JPH01312255A - Autotensioner - Google Patents

Abstract

PURPOSE:To sufficiently respond to a gradual tension varying factor and to nonresponsively respond to a sudden tension varying factor, without requiring a perfect seal, by constituting so that a shearing resistance is caused by viscous fluid to the relative turning motion of an eccentric body with regard to a fixed shaft. CONSTITUTION:A belt tension is adjusted by the turning force given to an eccentric body 13 by means of a spring 15, and by the shearing resistance of the viscous fluid enclosed in the chamber between a fixed shaft 12 and the eccentric body 13, the relative turning of both members 12, 13 is restricted. In other words, to the factor by which the belt tension is caused to be suddenly changed, the turning of the eccentric body 13 is restricted by a large shearing resistance or viscous resistance, so that the eccentric body scarcely responds to it. On the other hand, to the factor by which the belt tension is relatively and gradually varied, since the shearing resistance is small, the eccentric body can sufficiently respond. Further, since the shearing resistance of a viscous fluid is utilized, the mixture of air does not matter, and perfect seal is not required.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to an autotensioner for maintaining constant belt tension.

PRIOR ART AND THEIR PROBLEMS The applications of belt transmission devices have expanded significantly in recent years. For example, toothed healds are used to transmit power from the crankshaft of a vehicle engine to a camshaft. wrapped around each pulley. The toothed belt may also drive auxiliary equipment such as an alternator or water pump.

In such a belt drive system, a tensioner is often used to apply a predetermined tension to the belt.

By the way, this type of tensioner (usually referred to as an "auto tensioner") is required to have the following characteristics.

■Keep belt tension constant.

That is, to prevent the apparent belt length from changing due to changes in engine temperature, elongation of the belt over time, engine length variations, heald manufacturing tolerances, assembly variations, etc., and changes in belt tension.

2. Does not follow belt vibration (does not resonate) and does not move.

In other words, it does not move (does not resonate) due to engine-specific belt vibrations, belt tension changes and vibrations due to camshaft torque fluctuations, etc.

By the way, as a conventional auto tensioner of this type, there is one disclosed in Japanese Patent Application Laid-Open No. 62-62051. However, since this method basically utilizes the (viscous) flow resistance of oil through a narrow orifice, it has the following problems.

First, the orifice gap must be kept constant;
Requires a high degree of product precision.

(In other words, if the orifice gap changes, the performance characteristics will change.) Furthermore, if even a small amount of foreign fluid such as air gets mixed into the sealed chamber, the orifice resistance will change, which will not only change the performance characteristics, but also cause the worst In this case, the orifice resistance is lost and the belt loses its performance, leading to breakdown (belt vibration becomes large → rupture).

Therefore, complete sealing is required for each part, but complete sealing is virtually impossible.

In addition, enclosing the viscous fluid becomes complicated in order to prevent air from entering the fluid.

There is no means to compensate for the thermal expansion and contraction of the fluid in the sealed chamber (the oil temperature reaches a maximum of 130°C, and the volume changes by nearly 10%), and fluid flows out and inflow due to changes in internal pressure. do.

Means for Solving the Problems The present invention provides a fixed shaft, an eccentric body that is swingable relative to the fixed shaft,
A spring means for applying a turning force to the eccentric body, and a viscous fluid sealed in a chamber provided between the fixed shaft and the eccentric body, and a spring means for applying a turning force to the eccentric body, and a spring means for applying a turning force to the eccentric body, and a viscous fluid sealed in a chamber provided between the fixed shaft and the eccentric body. The above problem is solved by an auto tensioner in which the viscous fluid generates shear resistance.

The belt tension is adjusted by the pivoting force exerted on the eccentric by the action spring means. A viscous fluid enclosed in a chamber between the fixed shaft and the eccentric restricts the relative pivoting of both members through its shear resistance. In other words, the rotation of the eccentric body is restricted by the large shear resistance of the viscous fluid and hardly responds to factors that try to drastically change the belt tension.

On the other hand, since the shear resistance is small, the belt tension can be sufficiently responded to factors that cause the belt tension to change relatively slowly.

Therefore, the autotensioner of the present invention is a responsive type that operates the eccentric body in response to relatively gentle tension fluctuation factors, but is non-responsive to rapid tension fluctuation factors.

Example First, an example of how the auto tensioner 10 is mounted is shown in FIG.

