EP0569951A2 - Starter device for internal combustion engines - Google Patents

Abstract

The invention relates to an electrical starter device for internal combustion engines, especially for smaller single-cylinder engines, a simple, cheap and high-revving electric motor being used as starter motor, the speed of which is reduced by a step-down gear in the form of an intermediate shaft, where for smoothing the torque peaks a torsionally elastic element is accommodated, which comprises a spiral power spring, the outer spring end of which establishes the power flux by frictional contact and the inner spring end of which establishes the power flux by positive interlock. An elastic element of this type protects the toothing involved in the transmission by thus limiting the peak torques. <IMAGE>

Description

The invention relates to a starting device for internal combustion engines according to the preamble of claim 1.

Single-stage thrust starters are the rule for car and truck engines; Motorcycle engines have this type of start only occasionally. There, electric motors are also connected via chain drives to the crankshaft of the engine to be started with the interposition of an overrunning clutch in order to save weight and space. Most of the time, however, the pinions and chain drives are single-stage reduction gears. The thrust drive usually includes a magnetic switch that brings the small pinion connected to the starter motor into mesh with the flywheel teeth before the motor is energized. Screw drives can also be designed without engagement systems, with the moment of inertia of the single-pinion, if the bearing is correctly designed in a steep thread on the driving shaft, initially engages axially when the speed increases rapidly and transmits torque only when the axial limit is reached.

All such systems use relatively large motors, the torque of which is designed so that the resistance generated by the compression can be overcome in any operating situation.

For the purpose of saving weight, the invention has set itself the task of making substantially smaller and thus high-speed electric motors from other fields of application suitable for the electric start of small internal combustion engines. Costs and installation space should be kept small.

The solution to the problem is described in the characterizing part of claim 1.

The solution according to the invention offers advantages in terms of cost and weight through the use of electric motors which are used in toys or in motor vehicles to actuate the various control movements. Such small motors are manufactured in large numbers and are characterized by a favorable power-to-weight ratio and small installation space. If they interact with the flywheel of the engine to be coupled via a drive spring according to the invention, they can be designed for a starting torque that is comparable to the starting torque of the engine, since the drive spring, as a spring accumulator, slowly overcomes the first compression stroke with the help of the time gained in tensioning the drive spring helps and then causes a rotation of the flywheel beyond the starting speed of the starter motor, which leads to reliable starting of the engine.

During the first revolution, the mainspring "smoothes" the non-uniformity of the rotary movements, especially in single-cylinder engines. Advantages can therefore also be seen in the design of the flywheel's flywheel mass, since during the first revolutions during the starting process the mainspring partially takes over the tasks of the flywheel. The first revolution of the internal combustion engine is distributed by the mainspring over a larger revolution range of the starter engine.

A single-track device without a freewheel and engagement device, that is to say a tooth engagement geared purely to angular acceleration, is immediately disengaged, ie disengaged, when the driven flywheel overtakes and the transmitted torque approaches zero. Becomes a rigid drive without used elastic member, there is already this danger after the first ignition, since the inertia of the armature mass of the electric motor cannot accelerate accordingly quickly.

The spiral-shaped mainspring only rests on the outside in the annular space of a gear wheel provided for it, while it is positively connected to the shaft on the inside. In its rest position, the spring creates a frictional engagement on its outer diameter due to its preload, the limit torque of which slightly exceeds the starting torque. In the event of blockages on the engine side, reverse ignition, or the like, the spring is first wound inwards around the shaft until the external frictional engagement is reduced and the elastic shaft connection slips.

Finally, the design with an intermediate shaft has the advantage that there is installation space coaxial with the flywheel for accommodating, for example, a manual starter device.

Fig. 1

eine Starteinrichtung mit Elektromotor, Zwischenwelle und Schwungrad des teilweise dargestellten Verbrennungsmotors;

Fig. 2

eine Triebfeder in einer spiralenförmig gewickelten Ausführung;

Fig. 3

die Triebfeder im Schnitt in ihrem Einbauzustand in einen Zahnrad.

The invention is explained below with reference to drawings of an embodiment. Show it

Fig. 1

a starting device with an electric motor, intermediate shaft and flywheel of the partially illustrated internal combustion engine;

Fig. 2

a mainspring in a spiral wound design;

Fig. 3

the mainspring in its installed state in a gear.

