JPH0638197Y2 - Belt tensioning device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a belt tensioning device used for applying tension to a camshaft driving timing belt of an internal combustion engine, for example.

[Conventional technology]

Belt tensioning devices commonly used to tension a belt include a tensioner pulley that engages the belt, an arm that supports the tensioner pulley, and an end of the arm that is opposite the tensioner pulley. It comprises a pivoting portion pivotally attached to a fixed portion such as a head, and a spring for pressing the tensioner pulley against the belt. However, since it is difficult to suppress the vibration of the belt only by the spring force of the spring, the frictional engagement member made of a resin material or the like is engaged with the arm to limit the movement of the arm by the frictional force, thus absorbing the vibration of the belt. The invention has been made.

For example, Japanese Patent Application Laid-Open No. 58-72757 discloses a belt tensioning device in which a frictional engagement member is provided at a pivotally attached portion of an arm. At the end of this arm, there is provided an arm mounting cylindrical portion formed in a direction substantially perpendicular to the axis of the arm, and fitted to a cylindrical friction engagement bush fixedly arranged in the housing of the belt tensioning device. It has become so. Therefore, the mounting cylindrical portion is rotatable with respect to the fixed cylindrical friction engagement bush, and free rotational movement is limited by the frictional force. Such a cylindrical friction engagement bush can be arranged on the inner peripheral surface side or the outer peripheral surface side of the arm mounting cylindrical portion, or both.

Further, in such a structure, the cylindrical friction engagement bush easily expands due to heat received from the internal combustion engine, heat generated by friction between the arm mounting cylinder and the cylindrical friction engagement bush, and the like. If there is no escape area for expansion of the friction engagement bush, the contact pressure against the arm mounting cylinder portion becomes excessive, which causes problems such as excessive restriction of arm movement and severe wear. In order to solve this, in Japanese Utility Model Laid-Open No. 62-185958, a slit extending in the longitudinal direction is formed in the cylindrical friction engagement bush, and heat and expansion of the cylindrical friction engagement bush are circumferentially generated in the slit. I'm trying to escape.

[Problems to be solved by the device]

If the belt tensioning device is provided with the cylindrical friction engagement bush as described above, if dust or foreign matter enters the rotating friction surface between the arm attachment cylindrical portion and the cylindrical friction engagement bush,
There is a problem in that the cylindrical friction engagement bush is continuously damaged as it rotates, and durability is reduced. Further, in the case of the cylindrical friction engagement bush provided with slits, the strength in the circumferential direction of the cylindrical friction engagement bush is reduced, the friction engagement surface area of the cylindrical friction engagement bush is reduced, and Since the load is applied to the partitioned small area region, the surface pressure becomes high, which may cause creep deformation of the resin material, which causes a problem in durability.

[Means for Solving the Problems]

The belt tensioning device according to the present invention comprises a tensioner pulley that engages with the belt, an arm that supports the tensioner pulley, and a spring that presses the tensioner pulley against the belt, the end of the arm being the axis of the arm. And a cylindrical friction engagement bush fitted to the peripheral surface of the arm attachment cylinder, the attachment cylinder being provided with a cylindrical friction engagement bush. In a belt tensioning device that is rotatable with respect to each other and whose rotational movement is restricted by a frictional force, a groove extending in the longitudinal direction is formed on the contact peripheral surface of the cylindrical friction engagement bush with the mounting cylindrical portion. At the same time, a sub bush member made of a material softer than the cylindrical friction engagement bush is inserted into the groove.

[Action]

In the above configuration, the cylindrical friction engagement bush is formed with a groove extending in the longitudinal direction on the contact peripheral surface with the mounting cylinder portion of the arm, and the sub bush member made of a material softer than the cylindrical friction engagement bush is formed in this groove. Since it has been inserted, even if dust or foreign matter enters the rotary friction surface, such dust or foreign matter does not get caught in the sub-bushing member made of a soft material and does not damage the rotary friction surface. Further, the sub-bush member made of a soft material forms a substantially continuous full-circumferential friction surface with the cylindrical friction engagement bush, and thus does not cause a local increase in surface pressure, and further, the cylindrical friction engagement Since the surface of the combined bush on the side opposite to the groove has an integrated structure with no slits or the like, the strength in the circumferential direction does not decrease.

〔Example〕

 Hereinafter, the present invention will be described with reference to the drawings.

