JP2001191812A - Rotation transmitting device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a compact rotation transmitting device without requiring separate measures against slurry and dust. SOLUTION: A shaft end member 8 of a propeller shaft 4 as a first shaft is fitted on a shaft end of an input shaft 6 of a differential 5 as a second shaft, which is arranged on the same shaft, inside of a casing 7 for supporting the shaft end member 8 and the input shaft 6 with bearings 11, 12. An outer gear 14 is fitted to the inner diameter surface of the shaft end member 8 fitted on the input shaft, and a slide gear 18 as an engaging member energized by a coil spring 19 to a direction for removing from the outer gear 14 is inserted into the shaft end of the input shaft 6 freely to be slid, and an electromagnet is fitted in the casing 7. The magnetic attracting force of the electromagnet in a core part and the magnetic attracting force of the electromagnet in the gear part are used in common so as to operate the slide gear 18 with the compact design, and transmission of the rotation from the first shaft to the second shaft can be thereby turned on/off.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rotation transmission device for turning on and off the transmission of rotation, and more particularly to a rotation transmission device suitable for switching driving wheels of a part-time four-wheel drive vehicle.

[0002]

2. Description of the Related Art For the purpose of reducing fuel consumption during two-wheel drive, a part-time four-wheel drive vehicle is provided with a rotating hub mounted on a non-drive-side wheel or an inlet or outlet of a non-drive-side differential during two-wheel drive. There is a device provided with a rotation transmission device for turning transmission on and off. In the rotation transmission device provided on the input side or the output side of the differential, the engagement member is moved in the axial direction of the two rotation shafts arranged coaxially, and the gear engagement between the engagement member and the two rotation shafts is performed. Are engaged and disengaged to turn on and off the transmission of rotation.

As means for operating the engaging member in the axial direction, a motor in which the rotation of a motor is converted into a linear motion by a rack and pinion mechanism as in a driving force switching mechanism disclosed in Japanese Patent Application Laid-Open No. 10-297313. And Tokuhei 1-233
There is one using a push-pull cable, such as the split-type axle drive mechanism disclosed in Japanese Patent Publication No. 30. The actuation means of these engagement members are often arranged outside the rotation transmitting device, and are configured to move the engagement members in the axial direction via a shift fork or the like.

For this reason, the rotation transmission device is bulky,
In the case of equipping the vehicle as described above, it is necessary to take care that the operating means of the engaging member does not come into contact with the surrounding movable parts. In addition, it is necessary to take measures against muddy water and dust from this operating means. In some cases, the actuating means of the engagement member is incorporated in the casing of the rotation transmission device, but in this case, the outer diameter of the rotation transmission device becomes large, and there is a problem that the mounting place is limited. .

[0005]

SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a rotation transmission device which can be designed to be compact and does not require any additional measures against muddy water and dust.

[0006]

In order to solve the above-mentioned problems, according to the present invention, a first shaft for transmitting rotation from a rotation source and a second shaft for transmitting rotation of the first shaft are coaxial. The transmission of rotation from the first shaft to the second shaft is performed by meshing a gear having a tooth height in a radial direction, and an engaging member for engaging and disengaging the meshing of the gear is provided. The transmission of rotation from the first shaft to the second shaft is turned on and off by moving the mating member in the axial direction of the two shafts arranged coaxially to engage and disengage the meshing of the gears. And a second bearing rotatably supporting the first shaft and a second bearing rotatably supporting the second shaft, and the engaging member is connected to the first bearing. 1
A configuration is provided in which the engaging member is disposed between the bearing and the second bearing, and the engaging member is moved in the axial direction by a magnetic attraction force of an electromagnet disposed in the casing.

That is, a first bearing for supporting the first shaft,
A second bearing for supporting the second shaft is attached to an integral casing, and an engagement member for engaging and disengaging a gear for transmitting rotation from the first shaft to the second shaft is provided between the first bearing and the first bearing. 2 between the two bearings, the engaging member is moved in the axial direction by the magnetic attraction force of the electromagnet disposed in the casing,
By directly operating the engagement member with an electromagnet without using a shift fork or the like, the rotation transmission device can be designed to be compact, and no separate measures against muddy water and dust are required.

