Title:
STARTING ARRANGEMENT FOR INTERNAL COMBUSTION ENGINES
United States Patent 3670173


Abstract:
The electric starting motor for an internal combustion engine has its auxiliary field winding and series exciter coil so connected in an electric starting circuit that the field winding and exciter coil produce opposed magnetic fields that, together with the armature field, tend to turn, but do not actually turn, the armature shaft in reverse direction until the starting pinion and gear of the internal combustion engine mesh, whereupon a switch automatically changes the connection of the field winding so that the latter and the exciter coil produce aiding fields that, together with the armature field, turn the armature shaft in its normal direction.



Inventors:
PFLUGER GERHARD
Application Number:
05/090614
Publication Date:
06/13/1972
Filing Date:
11/18/1970
Assignee:
ROBERT BOSCH GMBH.
Primary Class:
International Classes:
F02N11/08; F02N15/06; (IPC1-7): F02N11/08
Field of Search:
290/38R,38A,38C,DIG
View Patent Images:
US Patent References:
2939964Starting systems1960-06-07Schneider et al.
2689310Electric starting motor for internal-combustion engines1954-09-14Kaufmann



Primary Examiner:
Gilheany, Bernard A.
Assistant Examiner:
Duncanson Jr., W. E.
Claims:
1. In a starting arrangement for an internal combustion engine, in combination, an electric starting circuit having an electric starting motor, the shaft of which carries a pinion adapted to mesh with a gear of the internal combustion engine, a current source for said starting motor, a master switch for connecting said starting motor to said current source, an electromagnetic starting relay for drivingly coupling said starting motor to said internal combustion engine when the relay is energized and for closing said master switch after the relay is energized and not before said starting motor is at least partly coupled to the internal combustion engine, a starting switch operable at volition for connecting said relay to said current source to energize the former, a coupling means for causing relative rotation between said pinion and said shaft whenever the teeth of said pinion contact the teeth of the gear of the internal combustion engine but do not mesh therewith, and a series exciter coil and an auxiliary field winding comprised by said starting motor and so connected in said starting circuit, when said starting switch is closed, that the resulting torque acting on the shaft of said starting motor, while said starting switch is closed but said master switch is open, is in the direction opposite to the normal direction of shaft rotation and is insufficient to turn said shaft.

2. In a starting arrangement as defined in claim 1, wherein said series exciter coil and auxiliary field winding are energized to produce opposing magnetic fields when said starting switch is closed but said master switch is open.

3. In a starting arrangement as defined in claim 1, wherein said series exciter coil and auxiliary field winding are energized to produce aiding magnetic fields when said starting switch and master switch are both closed.

4. In a starting arrangement as defined in claim 1, further including auxiliary switch means operated by said starting relay, and connected to said current source and said auxiliary field winding, for connecting said auxiliary field winding in said electric starting circuit so that the field of said winding opposes the field of said series exciter coil under the aforesaid conditions, and for changing the connection of said winding in said electric starting circuit when said master switch closes so that the field of said winding aids the field of said series exciter coil under the aforesaid conditions.

5. In a starting arrangement as defined in claim 4, wherein said starting relay has an armature for operating said master switch and said auxiliary switch.

6. In a starting arrangement as defined in claim 1, wherein said starting motor has an armature and said starting relay has a draw-in coil and a holding coil, and when said starting switch is closed and said master is open said series exciter coil and said draw-in coil are connected in series and shunted across said auxiliary field winding to form a parallel circuit, said parallel circuit being connected in series with said armature, starting switch, and current source.

7. In a starting arrangement as defined in claim 1, wherein when said starting switch and master switch are both closed, said series exciter coil and said armature constitute a series circuit that is connected directly to said current source, and said auxiliary field winding is shunted across said armature.

8. In a starting arrangement as defined in claim 1, wherein said pinion is rotatable about and shiftable along the axis of said shaft, said pinion being provided with a coupling member which has a first axial screw thread having a high pitch; said coupling means further comprising a sleeve mounted coaxially on said shaft and shiftable along the axis of the same, said sleeve having a second axial thread meshed with said first screw thread, said sleeve being movable along said axis toward said internal gear in response to actuation of said starting relay, whereby when said pinion engages said gear without being able to mesh therewith, relative axial movement between said pinion and said sleeve results in relative rotation of said pinion with respect to said shaft.

