JP2682801B2 - Auto tensioner - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an automatic tensioner which attenuates a belt reaction force as an external force while applying a tension to a timing belt of an automobile engine or a driving belt for accessories, for example, and more particularly to simplifying a damping mechanism. About measures.

[0002]

2. Description of the Related Art Conventionally, as this type of auto tensioner, a hydraulic type auto tensioner has been widely used, and an example thereof is disclosed in Japanese Utility Model Laid-Open No. 4-66448.

In this apparatus, a cylinder body filled with hydraulic oil, a piston reciprocally fitted into the cylinder body and partitioning the cylinder body into first and second oil chambers, A piston rod whose inner end is integrally connected to the piston by penetrating an end wall of the cylinder on the first oil chamber side, and a first rod which is compressed and contracted in the second oil chamber so that the cylinder extends; And a compression coil spring that urges and presses toward the oil chamber. The piston and the cylinder are each provided with a communication path that connects the two oil chambers to each other, and the piston-side communication path is provided with a check valve.

In the above-described check valve, the piston moves in the direction opposite to the biasing direction of the compression coil spring due to the action of an external force in the contracting direction of the cylinder, and the hydraulic oil in the second oil chamber will flow into the first oil chamber. When the cylinder is extended, the piston moves in the biasing direction and the hydraulic oil in the first oil chamber attempts to flow into the second oil chamber. When it does, it operates so as to open the communication passage to allow the movement of the piston. Thus, when the piston is pressed in a direction opposite to the biasing direction and an external force in the cylinder contraction direction is applied to the tip of the piston rod, the movement of the piston is suppressed, and thus the external force is attenuated. ing.

[0005]

However, the hydraulic auto-tensioner has several problems as described below, and it is required to solve those problems.

(1) Since the flow resistance of hydraulic oil is used, a high sealing property is required and the structure becomes complicated. Therefore, the number of parts tends to increase, and it takes time and effort to assemble, and it is difficult to reduce the cost.

(2) When an excessive external force is applied, the pressure of the hydraulic oil increases in proportion to the external force, and the auto tensioner itself may be damaged by high pressure.

(3) Since the damping characteristic is determined by the flow path resistance of the communication passage, the check valve, and the like, it is difficult to change and adjust the damping characteristic in an auto tensioner in which a predetermined damping characteristic is already set. And therefore
To change the damping characteristics, the auto tensioner itself must be replaced.

(4) Regarding the damping characteristic, the viscosity characteristic of the hydraulic oil is easily affected by the temperature change. For example, the flow resistance of the hydraulic oil increases at a lower temperature than at a normal temperature and the damping force becomes larger than a predetermined value. .

(5) Since the damping mechanism operates in its length direction, if a tension pulley is directly attached to the distal end of the piston rod to press the belt, the base end of the damping mechanism is moved from the engine. Since it protrudes toward the side, the damping mechanism must be arranged along the running direction of the belt.

(6) Damping mechanism and operating direction changing member 2
To attach two parts to the engine,
It takes time to install.

The present invention has been made in view of the above points, and its main purpose is to use a pulley member and a friction member such as a belt wound around the pulley member to reduce the number of parts. It is easy to assemble and reduce the cost, while providing a fail-safe function against excessive external force, facilitating tuning and setting of damping characteristics and reducing temperature dependence. The purpose is to simplify the work of attaching to the engine while achieving the improvement.

[0013]

In order to achieve the above object, the present invention provides that when the tensions of both spans of an endless friction member wound between two pulley members change,
By utilizing the fact that the grip force between the pulley member and the friction member changes, and by changing the grip force according to the external force to be damped, a damping force corresponding to the external force can be obtained. The number of parts can be reduced and assembly work can be facilitated to contribute to cost reduction.On the other hand, excessive external force can be dealt with by slipping between the pulley member and the friction member, and the span tension can be changed. The damping characteristic can be easily tuned by adjusting the rate, and the temperature dependence is reduced because hydraulic oil is not required. Furthermore, the size of the engine can be reduced while simplifying the installation work on the engine. I made it possible.

Specifically, a fixing member fixed to the fixed side and having a substantially arcuate friction surface and a shaft portion provided coaxially with the arc center of the friction surface and a eccentric position with respect to the center. An opening through which the shaft member is inserted is formed,
With respect to the fixed member with the arc center of the friction surface as the center of rotation
An eccentric cylindrical body which is supported to be freely eccentrically rotated Te, a tension pulley rotatably supported on the outer peripheral side of the eccentric cylindrical body, the rotation urging in a predetermined direction with respect to the fixed member the eccentric cylindrical body Elastic member, a tension converting member that is eccentrically supported rotatably on the end face of the eccentric cylinder, and has a substantially arc-shaped friction surface that is paired with the friction surface of the fixing member on the outer periphery, and the fixing member. And an endless belt wound around the friction surface of the tension converting member and the friction surface of the tension converting member. Further, the eccentric rotation center of the tension conversion member is the same as the rotation biasing direction of the elastic member with respect to a straight line connecting the arc center point of the friction surface of the fixed member and the arc center point of the friction surface of the tension conversion member. The tension converting member is set at a position deviated to the direction side, and a biasing member for biasing the tension converting member outwardly so as to apply an initial tension to the belt about its eccentric rotation center is provided.

According to a second aspect of the present invention, in the auto tensioner according to the first aspect, the eccentric cylinder is directed in a direction opposite to the eccentric direction of the eccentric rotation center of the tension converting member by the external force acting on the tension pulley. The eccentric cylinder rotates toward the eccentric direction of the eccentric rotation center of the tension conversion member due to the urging force of the elastic member that acts on the eccentric cylinder toward the member that slides with the belt when rotating. When the eccentric cylinder rotates due to an external force acting on the tension pulley, the eccentric cylinder rotates in a direction opposite to the eccentric direction of the eccentric rotation center of the tension conversion member. Is provided with a one-way restricting means that allows the occurrence of

According to a third aspect of the present invention, in the auto tensioner according to the second aspect, the friction surface of the eccentric cylinder and the friction surface of the tension converting member are set so as to have different radii of curvature, and act on the tension pulley. When the eccentric cylinder rotates in the direction opposite to the eccentric direction of the eccentric rotation center of the tension converting member due to an external force, the side of the eccentric cylinder and the tension converting member that has a friction surface with a small radius of curvature. The slippage between the belt and the belt occurs. Then, the one-way regulating means is configured to press the belt against the member having the friction surface having the small radius of curvature of the eccentric cylinder and the tension converting member.

