Hydraulic system for a vehicle and vehicle

Abstract

A hydraulic system for a vehicle comprises two hydraulic cylinders with movable working pistons and associated piston rods, and a pump. The working pistons divide the hydraulic cylinders into an upper and a lower chamber. The piston rods extend through the lower chambers. The upper chambers are connected to each other by an upper hydraulic line, and the lower chambers are connected to each other by a lower hydraulic line. The hydraulic system includes a reservoir and a dual-pressure valve. An upper inlet of the dual-pressure valve is connected to an upper port on the pump, a lower inlet of the dual-pressure valve is connected to a lower port on the pump, and an outlet of the dual-pressure valve is connected to the reservoir.A vehicle according to the invention comprises a chassis, two swing arms which are pivotably mounted about swing axes, wheels which are rotatably mounted on the swing arms, and a hydraulic system. The hydraulic cylinders are articulated to the chassis, and the piston rods are articulated to the swing arms.

Description

[0001] The invention relates to a hydraulic system for a vehicle, comprising a first hydraulic cylinder, a first working piston displaceable therein, a first piston rod connected to the first working piston, a second hydraulic cylinder, a second working piston displaceable therein, a second piston rod connected to the second working piston, an upper hydraulic line, a lower hydraulic line and a pump.The invention also relates to a vehicle, in particular an autonomous transport vehicle, which comprises a chassis, a first swing arm which is pivotably mounted about a first swing axis relative to the chassis, a second swing arm which is pivotably mounted about a second swing axis relative to the chassis, a first front wheel and a first rear wheel which are rotatably mounted on the first swing arm, and a second front wheel and a second rear wheel which are rotatably mounted on the second swing arm, and a hydraulic system according to the invention.

[0002] A vehicle of this type with a hydraulic system of this type is known from DE 10 2023 004 647 A1. The vehicle comprises a chassis, two swing arms, each pivotally mounted about a pivot axis relative to the chassis, and wheels rotatably mounted on the swing arms. The hydraulic system enables the swing arms to pivot about their pivot axis relative to the chassis.

[0003] From CN 1 18 208 459 A a hydraulic system is known which includes two hydraulic cylinders with movable working pistons and piston rods connected to the working pistons, as well as hydraulic lines, a tank and a pump.

[0004] WO 2018 / 077 330 A1 discloses a hydraulic system for clutch actuation or gearbox actuation which includes a reversible pump and two main lines.

[0005] The invention is based on the objective of further developing a hydraulic system for a vehicle as well as a vehicle.

[0006] The problem is solved by a hydraulic system for a vehicle with the features specified in claim 1. Advantageous embodiments and further developments are the subject of the dependent claims. The problem is also solved by a vehicle with the features specified in claim 9. Advantageous embodiments and further developments are the subject of the dependent claims.

[0007] A hydraulic system according to the invention for a vehicle comprises a first hydraulic cylinder, a first working piston slidable therein, a first piston rod connected to the first working piston, a second hydraulic cylinder, a second working piston slidable therein, a second piston rod connected to the second working piston, an upper hydraulic line, a lower hydraulic line, and a pump. The working pistons divide each hydraulic cylinder into an upper chamber and a lower chamber. The upper chambers and the lower chambers are filled with a fluid. The piston rods extend through the lower chamber of each cylinder. The upper chambers of the hydraulic cylinders are connected to each other by means of the upper hydraulic line, and the lower chambers of the hydraulic cylinders are connected to each other by means of the lower hydraulic line.An upper port of the pump is connected to the upper hydraulic line, and a lower port of the pump is connected to the lower hydraulic line. The hydraulic system includes a reservoir and a dual-pressure valve. An upper inlet of the dual-pressure valve is connected to the upper port of the pump, a lower inlet of the dual-pressure valve is connected to the lower port of the pump, and an outlet of the dual-pressure valve is connected to the reservoir.

[0008] When a working piston in one of the hydraulic cylinders is moved in one direction, one of the chambers is enlarged while the other is simultaneously reduced in size. The hydraulic lines allow the fluid in the working piston to flow back and forth between the upper and lower chambers. This causes the other working piston in the other hydraulic cylinder to move in the opposite direction.

[0009] The pump is designed to transfer fluid from the upper hydraulic line to the lower hydraulic line and vice versa. When the pump transfers fluid from the upper to the lower hydraulic line, the pistons in the hydraulic cylinders are moved synchronously, reducing the size of the upper chambers and increasing the size of the lower chambers. Conversely, when the pump transfers fluid from the lower to the upper hydraulic line, the pistons in the hydraulic cylinders are moved synchronously, increasing the size of the upper chambers and decreasing the size of the lower chambers.

[0010] Since the piston rods extend only through the lower chamber of the hydraulic cylinders, the sum of the volumes of the upper and lower chambers depends on the position of the working pistons within the hydraulic cylinders. When the working pistons move synchronously, a volume difference arises within the hydraulic cylinders. This volume difference can be compensated for by appropriately controlling the dual-pressure valve, either by pumping fluid into or out of the tank.

[0011] According to the invention, the hydraulic system comprises a double check valve, which has an upper check valve and a lower check valve. The upper port of the pump is connected to the upper hydraulic line via the upper check valve, and the lower port of the pump is connected to the lower hydraulic line via the lower check valve.

