WO2021192048A1 - Differential device - Google Patents

Abstract

Provided is a differential device for enabling a differential motion between a pair of axles, the differential device comprising: a differential gear group including a side gear capable of rotation in both a first direction and a second direction, which are opposite to each other, about a shaft, and a pinion gear in meshing engagement with the side gear so as to allow for said differential motion; a casing supporting the differential group and having a frictional surface facing the differential gear group; an output member in engagement with the side gear so as to drivingly couple the side gear and each of the axles and having a clutch surface; a casing supporting the differential group and having a frictional surface which faces the clutch surface and cooperates with the same to form a friction clutch that limits said differential motion; and a cam having a first cam surface for converting torque in said first direction to a first thrust force in the direction of the shaft and a second cam surface for converting torque in said second direction to a second thrust force in the direction of the shaft and configured so as to activate the friction clutch by the first thrust force or the second thrust force pushing the clutch surface against the frictional surface. The first cam surface and the second cam surface are each dimensioned such that the first thrust force and the second thrust force both exceed a reaction force from the meshing engagement of the side gear with the pinion gear.

Description

Differential device

The following disclosure relates to a differential device, especially a differential device with less judder and noise in both forward and backward directions.

In an automobile, the left and right axles do not always rotate at a constant speed, so it is necessary to allow a differential between them. A differential is used to allow differentials between the two axles. The differential can effectively transmit torque to both axles when both wheels have traction, but torque to either axle if one wheel loses traction and the other is capable of differential. Will not be transmitted. One means for avoiding such a situation is a so-called limited slip differential (LSD). The LSD comprises, for example, a friction clutch that operates in response to torque, and the friction clutch acts to limit the differential (torque sensitive LSD).

There are various types of torque-sensitive LSD, such as a planetary gear type that uses the tooth surface resistance of the planetary gear as a pressing force on the clutch, a multi-plate clutch type that uses a multi-plate clutch as a friction clutch, and a cone clutch. An example is a cone clutch type. The planetary gear type and the multi-plate clutch type tend to exert a relatively large differential limiting force, but have a drawback that the device tends to be large.

Patent Document 1 discloses a compact cone clutch type LSD technology. According to the disclosure, a cam mechanism is used to obtain a large pressing force. That is, when the differential device is rotating in the direction in which the vehicle travels (drive direction), the cam mechanism partially converts the torque into a thrust force, and the thrust force presses the cone clutch, thus differentially. To limit.

Japanese Patent Application Publication No. 2019-49345

Although not clearly described in Patent Document 1, it is possible to restrict the differential in the direction in which the vehicle reverses (coast direction). However, according to a further study by the present inventors, it has become clear that a slight phenomenon called judder occurs in the coastal direction, and the driver may feel uncomfortable.

The following disclosure was made in view of such problems and observations. According to one aspect, a differential that allows differentials between a pair of axles is a side gear that can rotate around the axles in both the first and second directions opposite to each other, and the difference. A differential gear set including a pinion gear that meshes with the side gear so as to allow movement, and an output member that engages with the side gear to drively connect the side gear and the axle, and is a clutch surface. A casing that supports the differential set and has a friction surface that constitutes a friction clutch whose combination with the clutch surface faces the clutch surface and limits the differential. , The first cam surface that converts the torque in the first direction into the first thrust force in the direction of the shaft, and the torque in the second direction is converted into the second thrust force in the direction of the shaft. A cam comprising a second cam surface, wherein the first thrust force and the second thrust force press the clutch surface against the friction surface to operate the friction clutch. Both the first thrust force and the second thrust force are the cams whose first cam surface and the second cam surface are respectively sized so as to exceed the meshing reaction force of the side gear with respect to the pinion gear. , Equipped with.

FIG. 1 is an elevation cross-sectional view of the differential device. FIG. 2 is an exploded perspective view of the output member and the side gear taken out. FIG. 3 is a perspective view showing a surface of the output member facing the side gear. FIG. 4 is a plan sectional view of the differential device, which is taken from the line IV-IV of FIG. FIG. 5 is a partially enlarged view of FIG. 4, and is a partial plan sectional view showing a cam in particular. FIG. 6 is a partial plan sectional view showing the relationship between the meshed pinion and the side gear, and is a diagram corresponding to the VI-VI line of FIG.

Some exemplary embodiments will be described below with reference to the accompanying drawings. Throughout the following description and the scope of the claim, unless otherwise specified, the axis means the axis of rotation of the differential, the axial direction means the direction parallel to it, and the radial direction means the direction orthogonal to it. ..

For example, referring to FIG. 1, the differential device according to the present embodiment is used, for example, in an application in which torque around a shaft C is output to a pair of (usually right and left) axles while allowing differential. can. Alternatively, it can be used for distributing torque to the front and rear drive wheels via a propeller shaft that connects the front and rear, and of course, it can also be used for various other applications that mediate the transmission of torque. The following description relates to an example of distributing torque to the axles, but this is just for convenience of explanation.