According to a fourth aspect of the present invention, in the auto tensioner according to the second aspect, the friction surface of the eccentric cylinder and the friction surface of the tension converting member are set so that the friction coefficients with the belt are different from each other, When the eccentric cylinder rotates in the direction opposite to the eccentric direction of the eccentric rotation center of the tension converting member due to the external force acting on the tension pulley, the friction of the above-mentioned friction coefficient of the eccentric cylinder and the tension converting member is small. Sliding occurs with the belt on the side of the member having the surface. Then, the one-way restricting means is configured to press the belt against the member having the friction surface having the small friction coefficient among the eccentric cylinder and the tension converting member.

According to a fifth aspect of the present invention, a damping force corresponding to the urging force of the elastic member and the external force acting on the tension pulley can be obtained for rotation in both directions.
Specifically, a fixed member fixed to the fixed side and having a substantially arc-shaped friction surface and a shaft portion provided coaxially with the arc center of the friction surface, and the shaft member at a position eccentric to the center. An opening is formed through which the friction surface of
Eccentric rotation with respect to the fixed member around the arc center
An eccentric cylindrical body supported on standing, and a tension pulley rotatably supported on the outer peripheral side of the eccentric cylindrical body, and an elastic member which rotates biased in a predetermined direction with respect to the fixed member the eccentric cylindrical body ,
A first tension converting member that is eccentrically supported rotatably on the end surface of the eccentric cylinder and has a substantially arc-shaped friction surface on the outer periphery that forms a pair with the friction surface of the fixed member, and the end surface of the eccentric cylinder. A second tension converting member that is rotatably supported eccentrically and that has a substantially arcuate friction surface that is paired with the friction surface of the fixing member on the outer periphery; the friction surface of the fixing member and the first tension converting member. And an endless second belt wound between the friction surface of the fixed member and the friction surface of the second tension converting member. Further, the eccentric rotation center of the first tension converting member is rotated with respect to a straight line connecting the arc center point of the friction surface of the first fixing member and the arc center point of the friction surface of the first tension converting member. The eccentric rotation center of the second tension converting member is set to a position deviated to the same direction as the dynamic urging direction, and the eccentric rotation center of the second tension converting member is set to the arc center point of the friction surface of the second fixing member and the friction surface of the second tension converting member. Of the elastic member is set to a position deviated to the direction opposite to the rotational biasing direction of the elastic member with respect to a straight line connecting the center point of the circular arc, and the first tension converting member is centered on its eccentric rotational center. A first urging member that urges outwardly to apply initial tension to the second belt, and the second tension converting member outwardly to apply initial tension to the second belt about its eccentric rotation center. A second biasing member that biases the rotation is provided.

[0019] The invention according to claim 6 is the invention according to claim 1,
In the auto tensioner according to 2, 3, 4 or 5,
The position of the center of gravity of the tension converting member should be outside the locus of movement of the center of eccentric rotation of the tension converting member when the eccentric cylinder rotates.
The configuration is set on the lap side .

[0020]

According to the above construction, the following effects can be obtained in the present invention. According to the first aspect of the invention, when the urging force acts on the eccentric cylinder by the elastic member so as to rotate the eccentric cylinder in the eccentric direction of the eccentric rotation center of the tension converting member, the fixing member. Is unrotatable, the tension of the span of the belt located in the direction opposite to the eccentric direction tends to rise according to the magnitude of the urging force. However, this increase in tension is caused by the tension conversion member rotating about the eccentric rotation center as a rotation center in the direction in which the distance between the arc centers of the friction surfaces of the fixed member and the tension conversion member is reduced. Be absorbed. For this reason, the tension of the belt does not increase, slippage occurs between at least one of the fixing member and the tension converting member and the belt, and the rotation of the eccentric cylinder is allowed. That is, the damping force in the turning direction is small.

On the other hand, when an external force acts on the eccentric cylinder so as to rotate the eccentric cylinder in a direction opposite to the eccentric direction of the eccentric rotation center of the tension converting member, the fixing member cannot rotate. Therefore, the tension of the span of the belt located in the eccentric direction increases according to the magnitude of the external force. Then, the amount of increase in the tension is the rotational force by which the tension conversion member rotates about the eccentric rotation center as a rotation center in a direction of increasing the distance between the arc centers of the friction surfaces of the fixed member and the tension conversion member. Becomes However, since the tension conversion member cannot rotate unless the belt is stretched, this turning force increases the tension of the span of the belt located in the direction opposite to the eccentric direction, and the tension of the belt as a whole is increased. As a result, the pressure applied to the fixing member and the tension converting member of the belt increases, and a high gripping force is generated between these members. For this reason, a large damping force (rotational reaction force) is generated with respect to the external force acting on the eccentric cylinder, and the eccentricity is generated unless slip occurs between at least one of the fixing member and the tension converting member and the belt. The rotation of the cylinder will be blocked. That is, the damping force in the rotating direction is set to be large.

Then, as the external force acting on the eccentric cylinder,
When a large external force that overcomes the grip force between the fixing member and the tension converting member and the belt is applied, slippage occurs between at least one of the fixing member and the tension converting member and the belt, which causes eccentricity. The cylindrical body will start to rotate.

