JP2015010692A - Electromagnetic clutch, drive force transmission, and detachment prevention structure - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electromagnetic clutch, a drive force transmission, and a detachment prevention mechanism capable of preventing detachment of a pair of members screwed with each other due to a difference in coefficient of thermal expansion between the members.SOLUTION: A housing 20 of a drive force transmission 1 comprises: a front housing 21 formed out of a cylindrical nonmagnetic material having a predetermined coefficient of thermal expansion, and including a female screw 21c on an inner peripheral surface of an opening end portion 21g; a rear housing 22 that includes a male screw 221a formed on an outer peripheral surface of the rear housing 22 and threaded with the female screw 21c of the front housing 21, that is formed out of a magnetic material having a coefficient of thermal expansion lower than the predetermined coefficient of thermal expansion, and that constitutes a part of a magnetic path of an electromagnetic force generated by an electromagnetic coil 53; and a detachment prevention member 23A that includes a screw portion 230 having a female screw 230a formed thereon and threaded with the male screw 221a of the rear housing 22 and a covering portion 231 covering the opening end portion 21g of the front housing 21 from an outer peripheral surface 21f side and suppressing thermal expansion of the front housing 21 accompanying a temperature increase.

Description

  The present invention relates to an electromagnetic clutch, a driving force transmission device, and a disengagement prevention structure that transmit driving force from an input shaft to an output shaft in, for example, an automobile.

  As a conventional driving force transmission device, for example, there is one that is mounted on a four-wheel drive vehicle and connects a pair of rotating members so as to transmit torque (see, for example, Patent Document 1).

  This type of driving force transmission device transmits torque between an outer case (outer rotating member), an inner shaft (inner rotating member) supported coaxially with the outer case and rotatable relative to the outer case, and the outer case and the inner shaft. A main clutch that can be connected, an electromagnetic clutch mechanism that is parallel to the main clutch along the rotational axis, and a cam mechanism that converts the rotational force from the outer case into a pressing force toward the main clutch by the operation of the electromagnetic clutch mechanism. And is configured.

  The cam mechanism includes a pair of cam members, and one cam member receives rotational force from the electromagnetic clutch mechanism and rotates with respect to the other cam member, and the other cam member presses the main clutch with this rotation. It is configured as follows.

The electromagnetic clutch mechanism includes an electromagnetic coil, an armature that receives the electromagnetic force of the electromagnetic coil,
The outer clutch plate and the inner clutch plate are pressed by the armature. The outer clutch plate is spline-engaged with the outer case, and the inner clutch plate is spline-engaged with one cam member of the cam mechanism.

  The outer case has a bottomed cylindrical shape, has a front housing (first outer rotating member) in which an internal thread is formed on the inner peripheral surface on the opening side, and an external thread that engages with the internal thread of the front housing, An annular rear housing (second outer rotating member) that covers a part of the opening of the housing and a male screw of the rear housing so as to eliminate play between the female screw of the front housing and the male screw of the rear housing. A nut member. The front housing is made of an aluminum alloy that is a nonmagnetic material to prevent leakage of magnetic flux from the outer case, and the rear housing is made of iron that is a magnetic material to form a magnetic path around the magnetic coil. Etc. are formed.

  When the electromagnetic coil is energized, the armature presses the outer clutch plate and the inner clutch plate, whereby the rotational force of the outer case is transmitted to one cam member, and this rotational force is converted into an axial pressing force. Then, the other cam member presses the main clutch. Thereby, an outer case and an inner shaft are connected so that torque transmission is possible.

JP-A-11-153156

  However, in the driving force transmission device described in Patent Document 1, there is a difference in coefficient of thermal expansion between the first outer rotating member made of aluminum alloy or the like and the second outer rotating member made of iron or the like. When the temperature rises due to heat generation of the clutch or the like, the difference between the inner diameter of the female screw of the first outer rotating member and the outer diameter of the male screw of the second outer rotating member, that is, the screw engagement margin decreases, and the first outer rotating member becomes smaller. If the strength of the rotating member is not sufficient, the second outer rotating member may be detached from the first outer rotating member. Therefore, for example, it is necessary to take measures such as suppressing the torque transmission amount according to the temperature of the housing.

