JP3438692B2 - Rotation angle detector - 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 detection device for detecting a rotation angle of an object to be detected by using a magnetic detection element and a magnet.

[0002]

2. Description of the Related Art In electronic throttle systems for automobiles,
For example, as shown in FIG. 8, a throttle body 1 made of metal (for example, aluminum) is provided with a throttle valve 2
Rotatably supporting the rotary shaft 3 of the throttle body 1
The throttle valve 2 is rotationally driven via the speed reduction mechanism 5 by the motor 4 attached to the lower side part. The rotary shaft 3 of the throttle valve 2 is connected to the rotor core 7 of the rotation angle detection device 6, and the magnet 8 is fixed to the inner peripheral surface of the rotor core 7. On the other hand, a stator core 10 molded in a resin cover 9 covering the opening of the throttle body 1 is positioned coaxially with the inner peripheral side of the rotor core 7, and the inner peripheral surface of the magnet 8 faces the outer peripheral surface of the stator core 10. At the same time, the Hall IC 52 is fixed to the magnetic detection gap portion 51 formed so as to penetrate the stator core 10 in the diametrical direction.

In this structure, the magnetic flux of the magnet 8 passes through the stator core 10 and the magnetic detection gap portion 51, and the output of the Hall IC 52 changes according to the magnetic flux density. The magnetic flux density passing through the magnetic detection gap portion 51 is
Since it changes depending on the rotation angle of the (rotor core 7), the rotation angle of the magnet 8 and thus the rotation angle of the throttle valve 2 (throttle opening) can be detected from the output signal of the Hall IC 52.

[0004]

In the above conventional rotation angle detecting device, the stator core 10 for fixing the Hall IC 52 is fixed.
The resin-made cover 9 formed by molding has a higher coefficient of thermal expansion than the metal throttle body 1 to which the cover 9 is attached. Moreover, since the cover 9 is formed in a vertically long shape so as to collectively cover the motor 4 and the reduction mechanism 5 arranged on the lower side of the throttle body 1, the amount of thermal deformation in the longitudinal direction is large. Become.

However, in the conventional structure, as shown in FIG. 8B, the magnetic detection direction of the Hall IC 52 (the direction orthogonal to the magnetic detection gap portion 51) and the longitudinal direction of the cover 9 are parallel to each other. Due to the thermal deformation of 9, the gap of the magnetic detection gap portion 51 and the gap between the stator core 10 and the magnet 8 change, and the magnetic detection gap portion 5
The magnetic flux density passing through 1 is easily changed. Therefore, due to thermal deformation of the cover 9, the Hall IC 5
The output of No. 2 is likely to fluctuate, and the detection accuracy of the rotation angle is reduced.

The present invention has been made in consideration of the above circumstances, and therefore an object thereof is to suppress the output fluctuation of the magnetic detection element due to the thermal deformation of the cover,
An object of the present invention is to provide a rotation angle detection device capable of improving the detection accuracy of the rotation angle.

[0007]

In order to achieve the above object, in the rotation angle detecting device according to claim 1 of the present invention, when the magnetic detecting element is fixed to the resin cover side, the magnetic detecting element is The magnetic detection direction and the longitudinal direction of the cover are orthogonal to each other. By doing so, the magnetic detection direction of the magnetic detection element becomes the short direction of the cover, and the dimensional change in the magnetic detection direction due to thermal deformation of the cover can be reduced, and the change in magnetic flux density in the magnetic detection direction can be reduced. You can Thereby, the output fluctuation of the magnetic detection element due to the thermal deformation of the cover can be suppressed to a small level, and the detection accuracy of the rotation angle can be improved.