[0012] When both check valves of the double check valve are closed, the pump is hydraulically isolated from the hydraulic lines and the hydraulic cylinders. This prevents, in particular, fluid from flowing from the hydraulic cylinders into the tank.

[0013] According to an advantageous embodiment of the invention, in a first position of the dual-pressure valve, the upper inlet is hydraulically connected to the outlet, and the lower inlet is hydraulically isolated from the outlet. In a second position of the dual-pressure valve, the lower inlet is hydraulically connected to the outlet, and the upper inlet is hydraulically isolated from the outlet.

[0014] When the pump transfers fluid from the upper hydraulic line to the lower hydraulic line, the sum of the volumes of the upper and lower chambers decreases. If the dual-pressure valve is in the first position, excess fluid from the upper hydraulic line is forced into the tank through the upper inlet and outlet of the dual-pressure valve.

[0015] When the pump transfers fluid from the lower hydraulic line to the upper hydraulic line, the combined volume of the upper and lower chambers increases. If the dual-pressure valve is in the second position, any missing fluid is drawn from the tank through the outlet and lower inlet of the dual-pressure valve and into the lower hydraulic line.

[0016] According to an advantageous embodiment of the invention, the check valves of the double check valve are coupled in such a way that both check valves open when there is a higher pressure at the upper port of the pump than in the upper hydraulic line, or when there is a higher pressure at the lower port of the pump than in the lower hydraulic line.

[0017] When the pump delivers fluid from the lower port to the upper port, the pressure at the upper port increases. This opens both check valves, and the pump delivers fluid from the lower hydraulic line to the upper hydraulic line. Conversely, when the pump delivers fluid from the upper port to the lower port, the pressure at the lower port increases. This opens both check valves, and the pump delivers fluid from the upper hydraulic line to the lower hydraulic line.

[0018] According to an advantageous embodiment of the invention, the check valves of the double check valve are coupled in such a way that both check valves close when the pressure at the upper port of the pump is lower or equal to that in the upper hydraulic line, and when the pressure at the lower port of the pump is lower or equal to that in the lower hydraulic line.

[0019] When the pump stops delivering fluid from the lower port to the upper port, the pressure at the upper port drops. This causes both check valves to close. When the pump stops delivering fluid from the upper port to the lower port, the pressure at the lower port drops. This causes both check valves to close.

[0020] According to an advantageous embodiment of the invention, a pressure sensor is connected to the upper hydraulic line, the lower hydraulic line, the upper connection of the pump and the lower connection of the pump.

[0021] The pressure sensors allow monitoring of the hydraulic system, especially for leaks or blockages.

[0022] According to an advantageous embodiment of the invention, the check valves are electrically controlled. The hydraulic system includes a control unit that receives measured values ​​from the pressure sensors. The control unit opens both check valves when the pressure at the upper connection of the pump is higher than in the upper hydraulic line, or when the pressure at the lower connection of the pump is higher than in the lower hydraulic line. According to an advantageous embodiment of the invention, the control unit closes both check valves when the pressure at the upper port of the pump is lower than or equal to that in the upper hydraulic line, and when the pressure at the lower port of the pump is lower than or equal to that in the lower hydraulic line.

[0023] According to an advantageous embodiment of the invention, the hydraulic system comprises at least one first shut-off valve connected to the upper hydraulic line, which, in an open position, hydraulically connects the upper chambers of the hydraulic cylinders to one another, and, in a closed position, hydraulically separates the upper chambers of the hydraulic cylinders from one another. The hydraulic system also comprises at least one second shut-off valve connected to the upper hydraulic line, which, in an open position, hydraulically connects the upper chambers of the hydraulic cylinders to one another, and, in a closed position, hydraulically separates the upper chambers of the hydraulic cylinders from one another. The upper port of the pump is connected to the upper hydraulic line in a region between the shut-off valves.

[0024] Closing one or both of these shut-off valves prevents fluid from flowing between the upper chambers and the lower chambers of the hydraulic cylinders. This also prevents the working pistons in the hydraulic cylinders from moving.

[0025] Closing exactly one shut-off valve prevents movement of the working piston in the adjacent hydraulic cylinder. However, the working piston of the other hydraulic cylinder can be moved by means of the pump, which delivers fluid from the upper hydraulic line to the lower hydraulic line, or vice versa.

[0026] A vehicle according to the invention, in particular an autonomous transport vehicle, comprises a chassis, a first swing arm pivotally mounted about a first pivot axis relative to the chassis, a second swing arm pivotally mounted about a second pivot axis relative to the chassis, a first front wheel and a first rear wheel rotatably mounted on the first swing arm, a second front wheel and a second rear wheel rotatably mounted on the second swing arm, and a hydraulic system according to the invention. The hydraulic cylinders are articulated to the chassis. The first piston rod is articulated to the first swing arm such that when the first working piston is displaced relative to the first hydraulic cylinder, the first swing arm pivots about the first pivot axis.The second piston rod is articulated to the second rocker arm in such a way that when the second working piston is displaced relative to the second hydraulic cylinder, the second rocker arm is pivoted around the second rocker arm axis.

[0027] The hydraulic system of the vehicle according to the invention allows the suspension arms to pivot around their axes in such a way that all wheels are always in contact with the ground on which the vehicle is located. When driving over uneven surfaces, corresponding pivoting movements of the suspension arms relative to the chassis occur. The vehicle's suspension is always statically determinate. Compared to a mechanical differential, the hydraulic cylinders occupy a relatively small installation space. When fluid in the working pistons flows back and forth through the hydraulic lines between the upper and lower chambers, the pivoting movements of the suspension arms relative to the chassis occur in opposite directions.

