JP3534484B2 - Magnetic position sensor - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic sensor, and more particularly to a magnetic position sensor for detecting displacement of a moving body.

[0002]

2. Description of the Related Art An example of this type of magnetic sensor is disclosed in Japanese Examined Patent Publication Sho 55.
It is described in JP-B-13286 and JP-B-55-9818. According to these, the movable magnetic core and the fixed magnetic core are magnetically coupled to form two closed magnetic paths. Then, when the length of the closed magnetic path changes due to the displacement of the movable magnetic core that interlocks with the moving body that is the detected body, the magnetic resistance of each closed magnetic path changes. By detecting the change in the magnetic flux density of each closed magnetic circuit with this, by detecting the coil provided on each closed magnetic circuit,
A signal indicating the displacement of the movable magnetic core, that is, the moving body is obtained.

As described above, the conventional example of the method of detecting the change in the magnetic resistance due to the change in the closed magnetic circuit length due to the displacement of the moving body is as follows.
All of these are mainly structural improvements and ingenuities of the members forming the magnetic circuit in order to improve the detection accuracy of the sensor, but further improvement in improving the detection sensitivity of the sensor is desired.

[0004]

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a magnetic position sensor which can improve the detection sensitivity of the sensor.

[0005]

A magnetic position sensor according to the present invention is a magnetic position sensor for detecting a relative position of a movable object to be detected, and at least one exciting coil for alternating current excitation, A closed magnetic path forming means that forms at least one closed magnetic path that allows the magnetic flux generated by the exciting coil to pass through; and at least one detection coil that detects the magnetic flux density in the closed magnetic path . Responsive to the displacement of the magnetoresistive part and the object to be detected.
At the coupling position corresponding to the position of the detected object at the end,
And a communicating <br/> forming a magnetic path forming unit provided with a movable magnetic unit which magnetoresistive portion and magnetically coupled, the magnetoresistive portion, the movable magnetic
Having a surface for magnetic coupling corresponding to the movable range of the body part,
It is characterized in that the electric conductivity is higher than that of the connecting magnetic path forming portion.

[0006]

According to the magnetic position sensor of the present invention, the electric conductivity of the magnetic resistance portion which gives a resistance component corresponding to the position of the object to be detected to a part of the closed magnetic circuit is higher than that of the other parts of the closed magnetic circuit. The eddy current generated in the magnetic resistance portion contributes to an increase in the magnetic resistance component.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail below with reference to the drawings. 1 is a plan view of a magnetic position sensor according to an embodiment of the present invention, and FIG. 2 is a sectional view taken along line AA of FIG. In FIGS. 1 and 2, the moving body 1 which is the detected body
Rotates about the rotation axis a. The moving body 1 is fixed to one end of the longitudinal magnetic member 2, and the longitudinal magnetic member 2 is rotatable around the rotation axis a together with the moving body 1. Around the longitudinal magnetic member 2, an inner surface that draws an arc centered on the rotation axis a on the inner surface and having a radius longer than the distance from the other end of the longitudinal magnetic member 2 to the rotation axis a (a table for magnetic coupling).
A fixed semi-annular magnetic member 3 having a surface) is arranged, and the inner surface and the other end surface of the longitudinal magnetic member 2 are not in contact with each other. The two legs of the semi-annular magnetic member 3 and one end of the longitudinal magnetic member 2 are provided with a fixed E-shaped magnetic member 4 (sub -magnetic member ).
Section) facing each of the three legs. The two legs of the semi-annular magnetic member 3 are joined to the legs at both ends of the E-shaped magnetic member 4, respectively. One end of the longitudinal magnetic member 2 has an annular shape centered on the rotation axis a and is in a fitted state with the moving body 1. The middle leg of the E-shaped magnetic member 4
The (fixed branch magnetic path member) has a shape facing and corresponding to the one end of the annular shape, and one end of the longitudinal magnetic member 2 and the middle leg of the E-shaped magnetic member 4 are also in non-contact with each other. Is.

