EP0197823A1 - Heat exchanger for a motor vehicle, particularly of the type for exhaust gases - Google Patents

Abstract

The invention relates to a heat exchanger for a motor vehicle, comprising a fluid box (10) into which open the ends of the tubes (22) of a bundle housed in an envelope (24), the box (10) and the tubes. (22) being traversed by the engine exhaust gases, while the engine coolant or the passenger compartment heating air circulates in the casing (24). This is connected to the fluid box (10) by a tubular element (30) and by a manifold (18). The invention applies in particular to vehicles equipped with internal combustion engines.

Description

The invention relates to a heat exchanger for a motor vehicle, in particular of the type comprising a circuit for passing the exhaust gases of the internal combustion engine fitted to the vehicle, making it possible, during cold engine operation, to quickly heat the coolant and / or lubricating oil for this engine.

It has already been proposed to use the heat of the exhaust gases to, during a start or a cold operation of the internal combustion engine, very quickly raise the temperature of the coolant and / or of the oil. engine lubrication, which results in a significant reduction in fuel consumption. However, the known exchangers are relatively heavy and in fact have utility only for a relatively very short period of time compared to the total engine operating time.

The invention provides a heat exchanger of the aforementioned type, which is relatively light.

The invention therefore provides a heat exchanger for a motor vehicle, comprising a bundle of tubes, the ends of which are mounted in a sealed manner in the holes of a manifold to which is fixed a fluid box into which the ends of the tubes open and which has at least one inlet and / or one outlet for a first fluid, characterized in that it comprises a tubular element interposed between the manifold and an envelope surrounding the bundle of tubes, this envelope being made of plastic or of a material light metal withstands high temperatures poorly, while the fluid box, manifold and tubular element are made of a material that withstands the high temperatures that exhaust gases can reach.

This results in significant weight gain.

Advantageously, the tubular element is formed in one piece with the manifold.

Preferably, the envelope is provided with an inlet and an outlet for a second fluid which circulates in said envelope and in the tubular element.

In general, the first fluid flowing in the box above ^the you and the tubes of the bundle is formed by the exhaust gases of the engine, and the second fluid flowing through the envelope is constituted by a liquid or by the air, in particular by the engine coolant or by the air for heating the passenger compartment of the vehicle.

The heat exchanger according to the invention provides aid for heating the passenger compartment of the vehicle, not only during the periods of starting and cold engine operation, but also outside these periods if desired.

The invention also provides that the aforementioned envelope contains a bundle of tubes traversed by the engine lubricating oil.

Thus, during a cold start or operation of the engine, the lubricating oil is also heated by the exhaust gases, by means of the fluid which circulates in said envelope. Furthermore, the fluid which circulates in said envelope can be an intermediate heat exchange fluid with the engine coolant or with the air for heating the passenger compartment of the vehicle, to avoid any possibility of pollution by gases. exhaust or lubricating oil.

• -la figure 1 est une vue schématique en coupe longitudinale d'un échangeur de chaleur selon l'invention;
• -la figure 2 est une vue en coupe longitudinale d'une variante de réalisation de cet échangeur;
• -la figure 3 est une vue partielle, à plus grande échelle, d'une partie d'un échangeur de chaleur selon l'invention;
• -la figure 4 est une vue schématique d'un exemple d'application d'un échangeur selon l'invention;
• -la figure 5 est une vue semblable à la figure 2, pour une variante de réalisation de l'invention.

In the description which follows, given by way of example, reference is made to the appended drawings, in which:

• FIG. 1 is a schematic view in longitudinal section of a heat exchanger according to the invention;
• FIG. 2 is a view in longitudinal section of an alternative embodiment of this exchanger;
• FIG. 3 is a partial view, on a larger scale, of part of a heat exchanger according to the invention;
• FIG. 4 is a schematic view of an example of application of an exchanger according to the invention;
• FIG. 5 is a view similar to FIG. 2, for an alternative embodiment of the invention.

Reference is first made to FIG. 1, which represents a heat exchanger according to the invention, intended to equip a motor vehicle comprising an internal combustion engine.

