Phase difference detector and rotation angle detection device including the same

Patent metadata

Field	Value
Publication number	US-9638509-B2
Application number	US-201314104647-A
Country	US
Kind code	B2
Filing date	Dec 12, 2013
Priority date	Dec 12, 2012
Publication date	May 2, 2017
Grant date	May 2, 2017

Abstract

In a phase difference detector, a first phase difference computation unit computes a value of E(i)·C corresponding to one and the same given magnetic pole sensed by the two magnetic sensors with use of six output signals sampled at three different timings while the two magnetic sensors are sensing the given magnetic pole when a rotary body is rotating. E is an angular width error correction value, and C is a phase difference between two signals. The first phase difference computation unit executes this process until values of E(i)·C corresponding to all the magnetic poles are computed. After that, the first phase difference computation unit computes the phase difference between the output signals with use of the values of E(i)·C corresponding to all the magnetic poles and the number (m) of the magnetic poles.

First claim

What is claimed is:

1. A phase difference detector comprising:
a multipolar magnet that rotates in accordance with rotation of a rotary body, and that has a plurality of magnetic poles;
two magnetic sensors that are a first magnetic sensor and a second magnetic sensor, and that respectively output sinusoidal signals having a predetermined phase difference in accordance with rotation of the multipolar magnet; and
a phase difference computation unit that computes the phase difference with use of the output signals from the two magnetic sensors, wherein
where an output signal S 1 from the first magnetic sensor is expressed by S 1 =A 1 sin(E 1 θ) in which A 1 is an amplitude of the output signal S 1 , E 1 is a magnetic pole width error correction value for a magnetic pole sensed by the first magnetic sensor, and θ is a rotation angle of the rotary body, an output signal S 2 from the second magnetic sensor is expressed by S 2 =A 2 sin(E 2 θ+C) in which A 2 is an amplitude of the output signal S 2 , E 2 is a magnetic pole width error correction value for a magnetic pole sensed by the second magnetic sensor, and C is a phase difference between the output signal S 2 from the second magnetic sensor and the output signal S 1 from the first magnetic sensor, m is the number of the magnetic poles of the multipolar magnet, i is a natural number from 1 to m, which is used to relatively identify each of the magnetic poles, and E(i) is a magnetic pole width error correction value corresponding to each of the magnetic poles,
the phase difference computation unit includes
a first computation unit that executes a process of computing a value of E(i)·C corresponding to one and a same given magnetic pole sensed by the two magnetic sensors with use of six output signals that are sampled at three different timings while the two magnetic sensors are sensing the given magnetic pole when the rotary body is rotating, until values of E(i)·C corresponding to all the magnetic poles are computed, and
a second computation unit that computes the phase difference C with use of the values of E(i)·C corresponding to all the magnetic poles computed by the first computation unit and the number m of the magnetic poles of the multipolar magnet.

2. The phase difference detector according to claim 1 ,
where n is a number of a present sampling period and the six output signals are expressed by expressions (a1) to (a6), the first computation unit is configured to compute the value of E(i)·C of the given magnetic pole according to an expression (b)

S
1

⁡

(
n
)

=

A
1

⁢

sin
⁡

(

E
⁡

(
i
)

·

θ
⁡

(
n
)

)

(
a1
)

S
1

⁡

(

n
-
1

)

=

A
1

⁢

sin
⁡

(

E
⁡

(
i
)

·

θ
⁡

(

n
-
1

)

)

(
a2
)

S
1

⁡

(

n
-
2

)

=

A
1

⁢

sin
⁡

(

E
⁡

(
i
)

·

θ
⁡

(

n
-
2

)

)

Assignees

• Jtekt Corp

Inventors

• Takaki Takeshi
• Kariatsumari Yuji
• Shimizu Yoshinobu

Classifications

• G01D5/244 Primary

  influencing characteristics of pulses or pulse trains; generating pulses or pulse trains · CPC title

• G01B7/30 Primary

  for measuring angles or tapers; for testing the alignment of axes · CPC title