EP3428444A1

EP3428444A1 - Starter motor for an internal combustion engine

Info

Publication number: EP3428444A1
Application number: EP17180489.1A
Authority: EP
Inventors: Jani MERKUN
Original assignee: Mahle International GmbH
Current assignee: Mahle International GmbH
Priority date: 2017-07-10
Filing date: 2017-07-10
Publication date: 2019-01-16

Abstract

The present invention relates to a starter (1) for an internal combustion engine, having a support housing (2) for mounting the starter (1) on the internal combustion engine, an electric motor (3) which is fixed on the support housing (2) and which has a motor shaft (4), a one way clutch (10) which has an inner ring (11), an outer ring (12) and a plurality of clamping bodies (13), a driveshaft (14) which has a pinion (15) and a toothed shaft portion (16), and an electromagnetic actuator (17) fixed on the support housing (2) for axial adjustment of the driveshaft (14) between an extended active position (AS), in which the pinion (15) is in engagement with a ring gear of the internal combustion engine, and a retracted passive position (PS), in which the pinion (15) is spaced apart from the ring gear, wherein the toothed shaft portion (16) is in engagement with a toothing (25) of the outer ring (12). A reduced mechanical loading of the actuator (17) arises by means of a limiting device (26) for limiting the extension of the driveshaft (14) to the active position (AS), wherein the limiting device (26) supports the driveshaft (14) directly or indirectly axially on the support housing (2) at least in the active position (AS) while avoiding the clamping bodies (13) and the outer ring (12).

