JP2685489B2 - Device that magnetically detects position and speed - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a device for detecting a position and a velocity, and in particular, it is suitable for temperature compensation of a detection device using a magnetoresistive effect element or for use in this. The present invention relates to a magnetic sensor.

[Conventional technology]

In a conventional device, a position detecting device using a magnetoresistive effect element generally does not consider a change in output amplitude with temperature. This is because the output of the magnetoresistive effect element is used as a square wave after being waveform-shaped, and therefore the influence on the square wave output is small even without temperature compensation.
However, a sine wave output device is required for the purpose of improving the position detection resolution. If the output is a sine wave, the resolution can be made higher than the conventional square wave by using an analog value. We have already proposed this technique in JP-A-62-204118.

[Problems to be solved by the invention]

However, if the amplitude of the sine wave output changes due to the influence of temperature, an error will occur and temperature compensation will be required. Further, even when the waveform is shaped into a square wave, if temperature compensation is performed, it is possible to achieve higher precision and higher resolution. However, in the above-mentioned conventional technique, consideration is not given to temperature compensation of the output amplitude of the magnetoresistive effect element, and the amplitude of the output voltage changes depending on the temperature, so that it is difficult to obtain high resolution.

A first object of the present invention is to obtain a device for detecting a position and velocity with high accuracy and high resolution by compensating that the output of a magnetoresistive effect element changes with temperature and removing the influence of temperature. And, a second object is to provide a magnetic sensor suitable for this device.

[Means for solving the problem]

The present invention relates to a first member and a second member that move close to each other, a magnetic recording medium carried by the first member, a magnetic signal recorded on the magnetic recording medium, and a second member.
Of the magnetic sensor carried by the member, a plurality of magnetoresistive effect elements which are carried by the base body and change in electric resistance in response to a magnetic signal of the magnetic recording, and electric power from these magnetoresistive effect elements. In a device for detecting a relative position or speed between a first member and a second member by a signal, the plurality of magnetoresistive effect elements are configured as three terminals or a bridge circuit so that an offset due to temperature is corrected, In addition to the plurality of magnetoresistive effect elements, the second element and the plurality of magnetoresistive effect elements carry a second element whose internal resistance changes in proportion to the temperature around which the magnetic sensor is arranged. The second element and the plurality of magnetoresistive effect elements are formed of the same material, and the second element and the plurality of magnetoresistive effect elements are formed on the same chip. The second element is supported on the base, the second element is arranged such that the longitudinal direction of the second element matches the magnetic field direction of the magnetic signal, and the longitudinal direction of the second element and the longitudinal directions of the plurality of magnetoresistive effect elements. Are arranged so as to be orthogonal to each other, and the input voltage or output amplitude of the magnetoresistive effect element circuit is corrected by the output of the second element.

[Action]

Since the output of the magnetoresistive element in the magnetic sensor that constitutes the position detecting device changes with temperature, this temperature is measured and the input voltage of the magnetic sensor is controlled so that the output becomes constant with respect to temperature. If the gain of the circuit for amplifying the output of the magnetoresistive effect element is made variable according to the temperature, the output of the position detecting device can be kept constant with respect to the temperature.

That is, the second element, the internal resistance of which changes according to the temperature of the atmosphere in which the magnetic sensor of the present invention is arranged, becomes the magnetoresistive effect element when the output of the magnetoresistive effect element tends to decrease due to the temperature change. Increase the applied input voltage,
Further, when the output of the magnetoresistive effect element tends to increase, it acts so as to reduce the input voltage applied to the magnetoresistive effect element.

