Crank device

Abstract

A crank device or crank drive is disclosed which has a crankshaft, into which a variable first force can be introduced by way of a transmission element over a variable first lever spacing. Here, the first variable force has a predefined profile and/or predefined change. A profile of the first variable lever spacing is designed in a manner which is dependent on the predefined profile of the first variable force in such a way that an effect of change in the first variable force on the crankshaft is at least partially compensated for. The compensation is provided over a rotational range of the crankshaft, which is preferably less than one revolution of the crankshaft.

Claims

1. A crank device, comprising: a crankshaft; and a transmission element configured to introduce into the crankshaft a first variable force by way of a first variable lever spacing, wherein the first variable force has a predefined profile, a profile of the first variable lever spacing is dependent on the predefined profile of the first variable force such that an effect of change in the first variable force on the crankshaft is at least partially compensated, the transmission element comprises a rotary body, the transmission element is fixed to the crankshaft, a first outer circumferential portion of the rotary body has a first monotonic changing spacing from the crankshaft, and the first monotonic changing spacing defines the first variable lever spacing, the transmission element is configured to introduce a second variable force into the crankshaft via a second variable lever spacing, a second outer circumferential portion of the rotary body has a second monotonic changing spacing from the crankshaft, and the second monotonic changing spacing defines the second variable lever spacing, and the first and second outer circumferential portions of the rotary body are point-symmetrical to the crankshaft.

2. The crank device according to claim 1, wherein the crank device is configured such that: a first force is introduced with a first lever spacing of the first variable lever spacing, a second force is introduced with a second lever spacing of the first variable lever spacing, the first lever spacing is greater than the second lever spacing, and the first force is less than the second force.

3. The crank device according to claim 1, further comprising a first spring, wherein the first variable force is a variable spring force that is introduced by the first spring to the crankshaft via the first variable lever spacing.

4. The crank device according to claim 3, wherein the first variable lever spacings is adapted to the first spring such that a torque applied by the first spring to the crankshaft through the first variable lever spacing is constant over a relaxation stroke of the first spring.

5. The crank device according to claim 3, wherein a first device configured to introduce the first variable force to the transmission element is positioned on the first outer circumferential portion of the rotary body.

6. The crank device according to claim 5, wherein the first device is a slack traction mechanism, one end section of which is coupled to a free end section of the first spring, and the other end section of which is configured to rest against the first outer circumferential portion of the rotary body.

7. The crank device according to claim 5, wherein: the first device is a rack guided along an axis and its rack-side teeth have a different spacing from the axis, and the rack-side teeth engage with rotating body-side teeth arranged on the first outer circumferential portion of the rotary body.

8. The crank device according to claim 1, wherein the crank device is configured such that: a third force is introduced with a third lever spacing of the second variable lever spacing, a fourth force is introduced at a fourth lever spacing of the second variable lever spacing, the third lever spacing is greater than the fourth lever spacing, and the third force is less than the fourth force.

9. The crank device according to claim 8, wherein the second variable force is a variable spring force that is introduced by a second spring to the crankshaft through the second variable lever spacing.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) A plurality of exemplary embodiments of a crank device according to the present disclosure are shown in the figures.

(2) Shown are:

(3) FIGS. 1a and 1b show the crank device according to the disclosure according to a first exemplary embodiment in a schematic representation in two states,

(4) FIGS. 2a and 2b show the crank device according to the disclosure according to a second double exemplary embodiment in two states,

(5) FIGS. 3a and 3b show the crank device according to the disclosure according to a third double exemplary embodiment in two states, and

(6) FIGS. 4a and 4b show the crank device according to the disclosure according to a fourth exemplary embodiment in two states.

DETAILED DESCRIPTION

(7) FIG. 1 shows the first exemplary embodiment of the crankshaft drive according to the disclosure in a schematic representation. The crank drive comprises a spring 1, which is configured as a compression spring. In the manner typical for such springs 1, it generates a spring force F1, F2 that depends on its compression. In FIG. 1a, a more compressed state with a greater spring force F2 is shown, while in FIG. 1b, a less compressed state with a lesser spring force F1 is shown.

(8) On the one hand, the spring 1 is clamped and supported via a pivot bearing 2 and, on the other hand, coupled to a lever arm 4 at its end section opposite the pivot bearing 2, to which it transmits its spring force F1, F2. The lever arm 4 can be coupled to a crankshaft 6 in a rotationally fixed manner at its end section opposite the spring 1. The lever arm 4 together with the spring 1 defines a lever spacing L1, L2, which is always the lateral distance that the spring 1 or the spring force F1, F2 has to the crank axis of the crankshaft 6. The spring force F1, F2 or spring 1 and the lever spacing L1, L2 are always exactly perpendicular to each other. This means that the lever spacing L1, L2 only coincides exactly with the lever arm 4 in a special case.

(9) In FIG. 1b, since the spring 1 is even more compressed, it applies a comparatively large spring force F2. This is transferred to the lifting arm 4, which forms an obtuse angle (significantly greater than 90) with the spring 1. This means that a lever spacing L1 significantly shorter compared to the length of the lifting arm 4 is effective.

(10) In FIG. 1b, the spring 1 is already partially relaxed, thus exerting a lower spring force F1. This is transferred to the lifting arm 4, which forms an acute angle (only slightly less than) 90 with the spring 1. This means that a lever spacing L2 that is only slightly shorter compared to the length of the lifting arm 4 is effective.

(11) So F2>F1 and L2>L1 apply. Spring 1 was selected and clamped such that M=F2*L1=F1*L2 applies. The shown exemplary embodiment of the crank device according to the present disclosure has a constant output torque over a sub-area of the rotation of the output crankshaft 6.