Each leg of the E-shaped magnetic member 4 has a coil (first
First to third coils) are provided. That is, the excitation coil 5 is wound as a third coil on the middle leg of the E-shaped magnetic member 4, and the first and second coils are provided on the legs at both ends of the E-shaped magnetic member 4. The coils 6 and 7 for detection are respectively wound. The excitation coil 5 is AC-excited by the AC power supply 10. As a result, when the exciting coil 5 generates a magnetomotive force, magnetic flux having a shape shown by a dotted line in FIG. 1 is distributed. The magnetic flux induced here interlinks with the detection coils 6 and 7, but the magnetic flux density of the magnetic flux interlinking with the detection coils 6 and 7 changes according to the position of the longitudinal magnetic member 2. That is, the length of the magnetic path Pa of the magnetic flux interlinking the detection coil 6 and the length of the magnetic path Pb of the magnetic flux interlinking the detection coil 7 are complementary by the position of the longitudinal magnetic member 2 facing the semi-annular magnetic member 3. That is, the magnetic flux density linked to the detection coil is changed by the change in the resistance component of each magnetic path. Detection coil 6,7
Generates an electromotive force according to the rate of change in the magnetic flux density that interlinks, so by comparing the output voltages of the detection coils 6 and 7, the position of the longitudinal magnetic member 2, that is, the moving body 1 (relative angle ) Can be detected.

This sensor can be classified into two types, a first magnetic path forming means and a second magnetic path forming means. First
The magnetic path forming means is composed of an E-shaped magnetic member 4 which is a fixed magnetic member, and a body portion and both end legs of the semi-annular magnetic member 3, and these magnetic portions are inside the body portion and the magnetic member 3. Opposite each other on the surface. The second magnetic path forming means magnetically connects the facing portions of the magnetic members 3 and 4 and has one end relatively moved (rotated) with respect to the semi-annular magnetic member 3.
It has a longitudinal magnetic member 2 as a possible movable branch magnetic member. The longitudinal magnetic member 2 forms a branch magnetic path that branches the first closed magnetic path formed by only the magnetic members 3 and 4 into two closed magnetic paths. When analyzed in more detail, in the second magnetic path forming means, the central leg portion of the E-shaped magnetic member 4 serves as the fixed branch magnetic path portion and forms the branch magnetic path together with the longitudinal magnetic member 2.

For the semi-annular magnetic member 3 which is the magnetic resistance portion and the E-shaped magnetic member 4 which is the connecting magnetic path forming portion, magnetic path materials having different electric conductivities are adopted for the reason described later. That is, the semi-annular magnetic member 3 is made of a magnetic material having a larger electric conductivity than the E-shaped magnetic member 4. Examples of magnetic materials having high electric conductivity include iron and nickel, and examples of magnetic materials having low electric conductivity include ferrite and laminated silicon steel sheets. Therefore, it is preferable that the semi-annular magnetic member 3 is made of iron or nickel based material and the E-shaped magnetic member 4 is made of ferrite or silicon steel plate. On the other hand, since ferrite has a smaller electric conductivity than a silicon steel sheet, a silicon steel sheet may be applied to the semi-annular magnetic member 3 and a ferrite may be applied to the E-shaped magnetic member 4. That is, in the present invention, the electrical conductivity of the semi-annular magnetic member 3 may be made larger than that of the E-shaped magnetic member 4, but the electrical conductivity of the semi-annular magnetic member 3 is larger than that of the E-shaped magnetic member 4. The larger is, the more preferable.

By making the electric conductivity of the semi-annular magnetic member 3 larger than that of the E-shaped magnetic member 4, the following operational effects can be obtained. FIG. 3 shows an equivalent circuit of the sensor shown in FIGS. 1 and 2 for explaining the action and effect peculiar to the present invention. In FIG. 3, the semi-annular magnetic member 3 is equivalently identified as the electric resistance element 3 on the electric circuit. The movable longitudinal magnetic member 2 is identified as the slider 2 whose one end is in contact with the resistance element 3 at a position corresponding to the rotation angle of the moving body 1, and the magnetic path P of the E-shaped magnetic member 4 is identified.
The portions 4a and 4b that carry a and Pb are regarded as the electric resistance elements 4a and 4b connected to the resistance element 3 at one end. The other ends of the resistance elements 4a and 4b are grounded via ammeters 6 and 7, which are equivalent to the detection coils 6 and 7. Slider 2
The other end of is connected to the positive end of the constant current source 5 equivalent to the exciting coil 5, and the negative end of the constant current source 5 is grounded.

