Joint effort values in ros?

Hi everyone,
I am simulating a UR3e in ros gazebo and i am trying to get the motor torques of all the joints. When I read out the effort values in the joint_states topic they always remain 0.0, even when the robot is moving. How can I get the joint torques?
Kind regards

I think, ROS answers is the better place to ask this, as this is not containing anything robot- or driver-related.

Gazebo brings along an own simulated hardware interface and controller manager that runs the respective controllers.

ok thanks i will ask there