Heat Exchanging System Having Cooling Fan, for Vehicle

This application relates to and incorporates herein by reference Japanese Patent Application No. Hei. 9-56489 filed on Mar. 11, 1997.

1. Field of the Invention

The present invention relates to a heat exchanging system for a vehicle, which adjusts a cooling performance of a cooling fan by controlling a rotational speed of an electric motor using a semiconductor switching element.

2. Related Art

JP-A-62-251418 proposes an automotive heat exchanging system for adjusting a cooling performance of a cooling fan by using a semiconductor switching element. This conventional system includes a suction-type cooling fan disposed on the vehicle rear side of a radiator which cools an engine cooling water. Air generated by the cooling fan flows from the vehicle front side to the vehicle rear side.

A fan shroud is disposed between the radiator and the cooling fan for guiding cool air to readily pass through the radiator. An electric motor for driving the cooling fan is disposed in a downstream air part of the fan shroud using a plurality of stays. A rotational speed of the electric motor is controlled according to a pulse width modulated control (i.e., PWM control) performed by a control device having a semiconductor switching element. Thus, the rotational speed of the cooling fan is controlled by the control device to control a ventilation performance of the cooling fan.

Further, the control device has a plurality of radiation fins for facilitate heat radiation of the semiconductor switching element. The control device having the radiation fins is attached to a downstream-air-side surface of a stay which is formed wider than the other stays, so that the attachment of the control device to the fan shroud is reinforced.

However, because the control device is attached to the wider stay, a ventilation resistance becomes larger in the wider stay, resulting in deterioration of the ventilation performance of the cooling fan. Even if the stay to which the control device is attached is narrower, the control device protrudes outwardly from the stay and interrupts air flow. Thus, there is a problem that the ventilation performance of the cooling fan is deteriorated.

It is an object of the present invention to provide a heat exchanging system for a vehicle, which cools a control device sufficiently and improves a ventilation performance of a cooling fan.

According to the present invention, an air guiding duct is disposed between a heat exchanger and a cooling fan, and a control device is attached to an outer surface of the air guiding duct in such a manner that a radiation fin unit of the control divice is disposed inside the air guiding duct. Therefore, it can prevent a ventilation performance of the cooling fan from being reduced by providing the control device. Further, because the radiation fin unit is disposed inside the air guiding duct, cool air generated by the cooling fan is also blown toward the radiation fin unit to sufficiently cool the control device having a semiconductor switching element.

Preferably, the air guiding duct has an air intake port at an upstream air side proximate to the radiation fin unit. Therefore, cool air flows into the air guiding duct from outside through the air intake port without passing through the heat exchanger. Thus, the radiation fin unit is sufficiently cooled by cool air to improve the heat radiation performance of the radiation fin unit. As a result, a heat exchanging system of the present invention cools the control device sufficiently while improving the ventilation performance of the cooling fan. Further, the radiation fin unit has a plurality of plate-like radiation fins laminated at an interval in parallel with a flow direction of air flowing through the air guiding duct. Therefore, cool air passes through the whole radiation fins without interrupting the flow of cool air. Thus, the heat exchanging system improves heat-radiating capacity of the radiation fin unit to sufficiently cool the control device.

More preferably, the cooling fan has a first fan portion and a second fan portion, and the radiation fan unit of the control device is disposed at a center portion between the first and second fan portions. Therefore, even when either one of the two fan portions stops operation, the control device can be cooled by the other fan portion.

Additional objects and advantages of the present invention will be more readily apparent from the following detailed description of a preferred embodiment with reference to the accompanying drawings, in which:

FIG. 1 is a schematic cross-sectional view showing a heat exchanging system according to a preferred embodiment of the present invention;

FIG. 2 is a block diagram of an electric control of the heat exchanging system according to the embodiment;

FIG. 3 is a front view of the heat exchanging system when viewed from a vehicle rear side toward a vehicle front side according to the embodiment;

FIG. 4 is a perspective view showing a plurality of radiation fins of a control device of the heat exchanging system according to the embodiment;

FIG. 5 is a schematic cross-sectional view showing the control device attached in a fan shroud of the heat exchanging system according to the embodiment;

FIG. 6 is a flow chart showing a control process of the heat exchanging system according to the embodiment;

FIG. 7. is a schematic cross-sectional view showing a heat exchanging system according to a modification of the embodiment; and

FIG. 8 is a front view of a heat exchanging system according to an another modification of the embodiment.

A preferred embodiment of the present invention will be described. In the embodiment, a heat exchanging system cools cooling water of an engine 1 for a vehicle, and cools and condenses refrigerant of a refrigerant cycle for an air conditioning device. The heat exchanging system 2 is disposed in an engine compartment of the vehicle so that cool air flows substantially perpendicularly to the vehicle width direction. The engine 1 is disposed in the engine compartment to be opposite to the heat exchanging system. The other various equipments (not shown) are also accommodated in the engine compartment.

