GB2077858A

GB2077858A - A Radially Pinion-moving Starter Motor

Info

Publication number: GB2077858A
Application number: GB8117053A
Authority: GB
Original assignee: Lucas Industries Ltd
Current assignee: ZF International UK Ltd
Priority date: 1980-06-13
Filing date: 1981-06-03
Publication date: 1981-12-23

Abstract

The device includes an electric motor having a rotor shaft (12, Fig. 2 not shown) which drives a first pinion 15. A second pinion 17 meshes with the first pinion 15 and is rotatably mounted on an axle carried by an arm 14 which is capable of angular movement relative to the shaft (12), and on which is mounted one end of a resilient lever 22 having its other end 23 releasably engaged between adjacent teeth of the second pinion 17. In response to energisation of the electric motor, the lever 22 causes the first pinion 15 to move the second pinion 17 and the arm 14 angularly relative to the shaft (12) from an inoperative position to an operative position, so that the second pinion 17 meshes in driving engagement with the ring gear 25 of an engine while the end 23 of the lever 22 rides over the teeth of the second pinion 17. <IMAGE>

Description

SPECIFICATION A Starter Motor This invention relates to a starter motor for use in an internal combustion engine, the starter motor being of the kind including an electric motor which drives a rotor shaft, a first pinion carried by and driven with the rotor shaft, a second pinion in meshing engagement with the first pinion and mounted on an axle which extends parallel with, but is spaced from, the rotor shaft, and means for moving the second pinion and said axle relative to the rotor shaft from an inoperative position to an operative position, while said second pinion remains in meshing engagement with the first pinion. In use, the starter motor will normally be arranged so that, in its operative position, the second pinion is in driving engagement with the ring gear of an engine.

Starter motors of the kind specified have been known for over 60 years, but since their inception the means for moving the second pinion between its operative and inoperative positions has been relatively complex and expensive. Thus, for example, one of the earliest known starter motors of this kind is described in British Patent No.

135,695, in which the arrangement for moving the second pinion from its inoperative to its operative position includes an electromagnetic device and a friction disc movable by the electromagnetic device against the second pinion to resist rotation thereof. The arrangement is such that, when the starter motor is initially energised, the electro-magnetic device is operated to urge the friction disc against the second pinion so that the first pinion moves the second pinion angularly into its operative position. When the second pinion is fully in mesh with the engine ring gear, the electro-magnetic device is de-energised so that the second pinion can be rotated to start the engine.Alternative starter motors of the kind specified have also been proposed but to date all have required the complexity of an actuating electro-magnetic device and/or a separate overrunning device, such as a roller clutch, to prevent the motor being driven by the second pinion when the engine is started.

An object of the present invention is therefore to provide a simplified starter motor of the kind specified.

Accordingly, the invention resides in a starter motor of the kind specified, wherein the means for moving the second pinion from its operative position to its inoperative position includes a lever which is resiliently mounted on a member movable with the second pinion so as to be pivotable about one end thereof relative to said member, the other end of the lever being engaged between adjacent teeth of the second pinion.

In use, when the starter motor described above is energised, the lever resists rotation of the second pinion about its axle so that the second pinion is driven by the first pinion from its inoerative position to its operative position. In its inoperative position, the second pinion is normally in meshing engagement with the ring gear of an engine so that the load applied to the second pinion then increases and when the load exceeds the resilience of the mounting of the lever, the first pinion drives the second pinion to rotate the ring gear, with the lever riding over the gear crests of the second pinion. If the engine starts, so that the ring gear is being driven by the engine while the starter motor is still energised, the second gear is thrown out of mesh with the ring gear.

Conveniently, the lever is formed of resilient material and is fixed at said one end to said member.

Alternatively, said one end of the lever is pivotally mounted on said member and resilient means acts on the lever to resist pivotal movement thereof.

Preferably, the lever is pivotally mounted on an arm which is movable angularly about said drive shaft and which supports said axle.

In the accompanying drawings, which illustrate one example of the invention, Figures 1 and 2 are front and side views respectively of part of a starter motor of the kind specified when in use in an internal combustion engine.

