Laser ignition system

Patent metadata

Field	Value
Publication number	US-9856849-B2
Application number	US-201414766343-A
Country	US
Kind code	B2
Filing date	Feb 7, 2014
Priority date	Feb 11, 2013
Publication date	Jan 2, 2018
Grant date	Jan 2, 2018

Abstract

A laser ignition system has: at least one arrangement for producing a pulsed laser beam; and at least one arrangement for focusing the produced pulsed laser beam onto a focus zone, e.g., in order to ignite a combustible gas mixture in an internal combustion engine or a burner. The laser ignition system is designed to produce a pulsed laser beam having a normed fluence volume greater than 0.1.

First claim

What is claimed is:

1. A laser ignition system, comprising:
at least one unit for producing a pulsed laser beam; and
at least one unit for focusing the produced pulsed laser beam onto a focus zone in order to ignite a combustible gas mixture;
wherein the laser ignition system is configured to produce a pulsed laser beam having a normed fluence volume greater than 0.1, a fluence volume being given by a volume in which a minimum fluence is everywhere exceeded, and the normed fluence volume resulting from the fluence volume normed to a maximum possible fluence volume, and the minimum fluence assuming a value in a range of from 10 J/mm 2 to 20 J/mm 2 .

2. The laser ignition system as recited in claim 1 , wherein the maximum possible fluence volume is a maximum fluence volume that can theoretically be achieved through variation of a numerical aperture of the focusing while simultaneously holding constant the minimum fluence and laser beam features including pulse energy and beam quality M 2 .

3. The laser ignition system as recited in claim 2 , wherein the minimum fluence is given by a value in the range of from 1/10 to ½ of a maximum fluence of the pulsed laser beam in the focus zone.

4. The laser ignition system as recited in claim 2 , wherein a maximum fluence of the pulsed laser beam in the focus zone is not less than 10 J/mm 2 .

5. The laser ignition system as recited in claim 2 , wherein a maximum fluence of the pulsed laser beam in the focus zone is between 10 J/mm 2 and 120 J/mm 2 .

6. The laser ignition system as recited in claim 2 , wherein the fluence volume has a minimum size of 1*10 −5 mm 3 .

7. The laser ignition system as recited in claim 2 , wherein a ratio between a longitudinal extension and a transverse extension of the fluence volume is not smaller than a factor of 20.

8. The laser ignition system as recited in claim 7 , wherein the ratio between a longitudinal extension and a transverse extension of the fluence volume is between a factor of 20 and a factor of 60.

9. The laser ignition system as recited in claim 2 , wherein at least one of:
the unit for producing the pulsed laser beam is at least one of a diode-pumped and passively Q-switched solid-state laser; and
the unit for focusing the pulsed laser beam includes a lens system.

10. The laser ignition system as recited in claim 9 , wherein the lens system is illuminated at a maximum level of 75% of free aperture of the lens system so that a Strehl ratio of the lens system of from 0.8 to 1 results.

11. The laser ignition system as recited in claim 7 , wherein a pulse energy of the pulsed laser beam is not less than 1 mJ.

12. The laser ignition system as recited in claim 11 , wherein the pulse energy of the pulsed laser beam is between 10 mJ and 25 mJ.

13. The laser ignition system as recited in claim 7 , wherein a pulse duration of the pulsed laser beam is not less than 0.5 ns.

14. The laser ignition system as recited in claim 13 , wherein a pulse duration of the pulsed laser beam is between 0.5 ns and 10 ns.

15. The laser ignition system as recited in claim 7 , wherein the pulsed laser beam has a beam quality M 2 less than 20.

16. The laser ignition system as recited in claim 2 , wherein the pulsed laser beam in the focus zone has a maximum intensity greater than 10 11 W/cm 2 .

17. The laser ignition system as recited in claim 2 , wherein the laser ignition system is a laser spark plug having at least one of an electrical line, an optical line, and a thermal line, wherein the thermal line is for cooling fluid.

18. The laser ignition system as recited in claim 1 , wherein the laser ignition system is configured to produce a pulsed laser beam having a normed fluence volume greater than 0.3.

19. The laser ignition system as recited in claim 1 , wherein the laser ignition system is configured to produce a pulsed laser beam having a normed fluence volume greater than 0.5.

Assignees

• Bosch Gmbh Robert

Inventors

• Ridderbusch Heiko
• Ostrinsky Joern

Classifications

• H01S3/0627

  the resonator being monolithic, e.g. microlaser · CPC title

• H01S5/005

  Optical components external to the laser cavity, specially adapted therefor, e.g. for homogenisation or merging of the beams or for manipulating laser pulses, e.g. pulse shaping (H01S5/026, H01S5/18388 take precedence) · CPC title

• H01S3/005

  Optical devices external to the laser cavity, specially adapted for lasers, e.g. for homogenisation of the beam or for manipulating laser pulses, e.g. pulse shaping (shaping laser beam for working metal or other materials B23K26/06; optical elements, systems or apparatus in general G02B) · CPC title

• H01S3/113

  using intracavity saturable absorbers · CPC title

• F02P23/04 Primary

  Other physical ignition means, e.g. using laser rays · CPC title