V belt with blocks

The present invention relates to a V-belt for high load transmission of the kind as referred in the preamble of claim 1 and known from EP-A-0 135 710.

V-belts of this kind are useable for continuously variable transmissions for motor vehicles and also for continuously variable or non-continuously variable transmissions for vehicles loaded with engines, such as agricultural machines and civil engineering machines.

Any V-belt to be used for such purposes is required to have a high torque transmitting ability. To this end the blocks that are used for the known V-belts are in general so shaped as to become gradually smaller to the lower part so that a center of gravity is obtained for each block which is usually situated at the upper side of the tensile members when the blocks are composed of a material of the same specific gravity. In the case where reinforcing members of a different specific gravity are embedded, the center of gravity varies with such reinforcing members, i.e. no consideration has so far been given to the situation of the center of gravity.

The pulleys on which such V belts are wound comprise movable sheaves and fixed sheaves, both of truncated cone shape of the same angle. As shown in Fig. 17(a) and Fig. 17(b), such a pulley is so designed that when a block 101 engaged with a load carrier advances into a pulley groove of a pulley 102 and engages with the pulley groove surfaces 102a, 102b, no gap is left between the side surfaces 101a, 101b of the block 101 and the pulley groove surfaces 102a, 102b, in the case where the block 101 stands perpendicularly in relation to the load carrier (namely, in the case where the center line S of the block 101 coincides with the radial direction R of the pulley 102 as shown in Fig. 17(b) ). W designates the center line of the tensile member of load carrier.

With the known V belts, as shown by Fig. 18(a), it may be observed that when a block 101 engages with the groove surfaces 102a, 102b of a pulley 102, if the upper part of the block 101 inclines to the T side in the rotational direction of the pulley, groove surfaces 102a, 102b of the pulley 102 take the shape of a hyperbolic curve, in the cross section at the center line, and also form the pulley angle which is smaller than the angle formed by both side surfaces 101a, 101b of the block 101 and therefore only the upper end portion of the block 101 makes contact with pulley groove surfaces 102a, 102b as shown in Fig.18(b). When the block 101 engages with the groove surfaces 102a, 102b of the pulley 102, rocking of the block 101 is caused, with P₁ (the upper end portion of the block 101 at which the block 101 and the pulley groove surfaces 102a, 102b make contact with each other) as a fulcrum and the groove in which the load carrier is fitted as a working point. This is proved by the following fact.

If comparison is made between the case where the point <u style="single">a</u> is given at the position above the groove 101c in which the load carrier of the block 101 is fitted and the center line of the block 101 coincides with the radial direction R of the pulley 102 with the point <u style="single">a</u> fixed on pulley groove surfaces 102a, 102b (refer to chain lines in Fig. 19) and the case where the center of the block 101 inclines at an angle ϑ to the radial direction R, it is found out that in the case of the latter (the block 101 inclines at an angle ϑ to the pulley radial direction R) the groove 101c of the block 101 in which the load carrier is fitted is situated more away from the center O of pulley rotation and accordingly the block 101 is moved to the position where it stands perpendicularly on the pulley due to pressing force F of the load carrier wound on the pulley 102 to the rotational center 0 of the pulley.

On the contrary, as shown by Fig. 20(a), if the lower part of the block 101 inclines to the T side in the pulley rotational direction when the block 101 engages with the pulley groove surfaces 102a, 102b of the pulley 102, the cross section at the center line of the block indicates that as shown by Fig. 20 (b), the pulley groove surfaces 102a, 102b take the shape of a hyperbolic curve and also form a small pulley angle in relation to the block angle. Therefore, similarly to the above-mentioned case, when the block 101 engages with pulley groove surfaces of the pulley 102, only the upper end portion of the block makes contact with the pulley groove surfaces 102a, 102b and rocking of the block 101 is caused, with the contact part P₂ as a fulcrum point and the groove in which the load carrier is fitted as a working point.

As mentioned above, in the case where the block 101 inclines to the pulley radial direction when the block engages with the pulley 102, rocking of the block 101 is caused and accordingly friction is generated at the part where the block 101 engages with the load carrier and this friction involves the generation of heat and resultant partial temperature rise of the block and the load carrier. This causes ageing due to heat on rubber composing the load carrier. Thus, the load carrier cracks and if cracks reach the tensile member, earlier breakage of the load carrier occurs.

