Endless transmission belt

An endless transmission belt for use in continuously variable transmissions of the chain type with a number of link plates interconnected in an endless manner. The belt has blocks arranged paired pins arranged longitudinally around its length and engaging with the blocks, link plates arranged transverse to the length of the belt and engaging the pins, and pin engagement grooves formed in the blocks and engaging the pins, wherein one or a plurality of sets of the link plates are interconnected by mutual pins in an endless manner. The pin engagement grooves are formed with recesses capable of compensating for the canting of the paired pins as they rotate about their longitudinal axes in passage around a pulley. Consequently, chattering movement of the blocks is reduced and, in addition, the amount by which the blocks slip in the circumferential direction when the belt is in engagement with the pulleys is reduced, thereby making the end faces of the pulleys and the blocks less vulnerable to wear, while reducing torque loss and thus improving transmission efficiency.

BACKGROUND OF THE INVENTION 
The present invention relates to endless transmission belts and, in 
particular, to endless belts for use in continuously variable 
transmissions of the chain type in which a number of link plates are 
interconnected in an endless manner. 
FIGS. 1 (a) and (b) are views showing the overall structure of parts of the 
conventional transmission belt, FIG. 1 (a) showing a portion in a straight 
run of the belt, i.e., in a portion which is not in engagement with the 
pulleys, and FIG. 1 (b) showing a bent portion of the belt, i.e., in a 
portion which is in engagement with a pulley. FIG. 2 is a side view 
showing the state of blocks and pins in contact with a driving pulley 
during operation of the belt, and FIG. 3 is a sectional view showing the 
state of the belt when engaged with a pulley. FIG. 2 shows the nontorque 
transmitting region a and the torque transmitting region b when rotation 
is counterclockwise as indicated by arrow R. 
As shown in FIGS. 1 and 2, a first block 1 and a second block 2 each have a 
groove 4 engaging a pin 3 and having a generally rectangular shape 
partially defined by a flat side surfaces 1a or 2a. In order to allow the 
pin 3 to can't whereby the inner side of a pin projects by an amount 
.DELTA. beyond the space normally occupied by the pin, as when the belt 
passes around a pulley, gaps corresponding to (2.times..DELTA.) must be 
provided between the pins 3 and the blocks 1 and 2 when these members are 
present in a straight portion of the belt. The dimension of the gap has to 
be determined using an amount .DELTA. by which the pin projects when the 
belt is bent at the minimum rotational radius. As a result, if the 
rotational radius of the belt is larger than the minimum rotational 
radius, a gap X may occur in the bent portion of the belt even in the 
non-torque transmitting region a, as shown in FIG. 2. In FIGS. 1 and 2, 
reference numerals 5 and 5' denote links engaging with the pins 3 and 3', 
and reference numeral 6 denotes a portion of contact between pins 3 and 3' 
and the grooves 4 and 4' of the blacks. 
The occurrence of such gaps X leads to the following problems: 
(1) The blocks 1 and 2 may slip a distance corresponding to the gaps X when 
the belt is in engagement with pulleys 7 (see FIG. 3), thereby making the 
surfaces of contact between the pulleys 7 and the blocks 1 and 2 more 
vulnerable to wear, and causing a reduction in transmission efficiency. 
(2) When the belt is in engagement with the pulleys 7, since the blocks 1' 
and 2' are inclined relative to the axis 8 of the pulleys 7, which 
inclination leads to abrasion of the surfaces of the pulleys 7. In FIG. 3, 
reference numerals 3' and 9 denote pins and sets of link plates, 
respectively. 
(3) In a straight portion of the belt, string vibration of the belt causes 
an increase in the chattering movement of the blocks 1 and 2, resulting in 
the generation of more noise. 
SUMMARY OF THE INVENTION 
An object of the present invention is to overcome the above-stated 
problems, and to provide an endless transmission belt which is capable of 
achieving smooth engagement between pins and blocks, and of restraining 
chattering movement of the blocks. 
In order to achieve the above-stated object, according to the present 
invention, an endless transmission belt is provided in which: blocks are 
arranged around the length of the belt; pins are arranged around the 
length of the belt in engagement with the blocks; link plates are arranged 
in parallel across the width of the belt and in engagement with the pins; 
and pin engagement grooves are formed in the blocks for containing the 
pins. Plural sets of the link plates are interconnected by mutual pins in 
an endless manner, the pin engagement grooves being formed with recesses 
capable of compensating for the canting (tilting) of the pins during 
passage around a pulley. 
