JPH02298815A - Rotational angle sensor - Google Patents

Abstract

PURPOSE:To make it possible to secure stable precision in detection by a construction wherein a pair of magnetic poles of a magnet member provided at the fore end of a shaft are made to face the opposite lateral sides of a magnetic sensor and thereby a magnetoresistance element is put in a uniform magnetic field. CONSTITUTION:A magnetoresistance element 12 is formed on a base 11 of a magnetic sensor 10 and a magnet member 20 provided at the fore end of a shaft 2 gearing with a throttle valve is disposed opposite to said element. A magnetic field of a parallel magnetic flux having a uniform flux density is formed by and between an N pole and an S pole of the fore end parts 22a and 23a of a pair of magnetic-substance arm parts 22 and 23 of the magnet member 20, and the aforesaid sensor base 11 is disposed in parallel to said magnetic flux. In this constitution, the magnetic field rotates in accordance with the rotation of the shaft 2, a resistance value of the magnetoresistance element 12 varies and a rotational angle is detected therefrom. Even when the shaft 2 is displaced in the axial direction, therefore, an output of the element is not varied and thus stable precision in detection can be maintained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a rotation angle sensor for detecting the rotation angle of a shaft, and particularly to a non-contact rotation angle sensor using a magnetoresistive element.

[Prior Art] Recently, the use of magnetic sensors has been attracting attention due to the need to construct a non-contact mechanism or to reduce the inertia loss of a shaft as a sensor for detecting rotational angle or rotational position. This magnetic sensor uses a magnetoresistive element,
The plate surface of the element is arranged to face a permanent magnet attached to the tip of the shaft.

Semiconductor magnetoresistive elements and ferromagnetic magnetoresistive elements are known as the above-mentioned magnetoresistive elements. The former utilizes the property that the electrical resistance of a semiconductor changes in a magnetic field. The latter utilizes the property that the resistance of a ferromagnetic material in a magnetic field changes anisotropically depending on the angle formed between the magnetization direction and the current direction. This is called an anisotropic magnetoresistive effect, and is distinguished from the negative magnetoresistive effect due to the magnitude of the magnetic field. That is, in a normal ferromagnetic material, due to the anisotropic magnetoresistance effect, the resistance is maximum when the current and the magnetization direction are parallel, and is minimum when they are perpendicular to each other. In order to take advantage of this effect, a thin film of ferromagnetic metal is adhered to the surface of the substrate in the form of a broken line to form a ferromagnetic magnetoresistive element.

A magnetic sensor including a ferromagnetic magnetoresistance element configured as described above, for example, as in the rotational position detection device described in JP-A No. 62-237302, is capable of detecting both the end surface of the shaft and the position opposite to this end surface. One side is provided with a permanent magnet, and the other side is provided with a permanent magnet.

Therefore, the plate surface of the magnetoresistive element and the permanent l1f1 stone are arranged to face each other.

[Problems to be Solved by the Invention] However, in the case of the rotational position detection device described in the above-mentioned publication, in which the permanent magnet and the plate surface of the magnetic resistance element are arranged to face each other, The movement changes the magnetic field applied on the magnetoresistive element. Although the ferromagnetic magnetoresistive element described above can function in a relatively small magnetic field, it will not function unless the distance from the permanent magnet is large and sufficient magnetic flux is applied to the magnetoresistive element, thus causing measurement errors. becomes. Therefore, it is necessary to maintain a predetermined distance between the plate surface of the magnetoresistive element and the permanent magnet. Although not specifically disclosed in the above publication, the shaft must be supported to prevent at least axial movement, the shaft support structure requires precision, and accurate assembly is required. becomes.

Therefore, an object of the present invention is to enable the magnetoresistive element in the rotation angle sensor to be placed in a uniform magnetic field at all times, and to ensure stable detection accuracy at all times without being affected by the normal displacement of the shaft. do.

