CA2189943A1 - Virtual center dynamometer - Google Patents
Virtual center dynamometerInfo
- Publication number
- CA2189943A1 CA2189943A1 CA 2189943 CA2189943A CA2189943A1 CA 2189943 A1 CA2189943 A1 CA 2189943A1 CA 2189943 CA2189943 CA 2189943 CA 2189943 A CA2189943 A CA 2189943A CA 2189943 A1 CA2189943 A1 CA 2189943A1
- Authority
- CA
- Canada
- Prior art keywords
- support cradle
- torque
- fixed frame
- measuring system
- support
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Abandoned
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- Force Measurement Appropriate To Specific Purposes (AREA)
Abstract
A virtual center dynamometer is provided for single axis torque measurement of static or rotary systems. The dynamometer comprises a support cradle mounted on a fixed or ground frame by a plurality of plate flexures. These plate flexures mount the support cradle for movement about a virtual center axis disposed in free space above the support cradle, while substantially constraining the support cradle against movement in other directions. A torque absorber is mounted on the support cradle, defining a rotable axis coinciding with the virtual center axis, and a load cell is provided to react between the support cradle and the ground frame to measure the torque load.
Description
21 899~3 VIRTUAL CENTER DYNAMOMETER
BACKGROUND OF THE INVENTION
This invention relates generally to systems and methods for measuring torque of a large load rotary system. More particularly, this invention relates to an improved torque measuring system designed to provide torque measurements with an improved and high degree of accuracy.
Manufacturers of power equipment have a need to measure torque in order to rate such equipment for power output or input capacity.
However, accurate and reliable torque measurements have been difficult to obtain, particularly with respect to large and heavy rotary systems such as large electrical motors and engines and the like.
In the past, a variety of techniques and devices have been employed to obtain torque measurements. In one early technique, a so-called pony brake was used to measure rotary shaft torque, but such devices generally lacked sufficient heat dissipation capability for use with high speed and/or high power rotary components. More recently dynamometers have been constructed wherein a rotary torque absorber such as a water brake, hysteresis brake or electrical generator, or combination thereof, is rotatably mounted within a housing that is rotatably supported in turn from a fixed base so that the torque absorber is allowed to rotate within the housing. Upon rotatable driving of the torque absor~er, a transducer reacting between the housing and the fixed base provides a reading reflective of torque. While this system offers significant improvements in torque measurement, energy losses attributable to the bearings of the torque absorber, wherein these losses vary with speed and load, preclude exact measurement of actual torque.
In an alternative approach, a torque meter is attached to a rotary shaft coupled between a drive source and a torque absorber mounted for rotation relative to a fixed base as described above. The torque meter typically includes a shaft segment supported by bearings for mounting in-line between the drive source and the torque absorber, with a strain gauge device mounted on the shaft segment to acquire and transmit a torsional strain signal during dynamic rotating conditions.
While the torque meter bearings may exhibit a lesser degree of energy loss than the bearings which support the torque absorber, sufficient energy losses along with other deficiencies that vary according to speed and load nevertheless occur which prevents accurate and consistently reliable torque measurements. Attempts to compensate for torque measurement errors attributable to dynamometer bearing losses have generally not resulted in precision torque measurements that can be relied upon with any significant degree of confidence.
The present invention is directed to an improved torque measuring system particularly for use in measuring torque load with respect to large and heavy rotary systems, by providing an improved dynamometer structure for movably supporting the rotary system in a manner which effectively eliminates measurement errors.
SUMMARY OF THE INVENTION
This invention relates to an improved and simplified dynamometer for measuring the torque load of a rotary system or component, particularly one of relatively large size and mass. The invention employs a support cradle movably supported from a fixed or ground frame by a plurality of plate flexures for single axis rotation about a virtual center axis disposed in free space above the support cradle.
In the preferred form, the support cradle has a size and shape to receive and support a torque absorber adapted to be rotatably driven by a drive source or motor mounted on the ground frame and coupled to 21 ~9~3 the torque absorber by a suitable flexible shaft coupling. The support cradle is movably supported from the ground frame by the plurality of plate flexures for substantially unconstrained movement relative to the single virtual center axis of rotation which corresponds with the axis of rotation of the torque absorber. However, the plate flexures substantially constrain the support cradle and torque absorber supported thereon against movement or degrees of freedom in other directions. A preferred plate flexure construction is available commercially from Ormond Inc., Santa Fe Springs, California under the product designation stabilized plate flexure type SPF. A load cell is connected between the support cradle and the ground frame for measuring the torque loads during operation of the rotary system.