〔Example〕

An embodiment of the present invention will be described below with reference to FIGS. 1 to 6. FIG. 1 shows the configuration of a rotational position detecting device using a magnetoresistive effect element. Reference numeral 1 is a rotating shaft such as a motor shaft. A magnetic drum 2 having a magnetic medium 21 on its surface is fixed to the rotary shaft 1. The magnetic signal N-S is continuously recorded on the magnetic medium 21 by magnetizing writing.
Reference numeral 3 is a magnetic sensor 3 arranged close to and facing the magnetic drum. The magnetic sensor 3 has a base 31.
31 has a plurality of magnetoresistive effect elements. Therefore,
When the magnetic drum 2 rotates, the magnetic field applied to the magnetoresistive effect element changes corresponding to the magnetic signal N-S, so that the rotational position of the magnetic drum 2 can be detected as the resistance change of the magnetoresistive effect element. FIG. 2 is an expanded view of the relationship between the magnetic drum 2 and the magnetic sensor 3. On the magnetic medium 21 of the magnetic drum 2, as shown in the drawing, the magnetic signals N-S, S of the recording pitch .lambda.
Keeps track -N is continuously constituted by the magnetoresistive element MR ₁ ~MR ₄ and MR ₅ The magnetic sensor 3 in response thereto. The magnetoresistive effect elements MR _{1 to} MR ₄ are arranged at λ / 2 intervals and
₅ is arranged in a direction orthogonal to these. Figure 3 constitute a bridge at each magnetoresistive element MR ₁ ~MR ₄ in connection diagram of the magnetoresistive element MR ₁ ~MR _4. Further, each of the magnetoresistive effect elements MR _{1 to} MR ₅ is made of a thin film such as permalloy or NiCO, and due to the magnetic H in the direction perpendicular to the longitudinal direction,
The internal electric resistance changes as shown in FIG. However, the electric resistance hardly changes with respect to the magnetic field in the longitudinal direction. Therefore, when the magnetic drum 2 of FIG. 1 rotates, the magnetic signal magnetic field H _m as shown in FIG. 4 is applied to each of the magnetoresistive effect elements MR _{1 to} MR ₄ of the magnetic sensor 3 by a magnetic signal.
Since this magnetic field H _m is continuously generated while the magnetic drum 2 is rotating, the resistance change of the magnetoresistive effect element MR _{1 and} the like has a continuous waveform as shown in the figure. In addition, the magnetoresistive effect element MR ₂ is M
Since the λ / 2 position is displaced with respect to R ₁ , the resistance changes as shown by the broken line in the figure. Similarly, the magnetoresistive effect elements MR ₃ and MR ₄
Also has a waveform as shown. Therefore, since the DC voltage V is applied to the input terminal of the bridge circuit of FIG. 3, an output like e ₀ of FIG. 4 is obtained at the output terminal e ₀ .

On the other hand, the resistance value of each magnetoresistive element changes with temperature, and the resistance value also increases as the temperature rises.
Therefore, when the temperature rises, the amplitude of the output e ₀ in FIG. 3 decreases, and the temperature characteristic of the output e ₀ with respect to the temperature changes with the temperature like e ₀₁ shown by the broken line in FIG.

FIG. 5 shows a circuit for compensating for this temperature change.
A magnetoresistive element MR ₅ and fixed resistors R _{1 to} R ₃ form a resistor bridge as shown in the figure.
It is connected to the input terminal of the amplifier OP ₁ via ₄ and R ₅ , and the feedback resistor R ₆ is connected between the negative input and the output of the amplifier. The magnetoresistive element M is connected to the output of the amplifier OP _1.
Connects the power supply terminals of the bridge circuit of R ₁ ~MR _4, the other end of the power terminals are added to the negative voltage -V. The input terminals of the amplifier OP ₂ are connected from the output terminals c and d of the bridge of the magnetoresistive effect elements MR _{1 to} MR ₄ through the resistors R ₇ and R ₈ . A feedback resistor R ₉ is connected between the negative input and the output of the amplifier OP ₂ .
In this circuit configuration, when the temperature is constant, the resistance of the magnetoresistive effect element MR ₅ is constant, and the output of the amplifier OP ₁ , that is, the input voltage V _m of the bridge of the magnetoresistive effect elements MR _{1 to} MR ₄ is constant. However, when the temperature rises, the magnetoresistive effect element
Voltage at the negative input of the amplifier OP ₁ is lowered since the resistance of the MR ₅ is raised, so that the input voltage V _in the bridge of the magnetoresistive element MR ₁ ~MR ₄ rises. This input voltage V over temperature
_in becomes like Vin _in Fig. 6. Therefore, the amplification of the output e ₀ of the bridge of the magnetoresistive effect elements MR _{1 to} MR ₄ shown in FIG. 5 is just offset with respect to the temperature, and the change due to the temperature is compensated. As a result, the amplitude of the output E ₀ of the increasing device OP ₂ which is the output of the position detecting device can be compensated without changing the amplitude as shown by the solid line in FIG. Since the magnetoresistive effect element MR ₅ is arranged in the longitudinal direction with respect to the magnetic signal of the magnetic drum 2, no resistance change occurs due to the magnetic signal magnetic field H _m . Further, since the magnetoresistive effect elements MR _{1 to} MR ₄ and the magnetoresistive effect element MR ₆ for temperature compensation are made of the same material and are formed on the same chip, they have almost the same change in temperature. Can be done almost completely.

