LinuxQuestions.org - kill -3 didn't generate core file on centos5

Hi,
I tried "kill -3 <pid>", but no core file was generated.
I tried "kill -6 <pid>" or "kill -11 <pid>", these two all generated core files, but the process were killed. So I think my other setting should be fine, including ulimit, core_pattern...
I don't know why "kill -3 <pid>" didn't generate core file. I need this because I need the core file. After I invoke "kill -3 <pid>", the process was still running when I checked using "ps -ef"

Code:

[ipbx@lab33 ~]$ ~/testS&

[1] 442416

[ipbx@lab33 ~]$ kill -s SIGQUIT 442416

[ipbx@lab33 ~]$ la ~/tmp

total 91032

drwxrwxr-x  2 ipbx ipbx    4096 Jun 20 10:00 .

drwxr-xr-x. 43 ipbx ipbx    4096 Jun 20 09:47 ..

-rw-------  1 ipbx ipbx  700416 Jun 20 10:00 core-bash-11-1001-1001-440636-1371747625

-rw-------  1 ipbx ipbx 62664704 Jun 20 06:35 core-java-6-1001-1001-431229-1371735344

-rw-------  1 ipbx ipbx 59412480 Jun 20 09:39 core-java-6-1001-1001-439925-1371746351

-rw-------  1 ipbx ipbx  319488 Jun 20 09:59 core-sleep-3-1001-1001-442350-1371747560

note that core file was not generated with that pid 442416

Code:

[ipbx@lab33 ~]$ uname -a

Linux lab33 2.6.32-279.5.2.el6.x86_64 #1 SMP Fri Aug 24 01:07:11 UTC 2012 x86_64 x86_64 x86_64 GNU/Linux

Thanks,
3rock