GB2546998A

GB2546998A - Gear inspection method and apparatus

Info

Publication number: GB2546998A
Application number: GB1601969.7A
Authority: GB
Inventors: Louis Grice James
Original assignee: Nylacast Ltd
Current assignee: Nylacast Ltd
Priority date: 2016-02-03
Filing date: 2016-02-03
Publication date: 2017-08-09
Anticipated expiration: 2036-02-03
Also published as: WO2017134450A1; GB2546998B; GB201601969D0

Abstract

The method and apparatus disclosed relate to a method which includes providing a first driving gear 201 and a second driving gear 202, locating a gear wheel 10 between the first and second driving gears, rotating the gear wheel between the driving gears by rotating the driving gears in opposite directions, and measuring a diametric characteristic of the gear wheel based upon a measured relative position of respective axes of rotation of the driving gears during rotation of the gear wheel by the driving gears. A method of advancing the gear into and out of the related apparatus using the driving gears is also disclosed.

Description

Gear Inspection Method and Apparatus

TECHNICAL FIELD

The present invention relates to methods of processing gear wheels post-manufacture. In particular, the invention relates to a method of measuring a gear wheel on an in-line machine on a production line.

BACKGROUND TO THE INVENTION

It has long been the case that, when gear wheels are manufactured and subsequently assembled into a gear assembly, a period of running-in is required before full performance of the gear assembly can be safely obtained. In the past such running-in has in some instances been entrusted to the first user, where, for example a first purchaser of a product such as a car is advised to run the car at low rpm and to not excessively strain the engine for the first few thousand miles. This can be unreliable, however, since different users will take varying levels of notice of such instructions, or may forget what those instructions were after a limited time. Automated methods of running-in gear assemblies exist, but do not necessarily complete the running-in exercise in the most time and resource-efficient manner. For a gear assembly which is expected to complete most, or all, of its lifecycle running in a single direction then it is a simple exercise to run the assembly on a running-in machine in that single direction to complete running-in in advance of sale of the product incorporating the assembly. Devices exist to perform at least some degree of running- in of individual components before they are assembled into a gear assembly, so that zero, or a reduced level, of running in of the assembly as a whole is required. Certain types of assemblies can need bespoke or individually specified and selected components to be incorporated into the overall assembly in order to account for unpredictable variations in key dimensions of the assembly. For example, in gear assemblies, carefully selected shims may need to be added, to retain a gear in close engagement with a meshing gear, to reduce and/or limit backlash resulting from excessive clearances between gear teeth once assembled. During a running-in period, particular peaks, troughs, inconsistencies and variations in the surface of the gear tooth profile, mainly those resulting from imperfections in material removal processes, can be worn off and can result in a relatively small but important change in the effective pitch circle diameter (PCD), and run-out, of the gear wheel after the running in process is complete. These factors contribute to the amount of backlash found in meshing gears in a gear assembly. Therefore, it is possible in certain cases for undesirable features such as backlash to be increased during the running-in period. In such cases, if running-in is done after assembling the gear assembly, then expert adjustment may be necessary to reduce back lash to acceptable levels, which can be inefficient and an inconvenience to users, if this maintenance must occur after sale of the product. Therefore, running-in of components before assembly into an overall gear assembly of a product can be desirable. In particular, effective running-in can be important in reversible gear systems, such as for gears in a steering system of a vehicle, where the wear during use of the product is balanced in each direction of rotation of the gears. Further, any variation in run-out or pitch circle diameter in a steering system can affect the symmetry of feel in the steering system and so it is beneficial to identify any eccentricity or rotational asymmetry in a gear wheel, such as a low point or a high point. The present invention seeks to address these issues in the prior art.

SUMMARY OF THE INVENTION

The method and apparatus disclosed relate to a method which includes providing a first driving gear and a second driving gear, locating a gear wheel between the first and second driving gears, rotating the gear wheel between the driving gears by rotating the driving gears in opposite directions, and measuring a diametric characteristic of the gear wheel based upon a measured relative position of respective axes of rotation of the driving gears during rotation of the gear wheel by the driving gears. A method of advancing the gear into and out of the related apparatus using the driving gears is also disclosed.

In addressing the drawbacks of the prior art, the invention therefore provides a method of measuring a diametric characteristic of a gear wheel, comprising the steps of: providing a first driving gear and a second driving gear; locating the gear wheel between the first and second driving gears; rotating the gear wheel between the driving gears by rotating the driving gears in opposite directions; measuring a diametric characteristic of the gear wheel based upon a measured relative position of respective axes of rotation of the driving gears during rotation of the gear wheel by the driving gears.

The first and second gears are preferably rotated at the same rotational speed, especially when they are of substantially the same diameter. One or more of the first and second driving gears may be provided on a fixed mount. One or more of the first and second gears may be provided on a movable mount. The movable mount may be movable diametrically with respect to a gear wheel placed between the driving gears.

