GB2266354A

GB2266354A - Rotor rotating apparatus for inspection of a jet engine

Info

Publication number: GB2266354A
Application number: GB9308112A
Authority: GB
Inventors: Koichi Saika
Original assignee: JUPITOR CORP
Current assignee: JUPITOR CORP
Priority date: 1992-04-20
Filing date: 1993-04-20
Publication date: 1993-10-27
Anticipated expiration: 2013-04-20
Also published as: JPH0756216B2; GB2266354B; GB9308112D0; JPH05296065A

Abstract

A rotor rotating apparatus for inspection of turbine or compressor blades of a jet engine includes a harmonic gear 26 driven by a pulse motor 20 for converting the high speed rotational driving force of the pulse motor into a low speed and high torque driving force to rotate a rotor of the jet engine intermittently or continuously for inspection purposes. <IMAGE>

Description

ROTOR ROTATING APPARATUS FOR INSPECTION OF JET ENGINE BACKGROUND OF THE INVENTION Field of the Invention The present invention relates to a rotor rotating apparatus for inspection of a compressor and turbine blades of a jet engine.

Related Background Art In a jet engine or the like which is used in particular with an airplane, when a compressor or a turbine blade is damaged, even if the damage is extremely small, it can cause a serious accident or a disaster. Therefore, the presence or absence of damage is periodically strictly inspected. As an inspecting method, in general, an endoscope called a "borescope" is inserted into the engine from an opening for inspection provided for each engine, and the state of a turbine blade is directly observed by the eyes through such a fibrescope or is indirectly observed through a monitor screen.

When carrying out the above inspecting work, in order to move the turbine blade of the jet engine as the work progresses, a rotor is continuously or intermittently rotated and this is controlled by a pulse motor.

However, in association with the realization of a high power and a large size of the engine, a high torque is needed for the rotation of the rotor in the inspecting work. There is a tendency such that a pulse motor for generating a driving force, increases in size and that a mechanism to transfer the driving force of the pulse motor to the rotor also increases in size especially since a speed reducing mechanism of a large scale using spur gears and the like is required to generate the high torque. Inspection working efficiency therefore deteriorates due to such increases in size and weight of the rotor rotating apparatus.

SUMMARY OF THE INVENTION To solve the above problem, it is an object of the invention to reduce the size and weight of the rotor rotating apparatus to generate a high torque.

For this purpose, a harmonic gear is used to transfer a rotational driving force of a pulse motor to a rotor. In spite of a small size and a light weight, the harmonic gear can remarkably reduce a rotational speed of the pulse motor which has been inputted and can generate an extremely high torque even when the rotational driving force of the pulse motor is not so large.

According to the present invention there is provided a rotor rotating apparatus for inspection of a jet engine, comprising: a pulse motor for generating a high speed rotational driving force; a harmonic gear for converting the high speed rotational driving force of the pulse motor into a rotational driving force of a low speed and a high torque for rotating a rotor of the jet engine; and a pulse motor driving unit for driving controllably said pulse motor to rotate through said harmonic gear the rotor of the jet engine continuously or intermittently according to the progress of inspection work of a turbine blade or a compressor of the jet engine.

According to another aspect of the present invention there is provided a rotor rotating apparatus for controlled rotation of a jet engine rotor, said rotor rotating apparatus comprising a drive unit connectable to a jet engine said drive unit comprising a rotational cam for converting a high speed rotational force into a low speed high torque rotational driving force.

The above and further features of the present invention are set forth in the appended claims and should become clearer from consideration of the following detailed description of an exemplary embodiment given with reference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a perspective view of a power supplying unit of a rotor rotating apparatus for inspection of a turbine blade of a jet engine according to an embodiment of the invention; Fig. 2 is a perspective view of a control unit of the rotating apparatus; Fig. 3 is a perspective view of a driving unit of the rotating apparatus; Fig. 4 is a sectional view of the driving unit of the rotating apparatus; Fig. 5 is a cross sectional view of a harmonic gear of the driving unit; and Fig. 6 is a plan view of a specific example of an accessory gear box which is used to transfer a rotational driving force from the driving unit to the jet engine rotor according to the invention.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT An embodiment of the present invention will now be described hereinbelow with reference to the drawings.

