JP2005147159A - Electromagnetic clutch - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electromagnetic clutch having less torque loss during high speed rotation than conventional one. <P>SOLUTION: When the electromagnetic clutch 23 is in the disconnected condition, a second clutch plate 32 separated from a first clutch plate 31 abuts on a movable stopper 63. At this time, the rotating speed of an output gear 23G2 is lower than a reference rotating speed, the movable stopper 63 is located at a first abutment position to make the second clutch plate 32 stay in such a separation range that it can be drawn to the first clutch plate 31 by an electromagnet 50. On the other hand, when the output gear 23G2 exceeds the reference rotating speed, a centrifugal operation mechanism 39 is operated for moving the movable stopper 63 to a second abutment position to increase a separation distance between the first and second clutch plates 31, 32. This reduces travel resistance due to the viscosity resistance of oil between the first and second clutch plates 31, 32 during high speed rotation exceeding the reference rotating speed. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an electromagnetic clutch, and more particularly to an electromagnetic clutch used for a drive system of an automobile.

2. Description of the Related Art In recent years, an automobile that has been developed has a front wheel (primary driving wheel) driven by a gasoline engine and a rear wheel (driven wheel) driven auxiliary by a motor. Since this vehicle does not have a speed change mechanism between the motor and the rear wheel, the electromagnetic clutch is engaged and the four-wheel drive is performed particularly at the time of starting and low-speed driving where the driving force of the rear wheel is required. On the other hand, when traveling at high speed, in order to prevent an increase in running resistance due to the rotation of the speed reducer or the motor or destruction due to centrifugal force, the electromagnetic clutch is in a disengaged state and the two-wheel drive running is performed.
JP 2003-113874 A (paragraphs [0065], [0081] to [0085], FIGS. 1 and 2)

  By the way, the above-described conventional electromagnetic clutch is dragged due to the viscous resistance of oil interposed between a plurality of clutch plates provided in the electromagnetic clutch even when the electromagnetic clutch is disengaged when the vehicle is traveling at high speed. Due to the torque, the speed reducer and the motor on the upstream side of the torque are rotated, and there is a problem that the running resistance may increase or the motor may be centrifugally broken.

  For this reason, the conventional electromagnetic clutch was arrange | positioned in the low-speed rotation part with the low relative rotational speed of the clutch plates after decelerating a motor output in the drive system of the above-mentioned motor vehicle. However, after the motor output is decelerated, the transmission torque becomes larger than before the deceleration, so that torque capacity and strength are required, and the problem arises that the electromagnetic clutch is enlarged.

  On the other hand, if the separation distance between the clutch plates is simply increased in order to suppress the torque loss at the time of the high-speed rotating part, a large electromagnet is required to attract the clutch plates that are largely separated, and the entire electromagnetic clutch is increased in size. End up. Further, since the moving distance of the clutch plate when the clutch is frictionally coupled is increased, the response of the clutch is also lowered.

  The present invention has been made in view of the above circumstances, and it is an object of the present invention to provide an electromagnetic clutch capable of reducing drag torque between clutch plates during high-speed rotation, and capable of suppressing a decrease in clutch responsiveness. And

  The electromagnetic clutch according to the invention of claim 1 made to achieve the above object is provided with a first rotating member and a second rotating member which are coaxially arranged and can be rotated independently of each other, and are integrated with the first rotating member. A first clutch plate that rotates, a second clutch plate that rotates integrally with the second rotating member, moves linearly in the axial direction of the second rotating member, and contacts and separates from the first clutch plate. In an electromagnetic clutch including an electromagnet that is attracted to the clutch plate and frictionally coupled, and a urging means for separating the second clutch plate from the first clutch plate, the electromagnetic clutch includes a first member that is first with respect to the second clutch plate. Abutting from the opposite side of the clutch plate and moving between a first abutment position relatively close to the first clutch plate and a second abutment position relatively distant, the second clutch at least at the first abutment position First clutch with electromagnet on plate A movable stopper that keeps the movable stopper in the separated range, a movable stopper urging means that urges the movable stopper to the first contact position, and a centrifugal force when the rotation speed of the second rotation member exceeds the reference rotation speed And a centrifugal force actuating mechanism for moving the movable stopper to the second contact position against the movable stopper urging means.

  The invention according to claim 2 is the electromagnetic clutch according to claim 1, wherein the centrifugal force actuating mechanism rotates together with the second rotating member and is movable in the radial direction of the second rotating member by the centrifugal force; A pair provided on the second rotating member and the movable stopper, facing each other in the axial direction of the second rotating member with the centrifugal moving member interposed therebetween, and approaching each other as the distance from the rotation center of the second rotating member increases It is characterized in that it is provided with an open / close facing wall.

  The invention of claim 3 is characterized in that, in the electromagnetic clutch according to claim 2, the centrifugally movable member is a sphere.

  According to a fourth aspect of the present invention, in the electromagnetic clutch according to the second or third aspect, the second rotating member is provided with a shaft member that penetrates the second clutch plate, and the one open / close facing wall is a shaft member. The movable stopper protrudes from the side, and the movable stopper includes a cylindrical portion that encloses one open / close facing wall and the centrifugal movable member, and the other open / close facing wall that protrudes radially inward from one end of the cylindrical portion. Have.

