JPH0518447A - Tension control device for engine belt - Google Patents

Abstract

PURPOSE:To prevent noise generation due to resonance by installing two tension pulleys having different distance from a crank pulley on the tension side of a timing belt, using two tension pulleys selectively according to the high or low rotating speed range, and differing the pulley engaging frequency from the belt chord oscillation frequency. CONSTITUTION:A timing belt 3 is set over a crank pulley 1 and cam pulleys 2, 2, and on the tension side of the timing belt 3, tension pulleys 6, 5 are installed in arrangement far and near relative to the crank pulley 1. The engine revolving speed is sensed by a sensor 13 and fed to a solenoid switch 12-in the low speed range, the tension pulley 5 is pressed by the belt 3, and in the high speed range, the other 6 is pressed. Accordingly chord oscillation of the timing belt 3 is suppressed in any speed range, and the engaging frequency of the pulley 5 can be put identical to the chord oscillation frequency so as to eliminate resonance, and thus noise generation due to resonance be precluded.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an engine belt tension control device, and more particularly to an engine belt tension control device suitable for reducing noise due to string vibration of a timing belt.

[0002]

2. Description of the Related Art A camshaft of an engine or auxiliary machinery such as a water pump is driven by a crank pulley connected to a crankshaft as a driving source and a timing belt wound around each driven timing pulley. . In this case, the timing belt is mounted at the time of assembling the engine and is adjusted by a tensioner so that a predetermined tension acts on the timing belt as disclosed in Japanese Patent Laid-Open No. 2-120543. Further, an idler is provided to increase the wrapping angle of the timing belt with respect to each pulley and effectively transmit power.

[0003]

However, in the above construction, the tension pulley is fixed, and the belt length between the crank pulley and the tension pulley (hereinafter referred to as free span) is constant. Therefore, the engagement frequency between the timing belt and the crank pulley, the tension acting on the timing belt, the free span,
If the string vibration frequency of the timing belt, which is determined by the belt properties such as belt rigidity, matches, a large noise is generated due to resonance, the quietness during engine operation is significantly impaired, and the timing belt is deteriorated by violent vibration. There was a problem of fear.

For this reason, the string vibration of the timing belt is prevented from occurring in the commonly used engine rotation range.
Measures such as adjusting the belt properties and taking into account the layout of auxiliary equipment such as water pumps are taken so that large resonance does not occur even if the meshing frequency of the crank pulley and the string vibration frequency of the timing belt match. However, it did not solve the fundamental problem.

The present invention has been made in view of the above problems, and an object thereof is to prevent generation of noise by eliminating the coincidence between the meshing frequency of the crank pulley and the string vibration frequency of the timing belt. It is possible,
Another object of the present invention is to provide an engine belt tension control device that can prevent deterioration of the timing belt.

[0006]

In order to achieve the above object, the present invention provides a belt tension adjusting means for adjusting the belt tension by pressing the tension side of a timing belt wound around a crank pulley and a driven timing pulley. According to the number of engine revolutions, the pressing position of the timing belt by the belt tension adjusting means is brought closer to the crank pulley in the low rotation area thereof, while the timing belt by the belt tension adjusting means is in the high rotation area thereof. And a pressing position changing means for separating the pressing position from the crank pulley.

Further, the belt tension adjusting means has a first tension pulley arranged in the vicinity of the crank pulley and a second tension pulley arranged in a space, and the pressing position changing means operates in the low rotation region at the first tension pulley. It is preferable that the first tension pulley is pressed against the timing belt and the second tension pulley is pressed against the timing belt in the high rotation region.

Alternatively, the belt tension adjusting means may be a single tension pulley provided so as to be movable toward and away from the crank pulley, and the pressing position changing means may move the tension pulley to the crank pulley in the low rotation region. It is desirable to move the tension pulley away from the crank pulley in the high rotation region while moving the pulley closer to the pulley.

[0009]

The operation of the present invention will be described. In the low rotation speed region of the engine, the pressing position of the timing belt by the belt tension adjusting means is brought close to the crank pulley in accordance with the engine speed, and the position between the crank pulley and the pressing position is increased. While the length of the timing belt is set short, the pressing position of the timing belt by the belt tension adjusting means is separated from the crank pulley in the high rotation area so that the length of the timing belt between the crank pulley and the pressing position is set long. Since the string vibration generation frequency of the timing belt is set to be high in the low rotation range and low in the high rotation range, the string vibration generation frequency of the timing belt and the meshing frequency of the crank pulley match and resonate. Does not occur.

Further, a first tension pulley arranged close to the crank pulley and a second tension pulley arranged apart from each other are provided, and the first tension pulley is pressed against the timing belt in the low rotation region, while the first tension pulley is pressed in the high rotation region. By pressing the two-tension pulley against the timing belt, the same operation as described above can be obtained.

Alternatively, a single tension pulley is provided which is movable toward and away from the crank pulley, and the tension pulley is moved closer to the crank pulley in the low rotation region, while the tension pulley is moved from the crank pulley in the high rotation region. The same effect as described above can be obtained by moving them apart.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT A preferred embodiment of the present invention will be described below with reference to the accompanying drawings. FIG. 1 is a schematic diagram showing the configuration of an embodiment of an engine belt tension adjusting device according to the present invention.