The exchanger comprises a fluid box 10 provided with an inlet pipe 12 and an outlet pipe 14, and comprising an internal partition 16, fixed or mobile, which divides the internal space of the tank 10 in two separate chambers which are connected respectively to the inlet manifold 12 and to the outlet manifold 14.

This box. fluid is sealingly mounted on the peripheral rim of a manifold 18, or tube plate, comprising holes 20 in which the ends of the tubes 22 of a bundle of U-shaped tubes are mounted in a conventional manner.

This bundle of tubes 22 is contained in a sealed manner in an envelope 24 comprising two tubes 26 and 28 by which it can be connected to a circuit of a fluid such as the coolant of the internal combustion engine or the heating air of the passenger compartment of the vehicle, or of an intermediate fluid, such as for example freon.

The manifold 18 of the exchanger is formed in one piece with a tubular element 30 having a peripheral rim 32 opposite the peripheral rim of the collector on which the fluid box is fixed 10. This peripheral rim 32 of the tubular element 30 cooperates with a peripheral rim 34 of the end of the casing 24, to ensure the fixing of this casing to the tubular element 30, for example by means of a system of lugs or clamps 36.

One or more seals 38 are interposed between the peripheral flanges 32 and 34 of the tubular element 30 and of the casing 24.

The inlet 12 and outlet 14 pipes of the fluid box 10 are connected to the exhaust manifold of the internal combustion engine, so that the exhaust gases of this engine enter the box 10 through the pipe 12 , circulate in the tubes 22 of the bundle, return to the box 10 and exit from this box via the outlet pipe 14.

The engine coolant, the intermediate fluid or the air for heating the passenger compartment of the vehicle, which enters the casing 24 through one or other of the pipes 26 and 28, which circulates in this casing and which leaves through the other of the tubes 26 or 28, scans the tubes 22 of the bundle which are inside the envelope 24.

During a cold start or a cold operation of the engine, the fluid which circulates in the casing 24 is heated by the exhaust gases of the engine, the temperature of which is between 400 and 900 or 1000 ° C. approximately, depending on the case. When this fluid is the engine coolant, its temperature rises very quickly by heat exchange with the exhaust gases, which reduces the duration of engine temperature rise and at the same time reduces fuel consumption. When the fluid which circulates in the envelope 24 is the air brought into the passenger compartment of the vehicle, this air is heated very quickly and makes it possible to heat the passenger compartment, even if the engine has not reached its normal operating temperature. .

Of course, when the engine coolant circulates in the casing 24, its increase in temperature can be used, not only to accelerate the temperature rise of the engine, but also to heat the air brought into the passenger compartment of the vehicle. .

The envelope 24, the temperature of which is permanently maintained at a relatively low value, for example less than 100 ° C., by the fluid which circulates therein, can be made of a plastic material, or of light metallic material, while the fluid box 10, the manifold 18 and the tubular element 30 will be made of one or more materials supporting the high temperatures of the exhaust gases. The tubular element 30 is in permanent contact with the fluid which circulates in the envelope 24, and its peripheral rim 32, on which the end of the envelope 24 is fixed, is maintained at a relatively low temperature not risking deteriorate the material of which the envelope 24 is made, while the collector 18 is itself brought to a much higher temperature.

Referring now to Figure 2, showing an alternative embodiment of this exchanger, in which the casing 24 also contains a bundle of tubes 40- opening at their ends in two supply tubes 42 which pass through the wall of the seal. the casing 24 and which are connected to the lubrication oil circuit of the internal combustion engine.

In this case, during a cold start or a cold operation of the engine, the lubricating oil circulating in the tubes 40 is heated by the fluid circulating in the casing 24, which is itself heated by the exhaust gas.

FIG. 3 shows, in more detail, a method of assembling the fluid box 10 and the casing 24 on the manifold 18.

In this case, the fluid box 10 comprises a peripheral flange 44 applied, by means of a seal 46, to a corresponding peripheral flange 48 of the manifold 18. Screws 50 passing through aligned holes of the flanges 44 and 48 and of the seal 46 allowing, with nuts 52, to secure the fixing of these flanges.