The heat exchanging system 2 includes a radiator 3, a condenser 30, two cooling fans 4, two electric motors 5, a fan shroud 6, a control device 8 and the like.

The radiator 3 is a heat exchanger. The cooling water of engine 1 flows inside the radiator 3, and is used as a heat exchanging medium. The radiator 3 is formed, in a rectangular shape having a thin thickness, by alternately laminating a plurality of flat tubes made of aluminum and a plurality of fins for improving a heat exchanging effective, as being known well. The condenser 30 is also a heat exchanger. Refrigerant flows inside the condenser 30, and is used as a heat exchanging medium. The condenser 30 is formed, in a rectangular shape having a thin thickness, by alternately laminating a plurality of flat tubes made of aluminum and a plurality of fins for improving a heat exchanging effective, as being known well. The condenser 30 is disposed at a vehicle front side of the radiator 3 to be opposite to the radiator 3. The radiator 3 and condenser 30 are disposed at a vehicle front side of the engine 1 in the engine compartment to be opposite to the engine 1. The cooling fans 4 are disposed between the engine 1 and the radiator 3. Each of the cooling fans 4 is an axial-flow fan and generates cool air toward the radiator 3 and the condenser 30 to cool the cooling water in the radiator 3 and the refrigerant in the condenser 30. The cooling fans 4 are suction-type cooling fans and disposed at a downstream air side of the condenser 30 and the radiator 3 as shown in FIG. 1.

The two electric motors 5 respectively drive the cooling fans 4 when electric power is supplied to the electric motors 5 from a battery mounted on the vehicle. Each rotational speed of the electric motors 5 is controlled by the control device 8 having a semiconductor switching element 7. As shown in FIG. 2, the control device 8 is connected to an ECU 10 which is a well-known computing unit provided with ROM, RAM and the like. Each of the rotational speed of the electric motors 5 is controlled according to signals from the ECU 10. The control device 8 and ECU 10 will be specifically described later.

The fan shroud 6 is disposed between the radiator 3 and the cooling fans 4 as shown in FIG. 1. The fan shroud 6 is made of resin such as polypropylene and formed into a duct. The fan shroud 6 guides cool air generated by the cooling fans 4 to passes through the radiator 3. The fan shroud 6 has a step portion 12 so that air flowing area is reduced as air flows from an upstream air side to a downstream air side of the cooling fan 4. Further, the fan shroud 6 has a duct portion 60 at an upstream air side of the cooling fan 4, and the duct portion 60 is approximately formed along the outer shape of the radiator 30. Furthermore, the fan shroud 6 has fan storage portions 13a and 13b for respectively accommodating the cooling fans 4, and each of the fan storage portions 13a and 13b are formed in a cylindrical shape to extend toward the vehicle rear side. As shown in FIG. 3, the two fan storage portions 13a and 13b are arranged in parallel in the vehicle width direction.

The fan shroud 6 further has an attachment portion 63 which connects a downstream-air-side end of the duct portion 60 and an upstream-air-side ends of the fan storage porions 13a and 13b. The attachment portion 63 extends in substantially up-down direction in FIG. 1 to be substantially parallel to a ventilation surface 3a of the radiator 3.

Four stays 15 for supporting each of the electric motors 5 are formed integrally with the fan shroud 6 at a downstream air side of the fan storage portions 13a and 13b for respectively holding the electric motors 5. Each of the stays 15 has a thickness slightly thicker than the fan shroud 6 so that the attachment of the electric motors 5 to the stays 15 is reinforced. The electric motors 5 are attached to the stays 15 with brackets 16 and screws 17 as shown in FIG. 1. The brackets 16 are fixed to the outer surface of the stays 15 of the electric motors 5.

As shown in FIGS. 1 and 3, within the fan shroud 6, a partition member 18 is integrally formed between the two cooling fans 4 to partition an interior of the fan shroud 6 into two air passages 14a and 14b corresponding to the cooling fan 4. The partition member 18 extends in a substantially vertical direction in FIG. 3 to prevent cool air generated by each cooling fan 4 from interfering with each other. Therefore, when each volume of cool air generated by the two cooling fans 4 increases, each ventilation performance of the two cooling fans 4 is improved. As shown in FIG. 3, an upper end of the partition member 18 is not connected to the fan shroud 6 to form a communication path 19 between the two air passages 14a and 14b.

The control device 8 has a cover 8a made of resin, and the semiconductor switching element 7 (i.e., MOS transistor) for controlling each rotational speed of the electric motors 5. The semiconductor switching element 7 is disposed within the cover 8a. The cover 8a also accommodates a driving circuit, a signal processing portion, a control portion and the like (not shown). Signals sent from the ECU 10 are input to the control portion of the control device 8.

