Abstract:
A ventilation device of an agricultural vehicle such as a combine, forage harvester or tractor having an engine ( 10 ) and a cooling device ( 12 ) for cooling the engine ( 10 ) and/or additional parts to be cooled that are in a heat conducting relationship. The ventilation device comprises a fan ( 20 ) a fan drive ( 18 ) and a control system ( 26 ) connected to the fan drive ( 18 ) to regulate the feeding rate of the fan ( 20 ). The control system ( 26 ) is arranged to control the fan drive ( 18 ) in the most energy-efficient way while making allowance for the amount of ambient air required by the cooling device ( 12 ) and the drive power requirements of the fan ( 20 ) using a flat logic (fuzzy control).

Description:
BACKGROUND OF THE INVENTION 
     The invention pertains to a ventilation device of a vehicle such as an agricultural vehicle, which has an engine and a cooling device, with which the engine and/or additional parts to be cooled are in a heat conducting relationship, while the ventilation device comprises a fan with a fan drive, by means of which ambient air is fed to the cooling device, and a control system connected to the fan drive, which is provided to regulate the air feed rate of the fan. 
     Known from U.S. Pat. No. 4,828,088 A is a ventilation device for use in trucks or automobiles, in which a control system with sensors for the temperature of the vehicle engine and the respective speed, is provided. By means of a viscous coupling, the rotary speed of a fan is adjusted in such a way that the engine is adequately cooled but the lowest possible energy requirement and a minimal noise generation are achieved. 
     Disclosed in U.S. Pat. No. 5,584,371 A is a similar ventilation device. Here the speed of a fan is regulated in relation to the temperature of the coolant and the rotary speed of the engine. In the normal operating range, the rotary speed of the fan is proportional to the rotary speed of the engine. 
     In the field of self-propelled harvesters, a tendency to ever-increasing engine power can be observed. Since the speed of these machines is often very low during the harvesting process and the rotary speed of the engine is comparatively high, suitable measures must be taken to cover the cooling output requirements. In addition, cooling output must be provided for a number of other systems. Consequently, the capacity for heat dissipation is, as a rule, made available by the air feeding capacity of large fans. 
     Inasmuch as known control devices for rotary speed of fan have not proven to be expedient in actual practice, e.g., due to high shifting frequencies and uncontrolled acceleration occurrences, fixed fan drives are generally in use at the present time. However, as a rule, the output requirement of fan increases with the square of drive motor speed and, depending upon the fan type, reaches as high as 10% of the total engine output at high engine rotary speeds. In many cases, e.g., in roadway driving—which can constitute as much as 30% of the machine operation—only a part of this fan output is really needed, so that the energy consumption of the harvester is unnecessarily high. 
     The problem underlying the invention is to make available an improved ventilation device. 
     SUMMARY OF THE INVENTION 
     The solution according to the invention makes allowance for two essential values as initial parameters: the requirement of the cooling device for ambient air and the feeding rate of the fan. In the light of these parameters, the feeding rate of the fan is adjusted in such a way that it is operated in a manner that maximizes energy-savings yet covers the cooling requirement. Thus, in keeping with the invention, allowance is made by the control system for both the requirement of the cooling device for ambient air and the operating energy of the fan. In particular, the control system makes it possible to execute the acceleration operations of the fan in a controlled manner. 
     In this way, an energy-saving ventilation device which lowers the fuel consumption and the operating costs of the vehicle is obtained. Furthermore, the disturbing noises of the fan, e.g., when the vehicle is operated on the roadway, are reduced to a minimum level. By virtue of the control system, it is possible to install a given fan on vehicles of various cooling requirements, since the feeding rate of the fan commensurately controls the respective requirement. Thereby the number of different parts which must be made ready for the production of various vehicles is reduced. 
     The control system specifically allows for the load moment of the fan dependent upon the quantitative feed, i.e., the relationship between the driving torque (or the driving power) and the respectively fed quantity of air. In addition, the moment of inertia of the fan is allowed for, which represents the energy for accelerating the fan to the rotary speed corresponding to the respective quantitative feed. Thus the control system is charged with information as to how much energy is required to accelerate the fan to a certain rotary speed (representing a certain quantitative feed). In this manner it is possible to make allowance for the “costs” of a change, especially an increase, of the feeding rate of the fan, when determining the feeding rate. Unnecessary rotary speed changes, which also place undue mechanical stress upon both the fan and the fan drive, are then reduced to a minimum. Allowance can also be made for the moments of loss of the fan; they are usually due to friction or slipping. With the energy-saving selection of the feeding rate, it is also possible to ensure that the engine does not unnecessarily heat up due to the driving torque build-up required for the fan. 
     It is additionally proposed that the control system calculate the requirement of the cooling device for a predetermined period of time and adjust the fan drive to a constant feeding rate for this period. A reasonable period of time is, e.g., one minute. 
     In order to determine the given requirement of the cooling device for ambient air, the control system can be connected to one or more sensors. In this manner, it is possible to monitor the temperature of the ambient air, the temperature of a coolant of the cooling device, the temperature of a hydraulic fluid and the rotary speed of the engine. Furthermore, the rotary speed or the feeding rate of the fan can be monitored, so that it can be compared with the reference value calculated by the control system and adjusted as necessary. 
     The control system can be equipped with a flat logic. Such logics are known and produce association functions for one or more input variables for the control system and determine, by way of a regulator, output values, with which the feeding rate of the fan is adjusted. 
     The opportunity of designing the feeding rate to be continuous, i.e., infinitely variable, presents itself, although a stepped adjustment would also be plausible, which is realizable, e.g., with a transmission with several gear settings. For the continuous adjustment of the feeding rate, hydraulic transmissions or so-called CVT transmissions (continuous variable transmission) present themselves. The latter are known from the automobile industry and have a drive belt running around two belt pulleys. One of the belt pulleys is conical and the drive belt is so arranged as to be laterally adjustable thereon. A hydraulic drive consists of a pump with an adjustable feeding output and a hydraulic motor. The use of a viscous coupling is also plausible, as described in the US patent documents cited above. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a schematic of a ventilation device according to the invention; and 