An end of one of the first shaft and the second shaft is externally fitted to an end of the other shaft, an outer gear is provided on an inner diameter side of an end of the shaft on the outer fitting side, and an inner gear is provided. A slide gear as the engaging member is slidably fitted in the axial direction on the outer diameter side of the end of the shaft, meshing of the gear is performed by meshing of the outer gear and the slide gear, and the casing is inserted into the casing. An electromagnet is attached to the shaft on the inner fitting side so that a part of the core of the electromagnet and the end face of the slide gear face each other inside the electromagnetic coil of the electromagnet. A guide member, which is internally fitted to the casing and has a cylindrical guide portion extending in the axial direction, is mounted in contact with the core of the electromagnet, and is slidably inserted into the cylindrical guide portion and slid. The guide member and the shaft end on the outer fitting side An elastic member for urging the slide gear in a direction to separate the slide gear from the outer gear to the side opposite to the electromagnet; an end of the shaft on the outer fitting side, an outer gear, a slide gear, a guide member, and a slider Are formed of a magnetic material, respectively, a part of the core facing the inside of the electromagnetic coil and a magnetic attraction force between both end surfaces of the slide gear, and the shaft end of the core, the guide member, the slider and the outer fitting side. The slide gear urged by the elastic member is moved to a position at which the slide gear meshes with the outer gear by magnetic attraction between the outer gear and the slide gear magnetized through the outer gear (claim 2). A magnetic attraction force that moves the slide gear as a member is also generated outside the electromagnetic coil, and the slide gear can be moved with a small power and compact electromagnet. Can.

[0009] A gear stopper made of a magnetic material, which is in contact with an end face of the slide gear moved to a position where it engages with the outer gear, is attached to an end face of the outer gear facing the slider, and the electromagnetic stopper is provided. The magnetic attraction between the outer gear and the slide gear outside the coil can be further increased.

[0010] The circumferential gap between the outer gear and the slide gear, which mesh with each other and have a tooth height in the radial direction, is set to 1 mm.
(Claim 4), the deviation of the gap between the tooth profile side surface of the outer gear and both sides of the tooth profile of the slide gear is regulated to be small, so that a large imbalance of magnetic attraction force does not occur in both the gaps. One of the tooth side surfaces of the slide gear is attracted to the tooth side surface of the outer gear, thereby preventing the slide resistance of the slide gear from increasing.

Further, the shaft ends of the first shaft and the second shaft are arranged to face each other, and the outer diameter surface of each of the opposed shaft ends is provided on the outer diameter surface.
Serrations or splines having the same tooth profile are provided, and serrations or splines that engage with these serrations or splines are formed on the inner diameter surface, and a slide gear as the engagement member having a flange formed on the outer diameter surface is provided. , Slidably fitted over the shaft ends, the gears are engaged by serrations or splines of the shaft end outer diameter surface and the slide gear inner diameter surface, and the gear is inserted into the casing. An electromagnet is attached to the shaft end on the side from which the slide gear separates, and a part of the core of the electromagnet faces the end face of the slide gear inside the electromagnetic coil of the electromagnet. On the side facing the flange of the gear, a fixing member facing the flange is attached in contact with the core of the electromagnet, An elastic member is provided for urging the ride gear in a direction away from the serration or spline of one of the opposed shaft ends, the slide gear and the fixed member are formed of a magnetic material, and are opposed inside the electromagnetic coil. The slide gear urged by the elastic member is disengaged by the magnetic attraction between a part of the core and both end faces of the slide gear and the magnetic attraction between the fixing member and the flange of the slide gear facing each other. (Embodiment 5)
Magnetic attraction for moving the slide gear as the engagement member is also generated outside the electromagnetic coil, and the slide gear can be moved by a small electric power and compact electromagnet.