If 1 denotes a motor housing of the internal combustion engine to be started, then a crankshaft 2 is mounted in it, at the free end of which a flywheel 3 is arranged in a rotationally fixed manner. This flywheel 3 has a ring gear 4 on its outer circumference, which is preferably connected in one piece to the flywheel 3. In the toothing of this ring gear 4 engages the toothing 6 of a pinion 5, which by means of a Steep thread 7 is rotatably arranged on an intermediate shaft 8 and axially displaceable in a helical manner. An axial compression spring 5a has the task of only holding the pinion 5 in its rest position; this spring 5 does not interfere with the function of the engagement mechanism based on the rotating mass of the pinion 5. The intermediate shaft 8 is rotatably mounted in a bearing 10 in the housing and carries at the opposite end a bearing bush 19 which rotatably supports a gear 11 on the intermediate shaft 8. The end of the intermediate shaft 8 has a positive entrainment - here in the form of a double flat 8a - which is positively connected to an inner spring end 18a of the previously described mainspring 18 - here via a driver 17.

In the relaxed state, the spiral spring rests with the majority of its windings and finally with its outer spring end 18b in a cylindrical recess in a gearwheel 11 and thus creates a frictional connection for the next starting process. Finally, the toothed wheel 11 is in permanent engagement with its toothing 12 with the toothing 13 of a drive pinion 14, which is non-rotatably connected to a starter shaft 16 of an electric motor 15.

The rotary movements coupled by the drive spring 18 between the electric motor 15 and the flywheel 3 require damping in order not to allow vibrations to occur which both release the frictional engagement of the drive spring 18 in its outer bearing in the gearwheel 11 prematurely and initiate the premature disengagement process of the pinion 5 could. This damping consists here in a space-saving disk 21, which is arranged in a rotationally fixed manner on the intermediate shaft 8 on its double surface 8a and is pressed against the gearwheel 11 by the force of a spring 22 on the outer ring surface thereof.

In our exemplary embodiment, a manual starter device 23 in the form of a cable pull starter 24 is arranged coaxially to the flywheel 3 and acts directly on the flywheel 3 in a known manner.

It should also be pointed out the advantage of a starting device equipped with a torsionally elastic member 20: The toothing 6 of the pinion 5 tracks into the toothed ring 4 "softly", ie there are no hard impacts when the teeth meet, as is known from thrust starters is where there is sometimes damage to the end faces of the teeth. Rather, the torsionally elastic member 20 allows a brief delay in the engagement process when the tooth is touched until the subsequent tooth gap is found. It is therefore also possible to integrate toothings in flywheels which are designed as magnet wheels and therefore have to be made of electrically non-conductive aluminum material.

The basic mode of operation of the starting device according to the invention can also be summarized as follows:
Before starting, the pinion 5 with its toothing 6 is out of engagement with the ring gear 4 of the flywheel 3. All parts of FIG. 1 are initially stationary. The electric motor 15 is then connected to the power supply, which can be formed in particular by the battery of the vehicle. The rotor of the motor 15 starts rotating. The drive pinion 14 rotates with it. This drive pinion 14 drives this latter gear 11 at a lower speed in accordance with the number of teeth ratio between the number of teeth of the teeth 13 of the drive pinion 14 and the number of teeth of the teeth 12 of the gear 11. The gear 11 takes the intermediate shaft 8 in the direction of arrow 30 of FIG. 2 with the spiral drive spring 18 and the driver 17. The entraining effect is based on the one hand on the frictional engagement between the outer spring end 18b and the inner circumferential surface 11i of the gear 11 and on the other hand on the at least one positive engagement of the inner spring end 18a in the driver 17. By the engagement of the high-helix thread 7 of the intermediate shaft 8 and of the corresponding internal part thread 6a of the pinion 6 there is a tendency for the pinion 6 to be carried along by the intermediate shaft 8. However, this tendency now counteracts the moment of inertia of the pinion 5. The pinion 5 tries to escape the entrainment by the intermediate shaft 8 by screwing it to the right on the intermediate shaft 8 thanks to the corresponding pitch of the intermeshing steep toothings 7 and 6a, namely against the action of the helical compression spring 5a. With this screwing of the pinion 5 to the right, the toothing 6 of the pinion 5 comes into engagement with the ring gear 4 of the flywheel 3.

The engagement of the toothing 6 in the ring gear 4 can take place essentially without bumps. If the toothing 6 with the axially directed tooth ends abuts against the axially directed tooth ends of the ring gear 4, the right-hand movement of the pinion 5 is briefly interrupted until tooth gaps and teeth of the toothing 6 and the ring gear 4 are in a further displacement axially opposite to the right of the pinion 5 allowing manner. Then the pinion 5 can move further to the right and come into full engagement with sufficient axial overlap with the ring gear 4 of the flywheel 3. Only now can the flywheel 3 be set in rotation, namely from the rotor 15a of the motor 15 via the output shaft 16, the drive pinion 14, the toothed wheel 11, the drive spring 18, the intermediate shaft 8, the steep threads 7 and 6a and the pinion 6. At this stage of the starting process, the mainspring 18 is deformed against elastic resistance, so that its turns progressively become narrower around the driver 17 from the radially innermost turn to the radially outer turns. This deformation of the mainspring 18 begins when the crankshaft 2 experiences a resistance to rotation with respect to the associated cylinder, for example in the course of a compression stroke of a piston assigned to it. H. can only be taken against increasing resistance to rotation.

