EP2891785A1 - Method for operation of a hand-held work device with an internal combustion engine - Google Patents

Abstract

A hand-held implement has an internal combustion engine (8) which drives at least one tool of the implement via a centrifugal clutch (24). The centrifugal clutch couples in an engagement speed range (n _K ) that extends between a lower engagement speed (n _u ) and an upper engagement speed (n _o ). The internal combustion engine (8) has a fuel supply device, an ignition device, a control device (41) and means for detecting the rotational speed (n) of the internal combustion engine (8). A method for operating the hand-held implement provides that the speed curve of the internal combustion engine (8) is monitored in the Einkuppeldrehzahlbereich (n _K ), and that the output power to drive the tool (P) of an operating power (P ₁ ) to an increased Power (P ₂ , P ₃ ) is increased when the speed curve over a predetermined period (.DELTA.t) coincides with a predetermined speed curve.

Description

The invention relates to a method for operating a hand-held implement with an internal combustion engine of the type specified in the preamble of claim 1.

From the DE 10 2011 103 125 A1 For example, a method of operating a hand-held implement with an internal combustion engine is known. The internal combustion engine drives a tool via a coupling. The clutch engages in a speed range between a lower and an upper Einkuppeldrehzahl.

In such hand-held implements may occur during operation that the tool sets at full load, for example, when a tooth of a saw chain hooked and blocked in the material to be cut. This leads to a speed drop of the internal combustion engine into the Einkuppeldrehzahlbereich. In the Einkuppeldrehzahlbereich the coupling can be damaged with a stationary tool. The DE 43 26 010 A1 In order to avoid damage to the clutch, it is intended to lower the speed of the internal combustion engine if the speed is operated too long within a critical speed range.

The invention has for its object to provide a method for operating a hand-held implement with an internal combustion engine, which facilitates the work of the operator with the implement.

This object is achieved by a method for operating a hand-held implement with an internal combustion engine with the features of claim 1.

It is envisaged to increase the output power for driving the tool from an operating power to an increased power when a speed curve of the internal combustion engine in the engagement speed range over a predetermined period of time coincides with a predetermined speed profile. By evaluating the speed curve in the Einkuppeldrehzahlbereich can be detected whether the tool blocks in the Einkuppeldrehzahlbereich so that no further acceleration of the tool is possible. By increasing the power, you can try to pull the tool loose, so that the speed can increase again. Due to the fact that the power increase takes place only when the speed curve coincides with the predetermined speed curve, an increase in power, which would lead to elevated temperatures and increased wear in continuous operation, is acceptable. If the increased power is sufficient to release the tool, the operator can continue working without interruption.

Preferably, the power delivered by the engine to drive the tool is increased. However, it may alternatively or additionally be provided to connect a further energy source for driving the tool.

The predetermined speed curve is advantageously a constant speed. If the speed remains constant in the engagement speed range over a predetermined period of time, this can be taken as an indication that the tool can not move, since the operator in the engagement speed range usually full throttle, so that the speed increases rapidly in Einkuppeldeldzahlbereich and the clutch engages quickly. The constant speed is a largely constant speed. In an internal combustion engine, speed fluctuations occur within one engine cycle due to the design. In particular, in the case of two-stroke engines, due to the function, fluctuations of the rotational speed occur over a number of cycles, in particular due to different degrees of burns and combustion misfires, which superimpose the constant speed per se. A constant speed is when the speed fluctuates during an engine cycle and over several engine cycles only within the usual speed fluctuations and the usual for the Einkuppelddrehzahlbereich speed increase does not occur. The predetermined period is advantageously at least about 0.1 s, in particular at least about 0.3 s, preferably at least about 0.5 s. As a result, a non-moving tool can be reliably detected. A very secure detection of the non-moving tool is made possible if the predetermined period is at least about 1 s. Advantageously, the predetermined period is less than about 30 s, in particular less than about 10 s, preferably less than about 5 s. The predetermined speed curve, for example, be a slightly increasing or decreasing speed. A slightly changing speed can result, for example, due to heating when grinding clutch.

