JP2521538B2 - Toothed belt - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a toothed belt used as a power transmission belt of an internal combustion engine, for example.

[Conventional technology]

The main body of an internal combustion engine is usually molded from cast iron or aluminum alloy casting, while the core of the toothed belt forming the power transmission belt is molded from glass fiber or aramid fiber. Toothed belt Attached to an internal combustion engine with a predetermined tension at room temperature, and when the internal combustion engine starts and the engine body reaches a substantially constant high temperature, the toothed belt is attached to the toothed belt due to the difference in coefficient of linear expansion between the core wire and the engine body. The tension that acts is about
Increase by 1.5 to 2 times.

Therefore, if the tension of the toothed belt at the time of installation at room temperature is too high, the tension of the toothed belt becomes too large when the temperature of the engine body rises due to the start of the engine,
Noise increases. Such noise occurs when the belt tooth bottom is struck against the pulley tooth tip or the belt tooth tip is rubbed against the side surface of the pulley groove when the belt tooth and the pulley tooth are meshed with each other. On the other hand, if the tension of the toothed belt during installation at room temperature is too low, the above noise can be prevented, but the toothed belt will drive the camshaft with a low tension for a while after the engine is started. The durability of the belt teeth becomes a problem.

As a structure for reducing noise due to such a toothed belt, a structure disclosed in, for example, Japanese Patent Laid-Open No. 62-113939 is known. This has a structure in which a special raised portion is formed at the top of the tooth and the height of the belt tooth is formed higher than the depth of the pulley groove.

[Problems to be Solved by the Invention]

Conventional toothed belts maintain a certain level of tension when the engine temperature is low, and to prevent the tension from becoming too high when the engine temperature rises, the belt tension must be within the specified range when attached to the engine body. Must be precisely adjusted so that

On the other hand, since the belt tooth described in the above publication has a special ridge on the tooth top, the mold for molding the toothed belt must be formed with a groove having a shape corresponding to the ridge. This makes it difficult to make the mold. Further, when the toothed belt is formed by this mold, the canvas has to be accurately pushed into the groove having a special shape in order to obtain an accurate belt tooth profile, and therefore the forming operation is difficult. Further, since this toothed belt has a special raised portion, new noise such as wind noise is generated during the operation of the engine.

An object of the present invention is to provide a toothed belt which does not require high-precision adjustment of tension when attached to an engine or the like, is easy to manufacture, and has sufficiently reduced noise.

[Means for solving the problem]

In the toothed belt according to the first aspect of the invention, the outer shape of the cross-sectional shape of the belt teeth is an arc-shaped curve, and the core wire is 6 × 10 ^{−6 to} 9
It is characterized by being molded from a material having a linear expansion coefficient of × 10 ^-6 / ° C.

In the toothed belt according to the second aspect of the invention, the outer shape of the cross-sectional shape of the belt teeth is an arcuate curve, and the rubber forming the belt teeth has a soft rubber layer on the surface side and a rigid rubber layer inside. It is characterized by having.

In the toothed belt according to the third aspect of the invention, the cross-sectional outer shape of the belt tooth is an arc-shaped curve, and the core wire is 6 × 10 ^{−6 to} 9 × 10.
^The rubber formed from a material having a linear expansion coefficient of ⁻⁶ / degree C and forming a belt tooth has a soft rubber layer on the surface side,
It is characterized by having a rigid rubber layer inside.

[Action]

According to the first aspect of the invention, since the outer shape of the cross-sectional shape of the belt teeth is the arc-shaped curve, the belt teeth are less likely to interfere with the pulley groove, and noise is reduced. Further, since the coefficient of linear expansion of the core wire approaches the coefficient of linear expansion of the engine, the increase in the tension of the belt during the operation of the engine is suppressed and the noise is reduced.

