JP6158448B2 - Coupling - Google Patents

Description

  The present invention relates to a coupling, and more particularly to a flexible joint.

  2. Description of the Related Art Conventionally, a coupling is known as a structure for connecting a drive shaft and a driven shaft whose end portions are abutted to each other (see Patent Document 1). In this coupling, a pair of joint parts composed of a high elastic body that is drive-coupled to each end of the drive shaft and the driven shaft, and a cylindrical shape composed of a low elastic body that fits outside the joint part. A sleeve is provided, and a plurality of teeth extending in the direction along the axis is formed on the outer periphery of the joint. On the other hand, a plurality of spline grooves parallel to the center line are formed on the inner peripheral surface of the sleeve, and by engaging the teeth of the joint portion with these spline grooves, the torque due to the rotation of the drive shaft is sleeved. It is the structure which transmits to a driven shaft via.

Japanese Patent No. 3539925

  In such a coupling, the misalignment between the drive and driven shafts (two rotating shafts) is adapted by the elasticity of the sleeve and the play provided between the sleeve and the tooth portion of the joint, so The quiet transmission can be realized. At this time, it is known that the less play between the tooth portion of the joint portion and the spline groove, the higher rigidity transmission is possible and the torque is efficiently transmitted from the drive shaft to the driven shaft. The technique is used in a connecting portion between a worm in an electric power steering apparatus for an automobile and an output shaft of a control motor including an electric motor that drives the worm.

  By the way, in the electric power steering device for automobiles described above, a technique for applying pressure to the worm in a direction perpendicular to the shaft center and pressing the worm against the worm wheel is known in order to eliminate backlash between the worm and the worm wheel. ing. In such a case, the worm and the output shaft of the control motor are eccentric, and a reaction force is generated by the contact between the joint teeth and the inner wall of the spline groove in the coupling sleeve. It interferes with transmission. Therefore, in such a case, an extremely low rigidity, that is, a slight “play” effect is required in the initial stage of eccentricity. However, if play is provided between the tooth portion of the joint portion and the spline groove, high rigidity in the torque transmission direction cannot be satisfied.

  The present invention has been made in view of such points, and the object of the present invention is to improve the structure of the coupling, thereby realizing high rigidity in the torque transmission (rotation) direction, In the direction in which the driven shaft is eccentric, an extremely low rigidity is realized in the initial stage.

  In order to achieve the above object, in the present invention, by providing a tapered portion on the tooth portion of the joint portion, when the driving shaft and the driven shaft are eccentric, the tapered portion does not contact the inner wall of the spline groove. While suppressing the occurrence of the eccentric reaction force, a portion having a uniform width of the tooth portion in the torque transmission direction immediately interferes with the spline groove so that high torque transmission can be realized.

  Specifically, the first invention is a coupling in which a driving shaft and a driven shaft whose end portions are abutted with each other are connected for torque transmission in a concentric state or an eccentric state in which an eccentric displacement amount varies. A pair of joint portions provided at end portions of the drive shaft and the driven shaft and arranged to face each other; and a cylindrical shape that is externally fitted between the pair of joint portions and connects the joint portions. A plurality of spline grooves having a constant groove width extending in a direction along the center line of the sleeve are provided at intervals in the circumferential direction. A plurality of tooth portions meshing with the spline grooves are formed on the outer peripheral surfaces of the pair of joint portions, and the tooth portions have a constant width along the axial direction. Uniform width and relative width Wherein the width of the teeth portion and a narrower tapered portion is provided toward the joint portion.

  By adopting the above configuration, since the tooth portion of the joint portion is tapered toward the joint portion facing in the taper, the tip of the tooth portion of the joint portion even when the drive shaft and the driven shaft are eccentric. There is no reaction force caused by contact between the details and the inner wall of the spline groove, and torque transmission is not hindered. This realizes extremely low rigidity in the initial direction in the direction in which the drive shaft and the driven shaft are eccentric.

  On the other hand, when torque is transmitted between the drive shaft and the driven shaft, the uniform width portion of the tooth portion of the joint portion and the spline groove are in immediate contact with each other, so that high-rigidity and efficient torque transmission can be performed. .

  The second invention is characterized in that, in the first invention, the tapered portion has a narrowed width due to an inclined surface inclined with respect to the axial direction.

