WO2010083991A2

WO2010083991A2 - Method for operating a load

Info

Publication number: WO2010083991A2
Application number: PCT/EP2010/000304
Authority: WO
Inventors: Daniel Witte; Helmut Schildknecht
Original assignee: List Holding Ag
Priority date: 2009-01-20
Filing date: 2010-01-20
Publication date: 2010-07-29
Also published as: WO2010083991A3; CH700301A2

Abstract

In a method for operating a load (4) by means of a hydraulic motor (3) that is supplied with fluid by a pump device (20), a drive shaft (12) is to be associated with the pump device (20) and a speed control of a drive shaft for the load (4) is to be carried out by a speed control of the drive shaft (12) and/or the pump device (20) is to have a constant displacement volume per revolution.

Description

Method of operating a consumer

The invention relates to a method for operating a consumer by means of a hydraulic motor, which is supplied by a pumping device with fluid.

State of the art

Hydraulic drives are used to transfer power from electric or diesel drives to slow-speed shafts with high torques. Conventional hydraulic actuators consist of: a) a drive motor for constant speed electric drives; b) a pump that pumps hydraulic oil to c) the hydraulic motor connected to d) hydraulic lines connecting the pump to the motors and e) various ancillary equipment, such as Oil reservoir that collects the leakage current, and a pump that pumps the leak oil back into the main circuit.

The hydraulic motor is connected to the hydraulic lines with flexible hoses. A major advantage of this drive system is that the hydraulic motor is flexibly mounted on the output shaft. This is particularly advantageous because the output axis z. B. by thermal expansion of the consumer during operation shifts. The hydraulic motor is relatively lightweight and can be mounted on the output shaft usually without additional support. Another advantage of this drive concept is that very short and extreme load fluctuations (vibrations) in the hydraulic oil are damped, thus preventing damage to the bearing and the output shaft. The pump unit can also be installed at some distance from the output shaft, which is particularly beneficial for consumers at risk of exfoliation.

The hydraulic motor has a constant displacement per revolution. Since the hydraulic pressures in the supply line at nominal and maximum conditions are usually standardized in order to standardize components, automatically results in a specific torque for each hydraulic motor, which must be taken into account in the design. The maximum transferable capacity corresponds to the hydraulic pressure gradient times the volume flow of hydraulic oil. Since the engine speed at constant engine displacement is proportional to the volume flow of hydraulic oil (the oil is approximately compressible) and the hydraulic pressure of the engine is approximately constant, the hydraulic pressure in the engine intake is a representative quantity to describe the torque. Since this hydraulic pressure can be limited by means of a pressure relief valve, it is possible with simple means to protect the output shaft from too high a torque load.

Another advantage of the hydrodrive is that you can distribute the torque to several hydraulic motors. This is how the output shaft of drive both sides with simple means. With two identical hydraulic motors, the drive torque is half that of a double-sided motor on one drive side. It is also often the case that the consumption of the torque on the output shaft takes place uniformly over a large part of the length. Then the shaft is additionally relieved of hydraulic motors, which are mounted on both sides, and the shaft deflection due to the load decreases.

A similar principle is used when the output shaft is to be retrofitted because of increased requirements. Then the drive can be retrofitted with simple means, as an additional hydromotor "piggyback" can be mounted on the existing engine.

In order to be able to adapt the oil consumption to the demand, the stroke volume of the pump is varied in conventional systems. There are two most common control concepts. In the case of the "volume compensated" control, the hydraulic pressure in the supply line is kept constant by the consuming hydraulic motor.As the oil consumption in the line increases, the stroke volume of the pump is adjusted automatically so that the pressure does not drop, and vice versa.The advantage of this control concept is that you can install any number of hydraulic motors for a pump station system that has an intake and an exhaust manifold for all hydraulic motors, but the torque for all hydraulic motors is then constant.

In the case of the "pressure compensated" control, the stroke of the pump is kept constant and the hydraulic pressure of the motor supply line is allowed to vary.This control concept means that each output shaft has its own pumping system, as otherwise the torques of the different output axles would be interfered with Since the stroke of the pump is kept constant, the speed of the output shaft also remains constant. If the hydraulic motors are very large, a pump to operate is no longer sufficient. The largest axial piston pumps currently available on the market have a stroke of 1000 cc. Up to 500 cc, the pumps can be operated at 1800 rpm, in addition, these pumps must be operated at a lower speed. Therefore, the achievable pumping volume of a 1000 cc pump is not twice as high as that of a 500 cc pump. The maximum continuous speed of a pump with 1000 cc is for example 1200 rpm, which also does not correspond to the electrical mains frequency. It is therefore necessary to have a gearbox for this pump in order to get from the mains speed of 50 Hz (1500 rpm) or 60 Hz (1800 rpm) to 1200 rpm, or one must use a lower-pole electric motor.

