Abstract
An apparatus for introducing an auxiliary torque and/or an additional steering angle into a steering shaft of an electromechanical power steering system may comprise a gearwheel that is attached fixedly on the steering shaft so as to rotate with the steering shaft and that is operatively connected to a drive element of a drive motor for driving the gearwheel. The apparatus may further include a sensor that is connected fixedly to the steering shaft so as to rotate with the steering shaft. So that the attachment of the sensor can take place with less complexity and use less installation space as far as possible, the sensor and the gearwheel may be connected to one another at contact faces.
Claims
1.-11. (canceled)
12. An apparatus for introducing at least one of an auxiliary torque or a steering angle into a steering shaft of an electromechanical power steering system, the apparatus comprising: a gearwheel that is fixedly attached on the steering shaft so as to rotate with the steering shaft, wherein the gearwheel is operatively connected to a drive element of a drive motor configured to rotationally drive the gearwheel; and a sensor that is fixedly connected to the steering shaft so as to rotate with the steering shaft, wherein the sensor and the gearwheel are connected to one another at contact faces.
13. The apparatus of claim 12 wherein the sensor is integrally connected to the gearwheel.
14. The apparatus of claim 13 wherein the gearwheel is welded to the sensor.
15. The apparatus of claim 13 wherein the gearwheel is adhesively bonded to the sensor.
16. The apparatus of claim 12 wherein the gearwheel and the sensor comprise plastic at least in regions of the contact faces.
17. The apparatus of claim 16 wherein the gearwheel is configured as a plastic injection-molded part that is molded onto the steering shaft.
18. The apparatus of claim 12 wherein the sensor is annular and is disposed coaxially on the steering shaft, wherein the contact face of the sensor extends substantially annularly.
19. The apparatus of claim 12 wherein the gearwheel and the sensor bear axially against one another in a region of the contact faces.
20. The apparatus of claim 12 wherein the sensor and the gearwheel comprise positively locking elements that can engage with one another in a positively locking manner.
21. The apparatus of claim 12 wherein the gearwheel and the sensor are disposed in a housing on which an assembly of a sensor arrangement is positioned in a manner that is fixed relative to the sensor.
22. A method for producing an apparatus for introducing at least one of an auxiliary torque or a steering angle into a steering shaft of an electromechanical power steering system, the method comprising: providing a gearwheel for the electromechanical power steering system; providing a sensor for a sensor arrangement; positioning the sensor at or on the gearwheel in a predefined arrangement position; and producing a non-releasable connection between the sensor and the gearwheel.
Description
DESCRIPTION OF THE DRAWINGS
[0021] Advantageous embodiments of the invention will be described in greater detail in the following text using the drawings, in which, in detail:
[0022] FIG. 1 shows a diagrammatic perspective illustration of a steering system of a motor vehicle having a power assistance means,
[0023] FIG. 2 shows a diagrammatic section through an apparatus for introducing an auxiliary torque into a steering shaft,
[0024] FIG. 3 shows a diagrammatic perspective view of an apparatus according to FIG. 2 in a state in which it is partially disassembled,
[0025] FIG. 4 shows a diagrammatic longitudinal section along the longitudinal axis of the steering shaft of an apparatus according to FIG. 2,
[0026] FIG. 5 shows a diagrammatic perspective illustration of the gearwheel with a sensor element which is mounted on it,
[0027] FIG. 6 shows an illustration as in FIG. 5 with a sensor element which is shown removed,
[0028] FIG. 7 shows a diagrammatic perspective illustration of a sensor element for an apparatus according to one of the preceding figures,
[0029] FIG. 8 shows a diagrammatic longitudinal section along the longitudinal axis of the steering shaft of a part arrangement from FIG. 5,
[0030] FIG. 9 shows a detailed illustration from FIG. 8 in a first embodiment,
[0031] FIG. 10 shows a detailed illustration from FIG. 8 in a second embodiment, and
[0032] FIG. 11 shows a detailed illustration from FIG. 8 in a third embodiment.
EMBODIMENTS OF THE INVENTION
[0033] In the various figures, identical parts are always provided with the same designations and are therefore also indicated or mentioned in each case only once as a rule.
[0034] FIG. 1 diagrammatically shows a motor vehicle steering system 100, it being possible for a driver to introduce a corresponding steering moment (steering torque) into a steering shaft 1 via a steering wheel 102 as a steering command. The steering torque is transmitted via the steering shaft 1 to a steering pinion 104 which meshes with a rack 106 which then for its part transmits the predefined steering angle to the steerable wheels 110 of the motor vehicle via a displacement of the track rods 108.