The increased power is advantageously at least 103%, in particular at least 105% of the operating power. As a result, in many cases, a tearing of a stuck tool can be achieved. The increased power is in particular at most 120%, preferably at most 110% of the operating power. This can prevent excessive heating of the motor and excessive wear during high power operation. A further increase in power can be achieved, for example, by connecting a further drive motor, in particular an electric motor, preferably the electric motor of an electric starting device for the internal combustion engine. The achievable with the further drive motor increased power to drive the tool, for example, be about 150% to about 250% of the operating power.

The performance is especially increased dramatically on the increased performance. As a result, a particularly effective tearing of the tool is achieved. It can be provided that the power is reduced at least once after the power increase and increased again. The power is advantageously reduced and increased several times after the power increase in short successive time intervals. In particular, the fluctuates Performance at an elevated level. This can improve the breakaway effect of the tool. The operator also receives feedback that the tool is stuck and can react accordingly, for example, reduce the feed force.

The power is advantageously reset to the operating power when the speed leaves the Einkuppelddrehzahlbereich. As a result, an increased performance is avoided in normal operation. The operating power is the power that sets at a certain speed and load at the corresponding operation of the throttle lever. The operating power varies depending on the speed and the load, so that the absolute power value after the power is reset may deviate from the power value before increasing the power. To reset to the operating power is advantageously the operating parameter, which was adjusted to increase the power, reset to its initial value before increasing the power. It can also be provided that an operating parameter is determined on the basis of a curve, for example as a function of the rotational speed, and that the operating parameter for the power increase is changed by a fixed value or determined using a second curve which is associated with an increased power.

In order to avoid an excessive load of the internal combustion engine due to the increased power, it is provided that the power is reset to the operating performance after a predetermined time. The predetermined time may be, for example, about 0.1 s to about 60 s. Advantageously, the predetermined time is about 0.5 s to about 30 s, in particular about 1 s to about 10 s. Different periods of time can be specified for different fields of application. Alternatively or additionally, it may be provided that the power is reset to the operating performance after reaching a predetermined temperature of the internal combustion engine. The criteria for resetting the power to the operating performance are advantageously selected so that damage to the internal combustion engine due to the short-term operation with increased power can be avoided. It can be provided for resetting the power set several criteria and return the service to operating performance once one of the criteria is met.

If the power is increased to drive the tool by connecting another drive motor, it is provided that the predetermined time is up to about 10 s. Advantageously, the predetermined time during which the further drive motor increases the power delivered for driving the tool, at least about 5 s.

To increase the outgoing of the engine power can be provided an adjustment of the ignition timing of the internal combustion engine. The ignition timing is adjusted to increase the power especially after "early". Additionally or alternatively, it may be provided that the power is increased by changing the amount of fuel supplied. The amount of fuel supplied is thereby reduced in particular, so the engine emaciated. This is especially provided when the engine is operated in the rich area. However, it can also be provided to increase the amount of fuel supplied to increase the power, so the engine to grease. This is preferably provided when the internal combustion engine is operated in the lean range. Alternatively or additionally, it may also be provided that the output power is increased by changing the amount of combustion air supplied to the internal combustion engine. In particular, the amount of combustion air is increased, so that the mixture supplied to the internal combustion engine is emaciated. It can also be provided to increase the output of the internal combustion engine power supplied to the amount of fuel / air mixture to increase, in particular to increase, for example by supplying fuel / air mixture via an additional mixture path. The individual measures for increasing the output of the engine power can be used individually or in any combination.

It can be provided that the internal combustion engine supplies at least one additional consumer of energy in addition to the tool. To increase the power can be provided in particular that the at least one further consumer switched off becomes. It may also be advantageous that the power is increased by reducing the energy supplied to the at least one further consumer. Further consumers may be, for example, a generator or an oil pump for conveying lubricating oil for the tool. Other consumers may be provided. Consumers may consume mechanical energy provided by the internal combustion engine or electrical energy generated by the internal combustion engine.

Advantageously, the implement has a further drive motor, and the output for driving the tool power is increased by connecting the other drive motor. The further drive motor is in particular an electric motor. With an electric motor can be achieved in a simple manner for a short time a significant increase in performance. Preferably, the drive motor is an already existing electric motor, in particular the electric motor of an electric Anwerfvorrichtung the implement.

