Patent Publication Number: US-7584722-B2

Title: Vehicle engine system

Description:
FIELD OF THE INVENTION 
     The present invention relates to an engine system for a vehicle, such as an agricultural or industrial utility vehicle. 
     BACKGROUND OF THE INVENTION 
     Agricultural or industrial utility vehicles have an engine system which includes an internal combustion engine, a cooler of a cooling circuit, a generator and a fan. The fan moves air through the cooler and is disposed adjacent to the cooler. The fan, the engine and the cooler are disposed in an engine compartment. Consequently, the fan could be disposed between the cooler and the engine or on that side of the cooler which faces away from the engine. In the latter case, the fan could be driven via a shaft which at one place is led through the cooler. The generator can be mechanically driven by the engine. The generator can be mechanically driven from a side of the engine which is other than that which faces the cooler. With the generator, electrical energy or electric power can be generated. 
     Engine systems of this type are known and used in passenger vehicles. In addition, these engine systems are commonly found in agricultural or industrial utility vehicles. However, at low driving speeds, high mechanical outputs must be engendered, for example in farm work with a tractor or in earth works with construction machinery. It is therefore necessary for a sufficient quantity of air to be moved constantly through the cooler with the aid of the fan. The output of the fan drive must therefore be sufficient to enable the engine to be sufficiently cooled even at low driving speeds. 
     Cooler fans are usually driven via a belt drive by the crankshaft of the engine. Consequently, a belt drive is normally mounted on the side of an engine which faces the cooler. With a belt or other mechanical fan drive, the cooler, because of the direct belt clutch, always has a rotation speed which is dependent on the speed of the engine, and the fan rotation speed cannot be tailored to the instantaneous cooling capacity requirement of the cooler. Fan speed could be varied with a belt adjusting gear mechanism between the belt pulley of the engine and the belt pulley of the fan. Such a solution, however, is costly and takes up a considerable installation space and is prone to repair, and involves a higher number of components. 
     Cooler fans in vehicles generate the air flow necessary to remove heat from the cooler or cooler element. The systems are designed for the so-called worst case, i.e. the operation of the vehicle under high load at low speeds and ambient temperatures. As already noted, the cooler fans are usually mechanically driven via a belt drive by the crankshaft of the vehicle. In order to reduce the drive output, a so-called Visco clutch, i.e. an element for the temperature-dependent rotation speed setting, is used. The rotation speed setting can be made solely in the “reduction” direction, i.e. the rotation speed of the fan is directly dependent on the rev speed of the engine, or less or zero if the Visco clutch is disengaged. This is based on the working principle of the generation of Viscous slip. A further possibility consists in the use of electromagnetically operated clutches. 
     Common to all previously used methods in the field of mechanical drives is the sole facility to reduce the rotation speed relative to that which would be produced by the transmission ratio of the belt drive. Hydrostatic drives can both reduce and increase the fan rotation speed. Their controllability, the usage characteristics at low temperatures, the small rotation speed adjustment range and unsatisfactory efficiency levels at higher rotation speeds constitute the associated drawbacks. 
     Electric fan drives are used in the automotive field. There are both two-point controller version (on/off), and rotation-speed-controlled drives in vehicles with high cooling capacity requirement. The fan drive capacities which are necessary in these vehicles amount to about 5-10% of the rated capacity of the engine and give rise to considerable requirements in terms of installation spaces and costs. Particularly, the direct drive version (i.e. the fan motor drives the fan without interposed gear mechanism) requires installation spaces which are not available in conventional engine compartments. 
     To use an electric fan drive in a utility vehicle, it is necessary to place the electric machine or motor in as favorable a position as possible. The volume of an electric motor is governed by the mechanical torque to be generated. Based on the power density, an electric motor offering the highest possible rotation speed is preferable. Engine compartments which are conventionally designed to drive the fan mechanically by the crankshaft via a belt drive do not permit the positioning of a direct-driving electric motor. A design alteration to the engine solely for this reason alone is out of the question. 
     SUMMARY OF THE INVENTION 
     Accordingly, an object of this invention is to provide an engine system wherein the fan is operable at a rotation speed which is tailored to the instantaneous cooling capacity requirements of the cooler or of the cooling system of the engine and is thus adjustable independently of the rev speed of the engine. 
