An engaging/disengaging mechanism including: an actuation mechanism capable of transmitting power to an engaging member to move the engaging member in a first direction to switch the engaging/disengaging mechanism into an engaged state and in a second direction to switch the engaging/disengaging mechanism into a disengaged state; and an elastic member capable of storing such elastic force that the engaging member is moved in the second direction to switch the engaging/disengaging mechanism into the disengaged state, wherein to switch the engaging/disengaging mechanism into the engaged state, the power transmitted by the actuation mechanism is reduced after the engaging member is moved by the power transmitted by the actuation mechanism so that the engaging/disengaging mechanism is switched into the engaged state, the elastic force of the elastic member being less intense when the engaging member is in the position than when the engaging/disengaging mechanism is switched into the disengaged state.

TECHNICAL FIELD

The present invention relates to an engaging/disengaging mechanism that, provided in a power transmission system for a vehicle or other like machinery, switches between an engaged state where power can be transmitted and a disengaged state where power cannot be transmitted.

BACKGROUND ART

Vehicles or other like machinery include an engaging/disengaging mechanism in their power transmission systems to selectively switch between power transmission and no power transmission. A well-known example of such an engaging/disengaging mechanism is the electromagnetic clutch. An electromagnetic clutch is structured, for example, to move an armature against the elastic force of an elastic member (clutch disengaging spring) by magnetic force generated by an electromagnetic coil when the electromagnetic coil is supplied with electric power, in order to switch the clutch (engaging/disengaging mechanism) to an engaged state (see, for example, Patent Documents 1 and 2).

CITATION LIST

Patent Literature

SUMMARY OF THE INVENTION

Problems to be Solved by the Invention

In the electromagnetic clutch (engaging/disengaging mechanism) described in Patent Documents 1 and 2, the magnetism coil needs to be always supplied with electric power during the engaged state in order to generate a magnetic force that is sufficiently intense to overcome the elastic force (repulsive force) of the elastic member (sufficiently intense to maintain the armature in the engaged position). This arrangement inevitably adds to power consumption.

The present invention, conceived in view of this problem, has an object to provide an engaging/disengaging mechanism capable of reducing energy consumption during the engaged state.

Solution to Problem

The present invention is an engaging/disengaging mechanism that enables/disables power transmission including: an actuation mechanism capable of transmitting power to an engaging member in order to move the engaging member in a first direction to switch the engaging/disengaging mechanism into an engaged state and in a second direction to switch the engaging/disengaging mechanism into a disengaged state; and an elastic member capable, as a result of the engaging member being moved in the first direction, of storing such elastic force that the engaging member is moved in the second direction to switch the engaging/disengaging mechanism into the disengaged state, wherein to switch the engaging/disengaging mechanism into the engaged state, the power transmitted by the actuation mechanism to the engaging member is reduced after the engaging member is moved in the first direction to a position by the power transmitted by the actuation mechanism to the engaging member so that the engaging/disengaging mechanism is switched into the engaged state, the elastic force of the elastic member being less intense when the engaging member is in the position than when the engaging/disengaging mechanism is switched into the disengaged state.

According to the present invention, to switch the engaging/disengaging mechanism into the engaged state, the engaging member (sleeve) is moved to a position (e.g., the position of stroke x1shown inFIG. 6(A)) at which the engaging member has a less intense elastic force than when the engaging/disengaging mechanism is switched into the disengaged state. After that, the power transmitted by the actuation mechanism is reduced. This arrangement eliminates the need for the power transmitted by the actuation mechanism to the engaging member to overcome the repulsive force of the elastic member while the engaging/disengaging mechanism is in the engaged state. The present invention is therefore capable of maintaining the engaging/disengaging mechanism in the engaged state while allowing for reduction in energy consumption.

In the present invention, to switch the engaging/disengaging mechanism into the disengaged state, the power transmitted by the actuation mechanism may be reduced after the engaging member is moved in the first direction to another position by the power transmitted by the actuation mechanism to the engaging member, the elastic force of the elastic member being such that the engaging/disengaging mechanism is switched into the disengaged state when the engaging member is in the other position.

The power transmitted by the actuation mechanism to the engaging member is reduced after the engaging member (sleeve) is moved to the other position (e.g., the position of stroke x2shown in FIG.6(B)), the elastic force stored in the elastic member being capable of disengaging the engaging/disengaging mechanism when the engaging member is in the other position. This reduction of the power allows for reduction of energy consumption while the engaging/disengaging mechanism is in the disengaged state.

A specific arrangement example of the present invention is such that: the actuation mechanism includes: an armature provided integrally to the engaging member; and an electromagnetic coil; and the actuation mechanism magnetically attracts the armature by supplying electricity to the electromagnetic coil in order to move the engaging member in the first direction.

In this arrangement, to switch the engaging/disengaging mechanism into the engaged state or to maintain the engaging/disengaging mechanism in the engaged state, the electromagnetic coil may be supplied with less electricity than to switch the engaging/disengaging mechanism into the disengaged state. This arrangement allows for reduction of electric power consumption when the engaging/disengaging mechanism is switched into the engaged state. The arrangement also allows for reduction of electric supply to the electromagnetic coil while maintaining the engaging/disengaging mechanism in the engaged state. The present invention is therefore capable of reduction of electric power consumption and reduction of heat generation by the electromagnetic coil.

In the engaging/disengaging mechanism arranged to include the electromagnetic coil, to maintain the engaging/disengaging mechanism in the engaged state, the electromagnetic coil may be stopped from being supplied with electricity. This arrangement allows for more effective reduction of electric power consumption while the engaging/disengaging mechanism is in the engaged state.