A gear stopper is provided which is in contact with the end surface of the slide gear urged by the elastic member and which positions the end point of the slide gear separation, and this gear stopper is made of a non-magnetic material. The magnetic loss of the magnetized slide gear can be reduced, and the magnetic attraction force inside and outside the electromagnetic coil can be increased.

[0013] By providing inclined surfaces parallel to each other on a part of the core facing the inside of the electromagnetic coil and on both end surfaces of the slide gear (claim 7), a part of the core inside the electromagnetic coil slides. The magnetic attraction between both end surfaces of the gear can be further increased.

The first shaft is a propeller shaft for transmitting a driving force from a drive source of a part-time four-wheel drive vehicle, and the second shaft is a differential input shaft for transmitting the rotation of the propeller shaft to a differential. (Claim 8) Alternatively, the first shaft is a differential output shaft of a part-time four-wheel drive vehicle, and the second shaft is the second shaft.
By providing a shaft as a drive shaft for transmitting rotation of the output shaft of the differential to wheels (claim 9), a compact rotation transmission device for switching drive wheels of a part-time four-wheel drive vehicle is provided. Can be.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. 1 to 3 show a first embodiment. As shown in FIG. 1, the rotation transmission device 1 includes a propeller shaft 4 and a differential 5 on a front wheel 3 side of a part-time four-wheel drive vehicle in which a rear wheel 2 is constantly driven.
As shown in FIG. 2, a shaft end member 8 of a propeller shaft 4 as a first shaft and an input shaft 6 of a differential 5 as a second shaft are coaxially arranged as shown in FIG.
The shaft end member 8 is externally fitted to the shaft end of the input shaft 6 in the casing 7. The casing 7 includes a lid member 7a on the propeller shaft 4 side and a main body member 7b on the differential 5 side.
The cover member 7a is sealed with a seal member 9, and the main body member 7b is connected to a differential case (not shown).

The shaft end member 8 is connected to the propeller shaft 4 by a yoke 10 and is rotatably supported by the casing 7 by a bearing 11. The input shaft 6 of the differential 5 is rotatably supported on the casing 7 by a bearing 12, and its shaft end is formed by a shaft end member 8 fitted externally by a bearing 13.
Is rotatably supported on the inner diameter surface of the.

An outer gear 14 is spline-fitted to the inner diameter surface of the distal end of the shaft end member 8 which is externally fitted to the shaft end of the input shaft 6 of the differential 5. A sleeve 15 is spline-fitted to the outer diameter surface of the shaft end of the input shaft 6,
A slide gear 18 is slidably fitted into a serration 16 formed on the outer diameter surface. The inner surface of the slide gear 18 is provided with serrations that engage with the serrations 16.
An inner gear 17 that meshes with the inner gear 4 is provided.

The shaft end member 8, sleeve 15 and slide gear 18 are all manufactured by carburizing and quenching structural alloy steel SCM415.
An effective hardened layer of 6 to 1.2 mm was formed, and the surface hardness was Rockwell hardness HRC 58 to 62. The outer gear 14 is manufactured by carburizing and quenching low-carbon steel, has an effective hardened layer of 0.3 to 0.7 mm formed on the surface thereof, and has a surface hardness of Rockwell hardness HRC 54 to 6.
It is 2. These are all magnetic materials.

The slide gear 18 is urged by a taper coil spring 19 in a direction in which the inner gear 17 is disengaged rightward from the outer gear 14, and its disengagement end position is set to a gear stopper 20 made of non-magnetic material made of aluminum.
It is positioned by. The gear stopper 20 may be made of a non-magnetic material such as a thermosetting resin.

In the casing 7, an electromagnetic coil 2 is provided.
An electromagnet composed of the core 1 and the core 22 is externally fitted to the shaft end of the input shaft 6 of the differential 5, and one end of the electromagnet is attached to the front end of the shaft end member 8 to which the outer gear 14 is attached. The electromagnet is prevented from rotating by a pin portion 23 provided on the inner wall surface of the casing 7 and is fixed in the axial direction by a guide member 24 described later.