A rotor rotating apparatus for inspection of a turbine blade of a jet engine according to the preferred embodiment is comprised of a power supplying unit, a control unit and a driving unit. Each unit will now be described hereinbelow.

Power supplying unit In Fig. 1, the power supplying unit receives electric power from a proper AC power source through terminal 1 and generates a pulse output for driving a pulse motor through terminal 2. Terminal 3 is connected to the control unit and is used to input a control signal. A breaker 4 is constructed by an on/off switch and is provided to protect the whole circuit from an excessive voltage.

Control unit Fig. 2 shows the control unit. An engine model display 5 lights up and displays the kind of jet engine as a target to be inspected. A state selection display 6 displays a state of a compressor or a turbine of an engine (for example, "HPT 1" is displayed). A turbine blade number display 7 is switched to a mode for a clockwise rotation CW or a mode for a counterclock rotation CCW. In the CW mode, a count value is increased and added from "1". When the count value reaches the total number of blades, the counting operation is stopped. In the CCW, the count value is subtracted from the total number of blades. When the count value reaches "1", the CCW is stopped. A CW/CCW display 8 displays information indicating whether the display state of the turbine blade number display 7 is CW or CCW.An engine model selecting switch 9 is switched to correspond with the engine as a target to be inspected. A reset switch 10 resets the blade number display. An interval switch 11 is used to select a time (a few seconds) to stop the blade in order to inspect the blade which is being rotated. A start/stop switch 12 is used to start or stop the rotation and driving of the rotor. A CW/CCW switch 13 is used to switch the rotating direction of the rotor. A blade position switch 14 is used to set an inspecting position of the blade. A speed switch 15 is used to adjust a rotational speed of the rotor to a value within a range from 80 to 1800/min. A foot switch jack 16 is a switch to connect to the foot switch. A cable 17 is connected to the control unit.

Driving unit Fig. 3 shows a driving unit 18 which is set into the jet engine and rotates the rotor. The drive unit 18 is fixed to the jet engine main body through an adaptor 19. A 5-phase step pulse motor 20 of the chopper style constant current driving type is provided in the driving unit 18. The motor 20 is rotated by receiving a pulse output of the power supplying unit through a terminal 21. A rotational driving force of the motor 20 is transferred through a reduction gear 22 including a harmonic gear shown in Fig. 4, which will be explained hereinafter, and rotates a shaft 23. The shaft 23 transfers the torque to a rotor driving gear of the jet engine.

Figs. 4 and 5 show the reduction gear 22 in detail. Fig. 4 shows a cross sectional view of the driving unit. The rotational driving force of the motor 20 is transmitted to a harmonic gear 26 through gears 24 and 25. The harmonic gear 26 comprises: a circular spline 27; a flex spline 28 which is engaged with the circular spline; and a wave generator 29 for deforming the flex spline 28 through a bearing 30 and sequentially allowing the teeth of the flex spline 28 to be partially engaged with the circular spline 27.

The wave generator 29 is rotated and driven at a high speed by a high speed rotational driving force transmitted through the gears 24 and 25 from the motor 20. In accordance with such a high speed rotation, the flex spline 28 is deformed and the portions of the circular spline 27 which are engaged with the flex spline 28 are sequentially rotated every rotation of the wave generator 29. Thus, the low speed and high torque rotational driving force generated in the circular spline 27 is transferred to the rotor of the jet engine. The operation of the harmonic gear 26 will now be further practically explained. The wave generator 29 comprises an elliptic cam and the ball bearing 30 fitted around the elliptic cam. Although the inner ring of the bearing 30 is fixed to the cam, the outer ring is elastically deformed through a ball.

The flex spline 28 is made of a metal elastic material and teeth are notched on the outer periphery. Teeth of the same pitch as that of the flex spline 28 are notched on the inner periphery of the circular spline 27. The number of teeth formed on the inner periphery of the circular spline 27 is larger than the number of teeth formed on the outer periphery of the flex spline 28. In association with the rotation of the wave generator 29, the teeth of the flex spline 28 sequentially come into engagement with the teeth of the circular spline 27. When the engaging positions once rotate, the flex spline 28 is rotated relative to the circular spline 27 because there is a difference of two teeth. The wave generator 29 is coupled to the motor 20 through the gears 24 and 25. The flex spline 28 is coupled to the rotor of the jet engine through the shaft 23.Therefore, the wave generator 29 rotates in association with the rotation of the motor 20. When the rotational driving force is transferred to the flex spline 28, the rotational speed is remarkably reduced. On the contrary, the torque is extremely increased. Further, the reduced rotational driving force is transferred to the rotor. For example, it is preferable to set the harmonic gear such that a speed reduction ratio is equal to 1/600 and a torque capacity is equal to 2200 kg.cm (maximum load value of the harmonic gear).