According to the second aspect of the invention, since the outer shape of the cross-sectional shape of the belt tooth is formed by the arc-shaped curve, the noise is reduced, and since the belt tooth has the soft rubber layer, the energy for noise generation is absorbed and the noise is further reduced. Will be reduced. Further, the rigid rubber layer of the belt teeth prevents the belt teeth from being deformed when meshing with the pulley teeth, thus ensuring the synchronous drive of the pulley by the toothed belt.

The third aspect of the invention has the effects of the first and second aspects of the invention, and noise is further reduced.

〔Example〕

 The present invention will be described below with reference to illustrated embodiments.

FIG. 1 shows a toothed belt according to the first embodiment of the present invention. The main body of this toothed belt is formed of synthetic rubber, the surface of the belt teeth 10 and the bottom surface 20 is covered with a canvas 30, and a core wire 40 extending along the longitudinal direction of the belt is provided inside the main body. Buried.

The outer shape of the cross-sectional shape of the belt tooth 10 is composed of a plurality of arc-shaped curves and has a symmetrical shape with respect to the center line. Ie tooth flank
The cross-sectional shapes of 11, the tooth root 12, and the tooth crest 13 each have an arcuate contour, and the arcs are smoothly connected to each other. The radius of curvature of the arc forming the tooth root 12 is 10/35 of the radius of curvature of the arc forming the tooth side surface 11. The cross-sectional shape of the tooth bottom surface 20 is linear, and the ends of the tooth bottom surface 20 are smoothly connected to the tooth root 12.

Although the outer shape of the cross-sectional shape of the belt tooth 10 in this embodiment has an arc shape, it need not be a strict arc, and may be any curve approximated by an arc, for example, a parabola. It may be a part, a part of an ellipse, a part of a cycloid curve, a part of a hyperbola, a part of a catenary curve, or the like.

The canvas 30 protects the tooth profile and is a base cloth made of synthetic fiber of nylon 6,6. The base fabric may be stretchable or non-stretchable. There is no particular limitation on the weaving of the base cloth, which may be plain weave, twill weave, satin weave, or modified weave. In addition, canvas 30
The material of Nylon 11, Nylon 12 or polyester fiber may be, but is not limited to,
Any synthetic fiber may be used as long as it has heat resistance.

The core wire 40 is composed of an improved glass fiber having a coefficient of linear expansion of 9 × 10 ^-6 / degree C. That is, the core wire 40 has a linear expansion coefficient about 1.2 to 1.5 times larger than that of the conventional glass fiber, and the difference from the linear expansion coefficient of the body of the internal combustion engine is smaller than that of the conventional one.

As a conventional glass fiber, for example, when describing the components of E glass, SiO ₂ is 52 to 56% by weight, CaO is 16 to 25% by weight, B ₂ O ₃ is 8 to 13% by weight, and Al ₂ O ₃ is 12% by weight. .About.16 wt%, MgO is 0 to 6 wt%, Na ₂ O, K ₂ O and Li ₂ O are 0 to 3 wt%, and the coefficient of linear expansion is 5 × 10 ^-6 / degree C.

On the other hand, in this example, the glass fiber improved as described above is used, and the components thereof are as follows. That is, compared to conventional glass fiber,
The composition ratio of SiO ₂ is increased, for example, 65 to 75% by weight. The composition ratio of Al ₂ O ₃ is small, for example, 0 to 10% by weight. The composition ratio of CaO is made small, for example, 3 to 15% by weight. The composition ratio of Na ₂ O, K ₂ O, and Li ₂ O should be further varied, for example, 0 to 20% by weight. ZrO ₂ may be added as another component.

By this component, a linear expansion coefficient of about 1.2 to 1.5 times as large as that of the conventional glass fiber is obtained as described above, but if the linear expansion coefficient is satisfied, the glass constituting the core wire 40 is formed. The fibers may have other ingredients.

The rubber constituting the belt body is hydrogenated nitrile rubber, and its hardness is substantially uniform over the entire belt.
In this embodiment, the hydrogenated nitrile rubber is used because the toothed belt is used in a thermal environment, but synthetic rubber such as chloroprene rubber, chlorosulfonated polyethylene, and polyurethane may be used.

