JP3335738B2 - 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 position sensor capable of detecting a change during linear movement or rotational movement.
In particular, the present invention relates to a magnetic position sensor applicable as a throttle position sensor (TPS) mounted on an automobile or the like.

[0002]

2. Description of the Related Art Conventionally, as such a magnetic position sensor,
A throttle position sensor (Throttle Position Senser) for detecting a throttle opening degree of an automobile or the like is known. One example is disclosed in, for example, Japanese Patent Application Laid-Open No. 5-26610. This individually detects the opening of the throttle valve of the internal combustion engine and the idling operation state.

The structure of such a sensor is such that a pair of permanent magnets are disposed opposite to each other on a rotation surface thereof so as to rotate integrally with a shaft that rotates in conjunction with a throttle valve. Thus, one Hall element is arranged on the axis of the shaft. According to this, a pair of permanent magnets forms a magnetic circuit with the rotation axis of the shaft interposed therebetween. Then, the direction of the magnetic field of the formed magnetic circuit changes according to the rotation angle of the shaft. Therefore, by detecting a change in magnetic flux passing through the Hall element provided between the pair of permanent magnets, the rotation angle of the shaft, and thus the opening of the throttle valve, can be detected.

Further, a pair of arc-shaped permanent magnets are juxtaposed along an arc centered on the rotation axis of the shaft, and one Hall element is provided at a position separated from these arc-shaped permanent magnets in the axial direction of the rotation axis. By arranging and detecting the direction of the magnetic field of the magnetic circuit formed by the pair of arc-shaped permanent magnets, the rotation angle of the shaft, and thus the idle operation state, can be detected.

However, each of these magnetic position sensors has a structure in which one Hall element is arranged in one magnetic circuit to detect a change in a magnetic field in the magnetic circuit. Further, when a Hall element or the like is used for the magnetic position sensor, an output drift occurs due to its temperature characteristics, so that it is necessary to perform temperature compensation. Until now, when a plurality of elements were used, temperature compensation was individually performed. Therefore, if the number of elements increases, temperature compensation using a thermistor or the like must be performed accordingly, and the productivity decreases. Further, differences in temperature characteristics between the elements must be considered, but no consideration has been given to them.

[0006]

SUMMARY OF THE INVENTION In view of the above-mentioned problems of the prior art, it is an object of the present invention to simplify the structure and to be affected by the ambient temperature or the temperature characteristics of the Hall element itself. It is an object of the present invention to provide a magnetic position sensor capable of detecting a displacement position such as a rotational movement or a linear movement with high accuracy without using the same.

[0007]

A magnetic sensor according to the present invention comprises: a pair of magnetic members which are long and opposed to each other at a predetermined distance; and both ends of at least one of the pair of magnetic members. And a pair of gaps formed between the magnetic member and the other magnetic member. The gap is supported by a member that is disposed between the pair of magnetic members and that can move in parallel in the longitudinal direction of the magnetic member. A magnetic force generating source for generating a magnetic flux flowing toward the magnetic member, magnetic flux density detecting means arranged in each of the pair of gaps and emitting a magnetic flux density signal representing a magnetic flux density in the gap, and A position signal generating means for generating a position signal of the magnetic force generating source, wherein the pair of magnetic flux density detecting means comprises a Hall element, The stage controls a bias current flowing through the pair of Hall elements in accordance with an added value of the Hall outputs of the pair of Hall elements, and uses at least one Hall output of the pair of Hall elements as a sensor output. Things.

[0008]

According to the present invention having such features, a pair of Hall elements disposed in a gap between a pair of magnetic members detects a magnetic flux density corresponding to a position of a magnetic force generating source. A difference signal is obtained by comparing the sum of the two detection outputs with the reference value.
By applying a bias current corresponding to the difference signal to the pair of Hall elements, the bias current flowing through the Hall elements is controlled such that the sum of the Hall outputs of the pair of Hall elements is always constant. Further, since the sum of the Hall outputs of the pair of Hall elements is always constant, the position of the magnetic force generation source is proportional to the Hall output of one Hall element. Accordingly, it is possible to accurately detect the position of the magnetic force generation source by the Hall output of one Hall element.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment according to the magnetic position sensor of the present invention will be described below with reference to the drawings. FIG. 1 shows an embodiment of a magnetic position sensor for detecting a rotation angle in a rotational movement. FIG. 1A is a plan view of the sensor,
FIG. 1B is a front view of the sensor, and FIG. 1C is a right side view of the sensor.

As shown in FIG. 1, a semi-circular magnetic member 2 having a rectangular cross section and an outer shape having upstanding portions 2a and 2b at both ends thereof is similarly formed at a predetermined distance from a semi-circular magnetic member. The member 3 is arranged to face. A pair of gaps 4a, 4b are formed between the ends of the upright portions 2a, 2b of the magnetic member 2 and the magnetic member 3, and the gaps 4a, 4b are formed.
Hall elements 5a and 5b as magnetic flux density detecting means for detecting a magnetic flux density (magnetic field) in the gap and generating a signal representing the magnetic flux density (magnetic field) are arranged in the gap 4b.