Description

The present invention relates to a starter for an internal combustion engine with the features of the preamble of Claim 1.
A generic starter is known, for example, from WO 2013/117161 A1 . It comprises a support housing for mounting the starter on the internal combustion engine. There is furthermore provided an electric motor which is fixed on the support housing and which has a motor shaft. This is supplemented by a planetary transmission, which has a sun gear, a plurality of planetary gears, an internal gear and a planetary carrier. A one way clutch is furthermore provided which has an inner ring, an outer ring and a plurality of clamping bodies, in particular clamping rollers. A driveshaft of the starter has a pinion and a toothed shaft portion. This is normally supplemented by an electromagnetic actuator for axial adjustment of the driveshaft between an extended active position, in which the pinion is in engagement with a ring gear of the internal combustion engine for starting the internal combustion engine, and a retracted passive position, in which the pinion is spaced apart from the ring gear. The sun gear is connected in a rotationally conjoint manner to the motor shaft. The planetary carrier is connected in a rotationally conjoint manner to the inner ring. The toothed shaft portion is in engagement with a toothing of the outer ring. In the case of this design, substantially only the driveshaft is adjusted with the aid of the actuator, while in particular the one way clutch can remain axially stationary in the support housing. As a result of this, only comparatively small masses have to be moved by the actuator, as a result of which the actuator can be produced to be smaller and thus more lightweight and at lower cost.
Other starters, in the case of which further components, such as e.g. the one way clutch, must be adjusted with the aid of the actuator in addition to the driveshaft, are known, for example, from US 5,156,057 , WO 00/26533 A1 , US 5,317,933 and US 2015 0130309 A1 .
The present invention deals with the problem of indicating an improved embodiment, which is characterized in particular by reduced wear, for a starter of the type described above.
This problem is solved according to the invention by the subject matter of the independent claim. Advantageous embodiments are the subject matter of the dependent claims.
The invention is based on the general concept of equipping the starter with a limiting device which serves to limit the extension of the driveshaft to the active position. By limiting the extension of the driveshaft to the active position, the actuator and the drive coupling provided between actuator and driveshaft are relieved of this function. It is precisely in the end phase of the extension movement that the electromagnetic actuator reaches its greatest actuating force and thus also its highest actuating speed. The driveshaft accordingly retracts with the highest actuating speed into the active position. If this is limited in a conventional manner by a stop in the actuator, the relatively large mass, in comparison to the actuator, of the driveshaft which has to be stopped abruptly leads to a high mechanical loading of the actuator and the drive coupling between actuator and driveshaft. In contrast, the limiting device according to the invention cooperates with the driveshaft and limits, in particular like a stop, its extension movement to the active position, as a result of which a retroactive effect on the actuator can be avoided.
The invention furthermore proposes configuring the limiting device so that it supports the driveshaft directly or indirectly axially on the support housing at least in the active position while avoiding, i.e. by-passing, the clamping bodies or clamping rollers of the one way clutch. In other words, axial support of the driveshaft for braking the driveshaft when the active position is reached is performed without an axial loading of the clamping bodies. The clamping bodies are thus protected from increased wear. The limiting device can furthermore expediently be configured so that it supports the driveshaft directly or indirectly axially at least in the active position while furthermore avoiding or by-passing, respectively, the outer ring of the one way clutch on the support housing. This means that both the clamping bodies and the outer ring are decoupled from the forces which occur during any abrupt braking of the driveshaft and are thus relieved of load. As a result of this, the wear of the clamping bodies and of the outer ring can also be reduced.
According to one advantageous embodiment, the limiting device can have a positioning ring fitted axially fixedly on the driveshaft and an annular collar formed on the inner ring, on which annular collar the positioning ring is supported directly or indirectly axially at least in the active position. Since this positioning ring is necessarily located within the inner ring and preferably within the one way clutch, this solution has a very compact design. As a result of the direct or indirect support between positioning ring and annular collar, the introduction of force is carried out during braking of the extending driveshaft on the inner ring. The positioning ring is accordingly arranged on the driveshaft in such a manner that the toothed shaft portion is located axially between the positioning ring and the pinion.
One embodiment in which the positioning ring is supported axially directly on the annular collar in the active position is particularly advantageous. In other words, the positioning ring comes to bear axially directly on the annular collar in the active position.
