Differential clutch device

Abstract

This invention provides a clutch device used in a differential gear set that differentially distributes torque to a pair of side gears from a case that is supported on a carrier via bearings and that rotates around an axis. Said clutch device comprises: a clutch member that engages the case in order to rotate together with the case, and that can move in an axial direction between an uncoupled position of being uncoupled from the differential gear set and a coupled position of coupling in a driving manner any gear of the differential gear set to the case; an actuator, which includes an electromagnetic coil that produces a magnetic flux, a core surrounding the electromagnetic coil in order to guide the magnetic flux, and a plunger fitted in contact with the core so as to be able to slide in the axial direction in order to receive the magnetic flux and generate thrust in the axial direction, the core slidably contacting the case and protruding axially outward from an axially inner end of the bearing, and the plunger being positioned between the bearing and the clutch member and coming into contact with the clutch member to transmit the thrust to the clutch member; and a rotation-stopping member fixed to the core and extended toward the carrier in order to engage the carrier and stop the core from rotating.

Description

[Technical field]

[0001] The following disclosure relates to a clutch device for being incorporated into a differential to control its function, and in particular to a clutch device for a differential that can be incorporated even if there is not enough clearance for the bearings, and yet the actuator can generate sufficient thrust. [Background technology]

[0002] Differentials are used in vehicles to output torque to a pair of output shafts, typically axles, while allowing differential motion. A compact differential provides various benefits, such as increasing the freedom of vehicle design and reducing the vehicle weight.

[0003] There are differentials that have a function to lock the differential (for example, called a lock-up differential) and a function to disconnect the output shaft from the power source (for example, called a free-running differential). In order to control these functions, a clutch device is usually built into the differential. There are certain technical difficulties in making the whole differential compact while including a clutch device, especially in making it compact in the axial direction.

[0004] Patent Document 1 discloses a related technique. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] International Patent Application Publication WO2021 / 192046A1 Summary of the Invention

[0006] In terms of axial dimensions only, the device can be made smaller by placing the actuator that drives the clutch outside the differential and connecting the actuator and the clutch with an appropriate intermediate member. However, such a structure inevitably increases the size of the entire device. A reasonable solution would be to make the actuator smaller and place it next to the differential, but there is a limit to how small the actuator can be, and the thrust force that can be generated is inevitably limited. If the thrust force is insufficient, there is a risk of not being able to maintain the clutch engagement, and if unintended disengagement occurs, the vehicle may behave in a way that the driver does not expect. The device disclosed below has been devised to solve these problems.

[0007] According to one aspect, a clutch device used in a differential gear set that differentially distributes torque to a pair of side gears from a case supported on a carrier via a bearing and rotating about an axis, includes an actuator including: a clutch member that fits on the case to rotate together with the case and is axially movable between a disengaged position where it is disengaged from the differential gear set and a coupled position where one of the differential gear sets is drivingly coupled to the case; an electromagnetic coil that generates magnetic flux; a core that surrounds the electromagnetic coil to guide the magnetic flux; and a plunger that is fitted in contact with the core and slidably in the axial direction to receive the magnetic flux and generate a thrust in the axial direction, the core being in slidable contact with the case and protruding outward in the axial direction from an inner end of the bearing, the plunger being located between the bearing and the clutch member and abutting against the clutch member to transmit the thrust to the clutch member; and an actuator including: a rotation stopper member that is fixed to the core and extends toward the carrier to engage with the carrier to stop the core from rotating; a bump extending radially inward from the core and axially outward from the bearing, the bump preventing the plunger from coming off in the axial direction; Equipped with The bump is sized so that the plunger is spaced from the bump even when the plunger contacts the bearing. . [Brief description of the drawings]

[0008] [Figure 1] FIG. 1 is a perspective view of a differential device incorporating a clutch device according to one embodiment. [Diagram 2]FIG. 2 is a cross-sectional elevation view of a differential device in which a clutch device is incorporated. [Diagram 3] FIG. 3 is an elevational cross-sectional view mainly showing the clutch device and its surroundings. [Figure 4] FIG. 4 is a side cross-sectional view mainly showing the relationship between the clutch and the carrier. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] Some exemplary embodiments will be described below with reference to the accompanying drawings. In the following description and the appended claims, unless otherwise specified, the axis means the rotation axis of the differential, which usually coincides with the central axis of the clutch. It should be noted that the drawings are not necessarily drawn to scale, and therefore the mutual dimensional relationships are not limited to those shown in the drawings.

