JP4639216B2 - Magnetic sensor - Google Patents

Description

  The present invention relates to a magnetic sensor.

  Conventionally, a non-contact type magnetic switch is configured using a magnetoresistive element. In the non-contact type magnetic switch according to this conventional example, a permanent magnet is disposed in the vicinity of a magnetoresistive element having a magnetoresistive effect, and a magnetic field generated by the permanent magnet is applied to the magnetoresistive element. Further, a shielding plate that shields the magnetic field of the permanent magnet that acts on the magnetoresistive effect element is movably disposed between the magnetoresistive effect element and the permanent magnet.

  The magnetoresistive element basically comprises a laminated structure of a free layer (free magnetic layer), a nonmagnetic layer, a fixed layer (pinned magnetic layer), and an exchange bias layer (antiferromagnetic layer). It is configured.

  A bias magnetic field is applied to the fixed layer from the exchange bias layer, the fixed layer is magnetized by the exchange bias layer, and the magnetization direction is fixed in a specific direction. On the other hand, the magnetization direction of the free layer is changed by an external magnetic field.

  Therefore, the above-described conventional non-contact type magnetic switch using a magnetoresistive effect element uses the permanent magnet as a magnet for applying an external magnetic field to the free layer, and the magnetization direction of the free layer is desired by the permanent magnet. Thus, the magnetization direction of the free layer by the permanent magnet is angularly rotated with respect to the magnetization direction of the fixed layer.

  Then, the strength of the magnetic field of the permanent magnet that acts on the magnetoresistive effect element is obtained by moving a shield plate that blocks the magnetic field of the permanent magnet that acts on the magnetoresistive effect element between the magnetoresistive effect element and the permanent magnet. Was changed to strength, and the resistance value was changed to large or small. The switching operation is switched by an output signal resulting from a change in the resistance value of the magnetoresistive element.

  However, in the conventional non-contact type switch, the resistance value of the magnetoresistive effect element changes depending on the strength of the magnetic field, that is, the entrance / exit of the shield plate, so that the shield plate approaches, that is, the shield plate becomes permanent with the magnetoresistive effect element. The resistance value of the magnetoresistive effect element gradually changes in accordance with the operation of entering between the magnets or moving away from the shield plate, that is, the shield plate withdraws from between the magnetoresistive effect element and the permanent magnet. That is, the output signal (change in resistance value) from the magnetoresistive element at the time of switching the switch changes gently.

  Therefore, conventional non-contact type magnetic switches using magnetoresistive effect elements are not suitable for switch operations such as those that instantaneously switch between ON and OFF, or those that instantaneously detect the movement of the detected member. Met.

  A similar problem occurs in a non-contact type magnetic sensor configured to detect the detected member using the shield plate of the non-contact type switch as a detected member having a magnetic field shielding action.

  An object of the present invention is to obtain a magnetic sensor that instantaneously switches an output signal from a magnetoresistive effect element by instantaneously changing the resistance value of the magnetoresistive effect element according to the direction of the magnetic field.

  The inventors of the present invention gradually change the strength of the magnetic field by magnetizing each magnetoresistive effect element with two magnets with the magnetization direction of the fixed layer in at least two magnetoresistive effect elements being opposite to each other. Even in such a configuration, a magnetic sensor that instantaneously switches the output signal can be obtained by abruptly changing the resistance value of the magnetoresistive element.

