JP3131524B2 - Rotation angle 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 rotation angle sensor for detecting a rotation angle of a shaft, and more particularly to a non-contact type rotation angle sensor using a ferromagnetic magnetoresistive element.

[0002]

2. Description of the Related Art Recently, with respect to a sensor for detecting a rotation angle or a rotation position, use of a magnetic sensor has attracted attention due to a demand for forming a non-contact mechanism or reducing inertia loss of a shaft. This magnetic sensor uses a magnetoresistive element, and is arranged such that the plate surface of the element faces a permanent magnet mounted on the tip of a shaft.

As the above-mentioned magnetoresistive element, a semiconductor magnetoresistive element and a ferromagnetic magnetoresistive element are known. The former utilizes the property that the electric resistance of a semiconductor changes in a magnetic field. The latter utilizes the property that the resistance of the ferromagnetic material in a magnetic field changes anisotropically depending on the angle between the magnetization direction and the current direction. This is called an anisotropic magnetoresistive effect and is distinguished from a negative magnetoresistive effect due to the magnitude of a magnetic field. That is, in a normal ferromagnetic material, the resistance becomes the maximum when the current and the magnetization direction become parallel due to the anisotropic magnetoresistance effect, and becomes the minimum when the current and the magnetization direction cross each other. In order to make use of this effect, a ferromagnetic metal thin film is linearly adhered to the surface of the substrate to form a ferromagnetic magnetoresistive element. For example, as described in JP-A-62-237302. There is known a rotational position detecting device in which a ferromagnetic magnetoresistive element is provided at one of an end face of a shaft and a position facing the end face, and a permanent magnet is provided at the other.

Further, a detection element having a bias magnet is known, and good linearity can be secured by applying a bias magnetic field to a ferromagnetic magnetoresistive element. For example, Japanese Unexamined Utility Model Publication No. 63-193866 discloses a bias magnetic field applying means for applying a bias magnetic field in a predetermined direction to a magnetic field from a detected object acting on a sensor unit. There has been proposed a magnetic sensor that detects a displacement direction of a detection target using a change in direction of a synthetic magnetic field with a magnetic field.

[0005]

In the magnetic sensor described in the above publication, the magnetic flux density at the position of the ferromagnetic magnetoresistive element due to the magnetic field of the permanent magnet as the bias magnetic field applying means and the magnetic field of the permanent magnet of the object to be detected is determined. When the ratio changes, the direction of the magnetic flux of the combined magnetic field of the two permanent magnets changes. Therefore, even if the displacement (rotation angle) of the detection target is the same, the resistance value change rate of the ferromagnetic magnetoresistive element changes, and the detection result differs. It will be. That is, when a permanent magnet is used as the object to be detected and the bias magnetic field applying means, if the magnetic flux density of each permanent magnet at the position of the ferromagnetic magnetoresistive element changes, the displacement of the object to be detected is constant. Also, the rate of change of the resistance value of the ferromagnetic magnetoresistive element fluctuates.

Accordingly, if the mounting position of the permanent magnet to which the bias magnetic field is applied to the substrate is different, the detection result of the magnetic sensor will be different, and the relative positional accuracy of the permanent magnet for the bias magnetic field with respect to the ferromagnetic magnetoresistive element will be output. It greatly affects characteristics. The permanent magnet for the bias magnetic field is fixed with an adhesive to the back surface of the substrate on which the ferromagnetic magnetoresistive element and the like are formed, as described in, for example, Japanese Utility Model Application Laid-Open No. 63-193866. In addition, the setting of the mounting position of the permanent magnet with respect to the substrate is generally based on the outer shape of the substrate, so that the tolerance of the outer shape (several tens of μm) at the time of manufacturing the substrate directly causes an error in the mounting position. . For this reason, an error when setting the mounting position of the permanent magnet,
Errors during solidification of the adhesive are superimposed, and sufficient positional accuracy cannot be obtained, and it is difficult to form a parallel magnetic field with respect to the ferromagnetic magnetoresistive element.

Therefore, the present invention relates to a non-contact type rotation angle sensor having a ferromagnetic magnetoresistive element, wherein a magnet member for applying a bias magnetic field forms an appropriate parallel magnetic field with respect to the ferromagnetic magnetoresistive element, thereby achieving stable output characteristics. The purpose is to ensure.

