Fisher & Paykel Appliances Limited

Fisher & Paykel Appliances Limtied

Zhuang Tian

John H Boyd, Jr

Ian Campbell McGill

Mervyn John Davies

David James Hammond

John H Boyd Jr

An electric fan with a self-cleaning mode to energise rotating fan blades in alternate forward and reverse directions to create a vibration in order to shake built-up dust or dirt particles from the blades in a frequency at which the rotational direction is alternated set to a known or detected resonant frequency of the blades thereby excite resonant modes and maximise the amplitude of vibrations. The self-cleaning operation may be triggered by detection of excessive/abnormal loading on the motor. The fan may be operated in a vibration detecting mode over a range of rotational speeds to locate speeds that produce resonance, or to detect a fault with the fan. Motor reversal frequencies corresponding to resonance-inducing speeds may be used in the self-cleaning mode. The vibration detecting mode may be carried out while the at least one blade is rotated in a direction opposite to its normal operational rotational direction.

Fan or pump arrangement and operating method

A free piston gas compressor has a cylinder, a piston, the piston reciprocable within the cylinder in alternating compression and expansion strokes. A reciprocating linear electric motor is drivably coupled to the piston. A controller is programmed to control or adjust power input to the linear motor on the basis of a relationship including at least one of the present compression stroke or expansion stroke durations, the relationship being indicative of the top dead center (TDC) position of the piston, including in the absence of any collision. In the preferred embodiment the controller obtains a measure reflecting the difference between the compression stroke duration and the expansion stroke duration and adjusts the power input in response to the obtained measure.

Linear motor controller improvements

A control for a linear compressor energises the linear motor in harmony with the present natural frequency of the compressor. The controller monitors the present operating frequency and compares the frequency with one or more outer limit thresholds. The control may remove power from the linear motor if the running frequency drops below a lower threshold. The control may reduce power to the linear motor if the running frequency rises above an upper threshold. The control uses compressor running frequency to operate the comperssor within safe operating limits.

Linear compressor controller

A sensorless method and apparatus for detecting piston collisions in a free piston linear compressor motor. The waveform of the back EMF induced in the motor stator windings is analysed for slope discontinuities and other aberrations in a time window centred on the back EMF zero-crossings. Waveform slope artefacts are indicative of piston collisions and cause the motor power to be decremented in response.

A free-piston linear compressor () controlled to achieve high volumetric efficiency by a controller including an algorithm () for ramping up input power until piston-cylinder head collisions are detected using a detection algorithm () which then decrements power input whereupon input power is again ramped up by algorithm (). Non-damaging low energy collisions are achieved by the controller including a perturbation algorithm () which perturbates the input power ramp with periodic transient pulses of power to ensure piston collisions are provoked during the transient power pulses.

A free piston gas compressor comprising a cylinder, a piston reciprocable within the cylinder and a reciprocating linear electric motor derivably coupled to the piston having at least one excitation winding. A measure of the reciprocation time of the piston is obtained, any change in the reciprocation time is detected and the power input to said excitation winding is adjusted in response to any detected change in reciprocation time.

Growing community of inventors

Auckland, New Zealand

Zhuang Tian