  Accordingly, an object of the present invention is to provide an electromagnetic clutch, a driving force transmission device, and a detachment prevention mechanism capable of preventing detachment of a member based on a difference in thermal expansion coefficient between a pair of members screwed together. And

  In order to achieve the above object, the present invention provides an outer rotating member having an inner peripheral spline portion on the inner peripheral surface, and is disposed inside the outer rotating member, and is supported so as to be relatively rotatable coaxially with the outer rotating member. An inner rotating member, an outer clutch plate made of a magnetic material engaged with the inner peripheral spline portion, an inner clutch plate made of a magnetic material facing the outer clutch plate, the outer clutch plate, and the inner clutch plate The outer rotating member is made of a cylindrical nonmagnetic material having a predetermined coefficient of thermal expansion, has the inner peripheral spline portion on the inner peripheral surface, and A first member made of a magnetic material having a first member having a female screw on the inner peripheral surface of the opening end and a male screw threadedly engaged with the female screw of the first member. A second annular member made of a non-magnetic material arranged inside the first annular member, and a third annular member made of a magnetic material arranged inside the second annular member, the predetermined heat A second member having a thermal expansion coefficient smaller than an expansion coefficient, a screw part formed with a female screw to be screwed into the male screw of the second member, and the opening end part of the first member are covered from the outer peripheral side; And a third member having a cover portion that suppresses thermal expansion of the first member due to a temperature rise.

  In order to achieve the above object, the present invention provides the electromagnetic clutch, an outer friction member that engages with the inner peripheral spline portion so as to be axially movable, and an outer peripheral spline formed on the outer peripheral surface of the inner rotating member. A first cam member and a second cam member that engage with each other in an axially movable manner, and the first cam member is moved against the second cam member by torque transmitted by the electromagnetic clutch. And a cam mechanism for outputting a pressing force for frictionally engaging the outer friction member and the inner friction member from the second cam member by relative rotation.

  In order to achieve the above object, the present invention comprises a first member made of a cylindrical nonmagnetic material having a predetermined coefficient of thermal expansion and having an internal thread on the inner peripheral surface of the opening end, and the first member The second member of the second member based on a difference in thermal expansion between the external member and a second member made of a magnetic material having a thermal expansion coefficient smaller than the predetermined thermal expansion coefficient is formed on the outer peripheral surface of the male screw that is screwed into the female screw. A disengagement preventing structure for preventing disengagement from the first member, wherein a threaded portion formed with a female screw to be engaged with the male screw of the second member, and the opening end of the first member from the outer peripheral surface side. Provided is a detachment prevention structure including a detachment prevention member that has a cover part that covers and suppresses thermal expansion of the first member as the temperature rises.

  ADVANTAGE OF THE INVENTION According to this invention, it becomes possible to suppress the loosening of the screw based on the thermal expansion coefficient difference between a pair of members screwed together.

1 is a schematic configuration diagram illustrating a configuration example of a four-wheel drive vehicle equipped with a driving force transmission device according to a first embodiment of the present invention. It is sectional drawing which shows the structural example of the driving force transmission apparatus which concerns on 1st Embodiment. (A) is principal part sectional drawing which shows the detachment prevention structure which concerns on 1st Embodiment, (b) is principal part sectional drawing which shows the middle of screwing of the detachment prevention member, (c) is a front housing. It is a figure which shows the reaction force received from a detachment prevention member. (A) is principal part sectional drawing which shows the detachment prevention structure which concerns on the 2nd Embodiment of this invention, (b) is principal part sectional drawing which shows the middle of the screwing of a detachment prevention member. (A) is principal part sectional drawing which shows the disconnection prevention structure which concerns on the 3rd Embodiment of this invention, (b) is an enlarged view of an internal thread and an external thread, (c) is a front housing after a temperature rise, It is principal part sectional drawing which shows the relationship with a removal prevention member.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In addition, in each figure, about the component which has the substantially same function, the same code | symbol is attached | subjected and the description is abbreviate | omitted.

[First Embodiment]
FIG. 1 is a schematic configuration diagram showing a configuration example of a four-wheel drive vehicle equipped with a driving force transmission device according to a first embodiment of the present invention.

  The four-wheel drive vehicle 1 includes an engine 102 as a drive source, a transaxle 103 having a transmission and a front differential, a pair of front wheels 104, a pair of rear wheels 105, a rear differential carrier 106, and a propeller shaft 107. The driving force transmission device 2 is provided.