[0035] An electric power assistance means can be provided in the form of a power assistance means 112 which is coupled to the steering shaft 1 on the input side, a power assistance means 114 which is coupled to the pinion 104, and/or a power assistance means 116 which is coupled to the rack 106. The respective power assistance means 112, 114 or 116 couples an auxiliary torque into the steering shaft 1 and/or the steering pinion 104 and/or an auxiliary force into the rack 106, as a result of which the driver is assisted during the steering work. The three different power assistance means 112, 114 and 116 which are shown in FIG. 1 show possible positions for arranging them.
[0036] Only a single one of the shown positions is usually fitted with a power assistance means 112, 114 or 116. The auxiliary torque or the auxiliary force which is to be applied by means of the respective power assistance means 112, 114 or 116 in order to assist the driver is defined with the consideration of a steering torque which is introduced by the driver and is determined by a torque sensor 118. As an alternative to or in combination with the introduction of the auxiliary torque, an additional steering angle can be introduced into the steering system by the power assistance means 112, 114, 116, which additional steering angle is summed with the steering angle which is applied by the driver via the steering wheel 102.
[0037] The steering shaft 1 has, on the input side, an input shaft 10 which is connected to the steering wheel 102 and, on the output side, an output shaft 12 which is connected to the rack 106 via the steering pinion 104. The input shaft 10 and the output shaft 12 are coupled to one another in a rotationally elastic manner via a torsion bar 130 which cannot be seen in FIG. 1 (see FIG. 4). In this way, a torque which is input into the input shaft 10 by a driver via the steering wheel 102 always leads to a relative rotation of the input shaft 10 with regard to the output shaft 12 when the output shaft 12 does not rotate in an exactly synchronous manner with respect to the input shaft 10. Said relative rotation between the input shaft 10 and the output shaft 12 can be measured via a rotary angle sensor, and a corresponding input torque relative to the output shaft 12 can be defined accordingly on the basis of the known torsional stiffness of the torsion bar 130. In this way, the torque sensor 118 is configured by way of the determination of the relative rotation between the input shaft 10 and the output shaft 12. A torque sensor 118 of this type is known in principle and can be, for example, an electromagnetic sensor arrangement, as will be described further below, or can be realized by way of another measurement of the relative rotation.
[0038] Accordingly, a steering torque which is applied to the steering shaft 1 or the input shaft 10 by the driver via the steering wheel 102 will bring about the input of an auxiliary torque by way of one of the power assistance means 112, 114, 116 only when the output shaft 12 is rotated relative to the input shaft 10 counter to the rotational resistance of the torsion bar 130.
[0039] As an alternative, the torque sensor 118 can also be arranged at the position 118, the break of the steering shaft 1 into the input shaft 10 and the output shaft 12 and the rotationally elastic coupling via the torsion bar 130 then accordingly being present at a different position, in order for it to be possible to determine a relative rotation and therefore correspondingly an input torque and/or an auxiliary torque to be applied from the relative rotation of the output shaft 12 which is coupled to the input shaft 10 via the torsion bar 130.
[0040] Furthermore, the steering shaft 1 in FIG. 1 comprises at least one cardan joint 120, by means of which the course of the steering shaft 1 in the motor vehicle can be adapted to the spatial conditions.
[0041] FIG. 2 shows a diagrammatic sectional illustration of an apparatus 2 for introducing an auxiliary torque into a motor vehicle steering system 100. A gearwheel 20 (here, a worm gear) is provided which is connected to a steering shaft 1 which is shown diagrammatically. A rotation of the gearwheel 20 about its rotational axis 200 which is also called a gearwheel or worm gear axis 200 and is configured here by way of the steering shaft 1 brings about the introduction of an auxiliary torque into the steering shaft 1, in order to correspondingly introduce an auxiliary force or an additional steering angle into the steering line.
[0042] The gearwheel 20 is driven via a drive worm 22 which for its part is driven via a diagrammatically shown electric motor 24, the output 240 of the electric motor 24 accordingly being coupled to the drive worm 22 for the transmission of torque. Here, the axis of the drive worm 22 and the gearwheel axis 200 do not intersect. The drive worm 22 is preferably produced from hardened steel.
[0043] The sectional illustration of FIG. 2 shows a housing 3 of the apparatus 2 for introducing an auxiliary torque, the housing 3 receiving a first anti-friction bearing 26 which radially supports the output shaft 240 of the electric motor 24. Furthermore, a second anti-friction bearing 28 is provided, in which the drive-side end of the drive worm 22 is supported radially.
[0044] That end 460 of the drive worm 22 which lies opposite the output 240 of the electric motor 24 is mounted in a bearing apparatus 4 which, in addition to the radial mounting of the drive worm 22, also makes an angular compensation possible.