[0028] The pump's transfer of fluid from the upper hydraulic line to the lower hydraulic line, and vice versa, causes the swing arms to pivot synchronously and in the same direction relative to the chassis. This allows the chassis to be aligned with the ground. For example, when driving uphill, fluid is transferred from the upper hydraulic line to the lower hydraulic line, and when driving downhill, fluid is transferred from the lower hydraulic line to the upper hydraulic line. This allows the chassis to be aligned so that the vehicle's transport platform remains in an approximately horizontal position.

[0029] According to a preferred embodiment of the invention, the first axis of oscillation extends in a transverse direction, and / or the second axis of oscillation extends in the transverse direction. Preferably, the first axis of oscillation and the second axis of oscillation are aligned with each other.

[0030] According to an advantageous embodiment of the invention, the front wheels are arranged longitudinally offset from the rear wheels, and the pivot axes are arranged longitudinally between the front wheels and the rear wheels. According to an advantageous embodiment of the invention, the front wheels and / or the rear wheels are each steerable about a steering axis extending in a vertical direction, and / or the front wheels and / or the rear wheels are each rotatable about a pivot axis extending in a horizontal direction.

[0031] The longitudinal direction runs perpendicular to the transverse direction. The vertical direction runs perpendicular to both the longitudinal and transverse directions. Horizontal directions extend perpendicular to the vertical direction. In particular, the longitudinal and transverse directions represent horizontal directions.

[0032] According to an advantageous embodiment of the invention, the vehicle has a first angle sensor for detecting a pivot angle of the first swing arm about the first pivot axis relative to the chassis and a second angle sensor for detecting a pivot angle of the second swing arm about the second pivot axis relative to the chassis. Detecting the pivot angle of one of the swing arms enables corresponding control of the other swing arm by means of a suitable actuator. This allows for active control of the vehicle's chassis.

[0033] According to an advantageous embodiment of the invention, the vehicle has a first drive motor for driving the first front wheel and / or the first rear wheel and a second drive motor for driving the second front wheel and / or the second rear wheel, wherein the first drive motor is arranged on the first swingarm and the second drive motor is arranged on the second swingarm. Preferably, transmissions are also provided through which the drive motors drive the wheels. The transmissions are also arranged on the swingarms. This allows the drive motors and the transmissions to be arranged in a space-saving manner.

[0034] According to an advantageous embodiment of the invention, the vehicle has a first braking device for braking the first front wheel and / or the first rear wheel and a second braking device for braking the second front wheel and / or the second rear wheel, wherein the first braking device is arranged on the first swingarm and the second braking device is arranged on the second swingarm. The braking devices are preferably electromagnetically actuated.

[0035] The invention is not limited to the combination of features stated in the claims. For a person skilled in the art, further meaningful combinations of claims and / or individual claim features and / or features of the description and / or the figures will become apparent, in particular from the problem statement and / or the problem arising from a comparison with the prior art.

[0036] The invention will now be explained in more detail with reference to the illustrations. The invention is not limited to the embodiments shown in the illustrations. The illustrations only depict the subject matter of the invention schematically. They show: Fig. 1: A schematic view of a hydraulic system for a vehicle and Fig. 2: A schematic perspective view of a vehicle on a flat surface.

[0037] Fig. Figure 1 shows a schematic view of a hydraulic system for a vehicle. The hydraulic system comprises a first hydraulic cylinder 41, a first working piston 43 movable therein, a first piston rod 45 connected to the first working piston 43, a second hydraulic cylinder 42, a second working piston 44 movable therein, and a second piston rod 46 connected to the second working piston 44.

[0038] The first working piston 43 separates the first hydraulic cylinder 41 into an upper chamber 51 and a lower chamber 52. The first piston rod 45 extends through the lower chamber 52 and penetrates a lower end face of the first hydraulic cylinder 41. The upper chamber 51 and the lower chamber 52 of the first hydraulic cylinder 41 are filled with a fluid, in particular hydraulic oil.

[0039] The second working piston 44 separates the second hydraulic cylinder 42 into an upper chamber 51 and a lower chamber 52. The second piston rod 46 extends through the lower chamber 52 and penetrates a lower end face of the second hydraulic cylinder 42. The upper chamber 51 and the lower chamber 52 of the second hydraulic cylinder 42 are filled with a fluid, in particular hydraulic oil.

[0040] The hydraulic system comprises an upper hydraulic line 53 and a lower hydraulic line 54. The upper chamber 51 of the first hydraulic cylinder 41 and the upper chamber 51 of the second hydraulic cylinder 42 are connected to each other by means of the upper hydraulic line 53. The lower chamber 52 of the first hydraulic cylinder 41 and the lower chamber 52 of the second hydraulic cylinder 42 are connected to each other by means of the lower hydraulic line 54. The hydraulic lines 53 and 54 are also filled with fluid.

[0041] The hydraulic system comprises a pump 55, which has an upper port 57 and a lower port 58. The upper port 57 of the pump 55 is connected to the upper hydraulic line 53, and the lower port 58 of the pump 55 is connected to the lower hydraulic line 54.

