JP2004353758A - Hydraulic tensioner - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To absolutely prevent a pole member from projecting outside a housing when a piston is pulled back. <P>SOLUTION: The hydraulic tensioner includes a housing 2 which has a piston hole 2a, a hollow piston 3 which is slidably inserted into the piston hole 2a, forms a fluid chamber 30 with the piston hole 2a, and has a rack teeth 3b formed in a part of the periphery, a piston spring 4 which powers the piston 3 in the projection direction, a pole member 5 which has a teeth portion 5a engaging with the rack teeth 3b of the piston 3, and a pole spring 6 which powers the pole member 5 to engage the teeth portion 5a of the pole member 5 with the rack teeth 3b. The thickness Te of the teeth portion 5a in the last end of the pole member 5 is smaller than the thickness To of the other teeth portion 5a, and the moment about an A point is generated in the direction to engage the pole member 5 with the rack teeth 3b when the piston is pulled back. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a hydraulic tensioner for applying an appropriate tension to a chain or a belt, and more particularly to a hydraulic tensioner having a ratchet mechanism for preventing the piston from retracting when the hydraulic pressure is reduced.
[0002]
[Prior art and its problems]
The hydraulic tensioner is generally defined by a housing, a hollow piston slidably inserted into a hole formed in the housing and urged in a projecting direction by a spring, and a piston and the hollow hole in the hole of the housing. And a fluid chamber. During operation of the tensioner, the pressing force acting on the piston tip from the chain or belt balances the elastic force of the spring and the drag force of the hydraulic pressure in the chamber.
[0003]
By the way, especially in a hydraulic tensioner applied to a timing system for an automobile, when a sufficient hydraulic pressure is not acting in the chamber, such as when starting an engine, a pressing force is applied from the chain to the tip of the piston. When this occurs, the piston is easily pushed into the housing and the piston retracts, which may result in noise and vibration.
[0004]
Therefore, in order to prevent such retraction of the piston, for example, a hydraulic tensioner provided with a ratchet mechanism as disclosed in JP-A-2002-147551 has been proposed.
[0005]
The ratchet mechanism includes a toothed pad-shaped pole member having rack teeth formed on the outer periphery of the piston, and teeth provided on a pole hole formed in the housing and capable of engaging with the rack teeth on the outer periphery of the piston. An annular pawl spring for urging the member in the direction of engagement with the rack teeth.
[0006]
In this case, when the piston moves in the protruding direction with the teeth of the pawl member engaged with the rack teeth of the piston, the rack teeth of the piston move over the teeth of the pawl member, thereby protruding the piston. Although the movement of the piston is permitted, the movement of the piston in the retreating direction is restricted by maintaining the state where the rack teeth of the piston are engaged with the teeth of the pole member when the piston moves in the retreating direction. ing.
[0007]
[Patent Document 1]
JP-A-2002-147551 (see FIGS. 3 and 6)
[0008]
However, in the conventional ratchet mechanism, when the pawl member receives the pressing force from the rack teeth in a state where the pawl member is engaged with the rack teeth of the piston during the retreat of the piston, the engagement state between the teeth of the pawl member and the rack teeth is changed. The moment in the disengagement direction is configured to act on the teeth of the pole member (for details, see [Means for Solving the Problems] below). As a result, when the piston is retracted, the pole member may jump out of the housing. Will act on the pole member.
[0009]
SUMMARY OF THE INVENTION The present invention has been made to solve such a conventional problem. In a hydraulic tensioner having a pole member, a hydraulic tensioner that can reliably prevent the pole member from jumping out of the housing when the piston is retracted. The purpose is to provide.
[0010]
[Means for Solving the Problems]
The hydraulic tensioner according to the first aspect of the present invention is a hydraulic tensioner that is slidably inserted into a hole of a housing, a hollow piston having rack teeth formed on a part of an outer periphery, a piston spring that biases the piston in a projecting direction, A pole member having teeth for engaging with the rack teeth of the piston and for allowing the piston to move in the protruding direction and preventing the piston from moving in the retreating direction; and a side on which the teeth of the pole member engage with the rack teeth. And a pole spring for urging the pole member, and the thickness of the last tooth portion of the pole member is smaller than the thickness of the other tooth portions.
