JPS59164961A - Rotation detector - Google Patents

Abstract

PURPOSE:To enable a highly accurate detection of rotation while reducing the size and the weight of a motor by a method wherein outputs of magnetic resistance elements corresponding to three phases of the motor are added up and the added value is subtracted from the outputs of the elements. CONSTITUTION:A magneto-resistance element MR1 is arranged to face a magnetized band for generating a signal magnetic field at a desired circumferential position, an element MR2 to face the magnetized band for generating a signal magnetic field at the position shifted circumferentially by (m-1/3)lambdaS (lambdaS is the wavelength of the signal magnetic field) from the element MR1 as reference and an element MR3 to face the magnetized band for generating a signal magnetic field at the position shifted circumferentially by (n-2/3)lambdaS from the element MR1. Output voltages of the elements MR1-MR3 are added A to obtain an output only with a noise component but zero in the signal component, which is multiplied by 1/3 times and the results thereof subtracted C1-C3 from output voltages of the elements MR1-MR3. The subtraction outputs are provided as rotation detecting signal of the first to the third phase via amplifiers AP1-AP3 respectively.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application This invention relates to a rotation detection device for detecting the rotation of a motor used in a video tape recorder, a record player, or the like.

Structure of the conventional example and its problems As shown in FIG. A signal magnetic field generation magnetized band 2 having a signal magnetic field generation magnetic pole is coaxially fixed, and a first magnetoresistive element plate made of a ferromagnetic thin film made of a nickel alloy is attached to the signal magnetic field generation magnetized band 2. A ferromagnetic thin film made of a nickel alloy is placed at a position facing each other in the circumferential direction, and is shifted in the circumferential direction by (m-T)λ8 of the signal distribution magnetic field generating magnetic pole with respect to the first magnetoresistive element plate as a reference. A second magnetoresistive element plate, which is arranged to face the entire signal magnetic field generation magnetized zone 2, is located in the local direction by (n a ) λB of the signal magnetic field generation magnetic pole with respect to the first magnetoresistive element type. A third magnetoresistive element made of a ferromagnetic thin film made of a nickel alloy is placed oppositely at a shifted position.

In this case, the wavelength λ8 is from the N pole of the signal magnetic field generating magnetic pole to the N&
or the distance from south pole to south pole, m and n
is an integer. In addition, 3 is the shaft, 4 is the driving magnet]
and a back plate that integrally fixes the signal magnetic field generation magnetized belt 2 to the shaft 3, which includes the drive magnet 1. Magnetized belt for signal magnetic field generation 2. The shaft 3 and the back plate 4 together constitute a rotor.

Moreover, as shown in FIG. The second and third magnetoresistive elements MR, MR3, MR, are resistors R.

R3 and R3 are connected in series, a DC voltage element V is applied to these series circuits, and the voltage at the connection point of each series circuit is applied to the amplifier AP1. Ar1. Amplify with Ar1, amplifier A
Pyor Ar1 + Ar1 output as 1st phase and 2nd phase.

This was used as the third phase rotation detection signal.

However, such a conventional rotation detection device uses a magnetoresistive element hm0. The signal magnetic field generating magnetized band 2, which is the object to be detected by MR3 and MR5, is formed on the outer periphery of the driving magnet.The signal magnetic field generated from the signal magnetic field generating magnetized band 2 is inside the rotor. There is a much larger driving magnetic field than the magnetoresistive element MR, and this driving magnetic field is the magnetoresistive element MR.
This caused a large detection error in the detection of the signal magnetic field by MR3. Therefore, conventionally, magnetoresistive elements MR1, MR
2. In order to improve the detection accuracy of the signal magnetic field of MR3,
It was necessary to install a physical barrier such as a magnetic shield plate between the drive magnet 1 and the signal magnetic field generation magnetized belt 2. For this reason, electric motors have disadvantages in terms of use, such as increased size and weight, and in addition, there has been a problem that a sufficient magnetic shielding effect cannot be obtained depending on the material processing method. For example, if the number of magnetized magnetic strips 2 for signal magnetic field generation is increased in order to perform high-precision rotation detection, the signal magnetic field acting on the magnetoresistive element will decrease, but since the magnetic field of the drive magnet 1 is the same, the signal It is unavoidable that the degree of separation between the magnetic field and the driving magnetic field deteriorates, and as a result, the size of the magnetic shield increases and the weight increases. It is an object of the present invention to provide a rotation detection device that can be used to detect rotation.

