JPH08189551A - Automatic tensioner - Google Patents

Abstract

PURPOSE: To provide a lightweight and inexpensive automatic tensioner by which a noise based on resonance is hardly generated when an engine is operated. CONSTITUTION: A swinging frame 7 is swung with a pivot 6 as the center by a rod 10 of an actuator 8, and a pulley 5 is elastically pressed toward a belt 1. The swinging frame 7 is manufactured by metal injection molding of magnesium alloy. Machine work is not particularly performed after molding, and it is combined with the other member. An automatic tensioner containing the swinging frame 7 made of magnesium alloy is lightweight, and a swinging displacement part hardly resonates with vibration of an engine. In the metal injection molding of magnesium alloy, since necessary dimensional accuracy and surface roughness can be obtained with out performing after-work, work cost can be reduced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The automatic tensioner according to the present invention is a belt for driving a timing belt of an automobile engine or an auxiliary machine such as an alternator or a compressor (hereinafter, these are collectively referred to simply as "belts"). It is used to give a proper tension to.

[0002]

2. Description of the Related Art Since a camshaft of an engine is rotationally driven in synchronization with a crankshaft, a drive device using a belt 1 as shown in FIG. 1 is widely used. In FIG. 1, 2 is a drive pulley that is driven to rotate by the crankshaft of the engine, 3 and 3 are driven pulleys fixed to the end of the camshaft, 4 and 4 are for guiding the belt 1,
Alternatively, a guide pulley or a driven pulley for driving an auxiliary machine such as a water pump, and 5 are pulleys for giving proper tension to the belt 1.

The pulley 5 is pivotally supported by a swing frame 7 which swings around a pivot 6 provided on the front surface of a cylinder block which is a fixed portion. Then, between the swing frame 7 and the front surface of the cylinder block,
An actuator 8 is provided. As is well known, the actuator 8 is constructed by incorporating a spring and a damper device in a cylinder cylinder 9 fixed to the front surface or the like, and the rod 10 which is given elastic force in the protruding direction by the elastic force of the spring, A part of the swing frame 7 is pressed. Therefore, the oscillating frame 7 is given an elastic force to oscillate in the clockwise direction in FIG.
To elastically press. Further, since the damper device serves as a resistance against the rod 10 being pushed into the cylinder cylinder 9, even if the belt 1 vibrates, the pulley 5 holds down the belt 1 and the vibration grows. Prevent things.

The basic structure of the automatic tensioner is as described above, but the combination portion of the swing frame 7 and the pulley 5 is conventionally structured as shown in FIGS. 2 to 3 or 4 to 5. Even in the case of the structure of the first example shown in FIGS.
Alternatively, also in the structure of the second example shown in FIGS. 4 to 5, the swing frame 7 is made by die casting of an aluminum alloy and has a cylindrical portion 11 at one end (lower end in FIGS. 2 to 5). Then, the cylindrical portion 11 is swingably supported around the pivot 6 via slide bearings 12, 12 provided on the inner peripheral surface of the cylindrical portion 11.

Further, the tip end (upper end of FIGS. 2 to 5) of the rocking plate portion 13 which is continuous from the outer peripheral surface of the end of the cylindrical portion 11 in the diametrical direction (upper side of FIGS. 2 to 5) has a short bottom. Cylindrical inner ring member 1
4 are fixed by bolts 15 and nuts 16.
The bolt 15 forms a displacement axis and is parallel to the pivot shaft 6. The pulley 5 is rotatably supported around the inner ring member 14 via a plurality of balls 17, 17. A deep groove type inner ring raceway 18 is formed on the outer peripheral surface of the inner ring member 14, and a deep groove type outer ring raceway 19 is formed on the inner peripheral surface of the pulley 5, respectively.
9 and the balls 17 and 17 constitute a deep groove type ball bearing.

Furthermore, the base end portion (lower end portion in FIGS. 2 to 5) of the rocking plate portion 13 extends continuously from the outer peripheral surface of the cylindrical portion 11 in the diametrical direction (leftward direction in FIGS. 3 and 5). The receiving piece 21 is fitted and fixed to the distal end portion (the left end portion in FIGS. 3 and 5) of the moving arm portion 20,
The tip of the rod 10 of the actuator 8 is abutted against the receiving piece 21. The receiving piece 21 is made of a hard metal such as bearing steel, and uses a roller for a roller bearing, for example. The receiving piece 21 prevents the swing frame 7 made of aluminum alloy from being scraped by the rod 10 made of hard metal.

