SE540675C2

SE540675C2 - Control system for an alternator installation, primarily intended for driving a cooling fan in a vehicle

Info

Publication number: SE540675C2
Application number: SE1550010A
Authority: SE
Inventors: Hall Ola
Original assignee: Scania Cv Ab
Priority date: 2015-01-09
Filing date: 2015-01-09
Publication date: 2018-10-09
Also published as: DE102015016342A1; SE1550010A1

Abstract

The invention relates to a control system (1), mainly intended for use in a vehicle with momentarily high need for cooling of the vehicle combustion engine (2) and for controlling an alternator installation primarily for driving one or more cooling fan(s)(4) in the vehicle, comprising at least one alternator (8a,b), at least one battery (6) and at least one cooling fan (4 ) . The invention is achieved by that a switch (14) is arranged to, at high engine load or high cooling need, connect the alternator (8a) directly to the fan(s) and disconnect the alternator (8a) and the fan(s) (4) from the general electrical system (1) in the vehicle and its consuming components/users (7), in such a way that the alternator (8a) may be arranged to drive the fan(s) (4) at a higher voltage level than the general electrical system (1).

Description

CONTROL SYSTEM FOR AN ALTERNATOR INSTALLATION, PRIMARILY INTENDED FOR DRIVING A COOLING FAN IN A VEHICLE TECHNICAL FIELD The present invention relates to a control system for an alternator installation primarily preferably for driving a cooling fan in a vehicle. The invention particularly relates to a control system intended for a heavy commercial vehicle with varying cooling need due to the actual driving conditions and possible momentarily high need for cooling of the vehicle combustion engine. The invention also relates to a vehicle equipped with such a control system.

BACKGROUND ART Most passenger cars on the market today are equipped with electric engine-cooling fans while heavy commercial vehicles like trucks and/or buses are often cooled by a clutch—driven fan system or a hydraulic driven fan system. This is due to the fact that trucks and/or buses are intended to pull/drive a vehicle with significant weight. When towing a heavy trailer or bus uphill, the engine's developed power can be a significant fraction of the rated power for quite a period of time, which means that a lot of heat has to be rejected.

Due to cost, weight and robustness electrical fans are a desired alternative. Electric fan systems, powered by the vehicles electrical system, provide good idle cooling but still have problems to provide the required fan power/speed under more heavy cooling conditions. The fan has to develop high mechanical power to be able to cool the one or more coolers located in the vehicle and to carry away all hot air. Using 24 volt systems means that very large currents have to be lead through the cables to the fan. The efficiency of the fan(s) and the alternator(s) varies significantly with load and speed. Since a large current have to be lead through the electrical cables from the battery and/or the alternator to the fan in the vehicle, electrical cables with large diameters have to be used. These cables are expensive, take a considerable space and are difficult to install in the vehicle.

Known solutions to solve these problems are often complex and contains many components, which makes them expensive to install.

The company Bosch has e.g. experimented with using variable voltage and a dedicated alternator for the operation of the fan. In this way the efficiency of the alternator and the electric motor of the fan are kept as high as possible.

Locking the electric system to a specific voltage level is not desirable. When the voltage is increased, more power is available from a single alternator. Up to 40 volt may be obtained from a normal 12 volt alternator according to the description of Bosch, please see SAE paper 1999-01-0242.

Electric fans have generally so far produced too poor cooling performance, or have used very high currents to be a suitable alternative. And the alternator capacity is too limited when the voltage in the system is locked to 24 volt. One possibility is to install a further alternator.

It is desirable to use electric fans but it is at the same time not desirable to install a further alternator, if not necessary, and it is desirable to avoid high currents in the powering system.

Different solutions to this problem exist in the market but none of these prior known systems illustrates any alternator installation that uses cost effective components and reasonable currents for driving the fan(s).

SUMMARY OF THE INVENTION One object of the present invention is to solve the above mentioned problems and to provide an alternator installation and a simple control system for the generation of maximal electric power to a cooling fan in order to meet any cooling need and at the same time keep the used currents as low as possible.

Another object of the invention is to provide a control system that does not need installation of new, heavy or space consuming components, like a new electric fan, a new alternator or a new complex electric system.

Another object of the invention is therefore to design a control system containing very few components.

A further object of the invention is that the control system should offer a more precise control of the fan speed in relation to the cooling need of the vehicle engine.

A further object of the invention is that installation of the control system should be easy.

These and further objects and advantages are achieved by the invention by an alternator control system designed in accordance with the features recited in claim 1.

