JP7345256B2 - auto tensioner - Google Patents

Description

The present invention relates to an autotensioner for automatically maintaining belt tension at an appropriate level.

For example, in an accessory drive belt system or a camshaft drive belt system of an automobile engine, an autotensioner has conventionally been employed as a mechanism for keeping belt tension constant.

For example, as shown in FIG. 1 of Patent Document 1, an auto tensioner includes a base that is fixed to an engine block (not shown) and has a swing shaft attached thereto, and a base that is rotatably supported by the base via the swing shaft. a pulley that is rotatably attached to the arm via a rolling bearing around an axis parallel to the swing axis (axis R), a coil spring that biases the arm to rotate in one direction, and a cylindrical portion. has a sliding member interposed between the arm and the swing shaft. The sliding member has a function as a bearing and a damping part that damps the swing of the arm.

An autotensioner is a component that adjusts the tension of a belt wrapped around a pulley. As the tension of the belt increases or decreases, the pulley and the arm supporting the pulley swing about the axis R, but the swing is attenuated by the damping portion. This makes it possible to attenuate the swinging of the pulley and arm due to vibrations and impacts from the belt. When a movable member (hereinafter referred to as an arm) of an autotensioner rotates in a direction in which the tension of the belt increases and the belt is loosened, the rotation of the arm is greatly attenuated. Conversely, when the belt tension decreases and the arm rotates in the direction of tensioning the belt, the rotation of the arm is not attenuated and the decrease in belt tension is sufficiently followed.

In a so-called main engine autotensioner applied to a camshaft drive belt system, the belt system is a mesh transmission, and in order to suppress deviations in valve timing, it is better not to rotate the arm so much. On the other hand, when applied to an auxiliary drive belt system, the auxiliary drive belt system uses friction transmission, and the arm must rotate significantly to prevent excessive tension from being generated on the belt. . Therefore, when applied to a camshaft-driven belt system, it is more important than when applied to an accessory-driven belt system that the arm rotates in a direction that loosens the belt when belt tension increases. It is preferable to suppress the rotation of the arm by attenuating the rotation more significantly.

For example, the autotensioner disclosed in Patent Document 1 includes a spring clutch on the outer peripheral side of a coil spring that has a C-shaped cross section and is capable of expanding and contracting. Since the spring clutch has a self-elastic restoring force in the direction of diameter reduction, the coil spring is held down by the spring clutch on the outer peripheral side. Since the coil spring is in contact with the inner peripheral surface of the spring clutch, when the tension of the belt changes, frictional torque is generated at the contact surface of the coil spring and the spring clutch.

When the belt tension increases, the arm rotates in a direction to loosen the belt tension, and the coil spring expands in diameter. At this time, a large frictional torque acts between the coil spring and the spring clutch, and the rotation of the arm is strongly damped. Conversely, when the tension on the belt decreases, the torsional restoring force of the coil spring causes the arm to rotate in a direction that increases the tension on the belt, and at this time the diameter of the coil spring is reduced. At this time, since the friction torque between the coil spring and the spring clutch is lower than that described above, the rotation of the arm in the direction of increasing the belt tension is hardly affected by damping torque. In other words, an asymmetrical damping characteristic is obtained in which the rotation of the arm is greatly damped in the direction of weakening the belt tension, and the rotation of the arm is not so damped in the direction of increasing the belt tension.

Japanese Patent Application Publication No. 2017-180820

By the way, in order to improve the posture stability of the coil spring disposed between the arm and the base, it is preferable to bend both ends of the coil spring radially outward and securely fix them to the arm and the base, respectively. However, in the autotensioner of Patent Document 1, since the clutch is present on the outer peripheral side of the coil spring, one end and the other end of the coil spring cannot be bent radially outward. For this reason, it is necessary to devise ways to stabilize the posture by allowing the coil spring to twist and improving the position of the coil spring itself.

In Patent Document 1, the posture of the coil spring is stabilized by assembling the coil spring in an axially compressed state to an arm. However, since the coil spring is compressed and assembled, the length of the coil spring becomes substantially longer than when the coil spring is assembled without compression, resulting in an increase in manufacturing costs.

In addition, a spiral retaining groove whose depth changes in the circumferential direction with respect to the axial direction is formed on the arm to lock one end of the coil spring, and a spiral retaining groove whose height changes in the circumferential direction with respect to the axial direction is formed in the arm to lock one end of the coil spring. The pedestal was also formed on the base to hold the other end of the coil spring. However, in the axial direction, there is a region of approximately the first turn from one end surface of the coil spring (hereinafter referred to as the one end side region) and a region of approximately the first turn from the other end surface of the coil spring (hereinafter referred to as the other end side region). Compared to the case where the facing surfaces of the opposing arm and base are simply formed into a flat surface perpendicular to the axial direction, they are formed into a special spiral shape, so the parts of the arm and base are expensive and the manufacturing cost is low. It will increase.

Further, the other end surface of the clutch, which contacts the spiral pedestal formed on the base, is formed into a spiral shape so as to match the spiral shape of the rear surface of the other end side region of the coil spring. However, since the other end surface in the axial direction of the clutch is formed into a special spiral shape compared to a case where the other end surface in the axial direction is simply formed into a flat surface perpendicular to the axial direction, the price of clutch parts is high and manufacturing costs increase. Resulting in.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide an autotensioner that does not require special measures to stabilize the posture of a coil spring and can reduce manufacturing costs.

The auto tensioner of the present invention includes a base to which a swing shaft is attached, an arm rotatably supported with respect to the base via the swing shaft, and a base that rotates about an axis parallel to the swing shaft. a pulley that is freely disposed and can come into contact with the belt; and a coil spring that is disposed around the swing axis and urges the arm to rotate in one direction with respect to the base, and the coil spring is set to contract in diameter when the arm rotates in a direction opposite to the one direction in which the belt is loosened, and is further provided on the inner peripheral side of the coil spring, It has a cylindrical clutch member that contacts the diameter-reduced coil spring on its outer peripheral surface.

