WO1994012780A1

WO1994012780A1 - Supercharger air cooler

Info

Publication number: WO1994012780A1
Application number: PCT/SE1993/001043
Authority: WO
Inventors: Odd Werner Hielm; Anders Edsfeldt
Original assignee: Ab Konstruktions-Bakelit
Priority date: 1992-12-02
Filing date: 1993-12-02
Publication date: 1994-06-09
Also published as: SE500057C2; SE9203639L; SE9203639D0

Abstract

A device in an internal combustion engine (10) provided with a supercharger air cooler and arranged in a vehicle equipped with an air-conditioning system, is disclosed. The supercharger air cooler (2) is so arranged in the vehicle that a current of air flows through it when the vehicle is propelled. The device is distinguished by the provision of an additional cooler (6) in which the air charge is cooled by means of a cooling medium having a comparatively low temperature. An evaporator (14), which is disposed inside the additional cooler (6), forms a cooling circuit together with the air-conditioning system. Furthermore, there are provided means conducting the air charge from the supercharger air cooler (2) through or to the additional cooler (6) and on to the combustion chamber of the engine (10).

Description

SUPERCHARGER AIR COOLER

This invention generally relates to cooling systems in motor vehicles, and more specifically concerns a new supercharger air cooler for a water-cooled internal com¬ bustion engine having a turbocharger. It is known in the art to increase the power of an internal combustion engine by means of a supercharger, which in everyday speech is referred to as a turbo¬ charger. This technique is based on a compressor drawing in air, which is compressed to a higher pressure. Then, the compressed air is conducted to the cylinders of the internal combustion engine. With a better volumetric efficiency, it is possible to achieve a higher power output at a constant cylinder volume.

Furthermore, an even higher power output can be achieved, if the compressed air, i.e. the air charge, is cooled before being conducted to the cylinders of the internal combustion engine. For this reason, some vehicles (including lorries as well as private cars) are provided with a cooler for the compressed air, a so-called supercharger air cooler.

Above all in small vehicles, such as private cars, it is difficult to efficiently cool the internal com¬ bustion engine and the air charge, especially when the vehicle is provided not only with a turbocharger but also with an air-conditioning system for cooling and dehumidifying the air in the coupe. As the cooling water of the engine, the air charge and the medium in the con¬ denser of the air-conditioning system are cooled sub¬ stantially by means of the airstream induced by the movement of the vehicle, three coolers have to be pro¬ vided at the front of the vehicle after one another in the longitudinal direction of the vehicle, namely the engine radiator, the condenser and the supercharger air cooler, usually in precisely that order.

Modern vehicle design, especially of private cars, along with a desire to lower the so-called cw value, i.e. the air resistance value of the vehicle, has resulted in increasingly lower car fronts, which reduces the available air intake and thus restricts the maximum air flow over the coolers. As a result of this adverse combination of modern design and a plurality of coolers, there may, under unfavourable circumstances, arise prob¬ lems of cooling the air charge, the air in the coupe and/or the cooling water of the engine. Of course, the situation as aggravated on hot summer days. If the vehi¬ cle in addition is heavily loaded or pulls a trailer or a caravan, the power output cannot be increased, since the supercharger air cooler is unable to cool the air charge to the extent required.

Naturally, the relative positions of the coolers can be altered, e.g. as in GB-A-2,200, 741 disclosing another cooler configuration. Here, there is provided an aftercooler for the supercharger air cooler foremost at the front of the vehicle, to be followed by the con¬ denser of the air-conditioning system and the engine radiator. The refrigeration demand on the engine coolant is at its highest when the vehicle is idling or moving at a crawl, since the cooling airstream induced by the movement of the vehicle then is non-existent or neglig¬ ible. Cooling is then brought about by an electric cooling fan or a cooling fan driven by the internal com- bustion engine, drawing surrounding air through the coolers into the engine compartment. The invention according to GB-A-2, 200, 741 resides in the parallel con¬ nection of the engine radiator and the aftercooler of the supercharger air cooler for increasing the total convection surface. This technique is based on the assumption that there will not arise any need of increasing the power output by means of the supercharger air cooler until a certain velocity V_x above zero has been attained.

The above solution has the disadvantage of being unsuited for use in vehicles with a so-called low-speed turbocharger, i.e. a turbocharger permitting an increase in power output even at low speeds.

Furthermore, the known solution has the disadvan¬ tage of permitting parallel connection of the circuit for cooling the engine and the circuit for cooling the air charge, which in actual practice means that the same cooling medium, namely water or a mixture of water and some suitable alcohol, circulates in both circuits. This is not an optimal arrangement, since the temperature of the cooling medium of the engine as a rule is far too high.

