Electromagnetic clutch

In this electromagnetic clutch, a compressive force is generated in a plate spring when an armature plate is contact with a first rotor. Therefore, a force in the direction away from the first rotor acts on a first bent portion of a plate spring. However, an extension portion of a second rotor is capable of abutting to the first bent portion from the direction opposite to the first rotor. So a stress generated in the first bent portion is dispersed to the extension portion.

BACKGROUND OF THE INVENTION

(i) Field of the Invention

The present invention relates to an electromagnetic clutch for transmitting power from a power source of a vehicle to a compressor of an air conditioner for vehicle, for example.

(ii) Description of the Related Art

A generally known electromagnetic clutch includes a first rotor rotated by power from outside, an armature plate arranged oppositely to one end face of the first rotor in the axial direction, an electromagnetic coil for attracting the armature plate to the first rotor side, a second rotor for transmitting a turning force transmitted from the armature plate side to a driven shaft on a driven device, and a plurality of plate springs in which one end side is connected to the armature plate and the other end side is connected to the second rotor for transmitting the turning force from the armature plate to the second rotor and for urging the armature plate in the direction away from the first rotor.

In the above electromagnetic clutch, the armature plate and the first rotor are connected only with a magnetic force of the electromagnetic coil. Therefore, it is necessary to enlarge the electromagnetic coil so as to increase a torque capacity which can be transmitted between the first rotor and the armature plate. That is, it is not possible to reduce weight and power consumption of the electromagnetic clutch.

On the other hand, an electromagnetic clutch for which the above point can be improved is provided with a first rotor similar to the above, not shown, an electromagnetic coil, not shown, an armature plate61, a second rotor62, and a plurality of plate springs63in which one end is connected to the armature plate61and the other end is connected to the second rotor for transmitting the turning force from the armature plate61to the second rotor62and for urging the armature plate61away from the first rotor (SeeFIGS. 13 to 15). To each of the plate springs63, a compression force is applied between its one end and the other end when the turning force is to be transmitted. An inclined portion63ais provided on the plate spring63, which is formed by bending a part thereof to the first rotor side. A part of the compression force applied to the plate spring63acts as a force for pressing the armature plate61onto the first rotor by the inclined portion63a.

However, in the latter electromagnetic clutch, a bent portion63bof the plate spring63is deformed in the direction away from the first rotor by reaction of the pressing when the compression force is applied to the plate spring63and the armature plate61is pressed onto the first rotor. Since a stress is concentrated to the bent portion63bby this, the stress needs to be alleviated.

SUMMARY OF THE INVENTION

An object of the present invention is to provide an electromagnetic clutch which has a plate spring capable of pressing an armature plate onto a first rotor side while transmitting a turning force from the armature plate to a second rotor and can alleviate a stress concentrating on a bent portion of a plate spring.

In order to achieve the above object, in the present invention, an electromagnetic clutch for transmitting a turning force of a first rotor rotated by power from outside to a rotational axis of a driven device is provided with an armature plate arranged oppositely to the first rotor in the axial direction, an electromagnetic coil for attracting the armature plate to the first rotor side, a second rotor for transmitting the turning force transmitted from the armature plate side to the rotational axis of the driven device, a plate spring in which one end side is connected to the second rotor and the other end side is connected to the armature plate, an inclined portion which is formed by bending a part of the plate spring to the first rotor side, and the inclined portion applies a pressing force to the armature plate directing toward the first rotor when the turning force is transmitted from the armature plate to the second rotor through the plate spring, and a contact portion which is capable of abutting to said part of the plate spring from the direction opposite to the first rotor.

By this, said part of the plate spring is a bent portion, and the contact portion is capable of contacting with the bent portion of the plate spring from the direction opposite to the first rotor. Therefore, even if a force in the direction away from the first rotor acts on the bent portion by reaction of the pressing force, the stress generated in the bent portion by the contact with the contact portion is dispersed to the contact portion side. That is, the stress concentrating on the bent portion is alleviated. Thus, no deformation or strength drop is generated in the plate spring even after use for a long time, and durability of the plate spring can be improved. Also, even if a force in the direction away from the first rotor acts on the bent portion by the reaction of the pressing force, deformation of the bent portion in the above direction is regulated by the contact portion. Therefore, the pressing force is applied to the armature plate without being decreased by deformation of the bent portion.