If the block inclines to the pulley radial direction when the block engages with the pulley, only the upper end portion of the block makes contact with the pulley groove surfaces of the pulley. This means that the lateral pressure which should be received by the whole of the block side surface concentrates upon the upper end portion of each block, causing chipping and early damage of the blocks. It is therefore necessary to engage each block with the pulley, whereby the block coincides with the pulley radial direction.

In view of such considerations the present invention accordingly deals with the object of providing a V-belt for high load transmission of the kind according to the preamble of claim 1 which is free from any rocking of its blocks when the belt is engaged with the pulleys.

The V-belt according to the present invention is characterized by the features of claim 1. Since with such features all blocks of the V-belt are supported substancially perpendicular to the load carrier they accordingly will receive an engagement with the pulleys in a state coinciding with the pulley radial direction so that thereby any rocking of the blocks will be positively avoided. No generation of heat will occur at the part where each block and the load carrier engage with each other so that thereby any concentration of lateral pressure on this part can be prevented. The belt life is accordingly prolonged especially when such expedient features are further realized which are claimed with the further claims.

The accompanying drawings show preferred embodiments of the present invention, in which: <ul id="ul0001" list-style="none"><li>Fig. 1 is a side view of a V belt for high load transmitting according to the present invention;</li><li>Fig. 2 is a cross sectional view, taken along the line II-II in Fig. 1;</li><li>Fig. 3 is a perspective view of a different block;</li><li>Fig. 4 is a cross sectional view of a block having a reinforcing member;</li><li>Fig. 5 and Fig. 6 are explanatory drawings of the method of testing;</li><li>Fig. 7 is a side view of a main part of a different block, partly in section;</li><li>Fig. 8 is a cross sectional view, taken along the line VIII-VIII in Fig. 7;</li><li>Fig. 9 is a cross sectional view of a further different block;</li><li>Fig. 10 is a cross sectional view, taken along the line X-X in Fig. 9;</li><li>Fig. 11 and Fig. 12 are a front view and a plan view of the block respectively;</li><li>Fig. 13 is a drawing, similar to Fig. 12, of a different embodiment;</li><li>Fig. 14 to Fig. 16 are front views of the block of the other embodiment;</li><li>Fig. 17(a) and Fig. 17(b) are drawings showing the relation between the block and the pulley, in the case where the block does not incline to the load carriers;</li><li>Fig. 18(a) and Fig. 18(b) are drawings, similar to Fig. 17(a) and Fig. 17(b), in the case where the upper part of the block inclines in the pulley rotational direction to the load carrier;</li><li>Fig. 19 is an explanatory drawing of the rocking of the block; and</li><li>Fig. 20(a) and Fig. 20(b) are drawings, similar to Fig. 17(a) and Fig. 17(b), in the case where the lower part of the the block inclines in the pulley rotational direction to the load carriers.</li></ul>

As shown in Fig. 1 and Fig. 2, the V belt 1 according to the present invention comprises a pair of load carriers 2, 3 and a plurality of blocks 4 engaged with these load carriers in the lengthwise direction thereof. Grooves 5, 6 in which the load carriers are fitted detachably and which are open at side surfaces 4a, 4b of the block 4 are formed at each side of each block. A convexed part (only a convexed part 7 is shown for the groove 6) is provided at the upper surface of each groove 5, 6 and the under surface is a curved convex surface (only a curved convex surface 8 is shown for the groove 6), namely, the block 4 comprises an upper beam part 4c, a lower beam part 4d and a center pillar part 4e which connects center parts of the upper and lower beam parts and extends in a vertical direction.

Each load carrier 2, 3 has a rubber member 9 and tensile members 10 embedded in the rubber member. Where necessary, canvas is provided at the upper and the lower surfaces of the rubber member 9. Provided at the upper and the lower surfaces of the load carriers 2, 3 are concaved parts (only concaved parts 11, 12 of the load carrier 3 are shown) which engage with the convexed part or the curved convex part of the grooves 5, 6 of each block 4. The convexed part 7 and the curved convex surface 8 are engaged with the concaved parts 11, 12. Thus, the load carriers 2, 3 and the blocks 4 are fixed together in the lengthwise direction of belt by the engagement of convex and concave parts.

