Position detector utilizing two magnetic field sensors and a scale

• US 6,549,003 B2
• Filed: 03/27/2001
• Issued: 04/15/2003
• Est. Priority Date: 03/29/2000
• Status: Expired due to Term

• Current Assignee: MORI Seiki Company Limited
• Original Assignee: Sony Precision Technology, Inc. (Sony Group Corp.)
• Inventors: Nekado, Yasuo
• Primary Examiner(s): Lefkowitz, Edward
• Assistant Examiner(s): Zaveri, Subhash
• Application Number:
  US09/818,050
• Publication Number:
  US 20010035749A1
• Time in Patent Office: 749 Days
• Field of Search: 324/207.15, 324/207.24, 324/207.2, 324/207.21, 324/207.19, 324/207.16, 338/32.R, 338/32.M
• US Class Current: 324/207.15
• CPC Class Codes: G01D 3/0365 the undesired influence being measured using a separate sensor, which produces an influence related signal
• CPC Class Codes: G01D 5/145 influenced by the relative movement between the Hall device and magnetic fields see G01R33/06
• CPC Class Codes: G01D 5/2033 controlling the saturation of a magnetic circuit by means of a movable element, e.g. a magnet
• CPC Class Codes: G01D 5/24438 Special design of the sensing element or scale
• CPC Class Codes: G01D 5/24476 Signal processing G01D5/2448 - G01D5/24495 take precedence

Abstract

A position transducer including a scale and magnetic sensor system consisting of a first sensor unit and second sensor unit disposed in different positions in a direction (Z-direction) perpendicular to a moving direction (X-direction) of the magnetic sensor relative to the scale. The first and second sensor units are driven in phase with each other with a high frequency signal, and a difference between outputs of these two sensor units is determined in order to detect a relative position of the magnetic sensor to the scale.

Claims

1. A position transducer comprising:

magnetic field developing means for developing a magnetic field whose strength and direction change in response to a position of the magnetic field developing means;

magnetic field detecting means moved relatively to the magnetic field developing means for detecting a magnetic field developed by the magnetic field developing means and for providing an electrical signal corresponding to the detected magnetic field; and

relative position detecting means for detecting a relative position of the magnetic field detecting means relative to the magnetic field developing means in response to the electrical signal provided from the magnetic field detecting means, wherein

the magnetic field detecting means consists of two sensor units each formed from a sensor coil wound on a high permeability core and driven in phase with each other with a high frequency, the two sensor units being disposed in different positions in a direction perpendicular to a moving direction of the magnetic field detecting means relative to the magnetic field developing means, and

the relative position detecting means detects the relative position of the magnetic field detecting means relative to the magnetic field developing means by determining a difference between outputs of the two sensor units.

2. The position transducer as set forth in claim 1, wherein a magnetic shielding member is provided between the two sensor units of the magnetic field detecting means.