In addition, to maintain the engaging/disengaging mechanism in the engaged state, the electromagnetic coil may be supplied with electricity that is less than to switch the engaging/disengaging mechanism into the engaged state, but sufficient to maintain the engaging/disengaging mechanism in the engaged state. This arrangement enables the engaging/disengaging mechanism to be reliably maintained in the engaged state even if the engaging/disengaging mechanism is subject to vibration or like disturbance.

In the engaging/disengaging mechanism arranged to include the electromagnetic coil, to switch the engaging/disengaging mechanism into the disengaged state, the electromagnetic coil may be stopped from being supplied with electricity after the engaging member is moved in the first direction to a further position by supplying electricity to the electromagnetic coil, the elastic force of the elastic member being such that the engaging/disengaging mechanism is switched into the disengaged state when the engaging member is in the further position. This arrangement allows for more effective reduction of electric power consumption while the engaging/disengaging mechanism is in the disengaged state.

In addition, to switch the engaging/disengaging mechanism into the disengaged state, the electromagnetic coil may be supplied with gradually decreasing electricity after the engaging member is moved in the first direction to a yet another position by supplying electricity to the electromagnetic coil, the elastic force of the elastic member being such that the engaging/disengaging mechanism is switched into the disengaged state when the engaging member is in yet the other position. This arrangement enables the gradual application of the repulsive force stored in the elastic member when the engaging/disengaging mechanism is switched into the disengaged state, hence restraining the engaging member from moving too rapidly in the second direction (disengaging direction).

Advantageous Effects of the Invention

The engaging/disengaging mechanism of the present invention is capable of reducing energy consumption while the engaging/disengaging mechanism is in an engaged state.

DESCRIPTION OF EMBODIMENTS

The following will describe embodiments of the present invention in reference to drawings.

First, an exemplary vehicle to which an engaging/disengaging mechanism of the present invention is applied will be described in reference toFIGS. 1 and 2.

This exemplary vehicle is a four-wheel-drive vehicle built around an FF (front engine, front wheel drive) vehicle with a transverse engine. The vehicle includes, to name a few, an engine (E/G)1, a transmission (T/M)2, and a power transmission device100. The engine (E/G)1is the power source for the traveling vehicle. The transmission (T/M)2shifts gears in relation to the rotation of the output shaft (crankshaft) of the engine1. The power transmission device100is coupled to the output end of the transmission2.

The following will describe each of these members: the engine1, transmission2, and power transmission device100.

Engine

The engine1is a publicly known power unit (power source) that burns hydrocarbon-based fuel, such as gasoline or diesel fuel, for power output. The engine1is configured to be capable of controlling operation conditions in, for example, fuel injection, ignition, and intake air regulation.

Transmission

The transmission2is a stepped (planetary gear-based) automatic transmission that shifts gears by means of, for example, frictional engaging devices, such as a clutch and a brake, and a planetary gear device. The transmission2may be another type of transmission, such as a manual transmission or a CVT (continuously variable transmission) that adjusts the gear ratio steplessly.

The output shaft (not shown) of the transmission2has an output gear2aprovided thereon so that the output shaft and the output gear2acan rotate integrally. The output gear2ameshes with a differential driven gear12of a front-wheel differential device10(described later in detail). The power transmitted (from the engine1) to the output shaft of the transmission2is transmitted to left and right front wheels (primary drive wheels)4L and4R via the front-wheel differential device10and front-wheel drive shafts3L and3R. In four-wheel drive state, the power transmitted to the output shaft of the transmission2is partly transmitted to left and right rear wheels (follower wheels)8L and8R via a transfer20, a propeller shaft5, a control clutch40, and a rear-wheel power transmission device50as will be described later in detail.

Power Transmission Device

The power transmission device100includes, among others, the front-wheel differential device10, the transfer20, the propeller shaft5, the control clutch40, and the rear-wheel power transmission device50.

Front-Wheel Differential Device

The front-wheel differential device10is capable of differential operation where torque is differentially distributed to the left and right front wheels4L and4R. The front-wheel differential device10includes, for example, a differential case11, the differential driven gear12, a pair of pinion gears14and14, and a pair of side gears15and15. The differential driven gear12is disposed on one of ends of the differential case11(close to the left front wheel4L) so that the differential driven gear12and the differential case11can rotate integrally. The pinion gears14and14are supported by the differential case11via a pinion shaft13so that the pinion gears14and14are freely rotatable. The side gears15and15mesh with the pinion gears14and14and are coupled respectively to the front wheels4L and4R via the front-wheel drive shafts3L and3R. This exemplary front-wheel differential device10further includes a drive gear16disposed on the other end of the differential case11(the end located opposite the differential driven gear12) so that the drive gear16and the differential case11can rotate integrally.

Transfer

The transfer20includes, for example, an input shaft21, an output shaft22, a driven gear23, a drive gear24, a drive pinion gear25, and a front-wheel engaging/disengaging mechanism30.

The input shaft21is a hollow shaft disposed concentrically with the front-wheel drive shaft3R. The output shaft22is a hollow shaft disposed concentrically with the input shaft21(front-wheel drive shaft3R).

