Patent Application
20200025208
The present disclosure relates to a variable pitch fan assembly.
It is common for vehicles to employ a fan for cooling purposes. The fan may be used to cool various components of the vehicle, such as the engine and coolers or other heat exchangers.
According to an aspect of the present disclosure, a variable pitch fan assembly comprises a fan configured to rotate about a fan rotation axis and comprising blades with a pitch that is variable, a piston connected to the fan and configured to move axially relative to the fan rotation axis to change the pitch of the blades, a rotary crank arm yieldably biased toward the piston, and a motion transmitter positioned in communication with the piston and the crank arm to transmit motion axially therebetween relative to the fan rotation axis, and a sensor positioned to detect an angular position of the crank arm, the angular position indicative of the pitch of the blades.
The variable pitch fan assembly may be included in a vehicle. The sensor may generate a position signal indicative of the angular position and thus indicative of the blade pitch. A control system of the vehicle may determine the blade pitch based on the position signal, and command the fan to a desired blade pitch to modulate airflow to a desired level. The control system may do so by controlling the axial position of the piston relative to the fan rotation axis.
The above and other features will become apparent from the following description and accompanying drawings.
The detailed description of the drawings refers to the accompanying figures in which:
Referring to
Referring to
The fan 14 comprises a hub 18 and a sheave 20, the hub 18 and the sheave 20 included in a fan housing 21 of the fan 14. The blades 16 are mounted to the hub 18 in, for example, a conventional manner to rotate with the hub 18 about the fan rotation axis 15. The sheave 20 is fastened to the hub 18 in fixed relation thereto. The sheave 20 is mounted to a housing 22 of the fan assembly 12 via a bearing 23 (e.g., double tapered roller bearing), positioned between the housing 22 and the sheave 20, for rotation relative to the housing 22 about the fan rotation axis 15. The bearing 23 is captured between a snap ring for the outer race and a retainer ring threaded onto the housing 22. As such, the fan 14 is supported for rotation relative to the housing 22 about the fan rotation axis 15.
Referring to
The piston 24 moves in first and second axial directions 26, 28 relative to the axis 15 to change the pitch of the blades 16. The piston 24 may be actuated fluidly, such as hydraulically, in the first axial direction 26 relative to the axis 15. In other embodiments, the piston 24 may be actuated pneumatically, or in another manner, in the first axial direction 26. The piston 24 is yieldably biased in the second axial direction 28 opposite to the first axial direction 26 by a plurality of springs 29 positioned about the axis 15 between the piston 24 and the fan housing 21 (e.g., the sheave 20 of the fan housing 21) and in respective spring-receiving pockets of the piston 24.
Movement of the piston 24 in either direction 26, 28 causes the blades 16 to rotate correspondingly about their respective axes of rotation to change their pitch. A rack and a pinion may be associated with each blade 16 to rotate the blade 16 (racks and pinions not shown). In such a case, each rack may be mounted to the piston 24 for axial movement therewith relative to the axis 15, and each blade 16 may be over-molded or otherwise connected to a respective pinion that meshes with a respective rack. Axial movement of the piston 24 and the racks mounted thereto causes the pinions and the blades 16 mounted respectively thereto to rotate and thereby change the pitch of the blades 16.
The fan assembly 12 comprises a rotary crank arm 30, a motion transmitter 32, and a sensor 34 (
Referring to
Referring to
The spacer 40 is supported on the outer race 42. A ring 46 of the spacer 40 surrounds the outer race 42. A lip 48 of the spacer 40 extends radially from the ring 46 relative to the fan rotation axis 15 and axially between the bearing 38 and the piston 24 relation to the fan rotation axis 14 so as to space the piston 24 axially apart from the inner race 44 relative to the fan rotation axis 15. The spacer 40 is configured, for example, as a cap pressed onto the outer race 42 to establish an interference fit therebetween, and is made, for example, of steel.
Referring to
The motion transmitter 32 is positioned to transmit motion linearly between the piston 24 and the crank arm 30 along the fan rotation axis 15. The motion transmitter 32 may be configured, for example, as a rod or other suitable linear member for such linear movement.
Referring to
A biaser 60 yieldably biases the crank arm 30 toward the piston 24. The biaser 60 is configured, for example, as a torsion spring. In such a case, one end of the biaser 60 presses against a post 62 mounted to the crank arm 30 (e.g., threaded or pressed into the crank arm 30), and the opposite end of the biaser 60 presses against a tab 64 of the housing 22 positioned in the cavity 50 (the portion of the tab 64 that the biaser 60 contacts is not actually shown but is indicated in
The motion transmitter 32 and the crank arm 30 are positioned in slidable contact with one another. The motion transmitter 32 and the crank arm 30 cooperate to provide a spherical interface 66 therebetween. The spherical interface 66 inhibits axial play of the crank arm 30 and the axle 56 along the crank rotation axis 36, and accommodates rotation of the motion transmitter 32 about the fan rotation axis 15.
The crank arm 30 comprises a groove 68, and the motion transmitter 32 comprises an end portion 60 received in the groove 68. Illustratively, the end portion 70 is spherical, and the groove 68 is a spherical groove receiving the spherical end portion 70. The groove 68 extends lengthwise along a periphery 72 of the crank arm 30, and lies in an imaginary plane 74 perpendicular to the crank rotation axis 36 (the plane 74 (the plane 74 coincides with the section plane of
The spherical interface 66 may be wear resistant. The motion transmitter 32 may be made, for example, of stainless steel so as to be anti-corrosive. The crank arm 30 and axle 56 may be made, for example, of hardened steel (e.g., heat-treated) so as to be wear-resistant and not wear prematurely.
As such, the motion transmitter 32 and the crank arm 30 slide against one another when the motion transmitter 32 and the piston 24 move along the fan rotation axis 15 in the first and second axial directions 26, 28. In this way, motion is converted between rotary motion of the crank arm 30 and linear motion of the motion transmitter 32 and the piston 24. As the motion transmitter 32 and the piston 24 move axially along the fan rotation axis 15, the blades 16 rotate proportionally to this axial and linear movement of the motion transmitter 32 and piston 24.
The axle 56 and the sensor 34 are connected to one another such that rotation of the crank arm 30 about the crank rotation axis 36 is detected by the sensor 34 via corresponding rotation of the axle 56 about the crank rotation axis 36. In an embodiment, the axle 56 and the sensor 34 may be keyed to one another such that rotation of the axle 56 causes rotation of a corresponding sleeve of the sensor 34. A key of the sleeve may be received by a keyway of the axle 56. In other embodiments, the axle 56 and the sleeve may have the key and the keyway, respectively. The axle 56 and the sensor 34 may be connected to one another in other ways (e.g., splined, or interference fit).
The sensor 34 detects the angular position of the crank arm 30 relative to the crank rotation axis 36, with the angular position being indicative of the pitch of the blades 16. The sensor 34 may be configured, for example, as a rotary potentiometer that outputs a position signal (e.g., analog), proportional to the pitch of the blades 16. The position signal is proportional to the angular position of the crank arm 30 and thus the blade pitch. As such, the position is indicative the angular position and the blade pitch. The position signal may be used in by a control system on board the vehicle 10 to control the blades 16 to a desired blade pitch to modulate airflow to a desired level. The control system (e.g., a controller thereof) may receive the position signal and determine the blade pitch based on the position signal. The control system may then control the blade pitch via the axial position of the piston 24 relative to the fan rotation axis 15.
While the above describes example embodiments of the present disclosure, these descriptions should not be viewed in a limiting sense. Rather, other variations and modifications may be made without departing from the scope and spirit of the present disclosure as defined in the appended claims.