[0010] Referring mainly to Fig. 1, the clutch device 1 according to this embodiment is used in combination with a differential device. Referring to Figs. 2 and 3 in combination with Fig. 1, the differential device generally includes a case 7 that is rotatable about an axis X on a carrier 3 via a bearing 5, and a differential gear set 9 that differentially distributes torque from the case 7 to a pair of side gears 11 and 13.

[0011] The case 7 has bosses 7B extending axially from both ends thereof, for example, and is rotatably supported by the carrier 3 with bearings 5 ​​interposed between the bosses 7B and the carrier 3. The case 7 also has a flange 7F extending radially outward from its outer periphery, and a ring gear 49 is fixed to the flange 7F. The ring gear 49 is drivingly meshed with a propeller shaft drivingly connected to a power source to receive torque, thereby rotating the case 7 about the axis X. Alternatively, without the ring gear, for example, the case 7 may be directly driven by the power source. The power source is, for example, an internal combustion engine, but the internal combustion engine may be combined with an electric motor, or the electric motor may be alone.

[0012] The differential gear set 9 is supported by the case 7 to receive torque and differentially distributes the torque to the side gears 11, 13. In the illustrated example, the differential gear set 9 is a bevel gear type consisting of a pinion 33 rotatably supported on a pinion shaft 31 supported by the case 7 and side gears 11, 13 meshed with the pinion 33, but may instead be a face gear type or a planetary gear type.

[0013] The clutch device 1 includes a clutch member 15 and an actuator 17 for driving the clutch member 15, and is used, for example, to lock the differential of the differential gear set 9 by drivingly connecting one of the side gears 11 to the case 7 with the clutch member 15. Alternatively, it can also be used to turn on and off the torque transmission from the case 7 to the differential gear set 9 (so-called free running differential). In the latter case, for example, the case 7 may be made up of an outer case that receives torque and an inner case that can rotate freely from the outer case, and the differential gear set 9 may be supported by the inner case. When the clutch member 15 is not engaged with the inner case, the differential gear set 9 is free from the power source (free running), and when engaged, the clutch member 15 is responsible for the torque transmission from the outer case to the inner case, and the differential gear set 9 differentially distributes the torque to the output shaft.

[0014] The actuator 17 includes a solenoid that generates magnetic flux, and a plunger 25 that is driven in the axial direction by the magnetic flux generated by the solenoid. The solenoid includes, for example, an electromagnetic coil 21 that generates magnetic flux in response to input power, and a core 23 that surrounds the electromagnetic coil 21 to guide the magnetic flux.

[0015] The core 23 is in slidable contact with one end wall of the case 7. The case 7 may have a circumferential groove corresponding to the core 23. For example, the case 7 has a boss portion 7B extending axially from the end wall and a circumferential wall 7W, and the core 23 fits into the circumferential groove surrounded by the boss portion 7B, the circumferential wall 7W and the end wall, so that the core 23 is supported by the case 7 and is rotatable relative to the case 7. A locking member 43 can be used to prevent the core 23 from falling out, and the locking member 43 is fixed to the case 7 by, for example, a bolt 45. The core 23 has, for example, a circumferential groove 41 on its outer periphery, and the locking member 43 slidably engages with the circumferential groove 41 to prevent the core 23 from falling out.

[0016] A rotation-stop member 19 is fixed to the core 23. The rotation-stop member 19 is, for example, a relatively thin plate-like piece made of a magnetic material such as mild steel. Prior to fixing, the core 23 may be provided with a recess corresponding to the rotation-stop member 19 so that the rotation-stop member 19 does not protrude from the core 23 in the axial direction, and preferably the surface of the core 23 and the surface of the rotation-stop member 19 are flush with each other. If the rotation-stop member 19 is made of a magnetic material, it may form a part of a magnetic path that guides magnetic flux. Fixing may be by any means such as welding, spot welding, brazing, pressure welding, engagement, fastening, or the like, or the two may be molded integrally. In the illustrated example, a single rotation-stop member 19 is used, but two or more rotation-stop members may be used, and preferably these are arranged symmetrically around the axis X.

[0017] The anti-rotation member 19 extends toward the carrier 3 and engages with a recess 3P of the carrier 3 as shown in Figures 3 and 4 to prevent the core 23 from rotating. That is, in an operating state, the electromagnetic coil 21 and the core 23 are stationary, but the case 7, the clutch member 15, and other related members rotate about the axis X. In the illustrated example, the anti-rotation member 19 extends generally radially outward, but it may extend in other directions, and may simply engage with the carrier 3, or may be sandwiched by the carrier 3 or fixed to the carrier 3 by an appropriate fixing device. If the anti-rotation member 19 is fixed, it can also play a role in positioning the core 23.