The input shaft21has an end (close to the left front wheel4L) on which the driven gear23is provided so that the driven gear23and the input shaft21can rotate integrally. The driven gear23meshes with the drive gear16of the front-wheel differential device10. The input shaft21can hence rotate in conjunction with the rotating differential case11of the front-wheel differential device10(in conjunction with the rotating engine1). The output shaft22has an end (close to the left front wheel4L) on which the drive gear24is provided so that the drive gear24and the output shaft22can rotate integrally. The drive gear24meshes with the drive pinion gear25. The drive pinion gear25is coupled to the propeller shaft5via a constant velocity universal joint111.

The front-wheel engaging/disengaging mechanism30is switched between an engaged state where the mechanism30transmits power from the input shaft21(engine1as the power source) to the output shaft22(propeller shaft5) and a disengaged state where the mechanism30does not transmit power from the input shaft21to the output shaft22. The front-wheel engaging/disengaging mechanism30is switched between the engaged state and the disengaged state by means of the movement of the sleeve32. The present invention is applied to the front-wheel engaging/disengaging mechanism30in the present embodiment. The front-wheel engaging/disengaging mechanism30will be described later in detail.

Control Clutch

The control clutch40is, for example, of a pilot clutch type and includes, for example, a housing41, an output shaft42, a main clutch, a pilot clutch (electromagnetic multi-plate clutch), a cam mechanism, an armature, and an electromagnetic coil. The housing41serves as an input shaft coupled to the propeller shaft5. The output shaft42can rotate relative to the housing41. The main clutch is constituted by a multi-plate frictional clutch. As the pilot clutch engages under an electromagnetic force from the electromagnetic coil, the pilot clutch transmits its engaging force to the main clutch via the cam mechanism so that the main clutch can engage (for more specific structures, see, for example, Japanese Patent Application Publications, Tokukai, Nos. 2010-254135, 2011-247306, and 2012-187954).

The housing (input shaft)41of the control clutch40is coupled to the propeller shaft5via a constant velocity universal joint112. The output shaft42has an end (close to the rear wheels8L and8R) on which the drive pinion gear6is formed integrally.

This exemplary control clutch40is configured to control torque capacity, i.e., coupling torque Tc, by controlling an excitation current Ie that is supplied to the electromagnetic coil. The control clutch40is capable of steplessly adjusting the driving force distribution ratio, or the ratio to the total driving force of the driving force distributed to the rear wheels8L and8R, in a range of, for example, 0 to 0.5. The excitation current Ie supplied to the electromagnetic coil in the control clutch40is controlled by an ECU9.

Rear-Wheel Power Transmission Device

Next, will be described the rear-wheel power transmission device50in reference toFIGS. 1 and 2.

The rear-wheel power transmission device50includes, for example, a ring gear51, a ring gear shaft52, a rear-wheel engaging/disengaging mechanism60, and a rear-wheel differential device70.

The ring gear51is disposed on the ring gear shaft52so that the ring gear51and the ring gear shaft52can rotate integrally. The ring gear51meshes with the drive pinion gear6formed integrally on the output shaft42of the control clutch40.

The rear-wheel differential device70is capable of differential operation where torque is differentially distributed to the left and right rear wheels8L and8R. The rear-wheel differential device70includes, for example, a differential case71, a pair of pinion gears73and73, and a pair of side gears74and74. The pinion gears73and73are supported by the differential case71via a pinion shaft72so that the pinion gears73and73are freely rotatable. The side gears74and74mesh with the pinion gears73and73and are coupled respectively to the rear wheels8L and8R via rear-wheel drive shafts7L and7R. On an end of the differential case71(close to the left rear wheel8L), this exemplary rear-wheel differential device70further includes a differential-end hub62for the rear-wheel engaging/disengaging mechanism60(described later in detail) so that the differential-end hub62and the differential case71can rotate integrally.

The rear-wheel engaging/disengaging mechanism60is disposed between the ring gear51and the rear-wheel differential device70. The rear-wheel engaging/disengaging mechanism60is switched between an engaged state where the mechanism60transmits power from the ring gear51(ring gear shaft52) to the rear-wheel differential device70and a disengaged state where the mechanism60does not transmit power from the ring gear51to the rear-wheel differential device70.

Specifically, the rear-wheel engaging/disengaging mechanism60includes, for example, a ring-gear-end hub61, the differential-end hub62, a sleeve63, a synchronizer mechanism64, and an actuator65. The ring-gear-end hub61is disposed on the other end of the ring gear shaft52(close to the right rear wheel8R) so that the ring-gear-end hub61and the ring gear shaft52can rotate integrally. The differential-end hub62is disposed on one of ends of the differential case71of the rear-wheel differential device70(close to the left rear wheel8L) so that the differential-end hub62and the differential case71can rotate integrally. The sleeve63switches these ring-gear-end hub61and differential-end hub62between engagement and disengagement.

The ring-gear-end hub61and the differential-end hub62are cylindrical hubs with central axes thereof lying on the rotating shaft line of the ring gear51(the rotating shaft line of the ring gear shaft52). The ring-gear-end hub61and the differential-end hub62have the same diameter and are located adjacent to each other in the axial direction of the ring gear shaft52. The ring-gear-end hub61and the differential-end hub62have formed on outer circumferential faces thereof spline external teeth that are aligned in the axial direction.

The sleeve63is a cylindrical member with a central axis thereof lying on the rotating shaft line of the ring gear51(the rotating shaft line of the ring gear shaft52). The sleeve63has a larger diameter than the hubs61and62. The sleeve63is capable of sliding in the axial direction of the ring gear shaft52. The sleeve63has a spline groove formed on an inner circumferential face thereof. The spline groove can be fitted to the spline external teeth formed on the outer circumferential faces of the ring-gear-end hub61and the differential-end hub62.