Advantageously, the implement has an operating element, and the power of the internal combustion engine is increased when the operating element is actuated. This allows the operator to trigger a short-term increase in output himself. The power increase takes place in particular in the Einkuppeldrehzahlbereich. However, a short-term power increase outside the Einkuppeldeldzahlbereichsbereich may be advantageous.

Fig. 1

eine schematische Darstellung einer Motorsäge,

Fig. 2

einen schematischen Schnitt durch die Motorsäge aus Fig. 1,

Fig. 3

eine schematische Darstellung des Vergasers der Motorsäge aus Fig. 1,

Fig. 4

ein Diagramm, das exemplarisch den Verlauf der Drehzahl des Verbrennungsmotors der Motorsäge aus Fig. 1 über der Zeit angibt,

Fig. 5

ein Diagramm, das schematisch einen möglichen Verlauf des Zündzeitpunkts über der Zeit angibt,

Fig. 6

ein Diagramm, das schematisch einen möglichen Verlauf der zugeführten Kraftstoffmenge über der Zeit angibt,

Fig. 7

ein Diagramm, das schematisch einen möglichen Verlauf der zugeführten Menge an Kraftstoff/Luft-Gemisch über der Zeit angibt,

Fig. 8

ein Diagramm, das schematisch mögliche Verläufe der Leistung des Verbrennungsmotors über der Zeit angibt,

Fig. 9

ein Diagramm, das schematisch einen weiteren möglichen Verlauf des Zündzeitpunkts über der Zeit angibt.

Embodiments of the invention are explained below with reference to the drawing. Show it:

Fig. 1

a schematic representation of a power saw,

Fig. 2

a schematic section through the chainsaw Fig. 1 .

Fig. 3

a schematic representation of the carburetor of the chainsaw Fig. 1 .

Fig. 4

a diagram showing the example of the course of the speed of the engine of the chainsaw Fig. 1 indicating over time

Fig. 5

a diagram which schematically shows a possible course of the ignition timing over time,

Fig. 6

a diagram which schematically shows a possible course of the supplied fuel quantity over time,

Fig. 7

a diagram which schematically shows a possible course of the supplied amount of fuel / air mixture over time,

Fig. 8

a diagram which schematically shows possible progressions of the performance of the internal combustion engine over time,

Fig. 9

a diagram which schematically indicates another possible course of the ignition timing over time.

Fig. 1 shows as an exemplary embodiment of a hand-held implement schematically a chainsaw 1. However, the present invention may also be provided in other hand-held implements such as cutters, rock cutters, hedge trimmers or the like. The power saw 1 has a housing 2, a rear handle 3 and a handle tube 4. On the housing 2, a guide rail 6 is fixed, on which a saw chain 7 is arranged circumferentially. At the guide rail 6 facing side of the handle tube 4, a hand guard 5 is arranged, which can serve at the same time to trigger a chain brake, not shown.

The internal combustion engine 8 is a single-cylinder engine, advantageously a mixture-lubricated engine such as a two-stroke engine or a mixture-lubricated four-stroke engine. The internal combustion engine 8 sucks in combustion air via an air filter 28 and a carburetor 9. Instead of the carburetor 9 may also be provided a fuel valve, which is the fuel directly into the engine 8 supplies. The internal combustion engine 8 has a spark plug 10, which is supplied with electrical energy by an ignition module 11.

To operate the internal combustion engine 8, a throttle lever 12 is provided, which is pivotally mounted on the rear handle 3. At the rear handle 3 also a throttle lock 13 is pivotally mounted, which prevents unintentional actuation of the throttle lever 12. On the housing 2, a mode selector 14 is arranged adjacent to the rear handle 3. The mode selector 14 is advantageously used to set at least one start position of the engine 8 and to turn off the engine 8. The chainsaw 1 also has an operating element 15 which is arranged adjacent to the mode selector 14 in the embodiment and its function will be explained in more detail below.