The differential device is generally transmitted by a casing 1 that receives torque and rotates around an axis C, and a differential gear set 3 that is drivenly coupled to the casing 1 and transmits torque while allowing differential. It includes an output member 5 that outputs torque to each axle, a cam 7 that partially converts torque into thrust force, and a friction clutch 9 that limits the differential using the thrust force.

Casing 1 is generally cylindrical and is rotatably supported by bosses protruding from both ends. The casing 1 can be provided with a flange that protrudes radially from the outer periphery of the cylindrical portion, and can receive torque via a ring gear coupled thereto. However, support and torque reception do not necessarily have to depend on such a configuration.

Further, the casing 1 may be of a two-piece type or a one-piece type which can be divided into a plurality of pieces for the convenience of carrying in the internal members. In the case of the one-piece type, as shown in FIG. 4, one or more openings 37 can be provided on the side surface thereof, and the differential gear set 3 and the output member 5 are carried in through the openings 37. The inner surface of the casing 1 is provided with a friction surface 31 so as to face the output member 5. As will be described in detail later, the friction surface 31 is an element constituting the friction clutch 9.

With reference to FIG. 1 again, the differential gear set 3 includes a pair of side gears 13 corresponding to a pair of axles. The differential gear set 3 also includes a pinion shaft 33 that is drivenly coupled to the casing 1 and a plurality of pinion gears 11 that are rotatably supported by the shaft 33. By engaging the pinion gears 11 with the side gears 13, torque is transmitted to the pair of side gears 13 while allowing differential.

The differential gear set 3 can be a so-called bevel gear type in which the gear teeth of the pinion gear and the side gear are tilted as shown in the figure, or may be a face gear type (not shown). The bevel gear type or face gear type can easily realize the following disclosure, or other types can be adopted if possible.

In reference to FIG. 2 in combination with FIGS. 1 and 4, in any case, the side gear 13 may be directly connected to the axle, but unlike a general differential gear, the side gear 13 is not directly connected to each axle. May be isolated from. It is the output member 5 that is integrated with or separate from the side gear 13 that drives the side gear 13 and the axle.

With reference to FIG. 3 in combination with FIG. 2, each output member 5 generally comprises a hub 23 and a flange portion 25 extending radially outward from the hub 23. A corresponding side gear 13 is fitted to the outer peripheral surface of each hub 23, and a corresponding axle is coupled to the inner surface. The inner surface is provided with, for example, a spline for coupling with the axle, but the coupling does not necessarily depend on the spline.

Although details will be described later, in the case of a separate body, the side gear 13 and the output member 5 are provided with a structure capable of transmitting torque by meshing with each other. That is, the torque output by the side gear 13 is transmitted to the axle via the output member 5 in either case of the integral body or the separate body.

As shown mainly in reference to FIG. 1 in combination with FIGS. To configure. The cone surface 27 and the friction surface 31 can be, for example, a conical surface that narrows outward in the axial direction, which is a so-called cone clutch type. Alternatively, instead of the conical surface, another suitable rotationally symmetric shape may be used. These forms make it possible to control the braking force of the friction clutch 9 according to the pressing force.

Further, an appropriate friction ring 29 may be interposed between the cone surface 27 and the friction surface 31, and the inner surface of the friction ring 29 may be a conical surface suitable for the cone surface 27. In this case, the cone surface 27 comes into contact with the friction surface 31 of the casing 1 via the friction ring 29. The friction ring 29 may be rotatable with respect to the casing 1, but may be provided with, for example, an engaging portion to be prevented from rotating with respect to the casing 1.

The above description relates exclusively to the cone clutch having the cone surface as the clutch surface, but this is only for convenience of explanation, and instead of the cone clutch, the combination of the output member 5 and the casing 1 is other than a disc clutch, a drum clutch, etc. The clutch of the form of may be configured. Needless to say, a multi-plate clutch may be used.

Mainly referring to FIG. 2, the side gear 13 includes, for example, a socket 19 which is a recess that opens outward in the axial direction. With reference to FIG. 3 instead of FIG. 2, each output member 5 includes a lug 21 corresponding to the socket 19. Each of the lugs 21 is arranged and dimensioned so as to fit into the socket 19, so that the output members 5 mesh with each other with the side gears 13 to transmit torque.

The relationship between the socket and the lug may be opposite to the above description, and the side gear may be provided with the lug and the output member may be provided with the socket. Alternatively, it may have another appropriate structure that meshes with each other to transmit torque.