In contrast, it can alternatively be provided that the limiting device furthermore has a return spring via which the positioning collar is axially supported on the annular collar. The arrangement of the return spring is carried out so that it is tensioned during extension of the driveshaft. The provision of such a return spring reduces the impact impulse of the driveshaft when the active position is reached.
According to a preferred embodiment, a transmission gear is provided for drive coupling the electric motor with the one way clutch, or in more details for drive coupling the motor shaft of the electric motor with the inner ring of the one way clutch. According to an advantageous embodiment a planetary transmission is provided, which has a sun gear, a plurality of planetary gears, an internal gear and a planetary carrier, wherein the sun gear is connected in a rotationally conjoint manner to the motor shaft, and wherein the planetary carrier is connected in a rotationally conjoint manner to the inner ring or forms the inner ring.
One embodiment is particularly advantageous in which the inner ring is formed by an integral portion of the planetary carrier. The production costs are reduced as a result of this integral design.
Another advantageous embodiment proposes axially supporting the planetary carrier on the internal gear or on an internal gear carrier, on which the internal gear is fixed, and mounting it rotatably thereon. This can be carried out, for example, via a bearing bushing. This measure supports a compact design.
The internal gear can thus expediently be fixed on the support housing. As a result of this, the internal gear is connected to the support housing in an axially fixed and rotationally conjoint manner. This can preferably be carried out with the aid of an internal gear carrier on which the internal gear is fixed and which itself is fixed on the support housing.
According to a particularly advantageous embodiment, the driveshaft can be supported by means of the limiting device in the active position via a force-transmission path on the support housing, which path leads from the driveshaft via the positioning ring, where applicable via the return spring, via the annular collar, via the inner ring, via the planetary carrier, where applicable via the bearing bushing, via the internal gear or the internal gear carrier up to the support housing. This force-transmission path bypasses the clamping bodies and the outer ring and as a result relieves the load on the one way clutch.
An alternative embodiment proposes equipping the limiting device with an annular disc which is arranged in an axially fixed manner on the driveshaft axially outside the one way clutch. As a result of this, the functionality of the limiting device, namely the braking of the driveshaft, is moved out of the interior of the one way clutch when the active position is reached. The limiting device can thus be embodied in a more space-saving manner and preferably accommodated in the support housing.
For example, the driveshaft can have a bearing portion which is arranged axially between the toothed shaft portion and the pinion and in which the driveshaft is mounted rotatably and axially displaceably on the support housing. A particularly reliable axial guidance for the driveshaft is produced as a result of this.
The annular disc of the limiting device can thus advantageously be arranged axially between the bearing portion and the toothed shaft portion axially fixedly on the driveshaft. As a result of this, the annular disc is located inside the support housing.
A different further development proposes mounting the driveshaft rotatably and axially displaceably with its bearing portion via an anti-friction bearing, like a ball and roller bearing, on the support housing. To this end, it can, for example, be provided that the bearing portion is mounted axially displaceably in a bearing inner ring of the anti-friction bearing, while the bearing inner ring is mounted rotatably on a bearing outer ring via anti-friction bodies, such as e.g. balls, rollers or cylinders. The bearing outer ring is mounted conventionally in an axially fixed manner and generally also rotationally conjointly on the support housing.
The annular disc can thus advantageously be supported directly or indirectly axially on the anti-friction bearing at least in the active position. In this manner, the anti-friction bearing can take on an additional function in that it absorbs the axial forces required for braking the driveshaft when the active position is reached.
The limiting device can expediently have a return spring via which the annular disc is supported axially on the anti-friction bearing and which is tensioned during extension of the driveshaft. In this manner, the impact impulse of the driveshaft when the active position is reached is reduced.
The return spring can preferably bear against the anti-friction bearing and against the annular disc in an axially pretensioned manner already in the passive position.
Further important features and advantages of the invention will become apparent from the subordinate claims, from the drawings and from the associated description of the figures on the basis of the drawings.
It will be obvious that the features mentioned above and the features still to be explained below can be used not only in the respectively indicated combination, but also in other combinations or on their own without departing from the scope of the present invention.
Preferred exemplary embodiments of the invention are represented in the drawings and are explained in greater detail in the following description, wherein identical reference numbers refer to identical or similar components or components which are functionally identical.
In the figures, in each case schematically,

