JPH03282213A - Magnetic encoder - Google Patents

Abstract

PURPOSE:To sharpen the edge of an REF signal, to improve detecting accuracy and to eliminate adverse effect on an INC signal by making the pitches of signal generating magnetic poles equal for both signals, and specifying the arrangement of magnetoresistance elements for the REF signals. CONSTITUTION:The pitch for REF-(reference) signal generating magnetic pole tracks 3 and the pitch of INC-(incremental) signal generating magnetic-pole tracks 4 are made equal. Two elements R7 and R8 of magnetoresistance effect elements R6-R9 corresponding to the REF-signal generating magnetic-pole tracks 3 are arranged so as to face elements R3 and R4 of magnetoresistance elements R2-R5 corresponding to the INC-signal generating magnetic-pole tracks 4. The other magnetoresistance elements R6 and R9 are surfficiently separated to the positions on both sides where the magnetism form the REF-signal generating magnetic tracks 3 is not sensed. The elements are inserted in the facing sides of a bridge.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a magnetic encoder, and particularly to a magnetic encoder using a magnetoresistive element.

[Conventional technology]

Conventionally, for example, an automobile crank angle sensor uses an incremental (INC) signal and a reference (INC) signal to know the crank angle.
REF) signal, which requires a wide signal and a narrow signal.

FIG. 4 shows a conventional magnetic encoder for obtaining such a signal, in which 1 is a magnetic drum, and 2 is a plate-shaped magnetic sensor disposed opposite to the outer peripheral surface of the magnetic drum l. As shown in FIG. 5, on the outer circumferential surface, a REF signal generating magnetic pole trunk 3 magnetized in the circumferential direction is formed in one of the axial parts, and the other part is similarly magnetized in the circumferential direction. A magnetic pole track 4 for generating an INC signal is formed.

Further, on the surface of the magnetic sensor 2 facing the magnetic drum 1, there is a fifth
As shown in the figure, a magnetoresistive element R2 such as permalloy corresponding to the magnetic pole track 3 for generating the REF signal of the magnetic drum 1 is arranged, and a permalloy element R2 forming a bridge corresponding to the magnetic pole trunk 4 for generating the INC signal is arranged. Four magnetoresistive elements R1 to R3 are arranged in line.

FIG. 6 is a waveform diagram showing the REF signal obtained by the magnetoresistive element R of the magnetic sensor 2 and the INC signal obtained by the magnetoresistive elements R2 to R2.

[Problem to be solved by the invention]

However, in the REF signal generation magnetic track 3 in a conventional magnetic encoder, each NS magnet is formed across a plurality of NS magnets in the NCNC signal generation magnetic track 4, so the magnetization width is small. becomes wider, and due to the leakage magnetic flux, the edges of the REF signal become distorted as shown in Figure 6.
There was a drawback that it adversely affected NC signal generation.

The present invention has been made to eliminate the above-mentioned drawbacks. [Means for Solving the Problems] The magnetic encoder of the present invention includes a rotating part in which a plurality of pieces of magnetic information are recorded along the movement direction, and a rotating part in which a plurality of pieces of magnetic information are recorded along the moving direction. In a magnetic encoder that has a magnetoresistive effect element placed opposite to the magneto-resistance effect element and extracts a position signal as a change in resistance value, the magnetic pole pitch of the magnetic pole trunk for generating the REF signal is adjusted by INC.
Two magnetoresistive effect elements are made equal to the magnetic pole pitch of the signal generation magnetic pole track, and the magnetoresistive effect element corresponding to the REF signal generation magnetic pole track is located at a position sensitive to the signal magnetic field, and two magnetoresistive effect elements are located at a position not sensitive to the signal magnetic field. A bridge circuit is formed by these magnetoresistive element groups, and the magnetoresistive elements positioned at non-sensitive positions are inserted on opposite sides of the bridge. shall be.

[For production]

In the magnetic encoder of the present invention, two magnetoresistive elements located at positions that are not sensitive to magnetism act as fixed resistances of the bridge, and the signal waveforms obtained by the other two magnetoresistive elements are subtracted from each other to form the bridge. A REF signal with sharp edges appears at the output terminal.

〔Example〕

The present invention will be explained in detail below with reference to the drawings.

In the present invention, as shown in FIG. 1, the magnetic poles in the REF signal generation magnetic pole trunk 3 are arranged at the same pitch as the magnetic poles in the INC signal generation magnetic pole trunk 4, and a plurality of magnetic poles are formed, and this REF signal generation magnetic pole track 3
Four magnetoresistive elements R6 to R9 are used as magnetoresistive elements of the magnetic sensor 2 corresponding to the magnetic sensor 2, of which two magnetoresistive elements R, , R correspond to the magnetic pole trunk 4 for generating the INC signal. Four magnetoresistive elements R, -
The two magnetoresistive elements Rh and Rq are arranged opposite to the two in the center among R3, and the other magnetoresistive elements Rh and Rq are arranged in positions where they are not sensitive to the magnetism of the REF signal generating magnetic pole trunk 3 which is sufficiently layered on both sides. At the same time, as shown in FIG. 2, the magnetoresistive elements R, , R, which are shifted to both sides, are inserted and used on the opposite sides of the bridge.

Since the magnetic encoder of the present invention has the above-described configuration, the magnetoresistive elements R6 and Rq do not change even if the magnetism of the magnetic drum I changes, and therefore the magnetoresistive elements R6 to R7 and the bridge R of output terminal e,,e2
The signal waveform of the EF signal and the output e out is as shown in FIG.

〔Effect of the invention〕

According to the magnetic encoder of the present invention, as shown in FIG.
The edges of the EF signal output are as sharp as the INC signal, thus improving accuracy and without the risk of adversely affecting the rNc signal.

Further, there is a great advantage that the pulse width can be arbitrarily adjusted by changing the number of magnetic elements constituting each NS magnet of the magnetic scratching trunk 3 for generating the REF signal.

[Brief Description of the Drawings] Fig. 1 is an explanatory diagram of the magnetic drum and magnetic sensor in the magnetic encoder of the present invention, Fig. 2 is a wiring diagram of its magnetoresistive element, Fig. 3 is a signal waveform opening of each part, Fig. 4 is an explanatory diagram of a magnetic encoder, Fig. 5 is an explanatory diagram of a magnetic drum and magnetic sensor in a conventional magnetic encoder, and Fig. 6 is an explanatory diagram of a magnetic drum and a magnetic sensor in a conventional magnetic encoder.
FIG. 3 is a waveform diagram of a signal obtained from the magnetic sensor shown in the figure. 1...-Magnetic drum, 2... Magnetic sensor, 3...R
Magnetic pole trunk for EF signal generation, 4... Magnetic pole trunk for INC signal generation, R1-R9... Magnetoresistive effect element.

Claims (1)

[Claims] (1) It has a rotating part on which a plurality of pieces of magnetic information are recorded along the direction of movement, and a magnetoresistive element placed opposite to this rotating part, and a position signal is extracted as a change in resistance value. In the magnetic encoder, the magnetic pole pitch of the magnetic pole track for generating the REF signal is made equal to the magnetic pole pitch of the magnetic pole track for generating the INC signal, and the magnetoresistive effect element corresponding to the magnetic pole track for generating the REF signal is set at a position sensitive to the signal magnetic field. A bridge circuit is formed by these magnetoresistive element groups, and the magnetoresistive element is set at the non-sensitive position. A magnetic encoder characterized in that elements are inserted on opposite sides of this bridge.