Toner collecting device for image forming apparatus

An image forming apparatus, comprising:

• an image forming portion configured to execute a printing operation of forming a toner image on a sheet;
• a collecting duct into which unnecessary toner generated inside or around the image forming portion flows together with an airflow;
• a toner collecting device communicating with the collecting duct, having a path of the airflow formed therein, and configured to collect the toner together with the airflow, the toner collecting device including
• a filter configured to collect the toner and let the airflow pass therethrough,
• an airflow generating portion disposed downstream of the filter in the path of the airflow, and configured to execute an intake operation of generating the airflow, and
• a vibrating portion configured to execute a vibrating operation of vibrating the filter;
• and
• a first control portion configured to control an operation condition of the vibrating operation, wherein the first control portion reduces the execution interval between vibrations or increases the magnitude of vibration or the execution time of the vibration when an image density of the toner image that is detected by a density sensor exceeds a predetermined threshold value.