GB2077361A

GB2077361A - Intermittently-operated compressed air starter

Info

Publication number: GB2077361A
Application number: GB8116342A
Authority: GB
Original assignee: G Duesterloh GmbH
Current assignee: G Duesterloh GmbH
Priority date: 1980-06-03
Filing date: 1981-05-28
Publication date: 1981-12-16
Also published as: DE3020930A1; GB2077361B; DE3020930C2; ES8300179A1; ES502421A0

Abstract

The starter pinion 10 is axially shiftable parallel to the axis of rotation of a geared flywheel 18 associated with the internal combustion engine and is arranged to be put into a slow rotation at least up to a meshing of the starter pinion 10 with the geared flywheel 18 by a force functionally independent of the axial shifting force exerted upon the starter pinion 10. The force for axially shifting the starter pinion 10 and/or the force causing the rotation thereof are exerted intermittently at least up to a partial meshing of the starter pinion 10 with the geared flywheel 18. <IMAGE>

Description

SPECIFICATION Method of and starter for starting a prime mover This invention relates to a method of and a starter for starting a prime mover in the form of an internal combustion engine or a gas turbine.

For starting internal combustion engines or gas turbines, it is known to associate with these prime movers geared flywheels into which powered starter pinions are tracked. During the starting process, the starter pinions are then shifted parallel to the axes of rotation of the flywheels.

Furthermore, they are slowly rotated in order to facilitate the tracking of their teeth into the tooth gaps of the flywheel gearing.

In those starters where the axial shifting effort upon the starter pinions is independent functionally from the effort causing the rotation of the starter pinions, it is observed, however, that after some time the tracking of the starter pinions into the flywheel gearing in part is possible only by overcoming strong resistances and in part is not possible at all any more. The cause of these difficulties has been determined to be worn edges at the starter pinions and at the flywhee: gearings as well as burr formations. These then have as a result in spite of bevelled tooth face edges after a more or less large number of starts that finally the teeth of the starter pinions come to lie facially of the teeth of the flywheel gearing and that thus a further tracking-in is blocked.Since in this condition an axial effort is continued to be exerted upon the starter pinions and additionally the continuous rotary motion is maintained, the edges of the starter pinions and flywheel gearings already damaged anyhow consequently are subjected to a further increased wear which initially renders difficult a soft tracking-in and finally obstructs same altogether.

With air-powered starters with overrunning clutches (German Patent 1245215), additional difficulties arise. It may for instance occur that the overrunning clutch has already engaged even if the starter pinion has not yet tracked in, because an increased resistance, for instance a result of wear and burr formation, has already activated the overrunning clutch. But since the motor of the starter continues to produce a torque, the required shifting effort is no longer able to be provided for by the starter pinion axially shiftable by compressed air in order to properly introduce the starter pinion into the flywheel gearing.

It is an object of the present invention to provide a method of and a starter for starting a prime mover which ensure a proper tracking-in of the starter pinion into the flywheel gearing of the prime mover even after a large number of starting operations.

According to one aspect of the invention a method of starting a prime mover in the form of an internal combustion engine or a gas turbine comprises axially shifting a starter pinion parallel to the axis of rotation of a geared flywheel associated with the prime mover, and putting the starter pinion into a slow rotation at least up to a meshing of the starter pinion with the geared flywheel by a force functionally independent of the axial shifting force exerted upon the starter pinion, the force for axially shifting the starter pinion and/or the force causing the rotation thereof being exerted intermittently at least up to a partial meshing of the starter pinion with the geared flywheel.

Consequently, the essence of the invention is to no longer provide the axial shifting effort and/or the effort required for initiating the rotation of the starter pinion uniformly, but to now have such an effort act intermittently. By the fact that the effort introduction is interrupted cyclically, no jamming is able to result during the tracking-in operation.

