Journal Cross and Universal Joint Comprising the Same

Abstract

The present invention relates to the field of drive technology and provides a space-saving possibility for determining forces or torques transmitted by a drive shaft with a journal cross of a universal joint with four journals projecting from a base, to which a strain sensor is attached for this purpose.

Claims

1. A journal cross of a universal joint with four journals projecting from a base, comprising at least one strain sensor fastened to the journal cross.

2. The journal cross according to claim 1, wherein the strain sensor is fastened to the base.

3. The journal cross according to claim 1, wherein the strain sensor has at least one sensor element fastened to the base between adjacent journals.

4. The journal cross according to claim 1, wherein the strain sensor comprises a sensor element measuring the strain by bending the journal relative to the base in a plane containing the journals.

5. The journal cross according to claim 1, wherein the strain sensor comprises a sensor element measuring the strain by bending the journal relative to the base transversely to a plane containing the journal.

6. The journal cross according to claim 3, wherein at least one sensor element is arranged between each of the journals.

7. The journal cross according to claim 4, wherein at least one sensor element is arranged between each of the journals.

8. The journal cross according to claim 5, wherein at least one sensor element is arranged between each of the journals.

9. A universal joint comprising two fork-shaped actuators which are each pivotally mounted on opposite journals of the journal cross according to claim 1.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0019] The present invention is explained in more detail below on the basis of embodiments in conjunction with the drawing. Therein:

[0020] FIG. 1: shows a perspective side view of a first embodiment of a universal joint;

[0021] FIG. 2: shows a perspective top view of a second embodiment of a universal joint, and

[0022] FIG. 3: shows a perspective side view of a journal cross which can be used in the universal joints according to FIG. 1 or 2.

DETAILED DESCRIPTION

[0023] FIG. 1 shows an example of a universal joint 2 with two fork-shaped actuators 4, each of which is pivotally mounted on opposite journals 6 of a journal cross 8. The fork-shaped actuators 4 comprise receptacles 10 for the torque-proof accommodation of a non-shown shaft body.

[0024] FIG. 2 shows an alternative example of a universal joint 2 with a journal cross 8, the journal 6 of which each is accommodated in journal receptacles 12, which can be mounted on the drive or output side via non-shown fastening screws. Compared to the embodiment shown in FIG. 1, the embodiment shown in FIG. 2 has a smaller axial structure. Both embodiments can, however, realize the invention explained below with reference to FIG. 3.

[0025] FIG. 3 shows an embodiment of a journal cross 8 with four journals 6 defining a plane E1 containing the central longitudinal axes of the journals 6. The journals 6 project from a middle base 14 and are realized with base 14 in a uniform forged component. The surface of base 14 is essentially unfinished. The circumferential surface of the journals 6 is turned down on a lathe to accommodate bearings.

[0026] On the outer circumferential surface of the base 14 and between two adjacent journals 6, a sensor element 16 is connected to the base 14 in the plane E1 on a smoothly milled surface of the base 14. This sensor element can be a strain gauge or a piezobased strain sensor.

[0027] According to the present invention, the mechanical stress of the journal cross 2 is measured directly at the journal cross 2 in order to deduce the torque transmitted via the universal joint 2 or the drive shaft or the axial force transmitted by these components. For this purpose the sensor element 16 is glued to the base 14 or otherwise connected to it in a material-locking manner. In the embodiment shown, at least one sensor element 16 is provided between each adjacent journal 6.

[0028] To determine the transmitted torque, the bending of the journal 6 in the plane E1 containing the journal 6 relative to the base 8 is determined. The degree of bending of the journal 6 in this plane E1 depends on the height of the torque transmitted via the journal cross 8.

[0029] Alternatively or additionally, the bending of the journal 6 in relation to the base 14 can be measured at right angles to the plane E1 containing the journal 6. This bending is in turn dependent on the axial force transmitted in the axial direction by a shaft connected via the journal cross 8. The axial direction corresponds to the axis of rotation of the journal cross 8, which penetrates the base 14 at right angles to the plane E1 at the center of the journal cross.

[0030] The present invention provides a simple and compact possibility to measure the mechanical stress of a drive shaft or a universal joint of such a shaft by attaching a strain sensor to the journal cross itself. In this way, the mechanical stress within the universal joint can be determined. The drive shaft may be designed solely for the desired application. There is no need to consider any torsional measurement requirements on the shaft when configuring the drive shaft.

[0031] The present invention is aware of the fact that mechanical stresses within the journal cross vary depending on the angle of rotation due to the drive shaft error. However, this variance can be eliminated by a logic connected to the strain sensor to evaluate the sensor signal.

[0032] The transmission of the sensor signal from the strain sensor is usually contact-free. The strain sensor can be equipped with an autonomous energy source so that wiring between the drive shaft containing the journal cross and a logic for evaluating the sensor signal and/or energizing the sensor can be completely omitted.

REFERENCE SIGN LIST

[0033] 2 universal joint [0034] 4 fork-shaped actuator [0035] 6 journal [0036] 8 journal cross [0037] 10 receptacle [0038] 12 journal [0039] 14 base [0040] 16 sensor element [0041] E1 plane containing the central longitudinal axes of the journals 6