[0011]
According to the first aspect of the present invention, when the piston moves in the direction protruding from the hole of the housing, the piston moves in the protruding direction by the rack teeth of the piston getting over some teeth of the pole member. Then, when the pressing force acting on the chain from the tip of the piston by the spring force of the piston spring and the liquid pressure in the fluid chamber is balanced with the pressing force acting on the tip of the piston from the chain by the chain tension, the movement of the piston stops.
[0012]
Next, when a pressing force acts on the tip of the piston from the chain in a situation where sufficient fluid pressure is not acting in the fluid chamber, as shown in FIG. The piston 3 moves in the retreating direction (the left side in the figure) together with the pawl member 5 while maintaining the state of engaging with the tooth portion 5a of the pawl member 5, and the rear end face 5c of the pawl member 5 2b is pressed against the inner wall surface 25. Thereby, the movement of the piston 3 stops.
[0013]
In this case, the pressing force acting on the teeth 5a of the pawl member 5 from the rack teeth 3b of the piston 3 is F, and the line of action of the force is m. When the corner below the rear end face 5c of the pole member 5 is point A, the thickness te at the root of the last tooth 5a of the pole member 5 is smaller than the thickness to of the other teeth 5a. Therefore, the point A is preferably disposed below the line of action m of the pressing force F. On the other hand, in the conventional pole member, since the rear end face 5c 'is disposed rearward of the rear end face 5c, the point A' below the rear end face 5c 'of the pole member is the action line m of the pressing force F. It is arranged above.
[0014]
Here, the moment of the force F around the points A and A 'will be considered.
The moment MA around the point A is represented by MA = F × dA where dA is the distance between the line of action m of the force F and the point A.
And MA is a moment for rotating the pole member 5 counterclockwise about the point A. On the other hand, the moment MA ′ around the point A ′ is MA ′ = F × dA ′ when the distance between the line of action m of the force F and the point A ′ is dA ′.
And MA ′ is a moment for rotating the pole member 5 clockwise about the point A ′.
[0015]
That is, the moment MA acts in a direction in which the teeth 5a of the pole member 5 mesh with the rack teeth 3b of the piston 3, while the moment MA 'causes the teeth 5a of the pole member 5 to move into the rack teeth of the piston 3. 3b.
[0016]
As described above, in the conventional hydraulic tensioner, when the pawl member 5 receives the pressing force F from the rack teeth 3b in a state where the pawl members 5 are engaged with the rack teeth 3b of the piston 3 when the piston retreats, the tooth portions of the pawl members 5 Since the moment MA ′ in the direction in which the engagement with the rack teeth 3b is disengaged acts on 5a, when the piston is retracted, a force that causes the pawl member 5 to jump out of the housing when the piston retreats is applied. Will work.
[0017]
On the other hand, according to the first aspect of the present invention, when the piston is retracted, a moment MA is applied in a direction in which the engagement between the teeth 5a of the pawl member 5 and the rack teeth 3b becomes stronger. Therefore, when the piston retreats, no force is exerted on the pawl member 5 so that the pawl member 5 protrudes out of the housing. This makes it possible to reliably prevent the pawl member from protruding when the piston retreats.
[0018]
According to the second aspect of the present invention, in the first aspect, a clearance is formed between the tooth surface of the rearmost tooth portion of the pole member and the tooth surface of the corresponding rack tooth of the piston.
[0019]
In claim 1, when the thickness of the last tooth portion of the pole member is smaller than the thickness of the other tooth portions, the strength of the last tooth portion is relatively reduced as compared with the other tooth portions. However, by forming a clearance between the rearmost teeth and the rack teeth as in the second aspect of the present invention, it is possible to avoid the pressing force from the rack teeth acting on the rearmost teeth. Thus, it is possible to prevent a failure such as breakage from occurring in the rearmost tooth portion.
[0020]
According to the third aspect of the present invention, the distance between the tooth surface of the rearmost tooth portion of the pole member and the tooth surface of the tooth portion that is one forward of the pole member is different from that of another tooth portion adjacent in the front-rear direction. It is larger than the distance between the surfaces.
