JPH01150058A - Automatic tensioner - Google Patents

Abstract

PURPOSE:To facilitate assembly stably obtaining performance for a long period by providing a one-way clutch inhibiting an intermediate member from rotating in a direction of separating an idler from a belt while providing high viscous oil to be interposed between the intermediate member and a movable eccentric member and applying torque tightening a fixed shaft when tension of the belt increases. CONSTITUTION:When a belt 25 rapidly loosens, an intermediate member 13 rotates for a fixed shaft 10 in a part of a one-way clutch 14, and an idler 20 promptly follows up to the loosening belt 25, holding it tension. Reversely contracting the belt 25, when its tension increases, the intermediate member 13 is inhibited from its rotation for the fixed shaft 10 by the one-way clutch 14, and a movable eccentric member 16 rotates for the intermediate member 13 in a direction of decreasing the tension against viscous resistance of interposing high viscous oil, slowly moving the idler 20 till it holds the tension to a predetermined value. Accordingly, suppressing a vibration of the idler 20 by the high viscous oil and stably obtaining performance for a long period while enabling the idler to be fixed only by the fixed shaft 10, assembly can be facilitated.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application This invention is applicable to autotensioners, more specifically, to apply a predetermined tension to a timing belt placed between a crankshaft pulley and a camshaft pulley in an automobile engine. Regarding the auto tensioner provided.

Conventional technology and its problems Timing belts such as those described above are equipped with idlers such as springs to absorb belt expansion and contraction due to engine temperature changes and belt elongation due to use, and to apply a predetermined tension to the belt. An auto tensioner is provided that presses the belt against the belt using the elastic force of the tensioner. Further, such an autotensioner is provided with a hydraulic damper in order to suppress resonance of the idler due to belt vibration or engine vibration. However, with a hydraulic damper type auto tensioner, oil leaks and it is necessary to replenish the oil pressure, making maintenance troublesome. Further, since a mechanism for preventing oil leakage, a mechanism for drilling the orifice and adjusting its size, etc. are required, the structure of the hydraulic damper becomes complicated and expensive.

Therefore, the present applicants have developed a cylindrical fixed member that is fixed to a fixed part such as an engine with a bolt, a cylindrical movable eccentric member that is eccentrically and rotatably attached to the outside of this fixed member, and A cylindrical idler rotatably attached to the outside of the movable eccentric member and in contact with the belt, and a spring provided between the fixed part and the movable eccentric member to bias the movable eccentric member in a direction in which the idler comes into pressure contact with the belt. proposed an autotensioner in which highly viscous oil is interposed in the gap between the outer circumferential surface of the fixed member and the inner circumferential surface of the movable eccentric member (see Japanese Patent Application No. 189250/1982).

According to this autotensioner, vibrations of the idler due to belt vibrations and engine vibrations can be suppressed by the viscous resistance of the high-viscosity oil. Further, in response to changes in tension due to expansion and contraction of the belt, the movable eccentric member rotates gently in a direction to keep the tension constant, thereby maintaining the tension of the belt at a predetermined value. However, if the belt suddenly loosens due to factors such as sudden acceleration of the engine, the rotation of the movable eccentric member is slow due to viscous resistance, so it is impossible for the idler to follow the sudden loosening of the belt. In particular, when an autotensioner is applied to a timing belt, if the idler is unable to follow sudden loosening of the belt, the problem of timing belt tooth skipping may occur, which is undesirable.

In addition, in order to reduce the number of parts in such an auto tensioner, it is conceivable to attach the movable eccentric member directly to the outside of the bolt-shaped fixed shaft that is screwed into the fixed part. Since the rotation of the movable eccentric member due to belt tension fluctuations is transmitted to the fixed shaft through high viscosity oil, there is a risk that the fixed shaft may loosen during use and the auto tensioner may not operate properly. Furthermore, in this case, when the autotensioner is assembled by screwing the fixed shaft into the fixed part, it is necessary to rotate the fixed shaft against the viscous resistance of the oil, making the work difficult.