Furthermore, when different materials are used for the magnetoresistive element MR ₅ and MR ₁ to MR ₄ , the temperature coefficients of the two differ, but the amplification factor determined by the resistors R ₅ and R ₆ of the amplifier OP ₁ is adjusted. Complete temperature compensation is possible.

Further, in this example, the temperature compensating resistor MR ₅ is composed of a magnetoresistive effect element, but the same effect can be obtained as long as the resistance changes with temperature with other materials. Further, in the example of FIG. 2, the magnetoresistive effect element MR ₅ is arranged so that the magnetic field from the magnetic drum 2 is received in the longitudinal direction, but if it is arranged at a position where the magnetic field from the magnetic drum 2 does not reach, The direction of the arrangement can be arbitrary.

FIG. 7 shows another embodiment of a magnetoresistive element for temperature compensation.
This is an example in which MR ₅ is arranged next to other magnetoresistive effect elements MR _{1 to} MR ₄ . In FIG. 7, L _{1 to} L ₅ are the magnetoresistive effect elements MR _{1 to} MR _{5 respectively.}
And has a width sufficiently wider than MR _{1 to} MR ₅ so that resistance change does not occur with respect to the signal magnetic field H _m from the magnetic drum 2. Further, since the magnetoresistive effect element MR ₅ is arranged in the longitudinal direction with respect to the signal magnetic field of the magnetic drum 2, the resistance change is not caused by the signal magnetic field. That is, since the magnetoresistive effect element MR ₅ causes a resistance change only with respect to a temperature change, it is possible to perform temperature compensation in combination with FIG.

FIG. 8 is a temperature compensation circuit showing another embodiment. Resistor bridge composed of resistors R _{1 to} R ₃ and magnetoresistive effect element MR ₅ for DC voltage V, and magnetoresistive effect elements MR _{1 to} MR ₄
The bridge configured in is connected. The output of each bridge is applied to the input terminals of amplifiers OP ₁ and OP ₂ via resistors R ₇ , R ₈ and R ₄ , R ₅ . Further connecting a feedback resistor R ₉ and R ₆ are between the negative input terminal and the output terminal of each amplifier OP ₁ and OP _2, the output of each amplifier OP ₁ and OP ₂ are applied to the input of the multiplier MP, a multiplier The output E _{0 of} MP is the output of the position detection device. The output V _c of the amplifier OP ₁ has exactly the same configuration as the output V _in of OP ₁ in FIG. 5, and changes in proportion to temperature as indicated by the one-dot broken line V _{c in} FIG. In addition, the magnetoresistive element MR _{1 to} M
Bridge output of R ₄ is the temperature as described in FIG. 5, the amplifier OP ₂ is output amplitude amplifying this because drops
Output e ₀₂ changes in inverse proportion to temperature as indicated by the broken line in FIG. Therefore, the product of the voltages V _c and e _{0 in} FIG. 9 is E ₀ where the output amplitude does not change with temperature.

FIG. 10 shows another embodiment of the temperature compensation circuit. Resistors R _{1 to} R ₃ and magnetoresistive elements MR ₅ and MR ₁ to DC voltage V
MR ₅ has the same structure as in FIG. 9, and the resistance of amplifier OP ₁ is also shown in FIG.
It is the same as the figure. The bridge outputs of the magnetoresistive elements MR _{1 to} MR ₄ are connected to the inputs of the variable gain amplifier VOP via resistors R ₄ and R ₅ . The variable gain amplifier VOP is an amplifier whose internal gain is determined by the output voltage of the amplifier OP ₁ . Therefore, the output amplitude of the magnetoresistive element MR ₁ ~MR ₄ changes as shown in dashed line in Fig. 9 by temperature. However, since the gain of the amplifier VOP that amplifies the output changes with the output indicated by the alternate long and short dash line in FIG. 9, its output E ₀ has a constant value with respect to temperature as shown by the solid line in FIG.

Although the rotating body has been described as an example of the position detecting device, the same operation and effect can be obtained even if the present invention is applied to a linear moving body.