That is, the present invention uses a pair of magnetoresistive effect elements in which a magnetoresistive effect element having a fixed layer whose magnetization direction is fixed and a free layer whose magnetization direction is changed by an external magnetic field is connected in series. And a magnetic sensor for detecting a moving position of a detected member having a magnetic field shielding function that moves to a second position, wherein the first magnet and the second magnet act as an external magnetic field to the pair of magnetoresistive elements. In the pair of magnetoresistive elements, the magnetization directions of the fixed layers of each other are fixed in opposite directions of 180 °, and the magnetization directions of the free layers are set in the same direction by the second magnet. The direction of the magnetic field of the first magnet is opposite to the direction of the magnetic field of the second magnet, and the magnitude of the magnetic field of the first magnet is Large magnetic field of the second magnet When the detected member is in the first position, both the magnetic field of the first magnet and the magnetic field of the second magnet act on the pair of magnetoresistive effect elements as external magnetic fields, The magnetization direction of the free layer of the pair of magnetoresistive elements is determined by the direction of the magnetic field of the first magnet, and the magnetization direction of one free layer by the first magnet is the same as the magnetization direction of the one fixed layer When the detected member is in the second position, the magnetization direction of the other free layer by the first magnet is opposite to the magnetization direction of the other pinned layer by 180 °. The magnetic field of the first magnet is shielded by the detected member, and only the magnetic field of the second magnet acts on the pair of magnetoresistive effect elements, and the magnetization of the free layer of the pair of magnetoresistive effect elements The direction is the direction of the magnetic field of the second magnet The magnetization direction of the one free layer by the second magnet is opposite to the magnetization direction of the one fixed layer by 180 °, and the magnetization of the other free layer by the second magnet. The direction is the same as the magnetization direction of the other fixed layer .

According to the present invention, it is possible to obtain a magnetic sensor that instantaneously switches the output signal from the magnetoresistive effect element by instantaneously changing the resistance value of the magnetoresistive effect element according to the direction of the magnetic field.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  As shown in FIGS. 1, 2, and 4, the magnetic switch holder 1 is formed in an inverted portal shape in which arms 3, 4 that are paired at both ends of a base 2 are provided in parallel to face each other. . A pair of arms 3 includes a magnetoresistive element 5 and a second permanent magnet (hereinafter referred to as a second magnet) 6, and the other arm 4 includes a first permanent magnet (hereinafter referred to as a first magnet). 7) are provided.

  The magnetoresistive effect element 5 is formed in an airtight structure using an IC package or resin sealing, is mounted on the substrate 8, and is attached to the inner surface of one arm 3 via the substrate 8.

  The second magnet 6 is attached to one arm 3 at a magnetic field action position that magnetizes the free layer 5d (see FIG. 5) of the magnetoresistive element 5 with a magnetic field. Here, the magnetic field action position is such that the magnetic lines of force 6a of the second magnet 6 act on the free layer 5d of the magnetoresistive effect element 5, and the free layer of the magnetoresistive effect element 5 by the magnetic field (external magnetic field) of the second magnet 6 5d is set to a magnetizable position. The second magnet 6 shown in FIGS. 1, 2, and 4 is provided separately from the magnetoresistive element 5, but may be configured to be provided integrally in the magnetoresistive element 5.

  The first magnet 7 is disposed at a position where the magnetic layer (external magnetic field) acts on the free layer 5d (see FIG. 5) of the magnetoresistive element 5 and the free layer 5d can be magnetized (magnetic field acting position). The magnetic field lines (direction of the magnetic field) 7a are attached to the other arm 4 so that the magnetic field lines (direction of the magnetic field) 6a of the second magnet 6 are opposite to each other at 180 °. As the first magnet 7, a magnet having a magnetic force several hundred gauss larger than the magnetic force of the second magnet 6 is used.

  Next, the magnetoresistive effect element 5 used for the magnetic switch will be specifically described with reference to FIG. This magnetoresistive effect element 5 shows an example of a structure in which the second magnet 6 is provided separately. The magnetoresistive effect element 5 basically has an exchange bias layer (antiferromagnetic layer) 5a, a fixed layer (pinned magnetic layer) 5b, a nonmagnetic layer 5c, and a free layer (free magnetic layer) 5d. Are formed as a magnetoresistive effect element which is a kind of GMR (Giant Magneto Resistance) element using a giant magnetoresistive effect.