[0045] FIGS. 3 and 4 likewise show the apparatus 2, the housing cover 31 being omitted in the perspective view of FIG. 3 for improved clarity. A sensor arrangement 5 can be seen in said figure, which sensor arrangement 5 comprises a sensor element 51 which is connected fixedly to the gearwheel 20 so as to rotate with it and an assembly 52 which is assigned to said sensor element 51 and is fastened to the housing 3 in a stationary manner relative to the gearwheel 20. The assembly 52 serves firstly to receive a measured signal which is output by the sensor element 51 and to conduct it to a controller, and can secondly be configured and positioned relative to the sensor element 51 in such a way that an angular position of the sensor element 51 relative to the housing 3, and therefore the angular position of the gearwheel 20 and the steering shaft 1, can be measured in this way, for example by the assembly 52 detecting an angle-dependent magnetic field of the sensor element 51.
[0046] It can be gathered from the sectional illustration of FIG. 4 that the gearwheel 20 is fastened on the output shaft 12 of the steering shaft 1. The output shaft 12 is connected in a rotationally elastic manner to the input shaft 10 of the steering shaft 1 via the torsion bar 130. In the embodiment which is shown, the sensor element 51 is connected fixedly to the output shaft 12; in alternative embodiments, it can also be connected to the input shaft 10. The input shaft 10 has a magnet arrangement (not shown in detail in the drawing) which is arranged coaxially in the sensor element 51. If a steering torque is introduced into the input shaft 10 by the driver via the steering wheel 102, said input shaft 10 rotates relative to the output shaft 12. Said relative rotation of the magnet arrangement which is dependent on the steering torque which is introduced by the driver is detected by means of the sensor element 51 and is utilized as a control variable for determining the auxiliary torque which is transmitted by the electric motor 24 to the output shaft 12 via the drive worm 22 and the gearwheel 20.
[0047] The sensor element 51 which is shown in detail in FIG. 7 has a substantially annular main body 53 which is preferably configured substantially from plastic, preferably as a plastic injection-molded part. Components of the actual electric measuring arrangement can be attached on the main body 53, for example in the form of stator laminations 54 which are distributed over the circumference, are embedded into the plastic, and are indicated merely diagrammatically in the drawing.
[0048] The annular main body 53 is placed coaxially onto the steering shaft 1, for example onto the output shaft 12, and is moved in the axial direction against the gearwheel 20, as indicated by way of the arrow in FIG. 6. Here, a tubular shoulder 55 which is configured on the main body 53 on the end side is pushed or pressed in the axial direction in a positively locking manner onto a cylindrical projection 210 which is configured on the gearwheel 20 on the end side, the sensor element 51 being centered relative to the gearwheel 20 and therefore also to the output shaft 12, and there being a certain prestress between the projection 210 and the shoulder 55.
[0049] The end position during the attachment of the sensor element 51 is shown in FIG. 5. The sensor element 51 bears tightly against an axial end side of the gearwheel 20 and forms a compact structure unit. It can be seen in the illustration how the input shaft 10 is inserted with its end which faces the gearwheel 20 axially into the open cross section of the main body 53 of the sensor element 51. As a result of the abovementioned magnet arrangement (not shown in detail) which is attached at the end of the input shaft 10, a relative rotation of the input shaft 10 with respect to the output shaft 12 can be detected by way of the sensor element 51.
[0050] FIG. 8 shows a longitudinal section in the direction of the gearwheel axis 200 through the output shaft 12 in a similar manner to FIG. 5, but shows merely the sensor element 51 instead of the complete sensor arrangement 5. It is apparent from this, in particular, how the gearwheel 20 which consists of plastic is attached on the output shaft 12 which preferably consists of steel. The connection can preferably take place by the gearwheel 20 being molded onto the output shaft 20 in an injection mold using plastic injection molding, that is to say the output shaft 12 is encapsulated by the molten plastic material. As shown here, this can take place by means of diaphragm gating or, as an alternative, by means of continuous casting. A fixed integrally joined connection is realized as a result. In addition, the output shaft 12 can have positively locking elements 121 on its outer circumference, for example ribs or grooves which are filled by the plastic and ensure a positively locking connection to the gearwheel 20.