Rather, the starter pinion smoothly slides into the flywheel gearing, because it so to say seeks the path of least resistance. Wear phenomena only occur after a very large number of starts, and then they do so only to a minor extent. By virtue of these facts, accordingly the life of the starter pinion and thus also that of the flywheel gearing is materially extended. This is of particular significance for instance in those cases where maintenance and repair of a starter and a prime mover bring about difficulties. Difficulties in this case are mainly understood to be the accessibility of these units, this meaning for instance their installation in seagoing ships.

In a starter provided with an overrunning clutch wherein the starter pinion is both axially shifted and set into rotation by a fluid, in particular compressed air, an advantageous embodiment of the method of this invention is one in which the fluidic force for axially shifting the starter pinion is applied uniformly continuously or increasingly intermittently and the fluidic force for rotating the starter pinion is applied intermittently.

According to this procedure, hence during the starting process the axial motion of the starter pinicn is produced by a force which acts upon the starter pinion in the same or in a varying magnitude until the starter pinion has tracked into the flywheel gearing. On the other hand, the force causing rotation is provided in a periodically alternating magnitude at least until the pinion has partially tracked into the flywheel gearing.

Thereby, the starter pinion is subjected cyclically to a short slow rotation which is stopped again subsequently by removing the force. In this way, a possibly jammed overrunning clutch immediately is released again so that the axial advancing force need not overcome any additional resistances.

According to another aspect of the invention a starter for starting a prime mover in the form of an internal combustion engine or a gas turbine equipped with a geared flywheel comprises a starter pinion which is trackable into the gearing of the geared flywheel by a fluidically pressurizable piston in counteraction to a resetting force and is able to be set in slow rotation by means of a fluidically pressurizable motor via a fluid supply, wherein an interrupter for cyclically interrupting the supply of the starter motor with fluid, in particular with compressed air, is incorporated into the fluid supply possibly provided with a restrictor.

This line interrupter ensures that the fluid initially supplied to the starter motor in a small quantity via a precontrol line and a precontrol valve incorporated therein for the purpose of a slow rotation is prevented to continue to flow in direction to the starter motor in predetermined intervals. The starter motor thereby is only periodically provided with driving energy, for instance in the form of compressed air or a hydraulic fluid, so that the starter pinion during tracking-in performs a non-uniform rotary motion.

Its axial movement which is likewise preferably produced by compressed air pressurization of a piston associated with the starter pinion on the other hand remains in the scope of this preferred embodiment uniformly continuous or in the scope of the pressure drop occurring in the fluid supply upon operation of the interrupter increasingly intermittent. The so to say pulsating pressurization of the starter motor upon tracking-in of the starter pinion accordingly ensures that an overrunning clutch provided, even it would temporarily be jammed, is immediately released again and accordingly the axial shifting effort is able to be exerted without any resistance.

In order to achieve a rapid pressure drop in the pressure space of the starter motor, it may be advantageous to provide the fluid supply with no throttle. Accordingly, the interrupter must then be deviced such that the pressure space is able to be relieved via it.

Depending on the configuration of the interrupter, however, it may also be convenient to incorporate a throttle into the fluid supply upon requirement. Tests have for instance shown that it is advantageous in certain instances, however, to not effect an all to great restriction. For in this way the pressure at the piston is slightly reduced so that an increasing force now acts thereupon. This process has the effect that the starter pinion during the tracking-in process lifts off the face of the flywheel gearing hardly appreciable and the tracking-in process if thereby facilitated.

According-to an advantageous embodiment, it is provided for by the invention that the interrupter is defined by a 2/2-way valve shiftable in counteraction to a resilient resetting force by an electrical pulse generator The way valve having a shut-off and a flow position is consequently shifted by means of electrical pulses in counteraction to the resilient resetting force of a spring. In the starting position, the spring keeps the valve in the open position. An electrical control for instance consisting of a start switch for initiating the starting operation, a pulse generator and the magnet coils of the 2/2-way valve as well as a precontrol valve then causes an intermitting shifting of the 2/2-way valve as long as the starting operation continues.

According to a further advantageous embodiment of the invention, the interrupter is defined by a 2/2-way valve reversible from the fluid supply. In this embodiment the 2/2-way valve also only has an open and a shut-off position.

