TEST BENCH FOR TESTING RAIL VEHICLE BOGES

Description

Technical field

[0001] The invention relates to a test bench for testing bogies of rail vehicles, comprising a load application unit for generating a linear force for a bogie to be tested, comprising a hydraulic cylinder with a piston rod and a transmission device for transmitting the force to the bogie, wherein the transmission unit is operatively connected to one end of the piston rod. The invention further relates to a method for testing bogies. State of the art

[0002] A bogie test bench is used to measure and test various parameters of rail vehicle bogies. Specifically, a load application unit applies forces to the bogie along one or more linear axes to simulate the expected operating forces due to the vehicle weight as well as static and dynamic influences. Various functions and parameters, such as wheel loads, axle distances, spring deflection, etc., are then tested or determined. Depending on the test bench's equipment, it is possible to fully automatically test the axle distance, axle parallelism, suspension, wheel concentricity, wheel diameter, etc.

[0003] After the test, all values ​​are saved in a database and can be printed out as a test report. The data can be transferred to a higher-level system.

[0004] In order to test different bogie models, such as motor and trailer bogies, different track gauges, 2- and 3-axle bogies, the relevant dimensions of the test bench can be adapted to the different requirements by manually or automatically adjusting individual components.

[0005] The load application unit exerts linear forces on the bogie, typically vertically downward forces. To achieve this, a defined position is reached using direct displacement measurement. The target force is then applied using force control. Typically, two load application units are installed, which are arranged on a crossbeam and can be moved relative to each other along a horizontal axis to adapt to different bogie dimensions or geometries. This allows forces such as those that occur when negotiating curves to be simulated.

[0006] Common load application units include hydraulic or electric load cylinders. Hydraulic load cylinders, for example, are designed as differential hydraulic cylinders and include a servo valve. They are controlled, for example, via an industrial PC. Such hydraulic cylinders are sensitive to transverse forces acting on the piston rod. Therefore, a so-called auxiliary yoke is usually present to absorb transverse forces. Accordingly, despite the hydraulic cylinders being inexpensive, the overall construction costs are relatively high. Maintenance and repair costs are also relatively high.

[0007] Electric load cylinders represent an alternative. These are designed, for example, as linear actuators with a ball screw drive. They are driven by a synchronous motor, which is usually controlled by a dedicated drive amplifier. However, such drives and corresponding spare parts are comparatively expensive.

[0008] Both hydraulic and electric load cylinders also require a relatively large amount of (electrical) energy during operation.

[0009] A test bench for testing a bogie is known from KR101773821 B1. Description of the invention

[0010] The object of the invention is to create a test bench for testing bogies belonging to the technical field mentioned at the beginning, which is cost- and energy-efficient.

[0011] The solution to the problem is defined by the features of claim 1. According to the invention, the load application unit of the test bench comprises a hydraulic cylinder with a piston rod, wherein the hydraulic cylinder is a double-acting cylinder whose cylinder chambers are supplied with hydraulic fluid by a bi-directional axial piston pump.

[0012] In the simplest case, the transmission device is the end face of the piston rod. This can also support a transmission piece. More complex transmission devices can also be used, for example, to distribute the force of the load application unit in a desired manner across one or more acting surfaces on the bogie. The transmission device can act directly on the bogie or on transmission elements specifically arranged on the bogie for the test.

[0013] Axial piston pumps are available that have very low internal leakage and can operate at very low speeds. This results in high efficiency: The energy required to drive the pump can be largely converted into the work of the hydraulic cylinder. This results in low energy costs.

[0014] Compared to electric load cylinders, they also offer lower manufacturing costs. Compared to hydraulic load cylinders, they offer significantly higher dynamic performance during operation, which—as described below—is advantageous for certain applications within a bogie test bench.

[0015] The axial piston pump advantageously includes a swash plate that interacts with multiple pistons on both sides. Such pumps are available from Bucher Hydraulics, Klettgau-Griessen, Germany, for example, under the type designation AXFM. These are 4-quadrant pumps that can be operated at speeds of less than 1 rpm. They are also characterized by particularly low internal leakage. These pumps were originally proposed for use in battery-powered mobile machines (e.g., in the mining sector).