Actuated by the actuator65, the sleeve63slides in the axial direction and moves to a position where the sleeve63splines only to the ring-gear-end hub61(“disengaged position”, shown inFIG. 1) and to a position where the sleeve63splines both to the ring-gear-end hub61and to the differential-end hub62(“engaged position,” shown inFIG. 2). When the sleeve63is in the position where the sleeve63splines only to the ring-gear-end hub61, power is not transmitted from the ring gear51(propeller shaft5) to the rear-wheel differential device70(differential case71) (“disengaged state”). In contrast, when the sleeve63is in the position where the sleeve63splines both to the ring-gear-end hub61and to the differential-end hub62, the differential case71rotates (around the rotating shaft line of the ring gear shaft52) in conjunction with the rotating ring gear51, thereby switching to a state (engaged state) where power can be transmitted from the ring gear51(propeller shaft5) to the rear-wheel differential device70. Power is hence transmitted to the left and right rear wheels8L and8R via the left and right rear-wheel drive shafts7L and7R.

While the sleeve63is moving from the disengaged position (shown inFIG. 1) to the engaged position (approaching the differential-end hub62), the synchronizer mechanism64synchronizes the rotational speed of the sleeve63with the rotational speed of the differential-end hub62. The rotational speed of the sleeve63is in sync with the rotational speed of the differential-end hub62when the sleeve63splines to the differential-end hub62.

These movements of the sleeve63are driven by the actuator65, and the actuator65is in turn controlled by the ECU9. The actuator65may be, for example, an electric actuator with an electric motor as a power source, an electromagnetic actuator with a solenoid as a power source, a hydraulic actuator, or a negative pressure actuator.

Switching Operation in Four-Wheel-Drive Vehicle

The four-wheel-drive vehicle configured as above can switch between two-wheel drive state where power is transmitted from the engine1only to the left and right front wheels4L and4R for traveling motion and four-wheel drive state where power is transmitted from the engine1both to the left and right front wheels4L and4R and to the left and right rear wheels8L and8R for traveling motion.

Specifically, referring toFIG. 1, to switch to two-wheel drive state, the control clutch40is released (non-transmitting state) to disengage both the front-wheel engaging/disengaging mechanism30and the rear-wheel engaging/disengaging mechanism60(to move the sleeve32and the sleeve63to the disengaged positions (shown inFIG. 1). The disengaged state (disengaged position) of the front-wheel engaging/disengaging mechanism30will be described later in detail.

In two-wheel drive state, the power transmission members (those members from the output shaft22of the transfer20to the ring-gear-end hub61(sleeve63) of the ring gear shaft52in the rear-wheel power transmission device50), including the propeller shaft5, are disconnected from the rotation system including, for example, the front wheels4L and4R and the rear wheels8L and8R. That takes the inertia of the disconnected power transmission members including the propeller shaft5off the load on the engine1, which allow for improvement in fuel economy (fuel consumption ratio).

The vehicle in two-wheel drive state is switched to four-wheel drive state, for example, if four-wheel-drive conditions are satisfied (e.g., if the rotational speed difference between the front and rear wheels is greater than or equal to a predetermined judgmental threshold) or if the driver manually operates a 2WD/4DW toggle switch (not shown). Specifically, the vehicle is switched from two-wheel drive state to four-wheel drive state by engaging both the front-wheel engaging/disengaging mechanism30and the rear-wheel engaging/disengaging mechanism60(moving the sleeve32and the sleeve63to the engaged positions (shown inFIG. 2)) and also supplying excitation current to the electromagnetic coil of the control clutch40so as to switch the control clutch40into the power transmitting state. The engaged state (engaged position) of the front-wheel engaging/disengaging mechanism30will be described later in detail.

In four-wheel drive state, the power transmitted (from the engine1) to the output shaft of the transmission2is partly transmitted to the left and right rear-wheel drive shafts7L and7R (left and right rear wheels8L and8R) via the transfer20, the propeller shaft5, the control clutch40, the ring gear51, the ring gear shaft52, the rear-wheel engaging/disengaging mechanism60, and the rear-wheel differential device70.

In four-wheel drive state, the transmission torque on the control clutch40(the power distribution ratio to the rear wheels8L and8R) is adjusted to maintain suitable vehicle travel stability by controlling, for example, the excitation current supply to the electromagnetic coil of the control clutch40in accordance with the rotational speed difference (slippage ratio) between the front and rear wheels.

The vehicle is switched from four-wheel drive state to two-wheel drive state (e.g., when the four-wheel-drive conditions are no longer satisfied or when the driver manually operates the 2WD/4DW toggle switch) by releasing the control clutch40(switching the control clutch40into the non-transmitting state) to disengage both the front-wheel engaging/disengaging mechanism30and the rear-wheel engaging/disengaging mechanism60(to move the sleeve32and the sleeve63to the disengaged positions (shown inFIG. 1)).

The switching between two-wheel drive state and four-wheel drive state, for example, by means of the control clutch40, the front-wheel engaging/disengaging mechanism30, and the rear-wheel engaging/disengaging mechanism60is controlled by the ECU9.

The front-wheel engaging/disengaging mechanism30is an exemplary embodiment of the present invention and will now be described in reference toFIGS. 1 to 10. Throughout the following description, the front-wheel engaging/disengaging mechanism30will be called simply the “engaging/disengaging mechanism30”.

