Starter for Internal Combustion Engines

The present invention relates to improvements made to electric starters for internal combustion engines.

It is known that outside the actual working periods of a starter of this kind its shaft is subjected to considerable vibration communicated to it by the engine with which it is associated.

In order to avoid the fracture of the shaft in question two methods are employed. The first consists in using a very rigid shaft of which the natural vibration frequency is outside the frequencies of the range of utilisation. The other solution provides for the shaft an intermediate bearing fastened to the yoke of the starter.

When a starter is constructed in accordance with the first solution, only radial vibrations of the shaft are limited by the stiffening of the shaft. With the second solution the amplitude of deformation of the shaft is limited to a greater extent, but the drive pinion assembly then behaves like an independent vibrating mass, so that there is premature wear of the grooves or splines of the shaft and drive pinion assembly.

The present invention seeks to obviate or reduce the above disadvantages in a simple way and at a minimum of extra cost. Indeed it has been found that starters of the present invention can be made more economically than some of the designs hitherto employed.

The present invention consists in providing a male conical surface on the drive pinion assembly of the starter and in locating intermediate of the ends of the motor shaft a member which is stationary, i.e. fixed in position in relation to the non-moving parts of the starter such as a housing or the yoke of the field magnet, there being a female conical surface on the said member into which fits the male conical surface on the drive pinion assembly when this is in its rest position.

The stationary member may be a plate-like member having a conical depression with an opening at the bottom of the depression through which the motor shaft passes. When the starter is energised and the drive pinion assembly moves into its active position, the conical surface on the drive pinion assembly moves out of contact with the plate-like member, and the motor shaft can rotate freely. The plate-like member may thus be termed a false bearing, as it holds the drive pinion assembly only when this is stationary.

The stationary member may be provided with locating means which cooperate with the yoke and a casing forming the nose portion of the starter to position the yoke correctly in relation to the nose portion. The locating means may comprise portions pressed out from the plate forming the said member. It is thus possible to make a flat joint between the elements in question so as to reduce considerably the cost of machining.

Where the design of starter utilises a solenoid with a shift lever between the solenoid and the drive pinion assembly, the stationary member may bear an abutment to act as fulcrum for the lever and may also hold a block which forms a seal between the yoke and the solenoid casing. A plate-like stationary member may have the external shape of the profile of the solenoid casing, so that the member will also be gripped between the said casing and the nose of the starter.

Further features which the starter of the invention may embody will be clear from the following description, given by way of example, of the forms of the invention illustrated in the accompanying drawings, in which:

FIG. 1 is an external view, partly broken away and partly in section, of an electric starter according to the invention;

FIG. 2 is an exploded view showing an alternative form of stationary member from that shown in FIG. 1 and also the parts between which it is gripped; and

FIG. 3 is a view of the stationary member in elevation.

The starter of FIG. 1 comprises an electric motor 1, a solenoid 2, and a drive pinion assembly 3 mounted for sliding on the motor shaft 4. In a manner known per se the drive pinion assembly 3 is movable from its rest position illustrated towards the left into its active position, that is to say in the direction of a bearing 5 mounted in a casing forming a nose portion 9, by means of a forked shift lever 6 of which one end is associated with the movable part 2a of the solenoid 2, while its opposite end embraces the drive pinion assembly 3. The lever 6 is spring-loaded into the position shown, but moves the drive pinion assembly 3 into its active position when the part 2a is attracted to the right on energisation of the solenoid.

