Continuously variable transmission

A continuously variable transmission includes an input shaft rotatably supported in a housing; a first speed change unit and a second speed change unit, provided within the housing and disposed facing each other symmetrically with respect to a plane normal to the axial direction of the input shaft, to continuously vary the speed of rotation of the input shaft using traction force; an output rotating gear supported to be able to rotate freely about the input shaft so that the rotation of the output rotating gear is synchronized with the rotation which has been varied in speed by the first speed change unit and the second speed change unit; and an output shaft. The torque of the input shaft can be doubled by the two speed change units while continuously varying the speed, and the thrust loads generated in the axial direction of the input shaft cancel each other out.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a continuously variable transmission that continuously varies the rotation speed of the input shaft and transmits the speed to the output shaft by using a traction drive using traction force, and more particularly relates to a continuously variable transmission that continuously varies the speed using conical planetary rollers.

2. Description of the Related Art

As shown inFIG. 1, a conventional continuously variable transmission that includes an input shaft3and an output shaft4rotatably supported via bearings2on flanges1aconnected to both sides of a cylindrical housing1, a sun roller (inner wheel)5in the shape of the frustum of a cone connected to the input shaft3using a key3aso that the sun roller5rotates integrally with the input shaft3, a holder6rotatably supported via a bearing3bon the input shaft3, a plurality of tapered rollers (planetary rollers)7rotatably supported on the holder6that roll on the outer peripheral surface of the sun roller5, an output ring (follower outer wheel)8that rotates integrally with the output shaft4and contacts the outside of the tapered rollers7, a speed change ring (rotationally fixed outer wheel)9that contacts the outside of conical portions7aintegrally provided on the tapered rollers7and that can only be driven reciprocally in the direction of the generating lines of the conical portions7a, and so on, is known. See, for example, Japanese Patent Application Laid-open No. H6-280961.

In this continuously variable transmission, when the input shaft3rotates, the sun roller5rotates integrally with it, the tapered rollers7that contact the outside of the sun roller5rotate and revolve, the output ring8rotates as a result of the rotation of the tapered rollers7, the output shaft4that is integral with the output ring8rotates, and the rotation speed of the output shaft4is increased or decreased in accordance with the position of the speed change ring9.

However, in this continuously variable transmission, the normal load at the contact surface of the tapered rollers (planetary rollers)7and the sun roller5, the normal load at the contact surface of the tapered rollers7and the output ring8, and the normal load at the contact surface of the conical portions7aof the tapered rollers7and the speed change ring9depends on the initial assembly accuracy. Also, there is no means of correcting the variation in the normal loads due to changes with time, and the like. Therefore it may not be possible to obtain the necessary traction force, and there is a possibility that the speed change effect will not be reliably obtained. In particular, the tapered rollers7are supported cantilevered from the holder5, so the conical portions7aof the tapered rollers7can be easily bent, so it is difficult to greatly increase the contact force with the speed change ring9.

Also, a thrust load is generated in the direction of the axes of the input shaft3and the output shaft4as the normal loads increase, and this thrust load is received by the bearings2of the input shaft3and the output shaft4or the housing1. Therefore, the bearings2and the housing1deform with time, or the temperature of the lubricating oil rises due to heat in the area around the bearings, and so on, so there is the danger of wear and reduction in power transmission efficiency, and so on. On the other hand, if the stiffness of the housing1is increased as a measure against deformation, this will cause the size or weight to increase.

SUMMARY OF THE INVENTION

With the foregoing in view, it is an aspect of the present invention to provide a continuously variable transmission capable of ensuring sufficient traction force or transmission torque, increasing the transmission efficiency, canceling out the thrust load in the input shaft direction associated with an increase in the normal load, and capable of stably and reliably changing the speed to the desired speed change ratio, while simplifying the structure, reducing the size, improving the functional reliability, reducing the cost, and so on.

The continuously variable transmission according to an embodiment of the present invention includes an input shaft rotatably supported in a housing; a first speed change unit and a second speed change unit, provided within the housing, facing each other and symmetrically disposed with respect to a plane normal to the axial direction of the input shaft, for continuously varying the speed of rotation of the input shaft in use of traction force; an output rotating body supported to be able to rotate freely about the input shaft so that the rotation of the output rotating body is synchronized with the rotation which has been varied in speed by the first speed change unit and the second speed change unit; and an output shaft rotatably supported in the housing to rotate in synchronization with the output rotating body.

According to this structure, the speed of the rotational drive force of the input shaft may be continuously varied by the first speed change unit and the second speed change unit, and output as rotational drive force from the output shaft via the output rotating body.