[0018] As shown in FIG. 2, the core 23 may have a bump 27 that protrudes slightly inward in the circumferential direction, for example, at one end. Before the device is assembled into the carrier 3, the bump 27 abuts against the plunger 25 to prevent it from falling off. The bump 27 may be integral with the core 23, or may be a separate body that is fixed to the core 23. Alternatively, instead of the core 23 having a protrusion, as best shown in FIG. 1, an inner end 29 of the rotation prevention member 19 may protrude beyond the inner circumference of the core 23 and reach the plunger 25 to prevent it from falling off. The end 29 is equivalent to the bump 27. Since the bump 27 or the end 29 prevents the plunger 25 from falling off, the boss portion 7B does not need to have a member for preventing it from falling off, which is advantageous for making the case 7 smaller in the axial direction.

[0019] In any event, the bump 27 or end 29 abuts the plunger 25 only before the device is assembled into the carrier 3, and after assembly, the plunger 25 is restrained between the bearing 5, particularly its inner race, and the clutch member 15, and is therefore spaced from the bump 27 or end 29, as best shown in Figure 3. In other words, the bump 27 or end 29 is dimensioned so that the plunger 25 abuts the axially inner end 5W of the inner race of the bearing 5 but is spaced from the bump 27 or end 29.

[0020] The end of the core 23 farther from the case 7 protrudes outward in the axial direction than the axially inner end 5W of the inner race of the bearing 5. Despite this, the end does not come into contact with the inner race or the rolling elements. Therefore, even when the case 7 rotates, the core 23 does not slide against the inner race or the rolling elements of the bearing 5, and no energy loss occurs. On the other hand, since the core 23 can protrude outward in the axial direction, it is possible to ensure the dimensions necessary to generate sufficient magnetic flux. This is advantageous for the actuator 17 to generate sufficient thrust.

[0021] On the other hand, bearing 5 is, for example, a tapered roller bearing, whose outer race is offset axially outward from the inner race. Therefore, even if core 23 protrudes axially outward, it is possible to avoid contact with the outer race. From the viewpoint of preventing leakage of magnetic flux, core 23 preferably does not contact either the outer race of bearing 5 or carrier 3. However, even if they do come into contact, these are stationary members like core 23, so no energy loss due to sliding occurs.

[0022] Core 23 may entirely cover electromagnetic coil 21, but may not cover it partially, and case 7 may partially function as a magnetic path for guiding magnetic flux in place of core 23. Furthermore, gap 39 may be left uncovered by the magnetic path consisting of core 23 and case 7. In the example of Fig. 3, gap 39 opens in the radial direction on the inner circumference of core 23, and magnetic flux is guided so as to jump across this gap 39.

[0023] The plunger 25 preferably faces the gap 39 so as to straddle it, and is in contact with the core 23 and slidably fitted thereto. With this structure, the magnetic flux jumping over the gap 39 is diverted to the plunger 25, and the plunger 25 receives the magnetic flux and generates a thrust in the axial direction. The plunger 25 includes a magnetic member 25M made of a magnetic material at least on the side facing the core 23. In order to prevent leakage of magnetic flux, the other portions may be made of a non-magnetic member 25N. The non-magnetic member 25N is in contact with the bearing 5, the boss portion 7B, and the clutch member 15, and the magnetic member 25M can be limited to the portion that receives the magnetic flux.

[0024] As already mentioned, the plunger 25 is disposed between the bearing 5 and the clutch member 15, and even when it is at its most backward position, it stops by abutting against the end 5W of the inner race of the bearing 5. To restrict the position of the plunger 25, for example, a stop ring engaged with the boss portion 7B is not required. This is advantageous in reducing the axial dimension. When it moves forward, the plunger 25 abuts against the clutch member 15 and drives it to the connected position.

[0025] 2 and 3, the plunger 25 fits on the inner periphery of the core 23, but instead, the plunger 25 may fit on the outer periphery of the core 23. In such a configuration, the bump 27 may protrude radially outward from the outer periphery of the core 23 to prevent the plunger 25 from coming off, or the extended anti-rotation member 19 may come into contact with the bump 27 to prevent the plunger 25 from coming off. Also, in such a configuration, it goes without saying that the gap 39 may be open on the outer periphery of the core 23, and the plunger 25 faces the gap 39 so as to straddle it.