Other features and advantages of the present invention will become more apparent from the following detailed description, taken in conjunction with the accompanying drawings which illustrate, by way of example, the principles of the invention.
BRIEF DESCRIPTION OF THE DRAWINGS
The accompanying drawings illustrate the invention. In such drawings:
FIGURE 1 is a side elevational view, shown somewhat in schematic form, depicting the improved torque measuring system of the present invention;
FIGURE 2 is a transverse vertical sectional view taken generally on the line A-A of FIG. 1;
FIGURE 3 is an enlarged sectional view, similar to a portion of FIG. 2, depicting a plate flexure for use in the invention;
FIGURE 4 is a somewhat schematic diagram illustrating precision measurement of the system moment arm, subsequent to assembly of system components; and ' 2189943 FIGURE 5 is a somewhat schematic diagram illustrating use of a suspended dead weight during a load cell calibration step.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
As shown in the exemplary drawings, an improved torque measuring system or dynamometer in accordance with the present invention is referred to generally in FIGURES 1 and 2 by the reference numeral 10. The dynamometer comprises a test stand structure which includes a support bed or cradle 12 mounted vertically above a fixed or ground frame 14 by means of a plurality of plate flexures 16 of the type shown and described in U.S. Patent 3,240,454, which is incorporated by reference herein. The support cradle 12 has a size and shape for nested receipt and support of a rotary driven torque absorber 18, and a load cell 36 is mounted between the support cradle 12 and the ground frame 14 to measure torque loads when the torque absorber 18 is rotatably driven.
The dynamometer 10 of the present invention is particularly suited for use with rotary system components which can be relatively large in size and mass, to provide torque load measurements with a high degree of precision and accuracy throughout the range of different speed and load conditions. In this regard, the present invention virtually eliminates potentially significant torque measurement errors inherent in prior dynamometer configurations, particularly such as error attributable to energy losses associated with bearings used to support the torque absorber or other components of the measurement system.
In general terms, the present invention utilizes a modified space center gimbal assembly of the type shown and described in U.S. Patent 3,240,454, to mount the support cradle 12 with single axis articulation about which torque can be measured statically. The axis of rotation of the support cradle 12 is disposed in free space at a position located vertically above the support cradle, and is identified in the drawings by ' 2~89q4~
reference numeral 22. This axis of rotation 22 is referred to a virtual center line and, in the preferred form of the invention, coincides with the rotational axis of the torque absorber 18 to be mounted on the support cradle 12.
More particularly, as shown best in FIG. 2, the illustrative support cradle 12 has an upwardly concave cross-sectional profile 20 disposed generally concentric to a center axis which conforms with the virtual center line 22. The torque absorber 18, typically a large and heavy device such as an electrical ac or dc generator or other known rotary type torque absorber, is securely mounted onto the support cradle 12 in a suitable manner as by means of bolting (not shown) or the like. The ground frame 14 is firmly supported on an appropriate and stable foundation such as a concrete floor structure, and the ground frame 14 may be fastened as by bolts (not shown) or the like to that foundation if desired.
The plate flexures 16 comprise a plurality of support arms and flexure units which generally conform in construction and operation to a single axis plate flexure available commercially from Ormond Inc., Santa Fe Springs, California, under the product designation stabilized plate flexure type SPF. In general terms, the plate flexures 16 comprise a mechanical linkage which permits substantially or relatively unconstrained rotational movement of the support cradle 12 and the torque absorber 18 thereon about a single axis of rotation corresponding to the virtual center line 22, while substantially constraining the support cradle and torque absorber against movement in all other directions.
FIGURE 3 shows one of the plate flexures 16 in more detail, for interconnection between the underlying ground frame 14 and the overlying support cradle 12. In particular, the plate flexure 16 comprises a rigid plate-like support arm 24 connected at opposite ends to a pair of flexure units 26 and 28 having X-shaped cross webs to define precision pivot points alon~ individual axes extending parallel to the virtual center 21 89~43 axis 22. The flexure units 26 and 28 are in turn secured as by bolts (not shown) or the like respectively to the ground frame 14 and the support cradle 12.
