Power transmission device

Abstract

To improve magnetic efficiency of an electromagnetic clutch in a power transmission device in which an engagement element type clutch and the electromagnetic clutch are combined.SOLUTION: An electromagnet 23 of an electromagnetic clutch 20 is formed by inserting and fixing a non-magnetic bobbin 26 around which a solenoid coil 27 is wound inside an annular field core 25 having a C-shaped cross section that opens in an axial direction toward an armature 22. A separating spring 24 for energizing the armature 22 in a direction separating from the electromagnet 23 is arranged in a state where its one end part is housed in an annular concave part 26a formed on an opposing surface to the armature 22 of the bobbin 26 and the other end part abuts against an opposing surface to the electromagnet 23 of the armature 22. Thereby, the concave part for supporting the separating spring of the conventional armature is no longer required so that a cross sectional area of a magnetic path passing through the armature 22 becomes larger and magnetic efficiency of the electromagnetic clutch 20 can be improved.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present invention relates to a power transmission device in which the power of a rotationally driven input member is transmitted to a stationary member, thereby enabling the input member to be stopped at any desired timing. [Background technology]

[0002] A known power transmission device that enables a rotationally driven input member to be stopped at any time uses a combination of an engagement type clutch and an electromagnetic clutch to switch between transmitting and cutting off power from the input member to a stationary member (see, for example, Patent Document 1).

[0003] As shown in FIG. 9, the power transmission device disclosed in Patent Document 1 comprises a shaft 51 as an input member that is rotated, a case 52 as a stationary member that is stationary relative to the shaft 51, an engagement type clutch 60 provided between the shaft 51 and the case 52, and an electromagnetic clutch 70 that switches the engagement type clutch 60 between an engaged state and a disengaged state.

[0004] The engagement type clutch 60 is assembled between an inner ring 61 formed integrally with the shaft 51 and an outer ring 62 fixed to the case 52, with a plurality of rollers 63 as engagement elements held by a cage 64. The electromagnetic clutch 70 has an armature 72 that engages with the cage 64 of the engagement type clutch 60 in the circumferential direction via an intermediate plate 71, an electromagnet 73 that faces the armature 72 with a specified gap in the axial direction, and a separation spring 74 that urges the armature 72 in a direction away from the electromagnet 73.

[0005] The electromagnet 73 of the electromagnetic clutch 70 is formed by winding a solenoid coil 76 around an annular field core 75. The separation spring 74 is disposed such that one end of the separation spring 74 abuts against the surface of the field core 75 facing the armature 72, and the other end of the separation spring 74 is accommodated in an annular recess 72a formed in the surface of the armature 72 facing the field core 75.

[0006] When the electromagnet 73 is energized, the armature 72 is attracted to the field core 75, and the engagement type clutch 60 is engaged when power (rotational torque) is applied to the shaft 51, and power is transmitted from the shaft 51 to the case 52 via the engagement type clutch 60, stopping the rotation of the shaft 51. On the other hand, when the electromagnet 73 is not energized, the armature 72 moves away from the electromagnet 73, the engagement type clutch 60 is disengaged, the transmission of power from the shaft 51 to the case 52 is cut off, and the shaft 51 is allowed to rotate freely. In other words, this power transmission device is an excitation type that operates (transmits power) when current is applied to the electromagnetic clutch 70. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] JP 2023-055395 A Summary of the Invention [Problem to be solved by the invention]

[0008] However, in the power transmission device of Patent Document 1, the armature 72 of the electromagnetic clutch 70 has an annular recess 72a on the surface facing the field core 75 to accommodate the other end of the separation spring 74, so this portion cannot be used as a magnetic path, resulting in a problem of poor magnetic efficiency of the electromagnetic clutch 70.

