HYDRAULIC DRIVE UNIT AND METHOD OF OPERATING

Abstract

A hydraulic drive unit for a shaping machine comprising a pump driven by a motor, a closed-loop or open-loop control unit for closed-loop and/or open-loop control of the drive unit to a reference operating point of the drive unit, and a memory connected to the closed-loop or open-loop control unit, wherein a relationship between a parameter characteristic of a sound directly or indirectly caused by the drive unit and a data set representing various operating points of the drive unit is stored in the memory and the closed-loop or open-loop control unit is adapted to select the reference operating point on the basis of the relationship.

Claims

1. A hydraulic drive unit for a shaping machine comprising a pump driven by a motor, a closed-loop or open-loop control unit for closed-loop and/or open-loop control of the drive unit to a reference operating point of the drive unit, and a memory connected to the closed-loop or open-loop control unit, wherein a relationship between a parameter characteristic of a sound directly or indirectly caused by the drive unit and a data set representing various operating points of the drive unit is stored in the memory and the closed-loop or open-loop control unit is adapted to select the reference operating point based on the relationship.

2. A drive unit as set forth in claim 1 wherein there is provided closed-loop or open-loop control of the motor of a rotary speed.

3. A drive unit as set forth in claim 1 wherein the characteristic parameter is one or a combination of the following: a sound pressure a measure for a vibration of installation parts a measure for pressure pulsations in hydraulic lines inputs of an operator on the basis of volume perception

4. A drive unit as set forth in claim 1 wherein the operating points of the data set include at least one pump speed and/or pump displacement.

5. A drive unit as set forth in claim 1 wherein given operating points of the data set are marked as unwanted and the closed-loop or open-loop control unit is adapted not to use ranges of unwanted operating points as the reference operating point or to alter the reference operating point if it is in a range of unwanted operating points.

6. A drive unit as set forth in claim 1 wherein given operating points of the data set are marked as desired and the closed-loop or open-loop control unit is adapted to select reference operating points from ranges of desired operating points.

7. A drive unit as set forth in claim 1 wherein there is provided a measuring device for measurement of the characteristic parameter.

8. A drive unit as set forth in claim 7 wherein the open-loop or closed-loop control unit is adapted to adapt the relationship stored in the memory on the basis of measurement values of the measuring device, in particular during operation.

9. A drive unit as set forth in claim 2 wherein there is provided a closed-loop control means for the motor, wherein the closed-loop or open-loop control unit is adapted to use the characteristic parameter as a feedback parameter.

10. A drive unit as set forth in claim 1 wherein the closed-loop or open-loop control unit is adapted in selection of the reference operating point to take account of a minimum delivery capacity, a minimum volume flow to be delivered and/or a minimum pressure to be maintained.

11. A drive unit as set forth in claim 1 wherein the closed-loop or open-loop control unit is adapted in selection of the reference operating point to take account of an energy effectiveness, in particular a level of efficiency of the hydraulic drive unit.

12. A shaping machine comprising a hydraulic drive unit as set forth in claim 1.

13. A method of operating a hydraulic drive unit for a shaping machine, in particular as set forth in claim 1, wherein a pump is driven by means of a motor, wherein a relationship is provided between a parameter characteristic of a sound directly or indirectly caused by the drive unit and a data set representing various operating points of the drive unit, and based on the relationship an operating point of the drive unit is selected as a reference operating point for closed-loop and/or open-loop control of the drive unit.

Description

[0050] Further advantages and details of the invention will be apparent from the Figures and the related specific description. In the Figures:

[0051] FIG. 1 shows the result of an investigation by the applicant, wherein the sound pressure level was measured in dependence on the pump speed,

[0052] FIG. 2 shows the view from FIG. 1, with wanted and unwanted ranges additionally being shown,

[0053] FIG. 3 shows the view from FIG. 2, with the efficiency of the drive unit additionally being shown,

[0054] FIG. 4 shows a diagrammatic view of the drive unit together with supplied consumers of an injection molding machine,

[0055] FIG. 5 shows a flow chart of a further embodiment of a method according to the invention, and

[0056] FIG. 6 shows a flow chart of an optional method for additional optimization of a level of efficiency.

[0057] FIG. 1 shows both a measured sound pressure level S and also the pump speed n plotted in each case in relation to time. In this case the speed was substantially linearly increased to produce a relationship between the sound pressure level S and the pump speed n.

