JPH01182662A - Belt transmission with automatic tension adjusting mechanism - Google Patents

Abstract

PURPOSE:To aim at the promotion of reduction in a floor space for a driving pulley and its lightweightiness by constituting both first and second pulley members in this driving pulley to be coupled together by a cam mechanism. CONSTITUTION:In an unloaded state, tension of a timing belt 10 comes to zero and each contact 6 and a cam 7 are engaged with each other in the state that shaft centers O1, O2 of both first and second pulley members 4, 5 for a driving pulley 3 are decentered at the peak. When driving force is added to a drive shaft 1, an engaging position between each contact 6 and the cam 7 is continuously shifted and varied according to this driving force, and each eccentric value of these pulley members 4, 5 is varied in the decreasing direction. Accordingly, the member 5 is shifted in direction of increasing belt pitch circumferential length, and since constant tension is always distributed to both tensile and loose sides of the belt 10, a skip phenomenon in the belt 10 is restrained from occurring. In this case, since these members 4, 5 are coupled together by a cam mechanism, rotation of the drive shaft 1 can be transmitted to the driving pulley at the transmission ratio of 1:1, so that even if a diameter of the pulley 3 grows larger, speed-up transmission is giveable to a driven pulley 9.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an improvement in a belt transmission device that automatically adjusts belt tension according to driving force to suppress the skip phenomenon.

(Prior art) Conventionally, in belt transmission devices that perform belt transmission by winding a timing belt around a toothed pulley, when the belt tension decreases, the teeth of the belt and the teeth of the pulley lose engagement. There is a problem that a so-called skip phenomenon occurs.

As a device for suppressing such a skip phenomenon, a tension mechanism is known in which a tension roller biased by a spring or the like presses the back surface of the slack side of the belt to apply tension to the belt according to the driving force. In this case, since the belt is bent by the tension roller in the back direction opposite to the normal bending direction, fatigue of the belt center body is accelerated and the durability of the belt is reduced.

Further, when a large torque is applied or when the belt elongates due to changes over time, the pressing force decreases due to the return of the tension roller's spring, etc., and the occurrence of the skip phenomenon is inevitable.

Therefore, in order to eliminate the above-mentioned problems, the
A belt transmission device equipped with an automatic tension adjustment mechanism disclosed in Japanese Patent No. 47592 has been proposed.

That is, in this proposal, for example, as shown in FIG. 6, a pair of rotational axes a and b are parallel to each other;
Driving and driven pulleys c and d each consisting of a toothed pulley are supported by b, and a timing belt e is provided which is wound around both pulleys c and d and transmits power between both rotating shafts a and b. , the driving or driven pulley c,
d, a first pulley member g which is rotationally integrally supported by rotating shafts a and b and has a gear f on its outer periphery;
The axis a of the first pulley member g is located on the outer periphery of the first pulley member g.
1, the first pulley member g
has a gear h meshing with the gear f on the inner periphery, and
a second pulley member j having teeth i on the outer periphery that mesh with the timing belt e;
The axial center of the second pulley member i is located in a slack side eccentric zone Z defined by a straight line 9A connecting llb+ and a straight line Us that is perpendicular to the straight line 9A and passes through the axial center a1 of the first pulley member g. The length of the belt e is set so that the belt 11 is eccentrically positioned by a predetermined amount.

(Problem to be Solved by the Invention) However, in this proposal, when the drive pulley C side is composed of the first and second pulley members g and i as shown in the figure, the diameters of both pulley members g and i are Due to the difference in the number of gears h on the second pulley member i side, the number of gears h on the first pulley member g
The number of gears f is greater than the number of gears f, and the rotation of the rotating shaft a is decelerated and transmitted to the second pulley member i, that is, the belt e.

Therefore, when applied to a bicycle drive system where rotation needs to be transmitted from drive pulley C to driven pulley d at increased speed,
In order to ensure the increased speed transmission, it is necessary to make the diameter of the drive pulley C larger than necessary in anticipation of the above-mentioned deceleration, which causes problems such as an increase in the space for its arrangement and an increase in weight. .

An object of the present invention is to provide the above-mentioned belt transmission device in which the first pulley member coupled and supported by the rotating shaft and the second pulley member meshingly connected to the belt are connected by means other than a gear mechanism. , the rotation of the first pulley member can be directly transmitted to the second pulley member without deceleration, and therefore the diameter of the drive pulley can be reduced even in a drive system where the rotation of the drive pulley is increased in speed and transmitted to the driven pulley. The purpose is to reduce the installation space and weight by maintaining the same.

(Means for Solving the Problem) In order to achieve this object, the solution of the present invention is to connect the first and second pulley members of the drive pulley by a cam mechanism.