In order to fit and fix the receiving piece 21 as described above,
In the case of the first example shown in FIGS.
A circular concave portion 22 is formed at the tip end of the above, and the receiving piece 21 is press-fitted into this circular concave portion 22 in the axial direction (upper and lower fragrance in FIG. 3). In the case of the structure of the first example, the tip of the rod 10 comes into contact with the axial end surface of the receiving piece 21 (the lower end surface in FIG. 3). In addition, in the case of the second example shown in FIGS. 4 to 5, a notched columnar notch 23 is formed in the tip end portion of the swing arm portion 20, and the notch 23 has an axial end opening. The receiving piece 2
1 is pressed (in the front and back directions in FIG. 5). In the case of the structure of the second example, the tip of the rod 10 abuts on the outer peripheral surface of the receiving piece 21 exposed from the notch 23.

6 to 8 show the swing frame 7 used in the structure of the first example, and FIGS. 9 to 11 show the swing frame 7 used in the structure of the second example. Each of the swing frames 7 retains the accuracy of each of these parts by die-casting an aluminum alloy and then machining (cutting) the following parts. A portion of one end of the oscillating plate portion 13 (upper half portion on the left side of FIGS. 8 and 11) to which one surface of the inner ring member 14 abuts. In order to secure the flatness accuracy in order to connect without sticking, cutting or grinding is performed. Inner peripheral surface of cylindrical portion 11 Since the slide bearings 12, 12 are mounted on the inner peripheral surface of the cylindrical portion 11, cutting or grinding is performed in order to improve dimensional accuracy and surface roughness. Both axial end faces of the cylindrical portion 11 A thrust slide bearing is provided between both axial end faces of the cylindrical portion 11 and the mating face (the front face of the cylinder block or one face of the fixing bolt head), so that the surface roughness is improved. To let
Cutting or grinding is performed. Circular recess 22 (in the case of the first example) or notch 23
Inner peripheral surface (in the case of the second example) Since the receiving piece 21 is press-fitted and fixed to each of these portions 22 and 23,
Cutting is performed to ensure dimensional accuracy.

[0009]

In the case of the conventional automatic tensioner as described above, there are the following points to be solved due to the material of the swing frame 7 and the processing method. First of all, the swing frame 7 is made by die-casting an aluminum alloy, but the specific gravity of the aluminum alloy is about 2.7 or more, which is the specific gravity of aluminum, and it is not always necessary to make sufficient improvements. I can't plan. Therefore, the weight of the auto tensioner including the swing frame 7 increases. In addition, since the weight of the swing displacement portion including the swing frame 7 is heavy, the resonance frequency of this swing displacement portion easily matches the frequency of vibration (about 20 to 200 Hz) due to the rotation of the engine. If they match, the swing displacement portion resonates during engine operation,
Generates annoying noise.

Further, when the swing frame 7 is manufactured, it is necessary to perform die machining on the above-mentioned parts after die-casting an aluminum alloy, which complicates the working process and causes the swing frame 7 to be complicated. The production cost will increase. The autotensioner of the present invention eliminates the above-mentioned inconvenience by devising the material and processing method of the swing frame 7.

[0011]

The autotensioner of the present invention, like the conventional autotensioner described above, has a pivot provided on a fixed portion and a rocker which is swingably supported about this pivot. A moving frame, a displacement shaft provided at an end of the swing frame and parallel to the pivot shaft, a pulley rotatably supported around the displacement shaft, the fixed portion, and the swing frame. And an actuator that applies an elastic force to the swing frame in the direction of rotation about the pivot axis.

Particularly, in the autotensioner of the present invention, the rocking frame is a metal injection molding (metal injection molding) of magnesium alloy having a specific gravity of 2.5 or less.
It is made by.

[0013]

The operation of the autotensioner of the present invention constructed as described above when pressing the belt by the pulley and preventing the belt from loosening is the same as that of the conventional autotensioner described above. . In particular, in the case of the autotensioner of the present invention, since the swing frame is made of a magnesium alloy having a small specific gravity and having a strength almost equal to that of the aluminum alloy, the weight of the swing portion including this swing frame is reduced. It can be reduced.

That is, when the swing frame is made to have the same size and shape as the swing frame made of a conventional aluminum alloy, the weight can be reduced because the specific gravity is light. Further, by taking advantage of the high strength of the magnesium alloy, the weight can be further reduced by reducing the wall thickness so that the same strength as that of the aluminum alloy can be secured. Further, the weight of the swing frame is reduced, so that the weight of the entire auto tensioner can be reduced. Moreover, as the weight of the swing displacement portion is reduced, the resonance frequency of this portion changes (becomes higher), so that it is possible to prevent the swing displacement portion from vibrating significantly due to engine vibration.