Composition of the Invention The rotation detecting device of the present invention has a magnetized signal magnetic field generating magnetic field having a plurality of signal magnetic field generating magnetic poles circumferentially fixed coaxially to a driving magnet having a plurality of driving magnetic field generating magnetic poles circumferentially. a first magnetoresistive element disposed opposite the signal magnetic field generating magnetized strip at an arbitrary circumferential position; )
a second magnetoresistive element disposed opposite to the signal magnetic field generation magnetized zone at a position shifted in the circumferential direction by a wavelength (m is an integer);
a third magnetoresistive element disposed opposite to the signal magnetic field generating magnetized zone at a position shifted in the circumferential direction by (n-T) wavelength (n is an integer) of the signal magnetic field generating magnetic pole with respect to the first magnetoresistive element; a magnetoresistive element, an addition circuit that adds the voltage drops of the first, second, and third magnetoresistive elements, a division circuit that divides the output voltage of the addition circuit by three, and a division circuit that divides the output voltage of the addition circuit by three; The first step is to subtract the output voltage of the dividing circuit from the voltage drops of the second and third magnetoresistive elements, respectively. a second and a third subtraction circuit; The output voltages of the second and third subtraction circuits are used as first, second, and third phase rotation detection signals.

DESCRIPTION OF THE EMBODIMENTS FIG. 3 shows a circuit diagram of a rotation detection device according to an embodiment of the present invention. This rotation detection device uses a magnetic resistance element wind 0.
Voltage V at the connection point between deer 31 plate and resistor R□, R3, R3, V2. V3 is added in addition circuit A, and the output voltage of this addition circuit A is divided by 3 in division circuit B.9, subtraction circuit C, c2. Voltage ■, due to c3.

■3. The output voltage of the divider circuit B is subtracted from v3, and the output voltages of the subtractor circuits C, C2, and C3 are amplified by the amplifier AP p Ar1 t AJ'3, and the output voltage VX is obtained.

vY and v2 are the rotation detection signals of the first phase and the second phase 2M3 phases. The other configurations are the same as those in FIGS. 1 and M2.

This will be explained in more detail below. First magnetoresistive element MR1
(il- facing the magnetized belt 2 for signal magnetic field generation at an arbitrary position in the circumferential direction, and using the first magnetoresistive element MR□ as a reference (m
-1) The second magnetoresistive element MR3 is opposed to the signal magnetic field generation magnetized band 2 at a position shifted by λB in the circumferential direction, and further (n a ) with respect to the first magnetoresistive element preformed. λ
The third magnetoresistive element MR3 is placed at a position shifted by 8 in the circumferential direction.
When the first .
Second. The phase components that the third magnetoresistive elements MR, MR3, and MR3 have with respect to the wavelength λ8 of the signal magnetic field are ψ, (ψ−dπ), (ψm−π), and similarly the wavelength λN of the driving magnetic field
(The phase component with respect to the distance from N pole to N pole or from S pole to S pole is θ, (θ−Δε>, <a−2
Δε), the voltage VY, ■2. As V3, the following formula is obtained.

y = -V -sing) 10vNsinθ
・=-(1) 1 8 v2= v, -= <rp-'-π)+V, -1in
(θ−Δε)・−・・・・(2)v3=vs−sIn(
ψ−dπ)+vN−i(θ−2Δε)・・・・・・(3
) However, vs is the phase signal voltage to be detected from the magnetized band 2 for generating a signal magnetic field, and ■ is the noise equivalent voltage detected from the driving magnet 1.

These voltages v, L, v3. v3'i As shown in FIG. 3, the output obtained by leading to the adder circuit A becomes as follows.

V□=V8(ai++ψ+rj++ (ψ−HK)+
mmCcp - Month + V.

(io1i(θ−Δε)+i(θ−2Δε))...
...(4) At this time, sin ψ + 5 in (ψ - - π) 15 in (f - 1 π) =
Since 0 −・−(5)3.

■□=■, (θ1i(θ1Δε)1i(θ+2Δε...(6) is obtained.In other words, the signal component is zero and the output contains only the noise component. Therefore, in the magnetized zone 2 for generating a signal magnetic field for the purpose of high-precision rotation detection, the wavelength λ
8 is sufficiently small with respect to the wavelength λ, and λ8 becomes a sufficiently small value when converted into λ. This value is Δe and p, Δε〈kuθ ・・・・・・
- Obtain (7).

Here, the output of the adder circuit A described above becomes as shown below.

vi== 3 VNsin tl
-・---(8) Therefore, the output of this adder circuit A is multiplied by 1 and each magnetoresistive element MR□, MR2, MR
3 output voltage V□.