As shown, in the preferred configuration, four of the plate flexures 16 are used at the four corners of the ground frame 14 to movably support the cradle 12 at the four corners thereof. That is, two of the plate flexures 16 are mounted at opposite corners of one end of the system, and the other two plate flexures are mounted at the opposite corners of an opposite end of the system. Importantly, the plate flexures 16 are oriented in a sloping fashion to extend upwardly and angularly inwardly from the ground frame 14 for connection to the support cradle 12, so that an imaginary, line representing an upward projection of each plate flexure 16 will intersect the virtual center line 22 (FIG. 2). With this configuration, the support cradle 12 is constrained for substantially one degree of freedom, namely, rotation relative to the virtual center line 22.
In use, the rotary torque absorber 18 mounted on the support cradle 12 has a driven shaft 30 (FIG.1) adapted for suitable connection via a flexible drive coupling 32 to an appropriate drive source or motor 34 which is mounted on the ground frame 14 or alternately on the fixed foundation of the ground frame. Reduction gear means 35 may also be provided. Rotary driving of the torque absorber shaft 30 relative to the center axis 22 results in a torque applied to the torque absorber 18 and the support cradle 12. The load cell 36 is mounted in position between the support cradle 12 and the ground frame 14 to reactively measure this torque. In this regard, FIG.2 shows the load cell 36 in one preferred form to be mounted pivotally between a pair of brackets 38 and 40 connected respectively to the ground frame 14 and the underside of the support cradle 12. The load cell is designed to measure the force of rotary motion of the support cradle 12 and torque absorber 18, wherein this force measurement can be translated to torque from a knowledge of the moment arm distance between the load cell 36 to the virtual center line 21 89~43 22. The load cell 36 measures this force in tension or compression, according to the direction of absorber rotation, and provides an appropriate force signal to instrumentation such as a monitor or digital display (not shown).
The above-described torque measuring system beneficially permits relative simple and highly accurate torque load measurements with respect to relatively heavy rotary components, including but not limited to devices which may weigh 25,000 pounds or more. Torque measurements are found to be very accurate over a large range without requiring system reconfiguration, such that a single measuring module can be used for a variety of different rotary components. In each application, all of the torque transmitted from the drive source 34 on the ground frame 14 to the absorber 18 and the support cradle 12, including that absorbed by gearing and the like, is measured by the load cell 36 without power loss. Calibration at the outset may be performed in a simple manner by use of a removable load cell and flexure string mounted in series with the torque measuring load cell in a fashion that permits application of a known external torque.
As shown in FIG. 2, a calibration load cell 42 is desirably mounted to react between the support cradle 12 and the ground frame 14, in tandem with and in direct opposition to the primary load cell 36.
This calibration load cell 42 permits in-place calibration to occur at any time. If desired, such calibration can be accomplished during rotary driving of the system by applying a load in opposition to the primary torque measuring load cell 36. Note that such measurements and/or calibrations taken during rotary system operation are nevertheless static measurements.
Because the torsional rotation during system operation is reacted by and calibrated by the load cells 36, 42 mounted between the support cradle 12 and the ground frame 14, the torsional moment or lever arm comprising the distance between the virtual center axis 22 and a 21 899~3 center line of the load cells must be accurately determined. In this regard, the dynamometer structure is constructed from an assembly of components which inherently encompass a range of tolerances, such that the precise length of the moment arm should be ascertained and verified after final assembly. In one technique, the ground frame 14 with plate flexures 16 and support cradle 12 assembled thereto can be oriented vertically as shown in FIG. 4, so that the moment arm (L) is oriented horizontally. In this orientation, as viewed in FIG. 4, a weight 43 to counterbalance the plate flexures 16 and cradle 12 is suspended from a fixture 44 attached to the cradle 12. If the weight 43 is suspended from the precise virtual center line or axis 22, the differential force as monitored by the load cell 36 will be zero. However, if the weight is suspended from a slightly misaligned position, a differential force will be indicated by the load cell 36. Such differential force can be used as a mathematical connection factor for subsequent torque readings.
Similarly, the vertical center line passing through the virtual axis 22 can be located if required.
