how can simulate the project contains a .qxp file by modelsim-altera???help!!

as the title.

I want to simulate the project which contains a .qxp file, I do it as follows:

1. New project 1 , named counter_ip, synthesis , and then Project-export design partition, so get the .qxp file;

2. New project 2, named top_prj, add the .qxp file generated by step 1 to project2, and instance it ; synthesis;

3. new testbench, and call the modelsim-altera for simulation;

4. got errors in modelsim-altera like this :

Error: (vsim-3033) C:/Users/Vinter/Desktop/Project_out/top_prj/top_prj.v(18): Instantiation of 'counter_ip' failed. The design unit was not found.

thanks very much!!!