CROSS REFERENCE TO RELATED APPLICATIONS

This application is a National Stage of International Application No. PCT/JP2020/046275 filed Dec. 11, 2020, claiming priority based on Japanese Patent Application No. 2019-225115 filed Dec. 13, 2019 and 2020-202934 filed Dec. 7, 2020.

TECHNICAL FIELD

The present invention relates to a power transmission path switching device for switching a transmission path of power between an input member and an output member, and a two-speed transmission including the power transmission path switching device.

BACKGROUND ART

In response to the trend of consumption reduction of fossil fuel in recent years, research on electric automobiles and hybrid automobiles has been progressing, and some of them has been implemented. Because an electric motor which is a power source for electric automobiles and hybrid automobiles is different from an internal combustion engine (engine), which is driven by directly combusting a fossil fuel, in that characteristics of torque and rotation speed of an output shaft are suitable for automobiles (generally, the maximum torque is generated at startup), electric automobiles and hybrid automobiles are not necessarily required to be equipped with a transmission, unlike general automobiles having the internal combustion engine as a drive source. However, even when the electric motor is used as a drive source, acceleration performance and high-speed performance can be improved by providing the transmission. Specifically, by providing the transmission, a relation between the travelling speed and the acceleration of the vehicles can be made smooth to the degree close to that of automobiles equipped with a gasoline engine and including the transmission in a power transmission system. This point will be described with reference toFIG. 39.

When a power transmission device having a large reduction ratio is arranged, for example, at a portion between the output shaft of the electric motor and an input part of a differential gear connected to a drive wheel, a relation between the acceleration (G) and the travelling speed (km/h) of the electric automobile is as indicated by a solid line a inFIG. 39. That is, although acceleration performance at a low speed is excellent, traveling at a high speed is not possible. To the contrary, when a power transmission device having a small reduction ratio is arranged at the portion therebetween, the relation is as indicated by a chain line b inFIG. 39. That is, although traveling at a high speed is possible, acceleration performance at a low speed is deteriorated. On the other hand, when a transmission is provided between the output shaft and the input part so that the reduction ratio of this transmission is changed according to a vehicle speed, characteristics such that a section of the solid line a on the left side of a point P and a section of the chain line b on the right side of the point P are continuously connected to each other is obtained. This characteristic is almost similar to that of gasoline engine automobiles having almost the same output as indicated by a broken line c inFIG. 39, which has revealed that in regard to the acceleration performance and the high-speed performance, performance equivalent to that of gasoline engine automobiles including the transmission in the power transmission system can be obtained.

JP05-116549A discloses the structure of a drive unit for electric automobiles for transmitting torque of the output shaft of the electric motor to the differential gear through a two-speed transmission (with the speed reduced by the two-speed transmission) which is formed by combining a pair of planetary gear mechanisms and a pair of brakes. In this drive unit for electric automobiles, by switching between a state where rotation of the components of the pair of planetary gear mechanisms is possible and a state where the rotation is not possible on the basis of switching a connected/disconnected state of the pair of brakes, the reduction ratio between the output shaft of the electric motor and the differential gear is able to be switched in high and low two speeds.

CITATION LIST

Patent Literature

[Patent Literature 1] JP05-116549A

SUMMARY OF INVENTION

Technical Problem

The device described in JP05-116549A is configured so that connection (engagement) of the brake is performed by pressing a friction engaging element supported by the component of the planetary gear mechanism and a friction engaging element supported by a housing against each other by servo pistons PL, PH which are operated with hydraulic pressure. However, in regard to electric automobiles and hybrid automobiles, in order to reduce the cost and enhance electricity cost performance due to simplification of the system, it is desirable that switching of the reduction ratio of the two-speed transmission is performed by an electric actuator so as to make a hydraulic pressure system unnecessary.

In view of the circumstances described above, an object of the present invention is to achieve structures of a power transmission path switching device capable of switching a transmission path of power by an electric actuator, and a two-speed transmission incorporating this power transmission path switching device.

Solution to Problem

A power transmission path switching device of the present invention includes:

a cam device having a drive cam supported so that rotation is possible and displacement in an axial direction is not possible, and a driven cam that is supported so that relative rotation with respect to the drive cam and displacement in the axial direction are possible, and is configured to displace in the axial direction according to rotation of the drive cam; and

a friction engagement device having at least one friction plate and at least one separation plate that are supported so that relative displacement in the axial direction with respect to each other is possible.