     These and other objects are achieved by the present invention, wherein a vehicle engine system includes a fan driven by an electric motor powered by an engine driven generator. 
     Usually, a dynamo, such as an electric generator, is driven by a belt drive and a belt pulley on the power take-off of the engine, and is thus located in the engine compartment on or adjacent to the side of the engine which faces the cooler. This is because the same belt normally drives both the generator and the fan. In a manner according to the invention, the electric generator is mechanically driven from a side of the engine which is other than that which faces the cooler. The generator could be a crankshaft generator as described in DE 10 2004 052 023, where the generator is disposed on that side of the engine which faces the gearbox downstream of the engine. The rotor of the generator is driven by the crankshaft of the engine, with which the gearbox and the traveling drive are also driven. This crankshaft generator is a asynchronous machine, which generates alternating current of a frequency which is dependent on the instantaneously speed of the engine. This current is converted to direct current by means of an AC/DC converter and is fed to a direct-current intermediate circuit. When an electric machine is operated with alternating current, between the direct-current intermediate circuit and the electric machine, a DC/AC converter should be provided, with which the direct current is converted into alternating or rotary current of appropriate frequency. 
     With at least a part of the current generated by the generator, an electric motor can then be driven, which in turn mechanically drives the fan. The motor is positioned in the engine compartment on or adjacent to a side of the engine which faces the cooler, such as where the conventional generator is usually mounted. 
     The electric motor could have an output shaft which mechanically drives the fan. Usually the rotor of the electric motor is rigidly connected to the output shaft. However, the rotor of the electric motor could be connected to the output shaft via an intermediate gearbox. This would be advantageous when the electric motor is operated at a very high rotation speed, though the initial rotation speed at which the fan is driven is designed to be less than the initial rotation speed of the electric motor. 
     Preferably, the electric motor is disposed in the engine compartment so that its output shaft is near the mechanical power take-off of the engine. Such a mechanical power take-off could be, for example, a free end of the engine crankshaft, upon which is mounted a belt pulley. The belt pulley drives the cooler fan, a coolant pump, an engine oil or gearbox oil pump, a generator and/or an air compressor. Since the fan drive shaft is usually disposed near the belt pulley, yet the fan is not driven by the belt directly from the engine, the electric motor and its output shaft are expediently likewise disposed in this region, so that the fan can be mechanically driven by the electric motor. Consequently, it is not necessary to alter the engine with an additional or modified mechanical power take-off. In addition, the mounting site of the cooler and the fan, as well as the other auxiliary units, can remain unaltered. 
     In one embodiment of the present invention, the electric motor could be located on the engine where normally a generator is located. 
     Preferably, further consumer units, such as an air compressor, can be mechanically driven with the electric motor. These consumer units can also be operated as a function of the instantaneous or currently prevailing power demand of the vehicle. 
     A power electronics component commanded by a control device is provided to enable the electric motor and/or of the generator to be efficiently commanded or controlled in accordance with the currently prevailing load state of the vehicle. The power electronics component controls the rotational direction, rotation speed and/or the torque of the electric motor as commanded. 
     In a preferred embodiment, at least one temperature sensor is provided to sense the temperature of a component, the coolant or oil. The temperature sensor generates a signal which can be transmitted to a control device. 
     Preferably, the fan is connected to the motor by a flexible drive, such as a belt and pulley driven by an engine crankshaft. In other words, the fan could be mounted just as before and at the traditional mounting site usually provided, but driven, not by a belt via the belt pulley of the engine, but rather, via a belt driven by a belt pulley of the electric motor. Thus, only the belt drive for the water and/or oil pump has to be modified so that the fan is no longer driven with this belt drive. The flexible drive could have a belt, a V-belt, V-ribs, a toothed belt or a chain. 
     The electric motor can be fitted in place of the dynamo and a belt drive can be provided to drive the fan, provided that the generator powering the electric motor is fitted at a different mounting site. The construction of the engine compartment components can thereby be modular and economical, particularly in the mass production of traditional vehicles and vehicles having a fan driven according to the invention, for this is feasible with a small number of different parts. 
