JP2936437B2 - Position detection device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a position detecting device,
More specifically, the present invention relates to a position detecting device that detects a rotational position of a rotating body such as a motor driving shaft.

[0002]

2. Description of the Related Art In a conventional position detecting device of this type, as shown in FIG. 10, a rotating magnet plate 51 is mounted on a driving shaft 50 of a motor, and the rotating magnet plate 51 is mounted on the rotating magnet plate 51. The detection magnet plate 52 is arranged opposite to the rotating magnet plate 51 and the detection magnet plate 52 and an annular detection coil 53 is arranged around the detection magnet plate 52.

According to this position detecting device, the detecting coil 5
3, the rotation angle of the rotating magnet plate 51 can be detected as an electric signal by detecting a change in magnetic flux between the rotating magnet plate 51 and the detection magnet plate 52 due to the rotation of the rotating magnet plate 51. .

However, in the case of the above-described position detection device, an output signal accompanying a change in the rotation angle of the detection coil 53 is:
Since it is based on the change in magnetic flux density as described above,
The output signal is not linear as shown in FIG. 11, but is smaller than an ideal output signal in a range where the rotation angle is relatively small, and larger than an ideal output signal in a range where the rotation angle is relatively large. As a result, there has been a problem that the rotation angle cannot be accurately detected.

For this reason, the detection coil 53 is
Is added to the output signal. This correction means sends the corrected output signal by doubling the level of the output signal of the detection coil 53. Even if such a correction means is used, the error of the output signal with respect to the change in the rotation angle is enlarged. However, there has been a problem that reliable correction cannot be performed.

SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a position detecting device which can eliminate an error of an output signal with respect to a rotational displacement of a rotating body or can perform position detection accurately with a very small amount.

[0007]

According to the present invention, there is provided a position detecting device provided with a detecting means for converting a change in the position of a rotating body into a change in magnetic flux and detecting the change in the magnetic flux. A cam body having a contour for correcting an output error based on a change in magnetic flux, and a cam follower arranged to abut on the contour of the cam body and transmitting a rotational displacement of the cam body to the detection means , The cam body
For contour, L = [(B-x 1) 2 + y 1 2] 1/2 + α [ where a horizontal line passing through the center of the shaft of the rotating body x
Axis, the vertical line passing through the center of the cam follower support pin
The y-axis and the coordinates of the shaft body are (B, 0), and the cam follower is
The distance between the contact pin and the support pin is r, and the shaft and the contact
The distance from the contact pin is L (when the contact pin is at the initial position,
Distance L ₀ ), rotation angle of contact pin from initial position (counterclockwise
Measurement) to θ ₀ , cam follower rotation angle (counterclockwise)
Is θ _2, and when 0 ≦ θ ₂ <θ ₀ , x ₁
= R × Cos θ _x , y ₁ = L ₀ −r × Sin θ _x (where θ
_x = θ ₀ −θ ₂ ), and when θ ₀ ≦ θ ₂ , x ₁ =
_{r × Cosθ x, y 1 =} L 0 + r × Sinθ x ( where theta _x
= −θ ₀ ), and α is a correction coefficient. ]
Holds .

[0008]

The operation of the above-described position detecting device will be described below. The cam body of this device is connected to a rotating body and rotates according to its position change. At this time, the cam follower comes into contact with the cam body and transmits the rotational displacement of the cam body to the detecting means. However, since the contour of the cam body has a shape for correcting an output error based on a change in magnetic flux in the detecting means, the detecting means Is corrected by the operation of the cam body and the cam follower, and the output of the detecting means accurately corresponds to the change in the position of the rotating body.

[0009]

Embodiments of the present invention will be described below. The position detecting device 1 shown in FIGS. 1 and 2 includes a total of four support plates 2a and 2b formed in a pair of plates, and bolts and nuts that support the support plates 2a and 2b in a parallel arrangement. A support member 3, a shaft body 5 penetrating through the center position of both support plates 2a, 2b, and rotatably arranged by bearings 4a, 4b, and attached to one protruding end of the shaft body 5. A plate-like cam body 6 having a contour described later;
A cam follower 8 which is rotatably arranged with the support pin 7 with respect to the support plate 2a and has a contact pin 8a which is in contact with the contour of the cam body 6, and the cam follower 8 is moved in the direction of arrow β in FIG. The apparatus includes a biasing spring 9 and a detecting means 10 connected to the support pin 7 inside the support plate 2a. A rotating body to be detected, for example, a rotating shaft of a robot arm or a motor, is connected to the other protruding end of the shaft body 5.

