Auxiliary steering device for a hydrostatic vehicle steering system

Abstract

The invention relates to an auxiliary steering device (10) for a hydrostatic vehicle steering system (16), comprising an input shaft (44), which can be actuated or set in rotation by means of a steering wheel (26), an output shaft (46) for actuating a steering metering valve (30), and a planetary gearing (48), comprising a planetary wheel carrier (50) with multiple planetary wheels (52), which mesh with a sun gear (54) and a surrounding ring gear (56), the input shaft (44) being connected to the planetary wheel carrier (50) and the output shaft (46) being connected to the sun gear (54) in each case for conjoint rotation. Furthermore, the auxiliary steering device (10) has an electric drive (58) for exerting a torque on the ring gear (56), a braking device (60) for fixing the input shaft (44), and a coupling device (62) for producing a rotationally fixed connection between the output shaft (46) and the planetary wheel carrier (50).

Description

[0001] Auxiliary steering device for a hydrostatic vehicle steering system

[0002] The invention relates to an auxiliary steering device for a hydrostatic vehicle steering system, such as is used in agricultural vehicles, but also forestry and construction machinery.

[0003] In general, such vehicle steering systems comprise a steering handle designed as a steering wheel, by means of which a steering metering valve in the form of an orbitrol, fed from a hydraulic high-pressure pump with pressurized hydraulic fluid, can be actuated in order to control a connected hydraulic steering cylinder for adjusting the steerable wheels of the vehicle. The function of the orbitrol is limited to adjusting the hydraulic flow in the direction of the hydraulic steering cylinder, whereas the provision of the hydraulic pressure, and therefore the hydraulic energy, is done by the hydraulic high-pressure pump. In this way, actuating forces can be generated without difficulty, which even take the conditions of heavy vehicles into account. On the other hand, a direct implementation of additional or auxiliary functions that require intervention in the hydrostatic vehicle steering is only possible with comparatively high expenditure.In contrast to so-called electro-hydraulic steering systems, there is, among other things, no direct mechanical connection between the steering handle and the steering cylinder, which would simplify such an intervention.

[0004] There is therefore a need for a universally applicable

[0005] Auxiliary steering device which allows the realisation of a multitude of additional and auxiliary functions in conjunction with a hydrostatic vehicle steering system at comparatively low cost.

[0006] This object is achieved by an auxiliary steering device having the features of patent claim 1.

[0007] Accordingly, the auxiliary steering device for a hydrostatic vehicle steering system comprises an input shaft that can be actuated or rotated by means of a steering handle, an output shaft for actuating a steering metering valve or orbitrol, and a planetary gear. The planetary gear comprises a planet gear carrier with a plurality of planet gears that mesh with a sun gear and a surrounding ring gear, the input shaft being connected in a rotationally fixed manner to the planet gear carrier and the output shaft being connected in a rotationally fixed manner to the sun gear. Furthermore, the auxiliary steering device has an electric drive for exerting a torque on the ring gear, a braking device for securing the input shaft, and a coupling device for establishing a rotationally fixed connection between the output shaft and the planet gear carrier.

[0008] Depending on the actuation state of the clutch or brake device on the one hand and the operating state of the electric drive on the other, it is possible to implement various additional and auxiliary functions for a hydrostatic vehicle steering system without having to modify the hydrostatic vehicle steering system itself. The auxiliary steering device according to the invention is also characterized by a comparatively simple and therefore particularly robust design and forms a unit that is structurally independent of the hydrostatic vehicle steering system, which makes it possible to retrofit it in existing vehicles or to offer it as an equipment variant for an additional charge. Universal use in conjunction with different types of hydrostatic vehicle steering systems is also possible, i.e. not only with those for front axle steering, but also for rear axle or articulated steering.

[0009] The steering handle is typically a steering wheel that is located in the driver's cab of the vehicle and is connected in a rotationally fixed manner to the input shaft of the auxiliary steering device.

[0010] Advantageous further developments of the auxiliary steering device according to the invention emerge from the subclaims.