As can be seen from this equivalent circuit, the semi-annular magnetic member 3 has a magnetic component passing through the detection coil 6 and a resistance component of the magnetic path Pa passing through the detection coil 6 depending on the position facing the longitudinal magnetic member 2. It plays the role of a magnetic path resistance portion that complementarily changes the resistance component of the path Pb. Here, the present invention focuses on the eddy current generated in the magnetic path due to the change in magnetic flux accompanying the excitation of the exciting coil 5. This eddy current acts in a direction to reduce the magnetic flux emitted from the exciting coil 5. That is, the eddy current action is considered to be a magnetic path resistance action (called iron loss) when the magnetic flux changes. Since this eddy current action is a current or magnetic field distributed in the magnetic path cross section, it cannot be expressed by the lumped constant equation, but it is considered to be proportional to the product of the magnetic flux change frequency f, electrical conductivity κ, and magnetic permeability μ. ,

[0013]

[Equation 1]

Can be written as Therefore, when a material having a high electric conductivity is used for the semi-annular magnetic member 3 of the magnetic path resistance portion, a magnetic path resistance having a large magnetic path resistance action can be formed for the magnetic path cross-sectional area. That is, when the magnetic flux generated from the exciting coil 5 acts on the detection coils 6 and 7, if the magnetic resistance 3 caused by the change in the magnetic flux is larger than the magnetic resistances 4a and 4b, the detection coil with respect to the movement amount of the rotor 2 is detected. 6,
The rate of change of the induced voltage generated at 7 becomes large, and the sensitivity of the sensor becomes good.

Thus, in the magnetic position sensor for detecting that the magnetic flux in the closed magnetic circuit due to the AC magnetic field changes due to the change of the object to be detected, the magnetic conductivity is increased by increasing the electric conductivity of the resistance portion of the closed magnetic circuit. The eddy current that increases the resistance component can be increased, and a large level of the detection coil output can be obtained even with a minute displacement of the detected object, so that the sensor detection capability can be improved.

The output of the sensor can be obtained by comparing the output voltages of the detection coils 6 and 7 with each other.
FIG. 4 shows the configuration of a sensor output circuit that receives the output voltages of the detection coils 6 and 7, and both ends of the detection coil 6 are the input ends of the voltage detector 11 and both ends of the detection coil 7 are the voltage detectors. Each of the voltage detectors 11 is connected to the input terminals of 12 and inputs a signal indicating the effective value of the output voltage of the detection coil 6 to the arithmetic circuit 15 via the amplifier 13 as the voltage V1. A signal indicating the effective value of the output voltage of No. 7 is input to the arithmetic circuit 15 via the amplifier 14 as the voltage V2. The arithmetic circuit 15 calculates the ratio of the electromotive force of both detection coils, that is, V1 / (V1 + V2) according to the input voltages V1 and V2 corresponding to the effective value of the output voltage of each detection coil, and the level according to the calculation result. Is output as a sensor output, that is, a position signal corresponding to the displacement of the object to be detected.

By obtaining the sensor output based on the output voltages of the two detection coils in this way, it is possible to achieve displacement detection with higher precision than that obtained by obtaining the sensor output by the output voltage of a single detection coil. . FIG. 5 is a plan view of a magnetic position sensor according to another embodiment of the present invention,
FIG. 6 shows a view as seen from the arrow B in FIG. 5, and the same parts as those in FIGS. 1 and 2 are designated by the same reference numerals.

In FIG. 5 and FIG. 6, the first magnetic path forming means comprises linear magnetic members 4a and 3'opposing each other and a columnar magnetic connecting member for positioning the magnetic members 4a and 3'in parallel to each other. It is composed of 4b and 4c. The detection coils 6 and 7 are wound around the magnetic coupling members 4b and 4c, respectively. The second magnetic path forming means includes a cylindrical magnetic member 4d around which the exciting coil 5 is wound, a magnetic member 4a,
It is composed of a linear auxiliary branch magnetic member 4e parallel to 3 ', and a movable branch magnetic member 2'which magnetically couples between the magnetic member 3'and the magnetic member 4e and moves in parallel. Magnetic member 4
d has one end fixed to the magnetic member 4a and the other end fixed to the magnetic member 4a.
It serves as a fixed branch magnetic member that is fixedly attached to e and magnetically connects the magnetic member 4a and the auxiliary branch magnetic member 4e. The magnetic member 2'is arranged in a non-contact manner between the auxiliary branch magnetic member 4e and the magnetic member 3 '. The magnetic part 2'is responsive to a linear displacement of an object to be detected, not shown, between the facing surfaces of the magnetic member 3'and the magnetic member 4e in the longitudinal direction of these magnetic members (direction of arrow M).
It is free to move along.

