DE102020103482A1 - Internal combustion engine with manual engine start device - Google Patents

Abstract

An internal combustion engine is specified with a piston (10) which can be moved back and forth in a cylinder (11) and is coupled to a crankshaft (13) via a connecting rod (12) in such a way that the crankshaft (13) at a movement of the piston (10) can be driven in rotation, as well as with a manual torque device for temporarily applying a manual torque by an operator to the crankshaft (13) during a starting phase of the internal combustion engine, and with an auxiliary torque device for temporarily applying an additional one Support torque on the crankshaft (13) exclusively in a support phase, the support phase being part of the start phase. The support phase is defined in such a way that it at least partially covers a period in which the torque required to rotate the crankshaft (13) in the starting phase is greater than the average torque during a full revolution of the crankshaft (13). In particular, the support phase can be defined in such a way that it covers a period of time which ends immediately before the piston (10) reaches top dead center.

Description

The invention relates to an internal combustion engine with a manual engine starting device.

Internal combustion engines are widely known. In their basic version they have a piston that can be moved back and forth in a cylinder and is coupled to a crankshaft via a connecting rod in such a way that the crankshaft is driven to rotate when the piston moves. The movement of the piston is in turn caused by the ignition of a fuel-air mixture (for example an air-gasoline mixture). In particular, two-stroke and four-stroke engines or diesel engines are known in this way.

Larger internal combustion engines usually have an electric starter. For smaller motors, which are used in particular in smaller devices (for example lawn mowers, leaf blowers, chain saws, joggers or vibratory rammers), manual motor start devices are often provided for reasons of cost and weight. Such manual engine starting devices are known as manual starters, pull-wire starters or reversing starters.

An internal combustion engine is started by first rotating the engine's crankshaft, which causes a gas exchange in the engine in the combustion chamber enclosed by the cylinder and piston. In this way, the fuel-air mixture prepared in a carburetor, for example, can be sucked into the combustion chamber and compressed there. After the fuel-air mixture has ignited, the piston is driven forward to drive the crankshaft. The burned fuel-air mixture can then leave the combustion chamber as exhaust gas before fresh fuel-air mixture can flow in.

The compression of the fuel-air mixture requires that the piston is moved with increasing force in the direction of its so-called top dead center (the extreme position of the piston caused by the crankshaft, at which the volume of the combustion chamber formed by the piston and cylinder is minimal). This is laborious in the case of manually started internal combustion engines, since the operator has to apply an operating force during the starting process, with which the compression in the cylinder is achieved until the top dead center is overcome and the subsequent combustion begins.

The compression of the fuel-air mixture during the starting process therefore requires a high level of force, which increases to its maximum until the top dead center is reached. After the piston has passed top dead center, the burning fuel-air mixture expands and causes the crankshaft to rotate, provided that the combustion is successful. During the subsequent compression, the crankshaft has enough momentum due to its mass inertia to ensure the compression of the fuel-air mixture in the next cycle, so that the engine finally picks up speed and moves from the starting phase to its operating phase.

Accordingly, internal combustion engines with a manual engine starter require considerable force, for example when pulling the starter rope, in order to overcome the engine's own friction and to ensure compression of the fuel-air mixture in the cylinder of the internal combustion engine. This can be particularly uncomfortable for an operator if, for example, when the carburettor has run empty, the pull starter has to be operated very frequently and the starter rope pulled until the carburetor is flooded and the fuel-air mixture is combustible.

Starting can also be found to be particularly troublesome if it has to be carried out in confined spaces or in a stooped position.

The invention is based on the object of specifying an internal combustion engine with a manual engine starting device which can be handled easily and comfortably by the operator.

According to the invention, the object is specified by an internal combustion engine having the features of claim 1. Advantageous configurations can be found in the dependent claims. In addition, a method for manually starting an internal combustion engine is specified.