SUMMARY OF THE INVENTION An object of the present invention is to provide an autotensioner that solves the above-mentioned problems.Means for solving the problems The autotensioner according to the present invention includes a fixed shaft that is screwed into a fixed part and fixed to the fixed part, and a a cylindrical intermediate member rotatably attached to the outside of the intermediate member; a cylindrical movable eccentric member eccentrically and rotatably attached to the outside of the intermediate member; and a cylindrical movable eccentric member rotatably attached to the outside of the movable eccentric member. a cylindrical idler that contacts the belt; a spring that is provided between the fixed part and the movable eccentric member and biases the movable eccentric member in a direction in which the idler comes into pressure contact with the belt; and a spring that is provided between the fixed shaft and the intermediate member. The one-way clutch is provided with a one-way clutch that allows rotation of the intermediate member in the direction of pressing the idler against the belt, but prevents rotation of the intermediate member in the direction of separating the idler from the belt. When high viscosity oil is interposed in the gap between the inner circumferential surfaces of the members and the belt tension increases, the direction of rotation of the movable eccentric member and the direction of tightening of the fixed shaft match, and the tension of the belt increases. When the torque increases, torque is applied to the fixed shaft from the movable eccentric member via a one-way clutch in a direction that tightens the fixed shaft.

If the working belt suddenly loosens, the intermediate member rotates relative to the fixed shaft in the area of the one-way clutch, and the idler quickly follows the loosening of the belt to maintain the tension at a predetermined value. Conversely, when the belt contracts and the tension increases, the rotation of the intermediate member relative to the fixed shaft is blocked by the one-way clutch, so the movable eccentric member resists the viscous resistance of the high-viscosity oil relative to the intermediate member. rotate gently in the direction of reducing tension.
The idler moves slowly until the tension is held at a predetermined value. The idler vibrations caused by belt vibrations and engine vibrations are suppressed by the viscosity of the high viscosity oil.

Furthermore, when the belt tension increases, the rotation of the intermediate member relative to the fixed shaft is blocked by the one-way clutch, so the rotation of the movable eccentric member is transmitted to the fixed shaft via the high-viscosity oil and the one-way clutch. Torque acts on the fixed shaft in a direction to tighten it further. Conversely, when the tension of the belt is reduced, the intermediate member rotates relative to the fixed shaft at the one-way clutch portion, so no torque is applied to the fixed shaft in the direction of loosening it. therefore,
There is no risk of the fixed shaft loosening during use. Furthermore, when the movable eccentric member and the intermediate member are rotated in the direction of tightening the fixed shaft with the fixed shaft fixed, the rotation is blocked by the one-way clutch. When the fixed shaft is rotated in the tightening direction in a fixed state, the rotation is allowed by the one-way clutch. Therefore, when assembling the autotensioner, only the fixed shaft can be freely rotated in the tightening direction, and the autotensioner can be easily fixed.

Embodiments Hereinafter, embodiments in which the present invention is applied to a timing belt for an automobile engine will be described with reference to the drawings.

The autotensioner of this embodiment is fixed to a fixed part of the engine (for example, a cylinder block) (11) by a single bolt-shaped fixed shaft (10).

An intermediate cylindrical portion (10a) is provided at one end of the fixed shaft (10).
A threaded portion (10b) having a slightly smaller outer diameter is provided, and a collar portion (10c) and a head portion (10d) are formed in a negative shape at the other end. On the threaded part (10b) of the fixed shaft (10),
A side plate (12) in the form of a perforated disk having approximately the same outer diameter as the flange (toe) is press-fitted. And the fixed part (11)
By screwing in the threaded part (1 (lb)) to fix the fixed shaft (10), the side plate (12) is clamped between the cylindrical part (LOa) of the fixed shaft (10) and the fixed part (11). It will be done.

A cylindrical portion (LOA) of the fixed shaft (10) is surrounded by a cylindrical portion (LOA).
A cylindrical intermediate member (13) that is slightly shorter than 10a) and has a smaller outer diameter than the collar portion (10c) and the side plate (12) is concentrically attached via a one-way clutch (14). The inner diameter of the portion of the intermediate member (13) on the flange (10c) side is slightly larger than the outer diameter of the cylindrical portion (log) of the fixed shaft (10), and the inner diameter of the remaining portion is larger than this. Then, the cylindrical part (10a) of the fixed shaft (10) on the side plate (■2) side
) and the intermediate member (13). A sleeve (15) is inserted between the sleeve (15) and the intermediate member (13).
) A one-way clutch (14) is provided in an annular space between the cylindrical portion (10a) and the intermediate member (13). This one-way clutch (14) is, for example, a known one-way roller clutch, and rotation of the intermediate member (13) in the counterclockwise direction in FIG. 1 with respect to the fixed shaft (10) is allowed because the clutch (14) becomes free. However, the clockwise rotation in the figure is caused by the clutch (1
4) is designed to lock and prevent it.