The end of the slide gear 18 on the side opposite to the inner gear 17 faces a part of the core 22 inside the electromagnetic coil 21, and these opposite end faces have inclined surfaces 25 parallel to each other, respectively. 26 are formed.

The guide member 24 is formed of a low carbon steel, which is a magnetic material, and has a cylindrical portion 24b provided at an inner peripheral end of a flange portion 24a for fixing the core 22 of the electromagnet. A slider 27 also made of low carbon steel is slidably fitted. The slider 27 is the guide member 2
An outwardly facing flange portion 27b is provided at one end of a cylindrical portion 27a fitted into the fourth cylindrical portion 24b. Further, a gear stopper 28 made of low carbon steel for positioning the engagement end position of the inner gear 17 is attached to the electromagnet-side end surface of the outer gear 14.

When power is supplied to the electromagnetic coil 21,
A slide gear 18 formed of a magnetic material facing the inside of the electromagnetic coil 21 and a part of the inclined surface 25 of the core 22;
A magnetic attraction force is generated between the shaft members 26, and the flange portion 27b of the slider 27 is magnetically attracted to the end surface of the shaft end member 8 made of a magnetic material.
Conduct between the two. For this reason, the outer gear 14 formed of a magnetic material is magnetized via the core 22, the guide member 24, the slider 27, and the shaft end member 8, and a magnetic attractive force is also generated between the inner gear 17 and the outer gear 14. This magnetic attraction is strengthened by a gear stopper 28 attached to the end face of the outer gear 14.

As shown in FIGS. 3A and 3B, the circumferential gap between the outer gear 14 and the inner gear 17 is formed to be narrower than 1 mm. Therefore, the inner gear 17
The deviation of the gap between the outer gear 14 and the side surface of the outer gear 14 on both side surfaces of the outer gear 14 is regulated to be small.
7 is smoothly engaged with the outer gear 14, and the shaft end member 8
Is transmitted to the input shaft 6 via the slide gear 18.

FIGS. 4 and 5 show a second embodiment. As shown in FIG. 4, the rotation transmitting device 29 includes a front wheel 3 of a part-time four-wheel drive vehicle in which a rear wheel 30 is constantly driven.
The output shaft 34 of the differential 32 as the first shaft and the drive shaft 33 as the second shaft are coaxially provided between the differential 32 on the first side and the drive shaft 33, as shown in FIG. The shaft end of the output shaft 34 in the casing 35 is
3 is fitted around the shaft end.

The casing 35 is formed by integrally connecting a cover member 35a on the differential 32 side and a main body member 35b on the drive shaft 33 side.
5a is connected to a differential case (not shown), and the body member 35b side is sealed with a seal member 36. The configuration inside the casing 35 and the mechanism for engaging and disengaging the slide gear 18 with the outer gear 14 by the magnetic attraction of the electromagnet are exactly the same as those in the first embodiment. Therefore, the reference numerals of each member in the casing 35 in FIG.
The same reference numerals are used as in the first embodiment shown in FIG.

FIGS. 6 and 7 show a third embodiment. As shown in FIG. 6, the rotation transmitting device 37 includes a rear wheel 3 of a part-time four-wheel drive vehicle in which a front wheel 38 is constantly driven.
As shown in FIG. 7, the shaft end member 44 of the propeller shaft 40 as the first shaft and the input shaft of the differential 41 as the second shaft are provided between the propeller shaft 40 on the ninth side and the differential 41. 42 are arranged coaxially, and a shaft end member 44 and an input shaft 42
Are disposed to face each other. The casing 43 is
The lid member 43a on the propeller shaft 40 side and the main body member 43b on the differential 41 side are integrally bolted together. The lid member 43a side is sealed with a seal member 45, and the main body member 43b is a differential case (not shown). It is connected to.

The shaft end member 44 is connected to the propeller shaft 40 by a yoke 46, and
3 rotatably supported. The input shaft 42 is a bearing 48
The casing 43 is rotatably supported by the casing 43.

