Hitachi, Ltd.

Hitachi Video Engineering, Incorporated

Toshio Osada

Nobuo Masuoka

Fumio Tajima

Shigeki Morinaga

Hiroshi Katayama

Ikuo Nishida

Hidekazu Takeda

Nobuyoshi Mutoh

Tadashi Saito

Taizo Miyazaki

Masao Iwakura

Juichi Morikawa

Makoto Ibe

Hideyuki Kawase

Yuji Sato

Seiichi Narushima

Toshio Nakamoto

Tetsuo Itou

Masanori Kochi

Hitoshi Takizawa

Hitoshi Okabe

Takashi Takahashi

Toshihiko Nakajima

Eiichi Hanawa

Tosio Uno

A speed control apparatus in which for sampling features of a speed fluctuation and generating a speed fluctuation correcting signal, an arithmetic operation can be simplified and can be performed by an inexpensive arithmetic and operation unit, thus requiring no expensive arithmetic operation unit. The speed control apparatus is also capable of reducing torque ripples and speed fluctuations quickly even when the load of an object to be controlled is changed.

Apparatus for controlling the speed of a moving object

A rotary head device having a rotary drum and a rotating motor within the rotary drum, with the stator of the motor being supported by a fixed arm attached to a fixed drum or to a fixed drum supporting member. The construction permits the manufacture of the rotary head device using the manufacturing equipment used for conventional rotary shaft type rotary head devices despite the rotary head device being a thin device. In this rotary head device the position of contact of a ground brush and a rotor can be set at the center of rotation or thereabouts, so despite it being a thin device, the sliding speed of the ground brush is low, and hence it is possible to prevent the abrasion of the ground brush and also to prevent increase of the rotative driving torque.

Rotary head device having a motor within the rotary drum, and magnetic

A rotary magnetic head cylinder device for use in a helical-scanning system video tape recorder has a projection provided on a tape running race of a stationary lower cylinder near a location at which a magnetic tape leaves from the lower cylinder. The projection is preferably integral with the tape running race and has a small area which is defined by a shoulder circumferentially extending identically with a tape guide shoulder contouring the lower edge of the tape running race and which spreads perpendicularly to the tape running race, and an upper surface coplanar with the top face of the lower cylinder, and a height defined by a protruded length radially outwardly toward the outer circumferential surface of the lower cylinder. The projection serves to reduce vibrations of the magnetic tape generated when the video head carried by the rotary upper cylinder leaves from the magnetic tape.

Rotary magnetic head cylinder device for suppressing vibrations ofa

There is provided a control circuit for a DC brushless motor suitable for use in acoustic devices or data cassette recorders which comprises a rotor magnet rotating synchronously with the motor rotor, three or more-phase stator windings opposing the rotor magnet and spaced apart therefrom by a slight gap, winding drive circuits for supplying exciting current to the stator windings, and Hall elements for detecting angular positions of the rotor magnet and producing output voltages supplied to the winding drive circuits. The control circuit further comprises a limit voltage setting circuit for setting two limit voltages respectively having upper and lower amplitudes which are symmetrically variable with respect to the central potential of the upper and lower amplitudes, an amplifier circuit associated with each of the Hall elements and amplifying the output voltage from the Hall element with respect to the central potential, and an amplitude limiter circuit limiting upper and lower amplitudes of the amplified output voltage from the amplifier circuit not to exceed the two reference voltages, thereby producing a trapezoidal waveform which in turn is applied to the winding drive circuit.

Control circuit for DC motors

Growing community of inventors

Katsuta, Japan

Toshio Osada