[0016] The axial piston pump and the hydraulic cylinder, together with a compensating accumulator, advantageously form a closed hydraulic system. The compensating accumulator (pressure accumulator) serves to compensate for any leaks and vent the system. The closed system results in a simple and compact design with a minimum number of components. Manufacturing and maintenance costs are correspondingly reduced.

[0017] Additional components may be provided in the closed hydraulic system, in particular pressure relief, regulating and control valves.

[0018] Advantageously, the piston rod runs on both sides of the piston and is always supported at both longitudinal ends of the cylinder housing, regardless of the extended state.

[0019] This eliminates the need for an auxiliary yoke, as with previous hydraulic cylinders, to absorb the transverse forces acting when the cylinder is extended. This results in reduced manufacturing costs.

[0020] In addition, the hydraulic cylinder can be designed as a synchronous cylinder, in which the entire volume of the hydraulic fluid can be used as a pendulum volume.

[0021] The axial piston pump is driven, in particular, by a servomotor. This is preferably a synchronous motor that drives the pump directly. Such motors are durable and enable precise and energy-efficient operation. Alternatively, asynchronous motors or DC motors can be used. The use of a single motor, e.g., a three-phase motor with a frequency converter and a separate encoder, is also possible in principle.

[0022] Particularly preferably, the load application unit of the test bench according to the invention thus comprises a double-acting hydraulic cylinder with a continuous piston rod which is always supported at both longitudinal ends of the cylinder housing regardless of the extended state, an expansion tank which forms a closed hydraulic system with the hydraulic cylinder and the axial piston pump, and an electric motor for driving the axial piston pump.

[0023] Compared to known load application units with hydraulic or electric load cylinders, such a load application unit offers advantages in terms of energy consumption and noise generation, in addition to low maintenance and spare parts costs, which are explained in more detail below.

[0024] Advantageously, a length measuring device and a force measuring device are arranged on the hydraulic cylinder, and a drive control device is provided, which is connected to the length measuring device and the force measuring device for receiving measurement signals and to the servo motor for transmitting control signals. The drive control device is controlled in such a way that the control signals are generated depending on the measurement signals.

[0025] Due to the servo drive, the load application unit of the test bench according to the invention can be controlled precisely and with a very short reaction time, which in particular also enables tests in which rapidly changing effects on the bogie are simulated.

[0026] In the bogie test rig according to the invention, two load application units for generating vertical forces are arranged on a crossbeam, movable relative to each other along a horizontal axis. This enables the simulation of forces such as those that occur when negotiating curves or other one-sided loads on the bogie. Combined with the aforementioned fast control, this results in a high degree of freedom in defining the test cycles.

[0027] The invention also relates to a method for testing bogies, in which, prior to a testing step, the bogie is repeatedly compressed and extended by the forces applied by a load application unit in order to condition spring and / or damper elements for the test. The testing step can comprise several sub-steps, e.g., a first sub-step or a first group of sub-steps for testing the bogie geometry and a second sub-step or a second group of sub-steps for testing the suspension. Conditioning is particularly advantageous with regard to the testing of bogies with spring and / or damper elements made of elastomeric materials, e.g., natural or synthetic rubber-based materials. It brings such elements to a realistic operating temperature that corresponds to the conditions during operational use of the bogie.

[0028] The bogie test bench according to the invention is particularly well suited for implementing this method because the force application can be varied with high dynamics. Accordingly, high compression and rebound frequencies are possible, which significantly reduces the time required for conditioning.

[0029] For example, compression and rebound preferably occur at a frequency of 1 Hz or more. This allows the corresponding elements to be conditioned within a short time, and the duration of the test cycle is not significantly extended by the conditioning. Furthermore, with conditioning at these frequencies, any interim cooling of the elements is negligible.

[0030] To ensure sufficient conditioning before the test step, at least 10 compression and rebound cycles are preferably carried out.

[0031] The forces acting on the spring compression and rebound are at least 70% of the maximum forces acting on the spring compression and rebound during at least part of the conditioning period.