  According to a fifth aspect of the present invention, in the electromagnetic clutch according to any one of the first to fourth aspects, the second rotating member has a cam on the opposite side of the first clutch plate with the second clutch plate interposed therebetween. A wall is provided, and a plurality of V-shaped grooves having a substantially V-shaped cross section when viewed from the radial direction of the second rotating member are formed on the opposing surfaces of the cam wall and the second clutch in the circumferential direction. A characteristic is that a cam member having a circular cross section as viewed from the radial direction of the second rotating member is accommodated between the opposed V-shaped grooves.

  The invention according to claim 6 is characterized in that, in the electromagnetic clutch according to claim 5, one of the open / close facing walls is also used as a cam wall.

  According to a seventh aspect of the present invention, in the electromagnetic clutch according to the fifth or sixth aspect, the second clutch plate abuts the movable stopper at the second contact position on the second clutch plate and the cam wall. Further, there is a feature in that a concave and convex engaging portion that engages with each other and prevents the second clutch plate from rotating around the cam wall is provided.

  The invention of claim 8 is the electromagnetic clutch according to any one of claims 1 to 7, wherein the electromagnetic clutch is arranged in a driving force transmission system of a driven wheel of a four-wheel drive vehicle, The first rotating member is connected to the drive source side of the driven wheel, and the second rotating member is connected to the driven wheel side.

  The invention according to claim 9 is characterized in that, in the electromagnetic clutch according to claim 8, the second rotating member meshes with a ring gear integrally provided on the outer peripheral surface of the differential of the driven wheel.

[Invention of Claim 1]
In the electromagnetic clutch according to the first aspect, the second clutch plate is pulled toward the first clutch plate by the electromagnet to be connected, while the second clutch plate is separated from the first clutch plate by the urging force of the separating urging means. Has been cut off. In the disconnected state, the second clutch plate separated from the first clutch plate comes into contact with the movable stopper. At this time, if the rotation speed of the second rotation member is equal to or lower than the reference rotation speed, the movable stopper is positioned at the first contact position, and the separation range in which the second clutch plate can be pulled toward the first clutch plate by the electromagnet. Keep on. On the other hand, when the rotation speed of the second rotating member exceeds the reference rotation speed, the centrifugal force actuation mechanism is activated and the movable stopper moves to the second contact position, thereby separating the first and second clutch plates from each other. The distance increases. As a result, drag torque due to the viscous resistance of the oil between the first and second clutch plates during high-speed rotation exceeding the reference rotation speed can be reduced. Further, when the rotation speed of the second rotation member is equal to or lower than the reference rotation speed, the movable stopper is positioned at the first contact position, so that the response of the electromagnetic clutch can be prevented from decreasing.
Therefore, when the electromagnetic clutch of the present invention is incorporated in a part of the drive system provided with the speed reduction means, the electromagnetic clutch can be arranged on the high speed side of the drive system, and thus the required torque capacity and strength. Can be reduced and downsizing can be achieved.

[Invention of claim 2]
In the electromagnetic clutch according to claim 2, when the second rotating member rotates exceeding the reference rotation speed, the centrifugal movable member moves to a narrow side of the pair of opening and closing facing walls and pushes between the opening and closing facing walls, The movable stopper can be moved from the first contact position to the second contact position.

[Invention of claim 3]
In the electromagnetic clutch according to the third aspect, since the centrifugally movable member is a sphere, the space between the pair of opening and closing opposing walls can be smoothly spread.

[Invention of claim 4]
In the electromagnetic clutch according to the fourth aspect of the invention, the cylindrical portion of the movable stopper surrounds the centrifugal movable member and also serves as a function of preventing scattering, so that a compact configuration can be achieved.

[Invention of claim 5]
In the electromagnetic clutch according to claim 5, when the second clutch plate is pulled toward the first clutch plate and receives friction torque, the opposed V-shaped grooves of the second clutch plate and the cam wall are displaced from each other, and the respective V-shaped grooves. The cam member moves to the shallow side. As a result, the second clutch plate is pressed against the first clutch plate, and the frictional engagement between the first and second clutch plates is deepened. That is, according to the configuration of the present invention, the second clutch plate can be pressed against the first clutch plate with a force greater than the attractive force of the electromagnet.

[Invention of claim 6]
In the electromagnetic clutch according to the sixth aspect, since one of the open / close facing walls is also used as the cam wall, a compact configuration can be achieved.

[Invention of Claim 7]
In the electromagnetic clutch according to claim 7, when the movable stopper moves to the second contact position and the separation distance between the first and second clutch plates becomes large, the second clutch plate and the cam wall are provided. The concave and convex engaging portions engage with each other, and the cam action of the second clutch plate and each V-shaped groove of the cam wall and the cam member is regulated. Thereby, the electromagnetic clutch can be stabilized in the disconnected state.

[Invention of Claim 8]
In the electromagnetic clutch according to the eighth aspect, since the first rotating member is connected to the drive source side of the driven wheel of the four-wheel drive vehicle and the second rotating member is connected to the driven wheel side, the rotational speed of the driven wheel is increased. Even if the first clutch plate and the second clutch plate are disconnected, the accompanying rotation of the speed reduction mechanism component upstream of the torque from the first rotating member can be suppressed, and the running resistance of the driven wheel can be reduced.