The rubber of the belt tooth 10 is filled with a tetrapot whisker or the like containing zinc oxide as a component, whereby the rigidity of the belt tooth 10 is increased. This whisker is
Since it has a micro size of 10 to 150 microns, it can be filled in rubber in a large amount. The whiskers have a specific gravity of 5.78 by themselves, and are intertwined with each other because they are in a tetrapot shape, thus forming a layer having a high specific gravity and exhibiting sufficient rigidity.

In the product of this embodiment, since the outer shape of the cross-sectional shape of the belt tooth is an arc-shaped curve, the belt tooth 10 is less likely to interfere with the pulley groove and noise is reduced. Further, in the product of this embodiment, since the belt teeth 10 are filled with the solid whiskers and the like as described above, the durability of the belt teeth 10 is improved. Further, since the core wire 40 having a linear expansion coefficient close to that of the internal combustion engine is provided, the belt itself does not expand much even when the engine temperature rises, and the increase rate of the tension from room temperature is higher than that of the conventional one. Is also small. Therefore, it is not necessary to adjust the belt tension with high accuracy when the belt is installed at room temperature, the belt assembling work is facilitated, and the rise of the belt tension during the operation of the engine is suppressed, resulting in further noise. Will be reduced.

FIG. 2 shows a second embodiment. This toothed belt has basically the same shape as that of the first embodiment, but the configurations of the core wire 40 and the rubber of the belt body are different.

That is, the core wire 40 is made of a conventionally known E glass fiber and has a coefficient of linear expansion of 5 × 10 ⁻⁶ / ° C. The belt body is made of a basic rubber material such as hydrogenated nitrile rubber as in the first embodiment, but has a back rubber layer 51, a rigid rubber layer 52, and a soft rubber layer 53. The back rubber layer 51 extends along the longitudinal direction of the belt body, and the rigid rubber layer 52 and the soft rubber layer 53 are located on the front side of the core wire 40. Soft rubber layer 53
Is along the back surface of the canvas 30, the rigid rubber layer 52 is located on the back side of the soft rubber layer 53, and the rigid rubber layer 52 has a layer thickness of a belt tooth.
The closer to the center of 10, the thicker.

The rigid rubber layer 52 is formed by filling tetrapod-shaped whiskers having a size of 10 to 150 microns with zinc oxide as a component. On the other hand, the soft rubber layer 53 may be formed by adding a softening agent or its equivalent to the basic rubber material made of hydrogenated nitrile rubber, or may be formed by blending a rubber having softness. .

The ratio of the back rubber layer 51, the rigid rubber layer 52 and the soft rubber layer 53 can be freely determined according to the purpose, and this ratio makes the belt rigidity and energy loss optimal for the internal combustion engine to which this belt is attached. It will be Further, this ratio is determined by appropriately setting the thickness of the sheet-shaped rubber material forming each rubber layer in the step before molding the belt. The rigid rubber layer 52 and the soft rubber layer
53, as described later, because they are in contact with each other in the unvulcanized state, in the toothed belt after heating and pressing, the boundary between the two is naturally integrated, and therefore each layer in the belt tooth 10 The hardness of the rubber at the boundary between 53 and 52 is determined by the soft rubber layer.
From 53 to the rigid rubber layer 52 increases continuously and in an inclined manner.

The hardness of each rubber layer is JIS A in the back rubber layer 51.
Around 72, in the rigid rubber layer 52, JIS A 74-80,
JIS A 62-70 is preferable for the soft rubber layer 53. The back rubber layer 51 has a 200% modulus of 75 to 98 kgf / cm ² , the rigid rubber layer 52 has a 200% modulus of 92 to 125 kgf / cm ² , and the soft rubber layer 53 has a 200% modulus of 48 to 89 kgf / cm ² . .