In FIG. 2, reference numeral 11 denotes a control circuit board mounted on the support plate 2a. FIG. 3 is a block diagram showing the overall configuration of the position detecting device 1. The rotation of the shaft 5 is transmitted to a detecting means 10 via a cam mechanism 12 including the cam 6 and a cam follower 8. I have. As shown in FIG. 4, the detecting means 10 includes a rotating magnet plate 51, a detecting magnet plate 52, and a detecting coil 53 similar to those of the conventional example, and connects the support pins 7 of the cam mechanism 12 to the rotating magnet plate 51. I have.

Next, referring to FIG. 1 and FIG.
Will be described. Considering an XY coordinate system whose origin is the intersection of a horizontal line passing through the center of the shaft 5 and a vertical line passing through the center of the support pin 7, the coordinates (B,
o), the coordinates of the initial position of the contact pin 8a are (x ₀ , y
_0), the distance between the support pins 7 and the contact pin 8a r, and the distance between the contact pins 8a and the shaft 5 L (the distance at the initial position and L _0.).

Further, it is assumed to take the rotation angle theta ₁ of the cam member 6, the rotation angle theta ₂ of the cam followers 8 respectively in the direction of the arrow. At this time, if the contact pin 8a rotates from the initial position by the rotation angle θ ₀ and comes on a horizontal line passing through the support pin 7,
The rotation angle is represented by θ ₀ = tan ⁻¹ (y ₀ / x ₀ ).

[0013] θ ₁ and θ ₂ are in the range of 0 to 180 degrees. The relationship between θ ₁ and θ ₂ can be set arbitrarily. For example, when θ ₁ and θ ₂ are one-to-one, θ
₁ = a theta _2, when theta ₁ and the theta ₂ is 2-to-1 is theta ₁ = theta _2/2, when theta ₁ and the theta ₂ is 1: 2 be a theta ₁ = 2 [Theta] ₂ When the cam follower 8 is rotated 85 degrees when the cam body 6 rotates 120 degrees, θ ₁ = θ ₂ × (120/85).

When the rotation angle θ _{2 of the} contact pin is ₀ to θ ₀ , θ _x = θ ₀ −θ ₂ (where θ is determined as described above according to the ratio relationship between θ ₂ and θ _1). is replaced by a value of _{one.) x 1 = r × Cosθ} x y 1 = L 0 -r × Sinθ x L = [(B-x 1) 2 + y 1 2] 1/2 + α the angle of rotation of the contact pin when theta ₂ is at theta ₀ or _{more, θ x = -θ 0 x 1} = r × Cosθ x y 1 = L 0 + r × Sinθ x L = [(B-x 1) 2 + y 1 2] 1/2 + α Is established.

A cam curve can be drawn using the above relational expression.

Here, α is a coefficient described later.

Here, the correction coefficient α will be described with reference to FIGS. When no correction is performed on the output signal of the detection means 10, as in the conventional example, for example, FIG.
It becomes as shown in. Therefore, it is assumed that the variation in the error of the output signal of the detection means 10 can be divided into four patterns as shown in FIG. FIG. 7 shows the rotation angle (degree) on the horizontal axis and the output error (%) on the vertical axis.

Next, a contour having a value of L represented by the above-described equation is added to each of the four patterns with a correction coefficient α for reversely correcting each output error as shown in FIG. The four cam bodies 6 are prepared, and each cam body 6 is attached to the shaft body 5 for each of the patterns, and the detection means 10 is actually set.
Measure the output signal of FIG. 9 shows five examples of the output error of the detection means 10 measured in this way.