The figure is a layout diagram of the belt area of a DOHC engine, including a crankshaft boot IJ80 and two camshaft boots 981.
．． A fixed idler 82 and an autotensioner 10 according to the first embodiment of the present invention are attached so as to press the back surface of the toothed belt 11 wound around the belt 81.

In addition, as shown in Fig. 5, the camshaft pulleys (II', 81' and crankshaft pulley 81' of the ■ type engine)
The autotensioner 10' of the present invention can also be used to adjust the tension of the toothed heald 11', which is wound around the heald 0', together with two fixed idlers 82', 82'.

FIG. 1 is an exploded perspective view of an autotensioner 10 according to a first embodiment. A toothed bell (11) wound around each pulley of the crankshaft and camshaft receives tension from its back surface by an autotensioner 10. The autotensioner 10 of this embodiment includes a fixed shaft 12 fixed to an engine block 50 and an eccentric body 13 mounted eccentrically to the fixed shaft 12. This rotation of the eccentric body 13 presses the back surface of the belt and applies tension to the toothed belt 11. The application of tension to the toothed belt 11 is achieved by a spring 15, one end of which is hooked to the engine block 50 and one end of the eccentric body 13, pulling the eccentric body 13 in the direction in which the toothed belt 11 is tensioned.

The fixed shaft 12 has an inner circumferential hole 21 through which the bolt 16 is inserted, and the end surface 22 on the engine block 50 side is polished so as to form a surface angle when the tensioner 10 is attached.

The outer periphery has smooth circumferential surfaces 23 and 24 from both ends and an enlarged diameter section 25 between the circumferential surfaces, and a spline 26 is formed in a slightly short range on the enlarged diameter section 25.

On the other hand, the eccentric body 13 is provided with a hollow hole 31 that is eccentric to the center of the outer peripheral surface. The hollow hole 31 has stepped portions 33 and 34 (see FIG. 2) inward from both ends, and the width of both stepped portions is approximately the same as the width of the circumferential surface 23 of the fixed shaft 12 on the bolt head side. . The space between the stepped portions becomes a reduced diameter portion 35, and this reduced diameter portion 3
A spline 36 is formed in an area slightly shorter than 5, and faces the spline 26 of the fixed shaft 12.

Therefore, the bolt head side circumferential surface 23 of the fixed shaft 12 and the one step part 33, the enlarged diameter part 25 and the reduced diameter part 35, and the splines 26 and 36 are opposed to each other with the same width in the axial direction.

The inner plate 20 fits into the spline 26 of the fixed shaft 12, and the outer plate 30 fits into the spline 36 of the eccentric body 13, respectively. These inner plates 20 and outer plates 30
are arranged alternately within the width of the splines 26,36. Such a structure is seen in a multi-disc clutch. The inner and outer plates 20.30 are each provided with a plurality of concentric holes 20a, 30a in the thickness direction. Further, a spacer ring 51 is located between the inner circumference of the outer plate 30 and the spline 26 of the fixed shaft 12 to positively create a gap between each adjacent inner plate 20, and regulates the gap. ing. In order to regulate the distance between the outer plates 30, a spacer ring may be provided on the outer peripheral side of the inner plate 20, and both may be used together.

Fixed shaft 12. Eccentric body 13. When the inner and outer plates 20° 30 and the spacer ring 51 are assembled, side brakes (43, 44) are inserted from the outside into both steps 33, 34 of the hollow hole 31.
are press-fitted. Both side plates 43, 44 have the same width as the stepped portion 33° 34 of the eccentric body 13, and the width of the reduced diameter portion 35.
The eccentric body 13 is guided in the axial direction in close proximity to the end 27 of the enlarged diameter portion 25 of the fixed shaft 12. This allows the fixed shaft 12. The eccentric body 13 and the side plate 43 are flush on one side. side play)43.
Although the inner circumference of 44 is exaggerated in FIG.
It is machined to such an extent that it can slide on the circumferential surfaces 23 and 24 of the ring, and has a clearance, and a groove is formed on the inner circumferential side to receive an O-ring 45 as a sealing means.

Fixed shaft 12. Eccentric body 13. The portion surrounded by the side plates 43 and 44 becomes a viscous fluid chamber. Inside this chamber 40 is an inner plate 20. Outer plate 30 and spacer ring 51
As mentioned above, is arranged.