A timing belt 3 is wound around a crank pulley 1 connected to a crankshaft of an engine and cam pulleys 2 and 2 connected to a camshaft, and the rotation of the crank pulley 1 is two cam pulleys 2. ，
2 is transmitted. In the drawing, the rotation direction of the crank pulley 1 is right rotation, and the timing belt 3 orbits clockwise. On the loose side of the timing belt 3, a tensioner 4 for adjusting the tension acting on the timing belt 3 to a predetermined value is pressed against the timing belt 3. This tensioner 4 is of a type in which the tension acting on the timing belt 3 is adjusted to a predetermined value by manually adjusting and fixing its position in advance, or a type in which the tension acting on the timing belt 3 is constantly and automatically adjusted to a predetermined value. Any of

On the other hand, on the tight side of the timing belt 3,
As the belt tension adjusting means, a first tension pulley 5 close to the crank pulley 1 and a second tension pulley 6 far from the crank pulley 1 are arranged, and any one of the tension pulleys is selectively timing according to the engine speed. It is adapted to be pressed by the belt 3. The first tension pulley 5 and the second tension pulley 6 are rotatably attached to both ends of a swing arm 7, and the swing arm 7 is pivotally supported at a substantially central portion thereof. . A rod 8 whose one end is rotatably attached to the swing arm 7 coaxially with the second tension pulley 6 is connected to an actuator 9 at the other end.

In the illustrated example, a diaphragm is used for the actuator 9. This diaphragm is adapted to impart a linear motion to the rod 8 against the elastic force of the built-in spring 10 by introducing a negative pressure of the intake pipe into the pressure chamber.

A three-way solenoid valve 11 is provided between the diaphragm and the intake pipe, and the pressure chamber is switched between the intake pipe and the atmosphere for communication.

The three-way solenoid valve 11 is switched and controlled by a solenoid switch 12. An engine speed signal is input from the engine speed sensor 13 to the solenoid switch 12, and the solenoid coil of the three-way solenoid valve 11 is energized or de-energized according to the value of the engine speed to switch the three-way solenoid valve 11 to operate. Then, the pressure chamber is communicated with the intake pipe or the atmosphere.

The actuator 9, the three-way solenoid valve 11, the solenoid switch 12, the engine rotation sensor 13 and the like constitute pressing position changing means.

Next, the operation of this embodiment will be described.
In a region where the engine speed input from the engine speed sensor 13 to the solenoid switch 12 is low, the solenoid switch 12 is closed and the three-way solenoid valve 11 is closed.
The solenoid coil is supplied with current from the battery 14 and is in an excited state, that is, in a state of being communicated with the intake pipe side. Therefore, the negative pressure of the intake pipe is introduced into the pressure chamber of the diaphragm, and the rod 8 keeps the state of moving to the diaphragm side while compressing the spring 10. At this time, the first tension pulley 5 close to the crank pulley 1 is pressed against the timing belt 3 by the swing of the swing arm 7 (state shown by a solid line in FIG. 1),
The tension-side free span of the timing belt 3 takes the shorter value L ₁ .

On the other hand, in a region where the engine speed input from the engine speed sensor 13 to the solenoid switch 12 is high, the solenoid switch 12 is open, and no current is supplied to the solenoid coil of the three-way solenoid valve 11 so that the solenoid coil 12 is in a non-excited state. That is, it is in a state of communicating with the atmosphere side. Therefore, the pressure chamber of the diaphragm is kept at atmospheric pressure, and the rod 8 is urged by the spring 10 to keep the state moved to the timing belt 3 side. At this time, the second tension pulley 6 farther from the crank pulley 1 is pressed by the timing belt 3 due to the swinging of the swing arm 7 (a state shown by a chain double-dashed line in FIG. 1), and the tension belt 3 is free from the tension side. The span takes the longer value L ₂ .

As described above, the relationship between the engine speed and the sound pressure level of the generated noise when the tension side free span of the timing belt 3 is changed according to the engine speed is shown in FIGS. This is shown using C).

When the tension free span is fixed to L ₂ , that is, when the second tension pulley 6 is pressed against the timing belt 3, as shown in FIG. 2 (A), the mesh frequency of the crank pulley 1 is relatively high. The string vibration of the timing belt 3 occurs at a low engine speed R ₂ .

Further, when the tension free span is fixed to L ₁ , that is, when the first tension pulley 5 is pressed against the timing belt 3, as shown in FIG. String vibration of the timing belt 3 occurs at a relatively high engine speed R ₁ .

In this embodiment, the tension side free span is switched at an engine speed R _C which is substantially intermediate between the engine speed R ₁ and the engine speed R _2, and the engine speed R ₂ is relatively included. The first tension pulley 5 is pressed against the timing belt 3 in the low engine speed region, and the second tension pulley 6 is pressed against the timing belt 3 in the relatively high engine speed region including the engine speed R ₁ . As shown in FIG. 2 (C), the occurrence of string vibration of the timing belt 3 can be suppressed in both the low rotation region and the high rotation region of the engine, and the peak of engine noise can be suppressed.

