Power tool

Patent metadata

Field	Value
Publication number	US-10329994-B2
Application number	US-201213707724-A
Country	US
Kind code	B2
Filing date	Dec 7, 2012
Priority date	Dec 7, 2011
Publication date	Jun 25, 2019
Grant date	Jun 25, 2019

Abstract

A power tool has an internal combustion engine with an injection valve through which fuel is supplied to the internal combustion engine; a crankcase; and a crankshaft arranged in the crankcase so as to be rotatable about an axis of rotation. A fan wheel housing is provided and a fan wheel is arranged in the fan wheel housing and conveys cooling air to the internal combustion engine. In the fan wheel housing a connecting opening is formed. The injection valve is arranged in a cooling area, wherein cooling air is supplied by the fan wheel through the connecting opening to the cooling area.

First claim

What is claimed is:

1. A power tool comprising:
an internal combustion engine comprising:
an injection valve through which fuel is supplied to the internal combustion engine;
a crankcase comprising a crankcase interior;
a cylinder connected to the crankcase;
a crankshaft arranged in the crankcase interior so as to be rotatable about an axis of rotation;

a fan wheel housing;
a fan wheel arranged in the fan wheel housing and conveying cooling air to the internal combustion engine;
wherein the crankcase comprises a first housing part and a second housing part embodied separate from the first housing part, wherein the first and the second housing parts are joined to each other at a joint surface, wherein the first housing part and the second housing part delimit the crankcase interior;
wherein the cylinder is embodied separate from the first and second housing parts;
wherein the cylinder is placed onto a cylinder connecting flange of the crankcase, wherein a first section of the cylinder connecting flange is formed by the first housing part and a second section of the cylinder connecting flange is formed by the second housing part;
wherein the joint surface is at least partially positioned in an imaginary parting plane extending perpendicularly to the axis of rotation of the crankshaft;
wherein the fan wheel housing and the injection valve are arranged on the first housing part;
wherein the internal combustion engine has an imaginary center plane;
wherein the internal combustion engine has a longitudinal cylinder axis that is located in the imaginary center plane;
wherein the imaginary center plane extends perpendicularly to the axis of rotation of the crankshaft;
wherein the parting plane has a spacing relative to the imaginary center plane and wherein the parting plane extends at the side of the imaginary center plane that is remote from the fan wheel housing.

2. The power tool according to claim 1 , further comprising a gasket interposed between the first housing part and the second housing part at the joint surface.

3. A power tool comprising:
a mixture-lubricated two-stroke internal combustion engine;
a fan wheel conveying cooling air to the two-stroke internal combustion engine;
a fan wheel housing comprising a back wall;
the two-stroke combustion engine comprising:
a crankcase;
a crankcase interior;
a cylinder comprising a bore;
a combustion chamber;
a piston reciprocatingly supported in the bore of the cylinder;
an intake passage;
a cooling area arranged on an exterior side of the crankcase;
a crankshaft; and
a fuel injection valve;

wherein the crankcase delimits the crankcase interior;
wherein the crankshaft is arranged in the crankcase interior so as to be rotatable about an axis of rotation;
wherein the crankshaft is driven in rotation about the axis of rotation by the piston;
wherein the intake passage opens into the bore of the cylinder through an inlet provided at a circumference of the bore of the cylinder, wherein the inlet is piston-controlled by the piston;
wherein the fuel injection valve supplies fuel into the crankcase interior;
wherein the fan wheel is arranged in an interior of the fan wheel housing;
wherein the back wall of the fan wheel housing is facing the crankcase;
wherein a connecting opening is formed in the back wall and the connecting opening connects an interior of the fan wheel housing to the cooling area;
wherein the fuel injection valve is arranged in the cooling area, wherein cooling air is supplied by the fan wheel to said cooling area;
wherein, in a position of the two-stroke combustion engine in which a longitudinal cylinder axis is vertically arranged and the crankcase interior is positioned at least partially below the combustion chamber, the fuel injection valve is arranged below the intake passage;
wherein the fan wheel conveys the cooling air from the interior of the fan wheel housing through the connecting opening in the back wall of the fan wheel housing into said cooling area on the exterior side of the crankcase so that the fuel injection valve is cooled separate from a cooling action that is cooling the cylinder.

4. The power tool according to claim 3 , wherein the connecting opening is arranged in an overpressure area of the fan wheel housing.

5. The power tool according to claim 3 , wherein the internal combustion engine further comprises a holder of plastic material that is attached to the crankcase, wherein the injection valve is arranged in the holder and wherein the holder is arranged at least partially in the cooling area.

6. The power tool according to claim 5 , wherein the holder is arranged on a receiving opening formed in the first housing part at an outer circumference of the crankcase.

7. A power tool comprising:
an internal combustion engine;
a fan wheel housing comprising a back wall; and
a fan wheel disposed in the fan wheel housing;
the combustion engine comprising:
an injection valve supplying fuel;
a cylinder having a longitudinal cylinder axis;
a crankcase;
a crankcase interior; and
a crankshaft;

wherein the crankcase interior is embodied in the crankcase;
wherein the crankshaft is arranged in the crankcase interior so as to be rotatable about an axis of rotation;
wherein the internal combustion engine has an imaginary center plane;
wherein the imaginary center plane extends perpendicularly to the axis of rotation of the crankshaft and contains the longitudinal cylinder axis;
wherein the crankcase comprises a first housing part and a second housing part, wherein the first housing part and the second housing part delimit the crankcase interior,
wherein the second housing part is embodied separate from the first housing part;
wherein the crankcase comprises a joint surface, wherein the first and the second housing parts are joined to each other at the joint surface;
wherein the joint surface is at least partially positioned in an imaginary parting plane extending perpendicularly to the axis of rotation of the crankshaft;
wherein at least one portion of the back wall of the fan wheel housing is formed as one piece together with the first housing part;
wherein the injection valve is mounted on the first housing part;
wherein the at least one portion of the back wall of the fan wheel housing formed as one piece together with the first housing part and the imaginary parting plane are arranged on opposite sides of the imaginary center plane.

8. The power tool according to claim 7 , wherein the imaginary center plane has a spacing relative to the imaginary parting plane, wherein the spacing is approximately 10% to approximately 50% of a width of the crankcase interior measured parallel to the axis of rotation of the crankshaft.

9. The power tool according to claim 7 , wherein the internal combustion engine has at least one sensor arranged on an outer circumference of the crankcase on the first housing part.

10. The power tool according to claim 7 , further comprising a gasket interposed between the first housing part and the second housing part at the joint surface.

Assignees

• Stihl Ag & Co Kg Andreas

Inventors

• Rieber Martin
• Schäffer Thorsten
• Riehmann Jens
• Kinnen Arno
• Donner Volker

Classifications

• F02M35/1017

  Small engines, e.g. for handheld tools, or model engines; Single cylinder engines · CPC title

• F01P5/06

  Guiding or ducting air to, or from, ducted fans · CPC title

• F01P1/10 Primary

  for cooling fuel injectors or sparking-plugs · CPC title

• F01P1/00 Primary

  Air cooling · CPC title

• F02M37/20

  characterised by means for preventing vapour lock · CPC title