The method may further comprise rotating the gear wheel through substantially 180 degrees to measure the diametric characteristic about the full circumference of the gearwheel.

The method may further comprise introducing the gear wheel between the first and second driving gears by rotating the first and second driving gears to provide differing tangential speeds at the respective pitch diameters of the first and second driving gears. The differing tangential speeds may be provided by rotating the driving gears at different respective rotational speeds.

The method may further comprise applying a diametric or radial force to the gear wheel via one or both of the first and second driving gears, to grip the gear wheel between the first and second driving gears.

The gear wheel may be maintained in alignment with the driving gears along its axis of rotation by a support, configured to permit radial translation and/or rotation of the gear wheel relative to the driving gears.

The method may further comprise measuring the diametric characteristic of the gear wheel using position measurement means arranged to detect a diametric position of at least one of the first and second driving gears relative to the other.

The method may further comprise comparing measured diametric data from the position measurement means with stored specification data for the diametric characteristic and providing an indication of whether the gear wheel is within predetermined parameters for the diametric characteristic based upon the comparison.

The method may further comprise removing the gear wheel from between the driving gears by rotating the first and second driving gears to provide differing tangential speeds at the respective pitch diameters of the first and second driving gears.

The differing tangential speeds may be provided by rotating the driving gears at different respective rotational speeds.

The invention further provides an apparatus for measuring a diametric characteristic of a gear wheel, comprising: first and second driving gears for driving the gear wheel in rotation; at least one of the first and second driving gears being moveable toward and away from the other while driving the gear wheel in rotation; an actuator for providing a compressive force to the gear wheel via the first and/or second driving gear; and position measurement means for detecting a position of at least one of the first and second driving gears, to measure a diametric characteristic of the gear wheel when positioned between the driving gears.

The first and second gears are preferably rotated at the same rotational speed, especially when they are of substantially the same diameter. At least one of the first and second driving gears may be provided on a fixed mount. At least one of the first and second gears may be provided on a movable mount. The movable mount may be movable diametrically with respect to a gear wheel placed between the driving gears.

The apparatus may further comprise position measurement means arranged to detect a diametric position of at least one of the first and second driving gears relative to the other, to measure the diametric characteristic of the gear wheel.

The apparatus may further comprise an actuator configured for applying a diametric force to the gear wheel via one or both of the first and second driving gears, to grip the gear wheel between the first and second driving gears.

The apparatus may further comprise a support, configured to permit radial translation of the gear wheel relative to the driving gears, and to maintain the gear wheel in alignment with the driving gears along its axis of rotation.

The apparatus may be configured to carry out the methods as described herein.

The invention can also comprise a method and apparatus for running-in teeth of a gear wheel are provided, the method comprises providing first and second driving gears in driving engagement with teeth of the gear wheel to drive the gear wheel in rotation and driving the first and second driving gears to apply forces to first and second opposing sides of teeth of the gear wheel such that the first and second opposing sides of the teeth of the gear wheel are simultaneously run-in, by rotation of the gear wheel in engagement with the first and second driving gears. Various apparatus for carrying out the method are also disclosed.

In addressing the drawbacks of the prior art, the invention can provide a method of running-in teeth of a gear wheel, comprising: providing a first driving gear in driving engagement with teeth of the gear wheel to drive the gear wheel in rotation; providing a second driving gear in driving engagement with teeth of the gear wheel; driving the first and second driving gears to apply forces to first and second opposing sides of teeth of the gear wheel; such that the first and second opposing sides of the teeth of the gear wheel are simultaneously run-in, by rotation of the gear wheel in engagement with the first and second driving gears.

The method may further comprise: driving the first driving gear to apply a first load to a first side of teeth of the gear wheel, to apply a torque to the gear wheel; and controlling rotation of the second gear wheel, to apply a second load to a second side of gear teeth of the gear wheel, to oppose the torque applied by the first driving gear.

The method may further comprise setting a demand torque required in the system and applying the demanded torque to teeth of the gear wheel. The method may further comprise setting a first demanded speed of rotation for the first driving gear. The method may further comprise deriving a drive signal for the second driving gear from the demanded torque. The method may further comprise setting a demanded speed of rotation for the second driving gear, which is lower than a demanded speed of rotation for the first driving gear. The method may further comprise driving the system at a working speed which is between the demanded speed of rotation for the first driving gear and the demanded speed of rotation for the second driving gear. The torque is preferably equal through the gear train so that there is a substantially equal (but substantially opposite) force simultaneously applied to both sides of gear teeth of the wheel as they are in contact with the driving gears.