Fig. 1: shows a view of a starter partially in longitudinal section,
Fig. 2: shows a sub-region of the starter in the longitudinal section in a passive position,
Fig. 3: shows the sub-region of the starter from Fig. 2 in an active position,
Fig. 4: shows a partially sectional view of the starter as in Fig. 1, but in the case of a different embodiment.

In accordance with Figs. 1 and 4, a starter 1 which serves to start an internal combustion engine, not shown here, comprises a support housing 2 with which the starter 1 can be mounted on the internal combustion engine. Starter 1 furthermore has an electric motor 3 which is fixed on support housing 2 and which has a motor shaft 4. A planetary transmission 5 is furthermore provided with which the rotational speed of motor shaft 4 can be reduced. Planetary transmission 5 has a sun gear 6, a plurality of planetary gears 7, an internal gear 8 and a planetary carrier 9. Starter 1 is furthermore equipped with a one way clutch 10 which is arranged inside support housing 2 and which has an inner ring 11, an outer ring 12 and a plurality of clamping bodies 13 which are preferably configured here as clamping rollers.
Starter 1 is furthermore equipped with a driveshaft 14 which has a pinion 15 and a toothed shaft portion 16. Moreover, starter 1 is equipped with an electromagnetic actuator 17 which is fixed on support housing 2 and which is coupled in terms of drive via a coupling device 18 to driveshaft 14. Actuator 17, which is preferably configured as a solenoid, serves the purpose of axial adjustment of driveshaft 14 between an extended active position AS, which is only indicated in Fig. 3 and in which pinion 15 is in engagement with a ring gear, not shown here, of the internal combustion engine, and a retracted passive position PS, which is shown in Figs. 1, 3 and 4 and in which pinion 15 is spaced apart from the ring gear. The axial direction, in which driveshaft 14 is adjustable, is defined by longitudinal central axis 19 of driveshaft 14 which here furthermore coincides with the axis of rotation of motor shaft 4 or of electric motor 3. The axial direction is indicated in the figures by a double arrow and designated by 20. In the present context, the terms "extended" and "retracted" relate to support housing 2, out of which driveshaft 14 extends in order to reach active position AS. In contrast, in passive position PS, driveshaft 14 is maximally retracted into support housing 2. In this case, pinion 15 remains outside support housing 2.
According to Figs. 1 and 4, sun gear 6 is connected in a rotationally conjoint manner to motor shaft 4. Sun gear 6 is in engagement with planetary gears 7. Planetary gears 7 are mounted rotatably on planetary carrier 9 via planetary support shafts 21. Planetary gears 7 are in engagement with internal gear 8. Internal gear 8 is supported in a suitable manner rotationally conjointly on support housing 2. This can in principle be carried out directly. However, in the case of the embodiments shown here, an internal gear carrier 22 is provided which is connected in an axially fixed and rotationally conjoint manner to support housing 2 and on which internal gear 8 is supported in a rotationally conjoint and axially fixed manner. In the case of the examples shown here, planetary carrier 9 is connected in a rotationally conjoint manner to inner ring 11. To be precise, planetary carrier 9 here itself forms inner ring 11. To this end, planetary carrier 9 possesses a sleeve body 23 which proceeds from a plate body 24 and extends concentrically into outer ring 16. Sleeve body 23 thus forms inner ring 11. Planetary support shafts 21 are fixed on plate body 24 so that plate body 24 has the support function for planetary gears 7. It is finally provided in the case of the embodiment shown here that inner ring 11 is formed by an integral portion of planetary carrier 9, namely by stated sleeve body 23.
Toothed shaft portion 16 is in engagement with a toothing 25 of outer ring 12. The teeth, not designated in greater detail, of toothed shaft portion 16 extend in a helix-like manner or spirally. Alternatively, a purely axial alignment of the teeth would in principle also be conceivable here.
Independently of the respective embodiment, it is furthermore provided in the case of starter 1 shown here that driveshaft 14 has a bearing portion 31 which is located on driveshaft 14 axially between toothed shaft portion 16 and pinion 15. In said bearing portion 31, driveshaft 14 is mounted rotatably and axially displaceably on support housing 2. For this purpose, support housing 2 is expediently equipped with an anti-friction bearing 32. Anti-friction bearing 32 possesses an inner bearing ring 33, a plurality of anti-friction bodies 34, which are configured here by way of example as balls, and an outer bearing ring 35. While outer bearing ring 35 is supported on support housing 2 and arranged in a stationary manner thereon, inner bearing ring 33 is mounted rotatably on outer bearing ring 35 via anti-friction bodies 34. Bearing portion 31 extends through inner bearing ring 33 and is supported radially on anti-friction bearing 32 via this. Bearing portion 31 is furthermore mounted axially displaceably on inner bearing ring 33.
Starter 1 presented here is furthermore equipped with a limiting device 26 with the aid of which the extension of driveshaft 14 can be limited to active position AS. Limiting device 26 is preferably designed so that it supports driveshaft 14 directly or indirectly axially on support housing 2 at least in active position AS while bypassing clamping bodies 13 and preferably also bypassing outer ring 12. A first embodiment of limiting device 26 is explained in greater detail below on the basis of Figs. 1 to 3 and a second embodiment of limiting device 26 is explained in greater detail on the basis of Fig. 4.
According to Figs. 1 to 3, limiting device 26 comprises, in the case of the first embodiment, a positioning ring 27 fitted in an axially fixed manner on driveshaft 14 and an annular collar 28 formed on inner ring 11. Positioning ring 27 can be supported directly or indirectly axially on said annular collar 28 at least in active position AS. In the case of the embodiment shown here, positioning ring 27 is supported directly on annular collar 28 exclusively in active position AS so that positioning ring 27 then bears directly against annular collar 28. In the case of a different embodiment, not shown here, limiting device 26 can furthermore have a return spring via which positioning ring 27 is supported axially, preferably permanently, on annular collar 28, wherein this return spring is tensioned during extension of driveshaft 14.
Positioning ring 27 is arranged within sleeve body 24 of planetary carrier 9 and is located on driveshaft 14 on a side of toothed shaft portion 16 facing away from pinion 15.
It is furthermore provided here that planetary carrier 9 is supported axially on internal gear 8 or on internal gear carrier 22 and is rotatably mounted thereon. This is achieved with the aid of a bearing bushing 29.
An axial gap 30 is normally formed axially between a front side of inner ring 11 and an internal annular step of outer ring 12 in order to avoid friction between inner ring 11 and outer ring 12. Limiting device 26 generates a force-transmission path via which driveshaft 14 is supported on support housing 2 in active position AS. This force-transmission path begins at positioning ring 27 and runs via annular collar 28, inner ring 11, bearing carrier 9, bearing bushing 29, internal gear carrier 22 up to support housing 2.
In the case of the second embodiment shown in Fig. 4, it is thus provided that limiting device 26 has an annular disc 36 which is arranged axially fixed on driveshaft 14 axially outside one way clutch 10. In the example shown, said annular disc 36 is located axially between bearing portion 31 and toothed shaft portion 16. In the example of Fig. 4, limiting device 26 is furthermore equipped with a return spring 37 which is supported axially on one hand on annular disc 36 and axially on the other hand on anti-friction bearing 32, in particular on inner bearing ring 33. Return spring 37 is arranged so that it is tensioned during extension of driveshaft 14. Return spring 37 can furthermore expediently be dimensioned so that it is also axially pretensioned in passive position PS and is correspondingly supported on anti-friction bearing 32 and on annular disc 36 under axial pretensioning.