In the present invention, when the tension of the belt increases and the arm rotates in a direction opposite to the direction in which the arm is urged to rotate, that is, in a direction that loosens the belt, the coil spring contracts in diameter. Moreover, a clutch member is arranged on the inner peripheral side of the coil spring. Therefore, when the arm rotates in a direction to loosen the belt, the reduced diameter coil spring and the clutch member on the inner peripheral side of the coil spring come into strong contact, and a large damping torque acts on the arm. In other words, although the arrangement of the clutch member with respect to the coil spring is reversed from the inside and outside of Patent Document 1, the same point as in Patent Document 1 is that strong damping is applied when the arm rotates in the direction of loosening the belt. It is.

According to the above configuration, since the clutch member is arranged on the inner circumferential side of the coil spring, it is possible to easily fix the ends of the coil spring by bending both ends of the coil spring outward in the radial direction. Become. Therefore, there is no need for special measures to stabilize the posture of the coil spring as described above, and manufacturing costs can be reduced.

In the autotensioner of the present invention, it is preferable that the clutch member has a C-shaped cross section with a slit, and contacts the coil spring from the inner peripheral side by self-elastic restoring force in the diametrically expanding direction.

According to the above configuration, since the clutch member has spring properties and is always in contact with the inner peripheral surface of the coil spring, it is possible to reliably apply a damping torque to the arm.

In the autotensioner of the present invention, one end and the other end of the coil spring are bent radially outward, and each bent portion is locked in a holding groove formed in the arm and the base, respectively. Preferably.

In the present invention, since the clutch member is arranged on the inner peripheral side of the coil spring, both ends of the coil spring can be bent radially outward and fixed to the arm and the base. In other words, the posture of the coil spring can be stabilized by simply performing a simple end treatment and without any other special measures.

In the auto tensioner of the present invention, it is preferable that the clutch member is arranged such that the one end is a free end and a gap is secured between the clutch member and the arm.

According to the above configuration, one end of the clutch member is a free end, that is, not fixed to the arm. In addition, a gap is ensured between the clutch member and the arm. Therefore, while the coil spring repeatedly expands and contracts in diameter as the tension of the belt increases and decreases, it does not come into contact with the arm and generate sound. This prevents one end surface of the clutch member from coming into contact with the arm and inadvertently restraining the rotation of the arm. Further, since the axial length of the clutch member can be shortened compared to the case where there is no gap between the clutch member and the arm, the manufacturing cost of the autotensioner can be further suppressed.

In the auto tensioner of the present invention, it is preferable that the clutch member is arranged such that the other end is a free end and a gap is secured between the clutch member and the base.

According to the above configuration, the other end of the clutch member is a free end, that is, it is not fixed to the base. In addition, a gap is ensured between the clutch member and the base. Therefore, while the coil spring repeatedly expands and contracts in diameter as the tension of the belt increases and decreases, it does not come into contact with the base and generate sound. Moreover, since the axial length of the clutch member can be shortened compared to the case where there is no gap between the clutch member and the base, the manufacturing cost of the autotensioner can be further suppressed.

In the autotensioner of the present invention, it is preferable that the coil spring is compressed in the direction of the axis.

According to the above configuration, the coil spring can maintain a stable posture while repeatedly deforming to expand or contract in diameter as the tension of the belt increases or decreases. Further, the clutch member disposed on the inner circumferential side of the coil spring and in contact with the outer circumferential surface thereof can also maintain a stable posture.

In the autotensioner of the present invention, the arm may be eccentrically supported by the base, and the arm may be housed inside an outer peripheral surface of the pulley.

According to the above configuration, the autotensioner of the present invention is suitable for a camshaft drive belt system in which it is better not to rotate the arm significantly.

The autotensioner of the present invention does not require any special measures to stabilize the posture of the coil spring, and can reduce manufacturing costs.

8 is a sectional view taken along the line BB in FIG. 7. FIG. FIG. 2 is a sectional view taken along line EE in FIG. 1. FIG. FIG. 2 is an exploded perspective view of the autotensioner of this embodiment. 2 is a sectional view taken along line DD in FIG. 1. FIG. 3 is a sectional view taken along line AA in FIG. 2. FIG. FIG. 2 is a sectional view taken along the line CC in FIG. 1. It is a front view of an auto tensioner. 7 is a sectional view (corresponding to the FF sectional view in FIG. 9 and the BB sectional view in FIG. 7) of a state in which a fastening bolt is inserted into an autotensioner according to another embodiment. FIG. 7 is a front view of a state in which a fastening bolt is inserted into an autotensioner according to another embodiment.

Next, embodiments of the present invention will be described. This embodiment shows an example in which the present invention is applied to an autotensioner that maintains constant tension on the slack side of a meshing power transmission belt (that is, a timing belt) that drives a camshaft of an automobile engine. In such a camshaft drive belt system, an autotensioner that does not rotate the arm very much is preferably used.

As shown in FIG. 1, the autotensioner 100 of this embodiment includes a base 1 to which a swing shaft 6 is attached, an arm 2 rotatably supported with respect to the base 1 via the swing shaft 6, A pulley 3 is attached to the arm 2 and is rotatable around an axis parallel to the swing shaft 6 while being able to contact the transmission belt 101. The clutch member 5 is provided on the inner peripheral side of the coil spring 4 and comes into contact with the coil spring 4 on its outer peripheral surface. Note that the left side in FIG. 1 is one end side, and the right side is the other end side. The end surface on one end side is referred to as one end surface, and the end surface on the other end side is referred to as the other end surface. Further, the left-right direction in FIG. 1 is defined as the front-back direction. Further, counterclockwise rotation in FIGS. 2, 4, and 6 is defined as the X direction, and clockwise rotation is defined as the Y direction. The axis of the swing axis is defined as axis R.