An internal combustion engine is specified with at least one piston that can be moved back and forth in a cylinder and is coupled to a crankshaft via a connecting rod such that the crankshaft can be driven in rotation when the piston moves, and with a manual torque device for the temporary application of a manual torque by an operator to the crankshaft during a starting phase of the locking element, and with an assisting torque device for temporarily applying an additional assisting torque to the crankshaft exclusively in an assisting phase, the assisting phase being part of the starting phase.

The internal combustion engine is thus constructed in a manner known per se, as described above, with regard to pistons, cylinders, connecting rods and crankshafts. The hand torque device can also be a device known from the prior art, for example a reversing starter or pull-wire starter or a starting crank or the like.

The assist torque device is thus provided in addition to the manual torque device and provides an additional assist torque. However, this support torque is not available during the entire start phase, but only temporarily during part of the start phase, in particular a part in which the torque support is helpful for the operator.

The start phase is understood to be the phase or the time segment that extends from the beginning of the operation of the manual torque device by the operator until the motor starts operating and automatically increases its speed.

The support is therefore provided exclusively during the support phase. Outside the support phase, there is no torque support during the start phase and therefore no support for manual force or manual torque.

The manual engine starting device according to the invention is thus formed from the combination of a manual torque device and an assist torque device.

The support phase can be defined in such a way that it at least partially covers a period in which the torque required to rotate the crankshaft in the starting phase is greater than the average torque during a full revolution of the crankshaft in the starting phase.

As already explained above, in order to rotate the crankshaft, it is not only necessary to overcome the engine's own friction, in particular due to the movement of the crankshaft, the connecting rod and the piston. In addition, the compression of the fuel-air mixture must also be effected before the piston reaches top dead center. This means that the torque varies greatly during a full rotation (360 ° rotation) of the crankshaft. It makes sense that the support by the torque support device is only provided in the time segment (support phase) or angle of rotation range of the crankshaft in which the torque required to rotate the crankshaft is above average.

The support phase can be defined in such a way that it covers a partial angle range during a full revolution of the crankshaft, the partial angle range being less than 180 °. This ensures that the support phase only begins at a point in time after the piston has reached bottom dead center (the extreme position of the piston caused by the crankshaft, at which the volume of the combustion chamber formed by the piston and cylinder is maximum).

The support phase can be defined in such a way that it covers a period of time which ends immediately before the piston reaches top dead center, this point in time being defined as the end time of the support phase immediately before top dead center is reached. The top dead center is known to be the point in time at which the piston has reached its topmost position in the cylinder. In this case, the volume of the combustion chamber in the cylinder is minimized and the compression of the fuel-air mixture is maximum. After passing the top dead center, the piston moves “down” again due to the interaction of the connecting rod and crankshaft and the volume of the combustion chamber increases.

Since the torque required to rotate the crankshaft - as explained above - is greatest before top dead center is reached, the torque assistance by the assisting torque device can be particularly effective in this assisting phase. After passing through top dead center, support is no longer required, so that top dead center or a point in time immediately before reaching top dead center can be defined as the end point in time of the support phase.

The support phase can be defined in such a way that it covers a period of time that begins at a start time and ends at the end time specified above, whereby the start time can be a predefined angle of rotation of the crankshaft before the end time and the angle of rotation can be selected from the Range 10 ° to 70 °. In order to provide good support through the support torque, an angle range between 30 ° and 60 °, for example around 45 °, has proven itself.

The points in time should be selected in such a way that the torque support takes place from a certain point of compression of the fuel-air mixture and lasts up to top dead center (or shortly before), when the greatest support is required.

If the internal combustion engine has a plurality of cylinders and, accordingly, also a plurality of pistons that drive the crankshaft, the auxiliary torque device can each have corresponding components that make it possible to work at the top dead center of a respective piston (or shortly before) to apply an additional assist torque to the crankshaft. The components of the assisting torque device can accordingly be appropriately arranged at an angular offset in order to provide the assisting torque at the correct point in time when the crankshaft is rotated.