An axis of rotation of at least one of the first and second driving gears may be moveable in a substantially radial direction relative to the gear wheel, o the gear wheel. This may be used to apply an equal but controlled force on both gear teeth in rolling contact with the driving & driven gear. This can be used to control the friction between drive and driven gears.

The method may further comprise rotatably mounting the gear wheel to a mount, which is maintained at a controlled position relative to the driving gears.

The method may further comprise rotating one or more of the driving gears prior to engagement with the gear wheel and advancing the one or more driving gears toward the gear wheel to engage teeth of the gear wheel.

The method may further comprise applying a radial pressure to the gear wheel by radial actuation of one or more of the first and second driving gears. The method may further comprise driving the gear wheel in rotation for a predetermined time, to run-in the gear wheel.

The method may further comprise: before, during or after the running in of the gear wheel, measuring a radial position of one or more of the driving gears relative to the axis of rotation of the gear wheel, to measure a run-out of the gear wheel.

The method may further comprise comparing the measured run-out data to stored runout data to determine whether the measured run-out is within one or more predetermined tolerance thresholds.

The method may further comprise further comprise determining a rotational position of the gear wheel corresponding to a predetermined criterion and marking the gear wheel with a marker corresponding to the predetermined criterion. The predetermined criterion may be a radial characteristic of the gear wheel. The predetermined criterion may be defined relative to the radial run-out of the gear wheel. The predetermined criterion may be a high point and/or a low point on the circumference of the gear wheel.

The method may further comprise retracting one or more of the driving gears to release the gear wheel from the system.

The invention can further provide an apparatus for running in a gear wheel, comprising: a mount for supporting the gear wheel in a rotatable configuration; a first driving gear for engaging with the gear wheel at a first circumferential location; a second driving gear for engaging with the gear wheel in a second circumferential location; the apparatus being configured to drive the first and second driving gears to rotate the gear wheel while providing opposing forces on opposing sides of teeth of the gear wheel, to run-in the gear wheel.

One or more of the first and second driving gears may be configured to be radially moveable relative to the mount. The apparatus may further comprise position sensing means for sensing a radial position of one or more of the driving gears relative to the mount.

The apparatus may further comprise one or more actuators for driving one or more of the driving gears radially toward the gear wheel.

The driving gears may be worm type gears and the gear wheel may be a worm wheel. The driving gears and/or the gear wheel may be spur gears, parallel drives or helical gears.

The apparatus may be configured for carrying out the method or methods as described herein.

Any or all of the above features of the invention can be combined, in any combination, to provide advantages which will become further apparent on reading the following detailed description.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will now be described, by way of example only, with reference to the accompanying drawings in which:

Figure 1 shows a schematic representation of a first apparatus for carrying out methods according to a first aspect of the invention;

Figure 2 shows a cross-section through a gear wheel being run-in on the apparatus of Figure 1;

Figure 3 shows an alternative arrangement of driving gears for running-in a gear wheel in embodiments of the invention;

Figure 4 shows an alternative arrangement of an apparatus for carrying out methods according to an aspect of the invention; and

Figure 5 shows a cross section through a gear wheel disposed in the apparatus of Figure 4.

DETAILED DESCRIPTION OF THE INVENTION

Figure 1 shows an apparatus 100 which is configured for carrying out a method according to a first aspect of the invention as described herein. General mechanical arrangements for providing the various relative arrangements of gears, shafts, motors, actuators and sensors represented schematically in the figures will be understood by the skilled reader and so are not described or illustrated in detail. However, the key aspects of how the different components of the apparatus interact with one another are described herein and represented in the Figures.

The apparatus 100 of the first embodiment is a gear running-in machine. The machine comprises a chassis 101 which is generally arranged to receive the various components described in relation to the Figure. Received within the apparatus 100 is a gear wheel 10. This is the gear wheel 10 to be run-in by the gear wheel running in method performed by the machine 100. Gear wheel 10 is rotatably mounted to a shaft 110. Shaft 110 is mounted in substantially fixed relation to the chassis 101. The main function of the shaft 110 is to maintain the gear wheel 10 in place between the first 201 and second 202 driving gears. The gear wheel 10 is retained in place and restricted from movement by the driving gears 201 and 202 in a first direction, in a plane of rotation of the gear wheel, and substantially perpendicular to direction of drive applied to the gear wheel 10 by one and/or the other of driving gears 201 and 202. The principal function of shaft 110 is to prevent movement of the gear wheel 10 in a direction of arrow 111, which direction is generally parallel with the direction of drive applied to the gear wheel 10 by one and/or the other of driving gears 201 and 202. Shaft 110 therefore provides a mount for reacting tangential forces applied to the gear wheel 10 by the driving gears 201 and 202. This allows the driving gears 201 and 202 to create a torque through the gear wheel 10. The torque through the gear wheel is preferably equal, or balanced.

