The present application is a 35 U.S.C. §§371 national phase conversion of PCT/SE2009/050211, filed Feb. 26, 2009, which claims priority of Swedish Application No. 0800960-7, filed Apr. 28, 2008, the contents of which are incorporated by reference herein. The PCT International Application was published in the English language.
The invention relates to a cooling fan for a vehicle engine, comprising a fan casing and a fan rotor which is movable axially relative to the fan casing during operation.
There are various known ways of controlling cooling fans for vehicle engines in order to save fuel by adapting their suction action to varying cooling requirements during operation. A commonly used method is to intermittently disconnect the driving power from the fan rotor in response to decreasing cooling requirement. Other solutions provide various ways of regulating the speed of the fan according to the cooling requirement.
A cooling fan with axially movable fan rotor is known from JP59046316 A, in which the rotor shaft is capable of linear movement against the force of a spring so that increasing engine speed causes the rotor to be drawn by its own suction force towards a constriction in the fan casing in order to increase the cooling air flow. In a cooling fan referred to in U.S. Pat. No. 4,387,780, the rotor is movable axially by a variable belt transmission upon increase in the speed of the belt transmission.
An object of the invention is to provide an improved cooling fan installation of the kind indicated in the introduction in which the axial position of the fan rotor can be varied more definitely with a view to increasing the efficiency of the fan.
According to a version of the invention, the cooling fan has an actuator for moving the rotor to positions which involve different amounts of protrusion from an end of the fan casing in order to optimise the fan's suction capacity and efficiency on the basis of current operating parameters such as fan speed and vehicle velocity. For example, when the cooling requirement is low, it is possible even at high fan speeds to allow the fan's suction power to decrease, and thereby save energy, by the actuator moving the fan rotor to a reduced-load position partly outside the fan casing.
The cooling fan may comprise sensors for detection of magnitudes relating to the cooling requirement, and a control unit for switching the actuator in response to signals from the sensors.
Although many different types of sensors may be used for detecting the cooling requirement, it is possible in an embodiment for them to comprise a temperature sensor for detection of cooling fluid temperature.
The actuator may be a fluid-powered actuator, in which case it is possible to use, for example, an existing compressed air source in the vehicle to power the actuator. However, other types of actuator may also be used.
The actuator may further comprise a cylinder and a piston rod.
The fan rotor may be supported for rotation relative to the piston rod, in which case the actuator may be adapted to supporting the rotor.
The cooling fan may have a telescopic shaft for the fan rotor, which shaft extends through the actuator, making it unnecessary for the actuator to be dimensioned for supporting only the rotor.
The telescopic shaft may be a drive shaft for the fan rotor. This embodiment may be used where the fan is driven by, for example, the crankshaft of the vehicle engine.
However, the fan rotor may also be driven by a belt transmission, in which case a hub of the rotor may comprise a pulley for a driving belt of the belt transmission.
Other features and advantages of the invention may be indicated by the claims and the following description of embodiments.
In the drawings, items with similar functions in the various embodiments are provided with the same reference numbers.
The speed of the cooling fan 10 may be regulated in various ways, e.g. by an undepicted electronically controlled fan coupling of viscosity type which may be situated in the fan hub, or in some other way in a belt circuit for the fan drive in cases where the fan is belt-driven as in the embodiment depicted in
As illustrated in
According to the invention, there is a positioning unit or an actuator 20 for moving the fan rotor 12 to positions which involve various amounts of protrusion “a” from an end at a terminating fan ring 62 of the fan casing 60. Although the actuator 20 may be of various kinds, e.g. an electrical or hydraulic actuator, a pneumatic actuator 20 is depicted in the embodiments according to
The pneumatic actuator 20 may in the various embodiments be regarded as comprising a cylinder 22 and, supported for movement therein, a hollow piston rod 24, which cylinder and piston rod delineate a chamber 26. As illustrated in
As may be seen in more detail in
As most clearly illustrated in
In the embodiment depicted in
In the embodiment depicted in
Reverting to
The control system comprises an electronic control unit 100 which receives input signals relating to the cooling requirement via a number of signal transmissions, e.g. signal lines 102. In response to these input signals, a processor in the control unit 100 calculates output signals for a signal transmission 104 for switching the actuator 20 to impart to the cooling fan 10 a degree of protrusion “a” from the end of the fan casing 60 which is optimum for the respective operating state.