[0009] SUMMARY OF THE PRESENT DISCLOSURE ... In view of the above, an object of the present invention is to improve the magnetic efficiency of an electromagnetic clutch in a power transmission device in which an engagement type clutch and an electromagnetic clutch are combined. [Means for solving the problem]

[0010] In order to solve the above problems, the present invention provides an engagement type clutch comprising an input side member which is driven to rotate, a stationary member which is stationary relative to the input side member, an inner ring fixed to one of the input side member and the stationary member, and an outer ring fixed to the other of the input side member and the stationary member, with an engagement element held by a retainer, wherein the retainer moves the engagement element relative to the inner ring and the outer ring in a circumferential direction, thereby switching between an engaged state in which the engagement element engages with the inner ring and the outer ring and a disengaged state in which the engagement element does not engage with the inner ring and the outer ring, and an electromagnetic clutch which switches the engagement state and disengaged state of the engagement type clutch, In an excitation type power transmission device, the electromagnetic clutch has an armature that engages with a retainer of the engagement type clutch in the circumferential direction, an electromagnet having a solenoid coil wound around an annular field core that faces the armature with a specified gap in the axial direction, and a separation spring that urges the armature in a direction away from the electromagnet, and when current is applied to the electromagnet, the armature is attracted to the field core, thereby putting the engagement type clutch in an engaged state, and when current is not applied to the electromagnet, the armature is separated from the electromagnet, thereby putting the engagement type clutch in a disengaged state, A non-magnetic member covering the side of the solenoid coil facing the armature is fixed to the field core of the electromagnetic clutch, and one end of the repulsion spring is accommodated in a recess formed in the surface of the non-magnetic member facing the armature (configuration 1). The method of fixing the input side member and the inner or outer ring, and the method of fixing the stationary member and the inner or outer ring include integral formation of both members to be fixed (the same applies below).

[0011] The present invention also provides an engagement type clutch comprising an input side member which is driven to rotate, a stationary member which is stationary relative to the input side member, an inner ring fixed to one of the input side member and the stationary member, and an outer ring fixed to the other of the input side member and the stationary member, with an engagement element held by a cage, and the cage moves the engagement element relative to the inner ring and the outer ring in the circumferential direction, thereby switching between an engaged state in which the engagement element engages with the inner ring and the outer ring and a disengaged state in which the engagement element does not engage with the inner ring and the outer ring, and an electromagnetic clutch which switches the engagement state and disengaged state of the engagement type clutch, a non-excitation type power transmission device in which the electromagnetic clutch has an armature that engages with a retainer of the engagement type clutch in the circumferential direction, an electromagnet having a solenoid coil wound around an annular field core that faces the armature with a specified gap in the axial direction, and a separation spring that urges the armature in a direction away from the electromagnet, the separation spring pressing the armature against a rotating ring which is one of the inner ring and outer ring that is fixed to the input side member, when current is applied to the electromagnet, the armature is attracted to the field core and moves away from the rotating ring, thereby disengaging the engagement type clutch, and when current is not applied to the electromagnet, the armature is pressed against the rotating ring, thereby engaging the engagement type clutch; A configuration (configuration 2) can also be adopted in which a non-magnetic member covering the side of the solenoid coil facing the armature is fixed to the field core of the electromagnetic clutch, and one end of the repulsion spring is accommodated in a recess formed in the surface of the non-magnetic member facing the armature.

[0012] In the power transmission device of the above configuration 1 or 2, by forming a recess for accommodating one end of the separation spring in a portion not related to the magnetic path of the electromagnet of the electromagnetic clutch, the recess in the armature for accommodating the other end of the conventional separation spring is not required, so that the cross-sectional area of ​​the magnetic path passing through the armature can be made larger than in the conventional case, thereby improving the magnetic efficiency of the electromagnetic clutch.

[0013] In the above configuration 1 or 2, the non-magnetic member may be a bobbin around which the solenoid coil is wound.

[0014] In any of the above configurations 1 to 3, if the non-magnetic member is provided with a metal plate that is in sliding contact with the repulsion spring inside the recess, wear of the non-magnetic member can be prevented even when the rotational speed of the input side member is high, which is preferable. Effect of the Invention

[0015] As described above, in the power transmission device of the present invention, a recess for supporting the repulsion spring is formed in a portion of the electromagnetic clutch that is not related to the magnetic path of the electromagnet, eliminating the need for a recess in the armature for supporting the repulsion spring. Therefore, the cross-sectional area of ​​the magnetic path passing through the armature can be made larger than in the conventional case, improving the magnetic efficiency of the electromagnetic clutch.