     FIG. 2 is a flow chart, according to which the control system works. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     The ventilation device shown in FIG. 1 can be used on a farm machine or an agricultural vehicle, such as a self-propelled forage harvester, a combine or a tractor. An engine  10  of the vehicle is a combustion engine which, as a rule, is the main engine and serves to propel the vehicle, is connected to a cooling device  12  by a coolant input line  14  and a coolant return line  16 . The coolant circulating in the coolant lines  14 ,  16  is, e.g., water. The engine can drive other additional parts, such as material processing mechanisms e.g., threshing or chopping devices, and/or an air conditioner. The heat given off by these mechanisms can be diverted into the ambient air by the cooling device  12  or an additional cooling device located near the cooling device  12 . 
     Ambient air is fed to the cooling device  12  by a ventilation device comprising a propeller-type fan  20 , a fan drive  18  and a control system  26  for the fan drive  18 . The ambient air flows through or around the cooling device  12  and carries the dissipated heat of the engine  10  to the environment. In case additional cooling devices are present for removing the dissipated heat of the additional mechanisms cited above, ambient air is also fed to them by the fan  20 . The mechanical drive of the fan  20  is accomplished by a shaft  24  connected to both the engine  10  and the fan drive  18 . The fan drive  18  can be remotely controlled electronically by the control system  26  via a control system circuit  28  and establishes the rotary speed and therefore the feeding rate, or air flow rate, of the fan  20 . The fan drive  18  can be realized in the form of a viscous coupling or a mechanical CVT transmission, so that the feeding rate of the fan is variable between standstill and a maximum value. The fan drive  18  is connected to the fan  20  by an additional shaft  22 . 
     The control system  26  has a total of five variable inputs. The first input  30  is connected to a sensor  40 , which is located on the fan drive  18  and acquires the rotary speed of the fan  20 . This input  30  serves to monitor whether or not the rotary speed of the fan prescribed by the control system  26  is maintained and can, in case of deviation, provide the operator of the vehicle with a commensurate warning. Alternatively or additionally, the value present at the input  30  can serve as a feedback value for regulating the rotary speed of the fan. 
     The second input  32  of the control system  26  is connected to a sensor  42  for acquiring the rotary speed of the engine  10 . The third input  34  is connected to a sensor  44  for acquiring the temperature of the ambient air, which is normally located near the fan  20  and upstream thereof. The fourth input  36  of the control system  26  is connected to a sensor  46 , which acquires the temperature of a hydraulic fluid circulating in a hydraulic layout driven by the engine  10 . Finally, the fifth input  38  of the control system  26  is connected to a sensor  48 , which acquires the temperature of the coolant of the motor  10  circulating in the coolant lines  14 ,  16 . Thus the control system  26  is provided with information regarding three temperatures, the rotary speed of the main engine  10  and the rotary speed of the fan  20 . Also plausible would be a temperature sensor positioned at the exit from the cooling device  12  and connected to the control system  26 , in order to measure the temperature of the air that has flowed past the cooling device  12 . Another sensor  50  produces an input  52  to the control system  26  monitors the operational status of a material processing device, e.g., a thresher or a chopper device. During a harvesting operation, the necessary cooling capacity is generally greater than during a transport operation, which can be taken into account in the control of the fan drive. 
     With reference to the flow chart depicted in FIG. 2, the functioning of the control system is explained in greater detail below. 
     After the start in step  100  (e.g., after engaging the engine  10 ), the total cooling capacity requirement is determined in step  102 . This consists of the cooling requirements of the component systems (here: the motor  10  and the hydraulic layout). The total requirement is the sum of the cooling capacity requirements of the component systems. Based on the temperature of the coolant (sensor  48  at input  38 ), the temperature of the hydraulic fluid (sensor  46  at input  36 ) and the reference or maximum temperatures for the coolant and the hydraulic fluid stored in a memory in the control system  26 , the respective difference between the existing temperature and the reference temperature is calculated. If the difference is zero or negative, no cooling is necessary and the fan  20  can remain at rest. Therefore, in step  104  a commensurate inquiry is carried out; if the requirement is not greater than zero, step  102  is repeated, otherwise step  106  ensues. 
     In step  106  an inquiry is made as to whether the machine is harvesting. To this end, the sensor  50  provides an input  52  regarding the operating state of a material processing device (chopper or thresher device) or the setting of a comparable switch with which the material processing device is controlled. Alternatively, if the controller  26  is also used to control the material processing device, the input as to the status of the material processing device may be internal to the controller  26 . When there is no harvesting action, step  108  ensues, in which the parameter Δt, which determines the time span in which the reference or maximum temperature should be reached, is set at a predefined value Δt harvesting . If it is determined in step  106  that harvesting is underway, step  110  ensues, in which the parameter Δt is set at the value x·Δt harvesting . The parameter x is selectable and is as a rule less than  1 , since the dissipated energy of the engine is greater when harvesting than in roadway travel and therefore the required cooling capacity must be made ready more quickly. Nevertheless, cases are also plausible in which x is greater than 1. 
     Subsequently, based on the temperature differences and the ambient air temperature (sensor  44  at input  34 ), the determination is made in step  112  as to the amount of air necessary to be fed in order to offset the temperature difference. In this step  112  it can be meaningful to measure both the temperature of the ambient air in front of the fan  20  and the temperature of the air that has flowed past the cooling device  12 . In this manner—and in consideration of the known air flow rate of the fan  20 —the quantity of the dissipated heat can, in each instance, be determined as a function of the temperature of the coolant and the ambient air temperature. Therefrom it is possible to determine the quantity of air that is required to dissipate a certain amount of heat from the cooling device  12 . When one knows the temperatures and the quantity of ambient air needed to dissipate a certain (uniform) amount of heat, calculation of the given amount of ambient air required is possible. It would also be plausible to store in the control system a mathematical function or a characteristic curve or table in which respective temperatures of the engine and the hydraulic fluid and the ambient air (or differences) are stored, and which contains information regarding the respective quantity of ambient air to be fed. In this manner, the amount of air to be supplied by the fan  20  is determined. The quantity of air is determined using the following equation: 
     
