GB2069614A

GB2069614A - Fluid-operated i.c. engine starter motor

Info

Publication number: GB2069614A
Application number: GB8004641A
Authority: GB
Original assignee: Becorit Ltd
Current assignee: Spare IPG 15 Ltd
Priority date: 1980-02-12
Filing date: 1980-02-12
Publication date: 1981-08-26
Also published as: GB2069614B

Abstract

The apparatus comprises a pressure fluid energised starter motor (11), a shaft (12) driven by the motor, a pinion (13) carried on and driven by the shaft (12), the pinion being movable along the shaft from an inoperative position (14) to an operative position (15) in the former of which it is out of driving relation with the engine to be started, and in the latter of which it is in driving relation therewith, energisation of the motor (11) being controlled by sensing means (25) responsive to the attainment of its operative position (15) by the pinion (13), the pinion (13) being moved to its operative position by pinion shifting means (16). The starting apparatus has particular but not exclusive application to starting a "flame- proofed" internal combustion engine, i.e. one constructed or arranged so as to avoid production of sparks capable of igniting the combustible constituent of the atmosphere in which it may be used. <IMAGE>

Description

SPECIFICATION Improvements in or relating to starter motors Description of invention The present invention relates to starting apparatus for starting an internal combustion engine and comprising a starter motor, a shaft driven by the motor, a pinion carried on and driven by the shaft, the pinion being movable along the shaft from an inoperative position to an operative position in the former of which it is out of driving relation with the engine to be started and in the latter of which it is in driving relation therewith. Such starting apparatus will hereinafter be referred to as being of the type specified.

Starting apparatus of the type specified has in the past incorporated a "bendix" drive between the shaft and the pinion, by means of which, when the motor is rotated, the pinion is moved along the shaft from its inoperative to its operative position due to the rotational inertia of the pinion.

Problems have occurred with the starters as described above since it is possible for the pinion to engage incorrectly with a part of the year wheel driving the engine and with which it makes contact during a starting procedure (normally a toothed ring provided on the flywheel of the engine), and in extreme cases damage can occur to the gear wheel and/or the pinion.

The problems become greater when it is required to use starting apparatus of the type specified in an environment where an explosive atmosphere may be present. In such an atmosphere the engine and all ancilliary equipment must be "flameproofed", i.e. so constructed or arranged as to avoid production of sparks capable of igniting the combustible constituent of the atmosphere.

In the case of starting apparatus including only a "bendix" drive to move the pinion to its operative position, the force with which the pinion can strike the part of the gear wheel with which it meshes can easily lead to a spark being produced, thus rendering such a system unsuitable for use in environments where an explosive atmosphere may be present.

It is an object of the present invention to provide new or improved starting apparatus of the type specified.

According to the present invention we provide starting apparatus of the type specified wherein the motor is energised by pressure fluid and energisation of the motor is controlled by sensing means responsive to the attainment of its operative position by the pinion and wherein the latter is moved into this position from its inoperative position by pressure fluid energised pinion shifting means other than the motor itself. The sensing means responds to the position of the pinion along the shaft rather than to the force required to move the pinion therealony.

Preferably the sensing means is such that it does not so respond until the pinion has reached the extremity of Its movement i.e. has attained a fully meshed relation with a gear wheel driving the engine.

Preferably also the fluid is in liquld form.

The sensing means is preferably associated respectively with the actuating device and, on sensing the attainment of the operative position reached by the pinion, connects the pressure fluid to the motor.

Preferably the connection between the shaft driven by the motor and the pinion comprises a "bendix" drive, that is the shaft and the pinion are provided respectively with co-operating respective external and internal screw threads of a hand such that drive transmitted from the shaft to the pinion moves the latter axially towards its operative position, and drive from the pinion to the shaft established when the engine starts, moves the pinion towards its inoperative position.

Disengagement means may be provided operative, once the engine has been started, to allow the pinion to come out of driving relationship with the engine so that the pinion may return from its operative position to its inoperative position.

Conveniently the disengagement means may comprise a valve which terminates the supply of pressure fluid to the actuating device when the lubricating oil of the engine reaches a predetermined pressure, such pressure only being attained when the engine has been started.