As stated above, in the case where each block of the V belt is composed of material of the sane specific gravity, the upper part of the block is larger in shape than its lower part and therefore the center of gravity is usually situated at the upper part of the tensile member. With this in view, in this embodiment a part of the upper and the lower parts of each block 4 is cut off to adjust the situation of the center of gravity. By this adjustment of the center of gravity, in the engagement of each block with the load carriers 2, 3 the center of gravity is situated near the tensile members 10 of the load carriers 2, 3 and accordingly the center line of each block 4 is supported perpendicularly in relation to the load carriers in the straight running state.

As shown in Fig. 3, the situation of the center of gravity can be adjusted by providing a concaved part 14d at an upper beam part 14a of the block 14 comprising the upper beam part 14a, a center pillar part 14b and a lower beam part 14c, and by varying the volume of the concaved part 14d. In the case where a concaved part is provided at the lower beam part 14c for the purpose of making the block lighter in weight, the situation of the center of gravity is adjusted by varying the volume of the concaved parts of the upper and the lower beam parts 14a, 14c.

The situation of the center of gravity can be adjusted by a partial cut of each block, formation of a concaved part, etc. In addition, adjustment of the situation of the center of gravity can be done by making the volume of the part above the tensile members smaller by reducing the height of the upper beam part of the block or by making the volume of the part below the tensile members larger by increasing the height of the lower beam part of each block.

Furthermore, in the case where a reinforcing member 16 (a reinforcing member made of metallic or other material having a higher specific strength than resin material composing the main part of each block and a larger specific gravity) is embedded in a block 15, the situation of the center of gravity can be adjusted by the weight regulation, such as by decreasing the volume of an upper side part 16a of the reinforcing member 16 in an upper beam part 15a of the block which is above the tensile members of the load carrier.

Resin materials which constitute the main part of each block are thermoplastic resin, such as 6.6 nylon, aromatic nylon, polyethyleneterephthalate, etc., thermosetting resin, such as phenol resin, hard polyurethane, unsaturated polyester, polyimide, epoxi resin, etc., hard rubber, such as ebonite. These are used singly or in compounding with short fiber, fillers, friction regulating agent or the like.

As to the reinforcing member, it is, for example, FRP reinforced with metallic material, long fiber, such as carbon fiber, glass fiber, alumina fiber, aramid fiber or the like.

Situation of the center of gravity of each block 4 near the tensile members 10 of the load carriers 2, 3 means that the center of gravity of the block 4 is situated within the range of the diameter of the tensile members 10 in the vertical direction of the block in the center pillar part 4e.

Under the above construction, before the V belt 1 engages with the pulley the load carriers 2, 3 are in linear state and the blocks 4 are substantially perpendicular to the load carriers. Engagement of the blocks 4 with the pulley in this state is such that each block 4 engages with the pulley in the state that it coincides with the diametrical direction of the pulley and rocking of the block 4 on the pulley does not occur. Therefore, generation of heat at the part where the block engages with the load carriers 2, 3 does not take place, with the result that degradation by heat of the rubber member 9 of each load carrier 2, 3 can be prevented and the partial striking of the block against the pulley can also be prevented. Thus, lateral pressure to the block 4 is dispersed and the belt life is prolonged.

An explanation is made below about the test carried out with the V belt according to the present invention.

As shown in Fig. 5, a sample belt 23 was wound round between a driving pulley 21 (pitch diameter 155mm, number of revolutions of pulley 5,600rpm, axial load D = 100kgf) and a driven pulley 22 (pitch diameter 80mm), and was run in a no-load state. The belt temperature was measured by measuring the temperature of the back of the belt wound on the driven pulley 22 by an infrared radiothermometer 24 (TTG-3200 made by Nihon Denshi K.K.). Measuring of the belt temperature at this part is most suitable for measuring the temperature of a running load carrier because the blocks on the back side of the belt 23 open by the belt being bent on the driven pulley 22 and therefore the load carrier becomes easy to see. The basic measurements of the blocks used in the test are, as shown in Fig. 6, ϑ=26° L₁=40mm and L₂=L₃=10mm (ℓ shows the situation of the tensile members of the load carrier). The diameter of each tensile member of the load carriers is 2mm.

The method employed for changing the situation of the center of gravity of each block was to cut off an upper end portion of the block and to rivet the part below the tensile member or to cut off a lower end portion of the block and to rivet the part above the tensile member. No change was made in the weight of a block by balancing the decrease in weight by cutting off with the increase in weight by riveting.