Driving wheel 201 can provide a first driving force in a first direction, at location 112, for example, in a direction of arrow 113. This creates a torque applied to the gear wheel 10. Second driving wheel 202 can provide a driving force on gear wheel 10 at location 113, in the direction of arrow 115, to oppose the torque created by driving gear 201. In this manner, the forces represented by arrows 113 and 115 create forces on opposite sides of teeth of the gear wheel 10 by applying opposing torque producing forces to the teeth of the gear wheel. The forces represented by arrows 113 and 115 are reacted by shaft 110, which can provide a reaction force in the direction of arrow 116. The sum of forces 113 and 115 will be equal to the force 116. However, the forces 113 and 115 may be unequal, to provide rotation in the gear wheel 10. All of the forces 113, 115 and 116 could be reversed in the system by reversing the directions of drive and resulting torque-producing forces provided by driving gears 201 and 202.

Driving gears 201 and 202 in the illustrated example are worm gears and so their axes of rotation 203 and 204 are substantially perpendicular to the axis of rotation of the gear wheel 10. However, alternative configurations for running-in different types of gears can be envisaged, as will be explained in relation to later Figures.

The first and second driving gears 201 and 202 are rotatably mounted to movable carriers 205 and 206. The carriers 205 and 206 are moveable toward and away from the axis of rotation 11 of the gear wheel 10. This movement can be provided by, for example, the illustrated tracks 221, 222, 223 and 224, but could be provided by any suitable form of translational engagement between chassis 101 and the carriers 205 and 206. An arrangement such as a ball screw could combine movement of the carriers with mounting of the carriers, for example. Actuators 230 and 231 can be provide to apply a force, to bias the driving gears 201 and 202 towards the gear wheel 10 via their respective carriers 205 and 206. Actuators 203 and 231 may be provided separately from, or integrally formed with, the tracks 221 to 224, for example in the mentioned ball screw arrangement. Position sensors can be provided in any known manner, and could be combined with actuators 231 and 230, or provided separately. Suitable position sensors may be, for example, Linear Variable Differential Transformer (LDTV) type sensors. The function of the position sensors is to detect the lateral position of the driving gears 201 and 202 relative to the gear wheel 10. This can be done by arranging them to detect relative movement and/or positions of one or both of the carriers 205 and 206 and the chassis, to detect movement of the driving gears 201 and 202 toward and away from the gear wheel 10 and its mount 110.

Drive means 241 and 242 can be provided to drive the drive gears 201 and 202 in rotation. These may take the form of electric or hydraulic motors or any other suitable source of rotational output. A controller 300 can be provided to control the running-in of the gearwheel 10 by the apparatus 100. The controller 300 may comprise a processor for carrying out instructions to direct the apparatus to carry out the methods as described herein. The controller comprises a series of data and/or power inputs and a series of data and/or power outputs for connection to actuators, drive means, sensors, user input devices and displays. As can be seen in the Figure, the controller 300 is connected to actuators 230 and may provide drive control signals and/or power to those actuators. The controller may receive position-related, or force-related data, or a combination thereof, from the actuators 231. Force sensors may be provided separately from actuators 230 and 231, for indicating to the controller a lateral force applied to the gear wheel 10 by the driving gears 201 and 202. Connections between the controller 300 and the drive means 241 and 242 are also provided. These can provide drive signals, power or data to the drive means 241 and 242 and may receive signals back from the drive means relating to speed or rotation and/or torque applied to the system. The controller can be connected to output indicators 310 and 311 and may be connected to input devices 320 and 321.

The method for running-in a gear wheel can be implemented by the apparatus 100 as follows. Gear wheel 10 is first located on the shaft 110 between the driving gears 201 and 202. For this step, the driving gears 201 and 202 may be retracted by a sufficient distance so that there is no tooth engagement between the driving gears and the gear wheel 10. Next the driving gears are engaged with the gear wheel 10. During this step, one or both of the driving gears may be rotated, such that teeth of the gear wheel and the driving gears do not just clash when they are brought together, preventing proper tooth engagement. By rotation of one or both of the driving gears, the driving gears can be gradually brought into engagement with the gear wheel 10, with gradual advancement of the carriers 205 and 206 toward the gear wheel 10. In a running-in step, actuators 231 and 230 can be employed to apply pressure to the gear wheel 10 in a substantially radial direction of the gear wheel 10. Once engaged, the driving gears 201 and 202 are driven in such a manner as to provide the opposing torques to opposing sides of teeth of the gear wheel as illustrated by arrows 113 and 115. The controller 300 may be configured in a manner of different ways to provide the desired torque through the system and forces 113 and 115. One method of doing so is to configure the controller 300 to receive a demand speed for rotation of a first of the driven gears 201. This can be input to the system via data input means 320, and may be displayed on a user display 310. The controller can also be configured to receive a demand torque to be applied through the gear wheel 10. This demand torque may be input to the controller by second data input means 321 and may be displayed on the same user display or on a further user display 311. The controller 300 can be configured to derive from the input demand speed and the input demand torque a demanded driving speed for each of the separate driving means 241 and 242. These demanded driving speeds for the first and second driving means 241 and 242 can be different. In this arrangement, with the driving means in a speed-controlled configuration, since each of the driving means will be seeking to achieve a different driving speed, they will provide opposing torques, working against one another through the gear wheel 10. Assuming equal power in the driving means 241 and 242, they will drive the system at approximately an average of the two demand speeds communicated to the respective driving means 241 and 242.

