Abstract:
Systems, methods and devices for the control of fans are presented. More specifically, the invention relates to a fan clutch control unit for a vehicle fan. The fan clutch control unit executes a control loop section and a strategy section to provide control functionality. The fan clutch control unit may be provided as a pre-packaged control board or integrated into a fan clutch.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     The present application claims benefit of priority to U.S. Provisional Application Ser. No. 60/920,819, filed Mar. 30, 2007, the entire contents of which is incorporated herein by reference. 
    
    
     FIELD OF THE INVENTION 
     The embodiments of the present invention relate generally to systems, methods and devices for controlling fans, including engine fans. More specifically, certain embodiments of the present invention relate to systems, methods and devices for controlling modulating fan clutches for engines via the use of discrete control units having embedded software and in communication with an engine or the control unit of an engine. Certain embodiments will be useful in heavy vehicle applications. 
     BACKGROUND OF THE INVENTION 
     In conjunction with increasingly demanding vehicle emission standards, the need for more precise control of machine cooling systems is being felt. In particular, vehicle emission standards are expected to become stricter, causing a need for increased control over vehicle engine fans. This is a particular need in the heavy truck market. 
     Vehicle manufacturers and OEMs have, however, had a difficult time integrating precise control over vehicle engine fans. This has resulted in the widespread use of simple binary (on-off) type fan systems that lack efficiency but are possible to implement. There is thus a need for a more precise technology for controlling machine cooling systems, and in particular vehicle engine fans. 
     SUMMARY OF THE INVENTION 
     Embodiments of the invention relate to a fan system, comprising: an engine control unit; a fan clutch control unit; a modulating fan clutch; and a fan; wherein the fan clutch control unit is connected to the fan clutch by one or more conducting wires and acts to control the fan clutch based on input data. The fan clutch control unit can be a pre-packaged control board or embedded in the modulating fan clutch. The fan system can comprise an MCU and a memory having embedded therein software comprising a control section and a strategy section. Optionally, the control section comprises a PID control loop and the fan clutch control unit comprises at least one of the following I/O interfaces: CAN, I 2 C, SPI, CSI, QSPI, UART, USART, USB. More preferably, the fan clutch control unit comprises a CAN interface in communication with an Engine Control Unit. Optionally, the MCU provides diagnostic data to the Engine Control Unit and does not perform an engine control function other than control of the fan clutch. 
     Further embodiments of the invention relate to a control unit, comprising: a pre-packaged board comprising an MCU; the MCU further comprising a CAN interface; wherein the control unit comprises software embedded in a memory in the control unit or MCU, and wherein the software when executed would perform a method comprising: accepting input data over the CAN interface; using at least a portion of the input data in a control loop calculation; and outputting control data to an output interface connectable to a fan clutch. The method may further comprise using the input data in a control loop calculation; executing a PID control loop; using at least a second portion of the input data to predict a future state; and generating further input data for the control loop calculation based on the future state. The method may also comprise receiving fan clutch data from the interface connectable to a fan clutch, performing a diagnostic check on the fan clutch data, and broadcasting diagnostic information over the CAN interface. 
     Additional embodiments of the invention relate to a vehicle, comprising: a passenger compartment; an engine, an Engine Control Unit in communication with the engine; a fan; a modulating fan clutch; and a modulating fan clutch control unit in communication with the Engine Control Unit and the fan. Optionally, the modulating fan clutch control unit is a pre-packaged control board or is embedded in the modulating fan clutch. 
     Still further embodiments of the invention relate to a method for providing control of a fan clutch, comprising: providing a fan and a fan clutch to an engine; connecting the fan via the fan clutch to a control unit; the control unit comprising at least an MCU; connecting the MCU via at least one I/O interface to an Engine Control Unit, such that when operated, data will be passed between the MCU and the Engine Control Unit over the I/O interface; and wherein the Engine Control Unit is usable to control portions of the engine; and providing control software to the MCU or a connected memory device for controlling the fan clutch based at least on data passed from the Engine Control Unit to the MCU. The method may also be performed where the MCU is specifically part of a pre-packaged control board or where the MCU is integrated into or onto the fan clutch. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a block diagram showing a vehicle system employing a control unit for a fan clutch. 
         FIG. 2  is a block diagram showing a vehicle system employing a control unit for a fan clutch. 