(Base 1)
The base (fixing member) 1 is an attachment part that is fixed to an engine block (not shown), and is formed of a metal component made of a rolled steel plate or the like. As shown in FIG. 1, the base 1 includes a pedestal part 11 and a cylindrical part 12 extending forward from the outer edge of the pedestal part 11, and is provided coaxially with the axis R of the swing shaft. .

As shown in FIGS. 1 and 5, the pedestal part 11 has a base insertion hole 13 in the center of the pedestal part 11 through which a fastening bolt 62 is inserted around the axis R of the swing shaft 6, and a rear surface of the pedestal part 11 ( A protrusion 14 for positioning with respect to the engine block is provided on the rear surface). As shown in FIGS. 1 and 5, the front and rear surfaces of the pedestal portion 11 are formed into flat surfaces perpendicular to the front-rear direction. Note that, as shown in FIG. 3, a pin-shaped convex portion 15 may be formed on the front surface of the pedestal portion 11.

As shown in FIGS. 1 and 5, the cylindrical portion 12 is provided coaxially with the axis R of the swing shaft 6, and has a concave base extending rearward as shown in FIGS. 2, 4, 5, and 6. One holding groove 12a is formed. This is a groove into which a bent portion 42, which is a portion where the other end of the coil spring 4 is bent radially outward, is fitted and locked. In the base holding groove 12a, the other end of the coil spring 4 presses the base contact surface 12b of the base 1 in the circumferential direction of the swing shaft 6.

(Swing axis 6)
As shown in FIG. 1, the swing shaft 6 has a substantially cylindrical shape, and a flange 61 is formed at the front end. The swing shaft 6 is attached to the base 1 and is a support of the auto tensioner 100. An axis R, which is the axis of the swing shaft 6, extends in the front-rear direction. The rear surface of the swing shaft 6 is in contact with the front surface of the base 1 via a fastening bolt 62. The swing shaft 6 and the base 1 are prevented from rotating relative to each other in the circumferential direction. As shown in FIG. 3, recesses 64 are formed at two diagonal positions in the circumferential direction on the rear surface of the swing shaft 6, and the recesses 64 and the pin-shaped protrusion 15 formed on the front surface of the pedestal 11 are connected to each other. By fitting, the swing shaft 6 and the base 1 may be prevented from rotating. Incidentally, the pivot shaft 6 and the base 1 may be prevented from rotating by providing female screw portions at two circumferentially diagonal positions on the rear surface of the pivot shaft 6 and screwing them together from the rear surface of the base 1. The swing shaft 6 supports the arm 2 via a bush 7 so that the arm 2 can rotate around an axis R.

As shown in FIG. 1, a hole 63 extending in the front-rear direction is formed in the center of the swing shaft 6, and a fastening bolt 62 is inserted into the hole 63 so as not to be relatively rotatable. This fastening bolt 62 also serves as a fastening bolt for fixing the auto tensioner 100 to the engine block.

(Bush 7)
As shown in FIG. 1, this bush 7 is a substantially cylindrical bearing member. More specifically, a flange 71 is formed at the front end of the bush 7 and includes a cylindrical portion 72 and the flange 71 . The flange 71 is seated between the front surface of the arm 2 and the rear surface of the flange 61 of the swing shaft 6. This bush 7 has a bearing function for the swing shaft 6 (stabilizing wear and sliding resistance, etc.). Furthermore, since the coil spring 4 is housed in the spring housing chamber 9 in a compressed state in the front-rear direction, the bush 7 also has a function as a damping part that damps the swinging motion of the arm 2 and the pulley 3. . The bush 7 is preferably a metal bearing (so-called metal bearing), but may also be a resin bearing such as polyacetal resin or polyamide resin.

(Arm 2)
As shown in FIG. 1, the arm 2 is rotatably eccentrically supported by the base 1 via a swing shaft 6, and is formed of a metal component made of aluminum alloy casting or the like. The arm 2 is eccentrically supported by the base 1 and is housed inside the outer peripheral surface of the pulley 3. This arm 2 includes a boss portion 21 disposed on one end side of the base 1 and on the outer periphery of the cylindrical portion 72 of the bush 7, and an outer edge portion 24 extending radially outward from the boss portion 21. , an inner cylinder part 22 extending rearward from the boss part 21 , and an outer cylinder part 23 formed on the radially outer side of the boss part 21 and spaced parallel to the inner cylinder part 22 . The inner cylinder part 22 and the outer cylinder part 23 are provided coaxially with the swing shaft 6. An arm insertion hole 25 is provided on the inner peripheral side of the arm 2 at a position eccentric to the center of the pulley. The swing shaft 6 is inserted into the arm insertion hole 25 via the bush 7. The rear surface of the outer edge portion 24 of the arm 2, which faces the spring housing chamber 9 in the front-rear direction, is formed into a flat surface perpendicular to the front-rear direction. The arm 2 swings about the axis R of the swing shaft 6 as the tension of the belt 101 increases or decreases.

As shown in FIGS. 4 and 6, the outer cylindrical portion 23 of the arm 2 is formed with one concave arm holding groove 23a that extends forward. This is a groove into which a bent portion 41, which is a portion where one end of the coil spring 4 is bent radially outward, is fitted and locked.

As shown in FIG. 5, the inner circumferential surface of the outer cylindrical portion 23 of the arm 2 functions as a lower limit side rotation regulating wall surface 27 of the arm 2. As shown in FIG. By bringing the arm 2 into contact with the outer peripheral surface of the coil spring 4, the lower limit of the range in which the arm 2 is biased to rotate in the X direction by the coil spring 4 can be regulated. As a result, even if the tension of the belt 101 is excessively reduced and the coil spring 4 is deformed to expand in diameter, the remaining amount of the expansion deformation does not become zero. Therefore, after the auto tensioner 100 is assembled, the engaged state of both ends of the coil spring 4 can be maintained in a stable state without wobbling. Further, it becomes easier to assemble the auto tensioner 100 to the engine block and to wind the belt around the pulley. Specifically, the arm 2 biases the coil spring 4 to rotate in the The lower limit of the range can be set to an appropriate value when the auto tensioner 100 is assembled.

