Driving-side pulley

1. Field of the Invention

The present invention relates to a driving-side pulley that is one component of a belt-type continuously variable transmission transmitting a rotational power from a driving shaft to a driven shaft while continuously varying a speed of the rotational power that has been transmitted in accordance with a change of a rotational speed of the driving shaft.

2. Related Art

There has been previously proposed a belt-type continuously variable transmission including a driving-side pulley supported by a driving shaft, a driven-side pulley supported by a driven shaft, a V-belt wounded between both the pulleys, and transmitting a rotational power from the driving shaft to the driven shaft while continuously varying a speed of the rotational power, which has been transmitted to the driven shaft, in accordance with a rotational speed of the driving shaft.

To explain in detail, the driving-side pulley includes a fixed sheave supported by the driving shaft in an immovable manner along an axis line of the driving shaft and in a non-rotatable manner around the axis line with respect thereto, a movable sheave supported by the driving shaft in a movable manner along the axis line of the driving shaft and in a non-rotatable manner around the axis line with respect thereto, a return spring pressing the movable sheave in a direction away from the fixed sheave, and a flyweight mechanism.

The flyweight mechanism presses the movable sheave in a direction toward the fixed sheave against a pressing force of the return spring with utilizing a centrifugal force that has a value corresponding to the rotational speed of the driving shaft.

Meanwhile, the belt-type continuously variable transmission is required to perform a belt clutch function when an engine is in an idle state and is also required to perform an engine braking function when a vehicle travels. The belt clutch function is a function that interrupts or reduces the power transmission from the driving shaft to the driven shaft so as to effectively prevent a creep phenomenon when the engine is in the idle state.

In order to achieve the two requirements, Japanese patent No. 2620490 discloses a driving-side pulley (hereinafter referred to as a first conventional configuration) including a fixed pulley immovable in the axis line of the driving shaft, a movable sheave movable in the axis line of the driving shaft, a one-way clutch that is interposed between the driving shaft and the fixed sheave and allows a power transmission only from the fixed sheave to the driving shaft while preventing a power transmission in a reverse direction, a return spring pressing the movable sheave in a direction away from the fixed sheave, a flyweight mechanism that presses the movable sheave in a direction toward the fixed sheave against a pressing force of the return spring with utilizing a centrifugal force that has a value corresponding to the rotational speed of the driving shaft, an auxiliary spring generating a force for pressing the movable sheave to one side surface of the belt in cooperation with the flyweight mechanism, and an engagement mechanism connecting the driving shaft and the fixed sheave with each other in a non-rotatable manner around the axis line as the movable sheave moves in a direction toward the fixed sheave by a predetermined distance.

In the first conventional configuration, when the engine is in an idle state, although the belt is brought into a tension state by pressing the movable sheave by the flyweight mechanism and the auxiliary spring, the rotational power is not transmitted from the driving shaft to the fixed sheave since the engagement mechanism is in a non-engagement state. Specifically, in this condition, the power transmission from the driving shaft to the belt is performed only via the movable sheave so that a torque of the rotational power that is transmitted from the driving shaft to the driven shaft is reduced, whereby the creep phenomenon can be prevented.

On the other hand, if the rotational speed of the driven shaft becomes higher than that of the driving shaft when the vehicle travels, the rotational power from the driven shaft is transmitted to the driving shaft from the belt via movable sheave as well as via the one-way clutch and the fixed sheave, whereby the engine braking function can be effectively performed.

However, the first conventional configuration has a problem in that the engine braking function cannot be sufficiently performed in a case where an operator releases an engine output operating member such as an accelerator pedal when the vehicle travels.

To explain in detail, if the engine output operating member is released when the vehicle travels, the belt moves inward in a radial direction with respect to the driving-side pulley and comes into contact with a bottom surface of a V-shaped groove of the driving-side pulley.

The fixed sheave that engages with one side surface (a first side surface) of the belt is immovable in the axis line direction. On the other hand, the movable sheave that engages with the other side surface (a second side surface) of the belt is subjected to the force generated by the flyweight mechanism when the engine is in an idle state and the force generated by the auxiliary spring, both the forces pressing the movable sheave in a direction toward the fixed sheave. However, the movable sheave is also subjected to the force generated by the return spring so as to press the movable sheave in a direction away from the fixed sheave.

More specifically, the movable sheave is pressed toward the fixed sheave only by a force obtained by subtracting the force generated by the return spring from a resultant force of the force generated by the flyweight mechanism and the force generated by the auxiliary spring.