In order for the magnetoresistive element 5 to exhibit the giant magnetoresistive effect, for example, the exchange bias layer 5a is an α-Fe ₂ O ₃ layer, the fixed layer 5b is a NiFe layer, the nonmagnetic layer 5c is a Cu layer, and the free layer 5d is Although formed from a NiFe layer, it is not limited to these, and any material can be used as long as it exhibits a giant magnetoresistance effect. Further, the magnetoresistive effect element 5 is not limited to the one having the laminated structure as long as it exhibits a giant magnetoresistive effect.

  The fixed layer 5b of the magnetoresistive element 5 shown in FIG. 5 is magnetized by the exchange bias layer 5a, and the magnetization direction is fixed (pinned) in a specific direction by the exchange bias layer 5a. In the free layer 5d, the magnetization direction with respect to the magnetization direction of the fixed layer 5b is changed by the magnetic field (external magnetic field) of the magnets 6 and 7. Terminal layers 9 are bonded to both ends of the magnetoresistive element 5. Then, a change in resistance value between the two terminal layers 9 is output depending on the direction of the magnetization direction of the free layer 5d by the external magnetic field with respect to the magnetization direction fixed to the fixed layer 5b.

  The fixed layer 5 b of the magnetoresistive effect element 5 is fixed and magnetized in a specific direction, and a magnet having a magnetic force larger than that of the second magnet 6 is used for the first magnet 7. The free layer 5d of the magnetoresistive effect element 5 is magnetized by the first magnet 7 and the second magnet 6 with the magnetization direction of the layer 5d oriented in the opposite direction of 180 °. In this embodiment, the magnetization direction of the free layer 5d by the second magnet 6 is directed in the same direction as the magnetization direction of the fixed layer 5b (or the opposite direction forming 180 °).

  Furthermore, it has the magnetic field shielding member 10 which consists of a ferromagnetic material from which the relative position with respect to the 1st, 2nd magnets 7 and 6 changes. The magnetic field shielding member 10 has a first position in which both the magnetic fields of the first and second magnets 7 and 6 act on the magnetoresistive element 5 so that the magnetization direction of the free layer 5d is the first direction; One of the magnetic fields of the first and second magnets 7 and 6 is caused to act on the magnetoresistive element 5 so that the magnetization direction of the free layer 5d is set to the second position opposite to the first direction. Moving.

  In the case of FIGS. 2, 3, and 4, the magnetic field shielding member 10 can be moved in and out between the first magnet 7 and the magnetoresistive element 5 through the pair of arms 3 and 4 arranged in parallel. Is arranged. In this embodiment, the plate-like magnetic shielding member 10 is guided by a guide (not shown) and linearly moved across the magnetoresistive effect element 5 and the first magnet 7, thereby causing the magnetic shielding member 10 to move. The magnetic field shielding member 10 is formed in a fan shape and is rotated to move the magnetoresistive element 5 and the first magnet 7 between the first magnet 7 and the magnetoresistive element 5. You may move in and out across the space.

  In this embodiment, the first position is set to a position where the magnetic field shielding member 10 is retracted from between the first magnet 7 and the magnetoresistive element 5. On the other hand, the second position is set to a position where the magnetic field shielding member 10 enters between the first magnet 7 and the magnetoresistive element 5.

  When the magnetic field shielding member 10 is moved to the second position by a driving means (not shown), the magnetic field shielding member 10 that has moved to the second position causes the magnetic force lines 7a of the first magnet 7 to pass through the free layer of the magnetoresistive effect element 5. The magnetic field of the first magnet 7 is shielded away from 5d, and only the magnetic field of the second magnet 6 acts on the magnetoresistive effect element 5 as an external magnetic field. Therefore, only the magnetic field of the second magnet 6 having a smaller magnetic force than the first magnet 7 acts on the magnetoresistive element 5 as an external magnetic field in the free layer 5 d of the magnetoresistive element 5.

  On the other hand, when the magnetic field shielding member 10 moves to the first position, both the magnetic fields of the first and second magnets 6 act on the magnetoresistive element 5 as external magnetic fields. In this case, the magnetic force of the first magnet 7 is greater than that of the second magnet 6, and the magnetization direction of the first magnet 7 and the second magnet 6 with respect to the free layer 5 d of the magnetoresistive effect element 5 is 180 °. It is directed in the opposite direction.

