Patent Application
20070234980
The present disclosure relates generally to an engine coolant pump drive system and apparatus, and particularly to a variable speed engine coolant pump drive system and apparatus.
A typical engine cooling system employs an engine driven water pump, driven by a belt for example, for circulating coolant fluid, such as a water-glycol mixture for example, that is circulated through the engine block and the radiator. Since the pump is driven directly by the engine using a belt, its speed is determined by that of the engine, and it operates continuously as long as the engine is running, resulting in continuous losses due to constant operation and constant circulation of the coolant fluid through the cooling loop, whether the cooling action is needed or not. Also, the pump has to be designed to provide the required flow and pressure for the worst-case engine speed, which could be near idle or during high grade towing. This results in much higher pump flow at higher engine speeds than is necessary, further increasing the losses in the coolant system, which results ultimately in increased fuel consumption.
Other water pump systems have been introduced to decouple the coolant pump from the engine and provide an on-demand coolant flow using an electric motor-driven or electrically operated clutch driven pump. Both of these systems offer improvement to the vehicle fuel economy by providing an on-demand coolant flow and minimizing and/or eliminating the parasitic losses associated with the engine belt-driven coolant pump. However, the electric motor-driven coolant pump needs a high power electric motor, power electronics for controlling the speed of the motor, and a reliable electrical power supply, which includes the engine driven alternator and the battery. The overall power losses in a typical electric motor-driven coolant pump still involves significant losses through the engine alternator, power electronics, electric motor, and pump system. An electrically operated clutch driven coolant pump, employing an electromagnetic clutch for example, may be either on or off, with no continuous adjustment of the output speed being possible, resulting in significant shock loads on the engine.
Accordingly, there is a need in the art for an engine coolant pump drive system that overcomes these drawbacks.
An embodiment of the invention includes an engine coolant pump drive system for a vehicle having an engine, an engine coolant system, and at least one sensor for sensing at least one operational condition of the vehicle. The pump drive system includes a magnetorheological fluid (MRF) clutch, and a coolant pump. The MRF clutch includes a torque input section coupled to a torque output section via a MRF, the torque input section being configured to receive a torque input from the engine. The coolant pump is configured for operable communication with the torque output section of the MRF clutch. In response to a signal from the at least one sensor, the MRF clutch is configured to provide a continuously variable torque transfer from the torque input section to the torque output section, thereby providing for variable coolant flow in the engine coolant system via the coolant pump capable of a continuously variable speed.
Another embodiment of the invention includes a magnetorheological fluid (MRF) clutch for coupling an engine coolant pump with an engine of a vehicle having at least one sensor productive of a signal representative of a temperature of the engine. The MRF clutch includes a torque input section coupled to a torque output section via a MRF, the torque input section being configured to receive a torque input from the engine. The torque input section includes first and second portions with a space therebetween, the first portion being radially outboard of the second portion, the first portion being configured to receive a torque input from the engine, the first and second portions being configured to rotate together about the same axis of rotation. The torque output section includes a rotor attached to a shaft, the rotor being disposed within the space between the first and second portions so as to form an annulus between the rotor and the first and second portions, the annulus containing a MRF, and the shaft being configured for operable communication with the coolant pump. The MRF clutch also includes a stationary magnetic field generator disposed radially inboard of the second portion. In response to a signal from the at least one sensor, the magnetic field generator is capable of generating a variable strength magnetic field that is in field communication with the first portion, the second portion, the rotor, and the MRF, thereby providing for a continuously variable torque transfer from the torque input section to the torque output section.
Referring to the exemplary drawings wherein like elements are numbered alike in the accompanying Figures:
An embodiment of the invention provides a means to directly control the speed of an engine driven coolant pump by using a magnetorheological fluid (MRF) coupling (clutch) integrated between an accessory drive of the engine and the engine coolant pump. The MRF clutch provides for a continuously adjustable pump speed by controlling the torque transmitted from the engine drive shaft to that of the engine coolant pump. The MRF clutch may be part of the pump assembly or part of a pulley assembly.
An electronic controller is used to interface engine sensors (engine rpm, throttle angle, manifold absolute pressure, coolant temperature, engine cylinder head temperature, for example) and vehicle sensors (speed, accelerator pedal position, brake pedal position, for example) with an electronic amplifier to generate a current signal to an excitation coil embedded in the MRF clutch, thereby enabling the speed of the pump to vary in a continuous manner. It is also envisioned that an integrated speed sensor within the pump and/or a pressure or flow sensor in the coolant lines may be used to provide additional control information to the electronic controller for adjusting the MRF clutch coil current.
An embodiment of the invention provides an engine coolant pump drive system having the MRF clutch integrally arranged with the coolant pump. Another embodiment provides the MRF clutch external to the coolant pump. Both pump drive systems are configured for efficiently cooling the engine of a vehicle by providing for variable coolant flow via the coolant pump, which may be operated by continuously varying its speed according to the operating conditions of the vehicle. As such, an embodiment of the invention may be employed for the purpose of minimizing parasitic power losses present in a belt driven-engine coolant pump by providing a variable speed direct drive or pulley drive.
In an embodiment, the control system 110 includes a set of sensors 130 disposed to receive signals representative of various operating conditions of the vehicle, a controller 135 in signal communication with the sensors 130, and an electronic amplifier 140 in signal communication with the controller 135 and productive of a control signal 145 directed to the pump drive system 105. The electronic amplifier may be of a Pulse Width Modulating (PWM) type, or a linear type, and are known in the art. Communication between sensors 130, controller 135, and electronic amplifier 140, may be by a communication bus or a CAN (controller area network) communication link (represented generally by the arrowhead lines in
In an embodiment, the pump drive system 105 includes a MRF clutch 160 in operable communication with a coolant pump 165, which may be integrally arranged with the MRF clutch 160 as will be described in more detail below.