That is, in the first conventional configuration, when the engine output operating member is released during traveling of the vehicle, the power transmission is mainly performed only through a path or a route extending from the inner circumferential surface of the belt to the bottom surface of the V-shaped groove. Therefore, enough frictional force cannot be obtained between the belt and the movable sheave and between the belt and the fixed sheave. As a result, the belt slips with respect to both the sheaves so that the engine braking function cannot be effectively performed.

In order to achieve the above-mentioned two requirements, Japanese patent No. 3524533 discloses a driving-side pulley (hereinafter referred to as a second conventional configuration) including a fixed pulley that is immovable in the axis line and non-rotatable with respect to the driving shaft, a movable sheave that is movable in the axis line and non-rotatable with respect to the driving shaft, a return spring pressing the movable sheave in a direction away from the fixed sheave, a flyweight mechanism that presses the movable sheave in a direction toward the fixed sheave against a pressing force of the return spring with utilizing a centrifugal force that has a value corresponding to the rotational speed of the driving shaft, a collar that is inserted around the driving shaft so as to be rotatable with respect to both the sheaves and form the bottom surface of the V-shaped groove by its outer circumferential surface, and a one-way clutch that is interposed between the driving shaft and the collar so as to allow a power transmission only from the collar to the driving shaft while preventing a power transmission in a reverse direction, wherein the collar is provided with a conical surface coming into contact with a first side surface of the belt that is positioned on a side near the fixed sheave when the belt is moved onto the bottom surface of the V-shaped groove.

In the second conventional configuration, when the engine is in an idle state, the belt is positioned so that the first side surface comes into contact with the conical surface of the collar and the inner circumferential surface comes into contact with the outer circumferential surface of the collar while a second side surface coming into contact with the movable sheave. As explained earlier, the power transmission from the driving shaft to the collar is interrupted by the one-way clutch. Accordingly, the power transmission from the driving shaft to the belt is performed only via the movable sheave so that a torque of the rotational power that is transmitted from the driving shaft to the driven shaft is reduced, whereby the creep phenomenon can be prevented.

On the other hand, if the rotational speed of the driven shaft becomes higher than that of the driving shaft when the vehicle travels, the rotational power from the driven shaft is transmitted to the driving shaft from the belt via movable sheave as well as via the collar and the one-way clutch, whereby the engine braking function can be effectively performed.

However, as with the first conventional configuration, the second conventional configuration has a problem in that the engine braking function cannot be sufficiently performed in a case where an operator releases the engine output operating member when the vehicle travels.

To explain in detail, if the engine output operating member is released when the vehicle travels, the belt moves inward in a radial direction with respect to the driving-side pulley and comes into contact with the bottom surface of the V-shaped groove of the driving-side pulley.

The collar that engages with the first side surface of the belt is immovable in the axis line direction. On the other hand, although the movable sheave that engages with the second side surface of the belt is subjected to the force generated by the flyweight mechanism so as to press the movable sheave in a direction toward the fixed sheave, the movable sheave is also subjected to the force generated by the return spring so as to press the movable sheave in a direction away from the fixed sheave.

More specifically, the movable sheave is pressed toward the fixed sheave only by a force obtained by subtracting the force generated by the return spring from the force generated by the flyweight mechanism when the engine in the idle state.

That is, as in the first conventional configuration, in the second conventional configuration, the power transmission is mainly performed only through a path or a route extending from the inner circumferential surface of the belt to the bottom surface of the V-shaped groove when the engine output operating member is released during traveling of the vehicle. Therefore, enough frictional force cannot be obtained between the belt and the collar and between the belt and the movable sheave. As a result, the belt slips with respect to the collar and the movable sheave so that the engine braking function cannot be effectively performed.

In view of the prior art, it is an object of the present invention to provide a driving-side pulley that is one component of a belt-type continuously variable transmission that transmits a rotational power from a driving shaft to a driven shaft while continuously changing a speed of the rotational power that has been transmitted to the driven shaft in accordance with a rotational speed of the driving shaft, the driving-side pulley being capable of realizing an engine braking function with a sufficient capacity when an engine output operating member is released during a traveling of a vehicle while realizing a belt clutch function when a rotational speed of an engine output is an idle rotational speed.

