DE102024139253A1 - A servo motor arrangement for remote control of trucks - Google Patents

Abstract

The invention relates to a servomotor arrangement (3) for remotely controlling a truck and for installation between a steering wheel and a hydraulic-mechanical power steering system (1). The servomotor arrangement (3) comprises: a shaft (10); a worm gear (24) arranged on the shaft (10) and having a worm wheel (11) engaging with a worm (17); an electric motor (4) mechanically connected to the worm (17); and a clutch (9) mechanically connected to the shaft (10) and arranged on the shaft (10) so as to be displaceable between a first and a second clutch position. The clutch (9) is further mechanically connectable to the worm wheel (11) and mechanically connected to the piston (8). The piston (8) is arranged in a fluid control cylinder (5) so as to be displaceable between a first and a second piston position, such that the first piston position corresponds to the first clutch position and the second piston position corresponds to the second clutch position. In the first clutch position (9), the clutch (9) is mechanically connected to the worm gear (11), and in the second clutch position (9), the clutch (9) is mechanically disconnected from the worm gear (11). The fluid control cylinder (5) is an air control cylinder (5) connected to a compressor, wherein in the first piston position, the air control cylinder (5) is filled with air. The piston (8) is provided with a spring (21) along its outer circumference to move the piston (8) to the second piston position, in which air is at least partially released from the air control cylinder (5).

Description

area of technology

The present invention relates to a servo motor arrangement for remotely controlling a truck.

State of the art

Power steering systems are known from the prior art. They are installed in most motor vehicles and generate an assist torque when steering, thereby reducing the steering torque applied by the driver to the steering column. Known power steering systems are based on a steering gear that transmits the drive force of a hydraulic or electric drive and forwards it to the steering column. Such steering gears are usually designed as helical gears, particularly as worm gears or worm wheels. This means they consist of a gear directly or indirectly connected to the steering shaft and a pinion meshing with it, which is driven by a drive via the shaft.

The US patent application US 2021086818 A1 describes an electro-hydraulic steering system, also known under the trade name Servotwin, from Robert Bosch (available on 21.12.2023 on https://www.bosch-mobility.com/en/solutions/steering/servotwin/ ), see 5 as well as the schematic figure and the video animation on this web link. This system uses a hydraulic-mechanical power steering unit (1) with a pre-assembled electric motor (4, designated as "H" in the figure on the link) directly on the hydraulic-mechanical power steering unit (1). The electric motor (4) is connected to the hydraulic-mechanical power steering unit (2) via a shaft (designated as "D" and "E" in the figure on the link) via a worm gear (24, designated as "J" in the figure on the link). This system is suitable for driving aids such as crosswind compensation, lane keeping assist, or autonomous driving in traffic jams. This system also enables autonomous driving of trucks when coupled with the on-board electronics. The disadvantage of this system is the permanent mechanical connection between the electric motor and the shaft. To avoid the driver having to overcome resistance in the transmission and electric motor while driving (even when the system is not in use), the electric motor must be continuously controlled, which increases the vehicle's fuel consumption. Furthermore, a larger contact area must be considered when installing the hydraulic-mechanical power steering system.

KNORR-BREMSE and Volvo Trucks also have similar systems. These systems also feature an electric gear motor as part of a hydraulic-mechanical power steering system with a permanent mechanical connection.

The Chinese patent application CN 106184352 A describes a steering system that allows switching between several steering modes, in particular manual electronic steering, manual mechanical steering and autonomous steering. The servo motor, which is integrated in the 2 to 5 of the same application, is generally and schematically connected to the steering column, without, however, giving details of the mechanical connection.