The damping mechanism has a simple structure similar to a belt transmission mechanism in which a transmission belt is wound between two pulleys, so that the number of parts is small and assembly is easy. Further, since the damping force changes in accordance with the change in the tension of each span, the damping characteristic can be changed by adjusting the amount of change in the tension of the span, so that the setting change of the damping characteristic is easy. Further, since a damping force is generated without using an operating body such as a working oil whose characteristics are easily changed by temperature, a stable damping characteristic with respect to a temperature change can be obtained. Further, a fail-safe function is provided by slipping between at least one of the fixing member and the tension converting member and the belt against an excessive external force. In addition, since a piston rod such as a hydraulic damping mechanism is not required, downsizing can be achieved, and since only one mounting point is required on the fixed side, the mounting operation can be simplified.

According to the second aspect of the invention, the one-way restricting means causes the belt to slip when the eccentric cylinder is rotated in the eccentric direction of the eccentric rotation center of the tension converting member by the external force acting on the tension pulley. While the occurrence of the belt is restricted, the occurrence of belt slippage is allowed when the eccentric cylinder rotates in the direction opposite to the eccentric direction of the eccentric rotation center of the tension converting member. That is, the belt circulates between the fixing member and the tension converting member in one direction as the eccentric cylinder reciprocates. For this reason, since the contact portion of the belt with respect to the fixing member and the tension converting member is changed, only a part of the belt is always in contact with each friction surface of the fixing member and the tension converting member and locally deteriorates. This can be avoided, and the life of the belt can be extended.

According to the third and fourth aspects of the present invention, when the eccentric cylinder body is rotated in the direction opposite to the eccentric direction of the eccentric rotation center of the tension conversion member by the external force acting on the tension pulley, the eccentric cylinder moves with the belt. Set the member on the side where slippage occurs between
It can be performed by a simple and highly practical configuration.

In the fifth aspect, the operation according to the first aspect of the invention can be obtained in both directions of rotation of the eccentric cylinder. That is, it is possible to obtain a high damping force in both directions of rotation of the eccentric cylinder. Further, according to this configuration, since the damping characteristic can be changed by adjusting the tension change amount of the span of each belt, it is easy to change the setting of different damping characteristics in both directions of the rotating direction of the eccentric cylinder. .

According to the sixth aspect of the invention, when the external force to be damped acting on the eccentric cylinder is an impact load, the center of gravity of the tension converting member has a center of gravity of the tension converting member when the eccentric cylinder rotates. Since the eccentric rotation center is located on the outer peripheral side with respect to the movement locus, the tension converting member is rotated by the inertial force so as to increase the tension of the span of the belt located in the direction opposite to the eccentric direction. Try to increase the axial load. In the span of the belt located in the direction opposite to the eccentric direction, as described above, the belt is elevated at a predetermined rate with the increase in the tension of the span of the belt located in the eccentric direction. In this way, the factors that increase the axial load occur at two locations and the axial load increases,
When an impact load is applied, the grip force between the belt and the fixing member and the tension converting member is larger than that when a static load is applied, and a large damping force can be generated. As a result, it is possible to avoid the situation in which the eccentric cylinder body accidentally rotates with respect to the impact load.

[0028]

EXAMPLE Next, the auto tensioner according to the present invention was
It will be described when applied as to impart a predetermined tension to the timing belt for the camshaft drive in the HC engine.

1 to 3 show the entire structure of the automatic tensioner according to this embodiment, and FIG. 1 shows the front side of the automatic tensioner (the side not facing the engine block 16).
2 is a sectional view taken along line II-II in FIG. 1 (the lower side is the front side, the upper side is the rear side), and FIG. 3 is the sectional view in FIG.
A sectional view along the line III-III (front is on the left and rear is on the right). FIG. 4 shows an exploded perspective view of this auto tensioner.

As shown in each of these figures, this autotensioner is mounted on a fixing member 11 fixed to an engine block 16 of an automobile engine, and is mounted on the fixing member 11 at a position eccentric to the central axis O1. Eccentric cylinder 13
And a torsion coil spring 17 as an elastic member that is compacted between the fixing member 11 and the eccentric cylinder body 13 and biases the eccentric cylinder body 13 in the counterclockwise direction of FIG. A tension converting member 12 rotatably supported by the eccentric cylinder 13 about a rotation axis O3; a belt 14 stretched around the fixing member 11 and the tension converting member 12;
3, and a tension pulley 18 for applying a predetermined tension to a timing belt 19 for driving the cam shaft of the engine. Hereinafter, each member will be described in detail.

The fixing member 11 includes a first fixing member 11a located on the front side and a second fixing member 1 located on the rear side.
1b are integrally assembled. The first fixing member 11a is a relatively large-diameter and flat disk-shaped pulley portion 11a.
and a shaft portion 11d having a relatively small diameter and a longer length than the pulley portion 11c on the rear side of the pulley portion 11c.
And a through hole 11e penetrating through each central portion from the pulley portion 11c to the shaft portion 11d. The outer peripheral surface of the pulley portion 11c is
Is applied to the friction surface 11f. The second fixing member 11b has a bottomed cylindrical cup shape with an opening on the front side (lower side in FIG. 2, left side in FIG. 3), and its central portion is integrated with the rear side end portion of the shaft portion 11d. Installed in place. Further, the second fixing member 11b is fixed with its rear side surface in contact with the engine block 16, whereby the entire fixing member 11 is fixed to the engine block 16. A spring rear end locking hole 11g extending in the radial direction and penetrating through the peripheral wall is formed at a position near the bottom of the peripheral wall of the second fixing member 11b.

The eccentric cylinder 13 is a cylindrical member and has an opening 13a at a position eccentric with respect to its center point O2, and the shaft portion 1 of the fixing member 11 is provided in this opening 13a.
1d is inserted through the sleeve member 20. Thereby, the eccentric cylinder 13 is connected to the shaft portion 11 of the fixing member 11.
It is rotatably supported around d by a predetermined amount of eccentricity (eccentricity t2). The rear side end of the eccentric cylinder 13 has a bottomed cylindrical cup shape with the rear side (upper side in FIG. 2, right side in FIG. 3) opened so as to face the second fixing member 11b. A spring front side end locking hole 13b extending in the radial direction and penetrating the peripheral wall is formed at a position near the bottom of the peripheral wall. Also, this eccentric cylinder 13
A shaft hole 13c for rotatably supporting the tension converting member 12 is formed on the front end face of the.