Serrations 49 and 50 are formed on the end outer diameter surface of the shaft end member 44 and the end outer diameter surface of the input shaft 42, respectively.
A slide gear 52 having serrations formed on the inner diameter surface that engages with 50 is slidably fitted to these outer diameter surfaces at both ends facing each other. A flange 51 is provided on the outer diameter of the end of the slide gear 52.

The input shaft 42, shaft end member 44 and slide gear 52 are all manufactured by carburizing and quenching structural alloy steel SCM415.
An effective hardened layer of 6 to 1.2 mm was formed, and the surface hardness was Rockwell hardness HRC 58 to 62.

The slide gear 52 is urged by a taper coil spring 53 in a direction in which the slide gear 52 is separated from the serration 50 of the input shaft 42 to the right.
The release end point is positioned by a gear stopper 54 made of aluminum, which is a nonmagnetic material.

In the casing 43, an electromagnet composed of an electromagnetic coil 55 and a core 56 is externally fitted to the shaft end of the input shaft 42, and one end of the electromagnet is attached to the flange 51 of the slide gear 52. ing. The electromagnet is prevented from rotating by a pin portion 57 provided on the inner wall surface of the casing 43, and is formed of a low-carbon steel annular pressing plate 5 made of a magnetic material.
8 fixed in the axial direction.

The end of the slide gear 52 on the side opposite to the flange 51 faces a part of the core 56 inside the electromagnetic coil 55, and these opposed end faces have inclined planes 59 parallel to each other. 60 are formed.

When power is supplied to the electromagnetic coil 55,
A magnetic attraction force is generated between the slide gear 52 facing the inside of the electromagnetic coil 55 and a part of the inclined surfaces 59 and 60 of the core 56, and abuts on the core 56 outside the flange 51 of the slide gear 52 and the electromagnetic coil 55. A magnetic attraction force is also generated between the pressing plates 58 in contact with each other, and the slide gear 52 moves to the left, engages with the serration 50 of the input shaft 42, and the rotation of the shaft end member 44 passes through the slide gear 52. Input shaft 4
2 is transmitted.

FIGS. 8 and 9 show a fourth embodiment. As shown in FIG. 8, the rotation transmitting device 61 includes a rear wheel 6 for a part-time four-wheel drive vehicle in which a front wheel 62 is constantly driven.
The output shaft 66 of the differential 64 as the first shaft and the drive shaft 65 as the second shaft are coaxially provided between the differential 64 on the third side and the drive shaft 65 as shown in FIG. The shaft end of the output shaft 66 and the shaft end of the drive shaft 65 are arranged in the casing 67 so as to face each other. Casing 67
Of the slide gear 5 due to the internal structure and the magnetic attraction of the electromagnet.
The mechanism for engaging and disengaging 2 is exactly the same as in the third embodiment. Therefore, the reference numerals of the members in the casing 67 in FIG. 9 are the same as those in the third embodiment shown in FIG.

In each of the embodiments described above, the rotation transmission device for switching the drive wheels of a part-time four-wheel drive vehicle is described. However, the rotation transmission device according to the present invention is required to have a compact design and It can also be adopted for other uses used in places where the external environment is not maintained. In the first and second embodiments, the end on the first shaft side is fitted to the end on the second shaft side, but the end on the second shaft side is the first shaft.
It may be fitted to the end on the shaft side.

[0037]

As described above, the rotation transmitting device of the present invention has a first bearing for supporting a first shaft as an input shaft of the rotation transmitting device and a second bearing for supporting a second shaft as an output shaft of the rotation transmitting device. And an engaging member for engaging and disengaging a gear for transmitting rotation from the first shaft to the second shaft is disposed between the first bearing and the second bearing. The engagement member is moved in the axial direction by the magnetic attractive force of the electromagnet arranged in the casing, and the engaging member is directly operated by the electromagnet without using a shift fork or the like. In addition, separate muddy water and dust prevention measures can be eliminated.

Further, since the magnetic attraction force for moving the engaging member is applied not only inside the magnetic coil of the electromagnet but also outside the magnetic coil, the engaging member can be formed with a small electric power and a compact electromagnet. It can be moved axially.