The engaging/disengaging mechanism30is an electromagnetic dog clutch and includes, for example, a clutch hub31, an engaging plate33, the sleeve32, a disc spring (elastic member)34, and an electromagnetic coil35. The sleeve32switches these clutch hub31and engaging plate33between engagement and disengagement. The clutch hub31is disposed at the other end of the input shaft21of the transfer20(close to the right front wheel4R) so that the clutch hub31and the input shaft21can rotate integrally. The engaging plate33is disposed at the other end of the output shaft22of the transfer20(close to the right front wheel4R) so that the engaging plate33and the output shaft22can rotate integrally.

The clutch hub31is a hub with a central axis thereof lying on the rotating shaft line of the input shaft21. The clutch hub31has formed on an outer circumferential face thereof spline external teeth31athat are aligned in the axial direction of the input shaft21and the output shaft22. The clutch hub31and the engaging plate33are separated by a predetermined distance in the axial direction.

The sleeve32is a member that is integrally constituted by a spline engaging section321, an armature322, and eight dog teeth323.

The spline engaging section321is a cylindrical member (having a larger diameter than the clutch hub31) with a central axis thereof lying on the rotating shaft line of the input shaft21and the output shaft22. The spline engaging section321has formed on an inner circumferential face thereof spline internal teeth321athat are aligned in the axial direction. The spline internal teeth321aon the spline engaging section321spline to the spline external teeth31aformed on the outer circumferential face of the clutch hub31. This spline connection enables the sleeve32to rotate integrally with the clutch hub31. The spline connection also enables the sleeve32to slide relative to the clutch hub31in the axial direction of the input shaft21and the output shaft22. Accordingly, the sleeve32can move in direction Xa (approaching the engaging plate33) and in direction Xb (away from the engaging plate33). Even when the sleeve32is moved in direction Xa reaching a motion-ending point described later in detail (the position represented in FIGS.6(B) and7(C)), the spline connection is maintained. Direction Xa corresponds to the “first direction” in the present invention, and direction Xb corresponds to the “second direction” in the present invention.

The armature322is a member shaped like a circular ring. The armature322is dispose on an end of the spline engaging section321(close to the left front wheel4L (engaging plate33)). The dog teeth323are members with a uniform cross-section that project from the armature322in direction Xa (approaching the engaging plate33) parallel to the axial direction of the input shaft21and the output shaft22. The eight dog teeth323are disposed on a circle around the rotating shaft line of the sleeve32(the rotating shaft line of the input shaft21) so that they are rotationally symmetric. The eight dog teeth323have the same cross-sectional shape (when they are cut up by a plane normal to the axial direction).

The number of dog teeth323is not limited to eight. Any other number of dog teeth323may be provided on the sleeve32. The same applies to engaging holes331(described later in detail) in the engaging plate33.

The engaging plate33is a member shaped like a circular ring with a central axis thereof lying on the rotating shaft line of the input shaft21and the output shaft22. The engaging plate33has a flange332formed integrally on an outer periphery thereof. The flange332projects from the outer periphery of the engaging plate33in direction Xa (approaching the left front wheel4L). The electromagnetic coil35is disposed between the flange332and the output shaft22. The electromagnetic coil35is supported by the engaging plate33. The electromagnetic coil35and the armature322of the sleeve32constitute the “actuation mechanism” of the present invention. The armature322(sleeve32) is magnetically attracted in direction Xa by the electromagnetic force (attractive force) generated by the electricity supplied to the electromagnetic coil35. The amount of electric supply to the electromagnetic coil35will be described later in detail. The supply of electricity to the electromagnetic coil35is controlled by the ECU9.

The engaging plate33has engaging holes (through holes)331at locations that respectively correspond to the dog teeth323on the sleeve32. The engaging holes331have a shape that corresponds to the cross-sectional shape of the dog teeth323. The engaging holes331have a larger size than the dog teeth323by a predetermined amount so that the dog teeth323can engage (fit into) the engaging holes331. The engaging holes331and the dog teeth323constitute a dog clutch section.

The armature322, formed integrally to the sleeve32, is located between the clutch hub31and the engaging plate33so that the armature322faces the engaging plate33. The disc spring34is located between the armature322and the engaging plate33so that the inner circumferential portion of the disc spring34that is on one of two sides of the disc spring34on which its diameter is smaller than on the other side is in contact with the outer circumferential face of the dog teeth323.

Positional Relationship

Next will be described the positional relationship between the sleeve32and the engaging plate33, both constituting the engaging/disengaging mechanism30. The stroke of the sleeve32will also be described.

First, as illustrated inFIGS. 3,6(A), and7(A), when the sleeve32is at the motion-ending point in direction Xb (when the armature322is positioned farthest from the engaging plate33), a side face322aof the armature322(that faces the engaging plate33) is separated from a side face33aof the engaging plate33(that faces the armature322) by a distance that is equal to Engaging Stroke x1+Height h1of Disc Spring34. When the sleeve32is located in this position (the motion-ending point in direction Xb), there exists a gap “a” between tip end faces323aof the dog teeth323on the sleeve32and the side face33aof the engaging plate33, so that the dog teeth323on the sleeve32do not engage the engaging holes331in the engaging plate33, that is, the engaging/disengaging mechanism30is in the disengaged state.

When the sleeve32, starting from the position represented inFIGS. 3,6(A), and7(A) (disengaged position), is moved in direction Xa by as much as engaging stroke x1by the attractive force Fm1(detailed later) generated by the electromagnetic coil35, the dog teeth323on the sleeve32engage (fit into) the engaging holes331in the engaging plate33, which switches the engaging/disengaging mechanism30into the engaged state (as shown inFIG. 7(B)). In the engaged state, the dog teeth323are inserted into the engaging holes331by the amount of “b”, and Engaging Stroke x1=a+b.