However, it now has two control connections which are connected via control lines to the fluid supply upstream and downstream of the way valve.

In the initial position, the way valve is reversed by the pressure existing in the fluid supply into the open position. The starter motor is then pressurized by virtue of the throttle possibly arranged downstream of the 2/2-way valve with a slight quantity of fluid, for instance with compressed air, and it slowly starts. By starting, a back pressure is produced, however, which shifts the 2/2-way valve into the shut-off position again.

The starter motor now does not receive any compressed air any more, the back pressure declines, sa that the 2/2-way valve is reversed into the open position, in which the starter motor receives compressed air again. For warranting the reversing operations, the control connection reversing the way valve into the open position has a small pressure area as well as a spring, and the control connection reversing the way valve into the shut-off position has a large pressurizing area for the work fluid.

A third advantageous embodiment of the invention is one in which the interrupter is defined by two 4/2-way valves mutually reversing each other by means of the fluid. In this embodiment, one of the two way 4/2-way valves has one control connection only, while the second way valve is provided with two control connections for the fluid. The retrograde movement of the first valve is caused by a resilient resetting force, for instance in the form of a compression spring.

In the initial position, for instance compressed air passes via the first way valve to a control connection of the second way valve and shifts same into a position in which the compressed air is able to pass via the second way valve to the control connection of the first way valve. Hence, same is shifted in counteraction to the resetting force in such a way that now compressed air is able to pass via the first way valve to the other control connection of the second way valve which consequently reverses, the compressed air thereby passing via the second way valve to the starter motor, and same starts to slowly move.

By reversing the second way valve, the supply line to the control connection of the first way valve is vented, and the resetting force of the spring shifts the first way valve into the initial position again so that now again compressed air is able to pass to the first control connection of the second way valve and same is shifted into the initial position in which the supply of compressed air to the starter motor is interrupted.

This alternating sequence of supply and shutoff of compressed air to the starter motor continues until by a manuai or automatic operation of the precontrol valve the compressed air is supplied from the compressed air source to the fluid supply. Only after the starter pinion has fully tracked into the flywheel gearing, it is ensured that the piston shifted by the axial shifting force releases a path for the compressed air to the control connection of a main valve which is now reversed from the shut-off position into the open position and supplies the compressed air at full rate to the starter motor for starting the prime mover which may be an internal combustion engine or a gas turbine.

The mutual reversing operation of the two 4/2way valves of the last mentioned embodiment is improved further to advantage in that adjustable throttle valves are incorporated into the supplies to the control connections of the 4/2-way valves.

The time of reversing may consequently be regulated sensitively. Also, it is further convenient in this context that check valves are incorporated into lines by-passing the adjustable throttle valves.

In the.case of the foregoing described embodiment, it is particularly advantageous that no restrictor is provided in the fluid supply.

Thereby, in the shut-off position of the second way valve the pressure space of the starter motor may be directly connected to ambient air via. this way valve so that a rapid pressure decrease may be effected.

Finally, it is provided for according to a fourth embodiment that the interrupter is defined by a rotary valve operated by a rotary motor. The rotary motor may for this purpose be designed for a small volume only. It controls the rotary valve during the tracking-in operation constantly in such a way that the rotary valve supplies compressed air to the starter motor in the one position and relieves the pressure space of the starter motor in the other position. Conveniently no restrictor is incorporated into the fluid supply in this instance, neither.

It is convenient in this context further that the rotary motor is connected to the precontrol line through the intermediary of an aperture.

Embodiments of the invention will now be described by way of example and with reference to the accompanying drawings in which: Fig. 1 is a vertical longitudinal section of a starter for a prime mover and a view of the control arrangement thereof; Fig. 2 is a similar section of the starter of Fig. 1 with a second embodiment of the control arrangement thereof; Fig. 3 is a similar section of the starter of Figs. 1 and 2 with a third embodiment of the control arrangement thereof, and Fig. 4 is a similar section of the starter of Figs. 1 to 3 with a fourth embodiment of the control arrangement thereof.

