Magnetic encoder with high resolution of data signal recording at reduced recording pitch

• US 5,036,276 A
• Filed: 04/04/1990
• Issued: 07/30/1991
• Est. Priority Date: 04/05/1989
• Status: Expired due to Term

• Current Assignee: Seiko Epson Corporation (Seiko Group)
• Original Assignee: Seiko Epson Corporation (Seiko Group)
• Inventors: Aizawa, Hitomi
• Primary Examiner(s): Strecker, Gerard R.
• Application Number:
  US07/504,590
• Time in Patent Office: 482 Days
• Field of Search: 324/173, 324/174, 324/207.21, 324/207.24, 324/207.25, 324/252, 338/32 R, 235/449, 360/113
• US Class Current: 324/207.21
• 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 5/24404 Interpolation using high frequency signals

Abstract

A magnetic encoder comprises a sensor having a plurality of magnetoresistive (MR) elements placed in juxtaposed position relative to a magnetic recording medium upon which data signals are recorded employing a recording pitch, A. Output signals produced by the MR elements connected in a plurality of bridge circuits are formed by relative movement between the MR elements and the magnetic recording medium. The MR elements are positioned at A/n intervals, wherein n is an integer and n≧8. A multiplier circuit is connected to receive the output signals from the MR element bridge circuits and provide a plurality of phase shifted output signals corresponding to a A/N pitch interval of recording pitch, A, wherein N is an integer and N≧2.

Claims

1. A magnetic encoder comprising a sensor having a plurality of MR elements placed in juxtaposed position relative to a magnetic recording medium upon which data signals are recorded at a recording pitch, A, and wherein output signals are derived from said MR elements from the relative movement between said sensor and said recording medium, the improvement in said encoder comprising:

2n MR elements positioned at A/n intervals over two recording pitches, A₁ and A₂, relative to said recording medium recording pitch, A, wherein n is an integer and n≧

8,

said MR elements coupled into n/2 bridge circuits to produce n/2 multiphase output signals, and

a multiplier circuit is connected to receive said multiphase output signals to produce resultant phase shifted output signals derived from said multiphase output signals corresponding to a duty cycle of A/N wherein N is an integer and N≧

2.

2. The magnetic encoder of claim 1 wherein there are sixteen MR elements distributed uniformly relative to two recording pitches, A₁ and A₂, said MR elements formed as groups of four into four bridge circuits relative to said two recording pitches to provide for an increase in output level and improved frequency response characteristic of said encoder.

3. A magnetic encoder circuit comprising

a sensor having at least sixteen MR elements placed in juxtaposed position relative to a magnetic recording medium upon which data signals are recorded at a recording pitch, A, and wherein output signals are derived from said MR elements from the relative movement between said sensor and said recording medium,

said MR elements positioned at A/8 intervals over two recording pitches, A₁ and A₂, relative to said recording medium recording pitch, A, said MR elements formed into four groups of MR elements connected into four bridge circuits to provide four MR output signals,

said MR elements as grouped in each of said bridge circuits positioned at A/2 intervals relative to said two recording pitches, A₁ and A₂,

a plurality of differential amplifiers each connected to receive one of said MR output signals from one of said bridge circuits and amplify said one MR output signal, a plurality of comparator circuits connected to respectively receive an amplified output signal from one of said differential amplifiers and produce a plurality of pulse signals based upon said MR amplified output signals, and

XOR gates connected to respectively receive combinations of said pulse signals from respective of said comparator circuits to produce multiple phase shifted output signals having a reduced duty cycle compared to said MR output signals.

4. A magnetic encoder having a sensor placed in juxtaposed position relative to a magnetic recording medium upon which data signals are recorded at a recording pitch, A, wherein high resolution of data signal recording is obtained without a reduction in the sensor/medium gap formed between said sensor and said recording medium and comprising:

2n MR elements uniformly positioned over the span of two recording pitches, 2A, wherein n MR elements are provided per pitch, A, n is an integer with n≧

8,

said MR elements coupled into n/2 bridge circuits comprising groups of four MR elements per bridge circuit for producing n/2 respective multiphase output signals,

said MR elements in each of said bridge circuit groups respectively placed at every n/2 position over the span of said two recording pitches, 2A, and

a multiplier circuit connected to receive said multiphase output signals to produce resultant phase shifted output signals derived from said multiphase output signals corresponding to a duty cycle of A/N wherein N is an integer and N≧

2.

5. A magnetic encoder having a sensor placed in juxtaposed position relative to a magnetic recording medium upon which data signals are recorded at a recording pitch, A, wherein high resolution of data signal recording is obtained without a reduction in the sensor/medium gap formed between said sensor and said recording medium and comprising:

at least sixteen MR elements uniformly positioned over the span of two recording pitches, 2A, wherein eight MR elements are provided per pitch, A,

said MR elements coupled into four bridge circuits comprising groups of four MR elements per bridge circuit for producing four respective multiphase output signals,

said MR elements in each of said bridge circuit groups respectively placed at every fourth position over the span of said two recording pitches, 2A, and

a multiplier circuit connected to receive said multiphase output signals to produce resultant phase shifted output signals derived from said multiphase output signals corresponding to a duty cycle of one-half of said recording pitch, A.