According to the magnetic position sensor having such a configuration, when the coil 5 is excited by the AC power source (not shown), the magnetic flux generated by the coil 5 passes through the magnetic member 4e and is generated between the magnetic member 4e and the magnetic member 2 '. It passes through the gap, the magnetic member 2 ', and the gap between the magnetic member 2'and the magnetic member 3', and enters the magnetic member 3 '. Then, in the magnetic member 3 ′, the magnetic flux is branched into two, and the magnetic coupling member 4
After passing through b and 4c, the magnetic member 4a is returned to the exciting coil 5 to join again. Therefore, in the magnetic member 3 ', there are two loops, one for passing a magnetic flux branched to one side (a magnetic flux passing through the magnetic coupling member 4b) and a loop passing a magnetic flux branching to the other (a magnetic flux passing through the magnetic coupling member 4c).
A closed magnetic circuit will be formed. Further, the direction of the flow of such magnetic flux changes in the forward and reverse directions according to the direction of the current flowing in the exciting coil 5.

In this sensor, the linear magnetic member 3
′ Corresponds to the magnetic resistance portion, and the other magnetic members 4a, 4b, 4
c, 4d, 4e and 2'correspond to the connecting magnetic path forming portion.
Therefore, similar to the above, the magnetic member 3'includes the magnetic members 4a,
A magnetic material having a larger electric conductivity than 4b, 4c, 4d, 4e and 2'is adopted. When the movable magnetic member 2 ′ moves linearly in response to the displacement of the object to be detected, the magnetic path length (that is, the magnetic resistance component) of each of the two closed magnetic paths changes in a complementary manner. Accordingly, the electromotive forces generated by the detection coils 6 and 7 change complementarily to each other, so that the detection coils 6 and 7 are generated by the sensor output circuit of FIG.
Therefore, a highly accurate position signal based on the output voltage of 1 can be obtained. Moreover, the magnetic resistance portion 3'has a large electric conductivity,
Eddy currents due to the alternating magnetic field are likely to occur, and a magnetic resistance effect larger than the apparent magnetic resistance amount is given to each closed magnetic circuit, so that the sensor detection sensitivity can be improved as in the above case.

In the embodiment shown in FIGS. 1 and 2, the exciting coil 5 serving as the magnetomotive force source is provided at the central leg of the E-shaped magnetic member 4, but two exciting coils are formed in the E-shape. The magnetic member 4 may be provided at both ends of the magnetic member 4 to supply an appropriate alternating current to each. In this case, if a detection coil is provided on the central leg of the E-shaped magnetic member 4, the relative position of the longitudinal magnetic member 2, that is, the moving body 1 can be detected from the output voltage of the detection coil. In addition, the E-shaped magnetic member 4 has two
Although the two detection coils are provided to detect the relative position of the moving body 1, basically, the relative position of the moving body 1 can be detected even with a configuration in which a single detection coil is provided. Further, although the E-shaped magnetic member 4 is described as being integrally formed, each leg of the E-shaped magnetic member 4 may be configured as a separate member, and the longitudinal magnetic member 2 or the semi-circular magnetic member 2 may be formed. The same applies to the member 3, as long as they have the structure or shape to be achieved in the magnetic circuit. And such an example of modification can be similarly applied to the embodiments of FIGS. 5 and 6.

[0022]

As described in detail above, according to the magnetic position sensor of the present invention, the electric conductivity of the magnetic resistance portion that gives a resistance component corresponding to the position of the object to be detected to a part of the closed magnetic circuit is The detection sensitivity of the sensor can be improved because the eddy current generated in the magnetic resistance portion is larger than the other portions of the closed magnetic circuit and acts to increase the magnetic resistance of the magnetic resistance portion.

[Brief description of drawings]

FIG. 1 is a plan view showing the configuration of a magnetic position sensor according to an embodiment of the present invention.

FIG. 2 is a sectional view taken along line AA of FIG.