Specifically, the present invention includes a pair of rotation axes parallel to each other;
The premise is a belt transmission device that includes driving and driven pulleys each consisting of a toothed pulley supported by the rotating shaft, and a timing belt that is wound between the pulleys and transmits power between the rotating shafts. .

The driving pulley is provided with a first pulley member which is rotatably supported by the rotating shaft and has a plurality of contacts or cams, and an outer periphery of the first pulley member that can be eccentric with respect to the axis of the first pulley member. and a second pulley member, which has a plurality of cams or contacts that are arranged in the first pulley member and engage with the contacts or cams of the first pulley member, respectively, and has teeth on the outer periphery that mesh with the timing belt.

Furthermore, as the driving force of the first pulley member increases, the engagement position of each cam of the first or second pulley member with the contact element that engages with the cam moves and changes, and the second pulley member The eccentricity with respect to the first pulley member is set to decrease continuously.

(Function) With the above configuration, in the present invention, the tension of the timing belt becomes zero in the no-load state, and when the axes of the first and second pulley members of the drive pulley are eccentric by the maximum amount, each contactor thereof and the cam are engaged. When a driving force is applied to the rotating shaft from this state and the rotating shaft becomes loaded, the engagement position between each of the contacts and the cam changes continuously according to the driving force, and the eccentricity of both pulley members decreases. The second
The pulley member moves in a direction that increases the belt pitch circumference, and as a result, a constant tension is always distributed between the tension side and the slack side of the belt, thereby suppressing the belt skipping phenomenon. In addition, when the belt is rotating, the axes of both pulley members are approximately aligned, and each contactor and cam are in contact with each other.
This allows the drive pulley to rotate smoothly.

In that case, since the first and second pulley members are connected by a cam mechanism consisting of a contact and a cam, the rotation of the rotation shaft can be transmitted to the drive pulley at a transmission ratio of 1:1, and the rotation of the drive pulley can be Even when the rotation is increased in speed and transmitted to the driven pulley, the drive pulley does not need to be made larger than necessary, so the space for disposing the drive pulley and its weight can be reduced.

(Example) Embodiments of the present invention will be described below based on the drawings.

1 and 2 show a first embodiment of the present invention, in which 1 is a drive shaft connected to a crank pedal (not shown) of a bicycle, 2 is a drive shaft disposed parallel to the drive shaft 1, and 2 is a drive shaft connected to a crank pedal (not shown) of a bicycle. A driven wheel supporting a rear wheel (not shown), the drive shaft l
A toothed drive pulley 3 is attached to the driven shaft 2, and a driven pulley 9 having a smaller diameter than the drive pulley 3 and having teeth 9a on the outer periphery is attached to the driven shaft 2.
are each rotatably supported. A timing belt 10 having teeth 10a on the bottom surface (inner peripheral surface) is wound between the driving and driven pulleys 3 and 9, and the timing belt 10 is wound around the driving and driven shafts 1 and 2.
It is designed to transmit power between the two.

The drive pulley 3 includes a first pulley member 4 that is rotationally integrally supported by the drive shaft 1, and is arranged around the outer periphery of the first pulley member 4. A ring-shaped second pulley member 5 having an axis 02 that can be eccentric with respect to the center. On the outer periphery of the first pulley member 4, eight contacts 6°6, . . . are formed that protrude outward in the radial direction. Further, on the inner periphery of the second pulley member 5, there is a contact 6° 6 of the first pulley member 4.
, eight cams 7.7. having cam surfaces 7a, 7a, . ... are formed, and a toothed portion 8 that meshes with the timing belt 10 is provided on the outer periphery. Then, as the driving force of the first pulley member 4 increases, each cam 7 of the second pulley member 5 rotates the engagement position with the contact 6 of the first pulley member 4 that engages with the cam 7. It is set so that the amount of eccentricity of the second pulley member 5 with respect to the first pulley member 4 is continuously decreased by moving forward in the direction.

Also, a straight line 9A connecting the drive and driven shafts 1 and 2
The axis 02 of the second pulley member 5 is eccentric by a predetermined amount in a slack side eccentric zone 2 defined by a straight line 9B that is orthogonal to the direct vAQA and passes through the axis 01 of the first pulley member 4. The length of the timing belt 10 is set so that the timing belt 10 is positioned at the right position.

Therefore, in the above embodiment, in a no-load state where no power is transmitted between the driving and driven pulleys 3 and 9,
The tension of the timing belt 10 becomes zero, and the drive pulley 3
The axis 02 of the second pulley member 5 is eccentric by the maximum amount with respect to the axis 01 of the first pulley 4, and in this state, some contacts 6, 6 . ... and the cam 7.7 on the inner circumference of the second pulley member 5. ... are engaged.