[0021]
In this case as well, a clearance is formed between the tooth surface of the rearmost tooth portion of the pole member and the tooth surface of the corresponding rack tooth of the piston, similarly to the second aspect of the invention. In addition, it is possible to avoid the pressing force from the rack teeth acting on the rearmost tooth portion, and to prevent the occurrence of troubles such as breakage on the rearmost tooth portion.
[0022]
According to the fourth and fifth aspects of the present invention, among the tooth surfaces forming the tooth portion of the pawl member, the angle between the tooth surface on the side engaged with the rack teeth when the piston is retracted and the front in the axial direction of the piston is more than 90 degrees. Is also growing.
[0023]
According to the fourth and fifth aspects of the present invention, as shown in FIG. 5B, when the angle between the tooth surface s of the pawl member and the axial direction L of the piston is θ, θ> 90 °
It has become. In FIG. 2B, for convenience of illustration, the angle θ is larger than θ in FIG.
[0024]
In FIG. 5B, the pressing force acting on the tooth surface s is represented by f, and the force f is decomposed in the axial direction of the piston and in a direction perpendicular thereto, and the component forces are represented by f ₁ and f ₂ . . As apparent from the figure, the component force f ₂ is acting tooth surface s of the pole member downwards, i.e. on the side facing the rack teeth of the piston. This prevents the pole member from jumping out of the housing. In the conventional hydraulic tensioner, the angle θ is set to 90 degrees or smaller than 90 degrees. Therefore, when the piston retreats, the pressing force against the tooth surface of the pole member causes the pole member to move to the pole member. In some cases, it acted on the side that protruded from the hole.
[0025]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.
1 is an overall perspective view of a hydraulic tensioner according to one embodiment of the present invention, FIG. 2 is a longitudinal sectional view of the hydraulic tensioner of FIG. 1, FIG. FIG. 5 is a front enlarged view of a pole member of the hydraulic tensioner. In FIG. 5, for convenience of illustration, the pole spring is removed.
[0026]
As shown in FIGS. 1 to 3, the hydraulic tensioner 1 includes a housing 2 having a piston hole 2 a extending in the axial direction and having an open end, and a piston 2 a in the housing 2. Direction) It is mainly composed of a hollow piston 3 slidably inserted, and a piston spring 4 arranged in the piston hole 2a of the housing 2 and for urging the piston 3 in a direction protruding from the piston hole 2a. .
[0027]
The housing 2 has bolt holes 20 and 21 into which mounting bolts for mounting the hydraulic tensioner 1 in, for example, an engine are inserted. In the housing 2, a fluid chamber 30 is formed from an internal space 3a formed in the piston 3 and an inner wall surface of the piston hole 2a. At the bottom of the housing 2, an introduction passage 10 for introducing engine oil as a working fluid into the fluid chamber 30 from an external pressurized fluid source (not shown) is formed.
[0028]
A check valve 7 is provided at the bottom of the piston hole 2 a in the housing 2. The check valve 7 allows the flow of the fluid from the introduction passage 10 to the fluid chamber 30, while preventing the flow of the fluid in the opposite direction. Here, a ball check valve is employed.
[0029]
A vent disc 8 is provided on the piston head side in the internal space 3a of the piston 3. The vent disk 8 is a member for discharging the air mixed in the fluid chamber 30 to the outside of the tensioner and for controlling the amount of leakage of the fluid from the fluid chamber 30. For example, a spiral groove is formed. On the other hand, an axial through hole 31 is formed in the piston head. The air in the fluid chamber 30 is discharged from the through hole 31 to the outside of the tensioner through the spiral groove of the vent disk 8 together with the fluid containing the air. The vent disk 8 has a shaft 8a. The piston spring 4 is disposed around the shaft portion 8a of the vent disc 8, and its tip urges the vent disc 8 toward the piston head.
[0030]
Rack teeth 3 b are formed on a part of the outer peripheral surface of the piston 3. On the other hand, a pole hole 2b communicating with the piston hole 2a is formed in the housing 2 (see FIGS. 4 and 5A). The pole member 5 is disposed in the pole hole 2b. On the lower surface of the pawl member 5, a tooth portion 5a that can engage with the rack teeth 3b of the piston 3 is formed.