In this way, the torque of the input shaft can be doubled by the two speed change units (the first speed change unit and the second speed change unit) while continuously varying the speed, and also the two speed change units (the first speed change unit and the second speed change unit) are disposed symmetrically with respect to a plane normal to the axial direction of the input shaft and facing each other, so the thrust loads generated in the two speed change units in the axial direction of the input shaft act in opposite directions and cancel each other out. Therefore, it is possible to prevent the application of unreasonable load on the housing or the bearing of the input shaft, and so on, also, the temperature rise in the area around the bearing and elsewhere can be reduced, so it is possible to form a lubricating oil film on the contact surfaces and reliably obtain the traction force.

In the above structure, a structure in which the first speed change unit includes a first sun roller with a frustum conical shape provided to rotate integrally with the input shaft; a plurality of first planetary rollers provided to roll on an outer peripheral surface of the first sun roller; a first output ring provided to contact internally with the first planetary rollers and to be able to freely rotate; and a first speed change ring provided to contact internally with conical portions formed integrally with the first planetary rollers and to be able to move in the axial direction of the input shaft to vary the speed by varying the position of internal contact, and the second speed change unit includes: a second sun roller with a frustum conical shape provided to rotate integrally with the input shaft; a plurality of second planetary rollers provided to roll on an outer peripheral surface of the second sun roller; a second output ring provided to contact internally with the second planetary rollers and be able to freely rotate; and a second speed change ring provided to contact internally with conical portions formed integrally with the second planetary rollers and to be able to move in the axial direction of the input shaft to vary the speed by varying the position of internal contact, may be adopted.

According to this structure, the rotation speed of the rotational drive force input from the input shaft may be varied in the first speed change unit by appropriately driving the first speed change ring through the first sun roller, the plurality of first planetary rollers, the first output ring, and varied in the second speed change unit by appropriately driving the second speed change ring through the second sun roller, the plurality of second planetary rollers, the second output ring, and output as rotational drive force with the speed changed from the output shaft via the output rotating body.

In particular, the thrust loads in opposite directions acting on the first sun roller and the second sun roller may be taken by the input shaft so the loads are cancelled out, so it is possible to reduce the thrust load acting on the bearing, and so on, so it is possible to increase the contact pressure (normal load) between the first sun roller and the first planetary rollers and the contact pressure (normal load) between the second sun roller and the second planetary rollers, and reliably obtain the traction force. Also, by adopting common components for the two speed change units it is possible to simplify the structure, reduce the number of types of components, and reduce the cost.

In the above structure, a structure may be adopted in which the output rotating body is disposed between the first output ring and the second output ring, and a loading cam mechanism that enables transmission of rotational power and generates pressing force in the axial direction of the input shaft is disposed at least either between the first output ring and the output rotating body, or between the second output ring and the output rotating body.

According to this structure, when a rotation difference occurs between the first output ring and the output rotating body and the second output ring and the output rotating body, a pressing force may be generated in the axial direction of the input shaft by the cam action of the loading cam mechanism, so the normal force of the first output ring acting on the first planetary rollers or the normal force of the second output ring acting on the second planetary rollers, in other words the traction force, increases. In this way, even if an external load torque is applied, traction force can be reliably obtained, and the output shaft is reliably rotated and driven at the required speed change ratio.

In the above structure, a structure in which the output rotating body is integrally formed to one of the first output ring and the second output ring, and a loading cam mechanism that enables transmission of rotational power and generates pressing force in the axial direction of the input shaft is disposed between one of the first output ring and the second output ring and the output rotating body, may be adopted.

According to this structure, when a rotation difference occurs between one of the first output ring and the second output ring (and the output rotating body) and the other of the first output ring and the second output ring, a pressing force is generated in the axial direction of the input shaft by the cam action of the loading cam mechanism, so the normal force of the first output ring acting on the first planetary rollers or the normal force of the second output ring acting on the second planetary rollers, in other words the traction force, increases. In this way, even if an external load torque is applied, traction force can be reliably obtained, and the output shaft is reliably rotated and driven at the required speed change ratio.

In the above structure, a structure that includes a drive mechanism that drives in synchronization the first speed change ring and the second speed change ring to approach each other or separate from each other in the axial direction of the input shaft may be adopted.

According to this structure, the drive mechanism drives the two speed change rings simultaneously, so no deviation in the speed change ratio of the two speed change units (first speed change unit and second speed change unit) is caused, so it is possible to reliably carry out drive force transmission from the single input shaft, the two speed change units, and the single output shaft.

In the above structure, a structure that includes a trigger mechanism that turns on or off the transmission of rotational power between the first sun roller and the first planetary rollers, and/or between the second sun roller and the second planetary rollers using traction force, in accordance with the rotational speed of the input shaft, may be adopted.