[0042] Pump 55 is thus connected to the upper hydraulic line 53 and to the lower hydraulic line 54. Pump 55 is designed to pump fluid from the upper hydraulic line 53 to the lower hydraulic line 54 and from the lower hydraulic line 54 to the upper hydraulic line 53.

[0043] The hydraulic system comprises a tank 65 and a dual-pressure valve 60. The dual-pressure valve 60 has an upper inlet 61, a lower inlet 62, and an outlet 64. The upper inlet 61 of the dual-pressure valve 60 is connected to the upper port 57 of the pump 55. The lower inlet 62 of the dual-pressure valve 60 is connected to the lower port 58 of the pump 55. The outlet 64 of the dual-pressure valve 60 is connected to the tank 65.

[0044] In the first position of the dual-pressure valve 60, the upper inlet 61 is hydraulically connected to the outlet 64, and the lower inlet 62 is hydraulically disconnected from the outlet 64. In the second position of the dual-pressure valve 60, the lower inlet 62 is hydraulically connected to the outlet 64, and the upper inlet 61 is hydraulically disconnected from the outlet 64.

[0045] The hydraulic system includes a double check valve 70. The double check valve 70 has an upper check valve 71 and a lower check valve 72. The upper check valve 71 and the lower check valve 72 are coupled to each other. The check valves 71 and 72 are always open or closed simultaneously.

[0046] The upper port 57 of the pump 55 is connected to the upper hydraulic line 53 via the upper check valve 71. The lower port 58 of the pump 55 is connected to the lower hydraulic line 54 via the lower check valve 72.

[0047] The check valves 71, 72 of the double check valve 70 are coupled such that both check valves 71, 72 close when the pressure at the upper port 57 of the pump 55 is equal to or lower than the pressure in the upper hydraulic line 53, and when the pressure at the lower port 58 of the pump 55 is equal to or lower than the pressure in the lower hydraulic line 54. Each check valve 71, 72 has a spring which exerts a spring force on the respective check valve 71, 72 to close it.

[0048] The check valves 71, 72 of the double check valve 70 are coupled such that both check valves 71, 72 open when the pressure at the upper port 57 of the pump 55 is higher than in the upper hydraulic line 53, or when the pressure at the lower port 58 of the pump 55 is higher than in the lower hydraulic line 54. The pressure difference must be sufficiently large to compensate for the spring force exerted by the respective spring on the respective check valve 71, 72.

[0049] In an alternative embodiment, the check valves 71 and 72 of the double check valve 70 are electrically actuated. In this case, the hydraulic system includes a control unit for actuating, in particular opening and closing, the check valves 71 and 72.

[0050] The hydraulic system includes several pressure sensors 75 for monitoring the fluid pressure within the hydraulic system. In this case, a pressure sensor 75 is connected to the upper hydraulic line 53, the lower hydraulic line 54, the upper port 57 of the pump 55, and the lower port 58 of the pump 55. If the hydraulic system includes a control unit for actuating the check valves 71 and 72, the control unit receives measured values ​​from the pressure sensors 75.

[0051] The hydraulic system includes a first check valve 77, which is connected to the upper hydraulic line 53 and the lower hydraulic line 54. In an open position, the first check valve 77 hydraulically connects the upper chambers 51 of the hydraulic cylinders 41 and 42. In the open position, the first check valve 77 also hydraulically connects the lower chambers 52 of the hydraulic cylinders 41 and 42. In a closed position, the first check valve 77 hydraulically separates the upper chambers 51 of the hydraulic cylinders 41 and 42 from each other. In the closed position, the first check valve 77 also hydraulically separates the lower chambers 52 of the hydraulic cylinders 41 and 42 from each other.

[0052] The hydraulic system comprises a first second check valve 78, which is connected to the upper hydraulic line 53 and the lower hydraulic line 54. In an open position, the second check valve 78 hydraulically connects the upper chambers 51 of the hydraulic cylinders 41 and 42. In the open position, the second check valve 78 also hydraulically connects the lower chambers 52 of the hydraulic cylinders 41 and 42. In a closed position, the second check valve 78 hydraulically separates the upper chambers 51 of the hydraulic cylinders 41 and 42 from each other. In the closed position, the second check valve 78 also hydraulically separates the lower chambers 52 of the hydraulic cylinders 41 and 42 from each other.

[0053] The first shut-off valve 77 and the second shut-off valve 78 are configured as 4 / 2-way valves and are each connected to both hydraulic lines 53 and 54. In an alternative embodiment, the first shut-off valve 77 and the second shut-off valve 78 are configured as simple valves and are connected only to the upper hydraulic line 53. In a further alternative embodiment, the first shut-off valve 77 and the second shut-off valve 78 are configured as simple valves and are connected only to the lower hydraulic line 54.

[0054] In another alternative embodiment, the hydraulic system comprises two first shut-off valves 77 and two second shut-off valves 78, each designed as a simple valve. One first shut-off valve 77 and one second shut-off valve 78 are connected to the upper hydraulic line 53, and another first shut-off valve 77 and another second shut-off valve 78 are connected to the lower hydraulic line 54.

[0055] The upper port 57 of the pump 55 is connected to the upper hydraulic line 53 in an area between the shut-off valves 77 and 78. The lower port 58 of the pump 55 is connected to the lower hydraulic line 54 in an area between the shut-off valves 77 and 78.