It can thus be seen that, during the starting process, the speed of the rotor 15a of the electric motor 15 can initially be increased considerably until the resistance to the crankshaft 2 rotating due to a compression stroke occurs. The acceleration of the rotor 15a can take place partially in the period until the pinion 6 has engaged in the ring gear 4. Subsequent acceleration is also conceivable until the flywheel 3 has reached an angular position in which resistance to further rotation occurs from the piston. Finally, a renewed acceleration is also conceivable in the initial phase of winding the drive spring 18 onto the driver 17. The rotor 15a and with it the gearwheel 11 and the parts connected to the gearwheel for common rotation receive increased speeds, whereby a kinetic energy is built up , which is composed of the kinetic energy of the individual rotating parts, for example the rotor 15a, the pinion 14 and the gear 11. The kinetic energy of these individual parts is determined by the respective speed of these parts and the respective moment of inertia of these parts. This kinetic energy is now available to overcome the rotational resistance applied to the crankshaft 2, which rests on the crankshaft 2 from the associated piston cylinder pair or several such piston cylinder pairs and must be overcome for starting.

When the mainspring 18 winds up around the driver 17 in the direction of arrow 30 in FIG. 2, the inner torsional moment of the mainspring 18 counteracting the further winding increases. This increasing torsional moment is available for torque transmission from the gear 11 on the intermediate shaft 8 and therefore also for further torque transmission to the crankshaft 2. If the inner torsional moment of the drive spring 18 becomes equal to the rotational resistance applied to the crankshaft 2, the crankshaft 2 can be taken against this rotational resistance, and the previously built-up kinetic energy is now available for this entrainment. Based on this kinetic energy, a torque which is possibly considerably greater than that of the engine 15 is available to overcome the rotational resistance on the crankshaft 2 could muster. Therefore, the crankshaft 2 is turned and the associated internal combustion engine can start after passing through the first or a further ignition point. A starting process is thus achieved, although the electric motor 15 is not or at least not sufficient under all operating conditions to overcome the rotational resistance occurring on the crankshaft 2.

It is particularly advantageous that the kinetic energy built up until the crankshaft 2 spins is not suddenly transmitted to the crankshaft, but rather via the elastically flexible drive spring 18.

By appropriate selection and dimensioning of the components involved in the starting process, it can be ensured that the drive pinion 14 can carry out a plurality of revolutions before the crankshaft 2 is set in rotation. In this way, even with a small dimensioning of these components, sufficient energy or, in other words, a sufficient angular momentum can be made available to crank the crankshaft 2 under all conceivable operating circumstances and thus to start the internal combustion engine.

It is also readily apparent that the choice of a spiral spring as the mainspring is only to be understood as an exemplary embodiment. In principle, other torsion springs between the gear 11 and the driver 17 are also conceivable.

A particular advantage of the spiral spring is, however, that it can be easily brought into frictional connection with the gear 11 by contacting the inner peripheral surface 11i of the gear 11. At this There is then an overload clutch available in the event of a blockage on the engine side, reverse ignition, and the like.

The above-described displacement of the pinion 5 in engagement with the ring gear 4 based solely on the moment of inertia of the pinion 5 likewise represents only a preferred exemplary embodiment. It is readily apparent that the pinion 5 also rotates with the intermediate shaft 8 as a result could inhibit the fact that one can engage a friction brake on the pinion 5 or a part firmly connected to the pinion 5 for common rotation, which alone or in support of the effect caused by the moment of inertia of the pinion 5 inhibit the entrainment of the pinion 5 by the intermediate shaft 8 and thus could initiate the axial displacement of the pinion 5 for engagement with the ring gear 4.

It can also be readily seen that the displacement of the pinion 5 into its engagement position with the ring gear 4 could also be externally controlled, for example by means of an electromagnet which, depending on the speed reached by the rotor 15 a, engages the toothing 6 with the ring gear 4 prompted. In such a case, the basic idea of the invention would nevertheless be realized that a small electric motor with low torque is used to overcome a larger starting torque on the crankshaft 2, by using the rotor of the motor and the gear elements connected downstream to this rotor until a predetermined kinetic structure is built up Allows energy to ramp up and then applies this kinetic energy to the crankshaft via a torsion spring for starting it.