         FIG. 3  depicts an engine fan as seen from the engine of a vehicle. 
         FIG. 4  depicts an engine fan as seen from the radiator of a vehicle. 
         FIG. 5  is a block diagram illustrating the functions of a control unit and communication with an engine control unit. 
         FIG. 6  is a schematic of an MCU in a control unit for a modulating fan clutch. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring to  FIG. 1 , there is shown a block diagram showing a vehicle system  100 . While the system  100  is shown as a vehicle system, it will be appreciated that the principles described herein can be applied to other systems that require cooling. The system  100  has an engine  102  having a plurality of sensors  104 . The sensors are attached, for example, to communications buses  106  and  108 , which allow them to be in communication with engine control unit  110 . 
     Engine control unit  110  is further in communication with fan clutch control unit  114  over bus  112 , which is in a preferred embodiment a Controller Area Network (CAN) bus conforming to revision 2.0A and 2.0B of the CAN standard. The CAN bus transmits differential signals and has a built in cyclic redundancy check, thereby allowing for accurate data transmission in an electromagnetically noisy environment. Any number of different interfaces could be used depending on conditions, however, for example I 2 C, SPI (Serial Peripheral Interface), CSI (Clocked Serial Interface), Microwire, UART (Universal Asynchronous Receive and Transmit), USART (Universal Synchronous/Asynchronous Receive and Transmit) and USB (Universal Serial Bus). Fan clutch control unit  114  controls fan clutch  116 , which controls the speed of fan  118 . 
     Engine  102  can be a standard engine of known type. Sensors  104  are positioned at various points within the engine  102 , and are used to measure the state of variables within the engine  102 . For example, one of the sensors  104  might measure the engine speed, coolant temperature, air conditioning system pressures, engine oil temperature, transmission oil temperature, etc. The sensors  104  provide their readings to engine control unit  110  over communication buses  106  and  108 . 
     A control unit as used in this specification is an electronic component that helps to guide the performance of another electrical or mechanical component. Correspondingly, an engine control unit is an electronic component that helps to guide the performance of an engine. Engine control unit  110  comprises a microcomputing unit (MCU) (not shown) such as a microcontroller or microprocessor. Data provided by sensors  104  are used by the MCU to evaluate the state of the vehicle, to predict future states and to provide control signals to make adjustments where necessary. The engine control unit  110  thus provides an overall control function for the vehicle system  100 . 
     The temperature of engine  102  is in part regulated by fan  118 , which is responsible for inducing the flow of outside air onto engine  102 . Fan  118  is controlled by a fan clutch  116 , which provides current over a coil to the fan clutch which in turn engages the fan. The fan clutch  116  is preferably a modulating fluid shear fan clutch, having a silicone fluid viscosity of approximately 4000 Cts. A modulating fan clutch is simply a fan clutch that can operate a fan at a range of speeds or a number of different discrete speeds, as opposed to a binary fan clutch, which can only operate the fan at a single speed or disengage the fan. The fan  118 , which is preferably a BEHR® Ring Fan with Nylon 6/6 Plastic ML500/9 blades, can be varied in speed depending on the temperature conditions within the engine  102 , as determined, for example, by the sensors  104 . Control of the fan clutch is provided by the fan clutch control unit  114 , which is shown here as a separate unit and provided in this embodiment as a separate board. 
     Fan clutch control unit  114  is in the embodiment of  FIG. 1  a pre-packaged control board, which means that the board is assembled and packaged prior to integration into the vehicle system  100 . The pre-packaged control board of fan clutch control unit  114  has embedded control software for controlling fan clutch  116  and is advantageous in that it allows the control programming to be separated from the engine control unit, thereby avoiding integration of the control routine into the overall engine control application of ECU  110 . This saves integration resources and efficiently partitions the integration work between fan system and vehicle system engineers. It also saves computing resources on the ECU  110  and reduces the wiring complexity of the system overall. 
     Fan clutch control unit  114  receives signals over communications bus  112  from the engine control unit  110 . These signals can include a variety of data points, including the current temperature, the vehicle speed, the oil pressure, etc. Fan clutch control unit  114  calculates the current system state and makes adjustments to various control signals to properly control fan clutch  116 . 
