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74results about How to "Increased freedom of setting" patented technology

Fluid pressure shock absorber

An object of the present invention is to generate a stable damping force and enhance durability of a main valve in a hydraulic shock absorber in which valve opening of the main valve is controlled by an inner pressure of a backpressure chamber. A first piston 3 and a second piston 4 coupled to a piston rod 10 are fitted in a cylinder 2 such that a piston chamber 2 C is defined between the first and second pistons 3, 4 . An extension-side main valve 18 and a compression-side main valve 23 are provided in the piston chamber 2 C. Valve opening of the main valves is controlled by an extension-side backpressure chamber 19 and a compression-side backpressure chamber 24 . A compression-side check valve 13 and an extension-side check valve 16 are provided at the first piston 3 and the second piston 4 .; During an extension stroke of the piston rod 10 , the compression-side check valve 13 is closed, whereby action of a pressure of a cylinder upper chamber 2 A on the compression-side main valve 23 is prevented. During a compression stroke of the piston rod 10 , the extension-side check valve 16 is closed, whereby action of a pressure of a cylinder lower chamber 2 B on the extension-side main valve 18 is prevented. Accordingly, it is possible to generate a stable damping force, and enhance durability of the extension-side main valve 18 and the compression-side main valve 23.
Owner:HITACHI AUTOMOTIVE SYST LTD

Power conversion device

The invention provides a power conversion device which comprises a plurality of power converters capable of converting alternating current power supply voltage to direct current voltage and converting the converted direct current voltage to alternating current voltage and can output a plurality of stages of alternating voltage through combination of alternating current outputs of the plurality of power converters, The power conversion device comprises a PWM modulator. The PWM modulator compares a carrier signal of triangular wave and a phase voltage instruction of sine wave and thus performs PWM control of the power converters which converting the direct current voltage to the alternating current voltage. The ratio between the frequency of the carrier signal of the triangular wave input in the PWM modulator and the frequency of the phase voltage instruction may be odd multiples of 3, even multiples of 3, and integral multiples of 3 except for the odd multiples and the even multiples. In the plurality of stages of the power conversion devices or tandem multiple power conversion devices characterized by synchronous PWM control, the stability of a system can be improved through increase of degree of freedom of setting of the frequency (fc) of the carrier wave of the triangular wave.
Owner:HITACHI IND PROD LTD
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