Preferably said actuating device comprises a co-operating piston and cylinder Preferably a circuit through which pressure fluid is supplied to the motor and actuating device includes a manually operable pump by means of which the fluid may be pressurised.

Conveniently the circuit further includes an engine-driven pump also adapted to pressurise a fluid in the circuit.

The pressure fluid circuit may include an accumulator adapted to store fluid under pressure until the starting operation is required.

One embodiment of the invention will now be described in detail by way of example only with reference to the accompanying drawing which is a schematic diagram of starting apparatus of the present invention and an associated pressure fluid circuit.

A starting apparatus of the type specified is generally indicated at 10 and comprises a motor 11 in the form of a pressure fluid energised motor which drives a shaft 12. The shaft 1 2 is coupled to a pinion 1 3 by a bendix drive. The pinion 1 3 is movable along the shaft from an operative position 1 4 as shown in the drawing to an operative position adjacent the end 1 5 of the shaft 12.

Actuating means for moving the pinion 1 3 along the shaft from its inoperative position 1 4 to its operative position adjacent the end 1 5 of the shaft 1 2 comprises a piston and cylinder unit indicated at 16, the unit comprising a cylinder 1 7 a piston 18 and biasing means in the form of a spring 19 The piston 1 8 is connected to a connecting rod 20 which is pivotally connected to a transfer member 21 pivotally connected at 22 to pivot in a direction as shown by arrow 23.

The end 24 of the transfer member 21 is adapted to engage with the pinion 1 3.

On movement of the connecting rod 20 in a downwards direction. the transfer member 21 pivots about its axis 22 and moves the pinion 1 3 along the shaft 1 2 from its inoperative position adjacent the end 1 5 of the shaft 1 2.

The piston 18 of the unit 1 6 is connected to valve means 25 which has two positions in one of which it connects a supply of pressure fluid 26 to a sump 27 and in its other position it isolates the supply 26 of pressure fluid from the sump 27.

The pressure fluid circuit further comprises a main flow control valve 28 having a supply line 29 connected to the motor 11 and a pressure fluid inlet line 30. The pressure fluid inlet line 30 interconnects an engine driven charge pump 31, via charge valve 32. a manual charge pump 33, via one-way valve 34, an accumulator 35 via isolation valve 36 and a manual start valve 37 via a one-way valve 38.

The manual start valve 37 is connected to the cylinder 1 7 via supply line 40, the supply line 40 also communicating with a re-engagement inhibiting valve 41.

Operation of the starter motor will now be described in detail with reference to the drawing. If the fluid in the pressure circuit is not under any pressure it will first be necessary to pressurise the fluid which is done by manual operation of the manual charge pump 33. The fluid in the circuit will then be pressurised, a pressure supply" being being accumulated by the accumulator 35 the pressure of which registers on a gauge 43.

When the accumulated pressure has reached a value adequate to cause operation of the starting apparatus, the accumulator isolation valve is opened and the manual start valve 37 is moved by manual means to its position other than the one illustrated, so that it connects the source of pressure fluid from accumulator 35 through supply line 30, manual start valve 37 and line 40 to the cylinder 17 of the unit 16 The piston 1 8 of the unit 1 6 will therefore be moved in a downwards direction against the force provided by the spring 1 9. Such movement causes pivotal movement of the transfer member 21 about its pivotal axis 22 and hence movement of the pinion 1 3 from its inoperative position 14 to its operative position adjacent the end 15 of the shaft 12.

When the piston 1 8 has completed its travel and, it can only complete its travel if the pinion 1 3 moves fully into its operative position, the sensing valve 25 will transfer to a position, other than that shown, in which it connects the pressure fluid supply line 30 to sump 27 through line 26. Connection of the line 26 to sump 27 removes pressure on the main control valve 28 and causes it to move to its other position and hence the main fluid pressure supply line 30 is connected via main control valve 28 through line 29 to the start motor 11. Thus the motor operates to start the engine.

Operation of the starter motor will continue, provided the manual start valve is not released, until the engine has been started.