  The driving force transmission device 2 is disposed on a driving force transmission path from the front wheel side to the rear wheel side in the four-wheel drive vehicle 1 and is supported by the vehicle body 101 via a rear differential carrier 106. The driving force transmission device 2 connects the propeller shaft (input shaft) 107 and the drive pinion shaft (output shaft) 108 so that torque can be transmitted. In this connected state, the driving force of the engine 102 is transmitted to the pair of rear wheels 105. It is configured to be able to communicate.

  The driving force transmission device 2 receives supply of current from the control device 10 and transmits driving force corresponding to the current from the propeller shaft 107 to the drive pinion shaft 108. The control device 10 supplies, for example, a current to be supplied to the driving force transmission device 2 based on a difference in rotational speed between the pair of front wheels 104 and the pair of rear wheels 105, an acceleration operation amount (accelerator pedal depression amount) by the driver, and the like. Increase / decrease control.

  With the above configuration, the engine 102 drives the pair of front wheels 104 by outputting the driving force to the front axle shaft 109 via the transaxle 103. Further, the engine 102 outputs the driving force to the rear axle shaft 111 via the transaxle 103, the propeller shaft 107, the driving force transmission device 2, the drive pinion shaft 108, and the rear differential 110, whereby a pair of rear wheels is output. 105 is driven.

(Configuration of the driving force transmission device 2)
FIG. 2 is a cross-sectional view illustrating a configuration example of the driving force transmission device 2. In FIG. 2, the upper side of the rotation axis O indicates the operating state (torque transmission state) of the driving force transmission device 2, and the lower side indicates the non-operational state (torque non-transmission state) of the driving force transmission device 2.

  The driving force transmission device 2 includes a housing 20 as an outer rotating member, a cylindrical inner shaft 24 as an inner rotating member supported coaxially with the housing 20 so as to be relatively rotatable, and the housing 20 and the inner shaft 24. A main clutch 3 that is coupled so as to be able to transmit torque, a cam mechanism 4 that generates a pressing force that presses the main clutch 3, and an electromagnetic clutch mechanism 5 that is disposed between the main clutch 3 so as to sandwich the cam mechanism 4. It is configured.

  The housing 20 includes a front housing 21 as a first member having a bottomed cylindrical shape, a rear housing 22 as an annular second member that covers a part of the opening side of the front housing 21, and a detachment prevention as a third member. And a member 23A. Lubricating oil (not shown) is sealed in the internal space of the housing 20.

  The front housing 21 integrally includes a cylindrical portion 21a and a bottom portion 21b. A female screw 21c is formed on the inner peripheral surface of the open end 21g of the cylindrical portion 21a. A propeller shaft 107 (see FIG. 1) is coupled to the bottom portion 21b so as not to be relatively rotatable, for example, via a cross joint. The front housing 21 is made of a nonmagnetic material made of aluminum having a predetermined coefficient of thermal expansion or aluminum alloy.

  An inner peripheral spline portion 210 including a plurality of inner peripheral spline protrusions 211 extending in the rotation axis direction is formed on the inner peripheral surface of the cylindrical portion 21a. The inner peripheral spline portion 210 has a first region 210a in which a first outer clutch plate 31 described later is spline engaged, and a second region 210b in which an armature 50 and a second outer clutch plate 51 described later are spline engaged. ing.

  The rear housing 22 includes a first annular member 221 made of a magnetic material such as mild steel, and a second annular member made of a non-magnetic material such as austenitic stainless steel integrally joined to the inner peripheral side of the first annular member 221 by welding or the like. 222 and a third annular member 223 made of a magnetic material such as mild steel integrally coupled to the inner peripheral side of the second annular member 222 by welding or the like. The first annular member 221, the second annular member 222, and the third annular member 223 have a thermal expansion coefficient smaller than the thermal expansion coefficient of the front housing 21, and the rear housing 22 has a thermal expansion coefficient of the front as a whole. It is smaller than the thermal expansion coefficient of the housing 21.

  The rear housing 22 constitutes a part of a magnetic path of electromagnetic force generated by the electromagnetic coil 53. Between the 1st annular member 221 and the 3rd annular member 223, the cyclic | annular accommodation space 22a which accommodates the electromagnetic coil 53 mentioned later is formed. A male screw 221 a that is screwed into the female screw 21 c of the front housing 21 is formed on the outer peripheral surface of the first annular member 221.