In one embodiment, the assist torque device can be arranged on a pole wheel of the internal combustion engine. Since the pole wheel is also coupled to the crankshaft or carried by the crankshaft, a transmission of the assist torque to the crankshaft is also possible in this variant.

The manual torque device can have a drive shaft which can be operated manually and which can be temporarily coupled to the crankshaft via a coupling device. Thus, it can in particular be a pull-wire or reversing starter in which a pull rope is wound onto a rope drum with a finger grip as a termination. The cable drum is provided on a freewheeling hub or centrifugal clutch and is usually arranged on an end of the crankshaft opposite the power take-off side of the engine.

To start the engine, the rope is pulled out vigorously using the finger grip. The cable drum or winding spool rotating as a result then acts on the crankshaft via the freewheel or a centrifugal clutch and transmits the manual torque to the crankshaft in order to set it rotating. The rope is then automatically rewound onto the rope drum with the help of a spiral spring. The process can then start again, so that the operator can pull the rope on the finger grip again.

The auxiliary torque device can have: a rotor device coupled to the crankshaft with at least one rotor pole, a stator device assigned to the rotor device with at least one stator pole, a control device for controlling an electromagnetic excitation of the stator pole and an energy store for storing and providing electrical energy for the electromagnetic Excitation of the stator pole.

The rotor device can be permanently or temporarily coupled to the crankshaft. In cooperation with the stator device, it generates the assist torque when the stator device is controlled accordingly by the control device. The rotor device can, for example, be realized in one piece with the crankshaft and thus form a fixed component of the crankshaft. The rotor device can also be attached to the crankshaft as a separate component.

The rotor or the rotor poles can have ferromagnetic and / or permanent magnetic elements which interact with the field coils of the stator poles.

In one embodiment, for example, two opposing rotor poles can be arranged on the crankshaft, to which two opposing stator poles are assigned on the stator side.

The stator poles can be designed, for example, as electromagnetic coils or field coils through which current flows when they are controlled accordingly by the control device. Thus, the stator constitutes an electromagnet device.

The control device can be designed very simply, since it only has to switch the excitation of the stator poles on and off at certain times. These points in time are in particular the start and end of support and can depend, for example, on the position of the crankshaft, as explained above.

The control device can be designed to activate an excitation of the stator pole at the start time of the support phase and to switch off the excitation of the stator pole at the end time of the support phase. Switching off is not only useful to minimize the consumption of electrical energy. Rather, it can also be prevented in this way that the interaction between the rotor and stator causes a generator operation, which would require the operator to overcome an additional load.

An energy generation device can be provided for generating electrical energy during an operating phase of the internal combustion engine, the energy store being chargeable by the electrical energy during the operating phase. The energy generation device can in particular be implemented by operating an ignition system in the internal combustion engine as a generator. It is also possible to operate the auxiliary torque device as a generator (see also the note above), so that the operator also charges the energy storage device, for example in the angle of rotation range in which the crankshaft requires only a small amount of torque to turn.

A conventional rechargeable battery (for example nickel cadmium or lithium) or a double-layer capacitor, for example, is suitable as an energy storage device.

• - Betätigen einer Hand-Drehmomentvorrichtung mit der Hand eines Bedieners und damit Aufbringen eines Hand-Drehmoments auf eine Kurbelwelle des Verbrennungsmotors;
• - Automatisches Aufbringen eines Unterstützungs-Drehmoments mithilfe einer eine Elektromagnet-Vorrichtung aufweisenden Unterstützungs-Drehmomentvorrichtung in einer Unterstützungsphase, bevor ein Kolben des Verbrennungsmotors den Oberen Totpunkt erreicht hat; und
• - Abschalten des Unterstützungs-Drehmoments nach Beenden der Unterstützungsphase.