One object of the present invention is, therefore, to provide a device in a supercharger air cooler for motor vehicles, which enables an increase in power out- put even when the vehicle is travelling at a low speed or starts from a standstill by ensuring that the com¬ pressed air charge supplied to the engine at all times has a relatively low temperature.

Another object of the invention is to provide a device in a supercharger air cooler for motor vehicles, which utilises any available cooling capacity of an air- conditioning system arranged in the vehicle.

A further object of the invention is to provide a device in a supercharger air cooler for motor vehicles, which has a cooling circuit that is separate from that of the engine.

In addition, the inventive device should be com¬ pact, the space available in the engine compartment being extremely limited. These and other objects of the invention are achieved by a device having the characteristics recited in appended claim 1.

Other features of the invention as well as advan- tageous embodiments thereof are stated in the appended subclaims.

One embodiment of the inventive device will be described in more detail below with reference to the accompanying drawings, in which Fig. 1 schematically illustrates an inventive device in a supercharger air cooler for motor vehicles;

Fig. 2 is a time-power diagram illustrating how the power output varies over time; and

Fig. 3 is a time-temperature diagram for a medium that can be used for increasing the cooling capacity of the inventive device.

Fig. 1 illustrates the inventive device in a super¬ charger air cooler for a motor vehicle having an inter¬ nal combustion engine provided with a turbocharger. The inventive device comprises a supercharger air cooler 2 of known type. The supercharger air cooler 2, a conven¬ tional engine radiator and the condenser 4 of an air- conditioning system in the vehicle are successively arranged behind an air intake at the front of the motor vehicle.

Furthermore, the device includes an additional cooler 6, in which cooling is achieved by means of the cold stored therein, for which reason the additional cooler 6 may be disposed at a site where it is unaffect- ed by the airstream induced by the movement of the vehi¬ cle.

As appears from Fig. 1, the device further com¬ prises a register 8 disposed in the passage of the air charge between the supercharger air cooler 2 and the engine 10 and controlled in accordance with the need of power output. A detector senses when the power output should be increased, e.g. when overtaking rapidly or travelling up a steep hill. As a function of an output signal from the detector, the position of the register 8 is altered so that all or some of the air charge having passed through the supercharger air cooler 2 is conduct¬ ed through the additional cooler 6. With respect to the flow path of the air charge, the additional cooler 6 can thus, if need be, be connected in series with the regu¬ lar supercharger air cooler 2, the flow through the additional cooler 6 preferably being adjustable between 0 and 100%.

The air charge compressed by the compressor 12 of the turbocharger has a temperature T_IN of about +140°C when reaching the supercharger air cooler 2. The cooled air charge supplied to the engine 10 should have a tem¬ perature T_ooτ that is as low as possible. By connecting the additional cooler 6 according to the invention, it is possible to obtain a temperature T_ouτ of about +20°C. When the temperature difference T_IN - T_ouτ is about +120°C, a considerable amount of heat has to be cooled off in the two supercharger air coolers 2 and 6. For this reason, the additional cooler 6 is a separate unit with respect to the cooling medium used therein. The additional cooler 6 is, like the engine radiator, filled with water or a mixture of water and alcohol and is, unlike the invention according to GB-A-2, 200, 741, not connected to the circuit for cooling the engine. As a result, a much lower temperature can be maintained in the additional cooler 6, which moreover is used only when additional cooling of the air charge is needed.

For producing such a low temperature, an evaporator 14 is arranged in the additional cooler and connected to the air-conditioning cooling system by means of an inlet 16 and an outlet 18. Thus, there is formed a separate cooling circuit utilising any available capacity of the air-conditioning cooling circuit for cooling the medium in the additional cooler 6.

The temperature of the medium in the additional cooler 6 is monitored by a detector 16' which, when a preset value, the so-called switching point, is passed, causes the additional cooler 6 to be "charged" with cold, e.g. via a valve 18' . Even on very hot days with intense sunshine, the air in the coupe is not conti¬ nuously cooled but the air-conditioning system operates intermittently. Moreover, the power output of the vehi¬ cle engine usually is increased for relatively short periods of time, e.g. when overtaking rapidly, as illu¬ strated by the time-power diagram in Fig. 2. The peaks in the diagram indicate increases in power output, while the valleys indicate periods of time during which the additional cooler 6 can be "charged". Thus, the addi¬ tional cooler 6 is "charged" when need be by utilising the overcapacity of the air-conditioning system, the heat absorbed by the evaporator 14 being, via the outlet 18, conveyed to the condenser 4 of the air-conditioning system, where it is cooled off. The cooling medium in the evaporator 14 is the same as in the air-conditioning system, since the evaporator and the air-conditioning system are interconnected and thus forms a common sys- tern. Heat is removed from the medium in the additional cooler 6, i.e. the medium is cooled, until the preset temperature value has been passed and the aimed-at low temperature been reached.