[0011] Preferably, the braking device is urged into an open position in the unactuated state under the action of a return means. The braking device is mounted to secure the input shaft to a vehicle-fixed chassis part or to a fastening structure of the auxiliary steering device, which in turn is attached to a vehicle-fixed chassis part. The braking device, in particular a brake caliper for engaging a brake disc which is connected in a rotationally fixed manner to the input shaft, is actuated, for example, by means of an electromagnetic actuator. The braking device assumes its open position under the action of the return means, provided the electric actuator is de-energized. In this state, the steering handle or the steering wheel can be actuated or rotated by a driver in the usual way.On the other hand, the maximum braking torque that can be generated by the braking device is limited in such a way that the driver can overcome it by manually operating the steering handle, so that the driver can intervene in the vehicle steering at any time.

[0012] Furthermore, it is possible for the clutch device to be forced into an engaged position in the unactuated state under the action of a preloading means. Here, too, an electromagnetic actuator can be provided to actuate the clutch device, with the input and output shafts being non-rotatably coupled to one another when the electromagnetic actuator is de-energized. In other words, when the clutch device is in the engaged position, the planetary gear and thus ultimately the auxiliary steering device are bypassed, so that the input and output shafts rotate synchronously with one another when the steering handle is actuated.

[0013] Using the auxiliary steering system, various auxiliary and additional functions can now be implemented in conjunction with the hydrostatic vehicle steering system within the appropriate operating modes. For this purpose, the auxiliary steering system is equipped with an electronic control unit.

[0014] First emergency operating mode

[0015] In a first emergency operating mode provided for a malfunction of the auxiliary steering device, it is possible that, at the instigation of the control device when the brake device is open, the clutch device is engaged and the electric drive is put into a drive-free state in which the ring gear can rotate freely when the steering handle is actuated.

[0016] Such a malfunction can occur, for example, in the event of a defect or failure of the electric drive, a power supply provided for its operation, the angle of rotation sensor, or even the control device itself or an actuating or regulating circuit contained therein which serves to control the electric drive. The control device can detect whether this is the case on the basis of a self-diagnosis and / or a plausibility check of the information exchanged between the aforementioned components via the CAN bus. The first emergency operating state ensures that the driver can continue to influence the hydrostatic vehicle steering by operating the steering handle.

[0017] Second emergency operating mode

[0018] On the other hand, in a second emergency operating mode provided for a malfunction of the hydrostatic vehicle steering, the clutch device can be engaged at the instigation of the control device when the brake device is open and the electric drive can be put into a steering-assisting drive state dependent on a detected actuation of the steering handle.

[0019] The second emergency operating mode takes into account the fact that, in the event of a defect, the hydrostatic vehicle steering can only be operated via the steering handle with considerable force. One possible cause is a failure of the hydraulic high-pressure pump feeding the steering metering valve or orbitrol, which is detectable by the control unit via a corresponding error message on the CAN bus. In the second emergency operating mode, the driver's steering operation is actively supported by the electric drive by bypassing the planetary gear.

[0020] This allows the control device to determine the direction and extent of the driver's steering input from the current direction and position of the steering handle, as detected by a rotation angle sensor. The steering command thus detected is then converted into corresponding steering interventions by controlling the electric drive via the control or regulating circuit included in the control device.

[0021] Neutral operating mode

[0022] Furthermore, it can be provided that, at the instigation of the control device in a neutral operating mode with the brake system open, the clutch device is engaged and the electric drive is placed into a drive state that compensates for any reaction of the auxiliary steering device on the steering handle. The neutral operating mode can be called up manually via a user interface communicating with the control device.

[0023] The neutral operating mode differs from the first emergency operating mode in that the breakaway and friction torques that must be overcome when the electric drive is de-energized are reduced to such an extent that the actuation characteristics transmitted via the steering handle largely correspond to those of a conventional hydrostatic vehicle steering system without an auxiliary steering device. Here, too, the steering interventions are implemented based on the angle information from the angle sensor provided via the CAN bus.

[0024] In addition, additional operating modes for active driver assistance can be provided. These can also be called up manually via the user interface communicating with the control unit.

[0025] First support mode

[0026] Thus, in a first support mode, at the instigation of the control device, when the brake device is open, the clutch device can be engaged and, by means of the electric drive, an actuating torque can be applied to the steering handle indicating a straight-ahead position of the steerable wheels.

[0027] This function provides support or relief for the driver, particularly during road transport journeys, as lane keeping on straight stretches is made considerably easier due to the haptic feedback provided via the steering handle.