The invention relates to a control system for cooling a vehicle engine, preferable a combustion engine, and where the system is equipped with one or two alternators. If two alternators are used, one of them could be adapted to produce the general voltage level used in the vehicle, such as 24 volt, and the other alternator could be at least temporarily adapted to produce a higher voltage and power level that the cooling fan momentarily needs, in order to achieve the best possible production efficiency in that alternator and during a specific time period.

Many buses are already equipped with two alternators. If one of the alternators is used and switched between the general voltage system for charging the batteries and providing all the electrical components in the vehicle with electricity, and the voltage level that gives the best efficiency when producing power to the fan(s), a compromise is used. The fan(s) can normally run on 24 volt, but since the cooling need may be very high one alternator could be decoupled from the battery voltage and just drive the cooling fan(s), and then at a higher voltage than 24 volt, thereby reducing the current in the cables. Also in another low load case, if the needed electric power is low (e.g. 24 volt), the alternator may advantageously drive the fan(s) with a lower voltage. The fan(s) can as an alternative be driven with a low voltage with pulse width modulation at 24 volt, if the 24 volt power need is high in the electrical system.

An alternator normally produces a higher efficiency working at a higher voltage as the rotational speed of the alternator increases. This is completely in line with the cooling need of the vehicle, as the cooling need increases with increasing speed of the vehicle. The cooling need and the alternators best operating point are therefore following each other in a natural way.

The electric power may be taken out in front of the rectifier diodes and the fan motor should than be a motor adapted for an alternating current.

Advantages of the inventive solution are that it offers: - significantly more efficient idle airflow - more precise control of engine coolant temperature and a/c head pressure - lower noise levels at equal airflow - fuel mileage improvements - start-up noise is eliminated and improved acceleration - that power is available for electric cabin heating This is achieved by means of existing alternators and preserved capacity to charge batteries except in time periods when extreme cooling is needed. With a constant 24 voltage the main part of the total alternator capacity would be used by the fans than would be the case with a variable voltage. This is due to the fact that the alternator produces more electric power at higher voltage than at lower voltage.

A main advantage with the present invention is that an electric fan can be used and at the same time it will be possible to keep the alternator size down and the current used can be limited. This will save space and weight in the vehicle.

Further features and advantages of the invention will be apparent from the following, more detailed description of the invention and the accompanying drawings and the claims.

BRIEF DESCRIPTION OF THE DRAWINGS The invention is described below in some preferred embodiments illustrated in the accompanying drawings.

Figure 1 is a block diagram schematically illustrating a combustion engine system including an electric system with two alternators for driving a cooling fan according to the invention.

Figure 2 is a principle block diagram illustrating the key components in the system according to the invention.

Figure 3 is a diagram illustrating the fan speed as a function of the coolant temperature according to the invention.

Figure 4 is a block diagram as illustrated in figure 1 schematically showing an electrical system in a vehicle comprising only one alternator.

Figure 5 is a further block diagram similar to figure 3 but including a transformer for charging the battery even during high cooling need.

DESCRIPTION OF PREFERRED EMBODIMENTS The present invention relates to an electrical system for controlling the current/voltage of one or more cooling fan(s) in a vehicle.

Figure 1 is a block diagram schematically illustrating a combustion engine system in a heavy commercial vehicle such as a truck or bus including an electric control system 1 according to the invention.

The engine system illustrated is typically equipped with an combustion engine 2, here a 6-cylinder diesel engine, one or more radiators 3a-c and a fan 4 for cooling the engine 2 via the radiators 3a-c, at least one battery 6, general system of electrical components/users 7 in the vehicle electrical system I, at least one alternator 8a,b, preferably one first and one second alternator 8a,b for charging the battery 6 and providing electrical power to the general system of electrical consuming components/users 7, an AC-system (not shown) with a separate radiator 3a for climate control of the cab or passenger compartment, a 24 volt regulator 10 intended for controlling the first alternator 8a and a main control unit II, such as an ECU.

The ECU 11 receives signals from different sensors 12a-c within the electric control system 1 such as sensors for pressure, temperature, voltage etc. The coolant temperature is for instance measured by a sensor 12b at the inflow side of the main radiator 3c. The ECU 11 sends signals for controlling e.g. the speed of the fan 4, increasing the fan speed when the temperature of the coolant increases and reducing the fan speed when the temperature of the coolant decreases.