When the present invention is carried out, a magnet is fixed to a cylindrical rotor core which rotates in accordance with the rotation of an object to be detected,
A configuration is conceivable in which a stator core arranged coaxially on the inner peripheral side of the rotor core is molded into a resin cover, and a magnetic detection element is fixed to a magnetic detection gap formed so as to penetrate the stator core in a diametrical direction. . In this case, it is preferable that the magnetic detection gap portion extends in the longitudinal direction of the cover. In this configuration, since the magnetic detection direction of the magnetic detection element is orthogonal to the longitudinal direction of the cover and the magnetic detection direction is the short direction of the cover,
The dimensional change in the magnetic detection direction due to thermal deformation of the cover can be reduced, the change in the magnetic detection gap and the change in the gap between the stator core and the magnet can be reduced, and the magnetic flux density passing through the magnetic detection gap can be reduced. The change can be reduced. Thereby, the output fluctuation of the magnetic detection element due to the thermal deformation of the cover can be suppressed to be small, and the detection accuracy of the rotation angle can be improved.

By the way, in the rotation angle detecting device using the magnetic detecting element, the detection accuracy becomes the highest in the vicinity where the output of the magnetic detecting element becomes zero. The reason for this is that the position where the output of the magnetic detection element becomes zero is the center point of the linear region of the output,
This is because the linearity is the best, and if the output of the magnetic detection element is zero, the influence of the temperature characteristic of the magnetic detection element is the smallest.

Focusing on this characteristic, it is preferable to arrange the magnet and the magnetic detection element so that the output of the magnetic detection element becomes zero at or near the rotation angle where the detection accuracy is most required, as in claim 3. With this configuration, the influence of the temperature characteristics of the magnetic detection element can be minimized in the rotation angle region where the detection accuracy is most required, and the rotation angle detection accuracy can be improved.

Further, as described in claim 4, the magnet and the magnetic detection element may be arranged so that the output of the magnetic detection element becomes zero at or near the reference rotation angle of the object to be detected. With this configuration, the influence of the temperature characteristics of the magnetic detection element can be minimized at or near the reference rotation angle, and the reference rotation angle can be detected with high accuracy.
The output of the magnetic detection element (detected rotation angle) can be calibrated with high accuracy based on this reference rotation angle, and the detection accuracy of the rotation angle can be improved.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS [Embodiment (1)] An embodiment (1) in which the present invention is applied to an electronic throttle system will be described below with reference to FIGS. 1 to 6.

First, a schematic structure of the electronic throttle system will be described with reference to FIG. The throttle valve 11 (object to be detected) that controls the intake air amount of the internal combustion engine is a rotating shaft 12.
The rotary shaft 12 is rotatably supported by a metallic (for example, aluminum) throttle body 15 (main body housing) via bearings 13 and 14.
A motor 16 for driving the throttle valve 11 is attached to the lower side of the throttle body 15, and the rotation of the motor 16 is reduced by a reduction mechanism 20 composed of a plurality of gears 17 to 19 and transmitted to the rotary shaft 12. As a result, the throttle valve 11 is rotationally driven.

The gear 19 fixed to the rotary shaft 12 of the throttle valve 11 is formed by molding a cylindrical cup-shaped rotor core 21 and a magnet 22 with resin.
As a result, the gear 19, the rotor core 21, and the magnet 22 are integrally fixed to the tip of the rotary shaft 12 by caulking or the like. The gear 19 is a torsion coil spring 2
The throttle valve 11 is urged in a predetermined rotation direction by 3 and is automatically urged by the urging force so as to return to the fully closed position described later.

On the other hand, the resin cover 24 which covers the right end opening of the throttle body 15 is formed by the throttle body 1.
5 is formed in a vertically long shape (see FIG. 2) so as to collectively cover the motor 16 and the reduction mechanism 20 arranged on the lower side of
Inside the upper part of the cover 24, a stator core 26 in which the Hall IC 25 is arranged and a spacer 27 are molded. By fixing the cover 24 to the throttle body 15 with bolts or the like, the stator core 26, the hole I
The C25 is assembled inside the cover 24 in a fixed state. As a result, in the empty space inside the cover 24, the rotor core 21, the magnet 22, and the stator core 2 are
6, a rotation angle detection device 28 including a Hall IC 25 and the like is housed. A connector housing 30 for connecting to the motor terminal 29 is integrally formed inside the lower portion of the cover 24, and a connector pin 31 in the connector housing 30 is connected to the motor terminal 29.