The socket 19 is not necessarily limited to this, but may be formed along the inner surface that fits on the outer peripheral surface, as best shown in FIG. Correspondingly, the lugs 21 can each be a protrusion that projects radially outward from the hub 23, as best shown in FIG. Such a structure is convenient for processing and is particularly useful for increasing strength and rigidity.

In this way, in the output member, the wide surface radially outside the lug (reference numeral 5A in FIG. 3) supports the wide surface radially outside the socket (reference numeral 13A in FIG. 2) in the side gear. Can be used for. Further, the surface 5A can be a recess that is sunk inward in the output member 5, and as can be understood from FIG. 1, the bottom portion of the side gear 13 can be accommodated. Needless to say, such a structure can also be applied to the other side gear 13 and the output member 5.

Such a structure helps to compress the dimensions of the combination of the side gear and the output member in the axial direction. Further, since the outer shape of such a combination matches the outer shape of the conventional side gear, it is advantageous in terms of compatibility of parts.

With reference to FIGS. 4 and 5 in combination with FIGS. 2 and 3, the side surfaces 21A and 21B of the lug 21 may be tapered inward in the direction of the side gear 13, that is, in the axial direction. Alternatively, or in addition to this, the side surfaces 19A and 19B of the socket 19 may also extend outward in the direction of the output member 5, that is, in the axial direction. Either or both of the side surfaces 21A, 21B and 19A, 19B are tilted in the direction of the axis C, and therefore the combination of the side surfaces 19A, 21A and the combination of the side surfaces 19B, 21B are in contact with each other in the socket 19 of the lug 21. The cam surfaces 19 and 21 that guide the sliding with respect to the cam surface 19 and 21 are defined. In these figures, both sides that abut each other are drawn flat, but only one may be flat and the other curved.

Since the cam surfaces 15 and 17 are tilted with respect to the direction of the axis C, the combination of the socket 19 and the lug 21 acts as a cam 7 that partially converts the torque into a thrust force when the torque is applied. .. The thrust force pushes the output member 5 outward in the axial direction to operate the friction clutch 9.

The thrust force generated by the cam 7 can be estimated by the following formula.

Here, T is the torque input to the differential device, θ is the angle of the cam surface with respect to the axis C, and Rc is the working radius of the cam. As understood from the equation (1), the larger the angle of the cam surface and the smaller the working radius of the cam, the larger the thrust force can be obtained.

As understood from the above explanation, if both the cam surfaces 15 and 17 are tilted with respect to the direction of the axis C, the differential limiting performance can be exhibited in both the drive direction and the coast direction. Therefore, in the present embodiment, when the angles formed by the cam surfaces 15 and 17 with the direction of the axis C are θ1 and θ2, respectively, as is clear from FIGS. 4 and 5, both θ1 and θ2 are larger than 0. .. That is, the cam 7 not only generates a thrust force f1 with respect to the rotation R1 in the drive direction, but also generates a thrust force f2 with respect to the rotation R2 in the coast direction.

The thrust forces f1 and f2 both operate the friction clutch 9 by pressing the output member 5 outward in the axial direction. Since the friction clutch 9 operates in a torque-sensitive manner, the differential device functions as a torque-sensitive LSD.

Thrust forces f1 and f2 may be equal to or different from each other. As understood from the equation (1), the thrust forces f1 and f2 can be adjusted independently by appropriately adjusting θ1 and θ2, respectively. For example, since a large differential limiting force is not required in the coast direction as compared with the drive direction, f1> f2 can be set, and in this case θ1> θ2 can be set. Of course, it may be adjusted by the radius of action instead of or in addition to the inclination of the cam surface.

An elastic body such as a countersunk spring can be added between the side gear 13 and the output member 5. Alternatively, the projectile may be interposed at other appropriate sites. The projectile always presses the cone surface 27 against the friction surface 31 regardless of the operation of the cam, and generates an initial torque. This can be a countermeasure against the delay of the differential limitation due to the delay of the initial movement of the cam 7.

On the other hand, referring to FIG. 6 in combination with FIG. 5, the tooth surface of the side gear 13 and the tooth surface of the pinion gear 11 are in contact with each other on the pitch circle P, and the common normal TL of these tooth surfaces is the radius line R. A pressure angle a is formed with respect to the pressure angle a. Depending on the pressure angle a, the side gear 13 meshes outward in the axial direction and a reaction force fG is generated. The meshing reaction force fG can be estimated by the following formula.

Where T is the torque inputted to the differential gear, a is the pressure angle of the pinion gear, [delta] ₀ is the pitch angle of the side gears, the d _m is the pitch diameter meshing side gears.