The control system 1 is, according to the invention, also equipped with a second voltage regulator 13 and an electronic switch 14. The second voltage regulator 13 is adapted to control the voltage from the second alternator 8b. The first alternator 8a is according to the invention adapted to drive the fan 4 at high engine load with high cooling need for the engine. The switch 14 is electrically arranged to in a first position connect the/all alternators 8a,8b to the general electrical system 1 including the electrical consuming users 7 as well as the battery/batteries 6. In the second position of the switch 14 the first alternator 8a and the cooling fan 4 is electrical disconnected from the second alternator 8b, the main part of the general electrical system 1 and its consuming users 7 as well as from its battery/batteries 6. The first alternator 8a and the cooling fan 4 is, in this second position of the switch 14, electrically connected to each other whereby the first alternator 8a solely drives the cooling fan 4.

By using one of the alternators 8a temporarily only for driving the cooling fan 4 this alternator 8a can be controlled to deliver electrical power, at the most efficient combination of current/voltage, e.g. vary the voltage to the best point of efficiency for that specific alternator 8a and the specific/current circumstances. This is done by first disconnecting the first alternator 8a from the general electrical system 1,7, by means of the electronic switch 14. This means that the first alternator 8a will solely deliver electrical power to and drive the cooling fan 4, meanwhile the second alternator 8b will continue to deliver electrical power to the general electrical system 1,7, including charging the battery/batteries 6, but do not provide any electric power to the cooling fan 4.

In this way the voltage from the first alternator 8a could be controlled, by the ECU 11 and the voltage regulator 10, to be increased from 24 volt up to as much as 60 volt (but is of cause not limited to this voltage level) and the first alternator 8a will thus deliver maximal power at a still reasonable current. By keeping the current as low as possible in the system, electric cables 15 with less area could be used, thereby saving space, weight and cost for the cables and for installing the cables.

Using the first alternator 8a only for feeding the cooling fan 4 means that the charging of the battery/batteries 6 will decrease, but this is only temporarily. When the cooling need decreases in the vehicle the first alternator 8a will again be switched/connected to the general electrical system 1,7 and will deliver power to it, and will thereby begin to charge the battery/batteries 6 again. The battery/batteries 6 and alternators 8a,b are both used for driving the fan 4 at normal cooling needs and the second alternator 8b remains connected to the general electrical system 1,7 during the hole procedure Figure 2 is a principle block diagram illustrating only the key components in the system according to the invention. The first alternator 8a is connected electrically to the switch 14 which in turn is connected to the fan 4. In one position of the switch 14 the alternator 8a is directly connected to the fan 4 and in the other position both alternators 8a,b is connected to the general electrical system 1 of the vehicle, and to its battery 6 and consuming components 7. When directly connected to the fan 4 the first alternator 8a is arranged to produce electrical power at a voltage different from the general voltage in the vehicles general electrical system 1 by means of a first voltage regulator 10.

Figure 3 is a diagram, a histogram, illustrating the fan 4 speed and the voltage across the first alternator 8a as a function of the coolant temperature, for a normal vehicle, and according to the invention. In the diagram line 17 is the voltage over the first alternator 8a, 16 is the voltage over the second alternator 8b, 18 is a histogram showing the time with a certain temperature and 19 is the fan speed expressed in % of maximal speed. The values in the diagram may of course be varied based on actual demands and design limits in the specific case.

As can be seen in the diagram the voltage from the first alternator 8a starts to increase at a coolant temperature of approximately 95 degree Celsius while the voltage across the second alternator 8b is maintained at 24 volt. Voltages over 24 volt is seldom used which means that it is not reasonable to use a dedicated alternator only for driving the cooling fan 4 all time. The risk that the battery/batteries 6 will be discharged during the short period of time the first alternator 8a only drives the cooling fan 4 is therefore minimal.

In surrounding conditions with high ambient temperatures, and warm climate, the histogram will shift upwards and in cold climates, the histogram will shift downwards, down to the opening temperatures for the thermostat (not shown) in the cooling system.

Normally the control system 1 uses a coolant temperature for controlling the fan speed but it is also possible to use the AC-pressure, e.g. in such a way that for instance 10 bar gives no fan speed and 17 bar gives full fan speed and the relationship there between will be approximately linear. The preset values may of course be possible to vary depending on the operating conditions in the specific design case.

It is also possible to use charge air temperature as parameter for controlling the fan speed (up to approximately 50 C° or 15K over the ambient temperature). Also these values may of course be varied.

The unit which demands/needs the highest fan speed, highest cooling, "wins" and controls the fan speed. Other possibilities are if the air in the engine compartment is too hot and therefore have to be ventilated etc.