According to this structure, the first sun roller (or the second sun roller) and the first planetary rollers (or the second planetary rollers) are not always directly connected (in close contact so that traction force is generated), but when the rotational speed of the input shaft increases, the trigger mechanism may be turned on and the rotational drive force of the first sun roller (or the second sun roller) is transmitted to the first planetary rollers (or second planetary rollers) via the traction force, so it is possible to couple the rotation of the input shaft to the output shaft at the required timing, on the other hand, when the rotational speed of the input shaft reduces, the trigger mechanism is turned off and the rotational drive force of the first sun roller (or the second sun roller) is not transmitted to the first planetary rollers (or second planetary rollers), so it is possible to make the output shaft free (capable of rotating in response to an external force) regardless of the rotation of the input shaft.

In the structure that includes the above trigger mechanism, a structure that includes impelling means for impelling the first sun roller in a direction to separate from the first planetary rollers, and/or impelling means for impelling the second sun roller in a direction to separate from the second planetary rollers may be adopted.

According to this structure, for example, if the rotational speed is slower than a predetermined speed level, the first sun roller (or the second sun roller) can be forcibly removed from the first planetary rollers (or second planetary rollers) in accordance with the rotational speed of the input shaft, whereby transmission of rotational power can be surely disconnected.

According to the continuously variable transmission with the above structure, it is possible to ensure sufficient traction force or transmission torque, improve the transmission efficiency, cancel out the thrust loads in the axial direction of the input shaft associated with an increase in normal load, and stably and reliably change the speed to the required speed change ratio, while simplifying the structure, reducing the size, improving the functional reliability, and reducing the cost, and so on.

EXPLANATION OF THE REFERENCE NUMERALS

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

As shown inFIGS. 2 and 3, the continuously variable transmission includes a housing10, an input shaft20, a first speed change unit U1and a second speed change unit U2symmetrically disposed with respect to a surface normal to the axial direction L of the input shaft20within the housing10, a drive mechanism70, a pair of trigger mechanisms80,80′, an output rotating gear as output rotating body90, a pair of loading cam mechanisms100,100′, and an output shaft110.

As shown inFIG. 3, the first speed change unit U1includes a first sun roller30formed in the shape of the frustum of a cone, a plurality of first planetary rollers40that roll on the outer peripheral surface of the first sun roller30, a first output ring50that contacts the first planetary rollers40internally and that is rotatably supported, and a first speed change ring60that rotatably contacts internally second conical portions42that are formed integrally on the first planetary rollers40and whose speed is varied by moving the internal contact position.

As shown inFIG. 3, the second speed change unit U2includes a second sun roller30′ formed in the shape of the frustum of a cone, a plurality of second planetary rollers40′ that roll on the outer peripheral surface of the second sun roller30′, a second output ring50′ that contacts the second planetary rollers40′ internally and that is rotatably supported, and a second speed change ring60′ that rotatably contacts internally second conical portions42that are formed integrally on the second planetary rollers40′ and whose speed is varied by moving the internal contact position.

In other words, as shown inFIG. 3, the first speed change unit U1(first sun roller30, first planetary roller40, first output ring50, first speed change ring60) and the second speed change unit U2(second sun roller30′, second planetary roller40′, second output ring50′, second speed change ring60′) sandwich the output rotating gear90and the pair of loading cam mechanisms100,100′, and are symmetrically disposed with respect to a normal plane (a surface normal to the axial direction of the input shaft20) located in a position in approximately the center position of the housing10in the axial direction L of the input shaft20.

As shown inFIGS. 2 and 3, the housing10includes a left and a right flange wall portion11that rotatably supports the input shaft20, a bearing12, a ring seal13, a connecting guide rod14that connects the left and right flange wall portions11, a cover15that covers the outer periphery, a cover16that supports the output shaft110as well as covers the surroundings of the output shaft110, a bearing17, and a ring seal18.

Lubricating oil is supplied inside the housing to the contact boundary surfaces of the two speed change units U1, U2where traction force is generated, other sliding surfaces, and rolling surfaces.

As shown inFIG. 3, the input shaft20is formed from an external shaft21that projects outside the housing10and transmits the drive force from an engine or the like, an internal input shaft22disposed within the housing10and connected so as to rotate integrally with the external input shaft21, and an end input shaft23connected to the end of the internal input shaft22.

As shown inFIG. 3, the external input shaft21includes a disk-shaped rotating flange21a, and a connecting hole21bfor connecting the internal input shaft22, and is rotatably supported on the housing10(flange wall portion11) via the bearing12. The rotating flange21ais disposed in a position in opposition to the end surface of the first sun roller30, and demarks an end surface82of the trigger mechanism80, which is described later.

