The present invention relates to jaw clutches for the drive of a motor vehicle in which a first clutch half is connected to a first wheel drive line and a second clutch half is connected to a main drive line and a second wheel drive line wherein one of the two clutch halves is selectively axially displaceable relative to the other and wherein each of the clutch halves has axially protruding from a contact surface thereof a plurality of profiled jaw clutch elements which are distributed uniformly in spaced relationship over the contact surface.
Jaw clutches are used in distributor gears or differential gears as described in EP-OS 510 457. The distributor gears can be either with a central differential or without a central differential. In the former case, the clutches in question serve as a differential lock and in the second case they serve to connect the front axle drive. As used herein, differential gears is understood to mean, in particular, axle differential gears or intermediate differential gears in vehicles having tandem axles in which case the clutches in question serve as a transverse lock.
In the application described above, under good road conditions, if neither locks nor front axle drives are connected, only slight differences in speed of rotation are present between the clutch halves. Upon worsening road conditions, the difference in speed of rotation between the clutch halves increases, which leads to connection or locking. Whether actuated manually or automatically, as long as the difference in speed of rotation does not exceed certain limit values, the jaw clutch can be switched without synchronization. In the case of the gears described in EP-OS 510 457, the engagement of the clutch is effected by an automatic control and it is possible to leave the disengagement of the clutch to a spring which operates when the torque drops below a predetermined value.
It is desirable that the range of speeds of rotation at which the jaw clutch can be engaged be sufficiently large so as to allow for the engagement to take place as fast and free of friction as possible. The foregoing saves time during which the vehicle would otherwise lose momentum or come entirely to a stop.
U.S. Pat. No. 3,550,738 discloses jaw clutches having jaw clutch elements the front surfaces of which are curved or rounded, as seen in circumferential section, specifically for the purpose described above. The curved surface extends over the entire front surface of the jaw clutch elements and are intended, upon engagement with difference in speed of rotation of the two clutch halves, to bump past each other with friction and thus reduce the difference in speed of rotation. This friction means wear, noise and loss of time. Furthermore, when using a jaw clutch in the drive line of a vehicle, in which, after all, neither of the clutch parts rotates freely (the two are coupled by the road more or less rigidly to each other), the torques are so great that synchronization by such friction is not possible.
Federal Republic of Germany OS 41 38 917 discloses a jaw clutch having a profile consisting of circular arcs. In the case of this clutch, the jaws are held continuously in engagement by a spring which urges the clutch in closing direction, and they can be disengaged under full load. With the arcuate profile, no edge pressure occurs during the disengagement of the clutch halves.
Undercut jaw elements are known from Federal Republic of Germany OS 37 30 889 which discloses clutches which are switched positively in both directions.
It is the principle object of the present invention to provide a jaw clutch which can be engaged quickly, reliably, and with low wear, over a sufficiently large range of differences in speeds of rotation.