     An intermediate gearbox could be provided between the electric motor and the fan. The transmission ratio can be adjusted to adjust the rotation speed of the fan, so that the electric motor can be operated at a higher rotation speed and the fan at a lower rotation speed. Since the costs of a direct-driving electric motor, i.e. running at fan rotation speed (with correspondingly lower rotation speed), are higher than those of a machine of equal power at a higher rotation speed level, the combination of an electric motor at high rotation speed level in conjunction with an intermediate or transmission gearbox can yield a reduction in costs. The transmission ratio could in this case lie—as also, however, in a pure belt drive of the fan of the electric motor with predefined transmission ratio—within similar ranges to those with the dynamo, i.e. roughly 1:3 to 1:4. The relatively high rotation speeds which are thereby obtained advantageously lead to a compact machine design and, in relation to a direct drive, correspondingly reduced costs for the electric motor. Since the rotation speeds and the size of the parts rotating within the machine are roughly equivalent to those of a dynamo, no drawback with regard to service life is expected. 
     As already indicated, the generator could be an asynchronous alternating current generator. A direct-voltage converter could convert the alternating voltage into DC voltage. The converted DC voltage could be fed to a DC intermediate circuit. 
     A frequency converter, preferably part of the power electronics unit, could covert the DC voltage (for example of the DC intermediate circuit) into AC voltage such that the electric motor can be operated at a variable predefined rotation speed. This rotation speed can then be chosen such that the expected air movement through the cooler, generated by the fan, yields a predefined necessary cooling capacity. Ultimately, the rotation speed of the electric motor can be commanded according to at least one of the above-stated command strategies. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The sole FIGURE is a schematic diagram of a vehicle engine system embodying the invention. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     The single FIGURE shows an engine system  10  for an agricultural utility vehicle, such as a tractor (not shown). The engine system  10  includes an internal combustion engine  12 , a cooler  14  of a cooling circuit  17 , a generator  18  and a fan  20 . The engine  12 , the cooler  14  and the generator  18  are disposed in an engine compartment  15  of the tractor. The cooling circuit  17  includes lines  16  which convey engine coolant through the engine  12  and the cooler  14 . 
     Fan  20  moves air through the cooler  14 , as indicated with the arrows  22 . Since the fan  20  is disposed between the cooler  14  and the engine  12 , the fan  20  sucks in air from that side of the engine  12  which faces away from the cooler  14 . 
     The generator  18  generates electrical energy and is mechanically driven by the crankshaft  24  of the engine  12 . The generator  18  is disposed on the side of the engine  12  which faces away from the cooler  14 . Preferably, the generator  18  is a crankshaft generator. 
     According to the invention, an electric motor or motor  26  is driven or powered by the electrical energy generated by the generator  18 . The motor  26  in turn mechanically drives the fan  20 . The motor  26  has an output shaft  28 , via which the fan  20  can be mechanically driven. 
     The motor  26  is disposed in the engine compartment  15  such that the output shaft  28  of the motor  26  is disposed in a region of the engine compartment  15  which has a mechanical power take-off  30  of the engine  12 . The mechanical power take-off  30  is a free end of the engine crankshaft, which is connected to a belt pulley  32 . The motor  26  is disposed at an installation site on the engine  12  where a traditional dynamo is usually provided. In addition to the fan  20 , the motor  26 , may mechanically drive further consumer units, such as a compressed-air compressor  34 . 
     The system also includes a power electronics unit  36 . Electric current generated by the generator  18  is fed to the power electronics unit  36  via the power supply line  40 . The power electronics unit  36  is connected to generator  18  via the power supply line  42 , and is commanded by a control device  38  so that the rotational direction and/or the rotation speed and/or the torque of the motor  26  can be commanded. 
     A temperature sensor  44  senses the temperature of the coolant of the cooling circuit  17  and generates electric signals, which are dependent on the detected temperature and which are fed to the control device  38  via the line  46 . A command strategy is provided such that the rotation speed of the motor  26  is controllable as a function of the coolant temperature of the cooling circuit  16 . 
     The oil cooler  48  cools engine oil and receives coolant (in this case a water-glycerol mixture), so that the oil cooler  48  is an oil-water heat exchanger. A charge-air cooler  50  of the engine  12  is also provided. Both the oil cooler  48  and the charge-air cooler  50  are cooled with coolant of the further cooling circuit  53 . The further or secondary cooling circuit  53 , with connecting lines  52 , has an air-coolant heat exchanger  54 , which is disposed on that side of the cooler  14  which faces away from the fan  20 . In a further control or adjustment strategy, the rotation speed of the motor  26  is commanded as a function of the oil temperature of the engine  12 . The oil temperature is sensed by temperature sensor  56 , which also generates an electric signal which is dependent on the detected temperature and which is fed via the line  58  to the control device  38 . 
