JP2005241579A - Torque sensor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a torque sensor that smoothes the rate of change of impedance at the boundary line where an overlapped area of the windows of two cylindrical members becomes from a positive value to a negative value, and enables suppressing the sense of incongruity in the feeling for manipulation. <P>SOLUTION: The torque sensor attaches a first cylindrical member with recesses and projections alternately formed in a circumferential direction to a first shaft that is formed with a conductive and a non-magnetic material; and attaches a second cylindrical member with windows, formed at positions corresponding to the recesses and projections of the first cylindrical member to a second shaft so as to encircle the first cylindrical member; and then detects torque, based on the overlapped status between the first and second cylindrical members. In the torque sensor, the circumferential both end surfaces of the first cylindrical member is formed so as to be in parallel with respect to a virtual surface passing through the center in the circumferential direction of the both end surfaces and a shaft center, and the circumferential both end surfaces of the windows of the second cylindrical member is formed so as to be in parallel with respect to a virtual surface passing through the center in the circumferential direction of the both end surfaces and the shaft center. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a torque sensor that detects a relative rotational displacement (torque) of an input shaft and an output shaft in an electric power steering apparatus.

  Conventionally, as a torque sensor, for example, a technique described in Patent Document 1 has been disclosed. In this publication, the torque sensor is connected such that a cylindrical member overlaps an input shaft and an output shaft connected via a torsion bar. Each cylindrical member is formed with windows extending in the axial direction, and the opening cross section of these windows is formed in a fan shape when viewed from the axial direction.

  The circumferential end surface of the window of the inner cylindrical member and the circumferential end surface of the window of the outer cylindrical member are formed so as to be aligned on the same straight line when their circumferential positions coincide. A coil is provided on the outer peripheral side of the cylindrical member, and a magnetic field is generated by passing a current through the coil.

  When torque is generated on the input / output shaft and the torsion bar is twisted, the overlapping state of the windows of both cylindrical members changes, and the amount of magnetic flux passing through these windows increases or decreases. The increase / decrease in the magnetic flux appears as a change in the impedance of the coil, and the torque generated between the input and output shafts is detected by detecting the change in the impedance.

The impedance of the coil decreases as the area where the windows of both cylindrical members overlap decreases, and the impedance decreases as the torsion bar twists even after the overlapping area becomes zero. Although the magnetic field has a certain degree of directivity, it has a characteristic that it can travel through a gap formed between the inner cylindrical member and the outer cylindrical member, thereby reducing the size of a small torsion bar. There is an effect that even a twist amount can be detected as a large impedance change (for example, refer to Patent Document 1).
JP-A-8-114518

  However, in the torque sensor, the overlapping area of the windows of both cylindrical members gradually decreases from a positive value (positive area), and the torsion bar is further twisted after the overlapping area becomes zero. In the region (negative region), the amount of impedance change (impedance change rate) with respect to the torque change is different. Since the impedance change rate is large in the positive region and small in the negative region, the impedance change rate changes rapidly at the boundary line between the positive region and the negative region. Therefore, there is a problem that the steering assist amount suddenly changes before and after the boundary line, and the steering feeling is deteriorated.

  The present invention has been made paying attention to the above problem, and provides a torque sensor that can smooth the impedance change rate at the boundary line between the positive region and the negative region and suppress the uncomfortable feeling of operation. The purpose is to provide.

  In order to achieve the above object, according to the present invention, a first shaft member and a second shaft connected by a torsion bar, and a first cylindrical member provided on the first shaft and having concave convex portions alternately formed in the circumferential direction. And a window formed on the second shaft so as to surround the first cylindrical member, made of a conductive and nonmagnetic material, and formed at a position corresponding to the concave convex portion of the first cylindrical member A torque sensor that detects torque based on an overlapping state of the first cylindrical member and the second cylindrical member, and has both circumferential ends of the concave convex portion of the first cylindrical member. The surface is formed in parallel to a virtual plane passing through the circumferential center of both end surfaces and the axis, and both circumferential surfaces of the window of the second cylindrical member are aligned with the circumferential center of the both ends. Parallel to the virtual plane passing through It was decided to be.

  Therefore, it is possible to provide a torque sensor that can smoothen the impedance change rate at the boundary line between the positive region and the negative region and suppress the uncomfortable feeling of operation.