The friction engagement device is configured so as to be put into a connected state by pressing the friction plate and the separation plate against each other on the basis of displacement of the driven cam in a direction so that an interval in the axial direction between the driven cam and the drive cam increases, and be put into a disconnected state by releasing a force that presses the friction plate and the separation plate against each other on the basis of displacement of the driven cam in a direction so that the interval in the axial direction between the driven cam and the drive cam decreases.

The power transmission path switching device of the present invention further includes a rotation transmission state switching device having a first member and a second member that are arranged coaxially with each other, and a mode selecting part configured to rotate or displace in the axial direction according to rotation of the drive cam.

The rotation transmission state switching device has at least one mode of a free mode in which rotation of the first member with respect to the second member is allowed regardless of a direction of relative rotation between the first member and the second member, and a lock mode in which rotation of the first member with respect to the second member is prevented regardless of a direction of relative rotation between the first member and the second member; and a one-way clutch mode in which only rotation of the first member with respect to the second member in a specified direction is allowed, and rotation of the first member with respect to the second member in a direction opposite to the specified direction is prevented.

The rotation transmission state switching device is configured so as to be able to switch between at least one mode of the free mode and the lock mode and the one-way clutch mode on the basis of rotation or displacement in the axial direction of the mode selecting part.

In the power transmission path switching device of one aspect of the present invention, the rotation transmission state switching device may be put into the one-way clutch mode during switching of the friction engagement device from the connected state to the disconnected state and/or during switching of the friction engagement device from the disconnected state to the connected state.

The power transmission path switching device of one aspect of the present invention may have a first mode in which the friction engagement device is in the connected state, and the rotation transmission state switching device is in the free mode.

The power transmission path switching device of one aspect of the present invention may have a second mode in which the friction engagement device is in the disconnected state, and the rotation transmission state switching device is in the lock mode.

The power transmission path switching device of one aspect of the present invention may have a neutral mode in which the friction engagement device is in the disconnected state, and the rotation transmission state switching device is in the free mode.

In the power transmission path switching device of one aspect of the present invention, one member of the first member and the second member may have engaging recess portions at a plurality of positions in a circumferential direction, and the mode selecting part may have protruding portions at a plurality of positions in the circumferential direction, the protruding portions protruding in a radial direction or in the axial direction, and

the rotation transmission state switching device may further include:

a first claw member having a first base portion that is pivotally supported by the other member of the first member and the second member, and a first engaging claw that extends from the first base portion toward one side in the circumferential direction;

a second claw member having a second base portion that is pivotally supported by the other member of the first member and the second member, and a second engaging claw that extends from the second base portion toward the other side in the circumferential direction;

a first claw biasing member configured to elastically bias the first engaging claw in a direction so that the first engaging claw engages with the engaging recess portion; and

a second claw biasing member configured to elastically bias the second engaging claw in a direction so that the second engaging claw engages with the engaging recess portion.

In the one-way clutch mode, one engaging claw of the first engaging claw and the second engaging claw is not pressed by the protruding portion so that the one engaging claw engages with the engaging recess portion, and the other engaging claw of the first engaging claw and the second engaging claw is pressed by the protruding portion so that the other engaging claw does not engage with the engaging recess portion, thereby allowing only rotation of the first member with respect to the second member in the specified direction, and preventing rotation of the first member with respect to the second member in the direction opposite to the specified direction.

When the power transmission path switching device of the present invention has the free mode, in the free mode, the first engaging claw is pressed by the protruding portion so that the first engaging claw does not engage with the engaging recess portion, and the second engaging claw is pressed by the protruding portion so that the second engaging claw does not engage with the engaging recess portion, thereby allowing rotation of the first member with respect to the second member regardless of a direction of relative rotation between the first member and the second member.

When the power transmission path switching device of the present invention has the lock mode, in the lock mode, the first engaging claw is not pressed by the protruding portion so that the first engaging claw engages with the engaging recess portion, and the second engaging claw is not pressed by the protruding portion so that the second engaging claw engages with the engaging recess portion, thereby preventing rotation of the first member with respect to the second member regardless of a direction of relative rotation between the first member and the second member.

The power transmission path switching device of one aspect of the present invention may further include a select plate that has the mode selecting part, and is configured to rotate or displace in the axial direction according to rotation of the drive cam.

The power transmission path switching device of one aspect of the present invention may further include a speed reducer between the drive cam and the select plate, the speed reducer being configured to transmit rotation of the drive cam to the select plate with reducing a speed of the rotation.

