TREA

Gear pump having a multishaft drive and method of operating same

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Information

  • Patent Grant
  • 6447256
  • Patent Number
    6,447,256
  • Date Filed
    Thursday, September 27, 2001
    23 years ago
  • Date Issued
    Tuesday, September 10, 2002
    22 years ago
Information
Abstract
A gear pump having two meshing gears which are each assigned to a shaft and which are each driven by a driving unit. The driving units are controllable by a control unit such that the shafts rotate at a definable angular velocity. The control units have a symmetrical construction, and a control device provided in each control unit, each control device being connected to the other by way of a data line.
Description




BACKGROUND AND SUMMARY OF THE INVENTION




This application claims the priority of European application 98 115 962.7, filed in the European Patent Office on Aug. 25, 1998, the disclosure of which is expressly incorporated by reference herein.




The present invention relates to a gear pump having two mutually meshing gears which are each assigned to a shaft and which are each driven by means of a driving unit, the driving units each being drivable by a control unit such that the shafts rotate at a definable rotational velocity.




Normally, gear pumps are driven by a single shaft which extends out of the pump casing. In cases with very high torques or when the flow medium is charged with fillers, two-shaft arrangements are occasionally also used in order to protect the tooth surfaces from wear or excess strain.




Known multishaft drives include timing gears which ensure that the tooth surfaces do not come in contact with one another. In the case of the known multishaft drives, a single driving unit is used, the force distribution onto the individual shafts taking place by means of the engaging gears by way of the above-mentioned timing gear.




Furthermore, a teaching is known from German Patent Document DE-32 30 550 C2 in which a two-shaft drive is described which has two driving units. In this case, direct-current motors are used with a control unit which is based on current measurements in the exciting circuit of both driving units and on a rotational velocity measurement in the case of one driving unit. In this known teaching, a desired rotational velocity and a desired power ratio can be defined.




The last-mentioned driving concept has the disadvantage that, as the result of the rotational velocity monitoring taking place only on one side, in the event of a clutch, transmission or pump gearing damage, the line in which the rotational velocity is not monitored may cause consequent damage by endeavoring to reach the desired power. Furthermore, the power ratio can be adjusted only in a narrow range of from 0.5 to 1. Finally, this system is not suitable for appropriately detecting and taking into account torque pulsations because of the intervention point shifting on the intervention line, because of minimal gearing inaccuracies or differences in the rigidities of the engine mounting and transmission mounting.




It is therefore an object of the present invention to provide a gear pump which does not have the above-mentioned disadvantages.




This object is achieved by providing a gear pump of the above noted type, wherein the control units are operably connected by way of a data line. Further advantageous features of preferred embodiments of the present invention are described below and in the claims.




Preferred embodiments of the invention have the following advantages. In that a completely symmetrical structure for the control units for controlling the driving units is provided and, in addition, a fast data transmission is provided between the two control devices contained in the control units, it is achieved that, despite possible torque pulses on the shafts, the tooth surfaces will neither lift off, nor can an excess torque which is too high be transmitted by way of the tooth surfaces.











Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.




BRIEF DESCRIPTION OF THE DRAWINGS




The single drawing FIGURE is a schematic representation of a gear pump having two identical control units according to preferred embodiments of the invention.











DETAILED DESCRIPTION OF THE DRAWINGS




The drawing FIGURE schematically depicts a gear pump having a two-shaft drive and two control units SE


1


and SE


2


according to the invention. The gear pump has two mutually meshing gears Z


1


and Z


2


which are assigned to two different gear shafts W


1


and W


2


. The gears Z


1


and Z


2


and the shafts WI and W


2


are contained in a pump casing G. The shafts W


1


and W


2


extend to the outside and the projecting ends of the shafts W


1


and W


2


are each coupled with a driving unit AE


1


and AE


2


.




According to the invention, the control units SE


1


and SE


2


have a symmetrical construction and include one control device KE


1


and KE


2


respectively, one inverse rectifier WR


1


and WR


2


respectively as a power converter, and one rotational velocity measuring unit DME


1


and DME


2


respectively as measuring units which are each connected with a signal generator of the known type mounted on the shafts W


1


and W


2


. In the rotational velocity measuring units DME


1


and DME


2


, the signal measured in the signal generator is processed for the determination of the angular velocities ω


1


and ω


2


, these then being transmitted to the control devices KE


1


and KE


2


.




In the control devices KE


1


and KE


2


, the respective control signals SS


1


and SS


2


are generated for controlling the respective inverse rectifiers WR


1


and WR


2


. For this purpose, in addition to the angular velocity ω


1


and ω


2


, output signals for the driving units AE


1


and AE


2


are also used which are generated by the inverse rectifier WR


1


and WR


2


, whereby possible non-linearities or asymmetries of the inverse rectifiers WR


1


and WR


2


are automatically compensated.




In a preferred embodiment of the invention, the driving units AE


1


and AE


2


are of the electric asynchronous machine type (Rolf Fischer, “Electric Machines”, 5th Edition, Carl Hanser Verlag, 1983, Pages 170 to 260). The output signals generated by the inverse rectifier WR


1


and WR


2


are indicated in the drawing figure by U


1


and U


2


for the electric voltage, and by I


1


and I


2


for the electric current and by F


1


and F


2


for the frequency.