  According to a third aspect, in the second aspect, the contact length between the joint portion and the sleeve is S, the gap between the pair of joint portions is G, and the maximum eccentricity that requires play between the drive shaft and the driven shaft is required. TanA ≧ D / (S + G), where D is the amount of displacement and A is the inclination angle between the tooth side surface of the tapered portion and the axial direction of the drive shaft and driven shaft.

  By adopting the configuration of these inventions, even if the amount of eccentric displacement between the drive shaft and the driven shaft is maximized, the tip of the tooth portion of the joint portion does not come into contact with the inner wall of the spline groove in the sleeve, Generation of a reaction force that inhibits torque transmission can be prevented.

  In a fourth aspect of the invention, in any one of the first to third aspects, when the contact length between the joint portion and the sleeve is S, and the axial length of the tapered portion is L, 0.8S <L <0.99S.

  By adopting the above configuration, it is possible to realize the suppression of the eccentric reaction force that is satisfactory with respect to a predetermined amount of eccentric displacement while taking into account variations during manufacturing.

  According to a fifth aspect of the present invention, in any one of the first to fourth aspects, the driven shaft is a worm that is drivingly connected to a steering shaft of an electric power steering apparatus for an automobile via a worm wheel, and the driving shaft Is an output shaft of a control motor for driving the worm.

  A sixth invention is characterized in that, in any one of the first to fifth inventions, the joint portion is made of a high elastic body, and the sleeve is made of a low elastic body.

  With the configurations of these inventions, the coupling of the present invention can be applied between the worm of the electric power steering apparatus in which eccentricity can occur and the output shaft of the control motor that drives the worm.

  As described above, according to the present invention, when torque is transmitted between the drive shaft and the driven shaft by a coupling in which the joint portion and the sleeve are combined, the tapered portion is provided on the tooth portion on the outer periphery of the joint. Even when the drive shaft and driven shaft are eccentric, the tip of the tooth portion of the joint portion contacts the inner wall of the spline groove of the sleeve and prevents the occurrence of an eccentric reaction force that inhibits torque transmission. Efficient torque transmission can be realized by contact between the width portion and the spline groove.

It is a perspective view showing the outline of the electric power steering device for vehicles concerning an embodiment. FIG. 2 is an enlarged view showing a control motor and a reduction gear portion in FIG. It is a perspective view of the joint part of the coupling concerning an embodiment. It is a perspective view which shows the connection structure of the joint part and sleeve of a coupling which concern on embodiment. It is a schematic diagram showing the connection state of the tooth part of a joint part, and a spline groove when the drive shaft and driven shaft which concern on embodiment are concentric. FIG. 6 is a view corresponding to FIG. 5 when the drive shaft and the driven shaft according to the embodiment are in a maximum eccentric state. It is a figure which shows the measurement result of the relationship between a twist angle and a transmission torque in an Example. It is a figure which shows the measurement result of the relationship between eccentric displacement and eccentric reaction force in an Example. FIG. 8 is a view corresponding to FIG. 7 and showing measurement results according to Comparative Example 1. FIG. 9 is a diagram corresponding to FIG. 8 and showing measurement results according to Comparative Example 1; FIG. 8 is a diagram corresponding to FIG. 7 and showing measurement results according to Comparative Example 2. FIG. 9 is a diagram corresponding to FIG. 8 and showing measurement results according to Comparative Example 2. 6 is a side view of a coupling according to Comparative Example 1. FIG. FIG. 14 is a diagram corresponding to FIG. 13 according to Comparative Example 2.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. Note that the following description of the embodiment is merely illustrative in nature, and is not intended to limit the present invention, its application, or its use.

  FIG. 1 shows an outline of an electric power steering apparatus 10 for an automobile according to an embodiment. A steering wheel 1 that is steered by a driver is attached to a rear end portion of a column shaft 2 at the center thereof so as to rotate together. The front end portion of the column shaft 2 is connected to the upper end portion of the intermediate shaft 6 (intermediate shaft) via the reduction gear portion 3. The lower end portion of the intermediate shaft 6 is connected to the pinion shaft 7. The pinion shaft 7 is provided with a pinion (not shown), and this pinion is meshed with a rack (not shown) in the rack housing 8 extending in the vehicle width direction. The rack is slidable within the rack housing 8, and both ends thereof are connected to the left and right front wheels (not shown) via tie rods 9, whereby the steering force of the steering wheel 1 by the driver is transmitted to the front wheels. The front wheels are steered. The reduction gear unit 3 is provided with a torque sensor 5. The torque sensor 5 detects the steering torque of the steering wheel 1 by the driver and controls the control motor 4.