Moreover, in the present invention, an electromagnetic clutch for transmitting a turning force of a first rotor rotated by power from outside to a rotational axis of a driven device is provided with an armature plate arranged oppositely to the first rotor in the axial direction, an electromagnetic coil for attracting the armature plate to the first rotor side, a second rotor for transmitting the turning force transmitted from the armature plate side to the rotational axis of the driven device, a plate spring in which one end side is connected to the second rotor and the other end side is connected to the armature plate, and the plate spring in which a part has a sectional area larger than that of the other part, and an inclined portion which is formed by bending said part of the plate spring to the first rotor side, and the inclined portion applies a pressing force to the armature plate directing toward the first rotor when the turning force is transmitted from the armature plate to the second rotor through the plate spring.

By this, said part of the plate spring is a bent portion, and the bent portion has a sectional area larger than the other part of the plate spring. Therefore, even if a force in the direction away from the first rotor acts on the bent portion by the reaction of the pressing force, a stress generated in the bent portion is dispersed by the larger sectional area. That is, the stress concentrating on the bent portion is alleviated. Thus, no deformation or strength drop is generated in the plate spring even after use for a long time, and durability of the plate spring can be improved.

Moreover, in the present invention, an electromagnetic clutch for transmitting a turning force of a first rotor rotated by power from outside to a rotational axis of a driven device is provided with an armature plate arranged oppositely to the first rotor in the axial direction, an electromagnetic coil for attracting the armature plate to the first rotor side, a second rotor for transmitting the turning force transmitted from the armature plate side to the rotational axis of the driven device, a plate spring in which one end side is connected to the second rotor and the other end side is connected to the armature plate, an inclined portion which is formed by bending a part of the plate spring to the first rotor side, and the inclined portion applies a pressing force to the armature plate directing toward the first rotor when the turning force is transmitted from the armature plate to the second rotor through the plate spring, and an other plate spring overlapping said plate spring.

By this, said part of the plate spring is a bent portion and the other plate spring overlaps the plate spring. Therefore, even if a force in the direction away from the first rotor acts on the bent portion by the reaction of the pressing force, a stress generated in the bent portion of the plate spring is dispersed by another plate spring. That is, the stress concentrating on the bent portion is alleviated. Therefore, no deformation or strength drop is generated in the plate spring even after use for a long time, and durability of the plate spring can be improved.

Furthermore, in the present invention, an electromagnetic clutch for transmitting a turning force of a first rotor rotated by power from outside to a rotational axis of a driven device is provided with an armature plate arranged oppositely to the first rotor in the axial direction, an electromagnetic coil for attracting the armature plate to the first rotor side, a second rotor for transmitting the turning force transmitted from the armature plate side to the rotational axis of the driven device, a plate spring formed by overlapping a plurality of spring members each other, and the plate spring in which one end side is connected to the second rotor and the other end side is connected to the armature plate, and an inclined portion which is formed by bending apart of the plate spring to the first rotor side, and the inclined portion applies a pressing force to the armature plate directing toward the first rotor when the turning force is transmitted from the armature plate to the second rotor through the plate spring.

By this, said part of the plate spring is a bent portion, and the plate spring is formed by overlapping a plurality of spring members each other. Therefore, even if a force in the direction away from the first rotor acts on the bent portion by the reaction of the pressing force, a stress is generated at each of the plate spring. Thus, compression deformation inward in the bending direction and tension deformation outward in the bending direction of each of the spring members is made smaller than the case where the bent portion is formed by a single plate spring. That is, the stress concentrating in the bent portion is alleviated. Therefore, no deformation or strength drop is generated in the plate spring even after use for a long time, and durability of the plate spring can be improved.

