Patent Description:
Starter devices of this type are known for example from <CIT>, <CIT> or <CIT>. In these starter devices, a solenoid-operable lever mechanism is used in order to bring a pinion wheel of the starter device in an axial actuation movement out of a disengaged retracted position into engagement with a ring gear of an internal combustion engine. In particular when the pinion wheel does not immediately mesh with the ring gear, which can be the case for example in a so-called tooth-on-tooth position, the pinion wheel has to be again retracted by way of the lever mechanism in order to be able to undertake a further engagement attempt. Because of burrs and/or surface irregularities present on internal toothings of the starter devices caused by the production there is the risk that the starter device in such a tooth-on-tooth position jams and seizes up, as a result of which the pinion wheel cannot be retracted into the retracted position. To rectify these problems it has been usual in the past to remove the causal burrs and/or surface irregularities by means of a mechanical reworking such as for example grinding. However, this reworking involves additional costs which with a view to the production costs for a starter device are undesirable.

The patent <CIT> is one example, which discloses the preamble of independent claim <NUM>.

The object of the invention therefore lies in providing an improved or at least another embodiment of a starter device. In particular, an internal combustion engine having such a starter device is to be stated.

In the present invention, this object is solved in particular through the subjects of the independent claims. Advantageous embodiments are subject of the dependent claims and of the description.

The basic idea of the invention lies in constructively adapting the internal toothings of the starter device so that burrs and/or regions with surface irregularities present on the same cannot, during the course of the actuation movement and of the operation of the starter device, come into contact with the internal toothings so that a jamming is excluded.

To this end, a starter device for cranking an internal combustion engine is proposed, which is equipped with a driveshaft defining a longitudinal centre axis along its main extension, which in turn comprises an external toothing arranged in particular on an outer circumferential surface of the driveshaft. Practically, the driveshaft is configured round-cylindrically and/or driveable round about the longitudinal centre axis by way of an electric starter motor of the starter device. Furthermore, the starter device has a pinion shaft which practically defines a pinion shaft longitudinal centre axis along its main extension, which has a pot-like driveshaft receptacle, in which the driveshaft or at least a portion of the same is received. Practically, the pinion shaft and the starter shaft are oriented coaxially to one another and/or mounted on one another so as to be rotationally and longitudinally adjustable by way of a suitable sliding bearing, which makes possible in particular a mounting free of coaxiality errors, which favours a safe operation of the starter device. Furthermore, the starter device has a transmission device, which is equipped for transmitting a torque from the driveshaft to the pinion shaft. The transmission device comprises an internal toothing arranged in particular on an inner circumferential surface of the transmission device, which can be meshed, i.e. brought into engagement with the said external toothing of the driveshaft. Furthermore it is provided that the transmission device and the pinion shaft are longitudinally adjustable axially with respect to the longitudinal centre axis jointly within the scope of an actuation movement, with respect to the driveshaft, between an engaged position, in which the said internal toothing and the said external toothing positively engage into one another for the torque transmission, and a basic position axially spaced apart thereto, in which the internal toothing and the external toothing are disengaged.

In order to avoid a jamming of the starter device during the course of the actuation movement and in the engaged position, i.e. during the operation of the starter device, it is provided that the external toothing has teeth which comprise tip edges arranged in the region of a tooth tip of a tooth, which in the engaged position and in the actuation movement are spaced apart with respect to the teeth of the internal toothing and/or that the internal toothing has teeth which comprise tip edges arranged for example in the region of a tooth tip of a tooth, which tip edges are spaced apart in the engaged position and in the actuation movement with respect to the teeth of the external toothing. Because of this, the tip edges in the engaged position and in the actuation movement are thus contact-free with respect to the internal toothing or the external toothing. During tests it has been established that because of this a contact between burrs and/or surface irregularities of the external toothing which are usually present on the tip edges of the teeth of the external toothing that are usually present there as a consequence of the manufacturing process chosen for the external toothing of the driveshaft, with the internal toothing of the transmission device can be prevented or vice versa. In this way, a jamming of the toothings of the starter device can be prevented so that the actuation movement of transmission device and pinion shaft is smooth and reliably repeatable and the comfort in utilising the starter device is increased. Apart from this, the mechanical removal of the burrs and/or surface irregularities on the external toothing of the driveshaft that has been customary in the past can be omitted so that a cost advantage is additionally achieved.