[0031]
As shown in FIG. 5A, the thickness te of the tooth 5a at the rearmost end of the pole member 5 is smaller than the thickness to of the root portion of the other tooth 5a. That is, te <to
It has become. More preferably, the thickness te is smaller than the thickness of the other tooth portion 5a on the action line m. Further, a clearance δ is provided between the tooth surface of the rearmost tooth portion 5a of the pole member 5 and the tooth surface of the corresponding rack tooth 3b of the piston 3. In other words, the distance pe between the tooth surface of the tooth portion 5a at the rearmost end of the pole member 5 and the tooth surface of the tooth portion 5a one side forward of the pole member 5 is different from that of the other tooth portions 5a adjacent in the front-rear direction. It is larger than the distance po between the tooth surfaces. That is, pe> po
It has become.
[0032]
In the opening of the pole hole 2b of the housing 2, a pole spring 6 for urging the pole member 5 to the side where the teeth 5a of the pole member 5 engage with the rack teeth 3 of the piston 3 is provided.
[0033]
The pole spring 6 is formed by performing a bending process on a strip-shaped member, and has a plurality of bent portions. When these bent portions come into contact with the pole member 5 from above, the spring force of the pole spring 6 acts on the pole member 5.
[0034]
Locking hook portions (not shown) are formed at both ends of the pole spring 6, and these locking hook portions are formed with locking recesses 22 and 22 ′ formed in the opening of the pole hole 2 b of the housing 2. (FIG. 4), the pole spring 6 is attached to the housing 2.
[0035]
In the housing 2, a through hole 23 in the width direction is formed near the opening of the piston hole 2a (see FIGS. 1 and 4). A locking groove 3e extending in the width direction is formed in the head of the piston 3 (see FIG. 2). The through holes 23 and the locking grooves 3e are for holding the piston 2 in a contracted state at the time of transporting the tensioner or the like. By inserting the retaining pin 9 shown in FIG. 3 into the through hole 23 and the locking groove 3e from the state where the through hole 23 and the locking groove 3e are aligned with the piston 2 in the retracted state, the piston 2 is It is kept in a degenerated state.
[0036]
In the piston 3, a stopper groove 3d is formed behind the rearmost tooth portion of the rack tooth 3b. The stopper groove 3 d is for preventing the piston 3 from further projecting by engaging with the tooth portion 5 a of the pawl member 5 when the piston 3 moves in the projecting direction. It has the function of retaining.
[0037]
Next, the operation and effect of this embodiment will be described.
If the chain becomes loose or the tension of the chain decreases during operation of the tensioner, the piston 3 moves in the direction in which the piston 3 projects from the housing 2 by the spring force of the piston spring 4. At this time, the rack teeth 3b of the piston 3 move over some teeth 5b of the pawl member 5.
[0038]
When the piston 3 moves in the protruding direction, the inside of the fluid chamber 30 becomes negative pressure, so that the check valve 7 is opened, and engine oil is introduced into the fluid chamber 30 from the introduction path 10 through the check valve 7. As a result, the resultant force of the spring force of the piston spring 4 and the liquid pressure in the fluid chamber 30 acts on the chain via the tensioner arm, and the tension of the chain is maintained.
[0039]
Next, when a pressing force is applied from the chain to the piston tip 3c in a state where sufficient fluid pressure is not acting in the fluid chamber 30, such as when starting the engine, the rack teeth 3b on the outer periphery of the piston are removed. While maintaining the state of engagement with the tooth portion 5a of the pole member 5, the piston 3 retreats together with the pole member 5, and the rear end face 5c of the pole member 5 contacts the inner wall surface 25 of the pole hole 2b of the housing 2 (FIG. 5 (a)). As a result, the backward movement of the piston 5 is stopped.
[0040]
At this time, since the thickness te of the last tooth portion 5a of the pole member 5 is smaller than the thickness to of the other tooth portions 5a, the point A below the rear end face 5c of the pole member 5 It is arranged below the line of action m of the pressing force F from the rack teeth 3b.
[0041]
The moment MA around the point A is represented by MA = F × dA where dA is the distance between the line of action m of the force F and the point A.
And MA is a moment for rotating the pole member 5 counterclockwise about the point A.
[0042]
By the way, in the conventional pole member, since the rear end face 5c 'is disposed behind the rear end face 5c, the point A' below the rear end face 5c 'of the pole member is located above the action line m of the pressing force F. Are located.
