Hitachi, Ltd.

Syooichi Kawamata

Hiroshi Kimura

Kunio Miyashita

Shigeki Morinaga

Fumio Tajima

Nobuyoshi Mutoh

Hideki Nihei

Seizi Yamashita

Hideaki Horie

Noboru Sugiura

Shotaro Naito

Hiroshi Kanazawa

Hirohisa Yamamura

Hiroshi Hayashida

Shigeru Horikoshi

Yasuo Noto

Shunichi Tanae

Ryoichi Naganuma

The object of the present invention is to provide a small precise insulating type current sensor system. Sensing portion is composed of a magnetoresistance element, a bias conductor, and a current conductor, all of which are arranged on an insulating substrate. Resistance change of the magnetoresistance element is taken into an amplifier, and an output of the amplifier flows as a bias current to the bias conductor. When a current flows in the current conductor, the current causes a magnetic field and the resistance of the magnetoresistance element must be changed. However a feedback of the resistance change by the amplifier changes the bias current and controls the bias current for keeping the magnetic field of the magnetoresistance element at a constant. Accordingly, the insulation type current sensing with a wide range and preferable preciseness without being affected with a hysteresis of the magnetoresistance element and Barkhausen noise became possible.

Current sensor system and detection method comprising magetoresistance

A portable-type disk apparatus for a 3.5-inch or less optical disk implemented in a thin, light-weight and miniaturized structure having a vibration-withstanding capability. An optical head assembly is disposed stationarily while an optical disk and a spindle motor for rotating the optical disk are disposed movably in a diametrical direction of the optical disk. The spindle motor is constituted by a brushless motor of a substantially semi-circular form in cross section and having a laterally truncated portion. The optical head assembly including an optical head and a laser circuit is disposed at the side of the laterally truncated portion.

Optical disk apparatus

A magnetic sensor has a elongate sensor region formed by an elongate magneto-resistive element and an overlapping elongate conductive element. The ends of the magneto-resistive element and the conductive element are connected to terminals which are arranged in an array which is spaced in a predetermined direction from the elongate sensor region. The array may be at one side or one end of the elongate sensor region, and the terminals may have a linear arrangement within the array. The two terminals connected to the magneto-resistive element are preferably adjacent, and preferably the terminals connected to the ends of the magneto-resistive element and the conductive element closer to the array are also adjacent. A common terminal may be provided. Two such sensors may form a sensor array which is particularly suitable for use in a position sensor in e.g. a torque sensor of a power steering system.

Magnetic sensor

A linear actuator for e.g. a disk drive has a fixed member and a movable member. One of those members carries at least one track of permanent magnets extending in the direction in which the movable member is to move, with adjacent permanent magnets having alternate magnetic polarity. The other member has first and second drive parts, each having at least one pair of opposing sets of teeth. The moveable member or each track passes between those teeth. Each pair of teeth is associated with a corresponding drive coil giving the teeth a magnetic polarity so that there is a magnetic alignment between a polarity of the teeth and the permanent magnets. The drive parts are arranged so that, for any given relative position of the first and second members, the magnetic alignment of the teeth of one drive part is out of phase with the magnetic alignment of the teeth of the other part. In order to ensure that the magnetic alignments are out of phase, there may be a physical displacement between the teeth of the two drive parts. This displacement may be (m.+-.1/2).multidot.T.sub.p, where m is an integer and T.sub.p is the teeth pitch. This gives a phase displacement of 180.degree.. Alternatively, the drive parts may be aligned, and two tracks of permanent magnets be provided with the magnets thereof having opposite polarity for a given track position, or the drive current to the drive coils may be controlled to be out of phase.

Linear actuator

In an apparatus of detecting an environmental physical quantity such as magnetism and temperature by utilizing a sensitive element having an internal, electrical physical quantity which changes as the environmental physical quantity changes, an external operator element is provided which acts, when the environmental physical quantity acting on the sensitive element changes, a physical quantity corresponding to the change on the sensitive element, an electrical quantity supplied to generate in the external operator a physical quantity corresponding to the change is detected, and the environmental physical quantity is detected from the electrical quantity to provide a detection signal devoid of hysteresis and 'depression'.

Method and apparatus for detection of physical quantities, servomotor

An apparatus for magnetically detecting a positional relation between first and second members the positions of which change relative to each other comprises a magnetic recording medium carried on the first member and a magnetic sensor substrate supported by the second member. Two or more tracks each including a multiplicity of magnetic poles arranged at a predetermined pitch are provided on the magnetic recording medium, corresponding to the respective phases of two or more detection signals to be detected by the apparatus and in a direction in which the positional relation between the first and second members changes. The magnetic poles in any one of the tracks are shifted with respect to the magnetic poles in the other track by an amount corresponding to a phase difference between the detection signal for the phase which corresponds to the one track and the detection signal for the phase which corresponds to the other track. The magnetic sensor substrate includes a plurality of magnetoresistive elements which are respectively provided corresponding to the tracks and the electrical resistance value of each of which changes in response to a magnetic field originating from the corresponding track. The magnetoresistive elements are combined to generate electric signals as the detection signals. Each of the magnetoresistive elements corresponding to any one of the tracks and the corresponding one of the magnetoresistive elements corresponding to the other track are placed at the same position when viewed in the direction in which the positional relation between the first and second members changes.