  Hereinafter, the best mode for realizing the torque sensor of the present invention will be described based on Example 1 shown in the drawings.

  FIG. 1 is a cross-sectional view illustrating a configuration in the vicinity of a torque sensor in the first embodiment. The power steering device is provided at an input shaft 1 connected to a steering wheel (not shown), an output shaft 2 connected to a rack and pinion mechanism for operating a steered wheel, and a connection portion between the input shaft 1 and the output shaft 2. Torque sensor TS. The torque sensor TS includes a sensor housing 3, two coil units 6, an inner ring 10 (corresponding to the first cylindrical member in the claims), an outer ring 20 (corresponding to the second cylindrical member in the claims), and A substrate 9 is provided.

  The input shaft 1, the output shaft 2, and the torque sensor TS are housed in a sensor housing 3 and a rack and pinion housing (hereinafter referred to as an R & P housing) 4. The input shaft 1 is made of a magnetic material and forms a magnetic field by the coil unit 6. Further, a through hole 1 a for receiving the torsion bar 5 is provided in the axis of the input shaft 1. Further, a thick portion 1 b that is fixed to the torsion bar 5 on the steering wheel side and holds the inner ring 10 is provided.

  The output shaft 2 and the torsion bar 5 are connected by serration fitting, and the input shaft 1 and the output shaft 2 are integrated via the torsion bar 5. An outer ring holding portion 2a, a second bearing support portion 2b, and a third bearing support portion 2c are provided on the outer periphery of the input shaft side end portion of the output shaft 2. The second and third bearing support portions 2 b and 2 c are also supported by the R & P housing 4, whereby the output shaft 2 is rotatably supported by the R & P housing 4. Further, a pinion shaft 50 is connected to the output shaft 2 and constitutes a rack and pinion type steering device together with the rack shaft 51.

  In the vicinity of the steering wheel side opening of the sensor housing 3, a dust seal holding portion 3 a that holds a dust seal 30 for dust prevention and a first bearing support portion 3 b that supports the input shaft 1 by a first bearing 31 are provided in order from the opening. ing.

  The inner ring 10 is fixed to the thick portion 1 b of the input shaft 1 and rotates integrally with the input shaft 1, and the outer ring 20 is held by the outer ring holding portion 2 a of the output shaft 2 and rotates integrally with the output shaft 2. The inner ring 10 and the outer ring 20 are made of a conductive and nonmagnetic material, and each have a plurality of windows provided in the axial direction.

  The coil unit 6 is housed in the sensor housing 3 and is urged to the axial output side by an elastic member 7 provided on the input side, and is fixed by a cylindrical holding member 8 press-fitted from the output side. Positioning in the axial direction is performed while preventing the contact with the substrate 9.

  When the driver performs a steering operation, the degree of overlap between the window of the inner ring 10 and the window of the outer ring 20 changes with torsion of the torsion bar 5 fixed between the input and output shafts. At this time, the steering torque is calculated by the substrate 9 from the impedance change generated in the coil unit 6. A drive current that generates a steering assist torque that reduces the steering torque based on the calculation result is supplied to an electric motor (not shown).

[Inner ring details]
FIG. 2 is an axial side view of the inner ring 10, and FIG. 3 is a circumferential sectional view of the inner ring 10. The inner ring 10 is a cylindrical member made of a conductive and nonmagnetic material (copper in this embodiment), and has a plurality of first windows 11 provided on the cylindrical surface. The first window 11 has a slit shape whose axial width is longer than the circumferential width, and is provided on the circumference of the inner ring 10 at equal intervals. The first window 11 is formed by punching.

  The first window circumferential end surface 11a (corresponding to the both circumferential end surfaces in the claims), which is the circumferential end surfaces of the first window 11, is the first window center 11b (patent). (Corresponding to the center in the circumferential direction of both end faces of the claims) and the axis of the inner ring 10, that is, the imaginary plane K passing through the axis O of the input shaft 1.