  As shown in an enlarged view in FIG. 2, a worm wheel 33 is rotatably and integrally attached to the column shaft 2 in the reduction gear portion 3. The worm wheel 33 is engaged with the worm 31. The worm wheel 33 is configured to rotate with the rotation of the worm 31. The worm 31 constitutes the driven shaft of the present invention, and at one end thereof, the output shaft 41 of the control motor 4 made of an electric motor is in a state in which the end thereof is confronted with one end of the worm 31 in a concentric state. Has been placed. The output shaft 41 of the control motor 4 constitutes a drive shaft, and a coupling 50 according to the embodiment of the present invention is provided to connect the output shaft 41 (drive shaft) and the worm 31 (driven shaft). It has been. The control motor is controlled in response to a control signal from a controller (not shown), and the output signal of the torque sensor 5 is input to the controller, whereby the torque detected by the torque sensor 5 is detected. The control motor 4 is actuated on the basis of the rotation of the output shaft 41, and the torque generated by the rotation of the output shaft 41 is transmitted to the worm 31 via the coupling 50 to rotate the worm wheel 33 engaged with the worm 31. 2, steering assist (assist) of the steering wheel 1 according to the torque generated by steering is performed, and the function as the electric power steering device 10 is realized.

  3 and 4 show the coupling 50 in an enlarged manner. The coupling 50 has a pair of joint portions 51 and 51 and a cylindrical shape that is externally fitted between the pair of joint portions 51 and 51. The sleeve 56 is provided. In FIG. 3, the sleeve 56 that fits outside the joint portion 51 is indicated by an imaginary line. FIG. 4 shows the coupling structure of the joint portion 51 and the sleeve 56 of the coupling 50. In order to make the structure easy to understand, half of the sleeve 56 and half of the joint portion 51 on one side (front side of the paper) are omitted. ing.

  The pair of joint portions 51, 51 are both cylindrical with a uniform diameter, and are composed of, for example, a highly elastic body (elastic modulus: 206 GPa) such as iron. Both joint portions 51, 51 are arranged to face each other, and one joint portion 51 has one end portion of the worm 31 (the end portion on the control motor 4 side) and the other joint portion 51 has the other joint portion 51. The output shaft 41 of the control motor 4 is inserted in a rotating manner. Thus, the pair of joint portions 51 and 51 are drivingly connected to the end portion of the output shaft 41 of the control motor 4 as the drive shaft and the end portion of the worm 31 as the driven shaft.

  A plurality of (for example, about 10 to 15) tooth portions 52, 52,... Extending in parallel with the axis of the joint portion 51 are provided on the outer peripheral surface of each joint portion 51 in the circumferential direction. Are arranged in a state where they are lined up at regular intervals. The height of the tooth portions 52, 52,... Is constant along the axis.

  On the other hand, the cylindrical sleeve 56 is externally fitted to the joint portions 51, 51 to connect the joint portions 51, 51, and is a low-elastic body such as rubber or resin (elastic modulus: 100 MPa to 1000 MPa). ). A plurality of spline grooves 57, 57,... Extending in the direction along the center line of the sleeve 56 across the longitudinal ends of the sleeve 56 are spaced at equal pitches in the circumferential direction on the inner peripheral surface of the sleeve 56. Is provided. Each spline groove 57 has a constant groove width and groove depth over the entire length (between both ends in the length direction of the sleeve 56), and the spline groove 57 of the sleeve 56 has the joint portion 51. The tooth part 52 is configured to mesh.

  As a feature of the present invention, each tooth part 52 on the outer peripheral surface of each joint part 51 has a uniform width part 53a having a constant width, and the width of the tooth part 52 increases toward the joint part 51 facing each other. A narrowing point 53b is provided. In the illustrated example, the tapered portion 53b has an inclined surface that is inclined with respect to the axial direction, and the width of the tooth portion 52 is tapered.

