Field of the invention

This invention relates to a method to determine position of a CAM-ring in a balanced variable vane pump.

This invention relates to a method of wear determination of a CAM-ring in a balanced variable vane pump.

Background of the invention

Variable vane pumps are widely used in a number of industries such as automotive, aerospace and the like. A variable vane pump is a pump wherein the flow rate of the pump can be varied as per the end requirement of the application in which it is used. Variable vane pumps known in the state of the art comprise at least a rotor on which are mounted pluralities of vanes. The rotor may be eccentrically located in the compression chamber and encompassed by the stator. As the rotor rotates eccentrically in the stator the fluid that is sucked into the compression chamber is pressurized due to the compression of the vanes along the walls of the stator. The variable flow to the pressurized fluid is imparted by means of CAM-ring which is mounted at the input and output side of the variable vane pump. The CAM-ring is provided with a number of input and output lobes which helps in introducing the fluid into the compression chamber and pumping the fluid out of the pump. A balanced variable vane pump is a variable vane pump with even number of lobes on the CAM-ring. The even number of lobes helps to balance the forces on the bearing of the variable vane pump. The CAM-ring is rotated by a variety of linear or rotary means, one such variable displacement vane pump with a rotating CAM-ring is known from the patent document numbered EP1384005.

Balanced variable vane pumps today are controlled via electronic means. Further, for accurate control there is a need that the position of the CAM-ring is known. One method to determine the position of CAM-ring known in the state of art disclosed in US7575420. The balanced variable vane pump disclosed comprises at least two locating ring which are used to determine the position of the CAM-ring. Further, other methods to determine the position of the CAM-ring may include the use of variety bf sensors that are mounted in proximity of the CAM-ring which determine the position of the CAM-ring.

It is also important there is possibility of evaluating the life of the balanced variable vane pump. The remaining useful life of the balanced variable vane pump can be determined based on the amount of wear that the various components of the balanced variable vane pump have undergone. The amount of wear can be measurable in terms of the amount of fluid that is output for a given back pressure from the balanced variable vane pump. This method of wear determination to determine the useful life of the balanced variable vane pump is a method which can be used only when there already existent leakage in the balanced variable pump. One such method of wear determination of the balanced variable vane pump is disclosed in EP1531270. The wear determination method discloses the use of components known as under vanes which are located in proximity of the vanes of the balanced variable vane pump. When the vanes are within wear limits, the leakage through the under vanes is minimal. However, as the vanes wear out, the leakage increases. The increase in leakage is checked against an allowable value of leakage, if the leakage is within a threshold leakage value then the balanced variable vane pump is determined useable else it is determined that the useful life of the balanced variable vane pump is over. However, failure of the balanced variable vane pump due to failure of any other component cannot be determined using this method.

It is object of this invention to provide a method of determination of position of the CAM-ring of the balanced variable vane pump and a method determination of useful life of the balanced variable vane pump based on the position of the CAM-ring.

Brief description of the accompanying drawings

Different modes of the invention are disclosed in detail in the description and illustrated in the accompanying drawing:

Figure 1 illustrates a device for position determination and wear determination in a balanced variable vane pump;

Figure 2 illustrates a flowchart representative of the steps in a method (represented as SP in the figure) to determine position of a CAM-ring in a balanced variable vane pump;

Figure 3 illustrates a flowchart representative of the steps in a method (represented as IND in the figure) of indexing movement of the CAM-ring during movement of the CAM-ring by the drive mechanism;

Figure 4 illustrates a flowchart representative of the steps in a method (represented as POS in the figure) of determining position of a CAM-ring in a balanced variable vane pump during normal working mode of the balanced variable vane pump; and Figure 5 represents a flowchart representative of the steps in a method (represented as WD in the figure) of wear determination of a CAM-ring in a balanced variable vane pump.

Detailed description of the invention

Figure 1 illustrates a device 10 for position determination and wear determination in a balanced variable vane pump 12. The device comprises a controller 14, a motor driver 16 and a current monitoring means 18. The current monitoring means 18 continuously monitors the current drawn from the motor driver 16 by the balanced variable vane pump 12. The controller receives current feedback from the current monitoring means 18. The controller also receives control signal 20 from the system in which the balanced variable vane pump 12 is used.

The balanced variable vane comprise at least a CAM-ring 22 being provided with teeth 24 on at least a part of the outer circumference of said CAM-ring 22 and a drive mechanism 26 adapted to engage the teeth on the outer circumference of said CAM-ring 12 to impart movement to said CAM-ring 22. For the purpose of determining the position of the CAM-ring 12 and for wear determination of the CAM-ring 22, the drive mechanism 26 is actuated to impart movement to the CAM-ring 22.The drive mechanism is actuated by the motor driver 16 of the device 10. The drive mechanism 26 comprises at least a worm gear 28 which is contact with the teeth on the outer circumference of the CAM-ring 22. Thus when the drive mechanism 26 is

Actuated by the motor driver 16 the worm gear 28 imparts movement to the CAM-ring 22 allowing flow from the output of the balanced variable vane pump 12 to vary. Based on the movement of the CAM-ring 22, the position and the wear are determined.