[Details of input shaft fitted with inner ring]
FIG. 4 is a perspective view of the input shaft 1 in which the inner ring 10 is fitted into the thick portion 1b. Concavities and convexities are formed on the cylindrical surface of the input shaft 1 into which the inner ring 10 is fitted by the first window 11 of the inner ring 10 and the surface of the input shaft 1 (on the concave convex portion of the first cylindrical member in the claims). Equivalent.) Since the input shaft 1 is made of magnetic material and the inner ring 10 is made of non-magnetic copper, the magnetic force is large in the window 11 of the inner ring 10, that is, the concave portion, and the inner ring 10 covers the input shaft 1, that is, in the convex portion. Decreases the magnetic force.

[Details of outer ring 20]
FIG. 5 is an axial side view of the outer ring 20, and FIG. 6 is a circumferential sectional view of the outer ring 20. The outer ring 20 is made of a conductive and nonmagnetic material (aluminum alloy in this embodiment), and a plurality of second windows 21 (corresponding to the through windows of the second cylindrical member in the claims) provided in the axial direction. ). The second window 21 is formed by punching.

  The second window 21 has a slit shape whose axial width is longer than the circumferential width, is provided at equal intervals in the cylindrical portion of the outer ring 20, and is formed at a position corresponding to the first window 11 of the inner ring 10. Yes. Further, an output shaft fitting portion 22 that fits the output shaft 2 is provided at one axial end of the outer ring 20. Further, the second window circumferential end surface 21a (corresponding to the both circumferential end surfaces in the claims) which is the circumferential end faces of the second window 21 is the second window center 21b which is the circumferential center of the second window 21. (Corresponding to the center in the circumferential direction of the both end faces of the claims) and the axis of the outer ring 20, that is, parallel to the virtual plane K ′ passing through the axis O of the input shaft 1.

[Positional relationship between inner ring and outer ring]
FIG. 7 is a diagram showing a positional relationship between the inner ring 10 and the outer ring 20 in the torque sensor. FIG. 7A is a diagram showing that the first window 11 and the second window 21 overlap each other, and FIG. 7B is a diagram where the first window 11 and the second window 21 are shielded from each other. FIG. In order to remove the inflection point of the impedance from the vicinity of frequently used neutral, the neutral position of the torque sensor is provided in the region where the first window 11 and the second window 21 overlap, that is, the position shown in FIG. 7B. .

  As shown in FIG. 7 (a), when the inner ring 10 is rotated clockwise while the rotation of the outer ring 20 is restricted from the state where the windows are completely overlapped with each other, as shown in FIG. The first window 11 and the second window 21 are provided at positions corresponding to each other so as to be in a shielding relationship. By rotating further clockwise from the neutral position shown in FIG. 7B, the neutral position is set so that the first window 11 and the second window 21 are completely shielded from each other. This neutral position is determined by the size of the window opening and the number of windows.

[Change in magnetic field near cylindrical member in conventional torque sensor]
FIG. 8 is a diagram showing the relationship between two cylindrical members and a magnetic field in a conventional torque sensor. FIG. 8A shows the position immediately before the overlapping area of the windows of both cylindrical members becomes 0 as both cylindrical members rotate relative to each other, and FIG. 8B shows the position where the overlapping area becomes 0. . In the conventional example, windows extending in the axial direction are formed in each cylindrical member at equal intervals in the circumferential direction. A coil is provided on the outer peripheral side of the cylindrical member, and a magnetic field is generated by passing a current through the coil to detect impedance. Magnetic flux J can be detected by detecting the torsion amount of a small torsion bar as a large impedance change using the characteristic that it can travel through a gap formed between the inner cylindrical member and the outer cylindrical member. doing.

  When the input shaft is rotated by steering and both cylindrical members rotate relative to each other due to the rotation of the torsion bar, the overlapping area of the windows of both cylindrical members gradually decreases from a positive value (positive region), and the overlapping area Passes the boundary line of the region (negative region) where the torsion bar is further twisted after becoming 0.

  However, in the conventional example, the opening cross section of the window is fan-shaped when viewed from the axial direction, the opening cross section is aligned on the boundary line, and the angle between the opening cross section and the cylinder tangential direction is always a right angle. . Therefore, as shown in FIGS. 8 (a) and 8 (b), the magnetic flux that flows almost linearly until just before the boundary line is suddenly bent when the window reaches the boundary line. Therefore, before and after the boundary line, there is a problem that the magnetic flux passing rate changes greatly, the impedance change rate changes abruptly, the steering assist amount changes abruptly, and the steering feeling deteriorates.