[0026] The clutch member 15 is fitted to the case 7 so as to rotate together with it, and is driven in the axial direction by contacting the plunger 25 and receiving a thrust. One end of the clutch member 15 has one or more legs extending in the axial direction. These legs each extend axially outward through an opening 7A opened in the case 7 and contact the end of the plunger 25. Alternatively, the end of the plunger 25 may extend and contact the clutch member 15, or the plunger 25 and the clutch member 15 may not directly contact each other, and other appropriate members may be interposed between them. The other end of the clutch member 15 faces the differential gear set 9 and has clutch teeth 37. The clutch teeth 37 are structured to mesh with the clutch teeth 35 of the side gear 11.

[0027] The clutch member 15 is normally on standby in a disengaged position where it is disengaged from the differential gear set 9. When the clutch member 15 is driven axially by the plunger 25 to move to the engaged position, the clutch teeth 35, 37 mesh with each other. Of course, the clutch member 15 may be constantly in the engaged position and move to the disengaged position for a limited period of time. When in the engaged position, the clutch member 15 drivingly connects the side gear 11 to the case 7, thereby locking the differential of the differential gear set 9. Also, as already mentioned, the clutch teeth 35 may be engraved on the inner case, and the clutch teeth 37 may mesh with the clutch teeth 35, whereby the clutch member 15 may mediate the transmission of torque from the outer case to the differential gear set 9.

[0028] The side of the opening 7A and the side of the leg of the clutch member 15 may be inclined in correspondence with each other to form a cam that converts part of the torque applied to the case 7 into an axial thrust. Such a structure is advantageous for using part of the torque to maintain the engagement of the clutch member 15, and is advantageous for reducing the thrust requirement of the actuator 17 and for making it smaller. Alternatively, no power is required to maintain the engagement, and is advantageous for improving energy efficiency. On the other hand, in order to promote disengagement, a spring 47 may be interposed between the side gear 11 and the clutch member 15, for example, as shown in FIG. 3. Of course, a spring may be used in a direction that promotes engagement, and as already mentioned, the actuator 17 may generate thrust in a direction that disengages the clutch member 15.

[0029] In any of the above-mentioned embodiments, the core is protruded in the axial direction, contrary to the demand for reducing the axial dimension. Nevertheless, the axial dimension is reduced as the distance between the bearings, while the core has a sufficient dimension, so that the actuator can generate a sufficient thrust. Such a structure does not impair the thickness of the differential case, and therefore does not sacrifice its strength and rigidity.

[0030] Although several embodiments have been described, the embodiments can be modified or altered based on the above disclosure.

Claims

1. A clutch device used in a differential gear set that differentially distributes torque from a case that is supported on a carrier via a bearing and rotates around a shaft to a pair of side gears, comprising: a clutch member engaged with the case to rotate together with the case, the clutch member being axially movable between a disengaged position where the clutch member is disengaged from the differential gear set and a connected position where the clutch member drivingly connects one of the differential gear sets to the case; an actuator comprising: an electromagnetic coil that generates a magnetic flux; a core that surrounds the electromagnetic coil to guide the magnetic flux; and a plunger that is in contact with the core and fitted to be slidable in the axial direction to receive the magnetic flux and generate a thrust in the axial direction, wherein the core is in slidable contact with the case and protrudes outward in the axial direction from an inner end of the bearing in the axial direction, and the plunger is located between the bearing and the clutch member and abuts against the clutch member to transmit the thrust to the clutch member; a rotation prevention member fixed to the core and extending toward the carrier to engage with the carrier and prevent the core from rotating; a bump extending radially inward from the core and axially outward from the bearing, the bump preventing the plunger from coming off in the axial direction; A clutch device comprising: The bump is sized so that the plunger is spaced from the bump when the plunger contacts the bearing.

2. 2. The clutch assembly of claim 1, wherein said core is sized so as not to contact said bearing and said carrier.

3. 2. The clutch device according to claim 1, wherein the bump is a projection extending radially from the core or from the anti-rotation member.

4. 2. The clutch device according to claim 1, wherein said core has a gap open in the radial direction, and said plunger is fitted to said core facing said gap, so that said plunger receives said magnetic flux jumping across said gap to generate said thrust.

5. 2. The clutch arrangement of claim 1, wherein said clutch member includes clutch teeth on a face facing said differential gear set.

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