3 is an equivalent circuit diagram of the magnetic position sensor of FIG.

FIG. 4 is a block diagram showing a sensor output circuit of the magnetic position sensor of FIG.

FIG. 5 is a plan view showing the configuration of a magnetic position sensor according to another embodiment of the present invention.

FIG. 6 is a view seen from an arrow B in FIG.

[Explanation of symbols for main parts]

DESCRIPTION OF SYMBOLS 1 Moving body 2 Longitudinal magnetic member 2'Movable branch magnetic member 3 Semi-annular magnetic member (magnetic resistance part) 3'Linear magnetic member (magnetic resistance part) 4 E-shaped magnetic member (connection magnetic path formation part) 4a, 4b, 4c, 4d, 4e Magnetic member (connection magnetic path formation part) 5 Excitation coil 6, 7 Detection coil a Rotation axis Pa, Pb Closed magnetic path

─────────────────────────────────────────────────── ─── Continuation of front page (58) Fields surveyed (Int.Cl. ⁷ , DB name) G01B 7/30

Claims (7)

(57) [Claims] 1. A magnetic position sensor for detecting a relative position of a movable object to be detected, comprising at least one exciting coil excited by an alternating current and at least one passing magnetic flux generated by the exciting coil. It has a closed magnetic circuit forming means for forming a closed magnetic circuit and at least one detection coil for detecting a magnetic flux density in the closed magnetic circuit, wherein the closed magnetic circuit forming means includes a magnetic resistance portion and the detected object.
It responds to the displacement and at one end depends on the position of the object to be detected.
Movable magnetism that is magnetically coupled to the magnetoresistive portion at the coupling position
A connecting magnetic path forming portion having a body portion , wherein the magnetoresistive portion corresponds to a movable range of the movable magnetic body portion.
A magnetic position sensor having a magnetic coupling surface having a higher electric conductivity than that of the coupling magnetic path forming portion. 2. The closed magnetic path forming means is a first magnetic path forming means forming at least one first closed magnetic path, and is relatively non-contact with the first magnetic path forming means over a predetermined range. And a second magnetic path forming means that is movable and forms a branch magnetic path that branches the first closed magnetic path into two closed magnetic paths, wherein the first magnetic path forming means includes at least one pair of facing portions. The second magnetic path forming means includes a movable branch magnetic member that connects the facing portions and is at least partially movable relative to at least one of the facing portions. The magnetic resistance portion is formed on at least one of the facing portions to which the movable branch magnetic member is movably coupled within the predetermined range, and the coupling magnetic path forming portion is one of the fixed magnetic members. The part excluding the magnetic resistance part and the movable branch A magnetic member, and the exciting coil includes a first coil and a second coil which are linked to the first closed magnetic path at positions sandwiching the predetermined range, and a third coil which is linked to the branched magnetic path. The magnetic position sensor according to claim 1, wherein the magnetic position sensor is at least one of the coils, and the detection coil is another coil of the first to third coils. 3. The second magnetic path forming means further includes a fixed branch magnetic path member having one end fixed to one of the facing portions, wherein the movable branch magnetic path member is the other of the fixed branch magnetic path members. 3. The magnet according to claim 2 , wherein the magnet is rotatable about a rotation center axis near the end and the other of the facing portions extends along a movement locus of the tip of the movable branch magnetic member. Position sensor. 4. The second magnetic path forming means includes an auxiliary branch magnetic member facing the facing portion, and a fixing member having one end fixed to one of the facing portions and the other end fixed to the auxiliary branch magnetic member. 4. A magnetic type according to claim 3 , further comprising a branch magnetic member, wherein the movable branch magnetic path member is movable in parallel between facing surfaces of the other of the facing portions and the auxiliary branch magnetic member. Position sensor. Wherein said third coil, magnetic position sensor according to claim 3, wherein that it is wound around the fixed branch magnetic member. 6. A means for AC-exciting the third coil, and a means for outputting a signal of a level corresponding to the ratio of electromotive forces of the first and second coils as a signal corresponding to the relative position of the object to be detected. magnetic position sensor according to any one of claims 1 to 5, characterized in that it has and. Wherein said magneto-resistance portion is made of iron or nickel, the connecting magnetic path forming unit, of any one of claims 1 to 6, characterized in that it consists of ferrite or silicon steel sheet according Magnetic position sensor.