The main body of the torsion coil spring 17 is the rear end 1
The rear end 17a is formed to have a left-hand winding from the front side to the front end 17b from the front side, and is located on the rear side.
Is in the spring rear end locking hole 11g of the second fixing member 11b,
The front end 17b located on the front side is the eccentric cylinder 1
3 are respectively fitted into the spring front side end locking holes 13b and compressed, so that the eccentric cylinder body 13 is moved in a predetermined direction with respect to the fixing member 11 (counterclockwise direction in FIG. 1).
To be urged to rotate.

The tension pulley 18 is rotatably supported on the outer peripheral portion of the eccentric cylinder 13 via a bearing B3.
Timing belt 1 hung between a crankshaft (not shown) of the engine and a cam pulley to drive the camshaft
9 is wound around as shown by an imaginary line in FIG. 1, and the urging force of the torsion coil spring 17 presses the timing belt 19 to give a predetermined tension.

The tension converting member 12 is, as shown in FIG.
A rotating shaft 12b protruding from the back side of a base portion 12a made of a substantially crescent-shaped plate is fitted into a shaft hole 13c of the eccentric cylinder body 13 and is rotatable around the rotating shaft 12b. There is. Further, a friction plate portion 12c having a substantially arc-shaped outer peripheral surface extending toward the front side is integrally formed with the outer peripheral edge portion of the base portion 12a, and the outer peripheral surface of the friction plate portion 12c becomes a friction surface 12d. I have.

A characteristic of the tension converting member 12 is that its rotation center O3 is eccentric to the center point O2 of the eccentric cylinder 13 downward by a predetermined dimension t1 in FIG. More specifically, the position of the rotating shaft 12b protruding from the back surface of the base portion 12a is set to a position near one side in the longitudinal direction of the base portion 12a. For this reason,
When the tension converting member 12 rotates in the clockwise direction in FIG. 1 around the eccentric axis O3, the tension converting member 1
The center of the arc of the second friction surface 12d (O2 in the state shown in FIG. 1)
And a central point O1 of the fixing member 11.
When the counterclockwise rotation is performed while the distance t2 between the center of the arc and the center point O1 of the fixing member 11 is reduced.
Is increased.

The belt 14 is stretched over the friction surfaces 11f and 12d of the fixed member 11 and the tension conversion member 12.

An initial tension applying spring 15 as a biasing member for applying a predetermined initial tension to the belt 14 is provided between the fixing member 11 and the tension converting member 12. Specifically, a concave portion 11h for inserting a spring is formed at a position facing the tension converting member 12 on a part of the outer peripheral surface of the pulley portion 11c of the fixing member 11, and the initial tension formed by a coil spring is formed in the concave portion 11h. The initial tension applying spring 15 is housed between the bottom of the concave portion 11h and the inner surface of the friction plate portion 12c of the tension converting member 12. Therefore, the urging force of the initial tension applying spring 15 is
It acts as a force for rotating the tension converting member 12 about the eccentric axis O3 in the counterclockwise direction in FIG. That is, the center of the arc of the tension conversion member 12 and the center point O1 of the fixed member 11
A predetermined tension is applied to the belt 14 by a rotational urging force in a direction to increase the distance between the belt 14 and the belt 14.
Is obtained as an initial tension in a state where no external force is applied. Further, the biasing force of the initial tension applying spring 15 is set to a value such that a predetermined frictional force is obtained between the friction surfaces 11 f and 12 d of the fixing member 11 and the tension conversion member 12 and the belt 4. .

Next, the operation of the automatic tensioner for the tamming belt constructed as described above will be described. still,
Here, the pulley portion 11c of the fixing member 11 and the eccentric cylinder 1
In the belt 14 stretched around the second friction plate portion 12c, the tension of the lower span in FIG. 1 is T1 and the tension of the upper span is T2.

Since the eccentric cylinder body 13 is given a counterclockwise biasing force A in FIG. 1 by the biasing force of the torsion coil spring 17, the tension pulley 18 to which the timing belt 19 is applied is While applying a pressing force to the timing belt 19, the timing belt 19 rotates as the timing belt 19 runs.

Then, if loosening occurs in the portion of the timing belt 19 where the tension pulley 18 is in contact with the engine due to a change in the operating state of the engine from this state,
In order to absorb this looseness, the eccentric cylinder 13 is rotated counterclockwise in FIG. 1 by the urging force of the torsion coil spring 17. When this rotation occurs, the fixing member 11 is not rotatable, so that the tension T2 of the upper span tends to rise in accordance with the urging force of the torsion coil spring 17. However, this increase in tension is
The tension converting member 12 is absorbed by being rotated clockwise about the eccentric shaft O3 as a rotation center. That is, the center of the arc of the tension conversion member 12 and the center point O1 of the fixed member 11
The tension of the belt 14 does not rise because the tension converting member 12 rotates in the direction in which the distance dimension between and becomes smaller. As a result, the friction surfaces 11f and 12d of the fixing member 11 and the tension converting member 12 and the belt 14 are brought into contact with each other only by the initial tension applied by the initial tension imparting spring 15, and the above-mentioned interval dimension is reduced, Friction surfaces 11f and 12d of the fixing member 11 and the tension converting member 12
Slippage occurs between at least one of the
As a result, rotation of the eccentric cylinder 13 in the counterclockwise direction is allowed. That is, the timing belt 19
The eccentric cylinder 13 is rotated to a position where the tension of the coil is balanced with the urging force of the torsion coil spring 17, and the tension pulley 18 presses the timing belt 19 to absorb the looseness. Therefore, the tension of the timing belt 19 is always maintained at a stable value even when such looseness occurs, and the crank (not shown) in which the timing belt 19 is synchronously rotating. A stable synchronous rotation state can be obtained between the shaft and the cam pulley. In other words, in this auto tensioner, such a timing belt 1
In the rotating direction of the eccentric cylinder 13, which is required in a situation where the slack has occurred in 9, the damping force is hardly generated,
The tension maintaining operation of the timing belt 19 can be quickly performed.