When the engine has started the lubricating oil which is pressurised by a pump provided in the engine in a normal manner will, when it has reached a predescribed value, cause operation of re-engagement inhibiting valve 41 which connects the cylinder 17 to sump 27 through line 40. Thus the piston 18 will return to the position as illustrated in the drawing under the force of spring 1 9 which, since the piston starts to move 1 8, will cause operation of valve 25 and hence the main flow control valve 28 will change position disconnecting the supply of pressure fluid to the motor 11. The pinion will thus return to its inoperative position 14.

Once the engine has been started the engine driven charge pump 31 will charge up the accumulator 35 thus storing pressurised fluid for a subsequent restarting operation.

If for any reason the system was subsequently depressurised it could be pressurised by operation of the manual charge pump 33.

The valve 25 may be replaced by the valve 50 which operates to perform the same function as valve 25. When the pinion 1 3 has attained its operative position, the information is relayed to valve 50 via a second transfer member 51 and valve 50 will operate to connect the motor 11 to the source of pressure fluid.

The starting apparatus of the present invention thus enables the pinion 1 3 to be moved from its inoperative to its operative position in a steady and controlled manner thereby greatly reducing the risk of any damage and eliminating the danger of possible sparks occuring due to contact between the pinion 1 3 and the part of the engine with which it cooperates to start the engine.

Claims

1. Starting apparatus of the type specified wherein the motor is energised by pressure fluid and energisation of the motor is controlled by sensing means responsive to the attainment of its operative position by the pinion and wherein the latter is moved into this position from its inoperative position by pressure fluid energised pinion shifting means other than the motor itself.

2. Starting apparatus according to Claim 1 wherein the sensing means is such that it does not so respond until the pinion has reached the extremity of its movement.

3. Starting apparatus as claimed in Claim 1 or Claim 2 wherein said sensing means is operatively associated with said pinion shifting means.

4. Starting apparatus as claimed in any one of claims 1 to 3 wherein cooperating surfaces between the pinion and the shaft by means of which the pinion is carried on and driven by the shaft, comprises a "bendix" drive.

5. Starting apparatus as claimed in any one of the preceding claims wherein disengagement means are provided to permit of or cause the return of the pinion from its operative position to its inoperative position once the engine has been started.

6. Starting apparatus as claimed in any one of the preceding claims wherein said pinion shifting means comprises a piston and cylinder assembly, one of which is operatively connected to the pinion to cause movement of the pinion from its inoperative to its operative position.

7. Starting apparatus as claimed in claim 6 wherein said starter motor is energised by the same source of pressure fluid as said actuating device.

8. Starting apparatus as claimed in any one of the preceding claims wherein said sensing means comprises a valve operatively coupled to sense attainment of its operative position of the pinion.

9. Starting apparatus as claimed in claim 7 wherein said sensing means comprises a valve operatively connected to said piston and cylinder unit, said valve being operative to connect the motor to a source of pressure fluid in response to the relative position reached between the piston and cylinder when the pinion has attained its operative position.

10. Starting apparatus as claimed in claim 7 wherein a circuit for supplying pressure fluid to said pinion shifting means and said motor includes a manually operable pump for pressurising the fluid in the circuit.

11. Starting apparatus as claimed in claim 10 wherein said circuit further includes an engine driven pump for pressurising the fluid in the circuit.

1 2. Starting apparatus as claimed in claim 10 or claim 11 wherein said circuit includes an accumulator for storing a pressure charge for pressurising the fluid in the circuit.

1 3. Starting apparatus as claimed in any one of the preceding claims wherein said pressure fluid comprises a liquid.

1 4. Starting apparatus as claimed in claim 5 wherein said disengagement means comprises a valve responsive to lubricating oil pressure of the engine and operative on said lubricating oil pressure reaching a predetermined value to initiate movement of the pinion from its operative position.

1 5. Starting apparatus as claimed in any one of the preceding claims in combination with an internal combustion engine.

1 6. Starting apparatus as claimed in any one of claims 1 to 1 5 in combination with an internal combustion engine which has been "flameproofed" as hereinbefore defined.

1 7. A method of starting an internal combustion engine using starting apparatus as claimed in any one of the preceding claims.

1 8. A method of starting an internal combustion engine using starting apparatus substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.

19. Starting apparatus substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.

20. Starting apparatus including any novel feature or combination of features as described herein and/or illustrated in the accompanying drawing.