  Accordingly, the magnetic force of the second magnet 6 is canceled by the magnetic force of the first magnet 7, the magnetic field of the first magnet 7 acts on the free layer 5 d of the magnetoresistive effect element 5, and the free resistance of the magnetoresistive effect element 5 The magnetization direction of the layer 5d is reversed and switched to the opposite direction that forms 180 ° with the magnetization direction of the second magnet 6.

  Based on the reversal switching of the magnetization direction of the free layer 5d of the magnetoresistive effect element 5 by the first magnet 7 and the second magnet 6, the resistance value of the magnetoresistive effect element 5 changes. Here, when the magnetization direction of the free layer 5d is reversed, the magnetization direction is directed in the opposite direction of 180 ° with respect to the fixed layer 5b of the magnetoresistive effect element 5, so that the resistance value changes instantaneously. It is.

  In this embodiment, by using at least two magnetoresistive effect elements 5 shown in FIG. 5, the resistance value of the magnetoresistive effect element 5 that instantaneously changes in the direction of the magnetic field is output as an output signal. The two magnetoresistive elements 5 are formed side by side on the substrate 8 as shown in FIG. 6A, or are formed side by side on the substrate 8 as shown in FIG. 6B. .

  The two magnetoresistive elements 5 formed on the substrate 8 are oriented in opposite directions in which the magnetization direction H2 of the fixed layer 5b forms 180 ° with each other, and the magnetization direction H1 of the free layer 5d is set by the second magnet 6. They are aligned in the same direction. In the example shown in FIG. 6, the magnetization direction H1 of the free layer 5d of one magnetoresistive effect element (GMR1) is directed in the opposite direction that forms 180 ° with the magnetization direction H2 of the fixed layer 5b, and the other magnetoresistive effect element ( The magnetization direction H1 of the free layer 5d of GMR2) is oriented in the same direction as the magnetization direction H2 of the fixed layer 5b.

  In FIG. 7, one terminal layer formed at both ends of the magnetoresistive element 5 is denoted by 9a, the other terminal layer is denoted by 9b, and the respective magnetoresistive elements are denoted by GMR1 and GMR2. The terminal layer 9b of the other magnetoresistive effect element GMR2 is coupled to the terminal layer 9b of one magnetoresistive effect element GMR1, and the two magnetoresistive effect elements GMR1 and GMR2 (5) are connected in series.

  In the bridge circuit shown in FIG. 7, a bridge circuit is formed using two magnetoresistive elements GMR1 and GMR2 on two sides and two fixed resistors 11 and 12 on the remaining two sides. That is, one terminal layer 9a of one magnetoresistive element GMR1 and one terminal 11a of one fixed resistor 11 are connected, and one terminal (Vdd) of the power source is connected to the connection point A1. The other terminal layer 9b of the other magnetoresistive effect element GMR2 and the other terminal 12b of the other fixed resistor 12 are connected, and the other terminal of the power source is connected to the connection point A2. Note that the two fixed resistors 11 and 12 may be replaced with two magnetoresistive elements GMR1 and GMR2.

  The other terminal layer 9b of one magnetoresistive effect element GMR1 is connected to one terminal layer 9a of the other magnetoresistive effect element GMR2, and the connection point B1 is connected to one input terminal of the comparator 13 via a fixed resistor R1. Connected. The other terminal 11b of one fixed resistor 11 and one terminal 12a of the other fixed resistor 12 are connected, and the connection point B2 is connected to the other input terminal of the comparator 13 via the fixed resistor R2.

  A fixed resistor R3 for feedback is connected between the output terminal of the comparator 13 and one input terminal. One terminal (Vdd) of the power source is connected to the other input terminal of the comparator 13 via a variable resistor R4 and a fixed resistor R5.