[0028] Second support mode

[0029] In a second support mode, it can be provided that, at the instigation of the control device, when the brake device is open, the clutch device is disengaged and the electric drive is controlled in such a way as to change the transmission ratio between the input and output shafts.

[0030] A typical application of the second assistance mode is the implementation of so-called parameter steering, as is known from the automotive sector. As the speed of a vehicle equipped with the auxiliary steering system increases, the transmission ratio can be reduced, and thus the gear reduction can increase. It is also conceivable to combine the first and second assistance modes, which is particularly useful for road haulage journeys. Information regarding the vehicle's current speed is available to the control device in the form of corresponding wheel speed information on the CAN bus or is derived from position information obtained from a satellite-based navigation system.

[0031] Au toma ti kmodu s

[0032] The automatic mode is characterized in this case by the fact that, at the instigation of the control device, the brake device is closed and the clutch device is disengaged, whereby the electric drive is controlled according to a steering command issued by an autonomous vehicle control system. By fixing the input shaft and thus the planetary gear carrier, the output shaft and thus the steering metering valve or orbitrol are rotated exclusively by the electric drive.

[0033] Autonomous vehicle control, for example, involves a steering system such as that offered by John Deere under the name “AutoTrac.” This system not only carries out driver-independent steering interventions but also influences the driving speed. To ensure that the driver retains control of the vehicle at all times, it is conceivable that the control unit will automatically end automatic mode when it detects that the steering handle has been operated and, for example, switch to neutral mode. The control unit can easily detect whether the steering handle has been deliberately operated by evaluating the angle of rotation information from the angle of rotation sensor that is available on the CAN bus.

[0034] The auxiliary steering device according to the invention for a hydrostatic vehicle steering system is explained in more detail below with reference to the accompanying drawings. Identical reference numerals refer to identical or functionally comparable components. They show:

[0035] Fig. 1 shows a schematically illustrated embodiment of the auxiliary steering device according to the invention, and

[0036] Fig. 2 shows a tabular overview of the auxiliary and additional functions that can be performed with the auxiliary steering device. Fig. 1 shows an exemplary embodiment of the auxiliary steering device 10 according to the invention in an agricultural vehicle 12.

[0037] The agricultural vehicle 12 in this case is an agricultural tractor 14 of conventional design. The agricultural tractor 14 is equipped with a hydrostatic or fully hydraulic vehicle steering system 16, by means of which the steering angle of steerable wheels 20, 22 arranged on a front axle 18 can be adjusted. More precisely, the hydrostatic vehicle steering system 16 comprises a steering handle 26 designed as a steering wheel 24 in a driver's cab 28 of the agricultural tractor 14, a steering metering valve 30 in the form of an orbitrol 32 that can be actuated by means of the steering wheel 24 and is fed with pressurized hydraulic fluid from a hydraulic high-pressure pump 34, and a hydraulic steering cylinder 36 that is connected to the orbitrol 32 and can be controlled by the orbitrol 32 for the purpose of adjusting the steerable wheels 20, 22.Depending on the direction of rotation of the orbitrol 32, the steering cylinder 36 is deflected either to one side or the other, the extent of the deflection resulting from the respective rotational position of the orbitrol 32, or more precisely from the proportional hydraulic volume that is pumped from the orbitrol 32 in the direction of the steering cylinder 36. In the present case, the steering cylinder 36 is designed to be double-acting, so that depending on the direction of rotation of the orbitrol 32, hydraulic fluid flows into one of the two working chambers 38, 40 and out of the other in the direction of a hydraulic reservoir 42. Starting from the illustration in Fig. 1, the auxiliary steering device 10 is located in the mechanical connection running between the steering wheel 24 and the orbitrol 32, for which purpose the auxiliary steering device 10 has on the input side a control which can be actuated or controlled by means of the steering wheel 24. has an input shaft 44 which can be set in rotation and an output shaft 46 on the output side for actuating the orbitrol 32.The steering wheel 24 and input shaft 44 on the one hand and the output shaft 46 and Orbitrol 32 on the other hand are each connected to one another in a rotationally fixed manner.