Finally, a method for manually starting an internal combustion engine is specified, with the following steps:

• Operating a manual torque device with the hand of an operator and thus applying a manual torque to a crankshaft of the internal combustion engine;
• - Automatic application of an assist torque with the aid of an assist torque device having an electromagnet device in an assist phase before a piston of the internal combustion engine has reached top dead center; and
• - Switching off the support torque after the end of the support phase.

The technical system described does not represent an independent engine starter, but rather reduces its function to an electromagnetically assisted aid in compressing the fuel-air mixture in the cylinder of an internal combustion engine. The pull starter used on the engine, for example, is retained. The engine can thus be started conventionally at any time.

The assist torque device is suitable for taking over all or part of the force that the operator has to apply when starting the engine. The compression of the fuel-air mixture can thus take place “powerless” without any strain or involvement on the part of the operator. In particular, the system can be designed in such a way that the increase in the torque on the crankshaft required to compress the fuel-air mixture is not perceived by the operator. The operator then perceives the actuation of the pull-rope starter as uniform, with an essentially constant torque (manual torque).

In the event of a discharged energy store or a defect in the assist torque device, the internal combustion engine can still be started conventionally in a known manner. This guarantees a high level of availability.

• 1 einen Schnitt durch einen beispielhaften Verbrennungsmotor mit einer erfindungsgemäßen Unterstützungs-Drehmomentvorrichtung;
• 2 einen schematischen Schnitt durch eine erfindungsgemäße Unterstützungs-Drehmomentvorrichtung zu Beginn der Verdichtung in einem Verbrennungsmotor;
• 3 die Unterstützungs-Drehmomentvorrichtung zu einem Zeitpunkt des Beginns einer Unterstützungsphase; und
• 4 die Unterstützungs-Drehmomentvorrichtung zu einem Zeitpunkt des Endes der Unterstützungsphase.

These and further advantages and features of the invention are explained in more detail below using an example with the aid of the accompanying figures. Show it:

• 1 a section through an exemplary internal combustion engine with an assist torque device according to the invention;
• 2 a schematic section through an assist torque device according to the invention at the beginning of compression in an internal combustion engine;
• 3 the assist torque device at a point in time of starting an assist phase; and
• 4th the assist torque device at a point in time of the end of the assist phase.

1 shows an internal combustion engine with a structure known per se, namely with a piston 10 that is in a cylinder 11 is movable back and forth and via a connecting rod 12th with a crankshaft 13th is coupled, the crankshaft 13th when the piston moves 10 is drivable in rotation and the linear back and forth movement of the piston 10 into a rotary motion of the crankshaft 13th transforms.

At the in 1 The illustration shown is the piston 10 in the so-called top dead center, ie in an extreme position at the one between the top of the piston 10 and the piston 10 enclosing cylinder 11 trained combustion chamber 14th is minimal. In 1 the piston stands 10 thus at its highest point.

The internal combustion engine can work according to a known principle and can be implemented as a two-stroke, four-stroke or diesel engine, for example. The in 1 The example shown is the internal combustion engine with only one cylinder 11 (and therefore only one piston 10 ) shown. The internal combustion engine can, however, also have several cylinders and be constructed, for example, as a two-cylinder, three-cylinder, four-cylinder engine or the like. These motors are widely known in the prior art, so that no further explanation is required at this point.

As already explained above, according to the invention, in the internal combustion engine, to assist an operator during the starting process, an assist torque device is to be provided, with the aid of which an assist torque is temporarily applied to the crankshaft 13th can be applied, so that an operator operating a manual starter (manual starter, for example pull-wire or reversing starter), not shown in the figures, is supported. The support should in particular take place at a point in time at which a particularly large force is required to actuate the starter. This is intended to increase the convenience for the operator.

This is done axially on the crankshaft 13th a rotor 1 arranged, whose respective rotational positions relevant to the following description in principle in the section of 2 until 4th are recognizable. the 2 until 4th accordingly show the operating principle of the assist torque device, whereby - as already the difference to 1 shows - in the specific design of the torque support device, design deviations can be useful.