■3. By subtracting with V3, the magnetoresistive element M
This means that noise components can be removed from the outputs of R□, MR2, and MR3. That is, noise components are removed using an electrical method. The mathematical wl is shown below.

-V-ψ1VNI! inθ−3 VN, (iθJuyu(
θ−Δε〕+5in(θ−2Δε))
...Track (9) Now, considering the above-mentioned equation Δε< θ θ Δεzof:, we get the following.

V, = V8awr rp +VNamθ−jV, (
3sinθ) 1■Ejiψ, ・・
...(10) Similarly, VY = V8m (ψ-T K ) ・
−・−・−(31) V2 = Vs sin (ψ
-1. π )......(In the calculation formula for 12 and above, the formula was simplified by setting the amplifier gain in Fig. 3 to 1, but the gain can be set arbitrarily and the calculation formula as a device It is clear that the value enhancement is optional and does not detract from the spirit of the invention.

This embodiment makes it possible to detect the rotation of the electric motor with high accuracy, and also makes it possible to obtain a small and lightweight electric motor. For example, if the ratio of λ and λ is set to 1:200, and the conventional magnetic shielding method is used, the signal magnetic field strength Hs is about 500 Gauss, and the leakage magnetic field HN
existed at about 5 Gauss. ■Since N/v8 is proportional to HN/HB, the detection signal of the magnetoresistive element contained a noise component of about IS. However, when the electrical signal processing method of this embodiment is used, the error in approximating Δε to zero is considered to be a noise component included in the detection signal of the magnetoresistive element.

If we calculate the Δε component here, it will be as follows.

Apricot λ8; city λN (λN/λ8=200) Δε=In [
radian] 0(Δε)=0.9999 That is, the detection error due to the zero approximation of Δε is 0.01%. In this way, although the conventional method includes one or more noise components in the detection signal, this method can reduce the noise components to 'to, o]%. In addition, the electric motor according to the detection method of this embodiment is extremely advantageous in practice because the magnetic shield portion can be simplified or eliminated.

In addition, in the above embodiment, the magnetoresistive elements MR0, MR3゜M
Voltage is divided between R3 and resistor R + Ra, R3, but instead of resistor R□, R2, R3, magnetoresistive element MR□
, MR2 and MR3 may be used to divide the voltage using three magnetoresistive elements installed at complementary positions. Note that the complementary positions are the three reference magnetoresistive elements MR, MR
2. In contrast to MR3, it is called a magnetized band for generating a signal magnetic field, and the three magnetoresistive elements arranged in complementary positions can be arranged in a positional relationship that does not contact the magnetized band 2 for generating a signal magnetic field. desirable.

Effects of the Invention The rotation detection device of the present invention can electrically reduce detection errors caused by a driving magnetic field, reduce or eliminate magnetic shielding in a motor, and make the motor smaller and lighter.

[Brief explanation of drawings]

Figure M1 (6) is a partially cutaway side view and plan view showing the configuration of the rotor section of a conventional rotation detection device, Figure 2 is an electrical block diagram, and Figure 3 is an embodiment of the present invention. FIG. 1... Drive magnet, 2... Magnetized belt for signal magnetic field generation,
Song, MR2, MR3... Magnetoresistive element, R□,
R3, R3...Resistor, A...Addition circuit, B...Division circuit, Cyu, C2゜C3...Subtraction circuit, AP□,
AP2. AP3... Amplifier agent Patent attorney Akio Miyai Figure 2

Claims (1)

[Claims] A signal magnetic field generating magnetized band having a plurality of signal magnetic field generating magnetic poles in the local direction and fixed coaxially to a driving magnet having a plurality of driving magnetic field generating magnetic poles in the circumferential direction, and the signal magnetic field generating magnetized band a first magnetoresistive element disposed facing each other at an arbitrary position in the circumferential direction; A second magnetoresistive element disposed opposite to the signal magnetic field generating magnetized strip at a shifted position, and a (n-) wavelength (n is a third magnetoresistive element disposed opposite to the signal magnetic field generating magnetized zone at a position offset in the circumferential direction by an integer; an addition circuit that adds the voltage drops of the second and third magnetoresistive elements, a division circuit that divides the output voltage of the addition circuit by the total 3, and a voltage drop of the first, second, and third magnetoresistive elements; first, second and third subtraction circuits that subtract the output voltages of the division circuits, respectively; the first, second and first . The output voltage of the subtraction circuit is -] phase,
A rotation detection device that uses second-phase and third-phase rotation detection signals.