[0038] An essential component of the auxiliary steering device 10 is a planetary gear 48. The planetary gear 48 comprises a planetary gear carrier 50 with a plurality of planetary gears 52 which mesh with a sun gear 54 and a surrounding ring gear 56, wherein the input shaft 44 is connected in a rotationally fixed manner to the planetary gear carrier 50 and the output shaft 46 is connected to the sun gear 54.

[0039] Furthermore, the auxiliary steering device 10 has an electric drive 58 for exerting a torque on the ring gear 56, a braking device 60 for fixing the input shaft 44, and a coupling device 62 for establishing a rotationally fixed connection between the output shaft 46 and the planet gear carrier 50.

[0040] The electric drive 58 is designed as an electric gear motor 64 and is in driving engagement with the ring gear 56 of the planetary gear 48 via an output-side spur gear 66. The electric gear motor 64, like the braking device 60 described below, is mounted on a fastening structure 68 of the auxiliary steering device 10, which serves for attachment to a vehicle-fixed chassis part 70 indicated in Fig. 1.

[0041] The braking device 60 is urged into an open position in the unactuated state under the action of a return means 74 designed as a compression spring 72. The actuation of the braking device 60, in this case a brake caliper 76 for engaging a brake disc 78 connected in a rotationally fixed manner to the input shaft 44, takes place by means of an electromagnetic actuator 80. The braking device 60 assumes its open position under the action of the return means 74, provided the electromagnetic actuator 80 is in a de-energized state. In this state, the steering wheel 24 can be rotated by the driver in the usual way. On the other hand, the maximum braking torque that can be generated by the braking device 60 is limited in such a way that the driver can overcome it by manually actuating the steering wheel 24, so that driver intervention in the vehicle steering system 16 remains possible at any time.

[0042] On the other hand, the clutch device 62 is urged into an engaged position in the unactuated state under the action of a pretensioning means 84 formed by two compression springs 82. A further electromagnetic actuator 86 is provided to actuate the clutch device 62, wherein the input and output shafts 44, 46 are coupled to one another in a rotationally fixed manner, provided that the electromagnetic actuator 86 is in a de-energized state. In other words, in the engaged position of the clutch device 62, the planetary gear 48 and thus ultimately the auxiliary steering device 10 are bypassed, so that the input and output shafts 44, 46 rotate synchronously with one another when the steering wheel 24 is turned. In this case, the clutch device 62 has, according to Fig.1 has a first clutch disc 88 which is connected in a rotationally fixed manner to the output shaft 46 and which can be deflected in the direction of a second clutch disc 90 which is connected in a rotationally fixed manner to the output shaft 46 in order to engage a collar 92 which runs on the planet gear carrier 50.

[0043] An electronic control device 94 assigned to the auxiliary steering device 10 is used to coordinate the electric drive 58 and the two electromagnetic actuators 80, 86. This electronic control device 94 communicates via a CAN bus 96 of the agricultural tractor 14 with an engine control unit 98 provided for operating the electric drive 58, as well as with first and second power switches 100, 102, which allow independent control of the two electromagnetic actuators 80, 86. In addition, there is a rotation angle sensor 104 for sensory detection of the steering wheel position, the rotation angle information from which is made available to the control device 94 via the CAN bus 96. The rotation angle sensor 104 is arranged, for example, in the area of ​​the input shaft 44 in order to detect its current direction of rotation and position. Alternatively, the rotation angle sensor 104 is located in the area of ​​the steering cylinder 36.

[0044] As can be seen from Fig. 1, the control device 94 is also connected to a central vehicle control unit 106, which in turn communicates with a user interface 108 in the form of a touch-sensitive display 110, a satellite-based navigation system 112, an autonomous vehicle control 114, and a data transmission interface 116, which serves to establish a wireless data exchange connection 118 with a farm management system 120 on a central cloud server 122.

[0045] The auxiliary steering system 10 performs various auxiliary and additional functions within the corresponding operating modes. A tabular overview is provided in Fig. 2.

[0046] First emergency operating mode

[0047] In a first emergency operating mode provided for a malfunction of the auxiliary steering device 10, at the instigation of the control device 94, with the brake device 60 open, the clutch device 62 is engaged by controlling the associated electric actuator 86 and the electric drive 58 is placed in a drive-free state in which the ring gear 56 can rotate freely when the steering wheel 24 is actuated.