As mentioned above, the output signals U


1


, I


1


, F


1


and U


2


, I


2


, F


2


are returned into the control device KE


1


and KE


2


for a precise adjustment. This provides a first internal control circuit for adjusting the rotational velocity of the shafts W


1


and W


2


. Specifically, if the driving units AE


1


and AE


2


are conceived as electromechanical converters, the voltage frequencies F


1


and F


2


are imaged on the angular velocities ω


1


and ω


2


, and the voltages U


1


and U


2


and currents I


1


and I


2


are imaged on corresponding driving torques (vector drives). Another control circuit is created by measuring the rotational shaft velocity by means of rotational velocity measuring units DME


1


and DME


2


and returning the measured signals into the respective control devices KE


1


and KE


2


. In the context of the present invention, this second control circuit will be called an external control circuit.




According to the invention, a fast data line DL, preferably in the form of a data bus, is provided between the two control units SE


1


and SE


2


, by way of which the angular velocities ω


1


and ω


2


of the two shafts W


1


and W


2


and the position of the gears Z


1


and Z


2


can be precisely coordinated or adjusted with respect to one another. The data line DL is provided so that angular velocity differences can be reliably processed within the control units SE


1


and SE and that, despite possible torque pulses, neither a lifting-off of the tooth surfaces, which are to remain in contact, is caused, nor is an excess torque, which is too high, transmitted by way of the tooth surfaces.




In another embodiment of the invention, it is provided that a computer unit is connected to the data line DL constructed as a data bus, by means of which computer unit a rotational velocity adjustment can, for example, take place, particularly in connection with other process components, with which the gear pump is connected.




The foregoing disclosure has been set forth merely to illustrate the invention and is not intended to be limiting. Since modifications of the disclosed embodiments incorporating the spirit and substance of the invention may occur to persons skilled in the art, the invention should be construed to include everything within the scope of the appended claims and equivalents thereof.



Claims
  • 1. Gear pump having two mutually meshing gears, which are each assigned to a shaft and which are each driven by means of a driving unit, the driving units each being drivable by a control unit such that the shafts rotate at a definable rotational velocity, wherein the control units are operably connected by way of a data line to thereby precisely coordinate the angular velocities to avoid excess torque forces on teeth of the meshing gears while preventing a lifting off of surfaces of the teeth, during pumping operations.
  • 2. Gear pump according to claim 1, wherein the control units are constructed symmetrically with respect to one another.
  • 3. Gear pump according to claim 1, wherein a power converter is provided for each driving unit, each power converter being operatively connected with a respective driving unit, andwherein a control device is provided in each control unit for generating control signals which act upon the corresponding power converters, the data line existing between the two control units being guided to the respective control devices.
  • 4. Gear pump according to claim 2, wherein a power converter is provided for each driving unit, each power converter being operatively connected with a respective driving unit, andwherein a control device is provided in each control unit for generating control signals which act upon the corresponding power converters, the data line existing between the two control units being guided to the respective control devices.
  • 5. Gear pump according claim 3, wherein the power converter output signals, or signals proportional thereto, are returned into the corresponding control device.
  • 6. Gear pump according to claim 4, wherein the power converter output signals, or signals proportional thereto, are returned into the corresponding control device.
  • 7. Gear pump according to claim 1, wherein the driving units are of the asynchronous machine type.
  • 8. Gear pump according to claim 2, wherein the driving units are of the asynchronous machine type.
  • 9. Gear pump according to claim 3, wherein the driving units are of the asynchronous machine type.
  • 10. Gear pump according to claim 5, wherein the driving units are of the asynchronous machine type.
  • 11. Gear pump according to claim 7, wherein the power converters are of the inverse rectifier type for generating current voltage and frequency.
  • 12. Gear pump according to claim 1, wherein a rotational velocity measuring unit is provided for each shaft for determining the respective rotational shaft velocity and/or the respective position of the shafts with respect to one another, the rotational velocity measuring units each being operatively connected with the corresponding control device.
  • 13. Gear pump according to claim 4, wherein a rotational velocity measuring unit is provided for each shaft for determining the respective rotational shaft velocity and/or the respective position of the shafts with respect to one another, the rotational velocity measuring units each being operatively connected with the corresponding control device.
  • 14. Gear pump according to claim 1, wherein the power ratio between the two driving units can be adjusted between 0.05 and 1.
  • 15. Gear pump according to claim 4, wherein the power ratio between the two driving units can be adjusted between 0.05 and 1.
  • 16. Gear pump according to claim 1, wherein a computer unit is connected to the data line.
  • 17. Gear pump according to claim 1, wherein said control unit is operable to assure that the angular velocities of the shafts avoid excess torque forces on teeth of the meshing gears while preventing a lifting off of surfaces on the teeth during pumping operations.
Priority Claims (1)
Number Date Country Kind
98115962 Aug 1998 EP
Parent Case Info

This application is a division of application Ser. No. 09/382,830, filed Aug. 25, 1999.

US Referenced Citations (4)
Number Name Date Kind
3780365 Porter et al. Dec 1973 A
5197861 Maruyama et al. Mar 1993 A
5329216 Hasegawa et al. Jul 1994 A
5767635 Steffens et al. Jun 1998 A
Foreign Referenced Citations (5)
Number Date Country
3230550 Jan 1984 DE
3928451 Mar 1991 DE
0472933 Mar 1992 EP
0502459 Sep 1992 EP
WO9429596 Dec 1994 WO
Non-Patent Literature Citations (1)
Entry
European Patent Office Search Report, Feb. 3, 1999.