In order to improve the possibilities of storing cold in the additional cooler 6, a container 20 filled with a saline solution can be provided. If so, use is made of the capacity of the saline solution, in a cer¬ tain region of state, to absorb heat from the cooling medium in the additional cooler without showing an increase in temperature. Fig. 3 is a time-temperature diagram illustrating the changes of state of a solution that may be used in this context. In a region of state δ₂ (between tempera¬ tures T₁ and T₂) , the solution is in solid state, e.g. in the form of crystals when a saline solution is used. When the temperature T₂ is reached at a point of time t_lf another region of state δ₂ begins, extending to a point of time t₂ at which the solution is in solid (crystalline) as well as liquid state. In this region of state δ₂, the temperature of the solution is essentially constant, while at the same time the proportion of solid state (the crystalline part of the solution) continuous¬ ly decreases as thermal energy is supplied. This fact is used for absorbing heat from the cooling medium in the additional cooler 6, such that this medium, via the con¬ denser 4 of the air-conditioning system, is cooled at longer time intervals, compared with the case where no container 20 is provided. If the supply of heat were to continue after the point of time t₂, the temperature of the solution in a region of state δ₃ would increase to a temperature T₃ at which the solution would start to boil, to be finally evaporated. However, this does not take place, since the cooling medium in the additional cooler 6 is cooled when passing a certain preset tempe- rature value, as stated above.

Thus, the invention provides a device in a super¬ charger air cooler, which comprises a "cold store" hav¬ ing a comparatively low temperature also when the vehi¬ cle is travelling slowly or is idling, thus enabling rapid cooling of the air charge when there is a sudden need of an increased power output. Since the cooling circuit of the device is totally separate from the cool¬ ing circuit of the engine, the two circuits can operate independently of one another, such that different and optimal temperatures can be maintained in the two cir¬ cuits . It goes without saying that those skilled in the art may devise other means and variants for obtaining the same technical effect. Thus, the present invention is applicable also to other systems for effectively uti¬ lising the excess cold from a cooling assembly. More¬ over, other suitable media can be used instead of the saline solution mentioned above. Thus, all variants and modifications covered by the underlying inventive idea are encompassed by the requested scope of protection.

Claims

1. A device in an internal combustion engine pro- vided with a supercharger air cooler and arranged in a vehicle equipped with an air-conditioning system, said supercharger air cooler (2) being so arranged in the vehicle that a current of air flows through it when the vehicle is propelled, c h a r a c t e r i s e d by an additional cooler (6) in which the air charge is cooled by means of a cooling medium having a comparatively low temperature; an evaporator (14) disposed inside the additional cooler (6) and forming a cooling circuit together with the air-conditioning system; and means adapted to conduct the air charge from the supercharger air cooler (2) through or to the additional cooler (6) and on to the combustion chamber of the engine (10) .

2. A device as set forth in claim 1, c h a r ¬ a c t e r i s e d in that the means for conducting the air charge comprise a register (8) for stepless distri¬ bution of the air charge to the additional cooler (6) .

3. A device as set forth in claim 2, c h a r ¬ a c t e r i s e d in that the means for conducting the air charge further comprise a detector which is adapted, depending on the required power output of the internal combustion engine, to control the register (8) for dis¬ tributing the air charge to the additional cooler (6) .

4. A device as set forth in any one of claims 1-3, c h a r a c t e r i s e d by a detector (16') which senses the temperature deviations of the cooling medium in the additional cooler (6) and which, in response to a deviation in a certain direction from a preset tempera¬ ture value (T₂) , initiates cooling of the cooling medium by actuating a valve (18') arranged in the cooling cir- cuit essentially consisting of the evaporator (14) and the air-conditioning system.

5. A device as set forth in claim 4, c h a r ¬ a c t e r i s e d in that the cooling medium in the additional cooler (6) is cooled intermittently during periods when the air-conditioning cooling system has available capacity.

6. A device as set forth in any one of claims 1-5, c h a r a c t e r i s e d in that the cooling medium in the additional cooler (6) consists of water or a mixture of water and a suitable antifreeze.

7. A device as set forth in any one of claims 1-6, c h a r a c t e r i s e d in that a closed container (20) is arranged in the additional cooler (6) and is filled with a medium having a comparatively large region of state (δ₂) in which it is in solid as well as liquid state, said medium being capable of absorbing heat from the cooling medium in the additional cooler (6) .

8. A device as set forth in claim 7, c h a r ¬ a c t e r i s e d in that the container (20) is inte¬ grated with the evaporator (14) .