[0051] FIGS. 9, 10 and 11 show sectional views from FIG. 8 on an enlarged scale, which sectional views illustrate in detail the connection of the main body 53 which consists of plastic to the gearwheel 20 which likewise consists of plastic. As has already been described above, the tubular shoulder 55 of the sensor element 51 is placed axially onto the projection 210 in a positively locking manner, as a result of which a centering action with regard to the gearwheel axis 200 takes place. Within the opening of the shoulder 55, an annular, axial end face on a radially inwardly projecting projection 56 forms an axial contact face 57. The contact face 57 is connected to a likewise annular, axial end face 211 of the gearwheel 20, that is to say a corresponding contact face 211 of the gearwheel 20. In other words, the contact faces 57 and 211 form the joining faces of the connection between the plastic of the gearwheel 20 and that of the sensor element 51.
[0052] One preferred embodiment of the invention provides that the sensor element 51 is connected to the gearwheel 20 in an integrally joined manner. In the embodiment which is shown, the integrally joined connection takes place in the region of the contact faces 57 and 211 which bear axially against one another, the joining faces of the integrally joined connection.
[0053] FIG. 9 diagrammatically shows a thermal welding operation by means of a laser 6. To this end, the laser beam 61 which is indicated by way of a dotted line is radiated axially into the projection 56. By virtue of the fact that the sensor element 51 is produced in the region of said projection 56 from a plastic material which is transparent for the laser light which is used, the laser beam 61 exits from the contact face 57 and strikes that contact face 211 of the gearwheel 20 which bears there against said contact face 57. By virtue of the fact that the gearwheel 20 consists in the region of said contact face 211 of a plastic which is not transparent for the laser light which is used, heat is released there which leads to melting of the plastic on both surfaces 57 and 211 and therefore to a welding operation. By virtue of the fact that compatible plastics with regard to an integrally joined connection are used for the gearwheel 20 and the sensor element 51, a particularly fixed, integrally joined connection is realized with an approximately homogeneously continuous plastic structure.
[0054] As shown in FIG. 10, it is possible as an alternative, instead of a laser beam, to use an ultrasonic welding unit 7, by way of the sonotrode 71 of which the contact face 57 is pressed axially against the contact face 211 and is welded thermally to the latter by way of the frictional heat which is coupled in by means of ultrasonic excitation. As a result, a durable integrally joined connection is likewise produced between the gearwheel 20 and the sensor element 51.
[0055] FIG. 11 diagrammatically shows a thermal welding operation by means of a laser 6. To this end, the laser beam 61 which is indicated by way of a dotted line is radiated in radially. The laser beam 61 strikes the contact face 211 of the gearwheel 20 which is present there. By virtue of the fact that the gearwheel 20, in the region of said contact face 211, and the sensor element 51, in the region of the contact face 57, consist of a plastic which is not transparent for the laser light which is used, heat is released there which leads to melting of the plastic on both surfaces 57 and 211 and therefore to a welding operation. By virtue of the fact that compatible plastics with regard to an integrally joined connection are used for the gearwheel 20 and the sensor element 51, a particularly fixed, integrally joined connection is realized with an approximately homogeneously continuous plastic structure.
[0056] As appropriate, the individual features which are shown in the individual exemplary embodiments can be combined with one another and/or exchanged for one another, without departing from the scope of the invention.
LIST OF DESIGNATIONS
[0057] 1 Steering shaft
[0058] 10 Input shaft
[0059] 12 Output shaft
[0060] 100 Motor vehicle steering system
[0061] 102 Steering wheel
[0062] 104 Steering pinion
[0063] 106 Rack
[0064] 108 Track rod
[0065] 110 Steerable wheel
[0066] 112 Power assistance means
[0067] 114 Power assistance means
[0068] 116 Power assistance means
[0069] 118 Torque sensor
[0070] 118 Torque sensor
[0071] 120 Cardan joint
[0072] 130 Torsion bar
[0073] 2 Apparatus for introducing an auxiliary torque
[0074] 20 Gearwheel
[0075] 200 Gearwheel axis
[0076] 210 Projection
[0077] 211 Contact face (joining face)
[0078] 22 Drive worm
[0079] 24 Electric motor
[0080] 26 Anti-friction bearing of the output shaft of the electric motor
[0081] 28 Anti-friction bearing for the drive worm
[0082] 29 Bearing apparatus
[0083] 220 Axis of the drive worm
[0084] 240 Output of the electric motor
[0085] 3 Housing
[0086] 31 Housing cover
[0087] 4 Bearing apparatus
[0088] 460 End of the axis 220
[0089] 5 Sensor arrangement
[0090] 51 Sensor element
[0091] 52 Assembly
[0092] 53 Main body
[0093] 54 Stator laminations
[0094] 55 Shoulder
[0095] 56 Projection
[0096] 57 Contact face (joining face)
[0097] 6 Laser
[0098] 61 Laser beam
[0099] 7 Ultrasonic welding unit
[0100] 71 Ultrasonic sonotrode