Next, another embodiment of the present invention will be described. FIG. 3 is a schematic diagram showing the configuration of another embodiment of the belt tension control device for an engine according to the present invention. Unlike the first embodiment, a single tension pulley 5a is provided on the tension side of the timing belt 3 in the present embodiment. The tension pulley 5a is rotatably supported by one end of the swing arm 7a, and the other end of the swing arm 7a is swingably supported by a support shaft P. Further, in the approximate center of the swing arm 7a,
One end of a rod 8 extending from the actuator 9 is pivotally attached. The spring 10a that biases the swing arm 7a in a direction away from the actuator 9 is provided to assist the restoring force of the spring 10 built in the actuator 9, and is sufficient by the spring 10 alone. It may be omitted if an operating force is obtained.

In the present embodiment having the above configuration,
The swing arm 7a swings around the support shaft P by the operation of the actuator 9, and the tension pulley 5a causes the tension side free span of the timing belt 3 to be L ₁ or L.
Thereby making it possible to take two positions to be set to _2. Further, since only one tension pulley 5a needs to be provided, the device can be downsized. Other functions are similar to those described in the first embodiment.

When the tension pulley 5a moves, since the contact point with the timing belt 3 draws an arc, the path length of the timing belt 3 changes transiently, so that the tension pulley 5a receives a drag force. However, in this embodiment, a so-called auto tensioner is used as the tensioner 4 in which the position is automatically adjusted so that the tension acting on the timing belt 3 becomes constant. You can move. When using a manual tensioner, if the trajectory when the tension pulley 5a moves is parallel to the path of the timing belt 3, the path length does not change, so the tension pulley 5a can be smoothly moved. It can be moved.

The actuator 9 in the first and second embodiments is not limited to the diaphragm but may be of another type using a solenoid coil, a motor or the like.

[0029]

As described in detail above, according to the present invention,
Depending on the engine speed, the pressing position of the timing belt by the belt tension adjusting means is brought close to the crank pulley in the low rotation range to set the length of the timing belt between the crank pulley and the pressing position to be short. In the high rotation area, the pressing position of the timing belt by the belt tension adjusting means is separated from the crank pulley so that the length of the timing belt between the crank pulley and the pressing position is set to be long. The generated frequency is set to be high in the low rotation range and set to be low in the high rotation range, so that the string vibration generation frequency of the timing belt and the meshing frequency of the crank pulley do not coincide with each other to cause resonance, and noise is generated due to resonance. It is possible to prevent the deterioration of the timing belt due to vibration as well as Further, a first tension pulley arranged close to the crank pulley and a second tension pulley arranged apart from each other are provided, and the first tension pulley is pressed against the timing belt in the low rotation region, while the second tension pulley is pressed in the high rotation region. By pressing the pulley against the timing belt, the same effect as described above can be obtained.

Alternatively, a single tension pulley is provided which is movable toward and away from the crank pulley, and the tension pulley is moved closer to the crank pulley in the low rotation area, while the tension pulley is moved from the crank pulley in the high rotation area. By moving them away from each other, the same effect as described above can be obtained, and at the same time, the size of the device can be reduced.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing the configuration of an embodiment of an engine belt tension control device according to the present invention.

FIG. 2 is an explanatory diagram showing a relationship between engine speed and generated noise sound pressure.

FIG. 3 is a schematic view showing the configuration of another embodiment of the belt tension control device for an engine according to the present invention.

[Explanation of symbols]

1 Crank Pulley 3 Timing Belt 4 Tensioner 5, 5a, 6 Tension Pulley 7, 7a Swing Arm 8 Rod 9 Actuator 10, 10a Spring 11 Three-way Solenoid Valve 12 Solenoid Switch 13 Engine Rotation Sensor 14 Battery

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Shogo Takeno             3-1, Shinchi, Fuchu-cho, Aki-gun, Hiroshima Prefecture Mazda             Within the corporation

Claims (3)

[Claims] 1. A belt tension adjusting means for adjusting a belt tension by pressing a tension side of a timing belt wound around a crank pulley and a driven timing pulley, and the belt in a low rotation region thereof according to an engine speed. Pressing position changing means for moving the pressing position of the timing belt by the tension adjusting means close to the crank pulley, and separating the pressing position of the timing belt by the belt tension adjusting means from the crank pulley in a high rotation region thereof. A belt tension control device for an engine, comprising: 2. The belt tension adjusting means has a first tension pulley arranged in proximity to the crank pulley and a second tension pulley arranged in a space, and the pressing position changing means operates in the low rotation region in the first rotation direction. 2. The belt tension control device for an engine according to claim 1, wherein one tension pulley is pressed against the timing belt, while the second tension pulley is pressed against the timing belt in the high rotation region. 3. The belt tension adjusting means is a single tension pulley provided so as to be able to move closer to and away from the crank pulley, and the pressing position changing means uses the tension pulley in the low rotation area to crank the tension pulley. The belt tension control device for an engine according to claim 1, wherein the tension pulley is moved away from the crank pulley in the high rotation region while being moved closer to the pulley.