[0016] Furthermore, since there is no need to form a recess in the armature for supporting the recoil spring, the armature can be formed only by pressing, which also reduces the manufacturing costs of the armature. [Brief description of the drawings]

[0017] [Figure 1] FIG. 1 is a longitudinal sectional front view of a power transmission device according to a first embodiment of the present invention; [Diagram 2] Cross-sectional view taken along line II-II in Figure 1. [Diagram 3] FIG. 2 is an enlarged longitudinal sectional front view of the main part of FIG. 1; [Figure 4] FIG. 4 is a longitudinal sectional front view of a main part showing a modified example of the separation spring accommodating portion corresponding to FIG. 3; [Diagram 5] FIG. 11 is a longitudinal sectional front view of a power transmission device according to a second embodiment of the present invention; [Figure 6] Cross-sectional view taken along line VI-VI in Figure 5. [Figure 7] FIG. 13 is a longitudinal sectional front view of a power transmission device according to a third embodiment of the present invention; [Figure 8] FIG. 8 is a longitudinal sectional front view showing a modified example of the armature and its vicinity shown in FIG. [Figure 9] FIG. 1 is a longitudinal sectional front view of a conventional power transmission device; DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0018] Hereinafter, an embodiment of the present invention will be described with reference to Fig. 1 to Fig. 8. Fig. 1 to Fig. 3 show an excitation type power transmission device according to a first embodiment of the present invention. The basic configuration and operation of the power transmission device of the first embodiment are the same as the conventional one shown in Fig. 9 above, and the configuration and operation will be described in detail below, along with the differences from the conventional one.

[0019] 1, this power transmission device includes a shaft 1 as an input member that is rotationally driven, a cylindrical case 2 as a stationary member that is stationary relative to the shaft 1, an engagement type clutch 10 provided between the shaft 1 and the case 2, and an electromagnetic clutch 20 that switches the engagement type clutch 10 between an engaged state and a disengaged state. A bearing 3 is disposed between the outer periphery of one end of the shaft 1 and the inner periphery of the case 2 to rotatably support the shaft 1.

[0020] As shown in Figures 1 and 2, the engagement type clutch 10 has a plurality of rollers 13 as engagement elements held by a retainer 14 between an inner ring 11 as a rotating ring formed integrally with the shaft 1 and an outer ring 12 fixed to a case 2, and has a centering spring 15 that is prevented from rotating by the inner ring 11 and the retainer 14.

[0021] The inner ring 11 is spline-fitted to the outer periphery of an input shaft such as a motor shaft (not shown), and is rotated integrally with the shaft 1 by the rotational torque transmitted from the input shaft. In this embodiment, the inner ring 11 and the shaft 1 are formed integrally, but the inner ring formed separately from the shaft to be rotated may be fixed to the shaft. A bearing 16 is disposed between the outer periphery of the inner ring 11 and the inner periphery of the outer ring 12 to rotatably support the inner ring 11.

[0022] The outer ring 12 is prevented from rotating relative to the case 2 by fitting a common key member 17 into a key groove 12 a formed on the outer periphery of the outer ring 12 and a key groove 2 a formed on the inner periphery of the case 2 .

[0023] A plurality of cam surfaces 11a are formed on the outer periphery of the inner ring 11, and each cam surface 11a faces radially an inner cylindrical surface 12b of the outer ring 12. As a result, a wedge-shaped space 18 that gradually narrows from the circumferential center toward both ends is formed between each cam surface 11a and the cylindrical surface 12b of the outer ring 12, and one roller 13 is disposed in each wedge-shaped space 18.

[0024] The cage 14 is an annular member in which a plurality of radially penetrating pockets 14a are formed at intervals in the circumferential direction, and is assembled so that, with each pocket 14a housing one roller 13, its axial movement is restricted and it is supported so as to be circumferentially movable with respect to the inner ring 11. When the rollers 13 held by the cage 14 are in the wide portion (circumferential center portion) of the wedge-shaped space 18, the engagement type clutch 10 is in a disengaged state in which the rollers 13 do not engage with the inner ring 11 and the outer ring 12, and when the cage 14 moves the rollers 13 relatively to the narrow portion of the wedge-shaped space 18, the engagement type clutch 10 is in an engaged state in which the rollers 13 engage with the inner ring 11 and the outer ring 12.