As shown inFIG. 3, the internal input shaft22includes a first end22a, a second end22b, and a stopper22c, the first sun roller30is connected to the shaft so that the first sun roller30rotates integrally with the shaft and is capable of moving only a predetermined amount in the axial direction L (so that movement to the left is restricted by the stopped22c), the second sun roller30′ is fixed to the shaft by a screwed joint so that the second sun roller30′ rotates integrally with the internal input shaft22, and the first sun roller30and the second sun roller30′ are disposed in mutual opposition (so that the small diameter sides of the frustum shapes face each other). Also, the first end22aof the internal input shaft22is inserted into the connecting hole21bof the external input shaft21, the second end22bis inserted into a connecting hole23b, which is described later, in the end input shaft23, all disposed on the same axis (defined by the common axis line L).

As shown inFIG. 3, the end input shaft23includes a disk-shaped rotating flange23a, and the connecting hole23bto which the internal input shaft22is connected, and the end input shaft23is rotatably supported by the housing10(flange wall portion11) via the bearing12.

The external input shaft21, the internal input shaft22, and the end input shaft23are connected so that they rotate integrally about the axis line L and are capable of moving relative to each other in the axis line direction L.

As shown inFIG. 3, the first sun roller30is formed approximately in the shape of the frustum of a cone, and has an outer peripheral surface that is partly shaped like a conical surface on which the first planetary rollers40roll, and an end surface formed as a depression portion32. The depression portion32of the first sun roller30is demarked by a sloping surface83that receives centrifugal weights81of the trigger mechanism80.

As shown inFIG. 3, the second sun roller30′ is formed approximately in the shape of the frustum of a cone, and has an outer peripheral surface that is partly shaped like a conical surface on which the second planetary rollers40′ roll, and an end surface formed as a depression portion32. The depression portion32of the second sun roller30′ is demarked by a sloping surface83that receives centrifugal weights81of the trigger mechanism80′.

As shown inFIG. 3, the first planetary roller40includes a first conical portion41that rolls on the first sun roller30(outer peripheral surface31), a second conical portion42with a tapering shape that contacts the first speed change ring60internally, and a common shaft43for the first conical portion41and the second conical portion42.

As shown inFIG. 3, the second planetary roller40′ includes a first conical portion41that rolls on the second sun roller30′ (outer peripheral surface31), a second conical portion42with a tapering shape that contacts the second speed change ring60′ internally, and a common shaft43for the first conical portion41and the second conical portion42.

As shown inFIGS. 3 and 4, the plurality of first sun rollers40contained in the first speed change unit U1are supported by a first movable holder44so that the respective shafts43are disposed at equal intervals on an imaginary conical surface having its apex A1on the right side within the housing10. Also, as shown inFIG. 4, the plurality of second sun rollers40′ contained in the second speed change unit U2are supported by a second movable holder44′ so that the respective shafts43are disposed at equal intervals on an imaginary conical surface having its apex A2on the left side within the housing10.

As shown inFIG. 4, the generating line M2(the edge line that contacts both the first speed change ring60and the second speed change ring60′) of the second conical portion42located furthest away from the internal input shaft22in the diametric direction is formed so that the generating line M2extends parallel to the axial direction L of the internal input shaft22.

The shaft43of the first planetary roller40is supported so that it can move within a predetermined range with respect to the first movable holder44. The shaft43of the second planetary roller40′ is supported so that it can move within a predetermined range with respect to the second movable holder44′.

The first movable holder44is formed with an assembly structure (bird cage shape), and is supported via bearings by the outer peripheral surface of the rotating flange21aof the external input shaft21and a small diameter sleeve93of the output shaft gear90, which is described later, so that the first movable holder44does not contact other components within the housing10, and so that the first movable holder44can rotate freely about the input shaft20(internal input shaft22), and is supported so that the first planetary rollers40can roll.

The second movable holder44′ is formed with an assembly structure (bird cage shape), and is supported via bearings by the outer peripheral surface of the rotating flange23aof the end input shaft23and a small diameter sleeve93′ of the output shaft gear90, which is described later, so that the second movable holder44′ does not contact other components within the housing10, and so that the second movable holder44′ can rotate freely about the input shaft20(internal input shaft22), and is supported so that the second planetary rollers40′ can roll.

As shown inFIG. 3, the first output ring50is formed to include an inner peripheral surface51which the first conical portions41of the first planetary rollers40contact and roll thereupon, and a ring-shaped end surface52which is associated with the output rotating gear90. The first output ring50is rotatably supported on a large diameter sleeve94of the output rotating gear90, which is described later, so that the first output ring50can move in the axial direction L, and by rotating and revolving the first planetary rollers40, the first output ring50is rotated by the traction force of the first planetary rollers40. Therefore, by increasing the normal load on the inner peripheral surface51, a greater traction force can be obtained, and the rotational power is more reliably transmitted.