The meshing reaction force fG cancels out with the thrust reaction forces f1R and f2R. The meshing reaction force fG exceeds the thrust reaction forces f1R and f2R, and the larger the meshing reaction force fG, the more advantageous it is to increase the braking force of the friction clutch 9. However, there is a problem that the meshing reaction force is not constant. That is, the meshing reaction force fluctuates with time according to the process in which the gears begin to mesh, rotate while sliding with each other, and then disengage. In particular, as already described, when the relationship of f1> f2 is established, the thrust reaction force f2R in the coast direction tends to be smaller than the meshing reaction force fG, and therefore the fluctuation of the meshing reaction force fG has a strong influence on the operation of the friction clutch 9. To exert. It was presumed that this was the cause of judder in the coast direction.

Therefore, in the present embodiment, contrary to the general recognition that the meshing reaction force should be increased, the meshing reaction force fG is kept at an appropriate size with respect to the thrust forces f1 and f2. That is, the cam surfaces 15 and 17 are dimensioned so that both the thrust forces f1 and f2 exceed the meshing reaction force fG. Such a configuration, as reiterated, is advantageous in suppressing judder.

On the other hand, the thrust reaction forces f1R and f2R are borne by the gear tooth surface, so if these are excessive, the differential gear set may be consumed. Therefore, in order to reduce the influence of the thrust reaction forces f1R and f2R, the block 35 may be interposed between the pair of side gears 13 or so as to slide with both of them. Since the thrust reaction forces acting on both side gears 13 have substantially the same magnitude and are opposite to each other, the thrust reaction forces cancel each other out in the block 35. As best shown in FIGS. 1 and 4, the block 35 is, for example, a cylinder around a shaft C, provided with a through hole through which the pinion shaft 33 penetrates, but is not necessarily limited to such a shape. No.

As understood from the explanation so far, various reaction forces act in the axial direction on the side gear 13, but they antagonize or cancel each other, and the block 35 protects the side gear 13 from the reaction force, so that the torque increases. However, the engagement between the side gear 13 and the pinion gear 11 is stable, and the gear operation is not unstable or the gear tooth surface is not damaged. These points are advantageous effects as compared with the case where the side gear itself functions as a friction clutch.

In addition to the above configuration, the differential device may further include an actuator that applies a pressing force to the clutch in order to control the differential limit from the outside. Further, in order to lock the differential, the clutch may have a structure such as a dog tooth. The clutch provided with such dog teeth may be independent of the friction clutch 9, and the actuator may be configured to drive the dog teeth.

Furthermore, this embodiment can be applied to a so-called free running differential. In the free-running differential, the casing is divided into an inner casing and an outer casing, and torque is transmitted to the axle only when they are connected to each other by a clutch or the like. The structure described so far can be used almost as it is for the inner casing of the free running differential and its internal structure, except for the flange and the boss portion.

Although some embodiments have been described, it is possible to modify or modify the embodiments based on the above disclosure contents.

Claims (7)

1. A differential device that allows differentials between a pair of axles.
   A differential gear set that includes side gears that can rotate around the shaft in both the first and second directions opposite to each other, and pinion gears that mesh with the side gears to allow the differential. When,
   An output member that engages with the side gear to drively connect the side gear and the axle, and includes an output member having a clutch surface.
   A casing that supports the differential set and has a friction surface that faces the clutch surface and constitutes a friction clutch whose combination with the clutch surface limits the differential.
   A first cam surface that converts torque in the first direction into a first thrust force in the direction of the shaft, and a first cam surface that converts torque in the second direction into a second thrust force in the direction of the shaft. A cam comprising two cam surfaces, wherein the first thrust force and the second thrust force press the clutch surface against the friction surface to operate the friction clutch. Both the first thrust force and the second thrust force are a cam in which the first cam surface and the second cam surface are respectively sized so as to exceed the meshing reaction force of the side gear with respect to the pinion gear.
   Differential device with.
2. The differential device according to claim 1, wherein the first cam surface forms a first angle (θ1) with respect to the direction of the axis, and the second cam surface forms the first angle (θ1) with respect to the direction of the axis. A differential device that forms a second angle (θ2) different from the first angle (θ1).
3. The differential device according to claim 2, wherein the first angle (θ1) and the second angle (θ2) satisfy the inequality θ1> θ2.
4. The differential device according to claim 1, wherein the output member includes a hub having an inner surface that is coupled to the axle, a flange portion that expands radially outward from the hub and has a clutch surface on the outer periphery thereof. A differential device comprising: One surface of the flange portion is sized to receive the side gear.
5. The differential device according to claim 1, wherein the output member is provided with a lug for engaging with the side gear, the side gear is provided with a socket for receiving the lug, and the surface where the lug and the socket are in contact is described as described above. A differential device that constitutes a first cam surface and the second cam surface.
6. The differential device according to claim 5, wherein the lug is a protrusion that protrudes radially outward from the hub, and the socket is a recess that is arranged and dimensioned so that the lug fits.
7. A block that slides on the side gear and bears the thrust reaction force exerted by the cam.
   The differential device according to claim 1, further comprising.

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