FIG. 3 is a view showing a belt tensioning device 10 according to an embodiment of the present invention attached to a cylinder block 14 with bolts 12. FIG. 4 is a diagram showing an example in which the belt tensioning device 10 is used to apply tension to the camshaft driving timing belt 16 of the internal combustion engine. The timing belt 16 includes a crankshaft pulley 18, a camshaft pulley 20, an oil pump pulley 22, and an idler pulley 24.
It is wound around.

Referring to FIGS. 3 and 4, the belt tensioning device 10 includes a tensioner pulley 26 that engages the timing belt 16. The tensioner pulley 26 is rotatably supported by one end of an arm 28 by a bearing (not shown) or the like. Arm 28
The other end of the tensioner pulley 26 is rotatably supported by the cylinder block 14 about the axis of the bolt 12, and the arm 28 is rotated, that is, oscillated, so that the tensioner pulley 26 is timed at various angular positions as shown in FIG. It is engageable with the belt 16. As shown in FIG. 3, a spring 29 is arranged around the bolt 12 located at the pivoted end of the arm 28,
The tensioner pulley 26 is pressed against the timing belt 16 so that a predetermined tension is applied. It should be noted that such a spring can be attached to any position of the arm 28.

At the other end of the arm 28, that is, at the pivotally attached end, an arm mounting cylindrical portion 30 is integrally formed in a direction substantially perpendicular to the axis of the arm 28. On the other hand, a sleeve 32 is arranged around the bolt 12 and fixed to the cylinder block 14 by the bolt 12 via a washer 34. Both ends of the sleeve 32 are slightly stepped with a small diameter. Split upper and lower housings 36,3
8 make substantial contact to form a single closed cylindrical housing, with the upper and lower bottom hole walls of the upper and lower housings 36, 38 being sleeve 32
It is adapted to be engaged with a step of small diameter at both ends of. Therefore, the upper and lower housings 36 and 38 are fixed between the cylinder block 14 and the washer 34 by screwing the bolts 12. The lower housing 38 is provided with an opening 40 through which the arm 28 can swing. The upper housing 36 is provided with a hole 42 for locking one end 29a of the spring 29. The other end 29b of the spring 29 is locked by a locking portion 44 provided near the base of the arm mounting cylindrical portion 30 of the arm 28. The spring 29 is first attached in a twisted state, and thus gives the arm 28 a rotational force for imparting belt tension.

The inner diameter of the arm mounting cylinder 30 of the arm 28 is sleeve 32
Larger than the outer diameter of the first cylindrical friction engagement bush 46.
Are inserted in the annular space between them. The first cylindrical friction engagement bush 46 rotatably supports the arm mounting cylindrical portion 30 around the axis of the bolt 12 and limits the rotational movement of the arm mounting cylindrical portion 30 by frictional force.
Further, the second cylindrical friction engagement bush 48 is arranged on the outer peripheral surface side of the arm mounting cylindrical portion 30. The second cylindrical friction engagement bush 48 also has an arm mounting cylindrical portion due to frictional force.
Limit the rotational movement of 30. The second cylindrical friction engagement bush 48 includes a flange 50 extending in a flat plate shape in the radial direction. further,
A third friction engagement plate 52 is arranged between the arm 28 and the bottom surface of the lower housing 38. The length of the arm mounting cylindrical portion 30 is such that the tip of the arm mounting portion is in contact with the bottom surface of the upper housing 36 or not, and the arm 28 is engaged with the third friction engagement plate 52 by the component force in the axial direction of the spring 29. It will be maintained in the matching position.

1A and 2A are perspective views showing in detail the first and second cylindrical friction engagement bushes 46, 48, respectively. As shown in FIG. 21, a detent groove 54 is provided on the inner surface of the first cylindrical friction engagement bush 46, which engages with a protrusion (not shown) provided on the outer surface of the sleeve 32. , The first cylindrical friction engagement bush 46 is prevented from rotating. As shown in FIG. 2A, a rib 56 extending in the radial direction is formed on the collar 50 on the second cylindrical friction engagement bush 48, and this rib 56 serves as a locking end 29a of the spring 29. The engagement prevents the second cylindrical friction engagement bush 48 from rotating.