9. In a starting arrangement as defined in claim 8, wherein said pinion and said sleeve are normally in predetermined relative positions; said arrangement further comprising engaging lever means controllable by said starting relay for advancing said sleeve and said pinion towards said gear of said combustion engine, to thereby engage said pinion with the latter.

10. In a starting arrangement as defined in claim 9, further comprising biasing means for restoring said pinion and said sleeve to their used position subsequent to a change in relative position in response to inability of said pinion to mesh with said engine internal gear.

Description:
BACKGROUND OF THE INVENTION

The invention relates to a starting arrangement, having an electric starting motor, for an internal combustion engine.

One common starting arrangement of this kind has a pinion, driven by the electric starting motor, and an electromagnetic starting relay energized by a starting switch operable at volition, the relay meshing the pinion with a gear of the internal combustion engine and, when the meshing is nearly completed, closing a master switch to turn on the starting motor. The starting arrangement also has a scheme for causing rotation of the pinion or of the armature shaft of the starting motor when the teeth of the pinion and of the gear of the internal combustion engine meet head on.

When designing electric starters for internal combustion engines, every attempt is made to obtain a satisfactory and reliable meshing between the pinion and the gear of the internal combustion engine and to reduce as much as possible the stresses that appear on the teeth when the pinion is driven.

The previously described arrangement of the prior art has a coarse thread that couples the pinion to a sleeve, which is slidably mounted on a shaft driven by the starting motor. The starting relay, when energized, pushes the sleeve and pinion toward the gear of the internal combustion engine and turns on the starting motor when the pinion and gear mesh. When the pinion and gear teeth meet head on (tooth-on-tooth), the sleeve continues to move forward so that the coarse thread causes the pinion to rotate until it can mesh with the gear. It sometimes happens, however, that the front edge of a pinion tooth strikes the front edge of the gear tooth (edge-on-edge), the pinion becoming locked with the gear. In this event, the coarse thread causes reverse rotation of the sleeve and armature shaft of the starting motor. The starter is so designed that, in these conditions, the starting relay cannot execute its full draw-in stroke, so that the starting motor is not turned on, and the internal combustion engine must be re-started from the beginning. Since the armature shaft has been turned backwards, the relative positions between the pinion and the gear are different, the pinion now being free to mesh with the gear.

This known arrangement, comprising mechanical armature and a pinion rotation device, has the disadvantage that the relay must provide the force for advancing the sleeve while turning the armature shaft backwards, this force being relatively large, particularly with powerful starters. Those starters having a connecting gear between the armature shaft and the pinion shaft require considerable force, because the armature torque rises in proportion with the gear ratio of the connecting gear. To abtain this force, heavy-duty relays must be used. Powerful electromagnets, however, require large windings, connecting leads with large cross sections, and contacts more resistant to burning. Aside from these disadvantages, more room is required.

SUMMARY OF THE INVENTION

An object of the invention is a starting arrangement for internal combustion engines that requires only a small amount of axial force from the starting relay when the pinion and the gear clash edge-on-edge, whereby the starting relay can be built as a very compact unit.

The invention consists essentially of an electric starting circuit having an electric starting motor, the shaft of which carrying a pinion adapted to mesh with a gear of the internal combustion engine, a current source for a starting motor, a master switch for connecting the starting motor to the current source, an electromagnetic starting relay for drivingly coupling the starting motor to the internal combustion engine when the relay is energized and for closing the master switch after the relay is energized and not before the starting motor is at least partly coupled to the internal combustion engine, a starting switch operable at volition for connecting the relay to the current source to energize the former, a coupling arrangement for causing relative rotation between said pinion and said shaft whenever the teeth of said pinion contact the teeth of the gear of the internal combustion engine but do not engage therewith, and a series exciter coil and an auxiliary field winding comprised by the starting motor and so connected in the starting circuit, when the starting switch is closed, that the resulting torque acting on the shaft of the starting motor, while the starting switch is closed but the master switch is open, is in the direction opposite to the normal direction of shaft rotation and is insufficient to turn the shaft.

Numbered among the electric starting motors of the prior art are those having in addition to the series winding a shunt winding, which during the early part of the starting procedure in connected in series with the armature of the starting motor, whereas later it is connected in parallel with the armature. These known arrangements do not have a mechanical armature and pinion rotation device: the armature shaft is not free to turn with respect to the pinion, and the shunt winding is of such a size that the motor turns slowly backwards during the early part of the starting procedure. Simultaneous reverse rotation and advance of the pinion does facilitate meshing, but, when the starting motor is turned on, the pinion teeth strike the gear with substantial force, which is sufficient to damage both the teeth of the pinion and of the gear with powerful starting motors.