[0056] The hydraulic system includes two pressure relief valves 68. One pressure relief valve 68 is connected between the upper port 57 of the pump 55 and the tank 65. The other pressure relief valve 68 is connected between the lower port 58 of the pump 55 and the tank 65. In the event of overpressure at the upper port 57 or the lower port 58 of the pump 55, the respective pressure relief valve 68 opens, and fluid flows through the open pressure relief valve 68 into the tank 65.

[0057] The hydraulic system also includes a leak line 69. The leak line 69 connects the pump 55 to the tank 65. In the event of a leak in the pump, fluid flows through the leak line 69 into the tank 65.

[0058] The hydraulic system includes two vent valves. One of the vent valves is connected to the upper hydraulic line 53, and one of the vent valves is connected to the lower hydraulic line 54.

[0059] Fig. Figure 2 shows a schematic perspective view of a vehicle on a flat surface. In this case, the vehicle is an autonomous transport vehicle. It is used to transport objects within a technical facility. This facility is an industrial application, such as a production plant or a paint shop. The vehicle can also be used, for example, to deliver goods to a private residence in a city or residential area.

[0060] A transverse direction Y runs perpendicular to a vertical direction Z. A longitudinal direction X runs perpendicular to both the vertical direction Z and the transverse direction Y. The vertical direction Z is perpendicular to the ground. The longitudinal direction X and the transverse direction Y represent horizontal directions. Any direction perpendicular to the vertical direction Z represents a horizontal direction. The longitudinal direction X corresponds at least approximately to the vehicle's usual direction of travel.

[0061] The vehicle comprises a chassis 12, a first swing arm 81, and a second swing arm 82. The first swing arm 81 is pivotally mounted about a first swing axis 91 relative to the chassis 12. The second swing arm 82 is pivotally mounted about a second swing axis 92 relative to the chassis 12. The first swing axis 91 extends in the transverse direction Y. The second swing axis 92 also extends in the transverse direction Y. The first swing axis 91 and the second swing axis 92 are aligned with each other.

[0062] The vehicle also includes a first front wheel 21, a first rear wheel 31, a second front wheel 22, and a second rear wheel 32. The first front wheel 21 and the first rear wheel 31 are rotatably mounted on the first swingarm 81. The second front wheel 22 and the second rear wheel 32 are rotatably mounted on the second swingarm 82. The front wheels 21, 22 are arranged offset longitudinally X from the rear wheels 31, 32. The swingarm pivots 91, 92 are arranged longitudinally X between the front wheels 21, 22 and the rear wheels 31, 32.

[0063] The first front wheel 21 and the first rear wheel 31 are each steerable about a steering axis extending in the vertical direction Z relative to the first swingarm 81. The first front wheel 21 and the first rear wheel 31 are each rotatable about a pivot axis extending in a horizontal direction relative to the first swingarm 81. In the illustration shown here, these pivot axes extend in the transverse direction Y. Depending on a steering movement of the first front wheel 21 and the first rear wheel 31 about these pivot axes, the pivot axes may extend in a different horizontal direction.

[0064] The second front wheel 22 and the second rear wheel 32 are each steerable about a steering axis extending in the vertical direction Z relative to the second swingarm 82. The second front wheel 22 and the second rear wheel 32 are each rotatable about a pivot axis extending in a horizontal direction relative to the second swingarm 82. In the illustration shown here, these pivot axes extend in the transverse direction Y. Depending on a steering movement of the second front wheel 22 and the second rear wheel 32 about these pivot axes, the pivot axes may extend in a different horizontal direction.

[0065] The vehicle has a first drive motor (not shown) for driving the first front wheel 21 and the first rear wheel 31. The first drive motor is located on the first swingarm 81. The vehicle also has a second drive motor (not shown) for driving the second front wheel 22 and the second rear wheel 32. The second drive motor is located on the second swingarm 82.

[0066] The vehicle has a first braking device (not shown) for braking the first front wheel 21 and the first rear wheel 31. The first braking device is located on the first swingarm 81. The vehicle also has a second braking device (not shown) for braking the second front wheel 22 and the second rear wheel 32. The second braking device is located on the second swingarm 82. These braking devices are electromagnetically actuated.

[0067] The vehicle has an electrical energy storage device (not shown). The vehicle also has a receiver unit (not shown) located on chassis 12, to which energy can be inductively transferred from a charging unit. The charging unit is designed, for example, as a linear conductor or a coil. The energy inductively transferred from the charging unit to the receiver unit is used, for example, to charge the vehicle's electrical energy storage device.

[0068] The vehicle has a first angle sensor for detecting the pivot angle of the first swing arm 81 about the first swing axis 91 relative to the chassis 12. The vehicle also has a second angle sensor for detecting the pivot angle of the second swing arm 82 about the second swing axis 92 relative to the chassis 12. The vehicle further has a tilt sensor for detecting the inclination of the ground, i.e., a slope or gradient.

[0069] The vehicle also includes a [unclear] in Fig. Figure 1 shows a hydraulic system. The first hydraulic cylinder 41 of the hydraulic system is articulated to the chassis 12, and the first piston rod 45 is articulated to the first rocker arm 81. The second hydraulic cylinder 42 of the hydraulic system is articulated to the chassis 12, and the second piston rod 46 is articulated to the second rocker arm 82.

[0070] The upper hydraulic line 53 and the lower hydraulic line 54 each lead from the hydraulic cylinders 41 and 42 into the chassis 12. The remaining components of the hydraulic system are located inside the chassis 12.