As shown in FIGS. 1A and 2A, the first and second cylindrical friction engagement bushes 46, 48 are respectively attached to the mounting cylindrical portion 3
Grooves 58 and 62 extending in the longitudinal direction are formed on the peripheral surface in contact with 0, and cylindrical friction engagement bushes 46 and 62 are formed in these grooves 58 and 62.
Sub-bushing members 60, 64 of a material softer than 48 are inserted. Preferably, as shown in FIGS. 1B and 2B, the first and second cylindrical friction engagement bushes 46, 48 are formed in the shape of a spline shaft having grooves 58, 62, respectively, to form a sub bush member. The members 60 and 64 are formed so as to hang down integrally from the ring members 60a and 64a located at one end. The sub-bush members 60,64 are respectively inserted in the grooves 58,62 to form continuous rolling friction surfaces with the first and second cylindrical friction engagement bushes 46,48.

Further, the first and second cylindrical friction engagement bushes 46, 48
Is formed of a suitable friction-imparting material, for example, a resin material such as 6-6 nylon having excellent heat resistance and abrasion resistance that is often used for such applications. On the other hand, the sub-bushing members 60, 64 include the first and second cylindrical friction engagement bushes 46, 64.
It is made of a material softer than 48, for example, a resin material such as tetrafluoroethylene copolymer. Sub bush members 60, 64 made of tetrafluoroethylene copolymer resin are 6
-6 It is inferior to -6 nylon in abrasion resistance, but can still give a certain amount of frictional force, and in terms of heat resistance, rather
Better than 6-6 nylon.

When the sub bush members 60, 64 are made of a material softer than the first and second cylindrical friction engagement bushes 46, 48,
Even if dust or foreign matter enters the rotating friction surface, such dust or foreign matter will be embedded in the sub-bushing members 60, 64 made of soft material, and the dust or foreign matter will not stay on the rotating friction surface for a long time. Disappears. Further, the sub-bushing members 60, 64 made of a soft material form a substantially continuous full-circumferential friction surface with the cylindrical friction engagement bushes 46, 48, so that they do not cause a local increase in surface pressure. , The cylindrical friction engagement bushes 60, 64 have grooves 58,
Since the surface on the side opposite to 62 has an integrated structure with no breaks such as slits, there is no decrease in strength in the circumferential direction. in this case,
Since the sub bush members 60, 64 made of a soft material have a certain degree of freedom in dimensional change, they can absorb the deformation of the first and second cylindrical friction engagement bushes 46, 48 due to heat,
Durability and reliability are improved.

[Effect of device]

As described above, according to the present invention, in the belt tensioning device that applies tension to the belt by the spring force of the spring and limits the rotational movement of the arm by the frictional force of the cylindrical friction engagement bush, Since a groove extending in the longitudinal direction is formed on the contact peripheral surface of the mounting cylinder of the arm on the cylindrical friction engagement bush, and a sub-bush of a material softer than the cylindrical friction engagement bush is inserted into the groove. It prevents dust and foreign matter from being taken into the sub-bushing and damaging the rotary friction surface, and does not cause a local increase in surface pressure unlike a bush with slits. The durability can be improved.

[Brief description of drawings]

FIG. 1A is a perspective view showing a first cylindrical friction engagement bush of the belt tensioning device shown in FIG. 3, and FIG. 1B is a sub bush member of FIG. 1A inserted into the first cylindrical friction engagement bush. FIG. 2A is a perspective view showing a second cylindrical friction engagement bush of the belt tensioning device shown in FIG.
2B is a view showing the sub bush member of FIG. 2A inserted into the second cylindrical friction engagement bush, FIG. 3 is a sectional view showing a belt tensioning device according to the present invention, and FIG. 4 is a third view.
It is a figure which shows the example which uses the belt tensioning device of the figure for the timing belt for camshaft drive of an internal combustion engine. 26 …… Tensioner pulley, 28 …… Arm, 29 …… Spring, 30 …… Mounting cylinder, 32 …… Sleeve, 46,48 …… Cylinder friction engagement bush, 58,62 …… Groove, 60,64 ...... Sub bush member.

Claims (1)

[Scope of utility model registration request] 1. A tensioner pulley that engages with a belt, an arm that supports the tensioner pulley, and a spring that presses the tensioner pulley against the belt, the end of the arm being substantially perpendicular to the axis of the arm. And a cylindrical friction engagement bush fitted to the peripheral surface of the arm attachment cylindrical portion, the attachment cylinder portion being relative to the cylindrical friction engagement bush. In a belt tensioning device which is rotatable and whose rotational movement is restricted by frictional force, a groove extending in the longitudinal direction is formed in the cylindrical friction engagement bush on a contact peripheral surface with the mounting cylindrical portion, and A belt tensioning device, wherein a sub-bushing member made of a material softer than the cylindrical friction engagement bush is inserted into the groove.