As shown inFIG. 3, the second output ring50′ is formed to include an inner peripheral surface51which the first conical portions41of the second planetary rollers40′ contact and roll thereupon, and a ring-shaped end surface52with the output rotating gear90disposed therebetween. The second output ring50′ is rotatably supported on a large diameter sleeve94′ of the output rotating gear90, which is described later, so that the second output ring50′ can move in the axial direction L, and by rotating and revolving the second planetary rollers40′, the second output ring50′ is rotated by the traction force of the second planetary rollers40′. Therefore, by increasing the normal load on the inner peripheral surface51, a greater traction force can be obtained, and the rotational power is more reliably transmitted.

As shown inFIG. 3, the first speed change ring60is formed to include an inner peripheral surface61that contacts the second conical portions42of the first planetary rollers40, a female screw portion62that is threaded onto a lead screw71that forms part of the drive mechanism70, a guided portion63that is fitted around and guided by the connecting guide rod14, and so on. The first speed change ring60is supported within the housing10so that it cannot rotate about the input shaft20(internal input shaft22), and is supported so that it can freely reciprocate within a predetermined range in the axial direction L of the input shaft20(internal input shaft22).

As shown inFIG. 3, the second speed change ring60′ is formed to include an inner peripheral surface61that contacts the second conical portions42of the second planetary rollers40′, a female screw portion62that is threaded onto a lead screw71that forms part of the drive mechanism70, a guided portion63that is fitted around and guided by a connecting guide rod14, and so on. The second speed change ring60′ is supported within the housing10so that it cannot rotate about the input shaft20(internal input shaft22), and is supported so that it can freely reciprocate within a predetermined range in the axial direction L of the input shaft20(internal input shaft22).

As shown inFIGS. 2 and 3, the drive mechanism70includes the lead screw71disposed within the housing10extending parallel to the input shaft20(internal input shaft22) and engaging with the female screw portions62of the first speed change ring60and the second speed change ring60′, a gear72fixed to the center of the lead screw71, a worm73that meshes with the gear72, and a motor74that drives and rotates the worm73.

When the motor74rotates in one direction, the two speed change rings60,60′ are driven (moved) in synchronization via the worm, gear72, and lead screw71at the same time towards the center in the axial direction L inFIG. 4so that the two speed change rings60,60′ approach each other. On the other hand, when the motor74is rotated in the opposite direction, the two speed change rings60,60′ are driven (moved) in synchronization via the worm73, gear72, and lead screw71at the same time towards the two outsides in the axial direction L inFIG. 4so that the two speed change rings60,60′ separate from each other.

In other words, by moving the first speed change ring60and the second speed change ring60′ in the axial direction L of the input shaft20, the internal contact position of the second conical portions42of the first planetary rollers40and the second planetary rollers40′ with the inner peripheral surface61is moved, and as a result the speed is changed.

Specifically, as shown inFIG. 4, when the first speed change ring60and the second speed change ring60′ contact the second conical portions42at a certain middle position N, the first planetary rollers40roll with respect to the first output ring50, and the second planetary rollers40′ roll with respect to the second output ring50′, the first output ring50and the second output ring50′ do not rotate but are stationary, so therefore the output shaft110is also stationary.

Next, if the contact position of the first speed change ring60and the second speed change ring60′ is moved towards the two sides within the housing10(as shown by the arrow D inFIG. 4), in other words the contact position is moved towards the small diameter end of the second conical portion42, the rotation speed of the first output ring50and the second output ring50′ gradually increases, and the output shaft110also rotates at a faster speed.

On the other hand, if the first speed change ring60and the second speed change ring60′ are moved to the opposite side from the center position N (to the center of the housing10) (as shown by the arrows R inFIG. 4), the contact position is moved towards the large diameter end of the second conical portion42, and the first output ring50and the second output ring50′ rotate in the opposite direction.

In this way the drive mechanism70drives the first speed change ring60and the second speed change ring60′ at the same time, so it is possible to ensure there is no deviation in the speed change ratio of the two speed change units U1, U2, and it is possible to obtain reliable power transmission from the input shaft20, the two speed change units U1, U2, the output rotating gear90, and the output shaft110.

The trigger mechanism80turns ON or OFF the transmission of rotational power in accordance with the rotational speed of the input shaft20, or in other words the first sun roller30, using the traction force between the first sun roller30and the first planetary rollers40, and as shown inFIG. 3, the trigger mechanism80includes a plurality of spherical-shaped centrifugal weights81, an end surface82formed in the rotating flange21aof the external input shaft21, a plurality of sloping surfaces83formed in the depression portion32of the first sun roller30, and a coil spring84as impelling means that applies an impelling force to the first sun roller30in the direction to separate the first sun roller30from the first planetary rollers40.