A short cylindrical movable eccentric member (16) having the same length as the intermediate member (13) is eccentrically and rotatably attached around the intermediate member (13). An eccentric hole (17) is formed in the eccentric member (1B), and an intermediate member (13) is fitted into this eccentric hole (17). The outer peripheral surface of the intermediate member (13) and the eccentric member (1
The gap between B) and the inner surface of the eccentric hole (17) is kept to a minimum, and this part has a viscosity of, for example, 100,000 cs.
The rotational torque of the eccentric member (1B) is increased by interposing the silicone oil (0) at a temperature of t (25° C.) or higher. Note that this rotational torque is determined not only by the viscosity of the oil but also by the outer diameter and length of the intermediate member (13), and the eccentric member (I).
It is set depending on the size of the gap with B). Furthermore, between both ends of the intermediate member (13) and both ends of the eccentric member (1B), there are O-rings (18) (19) for sealing oil (0).
) is provided.

A cylindrical idler (20) is attached to the outer periphery of the eccentric member (16).
is mounted through a plurality of spherical rolling elements (21) so that it rotates but hardly moves in the axial direction.

A fixed shaft (10) is attached to the side plate (12) side of the eccentric member (6).
A boss portion (16a) is formed substantially concentric with the boss portion (lea), and a torsion coil spring (22) is attached around the boss portion (lea). One end (22a) of the spring (22) is connected to the boss (16a) of the eccentric member (16) and the eccentric part (
The pin (2
3), and the other end (22b) is the fixed part (11)
It is hung on a pin (24) fixed to. The spring (22) biases the eccentric member (16) counterclockwise in FIG.
5) is pressed against the surface without teeth (26).

A pin insertion hole (27) is formed in the eccentric part (IBb) of the eccentric member (16) and passes through the eccentric part (IBb) in the axial direction. A set pin (28) is inserted from the side. This set bin (28) protrudes from the step (lee) of the eccentric member (16) to the outside of the boss (lea), and is hung by a spring (22) on the pin (24) of the fixed part (11).
) is hung on this set pin (28). Note that at this time, the spring force of the spring (22) is set to an appropriate value in advance.

In this state, the fixed shaft (1
0) and the side plate (12) to the fixed part (11), remove the set pin (28) from the eccentric member (16) and attach the end (22b) of the spring (22) to the fixed part (11).
The auto tensioner can be easily assembled by hooking it onto the pin (24).

If the belt (25) suddenly loosens due to factors such as sudden acceleration of the engine, the elastic force of the spring (22) will cause the eccentric member (1
6) tries to rotate counterclockwise in Figure 1, and the oil (
0), the intermediate member (13) also tries to rotate in the same direction. Since the rotation of the intermediate member (13) in this direction is permitted by the one-sided clutch (14) becoming free, the eccentric member (16) and the intermediate member (13) are integrated as shown in FIG. The idler (20) rapidly follows the loosening of the belt (25) and is pressed against it, maintaining a predetermined tension.

Therefore, the problem of tooth skipping of the timing belt (25) does not occur. Conversely, when the belt (25) contracts and the tension increases, the eccentric member (16) tries to rotate clockwise in FIG. 1 against the elastic force of the spring (22).
The intermediate member (13) also tries to rotate in the same direction due to the viscous resistance of the oil (0).

However, since the rotation of the intermediate member (13) in this direction is prevented by the one-sided clutch (14) being locked, only the eccentric member (16) resists the viscous resistance of the oil (0) and rotates as shown in FIG. The belt (2) rotates gently clockwise.
5) until the tension of the idler (20
) moves slowly.

Furthermore, vibrations of the idler (20) due to vibrations of the belt (25) and engine vibrations are suppressed by the viscous resistance of the silicone oil (0) to rotation.

Since the vibration damping effect is exerted by the viscous resistance of the silicone oil in this way, the performance is stable over a long period of time and there is no need to replenish the oil. Further, the structure is extremely simple and compact, and it is inexpensive and requires a small installation space.