[0043]
The moment MA ′ around the point A ′ is MA ′ = F × dA ′ when the distance between the line of action m of the force F and the point A ′ is dA ′.
And MA ′ is a moment for rotating the pole member 5 clockwise about the point A ′.
[0044]
Therefore, while the moment MA acts in the direction in which the teeth 5a of the pole member 5 mesh with the rack teeth 3b of the piston 3, the moment MA 'causes the teeth 5a of the pole member 5 to move to the rack 3 of the piston 3. It acts in the direction away from the teeth 3b.
[0045]
As described above, in the conventional hydraulic tensioner, when receiving the pressing force F from the rack teeth 3b of the piston 3 when the piston is retracted, the engagement state of the rack teeth 3b with respect to the teeth 5a of the pawl member 5 is disengaged. Since the moment MA ′ acts, a force is exerted on the pole member 5 so as to cause the pole member 5 to protrude outside (ie, outside the housing) from the pole hole 2b.
[0046]
On the other hand, in the present embodiment, when the piston retreats, the moment MA acts in a direction in which the engagement state between the teeth 5a of the pawl member 5 and the rack teeth 3b becomes stronger. A force that tries to protrude outward from the pole hole 2b does not act on the pole member 5, so that it is possible to reliably prevent the pole member from protruding from the pole hole to the outside of the housing when the piston is retracted.
[0047]
Moreover, in this case, as shown in FIG. 5 (b), among the tooth surfaces forming the tooth portions 5a of the pawl member 5, the tooth surface s on the side that engages with the rack teeth 3b when the piston retreats is the surface of the piston. The angle θ formed with the axial direction L is greater than 90 degrees when measured from the front in the axial direction. That is, θ> 90 °
It has become. In FIG. 5B, for convenience of illustration, the angle θ in FIG. 5A is exaggerated and drawn large.
[0048]
In FIG. 5 (b), the pressing force acting on the tooth surface s is f, and the force f is decomposed in the axial direction of the piston and in the direction orthogonal thereto, and the respective component forces are f ₁ and f _2. as can be seen, the component force f ₂ is the tooth surface s of the pawl member 5 downward, i.e. which act on the side of the rack teeth of the piston, this component force f _2, pole member 5 is the housing 2 From the pole hole 2b. In the conventional hydraulic tensioner, the angle θ is set to 90 degrees or smaller than 90 degrees. Therefore, when the piston retreats, the pressing force against the tooth surface of the pole member causes the pole member to move to the pole member. In some cases, it acted on the side that protruded from the hole.
[0049]
Also, in this case, the clearance δ is provided between the rearmost tooth portion 5a and the rack tooth 3b of the piston 3, so that the thickness is relatively thin and the strength is lower than the other tooth portions. It is possible to prevent the pressing force from the rack teeth 3b from acting on the rearmost tooth portion 5a, thereby preventing the rearmost rack tooth from being damaged or the like.
[0050]
In the above-described embodiment, the most preferred embodiment in which the point A of the pole member 5 is disposed below the line of action m of the pressing force F has been described as an example, but the application of the present invention is not limited to this. The point A of the pole member 5 may be disposed above the line of action m of the pressing force F. In this case, the moment around the point A has the same direction as the moment around the point A 'of the conventional pole member 5, but the moment around the point A' is smaller than the moment around the point A 'because the distance from the action line m is shorter. Can be reduced in size. Thereby, when the piston 3 retreats, the tooth portion 5a of the pawl member 5 can be suppressed from separating from the rack teeth 3b of the piston 3 as compared with the related art.
[0051]
In the above embodiment, the case where the concentrated load F acts as the pressing force acting on the teeth 5a of the pawl member 5 from the rack teeth 3b of the piston 3 when the piston 3 retreats has been described as an example. Is not limited thereto, and may be a distributed load distributed in a plane along both tooth surfaces. In this case, the action line of the resultant force of the distributed load may be obtained as the action line m of the load F.
[0052]
Further, in the above-described embodiment, the example in which the spring force is applied to the pole member 5 by the leaf spring-shaped pole spring 6 has been described, but a coil spring may be adopted as the pole spring. In this case, the coil spring is provided, for example, so as to be pressed against the front end face side of the pole member 5. When the pole member 5 moves, the coil spring expands and contracts in accordance with the movement of the pole member 5.