Further, in the metal injection molding of magnesium alloy, the dimensional accuracy and shape accuracy (surface roughness) of the molded product itself can be stabilized at a sufficiently high level. Therefore, it is not necessary to perform machining after molding, and the cost of the swing frame and the auto tensioner incorporating the swing frame can be reduced.

[0016]

EXAMPLE The structure itself of the autotensioner of the present invention is similar to that of the above-mentioned conventional example, and when used, it is assembled as shown in FIG. 1 to give proper tension to the belt 1. The swing frame 7 and the pulley 5 are combined as in the first example shown in FIGS. 2 to 3 or the second example shown in FIGS. The swing frame 7 of the first example is formed as shown in FIGS. 6 to 8, and the swing frame 7 of the second example is formed as shown in FIGS.

In particular, in the case of the autotensioner of the present invention, the swing frame 7 as shown in FIGS. 6 to 8 or 9 to 11 is formed by metal injection molding of a magnesium alloy having a specific gravity of 2.5 or less. make. After molding, it is combined with other members as it is without performing machining for improving dimensional accuracy and surface roughness. That is, as shown in FIGS. 2 to 5, in the swing frame 7 shown in FIGS.
2, the receiving pieces 21 are press-fitted into the notches 23 in the swing frame 7 shown in FIGS. Also, the swing plate portion 1
An inner ring member 14 is attached to the tip of the bolt 3, and a bolt 15 and a nut 1
It is fixed by binding with 6. Further, slide bearings 12, 12 are attached to the inner peripheral surface of the cylindrical portion 11.

Metal injection molding of a magnesium alloy can secure a sufficient level of dimensional accuracy and surface roughness by itself, so that it can be sufficiently combined with other members described above even if machining is not performed after molding. It is possible to obtain an auto tensioner that demonstrates its performance.

[0019]

Since the autotensioner of the present invention is constructed and operates as described above, the following effects (1) to (3) can be obtained. (1) By reducing the weight of the auto tensioner, it is possible to reduce the weight of the engine, etc. incorporating the auto tensioner. (2) By reducing the weight of the oscillating displacement portion, the oscillating displacement portion is less likely to resonate due to engine vibration, and the operating noise of the engine incorporating the auto tensioner can be reduced. (3) The man-hours for manufacturing the swing frame can be reduced, and the cost of the auto tensioner can be reduced.

[Brief description of drawings]

FIG. 1 is a front view showing a belt drive device incorporating an auto tensioner which is an object of the present invention.

FIG. 2 is a view showing a first example of the structure of an auto tensioner, FIG.
FIG.

FIG. 3 is a view seen from the right side of FIG. 2 with a part omitted.

FIG. 4 shows a second example of the structure of the auto tensioner, FIG.
FIG.

FIG. 5 is a view of the right side of FIG. 4 with a part omitted.

FIG. 6 is a view of the swing frame used in the first example as seen from the same direction as FIG.

FIG. 7 is a view seen from below in FIG. 6;

8 is a sectional view taken along line BB of FIG.

9 is a view of the swing frame used in the second example as seen from the same direction as FIG.

FIG. 10 is a view on arrow C of FIG.

11 is a cross-sectional view taken along the line DD of FIG.

[Explanation of symbols]

 1 Belt 2 Drive Pulley 3 Driven Pulley 4 Guide Pulley or Driven Pulley 5 Pulley 6 Axis 7 Swing Frame 8 Actuator 9 Cylinder Cylinder 10 Rod 11 Cylindrical Part 12 Sliding Bearing 13 Swing Plate Part 14 Inner Ring Member 15 Bolt 16 Nut 17 Ball 18 Inner ring raceway 19 Outer ring raceway 20 Swing arm 21 Receiving piece 22 Circular recess 23 Notch

Claims (1)

[Claims] 1. A pivot provided on a fixed portion, and a swing frame supported swingably around the pivot.
A displacement shaft provided at the end of the swing frame and parallel to the pivot shaft, a pulley rotatably supported around the displacement shaft, and a gap between the fixed portion and the swing frame. In an auto tensioner equipped with an actuator that imparts elasticity to the swing frame in the direction of rotation about the pivot, the swing frame is formed by metal injection molding of a magnesium alloy having a specific gravity of 2.5 or less. An auto tensioner characterized by being built.