On the other hand, when the tension of the portion of the timing belt 19 with which the tension pulley 18 is in contact increases with the change in the operating state of the engine from the above-mentioned state, the biasing force of the torsion coil spring 17 is increased. A large resisting force B is applied via the tension pulley 18 to the eccentric cylinder 13
Acts in the direction of turning clockwise in FIG. In this case, since the fixing member 11 cannot rotate, the tension T1 of the lower span is applied to the timing belt 19
Rise according to the amount of drag from. The increase in the tension T1 serves as a turning force for turning the tension converting member 12 counterclockwise about the eccentric shaft O3.
However, since the rotation of the tension converting member 12 is in the direction in which the distance between the center of the circular arc of the tension converting member 12 and the center point O1 of the fixing member 11 increases, the tension converting member 12 does not expand unless the belt 14 stretches. 12 cannot rotate. Therefore, this turning power increases the tension T2 of the upper span. That is, the turning force applied to the tension converting member 12 due to the increase in the tension T1 is converted into the tension T2.

In this way, the tension T2 also rises at a predetermined rate in proportion to the rise of the tension T1, so that the tension of the belt 14 as a whole increases, whereby the fixing member 11 and the tension converting member 12 of the belt 14 increase. Each friction surface 11f, 1
The pressure applied to 2d rises, and a high grip force is generated between these members. For this reason, a large damping force (rotational reaction force) is generated with respect to the force B from the timing belt 19 acting on the eccentric cylinder body 13, and the friction surfaces 11f of the fixed member 11 and the tension conversion member 12 are generated. Unless at least one of 12d and the belt 14 slips, the eccentric cylinder 13 is prevented from rotating in the clockwise direction.

Further, an axial load (arrow C in FIG. 1) acts on the eccentric shaft O3 of the tension converting member 12 as the above-mentioned high gripping force is generated. This axial load is the resultant of the tensions T1 and T2 of the upper and lower spans, and this load is
Is generated in a counterclockwise direction. This turning torque becomes a reaction force D acting in the opposite direction to the force B acting on the eccentric cylinder 13 from the timing belt 19. . In other words, the reaction force D also generates a large damping force (rotation reaction force) with respect to the force B acting on the eccentric cylinder 13, and the friction surfaces 11 f of the fixed member 11 and the tension conversion member 12. , 12d as long as no slippage occurs between the belt 14 and the eccentric cylinder 1
3 is prevented from rotating clockwise.

The force B exerted on the eccentric cylinder 13 from the timing belt 19 is a large force that overcomes the grip force between the friction surfaces 11f and 12d of the fixing member 11 and the tension converting member 12 and the belt 14. When the force acts, a slip occurs between at least one of the friction surfaces 11f and 12d and the belt 14, and as a result, the balance between the force B from the timing belt 19 and its reaction force D is lost, The eccentric cylinder body 13 starts to rotate in the clockwise direction. Further, the eccentric cylinder 1 due to the occurrence of such slippage
Since the damping force is generated due to the increase in the tensions T1 and T2 described above even at the time of rotation of the rotation of the eccentric cylinder 3, the amount of slip per unit time becomes small due to the balance between the external force B and the damping force. Gradually returns to the original position, and the timing belt 19 gradually returns to the original tension state.

That is, by suppressing the rotation of the eccentric cylinder 13 when the tension of the timing belt 19 increases, the tension can be controlled while avoiding the fluttering of the timing belt 19. That is, in the present auto-tensioner, a large damping force is generated in the rotating direction of the eccentric cylinder 13 in a situation where the tension of the timing belt 19 is increased, and the traveling of the timing belt 19 can be stably obtained. As a result, a stable synchronous rotation state between the crankshaft and the cam pulley can be obtained.

As described above, in the timing belt autotensioner of this example, the damping force for the rotation of the eccentric cylinder 13 in the direction to absorb the looseness of the timing belt 19 is small, and the tension of the timing belt 19 is small. The damping force with respect to the turning force applied to the eccentric cylinder 13 can be increased by the increase, and a high unidirectional damping characteristic can be obtained.

As described above, according to this embodiment, since the structure is similar to that of the belt transmission mechanism in which the transmission belt is wound between the two pulleys, the number of parts is small and the assembly is easy. Is. Furthermore, since the damping force changes in accordance with the change in the tension of each span, the damping characteristic can be changed by adjusting the amount of change in the span tension, and the setting of the damping characteristic can be easily changed. In addition, since the damping force can be generated without using an operating body whose operating characteristics such as hydraulic oil of a hydraulic auto tensioner are easily affected by a temperature change, a damping characteristic hardly affected by a temperature change can be obtained. . Further, a fail-safe function is provided by slipping between at least one of the fixing member and the tension converting member and the belt against an excessive external force. In addition, since a piston rod such as a hydraulic damping mechanism is not required, downsizing can be achieved, and since only one mounting point is required for the engine, the mounting operation can be simplified.

(Modifications) Next, three types of modifications in which the above-described auto tensioner is improved will be described. In addition, since the basic configuration of the auto-tensioner of each modified example is the same as that described above, in this modified example, particularly, only the components different from those described above will be described.

First, a modification of the first type will be described. In this modification, for example, the arc radius of the friction surface 12d of the tension converting member 12 is set to be smaller than the arc radius of the friction surface 11f of the fixed member 11. With this configuration, the belt in the friction surface 11f of the contact area is stationary member 11 of the belt 14 in the friction surface 12d of the tension converting member 12 14
Of the friction surface 12 of the tension converting member 12 when the eccentric cylinder 13 rotates.
The setting is such that slippage occurs between d and the belt 14 .