[0058] As can be seen from FIG. 1 the monotonic relationship hitherto assumed to apply in the state of the art between volume (as mentioned the sound pressure S was used as the characteristic parameter) and the pump speed n does not hold true. Rather, marked minima and maxima occur due to interference and resonance effects. In particular it can be advantageous to slightly increase the speed at certain operating points in order to achieve a reduction in sound pressure.

[0059] In specific terms a motor/pump system in the pressure-holding mode at 200 bars was increased from 200 rpm to 2600 rpm and the sound pressure level of the overall system was measured. The sound pressure level peaks of (81 and 80 dBA) can be very clearly seen at around 1700 rpm and around 1900 rpm, which with an only slightly altered rotary speed of around 1800 rpm, are markedly lower (around 73 dBA). An optimum pump speed N can now be read from that graph. As an alternative firstly desired ranges E are established. That is shown in FIG. 2.

[0060] As an additional condition for the optimum pump speed n or the desired ranges E, it is also possible to use a minimum pump speed (if for example an external delivery amount which is at least to be maintained is to be achieved only by a given minimum speed). In the present example a minimum speed of 1600 rpm was adopted as the basic starting point. As can be easily seen from the Figure it is precisely not actuation of the minimum speed that is optimum as that provides for louder operation than an operating point within the desired ranges E. The corresponding ranges with high sound pressures were marked as unwanted ranges U.

[0061] It is additionally also possible to optimize the efficiency W. That is shown in FIG. 3 in which the efficiency W is shown additionally.

[0062] Two points P1 and P2 were also plotted, which are each in a separate desired range E. As however the point P2 offers a higher level of efficiency P than the point P1, the point P2 was in fact used as the operating point.

[0063] The data shown in FIG. 3 can be stored in a memory 6 of an open-loop or closed-loop control unit 5. It can also be provided that that relationship is modified by measurement values of a measuring device 7 for detecting for example the sound pressure (for example if the corresponding measurement value indicates a different sound pressure occurring with the respective pump speed n, than the sound pressure curve S in FIG. 3 does).

[0064] FIG. 4 shows a drive unit 1 according to the invention together with a diagrammatically illustrated shaping machine 2. Only components of the shaping machine 2 that are essential for the invention are shown. These would be a closing cylinder 8 for closing the closing unit, a pressurizing cylinder 9 for pressurizing an injection nozzle, an injection cylinder 10 for injecting an amount of plastic material and a hydraulic motor 11 for metering an amount of plastic material.

[0065] The drive unit 1 includes a motor 3 and a pump 4 which is driven by the motor 3 and which in this case is in the form of a pump 4 with a variable pump displacement . Pressurized hydraulic fluid (preferably oil) is delivered from a tank 12 to the consumers by way of the pump 4.

[0066] The drive unit 1 also has an open-loop or closed-loop control unit 5 which provides for open-loop or closed-loop control both at the motor 3 and also the pump displacement of the pump 4.

[0067] Besides the relationship between the sound pressure S and the pump speed n relationships between the sound pressure S and both the pump speed n and also the pump displacement can naturally also be stored in the memory 6.

[0068] In this embodiment there is also a measuring device 7 for measuring the sound pressure 5.

[0069] FIG. 5 shows a flow chart for an alternative method according to the invention, which can be carried out during operation of the shaping machine 2. As in the various shaping cycles the respective metering method step is implemented with different pairs of values for the pump speed n.sub.1 through n.sub.n and the pump displacement .sub.1 through .sub.n. In addition the sound level S is measured in each shaping cycle. The open-loop or closed-loop control unit 5 can then extract the optimum value from the measurements and metering can thence be implemented with the optimum pump speed n and pump displacement .

[0070] FIG. 6 shows a flow chart of an optional additional method wherein the efficiency of the drive unit 1 is also subjected to an optimization procedure.

[0071] In this case operation is as shown in FIG. 5, but here it is not an individual optimum pair of values that is output, but a quantity of acceptable pairs of values.

[0072] In addition in each shaping cycle the power consumed by the motor 3 and the delivery capacity of the pump 4 are measured. It is then possible to select from the pairs of values recognized as acceptable, a pair of values which is optimized both in respect of sound level S and also efficiency W, for the pump speed N and the pump displacement .

[0073] Alternatively it is first possible to optimize the efficiency as shown in FIG. 6 and to optimize the sound level from pairs of values selected in that case, as shown in FIG. 5.