[0071] When the first working piston 43 is displaced relative to the first hydraulic cylinder 41, the first rocker arm 81 is pivoted about the first rocker arm axis 91. When the second working piston 44 is displaced relative to the second hydraulic cylinder 42, the second rocker arm 82 is pivoted about the second rocker arm axis 92.

[0072] The first rocker arm 81 and the second rocker arm 82 are coupled to each other via the hydraulic system in such a way that a pivoting movement of the first rocker arm 81 about the first pivoting axis 91 in a first pivoting direction causes a pivoting movement of the second rocker arm 82 about the second pivoting axis 92 in a second pivoting direction opposite to the first pivoting direction.

[0073] In the illustration shown here, the vehicle is on level ground. The contact points of the wheels 21, 22, 31, 32 with the ground lie in one plane. The working pistons 43, 44 are located approximately in the center of the hydraulic cylinders 41, 42. The piston rods 45, 46 protrude equally from the lower end faces of the hydraulic cylinders 41, 42.

[0074] If, for example, the first front wheel 21 drives over an obstacle, it is thereby raised in the vertical direction Z relative to the chassis 12. The first swingarm 81 is pivoted about the first swingarm axis 91, and the first rear wheel 31 is thereby lowered relative to the chassis 12 in the vertical direction Z. The pivoting movement of the first swingarm 81 about the first swingarm axis 91 pushes the first piston rod 45 further into the first hydraulic cylinder 41. This reduces the size of the upper chamber 51 of the first hydraulic cylinder 41 and enlarges the lower chamber 52 of the first hydraulic cylinder 41.

[0075] This causes fluid to flow from the upper chamber 51 of the first hydraulic cylinder 41 through the upper hydraulic line 53 to the upper chamber 51 of the second hydraulic cylinder 42. Fluid also flows from the lower chamber 52 of the second hydraulic cylinder 42 through the lower hydraulic line 54 to the lower chamber 52 of the first hydraulic cylinder 41. This enlarges the upper chamber 51 of the second hydraulic cylinder 42 and reduces the size of the lower chamber 52 of the second hydraulic cylinder 42.

[0076] This pushes the second piston rod 46 further out of the second hydraulic cylinder 42. This pivots the second swing arm 82 about the second swing arm axis 92. This lowers the second front wheel 22 in the vertical direction Z relative to the chassis 12, and raises the second rear wheel 32 in the vertical direction Z relative to the chassis 12. The contact points of the wheels 21, 22, 31, 32 with the ground are therefore no longer in the same plane.

[0077] When at least one of the shut-off valves 77, 78 is closed, fluid flow through the upper hydraulic line 53 between the upper chambers 51 of the hydraulic cylinders 41, 42, and through the lower hydraulic line 54 between the lower chambers 52 of the hydraulic cylinders 41, 42, is prevented. This also prevents movement of the working pistons 43, 44 in the hydraulic cylinders 41, 42. Consequently, pivoting movements of the swing arms 81, 82 relative to the chassis 12 are also prevented. The shut-off valves 77, 78 thus act like a switchable differential lock.

[0078] When the vehicle travels downhill, a gradient is detected, for example, by a tilt sensor. The dual-pressure valve 60 is then moved to the second position. The lower inlet 62 is thus hydraulically connected to the outlet 64, and the upper inlet 61 is hydraulically disconnected from the outlet 64. Furthermore, the pump 55 is controlled such that fluid is pumped from the lower port 58 to the upper port 57.

[0079] This increases the pressure at the upper port 57 of the pump 55. If the pressure at the upper port 57 of the pump 55 is higher than in the upper hydraulic line 53, both check valves 71 and 72 open. Fluid is then pumped from the lower hydraulic line 54 through the lower check valve 72, through the pump 55, and through the upper check valve 71 to the upper hydraulic line 53.

[0080] This causes fluid to flow through the upper hydraulic line 53 to the upper chambers 51 of the hydraulic cylinders 41, 42. Fluid also flows from the lower chambers 52 of the hydraulic cylinders 41, 42 to the lower hydraulic line 54. This enlarges the upper chambers 51 of the hydraulic cylinders 41, 42, and reduces the size of the lower chambers 52 of the hydraulic cylinders 41, 42.

[0081] This pushes the piston rods 45, 46 further out of the hydraulic cylinders 41, 42. This causes the swing arms 81, 82 to pivot about the swing axes 91, 92 relative to the chassis 12. As a result, the front wheels 21, 22 are lowered in the vertical direction Z relative to the chassis 12, and the rear wheels 31, 32 are raised in the vertical direction Z relative to the chassis 12.

[0082] During the aforementioned synchronous movement of the working pistons 43, 44, whereby the piston rods 45, 46 are pushed further out of the hydraulic cylinders 41, 42, a volume difference arises in the hydraulic cylinders 41, 42. More fluid flows into the upper chambers 51 than flows out of the lower chambers 52.

[0083] The aforementioned volume difference in the hydraulic cylinders 41, 42 is compensated by pumping fluid from the tank 65 out through the double pressure valve 60 to the lower connection 58 of the pump 55.

[0084] When the vehicle travels uphill, for example, a tilt sensor detects the incline. The dual-pressure valve 60 is then moved to the first position. The upper inlet 61 is thus hydraulically connected to the outlet 64, and the lower inlet 62 is hydraulically disconnected from the outlet 64. Furthermore, the pump 55 is controlled such that fluid is pumped from the upper port 57 to the lower port 58.