[Invention of claim 9]
In the electromagnetic clutch according to the ninth aspect, the second rotating member meshes with a ring gear integrally provided on the outer peripheral surface of the differential of the driven wheel of the four-wheel drive vehicle. In other words, since the electromagnetic clutch is arranged one stage before the final speed reduction part of the driving force transmission system for the driven wheels of the four-wheel drive vehicle, the torque transmission capacity of the electromagnetic clutch can be reduced and it can be obeyed when the clutch is disconnected. It is possible to effectively reduce the speed reduction mechanism parts that rotate with the driving wheels, and to achieve both reduction in size and weight and reduction in running resistance.

Hereinafter, an embodiment of the present invention will be described with reference to FIGS.
The four-wheel drive vehicle 10 shown in FIG. 1 has an engine 12 mounted on the front side (left side in FIG. 1), and the output of the engine 12 is a transmission 14 and a front differential 15 provided in the front-side transaxle 13. Is transmitted to the front wheel drive shafts 16 and 16 to drive the front wheels 17 and 17 as main drive wheels.

  On the rear side of the four-wheel drive vehicle 10, a motor 20 for driving the rear wheels 18, 18 as driven wheels is mounted. The output of the motor 20 is transmitted to the rear wheel drive shafts 25 and 25 through the electromagnetic clutch 23 and the rear differential 24 provided in the rear side transaxle 21, and the rear wheels 18 and 18 are driven.

  FIG. 2 shows a detailed structure of the rear transaxle 21. As shown in the figure, the electromagnetic clutch 23 includes an input gear 23G1 and an output gear 23G2 arranged on the same axis. A motor gear 20G fixed to the output shaft 20J of the motor 20 is engaged with the input gear 23G1, and a ring gear 24G fixed to the outer surface of the rear differential 24 is engaged with the output gear 23G2. The output gear 23G2 and the ring gear 24G constitute a final reduction part of the driving force transmission system of the driven wheel. The electromagnetic clutch 23 includes first and second clutch plates 31 and 32 in order to connect or disconnect between the input gear 23G1 and the output gear 23G2. When the input gear 23G1 and the output gear 23G2 are connected, the output rotation of the motor 20 is decelerated and transmitted to the rear differential 24.

  As shown in FIG. 3, the shaft shaft 30 (corresponding to the “shaft member” of the present invention) passes through the central portion of the first and second clutch plates 31, 32 of the electromagnetic clutch 23. . The shaft 30 is inserted between the opposing walls 21T and 21T of a casing 21A (hereinafter referred to as “trans-asscle case 21A”) provided in the rear-side transaxle 21, and both ends thereof are supported by bearings 40 and 41. It is pivotally supported so that it can rotate. A flange 30F protrudes from one end of the shaft 30, and the entire shaft 30 has a tapered structure from the flange 30F toward the other end (right side in FIG. 2).

  The first clutch plate 31 is inserted from the tapered tip end side of the shaft 30 and is fitted to the flange 30F side. The first clutch plate 31 includes an inner cylinder 31A and an outer cylinder 31B at an inner edge and an outer edge, and a structure in which one end of the inner cylinder 31A and the outer cylinder 31B is joined by a disk body 31C. It has become. Specifically, the inner cylindrical body 31A and the disk body 31C are integrally formed of a magnetic metal, the nonmagnetic body ring 31D is fitted to the outer peripheral surface of the disk body 31C, and the nonmagnetic body ring 31D is further fitted. The first clutch plate 31 is configured by fitting an outer cylindrical body 31B made of a magnetic material on the outside and welding them. The first clutch plate 31 is assembled to the shaft 30 so that the inner cylinder 31A and the outer cylinder 31B protrude toward the flange 30F.

  A clutch engaging portion 31M is provided on an end surface of the first clutch plate 31 facing the side opposite to the flange 30F. The clutch engaging portion 31M is formed by slightly projecting from the entire end surface of the first clutch plate 31 with both portions sandwiching the nonmagnetic ring 31D inside and outside being flush with each other. Further, the outer peripheral surface of the outer cylinder 31B is provided with a plurality of teeth to form an input gear 23G1. In other words, in the present embodiment, the first clutch plate 31 is configured integrally with the input gear 23G1 as the “first rotating member” according to the present invention. As described above, the motor gear 20G (see FIG. 2) is engaged with the input gear 23G1.

  An angular needle bearing 42 is assembled between the inner cylinder 31 </ b> A of the first clutch plate 31 and the shaft shaft 30. A thrust needle bearing 43 is provided between the front end surface of the inner cylinder 31 </ b> A and the flange 30 </ b> F of the shaft 30. Further, on the opposite side of the first clutch plate 31 from the flange 30F, a clip 46 is locked in a groove formed in the shaft shaft 30, and a shim 47 locked to the clip 46 and the first clutch A thrust needle bearing 44 is also provided between the end surfaces of the plate 31. The first clutch plate 31 is pivotally supported by the bearings 42, 43, and 44 so as to be rotatable with respect to the shaft shaft 30 and not linearly movable in the axial direction.

  A shaft hole 30Y is formed from the one end surface on the flange 30F side to the middle at the center of the shaft 30, and a horizontal hole 30Z is formed so as to be perpendicular to the tip of the shaft hole 30Y. The oil passes through the shaft hole 30Y and the lateral hole 30Z to lubricate the bearings 40, 42, 43, and 44.