[0025] The centering spring 15 is composed of a C-shaped annular portion 15a and a pair of hooks 15b extending radially outward from both ends of the C-shaped annular portion 15a. The C-shaped annular portion 15a is fitted into an annular groove 11b formed on one axial end face of the inner ring 11, and the pair of hooks 15b is fitted into a radial groove 11c penetrating from the annular groove 11b to the outer periphery of the inner ring 11. The hooks 15b protrude radially outward from the radial groove 11c of the inner ring 11 into a retainer groove 14b formed in the retainer 14 with the same circumferential width as the radial groove 11c, and are in contact with the inner groove inner surfaces at both circumferential ends of the radial groove 11c and the groove inner surfaces at both circumferential ends of the retainer groove 14b. As a result, the centering spring 15 is prevented from rotating by the inner ring 11, and elastically holds the retainer 14 in a position where the rollers 13 do not engage with the inner ring 11 and the outer ring 12.

[0026] As shown in Figures 1 and 3, the electromagnetic clutch 20 has a disk-shaped intermediate plate 21 that is fitted onto the outer periphery of the shaft 1 on one axial side of the engagement type clutch 10 (the right side of the drawing), a disk-shaped armature 22 that is fitted around the outer periphery of the shaft 1 on one axial side of the intermediate plate 21, an electromagnet 23 that faces the armature 22 on one axial side with a specified gap between them, and a separation spring 24 that urges the armature 22 in a direction away from the electromagnet 23.

[0027] The intermediate plate 21 is fitted onto the outer periphery of the shaft 1 in a state in which it is rotatable but immovable in the axial direction, and also serves to prevent the centering spring 15 of the engagement type clutch 10 from slipping out of the inner ring 11. An engagement protrusion 21a having an L-shaped cross section formed on the outer periphery of this intermediate plate 21 is inserted without any gap in the circumferential direction into both an engagement recess 14c formed in the cage 14 and an axial hole 22a formed in the armature 22. In other words, the cage 14 and the armature 22 are engaged with each other in the circumferential direction via this intermediate plate 21.

[0028] The armature 22 is made of a magnetic material (iron, silicon steel, etc.) and is fitted onto the outer periphery of the shaft 1 in a state in which it can rotate freely and move axially.

[0029] The electromagnet 23 has an annular field core 25 having a C-shaped cross section that opens toward the armature 22 in the axial direction, a resin bobbin 26 disposed inside the C-shaped cross section of the field core 25, and a solenoid coil 27 wound around the field core 25 via the bobbin 26, and is fixed inside the case 2. The bobbin 26 is inserted inside the C-shaped cross section of the field core 25 with the solenoid coil 27 wound around it, and is fixed to the field core 25 in a state where it covers the side of the solenoid coil 27 that faces the armature 22 by crimping several places on the open side of the field core 25. Examples of the type of resin that forms the bobbin 26 include PA66 (polyamide 66) and PPS (polyphenylene sulfide). In this example, the bobbin 26 is made of resin that has good workability, but the bobbin may be made of any non-magnetic material. The solenoid coil 27 is supplied with power from a lead wire 28 that passes through a through hole 2b formed at one end of the case 2. A rubber grommet 29 is attached between the lead wire 28 and the inner circumference of the through hole 2b of the case 2 to fill the gap.

[0030] The recoil spring 24 is made of an annular spring such as a wave washer, one end of which is accommodated in an annular recess 26a formed on the surface of the bobbin 26 facing the armature 22, and the other end of which is arranged in contact with the surface of the armature 22 facing the electromagnet 23.

[0031] In this electromagnetic clutch 20, when the electromagnet 23 is not energized and in a non-excited state, the biasing force of the separation spring 24 supports the armature 22 at a position axially spaced from the electromagnet 23, thereby enabling the armature 22 to rotate, and the cage 14 engaged with the armature 22 in the circumferential direction via the intermediate plate 21 also becomes rotatable. On the other hand, when the electromagnet 23 is energized, the electromagnet 23 becomes an excited state generating a magnetic circuit passing through the field core 25 and the armature 22, attracting the armature 22 toward the field core 25 against the elastic force of the separation spring 24, and the armature 22 compresses the separation spring 24 in the axial direction and presses it against the end face of the field core 25. At this time, the armature 22, the intermediate plate 21 and the cage 14 become non-rotatable due to the frictional resistance of the contact surfaces of the armature 22 and the field core 25.

[0032] This power transmission device can switch between transmitting and cutting off power from the shaft 1 to the case 2 by combining the operations of the above-mentioned engagement clutch 10 and electromagnetic clutch 20, thereby stopping the rotationally driven shaft 1 at any timing.