  The inner shaft 24 is supported on the inner peripheral side of the housing 20 by a ball bearing 61 and a needle roller bearing 62. An outer peripheral spline portion 240 including a plurality of outer peripheral spline protrusions 241 extending in the rotation axis direction is formed on the outer peripheral surface of the inner shaft 24. A spline fitting portion 242 is formed on the inner surface of one end portion of the inner shaft 24 so that one end portion of the drive pinion shaft 108 (see FIG. 1) is fitted so as not to be relatively rotatable.

  The main clutch 3 includes a first outer clutch plate 31 as a plurality of outer friction members and a first inner clutch plate 32 as a plurality of inner friction members that are alternately arranged along the rotation axis O of the housing 20. It consists of a multi-plate clutch. On the outer peripheral portion of the first outer clutch plate 31, a plurality of protrusions 311 that are spline-engaged with the inner peripheral spline portion 210 are provided. A plurality of protrusions 321 that are spline-engaged with the outer peripheral spline portion 240 of the inner shaft 24 are provided on the inner peripheral portion of the first inner clutch plate 32.

  The first outer clutch plate 31 is not rotatable relative to the front housing 21 and is movable in the axial direction. The first inner clutch plate 32 is not rotatable relative to the inner shaft 24 and is movable in the axial direction. Further, the first inner clutch plate 32 is formed with a plurality of oil holes 322 for circulating lubricating oil.

  The cam mechanism 4 includes a pilot cam 41 as a first cam member, a main cam 42 as a second cam member that presses the main clutch 3 in the axial direction, and a plurality of cam mechanisms 4 disposed between the pilot cam 41 and the main cam 42. And a spherical cam ball 43.

  The main cam 42 is in contact with the first inner clutch plate 32 at one end of the main clutch 3, and is provided with an annular plate-like pressing portion 421 that presses the main clutch 3, and on the inner peripheral side of the main cam 42 relative to the pressing portion 421. The cam portion 422 is integrally provided.

  Further, the main cam 42 is formed with spline teeth 421 b that are spline-engaged with the outer peripheral spline portion 240 of the inner shaft 24 inside the pressing portion 421. Thus, the main cam 42 is not rotatable relative to the inner shaft 24 and is movable in the axial direction. A disc spring 44 that urges the main cam 42 toward the pilot cam 41 is disposed between the main cam 42 and the step surface 24 a formed on the inner shaft 24.

A spline engaging portion 411 is formed on the outer peripheral portion of the pilot cam 41. Also,
A thrust needle roller bearing 45 is disposed between the pilot cam 41 and the third annular member 223 of the rear housing 22, and movement of the pilot cam 41 toward the rear housing 22 is restricted.

  A plurality of cam grooves 41 a and 422 a whose axial depth varies along the circumferential direction are formed on the opposing surface of the pilot cam 41 and the cam portion 422 of the main cam 42. A spherical cam ball 43 is disposed between the cam groove 41 a of the pilot cam 41 and the cam groove 422 a of the main cam 42. The cam mechanism 4 rotates the pilot cam 41 relative to the main cam 42 to generate an axial pressing force that presses the main cam 42 against the main clutch 3.

  The electromagnetic clutch mechanism 5 includes an armature 50, a plurality of second outer clutch plates 51, a plurality of second inner clutch plates 52, and an electromagnetic coil 53.

  The armature 50 is an annular member made of a magnetic material such as iron, and a plurality of protrusions 501 that are spline-engaged with the inner peripheral spline portion 210 of the front housing 21 are provided on the outer peripheral portion thereof. The armature 50 is not rotatable relative to the front housing 21 and is movable in the axial direction.

  The plurality of second outer clutch plates 51 and the plurality of second inner clutch plates 52 are alternately arranged along the rotation axis O between the armature 50 and the rear housing 22. On the outer peripheral portion of the second outer clutch plate 51, a plurality of protrusions 511 that are spline-engaged with the inner peripheral spline portion 210 of the front housing 21 are provided. A plurality of protrusions 521 that are spline engaged with the spline engaging portion 411 of the pilot cam 41 are provided on the inner peripheral portion of the second inner clutch plate 52.

  The second outer clutch plate 51 is not rotatable relative to the front housing 21 and is movable in the axial direction. The second inner clutch plate 52 is not rotatable relative to the pilot cam 41 and is movable in the axial direction.

