Method and device for determining torque exerted on a shaft including transferring torque to a gearbox by the shaft and exerting axial force on the shaft dependent on the torque exerted by the shaft to the gearbox

Abstract

A drive, method and a device for determining the torque of a shaft, wherein gear wheels engaged with one another in a gearbox serve to apply an axial force to the shaft, where the axial force is induced by helical teeth of the gear wheels, the axial force of the shaft is determined using a force sensor and/or a position sensor, and where the torque is determined arithmetically from the measured axial force such that a static and dynamic measurement of the torque on the shaft can be advantageously performed.

Claims

1. A method for determining a torque which is exerted on a shaft having a fixedly connected rotor, the method comprising: transmitting the torque to a gearbox via the shaft; exerting, by the gearbox, an axial force on the shaft as a function of the torque which is exerted onto the shaft; determining the axial force; and calculating the torque from the axial force; wherein the shaft is axially movable and the axial force causes an axial displacement of the shaft which is determined via a position sensor which determines a position of the rotor along an axial plane of the shaft, the axial force being determined based on the displacement; wherein the shaft is anchored in an axially fixed manner in a drive element; wherein the drive element and the gearbox are coupled via a force sensor and an axial displacement of the shaft by the axial force between the drive element; and wherein the gearbox creates a press force/tensile force between the gearbox and the drive element, the press force/tensile force being determined by the force sensor.

2. The method as claimed in claim 1, wherein the torque is partially converted into the axial force by two gear wheels of the gearbox engaging in one another.

3. The method according to claim 1, wherein the gearbox partially converts the torque of the shaft into the axial force via a helical gearing between gear wheels of the gearbox.

4. The method according to claim 1, wherein the shaft is the shaft of a drive element.

5. The device as claimed in claim 4, wherein the shaft is the shaft of a drive element.

6. The method according to claim 1, wherein the drive element comprises one of an electric machine and an internal-combustion engine.

7. A device for determining a torque of a shaft having a fixedly connected rotor which transmits the torque from a drive element to a gearbox configured to convert the torque into an axial force onto the shaft, comprising: a position sensor which determines an axial position of the rotor along an axial plane of the shaft in relation to the gearbox and which determines a displacement of the shaft by the axial force, the shaft being mounted so as to move axially; and a force sensor for determining the axial force; wherein the position sensor determines the axial force; wherein the torque is calculated based on the axial force; wherein the shaft is anchored in an axially fixed manner in a drive element; wherein the drive element and the gearbox are coupled via the force sensor and an axial displacement of the shaft by the axial force between the drive element; and wherein the gearbox creates a press force/tensile force between the gearbox and the drive element, the press force/tensile force being determined by the force sensor.

8. The device as claimed in claim 7, wherein the gearbox includes gear wheels; and wherein the gear wheels are helical.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The invention is further described and explained below using figures. The features shown in the figures can of course be combined by the person skilled in the art to form new embodiments without exceeding the boundaries of the invention, in which:

(2) FIG. 1 shows the schematic structure of a device for determining a torque of a shaft;

(3) FIG. 2 shows a possible device for determining the torque of a shaft;

(4) FIG. 3 shows a further possible device for determining the torque of a shaft;

(5) FIG. 4 shows a further embodiment of the device; and

(6) FIG. 5 is a flowchart of the method in accordance with the invention.

DETAILED DESCRIPTION OF THE EXEMPLARY EMBODIMENTS

(7) FIG. 1 shows the schematic structure of a device for determining the torque M of a shaft 3. What is shown is a gearbox 1, represented by two coupled gear wheels 1a, 1b. The coupled gear wheels 1a, 1b have helical teeth. The helical teeth of the gear wheels 1a, 1b result in an axial force F on the gear wheel 1a in the case of a torque M that is transmitted from the shaft 3 to a gear wheel 1a. For purposes of simplification, it is assumed that the gear wheel 1b is fixed in the gearbox 1 in an axially fixed manner. The axial force F that acts on the shaft 3 results in an axial displacement of the shaft 3. In this case the direction of the axial force F onto the shaft 3 is aligned based on the direction in which the torque M of the shaft 3 acts, and based the direction of the gearing of the gear wheels 1a, 1b.

(8) The displacement of the shaft 3 is enabled by variable bearings 7 of the shaft 3. The variable bearing 7 is in particular a ball bearing. Due to the axial displacement of the shaft 3, the force can be determined using a force sensor 5. Instead of the force sensor 5, a position sensor 50 can also determine the axial position of the shaft 3. In order to determine the axial force F using a position sensor 50, a spring element is however still required, which counteracts the axial force F of the shaft.

(9) Depending on how axially fixed the shaft 3 is mounted, a force sensor 5 or a position sensor 50 is more suitable for determining the axial force.

(10) FIG. 2 shows a possible device for determining the torque M of a shaft 3. In the embodiment of the device shown here, the gearbox 1 is connected to a drive element 100 via the shaft 3. Here, the drive element 100 is an electric machine. The drive element 100 has a rotor 11, where the rotor 11 is fixedly connected to the shaft 3. The drive element 100 induces the torque M onto the shaft 3. The shaft 3 transmits the torque M to the gearbox 1. The gearbox 1 comprises two gear wheels 1a, 1b with helical teeth. Due to the helical teeth of the gear wheels 1a, 1b, an axial force F on the shaft 3 results from the torque M. Due to the axial force F, the shaft is moved in an axial direction. The shaft 3 is mounted so as to move axially in the drive element 100. The axial force F results in a deformation of the spring element 13, where the spring element 13 here is associated with the drive element 100. The spring element 13 can also be associated with the gearbox 1. Due to the spring element 13 and the variable bearing 7, i.e., a ball bearing, the shaft 3 can move axially. If an axial force F acts on the shaft 3, the shaft 3 is deflected elastically in its axial position. The axial deflection of the shaft 3 can be measured by a position sensor 50. Here, the position sensor 50 is used to measure the position of the rotor 11 of the drive element 100. Here, the position sensor 50 is arranged in the drive element 100. Here, the position sensor 50 is used to determine the axial position of the rotor 11 in the drive element 100. In this embodiment, the axial position of the shaft 3 is determined in this embodiment using the position sensor 50, and the torque M is calculated from the axial position of the shaft 3.