[0033] That is, when the electromagnet 23 of the electromagnetic clutch 20 is not energized and in a non-excited state, the armature 22 is separated from the electromagnet 23 by the separation spring 24 and is in a state in which it can rotate together with the intermediate plate 21 and the retainer 14. At this time, even if power (rotational torque) is applied to the input shaft splined to the inner ring 11 and the shaft 1 and the inner ring 11 rotate together in either forward or reverse direction, the retainer 14 is rotated by the centering spring 15 which rotates together with the inner ring 11, so that the engagement type clutch 10 maintains a disengaged state in which the rollers 13 are not engaged with the inner ring 11 and the outer ring 12, power is not transmitted from the shaft 1 (the inner ring 11 integral with the shaft 1) to the case 2, and the shaft 1 (and the input shaft) are in an idling state in which they can rotate freely.

[0034] On the other hand, when the electromagnet 23 of the electromagnetic clutch 20 is energized to be in an excited state, the armature 22 is attracted to the electromagnet 23 against the elastic force of the separation spring 24, and is in frictional contact with the end face of the field core 25. At this time, when power is applied to the input shaft and the shaft 1 and the inner ring 11 rotate in either the forward or reverse direction, the power of the shaft 1 is transmitted from the centering spring 15, which rotates integrally with the input shaft 1, to the cage 14. However, since a braking force due to frictional resistance between the armature 22, which is engaged with the cage 14 in the circumferential direction via the intermediate plate 21, and the field core 25 acts on the cage 14, the inner ring 11 rotates relative to the cage 14 while the inner surface of the radial groove 11c pushes one of the pair of hooks 15b of the centering spring 15 in the circumferential direction and bends it. As a result, the rollers 13 held by the retainer 14 move relatively toward the narrow portion of the wedge-shaped space 18, and the engaging clutch 10 enters an engaged state in which the rollers 13 engage with the inner ring 11 and the outer ring 12, and power is transmitted from the shaft 1 to the case 2 via the engaging clutch 10, stopping the rotation of the shaft 1.

[0035] The configuration and operation of the power transmission device of this first embodiment are as described above, and the difference from the conventional one (FIG. 9) is in the support structure of the separation spring 24 of the electromagnetic clutch 20. That is, in the conventional one in FIG. 9, the other end of the separation spring 74 is accommodated in the annular recess 72a formed in the surface of the armature 72 facing the electromagnet 73, but in this first embodiment, one end of the separation spring 24 is accommodated in the annular recess 26a formed in the surface of the bobbin 26 facing the armature 22.

[0036] As a result, the power transmission device of the first embodiment has a larger cross-sectional area of ​​the magnetic path passing through the armature 22 than the conventional one, and the magnetic efficiency of the electromagnetic clutch 20 is high. Also, since the armature 22 can be formed only by pressing, the manufacturing cost can be reduced compared to the conventional one, which requires the formation of the recess 72a after pressing the armature 72.

[0037] 4 shows a modified example of the housing for the separation spring 24 of the electromagnetic clutch 20. In this modified example, an annular metal plate 30 that slides against one end of the separation spring 24 inside the recess 26a of the resin bobbin 26 is integrated by insert molding, thereby preventing wear of the bobbin 26 even when the rotation speed of the shaft 1 is high.

[0038] 5 and 6 show a power transmission device of a second embodiment. In this second embodiment, an engagement type clutch 40 having an inner ring fixed / outer ring rotating structure is incorporated instead of the engagement type clutch 10 having an outer ring fixed / inner ring rotating structure of the first embodiment. In addition, in accordance with this, a two-stage cylindrical case 4 different from that of the first embodiment is adopted, and the shaft 1 is fixed to the case 4 via an electromagnet 23 and becomes a part of the stationary member.

[0039] In the second embodiment, the case 4 has an opening on one end that is closed by a lid 5 that is fixed by welding or the like to the field core 25 of the electromagnet 23. The lid 5 has a through hole 5a through which the lead wire 28 of the electromagnet 23 passes, and a grommet 29 is attached between the inner periphery of the through hole 5a and the lead wire 28, and is fixed to the case 4 with screws.

[0040] The engagement type clutch 40 has a plurality of rollers 43 as engagement elements held by a retainer 44 between an inner ring 41 formed integrally with the shaft 1 and an outer ring 42 having a shaft portion 42a as an input side member, and has a centering spring 45 that is prevented from rotating by the outer ring 42 and the retainer 44.