Other control methods for creating the demand torque in the system can be envisaged, such as having force sensors which more directly measure the forces 113 and 115 generated in the system and reacted in the carriers 205 and 206, or in shaft 110. Suitable feedback control can then control the speed and/or torque applied by driving means 241 and 242 to generate the desired level of forces in the direction of arrows 113 and 115 and/or 116. Any of these arrangements can be used to provide a force on opposite sides of teeth of the gear wheel 10 while it is rotated by the driving gears 201 and 202.

As will be appreciated, the effect of this arrangement and method of operation is that teeth of the gear wheel 10 are driven on a first side of the teeth by first driving gear 201, while second driving gear 202 drives teeth of the gear wheel 10 on a second side. In this way, both sides of teeth of the gear wheel 10 are run-in substantially simultaneously during rotation of the gear wheel 10 in the apparatus 100. Individual teeth of the gear wheel are not run in on both sides at exactly the same time in the illustrated arrangement, however opposite sides of different gear teeth are run-in during the running in process.

This running-in of the gear teeth on opposite sides simultaneously is advantageous compared to prior known methods, where a gear wheel is normally rotated by a single driving gear in a first direction and then, in order to run-in a second side of the teeth of the gear wheel, the driving gear is subsequently rotated in an opposite direction. The illustrated system can therefore substantially halve the time necessary for running-in of the wheel, since opposite sides of gear teeth of the gear wheel are run-in simultaneously. Further advantages include that the opposing forces provided by carriers 205 and 206 to maintain the gear wheel in between the driving gears reduce the complexity of forces which must be reacted by shaft 110. The reaction force required from shaft 110 is reduced to essentially a force in a single direction, reacting the two tangential driving forces provided simultaneously by the first and second driving gears 201 and 202.

Once the running-in procedure is complete, the carriers 205 and 206 may be retracted to retract the driving gears from engagement with the gear wheel 10, and the gear wheel 10 can be removed from the system.

However, in an additional or alternative method of the system, one or both of the driving gears to 201 and 202 may be used to measure a radial characteristic of the gear wheel 10, such as a radial run-out. This can be carried out prior to the removal of the gear wheel, and may be carried out part way through, before or during the running-in procedure.

To measure a radial characteristic of the gear wheel, such as a radial run-out, while the gear wheel 10 is being rotated by one, the other, or both of the first and second driving gears, a position measuring device detects a position of the driving gear 201 or 202. This can be by direct detection of the position of the driving gear, its axis of rotation 203 or 204, and/or the carrier 205 or 206 to which it is mounted. Measuring movement of the driving gear relative to the axis of rotation 11 of the gear wheel can give a measurement of the run-out of the gear teeth of the gear wheel 10. This measured run-out of the gear wheel can be compared to a standard or datum run-out value, compare to a set of run-out values, or compare to acceptable ranges for run-out of the gear wheel 10. Depending upon whether the measured run-out of the gear wheel is within acceptable ranges, then the gear wheel may be categorised as acceptable or not acceptable. This can be indicated to a user, or to a further processing device in the production chain, either of which/whom can reject the part, or return it for re-work, for scrap, or for recycling if it is deemed NOT OK, or unacceptable. If the part is deemed OK or acceptable, then it can proceed to a further step in a manufacturing or assembly process or be sent for despatch to a customer or a further production or assembly line.

The run-out data for the part can also be used to record the position of a high point or a low point around the circumference of the gear wheel 10. This type of radial characteristic can also be checked or compared to determine whether it is within acceptable limits. It can be advantageous, in bi-directional systems, such as steering systems, to know where a high- or low-point is on a gear and to mount that high or low point at a substantially neutral position of the system. This could be, for example a position in a steering system which corresponds to straight steering. This can help provide a symmetrical feel in the steering system for a user. The controller 300 may therefore be configured to calculate the rotational position of the recorded high point or low point, and can be configured to instruct a gear marking means to apply a mark to the gear wheel 10 at a suitable position on the gear wheel, relating to the high point or low point. The marking may take any suitable form, such as a simple ink, stamp or impression made on the part at the high or low point, or may take the form of a code indicating a rotational position of the high or low point of the gear wheel. This marking can then be used by assemblers of the system to assemble the high or low point at a desired orientation, such as a neutral position, or other suitable configuration in the assembled system in which the gear wheel 10 is to be assembled.