The US patent US 5893427 A describes a servomotor assembly for steering a vehicle with hydraulic power steering and for eliminating the mechanical connection between a steering wheel (a steering mechanism) and wheels (a steering element). The assembly comprises a shaft; a worm gear arranged on the shaft and having a worm wheel engaging a worm; and an electric motor mechanically connected to the worm. The servomotor assembly further comprises a piston in a fluid control cylinder slidably mounted on the shaft between a first and a second piston position. The piston is also hydraulically controlled by a valve unit electronically controlled by axial displacement of the worm. The servomotor is electronically controlled by a control unit connected to the steering wheel. Furthermore, a chamber located upstream and downstream of the piston in the shaft direction is hydraulically connected to the valve unit and further to an accumulator or a pressure side of the pump or a reservoir. The fluid control cylinder is filled with fluid in the first and second piston positions, with the transition between the piston positions being achieved by alternating hydraulic connection of one of the chambers to the pressure accumulator or the pressure side of the pump and the other chamber to the reservoir. It is therefore a double-acting fluid control cylinder.

The Chinese patent application CN 112498473 A describes a servomotor assembly for remote or autonomous control of a truck and for installation on a steering column, i.e. between a steering wheel and a hydraulic-mechanical power steering system. This servomotor assembly comprises: a shaft (with a fixed engagement sleeve); a worm gear arranged on the shaft and which drives a having a worm gear engaged with a worm; and an electric motor mechanically connected to the worm. The servomotor assembly further includes a clutch slidably disposed on the shaft between first and second clutch positions. The clutch is mechanically connected to a piston. The piston is slidably disposed in a fluid control cylinder between first and second piston positions such that the first piston position corresponds to the first clutch position and the second piston position corresponds to the second clutch position. The clutch is further removably connected to the shaft and mechanically connected to the worm gear. In the first, upper clutch position, the clutch is mechanically connected to the shaft, and in the second, lower clutch position, the clutch is mechanically disconnected from the shaft. The fluid control cylinder is an air control cylinder connected to an air reservoir, wherein the air control cylinder is filled with air in the second, lower piston position. The piston has a spring along its outer circumference biasing the piston to a first, upper piston position in which air is expelled from the air control cylinder. The disadvantage is that the mechanical connection between the electric motor and the shaft must be actively deactivated, which reduces the safety of the autonomous control.

The US patent US 5803202 A describes a reaction simulator for a vehicle control system, comprising: a return spring biasing a control lever to a neutral position; and means for applying a force to the control lever to simulate a direct connection of the control lever to another control mechanism.

Thus, the prior art gives rise to a need and the object of the invention to provide a safer servo motor arrangement with a detachable mechanical connection between the electric motor and the shaft.

The essence of the invention

This object is achieved by a servomotor assembly for remotely controlling a truck, and for installation between a steering wheel and a hydraulic-mechanical power steering system (i.e., between steering spindles upstream of a hydraulic-mechanical power steering system), comprising: a shaft; a worm gear arranged on the shaft and having a worm wheel engaging a worm; an electric motor mechanically connected to the worm; and a clutch arranged on the shaft for displacement between a first and a second clutch position, the clutch being mechanically connected to the shaft. The clutch is further mechanically connected to the worm wheel and mechanically connected to a piston. The piston is arranged in a fluid control cylinder for displacement between a first and a second piston position, such that the first piston position corresponds to the first clutch position and the second piston position corresponds to the second clutch position. In the first clutch position, the clutch is mechanically coupled to the worm gear, and in the second clutch position, the clutch is mechanically disconnected from the worm gear.

The fluid control cylinder is an air control cylinder connected to a compressor, with the air control cylinder being filled with air in the first piston position and the air being (at least partially) exhausted from the cylinder in the second piston position. The advantage of using air over other pneumatic actuators or other fluids is its ready availability. The piston is provided with a spring along its outer circumference to move the piston to the second piston position, preferably after the air has been exhausted from the air control cylinder.

The essence of the servomotor assembly according to the present invention lies in a safer servomotor assembly, wherein the piston is advantageously mechanically and independently returned to the second piston position (e.g., via a valve) after the air is released. The spring serves as a safety device to prevent the electric motor from spontaneously switching on in the event of a broken compressed air or hydraulic oil hose.