[0048] Such a malfunction can occur, for example, in the event of a defect or failure of the electric drive 58, a power supply provided for its operation, the rotation angle sensor 104, but also of the control device 94 itself or of an actuating or regulating circuit contained therein which serves to control the electric drive 58. The control device 94 detects whether this is the case on the basis of a self-diagnosis and / or a plausibility check of the information exchanged between the aforementioned components via the CAN bus 96. The first emergency operating state ensures that the driver can continue to influence the hydrostatic vehicle steering system 16 by actuating the steering wheel 24.

[0049] Second emergency operating mode

[0050] On the other hand, in a second emergency operating mode provided for a malfunction of the hydrostatic vehicle steering 16, at the instigation of the control device 94 with the brake device 60 open, the clutch device 62 is engaged and the electric drive 58 is placed in a steering-assisting drive state dependent on a determined actuation of the steering wheel 24.

[0051] The second emergency operating mode takes into account the fact that, in the event of a defect, the hydrostatic vehicle steering system 16 can only be operated via the steering wheel 24 with considerable effort. A possible failure could be the hydraulic high-pressure pump 34 feeding the steering metering valve 30 or Orbitrol 32, which could be detected by the control device 94 via a corresponding error message on the CAN bus 96. Therefore, in the second emergency operating mode, the driver's steering operation is actively supported by the electric drive 58 by bypassing the planetary gear 48.

[0052] The control device 94 derives the direction and extent of the driver's steering operation from the current direction of rotation and position detected by the angle of rotation sensor 104 via the input shaft 44 on the steering wheel 24. The steering command thus detected is then converted into corresponding steering interventions by controlling the electric drive 58 by means of the control or regulating circuit included in the control device 94.

[0053] Neutral operating mode

[0054] Furthermore, a neutral operating mode is provided in which, at the instigation of the control device 94, the clutch device 62 is engaged when the brake device 60 is open, and the electric drive 58 is placed in a drive state that compensates for the reaction of the auxiliary steering device 10 on the steering wheel 24. The neutral operating mode is called up manually via the user interface 108 communicating with the control device 94.

[0055] The neutral operating mode differs from the first emergency operating mode in that the breakaway and friction torques to be overcome in the non-driven state of the electric drive 58 are reduced to such an extent that the actuation characteristics conveyed via the steering wheel 24 largely correspond to those of a conventional hydrostatic vehicle steering system without auxiliary steering device 10. Here, too, the steering interventions are implemented on the basis of the rotation angle information provided by the rotation angle sensor 104 via the CAN bus 96 with regard to the current direction of rotation and position of the steering wheel 24 detected via the input shaft 44.

[0056] In addition, additional operating modes for active driver assistance are provided. These can also be called up manually via the user interface 108, which communicates with the control device 94.

[0057] First support mode

[0058] Thus, when the driver selects a first assistance mode at the instigation of the control device 94 with the brake device 60 open, the clutch device 62 is engaged and an actuating torque indicating a straight-ahead position of the steerable wheels 20, 22 is impressed on the steering wheel 24 by means of the electric drive 58.

[0059] This function provides support or relief for the driver, particularly when carrying out road transport journeys, since lane keeping on straight stretches is made considerably easier due to the haptic feedback provided via the steering wheel 24.

[0060] Second support mode

[0061] Alternatively or additionally, a second assistance mode can be selected by the driver. In this mode, at the instigation of the control device 94, with the brake device 60 open, the clutch device 62 is disengaged and the electric drive 58 is activated to change the transmission ratio between the input and output shafts 44, 46.

[0062] The second assistance mode serves to implement so-called parameter steering, as is known from the automotive sector. Thus, as the traveling speed of the agricultural tractor 14 increases, the transmission ratio decreases, thus increasing the gear ratio. Information regarding the current traveling speed of the agricultural tractor 14 is available to the control device 94 in the form of corresponding wheel speed information on the CAN bus 96 or is derived from position information obtained by the satellite-based navigation system 112.

[0063] Au toma ti kmodu s

[0064] Furthermore, the driver can select an automatic mode in which, at the instigation of the control device 94, the braking device 60 is closed and the clutch device 62 is disengaged, wherein the electric drive 58 is controlled in accordance with a steering command specified by the autonomous vehicle control 114.