The above and other objects, features, and advantages of the present invention will become more apparent from the following description and the accompanying drawings.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIGS. 1 to 4show an embodiment of the present invention.FIG. 1is a side sectional view of an electromagnetic clutch,FIG. 2is a front view of the electromagnetic clutch,FIG. 3is a sectional view on A-A line inFIG. 2,FIG. 4is a front view of a plate with spring.

An electromagnetic clutch of this preferred embodiment is provided with a first rotor10to which power from an engine, not shown, is transmitted, an armature plate20arranged oppositely to one end face of the first rotor10in the axial direction, an electromagnetic coil30for attracting the armature plate20to the first rotor10side, a second rotor40for transmitting the turning force transmitted from the armature plate20side to a rotational axis2of a compressor1, and a plate with spring50provided between the armature plate20and the second rotor40.

The first rotor10is a known pulley with an outer circumferential face around which a V-belt, not shown, can be wound, and the first rotor10is rotatably supported by the compressor1through a bearing10a. An annular groove portion10bis provided on the other end face of the first rotor10. The other end face is a surface in the first rotor10opposite to the armature plate20. Within the groove portion10b,the electromagnetic coil30is arranged.

The armature plate20is made of a steel material and has a disk shape.

A predetermined gap is provided between the electromagnetic coil30and the groove portion10bof the first rotor10. The electromagnetic coil30is mounted on the compressor1through a mounting plate30a.

On one end face of the second rotor40is provided with a projection portion40aprojecting in the axial direction. The one end face is located on the compressor1side of the second rotor40. An inner circumferential surface of the projection portion40ais engaged with a spline2aof the rotational axis2in the rotating direction. The spline2ais provided at the tip end of the rotational axis2. Moreover, a disk-state extension portion40bwith an outer diameter smaller than the armature plate20is provided on the other end face side of the second rotor40. A predetermined gap is provided in the axial direction between the extension portion40band the armature plate20.

The plate with spring50is made of a plate-state member of a spring steel, and the plate with spring50has three plate springs51on its outer circumferential face side. Each of the plate springs51is arranged with an equal interval in the circumferential direction of the plate with spring50. At the center of the plate with spring50is provided with a hole50athrough which the projection portion40aof the second rotor40can be inserted. Each of the plate springs51extends in the direction opposite to the rotating direction of the first rotor from the outer circumferential face side of the plate with spring50. A first mounting hole51ais provided on one end side of each of the plate springs51. On the other end side of each of the plate springs51is provided with a second mounting hole51b. Each of the first mounting holes51ais mounted to a mounting hole40cprovided on the second rotor40with a rivet51c, and each of the second mounting holes51bis mounted on a mounting hole20aprovided on the armature plate20with a rivet51d. Approximately at the center of each of the plate springs51is provided with a first bent portion51ebent to the first rotor10side. Also, a second bent portion51fbent to the second rotor40side is provided on the second mounting hole51bside of each of the plate springs51. That is, an inclined portion51gis formed, which is inclined from the first bent portion51etoward the second bent portion51fon the first rotor10side. And the extension portion40bis brought into contact with each of the first bent portion51efrom the direction opposite to the first rotor10. That is, the extension portion40bcorresponds to a contact portion described in claims.

In the above electromagnetic clutch, when a predetermined electric current flows through the electromagnetic coil30, the armature plate20is attracted to one end face of the first rotor10against an urging force of each of the plate springs51. When the armature plate20is attracted to the first rotor10, the armature plate20is rotated together with the first rotor10. By this, a turning force is transmitted from the armature plate20to the second rotor40through each of the plate springs51. That is, the rotational axis2of the compressor1is rotated.