  In the first clutch plate 31, an electromagnet 50 enters the space between the inner cylinder 31A and the outer cylinder 31B. The electromagnet 50 is formed by assembling an electromagnetic coil 52 to a coil holder 51 made of a magnetic material. The coil holder 51 has a flat annular structure as a whole, and is provided with an annular groove 51A that is open at one end surface, whereby the longitudinal section of the coil holder 51 is U-shaped. The coil holder 51 is bolted to the inner surface of the transaxle case 21A with the opening of the annular groove 51A facing the first clutch plate 31 side. The electromagnetic coil 52 is accommodated in the annular groove 51A, and the end of the electromagnetic coil 52 is passed through a wire hole 51D formed through the bottom wall 51C of the annular groove 51A and the transaxle case 21A. It is led out of the case 21A.

  The tip of the coil holder 51 projects into the space between the inner cylinder 31A and the outer cylinder 31B in the first clutch plate 31 as described above. The outer cylindrical wall 51G outside the annular groove 51A of the coil holder 51 is adjacent to the inner peripheral surface of the outer cylindrical body 31B of the first clutch plate 31 with a slight gap, An inner cylinder wall 51N inside the annular groove 51A is adjacent to the outer peripheral surface of the inner cylinder 31A of the first clutch plate 31 with a slight gap. Thus, when the electromagnetic coil 52 is excited, the rotating magnetic flux generated around the electromagnetic coil 52 passes through the loop-shaped magnetic path indicated by the broken line 52J in FIG. That is, the magnetic flux is in order of the inner cylinder wall 51N of the coil holder 51, the inner cylinder 31A and the disc body 31C of the first clutch plate 31, the second clutch plate 32 described later, and the outer cylinder of the first clutch plate 31. It passes through the body 31B, the outer cylindrical wall 51G and the bottom wall 51C of the coil holder 51, and follows a looped magnetic path. Thereby, when the electromagnet 50 is excited, the second clutch plate 32 that constitutes a part of the magnetic path is drawn toward the first clutch plate 31 that also constitutes a part of the magnetic path.

  A flange 51E projects inward from the inner peripheral surface of the coil holder 51, and the flange 51E plays a role of fixing the bearing 40 to the transaxle case 21A.

  The second clutch plate 32 is made of an annular magnetic metal, is loosely fitted to the shaft 30 and is disposed adjacent to the first clutch plate 31. On the end surface of the second clutch plate 32 on the first clutch plate 31 side, a spring accommodating portion 32A is formed by recessing the inner portion in a stepped shape. A pair of separation urging springs 48, 48 as a “separation urging means” of the present invention are sandwiched between the inner surface of the spring accommodating portion 32 </ b> A and the shim 47 described above. Specifically, each separation biasing spring 48 has a disc spring structure in which an annular leaf spring material is distorted into a flat truncated cone shape. Then, the outer edge portions of the pair of separation biasing springs 48, 48 are joined to each other, and the inner edge portions of the pair of separation biasing springs 48, 48 are assembled in a separated state.

  The separation biasing springs 48, 48 are fitted and centered on the outer step surface 32B of the spring accommodating portion 32A. The separation biasing spring 48 on the shim 47 side is also centered by a clip 46 fitted inside.

  On the end face of the second clutch plate 32 on the first clutch plate 31 side, a flat portion slightly protruding from the central portion is provided at a portion near the outer edge, and this flat portion serves as a clutch engaging portion 32M. The clutch engaging portion 32M is frictionally engaged with the clutch engaging portion 31M of the first clutch plate 31.

  A clutch base 33 is fitted and fixed to the shaft 30 on the opposite side of the second clutch plate 32 from the first clutch plate 31. A self-lock mechanism 34 is provided between the clutch base 33 and the second clutch plate 32.

  More specifically, a spline is formed on the distal end side (the side away from the flange 30F) of the shaft shaft 30 where the second clutch plate 32 is fitted, and the male end further on the distal end side than the spline. A screw 30T is formed. The clutch base 33 has a structure in which a cam wall 33A protrudes from one end of a cylindrical portion 33B having a spline on the inner peripheral surface. The side provided with the cam wall 33A is arranged on the second clutch plate 32 side, and the cylindrical portion 33B is spline-fitted to the shaft shaft 30, whereby the clutch base 33 is prevented from rotating around the shaft shaft 30. . In addition, the clutch base 33 is abutted against a clip 54 that is locked in a groove in the middle of the shaft 30 with a shim 55 interposed therebetween. A cylindrical output gear 23G2 is spline-fitted to the shaft 30 after the clutch base 33, and a retaining nut 36 is fastened to the male screw 30T of the shaft 30. By this tightening, the clutch base 33 is sandwiched between the shim 55 and the output gear 23G2, and is fixed so as not to move in the axial direction.

  In the present embodiment, the above-described output gear 23G2, clutch base 33, and shaft shaft 30 are combined to constitute the “second rotating member” according to the present invention.