  The output terminal of the comparator 13 is connected to one input terminal of the comparator 14. The other input terminal of the comparator 14 is connected to one terminal (Vφc) of the power supply via the voltage dividing resistor R6 and the fixed resistor R7, and the voltage of the other input terminal of the comparator 14 is set to the reference voltage (Ref). ing. In the embodiment, this reference voltage is set to 2.5V. A fixed feedback resistor R8 is connected between the output terminal of the comparator 14 and the other input terminal.

  When the magnetic field shielding member 10 enters between the magnetoresistive effect elements GMR1, GMR2 (5) and the first magnet 7 (FIG. 2), the switch is turned on (ON), and the magnetic field shielding member 10 becomes the magnetoresistive effect element GMR1. The operation of the magnetic switch will be described assuming that the switch is off (OFF) when leaving from between the GMR 2 (5) and the first magnet 7 (FIG. 1). In this case, it is assumed that the magnetization directions of the fixed layers 5b and the magnetization directions of the free layers 5d of the two magnetoresistive elements GMR1 and GMR2 have the relationship shown in FIG.

In the case of switch-off, the magnetic field shielding member 10 retreats from between the magnetoresistive effect elements GMR1, GMR2 and the first magnet 7 as shown in FIG. 1, so that the magnetic field from the first magnet 7 has two magnetic fields. It acts on the resistance effect elements GMR1 and GMR2. In this case, since the magnitude of the magnetic field of the first magnet 7 is larger than the magnitude of the magnetic field of the second magnet 6, the magnetization directions of the free layers of the magnetoresistive effect elements GMR 1 and GMR 2 are the magnetic lines of force 7 a of the first magnet 7. It becomes the same as the direction. Therefore, in one magnetoresistive element GMR1, the magnetization direction of the free layer is the same as the magnetization direction of the fixed layer, and in the other magnetoresistive element GMR2, the magnetization direction of the free layer is 180 ° with respect to the magnetization direction of the fixed layer. The resistance value R _{GMR2 of the} magnetoresistive effect element _GMR2 becomes larger than the resistance value R _{GMR1 of the} magnetoresistive effect element GMR1 (R _GMR1 <R _GMR2 ), and the two magnetoresistive effect elements GMR1 and GMR2 are connected. The voltage at the point B1 becomes larger than 2.5V as shown in FIG.

When the switch is turned on, the magnetic field shielding member 10 enters between the magnetoresistive elements GMR1 and GMR2 and the first magnet 7 as shown in FIG. The magnetic field to GMR1 and GMR2 is interrupted, and the magnetic field of only the second magnet 6 acts on the two magnetoresistive elements GMR1 and GMR2. In this case, the magnetization directions of the free layers of the magnetoresistive effect elements GMR 1 and GMR 2 are the same as the direction of the magnetic force lines 6 a of the second magnet 6. Therefore, one magnetoresistive effect element GMR1 has an opposite direction in which the magnetization direction of the free layer and the magnetization direction of the fixed layer form 180 °, and the other magnetoresistive effect element GMR2 has the magnetization direction of the free layer and the fixed layer The magnetization direction becomes the same direction, and the resistance value R _{GMR1 of the} magnetoresistive effect element _GMR1 becomes larger than the resistance value R _{GMR2 of the} magnetoresistive effect element GMR2 (R _GMR2 <R _GMR1 ), and the two magnetoresistive effect elements GMR1 and GMR2 The voltage at the connection point B1 is smaller than 2.5V as shown in FIG.

  The voltages at these connection points B1 are amplified to the output side of the comparator 13, as shown in FIG. Further, a comparison process is performed with the reference voltage of the comparator 14. As shown in FIG. 8C, an output signal of 5V is output to the output side of the comparator 14 when the switch is off, and an output signal of 0V is output when the switch is on. This is because a change in resistance value of the magnetoresistive effect elements GMR1 and GMR2 is output as a change in voltage value.