As shown in FIG. 2, the eccentric body 13 has an axial hole 32 formed along the diameter line A--A in FIG. 3, and a bottle 42 is press-fitted into the hole 32. A groove is formed in the bin 42 for hooking a spring 15 that applies a turning force to the eccentric body 13. The eccentric body 13 is also provided with a communication hole 4G connected to the chamber 40 from the front side and a communication hole 47 shown in FIG. 3, the positions of which are shown for convenience in FIG. A viscous fluid is sealed within the chamber 40 .

An outer ring 48a is provided on the outside of the eccentric body 13 and rotates while being pressed against the back surface of the heald via rolling elements 48b. A pressing plate 49 is attached to the edge of the outer peripheral end surface of the eccentric body 13 to restrict movement of the rolling element 48b in the axial direction.

Installation of the auto tensioner 10 is completed by simply passing the spring washer 53 onto the bolt 16, inserting it through the inner circumferential hole 21 of the fixed shaft 12, and fixing it to the engine block 50. A spacer 54 is located between the eccentric body 13 and the engine block 50, and determines the axial position of the auto tensioner 10. Then, when a spring is applied to the pin 42 and the protrusion 52 of the engine block 50, the eccentric body 13 turns around the fixed shaft 12, and the outer ring 48a presses the back surface of the toothed bell 11. The auto tensioner 10 stops at a position where the spring tension and the belt tension are balanced, thereby eliminating the slack in the toothed belt 11.

The viscous fluid sealed in the chamber 40 is called viscous oil, and in this example silicone oil was used. Silicone oil goes from s, ooo to soo, oo.

A material with a viscosity within the range of cst can be selected, and has the characteristics of having a small change in viscosity with respect to temperature and excellent heat resistance. When sealing silicone oil in the chamber 40, 10 to 20% air is mixed. As a result, when the internal pressure increases, the air is compressed to compensate for the volume change of the silicone oil.

(internal/internal play) between 20.30, i.e. between fixed shaft 12 and eccentric body 1
If there is no relative movement of the two plates 20 and 30, silicone oil will only be present between the inner and outer plates 20 and 30. However, when a turning force is applied, shear stress is generated in the silicone oil between the inner and outer plates.

The reason why the holes 20a and 30a are provided in each plate 20.30 is to efficiently generate this shear stress (resistance). Note that this hole may have a slit-like shape.

When assembling the engine, as shown in Figures 4 and 5,
The toothed belt is wound around a crankshaft pulley, a camshaft pulley, and an auxiliary pulley (not shown). After that, install the fixed idler and install the engine block 5 as described above.
When the tensioner 10 is fixed at 0, the tension of the spring 15 causes the eccentric body 13 to pivot around the fixed shaft 12. Then, the silicone oil sealed in the chamber 40 becomes
Although shearing force is applied from the inner and outer plates 20, 30, if the pivoting movement is rapid, the eccentric body 13 cannot pivot because the shearing resistance is large. However, in response to an external force that continues for a certain period of time, the silicone oil flows between the inner and outer plates 20 and 30, and the eccentric body 13 stops under a constant tension where the spring tension and the belt tension are balanced.

When the engine is running, a load is applied to the eccentric body 13 in accordance with the heald tension. When the temperature of the engine block 50 rises during operation and the distance between the crankshaft and the camshaft increases, exceeding the elongation of the toothed belt 11, excessive tension is generated in the belt. In this way, the shear resistance force generated between the inner plate 20 and the outer plate 30 is small against the load applied to the eccentric body 13 relatively gently, so the silicone oil is allowed to flow.
Each plate gradually changes its relative position while the eccentric body 1
3 in the direction of decreasing belt tension.

In this manner, tensioner 10 settles into a position that balances the proper belt tension.

The same holds true when the eccentric body 13 pivots in the direction of tensioning the belt as the belt tension decreases relatively slowly. The inner plate 20 receives a turning force from the outer plate 30 in the clockwise direction in FIG. 3, that is, in the direction in which the spring 15 pulls the eccentric body 13 via the silicone oil. However, since the inner plate 20 is fixed to the fixed shaft 12, the outer plate 3
0 and the eccentric body 13 gradually flow the silicone oil,
Rotate to a position that balances the spring tension. by this,
The belt tension is increased.

Immediately after the engine starts, torque is generated from the crankshaft and belt tension increases instantaneously. Since the heald tension is balanced with the spring tension when the engine is stopped, a load is generated on the eccentric weight 3 in the counterclockwise direction in FIG.

At this time, a shearing force is generated between the inner and outer plates 20 and 30 by the difference between the belt tension and the spring tension, but the silicone oil has a large shearing resistance and cannot respond to such sudden and drastic changes in load. First, the rotation of the eccentric body 13 is restricted.