[0032] The possible uses of the device according to the invention are, of course, not limited to the specific method involving preconditioning. It also offers advantages when used in conventional testing procedures, where preconditioning of bogie elements is not necessary or desirable, for example.

[0033] Further advantageous embodiments and combinations of features of the invention result from the following detailed description and the entirety of the patent claims. Short description of the drawings

[0034] The drawings used to explain the embodiment show: Fig. 1: A schematic front view of a bogie test bench according to the invention; Fig. 2: An oblique view of the cross member of the bogie test bench with load application units arranged thereon; Fig. 3: A side view of a load application unit according to the invention; Fig. 4: An oblique view of the load application unit; Fig. 5: A hydraulic diagram of the load application unit; and Fig. 6: An illustration of the force curve during a test procedure with the bogie test bench according to the invention.

[0035] In principle, identical parts in the figures are provided with identical reference symbols. Ways to implement the invention

[0036] The Figure 1 shows a schematic front view of a bogie test bench according to the invention. Figure 2shows an oblique view of the cross member of the bogie test bench with load application units arranged thereon. The test bench 1 comprises supports 11, 12 for a bogie 50. These can be designed in a conventional manner, rail-like for each wheel of a track, or as separate units. The test bench 1 further comprises a gantry 20 with two supports 21, 22, on which a cross member 25 is mounted so as to be vertically displaceable along a linear guide. Each of the supports 21, 22 consists of two vertical supports 21.1, 21.2; 22.1, 22.2, which are arranged parallel to one another. The outer ends of the cross member 25 move in the space between the respective vertical supports 21.1, 21.2; 22.1, 22.2. The linear guide comprises vertical rails and a carriage 23.1, 23.2, each of which can be moved on it and to which the cross member 25 is attached. A drive motor 26.1, 26.2 for a spindle 27.1, 27.2 is arranged on each of the carriages 23.1, 23.2. The two spindles 27.1, 27.2 extend horizontally inward from the respective carriage 23.1, 23.2, parallel to the cross member 25, and serve to transversely adjust two load application units 100.1, 100.2 arranged on the cross member 25 via a further linear guide. The load application units 100.1, 100.2 are identical in design. They are described below in connection with the . Figures 3-5 , described in more detail. The cross member 25 further comprises a supply arrangement 28 with drag chains for supplying the load application units 100.1, 100.2 with electrical energy and control signals. Sensor signals from sensors arranged on the load application units 100.1, 100.2 are also transmitted via the drag chains of the supply arrangement 28 to a control and / or evaluation station.

[0037] The bogie 50 is in the Figure 1shown only schematically. It comprises a bogie frame 51, on which the wheel axle 54 with the wheels 55.1, 55.2 of the bogie 50 is mounted via secondary springs 52.1, 52.2 and wheel bearings 53.1, 53.2 with primary suspension.

[0038] The load application units 100.1, 100.2 have, at their lower ends, transmission pieces 120.1, 120.2 arranged on piston rods 114.1, 114.2, which interact with two application points 61, 62 on the bogie 50. In the example shown, the application points 61, 62 are located longitudinally centrally on the bogie frame and transversely in a plane approximately defined by the center of the running surfaces of the wheels of the corresponding side.

[0039] The forces exerted by the two load application units 100.1, 100.2 on the bogie 50 can be controlled independently of each other. Thus, both symmetrical and asymmetrical forces can be exerted on the bogie 50 in the transverse direction. Using suitable, conventional measuring devices, the reaction of the bogie 50 to the applied forces can be recorded.

[0040] The Figure 3 is a side view of a load application unit according to the invention, the Figure 4 shows an oblique view of the same. The load application unit 100 comprises a hydraulic cylinder 110 with a cylinder housing 111 in which a piston rod 114 with a piston 115 (cf. Figure 5) is sealed. A cylinder chamber 116, 117 is formed on each side of the piston. A transmission piece 120 is fixedly arranged at one of the free ends of the piston rod 115. The cylinder housing 111 also has two connections 118, 119, each of which opens into one of the cylinder chambers 116, 117. The cross-section of the cylinder housing 111 is constant, so that the hydraulic cylinder 110 functions as a double-acting cylinder.