The rotor core 21 and the stator core 26 of the rotation angle detecting device 28 are both made of a magnetic material such as iron.
As shown in, the stator core 26 is coaxially arranged on the inner peripheral side of the rotor core 21. The magnet 22 is formed in a cylindrical shape and is fixed to the inner peripheral surface of the rotor core 21 concentrically with the rotor core 21, and a uniform air gap G1 is formed between the inner peripheral surface of the magnet 22 and the outer peripheral surface of the stator core 26. Are formed. The magnet 22 is magnetized (radially magnetized) so that the direction of the magnetic lines of force inside the magnet is in the radial direction (radial direction), and the upper half of the magnet 22 has the N pole on the inner peripheral side and the S pole on the outer peripheral side. And the lower half of the magnet 22 is
It is magnetized so that the outer circumference side is the N pole and the inner circumference side is the S pole. The magnet 22 is divided into an upper half part and a lower half part,
A cylindrical magnet may be composed of individual magnets. This magnet 2
The magnets 2 may be magnetized (parallel magnetized) so that the lines of magnetic force inside the magnet are parallel to each other. The left side surface of the rotor core 21 has a plurality of through holes 3 for preventing a magnetic flux from being short-circuited.
2 (see FIG. 1) is formed so as to surround the rotary shaft 12.

On the other hand, the stator core 26 is divided into two parts on the left and right sides, and the gap between them is regulated by a spacer 27 made of resin to form a gap part 33 penetrating in the diameter direction. A magnetic detection gap portion 34 for forming a parallel magnetic field is formed at the center of the gap portion 33 with a predetermined gap G2 so as to extend in the longitudinal direction of the cover 24 (see FIG. 2). On both sides (upper side and lower side in FIG. 3) of the magnetic detection gap portion 34, large gap portions 35 recessed in an arc shape in the left-right direction are formed.
The gap G3 of No. 5 is larger than the gap G2 of the magnetic detection gap portion 34. As a result, the magnetic flux flowing through the stator core 26 concentrates on the magnetic detection gap portion 34. Further, by forming the large gap portion 35 in an arc shape, the gap G4 on the outer peripheral side of the stator core 26 is narrowed so that more magnetic flux from the magnet 22 can flow to the stator core 26. ing. However, the gap G4 on the outer peripheral side of the stator core 26 is equal to that of the magnet 22 and the stator core 26.
Is formed to be larger than the air gap G1 between them and the short circuit of the magnetic flux in the gap G4 is prevented.
The large gap portion 35 may not be formed.

In the magnetic detection gap portion 34, two Hall ICs 25 are arranged side by side in a direction perpendicular to the direction of the magnetic flux passing through the magnetic detection gap portion 34. Each hall IC2
Reference numeral 5 denotes an IC in which a Hall element (magnetic detection element) and a signal amplification circuit are integrated, and outputs a voltage signal corresponding to the magnetic flux density passing through the magnetic detection gap portion 34 (magnetic flux density interlinking with the Hall IC 25). To do. The Hall ICs 25 are arranged so that the magnetic detection direction thereof is orthogonal to the longitudinal direction of the cover 24 (see FIG. 2).

Each Hall IC 25 may have a function of performing output gain adjustment, offset adjustment, temperature characteristic correction with respect to magnetic flux density by electrical trimming, or a self-diagnosis function of disconnection or short circuit. The Hall IC 25 is positioned by the spacer 27, and the terminal (not shown) of the Hall IC 25 is connected to the connector pin 35 through the inside of the spacer 27 by welding or the like. The Hall IC is connected to a control circuit (not shown) via the connector pin 35.

As shown in FIG. 1, an arcuate recess 36 is formed on the upper peripheral edge of the cover 24 so as to be concentric with the stator core 26.
The arcuate concave portion 36 is fitted into the convex portion 37 formed on the upper edge portion of the opening of the throttle body 15 to ensure the coaxial accuracy of the rotor core 21 and the stator core 26.

