A RAIL VEHICLE AND A METHOD FOR OPERATION OF A RAIL VEHICLE

Abstract

A rail vehicle having a vehicle frame supported on on-track undercarriages and a hydraulic drive system powered by a motor. The drive system comprises a hydrodynamic drive associated with a first on-track undercarriage as well as a hydrostatic drive associated with a second on-track undercarriage. With the latter is associated a drive pump connected to a drive motor. The motor is designed for a higher power output than is necessary for the operation of the hydrodynamic drive. A pump distribution gear is switched between the motor and the hydrodynamic drive, via which the drive pump of the hydrostatic drive can be connected. This takes place in dependence on a friction value between the rail and wheel.

Claims

1. A rail vehicle (1) having a vehicle frame (4) supported on on-track undercarriages (2, 3) and a hydraulic drive system (6) powered by a motor (5), the drive system (6) comprising a hydrodynamic drive (7) associated with a first on-track undercarriage (2) as well as a hydrostatic drive (8), associated with a second on-track undercarriage (3), with which is associated a drive pump (10) connected to a drive motor (9), wherein the motor (5) is designed for higher power output than necessary for the operation of the hydrodynamic drive (7), and wherein a pump distribution gear (11) is switched between the motor (5) and the hydrodynamic drive (7), via which the drive pump (10) of the hydrostatic drive (8) can be connected.

2. The rail vehicle (1) according to claim 1, wherein at least one additional hydraulic pump (12) for operation of at least one additional hydraulic drive (13) for a work unit (14) is associated with the pump distribution gear (11).

3. A method for operation of the rail vehicle (1) with a hydraulic drive system (6) according to claim 1, wherein the hydrostatic drive (8) is added or removed in dependence on a friction value between the rail (18) and wheel (19).

4. The method according to claim 3, comprising the following steps: a) detecting a sinking friction value during operation with hydrodynamic drive (7), b) switching the hydrostatic drive (7) on by engaging the drive pump (10) and the drive motor (9), c) increasing the output of the motor (5), d) operating the rail vehicle (1) with hydrodynamic and hydrostatic drive (7, 8), e) reducing the output of the motor (5) upon exceeding a critical speed v.sub.K, f) switching the hydrostatic drive (8) off by disengaging the drive pump (10) and the drive motor (9), and g) operating the rail vehicle (1) with hydrodynamic drive (7).

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0013] The invention will be explained below by way of example with reference to the attached figures. There is shown in:

[0014] FIG. 1 a schematic side view of a rail vehicle,

[0015] FIG. 2 a drive scheme of the rail vehicle, and

[0016] FIG. 3 a speed/traction diagram.

DESCRIPTION OF THE EMBODIMENTS

[0017] Shown in FIG. 1 is a rail vehicle 1 designed as a track maintenance machine. The vehicle is essentially composed of a vehicle frame 4 supported on a first and a second on-track undercarriage 2, 3. The rail vehicle 1 has a hydraulic drive system 6 powered by a motor 5 preferably configured as an internal combustion engine. Said drive system 6 comprises a hydrodynamic drive 7 associated with the first on-track undercarriage 2, and a hydrostatic drive 8 associated with the second on-track undercarriage 3. As visible in FIG. 2, a drive pump 10 connected to the drive motor 9 is associated with the hydrostatic drive 8.

[0018] The motor 5 is designed for a higher power output than that required for the operation of the hydrodynamic drive 7. Switched between the motor 5 and the hydrodynamic drive 7 is a pump distribution gear 11. By means of the latter, the drive pump 10 of the hydrostatic drive 8 can be added.

[0019] Associated with the pump distribution gear 11 is at least one additional hydraulic pump 12 for operation of at least one additional hydraulic drive 13 for a work unit 14. Examples of such work units 14 would be a crane 15, lifting platform 16 or snow blower 17. In this, the number of the additional hydraulic pumps 12 may vary inasmuch as either a separate hydraulic pump 12 is associated with each work unit 14, or one hydraulic pump 12 alternatingly drives one of the work units 14.

[0020] The operation of the rail vehicle 1 will now be described briefly. The operation takes place in dependence on a friction value between a rail 18 and a wheel 19, wherein the hydrostatic drive 8 is added or removed.

[0021] Generally, the rail vehicle 1 is moved mainly by means of the hydrodynamic drive 7. With the aid of a measuring device 20, the sinking friction value is determined. Then, manual or automatic switching-on of the hydrostatic drive 8 takes place by engaging the clutch of the drive pump 10 and the drive motor 9. With increasing the output of the motor 5, the rail vehicle 1 is now operated with hydrodynamic and hydrostatic drive 7, 8. Upon exceeding a critical speed v.sub.K, the output of the motor 5 is reduced again and the hydrostatic drive 8 is switched off. This takes place by disengaging the drive pump 10 and the drive motor 9. Thereafter, the rail vehicle 1 is again powered only by the hydrodynamic drive 7.

[0022] As can be perceived from the diagram in FIG. 3, the critical speed v.sub.K is approximately 50 km/h. Up to this value, a combined drive (hydrodynamic and hydrostatic) with sufficient traction F.sub.Z is possible. At higher speeds v, a friction value =0.107 is already sufficient to employ the reduced motor output via the hydrodynamic drive 7.