Referring now to
In an embodiment, and with reference still to
In response to a signal from the set of sensors 130, electronic amplifier 140 provides a control signal 145 to MRF clutch 160, which energizes coil 200 in such a manner as to provide a magnetic field across torque input section 170, MRF 180, and torque output section 175, thereby activating the MRF 180 to provide a torque transfer from the torque input-section 170 to the torque output section 175. In response to a continuously variable control signal 145, a continuously variable torque transfer from the torque input section 170 to the torque output section 175 may be provided, thereby providing for variable coolant flow 205 directed to the engine block 210 via an impeller 215 in coolant pump 165, which operates under a continuously variable speed.
Referring now to
MRF clutch 160 also includes a magnetic field generator 270, having coil 200 and a stator 275, disposed radially inboard of the second portion 230 of the pulley wheel 220. Similar to the previous discussion-relating to
In general, the set of sensors 130 are configured to provide a variable signal representative of a variable temperature of the engine, and the MRF clutch 160 is responsive to a non-zero variable control signal 145 arising from at least one of the set of sensors 130, thereby providing continuously variable speed control to the coolant pump 165.
In an embodiment, stator 275, first portion 225, second portion 230, and rotor 250, are constructed using magnetic and non-magnetic materials that serve to direct the magnetic field created by coil 200 in such a manner as to efficiently excite MRF 180 in annulus 260, thereby resulting in efficient torque transfer to coolant pump 165.
During cold engine operation, such as at start up or where the ambient temperature is extremely low, an embodiment of the invention may generate only a small control signal 145 to coil 200, thereby resulting in low torque transfer from torque input section 170 to torque output section 175, and a slow operational speed of pump 165, thereby allowing the engine to get up to temperature quickly. During warm engine operation, such as when the engine is at a desired operating temperature, an embodiment of the invention may generate a large control signal 145 to coil 200, thereby resulting in high torque transfer from torque input section 170 to torque output section 175, and a fast operational speed of pump 165, thereby allowing the high coolant flow through a radiator to maintain the desired engine operating temperature. During periods of high vehicle speed, such as on a highway for example, where increased air flow across the vehicle radiator would typically provide for a greater heat transfer of engine heat to ambient, an embodiment of the invention may generate only a moderate control signal 145 to coil 200, thereby resulting in moderate torque transfer from torque input section 170 to torque output section 175, and a moderate operational speed of pump 165, thereby allowing for both effective and efficient cooling of the engine. As can be seen, strategically placed sensors 130 that sense a variety of vehicle operating characteristics, in combination with an appropriate algorithm in controller 135, may be employed to generate a variety of characteristics for control signal 145, depending on the cooling needs of a particular engine.
While certain combinations of sensors 130 have been described herein, it will be appreciated that these certain combinations are for illustration purposes only and that any combination of any of sensors 130 may be employed in accordance with an embodiment of the invention. Any and all such combinations are contemplated herein and are considered within the scope of the invention disclosed.
An embodiment of the invention may be embodied in the form of computer-implemented processes and apparatuses for practicing those processes. The present invention may also be embodied in the form of a computer program product having computer program code containing instructions embodied in tangible media, such as floppy diskettes, CD-ROMs, hard drives, USB (universal serial bus) drives, random access memory (RAM), read only memory (ROM), erasable programmable read only memory (EPROM), or any other computer readable storage medium, wherein, when the computer program code is loaded into and executed by a computer, the computer becomes an apparatus for practicing the invention. The present invention may also be embodied in the form of computer program code, for example, whether stored in a storage medium, loaded into and/or executed by a computer, or transmitted over some transmission medium, such as over electrical wiring or cabling, through fiber optics, or via electromagnetic radiation, wherein when the computer program code is loaded into and executed by a computer, the computer becomes an apparatus for practicing the invention. When implemented on a general-purpose microprocessor, the computer program code segments configure the microprocessor to create specific logic circuits. A technical effect of the executable instructions is to variably control the speed of an engine coolant pump.
As disclosed, some embodiments of the invention may include some of the following advantages: improved fuel economy due to elimination of losses due to double energy conversion present in an electrically driven pump; less packaging issues with the MRF clutch integrated into the engine coolant pump pulley; reduced cost due to a simple low current controller replacing a costly high-current power electronics of an electric drive system; variable coolant flow by controlling the pump speed allowing faster engine warm-up and potentially reduced emissions; reduced mass due to elimination of electric motor and high-current power electronics of an electric drive system; and, improved reliability due to reduced number of components.
While the invention has been described with reference to exemplary embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiment disclosed as the best or only mode contemplated for carrying out this invention, but that the invention will include all embodiments falling within the scope of the appended claims. Also, in the drawings and the description, there have been disclosed exemplary embodiments of the invention and, although specific terms may have been employed, they are unless otherwise stated used in a generic and descriptive sense only and not for purposes of limitation, the scope of the invention therefore not being so limited. Moreover, the use of the terms first, second, etc. do not denote any order or importance, but rather the terms first, second, etc. are used to distinguish one element from another. Furthermore, the use of the terms a, an, etc. do not denote a limitation of quantity, but rather denote the presence of at least one of the referenced item.