The trigger mechanism80′ turns ON or OFF the transmission of rotational power in accordance with the rotational speed of the input shaft20, or in other words the second sun roller30′, using the traction force between the second sun roller30′ and the second planetary rollers40′, and as shown inFIG. 3, the trigger mechanism80′ includes a plurality of spherical-shaped centrifugal weights81, an end surface82formed in the rotating flange23aof the end input shaft23, a plurality of sloping surfaces83formed in the depression portion32of the second sun roller30′, and a coil spring84as impelling means that applies an impelling force to the second sun roller30′ in the direction to separate the second sun roller30′ from the second planetary rollers40′.

When the rotation speed of the input shaft20(first sun roller30) is increased from the state in which the first sun roller30and the first planetary rollers40are idling relative to each other (the state in which there is no traction force acting on their contact surface), the centrifugal weights81of the trigger mechanism80move to the outside in the diametric direction and press on the sloping surface83, so the first sun roller30is pressed inwards in the axial direction L of the internal input shaft22(ON action). In other words, the first sun roller30is pressed by the plurality of first planetary rollers40. As a result, traction force is generated, the rotational drive force of the input shaft20(first sun roller30) is transmitted to the first planetary rollers40, and at the required timing is transmitted to the output shaft110.

On the other hand, when the rotational speed of the input shaft20(first sun roller30) reduces, the centrifugal weights81move towards the center in the diametric direction, the force pressing against the sloping surface83weakens, and the first sun roller30is withdrawn slightly from the plurality of first planetary rollers40by the impelling force of the coil spring84(OFF action). As a result the traction force reduces, the rotational drive force of the input shaft20(first sun roller30) is not transmitted to the first planetary rollers40, and the output shaft110can rotate freely (rotates due to an external force) regardless of the rotation of the input shaft20(first sun roller30).

In this way, the first sun roller30is formed so that its wedge action is strengthened when the trigger mechanism80is in the ON state, so it is possible to reliably obtain normal load, in other words traction force, at the contact surface between the first sun roller30and the first planetary rollers40.

The trigger mechanism80′ performs the same action with respect to the second sun roller30′ and the second planetary rollers40′ as described for the trigger mechanism80, so its explanation has been omitted.

As shown inFIG. 3, the output rotation gear90includes a gear91formed on the outer peripheral surface thereof, end surfaces92,92′, small diameter sleeves93,93′, and large diameter sleeves94,94′, and is rotatably supported by the internal input shaft22via a bearing95.

The end surface92is in opposition to the end surface52of the first output ring50, and the end surface92′ is in opposition to the end surface52of the second output ring50′.

As shown inFIGS. 3 through 5B, the loading cam mechanism100includes a plurality of circular arc shaped cam grooves101formed in the end surface52of the first output ring50, a plurality of cam grooves102formed in the end surface92of the output rotating gear90corresponding to the cam grooves101, and a rolling body103disposed between the two cam grooves101,102.

As shown inFIGS. 3 through 5B, the loading cam mechanism100′ includes a plurality of circular arc shaped cam grooves101formed in the end surface52of the second output ring50′, a plurality of cam grooves102formed in the end surface92of the output rotating gear90corresponding to the cam grooves101, and a rolling body103disposed between the two cam grooves101,102.

In other words, when a difference in relative rotation occurs between the first output ring50and the output rotating gear90, the rolling body103of the loading cam mechanism100moves and is subject to the cam action of the cam grooves101,102, and a thrust force is generated in the axial direction L of the input shaft20(internal input shaft22). Therefore, the normal force on the contact surface between the first output ring50and the first planetary rollers40(and the second output ring50′ and the second planetary rollers40′) increases, and, as a reaction to the thrust load, the first output ring50(and the second output ring50′) and the output rotating gear90rotate integrally.

Also, when a difference in relative rotation occurs between the second output ring50′ and the output rotating gear90, the rolling body103of the loading cam mechanism100′ moves and is subject to the cam action of the cam grooves101,102, and a thrust force is generated in the axial direction L of the input shaft20(internal input shaft22). Therefore, the normal force on the contact surface between the second output ring50′ and the second planetary rollers40′ (and the first output ring50and the first planetary rollers40) increases, and, as a reaction to the thrust load, the second output ring50′ (and the first output ring50) and the output rotating gear90rotate integrally.