[0008]

In order to achieve the above object, the present invention provides a ferromagnetic magnetoresistive element, a shaft rotating relative to the ferromagnetic magnetoresistive element, and an end of the shaft. A first magnet member mounted on the ferromagnetic magnetoresistive element for forming a magnetic field including the ferromagnetic magnetoresistive element; and a second magnet member for applying a bias magnetic field to the ferromagnetic magnetoresistive element. In a rotation angle sensor for detecting a rotation angle of the shaft by a change in magnetic flux accompanying rotation of the shaft with respect to an element, the second magnet member is provided so as to surround the first magnet member, and The relative position of the second magnet member with respect to the first magnet member in the rotation direction is always set in a predetermined rotation direction with respect to the first magnet member in a predetermined rotation range of the shaft. It as to those with disposing the magnetic force is generated position.

[0009]

In the rotation angle sensor having the above configuration,
When the shaft rotates, the first magnet member rotates relatively to the ferromagnetic magnetoresistive element. In accordance with the relative rotation, the magnetic field of the parallel magnetic flux including the ferromagnetic magnetoresistive element changes, so that the resistance value changes and a signal corresponding to the rotation of the shaft is output. At this time, since the bias magnetic field is applied to the ferromagnetic magnetoresistive element by the second magnet member, a combined magnetic field with the magnetic field of the first magnet member is formed, and the output characteristic according to the rotation angle of the shaft is , Having a wide range of linearity.

In this case, the second magnet member surrounds the first magnet member and always rotates in a predetermined rotation direction with respect to the first magnet member in a predetermined rotation range (for example, 90 °) of the shaft. Since the magnet is disposed at a relative position where the energizing magnetic force is generated, an appropriate parallel magnetic field is formed by the second magnet member with respect to the ferromagnetic magnetoresistive element.
A magnetic force is generated that constantly urges the first magnet member in a predetermined rotation direction. Thus, an error caused by a change in the position of the bias magnetic field relative to the ferromagnetic magnetoresistive element is suppressed to a small value, and desired output characteristics can be obtained. In addition, since a magnetic force that constantly urges the first magnet member in a predetermined rotation direction (for example, the initial position direction) is generated in a predetermined rotation range of the shaft, when the rotation force on the shaft is removed, the initial position is generated by the magnetic force. Is returned to.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment in which a rotation angle sensor according to the present invention is applied to a throttle position sensor of an internal combustion engine will be described below with reference to the drawings. In an internal combustion engine equipped with an electronic control fuel injection device, a throttle position sensor is mounted, and its output signal is used for fuel injection control and the like. The throttle position sensor is connected to a throttle valve shaft, and normally outputs a throttle opening signal that changes according to a throttle valve opening (hereinafter, referred to as a throttle opening) and an idle signal that turns on and off depending on whether the engine is in an idle range or an output range. Is done. A non-contact type rotation angle sensor is used as the throttle position sensor.

FIG. 1 shows a throttle position sensor 1 according to an embodiment of the present invention. The throttle position sensor 1 is mounted on a throttle body (not shown), and a shaft 2 is supported so as to rotate in conjunction with a throttle shaft (not shown). I have.
That is, the throttle position sensor 1 includes a synthetic resin housing 3 having two adjacent concave portions 3a and 3b, and the shaft 2 is mounted on a partition wall 3c between the concave portions 3a and 3b via, for example, a paramagnetic bearing 4. It is rotatably supported. 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).

The shaft 2 has a rotating shaft portion 2c and a flange portion 2a and a locking portion 2b integrally formed at one end thereof. The flange portion 2a and the locking portion 2b are provided in the present invention. Rotor magnet 20, which is a first magnet member,
It is housed in the recess 3 b of the housing 3. That is, a locking portion 2b connected to the flange portion 2a via a groove is formed at the tip of one end portion of the shaft 2, and a cylindrical magnet formed of a plastic magnet so as to fill the locking portion 2b. A rotor magnet 20 is provided. The plane shape of the rotor magnet 20 is not limited to a circle, but may be any shape such as a square. Thus, the rotor magnet 20 can be appropriately attached to the axis of the shaft 2, and a magnetic field is formed around the rotor magnet 20.
In this case, the shaft 2 is formed of a ferromagnetic material, and the rotor magnet 20 includes the flange portion 2a and the locking portion 2b.
As described later, a predetermined magnetic field can be formed as described later without increasing the size as compared with a case where a single plastic magnet is joined to the shaft end.