     In the command of the rotation speed of the motor, the control or adjustment strategy of the control device  38  also takes account of the instantaneous power demand of the compressed-air compressor  34 . 
     The power electronics unit  36  has a temperature sensor  62 , which generates an electric signal which is dependent on the detected temperature and is transmitted to the control device  38 . The rotation speed or the torque of the motor is commanded also as a function of the temperature of the power electronics  36 , to be precise such that the power electronics  36  cannot get overheated. 
     The fan  20  and the compressed-air compressor  34  are driven via flexible means  64  by the motor  26 . The flexible drive  64  is configured in the form of a V-belt. The fan  20  has a belt pulley  66 . The belt pulley  32  of the mechanical power take-off  30  of the engine  12  drives via a belt  68  the oil pump  70 . Although not shown in the Figure, the belt pulley  66 , and hence the fan  20 , could be arranged so that it could be driven by a belt driven by the belt pulley  32  of the engine  12 . 
     The generator  18  is preferably an alternating current generator. The power electronics unit  36  has a direct-voltage converter (not shown), with which the alternating voltage generated by the generator  18  is convertible into direct voltage. The power electronics unit  36  includes a frequency converter (not shown) which converts the direct voltage into alternating voltage such that the motor  26  can be operated with a variable pre-definable rotation speed. 
     The engine  12  drives a gearbox or traveling drive  60  of the utility vehicle. Gearbox oil of the gearbox  60  could be connected up to (not shown) and cooled by a cooling circuit, such as the further cooling circuit  52 . 
     A working tool (not shown) adaptable to the tractor includes an electric consumer unit  72  which is supplied with electric current by the power electronics unit  36  via the line  74  when the working tool is adapted to the tractor. To this end, a plug connection  76  is provided between the vehicle and the consumer unit  72 . 
     The rotation speed and/or the torque of the electric motor can be controlled as a function of the coolant temperature of the cooling circuit, or a further cooling circuit. If the coolant temperature is higher, the rotation speed of the fan is increased accordingly. This allows a command and control system which conforms to requirement and is tailored to the currently prevailing load state of the vehicle cooling system. 
     Additionally or alternatively, the rotation speed and/or the torque of the electric motor could be controllable as a function of the oil temperature of the engine, of the drive train and/or of a vehicle hydraulics. This allows a command and control system which conforms to requirement and is tailored to the currently prevailing load state of the engine and/or of the drive train or of the components of the vehicle hydraulics. 
     The rotation speed and/or the torque of the electric motor could also be controlled as a function of the power demand of further electrical consumer units of the vehicle, such as an air-conditioning system. In this case, a corresponding command system for the generator can also be incorporated. For example, the electric power supplied to the fan could be reduced where a further electrical consumer unit has to be powered and the coolant temperature of the cooling circuit permits this. 
     Particularly in the case of an agricultural utility vehicle, for instance a tractor, a working tool coupled to the utility vehicle could be at least partly electrically operated. An electrical consumer unit of the working tool could be powered by the generator of the utility vehicle. Also, the rotation speed and/or the torque of the electric motor could be controlled as a function of the power demand of an electrical consumer unit of such a working tool, such as a drilling or sowing machine. 
     In addition, the rotation speed and/or the torque of the electric motor could be controlled as a function of the demand of a air compressor, or as a function of the temperature of the coolant of a secondary cooling circuit. This is particularly of interest when the fan is used to move air through a cooler of the secondary cooling circuit. In comparable manner, the rotation speed and/or the torque of the electric motor could therefore be actuated as a function of the temperature of a charge-air cooler and/or the coolant temperature of a cooling circuit. 
     Such a control system could also respond to the operating temperature of the power electronics or of the power electronics unit, so that the rotation speed and/or the torque of the electric motor can be commanded as a function of the temperature of the power electronics. 
     While the present invention has been described in conjunction with a specific embodiment, it is understood that many alternatives, modifications and variations will be apparent to those skilled in the art in light of the foregoing description. Accordingly, this invention is intended to embrace all such alternatives, modifications and variations which fall within the spirit and scope of the appended claims.