A similar suspended weight technique can be used, as shown in FIG. 5, for static in-place calibration of the system. As shown, a known dead weight 46 can be suspended by a fixture 48 at one side of the support cradle 12. The dead weight 46 is located from the virtual center axis 22 by a known moment arm. Resultant readings of the load cell 36 can be reviewed and calibrated as needed for accuracy.
Accordingly, the invention provides an improved dynamometer having the capability to provide extremely accurate and reliable torque measurements over a wide range of speed and load conditions. The plate flexures 16 accommodate use with large and heavy rotary system components. Moreover, while the plate flexures 16 provide some minor degree of torsional resistance, the arrangement of components in the invention permits flexure stiffness to be part of the system calibration constant.
21 ~9943 ~_ g A variety of further modifications and improvements to the invention will be apparent to those skilled in the art. For example, while the invention has been described relative to providing torque measurements with respect to a rotary system, it will be recognized that the invention can be used to calibrate other types of transducers and torque meters statically or dynamically, when mounted onto the support cradle 12. By providing precision torque readings, the virtual center dynamometer of the present invention can be used as a standard to calibrate other less accurate torque measurement devices. Accordingly, no limitation on the invention is intended by way of the foregoing description and accompanying drawings, except as set forth in the appended claims.
BACKGROUND OF THE INVENTION
This invention relates generally to systems and methods for measuring torque of a large load rotary system. More particularly, this invention relates to an improved torque measuring system designed to provide torque measurements with an improved and high degree of accuracy.
Manufacturers of power equipment have a need to measure torque in order to rate such equipment for power output or input capacity.
However, accurate and reliable torque measurements have been difficult to obtain, particularly with respect to large and heavy rotary systems such as large electrical motors and engines and the like.
In the past, a variety of techniques and devices have been employed to obtain torque measurements. In one early technique, a so-called pony brake was used to measure rotary shaft torque, but such devices generally lacked sufficient heat dissipation capability for use with high speed and/or high power rotary components. More recently dynamometers have been constructed wherein a rotary torque absorber such as a water brake, hysteresis brake or electrical generator, or combination thereof, is rotatably mounted within a housing that is rotatably supported in turn from a fixed base so that the torque absorber is allowed to rotate within the housing. Upon rotatable driving of the torque absor~er, a transducer reacting between the housing and the fixed base provides a reading reflective of torque. While this system offers significant improvements in torque measurement, energy losses attributable to the bearings of the torque absorber, wherein these losses vary with speed and load, preclude exact measurement of actual torque.
In an alternative approach, a torque meter is attached to a rotary shaft coupled between a drive source and a torque absorber mounted for rotation relative to a fixed base as described above. The torque meter typically includes a shaft segment supported by bearings for mounting in-line between the drive source and the torque absorber, with a strain gauge device mounted on the shaft segment to acquire and transmit a torsional strain signal during dynamic rotating conditions.
While the torque meter bearings may exhibit a lesser degree of energy loss than the bearings which support the torque absorber, sufficient energy losses along with other deficiencies that vary according to speed and load nevertheless occur which prevents accurate and consistently reliable torque measurements. Attempts to compensate for torque measurement errors attributable to dynamometer bearing losses have generally not resulted in precision torque measurements that can be relied upon with any significant degree of confidence.
The present invention is directed to an improved torque measuring system particularly for use in measuring torque load with respect to large and heavy rotary systems, by providing an improved dynamometer structure for movably supporting the rotary system in a manner which effectively eliminates measurement errors.
SUMMARY OF THE INVENTION
This invention relates to an improved and simplified dynamometer for measuring the torque load of a rotary system or component, particularly one of relatively large size and mass. The invention employs a support cradle movably supported from a fixed or ground frame by a plurality of plate flexures for single axis rotation about a virtual center axis disposed in free space above the support cradle.
In the preferred form, the support cradle has a size and shape to receive and support a torque absorber adapted to be rotatably driven by a drive source or motor mounted on the ground frame and coupled to 21 ~9~3 the torque absorber by a suitable flexible shaft coupling. The support cradle is movably supported from the ground frame by the plurality of plate flexures for substantially unconstrained movement relative to the single virtual center axis of rotation which corresponds with the axis of rotation of the torque absorber. However, the plate flexures substantially constrain the support cradle and torque absorber supported thereon against movement or degrees of freedom in other directions. A preferred plate flexure construction is available commercially from Ormond Inc., Santa Fe Springs, California under the product designation stabilized plate flexure type SPF. A load cell is connected between the support cradle and the ground frame for measuring the torque loads during operation of the rotary system.