[Means for Solving the Problems] In order to achieve the above object, the present invention includes a detection element in which a magnetoresistive element is attached to the plate surface of a substrate. The rotation angle sensor for detecting the rotation angle of the shaft includes a magnet member having a pair of opposing magnetic poles on both sides of the substrate and forming a magnetic field that includes at least a plate surface of the substrate, the magnet member and One of the detection elements is mounted on the shaft, and the other is fixed at a predetermined position with respect to the shaft.

The magnet member is formed into a substantially U-shaped cross section by a permanent magnet disposed opposite to the plate surface of the substrate and a pair of magnetic arms provided on both sides of the permanent magnet, and has a substantially U-shaped cross section. It is preferable that the substrate is interposed therebetween and arranged so that the plate recess of the substrate is parallel to the direction of magnetic flux between the magnetic arms.

Further, the magnet member is formed with a permanent magnet having a substantially U-shaped cross section, and the substrate is interposed between both open ends of the permanent magnet, and the plate surface of the substrate is a magnetic flux between both open ends of the permanent magnet. The substrate can also be arranged parallel to the direction.

[Operation] In the rotation angle sensor configured as described above, either the magnet member or the detection element, for example, the magnet member, is attached to the shaft. A detection element is fixed at a predetermined position with respect to the shaft, and a magnetic field including the plate surface of the substrate of the detection element is formed between a pair of opposing magnetic poles of the magnet member.

As the shaft rotates, the magnetic field rotates, and the resistance value of the magnetoresistive element on the substrate changes due to the magnetoresistive effect.

Then, the rotation angle of the shaft is detected according to this resistance value change.

[Embodiments] Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings.

1 to 3 show an embodiment of the rotation angle sensor of the present invention, and a magnetic sensor 1 which is a detection element according to the present invention.
0 are mounted on the circuit board 30, and the magnet member 20 is arranged to face them.

In the magnetic sensor 10, as the cross section is shown in FIG. 1, a thin film of a ferromagnetic alloy such as a Ni--C0 alloy is adhered to an element substrate 11, and a magnetoresistive element 12 is constructed. This magnetoresistive element 12 is formed by integrated circuit manufacturing techniques such as vapor deposition and photoetching, and is connected to a plurality of leads 31 formed on a circuit board 30 via a plurality of terminals 13 shown in FIG. .

The magnetoresistive element 12 is formed by bending a strip-shaped thin film ferromagnetic alloy into a pattern as shown in FIG. 2 in order to increase the resistance. That is, blocks centered on elements whose longitudinal directions are horizontal and blocks whose centers are centered on elements whose longitudinal directions are vertical are alternately connected to form four blocks. Terminals 12a to 1 are provided at the connection points between each block.
2d is formed. The terminals 12a and 12b are so-called current terminals, with the terminal 12a being connected to the power supply Vc via a constant current circuit, and the terminal 12b being grounded.

The terminals 12c and 12d are so-called voltage terminals, and detection signals are output from these terminals.

The terminals 12a to 12d are connected to a terminal 13 shown in FIG. 3, and the terminal 13 is soldered to a board 31 on a circuit board 30. On the surface of the circuit board 30 opposite to the surface on which the magnetic sensor 10 is mounted, circuit elements constituting a detection circuit, which will be described later, are mounted. electrically connected.

On the other hand, the magnet member 20 consists of a permanent magnet 21 and a pair of magnetic arms 22 and 23 having an abbreviated cross-section joined to both sides of the permanent magnet. 2 is fixed to a permanent magnet 21. The magnetic arm portions 22 and 23 are bonded to the side surfaces of the permanent magnet 21 by adhesive or the like so that the end surfaces of the tip portions 22a and 23a of each bent portion face each other, and a gap is formed between the end surfaces of the tip portions 22a and 23a. has been done. Thus, the permanent magnet 21 attaches an N pole to the tips 22a and 23a of the magnetic arms 22 and 23, respectively.
An S pole is formed, and a magnetic field of parallel magnetic flux with uniform magnetic flux density is formed between the two.