FIG. 11 shows another embodiment of temperature compensation. This embodiment is an example in which the temperature detection is shared by the magnetoresistive effect elements MR _{1 to} MR ₄ for position detection, without using a temperature detection element specially. Resistors R ₁ and R ₂ are connected in series to the power source V, and the midpoint between them is connected to the positive input of the amplifier OP ₁ . Further, a resistor R ₃ is connected in series to the bridge of the magnetoresistive effect elements MR _{1 to} MR ₄ connected to the output of the amplifier OP _{1, and} the amplifier OP is connected via the resistor R ₄ from its midpoint a _0.
Connect to negative input of ₁ . Furthermore, magnetoresistive effect elements MR _{1 to} MR
_From the output of the bridge of ₄ to the amplifier O via the resistors R ₉ and R _10.
Connect to P ₂ input. The output of the amplifier OP ₁ has a resistance R ₆ ,
R ₇ is connected in series and the amplifier is connected from its midpoint through resistor R _8.
Connect to the input terminal of OP ₂ . Feedback resistors R ₅ and R ₁₁ are connected between the outputs of the amplifiers OP ₁ and OP ₂ and the negative inputs. The potential at the midpoint b ₀ of the resistors R ₁ and R ₂ biases the amplifier OP ₁ so that the voltage V _{in at} the output of OP ₁ is generated.
In addition, each magnetoresistive effect element MR ₁ and MR ₂ and MR ₄ and MR ₃ are
As shown in the figure, the resistance change phase is opposite to the magnetic field H _m due to the magnetic signal, so MR ₁ and MR ₂ and MR ₄ and MR ₃
Since the resistance change seen from the serial terminal of is not canceled and becomes a constant value, the potential at the point a ₀ is constant in the position detection operation. However, if the temperature rises, the magnetoresistive effect elements MR _{1 to} MR ₄
Resistance increases. Since the fixed resistance R ₃ hardly changes in resistance with temperature, the potential at the point a ₀ decreases with increasing temperature. Therefore, since the negative input potential of the increasing unit OP ₁ decreases, the output of OP ₁ operates so as to increase, so that the potential of the point a ₀ is kept constant. This is to compensate for the increase in the values of the magnetoresistive electrons MR _{1 to} MR ₄ due to the temperature and the resulting decrease in the amplitude of the position detection output. This position detection output E ₀ by controlling the voltage V _in applied to the magnetoresistive element MR ₁ ~MR ₄ by temperature as in the sixth Figure
The amplitude of is constant with respect to temperature changes. The resistors R ₆ and R ₇ are biased so that the offset of the circuit does not change with temperature. That is, when an offset occurs in the bridge outputs of the magnetoresistive elements MR _{1 to} MR ₄ , the voltage V _in changes due to the temperature change, and therefore the offset voltage also changes. So the resistance R ₆ , R
By canceling this offset with ₇ , it is possible to remove the offset change in the output of the amplifier OP ₂ . As described above, in this embodiment, temperature compensation is possible without using a temperature detecting element other than the position detecting magnetoresistive effect element.

Although the example of FIG. 11 is an example in which four magnetoresistive effect elements are used to form a bridge, the same can be applied to a position detecting device using two or one magnetoresistive effect element. Further, the resistance R ₃ of FIG. 11 is best one having a small temperature coefficient, but the same effect can be obtained if it is different from the temperature coefficient of the magnetoresistive effect element. Further, if the resistance R ₃ has a smaller value than that of the magnetoresistive effect element, the voltage applied to the magnetoresistive effect element can be increased, which is advantageous. Therefore, if the amplification factor of the amplifier OP ₁ is adjusted by the resistors R ₄ and R ₅ according to the value of the resistor R ₃ , good temperature compensation is possible.

FIG. 12 shows another configuration regarding the arrangement of the magnetoresistive effect element MR ₅ .

In FIG. 12, an element for detecting the ambient temperature is shown.
MR ₅ is carried on the insulating base 31, and the insulating base G is coated with an insulating coating G such as glass. Then, the magnetoresistive effect elements MR _{1 to} MR ₄ are carried on the insulating coating G. At this time, the element MR ₅ is positioned directly below the magnetoresistive effect element MR ₃ .

With this configuration, the magnetic signal N-S from the magnetic medium is generated.
As described above, the magnetic field H _m of MR ₃ acts on MR ₃ to change the magnetic resistance of MR _3.
Has a magnetic shield effect on MR ₅ . This is clear from the fact that the magnetic field from the magnetic signal N-S forms a magnetic closed circuit through MR ₃ . Therefore, MR ₅ changes its resistance only under the influence of temperature.

At this time, although heat when current flows through the MR _3, MR ₃
Since MR ₅ very close to the rear surface of the are arranged, MR ₅ is
The temperature condition of MR ₃ can be detected accurately, and the compensating sensitivity can be improved as compared with the one which is sensitive to the temperature of the arrangement space of the magnetic sensor shown in other examples.