  The electromagnetic coil 53 is held by an annular yoke 530 made of a magnetic material and is accommodated in the accommodating space 22 a of the rear housing 22. The yoke 530 is supported by the third annular member 223 of the rear housing 22 by the ball bearing 63, and the outer peripheral surface thereof faces the inner peripheral surface of the first annular member 221. Further, the inner peripheral surface of the yoke 530 faces the outer peripheral surface of the third annular member 223. Excitation current is supplied to the electromagnetic coil 53 from the control device 10 via the electric wire 531.

  FIG. 3 shows a detachment prevention structure for preventing the rear housing 22 from coming off from the front housing 21 based on the difference in thermal expansion coefficient between the front housing 21 and the rear housing 22.

  As shown in FIG. 3 (a), the front housing 21 has an outer inclination formed at a part of the outer peripheral surface 21f of the opening end 21g at an inclination angle θ so that the diameter gradually decreases toward the opening end 21e. It has an outer taper 21d as a surface.

  The detachment prevention member 23A integrally includes a screw portion 230 that is screwed into the rear housing 22 and a cover portion 231 that generates a pressing force. The detachment preventing member 23A is made of, for example, mild steel. An internal thread 230a is formed on the inner surface of the threaded portion 230 to be engaged with the external thread 221a of the rear housing 22, and an abutment surface 230b that abuts the opening end 21e of the front housing 21 is formed on one end surface in the axial direction. Is formed.

  The cover portion 231 has an inner taper 231a as an inner inclined surface inclined in the same direction as the outer taper 21d on the inner peripheral surface, covers the opening end portion 21g of the front housing 21 from the outer peripheral surface 21f side, and accompanies a rise in temperature. The thermal expansion of the front housing 21 is suppressed. The cover portion 231 is elastically deformed when the inner taper 231a abuts on the outer taper 21d and is expanded in diameter, and the opening end portion 21g of the front housing 21 is pressed toward the rear housing 22 by the restoring force. .

  As shown in FIG. 3B, as an example, the disengagement prevention member 23 </ b> A is in a state before being screwed to the male screw 221 a of the rear housing 22, and the outer peripheral surface of the cover portion 231 is a surface parallel to the axial direction. . In the detachment prevention member 23A, the distal end side of the cover portion 231 (the side opposite to the screw portion 230) is formed by the female screw 230a being screwed into the male screw 221a of the rear housing 22 and the inner taper 231a being pressed against the outer taper 21d. It is elastically deformed so as to be spread and generates a pressing force that presses the front housing 21 toward the rear housing 22.

The detachment prevention structure is assembled as follows. As shown in FIG. 3B, first, the female screw 230a of the disengagement prevention member 23A is screwed into the male screw 221a of the rear housing 22. Next, as shown in FIG. 3A, the disengagement preventing member 23 </ b> A is tightened until the abutment surface 230 b of the disengagement preventing member 23 </ b> A contacts the opening end 21 e of the front housing 21. As a result, the cover portion 231 of the detachment preventing member 23A is pushed and spread, and the inner taper 231a of the detachment preventing member 23A comes into surface contact with the outer taper 21d of the front housing 21 as shown in FIG. Receives a pressing force F in the normal direction from the cover portion 231 of the detachment preventing member 23A, and as a component force of the pressing force F, an axial pressing force F ₁ (= Fsin θ) and a radial pressing force F ₂ (= Fcos θ). ) Moreover, the opening end 21e of the front housing 21 receives a pressing force _{F 3} in the axial direction from the threaded portion 230 of the detachment prevention member 23A.

Detachment prevention member 23A is suppressed thermal expansion in the radial direction of the front housing 21 by the pressing force F _2. That is, when the main clutch 3 generates heat and the heat is transmitted to the housing 20, the coefficient of thermal expansion of the front housing 21 is larger than the coefficient of thermal expansion of the rear housing 22, and thus the inner diameter of the female screw 21 c of the front housing 21 and the rear housing 22. Although the difference with the outer diameter of the male screw 221a, that is, the engagement allowance, is reduced, the disengagement prevention member 23A presses the front housing 21 toward the rear housing 22 so that the decrease of the engagement allowance is suppressed, and the rear housing 22 is This prevents the housing 21 from being detached. Further, detachment prevention member 23A, by pressing the female screw 21c of the front housing 21 by the pressing force _{F 1} on the male screw 221a side of the rear housing 22, a gap between the external thread 221a of the internal thread 21c and the rear housing 22 of the front housing 21 Is prevented, and the rear housing 22 is prevented from being detached from the front housing 21.