Figs. 1 to 4 show a starter 1 which is pressurized with compressed air and possesses a rotary piston motor 2 equipped with two rotors 3 and 4. The starter motor 2 has a drive pinion 5 which meshes with the internal gearing 6 of a hollow shaft 8 rotatably mounted in the housing 7 of the starter 1. The hollow shaft 8 is couplable via an overrunning clutch 9 to a starter shaft 11 carrying a starter pinion 10 at the outboard end.

The starter shaft 11 has a recess 12 at the other end into which the piston rod 1 3 of a pneumatic cylinder 14 engages rotatably, but axially nonshiftable. The piston 15 of the pneumatic cylinder 14 is pressurizable with compressed air at its larger piston area 16, whereas the retrograde movement is caused by a compression spring 1 7 which surrounds the piston rod 13 and moves the piston 1 5 and thus the starter pinion 10 into the initial positions.

The geared flywheel of a prime mover not illustrated in closer detail is designated by the reference numeral 18, the gearing of this fiywheel 1 8 being designated by the reference numeral 19.

In further agreement in Figs. 1 to 4, the compressed-air source is designated by the reference numeral 20. A main supply line 21 leads from the compressed-air source 20 to the starter motor 2. The relieved air flows off in the direction of the arrow A. In the main supply line 21, a 2/2way valve 23 provided with a pneumatic control connection 22 is incorporated which is shifted by a resetting spring 24 into the shut-off position. In this shut-off position, the starter motor 2 is separated from the compressed-air source 20. The 2/2-way valve 23 thus defines the main valve for the starter 1.

In a line 25 branching from the main supply line 21 between the main valve 23 and the compressed-air source 20, a precontrol valve 26 is incorporated which serves to initiate the starting operation. The precontrol valve 26 is operable either manually directly or remotely and automatically, respectively. In the initial position, a resetting spring 27 urges the precontrol valve 26 into a position in which the precontrol line 25 is vented.

If the precontrol valve 26 is now switched into the other operating position, compressed air passes from the compressed-air source 20 via the precontrol line 25 to the large piston area 1 6. The piston 1 5 is axially shifted in counteraction to the resetting force of the spring 17, and thus the starter pinion 10 is moved in direction of the flywheel gearing 19. At the same time, the compressed air passed via the precontrol line 25 passes into a fluid supply 28 branching off therefrom and having a restrictor 29. The restrictor 29 is defined by an aperture combined with a check valve into a structural unit. The fluid supply 28 is on the other hand connected to the main supply line 21 between the main valve 23 and the starter motor 2. The restrictor 29 may possibly also be dispensed with.

In the embodiment of Fig. 1, a 2/2-way valve 32 shiftable by an electrical pulse generator 35 in counteraction to a resetting spring 31 is incorporated into the fluid supply 28 between the restrictor 29 and the precontrol line 25. The pulse generator 35 is a component of an electrical control 30 which furthermore includes a start switch 57 for initiating the starting operation, a magnetic coil 33 of the precontrol valve 26 and a magnetic coil 34 of the 2/2-way valve 32 to be explained in closer detail hereinafter. Upon actuating the start switch 57, the pulse generator 35 is also activated. The reference numeral 56 designates the switch of the electrical pulse generator 35.

In the illustrated initial position in which the resetting spring 31 holds the 2/2-way valve 32 in the open position, compressed air passes via the fluid supply 28 at a restricted rate to the starter motor 2 with the precontrol valve 26 activated, the motor thus slowly starting. By virtue of the electrical pulse generator 35, the 2/2-way valve 32 is transferred into the shut-off position, however, after a predetermined period of time, in which position the starter motor 2 is separated from compressed-air supply. When a predetermined period of time has again lapsed, the electrical pulse generator 35 switches off, and the compression spring 31 transfers the 2/2-way valve 32 into the illustrated initial position again in which the starter motor 2 again receives compressed air in a restricted quantity. This alternating sequence then is repeated subsequently several times.