[0041] The outer ring 42 has a shaft portion 42a spline-fitted to the outer periphery of an input shaft (not shown) and is rotationally driven by rotational torque transmitted from the input shaft. A bearing 46 is disposed between the outer periphery of the outer ring 42 and the inner periphery of the case 4 to rotatably support the outer ring 42.

[0042] A plurality of cam surfaces 42b are formed on the inner circumference of the outer ring 42, and each cam surface 42b faces radially an outer cylindrical surface 41a of the inner ring 41. As a result, a wedge-shaped space 47 that gradually narrows from the circumferential center toward both ends is formed between each cam surface 42b and the cylindrical surface 41a of the inner ring 41, and one roller 43 is disposed in each wedge-shaped space 47.

[0043] The cage 44 is an annular member that houses the rollers 43 one by one in a number of pockets 44a, as in the first embodiment, but is assembled so that its axial movement is restricted with respect to the outer ring 42 and it is supported so as to be movable in the circumferential direction. And, as in the first embodiment, the engagement type clutch 40 is switched between a disengaged state and an engaged state by changing the relative position of the rollers 43 held by the cage 44 with respect to the wedge-shaped space 47.

[0044] The centering spring 45 is composed of a C-shaped annular portion 45a and a pair of hooks 45b similar to those in the first embodiment, and the C-shaped annular portion 45a is fitted into an annular groove 44b formed on the inner circumference of the axial center portion of the cage 44, and the pair of hooks 45b is fitted into a cage groove 44c penetrating the cage 44 in the radial direction and a radial groove 42c formed on one axial end face of the outer ring 42. The cage groove 44c and the radial groove 42c of the outer ring 42 are formed to have the same circumferential width, and the hooks 45b are in contact with the inner groove surface at both circumferential ends of the cage groove 44c and the inner groove surface at both circumferential ends of the radial groove 42c of the outer ring 42, respectively. As a result, the centering spring 45 is prevented from rotating by the outer ring 42, and the cage 44 is elastically held in a position where the rollers 43 do not engage with the inner ring 41 and the outer ring 42.

[0045] As shown in Fig. 5, the electromagnetic clutch 20 does not have the intermediate plate 21 of the first embodiment, and an engagement protrusion 44d formed at one end of a cage 44 is inserted into an axial hole 22a of an armature 22 without a circumferential gap, so that the armature 22 is directly engaged with the cage 44 in the circumferential direction. Also, a field core 25 of an electromagnet 23 is fixed to the shaft 1 by a tolerance ring 31, so that the shaft 1 and the inner ring 41 are stationary with respect to the outer ring 42. In this example, the field core 25 and the shaft 1 are fixed via the tolerance ring 31, but a method of directly fixing the outer circumference of the shaft 1 to the inner circumference of the field core 25 (for example, by spline fitting) may also be used. The configuration and operation of other parts are the same as those of the first embodiment.

[0046] The power transmission device of the second embodiment has the above-mentioned configuration, and when the electromagnetic clutch 20 is in a non-excited state with no current flowing through it, even if the outer ring 42 rotates, the engagement type clutch 40 remains in a disengaged state, no power is transmitted from the outer ring 42 to the shaft 1, and the outer ring 42 is in an idling state. On the other hand, when the electromagnetic clutch 20 is in an excited state with current flowing through it, if the outer ring 42 rotates slightly, the engagement type clutch 40 enters an engaged state, power is transmitted from the outer ring 42 to the shaft 1 via the engagement type clutch 40, and the rotation of the outer ring 42 is stopped. The mechanism for switching between the state in which power transmission is possible and the state in which it is cut off is the same as in the first embodiment, and therefore a description thereof will be omitted.

[0047] In this second embodiment, as in the first embodiment, the electromagnetic clutch 20 accommodates one end of the separation spring 24 in the recess 26a of the bobbin 26, thereby achieving higher magnetic efficiency than the conventional one and reducing the manufacturing costs of the armature.

[0048] 7 shows a power transmission device of a third embodiment. This third embodiment is based on the excitation type power transmission device of the second embodiment, which is changed to a non-excitation type. The differences from the second embodiment will be described below.