[0053]
【The invention's effect】
As described above, according to the present invention, the thickness of the last tooth portion of the pole member is made smaller than the thickness of the other tooth portions, so that the pole member can be reliably prevented from jumping out of the housing. Further, according to the present invention, among the tooth surfaces constituting the tooth portion of the pole member, the angle formed by the tooth surface on the side engaging with the rack teeth of the piston when the piston is retracted with respect to the axial front of the piston is larger than 90 degrees. Accordingly, there is an effect that the pole member can be reliably prevented from protruding outside the housing.
[Brief description of the drawings]
FIG. 1 is an overall perspective view of a hydraulic tensioner according to an embodiment of the present invention.
FIG. 2 is a longitudinal sectional view of a hydraulic tensioner (FIG. 1).
FIG. 3 is a view taken in the direction of arrow III in FIG. 2;
FIG. 4 is an enlarged perspective view of a pole hole portion of a housing in the hydraulic tensioner (FIG. 1).
5A is an enlarged front view of a pole member in the hydraulic tensioner (FIG. 1), and FIG. 5B is an exploded view of a force acting on a tooth surface s of the pole member.
[Explanation of symbols]
1: hydraulic tensioner 2: housing 2a: (piston) hole 25: inner wall surface 25 ': conventional inner wall surface 3: piston 3a: inner space 3b: rack teeth 30: fluid chamber 4: piston spring 5: pole member 5a: Tooth portion 5c: rear end surface 5c ': conventional rear end surface 6: pole spring F: pressing force m: action line te: tooth thickness of last tooth portion to: tooth thickness of other tooth portions pe: last tooth tooth Distance between the tooth portion and the tooth portion on the front side thereof po: Distance between the tooth surfaces of other adjacent tooth portions in the front-rear direction δ: Clearance θ: Angle formed by the tooth surface with the axis

Claims (5)

A hydraulic tensioner for applying tension to the chain,
A housing having a hole opened at one end;
A hollow piston slidably inserted into the hole and having an internal space forming a fluid chamber between the hole and a rack tooth formed on at least a part of the outer periphery;
A piston spring for urging the piston in a projecting direction,
A pawl member having a tooth portion for engaging with the rack teeth of the piston and allowing movement of the piston in a protruding direction and preventing movement of the piston in a retreating direction;
A pole spring for biasing the pawl member on a side where the tooth portion of the pawl member engages with the rack teeth;
The thickness of the last tooth portion of the pole member is smaller than the thickness of the other tooth portions,
A hydraulic tensioner characterized in that: In claim 1,
A clearance is formed between the tooth surface of the tooth portion at the rearmost end of the pole member and the tooth surface of the rack tooth of the corresponding piston.
A hydraulic tensioner characterized in that: In claim 1,
The distance between the tooth surface of the tooth portion at the rearmost end of the pole member and the tooth surface of the tooth portion one forward of the pole member is the distance between the tooth surfaces of other tooth portions adjacent in the front-rear direction. Is larger than
A hydraulic tensioner characterized in that: In any one of claims 1 to 3,
Among the tooth surfaces forming the tooth portion of the pawl member, the angle formed by the tooth surface on the side engaging with the rack teeth of the piston when the piston retreats in the axial front of the piston is greater than 90 degrees. Is growing,
A hydraulic tensioner characterized in that: A hydraulic tensioner for applying tension to the chain,
A housing having a hole opened at one end;
A hollow piston slidably inserted into the hole and having an internal space forming a fluid chamber between the hole and a rack tooth formed on at least a part of the outer periphery;
A piston spring for urging the piston in a projecting direction,
A pawl member having a tooth portion for engaging with the rack teeth of the piston and allowing movement of the piston in a protruding direction and preventing movement of the piston in a retreating direction;
A pole spring for biasing the pawl member on a side where the tooth portion of the pawl member engages with the rack teeth;
Among the tooth surfaces forming the tooth portion of the pawl member, the angle formed by the tooth surface on the side engaging with the rack teeth of the piston when the piston retreats in the axial front of the piston is greater than 90 degrees. Is growing,
A hydraulic tensioner characterized in that:

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