The only way to realize high performance with pumps is to multiply the number of pumps. Several pumps can be installed on one drive axle, but typically not more than two for large drives. Thus, for a drive of e.g. 3 MW eight pumps with 500 cc stroke required (1500 rpm) and four electric motors. A disadvantage of this drive system is therefore the number of required (wear) parts and thus the required maintenance. Another disadvantage of this pump system is that the hydraulic efficiency of the

Axial piston pumps at part load decreases sharply. The efficiency of

Hydromotors are always considerably better than the pumps. It is therefore not only wasted electrical energy, but it must also be strongly cooled the oil circuit. This cooling performance is often underestimated, which limits the flexibility of the drive system.

The pumping stations must be connected to each other via manifolds and then to the engine. The piping effort, especially for drives with high power is very high. The line length increases at several pumping stations for a drive and thus also the power loss due to friction dissipation in the lines. It does not make sense, therefore Pumping stations too far away from the hydraulic motor to install. Since the pumping stations are very large and take up a lot of space, that is a disadvantage.

Another disadvantage is that with long feed lines, the volume of oil increases. If there are torque fluctuations on the output shaft, this will

Oil quantity elastically compressed and the oil flow rate at the engine decreases or decreases. This leads to speed fluctuations on the output shaft. The

Deviation from the average speed is proportional to the

Pressure change, not the pressure level in the supply line. Thus there is no direct relationship between the speed of the output shaft and the

Drehmomeηtniveau. A relief of the torque load by

Braking the shaft therefore does not take place.

By deceleration of the output shaft also additional torque is released, which adds to the torque of the drive. This

Torque is the inertia (moment of inertia) of the shaft and the

Hydraulic motor. Although the inertia of the hydraulic motor is small and thus adds little inertia to the output shaft in comparison to the direct drive with

Gearbox, the deceleration of the hydro drive is very high and accordingly the inert torque is not negligible. This inertia moment is proportional to the curvature of. According to the above-mentioned description

Hydraulic pressure curve. The strongest curvature agrees with the

Torque peaks match. Thus the wave connection of the

Hydraulic engine to the output axle relieved by this effect, but the torque peaks are not really 100% represented by the hydraulic pressure. This weakens the efficiency of the hydraulic pressure limitation to

Avert damage to the output shaft in the intervention of the consumer.

task

The object of the invention is to find a method of the type mentioned above, large hydraulic drives for rotating shafts, the large amounts of circulating Hydraulic oil need to be realized with little effort on hydraulic pump units, the method or a corresponding device provides a speed control with minimized speed fluctuations of the output shaft.

Solution of the task

To achieve the object that the pumping means is associated with a drive shaft and a speed control of an output shaft for the consumer takes place via a speed control of the drive shaft and / or the pumping device has a constant displacement per revolution.

The described disadvantages of the hydraulic drive at high powers are inventively improved so that the pump stations are replaced by hydraulic motors that act as pumps. These pump hydraulic motors are mounted on the drive axle and connected via a transmission gearbox with an electric motor or diesel engine. The electric or diesel drive has a variable speed z. B. with frequency converter. In a diesel engine then makes a diesel-electric drive with frequency converter sense.

The Pumphydromotoren have a much larger displacement per revolution than axial piston pumps. According to the invention, the nominal speed of these pumped-motor motors is most advantageously around 300 rpm, with a usual rotational speed of the output shaft of 30 rpm. Thus, the torque of the drive shaft of the pumped motor is 10 times smaller than that of the output shaft. This translation corresponds to a gearbox that covers the high, mechanically heavily loaded torque range of the drive. This is another advantage of this drive concept according to this invention. The number of required Pumphydromotoren is one to two per hydraulic motor on the output axis and thus by a factor of two to three lower. Only one electric motor per output shaft is needed, because the pump hydraulic motors can be mounted on a drive shaft. The distance between these pump hydraulic motors is lower and the piping effort is considerably reduced. Also reduced is the noise level of the hydro drive. Hydromotors cause comparatively little noise, while axial rotary lobe pumps produce considerable noise.

Another advantage of the inventive method is that the frequency converter can react very quickly to load fluctuations. Thus, it is possible to compensate for the oil volume flow fluctuations at the inlet of the hydraulic motor on the output shaft by the load adjustments of the electric motor. This is only partially possible with axial piston pumps, since the control here is hydraulic and therefore relatively sluggish.

Another advantage of the inventive drive concept is that the speed control of the drive by a frequency converter, the

Electric motor is fed, realized and this frequency converter can be installed relatively far away from the electric motor, without affecting the efficiency of the electric motor

Drive would deteriorate significantly. This takes up the space required

Drive equipment near the output shaft and problems of explosion protection are bypassed.

Another advantage of the inventive drive concept is that the hydraulic efficiency of the drive is much higher than in the conventional hydro drive. Thus, the required cooling capacity of the hydraulic circuit is smaller and less electrical energy is consumed.