A magnetic sensor 10 is provided so as to face the rotor magnet 20. The magnetic sensor 10 of the present embodiment has a rectangular element substrate 11, and a ferromagnetic element 12 (hereinafter simply referred to as a magnetoresistive element) made of a strip-shaped thin-film ferromagnetic alloy such as a Ni—Co alloy on one surface. 1
2) is attached. The shape of the element substrate 11 is not limited to a rectangle, but may be any shape. However, since the rotor magnet 20 forms a parallel magnetic flux field including the magnetoresistive element 12, as shown in FIG. , Having a larger diameter than the magnetoresistive element 12.

The magnetoresistive element 12 is formed by bending a strip-shaped thin-film ferromagnetic alloy to increase the resistance, and forming a pattern as shown in FIG. That is, in the pattern of the magnetoresistive element 12, four blocks are constituted by alternately connecting blocks centered on elements whose longitudinal direction is horizontal and blocks centered on elements whose longitudinal direction is vertical. Terminals 12a to 12d are formed at connection points between the blocks. The terminals 12a and 12b are so-called current terminals. The terminal 12a is connected to the power supply Vc, and the terminal 12b is grounded. The terminals 12c and 12d are so-called voltage terminals from which a detection signal is output.

As shown in FIG. 1, a bias magnet 13 as a second magnet member according to the present invention is disposed on the other surface of the element substrate 11 so as to surround the rotor magnet 20, and is fixed by, for example, an adhesive. Have been. Further, since the magnetoresistive element 12 is smaller than the rotor magnet 20 and is disposed near the center of the bias magnet 13, the magnetic field generated by the bias magnet 13 is a parallel magnetic field including the magnetoresistive element 12. Incidentally, the bias magnet 13 may be formed of a plastic magnet.

FIG. 2 is a plan view showing the relationship between the rotor magnet 20 and the bias magnet 13, and the polarities of both magnets are in the illustrated relationship. The rotor magnet 20 is moved by about 90 degrees from the initial fully closed position FC by the lever 5.
2. Rotation is driven in the counterclockwise direction indicated by the arrow in FIG. 2 until the fully open position FO is rotated in the counterclockwise direction. On the other hand, in a state where the rotor magnet 20 is rotationally driven to the fully open position FO,
A portion having the same polarity comes close to the bias magnet 13, a magnetic force acts as shown by a white arrow in the drawing, and the rotor magnet 20 rotates clockwise with respect to the bias magnet 13 at a predetermined position. Being energized.

With the opening operation of the throttle valve (not shown), the lever 5 linked to the throttle shaft is driven against the magnetic force between the rotor magnet 20 and the bias magnet 13, and the shaft 2 rotates. It is configured as follows. When the lever 5 is opened and the rotor magnet 20 is in a free state, it rotates clockwise by the magnetic force acting between the bias magnet 13 and returns to the fully closed position FC. As described above, since the rotor magnet 20 (and the shaft 2) can return to the fully closed position FC, which is the initial position, by a magnetic force, a conventional return spring is not required, and a lightweight and inexpensive configuration can be achieved.

The magnetic sensor 10 is a hybrid IC substrate 3
0 (hereinafter simply referred to as an IC board 30), and a plurality of terminals 7 are connected to the end thereof. The terminal 7 is buried in the housing 3 and extends sideways to form a connector 8 integrally with the housing 3. The IC substrate 30 is accommodated in a concave portion 3b of the housing 3, and the concave portion 3b is hermetically sealed by a ferromagnetic cover 9 via a rubber seal member 19. Note that a detection circuit element for processing the output signal of the magnetic sensor 10 and the like are mounted on the IC board 30, but the description is omitted because it is well known. Then, as shown in FIG.
It is attached to one surface of the C substrate 30. After that, the entire IC substrate 30 may be molded with a synthetic resin. Thus, the combined magnetic field of the rotor magnet 20 and the bias magnet 13 is applied to the magnetoresistive element 12.