• a) es wird ein Elektromotor verwendet, welcher auch unter Berücksichtigung einer etwaigen Untersetzung nicht oder nicht unter allen Umständen ausreicht, um ein an der Kurbelwelle auftretendes Anwerfmoment zu überwinden;
• b) der Elektromotor und etwaige ihm in starrer Drehwinkelbeziehung nachgeschaltete Getriebeteile werden in Drehung versetzt, bevor eine mitnahmewirksame Verbindung mit der Kurbelwelle hergestellt wird;
• c) die mitnahmewirksame Verbindung zwischen dem Elektromotor und der Kurbelwelle wird über ein torsionselastisches Zwischenglied hergestellt, und zwar erst dann, wenn die durch die erreichte Drehzahl des Elektromotors und der ihm ggf. in starrer Drehwinkelbeziehung nachgeschalteten Getriebeteile aufgebaute kinetische Energie ausreicht, um über das Zwischenglied das Anwerfmoment der Kurbelwelle zu überwinden.

The invention can accordingly also be presented in general form as a starting method for an internal combustion engine be with the characteristics

• a) an electric motor is used which, even taking into account any reduction, is insufficient or not sufficient under all circumstances to overcome a starting torque occurring on the crankshaft;
• b) the electric motor and any gear parts connected downstream of it in a rigid rotational angle relationship are set in rotation before an entrainment-effective connection is established with the crankshaft;
• c) the entrainment-effective connection between the electric motor and the crankshaft is established via a torsionally elastic intermediate member, and only when the kinetic energy built up by the rotational speed of the electric motor achieved and the gear parts possibly connected downstream in a rigid angle-of-rotation relationship is sufficient for the intermediate member to overcome the crankshaft starting torque.

Accordingly, the starting device and the connection of the starting device to an internal combustion engine should also be protected in general.

Claims (10)

Starting device for internal combustion engines, especially for smaller single-cylinder units, comprehensive * an electric motor as a starter motor * a reduction gear to reduce the starting speed * an intermediate shaft with a high helix thread * a pinion, the inside diameter of which has a high helix thread, which works together with the adjusting thread on the intermediate shaft a flywheel of the internal combustion engine to be started, which has a ring gear on the outside diameter in which the pinion of the intermediate shaft engages during the starting process, characterized in that a torsionally elastic member (20) is additionally arranged in the gear transmission between the electric motor (15) and the flywheel (3), which is created by the engagement of the pinion 5. Starting device according to claim 1, characterized in that the torsionally elastic member (20) consists of a drive spring (18) which is arranged as a spring accumulator between an intermediate shaft (8) and a gearwheel (11) mounted on it. Starting device according to claims 1 and 2, characterized in that the drive spring (18) for limiting the torque with an inner spring end (18a) in a form-fitting manner with the intermediate shaft (8) and with the outer spring end (18b) with the gearwheel (4) connected is. Starting device according to claims 1 to 3, characterized in that the design and coordination of the mainspring (18) permits a plurality of revolutions of the drive pinion (14) before the flywheel (3) begins to turn. Starting device according to claims 1 to 4, characterized in that during the starting process the toothing (6) of the pinion (5) is engaged in the ring gear (4) of the flywheel (3), has reliably assumed its working position, has come to a standstill there and Only after tensioning the mainspring (18) does the actual starting process begin by turning the flywheel (3). Starting device according to claims 1 to 5, characterized in that the drive spring (18) is associated with an attenuator, which generates forces which counter the rotational movement of the gear (11) on the intermediate shaft (8). Starting device according to claim 6, characterized in that the damping member consists of a disc (21) which is axially pressed by a spring (22) against the windings of the mainspring (18). Starting device according to claims 1 to 7, characterized in that the intermediate shaft (8) is so far away from the coaxial crankshaft (2) that a manual starting device (23) can be arranged in the carrier housing (9) coaxially with the crankshaft (2) . Starting device according to claims 1 to 8, characterized in that the electric motor (15), the intermediate shaft (8) with the elastic member (20) and the manual starting device (23) are arranged in the carrier housing (9). Method for starting an internal combustion engine, in particular a one-cylinder internal combustion engine, using an electric motor
characterized by the following measures: a) An electric motor (15) is used which, taking into account any reduction, is insufficient or not sufficient under all circumstances to overcome a cranking torque that occurs on the crankshaft; b) the electric motor (15) and any gear parts (14, 11) connected after it in a rigid rotational angle relationship are set in rotation before an entrainment-effective connection with the crankshaft (2) is established; c) the entrainment-effective connection between the electric motor (15) and the crankshaft (2) is established via a torsionally elastic intermediate member (18), and only when the speed reached by the electric motor (15) and the one possibly more rigid Kinetic energy built up after the rotational angle relationship of downstream gear parts (14, 11) is sufficient to overcome the starting torque of the crankshaft (2) via the intermediate member (18).

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