  Here, as shown in FIG. 4, the contact length between the joint portion 51 and the sleeve 56 is S, the length of the tip 53b in the axial direction is L, the gap between the pair of joint portions 51 and 51 is G, and output. D is the maximum eccentric displacement that requires play between the shaft 41 (drive shaft) and the worm 31 (driven shaft), and A is the inclination angle that the side surface of the tooth portion of the tapered portion 53b is in the axial direction of the output shaft 41 and the worm 31. In consideration of the geometric relationship between the joint portion 51 and the sleeve 56, an inclination angle A satisfying the relationship of tanA ≧ D / (S + G) can be applied to the tapered portion 53b of the tooth portion 52 of the joint portion 51. More preferably, the relationship 0.8S <L <0.99S is preferably satisfied. Here, the “maximum eccentric displacement that requires play” is an eccentric displacement that needs to suppress the eccentric reaction force when the output shaft 41 (drive shaft) and the worm 31 (driven shaft) are eccentric. It means the maximum value.

  Hereinafter, the operation of the electric power steering apparatus 10 will be described. Rotational torque due to steering of the steering wheel 1 by the driver is detected by the torque sensor 5, and the control motor 4 is operated and controlled by the controller according to the magnitude, and the output shaft 41 of the control motor 4 rotates. Here, since the output shaft 41 and the worm 31 in the reduction gear unit 3 are connected via the coupling 50, the rotation of the output shaft 41 is transmitted to the worm 31, thereby the worm 31 and the worm 31. The meshed worm wheel 33 is rotated.

  At this time, in order to eliminate backlash between the worm 31 and the meshing surface of the worm wheel 33, the worm 31 is pressurized in the direction perpendicular to the axis (the direction of pressing against the worm wheel 33). This preload is controlled by a pressurizing unit 32 provided at the end of the worm 31 opposite to the control motor 4, and due to this preload, the axis of the worm 31 is the axis of the output shaft 41 of the control motor 4. It becomes an eccentric state.

  FIG. 6 schematically shows a connection state between the joint portion 51 and the sleeve 56 when the output shaft 41 (drive shaft) and the worm 31 (driven shaft) of the control motor 4 are in the maximum eccentric state. The configuration of the sleeve 56 is drawn with virtual lines. Here, the joint portion 51 on the lower side in FIG. 6 connected to the worm 31 is the maximum eccentricity that requires play to the right in the drawing with respect to the joint portion 51 on the upper side in FIG. 6 connected to the output shaft 41 of the control motor 4. In this state, the displacement amount D is eccentric. At this time, the sleeve 56 is inclined due to the eccentricity of the joint portion 51 connected to the worm 31, and the spline groove 57 provided on the inner peripheral surface of the sleeve 56 is also inclined accordingly. However, at this time, since the tooth portion 52 of the joint portion 51 is provided with a tapered portion 53 b that becomes narrower toward the opposing joint portion 51, the tapered portion 53 b becomes a spline in the sleeve 56. There is no contact with the inner wall of the groove 57, and no eccentric reaction force that prevents torque transmission occurs. Thus, extremely low rigidity is realized at the initial stage in the direction in which the output shaft 41 (drive shaft) and the worm 31 (driven shaft) of the control motor 4 are eccentric.

  On the other hand, since the spline groove 57 and the uniform width portion 53a of the tooth portion 52 immediately interfere with each other in the torque transmission direction, high torque transmission can be realized.

  As a result, even if the connected joint portions 51 and 51 are decentered due to the eccentricity of the output shaft 41 of the control motor 4 and the worm 31, the output shaft 41 is realized with high rigidity in the torque transmission (rotation) direction. In the direction in which the worm 31 and the worm 31 are eccentric, extremely low rigidity can be realized at the initial stage.

  In this embodiment, the contact length S between the joint portion 51 and the sleeve 56, the length L in the axial direction of the tapered portion 53b, the gap G between the pair of joint portions 51 and 51, and the output shaft 41 (drive shaft). D is the maximum eccentric displacement that requires play between the worm 31 and the worm 31 (driven shaft), and the relationship between the inclination angle A between the tooth side surface of the tip 53b and the axial direction of the output shaft 41 and the worm 31 is tanA ≧ D / (S + G), so that even if the amount of eccentric displacement between the output shaft 41 and the worm 31 becomes maximum, the tapered portion 53b of the tooth portion 52 of the joint portion 51 contacts the inner wall of the spline groove 57 in the sleeve 56. Therefore, it is possible to more reliably prevent the generation of a reaction force that inhibits torque transmission.