As shown in FIG. 5, the outer circumferential surface of the inner cylindrical portion 22 of the arm 2 functions as an upper limit side rotation regulating wall surface 26 of the arm 2. As shown in FIG. If the tension of the belt 101 increases excessively, there is a risk that the coil spring 4 will undergo excessive diameter reduction deformation and the auto tensioner 100 will malfunction. However, in order to prevent the auto tensioner 100 from malfunctioning, an arm is installed on the inner peripheral surface of the clutch member 5. 2 in contact with each other, the upper limit of the range in which the arm 2 can rotate in the Y direction relative to the base 1 against the rotation biasing force of the coil spring 4 can be regulated. Specifically, by setting the size of the gap between the inner circumferential surface of the clutch member 5 and the outer circumferential surface of the inner cylinder portion 22 of the arm 2 facing thereto, the arm 2 can absorb the rotational biasing force of the coil spring 4. The upper limit of the range of rotation in the Y direction against the tension can be set to an appropriate value when assembling the auto tensioner 100.

(Rolling bearing 8 and pulley 3)
As shown in FIG. 1, the pulley 3 is attached to the outer peripheral side of the boss portion 21 of the arm 2, and is rotatably supported by the boss portion 21 via a rolling bearing 8. A timing belt 101 is wound around the pulley 3. As the tension of the timing belt 101 increases or decreases, the pulley 3 (and the arm 2) swings around the axis R rather than the rotation center of the pulley 3.

(Spring storage chamber 9)
As shown in FIG. 1, the spring housing chamber 9 is formed between the base 1 and the arm 2. Specifically, it is surrounded by the inner cylinder part 22 of the arm 2, the outer cylinder part 23 of the arm 2, the outer edge part 24 of the arm 2, the cylindrical part 12 of the base 1, and the pedestal part 11 of the base 1. Formed in space. The coil spring 4 and the clutch member 5 are housed in the spring housing chamber 9 .

(Coil spring 4)
Next, the coil spring 4 of this embodiment will be explained. The coil spring 4 is a torsion coil spring formed by spirally winding a metal wire having a circular cross section in a left-handed manner. The coil spring 4 biases the arm 2 to rotate in one direction relative to the base 1. Note that the coil spring 4 is set to be deformed to reduce its diameter when the arm 2 rotates in a direction that loosens the belt 101. Further, the coil spring 4 has a constant diameter over its entire length when no external force is applied to the autotensioner 100.

As shown in FIGS. 2, 3, 4, and 6, one end and the other end of the coil spring 4 are each bent radially outward. As shown in FIG. 6, the bent portion 41 at one end of the coil spring 4 is locked in the arm holding groove 23a of the arm 2 and pressed against the arm contact surface 23b. As shown in FIGS. 2, 4, and 6, the bent portion 42 at the other end of the coil spring 4 is engaged with the base holding groove 12a of the base 1 and pressed against the base contact surface 12b. Both ends of the coil spring 4 are firmly fixed to the arm 2 and the base 1.

The coil spring 4 is compressed in the front-rear direction (direction of the axis of the swing shaft 6) and is housed in the spring housing chamber 9. Therefore, even though the coil spring 4 repeatedly expands and contracts in diameter as the tension of the belt 101 increases and decreases, the coil spring 4 maintains a stable posture due to its self-elastic restoring force in the axial direction. Can be done. Further, the clutch member 5, which is disposed on the inner circumferential side of the coil spring 4 and is in contact with the outer circumferential surface thereof, can also maintain a stable posture.

The coil spring 4 of this embodiment is formed from a spring wire. The coil spring 4 is formed, for example, from an oil-tempered wire for springs (based on JIS G3560). The cross-sectional dimension of the spring wire forming the coil spring 4 is, for example, about 2.5 mm in diameter. Further, the effective number of turns (N) of the coil spring 4 is, for example, four.

(Clutch member 5)
As shown in FIGS. 1 and 5, the clutch member 5 is a cylindrical leaf spring extending in the front-rear direction, and is disposed on the inner peripheral side of the coil spring 4. As shown in FIG. 3, the clutch member 5 has a slit 51 and has a C-shaped cross section. The slit 51 is provided in the longitudinal direction of the clutch member 5 over the entire length of the clutch member 5, and both ends of the slit 51 in the circumferential direction are free ends over the entire length of the clutch member. Therefore, the clutch member 5 is a tight spring having a self-elastic restoring force in the radial direction.

The clutch member 5 has a constant diameter over its entire length when no external force is applied to the autotensioner 100. Furthermore, when no external force is applied to the autotensioner 100, the length of the clutch surface (outer circumferential surface) in the circumferential direction is approximately the same as that of the completely closed outer circumferential surface. Further, the clutch member 5 has a substantially constant thickness both in the radial direction and in the length direction. Further, the inner circumferential surface and outer circumferential surface of the clutch member 5 are flat.

As shown in FIGS. 1 and 5, the other end of the clutch member 5 in the longitudinal direction is a free end and is not fixed to the base 1. In addition, a gap is ensured between the base 1 and the base 1. Therefore, while the coil spring 4 repeatedly expands and contracts in diameter as the tension of the belt 101 increases and decreases, it does not come into contact with the base 1 and generate sound. Further, since the axial length of the clutch member 5 can be reduced compared to the case where there is no gap between the clutch member 5 and the base 1, the manufacturing cost of the auto tensioner 100 can be suppressed. Note that the other end surface of the clutch member 5 is simply a flat surface perpendicular to the front-rear direction.

As shown in FIGS. 1 and 5, one end of the clutch member 5 in the front-rear direction is a free end and is not fixed to the arm 2. In addition, a gap is ensured between the arm 2 and the arm 2. Therefore, it has the same effect as described in the case where the other end of the clutch member 5 in the longitudinal direction is a free end. In addition to this, one end surface of the clutch member 5 is prevented from coming into contact with the rear surface of the outer edge portion 24 of the arm 2, and the rotation of the arm 2 is prevented from being inadvertently suppressed.