In order to efficiently increase the pressing forces F ₁ and F ₂ to prevent the rear housing 22 from coming off, the inclination angle θ of the outer taper 21d is θ = 45 °, but the rigidity of the come-off prevention member 23A is also affected. Therefore, tuning is required between 30 ° and 60 °. That is, the inclination angle θ of the outer taper 21d is preferably 30 ° to 60 ° and more preferably 45 ° in order to prevent the rear housing 22 from coming off.

(Operation of driving force transmission device)
In the driving force transmission device 2 configured as described above, when an excitation current is supplied from the control device 10 to the electromagnetic coil 53, the yoke 530, the first annular member 221 and the third annular member 223 of the rear housing 22, Magnetic flux is generated in the magnetic path G passing through the second outer clutch plate 51, the plurality of second inner clutch plates 52, and the armature 50. The armature 50 is attracted toward the rear housing 22 by the electromagnetic force of the magnetic flux and moves in the axial direction, and presses the second outer clutch plate 51 and the second inner clutch plate 52.

  As a result, the second outer clutch plate 51 and the second inner clutch plate 52 frictionally slide, the rotational force of the housing 20 is transmitted to the pilot cam 41 of the cam mechanism 4, and the pilot cam 41 rotates relative to the main cam 42. To do. That is, the electromagnetic clutch mechanism 5 applies a rotational force that causes the pilot cam 41 and the main cam 42 to rotate relative to each other when the electromagnetic coil 53 is energized.

  Due to the relative rotation of the pilot cam 41 and the main cam 42, the cam ball 43 rolls in the cam grooves 41a and 422a, and axial thrust is generated in the direction in which the pilot cam 41 and the main cam 42 are separated from each other. The main cam 42 presses the main clutch 3 by this thrust, and the housing 20 and the inner shaft 24 are connected so as to transmit torque.

  On the other hand, when the excitation current to the electromagnetic coil 25 is interrupted, the main cam 42 is pushed back to the pilot cam 41 side by the biasing force of the disc spring 44, and the cam ball 43 moves to the deepest position of the cam grooves 41a and 422a. As a result, a gap is formed between the first outer clutch plate 31 and the first inner clutch plate 32 of the main clutch 3, and the lubricating oil flows into this gap, and the connection state between the housing 20 and the inner shaft 24 is released. That is, the driving force transmission device 2 is inactivated.

(Effects of the first embodiment)
According to the first embodiment, since the front housing 21 is pressed against the rear housing 22 side by the detachment preventing member 23A to suppress the thermal expansion of the front housing 21 due to the temperature rise, the front housing 21 and the rear housing 22, the difference between the inner diameter of the female screw 21 c of the front housing 21 and the outer diameter of the male screw 221 a of the rear housing 22 based on the difference in coefficient of thermal expansion from the front housing 21, that is, the reduction of the engagement allowance is suppressed. It can be prevented from coming off.

[Second Embodiment]
FIG. 4 is a cross-sectional view of a main part showing a detachment preventing structure according to the second embodiment of the present invention. The detachment prevention mechanism of the first embodiment has the inner taper 231a formed on the detachment prevention member 23A. However, the detachment prevention mechanism of the present embodiment has a curved contact surface 231b on the cover portion 231 of the detachment prevention member 23B. Formed. The following description will focus on differences from the first embodiment.

  The front housing 21 is formed with an outer taper 21d having a smaller area than that of the first embodiment, and the other configuration is the same as that of the first embodiment.

  The detachment preventing member 23B includes a screw portion 230 that is screwed into the rear housing 22 and a cover portion 231 that generates a pressing force. The cover portion 231 has a contact surface 231b that is curved so as to protrude inwardly on the inner peripheral surface. As shown in FIG. 4B, in the state before the disengagement preventing member 23B is screwed to the male screw 221a of the rear housing 22, as an example, the outer peripheral surface of the cover portion 231 is a surface parallel to the axial direction. . The disengagement prevention member 23B has a female screw 230a screwed into a male screw 221a of the rear housing 22 and a contact surface 231b pressed against the outer peripheral surface 21f, whereby the distal end side (the side opposite to the screw portion 230) of the cover portion 231 is pushed. It is elastically deformed so as to be spread and generates a pressing force that presses the front housing 21 toward the rear housing 22.