In other words, the load torque of the output shaft110increases the pressing load (normal load), in other words the traction force, of the first output ring50on the first planetary rollers40or the second output ring50′ on the second planetary rollers40′ via the loading cam mechanism100,100′.

Also, when the normal load of the first output ring50pressing on the first planetary rollers40increases, the contact pressure (normal load) between the first sun roller30and the first planetary rollers40also increases, so the contact pressure (normal load) between the second conical portions42of the first planetary rollers40and the first speed change ring60also increases, with the contact position of the first sun roller30and the first planetary rollers40as support points.

Further, when the normal load of the second output ring50′ pressing on the second planetary rollers40′ increases, the contact pressure (normal load) between the second sun roller30′ and the second planetary rollers40′ also increases, so the contact pressure (normal load) between the second conical portions42of the second planetary rollers40′ and the second speed change ring60′ also increases, with the contact position of the second sun roller30′ and the second planetary rollers40′ as support points.

Therefore, overall, when the normal load increases in the traction drive, traction force can be reliably obtained even if the load torque from the outside varies, so the output shaft110is reliably rotated and driven at the required speed change ratio.

As shown inFIGS. 2 and 3, the output shaft110is provided integrally with a gear111that meshes with the gear91of the output rotating gear90, and is rotatably supported by the housing10via the bearing17and the ring seal18.

Therefore, the rotational drive force of the input shaft20is changed in speed by the two speed change units U1, U2, and the rotational drive force after speed change is transmitted to the output shaft110via the output rotating gear90.

Next, the operation of the above continuously variable transmission is explained.

First, when the input shaft20is stationary, there is no traction force generated between the two speed change units (first speed change unit U1, second speed change unit U2) and torque is not transmitted, so the output shaft110can freely rotate (OFF state).

Then, when the input shaft20starts to rotate from the stationary state, as the rotational speed increases, the trigger mechanisms80,80′ are turned ON (the centrifugal weights81move to the outside in the diametric direction, the first sun roller30is moved into the first planetary rollers40, and the second sun roller30′ is moved into the second planetary rollers40′), the first sun roller30presses against the first planetary rollers40, and the second sun roller30′ presses against the second planetary rollers40′, and when a specific level or more of normal load, in other words traction force, is generated, torque (rotational drive force) is transmitted from the first sun roller30to the first planetary rollers40, and from the second sun roller30′ to the second planetary rollers40′.

Then, the first speed change ring60and the second speed change ring60′ are appropriately driven at the same time by the drive mechanism70, and the rotational speed that has been changed via the first sun roller30, the plurality of first planetary rollers40, the first output ring50, and the second sun roller30′, the plurality of second planetary rollers40′, and the second output ring50′ is transmitted to the output rotating gear90via the loading cam mechanisms100,100′, and the output shaft110rotates.

On the other hand, when the load torque is applied to the output shaft110, the loading cam mechanisms100,100′ operate, and the pressing force (normal load) of the first output ring50on the first planetary rollers40and the pressing force (normal load) of the second output ring50′ on the second planetary rollers40′, in other words the traction force, is increased. In this way, even if a load torque from outside is applied, the traction force can be reliably obtained, and the output shaft110is reliably rotated and driven at the required speed change ratio.

In the above traction drive, a thrust load is generated in the axial direction L of the input shaft20in the two speed change units U1, U2, but the two speed change units U1, U2are symmetrically disposed with respect to a surface normal to the axial direction L of the input shaft20, so the respective thrust loads act in opposite directions and can cancel each other out. As a result, it is possible to prevent the application of unreasonable loads to the housing10or to the bearing12of the input shaft20, and so on.

In particular, the thrust loads in opposite directions acting on the first sun roller30and the second sun roller30′ are taken by the input shaft20(internal input shaft22) so the loads are cancelled out, so it is possible to reduce the thrust load acting on the bearing12, so it is possible to increase the contact pressure (normal load) between the first sun roller30and the first planetary rollers40and the contact pressure (normal load) between the second sun roller30′ and the second planetary rollers40′, and reliably obtain the traction force. Also, by adopting common components for the two speed change units U1, U2it is possible to simplify the structure, reduce the number of types of components, and reduce the cost.

In other words, according to the embodiment described above, it is possible to ensure sufficient traction force or transmission torque, improve the transmission efficiency, cancel out the thrust load in the axial direction L of the input shaft20associated with the increase in the normal load, and stably and reliably change the speed to the required speed change ratio, while simplifying the structure, reducing the size, improving the functional reliability, and reducing the cost.

FIG. 6shows another embodiment of the continuously variable transmission according to the present invention, which apart from elimination of the coil spring84, adoption of a single trigger mechanism80and a single loading cam mechanism100, and forming the second output ring integral with the output rotating body, is the same as the embodiment described above. Therefore, for the constitution that is the same as the embodiment described above, the same reference numerals are used, and the explanation is omitted.