If the soft rubber layer 53 has a hardness of 62 or less, the soft rubber layer 53 absorbs the impact force generated when the belt and the pulley are meshed with each other, thereby reducing noise. But canvas 30
While the rigid rubber layer 52 is strong against shearing stress, the soft rubber layer 53 cannot sufficiently withstand the frictional stress generated by the belt teeth 10 slidingly contacting the side surface of the pulley groove, It may be damaged. On the other hand, the soft rubber layer 53
If the hardness exceeds 70, the durability against shearing is improved, but the impact force generated at the time of meshing with the pulley cannot be sufficiently absorbed, and the noise reduction effect is reduced. Therefore, the hardness of the soft rubber layer 53 is preferably JIS A 62-70.

If the hardness of the rigid rubber layer 52 is 74 or less, no problem will occur when the load is light, but when a high load is applied, the tooth profile of the belt is easily deformed, and the shape retention is deteriorated. On the other hand, when the hardness exceeds 80, there is no problem in maintaining the shape of the tooth profile, but the performance of maintaining the toughness for a long time deteriorates. Therefore, the hardness of the rigid rubber layer 52 is JIS A 74-80.
Is preferred.

The hardness of the back rubber layer 51 is preferably about 72 from the viewpoint of balance of power transmission performance between the toothed belt and the pulley and crack resistance on the back surface in a thermal environment.

A method for manufacturing the toothed belt of this embodiment will be described. First,
A cylindrical mold having a concave portion having the number and shape corresponding to the belt teeth 10 is formed on the outer periphery. Next, a cylindrical base cloth is fitted into this mold, and the core wire 40 is wound on the base cloth. And a rubber sheet material is wound on it. This time,
Soft rubber sheet material first, then rigid rubber sheet material,
Finally, wind the sheet material of the basic rubber material that will become the back rubber layer. Then, after the tooth profile is formed by heating and vulcanizing, the mold is removed and the tubular belt material is taken out. Here, the belt material includes three rubber layers 51, 5 as shown in FIG.
2, 53 are formed. After a predetermined finishing process such as back grinding, the belt material is cut into a predetermined width (for example, 19 mm), whereby a toothed belt is obtained.

In such a toothed belt of the second embodiment, since the outer shape of the cross-sectional shape of the belt teeth 10 is an arcuate curve, interference with the pulley does not occur, and thus noise is reduced. Also,
Since the belt teeth 10 have the soft rubber layer 53, the energy of noise generation is absorbed and the noise is further reduced. Further, the rigid rubber layer 52 of the belt teeth 10 prevents the belt teeth from being deformed when meshing with the pulley teeth, and therefore, the synchronous drive of the pulley by the toothed belt is ensured.

In the third embodiment of the present invention, although not shown, the core wire 40 is 9 ×.
It is molded from an improved glass fiber with a coefficient of linear expansion of 10 ^-6 / degree C. Other constructions are shown in FIG.
It is similar to the embodiment. That is, the outer shape of the cross-sectional shape of the belt tooth 10 is formed from a plurality of arcs, the rubber of the main body has a back rubber layer 51, a rigid rubber layer 52 and a soft rubber layer 53,
And the surface is covered with the canvas 30.

According to the configuration of the third embodiment, the operations of the first and second embodiments are combined and the noise is further reduced.

Next, the noise due to the toothed belts of the first to third embodiments will be described together with the noise due to the toothed belts of the comparative example.

Such noise measurement is performed by the device shown in FIG. The toothed belt 90 is wound around, for example, a crank pulley 91 having 20 teeth and a cam pulley 92 having 40 teeth, and a tension pulley 93 having a diameter of 60 mm is engaged with the outer surface of the toothed pulley 90. The crank pulley 91 is rotated at a rotation speed of 1000 rpm, for example, and the microphone 94 is arranged 300 mm away from the crank pulley 91. The noise is measured in this state.