In order to interpose the silicone oil (0) in the gap between the intermediate member (13) and the eccentric member (16), either the outer peripheral surface of the intermediate member (13) or the inner surface of the eccentric hole (17) of the eccentric member (16) All you have to do is apply silicone oil to one or both and then fit them together. Note that the outer peripheral surface of the intermediate member (13) or the eccentric hole (1
A small spiral groove or a small groove parallel to the axis is provided on the inner surface of 7), and silicone oil is poured into this groove by inserting the eccentric member (1B) into the intermediate member (13) and rotating it. It can also be easily distributed throughout. In addition, the intermediate member (
13) or the eccentric hole (17) of the eccentric member (16).
) may be provided with an annular groove on the inner surface to store silicone oil.

In the case of the above autotensioner, the threaded portion (10b) of the fixed shaft (1o) is formed with a right-handed thread, and the belt (2
The direction of rotation of the eccentric member (16) (clockwise in FIG. 1) when the tension of 5) increases is the same as the direction of tightening of this right-handed screw. For this reason, when the tension of the belt (25) increases, the one-way clutch (14)
) is locked, and a torque is applied to the fixed shaft (10) in a direction to further tighten it. Conversely, when the tension of the belt (25) decreases, the one-way clutch (14) becomes free as described above, so no torque is applied to the fixed shaft (lO) in the direction of loosening it. Therefore, there is no possibility that the fixed shaft (10) will loosen during use. In addition, with the fixed shaft (10) fixed, the movable eccentric member (1
6) and the intermediate member (13) are rotated in the direction in which the fixed shaft (10) is tightened, the one-way clutch (14) is locked. When the fixed shaft (10) is rotated in the tightening direction in the fixed state, the one-way clutch (14) becomes free. Therefore, when assembling the auto tensioner, sometimes
Freely rotate only the fixed shaft (10) in the direction of tightening.
Easy to fix and assemble.

Note that the autotensioner according to the present invention can of course be applied to belts other than the timing belt of an automobile engine.

Effects of the Invention According to the autotensioner of this invention, as described above,
The tension can be maintained at a predetermined value by quickly following sudden loosening of the belt, and the vibration of the idler can be suppressed by the viscous resistance of the high-viscosity oil. The vibration of the idler is suppressed by the viscous resistance of the high viscosity oil.
The performance is stable over a long period of time, the structure is simple and inexpensive, and there is no oil leakage, so maintenance is easy. In addition, there is no risk that the fixed shaft may loosen during use and prevent normal operation, and it is easy to assemble.

[Brief explanation of the drawing]

FIG. 1 is a vertical sectional view (cross-sectional view taken along the line 1-1 in FIG. 2) of an autotensioner showing one embodiment of the present invention;
3 is a cross-sectional view taken along the line ■--■ in FIG. 2, FIG. 4 is a cross-sectional view taken along the line IV--IV in FIG. 2. (10)...Fixed shaft, (11)...Fixed part, (1
3) ... intermediate member, (14) ... one-way clutch,
(16)...Movable eccentric member, (20)...Idler, (22)...Torsion coil spring, (25)...Timing belt. that's all

Claims (1)

[Claims] A fixed shaft screwed into the fixed part, a cylindrical intermediate member rotatably attached to the outside of the fixed shaft,
A cylindrical movable eccentric member that is eccentrically and rotatably attached to the outside of this intermediate member, a cylindrical idler that is rotatably attached to the outside of this movable eccentric member and contacts the belt, and a fixed part and a movable part. A spring is provided between the eccentric members and biases the movable eccentric member in a direction in which the idler comes into pressure contact with the belt, and a spring is provided between the fixed shaft and the intermediate member to rotate the intermediate member in a direction to press the idler against the belt. It is equipped with a one-way clutch that allows rotation of the intermediate member in the direction of separating the idler from the belt, but prevents rotation of the intermediate member, and high viscosity oil is interposed in the gap between the outer circumferential surface of the intermediate member and the inner circumferential surface of the movable eccentric member. , the rotation direction of the movable eccentric member when the belt tension increases is the same as the tightening direction of the fixed shaft, and when the belt tension increases, the one-way clutch is applied to the fixed shaft from the movable eccentric member. An auto tensioner that applies torque in the direction of tightening the fixed shaft through the tensioner.