Figure 2 illustrates a cross section through the gear wheel 10 and shows in greater detail how driving gears 201 and 202 may be engaged with gear wheel 10 and can be driven in contra-rotating directions as indicated by arrows 201A and 20IB. As can be seen, shaft 110 may be supported on one or more bearings 117 and 118 to journal the shaft 110 to the chassis 101 of the apparatus 100.

Figure 3 illustrates an alternative arrangement in which the driving gears 2010 and 2020 are mounted with their axes of rotation substantially coaxial with the axis of rotation 11 of the shaft 110a and/or gear wheel 10a. This arrangement may be preferred when the gear 10a is a spur type gear. Alternative arrangements of carriers 2050 and 2060 can be provided to provide driving means 2410 and 2420 to provide drive inputs for the respective driving gears 2010 and 2020. Such alternative arrangements can be implemented if the driving gears, such as driving gears 2010 and 2020 are to be spur gears, parallel drives or helical gears, for engaging with corresponding types of gear wheel 10a to be run-in. The procedures and modes of operation described herein with reference to gear wheel 10 can be applied to the arrangement of Figure 3.

Figure 4 illustrates an alternative arrangement of an apparatus for carrying out methods according to further aspects of the invention. Similar components are numbered as in Figures 1 to 3 where components are functionally equivalent, with the addition of a prime indication.

The primary function of the apparatus 100' is the measurement of a diametric characteristic of the gear wheel 10. This may be carried out before or after a running-in process of the gear wheel 10. Similarly to the apparatus of Figure 1, the apparatus 100' comprises first 201' and second 202' driving wheels. These are mounted to carriers 205' and 206'. In the example of Figure 4, one or the other of the first 201' and second 202' driving gears may be held at a fixed location relative to a chassis 101' of the apparatus 100'. Carrier 205', for example, may therefore be integrally formed or fixedly attached to the chassis 101' of the apparatus 100 in a machine configured for carrying out the methods described in relation to this figure. However, the methods can be carried out where both carriers 205' and 206' are moveable relative to chassis 10Γ, since the difference in position between the first and second driving gears 201' and 202' is what indicates the diametric characteristic measured in the device 100'. Therefore, in order to measure a diametric characteristic of the gear wheel 10, it is only necessary to understand an overall distance between the driving gears 20 Γ and 202'. For this reason, in the described process for measuring a diametric characteristic of the gear wheel 10, the gear wheel 10 need not be mounted to any shaft 110 as illustrated in Figure 1. On the contrary, the gear wheel 10 is free to "float" between driving gears 201' and 202', but is also retained between them by engagement with the teeth of the driving gears 201' and 202'. A lateral force may also be applied to the gear wheel 10 between the driving gears, in a substantially radial or diametric direction across the gear wheel 10 during the measurement process.

Controller 300' can be connected to any or all of the functional devices, inputs and outputs of Figure 4 and to any or all of equivalent devices illustrated in Figure 1 which can be provided for the apparatus of Figure 4. The relevant connections are not reproduced in their entirety in Figure 4 to avoid reproducing unnecessary complexity in the Figure.

To carry out the measurement process, the gear wheel 10 is located between the first and second driving gears 20 Γ and 202'. The first and second driving gears are rotated in opposite directions to rotate the gear wheel 10, preferably in a substantially fixed location. To rotate the gear wheel 10 in a fixed location, equal and opposite tangential motion is provided to the opposite sides of gear wheel 10 by driving gears 20 Γ and 202'. In this arrangement, no significant torque is intended to be generated through the gear wheel 10 and so the speeds of rotation applied at each side are substantially matched to retain the gear wheel 10 in a substantially fixed lateral location. During rotation of the gear wheel 10, a distance between driving gears 20 Γ and 202' can be measured by a position measurement means such as a LVDT, or other suitable position measurement device. Since the measurement is taken between opposing points around a diameter of the wheel, it is only necessary to rotate the gear wheel through substantially 180° in order to measure the diametric characteristic about the full circumference of the gear wheel. During rotation of the gear wheel in the measurement process, a controlled pressure is preferably applied to the gear wheel 10 by at least one of actuators 230' and 23 Γ, depending upon whether one of the two carriers 205' and 206' is held in a fixed location or not, as described above.