In order to achieve the object, the present invention provides a driving-side pulley forming one component of a belt-type continuously variable transmission that transmits a rotational power from a driving shaft to a driven shaft while continuously changing a speed of the rotational power that is transmitted to the driven shaft in accordance with a rotational speed of the driving shaft, the driving-side pulley including a fixed sheave immovable along an axis line and non-rotatable around the axis line with respect to the driving shaft, a movable sheave movable along the axis line and non-rotatable around the axis line with respect to the driving shaft, a return spring pressing the movable sheave in a direction away from the fixed sheave and a flyweight mechanism pressing the movable sheave in a direction toward the fixed sheave with a force having an amount corresponding to the rotational speed of the driving shaft against a pressing force of the return spring, wherein the fixed sheave is provided with a fixed sheave-side engagement surface capable of engaging with a first side surface of a belt while the movable sheave is provided with a movable sheave-side engagement surface that is capable of engaging with a second side surface of the belt and forms, in cooperation with the fixed sheave-side engagement surface, a V-shaped groove into which the belt is engaged, wherein the driving-side pulley includes a movable sleeve inserted around an axis-line-direction fixed member, which is formed by the driving shaft or the fixed sheave, in a movable manner along the axis line and in a rotatable manner around the axis line with respect thereto, and a one-way clutch inserted around the movable sleeve in such a manner as to form a bottom surface of the V-shaped groove, wherein the movable sleeve includes a tubular portion inserted around the axis-line-direction fixed member and a flange portion extending outward in a radial direction from the tubular portion, wherein the one-way clutch includes an inner ring body inserted around the tubular portion in a non-rotatable manner with respect thereto and an outer ring body surrounding the inner ring body and forming the bottom surface of the V-shaped groove, and is configured so that only a rotational power generated by a rotation of the outer ring body in a normal direction is transmitted to the inner ring body, wherein the flange portion is provided with a pressing surface capable of engaging with one of the first and second side surfaces of the belt in a state where the inner circumferential surface of the belt engages with the outer ring body, and wherein the driving-side pulley further includes a cam mechanism that presses the movable sleeve in a first direction by utilizing a relative rotation of the movable sleeve in the normal direction with respect to the axis-line-direction fixed member, the first direction being a direction that has the pressing surface pressed against a corresponding side surface of the belt.

The driving-side pulley according to the present invention makes it possible to realize the engine braking function with a sufficient capacity when the engine output operating member is released during the traveling of the vehicle while preventing or reducing a power transmission from the driving shaft to a belt when the rotational speed of the engine output is an idle rotational speed to effectively prevent an unintentional creep phenomenon.

Preferably, the driving-side pulley according to the present invention may include an auxiliary spring that presses the movable sleeve in a second direction along the axis line that is opposite the first direction.

In one embodiment, the flange portion of the movable sleeve extends outward in a radial direction from an end portion of the tubular portion that is positioned on a side close to the fixed sheave and is configured so that the pressing surface is capable of engaging with the first side surface of the belt, and the fixed sheave is provided with a concave portion that is arranged inward of the fixed sheave-side engagement surface in the radial direction and into which the flange portion of the movable sleeve can be engaged. In this case, when the movable sheave is pressed in a direction toward the fixed sheave by the flyweight mechanism that generates a force having an amount corresponding to the rotational speed of the driving shaft, the movable sleeve is moved via the belt by the movable sheave in a second direction opposite the first direction in the axis line to an initial position in which the flange portion is engaged into the concave portion, and the pressing surface is positioned on the same plane as the fixed sheave-side engagement surface when the movable sleeve is positioned at the initial position.

In the one embodiment, the fixed sheave-side engagement surface and the pressing surface are preferably arranged with respect to the radial direction in such a manner that both the surfaces engage with the first side surface of the belt when the inner circumferential surface of the belt engages with the outer ring body while the movable sleeve is positioned at the initial position.

The driving-side pulley according to the one embodiment may further include a spider that is arranged on a side opposite the fixed sheave across the movable sheave and is immovable along the axis line and non-rotatable around the axis line with respect to the driving shaft, and a base member that is arranged on a side opposite the movable sheave across the spider and is connected to the movable sheave via a connecting member.

In this case, the flyweight mechanism includes a flyweight that is arranged between the movable sheave and the spider and swings outward in a radial direction of the driving shaft in accordance with the rotational speed of the driving shaft, the return spring is arranged between the spider and the base member, and the auxiliary spring is arranged inward of the flyweight with respect to the radial direction while being arranged between the spider and an end portion of the tubular portion that is on a side opposite the flange portion with respect to the axis line direction.

In any one of the above-mentioned various configurations, the cam mechanism may include a convex-like member provided at one of the axis-line-direction fixed member and the tubular portion, and a spiral groove provided at the other one of the axis-line-direction fixed member and the tubular portion in such a manner as that the convex-like member can be engaged into the spiral groove.