[0065] By fixing the input shaft 44 and thus the planetary gear carrier 50, the output shaft 46 and thus the steering metering valve 30 or orbitrol 32 are rotated exclusively by the electric drive 58.

[0066] The autonomous vehicle control 114 is a steering system such as that offered by John Deere under the name "AutoTrac". In addition to carrying out driver-independent steering interventions, this also provides for influencing the driving speed. The route to be traveled autonomously is planned using the farm management system 120, with the associated control data being retrieved via the data transmission interface 116 and uploaded to the steering system of the autonomous vehicle control 114. To ensure that the driver always retains control of the agricultural tractor 14, the control device 94 automatically ends the automatic mode upon detecting actuation of the steering wheel 24 in order to switch to the neutral operating mode. The control device 94 detects whether the steering wheel 24 has been deliberately actuated by evaluating the angle of rotation information of the angle of rotation sensor 104 present on the CAN bus 96.

Claims

Claims: Auxiliary steering device for a hydrostatic vehicle steering system, comprising an input shaft (44) actuated by means of a steering handle (26), an output shaft (46) for actuating a steering metering valve (30), and a planetary gear set (48), comprising a planet carrier (50) with a plurality of planet gears (52) which mesh with a sun gear (54) and a surrounding ring gear (56), wherein the input shaft (44) is non-rotatably connected to the planet carrier (50) and the output shaft (46) is non-rotatably connected to the sun gear (54), wherein the auxiliary steering device (10) further comprises an electric drive (58) for exerting a torque on the ring gear (56), a braking device (60) for fixing the input shaft (44), and a coupling device (62) for establishing a non-rotatable connection between the output shaft (46) and the planet carrier (50).Auxiliary steering device according to claim 1, characterized in that the brake device (60) is forced into an open position in the unactuated state under the action of a return element (74). Auxiliary steering device according to claim 1 or 2, characterized in that the clutch device (62) is forced into an engaged position in the unactuated state under the action of a preloading element (84). An auxiliary steering device according to at least one of claims 1 to 3, characterized by a control device (94) at the instigation of which, in a first emergency operating mode provided for a malfunction of the auxiliary steering device (10) with the brake device (60) open, the clutch device (62) is engaged and the electric drive (58) is put into a drive-free state in which the ring wheel (56) can rotate freely when the steering handle (26) is actuated. An auxiliary steering device according to at least one of claims 1 to 3, characterized by a control device (94) at the instigation of which, in a second emergency operating mode provided for a malfunction of the hydrostatic vehicle steering (10) with the brake device (60) open, the clutch device (62) is engaged and the electric drive (58) is put into a steering-assist drive state dependent on a detected actuation of the steering handle (26).Auxiliary steering device according to claim 5, characterized in that the control unit (94) determines the direction and extent of the steering actuation from the current direction of rotation and position of the steering handle (26) detected by means of a rotation angle sensor (104). Auxiliary steering device according to at least one of claims 1 to 3, characterized by a control unit (94) at the instigation of which, in a neutral operating mode with the brake device (60) open, the clutch is engaged. The device (62) is engaged, and the electric drive (58) is placed in a drive state that compensates for any feedback from the auxiliary steering device (10) at the steering handle (26). The auxiliary steering device according to at least one of claims 1 to 3 is characterized by a control device (94), at the instigation of which, in a first support mode with the brake device (60) open, the clutch device (62) is engaged, and an actuating torque indicating a straight-ahead position of the steerable wheels (20, 22) is applied to the steering handle (26) by means of the electric drive (58).Auxiliary steering device according to at least one of claims 1 to 3, characterized by a control device (94) at the instigation of which, in a second support mode with the brake device (60) open, the clutch device (62) is disengaged and the electric drive (58) is controlled in the sense of changing the transmission ratio between the input and output shafts (44, 46). Auxiliary steering device according to the two preceding claims 8 and 9, characterized in that the control device (94) combines the first and second support modes. Auxiliary steering device according to at least one of claims 1 to 3, characterized by a control device (94) at the instigation of which, in an automatic mode, the... The braking device (60) is closed and the clutch device (62) is disengaged, with the electric drive (58) being controlled according to a steering command specified by an autonomous vehicle control system (114).

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