  The detachment prevention structure is assembled as follows. As shown in FIG. 4B, first, the female screw 230a of the disengagement prevention member 23B is screwed into the male screw 221a of the rear housing 22. Next, as shown in FIG. 4A, the disengagement prevention member 23B is tightened until the abutment surface 230b of the disengagement prevention member 23B comes into contact with the opening end 21e of the front housing 21. Thereby, the cover portion 231 of the detachment prevention member 23B is elastically deformed and spreads outward, the contact surface 231b of the detachment prevention member 23B comes into contact with the outer peripheral surface 21f of the front housing 21, and the thermal expansion in the radial direction of the front housing 21 is performed. suppress. Thereby, it is possible to prevent the rear housing 22 from being detached from the front housing 21 as in the first embodiment.

[Third Embodiment]
FIG. 5 is a cross-sectional view of a main part showing a detachment preventing structure according to the third embodiment of the present invention. The detachment prevention mechanism of the first embodiment has a structure in which the outer taper 21d of the front housing 21 and the inner taper 231a of the detachment prevention member 23A are in general contact at normal temperature (for example, 25 ° C.). When the temperature rise from room temperature becomes a certain level or more, a δ ₂ is provided between the outer taper 21d of the front housing 21 and the inner taper 231a of the detachment preventing member 23C at room temperature. The inner taper 231a comes into contact with the cover portion 231 of the detachment preventing member 23C to suppress thermal expansion of the front housing 21. The following description will focus on differences from the first embodiment.

The detachment preventing member 23C includes a screw portion 230 and a cover portion 231 as in the first embodiment. The screw portion 230 is formed with a female screw 230a and a contact surface 230b. The cover portion 231 has an inner taper 231a on the inner peripheral surface. As shown in FIG. 5A, the disengagement preventing member 23C has an inner taper 231a at normal temperature even if the female screw 230a is screwed into the male screw 221a of the rear housing 22 and the contact surface 230b contacts the opening end 21e. clearance [delta] ₂ is formed between the outer tapered 21d.

When the temperature rise from room temperature becomes a certain level or more, as shown in FIG. 5B, a gap δ ₁ is generated between the female screw 21c of the front housing 21 and the male screw 221a of the rear housing 22, but δ ₁ > δ _2. 5 (c), the inner taper 231a and the outer taper 21d are in surface contact with each other when the temperature rise from room temperature becomes a certain level or more, and the cover 231 is formed on the front housing 21. Suppresses thermal expansion.

  According to the detachment preventing structure using the detachment preventing member 23C according to the third embodiment, even if the inner taper 231a is not brought into contact with the outer taper 21d at room temperature, when the temperature rise from room temperature becomes a certain level or more, Since the front housing 21 can be pressed toward the rear housing 22 by the detachment preventing member 23C and the thermal expansion of the front housing 21 due to the temperature rise can be suppressed, the rear housing 22 can be moved to the front as in the first embodiment. It can prevent coming off from the housing 21.

  The electromagnetic clutch, the driving force transmission device, and the disengagement prevention structure of the present invention have been described based on the above embodiment, but the present invention is not limited to the above embodiment and does not depart from the gist thereof. It can be implemented in various ways within the scope.

  For example, in the first to third embodiments, the case where the detachment preventing members 23A to 23C are applied to prevent the detachment of the member between the front housing 21 and the rear housing 22 has been described. The present invention can also be applied to preventing the disengagement of a member between a first member made of a relatively large nonmagnetic material and a second member made of a magnetic material having a relatively low coefficient of thermal expansion.