The left column of FIG. 9 shows the output errors of the samples 1 to 5 before the mounting of the cams, and the right column shows the output errors of the samples 1 to 5 in the order of the four cams 6 as described above. 1 cam body 6, 2nd cam body, 3rd cam body, 2nd cam body, 2nd cam body
3 shows an output error when the cam body is mounted.
As is clear from FIG. 9, the output error of the first sample with the first cam body is 0.8% at the maximum, and the output error of the sample 2 with the second cam body is 1.5% at the maximum. The output error of the sample 3 with the third cam body was 1% at the maximum, and that of the sample 4 with the second cam body was 2.8% at the maximum.
The maximum output error was 1.9% for the sample 5 with the cam body
It turns out that it becomes.

Thus, according to the first embodiment, the equation L = 例 (B−x
₁ ) Since the contour of the cam body 6 is created by ² + y ₁ ² ｝ ^1/2 + α and the output error of the detecting means 10 is corrected, the output error is suppressed to 3% or less at the maximum. It is possible to provide a position detection device having extremely high practical value.

The present invention is not limited to the embodiment described above, and various modifications can be made within the scope of the invention.

For example, for a custom-made product, the output error of the detection means 10 is measured first, and then a correction coefficient α is set so as to completely reverse the output error, and based on the correction coefficient α. The contour of the cam body 6 is determined and the dedicated cam body 6 is determined.
And the correction of the detection means 10 is performed using the cam body 6, it is possible to manufacture the position detection device 1 in which the output error is reduced to 0.5% or less.

[0023]

According to the present invention described in detail above, an output error of the detecting means can be largely corrected by the cam body, and a position detecting apparatus capable of eliminating or minimizing the total output error is provided. be able to.

[Brief description of the drawings]

FIG. 1 is a front view of an apparatus according to an embodiment of the present invention.

FIG. 2 is a plan view of an apparatus according to an embodiment of the present invention.

FIG. 3 is a block diagram of an apparatus according to an embodiment of the present invention.

FIG. 4 is a side view of a detecting means in the apparatus according to the embodiment of the present invention.

FIG. 5 is a diagram showing the principle of producing a cam body in the apparatus according to the embodiment of the present invention.

FIG. 6 is a graph of an output signal of a detection unit when there is no cam body.

FIG. 7 is a graph showing four patterns of an output error of the detection means when there is no cam body.

FIG. 8 is a graph showing four correction patterns.

FIG. 9 is a graph showing five examples of output errors before and after mounting the cam body.

FIG. 10 is a side view of a conventional device.

FIG. 11 is a graph of an output signal of the conventional device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Position detection apparatus 5 Shaft body 6 Cam body 8 Cam follower 10 Detection means

Claims (1)

(57) [Claims] 1. A position detecting device comprising a detecting means for converting a change in position of a rotating body into a change in magnetic flux and detecting the change, the output error being connected to the rotating body and correcting the output error based on the change in magnetic flux in the detecting means. a cam member having a contour, arranged to abut against the contour of the cam member, the rotational displacement of the cam member comprises a cam follower for transmitting to said detection means, for the contour of the cam member, L = [(B−x ₁ ) ² + y ₁ ² ] ^1/2 + α [where the horizontal line passing through the center of the shaft of the rotating body is x
Axis, the vertical line passing through the center of the cam follower support pin
The y-axis and the coordinates of the shaft body are (B, 0), and the cam follower is
The distance between the contact pin and the support pin is r, and the shaft and the contact
The distance from the contact pin is L (when the contact pin is at the initial position,
Distance L ₀ ), rotation angle of contact pin from initial position (counterclockwise
Measurement) to θ ₀ , cam follower rotation angle (counterclockwise)
Is θ _2, and when 0 ≦ θ ₂ <θ ₀ , x ₁
= R × Cos θ _x , y ₁ = L ₀ −r × Sin θ _x (where θ
_x = θ ₀ −θ ₂ ), and when θ ₀ ≦ θ ₂ , x ₁ =
_{r × Cosθ x, y 1 =} L 0 + r × Sinθ x ( where theta _x
= −θ ₀ ), and α is a correction coefficient. ]
The position detection device characterized by the following.