As a truck often has one alternator and a bus often has two alternators it may also be possible to use a larger battery in for example a truck, and to use only one alternator in such a way that the main part of the electrical components 1,7 in the vehicle may be provided electric energy by the battery 6, when the cooling load is high, as long as the voltage from the alternator 8a is higher than the battery 6 voltage. During this period the alternator 8a is only connected to and driving the fan(s) 4.

Figure 4 is a block diagram as in figure 1 schematically illustrating an electrical system 1 in a vehicle comprising only one alternator 8a. In this case the only one alternator is connected electrically directly to the fan(s) 4, and disconnected by the switch 14 from the general electrical system 1 with its predetermined voltage level 24 volt in the vehicle, when the cooling need is high. When the alternator is solely connected to the fan 4 its voltage could be varied by the voltage regulator 10 and increased to a value above 24 volt.

Figure 5 is a further block diagram, similar to figure 3, schematically illustrating an electrical system 1 in a vehicle comprising one alternator 8a and one transformer 20. The transformer 20 is connected between the alternator 8a and the vehicle battery 6 and used to charge the battery 6 and prevent rapid drainage of battery 6 power, when the alternator 8a is disconnected from the battery 6 not charging it and works at a higher voltage than the normal vehicle voltage of 24 volt.

It is also possible, in the case and during the time periods that the alternator 8a produces a very high voltage, this voltage is transformed down via the transformer 20 to 24 volt for charging the battery 6 and providing the electrical system 1 and the consuming components 7 with electrical power.

The above description is primarily intended to facilitate the understanding of the invention. However the invention is of course not in any way restricted to only the disclosed embodiments, but many possibilities to modifications would be apparent to a person skilled in the art within the scope of the invention without departing from the basic idea of the invention as defined in the appended claims.

Claims

1. Control system (1), intended for use in a vehicle with momentarily high need for cooling of the vehicle combustion engine (2) and for controlling an alternator installation primarily for driving one or more cooling fan(s)(4) in the vehicle, comprising at least one alternator (8a,b), at least one battery (6) and at least one cooling fan (4), characterized in that - a switch (14) is arranged to, at high engine load or high cooling need in the vehicle, connect the alternator (8a) directly to the fan(s) in the vehicle working at a general predetermined voltage level, in such a way that the alternator (8a) may be arranged to drive the fan(s) (4) at a higher voltage level than the general electrical system (1), and - a voltage regulator (10) is arranged to control the alternator (8a) to produce electrical power, at a more efficient combination of current and voltage than what is possible at the predetermined voltage level in the general electrical system (1) - the switch (14) is arranged to connect the alternator (8a), when working at a higher voltage level, also to a transformer (20) in order to provide the battery (6) and/or the general electrical system (1) in the vehicle with electric energy at the predetermined general voltage level in the system (1).

2. Control system (1) according to claim 1, characterized in that the alternator (8a) is arranged to produce a variable voltage (17) in order to produce electrical power at the most efficient combination of current and voltage.

3. Control system (1) according to any of the preceding claims, characterized in that the alternator (8a), at high load and high demand/need for cooling, is arranged to work at a voltage level (17) substantially above the normal voltage level (16) in the general electrical system (1) in the vehicle.

4. Control system (1) according to any of the preceding claims, characterized in that the alternator (8a), at high load and high demand for cooling, is arranged to work at a voltage level (17) of up to 60 volt.

5. Control system (1) according to any of the preceding claims, characterized in that the switch (14) is an electronic switch controlled by a control unit (11) in the vehicle, such as an ECU.

6. Control system (1) according to any of the preceding claims, characterized in that the switch (14) is arranged to disconnect a second alternator (8b) from the cooling fan(s) (4) when the cooling need is large.

7. Control system (1) according to claim 6, characterized in that the second alternator (8b) is arranged to remain connected to the general electrical system (1) in the vehicle powering the battery (6) and/or the users (7) in the general electric system (1).

8. Method for improving the cooling system in a vehicle with momentarily high need for cooling, comprising controlling the connection of at least one alternator (8a), characterized in the following method steps, - connecting electrically the alternator (8a) directly to the fan(s) (4), in the vehicle working at a predetermined voltage level, in such a way that the alternator (8a) may be arranged to drive the fan(s) (4) at a higher voltage level, and - producing electrical power to the fan(s) (4) at a more efficient combination of current and voltage than what is possible at the predetermined general voltage level (16) in the vehicle - connecting the alternator (8a), when working at a higher voltage level, to a transformer (20) in order to provide the battery (6) and/or the general electrical system (1) in the vehicle with electric energy at the predetermined general voltage level in the system (1).

9. Vehicle provided with a control system (1) according to any of the claims 1-7.