[0049] The engagement type clutch 40 of the third embodiment has an inner ring fixed and an outer ring rotating like the second embodiment, but the configuration for switching between the disengaged state and the engaged state is similar to that of the first embodiment.

[0050] That is, first, the cage 44 is assembled so that its axial movement is restricted relative to the inner ring 41 and it is supported so as to be movable in the circumferential direction. Although not shown, a plurality of cam surfaces are formed on the outer periphery of the inner ring 41, the inner circumferential surface of the outer ring 42 is a cylindrical surface, and one roller 43 is disposed in a wedge-shaped space formed between each cam surface and the cylindrical surface of the outer ring 42. The centering spring 45 has a C-shaped annular portion 45a fitted into an annular groove 41b formed on one axial end surface of the inner ring 41, and a pair of hooks 45b inserted into the radial groove 41c of the inner ring 41 and the cage groove 44c of the cage 44, and is in contact with the inner surfaces of the radial groove 41c at both circumferential ends and the inner surfaces of the cage groove 44c at both circumferential ends.

[0051] In the electromagnetic clutch 20, like the first embodiment, the engaging protrusion 21a of the intermediate plate 21 is inserted into the engaging recess 44e of the retainer 44 and the axial hole 22a of the armature 22 with no circumferential gap, and the retainer 44 and the armature 22 are engaged in the circumferential direction via the intermediate plate 21. In addition, the separating spring 24 presses the armature 22 against the outer ring 42, which is a rotating ring of the engagement type clutch 40.

[0052] The power transmission device of the third embodiment has the above-mentioned configuration, and when the electromagnetic clutch 20 is not energized and in a non-excited state, the armature 22 is pressed against the outer ring 42, so that when the outer ring 42 rotates slightly, the cage 44 engaged with the armature 22 in the circumferential direction also rotates slightly, and the engagement type clutch 40 enters an engaged state, power is transmitted from the outer ring 42 to the shaft 1 via the engagement type clutch 40, and the rotation of the outer ring 42 is stopped. On the other hand, when the electromagnetic clutch 20 is energized and in an excited state, the armature 22 is attracted to the field core 25 and separated from the outer ring 42, so that the engagement type clutch 40 enters a disengaged state, power is not transmitted from the outer ring 42 to the shaft 1, and the outer ring 42 enters an idling state.

[0053] 8 shows a modification of the third embodiment. In this modification, a friction plate 32 that engages with the intermediate plate 21 in the circumferential direction is fixed by adhesion or the like to the other axial side surface of the armature 22 of the electromagnetic clutch 20, and the axial hole 22a of the armature 22 is eliminated. As a result, the armature 22 is pressed against the outer ring 42 via the friction plate 32, and is engaged with the cage 44 in the circumferential direction via the friction plate 32 and the intermediate plate 21. By using a friction plate 32 that has a larger friction resistance with the outer ring 42 than the armature 22, the outer ring 42 can be stopped more reliably by the power transmission from the outer ring 42 to the shaft 1 in the non-excited state.

[0054] In the above-described third embodiment and its modified example, the electromagnetic clutch 20 accommodates one end of the separation spring 24 in the recess 26a of the bobbin 26, and therefore the same effects as those of the first and second embodiments can be achieved.

[0055] The embodiments disclosed herein should be considered to be illustrative and not restrictive in all respects. The scope of the present invention is defined by the claims, not the above description, and is intended to include all modifications within the meaning and scope of the claims.

[0056] For example, in the above-described second and third embodiments and their modified examples, as in the modified example of the first embodiment, a bobbin for the electromagnetic clutch can be used that is integrated with a metal plate that comes into sliding contact with the separation spring.

[0057] Also, instead of the bobbin of the electromagnetic clutch, another non-magnetic member may be used that is fixed to the field core and covers the side of the solenoid coil that faces the armature, and a recess that accommodates one end of the recoil spring may be formed on the surface of the non-magnetic member that faces the armature. In this case, the non-magnetic member may be a simple disk-shaped member or one with an L-shaped cross section.