〔The invention's effect〕

As described above, according to the present invention, the first member and the second member that move close to each other and relatively move, the magnetic recording medium carried by the first member, and the recording on the magnetic recording medium. The magnetic signal, the base of the magnetic sensor carried by the second member, a plurality of magnetoresistive effect elements carried by the base, the electric resistance of which changes in response to the magnetic signal of the magnetic recording, and the magnetic properties of these elements. In a device for detecting the relative position and speed between the first and second members by an electric signal from the resistance effect element, the plurality of magnetoresistive effect elements are made into three terminals or a bridge circuit so that offset due to temperature is compensated. In addition to the plurality of magnetoresistive effect elements, the base body carries a second element whose internal resistance changes in comparison with the ambient temperature around which the magnetic sensor is arranged, and the second element and the plurality of elements. The magnetoresistive effect element is formed of the same material, and the second element and the plurality of magnetoresistive effect elements are formed on the same chip, and the second element and the plurality of magnetoresistive effect elements are formed through this chip. The element is carried on the base, and the second element is arranged so that the longitudinal direction of the element coincides with the magnetic field direction of the magnetic signal, and the longitudinal direction of the second element and the plurality of magnetoresistive effect elements. The apparatus is arranged so that the longitudinal directions thereof are orthogonal to each other, and the output of this second element corrects the input voltage or output amplitude of the magnetoresistive effect element circuit to magnetically detect the position and speed.

 The above configuration has the following advantages.

(1) Since the input or output of the former magnetoresistive effect element is corrected by the output of the second element, the output of the magnetoresistive effect element is not affected by temperature changes, and it is highly accurate and has high resolution. The device can be obtained.

(2) Since the magnetoresistive effect element and the second element are formed on the same chip, the size can be reduced.

(3) Since the second element is arranged so as to be orthogonal to the magnetoresistive effect element, the second element does not undergo resistance change due to change in the magnetic field of the magnetic signal. Therefore, temperature change compensation of the output of the magnetoresistive element is often performed.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a position detecting device of the present invention, FIG. 2 is an embodiment of a development view of a magnetic sensor and a magnetic drum of the present invention, and FIG.
FIG. 4 is a connection diagram of a magnetic sensor of the present invention, FIG. 4 is a characteristic and operation explanation diagram of a magnetoresistive effect element, FIG. 5 is an embodiment of a temperature compensation circuit of the present invention, and FIG. 6 is a characteristic of FIG. Explanatory drawing, FIG. 7 is a development view showing another embodiment of the magnetic sensor of the present invention, FIG.
FIG. 9 is a temperature compensation circuit diagram of another embodiment of the present invention, FIG. 9 is a characteristic explanatory diagram of FIG. 8, FIG. 10 is a temperature compensation circuit diagram of another embodiment of the present invention, and FIG. 11 is the present invention. FIG. 12 is a temperature compensation circuit diagram of another embodiment, and FIG. 12 is a sectional view showing the structure of another embodiment. 1 ... Rotary axis, 2 ... Magnetic drum, 3 ... Magnetic sensor,
21 ...... magnetic media, 31 ...... substrate, MR ₁ ~MR ₄ ...... magnetoresistive element, MR ₅ ...... temperature by element resistance varies.

Claims (1)

(57) [Claims] 1. A first member and a second member which move in close proximity to each other, a magnetic recording medium carried by the first member, a magnetic signal recorded on the magnetic recording medium, and Two
Of the magnetic sensor carried by the member, a plurality of magnetoresistive effect elements which are carried by the base body and change in electric resistance in response to a magnetic signal of the magnetic recording, and electric power from these magnetoresistive effect elements. In a device for detecting a relative position or speed between a first member and a second member by a signal, the plurality of magnetoresistive effect elements are configured as three terminals or a bridge circuit so that an offset due to temperature is corrected, In addition to the plurality of magnetoresistive elements, the second element and the plurality of magnetoresistive elements carry a second element whose internal resistance changes in proportion to the temperature around which the magnetic sensor is arranged. Made of the same material,
Further, the second element and the plurality of magnetoresistive effect elements are formed on the same chip, and the second element and the plurality of magnetoresistive effect elements are carried on the base through the chip,
Arranging the second element so that the longitudinal direction of the element of is aligned with the magnetic field direction of the magnetic signal, and arranging so that the longitudinal direction of the second element and the longitudinal directions of the plurality of magnetoresistive effect elements are orthogonal to each other, A device for magnetically detecting a position or velocity, characterized in that the output of the second element corrects the input voltage or output amplitude of the magnetoresistive effect element circuit.