JPS58121344A - Automatic tensioner for belt - Google Patents

Abstract

PURPOSE:To make the titlted tensioner into a state so that it is not influenced by an oscillation of either a belt or an engine even over absorption of a variation of belt tension resulting from a temperature variation, by combining a spring additing tension to the belt with a hydraulic pressure damper. CONSTITUTION:A variation of tension of a timing belt 18 resulting from a temperature variation is absorbed by a coil spring 60. A piston rod 36 is moved slowly, as the temperature variation is taken place gradually and movement of the piston rod 36 is not restrained as a speed of a liquid flowing through a restrictor 48 is very slow. When an idler 20 is oscillated by an oscillation of either the timing belt 18 or an engine while a titled tensioner is being applied, the piston rod 36 is oscillated by a bracket 22. At this time, although a liquid filled in liquid chambers 52 and 54 is apt to move suddenly, kinetic energy is made to disappear through the restrictor and the oscillation of the piston rod 36 is controlled.

Description

[Detailed description of the invention] The present invention relates to an autotensioner for a belt.

For example, in an automobile engine, the tension of the timing belt passed between the crankshaft pulley and the camshaft boot is generally set and used as follows.

A bracket that rotatably supports the eyelet is temporarily pivoted to the engine body, and this bracket is pulled and rotated by a coil spring to press the idler against the timing belt. After setting the initial tension on the timing belt in this way, the bracket is fixed to the engine body and the idler is put into use with no displacement.

When the engine body generates heat during use and the ambient temperature rises, both the engine body and the timing belt will thermally expand, but in this case, since the timing belt generally has a smaller thermal expansion coefficient, the timing belt tension will be The tension becomes higher than the initial tension. As a result, this causes an increase in noise and a decrease in durability. Conversely, when the ambient temperature decreases, the tension in the timing belt becomes smaller than the initial tension, causing loosening. As a result, the jump pink phenomenon occurs, causing engine malfunction, and the load sharing on one tooth of the timing belt increases, causing cracks to occur at the base of the tooth, resulting in severe deterioration of quality.

In order to solve the above problem, it may be possible to hold the bracket swingably even after setting the initial tension, and configure the coil spring to absorb changes in tension.

However, with this configuration, the idler is likely to resonate with the vibration of the timing belt or the imaging of the engine, and accidents such as breakage of the coil spring due to this resonance may occur, resulting in a lack of reliability.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide an autotensioner that eliminates the above-mentioned disadvantages.

According to the autotensioner of the present invention, the bracket that rotatably supports the idler is swingably supported by a fixed object such as the engine body. Dan ξ is placed between this σ bracket and the fixed object. The damper consists of a cylinder, a piston, and a piston/rod, and has two liquid chambers separated by the piston and a throttle that communicates the two liquid chambers. A coil spring that applies tension to the belt is installed inside or outside the damper, and one of the cylinder and the piston/rod is connected to the fixed object, and the other is connected to the bracket.

Embodiments of the present invention will be described below with reference to the accompanying drawings.

As shown in FIG. 1, the auto tensioner 10 of the present invention has a timing belt 18 installed between a crankshaft pulley 14 and a camshaft pulley 16 provided on an engine body 12 which is a fixed object. Timing belt 1 when rotating with timing
Most suitable for automatically adjusting the tension of 8.

The auto tensioner 10 is as shown in FIG.

It includes an idler 20, a bracket 22, and a dumbbell 24.

The idler 20 is rotatably supported by a bracket 22. On the other hand, the bracket 22 is pivotally connected to the engine body 12 by a pin 26. An arc-shaped elongated hole 28 having the center of the pin 26 as the center of the arc is provided in the bracket 22, and a stepped bolt 60 inserted through the elongated hole 28 and screwed into the engine body 12 prevents the bracket 22 from lifting up. It swings over the length of the elongated hole 28 in a prevented state. The idler 20 may be constituted by a bearing having an inner ring and an outer ring, the bracket and the inner ring may be fixedly attached, and the inner ring may be formed with the elongated hole to allow the bracket to swing.