The essence of the servomotor assembly according to the present invention further lies in a detachable mechanical connection between the electric motor and the worm gear on the one hand, and between the coupling and the shaft on the other. Thus, when manually steering a vehicle, which can also be remotely controlled by the servomotor assembly, the driver does not have to overcome the resistance in the gearbox and the electric motor. At the same time, the electric motor does not have to be continuously controlled during manual steering, thus reducing the vehicle's fuel consumption.

In an advantageous embodiment, the worm wheel is connected to a worm wheel hub (e.g., by a screw connection) which has a spline for mechanical connection to the coupling. The coupling also comprises a spline for mechanical connection to the Worm gear hub. In the first coupling position, the coupling is mechanically connected to the worm gear hub via the spline, and in the second coupling position, the coupling is mechanically separated from the worm gear hub. The advantage of the splined connection between the coupling and the worm gear hub is that the two components are securely connected, eliminating the risk of slippage between them. The worm gear hub can be housed in a sliding sleeve to mechanically separate the surfaces of the worm gear hub and the shaft. In the second coupling position, the worm gear hub can rotate freely on the shaft within the sliding sleeve, which is pressed into the worm gear hub.

In an advantageous design, the coupling is mechanically connected to the shaft by a positive fit. The advantage of a positive connection between the coupling and the shaft is that the two components are securely connected and there is no risk of slippage between them.

In an advantageous embodiment, the clutch is mechanically connected to the piston via a shift fork. The shift fork allows free rotation in the clutch groove and is relatively easy to manufacture.

In an advantageous embodiment, the electric motor is connected to a switch which detects the clutch in the first clutch position or the shift fork in a position corresponding to the first clutch position.

The servomotor assembly according to the invention thus makes it possible to remotely control a vehicle (in particular a truck) without the driver being present in the cab, allowing the vehicle to be driven even in hazardous environments (e.g., for firefighters or soldiers). The servomotor assembly is connected upstream of the vehicle's hydraulic-mechanical power steering system and can therefore preferably be easily integrated into a standard steering mechanism. The servomotor assembly can be installed in a chain of spindles from the steering wheel to the hydraulic-mechanical power steering system. The electric motor is switched on (i.e., switched to remote control) by filling the fluid (air) control cylinder with fluid (air), engaging the connected clutch in the first position, actuating the switch, and rotating the electric motor, thereby creating a mechanical connection between the shaft and the electric motor. Disabling the electric motor (i.e., switching to manual control) is achieved by stopping the electric motor, releasing the fluid (air) from the fluid (air) control cylinder, opening the connected clutch in the second position, and deactivating the switch, which breaks the mechanical connection between the shaft and the electric motor. This means that the vehicle can be steered manually from the cab without having to overcome the resistance in the servomotor's gearbox, thus increasing the steering forces of the manual steering.

Description of drawings

• 1 shows a perspective view of the servo motor arrangement in a vehicle.
• 2 shows a perspective view of a servo motor arrangement according to the invention.
• 3 shows the servo motor arrangement according to the invention in a section through the shaft and the fluid control cylinder.
• 4 shows the servo motor arrangement according to the invention in a section through the screw.
• Figure 5 shows the state-of-the-art servo motor arrangement (electrohydraulic control Servotwin from Robert Bosch) in a top view.
• 6 shows the backlash of the worm gear.

Examples

1 shows the servomotor arrangement 3, which is arranged between the steering spindles 2 in front of the hydraulic-mechanical power steering 1. The wheel position feedback is provided via an angle sensor 22, which detects the angle of the two-armed steering lever 23, which is part of the steering mechanism.

2 shows the servomotor assembly 3 in an external view, showing the housing 15 and the electric motor 4, the shaft 10, and the fluid (air) control cylinder 5 protruding therefrom. Also arranged on the outside of the housing 15 is a sensor 6 for detecting the clutch position (see below). Switching to remote control mode is accomplished by supplying fluid (compressed air) to the fluid (air) control cylinder 5 and rotating the electric motor 4. The electric motor 4 detects remote control mode by actuating the switch 6, which detects the clutch 9 in the first clutch position, i.e., the shift fork 7 (see below), which corresponds to the clutch in the first clutch position.