The invention, on the other hand, ensures reliable and gentle meshing with a starter having the so-called mechanical armature and pinion rotation device, without requiring a powerful electromagnet. If the pinion locks with the gear (edge-on-edge), the armature shaft is turned with only a small amount of additional force from the starting relay, since the armature shaft of the starting motor is already subject to a reverse torque. Consequently, the starting relay can be correspondingly small, and in every case the pinion is meshed reliably and gently.

The novel features which are considered as characteristic for the invention are set forth in particular in the appended claims. The invention itself, however, both as to its construction and its method of operation, together with additional objects and advantages thereof, will be best understood from the following description of specific embodiments when read in connection with the accompanying drawing.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 is a schematic diagram of a circuit of the invention; and

FIG. 2 is a side view, partly cut away, of the mechanical construction of the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT

With reference to FIG. 1, an electric starting motor 10, having an armature 11, a series exciter coil 12, and an auxiliary field winding 13, is connected by a master switch 15, operated by an electromagnetic starting relay 14, to a current source 16.

The motor 10 has an armature shaft 17, which mounts a sliding gear 18 with a so-called mechanical armature and pinion rotation device, shown in FIG. 2. The armature and pinion drive as is known, permits, under certain conditions, the armature shaft to turn with respect to the pinion. The sliding gear 18 has a sleeve 19, which is free to move axially along, but not to rotate with respect to the armature shaft 17. The circumferential surface of the sleeve 19 incorporates a coarse thread 20, which cooperates with a coupling member 21, the right-most face of which is provided with saw-tooth coupling teeth 22.

A bearing sleeve 24, which is fixed to the sleeve 19, mounts a pinion 23 free to turn and to move axially. The end of the pinion 23 facing the coupling member 21 has saw-tooth coupling teeth 25, which cooperate with the teeth 22 of the member 21 in a manner to be described.

A cup-shaped cover 26 is pulled over the sleeve 19, the left end of the cover holding a damping member 27. An annular disk 28 bears against the damping member 27. An annular shoulder 19' of the sleeve 19 holds the disk 28 in place. Arranged between the disk 28 and the coupling member 21 is a coil spring 29.

Another coil spring 30 is squeezed between the disk 28 and a sleeve 31, which loosely surrounds the coupling member 21 and is fixed to the rim of the teeth 25 of the pinion 23.

Slipped over one end of the sleeve 19 is a slidable sleeve 32, the right end of which abuts against the left and of the cover 26. A spring ring 33 cooperates with the annular shoulder 19' to prevent the sleeve 32 and the cover 26 from moving axially on the sleeve 19.

The slidable sleeve 32 is engaged by a starting, or engaging, lever 34, which is operated by the armature 35 of the starting relay 14. The starting lever 34 axially shifts the sliding gear 18 along the armature shaft 17 so that the pinion 23 meshes with the gear 36 of an internal combustion engine, not shown.

The core 37 of the starting relay 14 has a draw-in coil 38 and a holding coil 39. One end of the holding coil 39 is connected by a starting switch 40 to the current source 16, and the other end is connected to ground. One end of the draw-in coil 38 is connected to the dead terminal of the starting switch 40 and the other end is connected to the dead terminal of the master switch 15. The movable contacts of the master switch 15 and of an auxiliary switch 43 are mounted on the relay armature 35. The auxiliary switch 43 comprises a rest contact 41 and a make contact 42.

In its rest position the auxiliary switch 43 connects the armature 11 by way of the auxiliary field winding 13 to the dead contact of the starting switch 40, the live contact of which is directly connected to the current source 16. In this connection of the circuit, which, when the starting switch 40 is closed, corresponds to the pre-starting stage, the draw-in coil 12 of the motor, and this series connection is shunted across the auxiliary field winding 13. The windings 12 and 13, in this connection, are so energized that they have opposing magnetic fields.

When the relay armature 35 has been attracted all the way to the right, the master switch 15 is closed, and the movable contact of the auxiliary switch 43 contacts the make contact 42. In this connection of the circuit, which corresponds to the starting stage of the starter, the series exciter coil 12 is connected by way of a main switch 15 directly to the current source 16; and the auxiliary field winding is shunted across the armature 11 and connected to ground. The relay draw-in coil 38 is not energized, and the holding coil 39 is connected by the starting switch 40 in parallel with the starting motor 10 and to the current source 16.