When the piston 1 5 and thus the starter pinion 10 have travelled a distance which ensures a full meshing of the starter pinion 1 0 with the flywheel gearing 19, the piston 15 releases the compressed air pressurizing it to a line 36 which leads to the control connection 22 of the main valve. This valve is thereby transferred into the open position, and the compressed air is now able to be passed at full rate from the compressed-air source 20 to the starter motor 2.

When the prime mover has ignited, the current supply to the precontrol valve 26 and to the electrical pulse generator 35 is interrupted at the switch 57 so that the precontrol valve 26 and the 2/2-way valve 32 incorporated into the fluid supply 28 return into the initial positions illustrated. Thereby, the precontrol line 25 is vented so that the piston 1 5 is moved back into the initial position illustrated by the resetting spring 1 7. The starter pinion 1 0 slides out of the flywheel gearing 19, and the line 36 to the control connection 22 of the main valve 23 is likewise vented. The resetting spring 24 thereby urges the main valve 23 into the initial position illustrated, also. The supply of compressed air to the starter motor 2 is interrupted. The starting operation-is terminated.

In the embodiment of the control illustrated in Fig. 2 for the otherwise identical starter 1, a 2/2way valve 37 directly reversible from the fluid supply 28 is incorporated into the fluid supply 28 between the precontrol line 25 and the main air supppy line 21. The 2/2-way valve 37 possesses two control connections 38 and 39. The control connection 38 having the small pressurizing area is connected via a control line 40 to the fluid supply 28 between the 2/2-way valve 37 and the precontrol line 25, and the control connection 39 having the large pressurizing area is connected via a control line 41 to the fluid supply 28 between the restrictor 29 and the 2/2-way valve 37.

Additionally, the control connection 38 having the small pressurizing area may have a resilient resetting force which contributes to shift the 2/2way valve 37 into the open position illustrated.

When thus the precontrol valve 26 is operated, compressed air passes from the compressed-air source 20 via the precontrol line 25 to the large piston area 1 6 and thereby shifts the starter pinion 10 in direction of the flywheel gearing 1 9. At the same time, compressed air passes via the fluid supply 28 and the still open 2/2-way valve 37 at a restricted rate to the starter motor 2. Latter starts to move and thereby produce a back thrust which has an effect via the control line 41 to the large pressurizing area of the control connection 39 and thus transfers the 2/2-way valve 37 into the shutoff position. The supply of compressed air to the starter motor 2 is interrupted.

But since compressed air continues to pressurize the small pressurizing area of the control connection 38 via the control line 40, subsequently the 2/2-way valve 37 is transferred into the initial position illustrated again so that compressed air passes to the starter motor 2 again.

In this embodiment it is thus also ensured that parallel to the pressurizing of the piston 1 5 shifting the starter pinion 10 axially, the starter pinion 10 is put into an intermittent rotary motion.

The cyclic pressurizing of the starter motor 2 in the embodiment of Fig. 3 is defined by two 4/2way valves 42 and 43 mutually reversing each other by means of compressed air, said valves being incorporated as a valve group into the fluid supply 28 between the precontrol line 25 and the restrictor 29.

When the precontrol valve 26 is opened, the compressed air initially pressurizes the shifting piston 1 5 via the precontrol line 25. Parallel thereto, it also pressurizes a control connection 45 of the second 4/2-way valve 43 via the 4/2-way valve 42 and an adjustable throttle valve 44. In this way, the compressed air passes via a branch line 48, via the second 4/2-way valve 43 and an adjustable throttle valve 48 incorporated into a further branch line 47 to the control connection 49 of the first 4/2-way valve 43 and shifts same in counteraction to a resetting spring 50 into the second operating position. In this operating position, the compressed air now passes via the 4/2-way valve 42 and a further branch line 51 to the other control connection 52 of the second 4/2-way valve 43, shifts same into the other operating position so that now compressed air passes via the branch line 46, the 4/2-way valve 43 and the restrictor 29 to the starter motor 2, same slowly starting to move.

