this interval, of the total intake flow. The amount of exhaust gases which is recircu- lated at a given load condition on the combustion engine is usually regulated by a controllable valve device arranged in the exhaust gas recirculation line, a so called EGR valve. This EGR valve is in most cases controlled so that it is open or almost open at low load on the combustion engine and closed or only slightly open at high load on the same engine. The control of the EGR valve is with advantage based on information from a so called OBD (On Board Diagnosis) system. As the definition low load also includes the low load condition which is called idling, it should be mentioned that it occurs that the EGR valve of combustion engines according to the present state of the art turns off the exhaust gas recirculation during idling to restrict fuel consumption and achieve a more even engine operation.

It is a problem with prior art to ensure that, from an exhaust gas purification point of view, a sufficiently large portion of exhaust gases is recirculated at low load on the combustion engine. This is particularly problematic when using diesel engines, and the expression diesel engine used herein refers to combustion en- gines with compression ignition according to the process of Rudolf Diesel, the air intake of which is not regulated by any kind of dampers, as opposed to the condition with Otto cycle engines. The power output of diesel engines is regulated, as known, only by means of fuel supply controlled by an injection installation and consequently the air intake is always completely open. In addition, it often holds for super charged engines that the pressure conditions between the intake and outlet systems of the engine at higher load make exhaust gas recirculation to the engine impossible.

During low load on the combustion engine consequently the flow rate is so small and/or the pressure difference between the intake and outlet systems of the engine is so small that one not always gets the desired effect in terms of the portion of recircu- lated exhaust gases. To solve the above mentioned problem it is known to provide a device which has a venturi effect producing arrangement in an intake channel to the engine, which arrangement covers a first part of the intake cross section area of the engine, and that an exhaust gas recirculation line is connected to the intake channel in or nearby a throat included in the venturi effect producing arrangement.

Furthermore, it is also known that a device of the above men- tioned kind may comprise a valve arrangement arranged to regulate the flow through a second part of the intake cross section area of the engine, which second part is not covered by the venturi effect producing arrangement, and that the device also may comprise members to influence the valve arrangement to reduce the flow through the second part so as to increase the flow through the first part at low load on the engine.

OBJECT OF THE INVENTION

The object of the present invention is to provide regulation of the intake flow to an engine in an advantageous and simple manner such that a portion of the total intake flow to the engine which is suitable for achieving a desirable exhaust gas recirculation passes through a venturi effect producing arrangement at all load conditions on the engine.

This object is achieved by providing a device according to the preamble of the enclosed claim 1 , the valve arrangement comprising at least one damper which is arranged to be influenced by spring load in a closing direction so that the damper is brought to a completely or partially closed position at low load on the engine, so that the flow through the second part is reduced and the flow through the first part is increased.

In this way a very advantageous and simple regulation is achieved of how large the part of the total intake flow to the en- gine is that passes through the venturi effect producing arrangement, whereby it is ensured that the desired amount of recirculated exhaust gases in the intake flow to the engine can be obtained at all load conditions on the engine. In particular, an advantageous admixture of recirculated exhaust gases to the intake flow of the engine is obtained at low or partial load on the engine, since the spring loaded damper then completely or partially closes the part of the intake channel, which is not covered by the venturi effect producing arrangement. Accordingly, at low or partial load on the engine a favourable suction effect on the exhaust gas recirculation line is achieved in that a larger amount of the total intake flow passes the venturi effect producing arrangement. The regulation of how large the portion of the total intake flow to the engine is that passes through the venturi ef- feet producing arrangement is consequently done completely automatically in a very advantageous and simple manner.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will hereinafter be described in form of non limiting embodiments, which are illustrated in the following drawings.

In the drawings:

Fig 1 is an explanatory sketch of a combustion engine with associated exhaust gas recirculation system.

Fig 2 is the area within the dashed rectangle in fig 1 shown in enlarged scale.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

In fig 1 there is shown schematically a combustion engine, indicated at 1 , with a device for recirculation of exhaust gases ac- cording to the invention. From the exhaust pipe 2 of the engine exhaust gases can be recirculated to an intake channel 5 of the engine 1 through an exhaust gas recirculation line 3 and via a controllable valve device 4.

In fig 2 is shown a longitudinal section of the intake channel 5 of the engine 1 . The section covers a part 3a of the exhaust gas recirculation line 3 which is connected to and has its outlet 10 in the shown part 5a of the intake channel 5. Within the intake channel 5 is a, here indicated with 6, venturi effect producing arrangement arranged. In the arrangement 6 there is a throat 7, the inside diameter of the arrangement 6 being smaller at the throat 7 than at the inlet 8 and outlet 9 of the arrangement 6. The line 3 is, in the embodiment shown in fig 2, connected after the throat 7, but at the same time also before the venturi effect produced by the throat has ceased, which is equivalent to the in- side diameter at the connection point being in the closed interval constituted by the inside diameter at the throat 7 and the inside diameter at the beginning of the inlet 8.

It is emphasised that the line 3 can be connected to the intake channel 5 at arbitrary location where the venturi effect produced by the arrangement 6 contributes to a favourable suction effect on the line 3. The line 3 can for instance be connected to the intake channel 5 where the inside diameter of the arrangement 6 at the throat 7 is the smallest.