[0085] This increases the pressure at the lower port 58 of the pump 55. If the pressure at the lower port 58 of the pump 55 is higher than in the lower hydraulic line 54, both check valves 71 and 72 open. Fluid is then pumped from the upper hydraulic line 53 through the upper check valve 71, through the pump 55, and through the lower check valve 72 to the lower hydraulic line 54.

[0086] This causes fluid to flow through the lower hydraulic line 54 to the lower chambers 52 of the hydraulic cylinders 41, 42. Fluid also flows from the upper chambers 51 of the hydraulic cylinders 41, 42 to the upper hydraulic line 53. This enlarges the lower chambers 52 of the hydraulic cylinders 41, 42, and reduces the size of the upper chambers 51 of the hydraulic cylinders 41, 42.

[0087] This pushes the piston rods 45, 46 further into the hydraulic cylinders 41, 42. This causes the swing arms 81, 82 to pivot about the swing axes 91, 92 relative to the chassis 12. As a result, the front wheels 21, 22 are raised in the vertical direction Z relative to the chassis 12, and the rear wheels 31, 32 are lowered in the vertical direction Z relative to the chassis 12.

[0088] During the aforementioned synchronous movement of the working pistons 43, 44, whereby the piston rods 45, 46 are pushed further out into the hydraulic cylinders 41, 42, a volume difference arises in the hydraulic cylinders 41, 42. More fluid flows out of the upper chambers 51 than flows into the lower chambers 52.

[0089] The aforementioned volume difference in the hydraulic cylinders 41, 42 is compensated by pumping fluid from the upper port 57 of the pump 55 and through the double pressure valve 60 into the tank 65.

[0090] When the first shut-off valve 77 is closed, movement of the first working piston 43 and the first piston rod 45 in the first hydraulic cylinder 41 is blocked. This also prevents pivoting movement of the first rocker arm 81 relative to the chassis 12. However, pumping of fluid from the upper chamber 51 of the second hydraulic cylinder 42 to the lower chamber 52 of the second hydraulic cylinder 42, as well as from the lower chamber 52 of the second hydraulic cylinder 42 to the upper chamber 52 of the second hydraulic cylinder 42, is still possible. Thus, movement of the second working piston 44 and the second piston rod 46 in the second hydraulic cylinder 42 is possible. This also allows pivoting movement of the second rocker arm 82 relative to the chassis 12.

[0091] When the second shut-off valve 78 is closed, movement of the second working piston 44 and the second piston rod 46 in the second hydraulic cylinder 42 is blocked. This also prevents pivoting movement of the second rocker arm 82 relative to the chassis 12. However, pumping of fluid from the upper chamber 51 of the first hydraulic cylinder 41 to the lower chamber 52 of the first hydraulic cylinder 41, as well as from the lower chamber 52 of the first hydraulic cylinder 41 to the upper chamber 52 of the first hydraulic cylinder 41, is still possible. Thus, movement of the first working piston 43 and the first piston rod 45 in the first hydraulic cylinder 41 is possible. This also allows pivoting movement of the first rocker arm 81 relative to the chassis 12. Reference symbol list 12 chassis 21 first front wheel 31 first rear wheel 41 first hydraulic cylinder 43 first working piston 45 first piston rod 51 upper chamber 53 upper hydraulic line 55 pump 57 upper connection 60 Dual pressure valve 61 upper entrance 64 Exit 65 Tank 68 pressure relief valves 69 Leakage line 70 Double check valve 71 upper check valve 75 Pressure sensor 77 first shut-off valve 81 first swing arm 91 first swing axle X Longitudinal direction Y transverse direction Z Vertical direction 22 second front wheel 32 second rear wheel 42 second hydraulic cylinder 44 second working piston 46 second piston rod 52 lower chamber 54 lower hydraulic line 58 lower connection 62 lower entrance 72 lower check valve 78 second shut-off valve 82 second swing arm 92 second swing axle