With the above-stated arrangement of the endless transmission belt in 
accordance with the present invention, 
(1) Since the pin engagement grooves of the blocks are formed with recesses 
which compensate for the canting of the pins during passage around a 
pulley, the part of the blocks that defines the pin engagement grooves can 
possess the maximum possible thickness which enables the gaps between the 
pins and the blocks to be minimized. Consequently, chattering movement of 
the blocks can be restrained. 
(2) When the belt is in engagement with the pulleys, it is possible to 
reduce the amount by which the blocks slip in the circumferential 
direction. Consequently, the end faces of the pulleys and the blocks are 
less vulnerable to wear, thereby improving durability. In addition, toque 
loss is reduced, thereby improving transmission efficiency. 
(3) When the belt is in engagement with the pulleys, the blocks incline 
relative to the axis of the pulleys at reduced angles. Consequently, it is 
possible to avoid the risk that damage such as abrasion may occur on the 
surfaces of the pulleys, thereby improving the durability of the pulleys. 
(4) In a straight portion of the belt, the blocks can be restrained from 
any chattering movement even if the belt undergoes string vibration, 
thereby reducing noise.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
Embodiments of the present invention will now be described in detail with 
reference to the drawings. 
First, the structure of an endless transmission belt in accordance with the 
present invention will be described referring to FIGS. 4 through 7. 
As shown in FIGS. 4 and 5, an endless transmission belt 30 has first block 
members 31, paired with second block members 32, link plates 34 linking 
adjacent pairs of block members 31 and 32 and pins 33 engaging the link 
plates 34. Retainers 35 determine the position of the first and second 
block members 31 and 32 and sets of the link plates 34, while preventing 
the string vibration of straight portions of the belt as well as 
preventing displacement of the pins 33. Each retainer 35 has a 
horizontally symmetrical configuration including vertical portions 35a 
formed on either side of a central bridge portion, horizontal portions 35b 
continuous with each vertical portion 35a, and suspended portions 35c 
continuing with the horizontal portions 35b. 
The structure of these components will be described below. 
As shown in Fig.5, each first block member 31 has a generally trapezoidal 
configuration when viewed from the front, and includes an opening 36 in 
the center, notch portions 37a on either side of the opening 36, a head 
portion 31f, columns 31c, an upper span portion 31d, and a lower span 
portion 31e. Enlarged portions 31g are formed on the two ends of the upper 
span portion 31d, and enlarged portions 31h are formed on the two ends of 
the lower span portion 31e. The end faces 31i of the enlarged portions 31g 
and the end faces 31j of the enlarged portions 31h form surfaces of 
contact with pulleys (such as pulleys 7 shown in FIG. 3), and are 
positioned on contact planes 38 in such a manner as to come into smooth 
contact with the pulleys. Thus, each first block member 31 has a generally 
trapezoidal configuration in cross-section. The columns 31c of the first 
block members 31 have pin engagement grooves 39 (see FIG. 4) formed 
therein. Each groove 39 is formed at a middle portion of one of the 
front-side and back-side surfaces of the column 31c. 
Each of the second block members 32 has the same configuration as the first 
block member 31. Each second block member 32 is paired with a first block 
member 31, with the pin engagement grooves 39 formed at the middle 
portions of the side surfaces of the columns of the block members 31 and 
32 facing each other. 
Each of the pins 33 is bar-shaped with a cocoon-shaped cross-section (see 
FIG. 4). The pins 33 are formed into pairs, each pair comprising two pins 
33 received together in the mating pin engagement grooves 39 of the first 
and second block members 31 and 32, and engaged with the sets of link 
plates 34. 
The link plates 34 are arranged in parallel as sets. Adjacent sets have 
their link plates alternately intermeshed. As shown in FIG. 5, seven link 
plates are disposed in the openings 36 and eight link plates in total are 
disposed in the notch portions 37a on either sides of the openings 36, 
that is, fifteen link plates in total are arranged in parallel over the 
width of the belt, thereby forming each link set. 
Next, detailed descriptions will be given concerning the structure and the 
operation of the blocks in accordance with the present invention. As 
described before, the first block members and the second block members 
have the same configuration, though their positions are different when the 
block members are assembled to constitute the belt. Therefore, those 
detailed descriptions will be given concerning the first block members 31 
alone (which will hereafter be simply referred to as "blocks"). 