Other features and advantages of the present invention will become more apparent from the following detailed description, taken in conjunction with the accompanying drawings which illustrate, by way of example, the principles of the invention.
BRIEF DESCRIPTION OF THE DRAWINGS
The accompanying drawings illustrate the invention. In such drawings:
FIGURE 1 is a side elevational view, shown somewhat in schematic form, depicting the improved torque measuring system of the present invention;
FIGURE 2 is a transverse vertical sectional view taken generally on the line A-A of FIG. 1;
FIGURE 3 is an enlarged sectional view, similar to a portion of FIG. 2, depicting a plate flexure for use in the invention;
FIGURE 4 is a somewhat schematic diagram illustrating precision measurement of the system moment arm, subsequent to assembly of system components; and ' 2189943 FIGURE 5 is a somewhat schematic diagram illustrating use of a suspended dead weight during a load cell calibration step.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
As shown in the exemplary drawings, an improved torque measuring system or dynamometer in accordance with the present invention is referred to generally in FIGURES 1 and 2 by the reference numeral 10. The dynamometer comprises a test stand structure which includes a support bed or cradle 12 mounted vertically above a fixed or ground frame 14 by means of a plurality of plate flexures 16 of the type shown and described in U.S. Patent 3,240,454, which is incorporated by reference herein. The support cradle 12 has a size and shape for nested receipt and support of a rotary driven torque absorber 18, and a load cell 36 is mounted between the support cradle 12 and the ground frame 14 to measure torque loads when the torque absorber 18 is rotatably driven.
The dynamometer 10 of the present invention is particularly suited for use with rotary system components which can be relatively large in size and mass, to provide torque load measurements with a high degree of precision and accuracy throughout the range of different speed and load conditions. In this regard, the present invention virtually eliminates potentially significant torque measurement errors inherent in prior dynamometer configurations, particularly such as error attributable to energy losses associated with bearings used to support the torque absorber or other components of the measurement system.
In general terms, the present invention utilizes a modified space center gimbal assembly of the type shown and described in U.S. Patent 3,240,454, to mount the support cradle 12 with single axis articulation about which torque can be measured statically. The axis of rotation of the support cradle 12 is disposed in free space at a position located vertically above the support cradle, and is identified in the drawings by ' 2~89q4~
reference numeral 22. This axis of rotation 22 is referred to a virtual center line and, in the preferred form of the invention, coincides with the rotational axis of the torque absorber 18 to be mounted on the support cradle 12.
More particularly, as shown best in FIG. 2, the illustrative support cradle 12 has an upwardly concave cross-sectional profile 20 disposed generally concentric to a center axis which conforms with the virtual center line 22. The torque absorber 18, typically a large and heavy device such as an electrical ac or dc generator or other known rotary type torque absorber, is securely mounted onto the support cradle 12 in a suitable manner as by means of bolting (not shown) or the like. The ground frame 14 is firmly supported on an appropriate and stable foundation such as a concrete floor structure, and the ground frame 14 may be fastened as by bolts (not shown) or the like to that foundation if desired.
The plate flexures 16 comprise a plurality of support arms and flexure units which generally conform in construction and operation to a single axis plate flexure available commercially from Ormond Inc., Santa Fe Springs, California, under the product designation stabilized plate flexure type SPF. In general terms, the plate flexures 16 comprise a mechanical linkage which permits substantially or relatively unconstrained rotational movement of the support cradle 12 and the torque absorber 18 thereon about a single axis of rotation corresponding to the virtual center line 22, while substantially constraining the support cradle and torque absorber against movement in all other directions.
FIGURE 3 shows one of the plate flexures 16 in more detail, for interconnection between the underlying ground frame 14 and the overlying support cradle 12. In particular, the plate flexure 16 comprises a rigid plate-like support arm 24 connected at opposite ends to a pair of flexure units 26 and 28 having X-shaped cross webs to define precision pivot points alon~ individual axes extending parallel to the virtual center 21 89~43 axis 22. The flexure units 26 and 28 are in turn secured as by bolts (not shown) or the like respectively to the ground frame 14 and the support cradle 12.