As mentioned earlier the controller 14 receives control signal 20 from the system in which the balanced variable vane pump is installed. Depending on the amount by which the flow has to be varied the controller 14 instructs the motor driver 16 to drive the drive mechanism 26. The current drawn by the drive mechanism 26 is continuously monitored by the current monitoring means 18. The current monitoring means 18 sends the information to the controller 14. Based on the information received from the current monitoring means 18 the controller 20 determines position of the CAM-ring and also carries out wear determination of the CAM-ring. The determination of position of CAM-ring 22 is done by utilizing the absolute value of current and/or power consumption by the drive mechanism 26 of the balanced variable vane pump 12. The method of position determination and wear determination can be explained as follows.

Figure 2 illustrates a flowchart representative of the steps in a method (represented as SP in the figure) to determine position of a CAM-ring in a balanced variable vane pump. The step SP1 represents the step of indexing movement of the CAM-ring by moving said CAM-ring between two extreme moving positions of the CAM-ring on the drive mechanism. The step of indexing can be explained as the step of actuating the CAM-ring to move along the drive mechanism of the balanced variable vane pump and recording the distance moved by the CAM-ring when a certain value of current is supplied to the drive mechanism. The step SP2 represents the step of comparing the indexed value of movement of the CAM-ring with the existing CAM-ring movement data. The step SP3 represents the step of determining position of the CAM-ring in dependence of the comparison between the indexed movement and the existing CAM-ring movement data.

Figure 3 illustrates a flowchart representative of the steps in a method (represented as IND in the figure) of indexing movement of the CAM-ring during movement of the CAM-ring by the drive mechanism. The step IND1 represents the step actuating.

Movement in the CAM-ring by actuating the drive mechanism of the balanced variable vane pump. The movement is initiated such that the CAM-ring moves along the worm gear from the current position of the CAM-ring to one extreme moving position. Step IND2 represents the step of sensing the current required to make the CAM-ring move from its current position towards one extreme moving position on the worm gear. Step IND3 represents the step of sensing a current spike during movement of the CAM-ring on the worm gear. Step IND4 represents the step of marking one extreme moving position of movement of the CAM-ring in dependence of the sensed current spike. Step IND5 represents the step actuating movement in the CAM-ring by actuating the drive mechanism of the balanced variable vane pump. The movement is initiated such that the CAM-ring moves along the worm gear from one extreme moving position of the CAM-ring to the second extreme moving position. Step IND6 represents the step of sensing the current required to make the CAM-ring move from its current position towards one extreme moving position on the worm gear. Step IND7 represents the step of sensing a current spike during movement of the CAM-ring on the worm gear. Step IND8 represents the step of marking the second extreme moving position of movement of the CAM-ring in dependence of the sensed current spike. Step IND9 represents the step of logging the sensed current during movement of the CAM-ring from the current position to one extreme moving position of the CAM-ring on the worm gear. Step IND10 represents the step of logging the sensed current during movement of the CAM-ring from one extreme moving position to the second extreme moving position. The method of indexing movement of the CAM-ring is done during a indexing working mode of the balanced variable vane pump. During the indexing working mode the balanced variable vane pump does not perform the normal operations of the pump. The method of indexing the movement of the balanced variable vane pump can also be done during the normal working mode of the balanced variable vane pump.

Figure 4 illustrates a flowchart representative of the steps in a method (represented as POS in the figure) of determining position of a CAM-ring in a balanced variable vane pump during normal working mode of the balanced variable vane pump. In the normal working mode, the balanced variable vane pump is connected in the system in which it is used. The step POS1 represents the step of receiving a system signal indicative of the amount by which the CAM-ring should be moved from the current position of the CAM-ring to change the flow of the balanced variable vane pump. The step POS2 represents the step of checking the current required for moving the CAM-ring in a manner such that the CAM-ring position indicated by the system signal is reached. Step POS3 represents the step of actuating movement of the CAM-ring from its current position to the position indicated by the system signal. Step POS4 represents the step of recording the current drawn during the movement of the CAM-ring to the indicated position by the system signal. Step POS5 represents the step of comparing the current drawn during the movement of the CAM-ring with the amount of current required for this movement as recorded during the method of indexing movement of the CAM-ring. Step POS6 represents the step of checking if there exists some difference between the current drawn during the movement of the CAM-ring and the current drawn during the indexing movement. Step POS7 represents the step of compensating the movement CAM-ring by providing additional current for its movement based on the current drawn during indexing if the exists some difference. POS8 represents the step of comparing current drawn during movement of the CAM-ring with the exiting CAM-ring data movement. POS9 represents the step of indicating the current position of the CAM-ring in dependence of the comparison represented in step POS8.

