POWER STEERING ASSEMBLY WITH DIFFERENTIAL ANGLE SENSOR SYSTEM

Abstract

A power steering assembly for a hydraulic power steering system of motor vehicles includes an input shaft configured for connection to a steering wheel, an output shaft coupled to the input shaft configured for operational engagement with a steering rod, a hydraulic servo valve, an actuator, a sensor system, and an evaluation unit. The coupling between the input and output shafts is realized by a torsion bar and permits a first relative rotation between the input and output shafts. The hydraulic servo valve, which controls a hydraulic pressure and thus a steering assistance depending on the steering torque applied by a driver, has a rotatable control element engaged with, and driven by, the output shaft. An engagement between the output shaft and control element provides for a second relative rotation therebetween. This engagement includes a multi-stage planetary gear unit. The steering power assistance system is controlled depending on a third relative roation between the input shaft and control element. The actuator relatively displaces the control element in relation to the output shaft to influence the steering power assistance characteristics. The sensor system measures at least one differential angle between the control element and input shaft, wherein the control element is a valve sleeve disposed coaxially with the input and output shafts and the sensor system includes an encoder sleeve non-rotatably connected to the valve sleeve.

Claims

1. A power steering assembly for a hydraulic power steering system of motor vehicles, comprising: an input shaft configured for connection to a steering wheel; an output shaft coupled to the input shaft configured for operational engagement with a steering rod, wherein the coupling between the input shaft and the output shaft is realized by a torsion bar and permitting a first relative rotation between the input shaft and the output shaft; a hydraulic servo valve which controls a hydraulic pressure and thus a steering assistance depending on the steering torque applied by a driver, wherein the hydraulic servo valve has a rotatable control element engaged with the output shaft and driven by the output shaft, wherein an engagement between the output shaft and the control element provides for a second relative rotation between the output shaft and the control element, wherein said engagement between the output shaft and the control element comprises a multi-stage planetary gear unit, and the steering power assistance system is controlled depending on a third relative roation between the input shaft and the control element; an actuator configured for relatively displacing the control element in relation to the output shaft to influence the steering power assistance characteristics; a sensor system configured for measuring at least one differential angle between the control element and the input shaft, wherein the control element is a valve sleeve disposed coaxially with the input and the output shaft and the sensor system includes an encoder sleeve non-rotatably connected to the valve sleeve; an evaluation unit for evaluating the measurement values provided by the sensor system.

2. The power steering assembly according to claim 1, further including a steering rod, with a rack-and-pinion gear or a recirculating ball steering gear being provided between the output shaft and the steering rod.

3. The power steering assembly according to claim 1, wherein the actuator is a stepping motor.

4. The power steering assembly according to claim 1, further including a steering-gear housing with a valve tower, wherein the servo valve and the sensor system are accommodated in the valve tower and/or the servor valve and the sensor system are attached to the valve tower.

5. The power steering assembly according to claim 1, wherein the sensor system includes a differential angle sensor or at least two angle sensors.

6. A motor vehicle having a power steering assembly according to claim 1.

Description

BRIEF DESCRIPTION OF FIGURES

[0026] FIG. 1: shows a sectional view along the longitudinal axis of a first embodiment of the power steering assembly according to the disclosure;

[0027] FIG. 2: shows a cross-sectional view of a second embodiment;

[0028] FIG. 3: shows a cross-sectional view of a third embodiment;

[0029] FIG. 3A: shows a cross-sectional view of the third embodiment; and

[0030] FIG. 4: shows a cross-sectional view of the third embodiment.

DETAILED DESCRIPTION OF THE FIGURES

[0031] In the embodiment shown in FIG. 1, a differential angle sensor substantially comprising parts 20, 23, 25, and 27 is pushed over the input shaft 21 and attached to the housing above the valve tower 22. The main component 20 of the differential angle sensor is non-rotatably connected to the input shaft 21, and the magnet 23, by means of an encoder sleeve 27 that is non-rotatably connected to the valve sleeve 24 as a control element, leads the angle of rotation of the sleeve 24 out from the hydraulic region of the valve tower. The third part 25 of the sensor is stationarily connected to the valve tower 22 and provides the differential angle information concerning the differential angle between the input shaft 21 and the valve sleeve 24 to the evaluation unit 40 via a connector or the like.

[0032] An output shaft 29 (shown in FIGS. 3 and 3A) is coupled to the input shaft 21, wherein the coupling between the input shaft 21 and the output shaft 29 is realized by a torsion bar 30.

[0033] In the embodiment according to FIG. 1, the bearing (which is normally provided, as a rule, in hydraulic steering systems) comprises two concentrically disposed ball bearings 26 in order to center the input shaft 21 in the valve tower 22 and to compensate axial forces. The embodiment according to FIG. 2 shows a variation thereof. The valve tower 22 is made longer and the above-mentioned centering bearing 26 is installed above the sensor parts 20, 23, 25, and 27. The third part 25 of the differential angle sensor is stationarily connected to the valve tower 22 and provides the differential angle information concerning the differential angle between the input shaft 21 and the valve sleeve 24 to the evaluation unit 40 via a connector or the like. As shown in the embodiment according to FIG. 2, the sensor parts 20, 23, and 25 are accommodated within the valve tower 22 so that an opening 32 is provided in the valve tower 22 for electrical connection of the third part 25 to the evaluation unit 40.

[0034] FIG. 3 shows another embodiment, which, among other things, is different due to the use of an inductive sensor substantially comprising parts 27, 28, 35, and 36 for determining the differential angle between the input shaft 21 and the valve sleeve 24. To this end, the housing 28 of the inductive sensor is connected to the valve tower 22 and the differential angle is measured between a first rotor 35 non-rotatably connected to the input shaft 21 and a second rotor 36 non-rotatably connected to the encoder sleeve 27. The housing 28 of the inductive sensor is connected to the evaluation unit 40 in order to provide the differential angle information thereto.