The length (surface length) of the clutch member 5 in the longitudinal direction is approximately equal to the length of the coil spring 4 in the longitudinal direction. The outer circumferential surface of the clutch member 5 is in contact with the coil spring 4 from the inside by applying its own gripping force over substantially the entire length and circumferential direction of the coil spring 4 . Note that in order to prevent wear on the contact surfaces, an anti-wear agent such as grease may be interposed on the inner circumferential surface of the coil spring 4 or the outer circumferential surface of the clutch member 5. Moreover, the inner circumferential surface of the coil spring 4 or the outer circumferential surface of the clutch member 5 may be formed into a finely uneven surface so as to improve oil impregnation.

The clutch member 5 of this embodiment is formed from thin plate spring steel. The clutch member 5 is made of, for example, thin plate spring steel (carbon tool steel: SK-5) with a thickness of about 0.5 mm. The width of the slit 51 is, for example, about 1 mm when no external force is applied to the autotensioner 100. The generated torque ratio (TL/TS) (absolute value) acting on the clutch surface is, for example, about 3 in actual measurements. The generated torque ratio (TL/TS) (absolute value) acting on the clutch surface will be described later.

(Operation of auto tensioner 100)
The operation of the auto tensioner 100 will be explained below. As the tension of the transmission belt 101 increases or decreases, the arm 2 (and the pulley 3) swings about the axis R of the swing shaft 6.

○When the tension of the transmission belt 101 increases and the arm 2 rotates in the direction (Y direction) that loosens the belt 101.Receiving the load from the belt 101, the arm 2 receives the rotation biasing force of the coil spring 4 in the circumferential direction. It is rotated in a direction that resists. In this case, it is important to greatly attenuate the rotation of the arm 2 to suppress the rotation of the arm 2.

This will be explained in detail below. As shown in FIG. 7, when the tension of the transmission belt 101 increases, a belt load F _B , which is the resultant force of the belt tension, acts on the rotation center of the pulley 3. This belt load F _B generates a torque T around the axis R of the swing shaft 6 which is eccentric from the rotation center of the pulley 3, and the arm 2 resists the rotation biasing force of the coil spring 4 in the circumferential direction. , rotate in the Y direction. Note that the rotational torque T of the arm 2 is T=F _B ×e. (Here, e is the torque radius: the shortest distance from the axis R to the line of force of the belt load F _B , as shown in Fig. 7.) As shown in Fig. 6, the torque acting around the axis R Force Fa is transmitted to arm contact surface 23b by T.

The coil spring 4 receives a force Fa that resists the circumferential rotation biasing force of the coil spring 4 at a bent portion 41 at one end thereof, and is torsionally deformed in the Y direction to reduce its diameter. At this time, the coil spring 4 is pressed down from the inner peripheral side by the clutch member 5 having a gripping force, and is deformed to reduce its diameter. As a result, when the diameter of the arm 2 is reduced due to the rotation of the arm 2, as shown in FIGS. , lock torque (TL) is generated as friction torque. The direction in which the lock torque acts is the X direction, which is opposite to the direction in which the arm 2 rotates. When the tension of the transmission belt 101 increases, the absolute value of the damping torque that resists the rotational torque T of the arm 2 is calculated as follows: (TC) (absolute value + absolute value of TL). Therefore, a damping force that significantly damps the rotation of the arm 2 can be generated. Note that when the absolute value of the rotation torque T of the arm 2 is in a balanced relationship equal to the above (absolute value of TC+absolute value of TL), the rotation of the arm 2 stops at that rotation angle.

○When the tension of the transmission belt 101 decreases and the arm 2 rotates in the direction of tensioning the belt 101 (X direction) Under the circumferential rotation biasing force of the coil spring 4, the arm 2 rotates in the rotation bias direction. Rotated. In this case, it is important to rotate the arm 2 in a direction that increases (recovers) the tension of the belt 101 without attenuating the rotation of the arm 2, and to sufficiently follow the decrease in belt tension. .

This will be explained in detail below. The arm 2 is rotated in the rotational biasing direction by the circumferential rotational biasing force of the coil spring 4 . When the tension of the transmission belt 101 decreases, the torsional restoring force of the coil spring 4 becomes dominant, and the arm 2 rotates in the X direction. Then, as shown in FIGS. 2, 4, and 6, friction torque is generated at the engagement surface between the coil spring 4, which expands in diameter due to the rotation of the arm 2, and the clutch member 5, which has a gripping force on the coil spring 4. As a result, slip torque (TS) is generated. However, the absolute value of the slip torque that occurs when the coil spring 4 is deformed to expand its diameter is large due to the large relative sliding (slip) of the engagement surfaces. is relatively smaller than the absolute value of the locking torque. Therefore, only a smaller damping torque TS (absolute value) is generated at the engagement surface between the coil spring 4 and the clutch member 5 than when the arm 2 rotates in the Y direction. The direction in which the damping torque TS (absolute value) acts is the Y direction, which is opposite to the rotation direction of the arm 2. Therefore, the absolute value of the rotational torque T of the arm 2 when the tension of the transmission belt 101 decreases is (absolute value of TC - absolute value of TS). As described above, the arm 2 can sufficiently receive the torsional restoring force of the coil spring 4, and the rotation of the arm 2 can be made to sufficiently follow the decrease in belt tension without attenuating the rotation.

〇About the clutch effect of the clutch member When the clutch member is applied to the structure of an auto tensioner, the clutch effect is to generate friction torque on the clutch surface by bringing the coil spring into contact with the clutch surface, and to reduce the force of the arm relative to the base. This is the effect of regulating rotation. As described above, in this embodiment, the clutch effect occurs when the arm 2 rotates in the direction of increasing the tension of the belt 101 and loosening the belt 101 (when the arm 2 rotates due to the rotation of the coil spring 4). It is demonstrated when rotating in the direction opposite to the direction of force).