DESCRIPTION OF SYMBOLS 1 ... Four-wheel drive vehicle, 2 ... Driving force transmission device, 3 ... Main clutch, 4 ... Cam mechanism, 5 ... Electromagnetic clutch mechanism, 10 ... Control device, 20 ... Housing, 21 ... Front housing, 21a ... Tube part, 21b ... Bottom, 21c ... Female thread, 21d ... Outer taper, 21e ... Open end, 21f ... Outer peripheral surface, 21g ... Open end, 22 ... Rear housing, 22a ... Housing space, 23A-23C ... Detachment prevention member, 231a ... Inner taper 24 ... Inner shaft, 24a ... Step surface, 25 ... Electromagnetic coil, 31 ... First outer clutch plate, 32 ... First inner clutch plate, 41 ... Pilot cam, 41a ... Cam groove, 42 ... Main cam, 43 ... Cam ball, 44 ... disc spring, 45 ... thrust needle roller bearing, 50 ... armature, 51 ... second outer clutch plate, 52 ... second inner clutch Chi plate, 53 ... electromagnetic coil, 61 ... ball bearing, 62 ... needle roller bearing, 63 ... ball bearing, 101 ... vehicle body, 102 ... engine, 103 ... transaxle, 104 ... front wheel, 105 ... rear wheel, 106 ... rear differential Carrier 107, propeller shaft, 108 drive pinion shaft, 109 front axle shaft, 110 rear differential, 111 rear axle shaft, 210 inner spline, 210a first area, 210b second area, 211 Inner peripheral spline protrusion, 221 ... first annular member, 221a ... male screw, 222 ... second annular member, 223 ... third annular member, 230 ... screw portion, 230a ... female screw, 230b ... contact surface, 231 ... cover portion, 231a ... inner taper, 231b ... contact surface, 240 ... outer splice 241 ... Outer peripheral spline protrusion, 242 ... Spline fitting part, 311, 321 ... Protrusion, 322 ... Oil hole, 411 ... Spline engaging part, 421 ... Pressing part, 421a ... Outer peripheral surface, 421b ... Spline teeth, 422 ... Cam portion, 422a ... cam groove, 501 ... projection, 511, 521 ... projection, 530 ... yoke, 531 ... electric wire, G ... magnetic path, O ... rotation axis

Claims (6)

An outer rotating member having an inner peripheral spline portion on the inner peripheral surface;
An inner rotating member disposed inside the outer rotating member and supported so as to be relatively rotatable coaxially with the outer rotating member;
An outer clutch plate made of a magnetic material that engages with the inner peripheral spline portion;
An inner clutch plate made of a magnetic material facing the outer clutch plate;
An electromagnetic coil that generates an electromagnetic force for pressing the outer clutch plate and the inner clutch plate;
The outer rotating member is
A first member made of a cylindrical nonmagnetic material having a predetermined coefficient of thermal expansion, having the inner spline portion on the inner peripheral surface, and having an internal thread on the inner peripheral surface of the opening end;
A first annular member made of a magnetic material having an external thread formed on an outer peripheral surface thereof, and a second annular member made of a non-magnetic material disposed inside the first annular member; and A second member including a third annular member made of a magnetic material disposed inside the second annular member, and having a thermal expansion coefficient smaller than the predetermined thermal expansion coefficient;
A screw part formed with a female screw that is screwed to the male screw of the second member, and the opening end part of the first member are covered from the outer peripheral side, and a cover for suppressing thermal expansion of the first member due to temperature rise. A third member having a portion;
With electromagnetic clutch. The cover portion is elastically deformed by screwing the screw portion into the male screw, and presses the opening end portion of the first member by its restoring force.
The electromagnetic clutch according to claim 1. The first member has an outer inclined surface formed on the outer peripheral surface of the opening end portion so that the outer diameter gradually decreases toward the opening end,
The cover portion is elastically deformed by being in contact with the outer inclined surface and being expanded in diameter.
The electromagnetic clutch according to claim 2. The covering portion has an inner inclined surface inclined in the same direction as the outer inclined surface on an inner peripheral surface,
The electromagnetic clutch according to claim 3. The electromagnetic clutch according to any one of claims 1 to 4,
An outer friction member engaged with the inner peripheral spline portion so as to be axially movable;
An inner friction member engaged with an outer peripheral spline formed on an outer peripheral surface of the inner rotating member so as to be axially movable;
A first cam member and a second cam member, wherein the first cam member is rotated relative to the second cam member by a torque transmitted by the electromagnetic clutch, and thereby the outer side is separated from the second cam member. A cam mechanism for outputting a pressing force for frictionally engaging the friction member and the inner friction member;
A driving force transmission device comprising: A first member made of a cylindrical nonmagnetic material having a predetermined coefficient of thermal expansion, having a female screw on the inner peripheral surface of the opening end, and a male screw that engages with the female screw of the first member are formed on the outer peripheral surface. A detachment preventing structure for preventing the second member from detaching from the first member based on a difference in thermal expansion between the second member made of a magnetic material having a thermal expansion coefficient smaller than the predetermined thermal expansion coefficient. There,
Covering the threaded portion formed with the internal thread of the second member to be engaged with the external thread and the opening end of the first member from the outer peripheral surface side, the thermal expansion of the first member due to temperature rise is suppressed. A detachment preventing structure including a third member having a cover.

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