Claims

[1] Hydraulic system for a vehicle, comprising a first hydraulic cylinder (41), a first working piston (43) which can be moved therein, a first piston rod (45) connected to the first working piston (43), a second hydraulic cylinder (42), a second working piston (44) which can be moved therein, a second piston rod (46) connected to the second working piston (44), an upper hydraulic line (53), a lower hydraulic line (54), a tank (65) and a pump (55), wherein the working pistons (43, 44) separate the hydraulic cylinders (41, 42) into an upper chamber (51) and a lower chamber (52), and the upper chambers (51) and the lower chambers (52) are filled with a fluid, and the piston rods (45, 46) extend through the lower chamber (52), and wherein the upper chambers (51) of the hydraulic cylinders (41, 42) are connected to each other by means of the upper hydraulic line (53), and the lower chambers (52) of the hydraulic cylinders (41, 42) are connected to each other by means of the lower hydraulic line (54), and wherein an upper connection (57) of the pump (55) is connected to the upper hydraulic line (53), and a lower connection (58) of the pump (55) is connected to the lower hydraulic line (54), characterized by , that the hydraulic system includes a dual-pressure valve (60), and that an upper inlet (61) of the dual-pressure valve (60) is connected to the upper port (57) of the pump (55), and that a lower inlet (62) of the dual-pressure valve (60) is connected to the lower port (58) of the pump (55), and that an outlet (64) of the dual-pressure valve (60) is connected to the tank (65), and that the hydraulic system includes a double check valve (70) which has an upper check valve (71) and a lower check valve (72), and that the upper port (57) of the pump (55) is connected to the upper hydraulic line (53) via the upper check valve (71), and that the lower connection (58) of the pump (55) is connected to the lower hydraulic line (54) via the lower check valve (72). [2] Hydraulic system according to claim 1, characterized by , that in a first position of the dual-pressure valve (60) the upper inlet (61) is hydraulically connected to the outlet (64), and the lower inlet (62) is hydraulically separated from the outlet (64), and that in a second position of the dual-pressure valve (60) the lower inlet (62) is hydraulically connected to the outlet (64), and the upper inlet (61) is hydraulically separated from the outlet (64). [3] Hydraulic system according to any of the preceding claims, characterized by , that the check valves (71, 72) of the double check valve (70) are coupled in such a way that both check valves (71, 72) open when at the upper connection (57) of the pump (55) there is a higher pressure than in the upper hydraulic line (53), or if The pressure at the lower connection (58) of the pump (55) is higher than in the lower hydraulic line (54). [4] Hydraulic system according to any of the preceding claims, characterized by , that the check valves (71, 72) of the double check valve (70) are coupled in such a way that both check valves (71, 72) close when at the upper connection (57) of the pump (55) the pressure is lower or the same as in the upper hydraulic line (53), and when The pressure at the lower connection (58) of the pump (55) is lower or the same as in the lower hydraulic line (54). [5] Hydraulic system according to any one of the preceding claims, characterized by , that A pressure sensor (75) is connected to the upper hydraulic line (53), the lower hydraulic line (54), the upper connection (57) of the pump (55) and the lower connection (58) of the pump (55). [6] Hydraulic system according to claim 5, characterized by that the check valves (71, 72) are electrically controllable, and that the hydraulic system includes a control unit which receives measured values ​​from the pressure sensors (75), and that the control unit opens both check valves (71, 72) when at the upper connection (57) of the pump (55) there is a higher pressure than in the upper hydraulic line (53), or if The pressure at the lower connection (58) of the pump (55) is higher than in the lower hydraulic line (54). [7] Hydraulic system according to claim 6, characterized by , that the control unit closes both check valves (71, 72) when at the upper connection (57) of the pump (55) the pressure is lower or the same as in the upper hydraulic line (53), and when The pressure at the lower connection (58) of the pump (55) is lower or the same as in the lower hydraulic line (54). [8] Hydraulic system according to any of the preceding claims, characterized by , that the hydraulic system includes at least one first shut-off valve (77) which is connected to the upper hydraulic line (53), and which in an open position hydraulically connects the upper chambers (51) of the hydraulic cylinders (41, 42) to each other, and which in a closed position hydraulically separates the upper chambers (51) of the hydraulic cylinders (41, 42) from each other, and that the hydraulic system includes at least a second shut-off valve (78) which is connected to the upper hydraulic line (53), and which in an open position hydraulically connects the upper chambers (51) of the hydraulic cylinders (41, 42) to each other, and which in a closed position hydraulically separates the upper chambers (51) of the hydraulic cylinders (41, 42) from each other, and that the upper port (57) of the pump (55) is connected to the upper hydraulic line (53) in an area between the shut-off valves (77, 78). [9] vehicle, in particular autonomous transport vehicle, comprising a chassis (12), a first swing arm (81) which is pivotably mounted about a first swing axis (91) relative to the chassis (12), a second swing arm (82) which is pivotably mounted about a second pivot axis (92) relative to the chassis (12), a first front wheel (21) and a first rear wheel (31), which are rotatably mounted on the first swingarm (81), a second front wheel (22) and a second rear wheel (32), which are rotatably mounted on the second swingarm (82), and a hydraulic system according to one of the preceding claims, wherein the hydraulic cylinders (41, 42) are articulated to the chassis (12), and wherein the first piston rod (45) is articulated to the first rocker arm (81) such that when the first working piston (43) is displaced relative to the first hydraulic cylinder (41), the first rocker arm (81) is pivoted about the first rocker arm axis (91), and wherein the second piston rod (46) is articulated to the second rocker arm (82) such that when the second working piston (44) is displaced relative to the second hydraulic cylinder (42), the second rocker arm (82) is pivoted about the second rocker arm axis (92). [10] Vehicle according to claim 9, characterized by , that the first oscillation axis (91) runs in a transverse direction (Y), and / or that the second oscillation axis (92) runs in the transverse direction (Y), and / or that the first oscillation axis (91) and the second oscillation axis (92) are aligned with each other. [11] Vehicle according to one of claims 9 to 10, characterized by , that the front wheels (21, 22) are arranged offset in a longitudinal direction (X) to the rear wheels (31, 32), and that the swing axles (91, 92) are arranged in the longitudinal direction (X) between the front wheels (21, 22) and the rear wheels (31, 32). [12] Vehicle according to any one of claims 9 to 11, characterized by , that the front wheels (21, 22) and / or the rear wheels (31, 32) are each steerable about a steering axis extending in a vertical direction (Z), and / or that the front wheels (21, 22) and / or the rear wheels (31, 32) are each rotatable about a pivot axis extending in a horizontal direction.

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