The same effect applies to belt vibrations caused by camshaft torque fluctuations. That is, even if an alternating load acts on the eccentric body 13,
Due to the large shear resistance of the silicone oil, the eccentric body 13 does not follow this, thereby preventing belt flapping and resonance phenomena.

Factors that determine such response characteristics of the eccentric body 13 include the spacing and number of inner and outer plates, the shape of the plates (holes, slits, etc.), the viscosity of silicone oil, the air content, and the like. The characteristics of the movement of the eccentric body 13 can be changed by changing at least one of these factors. It is desirable to set the air content in these factors to 10 to 20% by volume, in other words, to set the silicone oil filling rate to 80 to 90%. Since air is a compressible fluid, it compensates for the volume change of silicone oil due to temperature rise,
The internal pressure within the chamber 40 is adjusted to prevent silicone oil from leaking.

Next, FIGS. 6 to 8 show a second embodiment of the present invention, which is a modification of the auto tensioner of the first embodiment.

In this embodiment, the chambers that house the inner and outer plates are offset in the axial direction with respect to the outer ring, which allows the outer diameters of the inner and outer plates to be increased to increase the shearing resistance that acts between the plates. By reducing the outer diameter of the outer ring, the moment of inertia of the eccentric body can be reduced, and vibration followability can be improved.

The auto tensioner 60 includes a fixed shaft 62 and an eccentric body 63 swingably attached to the fixed shaft 62.

The fixed shaft 62 is pressed against the engine block 64 and securely fixed by a flanged bolt 66, a spring washer 67, and a flat washer 68. Eccentric body 63
has a lower housing 72 and an upper housing 73, and a chamber 70 is formed between the fixed shaft 62 and the fixed shaft 62.

The fixed shaft 62 has a first cylindrical surface 62a on the engine block 64 side, a second cylindrical surface 62b on the head side of the flanged bolt 66, and is perpendicular to the axis at both ends between these cylindrical surfaces 62a and 62b. The step part 62c has a spline formed by forming a surface with an enlarged diameter.

The lower housing 72 is located on the first cylindrical surface 62a between the step portion 62c and the engine block 64, and is pivoted about the fixed shaft 62 between the bushing 74a interposed between the step portion 62c and the engine block 64. Be free. 72a is an annular recess concentric with the fixed shaft 62 and has a spline formed therein. 72b is an outer peripheral surface concentric with the fixed shaft 62.

On the other hand, the upper housing 73 has a second cylindrical surface 6 between the step portion 62c and the head of the flanged bolt 66.
2b and is interposed between the head of the bolt 6G and the bushing 74b, which allows the bushing 74b to freely pivot relative to the fixed shaft 62. 73a is an annular recess concentric with the fixed shaft 62, and 73b is an outer peripheral surface eccentric with respect to the fixed shaft 62.

The eccentric body 63 has inner and outer plates 71a, 71b and a spacer ring 1 between the splines of the stepped portion 62c of the fixed shaft 62 and the splines of the recess 72a of the lower housing 72.
1c and insert them into the recess 73 of the upper housing 73.
It is assembled by press-fitting into a. As before, the fixed shaft 62, lower housing 72 and upper housing 73
Thus, a cylindrical annular chamber 70 concentric with the fixed shaft 62 is formed.

75a, 75b, and 75c are O-rings that prevent the fluid sealed in the chamber 70 from leaking.

A pulley 7Ba is attached to the eccentric outer peripheral surface 73b of the upper housing 73 via two rows of ball bearings 7B+, which is rotatable together with its outer ring. Pulley 7
In some cases, the outer ring 8a is integrated with the outer ring of the pole bearing 78b, and in the claims, the term "outer ring" is intended to include something like the pulley 78a shown in FIG. The back surface of the toothed belt 61 contacts the pulley 78a, and the eccentric body 63 moves in an I-shape with respect to the fixed shaft 62, thereby adjusting the tension to 1i1.

The means for applying tension to the toothed belt 61 is a tension spring 65 as shown in FIG. A tension spring 65 that is engaged with a protrusion 76 provided on the upper housing 73 and a pin provided on the engine block 64 urges the eccentric body 63 in a direction that applies tension to the toothed belt 61. Note that the eccentric body 63 may be biased by a compression spring 65' as shown by the imaginary line.

The sealed fluid is silicone oil, which is the same as in the first embodiment. Reference numeral 79 is an injection port for sealing silicone oil into the chamber 70.