A specific example of a mechanism to transfer the rotational driving force from the driving unit to the driving unit of the jet engine will now be described.

The driving unit 18 transfers the rotational driving force to a drive shaft 33 of an accessory gear box 32 through a drive pad for an air starter or a manual crank pad 31. The rotational driving force is transferred to a rotor 35 of the jet engine through a gear 34 in the accessory gear box 32. A blade 36 as a target to be inspected is attached to the rotor 35.

The number of blades 36 differs depending on the kind of engine or each stage of the compressor and turbine. A load to rotate the rotor 35 also differs.

Therefore, in order to match the driving unit 18, it is necessary to change a gear ratio of the gear box 32 and the drive pad. For this purpose, a microcomputer having a memory is provided. Its change data is accumulated as data indicative of the number of driving pulses of the pulse motor which are required to feed one blade every engine and stage. On the basis of the accumulated data, the microcomputer instructs for a change the gear ratio of the gear box and the drive pad or displays such a change instruction. Further, the microcomputer reads the ON/OFF states of various kinds of switches of the control unit and allows the operating states of the switches to be displayed by various displays together with the driving state of the pulse motor. A display of a matrix of (5 x 7) dots can be used as a display here.

As described above, according to the present invention, the rotational driving force generated by the pulse motor is extremely reduced by the harmonic gear and is transferred as a high torque to the rotor of the jet engine, so that the motor and gears can be miniaturized and the structure can be simplified.

Thus having described the invention by reference to a particular embodiment, it is to be appreciated that the described embodiment is exemplary only and is susceptible to modification and variation without departure from the scope of the invention as determined by the appended claims.

Claims

CLAIMS:

1. A rotor rotating apparatus for inspection of a jet engine, comprising: a pulse motor for generating a high speed rotational driving force; a harmonic gear for converting the high speed rotational driving force of the pulse motor into a rotational driving force of a low speed and a high torque for rotating a rotor of the jet engine; and a pulse motor driving unit for driving controllably said pulse motor to rotate through said harmonic gear the rotor of the jet engine continuously or intermittently according to the progress of inspection work of a turbine blade or a compressor of the jet engine.

2. An apparatus according to claim 1, wherein said harmonic gear comprises: a circular spline; a flex spline engageable with said circular spline; and a wave generator for deforming said flex spline through a bearing, thereby allowing teeth of the flex spline to be partially sequentially engaged with the circular spline; and wherein said wave generator is rotated at a high speed by said pulse motor, the flex spline is deformed in accordance with said high speed rotation of the wave generator, and the portions of the circular spline which are engaged with the flex spline are sequentially rotated on every rotation of the wave generator, so that a rotational driving force having a low speed and a high torque is consequently generated in the circular spline and is transferrable to the rotor of the jet engine.

3. An apparatus according to claim 1 or 2, wherein said harmonic gear is small and lightweight and also has a high speed reduction ratio and a high torque allowance degree.

4. An apparatus according to any preceding claim, wherein said pulse motor operates at a high rotational speed and a low torque.

5. An apparatus according to any preceding claim, wherein said pulse motor driving unit has a microcomputer having a memory to accumulate data regarding a plurality of jet engine types and controls the driving of the pulse motor in correspondence with the engines of a plurality of different types.

6. An apparatus according to any preceding claim, further comprising a display to display a stage name of the jet engine as a target to be inspected.

7. A rotor rotating apparatus for controlled rotation of a jet engine rotor, said rotor rotating apparatus comprising a drive unit connectable to a jet engine, said drive unit comprising a rotational cam for converting a high speed rotational force into a low speed high torque rotational driving force.

8. A rotor rotating apparatus substantially as described herein with reference to the accompanying drawings.