According to the invention, the toothing profile of the external toothing or of the teeth of the external toothing is an involute profile and the toothing profile of the internal toothing or of the teeth of the internal toothing is a trapezoidal profile. In the invention, the term "involute profile" is to mean in particular a toothing profile in which a respective toothing comprises involute teeth or teeth that are configured involute at least in portions. In the invention, the term "trapezoidal profile" is to practically mean a toothing profile in which a respective toothing comprises teeth configured trapezoidal, i.e. such teeth which have a trapezoidal tooth cross-sectional profile. By way of these proposed different toothing profiles, any contact between burrs and/or surface irregularities present on the external toothing of the driveshaft and the internal toothing can be reliably prevented. An external toothing of the driveshaft with involute profile can be relatively cost-effectively produced for example by rolling. Furthermore, an internal toothing of the pinion shaft with trapezoidal profile, convex profile, spline profile or serration profile can be relatively cost-effectively produced for example by broaching. Because of this, a starter device that can be cost-effectively produced on the whole is stated, whose internal toothings cannot jam. According to an opposite solution, by way of which the same advantages can be achieved, it can be alternatively provided that the toothing profile of the external toothing or the teeth of the external toothing is realised by a trapezoidal profile, a convex profile, a spline profile or a serration profile and the toothing profile of the internal toothing or of the teeth of the internal toothing is realised by an involute profile.

Practically, tip lands of these teeth are configured flat or curved. Because of this, an involute tooth flank in the said engaged position and/or during the course of the actuation movement is always in contact with a flat or convex tooth flank. In the invention, a tooth flank curved in an involute manner is to practically mean a tooth flank that is realised in the manner of an involute. In the invention, a tooth flank configured flat is to practically mean such a tooth flank which defines a plane and lies within the said plane. Practically, a flat tooth flank differs from this plane merely within the scope of production-related tolerances. In the invention, a convexly curved tooth flank is to practically mean a tooth flank curved away from the tooth body. According to an opposite solution, by way of which the same advantages can be achieved, it can be alternatively provided that the tooth flanks of the external toothing are configured flat or convex and the tooth flanks of the internal toothing are configured so as to be convex. During further tests it has been established that by way of these specific flank pairings or the proposed flank configurations a contact between burrs and/or surface irregularities present on the external toothing of the driveshaft can be prevented.

It is practical when the tooth flanks are formed by tooth flank surfaces which extend between a said tip edge and a root surface or a root edge of a respective tooth. The entire tooth surface of a tooth can be composed of two opposite tooth flanks, a tip land connecting the same to one another and root surfaces. Because of this, the tooth flank surfaces are curved in an involute manner or configured flat or convexly curved, as a result of which the subject flank configuration is limited to the tooth flank surfaces of the teeth.

Furthermore, it can be practically provided that the said tooth flank surfaces form contact surfaces. By way of the contact surfaces, the teeth of the external toothing can be planned to be contactable or contacted with the teeth of the internal toothing for transmitting the torque. In other words, such tooth flank surfaces are to mean those surface regions of a tooth surface of a tooth of one of the said toothings which actually bring about the transmission of the torque between the toothings. Thus, the subject flank configuration is limited to the actually effective tooth flank surfaces or contact surfaces. This means in particular that the tooth flank surfaces or the contact surfaces can have an involute curvature, a flat configuration or a convex curvature.

Practically, the starter device comprises a pinion wheel that is non-rotatably arranged on the pinion shaft, which pinion wheel in the engaged position is in engagement with a ring gear of the internal combustion engine so that torque from the starter device to the internal combustion engine can be transmitted in order to crank the internal combustion engine. Further practically, the said transmission device, besides the internal toothing, also has a clutch device, by way of which the transmission device can be frictionally connected to the pinion shaft. For example, the clutch device can be realised in the form of a freewheel clutch.

According to a further basic idea of the invention, an internal combustion engine having a starter device equipped for cranking the internal combustion engine according to the preceding description and having a ring gear is provided, wherein the pinion shaft of the starter device is assigned a pinion wheel that is non-rotatable with respect to the pinion shaft, which pinion wheel is equipped in order to mesh with the ring gear in order to transmit torque from the starter device to the internal combustion engine. Because of this, an advantageous internal combustion engine having a smoothly-operating and reliably actuatable starter device is stated, as a result of which the comfort in utilising the internal combustion engine, in particular with a view to the reliability is increased.