The peripheral rim 32 of the tubular element 30 (which is formed in one piece with the manifold 18) is fixed to the peripheral rim 34 of the end of the casing 24 in the same way, by means of screws 54 passing in aligned holes of the flanges 32 and 34 and of the seal 38 and receiving nuts 56.

Of course, it is not essential that the tubular element 30 be formed in one piece with the collector 18. The latter could therefore have a usual constitution, while the tubular element 30 would then include a peripheral rim at its end upper, by which it would be assembled to the peripheral rim 44 of the fluid box 10 and to the periphery of the manifold 18, which could be a simple plate fixed to seal between the rim of the fluid box and the corresponding rim of the element tubular 30.

Furthermore, and as shown in FIGS. 1 and 2, partitions 25 forming baffles 25 can be placed in the envelope 24 to improve the heat exchange between the exhaust gases and the fluid circulating in the envelope.

As a variant, the fluid which circulates in the casing 24 is an intermediate heat exchange fluid with the engine coolant or with the passenger compartment heating air, which makes it possible to avoid any risk of pollution coolant or air through exhaust gases or lubricating oil.

Reference is now made to FIG. 4 which schematically represents an example of application of the exchanger of FIG. 2.

In this example, the pipes 26 and 28 of the casing 24 are connected to the coolant circuit 56 of an internal combustion engine 58.

The exhaust manifold 60 of this engine is connected by a valve 62, either to the inlet pipe 12 of the fluid box 10 of the exchanger, or to an exhaust duct 64 thereby short-circuiting the 'exchanger. The outlet pipe 14 of the fluid box 10 is also connected to the exhaust duct 64. The valve 62 can be controlled by a thermostat depending for example on the temperature of the engine coolant.

The two supply tubes 42 of the oil radiator, sealingly crossing the wall of the casing 24, are connected to the circuit 66 of the lubricating oil of the engine 58.

• Lors d'un démarrage à froid, ou lorsque le moteur 58 n'a pas encore atteint sa température normale de fonctionnement, les gaz d'échappement de ce moteur sont amenés par la vanne 62 à la tubulure d'entrée 12 de la boîte 10, circulent dans les tubes 22 du faisceau, reviennent dans la boîte 10 et sortent de cette boîte par la tubulure de sortie 14 reliée au conduit d'échappement 64. Le liquide de refroidissement du moteur pénètre dans l'enveloppe 24 par l'une ou l'autre des tubulures 26 et 28, circule dans cette enveloppe en balayant les tubes 40 du radiateur d'huile et sort de l'enveloppe 24 par l'autre des tubulures 26 et 28. L'huile de lubrification circulant dans les tubes 40 est chauffée par le liquide de refroidissement du moteur, qui est lui-même chauffé par les gaz d'échappement circulant dans les tubes 22 du faisceau contenu dans l'enveloppe 24.

This heat exchanger works as follows:

• During a cold start, or when the engine 58 has not yet reached its normal operating temperature, the exhaust gases from this engine are brought by the valve 62 to the inlet manifold 12 of the box 10 , circulate in the tubes 22 of the bundle, return to the box 10 and leave this box by the outlet pipe 14 connected to the exhaust duct 64. The engine coolant enters the casing 24 by one or the other of the tubes 26 and 28, circulates in this envelope by sweeping the tubes 40 of the oil radiator and leaves the envelope 24 through the other of the tubes 26 and 28. The lubricating oil circulating in the tubes 40 is heated by the engine coolant, which is itself heated by the exhaust gases circulating in the tubes 22 of the bundle contained in the casing 24.

When the engine 58 has reached its normal operating temperature, the valve 62 is switched, and the exhaust manifold 60 is then connected directly to the exhaust duct 64 without passing through the tubes 22 of the bundle. In this case, the coolant which circulates in the casing 24 makes it possible to cool the engine lubricating oil, which circulates in the tubes 40 of the oil radiator.

Reference is now made to FIG. 5 which represents an alternative embodiment of the exchanger of FIGS. 2 and 4.