  According to the magnetic switch according to this embodiment, in response to the switching operation of the switch, the magnetic resistance of the first magnet 7 and the second magnet 6 having opposite magnetic fields and different magnitudes is set as an external magnetic field. It selectively acts on the effect element 5, outputs a switching signal of the switch operation from the magnetoresistive effect element 5, and switches the switch based on the output signal. The direction of the magnetic field with respect to the effect element 5 (the magnetization direction of the magnetoresistive effect element) can be changed to the opposite direction of 180 °. Therefore, even if the magnetic field strength gradually changes, the resistance value of the magnetoresistive element can be changed abruptly, and the switch operation can be quickly performed based on the abrupt change in resistance value. Can do.

  In addition, as shown in FIG. 7, since at least two magnetoresistive elements are connected in series and incorporated in the bridge circuit, noise due to external noise magnetic field or ambient environmental magnetic field is removed to ensure accurate and reliable. The switch operation can be switched.

  In FIG. 7, at least two magnetoresistive elements are connected in series and assembled in a bridge circuit. However, the present invention is not limited to this. As shown in FIG. 9, magnetoresistive elements GMR1 and GMR2 connected in series may be incorporated in a voltage dividing circuit.

  In order to incorporate the magnetoresistive effect elements GMR1 and GMR2 connected in series into the voltage dividing circuit, one terminal (Vdd) of the power source is connected to one terminal layer 9a of one magnetoresistive effect element GMR1, and the other magnetoresistive effect is obtained. The other terminal of the power source is connected to the other terminal layer 9b of the element GMR2. The other terminal layer 9b of one magnetoresistive effect element GMR1 is connected to one terminal layer 9a of the other magnetoresistive effect element GMR2, and the connection point B1 is connected to one input terminal of the comparator 13 via a fixed resistor R1. Connecting. The other configurations of the comparators 13 and 14 are the same as those shown in FIG.

In the case of switch-off, the magnetic field shielding member 10 retreats from between the magnetoresistive effect elements GMR1, GMR2 and the first magnet 7 as shown in FIG. 1, so that the magnetic field from the first magnet 7 has two magnetic fields. It acts on the resistance effect elements GMR1 and GMR2. In this case, since the magnitude of the magnetic field of the first magnet 7 is larger than the magnitude of the magnetic field of the second magnet 6, the magnetization directions of the free layers of the magnetoresistive effect elements GMR 1 and GMR 2 are the magnetic lines of force 7 a of the first magnet 7. It becomes the same as the direction. Therefore, in one magnetoresistive element GMR1, the magnetization direction of the free layer is the same as the magnetization direction of the fixed layer, and in the other magnetoresistive element GMR2, the magnetization direction of the free layer is 180 ° with respect to the magnetization direction of the fixed layer. The resistance value R _{GMR2 of the} magnetoresistive effect element _GMR2 becomes larger than the resistance value R _{GMR1 of the} magnetoresistive effect element GMR1 (R _GMR1 <R _GMR2 ), and the two magnetoresistive effect elements GMR1 and GMR2 are connected. The voltage at the point B1 becomes larger than 2.5V as shown in FIG.

When the switch is turned on, the magnetic field shielding member 10 enters between the magnetoresistive elements GMR1 and GMR2 and the first magnet 7 as shown in FIG. The magnetic field to GMR1 and GMR2 is interrupted, and the magnetic field of only the second magnet 6 acts on the two magnetoresistive elements GMR1 and GMR2. In this case, the magnetization directions of the free layers of the magnetoresistive effect elements GMR 1 and GMR 2 are the same as the direction of the magnetic force lines 6 a of the second magnet 6. Therefore, one magnetoresistive effect element GMR1 has an opposite direction in which the magnetization direction of the free layer and the magnetization direction of the fixed layer form 180 °, and the other magnetoresistive effect element GMR2 has the magnetization direction of the free layer and the fixed layer The magnetization direction becomes the same direction, and the resistance value R _{GMR1 of the} magnetoresistive effect element _GMR1 becomes larger than the resistance value R _{GMR2 of the} magnetoresistive effect element GMR2 (R _GMR2 <R _GMR1 ), and the two magnetoresistive effect elements GMR1 and GMR2 The voltage at the connection point B1 is smaller than 2.5V as shown in FIG.