The magnet member 20 is arranged with a predetermined gap between the magnetic sensor 10 and the circuit board 30, as shown in FIG. That is, the tip portion 22a of the magnetic arm portion 22゜23,
The distance between the end faces of 23a is larger than the length of the longest planar part of the magnetic sensor 10, and the distance between the tip parts 22a, 23a and the circuit board 3
0 [L is set to a desired gap less than or equal to the thickness H of the magnetic sensor 10. Note that the width 1 of the tip portions 22a, 23a of the magnetic arm portions 22, 23 is set to be greater than the thickness H of the magnetic sensor 10. Therefore, even if the magnet member 20 approaches or separates from the magnetic sensor 10 in the axial direction due to the support structure of the shaft 2 as the shaft 2 rotates, it is prevented from coming into contact with the circuit board 30. and the circuit board 30
Between j! By setting iiL to be less than or equal to the thickness H of the magnetic sensor 10, the magnetoresistive element 12 on the plate surface of the magnetic sensor 10 is always located between the end faces of the tips 22a and 23a.

The magnetic sensor 10 is in a uniform parallel magnetic field formed between the tips 22a and 23a of the magnetic arms 22 and 23, and the plate surface of the element substrate 11 is located parallel to this. Uniform magnetic flux parallel to the plate surface is applied to the magnetoresistive element 12. When the permanent magnet 21 rotates around the magnetic sensor 10 due to the rotation of the shaft 2, the tip portions 22a, 23
The magnetic field between points a rotates, and the angle between the magnetization direction and the current direction with respect to the magnetoresistive element 12 changes. In this case, the current supplied to the magnetoresistive element 12 and the tip 22a,
The resistance value of the magnetoresistive element 12 is maximum when the magnetization directions due to the magnetic fields between the magnets 23a are parallel to each other, and minimum when they are perpendicular to each other. As a result, the outputs of the terminals 12c and 12d become substantially sinusoidal waves, and an output characteristic that is substantially linear with respect to the rotation angle of the shaft 2 is obtained except in the vicinity of the maximum and minimum values.

In the operation of the rotation angle sensor, if the shaft 2 is displaced in the axial direction due to the support structure of the shaft 2 or in a direction parallel to the magnetic sensor 10 due to misalignment, the magnetic member 20 Although it will be displaced relative to the sensor 10, the magnetic field formed between the tips 22a and 23d is a uniform parallel magnetic flux, so the magnetoresistive element 12
The magnetic flux applied to the magnetic flux does not change. Therefore, a stable voltage signal is output from the terminals 12c and 12d without being affected by the displacement of the shaft 2.

Although the rotation angle sensor configured as described above can be installed in various devices, for example, it is built into a throttle position sensor of an internal combustion engine.

344 and 5 show a throttle position sensor 1 incorporating the rotation angle sensor described above, which is mounted on a throttle body (not shown) and supported so that the shaft 2 rotates in conjunction with the throttle shaft (not shown). There is. That is, the throttle position sensor 1 includes a synthetic resin housing 3 having two adjacent recesses 3a and 3b, and a shaft 2 is rotatably supported via a bearing 4 on a partition wall 3c between these recesses 3a and 3b. has been done.

A lever 5 housed in one recess 3a of the housing 3 is fixed to one end of the shaft 2, and the lever 5 is connected to a throttle shaft (not shown). A return spring 6 is interposed between the housing 3 and the lever 5, and the lever 5 is urged toward a predetermined initial position.

Therefore, as the throttle valve (not shown) is opened, the lever 5 that is interlocked with the throttle shaft is driven against the biasing force of the return spring 6, and the shaft 2 is rotated. In this embodiment, a sintered oil-impregnated slag bearing is used as the bearing 4, but a ball bearing or the like may of course be used.