The motion-ending point in direction Xa for the sleeve32is the position, represented inFIGS. 6(B) and 7(C), that the sleeve32reaches when it is moved by stroke x2(disengaging stroke x2) in direction Xa from the position represented inFIGS. 6(A) and 7(A). As the sleeve32reaches this position (motion-ending point in direction Xa) (the movement is driven by the attractive force Fm2generated by the electromagnetic coil35, which will be detailed later), the disc spring34warps (elastic deformation). The disc spring34stores elastic force that switches the engaging/disengaging mechanism30into the disengaged state, i.e., elastic force capable of moving the sleeve32(engaging member) in direction Xb (second direction) to switch the engaging/disengaging mechanism30into the disengaged state. Note that Disengaging Stroke x2=x1+c (warpage of the disc spring34)=a+b+C.

The warpage (compression) “c” of the disc spring34is determined, for example, through experiments and simulations by considering the modulus of elasticity of the disc spring34and other factors. The warpage of the disc spring34generates elastic force (spring load Fs2) that switches the engaging/disengaging mechanism30into the disengaged state.

Switching of Engaging/Disengaging Mechanism

Next will be described the switching of the engaging/disengaging mechanism30in reference to, especially,FIGS. 3,6, and7.

First, when the engaging/disengaging mechanism30is in the disengaged state, no electric current flows in the electromagnetic coil35(the coil35is not magnetically excited); the sleeve32is in the position represented inFIGS. 6(A) and 7(A), i.e., in the motion-ending point in direction Xb; and the dog teeth323on the sleeve32do not engage the engaging holes331in the engaging plate33.

Next, to switch the engaging/disengaging mechanism30into the engaged state, electricity, or electric current (=I1), is supplied to the electromagnetic coil35(seeFIG. 10).

This electric current I1has such a value as to excite the electromagnetic coil35to generate attractive (electromagnetic) force Fm1(>Fμ1) that is sufficiently intense to magnetically attract the armature322(seeFIG. 8), but less intense than the force that warps the disc spring34when the disc spring34is interposed between the side face322aof the armature322and the side face33aof the engaging plate33as a result of the sleeve32being moved by magnetic attraction in direction Xa (approaching the engaging plate33) (elastic force less intense than the force that switches the engaging/disengaging mechanism into the disengaged state). Fμ1is resistance from the spline engaging section and other parts of the sleeve32(seeFIG. 7(B)).

As this particular electric current I1is supplied to the electromagnetic coil35(as the electric current I1flows in the electromagnetic coil35), the sleeve32in the disengaged position moves in direction Xa (approaching the engaging plate33), and during the course of the movement, the dog teeth323on the sleeve32fit into the engaging holes331in the engaging plate33. When the sleeve32is moved by engaging stroke x1in direction Xa, the front end (where the disc spring34has a smaller diameter) and the rear end (where the disc spring34has a larger diameter) of the non-deformed disc spring34strike the side face33aof the engaging plate33and the side face322aof the armature322respectively. That regulates the position of the sleeve32in the axial direction. The engaging/disengaging mechanism30is now in the engaged state (seeFIG. 7(B). In this engaged state (when the sleeve32is moved by engaging stroke x1in direction Xa), the disc spring34is not warped, and its spring load is 0 (seeFIG. 9). The duration of electric supply to the electromagnetic coil35in the switching to the engaged state is appropriately set to a value that, determined, for example, through experiments and simulations in advance, allows the dog teeth323to completely fit into the engaging holes331.

The sleeve32and the engaging plate33may have different rotational speeds when the engaging/disengaging mechanism30is to be switched into the engaged state. The dog teeth323on the sleeve32are pressed against the side face33aof the engaging plate33by the attractive force from the electromagnetic coil35. The dog teeth323slide on the side face33adue to the rotational speed difference between the sleeve32and the engaging plate33until the dog teeth323fit into the engaging holes331, when the difference is eliminated and the engaging/disengaging mechanism30is switched into the engaged state.

After completing the switching to the engaged state, the electric supply to the electromagnetic coil35is stopped (zero electric current in the electromagnetic coil35). Likewise, no electricity is supplied to the electromagnetic coil35while the engaging/disengaging mechanism30is in the engaged state (seeFIG. 10). The engaged state of the engaging/disengaging mechanism30shown inFIG. 7(B)can be maintained with no electricity being supply to the electromagnetic coil35because the disc spring34is not warped and the spring load (repulsive force from the disc spring34) is substantially 0.

Next will be described the switching of the engaging/disengaging mechanism30from the engaged state shown inFIG. 7(B)into the disengaged state.

To switch the engaging/disengaging mechanism30into the disengaged state, electricity, or electric current (=I2), is supplied to the electromagnetic coil35(seeFIG. 10).

This electric current I2has such a value as to excite the electromagnetic coil35to generate attractive (electromagnetic) force Fm2(=Fs2) that is sufficiently intense to magnetically attract the armature322(seeFIG. 8), or in other words, sufficiently intense to move the sleeve32against the elastic force (repulsive force) of the disc spring34in direction Xa from the position shown inFIGS. 6(A) and 7(A)to the position where disengaging stroke x2(x2=x1+c) is reached (i.e., where the warpage “c” of the disc spring34is reached).