As a characteristic construction of this embodiment, a belt pressing member 31 as a one-way restricting means is attached to the tension converting member 12 as shown by an imaginary line in FIG. One end of the belt pressing member 31 is the tension converting member 1
The belt 14 is attached to the rear side surface of the belt 2, and the other end is bent to the front side and is set at a position facing the friction surface 12d of the tension converting member 12, and is hung on the friction surface 12d of the tension converting member 12. It abuts against the back surface and presses the belt 14 toward the friction surface 12d. Also, this belt 1
When the eccentric cylinder 13 rotates in the counterclockwise direction in FIG. 1, sliding force between the friction surface 12d of the tension conversion member 12 and the belt 14 causes the pressing force of pressing the No. 4 toward the friction surface 12d. The friction surface 11 of the fixed member 11 without generating
It is set to such a degree that slippage occurs between f and the belt 14 .

With this configuration, when the eccentric cylinder 13 rotates in the counterclockwise direction in FIG. 1 during the operation of the present autotensioner, the belt pressing member 31 acts on the friction surface 12d of the tension converting member 12. by preventing the occurrence of slippage between the belt 14, the eccentric cylindrical body 13 while sliding is generated between the friction surface 11f and the belt 14 of the fixing member 11 will be rotated. On the other hand, the eccentric cylinder 1
When 3 rotates in the clockwise direction in FIG. 1, the belt 14 is pushed up by the friction surface 12d of the tension converting member 12 due to the increase of the belt tension, so that the fixing member 11 and the tension converting member 12 of the belt 14 are pressed. The pressurizing force against is hardly affected by the belt pressing member 31. And
In such a contact state, the circular arc radius of the friction surface 12d of the tension converting member 12 is equal to the friction surface 11f of the fixed member 11.
For than the arc radius is small, without slippage occurs between the friction surface 11f and the belt 14 of the fixing member 11, a slip between the friction surface 12d and the belt 14 tension converting member 12 Occur. Such operation is performed by the eccentric cylinder 13
It occurs continuously with the reciprocating rotation of. That is, when the eccentric cylinder 13 rotates counterclockwise in FIG. 1, slippage occurs in the fixing member 11, and when the eccentric cylinder 13 rotates clockwise, the tension conversion member 12 moves. Since slippage occurs, the belt 14 circulates in the direction indicated by arrow E in FIG. Therefore, the contact portion of the belt 14 with respect to the fixing member 11 and the tension converting member 12 is changed, so that only a part of the belt 14 is always in contact with the fixing member 11 and the tension converting member 12 and locally deteriorates. It is possible to avoid such a situation, and it is possible to extend the life of the belt 14 .

Further, instead of the structure described above, the fixing member 1
The radius of the arc of the friction surface 11f of No. 1 is smaller than that of the friction surface 12d of the tension converting member 12, and the fixing member 1
In the case where the belt pressing member 31 is attached to 1, the tension converting member 12 slips when the eccentric cylinder 13 rotates in the counterclockwise direction in FIG. When rotating in the rotating direction, the fixing member 1
In this case as well, only a part of the belt 4 always has the fixing member 11 and the tension converting member 1 because slippage occurs at 1.
It is possible to prevent the belt 14 from coming into contact therewith and locally deteriorating, and it is possible to extend the life of the belt 14 .

Further, in this example, the friction surfaces 11f and 12d are
By making the arc radii different from each other, when the eccentric cylinder body 13 rotates in the counterclockwise direction in FIG. 1, the members 11 and 12 on the side where the belt pressing member 31 is arranged are caused to slip. However, by causing the friction coefficient between the friction surfaces 11f and 12d of the respective members 11 and 12 and the belt 14 to be different, slippage occurs in the members 11 and 12 on the side where the belt pressing member 31 is arranged. Can be made.

Next, a modification of the second type will be described. As shown in FIGS. 6 to 8, in this modification, a damping force is generated in both rotation directions of the eccentric cylinder body 13. Specifically, the height dimension of the pulley portion 11c of the fixed member 11 is set to be large, and the second tension conversion member 22 having a substantially symmetrical shape with respect to the tension conversion member (hereinafter referred to as the first tension conversion member) 12 is provided. The first tension converting member 12 is rotatably supported on the end surface of the eccentric cylinder 13 at a position O4 which is eccentric in the direction opposite to the eccentric direction of the rotating shaft O3. Further, as a second biasing member for biasing the second tension converting member 22 in the clockwise direction in FIG. 6 between the base end portion of the second tension converting member 22 and the eccentric cylindrical body 13. The second initial tension applying spring 25 is installed. Further, as shown in FIG. 7, the friction plate portion 22 of the second tension converting member 22 is
The height dimension of c is set to be larger than the height dimension of the friction plate portion 12c of the first tension converting member 12, and projects more frontward than the friction plate portion 12c of the first tension converting member 12.

Further, the first tension converting member 12 and the pulley portion 1
1c and the second belt 14 over the friction surface 11f.
The second belt 24 is stretched over the tension conversion member 22 and the friction surface 11f of the pulley portion 11c. That is, both belts 14 and 24 are arranged in parallel such that the second belt 24 is located on the front side with respect to the first belt 14.

With such a structure, the same action as the damping action described above is exerted by the gripping force of the belts 14 and 24. That is, when the eccentric cylinder 13 rotates in the clockwise direction in FIG. 6, the first belt 14 and the first tension conversion member 12 around which the first belt 14 is stretched.
Also, a damping force that suppresses rotation is generated by the fixing member 11, and conversely, when the eccentric cylinder 13 rotates in the counterclockwise direction in FIG. A damping force that suppresses rotation is generated by the second tension converting member 22 and the fixing member 11 that are present.