The damper 24 consists of a cylinder 62, a piston 34, and a piston/rod 36. In the example of FIG. 2, the piston 64 and piston rod 66 are formed in the form of a plunger. The cylinder 62 is linked to the engine body 12. In the illustrated example, it is fixed to the engine body 12 by bolts passing through a pair of mounting seats 68. One end of this cylinder 32 is sealed to form a bottom 40, and the other end 41 is open, with a recess 4 formed on the inner surface approximately in the center of the cylinder in the axial direction.
2 is formed.

The piston rod 66 is slidably inserted into the cylinder roller 2 and slides between a shoulder 44 provided on the bottom 40 of the cylinder 32 and a stop ring 46 provided on the open end 41. A throttle 48 is formed between a portion of the piston rod 66 that is more inward than the portion corresponding to the recess 42 of the cylinder, that is, a portion that extends toward the bottom 40 of the cylinder, and the inner surface of the cylinder 62. On the other hand, the piston rod 66
An O-ring 50 is disposed at the outer end 64 of.

A seal is provided between the cylinder 32 and the piston/rod 36.

A liquid chamber 52 is provided inside the piston rod 66 and outwardly from the piston 64. On the other hand, a liquid chamber 54 is provided between the bottom 40 of the cylinder 62 and the piston 64, and both liquid chambers 52 and 54 are connected to the piston 64. 64. In the illustrated example, the solid piston rod 66 is bored 5
6, the piston 34 is press-fitted into the inner end of the piston rod 1-'' 66 to form the liquid chamber 52.

This liquid chamber 52 and the recess 42 of the cylinder communicate with each other via a passage 58, and on the other hand, a throttle 48 provided inward of this recess 42 communicates between the recess 42 and the liquid chamber 54. .

Therefore, the two liquid chambers 52 and 54 are communicated via the throttle 48. Both liquid chambers are filled with a highly viscous liquid such as silicone oil.

Previously, a coil spring 60 is disposed within the liquid chamber 54 between the bottom portion 40 of the cylinder 62 and the piston filter 4.

The piston rod 36 is biased toward the open end 41 of the cylinder 62. Outer end 64 of piston rod 66
, the hinge 62 attached to the bracket 22
The bracket 22 is linked via. In the illustrated example,
A recess 65 is formed in the end portion 64, and the spherical head of the pin 62 is inserted into the recess 65, and the pin 62 is inserted into the recess 65.
It is possible to swing with respect to 5.

When the piston rod 36 is pushed outward by the coil spring 60, the bracket 22 rotates around the pin 26 via the pin 62, pressing the idler 20 against the timing belt 18 and applying tension. Then, when the pressing force by the coil spring 60 and the tension of the timing belt 18 are balanced, the rotation of the bracket 220 stops.

When the ambient temperature rises during use, both the engine body 12 and the timing belt 18 undergo thermal expansion, but the thermal expansion of the engine body 12 is larger.

Therefore, the tension of the timing belt 18 tends to become larger than the initial tension, the coil spring 60 is compressed by an amount corresponding to the difference in tension, and the bracket 22 rotates in a direction to release the tension. vice versa.

When the ambient temperature drops, the coil spring 60 is expanded,
The bracket 22 rotates in a direction to increase the tension. As a result, timing belt 18 is maintained at substantially its initial tension regardless of temperature. Since the temperature change in each case occurs gradually, the piston rod 36 moves slowly and the velocity of the liquid flowing through the restriction 48 is so slow that it does not constrain the movement of the piston rod 66.

During use, if the idler 20 vibrates due to vibrations of the timing belt 18 or engine vibrations, the piston rod 66 will vibrate due to the bracket 22.

At this time, the liquid filled in both liquid chambers 52 and 54 will rapidly flow.

However, the kinetic energy is dissipated by the aperture 48.

Vibration of the piston rod 36 is suppressed.

The bolt chisel 70 shown in FIG. 6 applies tension to the timing belt 18 by pulling force. The idler 20 and bracket 22 have the same configuration as in the previous example. A piston rod 74 in the form of a plunger is slidable relative to the cylinder 72 of the damper 70.
4 is provided with a piston 76. The piston 76 separates liquid chambers 78 and 80, and communicates the two liquid chambers through a throttle 82 at the center thereof. In the figure, 84 is a rod guide, 86
is the 0 ring for the 7-rule.