A magnet member 20 is fixed to the other end of the shaft 2 and housed within the other four parts 3b of the housing 3. and,
A magnetic sensor 1o is disposed so as to face the permanent magnet 21 constituting the magnet member 20 and to be located between the magnetic arms 22 and 23 at both ends thereof. As described above, the magnetic sensor 10 includes an element substrate 11 and a magnetoresistive element 1 attached to the surface of the element substrate 11.
2, and is mounted on one surface of the circuit board 30. On the other side of the circuit board 30 are leads constituting a detection circuit,
Elements such as operational amplifiers are mounted. Although an example of the arrangement of these elements is shown in FIG. 5, the circuit configuration is not limited to this. A plurality of terminals 32 are provided at one end of the circuit board 30 to connect the leads on the front and back surfaces, and a plurality of lead members 7 are connected to the other end. These lead members 7 are embedded in the housing 3, and a circuit board 30 extending laterally and having a connector 8 integrally formed with the housing 3 is accommodated and fixed in the recess 3b of the housing 3. This recess 3b is sealed with a cover 9 made of synthetic resin.

FIG. 6 shows a block diagram of a detection circuit connected to the throttle position sensor 1. A Wheatstone bridge 40 is formed by the magnetoresistive element 12 consisting of the four blocks shown in FIG. 2, and a constant current circuit is connected to the terminal 12a. 41
are connected, and the terminal 12b is grounded. terminal 12c
, 12d are output terminals of the Wheatstone bridge 40 and are connected to a differential amplifier circuit 42 and a level shift circuit 43, respectively, and the output of the level shift circuit 43 is supplied to the differential amplifier circuit 42. Then, the output of the differential amplifier circuit 42 is output from the output terminal 42a as a rotation angle signal, and
The signal is supplied to the comparison circuit 44, and an idle area signal is output from the output terminal 44a. Note that the rotation angle signal is a voltage output proportional to the rotation angle of the shaft 2, and the idle range signal is a voltage output that changes from an off state to an on state when a throttle valve (not shown) moves to a closed position.

FIG. 7 is a specific circuit example of the block diagram in FIG.
c indicates a constant voltage power supply terminal, and GND indicates a ground terminal. Note that FIG. 7 shows one embodiment of FIG. 6, and the circuit configuration is not limited to this, and various electric circuits may be configured.

According to the throttle position sensor 1 of this embodiment, the lever 5 shown in FIG. 4 is driven in conjunction with a throttle valve (not shown), and the shaft 2 rotates around the bearing 4. According to this rotation of the shaft 2, the resistance value of the magnetoresistive element 12 of the magnetic sensor 10 changes as described above. This magnetoresistive element 12 has a Wheatstone bridge 40 as shown in FIG. 6, which is connected to a constant current circuit 4.
A constant current is supplied via 1. Therefore, depending on the change in the resistance value of each block of the magnetoresistive element 12, the terminal 12
The output voltages of the terminals c and 12d change, and the output of the terminal 12c is input to the differential amplifier circuit 42, and the output of the terminal 12d is input to the differential amplifier circuit 42 via the level shift circuit 43. Here, the difference in force between the two persons changes according to the rotation angle of the shaft 2, and a voltage output as a rotation angle signal is obtained from the output terminal 42a, which shows the output characteristics shown in FIG.

That is, the output voltage increases linearly with respect to the rotation angle except near the maximum and minimum values.

Further, the output of the differential amplifier circuit 42 is compared with a predetermined voltage value in a comparator circuit 44, and when a throttle valve (not shown) is in a substantially closed position, a voltage output is obtained from the output terminal 44a as an idle range signal. It will be done. As described above, according to the throttle position sensor 1 of this embodiment, not only the rotation angle signal of the throttle valve but also the idle range signal can be obtained simultaneously without contact.

FIG. 9 shows another embodiment of the rotation angle sensor of the present invention, in which the structure of the magnet member 20 is different from the embodiments shown in FIGS. 1 to 3. That is, in this embodiment, after the magnetic arms 22 and 23 are joined to the permanent magnet 21, both and the shaft 2 are fixed by resin molding. Annular grooves are formed in the grooves, and a resin portion 2a that includes these annular grooves is formed.