     Referring now to  FIG. 2 , there is shown an alternate system embodiment.  FIG. 2  shows a vehicle system  200 , having an engine  202  with corresponding sensors  204 . The sensors are connected over buses  206  and  208  to engine control unit  210 , which is similar to engine control unit  110  in  FIG. 1 . Engine control unit  210  communicates over bus  212  with integrated unit  214 . Integrated unit  214  comprises both a fan clutch control unit  216  and a fan clutch mounted in or on the same housing. The integrated unit  214  communicates with engine control unit  210  to receive information about the engine  202  and the state of the vehicle system  200 , in order to control fan  220  with the objective of optimal cooling. 
       FIG. 3  shows a fan system  300  corresponding to an embodiment shown in  FIG. 1 . System  300  has a fan unit  302 , which has a four-bolt hub  304 , behind which is a fan clutch (not shown). The fan  302  is positioned such as it would be observed from the perspective of a person in the position of the engine. The hub  304  is connected via the fan clutch (not shown) to the cable  312 , which is in turn connected via connector  310  to a pre-packaged control board  306 , which houses a fan clutch control unit. Pre-packaged control board  306  is in turn connected to a bus by connector  308 . The configuration shown in  FIG. 3  allows easy installation of a sophisticated fan clutch control system in the form of pre-packaged control board  306  without the necessity for extensive reprogramming of an engine control unit. 
       FIG. 4  depicts a similar fan system  400 , this time shown from the perspective of a person looking through the fan toward the engine. System  400  has a fan  402  with a hub  404 . Connected to the hub is fan clutch  416 , which is connected to cable  418  via connector  414 . Cable  418  is guided safely parallel to the fan and its insulation terminated by flange connector  412 . Cable  418  is connected at the other end to pre-packaged control board  406 , which houses a fan clutch control unit (not shown), via connector  410 . Pre-packaged control board  406  is further connected to a bus over connector  408 . 
       FIG. 5  illustrates the design of a fan control system  500 . The fan control system  500  has various external components  502  that interact with a fan clutch control unit  514 . The external components can comprise, for example, the various parts of a vehicle system, including a battery, an engine, sensors and an engine control unit (all not shown). The external components  502  provide an I/O (input/output) interface  506 , possibly one of many kinds of I/O interfaces but preferably a CAN interface. The I/O interface is in communication with a corresponding I/O interface  516  of fan clutch control unit  514  over a bus comprising, in a preferred embodiment, differential lines  510  and  512 . The external components  502  also provide a power source  504 , which is provided to the fan clutch control unit  514  via a power bus or line  508 . 
     Fan clutch control unit  514  is preferably implemented as a circuit board having an MCU (not shown) for executing software for the control of a fan clutch. Fan clutch control unit  514  comprises in a preferred embodiment an I/O interface  516 , which may be any of several types depending on the application, but is preferably configured to operate with the CAN protocol. I/O interface  516  can be implemented in software or hardware, and is preferably an integral part of the MCU. 
     Fan clutch control unit  514  further comprises an MCU with a corresponding memory (not shown). The memory may be an integral part of the MCU, or may be a separate discrete component. The memory has embedded therein (i.e. stores) software that performs a method for operating a control loop. The control loop takes input data, which may be of various types depending on the available information, including for example the engine speed, coolant temperature, air conditioning system pressures, engine oil temperature, transmission oil temperature, etc. In one preferred embodiment, the control loop receives information regarding the engine speed via the I/O interface, a fan speed from the fan clutch  532  and a target fan speed from strategy section  518 , while outputting a data representing a current to the fan clutch coil. 
     Fan clutch control unit  514  operates software that is divided into several sections, including a control loop section  520 , a strategy section  518 , and a clutch diagnostics section  522 . A section here refers to a portion of the fan clutch control unit software that performs a specific task. Sections are usually dividable from the overall software, and may be in the form of, for example, one or more software objects, one or more discrete subroutines, or an identifiable and contiguous section of assembly code. 
     The control loop section  520  is a section that makes decisions about how to change state variables to achieve a desired goal. Control loop section  520  executes a digital control loop, which mathematically may take on numerous forms but is in a preferred embodiment a proportional-integral-derivative (PID) control loop. Control loop section  520  has among its responsibilities the acceptance of input data directly or indirectly from I/O interface  516  as variables representing the state of the system to be controlled. In the present example, the system to be controlled includes a fan clutch, a fan, and an engine that has various temperature readings. The control loop section  520  also has access to state variables of the fan, for example the fan speed. 