That is, according to the configuration of this example, the damping force can be exerted in both rotation directions, and the magnitude of each damping force is determined by the rotation axis of each tension converting member 12, 22. Since the eccentricity of O3 and O4, the types of the belts 14 and 24, and the magnitude of the rotational biasing force of the initial tension applying springs 15 and 25 can be arbitrarily set, the tension of the timing belt 19 is particularly set. The tension of the timing belt 19 is reduced by setting a relatively small damping force in the rotation direction when the tension of the timing belt 19 is increased and a large damping force in the rotation direction when the tension of the timing belt 19 is increased. The tension of the timing belt 19 is suppressed while suppressing the rapid change of the contact pressure of the tension pulley with respect to the timing belt 19 at the time of occurrence to suppress the deterioration of the timing belt 19. It will be able to stably obtain the travel at the time of rising.

Next, a modification of the third type will be described. In this modification, in particular, the damping characteristic is improved by changing the shape of the tension converting member 12. More specifically, as shown by a phantom line in FIG. 1, a weight member 32 is integrally attached to the upper end portion of the tension converting member 12. Specifically, the friction surface 1 of the tension converting member 12
A weight member 32 having a relatively large weight is attached to a portion of the edge portion of the width direction 2d which does not interfere with the belt 4. Further, a gap (not shown) for disposing the belt 4 is formed between the lower end of the weight member 32 and the friction surface 12d of the tension converting member 12. With such a configuration, the tension conversion member 12
The position of the center of gravity is located on the outer peripheral side with respect to the locus of movement of the eccentric rotation center O3 of the tension conversion member 12 when the eccentric cylinder 13 rotates.

Next, the damping operation by this configuration will be described. When the reaction force B from the timing belt 19 (arrow B in FIG. 1) acts and the reaction force B from the belt 19 is a static load without impact, it is different from the case of the above-described embodiment. Similarly, a predetermined damping force is obtained by the gripping force between the belt 4 and the fixing member 11 and the tension converting member 12 due to the increase in the belt tension.

On the other hand, when the reaction force from the belt 19 is an impact load, as described above, the position of the center of gravity of the tension converting member 12 is determined by the tension converting member when the eccentric cylinder 13 rotates. Since the eccentric rotation center of 12 is located on the outer peripheral side with respect to the movement locus of the eccentric rotation center, the tension converting member 12 tries to rotate in the counterclockwise direction in FIG. 1 about the eccentric axis O3 by its inertial force. . That is, the shaft load is increased. Further, of the two spans, the upper span in FIG. 1 is increased at a predetermined increase rate as the tension T1 of the lower span is increased by the action of the load, as described in the above embodiment. In this way, the factors that increase the axial load occur at two locations, so that when an impact load is applied, the tension T2 of the upper span is further increased compared to when a static load is applied. Become. For this reason, the grip force between the belt 4 and the fixing member 11 and the tension converting member 12 also becomes large, and a large damping force is generated as compared with the case where a static load is applied.

As described above, in the configuration of this example, the belt 19
When the reaction force from is an impact load, a large damping force can be generated with respect to that load, and the damping force can be dependent on the speed of the load. Therefore, it is possible to avoid the situation where the eccentric cylinder 13 is accidentally rotated.

[0063]

As described above, according to the present invention, the following effects can be obtained. According to the first aspect of the present invention, since an auto-tensioner having a damping characteristic obtained by substantially the same configuration as a belt transmission mechanism in which a transmission belt is wound around a pulley is realized, the number of parts is reduced by simplifying the structure. It requires less and is easy to assemble. Furthermore, since the damping force changes in accordance with the change in the tension of each span of the belt, the damping characteristic can be changed by adjusting the amount of change in the tension of the span, and the setting of the damping characteristic can be easily changed. . In addition, since the damping force can be generated without using an operating body whose operating characteristics such as hydraulic oil of a hydraulic auto tensioner are easily affected by a temperature change, a damping characteristic hardly affected by a temperature change can be obtained. .
Further, a fail-safe function can be provided by slipping between the fixing member or the tension converting member and the belt against an excessive external force. Further, since a piston rod such as a hydraulic damping mechanism is not required, the size can be reduced, and since only one mounting position is required on the fixed side, the mounting work can be simplified.

According to the second aspect of the invention, since the belt is circulated in one direction between the fixing member and the tension converting member as the eccentric cylinder rotates and reciprocates, the belt contacts the respective members. It is possible to change the part, and it is possible to prevent only a part of the belt from constantly contacting the fixing member and the tension converting member and locally deteriorating, and it is possible to extend the life of the belt.

According to the third and fourth aspects of the invention, when the eccentric cylinder body is rotated in the direction opposite to the eccentric direction of the eccentric rotation center of the tension converting member by the external force acting on the tension pulley, the belt is rotated. It is possible to set the member on the side where slippage occurs between and by a simple and highly practical configuration, the effect according to the invention of claim 2 can be reliably obtained, and the reliability of the device is improved. You can improve the property.

According to the fifth aspect of the invention, it is possible to obtain a high damping force in both directions of rotation of the eccentric cylinder. Further, according to this configuration, since the damping characteristic can be changed by adjusting the tension change amount of the span of each belt, it is easy to change the setting of different damping characteristics in both directions of the rotation of the eccentric cylinder. , The utility value as an auto tensioner can be greatly improved.

According to the sixth aspect of the invention, when an impact load is applied, compared to a case where a static load is applied,
Since the gripping force between the belt and the fixing member and the tension converting member is increased so that a large damping force can be generated, the eccentric cylinder may be inadvertently rotated with respect to an impact load. Can be avoided, and the reliability of the damping operation can be improved.

[Brief description of the drawings]

FIG. 1 is a front view showing an auto tensioner according to an embodiment.

FIG. 2 is a sectional view taken along line II-II of FIG.

FIG. 3 is a sectional view taken along line III-III of FIG. 1;

FIG. 4 is an exploded perspective view of the auto tensioner.

FIG. 5 is a perspective view of a tension converting member.