DESCRIPTION OF THE FIGURES

Further advantages, features and details of the invention will become apparent from the following description of preferred embodiments and from the drawing; this shows in

Figure 1 is a block diagram representation of a hydraulic drive according to the prior art;

Figure 2 is a block diagram representation of an electrical drive of a consumer;

Figure 3 is a block diagram representation of a drive of a consumer with hydraulic speed control;

Figure 4 is a block diagram representation of an inventive electro-hydraulic drive concept for a consumer.

According to FIG. 1, three hydraulic piston pumps 1.1 to 1.3 are connected via a collecting line 2 to a hydraulic motor 3. This hydraulic motor 3 attacks a consumer 4.

The piston pumps 1.1 to 1.3 are operated by means of electric motors 9.1 to 9.3, so that hydraulic oil is pumped by the piston pumps 1.1 to 1.3 through the manifold 2 to the hydraulic motor 3. A return flow of the oil goes back to the piston pumps 1.1 to 1.3, which takes place via a common supply line 10.

A possible leakage flow flows into a reservoir 5 and is fed back via a pump 6, which in turn is driven by a motor 7, via a heat exchanger 8 in the collecting supply line 10. The motors 9.1 to 9.3 or 7 rotate with constant uncontrolled speed. The required amount of oil is adjusted by changing the stroke of a piston rod of the piston pumps 1.1 to 1.3.

For the electrical drive of a consumer 4, an electric motor 9 is provided according to Figure 2, to which a frequency converter 11 is assigned. This sets the frequency for the electric motor 9, wherein the phase angle of the drive axle is measured and used in the frequency converter computationally. For the frequency converter 11 is still a cooling 17 is provided

A drive axle 12 drives a transmission 13 for setting a speed range. An output shaft 14, which leads to the load 4, must be screened against expansion by means of a corresponding compensating device 15, furthermore, a safety clutch 16 is provided, which protects the output shaft 14 in case of overload.

According to FIG. 3, in the case of a drive with hydraulic speed control, an electric motor 9 with a constant and uncontrolled speed drives a hydraulic transmission 18. In this case, a speed of an output shaft 14 can be adjusted, wherein a speed range is adjusted via the transmission 13. The output shaft 14 must in turn be protected by a compensation device 15 against expansion and a safety clutch 16 against overload. It drives the consumer 4. The hydraulic transmission 18 must still be cooled by means of a cooling 17.

FIG. 4 shows an electrohydraulic drive concept according to the present invention. Again, a frequency converter 11 ensures the power frequency for an electric motor 9, wherein the phase angle of the drive axle is measured and used in the frequency converter 11 computationally. The drive axle 12 drives the transmission 13 to set a speed range. Furthermore, a hydraulic motor 20 sits on the drive axle, which consists in the present embodiment of two hydraulic pumps 21.2 and 21.2 with constant displacement.

The amount of oil from the hydraulic motor 20 is supplied via the manifold 2 to the hydraulic motor 3, which operates the consumer 4. A return line 22 connects the hydraulic motor 3 to the hydraulic motor 20.

A leakage flow flows into the reservoir 5 and is pumped back via the pump 6, which in turn is driven by the motor 7, via the heat exchanger 8 in the oil circuit.

LIST OF REFERENCE NUMBERS

Claims

claims

Method for operating a consumer (4) by means of a hydraulic motor (3) which is supplied with fluid by a pump device (20)

characterized,

in that the pumping device (20) is assigned a drive shaft (12) and a rotational speed control of an output shaft for the consumer (4) takes place via a rotational speed control of the drive shaft (12) and / or the pumping device (20) has a constant displacement volume per revolution.

2. The method according to claim 1, characterized in that the drive shaft (12) by an electric motor (9) is driven.

3. The method according to claim 1 or 2, characterized in that speed fluctuations of the drive shaft (12), which are induced by load changes of the output shaft, by adjusting the induced

Power of the drive axle (12) are compensated, so that the speed of the output shaft remains approximately constant.

4. Device for operating a consumer (4) by means of a hydraulic motor (3), which is supplied by a pumping device (20) with fluid, characterized in that the pumping device (20) on a drive shaft (12) sits.

5. Apparatus according to claim 4, characterized in that the pumping device (20) consists of one or more hydraulic motors (21.1,

21.2).

6. The device according to claim 5, characterized in that the / the hydraulic motor / s on a drive axle (12) is / s and thus only need a speed-controlled drive motor (9).

7. Device according to at least one of claims 4 to 6, characterized in that the drive shaft (12) with an electric motor (9) is connected.

8. Apparatus according to claim 7, characterized in that the motor (9) is associated with a frequency converter (11).

9. Apparatus according to claim 8, characterized in that the frequency converter (11) is cooled.

10. The device according to at least one of claims 7 to 9, characterized in that between the motor (9) and pumping means (20) a transmission (13) is arranged.