The rotation angle detecting device 28 constructed as described above
At a position where the switching portion of the magnetic poles of the magnet 22 (shown by a broken line in FIG. 3) is parallel to the magnetic detection gap portion 34 (hereinafter, the rotation angle of the rotor at this position is 0 °), the magnetic circuit is
One side of the magnet 22 → One side of the stator core 26 → Magnetic detection gap portion 34 → The other side of the stator core 26 → Magnet 2
The magnetic flux of the magnet 22 flows from one side of the stator core 26 to the other side (hereinafter, the flow direction of the magnetic flux is a positive direction). When the rotor core 21 rotates along with the rotation of the object to be detected such as the throttle valve, a part of the magnetic flux flows from the other side of the stator core 26 to the one side (opposite direction), and this flows in the positive direction at the magnetic detection gap portion 34. Since it cancels out with the flowing magnetic flux, the magnetic detection gap 3
4, the amount of magnetic flux corresponding to the difference between the amount of magnetic flux Φ1 flowing in the positive direction and the amount of magnetic flux Φ2 flowing in the opposite direction (Φ1 −Φ2)
Flows.

In this case, the rotation angle of the rotor core 21 is 0 to
In the range of 180 °, the amount of magnetic flux Φ in the positive direction depends on the rotation angle.
Since 1 decreases and the amount of magnetic flux Φ 2 in the opposite direction increases, as shown in FIG. 5, in the range of the rotation angle of 0 to 180 °, the magnetic flux density passing through the magnetic detection gap portion 34 depends on the rotation angle. Decrease. At this time, at the position where the rotation angle is 90 °, the amount of magnetic flux Φ1 in the positive direction and the amount of magnetic flux Φ2 in the opposite direction become the same, and the two cancel each other out, and the magnetic flux density of the magnetic detection gap portion 34 becomes zero. After that, the rotation angle is 180 ° to 360
When the angle becomes °, the magnetic flux amount Φ1 in the positive direction increases and the magnetic flux amount Φ2 in the opposite direction decreases according to the rotation angle, so the gradient of the change in the magnetic flux density of the magnetic detection gap portion 34 with respect to the rotation angle is 0 to 180 °. The opposite of the case. Therefore, the rotation angle is 2
The magnetic flux density of the magnetic detection gap portion 34 becomes 0 at the position of 70 °.

As described above, the magnetic flux density (magnetic flux density linked to the Hall IC 25) passing through the magnetic detection gap portion 34 of the stator core 26 changes according to the rotation angle of the rotor core 21, and the Hall IC 25 changes according to this magnetic flux density. Output changes. A control circuit (not shown) reads the output of the Hall IC 25 and detects the rotation angle of the rotor core 21 (the rotation angle of the throttle valve 11). At this time, the rotation angle is detected while comparing the outputs of the two Hall ICs 25 with each other to check whether there is any abnormality.

In the present embodiment (1), for the reason described later, the throttle opening during idle operation (for example, 15 °), which is the throttle opening near the fully closed position of the throttle valve 11 where the detection accuracy is most required, is set. , The output of the Hall IC 25 is set to zero (the rotation angle of the rotor core 21 is 270 °). In this case, the rotation range of the throttle valve 11 from the fully closed position to the fully open position is, for example, 8
If it is 5 °, as shown in FIG. 5, the rotation range of the throttle valve 11 is 255 at the rotation angle of the rotor core 21.
When the throttle valve 11 is in the fully closed position (the rotation angle of the rotor core 21 is 255 °), the switching portion of the magnetic poles of the magnet 22 is positioned relative to the magnetic detection gap portion 34, as shown in FIG. Is rotated by 105 ° in the counterclockwise direction (255 ° in the clockwise direction), and the throttle valve 11 is at the fully open position (the rotation angle of the rotor core 21 is 3 degrees).
40 °), as shown in FIG. 4, the switching portion of the magnetic poles of the magnet 22 is in a position rotated by 20 ° in the counterclockwise direction (340 ° in the clockwise direction) with respect to the magnetic detection gap portion 34.

The rotation range of the throttle valve 11 is
The rotation angle of the rotor core 21 is set to be in the range of 75 ° to 160 °, and the throttle opening 1 during idle operation is set to 1
The output of the Hall IC 25 may be zero (the rotation angle of the rotor core 21 is 90 °) at 5 °.