[Magnetic field change near cylindrical member in torque sensor of embodiment of present application]
FIG. 9 is a view showing the relationship between the inner ring 10 and the outer ring 20 in the torque sensor of the embodiment of the present application. In contrast to the conventional example, in the torque sensor of the present embodiment, the first window circumferential end surface 11a that is the circumferential end faces of the first window 11 is the first window that is the circumferential center of the first window 11. The center 11 b and the inner ring 10 are formed in parallel to an imaginary plane K passing through the axis O of the inner ring 10. Similarly, also in the outer ring 20, the second window circumferential end face 21 a that is the circumferential end face of the second window 21 is connected to the second window center 21 b that is the circumferential center of the second window 21 and the axis of the outer ring 20. It is formed parallel to a virtual plane K ′ passing through the center O ′. Further, the inner ring 10 is made of copper, and the outer ring 20 is made of an aluminum alloy.

  As a result, the first window circumferential end surface 11a or the second window circumferential end surface 21a has an obtuse angle φ greater than a right angle with respect to the tangential direction of the inner ring 10 or the outer ring 20, respectively. The two window circumferential end surfaces 21a are not arranged on the plane L passing through the axis O, and form first and second edges 11c and 21c with the outer circumference of the cylinder projecting from the plane L more than the inner circumference.

  Due to the first and second edges 11c and 21c, the magnetic flux J immediately before the boundary line passes straight through the first and second windows 11 and 21 in the conventional example, but is gradually bent in the present embodiment. Will pass through.

  Therefore, since the magnetic flux J is gradually bent even immediately before the boundary line, the magnetic flux passing rate gradually decreases immediately before the boundary line, and the rate of change of magnetic flux near the boundary line is gradual compared to the conventional example. . Further, since the inner ring 10 is conductive and non-magnetic, an eddy current is generated on the inner ring 10 side, and the magnetic field can be blocked.

[Contrast of conventional section and cylindrical member opening cross section in this application]
FIG. 10 is a diagram showing magnetic fields in the vicinity of two cylindrical member opening sections in the conventional example and the embodiment of the present application. The magnetic flux J in the conventional example is indicated by a broken line, and the magnetic flux J in the present embodiment is indicated by a solid line. In FIG. 10, it is assumed that the virtual planes K and K ′ are on the same plane K ″ for comparison. In the conventional example, the magnetic flux J that has passed straight through the two windows immediately before the boundary line is bent by the first and second edges 11c and 21c in the embodiment of the present application.

  As a result, in the embodiment of the present application, the magnetic flux is less likely to pass immediately before the boundary line between the positive region and the negative region as compared with the conventional example, so the magnetic flux immediately before the boundary line (the magnetic flux passing rate is gradually reduced). Changes gradually, and the rate of change in impedance also decreases accordingly.

[Contrast of impedance change rate between conventional example and this application]
FIG. 11 is a diagram showing a comparison of impedance change rates in the conventional example and the embodiment of the present application. A conventional example is indicated by a broken line, and an embodiment of the present application is indicated by a solid line. In the above boundary line, the impedance changes abruptly in the conventional example, but the change is gentle in the present embodiment.

  Therefore, the impedance change rate at the boundary line between the positive region and the negative region can be made smooth, and a power steering device with good operation feeling can be provided (corresponding to claim 1). Further, since the inner ring 10 is made of conductive and non-magnetic copper, an eddy current is also generated on the inner ring 10 side, so that the magnetic field blocking effect is improved and the torque detection accuracy is improved. Corresponding). Furthermore, since the angle φ of the opening in the inner circumferential direction of the first window circumferential end surface 11a and the second window circumferential end surface 21a is an obtuse angle with respect to the cylindrical tangential direction, a sudden change in magnetic flux in the vicinity of the boundary line is avoided. The operational feeling can be improved.

[Positioning during assembly]
FIG. 12 is a diagram showing a procedure for positioning the inner ring 10 and the outer ring 20 according to this embodiment. In this embodiment, the jig 40 used for positioning coincides with the first positioning portion 41 formed to coincide with the first window circumferential end surface 11a of the inner ring 10 and the second window circumferential end surface 21a of the outer ring 20. It has the 2nd positioning part 42 formed so that it might do. Corresponding to the fact that the first and second window circumferential direction end faces 11a and 21a are parallel, the first and second positioning portions 42 of the jig 40 are also provided in parallel in cross section. Further, the first positioning portion 41 is disposed below the second positioning portion 42.