In summary it remains to be noted: The present invention practically relates to a starter device for cranking an internal combustion engine with a driveshaft comprising an external toothing with a pinion shaft comprising a driveshaft receptacle, in which the driveshaft is slidably received, having a transmission device equipped for transmitting a torque from the driveshaft to the pinion shaft, which transmission device comprises an internal toothing, wherein the transmission device and the pinion shaft, in an actuation movement jointly engage into one another are adjustable between an engaged position, in which the internal toothing and the external toothing engage into one another, and a disengaged basic position. It is substantial for the invention that the external toothing and the internal toothing have different toothing profiles. The invention relates in particular to an internal combustion engine having such a starter device.

Further important features and advantages of the invention are obtained from the dependent claims, from the drawings and from the associated figure description by way of the drawings.

It is to be understood that the features mentioned above and still to be explained in the following cannot only be used in the respective combination stated but also in other combinations or by themselves without leaving the scope of the appended claims.

A preferred embodiment of the invention is shown in the drawings and explained in more detail in the following description, wherein same reference numbers relate to same or similar or functionally same components.

<FIG> show a preferred embodiment of a starter device marked in its entirety with the reference number <NUM> for cranking an internal combustion engine <NUM> which in <FIG> is merely symbolised by a ring gear <NUM> indicated in sections, which serves for transmitting a torque <NUM> provided by the starter device <NUM> into the internal combustion engine <NUM>.

According to <FIG>, the starter device <NUM> has a round-cylindrical driveshaft <NUM>, which in its main extension defines a longitudinal centre axis <NUM> and which can be driven by way of an electric starter motor <NUM> of the starter device <NUM> round about the longitudinal centre axis <NUM>. The driveshaft <NUM> is exemplarily embodied as solid round shaft and has a circumferential external toothing <NUM> arranged on a circumferential driveshaft lateral surface of the driveshaft <NUM> consisting of a multiplicity of teeth <NUM>. The external toothing <NUM> is embodied as helical toothing. The teeth <NUM> of the external toothing <NUM> comprise curved tip lands <NUM> defining a tip circle of the external toothing <NUM> and curved root surfaces <NUM> defining a root circle of the external toothing <NUM>. The teeth <NUM> of the external toothing <NUM> furthermore comprise, viewed in a circumferential direction about the longitudinal centre axis <NUM>, two opposite tooth flanks <NUM>, which, emanating from a tip land <NUM> of a respective tooth <NUM> extend as far as to a root surface <NUM> of a respective tooth <NUM>. The tip lands <NUM> and the tooth flanks <NUM> are each separated by a tip edge <NUM> that is substantially parallel with respect to the longitudinal centre axis <NUM>. The tip edges <NUM> can be formed by pointed edges, tip curves or tip chamfers. Further, the root surfaces <NUM> and the tooth flanks <NUM> are each separated by a root edge <NUM> which is substantially parallel with respect to the longitudinal centre axis <NUM>. The root edges <NUM> can be formed by root curves, root chamfers or undercuts.