  The voltages at these connection points B1 are amplified to the output side of the comparator 13, as shown in FIG. Further, a comparison process is performed with the reference voltage of the comparator 14. As shown in FIG. 8C, an output signal of 5V is output to the output side of the comparator 14 when the switch is off, and an output signal of 0V is output when the switch is on. This is because a change in resistance value of the magnetoresistive effect elements GMR1 and GMR2 is output as a change in voltage value.

  According to the magnetic switch of this embodiment, since the magnetoresistive effect elements connected in series form a voltage dividing circuit, the configuration of the circuit that picks up the change in the resistance value of the magnetoresistive effect element as the change in the voltage value is simplified. can do.

  The voltage dividing circuit and the bridge circuit may be properly used depending on the object to be switched.

  In the above description, although configured as a magnetic switch, the present invention is not limited to this, and a magnetoresistive element having a free layer whose magnetization direction is changed by an external magnetic field, which detects a detected member having a magnetic field shielding action. It can also be configured as the magnetic sensor used.

  This magnetic sensor is different from the magnetic switch in that the magnetic shielding member 10 of the magnetic switch is used as a member to be detected having a magnetic field shielding action and the member to be detected (10) is detected. Other configurations are the same as those of the magnetic switch.

  The detected member (10) moves so that the relative position with respect to the first and second magnets 7 and 6 changes. By changing the relative position of the detected member (10) with respect to the first and second magnets 7 and 6, both the magnetic fields (external magnetic fields) of the first and second magnets 7 and 6 are applied to the magnetoresistive effect element 5. The first member to be actuated and the second state in which one of the magnetic fields (external magnetic field) of the first and second magnets 7 and 6 is caused to act on the magnetoresistive effect element 5 are generated, and the member to be detected (10). Is detected.

  The first state is set to a state in which the magnetic field shielding member 10 is withdrawn from between the first magnet 7 and the magnetoresistive element 5. On the other hand, the second state is set to a state in which the magnetic field shielding member 10 has entered between the first magnet 7 and the magnetoresistive element 5. And the to-be-detected member (10) in a 2nd state shields the magnetic field of the 1st magnet 7 with larger magnetic force than the 2nd magnet 6, and only the magnetic field of the 2nd magnet 6 becomes a magnetic field as an external magnetic field. It acts on the resistive element 5.

  According to this magnetic sensor, in response to the movement of the member to be detected (10), the magnetic field of the first magnet 7 and the second magnet 6 having opposite magnetic field directions and different magnitudes is used as the magnetic field. It selectively acts on the effect element 5, outputs a detection signal of the detected member (10) from the magnetoresistive effect element 5, and detects the detected member (10) based on the output signal. By moving the detection member (10), the direction of the magnetic field with respect to the magnetoresistive effect element 5 (the magnetization direction of the magnetoresistive effect element) can be changed to the opposite direction of 180 °. Therefore, even if the strength of the magnetic field changes gradually, the resistance value of the magnetoresistive element can be changed abruptly, and the member to be detected (10) can be changed based on the abrupt change in resistance value. It can be detected quickly.

  As described above, according to the present invention, the magnetic field of the first magnet and the second magnet having opposite magnetic fields and different magnitudes is selectively applied to the magnetoresistive element as an external magnetic field, and the magnetic field An output signal corresponding to a sudden change in the resistance value of the resistance effect element is output, and based on the output signal, the switch operation and the detection of the member to be detected can be performed quickly.

