Rotation detection device and bearing unit equipped with rotation detection device

Patent metadata

Field	Value
Publication number	US-9823094-B2
Application number	US-201615001856-A
Country	US
Kind code	B2
Filing date	Jan 20, 2016
Priority date	Jul 26, 2013
Publication date	Nov 21, 2017
Grant date	Nov 21, 2017

Abstract

The rotation detection device includes: an encoder having to-be-detected patterns cyclically arranged in the circumferential direction; and a sensor configured to detect the to-be-detected patterns to generate pulses. The device further includes a reference pattern storage unit, a phase difference detection unit, and an error correction unit. The reference pattern storage unit measures pitch errors in the to-be-detected patterns prior to operation and stores the pitch errors as a reference pattern Pref. The phase difference detection unit determines a pitch error pattern Pm corresponding to one rotation of the to-be-detected patterns from rotation signals representing a plurality of rotations detected during operation, and performs comparison with a reference pattern Pref to determine a relative phase difference φ. Based on the phase difference φ obtained by the phase difference detection unit, the error correction unit corrects errors included in the rotation signals detected by the sensor.

First claim

What is claimed is:

1. A rotation detection device comprising:
an encoder rotatably provided and having a plurality of to-be-detected patterns cyclically arranged in a circumferential direction;
a sensor configured to detect the to-be-detected patterns of the encoder to generate a pulse signal;
a reference pattern storage unit configured to measure pitch errors included in the to-be-detected patterns prior to detecting the to-be-detected patterns of the encoder and to store the pitch errors as a reference pattern;
a phase difference detection unit configured to determine a pitch error pattern corresponding to one rotation of the to-be-detected patterns from rotation signals representing a plurality of rotations detected by the sensor during detection of the to-be-detected patterns of the encoder, and configured to compare the pitch error pattern with the reference pattern to determine a relative phase difference; and
an error correction unit configured to, based on the phase difference determined by the phase difference detection unit, correct errors included in the rotation signals detected by the sensor.

2. The rotation detection device as claimed in claim 1 , wherein each of the reference pattern and the pitch error pattern is obtained through normalization by use of an average value.

3. The rotation detection device as claimed in claim 1 , wherein the phase difference detection unit performs correlation calculation while shifting a phase of the reference pattern and a phase of the pitch error pattern relative to each other, to calculate the phase difference.

4. The rotation detection device as claimed in claim 3 , wherein the phase difference detection unit calculates the phase difference by performing correlation calculation in which low frequency components equal to or lower than a predetermined frequency included in the reference pattern and the pitch error pattern are excluded and only high frequency components higher than the low frequency components are used.

5. The rotation detection device as claimed in claim 1 , wherein the error correction unit includes a pulse counter configured to output, by use of the phase difference obtained by the phase difference detection unit, a Z phase signal as a reference position signal when a current rotation angle of the encoder is a specific angle.

6. The rotation detection device as claimed in claim 1 , wherein the error correction unit is further configured to output a status signal indicating that the phase difference is obtained.

7. The rotation detection device as claimed in claim 6 , wherein the error correction unit is configured to output a Z phase signal as the status signal, and to wait to output the Z phase signal until the phase difference is obtained.

8. The rotation detection device as claimed in claim 1 , wherein the error correction unit is configured to also calculate a corrected rotational speed value of the encoder, based on the phase difference and the reference pattern.

9. The rotation detection device as claimed in claim 1 , wherein the phase difference detection unit is configured to perform normalization using an average period of rotation signals detected by the sensor to determine the pitch error pattern corresponding to one rotation, to calculates a normalization correlation value between the pitch error pattern and the reference pattern while shifting data of the pitch error pattern and data of the reference pattern relative to each other, and to judge that the phase difference is obtained when the normalization correlation value is greater than a predetermined threshold value.

10. A rotation detection device-equipped bearing unit comprising:
a bearing; and
the rotation detection device as claimed in claim 1 mounted to the bearing.

Assignees

• Ntn Toyo Bearing Co Ltd

Inventors

• Takahashi Toru
• Nishikawa Kentaro

Classifications

• G01D5/145

  influenced by the relative movement between the Hall device and magnetic fields (see G01R33/06) · CPC title

• G01D5/249

  using pulse code · CPC title

• G01D5/2449 Primary

  using hard-stored calibration data · CPC title

• G01D5/2448

  Correction of gain, threshold, offset or phase control · CPC title