Claims

Starter for an internal combustion engine,
- with a support housing (2) for mounting the starter (1) on the internal combustion engine,

- with an electric motor (3) which is fixed on the support housing (2) and which has a motor shaft (4),

- with a one way clutch (10) which has an inner ring (11), an outer ring (12) and a plurality of clamping bodies (13),

- with a driveshaft (14) which has a pinion (15) and a toothed shaft portion (16),

- with an electromagnetic actuator (17) fixed on the support housing (2) for axial adjustment of the driveshaft (14) between an extended active position (AS), in which the pinion (15) is in engagement with a ring gear of the internal combustion engine, and a retracted passive position (PS), in which the pinion (15) is spaced apart from the ring gear,

- wherein the toothed shaft portion (16) is in engagement with a toothing (25) of the outer ring (12),
characterized by a limiting device (26) for limiting the extension of the driveshaft (14) to the active position (AS), wherein the limiting device (26) supports the driveshaft (14) directly or indirectly axially on the support housing (2) at least in the active position (AS) while avoiding the clamping bodies (13) and the outer ring (12).
Starter according to Claim 1,
characterized in that
the limiting device (26) has a positioning ring (27) fitted axially fixedly on the driveshaft (14) and an annular collar (28) formed on the inner ring (11), on which annular collar (28) the positioning ring (27) is supported directly or indirectly axially at least in the active position (AS).
Starter according to Claim 2,
characterized in that
- the positioning ring (27) is supported directly on the annular collar (28) in the active position (AS), or

- the positioning ring (27) is supported axially on the annular collar (28) via a return spring.
Starter according to Claim 1,
characterized in that
the limiting device (26) has an annular disc (36) which is arranged in an axially fixed manner on the driveshaft (14) axially outside the one way clutch (10).
Starter according to any one of Claims 1 to 4,
characterized in that
- a planetary transmission (5) is provided, which has a sun gear (6), a plurality of planetary gears (7), an internal gear (8) and a planetary carrier (9),

- the sun gear (6) is connected in a rotationally conjoint manner to the motor shaft (4),

- the planetary carrier (9) is connected in a rotationally conjoint manner to the inner ring (11) or forms the inner ring (11).
Starter according to Claim 5,
characterized in that
the inner ring (11) is formed by an integral portion (23) of the planetary carrier (9).
Starter according to Claim 5 or 6,
characterized in that
the planetary carrier (9) is supported axially on the internal gear (8) or on an internal gear carrier (22) and is mounted rotatably thereon.
Starter according to Claim 7,
characterized in that
the planetary carrier (9) is supported axially and rotatably mounted on the internal gear (8) or on the internal gear carrier (22) via a bearing bushing (29).
Starter according to any one of Claims 5 to 8,
characterized in that
the internal gear (8) is fixed indirectly via an internal gear carrier (22) or directly on the support housing (2).
Starter according to any one of Claims 1 to 9,
characterized in that
the driveshaft (14) has a bearing portion (31) which is arranged axially between the toothed shaft portion (16) and the pinion (15) and in which the driveshaft (14) is mounted rotatably and axially displaceable on the support housing (2).
Starter according to Claims 3 and 10,
characterized in that
the annular disc (36) is arranged axially between the bearing portion (31) and the toothed shaft portion (16) axially fixedly on the driveshaft (14).
Starter according to Claim 10 or 11,
characterized in that
the driveshaft (14) is mounted rotatably and axially displaceable with its bearing portion (31) via an anti-friction bearing (32) on the support housing (2).
Starter according to Claims 3 and 12,
characterized in that
the annular disc (36) is supported axially on the anti-friction bearing (32) at least in the active position (AS).
Starter according to Claim 13 or according to Claims 3 and 12,
characterized in that
the limiting device (26) has a return spring (37) via which the annular disc (36) is supported axially on the anti-friction bearing (32) and which is put under tension when extending the driveshaft (14).
Starter according to Claim 14,
characterized in that
the return spring (37), in the passive position (PS), is axially pretensioned on one hand on the anti-friction bearing (32) and is supported on the other hand on the annular disc (36).