In the power transmission path switching device of one aspect of the present invention,

the speed reducer may include:

a cam-side gear portion provided in the drive cam;

a plate-side gear portion provided in the select plate; and

a two-stage gear having a first gear portion that meshes with the cam-side gear portion, and a second gear portion that meshes with the plate-side gear portion.

Alternatively, in the power transmission path switching device of one aspect of the present invention, the speed reducer may include:

a cam-side groove that is provided in the drive cam, and extends in a direction further outward in the radial direction as going toward one side with respect to a direction of rotation;

a plate-side groove that is provided in the select plate, and extends in a direction further inward in the radial direction as going toward one side with respect to a direction of rotation; and

an engaging pin having a first engagement portion that engages with the cam-side groove so that displacement along the cam-side groove is possible, and a second engagement portion that engages with the plate-side groove so that displacement along the plate-side groove is possible, and

a length in the circumferential direction of the cam-side groove may be longer than a length in the circumferential direction of the plate-side groove.

In this case, the speed reducer further may include a guide plate having a guide groove extending in the radial direction, and being supported so that rotation is not possible, and

the engaging pin further may have a third engagement portion engaging with the guide groove so that displacement along the guide groove is possible.

Alternatively, in the power transmission path switching device of one aspect of the present invention,

the protruding portion may protrude in the axial direction, the select plate may have an engaging groove that has an inclined portion inclined with respect to the circumferential direction, and extends in the circumferential direction, and

the drive cam may have an engaging pin that protrudes in the radial direction, and engages with the engaging groove so that displacement along the engaging groove is possible.

In the power transmission path switching device of one aspect of the present invention, the drive cam may have the mode selecting part.

The power transmission path switching device of one aspect of the present invention may further include an elastic member that is arranged between the driven cam and the friction engagement device, and is configured to elastically bias the driven cam and the friction engagement device in directions away from each other.

In the power transmission path switching device of one aspect of the present invention, the friction engagement device may further have a return spring that is configured to elastically bias the friction plate and the separation plate in directions separating from each other.

In the power transmission path switching device of one aspect of the present invention, the cam device may include a plurality of rollers that have rotation axes directed in a radiation direction, and are sandwiched and held between the drive cam and the driven cam, and

the rollers may be supported by the driven cam so as to be able to freely rotate about the rotation axes.

A two-speed transmission of the present invention includes:

an input member;

an output member arranged coaxially with the input member;

a planetary gear mechanism arranged between the input member and the output member with respect to a direction of transmission of power; and

a power transmission path switching device configured to switch a power transmission path between the input member and the output member.

Particularly in the two-speed transmission of the present invention, the power transmission path switching device is the power transmission path switching device of the present invention, and the power transmission path switching device further includes an electric actuator configured to rotate and drive the drive cam.

The planetary gear mechanism includes:

a sun gear connected to the input member so as to rotate integrally with the input member;

a ring gear arranged coaxially with the sun gear and around the sun gear;

a carrier arranged coaxially with the sun gear, and connected to the output member so as to rotate integrally with the output member; and

a plurality of pinion gears that mesh with the sun gear and the ring gear, and are supported by the carrier so as to be able to freely rotate about their own center axes.

one of the friction plate and the separation plate is supported to the sun gear or the input member so that relative displacement in the axial direction is possible and relative rotation is not possible,

the other of the friction plate and the separation plate is supported to the carrier or the output member so that relative displacement in the axial direction is possible and relative rotation is not possible,

one of the first member and the second member is supported to a portion that does not rotate even in use so that relative rotation is not possible, and the other of the first member and the second member is supported to the ring gear so that relative rotation is not possible.

In the two-speed transmission of one aspect of the present invention, the drive cam may have a wheel gear portion on an outer circumferential surface thereof, and

the electric actuator may include a worm meshing with the wheel gear portion, and a transmission motor configured to rotate and drive the worm.

Effect of Invention

In the power transmission path switching device of one aspect of the present invention, a connected/disconnected state of the friction engagement device and a mode of the rotation transmission state switching device are switched on the basis of rotation of one drive cam. In short, with the power transmission path switching device of one aspect of the present invention, the transmission path of power is able to be switched on the basis that the drive cam is rotated and driven by one electric actuator including an electric motor or the like. In addition, with the two-speed transmission of one aspect of the present invention including the power transmission path switching device of one aspect of the present invention, a reduction ratio between the input member and the output member is able to be switched by the electric actuator in high and low two speeds.