This clutch effect is determined by the generated torque ratio (TL/TS) (absolute value) acting on the clutch surface, that is, the ratio (TL/TS) of the absolute value of lock torque (TL) to the absolute value of slip torque (TS). It can be regarded as an index (substitute characteristic). The larger the generated torque ratio (TL/TS), the more remarkable the clutch effect is. For example, in an auto tensioner using a simple cylindrical leaf spring without slits or the like as a clutch member, the generated torque ratio is (TL/TS)=e^(2×π×μ×N). Here, μ: coefficient of friction, N: effective number of turns of the coil spring.

In the case of this embodiment, it depends not only on the friction coefficient of the engagement surface and the effective number of turns of the coil spring 4, but also on design matters such as the cross-sectional characteristics of the clutch member 5 and the elastic modulus of the material.

(effect)
In this embodiment, when the tension of the belt 101 increases and the arm 2 rotates in a direction opposite to the direction in which the arm 2 is urged to rotate, that is, in a direction that loosens the belt 101, the coil spring 4 contracts in diameter. do. Furthermore, a clutch member 5 is arranged on the inner peripheral side of the coil spring 4. Therefore, when the arm 2 rotates in a direction to loosen the belt 101, the reduced diameter coil spring 4 and the clutch member 5 on the inner circumferential side of the coil spring 4 come into strong contact, and a large damping torque acts on the arm 2. In other words, although the arrangement of the clutch member 5 with respect to the coil spring 4 is reversed from the inside and outside of the above Patent Document 1, when the arm 2 rotates in the direction of loosening the belt 101, strong damping acts, and the clutch effect is significant. The effect of this is the same as in Patent Document 1 mentioned above.

Furthermore, since the clutch member 5 is arranged on the inner circumferential side of the coil spring 4, the ends of the coil spring 4 can be easily fixed by bending both ends of the coil spring 4 outward in the radial direction. Become. Therefore, there is no need for special measures to stabilize the posture of the coil spring 4 as in Patent Document 1, and manufacturing costs can be reduced.

In this embodiment, the clutch member 5 has a C-shaped cross section with a slit 51, and is in contact with the coil spring 4 from the inner circumferential side by self-elastic restoring force in the diametrically expanding direction. Since the clutch member 5 has spring properties and is always in contact with the inner circumferential surface of the coil spring 4, it is possible to reliably apply a damping torque to the arm 2.

In this embodiment, one end and the other end of the coil spring 4 are bent radially outward, and the respective bent portions 41 and 42 are formed in the base holding groove 12a formed in the base 1 and in the arm 2. They are respectively locked in the arm holding grooves 23a. Since the clutch member 5 is arranged on the inner peripheral side of the coil spring 4, both ends of the coil spring 4 can be bent radially outward and fixed to the arm 2 and the base 1. In other words, the posture of the coil spring 4 can be stabilized by simply performing a simple end treatment and without any other special measures.

In this embodiment, the arm 2 is eccentrically supported by the base 1, and the arm 2 is located inside the outer peripheral surface of the pulley 3, so it is better not to rotate the arm 2 significantly in the camshaft drive belt system. , autotensioner 100 is suitable.

(Modified example)
Although preferred embodiments of the present invention have been described above, the above embodiments can be modified and implemented as follows.

(1) In the above embodiment, the clutch member 5 has the slit 51 and is a cylinder with a C-shaped cross section, but the clutch member 5 is not limited to this. The clutch member may be, for example, a simple cylinder without a slit or the like.

(2) In the above embodiment, the wire of the coil spring 4 is formed to have a circular cross section, but the present invention is not limited to this. The wire rod of the coil spring may have a substantially rectangular cross section, for example.

(3) The length (surface length) of the clutch member in the front-rear direction does not have to be substantially equal to the length of the coil spring 4 in the front-rear direction.

(4) The outer circumferential surface of the clutch member does not need to be in contact with the coil spring over substantially the entire length and circumferential direction. The outer circumferential surface of the clutch member may be in contact with substantially the entirety of the coil spring in the circumferential direction, and may not be in contact with substantially the entire inner circumferential surface of the coil spring in the longitudinal direction.

(5) In the above embodiment, both ends of the coil spring 4 are bent, but both ends of the coil spring may remain in a spiral shape.

(6) One end of the clutch member in the longitudinal direction may be in contact with the arm instead of the free end, or the other end in the longitudinal direction may be in contact with the base rather than the free end. For example, one end in the front-back direction may be a free end, and the other end in the front-back direction may be provided with a protruding claw portion so that the other end in the front-back direction abuts the base and is prevented from rotating.

(7) The coil spring does not need to be compressed in the front-rear direction.

(8) The arm does not need to be eccentric to the base. Further, the arm does not need to be located inside the outer peripheral surface of the pulley.

(9) The present invention may be applied to an auto tensioner that maintains constant tension on the slack side of a power transmission belt that drives an auxiliary machine of an automobile engine.

(Other embodiments)
In the above embodiment, as shown in FIG. 1, the auto tensioner 100 (in addition, the pulley An example has been described in which the configuration of the present invention is adopted in the case where the central axis of the oscillating shaft 6 is eccentric with respect to the axis R that is the oscillating center of the oscillating shaft 6, but the present invention is not limited thereto. For example, as shown in FIGS. 8 and 9, the center axis R2 of the hole 263 formed in the swing shaft 206 and the axis R, which is the swing center of the swing shaft 206, do not match, and the hole 263 is The auto tensioner 200 of the present invention has a hole 263 formed in the swing shaft 206 so that the center axis R2 is at an eccentric position (a position away from the axis R, which is the swing center of the swing shaft 206). configuration may be adopted. According to this auto tensioner 200, as shown in FIG. 9, when the swing shaft 206 is fixed to an engine block (not shown), the center axis R3 (center axis R2 ) can be arranged eccentric not only from the center axis R4 of the pulley 203 but also from the axis R, which is the center of swing of the swing shaft 206.