The free end of the driver 7 of the drive pinion assembly 3 is frustoconical, an intermediate member 8 in the form of a plate being positioned at the junction between the yoke 1a of the motor and the nose portion 9 of the starter. This plate-like member 8 is provided with an opening 8a through which the shaft 4 passes and which is situated at the bottom of a conical depression constituting an abutment 8b for the driver 7 when the latter is at rest. The abutment 8b is so disposed that the drive pinion assembly 3 is situated as close as possible to the armature 1b of the motor 1, so as to provide for an adequate length of movement between the active and rest positions. The member 8 is rigidly fixed to the yoke 1a, and its depression or abutment 8b constitutes an intermediate false bearing for the shaft 4 which, outside periods of operation of the starter, is held radially at that point with the aid of the driver 7, but which freely rotates out of contact with the member 8 when the drive pinion assembly has moved to its active position. Because of the conical shape of the free end of the driver 7 and of the abutment 8b, and because of the action of the lever 6 holding these two parts abutting, it may be considered that the drive pinion assembly is fixed in relation to the yoke 1ain its rest position. The amplitudes of vibration of the shaft 4 are therefore limited to the play that may exist between the splines 4a, 7a of the shaft and the driver respectively.

The member 8 is provided with an extension or lug 8c which projects beyond the periphery of the yoke 1a to a point just below the solenoid 2. The front face of the lug 8c, that is to say the face which is towards the nose portion 9 of the starter, is provided with an abutment 10 against which the lever 6 is fulcrumed when the solenoid 2 is energised. The opposite face of the lug 8c carries a block 11 made of a relatively flexible material, which provides a cushioned seal between the yoke 1a and the casing of the solenoid 2. The driver 7 is preferably made from an extruded steel blank and provides, at the end remote from the abutment 8b, a cage 7b which houses the usual freewheel mechanism 12 through which is driven a pinion 12a freely mounted for rotation over the shaft 4. When the starter is fitted to an internal combustion engine and the drive pinion assembly 3 is moved into active position, the pinion 12a meshes with the flywheel of the engine. The freewheel mechanism ensures a positive drive of the pinion 12a until, on the starting of the internal combustion engine, the pinion starts to move at a greater rate than the rest of the drive pinion assembly, at which point the freewheel mechanism prevents the pinion 12a driving the rest of the assembly. The splines 7a in the driver can be formed during the extrusion, whether they are helicoidal or straight. They could alternatively be formed on the otherwise completed driver.

According to a modified embodiment of the invention shown in FIG. 2 the plate-like member 13 which provides the false bearing is gripped between the nose 9 on the one hand and the yoke 1a and the casing of the solenoid 2 on the other. In this embodiment the opposed faces of the above-mentioned elements are plane so as to reduce the cost of machining, the usual inter-engagement shown at the lower end of FIG. 1 being eliminated. The conical depression 13a of the member 13 corresponds to that of the member 8 of the previously mentioned embodiment. The member 13 is provided with an upwardly extending lug 13b (FIGS. 2 and 3), which has a shape corresponding to the outside shape of the casing 2b and to the facing portion 9a of the nose 9, so that this lug can be gripped between the mutually facing portions of these two elements. An opening 13c is provided in the lug 13b to permit the passage of the movable unit of the solenoid 2. The references 13f and 13g are given to the holes by which the connecting ties (not shown) pass respectively through the lug 13b and the main part of the member 13.

In order to enable the yoke to be centred in relation to the nose 9, locating means in the form of projections 13d and 13e, directed respectively towards the yoke and the nose, are provided in the member 13 around the depression 13a. These projections are preferably produced alternately by pressing portions out of the member 13. A series of projections 13d are thus obtained, which are directed towards the yoke 1a and which fit with functional clearance within the bore in the said yoke, while the series of projections 13e fit within the bore 9b formed in the nose 9.

It will readily be understood that the action of the connecting ties (not shown), which enable the corresponding faces of the yoke and nose to be held together, presses these parts against the plate-like member 13 with pressure such that sealing at this point is achieved by this action alone. Sealing can optionally be improved by providing the member 13 with a coating, for example of suitable plastics material.

Provision could also be made to form projections in the lug 13b of the member 13, in order to achieve centring of the casing 2b of the solenoid 2 in relation to the nose 9, but because of the construction of the starter this centring of the casing 2b is not necessary.

With the aid of the present invention a starter has thus been obtained whose shaft is held against whipping under the influence of vibrations.