(12) In a variant of the first exemplary embodiment of the crank device shown, which is not shown, the sub-area of rotation of the output crankshaft 6 extends with the continuously constant output torque M from the initial position shown in FIG. 1a to an end position in which the spring 1 and the lever arm 4 exactly form a right angle (90). The sub-area of rotation of the output crankshaft 6 thus ends with the continuously constant output torque M in the special case in which the lever arm 4 coincides with the lever spacing.

(13) FIGS. 2a and 2b show a double second exemplary embodiment of the crank assembly according to the disclosure. It has two springs 1 parallel to each other and directed against each other as compression springs. Between the directions or axes 18 of the springs 1 is arranged the crankshaft 6, to which a rotary body 8 is connected in a rotationally fixed manner.

(14) A chain 12 is attached to the free end portion of each spring 1, which are attached to the common rotary body 8 via a respective deflection wheel 10. The rotary body 8 is approximately oval or elliptical in shape, with two of the opposite outer circumferential portions 14 serving as contact areas for the respective chain 12.

(15) In FIG. 2a, the two outer circumferential portions 14 are approximately fully in contact with the respective chain 12. In FIG. 2b, the chains 12 are lifted off completely from the respective outer circumferential portion 14.

(16) As the rotary body 8 is approximately oval or elliptical, the distances of the outer circumferential portions 14 to the axis of rotation of the crankshaft 6 continuously change, so that the two variable lever arms L1, L2 are defined in the second exemplary embodiment.

(17) The two springs 1, the two chains 12, the two deflection wheels 10 and the two outer circumferential portions 14 are designed and arranged point-symmetrically to the crank axis of the crankshaft 6.

(18) FIGS. 3a and 3b show a double second exemplary embodiment of the crank assembly according to the disclosure. Again, it has two springs 1, which are parallel to each other and are directed oppositely towards each other as compression springs. Between the directions or axes 18 of the springs 1, the crankshaft 6 with the rotating body 8 is again arranged.

(19) A rack 16 is arranged on the free end section of each spring 1. The racks 16 can each be guided along the axis 18 and the force F1, F2 of the springs 1 (in FIGS. 3a and 3b perpendicular). This is done by changing the force F1, F2 of the respective spring 1.

(20) The rotary body 8 is in turn approximately oval or elliptical in shape, wherein two opposing outer circumferential portions 14 have teeth in this exemplary embodiment. The variable distances of the teeth of the outer circumferential portions 14 to the axis of rotation of the crankshaft 6 define the respective variable lever arm L1, L2 in the second exemplary embodiment.

(21) According to this change on the rotary body 8, the respective rack 16 is configured with a variable width. More specifically, the variable spacing of the teeth of rack 16 from axis 18 compensates for the variable radius of rotary body 8 or the variable spacing from its teeth to the rotational axis of crankshaft 6.

(22) The two springs 1, the two racks 16 and the two outer circumferential portions 14 with the teeth are designed and arranged point-symmetrically to the crank axis of the crankshaft 6.

(23) With regard to the second exemplary embodiment from FIGS. 2a and 2b and with regard to the third exemplary embodiment from FIGS. 3a and 3b, F2>F1 and L2>L1 apply. The two springs 1 were selected and clamped in such a way and the two outer circumferential portions 14 were curved such that M=F2*L1=F1*L2 applies. The second exemplary embodiment and the third exemplary embodiment have a constant output torque M over a sub-area of rotation of the output crankshaft 6. The sub-area of rotation extends from the respective tensioned state shown in Figure a to the relaxed state of the two springs 1 shown in the respective Figure b.

(24) FIGS. 4a and 4b show a fourth exemplary embodiment of the crank assembly according to the disclosure. It has a spring 1 configured as a compression spring. The crankshaft 6 is arranged at a distance to the direction or axis 18 of the spring 1, and a rotary body 8 is connected to it in a rotationally fixed manner. On the free end section of the spring 1, a slack traction mechanism 12, which is formed as a cable or wire, is attached to the rotary body 8 via a deflector wheel 10. The rotary body 8 is a cam disc with an outer circumferential portion 14, which serves as a contact area for the traction mechanism 12.

(25) In FIG. 4a, the outer circumferential portion 14 is approximately fully in contact with the traction mechanism 12. In FIG. 4b, the traction mechanism 12 is largely lifted off the outer circumferential portion 14.

(26) Due to the shape of the rotating body 8, the distance of the outer circumferential portion 14 to the axis of rotation of the crankshaft 6 continuously changes, so that the two variable lever arms L1, L2 are defined in the fourth exemplary embodiment.

(27) With regard to the fourth exemplary embodiment of FIGS. 4a and 4b, therefore, F2>F1 and L2>L1 apply. The spring 1 was selected and clamped in such a way and the two outer circumferential portions 14 were curved such that M=F2*L1=F1*L2 applies. The fourth exemplary embodiment has a constant output torque M over a sub-area of rotation of the output crankshaft 6. The sub-area of rotation extends at least from the tensioned state shown in FIG. 4a to the substantially relaxed state of the spring 1 shown in FIG. 4b.

LIST OF REFERENCE SIGNS

(28) 1 Spring 2 Pivot bearing 4 Lever 6 Crankshaft 8 Rotary body 10 Deflection wheel 12 Slack traction mechanism/chain 14 Outer circumferential portion 16 Rack 18 Axis L1 Shorter first lever spacing/shorter second lever spacing L2 Longer first lever spacing/longer second lever spacing F1 Weaker first force/weaker second force F2 Stronger first force/stronger second force M Torque