  Furthermore, at this time, by satisfying the relationship of 0.8S <L, the eccentric reaction force can be sufficiently suppressed with respect to the eccentric displacement amount. Further, since L <0.99S, the tapered portion 53b is within the range of the contact length S, and there is always a section where the interval between the joint portion 51 and the sleeve 56 is zero. Interfere immediately.

(Other embodiments)
In the above embodiment, the coupling of the present invention is used for the connection between the output shaft 41 of the control motor 4 and the worm 31 of the electric power steering apparatus 10 for an automobile. The present invention can also be applied to the connection between the motor and the driven shaft, and similar effects can be obtained.

  Next, specific examples will be described.

(Example)
It is the coupling 50 of the structure demonstrated by the said embodiment.

(Comparative Example 1)
As shown in FIG. 13, the tooth portion 52 of the joint portion 51 is not provided with the tapered portion 53b, and the play between the sleeve and the joint is eliminated.

(Comparative Example 2)
As shown in FIG. 14, the tooth portion 52 of the joint portion 51 is provided with a play between the sleeve and the joint without providing the tapered portion 53b.

  For these examples and comparative examples, the relationship between the torsion angle and the transmission torque, and the relationship between the eccentric displacement and the eccentric reaction force were obtained by numerical analysis using the finite element method, and the effects of the invention were verified. The results are shown in FIGS.

  As shown in FIG. 7, in the embodiment, the relationship between the torsion angle and the transmission torque is almost proportional, and it can be read that high torque transmission efficiency is realized.

  In FIG. 8, the eccentric displacement when the relationship between the axial length S along the axial center of the drive shaft and driven shaft of the tooth portion 52 and the axial length L of the tapered portion 53b is changed. And the relationship between the eccentric reaction force and the eccentric reaction force. From this figure, it can be read that by increasing the value of L, the occurrence of the eccentric reaction force can be suppressed even for a large amount of eccentric displacement. Here, in the width P in the graph when L = 0.85S, an effect of play due to the provision of the tapered portion 53b in the tooth portion 52 of the joint portion 51 appears.

  9 and 10 show measurement results of the transmission torque and the eccentric reaction force in Comparative Example 1. FIG. As shown in FIG. 9, when the play between the sleeve and the joint is eliminated, a high transmission torque proportional to the torsion angle can be realized. However, as shown in FIG. 10, the eccentric reaction force also increases at a high rate in a form proportional to the eccentric displacement. This is a result of decent influence of the eccentricity of the joint due to the absence of play between the sleeve and the joint.

  11 and 12 show measurement results of the transmission torque and the eccentric reaction force in Comparative Example 2. As shown in FIG. 12, when a play is provided between the sleeve and the joint, the eccentric reaction force hardly occurs until the eccentric displacement exceeds a predetermined value, and the play effect is equivalent to the width P in FIG. Appears. However, as shown in FIG. 11, almost no transmission torque is generated until the twist angle exceeds a predetermined value. This is because the effect of providing play between the sleeve and the joint appears by the width P in FIG.

  By verifying the above, in the embodiment, the torque transmission with respect to the torsional angle can realize a high torque transmission efficiency that appears when the play between the sleeve and the joint is eliminated, while it appears when the eccentric displacement occurs. Regarding the eccentric reaction force, it is possible to suppress the eccentric reaction force that appears when play is provided between the sleeve and the joint. Accordingly, it can be seen that in the coupling of the present invention, high rigidity is realized in the torque transmission direction, while extremely low rigidity is realized in the initial direction in the direction in which the two rotating shafts are eccentric.

  As described above, the present invention is extremely useful for a coupling used for connecting a drive shaft and a driven shaft, which may be eccentric, such as used in an electric power steering device of an automobile, for example.