[Positioning process]
In positioning, the following steps are performed.

  First, the 1st positioning part 41 of the jig 40 is penetrated to the 1st window 11 (equivalent to the 1st process of a claim).

  Next, the first window circumferential direction end surface 11a and the second window circumferential direction end surface 21a are brought into contact with the first positioning portion 41 and the second positioning portion 42 of the jig 40 (corresponding to the second stroke in the claims). .

  The jig 40 is removed, and the inner ring 10 or the outer ring 20 is rotated by a predetermined angle to obtain a neutral position (corresponding to the third stroke in the claims).

In this neutral position, the relative rotation between the inner ring 10 and the outer ring 20 is fixed (corresponding to the fourth stroke in the claims).
Thereby, the inner ring 10 and the outer ring 20 are positioned.

[Comparison with conventional positioning]
Since the neutral positions of the windows provided in the two cylindrical members are frequently used, it is desirable to easily detect impedance and to deviate from the inflection point of the impedance. Therefore, after positioning the windows of the two cylindrical members, it is simple and highly accurate to determine the neutral position by relatively rotating the cylindrical members.

  However, in the conventional example, since the opening cross section of the window has a fan shape when viewed from the axial direction, the jig must also have a fan shape when viewed from the axial direction, and the jig machining process is complicated. Furthermore, in order to prevent deformation of the window by hitting the circumferential end face of the window during positioning, it is necessary to increase the jig machining accuracy, but it is difficult to increase the machining accuracy while making the axial cross section of the jig a fan shape. It was.

  For this reason, in the conventional example, when the neutral position of the two cylindrical windows is determined, the mark provided on the cylinder is used. However, this complicates the operation and causes a problem in the accuracy of the neutral position.

  On the other hand, in the present embodiment, the first and second window circumferential end surfaces 11a and 21a are formed in parallel to the virtual surface K '', and therefore both end surfaces of the positioning jig 40 are provided in parallel. What is necessary is easy to process. In addition, since both axial end surfaces of the first and second windows 11 and 21 are parallel to each other, it is possible to avoid the piece contact without increasing the processing accuracy of the jig 40 more than necessary, and the first and second window circumferential end surfaces 11a. , 21a can be avoided.

As a result, the first window 11 and the second window 21 can be accurately positioned while avoiding the possibility of deformation, and the inner ring 10 and the outer ring 20 are relatively rotated while maintaining the positioning accuracy, so that the neutral position is obtained. Can be determined easily and with high accuracy.
(Other examples)

  In the first embodiment, the inner ring 10 having the first window 11 is provided on the input shaft to change the magnetic flux. However, as shown in FIG. Good.

  Further, technical ideas other than the claims that can be grasped from the respective embodiments will be described below together with the effects thereof.

(A) In the torque sensor according to any one of claims 1 to 4,
The neutral position of the torque sensor is provided in a region where the magnetic field of the first cylindrical member is strong and the window of the second cylindrical member overlaps.

  By removing the inflection point of the impedance from the vicinity of the frequently used neutral position, the uncomfortable feeling of steering can be suppressed.

(B) In the torque sensor according to any one of claims 1 to 4 and (a) above,
The first cylindrical member is made of copper.

  Since copper has higher electrical conductivity than aluminum and it is easy to ensure AC magnetic path resistance, the same performance as aluminum can be achieved with a thinner plate thickness. Therefore, the sensor gap can be reduced, and a stronger magnetic flux can be generated. In addition, workability is improved by reducing the plate thickness.

(C) In the torque sensor according to any one of claims 1 to 4 and (a) or (b) above,
The circumferential section of the recess in the first cylindrical member and the window in the second cylindrical member is an acute angle or an obtuse angle with respect to the tangential direction of the first cylindrical member and the second cylindrical member.

  The operational feeling can be improved by gradual change in the magnetic field at the boundary from the open state to the closed state of the window and smoothing the rate of impedance change.