FIG. 3 shows the first comparative example, which shows RMA (Rubber Manufactur).
es Association) IP-24 (1978) has a trapezoidal tooth profile L. Namely tooth flank 61, tooth top 63 and tooth bottom
The cross-sectional shape of 70 is linear, and the arc of the root 62 smoothly connects to the tooth flank 61 and the tooth bottom 70, and the tooth shoulder 64
The arc of is also smoothly connected to the tooth top 63. The belt tooth 60 and the tooth bottom surface 70 having such a structure are covered with the canvas 30 made of nylon 6,6 as in the first to third embodiments, and the core wire 40 is embedded along the longitudinal direction of the belt body. To be done.
The core wire 40 is made of ordinary E glass fiber and has a coefficient of linear expansion of 5 × 10 ⁻⁶ / ° C. The belt body is molded from hydrogenated nitrile rubber and its hardness is uniform throughout the body and is JIS A 74.

FIG. 4 shows the second comparative example, which is the same as the first comparative example.
Has an L tooth profile. The core wire 40 is made of modified glass fiber and has a coefficient of linear expansion of 9 × 10 ⁻⁶ / degree C. The rubber of the belt body has a back rubber layer 51, a rigid rubber layer 52 and a soft rubber layer 53, and the hardness of each rubber layer is 7
4, the rigid rubber layer 52 is 65, and the soft rubber layer 53 is 80. Canvas 3
0 is formed from nylon 6,6 fibers.

The third comparative example has the same structure as that shown in FIG. 1, that is, the outer shape of the tooth profile is formed by connecting a plurality of arcs, but the core wire 40 is made of a conventionally known E glass fiber. The coefficient of linear expansion is 5 × 10 ⁻⁶ / degree C. The rubber of the belt body is made of nylon 6,6 fiber and has a uniform hardness over the entire body, and the hardness of the rubber is JIS A 74.

In this noise comparison, the hardness of the rubber of the belt body of the first embodiment is uniform and the size thereof is JIS A.
74. Further, in the second and third embodiments, the rubber of the belt body is a composite type, and the hardness of the back rubber layer is 7
4, the hardness of the rigid rubber layer is 80, and the hardness of the soft rubber layer is 65
Is.

FIG. 7 shows the outline of the configurations of the first to third comparative examples and the first to third examples. In addition, in Figure 7, "symbol"
Means the symbols used in the graph of FIG.

FIG. 6 shows changes in noise with respect to temperature according to the above-mentioned examples and comparison.

As understood from this figure, in the first comparative example,
The noise is already loud at low temperatures and becomes louder as the temperature rises. As shown in the second comparative example, when an improved glass fiber having a large linear expansion coefficient is used as the core wire and a composite structure having a rigid rubber layer and a soft rubber layer is adopted as the rubber of the belt main body, noise of Although the rate of increase can be suppressed, since the original noise is high, a sufficient noise reduction effect cannot be obtained. Further, when the belt tooth profile is formed in an arc shape as in the third comparative example, the core wire is formed of the conventional E glass fiber, and the rubber of the belt main body has a uniform hardness, noise is generated at low temperature. Although small, it increases with increasing temperature and noise cannot be reduced sufficiently.

On the other hand, according to the first embodiment, since the core wire has a larger linear expansion coefficient (9 × 10 ⁻⁶ / degree C) than the conventional one, the tension is increased as the temperature of the internal combustion engine rises. It does not rise as much as before and therefore noise does not increase much with increasing temperature. In the second embodiment, the same core wire as the conventional one is used, but since the rubber of the belt body has a composite type including a rigid rubber layer and a soft rubber layer, the soft rubber layer has a vibration absorbing effect. The generation of noise is suppressed. Therefore, the increase in noise due to the rise in temperature is small as in the first embodiment. Further, in the third embodiment, since the core wire is made of the improved glass fiber having a large coefficient of linear expansion, the belt tension is not increased by the temperature rise of the internal combustion engine. Therefore, in the third embodiment, the rate of noise increase due to the temperature rise is further reduced.