As Fig. 2 shows the spark plug 10 protrudes into a combustion chamber 17 of the internal combustion engine 8. The combustion chamber 17 is bounded by a piston 16 which rotatably drives a crankshaft 19 via a connecting rod 18. The crankshaft 19 is driven to rotate about a rotation axis 20. On the crankshaft 19, a flywheel 21 is fixed, which may be, for example, a fan. The flywheel 21 has magnets, not shown, which induce a voltage at the ignition module 11, which serves to generate the spark on the spark plug 10. On the crankshaft 19, a generator 22 is also defined in the embodiment, which serves to generate electrical energy. In the exemplary embodiment, the generator 22 is arranged in the region of the flywheel 21. However, another arrangement may be advantageous. On the side facing away from the engine 8 of the flywheel 21, a starter device 23 for starting the engine 8 is arranged. In the exemplary embodiment, the starting device 23 is an electric starting device which comprises a drive motor 48. The starting device 23 has a coupling device 49, via which the drive motor 48 acts on the crankshaft 19. However, the starter device 23 may also be a manually operated picking device, for example a rope starting device.

On the flywheel 21 opposite side of the engine 8, a centrifugal clutch 24 is arranged. The drive part 43 of the centrifugal clutch 24 is rotatably connected to the crankshaft 19. The drive part 43 advantageously comprises one or more flyweights, which are mounted with respect to the axis of rotation 20 radially outwardly movable and spring-loaded. The output member 44 is formed as a clutch bell, which is rotatably connected to a drive pinion 26. The drive pinion 26 drives the in Fig. 2 not shown saw chain 7. The output member 44 also drives an in Fig. 2 schematically shown oil pump 25, which serves to promote lubricating oil for the saw chain 7.

As Fig. 2 schematically shows, the internal combustion engine 8 has a temperature sensor 42. In the embodiment, the temperature sensor 42 adjacent to the combustion chamber 17 is arranged. However, another arrangement may be advantageous. The temperature sensor 42 may be arranged, for example, on a crankcase of the internal combustion engine 8. The internal combustion engine 8 has a control device 41, which is integrated in the exemplary embodiment of the ignition module 11. However, a separate embodiment of the control device 41 may also be advantageous. The temperature sensor 42 is connected to the control device 41. For detecting the rotational speed of the internal combustion engine 8, the control device 41 advantageously evaluates the signal of the voltage induced at the ignition module 11. However, a separate speed sensor may also be advantageous. To determine the rotational speed of the internal combustion engine 8, a signal of the generator 22 can also be evaluated.

Fig. 3 shows the carburetor 9 and the air filter 28 schematically. Combustion air is sucked in a flow direction 30 by the internal combustion engine 8 through the air filter 28 and an intake passage 29 formed in the carburetor 9. In the intake passage 29, a choke flap 34 is pivotally mounted with a choke shaft 36. Based on the flow direction 30 downstream of the choke flap 34, a throttle valve 35 is pivotally mounted with a throttle shaft 37. Another design of a throttle element and a choke element may be advantageous. The choke element can also be omitted. In the intake passage 29, a Venturi 31 is formed. In the area of Venturi 31 opens one Main fuel port 32 in the intake passage 29. Downstream of the main fuel port 32, several auxiliary fuel ports 33 open into the intake passage 29. The fuel ports 32 and 33 may be fed by a fuel-filled control space of the carburetor 9. The carburetor 9 is advantageously a diaphragm carburetor, which supplies the fuel as a function of the negative pressure in the intake passage 29 and in dependence on a reference pressure. However, it can also be provided that the fuel openings 32 and 33 are fed via a fuel valve, for example an electromagnetic valve. It can also be provided that the fuel is not supplied via a carburetor 9, but directly into the internal combustion engine 8, for example via one or more fuel valves. The fuel supply can take place, for example, in the combustion chamber 17 or in a crankcase of the internal combustion engine 8.

To control the amount of fuel supplied, the throttle valve 35 is pivotally mounted. The fully open position of the throttle valve 35 is defined by an end stop 38, which with a in Fig. 3 shown schematically, rotatably connected to the throttle shaft 37 connected lever 47 cooperates. The lever 47 and the end stop 38 are outside the intake passage 29, advantageously arranged on the outside of a housing of the carburetor 9.