For each operating state, which may be defined as a combination of fan speed and vehicle velocity, there is an optimum fan protrusion (axial position of the fan) “a” which results in best efficiency of the fan and hence lowest fuel consumption. Correctly set fan protrusion also makes it possible to minimise the recirculation of warmed cooling air. Recirculation is mainly a problem in severely loaded cooling systems at low vehicle velocities and high fan speeds, such as when vehicles travel uphill in high ambient temperatures.
At a maximum cooling requirement, the fan rotor 12 is fully retracted in the casing 60, and at a minimum cooling requirement the fan rotor 12 is subjected to maximum protrusion from the casing 60.
As illustrated in
Other parameters relating to the cooling requirement may comprise current fan speed signalled by some other undepicted sensor or by a vehicle computer 112, which then calculates the current fan speed on the basis of, for example, current engine speed and likewise signals it to the processor of the control unit. The vehicle computer unit 112 or the control unit 100 may also have in a memory a ready-made “chart” of set-point values for the protrusion “a” of the fan rotor 12 in all conceivable operating states as a function of the various operating parameters, so that the fan rotor 12 is subjected, in each operating state, to a specified degree of protrusion “a” based on current operating parameters. The chart may for example be arranged to indicate the rotor protrusion values “a” which in each operating state result in a maximum efficiency of the fan.
In general terms it may be considered that the fan speed is determined by the cooling requirement and that the fan speed should be as low as possible. The required fan speed will itself require a corresponding optimum rotor protrusion which optimises the efficiency of the fan at the particular operating point. It is generally the case that a fully retracted rotor position, i.e. a minimum distance “a”, results in a substantially axial flow pattern downstream of the fan, whereas a fully extended rotor position, i.e. a maximum distance “a”, results in a large radial component in the cooling air flow pattern downstream of the fan. The position which is optimum may be regarded as depending partly on the particular installation and partly on the current operating state.
The description set out above is primarily intended to facilitate comprehension and no unnecessary limitations of the invention are to be inferred therefrom. The modifications which will be obvious to one skilled in the art from perusing the description may be implemented without departing from the concept of the invention or the scope of the claims set out below.
Number | Date | Country | Kind |
---|---|---|---|
0800960 | Apr 2008 | SE | national |
Filing Document | Filing Date | Country | Kind | 371c Date |
---|---|---|---|---|
PCT/SE2009/050211 | 2/26/2009 | WO | 00 | 10/26/2010 |
Publishing Document | Publishing Date | Country | Kind |
---|---|---|---|
WO2009/134185 | 11/5/2009 | WO | A |
Number | Name | Date | Kind |
---|---|---|---|
2995295 | Day | Aug 1961 | A |
4340123 | Fujikawa | Jul 1982 | A |
4387780 | Fujikawa | Jun 1983 | A |
6021747 | Gee et al. | Feb 2000 | A |
6600249 | Nelson et al. | Jul 2003 | B2 |
7063125 | Tembreull et al. | Jun 2006 | B2 |
7789049 | Duley | Sep 2010 | B2 |
20070098547 | Vinson et al. | May 2007 | A1 |
Number | Date | Country |
---|---|---|
2151345 | Feb 2010 | EP |
5904316 | Mar 1984 | JP |
Entry |
---|
International Search Report dated Apr. 22, 2009, issued in corresponding international application No. PCT/SE2009/050211. |
Number | Date | Country | |
---|---|---|---|
20110036311 A1 | Feb 2011 | US |