Here, each of the plate springs51extends in the direction opposite to the rotating direction of the first rotor10from the outer circumferential face side of the plate with spring50. Each of the plate springs51has one end side mounted on the second rotor40and the other end side on the armature plate20. Therefore, when the turning force is transmitted from the armature plate20to the second rotor40, a compression force is applied between the one end side and the other end side of each of the plate springs51. And the inclined portion51gis provided between the one end side and the other end side of each of the plate springs51. By this, a part of the compression force applied to each of the plate springs51acts as a pressing force for pressing the armature plate20to the first rotor10side. That is, a connecting force between the armature plate20and the first rotor10is increased by each of the plate springs51. Thus, a torque capacity which can be transmitted between the armature plate20and the first rotor10can be increased without requiring enlargement of the electromagnetic coil30.

Also, a force in the direction away from the first rotor10acts on the first bent portion51eby reaction of the pressing force for pressing the armature plate20. However, the extension portion40bof the second rotor40is brought into contact with the first bent portion51efrom the direction opposite to the first rotor10. Thus, a stress generated in the first bent portion51eof the plate spring51is dispersed to the extension portion40bside. Also, the first bent portion51eis not deformed in the direction away from the first rotor10. That is, the stress concentrating on the first bent portion51eis alleviated.

Moreover, a force in the direction away from the first rotor10acts on the first bent portion51eby the reaction of the pressing force for pressing the armature plate20. However, the extension portion40bof the second rotor40is brought into contact with the first bent portion51efrom the direction opposite to the first rotor10. Therefore, deformation of the first bent portion51ein the direction away from the first rotor10is regulated. Thus, the pressing force generated by the inclined portion51gacts on the armature plate20without being decreased by deformation of the first bent portion51e.

In this way, in the electromagnetic clutch of this preferred embodiment, the stress concentrating on the first bent portion51eof each of the plate springs51is alleviated. Therefore, deformation or strength drop is not generated in each of the plate springs51even in use for a long time, and durability of each of the plate springs51can be improved.

Also, the pressing force generated by the inclined portion51gacts on the armature plate20without being decreased by deformation of the first bent portion51e. Therefore, the connecting force between the armature plate20and the first rotor10can be surely increased by each of the plate springs51. That is, it is extremely advantageous in increasing the torque capacity which can be transmitted between the armature plate20and the first rotor10.

An electromagnetic clutch provided with three plate springs51is shown in this preferred embodiment. However, it is possible to provide two plate springs on the electromagnetic clutch and it is also possible to provide four or more plate springs51.

In this preferred embodiment, an example formed so that the plate spring51has a uniform width dimension between the one end side and the other end side is shown. However, it is possible to form a vicinity of the first bent portion51ewider than the other portion of the plate spring51(SeeFIG. 5). By this, the first bent portion51ehas a sectional area larger than the other portion of the plate spring51. Therefore, a stress generated in the first bent portion51eis dispersed by the larger sectional area, and the stress concentrating on the first bent portion51eis further alleviated. By this, even if the extension portion40bis not brought into contact with the first bent portion51e, a deformation amount that the first bent portion51eis deformed in the direction away from the first rotor10is suppressed. Also, the stress generated in the first bent portion51eis dispersed by the larger sectional area. That is, even if the contact member is not brought into contact with the first bent portion51ein the direction opposite to the first rotor10, the stress concentrating on the first bent portion51eis alleviated.

Also, it is possible to form one side of the plate spring51in the width direction in the arc state so that the vicinity of the first bent portion51ehas a sectional area larger than the other portion of the plate spring51(SeeFIG. 6).

In this preferred embodiment, a single plate with spring50is provided between the armature plate20and the second rotor40. However, it is possible to overlap another plate with spring50on the face of the plate with spring50on the first rotor10side (SeeFIG. 7). By this, it is worried that the urging force by each of the plate springs50becomes large.FIG. 8is an experiment result of measurement of the relations between a displacement amount of the armature plate20and a load with respect to the second rotor40. Referring toFIG. 8, a difference between a measurement result K1in the case of a single plate with spring50and a measurement result K2in the case of two plates with spring50is slight. That is, an increase in the urging force caused by overlapping of the plates with spring50is slight and it is not necessary to increase an attracting force by enlarging the electromagnetic coil30. Also, when the plate springs51are overlapped each other, the stress generated in the bent portion51eon one of the plate springs51is dispersed to the other overlapped plate spring51. Therefore, the stress concentrating on the first bent portion51eis further alleviated. That is, even if the extension portion40bis not brought into contact with the first bent portion51e, the deformation amount that the bent portion51eis deformed in the direction away from the first rotor10is suppressed by the amount of overlapping of the plate springs51. Also, the stress generated in the first bent portion51eof one of the plate springs51is dispersed to the other overlapped plate spring51. That is, even if the contact member is not brought into contact with the first bent portion51efrom the direction opposite to the first rotor10, the stress concentrating on the first bent portion51eis alleviated.