In the embodiment (1) described above, the resin cover 24 obtained by molding the stator core 26 for fixing the Hall IC 25 has a larger coefficient of thermal expansion than the metallic throttle body 15 to which the cover 24 is attached. Moreover, since the cover 24 is formed in a vertically long shape so as to collectively cover the motor 16 and the reduction mechanism 20 arranged on the lower side of the throttle body 15, the amount of thermal deformation in the longitudinal direction is large. Become.

In consideration of such circumstances, in the present embodiment (1), the magnetic detection gap portion 3 of the stator core 26 is provided.
4 is formed so as to extend in the longitudinal direction of the cover 24 so that the magnetic detection direction of the Hall IC 25 arranged in the magnetic detection gap portion 34 and the longitudinal direction of the cover 24 are orthogonal to each other. The direction becomes the short direction of the cover 24 (left and right direction in FIG. 2), and the cover 2
It is possible to reduce the dimensional change in the magnetic detection direction due to thermal deformation of No. 4, and to reduce the amount of positional deviation of the stator core 26 in the magnetic detection direction. This allows the cover 2
The change in the gap of the magnetic detection gap portion 34 and the change in the gap between the stator core 26 and the magnet 22 due to the thermal deformation of No. 4 can be reduced, and the change in the magnetic flux density passing through the magnetic detection gap portion 34 can be reduced. it can. Therefore, the output fluctuation of the Hall IC 25 due to the thermal deformation of the cover 24 can be suppressed to be small, and the detection accuracy of the throttle opening (rotation angle) can be improved.

The present inventors, as shown in FIG. 6 (a),
The stator core 26 with respect to the magnet 22 (rotor core 21)
6 (b) shows fluctuations in the output of the Hall IC 25 when the position is displaced in the direction perpendicular to the magnetic detection direction of the Hall IC 25.
As shown in, the output fluctuation of the Hall IC 25 when the stator core 26 was displaced with respect to the magnet 22 in the magnetic detection direction was measured. As a result, in comparison with the case where the stator core 26 is displaced in the magnetic detection direction [FIG. 6 (b)],
It was confirmed that the output variation of the Hall IC 25 was smaller in the case where the stator core 26 was displaced in the direction perpendicular to the magnetic detection direction [Fig. 6 (a)]. From this test result, as in the present embodiment (1), the magnetic detection direction of the Hall IC 25 and the longitudinal direction of the cover 24 are made orthogonal to each other, and the positional deviation amount of the stator core 26 in the magnetic detection direction due to thermal deformation of the cover 24 is reduced. It was confirmed that the variation of the output of the Hall IC 25 can be reduced by doing so.

By the way, the rotation angle detecting apparatus using the magnetic detecting element such as the Hall element has the highest detection accuracy in the vicinity of the output of the magnetic detecting element becoming zero. The reason for this is that the position where the output of the magnetic detection element is zero is the center point of the linear region of the output, and the linearity is the best, and if the output of the magnetic detection element is zero, the temperature of the magnetic detection element is zero. This is because the influence of the characteristics is the smallest. Conventionally, there is a method in which an output error due to the temperature characteristic of the magnetic detection element is compensated by a temperature correction element, but the output error due to the temperature characteristic is completely reduced to 0 due to the variation of the magnetic detection element and the variation of the temperature compensation element. Very difficult to do. Therefore, the position where the output of the magnetic detection element becomes zero is the position with the highest detection accuracy in the entire detection angle range.

Generally, the throttle opening for which the detection accuracy is most required is the throttle opening during idle operation (for example, 15) which is set near the fully closed position of the throttle valve 11.
°).

In consideration of such circumstances, in the present embodiment (1), the output of the Hall IC 25 is set to zero at the throttle opening of 15 ° during the idle operation where the detection accuracy is most required. Therefore, in the vicinity of the throttle opening during idle operation where detection accuracy is most required,
The influence of the temperature characteristics of the Hall IC 25 can be minimized, and the Hall IC due to the thermal deformation of the cover 24 described above
Combined with the effect of reducing the output fluctuation amount of 25, the detection accuracy in the vicinity of the throttle opening during idle operation can be considerably improved. Needless to say, the throttle opening during idle operation is not limited to 15 ° and may be changed as appropriate.