[0041] The load application unit 100 also has a drive part 130, which is mounted on a base plate 170 together with the hydraulic cylinder 110. The drive part 130 comprises a servo motor 131, to whose output end a pump support 132 is flanged. An axial piston pump 140 is in turn flanged to this pump support 132. This is driven via an I <upplung direkt vom Servomotor 131 angetrieben. Die Axialkolbenpumpe 140 trägt schliesslich einen Ventilblock 150. Die genannten, aneinander angeflanschten Komponenten sind zusammen mit einem Ausgleichsspeicher 160, der als Tank für die Hydraulikflüssigkeit ausgebildet ist, auf einem L-förmigen Trägerblech 175 befestigt und sind parallel zum Hydraulikzylinder 110 hintereinander angeordnet. Dieses wiederum ist mit seinem kürzeren Schenkel mit der Grundplatte 170 verschraubt.

[0042] The servo motor 131 used in the described embodiment is a type AM 8072 from Beckhoff Automation, Verl, Germany. It is controlled by a type AX 5112 drive amplifier from the same manufacturer.

[0043] The axial piston pump 140 used in the described example is a pump of the type AXFM / 18 from Bucher Hydraulics, Klettgau-Griessen, Germany. It is an axial piston pump with a swash plate that acts on multiple pistons on both sides. It can be operated in all four quadrants and at speeds of 1 rpm or less. The maximum speed is 5,000 rpm, and the displacement is 18 cm3 / revolution. The maximum nominal pressure is 450 bar (each according to data sheet 03.2019).

[0044] The 110 hydraulic cylinder has a piston diameter of 150 mm, a piston rod diameter of 100 mm, and a stroke of 800 mm. The maximum feed rate is 20 mm / s and the maximum load is 250 kN.

[0045] The valve block 150 connects the axial piston pump 140 with the hydraulic cylinder 110 and the compensating accumulator 160. Cartridge-type pressure relief valves are also arranged on it (see Figure 5 ).

[0046] The Figure 5shows a hydraulic diagram of the load application unit 100. The axial piston pump 140 is driven by the servomotor 131 via a coupling 135. The servomotor is fed by the drive amplifier 138. The axial piston pump 140 is connected by its pressure ports 141, 142 to the ports 118, 119 of the two cylinder chambers 116, 117 of the hydraulic cylinder 110. An adjustable pressure relief valve 161, 162 is arranged in each of the connecting lines. These limit the pressure in the line from the respective cylinder chamber 116, 117 to the axial piston pump 140. In the opposite direction, the hydraulic fluid can flow freely thanks to check valves 163, 164 arranged parallel to the pressure relief valves 161, 162. In the line between the connection 141 of the axial piston pump 140 and the connection 118 of the lower cylinder chamber 116, a controllable valve 165 is also arranged, with which a backflow from the cylinder chamber 116 to the axial piston pump 140 can be prevented.

[0047] The pressure ports 141, 142 of the axial piston pump 140 are also connected to the equalizing accumulator 160, again via adjustable pressure relief valves 166, 167, which limit the pressure in the line from the axial piston pump 140 to the equalizing accumulator 160. In the opposite direction, the hydraulic fluid can flow freely thanks to check valves 168, 169 arranged parallel to the pressure relief valves 166, 167.

[0048] Finally, the axial piston pump 140 is also connected to the compensating reservoir 160 via a leakage connection 143.

[0049] At the lower end of the hydraulic cylinder 110, a force measuring unit 191 in the form of a load cell is arranged, which measures the force exerted by the hydraulic cylinder 110 and transmits it to a controller. Also arranged on the hydraulic cylinder 110 is a displacement measuring unit 192, which determines the current position of the piston 115 or the piston rod 114 and also transmits it to the controller.