3 shows the servo motor arrangement 3 in section through the shaft 10 and the fluid (air) control cylinder 5, and 4 shows the servo motor Arrangement 3 in section through the worm 17. The servo motor 3 in the housing 15 comprises a shaft 10; a worm gear 24 arranged on the shaft 10 with a worm wheel 11 that engages with the worm 17; an electric motor 4 that is mechanically coupled to the worm 17; a clutch 9 arranged on the shaft 10, which is displaceable between a first and a second clutch position 9; and a fluid (air) control cylinder 5 that comprises a piston 8. The clutch 9 is mechanically connected to the worm wheel 11, mechanically via a shift fork 7 to the piston 8, and mechanically positively connected to the shaft 10.

The worm wheel 11 is coupled to the worm wheel hub 12 of the worm wheel 11 (e.g., by four screws 13), wherein the worm wheel hub 12 has a spline for mechanical engagement with the clutch 9, and the clutch 9 also has a spline for mechanical engagement with the worm wheel hub 12 of the worm wheel 11. In the first clutch position, the clutch 9 is mechanically connected to the worm wheel hub 12 of the worm wheel 11 via the spline, and in the second clutch position 9, the clutch 9 is mechanically separated from the worm wheel hub 12 of the worm wheel 11. The worm wheel hub 12 of the worm wheel 11 is arranged in a sliding sleeve 25.

The piston 8 is slidably arranged in the fluid (air) control cylinder 5 between the first and second piston positions, so that the first piston position corresponds to the first clutch position 9 and the second piston position corresponds to the second clutch position 9. The piston 8 is provided with a spring 21 along its outer circumference to move the piston 8 into the second piston position. A control fork 7 is screwed onto the piston 8 of the fluid (air) control cylinder 5. The end of the piston 8 is guided in the housing 15.

The remote control is engaged by the clutch 9, which moves along the shaft 10 to the first position. The torque is transmitted from the electric motor 4 to the worm 17 via a key 19 on the shaft of the electric motor 4, and through the engagement of the worm 17 and the worm gear 11 with the clutch 9, the torque is transmitted via the spline in the worm wheel hub 12 of the worm gear 11 and in the clutch 9. Furthermore, the torque is positively transmitted from the clutch 9 to the shaft 10. The remote control is disengaged by releasing fluid (air) from the fluid (air) control cylinder 5, with the spring 21 then moving the piston 8 to the second piston position and the clutch 9 from engagement with the worm wheel hub 12, also into the second clutch position. In the disengaged state, i.e. in conventional steering operation, the clutch 9 is in the second clutch position, the worm gear hub 12 rotates freely on the shaft 10 in the sliding sleeve 25, which is pressed into the worm gear hub 12 of the worm gear 11.

According to 3 the shaft 10 is mounted in two bearings 14, and the interior of the housing 15 is sealed by a pair of buffers 16. According 4 The worm gear 17 is also mounted in two bearings 14, the space being closed on one side by a cap 18 and on the side facing the electric motor 4 by a buffer 16. The electric motor 4 is mounted in the housing 15 of the servo motor 3 via an intermediate plate 20. The worm gear 24 is lubricated with oil, which also dissipates the heat. The tooth play of the worm gear 24 according to 6 is kept as low as possible to enable the most precise control possible.

The advantage of this design lies in the servomotor arrangement within the conventional steering mechanism, eliminating the need for a dedicated electro-hydraulic-mechanical power steering system. Another advantage is the minimal resistance in standard steering mode, which does not compromise driving comfort.