The rotor 1 has two rotor poles in the example shown 2 which are attached opposite each other and can consist, for example, of a ferromagnetic or permanent magnetic material. Depending on the embodiment, a different number of rotor poles can also be used 2 (e.g. 3, 4 or more) or just one rotor pole 2 be realized.

The rotor 1 can be placed directly on the crankshaft 13th be formed in one piece, as in 1 shown. But it is also possible to use the rotor 1 or at least the rotor poles 2 at a suitable point on the circumference of the crankshaft 13th to assemble.

The rotor 1 is - also in the appropriate place - from a stator 3 surrounded, the two stator poles in the example shown 4th having. The stator 3 can the rotor 1 surrounded in a ring, as in the 2 until 4th shown. The stator 3 can the rotor 1 but also only enclose them in brackets, as in the example of 1 shown. In the latter case, the stator poles are also not with respect to the axis of rotation of the rotor 1 arranged opposite one another (rotation by 180 degrees), but merely rotated angularly by an angle of, for example, approx. 145 degrees.

The stator poles 4th are in the in 1 The example shown is shown as poles of an electromagnet that has a field coil 5 having. In the example of the 2 until 4th Two electric motors can also be formed, each from a field coil 5 are enclosed. The current windings of the field coils 5 can be traversed by an electric current if necessary. The power supply is controlled by a control device (not shown).

The direction of rotation of the crankshaft 13th and with it the rotor 1 is in the 2 until 4th by an arrow in the rotor 1 shown.

The working principle of a two-stroke engine serving as an internal combustion engine consists of several phases, namely in particular flushing (filling the combustion chamber with the fuel-air mixture) - compression - ignition - working - exhausting (leading the combustion products out of the combustion chamber). Similar phases or cycles apply to a four-stroke engine, but they are widely known and therefore do not need to be discussed in more detail at this point.

The compression phase is of particular interest for the assist torque device explained here. At the time when compression begins, the crankshaft is located 13th in a position that the in 2 shown position of the rotor 1 is equivalent to. The piston 10 is accordingly still some distance below its top dead center.

With further rotation of the crankshaft 13th and thus the rotor 1 the fuel-air mixture in the combustion chamber ( 14th ) of the cylinder ( 11 ) increasingly compressed. This effect can be perceived as uncomfortable or even annoying by an operator when the internal combustion engine is started by hand, since the operator has to apply a correspondingly large amount of manual force in order to effect the compression.

3 shows a position in which the rotor 1 compared to the position of 2 was rotated further clockwise by approx. 60 °. Accordingly, it builds up in the combustion chamber 14th a pressure that is getting stronger. The operator operating the pull starter notices this from the fact that the force to be applied by him with the movement of the crankshaft 13th increases significantly.

3 but also shows that the rotor 1 with its rotor poles 2 now in the vicinity of the stator poles 4th got.

The control device is designed in such a way that, in the case of the in 3 position shown schematically the energization of the field coils 5 the stator poles 4th turns on. The stator poles unfold accordingly 4th a strong electromagnetic force acting on the respectively assigned rotor poles 2 acts and the rotor poles 2 attracts. This force effect results in a torque which is also referred to as the assist torque and serves to assist the manual torque applied by the operator with the aid of the rope starter.

3 shows a position of the rotor 1 before the ignition point and before the top dead center.

4th (as well as 1 ) shows a position in which the piston 10 has reached top dead center. The crankshaft was designed accordingly 13th with the rotor 1 compared to the position of 3 turned by approx. 30 ° further clockwise. The ignition is just before top dead center is reached and therefore just before the in 4th position shown takes place. Due to the ignition effect, the combustion of the fuel-air mixture is initiated, which leads to a strong expansion of the combustion gases and the piston 10 automatically drives from top dead center downwards in the direction of bottom dead center.