When a driving force is applied to the drive shaft 1 from this state and the drive shaft 1 becomes loaded, the engagement position between each of the contacts 6 and the cam 7 continuously moves forward in the rotational direction of the drive shaft 1 according to the driving force. However, the eccentricity between the axes 0+ and 02 of both pulley members 3°9 decreases, and the second pulley member 5 moves in the direction of increasing the belt pitch circumference, and as a result, the timing belt 10 increases. A constant tension is always distributed between the tight side and the loose side. Thereby, the skip phenomenon of the timing belt 10 can be suppressed.

When the timing belt 10 is running, the axes o1 and 02 of both the pulley members 3 and 9 substantially coincide with each other, and some of the contacts 6, 6, . ... and the cam 7.7°... come into contact with each other, thereby allowing the drive pulley 3 to rotate smoothly.

In this case, since the first and second pulley members 4°5 are connected by a cam mechanism consisting of a contactor 6 and a cam 7, the rotation of the drive shaft 1 is transmitted to the drive pulley 3 at a transmission ratio of 1:1. This eliminates the need to increase the diameter of the drive pulley 3 more than necessary even when the rotation of the drive pulley 3 is increased and transmitted to the driven pulley 9 due to the difference in the outer diameters of the drive and driven pulleys 3 and 9. Therefore, it is possible to reduce the installation space and weight of not only the drive pulley 3 but also the entire belt transmission device.

Further, as shown in FIG. 1, the tension of the timing belt 10 is zero in the no-load state, so there is no need to apply initial tension when installing the timing belt 10, and the installation can be easily performed. can.

Note that due to the change in the engagement position between the cam 7 of the second pulley member 5 and the contact 6 of the first pulley member 4, both pulley members 4,
5, the eccentricity of each cam 7 and contactor 6 is reduced.
It is sufficient to set the length of the timing belt 10 so as to maximize the length of the timing belt 10 that does not come out of engagement with the timing belt 10, which is more advantageous when the belt 10 is installed.

In the configuration of the above embodiment, a roller that rolls in contact with the cam surface 7a of the cam 7 may be attached to the tip of each contactor 6 in the first pulley member 4 of the drive pulley 3. In this case, since the roller reduces the frictional resistance when the contactor 6 contacts the cam surface 7a of the cam 7 in the second pulley member 5, there is an advantage that the torque loss when the cam contacts can be reduced.

FIG. 3 shows a second embodiment. Note that the same parts as in FIG. 2 are designated by the same reference numerals, and detailed explanation thereof will be omitted.

That is, in this embodiment, each contact 6 on the outer periphery of the first pulley member 4' of the drive pulley 3' is supported by an elastic member 11 such as a leaf spring so as to be movable in the radial direction. In this embodiment, each contact 6 is connected to the first pulley member 4
', the driving force of the first pulley member 4' is transferred to more contacts 6.6.'. ..., the receiver can be held and transmitted to the second pulley member 5, and the drive pulley 3
' can be rotated more smoothly and its durability can be improved. In addition to this, the same effects as described above can also be achieved when each of the contacts 6 is made of an elastic material such as polyurethane resin.

Further, FIGS. 4 and 5 show a third embodiment in which the members forming the contact 6 and the cam 7 that contacts the contact 6 are changed.

That is, the first pulley member 4' of the drive pulley 3' includes a boss part 12 that is rotationally integrally supported by the drive 1dll, and a ring that is arranged concentrically with the boss part 12 and integrally connected by a circular plate 13. eight cams 7.7 having a cam surface 7a on the inner periphery of the ring portion 14;
．． ... is formed.

On the other hand, the second pulley member 5' is connected to the first pulley member 4''.
an inner ring part 15 having an outer diameter smaller than the inner diameter of the ring part 14 and a larger inner diameter than the boss part 12; , an outer ring portion 17 having an inner diameter larger than the outer diameter of the ring portion 14 of the first pulley member 5', and a tooth portion 8 that meshes with the tooth portion 10a of the timing belt 10 on the outer periphery of the outer ring portion 17.
However, on the outer periphery of the inner ring 15, the cams 7.7. Eight contacts 6, 6 . . . ... are formed respectively.