The results of the above test are shown in the following table. As to the situation of the center of gravity, it was measured on the basis of the situation of tensile member = 0, upper side = positive, and lower side = negative. The temperature rise is the difference between the measured value and the room temperature. <tables id="tabl0001" num="0001"><table frame="all"><tgroup cols="7" colsep="1" rowsep="1"><colspec colnum="1" colname="col1" colwidth="22.50mm" /><colspec colnum="2" colname="col2" colwidth="22.50mm" /><colspec colnum="3" colname="col3" colwidth="22.50mm" /><colspec colnum="4" colname="col4" colwidth="22.50mm" /><colspec colnum="5" colname="col5" colwidth="22.50mm" /><colspec colnum="6" colname="col6" colwidth="22.50mm" /><colspec colnum="7" colname="col7" colwidth="22.50mm" /><thead valign="top"><row><entry namest="col1" nameend="col1" align="left">Sample number</entry><entry namest="col2" nameend="col2" align="center">1</entry><entry namest="col3" nameend="col3" align="center">2</entry><entry namest="col4" nameend="col4" align="center">3</entry><entry namest="col5" nameend="col5" align="center">4</entry><entry namest="col6" nameend="col6" align="center">5</entry><entry namest="col7" nameend="col7" align="center">6</entry></row></thead><tbody valign="top"><row><entry namest="col1" nameend="col1" align="left">Situation of the center of gravity (mm)</entry><entry namest="col2" nameend="col2" align="char" char=".">-0.77</entry><entry namest="col3" nameend="col3" align="left">0.23</entry><entry namest="col4" nameend="col4" align="char" char=".">0</entry><entry namest="col5" nameend="col5" align="char" char=".">0.2</entry><entry namest="col6" nameend="col6" align="left">0.5</entry><entry namest="col7" nameend="col7" align="left">1.0</entry></row><row><entry namest="col1" nameend="col1" align="left">Temperature rise (°C)</entry><entry namest="col2" nameend="col2" align="char" char=".">65.2</entry><entry namest="col3" nameend="col3" align="left">60</entry><entry namest="col4" nameend="col4" align="char" char=".">56.8</entry><entry namest="col5" nameend="col5" align="char" char=".">61.6</entry><entry namest="col6" nameend="col6" align="left">66.9</entry><entry namest="col7" nameend="col7" align="left">74.5</entry></row><row rowsep="1"><entry namest="col1" nameend="col1" align="left">Belt life (Hrs)</entry><entry namest="col2" nameend="col2" align="char" char=".">183</entry><entry namest="col3" nameend="col3" align="left">200 or more</entry><entry namest="col4" nameend="col4" align="char" char=".">200 or more</entry><entry namest="col5" nameend="col5" align="char" char=".">200 or more</entry><entry namest="col6" nameend="col6" align="left">187</entry><entry namest="col7" nameend="col7" align="left">91</entry></row></tbody></tgroup></table></tables>

From the above test results, it can be seen that the nearer the center of gravity to the situation of tensile member, the lower the running belt temperature is kept and in the case where the situation of the center of gravity coincides with the tensile member, the running belt temperature is kept the lowest. However, so long as the situation of the center of gravity is within the range of the diameter of the tensile members of the load carriers in the vertical direction of each block, it is all right from the point of belt life.

The above embodiment is applied to a V belt with two load carriers but is also applicable to a V belt with only one load carrier. Such V belt 33 as shown in Fig. 7 and Fig. 8 comprises one endless load carrier 31 and a plurality of blocks 32 through which the load carrier 31 passes and which are engaged with the load carrier 31. Each block 32 comprises a substantially U-shaped underside member 32a and an upper side member 32b which engages with the underside member 32a. A concaved part 32d formed at the upper side member 32b is engaged with a convexed part 32c formed at the underside member 32a in the belt width direction. Furthermore, each block 32 is applicable to V belt 33 with the upper surface 32e formed in convexed surface (convex in upper direction) and its under surface 32f formed in concaved surface (concave in upper direction).

The above embodiment is also applicable to a V belt 47 as shown in Fig. 9 and Fig. 10. This V belt comprises an endless load carrier 41 and a plurality of blocks 42. Each block 42 comprises two friction members 45, 46 that are connected by reinforcing members 43, 44, each having a hollow shape. The members 45, 46 have slanted side parts 45a, 46a and two leg parts 45b, 45c and 46b, 46c which are parallel with each other and inserted in the hollow space of the two reinforcing members 43, 44 for contact of the leg parts with each other so that each block 42 is fixed to the load carrier 41. The V belt 33 and the V belt 47 can be adjusted so that the situation of the center of gravity is near the tensile members by adjusting the volume of the upper side member 32b and the lower side member 32a and by adjusting the volume of the leg parts 45b, 46b and the leg parts 45c, 46c or by adjusting the specific gravity of the connected reinforcing member respectively.