FIG. 6 is a view corresponding to FIG. 1 in a modification of the second type.

FIG. 7 is a view corresponding to FIG. 2 in a modification of the second type.

FIG. 8 is a view corresponding to FIG. 3 in a modification of the second type.

[Explanation of symbols]

 11 Fixed Member 11d Shaft Part 11f Friction Surface 12 Tension Conversion Member 12d Friction Surface 13 Eccentric Cylindrical Body 14 Belt 15 Initial Tensioning Spring (Biasing Member) 16 Engine Block (Fixed Side) 17 Torsion Coil Spring (Elastic Member) 18 Tension Pulley 31 Belt pressing member (one-way restricting means)

Claims (6)

(57) [Claims] 1. A fixing member fixed to a fixed side and having a substantially arcuate friction surface and a shaft portion provided coaxially with an arc center of the friction surface, and the shaft member at a position eccentric to the center. An opening through which is inserted is formed, and the center of rotation is the center of the arc of the friction surface.
As an eccentric cylinder rotatably supported by a fixed member, a tension pulley rotatably supported on the outer peripheral side of the eccentric cylinder, and the eccentric cylinder in a predetermined direction with respect to the fixed member. A tension converting member that is rotatably eccentrically supported by the end surface of the eccentric cylinder and has a substantially arcuate friction surface that forms a pair with the friction surface of the fixing member on the outer periphery. And an endless belt wound between the friction surface of the fixed member and the friction surface of the tension conversion member, and the eccentric rotation center of the tension conversion member is the arc center point of the friction surface of the fixed member and the tension. The tension converting member is set at a position deviated to the same direction as the rotational urging direction of the elastic member with respect to a straight line connecting the circular arc center point of the friction surface of the converting member, and the eccentric rotational center of the tension converting member is Outward to give initial tension to the belt as center Auto tensioner, characterized in that a biasing member for rotationally biased. 2. The automatic tensioner according to claim 1, wherein the eccentric cylinder is rotated by an external force acting on the tension pulley when the eccentric cylinder rotates in a direction opposite to the eccentric direction of the eccentric rotation center of the tension converting member. When the eccentric cylinder is rotated toward the eccentric direction of the eccentric rotation center of the tension converting member by the biasing force of the elastic member acting on the eccentric cylinder, the belt slips on the side where the slip occurs between the eccentric cylinders. While controlling the generation of the belt, the external force acting on the tension pulley allows the belt to slip when the eccentric cylinder rotates in the direction opposite to the eccentric direction of the eccentric rotation center of the tension converting member. An auto tensioner characterized by being provided with a direction regulating means. 3. The auto tensioner according to claim 2, wherein the friction surface of the eccentric cylinder and the friction surface of the tension converting member have different radii of curvature, and the eccentric cylinder is tensioned by an external force acting on the tension pulley. When the conversion member rotates in the direction opposite to the eccentric direction of the eccentric rotation center, the eccentric cylinder and the tension conversion member slide on the side of the member having the friction surface having the small radius of curvature with the belt. The one-way restricting means is configured to press the belt against the eccentric cylinder and the tension converting member having a friction surface having a small radius of curvature. And the auto tensioner. 4. The auto tensioner according to claim 2, wherein the friction surface of the eccentric cylinder and the friction surface of the tension converting member are set so that the friction coefficients with the belt are different from each other.
When the eccentric cylinder rotates in the direction opposite to the eccentric direction of the eccentric rotation center of the tension converting member due to the external force acting on the tension pulley, the friction of the above-mentioned friction coefficient of the eccentric cylinder and the tension converting member is small. Sliding occurs on the side of the member having the surface with the belt, and the one-way restricting means sets the belt to the eccentric cylinder and the tension converting member with respect to the member having the friction surface with the small friction coefficient. The automatic tensioner is characterized in that it is configured to press. 5. A fixing member fixed to a fixed side and having a substantially arcuate friction surface and a shaft portion provided coaxially with an arc center of the friction surface, and the shaft member at a position eccentric to the center. An opening through which is inserted is formed, and the center of rotation is the center of the arc of the friction surface.
As an eccentric cylinder rotatably supported by a fixed member, a tension pulley rotatably supported on the outer peripheral side of the eccentric cylinder, and the eccentric cylinder in a predetermined direction with respect to the fixed member. A first tension having an elastic member urged to rotate in the direction of the eccentricity, and an eccentric rotatably supported end surface of the eccentric cylinder body, and having a substantially arc-shaped friction surface that is paired with the friction surface of the fixed member on the outer periphery. A conversion member, a second tension conversion member eccentrically supported rotatably on the end face of the eccentric cylinder, and having a substantially arc-shaped friction surface on the outer periphery that makes a pair with the friction surface of the fixed member; The endless first belt wound between the friction surface of the member and the friction surface of the first tension conversion member, and the friction surface of the fixed member and the friction surface of the second tension conversion member. The endless second belt and the eccentric rotation of the first tension converting member. The center of motion is biased toward the same direction as the rotational urging direction of the elastic member with respect to the straight line connecting the arc center point of the friction surface of the first fixing member and the arc center point of the friction surface of the first tension converting member. On the other hand, the eccentric rotation center of the second tension converting member is a straight line connecting the arc center point of the friction surface of the second fixing member and the arc center point of the friction surface of the second tension converting member. On the other hand, the elastic member is set at a position deviated to the side opposite to the direction in which the elastic member is urged to rotate, and the first tension converting member is adapted to apply an initial tension to the first belt about its eccentric rotation center. A first urging member that urges outwardly, and a second urging member that outwardly urges the second tension converting member so as to apply initial tension to the second belt about its eccentric rotation center. An auto tensioner characterized by being provided with a biasing member. 6. The autotensioner according to claim 1, 2, 3, 4 or 5, wherein the position of the center of gravity of the tension converting member is
An auto tensioner, which is set on an outer peripheral side with respect to a movement locus of an eccentric rotation center of a tension converting member when the eccentric cylinder rotates.