At a starting point of the measurement process, the position measuring means compares its initial measured diametric characteristic to a known set datum for the gear wheel 10 being measured. The measured diametric characteristic, such as a centre distance of the gear wheel, is recorded, and any deviation from the specified distance for the component in question can be recorded and/or displayed to a user. Both driving gears 201' and 202' are started simultaneously, rotating the gear wheel in opposite directions, without the need for any centre locator on the gear wheel. Any movement of the slide or slides 22Γ to 224' can be compared and, by measuring a difference between the movement measured for the opposing slides, a difference in the overall diametric characteristic of the gear wheel 10 can be measured. This characteristic can be recorded as the gear wheel rotates. An algorithm in the controller 300' can compare the measured data to pre-set and pre-recorded parameters for the diametric parameter, which may be a centre-distance or any radial or diametric run-out parameters. Depending upon whether the part is within, or exceeds, predefined limits for any deviation from the pre-recorded parameters, the gear wheel 10 being tested can be determined to be OK/acceptable or NOK/not acceptable. As described above, carrying out the measurement operation with at least one pair of counter-rotating driving gears in the described manner only requires the gear wheel 10 to be rotated through 180°, which provides a fast and accurate means for measuring a diametric characteristic of the gear wheel 10.

For control and measurement apparatus having a fixed time resolution and spatial resolution for measurements taken, a slower speed of rotation can result in a greater measurement accuracy, but of course increases time involved. Therefore, use of this technique, which can halve the amount of rotation required for a full diametric assessment of the piece can be beneficial in terms of time and/or accuracy. During the measurement operation, a pressure can be applied via one or both of the carriers 205' and 206', using one or both of actuators 230' and 23 Γ. After the measurement operation is complete, this pressure may be released. The part can then be removed from the system.

As illustrated in the Figure, the gear wheel 10 may be carried into and/or out of the apparatus 100' on conveyors 401 and 402. However, the conveyors alone can only carry out this full operation of locating the gear wheel 10 between the driving gears 201' and 202', if the driving gears are fully retracted from the teeth of the gear wheel 10. To facilitate location of gear wheel 10 between the first and second driving gears, it is possible to drive the driving gears 201' and 202' at differential speeds. By driving one of the driving gears faster than the other, the gear wheel 10 can be simultaneously rotated and translated to a suitable position between the driving gears 201' and 202'. To carry this out, the moveable carrier, 205' or 206' as the case may be, or indeed both of the movable carriers if both are movable, can be in a slightly retracted position relative to their fully engaged position for the measurement operation, but in a position which still provides good tooth engagement with the gear wheel 10. The gear wheel 10 to be measured is provided in a position of initial engagement with the driving gears 201' and 202'. This may be provided by a conveyor 401/402, or by rollers or another suitable input device for the gear wheel 10. When the driving gears 201' and 202' are driven at differential speeds, i.e. one faster than the other, the gear wheel 10 translates in a direction perpendicular to its axis of rotation, between the driving gears. The gear wheel 10 will be supported by the apparatus on its underside by, for example, conveying devices 401 and 402, or other suitable support means, such as a simple fixed platform. As described above, for the measurement operation, the driving gears are driven so as to provide equal and opposite tangential motion to the opposing sides of the gear wheel 10. Where the driving gears are of the same pitch and radius, this will involve rotating them at the same speed. However, if for any reason driving gears of differing pitches and/or diameters were used, then their speeds of rotation could be compensated accordingly to provide equal and opposite tangential motion to the gear wheel 10 at its two opposing sides.

Once the measurement operation is complete, the driving gears 201' and 202' can again be driven to provide differing tangential motion to the gear wheel 10 to rotate the gear wheel and to drive it out of the apparatus 100' to be extract by, for example, a user or the conveying means 401 and 402.

It is also possible to eject the gear wheel 10 from the apparatus by completely stopping one of the driving gears 201' or 202' while continuing to rotate the other.

It will be appreciated that, by providing a suitable degree of travel between driving gears 201 and 202 or 201' and 202', a wide range of gear wheels 10 can be tested. Further, by providing a range of different driving gears 201' and 202', gear wheels 10 having different tooth profiles and configurations can be measured by the apparatus 100'.

It will be appreciated in considering the examples of Figure 1 and Figure 4, that the principal difference between the two is that the shaft 110 is not used in the measurement process of Figure 4. However, the functionality of the two apparatus 100 and 100' could be combined by providing a deployable mount to perform the function of shaft 110, at a location between the driving gears 201' and 202' of the apparatus 100'. The method of drawing the gear wheel 10 into the machine by suitable rotation of the driving wheels 201' and 202' can be applied to the apparatus 100 if so desired. In this manner, a single apparatus can be provided which combines the functionality of apparatus 100 and apparatus 100' by providing such a deployable and retractable mount 110 in the apparatus 100' and configuring the controller 300' accordingly. The retractable mount could be provided in the form of a moveable shaft, for example, as is illustrated in Figure 5.