Since the toothed belts of the second and third embodiments have the rubber layer of the composite structure, the belt teeth 10 have sufficient durability,
Therefore, even if the toothed belt is attached to the internal combustion engine at a lower tension than the conventional one at room temperature, the belt teeth are not damaged when the engine is started. Further, since the tension of the toothed belt of the first to third embodiments does not increase as in the conventional toothed belt due to the temperature rise, the temperature of the engine rises even if it is attached to the engine at a high tension at room temperature. The rate of increase in tension due to is small, so that the increase in noise is suppressed.

Therefore, when the belt is attached to the engine at room temperature, it is not necessary to adjust the tension with high precision, and the attaching work is facilitated. Further, when the internal combustion engine is repeatedly operated and stopped frequently, the temperature changes greatly, and therefore the tension of the toothed belt also changes repeatedly. However, even in such a case, in the toothed belts of the first and third embodiments, the change in tension is small, and in the toothed belts of the second embodiment, the impact is caused by the action of the soft rubber layer. Are absorbed, and thus the generation of noise is suppressed.

Further, in each of the above-described embodiments, since the belt tooth 10 does not have a special raised portion as in the conventional case, it is easy to manufacture.

〔The invention's effect〕

As described above, according to the present invention, it is not necessary to adjust the tension with high precision at the time of attachment to an engine or the like, the manufacturing is easy, and the toothed belt with sufficiently reduced noise can be obtained.

[Brief description of drawings]

1 is a sectional view showing a first embodiment, FIG. 2 is a sectional view showing a second embodiment, FIG. 3 is a sectional view showing a first comparative example, and FIG. 4 is a sectional view showing a second comparative example. FIG. 5, FIG. 5 is a diagram showing a noise measuring device, FIG. 6 is a diagram showing noise measurement results, and FIG. 7 is a list of configurations of Examples 1 to 3 and Comparative Examples 1 to 3. FIG. 10 …… Belt teeth 40 …… Core wire 52 …… Rigid rubber layer 53 …… Soft rubber layer

Claims (3)

(57) [Claims] 1. A belt tooth whose cross-sectional outer shape is an arc-shaped curve, and whose SiO ₂ composition ratio is in the range of 65 to 75 wt%, Al.
The composition ratio of ₂ O ₃ is 0 to 10 wt%, the composition ratio of CaO is 3 to 15 wt%, the composition ratio of Na ₂ O is 0 to 20 wt%, and the composition ratio of K ₂ O is 0 to 20% by weight, the composition ratio of Li ₂ is 0 to 20% by weight, and 6 × 10 ^{-6 to} 9 × 10
A toothed belt having a core formed of glass fiber having a linear expansion coefficient of ⁻⁶ / degree C. 2. A belt tooth has a cross-sectional outer shape of an arc-shaped curve, a rubber forming the belt tooth has a soft rubber layer on the surface side, a rigid rubber layer inside, and the soft rubber. A toothed belt, characterized in that the hardness at the boundary between the layer and the rigid rubber layer increases continuously and obliquely from the soft rubber layer to the rigid rubber layer. 3. A belt tooth having a cross-sectional outer shape of an arc-shaped curve, a SiO ₂ composition ratio in the range of 65 to 75% by weight, and an Al ₂ O ₃ composition.
The composition ratio of CaO ranges from 0 to 10% by weight, and the composition ratio of CaO is 3
The composition ratio of Na ₂ O is 0 to 20% by weight, the composition ratio of K ₂ O is 0 to 20% by weight, and the composition ratio of Li ₂ O is 0 to 20% by weight. The range is 6 × 10 ^{−6 to} 9 × 10
Having a core wire formed of glass fiber having a coefficient of linear expansion of ^-6 / degree C, the rubber forming the belt teeth has a soft rubber layer on the surface side and a rigid rubber layer inside, Further, the hardness at the boundary between the soft rubber layer and the rigid rubber layer continuously and obliquely increases from the soft rubber layer to the rigid rubber layer.