  The self-locking mechanism 34 includes a V-shaped groove 60, 61 formed symmetrically on the opposing surface of the second clutch plate 32 and the cam wall 33A, and a cam ball sandwiched between the back surfaces of both the V-shaped grooves 60, 61. 62 (corresponding to the “cam member” of the present invention). Specifically, a plurality of (for example, six) V-shaped grooves 60 and 61 are provided on the opposing surfaces of the second clutch plate 32 and the cam wall 33A in a concentric circle at equal intervals (for example, six). 5). Each of the V-shaped grooves 60 and 61 has a semicircular cross section as shown in FIG. 3 at the cut surface including the center line of the second clutch plate 32, and the first groove when viewed from the axial direction of the second clutch plate 32. The inner edge near the center of the clutch plate 31 and the outer edge away from the center are curved so as to form a concentric arc (see FIG. 5). When the V-shaped grooves 60 and 61 are viewed from the radial direction of the second clutch plate 32, they are V-shaped as shown in FIG.

  A cam ball 62 is sandwiched and held between these V-shaped grooves 60 and 61. When the second clutch plate 32 is rotated by receiving torque due to friction with the first clutch plate 31, the cam ball 62 is placed at a shallow position in the V-shaped grooves 60 and 61 as shown in FIG. Moving. As a result, the second clutch plate 32 moves away from the cam wall 33 </ b> A and is pressed against the first clutch plate 31.

  That is, once the second clutch plate 32 is pulled toward the first clutch plate 31 side by the electromagnet 50, the second clutch plate 32 moves to the first clutch plate 31 side by the torque received from the first clutch plate 31, and first and second The clutch plates 31 and 32 are locked in a connected state. In this sense, the mechanism including the V-shaped grooves 60 and 61 and the cam ball 62 can be referred to as a “self-locking mechanism”.

  In the present embodiment, when the output torque of the motor 20 is transmitted from the first clutch plate 31 toward the second clutch plate 32, the first clutch plate 31 rotates in advance with respect to the second clutch plate 32. It will be in the state. Therefore, if the torque transmission is interrupted by stopping the excitation of the electromagnet 50 and stopping or reducing the power supply to the motor 20, the cam ball 62 moves to a deep position in the V-shaped grooves 60 and 61, and is separated. The second clutch plate 32 can be separated from the first clutch plate 31 by the elastic force of the urging spring 48 (that is, the electromagnetic clutch 23 is disengaged).

  A movable stopper 63 is attached to the outside of the clutch base 33. The movable stopper 63 includes a disk-shaped open / close facing wall 63C that protrudes inward from one end side of the cylindrical portion 63A fitted to the outside of the cam wall 33A. The other end of the cylindrical portion 63A is provided with an abutting wall 63B that expands in a tapered shape.

  The contact wall 63B protrudes from the cam wall 33A toward the second clutch plate 32, and the outer edge portion of the second clutch plate 32 that is separated from the first clutch plate 31 contacts the contact wall 63B. Thereby, the separation distance of the second clutch plate 32 from the first clutch plate 31 (see L1 in FIG. 3 and L2 in FIG. 4) is regulated.

  The open / close facing wall 63C faces the cam wall 33A (corresponding to the other “open / close facing wall” in the present invention). Further, the inner edge portion of the open / close facing wall 63 </ b> C is spline-fitted to one end of the cylindrical portion 33 </ b> B in the clutch base 33. As a result, the opening / closing facing wall 63C rotates integrally with the cam wall 33A and contacts and separates from the cam wall 33A.

  A plurality of (for example, three) centrifugal balls 64 (corresponding to the “centrifugal movable member” of the present invention) are accommodated between the cam wall 33A and the open / close facing wall 63C. The centrifugal operation mechanism 39 according to the present invention is configured by 63C and the centrifugal ball 64. Specifically, a guide groove 33G extending in the radial direction is formed at a plurality of circumferential positions (for example, three positions) on the surface of the cam wall 33A facing the open / close facing wall 63C. The inner surface of the guide groove 33G protrudes toward the open / close facing wall 63C from the center side of the clutch base 33 toward the outside. The open / close facing wall 63C is also inclined so that the outer side from the center side approaches the cam wall 33A side. That is, the distance between the inner surface of the guide groove 33G and the open / close facing wall 63C becomes narrower toward the outside. A centrifugal ball 64 is accommodated between the inner surface of the guide groove 33G and the open / close facing wall 63C.

  A stopper urging spring 65 as a “movable stopper urging means” according to the present invention is provided at a boundary portion between the clutch base 33 and the output gear 23G2. The stopper urging spring 65 has a disc spring structure in which an annular leaf spring material is distorted into a flat truncated cone shape, and its outer edge abuts against the outer edge of the open / close facing wall 63C, while the inner edge is a clutch base. 33 is sandwiched between the cylindrical portion 33B and the output gear 23G2. The open / close facing wall 63C is biased toward the cam wall 33A by the elastic force of the stopper biasing spring 65. Accordingly, the centrifugal ball 64 is normally accommodated on the wide side between the cam wall 33A (specifically, the inner surface of the guide groove 33G) and the open / close facing wall 63C, that is, on the rotation center side of the clutch base 33. . When the clutch base 33 reaches a predetermined reference rotational speed or higher, the centrifugal force applied to the centrifugal ball 64 overcomes the resilience of the stopper biasing spring 65 and pushes between the cam wall 33A and the open / close facing wall 63C. As a result, as shown in FIG. 4, the movable stopper 63 slides away from the first clutch plate 31.