[0035] FIG. 3A basically shows the embodiment of FIG. 3, but includes an actuator 50 for relatively displacing the control element 24 in relation to the output shaft 29. Furthermore, a multi-stage planetary gear unit 60 between the output shaft 29 and the control element 24 is schematically shown. In addition, a rack-pinion gear/recirculation ball steering gear 70 is schematically shown between the output shaft 29 and the steering rod 71.

[0036] FIG. 4 shows a more detailed cross-sectional view of the third embodiment shown in FIG. 3A. Particularly, FIG. 4 shows an exemplary embodiment of the multi-stage planetary gear unit 60 and the actuator 50.

[0037] In the embodiment shown, the planetary gear unit 60 comprises two planetary gear trains 80 and 90.

[0038] The input shaft 21 is connected to the output shaft 29 via the torsion bar 30, which is largely surrounded by the input shaft 21, the torsion bar 30 on its one end being non-rotatably connected to the input shaft 21 and on its other end non-rotatably connected to the output shaft 29. Moreover, the control element 24 is disposed concentrically with and around the input shaft 21. The control element 24 is mounted so as to be rotatable and/or displaceable relative to the input shaft 21.

[0039] The power steering assembly is encompassed by a housing 22. The first planetary gear train 80 and the second planetary gear train 90 are disposed in the housing 22. Each planetary gear train 80, 90 substantially comprises a sun gear 86, 96, several planet gears 84, 94 and a ring gear 82, 92. The first planetary geartrain 80 is associated with the control element 24 and the second planetary gear train 90 is associated with the output shaft 29, with the sun gears 86, 94 respectively being non-rotatably connected to the control element 24 or the output shaft 29. The ring gears 82, 92 of the two planetary gear trains 80, 90 are monnted so as to be rotatable independently from each other. Coupling of the two planetary gear trains 80, 90 is accomplished by means of a common planet carrier 98 which carries the planet gears 84, 94 of the two gear trains 80, 90, respectively, on common shafts 99. In this case, the planet gears 84, 94 are mounted so as to be rotatable independently from each other on the shafts 99.

[0040] The ring gears 82, 92 of the two planetary gear trains 80, 90 each comprise an external toothing as well as an internal toothing. In particular, the ring gears 82, 92 have different external toothings, with the number of teeth of the ring gear 92 generally being smaller than the number of teeth of the ring gear 82.

[0041] A two-stage pinion 54 is in rotational engagement with the external toothing of the two ring gears 82, 92. The two-stage pinion 54 also has two different toothings. The pinion 54 is non-rotatably connected to a drive shaft 52 of the actuator 50.

[0042] As can be seen in FIG. 4, the actuator 50 is disposed outside the housing 22. In the exemplary embodiment described here, the actuator 50 is an electric motor. In particular, the actuator 50 is a stepper motor. The actuator 50 drives the two-stage pinion 54 directly via the drive shaft 52. At the location where the actuator 50 is attached to the housing 22, the housing 22 has an opening through which the drive shaft 52 including the pinion 54 can be guided for assembly purposes. The seal between the actuator 50 and the planetary gear trains 80, 90 is realized by a shaft-sealing ring, O-ring or the like, which is not shown in FIG. 4. The common planet carrier 98 of the two planetary gear trains 80, 90 is rotatably mounted by means of corresponding bearings on the output shaft 29.

[0043] When the actuator 50 rotates the two-stage pinion 54, the two ring gears 82, 92 of the planetary gear trains 80, 90 are also made to rotate due to the rotational engagement with the pinion 54. Because the two ring gears 82, 92 have different external toothings, the result of the rotation is a difference angle between the ring gears 82, 92. This difference angle is transferred slightly amplified to a relative adjustment, particularly to a relative angle, between the control element 24 and the output shaft 29 by the transmission of the planetary gear trains 80, 90. If no relative adjustment is to be set between the control element 24 and the output shaft 29, the two ring gears 82, 92 are held in position through the two stage pinion 54.

[0044] If the input shaft 21 is rotated, the torque is transmitted through the torsion bar 30 onto the output shaft 29. Due to the torque transmission of the torsion bar 30, the latter is rotated, and thus the input shaft 21 relative to the output shaft 29. A steering movement or rotation of the output shaft 29 now leads to a rotation of the sun gear 96, which is non-rotatably connected to the output shaft 29. Since the ring gear 92 associated with the same planetary gear train 90 is retained on its external toothing by the pinion 54, the planetary gears 94 have to roll between the sun gear 96 and the ring gear 92. This process causes the common planet carrier 98 to rotate. Due to the rotation of the planet carrier 98 and the retention of the ring gears 82, 92 of the two planetary gear trains 80, 90 the planet gears 84 of the planetary gear train 80 associated with the control element 24 have to roll off the planetary gear train's ring gear 82. Thus, the rotation of these planet gears 84 causes a rotation of the sun gear 86, which is non-rotatably connected to the control element 24. Due to the identical transmissions of the two planetary gear trains 80, 90 the sun gear 86 associated with the control element 24 is rotated by the same angle as the sun gear 96 associated with the output shaft 29. Therefore, the control element 24 follows the rotation of the output shaft 29.

[0045] If a difference angle is now to be set, the two-stage pinion 54 is rotated by the actuator 50. This causes a difference angle between the two ring gears 82, 92 of the planetary gear trains 80, 90. This difference angle is transferred, amplified by the transmission of the planetary gear trains, to a relative adjustment, particularly to a relative angle, between the control element 24 and the output shaft 29.