The arrangement just described operates in the following manner.

When the starting switch 40 is closed, current flows by way of the rest contact 41 through the armature 11 and the auxiliary field winding 13. At the same time, current flows through the starting switch 40, the draw-in coil 38, the series exciter coil 12, and the armature 11 to ground. The dimensions and number of turns of the coils 12 and 15 are so chosen that, together with the field of armature 11, the resulting magnetic field tends to turn, but is too weak actually to turn, the armature shaft 17 in the direction opposite to its normal direction of rotation.

Current in the draw-in coil 38 energized the relay 14, so that the relay armature 35 is moved to the right. The arrangement is so designed that near the end of the draw-in movement of the armature, the make contact 42 is closed and the master switch 15 is closed.

The starting lever 34 transmits the draw-in movement of the relay armature to the slidable sleeve 32. The sliding gear 18 shifts towards the gear 36 of the internal combustion engine. If the teeth of the pinion 23 and the gear 36 are correctly positioned with respect to each other, the pinion and gear mesh. Once the two are in mesh, the make contact 42 and the master switch 15 are closed. The series exciter coil 12 and the auxiliary field winding 13, which latter now acts as a shunt winding, produce, together with the field of the armature 11, a torque that turns the armature shaft 17 in the normal direction of rotation of the electric starting motor 10. The torque is transmitted by the shaft 17, the sleeve 19, the coarse thread 20, the coupling member 21, and the coupling teeth 22 and 25 to the pinion 23 and the gear 36.

On the other hand, if the front face of the pinion teeth strikes the front face of the gear teeth (tooth-on-tooth), the sleeve 19 and the bearing sleeve 24 move, relative to the coupling member 21 and the pinion 23, nearer to the gear 36. The coarse thread 20 causes the coupling member 21 and the pinion 23 to turn; the pinion teeth move with respect to the gear teeth until the pinion 24 can mesh with the gear 36.

If the edge of a pinion tooth strikes and locks with the edge of a gear tooth (edge-on-edge), the pinion 23 can neither turn nor move axially toward the gear 36. In this event, the coil springs 29 and 30 compress, and the starting lever 34 moves the slidable sleeve 32, the cover 26, the sleeve 19, and the bearing sleeve 24 toward the gear 36, the pinion 23 remaining stationary. This forward movement comes to an end when the sleeve 19 strikes the pinion shaft 23'. The amount of forward movement is so limited that the draw-in stroke of the relay armature 35 is not sufficient to close the make contact 42 and the master switch 15.

Since the pinion 23 has locked with the gear 36 and is unable to move, the coarse thread 20 causes the sleeve 19 and the armature shaft 17 to turn in the direction opposite the normal direction of rotation. This turning is supported by the reverse direction torque exerted on the armature 11 as long as the starting switch 40 is closed and the master switch 15 is open, Consequently, the starting relay 14 virtually has only to supply the necessary axial force to compress the coil springs 29 and 30.

Since the relay 14 cannot close the master switch 15, the starting procedure must be repeated. After the relay 14 is deenergized, rotation of the armature shaft 17 and withdrawal of the pinion 23 changes the relative rotational positions between the pinion and gear 36, so that the pinion and gear can mesh when the starting switch 40 is again closed.

While turning over the internal combustion engine, the saw-tooth coupling teeth 22 and 25 provide a positive coupling between the sleeve 19 and the pinion 23. As soon as the internal combustion engine has started up, and the pinion 23 is turning faster than the armature shaft 17, the forces acting on the teeth 22 and 25 reverse direction, and these teeth release against the force of the spring 29 and break the coupling between the sleeve 19 and the pinion.

It will be understood that each of the elements described above, or two or more together, may also find a useful application in other types of circuits and construction differing from the types described above.

While the invention has been illustrated and described as embodied in a starting arrangement for internal combustion engines, it is not intended to be limited to the details shown, since various modifications and circuit changes may be made without departing in any way from the spirit of the present invention.

Without further analysis, the foregoing will so fully reveal the gist of the present invention that others can by applying current knowledge readily adapt it for various applications without omitting features that, from the standpoint of prior art, fairly constitute essential characteristics of the generic or specific aspects of this invention and, therefore such adaptations should and are intended to be comprehended within the meaning and range of equivalence of the following claims.