In this variant, the fixed partition 16 of the fluid box 10 is replaced by a movable partition 68 pivotally mounted about an axis 70 adjacent to the collector 18 or carried by the latter, to be movable by a temperature-sensitive member engine coolant (like the valve 62 in Figure 4) between a position shown in solid lines (where it separates the inlet 12 from the outlet 14 and where the exhaust gases entering the box 10 by the inlet 12 circulates in the tubes 22 to gain the outlet 14, and a position shown in dotted lines where the exhaust gases go directly from the inlet 12 to the outlet 14 of the fluid box 10, without circulating in the tubes 22 the inlet ends of which are isolated by the partition 68 of the inlet 12 of the box 10.

The casing 24 comprises at its lower end two nozzles 72 for entering and leaving the second engine coolant or liquid, separated by an internal partition 74 extending from the bottom of the casing 24 to the vicinity of the 'upper end of this envelope. A ra oil diator 76 is disposed in the casing 24, parallel to the tubes 20, and is connected to the oil circuit by two conduits 78 which pass through the bottom of the casing 24 in leaktightness.

The operation of this exchanger is essentially identical to that of the exchanger in FIG. 4.

Claims (8)

1. Heat exchanger for a motor vehicle, comprising a bundle of tubes, the ends of which are mounted in a sealed manner in the holes of a manifold on which is fixed a fluid box into which the ends of the tubes open and which comprises at least one inlet. and / or an outlet for a first fluid, characterized in that it comprises a tubular element (30) interposed between the manifold (18) and an envelope (24) surrounding the bundle of tubes (22), this envelope (24 ) being made of plastic material or light metallic material, while the fluid box (10), the manifold (18) and the tubular element (30) are made of a material which withstands high temperatures. 2. Exchanger according to claim 1, characterized in that the casing (24) is provided with an inlet and an outlet (26, 28) of a second fluid which circulates in the casing (24) and in the tubular element (30). 3. Exchanger according to claim 1 or 2, characterized in that the tubular element (30) is formed in one piece with the manifold (18). 4. Exchanger according to one of the preceding claims, characterized in that the casing (24) also contains at least one conduit (40, 42) through which the engine lubricating oil passes. 5. Exchanger according to one of claims 2 to 4, characterized in that the first fluid flowing in the box (10) and in the tubes (22) of the bundle consists of the exhaust gases d: a combustion engine internal, and in that the second fluid circulating in the envelope (24) is constituted by a liquid or by air, for example by the engine coolant or by the air for heating the passenger compartment vehicle. 6. Exchanger according to one of claims 2 to 4, characterized in that the first fluid flowing in the box (10) and in the tubes (22) of the bundle consists of the exhaust gases of a combustion engine internal and in that the second fluid is an intermediate heat exchange fluid with the engine coolant or with the air for heating the passenger compartment of the vehicle. 7. Exchanger according to all of claims 4 and 5, characterized in that the inlet (12) of the fluid box (10) is connected by a valve (62) to the exhaust manifold (66) of a internal combustion engine (58), this valve (60) allowing the exhaust gases to pass into the exchanger or to short-circuit it so that when the exhaust gases circulate in the exchanger, the second fluid circulating in the casing (24) and the lubricating oil circulating in the duct (40, 42) can be heated by the exhaust gases and, when the exhaust gases do not circulate in the exchanger, the oil can be cooled by the second fluid. 8. Exchanger according to all of claims 4 and 5, characterized in that the fluid-box (10) comprises a movable partition (76) movable between a first position where it isolates the inlet (12) from the outlet ( 14) of the fluid box and causes the exhaust gases to circulate in the tubes (22) of the harness, and a second position where it prevents the exhaust gases from circulating in the tubes (22) and directly connects the inlet (12) to outlet - (14) of the fluid box (10) so that, for the first position of the movable partition (76), the second fluid and the oil are heated by the exhaust gases , and for the second position of this movable partition, the oil is cooled by the second fluid. 9. Exchanger according to one of claims 2 to 8, characterized in that the envelope (24) comprises at least one internal partition (25, 74) for guiding the second fluid flowing in said envelope.

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