As shown, in the preferred configuration, four of the plate flexures 16 are used at the four corners of the ground frame 14 to movably support the cradle 12 at the four corners thereof. That is, two of the plate flexures 16 are mounted at opposite corners of one end of the system, and the other two plate flexures are mounted at the opposite corners of an opposite end of the system. Importantly, the plate flexures 16 are oriented in a sloping fashion to extend upwardly and angularly inwardly from the ground frame 14 for connection to the support cradle 12, so that an imaginary, line representing an upward projection of each plate flexure 16 will intersect the virtual center line 22 (FIG. 2). With this configuration, the support cradle 12 is constrained for substantially one degree of freedom, namely, rotation relative to the virtual center line 22.
In use, the rotary torque absorber 18 mounted on the support cradle 12 has a driven shaft 30 (FIG.1) adapted for suitable connection via a flexible drive coupling 32 to an appropriate drive source or motor 34 which is mounted on the ground frame 14 or alternately on the fixed foundation of the ground frame. Reduction gear means 35 may also be provided. Rotary driving of the torque absorber shaft 30 relative to the center axis 22 results in a torque applied to the torque absorber 18 and the support cradle 12. The load cell 36 is mounted in position between the support cradle 12 and the ground frame 14 to reactively measure this torque. In this regard, FIG.2 shows the load cell 36 in one preferred form to be mounted pivotally between a pair of brackets 38 and 40 connected respectively to the ground frame 14 and the underside of the support cradle 12. The load cell is designed to measure the force of rotary motion of the support cradle 12 and torque absorber 18, wherein this force measurement can be translated to torque from a knowledge of the moment arm distance between the load cell 36 to the virtual center line 21 89~43 22. The load cell 36 measures this force in tension or compression, according to the direction of absorber rotation, and provides an appropriate force signal to instrumentation such as a monitor or digital display (not shown).
The above-described torque measuring system beneficially permits relative simple and highly accurate torque load measurements with respect to relatively heavy rotary components, including but not limited to devices which may weigh 25,000 pounds or more. Torque measurements are found to be very accurate over a large range without requiring system reconfiguration, such that a single measuring module can be used for a variety of different rotary components. In each application, all of the torque transmitted from the drive source 34 on the ground frame 14 to the absorber 18 and the support cradle 12, including that absorbed by gearing and the like, is measured by the load cell 36 without power loss. Calibration at the outset may be performed in a simple manner by use of a removable load cell and flexure string mounted in series with the torque measuring load cell in a fashion that permits application of a known external torque.
As shown in FIG. 2, a calibration load cell 42 is desirably mounted to react between the support cradle 12 and the ground frame 14, in tandem with and in direct opposition to the primary load cell 36.
This calibration load cell 42 permits in-place calibration to occur at any time. If desired, such calibration can be accomplished during rotary driving of the system by applying a load in opposition to the primary torque measuring load cell 36. Note that such measurements and/or calibrations taken during rotary system operation are nevertheless static measurements.
Because the torsional rotation during system operation is reacted by and calibrated by the load cells 36, 42 mounted between the support cradle 12 and the ground frame 14, the torsional moment or lever arm comprising the distance between the virtual center axis 22 and a 21 899~3 center line of the load cells must be accurately determined. In this regard, the dynamometer structure is constructed from an assembly of components which inherently encompass a range of tolerances, such that the precise length of the moment arm should be ascertained and verified after final assembly. In one technique, the ground frame 14 with plate flexures 16 and support cradle 12 assembled thereto can be oriented vertically as shown in FIG. 4, so that the moment arm (L) is oriented horizontally. In this orientation, as viewed in FIG. 4, a weight 43 to counterbalance the plate flexures 16 and cradle 12 is suspended from a fixture 44 attached to the cradle 12. If the weight 43 is suspended from the precise virtual center line or axis 22, the differential force as monitored by the load cell 36 will be zero. However, if the weight is suspended from a slightly misaligned position, a differential force will be indicated by the load cell 36. Such differential force can be used as a mathematical connection factor for subsequent torque readings.
Similarly, the vertical center line passing through the virtual axis 22 can be located if required.