[Embodiment (2)] Next, an embodiment (2) of the present invention will be described with reference to FIG. However, parts that are substantially the same as in the above embodiment (1) are assigned the same reference numerals and explanations thereof are omitted.

In the present embodiment (2), the rotation angle detecting device 3
In the rotor core 39, one magnet 41 is fitted into each of the two notches 40 formed at diametrically opposite positions of the rotor core 39, and the magnets 8 are fixed by adhesion or the like. Each magnet 41 is formed in a flat plate shape and has N
The pole and the S pole are magnetized in parallel. The two magnets 41 are arranged such that the magnetic fields of the two magnets 41 repel each other inside the rotor core 39 by magnetically opposing magnetic poles of the same polarity via the semi-circular arc portion of the rotor core 39. ing. The inner peripheral surface of the rotor core 39 faces the outer peripheral surface of the stator core 26 via a minute air gap, except for the vicinity of each magnet 41. As a result, each magnet 41
The magnetic flux emitted from the N pole passes through the stator core 26 via the inside of the rotor core 39, and returns to the S pole of each magnet 41 via the inside of the rotor core 39. Further, the rotor core 39
In the vicinity of each magnet 41 on the inner peripheral side of the
A void portion 42 is formed for preventing a short circuit of magnetic flux between the two poles of No. 1 and the stator core 26.

Also in this embodiment (2), the output of the Hall IC 25 is zero (the rotation angle of the rotor core 39 is 270 °) at the throttle opening (for example, 15 °) during idle operation where the detection accuracy is most required. Thus, the rotational position of the magnet 41 with respect to the magnetic detection gap portion 34 (Hall IC 25) is set.

Also in this embodiment (2) described above, the magnetic detection gap portion 34 of the stator core 26 is formed so as to extend in the longitudinal direction of the cover 24, and the magnetic force of the Hall IC 25 arranged in the magnetic detection gap portion 34 is increased. Since the detection direction and the longitudinal direction of the cover 24 are orthogonal to each other, the output fluctuation of the Hall IC 25 due to the thermal deformation of the cover 24 can be suppressed to be small as in the first embodiment, and the throttle opening (rotation angle). ) Detection accuracy can be improved.

Further, in the present embodiment (2), two magnets 41 are provided at diametrically opposite positions of the rotor core 39 so that the magnetic fields repel each other, and the magnetic flux generated from the N pole of each magnet 41 is generated. It flows into the stator core 26 via the inside of the rotor core 39, and the magnetic detection gap portion 34 (Hall IC 2
5), it is not necessary to form an air gap between the magnet 41 and the stator core 26 at the magnetic pole surface of the magnet 41, and the magnet 41 has a shape that is easy to manufacture and a shape that is easily magnetized. It can be formed in a flat plate shape. As a result, the output error of the Hall IC 25 due to the manufacturing variation of the magnet 41 can be reduced, and the detection accuracy of the rotation angle can be improved. Moreover, the magnet 41 may be arranged at a position where the magnetic flux flows to the rotor core 39.
Since it is not necessary to dispose the magnet 41 on the inner peripheral side of the rotor core 39, the radial dimension of the rotor core 39 can be reduced and the rotation angle detecting device
Of the rotor core 39
The location of the magnet 41 in can be selected relatively freely,
The degree of freedom in design can also be increased.

In each of the embodiments described above, the output of the Hall IC 25 is set to zero at the throttle opening during idle operation where the detection accuracy is most required. The output of the Hall IC 25 may be zero at or near the (reference rotation angle). In this case, the reference position (reference rotation angle)
Can be accurately detected, the output of the Hall IC 25 (detected throttle opening) can be accurately calibrated with reference to this reference position (reference rotation angle), and the detection accuracy of the throttle opening can be improved. .