When the warpage of the disc spring34equals to “c”, the spring load Fs2on the disc spring34(i.e., the elastic force of the disc spring34) is larger than the resistance Fμ2from the spline engaging section and other parts of the sleeve32(seeFIG. 7(C)) (Fs2>Fμ2). In other words, the spring load Fs2is an elastic force capable of moving the sleeve32(engaging member) in direction Xb (second direction) from the position shown inFIG. 7(C)to switch the engaging/disengaging mechanism30into the disengaged state. The resistance Fμ2includes, for example, the engagement resistance between the dog teeth323and the engaging holes331.

As illustrated inFIG. 9, the spring load on the disc spring34starts to occur when the stroke of the sleeve32exceeds x1and reaches Fs2when the stroke of the sleeve32reaches x2.

After that, as the particular electric current I2is supplied to the electromagnetic coil35(as the electric current I2flows in the electromagnetic coil35), the sleeve32moves to the position of disengaging stroke x2, and as illustrated inFIG. 7(C), the warped disc spring34(warpage=c) is interposed between the armature322(side face322a) of the sleeve32and the engaging plate33(side face33a). When the electric supply to the electromagnetic coil35is stopped in this state (zero electric current in the electromagnetic coil35), the entire sleeve32moves in direction Xb due to the elastic force (repulsive force=Fs2) of the disc spring34(the sleeve32is thrown off in direction Xb by the repulsive force of the disc spring34). During the course of the movement of the sleeve32in direction Xb, the dog teeth323on the sleeve32come out of the engaging holes331in the engaging plate33, after which the sleeve32returns to the position shown inFIGS. 6(A) and 7(A)(disengaged position, or motion-ending point in direction Xa), thereby switching the engaging/disengaging mechanism30into the disengaged state.

The switching of the engaging/disengaging mechanism30, i.e., the electric supply to the electromagnetic coil35represented inFIG. 10is controlled (2-stage electric current control) by the ECU (control section)9.

Effects

As described so far, according to the present embodiment, the engaging/disengaging mechanism30is switched into the engaged state by moving the sleeve32to the position where the disc spring34does not warp (the position of stroke x1). There is no need to overcome the repulsive force of the disc spring34in switching the engaging/disengaging mechanism30into the engaged state. That allows for reduction in the electric supply to the electromagnetic coil35, which in turn allows for reduction in electric power consumption. Besides, the engaging/disengaging mechanism30can be maintained in the engaged state even if the electric supply to the electromagnetic coil35is stopped. That allows for reduction in electric power consumption and heat generation by the electromagnetic coil35.

The engaging/disengaging mechanism30is switched into the disengaged state by moving the sleeve32to the position where sufficient elastic force is generated that enables disengagement of the engaging/disengaging mechanism30(to the position where the warpage of the disc spring34reaches “c”) and thereafter stopping the electric supply to the electromagnetic coil35so that the sleeve32can be moved in direction Xb (disengaging direction) by the repulsive force of the disc spring34. That also allows for reduction in electric power consumption when the engaging/disengaging mechanism30is disengaged.

The engaging/disengaging mechanism30of the present embodiment, including the electromagnetic coil35, allows for more reduction in size than the engaging/disengaging mechanism including the actuator65and other relevant members shown inFIG. 1. This is a large advantage to FF vehicles with a transverse engine. The size reduction of the engaging/disengaging mechanism is a large advantage to the transverse-engine FF vehicle that has little space for the installation of components near the front wheels.

Variation Examples of Control of Electric Supply

In the embodiment above, the electric supply to the electromagnetic coil35is stopped (zero electric current in the electromagnetic coil35) after switching the engaging/disengaging mechanism30into the engaged state.

The present invention is by no means limited to this arrangement. Alternatively, as an example, as illustrated inFIG. 11, after switching the engaging/disengaging mechanism30into the engaged state, the electric supply to the electromagnetic coil35may be equal to I3(I3<I1<I2) so that the electric current I3can be supplied to the electromagnetic coil35while the engaging/disengaging mechanism30is maintained in the engaged state.

This electric current I3has such a value as to reliably maintain the engaging/disengaging mechanism30in the engaged state and is appropriately set to such an electric power (electric current) value, determined, for example, through experiments and simulations, as to prevent the dog teeth323from coming out of the fitting in the engaging holes331even if the engaging/disengaging mechanism30is subject to vehicle vibration or other forms of disturbance.

While the electric current I3is being supplied to the electromagnetic coil35to maintain the engaged state in this manner, the sleeve32is being pulled toward the engaging plate33. Therefore, even if the engaging/disengaging mechanism30is subject to vibration and another disturbances, the dog teeth323do not come out of the engaging holes331. That maintains the engaged state of the engaging/disengaging mechanism30more reliably.

The electric current (electric supply)13has such a value as to reliably maintain the engaged state and is preferably as small (low) as possible.

In the embodiments above, the engaging/disengaging mechanism30is disengaged by moving the sleeve32to the position where the elastic force of the disc spring34is sufficient (equal to the spring load Fs2) to switch the engaging/disengaging mechanism30into the disengaged state (the position of stroke x2). After that, the electric supply to the electromagnetic coil35is stopped (zero electric current in the electromagnetic coil35). The present invention is by no means limited to this arrangement. Alternatively, as an example, as illustrated inFIG. 11, the electric supply to the electromagnetic coil35may be gradually decreased in disengaging the engaging/disengaging mechanism30. This arrangement restrains the sleeve32from moving too rapidly in direction Xb (disengaging direction), which will be described next in detail.

