Handheld work apparatus

Patent metadata

Field	Value
Publication number	US-10570842-B2
Application number	US-201816129637-A
Country	US
Kind code	B2
Filing date	Sep 12, 2018
Priority date	Sep 15, 2017
Publication date	Feb 25, 2020
Grant date	Feb 25, 2020

Abstract

A handheld work apparatus has a combustion engine, a pull-rope starter, and a stop button for switching off the combustion engine. A throttle element is arranged in an intake channel of the combustion engine. The work apparatus has a control device for activating a spark plug and a fuel valve. The control device has a starting mode wherein the combustion engine can be started via the pull-rope starter, and an operating mode wherein the operator can adjust the throttle to vary the rotational speed (n) of the combustion engine. The operating and starting mode differ in terms of the control of ignition time and fuel quantity to be supplied. When the combustion engine is started from the switched-off state, the control device is automatically in starting mode, such that after the combustion engine is switched off, the work apparatus is immediately ready for restarting via the pull-rope starter.

First claim

What is claimed is:

1. A handheld work apparatus comprising:
a tool;
a combustion engine for driving said tool;
a manually actuated pull-rope starter for said combustion engine;
a stop button configured to be actuated by an operator for switching off said combustion engine;
a centrifugal clutch;
said combustion engine having a crankcase and a crankshaft mounted in said crankcase;
said crankshaft being operatively connected to said tool via said centrifugal clutch;
said combustion engine having an intake channel;
a throttle element arranged in said intake channel;
said combustion engine having a spark plug and a fuel valve;
a control device for activating said spark plug and said fuel valve;
said control device having a starting mode wherein said combustion engine can be started via said pull-rope starter;
said control device further having an operating mode wherein the operator can activate said combustion engine by adjustment of said throttle element in order to vary a rotational speed (n) of said combustion engine;
said operating mode and said starting mode differing in terms of control, via said control device, of ignition time (ZZP) and fuel quantity to be supplied; and,
wherein, in the case of said combustion engine being started from a switched-off state, said control device is automatically in said starting mode.

2. The work apparatus of claim 1 , wherein said operating mode and said starting mode of said control device differ only in terms of control, via said control device, of ignition time (ZZP) and fuel quantity to be supplied.

3. The work apparatus of claim 1 , wherein said throttle element is the only controllable throttle element arranged in said intake channel.

4. The work apparatus of claim 1 further comprising:
a throttle trigger configured to be adjustable by the operator between a first end position and a second end position; and,
said first end position being assigned to an idling state and said second end position being assigned to a full-load state.

5. The work apparatus of claim 4 , wherein said throttle element is disposed in said first end position during a starting process.

6. The work apparatus of claim 4 , wherein said throttle element defines at least one opening which, in said first end position, provides a defined opening cross section.

7. The work apparatus of claim 4 , wherein said control device is switched from said starting mode into said operating mode when said throttle element is adjusted by the operator from said first end position in the direction of said second end position.

8. The work apparatus of claim 7 further comprising:
a pressure sensor configured to detect a pressure of said combustion engine downstream of said throttle element; and,
wherein said pressure sensor is configured to detect the adjustment of said throttle element from said first end position in the direction of said second end position.

9. The work apparatus of claim 1 , wherein said control device is adjusted from the starting mode into the operating mode at the earliest when at least one combustion has taken place.

10. The work apparatus of claim 1 , wherein the control device is adjusted from the starting mode into the operating mode at the earliest when a predefined number of engine cycles have been run through after a first combustion, said predefined number of engine cycles lying in a range from 5 engine cycles to 100 engine cycles.

11. The work apparatus of claim 1 , wherein said control device is configured to limit the rotational speed (n) of said combustion engine in said starting mode to a starting rotational speed (n S ).

12. The work apparatus of claim 11 , wherein the limitation of the rotational speed (n) of said combustion engine in the starting mode is realized by at least one of adjustment of the ignition time (ZZP), suppression of the ignition spark, and by variation of the supplied fuel quantity.

13. The work apparatus of claim 9 , wherein:
said centrifugal clutch has a clutch-engagement rotational speed range (n k ) bounded by a lower clutch-engagement rotational speed (n u ) and an upper clutch-engagement rotational speed (n o );
said centrifugal clutch has a drive part and an output part;
said output part is not driven by said drive part below said lower clutch-engagement rotational speed (n u );
said drive part and said output part have the same rotational speed (n) above said upper clutch-engagement rotational speed (n o ); and,
said lower clutch-engagement rotational speed (n u ) is at least 25% higher than a starting rotational speed (n S ).

14. The work apparatus of claim 1 , wherein said crankcase defines a crankcase interior; and, said combustion engine has a temperature sensor configured to detect a temperature in said crankcase interior.

15. The work apparatus of claim 1 , wherein said fuel valve has a discharge opening which discharges into said intake channel downstream of said throttle element.

16. The work apparatus of claim 1 , wherein the entire fuel quantity to be supplied to said combustion engine is supplied via a single fuel valve.

17. The work apparatus of claim 1 , wherein:
said combustion engine has a piston;
said crankcase defines a crankcase interior;
said intake channel discharges into said crankcase interior via an inlet window;
said inlet window is controlled by said piston of said combustion engine; and,
said fuel valve is configured to supply fuel through said intake channel into said crankcase interior when said inlet window is open.

18. A handheld work apparatus comprising:
a tool;
a combustion engine for driving said tool;
a manually actuated pull-rope starter for said combustion engine;
a stop button configured to be actuated by an operator for switching off said combustion engine;
a centrifugal clutch;
said combustion engine having a crankcase and a crankshaft mounted in said crankcase;
said crankshaft being operatively connected to said tool via said centrifugal clutch;
said combustion engine having an intake channel;
a throttle element arranged in said intake channel;
a throttle trigger defining a first end position and a second end position;
said throttle element being adjustable by the operator using said throttle trigger between said first end position and said second end position;
said first end position being assigned to an idling state and said second end position being assigned to a full-load state;
said combustion engine having a spark plug and a fuel valve;
a control device for activating said spark plug and said fuel valve;
said control device having a starting mode wherein said combustion engine can be started via said pull-rope starter;
said control device further having an operating mode wherein the operator can activate said combustion engine by adjustment of said throttle element in order to vary a rotational speed (n) of said combustion engine;
wherein said throttle element is the only controllable throttle element arranged in said intake channel; and,
wherein said throttle element is disposed in said first end position during a starting process.

Assignees

• Stihl Ag & Co Kg Andreas

Inventors

• Klatt Clemens

Classifications

• F02D2400/04

  Two-stroke combustion engines with electronic control · CPC title

• F02D2400/06

  Small engines with electronic control, e.g. for hand held tools · CPC title

• F02D41/062

  for starting (F02D41/061 takes precedence) · CPC title

• F02B63/02 Primary

  for hand-held tools · CPC title

• F02N3/02

  having pull-cords · CPC title