In any of the above embodiments, it is intended to prolong the life of belt by supporting the blocks substantially perpendicular in relation to the load carriers in the straight running state and thereby preventing rocking of the blocks in their engagement with the load carriers. However, in view of possible rocking of the blocks due to misalignment, it is suggested to restrict the lowering of belt life by the following arrangement.

As shown in Fig. 11, in the cross section where upper side parts 51a, 51b and lower side parts 51c, 51d which are parts of the side surfaces of a block 51 make a right angle with the lengthwise direction of belt, each corner is formed in a roundish curved surface of a radius R₁, R₂ with a center in its inner part. Also, as shown in Fig. 12, in the cross section where a block 51 is horizontal and in parallel with the center line of the lengthwise direction of belt, each corner 51e, 51f, 51g, 51h is formed in a roundish curved surface of a radius R₃ with a center in its inner part.

Under the above formation, even if the width of pulley groove of the pulley on the driving side and that on the driven side varies when the speed is changed and misalignment is caused due to shifting of the center line and the V belt enters the pulley in a slant state, no partial load is applied to such a block 51 because the corner part of circular arc shape makes a linear contact with the pulley groove surface 102a, 102b of a pulley 102.

Instead of the formation shown in Fig. 12, as shown in Fig. 13 a different formation can be made, namely, in the cross section where the block 51A is horizontal and in parallel with the center line of the lengthwise direction of the belt, the whole of both side surfaces of the block 51A are formed in a curved surface of a radius corresponding to the length of the width (upper beam part W₁, lower beam part W₂) of the block 51A. In this case, even if compressing action is applied to the side surface 51i, 51j of the block 51A and the load carrier, such compressing action on the block 51 is small and breakage, cracking, etc. of the block can be avoided owing to the sliding surface which is a surface curved toward the outside of the block 51.

It is also suggested that as shown in Fig. 14, the side surface of the block is formed in a curved surface as a whole by making the portion between the roundish upper corner part 52a, 52b and the roundish lower corner part 52c, 52d into a surface 52e, 52f which is curved toward the outside of a block 52.

It is further suggested that as shown in Fig. 15, the surfaces which compose both side surfaces of a block 53 comprise a circular arc of a radius R₄ described at the corner part 53d of the opposite angle with the center O₁ placed near the corner part 53a, a circular arc of a radius R₅ described at the corner part 53c of the opposite angle with the center O₂ placed near the corner part 53b, a circular arc of a radius R₆ described at the corner part 53b of the opposite angle with the center O₃ placed near the corner part 53c, and a circular arc of a radius R₇ described at the corner part 53a of the opposite angle with the center O₄ placed near the corner part 53d.

It is still further suggested that as shown in Fig. 16, on the supposition that points P₁, P₂, P₃, P₄ (upper and lower corners) of both side surfaces of a block 54 are on the chain line showing the pulley groove surface 102a, 102b of the pulley, corner parts 54c, 54d, 54e, 54f are formed by forming side surfaces 54a, 54b of curved surface shape by a circular arc of almost the same radius which is shorter than the length of each perpendicular V₁, V₂ which is drawn from the point P₂ of the block 54 to the line P₁, P₃ and from point P₁ to the line P₂, P₄ respectively. There is a case where the side surface 54a, 54b makes a linear contact with the pulley.

Under the above formations, even if the V belt enters the pulley in a slanted state, the block will be held in the specified position or in slightly sunk state at the worst because both side surfaces 54a, 54b of the block 54 are of circular arc shape in cross section. Thus, application of partial load to the corner parts 54c, 54d, 54e, 54f and resultant breakage of the block 54 can be avoided.

Furthermore, it is suggested to combine the shape of block shown in Fig. 11, Fig. 14, Fig. 15 or Fig. 16 with that shown in Fig. 12 or Fig. 13. By making the whole of the side surfaces of the block a circular arc shape in cross section, it is possible to reduce compressing action on the block and also lessen the generation of virbation at every angle. Accordingly, no partial load is applied to the block and destructive power to the block can be avoided still further.