(11) It should be readily understood the position sensor 50 can also be positioned in the gearbox 1.

(12) FIG. 3 shows a further possible device for determining the torque M of a shaft 3. The helical gear wheels 1a, 1b result in the axial force F being applied to the shaft 3. The direction and amount of axial force F that is transmitted to the shaft 3 depends on the torque M which the shaft 3 transmits into the gearbox 1. The axial force F is exerted by the reciprocal effect of the helical gear wheels 1a, 1b on the shaft 3. The axial force is determined at the front of the drive unit 100.

(13) In the region of the end face of the drive element 100, the shaft exhibits a broadening 3a in some areas. The broadening 3a can be effected using a ring, where the ring is connected to the shaft in an axially fixed manner. The broadening 3a adjoins a force sensor 5 on both sides. In the embodiment shown, the force sensors 5 are attached to the housing of the drive unit 100. Depending on the direction of rotation (forward/backward) of the shaft 3, an axial force F acts on the shaft 3 in an associated axial direction.

(14) Depending on the direction of rotation of the shaft 3, the broadening 3a, which is shown on the end face of the drive element 100, hence impinges on the force sensor 5, or the force sensor that is positioned closer to the gearbox 1.

(15) Depending on the embodiment of the force sensor 5, a radially fixed broadening 3a of the shaft 3 is advantageous, or a rotatably mounted broadening 3a of the shaft 3.

(16) At least one of the force sensors 5 can also be associated with the gearbox 1. Advantageously, at least one of the force sensors 5 is then attached to the gearbox 1 (not shown in the FIG.).

(17) FIG. 4 shows a further embodiment of the device. In this embodiment, the gearbox 1 and the drive element 100 are arranged next to one another. The gearbox 1 is attached to the drive element 100 by at least one force sensor 5. The force sensor 5 is arranged between the gearbox 1 and the drive element 100. Here, the force sensor 5 is located between the housing 101 of the gearbox 1 and the housing 12 of the drive element 1. The force sensor 5 can also be integrated into the attachment of the drive element 100 to the gearbox 1. In each case, the shaft 3 is mounted in an axially fixed manner on those sides of the housings 101, 12 that do not adjoin the force sensor 5. The axially fixed mounting of the shaft 3 in the housing 12 can occur via a shaft bearing 7a, where the shaft bearing 7a ensures a rotatable and axially fixed mounting of the shaft 3.

(18) The shaft 3 is mounted in an axially fixed manner on the end face of the drive element 100, which is not connected to the power sensor 5. A bearing 7a, i.e., a roller bearing, is used for the axially fixed mounting of the shaft 3. The shaft 3 is mounted in the gearbox on the end face, that is not connected to the force sensor 5, either so as to move axially with a variable bearing 7 or in an axially fixed manner with a bearing 7a. In the case of the structure shown, an axial force F exerted on the shaft 3 causes the axial force F to be transmitted to at least one of the housings 12, 101. The press force or tensile force which the housings 12, 101 exert on one another is determined by the force sensor 5 between the housings 12, 101. The press force or tensile force is produced by the axial force F. The torque M present on the shaft can be arithmetically deduced from the change in the determined axial force F.

(19) In summary, the invention relates to a method and a device for determining the torque M of a shaft 3. In this case, gear wheels 1a, 1b engaging in one another in a gearbox 1 serve to apply an axial force F to the shaft 3. The axial force F is induced by helical teeth of the gear wheels 1a, 1 b. The axial force F of the shaft 3 is determined using a force sensor 5 and/or a position sensor 50. The torque M is determined arithmetically from the measured axial force F. The invention thus advantageously permits a static and dynamic measurement of the torque M on a shaft 3 to be performed.

(20) FIG. 5 is a flowchart of a method for determining a torque (M) which is exerted on a shaft (3). The method comprises transmitting via the shaft (3) transmits the torque (M) to a gearbox (1), as indicated in step 510. Next, an axial force (F) is exerted by the gearbox (1) on the shaft (3) as a function of the torque (M) which is exerted onto the shaft (3), as indicated in step 520. The axial force (F) is now determined, as indicated in step 530. The torque (M) is now calculated from the axial force (F), as indicated in step 540.

(21) Thus, while there have been shown, described and pointed out fundamental novel features of the invention as applied to a preferred embodiment thereof, it will be understood that various omissions and substitutions and changes in the form and details of the devices illustrated, and in their operation, may be made by those skilled in the art without departing from the spirit of the invention. For example, it is expressly intended that all combinations of those element steps which perform substantially the same function in substantially the same way to achieve the same results are within the scope of the invention. Moreover, it should be recognized that structures and/or elements shown and/or described in connection with any disclosed form or embodiment of the invention may be incorporated in any other disclosed or described or suggested form or embodiment as a general matter of design choice. It is the intention, therefore, to be limited only as indicated by the scope of the claims appended hereto.