3 Reduction gear 4 Control motor 10 Electric power steering device 31 Worm (driven shaft)
32 Pressurizing section 33 Worm wheel 41 Output shaft (drive shaft)
50 Coupling 51 Joint 52 Tooth 53a Uniform width 53b Tip 56 Sleeve 57 Spline groove

Claims (8)

A coupling in which the drive shaft and the driven shaft, whose ends are butted against each other, are connected for torque transmission in a concentric state or in an eccentric state where the eccentric displacement varies.
A pair of joint portions provided at end portions of the drive shaft and the driven shaft, respectively, and arranged to face each other;
A cylindrical sleeve that is externally fitted between the pair of joint portions and connects the joint portions;
With
On the inner peripheral surface of the sleeve, while a plurality of spline grooves having a constant groove width extending in a direction along the center line of the sleeve are provided at intervals in the circumferential direction,
Wherein the outer peripheral surfaces of the pair of joint portions, and tooth portions of the multiple that match teeth are formed in the spline grooves,
The tooth portion is continuously provided on the joint portion side facing the uniform width portion, and the uniform width portion in which the width of the tooth portion is constant along the axial direction, and the width of the tooth portion is A coupling that includes a tapered portion that narrows toward the joint portion and that has a uniform width portion and a height of the tooth portion including the tapered portion that is constant along the axial direction . In claim 1,
The tapered portion is a coupling in which the width of the tooth portion is narrowed by an inclined surface inclined with respect to the axial direction. In claim 2,
The contact length between the joint portion and the sleeve is S, the gap between the pair of joint portions is G, the maximum eccentric displacement that requires play between the drive shaft and the driven shaft is D, and the tooth portion at the tapered portion When the inclination angle between the side surface and the axial direction of the drive shaft and driven shaft is A,
tanA ≧ D / (S + G)
Coupling. In any one of Claims 1-3,
When the contact length between the joint part and the sleeve is S, and the axial length of the tapered portion is L,
0.8S <L <0.99S
Coupling. In any one of Claims 1-4,
The driven shaft is a worm that is drivingly connected to a steering shaft of an electric power steering device for an automobile via a worm wheel,
The drive shaft is a coupling that is an output shaft of a control motor that drives the worm. In any one of Claims 1-5,
The coupling portion is formed of a high elastic body, and the sleeve is formed of a low elastic body. A coupling in which the drive shaft and the driven shaft, whose ends are butted against each other, are connected for torque transmission in a concentric state or in an eccentric state where the eccentric displacement varies.
A pair of joint portions provided at end portions of the drive shaft and the driven shaft, respectively, and arranged to face each other;
A cylindrical sleeve that is externally fitted between the pair of joint portions and connects the joint portions;
With
On the inner peripheral surface of the sleeve, while a plurality of spline grooves having a constant groove width extending in a direction along the center line of the sleeve are provided at intervals in the circumferential direction,
A plurality of tooth portions that mesh with the spline grooves are formed on the outer peripheral surfaces of the pair of joint portions,
The tooth portion is provided with a uniform width portion in which the width of the tooth portion is constant along the axial direction, and a tapered portion where the width of the tooth portion becomes narrower toward the opposite joint portion,
The tapered portion is narrowed by an inclined surface inclined with respect to the axial direction, and the width of the tooth portion is narrow.
The contact length between the joint portion and the sleeve is S, the gap between the pair of joint portions is G, the maximum eccentric displacement that requires play between the drive shaft and the driven shaft is D, and the tooth portion at the tapered portion When the inclination angle between the side surface and the axial direction of the drive shaft and driven shaft is A,
tanA ≧ D / (S + G)
Coupling. A coupling in which the drive shaft and the driven shaft, whose ends are butted against each other, are connected for torque transmission in a concentric state or in an eccentric state where the eccentric displacement varies.
A pair of joint portions provided at end portions of the drive shaft and the driven shaft, respectively, and arranged to face each other;
A cylindrical sleeve that is externally fitted between the pair of joint portions and connects the joint portions;
With
On the inner peripheral surface of the sleeve, while a plurality of spline grooves having a constant groove width extending in a direction along the center line of the sleeve are provided at intervals in the circumferential direction,
A plurality of tooth portions that mesh with the spline grooves are formed on the outer peripheral surfaces of the pair of joint portions,
The tooth portion is provided with a uniform width portion in which the width of the tooth portion is constant along the axial direction, and a tapered portion where the width of the tooth portion becomes narrower toward the opposite joint portion,
When the contact length between the joint part and the sleeve is S, and the axial length of the tapered portion is L,
0.8S <L <0.99S
Coupling.

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