  As described above, when the movable stopper 63 slides, the contact position between the second clutch plate 32 and the movable stopper 63 (specifically, the contact wall 63B of the movable stopper 63) is changed. Here, as shown in FIG. 3, the position where the centrifugal ball 64 is placed on the rotation center side of the clutch base 33 and the movable stopper 63 approaches the first clutch plate 31 side is called a “first contact position”. As shown in FIG. 4, the position where the centrifugal ball 64 is placed on the side away from the rotation center of the clutch base 33 and the movable stopper 63 is separated from the first clutch plate 31 is referred to as a “second contact position”. When the second clutch plate 32 comes into contact with the movable stopper 63 at the second contact position, rather than when the second clutch plate 32 comes into contact with the movable stopper 63 at the contact position (specifically, the contact wall 63B). On the other hand, the second clutch plate 32 is separated from the first clutch plate 31.

  In the present embodiment, when the movable stopper 63 is located at the first contact position (see FIG. 3), the second clutch plate 32 can be drawn to the first clutch plate 31 by the magnetic force of the electromagnet 50. In addition, it is set so as to be fastened by the movable stopper 63. In this case, the distance between the first and second clutch plates 31 and 32 is indicated by a symbol L1 in FIG. On the other hand, when the movable stopper 63 is positioned at the second contact position (see FIG. 4), the second clutch plate 32 is not easily affected by the viscous resistance of the oil with the first clutch plate 31. It is set to be released. The separation distance between the first and second clutch plates 31 and 32 in this case is indicated by reference numeral L2 in FIG.

  Here, the separation distance indicated by L1 when the movable stopper 63 is located at the first contact position is preferably 0.2 to 0.6 mm. This is because the drag torque between the clutch plates is extremely large below this, and the problem that the response of the clutch is poor above this becomes obvious. Further, it is desirable that the separation distance indicated by L2 when the movable stopper 63 is positioned at the second contact position is 1 mm or more. This is because the effect of reducing the drag torque between the clutch plates cannot be sufficiently exhibited below this.

  In the second contact position, the second clutch plate 32 approaches the cam wall 33A and engages with the concave and convex portions, so that the second clutch plate 32 is fixed to the cam wall 33A so as not to rotate. Specifically, as shown in FIG. 7, engaging grooves 66 are formed at a plurality of locations in the circumferential direction of the second clutch plate 32, and the cam wall 33A corresponds to these engaging grooves 66. Thus, an engaging protrusion 67 is formed to protrude. 7A and 7B, when the second clutch plate 32 comes into contact with the movable stopper 63 at the first contact position, the engagement groove 66 and the engagement protrusion 67 are obtained. When the second clutch plate 32 comes into contact with the movable stopper 63 at the second contact position as shown in FIGS. 8A and 8B, the engagement grooves 66 are engaged. The protrusion 67 engages with the projections and depressions. As a result, even when torque is applied to the second clutch plate 32, the inner surface 66A of the engagement groove 66 facing the rotation direction and the outer surface 66B of the engagement protrusion 67 facing the rotation direction are in contact with each other. The second clutch plate 32 is prevented from rotating on the cam wall 33A.

Next, the operation of the present embodiment configured as described above will be described.
The four-wheel drive vehicle 10 of the present embodiment can be switched between a four-wheel drive mode and a two-wheel drive mode by a driver's operation. And ECU19 (refer FIG. 1) with which the four-wheel drive vehicle 10 was equipped controls the electromagnet 50 of the electromagnetic clutch 23 corresponding to each mode. Specifically, when the 4WD mode is selected, it is as follows. That is, while the four-wheel drive vehicle 10 is stopped, the electromagnet 50 is held in a non-excited state. When the four-wheel drive vehicle 10 starts, the engine 12 and the motor 20 output torque, and the electromagnet 50 is excited for a predetermined time.

  The output of the engine 12 is transmitted to the transmission 14 and the front differential 15, and the front wheels 17 are rotationally driven. On the other hand, the output of the motor 20 is transmitted from the motor gear 20G to the input gear 23G1 of the electromagnetic clutch 23, and the first clutch plate 31 integrally provided with the input gear 23G1 receives torque. At this time, since the second clutch plate 32 is attracted to the first clutch plate 31 side by the magnetic force of the electromagnet 50, the second clutch plate 32 receives torque from the first clutch plate 31 by friction engagement, and the torque is reduced. Utilizing the self-locking mechanism 34, the second clutch plate 32 is pressed against the first clutch plate 31, and the first and second clutch plates 31, 32 are locked in the connected state. And even if the electromagnet 50 shifts to the non-excited state after a predetermined time has elapsed from the start of the four-wheel drive vehicle 10, the connection state of the first and second clutch plates 31, 32 is maintained by the self-lock mechanism 34. . As a result, the output of the motor 20 is transmitted to the rear differential 24 via the input gear 23G1 and the output gear 23G2 of the electromagnetic clutch 23, and the rear wheel 18 is rotationally driven. That is, it can start by four-wheel drive.

  When the four-wheel drive vehicle 10 is switched from acceleration to deceleration, the torque transmission direction between the first and second clutch plates 31 and 32 can be reversed and the self-lock mechanism 34 can be unlocked. In order to maintain the connected state of the first and second clutch plates 31 and 32, the electromagnet 50 may be excited. In addition, by bringing the first and second clutch plates 31 and 32 into a connected state at the time of deceleration, the motor 20 can function as a generator to regenerate power in the battery 11.