As described before, each block 31 has an engagement groove 39 at the 
middle portion of the side surface of the column 31c. Details of this 
structure are shown in FIGS. 6 and 7. Each pin engagement groove 39 
comprises a first horizontal portion 31n continuing with a portion 31m of 
the side surface of the column 31c via a corner, a first corner portion 
31o consisting of a rounded portion continuing with the horizontal portion 
31n, a vertical portion 31p continuing with the corner portion 31o, a 
transitional portion 31q consisting of a rounded portion continuing with 
the vertical portion 31p, a tapering portion 31r continuing with the 
transitional portion 31q, a second corner portion 31s consisting of a 
rounded portion continuing with the tapering portion 31r, and a second 
horizontal portion 31t continuing with the second corner portion 31s, the 
second horizontal portion 31t also continuing with a lower portion 31u of 
the side surface via a corner. 
Thus, according to the present invention, in contrast with the prior art, 
the bottom of each pin engagement groove 39 is formed with a recess 
(concavity) 40 having the tapering portion 31r continuing with the 
transitional portion 31q, and the recess 40 is arranged to compensate for 
the projection .DELTA. of the pin 33. 
The other side surface of each column 31c is formed with a transitional 
portion 31w continuing with an upper portion 31v of the side surface, a 
vertical portion 31x continuing with the transitional portion 31w, a 
tapering portion 31y continuing with the vertical portion 31x, and a 
second transitional portion 31z continuing with the tapering portion 31y. 
By virtue of the above-described structure, when the blocks 31 and the 
associated members are present in a straight portion of the belt, the pin 
33 is brought into contact with the vertical portion 31p of the pin 
engagement groove 39 of the block 31, as shown in FIG. 8 (a). On the other 
hand, when these members are present in a bent portion of the belt, the 
projection .DELTA. of the pin 33 is compensated for by the recess 40 of 
the pin engagement groove 39 of the block 31, with the pin 33 being 
brought into contact with the transitional portion (rounded portion) 31q 
of the groove 39. Reference numerals 34 in FIGS. 8 (a) and (b) denote link 
plates. 
Therefore, it is no longer necessary to provide gaps (2.times..DELTA.), 
such as those provided in the prior art to cope with the projection 
.DELTA. of the pins 33, between the pins 33 and the blocks 31 in a 
straight portion of the belt by reducing the thickness of the portion of 
the blocks that defines the pin engagement grooves 39. Consequently, even 
with the maximum possible thickness for the block 31 and its portion 
defining the pin engagement groove 39, the belt can be smoothly bent. (see 
FIG. 8 (b)). 
when the blocks 31 and 32 are present in a straight portion of the belt, 
their vertical portions 31x contact each other, as shown in FIG. 8 (a). On 
the other hand, when these are present in a bent portion of the belt, they 
are slightly inclined and are in back-to-back engagement with each other, 
with their tapering portions 31y contacting each other, as shown in FIG. 8 
(b). 
A second embodiment of the present invention will now be described with 
reference to FIGS. 9 and 10. 
As shown in these figures, an endless transmission belt 50 has blocks 51 
each comprising a single block member, pins 61, and link plates 71 linking 
these members. 
The overall structure of the above-mentioned components will be described. 
As shown in FIG. 10, each block 51 is generally trapezoidal when viewed in 
cross-section, and has an upper span portion 52, a lower span portion 53, 
and columns 54 and 55 on either side of the span portions 52 and 53. The 
central portion of the block 51 is formed with a single opening 56, and 
the columns 54 and 55 are formed with grooves 57 and 58 having a similar 
configuration to that in the above-described first embodiment and engaging 
the end portions of the pins 61. The grooves 57 and 58 are formed in the 
front-side and back-side surfaces of each block 51, and with a 
configuration symmetrical with respect to the center line 59 of the block 
51. 
Each of the pins 61 is bar-shaped with a cocoon-shaped cross-section (see 
FIG. 9). The pins 61 are formed into pairs, each pair comprising two pins 
61 received together in the pin engagement grooves 57 and 58 of each block 
51, and engaged with the sets 70 of link plates 71. 
The link plates 71 are arranged in parallel to form sets 70. Adjacent sets 
have their link plates 71 alternately intermeshed. As shown in Fig. 10, in 
compliance with the single opening 56, seventeen link plates 71 are 
arranged in parallel across the width of the belt, thereby forming each 
set 70 of link plates 71. 
With the above-described structure, it is possible to achieve an endless 
transmission belt of simple construction that is capable of operating 
smoothly. 
The present invention is not limited to the abovedescribed embodiments; 
other various modifications based on the spirit of the present invention 
are possible and they are not excluded from the scope of the present 
invention.