[0058] The power transmission device of the present invention can be widely used in drive parts and steering devices of vehicles (including multipurpose vehicles), ships, construction machines, and the like. [Explanation of symbols]

[0059] 1-axis 2, 4 cases 10, 40 Engagement type clutch 11, 41 Inner circle 12, 42 Outer ring 13, 43 Roller (engagement element) 14, 44 retainer 20 Electromagnetic clutch 22 Armature 23 Electromagnet 24 Breakup spring 25 Field Core 26 Bobbin (non-magnetic part) 26a Recess 27 Solenoid coil 30 Metal Plate 32 Friction plate

Claims

1. An input side member that is rotationally driven; a stationary member that is stationary with respect to the input member; an engagement type clutch (10, 40) in which an engagement element (13, 43) is incorporated between an inner ring (11, 41) fixed to one of the input side member and the stationary member, and an outer ring (12, 42) fixed to the other of the input side member and the stationary member, in a state where the engagement element (13, 43) is held by a retainer (14, 44), and the retainer (14, 44) moves the engagement element (13, 43) relative to the inner ring (11, 41) and the outer ring (12, 42) in the circumferential direction, thereby switching between an engaged state in which the engagement element (13, 43) engages with the inner ring (11, 41) and the outer ring (12, 42) and a disengaged state in which the engagement element (13, 43) does not engage with the inner ring (11, 41) and the outer ring (12, 42); an electromagnetic clutch (20) for switching the engagement type clutch (10, 40) between an engaged state and a disengaged state, The electromagnetic clutch (20) includes an armature (22) that circumferentially engages with a retainer (14, 44) of the engagement type clutch (10, 40), an electromagnet (23) having a solenoid coil (27) wound around an annular field core (25) that faces the armature (22) with a predetermined gap in the axial direction, and a separation spring (24) that biases the armature (22) in a direction away from the electromagnet (23), In this excitation type power transmission device, when the electromagnet (23) is energized, the armature (22) is attracted to the field core (25), thereby bringing the engagement type clutch (10, 40) into an engaged state, and when the electromagnet (23) is not energized, the armature (22) is separated from the electromagnet (23), thereby bringing the engagement type clutch (10, 40) into a disengaged state, a non-magnetic member (26) covering the side of the solenoid coil (27) facing the armature (22) is fixed to a field core (25) of the electromagnetic clutch (20), and one end of the repulsion spring (24) is accommodated in a recess (26a) formed on the surface of the non-magnetic member (26) facing the armature (22).

2. An input side member that is rotationally driven; a stationary member that is stationary with respect to the input member; an engagement element type clutch (40) in which an engagement element (43) is incorporated between an inner ring (41) fixed to one of the input side member and the stationary member and an outer ring (42) fixed to the other of the input side member and the stationary member while being held by a retainer (44), and the retainer (44) moves the engagement element (43) relative to the inner ring (41) and the outer ring (42) in the circumferential direction, thereby switching between an engaged state in which the engagement element (43) engages with the inner ring (41) and the outer ring (42) and a disengaged state in which the engagement element (43) does not engage with the inner ring (41) and the outer ring (42); an electromagnetic clutch (20) for switching the engagement type clutch (40) between an engaged state and a disengaged state, The electromagnetic clutch (20) includes an armature (22) that engages with a retainer (44) of the engagement type clutch (40) in the circumferential direction, an electromagnet (23) having a solenoid coil (27) wound around an annular field core (25) that faces the armature (22) with a predetermined gap in the axial direction, and a separation spring (24) that biases the armature (22) in a direction away from the electromagnet (23), and the separation spring (24) presses the armature (22) against a rotating ring, which is one of the inner ring (41) and the outer ring (42) that is fixed to the input side member, In this non-excitation type power transmission device, when the electromagnet (23) is energized, the armature (22) is attracted to the field core (25) and separated from the rotating wheel, thereby disengaging the engagement type clutch (40), and when the electromagnet (23) is not energized, the armature (22) is pressed against the rotating wheel, thereby engaging the engagement type clutch (40), a non-magnetic member (26) covering the side of the solenoid coil (27) facing the armature (22) is fixed to a field core (25) of the electromagnetic clutch (20), and one end of the repulsion spring (24) is accommodated in a recess (26a) formed on the surface of the non-magnetic member (26) facing the armature (22).

3. 3. The power transmission device according to claim 1, wherein the non-magnetic member (26) is a bobbin (26) around which the solenoid coil (27) is wound.

4. 3. The power transmission device according to claim 1, wherein the non-magnetic member (26) is provided with a metal plate (30) that is in sliding contact with the separation spring (24) inside the recess (26a).

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