       
         Δ V (ω)/Δ t=M /(Δ t )  
       
     
     in which V is the volume and ΔV its change, ω is the angular frequency (rotational speed) of the fan, M is the air mass, ρ is the density of the air and Δt is the time in which the given quantity of heat is to be dissipated. 
     In the ensuing step  114 , the optimal rotary speed of the fan is determined. As a rule, the relationship between rotary speed and feeding rate is known. It can be mathematically approximated using polynomials. With a given time Δt, in which the required amount of air calculated in step  112  is to be supplied, the rotary speed can be determined. Here the value Δt is of fundamental significance for the efficiency of the ventilation device, since the rotary speed of the fan  20  is all the greater the lower the value Δt is, since then the quantity of air can be supplied in a shorter time. If the selected value is too low, the efficiency of the ventilation device is no longer obtained; if it is too great, the rotary speed selected is too low and too much time is required until the desired temperatures are reached. It is recommended that the parameter Δt be set, e.g., at a value of 60 seconds, which means that the calculated cooling energy should be ready in 60 seconds. However, the value At can be kept randomly selectable in the control system  26 . 
     In step  114 , allowance is made for the efficiency of the operation of the fan  20 . Its driving torque is composed of the actual load moment of the fan (dependent upon the rotary speed of the fan and therefore the fed quantity of air), the moment of inertia (relevant for acceleration operations) and the sum of the various moments of loss: 
     
       
         τ= P (ω)/ω+ J·dω/dt+τ   losses    
       
     
     in which T is the driving torque of the ventilator, P is the load moment resulting from the feeding of the air, w is the angular frequency of the fan, J is its moment of inertia and T losses  is the (constant) moments of loss due primarily to friction. 
     From this it can be concluded that, in respect to efficient drive control, abrupt acceleration operations are to be avoided to the extent possible. The driving torque can be mathematically determined by the control system  26  using appropriate equations (or tables); alternatively, the use of an appropriate sensor on one of the shafts  22  or  24  is also feasible. Efforts should also be made to keep the fan rotary speed calculated in step  114  as low, but also as constant, as possible. 
     In step  116 , the rotary speed of the fan is set at the calculated rotary speed. Here any acceleration operations are carried out by the control system. Following step  118 , in which the delay time Δt is observed, step  102  is repeated. The depicted control system  26  also permits rotary speed reductions of the fan (in case of continuing negative requirement), and corrects the rotary speed accordingly in steps  112  and  114 . 
     It should be noted that in the embodiment of the invention illustrated in FIG. 2, no allowance is made for changes of the fed quantities of air resulting from acceleration or slowing of the fan. However, provisions can also be made therefor in the embodiment form according to FIG. 2 in the step  114 . 
     The control system  26  can execute steps  102 - 118  by means of a flat logic (fuzzy control), since a classic, linear control system would require a great calculation capacity. The flat logic is based on mathematic equations representing steps  104  and  108 . 
     The invention should not be limited to the above-described embodiment, but should be limited solely by the claims that follow.