A magnet 7 is arranged in a space facing the semi-circular magnetic members 2 and 3 so as to form gaps 6a and 6b, and the magnet 7 is connected via a connecting rod 8 made of a non-magnetic material. And is fixed to the rotating shaft 9. Here, the radius of curvature of the pair of semicircular magnetic members 2 and 3 and the length of the connecting rod 8, that is, the turning radius of the magnet 7, are set to be the same, and the center of the curvature and the center of the turning coincide with each other. I have.

Therefore, the rotation of the rotating shaft 9 causes the magnet 7 to move between the pair of magnetic members 2 and 3 along the circumferential direction. According to the magnetic position sensor 1 having the above configuration, the magnetic flux from the N pole of the magnet 7 enters the magnetic member 3 through the gap 6a. The magnetic member 3 passes through the gaps 4a and 4b located at both ends, passes through the upright portions 2a and 2b, passes through the magnetic member 2, passes through the gap 6b, and is again guided to the S pole of the magnet 7. Will be.

As described above, the position of the magnet 7, that is, the rotation angle position of the rotation shaft 9 can be detected by detecting the magnetic flux density of each of the two divided magnetic circuits by the Hall elements 5a and 5b. it can. Regarding a specific application of the magnetic position sensor according to the present embodiment, a throttle position sensor can be obtained by connecting a rotating shaft to, for example, a throttle valve of an internal combustion engine.

The magnetic position sensor according to the above-described embodiments and the like can be further used as a position detecting means in an automatic machine tool, an automatic transfer machine, and the like, and can be preferably applied to factory automation (FA) and the like. It is.
Next, the operation principle of the above-described magnetic position sensor will be described based on the conceptual diagram of FIG. 1 are denoted by the same reference numerals. As shown in FIG. 2, the magnetic flux emitted from the magnetic force generating source 7 composed of a magnet passes through the gap 6a and enters the magnetic member 3, and passes through the gaps 4a and 4b located at both ends of the magnetic member 3, respectively. It enters the magnetic member 2.
Then, the magnetic member 2 returns to the magnetic force generating source 7 through the gap 6b again.

At this time, the amount of magnetic flux passing through each of the gaps 4a and 4b changes according to the position of the magnetic force generating source 7. For example, when the magnetic force generation source 7 moves to the gap 4a (to the left), the amount of magnetic flux passing through the gap 4a increases, and the amount of magnetic flux passing through the gap 4b decreases accordingly. On the other hand, if the magnetic force source 7 moves toward the gap 4b (to the right),
A phenomenon opposite to the above occurs.

Therefore, by providing a Hall element in each of the gaps 4a and 4b and detecting the magnetic flux (magnetic flux density) in each gap, the position of the magnetic force generating source 7 with respect to the magnetic members 2 and 3 can be calculated by the following equation. 1 can be obtained.

[0017]

(Equation 1)

Here, V1 and V2 are the gaps 4a, 4b
Represents the output voltage of the Hall element arranged at the position α, and α is a distance (L) from one end to the total length (La + Lb) of the magnetic member 3.
Indicates the ratio of b). The output voltage of the Hall element is given by the following equation 2.
Is calculated by

[0019]

(Equation 2)

Where K is a sensitivity constant, the type of element,
Determined by temperature and other factors. IC is a current flowing through the Hall element, and B is a magnetic flux density. Hereinafter, the detection principle will be described in detail with reference to the conceptual diagram of FIG. The magnetic permeability of the magnetic member 3 is μ,
The permeability of the magnetic member 2 is ∞, the permeability of air (gap) is μ ₀ , the width of the gaps 4a, 4b, 6a, 6b is E, the cross-sectional area through which the magnetic flux passes is S, and the magnetic fields are H1, H2,
Expressed as H3 and H4, by the theorem of amperage round integral,
Equation 3 below is derived.

[0021]

(Equation 3)

Further, the following equation 4 is derived by Gauss's theorem.

[0023]

(Equation 4)

Here, if L = La + Lb and α = Lb / L, the following equations (5) are derived from the above equations (3) and (4).

[0025]

(Equation 5) Here, if (Eμ / Lμ ₀ ) << 1, the following Expression 6 is obtained.

[0026]

(Equation 6)

As is clear from the above description, the output voltage V of the Hall element arranged in the pair of gaps 4a, 4b
By obtaining V1 and V2, the position of the magnetic force generating source 7, that is, the angular position of the rotating shaft 9 can be detected based on the voltage ratio as shown in Expression 6. V1 and V2 vary depending on the temperature characteristics of the Hall element. Here, if (V1 + V2) can always be controlled to a constant value irrespective of the temperature characteristic, the position α of the magnetic force generation source can be accurately represented only by V1, as is clear from Equation (6).