Pulley 7 receives tension from chamber 70 and timing belt 61
The pulleys 78a and the chambers 8a are arranged offset in the axial direction so as not to interfere with each other, and the dimensions of the pulley 78a and the chamber 70 can be set independently without being limited by the dimensions of the other.

In the first embodiment, the chamber was provided inside the outer ring, but
The pulley 78a achieves its purpose if a predetermined amount of eccentricity is secured, and the outer diameter of the pulley 78a can be reduced by axially shifting the pulley 78a in this manner. Therefore, the weight of the part that swings as an eccentric body is reduced, and as a result, the moment of inertia is reduced, and the timing belt 6
This improves the ability to follow minute tension fluctuations, making it an effective means for absorbing vibrations.

On the other hand, the dimensions of the pulley 78 (inside and outside play) 71a and 71b
It can be made large without being limited by the size of a, and since the shear resistance is proportional to the fourth power of the plate area, a large resistance force can be easily obtained. Shear resistance can also be varied by varying the size of the plates, as well as by various factors of the fluid enclosed.

Furthermore, since all parts are mounted on a fixed shaft, installation to the engine block is completed by simply tightening bolts and locking springs to pins.

Effects of the Invention The auto-tensioner of the present invention has the characteristics necessary for an auto-tensioner as described in the "Prior art and its problems" section, and has an integrated structure with a built-in tension adjustment mechanism, making it lightweight and compact. It is. Its installation is easily completed by simply tightening bolts and tightening springs.

Since the main performance is determined by the number of inner and outer plates, the performance is stable and manufacturing is easy.

In particular, with conventional oil and orifice combinations, performance degradation due to air entrainment is unavoidable, but the auto tensioner of the present invention utilizes the shear resistance of viscous fluid.
Complete sealing is not required since air intrusion is not a major problem. Even if air gets mixed into the oil chamber, the air only accumulates at the top and does not enter the inside of the plate, so the performance characteristics do not change. Even if a large amount of air or the like gets mixed in, the resistance will only decrease and no damage will occur.

In the configuration according to claim 4, in which the chamber is arranged axially shifted from the outer ring, the outer diameter of the plate can be increased, the shear resistance can be set to a desired value, and the moment of inertia of the eccentric body can be reduced. It becomes smaller and the followability to vibration improves.

Furthermore, since the filling rate of the viscous fluid is not 100%, changes in the volume of the viscous fluid due to temperature can be automatically compensated for.

[Brief explanation of the drawing]

The drawing shows an embodiment of the autotensioner of the present invention, and shows the first embodiment of the autotensioner of the present invention.
The figure is an exploded perspective view of the first embodiment, Figure 2 is a sectional view when installed on the engine block, Figure 3 is a front view with different cross-sectional views, and Figures 4 and 5 are examples of how the auto tensioner is used. FIG. 6 is a cross-sectional view of the auto tensioner of another embodiment when it is installed on the engine block, FIG. 7 is a front view of FIG. 6, and FIG. 8 is an exploded perspective view of the auto tensioner of FIG. 6. It is. 10.60...Auto tensioner 11.61...Toothed belt 12.62...Fixed shaft 13.63...Eccentric body 15.65.65'...Spring 20.71a...Inside Plate 26...Spline 30.71b...Outer plate 36...Spline 40.70...Chamber 48a, 78a...Outer ring 48b...Rolling elements Fig. 4 Fig. 5 Fig. 7 111---11---ko

Claims (1)

[Scope of Claims] 1) A fixed shaft, an eccentric body that is swingable with respect to the fixed shaft, a spring means that applies a turning force to the eccentric body, and a chamber provided between the fixed shaft and the eccentric body. An autotensioner comprising a viscous fluid sealed in an autotensioner, wherein the viscous fluid generates shear resistance against relative rotational movement of the eccentric body with respect to the fixed shaft. 2) The autotensioner according to claim 1, wherein an inner plate is spline-fitted to the fixed shaft, an outer plate is spline-fitted to the eccentric body, and a viscous fluid is interposed between the two plates. 3) The autotensioner according to claim 1 or 2, further comprising an outer ring which rotates in pressure contact with the back surface of the belt via a rolling bearing on the outside of the eccentric body. 4) The autotensioner according to claim 3, wherein the chamber is provided at a position offset in the axial direction with respect to the outer ring. 5) The autotensioner according to claim 1, wherein the viscous fluid is enclosed in the chamber at a ratio of 80 to 90%.