The configuration of the auto tensioner 200 will be briefly described with reference to FIGS. 8 and 9. Note that a description of the same configuration as the auto tensioner 100 will be omitted.

(Swing axis 206)
As shown in FIGS. 8 and 9, the swing shaft 206 is a support of the auto tensioner 200 that extends in the direction of the axis R, which is the center of swing, and the axis R of the swing shaft 206 is aligned with the central axis R4 of the pulley 203. It's eccentric. As a result, the pulley 203 and the arm 202 swing about the axis R as the tension of the transmission belt 101 increases or decreases. A flange 206A is formed integrally with the swing shaft 206 on the other end side of the swing shaft 206. Further, the outer circumferential surface of the swing shaft 206 is formed parallel to the axis R direction.

A hole 263 extending in the direction of the axis R is formed in the swing shaft 206 at a position eccentric to the axis R, as shown in FIG. As shown in FIG. 8, a fastening bolt 262 is inserted into this hole 263 to fix the swing shaft 206 to an engine block (not shown). As shown in FIG. 9, the central axis R3 of the fastening bolt 262 is eccentric with respect to the axis R when the swing shaft 206 is fixed to the engine block.

(Press member 218)
As shown in FIGS. 8 and 9, the holding member 218 is separately disposed on one end side of the swing shaft 206, which is the opposite side to the side fixed to the engine block, and is positioned relative to one end surface of the swing shaft 206. They are in contact with each other in a non-rotatable manner. Note that the holding member 218 may be formed integrally with the swing shaft 206. It is preferable that the holding member 218 is formed into a substantially hexagonal shape when viewed from one end side. This allows the swing shaft 206 to be rotated around the fastening bolt 262 temporarily secured to the engine block by gripping the substantially hexagonal side surface with a tool such as a spanner. The other end side surface of the holding member 218 is formed into an annular flat surface extending in a direction orthogonal to the axis R. This makes it parallel to one end surface of the boss portion 221 of the arm 202 and reliably contacts the flange 271 of the bush 207 over a wide area. The material of the holding member 218 is carbon steel (S45C), and in order to improve the wear resistance of the surface on the other end side that slides on the flange 271 of the bushing 207, the surface is hardened by soft nitriding.

(Base 201)
As shown in FIG. 8, the base 201 is a separate member from the swing shaft 206, and is provided coaxially with the axis R of the swing shaft 206. The base 201 is connected to a base inner cylinder part 201A and a base outer cylinder part 201B that face each other in the radial direction, and an edge on the other end side of the base inner cylinder part 201A and an edge on the other end side of the base outer cylinder part 201B. It has an annular bottom portion 201C. The base inner cylinder part 201A and the base outer cylinder part 201B are provided coaxially with the axis R of the swing shaft 206. A bottom portion 201C of the base 201 is formed into a flat surface parallel to the radial direction. The bottom 201C of the base 201 and the surface of one end of the flange 206A formed on the other end of the swing shaft 206 are in contact with each other, and the base 201 is fixed until the swing shaft 206 is fixed to the engine block. The space is configured to be rotatable relative to the swing shaft 206.

As shown in FIG. 8, the base 201 is fixed to the engine block together with the swing shaft 206 by a fastening bolt 262 so as not to be relatively rotatable. However, until the auto tensioner 200 is fixed to the engine block, the base 201 is configured to be rotatable relative to the swing shaft 206, and its position in the circumferential direction is fixed with respect to the engine block (non-rotating). ) is preferred. Thereby, the swing shaft 206 can be rotated around the fastening bolt 262 while the auto tensioner 200 is temporarily fixed to the engine block, and the swing shaft 206 can be placed at an appropriate position. The material of the base 201 may be, for example, cold rolled steel plate (SPCC), and in this case, the surface is preferably galvanized for rust prevention.

The anti-rotation portion 201D formed on the base 201 has a substantially L-shape, and includes an extending portion 201D1 extending radially outward from the base outer cylinder portion 201B, and a rearward portion from the tip of the extending portion 201D1 (see FIG. It has a locking portion 201D2 (extending in the depth direction in FIG. 9) that extends further while changing the direction by approximately 90 degrees (in the depth direction in FIG. 9). When the auto tensioner 200 is assembled to the engine block, the locking portion 201D2 of the rotation stopper 201D is engaged with an elongated groove (not shown) formed in one end surface of the engine block, and 201 is prevented from rotating relative to the engine block. Further, as shown in FIG. 9, a notch formed in an arc shape is provided at the tip of the extending portion 201D1.

Further, as shown in FIG. 9, the arm 202 is provided with an indicator portion 202A that extends outward in the radial direction and has a tapered tip. It is preferable that the protrusion radius, which is the length, is approximately equal to the protrusion radius, which is the length from the axis R, of the rotation stopper 201D, which is provided to protrude from the base 201. The portion 201D functions as a dowel between the arm 202 and the base 201 in the circumferential direction about the axis R.

(Significance of auto tensioner 200)
Due to unavoidable dimensional tolerances in the camshaft drive belt system, such as dimensional tolerances of each part of the auto tensioner 200 and distance tolerances between parts (e.g., variations in transmission belt length), the auto tensioner 200 cannot be held in the same position relative to the engine block. Even when assembled, the initial tension applied to the transmission belt varies depending on the device. Therefore, the autotensioner 200 of other embodiments is configured to be able to apply a predetermined initial belt tension to the power transmission belt when assembled to the engine block.

Specifically, as described above, the center axis R4, which is the center of rotation of the pulley 203, is arranged eccentrically with respect to the axis R of the swing shaft 206, and the fastening bolt 262 is arranged eccentrically with respect to the axis R of the swing shaft 206. It is placed eccentrically. The auto tensioner 200 operates on the arm 202 when a predetermined belt load is applied to the central axis R4 of the pulley 203, a predetermined initial tension is applied to the transmission belt, and the transmission belt is normally attached. The tip position of the indicator portion 202A of the base 201 is configured to match the circular arc center position of the notch of the rotation stopper portion 201D of the base 201 (that is, the matching marks match).