As described in the prior art, 5 The Servotwin electrohydraulic control system from Robert Bosch. This system uses a hydraulic-mechanical power steering system 1 with a pre-assembled electric motor 4 (designated as "H" in the figure) directly on the hydraulic-mechanical power steering unit 1. The electric motor 4 is connected to the hydraulic-mechanical power steering system 2, or more precisely, to the shaft (designated as "D" and "E" in the figure), via a worm gear 24 (designated as "J" in the figure). The disadvantage of this system is the permanent mechanical connection of the electric motor to the shaft.

Industrial applicability

The servo motor arrangement described above can be used for remote control of a truck.

List of reference symbols

1

hydraulic-mechanical power steering

2

Steering spindles

3

Servo motor

4

electric motor

5

Fluid control cylinder, air control cylinder

6

Switch

7

shift fork

8

Pistons

9

coupling

10

Wave

11

Worm gear

12

Worm wheel hub of worm wheel 11

13

screw

14

warehouse

15

Housing

16

buffer

17

Snail

18

cap

19

key

20

intermediate plate

21

Feather

22

Angle sensor

23

two-armed lever

24

Worm gear

25

sliding sleeve

QUOTES CONTAINED IN THE DESCRIPTION

This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• US 2021086818 A1 [0003]
• CN 106184352 A [0005]
• US 5893427 A [0006]
• CN 112498473 A [0007]
• US 5803202 A [0008]

Cited non-patent literature

• https://www.bosch-mobility.com/en/solutions/steering/servotwin/ [0003]

Claims (6)

A servomotor arrangement (3) for remotely controlling a truck and for installation between a steering wheel and a hydraulic-mechanical power steering system (1), comprising: a shaft (10); a worm gear (24) arranged on the shaft (10) and having a worm wheel (11) engaging with a worm (17); and an electric motor (4) mechanically connected to the worm (17); wherein the servomotor assembly (3) further comprises a clutch (9) arranged on the shaft (10) so as to be displaceable between a first and a second clutch position, wherein the clutch (9) is mechanically connected to a piston (8), wherein the piston (8) is arranged in a fluid control cylinder (5) so as to be displaceable between a first and a second piston position, such that the first piston position corresponds to the first clutch position and the second piston position corresponds to the second clutch position, wherein the fluid control cylinder (5) is an air control cylinder (5), characterized in that the clutch (9) is further mechanically connected to the shaft (10) and is mechanically connectable to the worm wheel (11), wherein in the first clutch position, the clutch (9) is mechanically connected to the worm wheel (11), and in the second clutch position, the clutch (9) is mechanically disconnected from the worm wheel (11), wherein the air control cylinder (5) is connected to a compressor and is filled with air in the first piston position, wherein the piston (8) is provided along its outer circumference with a spring (21) to move the piston (8) into the second piston position in which air is at least partially released from the air control cylinder (5). The servo motor arrangement (3) according to Claim 1 , characterized in that the worm wheel (11) is connected to a worm wheel hub (12) of the worm wheel (11), which has a spline profile for mechanical connection to the coupling (9), and in that the coupling (9) has a spline profile for mechanical connection to the worm wheel hub (12) of the worm wheel (11), wherein in the first coupling position (9), the coupling (9) is mechanically connected to the worm wheel hub (12) of the worm wheel (11) via the spline profile, and in the second coupling position (9), the coupling (9) is mechanically separated from the worm wheel hub (12) of the worm wheel (11). The servo motor arrangement (3) according to Claim 2 , characterized in that the worm wheel hub (12) of the worm wheel (11) is arranged in a sliding sleeve (25). The servo motor arrangement (3) according to one of the preceding claims, characterized in that the coupling (9) is mechanically connected to the shaft (10) in a form-fitting manner. The servo motor arrangement (3) according to one of the preceding claims, characterized in that the clutch (9) is mechanically connected to the piston (8) via a shift fork (7). The servo motor arrangement (3) according to one of the preceding claims, characterized in that the electric motor (4) is connected to a switch (6) in order to detect the first clutch position.

Images