The throttle lever 12 has an advantageous effect on the throttle valve 35. When fully actuated throttle lever 12, the lever 43 is located on the end stop 38. As in Fig. 3 indicated schematically by dashed line, the end stop 38 via an actuator 39 is adjustable. If the actuator 39 is actuated, the throttle valve can be placed, for example, in the in Fig. 3 shown with a dashed line position 35 'to be adjusted. By actuating the actuator 39, the amount of combustion air supplied to the engine 8 can be increased when the throttle lever 12 is fully actuated.

Fig. 4 shows schematically with a curve 40 a possible course of the rotational speed n of the internal combustion engine 8 over the time t. First, the speed n increases sharply. In this case, the rotational speed n rapidly passes through an engagement speed range n _K , which extends from a lower engagement rotational speed n _u to an upper engagement rotational speed n _o . Upon reaching the lower engagement speed n _u sets the at least one flyweight of the drive member 43 to the clutch drum of the output member 44 at. Until reaching the upper engagement speed n _o , the flyweight is pressed with increasing force to the clutch drum. As a result, with an increase in the rotational speed of the drive part 43, the power transferable via the centrifugal clutch 24 increases. The curve 40 shows the speed curve n at fully actuated throttle lever 12. The fluctuations of the speed n caused by different load, for example at different feed, so when the operator presses the power saw 1 more or less strongly in the workpiece to be cut. At time t ₁ , the speed n has dropped below the upper engagement speed n _o to a speed m. The speed remains constant after reaching the speed m.

The control device 41 monitors the course of the rotational speed n in the engagement rotational speed range n _K and recognizes that the rotational speed n ₁ remains constant up to a predetermined second time t ₂ over a period Δt. When determining the constant speed curve, speed fluctuations that occur in the case of an internal combustion engine within one engine cycle as well as over several engine cycles due to design reasons are disregarded. The period is advantageously at least 0.1 s, in particular at least 0.3 s, preferably at least 0.5 s. Advantageously, the time period Δt is less than about 30 s, in particular less than about 10 s, preferably less than about 5 s. After expiration of the predetermined period .DELTA.t, the control device 41 takes measures for the short-term increase of the output from the engine 8 to drive the saw chain 7 power. As a result, the speed of the drive member 43 is increased and pressed the at least one flyweight with greater force to the outside. As a result, the acting frictional force is increased and thus increases the power provided to drive the saw chain 7 available.

To increase the power, for example, the ignition ZZP can be adjusted. A possible course of the ignition timing is in Fig. 5 shown schematically. Until the ignition time ZZP ₂ , the ignition timing ZZP is subject to only slight fluctuations. The ignition timing ZZP can also be constant. At time t ₂ , so after the Speed n was constant over a period .DELTA.t, the ignition timing of an ignition timing ZZP _{1 is} suddenly adjusted to an ignition ZZP ₂ . The ignition timing ZZP ₂ is advantageously much earlier than the ignition timing ZZP. ₁ The ignition timing ZZP ₂ may be, for example, about 10 ° crankshaft angle before the first ignition ZZP ₁ . The ignition timing ZZP ₂ is closer to the power optimum ignition timing than the ignition ZZP. ₁ By adjusting the ignition timing from the first ignition timing ZZP1 to the second ignition timing ZZP2, the power output from the engine 8 is increased. This is schematically in Fig. 8 shown.

At the second time t ₂ , the power P delivered by the internal combustion engine corresponded to an operating power P ₁ . Upon adjustment of the ignition timing from the ignition timing ZZP ₁ to the ignition timing ZZP ₂ after "early", the power has increased rapidly to an increased power P ₂ . The increased power P ₂ remains as in Fig. 8 indicated by the line 45, until approximately a third time t ₃ approximately constant. As Fig. 4 shows the speed increases before reaching the third time t ₃ again on the upper engagement speed n _o . The power P can be advantageously reset to the operating power P ₁ , when the speed n leaves the Einkuppeldrehzahlbereich n _K. However, it may also be advantageous to reset the power P after a predetermined time .DELTA.t ₂ to the operating power P ₁ . The predetermined time Δt ₂ may advantageously be from about 0.1 s to about 60 s, in particular from about 0.5 s to about 30 s, preferably from about 1 s to about 10 s. The power P may alternatively be reset to the operating power P ₁ when the temperature of the internal combustion engine 8, which is detected by the temperature sensor 42, reaches a predetermined value. The power is reset from the increased power P ₂ to the operating power P ₁ at the third time t ₃ . Advantageously, several criteria for resetting the power to the operating power P _{1 are} monitored and the power is reset to the operating power P ₁ as soon as one of the criteria is met.