Then, both the pulley members 4'' and 5' are arranged facing each other, and the boss portion 12 of the first pulley member 4' is placed inside the inner ring portion 15 of the second pulley member 5', and the ring portion 14 is placed inside the inner ring portion 15 of the second pulley member 5'. The inner ring 1 of the second pulley member 5' is fitted between the ring part 15 and the outer ring part 17, and the inner ring 1 of the second pulley member 5' is fitted onto the cams 7, 7, etc. on the inner periphery of the ring part 14 of the first pulley member 4'.
5 outer circumferential contacts 6, 6. The drive pulley 3' is assembled by engaging the...

Therefore, in this embodiment, the moving direction of the cam 7 and the contactor 6 is the direction in which the first pulley member 4', which is the driving side, moves in the rotational direction with respect to the second pulley member 5', which is the driven side. Therefore, the contactor 6 and the cam 7 move smoothly, and even smoother rotational operation can be obtained.

Although the above embodiments are applied to a bicycle drive system, it goes without saying that the present invention can also be applied to various belt transmission devices that require high durability. It is about.

(Effects of the Invention) As explained above, according to the present invention, the driving pulley that transmits power between the driven pulley and the driven pulley by the timing belt is connected to the first pulley member which is rotationally integrally supported by the rotating shaft of the driving pulley and the driven pulley. A second pulley member is arranged on the outer periphery of the first pulley member so as to be eccentric to the center of the first pulley member, and meshes with the timing belt at the outer periphery, and as the driving force of the first pulley member increases, , by moving and changing the engagement position of each cam of the first or second pulley member and a contactor that engages with the cam, and continuously decreasing and changing the amount of eccentricity of the second pulley member with respect to the first pulley member. By doing so, the rotation of the first pulley member can be transmitted to the second pulley member at a rotation ratio of 1:1 without deceleration, and the drive system can accelerate the rotation of the drive pulley and transmit it to the driven pulley. However, the diameter of the drive pulley can be kept small, and the space and weight of the drive pulley and thus the belt transmission device can be reduced.

If a roller that contacts the cam is provided at the tip of the contact in the cam mechanism, the frictional resistance when the contact and the cam slide is reduced, so that torque loss in the drive pulley can be reduced.

Furthermore, if the contactor is coupled and supported by the first or second pulley member via an elastic member, or if the contactor itself is made of an elastic material such as polyurethane resin, the driving force can be received by a plurality of contacts. As a result, the rotation of the drive pulley can be made even smoother, and its durability can also be improved.

[Brief explanation of the drawing]

1 and 2 show a first embodiment of the present invention;
The figure is a front view showing the belt transmission device in a no-load state, and FIG. 2 is a front view showing the belt transmission device in a loaded state. FIG. 3 is a diagram corresponding to FIG. 2 showing the second embodiment. 4 and 5 show the third embodiment, and FIG. 4 shows the second embodiment.
FIG. 5 is an exploded perspective view of the drive pulley. FIG. 6 is a diagram corresponding to FIG. 2 showing a conventional example. 1... Drive shaft, 2... Driven wheel, 3.3', 3''...
・Drive pulley, 4.4', 4'... First pulley member, 5°5'... Second pulley member, 6... Contact, 7
...Cam, 8...Tooth section, 9...Driven pulley, 10
...Timing belt, 01...Axis of the first pulley member, 02...Axis of the second pulley member. Figure 1 1B Figure 2 Figure 3 Figure 4 Figure 5 Figure 6

Claims (4)

[Claims] (1) A driving and driven pulley consisting of a pair of rotating shafts parallel to each other, toothed pulleys each supported by the rotating shafts, and a drive and driven pulley that is wound between the two pulleys to transmit power between the two rotating shafts. and a timing belt, and the drive pulley includes a first pulley member that is rotatably supported by the rotating shaft and has a plurality of contacts or cams, and a first pulley member that is disposed on the outer periphery of the first pulley member and that is located at the axis of the first pulley member. a second pulley member that is eccentrically arranged with respect to the first pulley member, has a plurality of cams or contacts that engage with the contacts or cams of the first pulley member, and has teeth on the outer periphery that mesh with the timing belt; Each cam of the first or second pulley member moves and changes its engagement position with a contactor that engages with the cam as the driving force of the first pulley member increases, so that the second pulley member A belt transmission device having an automatic tension adjustment mechanism, characterized in that the eccentricity of the member relative to the first pulley member is set to continuously decrease and change. (2) A belt transmission device having an automatic tension adjustment mechanism according to claim (1), wherein a roller that rolls in contact with a cam is provided at the tip of the contactor. (3) A belt transmission device having an automatic tension adjustment mechanism according to claim (1) or (2), wherein the contactor is made of an elastic material such as polyurethane resin. (4) A belt transmission device having an automatic tension adjustment mechanism according to claim (1) or (2), wherein the contactor is coupled and supported by the first or second pulley member via an elastic member.