In this phase, support of the torque by the support torque device is no longer required, so that the control device provides the electrical supply to the field coils 5 turns off. Thus the field coils 5 switched off when the end of compression is reached, which means that there is no change from motor to generator operation.

The commutation of the field coils 5 is simple: They are supplied from an energy storage device (not shown), for example a rechargeable battery or a capacitor, and are switched on and off again when required.

The one in the 2 until 4th The sequence explained can be repeated several times until the engine has finally started, so that the start phase is ended and the actual operating phase follows. The system can then switch itself off. The disconnection can take place in particular with the aid of the control device, which then ensures that the field coils 5 stay de-energized.

The energy storage device that supplies the electrical current required to supply the field coils 5 or stator poles 4th can be supplied, for example, via an ignition system in the internal combustion engine. The starting system described can also generate electrical energy during regular operation of the motor (generator operation of the assist torque device) in order to charge the energy store.

The system described makes it possible to increase the comfort for the operator considerably, because he no longer has to overcome force peaks. The additional components and additional costs required for this are low. Even if the auxiliary starter (assist torque device) fails, the internal combustion engine can still be started in the conventional manner with the aid of the pull-wire starter.

Claims (10)

Internal combustion engine, with - At least one piston (10) which can be moved back and forth in a cylinder (11) and is coupled to a crankshaft (13) via a connecting rod (12) in such a way that the crankshaft (13) when the piston ( 13) can be driven in rotation; - A manual torque device for temporarily applying a manual torque by an operator to the crankshaft (13) during a starting phase of the internal combustion engine; and with - A support torque device for temporarily applying an additional support torque to the crankshaft (13) exclusively in a support phase, the support phase being part of the start phase. Internal combustion engine after Claim 1 , wherein the support phase is defined such that it at least partially covers a period in which the torque required to rotate the crankshaft (13) in the starting phase is greater than the average torque during a full revolution of the crankshaft (13). Internal combustion engine according to one of the preceding claims, wherein - The support phase is defined in such a way that it covers a partial angle range during a full revolution of the crankshaft (13); and where - the partial angle range is less than 180 degrees. Internal combustion engine according to one of the preceding claims, wherein - The support phase is defined in such a way that it covers a period of time which ends immediately before the piston (10) reaches top dead center; and where - this point in time immediately before reaching top dead center is defined as the end point in time of the support phase. Internal combustion engine according to one of the preceding claims, wherein the support phase is defined in such a way that it covers a period of time which begins at a starting point in time and ends at the end point in time; - the start time is a predefined angle of rotation of the crankshaft (13) before the end time; and where - the angle of rotation is selected from the range 10 degrees to 70 degrees. Internal combustion engine according to one of the preceding claims, wherein the manual torque device has a drive shaft which can be operated manually and which can be temporarily coupled to the crankshaft (13) via a coupling device. An internal combustion engine according to any preceding claim, wherein the assist torque device comprises: - A rotor device (1) which is coupled to the crankshaft (13) and has at least one rotor pole (2); - A stator device (3) assigned to the rotor device (1) and having at least one stator pole (4); - A control device for controlling an electromagnetic excitation of the stator pole (4); and - An energy store for storing and providing electrical energy for the electromagnetic excitation of the stator pole (4). Internal combustion engine after Claim 7 , wherein the control device is designed to activate an excitation of the stator pole (4) at the start of the support phase and to switch off the excitation of the stator pole (4) at the end of the support phase. Internal combustion engine according to one of the preceding claims, wherein - An energy generation device is provided for generating electrical energy during an operating phase of the internal combustion engine; and where - The energy store can be charged by the electrical energy during the operating phase. Method for manually starting an internal combustion engine, with the steps - Operating a manual torque device with the hand of an operator and thus applying a manual torque to a crankshaft (13) of the internal combustion engine; - Automatic application of an assist torque with the aid of an assist torque device having an electromagnet device in an assist phase before a piston (10) of the internal combustion engine has reached top dead center; and - Switching off the support torque after the end of the support phase.

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