Handheld work apparatus having a combustion engine

Patent metadata

Field	Value
Publication number	US-10495048-B2
Application number	US-201816132442-A
Country	US
Kind code	B2
Filing date	Sep 16, 2018
Priority date	Sep 15, 2017
Publication date	Dec 3, 2019
Grant date	Dec 3, 2019

Abstract

A handheld work apparatus has a combustion engine and an ignition device for controlling a spark plug. The ignition device includes an electronic control device having a short circuit button for switching off the combustion engine. A temperature sensor is for capturing an operating temperature. The short circuit button and the temperature sensor are connected to a common signal input of the control device via a common signal line. The temperature sensor is an ohmic resistance variable on the basis of the temperature. A measurement voltage dropped across the resistance of the temperature sensor is supplied, as an analog temperature signal, to a common analog signal input of the control device. The measurement voltage at the temperature sensor collapses in the button position of the short circuit button, as a result of which the analog temperature signal applied to the analog signal input of the control device is extinguished.

First claim

What is claimed is:

1. A handheld work apparatus comprising:
a motor housing;
a spark-ignition combustion engine arranged in said motor housing;
a spark plug;
an ignition device for controlling said spark plug;
said ignition device including an electronic control device;
a short circuit button with a button position for switching off said combustion engine;
a first temperature sensor for capturing an operating temperature;
said control device having a common signal input;
a common signal line;
said short circuit button and said first temperature sensor being connected to said common signal input of said control device via said common signal line;
said first temperature sensor including an ohmic resistance which is variable on the basis of temperature;
a measurement voltage (U T ) dropped across said ohmic resistance of said first temperature sensor being supplied, as an analog temperature signal (S), to a common analog signal input of said control device; and,
wherein said measurement voltage (U T ) at said first temperature sensor collapses in said button position of said short circuit button and said analog temperature signal (S) is extinguished.

2. The work apparatus of claim 1 , wherein:
said ohmic resistance of said first temperature sensor is a first ohmic resistance;
said short circuit button is in the form of a normally open contact and is in parallel with said first temperature sensor;
said first ohmic resistance of said first temperature sensor is greater than a second ohmic resistance of said short circuit button closed in said button position in a predefined temperature range.

3. The work apparatus of claim 1 , wherein said short circuit button is in the form of a normally closed contact and is open in said button position, and said short circuit button is in series with said first temperature sensor.

4. The work apparatus of claim 1 , wherein said control device includes a microprocessor.

5. The work apparatus of claim 1 , wherein said short circuit button is connected to said signal input of said control device via two signal lines.

6. The work apparatus of claim 1 further comprising:
an encapsulated housing;
said short circuit button and said first temperature sensor being arranged in said encapsulated housing.

7. The work apparatus of claim 1 , further comprising an encapsulated housing having a common connecting line for said short circuit button and said first temperature sensor.

8. The work apparatus of claim 1 , wherein said short circuit button is a microswitch.

9. The work apparatus of claim 1 further comprising:
a plurality of anti-vibration elements;
said combustion engine being held in said motor housing of the work apparatus with said anti-vibration elements; and,
said first temperature sensor being arranged on a vibration-decoupled side of said motor housing.

10. The work apparatus of claim 1 , wherein said first temperature sensor is configured to capture an ambient temperature of the work apparatus.

Assignees

• Stihl Ag & Co Kg Andreas

Inventors

• Klatt Clemens
• Unterkircher Michael

Classifications

• F02D41/042

  for stopping the engine · CPC title

• F02P5/14 Primary

  dependent on specific conditions other than engine speed or engine fluid pressure, e.g. temperature · CPC title

• F02D2400/06

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

• F02P11/00

  Safety means for electric spark ignition, not otherwise provided for · CPC title

• F02D41/22

  Safety or indicating devices for abnormal conditions {(in air/fuel ratio feedback systems F02D41/1495, in electric control linkage F02D11/107, in purge control systems F02M25/0809)} · CPC title