Furthermore, the starter device <NUM> according to <FIG> has a round-cylindrical pinion shaft <NUM>, which in its main extension defines a pinion shaft longitudinal centre axis <NUM> and which comprises a pot-like driveshaft receptacle <NUM>, in which the driveshaft <NUM> is coaxially received. Here, the pinion shaft <NUM> is guided on the driveshaft <NUM> so as to be longitudinally adjustable with respect to the longitudinal centre axis <NUM> or the pinion shaft longitudinal centre axis <NUM>. In order to realise the said longitudinal adjustability or guidance it is exemplarily provided that the driveshaft <NUM> and the pinion shaft <NUM> have or form a suitable sliding bearing in the region of the driveshaft receptacle <NUM>, which sliding bearing in particular makes possible a mounting free of coaxiality defects, so that the driveshaft <NUM> does not angularly tilt relative to the pinion shaft <NUM> by an unsymmetrical force loading during the course of an adjusting movement <NUM> still to be explained in the following and/or during the operation of the starter device <NUM>. Furthermore, the starter device <NUM> has a transmission device <NUM> arranged on the pinion shaft <NUM>, which is equipped for transmitting the torque <NUM> from the driveshaft <NUM> to the pinion shaft <NUM>. The transmission device <NUM> for this purpose exemplarily comprises a friction clutch device <NUM> interacting with the pinion shaft <NUM> in a frictionally connected manner, by way of which the torque <NUM> can be transmitted from the transmission device <NUM>, in particular frictionally, to the pinion shaft <NUM>. The friction clutch device <NUM> can be realised for example as a freewheel device. The transmission device <NUM>, furthermore, comprises an internal toothing <NUM> formed of a multiplicity of teeth <NUM> arranged on an inner circumferential surface of the transmission device <NUM>, which internal toothing <NUM> can be brought into engagement with the said external toothing <NUM> of the driveshaft <NUM>. The teeth <NUM> of the internal toothing <NUM> comprise curved tip lands <NUM> defining a tip circle of the internal toothing <NUM> and curved root surfaces <NUM> defining a root circle of the internal toothing <NUM>. The teeth <NUM> of the internal toothing <NUM>, furthermore, comprise, viewed in a circumferential direction about the longitudinal centre axis <NUM>, two opposite tooth flanks <NUM> which, originating from a tip land <NUM> of a respective tooth <NUM> of the internal toothing <NUM> extend as far as to a root surface <NUM> of a respective tooth <NUM> of the internal toothing <NUM>. These tip lands <NUM> and these tooth flanks <NUM> are each separated by a tip edge <NUM> of the internal toothing <NUM> which, with respect to the longitudinal centre axis <NUM>, is substantially parallel. The tip edges <NUM> can be formed by pointed edges, tip curves or tip chamfers. Furthermore, these root surfaces <NUM> and these tooth flanks <NUM> are each separated by a root edge <NUM> of the internal toothing <NUM>, which with respect to the longitudinal centre axis <NUM> is substantially parallel. The root edges <NUM> can be formed by root curves, root chamfers or undercuts. Furthermore, the pinion shaft <NUM> of the starter device <NUM> is assigned a pinion wheel <NUM> at an axial end protruding over a housing of the starter device <NUM> facing away from the electric starter motor <NUM>, which pinion wheel <NUM> is non-rotatably fixed on the pinion shaft <NUM>. The pinion wheel <NUM> is equipped in order to mesh with the said ring gear <NUM> of the internal combustion engine <NUM> in order to transmit the torque <NUM> from the starter device <NUM> to the internal combustion engine <NUM>.

In order to move the starter device <NUM> out of a rest position into an operating position, in which torque <NUM> is transmitted from the starter device <NUM> to the internal combustion engine <NUM>, it is provided that the transmission device <NUM> and the pinion shaft <NUM> are axially adjustable jointly for example by way of an actuating device <NUM> formed from a lever <NUM> and an electromagnetic actuation device <NUM> during the course of an actuation movement <NUM>, which in <FIG> is indicated by a double arrow, with respect to the driveshaft <NUM> between an engaged position <NUM>, in which the internal toothing <NUM> meshes with the external toothing <NUM>, and a disengaged basic position spaced axially therefrom. In the engaged position <NUM>, the torque <NUM> provided on the driveshaft <NUM> by the electric starter motor <NUM> is transmitted from the driveshaft <NUM> by way of the transmission device <NUM> to the pinion shaft <NUM>, wherein the torque <NUM> by way of the pinion wheel <NUM> arranged on the pinion shaft <NUM> is transmitted to the ring gear <NUM> of the internal combustion engine <NUM>.

In order to prevent that the starter device <NUM> in the engaged position <NUM> and/or during the course of the actuation movement <NUM> jams because of burrs and/or surface irregularities that remain on the tip edges <NUM> of the driveshaft <NUM> due to the manufacture, as a result of which the transmission device <NUM> and the pinion shaft <NUM> cannot, in particular, be retracted into the basic position, it is exemplarily provided that the tip edges <NUM> of the teeth <NUM> of the external toothing <NUM> are configured so that these, in the engaged position <NUM> and in the adjusting movement <NUM>, are spaced apart and free of contact with respect to the teeth <NUM> of the internal toothing <NUM>, in particular with respect to the tooth flanks <NUM> of the teeth <NUM> of the internal toothing <NUM> or tooth flank surfaces <NUM> of the tooth flanks <NUM> of the teeth <NUM> of the internal toothing <NUM>. For this purpose, the external toothing <NUM> and the internal toothing <NUM> comprise in particular different toothing profiles <NUM>, <NUM>.