Figure 5 represents a flowchart representative of the steps in a method (represented as WD in the figure) of wear determination of a CAM-ring in a balanced variable vane pump. For explaining the method for wear determination, the movement of the CAM-ring is indexed and recorded while moving the CAM-ring between the two extreme moving positions of the CAM-ring. Herein the step of indexing and recording movement of the CAM-ring is represented in the figure by the step WD1. Further the position of the CAM-ring indicated by comparing current values during indexing and based on the existing CAM-ring data represented by step WD2. During the indexing of the CAM-ring the time required for the movement of the CAM-ring from its current position to the next position is recorded represented by WD3. During the position determination the time required for the movement of the CAM-ring from the current position to the next position indicated by the system signal is recorded represented by WD4. Both the recorded time for actuation during indexing and during position determination is compared and the difference is calculated this is represented as WD5. If the difference between the time of actuation during indexing and during question determination is beyond a threshold value then end of service life of the CAM-ring is indicated represented by step WD6 and WD7.

It must be understood that the methods explained in the above description are only illustrative and do not limit the scope of the invention. The scope of the invention is only limited by the claims. Many modifications and alternate steps in the process are envisioned and lie within the scope of this invention.

We Claim:

1. A method to determine position of a CAM-ring (10) in a balanced variable vane pump (12) comprising the following steps:

Indexing movement of said CAM-ring by moving said CAM-ring between two extreme moving positions of said CAM-ring;

Comparing said indexed movement of said CAM-ring with existing CAM-ring position data; and

Determining position of said CAM-ring in dependence of said comparison.

2. The method as claimed in claim 1, wherein said determination of position of CAM-ring is done by utilizing the absolute value of current and/or power consumption by a drive mechanism of said balanced variable vane pump.

3. A method to determine position of a CAM-ring in a balanced variable vane pump comprising the steps for indexing movement of said CAM-ring, characterized in that method of indexing comprising the following steps:

Actuating movement of said CAM-ring from a current position to one extreme moving position;

Sensing current required for movement of said CAM-ring;

Sensing a current spike during movement of said CAM-ring;

Marking one extreme moving position in dependence of said sensed current spike;

Actuating movement of said CAM-ring from one extreme moving position to a second extreme moving position;

Sensing current required for movement of said CAM-ring;

Sensing a current spike during movement of said CAM-ring;

Marking said second extreme moving position in dependence of said sensed current spike;

Logging said sensed current during movement of said CAM-ring from current position of said one extreme moving position; and

Logging said sensed current during movement of said CAM-ring from said one extreme moving position to said second extreme moving position.

3. A method as claimed in claim 3, wherein said method of indexing is carried out during a normal working mode of said balanced variable vane pump.

5. A method as claimed in claim 3, wherein said method of indexing is carried out during a indexing working mode of said balanced variable vane pump.

6. A method to determine position of a CAM-ring in a balanced variable vane pump said method normal working mode of said balanced variable vane pump, said method comprising the following steps:

Actuating said CAM-ring to a predetermined position of said CAM-ring from a current position of said CAM-ring;

Monitoring current required during movement of CAM-ring from current position to said predetermined position;

Comparing said monitored current with current measured for moving said Cam-ring while performing an indexing operation;

Determining current position of said CAM-ring in dependence of the current sensed during movement of said CAM-ring and said sensed current during said indexing operation.

7. A method of wear determination of a CAM-ring in a balanced variable vane comprising the following steps:

Indexing movement of said CAM-ring by moving said CAM-ring between two extreme moving positions of said CAM-ring;

Comparing said indexed movement of said CAM-ring with existing CAM-ring position data; and

Determining position of said CAM-ring in dependence of said comparison, characterized in that said method comprising the following steps:
Monitoring time of actuation required for movement of CAM-ring from one position to another while performing said indexing;

Monitoring time of actuation required for movement of CAM-ring from one position to another while performing said position determination;

Comparing monitored time of actuation during indexing and during position determination; and

Indicating end of service life of said CAM-ring if monitored time during position determination is greater than the monitored time during indexing.

8. A device (10) for position determination and wear determination in a balanced variable vane pump (12), said device comprising:

A controller (14);

A motor driver (16); and

A current monitoring means (18); a current monitoring means (18) adapted to monitoring current drawn

By said balanced variable vane pump (12) from said motor driver (16); said controller (14) adapted to receive current feedback from said current monitoring means (18);

Said controller adapted to receive a control signal (20) from a system in which said balanced variable vane pump (12) is used; and

Said controller (14) adapted to determine position and determine wear of said balanced variable vane pump (12) in dependence of the current feedback and said control signal (20) from said system.