Further, the first shaft may be a propeller shaft for transmitting a driving force from a drive source, and the second shaft may be a differential input shaft for transmitting the rotation of the propeller shaft to a differential, or the first shaft may be a differential shaft. By providing a differential output shaft and a second shaft as a drive shaft for transmitting rotation of the differential output shaft to wheels, it is possible to provide a compact rotation transmission device for switching drive wheels of a part-time four-wheel drive vehicle. it can.

[Brief description of the drawings]

FIG. 1 is a schematic layout diagram showing a drive system of a part-time four-wheel drive vehicle equipped with a rotation transmission device according to a first embodiment.

FIG. 2 is a longitudinal sectional view showing the rotation transmitting device of FIG. 1;

3A is a sectional view showing a meshing portion of the gear of FIG. 2, and FIG.
Is an enlarged sectional view of a main part of a.

FIG. 4 is a schematic layout diagram showing a drive system of a part-time four-wheel drive vehicle equipped with a rotation transmission device according to a second embodiment.

FIG. 5 is a longitudinal sectional view showing the rotation transmitting device of FIG. 4;

FIG. 6 is a schematic layout diagram showing a drive system of a part-time four-wheel drive vehicle equipped with a rotation transmission device according to a third embodiment.

FIG. 7 is a longitudinal sectional view showing the rotation transmitting device of FIG. 6;

FIG. 8 is a schematic layout diagram showing a drive system of a part-time four-wheel drive vehicle equipped with a rotation transmission device according to a fourth embodiment.

FIG. 9 is a longitudinal sectional view showing the rotation transmitting device of FIG. 8;

[Explanation of symbols]

 Reference Signs List 1 rotation transmission device 2 rear wheel 3 front wheel 4 propeller shaft 5 differential 6 input shaft 7 casing 7a lid member 7b main body member 8 shaft end member 9 sealing member 10 yokes 11, 12, 13 bearing 14 outer gear 15 sleeve 16 serration 17 inner gear 18 slide Gear 19 Coil spring 20 Gear stopper 21 Electromagnetic coil 22 Core 23 Pin section 24 Guide member 24a Flange section 24b Cylindrical section 25, 26 Inclined surface 27 Slider 27a Cylindrical section 27b Flange section 28 Gear stopper 29 Rotation transmission device 30 Rear wheel 31 Front wheel 32 Differential 33 Drive shaft 34 Output shaft 35 Casing 35a Lid member 35b Body member 36 Sealing member 37 Rotation transmitting device 38 Front wheel 39 Rear wheel 40 Propeller shaft 41 Differential No. 42 Input shaft 43 Casing 43a Cover member 43b Main body member 44 Shaft end member 45 Seal member 46 Yoke 47, 48 Bearing 49, 50 Serration 51 Flange 52 Slide gear 53 Coil spring 54 Gear stopper 55 Electromagnetic coil 56 Core 57 Pin portion 58 Holding plate 59, 60 Inclined surface 61 Rotation transmission device 62 Front wheel 63 Rear wheel 64 Differential 65 Drive shaft 66 Output shaft 67 Casing

Claims (9)

