Abstract: The present application describes various embodiments regarding systems and methods for providing efficient heat rejection for a lightweight and durable compact computing system having a small form factor. The compact computing system can take the form of a desktop computer. The desktop computer can include a monolithic top case having an integrated support system formed therein, the integrated support system providing structural support that distributes applied loads through the top case preventing warping and bowing. A mixed flow fan is utilized to efficiently pull cooling air through the compact computing system.

Abstract: The described embodiments relate generally to optimizing airflow in a computer system. By modifying the external surface of centrifugal cooling fan enclosures the pressure drop associated with airflow moving around the enclosures can be reduced. This is generally accomplished by rounding off hard edges from the outside of the cooling fan enclosure as well as forming cover surfaces rather than simply using flat cover surfaces. In some cases this can also involve modifying the shape of the fan inlet, or even contouring the shape of the cooling fan blades to allow air to flow more easily through the computer enclosure.

Abstract: The described embodiments relate generally to improving performance characteristics of a low profile fan. More specifically configurations having sloped fan blade edges are disclosed. By applying a gradual slope to each of the fan blades, performance of the fan can be increased without risking contact or rubbing between the fan blades and a fan housing. In some embodiments, the sloped fan blades can be configured to prevent contact when bearings of the fan include a certain amount of tilt play.

Abstract: A method to reduce acoustic noise in a cooling fan motor is disclosed. The method includes reducing the slew rate of a PWM (pulse width modulation) voltage waveform applied to energize a coil of the fan motor. This slew rate reduction results in lower mechanical vibrations and acoustic noise in the fan motor. In one embodiment, the slew rate reduction is performed during startup of the fan motor, when the motor is spinning slowly and there is little air flow noise. In another embodiment, the slew rate reduction is not performed during high speed operation of the fan motor, when the fan motor is spinning very fast and air flow noise masks the motor noise. In one embodiment, there is variable slew rate control depending on the speed of the fan motor.

Abstract: A fan assembly for a computing device is disclosed. The device can include an impeller having a number of blades and a motor for turning the blades. The motor can turn the blades via a magnetic interaction between the impeller and the motor. A fluid dynamic thrust bearing can be used to control a position of the impeller relative to the motor. In particular, the impeller can be configured to rotate around an axis and the thrust bearing can be used to control movement of the impeller in a direction aligned with the rotational axis. In one embodiment, the thrust bearing can be configured to stabilize the impeller when vibratory forces act upon the fan assembly. More particularly, parameters associated with the thrust bearing can be selected to counteract vibratory forces emitted by a speaker system.

Abstract: The described embodiments relate generally to control of rotational components in a computer system. In one embodiment, the rotational component includes a cooling fan assembly, the cooling fan assembly being controlled in accordance with resonant frequency avoidance data. The resonant frequency avoidance data being characteristic of the computer system such that when the cooling fan assembly operates in accordance with the resonant frequency avoidance data, the cooling fan assembly does not operate at a fan speed that is coincident with a natural resonant frequency of the computer system.

Abstract: The described embodiments relate generally to optimizing airflow in a computer system. By modifying the external surface of centrifugal cooling fan enclosures the pressure drop associated with airflow moving around the enclosures can be reduced. This is generally accomplished by rounding off hard edges from the outside of the cooling fan enclosure as well as forming cover surfaces rather than simply using flat cover surfaces. In some cases this can also involve modifying the shape of the fan inlet, or even contouring the shape of the cooling fan blades to allow air to flow more easily through the computer enclosure.

Abstract: A method and apparatus to improve air flow in an air circulating fan assembly by forming an inlet opening in a fan assembly. A static air pressure profile is calculated along a top portion of the fan assembly configured to operate in an enclosure. The shape of a section of the inlet opening in the top portion of the fan assembly is changed based on a pressure contour of the calculated static air pressure profile. The method is repeated iteratively one or more times using an inlet opening changed by a previously calculated static air pressure profile when calculating a subsequent static air pressure profile. The inlet opening is positioned in the top surface of the fan assembly so that the centroid of the inlet opening is laterally offset with respect to the rotational axis of an impeller in the fan assembly.

Abstract: A centrifugal blower in a cooling system of an electronic device having asymmetrical blade spacing with acceptable balance. The asymmetrical blade spacing is determined according to a set of desired acoustic artifacts that are favorable and balance that is similar to that found with equal fan blade spacing. In one embodiment, the fan impeller can include thirty one fan blades. The perceived sound quality from the fan is improved with essentially no effect on the thermal performance of the fan.

Abstract: A centrifugal blower in a cooling system of an electronic device having asymmetrical blade spacing with acceptable balance. The asymmetrical blade spacing is determined according to a set of desired acoustic artifacts that are favorable and balance that is similar to that found with equal fan blade spacing. In one embodiment, the fan impeller can include thirty one fan blades.

Abstract: A centrifugal blower in a cooling system of an electronic device having asymmetrical blade spacing with acceptable balance. The asymmetrical blade spacing is determined according to a set of desired acoustic artifacts that are favorable and balance that is similar to that found with equal fan blade spacing. In one embodiment, the fan impeller can include sixty one fan blades.

Abstract: A fan assembly for a computing device is disclosed. The device can include an impeller having a number of blades and a motor for turning the blades. The motor can turn the blades via a magnetic interaction between the impeller and the motor. A thrust bearing can be used to control a position of the impeller relative to the motor. In particular, the impeller can be configured to rotate around an axis and the thrust bearing can be used to control movement of the impeller in a direction aligned with the axis. In one embodiment, the impeller can be configured to generate aerodynamic forces, such as lift, and the parameters associated with the thrust bearing can be selected to counteract the aerodynamic forces so that the impeller remains within a desired positional range relative to the motor.

Abstract: A method and apparatus to improve air flow in an air circulating fan assembly by forming an inlet opening in a fan assembly. A static air pressure profile is calculated along a top portion of the fan assembly configured to operate in an enclosure. The shape of a section of the inlet opening in the top portion of the fan assembly is changed based on a pressure contour of the calculated static air pressure profile. The method is repeated iteratively one or more times using an inlet opening changed by a previously calculated static air pressure profile when calculating a subsequent static air pressure profile. The inlet opening is positioned in the top surface of the fan assembly so that the centroid of the inlet opening is laterally offset with respect to the rotational axis of an impeller in the fan assembly.