(Assembling the auto tensioner 200 to the engine block and attaching the transmission belt)
Next, a procedure from assembling the auto tensioner 200 to the engine block to attaching the transmission belt will be explained. As shown in FIG. 9, the X direction is the direction in which the biasing force of the coil spring 204 in the circumferential direction is applied. The Y direction is a direction that resists the biasing force of the coil spring 204 in the circumferential direction.
(1) Pass the fastening bolt 262 through the hole 263 provided in the swing shaft 206 and temporarily secure it to the female threaded portion of the engine block.
(2) Engage the locking portion 201D2 of the rotation stopper 201D of the base 201 with the groove formed in the surface of one end of the engine block.
(3) In the temporarily fixed state, grasp the side surface (approximately hexagonal shape) of the holding member 218 with a tool such as a spanner, and rotate the swing shaft 206 in the X direction around the fastening bolt 262. As a result, the entire autotensioner 200 rotates in the X direction about the central axis R3 of the fastening bolt 262, and the position of the shaft R (that is, the pulley 203 and the arm 202) moves in the direction closer to the transmission belt.
(4) When the pulley 203 comes into contact with the transmission belt, the belt load acts on the center axis R4 of the pulley 203.
(5) Furthermore, when the swing shaft 206 is rotated in the X direction about the center axis R3 of the fastening bolt 262, the axis of the swing shaft 206 is eccentric from the center axis R4 of the pulley 203 due to this increase in belt load. Torque is generated around R, and the arm 202 begins to rotate in the Y direction against the circumferential urging force of the coil spring 204, and the tension of the transmission belt begins to increase.
(6) By further rotating the swing shaft 206 in the X direction around the center axis R3 of the fastening bolt 262 until a predetermined belt load acts on the center axis R4 of the pulley 203, the arm 202 and the pulley 203 are further rotated. It rotates in the Y direction around axis R, and can apply a predetermined initial tension to the transmission belt. Here, confirmation that a predetermined belt load has been applied to the central axis R4 of the pulley 203 and a predetermined initial tension has been applied to the transmission belt can be made from the indicator portion 202A of the arm 202 and the rotation stopper portion 201D of the base 201. This is done by checking whether the matching marks match.
(7) With the matching marks aligned, the fastening bolt 262 is completely fastened to the female threaded part of the engine block, and the fixed part such as the swing shaft 206 is fixed to the engine block.

(Different effects from auto tensioner 100)
When the central axis of the hole 63 formed in the swing shaft 6 and the axis R serving as the swing center of the swing shaft 6 are arranged coaxially as in the auto tensioner 100 according to the embodiment, In the temporarily fastened state, the operation of rotating the swing shaft 6 in the X direction around the fastening bolt 62 (step (3) of the item of assembling the auto tensioner 200 to the engine block and attaching the transmission belt) cannot be performed. Therefore, even if the fixed parts such as the swing shaft 6 are fixed to the engine block with the matching marks matched, the cam Shaft-driven belt systems tend to vary in the initial tension applied to the transmission belt.

On the other hand, as in the auto tensioner 200 shown in FIGS. 8 and 9, the center axis R3 (corresponding to the center axis R2) of the fastening bolt 262 inserted into the hole 263 is not only the center axis R4 of the pulley 203, but also the center axis R4 of the pulley 203. Even if there are unavoidable dimensional tolerances in the camshaft drive belt system during mass production, by locating the oscillating shaft 206 eccentrically from the axis R, which is the center of oscillation, the influence of all these dimensional tolerances can be minimized. By canceling (adjusting), a predetermined belt load can always be uniformly applied to the central axis R4 of the pulley 203, and a predetermined initial tension can be applied to the transmission belt.

1 Base 2 Arm 3 Pulley 4 Coil spring 5 Clutch member 6 Swing shaft 11 Pedestal part 12 Cylindrical part 12a Base holding groove 21 Boss part 22 Inner cylinder part 23 Outer cylinder part 23a Arm holding groove 24 Outer edge part 26 Upper limit rotation restriction Wall surface 27 Lower limit side rotation regulating wall surface 41 Bending portion 42 at one end of coil spring 4 Bending portion 100 at the other end of coil spring 4 Auto tensioner 101 Transmission belt

Claims (5)

a base to which a swing axis is attached;
an arm rotatably supported with respect to the base via the swing shaft;
a pulley rotatably provided around an axis parallel to the swing axis and capable of contacting the belt;
a coil spring disposed around the swing axis and biasing the arm to rotate in one direction relative to the base;
The coil spring is set to contract in diameter when the arm rotates in a direction opposite to the one direction, which is the direction in which the belt is loosened;
Further, a cylindrical clutch member is provided on the inner peripheral side of the coil spring and contacts the coil spring whose diameter is reduced on the outer peripheral surface thereof,
The clutch member has one free end and is arranged such that a gap is maintained between the clutch member and the arm,
The other end of the clutch member is also a free end, and is arranged so that a gap is secured between it and the base,
The clutch member is arranged such that a gap is ensured between the inner circumferential surface and the arm facing the inner circumferential surface , and when the coil spring is deformed in diameter by a load of a predetermined value or more, An auto tensioner characterized in that the inner circumferential surface contacts the arm . The auto according to claim 1, wherein the clutch member has a C-shaped cross section with a slit, and is in contact with the coil spring from the inner circumferential side by self-elastic restoring force in the direction of diameter expansion. tensioner. One end and the other end of the coil spring are bent radially outward, and each bent portion is locked in a holding groove formed in the arm and the base, respectively. The auto tensioner according to item 1 or 2. The autotensioner according to any one of claims 1 to 3, wherein the coil spring is compressed in the direction of the axis. The autotensioner according to any one of claims 1 to 4, wherein the arm is eccentrically supported by the base and is housed inside an outer peripheral surface of the pulley.

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