If the electric supply to the electromagnetic coil35is stopped (zero magnetically attractive force) after moving the sleeve32to the position of stroke x2to disengage the engaging/disengaging mechanism30, the repulsive force (spring load Fs2) stored in the disc spring34is applied suddenly to the sleeve32. The repulsive force could too rapidly throw the sleeve32off in direction Xb. In this situation, the sleeve32could collide with the clutch hub31, generating abnormal sound. In contrast, if the electric supply to the electromagnetic coil35is gradually decreased in disengaging the engaging/disengaging mechanism30, the repulsive force stored in the disc spring34is gradually applied to the sleeve32: This arrangement restrains the sleeve32from moving too rapidly in direction Xb (disengaging direction), reducing the generation of the abnormal sound.

Other Embodiments

The embodiments disclosed here are for illustrative purposes only in every respect and do not constitute support for restrictive interpretations. The scope of the present invention is defined only by the claims and never bound by the embodiments only. Those modifications and variations that may lead to equivalents of claimed elements are all included within the scope of the invention.

For example, in the embodiments-above, the disc spring34is located closer to the outer periphery than are the dog teeth323on the sleeve32. The present invention is by no means limited to this arrangement. Alternatively, as an example, as illustrated inFIG. 12, a disc spring34A may be provided closer to the center than dog teeth323A formed integrally to an armature322A of a sleeve32A.

Referring toFIG. 12, the electric current I1may be also supplied to the electromagnetic coil35when an engaging/disengaging mechanism30A arranged as shown inFIG. 12is in the disengaged state shown inFIG. 12(A), so as to move the sleeve32A in direction Xa and during the course of the movement, fit the dog teeth323A on the sleeve32A into the engaging holes331in the engaging plate33, which in turn switches the engaging/disengaging mechanism30A into the engaged state (FIG. 12(B)).

The embodiments above have described the exemplary applications of the present invention to the engaging/disengaging mechanism that includes a dog clutch section constituted by dog teeth and engaging holes. The present invention is by no means limited to this arrangements. An exemplary engaging/disengaging mechanism arranged in a different manner will be described in reference toFIG. 13.

In the example shown inFIG. 13, a cylindrical boss section323B is formed integrally to an armature322B of a sleeve32B, and spline internal teeth323C are formed on an inner circumferential face of the boss section323B. Spline external teeth331B are formed on an outer circumferential face of an engaging plate33B that is shaped like a circular disc. The spline external teeth331B mesh with the spline internal teeth323C on the inner circumferential face of the boss section323B.

In this example shown inFIG. 13, the electric current I1is supplied to the electromagnetic coil35when an engaging/disengaging mechanism30B is in the state shown inFIG. 13(A), so as to move the sleeve32B in direction Xa and during the course of the movement, spline-connect the spline internal teeth323C on the sleeve32B to the spline external teeth331B on the engaging plate33B, which switches the engaging/disengaging mechanism30B into the engaged state (FIG. 13(B)). A disc spring34B in this example shown inFIG. 13is provided between the armature322B and the engaging plate33B, closer to the outer periphery than is the boss section323B.

The clutch section provided in the engaging/disengaging mechanism may have a different structure from those described above. For example, the clutch section may be structured so that the dog teeth provided close to the input shaft can mesh with the dog teeth provided close to the output shaft or structured to include a frictional clutch plate. Alternatively, the clutch section may be structured to include a clutch section in which the armature by itself constitutes an input- or output-end engaging member.

In the embodiments above, the elastic member storing elastic force that moves the engaging member (sleeve) in the second direction (disengaging direction) to switch the engaging/disengaging mechanism into the disengaged state is a disc spring. The present invention is by no means limited to this arrangement. Alternatively, as examples, a coil spring or any other elastic member may be used.

In the embodiments above, the actuation mechanism that moves the engaging member (sleeve) is an actuation mechanism constituted by an electromagnetic coil and an armature. The present invention is by no means limited to this arrangement. Alternatively, as examples, a hydraulic actuation mechanism or a negative pressure (pneumatic) actuation mechanism may be used.

The embodiments above have described the exemplary applications of the present invention to the front-wheel engaging/disengaging mechanism. The present invention is by no means limited to this arrangement. Alternatively, the present invention may be applied to a rear-wheel engaging/disengaging mechanism. The present invention may be applied to both a front-wheel engaging/disengaging mechanism and a rear-wheel engaging/disengaging mechanism. The present invention may also be applied to an engaging/disengaging mechanism provided for a different power transmission system of the vehicle.

The embodiments above have described the applications of the present invention to the engaging/disengaging mechanism provided in four-wheel-drive FF vehicles. The present invention is by no means limited to this arrangement. Alternatively, the present invention is also applicable to an engaging/disengaging mechanism provided in four-wheel-drive FR (front engine, rear wheel drive) vehicles. The present invention is also applicable to an engaging/disengaging mechanism provided in two-wheel-drive FF and FR vehicles.

The embodiments above have described the applications of the present invention to a display device provided in vehicles that include gasoline engines, diesel engines, or other like engines as power sources. The present invention is by no means limited to this arrangement. Alternatively, the present invention is applicable to an engaging/disengaging mechanism provided in hybrid vehicles that include an engine and an electric motor (e.g., a motor generator) as power sources.

The present invention is by no means limited to applications to an engaging/disengaging mechanism that is provided in vehicles. Alternatively, the present invention is applicable to an engaging/disengaging mechanism used in power transmission systems of other various types of apparatus and devices.

INDUSTRIAL APPLICABILITY

The present invention may be effectively applied to an engaging/disengaging mechanism in vehicles and other power transmission systems that switches between an engaged state where power is transmitted and a disengaged state where power is not transmitted.

REFERENCE SIGNS LIST