A similar suspended weight technique can be used, as shown in FIG. 5, for static in-place calibration of the system. As shown, a known dead weight 46 can be suspended by a fixture 48 at one side of the support cradle 12. The dead weight 46 is located from the virtual center axis 22 by a known moment arm. Resultant readings of the load cell 36 can be reviewed and calibrated as needed for accuracy.
Accordingly, the invention provides an improved dynamometer having the capability to provide extremely accurate and reliable torque measurements over a wide range of speed and load conditions. The plate flexures 16 accommodate use with large and heavy rotary system components. Moreover, while the plate flexures 16 provide some minor degree of torsional resistance, the arrangement of components in the invention permits flexure stiffness to be part of the system calibration constant.
21 ~9943 ~_ g A variety of further modifications and improvements to the invention will be apparent to those skilled in the art. For example, while the invention has been described relative to providing torque measurements with respect to a rotary system, it will be recognized that the invention can be used to calibrate other types of transducers and torque meters statically or dynamically, when mounted onto the support cradle 12. By providing precision torque readings, the virtual center dynamometer of the present invention can be used as a standard to calibrate other less accurate torque measurement devices. Accordingly, no limitation on the invention is intended by way of the foregoing description and accompanying drawings, except as set forth in the appended claims.
Claims (11)
1. A torque measuring system, comprising;
a support cradle for receiving and supporting a rotary component;
a fixed frame;
a plurality of plate flexures connected between said fixed frame and said support cradle for movably supporting said support cradle from said fixed frame for single axis movement of said support cradle relative to said fixed frame; and a load cell coupled between said support cradle and said fixed frame for measuring support cradle movement relative to said fixed frame.
a support cradle for receiving and supporting a rotary component;
a fixed frame;
a plurality of plate flexures connected between said fixed frame and said support cradle for movably supporting said support cradle from said fixed frame for single axis movement of said support cradle relative to said fixed frame; and a load cell coupled between said support cradle and said fixed frame for measuring support cradle movement relative to said fixed frame.
2. The torque measuring system of claim 1 wherein said plurality of plate flexures comprises a plurality of at least two plate flexures connected between said support cradle and said fixed frame.
3. The torque measuring system of claim 1 wherein said plurality of plate flexures comprises four plate flexures.
4. The torque measuring system of claim 1 wherein said plate flexures support said support cradle for said single axis movement relative to an axis of rotation located in free space above said support cradle.
5. The torque measuring system of claim 1 including bracket means for connecting said load cell between said support cradle and said fixed frame.
6. The torque measuring system of claim 1 further including a calibration cell coupled between said support cradle and said fixed frame in tandem with said load cell.
7. The torque measuring system of claim 1 further including a rotary torque absorber mounted on said support cradle, said torque absorber having a rotational axis generally coinciding with the axis of movement of said support cradle.
8. A torque measuring system, comprising:
a support cradle for receiving and supporting a rotary component;
means for movably supporting said support cradle from said fixed frame for angle axis movement relative to a virtual center line disposed above said support cradle, said supporting means substantially preventing movement of said support cradle in other directions; and a load cell coupled between said support cradle and said fixed frame for measuring forces tending to move said support cradle relative to said fixed frame.
a support cradle for receiving and supporting a rotary component;
means for movably supporting said support cradle from said fixed frame for angle axis movement relative to a virtual center line disposed above said support cradle, said supporting means substantially preventing movement of said support cradle in other directions; and a load cell coupled between said support cradle and said fixed frame for measuring forces tending to move said support cradle relative to said fixed frame.
9. The torque measuring system of claim 8 wherein said supporting means comprises a plurality of plate flexures.
10. The torque measuring system of claim 8 further including a calibration cell coupled between said support cradle and said fixed frame in tandem with said load cell.
11. The torque measuring system of claim 8 further including a rotary torque absorber mounted on said support cradle, said torque absorber having a rotational axis generally coinciding with said virtual center line.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US733395P | 1995-11-09 | 1995-11-09 | |
| US60/007,333 | 1995-11-09 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2189943A1 true CA2189943A1 (en) | 1997-05-10 |
Family
ID=21725559
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA 2189943 Abandoned CA2189943A1 (en) | 1995-11-09 | 1996-11-08 | Virtual center dynamometer |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA2189943A1 (en) |
-
1996
- 1996-11-08 CA CA 2189943 patent/CA2189943A1/en not_active Abandoned
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| FZDE | Dead |
Effective date: 19991108 |