[Claims] A first shaft for transmitting rotation from a rotation source;
The second shaft to which the rotation of the first shaft is transmitted is arranged coaxially,
Transmission of the rotation from the first shaft to the second shaft is performed by engagement of a gear having a tooth height in a radial direction, and an engagement member for engaging and disengaging the engagement of the gear is provided, and the engagement member is coaxial. In a rotation transmission device that moves in the axial direction of the two shafts disposed above to engage and disengage the meshing of the gears, thereby turning on and off the transmission of rotation from the first shaft to the second shaft. A first bearing rotatably supporting the first shaft and a second bearing rotatably supporting the second shaft are attached to an integral casing, and the engaging member is connected to the first bearing and the second bearing. A rotation transmission device, which is disposed between bearings, and the engagement member is moved in the axial direction by magnetic attraction of an electromagnet disposed in the casing. 2. An end of one of the first shaft and the second shaft is externally fitted to an end of the other shaft, and an outer gear is provided on an inner diameter side of an end of the externally fitted shaft. A slide gear as the engagement member is slidably fitted in the axial direction on the end outer diameter side of the shaft on the fitting side, and the meshing of the gears is performed by the meshing of the outer gear and the slide gear. An electromagnet is attached by externally fitting to the shaft on the inner fitting side, and a part of the core of the electromagnet and the end face of the slide gear face each other inside the electromagnetic coil of the electromagnet. On the side facing the shaft end, a guide member having a cylindrical guide portion that is internally fitted in the casing and extends in the axial direction is attached to the core of the electromagnet, and is slidably fitted into the cylindrical guide portion. Slide the guide member and the shaft end on the outer fitting side An electrically conductive slider is provided, and an elastic member for urging the slide gear in a direction away from the outer gear to the side opposite to the electromagnet is provided. An end of the outer fitting shaft, an outer gear, a slide gear, a guide member, and a slider Are formed of a magnetic material, respectively, a part of the core facing the inside of the electromagnetic coil and a magnetic attraction force between both end surfaces of the slide gear, and the shaft end of the core, the guide member, the slider and the outer fitting side. 2. The rotation transmission device according to claim 1, wherein the slide gear biased by the elastic member is moved to a position where the slide gear meshes with the outer gear by a magnetic attraction force between the outer gear and the slide gear magnetized through the outer gear. 3. The rotation according to claim 2, wherein a gear stopper made of a magnetic material is attached to an end surface of the outer gear facing the slider, the end stopper being in contact with an end surface of the slide gear moved to a position where the outer gear meshes with the slider. Transmission device. 4. The rotation transmission device according to claim 2, wherein a circumferential gap between the outer gear and the slide gear that mesh with each other is restricted to less than 1 mm. 5. The shaft ends of the first shaft and the second shaft are arranged opposite to each other, and serrations or splines having the same tooth profile are provided on the outer diameter surface of each of the opposed shaft ends. The slide gear as the engagement member, in which the serrations or splines that engage with these serrations or splines are formed on the inner diameter surface and the flange is formed on the outer diameter surface, is inserted across each of the shaft ends to be slidable. The gears are engaged with each other by engaging the serrations or splines between the outer diameter surfaces of the respective shaft end portions and the inner diameter surface of the slide gear, and disengaged from the shaft end portion of the side where the slide gear is disengaged in the casing. The electromagnet is attached by fitting, a part of the electromagnet core and the end face of the slide gear face each other inside the electromagnetic coil of the electromagnet, On the side facing the flange, a fixing member facing the flange is attached in contact with the core of the electromagnet, and the slide gear is urged in a direction to separate from the serration or spline of one of the shaft ends opposed to the flange. The sliding gear and the fixing member are formed of a magnetic material, and the magnetic attractive force between a part of the core facing the inside of the electromagnetic coil and both end surfaces of the sliding gear and the fixing member facing each other are provided. 2. The rotation transmission according to claim 1, wherein the slide gear urged by the elastic member is moved to a position where the slide gear is engaged with the detached shaft end by a magnetic attraction force between the slide gear and a flange of the slide gear. 3. apparatus. 6. A gear stopper provided in contact with an end face of a slide gear urged by said elastic member to position a separation end point of said slide gear, wherein said gear stopper is formed of a non-magnetic material. The rotation transmission device according to any one of the above. 7. The rotation transmitting device according to claim 2, wherein inclined surfaces parallel to each other are provided on a part of the core facing the inside of the electromagnetic coil and both end surfaces of the slide gear. 8. The first shaft is a propeller shaft for transmitting a driving force from a drive source of a part-time four-wheel drive vehicle, and the second shaft is a differential input shaft for transmitting the rotation of the propeller shaft to a differential. The rotation transmission device according to any one of claims 1 to 7, wherein 9. The first shaft is a differential output shaft of a part-time four-wheel drive vehicle, and the second shaft is a drive shaft for transmitting rotation of the differential output shaft to wheels. The rotation transmission device according to any one of the above.