As shown inFIG. 6, this continuously variable transmission includes a housing10, an input shaft20′, a first speed change unit U1(first sun roller30, first planetary rollers40, first output ring50, first speed change ring60) and a second speed change unit U2(second sun roller30″, second planetary rollers40′, with second output ring50″ serving as an output rotating body, second speed change ring60), a drive mechanism70, a trigger mechanism80, a loading cam mechanism100, and an output shaft110.

As shown inFIG. 6, the input shaft20′ is formed from an external input shaft21and an internal input shaft22′.

As shown inFIG. 6, the internal input shaft22′ includes a first end22a, a second end22b, and a stopper22c, disposed so that the first sun roller30and the second sun roller30″ are in mutual opposition (so that the small diameter sides of the frustum of a cone shapes face each other), the first sun roller30is connected to the internal input shaft22′ so that the first sun roller30rotates integrally with the internal input shaft22′ and is capable of moving only a predetermined amount in the axial direction L (so that movement to the left is restricted by the stopper22c), and the second sun roller30″ is fixed by a threaded joint to rotate integrally.

As shown inFIG. 6, the second sun roller30″ is formed in approximately the shape of a frustum of a cone, and is formed to include an external peripheral surface31, a cylindrical portion32″, a reduced diameter cylindrical portion33″, and so on. The reduced diameter cylindrical portion33″ is rotatably supported by the housing10(flange wall portion11) via a bearing12.

As shown inFIG. 6, the second output ring50″ is formed to include an internal peripheral surface51, a ring shaped end surface52which is associated with an output rotating gear90, a large diameter sleeve53″ supporting the first output ring50, and a gear54″ that meshes with a gear111of the output shaft110.

The second output ring50″ is rotatably supported by the internal input shaft22′ via a bearing55″ so that a small amount of movement is possible in the axial direction L, and by rotating and revolving the second planetary roller40′, the traction force causes the second output ring50″ to rotate.

In other words, an item (gear54″) that corresponds to the output rotating gear90as described above is formed integrally with the second output ring50″.

In this embodiment also, as stated previously, the torque of the input shaft20′ can be doubled by the two speed change units U1, U2while continuously varying the speed, and also the two speed change units U1, U2are disposed facing each other and symmetrically with respect to a plane normal to the axial direction L of the input shaft20′, so the thrust loads generated in the two speed change units U1, U2in the axial direction L of the input shaft20′ act in opposite directions and cancel each other out. Therefore, it is possible to prevent the application of unreasonable load on the housing10or the bearing12of the input shaft20′. Also, the temperature rise in the area around the bearing12and elsewhere can be reduced, so it is possible to form a lubrication oil film on the contact surfaces and reliably obtain the traction force.

In other words, according to this embodiment, it is possible to ensure sufficient traction force or transmission torque, reduce the cost, improve the transmission efficiency, cancel out the thrust load in the axial direction L of the input shaft20′ associated with the increase in the normal load, and stably and reliably change the speed to the required speed change ratio, while simplifying the structure, reducing the size, and improving the functional reliability.

In the above embodiments, the two speed change units U1, U2were described as having the sun roller30,30′, the planetary rollers40,40′, the output rings50,50′, the speed change rings60,60′, and so on, but the embodiments are not limited to this, and speed change units with a different structure may be adopted provided speed change can be carried out using traction force.

In the above embodiments, cases where the loading cam mechanisms100,100′ were adopted were described, but the embodiments are not limited to this, and a constitution in which the drive force is directly transmitted from the output rings50,50′ to the output rotating gear90may be adopted.

In the above embodiments, cases in which the two trigger mechanisms80,80′ or a single trigger mechanism80were adopted were described, but the embodiments are not limited to this, and the trigger mechanisms80,80′ may be eliminated.

In the above embodiments, the case in which impelling means (coil spring84) was adopted as a part of the trigger mechanisms80,80′ was described, but the embodiments are not limited to this, and impelling means (coil spring84) may be adopted on one side only, or the impelling means (coil spring84) may be eliminated.

INDUSTRIAL APPLICABILITY

In the continuously variable transmission according to the embodiments described above, it is possible to ensure sufficient traction force or transmission torque, improve the transmission efficiency, and reliably change the speed to the required speed change ratio, while simplifying the structure, reducing the size, and improving the functional reliability, so of course it can be adopted as the speed change device mounted in a vehicle or the like, and it may be used in other drive devices, mechanical devices, working machines, and so on, provided the rotational speed of the rotational drive force input from the input shaft is continuously varied and output from the output shaft.