  As the traveling speed of the four-wheel drive vehicle 10 increases, the transmission ratio of the transmission 14 in the front transaxle 13 is changed. As a result, the engine 12 can cope with low-speed traveling to high-speed traveling. However, since the rear transaxle 21 is not provided with a speed change mechanism corresponding to the transmission 14, the output rotational speed of the motor 20 cannot follow the vehicle speed during medium speed and high speed travel. Therefore, it is necessary to disconnect the motor 20 and the rear wheel 18 by the electromagnetic clutch 23. Therefore, when the vehicle speed exceeds the predetermined speed and the vehicle travels at a medium speed, the electromagnetic clutch 23 is held in a non-excited state, and the output torque of the motor 20 is reduced. Thereby, the transmission of torque from the motor 20 to the rear wheel 18 side is interrupted, the lock by the self-lock mechanism 34 is released, and the first and second clutch plates 31 and 32 are separated. That is, when the vehicle speed becomes medium speed running, the motor 20 and the rear wheel 18 are disconnected and automatically switched to two-wheel drive running.

  When the four-wheel drive vehicle 10 is traveling at medium speed, the second clutch plate 32 is fastened by the movable stopper 63 in a range slightly separated from the first clutch plate 31 in preparation for shifting to low speed traveling. It is done. And when it transfers to low speed driving | running | working, it attracts to the 1st clutch board 31 side by the magnetic force of the electromagnet 50, and it becomes 4WD driving | running | working rapidly.

  By the way, if the relative rotational speed is increased with the first and second clutch plates 31 and 32 slightly separated from each other, the first and second clutch plates 31 and 32 are affected by the mutual viscous resistance of the oil. (Torque) is received and the running resistance of the rear wheel 18 is increased by so-called drag torque. There is also a concern that unexpected self-locking may occur by the self-lock mechanism 34 when the second clutch plate 32 receives torque due to the viscous resistance of the oil, particularly at low temperatures when the viscous resistance increases.

  However, in the electromagnetic clutch 23 of the present embodiment, as described in detail below, when the four-wheel drive vehicle 10 exceeds a predetermined reference vehicle speed, the separation distance between the first and second clutch plates 31 and 32 increases and torque loss is reduced. It is possible to suppress and prevent locking by the self-locking mechanism 34. That is, when the four-wheel drive vehicle 10 exceeds a predetermined reference vehicle speed and the output gear 23G2 that rotates in conjunction with the rear wheel 18 exceeds a predetermined reference rotation speed, the centrifugal ball 64 moves radially outward by centrifugal force, and the cam The wall 33A and the open / close facing wall 63C are pushed apart, whereby the movable stopper 63 moves from the first contact position to the second contact position. Then, the second clutch plate 32 follows the movable stopper 63 by the elastic force of the separation biasing spring 48, and the separation distance between the first and second clutch plates 31, 32 is from L1 shown in FIG. It spreads to L2 shown in. As a result, the first and second clutch plates 31 and 32 are not easily affected by the viscous resistance of the oil. At this time, the engagement groove 66 provided in the second clutch plate 32 engages with the engagement projection 67 provided in the cam wall 33A (see FIG. 8A), and the second clutch plate 32 is engaged. Is fixed to the cam wall 33A in a non-rotatable manner. As a result, the self-locking mechanism 34 is not activated, and the situation where the first and second clutch plates 31 and 32 are arbitrarily locked is prevented.

  When the four-wheel drive vehicle 10 is decelerated and the rotational speed of the output gear 23G2 becomes equal to or lower than a predetermined reference rotational speed, the centrifugal force applied to the centrifugal ball 64 is lost to the elastic force of the stopper biasing spring 65, and the centrifugal ball 64 moves radially inward, and the movable stopper 63 returns to the first contact position. And when the four-wheel drive vehicle 10 transfers to low speed driving | running | working, the electromagnet 50 is excited and it switches to four-wheel drive driving | running | working. In the case of the 2WD mode, the operation is the same as in the case of the 4WD mode except that the electromagnet 50 is always in a non-excited state.

  Thus, in the electromagnetic clutch 23 of the present embodiment, the separation distance between the first and second clutch plates 31 and 32 is widened at high speed rotation, and the running resistance due to the viscous resistance of oil can be reduced. As a result, when the electromagnetic clutch 23 is incorporated in a part of a drive system having a speed reduction unit, such as the four-wheel drive vehicle 10, the electromagnetic clutch can be arranged on the high speed side of the drive system, which is necessary. Therefore, the torque capacity and the strength are reduced, and the size can be reduced. Further, according to the configuration of the electromagnetic clutch 23 of the present embodiment, the movable stopper 63 surrounds the centrifugal ball 64 and also serves as a function for preventing scattering, so that a compact configuration can be achieved. In addition, since the centrifugal ball 64 is a sphere, the space between the cam wall 33A and the open / close facing wall 63C can be smoothly spread.

[Other Embodiments]
The present invention is not limited to the above-described embodiment. For example, the embodiments described below are also included in the technical scope of the present invention, and various other than the following can be made without departing from the scope of the invention. It can be changed and implemented.

  (1) Although the electromagnetic clutch 23 of the above embodiment is provided in the drive system of the four-wheel drive vehicle 10, it may be used for a tool, a machine tool, or the like, for example.