However, in the present invention, the Hall IC 2 is considered in consideration of the throttle valve rotation range of the electronic throttle system to which the invention is applied, the linear range of the output of the Hall IC 25, and the like.
The throttle opening (rotation angle) at which the output of 5 becomes zero may be changed as appropriate.

In addition, the present invention may be applied to a rotation angle detection device without a stator core, and the configuration of the rotation angle detection device may be changed as appropriate. In addition, a rotation angle detection device other than the rotation angle detection device of the throttle valve may be used. It may be applied to the device.

[Brief description of drawings]

FIG. 1 is a vertical sectional front view of an electronic throttle system showing an embodiment (1) of the present invention.

FIG. 2 is a vertical sectional side view of a rotation angle detection device provided inside a cover of an electronic throttle system.

FIG. 3 is a vertical cross-sectional side view of the main part of the rotation angle detection device showing a state in which the throttle valve is at the fully closed position.

FIG. 4 is a vertical cross-sectional side view of the main part of the rotation angle detection device showing a state in which the throttle valve is at the fully open position.

FIG. 5 is a diagram showing a change characteristic of a magnetic flux density in a magnetic detection gap portion with respect to a rotation angle of a rotor core.

6A is a diagram showing output fluctuation characteristics of the Hall IC when the stator core is displaced in a direction perpendicular to the magnetic detection direction of the Hall IC, and FIG. 6B is a Hall IC of the stator core.
Showing the output fluctuation characteristics of the Hall IC when the position is displaced in the magnetic detection direction of

FIG. 7 is a vertical sectional side view of a rotation angle detection device for an electronic throttle system showing an embodiment (2) of the present invention.

8A is a vertical sectional front view of a conventional electronic throttle system, and FIG. 8B is a vertical sectional side view of a rotation angle detection device of the conventional electronic throttle system.

[Explanation of symbols]

11 ... Throttle valve (object to be detected), 12 ... Rotating shaft,
15 ... Throttle body (main body housing), 16 ...
Motor, 20 ... Reduction mechanism, 21 ... Rotor core, 22 ... Magnet, 24 ... Cover, 25 ... Hall IC (magnetic detection element), 26 ... Stator core, 28 ... Rotation angle detection device, 3
3 ... Gap part, 34 ... Magnetic detection gap part, 35 ... Large gap part, 38 ... Rotation angle detection device, 39 ... Rotor core, 41 ... Magnet, 42 ... Void part.

Continuation of front page (56) Reference JP-A-6-229793 (JP, A) JP-A-9-26367 (JP, A) JP-A-9-189508 (JP, A) JP-A-9-68403 (JP , A) JP-A-11-325956 (JP, A) JP-A-8-68606 (JP, A) JP-A-8-35809 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB) Name) G01B 7/00-7/34 G01D 5/18

Claims (4)

(57) [Claims] 1. A magnet provided on the main body housing side to rotate in response to rotation of an object to be detected, and a magnetic detection element fixed to a resin cover side covering an opening of the main body housing, In a rotation angle detection device that detects a rotation angle of the object to be detected based on an output signal of the magnetic detection element that changes due to rotation of a magnet, the magnetic detection element has a magnetic detection direction orthogonal to a longitudinal direction of the cover. The rotation angle detection device is arranged so as to 2. The magnet is fixed to a cylindrical rotor core that rotates according to the rotation of an object to be detected, and a stator core coaxially located on the inner peripheral side of the rotor core is molded on the resin cover. 3. The magnetic detection element is fixed to a magnetic detection gap portion formed so as to penetrate the stator core in a diametrical direction, and the magnetic detection gap portion extends in the longitudinal direction of the cover. The rotation angle detection device according to. 3. The magnet and the magnetic detection element are arranged so that the output of the magnetic detection element becomes zero at or near a rotation angle where the detection accuracy is most required. Alternatively, the rotation angle detection device according to item 2. 4. The magnet and the magnetic detection element are arranged such that the output of the magnetic detection element becomes zero at or near a reference rotation angle of the object to be detected. The rotation angle detection device according to item 2.