According to the invention, it is provided, furthermore, that as toothing profile <NUM> of the teeth <NUM> of the external toothing <NUM> an involute profile and as toothing profile <NUM> of the teeth <NUM> of the internal toothing <NUM> a trapezoidal profile is provided. Because of this, the external toothing <NUM> has curved in an involute manner tooth flanks <NUM>, while the tooth flanks <NUM> of the internal toothing <NUM> are flat and configured angular with respect to the tip land <NUM>. As a further example, which is not part of the invention, it is also conceivable that the toothing profile <NUM> of the internal toothing <NUM> is embodied as an involute profile and that the toothing profile <NUM> of the external toothing <NUM> is realised as trapezoidal profile. Because of this, an involute tooth flank <NUM> is always in contact with a tooth flank <NUM> configured flat in the said engaged position <NUM> and during the course of the actuation movement <NUM>. During tests it was established that by way of these flank configurations a contact between the tip edges <NUM> of the external toothing <NUM> and of the internal toothing <NUM>, for example the tooth flank <NUM> of the internal toothing <NUM>, can be prevented, as a result of which a jamming of the starter device <NUM> in the engaged position <NUM> and during the course of the actuation movement <NUM> on account of the existing burrs and/or surface irregularity is prevented. According to a further example, which is not part of the invention, a variant indicated by way of dotted lines in <FIG> it can be provided that the tooth flanks <NUM> of the external toothing <NUM> are curved in an involute manner and tooth flanks <NUM> of the internal toothing <NUM> are convexly curved, as a result of which the described advantages are likewise achievable. According to a further example, which is not part of the invention and which is not illustrated, which realises an opposite solution, it can be provided that the internal toothing <NUM> comprises teeth <NUM> with tip edges <NUM> which in the engaged position <NUM> and in the actuation movement <NUM> are spaced apart with respect to the teeth <NUM> of the external toothing <NUM>.

Claim 1:
A starter device (<NUM>) for cranking an internal combustion engine (<NUM>)
- having a driveshaft (<NUM>) defining along its main extension a longitudinal centre axis (<NUM>), which driveshaft (<NUM>) comprises an external toothing (<NUM>),
- having a pinion shaft (<NUM>) which comprises a pot-like driveshaft receptacle (<NUM>) in which the driveshaft (<NUM>) is received,
- having a transmission device (<NUM>) equipped for transmitting a torque (<NUM>) from the driveshaft (<NUM>) to the pinion shaft (<NUM>), which transmission device (<NUM>) comprises an internal toothing (<NUM>) which can be meshed with the external toothing (<NUM>),
- wherein the transmission device (<NUM>) and the pinion shaft (<NUM>), in an actuation movement (<NUM>) are jointly axially adjustable with respect to the longitudinal centre axis (<NUM>) between an engaged position (<NUM>), in which the internal toothing (<NUM>) and the external toothing (<NUM>) engage into one another for transmitting the torque (<NUM>), and a basic position axially spaced apart thereto, in which the internal toothing (<NUM>) and the external toothing (<NUM>) are disengaged,
- wherein the external toothing (<NUM>) comprises teeth (<NUM>) with tip edges (<NUM>), which in the engaged position (<NUM>) and in the actuation movement (<NUM>) are spaced apart with respect to the teeth (<NUM>) of the internal toothing (<NUM>), and/or
- wherein the internal toothing (<NUM>) comprises teeth (<NUM>) with tip edges (<NUM>), which in the engaged position (<NUM>) and in the actuation movement (<NUM>) are spaced apart with respect to the teeth (<NUM>) of the external toothing (<NUM>), wherein a toothing profile (<NUM>) of the teeth (<NUM>) of the internal toothing (<NUM>) is realised by a trapezoidal profile;
characterised in that
a toothing profile (<NUM>) of the teeth (<NUM>) of the external toothing (<NUM>) is realised by an involute profile.