  (2) Although the electromagnetic clutch 23 of the above-described embodiment is incorporated in a part of the rear-side transaxle 21 provided with a speed reduction unit, an electromagnetic clutch may be used for a drive portion that does not perform the speed reduction.

  (3) Although the electromagnetic clutch 23 of the above-described embodiment includes the self-locking mechanism 34, the first and second clutch plates may be joined only by the magnetic force of the electromagnet.

  (4) The electromagnetic clutch 23 of the above embodiment has a configuration in which the excitation of the electromagnet 50 is stopped and the connected state is held by the self-locking mechanism 34. You may make it the structure hold | maintained and hold | maintain a connection state with a self-locking mechanism.

  (5) Although the spherical centrifugal ball 64 is employed as the centrifugal movable member in the electromagnetic clutch 23 of the above embodiment, the centrifugal movable member may be cylindrical.

The conceptual diagram which showed the drive system of the four-wheel drive vehicle which concerns on one Embodiment of this invention. Cross section of rear transaxle Cross section of electromagnetic clutch at low speed Cross section of electromagnetic clutch at high speed rotation A plan view of the second clutch plate for explaining the V-shaped groove Sectional view for explaining the self-locking mechanism Partial sectional view of the electromagnetic clutch at low speed rotation Partial sectional view of electromagnetic clutch during high-speed rotation

Explanation of symbols

23 Electromagnetic clutch 23G1 Input gear (first rotating member)
23G2 output gear (second rotating member)
30 shaft shaft (shaft member)
31 First clutch plate 32 Second clutch plate 33 Clutch base (second rotating member)
33A Cam wall 39 Centrifugal operation mechanism 48 Separation bias spring (separation bias means)
50 Electromagnet 60, 61 V-shaped groove 62 Cam ball (cam member)
63 Movable stopper 63A Cylindrical part 63C Open / close facing wall 64 Centrifugal ball (centrifugal movable member)
65 Stopper biasing spring (movable stopper biasing means)
66 engaging groove 67 engaging protrusion

Claims (9)

A first rotating member and a second rotating member arranged on the same axis and rotatable independently of each other;
A first clutch plate that rotates integrally with the first rotating member;
A second clutch plate that rotates integrally with the second rotating member and moves linearly in the axial direction of the second rotating member to contact and separate from the first clutch plate;
An electromagnet for pulling the second clutch plate toward the first clutch plate and frictionally coupling the second clutch plate;
In the electromagnetic clutch provided with the urging means for separation for separating the second clutch plate from the first clutch plate,
Abutting against the second clutch plate from the opposite side of the first clutch plate, and moving between a first contact position relatively close to the first clutch plate and a second contact position relatively far from the first clutch plate. A movable stopper that holds the second clutch plate in a separated range that can be pulled toward the first clutch plate by the electromagnet at least in the first contact position;
Movable stopper biasing means for biasing the movable stopper to the first contact position;
A centrifugal force actuating mechanism that operates by a centrifugal force when the rotational speed of the second rotating member exceeds a reference rotational speed and moves the movable stopper to the second contact position against the movable stopper biasing means. And an electromagnetic clutch. The centrifugal force actuating mechanism rotates with the second rotating member and is movable in the radial direction of the second rotating member by centrifugal force; and
The second rotating member and the movable stopper are provided on the movable stopper so as to face each other in the axial direction of the second rotating member with the centrifugal movable member interposed therebetween, and as the distance from the rotation center of the second rotating member increases. The electromagnetic clutch according to claim 1, comprising a pair of open / close facing walls that are close to each other.   The electromagnetic clutch according to claim 2, wherein the centrifugally movable member is a sphere. The second rotating member includes a shaft member that penetrates the second clutch plate,
One of the open / close facing walls projects laterally from the shaft member,
The movable stopper includes a cylindrical portion enclosing the one open / close facing wall and the centrifugal movable member, and the other open / close facing wall projecting radially inward from one end of the cylindrical portion. Item 4. The electromagnetic clutch according to item 2 or item 3.   The second rotating member is provided with a cam wall on the opposite side of the first clutch plate with the second clutch plate interposed therebetween, and the cam wall and the second clutch are arranged on the opposing surfaces of the second rotating member. A plurality of V-shaped grooves having a substantially V-shaped cross section when viewed from the radial direction of the rotating member are formed opposite to each other in the circumferential direction, and the V-shaped grooves between the opposed V-shaped grooves are viewed from the radial direction of the second rotating member. The electromagnetic clutch according to any one of claims 1 to 4, wherein a cam member having a circular cross section is accommodated.   The electromagnetic clutch according to claim 5, wherein one of the open / close facing walls is also used as the cam wall.   The second clutch plate and the cam wall are engaged with each other when the second clutch plate comes into contact with the movable stopper at the second contact position, and the second clutch plate is attached to the cam wall. The electromagnetic clutch according to claim 5, further comprising a concave and convex engaging portion that prevents rotation.   The electromagnetic clutch is disposed in a driving force transmission system of driven wheels of a four-wheel drive vehicle, the first rotating member is connected to a driving source side of the driven wheel, and the second rotating member is connected to the driven wheel side. The electromagnetic clutch according to claim 1, wherein the electromagnetic clutch is connected to the electromagnetic clutch. The electromagnetic clutch according to claim 8, wherein the second rotating member is meshed with a ring gear integrally provided on an outer peripheral surface of the differential of the driven wheel.

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