The control device 8 is provided with a radiation fin unit 20 for promoting radiation of heat generated by the semiconductor switching element 7. The radiation fin unit 20 includes a plurality of radiation fins 20a made of metal having a sufficient heat-transmission performance such as aluminum, and a substrate 21. As shown in FIG. 4, the radiation fins 20a are disposed on the substrate 21 so that the radiation fins 20a are laminated at an interval. Further, the radiation fins 20a are disposed to be parallel to an air flow direction indicated by the arrows in FIGS. 1 and 3. The duct portion 60 of the fan shroud 6 has an air intake portion 22 at an immediately upstream air side of the radiation fin unit 20.

As shown in FIG. 5, the radiation fin unit 20 is attached to the cover 8a of the control device. Two connectors 41 are used for electrical connection between the control device 8 and the two electric motors 5.

Next, the attachment structure of the control device 8 will be described with reference to FIGS. 1, 3 and 5. FIG. 5 is a top view showing the control device 8 attached to the fan shroud 6 when viewed from an upper side to a lower side in FIG. 3. The control device 8 is attached to an outer surface of the attachment portion 63 so that the radiation fin unit 20 is placed inside the fan shroud 6. Specifically, the control device 8 is located at a upper center portion between the fan storage portions 13a and 13b to be proximate to an outline B of the duct portion 60 as shown in FIG. 3. That is, the attachment portion 63 is set to an area C shown in FIG. 3. Therefore, the control device 8 is disposed at the area C having a comparatively large space. Because the area C is made large, the dimension of the radiation fin unit 20 can be increased to improve heat radiation of the control device 8.

To attach the control device 8 at the area of C in FIG. 3, the fan shroud 6 has an opening portion 24 through which inside air and outside air of the fan shroud 6 are communicated. The opening portion 24 is provided between the two cooling fans 4 to correspond to the communicating path 19. The opening portion 24 extends over both the air passages 14a and 14b as shown in FIG. 3.

As shown in FIG. 5, the control device 8 is attached to the outer surface of the attachment portion 63 using screws 23 so that the radiation fin unit 20 is disposed inside the fan shroud 6 through the opening portion 24. Therefore, the flow of air is not affected by providing the control device 8 to improve the ventilation performance of the cooling fans 4. Further, because the radiation fin unit 20 is exposed to cool air (indicated by the arrows in FIG. 1) sufficiently, the radiation fin unit 20 can sufficiently radiate heat generated by the semiconductor switching element 7 to sufficiently cool the control device 8.

Further, because the attachment portion 63 is disposed to extend in parallel with the ventilation surface 3a of the radiator 3, a space for accommodating the control device 8 is made relatively large to prevent the control device 8 from interfering other parts of the vehicle. As a result, the total dimension of the radiator 3, the fan shroud 6 and the cooling fans 4 in the arrangement direction (i.e., front-rear direction of the vehicle) thereof is reduced to readily dispose the control device 8 in the vehicle.

Furthermore, because the radiation fin unit 20 is disposed in the communication path 19 to cross the both air passages 14a and 14b, cool air generated by the both cooling fans 4 is used for cooling the radiation fin unit 20. Therefore, even when one cooling fan 4 stops operation due to some problems such as entanglement of a foreign matter, the control device 8 can be cooled by the other cooling fan 4.

Further, because of the pressure difference between inside and outside air of the fan shroud 6 during operation of the cooling fans 4, cool air which flows outside the fan shroud 6 without passing through the radiator 3 is introduced into the fan shroud 6 from the air intake 22 to be blown toward the radiation fin unit 20. Therefore, the radiation fin unit 20 is sufficiently cooled by cool air to improve the heat radiation performance of the radiation fin unit 20. Thus, in the embodiment, the control device 8 is sufficiently cooled.

Furthermore, because the radiation fins 20a are disposed to be parallel to the air flow direction in the fan shroud 6, cool air is blown to the whole radiation fins 20a to sufficiently cool the radiation fin unit 20 without interrupting the flow of cool air. This also improves the radiation performance of the radiation fin unit 20.

The ECU 10 is a well-known computing unit including ROM, RAM and the like for controlling the engine 1. As shown in FIG. 2, the ECU 10 is connected to input terminals such as a temperature sensor 31 and a pressure sensor 32. The temperature sensor 31 detects the temperature of the cooling water of the engine 1, and the pressure sensor 32 detects the pressure of the refrigerant in the condenser 30 (i.e., discharging pressure of the refrigerant from a compressor of the refrigerant cycle).