It is a front view which shows the magnetic switch which concerns on embodiment of this invention, Comprising: It is a figure which shows the state which made the magnetic field shielding member retreat from between a magnetoresistive effect element and a 1st permanent magnet. It is a front view which shows the magnetic switch which concerns on embodiment of this invention, Comprising: It is a figure which shows the state which made the magnetic field shielding member approach between the magnetoresistive effect element and the 1st permanent magnet. It is a figure which shows the magnetic switch which concerns on embodiment of this invention, Comprising: It is a side view which shows the state which puts in / out the magnetic field shielding member between a magnetoresistive effect element and a 1st permanent magnet. It is a figure which shows the magnetic switch which concerns on embodiment of this invention, Comprising: It is a perspective view which shows the state which puts in / out the magnetic field shielding member between a magnetoresistive effect element and a 1st permanent magnet. It is sectional drawing which shows an example of the magnetoresistive effect element used for the magnetic switch which concerns on embodiment of this invention. (A), (B) is a figure which shows the magnetization direction of the magnetoresistive effect element used for the magnetic switch which concerns on embodiment of this invention. It is a circuit diagram which incorporated the magnetoresistive effect element used for the magnetic switch which concerns on embodiment of this invention in the bridge circuit. It is a figure which shows the waveform of the output signal in each part of a bridge circuit. It is a circuit diagram which incorporated the magnetoresistive effect element used for the magnetic switch which concerns on embodiment of this invention in the voltage dividing circuit.

Explanation of symbols

1 Holder 2 Base 3 Arm 4 Arm 5 Magnetoresistive Element (GMR1 GMR2)
6 Second permanent magnet 7 First permanent magnet 8 Substrate 9 Terminal layer 10 Magnetic shielding member (detected member)
11 Fixed resistor 12 Fixed resistor 13 Comparator 14 Comparator

Claims (4)

Using a pair of magnetoresistive elements in which a magnetoresistive element having a fixed layer whose magnetization direction is fixed and a free layer whose magnetization direction is changed by an external magnetic field is connected in series, the first position and the second position are used. A magnetic sensor for detecting a moving position of a detected member having a moving magnetic field shielding function,
  A first magnet and a second magnet acting as an external magnetic field to the pair of magnetoresistive elements;
  In the pair of magnetoresistive effect elements, the magnetization directions of the fixed layers are fixed in opposite directions of 180 °, and the magnetization directions of the free layers are aligned in the same direction by the second magnet. ,
  The direction of the magnetic field of the first magnet is opposite to the direction of the magnetic field of the second magnet, which is 180 °, and the magnitude of the magnetic field of the first magnet is the same as that of the second magnet. Larger than the magnitude of the magnetic field,
  When the detected member is in the first position, both the magnetic field of the first magnet and the magnetic field of the second magnet act on the pair of magnetoresistance effect elements as external magnetic fields, and the pair of magnetoresistances The magnetization direction of the free layer of the effect element is determined by the direction of the magnetic field of the first magnet, and the magnetization direction of one free layer by the first magnet is oriented in the same direction as the magnetization direction of the one fixed layer; The magnetization direction of the other free layer by the first magnet is directed to the opposite direction of 180 ° with the magnetization direction of the other fixed layer,
  When the detected member is in the second position, the magnetic field of the first magnet is shielded by the detected member, and only the magnetic field of the second magnet serves as an external magnetic field to the pair of magnetoresistive effect elements. The magnetization direction of the free layer of the pair of magnetoresistive effect elements is determined by the direction of the magnetic field of the second magnet, and the magnetization direction of the one free layer by the second magnet is the one fixed layer The magnetization direction of the other free layer by the second magnet is oriented in the same direction as the magnetization direction of the other fixed layer,
Magnetic sensor characterized by. 2. The magnetic sensor according to claim 1, wherein the pair of magnetoresistive elements connected in series are incorporated in a bridge circuit. A voltage dividing circuit is configured using the pair of magnetoresistive effect elements connected in series, and an output from a connection point of the pair of magnetoresistive effect elements is compared with a reference voltage to determine a moving position of the detected member. The magnetic sensor according to claim 1, wherein the magnetic sensor is detected. A voltage dividing circuit is configured by using the pair of magnetoresistive effect elements connected in series, the output from the connection point of the pair of magnetoresistive effect elements is amplified, and then compared with a reference voltage, and the detected member The magnetic sensor according to claim 1, wherein the moving position of the magnetic sensor is detected.