Instead of adjusting the ignition timing ZZP, it may also be provided to change the fuel quantity x supplied to the internal combustion engine 8. This is schematically in Fig. 6 shown. At time t ₂ , the amount of fuel supplied to the engine 8 x changed from a first amount of fuel x ₁ to a second amount of fuel x ₂ . In the embodiment, the supplied amount of fuel x is reduced. Also by the reduction of the supplied amount of fuel x, the power P of the engine 8 is increased. The resulting course of the power P corresponds to that in Fig. 8 from the time t ₂ to the time t _{3 shown} by dashed line 45 course. However, it can also be provided to increase the amount of fuel supplied x to increase the power P when the engine 8 is operated lean. It may also be provided to increase the power P, to change the amount of fuel / air mixture supplied to the internal combustion engine 8, preferably to increase. This is schematically in Fig. 7 shown. At time t ₂ , the amount of fuel / air mixture supplied to the internal combustion engine 8 is changed from a first quantity y ₁ to a second quantity y ₂ , in the exemplary embodiment increased. Even then, the results in the Fig. 8 From the time t ₂ to the time t ₃ with dashed line 45 shown course of the power P.

In order to increase the power provided by the combustion engine 8 for driving the saw chain 7, it may also be provided to switch off at least one additional load of the power saw 1 or to reduce the energy supplied to this load. For example, it may be provided to switch off the oil pump 25. This is in Fig. 2 indicated schematically by the arrow 27. The oil pump 25 can be brought out of engagement with the drive pinion 26 or the output member 44, for example. Alternatively, the stroke of the oil pump 25 can be set to zero. To reduce the energy supplied to the oil pump 25, the stroke of the oil pump 25 can be reduced to reduce the flow rate. Alternatively or additionally, the energy supplied to the generator 22 can be reduced.

In order to increase the power provided for driving the saw chain 7, it may also be provided to additionally use the drive motor 48 of the starting device 23 for driving the saw chain 7. The drive motor 48 can exert an additional drive torque on the crankshaft 19 via the coupling device 49. As a result, a significant increase in performance can be achieved. For example, the increased performance about 150% to about 250% of the operating performance. The drive motor 48 is advantageously battery operated. For example, the drive motor of about 5 lithium-ion batteries can be powered. These batteries can be charged during operation of the engine 8. With such a drive motor 48, for example, an additional torque in the order of about 1 Nm can be generated. In order to avoid excessive heating of the drive motor 48, it is provided that the predetermined time after which the power is reset to the operating power is up to about 10 s. Advantageously, the predetermined time is at least about 5 s.

To increase the power of the engine 8, it may also be provided to change the amount of combustion air supplied to the engine 8, for example by adjusting the end stop 38 in the in Fig. 3 dashed position shown. As a result, the amount of combustion air supplied to the internal combustion engine 8 is increased, so the mixture supplied to the internal combustion engine 8 is emaciated. This results in an increase in performance.

It may also be advantageous to combine several measures to increase the power P output by the combustion engine 8 for driving the saw chain 7. The measures mentioned for increasing the power P can be used individually or in any combination for increasing the power P of the internal combustion engine 8.

In order to promote the tearing of a tool in section, it may be provided to lower the power P of the internal combustion engine 8 again after increasing the power and to increase again. In particular, it can be provided to increase the power P alternately. This is in Fig. 9 schematically shown for the ignition timing ZZP. The ignition timing is adjusted from the ignition ZZP ₁ initially to a previous ignition ZZP ₂ and then to a slightly later ignition ZZP ₃ , and then to be adjusted until the third time t ₃ between the ignition ZZP ₂ and ZZP ₃ . This results in a zigzag course of the ignition timing over time. One corresponding zigzag-shaped course results for the power P of the internal combustion engine 8, as in Fig. 8 is indicated schematically by the line 46. It can also be provided to adjust the power between the first power P ₁ and the second power P ₂ . This results from adjusting the ignition timing between the first ignition timing ZZP ₁ and the second ignition timing ZZP ₂ . If the ignition point is set to the third ignition point ZZP ₃ , which lies between the first ignition point ZZP ₁ and the second ignition point ZZP ₂ , the result is a third power P ₃ , which lies between the operating power P ₁ and the increased power P ₂ . A wave-shaped course of the power P and the ignition timing ZZP or a sudden change between two ignition times and thus between two power levels may also be advantageous.