FIG. 10 shows still another embodiment of the rotation angle sensor of the present invention, in which the tip of the shaft 2 is connected by a plastic magnet 21a instead of the permanent magnet 21 and magnetic arms 22, 23 of the previous embodiment. Contains and integrally molds magnet member 2
o. This reduces the number of parts and facilitates manufacturing.

[Effects of the Invention] Since the present invention is configured as described above, it produces the effects described below.

That is, in the rotation angle sensor of the present invention, magnetic poles are arranged opposite to both sides of the substrate of the detection element, and a magnetic field including the plate surface of the substrate is formed, so that the magnetoresistive element attached to the substrate is always uniformly distributed. It will be placed in a strong magnetic field. Therefore, even if the shaft is displaced in the axial direction or parallel to the substrate, the output of the detection element does not change, and stable detection accuracy can be ensured.

If the above magnet member is formed into a substantially U-shaped cross section by a permanent magnet and a pair of magnetic arms provided on both sides of the magnet, a uniform parallel magnetic flux can be formed between the end faces of both arms. Since it is sufficient to arrange the magnetoresistive element between the end faces, it can be easily manufactured without requiring special assembly accuracy.

Furthermore, if the magnet member is integrally formed with a plastic magnet, manufacturing becomes easier.

[Brief explanation of the drawing]

Fig. 1 is a partial sectional view of a rotation angle sensor according to an embodiment of the present invention, Fig. 2 is a plan view of a magnetoresistive element used in the rotation angle sensor, and Fig. 3 is a perspective view of the rotation angle sensor. 4 is a vertical sectional view of a throttle position sensor equipped with a rotation angle sensor according to an embodiment of the present invention, FIG. 5 is a plan view of the throttle position sensor with the cover removed, and FIG. is a block diagram of the detection circuit connected to the throttle position sensor, FIG. 7 is a specific electric circuit diagram of the detection circuit, FIG. 8 is an input/output characteristic diagram of the throttle position sensor, and FIG. 9 is a block diagram of the detection circuit connected to the throttle position sensor. FIG. 10 is a partial cross-sectional view of a rotation angle sensor according to still another embodiment of the present invention. FIG. 1... Throttle position sensor. 2...Shaft, 10...Magnetic sensor (detection element)
. 11... Element substrate, 12... Magnetoresistive element. 20... Magnet member, 21... Permanent magnet. 22.23...Magnetic arm. 22a, 23a=-Tip portion, 30...Circuit board.

Claims (3)

[Claims] (1) A rotation angle sensor that includes a detection element with a magnetoresistive element attached to the plate surface of a substrate, and detects the rotation angle of the shaft by changes in magnetic flux accompanying rotation of the shaft with respect to the detection element, on both sides of the substrate. A magnet member having a pair of magnetic poles facing each other on surfaces and forming a magnetic field including at least the plate surface of the substrate, one of the magnet member and the detection element is mounted on the shaft, and the other is attached to the shaft. A rotation angle sensor characterized in that it is fixed at a predetermined position. (2) The magnet member is formed into a substantially U-shaped cross section by a permanent magnet disposed facing the plate surface of the substrate and a pair of magnetic arm portions provided on both sides of the permanent magnet, and the magnetic member 2. The rotation angle sensor according to claim 1, wherein the substrate is interposed between the arm portions, and the substrate is arranged such that a plate surface of the substrate is parallel to a direction of magnetic flux between the magnetic arm portions. . (3) The magnet member is formed of a permanent magnet having a substantially U-shaped cross section, and the substrate is interposed between the open ends of the permanent magnet, and the plate surface of the substrate is between the open ends of the permanent magnet. 2. The rotation angle sensor according to claim 1, wherein the substrate is arranged parallel to a direction of magnetic flux.