Magnetic position detection apparatus having two magnetic recording

An actuator has a stepping motion function with a high stopping accuracy and resolution. The actuator includes a fixed portion and a movable portion constructed in combination so as to be movable relative to each other, a coil for imparting a moving force to the movable portion, a magnetic recording medium mounted on one of the fixed portion and the movable portion and recording magnetic signals, and a plurality of magnetic sensors mounted on the other thereof for detecting said magnetic signals in said magnetic recording medium, and wherein signals different in phase and output from said respective sensors are used by themselves, or signals inversely converted from the former signals are additionally used, and the coil is supplied with a driving force command by sequentially selecting and changing those signals.

Actuator with stepping motion function

The present invention relates to an apparatus for magnetically detecting positions and intends to provide a position detecting apparatus of the kind with high accuracy in which when recording magnetic signals of a predetermined length on magnetization tracks, a plurality of recording units are continuously arranged in the direction of the magnetization track and are set as the predetermined recording length, thereby sharpening the output waveform of the signal corresponding to the edge portion of the magnetization recording length. The present invention is suitable for the absolute type having a plurality of magnetization tracks.

Apparatus for magnetically detecting positions with minimum length

A device for detecting a load torque using angle detectors fitted with a certain spacing on a shaft which is rotated by a drive source and on the basis of a relative angular difference of angles detected by the angle detectors. The device includes two rotary drums or discs fitted with a certain spacing on the drive side and load side of the shaft, with a plurality of magnetic poles for generating magnetic signals being formed on the surface thereof, and a magnetic sensor disposed to confront the surface of the rotary drums or discs, with magnetic resistance effect elements which vary in internal resistance in response to the magnetism of the magnetic poles being provided thereon. The amount of torsion created by the load on the load side of the rotary shaft is measured as a phase difference of outputs of the magnetic sensor, and the torque is detected in terms of the angular difference between the magnetic drums or discs. The device is operative to detect a torque in both storage and rotation, and capable of detection within a period of magnetic signal, whereby high-accuracy, high-resolution torque detection is made possible.

Torque detecting apparatus

Magnetic poles are provided continuously with a pitch .lambda. on the peripheral portion of a drum rotated in accordance with a movement of a moving body. A magnetic sensor is provided in opposition to these poles. The sensor is formed of two magnetoresistive element pairs which are spaced from each other at .lambda./6, and the two elements in each pair are arranged in positions spaced from each other at .lambda./2. The two elements in each pair are connected in series to form a bridge circuit. The signals obtained from the nodes of the series-connected elements in the two element pairs are differentially amplified so that third harmonic wave components are eliminated, and a signal having no distortion and representative of the position or speed of the moving body can be obtained.

Apparatus for magnetically detecting position or speed or moving body

A magnetic position detector having a rotary magnetic recording medium which is movable with a movable body the position of which is to be detected. The rotary magnetic recording medium is divided into plural channels, each of which includes two tracks. A magnetic sensor is disposed to face the magnetic recording medium with a predetermined air gap therebetween and includes two sets of magnetoresistive elements spaced by a predetermined distance for each channel. Each set of magnetoresistive elements includes two elements wherein the first elements of the two sets face one of the tracks of a channel and the second elements of the other of the two sets faces the other track and the first and second elements of the two sets are formed as one body with adjacent ends of the first and second elements being coupled with each other. The coupled adjacent ends are connected to either one of first terminals for deriving output voltages from the magnetoresistive elements or to second terminals for supplying the magnetoresistive elements with source voltage. The non-adjacent ends of the first and second elements which are opposite to the coupled ends are connected to the other of the first and second terminals. In this manner, the sensor can be made small in size and the resistivity against noise is enhanced.

Magnetic sensor for magnetically detecting the position of a movable body

A device for magnetically detecting displacement, in which the middle points between the magnetic poles N and S of the magnetic signals recorded in different tracks, which are adjacent to each other, stand on common straight lines perpendicular to the direction of displacement and the direction from N to S of the magnetic signals is always the same, so that the magnetic signals in the different tracks, which are adjacent to each other, are aligned side by side and magnetic leakage between them is prevented.

Device for magnetically detecting displacement of non-magnetic movable

In a magnetic detector for receiving a reference position signal in movement from an encoder track and a reference track arranged on a member included in a magnetic position sensor, magnetic pickups respectively confronting to the encoder track and the reference track are provided and both tracks jointly yield a position reference signal.

Magnetic position sensor

A crank angle sensor comprises a magnetic recording medium rotating synchronously with crankshaft on which data is magnetically recorded and a magnetic sensor spaced apart from the magnetic medium and detecting the signals to produce rotational angle information. The magnetic recording medium is divided into plural tracks including an angle track and a cylinder track. On the angle track, unitary magnetic poles, serving as the magnetically recorded data are provided with a pitch P corresponding to the angle to be detected. The cylinder track contains unitary magnetic poles arranged adjacent those with a angle track in the pitch P and at locations which are determined by the number of cylinders of the engine. The polarities of the unitary magnetic poles on the cylinder track are the in same arrangement as those of the unitary magnetic poles of the angle track. No magnetic interference occurs between the unitary magnetic poles of the angle track and three of the cylinder track, so that angle signals and cylinder signals can be obtained with high accuracy.

Crank angle sensor

An apparatus for detecting the position of a moving member comprising a moving member having a magnetic substance with magnetical signals recorded thereon, and a stationary magnetic sensor confronting the moving member and having a plurality of magnetoresistive elements, wherein the magnetoresistive elements are disposed in the magnetic sensor such that the elements have a phase difference of .pi./m in electrical angle, where m is an even number larger than or equal to four, for obtaining the positional signal of the moving member.

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Hitachi, Japan

Syooichi Kawamata