To increase the power P of the internal combustion engine 8, the operator can also operate the operating element 15. The operation of the operating element 15 causes an increase in the operating power P ₁ to an increased power P ₂ or P ₃ . The increased power can be maintained over a given period or until reaching a predetermined, elevated temperature of the internal combustion engine 8, to then be set back to the operating power P ₁ again. If the increased power P ₂ , P _{3 is} so low that it is suitable for continuous operation, provision may also be made for the power to be reset to the operating power P ₁ only when the operator releases the operating element 15.

Claims (18)

A method of operating a hand-held implement with an internal combustion engine (8) that drives at least one tool of the implement via a centrifugal clutch (24), wherein the centrifugal clutch (24) engages in an engagement speed range (n _K ) that varies between a lower engagement speed (n _u ) and an upper engagement speed (n _o ), wherein the internal combustion engine (8) has a fuel supply device, an ignition device, a control device (41) and means for detecting the rotational speed (n) of the internal combustion engine (8),
characterized in that the speed curve of the internal combustion engine (8) in the Einkuppeldrehzahlbereich (n _K ) is monitored and that the output power to drive the tool (P) of an operating power (P ₁ ) to an increased power (P ₂ , P ₃ ) is increased when the speed curve over a predetermined period (.DELTA.t) coincides with a predetermined speed curve. Method according to claim 1,
characterized in that the predetermined speed curve is a constant speed (m). Method according to claim 1 or 2,
characterized in that the predetermined period of time (Δt) is at least 0.1 s. Method according to one of claims 1 to 3,
characterized in that the increased power (P ₂ , P ₃ ) is at least 103% of the operating power (P ₁ ). Method according to one of claims 1 to 4,
characterized in that the power (P) is increased suddenly. Method according to one of claims 1 to 5,
characterized in that the power (P) is reduced at least once after the power increase and increased again. Method according to one of claims 1 to 6,
characterized in that the power (P) is reset to the operating power (P ₁ ) when the speed (n) leaves the engagement speed range (n _K ). Method according to one of claims 1 to 7,
characterized in that the power (P) after a predetermined time (At ₂ ) to the operating power (P ₁ ) is reset. Method according to one of claims 1 to 8,
characterized in that the power (P) after reaching a predetermined temperature of the internal combustion engine (8) to the operating power (P ₁ ) is reset. Method according to one of claims 1 to 9,
characterized in that the output from the internal combustion engine (8) power (P) by adjusting the ignition timing (ZZP) of the internal combustion engine (8) is increased. Method according to one of claims 1 to 10,
characterized in that the output from the internal combustion engine (8) power (P) by changing the amount of fuel supplied (x) is increased. Method according to one of claims 1 to 11,
characterized in that the output from the internal combustion engine (8) power (P) by changing the combustion engine (8) supplied combustion air amount is increased. Internal combustion engine according to one of claims 1 to 12,
characterized in that the output from the internal combustion engine (8) power (P) by changing the internal combustion engine (8) supplied amount (y) of fuel / air mixture is increased. Method according to one of claims 1 to 13,
characterized in that the internal combustion engine (8) supplies at least one further consumer of energy in addition to the tool with energy. Method according to claim 14,
characterized in that the power (P) is increased by switching off the at least one further consumer. Method according to claim 14,
characterized in that the power (P) is increased by reducing the energy supplied to the at least one further consumer. Method according to one of claims 1 to 16,
characterized in that the working device has a further drive motor (48) and that the power (P) is increased by connecting the further drive motor (48). Method according to one of claims 1 to 17,
characterized in that the working device has a control element (15), and that the power (P) of the internal combustion engine (8) is increased when the operating element (15) is actuated.

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