Also in fig 2 is shown the controllable valve device 4 arranged in the recirculation line 3. This valve device 4 is in most cases controlled such that it is open or almost open at low load on the engine 1 and closed or only slightly open at high load on the en- gine 1 .

In the embodiment shown in fig 2 the venturi effect producing arrangement 6 covers a first part 1 1 of the intake cross section area of the engine. Thus, it remains a second part 12 of the intake cross section area of the engine, which here is constituted by the part of the intake channel 5 which is not covered by the venturi effect producing arrangement 6. Another possible embodiment is that the second part consists of a separate line extending in parallel with the first part.

The device according to the invention comprises a valve arrangement, indicated at 13 in fig 2, arranged to regulate the flow through the second part 12 of the intake cross section area of the engine 1 . The device also comprises members for, at low load on the engine 1 , influencing the valve arrangement 13 to reduce the flow through the second part 12 so as to increase the flow through the first part 1 1 . Thus, the valve arrangement 13 is arranged so as to have a position closing the second part 12 at low load and so as to have a position opening the second part 12 at high load. The valve arrangement comprises at least one damper 14 which is arranged to be influenced by spring load in a closing direction so that the damper 14 is brought to a completely or partially closed position at low load on the engine, so that the flow through the first part 1 1 is increased. The spring load is achieved by a spring 15. The damper 14 is rotatable around a geometrical axis 16. This axis 16 can be realised in manners known per se, for instance by the damper having a bearing sleeve, in which a shaft pivot is received. In such a case the shaft pivot is secured to the wall of the intake channel 5a. The spring 15 is in the embodiment realised by means of a coil spring, one end of which is secured to the damper 14 and the other end of which is secured relative to the intake channel 5a, for instance at an attachment 17 formed on the wall thereof. It is envisaged that the spring 15 in the example is received in an opening in the damper.

In this preferred embodiment the spring 15 is realised by means of a coil spring, but also other types of springs, for instance springs with viscous or magnetic resilient action, are possible. The spring can either be a draw spring or a pressure spring. The damper 14 and the spring 15 are arranged so that the air/air-fuel flow through the intake channel 5 towards the engine tends to move the damper in an opening direction against the action of the spring . At low load on the engine the spring force is, however, envisaged to be sufficient for keeping the damper closed while at high load the air/air-fuel flow is able to control the damper to a completely or partially open position in the direction of the arrow 18.

Variants of the above described embodiment include for instance that, where the spring 15 is mentioned, there is arranged a plurality of springs and that, where the damper 14 is mentioned, there is arranged several dampers.

The invention is here described in a very simple and pure situation. Of course it is just as usable in arrangements where catalytic converters, particulate filtering devices or other exhaust gas purification apparatus are mounted in the exhaust gas recirculation line 3 and the exhaust pipe 2.

Although the invention is especially advantageous at diesel engines it is pointed out that it also can be quite usable at other kinds of engines. Furthermore, the invention works irrespective of the engine being super charged or not, i.e. if the air supply to the engine is forced or generated by suction due to piston movements in the engine. Super charging can generally be done by means of a compressor operated in any way, for instance mechanically via the engine or suitable auxiliary equipment. Other possible compressor drive can be by means of the exhaust gas flow from the engine. If the engine in question would be super charged, the exhaust gas recirculation line should be connected to the air intake channel on the suction side of the super charging unit.

It is pointed out that the device according to the invention could be applied to the engine already in connection with the manu- facturing thereof, but it is also possible to apply the device to an already used engine afterwards to improve the EGR-function.

Claims

1 . A device for recirculation of a portion of the exhaust gases from a combustion engine (1 ) to an intake of the engine via an exhaust gas recirculation line (3), an intake channel (5) of the engine having a venturi effect producing arrangement (6), which covers a first part (1 1 ) of the intake cross section area of the engine, the exhaust gas recirculation line (3) being connected to the intake channel (5) in or nearby a throat (7) included in the venturi effect producing arrangement (6), the device comprising a valve arrangement (13) arranged to regulate the flow through a second part (12) of the intake cross section area of the engine, which second part (12) is not covered by the venturi effect producing ar- rangement (6), characterized in that the valve arrangement

(13) comprises at least one damper (14) which is arranged to be influenced by spring load (15) in a closing direction so that the damper (14) is brought to a completely or partially closed position at low load on the engine (1 ), so that the flow through the second part (12) is reduced and the flow through the first part (1 1 ) is increased.

2. A device according to claim 1 , characterized in that the damper (14) is arranged to be controllable against the ac- tion of the spring load (15) at high load on the engine (1 ) so as to have a position completely or partially opening the second part (12), so that the flow through the second part (12) is increased and the flow through the first part (1 1 ) is reduced.

A device according to any of preceding claims, characterized in that a controllable valve device (4) is arranged in the exhaust gas recirculation line (3) to regulate the flow of recirculated exhaust gases.

4. A device according to any of preceding claims, characterized in that a spring is arranged to achieve said spring load (15).

5. A device according to claim 4, characterized in that said spring is a coil spring .