In this preferred embodiment, a single plate with spring50is provided between the armature plate20and the second rotor40. However, it is possible to overlap a first reinforcing plate54and a second reinforcing plate55on the first rotor10side of the plate with spring50(SeeFIG. 9). Each of the reinforcing plates54and55has the thickness equivalent to the plate with spring50. Each of the reinforcing plates54and55is formed conforming to the plate with spring50. Each of the reinforcing plates54and55is provided with plate springs for reinforcement54aand55a. Each of the plate springs for reinforcement54aand55ais formed shorter than the plate spring51. Here, each of the plate springs for reinforcement54aand55aextends to the middle of the inclined portion51gof the plate spring51, and each of the plate springs51,54aand55ais bonded to each other by welding or the like. By this, a stress generated in the first bent portion51eof the plate spring51is dispersed to each of the plate springs for reinforcement54aand55a. That is, the stress concentrating on the first bent portion51eis further alleviated. Even if the extension portion40bis not brought into contact with the first bent portion51e, the deformation amount that the first bent portion51eis deformed in the direction away from the first rotor10is suppressed by the amount of overlapping each of the plate springs for reinforcement54aand55aon the plate spring51. Also, the stress generated in the first bent portion51eis dispersed to each of the plate springs for reinforcement54aand55a. That is, even if the contact member is not brought into contact with the first bent portion51efrom the direction opposite to the first rotor10, the stress concentrating on the first bent portion51eis alleviated.

It is also possible to overlap each of the reinforcing plates54and55on the face side of the plate with spring50opposite to the first rotor10(SeeFIG. 10). Even if each of the plate springs51,54aand55ais not bonded to each other, the stress generated in the first bent portion51eof the plate spring51is dispersed to each of the plate springs for reinforcement54aand55a. Also, the deformation of the first bent portion51ein the direction opposite to the first rotor10is regulated by each of the plate springs for reinforcement54aand55a. By this, the stress concentrating on the first bent portion51eis alleviated.

In this preferred embodiment, a single plate with spring50is provided between the armature plate20and the second rotor40. However, it is possible to provide three plate with springs52having the same shape as the plate with spring50(SeeFIGS. 11 and 12) in place of the plate with spring50. Each of the plate with springs52has the thickness of one third of that of the plate with spring50. The thickness of each of the plate with springs52in which three plate springs53are overlapped has the thickness equivalent to that of the plate spring51. Therefore, even if a force in the direction away from the first rotor10acts on a bent portion53aof each of the plate springs53by reaction of the pressing force for pressing the armature plate20onto the first rotor10side, a stress is generated in each of the plate springs53individually. Therefore, when compared with the bent portion51eof the single plate spring51, a compression deformation of each of the plate springs53inward in the bending direction and a tension deformation outward in the bending direction are small. That is, the stress concentrating on the bent portion53aof each of the plate springs53is further alleviated. Thus, even if the contact member is not brought into contact with the bent portion53afrom the direction opposite to the first rotor10, the deformation in the bent portion53ainward in the bending direction and outward in the bending direction is small as compared with the case formed by a single plate spring51when the bent portion53ais deformed in the direction opposite to the first rotor10. That is, the stress concentrating on the bent portion53aof each of the plate springs53is alleviated.

The preferred embodiments described in this specification are illustrative and not restrictive. The scope of invention is given by the appended claims, and all changes and modifications included in the meaning of claims are embraced in the present invention.