3 is a cross-sectional view illustrating a configuration in the vicinity of a torque sensor in Embodiment 1. FIG. It is an axial side view of the inner ring in Example 1. FIG. 3 is a circumferential sectional view of the inner ring in the first embodiment. FIG. 3 is a perspective view of an input shaft fitted with an inner ring in the first embodiment. FIG. 3 is an axial side view of the outer ring in the first embodiment. FIG. 3 is a circumferential cross-sectional view of the outer ring in the first embodiment. It is a figure which shows the positional relationship of the inner ring and outer ring in the torque sensor of Example 1. It is a figure which shows the relationship between the two cylindrical members and the magnetic field in the torque sensor of a prior art example. It is a figure which shows the relationship between the inner ring and the outer ring in the torque sensor of an Example of this application. It is a figure which shows the magnetic field of two cylindrical member opening cross-section vicinity in a prior art example and this-application Example. It is a figure which shows the contrast of the impedance change rate in a prior art example and this-application Example. It is a figure which shows the procedure of the positioning of an inner ring and an outer ring in Example 1. FIG. It is a figure which shows other embodiment of this-application Example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Input shaft 1a Through-hole 1b Thick part 2 Output shaft 2a Outer ring holding | maintenance part 2b 2nd bearing support part 2c 3rd bearing support part 3 Sensor housing 3a Dust seal holding part 3b 1st bearing support part 4 Rack & pinion housing 5 Torsion Bar 6 Coil unit 7 Elastic member 8 Holding member 9 Substrate 10 Inner ring 11 First window 11a First window circumferential end surface 11b First window center 11c First edge 20 Outering 21 Second window 21a Second window circumferential end surface 21b 2nd window center 21c 2nd edge 22 Output shaft fitting part 30 Dust seal 31 1st bearing 32 2nd bearing 33 3rd bearing 40 Jig 41 1st positioning part 42 2nd positioning part
J magnetic flux
K virtual plane
O axis
TS Torque sensor

Claims (3)

A first shaft and a second shaft connected by a torsion bar;
A first cylindrical member which is provided on the first shaft and in which concave convex portions are alternately formed in the circumferential direction;
A through window formed on the second shaft so as to surround the first cylindrical member, formed of a conductive and nonmagnetic material, and formed at a position corresponding to the concave convex portion of the first cylindrical member. A second cylindrical member having
In the torque sensor configured to detect torque based on the overlapping state of the first cylindrical member and the second cylindrical member,
Both end surfaces in the circumferential direction of the concave convex portion of the first cylindrical member are formed in parallel to a virtual plane passing through the center portion in the circumferential direction of the both end surfaces and the axis,
The torque sensor according to claim 1, wherein both end surfaces in the circumferential direction of the window of the second cylindrical member are formed in parallel to a virtual plane passing through the center portion in the circumferential direction of both end surfaces and the axis. The torque sensor according to claim 1,
The first shaft is formed in a cylindrical shape by a magnetic material,
The first cylindrical member is provided on the outer peripheral side of the first shaft, is formed of a conductive and nonmagnetic material, and has a plurality of through windows provided in the circumferential direction. . A first shaft and a second shaft connected by a torsion bar;
A first cylindrical member which is provided on the first shaft and in which concave convex portions are alternately formed in the circumferential direction;
The window is provided on the second shaft so as to surround the first cylindrical member, is formed of a conductive and nonmagnetic material, and has a window formed at a position corresponding to the concave convex portion of the first cylindrical member. A second cylindrical member,
Both end surfaces in the circumferential direction of the concave convex portion of the first cylindrical member are formed in parallel to a virtual plane passing through the center portion in the circumferential direction of the both end surfaces and the axis,
In the method of adjusting the torque sensor, the circumferential end faces of the second cylindrical member window are formed in parallel to a virtual plane passing through the circumferential center of the both ends and the axis.
A first step of allowing a jig formed so that at least one circumferential end surface thereof coincides with the circumferential end surface of the recess and the window to pass through the recess and the window;
A second step of contacting the circumferential end face of the jig with the circumferential end face of the recess and the window;
A third step of removing the jig and rotating the first cylindrical member or the second cylindrical member by a predetermined angle;
A fourth step of fixing relative rotation between the first cylindrical member and the second cylindrical member;
A method for adjusting a torque sensor, comprising:

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