     Control loop section  520  executes its PID digital control loop with the aim of minimizing the difference between one or more key state variables and a target value or target values. In a preferred embodiment, the key state variables include an engine-related temperature. The control loop section  520  adjusts the speed of modulating fan  530 . 
     Control loop section  520  also accepts input from strategy section  518 . Strategy section  518  is a section that attempts to predict future system states based on current state variables, historical state variables and/or stored data. For example strategy section  518  can have information regarding system (engine) performance stored in a compact database or data table, and use the information to guess at trends in the engine. Strategy section  520  can also be configured to extrapolate trends in system state variables based on recent values. Strategy section  518  provides input data to control loop section  520  which affects the performance of control loop section  520  so that control loop section  520  can effectively “anticipate” changes in the system that would otherwise cause poorer tracking on its target system state. In a preferred embodiment, the strategy section  518  receives most of the input data from outside the control unit  514 , whereas the control loop section  520  receives the engine speed and the current fan speed, as well as a desired fan speed from the strategy section  518 . In a preferred embodiment, the strategy section  518  receives most of the input over I/) interface  516 , and passes a target fan speed to control loop section  520 . 
     In an alternative embodiment, strategy section is implemented in an external component, such as an engine control unit  110  as shown in  FIG. 1 . In that case, the input data from the strategy section is provided over the I/O interface  516  ( FIG. 5 ), and is used in the control loop section  520 . 
     The primary output of the control loop section  520  is data representing the fan speed coil current  524 . This coil current is provided at  528  to hardware  526  which comprises the fan clutch  532  and a fan  530 . The coil current provides the driving force for fan  530  and thus determines its speed. Through fan speed coil current  524 , then, control loop  520  can alter the state (principally, the temperature) of the engine system. 
     Hardware  526  also returns information such as the actual fan speed or fan speed coil conditions at  528  to the fan clutch control unit  514 . These values can be used in the control loop section  520  and by clutch diagnostics section  522 . Clutch diagnostics section  522  is responsible for monitoring the fan clutch  532  and fan clutch control unit  514  for system health. Clutch diagnostics section  522  also allows components to be queried for easier maintenance. Clutch diagnostics section  522  can communicate with external components, such as an engine electronic control unit, by broadcasting over I/O interface  516 . 
       FIG. 6  shows an exemplary MCU  600  appropriate for use in a pre-packaged control board embodiment or integrated embodiment of a fan clutch control unit. MCU  600  is in the present example part no. AT89C51 CC03 from ATMEL® and belongs to a line of microcontrollers with integrated CAN bus capabilities. MCU  600  executes in a preferred embodiment software embodying a control loop section, a strategy section and a clutch diagnostics section, as well as software controlling the various input/output functions of the fan clutch control unit. 
     MCU  600  is connected via a pin to line  602  which carries a supply voltage for the MCU  600 . MCU  600  is further connected via a pin to line  604  which is the circuit ground. A reset pin is connected to line  606  which contains a pull down resistor to the circuit ground or Vss. An external memory enabling signal  608  is switched directly to ground. Correspondingly, an “external access” pin is held  610  high by pull up resistor  630 , reflecting that in the current embodiment program instructions should be fetched from internal Flash memory. 
     Data is transferred to and from the MCU  600  using several of its input/output facilities. Data input from a fan is to one of the ports of MCU  600  on line  616 . Data output is performed on line  618  from a second port of MCU  600 . Lines  612  and  614  represent a CAN bus, used to exchange data with external components and an integrated CAN interface driver on MCU  600 . 
     MCU  600  is driven by a clock oscillator circuit with an external crystal resonator  622 . The oscillator circuit is connected to the MCU  600  over lines  625  and  624 . The oscillator circuit has a nominal oscillation frequency of around 12 Megahertz. Trimming capacitors  626  and  628  are connected at both terminals of the crystal  622  resonator and to ground. 
     MCU  600  so connected executes software as described principally in relation to  FIG. 5 , and can be used in a fan clutch control unit as described herein. The MCU may be contained in its own pre-packaged control board or integrated into or onto the fan / fan clutch assembly and sold as a fan system. 
     It will be apparent to those of skill in the art that the teachings of this disclosure are useful in a variety of different forms and applications, and that the intent of this disclosure is to provide exemplary embodiments, not limited by the specificity with which they are presented.