In a configuration including the auxiliary spring, one of the fixed sheave and the movable sheave that engages with the side surface of the belt facing the pressing surface is formed with a concave portion that is arranged inward of the engagement surface of the one sheave in the radial direction and into which the flange portion of the movable sleeve can be engaged, so that the movable sleeve is pressed by the auxiliary spring toward the initial position in which the flange portion is engaged into the concave portion at a normal state in which the cam mechanism does not apply the pressing force in the first direction along the axis line to the movable sleeve.

In the thus configuration, the cam mechanism may include an engagement groove provided at one of a rear surface of the flange portion that is opposite the pressing surface and a bottom surface of the concave portion, and a convex-like portion provided at the other one of the rear surface and the bottom surface in such a manner as to be engaged into the engagement groove.

In this case, the engagement groove is configured so as to include a deepest area with which the convex-like portion engages when the movable sleeve is positioned at the initial position, and an inclined area with which the convex-like portion engages when the movable sleeve rotates in a normal direction around the axis line with respect to the axis-line-direction fixed member from a state where the convex-like portion engages with the deepest area.

The inclined area is inclined in such a manner as that an engagement point at which the convex-like portion engages with the inclined area becomes narrower as the movable sleeve farther rotates in the normal direction around the axis line with respect to the axis-line-direction fixed member.

First Embodiment

Hereinafter, one embodiment of a driving-side pulley according to the present invention will be explained, with reference to the attached drawings.

The driving-side pulleyforms a belt-type continuously variable transmissionin cooperation with a driven-side pulleyand a beltsuch as a V-belt.

The belt-type continuously variable transmissionis interposed in a traveling system power transmitting path extending from a driving power sourcesuch as an engine to a driving wheel, for example.

is a schematic view of the traveling system power transmitting path to which the belt-type continuously variable transmissionis applied.

As shown in, the belt-type continuously variable transmissionperforms a variable speed-change operation between a driving shaftoperatively connected to the driving power sourceand a driven shaftoperatively connected to the driving wheel, and includes the driving-side pulleysupported by the driving shaft, the driven-side pulleysupported by the driven shaftand the beltwound, around the driving-side pulleyand the driven-side pulley.

As shown in, the driven-side pulleyincludes a driven-side fixed sheavesupported by the driven shaftin a rotatable manner around the axis line with respect thereto and in an immovable manner along the axis line direction thereof, a driven-side movable sheavesupported by the driven shaftin a rotatable manner around the axis line with respect thereto and in a movable manner along the axis line direction thereof, a spidersupported by the driven shaftin a non-rotatable manner around the axis line with respect thereto and in an immovable manner along the axis line, and a biasing memberthat presses the driven-side movable sheavein a downshift direction toward the driven-side fixed sheave.

The driven-side fixed sheavehas a fixed sheave-side engagement surfacea that engages with one side surface of the beltand the driven-side movable sheavehas a movable sheave-side engagement surfacea that engages with the other side surface of the beltso that both the engagement surfacesa,a form a V-shaped groove into which the belt is engaged.

As shown in, the driven-side pulleyfurther includes a main torque-cam mechanismthat presses the driven-side movable sheavein the downshift direction by a force having an amount in accordance with a relative difference in a rotational angle between the spiderand the driven-side movable sheaveand a sub torque-cam mechanismthat presses the driven-side movable sheavealong the axis line of the driven shaftby a force having an amount in accordance with the relative difference in the rotational angle between the driven-side fixed sheaveand the driven-side movable sheave

The sub torque-cam mechanismcan be configured so as to generate a pressing force for the driven-side movable sheavein a direction (that is, the downshift direction) same as or a direction (that is,aanupshift direction) opposite to the direction in which the main torque-cam mechanismpresses the driven-side movable sheavein accordance with a specification or requirement.

is a vertical cross sectional view of the driving-side pulley. As shown in, the driving-side pulleyis configured so that an effective radius of the belt, which is a distance from an axial center of the corresponding driving shaftto a position on which the beltruns in the driving-side pulley, varies in accordance with a rotational speed of the driving shaftthat varies in accordance with a manual operation or the like.

That is, the driving-side pulleyis configured so that the effective radius of the beltbecomes larger as the rotational speed of the driving shaftincreases and the effective radius of the beltbecomes smaller as the rotational speed of the driving shaftdecreases.

In particular, as shown in, the driving-side pulleyincludes a driving-side fixed sheave, a driving-side movable sheave, a return springand a flyweight mechanism.

The driving-side fixed sheaveis immovable along the axis line and non-rotatable around the axis line with respect to the driving shaft, and includes a fixed sheave-side engagement surfacea capable of engaging with the first side surfacea of the belt.