[0050] The Figure 6 is a representation of the force curve during a test procedure using the bogie test rig according to the invention. The cycle shown is divided into the following phases: phase Beginn [min] End [min] Actions Feed 0 3 Feeding and positioning the bogie Condition 3 6 Oscillations between 15 and 150 kN, frequency 1 Hz Geometry testing 6 16 1st phase at 75 kN, 2nd phase at 150 kN Air spring test 16 27 1st phase at 5 kN, 2nd phase at 75 kN, 3rd phase at 150 kN Remove 27 3 Removing the bogie

[0051] During conditioning, the bogie components, especially those made of elastomeric materials, are thoroughly tumbled and brought into a condition that corresponds to normal operating conditions during rail service. The two sub-steps of the test correspond to those of common testing procedures.

[0052] For the test, the hydraulic cylinder 110 moves to a defined position based on the signals from the position measuring unit 192. Subsequently, the force target values ​​are approached in a force-controlled manner based on the signals from the force measuring unit 191.

[0053] To compare the inventive load application unit with known variants, the described cycle was used as a test cycle. During conditioning, only three low-frequency oscillations were performed because higher frequencies were not achievable for the purely hydraulic load application unit. The results of a one-hour test run were as follows: hydraulic LEE electrical LLE LLE according to the invention Connected load [kW] 7.5 8.0 4.5 Total energy consumption [kWh] 2.35 1.80 0.85 max. noise level [dB(A)] 75 70 65 Efficiency 0.7 0.6 0.85

[0054] The load application unit according to the invention thus has significantly lower energy requirements. It is also characterized by low noise generation.

[0055] The invention is not limited to the illustrated embodiment. In particular, individual components of the system may be designed differently, and the geometric arrangement of the elements of the load application unit and the mounting of the load application unit on the test bench may be implemented differently.

[0056] In summary, the invention creates a test bench for testing bogies that is cost- and energy-efficient.

Claims

1. A test stand (1) for testing bogies (50) of rail vehicles, comprising: two load application units (100.1, 100.2) for generating vertical application forces to a bogie (50) to be tested, each comprising a hydraulic cylinder (110) with a piston rod (114) as well as a transmission unit for transmitting the application force to the bogie (50), the transmission unit being operatively connected to one end of the piston rod (114), characterized in that the hydraulic cylinders (110) are double-acting cylinders whose cylinder chambers (116, 117) are pressurized with hydraulic fluid by a bidirectional axial piston pump (140), wherein the load application units (100.1, 100.2) for generating a linear application force are arranged on a cross member (25) so as to be displaceable relative to one another along a horizontal axis.

2. Test stand according to claim 1, characterized in that the axial piston pump (140) comprises a swash plate which cooperates on both sides with several pistons (115) in each case.

3. Test stand according to claim 1 or 2, characterized in that the axial piston pump (140) and the hydraulic cylinder (110) together with a compensating reservoir (160) form a closed hydraulic system.

4. Test stand according to one of claims 1 to 3, characterized in that the piston rod extends on both sides of the piston (115) and is always supported at both longitudinal ends of a cylinder housing (111) regardless of an extension state.

5. Test stand according to one of claims 1 to 4, characterized in that the axial piston pump (140) is driven by a servomotor (131).

6. Test stand according to claim 5, characterized in that a length measuring device and a force measuring device are arranged on the hydraulic cylinder (110) and that a drive control device is provided which is connected to the length measuring device and the force measuring device for receiving measuring signals and to the servomotor (131) for transmitting control signals, the drive control device being controlled in such a way that the control signals are generated as a function of the measuring signals.

7. A method for testing bogies (50) with a test stand according to one of claims 1 to 6, characterized in that, before a testing step, the bogie (50) is deflected in and out several times by application forces of a load application unit (100.1, 100.2) in order to condition spring and / or damper elements for the test.

8. The method according to claim 7, characterized in that the springing in and out occurs at a frequency of 1 Hz or more.

9. The method according to claim 7 or 8, characterized in that at least 10 spring-in and spring-out operations are performed before the testing step.¨10. The method according to one of the claims 7 to 9, characterized in that the application forces for springing in and springing out are at least 70% of the maximum application forces in the subsequent testing step.