Referring to the drawings, the starter motor includes a housing 11 which accommodates an electric motor (not shown) which drives a rotor shaft 12 which at one end projects from an end bracket 1 3 of the housing 11. The projecting end of the shaft 12 supports an arm 14, which is capable of angular movement relative to the shaft 12, and also supports a first pinion 1 5 which is fixed to the shaft so as to be driven by the electric motor. At one end, the arm 14 supports a stub axle 1 6 which at its free end carries a second pinion 1 7 which is in meshing engagement with the first pinion 15.

A helical tension spring 1 8 acts between the other end of the arm 14 and a post 19 on the end bracket 13 to urge the arm 14 and pinion 17 to a stable operative position in which said other end of the arm 14 engages a first stop 21. This is the position of the spring 18, arm 14 and pinion 17 indicated by the continuous lines in Figure 1.

Secured to the arm 14 is one end of a resilient lever 22 which at its opposite end includes a curved portion 23 which is engaged between a pair of adjacent teeth of the pinion 1 7. As will be described in detail below, the lever 22 serves to move the arm 14 and pinion 17 to an unstable operative position, in which the spring 1 8 is flexed and the arm 14 abuts against a second stop 24.

The angular spacing between the stops 21,24 is such that the arm 14 and pinion 17 move through 900 in the direction of arrow A in Figure 1 in moving from their inoperative position to their operative position. In the operative position, the spring 18, arm 14 and pinion 1 7 adopt the positions shown by the broken lines in Figure 1.

The operation of the starter motor of the above example in starting an internal combustion engine is as follows: When the starter motor is energised, the lever 22. resists rotational movement of the pinion 1 7 about its axle 22 so that the pinion 1 5 causes the arm 14 and pinion 17 to move angularly towards the operative position as defined by the stop 24.

The position of the stop 24 is such that, when the arm 14 abuts against the stop 24, the pinion 1 7 is fully in mesh with the ring gear 25 of the engine.

If, however, during movement of the arm 14 into its operative position, the pinion 17 meets the ring gear 25 in tooth-to-tooth abutment, then the resilience of the lever 22 permits relative driving motion to occur between the pinions 1 5, 17 so that the pinion 1 7 is able to adopt a seeking role to achieve full meshing engagement with the ring gear 25.

When the pinion 17 is fuily in mesh with the ring gear 25, the increased load applied to the pinion 1 7 overcomes the resilience of the spring 22 so that the pinion 1 5 then drives the ring gear 25, while the end portion 23 of the lever 22 rides over the gear crests of the pinion 17. If the engine then starts, the resultant rotation of the ring gear by the engine applies a disengaging force to the pinion 17 thereby causing the arm 14 to rotate back towards its inoperative position. The pinion 17 is thereby disengaged from the ring gear 25 so that the engine is prevented from driving the electric motor above its normal maximum operating speed.As soon as the pinion 17 is disengaged from the ring gear 25, the lever 22 again operates to urge the arm 14 back towards its operative position so that, if the switch controlling the starter motor remains closed, there will be transient and intermittent contact between the gear crests of the pinion 17 and ring gear 25.

Thus, if the engine falters, the pinion 17 automatically re-meshes with the ring gear 25 to continue the starting cycle. When the engine has started satisfactorily and the starter motor is deenergised, the spring 1 8 returns the arm 14 and pinion 1 7 to the inoperative position.

In order to reduce noise during the situation when the ring gear 25 is being rotated by the engine but the starter motor is still energised, it may be desirable to provide an arrangement for pivoting the arm 14 sufficiently from the ring gear to prevent it re-meshing with the ring gear until the ring gear is no longer driven by the engine.

Claims

1. A starter motor of the kind specified, wherein the means for moving the second pinion from its operative position to its inoperative position includes a lever which is resiliently mounted on a member movable with the second pinion so as to be pivotable about one end thereof relative to said member, the other end of the lever being engaged between adjacent teeth of the second pinion.

2. A starter motor as claimed in Claim 1, wherein the lever is formed of resilient material and is fixed at said one end to said member.

3. A starter motor as claimed in Claim 1, wherein said one end of the lever is pivotally mounted on said member and resilient means acts on the lever to resist pivotal movement thereof.

4. A starter motor as claimed in any preceding claim, wherein the lever is pivotally mounted on an arm which is movable angularly about said drive shaft and which supports said axle.

5. A starter motor as claimed in Claim 1, comprising the combination and arrangement of parts substantially as hereinbefore described with refernece to, and as shown in, the accompanying drawings.