In the throttle position sensor 1 of the present embodiment having the above-described configuration, the lever 5 shown in FIG.
Rotates in the bearing 4. As the shaft 2 rotates, the magnetic field generated by the rotor magnet 20 also rotates, and the direction of the magnetic field of the parallel magnetic flux including the magnetic field changes with respect to the magnetoresistive element 12. That is, the direction of the combined magnetic field of the magnetic field of the rotor magnet 20 and the bias magnetic field of the bias magnet 13 changes. Thus, the magnetoresistive element 1 is formed by the anisotropic magnetoresistance effect.
2 change, and a signal corresponding to the rotation of the shaft 2 is output from the magnetic sensor 10.
The output characteristics of the magnetic sensor 10 with respect to the rotation angle are characteristics having a wide range of linearity.

In the present embodiment, a stable parallel magnetic field is formed on the magnetoresistive element 12 by the bias magnet 13. 4 and 5 show the magnetic flux distribution of the magnetic field formed by the bias magnet 13 of the present embodiment and the conventional bias magnet 13p. In the present embodiment, as shown in FIG. Are located at the center in a plan view, and on one end face of the bias magnet 13 in a front view. On the other hand, the conventional magnetoresistive element 12 is positioned below and parallel to the rectangular bias magnet 13p having a smaller area. Therefore, in the magnetic flux distribution in the direction orthogonal to the axis of the conventional shaft 2 (Y-Y direction), the difference in magnetic flux between the central portion and the peripheral portion of the magnetoresistive element 12 is large as shown in FIG. The magnetic flux distribution in the direction (Y-Y direction) orthogonal to the axis of the shaft 2 in this embodiment is as shown in FIG.
The variation width of the magnetic flux with respect to the same ΔY is smaller than that of the related art, so that an error in the axial direction is small and an appropriate parallel magnetic field is formed.

[0022]

Since the present invention is configured as described above, the following effects can be obtained. That is, in the rotation angle sensor according to the present invention, the second magnet member surrounds the first magnet member and always urges the first magnet member in a predetermined rotation direction in a predetermined rotation range of the shaft. Since the second magnetic member is disposed at a relative position where a magnetic force is generated, an appropriate parallel magnetic field is formed by the second magnet member with respect to the ferromagnetic magnetoresistive element, and stable output characteristics can be obtained. In addition, a magnetic force is generated that urges the first magnet member in a predetermined rotational direction, and when the rotation with respect to the shaft is removed, the magnetic force returns to, for example, an initial position. And it becomes cheap.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view of a throttle position sensor according to an embodiment of a rotation angle sensor of the present invention.

FIG. 2 is a plan view showing a relationship between a rotor magnet and a bias magnet in one embodiment of the present invention.

FIG. 3 is a plan view of a magnetic sensor used in one embodiment of the present invention.

FIG. 4 is an explanatory diagram showing a magnetic flux distribution by a bias magnet with respect to a magnetoresistive element according to one embodiment of the present invention.

FIG. 5 is an explanatory diagram showing a magnetic flux distribution by a bias magnet with respect to a conventional magnetoresistive element.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 throttle position sensor (rotation angle sensor) 2 shaft 10 magnetic sensor 11 element substrate 12 ferromagnetic resistance element 13 bias magnet (second magnet member) 20 rotor magnet (first magnet member) 30 hybrid IC substrate

──────────────────────────────────────────────────続 き Continued on the front page (58) Fields surveyed (Int. Cl. ⁷ , DB name) G01B ⁷ /00-7/34 102 G01D 5/00-5/252 G01D 5/39-5/62

Claims (1)

(57) [Claims] 1. A ferromagnetic magnetoresistive element, a shaft that rotates relative to the ferromagnetic magnetoresistive element, and a shaft mounted on an end of the shaft for forming a magnetic field including the ferromagnetic magnetoresistive element. And a second magnet member for applying a bias magnetic field to the ferromagnetic magnetoresistive element, wherein the rotation angle of the shaft is determined by a change in magnetic flux accompanying rotation of the shaft with respect to the ferromagnetic magnetoresistive element. In the rotation angle sensor for detecting the first magnet member, the second magnet member is disposed so as to surround the first magnet member, and the second magnet member with respect to the first magnet member in the rotation direction of the shaft. Is disposed at a position where a magnetic force that constantly urges the first magnet member in a predetermined rotation direction is generated in a predetermined rotation range of the shaft. Angle sensor.