The control device 8 is electrically connected to the ECU 10 by a connection portion 40 shown in FIG. 5. The control device 8 receives signals from the temperature sensor 31 and the pressure sensor 32 via the ECU 10 and controls the electric motors 5 according to a pulse width modulated control (i.e., PWM control). That is, the control device 8 controls each rotational speed of the electric motors 5 according to the conditions of the heat exchanging mediums flowing inside the radiator 3 and the condenser 30.

Next, the control process of the control device 8 will be now described with reference to FIG. 6.

First, at step S60, the control device 8 reads and records the signals sent from the temperature sensor 31 and the pressure sensor 32. Next, each rotational speeds of the two electric motors 5 is set at step S70. That is, a first rotational speed is determined according to the water temperature detected by the temperature sensor 31 and then a second rotational speed is determined according to the refrigerant pressure detected by the pressure sensor 32. The faster speed of either the first and second rotational speeds is determined as target rotational speeds of each electric motors 5 (hereinafter, the determination method is referred to as "general control"). When the refrigerant cycle does not operate, the target rotational speeds of each electric motor 5 are determined only by the water temperature detected by the temperature sensor 32. Next, at step S80, the control device 8 determines whether nor not the cooling fans 4 have an abnormity. For example, the abnormity of the cooling fans 4 is that foreign matters are entangled in one of the cooling fans 4 to stop the operation of the cooling fan 4. In this case, because a current value of the cooling fan 4 becomes larger, the control device 8 can detect the abnormity of the cooling fan 4 by measuring the current value. When both the two cooling fans 4 operate normally, the general control is performed in the control device 8 at step S90. When either one of the cooling fans 4 has the abnormity, the control device 8 proceeds to step S100 and increases the rotational speed of the electric motor 5 connected to the other cooling fan 4. In this embodiment, the rotational speed of the electric motor 5 is increased to maximize the rotational speed of the electric motor 5. Thus, even when either one of the cooling fans 4 is stopped, the other cooling fan 4 can generate cool air in the maximum operation to sufficiently cool the engine cooling water in the radiator 3 and the refrigerant in the condenser 30.

Although the present invention has been fully described in connection with preferred embodiment thereof with reference to the accompanying drawings, it is to be noted that various changes and modifications will become apparent to those skilled in the art.

For example, in the above-described embodiment, the heat exchanging system 2 has both the radiator 3 and the condenser 30; however, the heat exchanging system 2 may have either one of them. In the above-described embodiment, the radiation fins 20a are disposed to be parallel to the air flow direction in the fan shroud 6; however, the radiation fins 20a may be disposed perpendicular to the air flow direction. Further, pin-like radiation fins may be used instead of the plate-like radiation fins 20a. The radiation fins 20a may have notches such as louvers to improve heat-radiating performance of the radiation fins 20a.

In the above-described embodiment, the fan shroud 6 has the air intake port 22; however, the air intake port 22 may be not formed in the fan shroud 6 as shown in FIG. 7. Further, in the above-described embodiment, the control device 8 is attached to the attachment portion 63; however, the control device 8 may be attached to anywhere on the outer surface of the fan shroud 6. In the above-described embodiment, the control device 8 is disposed at the upper center position between the air passages 14a an 14b so that cool air generated by the two cooling fans 4 is blown toward the control device 8. However, the control device 8 may be disposed in the air passage 14b as shown in FIG. 8.

Further, in the above-described embodiment, when either one of the cooling fans 4 has an abnormity and stops operation, the electric motor 5 of the other cooling fan 4 is set at the maximum rotational speed. However, the other cooling fan 4 may be set at a predetermined high rotational speed. In the above-described embodiment, the heat exchanging system 2 employs suction-type cooling fans, and the radiator 3, the fan shroud 6 and the cooling fans 4 are disposed in this order from the vehicle front side to the vehicle rear side. However, the heat exchanging system 2 may employ forcing-type cooling fans, and the cooling fans 4, the fan shroud 6 and the radiator 3 are disposed in this order from the vehicle front side to the vehicle rear side.

In the above-described embodiment, the heat exchanging system 2 has two cooling fans 4 and two electric motors 5; however, the heat exchanging system 2 may have one cooling fan 4 and one electric motor 5. Further, in the above-described embodiment, the attachment portion 63 extends to be parallel to the ventilation surface 3a of the radiator 3; however, the attachment portion 63 may be slightly inclined.

Further, in the above-described embodiment, the heat exchanging system 2 is applied to the radiator 3 for cooling the engine cooling water and the condenser 30 for cooling refrigerant of the refrigerant cycle. However, the heat exchanging system 2 may be applied to an oil cooler for cooling vehicle operation oil (e.g., engine oil), an inter-cooler for lowering an intake-air temperature of the engine 1, and the like.

Such changes and modifications are to be understood as being within the scope of the present invention as defined in the appended claims.