Next, FIG. 3 shows a position as a position signal generating means for generating a position signal indicating the position of the magnetic force generating source based on the Hall output from the Hall element as the magnetic flux density detecting means used in FIG. 1 shows an embodiment of a signal generation circuit. FIG.
The same reference numerals are given to the same parts. 3 includes two Hall elements 5a and 5b and a differential amplifier 1
0, 11, 12, and resistors 13, 14, 15, and 16. The two Hall elements 5a and 5b detect the magnetic flux density corresponding to the position of the magnetic force generating source 7 (see FIG. 1),
A minute voltage proportional to the magnitude of the magnetic flux density is output as a Hall output between the output terminals 5a1, 5a2 and 5b1, 5b2, and is amplified by the differential amplifiers 10 and 11, respectively. Assuming that the Hall output voltages are V1 and V2 respectively, these become the output V3 at the connection point through the resistors 15 and 16 having the same impedance. Here, there is a relationship of V3 = (V1 + V2) / 2. Next, this output V3 becomes one input of the differential amplifier 12. Note that the other input of the differential amplifier 12 is
Reference voltage Vre obtained by dividing power supply voltage Vcc by resistors 13 and 14
f. The output of the differential amplifier 12 is applied as a bias voltage of the Hall element, and controls the bias current flowing between the bias terminals 5a3, 5a4 and 5b3, 5b4 of both Hall elements 5a, 5b. Here, both Hall elements 5a, 5b
Are connected in series, the bias currents flowing through both Hall elements are equal.

According to this position signal generating circuit, it is possible to always keep the sum (V1 + V2) of the outputs of the two Hall elements constant. According to the above equation (6), the position of the magnetic force generating means is proportional to the output V1 of one Hall element since (V1 + V2) is always constant. That is, according to the position signal generation circuit of the present invention, the bias current flowing through the pair of Hall elements is controlled so that the sum of the Hall outputs of the two Hall elements becomes constant, and therefore, regardless of the temperature characteristics of each element. Thus, a highly accurate sensor output is always obtained. Further, the position of the magnetic force generation source can be accurately detected by the detection output of one Hall element.

Although V1 is used as the sensor position output in the above embodiment, it goes without saying that V2 may be used as the sensor position output.

[0031]

As described above, according to the magnetic position sensor of the present invention, the magnetic circuit for dividing the magnetic flux generated from the magnetic force generating source into two is formed, and each of the magnetic circuits according to the displacement of the magnetic force generating source is formed. Since the magnetic flux density in the magnetic circuit is configured to be detected by each Hall element, the structure can be simplified, and the position of the fluctuation can be accurately determined without being affected by the magnetic force of the magnetic force source. Can be detected,
Since the circuit configuration is such that the sum of the output voltages of the plurality of Hall elements is always constant, a highly accurate magnetic position sensor output that is not affected by the temperature characteristics of each Hall element can be obtained.

Further, since the sum of the output voltages of the pair of Hall elements is always constant, the position of the magnetic force source, that is, the position of the member carrying the magnetic force can be accurately detected by the Hall output of one Hall element. Becomes

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing an embodiment of a magnetic position sensor according to the present invention, FIG. 1 (a) is a plan view thereof, and FIG. 1 (b).
Is a front view thereof, and FIG. 1 (c) is a right side view thereof.

FIG. 2 is a conceptual diagram showing the principle of a magnetic position sensor according to the present invention.

FIG. 3 is an electric circuit diagram showing a configuration of a position signal generating circuit of the magnetic position sensor according to the present invention.

[Explanation of Signs of Main Parts]

 2,3 Magnetic member 4a, 4b Gap 5a, 5b Hall element 7 Magnet (magnetic force generating source) 8 Connecting member 9 Rotating shaft 10,11,12 Differential amplifier 13,14,15,16 Electric resistance

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ identification code FI H01L 43/06 H01L 43/06 A (58) Field surveyed (Int.Cl. ⁷ , DB name) G01D 5/00-5 / 62 G01B 7/00-7/34

Claims (3)

(57) [Claims] 1. A pair of magnetic members which are opposed to each other over a long length at a predetermined distance, and are formed between both ends of at least one magnetic member of the pair of magnetic members and the other magnetic member. And a pair of gaps, and a magnetic force disposed between the pair of magnetic members and supported by a member movable in parallel in the longitudinal direction of the magnetic members to generate a magnetic flux flow from one magnetic member to the other magnetic member. Source and
A magnetic flux density detecting unit that is arranged in each of the pair of gaps and emits a magnetic flux density signal representing a magnetic flux density in the gap; and a position signal generating unit that generates a position signal of the magnetic force generating source according to the magnetic flux density signal. Wherein the pair of magnetic flux density detecting means comprises a Hall element, and the position signal generating means comprises a pair of Hall elements according to an added value of Hall outputs of the pair of Hall elements. A magnetic position sensor characterized by controlling a flowing bias current. 2. The magnetic position sensor according to claim 1, wherein the position signal generating means adds a Hall output of the pair of Hall elements, and compares the added value with a reference value to generate a difference signal. A comparison unit that generates a bias current according to the difference signal, an output unit that sets at least one Hall output of the pair of Hall elements as a detection output representing a position of a magnetic force generation source, A magnetic position sensor, comprising: 3. The magnetic position sensor according to claim 2, wherein one of the bias terminals of each of the Hall elements is connected to each other, and the adjusting means is provided between the other of the bias terminals of the Hall element. And a voltage applying means for applying a voltage corresponding to the difference signal.