Figure 5 shows a cross-section through the gear wheel 10 and first and second driving gears 20Γ and 202'. A retractable shaft 50 can be provided, which may be deployable and retractable along an axis of rotation 1Γ of the gear wheel 10. The shaft 50 may be carried on a carrier 51 and journalled by bearings 52 and 53. The carrier 51 can be actuated and movably mounted relative to the chassis 10Γ by any suitable movable mounting means, such as tracks or ball screws discussed in relation to Figure 1.

During the diametric characteristic measurement operation, the first and second driving gears are rotated in the directions indicated by arrows 501 and 502 with the shaft in the retracted position shown in Figure 5.

In order to carry out a running-in procedure as described in relation to the apparatus of Figure 1, the shaft 50 can be advanced into the centre of gear wheel 10. Then the apparatus 100' can be controlled to carry out the running-in method described in relation to Figure 1.

The radial characteristic measurement procedure described in relation to the apparatus of Figure 1 can also be carried out with the gear wheel 10 mounted to the shaft 50.

The described procedures can, therefore, all be carried out on the same machine if so desired, and in any order.

As can therefore be appreciated, any or all of the features of the methods and apparatus described in relation to Figures 1 to 3 and 4 to 5, can be implemented in any combination and the related advantages of those features realised in isolation or in combination.

Claims

1. A method of measuring a diametric characteristic of a gear wheel, comprising the steps of: providing a first driving gear and a second driving gear; locating the gear wheel between the first and second driving gears; rotating the gear wheel between the driving gears by rotating the driving gears in opposite directions; measuring a diametric characteristic of the gear wheel based upon a measured relative position of respective axes of rotation of the driving gears during rotation of the gear wheel by the driving gears.

2. A method according to claim 1, wherein one of the first and second driving gears is provided on a fixed mount and the other of the first and second gears is provided on a movable mount.

3. A method according to claim 2, wherein the movable mount is movable diametrically with respect to a gear wheel placed between the driving gears.

4. A method according to any of the preceding claims, further comprising rotating the gear wheel through substantially 180 degrees to measure the diametric characteristic about the full circumference of the gear wheel.

5. A method according to any of the preceding claims, further comprising introducing the gear wheel between the first and second driving gears by rotating the first and second driving gears to provide differing tangential speeds at the respective pitch diameters of the first and second driving gears.

6. A method according to claim 5, wherein the differing tangential speeds are provided by rotating the driving gears at different respective rotational speeds.

7. A method according to any of the preceding claims, further comprising applying a diametric force to the gear wheel via one or both of the first and second driving gears, to grip the gear wheel between the first and second driving gears.

8. A method according to any if the preceding claims, wherein the gear wheel is maintained in alignment with the driving gears along its axis of rotation by a support, configured to permit radial translation of the gear wheel relative to the driving gears.

9. A method according to any of the preceding claims, further comprising measuring the diametric characteristic of the gear wheel using position measurement means arranged to detect a diametric position of at least one of the first and second driving gears relative to the other.

10. A method according to claim 9, further comprising comparing measured diametric data from the position measurement means with stored specification data for the diametric characteristic and providing an indication of whether the gear wheel is within predetermined parameters for the diametric characteristic based upon the comparison.

11. A method according to any of the preceding claims, further comprising removing the gear wheel from between the driving gears by rotating the first and second driving gears to provide differing tangential speeds at the respective pitch diameters of the first and second driving gears.

12. A method according to claim 11, wherein the differing tangential speeds are provided by rotating the driving gears at different respective rotational speeds.

13. An apparatus for measuring a diametric characteristic of a gear wheel, comprising: first and second driving gears for driving the gear wheel in rotation, at least one of the first and second driving gears being moveable toward and away from the other while driving the gear wheel in rotation; an actuator for providing a compressive force to the gear wheel via the first and/or second driving gear; and position measurement means for detecting a position of at least one of the first and second driving gears, to measure a diametric characteristic of the gear wheel when positioned between the driving gears.

14. An apparatus according to claim 13, wherein one of the first and second driving gears is provided on a fixed mount and the other of the first and second gears is provided on a movable mount.

15. An apparatus according to claim 13 or claim 14, wherein the movable mount is movable diametrically with respect to a gear wheel placed between the driving gears.

16. An apparatus according to any of claims 13 to 15, further comprising position measurement means arranged to detect a diametric position of at least one of the first and second driving gears relative to the other, to measure the diametric characteristic of the gear wheel.

17. An apparatus according to any of claims 13 to 16, further comprising an actuator configured for applying a diametric force to the gear wheel via one or both of the first and second driving gears, to grip the gear wheel between the first and second driving gears.

18. An apparatus according to any of claims 13 to 17, further comprising a support, configured to permit radial translation of the gear wheel relative to the driving gears, and to maintain the gear wheel in alignment with the driving gears along its axis of rotation.

19. An apparatus according to any of claims 13 to 18, configured to carry out the method of any of claims 1 to 12.