By the shifting of the second 4/2-way valve 43, the line 47 leading to the control connection 49 of the first 4/2-way valve 42 is vented so that the resetting spring 50 transfers the first 4/2-way valve 42 into the illustrated initial position again. The compressed air now passes via this first 4/2-way valve 42 and the adjustable throttle valve 44 to the control connection 45 of the second 4/2-way valve 43 shifting same into the initial position and interrupting the supply of compressed air to the starter motor 2.

The foregoing mentioned alternating sequence again lasts as long as the starter pinion 10 has fully tracked into the flywheel gearing 19, the starter motor 2 receives the full compressed-air rate with the main valve 23 shifted into the open position and the prime mover has ignited.

It has to be supplemented that the throttle valve 44 incorporated into a supply line 53 and the throttle valve 48 incorporated into the branch line 47 are by-passed by lines 54 into which check va!ves 55 are incorporated.

When no restrictors 29 are provided in the fluid supply 28, the pressure space of the starter motor 2 may rapidly be vented via the 4/2-way valve 43 in the illustrated operating position.

In the embodiment of Fig. 4, the interrupter is defined by a rotary valve 58 incorporated into the fluid supply 28. The rotary valve 58 is operated by a small-volume rotary motor 59 which receives air from the precontrol line 25 via an aperture 60.

Upon operating the precontrol valve 26, the rotary motor 59 shifts the rotary valve 58 constantly from a position in which the starter motor 2 is supplied with compressed air (illustrated operating position) into a position in which the pressure space of the starter motor 2 is vented and vice versa. In this case no restrictor is incorporated into the fluid supply 28, neither.

Claims

1. A method of starting a prime mover in the form of an internal combustion engine or a gas turbine comprising (i) axially shifting a starter pinion parallel to the axis of rotation of a geared flywheel associated with the prime mover, and (ii) putting the starter pinion into a slow rotation at least up to a meshing of the starter pinion with the geared flywheel by a force functionally independent of the axial shifting force exerted upon the starter pinion, ths force for axially shifting the starter pinion and/or the force causing the rotation thereof being exerted intermittently at least up to a partial meshing of the starter pinion with the geared flywheel.

2. A method as claimed in claim 1 in the application to a starter having an overrunning clutch wherein the starter pinion is both axially shifted and put into rotation by a fluid, in particular compressed air, wherein the fluidic force for axially shifting the starter pinion is applied uniformly continuously or increasingly intermittently and the fluidic force for rotating the starter pinion is applied intermittently.

3. A starter for starting a prime mover in the form of an internal combustion engine or a gas turbine equipped with a geared flywheel, said starter comprising a starter pinion which is trackable into the gearing of the geared flywheel by a fluidically pressurizable piston in counteraction to a resetting force and is able to be set into a slow rotation by means of a fluidicaliy pressurizable motor via a fluid supply, wherein an interrupter for cyclically interrupting the supply of the starter motor with fluid, in particular with compressed air, is incorporated into the fluid supply possibly provided with a restrictor.

4. A starter as claimed in claim 3, wherein the interrupter is defined by a 2/2-way valve shiftable in counteraction to a resilient resetting force by an electrical pulse generator.

5. A starter as claimed in claim 3, wherein the interrupter is defined by a 2/2-way valve reversible from the fluid supply.

6. A starter as claimed in claim 3, wherein the interrupter is defined by two 4/2-way valves mutually reversing each other by means of the fluid.

7. A starter as claimed in claim 6, wherein adjustable throttle valves are incorporated into the supplies to control connections of the 4/2-way valves.

8. A starter as claimed in claim 3, wherein the interrupter is defined by a rotary valve operated by a rotary motor.

9. A starter as claimed in claim 8, wherein the rotary motor is connected to a precontrol line through the intermediary of an aperture.

10, A method of starting a prime mover in the form of an internal combusion engine or a gas turbine, the methods being substantially as herein particularly described with reference to the accompanying drawings.

11. A starter for starting a prime mover in the form of an internal combustion engine or a gas turbine, the starter being constructed and arranged substantially as herein particularly described with reference to the accompanying drawings.

1 2. Any novel feature or combination of features described herein.