A hook 88 fixed to the cylinder 72 of the damper 70 is connected to a hole 89 of the bracket 22, and a hook 90 fixed to the piston rod 74 is connected to a pin 91 protruding from the engine body 12 by hooks. There is.

The coil spring 92 is coaxially distributed with electricity to the damper puff 0 and is externally covered. One end 94 of this coil spring 92 is hooked to a hole 95 of the bracket 22, and the other end 96 is hooked to a pin 97 protruding from the engine body 12, respectively, for use.

The damper 100 shown in FIG. 4 has a piston rod 104 extending over the entire length of the cylinder 102! I can do it. One end 106 of the piston rod 104 projects outward through a plug 110 screwed into the open end of the cylinder '102 via a seal member 108, and the other end 107
is fitted into a guide portion 103 provided at the closed end of the cylinder 102. The piston rod 104 is the plug 11
0 and the guide part 106 in a sealed state by sealing elements 112, 114 arranged respectively on the guide part 106. In the figure, 116 is a space 118 inside the guide section 106.
This is an air vent connected to.

A piston 120 is fixed to the piston rod 104, and separates two liquid chambers 122 and 124, and a throttle 1.
26 communicates both liquid chambers 122 and 124. A coil spring 128 is disposed between the piston 120 and the plug 110. In the figure, 160 is a linking hook.

In the damper 140 shown in FIG. 5, the liquid chambers 144 and 146 separated by the piston 142 are
8 and communicated by a bore 150 and a throttle 152 provided in the piston rod.

Piston 142 and piston rod 148 are sealed by seal members 154 and 156, respectively.

A boring 160 is machined into a portion of the piston rod 148 that protrudes from the piston 142 toward the plug 158 to form a cylindrical portion 161.
The plug 158 enters into an annular space 164 formed between the outer peripheral surface of the plug 158 and the cylinder 162, and is sealed by a seal member 166 disposed on the plug 158. The liquid chamber 1
A coil spring 168 is arranged at 44 . 170 in the diagram
is an air vent connected to the space 164.

j Figure 16 above Figure 5 0 Other 0 Configuration 3
'-1 operation is the same as that in FIG. 2, so it will be omitted. In the examples shown in FIGS. 2 and 6, the cylinder of the damper is linked to the bracket, and the piston rod is linked to the engine body, but the arrangement may be reversed.

The sides described above are most suitable for tensioning timing belts, but can also be applied to tensioning other belts.

The autotensioner of the present invention maintains belt tension substantially constant regardless of ambient temperature.

Therefore, noise at high temperatures and jumping at low temperatures do not occur. Additionally, since it operates under constant tension, the durability of the belt is greatly improved. Furthermore, the damper exerts a damping effect on vibrations transmitted from a vibrating body such as a belt or an engine to the idler, so that the idler does not resonate.

[Brief explanation of the drawing]

FIG. 1 is a front view of an engine to which the auto tensioner of the present invention is applied, FIGS. 2 and 6 are partially sectional front views of the auto tensioner of the present invention, and FIGS. 4 and 5 are front views of the auto tensioner of the present invention. FIG. 3 is a cross-sectional view of a damper applicable to. 10: Auto tensioner 12: Engine body 14.1
6: Pulley, 18: Timing belt. 20: Idler, 22: Bracket. 48.82, 126, 152: Aperture. 24.70.100.140: Damper, 32.72,
102,162 Niji Linda. 54.76.120.142: Piston, 36.74
．． 104.148: Piston rod. Agent Patent Attorney Nobuyuki Matsunaga Figure 3 Figure 4

Claims (1)

[Claims] An auto tensioner that adjusts belt tension by moving an idler pressed by a belt relative to a fixed object to change the pressing force, the idler being rotatably supported and swingably pivoted to the fixed object. A damper comprising a bracket attached to the cylinder, two liquid chambers formed by a cylinder, a piston, and a piston rond, separated by the piston, and a throttle communicating the two liquid chambers. A damper for which one of the piston ronds is linked to the fixed object and the other to the bracket, and a coil spring that is installed inside or outside the damper and applies tension to the belt. auto tensioner.